Science.gov

Sample records for protein breakdown represents

  1. Protein breakdown in cancer cachexia.

    PubMed

    Sandri, Marco

    2016-06-01

    Skeletal muscle is a highly adaptive tissue, capable of altering muscle fiber size, functional capacity and metabolism in response to physiological stimuli. However, pathological conditions such as cancer growth compromise the mechanisms that regulate muscle homeostasis, resulting in loss of muscle mass, functional impairment and compromised metabolism. This tumor-induced condition is characterized by enhanced muscle protein breakdown and amino acids release that sustain liver gluconeogenesis and tissue protein synthesis. Proteolysis is controlled by the two most important cellular degradation systems, the ubiquitin proteasome and autophagy lysosome. These systems are carefully regulated by different signalling pathways that determine protein and organelle turnover. In this review we will describe the involvement of the ubiquitin proteasome and autophagy lysosome systems in cancer cachexia and the principal signalling pathways that regulate tumor-induced protein breakdown in muscle. PMID:26564688

  2. Human skeletal muscle protein breakdown during spaceflight

    NASA Technical Reports Server (NTRS)

    Stein, T. P.; Schluter, M. D.

    1997-01-01

    Human spaceflight is associated with a loss of body protein. Excretion of 3-methylhistidine (3-MH) in the urine is a useful measurement of myofibrillar protein breakdown. Bed rest, particularly with 6 degrees head-down tilt, is an accepted ground-based model for human spaceflight. The objectives of this report were to compare 3-MH excretion from two Life Sciences shuttle missions (duration 9.5 and 15 days, n = 9) and from 17 days of bed rest (n = 7) with 6 degrees head-down tilt. The bed rest study was designed to mimic an actual Life Sciences spaceflight and so incorporated an extensive battery of physiological tests focused on the musculoskeletal system. Results showed that nitrogen retention, based on excretion of nitrogen in the urine, was reduced during both bed rest [from 22 +/- 1 to 1 +/- 5 mg N x kg(-1) x day(-1) (n = 7; P < 0.05)] and spaceflight [from 57 +/- 9 to 19 +/- 3 mg N x kg(-1) x day(-1) (n = 9; P < 0.05)]. 3-MH excretion was unchanged with either bed rest [pre-bed rest 5.30 +/- 0.29 vs. bed rest 5.71 +/- 0.30 micromol 3-MH x kg(-1) x day(-1), n = 7; P = not significant (NS)] or spaceflight [preflight 4.98 +/- 0.37 vs. 4.59 +/- 0.39 micromol 3-MH x kg(-1) x day(-1) in-flight, n = 9; P = NS]. We conclude that 1) 3-MH excretion was unaffected by spaceflight on the shuttle or with bed rest plus exercise, and 2) because protein breakdown (elevated 3-MH) was increased on Skylab but not on the shuttle, it follows that muscle protein breakdown is not an inevitable consequence of spaceflight.

  3. Effects of elevated temperature on protein breakdown in muscles from septic rats

    SciTech Connect

    Hall-Angeras, M.A.; Angeras, U.H.; Hasselgren, P.O.; Fischer, J.E. )

    1990-04-01

    Elevated temperature has been proposed to contribute to accelerated muscle protein degradation during fever and sepsis. The present study examined the effect of increased temperature in vitro on protein turnover in skeletal muscles from septic and control rats. Sepsis was induced by cecal ligation and puncture (CLP); control rats were sham operated. After 16 h, the extensor digitorum longus (EDL) and soleus (SOL) muscles were incubated at 37 or 40 degrees C. Protein synthesis was determined by measuring incorporation of (14C)phenylalanine into protein. Total and myofibrillar protein breakdown was assessed from release of tyrosine and 3-methylhistidine (3-MH), respectively. Total protein breakdown was increased at 40 degrees C by 15% in EDL and by 29% in SOL from control rats, whereas 3-MH release was not affected. In muscles from septic rats, total and myofibrillar protein breakdown was increased by 22 and 30%, respectively, at 40 degrees C in EDL but was not altered in SOL. Protein synthesis was unaffected by high temperature both in septic and nonseptic muscles. The present results suggest that high temperature is not the primary mechanism of increased muscle protein breakdown in sepsis because the typical response to sepsis, i.e., a predominant increase in myofibrillar protein breakdown, was not induced by elevated temperature in normal muscle. It is possible, however, that increased temperature may potentiate protein breakdown that is already stimulated by sepsis because elevated temperature increased both total and myofibrillar protein breakdown in EDL from septic rats.

  4. The role of protein breakdown in growth, quiescence, and starvation of vascular smooth muscle cells.

    PubMed

    Libby, P; O'Brien, K V

    1984-03-01

    Protein accumulation in growing cells may be due in part to a reduction in the rate of protein breakdown. Previous studies of the relation of cell proliferation to protein degradation often produced growth arrest by conditions that may involve nutritional deprivation. However, nutrient lack can itself accelerate proteolysis and produce negative protein balance. We therefore reexamined the relation between growth and protein breakdown using a more selective method for limiting cell growth. We produced quiescent cell cultures using a chemically defined, serum-free medium supplemented with hormones and nutrients. Such media can maintain viability and near neutral protein balance in cultured vascular smooth muscle cells, in part because of reduced breakdown of cellular protein. We then compared rates of protein degradation in these quiescent but not starving cells, to those of cultures stimulated to grow by addition of mitogenic substances. Platelet-derived growth factor, fibroblast growth factor, or fetuin added to insulin-containing medium stimulated growth of smooth muscle cells, but further reduced protein breakdown only slightly. Contrary to the implications of certain previous studies, our results show that proliferating cells can accumulate protein without an appreciable reduction in the rates of protein breakdown. Thus, while accelerated proteolysis appears to be an important adaptation to adverse nutritional conditions, growth of smooth muscle cells does not require changes in overall protein breakdown, but occurs primarily through an increase in protein synthesis. PMID:6365933

  5. A tomato xylem sap protein represents a new family of small cysteine-rich proteins with structural similarity to lipid transfer proteins.

    PubMed

    Rep, Martijn; Dekker, Henk L; Vossen, Jack H; de Boer, Albert D; Houterman, Petra M; de Koster, Chris G; Cornelissen, Ben J C

    2003-01-16

    The coding sequence of a major xylem sap protein of tomato was identified with the aid of mass spectrometry. The protein, XSP10, represents a novel family of extracellular plant proteins with structural similarity to plant lipid transfer proteins. The XSP10 gene is constitutively expressed in roots and lower stems. The decline of XSP10 protein levels in tomato infected with a fungal vascular pathogen may reflect breakdown or modification by the pathogen. PMID:12527365

  6. The crystal structure of the thiocyanate-forming protein from Thlaspi arvense, a kelch protein involved in glucosinolate breakdown.

    PubMed

    Gumz, Frauke; Krausze, Joern; Eisenschmidt, Daniela; Backenköhler, Anita; Barleben, Leif; Brandt, Wolfgang; Wittstock, Ute

    2015-09-01

    Kelch repeat-containing proteins are involved in diverse cellular processes, but only a small subset of plant kelch proteins has been functionally characterized. Thiocyanate-forming protein (TFP) from field-penny cress, Thlaspi arvense (Brassicaceae), is a representative of specifier proteins, a group of kelch proteins involved in plant specialized metabolism. As components of the glucosinolate-myrosinase system of the Brassicaceae, specifier proteins determine the profile of bioactive products formed when plant tissue is disrupted and glucosinolates are hydrolyzed by myrosinases. Here, we describe the crystal structure of TaTFP at a resolution of 1.4 Å. TaTFP crystallized as homodimer. Each monomer forms a six-blade β-propeller with a wide "top" and a narrower "bottom" opening with distinct strand-connecting loops protruding far beyond the lower propeller surface. Molecular modeling and mutational analysis identified residues for glucosinolate aglucone and Fe(2+) cofactor binding within these loops. As the first experimentally determined structure of a plant kelch protein, the crystal structure of TaTFP not only enables more detailed mechanistic studies on glucosinolate breakdown product formation, but also provides a new basis for research on the diverse roles and mechanisms of other kelch proteins in plants. PMID:26260516

  7. Role of the alpha-amino group of protein in ubiquitin-mediated protein breakdown.

    PubMed Central

    Hershko, A; Heller, H; Eytan, E; Kaklij, G; Rose, I A

    1984-01-01

    Previous studies suggest that the conjugation of ubiquitin to NH2 groups of proteins is required for protein breakdown. We now show that the selective modification of NH2-terminal alpha-NH2 groups of globin and lysozyme prevents their degradation by the ubiquitin proteolytic system from reticulocytes. The conjugation by ubiquitin of epsilon-NH2 groups of lysine residues, usually seen in multiples, was also inhibited in alpha-NH2-blocked proteins. Naturally occurring N alpha-acetylated proteins are not degraded by the ubiquitin system at a significant rate, while their nonacetylated counterparts from other species are good substrates. This suggests that one function of N alpha-acetylation of cellular proteins is to prevent their degradation by the ubiquitin system. alpha-NH2-blocked proteins can have their activity as substrates for degradation increased by incorporation of alpha-NH2 groups through the introduction of polyalanine side chains. Proteins in which most epsilon-NH2 groups are blocked but the alpha-NH2 group is free are degraded by the ubiquitin system, but at a reduced rate. It is therefore suggested that the exposure of a free NH2 terminus of proteins is required for degradation and probably initiates the formation of ubiquitin conjugates committed for degradation. Images PMID:6095265

  8. Elastin: a representative ideal protein elastomer.

    PubMed Central

    Urry, D W; Hugel, T; Seitz, M; Gaub, H E; Sheiba, L; Dea, J; Xu, J; Parker, T

    2002-01-01

    During the last half century, identification of an ideal (predominantly entropic) protein elastomer was generally thought to require that the ideal protein elastomer be a random chain network. Here, we report two new sets of data and review previous data. The first set of new data utilizes atomic force microscopy to report single-chain force-extension curves for (GVGVP)(251) and (GVGIP)(260), and provides evidence for single-chain ideal elasticity. The second class of new data provides a direct contrast between low-frequency sound absorption (0.1-10 kHz) exhibited by random-chain network elastomers and by elastin protein-based polymers. Earlier composition, dielectric relaxation (1-1000 MHz), thermoelasticity, molecular mechanics and dynamics calculations and thermodynamic and statistical mechanical analyses are presented, that combine with the new data to contrast with random-chain network rubbers and to detail the presence of regular non-random structural elements of the elastin-based systems that lose entropic elastomeric force upon thermal denaturation. The data and analyses affirm an earlier contrary argument that components of elastin, the elastic protein of the mammalian elastic fibre, and purified elastin fibre itself contain dynamic, non-random, regularly repeating structures that exhibit dominantly entropic elasticity by means of a damping of internal chain dynamics on extension. PMID:11911774

  9. In vivo breakdown products of the 32 kDa thylakoid herbicide binding protein. [Spirodela oligorrhiza

    SciTech Connect

    Greenberg, B.M.; Mattoo, A.K.; Gaba, V.; Edelman, M.

    1986-04-01

    The 32 kDa herbicide binding protein of PSII is degraded rapidly in the light. This phenomenon was investigated in Spirodela oligorrhiza. When fronds were radiolabeled in the presence of cycloheximide only the chloroplast-encoded proteins were labeled. Under these conditions, a breakdown product of 23.5 kDa was observed. This polypeptide was further degraded with kinetics similar to that of the 32 kDa protein. The 23.5 kDa polypeptide cross-reacted with an antibody specific to the 32 kDa protein. By protease digestion it was determined that the 23.5 kDa polypeptide is the intact N-terminal piece of the 32 kDa protein. Thus, this product corresponds to the membrane anchor of the 32 kDa protein. Using the same antibody, breakdown products of 16 kDa, 14 kDa and 12 kDa were observed. These products have also been observed in Zea mays and Solanum nigrum. Using DCMU during pulse-chase experiments at different light intensities, evidence was obtained that the 23.5 kDa breakdown product is generated in vivo.

  10. Does exercise stimulate protein breakdown in humans. Isotopic approaches to the problem

    SciTech Connect

    Wolfe, R.R.

    1987-10-01

    Protein metabolism in exercise has been investigated for 100 yr, yet it is still unclear if exercise induces an increased rate of protein breakdown. We have recently addressed this general question in a series of experiments in human subjects using stable isotopic tracers. In this paper, the results of those studies are reviewed. We have found that in light exercise the de-carboxylation of leucine is increased. However, urea production is not increased correspondingly, nor is the rate of incorporation into urea of nitrogen from either leucine or lysine. Further complicating the picture is the fact that lysine de-carboxylation is not markedly elevated in exercise. From these studies, we must conclude that isotopic techniques which have achieved general acceptance in other circumstances cannot reliably be used to answer the question of whether exercise stimulates protein breakdown in humans. However, these methods do provide results which enable a better understanding of the metabolism of the individual amino acids in exercise.

  11. Nuclear envelope breakdown induced by herpes simplex virus type 1 involves the activity of viral fusion proteins

    SciTech Connect

    Maric, Martina; Haugo, Alison C.; Dauer, William; Johnson, David; Roller, Richard J.

    2014-07-15

    Herpesvirus infection reorganizes components of the nuclear lamina usually without loss of integrity of the nuclear membranes. We report that wild-type HSV infection can cause dissolution of the nuclear envelope in transformed mouse embryonic fibroblasts that do not express torsinA. Nuclear envelope breakdown is accompanied by an eight-fold inhibition of virus replication. Breakdown of the membrane is much more limited during infection with viruses that lack the gB and gH genes, suggesting that breakdown involves factors that promote fusion at the nuclear membrane. Nuclear envelope breakdown is also inhibited during infection with virus that does not express UL34, but is enhanced when the US3 gene is deleted, suggesting that envelope breakdown may be enhanced by nuclear lamina disruption. Nuclear envelope breakdown cannot compensate for deletion of the UL34 gene suggesting that mixing of nuclear and cytoplasmic contents is insufficient to bypass loss of the normal nuclear egress pathway. - Highlights: • We show that wild-type HSV can induce breakdown of the nuclear envelope in a specific cell system. • The viral fusion proteins gB and gH are required for induction of nuclear envelope breakdown. • Nuclear envelope breakdown cannot compensate for deletion of the HSV UL34 gene.

  12. Loss of Myelin Basic Protein Function Triggers Myelin Breakdown in Models of Demyelinating Diseases.

    PubMed

    Weil, Marie-Theres; Möbius, Wiebke; Winkler, Anne; Ruhwedel, Torben; Wrzos, Claudia; Romanelli, Elisa; Bennett, Jeffrey L; Enz, Lukas; Goebels, Norbert; Nave, Klaus-Armin; Kerschensteiner, Martin; Schaeren-Wiemers, Nicole; Stadelmann, Christine; Simons, Mikael

    2016-07-12

    Breakdown of myelin sheaths is a pathological hallmark of several autoimmune diseases of the nervous system. We employed autoantibody-mediated animal models of demyelinating diseases, including a rat model of neuromyelitis optica (NMO), to target myelin and found that myelin lamellae are broken down into vesicular structures at the innermost region of the myelin sheath. We demonstrated that myelin basic proteins (MBP), which form a polymer in between the myelin membrane layers, are targeted in these models. Elevation of intracellular Ca(2+) levels resulted in MBP network disassembly and myelin vesiculation. We propose that the aberrant phase transition of MBP molecules from their cohesive to soluble and non-adhesive state is a mechanism triggering myelin breakdown in NMO and possibly in other demyelinating diseases. PMID:27346352

  13. The effect of eicosapentaenoic and docosahexaenoic acid on protein synthesis and breakdown in murine C2C12 myotubes

    SciTech Connect

    Kamolrat, Torkamol; Gray, Stuart R.

    2013-03-22

    Highlights: ► EPA can enhance protein synthesis and retard protein breakdown in muscle cells. ► These effects were concurrent with increases in p70s6k and FOXO3a phosphorylation. ► EPA may be a useful tool in the treatment of muscle wasting conditions. -- Abstract: Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have been found to stimulate protein synthesis with little information regarding their effects on protein breakdown. Furthermore whether there are distinct effects of EPA and DHA remains to be established. The aim of the current study was to determine the distinct effects of EPA and DHA on protein synthesis, protein breakdown and signalling pathways in C2C12 myotubes. Fully differentiated C2C12 cells were incubated for 24 h with 0.1% ethanol (control), 50 μM EPA or 50 μM DHA prior to experimentation. After serum (4 h) and amino acid (1 h) starvation cells were stimulated with 2 mM L-leucine and protein synthesis measured using {sup 3}H-labelled phenylalanine. Protein breakdown was measured using {sup 3}H-labelled phenylalanine and signalling pathways (Akt, mTOR, p70S6k, 4EBP1, rps6 and FOXO3a) via Western blots. Data revealed that after incubation with EPA protein synthesis was 25% greater (P < 0.05) compared to control cells, with no effect of DHA. Protein breakdown was 22% (P < 0.05) lower, compared to control cells, after incubation with EPA, with no effect of DHA. Analysis of signalling pathways revealed that both EPA and DHA incubation increased (P < 0.05) p70s6k phosphorylation, EPA increased (P < 0.05) FOXO3a phosphorylation, with no alteration in other signalling proteins. The current study has demonstrated distinct effects of EPA and DHA on protein metabolism with EPA showing a greater ability to result in skeletal muscle protein accretion.

  14. Effects of Pharmacological Interventions on Muscle Protein Synthesis and Breakdown in Recovery from Burns

    PubMed Central

    Diaz, Eva C.; Herndon, David N.; Porter, Craig; Sidossis, Labros S.; Suman, Oscar E.; Børsheim, Elisabet

    2014-01-01

    Objective The pathophysiological response to burn injury disturbs the balance between skeletal muscle protein synthesis and breakdown, resulting in severe muscle wasting. Muscle loss after burn injury is related to increased mortality and morbidity. Consequently, mitigation of this catabolic response has become a focus in the management of these patients. The aim of this review is to discuss the literature pertaining to pharmacological interventions aimed at attenuating skeletal muscle catabolism in severely burned patients. Data selection Review of the literature related to skeletal muscle protein metabolism following burn injury was conducted. Emphasis was on studies utilizing stable isotope tracer kinetics to assess the impact of pharmacological interventions on muscle protein metabolism in severely burned patients. Conclusion Data support the efficacy of testosterone, oxandrolone, human recombinant growth hormone, insulin, metformin, and propranolol in improving skeletal muscle protein net balance in patients with severe burns. The mechanisms underlying the improvement of protein net balance differ between types and dosages of drugs, but their main effect is on protein synthesis. Finally, the majority of studies have been conducted during the acute hypermetabolic phase of the injury. Except for oxandrolone, the effects of drugs on muscle protein kinetics following discharge from the hospital are largely unknown. PMID:25468473

  15. Transport of large breakdown products of dietary protein through the gut wall.

    PubMed Central

    Hemmings, W A; Williams, E W

    1978-01-01

    Ferritin or tritium labelled immunoglobulin G may, by electron microscopy, be demonstrated entering, within, and leaving the epithelial cells. Quantitative studies using various proteins labelled with radioiodine show that large amounts of protein bound radioactivity may be demonstrated in the tissues after feeding the labelled protein to adult rats by stomach tube. The molecular size of this material as determined by sugar gradient ultracentrifugation of tissue extracts ranges when IgG is fed from 50,000-20,000 Daltons. The material retains its ability to react as antigen with antisera specific to the original molecule: precipitation reactions may be obtained in gels and quantitative studies show that cnosiderable amounts of the protein-bound radioactivity are still specifically precipitable. Such studies have been carried out with alpha-gliadin as well as bovine IgG. At 100 days old rats may absorb as much as 40% of a dose of bovine IgG in the form of these large molecular breakdown products. PMID:680603

  16. SUN proteins facilitate the removal of membranes from chromatin during nuclear envelope breakdown

    PubMed Central

    Turgay, Yagmur; Champion, Lysie; Balazs, Csaba; Held, Michael; Toso, Alberto; Gerlich, Daniel W.; Meraldi, Patrick

    2014-01-01

    SUN proteins reside in the inner nuclear membrane and form complexes with KASH proteins of the outer nuclear membrane that connect the nuclear envelope (NE) to the cytoskeleton. These complexes have well-established functions in nuclear anchorage and migration in interphase, but little is known about their involvement in mitotic processes. Our analysis demonstrates that simultaneous depletion of human SUN1 and SUN2 delayed removal of membranes from chromatin during NE breakdown (NEBD) and impaired the formation of prophase NE invaginations (PNEIs), similar to microtubule depolymerization or down-regulation of the dynein cofactors NudE/EL. In addition, overexpression of dominant-negative SUN and KASH constructs reduced the occurrence of PNEI, indicating a requirement for functional SUN–KASH complexes in NE remodeling. Codepletion of SUN1/2 slowed cell proliferation and resulted in an accumulation of morphologically defective and disoriented mitotic spindles. Quantification of mitotic timing revealed a delay between NEBD and chromatin separation, indicating a role of SUN proteins in bipolar spindle assembly and mitotic progression. PMID:24662567

  17. Laser-induced breakdown spectroscopy of bacterial spores, molds, pollens, and protein: initial studies of discrimination potential

    NASA Astrophysics Data System (ADS)

    Samuels, Alan C.; Delucia, Frank C.; McNesby, Kevin L.; Miziolek, Andrzej W.

    2003-10-01

    Laser-induced breakdown spectroscopy (LIBS) has been used to study bacterial spores, molds, pollens, and proteins. Biosamples were prepared and deposited onto porous silver substrates. LIBS data from the individual laser shots were analyzed by principal-components analysis and were found to contain adequate information to afford discrimination among the different biomaterials. Additional discrimination within the three bacilli studied appears feasible.

  18. Human traumatic brain injury induces autoantibody response against glial fibrillary acidic protein and its breakdown products.

    PubMed

    Zhang, Zhiqun; Zoltewicz, J Susie; Mondello, Stefania; Newsom, Kimberly J; Yang, Zhihui; Yang, Boxuan; Kobeissy, Firas; Guingab, Joy; Glushakova, Olena; Robicsek, Steven; Heaton, Shelley; Buki, Andras; Hannay, Julia; Gold, Mark S; Rubenstein, Richard; Lu, Xi-Chun May; Dave, Jitendra R; Schmid, Kara; Tortella, Frank; Robertson, Claudia S; Wang, Kevin K W

    2014-01-01

    The role of systemic autoimmunity in human traumatic brain injury (TBI) and other forms of brain injuries is recognized but not well understood. In this study, a systematic investigation was performed to identify serum autoantibody responses to brain-specific proteins after TBI in humans. TBI autoantibodies showed predominant immunoreactivity against a cluster of bands from 38-50 kDa on human brain immunoblots, which were identified as GFAP and GFAP breakdown products. GFAP autoantibody levels increased by 7 days after injury, and were of the IgG subtype predominantly. Results from in vitro tests and rat TBI experiments also indicated that calpain was responsible for removing the amino and carboxyl termini of GFAP to yield a 38 kDa fragment. Additionally, TBI autoantibody staining co-localized with GFAP in injured rat brain and in primary rat astrocytes. These results suggest that GFAP breakdown products persist within degenerating astrocytes in the brain. Anti-GFAP autoantibody also can enter living astroglia cells in culture and its presence appears to compromise glial cell health. TBI patients showed an average 3.77 fold increase in anti-GFAP autoantibody levels from early (0-1 days) to late (7-10 days) times post injury. Changes in autoantibody levels were negatively correlated with outcome as measured by GOS-E score at 6 months, suggesting that TBI patients with greater anti-GFAP immune-responses had worse outcomes. Due to the long lasting nature of IgG, a test to detect anti-GFAP autoantibodies is likely to prolong the temporal window for assessment of brain damage in human patients. PMID:24667434

  19. Glucose and insulin administration while maintaining normoglycemia inhibits whole body protein breakdown and synthesis after cardiac surgery.

    PubMed

    Hatzakorzian, Roupen; Shum-Tim, Dominique; Wykes, Linda; Hülshoff, Ansgar; Bui, Helen; Nitschmann, Evan; Lattermann, Ralph; Schricker, Thomas

    2014-12-01

    We investigated the effect of insulin administered as part of a hyperinsulinemic-normoglycemic clamp on protein metabolism after coronary artery bypass grafting (CABG) surgery. Eighteen patients were studied, with nine patients in the control group receiving standard metabolic care and nine patients receiving insulin (5 mU·kg(-1)·min(-1)). Whole body glucose production, protein breakdown, synthesis, and oxidation were determined using stable isotope tracer kinetics (l-[1-(13)C]leucine, [6,6-(2)H2]glucose) before and 6 h after the procedure. Plasma amino acids, cortisol, and lactate were also measured. Endogenous glucose production (preoperatively 10.0 ± 1.6, postoperatively 3.7 ± 2.5 μmol·kg(-1)·min(-1); P = 0.0001), protein breakdown (preoperatively 105.3 ± 9.8, postoperatively 85.2 ± 9.2 mmol·kg(-1)·h(-1); P = 0.0005) and synthesis (preoperatively 88.7 ± 8.7, postoperatively 72.4 ± 8.4 mmol·kg(-1)·h(-1); P = 0.0005) decreased in the presence of hyperinsulinemia, whereas both parameters remained unchanged in the control group. A positive correlation between endogenous glucose production and protein breakdown was observed in the insulin group (r(2) = 0.385). Whole body protein oxidation and balance decreased after surgery in patients receiving insulin without reaching statistical significance. In the insulin group the plasma concentrations of 13 of 20 essential and nonessential amino acids decreased to a significantly greater extent than in the control group. In summary, supraphysiological hyperinsulinemia, while maintaining normoglycemia, decreased whole body protein breakdown and synthesis in patients undergoing CABG surgery. However, net protein balance remained negative. PMID:25257875

  20. Effects of protein kinase C activators on germinal vesicle breakdown and polar body emission of mouse oocytes

    SciTech Connect

    Bornslaeger, E.A.; Poueymirou, W.T.; Mattei, P.; Schultz, R.M.

    1986-01-01

    Protein phosphorylation mediated by cAMP-dependent protein kinase is instrumental in maintaining meiotic arrest of mouse oocytes. To assess whether protein phosphorylation mediated by calcium/phospholipid-dependent protein kinase (protein kinase C) might also inhibit the resumption of meiosis, oocytes were treated with activators of this enzyme. The active phorbol esters 12-O-tetra-decanoyl phorbol-13-acetate (TPA) and 4..beta..-phorbol, 12,13-didecanoate (4..beta..-PDD) inhibited germinal vesicle breakdown (GVBD), as did a more natural activator of protein kinase, C, sn-1,2-dioctanoylglycerol (diC/sub 8/). An inactive phorbol ester, 4a-phorbol 12,13-didecanoate (4..cap alpha..-PDD), did not inhibit GVBD. TPA did not inhibit the maturation-associated decrease in oocyte cAMP. Microinjected heat-stable protein inhibitor of a cAMP-dependent protein kinase failed to induce GVBD in the presence of TPA. Both TPA and diC/sub 8/ partially inhibited specific changes in oocyte phosphoprotein metabolism that are tightly correlated with resumption of meiosis; these agents also induced the apparent phosphorylation of specific oocyte proteins. These results suggest that protein kinase C activators may inhibit resumption of meiosis by acting distal to a decrease in cAMP-dependent protein kinase activity, but prior to changes in oocyte phosphoprotein metabolism that are presumably required for resumption of meiosis.

  1. Intra-crystalline protein diagenesis (IcPD) in Patella vulgata. Part II: Breakdown and temperature sensitivity

    PubMed Central

    Demarchi, B.; Collins, M.J.; Tomiak, P.J.; Davies, B.J.; Penkman, K.E.H.

    2013-01-01

    Artificial diagenesis of the intra-crystalline proteins isolated from Patella vulgata was induced by isothermal heating at 140 °C, 110 °C and 80 °C. Protein breakdown was quantified for multiple amino acids, measuring the extent of peptide bond hydrolysis, amino acid racemisation and decomposition. The patterns of diagenesis are complex; therefore the kinetic parameters of the main reactions were estimated by two different methods: 1) a well-established approach based on fitting mathematical expressions to the experimental data, e.g. first-order rate equations for hydrolysis and power-transformed first-order rate equations for racemisation; and 2) an alternative model-free approach, which was developed by estimating a “scaling” factor for the independent variable (time) which produces the best alignment of the experimental data. This method allows the calculation of the relative reaction rates for the different temperatures of isothermal heating. High-temperature data were compared with the extent of degradation detected in sub-fossil Patella specimens of known age, and we evaluated the ability of kinetic experiments to mimic diagenesis at burial temperature. The results highlighted a difference between patterns of degradation at low and high temperature and therefore we recommend caution for the extrapolation of protein breakdown rates to low burial temperatures for geochronological purposes when relying solely on kinetic data. PMID:23956808

  2. Skeletal Muscle Protein Breakdown Remains Elevated in Pediatric Burn Survivors up to One-Year Post-Injury.

    PubMed

    Chao, Tony; Herndon, David N; Porter, Craig; Chondronikola, Maria; Chaidemenou, Anastasia; Abdelrahman, Doaa Reda; Bohanon, Fredrick J; Andersen, Clark; Sidossis, Labros S

    2015-11-01

    Acute alterations in skeletal muscle protein metabolism are a well-established event associated with the stress response to burns. Nevertheless, the long-lasting effects of burn injury on skeletal muscle protein turnover are incompletely understood. This study was undertaken to investigate fractional synthesis (FSR) and breakdown (FBR) rates of protein in skeletal muscle of pediatric burn patients (n  =  42, >30% total body surface area burns) for up to 1 year after injury. Skeletal muscle protein kinetics were measured in the post-prandial state following bolus injections of C6 and N phenylalanine stable isotopes. Plasma and muscle phenylalanine enrichments were quantified using gas chromatography-mass spectrometry. We found that the FSR in burn patients was 2- to 3-fold higher than values from healthy men previously reported in the literature (P ≤ 0.05). The FBR was 4- to 6-fold higher than healthy values (P  <  0.01). Therefore, net protein balance was lower in burn patients compared with healthy men from 2 weeks to 12 months post-injury (P  <  0.05). These findings show that skeletal muscle protein turnover stays elevated for up to 1 year after burn, an effect attributable to simultaneous increases in FBR and FSR. Muscle FBR exceeds FSR during this time, producing a persistent negative net protein balance, even in the post-prandial state, which likely contributes to the prolonged cachexia seen in burned victims. PMID:26263438

  3. Cyclophilin represents a novel class of protein kinases

    SciTech Connect

    Harding, M.W.; Gorelick, F.S.; Handschumacher, R.E.

    1987-05-01

    Cyclophilin (CyP, Mr 17,737, pI 9.6), a highly specific cytosolic receptor for cyclosporin A (CsA) has ser/thr protein kinase activity. Incorporation of /sup 32/P into bovine histone H/sub 3/ (BH/sub 3/) was catalyzed by major and minor CyP isozymes at the same rate. Salt effects were biphasic with optimal kinase activity between 50-100 mM Na/sup +/ or K/sup +/. Kinase activity was maximal at 37/sup 0/C, stable for 5 min at 45/sup 0/, labile at 56/sup 0/, optimal between pH 6.8 and 8.0 and had an apparent Km of 20 uM ATP with both isozymes. The specific activity of CyP was 1.0 nmole P/mg protein/min with chicken histone H/sub 1/ (CH/sub 1/), 0.2 nmoles P/mg prot/min with BH/sub 3/ and less than 0.01 nmoles P/mg prot/min with synapsin, casein, phosvitin, and ribosomal protein S6. Cofactors including Mn/sup + +/, Zn/sup + +/, Ca/sup + +/, phosphatidyl serine, diolein and phorbol ester, cAMP, cGMP and Ca/sup + +/ did not affect basal CyP kinase activity. CsA (<200 ng/ml) inhibited phosphorylation of CH/sub 3/ by 50% but did not inhibit phosphorylation of other histones; 2ug CsA/ml was required to cause 50% inhibition of cAMP and Ca/sup + +//CaM dependent kinases. A non-immunosuppressive analog (Me-leu-11-CsA) that does not bind to CyP did not inhibit CH/sub 3/ phosphorylation. Thus, CyP is a novel protein kinase that mediates immunosuppression by CsA.

  4. MES16, a member of the methylesterase protein family, specifically demethylates fluorescent chlorophyll catabolites during chlorophyll breakdown in Arabidopsis.

    PubMed

    Christ, Bastien; Schelbert, Silvia; Aubry, Sylvain; Süssenbacher, Iris; Müller, Thomas; Kräutler, Bernhard; Hörtensteiner, Stefan

    2012-02-01

    During leaf senescence, chlorophyll (Chl) is broken down to nonfluorescent chlorophyll catabolites (NCCs). These arise from intermediary fluorescent chlorophyll catabolites (FCCs) by an acid-catalyzed isomerization inside the vacuole. The chemical structures of NCCs from Arabidopsis (Arabidopsis thaliana) indicate the presence of an enzyme activity that demethylates the C13(2)-carboxymethyl group present at the isocyclic ring of Chl. Here, we identified this activity as methylesterase family member 16 (MES16; At4g16690). During senescence, mes16 leaves exhibited a strong ultraviolet-excitable fluorescence, which resulted from large amounts of different FCCs accumulating in the mutants. As confirmed by mass spectrometry, these FCCs had an intact carboxymethyl group, which slowed down their isomerization to respective NCCs. Like a homologous protein cloned from radish (Raphanus sativus) and named pheophorbidase, MES16 catalyzed the demethylation of pheophorbide, an early intermediate of Chl breakdown, in vitro, but MES16 also demethylated an FCC. To determine the in vivo substrate of MES16, we analyzed pheophorbide a oxygenase1 (pao1), which is deficient in pheophorbide catabolism and accumulates pheophorbide in the chloroplast, and a mes16pao1 double mutant. In the pao1 background, we additionally mistargeted MES16 to the chloroplast. Normally, MES16 localizes to the cytosol, as shown by analysis of a MES16-green fluorescent protein fusion. Analysis of the accumulating pigments in these lines revealed that pheophorbide is only accessible for demethylation when MES16 is targeted to the chloroplast. Together, these data demonstrate that MES16 is an integral component of Chl breakdown in Arabidopsis and specifically demethylates Chl catabolites at the level of FCCs in the cytosol. PMID:22147518

  5. Breakdown of Diazotized Proteins and Synthetic Substrates by Rumen Bacterial Proteases

    PubMed Central

    Wallace, R. John; Kopecny, Jan

    1983-01-01

    Several different kinds of substrate were used to investigate the proteolytic activity of rumen bacteria and of proteases released from rumen bacteria by blending (“coat proteases”). These substrates included diazotized feed proteins and diazotized soluble and insoluble pure proteins. It was concluded that, while solubility was an important factor, the secondary and tertiary structure of a protein had a major influence on its rate of digestion. The resistance of elastin congo red to digestion indicated that similar fibrous proteins in plant material might resist proteolytic attack by rumen bacteria. Coat proteases had a broad specificity, including several exo- and endopeptidase activities, as determined by using synthetic peptide substrates. PMID:16346167

  6. Clinical usefulness of urinary 3-methylhistidine excretion in indicating muscle protein breakdown.

    PubMed Central

    Elia, M; Carter, A; Bacon, S; Winearls, C G; Smith, R

    1981-01-01

    Urinary excretion of the post-translationally modified amino-acid 3-methylhistidine, derived from the contractile proteins actin and myosin, was measured in patients with conditions associated with nitrogen loss. The ratio of 3-methylhistidine:creatinine excretion, a measure of the fractional catabolic rate of myofibrillar protein was increased in severe injury, thyrotoxicosis, neoplastic disease, prednisolone administration, and sometimes Duchenne muscular dystrophy. In myxoedema, osteomalacia, and hypothermia the ratio was decreased; and starvation, elective operations, and rheumatoid arthritis had little effect. Provided that the diet is meat free, measurement of urinary 3-methylhistidine may provide useful information on the cause of protein loss. PMID:6780020

  7. Human Skeletal Muscle Disuse Atrophy: Effects on Muscle Protein Synthesis, Breakdown, and Insulin Resistance-A Qualitative Review.

    PubMed

    Rudrappa, Supreeth S; Wilkinson, Daniel J; Greenhaff, Paul L; Smith, Kenneth; Idris, Iskandar; Atherton, Philip J

    2016-01-01

    The ever increasing burden of an aging population and pandemic of metabolic syndrome worldwide demands further understanding of the modifiable risk factors in reducing disability and morbidity associated with these conditions. Disuse skeletal muscle atrophy (sometimes referred to as "simple" atrophy) and insulin resistance are "non-pathological" events resulting from sedentary behavior and periods of enforced immobilization e.g., due to fractures or elective orthopedic surgery. Yet, the processes and drivers regulating disuse atrophy and insulin resistance and the associated molecular events remain unclear-especially in humans. The aim of this review is to present current knowledge of relationships between muscle protein turnover, insulin resistance and muscle atrophy during disuse, principally in humans. Immobilization lowers fasted state muscle protein synthesis (MPS) and induces fed-state "anabolic resistance." While a lack of dynamic measurements of muscle protein breakdown (MPB) precludes defining a definitive role for MPB in disuse atrophy, some proteolytic "marker" studies (e.g., MPB genes) suggest a potential early elevation. Immobilization also induces muscle insulin resistance (IR). Moreover, the trajectory of muscle atrophy appears to be accelerated in persistent IR states (e.g., Type II diabetes), suggesting IR may contribute to muscle disuse atrophy under these conditions. Nonetheless, the role of differences in insulin sensitivity across distinct muscle groups and its effects on rates of atrophy remains unclear. Multifaceted time-course studies into the collective role of insulin resistance and muscle protein turnover in the setting of disuse muscle atrophy, in humans, are needed to facilitate the development of appropriate countermeasures and efficacious rehabilitation protocols. PMID:27610086

  8. Human Skeletal Muscle Disuse Atrophy: Effects on Muscle Protein Synthesis, Breakdown, and Insulin Resistance—A Qualitative Review

    PubMed Central

    Rudrappa, Supreeth S.; Wilkinson, Daniel J.; Greenhaff, Paul L.; Smith, Kenneth; Idris, Iskandar; Atherton, Philip J.

    2016-01-01

    The ever increasing burden of an aging population and pandemic of metabolic syndrome worldwide demands further understanding of the modifiable risk factors in reducing disability and morbidity associated with these conditions. Disuse skeletal muscle atrophy (sometimes referred to as “simple” atrophy) and insulin resistance are “non-pathological” events resulting from sedentary behavior and periods of enforced immobilization e.g., due to fractures or elective orthopedic surgery. Yet, the processes and drivers regulating disuse atrophy and insulin resistance and the associated molecular events remain unclear—especially in humans. The aim of this review is to present current knowledge of relationships between muscle protein turnover, insulin resistance and muscle atrophy during disuse, principally in humans. Immobilization lowers fasted state muscle protein synthesis (MPS) and induces fed-state “anabolic resistance.” While a lack of dynamic measurements of muscle protein breakdown (MPB) precludes defining a definitive role for MPB in disuse atrophy, some proteolytic “marker” studies (e.g., MPB genes) suggest a potential early elevation. Immobilization also induces muscle insulin resistance (IR). Moreover, the trajectory of muscle atrophy appears to be accelerated in persistent IR states (e.g., Type II diabetes), suggesting IR may contribute to muscle disuse atrophy under these conditions. Nonetheless, the role of differences in insulin sensitivity across distinct muscle groups and its effects on rates of atrophy remains unclear. Multifaceted time-course studies into the collective role of insulin resistance and muscle protein turnover in the setting of disuse muscle atrophy, in humans, are needed to facilitate the development of appropriate countermeasures and efficacious rehabilitation protocols. PMID:27610086

  9. G/sub o/ protein of fat cells: role in hormonal regulation of agonist-stimulated phosphatidyl inositol breakdown

    SciTech Connect

    Rapiejko, P.J.; Northup, J.K.; Malbon, C.C.

    1986-05-01

    Incubating rat fat cell membranes in the presence of (/sup 32/P)NAD/sup +/ and pertussis toxin (PT) results in the ADP-ribosylation of two peptides (M/sub r/ = 41,000 and 40,000). The 41,000-M/sub r/ peptide is the inhibitory G-protein of adenylate cyclase (G/sub i/). The 40,000-M/sub r/ peptide radiolabeled in the presence of (/sup 32/P)NAD/sup +/ and PT has been purified from rabbit heart and bovine brain, but has not been identified uniformly in membranes of fat cells. Two rabbit polyclonal antisera raised against the alpha-subunit of bovine brain G/sub o/ were used to probe the nature of the 40,000-M/sub r/ peptide in rat fat cell membranes that had been separated by gel electrophoresis in the presence of sodium dodecyl sulfate and transferred electrophoretically to nitrocellulose. Both antisera specific for the alpha-subunit of G/sub o/ recognized the M/sub r/ = 40,000 peptide of fat cells that is ADP-ribosylated in the presence of PT. PT treatment of rat fat cells blocks epinephrine-stimulated inositol 1,4,5 trisphosphate (IP/sub 3/) generation. The inhibition of IP/sub 3/ generation by PT suggests a role for either G/sub i/ or G/sub o/ in receptor-mediated phosphatidyl inositol breakdown in the rat fat cell.

  10. Nuclear envelope breakdown may deliver an inhibitor of protein phosphatase 1 which triggers cyclin B translation in starfish oocytes.

    PubMed

    Lapasset, Laure; Pradet-Balade, Bérengère; Lozano, Jean-Claude; Peaucellier, Gérard; Picard, André

    2005-09-01

    In vertebrates, enhanced translation of mRNAs in oocytes and early embryos entering M-phase is thought to occur through polyadenylation, involving binding, hyperphosphorylation and proteolytic degradation of Aurora-activated CPEB. In starfish, an unknown component of the oocyte nucleus is required for cyclin B synthesis following the release of G2/prophase block by hormonal stimulation. We have found that CPEB cannot be hyperphosphorylated following hormonal stimulation in starfish oocytes from which the nucleus has been removed. Activation of Aurora kinase, known to interact with protein phosphatase 1 and its specific inhibitor Inh-2, is also prevented. The microinjection of Inh-2 restores Aurora activation, CPEB hyperphosphorylation and cyclin B translation in enucleated oocytes. Nevertheless, we provide evidence that CPEB is in fact hyperphosphorylated by cdc2, without apparent involvement of Aurora or MAP kinase, and that cyclin B synthesis can be stimulated without previous degradation of phosphorylated CPEB. Thus, the regulation of cyclin B synthesis necessary for progression through meiosis can be explained by an equilibrium between CPEB phosphorylation and dephosphorylation, and both aspects of this control may rely on the sole activation of Cdc2 and subsequent nuclear breakdown. PMID:16081061

  11. Proposed role of ATP in protein breakdown: conjugation of protein with multiple chains of the polypeptide of ATP-dependent proteolysis.

    PubMed Central

    Hershko, A; Ciechanover, A; Heller, H; Haas, A L; Rose, I A

    1980-01-01

    The heat-stable polypeptide ATP-dependent proteolysis factor 1 (APF-1) of the reticulocyte proteolytic system forms covalent compounds with proteins in an ATP-requiring reaction. APF-1 and lysozyme, a good substrate for ATP-dependent proteolysis, form multiple conjugates, as was shown by comigration of label from each upon gel electrophoresis. Multiple bands were also seen with other substrates of the ATP-dependent proteolytic system, such as globin or alpha-lactalbumin. Analysis of the ratio of APF-1 to lysozyme radioactivities and of the molecular weights of the bands indicated that they consist of increasing numbers of the APF-1 polypeptide bound to one molecule of lysozyme. The covalent linkage is probably of an isopeptide nature, because it is stable to hydroxylamine and alkali, and polylysine is able to give conjugates of APF-1. Removal of ATP after formation of the 125I-labeled APF-1 conjugates with endogenous proteins caused the regeneration of APF-1, indicating presence of an amidase. This reaction is thought to compete with proteases that may act on APF-1-protein conjugates, especially those containing several APF-1 ligands. A sequence of reactions in which the linkage of APF-1 to the substrate is followed by the proteolytic breakdown of the substrate is proposed to explain the role of ATP. Images PMID:6990414

  12. Sensitivity of periparturient breakdown of immunity to parasites to dietary protein source.

    PubMed

    Sakkas, P; Houdijk, J G M; Athanasiadou, S; Kyriazakis, I

    2012-11-01

    Effects of increased MP supply on the degree of periparturient relaxation of immunity (PPRI) in sheep may be dependent on quality of supplied MP. Here we tested the hypothesis that additional MP supply from rations based on xylose-treated soybean meal would be more effective than from rations based on faba beans in reducing the degree of PPRI, as indicated by nematode egg excretion. Twenty-four multiple-bearing ewes were trickle infected with Teladorsagia circumcincta larvae from d -56 to d 31 relative to start of lactation (d 0). From d -26 onwards, ewes were fed at either 0.8 (LP) or at 1.2 times their respective calculated MP requirements using either xylose-treated soybean (HPS) or faba beans (HPB). Litter size was adjusted to 2 lambs at parturition. Feeding treatments did not affect nematode egg excretion, ewe BW or BCS during late pregnancy (P > 0.10), but HPS and HPB ewes had reduced plasma pepsinogen concentrations (P = 0.003). During lactation, HPS and HPB feeding increased ewe BW gain (P < 0.001) and BCS (P = 0.017), and reduced plasma pepsinogen concentrations (P = 0.008) to the same extent, compared with LP feeding. However, only HPS feeding increased litter weight gain (P = 0.017) and reduced nematode egg excretion (P = 0.015), which were both similar between HPB and LP (P > 0.10). The results support the view that extra MP supply from xylose-treated soybean based rations is more effective in reducing parasitism than MP from faba bean-based rations, suggesting that protein source and/or quality are important factors to consider for the nutritional control of parasitism. PMID:22665670

  13. Over-represented localized sequence motifs in ribosomal protein gene promoters of basal metazoans.

    PubMed

    Perina, Drago; Korolija, Marina; Roller, Maša; Harcet, Matija; Jeličić, Branka; Mikoč, Andreja; Cetković, Helena

    2011-07-01

    Equimolecular presence of ribosomal proteins (RPs) in the cell is needed for ribosome assembly and is achieved by synchronized expression of ribosomal protein genes (RPGs) with promoters of similar strengths. Over-represented motifs of RPG promoter regions are identified as targets for specific transcription factors. Unlike RPs, those motifs are not conserved between mammals, drosophila, and yeast. We analyzed RPGs proximal promoter regions of three basal metazoans with sequenced genomes: sponge, cnidarian, and placozoan and found common features, such as 5'-terminal oligopyrimidine tracts and TATA-boxes. Furthermore, we identified over-represented motifs, some of which displayed the highest similarity to motifs abundant in human RPG promoters and not present in Drosophila or yeast. Our results indicate that humans over-represented motifs, as well as corresponding domains of transcription factors, were established very early in metazoan evolution. The fast evolving nature of RPGs regulatory network leads to formation of other, lineage specific, over-represented motifs. PMID:21457775

  14. Aggresomes do not represent a general cellular response to protein misfolding in mammalian cells

    PubMed Central

    Beaudoin, Simon; Goggin, Kevin; Bissonnette, Cyntia; Grenier, Catherine; Roucou, Xavier

    2008-01-01

    Background Aggresomes are juxtanuclear inclusion bodies that have been proposed to represent a general cellular response to misfolded proteins in mammalian cells. Yet, why aggresomes are not a pathological characteristic of protein misfolding diseases is unclear. Here, we investigate if a misfolded protein inevitably forms aggresomes in mammalian cells. Results We show that a cytoplasmic form of the prion protein may form aggresomes or dispersed aggregates in different cell lines. In contrast to aggresomes, the formation of dispersed aggregates is insensitive to histone deacetylase 6 inhibitors and does not result in cytoskeleton rearrangements. Modulation of expression levels or proteasome inhibitors does not alter the formation of dispersed aggregates. Conclusion Our results establish that aggresomes are not obligatory products of protein misfolding in vivo. PMID:18937858

  15. An estimated 5% of new protein structures solved today represent a new Pfam family

    SciTech Connect

    Mistry, Jaina; Kloppmann, Edda; Rost, Burkhard; Punta, Marco

    2013-11-01

    This study uses the Pfam database to show that the sequence redundancy of protein structures deposited in the PDB is increasing. The possible reasons behind this trend are discussed. High-resolution structural knowledge is key to understanding how proteins function at the molecular level. The number of entries in the Protein Data Bank (PDB), the repository of all publicly available protein structures, continues to increase, with more than 8000 structures released in 2012 alone. The authors of this article have studied how structural coverage of the protein-sequence space has changed over time by monitoring the number of Pfam families that acquired their first representative structure each year from 1976 to 2012. Twenty years ago, for every 100 new PDB entries released, an estimated 20 Pfam families acquired their first structure. By 2012, this decreased to only about five families per 100 structures. The reasons behind the slower pace at which previously uncharacterized families are being structurally covered were investigated. It was found that although more than 50% of current Pfam families are still without a structural representative, this set is enriched in families that are small, functionally uncharacterized or rich in problem features such as intrinsically disordered and transmembrane regions. While these are important constraints, the reasons why it may not yet be time to give up the pursuit of a targeted but more comprehensive structural coverage of the protein-sequence space are discussed.

  16. Serum Glial Fibrillary Acidic Protein Predicts Tissue Glial Fibrillary Acidic Protein Break-Down Products and Therapeutic Efficacy after Penetrating Ballistic-Like Brain Injury.

    PubMed

    Boutté, Angela M; Deng-Bryant, Ying; Johnson, David; Tortella, Frank C; Dave, Jitendra R; Shear, Deborah A; Schmid, Kara E

    2016-01-01

    Acute traumatic brain injury (TBI) is associated with neurological dysfunction, changes in brain proteins, and increased serum biomarkers. However, the relationship between these brain proteins and serum biomarkers, and the ability of these serum biomarkers to indicate a neuroprotective/therapeutic response, remains elusive. Penetrating ballistic-like brain injury (PBBI) was used to systematically analyze several key TBI biomarkers, glial fibrillary acidic protein (GFAP) and its break-down products (BDPs)-ubiquitin C-terminal hydrolase-L1 (UCH-L1), α-II spectrin, and α-II spectrin BDPs (SBDPs)-in brain tissues and serum during an extended acute-subacute time-frame. In addition, neurological improvement and serum GFAP theranostic value was evaluated after neuroprotective treatment. In brain tissues, total GFAP increased more than three-fold 2 to 7 d after PBBI. However, this change was primarily due to GFAP-BDPs which increased to 2.7-4.8 arbitrary units (AU). Alpha-II spectrin was nearly ablated 3 d after PBBI, but somewhat recovered after 7 d. In conjunction with α-II spectrin loss, SBDP-145/150 increased approximately three-fold 2 to 7 d after PBBI (vs. sham, p<0.05). UCH-L1 protein levels were slightly decreased 7 d after PBBI but otherwise were unaffected. Serum GFAP was elevated by 3.2- to 8.8-fold at 2 to 4 h (vs. sham; p<0.05) and the 4 h increase was strongly correlated to 3 d GFAP-BDP abundance (r=0.66; p<0.05). Serum GFAP showed such a strong injury effect that it also was evaluated after therapeutic intervention with cyclosporin A (CsA). Administration of 2.5 mg/kg CsA significantly reduced serum GFAP elevation by 22.4-fold 2 h after PBBI (vs. PBBI+vehicle; p<0.05) and improved neurological function 1 d post-injury. Serum biomarkers, particularly GFAP, may be correlative tools of brain protein changes and feasible theranostic markers of TBI progression and recovery. PMID:25789543

  17. Neandertals' large lower thorax may represent adaptation to high protein diet.

    PubMed

    Ben-Dor, Miki; Gopher, Avi; Barkai, Ran

    2016-07-01

    Humans are limited in their capacity to convert protein into energy. We present a hypothesis that a "bell" shaped thorax and a wide pelvis evolved in Neandertals, at least in part, as an adaptation to a high protein diet. A high protein diet created a need to house an enlarged liver and urinary system in a wider lower trunk. To test the hypothesis, we applied a model developed to identify points of nutritional stress. A ratio of obligatory dietary fat to total animal fat and protein sourced calories is calculated based on various known and estimated parameters. Stress is identified when the obligatory dietary fat ratio is higher than fat content ratios in available prey. The model predicts that during glacial winters, when carbohydrates weren't available, 74%-85% of Neandertals' caloric intake would have had to come from animal fat. Large animals contain around 50% fat calories, and their fat content is diminished during winter, so a significant stressful dietary fat deficit was identified by the model. This deficit could potentially be ameliorated by an increased capability to convert protein into energy. Given that high protein consumption is associated with larger liver and kidneys in animal models, it appears likely that the enlarged inferior section of the Neandertals thorax and possibly, in part, also his wide pelvis, represented an adaptation to provide encasement for those enlarged organs. Behavioral and evolutionary implications of the hypothesis are also discussed. Am J Phys Anthropol 160:367-378, 2016. © 2016 Wiley Periodicals, Inc. PMID:26973080

  18. Catalytically-inactive beta-amylase BAM4 required for starch breakdown in Arabidopsis leaves is a starch-binding-protein.

    PubMed

    Li, Jing; Francisco, Perigio; Zhou, Wenxu; Edner, Christoph; Steup, Martin; Ritte, Gerhard; Bond, Charles S; Smith, Steven M

    2009-09-01

    Of the four chloroplast beta-amylase (BAM) proteins identified in Arabidopsis, BAM3 and BAM4 were previously shown to play the major roles in leaf starch breakdown, although BAM4 apparently lacks key active site residues and beta-amylase activity. Here we tested multiple BAM4 proteins with different N-terminal sequences with a range of glucan substrates and assay methods, but detected no alpha-1,4-glucan hydrolase activity. BAM4 did not affect BAM1, BAM2 or BAM3 activity even when added in 10-fold excess, nor the BAM3-catalysed release of maltose from isolated starch granules in the presence of glucan water dikinase. However, BAM4 binds to amylopectin and to amylose-Sepharose whereas BAM2 has very low beta-amylase activity and poor glucan binding. The low activity of BAM2 may be explained by poor glucan binding but absence of BAM4 activity is not. These results suggest that BAM4 facilitates starch breakdown by a mechanism involving direct interaction with starch or other alpha-1,4-glucan. PMID:19664588

  19. The Use of Helical Net-Diagrams to Represent Protein Structures

    PubMed Central

    Dunnill, P.

    1968-01-01

    The arrangement of side chains in α-helical regions of protein can be represented by helical net-diagrams. The addition of quantitative indices of the character of the residue at each net-point facilitates a straightforward examination of the groupings of residues of different character. As such the method complements that of Schiffer and Edmundson (1967). In addition, the reasons for non-helicity in some regions may be seen to be correlated with particular side-chain distributions. The method is illustrated with respect to myoglobin and lysozyme. PMID:5699810

  20. Rv1698 of Mycobacterium tuberculosis represents a new class of channel-forming outer membrane proteins.

    PubMed

    Siroy, Axel; Mailaender, Claudia; Harder, Daniel; Koerber, Stephanie; Wolschendorf, Frank; Danilchanka, Olga; Wang, Ying; Heinz, Christian; Niederweis, Michael

    2008-06-27

    Mycobacteria contain an outer membrane composed of mycolic acids and a large variety of other lipids. Its protective function is an essential virulence factor of Mycobacterium tuberculosis. Only OmpA, which has numerous homologs in Gram-negative bacteria, is known to form channels in the outer membrane of M. tuberculosis so far. Rv1698 was predicted to be an outer membrane protein of unknown function. Expression of rv1698 restored the sensitivity to ampicillin and chloramphenicol of a Mycobacterium smegmatis mutant lacking the main porin MspA. Uptake experiments showed that Rv1698 partially complemented the permeability defect of the M. smegmatis porin mutant for glucose. These results indicated that Rv1698 provides an unspecific pore that can partially substitute for MspA. Lipid bilayer experiments demonstrated that purified Rv1698 is an integral membrane protein that indeed produces channels. The main single channel conductance is 4.5 +/- 0.3 nanosiemens in 1 M KCl. Zero current potential measurements revealed a weak preference for cations. Whole cell digestion of recombinant M. smegmatis with proteinase K showed that Rv1698 is surface-accessible. Taken together, these experiments demonstrated that Rv1698 is a channel protein that is likely involved in transport processes across the outer membrane of M. tuberculosis. Rv1698 has single homologs of unknown functions in Corynebacterineae and thus represents the first member of a new class of channel proteins specific for mycolic acid-containing outer membranes. PMID:18434314

  1. Short communication: Proteins from circulating exosomes represent metabolic state in transition dairy cows.

    PubMed

    Crookenden, M A; Walker, C G; Peiris, H; Koh, Y; Heiser, A; Loor, J J; Moyes, K M; Murray, A; Dukkipati, V S R; Kay, J K; Meier, S; Roche, J R; Mitchell, M D

    2016-09-01

    Biomarkers that identify prepathological disease could enhance preventive management, improve animal health and productivity, and reduce costs. Circulating extracellular vesicles, particularly exosomes, are considered to be long-distance, intercellular communication systems in human medicine. Exosomes provide tissue-specific messages of functional state and can alter the cellular activity of recipient tissues through their protein and microRNA content. We hypothesized that exosomes circulating in the blood of cows during early lactation would contain proteins representative of the metabolic state of important tissues, such as liver, which play integral roles in regulating the physiology of cows postpartum. From a total of 150 cows of known metabolic phenotype, 10 cows were selected with high (n=5; high risk) and low (n=5; low risk) concentrations of nonesterified fatty acids, β-hydroxybutyrate, and liver triacylglycerol during wk 1 and 2 after calving. Exosomes were extracted from blood on the day of calving (d 0) and postcalving at wk 1 and wk 4, and their protein composition was determined by mass spectroscopy. Extracellular vesicle protein concentration and the number of exosome vesicles were not affected by risk category; however, the exosome protein cargo differed between the groups, with proteins at each time point identified as being unique to the high- and low-risk groups. The proteins α-2 macroglobulin, fibrinogen, and oncoprotein-induced transcript 3 were unique to the high-risk cows on d 0 and have been associated with metabolic syndrome and liver function in humans. Their presence may indicate a more severe inflammatory state and a greater degree of liver dysfunction in the high-risk cows than in the low-risk cows, consistent with the high-risk cows' greater plasma β-hydroxybutyrate and liver triacylglycerol concentrations. The commonly shared proteins and those unique to the low-risk category indicate a role for exosomes in immune function. The data

  2. [Study of the process of thermal aggregation of several representative tobamovirus coat proteins].

    PubMed

    Abu-Eid, M; Kust, S V; Makeeva, I V; Novikov, V K; Dobrov, E N

    1994-01-01

    The role of the specific region of the tobacco mosaic virus (TMV) coat protein (CP) molecule (called "70A degree-region") in the regulation of ordered and unordered CP aggregation was investigated. CPs of the wild type TMV (strain U1), of temperature sensitive mutant with two amino acid substitutions in the "70A degree-region", and of cucumber virus 3 which is related to TMV but has a completely different structure in the "70A degree-region" were used. With the help of two different tests the processes of temperature-induced unordered aggregation of these three CPs were compared in solutions of different ionic strength and pH. On the basis of the data obtained it was concluded that the "70A-region" represents the most thermolabile region in the TMV CP molecule and that local thermal denaturation of this region results in unordered aggregation, when solution conditions (ionic strength and pH) favor formation of relatively large ordered aggregates (20S-"disks" or helical repolymerized protein). PMID:8065382

  3. DC Breakdown Experiments

    SciTech Connect

    Calatroni, S.; Descoeudres, A.; Levinsen, Y.; Taborelli, M.; Wuensch, W.

    2009-01-22

    In the context of the CLIC (Compact Linear Collider) project investigations of DC breakdown in ultra high vacuum are carried out in parallel with high power RF tests. From the point of view of saturation breakdown field the best material tested so far is stainless steel, followed by titanium. Copper shows a four times weaker breakdown field than stainless steel. The results indicate clearly that the breakdown events are initiated by field emission current and that the breakdown field is limited by the cathode. In analogy to RF, the breakdown probability has been measured in DC and the data show similar behaviour as a function of electric field.

  4. Phenylbutyrate improves nitrogen disposal via an alternative pathway without eliciting an increase in protein breakdown and catabolism in control and ornithine transcarbamylase–deficient patients123

    PubMed Central

    Marini, Juan C; Lanpher, Brendan C; Scaglia, Fernando; O'Brien, William E; Sun, Qin; Garlick, Peter J; Jahoor, Farook

    2011-01-01

    Background: Phenylbutyrate is a drug used in patients with urea cycle disorder to elicit alternative pathways for nitrogen disposal. However, phenylbutyrate administration decreases plasma branched-chain amino acid (BCAA) concentrations, and previous research suggests that phenylbutyrate administration may increase leucine oxidation, which would indicate increased protein degradation and net protein loss. Objective: We investigated the effects of phenylbutyrate administration on whole-body protein metabolism, glutamine, leucine, and urea kinetics in healthy and ornithine transcarbamylase–deficient (OTCD) subjects and the possible benefits of BCAA supplementation during phenylbutyrate therapy. Design: Seven healthy control and 7 partial-OTCD subjects received either phenylbutyrate or no treatment in a crossover design. In addition, the partial-OTCD and 3 null-OTCD subjects received phenylbutyrate and phenylbutyrate plus BCAA supplementation. A multitracer protocol was used to determine the whole-body fluxes of urea and amino acids of interest. Results: Phenylbutyrate administration reduced ureagenesis by ≈15% without affecting the fluxes of leucine, tyrosine, phenylalanine, or glutamine and the oxidation of leucine or phenylalanine. The transfer of 15N from glutamine to urea was reduced by 35%. However, a reduction in plasma concentrations of BCAAs due to phenylbutyrate treatment was observed. BCAA supplementation did not alter the respective baseline fluxes. Conclusions: Prolonged phenylbutyrate administration reduced ureagenesis and the transfer of 15N from glutamine to urea without parallel reductions in glutamine flux and concentration. There were no changes in total-body protein breakdown and amino acid catabolism, which suggests that phenylbutyrate can be used to dispose of nitrogen effectively without adverse effects on body protein economy. PMID:21490144

  5. YcgC represents a new protein deacetylase family in prokaryotes

    PubMed Central

    Tu, Shun; Guo, Shu-Juan; Chen, Chien-Sheng; Liu, Cheng-Xi; Jiang, He-Wei; Ge, Feng; Deng, Jiao-Yu; Zhou, Yi-Ming; Czajkowsky, Daniel M; Li, Yang; Qi, Bang-Ruo; Ahn, Young-Hoon; Cole, Philip A; Zhu, Heng; Tao, Sheng-Ce

    2015-01-01

    Reversible lysine acetylation is one of the most important protein posttranslational modifications that plays essential roles in both prokaryotes and eukaryotes. However, only a few lysine deacetylases (KDACs) have been identified in prokaryotes, perhaps in part due to their limited sequence homology. Herein, we developed a ‘clip-chip’ strategy to enable unbiased, activity-based discovery of novel KDACs in the Escherichia coli proteome. In-depth biochemical characterization confirmed that YcgC is a serine hydrolase involving Ser200 as the catalytic nucleophile for lysine deacetylation and does not use NAD+ or Zn2+ like other established KDACs. Further, in vivo characterization demonstrated that YcgC regulates transcription by catalyzing deacetylation of Lys52 and Lys62 of a transcriptional repressor RutR. Importantly, YcgC targets a distinct set of substrates from the only known E. coli KDAC CobB. Analysis of YcgC’s bacterial homologs confirmed that they also exhibit KDAC activity. YcgC thus represents a novel family of prokaryotic KDACs. DOI: http://dx.doi.org/10.7554/eLife.05322.001 PMID:26716769

  6. The highly abundant protein Ag-lbp55 from Ascaridia galli represents a novel type of lipid-binding proteins.

    PubMed

    Jordanova, Rositsa; Radoslavov, Georgi; Fischer, Peter; Torda, Andrew; Lottspeich, Friedrich; Boteva, Raina; Walter, Rolf D; Bankov, Ilia; Liebau, Eva

    2005-12-16

    Lipid-binding proteins exhibit important functions in lipid transport, cellular signaling, gene transcription, and cytoprotection. Their functional analogues in nematodes are nematode polyprotein allergens/antigens and fatty acid and retinoid-binding proteins. This work describes a novel 55-kDa protein, Ag-lbp55, purified from the parasitic nematode Ascaridia galli. By direct N-terminal sequencing, a partial amino acid sequence was obtained that allowed the design of oligonucleotide primers to obtain the full-length cDNA sequence. Sequence analysis revealed the presence of an N-terminal signal peptide of 25 amino acid residues and a FAR domain at the C terminus. Data base searches showed almost no significant homologies to other described proteins. The secondary structure of Ag-lbp55 was predominantly alpha-helical (65%) as shown by CD spectroscopy. It was found to bind with high affinity fatty acids (caprylic, oleic, and palmitic acid) and their fluorescent analogue dansylaminoundecanic acid. Immunolocalization showed that Ag-lbp55 is a highly abundant protein, mainly distributed in the inner hypodermis and extracellularly in the pseudocoelomatic fluid. A similar staining pattern was observed in other pathogenic nematodes, indicating the existence of similar proteins in these species. PMID:16210327

  7. Structures of Two Arabidopsis thaliana Major Latex Proteins Represent Novel Helix-Grip Folds

    PubMed Central

    Lytle, Betsy L.; Song, Jikui; de la Cruz, Norberto B.; Peterson, Francis C.; Johnson, Kenneth A.; Bingman, Craig A.; Phillips, George N.; Volkman, Brian F.

    2010-01-01

    The major latex proteins (MLP) are a protein family first identified in the latex of opium poppy. They are found only in plants and have 24 identified members in Arabidopsis alone as well as in other plants such as peach, strawberry, melon, cucumber, and soybean. While the function of the MLPs is unknown, they have been associated with fruit and flower development and in pathogen defense responses. Based on modest sequence similarity, they have been characterized as members of the Bet v 1 protein superfamily; however, no structures have yet been reported. As part of an ongoing structural genomics effort, we determined the structures of two Arabidopsis thaliana MLPs: the solution structure of MLP28 (gene product of At1g70830.1) and the crystal structure of At1g24000.1. The structures revealed distinct differences when compared to one another and to the typical Bet v 1 fold. Nevertheless, NMR titration experiments demonstrated that the characteristic Bet v 1 hydrophobic binding pocket of At1g24000.1 is able to bind a ligand, suggesting that it plays a role in the function of the MLPs. A structure-based sequence analysis identified conserved hydrophobic residues in the long alpha helix that contribute to the binding cavity and may specify preferred ligands for the MLP family. PMID:19326460

  8. Ser/Thr/Tyr Protein Phosphorylation in the Archaeon Halobacterium salinarum—A Representative of the Third Domain of Life

    PubMed Central

    Gnad, Florian; Reichelt, Peter; Mann, Matthias; Oesterhelt, Dieter

    2009-01-01

    In the quest for the origin and evolution of protein phosphorylation, the major regulatory post-translational modification in eukaryotes, the members of archaea, the “third domain of life”, play a protagonistic role. A plethora of studies have demonstrated that archaeal proteins are subject to post-translational modification by covalent phosphorylation, but little is known concerning the identities of the proteins affected, the impact on their functionality, the physiological roles of archaeal protein phosphorylation/dephosphorylation, and the protein kinases/phosphatases involved. These limited studies led to the initial hypothesis that archaea, similarly to other prokaryotes, use mainly histidine/aspartate phosphorylation, in their two-component systems representing a paradigm of prokaryotic signal transduction, while eukaryotes mostly use Ser/Thr/Tyr phosphorylation for creating highly sophisticated regulatory networks. In antithesis to the above hypothesis, several studies showed that Ser/Thr/Tyr phosphorylation is also common in the bacterial cell, and here we present the first genome-wide phosphoproteomic analysis of the model organism of archaea, Halobacterium salinarum, proving the existence/conservation of Ser/Thr/Tyr phosphorylation in the “third domain” of life, allowing a better understanding of the origin and evolution of the so-called “Nature's premier” mechanism for regulating the functional properties of proteins. PMID:19274099

  9. Vortex breakdown simulation

    NASA Technical Reports Server (NTRS)

    Nakamura, Y.; Leonard, A.; Spalart, P. R.

    1985-01-01

    A vortex breakdown was simulated by the vortex filament method, and detailed figures are presented based on the results. Deformations of the vortex filaments showed clear and large swelling at a particular axial station which implied the presence of a recirculation bubble at that station. The tendency for two breakdowns to occur experimentally was confirmed by the simulation, and the jet flow inside the bubble was well simulated. The particle paths spiralled with expansion, and the streamlines took spiral forms at the breakdown with expansion.

  10. Structures of two Arabidopsis thaliana major latex proteins represent novel helix-grip folds

    SciTech Connect

    Lytle, Betsy L.; Song, Jikui; de la Cruz, Norberto B.; Peterson, Francis C.; Johnson, Kenneth A.; Bingman, Craig A.; Phillips, Jr., George N.; Volkman, Brian F.

    2009-06-02

    Here we report the first structures of two major latex proteins (MLPs) which display unique structural differences from the canonical Bet v 1 fold described earlier. MLP28 (SwissProt/TrEMBL ID Q9SSK9), the product of gene At1g70830.1, and the At1g24000.1 gene product (Swiss- Prot/TrEMBL ID P0C0B0), proteins which share 32% sequence identity, were independently selected as foldspace targets by the Center for Eukaryotic Structural Genomics. The structure of a single domain (residues 17-173) of MLP28 was solved by NMR spectroscopy, while the full-length At1g24000.1 structure was determined by X-ray crystallography. MLP28 displays greater than 30% sequence identity to at least eight MLPs from other species. For example, the MLP28 sequence shares 64% identity to peach Pp-MLP119 and 55% identity to cucumber Csf2.20 In contrast, the At1g24000.1 sequence is highly divergent (see Fig. 1), containing a gap of 33 amino acids when compared with all other known MLPs. Even when the gap is excluded, the sequence identity with MLPs from other species is less than 30%. Unlike some of the MLPs from other species, none of the A. thaliana MLPs have been characterized biochemically. We show by NMR chemical shift mapping that At1g24000.1 binds progesterone, demonstrating that despite its sequence dissimilarity, the hydrophobic binding pocket is conserved and, therefore, may play a role in its biological function and that of the MLP family in general.

  11. The multiple phenylpropene synthases in both Clarkia breweri and Petunia hybrida represent two distinct protein lineages

    PubMed Central

    Koeduka, Takao; Louie, Gordon V.; Orlova, Irina; Kish, Christine M.; Ibdah, Mwafaq; Wilkerson, Curtis G.; Bowman, Marianne E.; Baiga, Thomas J.; Noel, Joseph P.; Dudareva, Natalia; Pichersky, Eran

    2009-01-01

    Summary Many plants synthesize the volatile phenylpropene compounds eugenol and isoeugenol to serve in defense against herbivores and pathogens and to attract pollinators. Clarkia breweri flowers emit a mixture of eugenol and isoeugenol, while Petunia hybrida flowers emit mostly isoeugenol with small amounts of eugenol. We recently reported the identification of a petunia enzyme, PhIGS1, that catalyzes the formation of isoeugenol, and an Ocimum basilicum (basil) enzyme, ObEGS1, that produces eugenol. ObEGS1 and PhIGS1 both utilize coniferyl acetate, are 52% sequence identical, and belong to a family of NADPH-dependent reductases involved in secondary metabolism. Here we show that C. breweri flowers have two closely related proteins (96% identity), CbIGS1 and CbEGS1, that are similar to ObEGS1 (58% and 59%) and catalyze the formation of isoeugenol and eugenol, respectively. In vitro mutagenesis experiments demonstrate that substitution of only a single residue can substantially affect the product specificity of these enzymes. A third C. breweri enzyme identified, CbEGS2, also catalyzes the formation of eugenol from coniferyl acetate and is only 46% identical to CbIGS1 and CbEGS1 but more similar (>70%) to other types of reductases. We also found that petunia flowers contain an enzyme, PhEGS1, that is highly similar to CbEGS2 (82% identity) and that converts coniferyl acetate to eugenol. Our results indicate that plant enzymes with EGS and IGS activities have arisen multiple times and in different protein lineages. PMID:18208524

  12. Large oncosomes contain distinct protein cargo and represent a separate functional class of tumor-derived extracellular vesicles.

    PubMed

    Minciacchi, Valentina R; You, Sungyong; Spinelli, Cristiana; Morley, Samantha; Zandian, Mandana; Aspuria, Paul-Joseph; Cavallini, Lorenzo; Ciardiello, Chiara; Reis Sobreiro, Mariana; Morello, Matteo; Kharmate, Geetanjali; Jang, Su Chul; Kim, Dae-Kyum; Hosseini-Beheshti, Elham; Tomlinson Guns, Emma; Gleave, Martin; Gho, Yong Song; Mathivanan, Suresh; Yang, Wei; Freeman, Michael R; Di Vizio, Dolores

    2015-05-10

    Large oncosomes (LO) are atypically large (1-10 µm diameter) cancer-derived extracellular vesicles (EVs), originating from the shedding of membrane blebs and associated with advanced disease. We report that 25% of the proteins, identified by a quantitative proteomics analysis, are differentially represented in large and nano-sized EVs from prostate cancer cells. Proteins enriched in large EVs included enzymes involved in glucose, glutamine and amino acid metabolism, all metabolic processes relevant to cancer. Glutamine metabolism was altered in cancer cells exposed to large EVs, an effect that was not observed upon treatment with exosomes. Large EVs exhibited discrete buoyant densities in iodixanol (OptiPrep(TM)) gradients. Fluorescent microscopy of large EVs revealed an appearance consistent with LO morphology, indicating that these structures can be categorized as LO. Among the proteins enriched in LO, cytokeratin 18 (CK18) was one of the most abundant (within the top 5th percentile) and was used to develop an assay to detect LO in the circulation and tissues of mice and patients with prostate cancer. These observations indicate that LO represent a discrete EV type that may play a distinct role in tumor progression and that may be a source of cancer-specific markers. PMID:25857301

  13. Partial cloning of CYP2C23a genes and hepatic protein expression in eight representative avian species.

    PubMed

    Watanabe, K P; Kawai, Y K; Nakayama, S M M; Ikenaka, Y; Mizukawa, H; Takaesu, N; Ito, M; Ikushiro, S-I; Sakaki, T; Ishizuka, M

    2015-04-01

    Large interspecies differences in avian xenobiotic metabolism have been revealed by microsome-based studies, but specific enzyme isoforms in different bird species have not yet been compared. We have previously shown that CYP2C23 genes are the most induced CYP isoforms in chicken liver. In this study, we collected partial CYP2C23a gene sequences from eight avian species (ostrich, blue-eared pheasant, snowy owl, great-horned owl, Chilean flamingo, peregrin falcon, Humboldt penguin, and black-crowned night heron) selected to cover the whole avian lineage: Paleognathae, Galloanserae, and Neoaves. Genetic analysis showed that CYP2C23 genes of Galloanserae species (chicken and blue-eared pheasant) had unique characteristics. We found some duplicated genes (CYP2C23a and CYP2C23b) and two missing amino acid residues in Galloanserae compared to the other two lineages. The genes have lower homology than in other avian lineages, which suggests Galloanserae-specific rapid evolutionary changes. These genetic features suggested that the Galloanserae are not the most representative avian species, considering that the Neoaves comprise more than 95% of birds. Moreover, we succeeded in synthesizing an antipeptide polyclonal antibody against the region of CYP2C23 protein conserved in avians. However, comparative quantitation of CYP2C23 proteins in livers from six species showed that expression levels of these proteins differed no more than fourfold. Further study is needed to clarify the function of avian CYP2C23 proteins. PMID:25229839

  14. Effect of sepsis on calcium uptake and content in skeletal muscle and regulation in vitro by calcium of total and myofibrillar protein breakdown in control and septic muscle: Results from a preliminary study

    SciTech Connect

    Benson, D.W.; Hasselgren, P.O.; Hiyama, D.T.; James, J.H.; Li, S.; Rigel, D.F.; Fischer, J.E.

    1989-07-01

    Because high calcium concentration in vitro stimulates muscle proteolysis, calcium has been implicated in the pathogenesis of increased muscle breakdown in different catabolic conditions. Protein breakdown in skeletal muscle is increased during sepsis, but the effect of sepsis on muscle calcium uptake and content is not known. In this study the influence of sepsis, induced in rats by cecal ligation and puncture, on muscle calcium uptake and content was studied. Sixteen hours after cecal ligation and puncture or sham operation, calcium content of the extensor digitorum longus (EDL) and soleus (SOL) muscles was determined with an atomic absorption spectrometer. Calcium uptake was measured in intact SOL muscles incubated in the presence of calcium 45 (45Ca) for between 1 and 120 minutes. Total and myofibrillar protein breakdown was determined in SOL muscles, incubated in the presence of different calcium concentrations (0; 2.5; 5.0 mmol/L), and measured as release into the incubation medium of tyrosine and 3-methylhistidine (3-MH), respectively. Calcium content was increased by 51% (p less than 0.001) during sepsis in SOL and by 10% (p less than 0.05) in EDL muscle. There was no difference in 45Ca uptake between control and septic muscles during the early phase (1 to 5 minutes) of incubation. During more extended incubation (30 to 120 minutes), muscles from septic rats took up significantly more 45Ca than control muscles (p less than 0.05). Tyrosine release by incubated SOL muscles from control and septic rats was increased when calcium was added to the incubation medium, and at a calcium concentration of 2.5 mmol/L, the increase in tyrosine release was greater in septic than in control muscle. Addition of calcium to the incubation medium did not affect 3-MH release in control or septic muscle.

  15. Sequence and structural implications of a bovine corneal keratan sulfate proteoglycan core protein. Protein 37B represents bovine lumican and proteins 37A and 25 are unique

    NASA Technical Reports Server (NTRS)

    Funderburgh, J. L.; Funderburgh, M. L.; Brown, S. J.; Vergnes, J. P.; Hassell, J. R.; Mann, M. M.; Conrad, G. W.; Spooner, B. S. (Principal Investigator)

    1993-01-01

    Amino acid sequence from tryptic peptides of three different bovine corneal keratan sulfate proteoglycan (KSPG) core proteins (designated 37A, 37B, and 25) showed similarities to the sequence of a chicken KSPG core protein lumican. Bovine lumican cDNA was isolated from a bovine corneal expression library by screening with chicken lumican cDNA. The bovine cDNA codes for a 342-amino acid protein, M(r) 38,712, containing amino acid sequences identified in the 37B KSPG core protein. The bovine lumican is 68% identical to chicken lumican, with an 83% identity excluding the N-terminal 40 amino acids. Location of 6 cysteine and 4 consensus N-glycosylation sites in the bovine sequence were identical to those in chicken lumican. Bovine lumican had about 50% identity to bovine fibromodulin and 20% identity to bovine decorin and biglycan. About two-thirds of the lumican protein consists of a series of 10 amino acid leucine-rich repeats that occur in regions of calculated high beta-hydrophobic moment, suggesting that the leucine-rich repeats contribute to beta-sheet formation in these proteins. Sequences obtained from 37A and 25 core proteins were absent in bovine lumican, thus predicting a unique primary structure and separate mRNA for each of the three bovine KSPG core proteins.

  16. Analysis of Laser Breakdown Data

    NASA Astrophysics Data System (ADS)

    Becker, Roger

    2009-03-01

    Experiments on laser breakdown for ns pulses of 532 nm or 1064 nm light in water and dozens of simple hydrocarbon liquids are analyzed and compared to widely-used models and other laser breakdown experiments reported in the literature. Particular attention is given to the curve for the probability of breakdown as a function of the laser fluence at the beam focus. Criticism is made of the na"ive forms of both ``avalanche'' breakdown and multi-photon breakdown. It appears that the process is complex and is intimately tied to the chemical group of the material. Difficulties with developing an accurate model of laser breakdown in liquids are outlined.

  17. Beauty in the Breakdown

    ERIC Educational Resources Information Center

    Brisco, Nicole

    2008-01-01

    Most human beings look at erosion as the destruction of a surface, but artists can see that erosion often creates indefinable beauty. Where do you see beauty in the breakdown? In this article, the author presents an innovative lesson that would allow students to observe both human and physical nature. In this activity students will create a work…

  18. Measuring Breakdown Voltage.

    ERIC Educational Resources Information Center

    Auer, Herbert J.

    1978-01-01

    The article discusses an aspect of conductivity, one of the electrical properties subdivisions, and describes a tester that can be shop-built. Breakdown voltage of an insulation material is specifically examined. Test procedures, parts lists, diagrams, and test data form are included. (MF)

  19. Endosperm breakdown in Arabidopsis requires heterodimers of the basic helix-loop-helix proteins ZHOUPI and INDUCER OF CBP EXPRESSION 1.

    PubMed

    Denay, Grégoire; Creff, Audrey; Moussu, Steven; Wagnon, Pauline; Thévenin, Johanne; Gérentes, Marie-France; Chambrier, Pierre; Dubreucq, Bertrand; Ingram, Gwyneth

    2014-03-01

    In Arabidopsis seeds, embryo growth is coordinated with endosperm breakdown. Mutants in the endosperm-specific gene ZHOUPI (ZOU), which encodes a unique basic helix-loop-helix (bHLH) transcription factor, have an abnormal endosperm that persists throughout seed development, significantly impeding embryo growth. Here we show that loss of function of the bHLH-encoding gene INDUCER OF CBP EXPRESSION 1 (ICE1) causes an identical endosperm persistence phenotype. We show that ZOU and ICE1 are co-expressed in the endosperm and interact in yeast via their bHLH domains. We show both genetically and in a heterologous plant system that, despite the fact that both ZOU and ICE1 can form homodimers in yeast, their role in endosperm breakdown requires their heterodimerization. Consistent with this conclusion, we confirm that ZOU and ICE1 regulate the expression of common target genes in the developing endosperm. Finally, we show that heterodimerization of ZOU and ICE1 is likely to be necessary for their binding to specific targets, rather than for their nuclear localization in the endosperm. By comparing our results with paradigms of bHLH function and evolution in animal systems we propose that the ZOU/ICE1 complex might have ancient origins, acquiring novel megagametophyte-specific functions in heterosporous land plants that were conserved in the angiosperm endosperm. PMID:24553285

  20. Isoaspartic acid is present at specific sites in myelin basic protein from multiple sclerosis patients: could this represent a trigger for disease onset?

    PubMed

    Friedrich, Michael G; Hancock, Sarah E; Raftery, Mark J; Truscott, Roger J W

    2016-01-01

    Multiple sclerosis (MS) is associated with breakdown of the myelin sheath that coats neurons in the central nervous system. The cause of MS is not known, although the pathogenesis involves destruction of myelin by the immune system. It was the aim of this study to examine the abundant myelin protein, myelin basic protein (MBP), to determine if there are sites of modification that may be characteristic for MS. MBP from the cerebellum was examined from controls and MS patients across the age range using mass spectrometry and amino acid analysis. Amino acid racemization data indicated that myelin basic protein is long-lived and proteomic analysis of MBP showed it to be highly modified. A common modification of MBP was racemization of Asp and this was significantly greater in MS patients. In long-lived proteins, L-Asp and L-Asn can racemize to three other isomers, D-isoAsp, L-isoAsp and D-Asp and this is significant because isoAsp formation in peptides renders them immunogenic.Proteomic analysis revealed widespread modifications of MBP with two surface regions that are altered in MS. In particular, isoAsp was significantly elevated at these sites in MS patients. The generation of isoAsp could be responsible for eliciting an immune response to modified MBP and therefore be implicated in the etiology of MS. PMID:27519525

  1. Space Charge Modulated Electrical Breakdown

    PubMed Central

    Li, Shengtao; Zhu, Yuanwei; Min, Daomin; Chen, George

    2016-01-01

    Electrical breakdown is one of the most important physical phenomena in electrical and electronic engineering. Since the early 20th century, many theories and models of electrical breakdown have been proposed, but the origin of one key issue, that the explanation for dc breakdown strength being twice or higher than ac breakdown strength in insulating materials, remains unclear. Here, by employing a bipolar charge transport model, we investigate the space charge dynamics in both dc and ac breakdown processes. We demonstrate the differences in charge accumulations under both dc and ac stresses and estimate the breakdown strength, which is modulated by the electric field distortion induced by space charge. It is concluded that dc breakdown initializes in the bulk whereas ac breakdown initializes in the vicinity of the sample-electrode interface. Compared with dc breakdown, the lower breakdown strength under ac stress and the decreasing breakdown strength with an increase in applied frequency, are both attributed to the electric field distortion induced by space charges located in the vicinity of the electrodes. PMID:27599577

  2. Space Charge Modulated Electrical Breakdown.

    PubMed

    Li, Shengtao; Zhu, Yuanwei; Min, Daomin; Chen, George

    2016-01-01

    Electrical breakdown is one of the most important physical phenomena in electrical and electronic engineering. Since the early 20(th) century, many theories and models of electrical breakdown have been proposed, but the origin of one key issue, that the explanation for dc breakdown strength being twice or higher than ac breakdown strength in insulating materials, remains unclear. Here, by employing a bipolar charge transport model, we investigate the space charge dynamics in both dc and ac breakdown processes. We demonstrate the differences in charge accumulations under both dc and ac stresses and estimate the breakdown strength, which is modulated by the electric field distortion induced by space charge. It is concluded that dc breakdown initializes in the bulk whereas ac breakdown initializes in the vicinity of the sample-electrode interface. Compared with dc breakdown, the lower breakdown strength under ac stress and the decreasing breakdown strength with an increase in applied frequency, are both attributed to the electric field distortion induced by space charges located in the vicinity of the electrodes. PMID:27599577

  3. Electrical Breakdown in Solids

    NASA Astrophysics Data System (ADS)

    Hjalmarson, Harold; Zutavern, Fred; Kambour, Kenneth; Moore, Chris; Mar, Alan

    During electron breakdown of a solid subjected to a large electric field, impact ionization causes growth of an electron-hole plasma. This growth process is opposed by Auger recombination of the electron-hole pairs. In our work, such breakdown is investigated by obtaining steady-state solutions to the Boltzmann equation. In these calculations, the carriers are heated by the electric field and cooled by phonon emission. Our results imply that breakdown may lead to high carrier-density current filaments. Conductive filaments have been observed in optically-triggered, high-power photoconductive semiconductor switch (PCSS) devices being developed at Sandia Labs. The relationship between the steady-state computed solutions to the observed filaments will be discussed in the presentation. This work was supported by the Laboratory Directed Research and Development program at Sandia National Laboratories. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000.

  4. Bone morphogenetic protein-2 may represent the molecular link between oxidative stress and vascular stiffness in chronic kidney disease.

    PubMed

    Dalfino, G; Simone, S; Porreca, S; Cosola, C; Balestra, C; Manno, C; Schena, F P; Grandaliano, G; Pertosa, G

    2010-08-01

    Oxidative stress and vascular calcifications are emergent risk factors for the accelerated atherosclerosis process featuring chronic kidney disease (CKD). Vascular calcification is an active process similar to bone modelling, where BMP-2 may play a pathogenic role. Aim of our study was to investigate the link between oxidative stress, BMP-2 protein expression and vascular disease in CKD. We enrolled 85 CKD patients (K-DOQI stage II or higher) and 41 healthy individuals. 8-Oxo-7,8-dihydro-2'-deoxyguanosine (8-OHdG) was used as a marker of oxidative stress. Brachial-ankle pulse wave velocity (baPWV) was used as a measure of arterial stiffness. BMP-2 serum levels were significantly higher in CKD patients than in controls (p<0.0001). Serum 8-OHdG levels were significantly higher in CKD patients compared to controls (p<0.05). BMP-2 serum levels were inversely associated with eGFR (r=-0.3; p=0.01) and directly correlated with 8-OHdG serum concentrations (r=-0.3; p=0.03). Arterial stiffness was inversely correlated with eGFR (r=-0.4; p=0.001) and directly correlated with BMP-2 (r=0.3; p=0.03), 8-OHdG (r=0.4, p=0.02) and phosphorus serum levels (r=0.3; p=0.007). In a multiple regression model, phosphorus and BMP-2 were independently correlated with baPWV. In vitro exposure to H(2)O(2) induced a time and dose-dependent increase in BMP-2 expression in an immortalized endothelial cell line. Moreover, H(2)O(2) pre-incubation of cultured vascular smooth muscle cell enhanced the BMP-2-induced up-regulation of ALPL, an osteoblastic phenotype marker. Our data suggest that in CKD BMP-2 may represent the molecular link between oxidative stress and arterial stiffness due to vascular calcification. PMID:20537331

  5. Heme content and breakdown in developing chloroplasts

    SciTech Connect

    Thomas, J.; Weinstein, J.D. )

    1990-05-01

    Heme regulates tetrapyrrole biosynthesis in plants by inhibition of {delta}-aminolevulinic acid (ALA) synthesis, product inhibition of heme synthesis, and possibly other mechanisms. Plastid heme levels may be modulated by heme synthesis, breakdown and/or efflux. Heme breakdown may be catalyzed by a chloroplast localized heme oxygenase. Chloroplasts isolated from greening cucumber cotyledons were incubated in the presence or absence of various components thought to modulate heme breakdown. Following the incubations, the chloroplasts were broken (freeze-thaw) and then supplemented with horseradish peroxidase apoenzyme. The reconstituted peroxidase activity was used to determine the amount of free heme remaining (Thomas Weinstein (1989) Plant Physiol. 89S: 74). Chloroplasts, freshly isolated from seedlings greened for 16 hours, contained approximately 37 pmol heme/mg protein. When chloroplasts were incubated with 5 mM NADPH for 30 min, the endogenous heme dropped to unmeasurable levels. Exogenous heme was also broken down when NADPH was included in the incubation. Heme levels could be increased by the inclusion of 50 {mu}M ALA and/or p-hydroxymercuribenzoate. The increase due to exogenous ALA was blocked by levulinic acid, an inhibitor of ALA utilization. NADPH-dependent heme breakdown acid was inhibited by p-hydroxymercuribenzoate.

  6. Work breakdown structure guide

    SciTech Connect

    Not Available

    1987-02-06

    Utilization of the work breakdown structure (WBS) technique is an effective aid in managing Department of Energy (DOE) programs and projects. The technique provides a framework for project management by focusing on the products that are being developed or constructed to solve technical problems. It assists both DOE and contractors in fulfilling their management responsibilities. This document provides guidance for use of the WBS technique for product oriented work identification and definition. It is one in a series of policy and guidance documents supporting DOE's project manaagement system.

  7. On Preliminary Breakdown

    NASA Astrophysics Data System (ADS)

    Beasley, W. H.; Petersen, D.

    2013-12-01

    The preliminary breakdown phase of a negative cloud-to-ground lightning flash was observed in detail. Observations were made with a Photron SA1.1 high-speed video camera operating at 9,000 frames per second, fast optical sensors, a flat-plate electric field antenna covering the SLF to MF band, and VHF and UHF radio receivers with bandwidths of 20 MHz. Bright stepwise extensions of a negative leader were observed at an altitude of 8 km during the first few milliseconds of the flash, and were coincident with bipolar electric field pulses called 'characteristic pulses'. The 2-D step lengths of the preliminary processes were in excess of 100 meters, with some 2-D step lengths in excess of 200 meters. Smaller and shorter unipolar electric field pulses were superposed onto the bipolar electric field pulses, and were coincident with VHF and UHF radio pulses. After a few milliseconds, the emerging negative stepped leader system showed a marked decrease in luminosity, step length, and propagation velocity. Details of these events will be discussed, including the possibility that the preliminary breakdown phase consists not of a single developing lightning leader system, but of multiple smaller lightning leader systems that eventually join together into a single system.

  8. Elevaed Levels of Serum Glial FibrillaryAcidic Protein Breakdown Products in Mild and Moderate Traumatic Brain Injury are Associated With Intracranial Lesions and Neurosurgical Intervention

    PubMed Central

    Papa, Linda; Lewis, Lawrence M.; Falk, Jay L.; Zhang, Zhiqun; Silvestri, Salvatore; Giordano, Philip; Brophy, Gretchen M.; Demery, Jason; Dixit, Neha K.; Ferguson, Ian; Liu, Ming Cheng; Mo, Jixiang; Akinyi, Linnet; Schmid, Kara; Mondello, Stefania; Robertson, Claudia S.; Tortella, Frank C.; Hayes, Ronald L.; Wang, Kevin K. W.

    2013-01-01

    Objective This study examined whether serum levels of GFAP breakdown products (GFAP-BDP) were elevated in mild and moderate TBI compared to controls and if they were associated with traumatic intracranial lesions on CT scan (+CT) and having a neurosurgical intervention (NSI). Methods This prospective cohort study enrolled adult patients presenting to three Level 1 Trauma Centers following blunt head trauma with loss of consciousness, amnesia, or disorientation and a GCS 9–15. Control groups included normal uninjured controls and trauma controls presenting to the ED with orthopedic injuries or an MVC without TBI. Blood samples were obtained in all patients within 4 hours of injury and measured by ELISA for GFAP-BDP (ng/ml). Results Of the 307 patients enrolled, 108 were TBI patients (97 with GCS 13–15, and 11 with GCS 9–12) and 199 were controls (176 normal controls and 16 MVC controls and 7 orthopedic controls). ROC curves demonstrated that early GFAP-BDP levels were able to distinguish TBI from uninjured controls with an AUC of 0.90 (95%CI 0.86–0.94) and differentiated TBI with a GCS 15 with an AUC 0.88 (95%CI 0.82–0.93). Thirty two TBI patients (30%) had lesions on CT. The AUC for discriminating those patients with CT lesions versus those without CT lesions was 0.79 (95%CI 0.69–0.89). Moreover, the ROC curve for distinguishing NSI from no NSI yielded an AUC of 0.87 (95%CI 0.77–0.96). Conclusions GFAP-BDP is detectable in serum within an hour of injury and is associated with measures of injury severity including the GCS score, CT lesions and neurosurgical intervention. Further study is required to validate these findings before clinical application. PMID:22071014

  9. Grammatical Errors and Communication Breakdown.

    ERIC Educational Resources Information Center

    Tomiyama, Machiko

    This study investigated the relationship between grammatical errors and communication breakdown by examining native speakers' ability to correct grammatical errors. The assumption was that communication breakdown exists to a certain degree if a native speaker cannot correct the error or if the correction distorts the information intended to be…

  10. Breakdown of organic insulators

    NASA Technical Reports Server (NTRS)

    Cuddihy, E. F.

    1983-01-01

    Solar cells and their associated electrical interconnects and leads were encapsulated in transparent elastomeric materials. Their purpose in a photovoltaic module, one of the most important for these elastomeric encapsulation materials, is to function as electrical insulation. This includes internal insulation between adjacent solar cells, between other encapsulated electrical parts, and between the total internal electrical circuitry and external metal frames, grounded areas, and module surfaces. Catastrophic electrical breakdown of the encapsulant insulation materials or electrical current through these materials or module edges to external locations can lead to module failure and can create hazards to humans. Electrical insulation stability, advanced elastomeric encapsulation materials are developed which are intended to be intrinsically free of in-situ ionic impurities, have ultralow water absorption, be weather-stable (UV, oxygen), and have high mechanical flexibility. Efforts to develop a method of assessing the life potential of organic insulation materials in photovoltaic modules are described.

  11. Phenylbutyrate improves nitrogen disposal via alternative pathway without eliciting an increase in protein breakdown and catabolism in control and ornithine transcarbamylace-deficient patients

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Phenylbutyrate (PB) is a drug used in urea cycle disorder patients to elicit alternative pathways for nitrogen disposal. However, PB decreases plasma branched chain amino acid (BCAA) concentrations and prior research suggests that PB may increase leucine oxidation, indicating increased protein degra...

  12. Auracyanin A from the thermophilic green gliding photosynthetic bacterium Chloroflexus aurantiacus represents an unusual class of small blue copper proteins.

    PubMed Central

    Van Driessche, G.; Hu, W.; Van de Werken, G.; Selvaraj, F.; McManus, J. D.; Blankenship, R. E.; Van Beeumen, J. J.

    1999-01-01

    The amino acid sequence of the small copper protein auracyanin A isolated from the thermophilic photosynthetic green bacterium Chloroflexus aurantiacus has been determined to be a polypeptide of 139 residues. His58, Cys123, His128, and Met132 are spaced in a way to be expected if they are the evolutionary conserved metal ligands as in the known small copper proteins plastocyanin and azurin. Secondary structure prediction also indicates that auracyanin has a general beta-barrel structure similar to that of azurin from Pseudomonas aeruginosa and plastocyanin from poplar leaves. However, auracyanin appears to have sequence characteristics of both small copper protein sequence classes. The overall similarity with a consensus sequence of azurin is roughly the same as that with a consensus sequence of plastocyanin, namely 30.5%. We suggest that auracyanin A, together with the B forms, is the first example of a new class of small copper proteins that may be descendants of an ancestral sequence to both the azurin proteins occurring in prokaryotic nonphotosynthetic bacteria and the plastocyanin proteins occurring in both prokaryotic cyanobacteria and eukaryotic algae and plants. The N-terminal sequence region 1-18 of auracyanin is remarkably rich in glycine and hydroxy amino acids, and required mass spectrometric analysis to be determined. The nature of the blocking group X is not yet known, although its mass has been determined to be 220 Da. The auracyanins are the first small blue copper proteins found and studied in anoxygenic photosynthetic bacteria and are likely to mediate electron transfer between the cytochrome bc1 complex and the photosynthetic reaction center. PMID:10338005

  13. Drainin required for membrane fusion of the contractile vacuole in Dictyostelium is the prototype of a protein family also represented in man.

    PubMed Central

    Becker, M; Matzner, M; Gerisch, G

    1999-01-01

    The contractile vacuole expels water by forming a channel with the plasma membrane and thus enables cells to survive in a hypo-osmotic environment. Here we characterize drainin, a Dictyostelium protein involved in this process, as the first member of a protein family represented in fission yeast, Caenorhabditis elegans and man. Gene replacement in Dictyostelium shows that drainin acts at a checkpoint of channel formation between the contractile vacuole and the plasma membrane. A green fluorescent protein fusion of drainin localizes specifically to the contractile vacuole and rescues its periodic discharge in drainin-null cells. Drainin is a peripheral membrane protein, requiring a short hydrophobic stretch in its C-terminal region for localization and function. We suggest that drainin acts in a signaling cascade that couples a volume-sensing device in the vacuolar membrane to the membrane fusion machinery. PMID:10369671

  14. High gradient RF breakdown studies

    NASA Astrophysics Data System (ADS)

    Laurent, Lisa Leanne

    Higher accelerating gradients are required by future demands for TeV electron linear colliders. With higher energy comes the challenge of handling stronger electromagnetic fields in the accelerator structures and in the microwave sources that supply the power. A limit on the maximum field gradient is imposed by rf electrical breakdown. Investigating methods to achieve higher gradients and to better understand the mechanisms involved in the rf breakdown process has been the focal point of this study. A systematic series of rf breakdown experiments have been conducted at Stanford Linear Accelerator Center utilizing a transmission cavity operating in the TM020 mode. A procedure was developed to examine the high gradient section of the cavity in an electron microscope. The results have revealed that breakdown asymmetry exists between opposing high gradient surfaces. During breakdown, a plasma formation is detected localized near the surface with no visible evidence of an arc traversing the gap. These findings support the theory that high frequency rf breakdown is a single surface phenomenon. Other results from this study have shown that breakdown can occur at relatively low voltages when surface irregularities exist and along grain boundaries. A series of steps have been developed through this study that have significantly reduced the number of breakdowns that occur along grain boundaries. Testing under various vacuum conditions (10-11--10 -5 Torr) have revealed that while the breakdown threshold remained the same, the field emitted current density increased by almost two orders of magnitude. This suggests that the total field emitted current density is not the critical parameter in the initiation of high frequency vacuum breakdown. In the course of this study, microparticles were carefully tracked before and after rf processing. The outcome of this research suggests that expensive cleanroom facilities may not offer any advantage over practicing good cleaning and

  15. RF breakdown experiments at SLAC

    SciTech Connect

    Laurent, L.; Vlieks, A.; Pearson, C.; Caryotakis, G.; Luhmann, N.C.

    1999-05-01

    RF breakdown is a critical issue in the conditioning of klystrons, accelerator sections, and rf components for the next linear collider (NLC), as well as other high gradient accelerators and high power microwave sources. SLAC is conducting a series of experiments using an X-band traveling wave ring to characterize the processes and trigger mechanisms associated with rf breakdown. The goal of the research is to identify materials, processes, and manufacturing methods that will increase the breakdown threshold and minimize the time required for conditioning. {copyright} {ital 1999 American Institute of Physics.}

  16. Breakdown in the pretext tokamak

    SciTech Connect

    Benesch, J.F.

    1981-06-01

    Data are presented on the application of ion cyclotron resonance RF power to preionization in tokamaks. We applied 0.3-3 kW at 12 MHz to hydrogen and obtained a visible discharge, but found no scaling of breakdown voltage with any parameter we were able to vary. A possible explanation for this, which implies that higher RF power would have been much more effective, is discussed. Finally, we present our investigation of the dV/dt dependence of breakdown voltage in PRETEXT, a phenomenon also seen in JFT-2. The breakdown is discussed in terms of the physics of Townsend discharges.

  17. Apparent inhibition of. beta. -fructosidase secretion by tunicamycin may be explained by breakdown of the unglycosylated protein during secretion. [Daucus carota

    SciTech Connect

    Faye, L. ); Chrispeels, M.J. )

    1989-03-01

    Suspension-cultured carrot (Daucus carota) cells synthesize and secrete {beta}-fructosidase, a glycoprotein with asparagine-linked glycans. Treatment of the cells with tunicamycin completely inhibits the apparent secretion of {beta}-fructosidase as measured by the accumulation of the {sup 35}S-labelled protein in the cell wall or the culture medium. In the past, such a result has been interpreted as an inhibition of secretion by tunicamycin, but we suggest another explanation based on the following results. In the presence of tunicamycin, unglycosylated {beta}-fructosidase is synthesized and is associated with an endoplasmic-reticulum-rich microsomal fraction. Pulse-chase experiments show that the unglycosylated {beta}-fructosidase does not remain in the cells and appears to be secreted in the same way as glycosylated {beta}-fructosidase; however, no radioactive, unglycosylated {beta}-fructosidase accumulates extracellularly (cell wall or medium). Protoplasts obtained from carrot cells secrete {beta}-fructosidase protein and activity, and treatment of the protoplasts with tunicamycin results in the synthesis of unglycosylated {beta}-fructosidase. In the presence of tunicamycin, there is no accumulation of {beta}-fructosidase activity or unglycosylated {beta}-fructosidase polypeptide in the protoplast incubation medium. These results are consistent with the interpretation that the glycans of {beta}-fructosidase are necessary for its stability, and that in these suspension-cultured cells, the unglycosylated enzyme is degraded during the last stage(s) of secretion, or immediately after its arrival in the wall.

  18. Nonlinear Theory and Breakdown

    NASA Technical Reports Server (NTRS)

    Smith, Frank

    2007-01-01

    The main points of recent theoretical and computational studies on boundary-layer transition and turbulence are to be highlighted. The work is based on high Reynolds numbers and attention is drawn to nonlinear interactions, breakdowns and scales. The research focuses in particular on truly nonlinear theories, i.e. those for which the mean-flow profile is completely altered from its original state. There appear to be three such theories dealing with unsteady nonlinear pressure-displacement interactions (I), with vortex/wave interactions (II), and with Euler-scale flows (III). Specific recent findings noted for these three, and in quantitative agreement with experiments, are the following. Nonlinear finite-time break-ups occur in I, leading to sublayer eruption and vortex formation; here the theory agrees with experiments (Nishioka) regarding the first spike. II gives rise to finite-distance blowup of displacement thickness, then interaction and break-up as above; this theory agrees with experiments (Klebanoff, Nishioka) on the formation of three-dimensional streets. III leads to the prediction of turbulent boundary-layer micro-scale, displacement-and stress-sublayer-thicknesses.

  19. Influence of pigments and protein aging on protein identification in historically representative casein-based paints using enzyme-linked immunosorbent assay.

    PubMed

    Ren, Fang; Atlasevich, Natalya; Baade, Brian; Loike, John; Arslanoglu, Julie

    2016-01-01

    A systematic study on the influence of pigments and sample aging on casein identification was performed on 30 reconstructed paints. The protein in all the paints was extracted into solution for analysis. The amount of protein that can be retrieved for solution-based analysis in each of the reconstructed paints was studied with a well-developed NanoOrange method before and after artificial aging. The results showed that in the paints with calcium phosphate (in bone black) and copper carbonate, hydroxide, or acetate (in verdigris and azurite), the amount of protein that can be retrieved for liquid-phase analysis is much smaller than the other paints, indicating that the protein degradation was accelerated significantly in those paints. Carbon (in vine black), calcium carbonate (in natural chalk), and calcium sulfate (terra alba gypsum and ground alabaster) did not affect much the amount of protein that can be retrieved in the paints compared to non-pigmented binder, meaning that the protein degradation rate was not affected much by those pigments. Artificial aging was observed to decrease the amount of retrievable protein in all the reconstructed paints that were studied. The enzyme-linked immunosorbent assay (ELISA) method was applied to the 28 reconstructed paints (except two verdigris paints) to assess the protein identification. The ELISA responses from the different paints were compared at fixed protein concentrations. Natural chalk, bone black, raw sienna, stack lead white, and cochineal red-violet lake had the lowest ELISA signal in this study, which indicated that the binding sites (epitopes) on the target protein in these paints are likely to deteriorate more than those in the other paints. Artificial aging did not influence the ELISA response as much as the pigments when the protein concentration was kept the same for the paints that were studied. PMID:26472321

  20. Moderate hypoxia followed by reoxygenation results in blood-brain barrier breakdown via oxidative stress-dependent tight-junction protein disruption.

    PubMed

    Zehendner, Christoph M; Librizzi, Laura; Hedrich, Jana; Bauer, Nina M; Angamo, Eskedar A; de Curtis, Marco; Luhmann, Heiko J

    2013-01-01

    Re-canalization of cerebral vessels in ischemic stroke is pivotal to rescue dysfunctional brain areas that are exposed to moderate hypoxia within the penumbra from irreversible cell death. Goal of the present study was to evaluate the effect of moderate hypoxia followed by reoxygenation (MHR) on the evolution of reactive oxygen species (ROS) and blood-brain barrier (BBB) integrity in brain endothelial cells (BEC). BBB integrity was assessed in BEC in vitro and in microvessels of the guinea pig whole brain in situ preparation. Probes were exposed to MHR (2 hours 67-70 mmHg O2, 3 hours reoxygenation, BEC) or towards occlusion of the arteria cerebri media (MCAO) with or without subsequent reperfusion in the whole brain preparation. In vitro BBB integrity was evaluated using trans-endothelial electrical resistance (TEER) and transwell permeability assays. ROS in BEC were evaluated using 2',7'-dichlorodihydrofluorescein diacetate (DCF), MitoSox and immunostaining for nitrotyrosine. Tight-junction protein (TJ) integrity in BEC, stainings for nitrotyrosine and FITC-albumin extravasation in the guinea pig brain preparation were assessed by confocal microscopy. Diphenyleneiodonium (DPI) was used to investigate NADPH oxidase dependent ROS evolution and its effect on BBB parameters in BEC. MHR impaired TJ proteins zonula occludens 1 (ZO-1) and claudin 5 (Cl5), decreased TEER, and significantly increased cytosolic ROS in BEC. These events were blocked by the NADPH oxidase inhibitor DPI. MCAO with or without subsequent reoxygenation resulted in extravasation of FITC-albumin and ROS generation in the penumbra region of the guinea pig brain preparation and confirmed BBB damage. BEC integrity may be impaired through ROS in MHR on the level of TJ and the BBB is also functionally impaired in moderate hypoxic conditions followed by reperfusion in a complex guinea pig brain preparation. These findings suggest that the BBB is susceptible towards MHR and that ROS play a key role in this

  1. Moderate Hypoxia Followed by Reoxygenation Results in Blood-Brain Barrier Breakdown via Oxidative Stress-Dependent Tight-Junction Protein Disruption

    PubMed Central

    Zehendner, Christoph M.; Librizzi, Laura; Hedrich, Jana; Bauer, Nina M.; Angamo, Eskedar A.; de Curtis, Marco; Luhmann, Heiko J.

    2013-01-01

    Re-canalization of cerebral vessels in ischemic stroke is pivotal to rescue dysfunctional brain areas that are exposed to moderate hypoxia within the penumbra from irreversible cell death. Goal of the present study was to evaluate the effect of moderate hypoxia followed by reoxygenation (MHR) on the evolution of reactive oxygen species (ROS) and blood-brain barrier (BBB) integrity in brain endothelial cells (BEC). BBB integrity was assessed in BEC in vitro and in microvessels of the guinea pig whole brain in situ preparation. Probes were exposed to MHR (2 hours 67-70 mmHg O2, 3 hours reoxygenation, BEC) or towards occlusion of the arteria cerebri media (MCAO) with or without subsequent reperfusion in the whole brain preparation. In vitro BBB integrity was evaluated using trans-endothelial electrical resistance (TEER) and transwell permeability assays. ROS in BEC were evaluated using 2′,7′-dichlorodihydrofluorescein diacetate (DCF), MitoSox and immunostaining for nitrotyrosine. Tight-junction protein (TJ) integrity in BEC, stainings for nitrotyrosine and FITC-albumin extravasation in the guinea pig brain preparation were assessed by confocal microscopy. Diphenyleneiodonium (DPI) was used to investigate NADPH oxidase dependent ROS evolution and its effect on BBB parameters in BEC. MHR impaired TJ proteins zonula occludens 1 (ZO-1) and claudin 5 (Cl5), decreased TEER, and significantly increased cytosolic ROS in BEC. These events were blocked by the NADPH oxidase inhibitor DPI. MCAO with or without subsequent reoxygenation resulted in extravasation of FITC-albumin and ROS generation in the penumbra region of the guinea pig brain preparation and confirmed BBB damage. BEC integrity may be impaired through ROS in MHR on the level of TJ and the BBB is also functionally impaired in moderate hypoxic conditions followed by reperfusion in a complex guinea pig brain preparation. These findings suggest that the BBB is susceptible towards MHR and that ROS play a key role in

  2. Structures of Domains I and IV from YbbR are Representative of a Widely Distributed Protein Family

    SciTech Connect

    A Barb; J Cort; J Seetharaman; S Lew; H Lee; T Acton; L Tong; G Montelione; J Prestegard; et al.

    2011-12-31

    YbbR domains are widespread throughout Eubacteria and are expressed as monomeric units, linked in tandem repeats or cotranslated with other domains. Although the precise role of these domains remains undefined, the location of the multiple YbbR domain-encoding ybbR gene in the Bacillus subtilis glmM operon and its previous identification as a substrate for a surfactin-type phosphopantetheinyl transferase suggests a role in cell growth, division, and virulence. To further characterize the YbbR domains, structures of two of the four domains (I and IV) from the YbbR-like protein of Desulfitobacterium hafniense Y51 were solved by solution nuclear magnetic resonance and X-ray crystallography. The structures show the domains to have nearly identical topologies despite a low amino acid identity (23%). The topology is dominated by {beta}-strands, roughly following a 'figure 8' pattern with some strands coiling around the domain perimeter and others crossing the center. A similar topology is found in the C-terminal domain of two stress-responsive bacterial ribosomal proteins, TL5 and L25. Based on these models, a structurally guided amino acid alignment identifies features of the YbbR domains that are not evident from naive amino acid sequence alignments. A structurally conserved cis-proline (cis-Pro) residue was identified in both domains, though the local structure in the immediate vicinities surrounding this residue differed between the two models. The conservation and location of this cis-Pro, plus anchoring Val residues, suggest this motif may be significant to protein function.

  3. Tetrabromocinnamic acid (TBCA) and related compounds represent a new class of specific protein kinase CK2 inhibitors.

    PubMed

    Pagano, Mario A; Poletto, Giorgia; Di Maira, Giovanni; Cozza, Giorgio; Ruzzene, Maria; Sarno, Stefania; Bain, Jenny; Elliott, Matthew; Moro, Stefano; Zagotto, Giuseppe; Meggio, Flavio; Pinna, Lorenzo A

    2007-01-01

    Abnormally high constitutive activity of protein kinase CK2, levels of which are elevated in a variety of tumours, is suspected to underlie its pathogenic potential. The most widely employed CK2 inhibitor is 4,5,6,7-tetrabromobenzotriazole (TBB), which exhibits a comparable efficacy toward another kinase, DYRK1 a. Here we describe the development of a new class of CK2 inhibitors, conceptually derived from TBB, which have lost their potency toward DYRK1 a. In particular, tetrabromocinnamic acid (TBCA) inhibits CK2 five times more efficiently than TBB (IC50 values 0.11 and 0.56 microM, respectively), without having any comparable effect on DYRK1 a (IC50 24.5 microM) or on a panel of 28 protein kinases. The usefulness of TBCA for cellular studies has been validated by showing that it reduces the viability of Jurkat cells more efficiently than TBB through enhancement of apoptosis. Collectively taken, the reported data support the view that suitably derivatized tetrabromobenzene molecules may provide powerful reagents for dissecting the cellular functions of CK2 and counteracting its pathogenic potentials. PMID:17133643

  4. Plasma breakdown and combustion ignition

    NASA Astrophysics Data System (ADS)

    McNeill, Donald H.; Tran, Phuoc

    2001-10-01

    Ignition in chemically reactive media and electrical breakdown are among the most widely used transient processes. The two phenomena operate together during electrical (and laser) spark ignition of combustible gases. Analogs between them show up in Semenov's early (1920's) work on chemical chain reactions and on thermal breakdown of dielectrics. Both breakdown and ignition are under active study today. The energy source for breakdown is an applied electric field, and that for ignition, an applied flux of heat or radicals. Electrons and intermediate reactants are the corresponding driver particles, with a velocity difference that implies a vast difference in the growth rates for the two processes. Combustion takes place in a fuel-oxidant mixture, and an ignited reaction can proceed until the fuel or oxidant is depleted, while a (non-afterglow, non-fusion) plasma is sustained by an external power supply. The energy balance, propagation behavior, and time evolution of some specific forms of plasma breakdown and chemical ignition are further compared in order to illustrate their physical nature.

  5. Crystal structures of MW1337R and lin2004: Representatives of a novel protein family that adopt a four-helical bundle fold

    SciTech Connect

    Kozbial, Piotr; Xu, Qingping; Chiu, Hsiu-Ju; McMullan, Daniel; Krishna, S. Sri; Miller, Mitchell D.; Abdubek, Polat; Acosta, Claire; Astakhova, Tamara; Axelrod, Herbert L.; Carlton, Dennis; Clayton, Thomas; Deller, Marc; Duan, Lian; Elias, Ylva; Elsliger, Marc-André; Feuerhelm, Julie; Grzechnik, Slawomir K.; Hale, Joanna; Han, Gye Won; Jaroszewski, Lukasz; Jin, Kevin K.; Klock, Heath E.; Knuth, Mark W.; Koesema, Eric; Kumar, Abhinav; Marciano, David; Morse, Andrew T.; Murphy, Kevin D.; Nigoghossian, Edward; Okach, Linda; Oommachen, Silvya; Reyes, Ron; Rife, Christopher L.; Spraggon, Glen; Trout, Christina V.; ban den Bedem, Henry; Weekes, Dana; White, Aprilfawn; Wolf, Guenter; Zubieta, Chloe; Hodgson, Keith O.; Wooley, John; Deacon, Ashley M.; Godzik, Adam; Lesley, Scott A.; Wilson, Ian A.

    2009-08-28

    To extend the structural coverage of proteins with unknown functions, we targeted a novel protein family (Pfam accession number PF08807, DUF1798) for which we proposed and determined the structures of two representative members. The MW1337R gene of Staphylococcus aureus subsp. aureus Rosenbach (Wood 46) encodes a protein with a molecular weight of 13.8 kDa (residues 1-116) and a calculated isoelectric point of 5.15. The lin2004 gene of the nonspore-forming bacterium Listeria innocua Clip11262 encodes a protein with a molecular weight of 14.6 kDa (residues 1-121) and a calculated isoelectric point of 5.45. MW1337R and lin2004, as well as their homologs, which, so far, have been found only in Bacillus, Staphylococcus, Listeria, and related genera (Geobacillus, Exiguobacterium, and Oceanobacillus), have unknown functions and are annotated as hypothetical proteins. The genomic contexts of MW1337R and lin2004 are similar and conserved in related species. In prokaryotic genomes, most often, functionally interacting proteins are coded by genes, which are colocated in conserved operons. Proteins from the same operon as MW1337R and lin2004 either have unknown functions (i.e., belong to DUF1273, Pfam accession number PF06908) or are similar to ypsB from Bacillus subtilis. The function of ypsB is unclear, although it has a strong similarity to the N-terminal region of DivIVA, which was characterized as a bifunctional protein with distinct roles during vegetative growth and sporulation. In addition, members of the DUF1273 family display distant sequence similarity with the DprA/Smf protein, which acts downstream of the DNA uptake machinery, possibly in conjunction with RecA. The RecA activities in Bacillus subtilis are modulated by RecU Holliday-junction resolvase. In all analyzed cases, the gene coding for RecU is in the vicinity of MW1337R, lin2004, or their orthologs, but on a different operon located in the complementary DNA strand. Here, we report the crystal structures

  6. Electrical breakdown in tissue electroporation.

    PubMed

    Guenther, Enric; Klein, Nina; Mikus, Paul; Stehling, Michael K; Rubinsky, Boris

    2015-11-27

    Electroporation, the permeabilization of the cell membrane by brief, high electric fields, has become an important technology in medicine for diverse application ranging from gene transfection to tissue ablation. There is ample anecdotal evidence that the clinical application of electroporation is often associated with loud sounds and extremely high currents that exceed the devices design limit after which the devices cease to function. The goal of this paper is to elucidate and quantify the biophysical and biochemical basis for this phenomenon. Using an experimental design that includes clinical data, a tissue phantom, sound, optical, ultrasound and MRI measurements, we show that the phenomenon is caused by electrical breakdown across ionized electrolysis produced gases near the electrodes. The breakdown occurs primarily near the cathode. Electrical breakdown during electroporation is a biophysical phenomenon of substantial importance to the outcome of clinical applications. It was ignored, until now. PMID:26482855

  7. Breakdown properties of epoxy nanodielectric

    SciTech Connect

    Tuncer, Enis; Cantoni, Claudia; More, Karren Leslie; James, David Randy; Polyzos, Georgios; Sauers, Isidor; Ellis, Alvin R

    2010-01-01

    Recent developments in polymeric dielectric nanocomposites have shown that these novel materials can improve design of high voltage (hv) components and systems. Some of the improvements can be listed as reduction in size (compact hv systems), better reliability, high energy density, voltage endurance, and multifunctionality. Nanodielectric systems demonstrated specific improvements that have been published in the literature by different groups working with electrical insulation materials. In this paper we focus on the influence of in-situ synthesized titanium dioxide (TiO{sub 2}) nanoparticles on the dielectric breakdown characteristics of an epoxy-based nanocomposite system. The in-situ synthesis of the particles creates small nanoparticles on the order of 10 nm with narrow size distribution and uniform particle dispersion in the matrix. The breakdown strength of the nanocomposite was studied as a function of TiO{sub 2} concentration at cryogenic temperatures. It was observed that between 2 and 6wt% yields high breakdown values for the nanodielectric.

  8. Vortex breakdown incipience: Theoretical considerations

    NASA Technical Reports Server (NTRS)

    Berger, Stanley A.; Erlebacher, Gordon

    1992-01-01

    The sensitivity of the onset and the location of vortex breakdowns in concentrated vortex cores, and the pronounced tendency of the breakdowns to migrate upstream have been characteristic observations of experimental investigations; they have also been features of numerical simulations and led to questions about the validity of these simulations. This behavior seems to be inconsistent with the strong time-like axial evolution of the flow, as expressed explicitly, for example, by the quasi-cylindrical approximate equations for this flow. An order-of-magnitude analysis of the equations of motion near breakdown leads to a modified set of governing equations, analysis of which demonstrates that the interplay between radial inertial, pressure, and viscous forces gives an elliptic character to these concentrated swirling flows. Analytical, asymptotic, and numerical solutions of a simplified non-linear equation are presented; these qualitatively exhibit the features of vortex onset and location noted above.

  9. Degradation of some representative polycyclic aromatic hydrocarbons by the water-soluble protein extracts from Zea mays L. cv PR32-B10.

    PubMed

    Barone, Roberto; de Biasi, Margherita-Gabriella; Piccialli, Vincenzo; de Napoli, Lorenzo; Oliviero, Giorgia; Borbone, Nicola; Piccialli, Gennaro

    2016-10-01

    The ability of the water-soluble protein extracts from Zea mais L. cv. PR32-B10 to degrade some representative polycyclic aromatic hydrocarbons (PAHs), has been evaluated. Surface sterilized seeds of corn (Zea mais L. Pioneer cv. PR32-B10) were hydroponically cultivated in a growth chamber under no-stressful conditions. The water-soluble protein extracts isolated from maize tissues showed peroxidase, polyphenol oxidase and catalase activities. Incubation of the extracts with naphthalene, fluorene, phenanthrene and pyrene, led to formation of oxidized and/or degradation products. GC-MS and TLC monitoring of the processes showed that naphthalene, phenanthrene, fluorene and pyrene underwent 100%, 78%, 92% and 65% oxidative degradation, respectively, after 120 min. The chemical structure of the degradation products were determined by (1)H NMR and ESI-MS spectrometry. PMID:27391049

  10. A New Model for Nuclear Envelope BreakdownV⃞

    PubMed Central

    Terasaki, Mark; Campagnola, Paul; Rolls, Melissa M.; Stein, Pascal A.; Ellenberg, Jan; Hinkle, Beth; Slepchenko, Boris

    2001-01-01

    Nuclear envelope breakdown was investigated during meiotic maturation of starfish oocytes. Fluorescent 70-kDa dextran entry, as monitored by confocal microscopy, consists of two phases, a slow uniform increase and then a massive wave. From quantitative analysis of the first phase of dextran entry, and from imaging of green fluorescent protein chimeras, we conclude that nuclear pore disassembly begins several minutes before nuclear envelope breakdown. The best fit for the second phase of entry is with a spreading disruption of the membrane permeability barrier determined by three-dimensional computer simulations of diffusion. We propose a new model for the mechanism of nuclear envelope breakdown in which disassembly of the nuclear pores leads to a fenestration of the nuclear envelope double membrane. PMID:11179431

  11. Threshold criteria for undervoltage breakdown

    NASA Astrophysics Data System (ADS)

    Cooley, James E.; Choueiri, Edgar Y.

    2008-05-01

    The conditions under which an externally supplied pulse of electrons will induce breakdown in an undervoltaged, low-gain discharge gap are experimentally and theoretically explored. The minimum number of injected electrons required to achieve breakdown in a parallel-plate gap is measured in argon at pd values of 3-10 Torr m using ultraviolet laser pulses to photoelectrically release electrons from the cathode. This value was found to scale inversely with voltage at constant pd and with pressure within the parameter range explored. A dimensionless theoretical description of the phenomenon is formulated and numerically solved. It is found that a significant fraction of the charge on the plates must be injected for breakdown to be achieved at low gain. It is also found that fewer electrons are required as the gain due to electron-impact ionization (α process) is increased, or as the sensitivity of the α process to electric field is enhanced by increasing the gas pressure. A predicted insensitivity to ion mobility implies that the breakdown is determined during the first electron avalanche when space-charge distortion is greatest.

  12. Representing dispositions

    PubMed Central

    2011-01-01

    Dispositions and tendencies feature significantly in the biomedical domain and therefore in representations of knowledge of that domain. They are not only important for specific applications like an infectious disease ontology, but also as part of a general strategy for modelling knowledge about molecular interactions. But the task of representing dispositions in some formal ontological systems is fraught with several problems, which are partly due to the fact that Description Logics can only deal well with binary relations. The paper will discuss some of the results of the philosophical debate about dispositions, in order to see whether the formal relations needed to represent dispositions can be broken down to binary relations. Finally, we will discuss problems arising from the possibility of the absence of realizations, of multi-track or multi-trigger dispositions and offer suggestions on how to deal with them. PMID:21995952

  13. Predicting Flow Breakdown Probability and Duration in Stochastic Network Models: Impact on Travel Time Reliability

    SciTech Connect

    Dong, Jing; Mahmassani, Hani S.

    2011-01-01

    This paper proposes a methodology to produce random flow breakdown endogenously in a mesoscopic operational model, by capturing breakdown probability and duration. Based on previous research findings that probability of flow breakdown can be represented as a function of flow rate and the duration can be characterized by a hazard model. By generating random flow breakdown at various levels and capturing the traffic characteristics at the onset of the breakdown, the stochastic network simulation model provides a tool for evaluating travel time variability. The proposed model can be used for (1) providing reliability related traveler information; (2) designing ITS (intelligent transportation systems) strategies to improve reliability; and (3) evaluating reliability-related performance measures of the system.

  14. Proposed RF Breakdown Studies at the AWA

    SciTech Connect

    Antipov, S.; Conde, M.; Gai, W.; Power, J.G.; Spentzouris, L.; Yusof, Z.; Dolgashev, V.; /SLAC

    2007-03-21

    A study of breakdown mechanism has been initiated at the Argonne Wakefield Accelerator (AWA). Breakdown may include several factors such as local field enhancement, explosive electron emission, Ohmic heating, tensile stress produced by electric field, and others. The AWA is building a dedicated facility to test various models for breakdown mechanisms and to determine the roles of different factors in the breakdown. We plan to trigger breakdown events with a high-powered laser at various wavelengths (IR to UV) to determine the role of explosive electron emission in the breakdown process. Another experimental idea follows from the recent work on a Schottky-enabled photoemission in an RF photoinjector [1] that allows us to determine in situ the field enhancement factor on a cathode surface. Monitoring the field enhancement factor before and after the breakdown can shed some light on a number of observations such as the crater formation process.

  15. Breakdown

    ERIC Educational Resources Information Center

    Moskowitz, Eva

    2006-01-01

    The multiplicity of ills facing the nation's public schools can depress even the most optimistic. In this article, the author presents her views about the school system and the negative effects that labor agreements have had on it. Her views on how to solve some seemingly intractable education problems have been informed by two experiences: her…

  16. Integrating nanopore sensors within microfluidic channel arrays using controlled breakdown.

    PubMed

    Tahvildari, Radin; Beamish, Eric; Tabard-Cossa, Vincent; Godin, Michel

    2015-03-21

    Nanopore arrays are fabricated by controlled dielectric breakdown (CBD) in solid-state membranes integrated within polydimethylsiloxane (PDMS) microfluidic devices. This technique enables the scalable production of independently addressable nanopores. By confining the electric field within the microfluidic architecture, nanopore fabrication is precisely localized and electrical noise is significantly reduced. Both DNA and protein molecules are detected to validate the performance of this sensing platform. PMID:25631885

  17. On a criterion for vortex breakdown

    NASA Technical Reports Server (NTRS)

    Spall, R. E.; Gatski, T. B.; Grosch, C. H.

    1987-01-01

    A criterion for the onset of vortex breakdown is proposed. Based upon previous experimental, computational, and theoretical studies, an appropriately defined local Rossby number is used to delineate the region where breakdown occurs. In addition, new numerical results are presented which further validate this criterion. A number of previous theoretical studies concentrating on inviscid standing-wave analyses for trailing wing-tip vortices are reviewed and reinterpreted in terms of the Rossby number criterion. Consistent with previous studies, the physical basis for the onset of breakdown is identified as the ability of the flow to sustain such waves. Previous computational results are reviewed and re-evaluated in terms of the proposed breakdown criterion. As a result, the cause of breakdown occurring near the inflow computational boundary, common to several numerical studies, is identified. Finally, previous experimental studies of vortex breakdown for both leading edge and trailing wing-tip vortices are reviewed and quantified in terms of the Rossby number criterion.

  18. Internal structure of a vortex breakdown

    NASA Technical Reports Server (NTRS)

    Nakamura, Y.; Leonard, A.; Spalart, P. R.

    1986-01-01

    An axisymmetric vortex breakdown was well simulated by the vortex filament method. The agreement with the experiment was qualitatively good. In particular, the structure in the interior of the vortex breakdown was ensured to a great degree by the present simulation. The second breakdown, or spiral type, which occurs downstream of the first axisymmetric breakdown, was simulated more similarly to the experiment than before. It shows a kink of the vortex filaments and strong three-dimensionality. Furthermore, a relatively low velocity region was observed near the second breakdown. It was also found that it takes some time for this physical phenomenon to attain its final stage. The comparison with the experiment is getting better as time goes on. In this paper, emphasis is placed on the comparison of the simulated results with the experiment. The present results help to make clear the mechanism of a vortex breakdown.

  19. Time dependent breakdown in silicon dioxide films

    NASA Technical Reports Server (NTRS)

    Svensson, C.; Shumka, A.

    1975-01-01

    An investigation was conducted regarding the possible existence of a time-dependent breakdown mechanism in thermal oxides of the type used as gate oxide in MOS circuits. Questions of device fabrication are discussed along with details concerning breakdown measurements and the determination of C-V characteristics. A relatively large prebreakdown current observed in one of the cases is related to the time-dependent breakdown.

  20. Laser-induced electric breakdown in solids

    NASA Technical Reports Server (NTRS)

    Bloembergen, N.

    1974-01-01

    A review is given of recent experimental results on laser-induced electric breakdown in transparent optical solid materials. A fundamental breakdown threshold exists characteristic for each material. The threshold is determined by the same physical process as dc breakdown, namely, avalanche ionization. The dependence of the threshold on laser pulse duration and frequency is consistent with this process. The implication of this breakdown mechanism for laser bulk and surface damage to optical components is discussed. It also determines physical properties of self-focused filaments.

  1. A novel sterol 14alpha-demethylase/ferredoxin fusion protein (MCCYP51FX) from Methylococcus capsulatus represents a new class of the cytochrome P450 superfamily.

    PubMed

    Jackson, Colin J; Lamb, David C; Marczylo, Timothy H; Warrilow, Andrew G S; Manning, Nigel J; Lowe, David J; Kelly, Diane E; Kelly, Steven L

    2002-12-01

    Sterol 14alpha-demethylase encoded by CYP51 is a member of the cytochrome P450 (CYP) superfamily of enzymes and has been shown to have an essential role in sterol biosynthesis in eukaryotes, with orthologues recently being described in some bacteria. Examination of the genome sequence data for the proteobacterium Methylococcus capsulatus, a bacterial species known to produce sterol, revealed the presence of a single CYP with strong homology to CYP51, particularly to a form in Mycobacterium tuberculosis. This M. capsulatus CYP51 protein represents a new class of CYP consisting of the CYP domain naturally fused to a ferredoxin domain at the C terminus via an alanine-rich linker. Expression of the M. capsulatus MCCYP51FX fusion in Escherichia coli yielded a P450, which, when purified to homogeneity, had the predicted molecular mass approximately 62 kDa on SDS/PAGE and bound lanosterol as a putative substrate. Sterol 14alpha-demethylase activity was shown (0.24 nmol of lanosterol metabolized per minute per nanomole of MCCYP51FX fusion) by gas chromatography/mass spectrometry with the activity dependent upon the presence of ferredoxin reductase and NADPH. Our unique findings describe a new class of naturally existing cytochrome P450, which will provide pivotal information for CYP structure/function in general. PMID:12235134

  2. Work Breakdown Structure (WBS) Handbook

    NASA Technical Reports Server (NTRS)

    2010-01-01

    The purpose of this document is to provide program/project teams necessary instruction and guidance in the best practices for Work Breakdown Structure (WBS) and WBS dictionary development and use for project implementation and management control. This handbook can be used for all types of NASA projects and work activities including research, development, construction, test and evaluation, and operations. The products of these work efforts may be hardware, software, data, or service elements (alone or in combination). The aim of this document is to assist project teams in the development of effective work breakdown structures that provide a framework of common reference for all project elements. The WBS and WBS dictionary are effective management processes for planning, organizing, and administering NASA programs and projects. The guidance contained in this document is applicable to both in-house, NASA-led effort and contracted effort. It assists management teams from both entities in fulfilling necessary responsibilities for successful accomplishment of project cost, schedule, and technical goals. Benefits resulting from the use of an effective WBS include, but are not limited to: providing a basis for assigned project responsibilities, providing a basis for project schedule development, simplifying a project by dividing the total work scope into manageable units, and providing a common reference for all project communication.

  3. Relativistic breakdown in planetary atmospheres

    SciTech Connect

    Dwyer, J. R.

    2007-04-15

    In 2003, a new electrical breakdown mechanism involving the production of runaway avalanches by positive feedback from runaway positrons and energetic photons was introduced. This mechanism, which shall be referred to as 'relativistic feedback', allows runaway discharges in gases to become self-sustaining, dramatically increasing the flux of runaway electrons, the accompanying high-energy radiation, and resulting ionization. Using detailed Monte Carlo calculations, properties of relativistic feedback are investigated. It is found that once relativistic feedback fully commences, electrical breakdown will occur and the ambient electric field, extending over cubic kilometers, will be discharged in as little as 2x10{sup -5} s. Furthermore, it is found that the flux of energetic electrons and x rays generated by this mechanism can exceed the flux generated by the standard relativistic runaway electron model by a factor of 10{sup 13}, making relativistic feedback a good candidate for explaining terrestrial gamma-ray flashes and other high-energy phenomena observed in the Earth's atmosphere.

  4. Leaf breakdown in streams differing in catchment land use

    USGS Publications Warehouse

    Paul, M.J.; Meyer, J.L.; Couch, C.A.

    2006-01-01

    1. The impact of changes in land use on stream ecosystem function is poorly understood. We studied leaf breakdown, a fundamental process of stream ecosystems, in streams that represent a range of catchment land use in the Piedmont physiographic province of the south-eastern United States. 2. We placed bags of chalk maple (Acer barbatum) leaves in similar-sized streams in 12 catchments of differing dominant land use: four forested, three agricultural, two suburban and three urban catchments. We measured leaf mass, invertebrate abundance and fungal biomass in leaf bags over time. 3. Leaves decayed significantly faster in agricultural (0.0465 day-1) and urban (0.0474 day-1) streams than in suburban (0.0173 day-1) and forested (0.0100 day-1) streams. Additionally, breakdown rates in the agricultural and urban streams were among the fastest reported for deciduous leaves in any stream. Nutrient concentrations in agricultural streams were significantly higher than in any other land-use type. Fungal biomass associated with leaves was significantly lower in urban streams; while shredder abundance in leaf bags was significantly higher in forested and agricultural streams than in suburban and urban streams. Storm runoff was significantly higher in urban and suburban catchments that had higher impervious surface cover than forested or agricultural catchments. 4. We propose that processes accelerating leaf breakdown in agricultural and urban streams were not the same: faster breakdown in agricultural streams was due to increased biological activity as a result of nutrient enrichment, whereas faster breakdown in urban streams was a result of physical fragmentation resulting from higher storm runoff. ?? 2006 The Authors.

  5. Fundamental studies on passivity and passivity breakdown

    SciTech Connect

    Macdonald, D.D.; Urquidi-Macdonald, M.

    1993-06-01

    Using photoelectrochemical impedance and admittance spectroscopies, a fundamental and quantitative understanding of the mechanisms for the growth and breakdown of passive films on metal and alloy surfaces in contact with aqueous environments is being developed. A point defect model has been extended to explain the breakdown of passive films, leading to pitting and crack growth and thus development of damage due to localized corrosion.

  6. Breakdown of interdependent directed networks.

    PubMed

    Liu, Xueming; Stanley, H Eugene; Gao, Jianxi

    2016-02-01

    Increasing evidence shows that real-world systems interact with one another via dependency connectivities. Failing connectivities are the mechanism behind the breakdown of interacting complex systems, e.g., blackouts caused by the interdependence of power grids and communication networks. Previous research analyzing the robustness of interdependent networks has been limited to undirected networks. However, most real-world networks are directed, their in-degrees and out-degrees may be correlated, and they are often coupled to one another as interdependent directed networks. To understand the breakdown and robustness of interdependent directed networks, we develop a theoretical framework based on generating functions and percolation theory. We find that for interdependent Erdős-Rényi networks the directionality within each network increases their vulnerability and exhibits hybrid phase transitions. We also find that the percolation behavior of interdependent directed scale-free networks with and without degree correlations is so complex that two criteria are needed to quantify and compare their robustness: the percolation threshold and the integrated size of the giant component during an entire attack process. Interestingly, we find that the in-degree and out-degree correlations in each network layer increase the robustness of interdependent degree heterogeneous networks that most real networks are, but decrease the robustness of interdependent networks with homogeneous degree distribution and with strong coupling strengths. Moreover, by applying our theoretical analysis to real interdependent international trade networks, we find that the robustness of these real-world systems increases with the in-degree and out-degree correlations, confirming our theoretical analysis. PMID:26787907

  7. Scintillation Breakdowns in Chip Tantalum Capacitors

    NASA Technical Reports Server (NTRS)

    Teverovsky, Alexander

    2008-01-01

    Scintillations in solid tantalum capacitors are momentarily local breakdowns terminated by a self-healing or conversion to a high-resistive state of the manganese oxide cathode. This conversion effectively caps the defective area of the tantalum pentoxide dielectric and prevents short-circuit failures. Typically, this type of breakdown has no immediate catastrophic consequences and is often considered as nuisance rather than a failure. Scintillation breakdowns likely do not affect failures of parts under surge current conditions, and so-called "proofing" of tantalum chip capacitors, which is a controllable exposure of the part after soldering to voltages slightly higher than the operating voltage to verify that possible scintillations are self-healed, has been shown to improve the quality of the parts. However, no in-depth studies of the effect of scintillations on reliability of tantalum capacitors have been performed so far. KEMET is using scintillation breakdown testing as a tool for assessing process improvements and to compare quality of different manufacturing lots. Nevertheless, the relationship between failures and scintillation breakdowns is not clear, and this test is not considered as suitable for lot acceptance testing. In this work, scintillation breakdowns in different military-graded and commercial tantalum capacitors were characterized and related to the rated voltages and to life test failures. A model for assessment of times to failure, based on distributions of breakdown voltages, and accelerating factors of life testing are discussed.

  8. Breakdown characteristics of xenon HID Lamps

    NASA Astrophysics Data System (ADS)

    Babaeva, Natalia; Sato, Ayumu; Brates, Nanu; Noro, Koji; Kushner, Mark

    2009-10-01

    The breakdown characteristics of mercury free xenon high intensity discharge (HID) lamps exhibit a large statistical time lag often having a large scatter in breakdown voltages. In this paper, we report on results from a computational investigation of the processes which determine the ignition voltages for positive and negative pulses in commercial HID lamps having fill pressures of up to 20 atm. Steep voltage rise results in higher avalanche electron densities and earlier breakdown times. Circuit characteristics also play a role. Large ballast resistors may limit current to the degree that breakdown is quenched. The breakdown voltage critically depends on cathode charge injection by electric field emission (or other mechanisms) which in large part controls the statistical time lag for breakdown. For symmetric lamps, ionization waves (IWs) simultaneously develop from the bottom and top electrodes. Breakdown typically occurs when the top and bottom IWs converge. Condensed salt layers having small conductivities on the inner walls of HID lamps and on the electrodes can influence the ignition behavior. With these layers, IWs tend to propagate along the inner wall and exhibit a different structure depending on the polarity.

  9. Fundamental studies of passivity and passivity breakdown

    SciTech Connect

    Macdonald, D.D.; Urquidi-Macdonald, M.; Song, H.; Biaggio-Rocha, S.; Searson, P.

    1991-11-01

    This report summarizes the findings of our fundamental research program on passivity and passivity breakdown. During the past three and one half years in this program (including the three year incrementally-funded grant prior to the present grant), we developed and experimentally tested various physical models for the growth and breakdown of passive films on metal surfaces. These models belong to a general class termed point defects models'' (PDMs), in which the growth and breakdown of passive films are described in terms of the movement of anion and cation vacancies.

  10. Gas breakdown and secondary electron yields

    NASA Astrophysics Data System (ADS)

    Marić, Dragana; Savić, Marija; Sivoš, Jelena; Škoro, Nikola; Radmilović-Radjenović, Marija; Malović, Gordana; Petrović, Zoran Lj.

    2014-06-01

    In this paper we present a systematic study of the gas breakdown potentials. An analysis of the key elementary processes in low-current low-pressure discharges is given, with an aim to illustrate how such discharges are used to determine swarm parameters and how such data may be applied to modeling discharges. Breakdown data obtained in simple parallel-plate geometry are presented for a number of atomic and molecular gases. Ionization coefficients, secondary electron yields and their influence on breakdown are analyzed, with special attention devoted to non-hydrodynamic conditions near cathode.

  11. Pulsed electric breakdown in adipose tissue

    NASA Astrophysics Data System (ADS)

    Kolb, Juergen F.; Scully, Noah; Paithankar, Dilip

    2011-08-01

    High voltage pulses of sub-microsecond duration can instigate electrical breakdown in adipose tissue, which is followed by a spark discharge. Breakdown voltages are generally lower than observed for purified lipids but higher than for air. Development of breakdown for the repetitive application of pulses resembles a gradual and stochastic process as reported for partial discharges in solid dielectrics. The inflicted tissue damage itself is confined to the gap between electrodes, providing a method to use spark discharges as a precise surgical technique.

  12. Breakdown of Benford's law for birth data

    NASA Astrophysics Data System (ADS)

    Ausloos, M.; Herteliu, C.; Ileanu, B.

    2015-02-01

    Long birth time series for Romania are investigated from Benford's law point of view, distinguishing between families with a religious (Orthodox and Non-Orthodox) affiliation. The data extend from Jan. 01, 1905 till Dec. 31, 2001, i.e. over 97 years or 35 429 days. The results point to a drastic breakdown of Benford's law. Some interpretation is proposed, based on the statistical aspects due to population sizes, rather than on human thought constraints when the law breakdown is usually expected. Benford's law breakdown clearly points to natural causes.

  13. Breakdown-Resistant RF Connectors for Vacuum

    NASA Technical Reports Server (NTRS)

    Caro, Edward R.; Bonazza, Walter J.

    1987-01-01

    Resilient inserts compensate for insulation shrinkage. Coaxial-cable connector for radio-frequency (RF) energy resists electrical breakdown in vacuum. Used on RF equipment in vacuum chambers as well as in spaceborne radar and communication gear.

  14. Microwave air breakdown enhanced with metallic initiators

    SciTech Connect

    Herring, G. C.; Popovic, S.

    2008-03-31

    We have determined X-band (9.4 GHz) electric field strengths required to obtain air breakdown at atmospheric pressure in the presence of metallic initiators, which are irradiated with repetitive (30 pulses/s) microwave pulses of 3 {mu}s duration and 200 kW peak power. Using a half-wavelength initiator, a factor of 40 reduction (compared to no initiator) was observed in the electric field required to achieve breakdown. The present measurements are compared to a previously published model for air breakdown, which was originally validated with S-band (3 GHz) frequencies and single 40 {mu}s pulses. We find good agreement between this previous model and our present measurements of breakdown with X-band frequencies and repetitive 3 {mu}s pulses.

  15. Surface breakdown igniter for mercury arc devices

    DOEpatents

    Bayless, John R.

    1977-01-01

    Surface breakdown igniter comprises a semiconductor of medium resistivity which has the arc device cathode as one electrode and has an igniter anode electrode so that when voltage is applied between the electrodes a spark is generated when electrical breakdown occurs over the surface of the semiconductor. The geometry of the igniter anode and cathode electrodes causes the igniter discharge to be forced away from the semiconductor surface.

  16. Spark gap with low breakdown voltage jitter

    DOEpatents

    Rohwein, G.J.; Roose, L.D.

    1996-04-23

    Novel spark gap devices and electrodes are disclosed. The novel spark gap devices and electrodes are suitable for use in a variety of spark gap device applications. The shape of the electrodes gives rise to local field enhancements and reduces breakdown voltage jitter. Breakdown voltage jitter of approximately 5% has been measured in spark gaps according the invention. Novel electrode geometries and materials are disclosed. 13 figs.

  17. Spark gap with low breakdown voltage jitter

    DOEpatents

    Rohwein, Gerald J.; Roose, Lars D.

    1996-01-01

    Novel spark gap devices and electrodes are disclosed. The novel spark gap devices and electrodes are suitable for use in a variety of spark gap device applications. The shape of the electrodes gives rise to local field enhancements and reduces breakdown voltage jitter. Breakdown voltage jitter of approximately 5% has been measured in spark gaps according the invention. Novel electrode geometries and materials are disclosed.

  18. Contributions to theory of vortex breakdown

    NASA Astrophysics Data System (ADS)

    Shivamoggi, B. K.; Uberoi, M. S.

    A study is made of vortex breakdown in stratified flows, and it is found that a positive stratification in the vortex where the density is increasing away from the axis, postpones the vortex breakdown and vice versa. This is apparent due to the density increasing in a direction opposite to that of an effective gravity which would correspond to a topheavy arrangement under gravity. It is also shown that a wavemotion promotes the possibility of axisymmetric flow downstream of the transaction.

  19. Dielectric breakdown and avalanches at nonequilibrium metal-insulator transitions.

    PubMed

    Shekhawat, Ashivni; Papanikolaou, Stefanos; Zapperi, Stefano; Sethna, James P

    2011-12-30

    Motivated by recent experiments on the finite temperature Mott transition in VO(2) films, we propose a classical coarse-grained dielectric breakdown model where each degree of freedom represents a nanograin which transitions from insulator to metal with increasing temperature and voltage at random thresholds due to quenched disorder. We describe the properties of the resulting nonequilibrium metal-insulator transition and explain the universal characteristics of the resistance jump distribution. We predict that by tuning voltage, another critical point is approached, which separates a phase of boltlike avalanches from percolationlike ones. PMID:22243320

  20. Effect of surface conditions affecting voltage breakdowns

    NASA Astrophysics Data System (ADS)

    Flauta, Randolph; Aghazarian, Maro; Caughman, John; Ruzic, David

    2008-11-01

    The maximum power transferred by ion cyclotron range of frequency (ICRF) antennas is dependent on the breakdown threshold when operated at high voltages. The voltage that these antennas can withstand is lowered and hence breakdowns occur due to many factors. The Surface Plasma Arcs by Radiofrequency - Control Study or SPARCS facility has a 0-15kV DC power supply to deliver power to flat cathode surface and semi-spherical anode made of Cu and Al under 10-8-10-6 torr vacuum conditions. The effects of different surface conditions on the breakdown threshold were then investigated. Also, as the ICRF antennas used for heating plasmas may come into contact with contaminants from the plasma, Li was also deposited on the cathode surface through in-situ evaporation coating and its effect on the breakdown threshold was investigated. Results on surface roughness showed no significant dependence of the breakdown threshold on macroscopic surface roughness in the cathode arithmetic roughness range of ˜77-1139nm. Microscopic surface features such as grain boundaries, impurities and imperfections may play a more visible role in affecting the vacuum breakdown.

  1. Humidity effects on wire insulation breakdown strength.

    SciTech Connect

    Appelhans, Leah

    2013-08-01

    Methods for the testing of the dielectric breakdown strength of insulation on metal wires under variable humidity conditions were developed. Two methods, an ASTM method and the twisted pair method, were compared to determine if the twisted pair method could be used for determination of breakdown strength under variable humidity conditions. It was concluded that, although there were small differences in outcomes between the two testing methods, the non-standard method (twisted pair) would be appropriate to use for further testing of the effects of humidity on breakdown performance. The dielectric breakdown strength of 34G copper wire insulated with double layer Poly-Thermaleze/Polyamide-imide insulation was measured using the twisted pair method under a variety of relative humidity (RH) conditions and exposure times. Humidity at 50% RH and below was not found to affect the dielectric breakdown strength. At 80% RH the dielectric breakdown strength was significantly diminished. No effect for exposure time up to 140 hours was observed at 50 or 80%RH.

  2. 7 CFR 51.1582 - Soft rot or wet breakdown.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 2 2013-01-01 2013-01-01 false Soft rot or wet breakdown. 51.1582 Section 51.1582... Soft rot or wet breakdown. Soft rot or wet breakdown means any soft, mushy, or leaky condition of the tissue such as slimy soft rot, leak, or wet breakdown following freezing injury, scald, or other injury....

  3. 7 CFR 51.1563 - Soft rot or wet breakdown.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 2 2013-01-01 2013-01-01 false Soft rot or wet breakdown. 51.1563 Section 51.1563....1563 Soft rot or wet breakdown. Soft rot or wet breakdown means any soft, mushy, or leaky condition of the tissue such as slimy soft rot, leak, or wet breakdown following freezing injury....

  4. 7 CFR 51.1582 - Soft rot or wet breakdown.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 2 2014-01-01 2014-01-01 false Soft rot or wet breakdown. 51.1582 Section 51.1582... Soft rot or wet breakdown. Soft rot or wet breakdown means any soft, mushy, or leaky condition of the tissue such as slimy soft rot, leak, or wet breakdown following freezing injury, scald, or other injury....

  5. 7 CFR 51.1563 - Soft rot or wet breakdown.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 2 2014-01-01 2014-01-01 false Soft rot or wet breakdown. 51.1563 Section 51.1563....1563 Soft rot or wet breakdown. Soft rot or wet breakdown means any soft, mushy, or leaky condition of the tissue such as slimy soft rot, leak, or wet breakdown following freezing injury....

  6. A computational study of the topology of vortex breakdown

    NASA Technical Reports Server (NTRS)

    Spall, Robert E.; Gatski, Thomas B.

    1991-01-01

    A fully three-dimensional numerical simulation of vortex breakdown using the unsteady, incompressible Navier-Stokes equations has been performed. Solutions to four distinct types of breakdown are identified and compared with experimental results. The computed solutions include weak helical, double helix, spiral, and bubble-type breakdowns. The topological structure of the various breakdowns as well as their interrelationship are studied. The data reveal that the asymmetric modes of breakdown may be subject to additional breakdowns as the vortex core evolves in the streamwise direction. The solutions also show that the freestream axial velocity distribution has a significant effect on the position and type of vortex breakdown.

  7. Changes in the Cytoplasmic Composition of Amino Acids and Proteins Observed in Staphylococcus aureus during Growth under Variable Growth Conditions Representative of the Human Wound Site

    PubMed Central

    Alreshidi, Mousa M.; Dunstan, R. Hugh; Gottfries, Johan; Macdonald, Margaret M.; Crompton, Marcus J.; Ang, Ching-Seng; Williamson, Nicholas A.; Roberts, Tim K.

    2016-01-01

    Staphylococcus aureus is an opportunistic pathogen responsible for a high proportion of nosocomial infections. This study was conducted to assess the bacterial responses in the cytoplasmic composition of amino acids and ribosomal proteins under various environmental conditions designed to mimic those on the human skin or within a wound site: pH6-8, temperature 35–37°C, and additional 0–5% NaCl. It was found that each set of environmental conditions elicited substantial adjustments in cytoplasmic levels of glutamic acid, aspartic acid, proline, alanine and glycine (P< 0.05). These alterations generated characteristic amino acid profiles assessed by principle component analysis (PCA). Substantial alterations in cytoplasmic amino acid and protein composition occurred during growth under conditions of higher salinity stress implemented via additional levels of NaCl in the growth medium. The cells responded to additional NaCl at pH 6 by reducing levels of ribosomal proteins, whereas at pH 8 there was an upregulation of ribosomal proteins compared with the reference control. The levels of two ribosomal proteins, L32 and S19, remained constant across all experimental conditions. The data supported the hypothesis that the bacterium was continually responding to the dynamic environment by modifying the proteome and optimising metabolic homeostasis. PMID:27442022

  8. Photoreceptor proteins, "star actors of modern times": a review of the functional dynamics in the structure of representative members of six different photoreceptor families.

    PubMed

    van der Horst, Michael A; Hellingwerf, Klaas J

    2004-01-01

    Six well-characterized photoreceptor families function in Nature to mediate light-induced signal transduction: the rhodopsins, phytochromes, xanthopsins, cryptochromes, phototropins, and BLUF proteins. The first three catalyze E/Z isomerization of retinal, phytochromobilin, and p-coumaric acid, respectively, while the last three all have a different flavin-based photochemistry. For many of these photoreceptor proteins, (many of) the details of the conversion of the light-induced change in configuration of their chromophore into a signaling state and eventually a biological response have been resolved. Some members of the rhodopsins, the xanthopsins, and the phototropins are so well characterized that they function as model systems to study (receptor) protein dynamics and (un)folding. PMID:14730990

  9. Dielectric breakdown in mineral oil ITO 100 based magnetic fluid

    NASA Astrophysics Data System (ADS)

    Kudelcik, J.; Bury, P.; Kopcansky, P.; Timko, M.

    The development of dielectric breakdown and the DC dielectric breakdown voltage of magnetic fluids based on inhibited transformer oil ITO 100 were investigated in parallel orientations of external magnetic field. It was shown that the breakdown voltage is strongly influenced by the magnetic nanoparticles. The magnetic fluids with the volume concentration 1and 0.2% had better dielectric properties than pure transformer oil. The increase of breakdown voltage was interpreted on the base of the bubble theory of breakdown.

  10. Signaling Proteins Are Represented in Tissue Fluid/Lymph from Soft Tissues of Normal Human Legs at Concentrations Different from Serum

    PubMed Central

    Zaleska, Marzanna; Durlik, Marek; Miller, Norman E.

    2013-01-01

    Abstract Background: The mobile intercellular fluid flowing to and in the lymphatics contains filtered plasma products and substances synthesized and excreted by tissue cells. Among them are signaling proteins such as cytokines, chemokines, enzymes, and growth factors. They act locally in autocrine and paracrine systems regulating cell metabolism, proliferation, and formation of the ground matrix. They play an immunoregulatory role in infections, wound healing, and tumor cell growth. Methods and Results: In this study we measured the concentration of selected cytokines, chemokines, tissue enzymes, and growth factors in tissue fluid/lymph drained from normal human leg soft tissues. Legs exposed to infections and trauma often result in development of lymphedema. Lymph was drained from superficial calf lymphatics using microsurgical techniques. Our studies showed generally higher concentrations of cytokines, chemokines, enzymes, and growth factors in lymph than in serum. The total protein L/S ratio was 0.22, whereas that of various lymph signaling proteins ranged between 1 and 10. Conclusions: This indicates that in addition to proteins filtered from blood, local cells contribute to lymph concentration by own production, depending on the actual cell requirement. Moreover, there were major individual differences of lymph levels with simultaneous stable serum levels. This suggests existence of a local autonomous regulatory humoral mechanism in tissues, not reflected in serum. PMID:24364843

  11. The human complement regulatory factor-H-like protein 1, which represents a truncated form of factor H, displays cell-attachment activity.

    PubMed Central

    Hellwage, J; Kühn, S; Zipfel, P F

    1997-01-01

    Complement factor H (FH) and factor-H-like protein 1 (FHL-1) are human plasma proteins with regulatory functions in the alternative pathway of complement activation. FH and FHL-1 are organized in repetitive elements termed short consensus repeats (SCRs) and the seven SCRs of FHL-1 are identical with the N-terminal domain of the 20 SCRs of FH. The fourth SCR of both proteins (SCR 4) includes the sequence Arg-Gly-Asp (RGD), a motif that is responsible for the major adhesive activity of matrix proteins like fibronectin. A synthetic hexapeptide with the sequence ERGDAV derived from the RGD domain of FH/FHL-1 interferes with cell attachment to a fibronectin matrix. Although the identical motif is present in both FH and FHL-1, only FHL-1 acts as a matrix for cell spreading and attachment, thus the two proteins differ in function. The adhesive activity of FHL-1 is localized to the RGD-containing SCR 4 by the use of recombinant fragments. All three analysed anchorage-dependent cell lines (CCl64, C32 and MRC-5) adhere to an FHL-1 matrix. The use of synthetic peptides in competition assays, on either FHL-1-derived or fibronectin matrices, shows that the cellular receptors binding to the FH/FHL-1-derived RGD motif are related to or identical with integrin receptors which interact with fibronectin. The identification of a functional adhesive domain in the FH/FHL-1 sequence demonstrates, at least for FHL-1, a role in cell attachment and adhesion. PMID:9291099

  12. Repression of phosphoinositide-dependent protein kinase 1 expression by ciglitazone via Egr-1 represents a new approach for inhibition of lung cancer cell growth

    PubMed Central

    2014-01-01

    Background Peroxisome proliferator-activated receptors gamma (PPARγ) ligands have been shown to inhibit the growth of non-small cell lung cancer (NSCLC) cells. However, the mechanisms underlying this effect remain incompletely elucidated. Methods Cell proliferation and apoptosis were measured by cell viability, MTT and caspase3/7 activity assays. Phosphorylation/protein expression and gene silence/overexpression of AMPKα, phosphoinositide-dependent protein kinase 1 (PDK1), Egr-1 and PPARγ were performed by Western blot and siRNA/transfection assays. Dual-Luciferase Reporter Kit was used to measure the PPAR response elements (PPRE) reporter and PDK1 promoter activities, and ChIP assay was used to detect the Egr-1 protein binding to the DNA site in the PDK1 gene promoter. Results We found that ciglitazone, one synthetic PPARγ ligand, inhibited growth and induced apoptosis of NSCLC cells through decreased expression of PDK1, which was not blocked by GW9662 (a specific PPARγ antagonist). Overexpression of PDK1 overcame the effect of ciglitazone on cell growth and caspase 3/7 activity. Ciglitazone increased the phosphorylation of AMPKα and c-Jun N-terminal kinase (JNK), and the inhibitor of AMPK (compound C), but not JNK (SP600125), reversed the effect of ciglitazone on PDK1 protein expression. Ciglitazone reduced PDK1 gene promoter activity, which was not observed in cells exposed to compound C, but not silenced of PPARγ siRNA. Combination of ciglitazone and metformin further reduced PDK1 expression and promoter activity. Furthermore, we showed that ciglitazone induced the protein expression of Egr-1, which was not observed in cells silencing of AMPKα. Moreover, silencing of Egr-1 abrogated the effect of ciglitazone on PDK1 promoter activity and cell growth. On the contrary, overexpression of Egr-1 enhanced the effect of ciglitazone on PDK1 gene promoter activity. ChIP assays demonstrated that ciglitazone induced Egr-1 protein bind to the specific DNA site

  13. Planned waveguide electric field breakdown studies

    SciTech Connect

    Wang Faya; Li Zenghai

    2012-12-21

    This paper presents an experimental setup for X-band rf breakdown studies. The setup is composed of a section of WR90 waveguide with a tapered pin located at the middle of the waveguide E-plane. Another pin is used to rf match the waveguide so it operates in a travelling wave mode. By adjusting the penetration depth of the tapered pin, different surface electric field enhancements can be obtained. The setup will be used to study the rf breakdown rate dependence on power flow in the waveguide for a constant maximum surface electric field on the pin. Two groups of pins have been designed. The Q of one group is different and very low. The other has a similar Q. With the test of the two groups of pins, we should be able to discern how the net power flow and Q affect the breakdown. Furthermore, we will apply an electron beam treatment to the pins to study its effect on breakdown. Overall, these experiments should be very helpful in understanding rf breakdown phenomena and could significantly benefit the design of high gradient accelerator structures.

  14. Obstacle-induced spiral vortex breakdown

    NASA Astrophysics Data System (ADS)

    Pasche, Simon; Gallaire, François; Dreyer, Matthieu; Farhat, Mohamed

    2014-08-01

    An experimental investigation on vortex breakdown dynamics is performed. An adverse pressure gradient is created along the axis of a wing-tip vortex by introducing a sphere downstream of an elliptical hydrofoil. The instrumentation involves high-speed visualizations with air bubbles used as tracers and 2D Laser Doppler Velocimeter (LDV). Two key parameters are identified and varied to control the onset of vortex breakdown: the swirl number, defined as the maximum azimuthal velocity divided by the free-stream velocity, and the adverse pressure gradient. They were controlled through the incidence angle of the elliptical hydrofoil, the free-stream velocity and the sphere diameter. A single helical breakdown of the vortex was systematically observed over a wide range of experimental parameters. The helical breakdown coiled around the sphere in the direction opposite to the vortex but rotated along the vortex direction. We have observed that the location of vortex breakdown moved upstream as the swirl number or the sphere diameter was increased. LDV measurements were corrected using a reconstruction procedure taking into account the so-called vortex wandering and the size of the LDV measurement volume. This allows us to investigate the spatio-temporal linear stability properties of the flow and demonstrate that the flow transition from columnar to single helical shape is due to a transition from convective to absolute instability.

  15. Vortex Breakdown in Atmospheric Columnar Vortices.

    NASA Astrophysics Data System (ADS)

    Lugt, H. J.

    1989-12-01

    Vortex breakdown occurs in tornadoes and waterspouts. This phenomenon may give information on the state and future behavior of those whirlwinds. Because of the rarity of recorded events, archival sources are consulted for qualitative descriptions from earlier times and compared with contemporary sources. Drawings and eyewitness reports from earlier times, rare photographs, movies, and observations from recent years indicate the occurrence of vortex breakdown in tornadoes and waterspouts near the ground, in the midsection of the funnel, and close to or inside the parent cloud. Since the contour of the whirlwind's funnel is delineated only by markers in the form of condensates, dust, or other debris, these markers may distort or obscure the evidence of vortex breakdown. This is a likely reason for the rare observation and identification of vortex breakdown which might be more common in whirlwinds than has been previously thought. According to the records examined, meteorologists deserve the honor for discovering and describing vortex breakdown long before the systematic investigation of recent years.

  16. Anticipating electrical breakdown in dielectric elastomer actuators

    NASA Astrophysics Data System (ADS)

    Muffoletto, Daniel P.; Burke, Kevin M.; Zirnheld, Jennifer L.

    2013-04-01

    The output strain of a dielectric elastomer actuator is directly proportional to the square of its applied electric field. However, since the likelihood of electric breakdown is elevated with an increased applied field, the maximum operating electric field of the dielectric elastomer is significantly derated in systems employing these actuators so that failure due to breakdown remains unlikely even as the material ages. In an effort to ascertain the dielectric strength so that stronger electric fields can be applied, partial discharge testing is used to assess the health of the actuator by detecting the charge that is released when localized instances of breakdown partially bridge the insulator. Pre-stretched and unstretched samples of VHB4910 tape were submerged in dielectric oil to remove external sources of partial discharges during testing, and the partial discharge patterns were recorded just before failure of the dielectric sample.

  17. The outer capsid protein VP4 of equine rotavirus strain H-2 represents a unique VP4 type by amino acid sequence analysis.

    PubMed

    Hardy, M E; Gorziglia, M; Woode, G N

    1993-03-01

    The nucleotide and deduced amino acid sequence of G serotype 3 equine rotavirus strain H-2 was determined. A predicted 776-amino-acid H-2 VP4 shows less than or equal to 85.3% identity to other rotavirus VP4 types sequenced to date and thus represents a new P serotype. A PCR-generated probe derived from a cDNA clone of H-2 gene 4 hybridized to gene 4 of several tissue-culture-adapted equine rotavirus isolates, demonstrating that the gene 4 allele present in the H-2 strain is present in the equine rotavirus population. PMID:8382410

  18. IscR of Rhodobacter sphaeroides functions as repressor of genes for iron-sulfur metabolism and represents a new type of iron-sulfur-binding protein

    PubMed Central

    Remes, Bernhard; Eisenhardt, Benjamin D; Srinivasan, Vasundara; Klug, Gabriele

    2015-01-01

    IscR proteins are known as transcriptional regulators for Fe–S biogenesis. In the facultatively phototrophic bacterium, Rhodobacter sphaeroides IscR is the product of the first gene in the isc-suf operon. A major role of IscR in R. sphaeroides iron-dependent regulation was suggested in a bioinformatic study (Rodionov et al., PLoS Comput Biol 2:e163, 2006), which predicted a binding site in the upstream regions of several iron uptake genes, named Iron-Rhodo-box. Most known IscR proteins have Fe–S clusters featuring (Cys)3(His)1 ligation. However, IscR proteins from Rhodobacteraceae harbor only a single-Cys residue and it was considered unlikely that they can ligate an Fe–S cluster. In this study, the role of R. sphaeroides IscR as transcriptional regulator and sensor of the Fe–S cluster status of the cell was analyzed. A mutant lacking IscR is more impaired in growth under iron limitation than the wild-type and exhibits significantly increased ROS levels in iron-replete and iron-deplete conditions. Expression studies reveal that R. sphaeroides IscR in its cluster-bound form functions as transcriptional repressor of genes involved in iron metabolism by direct binding to the promoter region of genes preceded by the motif. A total of 110 genes are directly or indirectly affected by IscR. Furthermore, IscR possesses a unique Fe–S cluster ligation scheme with only a single cysteine involved. PMID:26235649

  19. IscR of Rhodobacter sphaeroides functions as repressor of genes for iron-sulfur metabolism and represents a new type of iron-sulfur-binding protein.

    PubMed

    Remes, Bernhard; Eisenhardt, Benjamin D; Srinivasan, Vasundara; Klug, Gabriele

    2015-10-01

    IscR proteins are known as transcriptional regulators for Fe-S biogenesis. In the facultatively phototrophic bacterium, Rhodobacter sphaeroides IscR is the product of the first gene in the isc-suf operon. A major role of IscR in R. sphaeroides iron-dependent regulation was suggested in a bioinformatic study (Rodionov et al., PLoS Comput Biol 2:e163, 2006), which predicted a binding site in the upstream regions of several iron uptake genes, named Iron-Rhodo-box. Most known IscR proteins have Fe-S clusters featuring (Cys)3 (His)1 ligation. However, IscR proteins from Rhodobacteraceae harbor only a single-Cys residue and it was considered unlikely that they can ligate an Fe-S cluster. In this study, the role of R. sphaeroides IscR as transcriptional regulator and sensor of the Fe-S cluster status of the cell was analyzed. A mutant lacking IscR is more impaired in growth under iron limitation than the wild-type and exhibits significantly increased ROS levels in iron-replete and iron-deplete conditions. Expression studies reveal that R. sphaeroides IscR in its cluster-bound form functions as transcriptional repressor of genes involved in iron metabolism by direct binding to the promoter region of genes preceded by the motif. A total of 110 genes are directly or indirectly affected by IscR. Furthermore, IscR possesses a unique Fe-S cluster ligation scheme with only a single cysteine involved. PMID:26235649

  20. Spectrometers for RF breakdown studies for CLIC

    NASA Astrophysics Data System (ADS)

    Jacewicz, M.; Ziemann, V.; Ekelöf, T.; Dubrovskiy, A.; Ruber, R.

    2016-08-01

    An e+e- collider of several TeV energy will be needed for the precision studies of any new physics discovered at the LHC collider at CERN. One promising candidate is CLIC, a linear collider which is based on a two-beam acceleration scheme that efficiently solves the problem of power distribution to the acceleration structures. The phenomenon that currently prevents achieving high accelerating gradients in high energy accelerators such as the CLIC is the electrical breakdown at very high electrical field. The ongoing experimental work within the CLIC collaboration is trying to benchmark the theoretical models focusing on the physics of vacuum breakdown which is responsible for the discharges. In order to validate the feasibility of accelerating structures and observe the characteristics of the vacuum discharges and their eroding effects on the structure two dedicated spectrometers are now commissioned at the high-power test-stands at CERN. First, the so called Flashbox has opened up a possibility for non-invasive studies of the emitted breakdown currents during two-beam acceleration experiments. It gives a unique possibility to measure the energy of electrons and ions in combination with the arrival time spectra and to put that in context with accelerated beam, which is not possible at any of the other existing test-stands. The second instrument, a spectrometer for detection of the dark and breakdown currents, is operated at one of the 12 GHz stand-alone test-stands at CERN. Built for high repetition rate operation it can measure the spatial and energy distributions of the electrons emitted from the acceleration structure during a single RF pulse. Two new analysis tools: discharge impedance tracking and tomographic image reconstruction, applied to the data from the spectrometer make possible for the first time to obtain the location of the breakdown inside the structure both in the transversal and longitudinal direction thus giving a more complete picture of the

  1. Breakdowns in Coordination Between Air Traffic Controllers

    NASA Technical Reports Server (NTRS)

    Bearman, Chris; Orasanu, Judith; Miller, Ronald C.

    2011-01-01

    This talk outlines the complexity of coordination in air traffic control, introduces the NextGen technologies, identifies common causes for coordination breakdowns in air traffic control and examines whether these causes are likely to be reduced with the introduction of NextGen technologies. While some of the common causes of breakdowns will be reduced in a NextGen environment this conclusion should be drawn carefully given the current stage of development of the technologies and the observation that new technologies often shift problems rather than reduce them.

  2. Dynamics of the breakdown of granular clusters

    NASA Astrophysics Data System (ADS)

    Coppex, François; Droz, Michel; Lipowski, Adam

    2002-07-01

    Recently van der Meer et al. studied the breakdown of a granular cluster [Phys. Rev. Lett. 88, 174302 (2002)]. We reexamine this problem using an urn model, which takes into account fluctuations and finite-size effects. General arguments are given for the absence of a continuous transition when the number of urns (compartments) is greater than two. Monte Carlo simulations show that the lifetime of a cluster τ diverges at the limits of stability as τ~N1/3, where N is the number of balls. After the breakdown, depending on the dynamical rules of our urn model, either normal or anomalous diffusion of the cluster takes place.

  3. Solution conformation of a peptide fragment representing a proposed RNA-binding site of a viral coat protein studied by two-dimensional NMR

    SciTech Connect

    van der Graaf, M.; van Mierlo, C.P.M.; Hemminga, M.A. )

    1991-06-11

    The first 25 amino acids of the coat protein of cowpea chlorotic mottle virus are essential for binding the encapsidated RNA. Although an {alpha}-helical conformation has been predicted for this highly positively charged N-terminal region. No experimental evidence for this conformation has been presented so far. In this study, two-dimensional proton NMR experiments were performed on a chemically synthesized pentacosapeptide containing the first 25 amino acids of this coat protein. All resonances could be assigned by a combined use of two-dimensional correlated spectroscopy and nuclear Overhauser enhancement spectroscopy carried out at four different temperatures. Various NMR parameters indicate the presence of a conformational ensemble consisting of helical structures rapidly converting into more extended states. Differences in chemical shifts and nuclear Overhauser effects indicate that lowering the temperature induces a shift of the dynamic equilibrium toward more helical structures. At 10{degrees}C, a perceptible fraction of the conformational ensemble consists of structures with an {alpha}-helical conformation between residues 9 and 17, likely starting with a turnlike structure around Thr9 and Arg10. Both the conformation and the position of this helical region agree well with the secondary structure predictions mentioned above.

  4. Effects of salinity on leaf breakdown: Dryland salinity versus salinity from a coalmine.

    PubMed

    Sauer, Felix G; Bundschuh, Mirco; Zubrod, Jochen P; Schäfer, Ralf B; Thompson, Kristie; Kefford, Ben J

    2016-08-01

    Salinization of freshwater ecosystems as a result of human activities represents a global threat for ecosystems' integrity. Whether different sources of salinity with their differing ionic compositions lead to variable effects in ecosystem functioning is unknown. Therefore, the present study assessed the impact of dryland- (50μS/cm to 11,000μS/cm) and coalmine-induced (100μS/cm to 2400μS/cm) salinization on the leaf litter breakdown, with focus on microorganisms as main decomposer, in two catchments in New South Wales, Australia. The breakdown of Eucalyptus camaldulensis leaves decreased with increasing salinity by up to a factor of three. Coalmine salinity, which is characterised by a higher share of bicarbonates, had a slightly but consistently higher breakdown rate at a given salinity relative to dryland salinity, which is characterised by ionic proportions similar to sea water. Complementary laboratory experiments supported the stimulatory impact of sodium bicarbonates on leaf breakdown when compared to sodium chloride or artificial sea salt. Furthermore, microbial inoculum from a high salinity site (11,000μS/cm) yielded lower leaf breakdown at lower salinity relative to inoculum from a low salinity site (50μS/cm). Conversely, inoculum from the high salinity site was less sensitive towards increasing salinity levels relative to inoculum from the low salinity site. The effects of the different inoculum were the same regardless of salt source (sodium bicarbonate, sodium chloride and artificial sea salt). Finally, the microorganism-mediated leaf litter breakdown was most efficient at intermediate salinity levels (≈500μS/cm). The present study thus points to severe implications of increasing salinity intensities on the ecosystem function of leaf litter breakdown, while the underlying processes need further scrutiny. PMID:27393920

  5. Fear of breakdown and the unlived life.

    PubMed

    Ogden, Thomas H

    2014-04-01

    Winnicott's Fear of breakdown is an unfinished work that requires that the reader be not only a reader, but also a writer of this work which often gestures toward meaning as opposed to presenting fully developed ideas. The author's understanding of the often confusing, sometimes opaque, argument of Winnicott's paper is as follows. In infancy there occurs a breakdown in the mother-infant tie that forces the infant to take on, by himself, emotional events that he is unable to manage. He short-circuits his experience of primitive agony by generating defense organizations that are psychotic in nature, i.e., they substitute self-created inner reality for external reality, thus foreclosing his actually experiencing critical life events. By not experiencing the breakdown of the mother-infant tie when it occurred in infancy, the individual creates a psychological state in which he lives in fear of a breakdown that has already happened, but which he did not experience. The author extends Winnicott's thinking by suggesting that the driving force of the patient's need to find the source of his fear is his feeling that parts of himself are missing and that he must find them if he is to become whole. What remains of his life feels to him like a life that is mostly an unlived life. PMID:24620827

  6. How to Avoid Language Breakdown? Circumlocution!

    ERIC Educational Resources Information Center

    Salomone, Ann Masters; Marsal, Florence

    1997-01-01

    Circumlocution can prevent communication breakdown and is a required function at the Advanced level on the American Council on the Teaching of Foreign Languages (ACTFL) Oral Proficiency Scale. To encourage this communicative strategy, researchers conducted a study of two intermediate college French classes: one that encouraged circumlocution and…

  7. Numerical Borehole Breakdown Investigations using XFEM

    NASA Astrophysics Data System (ADS)

    Beckhuis, Sven; Leonhart, Dirk; Meschke, Günther

    2016-04-01

    During pressurization of a wellbore a typical downhole pressure record shows the following regimes: first the applied wellbore pressure balances the reservoir pressure, then after the compressive circumferential hole stresses are overcome, tensile stresses are induced on the inside surface of the hole. When the magnitude of these stresses reach the tensile failure stress of the surrounding rock medium, a fracture is initiated and propagates into the reservoir. [1] In standard theories this pressure, the so called breakdown pressure, is the peak pressure in the down-hole pressure record. However experimental investigations [2] show that the breakdown did not occur even if a fracture was initiated at the borehole wall. Drilling muds had the tendency to seal and stabilize fractures and prevent fracture propagation. Also fracture mechanics analysis of breakdown process in mini-frac or leak off tests [3] show that the breakdown pressure could be either equal or larger than the fracture initiation pressure. In order to gain a deeper understanding of the breakdown process in reservoir rock, numerical investigations using the extended finite element method (XFEM) for hydraulic fracturing of porous materials [4] are discussed. The reservoir rock is assumed to be pre-fractured. During pressurization of the borehole, the injection pressure, the pressure distribution and the position of the highest flux along the fracture for different fracturing fluid viscosities are recorded and the influence of the aforementioned values on the stability of fracture propagation is discussed. [1] YEW, C. H. (1997), "Mechanics of Hydraulic Fracturing", Gulf Publishing Company [2] MORITA, N.; BLACK, A. D.; FUH, G.-F. (1996), "Borehole Breakdown Pressure with Drilling Fluids". International Journal of Rock Mechanics and Mining Sciences 33, pp. 39-51 [3] DETOURNAY, E.; CARBONELL, R. (1996), "Fracture Mechanics Analysis of the Breakdown Process in Minifrac or Leakoff Test", Society of Petroleum

  8. Characterization of a Low-Molecular-Weight Glutenin Subunit Gene from Bread Wheat and the Corresponding Protein That Represents a Major Subunit of the Glutenin Polymer1

    PubMed Central

    Masci, Stefania; D'Ovidio, Renato; Lafiandra, Domenico; Kasarda, Donald D.

    1998-01-01

    Both high- and low-molecular-weight glutenin subunits (LMW-GS) play the major role in determining the viscoelastic properties of wheat (Triticum aestivum L.) flour. To date there has been no clear correspondence between the amino acid sequences of LMW-GS derived from DNA sequencing and those of actual LMW-GS present in the endosperm. We have characterized a particular LMW-GS from hexaploid bread wheat, a major component of the glutenin polymer, which we call the 42K LMW-GS, and have isolated and sequenced the putative corresponding gene. Extensive amino acid sequences obtained directly for this 42K LMW-GS indicate correspondence between this protein and the putative corresponding gene. This subunit did not show a cysteine (Cys) at position 5, in contrast to what has frequently been reported for nucleotide-based sequences of LMW-GS. This Cys has been replaced by one occurring in the repeated-sequence domain, leaving the total number of Cys residues in the molecule the same as in various other LMW-GS. On the basis of the deduced amino acid sequence and literature-based assignment of disulfide linkages, a computer-generated molecular model of the 42K subunit was constructed. PMID:9847089

  9. Electrical breakdown of carbon nanotube devices and the predictability of breakdown position

    NASA Astrophysics Data System (ADS)

    Goswami, Gopal Krishna; Nanda, Karuna Kar

    2012-06-01

    We have investigated electrical transport properties of long (>10 μm) multiwalled carbon nanotubes (NTs) by dividing individuals into several segments of identical length. Each segment has different resistance because of the random distribution of defect density in an NT and is corroborated by Raman studies. Higher is the resistance, lower is the current required to break the segments indicating that breakdown occurs at the highly resistive segment/site and not necessarily at the middle. This is consistent with the one-dimensional thermal transport model. We have demonstrated the healing of defects by annealing at moderate temperatures or by current annealing. To strengthen our mechanism, we have carried out electrical breakdown of nitrogen doped NTs (NNTs) with diameter variation from one end to the other. It reveals that the electrical breakdown occurs selectively at the narrower diameter region. Overall, we believe that our results will help to predict the breakdown position of both semiconducting and metallic NTs.

  10. Experimental breakdown of selected anodized aluminum samples in dilute plasmas

    NASA Technical Reports Server (NTRS)

    Grier, Norman T.; Domitz, Stanley

    1992-01-01

    Anodized aluminum samples representative of Space Station Freedom structural material were tested for electrical breakdown under space plasma conditions. In space, this potential arises across the insulating anodized coating when the spacecraft structure is driven to a negative bias relative to the external plasma potential due to plasma-surface interaction phenomena. For anodized materials used in the tests, it was found that breakdown voltage varied from 100 to 2000 volts depending on the sample. The current in the arcs depended on the sample, the capacitor, and the voltage. The level of the arc currents varied from 60 to 1000 amperes. The plasma number density varied from 3 x 10 exp 6 to 10 exp 3 ions per cc. The time between arcs increased as the number density was lowered. Corona testing of anodized samples revealed that samples with higher corona inception voltage had higher arcing inception voltages. From this it is concluded that corona testing may provide a method of screening the samples.

  11. Recirculation in swirling flow - A manifestation of vortex breakdown

    NASA Astrophysics Data System (ADS)

    Escudier, M. P.; Keller, J. J.

    1985-01-01

    The addition of a sufficiently high degree of swirl to flow going into a circular pipe produces a limited region of reversed flow. Such a vortex breakdown, as it is termed, represents a zone of transition from a supercritical to a subcritical flow state. If the flow remains subcritical, an unavoidable consequence is that the geometry and conditions downstream directly affect the upstream flow up to, and including, the breakdown region. Laser Dopper anemometer measurements of the swirl and axial velocity components, as well as the corresponding streamline patterns, are presented for water flow in a model based upon the geometry of a swirl combustor. It is shown that a strong exit contraction (55 percent of the diameter) has practically no influence on a flow which reverts to supercritical, whereas even a weak contraction (15 percent of the diameter) has a significant influence on a flow which remains subcritical. It is argued that a cold flow is likely to be totally unrepresentative of a reacting flow through the same geometry, and, also, that great care has to be taken over the boundary conditions to be imposed for the numerical computation of subcritical flows.

  12. Dielectric breakdown in nano-porous thin films

    NASA Astrophysics Data System (ADS)

    Borja, Juan Pablo

    Unknown to most computer users and mobile device enthusiasts, we have finally entered into a critical age of chip manufacturing. January of 2014 marks the official start of the quest by the semiconductor industry to successfully integrate sub 14nm process technology nodes in accordance to the International Technology Roadmap for Semiconductors (ITRS). The manufacturing of nano-scale features represents a major bottleneck of its own. However, a bigger challenge lies in reliably isolating the massive chip interconnect network. The present work is aimed at generating a theoretical and experimental framework to predict dielectric breakdown for thin films used in computer chip components. Here, a set of experimental techniques are presented to assess and study dielectric failure in novel thin films. A theory of dielectric breakdown in thin nano-porous films is proposed to describe combined intrinsic and metal ion catalyzed failure. This theory draws on experimental evidence as well as fundamental concepts from mass and electronic charge transport. The drift of metal species was found to accelerate intrinsic dielectric failure. The solubility of metals species such as Cu was found to range from 7.0x1025 ions/m3 to 1.86x1026 ions/m3 in 7% porous SiCOH films. The diffusion coefficient for Cu species was found to span from 4.2x10-19 m2/s to 1.86x10-21 m2/s. Ramped voltage stress experiments were used to identify intrinsic failure from metal catalyzed failure. Intrinsic breakdown is defined when time to failure against applied field ramp rate results in ∂(ln(TTF))/∂(ln(R)) ≈ -1. Intrinsic failure was studied using Au. Here, ∂(ln(TTF))/∂(ln(R)) ≈ -0.95, which is an experimental best case scenario for intrinsic failure. Au is commonly reluctant to ionize which means that failure occurs in the absence of ionic species. Metal catalyzed failure was investigated using reactive electrodes such as Cu, and Ag. Here, trends for ∂(ln(TTF))/∂(ln(R)) significantly

  13. A computational study of the taxonomy of vortex breakdown

    NASA Technical Reports Server (NTRS)

    Spall, Robert E.; Gatski, Thomas B.

    1990-01-01

    The results of a fully three-dimensional numerical simulation of vortex breakdown using the unsteady, incompressible Navier-Stokes equations are presented. The solutions show that the freestream axial velocity distribution has a significant effect on the position and type of vortex breakdown. Common features between bubble-type and spiral-type breakdown are identified and the role of flow stagnation and the critical state are discussed as complimentary ideas describing the initiation of breakdown.

  14. Protein tyrosine kinase inhibition and cell proliferation: is the [3H]-thymidine uptake assay representative of the T-lymphocyte proliferation rate?

    PubMed

    Spinozzi, F; Pagliacci, M C; Agea, E; Migliorati, G; Riccardi, C; Bertotto, A; Nicoletti, I

    1995-01-01

    T-cell growth is controlled to a large degree by extracellular signals that bind to specific receptors on the surface of cells. A number of these receptors have intrinsic protein tyrosine kinase (PTK) activity. Their action on second messenger generation, and thus on cell proliferation, has been indirectly demonstrated by the decrease in [3H]-thymidine (TdR) uptake that follows co-stimulation of T-cells with mitogens and PTK inhibitors such as genistein (GEN). In this paper we report that the [3H]-TdR uptake assay is not a valid and reliable tool for investigating the proliferative activity of certain T-cell lines. In fact, a concomitant assessment of both [3H]-TdR uptake and cell cycle progression demonstrated that GEN is able to block G2/M progression of Jurkat T-lymphocytes even at doses (5 micrograms/ml) that do not influence [3H]-TdR uptake. Pretreatment with sodium o-vanadate (100 nM) could not reverse the GEN-related cell cycle perturbation, but was able to restore optimal [3H]-TdR uptake. Finally, GEN treatment was able to induce concentration-dependent apoptotic cell death of Jurkat T-cells. The control of cell activation, proliferation and programmed cell death is undoubtedly influenced by receptor-associated PTKs. The final effect on cell survival is almost entirely dependent on the activation state of the cell. The [3H]-TdR uptake assay seems to be inadequate for a correct interpretation of the expected results. PMID:7655707

  15. Analytical application of femtosecond laser-induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Melikechi, Noureddine; Markushin, Yuri

    2015-05-01

    We report on significant advantages provided by femtosecond laser-induced breakdown spectroscopy (LIBS) for analytical applications in fields as diverse as protein characterization and material science. We compare the results of a femto- and nanosecond-laser-induced breakdown spectroscopy analysis of dual-elemental pellets in terms of the shot-to-shot variations of the neutral/ionic emission line intensities. This study is complemented by a numerical model based on two-dimensional random close packing of disks in an enclosed geometry. In addition, we show that LIBS can be used to obtain quantitative identification of the hydrogen composition of bio-macromolecules in a heavy water solution. Finally, we show that simultaneous multi-elemental particle assay analysis combined with LIBS can significantly improve macromolecule detectability up to near single molecule per particle efficiency. Research was supported by grants from the National Science Foundation Centers of Research Excellence in Science and Technology (0630388), National Aeronautics and Space Administration (NX09AU90A). Our gratitude to Dr. D. Connolly, Fox Chase Cancer Center.

  16. 7 CFR 51.1582 - Soft rot or wet breakdown.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 2 2012-01-01 2012-01-01 false Soft rot or wet breakdown. 51.1582 Section 51.1582... STANDARDS) United States Consumer Standards for Potatoes Definitions § 51.1582 Soft rot or wet breakdown. Soft rot or wet breakdown means any soft, mushy, or leaky condition of the tissue such as slimy...

  17. 7 CFR 51.1563 - Soft rot or wet breakdown.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Soft rot or wet breakdown. 51.1563 Section 51.1563... STANDARDS) United States Standards for Grades of Potatoes 1 Definitions § 51.1563 Soft rot or wet breakdown. Soft rot or wet breakdown means any soft, mushy, or leaky condition of the tissue such as slimy...

  18. 7 CFR 51.1563 - Soft rot or wet breakdown.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 2 2011-01-01 2011-01-01 false Soft rot or wet breakdown. 51.1563 Section 51.1563... STANDARDS) United States Standards for Grades of Potatoes 1 Definitions § 51.1563 Soft rot or wet breakdown. Soft rot or wet breakdown means any soft, mushy, or leaky condition of the tissue such as slimy...

  19. 7 CFR 51.1582 - Soft rot or wet breakdown.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 2 2011-01-01 2011-01-01 false Soft rot or wet breakdown. 51.1582 Section 51.1582... STANDARDS) United States Consumer Standards for Potatoes Definitions § 51.1582 Soft rot or wet breakdown. Soft rot or wet breakdown means any soft, mushy, or leaky condition of the tissue such as slimy...

  20. 7 CFR 51.1563 - Soft rot or wet breakdown.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 2 2012-01-01 2012-01-01 false Soft rot or wet breakdown. 51.1563 Section 51.1563... STANDARDS) United States Standards for Grades of Potatoes 1 Definitions § 51.1563 Soft rot or wet breakdown. Soft rot or wet breakdown means any soft, mushy, or leaky condition of the tissue such as slimy...

  1. 7 CFR 51.1582 - Soft rot or wet breakdown.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Soft rot or wet breakdown. 51.1582 Section 51.1582... STANDARDS) United States Consumer Standards for Potatoes Definitions § 51.1582 Soft rot or wet breakdown. Soft rot or wet breakdown means any soft, mushy, or leaky condition of the tissue such as slimy...

  2. Recent Studies of RF Breakdown Physics in Normal Conducting Cavities

    SciTech Connect

    Dolgashev, Valery; /SLAC

    2012-06-11

    The operating accelerating gradient in normal conducting accelerating structures is often limited by rf breakdown. The behavior of the rf breakdown depends on multiple parameters, including the input rf power, rf circuit, cavity shape and material. Here we discuss recent experimental data and theoretical studies of rf breakdown physics.

  3. Prevention of breakdown behind railgun projectiles

    SciTech Connect

    Hawke, R.S.

    1989-04-20

    An electromagnetic railgun accelerator system, for accelerating projectiles by a plasma arc, introduces a breakdown inhibiting gas into the railgun chamber behind the accelerating projectile. The breakdown inhibiting gas, which absorbs electrons, is a halide or a halide compound such as fluorine or SF{sub 6}. The gas is introduced between the railgun rails after the projectile has passed through inlets in the rails or the projectile; by coating the rails or the projectile with a material which releases the gas after the projectile passes over it; by fabricating the rails or the projectile or insulators out of a material which releases the gas into the portions of the chamber through which the projectile has traveled. The projectile may have a cavity at its rear to control the release of ablation products. 9 figs.

  4. Prevention of breakdown behind railgun projectiles

    DOEpatents

    Hawke, Ronald S.

    1992-01-01

    An electromagnetic railgun accelerator system, for accelerating projectiles (14, 15, 114, 214, 314, 414) by a plasma arc (3), introduces a breakdown inhibiting gas into the railgun chamber (26) behind the accelerating projectile (14). The breakdown inhibiting gas, which absorbs electrons, is a halide or a halide compound such as fluorine or SF.sub.6. The gas is introduced between the railgun rails (12) after the projectile (14) has passed through inlets (16) in the rails (12) or the projectile (114); by coating the rails (12) or the projectile (15) with a material (28) which releases the gas after the projectile (14) passes over it; by fabricating the rails (12) or the projectile (15) or insulators out of a material which releases the gas into the portions of the chamber (26) through which the projectile has travelled. The projectile (214, 314, 414) may have a cavity (232, 332, 432) at its rear to control the release of ablation products (4).

  5. Prevention of breakdown behind railgun projectiles

    DOEpatents

    Hawke, Ronald S.

    1992-01-01

    An electromagnetic railgun accelerator system, for accelerating projectiles (14, 15, 114, 214, 314, 444) by a plasma arc (3), introduces a breakdown inhibiting gas into the railgun chamber (26) behind the accelerating projectile (14). The breakdown inhibiting gas, which absorbs electrons, is a halide or a halide compound such as fluorine or SF.sub.6. The gas is introduced between the railgun rails (12) after the projectile (14) has passed through inlets (16) in the rails (12) or the projectile (114); by coating the rails (12) or the projectile (15) with a material (28) which releases the gas after the projectile (14 ) passes over it; by fabricating the rails (12) or the projectile (15) or insulators out of a material which releases the gas into the portions of the chamber (26) through which the projectile has travelled. The projectile (214, 314, 414) may have a cavity (232, 332, 432) at its rear to control the release of ablation products (4).

  6. Breakdown and partial discharges in magnetic liquids.

    PubMed

    Herchl, F; Marton, K; Tomčo, L; Kopčanský, P; Timko, M; Koneracká, M; Kolcunová, I

    2008-05-21

    The dielectric properties (permittivity, loss factor, dielectric breakdown strength) of magnetic liquids were investigated. The magnetic liquids were composed of magnetite particles coated with oleic acid as surfactant and dispersed in transformer oil. To determine their dielectric properties they were subjected to a uniform magnetic field at high alternating electric fields up to 14 MV m(-1). Nearly constant permittivity of magnetic liquid with particle volume concentration Φ = 0.0019 as a function of electric field was observed. Magnetic liquids with concentrations Φ = 0.019 and 0.032 showed significant changes of permittivity and loss factor dependent on electric and magnetic fields. The best concentration of magnetic fluid was found at which partial current impulse magnitudes were the lowest. The breakdown strength distribution of the magnetic liquid with Φ = 0.0025 was fitted with the Duxbury-Leath, Weibull and Gauss distribution functions. PMID:21694240

  7. Electrical breakdown studies with Mycalex insulators

    SciTech Connect

    Waldron, W.; Greenway, W.; Eylon, S.; Henestroza, E.; Yu, S.

    2003-05-01

    Insulating materials such as alumina and glass-bonded mica (Mycalex) are used in accelerator systems for high voltage feedthroughs, structural supports, and barriers between high voltage insulating oil and the vacuum beam pipe in induction accelerator cells. Electric fields in the triple points should be minimized to prevent voltage breakdown. Mechanical stress can compromise seals and result in oil contamination of the insulator surface. We have tested various insulator cleaning procedures including ultrasonic cleaning with a variety of aqueous-based detergents, and manual scrubbing with various detergents. Water sheeting tests were used to determine the initial results of the cleaning methods. Ultimately, voltage breakdown tests will be used to quantify the benefits of these cleaning procedures.

  8. Supersonic quasi-axisymmetric vortex breakdown

    NASA Technical Reports Server (NTRS)

    Kandil, Osama A.; Kandil, Hamdy A.; Liu, C. H.

    1991-01-01

    An extensive computational study of supersonic quasi-axisymmetric vortex breakdown in a configured circular duct is presented. The unsteady, compressible, full Navier-Stokes (NS) equations are used. The NS equations are solved for the quasi-axisymmetric flows using an implicit, upwind, flux difference splitting, finite volume scheme. The quasi-axisymmetric solutions are time accurate and are obtained by forcing the components of the flowfield vector to be equal on two axial planes, which are in close proximity of each other. The effect of Reynolds number, for laminar flows, on the evolution and persistence of vortex breakdown, is studied. Finally, the effect of swirl ration at the duct inlet is investigated.

  9. Prevention of breakdown behind railgun projectiles

    DOEpatents

    Hawke, R.S.

    1992-10-13

    An electromagnetic railgun accelerator system, for accelerating projectiles by a plasma arc, introduces a breakdown inhibiting gas into the railgun chamber behind the accelerating projectile. The breakdown inhibiting gas, which absorbs electrons, is a halide or a halide compound such as fluorine or SF[sub 6]. The gas is introduced between the railgun rails after the projectile has passed through inlets in the rails or the projectile; by coating the rails or the projectile with a material which releases the gas after the projectile passes over it; by fabricating the rails or the projectile or insulators out of a material which releases the gas into the portions of the chamber through which the projectile has travelled. The projectile may have a cavity at its rear to control the release of ablation products. 12 figs.

  10. Prevention of breakdown behind railgun projectiles

    DOEpatents

    Hawke, R.S.

    1992-09-01

    An electromagnetic railgun accelerator system, for accelerating projectiles by a plasma arc, introduces a breakdown inhibiting gas into the railgun chamber behind the accelerating projectile. The breakdown inhibiting gas, which absorbs electrons, is a halide or a halide compound such as fluorine or SF[sub 6]. The gas is introduced between the railgun rails after the projectile has passed through inlets in the rails or the projectile; by coating the rails or the projectile with a material which releases the gas after the projectile passes over it; by fabricating the rails or the projectile or insulators out of a material which releases the gas into the portions of the chamber through which the projectile has travelled. The projectile may have a cavity at its rear to control the release of ablation products. 12 figs.

  11. Microcontroller based system for electrical breakdown time delay measurement in gas-filled devices

    SciTech Connect

    Pejovic, Milic M.; Denic, Dragan B.; Pejovic, Momcilo M.; Nesic, Nikola T.; Vasovic, Nikola

    2010-10-15

    This paper presents realization of a digital embedded system for measuring electrical breakdown time delay. The proposed system consists of three major parts: dc voltage supply, analog subsystem, and a digital subsystem. Any dc power source with the range from 100 to 1000 V can be used in this application. The analog subsystem should provide fast and accurate voltage switching on the testing device as well as transform the signals that represent the voltage pulse on the device and the device breakdown into the form suitable for detection by a digital subsystem. The insulated gate bipolar transistor IRG4PH40KD driven by TC429 MOSFET driver is used for high voltage switching on the device. The aim of a digital subsystem is to detect the signals from the analog subsystem and to measure the elapsed time between their occurrences. Moreover, the digital subsystem controls various parameters that influence time delay and provides fast data storage for a large number of measured data. For this propose, we used the PIC18F4550 microcontroller with a full-speed compatible universal serial bus (USB) engine. Operation of this system is verified on different commercial and custom made gas devices with different structure and breakdown mechanisms. The electrical breakdown time delay measurements have been carried out as a function of several parameters, which dominantly influence electrical breakdown time delay. The obtained results have been verified using statistical methods, and they show good agreement with the theory. The proposed system shows good repeatability, sensitivity, and stability for measuring the electrical breakdown time delay.

  12. Microcontroller based system for electrical breakdown time delay measurement in gas-filled devices

    NASA Astrophysics Data System (ADS)

    Pejović, Milić M.; Denić, Dragan B.; Pejović, Momčilo M.; Nešić, Nikola T.; Vasović, Nikola

    2010-10-01

    This paper presents realization of a digital embedded system for measuring electrical breakdown time delay. The proposed system consists of three major parts: dc voltage supply, analog subsystem, and a digital subsystem. Any dc power source with the range from 100 to 1000 V can be used in this application. The analog subsystem should provide fast and accurate voltage switching on the testing device as well as transform the signals that represent the voltage pulse on the device and the device breakdown into the form suitable for detection by a digital subsystem. The insulated gate bipolar transistor IRG4PH40KD driven by TC429 MOSFET driver is used for high voltage switching on the device. The aim of a digital subsystem is to detect the signals from the analog subsystem and to measure the elapsed time between their occurrences. Moreover, the digital subsystem controls various parameters that influence time delay and provides fast data storage for a large number of measured data. For this propose, we used the PIC18F4550 microcontroller with a full-speed compatible universal serial bus (USB) engine. Operation of this system is verified on different commercial and custom made gas devices with different structure and breakdown mechanisms. The electrical breakdown time delay measurements have been carried out as a function of several parameters, which dominantly influence electrical breakdown time delay. The obtained results have been verified using statistical methods, and they show good agreement with the theory. The proposed system shows good repeatability, sensitivity, and stability for measuring the electrical breakdown time delay.

  13. Three-dimensional simulation of vortex breakdown

    NASA Technical Reports Server (NTRS)

    Kuruvila, G.; Salas, M. D.

    1990-01-01

    The integral form of the complete, unsteady, compressible, three-dimensional Navier-Stokes equations in the conservation form, cast in generalized coordinate system, are solved, numerically, to simulate the vortex breakdown phenomenon. The inviscid fluxes are discretized using Roe's upwind-biased flux-difference splitting scheme and the viscous fluxes are discretized using central differencing. Time integration is performed using a backward Euler ADI (alternating direction implicit) scheme. A full approximation multigrid is used to accelerate the convergence to steady state.

  14. Breakdown of cyclotron resonance in semiconductor superlattices

    NASA Astrophysics Data System (ADS)

    Duffield, T.; Bhat, R.; Koza, M.; Hwang, D. M.; DeRosa, F.; Grabbe, P.; Allen, S. J.

    1988-03-01

    We have observed breakdown of cyclotron resonance in large magnetic fields oriented perpendicular to the growth direction in semiconductor superlattices. At small magnetic fields conventional cyclotron resonance is observed with the mass related to the miniband mass. At large magnetic fields, when the cyclotron diameter approaches the superlattice period, the resonance frequency appears to saturate and is determined by orbits impaled on the barrier. A model calculation gives good account of the magnetic field dependence of the resonance position and line width.

  15. Shock/vortex interaction and vortex-breakdown modes

    NASA Technical Reports Server (NTRS)

    Kandil, Osama A.; Kandil, H. A.; Liu, C. H.

    1992-01-01

    Computational simulation and study of shock/vortex interaction and vortex-breakdown modes are considered for bound (internal) and unbound (external) flow domains. The problem is formulated using the unsteady, compressible, full Navier-Stokes (NS) equations which are solved using an implicit, flux-difference splitting, finite-volume scheme. For the bound flow domain, a supersonic swirling flow is considered in a configured circular duct and the problem is solved for quasi-axisymmetric and three-dimensional flows. For the unbound domain, a supersonic swirling flow issued from a nozzle into a uniform supersonic flow of lower Mach number is considered for quasi-axisymmetric and three-dimensional flows. The results show several modes of breakdown; e.g., no-breakdown, transient single-bubble breakdown, transient multi-bubble breakdown, periodic multi-bubble multi-frequency breakdown and helical breakdown.

  16. Runaway breakdown and electrical discharges in thunderstorms

    NASA Astrophysics Data System (ADS)

    Milikh, Gennady; Roussel-Dupré, Robert

    2010-12-01

    This review considers the precise role played by runaway breakdown (RB) in the initiation and development of lightning discharges. RB remains a fundamental research topic under intense investigation. The question of how lightning is initiated and subsequently evolves in the thunderstorm environment rests in part on a fundamental understanding of RB and cosmic rays and the potential coupling to thermal runaway (as a seed to RB) and conventional breakdown (as a source of thermal runaways). In this paper, we describe the basic mechanism of RB and the conditions required to initiate an observable avalanche. Feedback processes that fundamentally enhance RB are discussed, as are both conventional breakdown and thermal runaway. Observations that provide clear evidence for the presence of energetic particles in thunderstorms/lightning include γ-ray and X-ray flux intensifications over thunderstorms, γ-ray and X-ray bursts in conjunction with stepped leaders, terrestrial γ-ray flashes, and neutron production by lightning. Intense radio impulses termed narrow bipolar pulses (or NBPs) provide indirect evidence for RB particularly when measured in association with cosmic ray showers. Our present understanding of these phenomena and their enduring enigmatic character are touched upon briefly.

  17. Dielectric breakdown induced by picosecond laser pulses

    NASA Technical Reports Server (NTRS)

    Smith, W. L.; Bechtel, J. H.; Bloembergen, N.

    1976-01-01

    The damage thresholds of transparent optical materials were investigated. Single picosecond pulses at 1.06 microns, 0.53 microns and 0.35 microns were obtained from a mode locked Nd-YAG oscillator-amplifier-frequency multiplier system. The pulses were Gaussian in space and time and permitted the determination of breakdown thresholds with a reproducibility of 15%. It was shown that the breakdown thresholds are characteristic of the bulk material, which included nine alkali halides, five different laser host materials, KDP, quartz, sapphire and calcium fluoride. The extension of the damage data to the ultraviolet is significant, because some indication was obtained that two- and three-photon absorption processes begin to play a role in determining the threshold. Throughout the visible region of the spectrum the threshold is still an increasing function of frequency, indicating that avalanche ionization is the dominant factor in determining the breakdown threshold. This was confirmed by a detailed study of the damage morphology with a high resolution microscope just above the threshold. The influence of self focusing is discussed, and evidence for beam distortion below the power threshold for complete self focusing is presented, confirming the theory of Marburger.

  18. Kinetic Simulations of Dense Plasma Focus Breakdown

    NASA Astrophysics Data System (ADS)

    Schmidt, A.; Higginson, D. P.; Jiang, S.; Link, A.; Povilus, A.; Sears, J.; Bennett, N.; Rose, D. V.; Welch, D. R.

    2015-11-01

    A dense plasma focus (DPF) device is a type of plasma gun that drives current through a set of coaxial electrodes to assemble gas inside the device and then implode that gas on axis to form a Z-pinch. This implosion drives hydrodynamic and kinetic instabilities that generate strong electric fields, which produces a short intense pulse of x-rays, high-energy (>100 keV) electrons and ions, and (in deuterium gas) neutrons. A strong factor in pinch performance is the initial breakdown and ionization of the gas along the insulator surface separating the two electrodes. The smoothness and isotropy of this ionized sheath are imprinted on the current sheath that travels along the electrodes, thus making it an important portion of the DPF to both understand and optimize. Here we use kinetic simulations in the Particle-in-cell code LSP to model the breakdown. Simulations are initiated with neutral gas and the breakdown modeled self-consistently as driven by a charged capacitor system. We also investigate novel geometries for the insulator and electrodes to attempt to control the electric field profile. The initial ionization fraction of gas is explored computationally to gauge possible advantages of pre-ionization which could be created experimentally via lasers or a glow-discharge. Prepared by LLNL under Contract DE-AC52-07NA27344.

  19. Ferroelectric Polymer Composite with Enhanced Breakdown Strength

    NASA Astrophysics Data System (ADS)

    Han, Kuo; Gadinski, Matthew; Wang, Qing

    2013-03-01

    Numerous efforts have been made in the past decades to improve the energy storage capability of dielectric capacitors by incorporating ceramic addictives into polymers. Ferroelectric polymers have been particularly interesting as matrix for dielectric composites because of their highest dielectric permittivity and energy density. However, most polymer composites suffer from significantly reduced breakdown strength, which compromises the potential gain in energy density. In this work, various metallic alkoxide were introduced into the functionalized ferroelectric poly(vinylidene fluoride-co- chlorotrifluoroethylene), P(VDF-CTFE), via covalent bonding. The composite with the optimized composition exhibited the Weibull statistical breakdown strength of 504.8 MV/m, 67.6 % higher than the pristine polymer. The enhanced breakdown strength was mainly ascribed to the cross-linking and the formation of deep traps, which effectively reduced the conduction and further lowered the energy loss. Additionally, the homogeneous dispersion of the inorganic phase and the small contrast in permittivity between the polymer and amorphous oxides also contribute to the improved dielectric strength. The dielectric spectra of the composites have been recorded at varied temperatures and frequencies, which revealed the presence of the interfacial polarization layer in the composites.

  20. Space platform expendables resupply concept definition study. Volume 3: Work breakdown structure and work breakdown structure dictionary

    NASA Technical Reports Server (NTRS)

    1984-01-01

    The work breakdown structure (WBS) for the Space Platform Expendables Resupply Concept Definition Study is described. The WBS consists of a list of WBS elements, a dictionary of element definitions, and an element logic diagram. The list and logic diagram identify the interrelationships of the elements. The dictionary defines the types of work that may be represented by or be classified under each specific element. The Space Platform Expendable Resupply WBS was selected mainly to support the program planning, scheduling, and costing performed in the programmatics task (task 3). The WBS is neither a statement-of-work nor a work authorization document. Rather, it is a framework around which to define requirements, plan effort, assign responsibilities, allocate and control resources, and report progress, expenditures, technical performance, and schedule performance. The WBS element definitions are independent of make-or-buy decisions, organizational structure, and activity locations unless exceptions are specifically stated.

  1. RF BREAKDOWN STUDIES USING PRESSURIZED CAVITIES

    SciTech Connect

    Johnson, Rolland

    2014-09-21

    Many present and future particle accelerators are limited by the maximum electric gradient and peak surface fields that can be realized in RF cavities. Despite considerable effort, a comprehensive theory of RF breakdown has not been achieved and mitigation techniques to improve practical maximum accelerating gradients have had only limited success. Part of the problem is that RF breakdown in an evacuated cavity involves a complex mixture of effects, which include the geometry, metallurgy, and surface preparation of the accelerating structures and the make-up and pressure of the residual gas in which plasmas form. Studies showed that high gradients can be achieved quickly in 805 MHz RF cavities pressurized with dense hydrogen gas, as needed for muon cooling channels, without the need for long conditioning times, even in the presence of strong external magnetic fields. This positive result was expected because the dense gas can practically eliminate dark currents and multipacting. In this project we used this high pressure technique to suppress effects of residual vacuum and geometry that are found in evacuated cavities in order to isolate and study the role of the metallic surfaces in RF cavity breakdown as a function of magnetic field, frequency, and surface preparation. One of the interesting and useful outcomes of this project was the unanticipated collaborations with LANL and Fermilab that led to new insights as to the operation of evacuated normal-conducting RF cavities in high external magnetic fields. Other accomplishments included: (1) RF breakdown experiments to test the effects of SF6 dopant in H2 and He gases with Sn, Al, and Cu electrodes were carried out in an 805 MHz cavity and compared to calculations and computer simulations. The heavy corrosion caused by the SF6 components led to the suggestion that a small admixture of oxygen, instead of SF6, to the hydrogen would allow the same advantages without the corrosion in a practical muon beam line. (2) A

  2. Insulator breakdown measurements in a poor vacuum and their interpretation

    SciTech Connect

    Vogtlin, G.E.

    1990-06-01

    Breakdown measurements have been made on insulators with 0 and 45 degree angle surfaces. A technique of observing the electrons produced from the process has given some insight into the mechanisms involved. A three nanosecond pulse was used to induce breakdown. The electrons striking the anode were observed with a plastic fluor and open shutter camera. Two breakdown patterns were interpreted as cathode initiated and anode initiated breakdown. The breakdown process normally encountered was anode initiated with a positive 45 degree insulator. If the anode side was relieved with an internal electrode, the breakdown changed to cathode initiated at a higher level. If the cathode surface was then anodized, the breakdown switched back to the anode at an even higher level. Individual explosive emission sites on the cathode surface could be observed. Insulator breakdown was usually not associated with these sites. Multiple pulses allowed measurement of plasma expansion of the explosive emission sites. It is believed that breakdown with longer pulses is due to the expansion of the explosive emission site plasma to the insulator surface. Measurements were conducted with and without voltage conditioning. It appears that conditioning is achieved without explosive emission. It is believed that this is due to organic fibers that are removed by the conditioning. Organic fibers were used to induce both anode and cathode breakdown. Measurements of fiberous material have shown explosive emission a low as 100 kV on a three nanosecond time scale and below 20 kv/cm on a longer time scale. 8 refs., 5 figs.

  3. Magnetic control of breakdown: Toward energy-efficient hollow-cathode magnetron discharges

    SciTech Connect

    Baranov, O.; Romanov, M.; Kumar, S.; Zong, X. X.; Ostrikov, K.

    2011-03-15

    Characteristics of electrical breakdown of a planar magnetron enhanced with an electromagnet and a hollow-cathode structure, are studied experimentally and numerically. At lower pressures the breakdown voltage shows a dependence on the applied magnetic field, and the voltage necessary to achieve the self-sustained discharge regime can be significantly reduced. At higher pressures, the dependence is less sensitive to the magnetic field magnitude and shows a tendency of increased breakdown voltage at the stronger magnetic fields. A model of the magnetron discharge breakdown is developed with the background gas pressure and the magnetic field used as parameters. The model describes the motion of electrons, which gain energy by passing the electric field across the magnetic field and undergo collisions with neutrals, thus generating new bulk electrons. The electrons are in turn accelerated in the electric field and effectively ionize a sufficient amount of neutrals to enable the discharge self-sustainment regime. The model is based on the assumption about the combined classical and near-wall mechanisms of electron conductivity across the magnetic field, and is consistent with the experimental results. The obtained results represent a significant advance toward energy-efficient multipurpose magnetron discharges.

  4. Correlation between astrocyte activity and recovery from blood-brain barrier breakdown caused by brain injury.

    PubMed

    Ikeshima-Kataoka, Hiroko; Yasui, Masato

    2016-08-17

    Glial activation is associated with cell proliferation and upregulation of astrocyte marker expression following traumatic injury in the brain. However, the biological significance of these processes remains unclear. In the present study, astrocyte activation was investigated in a murine brain injury model. Brain injury induces blood-brain barrier (BBB) breakdown and immunoglobulin G (IgG) leak into the brain parenchyma. The recovery of BBB breakdown was evaluated by analyzing immunofluorescent staining with mouse IgG antibody. IgG leakage was greatest at 1 day after stab wound injury and decreased thereafter, and almost diminished after 7 days. Bromodeoxy uridine incorporation was used, and astrocyte proliferation rates were examined by coimmunostaining with anti-bromodeoxy uridine and anti-glial fibrillary acid protein antibodies. Consistent with IgG leakage assays, astrocyte activation was the highest at day 3 and decreased after 7 days. Moreover, in reverse transcriptase-quantitative-PCR experiments, genes associated with BBB integrity were downregulated immediately after BBB breakdown and recovered to basal expression levels within 7 days. These data indicated that astrocyte activation correlated with BBB recovery from breakdown following brain injury. PMID:27362437

  5. Nonlinear breakdowns in boundary layer transition

    NASA Technical Reports Server (NTRS)

    Smith, Frank T.

    1990-01-01

    Theoretical studies of boundary-layer transition are described, based on high Reynolds numbers and with attention drawn to nonlinear interactions, breakdowns and scales. The article notes in particular truly nonlinear theories for which the mean-flow profile is completely altered from its original state. Two- and three-dimensional flow theory and conjectures on turbulent boundary-layer structures are included. Specific recent findings noted, and in qualitative agreement with experiments, are: nonlinear finite-time break-ups in unsteady interactive boundary layers; strong vortex/wave interactions; and prediction of turbulent boundary-layer displacement- and stress sublayer-thicknesses.

  6. Kinetic theory of runaway air-breakdown

    SciTech Connect

    Roussel-Dupre, R.A.; Gurevich, A.V.; Tunnell, T.; Milikh, G.M.

    1993-09-01

    The kinetic theory for a new air breakdown mechanism advanced in a previous paper is developed. The relevant form of the Boltzmann equation is derived and the particle orbits in both velocity space and configuration space are computed. A numerical solution of the Boltzmann equation, assuming a spatially uniform electric field, is obtained and the temporal evolution of the electron velocity distribution function is described. The results of our analysis are used to estimate the magnitude of potential x-ray emissions from discharges in thunderstorms.

  7. Kinetic theory of runaway air breakdown

    SciTech Connect

    Roussel-Dupre, R.A. ); Gurevich, A.V. ); Tunnell, T. ); Milikh, G.M. )

    1994-03-01

    The kinetic theory for an air breakdown mechanism advanced in a previous paper [Phys. Lett. A 165, 463 (1992)] is developed. The relevant form of the Boltzmann equation is derived and the particle orbits in both velocity space and configuration space are computed. A numerical solution of the Boltzmann equation, assuming a spatially uniform electric field, is obtained and the temporal evolution of the electron velocity distribution function is described. The results of our analysis are used to estimate the magnitude of potential x-ray emissions from discharges in thunderstorms.

  8. Theoretical and experimental investigation of vortex breakdown

    NASA Technical Reports Server (NTRS)

    Krause, E.

    1986-01-01

    The slender-vortex approximation was analyzed for incompressible and compressible flow. First the equations of motion were reduced in an order of magnitude analysis. Then compatibility conditions were formulated for the inflow conditions. Thereafter finite-difference-solutions were constructed for incompressible and compressible flow. Finally it was shown that these solutions can be used to describe the flow in slender vortices. The analysis of the breakdown process must, however, be excluded, since its upstream influence cannot be predicted with the slender vortex approximation. The investigaton of this problem is left for future work.

  9. Time-dependent MOS breakdown. [of Na contaminated capacitors

    NASA Technical Reports Server (NTRS)

    Li, S. P.; Bates, E. T.; Maserjian, J.

    1976-01-01

    A general model for time-dependent breakdown in metal-oxide-silicon (MOS) structures is developed and related to experimental measurements on samples deliberately contaminated with Na. A statistical method is used for measuring the breakdown probability as a function of log time and applied field. It is shown that three time regions of breakdown can be explained respectively in terms of silicon surface defects, ion emission from the metal interface, and lateral ion diffusion at the silicon interface.

  10. Effect of sample preparation on the discrimination of bacterial isolates cultured in liquid nutrient media using laser induced breakdown spectroscopy

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Laser induced breakdown spectroscopy (LIBS) is used as the basis for discrimination between 2 genera of gram-negative bacteria and 2 genera of gram-positive bacteria representing pathogenic threats commonly found in poultry processing rinse waters. Because LIBS-based discrimination relies primarily ...

  11. Laser radiation attenuation by sparks of optical breakdown

    NASA Astrophysics Data System (ADS)

    Budnik, A. P.; Semenov, L. P.; Skripkin, A. M.; Volkovitskii, O. A.

    1989-06-01

    A breakdown generated by laser radiation in a gas contaminated by aerosol particles is known to occur at much lower radiation intensities than in case of pure gases. Laser radiation is heavily attenuated by sparks of plasma formed at breakdowns. Energy loss estimation is important at radiation propagation in the atmosphere and in laser resonators. The breakdown phenomenon may be used in diagnostics of the atmospheric aerosol contamination events. The report presents experimental data on the influence of aerosol size distribution and concentration on optical breakdown generation and other results.

  12. Laser Radiation Attenuation By Sparks Of Optical Breakdown

    NASA Astrophysics Data System (ADS)

    Budnik, A. P.; Semenov, L. P.; Skripkin, A. M.; Volkovitsky, O. A.

    1990-01-01

    A breakdown generated by laser radiation in a gas contaminated by aerosol particles is known to occur at much lower radiation intensities than in case of pure gases, Laser radiation is heavily attenuated by sparks of plasma formed at breakdowns. Energy loss estimation is important at radiation propagation in the atmosphere and in laser resonators. The breakdown phenomenon may be used in diagnostics of the atmospheric aerosol contamination events. The report presents experimental data on the influence of aerosol size distribution and concentration on optical breakdown generation and other results.

  13. Pre-breakdown evaluation of gas discharge mechanisms in microgaps

    SciTech Connect

    Semnani, Abbas; Peroulis, Dimitrios; Venkattraman, Ayyaswamy; Alexeenko, Alina A.

    2013-04-29

    The individual contributions of various gas discharge mechanisms to total pre-breakdown current in microgaps are quantified numerically. The variation of contributions of field emission and secondary electron emission with increasing electric field shows contrasting behavior even for a given gap size. The total current near breakdown decreases rapidly with gap size indicating that microscale discharges operate in a high-current, low-voltage regime. This study provides the first such analysis of breakdown mechanisms and aids in the formulation of physics-based theories for microscale breakdown.

  14. Effect of droplet-induced breakdown on CARS temperature measurements

    SciTech Connect

    Dunn-Rankin, D. ); Switzer, G.L. ); Obringer, C.A.; Jackson, T. )

    1990-07-20

    This research examines the potential for coherent anti-Stokes Raman scattering (CARS) to rovide reliable gas temperature measurements in the presence of liquid droplets. The droplets cause dielectric breakdown by focusing the CARS laser beams. This breakdown produces a plasma that can disrupt or obscure the CARS signal. Specifically, we examine the influence of laser induced breakdown on the CARS signal, and we determine the importance of droplet position relative to the CARS focal volume and droplet concentration on the reliability of CARS temperature measurements in droplet-laden flows. In addition, we propose a reliable data reduction procedure to minimize the disruptive influence of laser induced breakdown on CARS temperature.

  15. Structure of Bacteroides thetaiotaomicron BT2081 at 2.05 Å resolution: the first structural representative of a new protein family that may play a role in carbohydrate metabolism

    PubMed Central

    Yeh, Andrew P.; Abdubek, Polat; Astakhova, Tamara; Axelrod, Herbert L.; Bakolitsa, Constantina; Cai, Xiaohui; Carlton, Dennis; Chen, Connie; Chiu, Hsiu-Ju; Chiu, Michelle; Clayton, Thomas; Das, Debanu; Deller, Marc C.; Duan, Lian; Ellrott, Kyle; Farr, Carol L.; Feuerhelm, Julie; Grant, Joanna C.; Grzechnik, Anna; Han, Gye Won; Jaroszewski, Lukasz; Jin, Kevin K.; Klock, Heath E.; Knuth, Mark W.; Kozbial, Piotr; Krishna, S. Sri; Kumar, Abhinav; Lam, Winnie W.; Marciano, David; McMullan, Daniel; Miller, Mitchell D.; Morse, Andrew T.; Nigoghossian, Edward; Nopakun, Amanda; Okach, Linda; Puckett, Christina; Reyes, Ron; Tien, Henry J.; Trame, Christine B.; van den Bedem, Henry; Weekes, Dana; Wooten, Tiffany; Xu, Qingping; Hodgson, Keith O.; Wooley, John; Elsliger, Marc-André; Deacon, Ashley M.; Godzik, Adam; Lesley, Scott A.; Wilson, Ian A.

    2010-01-01

    BT2081 from Bacteroides thetaiotaomicron (GenBank accession code NP_810994.1) is a member of a novel protein family consisting of over 160 members, most of which are found in the different classes of Bacteroidetes. Genome-context analysis lends support to the involvement of this family in carbohydrate metabolism, which plays a key role in B. thetaiotaomicron as a predominant bacterial symbiont in the human distal gut microbiome. The crystal structure of BT2081 at 2.05 Å resolution represents the first structure from this new protein family. BT2081 consists of an N-terminal domain, which adopts a β-sandwich immunoglobulin-like fold, and a larger C-terminal domain with a β-sandwich jelly-roll fold. Structural analyses reveal that both domains are similar to those found in various carbohydrate-active enzymes. The C-terminal β-jelly-roll domain contains a potential carbohydrate-binding site that is highly conserved among BT2081 homologs and is situated in the same location as the carbohydrate-binding sites that are found in structurally similar glycoside hydrolases (GHs). However, in BT2081 this site is partially occluded by surrounding loops, which results in a deep solvent-accessible pocket rather than a shallower solvent-exposed cleft. PMID:20944224

  16. Functions of Carotenoid Metabolites and Breakdown Products

    NASA Astrophysics Data System (ADS)

    Britton, George

    It is not only intact carotenoids but also fragments of carotenoid molecules that have important natural functions and actions. The electron-rich polyene chain of the carotenoids is very susceptible to oxidative breakdown, which may be enzymic or non-enzymic. Central cleavage gives C20 compounds, retinoids, as described in Chapter 16. Cleavage at other positions gives smaller fragments, notably C10, C13 and C15 compounds that retain the carotenoid end group. The formation of these is described in Chapter 17 and in Volume 3, Chapter 4. Oxidative breakdown can also take place during storage, processing and curing of plant material, and the products contribute to the desired aroma/flavour properties of, for example, tea, wine and tobacco. The importance of vitamin A (C20) in animals is well known. Vitamin A deficiency is still a major concern in many parts of the world. It can lead to blindness and serious ill-health or death, especially in young children. Volatile smaller carotenoid fragments (`norisoprenoids') are widespread scent/flavour compounds in plants.

  17. Representative Amino Acid Side-Chain Interactions in Protein-DNA Complexes: A Comparison of Highly Accurate Correlated Ab Initio Quantum Mechanical Calculations and Efficient Approaches for Applications to Large Systems.

    PubMed

    Hostaš, Jiří; Jakubec, Dávid; Laskowski, Roman A; Gnanasekaran, Ramachandran; Řezáč, Jan; Vondrášek, Jiří; Hobza, Pavel

    2015-09-01

    Representative pairs of amino acid side chains and nucleic acid bases extracted from available high-quality structures of protein-DNA complexes were analyzed using a range of computational methods. CCSD(T)/CBS interaction energies were calculated for the chosen 272 pairs. These reference interaction energies were used to test the MP2.5/CBS, MP2.X/CBS, MP2-F12, DFT-D3, PM6, and Amber force field methods. Method MP2.5 provided excellent agreement with reference data (root-mean-square error (RMSE) of 0.11 kcal/mol), which is more than 1 order of magnitude faster than the CCSD(T) method. When MP2-F12 and MP2.5 were combined, the results were within reasonable accuracy (0.20 kcal/mol), with a computational savings of almost 2 orders of magnitude. Therefore, this method is a promising tool for accurate calculations of interaction energies in protein-DNA motifs of up to ∼100 atoms, for which CCSD(T)/CBS benchmark calculations are not feasible. B3-LYP-D3 calculated with def2-TZVPP and def2-QZVP basis sets yielded sufficiently good results with a reasonably small RMSE. This method provided better results for neutral systems, whereas positively charged species exhibited the worst agreement with the benchmark data. The Amber force field yielded unbalanced results-performing well for systems containing nonpolar amino acids but severely underestimating interaction energies for charged complexes. The semiempirical PM6 method with corrections for hydrogen bonding and dispersion energy (PM6-D3H4) exhibited considerably smaller error than the Amber force field, which makes it an effective tool for modeling extended protein-ligand complexes (of up to 10,000 atoms). PMID:26575904

  18. Proteins.

    ERIC Educational Resources Information Center

    Doolittle, Russell F.

    1985-01-01

    Examines proteins which give rise to structure and, by virtue of selective binding to other molecules, make genes. Binding sites, amino acids, protein evolution, and molecular paleontology are discussed. Work with encoding segments of deoxyribonucleic acid (exons) and noncoding stretches (introns) provides new information for hypotheses. (DH)

  19. Protein

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Proteins are the major structural and functional components of all cells in the body. They are macromolecules that comprise 1 or more chains of amino acids that vary in their sequence and length and are folded into specific 3-dimensional structures. The sizes and conformations of proteins, therefor...

  20. Divergent Role for MMP-2 in Myelin Breakdown and Oligodendrocyte Death Following Transient Global Ischemia

    PubMed Central

    Walker, Espen J.; Rosenberg, Gary A.

    2016-01-01

    Transient global ischemia causes delayed white matter injury to the brain with oligodendrocyte (OLG) death and myelin breakdown. There is increasing evidence that hypoxia may be involved in several diseases of the white matter, including multiple sclerosis, vascular dementia, and ischemia. Matrix metalloproteinases (MMPs) are increased in rat and mouse models of hypoxic hypoperfusion and have been associated with OLG death. However, whether the MMPs act on myelin or OLGs remains unresolved. We hypothesized that delayed expression of MMPs caused OLG death and myelin breakdown. To test the hypothesis, adult mice underwent hypoxic hypoperfusion with transient bilateral occlusion of the carotid arteries. After 3 days of reperfusion, ischemic white matter had increased reactivity of astrocytes and microglia, MMP-2 localization in astrocytes, and increased protein expression and activity of MMP-2. In addition, there was a significant loss of myelin basic protein (MBP) by Western blot and caspase-3- mediated OLG death. Treatment with the broad-spectrum MMP inhibitor, BB-94, significantly decreased astrocyte reactivity and MMP-2 activity. More importantly, it reduced MBP breakdown. However, MMP inhibition had no effect on OLG loss. Our results implicate MMPs released by reactive astrocytes in delayed myelin degradation, while OLG death occurs by an MMP-independent mechanism. We propose that MMP-mediated myelin loss is important in hypoxic injury to the white matter. PMID:19830840

  1. Modeling optical breakdown in dielectrics during ultrafast laser processing.

    PubMed

    Fan, C H; Longtin, J P

    2001-06-20

    Laser ablation is widely used in micromachining, manufacturing, thin-film formation, and bioengineering applications. During laser ablation the removal of material and quality of the features depend strongly on the optical breakdown region induced by the laser irradiance. The recent advent of amplified ultrafast lasers with pulse durations of less than 1 ps has generated considerable interest because of the ability of the lasers to process virtually all materials with high precision and minimal thermal damage. With ultrashort pulse widths, however, traditional breakdown models no longer accurately capture the laser-material interaction that leads to breakdown. A femtosecond breakdown model for dielectric solids and liquids is presented that characterizes the pulse behavior and predicts the time- and position-dependent breakdown region. The model includes the pulse propagation and small spatial extent of ultrashort laser pulses. Model results are presented and compared with classical breakdown models for 1-ns, 1-ps, and 150-fs pulses. The results show that the revised model is able to model breakdown accurately in the focal region for pulse durations of less than 10 ps. The model can also be of use in estimating the time- and position-resolved electron density in the interaction volume, the breakdown threshold of the material, shielding effects, and temperature distributions during ultrafast processing. PMID:18357333

  2. Experimental Study on Electrical Breakdown for Devices with Micrometer Gaps

    NASA Astrophysics Data System (ADS)

    Meng, Guodong; Cheng, Yonghong; Dong, Chengye; Wu, Kai

    2014-12-01

    The understanding of electrical breakdown in atmospheric air across micrometer gaps is critically important for the insulation design of micro & nano electronic devices. In this paper, planar aluminum electrodes with gaps ranging from 2 μm to 40 μm were fabricated by microelectromechanical system technology. The influence factors including gap width and surface dielectric states were experimentally investigated using the home-built test and measurement system. Results showed that for SiO2 layers the current sustained at 2-3 nA during most of the pre-breakdown period, and then rose rapidly to 10-30 nA just before breakdown due to field electron emission, followed by the breakdown. The breakdown voltage curves demonstrated three stages: (1) a constantly decreasing region (the gap width d < 5 μm), where the field emission effect played an important role just near breakdown, supplying enough initial electrons for the breakdown process; (2) a plateau region with a near constant breakdown potential (5 μm < d < 10 μm) (3) a region for large gaps that adhered to Paschen's curve (d > 10 μm). And the surface dielectric states including the surface resistivity and secondary electron yield were verified to be related to the propagation of discharge due to the interaction between initial electrons and dielectrics.

  3. Confusion and its dynamics during device comprehension with breakdown scenarios.

    PubMed

    D'Mello, Sidney; Graesser, Art

    2014-09-01

    The incidence and dynamics of confusion during complex learning and problem solving were investigated in an experiment where participants first read illustrated texts on everyday devices (e.g., an electric bell) followed by breakdown scenarios reflecting device malfunctions (e.g., "When a person rang the bell there was a short ding and then no sound was heard"). The breakdown scenarios were expected to trigger impasses and put participants in a state of cognitive disequilibrium where they would experience confusion and engage in effortful confusion resolution activities in order to restore equilibrium. The results confirmed that participants reported more confusion when presented with the breakdown scenarios compared to control scenarios that involved focusing on important device components in the absence of malfunctions. A second-by-second analysis of the dynamics of confusion yielded two characteristic trajectories that distinguished participants who partially resolved their confusion from those who remained confused. Participants who were successful in partial confusion resolution while processing the breakdowns outperformed their counterparts on knowledge assessments after controlling for scholastic aptitude, engagement, and frustration. This effect was amplified for those who were highly confused by the breakdowns. There was no direct breakdown vs. control effect on learning, but being actively engaged and partially resolving confusion during breakdown processing were positive predictors of increased learning with the breakdown compared to control scenarios. Implications of our findings for theories that highlight the role of impasses, cognitive disequilibrium, and confusion to learning are discussed. PMID:24973629

  4. 7 CFR 51.1009 - Stylar end breakdown.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Stylar end breakdown. 51.1009 Section 51.1009... STANDARDS) United States Standards for Persian (Tahiti) Limes Definitions § 51.1009 Stylar end breakdown... affected area becomes darker and usually sinks below the healthy surface, but the area remains firm...

  5. Update on the biochemistry of chlorophyll breakdown.

    PubMed

    Hörtensteiner, Stefan

    2013-08-01

    In land plants, chlorophyll is broken down to colorless linear tetrapyrroles in a highly conserved multi-step pathway. The pathway is termed the 'PAO pathway', because the opening of the chlorine macrocycle present in chlorophyll catalyzed by pheophorbide a oxygenase (PAO), the key enzyme of the pathway, provides the characteristic structural basis found in all further downstream chlorophyll breakdown products. To date, most of the biochemical steps of the PAO pathway have been elucidated and genes encoding many of the chlorophyll catabolic enzymes been identified. This review summarizes the current knowledge on the biochemistry of the PAO pathway and provides insight into recent progress made in the field that indicates that the pathway is more complex than thought in the past. PMID:22790503

  6. Vortex Breakdown-Aircraft Tail Interaction

    NASA Astrophysics Data System (ADS)

    Kim, Younjong; Rockwell, Donald

    2003-11-01

    The interaction of vortex breakdown with the tail of an aircraft can lead to severe unsteady loading and vibration. A technique of high-image-density particle image velocimetry is employed to characterize the instantaneous and averaged structure of a broken-down vortex with a generic tail configuration. Interaction of the primary (incident) vortex with the tail results in formation of a relatively large-scale cluster of secondary vorticity. The coexistence of these primary and secondary vortical structures is intimately associated with the unsteadiness of the vortex system, and thereby the near-surface fluctuations associated with buffet loading. Instantaneous and averaged representations of the vortex-tail interaction provide insight into the complex physics. Furthermore, a low order POD model is employed to characterize the most energetic modes of the vortex-tail interaction.

  7. Vortex breakdown in a truncated conical bioreactor

    NASA Astrophysics Data System (ADS)

    Balci, Adnan; Brøns, Morten; Herrada, Miguel A.; Shtern, Vladimir N.

    2015-12-01

    This numerical study explains the eddy formation and disappearance in a slow steady axisymmetric air-water flow in a vertical truncated conical container, driven by the rotating top disk. Numerous topological metamorphoses occur as the water height, Hw, and the bottom-sidewall angle, α, vary. It is found that the sidewall convergence (divergence) from the top to the bottom stimulates (suppresses) the development of vortex breakdown (VB) in both water and air. At α = 60°, the flow topology changes eighteen times as Hw varies. The changes are due to (a) competing effects of AMF (the air meridional flow) and swirl, which drive meridional motions of opposite directions in water, and (b) feedback of water flow on AMF. For small Hw, the AMF effect dominates. As Hw increases, the swirl effect dominates and causes VB. The water flow feedback produces and modifies air eddies. The results are of fundamental interest and can be relevant for aerial bioreactors.

  8. Laser-induced breakdown spectroscopy in China

    NASA Astrophysics Data System (ADS)

    Wang, Zhe; Yuan, Ting-Bi; Hou, Zong-Yu; Zhou, Wei-Dong; Lu, Ji-Dong; Ding, Hong-Bin; Zeng, Xiao-Yan

    2014-08-01

    Laser-induced breakdown spectroscopy (LIBS) has been regarded as a future superstar for chemical analysis for years due to its unique features such as little or no sample preparation, remote sensing, and fast and multi-element analysis. Chinese LIBS community is one of the most dynamically developing communities in the World. The aim of the work is to inspect what have been done in China for LIBS development and, based on the understanding of the overall status, to identify the challenges and opportunities for the future development. In this paper, the scientific contributions from Chinese LIBS community are reviewed for the following four aspects: fundamentals, instrumentation, data processing and modeling, and applications; and the driving force of LIBS development in China is analyzed, the critical issues for successful LIBS application are discussed, and in our opinion, the potential direction to improve the technology and to realize large scale commercialization in China is proposed.

  9. State Regulation, Family Breakdown, and Lone Motherhood

    PubMed Central

    Meek, Jeff

    2014-01-01

    Using a range of parish records, records from the Registrar General of Scotland, charity organizations, and media reports, this article contributes to the historiography which evaluates the effects of World War I in Britain as well as the history of lone mothers and their children. It highlights how during the war, women, especially lone mothers, made significant gains through the welfare system, changing approaches to illegitimacy and the plentiful nature of women’s work but also how in doing so this brought them under greater surveillance by the state, local parishes, and charity organizations. Moreover, as this article will demonstrate, many of the gains made by women were short-lived and in fact the war contributed to high levels of family breakdown and gendered and intergenerational poverty endured by lone mothers and their children. PMID:26538794

  10. Does Initial Leaf Chemistry Affect the Contribution of Insects, Fungi, and Bacteria to Leaf Breakdown in a Lowland Tropical Stream?

    NASA Astrophysics Data System (ADS)

    Ardon, M.; Pringle, C. M.

    2005-05-01

    We examined effects of initial leaf chemistry of six common riparian species on the relative contribution of fungi, bacteria, and invertebrates to leaf breakdown in a lowland stream in Costa Rica. We hypothesized that fungi and bacteria would contribute more to the breakdown of species with low concentrations of secondary (tannins and phenolics) and structural (cellulose and lignin) compounds, while invertebrates would be more important in the processing of species with high concentrations of secondary and structural compounds. We incubated single species leaf bags of six common riparian species, representing a range in secondary and structural compounds, in a third-order stream at La Selva Biological Station, Costa Rica. We measured leaf chemistry during the breakdown process. We determined fungal biomass using ergosterol methods, bacteria using DAPI counts, and invertebrate biomass using length-weight regressions. We then used biomass estimates for each group to determine their contribution to the overall breakdown process. Breakdown rates ranged from very fast (Trema integerima, k = 0.23 day-1) to slow (Zygia longifolia , k = 0.011 day-1). While analyses are still under way, preliminary results support our initial hypothesis that fungi contribute more to the break down of leaves from tree species with low concentrations of secondary and structural compounds.

  11. Rotation prevents finite-time breakdown

    NASA Astrophysics Data System (ADS)

    Liu, Hailiang; Tadmor, Eitan

    2004-02-01

    We consider a two-dimensional (2D) convection model augmented with the rotational Coriolis forcing, Ut+ U·∇ xU=2 kU⊥, with a fixed 2 k being the inverse Rossby number. We ask whether the action of dispersive rotational forcing alone, U⊥, prevents the generic finite-time breakdown of the free nonlinear convection. The answer provided in this work is a conditional yes. Namely, we show that the rotating Euler equations admit global smooth solutions for a subset of generic initial configurations. With other configurations, however, finite-time breakdown of solutions may and actually does occur. Thus, global regularity depends on whether the initial configuration crosses an intrinsic, O(1) critical threshold (CT), which is quantified in terms of the initial vorticity, ω0=∇× U0, and the initial spectral gap associated with the 2×2 initial velocity gradient, η0≔ λ2(0)- λ1(0), λj(0)= λj(∇ U0). Specifically, global regularity of the rotational Euler equation is ensured if and only if 4kω 0(α)+η 20(α)<4k 2,∀α∈ R2. We also prove that the velocity field remains smooth if and only if it is periodic. An equivalent Lagrangian formulation reconfirms the CT and shows a global periodicity of velocity field as well as the associated particle orbits. Moreover, we observe yet another remarkable periodic behavior exhibited by the gradient of the velocity field. The spectral dynamics of the Eulerian formulation [SIAM J. Math. Anal. 33 (2001) 930] reveals that the vorticity and the divergence of the flow evolve with their own path-dependent period. We conclude with a kinetic formulation of the rotating Euler equation.

  12. Structure and Mechanism of Enzymes Involved in Biosynthesis and Breakdown of the Phosphonates Fosfomycin, Dehydrophos, and Phosphinothricin

    PubMed Central

    Nair, Satish K.; van der Donk, Wilfred A.

    2011-01-01

    Recent years have seen a rapid increase in the mechanistic and structural information on enzymes that are involved in the biosynthesis and breakdown of naturally occurring phosphonates. This review focuses on these recent developments with an emphasis on those enzymes that have been characterized crystallographically in the past five years, including proteins involved in the biosynthesis of phosphinothricin, fosfomycin, and dehydrophos and proteins involved in resistance mechanisms. PMID:20854789

  13. Breakdown voltage of metal-oxide resistors in liquid argon

    SciTech Connect

    Bagby, L. F.; Gollapinni, S.; James, C. C.; Jones, B. J.P.; Jostlein, H.; Lockwitz, S.; Naples, D.; Raaf, J. L.; Rameika, R.; Schukraft, A.; Strauss, T.; Weber, M. S.; Wolbers, S. A.

    2014-11-07

    We characterized a sample of metal-oxide resistors and measured their breakdown voltage in liquid argon by applying high voltage (HV) pulses over a 3 second period. This test mimics the situation in a HV-divider chain when a breakdown occurs and the voltage across resistors rapidly rise from the static value to much higher values. All resistors had higher breakdown voltages in liquid argon than their vendor ratings in air at room temperature. Failure modes range from full destruction to coating damage. In cases where breakdown was not catastrophic, subsequent breakdown voltages were lower in subsequent measuring runs. One resistor type withstands 131 kV pulses, the limit of the test setup.

  14. On the electric breakdown in liquid argon at centimeter scale

    NASA Astrophysics Data System (ADS)

    Auger, M.; Blatter, A.; Ereditato, A.; Goeldi, D.; Janos, S.; Kreslo, I.; Luethi, M.; von Rohr, C. Rudolf; Strauss, T.; Weber, M. S.

    2016-03-01

    We present a study on the dependence of electric breakdown discharge properties on electrode geometry and the breakdown field in liquid argon near its boiling point. The measurements were performed with a spherical cathode and a planar anode at distances ranging from 0.1 mm to 10.0 mm. A detailed study of the time evolution of the breakdown volt-ampere characteristics was performed for the first time. It revealed a slow streamer development phase in the discharge. The results of a spectroscopic study of the visible light emission of the breakdowns complement the measurements. The light emission from the initial phase of the discharge is attributed to electro-luminescence of liquid argon following a current of drifting electrons. These results contribute to set benchmarks for breakdown-safe design of ionization detectors, such as Liquid Argon Time Projection Chambers (LAr TPC).

  15. Development of Hybrid Product Breakdown Structure for NASA Ground Systems

    NASA Technical Reports Server (NTRS)

    Monaghan, Mark W.; Henry, Robert J.

    2013-01-01

    The Product Breakdown Structure is traditionally a method of identification of the products of a project in a tree structure. It is a tool used to assess, plan, document, and display the equipment requirements for a project. It is part of a product based planning technique, and attempts to break down all components of a project in as much detail as possible, so that nothing is overlooked. The PBS for ground systems at the Kennedy Space Center is being developed to encompass the traditional requirements including the alignment of facility, systems, and components to the organizational hierarchy. The Ground Operations Product Breakdown Structure is a hybrid in nature in that some aspects of a work breakdown structure will be incorporated and merged with the Architecture Concept of Operations, Master Subsystem List, customer interface, and assigned management responsibility. The Ground Operations Product Breakdown Structure needs to be able to identify the flexibility of support differing customers (internal and external) usage of ground support equipment within the Kennedy Space Center launch and processing complex. The development of the Product Breakdown Structure is an iterative activity Initially documenting the organization hierarchy structure and relationships. The Product Breakdown Structure identifies the linkage between the customer program requirements, allocation of system resources, development of design goals, and identification logistics products. As the Product Breakdown Structure progresses the incorporation of the results of requirement planning for the customer occurs identifying facility needs and systems. The mature Product Breakdown Structure is baselined with a hierarchical drawing, the Product Breakdown Structure database, and an associated document identifying the verification of the data through the life cycle of the program/product line. This paper will document, demonstrate, and identify key aspects of the life cycle of a Hybrid Product

  16. The anabolic response to a meal containing different amounts of protein is not limited by the maximal stimulation of protein synthesis in healthy young adults.

    PubMed

    Kim, Il-Young; Schutzler, Scott; Schrader, Amy; Spencer, Horace J; Azhar, Gohar; Ferrando, Arny A; Wolfe, Robert R

    2016-01-01

    We have determined whole body protein kinetics, i.e., protein synthesis (PS), breakdown (PB), and net balance (NB) in human subjects in the fasted state and following ingestion of ~40 g [moderate protein (MP)], which has been reported to maximize the protein synthetic response or ~70 g [higher protein (HP)] protein, more representative of the amount of protein in the dinner of an average American diet. Twenty-three healthy young adults who had performed prior resistance exercise (X-MP or X-HP) or time-matched resting (R-MP or R-HP) were studied during a primed continuous infusion of l-[(2)H5]phenylalanine and l-[(2)H2]tyrosine. Subjects were randomly assigned into an exercise (X, n = 12) or resting (R, n = 11) group, and each group was studied at the two levels of dietary protein intake in random order. PS, PB, and NB were expressed as increases above the basal, fasting values (mg·kg lean body mass(-1)·min(-1)). Exercise did not significantly affect protein kinetics and blood chemistry. Feeding resulted in positive NB at both levels of protein intake: NB was greater in response to the meal containing HP vs. MP (P < 0.00001). The greater NB with HP was achieved primarily through a greater reduction in PB and to a lesser extent stimulation of protein synthesis (for all, P < 0.0001). HP resulted in greater plasma essential amino acid responses (P < 0.01) vs. MP, with no differences in insulin and glucose responses. In conclusion, whole body net protein balance improves with greater protein intake above that previously suggested to maximally stimulating muscle protein synthesis because of a simultaneous reduction in protein breakdown. PMID:26530155

  17. The representative animal

    PubMed Central

    Harrison, J. M.

    1994-01-01

    The anthropocentric approach to the study of animal behavior uses representative nonhuman animals to understand human behavior. This approach raises problems concerning the comparison of the behavior of two different species. The datum of behavior analysis is the behavior of humans and representative animal phenotypes. The behavioral phenotype is the product of the ontogeny and phylogeny of each species, and this requires that contributions of genotype as well as behavioral history to experimental performance be considered. Behavior analysis tends to favor the ontogenetic over the phylogenetic component, yet both components are responsible for the performance of each individual animal. This paper raises questions about the role of genotype variables in the use of representative animals to understand human behavior. Examples indicating the role of genotype in human behavior are also discussed. The final section of the paper deals with considerations of genotype in the design of animal experiments. PMID:22478186

  18. The breakdown of meaning and adolescent problem behavior.

    PubMed

    Hazani, Moshe

    2003-01-01

    This paper attempts to account for the upsurge of adolescents' problem behavior in high-income countries in terms of Lifton's paradigm of symbolic immortality. Whilst most of the works dealing with this subject focus on the level of the individual adolescent and his or her surrounding, Lifton shows that societal processes can affect the individual. Drawing upon his approach, it was argued that desymbolization,--the collapse of society's symbols system--produces "divided selves," individuals who harbor an 'aggressor-victim double' in their psyche, wherein an internal conflict between the aggressor and the victim engenders self-destructive impulses. In this study it is hypothesized that problem behaviors are external manifestations of underlying self-destructiveness. Thirty-four Jewish-Israeli adolescents involved in sexual promiscuity, drug abuse, anorexia nervosa, and violence were interviewed. It was found that despite individual and social dissimilarities, and the different problem behaviors, the participants were marked by inner-directed destructiveness as well as a sense of meaninglessness of life and lack of symbolic relationship to what transcends their here-and-now selves. Significantly, violent adolescents whose aggression is other-directed were found to be marked by underlying self-directed aggression as well. If the findings of this study are representative of Israeli society at large or of other affluent societies, then the epidemic proportions of youth problem behavior may indicate that these societies are undergoing desymbolization, a psychocultural breakdown. PMID:12964443

  19. Laser-induced breakdown plasma-based sensors

    NASA Astrophysics Data System (ADS)

    Griffin, Steven T.

    2010-04-01

    Laser Induced Breakdown Spectroscopy (LIBS) is dependent on the interaction between the initiating Laser sequence, the sampled material and the intermediate plasma states. Pulse shaping and timing have been empirically demonstrated to have significant impact on the signal available for active/passive detection and identification. The transient nature of empirical LIBS work makes data collection for optimization an expensive process. Guidance from effective computer simulation represents an alternative. This computational method for CBRNE sensing applications models the Laser, material and plasma interaction for the purpose of performance prediction and enhancement. This paper emphasizes the aspects of light, plasma, and material interaction relevant to portable sensor development for LIBS. The modeling structure emphasizes energy balances and empirical fit descriptions with limited detailed-balance and finite element approaches where required. Dusty plasma from partially decomposed material sample interaction with pulse dynamics is considered. This heuristic is used to reduce run times and computer loads. Computer simulations and some data for validation are presented. A new University of Memphis HPC/super-computer (~15 TFLOPS) is used to enhance simulation. Results coordinated with related effort at Arkansas State University. Implications for ongoing empirical work are presented with special attention paid to the application of compressive sensing for signal processing, feature extraction, and classification.

  20. High Voltage Breakdown Levels in Various EPC Potting Materials

    NASA Technical Reports Server (NTRS)

    Komm, David S.

    2006-01-01

    This viewgraph presentation reviews exploration activities at JPL into various potting materials. Since high power space-borne microwave transmitters invariably use a vacuum tube as a final power amplifier, and this tube requires high electrode voltages for operation. The associated high voltage insulation typically represents a significant fraction of the mass of the transmitter. Since mass is always a premium resource on board spacecraft, we have been investigating materials with the potential to reduce the mass required for our applications here at JPL. This paper describes electrical breakdown results obtained with various potting materials. Conathane EN-11 (polyurethane) is the traditional HVPS encapsulant at JPL, but due to temperature limitations and durability issues it was deemed inappropriate for the particular application (i.e., CloudSat radar). The choices for the best available materials were epoxies, or silicones. Epoxies are too rigid, and were deemed inadvisable. Two silicones were further investigated (i.e.,ASTM E595- 93e2: GE RTV566(R) and Dow Corning 93-500X(R), another compound was considered (i.e., DC material, Sylgard 184(R)). "Loading" (adding filler materials) the potting compound will frequently alter the final material properties. Powdered alumina and borosilicate glass known as "microballoons" were investigated as possible loading materials. The testing of the materials is described. Each of the two loading materials offers advantages and disadvantages. The advantages and disadvantages are described.

  1. Implications of dielectric breakdown weathering for the lunar regolith

    NASA Astrophysics Data System (ADS)

    Jordan, A.; Stubbs, T. J.; Wilson, J. K.; Schwadron, N.; Spence, H. E.; Izenberg, N.

    2015-12-01

    Solar energetic particles (SEPs) penetrate the lunar regolith to depths of ~1 mm and cause deep dielectric charging. The greatest charging occurs in permanently shadowed regions (PSRs), where temperatures make the electrical conductivity extremely low, which inhibits dissipating the charge buildup. Charging by very large SEP events may create subsurface electric fields that are strong enough to cause dielectric breakdown, or sparking, in the upper ~1 mm. Previous work has shown that, in PSRs, this breakdown weathering may have affected 10-25% of the meteoritically gardened regolith in PSRs and may thus be comparable to meteoritic weathering. But even regolith at lower latitudes can reach temperatures <100 K at night, causing it to dissipate charging in a few days--still enough to allow significant charging during large SEP events. Consequently, regolith at lower latitudes may also be susceptible to breakdown. We show how up to a few percent of gardened regolith at lower latitudes may have experienced breakdown. We also estimate the percentage of regolith that experienced breakdown during the two events detected in January and March 2012 by the Cosmic Ray Telescope for the Effects of Radiation (CRaTER) aboard the Lunar Reconnaissance Orbiter (LRO). Finally, we discuss what this more global view of breakdown weathering implies about the possibility of Apollo and Luna soil samples containing material that may have experienced breakdown.

  2. Observations of fast VHF-bright positive breakdown

    NASA Astrophysics Data System (ADS)

    Stock, M.; Krehbiel, P. R.; Rison, W.; Lapierre, J. L.; Edens, H. E.

    2014-12-01

    Positive breakdown during lightning discharges is generally considered to be weak and slowly propagating, as high speed video observations show it to be optically weak, and studies of the development of cloud-to-ground (CG) and intracloud (IC) flashes show development in the negative charge region to be slow. With the proper instrumentation, however, fast positive breakdown is a relatively common feature of both CG and IC flashes. The breakdown is bright at VHF, but is smoothly continuous so that time-of-arrival VHF mapping systems such as the Lightning Mapping Array are usually unable to detect or locate its occurrence. However, the breakdown is easily locatable using interferometric mapping techniques. Such an interferometer was developed at NM Tech in the 1980s and used in the CaPE studies at Kennedy Space Center in 1991, where it observed fast (1-6 × 107 m/s), VHF-bright positive leaders propagating away from the source region of negative CG return strokes (Shao et al., 1995). Here we report new observations of fast positive breakdown, obtained with Langmuir Laboratory's flash-continuous broadband VHF interferometer, that confirm and substantially expand our understanding of the phenomena. Numerous examples have been observed following return strokes of negative CG flashes, including bolt-from-blue discharges, and during K-processes of both IC and CG flashes. The breakdown typically propagates a few kilometers at speeds on the order of 107 m/s and frequently produces some of the brightest radiation of the flash. A particularly interesting feature of the breakdown is that it propagates into regions of previously un-ionized air. Then following the breakdown, frequently no further VHF emission is seen along or beyond its channel, indicating that the channel formed is not conducting. But on occasion, especially during cloud-to-ground flashes, the end of the fast positive breakdown turns into a normal, slowly propagating positive leader.

  3. Thickness and temperature dependences of the degradation and the breakdown for MgO-based magnetic tunnel junctions

    NASA Astrophysics Data System (ADS)

    Lee, Jung-Min; Song, Yun-Heub

    2015-03-01

    The reliability of a magnetic tunnel junction (MTJ) with an MgO tunnel barrier was evaluated. In particular, various voltage tests were used to investigate the effects of the barrier thickness and the temperature on the resistance drift. We compared the resistance change during a constant voltage stress (CVS) test and confirmed a trap/detrap phenomenon during the interval stress for different barrier thicknesses and temperatures. The resistance drift representing degradation and the time to breakdown (T BD ) representing the breakdown characteristic were better for a thicker barrier and lower temperature, but were worse for a thinner barrier and a higher temperature. The results suggest that breakdown and degradation due to trap generation strongly depend on both the barrier thickness and the temperature. Furthermore, as the TBD varies at steady rates with changing barrier thickness, temperature, and electric field, we assume that a MTJ with an adnormal thin layer of MgO can be screened effectively based on the predicted T BD . As a result, the barrier thickness and the temperature are very important in determining the reliability of a MTJ, and this study is expected to be helpful in understanding the degradation and the breakdown of a MTJ.

  4. A doping concentration-dependent upper limit of the breakdown voltage cutoff frequency product in Si bipolar transistors

    NASA Astrophysics Data System (ADS)

    Rieh, Jae-Sung; Jagannathan, Basanth; Greenberg, David; Freeman, Greg; Subbanna, Seshadri

    2004-02-01

    Recent high-speed Si-based bipolar transistors apparently exceed the Johnson Limit in terms of breakdown voltage-cutoff frequency product, and this paper addresses the relevant issues. First, BV CES rather than BV CEO is shown to be the representative breakdown voltage in describing the breakdown-speed trade-off in collector design, since BV CEO is modulated by the current gain which is irrelevant of the collector design and also practical bipolar circuits are rarely operated with open-base condition for which BV CEO is defined. In the same context, it is suggested BV CES be employed in representing the upper limit of breakdown voltage-cutoff frequency product. Second, a collector doping concentration-dependent upper limit of BV CES· fT product is proposed incorporating the doping concentration-dependent critical electric field and accurate values for related device parameters. With this new approach, it is shown that the limit is far larger than the Johnson Limit and the limit is still yet to be reached.

  5. Fundamental studies of passivity and passivity breakdown. Final report

    SciTech Connect

    Macdonald, D.D.; Urquidi-Macdonald, M.; Song, H.; Biaggio-Rocha, S.; Searson, P.

    1991-11-01

    This report summarizes the findings of our fundamental research program on passivity and passivity breakdown. During the past three and one half years in this program (including the three year incrementally-funded grant prior to the present grant), we developed and experimentally tested various physical models for the growth and breakdown of passive films on metal surfaces. These models belong to a general class termed ``point defects models`` (PDMs), in which the growth and breakdown of passive films are described in terms of the movement of anion and cation vacancies.

  6. Breakdown simulations in a focused microwave beam within the simplified model

    NASA Astrophysics Data System (ADS)

    Semenov, V. E.; Rakova, E. I.; Glyavin, M. Yu.; Nusinovich, G. S.

    2016-07-01

    The simplified model is proposed to simulate numerically air breakdown in a focused microwave beam. The model is 1D from the mathematical point of view, but it takes into account the spatial non-uniformity of microwave field amplitude along the beam axis. The simulations are completed for different frequencies and different focal lengths of microwave beams. The results demonstrate complicated regimes of the breakdown evolution which represents a series of repeated ionization waves. These waves start at the focal point and propagate towards incident microwave radiation. The ionization wave parameters vary during propagation. At relatively low frequencies, the propagation regime of subsequent waves can also change qualitatively. Each next ionization wave is less pronounced than the previous one, and the breakdown evolution approaches the steady state with relatively small plasma density. The ionization wave parameters are sensitive to the weak source of external ionization, but the steady state is independent on such a source. As the beam focal length decreases, the stationary plasma density increases and the onset of the steady state occurs faster.

  7. Back gate induced breakdown mechanisms for thin layer SOI field P-channel LDMOS

    NASA Astrophysics Data System (ADS)

    Zhou, Xin; Qiao, Ming; He, Yitao; Yang, Wen; Li, Zhaoji; Zhang, Bo

    2016-01-01

    The back gate (BG) induced breakdown mechanisms for thin layer SOI Field P-channel LDMOS (FPLDMOS) are investigated in this paper. Surface breakdown, bulk breakdown and punch-through breakdown are discussed, revealing that the block capability depends on not drain voltage (Vd), but also BG voltage (VBG). For surface breakdown, the breakdown voltage (BVs) increases linearly with VBG increasing. An expression of BVs on VBG is given, providing a good fitting to measured and simulated results. Bulk breakdown with a low breakdown voltage is attributed to high VBG. VBG induces depletion in n-well, giving rise to punch-through breakdown. A design requirement for the thin layer SOI FPLDMOS is proposed that breakdown voltages for the three breakdown mechanisms are compelled to be higher than the supply voltage of switching IC.

  8. Novel laser breakdown spectrometer for environmental monitoring

    NASA Astrophysics Data System (ADS)

    Mirov, Sergey B.; Pitt, Robert E.; Dergachev, Alex Y.; Lee, Wonwoo; Martyshkin, Dmitri V.; Mirov, Olga D.; Randolph, Jeremy J.; DeLucas, Lawrence J.; Brouillette, Christie G.; Basiev, Tasoltan T.; Orlovskii, Yurii V.; Alimov, Olimkhon K.; Vorob'ev, Ivan N.

    1999-11-01

    A novel experimental set-up using laser-induced breakdown spectroscopy (LIBS) for environmental analyses of heavy metals is described in this paper. It is based on state-of-the-art spectroscopic equipment, advanced detectors, and laser atomizers: a 0.75 m spectrometer ARC-750, intensified TE- cooled 256 X 1024 CCD camera, probe with fiber optic guide for signal transportation, and Nd:YAG laser plasma atomizers with two different methods for sample delivery. In the first method the liquid solution containing the atoms to be investigated is drawn into the chamber of the nebulizer. The mixture passes through the nozzle, accompanied by argon gas along with formed aerosol, and enters the plasma plume, which is generated by the laser spark in argon. The second method is based on direct generating of the plasma in the water jet of a continuously circulating sample. LIBS testing of samples containing Al, Cd, Cu, Fe, Pb, Zn, and Cr ions was compared with results using atomic absorption spectrophotometry. Initial indications showed good agreement between these two methods. Detection levels of less than 100 ppb were observed for copper and chromium. The described spectroscopic system exhibits high sensitivity, accumulation of luminescence spectrum in real time; and high dynamic range for concentrations detection from 100 ppb to 1000 ppm.

  9. Theoretical studies of breakdown in random media

    SciTech Connect

    Duxbury, P.M.

    1993-01-01

    Failure initiates in local regions of a material microstructure which are either especially weak, or which carry an especially large field. The size and location of these weak or hotspots'' depends on the microstructure, and is especially sensitive to microstructural disorder. Using model random microstructures, we have developed analytic and numerical tools to predict where failure initiates, its initiation field, and how it propagates from the initiation sites. We have found it useful to divide the failure process into a nucleation stage, in which damage occurs quite randomly throughout the material, a localisation stage, where a critical crack nucleates, and a catastrophic failure stage during which an unstable crack propagates through the material. Results are being compared with experiments on: Highly porous materials (porous glass, and porous gold); dielectric breakdown of metal loaded insulators (e.g. aluminum in poly-ethyelene) and; the critical current of superconductors containing cracks (Nb and Nb[sub 3]Ge). This report summarises our efforts in these areas.

  10. Nanopore Fabrication by Controlled Dielectric Breakdown

    PubMed Central

    Tabard-Cossa, Vincent

    2014-01-01

    Nanofabrication techniques for achieving dimensional control at the nanometer scale are generally equipment-intensive and time-consuming. The use of energetic beams of electrons or ions has placed the fabrication of nanopores in thin solid-state membranes within reach of some academic laboratories, yet these tools are not accessible to many researchers and are poorly suited for mass-production. Here we describe a fast and simple approach for fabricating a single nanopore down to 2-nm in size with sub-nm precision, directly in solution, by controlling dielectric breakdown at the nanoscale. The method relies on applying a voltage across an insulating membrane to generate a high electric field, while monitoring the induced leakage current. We show that nanopores fabricated by this method produce clear electrical signals from translocating DNA molecules. Considering the tremendous reduction in complexity and cost, we envision this fabrication strategy would not only benefit researchers from the physical and life sciences interested in gaining reliable access to solid-state nanopores, but may provide a path towards manufacturing of nanopore-based biotechnologies. PMID:24658537

  11. Electric field breakdown in single molecule junctions.

    PubMed

    Li, Haixing; Su, Timothy A; Zhang, Vivian; Steigerwald, Michael L; Nuckolls, Colin; Venkataraman, Latha

    2015-04-22

    Here we study the stability and rupture of molecular junctions under high voltage bias at the single molecule/single bond level using the scanning tunneling microscope-based break-junction technique. We synthesize carbon-, silicon-, and germanium-based molecular wires terminated by aurophilic linker groups and study how the molecular backbone and linker group affect the probability of voltage-induced junction rupture. First, we find that junctions formed with covalent S-Au bonds are robust under high voltage and their rupture does not demonstrate bias dependence within our bias range. In contrast, junctions formed through donor-acceptor bonds rupture more frequently, and their rupture probability demonstrates a strong bias dependence. Moreover, we find that the junction rupture probability increases significantly above ∼1 V in junctions formed from methylthiol-terminated disilanes and digermanes, indicating a voltage-induced rupture of individual Si-Si and Ge-Ge bonds. Finally, we compare the rupture probabilities of the thiol-terminated silane derivatives containing Si-Si, Si-C, and Si-O bonds and find that Si-C backbones have higher probabilities of sustaining the highest voltage. These results establish a new method for studying electric field breakdown phenomena at the single molecule level. PMID:25675085

  12. Medical Applications of Laser Induced Breakdown Spectroscopy

    NASA Astrophysics Data System (ADS)

    Pathak, A. K.; Rai, N. K.; Singh, Ankita; Rai, A. K.; Rai, Pradeep K.; Rai, Pramod K.

    2014-11-01

    Sedentary lifestyle of human beings has resulted in various diseases and in turn we require a potential tool that can be used to address various issues related to human health. Laser Induced Breakdown Spectroscopy (LIBS) is one such potential optical analytical tool that has become quite popular because of its distinctive features that include applicability to any type/phase of samples with almost no sample preparation. Several reports are available that discusses the capabilities of LIBS, suitable for various applications in different branches of science which cannot be addressed by traditional analytical methods but only few reports are available for the medical applications of LIBS. In the present work, LIBS has been implemented to understand the role of various elements in the formation of gallstones (formed under the empyema and mucocele state of gallbladder) samples along with patient history that were collected from Purvancal region of Uttar Pradesh, India. The occurrence statistics of gallstones under the present study reveal higher occurrence of gallstones in female patients. The gallstone occurrence was found more prevalent for those male patients who were having the habit of either tobacco chewing, smoking or drinking alcohols. This work further reports in-situ LIBS study of deciduous tooth and in-vivo LIBS study of human nail.

  13. Control of vortex breakdown by temperature gradients

    NASA Astrophysics Data System (ADS)

    Herrada, Miguel Angel; Shtern, Vladimir

    2003-11-01

    An axial gradient of temperature can either suppress or enhance vortex breakdown (VB). The underlying mechanism of such VB control is centrifugal or/and gravitational convection. An additional thermal-convection flow directed oppositely to the base flow suppresses VB while a co-flow enhances VB. Our numerical simulations of a compressible flow in a sealed cylinder induced by a rotating bottom disk clearly reveal these effects. We vary the temperature gradient (ɛ), Mach (Ma), Froude (Fr), and Reynolds (Re) numbers, and the aspect ratio (h). As ɛ increases (ɛ>0 corresponding to a temperature gradient parallel to the downward near-axis flow), the VB "bubble," which occurs at ɛ=0, diminishes and then totally disappears. The opposite temperature gradient (ɛ<0) enlarges the VB bubble and makes the flow unsteady. These effects of centrifugal convection become more prominent with increasing Ma and Re. Density variations induced by the temperature gradients are more important for VB control than those induced by the increase in Ma. A new efficient time-evolution code for axisymmetric flows of an ideal gas has facilitated these simulations.

  14. Magnetic breakdown in double quantum wells

    SciTech Connect

    Harff, N.E. |; Simmons, J.A.; Klem, J.F.; Boebinger, G.S.; Pfeiffer, L.N.; West, K.W.

    1996-08-01

    The authors find that a sufficiently large perpendicular magnetic field (B{sub {perpendicular}}) causes magnetic breakdown (MB) in coupled double quantum wells (QWs) that are subject to an in-plane magnetic field (B{sub {parallel}}). B{sub {parallel}} shifts one QW dispersion curve with respect to that of the other QW, resulting in an anticrossing and an energy gap. When the gap is below the Fermi level the resulting Fermi surface (FS) consists of two components, a lens-shaped inner orbit and an hour-glass shaped outer orbit. B{sub {perpendicular}} causes Landau level formation and Shubnikov-de Haas (SdH) oscillations for each component of the FS. MB occurs when the magnetic forces from B{sub {perpendicular}} become dominant and the electrons move on free-electron circular orbits rather than on the lens and hour-glass orbits. MB is observed by identifying the peaks present in the Fourier power spectrum of the longitudinal resistance vs. 1/B{sub {perpendicular}} at constant B{sub {parallel}}, an arrangement achieved with an in-situ tilting sample holder. Results are presented for two strongly coupled GaAs/AlGaAs DQW samples.

  15. Rupture models with dynamically determined breakdown displacement

    USGS Publications Warehouse

    Andrews, D.J.

    2004-01-01

    The critical breakdown displacement, Dc, in which friction drops to its sliding value, can be made dependent on event size by specifying friction to be a function of variables other than slip. Two such friction laws are examined here. The first is designed to achieve accuracy and smoothness in discrete numerical calculations. Consistent resolution throughout an evolving rupture is achieved by specifying friction as a function of elapsed time after peak stress is reached. Such a time-weakening model produces Dc and fracture energy proportional to the square root of distance rupture has propagated in the case of uniform stress drop. The second friction law is more physically motivated. Energy loss in a damage zone outside the slip zone has the effect of increasing Dc and limiting peak slip velocity (Andrews, 1976). This article demonstrates a converse effect, that artificially limiting slip velocity on a fault in an elastic medium has a toughening effect, increasing fracture energy and Dc proportionally to rupture propagation distance in the case of uniform stress drop. Both the time-weakening and the velocity-toughening models can be used in calculations with heterogeneous stress drop.

  16. Characterization of soy protein nanoparticles prepared by high shear microfluidization

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soy protein nanoparticles were produced with a microfluidizer and characterized in terms of particle size, size distribution, morphology, rheological properties, and aggregate structure. Three stages of structure breakdown were observed when the soy protein dispersion was passed through the microflu...

  17. Structural characterization of soy protein nanoparticles from high shear microfluidization

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soy protein nanoparticles were produced with a microfluidizer and characterized in terms of particle size, size distribution, morphology, rheological properties, and aggregate structure. Three stages of structure breakdown were observed when the soy protein dispersion was passed through the microflu...

  18. Soft breakdown characteristics of ultralow-k time-dependent dielectric breakdown for advanced complementary metal-oxide semiconductor technologies

    NASA Astrophysics Data System (ADS)

    Chen, Fen; Shinosky, Michael

    2010-09-01

    During technology development, the study of ultralow-k (ULK) time-dependent dielectric breakdown (TDDB) is important for assuring robust reliability. As the technology advances, the increase in ULK leakage current noise level and reversible current change induced by soft breakdown (SBD) during stress has been observed. In this paper, the physical origin of SBD and reversible breakdown, and its correlation to conventional hard breakdowns (HBDs) were extensively studied. Based on constant voltage stress (CVS) and constant current stress (CCS) results, it was concluded that SBD in ULK is an intrinsic characteristic for ULK material, and all first breakdown events most likely are soft instead of hard. Therefore, a unified understanding of SBD and HBD for low-k TDDB was established. Furthermore, the post-SBD and HBD breakdown conduction characteristics were explored and their impacts on circuit operation were discussed. Based on current limited constant voltage stress studies, it was found that the power dissipation, not the stored energy, determined the severity of ULK dielectric breakdown, and the postbreakdown conduction properties. A percolation-threshold controlled, variable-range-hopping (VRH) model was proposed to explain all postbreakdown aspects of SBD and HBD of ULK material.

  19. Vortex breakdown in closed containers with polygonal cross sections

    SciTech Connect

    Naumov, I. V. Dvoynishnikov, S. V.; Kabardin, I. K.; Tsoy, M. A.

    2015-12-15

    The vortex breakdown bubble in the confined flow generated by a rotating lid in closed containers with polygonal cross sections was analysed both experimentally and numerically for the height/radius aspect ratio equal to 2. The stagnation point locations of the breakdown bubble emergence and the corresponding Reynolds number were determined experimentally and in addition computed numerically by STAR-CCM+ CFD software for square, pentagonal, hexagonal, and octagonal cross section configurations. The flow pattern and the velocity were observed and measured by combining the seeding particle visualization and the temporal accuracy of laser Doppler anemometry. The vortex breakdown size and position on the container axis were determined for Reynolds numbers, ranging from 1450 to 2400. The obtained results were compared with the flow structure in the closed container of cubical and cylindrical configurations. It is shown that the measured evolution of steady vortex breakdown is in close agreement with the numerical results.

  20. 19 CFR 141.87 - Breakdown on component materials.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... OF THE TREASURY (CONTINUED) ENTRY OF MERCHANDISE Invoices § 141.87 Breakdown on component materials. Whenever the classification or appraisement of merchandise depends on the component materials, the...

  1. Suppressing the cellular breakdown in silicon supersaturated with titanium

    NASA Astrophysics Data System (ADS)

    Liu, Fang; Prucnal, S.; Hübner, R.; Yuan, Ye; Skorupa, W.; Helm, M.; Zhou, Shengqiang

    2016-06-01

    Hyper doping Si with up to 6 at.% Ti in solid solution was performed by ion implantation followed by pulsed laser annealing and flash lamp annealing. In both cases, the implanted Si layer can be well recrystallized by liquid phase epitaxy and solid phase epitaxy, respectively. Cross-sectional transmission electron microscopy of Ti-implanted Si after liquid phase epitaxy shows the so-called growth interface breakdown or cellular breakdown owing to the occurrence of constitutional supercooling in the melt. The appearance of cellular breakdown prevents further recrystallization. However, the out-diffusion and cellular breakdown can be effectively suppressed by solid phase epitaxy during flash lamp annealing due to the high velocity of amorphous-crystalline interface and the low diffusion velocity for Ti in the solid phase.

  2. Implications of Dielectric Breakdown Weathering for the Lunar Polar Regolith

    NASA Astrophysics Data System (ADS)

    Jordan, A. P.; Wilson, J. K.; Stubbs, T. J.; Schwadron, N. A.; Spence, H. E.; Izenberg, N. R.

    2015-10-01

    Dielectric breakdown weathering may significantly affect lunar regolith in permanently shadowed regions. We estimate how it may evolve the distribution of grain sizes and properties, which could have operational implications for rovers.

  3. D STAND DELIVERY END OF #44 TANDEM BREAKDOWN MILL WITH ...

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

    D STAND DELIVERY END OF #44 TANDEM BREAKDOWN MILL WITH UPCOILER. BACKUP ROLLS, 40 TONS. WORK ROLLS, 20 TONS., C. 1900. OPERATING SPEED, 600'/MINUTE. AUTOMATIC GAUGE CONTROL. - American Brass Foundry, 70 Sayre Street, Buffalo, Erie County, NY

  4. Vortex breakdown in closed containers with polygonal cross sections

    NASA Astrophysics Data System (ADS)

    Naumov, I. V.; Dvoynishnikov, S. V.; Kabardin, I. K.; Tsoy, M. A.

    2015-12-01

    The vortex breakdown bubble in the confined flow generated by a rotating lid in closed containers with polygonal cross sections was analysed both experimentally and numerically for the height/radius aspect ratio equal to 2. The stagnation point locations of the breakdown bubble emergence and the corresponding Reynolds number were determined experimentally and in addition computed numerically by STAR-CCM+ CFD software for square, pentagonal, hexagonal, and octagonal cross section configurations. The flow pattern and the velocity were observed and measured by combining the seeding particle visualization and the temporal accuracy of laser Doppler anemometry. The vortex breakdown size and position on the container axis were determined for Reynolds numbers, ranging from 1450 to 2400. The obtained results were compared with the flow structure in the closed container of cubical and cylindrical configurations. It is shown that the measured evolution of steady vortex breakdown is in close agreement with the numerical results.

  5. Electric field-free gas breakdown in explosively driven generators

    SciTech Connect

    Shkuratov, Sergey I.; Baird, Jason; Talantsev, Evgueni F.; Altgilbers, Larry L.

    2010-07-15

    All known types of gas discharges require an electric field to initiate them. We are reporting on a unique type of gas breakdown in explosively driven generators that does not require an electric field.

  6. On the breakdown of passivity of iron by thiocyanate

    SciTech Connect

    Melendres, C.A.; Acho, J.; Knight, R.L. )

    1991-03-01

    In this paper, the authors report that small amounts (0.001 to 0.02M) of SCN{sup {minus}} significantly increased the rate of anodic dissolution of copper and iron; SCN{sup {minus}} causes a breakdown of the passivity of iron but not of copper. The authors communicate results of our studies using the surface enhanced Raman (SER) effect in order to further elucidate the passivity of iron and its breakdown by thiocyanate.

  7. Ionizing potential waves and high-voltage breakdown streamers.

    NASA Technical Reports Server (NTRS)

    Albright, N. W.; Tidman, D. A.

    1972-01-01

    The structure of ionizing potential waves driven by a strong electric field in a dense gas is discussed. Negative breakdown waves are found to propagate with a velocity proportional to the electric field normal to the wavefront. This causes a curved ionizing potential wavefront to focus down into a filamentary structure, and may provide the reason why breakdown in dense gases propagates in the form of a narrow leader streamer instead of a broad wavefront.

  8. Mapping of mechanical specimens by laser induced breakdown spectroscopy method: Application to an engine valve

    NASA Astrophysics Data System (ADS)

    Lopez-Quintas, I.; Mateo, M. P.; Piñon, V.; Yañez, A.; Nicolas, G.

    2012-08-01

    In this work, an engine valve composed of different alloys has been analyzed by laser- induced breakdown spectroscopy to prove the capability of this technique to characterize mechanical parts which are complex in terms of shape and composition. With the acquired spectral data, 3D chemical maps have been plotted using a computer application for four representative elements: Fe, Cr, Ni and Mn. In addition, information about the in-depth distribution of Cr and Fe in different parts of the valve is shown. Results prove the potential of this technique to be implemented as an evaluation tool for quality control.

  9. Extrapolation of electrical breakdown currents from the laboratory to Space Station

    NASA Astrophysics Data System (ADS)

    Vaughn, Jason A.; Carruth, Melvin R., Jr.; Katz, Ira; Mandell, Myron J.; Jongeward, Gary A.

    1992-01-01

    Recent experiments conducted in a plasma chamber at NASA/MSFC on anodized aluminum coatings representative of Space Station Freedom design show that if the aluminum used as a thermal control coating is biased more than 80 V negative with respect to the plasma, the anodization will experience dielectric breakdown. As the thin anodization layer creates a capacitive charge buildup, large currents are observed during the arc. How plasma generation at the arc site can support large currents and discharge the surface charge layer is investigated. The importance for Space Station Freedom is that currents similar to those observed in the laboratory can be observed on orbit.

  10. Dielectric breakdown weathering of the Moon's polar regolith

    NASA Astrophysics Data System (ADS)

    Jordan, A. P.; Stubbs, T. J.; Wilson, J. K.; Schwadron, N. A.; Spence, H. E.

    2015-02-01

    Galactic cosmic rays and solar energetic particles (SEPs) can charge the Moon's subsurface, a process expected to be particularly important in the polar regions. Experiments have shown that sufficient fluences (i.e., time-integrated fluxes) of energetic charged particles can cause dielectric breakdown, in which the electric field rapidly vaporizes small, filamentary channels within a dielectric. Lunar regolith has both the characteristics and, in some polar locations, the environment needed to make breakdown likely. We combine the Jet Propulsion Laboratory proton fluence model with temperature measurements from the Lunar Reconnaissance Orbiter's (LRO's) Diviner instrument and related temperature modeling to estimate how often breakdown occurs in the polar regions. We find that all gardened regolith within permanently shadowed regions (PSRs) has likely experienced up to 2×106 SEP events capable of causing breakdown, while the warmest polar regions have experienced about 2 orders of magnitude fewer events. We also use measurements from the Cosmic Ray Telescope for the Effects of Radiation on LRO to show that at least two breakdown-inducing events may have occurred since LRO arrived at the Moon in 2009. Finally, we discuss how such "breakdown weathering" may increase the percentage of fine and monomineralic grains within PSRs; explain the presence of so-called "fairy castle" regolith structures; and contribute to other low-albedo features detected by LRO's Lyman Alpha Mapping Project, possibly establishing a correlation between these features and the average temperatures within craters that are only partly in permanent shadow.