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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 - 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

3

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

4

Sulfhydryl systems are a critical factor in the zebrafish developmental toxicity of the dithiocarbamate sodium metam (NaM)  

PubMed Central

Dithiocarbamates (DTCs) are sulfhydryls (thiol)-containing compounds, often associated with metals, and have both antioxidant and pro-oxidant abilities depending on the compound, experimental system and condition. In this study we investigated whether cell death plays a role in the manifestation of DTC-induced notochord distortions in the developing zebrafish and if thiol-containing compounds or antioxidants could modify this developmental toxicity. Sodium metam (NaM) induced notochord distortions could not be protected with the antioxidants ascorbic acid, trolox (synthetic vitamin E) or lipoic acid. However, NaM-induced distortions could be protected with co-exposure to glutathione or N-Acetyl Cysteine. Staggering the NaM and glutathione exposures in consecutive 10 h developmental windows also resulted in protection. There were no discernable changes in TUNEL positive cells, a marker of apoptotic cells, at 24 h post-fertilization (hpf) in NaM, dimethyl-dithiocarbamate, carbon disulfide, or neocuproine exposed embryos. Live NaM-exposed embryos incubated with acridine orange, a general stain for cell death, for 1 h beginning at 11, 18 and 24 hpf showed clusters of stained nuclei near the somitogenic front but not in the cells making up the notochord. Overall, induction of apoptotic pathways and widespread cell death are not involved in the manifestation of the adverse developmental outcomes following NaM exposure. However, cellular thiol status or critical sulfhydryl moieties are important considerations in the mechanisms of DTC developmental toxicity. PMID:18823668

Tilton, Fred; La Du, Jane K.; Tanguay, Robert L.

2012-01-01

5

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

Cancer.gov

Prevention Workshop Attendee List Elizabeth H. Jeffery, Ph.D., Chair Professor Nutritional Sciences Research Group Division of Cancer Prevention National Cancer Institute National Institutes of Health Bethesda, Maryland Daniel E.

6

PTIP Promotes Chromatin Changes Critical for Immunoglobulin Class Switch Recombination  

PubMed Central

Programmed genetic rearrangements in lymphocytes require transcription at antigen receptor genes to promote accessibility for initiating double-strand break (DSB) formation critical for DNA recombination and repair. Here, we showed that activated B cells deficient in the PTIP component of the MLL3 (mixed-lineage leukemia 3)–MLL4 complex display impaired trimethylation of histone 3 at lysine 4 (H3K4me3) and transcription initiation of downstream switch regions at the immunoglobulin heavy-chain (Igh) locus, leading to defective immunoglobulin class switching. We also showed that PTIP accumulation at DSBs contributes to class switch recombination (CSR) and genome stability independently of Igh switch transcription. These results demonstrate that PTIP promotes specific chromatin changes that control the accessibility of the Igh locus to CSR and suggest a nonredundant role for the MLL3-MLL4 complex in altering antibody effector function. PMID:20671152

Daniel, Jeremy A.; Santos, Margarida Almeida; Wang, Zhibin; Zang, Chongzhi; Schwab, Kristopher R.; Jankovic, Mila; Filsuf, Darius; Chen, Hua-Tang; Gazumyan, Anna; Yamane, Arito; Cho, Young-Wook; Sun, Hong-Wei; Ge, Kai; Peng, Weiqun; Nussenzweig, Michel C.; Casellas, Rafael; Dressler, Gregory R.; Zhao, Keji; Nussenzweig, André

2010-01-01

7

The thrombin receptor is a critical extracellular switch controlling myelination.  

PubMed

Hemorrhagic white matter injuries in the perinatal period are a growing cause of cerebral palsy yet no neuroprotective strategies exist to prevent the devastating motor and cognitive deficits that ensue. We demonstrate that the thrombin receptor (protease-activated receptor 1, PAR1) exhibits peak expression levels in the spinal cord at term and is a critical regulator of the myelination continuum from initiation to the final levels achieved. Specifically, PAR1 gene deletion resulted in earlier onset of spinal cord myelination, including substantially more Olig2-positive oligodendrocytes, more myelinated axons, and higher proteolipid protein (PLP) levels at birth. In vitro, the highest levels of PAR1 were observed in oligodendrocyte progenitor cells (OPCs), being reduced with differentiation. In parallel, the expression of PLP and myelin basic protein (MBP), in addition to Olig2, were all significantly higher in cultures of PAR1-/- oligodendroglia. Moreover, application of a small molecule inhibitor of PAR1 (SCH79797) to OPCs in vitro increased PLP and MBP expression. Enhancements in myelination associated with PAR1 genetic deletion were also observed in adulthood as evidenced by higher amounts of MBP and thickened myelin sheaths across large, medium, and small diameter axons. Enriched spinal cord myelination in PAR1-/- mice was coupled to increases in extracellular-signal-regulated kinase 1/2 and AKT signaling developmentally. Nocturnal ambulation and rearing activity were also elevated in PAR1-/- mice. These studies identify the thrombin receptor as a powerful extracellular regulatory switch that could be readily targeted to improve myelin production in the face of white matter injury and disease. GLIA 2015;63:846-859. PMID:25628003

Yoon, Hyesook; Radulovic, Maja; Drucker, Kristen L; Wu, Jianmin; Scarisbrick, Isobel A

2015-05-01

8

Dipolar field effects on the critical current for spin transfer switch of iron and permalloy nanoelements  

SciTech Connect

We report a theoretical study of dipolar effects on the switching current density of soft ferromagnetic elliptical nanoelements. Relevant changes on the critical current value are found according to the orientation of the magnetization and the spin polarization with the major axis. We show that the critical current density may be reduced by as much as 92% for thin nanoelements magnetized along the minor axis direction, using in-plane spin polarization parallel to the magnetization.

Oliveira, L. L.; Dantas, J. T. S.; Souza, R. M.; Carriço, A. S., E-mail: ascarrico@gmail.com [Departamento de Física, Universidade Federal do Rio Grande do Norte, 59072-970 Natal, RN (Brazil); Dantas, Ana L. [Departamento de Física, Universidade do Estado do Rio Grande do Norte, 59610-210 Mossoró, RN (Brazil)

2014-05-07

9

Confirmation of a blocked amino terminus of sulfhydryl oxidase  

SciTech Connect

The isolation of sulfhydryl oxidase from bovine milk in a suitably pure form for sequencing was carried out by transient covalent affinity chromatography of diafiltered whey using cysteinylsuccinamidopropyl-glass as matrix. The glutathione-eluted proteins were separated by SDS-PAGE. By radiolabeling the affinity chromatography-purified enzyme with ({sup 14}C)iodoacetate before subjecting to SDS-PAGE, the sulfhydryl oxidase band was identified, because sulfhydryl oxidase is known to be inactivated by alkylation of one sulfhydryl group per mole. The results confirmed that sulfhydryl oxidase corresponds to the 85 ({plus minus} 5)-kDa band observed on SDS-PAGE. The protein band corresponding to radiolabeled sulfhydryl oxidase was recovered from SDS-PAGE gels by electrophoretic elution and by electroblotting on polyvinylidene difluoride membrane and subjected to gas phase sequencing. Precautions were taken during electrophoretic elution to prevent reactions that result in N-terminal blocking. Both methods of protein recovery yielded negative results when subjected to sequence analysis indicating that the N-terminus of sulfhydryl oxidase is blocked.

Janolino, V.G.; Morrison-Rowe, S.J.; Swaisgood, H.E. (North Carolina State Univ., Raleigh (USA))

1990-09-01

10

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

11

Prevention of acrylonitrile-induced gastrointestinal bleeding by sulfhydryl compounds, atropine and cimetidine  

SciTech Connect

We have recently demonstrated that acrylonitrile (VCN) causes acute gastric hemorrhage and mucosal erosions. The current studies were undertaken to investigate the effects of the sulfhydryl-containing compounds, cysteine and cysteamine, the cholinergic blocking agent atropine and the histamine H2 receptor antagonist, cimetidine on the VCN-induced gastrointestinal (GI) bleeding in rats. Our data shows that pretreatment with L-cysteine, cysteamine, atropine or cimetidine has significantly protected rats against the VCN-induced GI bleeding. A possible mechanism of the VCN-induced GI bleeding may involve the interaction of VCN with critical sulfhydryl groups that, in turn, causes alteration of acetylcholine muscarinic receptors to lead to gastric hemorrhagic lesions and bleeding.

Ghanayem, B.I.; Ahmed, A.E.

1986-07-01

12

Thermal-Electromagnetic Analysis of a Fault-Tolerant Dual Star Flux-Switching Permanent Magnet Motor for Critical  

E-print Network

1 Thermal-Electromagnetic Analysis of a Fault-Tolerant Dual Star Flux-Switching Permanent Magnet of a fault-tolerant dual star Flux-Switching Permanent Magnet (FSPM) motor. The analytical results in terms permanent magnet motors have attracted increasing attentions in safety critical applications such as Hybrid

Paris-Sud XI, Université de

13

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

14

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

NASA Astrophysics Data System (ADS)

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

2014-01-01

15

Pin1 plays a critical role as a molecular switch in canonical BMP signaling.  

PubMed

Pin1 is a peptidyl prolyl cis-trans isomerase that specifically binds to the phosphoserine-proline or phosphothreonine-proline motifs of numerous proteins. Previously, we reported that Pin1 deficiency resulted in defects in osteoblast differentiation during early bone development. In this study, we found that adult Pin1-deficient mice developed osteoporotic phenotypes compared to age-matched controls. Since BMP2 stored in the bone matrix plays a critical role in adult bone maintenance, we suspected that BMP R-Smads (Smad1 and Smad5) could be critical targets for Pin1 action. Pin1 specifically binds to the phosphorylated linker region of Smad1, which leads to structural modification and stabilization of the Smad1 protein. In this process, Pin1-mediated conformational modification of Smad1 directly suppresses the Smurf1 interaction with Smad1, thereby promoting sustained activation of the Smad1 molecule. Our data demonstrate that post-phosphorylational prolyl isomerization of Smad1 is a converging signal to stabilize the Smad1 molecule against the ubiquitination process mediated by Smurf1. Therefore, Pin1 is a critical molecular switch in the determination of Smad1 fate, opposing the death signal transmitted to the Smad1 linker region by phosphorylation cascades after its nuclear localization and transcriptional activation. Thus, Pin1 could be developed as a major therapeutic target in many skeletal diseases. PMID:25187260

Yoon, Won-Joon; Islam, Rabia; Cho, Young-Dan; Ryu, Kyung-Min; Shin, Hye-Rim; Woo, Kyung-Mi; Baek, Jeong-Hwa; Ryoo, Hyun-Mo

2015-03-01

16

Caveolin-1 Is a Critical Determinant of Autophagy, Metabolic Switching, and Oxidative Stress in Vascular Endothelium  

PubMed Central

Caveolin-1 is a scaffolding/regulatory protein that interacts with diverse signaling molecules. Caveolin-1null mice have marked metabolic abnormalities, yet the underlying molecular mechanisms are incompletely understood. We found the redox stress plasma biomarker plasma 8-isoprostane was elevated in caveolin-1null mice, and discovered that siRNA-mediated caveolin-1 knockdown in endothelial cells promoted significant increases in intracellular H2O2. Mitochondrial ROS production was increased in endothelial cells after caveolin-1 knockdown; 2-deoxy-D-glucose attenuated this increase, implicating caveolin-1 in control of glycolytic pathways. We performed unbiased metabolomic characterizations of endothelial cell lysates following caveolin-1 knockdown, and discovered strikingly increased levels (up to 30-fold) of cellular dipeptides, consistent with autophagy activation. Metabolomic analyses revealed that caveolin-1 knockdown led to a decrease in glycolytic intermediates, accompanied by an increase in fatty acids, suggesting a metabolic switch. Taken together, these results establish that caveolin-1 plays a central role in regulation of oxidative stress, metabolic switching, and autophagy in the endothelium, and may represent a critical target in cardiovascular diseases. PMID:24498385

Sugiyama, Toru; Sartoretto, Juliano L.; Kalwa, Hermann; Yan, Zhonghua; Shimokawa, Hiroaki; Michel, Thomas

2014-01-01

17

Disulfide reduction and sulfhydryl uptake by Streptococcus mutans.  

PubMed Central

Incubation of Streptococcus mutans cells with certain disulfide compounds resulted in accumulation of reduced sulfhydryl compounds in the extracellular medium or in both the medium and the cells. Oxidized lipoic acid and lipoamide competed for reduction. At high concentrations, these compounds were reduced at rates comparable to that of glucose metabolism, and all of the increase in sulfhydryls was in the medium. Cystamine did not compete with these compounds for reduction but was also reduced at high rates and low apparent affinity, and all of the cysteamine produced from cystamine accumulated in the medium. In contrast, glutathione disulfide (GSSG) and L-cystine were reduced slowly but with high apparent affinity, and 60 to 80% of the increase in sulfhydryls was intracellular. NADH-dependent lipoic acid or lipoamide reductase activity was present in the particulate (wall-plus-membrane) fraction, whereas NADPH-dependent GSSG reductase activity was present in the soluble (cytoplasmic) fraction. Two transport systems for disulfide and sulfhydryl compounds were distinguished. GSSG, L-cystine, and reduced glutathione competed for uptake. L-Cysteine was taken up by a separate system that also accepted L-penicillamine and D-cysteine as substrates. Uptake of glutathione or L-cysteine, or the uptake and reduction of GSSG or L-cystine, resulted in up to a 10-fold increase in cell sulfhydryl content that raised intracellular concentrations to between 30 and 40 mM. These reductase and transport systems enable S. mutans cells to create a reducing environment in both the extracellular medium and the cytoplasm. PMID:6690421

Thomas, E L

1984-01-01

18

Sulfhydryl oxidase immunoreactivity in seminiferous tubules of infertile men  

Microsoft Academic Search

Sulfhydryl oxidase (SOx) immunoreactivity was investigated in the seminiferous epithelium of human biopsy material from the testes of 33 adult men with disturbed fertility. SOx immunoreactivity was expressed in normal seminiferous epithelium in type-A spermatogonia (27±4% of all spermatogonia) (n=4), in spermatocytes and round spermatids. Mature spermatozoa as well as Sertoli cells were unlabelled. within the interstitium, Leydig cells were

M. Bergmann; G. Aumiiller; J. Seitz; E. Nieschlag

1992-01-01

19

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

20

The Dynamic Disulfide Relay of Quiescin Sulfhydryl Oxidase  

PubMed Central

Protein stability, assembly, localization, and regulation often depend on formation of disulfide cross-links between cysteine side chains. Enzymes known as sulfhydryl oxidases catalyze de novo disulfide formation and initiate intra- and intermolecular dithiol/disulfide relays to deliver the disulfides to substrate proteins1,2. Quiescin sulfhydryl oxidase (QSOX) is a unique, multi-domain disulfide catalyst that is localized primarily to the Golgi apparatus and secreted fluids3 and has attracted attention due to its over-production in tumors4,5. In addition to its physiological importance, QSOX is a mechanistically intriguing enzyme, encompassing functions typically carried out by a series of proteins in other disulfide formation pathways. How disulfides are relayed through the multiple redox-active sites of QSOX and whether there is a functional benefit to concatenating these sites on a single polypeptide are open questions. We determined the first crystal structure of an intact QSOX enzyme, derived from a trypanosome parasite. Notably, sequential sites in the disulfide relay were found more than 40 Å apart in this structure, too far for direct disulfide transfer. To resolve this puzzle, we trapped and crystallized an intermediate in the disulfide hand-off, which showed a 165° domain rotation relative to the original structure, bringing the two active sites within disulfide bonding distance. The comparable structure of a mammalian QSOX enzyme, also presented herein, reveals additional biochemical features that facilitate disulfide transfer in metazoan orthologs. Finally, we quantified the contribution of concatenation to QSOX activity, providing general lessons for the understanding of multi-domain enzymes and the design of novel catalytic relays. PMID:22801504

Alon, Assaf; Grossman, Iris; Gat, Yair; Kodali, Vamsi K.; DiMaio, Frank; Mehlman, Tevie; Haran, Gilad; Baker, David; Thorpe, Colin; Fass, Deborah

2012-01-01

21

Switches and switch interconnects  

Microsoft Academic Search

Switched networks are receiving much attention and supplying a major class of interconnect networks. This paper discusses major issues in switch design and switch interconnects. Due to the importance of high-speed switches in building switched LANs, major design issues are studied and several commercial switches are reviewed. Among different techniques used in switch design, cut-through switching promises short latency delivery

Lionel M. Ni; Wenjian Qiao; Mingyao Yang

1997-01-01

22

Possible role of sulfhydryls in mucosal protection induced by aluminum hydroxide  

Microsoft Academic Search

The involvement of sulfhydryl-containing compounds was investigated in the cytoprotective effect of certain antacids against ethanol-induced gastric mucosal damage in the rat. Not only the protective effect of a sulfhydryl containing compound,N-acetylcysteine, was abolished after pretreatment withN-ethylmaleimid, but also the adaptive cytoprotection induced by 20% ethanol. Pretreatment of the animals with the cyclooxygenase inhibitor indomethacin or with the thiol reagentN-ethylmaleimide

Istvan Szelenyi; Kay Brune

1986-01-01

23

The role of microorganisms in the production of volatile sulfhydryl compounds in cheddar cheese slurries  

E-print Network

THE ROLE OF MICROORGANISMS IN THE PRODUCTION OF VOLATILE SULFHYDRYL COMPOUNDS IN CHEDDAR CHEESE SLURRIES A Thesis By RAUL PONCE-TREVINO Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment... of the requirements for the degree of MASTER OF SCIENCE December 1988 Major Subject: Food Science and Technology THE ROLE OF MICROORGANISMS IN THE PRODUCTION OF VOLATILE SULFHYDRYL COMPOUNDS IN CHEDDAR CHEESE SLURRIES A Thesis By RAUL PONCE-TREVINO Approved...

Ponce-Trevino, Raul

1988-01-01

24

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

25

Lactoperoxidase, peroxide, thiocyanate antimicrobial system: correlation of sulfhydryl oxidation with antimicrobial action.  

PubMed Central

The antimicrobial activity of the lactoperoxidase, peroxide, thiocyanate system against Escherichia coli was directly related to the oxidation of bacterial sulfhydryls. Lactoperoxidase catalyzed the oxidation of thiocyanate, which resulted in the accumulation of hypothiocyanite ion, OSCN-. A portion of the bacterial sulfhydryls were oxidized by OSCN- to yield sulfenic acid and sulfenyl thiocyanate derivatives. The remaining sulfhydryls were not oxidized, although OSCN- was present in large excess. The oxidation of sulfhydryls to sulfenyl derivatives inhibited bacterial respiration. This inhibition could be reversed by adding sulfhydryl compounds to reduce the sulfenyl derivatives and the excess OSCN-. Also, this inhibition could be reversed by washing the cells so as to remove the excess unreacted OSCN-. After washing, the bacteria underwent a time-dependent recovery of their sulfhydryl content. This recovery resulted in recovery of the ability to respire. The inhibited cells were viable if diluted and plated shortly after the incubation with the lactoperoxidase, peroxide, thiocyanate system. On the other hand, long-term incubation in the presence of the excess OSCN- resulted in loss of viability. Also, the inhibition of respiration became irreversible. During this long-term incubation, the excess OSCN- was consumed and the sulfenyl derivatives disappeared. PMID:352945

Thomas, E L; Aune, T M

1978-01-01

26

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

27

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

28

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...

29

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

Microsoft Academic Search

Activation-induced cytidine deaminase (AID) is a single-stranded (ss) DNA-specific cytidine deaminase that initiates Ig heavy chain (IgH) class switch recombination (CSR) and Ig somatic hypermutation (SHM) by deaminating cytidines within, respectively, IgH switch (S) regions and Ig variable region (V) exons. AID that is phosphorylated on serine residue 38 interacts with replication protein A (RPA), a ssDNA binding protein, to

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

2009-01-01

30

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

31

Thimerosal decreases TRPV1 activity by oxidation of extracellular sulfhydryl residues.  

PubMed

TRPV1, a receptor for capsaicin, plays a key role in mediating thermal and inflammatory pain. Because the modulation of ion channels by the cellular redox state is a significant determinant of channel function, we investigated the effects of sulfhydryl modification on the activity of TRPV1. Thimerosal, which oxidizes sulfhydryls, blocked the capsaicin-activated inward current (I(cap)) in cultured sensory neurons, in a reversible and dose-dependent manner, which was prevented by the co-application of the reducing agent, dithiothreitol. Among the three cysteine residues of TRPV1 that are exposed to the extracellular space, the oxidation-induced effect of thimerosal on I(cap) was blocked only by a point mutation at Cys621. These results suggest that the modification of an extracellular thiol group can alter the activity of TRPV1. Consequently, we propose that such a modulation of the redox state might regulate the physiological activity of TRPV1. PMID:15464274

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

2004-10-21

32

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

PubMed Central

Abstract Flavin-linked sulfhydryl oxidases participate in the net generation of disulfide bonds during oxidative protein folding in the endoplasmic reticulum. Members of the Quiescin-sulfhydryl oxidase (QSOX) family catalyze the facile direct introduction of disulfide bonds into unfolded reduced proteins with the reduction of molecular oxygen to generate hydrogen peroxide. Current progress in dissecting the mechanism of QSOX enzymes is reviewed, with emphasis on the CxxC motifs in the thioredoxin and Erv/ALR domains and the involvement of the flavin prosthetic group. The tissue distribution and intra- and extracellular location of QSOX enzymes are discussed, and suggestions for the physiological role of these enzymes are presented. The review compares the substrate specificity and catalytic efficiency of the QSOX enzymes with members of the Ero1 family of flavin-dependent sulfhydryl oxidases: enzymes believed to play key roles in disulfide generation in yeast and higher eukaryotes. Finally, limitations of our current understanding of disulfide generation in metazoans are identified and questions posed for the future. Antioxid. Redox Signal. 13, 1217–1230. PMID:20136510

Kodali, Vamsi K.

2010-01-01

33

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

34

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

PubMed Central

Activation-induced cytidine deaminase (AID) is a single-stranded (ss) DNA-specific cytidine deaminase that initiates Ig heavy chain (IgH) class switch recombination (CSR) and Ig somatic hypermutation (SHM) by deaminating cytidines within, respectively, IgH switch (S) regions and Ig variable region (V) exons. AID that is phosphorylated on serine residue 38 interacts with replication protein A (RPA), a ssDNA binding protein, to promote deamination of transcribed double-stranded DNA in vitro, which, along with other evidence, suggests that AID may similarly gain access to transcribed S regions and V exons in vivo. However, the physiological role of AID phosphorylation at serine residue 38 (S38), and even the requirement for the S38 residue, with respect to CSR or SHM has been debated. To address this issue, we used gene targeting to generate an endogenous mouse AID locus that produces AID in which S38 is substituted with alanine (AIDS38A), a mutant form of AID that retains similar catalytic activity on ssDNA as WT AID (AIDWT). B cells homozygous for the AIDS38A mutation show substantially impaired CSR and SHM, correlating with inability of AIDS38A to interact with endogenous RPA. Moreover, mice haploinsufficient for AIDS38A have even more severely impaired CSR when compared with mice haploinsufficient for AIDWT, with CSR levels reduced to nearly background levels. These results unequivocally demonstrate that integrity of the AID S38 phosphorylation site is required for normal CSR and SHM in mice and strongly support a role for AID phosphorylation at S38 and RPA interaction in regulating CSR and SHM. PMID:19196992

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

2009-01-01

35

Volatile sulfhydryl compounds produced in Cheddar cheese slurries upon the addition of whey protein and casein  

E-print Network

. . . . . 16 19 19 20 21 23 23 25 26 26 31 32 40 Page Concentration of Reactive Sulfhydryl Groups in Slurries. . . . . 43 Effects of Added Milk Proteins on VSH Production. . . CONCLUSIONS. APPENDIX. VITA. 47 66 69 78 132 LIST OF TABLES... and pH of the milk (Table 1), 5 ml of frozen culture (Redi Set DVS ?980, Chr. Hansen' s Laboratory, Inc. , Milwaukee, WI) and rennet (Standard Calf Rennet, 100% high strength, Chr. Hansen's Laboratory) were added directly to the cheese vat and gently...

Sheffield, Amelia Rose

1992-01-01

36

A non-radioactive in situ hybridization method based on mercurated nucleic acid probes and sulfhydryl-hapten ligands.  

PubMed Central

Mercurated nucleic acid probes can be used for non-radioactive in situ hybridization. The principle of the method is based on the reaction of the mercurated pyrimidine residues of the in situ hybridized probe with the sulfhydryl group of a ligand which contains a hapten. Next, the hapten is immunocytochemically detected. Previous experiments showed that stable coupling of the sulfhydryl ligands could only be obtained when positively charged amino groups are present in the ligand. On basis of this finding, ligands were synthesized containing a sulfhydryl group, two lysyl residues and hapten groups such as trinitrophenyl, fluorescyl and biotinyl. The ligands, free or bound to mercurated nucleic acids, were immunochemically characterized in ELISAs. The method was shown to be specific and sensitive in the detection of target DNA in situ on microscopic preparations and in dot-blot hybridization reactions on nitrocellulose. Images PMID:3748817

Hopman, A H; Wiegant, J; Tesser, G I; Van Duijn, P

1986-01-01

37

Changes in sulfhydryl groups of honeybee glyceraldehyde phosphate dehydrogenase associated with generation of the intermediate plateau in its saturation kinetics  

NASA Technical Reports Server (NTRS)

Honeybee and rabbit muscle GPDH were studied to obtain information at the chemical level regarding anomolous saturation kinetics of the honeybee enzyme. Results demonstrate that the enzyme's sulfhydryl groups are implicated in the process. Measured by DTNB titration, native honeybee GPDH has one less active SH than the native rabbit muscle enzyme and displays changes in overall sulfhydryl reactivity after preincubation with G-3-P or G-3-P plus NAD+. The total DTNB reactive sulfhydryls of rabbit muscle GPDH are not changed by preincubation with NAD+ or G-3-P; honeybee GPDH, under certain conductions of preincubation with these ligands, shows a decrease of two total DTNB reactive SH groups. This difference has been confirmed by an independent experiment in which the two enzymes were carboxymethylated with C-14 bromoacetic acid.

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

1973-01-01

38

Reusable fast opening switch  

DOEpatents

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

39

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

40

Simple radiometric method for accurately quantitating epitope densities of hapten-protein conjugates with sulfhydryl linkages.  

PubMed

Control of small molecule hapten epitope densities on antigenic carrier proteins is essential for development and testing of optimal conditions for vaccines. Yet, accurate determination of epitope density can be extremely difficult to accomplish, especially with the use of small haptens, large molecular weight carrier proteins, and limited amounts of protein. Here we report a simple radiometric method that uses (14)C-labeled cystine to measure hapten epitope densities during sulfhydryl conjugation of haptens to maleimide activated carrier proteins. The method was developed using a (+)-methamphetamine (METH)-like hapten with a sulfhydryl terminus, and two prototype maleimide activated carrier proteins, bovine serum albumin (BSA) and immunocyanin monomers of keyhole limpet hemocyanin. The method was validated by immunochemical analysis of the hapten-BSA conjugates, and least-squares linear regression analysis of epitope density values determined by the new radiometric method versus values determined by matrix-assisted laser desorption/ionization mass spectrometry. Results showed that radiometric epitope density values correlated extremely well with the mass spectrometrically derived values (r(2) = 0.98, y = 0.98x + 0.91). This convenient and simple method could be useful during several stages of vaccine development including the optimization and monitoring of conditions for hapten-protein conjugations, and choosing the most effective epitope densities for conjugate vaccines. PMID:25426820

Peterson, Eric C; Hambuchen, Michael D; Tawney, Rachel L; Gunnell, Melinda G; Cowell, James L; Lay, Jackson O; Blough, Bruce E; Carroll, F Ivy; Owens, S Michael

2014-12-17

41

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

42

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

PubMed Central

Two techniques were developed for the immobilization of proteins and other ligands to silica through sulfhydryl groups. These methods made use of maleimide-activated silica (the SMCC method) or iodoacetyl-activated silica (the SIA method). The resulting supports were tested for use in high-performance affinity chromatography by employing human serum albumin (HSA) as a model protein. Studies with normal and iodoacetamide-modified HSA indicated that these methods had a high selectivity for sulfhydryl groups on this protein, which accounted for the coupling of 77–81% of this protein to maleimide- or iodacetyl-activated silica. These supports were also evaluated in terms of their total protein content, binding capacity, specific activity, non-specific binding, stability and chiral selectivity for several test solutes. HSA columns prepared using maleimide-activated silica gave the best overall results for these properties when compared to HSA that had been immobilized to silica through the Schiff base method (i.e., an amine-based coupling technique). A key advantage of the supports developed in this work is that they offer the potential of giving greater site-selective immobilization and ligand activity than amine-based coupling methods. These features make these supports attractive in the development of protein columns for such applications as the study of biological interactions and chiral separations. PMID:17297940

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

2008-01-01

43

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

SciTech Connect

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

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

1986-05-01

44

Hydrogen sulfide inhibits L-type calcium currents depending upon the protein sulfhydryl state in rat cardiomyocytes.  

PubMed

Hydrogen sulfide (H(2)S) is a novel gasotransmitter that inhibits L-type calcium currents (I (Ca, L)). However, the underlying molecular mechanisms are unclear. In particular, the targeting site in the L-type calcium channel where H(2)S functions remains unknown. The study was designed to investigate if the sulfhydryl group could be the possible targeting site in the L-type calcium channel in rat cardiomyocytes. Cardiac function was measured in isolated perfused rat hearts. The L-type calcium currents were recorded by using a whole cell voltage clamp technique on the isolated cardiomyocytes. The L-type calcium channel containing free sulfhydryl groups in H9C2 cells were measured by using Western blot. The results showed that sodium hydrosulfide (NaHS, an H(2)S donor) produced a negative inotropic effect on cardiac function, which could be partly inhibited by the oxidant sulfhydryl modifier diamide (DM). H(2)S donor inhibited the peak amplitude of I( Ca, L) in a concentration-dependent manner. However, dithiothreitol (DTT), a reducing sulfhydryl modifier markedly reversed the H(2)S donor-induced inhibition of I (Ca, L) in cardiomyocytes. In contrast, in the presence of DM, H(2)S donor could not alter cardiac function and L type calcium currents. After the isolated rat heart or the cardiomyocytes were treated with DTT, NaHS could markedly alter cardiac function and L-type calcium currents in cardiomyocytes. Furthermore, NaHS could decrease the functional free sulfhydryl group in the L-type Ca(2+) channel, which could be reversed by thiol reductant, either DTT or reduced glutathione. Therefore, our results suggest that H(2)S might inhibit L-type calcium currents depending on the sulfhydryl group in rat cardiomyocytes. PMID:22590646

Zhang, Rongyuan; Sun, Yan; Tsai, Haojan; Tang, Chaoshu; Jin, Hongfang; Du, Junbao

2012-01-01

45

Hydrogen Sulfide Inhibits L-Type Calcium Currents Depending upon the Protein Sulfhydryl State in Rat Cardiomyocytes  

PubMed Central

Hydrogen sulfide (H2S) is a novel gasotransmitter that inhibits L-type calcium currents (I Ca, L). However, the underlying molecular mechanisms are unclear. In particular, the targeting site in the L-type calcium channel where H2S functions remains unknown. The study was designed to investigate if the sulfhydryl group could be the possible targeting site in the L-type calcium channel in rat cardiomyocytes. Cardiac function was measured in isolated perfused rat hearts. The L-type calcium currents were recorded by using a whole cell voltage clamp technique on the isolated cardiomyocytes. The L-type calcium channel containing free sulfhydryl groups in H9C2 cells were measured by using Western blot. The results showed that sodium hydrosulfide (NaHS, an H2S donor) produced a negative inotropic effect on cardiac function, which could be partly inhibited by the oxidant sulfhydryl modifier diamide (DM). H2S donor inhibited the peak amplitude of I Ca, L in a concentration-dependent manner. However, dithiothreitol (DTT), a reducing sulfhydryl modifier markedly reversed the H2S donor-induced inhibition of I Ca, L in cardiomyocytes. In contrast, in the presence of DM, H2S donor could not alter cardiac function and L type calcium currents. After the isolated rat heart or the cardiomyocytes were treated with DTT, NaHS could markedly alter cardiac function and L-type calcium currents in cardiomyocytes. Furthermore, NaHS could decrease the functional free sulfhydryl group in the L-type Ca2+ channel, which could be reversed by thiol reductant, either DTT or reduced glutathione. Therefore, our results suggest that H2S might inhibit L-type calcium currents depending on the sulfhydryl group in rat cardiomyocytes. PMID:22590646

Tsai, Haojan; Tang, Chaoshu; Jin, Hongfang; Du, Junbao

2012-01-01

46

Critical angle for irreversible switching of the exchange-bias direction in NiO-Cu-Ni81Fe19 films O. de Haas, R. Schafer,* L. Schultz, and C. M. Schneider  

E-print Network

magnetization reversals. Moving 180° domain walls are able to permanently switch the pinning direction by 180 the antiferromagnetic film by motion of a Bloch wall parallel to the film plane. We determined a critical angle C / Permalloy 10 nm layers was investigated by Kerr microscopic domain studies in an optical cryostat

Lin, Minn-Tsong

47

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

Microsoft Academic Search

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

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

1989-01-01

48

Measurement of Tissue Sulfhydryls and Disulfides in Tissue Protein and Nonprotein Fractions by High Performance Liquid Chromatography Using Electrochemical Detection  

Microsoft Academic Search

A specific, sensitive and quantitative method for measuring tissue sulfhydryl (SH) and disulfide levels in nonprotein, protein, and protein-bound fraction has been developed by using HPLC with electrochemical detection. Protein and nonprotein fractions are separated through perchloric acid precipitation. The protein fraction is divided into two aliquots: one which undergoes protein hydrolysis in HCl and the other which undergoes sodium

D. Dupuy; S. Szabo

1987-01-01

49

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

50

Inward rectifier potassium channel Kir 2.3 is inhibited by internal sulfhydryl modification.  

PubMed

Regions of the hippocampal inward rectifier potassium channel Kir 2.3 that contact the aqueous environment were investigated by identification of native cysteine residues that confer sulfhydryl reagent sensitivity to the channel conductance. Kir 2.3 currents were inhibited by N-ethylmaleimide (NEM), whereas currents of Kir 2.1 were unaffected. The reactive residues were identified as Kir 2.3 Cys28 and Cys50 using chimeric constructs and mutagenesis. These sites were not accessible to p-chloromercuriphenylsulfonate (pCMPS) applied extracellularly. However, both Cys28 and Cys50 were accessible to 2-(trimethylammoniumethyl) methanethiosulfonate (MTSET) applied to the intracellular surface of the membrane. These studies demonstrate that Cys28 and Cys50 lie in a cytoplasmic aqueous accessible region of the channel, and suggest that the channel N-terminus is a key constituent of the internal vestibule of the pore and/or modulates channel gating. PMID:10599834

Radeke, C M; Conti, L R; Vandenberg, C A

1999-11-01

51

Intracellular catalysis of disulfide bond formation by the human sulfhydryl oxidase, QSOX1  

PubMed Central

The discovery that the flavoprotein oxidase, Erv2p, provides oxidizing potential for disulfide bond formation in yeast, has led to investigations into the roles of the mammalian homologues of this protein. Mammalian homologues of Erv2p include QSOX (sulfhydryl oxidases) from human lung fibroblasts, guinea-pig endometrial cells and rat seminal vesicles. In the present study we show that, when expressed in mammalian cells, the longer version of human QSOX1 protein (hQSOX1a) is a transmembrane protein localized primarily to the Golgi apparatus. We also present the first evidence showing that hQSOX1a can act in vivo as an oxidase. Overexpression of hQSOX1a suppresses the lethality of a complete deletion of ERO1 (endoplasmic reticulum oxidase 1) in yeast and restores disulfide bond formation, as assayed by the folding of the secretory protein carboxypeptidase Y. PMID:17331072

Chakravarthi, Seema; Jessop, Catherine E.; Willer, Martin; Stirling, Colin J.; Bulleid, Neil J.

2007-01-01

52

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

53

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

PubMed Central

The zinc metalloenzyme porphobilinogen synthase (PBGS) contains several functionally important, but previously unidentified, reactive sulfhydryl groups. The enzyme has been modified with the reversible sulfhydryl-specific nitroxide spin label derivative of methyl methanethiosulfonate (MMTS), (1-oxyl-2,2,5,5-tetramethyl-delta 3-pyrroline-3-methyl)methanethiosulfonate (SL-MMTS) (Berliner, L. J., Grunwald, J., Hankovszky, H. O., & Hideg, K., 1982, Anal. Biochem. 119, 450-455). EPR spectra show that SL-MMTS labels three groups per PBGS subunit (24 per octamer), as does MMTS. EPR signals reflecting nitroxides of different mobilities are observed. Two of the three modified cysteines have been identified as Cys-119 and Cys-223 by sequencing peptides produced by an Asp-N protease digest of the modified protein. Because MMTS-reactive thiols have been implicated as ligands to the required Zn(II), EPR spectroscopy has been used to determine the spatial proximity of the modified cysteine residues. A forbidden (delta m = 2) EPR transition is observed indicating a through-space dipolar interaction between at least two of the nitroxides. The relative intensity of the forbidden and allowed transitions show that at least two of the unpaired electrons are within at most 7.6 A of each other. SL-MMTS-modified PBGS loses all Zn(II) and cannot catalyze product formation. The modified enzyme retains the ability to bind one of the two substrates at each active site. Binding of this substrate has no influence on the EPR spectral properties of the spin-labeled enzyme, or on the rate of release of the nitroxides when 2-mercaptoethanol is added.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8382991

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

1993-01-01

54

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

55

Limits to the critical transport current in superconducting (Bi,Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10} silver-sheathed tapes: The railway-switch model  

SciTech Connect

We have proposed the ``railway-switch`` model to describe the superconducting transport current in (Bi,Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10} silver-sheathed tapes. The model assumes that in the textured polycrystalline filament the frequent small-angle {ital c}-axis tilt grain boundaries (``railway switches``) constitute strong links for the supercurrent. With the objective to identify the mechanisms that limit the critical-current density in the tapes we present measurements of the transport critical current normal to the tape plane and of the current-transfer length along the tape axis. From {ital I}-{ital V} curves we obtain the longitudinal critical-current distribution and compare it to the thickness variation of the filament. The experiments have been performed on monofilamentary powder-in-tube samples prepared in long lengths by rolling as the only tape-forming process. For all investigated samples the critical-current density at {ital T}=77 K in self-field was in the range {ital j}{sub {ital c}}=20--30 kA/cm{sup 2}. We conclude that the dominant limitation for the transport critical current in the tapes is imposed by the low intragrain critical-current density {ital j}{sub {ital c}}{sup {ital c}} along the {ital c} axis (as compared to the in-plane critical-current density {ital j}{sub {ital c}}{sup {ital a}{ital b}}) and by the even lower critical-current density {ital j}{sub {ital c}}{sup {ital t}} across twist boundaries or intergrowths. Possibilities for an improvement of the performance of the (Bi,Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10} silver-sheathed tapes are discussed.

Hensel, B.; Grasso, G.; Fluekiger, R. [Universite de Geneve, Departement de Physique de la Matiere Condensee, 24, quai Ernest-Ansermet, 1211 Geneve 4 (Switzerland)] [Universite de Geneve, Departement de Physique de la Matiere Condensee, 24, quai Ernest-Ansermet, 1211 Geneve 4 (Switzerland)

1995-06-01

56

A simple figure of merit for high temperature superconducting switches  

SciTech Connect

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

Honig, E.M.

1989-01-01

57

Probable involvement of sulfhydryl groups and a metal as essential components of the cellulase of Clostridium thermocellum  

Microsoft Academic Search

The crude extracellular cellulase from Clostridium thermocellum was oxidatively inactivated by air and inhibited by sulfhydryl reagents. Activity-loss was prevented and reversed by the addition of a high concentration (10 mM) dithiothreitol (DDT) at zero time and up to 24 h respectively. In the presence of a low concentration (0.4 mM) of DTT, the enzyme was more rapidly inactivated than

Eric A. Johnson; Arnold L. Demain

1984-01-01

58

Effect of membrane-permeable sulfhydryl reagents and depletion of glutathione on calcium mobilisation in human platelets.  

PubMed

Exposure to peroxides is known to increase the sensitivity of platelets towards activation by agonists. Similar platelet-activating effects are induced by sulfhydryl reagents that evoke Ca2+-induced Ca2+ release (CICR) by stimulating the Ca2+-releasing property of the inositol-1,4,5-trisphosphate receptor. We questioned whether these compounds may act by mobilising intracellular calcium in platelets by altering the intracellular glutathione redox state. Using FURA2-loaded, aspirin-treated platelets, Ca2+ signals were studied following exposure to the membrane-permeable sulfhydryl reagents, thimerosal and disulfiram, the glutathione peroxidase substrate, tert-butyl hydroperoxide, and the inhibitor of glutathione reductase, 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU). In single platelets monitored by fluorescence imaging techniques, thimerosal and disulfiram elicited repetitive spiking in [Ca2+]i after variable lag times, indicating that these compounds stimulated CICR. BCNU caused [Ca2+]i spiking of only low amplitude, whereas tert-butyl hydroperoxide was inactive. In platelets in suspension devoid of extracellular CaCl2, the sulfhydryl reagents, at concentrations which decreased glutathione by 25%, strongly increased the Ca2+ responses of agonists that stimulated phospholipase C (thrombin) or acted independently of phospholipase C stimulation (thapsigargin). However, Ca2+ release was only slightly promoted by concentrations of BCNU that resulted in substantial depletion of the glutathione level. Tert-butyl hydroperoxide was without effect on glutathione, but partially inhibited Ca2+ mobilisation with these agonists. It is concluded that, in platelets, the potent CICR-promoting effects of sulfhydryl reagents are not solely due to their reaction with intracellular glutathione, but that extensive reduction in glutathione content is associated with Ca2+ mobilisation and CICR. PMID:9260881

van Gorp, R M; van Dam-Mieras, M C; Hornstra, G; Heemskerk, J W

1997-05-15

59

Sulfhydryl-reactive heavy metals increase cell membrane K + and Ca 2+ transport in renal proximal tubule  

Microsoft Academic Search

Summary The cellular mechanisms by which nephrotoxic heavy metals injure the proximal tubule are incompletely defined. We used extracellular electrodes to measure the early effects of heavy metals and other sulfhydryl reagents on net K+ and Ca2+ transport and respiration (QO2) of proximal tubule suspensions. Hg2+, Cu2+, and Au3+ (10-4m) each caused a rapid net K+ efflux and a delayed

Bruce C. Kone; Robert M. Brenner; Steven R. Gullans

1990-01-01

60

Facile preparation of biocompatible sulfhydryl cotton fiber-based sorbents by "thiol-ene" click chemistry for biological analysis.  

PubMed

Sulfhydryl cotton fiber (SCF) has been widely used as adsorbent for a variety of metal ions since 1971. Thanks to the abundant thiols on SCF, in this study, we reported a universal method for the facile preparation of SCF-based materials using "thiol-ene" click chemistry for the first time. With the proposed method, two types of SCF-based materials, phenylboronic acid grafted sulfhydryl cotton fiber (SCF-PBA) and zirconium phosphonate-modified sulfhydryl cotton fiber (SCF-pVPA-Zr(4+)), were successfully prepared. The grafted functional groups onto the thiol group of SCF were demonstrated by X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray spectroscopy (EDX). The prepared fibrous materials exhibited excellent fiber strength, good stability in aqueous or nonaqueous solutions, and great biocompatibility. Moreover, we developed filter-free in-pipet-tip SPE using these SCF-based materials as adsorbent for the enrichment of ribonucleosides, glycopeptides and phosphopeptides. Our results showed that SCF-PBA adsorbent can selectively capture ribonucleosides and glycopeptides from complex biological samples. And SCF-pVPA-Zr(4+) adsorbent exhibited high selectivity and capacity in the enrichment of phosphopeptides from the digestion mixture of ?-casein and bovine serum albumin (BSA), as well as human serum and nonfat milk digest. Generally, the preparation strategy can be a universal method for the synthesis of other functionalized cotton-based adsorbents with special requirement in microscale biological analysis. PMID:25268138

He, Xiao-Mei; Zhu, Gang-Tian; Zhu, Yuan-Yuan; Chen, Xi; Zhang, Zheng; Wang, Shao-Ting; Yuan, Bi-Feng; Feng, Yu-Qi

2014-10-22

61

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

62

Mechanism of Kir6.2 channel inhibition by sulfhydryl modification: pore block or allosteric gating?  

PubMed Central

Chemical modification can inhibit ion channels either by reacting with pore-lining residues and directly occluding the channel or by closing the channel allosterically. A general method to distinguish between these two mechanisms does not exist. Previously, sulfhydryl (SH) modification has been shown to inhibit ATP-sensitive K+ (KATP) channels. The crucial modification has been localized to C42 near the N-terminus of Kir6.2, a pore-forming subunit of KATP channels, but little is known about how SH modification of C42 causes channel inhibition. To investigate this mechanism, we used the membrane-impermeable methanethiosulfonates, MTSET and MTS-TEAH, to modify Kir6.2 channels. While intracellular application of MTSET irreversibly inhibited channels, MTS-TEAH failed to do so. Instead, MTS-TEAH treatment prolonged channel openings and prevented the effect of subsequent MTSET treatment. Similar observations were made in mutants in which cysteines other than C42 had been mutated. Neither MTSET nor MTS-TEAH, however, affected mutant channels in which valines were substituted for C42 residues in all subunits. The reagents were effective when two of four C42 residues in the tetramer were replaced by valines. These results can be interpreted as indicating that both reagents modify C42. We then employed spermine, a known inner pore blocker, as a probe to examine whether MTS-TEAH modification alters pore accessibility. We found that spermine block was not changed by MTS-TEAH modification. Based on these data, we postulate that C42 faces either the cytoplasm or a vestibule section wide enough to allow spermine to pass freely after modification by MTS-TEAH. Our study suggests that channel inhibition caused by SH modification of Kir6.2 is an allosteric effect, and is not caused by direct pore blockage. PMID:11986364

Cui, Yijun; Fan, Zheng

2002-01-01

63

Protection against alpha-naphthylisothiocyanate-induced liver injury by decreased hepatic non-protein sulfhydryl content.  

PubMed

alpha-Naphthylisothiocyanate (ANIT) injures bile duct epithelium and hepatic parenchymal cells in rats. It is commonly believed that ANIT must undergo bioactivation by hepatic, cytochrome P450-dependent mixed-function oxidases (MFO), since agents which are inducers or inhibitors of hepatic MFO activity enhance or attenuate, respectively, the liver injury associated with ANIT. Several of these agents also affect hepatic glutathione (GSH) content and/or GSH S-transferase activity in a manner to suggest a causal role for GSH in ANIT-induced hepatotoxicity. To determine whether GSH might be involved in the mechanism of injury, buthionine sulfoximine (BSO), diethyl maleate (DEM), or phorone was used to reduce hepatic non-protein sulfhydryl (NPSH) content, an indicator of GSH content. Twenty-four hours after ANIT treatment, rats exhibited cholestasis and elevations in serum of total bilirubin concentration, total bile acid concentration, aspartate aminotransferase (AST) activity, and gamma-glutamyltransferase activity. Cotreatment of rats with BSO decreased NPSH content by 70% at 24 hr and prevented the cholestasis and elevations in serum markers of liver injury caused by ANIT. Likewise, cotreatment of rats with DEM afforded protection against markers of liver injury. Phorone treatment attenuated ANIT-induced elevations in serum total bilirubin concentration and AST activity. Although BSO treatment afforded protection against ANIT-induced liver injury at 24 hr, the injury was evident at 48 hr, and it appeared to coincide with a return of hepatic NPSH content. These results suggest that GSH plays a causal or permissive role in the liver injury caused by ANIT. PMID:1679629

Dahm, L J; Roth, R A

1991-08-22

64

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

65

Bcl-2-mediated potentiation of neocarzinostatin-induced apoptosis: requirement for caspase-3, sulfhydryl groups, and cleavable Bcl-2.  

PubMed

Overexpression of antiapoptotic Bcl-2 family members is thought to contribute to chemotherapeutic resistance of neural crest tumors. Paradoxical potentiation by Bcl-2 of apoptosis induced by the antineoplastic prodrug, neocarzinostatin (NCS), has been observed in PC12 pheochromocytoma cells. Prior studies have indicated that the cleavage of Bcl-2 to its proapoptotic counterpart mediated by caspase-3 is responsible for this potentiation of apoptosis. This has led to the hypothesis that induction of caspase-3 expression in bcl-2-transfected, caspase-3-deficient MCF-7 cells, will result in Bcl-2 cleavage and Bcl-2-dependent potentiation of NCS-induced apoptosis. These studies have further led to the hypothesis that both cleavable Bcl-2 and sulfhydryl groups are required for the activity of caspase-3 in this regard. As hypothesized, co-transfection of bcl-2-transfected MCF-7 cells with a caspase-3 expression construct results in cleavage of Bcl-2 and potentiation of dose-dependent, NCS-mediated cell death. Furthermore, PC12 cells transfected with an expression construct for cleavage-resistant Bcl-2 demonstrated attenuated potentiation of apoptosis relative to their counterparts transfected with wild-type bcl-2. Finally, irreversible oxidative titration of sulfhydryl groups resulted in concentration-dependent attenuation of apoptosis in PC12 cells, along with prevention of caspase-3 activation and Bcl-2 cleavage. These results definitively demonstrate the requirement for caspase-3, cleavable Bcl-2, and available sulfhydryl groups (separate from those required for NCS activation) in potentiation of NCS-induced apoptosis by Bcl-2. PMID:16001169

Mi, Zhiping; Hong, Borah; Mirnics, Zeljka Korade; Tyurina, Yulia Y; Kagan, Valerian E; Liang, Ye; Schor, Nina Felice

2006-02-01

66

Diplexer switch  

NASA Technical Reports Server (NTRS)

Switch achieves high isolation and continuous input/output matching by using resonant coupling structure of diplexer. Additionally, dc bias network used to control switch is decoupled from RF input and output lines. Voltage transients in external circuits are thus minimized.

Grauling, C. H., Jr.; Parker, T. W.

1977-01-01

67

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.

68

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

69

Sulfhydryl-dependent attachment of Treponema denticola to laminin and other proteins.  

PubMed Central

Attachment of Treponema denticola ATCC 35405 to laminin, a major basement membrane protein, and to other proteins was studied. Microdilution plates were coated with the proteins, and the attachment of T. denticola was measured by the enzyme-linked immunosorbent assay technique. Compared with bovine serum albumin (BSA), T. denticola had a high affinity to laminin, fibronectin, fibrinogen, and gelatin, as well as to type I and type IV collagens. Attachment to RGD peptide (Gly-Arg-Gly-Asp-Ser, the integrin recognition sequence) was only about 30% of that to laminin and was comparable to attachment to BSA. Tests with laminin fragments obtained through elastase digestion showed that the spirochetes attached well to an A-chain 140-kDa fragment involved in eukaryote cell attachment but did not attach to a 50-kDa fragment that includes the heparin binding site. Pretreatment of T. denticola with soluble laminin, fibronectin, gelatin, BSA, or fibrinogen had no effect on the attachment of the bacteria to laminin or fibronectin. A wide variety of compounds were tested for their possible inhibitory actions on the attachment. While most treatments of T. denticola ATCC 35405 had little or no effect on the attachment to proteins, sulfhydryl reagents p-chloromercuribenzoic acid (pCMBA) and oxidized glutathione inhibited the attachment by 70 to 99%, depending on the protein. When T. denticola was first allowed to attach to proteins, addition of pCMBA or oxidized glutathione could no longer reverse the attachment. Heat treatment of the spirochetes also markedly reduced the attachment to laminin, gelatin, and fibrinogen but not to BSA. Mixed glycosidase treatment of the spirochetes inhibited the attachment by 20 to 80%. None of the above treatments of the substrate proteins had any marked effect on the spirochete attachment. The results indicate that T. denticola has the capacity to bind to many different kinds of proteins by utilizing specific attachment mechanisms. The binding appears to involve protein SH groups and/or carbohydrate residues on the surface of T. denticola. Images PMID:1937780

Haapasalo, M; Singh, U; McBride, B C; Uitto, V J

1991-01-01

70

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

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

71

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

72

The Disulfide Linkage and the Free Sulfhydryl Accessibility of Acyl-Coenzyme A:Cholesterol Acyltransferase 1 As Studied by Using mPEG5000-Maleimide  

E-print Network

The Disulfide Linkage and the Free Sulfhydryl Accessibility of Acyl-Coenzyme AVed December 9, 2004; ReVised Manuscript ReceiVed February 24, 2005 ABSTRACT: Acyl-coenzyme A lumen, while all other free Cs are located within the hydrophobic region(s) of the enzyme. Acyl-coenzyme

Tian, Weidong

73

In vivo sulfhydryl modification of the ligand-binding site of Tsr, the Escherichia coli serine chemoreceptor.  

PubMed Central

The Escherichia coli chemoreceptor Tsr mediates an attractant response to serine. We substituted Cys for Thr-156, one of the residues involved in serine sensing. The mutant receptor Tsr-T156C retained serine- and repellent-sensing abilities. However, it lost serine-sensing ability when it was treated in vivo with sulfhydryl-modifying reagents such as N-ethylmaleimide (NEM). Serine protected Tsr-T156C from these reagents. We showed that [3H]NEM bound to Tsr-T156C and that binding decreased in the presence of serine. By pretreating cells with serine and cold NEM, Tsr-T156C was selectively labeled with radioactive NEM. These results are consistent with the location of Thr-156 in the serine-binding site. Chemical modification of the Tsr ligand-binding site provides a basis for simple purification and should assist further in vivo and in vitro investigations of this chemoreceptor protein. PMID:7721714

Iwama, T; Kawagishi, I; Gomi, S; Homma, M; Imae, Y

1995-01-01

74

PAINS in the Assay: Chemical Mechanisms of Assay Interference and Promiscuous Enzymatic Inhibition Observed during a Sulfhydryl-Scavenging HTS  

PubMed Central

Significant resources in early drug discovery are spent unknowingly pursuing artifacts and promiscuous bioactive compounds, while understanding the chemical basis for these adverse behaviors often goes unexplored in pursuit of lead compounds. Nearly all the hits from our recent sulfhydryl-scavenging high-throughput screen (HTS) targeting the histone acetyltransferase Rtt109 were such compounds. Herein, we characterize the chemical basis for assay interference and promiscuous enzymatic inhibition for several prominent chemotypes identified by this HTS, including some pan-assay interference compounds (PAINS). Protein mass spectrometry and ALARM NMR confirmed these compounds react covalently with cysteines on multiple proteins. Unfortunately, compounds containing these chemotypes have been published as screening actives in reputable journals and even touted as chemical probes or preclinical candidates. Our detailed characterization and identification of such thiol-reactive chemotypes should accelerate triage of nuisance compounds, guide screening library design, and prevent follow-up on undesirable chemical matter. PMID:25634295

2015-01-01

75

Functional consequences of sulfhydryl modification of the ?-aminobutyric acid transporter 1 at a single solvent-exposed cysteine residue.  

PubMed

The aims of this study were to optimize the experimental conditions for labeling extracellularly oriented, solvent-exposed cysteine residues of ?-aminobutyric acid transporter 1 (GAT1) with the membrane-impermeant sulfhydryl reagent [2-(trimethylammonium)ethyl]methanethiosulfonate (MTSET) and to characterize the functional and pharmacological consequences of labeling on transporter steady-state and presteady-state kinetic properties. We expressed human GAT1 in Xenopus laevis oocytes and used radiotracer and electrophysiological methods to assay transporter function before and after sulfhydryl modification with MTSET. In the presence of NaCl, transporter exposure to MTSET (1-2.5 mM for 5-20 min) led to partial inhibition of GAT1-mediated transport, and this loss of function was completely reversed by the reducing reagent dithiothreitol. MTSET treatment had no functional effect on the mutant GAT1 C74A, whereas the membrane-permeant reagents N-ethylmaleimide and tetramethylrhodamine-6-maleimide inhibited GABA transport mediated by GAT1 C74A. Ion replacement experiments indicated that MTSET labeling of GAT1 could be driven to completion when valproate replaced chloride in the labeling buffer, suggesting that valproate induces a GAT1 conformation that significantly increases C74 accessibility to the extracellular fluid. Following partial inhibition by MTSET, there was a proportional reduction in both the presteady-state and steady-state macroscopic signals, and the functional and pharmacological properties of the remaining signals were indistinguishable from those of unlabeled GAT1. Therefore, covalent modification of GAT1 at C74 results in completely nonfunctional as well as electrically silent transporters. PMID:22918627

Omoto, Jaison J; Maestas, Matthew J; Rahnama-Vaghef, Ali; Choi, Ye E; Salto, Gerardo; Sanchez, Rachel V; Anderson, Cynthia M; Eskandari, Sepehr

2012-12-01

76

Information Switching Processor (ISP) contention analysis and control  

NASA Astrophysics Data System (ADS)

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

1995-07-01

77

B7-1 and B7-2 Have Overlapping, Critical Roles in Immunoglobulin Class Switching and Germinal Center Formation  

Microsoft Academic Search

Humoral immune responses were characterized in mouse strains lacking either or both B7 molecules. Mice deficient in both B7-1 and B7-2 failed to generate antigen-specific IgG1 and IgG2a responses and lacked germinal centers when immunized by a number of routes and even in the presence of complete Freund's adjuvant. These results demonstrate that B7-mediated signaling plays a critical role in

Frank Borriello; Michael P Sethna; Scott D Boyd; A. Nicola Schweitzer; Elizabeth A Tivol; Douglas Jacoby; Terry B Strom; Elizabeth M Simpson; Gordon J Freeman; Arlene H Sharpe

1997-01-01

78

IP switching for scalable IP services  

Microsoft Academic Search

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

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

1997-01-01

79

Reset Switching Probability of Resistive Switching Devices  

Microsoft Academic Search

The reset switching probability of resistive switching devices is characterized in array testing. The measured switching probability can be quantitatively explained based on the mecha- nism of a thermally activated reset process. An analytical model of switching probability is developed to describe the dependence of reset probability on operation parameters, including applied voltage, selection transistor gate voltage, and pulsewidth. The

An Chen; Ming-Ren Lin

2011-01-01

80

Optical switching: switch fabrics, techniques, and architectures  

Microsoft Academic Search

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

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

2003-01-01

81

FAST TRACK COMMUNICATION: Synthesis and electron transfer property of sulfhydryl-containing multi-walled carbon nanotube/gold nanoparticle heterojunctions  

NASA Astrophysics Data System (ADS)

One-dimensional metal/semiconductor heterojunction nanomaterials have opened many new opportunities for future nanodevices because of their novel structures and unique electrical and optical properties. In this work, sulfhydryl-containing multi-walled carbon nanotube/gold nanoparticle (MWCNT/Au) heterojunctions were synthesized in high yield by a sulfhydryl- functionalized self-assembly strategy. The component, size, structure, morphology and bond mode of the MWCNT/Au heterojunctions thus prepared were investigated and demonstrated by transmission electron microscopy, scanning electron microscopy, x-ray diffraction, energy-dispersive x-ray spectroscopy, Fourier-transform infrared and UV-visible measurements. Cyclic voltammogram and electrochemical impedance spectroscopy studies indicate that the MWCNT/Au heterojunctions have a novel electron transfer property, which retards electron transfer of the horseradish peroxidase or the ferricyanide in the underlying electrodes. We believe that MWCNT/Au heterojunctions with high stability and a unique electrical property are expected to find potential applications for nanodevices.

Feng, Xiumei; Hu, Jianqiang; Chen, Xiaohua; Xie, Jingsi; Liu, Yuying

2009-02-01

82

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

83

Thiol-dependent passive K\\/Cl transport in sheep red cells: VII. Volume-independent freezing by iodoacetamide, and sulfhydryl group heterogeneity  

Microsoft Academic Search

Summary The sulfhydryl (SH) reagent iodoacetamide (IAAM) inhibits stimulation of Cl-dependent K transport in low K (LK) sheep red cells by another SH reagent, N-ethylmaleimide (NEM), without itself activating this transport pathway (J. Membrane Biol., 1983,73:257–261). We now report that IAAM alone, acting with a kinetic slower than NEM, sharply reduced the capability of the Cl-dependent K transport system to

P. K. Lauf

1987-01-01

84

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

85

Improvement of switching time in a thermocapillarity optical switch  

Microsoft Academic Search

The switching time of existing thermocapillarity optical switches is about two orders of magnitude larger than that of other optical switches, such as a thermooptics switch and a free-space switch using microelectromechanical system technology. This paper reports a thermocapillarity switch whose switching time is comparable to that of the thermooptics and free-space switches. The greatly improved switching time is achieved

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

2001-01-01

86

Eosinophil peroxidase oxidation of thiocyanate. Characterization of major reaction products and a potential sulfhydryl-targeted cytotoxicity system.  

PubMed

Although the pseudohalide thiocyanate (SCN(-)) is the preferred substrate for eosinophil peroxidase (EPO) in fluids of physiologic halide composition, the product(s) of this reaction have not been directly identified, and mechanisms underlying their cytotoxic potential are poorly characterized. We used nuclear magnetic resonance spectroscopy (NMR), electrospray ionization mass spectrometry, and quantitative chemical analysis to identify the principal reaction products of both the EPO/SCN(-)/H(2)O(2) system and activated eosinophils as roughly equimolar amounts of OSCN(-) (hypothiocyanite) and OCN(-) (cyanate). Red blood cells exposed to increasing concentrations of OSCN(-)/OCN(-) are first depleted of glutathione, after which glutathione S-transferase and glyceraldehyde-3-phosphate dehydrogenase then ATPases undergo sulfhydryl (SH) reductant-reversible inactivation before lysing. OSCN(-)/OCN(-) inactivates red blood cell membrane ATPases 10-1000 times more potently than do HOCl, HOBr, and H(2)O(2). Exposure of glutathione S-transferase to [(14)C]OSCN(-)/OCN(-) causes SH reductant-reversible disulfide bonding and covalent isotope labeling. We propose that EPO/SCN(-)/H(2)O(2) reaction products comprise a potential SH-targeted cytotoxic system that functions in striking contrast to HOCl, the highly but relatively indiscriminantly reactive product of the neutrophil myeloperoxidase system. PMID:11013238

Arlandson, M; Decker, T; Roongta, V A; Bonilla, L; Mayo, K H; MacPherson, J C; Hazen, S L; Slungaard, A

2001-01-01

87

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

88

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

89

Surface modification of titanium substrates with silver nanoparticles embedded sulfhydrylated chitosan/gelatin polyelectrolyte multilayer films for antibacterial application.  

PubMed

To develop Ti implants with potent antibacterial activity, a novel "sandwich-type" structure of sulfhydrylated chitosan (Chi-SH)/gelatin (Gel) polyelectrolyte multilayer films embedding silver (Ag) nanoparticles was coated onto titanium substrate using a spin-assisted layer-by-layer assembly technique. Ag ions would be enriched in the polyelectrolyte multilayer films via the specific interactions between Ag ions and -HS groups in Chi-HS, thus leading to the formation of Ag nanoparticles in situ by photo-catalytic reaction (ultraviolet irradiation). Contact angle measurement and field emission scanning electron microscopy equipped with energy dispersive X-ray spectroscopy were employed to monitor the construction of Ag-containing multilayer on titanium surface, respectively. The functional multilayered films on titanium substrate [Ti/PEI/(Gel/Chi-SH/Ag) n /Gel] could efficiently inhibit the growth and activity of Bacillus subtitles and Escherichia coli onto titanium surface. Moreover, studies in vitro confirmed that Ti substrates coating with functional multilayer films remained the biological functions of osteoblasts, which was reflected by cell morphology, cell viability and ALP activity measurements. This study provides a simple, versatile and generalized methodology to design functional titanium implants with good cyto-compatibility and antibacterial activity for potential clinical applications. PMID:24664672

Li, Wen; Xu, Dawei; Hu, Yan; Cai, Kaiyong; Lin, Yingcheng

2014-06-01

90

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

PubMed

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

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

2013-07-01

91

A Linear Transformer Driver (LTD) with multiple self triggered switches  

Microsoft Academic Search

Multiple switches are normally required for the generation of very high pulse power levels. The critical problem related to multiple switches is how to synchronize them in a short time interval and how to obtain current\\/voltage balance. A multiple-switch technique based on a TLT (Transmission-Line-Transformer) can solve this problem. It provides a failure-free solution to synchronize multiple switches automatically like

A. J. M. Pemen; Z. Liu; E. J. M. van Heesch

2011-01-01

92

Antiulcer activity of Muntingia calabura leaves involves the modulation of endogenous nitric oxide and nonprotein sulfhydryl compounds.  

PubMed

Abstract Context: Muntingia calabura L. (Muntingiaceae) is a native plant species of the American continent and is widely cultivated in warm areas in Asia, including Malaysia. The plant is traditionally used to relieve pain from gastric ulcers. Objective: This study was designed to determine the antiulcer activity of a methanol extract of M. calabura leaves (MEMC) and the possible mechanisms of action involved. Materials and methods: An acute toxicity study was conducted using a single oral dose of 2000?mg/kg MEMC. The antiulcer activity of MEMC was evaluated in absolute ethanol- and indomethacin-induced gastric ulcer rat models. MEMC was administered orally (dose range 25-500?mg/kg) to rats fasted for 24?h. The animals were pretreated with N(G)-nitro-l-arginine methyl esters (l-NAME) or N-ethylmaleimide (NEM) prior to MEMC treatment to assess the possible involvement of endogenous nitric oxide (NO) and nonprotein sulfhydryl (NP-SH) compounds in the gastroprotective effect of MEMC. Results: As the administered dose did not cause toxicity in the rats, the oral median lethal dose (LD50) of MEMC was >2000?mg/kg in rats. MEMC exerted significant (p?

Balan, Tavamani; Mohd Sani, Mohd Hijaz; Suppaiah, Velan; Mohtarrudin, Norhafizah; Suhaili, Zarizal; Ahmad, Zuraini; Zakaria, Zainul Amiruddin

2013-11-01

93

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

94

Effects of sulfhydryl compounds, carbohydrates, organic acids, and sodium sulfite on the formation of lysinoalanine in preserved egg.  

PubMed

To identify inhibitors for lysinoalanine formation in preserved egg, sulfhydryl compounds (glutathione, L-cysteine), carbohydrates (sucrose, D-glucose, maltose), organic acids (L-ascorbic acid, citric acid, DL-malic acid, lactic acid), and sodium sulfite were individually added at different concentrations to a pickling solution to prepare preserved eggs. Lysinoalanine formation as an index of these 10 substances was determined. Results indicate that glutathione, D-glucose, maltose, L-ascorbic acid, citric acid, lactic acid, and sodium sulfite all effectively diminished lysinoalanine formation in preserved egg albumen and yolk. When 40 and 80 mmol/L of sodium sulfite, citric acid, L-ascorbic acid, and D-glucose were individually added into the pickling solution, the inhibition rates of lysinoalanine in the produced preserved egg albumen and yolk were higher. However, the attempt of minimizing lysinoalanine formation was combined with the premise of ensuring preserved eggs quality. Moreover, the addition of 40 and 80 mmol/L of sodium sulfite, 40 and 80 mmol/L of D-glucose, 40 mmol/L of citric acid, and 40 mmol/L of L-ascorbic acid was optimal to produce preserved eggs. The corresponding inhibition rates of lysinoalanine in the albumen were approximately 76.3% to 76.5%, 67.6% to 67.8%, 74.6%, and 74.6%, and the corresponding inhibition rates of lysinoalanine in the yolk were about 68.7% to 69.7%, 50.6% to 51.8%, 70.4%, and 57.8%. It was concluded that sodium sulfite, D-glucose, L-ascorbic, and citric acid at suitable concentrations can be used to control the formation of lysinoalanine during preserved egg processing. PMID:25047093

Luo, Xu-Ying; Tu, Yong-Gang; Zhao, Yan; Li, Jian-Ke; Wang, Jun-Jie

2014-08-01

95

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

96

Energy surface model and magnetization switching for exchange coupled magnetic particles  

Microsoft Academic Search

This paper describes the energy surface model for two exchange coupled magnetic particles and a study of the critical switching field in this coupled system. It is shown that for static switching, the total energy is continuously reduced during the reversal process. The critical switching fields versus applied field angle can be directly obtained from the energy surface model. The

Kai-Zhong Gao; Juan Fernandez-de-Castro

2006-01-01

97

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

PubMed Central

In leaves of Egeria densa Planchon, N-ethylmaleimide (NEM) and other sulfhydryl-binding reagents induce a temporary increase in nonmitochondrial respiration (?QO2) that is inhibited by diphenylene iodonium and quinacrine, two known inhibitors of the plasma membrane NADPH oxidase, and are associated with a relevant increase in electrolyte leakage (M. Bellando, S. Sacco, F. Albergoni, P. Rocco, M.T. Marré [1997] Bot Acta 110: 388–394). In this paper we report data indicating further analogies between the oxidative burst induced by sulfhydryl blockers in E. densa and that induced by pathogen-derived elicitors in animal and plant cells: (a) NEM- and Ag+-induced ?QO2 was associated with H2O2 production and both effects depended on the presence of external Ca2+; (b) Ca2+ influx was markedly increased by treatment with NEM; (c) the Ca2+ channel blocker LaCl3 inhibited ?QO2, electrolyte release, and membrane depolarization induced by the sulfhydryl reagents; and (d) LaCl3 also inhibited electrolyte leakage induced by the direct infiltration of the leaves with H2O2. These results suggest a model in which the interaction of sulfhydryl blockers with sulfhydryl groups of cell components would primarily induce an increase in the Ca2+ cytosolic concentration, followed by membrane depolarization and activation of a plasma membrane NADPH oxidase. This latter effect, producing active oxygen species, might further influence plasma membrane permeability, leading to the massive release of electrolytes from the tissue. PMID:9847112

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

1998-01-01

98

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

99

Temporal switching jitter in photoconductive switches  

SciTech Connect

This paper reports on a recent comparison made between the Air Force Research Laboratory (AFRL) gallium arsenide, optically-triggered switch test configuration and the Sandia National Laboratories (SNL) gallium arsenide, optically-triggered switch test configuration. The purpose of these measurements was to compare the temporal switch jitter times. It is found that the optical trigger laser characteristics are dominant in determining the PCSS jitter.

GAUDET,JOHN A.; SKIPPER,MICHAEL C.; ABDALLA,MICHAEL D.; AHERN,SEAN M.; MAR,ALAN; LOUBRIEL,GUILLERMO M.; ZUTAVERN,FRED J.; O'MALLEY,MARTIN W.; HELGESON,WESLEY D.; ROMERO,SAMUEL P.

2000-04-13

100

Latching micro optical switch  

DOEpatents

An optical switch reliably maintains its on or off state even when subjected to environments where the switch is bumped or otherwise moved. In addition, the optical switch maintains its on or off state indefinitely without requiring external power. External power is used only to transition the switch from one state to the other. The optical switch is configured with a fixed optical fiber and a movable optical fiber. The movable optical fiber is guided by various actuators in conjunction with a latching mechanism that configure the switch in one position that corresponds to the on state and in another position that corresponds to the off state.

Garcia, Ernest J; Polosky, Marc A

2013-05-21

101

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

102

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

103

Latching relay switch assembly  

SciTech Connect

A latching relay switch assembly is described 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. 9 figures.

Duimstra, F.A.

1991-03-05

104

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

105

Heat switches for ADRs  

NASA Astrophysics Data System (ADS)

Heat switches are key elements in the cyclic operation of Adiabatic Demagnetization Refrigerators (ADRs). Several of the types of heat switches that have been used for ADRs are described in this paper. Key elements in selection and design of these switches include not only ON/OFF switching ratio, but also method of actuation, size, weight, and structural soundness. Some of the trade-off are detailed in this paper.

DiPirro, M. J.; Shirron, P. J.

2014-07-01

106

Optically Controlled 22 Switching Cell for Packet-Switched Networks  

E-print Network

Optically Controlled 2Ã?2 Switching Cell for Packet-Switched Networks C. C. Lee1 , L. F. K. Lui1 a 10 Gb/s optically controlled 2Ã?2 switching cell which can be used to construct NÃ?N all-optical switches for all-optical packet-switched networks. All-optical packet-switching is performed based

Wai, Ping-kong Alexander

107

Apollo Ring Optical Switch  

SciTech Connect

An optical switch was designed, built, and installed at Sandia National Laboratories in Albuquerque, New Mexico, to facilitate the integration of two Apollo computer networks into a single network. This report presents an overview of the optical switch as well as its layout, switch testing procedure and test data, and installation.

Maestas, J.H.

1987-03-01

108

Reproducible resistance switching in polycrystalline NiO films  

NASA Astrophysics Data System (ADS)

Negative resistance behavior and reproducible resistance switching were found in polycrystalline NiO films deposited by dc magnetron reactive sputtering methods. Oxygen to argon gas ratio during deposition was critical in deciding the detailed switching characteristics of either bi-stable memory switching or mono-stable threshold switching. Both metallic nickel defects and nickel vacancies influenced the negative resistance and the switching characteristics. We obtained a distribution of low resistance values which were dependent on the compliance current of high-to-low resistance switching. At 200°C, the low-resistance state kept its initial resistance value while the high-resistance state reached 85% of its initial resistance value after 5×105s. We suggested that the negative resistance and the switching mechanism could be described by electron conduction related to metallic nickel defect states existing in deep levels and by small-polaron hole hopping conduction.

Seo, S.; Lee, M. J.; Seo, D. H.; Jeoung, E. J.; Suh, D.-S.; Joung, Y. S.; Yoo, I. K.; Hwang, I. R.; Kim, S. H.; Byun, I. S.; Kim, J.-S.; Choi, J. S.; Park, B. H.

2004-12-01

109

Polarization switching kinetics in ultrathin ferroelectric barium titanate film  

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

110

Modeling a Snap-Action, Variable-Delay Switch  

E-print Network

Modeling a Snap-Action, Variable-Delay Switch Controlling Extrinsic Cell Death John G. Albeck1 the cell. Thus, extrinsic apoptosis is controlled by an unusual variable-delay, snap- action switch assembly are all critical for snap-action control. Citation: Albeck JG, Burke JM, Spencer SL, Lauffenburger

111

Critical pulse power components  

SciTech Connect

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

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

1981-01-01

112

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

113

Solid state switch  

DOEpatents

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

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

1994-01-01

114

Thermally actuated thermionic switch  

DOEpatents

A thermally actuated thermionic switch which responds to an increase of temperature by changing from a high impedance to a low impedance at a predictable temperature set point. The switch has a bistable operation mode switching only on temperature increases. The thermionic material may be a metal which is liquid at the desired operation temperature and held in matrix in a graphite block reservoir, and which changes state (ionizes, for example) so as to be electrically conductive at a desired temperature.

Barrus, D.M.; Shires, C.D.

1982-09-30

115

Thermally actuated thermionic switch  

DOEpatents

A thermally actuated thermionic switch which responds to an increase of temperature by changing from a high impedance to a low impedance at a predictable temperature set point. The switch has a bistable operation mode switching only on temperature increases. The thermionic material may be a metal which is liquid at the desired operation temperature and held in matrix in a graphite block reservoir, and which changes state (ionizes, for example) so as to be electrically conductive at a desired temperature.

Barrus, Donald M. (San Jose, CA); Shires, Charles D. (San Jose, CA)

1988-01-01

116

Alarm toe switch  

DOEpatents

An alarm toe switch inserted within a shoe for energizing an alarm circuit n 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. The reed switch is hermetically sealed with the magnet acting through the wall so the switch assembly S is capable of reliable operation even in wet and corrosive environments.

Ganyard, Floyd P. (Albuquerque, NM)

1982-01-01

117

Reflective HTS switch  

DOEpatents

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

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

1994-09-27

118

Reflective HTS switch  

SciTech Connect

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

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

1994-01-01

119

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

Michael Horton

2009-05-30

120

Erected mirror optical switch  

DOEpatents

A microelectromechanical (MEM) optical switching apparatus is disclosed that is based on an erectable mirror which is formed on a rotatable stage using surface micromachining. An electrostatic actuator is also formed on the substrate to rotate the stage and mirror with a high angular precision. The mirror can be erected manually after fabrication of the device and used to redirect an incident light beam at an arbitrary angel and to maintain this state in the absence of any applied electrical power. A 1.times.N optical switch can be formed using a single rotatable mirror. In some embodiments of the present invention, a plurality of rotatable mirrors can be configured so that the stages and mirrors rotate in unison when driven by a single micromotor thereby forming a 2.times.2 optical switch which can be used to switch a pair of incident light beams, or as a building block to form a higher-order optical switch.

Allen, James J.

2005-06-07

121

Optical Circuit Switched Protocol  

NASA Technical Reports Server (NTRS)

The present invention is a system and method embodied in an optical circuit switched protocol for the transmission of data through a network. The optical circuit switched protocol is an all-optical circuit switched network and includes novel optical switching nodes for transmitting optical data packets within a network. Each optical switching node comprises a detector for receiving the header, header detection logic for translating the header into routing information and eliminating the header, and a controller for receiving the routing information and configuring an all optical path within the node. The all optical path located within the node is solely an optical path without having electronic storage of the data and without having optical delay of the data. Since electronic storage of the header is not necessary and the initial header is eliminated by the first detector of the first switching node. multiple identical headers are sent throughout the network so that subsequent switching nodes can receive and read the header for setting up an optical data path.

Monacos, Steve P. (Inventor)

2000-01-01

122

Solid state switch  

DOEpatents

A solid state switch, with reverse conducting thyristors, is designed to operate at 20 kV hold-off voltage, 1,500 A peak, 1.0 [mu]s pulsewidth, and 4,500 pps, to replace thyratrons. The solid state switch is more reliable, more economical, and more easily repaired. The switch includes a stack of circuit card assemblies, a magnetic assist and a trigger chassis. Each circuit card assembly contains a reverse conducting thyristor, a resistor capacitor network, and triggering circuitry. 6 figs.

Merritt, B.T.; Dreifuerst, G.R.

1994-07-19

123

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. M.

124

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

125

[Analysis of Pb(II), Cd(II) and Cu(II) in Chinese medicine by the system of porphyrin complexes and sulfhydryl cotton fiber].  

PubMed

The reaction of alpha beta gamma delta-tetra(p-sulfophenyl)porphyrin (TPPS4) with Pb(II), Cd(II) or Cu(II) has been studied in this article, and the spectra of the Pb(II)-TPPS4, Cd(II)-TPPS4 and Cu(II)-TPPS4 show the spectral absorption of these complexes with high sensitivity. The molar absorptivities of Pb(II)-TPPS4, Cd(II)-TPPS4 and Cu(II)-TPPS4 are 2.5 x 10(5) L x mol(-1) x cm(-1), 5.2 x 10(5) L x mol(-1) x cm(-1) and 4.2 x 10(5) L x mol(-1) x cm(-1), respectively. With the sulfhydryl cotton fiber separation-enrichment method, this analytical system of porphyrin complexes has been successfully applied to determining the trace amounts of Pb(II), Cd(II) and Cu(II) in Ginkgo bilobal leaves and tea leaves. The RSD of determining 10(-6)-10(-7) g x g(-1) Pb(II), Cd(II) or Cu(II) in samples lies between 3.3%-9.6%, and the recovery of added standard lies between 90%-103%. The proposed analytical method has the advantage of high sensitivity, simplicity and high efficiency of interfere-resisting. PMID:15769016

Li, Fang; Zheng, Huai-li

2004-02-01

126

Significance of sulfhydryl compounds in the manifestation of fluoroacetate toxicity to the rat, brush-tailed possum, woylie and western grey kangaroo.  

PubMed

Levels of citrate in kidneys and livers of rats with normal glutathione levels increased 6.8 and 1.7-fold respectively 2 h after dosing with 1.5 mg of compound 1080 (= 95% sodium fluoroacetate) per kilogram body weight. In animals with liver glutathione levels 15% of normal, increases in plasma and liver citrate levels after dosing with fluoroacetate were significantly greater than those of control animals. Cysteamine and N-acetylcysteine, like glutathione, partially protected aconitate hydratase from fluorocitrate inhibition in rat liver preparations but were unable to replace glutathione as a substrate for the defluorination of fluoroacetate in vitro. N-Acetylcysteine did not diminish plasma citrate levels of glutathione-deficient rats dosed with fluoroacetate, while cysteamine inhibited the rate of in vivo defluorination in glutathione-deficient brush-tailed possums. It is suggested that non-physiological sulfhydryl compounds are ineffective antidotes to fluoroacetate intoxication in vivo. The in vivo defluorination patterns of four mammal species with differing sensitivities to fluoroacetate did not indicate a direct relationship between tolerance and rate of defluorination and it is also suggested that a high level of activity of the glutathione-S-transferase responsible for the defluorination of fluoroacetate is not the major mechanism for circumventing fluoroacetate toxicity in resistant mammals. PMID:4051904

Mead, R J; Moulden, D L; Twigg, L E

1985-01-01

127

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

128

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

129

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

130

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.

131

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

132

Cygnus PFL 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 rads at 1 m, 50-ns full-widthhalf-maximum. 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 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, threecell inductive voltage adder, and rod-pinch diode. A primary source of fluctuation in Cygnus shot-to-shot performance may be 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 source X-ray spectrum and dose. Therefore, PFL switch jitter may contribute to shot-to-shot variation in these parameters, which are crucial to radiographic quality. In this paper we will present PFL switch jitter analysis for both Cygnus machines and present the correlation with dose. 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 the PFL switch performance for one larger switch gap setting will be examined.

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

2007-07-21

133

Switching power supply filter  

NASA Technical Reports Server (NTRS)

A filter for a switching power supply. The filter includes a common mode inductor with coil configurations allowing differential mode current from a dc source to pass through but attenuating common mode noise from the power supply so that the noise does not reach the dc source. The invention also includes the use of feed through capacitors at the switching power supply input terminals to provide further high-frequency noise attenuation.

Kumar, Prithvi R. (Inventor); Abare, Wayne (Inventor)

1989-01-01

134

High Power Switching Transistor  

NASA Technical Reports Server (NTRS)

Improved switching transistors handle 400-A peak currents and up to 1,200 V. Using large diameter silicon wafers with twice effective area as D60T, form basis for D7 family of power switching transistors. Package includes npn wafer, emitter preform, and base-contact insert. Applications are: 25to 50-kilowatt high-frequency dc/dc inverters, VSCF converters, and motor controllers for electrical vehicles.

Hower, P. L.; Kao, Y. C.; Carnahan, D. C.

1983-01-01

135

A CMOS Switched Transconductor Mixer  

Microsoft Academic Search

A new CMOS active mixer topology can operate at low supply voltages by the use of switches exclusively connected to the supply voltages. Such switches require less voltage headroom and avoid gate-oxide reliability problems. Mixing is achieved by exploiting two transconductors with cross-coupled outputs, which are alternatingly activated by the switches. For ideal switching, the operation is equivalent to a

Eric A. M. Klumperink; Simon M. Louwsma; Gerard J. M. Wienk; Bram Nauta

2004-01-01

136

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

137

Stochastic switching of cantilever motion  

NASA Astrophysics Data System (ADS)

The cantilever is a prototype of a highly compliant mechanical system and has an instrumental role in nanotechnology, enabling surface microscopy, and ultrasensitive force and mass measurements. Here we report fluctuation-induced transitions between two stable states of a strongly driven microcantilever. Geometric nonlinearity gives rise to an amplitude-dependent resonance frequency and bifurcation occurs beyond a critical point. The cantilever response to a weak parametric modulation is amplified by white noise, resulting in an optimum signal-to-noise ratio at finite noise intensity. This stochastic switching suggests new detection schemes for cantilever-based instrumentation, where the detection of weak signals is mediated by the fluctuating environment. For ultrafloppy, cantilevers with nanometer-scale dimensions operating at room temperature—a new transduction paradigm emerges that is based on probability distributions and mimics nature.

Venstra, Warner J.; Westra, Hidde J. R.; van der Zant, Herre S. J.

2013-10-01

138

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

139

Low inductance gas switching.  

SciTech Connect

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

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

2007-10-01

140

FLEXBAR: A crossbar switching fabric with improved performance and utilization  

Microsoft Academic Search

Crossbar based switching fabrics form a critical component of many modern high-performance electronic systems, including network routers and switches, multi-processor computing systems, and high-end application-specific integrated circuits (ASICs). This paper describes a simple, yet effective, hardware modification to enhance the performance and utilization of a generic crossbar. The proposed structure, called FLEXBAR, is based on the addition of lightweight, configurable,

J. Chang; S. Ravi; A. Raghunathan

2002-01-01

141

Switching power pulse system  

DOEpatents

A switching system for delivering pulses of power from a source to a load using a storage capacitor charged through a rectifier, and maintained charged to a reference voltage level by a transistor switch and voltage comparator. A thyristor is triggered to discharge the storage capacitor through a saturable reactor and fractional turn saturable transformer having a secondary to primary turn ratio N of n:l/n = n[sup 2]. The saturable reactor functions as a soaker'' while the thyristor reaches saturation, and then switches to a low impedance state. The saturable transformer functions as a switching transformer with high impedance while a load coupling capacitor charges, and then switches to a low impedance state to dump the charge of the storage capacitor into the load through the coupling capacitor. The transformer is comprised of a multilayer core having two secondary windings tightly wound and connected in parallel to add their output voltage and reduce output inductance, and a number of single turn windings connected in parallel at nodes for the primary winding, each single turn winding linking a different one of the layers of the multilayer core. The load may be comprised of a resistive beampipe for a linear particle accelerator and capacitance of a pulse forming network. To hold off discharge of the capacitance until it is fully charged, a saturable core is provided around the resistive beampipe to isolate the beampipe from the capacitance until it is fully charged. 5 figs.

Aaland, K.

1983-08-09

142

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

143

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

144

Switching power supply  

DOEpatents

The invention is a repratable capacitor charging, switching power supply. A ferrite transformer steps up a dc input. The transformer primary is in a full bridge configuration utilizing power MOSFETs as the bridge switches. The transformer secondary is fed into a high voltage, full wave rectifier whose output is connected directly to the energy storage capacitor. The transformer is designed to provide adequate leakage inductance to limit capacitor current. The MOSFETs are switched to the variable frequency from 20 to 50 kHz to charge a capacitor from 0.6 kV. The peak current in a transformer primary and secondary is controlled by increasing the pulse width as the capacitor charges. A digital ripple counter counts pulses and after a preselected desired number is reached an up-counter is clocked.

Mihalka, A.M.

1984-06-05

145

SWITCH user's manual  

NASA Technical Reports Server (NTRS)

The planning program, SWITCH, and its surrounding changed-goal-replanning program, Runaround, are described. The evolution of SWITCH and Runaround from an earlier planner, DEVISER, is recounted. SWITCH's plan representation, and its process of building a plan by backward chaining with strict chronological backtracking, are described. A guide for writing knowledge base files is provided, as are narrative guides for installing the program, running it, and interacting with it while it is running. Some utility functions are documented. For the sake of completeness, a narrative guide to the experimental discrepancy-replanning feature is provided. Appendices contain knowledge base files for a blocksworld domain, and a DRIBBLE file illustrating the output from, and user interaction with, the program in that domain.

1987-01-01

146

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

147

Polariton Condensate Transistor Switch  

E-print Network

A polariton condensate transistor switch is realized through optical excitation of a microcavity ridge with two beams. The ballistically ejected polaritons from a condensate formed at the source are gated using the 20 times weaker second beam to switch on and off the flux of polaritons. In the absence of the gate beam the small built-in detuning creates potential landscape in which ejected polaritons are channelled toward the end of the ridge where they condense. The low loss photon-like propagation combined with strong nonlinearities associated with their excitonic component makes polariton based transistors particularly attractive for the implementation of all-optical integrated circuits.

Gao, T; Liew, T C H; Tsintzos, S I; Stavrinidis, G; Deligeorgis, G; Hatzopoulos, Z; Savvidis, P G

2012-01-01

148

Thermionic gas switch  

DOEpatents

A temperature responsive thermionic gas switch having folded electron emitting surfaces. An ionizable gas is located between the emitter and an interior surface of a collector, coaxial with the emitter. In response to the temperature exceeding a predetermined level, sufficient electrons are derived from the emitter to cause the gas in the gap between the emitter and collector to become ionized, whereby a very large increase in current in the gap occurs. Due to the folded emitter surface area of the switch, increasing the "on/off" current ratio and adjusting the "on" current capacity is accomplished.

Hatch, George L. (San Francisco, CA); Brummond, William A. (Livermore, CA); Barrus, Donald M. (San Jose, CA)

1986-01-01

149

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

150

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

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

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

151

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

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

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

152

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

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

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

153

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

154

Switch Design to Enable Predictive Multiplexed Switching in Multiprocessor Networks  

Microsoft Academic Search

Predictive multiplexed switching is a new approach for building interconnection switches for high perfor- mance parallel systems. This approach advocates sacrific- ing some link bandwidth in return for more efficient network control and simpler connection management. The main idea is to depart from the traditional packet and worm- hole switching in favor of row data communication over established communication pipes

Zhu Ding; Raymond R. Hoare; Alex K. Jones; Dan Li; Shou-kuo Shao; Shen-chien Tung; Jiang Zheng; Rami G. Melhem

2005-01-01

155

Dynamic switch matrix for the TDMA satellite switching system  

Microsoft Academic Search

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

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

1982-01-01

156

Formulations for switching transformation matrices of large switched networks  

Microsoft Academic Search

The author describes formulations of switching transformation matrices (STMs) which express the discontinuities of the state variables at the switching instances in active switched networks. The formulations are derived by using the initial-value-theorem of the Laplace transformation. Charge and flux conservations are not used. It is clear that the discontinuities are related to the first component of special resolution, which

Mamoru Tanaka

1988-01-01

157

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

158

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

159

Switching surface wettability properties  

Microsoft Academic Search

In this work, recent developments regarding design and preparation of surfaces to modify their wettability behavior by switching between the superhydrophobic and the superhydrophilic state under physical and chemical stimuli are summarized. The complex systems and the strategies developed in nature are investigated as a fundamental support considering the potential applications of these two ‘superstates’ in basic research and in

Michele Ferrari

2012-01-01

160

RNA switch at enhancers.  

PubMed

Polycomb/Trithorax response elements (PRE/TREs) are genetic elements that can stably silence or activate genes. A new study describes how long noncoding RNAs (lncRNAs) transcribed from opposite strands of the Drosophila melanogaster vestigial PRE/TRE throw the switch between these two opposing epigenetic states. PMID:25162802

Quinn, Jeffrey J; Chang, Howard Y

2014-09-01

161

Automatic thermal switch. [spacecraft applications  

NASA Technical Reports Server (NTRS)

An automatic thermal switch to control heat flow includes two thermally conductive plates and a thermally conductive switch saddle pivotally mounted to the first plate. A flexible heat carrier is connected between the switch saddle and the second plate. A phase-change power unit, including a piston coupled to the switch saddle, is in thermal contact with the first thermally conductive plate. A biasing element biases the switch saddle in a predetermined position with respect to the first plate. When the phase-change power unit is actuated by an increase in heat transmitted through the first place, the piston extends and causes the switch saddle to pivot, thereby varying the thermal conduction between the two plates through the switch saddle and flexible heat carrier. The biasing element, switch saddle, and piston can be arranged to provide either a normally closed or normally opened thermally conductive path between the two plates.

Cunningham, J. W.; Wing, L. D. (inventors)

1983-01-01

162

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

163

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

164

Switching power pulse system  

DOEpatents

A switching system for delivering pulses of power from a source (10) to a load (20) using a storage capacitor (C3) charged through a rectifier (D1, D2), and maintained charged to a reference voltage level by a transistor switch (Q1) and voltage comparator (12). A thyristor (22) is triggered to discharge the storage capacitor through a saturable reactor (18) and fractional turn saturable transformer (16) having a secondary to primary turn ratio N of n:l/n=n.sup.2. The saturable reactor (18) functions as a "soaker" while the thyristor reaches saturation, and then switches to a low impedance state. The saturable transformer functions as a switching transformer with high impedance while a load coupling capacitor (C4) charges, and then switches to a low impedance state to dump the charge of the storage capacitor (C3) into the load through the coupling capacitor (C4). The transformer is comprised of a multilayer core (26) having two secondary windings (28, 30) tightly wound and connected in parallel to add their output voltage and reduce output inductance, and a number of single turn windings connected in parallel at nodes (32, 34) for the primary winding, each single turn winding linking a different one of the layers of the multilayer core. The load may be comprised of a resistive beampipe (40) for a linear particle accelerator and capacitance of a pulse forming network (42). To hold off discharge of the capacitance until it is fully charged, a saturable core (44) is provided around the resistive beampipe (40) to isolate the beampipe from the capacitance (42) until it is fully charged.

Aaland, Kristian (Livermore, CA)

1983-01-01

165

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.

166

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

167

Organic Materials For Optical Switching  

NASA Technical Reports Server (NTRS)

Equations predict properties of candidate materials. Report presents results of theoretical study of nonlinear optical properties of organic materials. Such materials used in optical switching devices for computers and telecommunications, replacing electronic switches. Optical switching potentially offers extremely high information throughout in compact hardware.

Cardelino, Beatriz H.

1993-01-01

168

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

169

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

170

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

171

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

172

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

173

Micromachined low-loss microwave switches  

Microsoft Academic Search

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

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

1999-01-01

174

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

175

Multiple pulse photoconductive semiconductor switching  

NASA Astrophysics Data System (ADS)

Photoconductive semiconductor switches (PCSS) with short carrier recombination lifetimes (1 to 100 ns) have exhibited comparable opening times in high power (57 kV, 1.0 kA) circuits. Such extremely fast recovery times are not available with the switches generally used for high power (greater than 10 kW) switching, e.g., spark gaps, thyratrons, and silicon controlled rectifiers. Furthermore, since these switches were made with relatively small pieces of semiconductor, and since PCSS scales linearly in two dimensions to higher voltages and currents, much higher power switches may be developed. New high power switches which have the ability to open and close in a 1 to 10 ns time scale provide the tools to switch high power radiofrequency (RF) circuits above 10 MHz actively. This paper presents three methods to create RF bursts with PCSS. The feasibility of each method is explored, and experiments being performed to test these techniques are described.

Zutavern, F. J.; McKenzie, B. B.; Loubriel, G. M.; Omalley, M. W.; Hamil, R. A.; Schanwald, L. P.

1988-05-01

176

Optical fiber switch  

DOEpatents

Optical fiber switches operated by electrical activation of at least one laser light modulator through which laser light is directed into at least one polarizer are used for the sequential transport of laser light from a single laser into a plurality of optical fibers. In one embodiment of the invention, laser light from a single excitation laser is sequentially transported to a plurality of optical fibers which in turn transport the laser light to separate individual remotely located laser fuel ignitors. The invention can be operated electro-optically with no need for any mechanical or moving parts, or, alternatively, can be operated electro-mechanically. The invention can be used to switch either pulsed or continuous wave laser light.

Early, James W. (Los Alamos, NM); Lester, Charles S. (San Juan Pueblo, NM)

2002-01-01

177

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.

178

Cryogenic switched MOSFET characterization  

NASA Technical Reports Server (NTRS)

Both p channel and n channel enhancement mode MOSFETs can be readily switched on and off at temperatures as low as 2.8 K so that switch sampled readout of a VLWIR Ge:Ga focal plane is electronically possible. Noise levels as low as 100 rms electrons per sample (independent of sample rate) can be achieved using existing p channel MOSFETs, at overall rates up to 30,000 samples/second per multiplexed channel (e.g., 32 detectors at a rate of almost 1,000 frames/second). Run of the mill devices, including very low power dissipation n channel FETs would still permit noise levels of the order of 500 electrons/sample.

1981-01-01

179

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

180

Automatic emergency hydraulic switch  

Microsoft Academic Search

tem automatically when large leaks appear in the system, or when the process piping ruptures suddenly, has been developed and tested at Penza Polytechnic Institute. This emergency hydraulic switch can be employed in various hydraulic systems serviug process machinery and equipment. It is designed to handle maximum flowrates at i00 liters\\/min, and to take pressures up to 200 kgf\\/cm 2.

B. T. Sitnikov; I. B. Matveev; V. N. Denisov

1972-01-01

181

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

182

Automatic switching matrix  

DOEpatents

An automatic switching matrix that includes an apertured matrix board containing a matrix of wires that can be interconnected at each aperture. Each aperture has associated therewith a conductive pin which, when fully inserted into the associated aperture, effects electrical connection between the wires within that particular aperture. Means is provided for automatically inserting the pins in a determined pattern and for removing all the pins to permit other interconnecting patterns.

Schlecht, Martin F. (Cambridge, MA); Kassakian, John G. (Newton, MA); Caloggero, Anthony J. (Lynn, MA); Rhodes, Bruce (Dorchester, MA); Otten, David (Newton, MA); Rasmussen, Neil (Sudbury, MA)

1982-01-01

183

CREE: Making the Switch  

ScienceCinema

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

2014-04-09

184

MCT/MOSFET Switch  

NASA Technical Reports Server (NTRS)

Metal-oxide/semiconductor-controlled thyristor (MCT) and metal-oxide/semiconductor field-effect transistor (MOSFET) connected in switching circuit to obtain better performance. Offers high utilization of silicon, low forward voltage drop during "on" period of operating cycle, fast turnon and turnoff, and large turnoff safe operating area. Includes ability to operate at high temperatures, high static blocking voltage, and ease of drive.

Rippel, Wally E.

1990-01-01

185

Structural Determinants for Naturally Evolving H5N1 Hemagglutinin to Switch Its Receptor Specificity  

E-print Network

Of the factors governing human-to-human transmission of the highly pathogenic avian-adapted H5N1 virus, the most critical is the acquisition of mutations on the viral hemagglutinin (HA) to “quantitatively switch” its binding ...

Tharakaraman, Kannan

186

Nonlinear internal-model control for switched reluctance drives  

Microsoft Academic Search

A nonlinear internal-model control (IMC) based on suitable commutation strategy for switched reluctance motors (SRMs) is proposed. In the commutation strategy, a fixed critical rotor position is defined as the commutation point, which results in reduced computation. Combined the simplicity of the feedback linearization control and the robustness of IMC structure, the proposed drive has excellent dynamic and static performances

Ge Baoming; Wang Xiangheng; Su Pengsheng; Jiang Jingping

2002-01-01

187

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 ...

188

Task switching and the measurement of "switch costs".  

PubMed

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

Wylie, G; Allport, A

2000-01-01

189

Low-Crosstalk Composite Optical Crosspoint Switches  

NASA Technical Reports Server (NTRS)

Composite optical switch includes two elementary optical switches in tandem, plus optical absorbers. Like elementary optical switches, composite optical switches assembled into switch matrix. Performance enhanced by increasing number of elementary switches. Advantage of concept: crosstalk reduced to acceptably low level at moderate cost of doubling number of elementary switches rather than at greater cost of tightening manufacturing tolerances and exerting more-precise control over operating conditions.

Pan, Jing-Jong; Liang, Frank

1993-01-01

190

Analysis of reliable sub-ns spin-torque switching under transverse bias magnetic fields  

NASA Astrophysics Data System (ADS)

The switching process of a magnetic spin-valve nanosystem subject to spin-polarized current pulses is considered. The dependence of the switching probability on the current pulse duration is investigated. The further application of a transverse field along the intermediate anisotropy axis of the particle is used to control the quasi-random relaxation of magnetization to the reversed magnetization state. The critical current amplitudes to realize the switching are determined by studying the phase portrait of the Landau-Lifshtz-Slonczewski dynamics. Macrospin numerical simulations are in good agreement with the theoretical prediction and demonstrate reliable switching even for very short (below 100 ps) current pulses.

d'Aquino, M.; Perna, S.; Serpico, C.; Bertotti, G.; Mayergoyz, I. D.

2015-05-01

191

Microwave-assisted switching of a single perpendicular magnetic tunnel junction nanodot  

NASA Astrophysics Data System (ADS)

We used a magnetic tunnel junction (MTJ) to study the microwave-assisted switching (MAS) of a perpendicular magnetic nanodot. Because the sample structure enables the direct observation of fast magnetization dynamics through MTJ signals, the switching behavior is examined in relation with the induced magnetization excitation. By utilizing the MTJ signals, we observe several ferromagnetic resonance (FMR) modes and identify the lowest FMR mode as the cause of switching field reduction. The switching field decreases as the microwave frequency increases, and this frequency–magnetic field relationship coincides with that of the lowest FMR mode near a critical frequency. We also investigate the size dependence of MAS.

Suto, Hirofumi; Nagasawa, Tazumi; Kudo, Kiwamu; Mizushima, Koichi; Sato, Rie

2015-02-01

192

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

193

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

194

Dilated Networks for Photonic Switching  

Microsoft Academic Search

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

K. Padmanabhan; A. Netravali

1987-01-01

195

Switch-level VHDL descriptions  

Microsoft Academic Search

The authors show that switched-level models can be written in VHDL (VHSIC hardware descriptive language) without special-purpose knowledge in the VHDL simulator. As a result, such VHDL switch-level descriptions may be executed on any simulator supporting the VHDL. The authors present a VHDL switch-level value system, discuss resolution functions, modeling tools written in VHDL, and describe an algorithm coded in

A. G. Stanculescu; A. S. Tsay; A. N. D. Zamfirescu; D. L. Perry

1989-01-01

196

DNA-Controlled Excitonic Switches  

PubMed Central

Fluorescence resonance energy transfer (FRET) is a promising means of enabling information processing in nanoscale devices, but dynamic control over exciton pathways is required. Here, we demonstrate the operation of two complementary switches consisting of diffusive FRET transmission lines in which exciton flow is controlled by DNA. Repeatable switching is accomplished by the removal or addition of fluorophores through toehold-mediated strand invasion. In principle, these switches can be networked to implement any Boolean function. PMID:22401838

2012-01-01

197

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

198

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

199

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

200

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

201

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

202

Switching efficiency improvement in spin torque majority gates  

NASA Astrophysics Data System (ADS)

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.; Manipatruni, Sasikanth; Young, Ian A.

2014-05-01

203

Code-switching effects in bilingual word recognition  

PubMed Central

Two experiments tested language switching effects with bilingual participants in a priming paradigm with masked primes (duration of 50 ms in Experiment 1 and 100 ms in Experiment 2). Participants had to monitor target words for animal names, and ERPs were recorded to critical (non-animal) words in L1 and L2 primed by unrelated words from the same or the other language. Both experiments revealed language priming (switching) effects that depended on target language. For target words in L1, most of the language switch effect appeared in the N400 ERP component, with L2 primes generating a more negative going wave than L1 primes. For L2 target words, on the other hand, the effects of a language switch appeared mainly in an earlier ERP component (N250) peaking at approximately 250 ms post-target onset, and showing greater negativity following an L1 prime than an L2 prime. This is the first evidence for fast-acting language-switching effects occurring in the absence of overt task switching. PMID:18191445

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

2009-01-01

204

Neuromorphic Atomic Switch Networks  

PubMed Central

Efforts to emulate the formidable information processing capabilities of the brain through neuromorphic engineering have been bolstered by recent progress in the fabrication of nonlinear, nanoscale circuit elements that exhibit synapse-like operational characteristics. However, conventional fabrication techniques are unable to efficiently generate structures with the highly complex interconnectivity found in biological neuronal networks. Here we demonstrate the physical realization of a self-assembled neuromorphic device which implements basic concepts of systems neuroscience through a hardware-based platform comprised of over a billion interconnected atomic-switch inorganic synapses embedded in a complex network of silver nanowires. Observations of network activation and passive harmonic generation demonstrate a collective response to input stimulus in agreement with recent theoretical predictions. Further, emergent behaviors unique to the complex network of atomic switches and akin to brain function are observed, namely spatially distributed memory, recurrent dynamics and the activation of feedforward subnetworks. These devices display the functional characteristics required for implementing unconventional, biologically and neurally inspired computational methodologies in a synthetic experimental system. PMID:22880101

Martin-Olmos, Cristina; Shieh, Hsien Hang; Aono, Masakazu; Stieg, Adam Z.; Gimzewski, James K.

2012-01-01

205

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

206

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

207

EDITORIAL: Molecular switches at surfaces Molecular switches at surfaces  

NASA Astrophysics Data System (ADS)

In nature, molecules exploit interaction with their environment to realize complex functionalities on the nanometer length scale. Physical, chemical and/or biological specificity is frequently achieved by the switching of molecules between microscopically different states. Paradigmatic examples are the energy production in proton pumps of bacteria or the signal conversion in human vision, which rely on switching molecules between different configurations or conformations by external stimuli. The remarkable reproducibility and unparalleled fatigue resistance of these natural processes makes it highly desirable to emulate nature and develop artificial systems with molecular functionalities. A promising avenue towards this goal is to anchor the molecular switches at surfaces, offering new pathways to control their functional properties, to apply electrical contacts, or to integrate switches into larger systems. Anchoring at surfaces allows one to access the full range from individual molecular switches to self-assembled monolayers of well-defined geometry and to customize the coupling between molecules and substrate or between adsorbed molecules. Progress in this field requires both synthesis and preparation of appropriate molecular systems and control over suitable external stimuli, such as light, heat, or electrical currents. To optimize switching and generate function, it is essential to unravel the geometric structure, the electronic properties and the dynamic interactions of the molecular switches on surfaces. This special section, Molecular Switches at Surfaces, collects 17 contributions describing different aspects of this research field. They analyze elementary processes, both in single molecules and in ensembles of molecules, which involve molecular switching and concomitant changes of optical, electronic, or magnetic properties. Two topical reviews summarize the current status, including both challenges and achievements in the field of molecular switches on metal surfaces, focusing on electronic and vibrational spectroscopy in one case and scanning tunneling microscopy studies in the other. Original research articles describe results in many aspects of the field, including: Self-assembly, self-organization, and controlled growth of molecular layers on various substrates. Highly-ordered arrays provide model systems with extraordinary structural properties, allowing one to adjust interactions between molecules and between molecule and substrate, and can be robustly prepared from solution, an essential prerequisite for applications. Conformational or electronic switching of molecules adsorbed at metal and semiconductor surfaces. These studies highlight the elementary processes governing molecular switching at surfaces as well as the wide range of possible stimuli. Carbon-based substrates such as graphene or carbon nanotubes. These substrates are attractive due to their effective two-dimensionality which implies that switching of adsorbed molecules can effect a significant back-action on the substrate. Mechanisms of conformational switching. Several contributions study the role of electron-vibron coupling and heating in current-induced conformational switching. We hope that the collection of articles presented here will stimulate and encourage researchers in surface physics and interfacial chemistry to contribute to the still emerging field of molecular switches at surfaces. We wish to acknowledge the support and input from many colleagues in preparing this special section. A significant part of this work has been conducted in the framework of the Sonderforschungsbereich 658 Elementary Processes in Molecular Switches at Surfaces of the Deutsche Forschungsgemeinschaft, to which we are grateful for financial support. Molecular surfaces at switches contents Molecular switches at surfacesMartin Weinelt and Felix von Oppen Optically and thermally induced molecular switching processes at metal surfacesPetra Tegeder Effects of electron-vibration coupling in transport through single moleculesKatharina J Franke and Jose Ignaci

Weinelt, Martin; von Oppen, Felix

2012-10-01

208

Switched Broadband Services For The Home  

NASA Astrophysics Data System (ADS)

In considering the deployment of fiber optics to the residence, two critical questions arise: what are the leading services that could be offered to justify the required investment; and what is the nature of the business that would offer these services to the consumer ? This talk will address these two questions together with the related issue of how the "financial engine" of today's television distribution infrastructure - TV advertising - would be affected by an open access system based on fiber optics coupled with broadband switching. On the business side, the talk concludes that the potential for open ended capacity expansion, fair competition between service providers, and new interactive services inherent in an open access, switched broadband system are the critical items in differentiating it from existing video and TV distribution systems. On the question of broadband services, the talk will highlight several new opportunities together with some findings from recent market research conducted by BNR. The talk will show that there are variations on existing services plus many new services that could be offered and which have real consumer appeal. The postulated open access system discussed here is visualized as having ultimately 1,000 to 2,000 video channels available to the consumer. Although this may appear to hopelessly fragment the TV audience and destroy the current TV advertising infrastructure, the technology of open access, switched broadband will present many new advertising techniques, which have the potential to be far more effective than those available today. Some of these techniques will be described in this talk.

Sawyer, Don M.

1990-01-01

209

Study of optoelectronic switch for satellite-switched time-division multiple access  

NASA Technical Reports Server (NTRS)

The use of optoelectronic switching for satellite switched time division multiple access will improve the isolation and reduce the crosstalk of an IF switch matrix. The results are presented of a study on optoelectronic switching. Tasks include literature search, system requirements study, candidate switching architecture analysis, and switch model optimization. The results show that the power divided and crossbar switching architectures are good candidates for an IF switch matrix.

Su, Shing-Fong; Jou, Liz; Lenart, Joe

1987-01-01

210

Criticality Model  

SciTech Connect

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

A. Alsaed

2004-09-14

211

Reversible thermal switching of aqueous dispersibility of multiwalled carbon nanotubes.  

PubMed

Easily reversible aqueous dispersion/precipitation of multiwalled carbon nanotubes (MWNTs) has been demonstrated using small-molecule non-ionic pyrene-based surfactants, which exhibit lower critical solution temperature (LCST) phase behaviour. The MWNTs are dispersed by means of non-covalent interactions. The dispersibility can be switched "off" (i.e., MWNTs precipitated) upon heating and switched "on" (i.e., MWNTs re-dispersed) upon cooling and merely swirling the sample at room temperature, that is, under very mild conditions. This effect is also observed under high ionic strength conditions with NaCl in the aqueous phase. PMID:25639258

O'Driscoll, Luke J; Welsh, Daniel J; Bailey, Steven W D; Visontai, David; Frampton, Harry; Bryce, Martin R; Lambert, Colin J

2015-03-01

212

Defect-mediated polarization switching in ferroelectrics and related materials: from mesoscopic mechanisms to atomistic control  

SciTech Connect

The plethora of lattice and electronic behaviors in ferroelectric and multiferroic materials and heterostructures opens vistas into novel physical phenomena including magnetoelectric coupling and ferroelectric tunneling. The development of new classes of electronic, energy-storage, and information-technology devices depends critically on understanding and controlling field-induced polarization switching. Polarization reversal is controlled by defects that determine activation energy, critical switching bias, and the selection between thermodynamically equivalent polarization states in multiaxial ferroelectrics. Understanding and controlling defect functionality in ferroelectric materials is as critical to the future of oxide electronics and solid-state electrochemistry as defects in semiconductors are for semiconductor electronics. Here, recent advances in understanding the defect-mediated switching mechanisms, enabled by recent advances in electron and scanning probe microscopy, are discussed. The synergy between local probes and structural methods offers a pathway to decipher deterministic polarization switching mechanisms on the level of a single atomically defined defect.

Kalinin, Sergei V [ORNL; Rodriguez, Brian J [ORNL; Baddorf, Arthur P [ORNL; Balke, Nina [ORNL; Borisevich, Albina Y [ORNL; Chang, Hye Jung [ORNL; Chen, Long-Qing [Pennsylvania State University; Jesse, Stephen [ORNL; Maksymovych, Petro [ORNL; Nikiforov, Maxim [ORNL; Pennycook, Stephen J [ORNL

2010-01-01

213

Switching Matrix For Optical Signals  

NASA Technical Reports Server (NTRS)

Proposed matrix of electronically controlled shutters switches signals in optical fibers between multiple input and output channels. Size, weight, and power consumption reduced. Device serves as building block for small, low-power, broad-band television- and data-signal-switching systems providing high isolation between nominally disconnected channels.

Grove, Charles H.

1990-01-01

214

IP switching and gigabit routers  

Microsoft Academic Search

To cope with the growth in the Internet and corporate IP networks, we require IP routers capable of much higher performance than is possible with existing architectures. This article examines two approaches to the design of a high-performance router, the gigabit router and the IP switch, and then provides some detail on the implementation of an IP switch and the

P. Newman; G. Minshall; T. Lyon; L. Huston

1997-01-01

215

Battery switch for downhole tools  

SciTech Connect

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

Boling, Brian E. (Sugar Land, TX)

2010-02-23

216

Dual switched mode power converter  

Microsoft Academic Search

A dual power converter is introduced which addresses the problem of output ripple and switching losses in a switched power converter. One stage of the power converter is a conventional PWM (pulse-width modulated) converter, and the other stage is a linear source. The linear source controls the voltage directly, and the output current of the linear stage is used to

PALLAB MIDYA; FRED H. SCHLERETH

1989-01-01

217

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

218

''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

219

"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

220

High voltage coaxial switch  

DOEpatents

A coaxial high voltage, high current switch having a solid cylindrical cold cathode coaxially surrounded by a thin hollow cylindrical inner electrode and a larger hollow cylindrical outer electrode. A high voltage trigger between the cathode and the inner electrode causes electrons to be emitted from the cathode and flow to the inner electrode preferably through a vacuum. Some of the electrons penetrate the inner electrode and cause a volumetric discharge in the gas (which may be merely air) between the inner and outer electrodes. The discharge provides a low impedance path between a high voltage charge placed on the outer electrode and a load (which may be a high power laser) coupled to the inner electrode. For high repetition rate the gas between the inner and outer electrodes may be continuously exchanged or refreshed under pressure.

Rink, John P. (Los Alamos, NM)

1983-07-19

221

High voltage coaxial switch  

DOEpatents

A coaxial high voltage, high current switch having a solid cylindrical cold cathode coaxially surrounded by a thin hollow cylindrical inner electrode and a larger hollow cylindrical outer electrode. A high voltage trigger between the cathode and the inner electrode causes electrons to be emitted from the cathode and flow to the inner electrode preferably through a vacuum. Some of the electrons penetrate the inner electrode and cause a volumetric discharge in the gas (which may be merely air) between the inner and outer electrodes. The discharge provides a low impedance path between a high voltage charge placed on the outer electrode and a load (which may be a high power laser) coupled to the inner electrode. For high repetition rate the gas between the inner and outer electrodes may be continuously exchanged or refreshed under pressure. 3 figs.

Rink, J.P.

1983-07-19

222

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

223

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

224

CRITICAL CONSUMPTION  

Microsoft Academic Search

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

Luke S. Yates

2011-01-01

225

High-level synthesis of switched-capacitor, switched-current and continuous-time ?? modulators using SIMULINK-based time-domain behavioral models  

Microsoft Academic Search

This paper presents a high-level synthesis tool for ?? modulators (??Ms) that combines an accurate SIMULINK-based time-domain behavioral simulator with a statistical optimization core. Three different circuit techniques for the modulator implementation are considered: switched-capacitor, switched-current and continuous-time. The behavioral models of these circuits, that take into account the most critical limiting factors, have been incorporated into the SIMULINK environment

Jesús Ruiz-Amaya; José M. de la Rosa; Francisco V. Fernández; Fernando Medeiro; Rocío del Río; Belén Pérez-Verdú; Angel Rodríguez-Vázquez

2005-01-01

226

Investigation of fullerenes for high speed low latency, photonic switching  

SciTech Connect

The components in high-speed, all-optical photonic systems must satisfy two essential requirements: (1) high switching speeds in the range of Tbit/s, and (2) low latency, where the latency is the amount of time that the optical signal remains in the device. An important problem precluding the practical implementation of high-speed, all- optical switching is the lack of a material with appropriate nonlinear optical properties needed to effect the switching. Numerous material systems have been studied in the past, but none have met all the necessary requirements. Development of such a material and its incorporation into photonic devices would advance the field tremendously. This Lab-wide LDRD project resolved this critical problem.

Lee, H. W. H; Shelton, R.N. [California Univ., Davis, CA (United States)

1997-02-13

227

Foil fuses as opening switches for slow discharge circuits  

SciTech Connect

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

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

1985-01-01

228

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

229

Analysis and design considerations of zero-voltage and zero-current-switching (ZVZCS) full-bridge PWM converters  

Microsoft Academic Search

In this paper, a detailed analysis of the zero-voltage and zero-current-switching (ZVZCS) full-bridge PWM converters is performed. The differences of the zero-voltage-switching (ZVS) operation between the conventional ZVS full-bridge PWM converters and the ZVZCS full-bridge PWM converters are analyzed in depth. Circuit parameters that affect the soft-switching conditions are examined and the critical parameters are identified. Based on the analysis,

Hang-Seok Choi; J. H. Lee; B. H. Cho; J. W. Kim

2002-01-01

230

Multiple pulse photoconductive semiconductor switching  

SciTech Connect

Photoconductive semiconductor switches (PCSS) with short carrier recombination lifetimes (1-100ns) have exhibited comparable opening times in high power (57 kV, 1.0 kA) circuits. Such extremely fast recovery times are not available with the switches generally used for high power (>10kW) switching, e.g., spark gaps, thyratrons, and silicon controlled rectifiers. Furthermore, since these switches were made with relatively small pieces of semiconductor (2.54 cm dia. by 625 ..mu..m thick), and since PCSS scales linearly in two dimensions to higher voltages and currents, much higher power switches may be developed. New high power switches which have the ability to open and close in a 1-10 ns time scale provide the tools to switch high power radiofrequency (RF) circuits above 10 MHz actively. This paper presents three methods to create RF bursts with PCSS. The feasibility of each method is explored, and experiments being performed to test these techniques are described. 9 refs., 11 figs.

Zutavern, F.J.; McKenzie, B.B.; Loubriel, G.M.; O'Malley, M.W.; Hamil, R.A.; Schanwald, L.P.

1988-01-01

231

Ultrafast optical switch evaluation facility  

NASA Astrophysics Data System (ADS)

The current major limiting factor in digital optical computing is the absence of a fast, efficient, cascadable optical switch. Material and processing approaches to optical switch construction are not limited to the well known semiconductors and fabrication methods of electronics. A facility to evaluate candidate devices has been constructed. Multiline and tunable femtosecond and picosecond laser systems, as well as frequency mixing systems, are used as light sources. The facility has at least picosecond source capability from 200 nm to 2 micrometers . The switch transfer function is evaluated in a pump-probe system with femtosecond and picosecond autocorrelators to measure temporal properties, an optical multichannel analyzer to measure spectral properties, a CCD or pyroelectric camera system to measure mode modification, and a multi-detector system to measure switching energy and insertion loss both in absorption and in reflection. The switch or switching array under test is mounted in a 6 axis micropositioner system with a 0 - 20 goniometer, x, y, and z translators, and a tilt goniometer. The system's design, as well as initial measurements of nonlinear interface optical switches based on photorefractive thin films are presented.

Osman, Joseph M.; Chaiken, Joseph; DeVaul, Brian

1993-01-01

232

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

233

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

234

Fiber-Optic Controlled PCSS Triggers for High Voltage Pulsed Power Switches  

Microsoft Academic Search

Triggers for high voltage (HV) switches have always been critical components for reliable, efficient pulsed power systems because they control the timing synchronization and amplitude variation of multiple pulse forming lines that combine to produce the total system output pulse. In pulsed power systems of the future, the role of trigger systems are even more critical as they trigger more

F. J. Zutavern; K. W. Reed; S. F. Glover; A. Mar; M. H. Ruebush; M. L. Horry; M. E. Swalby; J. A. Alexander; T. L. Smith

2005-01-01

235

Four switching categories of ferroelectrics  

NASA Astrophysics Data System (ADS)

We classify the switching kinetics of ferroelectrics including both epitaxial/polycrystalline thin films and single-crystalline/ceramic bulks at various applied fields into four categories, depending on whether the depolarization field and/or the polarization reversal induced by the switching promotion effect between adjacent parts can be neglected. We show that our statistical model developed very recently [X. J. Lou, J. Phys.: Condens. Matter 21, 012207 (2009)] in its generalized form applies to all these four categories. Finally, we make the comparison between our model and the conventional Kolmogorov-Avrami-Ishibashi model and discuss the behavior of the switching currents for different n.

Lou, X. J.

2009-05-01

236

Conduction switching of photochromic molecules.  

PubMed

We report a theoretical study of single molecule conduction switching of photochromic dithienylethene molecules. The light-induced intramolecular transformation drives a swapping of the highest occupied molecular orbital and lowest unoccupied molecular orbital between two distinct conjugated paths. The shuffling of single and double bonds produces a significant conductance change when the molecule is sandwiched between metal electrodes. We model the switching event using quantum molecular dynamics and the conductance changes using Green's function electronic transport theory. We find large on-off conductance ratios (between 10 and over 100) depending on the side group outside the switching core. PMID:15697867

Li, Jun; Speyer, Gil; Sankey, Otto F

2004-12-10

237

Characteristics of switching plasma in an inverse-pinch switch  

NASA Technical Reports Server (NTRS)

Characteristics of the plasma that switches on tens of giga volt-ampere in an inverse-pinch plasma switch (INPIStron) have been made. Through optical and spectroscopic diagnostics of the current carrying plasma, the current density, the motion of current paths, dominant ionic species have been determined in order to access their effects on circuit parameters and material erosion. Also the optimum operational condition of the plasma-puff triggering method required for azimuthally uniform conduction in the INPIStron has been determined.

Lee, Ja H.; Choi, Sang H.; Venable, Demetrius D.; Han, Kwang S.; Nam, Sang H.

1993-01-01

238

Switching performance of a cryogenic silicon photoconductive power switch  

Microsoft Academic Search

The silicon photoconductive power switch has the potential to replace gaseous discharge switches like thyratrons, krytrons, ignitrons, and spark gaps, that are commonly found in high-voltage and high-current pulse circuits. This offers the possibility of developing advanced laser and radar drive circuits that are all-solid state, and which enjoy the advantages of improved efficiency, compactness, and life expectancy. Silicon operating

R. A. Petr; W. C. Nunnally; C. V. Smith

1988-01-01

239

Switching performance of Nb3Sn persistent current switch  

Microsoft Academic Search

We designed a persistent current switch consisting of Nb3Sn superconducting wire for Superconducting Magneto-Hydro-Dynamic Propulsion Ship (MHDS). Nb3Sn has Tc higher than NbTi, which is commonly used for the conventional persistent current switch, and thus is expected to show a higher stability against the disturbance. We therefore performed numerical simulations for the heat transfer in a 10kA-class Nb3Sn persistent current

M. Tomita; K. Nemoto; K. Sugawara; M. Murakami

2000-01-01

240

Regenerative switching CMOS system  

DOEpatents

Complementary Metal Oxide Semiconductor (CMOS) Schottky barrier Field Effect Transistor systems, which are a seriesed combination of N and P-Channel MOSFETS, in which Source Schottky barrier junctions of the N and P-Channel Schottky barrier MOSFETS are electically interconnected, (rather than the Drains as in conventional diffused junction CMOS), which Schottky barrier MOSFET system demonstrates Regenerative Inverting Switching Characteristics in use are disclosed. Both the N and P-Channel Schottky barrier MOSFET devices are unique in that they provide operational Drain Current vs. Drain to Source voltage as a function of Gate voltage only where the polarities of the Drain voltage and Gate voltage are opposite, referenced to the Source as a common terminal, and where the polarity of the voltage applied to the Gate is appropriate to cause Channel inversion. Experimentally derived results which demonstrate and verify the operation of N and P-Channel Schottky barrier MOSFETS actually fabricated on P and N-type Silicon respectively, by a common procedure using vacuum deposited Chromium as a Schottky barrier forming metal, are also provided.

Welch, James D. (10328 Pinehurst Ave., Omaha, NE 68124)

1998-01-01

241

Regenerative switching CMOS system  

DOEpatents

Complementary Metal Oxide Semiconductor (CMOS) Schottky barrier Field Effect Transistor systems, which are a series combination of N and P-Channel MOSFETS, in which Source Schottky barrier junctions of the N and P-Channel Schottky barrier MOSFETS are electrically interconnected, (rather than the Drains as in conventional diffused junction CMOS), which Schottky barrier MOSFET system demonstrates Regenerative Inverting Switching Characteristics in use are disclosed. Both the N and P-Channel Schottky barrier MOSFET devices are unique in that they provide operational Drain Current vs. Drain to Source voltage as a function of Gate voltage only where the polarities of the Drain voltage and Gate voltage are opposite, referenced to the Source as a common terminal, and where the polarity of the voltage applied to the Gate is appropriate to cause Channel inversion. Experimentally derived results which demonstrate and verify the operation of N and P-Channel Schottky barrier MOSFETS actually fabricated on P and N-type Silicon respectively, by a common procedure using vacuum deposited Chromium as a Schottky barrier forming metal, are also provided. 14 figs.

Welch, J.D.

1998-06-02

242

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

243

Investigation of a hybrid optical-electronic switch supporting different service classes  

NASA Astrophysics Data System (ADS)

Optical fiber is considered the most competitive wired transmission support thanks to its low attenuation, wide optical bandwidth, long reach, and low cost. However, optics do not yet perform higher functionalities such as switching. In fact, all-optical switches face a contention issue, due to the lack of practical optical buffers. Thus, the switching function is still performed electronically, which requires energetically costly optical-to-electronic conversions. The energy consumption is a critical issue within the growing data traffic. Thus, a proposition of hybrid switch architecture supplementing optical switch with an electronic buffer. In this paper, we propose to investigate the performance of hybrid switch that supports different priority classes where the priority is defined in terms of Packet Loss Ratio (PLR). We show that the hybrid switch is a good trade off since it allows significant performance improvements towards a buffer-less all optical switch in terms of PLR and sustainable load, for relatively few electronic ports of the buffer, which would reduce energy consumption compared to an electronic switch.

Samoud, Wiem; Ware, Cédric; Lourdiane, Mounia

2014-09-01

244

Theory of molecular hysteresis switch  

NASA Astrophysics Data System (ADS)

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

Kozhushner, Mortko; Oleynik, Ivan

2006-03-01

245

Electron collisions in gas switches  

SciTech Connect

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

Christophorou, L.G.

1989-01-01

246

Wide Bandgap Extrinsic Photoconductive Switches  

SciTech Connect

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

Sullivan, J S

2012-01-17

247

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

248

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

249

Micromachined Planar Triggered Spark Gap Switch  

Microsoft Academic Search

High voltage switches capable of operating at high speeds with high current levels are used in a variety of applications in commercial and government systems. This paper discusses the fabrication and characterization of a novel micromachined planar triggered spark gap switch. The switch provides a low cost alternative to conventional triggered spark gap switches. The structure is designed for direct

Thomas A. Baginski; Robert Neal Dean; Edwin J. Wild

2011-01-01

250

Advanced semiconductor switches for EM launchers  

Microsoft Academic Search

Electric launchers may be energized by switching pulses of variable magnitude and time from a pulsed alternator or a pulse forming network. In order to achieve the desired muzzle energy, the switches must withstand the action of the current pulse: the square of current integrated over time. High pressure spark gap switches and vacuum switches of various architectures have been

Hardev Singh; Charles R. Hummer

2001-01-01

251

Optical Packet Switching -1 Optical Networks  

E-print Network

Optical Packet Switching - 1 Optical Networks: from fiber transmission to photonic switching Optical Packet Switching Fabio Neri and Marco Mellia TLC Networks Group ­ Electronics Department e.mellia@polito.it ­ tel. 011 564 4173 #12;Optical Packet Switching - 2 · This work is licensed under the Creative Commons

Mellia, Marco

252

Sealed reed relay limit switches  

NASA Astrophysics Data System (ADS)

Sealed reed relay limit switches are described which overcome the inherent deficiencies traditionally present in these devices: high material, labor consumption, and difficult operation. Series VSG limit switches developed at the All-Union Scientific Research and Technological Planning Institute for Relay Engineering (Cheboksary) for use in buildings are described. The VSG1 has a single switching contact, the VSG2 a single normally open contact, and the VSG3 a single normally closed contact. The VSG1 employs type MKS-27103 sealed reed relays, while the VSG2 and VSG3 employ KEM-1 reed relays. The magnet system, which consists of magnets and a plate, and the sealed reed relay are contained in a nonmagnetic casing with a slit in it. The mathematical expression defining the geometric dimensions of the magnet system is given. The basic parameteres of all three types of switches are tabulated. The VSG series switches can be used to replace VBK and BVK switches, thus saving electricity, labor, and materials, including silver.

Ivanov, I. P.; Svintsov, G. P.; Yefimova, M. A.; Lebedev, A. V.; Samsonov, Y. P.

1986-01-01

253

Nanomechanical switch for integration with CMOS logic.  

SciTech Connect

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

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

2008-11-01

254

A developmental switch in B lymphopoiesis.  

PubMed Central

B and T lymphocytes are generated from hematopoietic stem cells during both fetal and adult life. A critical unresolved issue is whether the differentiation pathways in lymphopoiesis are the same in fetal and adult animals or whether they differ, similar to the hemoglobin switch in erythropoiesis. We report here that a developmental switch occurs in B lymphopoiesis. We isolated "pro-B" cells (i.e., cells that have initiated, but not completed, heavy-chain gene rearrangement) from fetal and adult sources and investigated their B-cell progeny generated both in vitro and in vivo. Most of the cells from fetal liver, but few from adult bone marrow, expressed CD5. Further, fetal pro-B cells failed to generate cells expressing high levels of IgD in severe combined immunodeficiency mice, whereas adult pro-B cells gave rise to CD5-B cells bearing IgD at levels comparable to the bulk of cells in the spleen of adult mice. Thus, all committed B progenitors in fetal liver of day 16 gestation mice give rise to phenotypically distinct progeny when compared to cells at a comparable differentiation stage in the bone marrow of adult animals. We conclude that the cohort of B-lineage progenitors in early fetal development is committed to a differentiation pathway distinct from that seen in the adult. Images PMID:1722338

Hardy, R R; Hayakawa, K

1991-01-01

255

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

256

Magnetic Cellular Switches  

PubMed Central

This paper focuses on the development of magnetic cellular switches to enable magnetic control of intracellular functions in living mammalian cells, including receptor signal transduction and gene transcription. Our approach takes advantage of the mechanosensitivity of adenosine 3?,5?-monophosphate (cAMP) induction and downstream transcription controlled by the cAMP regulatory element (CRE) to engineer gene constructs that optically report gene expression in living cells. We activate transcription of these gene reporters by applying magnetic (mechanical) stress to magnetic microbeads bound to cell surface integrin receptors. In these gene reporter constructs, CRE motifs drive the expression of fluorescent proteins or enzymes that produce fluorescent products, such as DsRed and ?-lactamase (BLA), respectively. We demonstrate that a chemical inducer of cAMP (forskolin) increases expression of CRE-DsRed in living cells. More importantly, a threefold increase in CRE-BLA expression is induced by application of mechanical stress to magnetic microbeads (4.5 µm) bound to cell surface integrin receptors. Induction of cAMP could be detected within 5 min using a protein fragment complementation assay involving interactions between the KID and KIX domains of the CRE binding protein linked to complementary halves of the BLA enzyme. These studies confirm that application of magnetic stress to integrins induces gene transcription by activating the cAMP-dependent transcription factor CREB. Ongoing studies focus on optimizing sensitivity and reducing signal-to-noise by establishing stable cell lines that express these gene reporters. These studies collectively demonstrate the feasibility of using magnetic technologies to control function in living mammalian cells and, hence, support the possibility of developing magnetically-actuated cellular components for use in future micro- and nanotechnologies. PMID:23097592

Overby, Darryl R.; Alenghat, Francis J.; Montoya-Zavala, Martín; Bei, HuCheng; Oh, Philmo; Karavitis, John; Ingber, Donald E.

2012-01-01

257

Packaging of RF Mems Switching Functions on Alumina Substrate  

E-print Network

Recently the strong demands in wireless communication requires expanding development for the application of RF MEMS (Radio Frequency micro electro mechanical systems) sensing devices such as micro-switches, tunable capacitors because it offers lower power consumption, lower losses, higher linearity and higher Q factors compared with conventional communications components. To accelerate commercialisation of RF MEMS products, development for packaging technologies is one of the most critical issues should be solved beforehand.

Khatib, M -K El; Blondy, P

2007-01-01

258

Oxide thin film based inverse superconducting spin switches  

Microsoft Academic Search

Thin film F\\/S\\/F trilayers made of YBa2Cu3O7 (S, YBCO) and La0.7Ca0.3MnO3 (F, LCMO) behave as inverse superconducting spin switches (SSS) as the critical temperature of the superconductor depends on the relative orientation of the magnetization of the F layers in a way that the resistivity is increased in the antiparallel configuration. This is caused by enhanced pair-breaking due to the

Norbert M. Nemes; C. Visani; C. Miller; M. Rocci; F. Bruno; J. Garcia-Barriocanal; Z. Sefrioui; C. Leon; J. Santamaria; M. Iglesias; F. Mompean; M. Garcia-Hernandez; A. Hoffmann; S. G. E. Te Velthuis

2009-01-01

259

The UniMIN switch architecture for large-scale ATM switches  

Microsoft Academic Search

A general expansion architecture is proposed that can be used in building large-scale switches using any type of asynchronous transfer mode (ATM) switch. The proposed universal multistage interconnection network (UniMIN) switch is composed of a buffered distribution network (DN) and a column of output switch modules (OSM's), which can be any type of ATM switch. ATM cells are routed to

Sung Hyuk Byun; Dan Keun Sung

2000-01-01

260

All-optical switching in a highly efficient parametric fiber mixer: design study.  

PubMed

Ultrafast all-optical switching in a highly nonlinear fiber with a longitudinally varied zero-dispersion wavelength was investigated theoretically and experimentally. We describe fiber-matched methodology for construction of a fast, low energy photon switch. The design relies on static and dynamic models and allows performance target selection, under constraints of physical fiber characteristic. The new design methodology was used to construct one-pump switch in the highly efficient parametric mixer. We demonstrate that such a parametric gate can operate at 100 GHz rate, with 2 aJ control energy, while achieving better than 50% extinction ratio. Theoretical analysis and experimental measurements indicate that accurate mapping of the fiber local dispersion is critical in optimizing the bandwidth and control energy of the switch. Switching performance limits are discussed and means for impairment mitigation are described. PMID:25321820

Pejkic, Ana; Nissim, Ron R; Myslivets, Evgeny; Wiberg, Andreas O J; Alic, Nikola; Radic, Stojan

2014-09-22

261

Fast magnetization switching by linear vertical microwave-assisted spin-transfer torque.  

PubMed

The effect of vertical microwave magnetic field on spin-transfer torque switching in elliptical magnetic spin valve has been investigated by performing micromagnetic simulations including a spin-transfer torque term. The speed of magnetization switching can be accelerated by applying a vertical microwave magnetic field. Magnetization switching time decreases with the increase of the amplitude of vertical microwave magnetic field for both the fixed microwave frequency and current density. When the frequency of the microwave magnetic field coincides with the natural ferromagnetic resonance frequency of the elliptical spin valve, magnetization switching time is reduced to the minimum. Magnetization switching time can be reduced from 9.44 to 2.4 ns due to an effect of vertical microwave magnetic field. In addition, critical current density of magnetization reversal is strongly lowered in the presence of vertical microwave magnetic field. PMID:23035495

Mu, Congpu; Wang, Weiwei; Xia, Haiyan; Zhang, Bin; Liu, Qingfang; Wang, Jianbo

2012-09-01

262

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

263

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

264

Ad Critic  

NSDL National Science Digital Library

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

265

Critical Load  

NSDL National Science Digital Library

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

IEEE

2014-05-22

266

Optimized Switch Allocation to Improve the Restoration Energy in Distribution Systems  

NASA Astrophysics Data System (ADS)

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

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

2012-01-01

267

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

268

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

269

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

270

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

271

Adaptive optical label packet switching  

NASA Astrophysics Data System (ADS)

This paper introduces a kind of Adaptive Optical Label Packet Switching (AOLPS) technology. Based on Optical Packet Switching (OPS), AOLPS uses optical label to achieve self-routing, and the size of optical packet is self-adaptive. At the edge nodes, IP packets are fist classified into different first-in-fist-out memories (FIFOs) according to their priority levels and destinations, and then being encapsulated into optical packets. The traffic at each FIFO is real-time monitored, and the controller in edge node employs an optimal strategy to generate suitable sized packets for transmission. Large sized packets will be adopted when traffic is heavy, and small sized packets will be used when traffic is light. This self-adaptive switching granularity can greatly improve the network performance.

Xiao, Shilin; Liu, Zhixin; Liang, Zheng; Zhao, Zhihui; Qu, Kefeng

2007-11-01

272

Explosive opening switch work at Westinghouse  

NASA Astrophysics Data System (ADS)

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

Aivaliotis, E.; Peterhans, M.

1989-01-01

273

Liquid metal switches for electromagnetic railgun systems  

NASA Astrophysics Data System (ADS)

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

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

1991-01-01

274

System for automatically switching transformer coupled lines  

NASA Technical Reports Server (NTRS)

A system is presented for automatically controlling transformer coupled alternating current electric lines. The secondary winding of each transformer is provided with a center tap. A switching circuit is connected to the center taps of a pair of secondary windings and includes a switch controller. An impedance is connected between the center taps of the opposite pair of secondary windings. The switching circuit has continuity when the AC lines are continuous and discontinuity with any disconnect of the AC lines. Normally open switching means are provided in at least one AC line. The switch controller automatically opens the switching means when the AC lines become separated.

Dwinell, W. S. (inventor)

1979-01-01

275

Molecular DNA switches and DNA chips  

NASA Astrophysics Data System (ADS)

We present an assay to detect single-nucleotide polymorphisms on a chip using molecular DNA switches and isothermal rolling- circle amplification. The basic principle behind the switch is an allele-specific oligonucleotide circularization, mediated by DNA ligase. A DNA switch is closed when perfect hybridization between the probe oligonucleotide and target DNA allows ligase to covalently circularize the probe. Mismatches around the ligation site prevent probe circularization, resulting in an open switch. DNA polymerase is then used to preferentially amplify the closed switches, via rolling-circle amplification. The stringency of the molecular switches yields 102 - 103 fold discrimination between matched and mismatched sequences.

Sabanayagam, Chandran R.; Berkey, Cristin; Lavi, Uri; Cantor, Charles R.; Smith, Cassandra L.

1999-06-01

276

Switch Using Radio Frequency Identification  

NASA Technical Reports Server (NTRS)

Disclosed is an apparatus for use as a switch. In one embodiment, the switch comprises at least one RFID tag, each RFID tag comprising an antenna element and an RFID integrated circuit, at least one source element, and at least one lever arm. Each lever arm is connected to one of the RFID tags, and each lever arm is capable of two positions. One of the positions places the lever arm and the RFID tag connected thereto into alignment with the source element. Other embodiments are also described.

Fink, Patrick W. (Inventor); Lin, Gregory Y. (Inventor); Kennedy, Timothy F. (Inventor); Ngo, Phong H. (Inventor)

2015-01-01

277

Integrated indium phosphide photonic switches  

NASA Astrophysics Data System (ADS)

Photonic switches are becoming key components in advanced optical networks because of the large variety of applications that they can perform. One of the key advantages of photonic switches is that they redirect or convert light without having to make any optical to electronic conversions and vice versa, thus allowing networking functions to be lowered into the optical layer. InP-based switches are particularly attractive because of their small size, low electrical power consumption, and compatibility with integration of laser sources, photo-detectors, and electronic components. In this dissertation the development of integrated InP photonic switches using an area-selective zinc diffusion process has been investigated. The zinc diffusion process is implemented using a semi-sealed open-tube diffusion technique. The process has proven to be highly controllable and reproducible by carefully monitoring of the diffusion parameters. Using this technique, isolated p-n junctions exhibiting good I-V characteristics and breakdown voltages greater than 10 V can be selectively defined across a semiconductor wafer. A series of Mach-Zehnder interferometric (MZI) switches/modulators have been designed and fabricated. Monolithic integration of 1x2 and 2x2 MZI switches has been demonstrated. The diffusion process circumvents the need for isolation trenches, and hence optical losses can be significantly reduced. An efficient optical beam steering device based on InGaAsP multiple quantum wells is also demonstrated. The degree of lateral current spreading is easily regulated by controlling the zinc depth, allowing optimization of the injected currents. Beam steering over a 21 microns lateral distance with electrical current values as low as 12.5 mA are demonstrated. Using this principle, a reconfigurable 1x3 switch has been implemented with crosstalk levels better than -17 dB over a 50 nm wavelength range. At these low electrical current levels, uncooled and d.c. bias operation is made feasible. The use of multimode interference (MMI) structures as active devices have also been investigated. These devices operate by selective refractive index perturbation on very specific areas within the MMI structure, and this is again realized using zinc diffusion. Several variants such as a compact MMI modulator that is as short as 350 microm, a robust 2x2 photonic switch and a tunable MMI coupler have been demonstrated.

May Arrioja, Daniel Alberto

278

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

279

Optical Switch Using Risley Prisms  

DOEpatents

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

280

SWITCH-WECC http://rael.berkeley.edu/switch  

E-print Network

and solar power in California. Ph.D. Dissertation, University of California, Berkeley, Energy and Resources., 2013. SunShot solar power reduces costs and uncertainty in future low-carbon electricity systems University of California, Berkeley September 2013 #12;The SWITCH Model · Model created to study the cost

Kammen, Daniel M.

281

The Optical Switching Spectrum: A Primer on Wavelength Switching Technologies  

Microsoft Academic Search

Anyone touring a local telephone company's central office, as recently as five or ten years ago, remembers the relay room. This room held the still-functioning legacy mechanical relay switches designed into the network to replace the human patchcord operator. Stepping in, one heard the cacophony of clicks as the mechanical relays opened and closed to process the electrical signals in

Amy Dugan

282

Bacterial cytotoxins: targeting eukaryotic switches  

Microsoft Academic Search

Many bacterial cytotoxins act on eukaryotic cells by targeting the regulators that are involved in controlling the cytoskeleton or by directly modifying actin, with members of the Rho GTPase family being particularly important targets. The actin cytoskeleton, and especially the GTPase 'molecular switches' that are involved in its control, have crucial functions in innate and adaptive immunity, and have pivotal

Joseph T. Barbieri; Klaus Aktories

2005-01-01

283

Reversible electronic logic using switches  

Microsoft Academic Search

Two methods of using switches to implement reversible computations are discussed. The first method has an energy dissipation which is proportional to the square of the error in the voltage, while the second method has an energy dissipation which can in principle be reduced indefinitely by slowing the speed of computation. The first method is basically an extension to 'pass

R. C. Merkle

1993-01-01

284

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

285

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

286

Anode initiated surface flashover switch  

DOEpatents

A high voltage surface flashover switch has a pair of electrodes spaced by an insulator. A high voltage is applied to an anode, which is smaller than the opposing, grounded, cathode. When a controllable source of electrons near the cathode is energized, the electrons are attracted to the anode where they reflect to the insulator and initiate anode to cathode breakdown.

Brainard, John P. (Albuquerque, NM); Koss, Robert J. (Albuquerque, NM)

2003-04-29

287

High voltage MOSFET switching circuit  

DOEpatents

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

McEwan, T.E.

1994-07-26

288

Switching Surge Testing of Transformers  

Microsoft Academic Search

In this paper, the authors discuss the desirability of introducing a switching surge test on transformers having system voltages 400 kV and above. A practical method for executing such tests is described, one which utilizes impulse-voltage testing techniques. This method is illustrated by test results from transformers. It is shown that the duration of the surges can be extended by

A. Algbrant; A. E. Brierley; N. Hylten-Cavallius; D. H. Ryder

1966-01-01

289

A Scaffold Makes the Switch  

NSDL National Science Digital Library

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

Henrik G. Dohlman (Chapel Hill; University of North Carolina REV)

2008-10-21

290

Osmosis in Pocket Switched Networks  

Microsoft Academic Search

The increase in the variety and capability of mobile communications devices carried by people today has made it possible to envision a new class of networks called pocket switched networks (PSNs). In a PSN, because the nodes are constantly moving and their communication abilities are limited, the design of networking protocols and applications is challenging. This paper presents a new

Pan Huiitt; J'er'emie Leguay; Jon Crowcroft; James Scott; T. Friedmani; Vania Conan

2006-01-01

291

Osmosis in Pocket Switched Networks  

Microsoft Academic Search

The increase in the variety and capability of mobile communications devices carried by people today has made it pos- sible to envision a new class of networks called Pocket Switched Networks (PSNs). In a PSN, because the nodes are constantly moving and their communication abilities are limited, the design of networking protocols and applications is challenging. This paper presents a

Thales Communications

292

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

293

30 CFR 56.9308 - Switch throws.  

Code of Federal Regulations, 2010 CFR

...STANDARDS-SURFACE METAL AND NONMETAL MINES Loading, Hauling, and Dumping Safety Devices, Provisions, and Procedures for Roadways, Railroads, and Loading and Dumping Sites § 56.9308 Switch throws. Switch throws shall be...

2010-07-01

294

30 CFR 57.9308 - Switch throws.  

Code of Federal Regulations, 2010 CFR

...STANDARDS-UNDERGROUND METAL AND NONMETAL MINES Loading, Hauling, and Dumping Safety Devices, Provisions, and Procedures for Roadways, Railroads, and Loading and Dumping Sites § 57.9308 Switch throws. Switch throws shall be...

2010-07-01

295

Stability control of the polarization switching  

NASA Astrophysics Data System (ADS)

Pulse polarization switching is an important new method to eliminate the polarization-induced fading (PIF) in the interferometric fiber sensing system. An integrated Ti-indiffused LiNbO3 Mach-Zehnder modulator is used to achieve high-speed switch of the polarization state by switching the voltage between two appropriate voltages applied to the modulator. The stability of the polarization switching is affected by environmental factors, especially the temperature. In this paper, the stability of the polarization switching is studied. Firstly, the structure of the modulator and the principle of the polarization switching are introduced. Secondly, a feedback control method to overcome the switch instability is proposed. The output polarization state could be obtained by monitoring the intensity of the output light. Finally, the high-speed and high-accuracy stable switching between two orthogonal polarization states is realized using this method and experimentally demonstrated.

Yin, Xiaobing; Lin, Huizu; Hu, Zhengliang; Hu, Yongming

2013-08-01

296

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

297

An integrated nine-switch power conditioner  

Microsoft Academic Search

A nine-switch power converter having two sets of output terminals was recently proposed in place of the traditional back-to-back power converter that uses twelve switches in total. The nine-switch converter has already been proven to have certain advantages, in addition to its component saving topological feature. Despite these advantages, the nine-switch converter has so far found limited applications due to

Lei Zhang; Poh Chiang Loh; Feng Gao

2010-01-01

298

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.

299

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

300

A switched beam single arm rectangular spiral antenna with hybrid switch network  

Microsoft Academic Search

A single-arm rectangular spiral antenna with a hybrid (short and open) switch network is proposed for switched beam applications. The excitation of switches in the hybrid network introduces variation in the current distribution on the antenna arm, thus causing the beam to steer into various directions. A shorting switch is implemented as an element to short-circuit a point on the

A. Mehta; D. Mirshekar-Syahkal; H. Nakano

2005-01-01

301

A soft-switching active rectifier using a concept of magnetic energy recovery switch  

Microsoft Academic Search

Converters using active switches can improve harmonic components of input current and power factor. Moreover, these converters contribute to the footprint downsizing. However, increase of switching losses and EMI due to high frequency switching is one challenge of these types of converters. This paper proposes a new active rectifier circuit topology, which can reduce the switching losses and EMI with

Yoshitsugu Miyaji; Takanori Isobe; Ryuichi Shimada

2010-01-01

302

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

303

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

304

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

305

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

306

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

307

Maximizing Throughput for Optical Burst Switching Networks  

Microsoft Academic Search

Abstract - A key problem in Optical Burst Switching (OBS) is optical circuit switching and optical packet switching was pro to schedule as many bursts as possible on wavelength channels so posed in [1] [2], and has received increasing amount of attention that the throughput is maximized and the burst loss is minimized from both academia and industry worldwide [3

Jikai Li; Chunming Qiao; Jinhui Xu; Dahai Xu

2004-01-01

308

A gain-coefficient switched Alexandrite laser  

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

309

A gain-coefficient switched Alexandrite laser  

E-print Network

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

Lee, Chris J; Boller, Klaus-J

2012-01-01

310

January, 1988 SWITCHING SYSTEMS AND PERIODICITY 1  

E-print Network

for this theory of certain anomalous points on the switching surface is shown by an example with no periodic topologically general results for periodicity of switching systems. The principal thrust of this material is the importance to the theory of considering certain anomalous points on the switching surfaces

Seidman, Thomas I.

311

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.

312

A Bilingual Advantage in Task Switching  

ERIC Educational Resources Information Center

This study investigated the possibility that lifelong bilingualism may lead to enhanced efficiency in the ability to shift between mental sets. We compared the performance of monolingual and fluent bilingual college students in a task-switching paradigm. Bilinguals incurred reduced switching costs in the task-switching paradigm when compared with…

Prior, Anat; MacWhinney, Brian

2010-01-01

313

A Mechanism for Efficient Context Switching  

Microsoft Academic Search

Context switches are slow in conventional processorsbecause the entire processor state must be savedand restored, even if much of the restored state is notused before the next context switch. This unnecessarydata movement is required because of the coarsegranularity of binding between names and registers.In this paper we introduce the Context Cache, whichbinds variable names to individual registers. This allowscontext switches

Peter R. Nuth; William J. Dally

1991-01-01

314

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.

315

Electrostatically actuated MEMS switch with resistive contact  

NASA Astrophysics Data System (ADS)

MEMS switch with the electrostatic actuation and the resistive contact was fabricated using surface micromachining. The movable electrode of the switch was the three-layer metallic cantilever having nanoscale thickness and high lengthto- thickness ratio. Low stiffness of the cantilever allowed to approach relatively low values of the actuation voltage. The theoretical analysis and experimental study of the switching characteristics was performed.

Uvarov, Ilya V.; Naumov, Victor V.; Selyukov, Roman V.

2014-12-01

316

47 CFR 32.2211 - Non-digital switching.  

Code of Federal Regulations, 2011 CFR

...switches. (3) Original cost of non-electronic circuit-switching equipment such as Step-by-Step, Crossbar, and Other Electro-Mechanical Switching. (b) Switching plant excludes switchboards which perform an operator assistance...

2011-10-01

317

47 CFR 32.2211 - Non-digital switching.  

Code of Federal Regulations, 2010 CFR

...switches. (3) Original cost of non-electronic circuit-switching equipment such as Step-by-Step, Crossbar, and Other Electro-Mechanical Switching. (b) Switching plant excludes switchboards which perform an operator assistance...

2010-10-01

318

49 CFR 236.817 - Switch, electro-pneumatic.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 false Switch, electro-pneumatic. 236.817 Section 236...APPLIANCES Definitions § 236.817 Switch, electro-pneumatic. A switch operated by an electro-pneumatic switch-and-lock...

2010-10-01

319

49 CFR 236.817 - Switch, electro-pneumatic.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false Switch, electro-pneumatic. 236.817 Section 236...APPLIANCES Definitions § 236.817 Switch, electro-pneumatic. A switch operated by an electro-pneumatic switch-and-lock...

2011-10-01

320

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

321

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

322

The cortical dynamics underlying effective switching of auditory spatial attention  

PubMed Central

Successful rapid deployment of attention to relevant sensory stimuli is critical for survival. In a complex environment, attention can be captured by salient events or be deployed volitionally. Furthermore, when multiple events are of interest concurrently, effective interaction with one's surroundings hinges on efficient top-down control of shifting attention. It has been hypothesized that two separate cortical networks coordinate attention shifts across multiple modalities. However, the cortical dynamics of these networks and their behavioral relevance to switching of auditory attention are unknown. Here we show that the strength of each subject's right temporal-parietal junction (RTPJ, part of the ventral network) activation was highly correlated with their behavioral performance in an auditory task. We also provide evidence that the recruitment of the RTPJ likely precedes the right frontal eye fields (FEF; participating in both the dorsal and ventral networks) and middle frontal gyrus (MFG) by around 100 ms when subjects switch their auditory spatial attention. PMID:22974974

Larson, Eric; Lee, Adrian KC

2012-01-01

323

Electrical switching to probe complex phases in a frustrated manganite  

NASA Astrophysics Data System (ADS)

Electrical switching was used to investigate complex phases induced by Cr-substitution in (Pr1/3Sm2/3)2/3Sr1/3MnO3. This system was expected to transform from a Type I (Mn4+/Mn3+?3/7) to Type II (Mn4+/Mn3+?1) manganite at critical Cr content, satisfying a virtual Mn4+/Mn3+ ratio close to unity. The phase diagram of (Pr1/3Sm2/3)2/3Sr1/3Mn0.8Cr0.2O3 including charge/spin ordered/disordered phases was probed by electrical switching. The ferromagnetic insulating phase at <~100 K, located next to the charge-ordered antiferromagnetic phase, exhibited a sudden rise in conductivity upon electric-field biasing. This resulted from the melting of charge ordering, and demonstrated the presence of a crossover regime of two coexisting magnetic orderings.

Asthana, Saket; Fujiwara, Kohei; Tanaka, Hidekazu

2014-06-01

324

Ultrafast magnetization switching by spin-orbit torques  

NASA Astrophysics Data System (ADS)

Spin-orbit torques induced by spin Hall and interfacial effects in heavy metal/ferromagnetic bilayers allow for a switching geometry based on in-plane current injection. Using this geometry, we demonstrate deterministic magnetization reversal by current pulses ranging from 180 ps to ms in Pt/Co/AlOx dots with lateral dimensions of 90 nm. We characterize the switching probability and critical current Ic as a function of pulse length, amplitude, and external field. Our data evidence two distinct regimes: a short-time intrinsic regime, where Ic scales linearly with the inverse of the pulse length, and a long-time thermally assisted regime, where Ic varies weakly. Both regimes are consistent with magnetization reversal proceeding by nucleation and fast propagation of domains. We find that Ic is a factor 3-4 smaller compared to a single domain model and that the incubation time is negligibly small, which is a hallmark feature of spin-orbit torques.

Garello, Kevin; Avci, Can Onur; Miron, Ioan Mihai; Baumgartner, Manuel; Ghosh, Abhijit; Auffret, Stéphane; Boulle, Olivier; Gaudin, Gilles; Gambardella, Pietro

2014-11-01

325

Distribution of supercurrent switching in graphene under the proximity effect.  

SciTech Connect

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

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

2012-01-01

326

The Knockout Switch: A Simple, Modular Architecture for High-Performance Packet Switching  

Microsoft Academic Search

A new, high-performance packet-switching architecture, called the Knockout Switch, is proposed. The Knockout Switch uses a fully interconnected switch fabric topology (i.e., each input has a direct path to every output) so that no switch blocking occurs where packets destined for one output interfere with (i.e., block or delay) packets going to different Outputs. It is only at each output

Yu-Shuan Yeh; M. Hluchyj; A. Acampora

1987-01-01

327

Switch over from intravenous to oral therapy: A concise overview  

PubMed Central

Majority of the patients admitted to a hospital with severe infections are initially started with intravenous medications. Short intravenous course of therapy for 2-3 days followed by oral medications for the remainder of the course is found to be beneficial to many patients. This switch over from intravenous to oral therapy is widely practiced in the case of antibiotics in many developed countries. Even though intravenous to oral therapy conversion is inappropriate for a patient who is critically ill or who has inability to absorb oral medications, every hospital will have a certain number of patients who are eligible for switch over from intravenous to oral therapy. Among the various routes of administration of medications, oral administration is considered to be the most acceptable and economical method of administration. The main obstacle limiting intravenous to oral conversion is the belief that oral medications do not achieve the same bioavailability as that of intravenous medications and that the same agent must be used both intravenously and orally. The advent of newer, more potent or broad spectrum oral agents that achieve higher and more consistent serum and tissue concentration has paved the way for the popularity of intravenous to oral medication conversion. In this review, the advantages of intravenous to oral switch over therapy, the various methods of intravenous to oral conversion, bioavailability of various oral medications for the switch over program, the patient selection criteria for conversion from parenteral to oral route and application of intravenous to oral switch over through case studies are exemplified. PMID:24799810

Cyriac, Jissa Maria; James, Emmanuel

2014-01-01

328

A new soft single switched PWM DC-DC converter  

Microsoft Academic Search

com Abstract-In this paper, a new soft switching isolated PWM converter without any auxiliary switch is proposed. The auxiliary circuit contains of two coupled inductors and one snubber capacitor. In this converter, switch is turned on under zero current switching and turn off under almost zero voltage switching. Switch is PWM controlled which simplifies the control implementation. One of the

M. Mahdavian; M. Delshad

2011-01-01

329

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

330

TOPO3a Influences Antigenic Variation by Monitoring Expression-Site-Associated VSG Switching in  

E-print Network

Homologous recombination (HR) mediates one of the major mechanisms of trypanosome antigenic variation by placing a different variant surface glycoprotein (VSG) gene under the control of the active expression site (ES). It is believed that the majority of VSG switching events occur by duplicative gene conversion, but only a few DNA repair genes that are central to HR have been assigned a role in this process. Gene conversion events that are associated with crossover are rarely seen in VSG switching, similar to mitotic HR. In other organisms, TOPO3a (Top3 in yeasts), a type IA topoisomerase, is part of a complex that is involved in the suppression of crossovers. We therefore asked whether a related mechanism might suppress VSG recombination. Using a set of reliable recombination and switching assays that could score individual switching mechanisms, we discovered that TOPO3a function is conserved in Trypanosoma brucei and that TOPO3a plays a critical role in antigenic switching. Switching frequency increased 10–40-fold in the absence of TOPO3a and this hyper-switching phenotype required RAD51. Moreover, the preference of 70-bp repeats for VSG recombination was mitigated, while homology regions elsewhere in ES were highly favored, in the absence of TOPO3a. Our data suggest that TOPO3a may remove undesirable recombination intermediates constantly arising between active and silent ESs, thereby balancing ES

331

TOPO3? Influences Antigenic Variation by Monitoring Expression-Site-Associated VSG Switching in Trypanosoma brucei  

PubMed Central

Homologous recombination (HR) mediates one of the major mechanisms of trypanosome antigenic variation by placing a different variant surface glycoprotein (VSG) gene under the control of the active expression site (ES). It is believed that the majority of VSG switching events occur by duplicative gene conversion, but only a few DNA repair genes that are central to HR have been assigned a role in this process. Gene conversion events that are associated with crossover are rarely seen in VSG switching, similar to mitotic HR. In other organisms, TOPO3? (Top3 in yeasts), a type IA topoisomerase, is part of a complex that is involved in the suppression of crossovers. We therefore asked whether a related mechanism might suppress VSG recombination. Using a set of reliable recombination and switching assays that could score individual switching mechanisms, we discovered that TOPO3? function is conserved in Trypanosoma brucei and that TOPO3? plays a critical role in antigenic switching. Switching frequency increased 10–40-fold in the absence of TOPO3? and this hyper-switching phenotype required RAD51. Moreover, the preference of 70-bp repeats for VSG recombination was mitigated, while homology regions elsewhere in ES were highly favored, in the absence of TOPO3?. Our data suggest that TOPO3? may remove undesirable recombination intermediates constantly arising between active and silent ESs, thereby balancing ES integrity against VSG recombination. PMID:20628569

Kim, Hee-Sook; Cross, George A. M.

2010-01-01

332

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

333

Efficiency consideration of DC link soft-switching inverters for motor drive applications  

SciTech Connect

This paper critically evaluates efficiency of soft switching inverters including an actively clamped resonant dc link inverter and a clamped-mode resonant pole inverter. An analytical approach to evaluating efficiency of the clamped-mode soft switching inverter has been developed. The evaluation results are compared with that of the standard pulse-width-modulation (PWM) inverter. A 50-kW induction motor is used as the variable load, and the inverter efficiency is evaluated under different speed and torque conditions. The clamped-mode soft-switching inverter, although eliminating the switching loss, shows poor efficiency over the entire load range. Under low load conditions, the efficiency profile is even worse. The actively clamped resonant dc link inverter shows highest efficiency over the entire speed and torque range. However, its energy saving over the standard PWM inverter is marginal under full load or high speed conditions.

Lai, J.S.; Young, R.W.; McKeever, J.W.

1994-12-31

334

Satellite on-board baseband switching architectures  

NASA Astrophysics Data System (ADS)

On-board baseband processing has been actively pursued by a number of organizations for potential implementation in future communications satellites. This paper examines some of the benefits of on-board regeneration, baseband processing, and switching. It describes alternate switching concepts, i.e., circuit switching and fast packet switching, their advantages and shortcomings, and potential applications for future commercial satellite communications. In particular, fast packet switching is a relatively new concept for on-board applications and shows a great promise for the integrated operation of digital satellite networks. Key design issues for this system are also discussed. The paper presents several switch configurations for each type of switching concept, and a sample network architecture and its processing payload configuration for potential future communications satellites.

Inukai, Thomas; Pontano, Benjamin A.

1993-02-01

335

Electrical switching in cadmium boracite single crystals  

NASA Astrophysics Data System (ADS)

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.

336

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

337

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

338

Ultrafast switching of photonic entanglement.  

PubMed

To deploy and operate a quantum network which utilizes existing telecommunications infrastructure, it is necessary to be able to route entangled photons at high speeds, with minimal loss and signal-band noise, and--most importantly--without disturbing the photons' quantum state. Here we present a switch which fulfills these requirements and characterize its performance at the single photon level. Furthermore, because this type of switch couples the temporal and spatial degrees of freedom, it provides an important new tool with which to encode multiple-qubit states in a single photon. As a proof-of-principle demonstration of this capability, we demultiplex a single quantum channel from a dual-channel, time-division-multiplexed entangled photon stream, effectively performing a controlled-bit-flip on a two-qubit subspace of a five-qubit, two-photon state. PMID:21405397

Hall, Matthew A; Altepeter, Joseph B; Kumar, Prem

2011-02-01

339

Polychromatic polariton laser selector switch  

E-print Network

Integration of optical elements into scalable chips has been at the center of a large effort in recent years. Concurrently, the separation between the diverse functions, namely switches, detectors or emitters increases significantly the final number of components on chip. Such technical limitations may be overcome by introducing agile devices able, for example, to simultaneously detect, process and emit a coherent signal. Such a pathway has been explored with different approaches that bear advantages and drawbacks. Polaritons have often been proposed as promising candidates for multifunctional devices. Here we present an optical switch based on polariton lasing. An incident monochromatic signal is channeled into several polariton laser beams at different wavelengths by a novel relaxation mechanism which combines bistability, phonon interactions, long polariton lifetime and bosonic stimulation. We demonstrate spin logic operations conserving the original polarization state that is fully imprinted onto the cohe...

Grosso, G; Wouters, M; Morier-Genoud, F; Portella-Oberli, M T; Deveaud, B

2013-01-01

340

Shape memory thermal conduction switch  

NASA Technical Reports Server (NTRS)

A thermal conduction switch includes a thermally-conductive first member having a first thermal contacting structure for securing the first member as a stationary member to a thermally regulated body or a body requiring thermal regulation. A movable thermally-conductive second member has a second thermal contacting surface. A thermally conductive coupler is interposed between the first member and the second member for thermally coupling the first member to the second member. At least one control spring is coupled between the first member and the second member. The control spring includes a NiTiFe comprising shape memory (SM) material that provides a phase change temperature <273 K, a transformation range <40 K, and a hysteresis of <10 K. A bias spring is between the first member and the second member. At the phase change the switch provides a distance change (displacement) between first and second member by at least 1 mm, such as 2 to 4 mm.

Vaidyanathan, Rajan (Inventor); Krishnan, Vinu (Inventor); Notardonato, William U. (Inventor)

2010-01-01

341

Gyrotropic photonic crystal waveguide switches  

NASA Astrophysics Data System (ADS)

Functional photonic crystals fabricated in iron garnet films are shown to provide magnetically-controllable optical switching. Transverse-electric and transverse-magnetic stop band separation in conjunction with optical gyrotropy are utilized to selectively block and transmit near-infrared light in waveguide geometries. Geometrical birefringence allows the simultaneous low- and high-birefringence in different modes necessary to create band gap separation and effective magneto-optic gyrotropy in a single device.

Wu, Z.; Levy, Miguel; Fratello, V. J.; Merzlikin, A. M.

2010-02-01

342

Magnetoelectric Switching of Exchange Bias  

Microsoft Academic Search

The perpendicular exchange bias field, HEB, of the magnetoelectric heterostructure Cr2O3(111)\\/(Co\\/Pt)3 changes sign after field cooling to below the Néel temperature of Cr2O3 in either parallel or antiparallel axial magnetic and electric freezing fields. The switching of HEB is explained by magnetoelectrically induced antiferromagnetic single domains which extend to the interface, where the direction of their end spins controls the

Pavel Borisov; Andreas Hochstrat; Xi Chen; Wolfgang Kleemann; Christian Binek

2005-01-01

343

Switch for Good Community Program  

SciTech Connect

Switch4Good is an energy-savings program that helps residents reduce consumption from behavior changes; it was co-developed by Balfour Beatty Military Housing Management (BB) and WattzOn in Phase I of this grant. The program was offered at 11 Navy bases. Three customer engagement strategies were evaluated, and it was found that Digital Nudges (a combination of monthly consumption statements with frequent messaging via text or email) was most cost-effective.

Crawford, Tabitha; Amran, Martha

2013-11-19

344

Packet-switched optical networks  

Microsoft Academic Search

We describe a testbed to study both the theoretical aspects and physical implementation issues associated with high-bit-rate, multihop, packet-switched OTDM networks. We have found that using optical time-division-multiplexed (OTDM) techniques can greatly increase the bandwidth of a single-wavelength channel. Ultrafast OTDM networks are excellent candidates for meeting the system requirements for massively parallel processor interconnects, which include low latency, high

Ben Y. Yu; P. Tollver; Robert J. Runser; Kung-Li Deng; Deyu Zhou; Ivan Glesk; Paul R. Prucnal

1998-01-01

345

The intricate workings of a bacterial epigenetic switch.  

PubMed

Bacteria have developed epigenetic mechanisms to control the reversible Off-to-On switching of cell surface structures such as pyelonephritis-associated pili (PAP). The pap pili switch is primarily controlled by the global regulator leucine-responsive regulatory protein (Lrp), the local regulator PapI, and DNA adenine methylase (Dam). There are two sets of binding sites for Lrp in the pap regulatory region: promoter proximal sites 1,2,3 and promoter distal sites 4,5,6. The pilin promoter proximal (GATCprox) and distal (GATCdist) targets for Dam are located within Lrp binding sites 2 and 5, respectively. In the Off state, Lrp binds cooperatively to sites 1,2,3 overlapping the papBA pilin promoter, shutting off pilin transcription, and blocking methylation of GATCprox. Binding of Lrp at sites 1,2,3, together with methylation of GATCdist, reduces the affinity of Lrp for sites 4,5,6, preventing simultaneous binding of Lrp at sites 4,5,6 upstream. Switching to the phase. On state requires the environmentally regulated PapI co-regulator, which increases the affinity of Lrp for sites 5 and 2. PapI binds specifically to Lrp-pap DNA complexes via binding with Lrp as well as contact with DNA sequences within pap sites 5 and 2. Directionality in switching from Off to On appears to be due to methylation of GATCprox, which prevents formation of the PapI-Lrp-pap site 2 ternary complex. A switch model is presented in which DNA replication is proposed to play a critical role by generating a hemimethylated GATCdist site and displacing Lrp from sites 1,2,3. This facilitates methylation of GATCprox and binding of PapI-Lrp to sites 4,5,6, with subsequent activation of pap transcription. The first gene product of the pap operon, PapB, positively regulates papI transcription, resulting in a positive feedback loop that helps maintain the On state. The pap switch is environmentally regulated by a number of factors including the CpxAR two-component regulatory system, the Histone-like nucleoid structuring protein H-NS, and cAMP-Catabolite Gene Activator Protein (CAP), which all involve binding of regulatory binding proteins to pap DNA sequences with subsequent alteration of PapI and Lrp binding. The Pap switch mechanism, with interesting variations, is conserved among a number of enteric bacteria, controlling expression of many unrelated pili-adhesin complexes. PMID:15230094

Hernday, Aaron; Braaten, Bruce; Low, David

2004-01-01

346

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

347

In situ analysis of nitrogen fixation and metabolic switching in unicellular thermophilic cyanobacteria  

E-print Network

F, cpcE, psaB, and psbB) and respiration (coxA and cydA) genes declined in the evening. In contrast, our data suggest that there are critical regulatory switches in situ that are linked to the diel cycle are an ecologically diverse group of or- ganisms distributed along horizontal thermal and vertical light and O2

348

Still Clever After All These Years: Searching for the Homunculus in Explicitly Cued Task Switching  

E-print Network

and targets often appear in random order, and trials are sorted post hoc into repetitions and alternations that highlights empirical problems with their evidence and reports an experi- ment that challenges critical assumptions of their theoretical account. Keywords: task switching, endogenous control, sequential comparison

Logan, Gordon D.

349

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

350

Measuring IC switching current waveforms using a GMI probe for power integrity studies  

Microsoft Academic Search

IC switching current is the main noise source of many power integrity issues in printed circuit boards. Accurate measurement of the current waveforms is critical for an effective power distribution network design. In this paper, using a giant magnetoimpedance (GMI) probe for this purpose is studied. A side-band detection and demodulation system is built up to measure various time-domain waveforms

Fan Zhou; Songping Wu; David Pommerenke; Yoshiki Kayano; Hiroshi Inoue; Kenji Tan; Jun Fan

2010-01-01

351

Distributed Singlehop-Multihop Switch(DSMS) Routing Protocol for Wireless Sensor Networks  

Microsoft Academic Search

Wireless sensor n¿etworks (WSNs) constitute numerous microsensors that are energy limited. How to design the routing protocol to use energy with high efficiency is one of the most critical issues. In this paper, we propose a distributed singlehop-multihop switch (DSMS) routing protocol for wireless sensor networks. The main idea of DSMS is that the sensor area is divided into several

Jinfen Zhang; Kezhong Liu; Xing Yang; Yongqiang Cui

2009-01-01

352

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

353

Mechanisms of the ultrafast magnetization switching in bistable amorphous microwires  

NASA Astrophysics Data System (ADS)

Two magnetization reversal regimes were found in magnetically bistable Fe-rich microwires. The first one, exhibiting an almost linear dependence of the domain wall velocity v on magnetic field H reaching 1.7 km/s, is related to single DW propagation. The second essentially nonlinear regime is observed when H exceeds some critical magnetic field, HN, determined by the microwire inhomogeneities. At H >HN, new reverse domains can be nucleated, and consequently a tandem remagnetization mechanism can be realized. Ultrafast magnetization switching through additional nucleation centers created artificially can be applied in spintronic devices for enhancing their performance.

Ipatov, M.; Zhukova, V.; Zvezdin, A. K.; Zhukov, A.

2009-11-01

354

Optically-switched submillimeter-wave oscillator and radiator having a switch-to-switch propagation delay  

NASA Technical Reports Server (NTRS)

A submillimeter wave-generating integrated circuit includes an array of N photoconductive switches biased across a common voltage source and an optical path difference from a common optical pulse of repetition rate f sub 0 providing a different optical delay to each of the switches. In one embodiment, each incoming pulse is applied to successive ones of the N switches with successive delays. The N switches are spaced apart with a suitable switch-to-switch spacing so as to generate at the output load or antenna radiation of a submillimeter wave frequency f on the order of N f sub 0. Preferably, the optical pulse has a repetition rate of at least 10 GHz and N is of the order of 100, so that the circuit generates radiation of frequency of the order of or greater than 1 Terahertz.

Spencer, Michael G. (inventor); Maserjian, Joseph (inventor)

1995-01-01

355

Finite Ground Coplanar Waveguide Shunt MEMS Switches for Switched Line Phase Shifters  

NASA Technical Reports Server (NTRS)

Switches with low insertion loss and high isolation are required for switched line phase shifters and the transmit/receive switch at the front end of communication systems. A Finite Ground Coplanar (FGC) waveguide capacitive, shunt MEMS switch has been implemented on high resistivity Si. The switch has demonstrated an insertion loss of less than 0.3 dB and a return loss greater than 15 dB from 10 to 20, GHz. The switch design, fabrication, and characteristics are presented.

Ponchak, George E.; Simons, Rainee N.; Scardelletti, Maximillian; Varaljay, Nicholas C.

2000-01-01

356

Packet Switching Networks for Adaptive Optics Systems  

NASA Astrophysics Data System (ADS)

High Performance and Extremely Large Adaptive Optics systems place great demands on the data distribution and electronic control sub-systems. These servo-loop sub-systems acquire, process, and drive electro-optical/mechanical devices with large degrees of freedom. Two of the key parameters which affect AO loop performance are latency and jitter. To minimize these parameters, data must be efficiently acquired from sensors, processed into servo commands and then distributed to actuators. In addition to these critical path activities, there is also a requirement to "tap" into many points in the processing pipeline to monitor, characterize and perform high-level corrections. One answer to this communications dilemma is the use of a low-latency packet switched network. This paper illustrates the actual performance and flexibility of such a network by describing the high-performance system used at the Starfire Optical Range. The paper will then demonstrate the adaptability of this network architecture to accommodate the more complex communication requirements of extremely large AO systems.

Eager, R.

357

Voltage-impulse-induced non-volatile ferroelastic switching of ferromagnetic resonance for reconfigurable magnetoelectric microwave devices.  

PubMed

A critical challenge in realizing magnetoelectrics based on reconfigurable microwave devices, which is the ability to switch between distinct ferromagnetic resonances (FMR) in a stable, reversible and energy efficient manner, has been addressed. In particular, a voltage-impulse-induced two-step ferroelastic switching pathway can be used to in situ manipulate the magnetic anisotropy and enable non-volatile FMR tuning in FeCoB/PMN-PT (011) multiferroic heterostructures. PMID:23857709

Liu, Ming; Howe, Brandon M; Grazulis, Lawrence; Mahalingam, Krishnamurthy; Nan, Tianxiang; Sun, Nian X; Brown, Gail J

2013-09-20

358

Virus phenotype switching and disease progression in HIV-1 infection.  

PubMed Central

One of the phenotypic distinctions between different strains of human immunodeficiency virus type 1 (HIV-1) has to do with the ability to cause target cells to form large multinucleate bodies known as syncytia. There are two phenotypes according to this characterization: syncytium-inducing (SI) and non-syncytium-inducing (NSI). NSI strains are usually present throughout infection, while SI strains are typically seen at the beginning of the infection and near the onset of AIDS. The late emergence of SI strains is referred to as phenotype switching. In this paper we analyse the factors that lead to phenotype switching and contribute to the dynamics of disease progression. We show that a strong immune system selects for NSI strains while a weak immune system favours SI strains. The model explicitly accounts for the fact that CD4+ cells are both targets of HIV infection and crucial for activating immune responses against HIV In such a model, SI strains can emerge after a long and variable period of NSI dominated infection. Furthermore, versions of the model which do not explicitly account for HIV-specific, activated CD4+ cells do not exhibit phenotype switching, emphasizing the critical importance of this pool of cells. PMID:10693824

Callaway, D S; Ribeiro, R M; Nowak, M A

1999-01-01

359

Superconducting flux coupled fast switching device from YBCO films  

NASA Astrophysics Data System (ADS)

Applications of high-temperature superconducting (HTSC) materials, especially thin-film YBaCuO, to microelectronic devices have been limited by materials-related fabrication problems. Magnetic-flux-coupled devices are less limited by these problems but have not been widely explored. The innovation for this program was demonstration of a flux-coupled device that was: (1) simple to fabricate, (2) based on silicon substrates, (3) shows excellent flux-flow dynamics, and (4) can be implemented in switching or amplifying circuits. In Phase 1 we have demonstrated our potential for developing this device utilizing high critical-current YBCO thin films on yttria-stabilized zirconia (YSZ)-buffered Si substrates. Our devices are designed to take advantage of these new materials opportunities, are within realistic materials and fabrication constraints, and are projected to operate from dc to at least 10 GHz. The flux-flow devices (FFD) we have fabricated, include: externally-activated magnetic switch, superconducting transformer, and flux-flow (transistor-like) switch. The use of Si wafers not only allows high-quality quality films on large (or very thin) and inexpensive substrates, but also many design configurations with great potential for wafer-scale, hybrid integration with semiconductor electronics.

Fenner, David B.

1992-04-01

360

Stable nonlinear Mach-Zehnder fiber switch  

DOEpatents

An all-optical fiber switch is implemented within a short Mach-Zehnder interferometer configuration. The Mach-Zehnder switch is constructed to have a high temperature stability so as to minimize temperature gradients and other thermal effects which result in undesirable instability at the output of the switch. The Mach-Zehnder switch of the preferred embodiment is advantageously less than 2 cm in length between couplers to be sufficiently short to be thermally stable, and full switching is accomplished by heavily doping one or both of the arms between the couplers so as to provide a highly nonlinear region within one or both of the arms. A pump input source is used to affect the propagation characteristics of one of the arms to control the output coupling ratio of the switch. Because of the high nonlinearity of the pump input arm, low pump powers can be used, thereby alleviating difficulties and high cost associated with high pump input powers.

Digonnet, Michel J. F. (Palo Alto, CA); Shaw, H. John (Palo Alto, CA); Pantell, Richard H. (Menlo Park, CA); Sadowski, Robert W. (Camp Doha, KW)

1999-01-01

361

MEMS switches having non-metallic crossbeams  

NASA Technical Reports Server (NTRS)

A RF MEMS switch comprising a crossbeam of SiC, supported by at least one leg above a substrate and above a plurality of transmission lines forming a CPW. Bias is provided by at least one layer of metal disposed on a top surface of the SiC crossbeam, such as a layer of chromium followed by a layer of gold, and extending beyond the switch to a biasing pad on the substrate. The switch utilizes stress and conductivity-controlled non-metallic thin cantilevers or bridges, thereby improving the RF characteristics and operational reliability of the switch. The switch can be fabricated with conventional silicon integrated circuit (IC) processing techniques. The design of the switch is very versatile and can be implemented in many transmission line mediums.

Scardelletti, Maximillian C (Inventor)

2009-01-01

362

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

363

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.

2014-09-18

364

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

365

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

366

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

367

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

368

Optical switching system and method  

DOEpatents

An optically bistable device is disclosed. The device includes a uniformly thick layer of amorphous silicon to constitute a Fabry-Perot chamber positioned to provide a target area for a probe beam. The probe beam has a maximum energy less than the energy band gap of the amorphous semiconductor. In a preferred embodiment, a multilayer dielectric mirror is positioned on the Fabry-Perot chamber to increase the finesse of switching of the device. The index of refraction of the amorphous material is thermally altered to alter the transmission of the probe beam.

Ranganathan, Radha (N. Tonawanda, NY); Gal, Michael (Engadine, AU); Taylor, P. Craig (Salt Lake City, UT)

1992-01-01

369

Laser-triggered vacuum switch  

DOEpatents

A laser-triggered vacuum switch has a material such as a alkali metal halide on the cathode electrode for thermally activated field emission of electrons and ions upon interaction with a laser beam, the material being in contact with the cathode with a surface facing the discharge gap. The material is preferably a mixture of KCl and Ti powders. The laser may either shine directly on the material, preferably through a hole in the anode, or be directed to the material over a fiber optic cable. 10 figs.

Brannon, P.J.; Cowgill, D.F.

1990-12-18

370

A new switched power linac structure  

SciTech Connect

A new pulse power structure has been described that utilizes an easily accessible rectilinear switch. The new structure is more ''forgiving'' (as far as risetime is concerned) than the radial line transformer, and contains fewer switching structures/unit length. The combination of the new structure with the switch proposed seems to offer interesting possibilities for a future linear collider. 13 refs., 6 figs., 2 tabs.

Villa, F.

1989-03-01

371

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

372

Switching X-Ray Tubes Remotely  

NASA Technical Reports Server (NTRS)

Convenient switch and relay circuit reduces risk of accidents. Proposed switching circuit for x-ray inspection system enables operator to change electrical connections to x-ray tubes remotely. Operator simply flips switch on conveniently-located selector box to change x-ray heads. Indicator lights on selector box show whether 160 or 320-kV head connected. Relays in changeover box provides proper voltages and coolants. Chance of making wrong connections and damaging equipment eliminated.

Bulthuis, Ronald V.

1990-01-01

373

Defense switched network technology and experiments program  

Microsoft Academic Search

This report documents work performed during FY 1983 on the DCA-sponsored Defense Switched Network Technology and Experiments Program. The areas of work reported are: (1) development of routing algorithms for application in the Defense Switched Network (DSN); (2) instrumentation and integration of the Experimental Integrated Switched Network (EISN) test facility; (3) development and test of data communication techniques using DoD-standard

C. J. Weinstein

1983-01-01

374

Gas-phase pulsed power switches  

Microsoft Academic Search

A review of plasma science that is related to gas-phase pulsed power switching is presented. Switch plasmas include uniform glow-type plasmas and constricted arc-type plasmas, and the science involves understanding transport processes in hydrogen, helium, metal vapor, and other plasmas, and electrode processes including limitations related to cathode emission and sheaths. Gas-phase pulsed power switches include spark gaps, vacuum, metal

Martin A. Gundersen

1991-01-01

375

Fairness enforcement in switch on event multithreading  

Microsoft Academic Search

The need to reduce power and complexity will increase the interest in Switch On Event multithreading (coarse-grained multithreading). Switch On Event multithreading is a low-power and low-complexity mechanism to improve processor throughput by switching threads on execution stalls. Fairness may, however, become a problem in a multithreaded processor. Unless fairness is properly handled, some threads may starve while others consume

Ron Gabor; Shlomo Weiss; Avi Mendelson

2007-01-01

376

Array E PCU Failure Modes, Effects and Criticality Analysis ,...  

E-print Network

PREDICTION The reliability prediction for the Power Conditioning Unit operating in standby redundant the Failure Modes, Effect and Criticality Analysis on the Bendix designed Power Con- ditioning Unit- ditioning Unit. The redundant circuits are in power standby. 2.I SWITCHING CIRCUIT Output voltages

Rathbun, Julie A.

377

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

378

Morphological priming survives a language switch.  

PubMed

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 by morphologically related primes in both non-switch and switch blocks with equal magnitude. These results contrast some assumptions of sustained reactive inhibition models. However, models that do not assume bilinguals having to reactively suppress all activation of the non-target language can account for these data. PMID:22743054

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

2012-09-01

379

All optical switching in henna thin film  

NASA Astrophysics Data System (ADS)

The optical nonlinearity in henna (Lawson (2- hydroxyl-1,4 naphthoquinone) film was utilized to demonstrate all optical switching. The nonlinear absorption of the henna film was calculated by measuring the transmission of the laser beam ( ? = 488 nm) as a function of incident light intensities. The observed nonlinear absorption is attributed to a two-photon absorption process. The pump and probe technique was used to demonstrate all optical switching. The switching characteristics can be utilized to generate all-optical logic gates such as simple inverter switches (NOT) NOR, AND NAND logic functions.

Henari, Fryad Z.; Jasim, Khalil E.

2013-08-01

380

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

381

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

382

Switching and control in stochastic double gyres  

NASA Astrophysics Data System (ADS)

We consider the problem of stochastic transport in a driven double gyre with time dependent basin boundaries. Noise typically creates almost invariant sets, or meta-stable states. Mixing occurs between these states as a result of stochastic transport. Using stochastic Markov operator theory, we approximate the almost invariant sets and regions with most probable switching. These sets define regions for which control perturbations can facilitate or prevent switching. Switching rates using these control schemes will be derived and compared to numerical simulations. We show how scaling laws change exponentially in the presence of control when compared to the natural switching rate.

Billings, Lora; Forgoston, Eric; Schwartz, Ira

2010-03-01

383

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

384

The Application of High Temperature Superconducting Materials to Power Switches  

E-print Network

Superconducting switches may find application in superconducting magnet systems that require energy extraction. Such superconducting switches could be bypass-switches that are operated in conjunction with a parallel resistor or dump-switches where all of the energy is dissipated in the switch itself. Bypass-switches are more suited to higher energy circuits as a portion of the energy can be dissipated in the external dump resistor. Dump- switches require less material and triggering energy as a lower switch resistance is needed to achieve the required total dump resistance. Both superconducting bypass-switches and superconducting dump-switches can be ther- mally activated. Switching times that are comparable to those obtained with mechanical bypass-switch systems can be achieved using a co-wound heater that is powered by a ca- pacitor discharge. Switches that have fast thermal diffusion times through the insulation can be modelled as a lumped system whereas those with slow thermal diffusion times were modelle...

March, S A; Ballarino, A

2009-01-01

385

Task switching in traumatic brain injury relates to cortico-subcortical integrity.  

PubMed

Suppressing and flexibly adapting actions are a critical part of our daily behavioral repertoire. Traumatic brain injury (TBI) patients show clear impairments in this type of action control; however, the underlying mechanisms are poorly understood. Here, we tested whether white matter integrity of cortico-subcortical pathways could account for impairments in task switching, an important component of executive functioning. Twenty young adults with TBI and eighteen controls performed a switching task requiring attention to global versus local stimulus features. Diffusion weighted images were acquired and whole brain tract-based spatial statistics (TBSS) were used to explore where white matter damage was associated with switching impairment. A crossing fiber model and probabilistic tractography further identified the specific fiber populations. Relative to controls, patients with a history of TBI had a higher switch cost and were less accurate. The TBI group showed a widespread decline in fractional anisotropy (FA) throughout the TBSS skeleton. FA in the superior corona radiata showed a negative relationship with switch cost. More specifically, this involved cortico-subcortical loops with the (pre-)supplementary motor area and superior frontal gyrus. These findings provide evidence for damage to frontal-subcortical projections in TBI, which is associated with task switching impairments. PMID:23913872

Leunissen, Inge; Coxon, James P; Caeyenberghs, Karen; Michiels, Karla; Sunaert, Stefan; Swinnen, Stephan P

2014-05-01

386

The mechanism of electroforming of metal oxide memristive switches.  

PubMed

Metal and semiconductor oxides are ubiquitous electronic materials. Normally insulating, oxides can change behavior under high electric fields--through 'electroforming' or 'breakdown'--critically affecting CMOS (complementary metal-oxide-semiconductor) logic, DRAM (dynamic random access memory) and flash memory, and tunnel barrier oxides. An initial irreversible electroforming process has been invariably required for obtaining metal oxide resistance switches, which may open urgently needed new avenues for advanced computer memory and logic circuits including ultra-dense non-volatile random access memory (NVRAM) and adaptive neuromorphic logic circuits. This electrical switching arises from the coupled motion of electrons and ions within the oxide material, as one of the first recognized examples of a memristor (memory-resistor) device, the fourth fundamental passive circuit element originally predicted in 1971 by Chua. A lack of device repeatability has limited technological implementation of oxide switches, however. Here we explain the nature of the oxide electroforming as an electro-reduction and vacancy creation process caused by high electric fields and enhanced by electrical Joule heating with direct experimental evidence. Oxygen vacancies are created and drift towards the cathode, forming localized conducting channels in the oxide. Simultaneously, O(2-) ions drift towards the anode where they evolve O(2) gas, causing physical deformation of the junction. The problematic gas eruption and physical deformation are mitigated by shrinking to the nanoscale and controlling the electroforming voltage polarity. Better yet, electroforming problems can be largely eliminated by engineering the device structure to remove 'bulk' oxide effects in favor of interface-controlled electronic switching. PMID:19423925

Joshua Yang, J; Miao, Feng; Pickett, Matthew D; Ohlberg, Douglas A A; Stewart, Duncan R; Lau, Chun Ning; Williams, R Stanley

2009-05-27

387

New Optical Switching Fabric Architecture Incorporating Load Balanced Parallel Rapidly Switching All-Optical  

E-print Network

New Optical Switching Fabric Architecture Incorporating Load Balanced Parallel Rapidly Switching All-Optical Variable Delay Buffer Arrays Haijun Yang and S. J. Ben Yoo Department of Electrical-8428 Email: yoo@ece.ucdavis.edu Abstract: We propose a novel optical switching fabric architecture employing

Kolner, Brian H.

388

A New Optical Switching Fabric Architecture Incorporating Rapidly Switching All-Optical Variable Delay Buffers  

E-print Network

1 A New Optical Switching Fabric Architecture Incorporating Rapidly Switching All-Optical Variable@ece.ucdavis.edu Abstract: This paper discusses new optical packet switch architectures utilizing all-optical variable delay the simulation performance of the proposed architectures. ? 2004 Optical Society of America OCIS codes: (060

Kolner, Brian H.

389

The UniMIN Switch Architecture for Large-Scale  

Microsoft Academic Search

A general expansion architecture is proposed that can be used in building large-scale switches using any type of asynchronous transfer mode (ATM) switch. The proposed universal multistage interconnection network (UniMIN) switch is composed of a buffered distribution network (DN) and a column of output switch modules (OSM's), which can be any type of ATM switch. ATM cells are routed to

ATM Switches

390

Critical Viewing: Stimulant to Critical Thinking.  

ERIC Educational Resources Information Center

This document is intended to improve the critical viewing skills and increase the understanding and appreciation of what is viewed. Included are the chapters: (1) "Critical Thinking: The Parts of an Argument," intended to develop a process to help a person judge arguments in what is read, seen, and heard; (2) "Critical Viewing: Concepts, Skills,…

O'Reilly, Kevin; Splaine, John

391

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

392

Language Switching in the Production of Phrases  

ERIC Educational Resources Information Center

The language switching task has provided a useful insight into how bilinguals produce language. So far, however, the studies using this method have been limited to lexical access. The present study provides empirical evidence on language switching in the production of simple grammar structures. In the reported experiment, Polish-English unbalanced…

Tarlowski, Andrzej; Wodniecka, Zofia; Marzecova, Anna

2013-01-01

393

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

394

Differentiation-Induced Switching Costs and Poaching  

Microsoft Academic Search

We show that the presence of sufficiently significant switching costs, which are increasing in the degree of product differentiation, generates an equilibrium configuration with maximal differentiation within the framework of a Hotelling model with linear transportation costs. The equilibrium with maximal differentiation offers a formalization of the idea that competing firms have noncooperative incentives to establish maximal switching cost barriers.

Thomas Gehrig; Rune Stenbacka

2004-01-01

395

Micromechanical membrane switches for microwave applications  

Microsoft Academic Search

This paper proposes the fabrication of low-cost, low-loss microwave switches using thin metal membranes actuated by electrostatic fields. Measurement of switch test structures and modeling indicates that these devices have a potential 1000 to 2000-GHz figure-of-merit. Various aspects of fabrication, design, performance, and application of these devices are discussed

Chuck Goldsmith; Tsen-Hwang Lin; B. Powers; Wen-Rong Wu; B. Norvell

1995-01-01

396

Miniature mercury contact switch for chromatographic applications  

Microsoft Academic Search

Temperature control for the components of gas chromatographic instrumentation is achieved in a variety of ways. Depending on the level of accuracy required, contact switches, thermocouples, thermistors, and resistance devices are commonly used to control the power applied to heaters. Thermistors and resistance devices are well suited to proportional control of the power input. Contact switches and thermocouples are easily

Thomas J. Bruno; Jerry G. Shepherd

1986-01-01

397

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)

398

Microelectromechanical Switches for Phased Array Antennas  

NASA Technical Reports Server (NTRS)

Preliminary results are presented on the fabrication and testing of a MicroElectro-Mechanical (MEM) microstrip series switch. This switch is being developed for use in a K-band phased array antenna that NASA will use for communication links in its Earth orbiting satellites. Preliminary insertion loss and isolation measurements are presented.

Ponchak, George E.; Simons, Rainee N.; Scardelletti, Maximillian; Varaljay, Nicholas C.

2000-01-01

399

Proceedings of the switched power workshop  

SciTech Connect

These proceedings contain most of the presentations given at a workshop on the current state of research in techniques for switched power acceleration. The proceedings are divided, as was the workshop itself, into two parts. Part 1, contains the latest results from a number of groups active in switched power research. The major topic here is a method for switching externally supplied power onto a transmission line. Advocates for vacuum photodiode switching, solid state switching, gas switching, and synthetic pulse generation are all presented. Other important areas of research described in this section concern: external electrical and laser pulsing systems; the properties of the created electromagnetic pulse; structures used for transporting the electromagnetic pulse to the region where the electron beam is located; and possible applications. Part 2 of the proceedings considers the problem of designing a high brightness electron gun using switched power as the power source. This is an important first step in demonstrating the usefulness of switched power techniques for accelerator physics. In addition such a gun could have immediate practical importance for advanced acceleration studies since the brightness could exceed that of present sources by several orders of magnitude. I would like to take this opportunity to thank Kathleen Tuohy and Patricia Tuttle for their assistance in organizing and running the workshop. Their tireless efforts contribute greatly to a very productive meeting.

Fernow, R.C. (ed.)

1988-01-01

400

High-Performance Switched Reluctance Brushless Drives  

Microsoft Academic Search

Switched reluctance (SR) drives offer the advantages of simple and robust motor construction, high speeds, high overall efficiencies over a wide operating range of torque and speed, simple power converter circuits with a reduced number of switches, and excellent controllability. The basis of these claims is explained. The history of the SR system, in particular the extensive research at Nottingham

William F. Ray; Peter J. Lawrenson; Rex M. Davis; J. Michael Stephenson; Norman N. Fulton; Roy J. Blake

1986-01-01

401

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

402

FPGA-Controlled Switch-Reconfigured Antenna  

Microsoft Academic Search

In this letter, p-i-n diodes are used as switches to connect and disconnect four patch sections to a midsection of a planar antenna. The antenna system is connected to the field programmable gate array (FPGA) board controlling the activation of these switches. The antenna with the incorporated diodes is designed, installed, and measured. The methodology for using an FPGA to

Severn Shelley; Joseph Costantine; Christos G. Christodoulou; Dimitris E. Anagnostou; James C. Lyke

2010-01-01

403

Optically triggered pseudospark switches with metal photocathodes  

Microsoft Academic Search

Pseudospark switches have been successfully employed in a variety of pulsed power applications including high power electron beam sources, high power microwaves, and transient plasma ignition for pulsed detonation engines [1–3]. Investigation of magnesium, copper and molybdenum photocathode candidates for optically triggered pseudospark switches, also called back-lighted thyratrons (BLTs), has shown that magnesium has a higher quantum efficiency (up to

Esin B Sozer; Chunqi Jiang; Martin A. Gundersen

2011-01-01

404

A sub-1-volt nanoelectromechanical switching device.  

PubMed

Nanoelectromechanical (NEM) switches have received widespread attention as promising candidates in the drive to surmount the physical limitations currently faced by complementary metal oxide semiconductor technology. The NEM switch has demonstrated superior characteristics including quasi-zero leakage behaviour, excellent density capability and operation in harsh environments. However, an unacceptably high operating voltage (4-20 V) has posed a major obstacle in the practical use of the NEM switch in low-power integrated circuits. To utilize the NEM switch widely as a core device component in ultralow power applications, the operation voltage needs to be reduced to 1 V or below. However, sub-1 V actuation has not yet been demonstrated because of fabrication difficulties and irreversible switching failure caused by surface adhesion. Here, we report the sub-1 V operation of a NEM switch through the introduction of a novel pipe clip device structure and an effective air gap fabrication technique. This achievement is primarily attributed to the incorporation of a 4-nm-thick air gap, which is the smallest reported so far for a NEM switch generated using a 'top-down' approach. Our structure and process can potentially be utilized in various nanogap-related applications, including NEM switch-based ultralow-power integrated circuits, NEM resonators, nanogap electrodes for scientific research and sensors. PMID:23178336

Lee, Jeong Oen; Song, Yong-Ha; Kim, Min-Wu; Kang, Min-Ho; Oh, Jae-Sub; Yang, Hyun-Ho; Yoon, Jun-Bo

2013-01-01

405

Nanosecond, electrical triggering of water switches  

Microsoft Academic Search

Spark gaps, which use water as a switching medium, allow fast closing and high repetition rate operation for high power and high voltage switching. They are usually operated in the pulse-charging mode and have a large jitter. To reduce the jitter, a trigger electrode with positive polarity is used to initiate breakdown between a negative high voltage electrode and a

Shu Xiao; K. H. Schoenbach; R. P. Joshi; J. F. Kolb

2009-01-01

406

49 CFR 213.135 - Switches.  

Code of Federal Regulations, 2011 CFR

...worn switch points shall be repaired or replaced. Metal flow shall be removed to insure proper closure. (i) Tongue & Plain Mate switches, which by design exceed Class 1 and excepted track maximum gage limits, are permitted in Class 1 and excepted...

2011-10-01

407

49 CFR 213.135 - Switches.  

Code of Federal Regulations, 2014 CFR

...worn switch points shall be repaired or replaced. Metal flow shall be removed to insure proper closure. (i) Tongue & Plain Mate switches, which by design exceed Class 1 and excepted track maximum gage limits, are permitted in Class 1 and excepted...

2014-10-01

408

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

409

Rainflow Matrix for Switching Random Loads  

Microsoft Academic Search

A switching random load, which is a sequential mixture of different random subloads, is modelled by using a hidden Markov model. The basic assumptions are that the turning points of each subload is modelled by a Markov chain, and that the switching between the subloads follow a Markov chain. An algorithm for computing the rainflow matrix for such a load

Pär Johannesson

1998-01-01

410

Stability of switched and hybrid systems  

Microsoft Academic Search

This paper outlines some preliminary work on the stability analysis of switched and hybrid systems. The hybrid systems considered are those that combine continuous dynamics, represented by differential or difference equations, with finite dynamics usually thought of as being a finite automaton. Here, we concentrate on the continuous dynamics and model the finite dynamics as switching among finitely many continuous

M. S. Branicky

1994-01-01

411

Figure of Merit of Electronic Switching Devices  

Microsoft Academic Search

To specify the amplifying properties of various active electronic devices the gain-bandwidth product GNB is commonly used. The aim of this paper is to show that for active electronic (not electromagnetic) devices working in switching circuits, another figure of merit (analogous to the reciprocal of the gain-bandwidth product) could be derived from a simple model of an electronic switch.

Otakar A. Horna

1965-01-01

412

Design of a linear switched reluctance machine  

Microsoft Academic Search

A standard design procedure for a single-sided and longitudinal flux-based linear switched reluctance machine is developed in this paper. The proposed design procedure utilizes the rotating switched reluctance machine design by converting the specifications of the linear machine into the equivalent rotary machine. The machine design is carried out in the rotary domain, which is then transformed back into the

Byeong-Seok Lee; Han-Kyung Bae; Praveen Vijayraghavan; R. Krishnan

2000-01-01

413

Design of a linear switched reluctance machine  

Microsoft Academic Search

A standard design procedure for a single sided and longitudinal flux based linear switched reluctance machine is developed in this paper. The proposed design procedure utilises the rotating switched reluctance machine design by converting the specifications of the linear machine in to the equivalent rotary machine. The machine design is carried out in the rotary domain which is then transformed

Byeong-Seok Lee; Han-Kyung Bae; Praveen Vijayraghavan; R. Krishnan

1999-01-01

414

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

415

Queueing analysis for multicast packet switching  

Microsoft Academic Search

The development of broadband transmission and ATM switching technologies opens up an opportunity for providing high bit-rate multipoint and multimedia services such as video conferencing. Also, wireless communication has the inherent advantage of multicast transmission and may be used for multipoint information services. The authors consider multicast packet switching for which an input may send the same packet to many

Joseph Y. Hui; Thomas Renner

1994-01-01

416

14 CFR 27.1361 - Master switch.  

Code of Federal Regulations, 2010 CFR

...so that they remain energized after the switch is opened, if they are protected by circuit protective devices, rated at five amperes or less, adjacent to the electric power source. (c) The master switch or its controls must be installed so that the...

2010-01-01

417

Door Sensors for Automatic Light Switching System  

Microsoft Academic Search

Door sensor for automatic lighting control is widely being developed for energy saving and security purposes. An infrared door sensor based on electrical and electronics combinational circuit technology is used to develop the automatic light switching system. The automatic light switching system will lead to energy saving and efficient energy usage which could benefit every single individual. Furthermore, the system

Ranjit Singh Sarban Singh; Ahamed Fayeez Tuani Ibrahim; Wong Yan Chiew

2009-01-01

418

Low contact resistance series MEMS switches  

Microsoft Academic Search

This paper reports on the design and development of a novel DC-contact MEMS switch for microwave applications. The switching operation utilizes two different forces: electrostatic and stress-induced forces. The former is employed as the actuation force, while the latter is responsible for achieving the actual DC contact. In particular, when no bias voltage is applied, the deformation of a metallic

Dimitrios Peroulis; Kamal Sarabandi; Linda P. B. Katehi

2002-01-01

419

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

420

Al-doped ZnO as a switching layer for transparent bipolar resistive switching memory  

NASA Astrophysics Data System (ADS)

In this report, we employ an Al-doped ZnO (AZO) layer as a resistive switching layer for transparent resistive switching random access memory devices. An Indium-Tin-Oxide (ITO)/AZO/ITO/glass device exhibits a transmittance of ˜80% (including a glass substrate) in the visible wavelength region and demonstrates reliable bipolar resistive switching behavior over d.c. 300 sweeping cycles with a low operation voltage and a very low variation in the switching threshold voltage. These results indicate that the AZO film is a promising transparent resistive switching layer.

Yu, Hyeongwoo; Kim, Minho; Kim, Yoonsu; Lee, Jeongsup; Kim, Kyoung-Kook; Choi, Sang-Jun; Cho, Soohaeng

2014-03-01

421

Theoretical study of thermally activated magnetization switching under microwave assistance: Switching paths and barrier height  

NASA Astrophysics Data System (ADS)

Energy barrier height for magnetization switching is theoretically studied for a system with uniaxial anisotropy in a circularly polarized microwave magnetic field. A formulation of the Landau-Lifshitz-Gilbert equation in a rotating frame introduces an effective energy that includes the effects of both the microwave field and static field. This allows the effective-energy profiles to rigorously describe the switching paths and corresponding barrier height, which govern thermally activated magnetization switching under microwave assistance. We show that fixed points and limit cycles in the rotating frame lead to various switching paths and that under certain conditions, switching becomes a two-step process with an intermediate state.

Suto, H.; Kudo, K.; Nagasawa, T.; Kanao, T.; Mizushima, K.; Sato, R.; Okamoto, S.; Kikuchi, N.; Kitakami, O.

2015-03-01

422

Digital SPC switching technology: Foreign technology assessment  

NASA Astrophysics Data System (ADS)

This paper provides a foreign technology assessment of digital switching technology. Leading suppliers of digital switching technology are identified; although the United States holds a large part of the market, major companies in France, Sweden, Japan, the U.K., and Germany are also important. These countries, along with Belgium and Canada, are the most innovative and technically advanced. A listing is provided of transfers of digital switching technology to non-COCOM countries through licensing and joint ventures which reflects the widespread dissemination of this technology. Detailed technical specifications are provided for selected digital switching systems worldwide. The report concludes that considering the degree to which the technology is in place, that control of digital switching technology may not be feasible.

Fischman, Kurt; Jorstad, Norman D.

1990-12-01

423

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

424

Laser with optically driven Q-switch  

NASA Technical Reports Server (NTRS)

An optically driven interactive Q-switch, i.e., a Q-switch that responds to a short pulse of light, for example, from external light-emitting diodes (LEDs) or diode lasers, is provided for producing an output laser pulse from electronic energy stored in a laser medium. Q-switching is thus achieved on demand by electrically pulsing the light source to produce a pulse of light directed onto a Q-switch medium in the laser cavity. Electronic control of the light pulse from the external source will thus provide not only efficient Q-switching frequency but also independent control of output laser pulse width with a fast rise time for each output laser pulse.

Hemmati, Hamid (inventor)

1993-01-01

425

Laser with optically driven Q-switch  

NASA Technical Reports Server (NTRS)

An optically driven interactive Q-switch, i.e., a Q-switch that responds to a short pulse of light, for example, from external light-emitting diodes (LED's) or diode lasers, is provided for producing an output laser pulse from electronic energy stored in a laser medium. Q-switching is thus achieved on demand by electrically pulsing the light source to produce a pulse of light directed onto a Q-switch medium in the laser cavity. Electronic control of the light pulse from the external source will thus provide not only efficient Q-switching frequency but also independent control of output laser pulse width with a fast rise time for each output laser pulse.

Hemmati, Hamid (inventor)

1995-01-01

426

Instabilities and switching of magnetic grains  

NASA Astrophysics Data System (ADS)

Recent advances in magnetic recording densities have pushed recording rates close to the limit (a few nanoseconds) below which quasistatic approaches to switching are invalid. At present recording rates it is important to understand the details of the switching dynamics. Coherent switching modes of a single, relatively small, grain have been extensively studied in the past. For certain larger grains, or in the presence of interaction between grains, it has been shown numerically that the switching is incoherent. In this work we have studied the role of spin waves in the switching process both by numerical micromagnetic modeling, and using simple but fairly realistic analytic treatment. We identified an instability region for the spin wave reversal mode. This allows us to understand the previous numerical results, and the role of the physical parameters in the spin wave reversal mechanism.

Benakli, Mourad; Visscher, Pieter B.

2000-03-01

427

A Mechanical Switch Using Spectral Microshifts  

NASA Astrophysics Data System (ADS)

Among the simplest fiber optic sensors, are those which operate in a binary fashion; they were the first sensor types to be developed. Early experiments with fiber bundles and shutters produced demonstrations of, for example, displacement sensors. Typical applications range from position sensing for aircraft landing gear to counting objects on a production line. Because they frequently replace electrical snap action switches, binary sensors are generally called optical switches. Optical switch applications account for a much larger market than the more complex analog measurements discussed in the balance of this volume. This paper presents an optical switch concept that uses a single fiber and is tolerant of back reflections. The sensor element is a low finesse Fabry-Perot pressure sensor which replaces the electrical contact in a conventional snap action switch.

Mitchell, Gordon L.; Saaski, Elric W.; Hartl, James C.

1989-02-01

428

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

429

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

430

Subpicosecond photonic switching based on bacteriorhodopsin  

NASA Astrophysics Data System (ADS)

All-optical data processing is the most promising approach for further improvement in data trafficking. We present a subpicosecond photonic switch where the active role is performed by the chromoprotein bacteriorhodopsin. The changes in the refractive index that accompany the steps of the photocycle of bacteriorhodopsin are used for all optical switching in appropriate integrated optical devices. We use grating coupled planar waveguides and the coupling is modulated by the light induced refractive index changes of bacteriorhodopsin. The switching is demonstrated in ultrafast pump-probe experiments. Different transitions of the photocycle are explored for switching applications. We show that by using the bR to I transition subpicosecond switching can be readily achieved. The approach is a basis for protein-based integrated optical devices, eventually leading to a conceptual revolution in telecommunications technologies.

Ormos, Pal; Fabian, Laszlo; Heiner, Zsuzsanna; Mero, Mark; Kiss, Miklos; Wolff, Elmar; Osvay, Karoly; der, Andras

2011-03-01

431

Nanoscale resistive switching devices: mechanisms and modeling  

NASA Astrophysics Data System (ADS)

Resistive switching devices (also termed memristive devices or memristors) are two-terminal nonlinear dynamic electronic devices that can have broad applications in the fields of nonvolatile memory, reconfigurable logic, analog circuits, and neuromorphic computing. Current rapid advances in memristive devices in turn demand better understanding of the switching mechanism and the development of physics-based as well as simplified device models to guide future device designs and circuit-level applications. In this article, we review the physical processes behind resistive switching (memristive) phenomena and discuss the experimental and modeling efforts to explain these effects. In this article three categories of devices, in which the resistive switching effects are driven by cation migration, anion migration, and electronic effects, will be discussed. The fundamental driving forces and the stochastic nature of resistive switching will also be discussed.

Yang, Yuchao; Lu, Wei

2013-10-01

432

Fast optically triggered superconducting opening switches  

NASA Astrophysics Data System (ADS)

High-Tc superconducting thin films are used to design a new type of opening switch. The superconducting film screens the magnetic flux linkage between the primary and the secondary coils of a transformer. Short laser pulses (150 ps) are used to trigger the transition of the superconductor to its normal state allowing the flux produced by a primary current to couple to the secondary. This results in an induced voltage pulse in the load across the secondary and corresponds to the open state of the switch. Experiments have confirmed the feasibility of this inductively coupled switch, and rise times of 50 ns have been observed for the secondary voltage pulse. The switch has the potential for high current (1 kA) and fast switching times (< 1 ns).

Gupta, Deepnarayan; Donaldson, William R.; Kadin, Alan M.

1993-06-01

433

Benchtop fabrication of memristive atomic switch networks.  

PubMed

Recent advances in nanoscale science and technology provide possibilities to directly self-assemble and integrate functional circuit elements within the wiring scheme of devices with potentially unique architectures. Electroionic resistive switching circuits comprising highly interconnected fractal electrodes and metal-insulator-metal interfaces, known as atomic switch networks, have been fabricated using simple benchtop techniques including solution-phase electroless deposition. These devices are shown to activate through a bias-induced forming step that produces the frequency dependent, nonlinear hysteretic switching expected for gapless-type atomic switches and memristors. By eliminating the need for complex lithographic methods, such an approach toward device fabrication provides a more accessible platform for the study of ionic resistive switches and memristive systems. PMID:24734692

Sillin, Henry O; Sandouk, Eric J; Avizienis, Audrius V; Aono, Masakazu; Stieg, Adam Z; Gimzewski, James K

2014-04-01

434

Micromechanical Electrostatic K-Band Switches Student Paper  

E-print Network

Micromechanical Electrostatic K-Band Switches Student Paper Sergio Pacheco, Clark T. Nguyen -- Two novel designs of micromechanical capaci- tive switches using serpentine and cantilever springs of intricate three-dimensional structures with great reliabil- ity. Micromechanical switches were first

Nguyen, Clark T.-C.

435

47 CFR 32.6211 - Non-digital switching expense.  

Code of Federal Regulations, 2010 CFR

...Expense Accounts § 32.6211 Non-digital switching expense. This account shall include expenses associated with non-digital electronic switching and electro-mechanical switching. [67 FR 5695, Feb. 6,...

2010-10-01

436

47 CFR 32.6211 - Non-digital switching expense.  

Code of Federal Regulations, 2011 CFR

...Expense Accounts § 32.6211 Non-digital switching expense. This account shall include expenses associated with non-digital electronic switching and electro-mechanical switching. [67 FR 5695, Feb. 6,...

2011-10-01

437

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

438

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

439

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.

440

Transparent electrode for optical switch  

DOEpatents

A low pressure gas electrode utilizing ionized gas in a glow discharge regime forms a transparent electrode for electro-optical switches. The transparent electrode comprises a low pressure gas region on both sides of the crystal. When the gas is ionized, e.g., by a glow discharge in the low pressure gas, the plasma formed is a good conductor. The gas electrode acts as a highly uniform conducting electrode. Since the plasma is transparent to a high energy laser beam passing through the crystal, the electrode is a transparent electrode. A crystal exposed from two sides to such a plasma can be charged up uniformly to any desired voltage. The plasma can be created either by the main high voltage pulser used to charge up the crystal or by auxiliary discharges or external sources of ionization. A typical configuration utilizes 10 torr argon in the discharge region adjacent to each crystal face.

Goldhar, Julius (San Ramon, CA); Henesian, Mark A. (Livermore, CA)

1986-01-01

441

Assessing Critical Thinking.  

ERIC Educational Resources Information Center

Critical thinking is a socially constructed, contextual process not well measured by standardized tests. Better, locally grounded methods are pre/posttest (scenario building), experiential (critical practice audit), behavioral (critical debate), and conversational (storytellers and detectives). (SK)

Brookfield, Stephen D.

1997-01-01

442

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

443

Critical Materials Institute  

SciTech Connect

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

2013-01-09

444

Switch to second-line ART in West African routine care: incidence and reasons for switching.  

PubMed

In sub-Saharan Africa, while antiretroviral therapy (ART) becomes widely available, access to biological measurements to monitor patients under ART remains scarce, making the management of ART difficult. We described the management of switching to second-line ART where HIV care is provided mainly in secondary health-care structures, in the region of Segou, Mali. Of 865 patients, followed under ART for a median time of 15 months, 40 switched to second-line ART (3.3 switches/100 person years). Reason for switching was failure in 18 patients (after 21 months in median) and severe intolerance in 13 (after three months in median). Switching to second-line ART occurred earlier when motivated by intolerance than by failure. The low rate of switch compares well with other studies, but was low compared to the expected rate of failure, and may indicate that physicians are reluctant to switch ART when treatment options are limited. PMID:21218279

Landier, Jordi; Akonde, Alain; Pizzocolo, Cecilia; Haidara, Ibrahim; Drabo, Mahamadou; Pizarro, Louis; Fontanet, Arnaud; Katlama, Christine; Madec, Yoann

2011-01-01

445

Actively Q-switched erbium-doped fiber ring laser with a nanosecond ceramic optical switch  

NASA Astrophysics Data System (ADS)

An actively Q-switched erbium-doped fiber laser with a fiber-pigtailed nanosecond ceramic optical switch is experimentally investigated in this paper. Firstly, the ceramic optical switch was systematically characterized. Then, it was used to actively Q-switch an all-fiber erbium-doped fiber ring laser. Stable Q-switching laser pulses with a repetition rate from 2?kHz–40?kHz were achieved. The minimum pulse width was measured to be ~25?ns at 2?kHz when pumped at 150?mW, and the corresponding maximum peak power was ~2.9?W. Multi-peak pulses were observed at low repetition rates and the reasons for these were analyzed. This study shows that a nanosecond ceramic switch can be used as a good Q switch due to its low insertion loss, high on/off ratio, ultrafast response, and low electrical power consumption.

Lü, Xiaoying; Han, Qun; Liu, Tiegen; Chen, Yaofei; Ren, Kun

2014-11-01

446

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

447

Metal contact reliability of RF MEMS switches  

NASA Astrophysics Data System (ADS)

It is well-recognized that MEMS switches, compared to their more traditional solid state counterparts, have several important advantages for wireless communications. These include superior linearity, low insertion loss and high isolation. Indeed, many potential applications have been investigated such as Tx/Rx antenna switching, frequency band selection, tunable matching networks for PA and antenna, tunable filters, and antenna reconfiguration. However, none of these applications have been materialized in high volume products to a large extent because of reliability concerns, particularly those related to the metal contacts. The subject of the metal contact in a switch was studied extensively in the history of developing miniaturized switches, such as the reed switches for telecommunication applications. While such studies are highly relevant, they do not address the issues encountered in the sub 100?N, low contact force regime in which most MEMS switches operate. At such low forces, the contact resistance is extremely sensitive to even a trace amount of contamination on the contact surfaces. Significant work was done to develop wafer cleaning processes and storage techniques for maintaining the cleanliness. To preserve contact cleanliness over the switch service lifetime, several hermetic packaging technologies were developed and their effectiveness in protecting the contacts from contamination was examined. The contact reliability is also very much influenced by the contact metal selection. When pure Au, a relatively soft metal, was used as the contact material, significant stiction problems occurred when clean switches were cycled in an N II environment. In addition, various mechanical damages occurred after extended switching cycling tests. Harder metals, while more resistant to deformation and stiction, are more sensitive to chemical reactions, particularly oxidation. They also lead to higher contact resistance because of their lower electrical conductivity and smaller real contact areas at a given contact force. Contact reliability issues could also be tackled by improving mechanical designs. A novel collapsing switch capable of generating large contact forces (>300?N) was shown to be less vulnerable to contamination and stiction.

Ma, Qing; Tran, Quan; Chou, Tsung-Kuan A.; Heck, John; Bar, Hanan; Kant, Rishi; Rao, Valluri

2007-01-01

448

Three-Phase Soft-Switching Inverter With Minimum Components  

Microsoft Academic Search

In this paper, a novel three-phase soft-switching in- verter is presented. The inverter-switch turn on and turn off are performed under zero-voltage switching condition. This inverter has only one auxiliary switch, which is also soft switched. Having one auxiliary switch simplifies the control circuit considerably. The proposed inverter is analyzed, and its operating modes are explained in details. The design

Mohammad Reza Amini; Hosein Farzanehfard

2011-01-01

449

Nuclear criticality safety guide  

SciTech Connect

This technical reference document cites information related to nuclear criticality safety principles, experience, and practice. The document also provides general guidance for criticality safety personnel and regulators.

Pruvost, N.L.; Paxton, H.C. [eds.] [eds.

1996-09-01

450

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

451

Universal Ferroelectric Switching Dynamics of Vinylidene Fluoride-trifluoroethylene Copolymer Films  

PubMed Central

In this work, switching dynamics of poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] copolymer films are investigated over unprecedentedly wide ranges of temperature and electric field. Remarkably, domain switching of copolymer films obeys well the classical domain nucleation and growth model although the origin of ferroelectricity in organic ferroelectric materials inherently differs from the inorganic counterparts. A lower coercivity limit of 50?MV/m and 180° domain wall energy of 60?mJ/m2 are determined for P(VDF-TrFE) films. Furthermore, we discover in copolymer films an anomalous temperature-dependent crossover behavior between two power-law scaling regimes of frequency-dependent coercivity, which is attributed to the transition between flow and creep motions of domain walls. Our observations shed new light on the switching dynamics of semi-crystalline ferroelectric polymers, and such understandings are critical for realizing their reliable applications. PMID:24759786

Hu, Wei Jin; Juo, Deng-Ming; You, Lu; Wang, Junling; Chen, Yi-Chun; Chu, Ying-Hao; Wu, Tom

2014-01-01

452

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

453

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

PubMed Central

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

2014-01-01

454

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

455

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

456

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

457

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

458

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

459

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

460

Anomalous critical fields in quantum critical superconductors  

E-print Network

-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... mixing of antiferromagnetism and superconductivity, suggesting that a highly unusual vortex state is realised in quantum critical superconductors. Quantum critical points (QCPs) can be associated with a variety of different order-disorder phenomena...

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.

2015-01-01

461

Class E/F switching power amplifiers  

NASA Technical Reports Server (NTRS)

The present invention discloses a new family of switching amplifier classes called class E/F amplifiers. These amplifiers are generally characterized by their use of the zero-voltage-switching (ZVS) phase correction technique to eliminate of the loss normally associated with the inherent capacitance of the switching device as utilized in class-E amplifiers, together with a load network for improved voltage and current wave-shaping by presenting class-F.sup.-1 impedances at selected overtones and class-E impedances at the remaining overtones. The present invention discloses a several topologies and specific circuit implementations for achieving such performance.

Hajimiri, Seyed-Ali (Inventor); Aoki, Ichiro (Inventor); Rutledge, David B. (Inventor); Kee, Scott David (Inventor)

2004-01-01

462

Fast switching liquid crystal display modes  

NASA Astrophysics Data System (ADS)

We present two LCD modes enabling short rise and fall switching time, being in the microsecond range in most of the modes. Polymeric network, created in the liquid crystal bulk, as well as in the presence of flexoelectric polarization are among those employed for achieving of fast switching modes in LCDs. Proper assembling and electronic driving of two parallel liquid crystal cells, arranged in a double cell configuration, is another approach enabling a fast switching mode between bright and dark state of the device. We discuss these modes in terms of device performance and their suitability for application in LCDs.

Komitov, Lachezar; Hegde, Gurumurthy

2012-03-01

463

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

464

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

465

Thermally assisted magnetic switching of a single perpendicularly magnetized layer induced by an in-plane current  

SciTech Connect

We report that by heating samples the critical current density for magnetization reversal (J{sub c}) in a single perpendicularly magnetized layer can be decreased from 2.6?×?10{sup 7?}A/cm{sup 2} to about 1?×?10{sup 6?}A/cm{sup 2} for a temperature increase of 143?K. The nonlinear dependence of J{sub c} on the perpendicular anisotropy field indicates that the coherent magnetic switching model cannot fully explain the current-induced perpendicular switching. By considering the current-induced domain nucleation and expansion during switching, we conclude that J{sub c} also depends on current-induced domain behavior. Moreover, by reversing the heat flow direction, we demonstrate that the thermal related spin transfer torques have little influence on the thermally assisted magnetic switching.

Bi, Chong; Long, Shibing; Liu, Qi; Yao, Zhihong; Li, Ling; Huo, Zongliang; Liu, Ming, E-mail: liuming@ime.ac.cn [Laboratory of Nano-fabrication and Novel Devices Integrated Technology, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029 (China); Huang, Lin; Pan, Liqing [Collaborative Innovation Center for Magnetoelectric Industry CTGU, College of Science, China Three Gorges University, Yichang 443002 (China)

2014-07-14

466

Interaction of two sulfhydryl reagents with a cation recognition site on the neuronal dopamine carrier evidences small differences between [3H]GBR 12783 and [3H]cocaine binding sites.  

PubMed

We have compared the effect of treating rat striatal cell membranes with ionic hydrophilic sulfhydryl reagents on the specific bindings of [3H]cocaine and of [3H]GBR 12783 (1-[2-(diphenylmethoxy)ethyl]4-(3-phenyl-2-[1-3H]propenyl)-piperaz ine) to the neuronal transporter of dopamine. Treatment with 1 mmol/l 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB) resulted in similar time- and concentration-dependent reductions of the specific binding of both radioligands. None of the uptake blockers tested afforded any protection against 1 mmol/l DTNB. Addition of (sub)millimolar concentrations of CaCl2 or MgCl2, or 250 mmol/l KCl to a treatment medium containing 10 mmol/l Na+ significantly increased the DTNB-induced reduction of the specific binding of both radioligands. Cations were likely to be responsible for this effect since ions in combination with DTNB induced similar reductions in binding when either 1 mmol/l CaCl2 or 50-250 mmol/NaCl were added. Effects of cations on the DTNB-induced inhibition of binding were generally more marked on [3H]GBR 12783 than on [3H]cocaine binding. When added to a medium containing 10 mmol/l Na+ 1 mmol/l DTNB induced a reduction in the Bmax of the specific binding of both radioligands. Addition of 1 mmol/l Ca2+ maintained or increased this Bmax reduction and elicited a decrease in affinity which was significant for [3H]GBR 12783 binding. Treatment of membranes with the sodium salt of p-hydroxymercurybenzenesulfonate (pHMBS) induced time- and concentration-dependent decreases in [3H]GBR 12783 binding which were significantly greater than decreases in [3H]cocaine binding. However, 50 mumol/l pHMBS produced a similar decrease in the Bmax of the specific binding of both radioligands. The pHMBS-induced reduction of [3H]GBR 12783 binding was not reversed by drugs whose action is purely that of uptake inhibition or by substrates of the dopamine carrier. Some of these drugs (100 mumol/l dopamine, 1 mumol/l mazindol or 100 mumol/l cocaine) protected the specific binding of [3H]cocaine against the effects of pHMBS, whereas 1 mmol/l p-tyramine, 10 mumol/l nomifensine and 10 nmol/l GBR 12783 were ineffective. Addition of 120 mmol/l Na+, 1 mmol/l Ca2+ or 10 mmol/l Mg2+ to a treatment medium containing 10 mmol/l Na+ significantly reduced the effects of pHMBS on the specific binding of both radioligands. When striatal cell membranes were treated in a medium containing 130 mmol/l Na+, there was a general decrease in the effects of ions on the reductions of specific binding produced by DTNB or pHMBS.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:7770096

Refahi-Lyamani, F; Saadouni, S; Costentin, J; Bonnet, J J

1995-02-01

467

Nuclear criticality accidents.  

PubMed

Criticality occurs when a sufficient quantity of fissionable material is accumulated, and it results in the liberation of nuclear energy. All process accidents have involved plutonium or highly enriched uranium, as have most of the critical experiment accidents. Slightly enriched uranium systems require much larger quantities of material to achieve criticality. An appreciation of criticality accidents should be based on an understanding of factors that influence criticality, which are discussed in this article. PMID:1962246

Smith, D R

1991-01-01

468

Edge detection using fuzzy switch  

NASA Astrophysics Data System (ADS)

Edge detection is the first step for some boundary extraction and boundary representation algorithms. In this paper, a fuzzy switch approach is proposed. Different existing edge filters, such as Sobel filter, Prewitt filter, Roberts filter, Isotropic filter and Canny filter, are viewed as different expert systems. In order to capture the knowledge from these expert systems, a fuzzifier is employed, which normalizes the output of each edge filter to a matrix with the values of its elements being in between zero and one. By comparing the corresponding elements in these matrices, those with the highest values are with the highest fuzzy membership values of being at an edge point. A fuzzy engine can then be designed to select the highest fuzzy membership values. Then, a defuzzifier maps the selected membership value to a crisp point, which is either zero or one. Simulations were carried out using the Sobel filter, Prewitt filter, Roberts filter, Isotropic filter and Canny filter as the edge filters. It can be concluded from the simulations that the proposed algorithm captures the advantages of the expert filters.

Ling, Wing-Kuen; Tam, Kwong-Shun

2002-05-01

469

Contralateral disconnection of the rat prelimbic cortex and dorsomedial striatum impairs cue-guided behavioral switching.  

PubMed

Switches in reward outcomes or reward-predictive cues are two fundamental ways in which information is used to flexibly shift response patterns. The rat prelimbic cortex and dorsomedial striatum support behavioral flexibility based on a change in outcomes. The present experiments investigated whether these two brain regions are necessary for conditional discrimination performance in which a switch in reward-predictive cues occurs every three to six trials. The GABA agonists baclofen and muscimol infused into the prelimbic cortex significantly impaired performance leading rats to adopt an inappropriate turn strategy. The NMDA receptor antagonist D-AP5 infused into the dorsomedial striatum or prelimbic cortex and dorsomedial striatum contralateral disconnection impaired performance due to a rat failing to switch a response choice for an entire trial block in about two out of 13 test blocks. In an additional study, contralateral disconnection did not affect nonswitch discrimination performance. The results suggest that the prelimbic cortex and dorsomedial striatum are necessary to support cue-guided behavioral switching. The prelimbic cortex may be critical for generating alternative response patterns while the dorsomedial striatum supports the selection of an appropriate response when cue information must be used to flexibly switch response patterns. PMID:25028395

Baker, Phillip M; Ragozzino, Michael E

2014-08-01

470

Bipolar resistive switching characteristics in CuO/ZnO bilayer structure  

NASA Astrophysics Data System (ADS)

Resistive switching characteristics in Cu/ZnO/AZO (Al-doped ZnO) were investigated. Reproducible bipolar resistance switching properties were observed in the single oxide layer (SL)-based device. To improve the switching performance, a CuO-ZnO bilayer (BL) was used to form a Cu/CuO/ZnO/AZO structure. RS characteristics such as retention time, endurance, variations of threshold voltage as well as distribution of resistance were investigated. The results demonstrated that the BL devices exhibit more excellent switching performance than SL devices. The conduction mechanisms of high and low resistance states can be explained by trap-controlled space charge limited current (SCLC) and Ohmic's Law, respectively. The CuO layer is proposed as a "reservoir" of oxygen ions in set process and acting as an oxygen ions "supplier" in reset process, which plays a critical role in recovery/rupture of filament paths and greatly improves the switching characteristics of the device.

Yang, F.; Wei, M.; Deng, H.

2013-10-01

471

Evolution of the shape of the conducting channel in complementary resistive switching transition metal oxides.  

PubMed

Ultimate control of the defect distribution and local conduction path in a bipolar resistive switching (BRS) Pt/TiO2/Pt sample, which was in a unipolar reset state, is provided by means of voltage pulsing and the resulting time-transient current analysis. The limited amount of oxygen vacancies in this system allowed reversibly switching-diode-like current-voltage curves, which was also confirmed in another Magnéli-phase-containing Pt/WO3/Pt sample. Such careful control of the defect distribution allowed the achievement of a complementary resistive switching (CRS) curve even from a single switching layer. The unlimited vacancy source in the Pt/TiO2/TiO2-x/Pt sample did not allow the switching-diode type and the CRS behavior. The data retention of the on-state in the BRS was critically dependent on the shape of the rejuvenated conduction channel. The required time to lead to the rejuvenation of the conducting channel was ?70-100 ns when the threshold voltage for the BRS set of ?-1 V was applied. PMID:24366553

Yoon, Kyung Jean; Song, Seul Ji; Seok, Jun Yeong; Yoon, Jung Ho; Park, Tae Hyung; Kwon, Dae Eun; Hwang, Cheol Seong

2014-02-21

472

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

473

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

474

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

475

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

476

Pronounced switching bistability in a feedback coupled nanoelectronic Y-branch switch  

NASA Astrophysics Data System (ADS)

Electron Y-branch switches (YBSs) were fabricated in modulation-doped GaAs/AlGaAs heterostructures by electron-beam lithography and etching techniques. The YBS is controlled by two lateral sidegates. Feedback coupling of one of the branches to the adjacent sidegate leads to a pronounced switching bistability when varying the voltage at the other sidegate. This mode of operation is associated with a Schmitt-Trigger-like switching hysteresis of up to 135 mV.

Reitzenstein, S.; Worschech, L.; Hartmann, P.; Forchel, A.

2003-03-01

477

An improved soft-switching inverter with an unidirectional auxiliary switch  

Microsoft Academic Search

In this paper, novel unidirectional auxiliary resonant commutated pole is proposed to improve the performance of the zero-voltage soft-switching inverter. The proposed circuit keeps the advantages of the original soft-switching inverter, while providing more effective resetting capability in magnetizing current. Based on the advanced reset mechanism, auxiliary switches operate under a complete zero-current condition. The operating principle and steady-state analysis

Se-Jin Sohn; Kui-Jun Lee; Rae-Young Kim; Dong-Seok Hyun

2010-01-01

478

A Modified Dummy-Switch Technique for Tunable Feedthrough Cancellation in Switched-Current Circuits  

Microsoft Academic Search

A tunable\\/adaptive feedthrough-error cancelation technique for switched-current circuits is presented. A comparison, based on measurements from silicon prototypes designed with the same technology and equal geometries, shows an improvement of more than one order of magnitude as compared to the conventional dummy-switch technique. Robustness against local process or switch-geometry variations has been observed, ensuring global adaptability of several track-and-hold stages.

S. Espejo; A. Rodriguez-Vazquez; R. Dominguez-Castro; J. L. Huertas

1993-01-01

479

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

480

Switching Quantum Dynamics for Fast Stabilization  

E-print Network

Control strategies for dissipative preparation of target quantum states, both pure and mixed, and subspaces are obtained by switching between a set of available semigroup generators. We show that the class of problems of interest can be recast, from a control--theoretic perspective, into a switched-stabilization problems for linear dynamics. This is attained by a suitable affine transformation of the coherence-vector representation. In particular, we propose and compare stabilizing time-based and state-based switching rules for entangled state preparation, showing that the latter not only ensure faster convergence with respect to non-switching methods, but can designed so that it retains robustness with respect to initialization, as long as the target is a pure state or a subspace.

Pierre Scaramuzza; Francesco Ticozzi

2015-02-25

481

Nonlinear dynamic modeling of micromachined microwave switches  

Microsoft Academic Search

Nonlinear dynamic lumped models of micromachined microwave switches have been formulated and successfully applied to analyses of transient characteristics and geometrical scaling. Parameter extraction through electrical measurements is summarized. The results are compared to transient quasi-2D simulations

E. K. Chan; E. C. Kan; R. W. Dutton; P. M. Pinsky

1997-01-01

482

Strategy switch costs in arithmetic problem solving.  

PubMed

Three experiments tested whether switching between strategies involves a cost. In three experiments, participants had to give approximate products to two-digit multiplication problems (e.g., 47 x 76). They were told which strategy to use (Experiments 1 and 2) or could choose among strategies (Experiment 3). The participants showed poorer performance when they used different strategies on two consecutive trials than when they used the same strategy. They also used the same strategy over two consecutive problems more often than they used different strategies. These effects, termed strategy switch costs, were found when the participants executed the easiest strategy and when they solved easy problems. We discuss possible processes underlying these strategy switch costs and the implications of these strategy switch costs for models of strategy choices. PMID:20234022

Lemaire, Patrick; Lecacheur, Mireille

2010-04-01