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Sample records for p-type cytotoxins interact

  1. Snake cytotoxins bind to membranes via interactions with phosphatidylserine head groups of lipids.

    Directory of Open Access Journals (Sweden)

    Anastasia G Konshina

    Full Text Available The major representatives of Elapidae snake venom, cytotoxins (CTs, share similar three-fingered fold and exert diverse range of biological activities against various cell types. CT-induced cell death starts from the membrane recognition process, whose molecular details remain unclear. It is known, however, that the presence of anionic lipids in cell membranes is one of the important factors determining CT-membrane binding. In this work, we therefore investigated specific interactions between one of the most abundant of such lipids, phosphatidylserine (PS, and CT 4 of Naja kaouthia using a combined, experimental and modeling, approach. It was shown that incorporation of PS into zwitterionic liposomes greatly increased the membrane-damaging activity of CT 4 measured by the release of the liposome-entrapped calcein fluorescent dye. The CT-induced leakage rate depends on the PS concentration with a maximum at approximately 20% PS. Interestingly, the effects observed for PS were much more pronounced than those measured for another anionic lipid, sulfatide. To delineate the potential PS binding sites on CT 4 and estimate their relative affinities, a series of computer simulations was performed for the systems containing the head group of PS and different spatial models of CT 4 in aqueous solution and in an implicit membrane. This was done using an original hybrid computational protocol implementing docking, Monte Carlo and molecular dynamics simulations. As a result, at least three putative PS-binding sites with different affinities to PS molecule were delineated. Being located in different parts of the CT molecule, these anion-binding sites can potentially facilitate and modulate the multi-step process of the toxin insertion into lipid bilayers. This feature together with the diverse binding affinities of the sites to a wide variety of anionic targets on the membrane surface appears to be functionally meaningful and may adjust CT action against

  2. Naja naja oxiana Cobra Venom Cytotoxins CTI and CTII Disrupt Mitochondrial Membrane Integrity: Implications for Basic Three-Fingered Cytotoxins.

    Science.gov (United States)

    Gasanov, Sardar E; Shrivastava, Indira H; Israilov, Firuz S; Kim, Aleksandr A; Rylova, Kamila A; Zhang, Boris; Dagda, Ruben K

    2015-01-01

    Cobra venom cytotoxins are basic three-fingered, amphipathic, non-enzymatic proteins that constitute a major fraction of cobra venom. While cytotoxins cause mitochondrial dysfunction in different cell types, the mechanisms by which cytotoxins bind to mitochondria remain unknown. We analyzed the abilities of CTI and CTII, S-type and P-type cytotoxins from Naja naja oxiana respectively, to associate with isolated mitochondrial fractions or with model membranes that simulate the mitochondrial lipid environment by using a myriad of biophysical techniques. Phosphorus-31 nuclear magnetic resonance (31P-NMR) spectroscopy data suggest that both cytotoxins bind to isolated mitochondrial fractions and promote the formation of aberrant non-bilayer structures. We then hypothesized that CTI and CTII bind to cardiolipin (CL) to disrupt mitochondrial membranes. Collectively, 31P-NMR, electron paramagnetic resonance (EPR), proton NMR (1H-NMR), deuterium NMR (2H-NMR) spectroscopy, differential scanning calorimetry, and erythrosine phosphorescence assays suggest that CTI and CTII bind to CL to generate non-bilayer structures and promote the permeabilization, dehydration and fusion of large unilamellar phosphatidylcholine (PC) liposomes enriched with CL. On the other hand, CTII but not CTI caused biophysical alterations of large unilamellar PC liposomes enriched with phosphatidylserine (PS). Mechanistically, single molecule docking simulations identified putative CL, PS and PC binding sites in CTI and CTII. While the predicted binding sites for PS and PC share a high number of interactive amino acid residues in CTI and CTII, the CL biding sites in CTII and CTI are more divergent as it contains additional interactive amino acid residues. Overall, our data suggest that cytotoxins physically associate with mitochondrial membranes by binding to CL to disrupt mitochondrial structural integrity.

  3. Anti-tumour cytotoxin produced by human monocytes: studies on its mode of action.

    OpenAIRE

    Matthews, N.

    1983-01-01

    Human monocytes can be induced to synthesize a cytotoxin which affects certain tumour cell lines. The interaction of monocyte cytotoxin with a susceptible cell line (L929) has been studied to obtain clues to the mode of action of the cytotoxin. The cytotoxin acts directly on the cells rather than on the culture medium and is cytotoxic at higher concentrations and cytostatic at lower concentrations. First signs of cell damage appear about 20 h after contact with the cytotoxin which must be pre...

  4. Essential domain of receptor tyrosine phosphatase beta (RPTPbeta) for interaction with Helicobacter pylori vacuolating cytotoxin

    DEFF Research Database (Denmark)

    Yahiro, Kinnosuke; Wada, Akihiro; Yamasaki, Eiki

    2004-01-01

    Helicobacter pylori produces a potent exotoxin, VacA, which causes progressive vacuolation as well as gastric injury. Although VacA was able to interact with two receptor-like protein tyrosine phosphatases, RPTPbeta and RPTPalpha, RPTPbeta was found to be responsible for gastric damage caused...

  5. Nutritional aspects of cytotoxin production by Clostridium difficile.

    OpenAIRE

    Osgood, D P; Wood, N. P.; Sperry, J F

    1993-01-01

    Arginine was the only amino acid used by Clostridium difficile that permitted cytotoxin synthesis in a peptone-based medium. Synthesis of cytotoxin was delayed when glucose was used as the substrate. Addition of rifampin or puromycin to cultures prior to release of cytotoxin inhibited the release of cytotoxin, suggesting that a protein essential for cytotoxin release is synthesized after cytotoxin is synthesized.

  6. Inhibition of cytotoxicity by the Nhe cytotoxin of Bacillus cereus through the interaction of dodecyl maltoside with the NheB component.

    Science.gov (United States)

    Phung, Danh; Granum, Per Einar; Dietrich, Richard; Märtlbauer, Erwin; Hardy, Simon P

    2012-05-01

    Nhe ('nonhaemolytic enterotoxin') is a three-component cytotoxin implicated in the pathogenesis of diarrhoea by Bacillus cereus. Nhe forms pores in pure lipid bilayers, but the function of the individual components (NheA, NheB and NheC) remains unclear. NheB and NheC are structural homologues of ClyA, a pore-forming cytotoxin of Escherichia coli. The non-ionic detergent dodecyl maltoside (DDM) has been shown to inhibit haemolysis of ClyA. We used DDM as a probe to examine the response of the Nhe proteins to DDM micelles. At its critical micellar concentration (0.2 mM), DDM inhibited propidium uptake by the native Nhe complex in Vero and HT29 cell suspensions. Pre-incubation of NheC with DDM did not inhibit cytotoxicity. NheB exhibited marked changes in 1-anilinonaphthalene-8-sulphonic acid (ANS) fluorescence after pre-exposure to DDM. Pre-incubation of NheB with DDM resulted in large molecular weight complexes as detected by size exclusion chromatography and diffusion through sized dialysis membranes and prevented binding of NheB to Vero cell monolayers. These data support a model in which conformational changes and oligomerization of NheB are prerequisite events in the process of pore formation.

  7. Biological activity of Serratia marcescens cytotoxin

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    G.V. Carbonell

    2003-03-01

    Full Text Available Serratia marcescens cytotoxin was purified to homogeneity by ion-exchange chromatography on a DEAE Sepharose Fast Flow column, followed by gel filtration chromatography on a Sephadex G100 column. The molecular mass of the cytotoxin was estimated to be about 50 kDa. Some biological properties of the cytotoxin were analyzed and compared with well-characterized toxins, such as VT1, VT2 and CNF from Escherichia coli and hemolysin produced by S. marcescens. The sensitivity of the cell lines CHO, HeLa, HEp-2, Vero, BHK-21, MA 104 and J774 to the cytotoxin was determined by the cell viability assay using neutral red. CHO and HEp-2 were highly sensitive, with massive cellular death after 1 h of treatment, followed by BHK-21, HeLa, Vero and J774 cells, while MA 104 was insensitive to the toxin. Cytotoxin induced morphological changes such as cell rounding with cytoplasmic retraction and nuclear compactation which were evident 15 min after the addition of cytotoxin. The cytotoxic assays show that 15 min of treatment with the cytotoxin induced irreversible intoxication of the cells, determined by loss of cell viability. Concentrations of 2 CD50 (0.56 µg/ml of purified cytotoxin did not present any hemolytic activity, showing that the cytotoxin is distinct from S. marcescens hemolysin. Antisera prepared against S. marcescens cytotoxin did not neutralize the cytotoxic activity of VT1, VT2 or CNF toxin, indicating that these toxins do not share antigenic determinants with cytotoxin. Moreover, we did not detect gene sequences for any of these toxins in S. marcescens by PCR assay. These results suggest that S. marcescens cytotoxin is not related to any of these toxins from E. coli.

  8. Biological activity of Serratia marcescens cytotoxin.

    Science.gov (United States)

    Carbonell, G V; Amorim, C R N; Furumura, M T; Darini, A L C; Fonseca, B A L; Yano, T

    2003-03-01

    Serratia marcescens cytotoxin was purified to homogeneity by ion-exchange chromatography on a DEAE Sepharose Fast Flow column, followed by gel filtration chromatography on a Sephadex G100 column. The molecular mass of the cytotoxin was estimated to be about 50 kDa. Some biological properties of the cytotoxin were analyzed and compared with well-characterized toxins, such as VT1, VT2 and CNF from Escherichia coli and hemolysin produced by S. marcescens. The sensitivity of the cell lines CHO, HeLa, HEp-2, Vero, BHK-21, MA 104 and J774 to the cytotoxin was determined by the cell viability assay using neutral red. CHO and HEp-2 were highly sensitive, with massive cellular death after 1 h of treatment, followed by BHK-21, HeLa, Vero and J774 cells, while MA 104 was insensitive to the toxin. Cytotoxin induced morphological changes such as cell rounding with cytoplasmic retraction and nuclear compactation which were evident 15 min after the addition of cytotoxin. The cytotoxic assays show that 15 min of treatment with the cytotoxin induced irreversible intoxication of the cells, determined by loss of cell viability. Concentrations of 2 CD50 (0.56 g/ml) of purified cytotoxin did not present any hemolytic activity, showing that the cytotoxin is distinct from S. marcescens hemolysin. Antisera prepared against S. marcescens cytotoxin did not neutralize the cytotoxic activity of VT1, VT2 or CNF toxin, indicating that these toxins do not share antigenic determinants with cytotoxin. Moreover, we did not detect gene sequences for any of these toxins in S. marcescens by PCR assay. These results suggest that S. marcescens cytotoxin is not related to any of these toxins from E. coli.

  9. Comparison of junctionless and inversion-mode p-type metal-oxide-semiconductor field-effect transistors in presence of hole-phonon interactions

    Energy Technology Data Exchange (ETDEWEB)

    Dib, E., E-mail: elias.dib@for.unipi.it [Dipartimento di Ingegneria dell' Informazione, Università di Pisa, 56122 Pisa (Italy); Carrillo-Nuñez, H. [Integrated Systems Laboratory ETH Zürich, Gloriastrasse 35, 8092 Zürich (Switzerland); Cavassilas, N.; Bescond, M. [IM2NP, UMR CNRS 6242, Bât. IRPHE, Technopôle de Château-Gombert, 13384 Marseille Cedex 13 (France)

    2016-01-28

    Junctionless transistors are being considered as one of the alternatives to conventional metal-oxide field-effect transistors. In this work, it is then presented a simulation study of silicon double-gated p-type junctionless transistors compared with its inversion-mode counterpart. The quantum transport problem is solved within the non-equilibrium Green's function formalism, whereas hole-phonon interactions are tackled by means of the self-consistent Born approximation. Our findings show that junctionless transistors should perform as good as a conventional transistor only for ultra-thin channels, with the disadvantage of requiring higher supply voltages in thicker channel configurations.

  10. Limits on light weakly interacting massive particles from the CDEX-1 experiment with a p -type point-contact germanium detector at the China Jinping Underground Laboratory

    Science.gov (United States)

    Yue, Q.; Zhao, W.; Kang, K. J.; Cheng, J. P.; Li, Y. J.; Lin, S. T.; Chang, J. P.; Chen, N.; Chen, Q. H.; Chen, Y. H.; Chuang, Y. C.; Deng, Z.; Du, Q.; Gong, H.; Hao, X. Q.; He, H. J.; He, Q. J.; Huang, H. X.; Huang, T. R.; Jiang, H.; Li, H. B.; Li, J. M.; Li, J.; Li, J.; Li, X.; Li, X. Y.; Li, Y. L.; Liao, H. Y.; Lin, F. K.; Liu, S. K.; Lü, L. C.; Ma, H.; Mao, S. J.; Qin, J. Q.; Ren, J.; Ren, J.; Ruan, X. C.; Shen, M. B.; Singh, L.; Singh, M. K.; Soma, A. K.; Su, J.; Tang, C. J.; Tseng, C. H.; Wang, J. M.; Wang, L.; Wang, Q.; Wong, H. T.; Wu, S. Y.; Wu, Y. C.; Wu, Y. C.; Xianyu, Z. Z.; Xiao, R. Q.; Xing, H. Y.; Xu, F. Z.; Xu, Y.; Xu, X. J.; Xue, T.; Yang, L. T.; Yang, S. W.; Yi, N.; Yu, C. X.; Yu, H.; Yu, X. Z.; Zeng, X. H.; Zeng, Z.; Zhang, L.; Zhang, Y. H.; Zhao, M. G.; Zhou, Z. Y.; Zhu, J. J.; Zhu, W. B.; Zhu, X. Z.; Zhu, Z. H.; CDEX Collaboration

    2014-11-01

    We report results of a search for light dark matter weakly interacting massive particles (WIMPs) with CDEX-1 experiment at the China Jinping Underground Laboratory, based on 53.9 kg-days of data from a p -type point-contact germanium detector enclosed by a NaI(Tl) crystal scintillator as anti-Compton detector. The event rate and spectrum above the analysis threshold of 475 eVee are consistent with the understood background model. Part of the allowed regions for WIMP-nucleus coherent elastic scattering at WIMP mass of 6-20 GeV are probed and excluded. Independent of interaction channels, this result contradicts the interpretation that the anomalous excesses of the CoGeNT experiment are induced by dark matter, since identical detector techniques are used in both experiments.

  11. The effect of electronic orbital interactions on p-type doping tendency in ZnO series: First-principles calculations

    Institute of Scientific and Technical Information of China (English)

    Zhang Fang-Ying; You Jian-Qiang; Zeng Zhi; Zhong Guo-Hua

    2007-01-01

    The electronic structures and optical properties of B3 ZnO series of Zn4X4-yMy(X =O, S, Se or Te; M = N,Sb, Cl or I; y = 0 or 1) are studied by first-principles calculations using a pseudopotential plane-wave method. The results show that Zn d-X p orbital interactions play an important role in the p-type doping tendency in zinc-based Ⅱ-Ⅵ semiconductors. In ZnX, with increasing atomic number of X, Zn d-X p orbital interactions decrease and Zn s-X p orbital interactions increase. Additionally, substituting group-Ⅴ elements for X will reduce the Zn d-X p orbital interactions while substituting group-Ⅶ elements for X will increase the Zn d-X p orbital interactions. The results also show that group-Ⅴ-doped ZnX and group-Ⅶ-doped ZnX exhibit different optical behaviours due to their different orbital interaction effects.

  12. Neutralizing antibodies to Haemophilus ducreyi cytotoxin.

    OpenAIRE

    Lagergård, T; Purvén, M

    1993-01-01

    Neutralizing antibodies against cytotoxin produced by Haemophilus ducreyi bacteria were studied in rabbits by an assay employing HEp-2 cells and diluted crude cytotoxin preparations from the organism. Antisera to 12 different H. ducreyi strains were prepared by immunization of rabbits with bacterial sonicates combined with Freund's adjuvant. The antibody response during infection with H. ducreyi was studied in two groups of rabbits which were infected with five live strains by either single o...

  13. Acridine-intercalator based hypoxia selective cytotoxins

    Science.gov (United States)

    Papadopoulou-Rosenzweig, Maria; Bloomer, William D.; Bloomer, William D.

    1994-01-01

    Hypoxia selective cytotoxins of the general formula ##STR1## wherein n is from 1 to 5, and NO.sub.2 is in at least one of the 2, 4 or 5-positions of the imidazole. Such compounds have utility as radiosensitizers and chemosensitizers.

  14. Acridine-intercalator based hypoxia selective cytotoxins

    Energy Technology Data Exchange (ETDEWEB)

    Papadopoulou-Rosenzweig, M.; Bloomer, W.D.

    1994-03-15

    Hypoxia selective cytotoxins of the general formula STR1 wherein n is from 1 to 5, and NO[sub 2] is in at least one of the 2, 4 or 5-positions of the imidazole are developed. Such compounds have utility as radiosensitizers and chemosensitizers. 9 figs.

  15. The cytotoxin of Pseudomonas aeruginosa : Cytotoxicity requires proteolytic activation

    NARCIS (Netherlands)

    Orlik-Eisel, Gabriele; Lutz, Frieder; Henschen, Agnes; Eisel, Ulrich; Struckmeier, Martin; Kräuter, Josef; Niemann, Heiner

    1990-01-01

    The primary structure of a cytotoxin from Pseudomonas aeruginosa was determined by sequencing of the structural gene. The cytotoxin (31,700 Mr) lacks an N-terminal signal sequence for bacterial secretion but contains a pentapeptide consensus sequence commonly found in prokaryotic proteins which func

  16. The cytotoxin of Pseudomonas aeruginosa : Cytotoxicity requires proteolytic activation

    NARCIS (Netherlands)

    Orlik-Eisel, Gabriele; Lutz, Frieder; Henschen, Agnes; Eisel, Ulrich; Struckmeier, Martin; Kräuter, Josef; Niemann, Heiner

    The primary structure of a cytotoxin from Pseudomonas aeruginosa was determined by sequencing of the structural gene. The cytotoxin (31,700 Mr) lacks an N-terminal signal sequence for bacterial secretion but contains a pentapeptide consensus sequence commonly found in prokaryotic proteins which

  17. The cytotoxin of Pseudomonas aeruginosa : Cytotoxicity requires proteolytic activation

    NARCIS (Netherlands)

    Orlik-Eisel, Gabriele; Lutz, Frieder; Henschen, Agnes; Eisel, Ulrich; Struckmeier, Martin; Kräuter, Josef; Niemann, Heiner

    1990-01-01

    The primary structure of a cytotoxin from Pseudomonas aeruginosa was determined by sequencing of the structural gene. The cytotoxin (31,700 Mr) lacks an N-terminal signal sequence for bacterial secretion but contains a pentapeptide consensus sequence commonly found in prokaryotic proteins which func

  18. Natural Diversity in the N Terminus of the Mature Vacuolating Cytotoxin of Helicobacter pylori Determines Cytotoxin Activity

    OpenAIRE

    Letley, D. P.; Atherton, J C

    2000-01-01

    Naturally occurring noncytotoxic vacA type s2 strains of Helicobacter pylori have a 12-residue extension to the vacuolating cytotoxin (VacA) compared with cytotoxic type s1 strains. We show that adding the region encoding this extension to type s1 vacA completely abolishes vacuolating cytotoxin activity but has no effect on VacA production.

  19. Cobra venom cytotoxins; apoptotic or necrotic agents?

    Science.gov (United States)

    Ebrahim, Karim; Shirazi, Farshad H; Mirakabadi, Abbas Zare; Vatanpour, Hossein

    2015-12-15

    Organs homeostasis is controlled by a dynamic balance between cell proliferation and apoptosis. Failure to induction of apoptosis has been implicated in tumor development. Cytotoxin-I (CTX-I) and cytotoxin-II (CTX-II) are two physiologically active polypeptides found in Caspian cobra venom. Anticancer activity and mechanism of cell death induced by these toxins have been studied. The toxins were purified by different chromatographic steps and their cytotoxicity and pattern of cell death were determined by MTT, LDH release, acridine orange/ethidium bromide (AO/EtBr) double staining, flow cytometric analysis, caspase-3 activity and neutral red assays. The IC50 of CTX-II in MCF-7, HepG2, DU-145 and HL-60 was 4.1 ± 1.3, 21.2 ± 4.4, 9.4 ± 1.8 μg/mL and 16.3 ± 1.9 respectively while the IC50 of this toxin in normal MDCK cell line was 54.5 ± 3.9 μg/mL. LDH release suddenly increase after a specific toxins concentrations in all cell lines. AO/EtBr double staining, flow cytometric analysis and caspase-3 activity assay confirm dose and time-dependent induction of apoptosis by both toxins. CTX-I and CTX-II treated cells lost their lysosomal membrane integrity and couldn't uptake neutral red day. CTX-I and CTX-II showed significant anticancer activity with minimum effects on normal cells and better IC50 compared to current anticancer drug; cisplatin. They induce their apoptotic effect via lysosomal pathways and release of cathepsins to cytosol. These effects were seen in limited rage of toxins concentrations and pattern of cell death rapidly changes to necrosis by increase in toxin's concentration. In conclusion, significant apoptogenic effects of these toxins candidate them as a possible anticancer agent.

  20. Morphological and intracellular alterations induced by Serratia marcescens cytotoxin.

    Science.gov (United States)

    Carbonell, Gleize Villela; Falcón, Rosabel; Yamada, Aureo T; da Fonseca, Benedito Antonio Lopes; Yano, Tomomasa

    2004-01-01

    In the present work, in vitro assays were used to investigate the toxicity of Serratia marcescens cytotoxin in cultured Chinese hamster ovary (CHO) cells. The time necessary to detect cellular alterations such as the onset of apoptosis, the perturbation of mitochondrial function, and cytoskeletal changes was assessed. The internalization of the cytotoxin by CHO cells was also examined. Within 10-15 min of exposure to cytotoxin, CHO cells became round, the nucleus shrank, the chromatin became more compact, and cytoplasmic blebs appeared on the cell surface. TUNEL (TdT-mediated dUTP nick end labeling) and propidium iodide staining identified some nuclei with fragmented DNA, and electrophoresis of CHO cell DNA obtained after 30-min exposure to S. marcescens toxin showed a pattern of DNA fragments typically associated with apoptosis. The cells also lost their characteristic actin organization within 10 min of exposure to cytotoxin. Lactate dehydrogenase leakage was detected after 20-min exposure to the cytotoxin and increased with time thereafter. Concomitantly, there was a time-dependent reduction in mitochondrial activity. Fluorescein-labeled S. marcescens cytotoxin was detected only on the surface of CHO cells, even after 30-min exposure to the toxin. These results show that there was no internalization of the toxin by CHO cells, and that, once bound to the cell surface, the toxin was able to induce changes in intracellular metabolism and to trigger cell death by apoptosis.

  1. Antigen epitope of Helicobacter pylorivacuolating cytotoxin A

    Institute of Scientific and Technical Information of China (English)

    Xiu-Li Liu; Shu-Qin Li; Chun-Jie Liu; Hao-Xia Tao; Zhao-Shan Zhang

    2004-01-01

    AIM: To construct and select antigen epitopes of vacuolating cytotoxin A (VacA) for nontoxic VacA vaccine against Helicobacter pylori (H pylori) infection.METHODS: Eleven VacA epitopes were predicted according to VacA antigenic bioinformatics. Three candidates of VacA epitope were constructed through different combined epitopes. The candidate was linked with E. coli heat-labile enterotoxin B (LTB) by a linker of 7 amino acids, and cloned into plasmid pQE-60 in which fusion LTB-VacA epitope was efficiently expressed. To test the antigencity of the candidate, 6 BALB/c mice were treated with the fusion LTB-VacA epitope through intraperitoneal injection. To explore the ability of inhibiting the toxicity of VacA, cantiserum against the candidate was used to counteract VacA that induced HeLa cells to produce cell vacuoles in vitro.RESULTS: Serum IgG against the candidate was induced in the BALB/c mice. In vitro, the three antisera against the candidate efficiently counteracted the toxicity of VacA, and decreased the number of cell vacuoles by 14.17%, 20.20%and 30.41% respectively.CONCLUSION: Two of the three candidates, LZ-VacA1and LZ-VacA2, can be used to further study the mechanism of vacuolating toxicity of VacA, and to construct nontoxic VacA vaccine against H pylori infection.

  2. Adenoviral vector-mediated gene transfer of IL-13Ralpha2 chain followed by IL-13 cytotoxin treatment offers potent targeted therapy for cytotoxin-resistant cancers.

    Science.gov (United States)

    Saito, Makoto; Murata, Takashi; Watanabe, Ken; Kawakami, Koji; Suzuki, Motoyoshi; Koji, Takehiko; Puri, Raj K; Kitazato, Kaio; Kobayashi, Nobuyuki

    2005-08-10

    Previous studies demonstrated that IL-13Ralpha2 chain-overexpressing cancer cells were highly sensitive to IL-13 cytotoxin (IL13-PE38QQR) and could be targeted by cytotoxin treatment. However, the majority of human tumors do not express high levels of IL-13Ralpha2 chain. To expand the IL-13 cytotoxin-mediated cancer targeting therapy, we combined cytotoxin treatment with gene transfer of IL-13Ralpha2 chain. We constructed a recombinant adenoviral vector carrying the human IL-13Ralpha2 gene (Ad-IL-13Ralpha2), which expresses high levels of IL-13Ralpha2 chain on infected cells. Human cancer cell lines A549 and HOS, which originally show no IL-13Ralpha2 expression and little sensitivity to IL-13 cytotoxin, were effectively converted to become sensitive to this cytotoxin after Ad-IL-13Ralpha2 infection. The CC(50) of IL-13 cytotoxin for Ad-IL-13Ralpha2-infected A549 cells was 500 ng/ml. We also examined the antitumor activity of IL-13 cytotoxin in an established xenograft model of cytotoxin-resistant human lung tumor. Only a single i.t. injection of Ad-IL-13Ralpha2 markedly enhanced the sensitivity of established tumors to IL-13 cytotoxin treatment; furthermore, this antitumor effect was significantly sustained for more than 1 month after the last treatment with IL-13 cytotoxin. Taken together, these results suggest the combination of adenoviral vector-mediated IL-13Ralpha2 gene transfer and IL-13 cytotoxin administration can be an effective targeting approach for several types of IL-13 cytotoxin-resistant cancers which show no or little expression of IL-13Ralpha2 chain.

  3. Purification and characterization of Ophiophagus hannah cytotoxin-like proteins.

    Science.gov (United States)

    Chang, Long-Sen; Chen, Ku-Chung; Lin, Shinne-Ren; Huang, Hsien-Bin

    2006-09-15

    Three cytotoxin-like proteins from the venom of Ophiophagus hannah were isolated by a combination of ion exchange chromatography and reverse phase HPLC. Amino acid sequence analysis revealed that these proteins all consisted of 63 amino acids and shared approximate 50% and 56% sequence identity with Naja naja atra cardiotoxins and cardiotoxin-like basic proteins (CLBPs), respectively. CD spectra revealed that their secondary structure was dominated with beta-sheet as those noted with cardiotoxins and CLBPs. O. hannah cytotoxin-like protein exhibited a cell-lytic activity on SK-N-SH cells, but its activity was more weak than that noted for N. naja atra cardiotoxin 3. Alternatively, apoptotic cell death was induced by the addition of N. naja atra CLBP. Based on the sequence information with the toxin molecules, the functional residues and regions related to the differential activity with O. hannah cytotoxin-like protein, cardiotoxin and CLBP are discussed.

  4. Identification and characterization of receptors for vacuolating activity of subtilase cytotoxin.

    Science.gov (United States)

    Yahiro, Kinnosuke; Morinaga, Naoko; Satoh, Mamoru; Matsuura, Gen; Tomonaga, Takeshi; Nomura, Fumio; Moss, Joel; Noda, Masatoshi

    2006-10-01

    Some shiga toxin-producing Escherichia coli secrete a novel AB5 cytotoxin, named subtilase cytotoxin (SubAB), which induces vacuole formation in addition to cytotoxicity in susceptible cells. By immunoprecipitation with SubAB from Vero cells, we discovered proteins of 100 kDa, 135 kDa and 155 kDa as potential candidates for its receptor. These proteins were N-glycosylated in their extracellular domains, a modification that was necessary for interaction with SubAB. Biotinylated receptors were partially purified by Datura stramonium agglutinin affinity chromatography and avidin-agarose and analysed by TOF mass spectroscopy. The peptide sequences of p135 were identical to beta1 integrin, and its identification was confirmed with anti-integrin beta1 antibody. The p155 protein was identified as alpha2 integrin using anti-integrin alpha2 antibody. In addition, treatment of Vero cells with beta1 integrin RNAi before exposure to SubAB prevented vacuolating activity. These results suggested that SubAB recognizes alpha2beta1 integrin as a functional receptor; this first interaction may be an important key step leading to the SubAB-induced morphological changes in Vero cells.

  5. Piezoresistance in p-type silicon revisited

    DEFF Research Database (Denmark)

    Richter, Jacob; Pedersen, Jesper; Brandbyge, Mads;

    2008-01-01

    We calculate the shear piezocoefficient pi44 in p-type Si with a 6×6 k·p Hamiltonian model using the Boltzmann transport equation in the relaxation-time approximation. Furthermore, we fabricate and characterize p-type silicon piezoresistors embedded in a (001) silicon substrate. We find that the ...

  6. Cancer cell injury by cytotoxins from cobra venom is mediated through lysosomal damage.

    Science.gov (United States)

    Feofanov, Alexei V; Sharonov, George V; Astapova, Maria V; Rodionov, Dmitriy I; Utkin, Yuriy N; Arseniev, Alexander S

    2005-08-15

    Cytotoxins from cobra venom are known to manifest cytotoxicity in various cell types. It is widely accepted that the plasma membrane is a target of cytotoxins, but the mechanism of their action remains obscure. Using the confocal spectral imaging technique, we show for the first time that cytotoxins from cobra venom penetrate readily into living cancer cells and accumulate markedly in lysosomes. Cytotoxins CT1 and CT2 from Naja oxiana, CT3 from Naja kaouthia and CT1 from Naja haje are demonstrated to possess this property with respect to human lung adenocarcinoma A549 and promyelocytic leukaemia HL60 cells. Immobilized plasma membrane binding accompanies the internalization of CT3 from Naja kaouthia in the HL60 cells, but it is very weak for other cytotoxins. Detectable membrane binding is not a property of any of the cytotoxins tested in A549 cells. The kinetics and concentration-dependence of cytotoxin accumulation in lysosomes correlate well with their cytotoxic effects. On the basis of the results obtained, we propose that lysosomes are a primary target of the lytic action of cytotoxins. Plasma membrane permeabilization seems to be a downstream event relative to lysosome rupture. Direct damage to the plasma membrane may be a complementary mechanism, but its relative contribution to the cytotoxic action depends on the cytotoxin structure and cell type.

  7. Evolution of plant P-type ATPases

    Directory of Open Access Journals (Sweden)

    Christian N.S. Pedersen

    2012-02-01

    Full Text Available Five organisms having completely sequenced genomes and belonging to all major branches of green plants (Viridiplantae were analyzed with respect to their content of P-type ATPases encoding genes. These were the chlorophytes Ostreococcus tauria and Chlamydomonas reinhardtii, and the streptophytes Physcomitrella patens (a moss, Selaginella moellendorffii (a primitive vascular plant, and Arabidopsis thaliana (a model flowering plant. Each organism contained sequences for all five subfamilies of P-type ATPases. Our analysis demonstrates when specific subgroups of P-type ATPases disappeared in the evolution of Angiosperms. Na/K-pump related P2C ATPases were lost with the evolution of streptophytes whereas Na+ or K+ pumping P2D ATPases and secretory pathway Ca2+-ATPases remained until mosses. An N-terminally located calmodulin binding domain in P2B ATPases can only be detected in pumps from Streptophytae, whereas, like in animals, a C-terminally localized calmodulin binding domain might be present in chlorophyte P2B Ca2+-ATPases. Chlorophyte genomes encode P3A ATPases resembling protist plasma membrane H+-ATPases and a C-terminal regulatory domain is missing. The complete inventory of P-type ATPases in the major branches of Viridiplantae is an important starting point for elucidating the evolution in plants of these important pumps.

  8. Inflammatory mediators and cytotoxins in cardiac allograft rejection

    Energy Technology Data Exchange (ETDEWEB)

    Lowry, R.P.; Powell, W.S.; Blais, D.; Marghesco, D.

    1986-03-01

    Though organ allograft rejection in rats has been linked to delayed type hypersensitivity (DTH) the pathogenesis of DTH induced tissue injury is uncertain. Accordingly, the authors have undertaken to identify the following inflammatory mediators/cytotoxins in rejecting rat cardiac allografts (WF ..-->.. LEW, day 5): phospholipase A/sub 2/(PLA/sub 2/ in cardiac homogenates assessed using /sup 14/C oleate labelled E Coli), PAF in lipid extracts of grafts measured by aggregation of rabbit platelets, arachidonic acid (AA) metabolites (HPLC analysis of products released from isolated perfused hearts and slices prelabelled with /sup 3/H-AA), lymphotoxin and/or tumor necrosis factor (LT/TNF release in vitro from infiltrating mononuclear cells assayed using cell line varies as L929. Briefly, aliquots of homogenates (10ml) of rejecting grafts demonstrated PLA/sub 2/ activity as evidenced by liberation of FFA from bacterial phospholipids (baseline 3%, 1 ..mu..1 4%, 25 ..mu..l 24%, 100 /sup +/l 29%, 200 ..mu..l 39%; control hearts, 200 ..mu..l 5%). Rejecting cardiac allografts contained approximately 10 ng PAF while PAF recovered from syngeneic grafts was less than or equal to 5 ng. Observed changes in eicosanoid biosynthesis with rejection were limited to a decrement in 6 oxo PGF/sub /sub 1/..cap alpha../ release. Infiltrating mononuclear cells recovered from rejecting grafts released greater than or equal to 64 units of cytotoxin (LT and/or TNF). The author present results, documenting a decrement in prostacyclin release by rejecting heart grafts, the presence of PLA/sub 2/ and PAF and the release of cytotoxins (LT and/or TNF) by infiltrating mononuclear cells are compatible with the thesis that allograft rejection must be viewed as a complex immune/inflammatory process. Additional studies are clearly required to define roles of these and other soluble factors in homograft destruction.

  9. Comparison of the primary structures, cytotoxicities, and affinities to phospholipids of five kinds of cytotoxins from the venom of Indian cobra, Naja naja.

    Science.gov (United States)

    Suzuki-Matsubara, Mieko; Athauda, Senarath B P; Suzuki, Yoshiyuki; Matsubara, Kazumi; Moriyama, Akihiko

    2016-01-01

    The molecular mechanism underlying the hemolytic and cytolytic processes of cobra cytotoxins (CTXs) is not yet fully elucidated. To examine this, we analyzed the amino acid sequences, hemolytic and cytotoxic activities, and affinities to phospholipids of the five major CTXs purified from the venom of Indian cobra, Naja naja. CTX2, CTX7, and CTX8 belonged to S-type, and CTX9 and CTX10 to P-type. Comparisons of CTX7 with CTX8 and CTX9 with CTX10 revealed similar primary structures and hemolytic and cytolytic activities. CTX2, whose primary structure was rather different from the others, showed several times weaker hemolytic and cytolytic biological activities than the others. The comparison of CTX2 with CTX7 suggested the importance of Lys30 in loop II for the strong hemolytic and cytolytic activities of S-type CTXs. Cloning of 12 CTX cDNAs from the Naja naja venom cDNA library revealed that 18 out of 23 substitutions found in CTX cDNAs were nonsynonymous. This clearly indicated the accelerated evolution of CTX genes. Multiple sequence alignment of 51 kinds of CTX cDNAs and calculations of nonsynonymous and synonymous substitutions indicated that the codons coding the three loops' regions, which may interact with the hydrophobic tails of phospholipids, have undergone an accelerated evolution. In contrast, the codons coding for amino acid residues considered to participate in the recognition and binding of the hydrophilic head groups of phospholipids, eight Cys residues, and those likely stabilizing β core structure, were all conserved.

  10. Effects of Actinobacillus pleuropneumoniae cytotoxins on generation of oxygen radicals by porcine neutrophils

    Directory of Open Access Journals (Sweden)

    Simson Tarigan

    1999-03-01

    Full Text Available Cytotoxins produced by Actinobacillus pleuropneumoniae (App suggested to be the most important pathogenic and virulent factors for this organism. However, the mechanisms on how the cytotoxins contribute to the disease process remain unclear. The purpose of this study is to investigate the effect of the cytotoxins on the oxidative-burst metabolism of porcine neutrophils. In this study, neutrophils were firstly loaded with an oxidative probe dichlorofluorescin diacetate (DCFHDA then expose to cytotoxins. Cells producing oxygen radicals emitted fluorescence and its intensity was measured with a FACScan flow cytometer. All cytotoxins derived from either App serotypes producing ApxI and ApxII, App serotypes producing ApxII only, or App serotypes producing ApxII and ApxIII were capable of stimulating neutrophils for oxygen-radical generation. However, compared with phorbol myristate acetate (PMA, App cytotoxins were much weaker as stimulants for oxygen radicals. In addition, Apx preparation stimulated an oxidative-burst metabolism of neutrophils at a low, narrow range of Apx doses. At higher doses, the toxins inhibit the oxidative burst metabolism. The effects of cytotoxins produced by App during infection on recruited neutrophils into the lungs are assumed to be comparable to those observed in this in vitro study. Neutrophils, and other host cells, adjacent to the bacteria become lysis due to high toxin concentration, whereas those at some distance to the bacteria produce oxygen radicals which in turn cause tissue damage or necrosis.

  11. Application of protein purification methods for the enrichment of a cytotoxin from Campylobacter jejuni

    Directory of Open Access Journals (Sweden)

    Gatsos Xenia

    2012-12-01

    Full Text Available Abstract Background Campylobater jejuni, a major foodborne diarrhoeal pathogen is reported to produce a number of cytotoxins of which only a cytolethal distending toxin (CDT has been characterised so far. One or more additional cytotoxins other than CDT, including a Chinese hamster ovary (CHO cell active, Vero cell inactive cytotoxin, may mediate inflammatory diarrhoea. Our objective was to develop a method to enrich and thus partially characterise this cytotoxin, as a pathway to the eventual identification and characterisation of the toxin. Results A number of biochemical methods including cation- and anion-exchange chromatography were evaluated to enrich the cytotoxin from a cell lysate of a known cytotoxin-producing C. jejuni, C31. The cytotoxin in crude lysate was initially prepared by size-exclusion desalting and then subjected to high pressure liquid chromatography (HPLC ion-exchange fractionation. One pooled fraction (pool B was cytotoxic for CHO cells equivalent to crude toxin (tissue culture infectivity dose 50 [TCID50] of 1–2 μg/ml. The proteins of pool B were identified by mass spectrometry (MS after separation by SDS-PAGE and trypsin digestion. Also, pool B was directly digested with trypsin and then subjected to liquid chromatography tandem mass spectrometry (LCMS analysis for identification of lesser abundant proteins in the fraction. A total of 41 proteins were found in the fraction, which included enzymes involved in metabolic and transport functions. Eighteen non-cytoplasmic proteins including 2 major antigenic peptide proteins (PEB2 and PEB3 and 3 proteins of unknown function were also identified in the screen. Cytotoxicity in pool B was trypsin-sensitive indicating its protein nature. The cytotoxic activity was heat-stable to 50°C, and partially inactivated at 60-70°C. The pool B fraction also induced fluid accumulation in the adult rabbit ileal loop assay with cytotoxicity for mucosa confirming the presence of the

  12. A novel mechanism of P-type ATPase autoinhibition involving both termini of the protein

    DEFF Research Database (Denmark)

    Ekberg, Kira; Palmgren, Michael; Veierskov, Bjarke;

    2010-01-01

    The activity of many P-type ATPases is found to be regulated by interacting proteins or autoinhibitory elements located in N- or C-terminal extensions. An extended C terminus of fungal and plant P-type plasma membrane H+-ATPases has long been recognized to be part of a regulatory apparatus...

  13. P-type transparent conducting oxides

    Science.gov (United States)

    Zhang, Kelvin H. L.; Xi, Kai; Blamire, Mark G.; Egdell, Russell G.

    2016-09-01

    Transparent conducting oxides constitute a unique class of materials combining properties of electrical conductivity and optical transparency in a single material. They are needed for a wide range of applications including solar cells, flat panel displays, touch screens, light emitting diodes and transparent electronics. Most of the commercially available TCOs are n-type, such as Sn doped In2O3, Al doped ZnO, and F doped SnO2. However, the development of efficient p-type TCOs remains an outstanding challenge. This challenge is thought to be due to the localized nature of the O 2p derived valence band which leads to difficulty in introducing shallow acceptors and large hole effective masses. In 1997 Hosono and co-workers (1997 Nature 389 939) proposed the concept of ‘chemical modulation of the valence band’ to mitigate this problem using hybridization of O 2p orbitals with close-shell Cu 3d 10 orbitals. This work has sparked tremendous interest in designing p-TCO materials together with deep understanding the underlying materials physics. In this article, we will provide a comprehensive review on traditional and recently emergent p-TCOs, including Cu+-based delafossites, layered oxychalcogenides, nd 6 spinel oxides, Cr3+-based oxides (3d 3) and post-transition metal oxides with lone pair state (ns 2). We will focus our discussions on the basic materials physics of these materials in terms of electronic structures, doping and defect properties for p-type conductivity and optical properties. Device applications based on p-TCOs for transparent p-n junctions will also be briefly discussed.

  14. Complete amino acid sequence of the Aspergillus cytotoxin mitogillin

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez-Luna, J.L.; Lopez-Otin, C.; Soriano, F.; Mendez, E.

    1985-02-12

    The complete amino acid sequence of the cytotoxin mitogillin has been determined by sequencing the intact chain and peptide fragments produced by cleavage at methionyl, arginyl, lysyl, and tryptophanyl residues and at one aspartic acid-proline bond. The protein consists of 149 amino acid residues with alanine at the NH/sub 2/ terminus and histidine at the COOH terminus. The calculated Mr of the native mitogillin was 16,867. The native molecule presents two disulfide bridges, one between cysteine residues at positions 5 and 147 and another one between cysteine residues at positions 75 and 131. The amino acid sequence of mitogillin shows 86% homology with another cytotoxic protein called alpha-sarcin.

  15. Rational design and evaluation of mammalian ribonuclease cytotoxins.

    Science.gov (United States)

    Lomax, Jo E; Eller, Chelcie H; Raines, Ronald T

    2012-01-01

    Mammalian pancreatic-type ribonucleases (ptRNases) comprise an enzyme family that is remarkably well suited for therapeutic exploitation. ptRNases are robust and prodigious catalysts of RNA cleavage that can naturally access the cytosol. Instilling cytotoxic activity requires endowing them with the ability to evade a cytosolic inhibitor protein while retaining other key attributes. These efforts have informed our understanding of ptRNase-based cytotoxins, as well as the action of protein-based drugs with cytosolic targets. Here, we address the most pressing problems encountered in the design of cytotoxic ptRNases, along with potential solutions. In addition, we describe assays that can be used to evaluate a successful design in vitro, in cellulo, and in vivo. The emerging information validates the continuing development of ptRNases as chemotherapeutic agents.

  16. Pleiotropic actions of Helicobacter pylori vacuolating cytotoxin, VacA.

    Science.gov (United States)

    Isomoto, Hajime; Moss, Joel; Hirayama, Toshiya

    2010-01-01

    Helicobacter pylori produces a vacuolating cytotoxin, VacA, and most virulent H. pylori strains secrete VacA. VacA binds to two types of receptor-like protein tyrosine phosphatase (RPTP), RPTPalpha and RPTPbeta, on the surface of host cells. VacA bound to RPTPbeta, relocates and concentrates in lipid rafts in the plasma membrane. VacA causes vacuolization, membrane anion-selective channel and pore formation, and disruption of endosomal and lysosomal activity in host cells. Secreted VacA is processed into p33 and p55 fragments. The p55 domain not only plays a role in binding to target cells but also in the formation of oligomeric structures and anionic membrane channels. Oral administration of VacA to wild-type mice, but not to RPTPbeta knockout mice, resulted in gastric ulcers, in agreement with the clinical effect of VacA. VacA with s1/m1 allele has more potent cytotoxic activity in relation to peptic ulcer disease and appears to be associated with human gastric cancer. VacA activates pro-apoptotic Bcl-2 family proteins, and induces apoptosis via a mitochondria-dependent pathway. VacA can disrupt other signal transduction pathways; VacA activates p38 MAPK, enhancing production of IL-8 and PGE(2), and PI3K/Akt, suppressing GSK-3beta activity. VacA has immunomodulatory actions on T cells and other immune cells, possibly contributing to the chronic infection seen with this organism. H. pylori virulence factors including VacA and CagA, which is encoded by cytotoxin-associated gene A, along with host genetic and environmental factors, constitute a complex network to regulate chronic gastric injury and inflammation, which is involved in a multistep process leading to gastric carcinogenesis.

  17. Experimental model of swine pneumonic pasteurellosis using crude Actinobacillus pleuropneumoniae cytotoxin and Pasteurella multocida given endobronchially.

    OpenAIRE

    Chung, W. B.; Bäckström, L R; Collins, M T

    1994-01-01

    This study was designed to develop and characterize a swine pneumonic pasteurellosis model by concurrent introduction of Pasteurella multocida type A and Actinobacillus pleuropneumoniae crude cytotoxin. After a series of preliminary experiments, a combination of 4 x 10(9) P. multocida and 4,000 toxic units of A. pleuropneumoniae crude cytotoxin was determined to produce optimal results. A total of 48 pigs were divided into four groups of 12 pigs each. The control group received buffered salin...

  18. Nitric oxide accelerates interleukin-13 cytotoxin-mediated regression in head and neck cancer animal model.

    Science.gov (United States)

    Kawakami, Koji; Kawakami, Mariko; Puri, Raj K

    2004-08-01

    Receptors for interleukin-13 (IL-13R) are overexpressed on several types of solid cancers including gliobastoma, renal cell carcinoma, AIDS Kaposi's sarcoma, and head and neck cancer. Recombinant fusion proteins IL-13 cytotoxin (IL13-PE38QQR or IL13-PE38) have been developed to directly target IL-13R-expressing cancer cells. Although it has been found that IL-13 cytotoxin has a direct potent antitumor activity in vivo in nude mice models of human cancers, the involvement of indirect antitumor effecter molecules such as nitric oxide (NO) is unknown. To address this issue, we assessed the effect of NO inhibiter N(omega)-monomethyl-l-arginine on IL-13 cytotoxin-mediated cytotoxicity and NO2/NO3 production in HN12 head and neck cancer cells. In addition, antitumor effects and NO levels in HN12 and KCCT873 head and neck tumors xenografted s.c. in nude mice when treated with IL-13 cytotoxin were evaluated by tumor measurement, Western blot, and immunohistochemistry analyses. Pretreatment of animals with N(omega)-monomethyl-l-arginine significantly decreased the NO levels and IL-13 cytotoxin-mediated antitumor effects. In addition, depletion of macrophages, known to produce NO, also decreased antitumor activity of IL-13 cytotoxin. Based on these studies, we concluded that NO accelerates antitumor effect of IL-13 cytotoxin on head and neck tumor cells. Because IL-13 cytotoxin is currently being tested in the clinic for the treatment of patients with recurrent glioblastoma maltiforme, our current findings suggest maintaining macrophage and NO-producing cellular function for optimal therapeutic effect of this targeted agent.

  19. Isolation and characterization of a cytotoxin produced by Plesiomonas shigelloides P-1 strain.

    Science.gov (United States)

    Okawa, Yoshio; Ohtomo, Yuko; Tsugawa, Hitoshi; Matsuda, Yuko; Kobayashi, Hidemitsu; Tsukamoto, Teizo

    2004-10-01

    In order to clarify the enteropathogenicity of Plesiomonas shigelloides, we investigated a cytotoxin produced by the P-1 strain isolated from patients suffering from diarrhea. The cytotoxicity of the culture filtrate of the strain reached a maximum in culture at 37 degrees C after 12 h shaken in BHI medium. The cytotoxin in the cultures was purified by (NH4)2SO4 precipitation, and Sephacryl S-100, Mono Q HR, and Superdex 200 HR column chromatographies. An approximate 340-fold purification was achieved, with a recovery of about 1.4%, from the culture supernatant. The cytotoxin is heat-stable, and is a complex of three major proteins (LPS-binding proteins with molecular weights of 32, 40, and 48 kDa), with lipopolysaccharide (LPS) giving a total a molecular weight of more than 600 kDa. The ratio of protein to LPS in the cytotoxin was 6-5. The cytotoxic activity was reduced by about 80% by proteinase K treatment or when incubated with anti-cholera toxin antibody (Anti-CT). Western blotting of the cytotoxin with Anti-CT demonstrated the presence of two anti-cholera toxin-reactive protein (ACRP) bands with molecular weights of 40 kDa (a major single protein band) and 48 kDa. The N-terminal amino acid sequence (20 residues) of the 40 kDa protein was 75% identical to Pasteurella multocida cell membrane proteins. The cytotoxin gave a positive reaction in the suckling mouse assay whereas LPS alone hardly exhibited any cytotoxic or enterotoxigenic activity. In conclusion, P. shigelloides produces a cytotoxin that consists of a complex of protein and LPS with the former component exhibiting both cytotoxicity and enteropathogenicity. This cytotoxin has the potential to have an important role in the enteropathogenicity of P. shigelloides.

  20. Purification and identification of Haemophilus ducreyi cytotoxin by use of a neutralizing monoclonal antibody.

    OpenAIRE

    Purvén, M; Frisk, A.; Lönnroth, I.; Lagergard, T

    1997-01-01

    Haemophilus ducreyi produces a cytotoxin responsible for the killing of cultured human epithelial cells. Cytotoxin-neutralizing antibodies were detected in the majority of sera from patients with culture-proven chancroid, and a significantly higher level of such antibodies in patients than in blood donors was noted both in areas where the disease is endemic and those where it is not. We produced neutralizing monoclonal antibodies (MAbs) in mice with a crude osmotic preparation of the cytotoxi...

  1. Actinobacillus pleuropneumoniae cytotoxins on size, granularity and viability of porcine neutrophils

    Directory of Open Access Journals (Sweden)

    Simson Tarigan

    1998-10-01

    Full Text Available Cytotoxins produced by Actinobacillus pleuropneumoniae are supposed to play major roles in bacterial pathogenicity and virulence. To gain better understanding in the mechanism of the pathogenicity, cytotoxic activities of the toxins on porcine neutrophils were investigated in vitro. Changes in cell size, granularity and viability were examined with a flow cytometer. Cell size and granularity correlate with forward light scatter and right angle light scatter, respectively; whereas, cell viability corresponds with fluorescent intensity of cells stained with propidium iodide . At low concentrations (dilutions between 1/10 and 1/100 of bacterial culture supernatants, the cytotoxins induced severe swelling and degranulation of neutrophils; whereas, at higher concentrations (dilutions of 51/10 bacterial culture supernatants, the cytotoxins caused rapid cell death. There was no significant difference in cytotoxic activities of Cyooxins derived from various serotypes (serotypes 1, 2, 3, 5 and 7 of A. pleuropneumoniae . Morphologically, the cytotoxin-treated neutrophils stained with Giemsa showed profound changes. Neutrophils treated with low dosages of Cyooxins became swollen with spherical nuclei . Higher concentration of cytotoxins study indicates strongly that important mechanism in the caused vactiolation of cytoplasts, enlargement or disintegration of nuclei . This in vitro intoxication of neutrophils by cytotoxins produced by A. pleuropneumoniae comprises anpathogenicity of the bacteria.

  2. MOLECULAR MODEL OF CYTOTOXIN-1 FROM NAJA MOSSAMBICA MOSSAMBICA VENOM IN COMPLEX WITH CHYMOTRYPSIN.

    Science.gov (United States)

    Munawar, Aisha; Akrem, Ahmed; Hussain, Ashiq; Spencer, Patrick; Betzel, Christian

    2015-01-01

    Snake venom is a myriad of biologically active proteins and peptides. Three finger toxins are highly conserved in their molecular structure, but interestingly possess diverse biological functions. During the course of evolution the introduction of subtle mutations in loop regions and slight variations in the three dimensional structure, has resulted in their functional versatility. Cytotoxin-1 (UniProt ID: P01467), isolated from Naja mossambica mossambica, showed the potential to inhibit chymotrypsin and the chymotryptic activity of the 20S proteasome. In the present work we describe a molecular model of cytotoxin-1 in complex with chymotrypsin, prepared by the online server ClusPro. Analysis of the molecular model shows that Cytotoxin-1 (P01467) binds to chymotrypsin through its loop I located near the N-terminus. The concave side of loop I of the toxin fits well in the substrate binding pocket of the protease. We propose Phe10 as the dedicated P1 site of the ligand. Being a potent inhibitor of the 20S proteasome, cytotoxin-1 (P01467) can serve as a potential antitumor agent. Already snake venom cytotoxins have been investigated for their ability as an anticancer agent. The molecular model of cytotoxin-1 in complex with chymotrypsin provides important information towards understanding the complex formation.

  3. Pasteurella haemolytica cytotoxin: purification, characterization, and an evaluation of its immunogenicity

    Energy Technology Data Exchange (ETDEWEB)

    Mosier, D.A.

    1985-01-01

    The primary goal of the study was to purify P. haemolytica cytotoxin from crude bacterial supernatants. A variety of column chromatographic techniques were evaluated. For each chromatographic procedure factions were evaluated by /sup 51/Cr release assays and enzyme-linked immunosorbent assays (ELISA). Native P. haemolytica cytotoxin is a 160 kilodalton (kDa) protein which is both cytotoxic and immunogenic. With SDS-PAGE it can be degraded into 4 primary proteins of 160, 66, 57, and 23 kDa. The 57 and 66 kDa proteins are antigenic in the bovine as determined by immunoblotting. The ELISA developed for the detection of anticytotoxin antibodies is highly specific for cytotoxic antigens and yields information similar to that obtained by cytotoxin neutralization assays. Cattle with high antibody titers to cytotoxin were found to be better protected against experimental transthoracic exposure to P. haemolytica than were cattle with low titers to cytotoxin. As a predictor of resistance to pneumonic pasteurellosis, cytotoxin ELISA titers were better than titers to somatic antigens.

  4. High prevalence of cytotoxin positive Helicobacter pylori in patients unrelated to the presence of peptic ulcers in Japan

    OpenAIRE

    Ogura, K.; Kanai, F; Maeda, S; Yoshida, H.; Ogura, M; Lan, K; Hirota, K; Kawabe, T; Shiratori, Y.; Omata, M

    1997-01-01

    Background—It has been reported that infection with vacuolating cytotoxin positive Helicobacter pylori strains is associated with gastroduodenal disease in Western countries. 
Aims—To evaluate the prevalence of cytotoxin producing strains among patients with H pylori infection in relation to gastrointestinal diseases in Japan. 
Patients—Ninety seven patients undergoing endoscopy. 
Methods—A Western blot assay was conducted to detect serum antibodies against the cytotoxin usi...

  5. Analysis of target genes induced by IL-13 cytotoxin in human glioblastoma cells.

    Science.gov (United States)

    Han, Jing; Yang, Liming; Puri, Raj K

    2005-03-01

    IL-13 cytotoxin comprised of IL-13 and a mutated form of Pseudomonas exotoxin (fusion protein termed IL-13-PE38QQR) has been shown to inhibit protein synthesis leading to necrotic and apoptotic cell death in glioblastoma cells that express high levels of interleukin-13 receptors (IL-13R). To identify target genes of cell death and other cellular genes with IL-13 receptors in glioblastoma cells, we utilized the cDNA microarrays to analyze global gene expression profiles after IL-13 cytotoxin and IL-13 treatment. IL-13 cytotoxin mediated cytotoxicity to U251 cells in a dose-dependent manner. Hierarchical cluster analysis of differentially expressed genes in U251 glioma cells at different time points after IL-13 cytotoxin treatment showed three major groups, each representing a specific expression pattern. Randomly selected differentially expressed genes from each group were confirmed by RT-PCR analysis. Most down-regulated genes belong to cell adhesion, motility, angiogenesis, DNA repair, and metabolic pathways. While up-regulated genes belong to cell cycle arrest, apoptosis, signaling and various metabolic pathways. Unexpectedly, at early time points, both IL-13 and IL-13 cytotoxin induced several genes belonging to different pathways most notably IL-8, DIO2, END1, and ALDH1A3 indicating that these genes are early response genes and their products may be associated with IL-13R. In addition, IL-13 cytotoxin induced IL-13Ralpha2 mRNA expression during the treatment in glioma cells. Our results indicate that novel cellular genes are involved with IL-13 receptors and that IL-13 cytotoxin induced cell death involves various target genes in human glioblastoma cells. On going studies will determine the role of associated genes and their products in the IL-13R functions in glioma cells.

  6. Ulcerative colitis and Crohn's disease tissue cytotoxins

    Energy Technology Data Exchange (ETDEWEB)

    McLaren, L.C.; Gitnick, G.

    1982-06-01

    Bowel-wall tissue filtrates from patients with inflammatory bowel disease produce cytopathic effects in tissue culture. The cytopathic effects inducers have been reported to have the characteristics of a small RNA virus. Clostridium difficile toxin also produces cytopathic effects and has been found in the stools of patients with Crohn's disease and ulcerative colitis. The present study concerns the further characterization of the cytopathic inducers in tissues of inflammatory bowel disease patients. It was found that they are nonsedimentable at 148,000 g for 2 h and resistant to inactivation by UV light. They are proteins that are distinct from C. difficile toxin and are unique cytotoxins which are associated with the early cytopathic effects observed in Riff-free chick embryo and rabbit ileum cell cultures. These results suggest that the early cytopathic effects previously described are not produced by a virus. They do not explain the delayed cytopathic effects seen in rabbit ileum or WI-38 cells.

  7. Total synthesis of a chlorosulpholipid cytotoxin associated with seafood poisoning.

    Science.gov (United States)

    Nilewski, Christian; Geisser, Roger W; Carreira, Erick M

    2009-01-29

    Each year, there are many cases of seafood poisoning in humans worldwide. Among the various toxins isolated that contribute to these poisonings, the chlorosulpholipids are particularly intriguing because of their structural and stereochemical complexity. The mechanism of biological activity remains unknown and, although chlorosulpholipids are associated with membranes in the organisms from which they are isolated, little is understood about their role within biological membranes. The lack of availability of the natural products has impaired more in-depth biochemical studies. So far, none of the chlorosulpholipids have been obtained from total synthesis, and efficient routes to their synthesis would be desirable for the preparation of material for pharmacological characterization and proper evaluation of the risk to human health. Despite the notable advances in the science of organic synthesis, reliable methods for stereoselective construction of polychlorinated acyclic substrates are lacking, although some preliminary investigations have appeared. Here we report the synthesis of a chlorosulpholipid cytotoxin, leading to confirmation of the proposed structure and the discovery of unanticipated reactivity of polychlorinated hydrocarbons. The concise synthetic approach should enable the preparation of material in sufficient quantities to facilitate biological studies.

  8. Characterization of a new cytotoxin that contributes to Staphylococcus aureus pathogenesis.

    Science.gov (United States)

    Dumont, Ashley L; Nygaard, Tyler K; Watkins, Robert L; Smith, Amanda; Kozhaya, Lina; Kreiswirth, Barry N; Shopsin, Bo; Unutmaz, Derya; Voyich, Jovanka M; Torres, Victor J

    2011-02-01

    Staphylococcus aureus is an important pathogen that continues to be a significant global health threat because of the prevalence of methicillin-resistant S. aureus strains (MRSA). The pathogenesis of this organism is partly attributed to the production of a large repertoire of cytotoxins that target and kill innate immune cells, which provide the first line of defence against S. aureus infection. Here we demonstrate that leukocidin A/B (LukAB) is required and sufficient for the ability of S. aureus, including MRSA, to kill human neutrophils, macrophages and dendritic cells. LukAB targets the plasma membrane of host cells resulting in cellular swelling and subsequent cell death. We found that S. aureus lacking lukAB are severely impaired in their ability to kill phagocytes during bacteria-phagocyte interaction, which in turn renders the lukAB-negative staphylococci more susceptible to killing by neutrophils. Notably, we show that lukAB is expressed in vivo within abscesses in a murine infection model and that it contributes significantly to pathogenesis of MRSA in an animal host. Collectively, these results extend our understanding of how S. aureus avoids phagocyte-mediated clearance, and underscore LukAB as an important factor that contributes to staphylococcal pathogenesis.

  9. Hodgkin lymphoma therapy with interleukin-4 receptor-directed cytotoxin in an infiltrating animal model.

    Science.gov (United States)

    Kawakami, Mariko; Kawakami, Koji; Kioi, Mitomu; Leland, Pamela; Puri, Raj K

    2005-05-01

    Hodgkin lymphoma represents unique clinicopathologic features because Hodgkin and Reed-Sternberg (H-RS) cells produce a variety of cytokines, express a variety of cytokine receptors, and are surrounded by numerous nonmalignant immunoreactive cells. We found that receptors for interleukin-4 (IL-4R) are highly expressed in H-RS cells. To target interleukin-4 receptor (IL-4R), we used a recombinant protein fusing circularly permuted human IL-4 and Pseudomonas exotoxin termed IL4(38-37)-PE38KDEL, or IL-4 cytotoxin. The cytotoxic effect of IL-4 cytotoxin on H-RS cell lines was determined to be moderate to high in vitro. We developed an infiltrating model of Hodgkin disease (HD) by injecting an adherent population of HD-MyZ cells subcutaneously into the flanks of beige/nude/X-linked immunodeficient mice. The animal model exhibited spontaneous metastasis of H-RS cells to lymph nodes and dissemination to vital organs, including the lungs. Intraperitoneal or intratumoral treatment of these mice with IL-4 cytotoxin resulted in regression of the primary tumor mass and a decrease in the incidence of lymph node metastasis. Mice injected with HD-MyZ cells demonstrated 203% prolonged survival (mean survival, 63 days) compared with control (mean survival, 31 days) when they received systemic IL-4 cytotoxin treatment. Because numerous H-RS cell lines express receptors for IL-4, IL-4 cytotoxin may be a unique agent for the treatment of Hodgkin lymphoma.

  10. Susceptibility of phagocytes from elk, deer, bighorn sheep, and domestic sheep to Pasteurella haemolytica cytotoxins.

    Science.gov (United States)

    Silflow, R M; Foreyt, W J

    1994-10-01

    Alveolar macrophages and peripheral blood neutrophils from elk (Cervus elaphus), bighorn sheep (Ovis canadensis canadensis), and domestic sheep were exposed to culture supernatants from Pasteurella haemolytica isolated from bighorn sheep and domestic sheep. In a second experiment, peripheral blood neutrophils from mule deer (Odocoileus hemionus), elk, and bighorn sheep were exposed to culture supernatants from P. haemolytica isolated from elk, bighorn sheep and domestic sheep. Alveolar macrophages from elk, bighorn sheep and domestic sheep were resistant to killing by P. haemolytica supernatants from bighorn sheep and domestic sheep; susceptibility of neutrophils to cell death, as measured by release of lactate dehydrogenase, differed significantly (P sheep and domestic sheep neutrophils were susceptible to cytotoxin damage by the P. haemolytica isolates used; bighorn sheep neutrophils were four- to eight-fold more susceptible to cytotoxin damage than domestic sheep neutrophils. Neutrophils from deer and elk were resistant to killing by P. haemolytica cytotoxins from any species tested.

  11. Is Cytotoxin K from Bacillus cereus a bona fide enterotoxin?

    Science.gov (United States)

    Castiaux, Virginie; Liu, Xiaojin; Delbrassinne, Laurence; Mahillon, Jacques

    2015-10-15

    Cytotoxin K (CytK) produced by Bacillus cereus s.l. has generally been considered to be associated with the foodborne diarrhoeal syndrome. Two distinct variants of CytK have been reported: CytK-1 from Bacillus cytotoxicus and CytK-2 from B. cereus. In order to determine whether CytK plays a significant role in the diarrhoeal disease, the occurrence of cytK genes was assessed among 390 B. cereus isolates with different origins including clinical and food poisoning samples and was found to be 46%. Interestingly, the cytK occurrence was slightly lower in food poisoning and clinical isolates than in environmental samples. Seventy cytK-2 positive strains (including 28 isolates from foodborne outbreaks) were then selected in order to assess their genetic diversity. A genetic dendrogram based on the cytK-2 sequences of these 70 strains and on two cytK-1 sequences from strains NVH 391-98 and 883-00 showed an important diversity. However, no strain clustering according to the origin or source of isolation was observed. These observations were confirmed by Multi-Locus Sequences Typing (MLST) based on five different loci of housekeeping genes (ccpA, recF, sucC, purF and gdpD) for which no grouping of foodborne outbreak strains could be identified. Therefore, the choice of cytK as virulence factor for the diarrhoeal pathotype does not seem to be relevant per se, even though the involvement of CytK in the diarrhoeal syndrome cannot be fully excluded. Potential synergistic effects between CytK and other virulence factors, together with their potential variable expression levels should be further investigated.

  12. Origin of the p-type character of AuCl3 functionalized carbon nanotubes

    KAUST Repository

    Murat, Altynbek

    2014-02-13

    The microscopic origin of the p-type character of AuCl3 functionalized carbon nanotubes (CNTs) is investigated using first-principles self-interaction corrected density functional theory (DFT). Recent DFT calculations suggest that the p-type character of AuCl3 functionalized CNTs is due to the Cl atoms adsorbed on the CNTs. We test this hypothesis and show that adsorbed Cl atoms only lead to a p-type character for very specific concentrations and arrangements of the Cl atoms, which furthermore are not the lowest energy configurations. We therefore investigate alternative mechanisms and conclude that the p-type character is due to the adsorption of AuCl4 molecules. The unraveling of the exact nature of the p-doping adsorbates is a key step for further development of AuCl3 functionalized CNTs in water sensor applications. © 2014 American Chemical Society.

  13. Theoretical prediction of p-type transparent conductivity in Zn-doped TiO2.

    Science.gov (United States)

    Han, Xiaoping; Shao, Guosheng

    2013-06-28

    It is very difficult and yet extremely important to fill the wide technological gap in developing transparent conducting oxides (TCOs) that exhibit excellent p-type conducting characteristics. Here, on the basis of extensive first-principles calculations, we discover for the first time potentially promising p-type transparent conductivity in Zn-doped TiO2 under oxygen rich conditions. Efforts have been made to elaborate the effects of possible defects and their interaction with Zn doping on the p-type transparent conductivity. This work offers a fundamental road map for cost-effective development of p-type TCOs based on TiO2, which is a cheap and stable material system of large natural resources.

  14. Purification and characterization of cytotoxin produced by a clinical isolate of Vibrio cholerae O54 TV113.

    Science.gov (United States)

    Isac, Sree Renjini; Nair, Gopinath Balakrish; Singh, Durg Vijai

    2012-06-01

    Vibrio cholerae O54 TV113 isolated from a diarrheal patient produces an extracellular cytotoxin that caused alteration in the morphology of Chinese hamster ovary cells manifested as cell shrinkage with intact cell boundaries and finally causing cell death. Syncase medium supplemented with lincomycin (50 μg/ml), pH 7.2, and 18 h incubation with shaking at 37 °C supported optimal cytotoxin production. We isolated and purified this cytotoxin to homogeneity by ultrafiltration, 40-80 % ammonium sulfate precipitation, gradient-anion exchange chromatography, stepwise-anion exchange chromatography, and size exclusion chromatography increasing the specific activity by 866-fold. The cytotoxin is heat-labile, sensitive to protease and papain, and has a molecular weight of 64 kDa determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and enterotoxic activity in rabbit ileal loop assay. Both cytotoxic and enterotoxic activity could be inhibited or neutralized by antiserum raised against purified cytotoxin but not by preimmune serum. Immunodiffusion test between purified cytotoxin and its antiserum gave a single well-defined precipitin band showing reaction of complete identity and a well-defined single band in an immunoblot assay. This study thus indicate that the cytotoxin expressed by strain TV113 has both cytotoxic and enterotoxic activity and appears to contribute in pathogenesis of non-O1, non-O139 strains.

  15. Vero cytotoxin binding to polymorphonuclear leukocytes among households with children with hemolytic uremic syndrome.

    NARCIS (Netherlands)

    Loo, D.M.W.M. te; Heuvelink, A.E.; Boer, E. de; Nauta, J.; Walle, J. van der; Schröder, C.H.; Hinsbergh, V.W.H. van; Chart, H.; Kar, N.C.A.J. van de; Heuvel, L.P.W.J. van den

    2001-01-01

    Hemolytic uremic syndrome (HUS), the leading cause of acute renal failure in childhood, can be caused by different serotypes of vero cytotoxin (VT; i.e., Shiga toxin)-producing Escherichia coli (VTEC). Recently, VT was shown to bind to polymorphonuclear leukocytes (PMNL) in the systemic circulation

  16. Chemical modification of methionines in a cobra venom cytotoxin differentiates between lytic and binding domains.

    Science.gov (United States)

    Stevens-Truss, R; Hinman, C L

    1996-08-01

    Cytotoxin-III from Naja naja atra (CTX) was chemically modified at either or both of its two methionine residues: Over 50% oxidation of methionine-26 occurred with a 1:1 molar ratio of chloramine-T:methionine; at a 5:1 molar ratio, methionine-26 was almost completely oxidized, while methionine-24 was modified only 26%; at a 10:1 molar ratio, both methionines were completely oxidized. Each oxidized derivative demonstrated a lower toxicity toward T-cells than toward heart cells. Conversely, binding to heart cells was affected more than binding to T-cells. Cyanogen bromide cleaved native CTX at both methionines, excising phenyl-alanine-25 and methionine-26 and converting methionine-24 to homoserine lactone. This treatment of CTX eliminated cytotoxicity toward both heart and T-cells, but had only a modest effect upon T-cell binding, as had 50% oxidation of methionine-26, suggesting that CTX lytic and binding regions may be distinct. A selective loss in heart cell binding following oxidation of methionine-24 further suggests that different parts of CTX may interact with the two types of target cells. Perturbation of the relatively flat hydrophobic surface of the CTX' triple-stranded beta-sheet could result from the introduction of negative charge due to methionine-24 oxidation. Alternatively, amino acid side chain participation in a CTX binding domain may be altered by the potential formation of a new hydrogen bond between tyrosine-51 and methionine-24 sulfoxide, as revealed by computer modeling of the completely oxidized CTX derivative.

  17. [Effects of intratumoral injection of microspheres containing cobra venom cytotoxin on transplanted human hepatoma in nude mice].

    Science.gov (United States)

    Wang, Yan; Lin, Li-wu; Chen, Zhi-kui; Xue, En-sheng; Lin, Xiao-dong; Yu, Li-Yun; Lin, Zhen-hu

    2009-09-01

    To evaluate the safety and efficacy of intratumoral injection of polylactic-co-glycolic acid (PLGA) microspheres containing cobra venom cytotoxin in nude mice with transplanted human hepatoma. Cytotoxic activity of cytotoxin from cobra venom was determined by using methyl thiazolyl tetrazolium method in vitro. Microspheres containing cobra venom cytotoxin were prepared with a double emulsion-solvent evaporation method. Forty BALB/c nude mice were inoculated subcutaneously in right flank with hepatoma BEL-7404 cells. Thirty-two mice whose tumor size reached about 1.0 cm in diameter, were randomly assigned into normal saline group, blank microsphers group, cytotoxin group and cytotoxin-PLGA group. Nude mice were intratumorally injected with normal saline, blank microspheres, cytotoxin or cytotoxin-PLGA microspheres respectively. Internal echo characteristics and blood flow of tumors were observed by high-frequency ultrasound every week after treatment. Twenty-six days after treatment, the tumors were removed to calculate the inhibition rate of tumor growth. The tumor, heart, liver and kidney tissues were obtained for histopathological examination. The cytotoxin separated and purified from crude cobra venom caused intense cytotoxic effects to the BEL-7404 cells in vitro. The diameter of PLGA microspheres containing cobra venom cytotoxin was about (34.45+/-9.85)microm. Encapsulation rate was up to (78.13+/-8.92)%, and cumulative amount of cobra venom cytotoxin released from the PLGA microspheres in vitro during 30 days was up to 84.3%. After intratumoral injection, tumor volumes and weights in the cytotoxin-PLGA group were lower than those in the normal saline group, with a tumor growth inhibition rate of 52.36%. Observed under a light microscope, most tumor tissues were necrotic. No obvious morphological change could be seen on the liver, kidney and heart tissues. The above findings indicate that intratumoral injection of cytotoxin-PLGA microspheres has strong

  18. (Ga,Fe)Sb: A p-type ferromagnetic semiconductor

    Energy Technology Data Exchange (ETDEWEB)

    Tu, Nguyen Thanh; Anh, Le Duc; Tanaka, Masaaki [Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656 (Japan); Hai, Pham Nam [Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656 (Japan); Department of Physical Electronics, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro, Tokyo 152-0033 (Japan)

    2014-09-29

    A p-type ferromagnetic semiconductor (Ga{sub 1−x},Fe{sub x})Sb (x = 3.9%–13.7%) has been grown by low-temperature molecular beam epitaxy (MBE) on GaAs(001) substrates. Reflection high energy electron diffraction patterns during the MBE growth and X-ray diffraction spectra indicate that (Ga,Fe)Sb layers have the zinc-blende crystal structure without any other crystallographic phase of precipitates. Magnetic circular dichroism (MCD) spectroscopy characterizations indicate that (Ga,Fe)Sb has the zinc-blende band structure with spin-splitting induced by s,p-d exchange interactions. The magnetic field dependence of the MCD intensity and anomalous Hall resistance of (Ga,Fe)Sb show clear hysteresis, demonstrating the presence of ferromagnetic order. The Curie temperature (T{sub C}) increases with increasing x and reaches 140 K at x = 13.7%. The crystal structure analyses, magneto-transport, and magneto-optical properties indicate that (Ga,Fe)Sb is an intrinsic ferromagnetic semiconductor.

  19. Interleukin 4 receptor on human lung cancer: a molecular target for cytotoxin therapy.

    Science.gov (United States)

    Kawakami, Mariko; Kawakami, Koji; Stepensky, Vitaly A; Maki, Richard A; Robin, Howard; Muller, Wayne; Husain, Syed R; Puri, Raj K

    2002-11-01

    Previous studies have demonstrated that human lung tumor cell lines express interleukin 4 (IL-4) receptors, and IL-4 can mediate modest to moderate antiproliferative activity in vitro and in vivo in animal models of human lung tumors. On the basis of these studies, IL-4 was tested in clinical trials; however, it showed little antitumor activity in lung cancer patients. In the present study, we examined the expression of IL-4 receptors (IL-4Rs) in lung tumor samples and normal lung tissues and tested whether an IL-4R targeted agent will have better antitumor activity in vitro and in vivo compared with IL-4. IL-4R expression was tested by immunohistochemistry in 54 lung tumor samples and normal lung tissues in a tissue array, by reverse-transcription PCR and Northern blot analyses in lung tumor cell lines. Cytotoxic activity of IL-4 cytotoxin [IL-4(38-37)-PE38KDEL], composed of a circular permuted IL-4 and a mutated form of Pseudomonas exotoxin (PE38KDEL) was tested by protein synthesis inhibition and clonogenic assays in seven lung tumor cell lines. Antitumor activity of IL-4 cytotoxin was tested in vitro and in immunodeficient animal models of human lung tumors. We observed that IL-4Rs are expressed at higher levels in situ in lung tumor samples compared with normal lung tissues and IL-4 cytotoxin is highly and specifically cytotoxic to lung tumor cell lines in vitro. Intratumoral and i.p. administration of IL-4 cytotoxin to immunodeficient mice with s.c. established human lung H358 non-small cell lung cancer tumors mediated considerable antitumor activity in a dose-dependent manner with the higher dose producing durable complete responses. On the other hand, H460 non-small cell lung cancer tumors expressing low levels of IL-4R did not respond to IL-4 cytotoxin therapy. Because IL-4 cytotoxin mediates its antitumor activity through IL-4R, and a variety of lung tumors expressed high levels of IL-4R, we propose testing the safety of this agent in patients with lung

  20. Characterization, synthesis and self-aggregation of (-)-alternarlactam: a new fungal cytotoxin with cyclopentenone and isoquinolinone scaffolds.

    Science.gov (United States)

    Zhang, Ai Hua; Jiang, Nan; Gu, Wen; Ma, Jing; Wang, Yu Rong; Song, Yong Chun; Tan, Ren Xiang

    2010-12-27

    (-)-Alternarlactam [(-)-1], a new promising cytotoxin against two human cancer cell lines, was isolated from an endophyte culture and synthesized (along with (+)-1) from readily available starting materials. The absolute configuration, chirality-activity relevance and self-aggregation of (-)-1 were assigned by a combination of synthetic, spectroscopic and computational approaches. The full characterization of the new fungal cytotoxin may provide valuable information in the discovery of new antitumor agents.

  1. Cytotoxin-induced NADPH oxides activation: roles in regulation of cell death.

    Science.gov (United States)

    Zhang, Yongtao; Bi, Xiaolei; Jiang, Fan

    2015-07-01

    Numerous studies have shown that a variety of cytotoxic agents can activate the NADPH oxidase system and induce redox-dependent regulation of cellular functions. Cytotoxin-induced NADPH oxidase activation may either exert cytoprotective actions (e.g., survival, proliferation, and stress tolerance) or cause cell death. Here we summarize the experimental evidence showing the context-dependent dichotomous effects of NADPH oxidase on cell fate under cytotoxic stress conditions and the potential redox signaling mechanisms underlying this phenomenon. Clearly, it is difficult to create a unified paradigm on the toxicological implications of NADPH oxidase activation in response to cytotoxic stimuli. We suggest that interventional strategies targeting the NADPH oxidase system to prevent the adverse impacts of cytotoxins need to be contemplated in a stimuli- and cell type-specific manner.

  2. Isolation of a gene that is involved in Campylobacter jejuni 81116 cytotoxin activation.

    Science.gov (United States)

    Liu, Kaiyan; Fry, Benjamin N; Coloe, Peter J

    2007-02-01

    Cytotoxin fractions were isolated from Campylobacter jejuni 81116 and semi-purified by size-exclusion liquid chromatography. The fraction showing the strongest toxicity was injected into mice to produce antiserum. The antiserum was used to screen a C. jejuni 81116 cosmid library. Nine genes were identified in overlapping cosmid inserts that induced reactivity with the antiserum. One of these genes showed high similarity to a periplasmic protein of unknown function and its isogenic mutant showed decreased toxicity compared to the C. jejuni 81116 wild type. This gene contains a Gram-negative bacterial RTX toxin-activating protein C signature, which suggests it may play a role in C. jejuni 81116 cytotoxin activation.

  3. Ocular immune responses in steers following intranasal vaccination with recombinant Moraxella bovis cytotoxin adjuvanted with polyacrylic acid.

    Science.gov (United States)

    Angelos, John A; Edman, Judy M; Chigerwe, Munashe

    2014-02-01

    Infectious bovine keratoconjunctivitis (IBK) caused by Moraxella bovis is the most common eye disease of cattle. The pathogenesis of M. bovis requires the expression of pili that enable the organism to attach to the ocular surface and an RTX (repeats in the structural toxin) toxin (cytotoxin or hemolysin), which is cytotoxic to corneal epithelial cells. In this pilot study, ocular mucosal immune responses of steers were measured following intranasal (i.n.) vaccination with a recombinant M. bovis cytotoxin adjuvanted with polyacrylic acid. Beef steers were vaccinated with either 500 μg (n = 3) or 200 μg (n = 3) of recombinant M. bovis cytotoxin plus adjuvant. Control group steers (n = 2) were vaccinated with adjuvant alone, and all steers were given a booster on day 21. Antigen-specific tear IgA and tear IgG, tear cytotoxin-neutralizing antibody responses, and serum cytotoxin-neutralizing antibody responses were determined in samples collected prevaccination and on days 14, 28, 42, and 55. Changes in tear antigen-specific IgA levels from day 0 to days 28, 42, and 55 were significantly different between groups; however, in post hoc comparisons between individual group pairs at the tested time points, the differences were not significant. Our results suggest that i.n. vaccination of cattle with recombinant M. bovis cytotoxin adjuvanted with polyacrylic acid effects changes in ocular antigen-specific IgA concentrations. The use of intranasally administered recombinant M. bovis cytotoxin adjuvanted with polyacrylic acid could provide an alternative to parenteral vaccination of cattle for immunoprophylaxis against IBK.

  4. The vacuolating cytotoxin of Helicobacter pylori%幽门螺杆菌空泡毒素研究进展

    Institute of Scientific and Technical Information of China (English)

    刘纯杰; 陶好霞; 张兆山

    2001-01-01

    幽门螺杆菌空泡毒素是该菌产生的与已知其它细菌毒素无明显同源性的唯一蛋白毒素。该毒素是幽门螺杆菌重要的毒力致病因子,它的产生与感染者胃肠上皮损伤和溃疡形成密切相关。本文就幽门螺杆菌空泡毒素的结构与功能研究进展以及在未来免疫预防与免疫治疗中的作用进行了简述。%The vacuolating cytotoxin is a unique proteinous cytotoxin producted by H. pylori that showed no striking primary sequence homology with other known baterial toxins. The cytotoxin is an important fator in the pathogenesis of H. pylori, which induces vacuolation of epithelial cells and plays an important role in gastric epithelial necrosis and peptic ulceration. In the paper, the progress on structure and function of the vacuolating cytotoxin of H. pylori and the roles of the H. pylori vacuolating cytotoxin in the future immunoprophylaxis and immunotherapy were reviewed.

  5. Kinetics of self-interstitials reactions in p-type silicon irradiated with alpha particles

    Energy Technology Data Exchange (ETDEWEB)

    Makarenko, L.F., E-mail: makarenko@bsu.by [Department of Applied Mathematics and Computer Science, Belarusian State University, Independence Ave. 4, 220030 Minsk (Belarus); Moll, M. [CERN, Geneva (Switzerland); Evans-Freeman, J.H. [University of Canterbury, Christchurch (New Zealand); Lastovski, S.B.; Murin, L.I.; Korshunov, F.P. [Scientific-Practical Materials Research Centre of NAS of Belarus, Minsk (Belarus)

    2012-08-01

    New findings on the self-interstitial migration in p-type silicon are presented. They are based on experimental studies of the formation kinetics of defects related to interstitial carbon after irradiation with alpha particles. The main parameters characterizing the interaction rate of silicon self-interstitials with substitutional carbon atoms have been determined. A preliminary interpretation of the experimental data is given. The interpretation takes into account different diffusivities of self-interstitials in their singly and doubly ionized states.

  6. Characterization of the Vacuolating Cytotoxin in Helicobacter pylori Strains Isolated from Iran

    Directory of Open Access Journals (Sweden)

    Akbar Oghalaie

    2010-01-01

    Full Text Available Objective: Helicobacter pylori (H. pylori cytotoxin and its heterogeneity amongst strains hasbeen closely linked to the varying infection-associated clinical outcomes. In order to determinethe decisive role of the vacuolating cytotoxin (vacA gene mosaicism in its corresponding geneexpression and phenotype, we aimed to characterize vacA alleles of different H. pylori strainsin addition to the resulting protein and its vacuolating activity in epithelial cell culture.Materials and Methods: vacA gene polymorphism was determined for 80 H. pylori strainsisolated from dyspeptic patients, using multiplex gene-specific polymerase chain reaction(PCR. VacA protein was detected by immuno-blotting assay using a polyclonal anti-VacAantibody. In vitro cytotoxicity assay was conducted on HeLa cells in order to evaluate thevacuolating cytotoxin activity.Results: Genotyping revealed the following strain distribution: 26 (32.5% s1m1, 35(43.8% s1m2, and 19 (23.8% s2m2 subtypes. Infection with s1m1 type strain was significantlyassociated with gastric cancer as compared to non-ulcer dyspepsia (p=0.005and peptic ulcer disease (p=0.008. A 95-kDa immuno-reactive band that represented thevacuolating toxin was demonstrated in SDS-PAGE analysis of concentrated culture filtrate(CCF of H. pylori strains. H. pylori CCFs induced HeLa cell vacuolation which correlatedwith the strain genotype; s1m1 strains demonstrated higher levels of vacuolation as comparedto s1m2 strains, whereas s2m2 strains showed no detectable cytotoxic activity.Conclusion: The current study confirmed the relatively high cytotoxic activity of s1m1type H. pylori strains which infect the majority of patients suffering from gastric cancer andmay be partly responsible for the pathogenesis of this mortal disease.

  7. Transient expression of P-type ATPases in tobacco epidermal cells

    DEFF Research Database (Denmark)

    Pedas, Lisbeth Rosager; Palmgren, Michael Broberg; Lopez Marques, Rosa Laura

    2016-01-01

    Transient expression in tobacco cells is a convenient method for several purposes such as analysis of protein-protein interactions and the subcellular localization of plant proteins. A suspension of Agrobacterium tumefaciens cells carrying the plasmid of interest is injected into the intracellular...... for example protein-protein interaction studies. In this chapter, we describe the procedure to transiently express P-type ATPases in tobacco epidermal cells, with focus on subcellular localization of the protein complexes formed by P4-ATPases and their β-subunits....

  8. Development in p-type Doping of ZnO

    Institute of Scientific and Technical Information of China (English)

    YU Liping; ZHU Qiqiang; FAN Dayong; LAN Zili

    2012-01-01

    Zinc oxide (ZnO) is a wide band-gap material of the Ⅱ-Ⅵ group with excellent optical properties for optoelectronics applications,such as the flat panel displays and solar cells used in sports tournament.Despite its advantages,the application of ZnO is hampered by the lack of stable p-type doping.In this paper,the recent progress in this field was briefly reviewed,and a comprehensive summary of the research was carried out on ZnO fabrication methods and its electrical,optical,and magnetic properties were presented.

  9. P-type conductivity in annealed strontium titanate

    Energy Technology Data Exchange (ETDEWEB)

    Poole, Violet M.; Corolewski, Caleb D.; McCluskey, Matthew D., E-mail: mattmcc@wsu.edu [Department of Physics and Astronomy, Washington State University, Pullman, WA 99164-2814 (United States)

    2015-12-15

    Hall-effect measurements indicate p-type conductivity in bulk, single-crystal strontium titanate (SrTiO{sub 3}, or STO) samples that were annealed at 1200°C. Room-temperature mobilities above 100 cm{sup 2}/V s were measured, an order of magnitude higher than those for electrons (5-10 cm{sup 2}/V s). Average hole densities were in the 10{sup 9}-10{sup 10} cm{sup −3} range, consistent with a deep acceptor.

  10. Bi-Se doped with Cu, p-type semiconductor

    Science.gov (United States)

    Bhattacharya, Raghu Nath; Phok, Sovannary; Parilla, Philip Anthony

    2013-08-20

    A Bi--Se doped with Cu, p-type semiconductor, preferably used as an absorber material in a photovoltaic device. Preferably the semiconductor has at least 20 molar percent Cu. In a preferred embodiment, the semiconductor comprises at least 28 molar percent of Cu. In one embodiment, the semiconductor comprises a molar percentage of Cu and Bi whereby the molar percentage of Cu divided by the molar percentage of Bi is greater than 1.2. In a preferred embodiment, the semiconductor is manufactured as a thin film having a thickness less than 600 nm.

  11. Measurement of the dead layer thickness in a p-type point contact germanium detector

    Science.gov (United States)

    Jiang, Hao; Yue, Qian; Li, Yu-Lan; Kang, Ke-Jun; Li, Yuan-Jing; Li, Jin; Lin, Shin-Ted; Liu, Shu-Kui; Ma, Hao; Ma, Jing-Lu; Su, Jian; Tsz-King Wong, Henry; Yang, Li-Tao; Zhao, Wei; Zeng, Zhi

    2016-09-01

    A 994 g mass p-type PCGe detector has been deployed during the first phase of the China Dark matter EXperiment, aiming at direct searches for light weakly interacting massive particles. Measuring the thickness of the dead layer of a p-type germanium detector is an issue of major importance since it determines the fiducial mass of the detector. This work reports a method using an uncollimated 133Ba source to determine the dead layer thickness. The experimental design, data analysis and Monte Carlo simulation processes, as well as the statistical and systematic uncertainties are described. A dead layer thickness of 1.02 mm was obtained based on a comparison between the experimental data and the simulated results. Supported by National Natural Science Foundation of China (10935005, 10945002, 11275107, 11175099)

  12. Metal Fluoride Inhibition of a P-type H+ Pump

    Science.gov (United States)

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

    2015-01-01

    The plasma membrane H+-ATPase is a P-type ATPase responsible for establishing electrochemical gradients across the plasma membrane in fungi and plants. This essential proton pump exists in two activity states: an autoinhibited basal state with a low turnover rate and a low H+/ATP coupling ratio and an activated state in which ATP hydrolysis is tightly coupled to proton transport. Here we characterize metal fluorides as inhibitors of the fungal enzyme in both states. In contrast to findings for other P-type ATPases, inhibition of the plasma membrane H+-ATPase by metal fluorides was partly reversible, and the stability of the inhibition varied with the activation state. Thus, the stability of the ATPase inhibitor complex decreased significantly when the pump transitioned from the activated to the basal state, particularly when using beryllium fluoride, which mimics the bound phosphate in the E2P conformational state. Taken together, our results indicate that the phosphate bond of the phosphoenzyme intermediate of H+-ATPases is labile in the basal state, which may provide an explanation for the low H+/ATP coupling ratio of these pumps in the basal state. PMID:26134563

  13. Staphylococcus epidermidis and Staphylococcus haemolyticus: Molecular Detection of Cytotoxin and Enterotoxin Genes.

    Science.gov (United States)

    Pinheiro, Luiza; Brito, Carla Ivo; de Oliveira, Adilson; Martins, Patrícia Yoshida Faccioli; Pereira, Valéria Cataneli; da Cunha, Maria de Lourdes Ribeiro de Souza

    2015-09-14

    Although opportunistic pathogens, coagulase-negative staphylococci (CoNS), including Staphylococcus epidermidis and Staphylococcus haemolyticus, have long been regarded as avirulent organisms. The role of toxins in the development of infections caused by CoNS is still controversial. The objective of this study was to characterize the presence of enterotoxin and cytotoxin genes in S. epidermidis and S. haemolyticus isolates obtained from blood cultures. Cytotoxin genes were detected by PCR using novel species-specific primers. Among the 85 S. epidermidis and 84 S. haemolyticus isolates, 95.3% and 79.8%, respectively, carried at least one enterotoxin gene. The most frequent enterotoxin genes were sea (53.3%), seg (64.5%) and sei (67.5%). The seg gene was positively associated with S. epidermidis (p = 0.02), and this species was more toxigenic than S. haemolyticus. The hla/yidD gene was detected in 92.9% of S. epidermidis and the hla gene in 91.7% of S. haemolyticus isolates; hlb was detected in 92.9% of the S. epidermidis isolates and hld in 95.3%. Nosocomial Staphylococcus epidermidis and S. haemolyticus isolates exhibited a high toxigenic potential, mainly producing the non-classical enterotoxins seg and sei. The previously unreported detection of hla/yidD and hlb in S. epidermidis and S. haemolyticus using species-specific primers showed that these hemolysin genes differ between CoNS species and that they are highly frequent in blood culture isolates.

  14. Recombinant Moraxella bovoculi cytotoxin-ISCOM matrix adjuvanted vaccine to prevent naturally occurring infectious bovine keratoconjunctivitis.

    Science.gov (United States)

    Angelos, John A; Lane, V Michael; Ball, Louise M; Hess, John F

    2010-03-01

    A randomized, blinded, controlled field trial was conducted during summer 2006 in a northern California, USA, herd of beef cattle to evaluate the efficacy of a recombinant Moraxella bovoculi cytotoxin subunit vaccine to prevent naturally occurring infectious bovine keratoconjunctivitis (IBK; pinkeye). A convenience sample comprised of 127 steers were administered a subcutaneous dose of either adjuvant alone (ISCOM matrices; control group) or recombinant M. bovoculi cytotoxin carboxy terminus adjuvanted with ISCOM matrices (MbvA group) and were boostered 21 days later. The steers were examined once weekly for 15 weeks for evidence of IBK. No significant difference in the cumulative proportion of corneal ulcerations was detected between groups. Compared to the control calves, the MbvA vaccinates had significantly higher increases in serum neutralizing titers to M. bovoculi hemolysin between week 0 and week 6. The prevalence of M. bovis isolations was higher from ulcerated eyes of calves vaccinated with MbvA as compared to control calves. Vaccination of calves against the carboxy terminus of M. bovoculi RTX toxin resulted in significant increases in serum hemolysin neutralizing titers and may modulate organism type cultured from ulcerated eyes of calves in herds where both M. bovis and M. bovoculi exist. Use of M. bovoculi antigens alone in vaccines to prevent IBK may not be beneficial in herds where IBK is associated with both M. bovoculi and M. bovis.

  15. Prevalence of Helicobacter pylori vacuolating cytotoxin and its allelic mosaicism as a predictive marker for Iranian dyspeptic patients

    DEFF Research Database (Denmark)

    Mohammadi, M; Oghalaie, A; Mohajerani, N

    2003-01-01

    Helicobacter pylori infects the majority of the population in the developing countries. However, the rate of gastrointestinal complications such as peptic ulcers and gastric malignancies has no parallel with the infection. In order to determine whether cytotoxin (vacA) and its allelic polymorphis...

  16. Tolevamer is not efficacious in the neutralization of cytotoxin in a human gut model of Clostridium difficile infection.

    Science.gov (United States)

    Baines, Simon D; Freeman, Jane; Wilcox, Mark H

    2009-05-01

    The efficacy of tolevamer, a nonantimicrobial styrene derivative toxin-binding agent, in treating simulated Clostridium difficile infection in an in vitro human gut model was investigated. Tolevamer reduced neither the duration nor magnitude of cytotoxin activity by C. difficile, reflecting poor efficacy observed in recent phase III clinical trials.

  17. The occurrence of subtilase-cytotoxin-encoding genes in environmental Escherichia coli isolated from a Northern California estuary.

    Science.gov (United States)

    Pereira, Maria das Graças C; Byrne, Barbara A; Nguyen, Trân B H; Lewis, David J; Atwill, E Robert

    2013-06-01

    The presence of subtilase-cytotoxin-encoding genes was determined in 397 environmental Escherichia coli strains isolated from water, suspended solids, and sediments sampled from different hydrological and environmental conditions in a California estuary. A total of 7 strains (1.76%) were found to harbor subtilase-cytotoxin-encoding genes. Using primers targeting subA only, we generated PCR amplicons from 2 strains; while using primers targeting the 3' end of SubA downstream to the 5' end of SubB, amplicons of 232 bp were generated from 5 additional strains. The 556 bp subA sequences were almost identical to that in the subtilase-cytotoxin-positive strain ED 591 (98%), while subAB sequences of 2 non-Shiga-toxigenic strains revealed 100% similarity with the Shiga-toxigenic E. coli O113:H21 strain 98NK2 that was isolated from an outbreak of hemolytic uremic syndrome. Additionally, the serogroup O113:H21 was present in this collection of environmental E. coli, and it was found to harbor stx2d, hra1 that encodes the heat resistant agglutinin 1, and a subAB sequence similar to that in the non-Shiga-toxigenic E. coli subtilase cytotoxin strain ED 591. To further understand potential health risks posed by strains encoding SubAB, future epidemiological studies should consider screening isolates for subAB regardless of the presence of Shiga-toxin-encoding genes.

  18. p-Type NiO Hybrid Visible Photodetector.

    Science.gov (United States)

    Mallows, John; Planells, Miquel; Thakare, Vishal; Bhosale, Reshma; Ogale, Satishchandra; Robertson, Neil

    2015-12-23

    A novel hybrid visible-light photodetector was created using a planar p-type inorganic NiO layer in a junction with an organic electron acceptor layer. The effect of different oxygen pressures on formation of the NiO layer by pulsed laser deposition shows that higher pressure increases the charge carrier density of the film and lowers the dark current in the device. The addition of a monolayer of small molecules containing conjugated π systems and carboxyl groups at the device interface was also investigated and with correct alignment of the energy levels improves the device performance with respect to the quantum efficiency, responsivity, and photogeneration. The thickness of the organic layer was also optimized for the device, giving a responsivity of 1.54 × 10(-2) A W(-1) in 460 nm light.

  19. Elucidating Functional Aspects of P-type ATPases

    DEFF Research Database (Denmark)

    Autzen, Henriette Elisabeth

    2015-01-01

    similar to that of the wild type (WT) protein. The discrepancy between the newly determined crystal structure of LpCopA and the functional manifestations of the missense mutation in human CopA, could indicate that LpCopA is insufficient in structurally elucidating the effect of disease-causing mutations...... cancer and pathogenic microbes. The goal of this Ph.D. dissertation was to functionally characterize SERCA1a and CopA from Legionella pneumophila (LpCopA) through a range of different methods within structural biology. Crystallographic studies of SERCA1a led to a newly determined crystal structure......P-type ATPases are proteins that act to maintain ion homeostasis and electrochemical gradients through the translocation of cations across cell membranes. Underscoring their significance in humans, dysfunction of the ATPases can lead to crucial diseases. Dysfunction of the sarco...

  20. Study on the p-type QWIP-LED device

    Institute of Scientific and Technical Information of China (English)

    ZHEN; Honglou; XIONG; Dayuan; ZHOU; Xuchang; LI; Ning; SHAO; Jun; LU; Wei

    2006-01-01

    A p-type quantum well infrared photodetector (QWIP) integrated with a light-emitting diode (LED) (named QWIP-LED) was fabricated and studied. The infrared photo-response spectrum was obtained from the device resistance variation and the near-infrared photo-emission intensity variation. A good agreement between these two spectra was observed, which demonstrates that the long-wavelength infrared radiation around 7.5 μm has been transferred to the near-infrared light at 0.8 μm by the photo-electronic process in the QWIP-LED structure. Moreover, the experimentally observed infrared response wavelength is in good agreement with the theoretical calculation value of 7.7 μm. The results on the upconversion of the infrared radiation will be very useful for the new infrared focal plane array technology.

  1. Vacuolating cytotoxin A (VacA) - A multi-talented pore-forming toxin from Helicobacter pylori.

    Science.gov (United States)

    Junaid, Muhammad; Linn, Aung Khine; Javadi, Mohammad Bagher; Al-Gubare, Sarbast; Ali, Niaz; Katzenmeier, Gerd

    2016-08-01

    Helicobacter pylori is associated with severe and chronic diseases of the stomach and duodenum such as peptic ulcer, non-cardial adenocarcinoma and gastric lymphoma, making Helicobacter pylori the only bacterial pathogen which is known to cause cancer. The worldwide rate of incidence for these diseases is extremely high and it is estimated that about half of the world's population is infected with H. pylori. Among the bacterial virulence factors is the vacuolating cytotoxin A (VacA), which represents an important determinant of pathogenicity. Intensive characterization of VacA over the past years has provided insight into an ample variety of mechanisms contributing to host-pathogen interactions. The toxin is considered as an important target for ongoing research for several reasons: i) VacA displays unique features and structural properties and its mechanism of action is unrelated to any other known bacterial toxin; ii) the toxin is involved in disease progress and colonization by H. pylori of the stomach; iii) VacA is a potential and promising candidate for the inclusion as antigen in a vaccine directed against H. pylori and iv) the vacA gene is characterized by a high allelic diversity, and allelic variants contribute differently to the pathogenicity of H. pylori. Despite the accumulation of substantial data related to VacA over the past years, several aspects of VacA-related activity have been characterized only to a limited extent. The biologically most significant effect of VacA activity on host cells is the formation of membrane pores and the induction of vacuole formation. This review discusses recent findings and advances on structure-function relations of the H. pylori VacA toxin, in particular with a view to membrane channel formation, oligomerization, receptor binding and apoptosis.

  2. Recycling of p-type mc-si Top Cuts into p-type mono c-Si Solar Cells

    Energy Technology Data Exchange (ETDEWEB)

    Bronsveld, P.C.P.; Manshanden, P.; Lenzmann, F.O. [ECN Solar Energy, Westerduinweg 3, P.O. Box 1, NL-1755 ZG Petten (Netherlands); Gjerstad, O. [Si Pro Holding AS, Ornesveien 3, P.O. Box 37, 8161, Glomfjord (Norway); Oevrelid, E.J. [SINTEF, Alfred Getz Vei 2, 7465, Trondheim (Norway)

    2013-07-01

    Solar cell results and material analysis are presented of 2 p-type Czochralski (Cz) ingots pulled from a charge consisting of 100% and 50% recycled multicrystalline silicon top cuts. The top cuts were pre-cleaned with a dedicated low energy consuming technology. No structure loss was observed in the bodies of the ingots. The performance of solar cells made from the 100% recycled Si ingot decreases towards the seed end of the ingot, which could be related to a non-optimal pulling process. Solar cells from the tail end of this ingot and from the 50% recycled Si ingot demonstrated an average solar cell efficiency of 18.6%. This is only 0.1% absolute lower than the efficiency of higher resistivity reference solar cells from commercially available wafers that were co-processed.

  3. Symplocamide A, a potent cytotoxin and chymotrypsin inhibitor from the marine Cyanobacterium Symploca sp.

    Science.gov (United States)

    Linington, Roger G; Edwards, Daniel J; Shuman, Cynthia F; McPhail, Kerry L; Matainaho, Teatulohi; Gerwick, William H

    2008-01-01

    Investigation of a Symploca sp. from Papua New Guinea has led to the isolation of symplocamide A (1), a potent cancer cell cytotoxin, which also inhibits serine proteases with a 200-fold greater inhibition of chymotrypsin over trypsin. The complete stereostructure of symplocamide A was determined by detailed NMR and MS analysis as well as chiral HPLC analysis of the component amino acid residues. The presence of several unusual structural features in symplocamide A provides new insights into the pharmacophore model for protease selectivity in this drug class and may underlie the potent cytotoxicity of this compound to H-460 lung cancer cells (IC50=40 nM) as well as neuro-2a neuroblastoma cells (IC50=29 nM).

  4. Infrared Transparent Spinel Films with p -Type Conductivity

    Energy Technology Data Exchange (ETDEWEB)

    Windisch, Charles F.; Exarhos, Gregory J.; Ferris, Kim F.; Engelhard, Mark H.; Stewart, Donald C.

    2001-11-29

    Spinel oxide films containing at least two transition metal cations were found to exhibit p-type conductivity with high optical transparency from the visible to wavelengths near 15 micrometers. Resistivities as low as 0.003 ohm-cm were measured on 100 nm thick rf sputter deposited films that contained nickel and cobalt. Optical spectra, Raman scattering and XPS measurements indicated the valency of nickel localized on octahedral sites within the spinel lattice determines these properties. Electronic band structure calculations corroborated the experimental results. A resistivity minimum was found at the composition NiCo2O4 deposited from aqueous or alcoholic solutions followed by subsequent annealing at 400 degrees C in air. Solution deposited films richer in nickel than this stoichiometry always were found to phase separate into nickel oxide and a spinel phase with concomitant loss in conductivity. However, the phase stability region could be extended to higher nickel contents when rf-sputter deposition techniques were used. Sputter deposited spinel films having a nickel to cobalt ratio less than 2 were found to exhibit the highest conductivity. Results suggest that the phase stability region for these materials can be extended through appropriate choice of deposition conditions. A possible mechanism that promotes high conductivity in this system is thought to be charge transfer between the resident di- and trivalent cations that may be assisted by the magnetic nature of the oxide film.

  5. Electronic processes in uniaxially stressed p-type germanium

    Energy Technology Data Exchange (ETDEWEB)

    Dubon, Jr., Oscar Danilo [Univ. of California, Berkeley, CA (United States)

    1996-02-01

    Effect of uniaxial stress on acceptor-related electronic processes in Ge single crystals doped with Ga, Be, and Cu were studied by Hall and photo-Hall effect measurements in conjunction with infrared spectroscopy. Stress dependence of hole lifetime in p-type Ge single crystals is used as a test for competing models of non-radiative capture of holes by acceptors. Photo-Hall effect shows that hole lifetime in Ga- and Be-doped Ge increases by over one order of magnitude with uniaxial stress at liq. He temps. Photo-Hall of Ge:Be shows a stress-induced change in the temperature dependence of hole lifetime. This is consistent with observed increase of responsivity of Ge:Ga detectors with uniaxial stress. Electronic properties of Ge:Cu are shown to change dramatically with uniaxial stress; the results provide a first explanation for the performance of uniaxially stressed, Cu-diffused Ge:Ga detectors which display a high conductivity in absence of photon signal and therefore have poor sensitivity.

  6. P type porous silicon resistivity and carrier transport

    Energy Technology Data Exchange (ETDEWEB)

    Ménard, S., E-mail: samuel.menard@st.com [STMicroelectronics, 10, rue Thalès de Milet, 37071 Tours Cedex 2 (France); Fèvre, A. [STMicroelectronics, 10, rue Thalès de Milet, 37071 Tours Cedex 2 (France); Université François Rabelais de Tours, CNRS, CEA, INSA CVL, GREMAN UMR 7347, Tours (France); Billoué, J.; Gautier, G. [Université François Rabelais de Tours, CNRS, CEA, INSA CVL, GREMAN UMR 7347, Tours (France)

    2015-09-14

    The resistivity of p type porous silicon (PS) is reported on a wide range of PS physical properties. Al/PS/Si/Al structures were used and a rigorous experimental protocol was followed. The PS porosity (P{sub %}) was found to be the major contributor to the PS resistivity (ρ{sub PS}). ρ{sub PS} increases exponentially with P{sub %}. Values of ρ{sub PS} as high as 1 × 10{sup 9} Ω cm at room temperature were obtained once P{sub %} exceeds 60%. ρ{sub PS} was found to be thermally activated, in particular, when the temperature increases from 30 to 200 °C, a decrease of three decades is observed on ρ{sub PS}. Based on these results, it was also possible to deduce the carrier transport mechanisms in PS. For P{sub %} lower than 45%, the conduction occurs through band tails and deep levels in the tissue surrounding the crystallites. When P{sub %} overpasses 45%, electrons at energy levels close to the Fermi level allow a hopping conduction from crystallite to crystallite to appear. This study confirms the potential of PS as an insulating material for applications such as power electronic devices.

  7. Photoconduction spectroscopy of p-type GaSb films

    Energy Technology Data Exchange (ETDEWEB)

    Shura, M.W., E-mail: Megersa.Shura@live.nmmu.ac.za [Department of Physics, P.O. Box 77000, Nelson Mandela Metropolitan University, Port Elizabeth 6031 (South Africa); Wagener, V.; Botha, J.R.; Wagener, M.C. [Department of Physics, P.O. Box 77000, Nelson Mandela Metropolitan University, Port Elizabeth 6031 (South Africa)

    2012-05-15

    Excess carrier lifetimes (77 K) have been measured as function of the absorbed flux density in undoped p-type gallium antimonide films (GaSb/GaAs) using steady state photoconductivity measurements with the illumination wavelength of 1.1 {mu}m. Using the results from Hall effect measurements along with the relations describing the lifetimes of the excess minority carriers in the bulk of the films and at the surface, the theoretical values of the effective excess carrier lifetime in the materials were also calculated. Discrepancies between the experimental and theoretical results were described using a two-layer model, by considering the variation in the charge distribution within the layer due to the presence of surface states, as well as the band offset between the layer and the substrate. Theoretical modeling of the experimental result yields values of different parameters such as band bending at the surface, minimum value of Shockley-Read-Hall lifetime and maximum value of the surface recombination velocity.

  8. An outbreak of Vero cytotoxin producing Escherichia coli O157 infection associated with takeaway sandwiches.

    LENUS (Irish Health Repository)

    McDonnell, R J

    1997-12-12

    An outbreak of food poisoning due to Escherichia coli O157 phage type 2 Vero cytotoxin 2 affected 26 people in southern counties of England in May and June 1995. The organism was isolated from faecal specimens from 23 patients, 16 of whom lived in Dorset and seven in Hampshire. Isolates were indistinguishable by phage typing, Vero cytotoxin gene typing, restriction fragment length polymorphism, and pulsed field gel electrophoresis. Three associated cases, linked epidemiologically to the outbreak, were confirmed serologically by detection of antibodies to E. coli O157 lipopolysaccharide. Twenty-two of the 26 patients were adults: four were admitted to hospital with haemorrhagic colitis. Four cases were children: two were admitted to hospital with haemolytic uraemic syndrome (HUS). There were no deaths. Although E. coli O157 was not isolated from any food samples, illness was associated with having eaten cold meats in sandwiches bought from two sandwich producers, in Weymouth and in Portsmouth. Both shops were supplied by the same wholesaler, who kept no records and obtained cooked meats from several sources in packs that did not carry adequate identification marks. It was, therefore, impossible to trace back to the original producer or to investigate further to determine the origin of contamination with E. coli O157. To protect the public health it is essential that all wholesale packs of ready-to-eat food carry date codes and the producer\\'s identification mark. Detailed record keeping should be part of hazard analysis critical control point (HACCP) systems and should be maintained throughout the chain of distribution from the producer to retail outlets.

  9. Serotype-related differences in production and type of heat-labile hemolysin and heat-labile cytotoxin of Actinobacillus (Haemophilus) pleuropneumoniae.

    OpenAIRE

    Kamp, E M; van Leengoed, L A

    1989-01-01

    Reference strains of serotypes 1 to 12 of Actinobacillus (Haemophilus) pleuropneumoniae were cultured in Eagle minimal essential medium with 10% Serum Plus. Culture supernatants were examined for cytotoxicity to alveolar macrophages and for the ability to hemolyze sheep erythrocytes. All strains except the reference strain of serotype 6 produced cytotoxin, whereas only serotypes 1, 5, 9, 10, and 11 produced hemolysin. Both cytotoxin and hemolysin appeared to be heat labile. Antisera were rais...

  10. Selective permeabilization of cervical cancer cells to an ionic DNA-binding cytotoxin by activation of P2Y receptors.

    Science.gov (United States)

    Bukhari, Maurish; Deng, Han; Jones, Noelle; Towne, Zachary; Woodworth, Craig D; Samways, Damien S K

    2015-06-04

    Extracellular ATP is known to permeabilize certain cell types to polyatomic cations like YO-PRO1. Here, we report that extracellularly applied ATP stimulated rapid uptake and accumulation of an otherwise weakly membrane permeable fluorescent DNA-binding cytotoxin, Hoechst 33258, into cervical cancer cells. While ATP stimulated Hoechst 33258 uptake in 20-70% of cells from seven cervical cancer cell lines, it stimulated uptake in less than 8% of cervical epithelial cells obtained from the normal transformation zone and ectocervix tissue of 11 patients. ATP-evoked Hoechst 33258 uptake was independent of ionotropic P2X receptors, but dependent on activation of P2Y receptors. Thus, we show here that cervical cancer cells can be selectively induced to take up and accumulate an ionic cytotoxin by exposure to extracellular ATP.

  11. 3,5-Bis(3-alkylaminomethyl-4-hydroxybenzylidene)-4-piperidones: A Novel Class of Potent Tumor-Selective Cytotoxins.

    Science.gov (United States)

    Karki, Subhas S; Das, Umashankar; Umemura, Naoki; Sakagami, Hiroshi; Iwamoto, Shoko; Kawase, Masami; Balzarini, Jan; De Clercq, Erik; Dimmock, Stephen G; Dimmock, Jonathan R

    2016-01-28

    Novel 4-piperidone derivatives 2a-f are disclosed as potent cytotoxins. Many of these compounds are more potent than the reference drug melphalan. The compounds in series 2, 4-7 display selective toxicities toward various neoplasms compared to some normal cells. 2a is one of the promising lead molecules that display >11-fold higher growth inhibiting potency than 5-fluorouracil against human colon cancer cells. 2a induces apoptosis, DNA fragmentation, and cleavage of poly ADP-ribose polymerase.

  12. Increased seropositivity of Helicobacter pylori cytotoxin-associated gene-A in Behçet's disease.

    Science.gov (United States)

    Apan, Teoman Zafer; Gürsel, Ragip; Dolgun, Alp

    2007-06-01

    Behçet's disease is a systemic vasculitic syndrome with unknown etiology. The aim of the present study was to compare the Helicobacter pylori seropositivity and cytotoxin associated gene-A status in patients with Behçet's disease. Ninety-one patients with Behçet's disease and 83 age- and sex-matched persons with or without any gastrointestinal complaints were included in the study. Demographic characteristics and H. pylori IgG, IgM, and cytotoxin-associated gene-A IgG status of the Behçet's disease and the control groups were analyzed. The influence of eradication therapy on clinical findings was also determined. The prevalence of H. pylori IgG seropositivity was slightly but not significantly higher in patients with Behçet's disease compared to the controls [72 (79.1%) vs 56 (67.5%), (p = 0.082)]. The prevalence of cytotoxin-associated gene A positivity was significantly higher in Behçet's disease compared to the controls [59 (64.8.%) vs 32 (38.5%), respectively, (p = 0.002)]. Eradication of H. pylori has significantly decreased clinical manifestations such as oral and genital ulceration, arthritis/arthralgia, and cutaneous findings of Bahçet's disease. Our study indicates that H. pylori may be involved in the pathogenesis of Behçet's disease or disease activity might be enhanced due to induced inflammation or altered immunity.

  13. Carrier induced local moment magnetization in p-type Sn1-xMnxTe

    Science.gov (United States)

    Behera, Sashi S.; Tripathi, Pratibha; Nayak, Sanjeev K.; Tripathi, Gouri S.

    2017-08-01

    We derive a theory of carrier induced local moment magnetization of p-type Sn1-xMnxTe based on the Hubbard model, k → · π → electronic structure method (k → is the electronic wave vector and π → is the relativistic momentum operator) and the statistical paramagnetic approach for the localized moments. The Hubbard model is used to derive an internal exchange magnetic field. The difference in exchange self-energy is expressed in terms of an internal exchange field that is proportional to the parameter U, the onsite Coulomb repulsion, and the spin-density of carriers. In the present theory, the k → · π → + U model is integrated with the statistical paramagnetic theory for localized spins, which is then solved in a self-consistent manner by adding the exchange field to the applied field. The technique is applied to study the magnetic properties of p-type Sn1-xMnxTe, an important material for spintronics devices. The local moment magnetization calculated using the total magnetic field self-consistently agrees with the experimental observations. Magnetization and the exchange field studied as functions of the applied field, temperature and carrier concentration yield results on expected lines. Ours is a mechanism that is different from the RKKY interaction, normally invoked for carrier induced ferromagnetism and is thus a novelty.

  14. Ultraviolet light-emitting diodes with polarization-doped p-type layer

    Science.gov (United States)

    Hu, Wenxiao; Qin, Ping; Song, Weidong; Zhang, Chongzhen; Wang, Rupeng; Zhao, Liangliang; Xia, Chao; Yuan, Songyang; Yin, Yian; Li, Shuti

    2016-09-01

    We report ultraviolet light emitting diode (LEDs) with polarization doped p-type layer. Fabricated LEDs with polarization doped p-type layer exhibited reduced forward voltage and enhanced light output power, compared to those with traditional p-type AlGaN layer. The improvement is attributed to improved hole concentration and the smooth valence band by the polarization enhanced p-type doping. Our simulated results reveal that this p-type layer can further enhance the performance of ultraviolet LEDs by removing the electron blocking layer (EBL).

  15. [A single strand comformation polymorphism of vacuolating cytotoxin gene in H. pylori].

    Science.gov (United States)

    Peng, H; Pan, G; Chao, S

    1999-03-01

    To use PCR/SSCP analysis of the vacuolating cytotoxin gene (vacA) of H. pylori for differentiation of various strains of H. pylori. PCR was performed using the primers amplifing vacA gene of the bacteria embeded in the gastric mucosa of 159 patients with various gastric duodenal diseases. The products of PCR were further processed for SSCP analysis and southern blot hybridization. In the meantime, vacA genes of three different SSCP-patterns from three patients with duodenal ulcers were sequenced. The rate of detection of H. pylori with the method was 100%. vacA1 and vacA2, the two subtypes of vacA, were 76.5% (114/149) and 23.5%(35/149), respectively. Eight different SSCP-patterns were distributed in various gastroduodenal diseases, and that 80% of duodenal ulcers was predominated with B pattern. Sequencing of DNA indicated a diversity of vacA gene structure. PCR/SSCP can be used in the differentiation of different strains of H. pylori in epidemology, and in the follow up study after H. pylori eradication, especially in the differentiation between H. pylori recrudescence and reinfection.

  16. Relationship between Helicobacterpylori bearing the cytotoxin associated gene-A and cerebral infarction

    Institute of Scientific and Technical Information of China (English)

    Li Yajun; An Eenglian; Zhu Yongqing; MaoXiaolin; Wang Yumei

    2000-01-01

    Objective To explore the relationship between virulent Helicobacter pylori strains infection and cerebral infarction. Method We assessed the prevalence of infection by strains bearing the cytotoxin -associated gene-A(Cag-A),a strong virulence factor ,in 83 patients with cerebral infarction and in 71 age- and sex-matched controls with similar social background. Result Prevalence of Helicobacter pylori infection was significantly higher in patients than in controls(78.3% versus 56.3%,p<0.05),with an odds ratio of 2.8(95%CI,1.46 to 5.36) adjusted for age, sex, main stroke factors. Patients with cerebral infarction also had a higher prevalence of Cag-A-positive strains(45.8% versus 19.7%, P<0.01),with an adjusted odds ratio of 3.43(95%CI 1.5 to 7.24).Conclusion It was suggested that chronic Helicobacter pylori infection, especially Cag-A-positive strains infection is an independent risk factor for cerebral infarction.

  17. DXD Motif-Dependent and -Independent Effects of the Chlamydia trachomatis Cytotoxin CT166

    Directory of Open Access Journals (Sweden)

    Miriam Bothe

    2015-02-01

    Full Text Available The Gram-negative, intracellular bacterium Chlamydia trachomatis causes acute and chronic urogenital tract infection, potentially leading to infertility and ectopic pregnancy. The only partially characterized cytotoxin CT166 of serovar D exhibits a DXD motif, which is important for the enzymatic activity of many bacterial and mammalian type A glycosyltransferases, leading to the hypothesis that CT166 possess glycosyltransferase activity. CT166-expressing HeLa cells exhibit actin reorganization, including cell rounding, which has been attributed to the inhibition of the Rho-GTPases Rac/Cdc42. Exploiting the glycosylation-sensitive Ras(27H5 antibody, we here show that CT166 induces an epitope change in Ras, resulting in inhibited ERK and PI3K signaling and delayed cell cycle progression. Consistent with the hypothesis that these effects strictly depend on the DXD motif, CT166 with the mutated DXD motif causes neither Ras-ERK inhibition nor delayed cell cycle progression. In contrast, CT166 with the mutated DXD motif is still capable of inhibiting cell migration, suggesting that CT166 with the mutated DXD motif cannot be regarded as inactive in any case. Taken together, CT166 affects various fundamental cellular processes, strongly suggesting its importance for the intracellular survival of chlamydia.

  18. DXD motif-dependent and -independent effects of the chlamydia trachomatis cytotoxin CT166.

    Science.gov (United States)

    Bothe, Miriam; Dutow, Pavel; Pich, Andreas; Genth, Harald; Klos, Andreas

    2015-02-17

    The Gram-negative, intracellular bacterium Chlamydia trachomatis causes acute and chronic urogenital tract infection, potentially leading to infertility and ectopic pregnancy. The only partially characterized cytotoxin CT166 of serovar D exhibits a DXD motif, which is important for the enzymatic activity of many bacterial and mammalian type A glycosyltransferases, leading to the hypothesis that CT166 possess glycosyltransferase activity. CT166-expressing HeLa cells exhibit actin reorganization, including cell rounding, which has been attributed to the inhibition of the Rho-GTPases Rac/Cdc42. Exploiting the glycosylation-sensitive Ras(27H5) antibody, we here show that CT166 induces an epitope change in Ras, resulting in inhibited ERK and PI3K signaling and delayed cell cycle progression. Consistent with the hypothesis that these effects strictly depend on the DXD motif, CT166 with the mutated DXD motif causes neither Ras-ERK inhibition nor delayed cell cycle progression. In contrast, CT166 with the mutated DXD motif is still capable of inhibiting cell migration, suggesting that CT166 with the mutated DXD motif cannot be regarded as inactive in any case. Taken together, CT166 affects various fundamental cellular processes, strongly suggesting its importance for the intracellular survival of chlamydia.

  19. Effect of Helicobacter pylori's vacuolating cytotoxin on the autophagy pathway in gastric epithelial cells.

    Science.gov (United States)

    Terebiznik, Mauricio R; Raju, Deepa; Vázquez, Cristina L; Torbricki, Karl; Kulkarni, Reshma; Blanke, Steven R; Yoshimori, Tamotsu; Colombo, María I; Jones, Nicola L

    2009-04-01

    Host cell responses to Helicobacter pylori infection are complex and incompletely understood. Here, we report that autophagy is induced within human-derived gastric epithelial cells (AGS) in response to H. pylori infection. These autophagosomes were distinct and different from the large vacuoles induced during H. pylori infection. Autophagosomes were detected by transmission electron microscopy, conversion of LC3-I to LC3-II, GFP-LC3 recruitment to autophagosomes, and depended on Atg5 and Atg12. The induction of autophagy depended on the vacuolating cytotoxin (VacA) and, moreover, VacA was sufficient to induce autophagosome formation. The channel-forming activity of VacA was necessary for inducing autophagy. Intracellular VacA partially co-localized with GFP-LC3, indicating that the toxin associates with autophagosomes. The inhibition of autophagy increased the stability of intracellular VacA, which in turn resulted in enhanced toxin-mediated cellular vacuolation. These findings suggest that the induction of autophagy by VacA may represent a host mechanism to limit toxin-induced cellular damage.

  20. The production and detoxification of a potent cytotoxin, nitric oxide, by pathogenic enteric bacteria.

    Science.gov (United States)

    Arkenberg, Anke; Runkel, Sebastian; Richardson, David J; Rowley, Gary

    2011-12-01

    The nitrogen cycle is based on several redox reactions that are mainly accomplished by prokaryotic organisms, some archaea and a few eukaryotes, which use these reactions for assimilatory, dissimilatory or respiratory purposes. One group is the Enterobacteriaceae family of Gammaproteobacteria, which have their natural habitats in soil, marine environments or the intestines of humans and other warm-blooded animals. Some of the genera are pathogenic and usually associated with intestinal infections. Our body possesses several physical and chemical defence mechanisms to prevent pathogenic enteric bacteria from invading the gastrointestinal tract. One response of the innate immune system is to activate macrophages, which produce the potent cytotoxin nitric oxide (NO). However, some pathogens have evolved the ability to detoxify NO to less toxic compounds, such as the neuropharmacological agent and greenhouse gas nitrous oxide (N₂O), which enables them to overcome the host's attack. The same mechanisms may be used by bacteria producing NO endogenously as a by-product of anaerobic nitrate respiration. In the present review, we provide a brief introduction into the NO detoxification mechanisms of two members of the Enterobacteriaceae family: Escherichia coli and Salmonella enterica serovar Typhimurium. These are discussed as comparative non-pathogenic and pathogenic model systems in order to investigate the importance of detoxifying NO and producing N₂O for the pathogenicity of enteric bacteria.

  1. Methods to monitor autophagy in H. pylori vacuolating cytotoxin A (VacA)-treated cells.

    Science.gov (United States)

    Raju, Deepa; Jones, Nicola L

    2010-01-01

    Helicobacter pylori is a gram negative pathogen that infects at least half of the world's population and is associated not only with gastric cancer but also with other diseases such as gastritis and peptic ulcers. Indeed, H. pylori is considered the single most important risk factor for the development of gastric cancer. The vacuolating cytotoxin VacA, secreted by H. pylori, promotes intracellular survival of the bacterium and modulates host immune responses. In a recent study, we reported that VacA induces autophagy. Multilamellar autophagosomes are detected in gastric epithelial cells that are distinct from the large vacuoles formed by VacA. Furthermore, inhibition of autophagy stabilizes VacA and reduces vacuolation in the cells indicating that the toxin is being degraded by autophagy, thus limiting toxin-induced host cell damage. Many of the methods that were used for this study are commonly employed techniques that were adapted for H. pylori infection and VacA intoxication. In this paper, we describe the various methods and specific protocols used for the assessment and monitoring of autophagy during H. pylori infection.

  2. Nitric oxide: perspectives and emerging studies of a well known cytotoxin.

    Science.gov (United States)

    Paradise, William A; Vesper, Benjamin J; Goel, Ajay; Waltonen, Joshua D; Altman, Kenneth W; Haines, G Kenneth; Radosevich, James A

    2010-07-16

    The free radical nitric oxide (NO(*)) is known to play a dual role in human physiology and pathophysiology. At low levels, NO(*) can protect cells; however, at higher levels, NO(*) is a known cytotoxin, having been implicated in tumor angiogenesis and progression. While the majority of research devoted to understanding the role of NO(*) in cancer has to date been tissue-specific, we herein review underlying commonalities of NO(*) which may well exist among tumors arising from a variety of different sites. We also discuss the role of NO(*) in human physiology and pathophysiology, including the very important relationship between NO(*) and the glutathione-transferases, a class of protective enzymes involved in cellular protection. The emerging role of NO(*) in three main areas of epigenetics-DNA methylation, microRNAs, and histone modifications-is then discussed. Finally, we describe the recent development of a model cell line system in which human tumor cell lines were adapted to high NO(*) (HNO) levels. We anticipate that these HNO cell lines will serve as a useful tool in the ongoing efforts to better understand the role of NO(*) in cancer.

  3. Safety and vaccine efficacy of an attenuated Vibrio vulnificus strain with deletions in major cytotoxin genes.

    Science.gov (United States)

    Kim, Young Ran; Lee, Shee Eun; Kim, Jong Ro; Rhee, Joon Haeng

    2015-12-01

    Vibrio vulnificus is a human pathogen causing a rapidly progressing fatal septicemia. We have previously reported that a V. vulnificus large toxin RtxA1 causes programmed necrotic cell death through calcium-mediated mitochondrial dysfunction. Here we developed a live attenuated vaccine strain (CMM781) having deletions in three genes encoding major virulence factors: RTX cytotoxin (rtxA1), hemolysin/cytolysin (vvhA) and metalloprotease (vvpE) of a clinical isolate strain CMCP6. The CMM781 strain showed significant attenuation in cytotoxicity and mouse lethality. The safety of CMM781 was also confirmed by measuring the transepithelial electric resistance of Caco-2 cell monolayers. Intragastric immunization of mice with the live attenuated V. vulnificus strain resulted in induction of systemic and mucosal antibodies specific to the pathogen. Moreover, the vaccinated mice were protected from challenges with high doses of the virulent strain through various injection routes. These results suggest that CMM781 appears to be a safe and effective vaccine candidate that would provide significant protection against V. vulnificus infection.

  4. Estimating risk of C. difficile transmission from PCR positive but cytotoxin negative cases.

    Directory of Open Access Journals (Sweden)

    Mini Kamboj

    Full Text Available BACKGROUND: The use of molecular methods to diagnose Clostridium difficile infection (CDI has improved diagnostic yield compared to conventional methods. However, PCR testing can detect colonization and has introduced several practical challenges pertaining to need for treatment and isolation of cases. METHODS: For all new cases detected by real-time PCR, concurrent cytotoxin assay was performed and genetic characterization with MLVA (multi-locus variable number tandem repeat analysis was done to determine relatedness. We used PCR cycle threshold (Ct of detection as surrogate marker for bacterial burden in stool. RESULTS: Overall, 54 cases of CDI were detected during the study period. 42 were concurrently tested by CYT and characterized by MLVA .MLVA analysis revealed marked genetic diversity with no ongoing outbreaks; four cases were due to NAP1 strain. CYT -/PCR + cases had a higher median Ct value of detection compared to CYT+/PCR + cases (28.2 vs 22.5; p = 0.01. Among 25 strains that were genetically related, 9/11 isolates in this dominant cluster were positive by CYT compared to 4/14 in non-dominant clusters (p = 0.02. CONCLUSION: CYT-/PCR+ cases contribute to hospital based transmission. However, the risk of transmission of C. difficile from CYT +/PCR+ cases may be higher than those that are CYT-/PCR+.

  5. Chaperone-Targeting Cytotoxin and Endoplasmic Reticulum Stress-Inducing Drug Synergize to Kill Cancer Cells

    Directory of Open Access Journals (Sweden)

    Joseph M. Backer

    2009-11-01

    Full Text Available Diverse physiological and therapeutic insults that increase the amount of unfolded or misfolded proteins in the endoplasmic reticulum (ER induce the unfolded protein response, an evolutionarily conserved protective mechanism that manages ER stress. Glucose-regulated protein 78/immunoglobulin heavy-chain binding protein (GRP78/BiP is an ER-resident protein that plays a central role in the ER stress response and is the only known substrate of the proteolytic A subunit (SubA of a novel bacterial AB5 toxin. Here, we report that an engineered fusion protein, epidermal growth factor (EGF-SubA, combining EGF and SubA, is highly toxic to growing and confluent epidermal growth factor receptor-expressing cancer cells, and its cytotoxicity is mediated by a remarkably rapid cleavage of GRP78/BiP. Systemic delivery of EGF-SubA results in a significant inhibition of human breast and prostate tumor xenografts in mouse models. Furthermore, EGF-SubA dramatically increases the sensitivity of cancer cells to the ER stress-inducing drug thapsigargin, and vice versa, demonstrating the first example of mechanism-based synergism in the action of a cytotoxin and an ER-targeting drug.

  6. A new oxytocin-saporin cytotoxin for lesioning oxytocin-receptive neurons in the rat hindbrain.

    Science.gov (United States)

    Baskin, Denis G; Kim, Francis; Gelling, Richard W; Russell, Brian J; Schwartz, Michael W; Morton, Gregory J; Simhan, Hyagriv N; Moralejo, Daniel H; Blevins, James E

    2010-09-01

    Evidence suggests that release of oxytocin in the nucleus tractus solitarius (NTS) of the hindbrain from descending projections that originate in the paraventricular nucleus can inhibit food intake by amplifying the satiety response to cholecystokinin (CCK). To further evaluate this mechanism in rats, we used a novel cytotoxin, saporin conjugated to oxytocin (OXY-SAP), a compound designed to destroy cells that express oxytocin receptors (OXYr). OXY-SAP was injected directly into the NTS to lesion neurons that express OXYr and that are implicated in potentiating CCK's satiety effects. The control consisted of injection of saporin conjugated to a nonsense peptide. We found that OXY-SAP was cytotoxic to human uterine smooth muscle cells in vitro, demonstrating that OXY-SAP can lesion cells that express OXYr. Using laser capture microdissection and real-time quantitative PCR, we demonstrated that OXYr mRNA levels were reduced in the NTS after OXY-SAP administration. Moreover, we found that OXY-SAP attenuated the efficacy of CCK-8 to reduce food intake and blocked the actions of an OXYr antagonist to stimulate food intake. The findings suggest that OXY-SAP is an effective neurotoxin for in vivo elimination of cells that express OXYr and is potentially useful for studies to analyze central nervous system mechanisms that involve the action of oxytocin on food intake and other physiological processes.

  7. Nitric Oxide: Perspectives and Emerging Studies of a Well Known Cytotoxin

    Directory of Open Access Journals (Sweden)

    James A. Radosevich

    2010-07-01

    Full Text Available The free radical nitric oxide (NO● is known to play a dual role in human physiology and pathophysiology. At low levels, NO● can protect cells; however, at higher levels, NO● is a known cytotoxin, having been implicated in tumor angiogenesis and progression. While the majority of research devoted to understanding the role of NO● in cancer has to date been tissue-specific, we herein review underlying commonalities of NO● which may well exist among tumors arising from a variety of different sites. We also discuss the role of NO● in human physiology and pathophysiology, including the very important relationship between NO● and the glutathione-transferases, a class of protective enzymes involved in cellular protection. The emerging role of NO● in three main areas of epigenetics—DNA methylation, microRNAs, and histone modifications—is then discussed. Finally, we describe the recent development of a model cell line system in which human tumor cell lines were adapted to high NO● (HNO levels. We anticipate that these HNO cell lines will serve as a useful tool in the ongoing efforts to better understand the role of NO● in cancer.

  8. Bacillus cereus cytotoxins Hbl, Nhe and CytK are secreted via the Sec translocation pathway

    Directory of Open Access Journals (Sweden)

    Lindbäck Toril

    2010-11-01

    Full Text Available Abstract Background Bacillus cereus and the closely related Bacillus thuringiensis are Gram positive opportunistic pathogens that may cause food poisoning, and the three secreted pore-forming cytotoxins Hbl, Nhe and CytK have been implicated as the causative agents of diarrhoeal disease. It has been proposed that the Hbl toxin is secreted using the flagellar export apparatus (FEA despite the presence of Sec-type signal peptides. As protein secretion is of key importance in virulence of a microorganism, the mechanisms by which these toxins are secreted were further investigated. Results Sec-type signal peptides were identified in all toxin components, and secretion of Hbl component B was shown to be dependent on an intact Sec-type signal peptide sequence. Further indication that secretion of Hbl, Nhe and CytK is dependent on the Sec translocation pathway, the main pathway on which bacterial secretion relies, was suggested by the observed intracellular accumulation and reduced secretion of the toxins in cultures supplemented with the SecA inhibitor sodium azide. Although a FEA deficient strain (a flhA mutant showed reduced toxin expression and reduced cytotoxicity, it readily secreted overexpressed Hbl B, showing that the FEA is not required for Hbl secretion. Thus, the concurrent lack of flagella and reduced toxin secretion in the FEA deficient strain may point towards the presence of a regulatory link between motility and virulence genes, rather than FEA-dependent toxin secretion. Conclusions The Hbl, Nhe and CytK toxins appear to be secreted using the Sec pathway, and the reduced Hbl expression of a FEA deficient strain was shown not to be due to a secretion defect.

  9. Action of shiga toxin type-2 and subtilase cytotoxin on human microvascular endothelial cells.

    Directory of Open Access Journals (Sweden)

    María M Amaral

    Full Text Available The hemolytic uremic syndrome (HUS associated with diarrhea is a complication of Shiga toxin (Stx-producing Escherichia coli (STEC infection. In Argentina, HUS is endemic and responsible for acute and chronic renal failure in children younger than 5 years old. The human kidney is the most affected organ due to the presence of very Stx-sensitive cells, such as microvascular endothelial cells. Recently, Subtilase cytotoxin (SubAB was proposed as a new toxin that may contribute to HUS pathogenesis, although its action on human glomerular endothelial cells (HGEC has not been described yet. In this study, we compared the effects of SubAB with those caused by Stx2 on primary cultures of HGEC isolated from fragments of human pediatric renal cortex. HGEC were characterized as endothelial since they expressed von Willebrand factor (VWF and platelet/endothelial cell adhesion molecule 1 (PECAM-1. HGEC also expressed the globotriaosylceramide (Gb3 receptor for Stx2. Both, Stx2 and SubAB induced swelling and detachment of HGEC and the consequent decrease in cell viability in a time-dependent manner. Preincubation of HGEC with C-9 -a competitive inhibitor of Gb3 synthesis-protected HGEC from Stx2 but not from SubAB cytotoxic effects. Stx2 increased apoptosis in a time-dependent manner while SubAB increased apoptosis at 4 and 6 h but decreased at 24 h. The apoptosis induced by SubAB relative to Stx2 was higher at 4 and 6 h, but lower at 24 h. Furthermore, necrosis caused by Stx2 was significantly higher than that induced by SubAB at all the time points evaluated. Our data provide evidence for the first time how SubAB could cooperate with the development of endothelial damage characteristic of HUS pathogenesis.

  10. Pulse radiolysis studies on the release of cytotoxins from electron affinic anticancer prodrugs following their one-electron reduction

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, R.F.; Ware, D.C.; Denny, W.A.; Lee, H.; Tercel, M.; Wilson, W.R. [Auckland Univ. (New Zealand)

    1996-12-31

    New approaches to killing chemoresistant and radioresistant hypoxic cells of solid tumours include the selective release of potent cytotoxins from relatively non-toxic prodrugs through reductive metabolism and/or radiolytic reduction. Central to these studies, is an understanding of the mechanism of cytotoxin release and the basis of hypoxia-selectivity, since such information can be used to design compounds of high potency against solid tumours. Pulse radiolysis studies can offer unique insights into these underlying mechanisms in aqueous solution through the determination of thermodynamic one-electron reduction potentials of the prodrugs, rate constants for the formation and spectral charaterization of one-electron reduced prodrugs, the kinetics release of the cytotoxins from one-electron reduced prodrugs and the influence of molecular oxygen on the obligate radical intermediates. A series of different triggers, which are found to vary greatly in the rate constant for release of the effectors upon one-electron reduction of the prodrugs, will be discussed. Release of effector from a prodrug does not solely depend upon the type of trigger but can also be dependent on the type of linker and released effector. For example, whereas fast quantitative release of the mustard effector mechlorethamine is seen from the quaternary nitroimidazole upon one electron reduction, release of N-[2-(dimethylamino)ethyl] acridine-4-carboxamide (DACA), requires a higher level of reduction of the same trigger. Release of cytotoxic ligands from metal complexes requires that the metal centre is reduced. When the metal centre is lower than DACA bound as a ligand, reduction is seen to occur solely on the ligand without release from the metal centre. 1 ref., 1 fig.

  11. A novel toxin homologous to large clostridial cytotoxins found in culture supernatant of Clostridium perfringens type C.

    Science.gov (United States)

    Amimoto, Katsuhiko; Noro, Taichi; Oishi, Eiji; Shimizu, Mitsugu

    2007-04-01

    An unknown cytotoxin was identified in the culture supernatant of Clostridium perfringens type C. The cytotoxin, named TpeL, which was purified using mAb-based affinity chromatography, had a lethal activity of 62 minimum lethal dose (MLD) mg(-1) in mice and a cytotoxic activity of 6.2x10(5) cytotoxic units (CU) mg(-1) in Vero cells. The nucleotide sequence of TpeL was determined. The entire ORF had a length of 4953 bases, and the same nucleotide sequence was not recorded in the GenBank/EMBL/DDBJ databases. The molecular mass calculated from the deduced amino acid sequence was 191 kDa, and a signal peptide region was not found within the ORF. The deduced amino acid sequence exhibited 30-39 % homology to Clostridium difficile toxins A (TcdA) and B (TcdB), Clostridium sordellii lethal toxin (TcsL) and Clostridium novyi alpha-toxin (TcnA). The amino acid sequence of TpeL is shorter than these toxins, and the homologous region was located at the N-terminal site. Eighteen strains of C. perfringens types A, B and C were surveyed for the presence of the tpeL gene by PCR. The tpeL gene was detected in all type B (one strain) and C strains (five strains), but not in any type A strains (12 strains). TpeL was detected in culture filtrates of the five type C strains by dot-blot analysis, but not in the type B strain. It was concluded that TpeL is a novel toxin similar to the known large clostridial cytotoxins. Furthermore, the data indicated that TpeL is produced by many C. perfringens type C strains.

  12. A novel, potent, and specific ephrinA1-based cytotoxin against EphA2 receptor expressing tumor cells.

    Science.gov (United States)

    Wykosky, Jill; Gibo, Denise M; Debinski, Waldemar

    2007-12-01

    We have previously shown that the EphA2 receptor tyrosine kinase is overexpressed in glioblastoma multiforme (GBM) and represents a novel, attractive therapeutic target for the treatment of brain tumors. Here, we have developed an EphA2-targeted agent, ephrinA1-PE38QQR, a novel cytotoxin composed of ephrinA1, a ligand for EphA2, and PE38QQR, a mutated form of Pseudomonas aeruginosa exotoxin A. EphrinA1-PE38QQR showed potent and dose-dependent killing of GBM cells overexpressing the EphA2 receptor in cell viability and clonogenic survival assays, with an average IC(50) of approximately 10(-11) mol/L. The conjugate was also highly effective in killing breast and prostate cancer cells overexpressing EphA2. The cytotoxic effect of ephrinA1-PE38QQR was specific, as it was neutralized by an excess of EphA2 ligands. Moreover, normal human endothelial cells and breast cancer cells that do not overexpress EphA2, as well as GBM cells that have down-regulated EphA2, were not susceptible to the cytotoxin. EphrinA1-PE38QQR-mediated cytotoxicity induced caspase-dependent apoptosis, which was, however, not responsible for cell death in response to the conjugate. In addition, the conjugate elicited no changes in the activity of survival pathways such as phosphoinositide 3-kinase, measured by AKT phosphorylation. This is the first attempt to create a cytotoxic therapy using any of the ephrin ligands of either class (A or B) conjugated to a bacterial toxin. EphrinA1-PE38QQR is very potent and specific, produces cell death that is caspase independent, and forms the basis for the further development of clinically applicable EphA2-targeted cytotoxins.

  13. Complete stereochemistry and preliminary structure-activity relationship of rakicidin A, a hypoxia-selective cytotoxin from Micromonospora sp.

    Science.gov (United States)

    Oku, Naoya; Matoba, Shouhei; Yamazaki, Yohko Momose; Shimasaki, Ryoko; Miyanaga, Satoshi; Igarashi, Yasuhiro

    2014-11-26

    The complete stereochemistry of rakicidin A, a hypoxia-selective cytotoxin produced by Micromonospora sp., was unambiguously established by extensive chemical degradation and derivatization studies. During the PGME derivatization-based configurational analysis of 3-hydroxy-2,4,16-trimethylheptadecanoic acid, an irregular Δδ distribution was observed, which necessitated further acylation of the 3-hydroxy group to resolve the inconsistency. A hydrogenated derivative of rakicidin A, its ring-opened product, and two congeners with different alkyl chain lengths were tested for hypoxia-selective cytotoxicity. The results indicated that both the conjugated diene unit and appropriate chain length are essential for the unique activity of rakicidin A.

  14. Combination of Culture, Antigen and Toxin Detection, and Cytotoxin Neutralization Assay for Optimal Clostridium difficile Diagnostic Testing

    Directory of Open Access Journals (Sweden)

    Michelle J Alfa

    2013-01-01

    Full Text Available BACKGROUND: There has been a growing interest in developing an appropriate laboratory diagnostic algorithm for Clostridium difficile, mainly as a result of increases in both the number and severity of cases of C difficile infection in the past decade. A C difficile diagnostic algorithm is necessary because diagnostic kits, mostly for the detection of toxins A and B or glutamate dehydrogenase (GDH antigen, are not sufficient as stand-alone assays for optimal diagnosis of C difficile infection. In addition, conventional reference methods for C difficile detection (eg, toxigenic culture and cytotoxin neutralization [CTN] assays are not routinely practiced in diagnostic laboratory settings.

  15. Odd-Integer Quantum Hall States and Giant Spin Susceptibility in p -Type Few-Layer WSe2

    Science.gov (United States)

    Xu, Shuigang; Shen, Junying; Long, Gen; Wu, Zefei; Bao, Zhi-qiang; Liu, Cheng-Cheng; Xiao, Xiao; Han, Tianyi; Lin, Jiangxiazi; Wu, Yingying; Lu, Huanhuan; Hou, Jianqiang; An, Liheng; Wang, Yuanwei; Cai, Yuan; Ho, K. M.; He, Yuheng; Lortz, Rolf; Zhang, Fan; Wang, Ning

    2017-02-01

    We fabricate high-mobility p -type few-layer WSe2 field-effect transistors and surprisingly observe a series of quantum Hall (QH) states following an unconventional sequence predominated by odd-integer states under a moderate strength magnetic field. By tilting the magnetic field, we discover Landau level crossing effects at ultralow coincident angles, revealing that the Zeeman energy is about 3 times as large as the cyclotron energy near the valence band top at the Γ valley. This result implies the significant roles played by the exchange interactions in p -type few-layer WSe2 , in which itinerant or QH ferromagnetism likely occurs. Evidently, the Γ valley of few-layer WSe2 offers a unique platform with unusually heavy hole carriers and a substantially enhanced g factor for exploring strongly correlated phenomena.

  16. Demethoxycurcumin is a potent inhibitor of P-type ATPases from diverse kingdoms of life

    DEFF Research Database (Denmark)

    Dao, Trong Tuan; Sehgal, Pankaj; Thanh Tung, Truong;

    2016-01-01

    P-type ATPases catalyze the active transport of cations and phospholipids across biological membranes. Members of this large family are involved in a range of fundamental cellular processes. To date, a substantial number of P-type ATPase inhibitors have been characterized, some of which are used ...

  17. Luminance behavior of lithium-doped ZnO nanowires with p-type conduction characteristics.

    Science.gov (United States)

    Ko, Won Bae; Lee, Jun Seok; Lee, Sang Hyo; Cha, Seung Nam; Sohn, Jung Inn; Kim, Jong Min; Park, Young Jun; Kim, Hyun Jung; Hong, Jin Pyo

    2013-09-01

    The present study describes the room-temperature cathodeluminescence (CL) and temperature-dependent photoluminescence (PL) properties of p-type lithium (Li)-doped zinc oxide (ZnO) nanowires (NWs) grown by hydrothermal doping and post-annealing processes. A ZnO thin film was used as a seed layer in NW growth. The emission wavelengths and intensities of undoped ZnO NWs and p-type Li-doped ZnO NWs were analyzed for comparison. CL and PL observations of post-annealed p-type Li-doped ZnO NWs clearly exhibited a dominant sharp band-edge emission. Finally, a n-type ZnO thin film/p-type annealed Li-doped ZnO NW homojunction diode was prepared to confirm the p-type conduction of annealed Li-doped ZnO NWs as well as the structural properties measured by transmission electron microscopy.

  18. Application of neutron transmutation doping method to initially p-type silicon material.

    Science.gov (United States)

    Kim, Myong-Seop; Kang, Ki-Doo; Park, Sang-Jun

    2009-01-01

    The neutron transmutation doping (NTD) method was applied to the initially p-type silicon in order to extend the NTD applications at HANARO. The relationship between the irradiation neutron fluence and the final resistivity of the initially p-type silicon material was investigated. The proportional constant between the neutron fluence and the resistivity was determined to be 2.3473x10(19)nOmegacm(-1). The deviation of the final resistivity from the target for almost all the irradiation results of the initially p-type silicon ingots was at a range from -5% to 2%. In addition, the burn-up effect of the boron impurities, the residual (32)P activity and the effect of the compensation characteristics for the initially p-type silicon were studied. Conclusively, the practical methodology to perform the neutron transmutation doping of the initially p-type silicon ingot was established.

  19. Effect of NaCl and Helicobacter pylori vacuolating cytotoxin on cytokine expression and viability

    Institute of Scientific and Technical Information of China (English)

    Juan Sun; Kazuo Aoki; Jin-Xu Zheng; Bing-Zhong Su; Xiao-Hui Ouyang; Junichi Misumi

    2006-01-01

    AIM: To determine whether Helicobacter pylori (H pylori) vacuolating cytotoxin (VacA) regulates release of proinflammatory cytokines (IL-1β, IL-8, TNF-α, and IL-6)or alters gastric epithelial cell viability and to determine whether NaCl affects these VacA-induced changes.METHODS: Vacuolating activity was determined by measuring the uptake of neutral red into vacuoles of VacA-treated human gastric epithelial (AGS) cells. AGS cell viability was assessed by direct cell counting. Specific enzyme-linked immunosorbent assays (ELISA) and reverse transcriptase-polymerase chain reaction(RT-PCR)were performed to examine the effects of Hpylori VacA and NaCl on cell pro-inflammatory cytokine production in AGS cells. Immunohistochemical staining of gastric tissue from Mongolian gerbils was used to confirm VacA-induced pro-inflammatory cytokine production and the effects of NaCl on this VacA-induced response.RESULTS: Addition of VacA alone reduced AGS cell viability (P< 0.05), and this reduction was enhanced by high doses of NaCl (P< 0.05). VacA alone induced expression of TNF-α, IL-8 and IL-1β, while NaCl alone induced expression of TNF-α and IL-1β. Changes in mRNA levels in the presence of both VacA and NaCl were more complicated. For the case of TNF-a, expression was dosedependent on NaCl. IL-6 mRNA was not detected. However, low levels of IL-6 were detected by ELISA. Positive immunohistochemical staining of IL- 1, IL-6, and TNF-αwas found in gastric tissue of H pylori-infected gerbils fed with either a normal diet or a high salt diet. However,the staining of these three cytokines was stronger in H pylori-infected animals fed with a 5g/kg NaCl diet.CONCLUSION: VacA decreases the viability of AGS cells, and this effect can be enhanced by NaCl. NaCl also affects the production of pro-inflammatory cytokines induced by Vac A, suggesting that NaCl plays an important role in Hpylori-induced gastric epithelial cell cytotoxicity.

  20. Evidence for an iron-hydrogen complex in p-type silicon

    Science.gov (United States)

    Leonard, S.; Markevich, V. P.; Peaker, A. R.; Hamilton, B.; Murphy, J. D.

    2015-07-01

    Interactions of hydrogen with iron have been studied in Fe contaminated p-type Czochralski silicon using capacitance-voltage profiling and deep level transient spectroscopy (DLTS). Hydrogen has been introduced into the samples from a silicon nitride layer grown by plasma enhanced chemical vapor deposition. After annealing of the Schottky diodes on Si:Fe + H samples under reverse bias in the temperature range of 90-120 °C, a trap has been observed in the DLTS spectra which we have assigned to a Fe-H complex. The trap is only observed when a high concentration of hydrogen is present in the near surface region. The trap concentration is higher in samples with a higher concentration of single interstitial Fe atoms. The defect has a deep donor level at Ev + 0.31 eV. Direct measurements of capture cross section of holes have shown that the capture cross section is not temperature dependent and its value is 5.2 × 10-17 cm2. It is found from an isochronal annealing study that the Fe-H complex is not very stable and can be eliminated completely by annealing for 30 min at 125 °C.

  1. Thermal effect mechanism of magnetoresistance in p-type diamond films

    Institute of Scientific and Technical Information of China (English)

    Qin Guo-Ping; Kong Chun-Yang; Ruan Hai-Bo; Huang Gui-Juan; Cui Yu-Ting; Fang Liang

    2010-01-01

    Based on the analysis and the discussion of the influence of thermal ionization energy and various scatterings on magnetoresistance(MR) of p-type diamond films, a revised model of valence band split-off over temperature is put forward, and a corresponding calculation formula is given for the MR of p-type diamond films (Corbino discs). It is shown that the theoretical calculation that the MR of diamond films changes with temperature is consistent with the experiment. The influence of Fermi energy level on MR of diamond films is discussed. Additionally, the thermal effect mechanism of MR in p-type diamond films is also explored.

  2. Characterization of plasma etching damage on p -type GaN using Schottky diodes

    OpenAIRE

    2008-01-01

    The plasma etching damage in p-type GaN has been characterized. From current-voltage and capacitance-voltage characteristics of Schottky diodes, it was revealed that inductively coupled plasma (ICP) etching causes an increase in series resistance of the Schottky diodes and compensation of acceptors in p-type GaN. We investigated deep levels near the valence band of p-type GaN using current deep level transient spectroscopy (DLTS), and no deep level originating from the ICP etching damage was ...

  3. A Search of Low-Mass WIMPs with p-type Point Contact Germanium Detector in the CDEX-1 Experiment

    CERN Document Server

    Zhao, W; Kang, K J; Cheng, J P; Li, Y J; Wong, H T; Lin, S T; Chang, J P; Chen, J H; Chen, Q H; Chen, Y H; Deng, Z; Du, Q; Gong, H; Hao, X Q; He, H J; He, Q J; Huang, H X; Huang, T R; Jiang, H; Li, H B; Li, J; Li, J M; Li, X; Li, X Y; Li, Y L; Lin, F K; Liu, S K; Lü, L C; Ma, H; Ma, J L; Mao, S J; Qin, J Q; Ren, J; Ruan, X C; Sharma, V; Shen, M B; Singh, L; Singh, M K; Soma, A K; Su, J; Tang, C J; Wang, J M; Wang, L; Wang, Q; Wu, S Y; Wu, Y C; Xianyu, Z Z; Xiao, R Q; Xing, H Y; Xu, F Z; Xu, Y; Xu, X J; Xue, T; Yang, L T; Yang, S W; Yi, N; Yu, C X; Yu, H; Yu, X Z; Zeng, M; Zeng, X H; Zeng, Z; Zhang, L; Zhang, Y H; Zhao, M G; Zhou, Z Y; Zhu, J J; Zhu, W B; Zhu, X Z; Zhu, Z H

    2016-01-01

    The CDEX-1 experiment conducted a search of low-mass (< 10 GeV/c2) Weakly Interacting Massive Particles (WIMPs) dark matter at the China Jinping Underground Laboratory using a p-type point-contact germanium detector with a fiducial mass of 915 g at a physics analysis threshold of 475 eVee. We report the hardware set-up, detector characterization, data acquisition and analysis procedures of this experiment. No excess of unidentified events are observed after subtraction of known background. Using 335.6 kg-days of data, exclusion constraints on the WIMP-nucleon spin-independent and spin-dependent couplings are derived.

  4. Origin and evolution of metal P-type ATPases in Plantae (Archaeplastida)

    OpenAIRE

    2014-01-01

    Metal ATPases are a subfamily of P-type ATPases involved in the transport of metal cations across biological membranes. They all share an architecture featuring eight transmembrane domains in pairs of two and are found in prokaryotes as well as in a variety of Eukaryotes. In Arabidopsis thaliana, eight metal P-type ATPases have been described, four being specific to copper transport and four displaying a broader metal specificity, including zinc, cadmium and possibly copper and calcium. So fa...

  5. Convergence of valence bands for high thermoelectric performance for p-type InN

    Science.gov (United States)

    Li, Hai-Zhu; Li, Ruo-Ping; Liu, Jun-Hui; Huang, Ming-Ju

    2015-12-01

    Band engineering to converge the bands to achieve high valley degeneracy is one of effective approaches for designing ideal thermoelectric materials. Convergence of many valleys in the valence band may lead to a high Seebeck coefficient, and induce promising thermoelectric performance of p-type InN. In the current work, we have systematically investigated the electronic structure and thermoelectric performance of wurtzite InN by using the density functional theory combined with semiclassical Boltzmann transport theory. Form the results, it can be found that intrinsic InN has a large Seebeck coefficient (254 μV/K) and the largest value of ZeT is 0.77. The transport properties of p-type InN are better than that of n-type one at the optimum carrier concentration, which mainly due to the large Seebeck coefficient for p-type InN, although the electrical conductivity of n-type InN is larger than that of p-type one. We found that the larger Seebeck coefficient for p-type InN may originate from the large valley degeneracy in the valence band. Moreover, the low minimum lattice thermal conductivity for InN is one key factor to become a good thermoelectric material. Therefore, p-type InN could be a potential material for further applications in the thermoelectric area.

  6. General outbreaks of vero cytotoxin producing Escherichia coli O157 in England and Wales from 1992 to 1994.

    LENUS (Irish Health Repository)

    Wall, P G

    1996-02-02

    We have reviewed all general outbreaks of infection due to Vero cytotoxin producing Escherichia coli (VTEC) O157 reported in England and Wales from 1992 to 1994. One hundred and seventy-three people were affected in 18 outbreaks, compared with 76 people in seven outbreaks in the preceding three years (1989 to 1991). Outbreaks occurred throughout England and Wales. Thirty-eight per cent of cases were admitted to hospital, 21% developed haemolytic uraemic syndrome, and 3% died. VTEC O157 infection causes particular concern because of its serious complications--haemorrhagic colitis and haemolytic uraemic syndrome, its capacity to spread from person to person as well as by food and water, and its reservoir in dairy and beef cattle.

  7. Crystal Structure of Okadaic Acid Binding Protein 2.1: A Sponge Protein Implicated in Cytotoxin Accumulation.

    Science.gov (United States)

    Ehara, Haruhiko; Makino, Marie; Kodama, Koichiro; Konoki, Keiichi; Ito, Takuhiro; Sekine, Shun-ichi; Fukuzawa, Seketsu; Yokoyama, Shigeyuki; Tachibana, Kazuo

    2015-07-06

    Okadaic acid (OA) is a marine polyether cytotoxin that was first isolated from the marine sponge Halichondria okadai. OA is a potent inhibitor of protein serine/threonine phosphatases (PP) 1 and 2A, and the structural basis of phosphatase inhibition has been well investigated. However, the role and mechanism of OA retention in the marine sponge have remained elusive. We have solved the crystal structure of okadaic acid binding protein 2.1 (OABP2.1) isolated from H. okadai; it has strong affinity for OA and limited sequence homology to other proteins. The structure revealed that OABP2.1 consists of two α-helical domains, with the OA molecule deeply buried inside the protein. In addition, the global fold of OABP2.1 was unexpectedly similar to that of aequorin, a jellyfish photoprotein. The presence of structural homologues suggested that, by using similar protein scaffolds, marine invertebrates have developed diverse survival systems adapted to their living environments.

  8. Dual-function 2-nitroimidazoles as hypoxic cell radiosensitizers and bioreductive cytotoxins: In vivo evaluation in KHT murine sarcomas

    Energy Technology Data Exchange (ETDEWEB)

    Cole, S.; Stratford, I.J.; Adams, G.E.; Fielden, E.M.; Jenkins, T.C. (Medical Research Council, Didcot, Oxon (England))

    1990-10-01

    The efficacies of a series of potential prodrugs of RSU-1069 and its alkyl-aziridine analogues were assessed. These 1-(2-haloethylamino)-3-(2-nitro-1-imidazolyl)-2-propanol compounds were designed to cyclize in vivo to generate 2-nitro-imidazoles with aziridine (RSU-1069) or alkyl-substituted aziridine (RSU-1164, RB-7040, or RSU-1150) functions. Maximum tolerated single, intraperitoneal doses (MTD) were determined in C3H/He mice bearing subcutaneous KHT sarcomas, and a drug dose-response relationship for radiosensitization was established for each compound administered at the optimum time (45-60 min) before local irradiation of tumors with a 10-Gy dose of X-rays. The potentials of the compounds as bioreductive cytotoxins were studied by administering them immediately after irradiation. Tumor cell survival was measured 18-24 h after treatment in an in vitro soft agar clonogenic assay. Results of toxicity, radiosensitization, and bioreductive cytotoxicity assays for each of the prodrugs (RB-6171, RB-6172, RB-6173, RB-6174, and RB-6175) of the alkyl-substituted aziridines were entirely consistent with complete conversion to their respective target compounds. For example, RB-6171 (the prodrug form of RSU-1164) was only about four times less efficient than RSU-1069 as a radiosensitizer and bioreductive cytotoxin but had an MTD 7.5 times higher. In contrast, prodrugs of RSU-1069 (RB-6144 and RB-6145) were two- to threefold less toxic than their expected product. RB-6144 was a poor radiosensitizer and bioreductive agent compared with RSU-1069 and was similar to RB-6170, a nonalkylating nitroimidazole. This is consistent with the observation that there is limited conversion of RB-6144 to RSU-1069 in vitro. However, radiosensitization and bioreductive cytotoxicity produced by RB-6145 were only slightly less than the effects produced by RSU-1069.

  9. Targeting the tumour vasculature: exploitation of low oxygenation and sensitivity to NOS inhibition by treatment with a hypoxic cytotoxin.

    Science.gov (United States)

    Baker, Jennifer H E; Kyle, Alastair H; Bartels, Kirsten L; Methot, Stephen P; Flanagan, Erin J; Balbirnie, Andrew; Cran, Jordan D; Minchinton, Andrew I

    2013-01-01

    Many cancer research efforts focus on exploiting genetic-level features that may be targeted for therapy. Tissue-level features of the tumour microenvironment also represent useful therapeutic targets. Here we investigate the presence of low oxygen tension and sensitivity to NOS inhibition of tumour vasculature as potential tumour-specific features that may be targeted by hypoxic cytotoxins, a class of therapeutics currently under investigation. We have previously demonstrated that tirapazamine (TPZ) mediates central vascular dysfunction in tumours. TPZ is a hypoxic cytotoxin that is also a competitive inhibitor of NOS. Here we further investigated the vascular-targeting activity of TPZ by combining it with NOS inhibitor L-NNA, or with low oxygen content gas breathing. Tumours were analyzed via multiplex immunohistochemical staining that revealed irreversible loss of perfusion and enhanced tumour cell death when TPZ was combined with either low oxygen or a NOS inhibitor. Tumour growth rate was reduced by TPZ + NOS inhibition, and tumours previously resistant to TPZ-mediated vascular dysfunction were sensitized by low oxygen breathing. Additional mapping analysis suggests that tumours with reduced vascular-associated stroma may have greater sensitivity to these effects. These results indicate that poorly oxygenated tumour vessels, also being abnormally organized and with inadequate smooth muscle, may be successfully targeted for significant anti-cancer effects by inhibition of NOS and hypoxia-activated prodrug toxicity. This strategy illustrates a novel use of hypoxia-activated cytotoxic prodrugs as vascular targeting agents, and also represents a novel mechanism for targeting tumour vessels.

  10. Formation of p-type ZnO thin film through co-implantation

    Science.gov (United States)

    Chuang, Yao-Teng; Liou, Jhe-Wei; Woon, Wei-Yen

    2017-01-01

    We present a study on the formation of p-type ZnO thin film through ion implantation. Group V dopants (N, P) with different ionic radii are implanted into chemical vapor deposition grown ZnO thin film on GaN/sapphire substrates prior to thermal activation. It is found that mono-doped ZnO by N+ implantation results in n-type conductivity under thermal activation. Dual-doped ZnO film with a N:P ion implantation dose ratio of 4:1 is found to be p-type under certain thermal activation conditions. Higher p-type activation levels (1019 cm-3) under a wider thermal activation range are found for the N/P dual-doped ZnO film co-implanted by additional oxygen ions. From high resolution x-ray diffraction and x-ray photoelectron spectroscopy it is concluded that the observed p-type conductivities are a result of the promoted formation of PZn-4NO complex defects via the concurrent substitution of nitrogen at oxygen sites and phosphorus at zinc sites. The enhanced solubility and stability of acceptor defects in oxygen co-implanted dual-doped ZnO film are related to the reduction of oxygen vacancy defects at the surface. Our study demonstrates the prospect of the formation of stable p-type ZnO film through co-implantation.

  11. Nanostructured p-Type Semiconductor Electrodes and Photoelectrochemistry of Their Reduction Processes

    Directory of Open Access Journals (Sweden)

    Matteo Bonomo

    2016-05-01

    Full Text Available This review reports the properties of p-type semiconductors with nanostructured features employed as photocathodes in photoelectrochemical cells (PECs. Light absorption is crucial for the activation of the reduction processes occurring at the p-type electrode either in the pristine or in a modified/sensitized state. Beside thermodynamics, the kinetics of the electron transfer (ET process from photocathode to a redox shuttle in the oxidized form are also crucial since the flow of electrons will take place correctly if the ET rate will overcome that one of recombination and trapping events which impede the charge separation produced by the absorption of light. Depending on the nature of the chromophore, i.e., if the semiconductor itself or the chemisorbed dye-sensitizer, different energy levels will be involved in the cathodic ET process. An analysis of the general properties and requirements of electrodic materials of p-type for being efficient photoelectrocatalysts of reduction processes in dye-sensitized solar cells (DSC will be given. The working principle of p-type DSCs will be described and extended to other p-type PECs conceived and developed for the conversion of the solar radiation into chemical products of energetic/chemical interest like non fossil fuels or derivatives of carbon dioxide.

  12. Recent Developments in p-Type Oxide Semiconductor Materials and Devices

    KAUST Repository

    Wang, Zhenwei

    2016-02-16

    The development of transparent p-type oxide semiconductors with good performance may be a true enabler for a variety of applications where transparency, power efficiency, and greater circuit complexity are needed. Such applications include transparent electronics, displays, sensors, photovoltaics, memristors, and electrochromics. Hence, here, recent developments in materials and devices based on p-type oxide semiconductors are reviewed, including ternary Cu-bearing oxides, binary copper oxides, tin monoxide, spinel oxides, and nickel oxides. The crystal and electronic structures of these materials are discussed, along with approaches to enhance valence-band dispersion to reduce effective mass and increase mobility. Strategies to reduce interfacial defects, off-state current, and material instability are suggested. Furthermore, it is shown that promising progress has been made in the performance of various types of devices based on p-type oxides. Several innovative approaches exist to fabricate transparent complementary metal oxide semiconductor (CMOS) devices, including novel device fabrication schemes and utilization of surface chemistry effects, resulting in good inverter gains. However, despite recent developments, p-type oxides still lag in performance behind their n-type counterparts, which have entered volume production in the display market. Recent successes along with the hurdles that stand in the way of commercial success of p-type oxide semiconductors are presented.

  13. CuNb3O8: A p-Type Semiconducting Metal Oxide Photoelectrode.

    Science.gov (United States)

    Joshi, Upendra A; Maggard, Paul A

    2012-06-07

    A new p-type CuNb3O8 polycrystalline photoelectrode was investigated and was determined to have indirect and direct bandgap sizes of 1.26 and 1.47 eV, respectively. The p-type polycrystalline film could be prepared on fluorine-doped tin oxide glass and yielded a cathodic photocurrent under visible-light irradiation (λ > 420 nm) with incident photon-to-current efficiencies of up to ∼6-7% and concomitant hydrogen evolution. A Mott-Schottky analysis yielded a flat band potential of +0.35 V versus RHE (pH = 6.3) and a calculated p-type dopant concentration of ∼7.2 × 10(15) cm(-3). The conduction band energies are found to be negative enough for the reduction of water under visible light irradiation. A hole mobility of ∼145 cm(2)/V·s was obtained from J(I)-V(2) measurements using the Mott-Gurney relation, which is ∼50% higher than that typically found for p-type Cu2O. DFT-based electronic structure calculations were used to probe the atomic and structural origins of the band gap transitions and carrier mobility. Thus, a new p-type semiconductor is discovered for potential applications in solar energy conversion.

  14. Chemical-free n-type and p-type multilayer-graphene transistors

    Energy Technology Data Exchange (ETDEWEB)

    Dissanayake, D. M. N. M., E-mail: nandithad@voxtel-inc.com [Voxtel Inc, Lockey Laboratories, University of Oregon, Eugene Oregon 97402 (United States); Eisaman, M. D. [Sustainable Energy Technologies Department, Brookhaven National Laboratory, Upton, New York 11973 (United States); Department of Electrical and Computer Engineering, Stony Brook University, Stony Brook, New York 11794 (United States); Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794 (United States)

    2016-08-01

    A single-step doping method to fabricate n- and p-type multilayer graphene (MG) top-gate field effect transistors (GFETs) is demonstrated. The transistors are fabricated on soda-lime glass substrates, with the n-type doping of MG caused by the sodium in the substrate without the addition of external chemicals. Placing a hydrogen silsesquioxane (HSQ) barrier layer between the MG and the substrate blocks the n-doping, resulting in p-type doping of the MG above regions patterned with HSQ. The HSQ is deposited in a single fabrication step using electron beam lithography, allowing the patterning of arbitrary sub-micron spatial patterns of n- and p-type doping. When a MG channel is deposited partially on the barrier and partially on the glass substrate, a p-type and n-type doping profile is created, which is used for fabricating complementary transistors pairs. Unlike chemically doped GFETs in which the external dopants are typically introduced from the top, these substrate doped GFETs allow for a top gate which gives a stronger electrostatic coupling to the channel, reducing the operating gate bias. Overall, this method enables scalable fabrication of n- and p-type complementary top-gated GFETs with high spatial resolution for graphene microelectronic applications.

  15. Recent Developments in p-Type Oxide Semiconductor Materials and Devices.

    Science.gov (United States)

    Wang, Zhenwei; Nayak, Pradipta K; Caraveo-Frescas, Jesus A; Alshareef, Husam N

    2016-05-01

    The development of transparent p-type oxide semiconductors with good performance may be a true enabler for a variety of applications where transparency, power efficiency, and greater circuit complexity are needed. Such applications include transparent electronics, displays, sensors, photovoltaics, memristors, and electrochromics. Hence, here, recent developments in materials and devices based on p-type oxide semiconductors are reviewed, including ternary Cu-bearing oxides, binary copper oxides, tin monoxide, spinel oxides, and nickel oxides. The crystal and electronic structures of these materials are discussed, along with approaches to enhance valence-band dispersion to reduce effective mass and increase mobility. Strategies to reduce interfacial defects, off-state current, and material instability are suggested. Furthermore, it is shown that promising progress has been made in the performance of various types of devices based on p-type oxides. Several innovative approaches exist to fabricate transparent complementary metal oxide semiconductor (CMOS) devices, including novel device fabrication schemes and utilization of surface chemistry effects, resulting in good inverter gains. However, despite recent developments, p-type oxides still lag in performance behind their n-type counterparts, which have entered volume production in the display market. Recent successes along with the hurdles that stand in the way of commercial success of p-type oxide semiconductors are presented.

  16. CoGeNT: A Search for Low-Mass Dark Matter using p-type Point Contact Germanium Detectors

    CERN Document Server

    Aalseth, C E; Colaresi, J; Collar, J I; Leon, J Diaz; Fast, J E; Fields, N E; Hossbach, T W; Knecht, A; Kos, M S; Marino, M G; Miley, H S; Miller, M L; Orrell, J L; Yocum, K M

    2013-01-01

    CoGeNT employs p-type point-contact (PPC) germanium detectors to search for Weakly Interacting Massive Particles (WIMPs). By virtue of its low energy threshold and ability to reject surface backgrounds, this type of device allows an emphasis on low-mass dark matter candidates (WIMP mass around 10 GeV/c2). We report on the characteristics of the PPC detector presently taking data at the Soudan Underground Laboratory, elaborating on aspects of shielding, data acquisition, instrumental stability, data analysis, and background estimation. A detailed background model is used to investigate the low energy excess of events previously reported, and to assess the possibility of temporal modulations in the low-energy event rate. We conclude that the technique is ideally suited to search for the annual modulation signature expected from dark matter particle interactions in the region of WIMP mass and coupling favored by the DAMA/LIBRA claim.

  17. Effective field theory and Ab-initio calculation of p-type (Ga, Fe)N within LDA and SIC approximation

    Energy Technology Data Exchange (ETDEWEB)

    Salmani, E. [LMPHE, associe au CNRST (URAC 12), Faculte des Sciences, Universite Mohammed V-Agdal, Rabat (Morocco); Mounkachi, O. [Institute of Nanomaterials and Nanotechnology, MAScIR, Rabat (Morocco); Ez-Zahraouy, H., E-mail: ezahamid@fsr.ac.ma [LMPHE, associe au CNRST (URAC 12), Faculte des Sciences, Universite Mohammed V-Agdal, Rabat (Morocco); El Kenz, A. [LMPHE, associe au CNRST (URAC 12), Faculte des Sciences, Universite Mohammed V-Agdal, Rabat (Morocco); Hamedoun, M. [Institute of Nanomaterials and Nanotechnology, MAScIR, Rabat (Morocco); Benyoussef, A. [LMPHE, associe au CNRST (URAC 12), Faculte des Sciences, Universite Mohammed V-Agdal, Rabat (Morocco); Institute of Nanomaterials and Nanotechnology, MAScIR, Rabat (Morocco); Hassan II Academy of Science and Technology, Rabat (Morocco)

    2013-03-15

    Based on first-principles spin-density functional calculations, using the Korringa-Kohn-Rostoker method combined with the coherent potential approximation, we investigated the half-metallic ferromagnetic behavior of (Ga, Fe)N co-doped with carbon within the self-interaction-corrected local density approximation. Mechanism of hybridization and interaction between magnetic ions in p-type (Ga, Fe)N is investigated. Stability energy of ferromagnetic and disorder local moment states was calculated for different carbon concentration. The local density and the self-interaction-corrected approximations have been used to explain the strong ferromagnetic interaction observed and the mechanism that stabilizes this state. The transition temperature to the ferromagnetic state has been calculated within the effective field theory, with a Honmura-Kaneyoshi differential operator technique. - Highlights: Black-Right-Pointing-Pointer The paper focus on the study the magnetic properties and electronic structure of p-type (Ga, Fe)N within LDA and SIC approximation. Black-Right-Pointing-Pointer These methods allow us to explain the strong ferromagnetic interaction observed and the mechanism for its stability and the mechanism of hybridization and interaction between magnetic ions in p-type (Ga, Fe). Black-Right-Pointing-Pointer The results obtained are interesting and can be serve as a reference in the field of dilute magnetic semi conductor.

  18. Transparent p-type SnO nanowires with unprecedented hole mobility among oxide semiconductors

    KAUST Repository

    Caraveo-Frescas, J. A.

    2013-11-25

    p-type tin monoxide (SnO) nanowire field-effect transistors with stable enhancement mode behavior and record performance are demonstrated at 160 °C. The nanowire transistors exhibit the highest field-effect hole mobility (10.83 cm2 V−1 s−1) of any p-type oxide semiconductor processed at similar temperature. Compared to thin film transistors, the SnO nanowire transistors exhibit five times higher mobility and one order of magnitude lower subthreshold swing. The SnO nanowire transistors show three times lower threshold voltages (−1 V) than the best reported SnO thin film transistors and fifteen times smaller than p-type Cu 2O nanowire transistors. Gate dielectric and process temperature are critical to achieving such performance.

  19. DyP-type peroxidases comprise a novel heme peroxidase family.

    Science.gov (United States)

    Sugano, Y

    2009-04-01

    Dye-decolorizing peroxidase (DyP) is produced by a basidiomycete (Thanatephorus cucumeris Dec 1) and is a member of a novel heme peroxidase family (DyP-type peroxidase family) that appears to be distinct from general peroxidases. Thus far, 80 putative members of this family have been registered in the PeroxiBase database (http://peroxibase.isbsib.ch/) and more than 400 homologous proteins have been detected via PSI-BLAST search. Although few studies have characterized the function and structure of these proteins, they appear to be bifunctional enzymes with hydrolase or oxygenase, as well as typical peroxidase activities. DyP-type peroxidase family suggests an ancient root compared with other general peroxidases because of their widespread distribution in the living world. In this review, firstly, an outline of the characteristics of DyP from T. cucumeris is presented and then interesting characteristics of the DyP-type peroxidase family are discussed.

  20. Demethoxycurcumin is a potent inhibitor of P-type ATPases from diverse kingdoms of life

    DEFF Research Database (Denmark)

    Dao, Trong Tuan; Sehgal, Pankaj; Thanh Tung, Truong;

    2016-01-01

    the curcuminoids, demethoxycurcumin was the most potent inhibitor of all tested P-type ATPases from fungal (Pma1p; H+-ATPase), plant (AHA2; H+-ATPase) and animal (SERCA; Ca2+-ATPase) cells. All three curcuminoids acted as non-competitive antagonist to ATP and hence may bind to a highly conserved allosteric site......P-type ATPases catalyze the active transport of cations and phospholipids across biological membranes. Members of this large family are involved in a range of fundamental cellular processes. To date, a substantial number of P-type ATPase inhibitors have been characterized, some of which are used...... as drugs. In this work a library of natural compounds was screened and we first identified curcuminoids as plasma membrane H+-ATPases inhibitors in plant and fungal cells. We also found that some of the commercial curcumins contain several curcuminoids. Three of these were purified and, among...

  1. A simple model to estimate the optimal doping of p - Type oxide superconductors

    Directory of Open Access Journals (Sweden)

    Adir Moysés Luiz

    2008-12-01

    Full Text Available Oxygen doping of superconductors is discussed. Doping high-Tc superconductors with oxygen seems to be more efficient than other doping procedures. Using the assumption of double valence fluctuations, we present a simple model to estimate the optimal doping of p-type oxide superconductors. The experimental values of oxygen content for optimal doping of the most important p-type oxide superconductors can be accounted for adequately using this simple model. We expect that our simple model will encourage further experimental and theoretical researches in superconducting materials.

  2. Dual ohmic contact to N- and P-type silicon carbide

    Science.gov (United States)

    Okojie, Robert S. (Inventor)

    2013-01-01

    Simultaneous formation of electrical ohmic contacts to silicon carbide (SiC) semiconductor having donor and acceptor impurities (n- and p-type doping, respectively) is disclosed. The innovation provides for ohmic contacts formed on SiC layers having n- and p-doping at one process step during the fabrication of the semiconductor device. Further, the innovation provides a non-discriminatory, universal ohmic contact to both n- and p-type SiC, enhancing reliability of the specific contact resistivity when operated at temperatures in excess of 600.degree. C.

  3. High surface hole concentration p-type GaN using Mg implantation

    CERN Document Server

    Long Tao; Zhang Guo Yi

    2001-01-01

    Mg ions were implanted on Mg-doped GaN grown by metalorganic chemical vapor deposition (MOCVD). The p-type GaN was achieved with high hole concentration (8.28 x 10 sup 1 sup 7 cm sup - sup 3) conformed by Van derpauw Hall measurement after annealing at 800 degree C for 1 h. this is the first experimental report of Mg implantation on Mg-doped GaN and achieving p-type GaN with high surface hole concentration

  4. Hall and thermoelectric evaluation of p-type InAs

    Energy Technology Data Exchange (ETDEWEB)

    Wagener, M.C., E-mail: magnus.wagener@nmmu.ac.z [Department of Physics, Nelson Mandela Metropolitan University, Port Elizabeth (South Africa); Wagener, V.; Botha, J.R. [Department of Physics, Nelson Mandela Metropolitan University, Port Elizabeth (South Africa)

    2009-12-15

    This paper compares the galvanometric and thermoelectric evaluation of the electrical characteristics of narrow gap semiconductors. In particular, the influence of a surface inversion layer is incorporated into the analysis of the temperature-dependent Hall and thermoelectric measurements of p-type InAs. The temperature at which the Seebeck coefficient of p-type material changes sign is shown to be unaffected by the presence of degenerate conduction paths. This finding consequently facilitated the direct determination of the acceptor density of lightly doped thin film InAs.

  5. Realization of Ag-S codoped p-type ZnO thin films

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Tian Ning, E-mail: xtn9886@zju.edu.cn [Department of Science, Zhijiang College of Zhejiang University of Technology, Hangzhou, Zhejiang 310024 (China); Department of Physics, State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou, Zhejiang 310027 (China); Li, Xiang; Lu, Zhong [Department of Science, Zhijiang College of Zhejiang University of Technology, Hangzhou, Zhejiang 310024 (China); Chen, Yong Yue [Department of Physics, State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou, Zhejiang 310027 (China); Sui, Cheng Hua [Department of Science, Zhijiang College of Zhejiang University of Technology, Hangzhou, Zhejiang 310024 (China); Wu, Hui Zhen [Department of Physics, State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou, Zhejiang 310027 (China)

    2014-10-15

    Highlights: • Ag-S codoped p-type ZnO thin films have been fabricated. • The films exhibit low resistivity and high Hall mobility and hole concentration. • A ZnO:(Ag, S)/i-ZnO/ZnO:Al homojunction has been fabricated and shows rectifying behaviors. - Abstract: Ag-S codoped ZnO films have been grown on quartz substrates by e-beam evaporation at low temperature (100 °C). The effects of Ag{sub 2}S content on the structural and electrical properties of the films were investigated. The results showed that 2 wt% Ag{sub 2}S doped films exhibited p-type conduction, with a resistivity of 0.0347 Ω cm, a Hall mobility of 9.53 cm{sup 2} V{sup −1} s{sup −1}, and a hole concentration of 1.89 × 10{sup 19} cm{sup −3} at room temperature. The X-ray photoelectron spectroscopy measurements showed that Ag and S have been incorporated into the films. To further confirm the p-type conduction of Ag-S codoped ZnO films, a ZnO:(Ag, S)/i-ZnO/ZnO:Al homojunction was fabricated and rectifying behaviors of which was measured. High electrical performance and low growth temperature indicate that Ag{sub 2}S is a promising dopant to fabricate p-type Ag-S codoped ZnO films.

  6. Relative Frequencies of G and P Types among Rotaviruses from Indian Diarrheic Cow and Buffalo Calves

    Science.gov (United States)

    Gulati, Baldev R.; Nakagomi, Osamu; Koshimura, Yumi; Nakagomi, Toyoko; Pandey, Ramayan

    1999-01-01

    While an increasing number of studies suggest that there is a high prevalence of rotaviruses with P8[11], a typical P type of bovine rotavirus (BRV), among human neonates or infants in India, no data are available on the distribution of G and P types of Indian BRVs. Thus, fecal specimens were collected from cow and buffalo calves under 1 month of age on organized dairy farms in India during the period between 1994 and 1997, and 36 rotavirus-positive specimens were used to determine the relative frequencies of the G and P types of Indian BRVs. As to the G type, G10 was predominant (83%), followed by G6 (6%). The majority (94%) of BRVs had P8[11], and only one isolate possessed P6[1]. The most common combination of G and P types was G10P8[11] (81%), followed by G6P6[1] (3%) and G6P8[11] (3%). The high prevalence of BRVs possessing P8[11] VP4s strongly supports the hypothesis that BRVs may cross the host species barrier and circulate among neonates in India. PMID:10325385

  7. Characterization of 3D-DDTC detectors on p-type substrates

    CERN Document Server

    Betta, G -F Dalla; Bosisio, Luciano; Darbo, Giovanni; Gabos, Paolo; Gemme, Claudia; Koehler, Michael; La Rosa, Alessandro; Parzefall, Ulrich; Pernegger, Heinz; Piemonte, Claudio; Povoli, Marco; Rachevskaia, Irina; Ronchin, Sabina; Wiik, Liv; Zoboli, Aanrea; Zorzi, Nicola

    2009-01-01

    We report on the electrical and functional characterization of 3D Double-side, Double-Type-Column (3D- DDTC) detectors fabricated on p-type substrates. Results relevant to detectors in the diode, strip and pixel configurations are presented, and demonstrate a clear improvement in the charge collection performance compared to the first prototypes of these detectors.

  8. Origin and evolution of metal p-Type ATPases in Plantae (Archaeplastida

    Directory of Open Access Journals (Sweden)

    Marc eHanikenne

    2014-01-01

    Full Text Available Metal ATPases are a subfamily of P-type ATPases involved in the transport of metal cations across biological membranes. They all share an architecture featuring eight transmembrane domains in pairs of two and are found in prokaryotes as well as in a variety of Eukaryotes. In Arabidopsis thaliana, eight metal P-type ATPases have been described, four being specific to copper transport and four displaying a broader metal specificity, including zinc, cadmium and possibly copper and calcium. So far, few efforts have been devoted to elucidating the origin and evolution of these proteins in Eukaryotes. In this work, we use large-scale phylogenetics to show that metal P-type ATPases form a homogenous group among P-type ATPases and that their specialisation into either monovalent (Cu or divalent (Zn, Cd… metal transport stems from a gene duplication that took place early in the evolution of Life. Then, we demonstrate that the four subgroups of plant metal ATPases all have a different evolutionary origin and a specific taxonomic distribution, only one tracing back to the cyanobacterial progenitor of the chloroplast. Finally, we examine the subsequent evolution of these proteins in green plants and conclude that the genes thoroughly characterised in model organisms are often the result of lineage-specific gene duplications, which calls for caution when attempting to infer function from sequence similarity alone in non-model organisms.

  9. Synthesis of p-type and n-type nickel ferrites and associated electrical properties

    Energy Technology Data Exchange (ETDEWEB)

    Šutka, Andris, E-mail: andris.sutka@rtu.lv [Faculty of Material Science and Applied Chemistry, Riga Technical University, Paula Valdena 3, Riga, LV-1048 (Latvia); Institute of Physics, University of Tartu, Ravila 14c, 50411, 51014 Tartu (Estonia); Pärna, Rainer [Institute of Physics, University of Tartu, Ravila 14c, 50411, 51014 Tartu (Estonia); Estonian Nanotechnology Competence Centre, Ravila 14c, 50411, 51014 Tartu (Estonia); Käämbre, Tanel [Institute of Physics, University of Tartu, Ravila 14c, 50411, 51014 Tartu (Estonia); Kisand, Vambola [Institute of Physics, University of Tartu, Ravila 14c, 50411, 51014 Tartu (Estonia); Estonian Nanotechnology Competence Centre, Ravila 14c, 50411, 51014 Tartu (Estonia)

    2015-01-01

    We used sol–gel auto combustion to synthesize nickel ferrites of p-type and n-type conductivity by controlling the relative amounts of nickel and iron during synthesis. The obtained samples have been characterized by XRD, FE-SEM, electrical measurements and XPS. We observe huge differences in the effect of grain size on the electrical resistivity between the p-type and the n-type material when the grain size increases from nano to micro scale during annealing at temperatures from 900 {sup o}C to 1300 {sup o}C. The observed resistivity decrease (due to grain size) is four orders of magnitude in the n-type nickel ferrite, whereas the p-type material remains virtually unaffected. We rationalize this drastic difference to stem from a reverse contrast of the surface (grain shell) versus bulk (grain core) conductivity between p- and n-type ferrite. With the grain shells in p-type the easier charge carrier path the effect of scatter at grain boundaries is accordingly diminished, whereas in the n-type charge transport properties are controlled by (the number of) grain boundaries in a conduction path.

  10. A structural and functional perspective of DyP-type peroxidase family.

    Science.gov (United States)

    Yoshida, Toru; Sugano, Yasushi

    2015-05-15

    Dye-decolorizing peroxidase from the basidiomycete Bjerkandera adusta Dec 1 (DyP) is a heme peroxidase. This name reflects its ability to degrade several anthraquinone dyes. The substrate specificity, the amino acid sequence, and the tertiary structure of DyP are different from those of the other heme peroxidase (super)families. Therefore, many proteins showing the similar amino acid sequences to that of DyP are called DyP-type peroxidase which is a new family of heme peroxidase identified in 2007. In fact, all structures of this family show a similar structure fold. However, this family includes many proteins whose amino acid sequence identity to DyP is lower than 15% and/or whose catalytic efficiency (kcat/Km) is a few orders of magnitude less than that of DyP. A protein showing an activity different from peroxidase activity (dechelatase activity) has been also reported. In addition, the precise physiological roles of DyP-type peroxidases are unknown. These facts raise a question of whether calling this family DyP-type peroxidase is suitable. Here, we review the differences and similarities of structure and function among this family and propose the reasonable new classification of DyP-type peroxidase family, that is, class P, I and V. In this contribution, we discuss the adequacy of this family name.

  11. Towards universal approach for bacterial production of three-finger Ly6/uPAR proteins: Case study of cytotoxin I from cobra N. oxiana.

    Science.gov (United States)

    Shulepko, M A; Lyukmanova, E N; Shenkarev, Z O; Dubovskii, P V; Astapova, M V; Feofanov, A V; Arseniev, A S; Utkin, Y N; Kirpichnikov, M P; Dolgikh, D A

    2017-02-01

    Cytotoxins or cardiotoxins is a group of polycationic toxins from cobra venom belonging to the 'three-finger' protein superfamily (Ly6/uPAR family) which includes small β-structural proteins (60-90 residues) with high disulfide bond content (4-5 disulfides). Due to a high cytotoxic activity for cancer cells, cytotoxins are considered as potential anticancer agents. Development of the high-throughput production methods is required for the prospective applications of cytotoxins. Here, efficient approach for bacterial production of recombinant analogue of cytotoxin I from N. oxiana containing additional N-terminal Met-residue (rCTX1) was developed. rCTX1 was produced in the form of E. coli inclusion bodies. Refolding in optimized conditions provided ∼6 mg of correctly folded protein from 1 L of bacterial culture. Cytotoxicity of rCTX1 for C6 rat glioma cells was found to be similar to the activity of wild type CTX1. The milligram quantities of (13)C,(15)N-labeled rCTX1 were obtained. NMR study confirmed the similarity of the spatial structures of recombinant and wild-type toxins. Additional Met residue does not perturb the overall structure of the three-finger core. The analysis of available data for different Ly6/uPAR proteins of snake and human origin revealed that efficiency of their folding in vitro is correlated with the number of proline residues in the third loop and the surface area of hydrophobic residues buried within the protein interior. The obtained data indicate that hydrophobic core is important for the folding of proteins with high disulfide bond content. Developed expression method opens new possibilities for structure-function studies of CTX1 and other related three-finger proteins.

  12. Comparison of Austrian, Hungarian and Macedonian methicillin-resistant and methicillin-sensitive Staphylococcus aureus strains in relation to prevalence of cytotoxin genes.

    Science.gov (United States)

    Kocsis, Erika; Lagler, Heimo; Pesti, Natasa; Stich, Karin; Kristóf, Katalin; Nagy, Károly; Hermann, Péter; Komka, Kinga; Cekovska, Zaklina; Graninger, Wolfgang; Rozgonyi, Ferenc

    2009-06-01

    Cytotoxin genes in 128 Austrian (AT) MSSA, 48 MRSA, 94 Hungarian (HU) MSSA, 110 MRSA and 67 Macedonian (MK) MSSA, 81 MRSA strains were examined. The presence of alfa-haemolysin gene (hla) was more common in HU MSSA strains compared to AT and MK (99%, 86%, 72%: pcytotoxin genes and combinations differed significantly in Staphylococcus aureus strains according to geographical origin and methicillin-resistance.

  13. New quinoxaline 1,4-di-N-oxides. Part 1: Hypoxia-selective cytotoxins and anticancer agents derived from quinoxaline 1,4-di-N-oxides.

    Science.gov (United States)

    Amin, Kamelia M; Ismail, Magda M F; Noaman, Eman; Soliman, Dalia H; Ammar, Yousry A

    2006-10-15

    Hypoxic cells which are common feature of solid tumors are resistant to both anticancer drugs and radiation therapy. Thus, the identification of drugs with the selective toxicity toward hypoxic cells is an important target in anticancer chemotherapy. Tirapazamine has been shown to be an efficient and selective cytotoxin after bioreductive activation in hypoxic cells which is thought to be due to the presence of the 1,4-di-N-oxide. A new series of quinoxaline 1,4-di-N-oxides and fused quinoxaline di-N-oxides were synthesized and evaluated for hypoxic-cytotoxic activity on EAC cell line. Compound 10a was the most potent cytotoxin IC(50) 0.9 microg/mL, potency 75 microg/mL, and was approximately 15 times more selective cytotoxin (HCR>111) than 3-aminoquinoxaline-2-carbonitrile which has been used as a standard (HCR>7.5). Compounds 4 and 3a,b were more selective than the standard. In addition, antitumor activity against Hepg2 (liver) and U251 (brain) human cell lines was evaluated, compounds 9c and 8a were the most active against Hepg2 with IC(50) values 1.9 and 2.9 microg/mL, respectively, however, all the tested compounds were nontoxic against U251 cell line.

  14. Novel role of IL-13 in fibrosis induced by nonalcoholic steatohepatitis and its amelioration by IL-13R-directed cytotoxin in a rat model.

    Science.gov (United States)

    Shimamura, Takeshi; Fujisawa, Toshio; Husain, Syed R; Kioi, Mitomu; Nakajima, Atsushi; Puri, Raj K

    2008-10-01

    Nonalcoholic steatohepatitis (NASH), the most common cause of chronic liver fibrosis, progresses to cirrhosis in up to 20% of patients. We report that hepatic stellate cells (HSC) in sinusoidal lesions of liver of patients with NASH express high levels of high-affinity IL-13R (IL-13Ralpha2), which is colocalized with smooth muscle actin, whereas fatty liver and normal liver specimens do not express IL-13Ralpha2. HSCs engineered to overexpress IL-13Ralpha2 respond to IL-13 and induce TGFB1 promoter activity and TGF-beta1 production. We also developed NASH in rats by feeding a choline-deficient l-amino acid diet. These rats developed liver fibrosis as assessed by H&E staining, Masson's trichrome and Sirius red staining, and hydroxyproline assays. Treatment of these rats with IL-13R-directed cytotoxin caused a substantial decline in fibrosis and liver enzymes without organ toxicity. These studies demonstrate that functional IL-13Ralpha2 are overexpressed in activated HSCs involved in NASH and that IL-13 cytotoxin ameliorates pathological features of NASH in rat liver, indicating a novel role of this cytotoxin in potential therapy.

  15. Fabrication and Characterization of a Single Hole Transistor in p-type GaAs/AlGaAs Heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Tracy, Lisa A [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States); Reno, John L. [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States); Hargett, Terry W. [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States)

    2015-09-01

    Most spin qubit research to date has focused on manipulating single electron spins in quantum dots. However, hole spins are predicted to have some advantages over electron spins, such as reduced coupling to host semiconductor nuclear spins and the ability to control hole spins electrically using the large spin-orbit interaction. Building on recent advances in fabricating high-mobility 2D hole systems in GaAs/AlGaAs heterostructures at Sandia, we fabricate and characterize single hole transistors in GaAs. We demonstrate p-type double quantum dot devices with few-hole occupation, which could be used to study the physics of individual hole spins and control over coupling between hole spins, looking towards eventual applications in quantum computing. Intentionally left blank

  16. Infrared absorption and visible transparency in heavily doped p-type BaSnO3

    Science.gov (United States)

    Li, Yuwei; Sun, Jifeng; Singh, David J.

    2017-01-01

    The recent experimental work shows that perovskite BaSnO3 can be heavily doped by K to become a stable p-type semiconductor. Here, we find that p-type perovskite BaSnO3 retains transparency for visible light while absorbing strongly in the infrared below 1.5 eV. The origin of the remarkable optical transparency even with heavy doping is that the interband transitions that are enabled by empty states at the top of the valence band are concentrated mainly in the energy range from 0.5 to 1.5 eV, i.e., not extending past the near IR. In contrast to n-type, the Burstein-Moss shift is slightly negative, but very small reflecting the heavier valence bands relative to the conduction bands.

  17. CCE measurements and annealing studies on proton-irradiated p-type MCz silicon diodes

    CERN Document Server

    Hoedlmoser, H; Köhler, M; Nordlund, H

    2007-01-01

    Magnetic Czochralski (MCz) silicon has recently been investigated for the development of radiation tolerant detectors for future high-luminosity HEP experiments. A study of p-type MCz Silicon diodes irradiated with protons up to a fluence of has been performed by means of Charge Collection Efficiency (CCE) measurements as well as standard CV/IV characterizations. The changes of CCE, full depletion voltage and leakage current as a function of fluence are reported. A subsequent annealing study of the irradiated detectors shows an increase in effective doping concentration and a decrease in the leakage current, whereas the CCE remains basically unchanged. Two different series of detectors have been compared differing in the implantation dose of p-spray isolation as well as effective doping concentration (Neff) of the p-type bulk presumably due to a difference in thermal donor (TD) activation during processing. The series with the higher concentration of TDs shows a delayed reverse annealing of Neff after irradia...

  18. Fabrication of p-type lithium niobate crystals by molybdenum doping and polarization

    Science.gov (United States)

    Tian, Tian; Kong, Yongfa; Liu, Hongde; Liu, Shiguo; Li, Wei; Chen, Shaolin; Xu, Jiayue

    2017-06-01

    The lack of p-type lithium niobate limits it serving as an active material. A series of Mo-doped and pure congruent lithium niobate crystals were grown by Czochralski method under different polarization conditions. Their dominant carrier species were characterized by holographic experiment. The results showed dominant charge carrier species may be changed from electrons to holes when lithium niobate crystal was doped with Mo ions and polarized under the current of 70mA for 30 minutes. It indicated that p-type lithium niobate crystal could be fabricated by Mo-doping and suitably controlling the polarization condition. Mo-doped lithium niobate crystals can be a promising candidate for active components.

  19. Enhancement of p-type mobility in tin monoxide by native defects

    KAUST Repository

    Granato, D. B.

    2013-05-31

    Transparent p-type materials with good mobility are needed to build completely transparent p-n junctions. Tin monoxide (SnO) is a promising candidate. A recent study indicates great enhancement of the hole mobility of SnO grown in Sn-rich environment [E. Fortunato et al., Appl. Phys. Lett. 97, 052105 (2010)]. Because such an environment makes the formation of defects very likely, we study defect effects on the electronic structure to explain the increased mobility. We find that Sn interstitials and O vacancies modify the valence band, inducing higher contributions of the delocalized Sn 5p orbitals as compared to the localized O 2p orbitals, thus increasing the mobility. This mechanism of valence band modification paves the way to a systematic improvement of transparent p-type semiconductors.

  20. A Density Functional Theory Study of Doped Tin Monoxide as a Transparent p-type Semiconductor

    KAUST Repository

    Bianchi Granato, Danilo

    2012-05-01

    In the pursuit of enhancing the electronic properties of transparent p-type semiconductors, this work uses density functional theory to study the effects of doping tin monoxide with nitrogen, antimony, yttrium and lanthanum. An overview of the theoretical concepts and a detailed description of the methods employed are given, including a discussion about the correction scheme for charged defects proposed by Freysoldt and others [Freysoldt 2009]. Analysis of the formation energies of the defects points out that nitrogen substitutes an oxygen atom and does not provide charge carriers. On the other hand, antimony, yttrium, and lanthanum substitute a tin atom and donate n-type carriers. Study of the band structure and density of states indicates that yttrium and lanthanum improves the hole mobility. Present results are in good agreement with available experimental works and help to improve the understanding on how to engineer transparent p-type materials with higher hole mobilities.

  1. Efficiency Improvement of HIT Solar Cells on p-Type Si Wafers

    Directory of Open Access Journals (Sweden)

    Chun-You Wei

    2013-11-01

    Full Text Available Single crystal silicon solar cells are still predominant in the market due to the abundance of silicon on earth and their acceptable efficiency. Different solar-cell structures of single crystalline Si have been investigated to boost efficiency; the heterojunction with intrinsic thin layer (HIT structure is currently the leading technology. The record efficiency values of state-of-the art HIT solar cells have always been based on n-type single-crystalline Si wafers. Improving the efficiency of cells based on p-type single-crystalline Si wafers could provide broader options for the development of HIT solar cells. In this study, we varied the thickness of intrinsic hydrogenated amorphous Si layer to improve the efficiency of HIT solar cells on p-type Si wafers.

  2. Comment on 'Electronic Properties of Red P-Type T12S5 Single Crystals'

    Institute of Scientific and Technical Information of China (English)

    M. Cankurtaran; H. (C)elik

    2007-01-01

    Recently, Gamal et al. [Chin. Phys. Lett. 22 (2005) 1530] reported the results of electrical conductivity, Hall effect and thermoelectric measurements on p-type Th2S5 single crystals. From the experimental data for the temperature dependence of differential thermoelectric power, Gamal et al. determined the values of 2.66 × 10-41 kg and 2.50 × 10-41 kg, respectively, for the effective masses of electrons and holes in p-type Tl2S5, which are about ten orders of magnitude smaller than the free electron mass (9.11 × 10-31 kg). We argue that the anomalously small values obtained for the effective mass of charge carriers in Tl2S5 have no physical significance.

  3. An integrated driving circuit implemented with p-type LTPS TFTs for AMOLED

    Institute of Scientific and Technical Information of China (English)

    ZHAO Li-qing; WU Chun-ya; HAO Da-shou; YAO Ying; MENG Zhi-guo; XIONG Shao-zhen

    2009-01-01

    Based on the technology of low temperature poly silicon thin film transistors (poly-Si-TFTs), a novel p-type TFT AMOLED panel with self-scanned driving circuit is introduced in this paper. A shift register formed with novel p-type TFTs is pro-posed to realize the gate driver. A flip-latch cooperated with the shift register is designed to conduct the data writing. In order to verify the validity of the proposed design, the circuits are simulated with SILVACO TCAD tools, using the MODEL in which the parameters of LTPS TFTs were extracted from the LTPS TFTs made in our lab. The simulation results indicate that the circuit can fulfill the driving function.

  4. Preparation and Photovoltaic Properties of p-Type Nano-ZnFe2O4

    Institute of Scientific and Technical Information of China (English)

    LI Zi-heng; ZOU Xu; LI Gen; ZOU Guang-tian

    2012-01-01

    p-Type nano-ZnFe2O4 semiconductors were gained by high-prssure treatment.Surface photovoltaic spectrum(SPS) and transient photovoltaic technology(TPV) were used for studying the photogenerated charge of nano-ZnFe2O4.Results show that the photovoltaic behavior of nano-ZnFe2O4 changed as the processing pressure increased.When the processing pressure was higher than 2 GPa,both SPS response interval and peak changed significantly.XPS results show that the non-lattice oxygen entered into the lattice and the content of lattice oxygen increased with the increase of processing pressure.The material changed from oxygen vacancy type to oxygen excess type and the photoelectric properties changed from n-type to p-type when the processing pressure is higher than 2GPa.

  5. Piezoelectric Nanogenerator Using p-Type ZnO Nanowire Arrays

    KAUST Repository

    Lu, Ming-Pei

    2009-03-11

    Using phosphorus-doped ZnO nanowire (NW) arrays grown on silicon substrate, energy conversion using the p-type ZnO NWs has been demonstrated for the first time. The p-type ZnO NWs produce positive output voltage pulses when scanned by a conductive atomic force microscope (AFM) in contact mode. The output voltage pulse is generated when the tip contacts the stretched side (positive piezoelectric potential side) of the NW. In contrast, the n-type ZnO NW produces negative output voltage when scanned by the AFM tip, and the output voltage pulse is generated when the tip contacts the compressed side (negative potential side) of the NW. In reference to theoretical simulation, these experimentally observed phenomena have been systematically explained based on the mechanism proposed for a nanogenerator. © 2009 American Chemical Society.

  6. In and out of the cation pumps: P-type ATPase structure revisited

    DEFF Research Database (Denmark)

    Bublitz, Maike; Poulsen, Hanne; Morth, Jens Preben

    2010-01-01

    Active transport across membranes is a crucial requirement for life. P-type ATPases build up electrochemical gradients at the expense of ATP by forming and splitting a covalent phosphoenzyme intermediate, coupled to conformational changes in the transmembrane section where the ions are translocated....... The marked increment during the last three years in the number of crystal structures of P-type ATPases has greatly improved our understanding of the similarities and differences of pumps with different ion specificities, since the structures of the Ca2+-ATPase, the Na+,K+-ATPase and the H+-ATPase can now...... be compared directly. Mechanisms for ion gating, charge neutralization and backflow prevention are starting to emerge from comparative structural analysis; and in combination with functional studies of mutated pumps this provides a framework for speculating on how the ions are bound and released as well...

  7. Perspectives of High-Temperature Thermoelectric Applications and p-type and n-type Aluminoborides

    Science.gov (United States)

    Mori, T.

    2016-10-01

    A need exists to develop high-temperature thermoelectric materials which can utilize high-temperature unutilized/waste heat in thermal power plants, steelworks, factories, incinerators, etc., and also focused solar power. The thermal power plant topping application is of potential high impact since it can sizably increase the efficiency of power plants which are the major supply of electrical power for many countries. Higher borides are possible candidates for their particular high-temperature stability, generally large Seebeck coefficients, α, and intrinsic low thermal conductivity. Excellent (|α| > 200 μV/K) p-type or n-type behavior was recently achieved in the aluminoboride YAl x B14 by varying the occupancy of Al sites, x. Finding p-type and n-type counterparts has long been a difficulty of thermoelectric research not limited to borides. This paper reviews possible high-temperature thermoelectric applications, and recent developments and perspectives of thermoelectric aluminoborides.

  8. CALCULATING THE HABITABLE ZONE OF BINARY STAR SYSTEMS. II. P-TYPE BINARIES

    Energy Technology Data Exchange (ETDEWEB)

    Haghighipour, Nader [Institute for Astronomy and NASA Astrobiology Institute, University of Hawaii-Manoa, Honolulu, HI 96822 (United States); Kaltenegger, Lisa [MPIA, Koenigstuhl 17, Heidelberg, D-69117 (Germany)

    2013-11-10

    We have developed a comprehensive methodology for calculating the circumbinary habitable zone (HZ) in planet-hosting P-type binary star systems. We present a general formalism for determining the contribution of each star of the binary to the total flux received at the top of the atmosphere of an Earth-like planet and use the Sun's HZ to calculate the inner and outer boundaries of the HZ around a binary star system. We apply our calculations to the Kepler's currently known circumbinary planetary systems and show the combined stellar flux that determines the boundaries of their HZs. We also show that the HZ in P-type systems is dynamic and, depending on the luminosity of the binary stars, their spectral types, and the binary eccentricity, its boundaries vary as the stars of the binary undergo their orbital motion. We present the details of our calculations and discuss the implications of the results.

  9. Sensitization of p-type NiO using n-type conducting polymers

    NARCIS (Netherlands)

    Chavhan, S.D.; Abellon, R.D.; Breemen, A.J.J.M. van; Koetse, M.M.; Sweelssen, J.; Savenije, T.J.

    2010-01-01

    We report on the sensitization of a p-type inorganic semiconductor, NiO, by n-type conjugated polymers. NiO thin films were deposited using RF sputtering in pure Ar (NiO A) or in Ar + O2 (90% + 10%) (NiO B). XPS and Kelvin probe measurements indicate the incorporation of oxygen in NiO B

  10. Sensitization of p-type NiO using n-type conducting polymers

    NARCIS (Netherlands)

    Chavhan, S.D.; Abellon, R.D.; Breemen, A.J.J.M. van; Koetse, M.M.; Sweelssen, J.; Savenije, T.J.

    2010-01-01

    We report on the sensitization of a p-type inorganic semiconductor, NiO, by n-type conjugated polymers. NiO thin films were deposited using RF sputtering in pure Ar (NiO A) or in Ar + O2 (90% + 10%) (NiO B). XPS and Kelvin probe measurements indicate the incorporation of oxygen in NiO B l

  11. Investigation of negative photoconductivity in p-type Pb1-xSnxTe film

    Science.gov (United States)

    Tavares, M. A. B.; da Silva, M. J.; Peres, M. L.; de Castro, S.; Soares, D. A. W.; Okazaki, A. K.; Fornari, C. I.; Rappl, P. H. O.; Abramof, E.

    2017-01-01

    We investigated the negative photoconductivity (NPC) effect that was observed in a p-type Pb1-xSnxTe film for temperatures varying from 300 K down to 85 K. We found that this effect is a consequence of defect states located in the bandgap which act as trapping levels, changing the relation between generation and recombination rates. Theoretical calculations predict contributions to the NPC from both conduction and valence bands, which are in accordance with the experimental observations.

  12. Sensitization of p-type NiO using n-type conducting polymers

    NARCIS (Netherlands)

    Chavhan, S.D.; Abellon, R.D.; Breemen, A.J.J.M. van; Koetse, M.M.; Sweelssen, J.; Savenije, T.J.

    2010-01-01

    We report on the sensitization of a p-type inorganic semiconductor, NiO, by n-type conjugated polymers. NiO thin films were deposited using RF sputtering in pure Ar (NiO A) or in Ar + O2 (90% + 10%) (NiO B). XPS and Kelvin probe measurements indicate the incorporation of oxygen in NiO B l

  13. Radiation damage studies of multi-guard ring p-type bulk diodes

    CERN Document Server

    Bortoletto, D; Günther, M; Grim, G P; Lander, R L; Willard, S; Li, Z

    1999-01-01

    Several diodes with different multi-guard ring structures were fabricated from 10 k OMEGA cm p-type bulk material. Studies on the performance of such devices are presented here. They include the measurement of the leakage current, breakdown voltage and charge collection efficiency before and after 2x10 sup 1 sup 4 p/cm sup 2 irradiation with 63.3 MeV kinetic protons. (author)

  14. Method for producing high carrier concentration p-Type transparent conducting oxides

    Science.gov (United States)

    Li, Xiaonan; Yan, Yanfa; Coutts, Timothy J.; Gessert, Timothy A.; Dehart, Clay M.

    2009-04-14

    A method for producing transparent p-type conducting oxide films without co-doping plasma enhancement or high temperature comprising: a) introducing a dialkyl metal at ambient temperature and a saturated pressure in a carrier gas into a low pressure deposition chamber, and b) introducing NO alone or with an oxidizer into the chamber under an environment sufficient to produce a metal-rich condition to enable NO decomposition and atomic nitrogen incorporation into the formed transparent metal conducting oxide.

  15. Ouabain Protects Human Renal Cells against the Cytotoxic Effects of Shiga Toxin Type 2 and Subtilase Cytotoxin

    Directory of Open Access Journals (Sweden)

    María M. Amaral

    2017-07-01

    Full Text Available Hemolytic uremic syndrome (HUS is one of the most common causes of acute renal failure in children. The majority of cases are associated with Shiga toxin (Stx-producing Escherichia coli (STEC. In Argentina, HUS is endemic and presents the highest incidence rate in the world. STEC strains expressing Stx type 2 (Stx2 are responsible for the most severe cases of this pathology. Subtilase cytotoxin (SubAB is another STEC virulence factor that may contribute to HUS pathogenesis. To date, neither a licensed vaccine nor effective therapy for HUS is available for humans. Considering that Ouabain (OUA may prevent the apoptosis process, in this study we evaluated if OUA is able to avoid the damage caused by Stx2 and SubAB on human glomerular endothelial cells (HGEC and the human proximal tubule epithelial cell (HK-2 line. HGEC and HK-2 were pretreated with OUA and then incubated with the toxins. OUA protected the HGEC viability from Stx2 and SubAB cytotoxic effects, and also prevented the HK-2 viability from Stx2 effects. The protective action of OUA on HGEC and HK-2 was associated with a decrease in apoptosis and an increase in cell proliferation. Our data provide evidence that OUA could be considered as a therapeutic strategy to avoid the renal damage that precedes HUS.

  16. Sat, the secreted autotransporter toxin of uropathogenic Escherichia coli, is a vacuolating cytotoxin for bladder and kidney epithelial cells.

    Science.gov (United States)

    Guyer, Debra M; Radulovic, Suzana; Jones, Faye-Ellen; Mobley, Harry L T

    2002-08-01

    The secreted autotransporter toxin (Sat) of uropathogenic Escherichia coli exhibits cytopathic activity upon incubation with HEp-2 cells. We further investigated the effects of Sat on cell lines more relevant to the urinary tract, namely, those derived from bladder and kidney epithelium. Sat elicited elongation of cells and apparent loosening of cellular junctions upon incubation with Vero kidney cells. Additionally, incubation with Sat triggered significant vacuolation within the cytoplasm of both human bladder (CRL-1749) and kidney (CRL-1573) cell lines. This activity has been associated with only a few other known toxins. Following transurethral infection of CBA mice with a sat mutant, no reduction of CFU in urine, bladder, or kidney tissue was seen compared to that in mice infected with wild-type E. coli CFT073. However, significant histological changes were observed within the kidneys of mice infected with wild-type E. coli CFT073, including dissolution of the glomerular membrane and vacuolation of proximal tubule cells. Such damage was not observed in kidney sections of mice infected with a Sat-deficient mutant. These results indicate that Sat, a vacuolating cytotoxin expressed by uropathogenic E. coli CFT073, elicits defined damage to kidney epithelium during upper urinary tract infection and thus contributes to pathogenesis of urinary tract infection.

  17. Pseudolipasin A is a specific inhibitor for phospholipase A2 activity of Pseudomonas aeruginosa cytotoxin ExoU.

    Science.gov (United States)

    Lee, Vincent T; Pukatzki, Stefan; Sato, Hiromi; Kikawada, Eriya; Kazimirova, Anastasia A; Huang, Jin; Li, Xiaohua; Arm, Jonathan P; Frank, Dara W; Lory, Stephen

    2007-03-01

    A number of bacterial pathogens utilize the type III secretion pathway to deliver effector proteins directly into the host cell cytoplasm. Certain strains of Pseudomonas aeruginosa associated with acute infections express a potent cytotoxin, exoenzyme U (ExoU), that is delivered via the type III secretion pathway directly into contacting host cells. Once inside the mammalian cell, ExoU rapidly lyses the intoxicated cells via its phospholipase A(2) (PLA(2)) activity. A high-throughput cell-based assay was developed to screen libraries of compounds for those capable of protecting cells against the cytotoxic effects of ExoU. A number of compounds were identified in this screen, including one group that blocks the intracellular activity of ExoU. In addition, these compounds specifically inhibited the PLA(2) activity of ExoU in vitro, whereas eukaryotic secreted PLA(2) and cytosolic PLA(2) were not inhibited. This novel inhibitor of ExoU-specific PLA(2) activity, named pseudolipasin A, may provide a new lead for virulence factor-based therapeutic design.

  18. Impact of cytotoxin-associated gene A of Helicobacter pylori strains on microalbuminuria in type 2 diabetes

    Directory of Open Access Journals (Sweden)

    Ibrahim Amany

    2010-01-01

    Full Text Available Cytotoxin-associated gene A (CagA positive strains of H. pylori have a significant correlation with gastritis and peptic ulcer, and may induce persistent systemic inflammatory response, increase vascular damage, and compromise glycemic control in diabetic patients. To evaluate correlation between infection by cagA positive strains of H. pylori and occurrence of microalbuminuria and glycemic control in type 2 diabetic patients, we prospectively studied 98 dyspeptic type 2 diabetic patients as a study group and 102 dyspeptic non-diabetic subjects as a control group. Gastric biopsy specimens obtained with endoscopy were cultured to isolate H. pylori. All the isolated H. pylori strains from cultures were used for detection of cagA gene by polymerase chain reaction. There was no significant difference between study and control groups regarding infection with cagA positive strains of H. pylori ( P= 0.145. Furthermore, there was no significant differences between both groups concerning the incidence of microalbuminuria ( P= 0.145. On the other hand, there was an extremely statistically significant difference in the inci-dence of microalbuminuria and glycemic control in the diabetic patients between those infected with cagA positive strains of H. pylori and cag A negative starins (P= 0.000. We conclude that infection with cagA positive strains of H. pylori are strongly associated with the increased inci-dence of microalbuminuria and poor glycemic control in type 2 diabetic patients.

  19. Sequence and apoptotic activity of VacA cytotoxin cloned from a Helicobacter pylori Thai clinical isolate.

    Science.gov (United States)

    Junaid, Muhammad; Al-Gubare, Sarbast; Yousef, Muhammad; Ubol, Mathukorn Na; Leetachewa, Somphob; Muanprasat, Chatchai; Angsuthanasombat, Chanan; Chaicumpa, Wanpen; Ali, Niaz; Katzenmeier, Gerd

    2014-01-01

    The vacuolating cytotoxin VacA produced by Helicobacter pylori induces the formation of large cytoplasmic vacuoles in host gastric epithelial cells as well as a release of cytochrome C from mitochondria resulting in cell apoptosis. Considerable sequence diversity in VacA relating to different degrees of disease severity is observed with clinical samples from a multitude of geographic places. In this study we describe expression in Escherichia coli, purification to homogeneity and in vitro assay of its apoptotic activity of a VacA toxin from a H. pylori isolate of a Thai patient with gastrointestinal lymphoma. Sequencing revealed that the deduced amino acid sequence of the cloned Thai isolate VacA is similar to H. pylori s1/m2 type strains. The percent sequence similarity to the model strain 60190 was lower due to the presence of extra amino acids in the mid (m) region. The purified VacA toxin exhibited significant apoptotic activity on both T84 and MDCK epithelial cell lines, as revealed by DAPI staining, whereby the observed activity was significantly higher on MDCK cells. These findings could relate to a modulation of VacA activity on host cells in the Thai isolate-VacA toxin that may differ from those of the model strain.

  20. Sequence and Apoptotic Activity of VacA Cytotoxin Cloned from a Helicobacter pylori Thai Clinical Isolate

    Directory of Open Access Journals (Sweden)

    Muhammad Junaid

    2014-01-01

    Full Text Available The vacuolating cytotoxin VacA produced by Helicobacter pylori induces the formation of large cytoplasmic vacuoles in host gastric epithelial cells as well as a release of cytochrome C from mitochondria resulting in cell apoptosis. Considerable sequence diversity in VacA relating to different degrees of disease severity is observed with clinical samples from a multitude of geographic places. In this study we describe expression in Escherichia coli, purification to homogeneity and in vitro assay of its apoptotic activity of a VacA toxin from a H. pylori isolate of a Thai patient with gastrointestinal lymphoma. Sequencing revealed that the deduced amino acid sequence of the cloned Thai isolate VacA is similar to H. pylori s1/m2 type strains. The percent sequence similarity to the model strain 60190 was lower due to the presence of extra amino acids in the mid (m region. The purified VacA toxin exhibited significant apoptotic activity on both T84 and MDCK epithelial cell lines, as revealed by DAPI staining, whereby the observed activity was significantly higher on MDCK cells. These findings could relate to a modulation of VacA activity on host cells in the Thai isolate-VacA toxin that may differ from those of the model strain.

  1. Record mobility in transparent p-type tin monoxide films and devices by phase engineering

    KAUST Repository

    Caraveo-Frescas, Jesus Alfonso

    2013-06-25

    Here, we report the fabrication of nanoscale (15 nm) fully transparent p-type SnO thin film transistors (TFT) at temperatures as low as 180 C with record device performance. Specifically, by carefully controlling the process conditions, we have developed SnO thin films with a Hall mobility of 18.71 cm2 V-1 s-1 and fabricated TFT devices with a linear field-effect mobility of 6.75 cm2 V-1 s -1 and 5.87 cm2 V-1 s-1 on transparent rigid and translucent flexible substrates, respectively. These values of mobility are the highest reported to date for any p-type oxide processed at this low temperature. We further demonstrate that this high mobility is realized by careful phase engineering. Specifically, we show that phase-pure SnO is not necessarily the highest mobility phase; instead, well-controlled amounts of residual metallic tin are shown to substantially increase the hole mobility. A detailed phase stability map for physical vapor deposition of nanoscale SnO is constructed for the first time for this p-type oxide. © 2013 American Chemical Society.

  2. Electronic inhomogeneity in n- and p-type PbTe detected by 125Te NMR

    Science.gov (United States)

    Levin, E. M.; Heremans, J. P.; Kanatzidis, M. G.; Schmidt-Rohr, K.

    2013-09-01

    125Te nuclear magnetic resonance spectra and spin-lattice relaxation of n- and p-type PbTe, self-doping narrow band-gap semiconductors, have been studied and compared to those of p-type GeTe. Spin-lattice relaxation in GeTe can be fit by one component, while that in both PbTe samples must be fit by at least two components, showing electronically homogeneous and inhomogeneous materials, respectively. For PbTe-based materials, the spin-lattice relaxation rate 1/T1 increases linearly with carrier concentration. The data for GeTe fall on the same line and allow us to extend this plot to higher concentrations. Long and short T1 components in both PbTe samples reflect “low,” ˜1017 cm-3, and “high,” ˜1018 cm-3, carrier concentration components. Carrier concentrations in both n- and p-type PbTe samples obtained from the Hall and Seebeck effects generally match the “high” carrier concentration component, and to some extent, ignore the “low” one. This demonstrates that the Hall and Seebeck effects may have a limited ability for the determination of carrier concentration in complex thermoelectric PbTe-based and other multicomponent materials.

  3. Comparing n- and p-type polycrystalline silicon absorbers in thin-film solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Deckers, J. [imec, Kapeldreef 75, B-3001 Heverlee, Leuven (Belgium); ESAT, KU Leuven, Kardinaal Mercierlaan 94, B-3001 Heverlee, Leuven (Belgium); Bourgeois, E. [Institute for Materials Research (IMO), Hasselt University, Wetenschapspark 1, B-3590 Diepenbeek (Belgium); IMOMEC, IMEC vzw, Wetenschapspark 1, B-3590 Diepenbeek (Belgium); Jivanescu, M. [Department of Physics and Astronomy, University of Leuven, Celestijnenlaan 200D, B-3001 Heverlee, Leuven (Belgium); Abass, A. [Photonics Research Group (INTEC), Ghent University-imec, Sint-Pietersnieuwstraat 41, B-9000 Ghent (Belgium); Van Gestel, D.; Van Nieuwenhuysen, K.; Douhard, B. [imec, Kapeldreef 75, B-3001 Heverlee, Leuven (Belgium); D' Haen, J.; Nesladek, M.; Manca, J. [Institute for Materials Research (IMO), Hasselt University, Wetenschapspark 1, B-3590 Diepenbeek (Belgium); IMOMEC, IMEC vzw, Wetenschapspark 1, B-3590 Diepenbeek (Belgium); Gordon, I.; Bender, H. [imec, Kapeldreef 75, B-3001 Heverlee, Leuven (Belgium); Stesmans, A. [Department of Physics and Astronomy, University of Leuven, Celestijnenlaan 200D, B-3001 Heverlee, Leuven (Belgium); Mertens, R.; Poortmans, J. [imec, Kapeldreef 75, B-3001 Heverlee, Leuven (Belgium); ESAT, KU Leuven, Kardinaal Mercierlaan 94, B-3001 Heverlee, Leuven (Belgium)

    2015-03-31

    We have investigated fine grained polycrystalline silicon thin films grown by direct chemical vapor deposition on oxidized silicon substrates. More specifically, we analyze the influence of the doping type on the properties of this model polycrystalline silicon material. This includes an investigation of defect passivation and benchmarking of minority carrier properties. In our investigation, we use a variety of characterization techniques to probe the properties of the investigated polycrystalline silicon thin films, including Fourier Transform Photoelectron Spectroscopy, Electron Spin Resonance, Conductivity Activation, and Suns-Voc measurements. Amphoteric silicon dangling bond defects are identified as the most prominent defect type present in these layers. They are the primary recombination center in the relatively lowly doped polysilicon thin films at the heart of the current investigation. In contrast with the case of solar cells based on Czochralski silicon or multicrystalline silicon wafers, we conclude that no benefit is found to be associated with the use of n-type dopants over p-type dopants in the active absorber of the investigated polycrystalline silicon thin-film solar cells. - Highlights: • Comparison of n- and p-type absorbers for thin-film poly-Si solar cells • Extensive characterization of the investigated layers' characteristics • Literature review pertaining the use of n-type and p-type dopants in silicon.

  4. P-type electronic and thermal transport properties of Mg2Sn1-xSix

    Science.gov (United States)

    Kim, Sunphil; Wiendlocha, Bartlomiej; Heremans, Joseph P.

    2013-03-01

    P-type Mg2Sn doped with various acceptors(1)(2) has been studied as a potential thermoelectric material. Because of its narrow band gap and high lattice thermal conductivity, the zT values of the binary compound are limited: zTmax reported is 0.3(3). In this work, we synthesize and characterize p-type-doped Mg2Sn1-xSix with various acceptors. Silicon is added in order to widen the band gap and scatter the phonons. The conduction band degeneracy that yields excellent zT in n-type material in the Mg2Sn1-xSix alloy system unfortunately does not apply to p-type material. Thermomagnetic and galvanomagnetic properties (electrical resistivity, Seebeck, Hall, and Nernst coefficients) are measured, along with thermal conductivity and band gap measurements. Finally, zT values are reported. (1) H. Y. Chen et al. Journal of Electronic Materials, Vol. 38, No. 7, 2009 (2) S. Choi et al. Journal of Electronic Materials, Vol. 41, No. 6, 2012 (3) H. Y. Chen et al. Phys. Status Solidi A 207, No. 11, 2523-2531 (2010) The work is supported by the joint NSF/DOE program on thermoelectrics, NSF-CBET-1048622

  5. Effective p-type N-doped WS{sub 2} monolayer

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Xu, E-mail: zhaoxu@htu.cn; Xia, Congxin; Wang, Tianxing; Peng, Yuting; Dai, Xianqi

    2015-11-15

    Based on density functional theory, the characteristics of n- and p-type dopants are investigated by means of group V and VII atoms substituting sulfur in the WS{sub 2} monolayer. Numerical results show that for each doping case, the formation energy is lower under W-rich condition, which indicates that it is energy favorable to incorporate group V and VII atoms into WS{sub 2} under W-rich experimental conditions. Moreover, compared with other dopant cases, N-doped WS{sub 2} monolayer owns the lowest formation energy. In particular, the transition level of (−1/0) is only 75 meV in the N-doped case, which indicates that N impurities can offer effective p-type carriers in the WS{sub 2} monolayer. - Highlights: • The formation energy is lower under W-rich conditions. • N-doped system owns the lowest formation energy compared with other atoms. • The transition level of N-doping in WS{sub 2} is 75 meV. • N impurities can offer effective p-type carriers in the WS{sub 2}.

  6. Demethoxycurcumin Is A Potent Inhibitor of P-Type ATPases from Diverse Kingdoms of Life.

    Science.gov (United States)

    Dao, Trong Tuan; Sehgal, Pankaj; Tung, Truong Thanh; Møller, Jesper Vuust; Nielsen, John; Palmgren, Michael; Christensen, Søren Brøgger; Fuglsang, Anja Thoe

    2016-01-01

    P-type ATPases catalyze the active transport of cations and phospholipids across biological membranes. Members of this large family are involved in a range of fundamental cellular processes. To date, a substantial number of P-type ATPase inhibitors have been characterized, some of which are used as drugs. In this work a library of natural compounds was screened and we first identified curcuminoids as plasma membrane H+-ATPases inhibitors in plant and fungal cells. We also found that some of the commercial curcumins contain several curcuminoids. Three of these were purified and, among the curcuminoids, demethoxycurcumin was the most potent inhibitor of all tested P-type ATPases from fungal (Pma1p; H+-ATPase), plant (AHA2; H+-ATPase) and animal (SERCA; Ca2+-ATPase) cells. All three curcuminoids acted as non-competitive antagonist to ATP and hence may bind to a highly conserved allosteric site of these pumps. Future research on biological effects of commercial preparations of curcumin should consider the heterogeneity of the material.

  7. p-Type Quasi-Mono Silicon Solar Cell Fabricated by Ion Implantation

    Directory of Open Access Journals (Sweden)

    Chien-Ming Lee

    2013-01-01

    Full Text Available The p-type quasi-mono wafer is a novel type of silicon material that is processed using a seed directional solidification technique. This material is a promising alternative to traditional high-cost Czochralski (CZ and float-zone (FZ material. Here, we evaluate the application of an advanced solar cell process featuring a novel method of ion implantation on p-type quasi-mono silicon wafer. The ion implantation process has simplified the normal industrial process flow by eliminating two process steps: the removal of phosphosilicate glass (PSG and the junction isolation process that is required after the conventional thermal POCl3 diffusion process. Moreover, the good passivation performance of the ion implantation process improves Voc. Our results show that, after metallization and cofiring, an average cell efficiency of 18.55% can be achieved using 156 × 156 mm p-type quasi-mono silicon wafer. Furthermore, the absolute cell efficiency obtained using this method is 0.47% higher than that for the traditional POCl3 diffusion process.

  8. Enhanced thermopower and low thermal conductivity in p-type polycrystalline ZrTe5

    Science.gov (United States)

    Hooda, M. K.; Yadav, C. S.

    2017-07-01

    Thermoelectric properties of polycrystalline p-type ZrTe5 are reported in the temperature (T) range of 2-340 K. Thermoelectric power (S) is positive and reaches up to 458 μV/K at 340 K on increasing T. The value of Fermi energy 16 meV suggests a low carrier density of ≈9.5 × 1018 cm-3. A sharp anomaly in S data is observed at 38 K, which seems intrinsic to p-type ZrTe5. The thermal conductivity (κ) value is low (2 W/m K at T = 300 K) with major contribution from the lattice part. Electrical resistivity data show the metal to semiconductor transition at T ˜ 150 K and non-Arrhenius behavior in the semiconducting region. The figure of merit zT (0.026 at T = 300 K) is ˜63% higher than that of HfTe5 (0.016) and better than those of the conventional SnTe, p-type PbTe, and bipolar pristine ZrTe5 compounds.

  9. Efficient synthesis of triarylamine-based dyes for p-type dye-sensitized solar cells

    Science.gov (United States)

    Wild, Martin; Griebel, Jan; Hajduk, Anna; Friedrich, Dirk; Stark, Annegret; Abel, Bernd; Siefermann, Katrin R.

    2016-05-01

    The class of triarylamine-based dyes has proven great potential as efficient light absorbers in inverse (p-type) dye sensitized solar cells (DSSCs). However, detailed investigation and further improvement of p-type DSSCs is strongly hindered by the fact that available synthesis routes of triarylamine-based dyes are inefficient and particularly demanding with regard to time and costs. Here, we report on an efficient synthesis strategy for triarylamine-based dyes for p-type DSSCs. A protocol for the synthesis of the dye-precursor (4-(bis(4-bromophenyl)amino)benzoic acid) is presented along with its X-ray crystal structure. The dye precursor is obtained from the commercially available 4(diphenylamino)benzaldehyde in a yield of 87% and serves as a starting point for the synthesis of various triarylamine-based dyes. Starting from the precursor we further describe a synthesis protocol for the dye 4-{bis[4‧-(2,2-dicyanovinyl)-[1,1‧-biphenyl]-4-yl]amino}benzoic acid (also known as dye P4) in a yield of 74%. All synthesis steps are characterized by high yields and high purities without the need for laborious purification steps and thus fulfill essential requirements for scale-up.

  10. Ivermectin is a nonselective inhibitor of mammalian P-type ATPases.

    Science.gov (United States)

    Pimenta, Paulo Henrique Cotrim; Silva, Claudia Lucia Martins; Noël, François

    2010-02-01

    Ivermectin is a large spectrum antiparasitic drug that is very safe at the doses actually used. However, as it is being studied for new applications that would require higher doses, we should pay attention to its effects at high concentrations. As micromolar concentrations of ivermectin have been reported to inhibit the sarco-endoplasmic reticulum Ca(2+)-ATPase (SERCA), we decided to investigate its putative inhibitory effect on other two important P-type ATPases, namely the Na(+) , K(+)-ATPase and H(+)/K(+)-ATPase. We first extended the data on SERCA, using preparations from rat enriched in SERCA1a (extensor digitorum longus) and 1b (heart) isoforms. Secondly, we tested the effect of ivermectin in two preparations of rat Na(+), K(+)-ATPase in order to appreciate its putative selectivity towards the alpha(1) isoform (kidney) and the alpha(2)/alpha(3) isoforms (brain), and in an H(+)/K(+)-ATPase preparation from rat stomach. Ivermectin inhibited all these ATPases with similar IC(50) values (6-17 microM). With respect to the inhibition of the Na(+), K(+)-ATPase, ivermectin acts by a mechanism different from the classical cardiac glycosides, based on selectivity towards the isoforms, sensibility to the antagonistic effect of K(+) and to ionic conditions favoring different conformations of the enzyme. We conclude that ivermectin is a nonselective inhibitor of three important mammalian P-type ATPases, which is indicative of putative important adverse effects if this drug were used at high doses. As a consequence, we propose that novel analogs of ivermectin should be developed and tested both for their parasitic activity and in vitro effects on P-type ATPases.

  11. Enhanced photovoltaic effect of ruthenium complex-modified graphene oxide with P-type conductivity

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Wei, E-mail: jj_zw_js@sina.com.cn; Bai, Huicong; Zhang, Yu; Sun, Ying; Lin, Shen; Liu, Jian; Yang, Qi; Song, Xi-Ming, E-mail: songlab@lnu.edu.cn

    2014-10-15

    A graphene oxide nanocomposite with bis(1,10-phenanthroline)(N-(2-aminoethyl)-4-(4-methyl-2,2-bipyridine-4-yl) formamide) ruthenium (Ru(phen){sub 2}(bpy-NH{sub 2})(PF{sub 6}){sub 2}), a ruthenium complex, was synthesized by amidation reaction between amino group of the ruthenium complex and carboxyl group of GO. The as-prepared Ru(II)–GO composite was characterized by infrared (IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), ultraviolet–visible (UV–Vis) absorption spectra, fluorescence spectra, surface photovoltage (SPV) spectrum and transient photovoltage (TPV) technology. This nanocomposite showed a typical p-type character and an enhanced photovoltaic effect at long timescale of about 3 × 10{sup −3} s compared to GO alone. A reversible rise/decay of the photocurrent in response to the on/off illumination step was also observed in a photoelectrochemical cell of the Ru(II)–GO composite. The photocurrent response of the Ru(II)–GO film was remarkably higher than that of GO film. Therefore, this Ru(II)–GO composite is believed to be a promising p-type photoelectric conversion material for further photovoltaic applications. - Highlights: • A new dye-sensitized graphene oxide nanocomposite was reported. • A photo-induced charge transfer process in this nanocomposite was confirmed. • This composite showed a typical p-type conductivity. • This composite showed an enhanced photovoltaic effect at a long timescale.

  12. Quasi-perpetual discharge behaviour in p-type Ge-air batteries.

    Science.gov (United States)

    Ocon, Joey D; Kim, Jin Won; Abrenica, Graniel Harne A; Lee, Jae Kwang; Lee, Jaeyoung

    2014-11-07

    Metal-air batteries continue to become attractive energy storage and conversion systems due to their high energy and power densities, safer chemistries, and economic viability. Semiconductor-air batteries - a term we first define here as metal-air batteries that use semiconductor anodes such as silicon (Si) and germanium (Ge) - have been introduced in recent years as new high-energy battery chemistries. In this paper, we describe the excellent doping-dependent discharge kinetics of p-type Ge anodes in a semiconductor-air cell employing a gelled KOH electrolyte. Owing to its Fermi level, n-type Ge is expected to have lower redox potential and better electronic conductivity, which could potentially lead to a higher operating voltage and better discharge kinetics. Nonetheless, discharge measurements demonstrated that this prediction is only valid at the low current regime and breaks down at the high current density region. The p-type Ge behaves extremely better at elevated currents, evident from the higher voltage, more power available, and larger practical energy density from a very long discharge time, possibly arising from the high overpotential for surface passivation. A primary semiconductor-air battery, powered by a flat p-type Ge as a multi-electron anode, exhibited an unprecedented full discharge capacity of 1302.5 mA h gGe(-1) (88% anode utilization efficiency), the highest among semiconductor-air cells, notably better than new metal-air cells with three-dimensional and nanostructured anodes, and at least two folds higher than commercial Zn-air and Al-air cells. We therefore suggest that this study be extended to doped-Si anodes, in order to pave the way for a deeper understanding on the discharge phenomena in alkaline metal-air conversion cells with semiconductor anodes for specific niche applications in the future.

  13. Electroforming-free resistive switching memory effect in transparent p-type tin monoxide

    KAUST Repository

    Hota, M. K.

    2014-04-14

    We report reproducible low bias bipolar resistive switching behavior in p-type SnO thin film devices without extra electroforming steps. The experimental results show a stable resistance ratio of more than 100 times, switching cycling performance up to 180 cycles, and data retention of more than 103 s. The conduction mechanism varied depending on the applied voltage range and resistance state of the device. The memristive switching is shown to originate from a redox phenomenon at the Al/SnO interface, and subsequent formation/rupture of conducting filaments in the bulk of the SnO layer, likely involving oxygen vacancies and Sn interstitials.

  14. Does p-type ohmic contact exist in WSe2-metal interfaces?

    Science.gov (United States)

    Wang, Yangyang; Yang, Ruo Xi; Quhe, Ruge; Zhong, Hongxia; Cong, Linxiao; Ye, Meng; Ni, Zeyuan; Song, Zhigang; Yang, Jinbo; Shi, Junjie; Li, Ju; Lu, Jing

    2015-12-01

    Formation of low-resistance metal contacts is the biggest challenge that masks the intrinsic exceptional electronic properties of two dimensional WSe2 devices. We present the first comparative study of the interfacial properties between monolayer/bilayer (ML/BL) WSe2 and Sc, Al, Ag, Au, Pd, and Pt contacts by using ab initio energy band calculations with inclusion of the spin-orbital coupling (SOC) effects and quantum transport simulations. The interlayer coupling tends to reduce both the electron and hole Schottky barrier heights (SBHs) and alters the polarity for the WSe2-Au contact, while the SOC chiefly reduces the hole SBH. In the absence of the SOC, the Pd contact has the smallest hole SBH. Dramatically, the Pt contact surpasses the Pd contact and becomes the p-type ohmic or quasi-ohmic contact with inclusion of the SOC. Therefore, p-type ohmic or quasi-ohmic contact exists in WSe2-metal interfaces. Our study provides a theoretical foundation for the selection of favorable metal electrodes in ML/BL WSe2 devices.Formation of low-resistance metal contacts is the biggest challenge that masks the intrinsic exceptional electronic properties of two dimensional WSe2 devices. We present the first comparative study of the interfacial properties between monolayer/bilayer (ML/BL) WSe2 and Sc, Al, Ag, Au, Pd, and Pt contacts by using ab initio energy band calculations with inclusion of the spin-orbital coupling (SOC) effects and quantum transport simulations. The interlayer coupling tends to reduce both the electron and hole Schottky barrier heights (SBHs) and alters the polarity for the WSe2-Au contact, while the SOC chiefly reduces the hole SBH. In the absence of the SOC, the Pd contact has the smallest hole SBH. Dramatically, the Pt contact surpasses the Pd contact and becomes the p-type ohmic or quasi-ohmic contact with inclusion of the SOC. Therefore, p-type ohmic or quasi-ohmic contact exists in WSe2-metal interfaces. Our study provides a theoretical foundation for

  15. Initial results from 3D-DDTC detectors on p-type substrates

    Energy Technology Data Exchange (ETDEWEB)

    Zoboli, A., E-mail: zoboli@disi.unitn.i [Dipartimento di Ingegneria e Scienza dell' Informazione, Universita di Trento, and INFN, Sezione di Padova (Gruppo Collegato di Trento), Via Sommarive, 14, I-38100 Povo di Trento (Italy); Boscardin, M. [Fondazione Bruno Kessler, Centro per i Materiali e i Microsistemi, Via Sommarive, 18, I-38100 Povo di Trento (Italy); Bosisio, L. [Dipartimento di Fisica, Universita di Trieste, and INFN, Sezione di Trieste, Via A. Valerio, 2, I-34127 Trieste (Italy); Dalla Betta, G.-F. [Dipartimento di Ingegneria e Scienza dell' Informazione, Universita di Trento, and INFN, Sezione di Padova (Gruppo Collegato di Trento), Via Sommarive, 14, I-38100 Povo di Trento (Italy); Piemonte, C.; Ronchin, S.; Zorzi, N. [Fondazione Bruno Kessler, Centro per i Materiali e i Microsistemi, Via Sommarive, 18, I-38100 Povo di Trento (Italy)

    2010-01-11

    Owing to their superior radiation hardness compared to planar detectors, 3D detectors are one of the most promising technologies for the LHC upgrade foreseen in 2017. Fondazione Bruno Kessler has developed 3D Double-side Double-Type Column (3D-DDTC) detectors providing a technological simplifications with respect to a standard 3D process while aiming at comparable detector performance. We present selected results from the electrical characterization of 3D-DDTC structures from the second batch made on p-type substrates, supported also by TCAD simulations.

  16. Structure and mechanism of Zn2+-transporting P-type ATPases

    DEFF Research Database (Denmark)

    Wang, Kaituo; Sitsel, Oleg; Meloni, Gabriele

    2014-01-01

    Zinc is an essential micronutrient for all living organisms. It is required for signalling and proper functioning of a range of proteins involved in, for example, DNA binding and enzymatic catalysis1. In prokaryotes and photosynthetic eukaryotes, Zn2+-transporting P-type ATPases of class IB (Znt....... The structures reveal a similar fold to Cu+-ATPases, with an amphipathic helix at the membrane interface. A conserved electronegative funnel connects this region to the intramembranous high-affinity ion-binding site and may promote specific uptake of cellular Zn2+ ions by the transporter. The E2P structure...

  17. P-Type Silicon Strip Sensors for the new CMS Tracker at HL-LHC

    Science.gov (United States)

    Adam, W.; Bergauer, T.; Brondolin, E.; Dragicevic, M.; Friedl, M.; Frühwirth, R.; Hoch, M.; Hrubec, J.; König, A.; Steininger, H.; Waltenberger, W.; Alderweireldt, S.; Beaumont, W.; Janssen, X.; Lauwers, J.; Van Mechelen, P.; Van Remortel, N.; Van Spilbeeck, A.; Beghin, D.; Brun, H.; Clerbaux, B.; Delannoy, H.; De Lentdecker, G.; Fasanella, G.; Favart, L.; Goldouzian, R.; Grebenyuk, A.; Karapostoli, G.; Lenzi, Th.; Léonard, A.; Luetic, J.; Postiau, N.; Seva, T.; Vanlaer, P.; Vannerom, D.; Wang, Q.; Zhang, F.; Abu Zeid, S.; Blekman, F.; De Bruyn, I.; De Clercq, J.; D'Hondt, J.; Deroover, K.; Lowette, S.; Moortgat, S.; Moreels, L.; Python, Q.; Skovpen, K.; Van Mulders, P.; Van Parijs, I.; Bakhshiansohi, H.; Bondu, O.; Brochet, S.; Bruno, G.; Caudron, A.; Delaere, C.; Delcourt, M.; De Visscher, S.; Francois, B.; Giammanco, A.; Jafari, A.; Komm, M.; Krintiras, G.; Lemaitre, V.; Magitteri, A.; Mertens, A.; Michotte, D.; Musich, M.; Piotrzkowski, K.; Quertenmont, L.; Szilasi, N.; Vidal Marono, M.; Wertz, S.; Beliy, N.; Caebergs, T.; Daubie, E.; Hammad, G. H.; Härkönen, J.; Lampén, T.; Luukka, P.; Peltola, T.; Tuominen, E.; Tuovinen, E.; Eerola, P.; Tuuva, T.; Baulieu, G.; Boudoul, G.; Caponetto, L.; Combaret, C.; Contardo, D.; Dupasquier, T.; Gallbit, G.; Lumb, N.; Mirabito, L.; Perries, S.; Vander Donckt, M.; Viret, S.; Agram, J.-L.; Andrea, J.; Bloch, D.; Bonnin, C.; Brom, J.-M.; Chabert, E.; Chanon, N.; Charles, L.; Conte, E.; Fontaine, J.-Ch.; Gross, L.; Hosselet, J.; Jansova, M.; Tromson, D.; Autermann, C.; Feld, L.; Karpinski, W.; Kiesel, K. M.; Klein, K.; Lipinski, M.; Ostapchuk, A.; Pierschel, G.; Preuten, M.; Rauch, M.; Schael, S.; Schomakers, C.; Schulz, J.; Schwering, G.; Wlochal, M.; Zhukov, V.; Pistone, C.; Fluegge, G.; Kuensken, A.; Pooth, O.; Stahl, A.; Aldaya, M.; Asawatangtrakuldee, C.; Beernaert, K.; Bertsche, D.; Contreras-Campana, C.; Eckerlin, G.; Eckstein, D.; Eichhorn, T.; Gallo, E.; Garay Garcia, J.; Hansen, K.; Haranko, M.; Harb, A.; Hauk, J.; Keaveney, J.; Kalogeropoulos, A.; Kleinwort, C.; Lohmann, W.; Mankel, R.; Maser, H.; Mittag, G.; Muhl, C.; Mussgiller, A.; Pitzl, D.; Reichelt, O.; Savitskyi, M.; Schuetze, P.; Walsh, R.; Zuber, A.; Biskop, H.; Buhmann, P.; Centis-Vignali, M.; Garutti, E.; Haller, J.; Hoffmann, M.; Lapsien, T.; Matysek, M.; Perieanu, A.; Scharf, Ch.; Schleper, P.; Schmidt, A.; Schwandt, J.; Sonneveld, J.; Steinbrück, G.; Vormwald, B.; Wellhausen, J.; Abbas, M.; Amstutz, C.; Barvich, T.; Barth, Ch.; Boegelspacher, F.; De Boer, W.; Butz, E.; Caselle, M.; Colombo, F.; Dierlamm, A.; Freund, B.; Hartmann, F.; Heindl, S.; Husemann, U.; Kornmayer, A.; Kudella, S.; Muller, Th.; Simonis, H. J.; Steck, P.; Weber, M.; Weiler, Th.; Anagnostou, G.; Asenov, P.; Assiouras, P.; Daskalakis, G.; Kyriakis, A.; Loukas, D.; Paspalaki, L.; Siklér, F.; Veszprémi, V.; Bhardwaj, A.; Dalal, R.; Jain, G.; Ranjan, K.; Bakhshiansohl, H.; Behnamian, H.; Khakzad, M.; Naseri, M.; Cariola, P.; Creanza, D.; De Palma, M.; De Robertis, G.; Fiore, L.; Franco, M.; Loddo, F.; Silvestris, L.; Maggi, G.; Martiradonna, S.; My, S.; Selvaggi, G.; Albergo, S.; Cappello, G.; Chiorboli, M.; Costa, S.; Di Mattia, A.; Giordano, F.; Potenza, R.; Saizu, M. A.; Tricomi, A.; Tuve, C.; Barbagli, G.; Brianzi, M.; Ciaranfi, R.; Ciulli, V.; Civinini, C.; D'Alessandro, R.; Focardi, E.; Latino, G.; Lenzi, P.; Meschini, M.; Paoletti, S.; Russo, L.; Scarlini, E.; Sguazzoni, G.; Strom, D.; Viliani, L.; Ferro, F.; Lo Vetere, M.; Robutti, E.; Dinardo, M. E.; Fiorendi, S.; Gennai, S.; Malvezzi, S.; Manzoni, R. A.; Menasce, D.; Moroni, L.; Pedrini, D.; Azzi, P.; Bacchetta, N.; Bisello, D.; Dall'Osso, M.; Pozzobon, N.; Tosi, M.; De Canio, F.; Gaioni, L.; Manghisoni, M.; Nodari, B.; Riceputi, E.; Re, V.; Traversi, G.; Comotti, D.; Ratti, L.; Alunni Solestizi, L.; Biasini, M.; Bilei, G. M.; Cecchi, C.; Checcucci, B.; Ciangottini, D.; Fanò, L.; Gentsos, C.; Ionica, M.; Leonardi, R.; Manoni, E.; Mantovani, G.; Marconi, S.; Mariani, V.; Menichelli, M.; Modak, A.; Morozzi, A.; Moscatelli, F.; Passeri, D.; Placidi, P.; Postolache, V.; Rossi, A.; Saha, A.; Santocchia, A.; Storchi, L.; Spiga, D.; Androsov, K.; Azzurri, P.; Arezzini, S.; Bagliesi, G.; Basti, A.; Boccali, T.; Borrello, L.; Bosi, F.; Castaldi, R.; Ciampa, A.; Ciocci, M. A.; Dell'Orso, R.; Donato, S.; Fedi, G.; Giassi, A.; Grippo, M. T.; Ligabue, F.; Lomtadze, T.; Magazzu, G.; Martini, L.; Mazzoni, E.; Messineo, A.; Moggi, A.; Morsani, F.; Palla, F.; Palmonari, F.; Raffaelli, F.; Rizzi, A.; Savoy-Navarro, A.; Spagnolo, P.; Tenchini, R.; Tonelli, G.; Venturi, A.; Verdini, P. G.; Bellan, R.; Costa, M.; Covarelli, R.; Da Rocha Rolo, M.; Demaria, N.; Rivetti, A.; Dellacasa, G.; Mazza, G.; Migliore, E.; Monteil, E.; Pacher, L.; Ravera, F.; Solano, A.; Fernandez, M.; Gomez, G.; Jaramillo Echeverria, R.; Moya, D.; Gonzalez Sanchez, F. J.; Vila, I.; Virto, A. L.; Abbaneo, D.; Ahmed, I.; Albert, E.; Auzinger, G.; Berruti, G.; Bianchi, G.; Blanchot, G.; Bonnaud, J.; Caratelli, A.; Ceresa, D.; Christiansen, J.; Cichy, K.; Daguin, J.; D'Auria, A.; Detraz, S.; Deyrail, D.; Dondelewski, O.; Faccio, F.; Frank, N.; Gadek, T.; Gill, K.; Honma, A.; Hugo, G.; Jara Casas, L. M.; Kaplon, J.; Kornmayer, A.; Kottelat, L.; Kovacs, M.; Krammer, M.; Lenoir, P.; Mannelli, M.; Marchioro, A.; Marconi, S.; Mersi, S.; Martina, S.; Michelis, S.; Moll, M.; Onnela, A.; Orfanelli, S.; Pavis, S.; Peisert, A.; Pernot, J.-F.; Petagna, P.; Petrucciani, G.; Postema, H.; Rose, P.; Tropea, P.; Troska, J.; Tsirou, A.; Vasey, F.; Vichoudis, P.; Verlaat, B.; Zwalinski, L.; Bachmair, F.; Becker, R.; di Calafiori, D.; Casal, B.; Berger, P.; Djambazov, L.; Donega, M.; Grab, C.; Hits, D.; Hoss, J.; Kasieczka, G.; Lustermann, W.; Mangano, B.; Marionneau, M.; Martinez Ruiz del Arbol, P.; Masciovecchio, M.; Meinhard, M.; Perozzi, L.; Roeser, U.; Starodumov, A.; Tavolaro, V.; Wallny, R.; Zhu, D.; Amsler, C.; Bösiger, K.; Caminada, L.; Canelli, F.; Chiochia, V.; de Cosa, A.; Galloni, C.; Hreus, T.; Kilminster, B.; Lange, C.; Maier, R.; Ngadiuba, J.; Pinna, D.; Robmann, P.; Taroni, S.; Yang, Y.; Bertl, W.; Deiters, K.; Erdmann, W.; Horisberger, R.; Kaestli, H.-C.; Kotlinski, D.; Langenegger, U.; Meier, B.; Rohe, T.; Streuli, S.; Cussans, D.; Flacher, H.; Goldstein, J.; Grimes, M.; Jacob, J.; Seif El Nasr-Storey, S.; Cole, J.; Hoad, C.; Hobson, P.; Morton, A.; Reid, I. D.; Auzinger, G.; Bainbridge, R.; Dauncey, P.; Hall, G.; James, T.; Magnan, A.-M.; Pesaresi, M.; Raymond, D. M.; Uchida, K.; Garabedian, A.; Heintz, U.; Narain, M.; Nelson, J.; Sagir, S.; Speer, T.; Swanson, J.; Tersegno, D.; Watson-Daniels, J.; Chertok, M.; Conway, J.; Conway, R.; Flores, C.; Lander, R.; Pellett, D.; Ricci-Tam, F.; Squires, M.; Thomson, J.; Yohay, R.; Burt, K.; Ellison, J.; Hanson, G.; Olmedo, M.; Si, W.; Yates, B. R.; Gerosa, R.; Sharma, V.; Vartak, A.; Yagil, A.; Zevi Della Porta, G.; Dutta, V.; Gouskos, L.; Incandela, J.; Kyre, S.; Mullin, S.; Patterson, A.; Qu, H.; White, D.; Dominguez, A.; Bartek, R.; Cumalat, J. P.; Ford, W. T.; Jensen, F.; Johnson, A.; Krohn, M.; Leontsinis, S.; Mulholland, T.; Stenson, K.; Wagner, S. R.; Apresyan, A.; Bolla, G.; Burkett, K.; Butler, J. N.; Canepa, A.; Cheung, H. W. K.; Chramowicz, J.; Christian, D.; Cooper, W. E.; Deptuch, G.; Derylo, G.; Gingu, C.; Grünendahl, S.; Hasegawa, S.; Hoff, J.; Howell, J.; Hrycyk, M.; Jindariani, S.; Johnson, M.; Kahlid, F.; Lei, C. M.; Lipton, R.; Lopes De Sá, R.; Liu, T.; Los, S.; Matulik, M.; Merkel, P.; Nahn, S.; Prosser, A.; Rivera, R.; Schneider, B.; Sellberg, G.; Shenai, A.; Spiegel, L.; Tran, N.; Uplegger, L.; Voirin, E.; Berry, D. R.; Chen, X.; Ennesser, L.; Evdokimov, A.; Evdokimov, O.; Gerber, C. E.; Hofman, D. J.; Makauda, S.; Mills, C.; Sandoval Gonzalez, I. D.; Alimena, J.; Antonelli, L. J.; Francis, B.; Hart, A.; Hill, C. S.; Parashar, N.; Stupak, J.; Bortoletto, D.; Bubna, M.; Hinton, N.; Jones, M.; Miller, D. H.; Shi, X.; Tan, P.; Baringer, P.; Bean, A.; Khalil, S.; Kropivnitskaya, A.; Majumder, D.; Wilson, G.; Ivanov, A.; Mendis, R.; Mitchell, T.; Skhirtladze, N.; Taylor, R.; Anderson, I.; Fehling, D.; Gritsan, A.; Maksimovic, P.; Martin, C.; Nash, K.; Osherson, M.; Swartz, M.; Xiao, M.; Bloom, K.; Claes, D. R.; Fangmeier, C.; Gonzalez Suarez, R.; Monroy, J.; Siado, J.; Hahn, K.; Sevova, S.; Sung, K.; Trovato, M.; Bartz, E.; Gershtein, Y.; Halkiadakis, E.; Kyriacou, S.; Lath, A.; Nash, K.; Osherson, M.; Schnetzer, S.; Stone, R.; Walker, M.; Malik, S.; Norberg, S.; Ramirez Vargas, J. E.; Alyari, M.; Dolen, J.; Godshalk, A.; Harrington, C.; Iashvili, I.; Kharchilava, A.; Nguyen, D.; Parker, A.; Rappoccio, S.; Roozbahani, B.; Alexander, J.; Chaves, J.; Chu, J.; Dittmer, S.; McDermott, K.; Mirman, N.; Rinkevicius, A.; Ryd, A.; Salvati, E.; Skinnari, L.; Soffi, L.; Tao, Z.; Thom, J.; Tucker, J.; Zientek, M.; Akgün, B.; Ecklund, K. M.; Kilpatrick, M.; Nussbaum, T.; Zabel, J.; Betchart, B.; Covarelli, R.; Demina, R.; Hindrichs, O.; Petrillo, G.; Eusebi, R.; Osipenkov, I.; Perloff, A.; Ulmer, K. A.

    2017-06-01

    The upgrade of the LHC to the High-Luminosity LHC (HL-LHC) is expected to increase the LHC design luminosity by an order of magnitude. This will require silicon tracking detectors with a significantly higher radiation hardness. The CMS Tracker Collaboration has conducted an irradiation and measurement campaign to identify suitable silicon sensor materials and strip designs for the future outer tracker at the CMS experiment. Based on these results, the collaboration has chosen to use n-in-p type silicon sensors and focus further investigations on the optimization of that sensor type. This paper describes the main measurement results and conclusions that motivated this decision.

  18. About the Nature of Electroluminescence Centers in Plastically Deformed Crystals of p-type Silicon

    Directory of Open Access Journals (Sweden)

    B.V. Pavlyk

    2015-10-01

    Full Text Available The paper describes research of dislocation electroluminescence of single crystal p-type silicon with a high concentration of dislocations on the surface (111. It is shown the reaction of the luminescence spectra and capacitive-modulation spectra of samples after high-temperature annealing in an atmosphere of flowing oxygen. The analysis of the results lets us to establish the nature of recombination centers and their reorganization under high-temperature annealing. It is shown that deposition of Al film on the substrate p-Si leads to the formation of strain capacity and the localization of defects in the surface layer that corresponds to luminescence centers.

  19. Elastic constants determined by nanoindentation for p-type thermoelectric half-Heusler

    Energy Technology Data Exchange (ETDEWEB)

    Gahlawat, S.; Wheeler, L.; White, K. W., E-mail: zren@uh.edu, E-mail: kwwhite@uh.edu [Department of Mechanical Engineering, University of Houston, Houston, Texas 77204 (United States); He, R.; Chen, S.; Ren, Z. F., E-mail: zren@uh.edu, E-mail: kwwhite@uh.edu [Department of Physics and TcSUH, University of Houston, Houston, Texas 77204 (United States)

    2014-08-28

    This paper presents a study of the elastic properties of the p-type thermoelectric half-Heusler material, Hf{sub 0.44}Zr{sub 0.44}Ti{sub 0.12}CoSb{sub 0.8}Sn{sub 0.2}, using nanoindentation. Large grain-sized polycrystalline specimens were fabricated for these measurements, providing sufficient indentation targets within single grains. Electron Backscatter Diffraction methods indexed the target grains for the correlation needed for our elastic analysis of individual single crystals for this cubic thermoelectric material. Elastic properties, including the Zener ratio and the Poisson ratio, obtained from the elasticity tensor are also reported.

  20. Ferromagnetic-resonance induced electromotive forces in Ni81Fe19 | p-type diamond

    Science.gov (United States)

    Fukui, Naoki; Morishita, Hiroki; Kobayashi, Satoshi; Miwa, Shinji; Mizuochi, Norikazu; Suzuki, Yoshishige

    2016-10-01

    We report on direct-current (DC) electromotive forces (emfs) in a nickel-iron alloy (Ni81 Fe19) | p-type diamond under the ferromagnetic resonance of the Ni81Fe19 layer at room temperature. The observed DC emfs take its maximum around the ferromagnetic resonant frequency of the Ni81Fe19, and their signs are reversed by reversing the direction of an externally-applied magnetic field; it shows that the observed DC emfs are spin-related emfs.

  1. Single-structure heater and temperature sensor using a p-type polycrystalline diamond resistor

    Energy Technology Data Exchange (ETDEWEB)

    Yang, G.S.; Aslam, D.M. [Michigan State Univ., East Lansing, MI (United States). Dept. of Electrical Engineering

    1996-05-01

    Heat generation and temperature sensing are required for heating applications and for liquid level sensors, mass flow meters, and vacuum and pressure gauges which are based on variations of heat dissipation. Heat generation and temperature sensing are reported in a single p-type diamond resistor fabricated on an oxidized Si substrate using diamond film technology compatible with integrated circuit (IC) processing. Power densities in excess of 600 W/in.{sup 2} are observed for the heaters. The temperature response of the sensor is characterized in the temperature range of 300--725 K. Such a diamond heater/sensor device is reported for the first time.

  2. Photovoltaic properties of ZnO nanorods/p-type Si heterojunction structures

    Directory of Open Access Journals (Sweden)

    Rafal Pietruszka

    2014-02-01

    Full Text Available Selected properties of photovoltaic (PV structures based on n-type zinc oxide nanorods grown by a low temperature hydrothermal method on p-type silicon substrates (100 are investigated. PV structures were covered with thin films of Al doped ZnO grown by atomic layer deposition acting as transparent electrodes. The investigated PV structures differ in terms of the shapes and densities of their nanorods. The best response is observed for the structure containing closely-spaced nanorods, which show light conversion efficiency of 3.6%.

  3. Methods for enhancing P-type doping in III-V semiconductor films

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Feng; Stringfellow, Gerald; Zhu, Junyi

    2017-08-01

    Methods of doping a semiconductor film are provided. The methods comprise epitaxially growing the III-V semiconductor film in the presence of a dopant, a surfactant capable of acting as an electron reservoir, and hydrogen, under conditions that promote the formation of a III-V semiconductor film doped with the p-type dopant. In some embodiments of the methods, the epitaxial growth of the doped III-V semiconductor film is initiated at a first hydrogen partial pressure which is increased to a second hydrogen partial pressure during the epitaxial growth process.

  4. P-Type Doping of GaN by Mg+ Implantation

    Institute of Scientific and Technical Information of China (English)

    YAO Shu-De; ZHAO Qiang; ZHOU Sheng-Qiang; YANG Zi-Jian; LU Yi-Hong; SUN Chang-Chun; SUN Chang; ZHANG Guo-Yi; VANTOMME Andre; PIPELEERS Bert

    2003-01-01

    Mg+ and Mg++P+ were introduced into GaN by ion implantation. The structure and crystalline quality of the GaN samples were analysed by Rutherford backscattering and channelling spectrometry before (xmin = 1.6%) and after implantation (Xmin = 4.1%). X-ray diffraction reveals the existence of implantation-induced damage in the case of post-implantation followed by rapid thermal annealing. The resistivity, average factor, carrier concentration and carrier mobility were measured by the Hall effect. The transformation from n-type to p-type for GaN was observed.

  5. Above bandgap luminescence of p-type GaAs epitaxial layers

    Science.gov (United States)

    Sapriel, J.; Chavignon, J.; Alexandre, F.; Azoulay, R.; Sermage, B.; Rao, K.; Voos, M.

    1991-08-01

    New photoluminescence bands are observed in p-type GaAs epitaxial layers at 300 and 80 K, above the bandgap. These bands are independent of the nature of the dopant (Zn, Be, C) and of the growth technique (MBE or MOCVD). Their intensities increase as a function of the p doping (1 × 10 17 < p < 2 × 10 20cm-3) and peak at energies which correspond to transitions between the Γ 6, L 6 and X 6 minima of the conduction band and the Γ 8 and Γ 7 maxima of the valence band.

  6. Activities of cobra venom cytotoxins toward heart and leukemic T-cells depend on localized amino acid differences.

    Science.gov (United States)

    Stevens-Truss, R; Hinman, C L

    1997-05-01

    Several studies have suggested that along the concave surface of cobra venom cytotoxins, a hydrophobic region flanked by positively charged amino acid side-chains, as well as by tyrosine and/or serine/threonine, allows these toxins to depolarize muscle or cause cytolysis. Comparison of biological activities among structurally homologous toxins, however, has revealed significant functional diversity. The objective of the present study was to examine several toxins purified from different cobra venoms with regard to their ability to bind to and kill human T-lymphocytes and rat heart cell myoblasts. The activities observed were then correlated with differences in amino acid residues which occur in restricted regions of the toxins. The absence of an aromatic residue at position 11 (Loop 1) resulted in a lower cytolytic response at every concentration tested. A simple inversion of two residues in the amino acid sequence of toxin Loop 3 selectively impaired heart cell binding and cytolysis, but had no effect on T-cells. Loss of a positively charged residue in the tip of Loop 2 minimally affected binding but significantly reduced cytolysis. Replacement of valine at positions 27 and 32, along with the introduction of a negative charge at the tip of Loop 2, interfered with binding to either cell type and caused a reduction in cytolysis. The results of this study suggest that no one loop or region is solely responsible for the toxin's biological activity. However, because the binding and cytolytic sites within these toxins are distinct, it may become possible to develop toxin derivatives in which only selected activities are enhanced.

  7. Variations in Helicobacter pylori cytotoxin-associated genes and their influence in progression to gastric cancer: implications for prevention.

    Directory of Open Access Journals (Sweden)

    Cosmeri Rizzato

    Full Text Available Helicobacter pylori (HP is a bacterium that colonizes the human stomach and can establish a long-term infection of the gastric mucosa. Persistent Hp infection often induces gastritis and is associated with the development of peptic ulcer disease, atrophic gastritis, and gastric adenocarcinoma. Virulent HP isolates harbor the cag (cytotoxin-associated genes pathogenicity island (cagPAI, a 40 kb stretch of DNA that encodes components of a type IV secretion system (T4SS. This T4SS forms a pilus for the injection of virulence factors into host target cells, such as the CagA oncoprotein. We analyzed the genetic variability in cagA and other selected genes of the HP cagPAI (cagC, cagE, cagL, cagT, cagV and cag Gamma using DNA extracted from frozen gastric biopsies or from clinical isolates. Study subjects were 95 cagA+ patients that were histologically diagnosed with chronic gastritis or gastric cancer in Venezuela and Mexico, areas with high prevalence of Hp infection. Sequencing reactions were carried out by both Sanger and next-generation pyrosequencing (454 Roche methods. We found a total of 381 variants with unambiguous calls observed in at least 10% of the originally tested samples and reference strains. We compared the frequencies of these genetic variants between gastric cancer and chronic gastritis cases. Twenty-six SNPs (11 non-synonymous and 14 synonymous showed statistically significant differences (P<0.05, and two SNPs, in position 1039 and 1041 of cagE, showed a highly significant association with cancer (p-value = 2.07×10⁻⁶, and the variant codon was located in the VirB3 homology domain of Agrobacterium. The results of this study may provide preliminary information to target antibiotic treatment to high-risk individuals, if effects of these variants are confirmed in further investigations.

  8. Effects of Escherichia Coli Subtilase Cytotoxin and Shiga Toxin 2 on Primary Cultures of Human Renal Tubular Epithelial Cells

    Science.gov (United States)

    Márquez, Laura B.; Velázquez, Natalia; Repetto, Horacio A.; Paton, Adrienne W.; Paton, James C.; Ibarra, Cristina; Silberstein, Claudia

    2014-01-01

    Shiga toxin (Stx)-producing Escherichia coli (STEC) cause post-diarrhea Hemolytic Uremic Syndrome (HUS), which is the most common cause of acute renal failure in children in many parts of the world. Several non-O157 STEC strains also produce Subtilase cytotoxin (SubAB) that may contribute to HUS pathogenesis. The aim of the present work was to examine the cytotoxic effects of SubAB on primary cultures of human cortical renal tubular epithelial cells (HRTEC) and compare its effects with those produced by Shiga toxin type 2 (Stx2), in order to evaluate their contribution to renal injury in HUS. For this purpose, cell viability, proliferation rate, and apoptosis were assayed on HRTEC incubated with SubAB and/or Stx2 toxins. SubAB significantly reduced cell viability and cell proliferation rate, as well as stimulating cell apoptosis in HRTEC cultures in a time dependent manner. However, HRTEC cultures were significantly more sensitive to the cytotoxic effects of Stx2 than those produced by SubAB. No synergism was observed when HRTEC were co-incubated with both SubAB and Stx2. When HRTEC were incubated with the inactive SubAA272B toxin, results were similar to those in untreated control cells. Similar stimulation of apoptosis was observed in Vero cells incubated with SubAB or/and Stx2, compared to HRTEC. In conclusion, primary cultures of HRTEC are significantly sensitive to the cytotoxic effects of SubAB, although, in a lesser extent compared to Stx2. PMID:24466317

  9. Cytotoxin-associated gene-A-seropositive virulent strains of Helicobacter pylori and atherosclerotic diseases: a systematic review

    Institute of Scientific and Technical Information of China (English)

    ZHANG Shuo; GUO Yang; MA Yan; TENG Yue

    2008-01-01

    Objective A systematic meta-analysis was performed to explore the role of cytotoxin-associated gene-A (CagA)seropositive strains of Helicobacterpylori (H. pylon) in the pathogenesis of atherosclerotic diseases.Data sources Data from Medline, EMBASE, CBMdisc, CNKI and the Cochrane Collaboration database were searched.Similar search strategies were applied to each of these databases.Study selection The review was restricted to the case-control studies on infective, chronic virulent CagA strains of H.pylori, involving the risk of ischemic stroke and coronary heart disease, ineligible studies were excluded. Two reviewers independently extracted the data and assessed study quality.Results Totally 26 case-control studies (11 studies on ischemic stroke and 15 studies on coronary heart disease) were retrieved and considered. The combined data revealed that the chronic seropositive virulent strains of H. pylori infection had a trend of increasing the risk of ischemic strokes and coronary heart diseases, yielding pooled Ors of 2.68 (95% CI: 2.20, 3.27)and 2.11 (95% CI: 1.70, 2.62), respectively. We also performed subgroup analyses, dividing the total population into Caucasian and Chinese subgroups. Through the subgroup analysis, no significant difference was found between the subgroups.Conclusions Our results support the hypothesis that CagA-seropositive strains infection is significantly associated with susceptibility to ischemic strokes and coronary heart diseases. The magnitude of the association with atherosclerotic diseases needs to be confirmed by prospective studies and the studies on CagA-seropositive strains eradication are more important.

  10. Effects of Escherichia coli subtilase cytotoxin and Shiga toxin 2 on primary cultures of human renal tubular epithelial cells.

    Directory of Open Access Journals (Sweden)

    Laura B Márquez

    Full Text Available Shiga toxin (Stx-producing Escherichia coli (STEC cause post-diarrhea Hemolytic Uremic Syndrome (HUS, which is the most common cause of acute renal failure in children in many parts of the world. Several non-O157 STEC strains also produce Subtilase cytotoxin (SubAB that may contribute to HUS pathogenesis. The aim of the present work was to examine the cytotoxic effects of SubAB on primary cultures of human cortical renal tubular epithelial cells (HRTEC and compare its effects with those produced by Shiga toxin type 2 (Stx2, in order to evaluate their contribution to renal injury in HUS. For this purpose, cell viability, proliferation rate, and apoptosis were assayed on HRTEC incubated with SubAB and/or Stx2 toxins. SubAB significantly reduced cell viability and cell proliferation rate, as well as stimulating cell apoptosis in HRTEC cultures in a time dependent manner. However, HRTEC cultures were significantly more sensitive to the cytotoxic effects of Stx2 than those produced by SubAB. No synergism was observed when HRTEC were co-incubated with both SubAB and Stx2. When HRTEC were incubated with the inactive SubAA272B toxin, results were similar to those in untreated control cells. Similar stimulation of apoptosis was observed in Vero cells incubated with SubAB or/and Stx2, compared to HRTEC. In conclusion, primary cultures of HRTEC are significantly sensitive to the cytotoxic effects of SubAB, although, in a lesser extent compared to Stx2.

  11. A P-type ATPase importer that discriminates between essential and toxic transition metals.

    Science.gov (United States)

    Lewinson, Oded; Lee, Allen T; Rees, Douglas C

    2009-03-24

    Transition metals, although being essential cofactors in many physiological processes, are toxic at elevated concentrations. Among the membrane-embedded transport proteins that maintain appropriate intracellular levels of transition metals are ATP-driven pumps belonging to the P-type ATPase superfamily. These metal transporters may be differentiated according to their substrate specificities, where the majority of pumps can extrude either silver and copper or zinc, cadmium, and lead. In the present report, we have established the substrate specificities of nine previously uncharacterized prokaryotic transition-metal P-type ATPases. We find that all of the newly identified exporters indeed fall into one of the two above-mentioned categories. In addition to these exporters, one importer, Pseudomonas aeruginosa Q9I147, was also identified. This protein, designated HmtA (heavy metal transporter A), exhibited a different substrate recognition profile from the exporters. In vivo metal susceptibility assays, intracellular metal measurements, and transport experiments all suggest that HmtA mediates the uptake of copper and zinc but not of silver, mercury, or cadmium. The substrate selectivity of this importer ensures the high-affinity uptake of essential metals, while avoiding intracellular contamination by their toxic counterparts.

  12. Thermal oxidation of Ni films for p-type thin-film transistors

    KAUST Repository

    Jiang, Jie

    2013-01-01

    p-Type nanocrystal NiO-based thin-film transistors (TFTs) are fabricated by simply oxidizing thin Ni films at temperatures as low as 400 °C. The highest field-effect mobility in a linear region and the current on-off ratio are found to be 5.2 cm2 V-1 s-1 and 2.2 × 103, respectively. X-ray diffraction, transmission electron microscopy and electrical performances of the TFTs with "top contact" and "bottom contact" channels suggest that the upper parts of the Ni films are clearly oxidized. In contrast, the lower parts in contact with the gate dielectric are partially oxidized to form a quasi-discontinuous Ni layer, which does not fully shield the gate electric field, but still conduct the source and drain current. This simple method for producing p-type TFTs may be promising for the next-generation oxide-based electronic applications. © 2013 the Owner Societies.

  13. Analysis of carrier concentration, lifetime, and electron mobility on p-type HgCdTe

    Science.gov (United States)

    Yoo, Sang Dong; Kwack, Kae Dal

    1998-03-01

    Minority carrier transport characteristics of vacancy-doped p-type HgCdTe such as carrier concentration, lifetime, and mobility are investigated. In the calculation of the carrier concentration two acceptor levels—a donor level and a trap level—were taken into account. The acceptor levels have been described by two models—two independent singly ionized levels and a divalent level with two ionization energies. When each model was examined by calculating electron mobility as a function of temperature, the latter was found to be more accurate. Electron mobility as a function of majority carrier concentration was also presented for both n-type and p-type HgCdTe with 0.225 Cd mole fraction. Steady state electron lifetime was computed assuming the acceptor levels and the trap level would act as Schokley-Read-Hall type recombination centers. The calculated results using the divalent acceptor model were in good agreement with the experimental data.

  14. The development of p-type silicon detectors for the high radiation regions of the LHC

    CERN Document Server

    Hanlon, M D L

    1998-01-01

    This thesis describes the production and characterisation of silicon microstrip detectors and test structures on p-type substrates. An account is given of the production and full parameterisation of a p-type microstrip detector, incorporating the ATLAS-A geometry in a beam test. This detector is an AC coupled device incorporating a continuous p-stop isolation frame and polysilicon biasing and is typical of n-strip devices proposed for operation at the LHC. It was successfully read out using the FELix-128 analogue pipeline chip and a signal to noise (s/n) of 17+-1 is reported, along with a spatial resolution of 14.6+-0.2 mu m. Diode test structures were fabricated on both high resistivity float zone material and on epitaxial material and subsequently irradiated with 24 GeV protons at the CERN PS up to a dose of (8.22+-0.23) x 10 sup 1 sup 4 per cm sup 2. An account of the measurement program is presented along with results on the changes in the effective doping concentration (N sub e sub f sub f) with irradiat...

  15. Synthesis and characterization of p-type boron-doped IIb diamond large single crystals

    Institute of Scientific and Technical Information of China (English)

    Li Shang-Sheng; Ma Hong-An; Li Xiao-Lei; Su Tai-Chao; Huang Guo-Feng; Li Yong; Jia Xiao-Peng

    2011-01-01

    High-quality p-type boron-doped II0b diamond large single crystals are successfully synthesized by the temperature gradient method in a china-type cubic anvil high-pressure apparatus at about 5.5 GPa and 1600 K. The morphologies and surface textures of the synthetic diamond crystals with different boron additive quantities are characterized by using an optical microscope and a scanning electron microscope respectively. The impurities of nitrogen and boron in diamonds are detected by micro Fourier transform infrared technique. The electrical properties including resistivities, Hall coefficients, Hall mobilities and carrier densities of the synthesized samples are measured by a four-point probe and the Hall effect method. The results show that large p-type boron-doped diamond single crystals with few nitrogen impurities have been synthesized. With the increase of quantity of additive boron, some high-index crystal faces such as {113} gradually disappear, and some stripes and triangle pits occur on the crystal surface. This work is helpful for the further research and application of boron-doped semiconductor diamond.

  16. EEG/MEG forward simulation through h- and p-type finite elements

    Energy Technology Data Exchange (ETDEWEB)

    Pursiainen, S [Institute of Mathematics, Box 1100, FI-02015 Helsinki University of Technology (Finland)], E-mail: sampsa.pursiainen@tkk.fi

    2008-07-15

    Electro/Magnetoencephalography (EEG/MEG) is a non-invasive imaging modality, in which a primary current density generated by the neural activity in the brain is to be reconstructed from external electric potential/magnetic field measurements. This work focuses on effective and accurate simulation of the EEG/MEG forward model through the h- and p-versions of the finite element method (h- and p-FEM). The goal is to compare the effectiveness of these two versions in forward simulation. Both h- and p-type forward simulations are described and implemented, and the technical solutions found are discussed. These include, for example, suitable ways to generate a finite element mesh for a real head geometry through the use of different element types. Performances of the two implemented forward simulation types are compared by measuring directly the forward modeling error, as well as by computing reconstructions through a regularized FOCUSS (FOCal Underdetermined System Solver) algorithm. The results obtained suggest that the p-type performs better in terms of the forward modeling error. However, both types perform well in regularized FOCUSS reconstruction.

  17. Wide band gap p-type windows by CBD and SILAR methods

    Energy Technology Data Exchange (ETDEWEB)

    Sankapal, B.R.; Goncalves, E.; Ennaoui, A.; Lux-Steiner, M.Ch

    2004-03-22

    Chemical deposition methods, namely, chemical bath deposition (CBD) and successive ionic layer adsorption and reaction (SILAR) have been used to deposit wide band gap p-type CuI and CuSCN thin films at room temperature (25 deg. C) in aqueous medium. Growth of these films requires the use of Cu (I) cations as a copper ions source. This is achieved by complexing Cu (II) ions using Na{sub 2}S{sub 2}O{sub 3}. The anion sources are either KI as iodine or KSCN as thiocyanide ions for CuI and CuSCN films, respectively. The preparative parameters are optimized with the aim to use these p-type materials as windows for solar cells. Different substrates are used, namely: glass, fluorine doped tin oxide coated glass and CuInS{sub 2} (CIS). X-ray diffraction, scanning electron microscopy, atomic force microscopy and optical absorption spectroscopy are used for structural, surface morphological and optical studies, and the results are discussed.

  18. Anabaena sp. DyP-type peroxidase is a tetramer consisting of two asymmetric dimers.

    Science.gov (United States)

    Yoshida, Toru; Ogola, Henry Joseph Oduor; Amano, Yoshimi; Hisabori, Toru; Ashida, Hiroyuki; Sawa, Yoshihiro; Tsuge, Hideaki; Sugano, Yasushi

    2016-01-01

    DyP-type peroxidases are a newly discovered family of heme peroxidases distributed from prokaryotes to eukaryotes. Recently, using a structure-based sequence alignment, we proposed the new classes, P, I and V, as substitutes for classes A, B, C, and D [Arch Biochem Biophys 2015;574:49-55]. Although many class V enzymes from eukaryotes have been characterized, only two from prokaryotes have been reported. Here, we show the crystal structure of one of these two enzymes, Anabaena sp. DyP-type peroxidase (AnaPX). AnaPX is tetramer formed from Cys224-Cys224 disulfide-linked dimers. The tetramer of wild-type AnaPX was stable at all salt concentrations tested. In contrast, the C224A mutant showed salt concentration-dependent oligomeric states: in 600 mM NaCl, it maintained a tetrameric structure, whereas in the absence of salt, it dissociated into monomers, leading to a reduction in thermostability. Although the tetramer exhibits non-crystallographic, 2-fold symmetry in the asymmetric unit, two subunits forming the Cys224-Cys224 disulfide-linked dimer are related by 165° rotation. This asymmetry creates an opening to cavities facing the inside of the tetramer, providing a pathway for hydrogen peroxide access. Finally, a phylogenetic analysis using structure-based sequence alignments showed that class V enzymes from prokaryotes, including AnaPX, are phylogenetically closely related to class V enzymes from eukaryotes.

  19. Valence band states in Si-based p-type delta-doped field effect transistors

    Energy Technology Data Exchange (ETDEWEB)

    Martinez-Orozco, J C; Vlaev, Stoyan J, E-mail: jcmover@correo.unam.m [Unidad Academica de Fisica, Universidad Autonoma de Zacatecas, Calzada Solidaridad esquina con Paseo la Bufa S/N, C.P. 98060, Zacatecas, Zac. (Mexico)

    2009-05-01

    We present tight-binding calculations of the hole level structure of delta-doped Field Effect Transistor in a Si matrix within the first neighbors sp{sup 3}s* semi-empirical tight-binding model including spin. We employ analytical expressions for Schottky barrier potential and the p-type delta-doped well based on a Thomas-Fermi approximation, we consider these potentials as external ones, so in the computations they are added to the diagonal terms of the tight-binding Hamiltonian, by this way we have the possibility to study the energy levels behavior as we vary the backbone parameters in the system: the two-dimensional impurity density (p{sub 2d}) of the p-type delta-doped well and the contact voltage (V{sub c}). The aim of this calculation is to demonstrate that the tight-binding approximation is suitable for device characterization that permits us to propose optimal values for the input parameters involved in the device design.

  20. Use of hexamethyldisiloxane for p-type microcrystalline silicon oxycarbide layers

    Directory of Open Access Journals (Sweden)

    Goyal Prabal

    2016-01-01

    Full Text Available The use of hexamethyldisiloxane (HMDSO as an oxygen source for the growth of p-type silicon-based layers deposited by Plasma Enhanced Chemical Vapor Deposition is evaluated. The use of this source led to the incorporation of almost equivalent amounts of oxygen and carbon, resulting in microcrystalline silicon oxycarbide thin films. The layers were examined with characterisation techniques including Spectroscopic Ellipsometry, Dark Conductivity, Fourier Transform Infrared Spectroscopy, Secondary Ion Mass Spectrometry and Transmission Electron Microscopy to check material composition and structure. Materials studies show that the refractive indices of the layers can be tuned over the range from 2.5 to 3.85 (measured at 600 nm and in-plane dark conductivities over the range from 10-8 S/cm to 1 S/cm, suggesting that these doped layers are suitable for solar cell applications. The p-type layers were tested in single junction amorphous silicon p-i-n type solar cells.

  1. Lateral photovoltaic effect in p-type silicon induced by surface states

    Science.gov (United States)

    Huang, Xu; Mei, Chunlian; Gan, Zhikai; Zhou, Peiqi; Wang, Hui

    2017-03-01

    A colossal lateral photovoltaic effect (LPE) was observed at the surface of p-type silicon, which differs from the conventional thought that a large LPE is only observed in Schottky junctions and PN junctions consisting of several layers with different conductivities. It shows a high sensitivity of 499.24 mV/mm and an ultra-broadband spectral responsivity (from 405 nm to 980 nm) at room temperature, which makes it an attractive candidate for near-infrared detection. We propose that this phenomenon can be understood by considering the surface band bending near the surface of p-Si induced by charged surface states. The energy band diagrams of the samples are shown based on X-ray photoelectron spectroscopy suggesting the correlation between the LPE and surface band bending. The conjectures are validated by changing the surface states of p-type silicon using Ni nano-films. These findings reveal a generation mechanism of the LPE and may lead to p-Si based, broadband-responsivity, low-cost, and high-precision optical and optoelectronic applications.

  2. Atomic layer deposition of undoped TiO2 exhibiting p-type conductivity.

    Science.gov (United States)

    Iancu, Andrei T; Logar, Manca; Park, Joonsuk; Prinz, Fritz B

    2015-03-11

    With prominent photocatalytic applications and widespread use in semiconductor devices, TiO2 is one of the most popular metal oxides. However, despite its popularity, it has yet to achieve its full potential due to a lack of effective methods for achieving p-type conductivity. Here, we show that undoped p-type TiO2 films can be fabricated by atomic layer deposition (ALD) and that their electrical properties can be controlled across a wide range using proper postprocessing anneals in various ambient environments. Hole mobilities larger than 400 cm(2)/(V·s) are accessible superseding the use of extrinsic doping, which generally produces orders of magnitude smaller values. Through a combination of analyses and experiments, we provide evidence that this behavior is primarily due to an excess of oxygen in the films. This discovery enables entirely new categories of TiO2 devices and applications, and unlocks the potential to improve existing ones. TiO2 homojunction diodes fabricated completely by ALD are developed as a demonstration of the utility of these techniques and shown to exhibit useful rectifying characteristics even with minimal processing refinement.

  3. Piezo-phototronic effect on electroluminescence properties of p-type GaN thin films.

    Science.gov (United States)

    Hu, Youfan; Zhang, Yan; Lin, Long; Ding, Yong; Zhu, Guang; Wang, Zhong Lin

    2012-07-11

    We present that the electroluminescence (EL) properties of Mg-doped p-type GaN thin films can be tuned by the piezo-phototronic effect via adjusting the minority carrier injection efficiency at the metal-semiconductor (M-S) interface by strain induced polarization charges. The device is a metal-semiconductor-metal structure of indium tin oxide (ITO)-GaN-ITO. Under different straining conditions, the changing trend of the transport properties of GaN films can be divided into two types, corresponding to the different c-axis orientations of the films. An extreme value was observed for the integral EL intensity under certain applied strain due to the adjusted minority carrier injection efficiency by piezoelectric charges introduced at the M-S interface. The external quantum efficiency of the blue EL at 430 nm was changed by 5.84% under different straining conditions, which is 1 order of magnitude larger than the change of the green peak at 540 nm. The results indicate that the piezo-phototronic effect has a larger impact on the shallow acceptor states related EL process than on the one related to the deep acceptor states in p-type GaN films. This study has great significance on the practical applications of GaN in optoelectronic devices under a working environment where mechanical deformation is unavoidable such as for flexible/printable light emitting diodes.

  4. New photovoltaic devices based on the sensitization of p-type semiconductors: challenges and opportunities.

    Science.gov (United States)

    Odobel, Fabrice; Le Pleux, Loïc; Pellegrin, Yann; Blart, Errol

    2010-08-17

    Because solar energy is the most abundant renewable energy resource, the clear connection between human activity and global warming has strengthened the interest in photovoltaic science. Dye-sensitized solar cells (DSSCs) provide a promising low-cost technology for harnessing this energy source. Until recently, much of the research surrounding DSSCs had been focused on the sensitization of n-type semiconductors, such as titanium dioxide (Gratzel cells). In an n-type dye-sensitized solar cell (n-DSSC), an electron is injected into the conduction band of an n-type semiconductor (n-SC) from the excited state of the sensitizer. Comparatively few studies have examined the sensitization of wide bandgap p-type semiconductors. In a p-type DSSC (p-DSSC), the photoexcited sensitizer is reductively quenched by hole injection into the valence band of a p-type semiconductor (p-SC). The study of p-DSSCs is important both to understand the factors that control the rate of hole photoinjection and to aid the rational design of efficient p-DSSCs. In theory, p-DSSCs should be able to work as efficiently as n-DSSCs. In addition, this research provides a method for preparing tandem DSSCs consisting of a TiO(2)-photosensitized anode and a photosensitized p-type SC as a cathode. Tandem DSSCs are particularly important because they represent low-cost photovoltaic devices whose photoconversion efficiencies could exceed 15%. This Account describes recent research results on p-DSSCs. Because these photoelectrochemical devices are the mirror images of conventional n-DSSCs, they share some structural similarities, but they use different materials and have different charge transfer kinetics. In this technology, nickel oxide is the predominant p-SC material used, but much higher photoconversion efficiencies could be achieved with new p-SCs materials with deeper valence band potential. Currently, iodide/triiodide is the main redox mediator of electron transport within these devices, but we expect

  5. p-Type semiconducting nickel oxide as an efficiency-enhancing anodal interfacial layer in bulk heterojunction solar cells

    Science.gov (United States)

    Irwin, Michael D; Buchholz, Donald B; Marks, Tobin J; Chang, Robert P. H.

    2014-11-25

    The present invention, in one aspect, relates to a solar cell. In one embodiment, the solar cell includes an anode, a p-type semiconductor layer formed on the anode, and an active organic layer formed on the p-type semiconductor layer, where the active organic layer has an electron-donating organic material and an electron-accepting organic material.

  6. Protein Characterization of Extracellular Microvesicles/Exosomes Released from Cytotoxin-Challenged Rat Cerebrocortical Mixed Culture and Mouse N2a Cells.

    Science.gov (United States)

    Kumar, Dhwani; Manek, Rachna; Raghavan, Vijaya; Wang, Kevin K

    2017-03-10

    A number of neuronal and glial proteins were previously found to be released in free-standing soluble form from cultured brain cells into cell-conditioned media. Here, we sought to examine if similar proteins are also contained in neural and astroglial cell-released extracellular microvesicles/exosomes (MV/E). In this study, MV/E were isolated from cell-conditioned media from control and cytotoxin-challenged rat cerebrocortical mixed culture (CTX) and mouse neuroblastoma N2a cells. Cytotoxin challenges included pro-necrosis calcium ionophore A23187, pro-apoptosis staurosporine (STS), and excitotoxin N-methyl-D-aspartate. Based on established nanoparticle characterization method (dynamic light scattering, NanoTracker, and transmission electron microscopy), we confirmed that these released vesicles are in fact characteristic representation of MV/E by morphology (lipid bilayered vesicles) and by particle size (132-142 nm for CTX and 49-77 nm for N2a cells). We indeed identified neural cell body protein UCH-L1, axonal injury marker αII-spectrin and its breakdown products (SBDPs), astroglial markers GFAP and its breakdown products (GFAP-BDP), dendritic protein BIII-tubulin, synaptic protein synaptophysin, and exosome marker Alix in microvesicles from CTX and/or N2a cells. Furthermore, SBDPs, GFAP-BDP, UCH-L1, and synaptophysin are especially dominant in MV/E isolated from cytotoxin-treated CTX cells. Similarly, SBDPs, βIII-tubulin, and UCH-L1 are more prominently observed in cytotoxin-challenged N2a cells. Lastly, when isolated MV/E from A23187- or STS-challenged N2a cells were introduced to healthy N2a culture, they are capable of evoking cytotoxicity in the latter. Taken together, our study identified that microvesicles/exosomes isolated form healthy and injured brain cells contain certain neural and astroglial proteins, as well as possibly other cytotoxic factors that are capable of propagating cytotoxic effects.

  7. 眼镜蛇毒粗毒毒素Ⅳ对小鼠吗啡行为敏化的影响%The effects of cobravenom cytotoxin IV on morphine-induced behavioral sensitization in mice

    Institute of Scientific and Technical Information of China (English)

    仲维高; 崔跃; 孔天翰

    2012-01-01

    Objective To investigate the effects of cobravenom cytotoxin IV on morphine-induced sensitization in mice. Methods Locomotor activity was measured every 5 minutes for 1 hour immediately after administration with cobravenom cytotoxin IV in mice. The morphine-induced sensitization models were established in mice by subcutaneous injection with morphine 10mg/kg,once a day,for 7 days,and the mice were treated with the combination of morphine ( sc) with cytotoxin IV ( ip) to observe the effects of cytotoxin IV on the behavioral sensitization to morphine in mice. Results After treated with different doses of cytotoxin IV ( 0. 027,0. 04, 0. 08mg/kg,respectively), the locomotor activity of the mice was reduced, hyperactivity was inhibited, and the expression of morphine-induced behavioral sensitization was blocked, in which the effects of middle and high-dose of cytotoxin IV were more significant. Conclusion The cobravenom cytotoxin IV has inhibitory effects on central nervous system and can prohibit the formation of morphine addictive behavior, which suggests that cobravenom cytotoxin IV may have intervention effect on psychological dependence to morphine.%目的 探讨眼镜蛇毒毒素Ⅳ对吗啡行为敏化的影响.方法 测定小鼠自主活动,观察毒素Ⅳ对小鼠自主活动影响.昆明种小鼠慢性吗啡处理,建立吗啡诱导行为敏化模型,观察毒素Ⅳ对吗啡行为敏化影响.结果 毒素Ⅳ(0.027、0.04、0.08 mg/kg)腹腔注射后,均能减少小鼠自主活动,降低吗啡诱导的高活动性,抑制小鼠吗啡行为敏化的获得,阻断小鼠吗啡行为敏化表达,其中中、高剂量毒素Ⅳ作用较显著.结论 毒素Ⅳ对中枢神经系统具有抑制作用,可以阻止吗啡成瘾行为形成,对吗啡诱导的敏化行为具有抑制作用,提示毒素Ⅳ对吗啡精神依赖性可能具有干预作用.

  8. NbFeSb based p-type half-Heusler for power generation applications

    Science.gov (United States)

    Joshi, Giri; He, Ran; Engber, Michael; Samsonidze, Georgy; Pantha, Tej; Dahal, Ekraj; Dahal, Keshab; Yang, Jian; Lan, Yucheng; Kozinsky, Boris; Ren, Zhifeng

    2015-03-01

    We report a peak dimensionless figure-of-merit (ZT) of ~1 at 700 oC in nanostructured p-type Nb0.6Ti0.4FeSb0.95Sn0.05composition. Even though the power factor of the Nb0.6Ti0.4FeSb0.95Sn0.05 composition is improved by 25% in comparison to the previously reported p-type Hf0.44Zr0.44Ti0.12CoSb0.8Sn0.2, the ZT value is not increased due to a higher thermal conductivity. However, the higher power factor of the Nb0.6Ti0.4FeSb0.95Sn0.05 composition led to a 15% increase in power output of a thermoelectric device in comparison to a device made from the previous best material Hf0.44Zr0.44Ti0.12CoSb0.8Sn0.2. The n-type material used to make the unicouple device is the best reported nanostructured Hf0.25Zr0.75NiSn0.99Sb0.01 composition with the lowest hafnium (Hf) content. Both the p- and n-type nanostructured samples are prepared by ball milling the arc melted ingot and hot pressing the finely ground powders. Moreover, the raw material cost of the Nb0.6Ti0.4FeSb0.95Sn0.05 composition is more than six times lower compared to the cost of the previous best p-type Hf0.44Zr0.44Ti0.12CoSb0.8Sn0.2. This cost reduction is crucial for these materials to be used in large-scale quantities for vehicle and industrial waste heat recovery applications. DOE:DE-EE0004840.

  9. Effective field theory and Ab-initio calculation of p-type (Ga, Fe)N within LDA and SIC approximation

    Science.gov (United States)

    Salmani, E.; Mounkachi, O.; Ez-Zahraouy, H.; El Kenz, A.; Hamedoun, M.; Benyoussef, A.

    2013-03-01

    Based on first-principles spin-density functional calculations, using the Korringa-Kohn-Rostoker method combined with the coherent potential approximation, we investigated the half-metallic ferromagnetic behavior of (Ga, Fe)N co-doped with carbon within the self-interaction-corrected local density approximation. Mechanism of hybridization and interaction between magnetic ions in p-type (Ga, Fe)N is investigated. Stability energy of ferromagnetic and disorder local moment states was calculated for different carbon concentration. The local density and the self-interaction-corrected approximations have been used to explain the strong ferromagnetic interaction observed and the mechanism that stabilizes this state. The transition temperature to the ferromagnetic state has been calculated within the effective field theory, with a Honmura-Kaneyoshi differential operator technique.

  10. Electronic characteristics of p-type transparent SnO monolayer with high carrier mobility

    Science.gov (United States)

    Du, Juan; Xia, Congxin; Liu, Yaming; Li, Xueping; Peng, Yuting; Wei, Shuyi

    2017-04-01

    More recently, two-dimensional (2D) SnO nanosheets are attaching great attention due to its excellent carrier mobility and transparent characteristics. Here, the stability, electronic structures and carrier mobility of SnO monolayer are investigated by using first-principles calculations. The calculations of the phonon dispersion spectra indicate that SnO monolayer is dynamically stable. Moreover, the band gap values are decreased from 3.93 eV to 2.75 eV when the tensile strain is applied from 0% to 12%. Interestingly, SnO monolayer is a p-type transparent semiconducting oxide with hole mobility of 641 cm2 V-1 s-1, which is much higher than that of MoS2 monolayer. These findings make SnO monolayer becomes a promising 2D material for applications in nanoelectronic devices.

  11. Chemical synthesis of p-type nanocrystalline copper selenide thin films for heterojunction solar cells

    Science.gov (United States)

    Ambade, Swapnil B.; Mane, R. S.; Kale, S. S.; Sonawane, S. H.; Shaikh, Arif V.; Han, Sung-Hwan

    2006-12-01

    Nanocrystalline thin films of copper selenide have been grown on glass and tin doped-indium oxide substrates using chemical method. At ambient temperature, golden films have been synthesized and annealed at 200 °C for 1 h and were examined for their structural, surface morphological and optical properties by means of X-ray diffraction (XRD), scanning electron microscopy and UV-vis spectrophotometry techniques, respectively. Cu 2- xSe phase was confirmed by XRD pattern and spherical grains of 30 ± 4 - 40 ± 4 nm in size aggregated over about 130 ± 10 nm islands were seen by SEM images. Effect of annealing on crystallinity improvement, band edge shift and photoelectrochemical performance (under 80 mW/cm 2 light intensity and in lithium iodide electrolyte) has been studied and reported. Observed p-type electrical conductivity in copper selenide thin films make it a suitable candidate for heterojunction solar cells.

  12. How thermoelectric properties of p-type Tl-filled skutterudites are improved

    Directory of Open Access Journals (Sweden)

    Donghun Kim

    2013-09-01

    Full Text Available The high-temperature thermoelectric properties of p-type Tl-filled skutterudites TlxFe1Co3Sb12 (x = 0, 0.2, 0.4, 0.6, and 0.8 were examined. While samples with x ≤ 0.4 were single-phase Tl-filled skutterudite, samples with x = 0.6 and 0.8 were composed of two phases: TlxFe1Co3Sb12 (x ≈ 0.4 as the matrix phase and a Tl-Fe-Sb ternary alloy. The thermal conductivity (κ was reduced effectively by Tl addition, but the secondary phase increased κ slightly. The maximum value of the dimensionless figure of merit ZT (=S2T/ρ/κ, where T is the absolute temperature was 0.36 at 723 K for Tl0.2Fe1Co3Sb12.

  13. P-type calcium channels are blocked by the alkaloid daurisoline.

    Science.gov (United States)

    Lu, Y M; Fröstl, W; Dreessen, J; Knöpfel, T

    1994-07-21

    IN looking for a structurally defined non-peptide P-channel blocker we have tested the alkaloid daurisoline which has been isolated from traditional Chinese medicinal herb (Menispermum dauricum) used for the treatment of epilepsy, hypertension and asthma. We have found that daurisoline is an inhibitor of omega-Aga-IVA sensitive barium currents in cerebellar Purkinje cells and of excitatory postsynaptic potentials evoked in Purkinje cells by stimulating parallel fibres in acutely prepared cerebellar slices. Daurisoline did not significantly affect omega-Aga-IVA-insensitive barium currents recorded from granule cells freshly isolated from rat cerebellum. Daurisoline passes the blood-brain barrier and will, therefore, facilitate the functional characterization of brain calcium channels as well as the exploration of P-type calcium channels as possible drug targets.

  14. A re-examination of cobalt-related defects in n- and p-type silicon

    Energy Technology Data Exchange (ETDEWEB)

    Scheffler, Leopold; Kolkovsky, Vladimir; Weber, Joerg [Technische Universitaet Dresden, 01069 Dresden (Germany)

    2012-10-15

    In the present work cobalt-doped n- and p-type silicon samples were studied by means of deep level transient spectroscopy (DLTS) and Laplace-DLTS (LDLTS). We demonstrate that two dominant DLTS peaks previously assigned to a substitutional Co defect have different annealing behaviour and therefore belong to different defects. After wet chemical etching three other peaks (E90, E140 and H160) were observed in the samples. The intensity of the peaks becomes larger in the H-plasma treated samples. This together with depth profiling demonstrates that the peaks are hydrogen-related defects. The origin of the peaks will be discussed. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  15. Nanoscale Cross-Point Resistive Switching Memory Comprising p-Type SnO Bilayers

    KAUST Repository

    Hota, Mrinal Kanti

    2015-02-23

    Reproducible low-voltage bipolar resistive switching is reported in bilayer structures of p-type SnO films. Specifically, a bilayer homojunction comprising SnOx (oxygen-rich) and SnOy (oxygen-deficient) in nanoscale cross-point (300 × 300 nm2) architecture with self-compliance effect is demonstrated. By using two layers of SnO film, a good memory performance is obtained as compared to the individual oxide films. The memory devices show resistance ratio of 103 between the high resistance and low resistance states, and this difference can be maintained for up to 180 cycles. The devices also show good retention characteristics, where no significant degradation is observed for more than 103 s. Different charge transport mechanisms are found in both resistance states, depending on the applied voltage range and its polarity. The resistive switching is shown to originate from the oxygen ion migration and subsequent formation/rupture of conducting filaments.

  16. Improved thermoelectric efficiency in p-type ZnSb through Zn deficiency

    Science.gov (United States)

    Guo, Qilong; Luo, Sijun

    2015-12-01

    We herein report a feasible approach to improve the thermoelectric performance of p-type ZnSb compound by Zn content regulation. It is found that Zn vacancies formed by Zn deficiency not only efficiently enhance the electrical conductivity due to the improved hole concentration but also markedly lower the lattice thermal conductivity on account of the reinforced point defect scattering of phonons. The ZnSb compound with a nominal 3 mol.% Zn deficiency shows a maximum thermoelectric figure of merit ZT of 0.8 at 700 K which is a 60% improvement over the pristine sample. The strategies of further enhancing the performance of ZnSb-based material have been discussed.

  17. Low-temperature TCT characterization of heavily proton irradiated p-type magnetic Czochralski silicon detectors

    CERN Document Server

    Härkönen, J; Luukka, P; Kassamakov, I; Autioniemi, M; Tuominen, E; Sane, P; Pusa, P; Räisänen, J; Eremin, V; Verbitskaya, E; Li, Z

    2007-01-01

    n+/p−/p+ pad detectors processed at the Microelectronics Center of Helsinki University of Technology on boron-doped p-type high-resistivity magnetic Czochralski (MCz-Si) silicon substrates have been investigated by the transient current technique (TCT) measurements between 100 and 240 K. The detectors were irradiated by 9 MeV protons at the Accelerator Laboratory of University of Helsinki up to 1 MeV neutron equivalent fluence of 2×1015 n/cm2. In some of the detectors the thermal donors (TD) were introduced by intentional heat treatment at 430 °C. Hole trapping time constants and full depletion voltage values were extracted from the TCT data. We observed that hole trapping times in the order of 10 ns were found in heavily (above 1×1015 neq/cm2) irradiated samples. These detectors could be fully depleted below 500 V in the temperature range of 140–180 K.

  18. Origin of resistivity anomaly in p-type leads chalcogenide multiphase compounds

    Energy Technology Data Exchange (ETDEWEB)

    Aminorroaya Yamini, Sima, E-mail: sima@uow.edu.au, E-mail: jsnyder@caltech.edu; Dou, Shi Xue [Australian Institute for Innovative Materials (AIIM), Innovation Campus, University of Wollongong, NSW 2500 (Australia); Mitchell, David R. G. [Electron Microscopy Centre (EMC), Australian Institute for Innovative Materials (AIIM), Innovation Campus, University of Wollongong, NSW 2500 (Australia); Wang, Heng [Materials Science, California Institute of Technology, Pasadena, CA 91125 (United States); Gibbs, Zachary M. [Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125 (United States); Pei, Yanzhong [School of Materials Science and Engineering, Tongji University, 4800 Caoan Road, Shanghai 201804 (China); Snyder, G. Jeffrey, E-mail: sima@uow.edu.au, E-mail: jsnyder@caltech.edu [Electron Microscopy Centre (EMC), Australian Institute for Innovative Materials (AIIM), Innovation Campus, University of Wollongong, NSW 2500 (Australia); ITMO University, Saint Petersburg (Russian Federation)

    2015-05-15

    The electrical resistivity curves for binary phase compounds of p-type lead chalcogenide (PbTe){sub (0.9−x)}(PbSe){sub 0.1}(PbS){sub x,} (x = 0.15, 0.2, 0.25), which contain PbS-rich secondary phases, show different behaviour on heating and cooling between 500-700 K. This is contrast to single phase compounds which exhibit similar behaviour on heating and cooling. We correlate these anomalies in the electrical resistivities of multiphase compounds to the variation in phase composition at high temperatures. The inhomogeneous distribution of dopants between the matrix and secondary phase is found to be crucial in the electronic transport properties of the multiphase compounds. These results can lead to further advances in designing composite Pb-chalcogenides with high thermoelectric performance.

  19. Microhardness of carbon-doped (111) p-type Czochralski silicon

    Science.gov (United States)

    Danyluk, S.; Lim, D. S.; Kalejs, J.

    1985-01-01

    The effect of carbon on (111) p-type Czochralski silicon is examined. The preparation of the silicon and microhardness test procedures are described, and the equation used to determine microhardness from indentations in the silicon wafers is presented. The results indicate that as the carbon concentration in the silicon increases the microhardness increases. The linear increase in microhardness is the result of carbon hindering dislocation motion, and the effect of temperature on silicon deformation and dislocation mobility is explained. The measured microhardness was compared with an analysis which is based on dislocation pinning by carbon; a good correlation was observed. The Labusch model for the effect of pinning sites on dislocation motion is given.

  20. Photostable p-type dye-sensitized photoelectrochemical cells for water reduction.

    Science.gov (United States)

    Ji, Zhiqiang; He, Mingfu; Huang, Zhongjie; Ozkan, Umit; Wu, Yiying

    2013-08-14

    A photostable p-type NiO photocathode based on a bifunctional cyclometalated ruthenium sensitizer and a cobaloxime catalyst has been created for visible-light-driven water reduction to produce H2. The sensitizer is anchored firmly on the surface of NiO, and the binding is resistant to the hydrolytic cleavage. The bifunctional sensitizer can also immobilize the water reduction catalyst. The resultant photoelectrode exhibits superior stability in aqueous solutions. Stable photocurrents have been observed over a period of hours. This finding is useful for addressing the degradation issue in dye-sensitized photoelectrochemical cells caused by desorption of dyes and catalysts. The high stability of our photocathodes should be important for the practical application of these devices for solar fuel production.

  1. Phonon bottleneck in p-type Ge/Si quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Yakimov, A. I., E-mail: yakimov@isp.nsc.ru [Rzhanov Institute of Semiconductor Physics, Siberian Branch of the Russian Academy of Science, 630090 Novosibirsk (Russian Federation); Tomsk State University, 634050 Tomsk (Russian Federation); Kirienko, V. V.; Armbrister, V. A. [Rzhanov Institute of Semiconductor Physics, Siberian Branch of the Russian Academy of Science, 630090 Novosibirsk (Russian Federation); Bloshkin, A. A.; Dvurechenskii, A. V. [Rzhanov Institute of Semiconductor Physics, Siberian Branch of the Russian Academy of Science, 630090 Novosibirsk (Russian Federation); Novosibirsk State University, 630090 Novosibirsk (Russian Federation)

    2015-11-23

    We study the effect of quantum dot size on the mid-infrared photo- and dark current, photoconductive gain, and hole capture probability in ten-period p-type Ge/Si quantum dot heterostructures. The dot dimensions are varied by changing the Ge coverage and the growth temperature during molecular beam epitaxy of Ge/Si(001) system in the Stranski-Krastanov growth mode. In all samples, we observed the general tendency: with decreasing the size of the dots, the dark current and hole capture probability are reduced, while the photoconductive gain and photoresponse are enhanced. Suppression of the hole capture probability in small-sized quantum dots is attributed to a quenched electron-phonon scattering due to phonon bottleneck.

  2. Improved performance of P-type DSCs with a compact blocking layer coated by different thicknesses

    Science.gov (United States)

    Ho, Phuong; Bao, Le Quoc; Cheruku, Rajesh; Kim, Jae Hong

    2016-09-01

    The introduction of different thicknesses of a compact NiO blocking layer coating with different spin speeds on FTO and followed by a coating of photoactive NiO electrode for p-type dye-sensitized solar cells ( p-DSCs). This study examined the fabrication of a compact NiO blocking layer by decomposing an ethanolic precursor solution of nickel acetate tetrahydrate. The DCBZ dye used as the photosensitizer for the NiO electrode in the p-DSCs device and their performances have been analyzed. The enhancement of photovoltaic performance and resulted from an increase in the power conversion efficiency ( η). The electrochemical impedance spectroscopy (EIS) measurement demonstrated that charge recombination was suppressed when a compact NiO blocking layer was applied. The results showed that the best p-DSC was achieved by employing 3000 rpm spin-coated process for different times of blocking layer.

  3. Ge-intercalated graphene: The origin of the p-type to n-type transition

    KAUST Repository

    Kaloni, Thaneshwor P.

    2012-09-01

    Recently huge interest has been focussed on Ge-intercalated graphene. In order to address the effect of Ge on the electronic structure, we study Ge-intercalated free-standing C 6 and C 8 bilayer graphene, bulk C 6Ge and C 8Ge, as well as Ge-intercalated graphene on a SiC(0001) substrate, by density functional theory. In the presence of SiC(0001), there are three ways to obtain n-type graphene: i) intercalation between C layers; ii) intercalation at the interface to the substrate in combination with Ge deposition on the surface; and iii) cluster intercalation. All other configurations under study result in p-type states irrespective of the Ge coverage. We explain the origin of the different doping states and establish the conditions under which a transition occurs. © Copyright EPLA, 2012.

  4. Nanopore formation on low-doped p-type silicon under illumination

    Energy Technology Data Exchange (ETDEWEB)

    Chiboub, N. [UDTS, 02 Bd. Frantz Fanon, B.P. 140, Alger-7 Merveilles, 16200 Algiers (Algeria); Gabouze, N., E-mail: ngabouze@yahoo.fr [UDTS, 02 Bd. Frantz Fanon, B.P. 140, Alger-7 Merveilles, 16200 Algiers (Algeria); Chazalviel, J.-N.; Ozanam, F. [Physique de la Matiere Condensee, Ecole Polytechnique, CNRS, 91128 Palaiseau (France); Moulay, S. [Universite Saad Dahleby, B.P. 270, Route de Soumaa, Blida (Algeria); Manseri, A. [UDTS, 02 Bd. Frantz Fanon, B.P. 140, Alger-7 Merveilles, 16200 Algiers (Algeria)

    2010-04-01

    Porous silicon layers were elaborated by anodization of highly resistive p-type silicon in HF/ethylene glycol solution under front side illumination, as a function of etching time, HF concentration and illumination intensity. The porous layer morphology was investigated by scanning electron microscopy (SEM). The illumination during anodization was provided by a tungsten lamp or lasers of different wavelengths. Under anodization, a microporous layer is formed up to a critical thickness above which macropores appear. Under illumination, the instability limiting the growth of the microporous layer occurs at a critical thickness much larger than in the dark. This critical thickness depends on HF concentration, illumination wavelength and intensity. These non-trivial dependencies are rationalized in a model in which photochemical etching in the electrochemically formed porous layer plays the central role.

  5. Empirical model predicting the layer thickness and porosity of p-type mesoporous silicon

    Science.gov (United States)

    Wolter, Sascha J.; Geisler, Dennis; Hensen, Jan; Köntges, Marc; Kajari-Schröder, Sarah; Bahnemann, Detlef W.; Brendel, Rolf

    2017-04-01

    Porous silicon is a promising material for a wide range of applications because of its versatile layer properties and the convenient preparation by electrochemical etching. Nevertheless, the quantitative dependency of the layer thickness and porosity on the etching process parameters is yet unknown. We have developed an empirical model to predict the porosity and layer thickness of p-type mesoporous silicon prepared by electrochemical etching. The impact of the process parameters such as current density, etching time and concentration of hydrogen fluoride is evaluated by ellipsometry. The main influences on the porosity of the porous silicon are the current density, the etching time and their product while the etch rate is dominated by the current density, the concentration of hydrogen fluoride and their product. The developed model predicts the resulting layer properties of a certain porosification process and can, for example be used to enhance the utilization of the employed chemicals.

  6. Membrane Anchoring and Ion-Entry Dynamics in P-type ATPase Copper Transport

    DEFF Research Database (Denmark)

    Grønberg, Christina; Sitsel, Oleg; Lindahl, Erik

    2016-01-01

    Cu(+)-specific P-type ATPase membrane protein transporters regulate cellular copper levels. The lack of crystal structures in Cu(+)-binding states has limited our understanding of how ion entry and binding are achieved. Here, we characterize the molecular basis of Cu(+) entry using molecular......-dynamics simulations, structural modeling, and in vitro and in vivo functional assays. Protein structural rearrangements resulting in the exposure of positive charges to bulk solvent rather than to lipid phosphates indicate a direct molecular role of the putative docking platform in Cu(+) delivery. Mutational analyses...... and simulations in the presence and absence of Cu(+) predict that the ion-entry path involves two ion-binding sites: one transient Met148-Cys382 site and one intramembranous site formed by trigonal coordination to Cys384, Asn689, and Met717. The results reconcile earlier biochemical and x-ray absorption data...

  7. Inkjet printed circuits based on ambipolar and p-type carbon nanotube thin-film transistors

    Science.gov (United States)

    Kim, Bongjun; Geier, Michael L.; Hersam, Mark C.; Dodabalapur, Ananth

    2017-02-01

    Ambipolar and p-type single-walled carbon nanotube (SWCNT) thin-film transistors (TFTs) are reliably integrated into various complementary-like circuits on the same substrate by inkjet printing. We describe the fabrication and characteristics of inverters, ring oscillators, and NAND gates based on complementary-like circuits fabricated with such TFTs as building blocks. We also show that complementary-like circuits have potential use as chemical sensors in ambient conditions since changes to the TFT characteristics of the p-channel TFTs in the circuit alter the overall operating characteristics of the circuit. The use of circuits rather than individual devices as sensors integrates sensing and signal processing functions, thereby simplifying overall system design.

  8. Chemical synthesis of p-type nanocrystalline copper selenide thin films for heterojunction solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Ambade, Swapnil B. [Department of Chemical Engineering, Vishwakarma Institute of Technology, Pune 411037 (India); Mane, R.S. [Inorganic Nanomaterials Laboratory, Department of Chemistry, Hanyang University, Sungdong-Ku, Haengdang-dong 17, Seoul 133-791 (Korea, Republic of); Kale, S.S. [Inorganic Nanomaterials Laboratory, Department of Chemistry, Hanyang University, Sungdong-Ku, Haengdang-dong 17, Seoul 133-791 (Korea, Republic of); Sonawane, S.H. [Department of Chemical Engineering, Vishwakarma Institute of Technology, Pune 411037 (India); Shaikh, Arif V. [Department of Electronic Science, AKI' s Poona College of Arts, Science and Commerce, Camp, Pune 411 001 (India); Han, Sung-Hwan [Inorganic Nanomaterials Laboratory, Department of Chemistry, Hanyang University, Sungdong-Ku, Haengdang-dong 17, Seoul 133-791 (Korea, Republic of)]. E-mail: shhan@hanyang.ac.kr

    2006-12-15

    Nanocrystalline thin films of copper selenide have been grown on glass and tin doped-indium oxide substrates using chemical method. At ambient temperature, golden films have been synthesized and annealed at 200 deg. C for 1 h and were examined for their structural, surface morphological and optical properties by means of X-ray diffraction (XRD), scanning electron microscopy and UV-vis spectrophotometry techniques, respectively. Cu{sub 2-x}Se phase was confirmed by XRD pattern and spherical grains of 30 {+-} 4 - 40 {+-} 4 nm in size aggregated over about 130 {+-} 10 nm islands were seen by SEM images. Effect of annealing on crystallinity improvement, band edge shift and photoelectrochemical performance (under 80 mW/cm{sup 2} light intensity and in lithium iodide electrolyte) has been studied and reported. Observed p-type electrical conductivity in copper selenide thin films make it a suitable candidate for heterojunction solar cells.

  9. Bulk and Surface Event Identification in p-type Germanium Detectors

    CERN Document Server

    Yang, L T; Jia, L P; Jiang, H; Li, J; Lin, F K; Lin, S T; Liu, S K; Ma, J L; Sharma, V; Singh, L; Singh, M K; Soma, A K; Yang, S W; Wang, L; Wang, Q; Wong, H T; Yue, Q; Zhao, W

    2016-01-01

    The p-type point-contact germanium detectors, due to its sub-keV sensitivities and low internal radioactivity background, are demonstrated to be competitive tools for light dark matter WIMPs searches and may have potential applications in neutrino physics. These detectors exhibit anomalous surface behavior, which has been characterized and dealt with in previous analysis. However, the analysis method rely on spectral shape assumptions and must use external calibration sources. In this report, we purpose an improved method, where in situ data could be used as calibration sources. Data from CDEX-1 and TEXONO experiments will be re-examined and the results are shown to be consistent with both analysis.

  10. Wide bandgap n-type and p-type semiconductor porous junction devices as photovoltaic cells

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Yuan-Pai; Horng, Sheng-Fu [Institute of Electronics Engineering, National Tsing Hua University, Hsinchu 300, Taiwan (China); Chao, Yu-Chiang; Meng, Hsin-Fei [Institute of Physics, National Chiao Tung University, Hsinchu 300, Taiwan (China); Zan, Hsiao-Wen, E-mail: yuchiangchao@gmail.com, E-mail: meng@mail.nctu.edu.tw [Department of Photonics and Institute of Electro-Optical Engineering, National Chiao Tung University, Hsinchu 300, Taiwan (China)

    2011-10-12

    In junction absorber photovoltaics doped wide bandgap n-type and p-type semiconductors form a porous interpenetrating junction structure with a layer of low bandgap absorber at the interface. The doping concentration is high enough such that the junction depletion width is smaller than the pore size. The highly conductive neutral region then has a dentrite shape with fingers reaching the absorber to effectively collect the photo-carriers swept out by the junction electric field. With doping of 10{sup 19} cm{sup -3} corresponding to a depletion width of 25 nm, pore size of 32 nm, absorber thickness close to exciton diffusion length of 17 nm, absorber bandgap of 1.4 eV and carrier mobility over 10{sup -5} cm{sup 2} V{sup -1} s{sup -1}, numerical calculation shows the power conversion efficiency is as high as 19.4%. It rises to 23% for a triplet exciton absorber.

  11. Chemical Composition of Nanoporous Layer Formed by Electrochemical Etching of p-Type GaAs

    Science.gov (United States)

    Bioud, Youcef A.; Boucherif, Abderraouf; Belarouci, Ali; Paradis, Etienne; Drouin, Dominique; Arès, Richard

    2016-10-01

    We have performed a detailed characterization study of electrochemically etched p-type GaAs in a hydrofluoric acid-based electrolyte. The samples were investigated and characterized through cathodoluminescence (CL), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS). It was found that after electrochemical etching, the porous layer showed a major decrease in the CL intensity and a change in chemical composition and in the crystalline phase. Contrary to previous reports on p-GaAs porosification, which stated that the formed layer is composed of porous GaAs, we report evidence that the porous layer is in fact mainly constituted of porous As2O3. Finally, a qualitative model is proposed to explain the porous As2O3 layer formation on p-GaAs substrate.

  12. InP nanowire p-type doping via Zinc indiffusion

    Science.gov (United States)

    Haggren, Tuomas; Otnes, Gaute; Mourão, Renato; Dagyte, Vilgaile; Hultin, Olof; Lindelöw, Fredrik; Borgström, Magnus; Samuelson, Lars

    2016-10-01

    We report an alternative pathway for p-type InP nanowire (NW) doping by diffusion of Zn species from the gas phase. The diffusion of Zn was performed in a MOVPE reactor at 350-500 °C for 5-20 min with either H2 environment or additional phosphorus in the atmosphere. In addition, Zn3P2 shells were studied as protective caps during post-diffusion annealing. This post-diffusion annealing was performed to outdiffuse and activate Zn in interstitial locations. The characterization methods included photoluminescence and single NW conductivity and carrier concentration measurements. The acquired carrier concentrations were in the order of >1017 cm-3 for NWs without post-annealing, and up to 1018 cm-3 for NWs annealed with the Zn3P2 shells. The diffused Zn caused redshift to the photoluminescence signal, and the degree of redshift depended on the diffusion process.

  13. Inkjet printed circuits based on ambipolar and p-type carbon nanotube thin-film transistors

    Science.gov (United States)

    Kim, Bongjun; Geier, Michael L.; Hersam, Mark C.; Dodabalapur, Ananth

    2017-01-01

    Ambipolar and p-type single-walled carbon nanotube (SWCNT) thin-film transistors (TFTs) are reliably integrated into various complementary-like circuits on the same substrate by inkjet printing. We describe the fabrication and characteristics of inverters, ring oscillators, and NAND gates based on complementary-like circuits fabricated with such TFTs as building blocks. We also show that complementary-like circuits have potential use as chemical sensors in ambient conditions since changes to the TFT characteristics of the p-channel TFTs in the circuit alter the overall operating characteristics of the circuit. The use of circuits rather than individual devices as sensors integrates sensing and signal processing functions, thereby simplifying overall system design. PMID:28145438

  14. Luminescence properties of p-type thin CdS films prepared by laser ablation

    Energy Technology Data Exchange (ETDEWEB)

    Ullrich, B. [Tokyo Univ. (Japan). Dept. of Physics; Ezumi, H. [Department of Electrical Engineering, Hiroshima-Denki Institute of Technology, Hiroshima 739-03 (Japan); Keitoku, S. [Hiroshima Women`s University, Hiroshima 734 (Japan); Kobayashi, T. [Tokyo Univ. (Japan). Dept. of Physics

    1995-12-01

    Investigations of the luminescence of p-type CdS:Cu thin (less than or equal to 2 {mu}m) films on glass substrate prepared by laser ablation were performed for the first time. The dependences of the luminescence on the Cu content in the thin films were studied at 300 K with argon laser lines at 457.9 nm, 488.0 nm and 514.5 nm. It is demonstrated that the luminescence excited with the 514.5 nm line corresponds to the donor-acceptor transition. Furthermore, it is shown that the intensity of the red emission of CdS:Cu films can be efficiently bleached by Cu doping. (orig.)

  15. Inkjet printed circuits based on ambipolar and p-type carbon nanotube thin-film transistors.

    Science.gov (United States)

    Kim, Bongjun; Geier, Michael L; Hersam, Mark C; Dodabalapur, Ananth

    2017-02-01

    Ambipolar and p-type single-walled carbon nanotube (SWCNT) thin-film transistors (TFTs) are reliably integrated into various complementary-like circuits on the same substrate by inkjet printing. We describe the fabrication and characteristics of inverters, ring oscillators, and NAND gates based on complementary-like circuits fabricated with such TFTs as building blocks. We also show that complementary-like circuits have potential use as chemical sensors in ambient conditions since changes to the TFT characteristics of the p-channel TFTs in the circuit alter the overall operating characteristics of the circuit. The use of circuits rather than individual devices as sensors integrates sensing and signal processing functions, thereby simplifying overall system design.

  16. Asymptotics of the trap-dominated Gunn effect in p-type Ge

    Science.gov (United States)

    Bonilla, L. L.; Hernando, P. J.; Herrero, M. A.; Kindelan, M.; Velázquez, J. J. L.

    1997-09-01

    We present an asymptotic analysis of the Gunn effect in a drift-diffusion model - including electric-field-dependent generation-recombination processes - for long samples of strongly compensated p-type Ge at low temperature and under d.c. voltage bias. During each Gunn oscillation, there are different stages corresponding to the generation, motion and annihilation of solitary waves. Each stage may be described by one evolution equation for only one degree of freedom (the current density), except for the generation of each new wave. The wave generation is a faster process that may be described by solving a semiinfinite canonical problem. As a result of our study we have found that (depending on the boundary condition) one or several solitary waves may be shed during each period of the oscillation. Examples of numerical simulations validating our analysis are included.

  17. DLTS of p-type Czochralski Si wafers containing processing-induced macropores

    Science.gov (United States)

    Simoen, E.; Depauw, V.; Gordon, I.; Poortmans, J.

    2012-01-01

    The deep levels present in p-type Czochralski silicon with processing-induced macropores in the depletion region have been studied by the deep-level transient (DLT) spectroscopy technique. It is shown that a broad band is present for a bias pulse close to the interface with the Al Schottky contact, which exhibits anomalously slow hole capture and is ascribed to the internal interface states of the macropores. For depths beyond the pore region, other deep levels, associated with point defects—possibly metal contamination during the high-temperature annealing step under H2 ambient--have been observed. The impact of the observed defects on the lifetime of thin-film solar cells, fabricated using macropore-based layer transfer is discussed. Finally, it is shown that the presence of pores in the depletion region, which also affects the DLT-spectrum, alters the capacitance-voltage characteristics.

  18. Large area growth and electrical properties of p-type WSe2 atomic layers.

    Science.gov (United States)

    Zhou, Hailong; Wang, Chen; Shaw, Jonathan C; Cheng, Rui; Chen, Yu; Huang, Xiaoqing; Liu, Yuan; Weiss, Nathan O; Lin, Zhaoyang; Huang, Yu; Duan, Xiangfeng

    2015-01-14

    Transition metal dichacogenides represent a unique class of two-dimensional layered materials that can be exfoliated into single or few atomic layers. Tungsten diselenide (WSe(2)) is one typical example with p-type semiconductor characteristics. Bulk WSe(2) has an indirect band gap (∼ 1.2 eV), which transits into a direct band gap (∼ 1.65 eV) in monolayers. Monolayer WSe(2), therefore, is of considerable interest as a new electronic material for functional electronics and optoelectronics. However, the controllable synthesis of large-area WSe(2) atomic layers remains a challenge. The studies on WSe(2) are largely limited by relatively small lateral size of exfoliated flakes and poor yield, which has significantly restricted the large-scale applications of the WSe(2) atomic layers. Here, we report a systematic study of chemical vapor deposition approach for large area growth of atomically thin WSe(2) film with the lateral dimensions up to ∼ 1 cm(2). Microphotoluminescence mapping indicates distinct layer dependent efficiency. The monolayer area exhibits much stronger light emission than bilayer or multilayers, consistent with the expected transition to direct band gap in the monolayer limit. The transmission electron microscopy studies demonstrate excellent crystalline quality of the atomically thin WSe(2). Electrical transport studies further show that the p-type WSe(2) field-effect transistors exhibit excellent electronic characteristics with effective hole carrier mobility up to 100 cm(2) V(-1) s(-1) for monolayer and up to 350 cm(2) V(-1) s(-1) for few-layer materials at room temperature, comparable or well above that of previously reported mobility values for the synthetic WSe(2) and comparable to the best exfoliated materials.

  19. Room temperature p-type conductivity and coexistence of ferroelectric order in ferromagnetic Li doped ZnO nanoparticles

    KAUST Repository

    Awan, Saif Ullah

    2014-10-28

    Memory and switching devices acquired new materials which exhibit ferroelectric and ferromagnetic order simultaneously. We reported multiferroic behavior in Zn1-yLiyO(0.00≤y≤0.10) nanoparticles. The analysis of transmission electron micrographs confirmed the hexagonal morphology and wurtzite crystalline structure. We investigated p-type conductivity in doped samples and measured hole carriers in range 2.4×1017/cc to 7.3×1017/cc for different Li contents. We found that hole carriers are responsible for long range order ferromagnetic coupling in Li doped samples. Room temperature ferroelectric hysteresis loops were observed in 8% and 10% Li doped samples. We demonstrated ferroelectric coercivity (remnant polarization) 2.5kV/cm (0.11 μC/cm2) and 2.8kV/cm (0.15 μC/cm2) for y=0.08 and y=0.10 samples. We propose that the mechanism of Li induced ferroelectricity in ZnO is due to indirect dipole interaction via hole carriers. We investigated that if the sample has hole carriers ≥5.3×1017/cc, they can mediate the ferroelectricity. Ferroelectric and ferromagnetic measurements showed that higher electric polarization and larger magnetic moment is attained when the hole concentration is larger and vice versa. Our results confirmed the hole dependent coexistence of ferromagnetic and ferroelectric behavior at room temperature, which provide potential applications for switchable and memory devices.

  20. An MCMC-based waveform analysis with p-type point contact detectors in the MAJORANA DEMONSTRATOR

    Science.gov (United States)

    Shanks, Benjamin; MAJORANA Collaboration

    2017-01-01

    Statistical signal processing can be a powerful tool for extracting as much information as possible from raw data. By fitting data to a physical model of signal generation on an event-by-event basis, it can be used to perform precise event reconstruction and enable efficient background rejection. Searches for neutrinoless double-beta decay must achieve extremely low backgrounds to reach sensitivities required for discovery, and so can benefit greatly from this analysis technique. The MAJORANA DEMONSTRATOR has implemented a Markov Chain Monte Carlo (MCMC) signal processing algorithm to fit waveforms from p-type point contact (PPC) germanium detectors. After a machine learning step to tune detector fields and electronics response parameters, the MCMC algorithm is able to reconstruct the time, energy and position of interactions within the PPC detector. The parameters estimated with this method will find many applications within the DEMONSTRATOR physics program, including background identification and rejection. This will prove important as the DEMONSTRATOR aims to reach its background goal of < 3 counts/tonne/yr in the region of interest. This work is supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, the Particle Astrophysics and Nuclear Physics Programs of the National Science Foundation, and the Sanford Underground Research Facility.

  1. Pathologic changes in mice induced by subtilase cytotoxin, a potent new Escherichia coli AB5 toxin that targets the endoplasmic reticulum.

    Science.gov (United States)

    Wang, Hui; Paton, James C; Paton, Adrienne W

    2007-10-01

    Subtilase cytotoxin (SubAB) is the prototype of a recently discovered AB(5) cytotoxin family produced by certain strains of Shiga toxigenic Escherichia coli (STEC). The catalytic A subunit is a highly specific subtilase-like serine protease that cleaves the endoplasmic reticulum chaperone BiP. The toxin is lethal for mice, but the pathology it induces is poorly understood. Here, we show that intraperitoneal injection of SubAB causes microangiopathic hemolytic anemia, thrombocytopenia, and renal impairment in mice--characteristics typical of Shiga toxin-induced hemolytic uremic syndrome. SubAB caused extensive microvascular thrombosis and other histologic damage in the brain, kidneys, and liver, as well as dramatic splenic atrophy. Peripheral blood leukocyte levels were increased at 24 h; there was also significant neutrophil infiltration in the liver, kidneys, and spleen and toxin-induced apoptosis at these sites. These findings raise the possibility that SubAB directly contributes to pathology in humans infected with strains of STEC that produce both Shiga toxin and SubAB.

  2. Vacuolating cytotoxin genotypes are strong markers of gastric cancer and duodenal ulcer-associated Helicobacter pylori strains: a matched case-control study.

    Science.gov (United States)

    Memon, Ameer A; Hussein, Nawfal R; Miendje Deyi, Véronique Y; Burette, Alain; Atherton, John C

    2014-08-01

    The Helicobacter pylori virulence gene, cagA, and active forms of the vacuolating cytotoxin gene, vacA, are major determinants of pathogenesis. However, previous studies linking these factors to disease risk have often included patients using aspirin/nonsteroidal anti-inflammatory agents (NSAIDs) or acid-suppressing drugs, both of which may confound results. Also, particularly for gastric cancer (GC), controls have often been of quite different ages. Here, we performed a careful study in a "clean" Belgian population with gastric cancer cases age and sex matched to 4 controls and with a parallel duodenal ulcer (DU) group. As in other populations, there was a close association between the presence of cagA and the vacA s1 genotype. For GC, associations were found for vacA s1-positive (P = 0.01, odds ratio [OR], 9.37; 95% confidence interval [CI], 1.16 to 201.89), i1-positive (P = 0.003; OR, 12.08; 95% CI, 1.50 to 259.64), and cagA-positive status (P ulcer-associated strains are the vacA s1 and i1 genotypes. This fits with experimental data showing that the s and i regions are the key determinants of vacuolating cytotoxin activity.

  3. The Helicobacter pylori cytotoxin CagA is essential for suppressing host heat shock protein expression.

    Science.gov (United States)

    J Lang, Ben; J Gorrell, Rebecca; Tafreshi, Mona; Hatakeyama, Masanori; Kwok, Terry; T Price, John

    2016-05-01

    Bacterial infections typically elicit a strong Heat Shock Response (HSR) in host cells. However, the gastric pathogen Helicobacter pylori has the unique ability to repress this response, the mechanism of which has yet to be elucidated. This study sought to characterize the underlying mechanisms by which H. pylori down-modulates host HSP expression upon infection. Examination of isogenic mutant strains of H. pylori defective in components of the type IV secretion system (T4SS), identified the secretion substrate, CagA, to be essential for down-modulation of the HSPs HSPH1 (HSP105), HSPA1A (HSP72), and HSPD1 (HSP60) upon infection of the AGS gastric adenocarcinoma cell line. Ectopic expression of CagA by transient transfection was insufficient to repress HSP expression in AGS or HEK293T cells, suggesting that additional H. pylori factors are required for HSP repression. RT-qPCR analysis of HSP gene expression in AGS cells infected with wild-type H. pylori or isogenic cagA-deletion mutant found no significant change to account for reduced HSP levels. In summary, this study identified CagA to be an essential bacterial factor for H. pylori-mediated suppression of host HSP expression. The novel finding that HSPH1 is down-modulated by H. pylori further highlights the unique ability of H. pylori to repress the HSR within host cells. Elucidation of the mechanism by which H. pylori achieves HSP repression may prove to be beneficial in the identification of novel mechanisms to inhibit the HSR pathway and provide further insight into the interactions between H. pylori and the host gastric epithelium.

  4. Chemical construction and structural permutation of potent cytotoxin polytheonamide B: discovery of artificial peptides with distinct functions.

    Science.gov (United States)

    Itoh, Hiroaki; Inoue, Masayuki

    2013-07-16

    Polytheonamide B (1), isolated from the marine sponge Theonella swinhoei, is a posttranslationally modified ribosomal peptide (MW 5030 Da) that displays extraordinary cytotoxicity. Among its 48 amino acid residues, this peptide includes a variety D- and L-amino acids that do not occur in proteins, and the chiralities of these amino acids alternate in sequence. These structural features induce the formation of a stable β6.3-helix, giving rise to a tubular structure of over 4 nm in length. In the biological setting, this fold is believed to transport cations across the lipid bilayer through a pore, thereby acting as an ion channel. In this Account, we discuss the construction and structural permutations of this potent cytotoxin. First we describe the 161-step chemical construction of this unusual peptide 1. By developing a synthetic route to 1, we established the chemical basis for subsequent SAR studies to pinpoint the proteinogenic and nonproteinogenic building blocks within the molecule that confer its toxicity and channel function. Using fully synthetic 1, we generated seven analogues with point mutations, and studies of their activity revealed the importance of the N-terminal moiety. Next, we simplified the structure of 1 by substituting six amino acid residues of 1 to design a more synthetically accessible analogue 9. This dansylated polytheonamide mimic 9 was synthesized in 127 total steps, and we evaluated its function to show that it can emulate the toxic and ion channel activities of 1 despite its multiple structural modifications. Finally, we applied a highly automated synthetic route to 48-mer 9 to generate 13 substructures of 27-39-mers. The 37-mer 12 exhibited nanomolar level toxicity through a potentially distinct mode of action from 1 and 9. The SAR studies of polytheonamide B and the 21 artificial analogues have deepened our understanding of the precise structural requirements for the biological functions of 1. They have also led to the discovery of

  5. Gene therapy-mediated delivery of targeted cytotoxins for glioma therapeutics.

    Science.gov (United States)

    Candolfi, Marianela; Xiong, Weidong; Yagiz, Kader; Liu, Chunyan; Muhammad, A K M G; Puntel, Mariana; Foulad, David; Zadmehr, Ali; Ahlzadeh, Gabrielle E; Kroeger, Kurt M; Tesarfreund, Matthew; Lee, Sharon; Debinski, Waldemar; Sareen, Dhruv; Svendsen, Clive N; Rodriguez, Ron; Lowenstein, Pedro R; Castro, Maria G

    2010-11-16

    Restricting the cytotoxicity of anticancer agents by targeting receptors exclusively expressed on tumor cells is critical when treating infiltrative brain tumors such as glioblastoma multiforme (GBM). GBMs express an IL-13 receptor (IL13Rα2) that differs from the physiological IL4R/IL13R receptor. We developed a regulatable adenoviral vector (Ad.mhIL-4.TRE.mhIL-13-PE) encoding a mutated human IL-13 fused to Pseudomonas exotoxin (mhIL-13-PE) that specifically binds to IL13Rα2 to provide sustained expression, effective anti-GBM cytotoxicity, and minimal neurotoxicity. The therapeutic Ad also encodes mutated human IL-4 that binds to the physiological IL4R/IL13R without interacting with IL13Rα2, thus inhibiting potential binding of mhIL-13-PE to normal brain cells. Using intracranial GBM xenografts and syngeneic mouse models, we tested the Ad.mhIL-4.TRE.mhIL-13-PE and two protein formulations, hIL-13-PE used in clinical trials (Cintredekin Besudotox) and a second-generation mhIL-13-PE. Cintredekin Besudotox doubled median survival without eliciting long-term survival and caused severe neurotoxicity; mhIL-13-PE led to ∼40% long-term survival, eliciting severe neurological toxicity at the high dose tested. In contrast, Ad-mediated delivery of mhIL-13-PE led to tumor regression and long-term survival in over 70% of the animals, without causing apparent neurotoxicity. Although Cintredekin Besudotox was originally developed to target GBM, when tested in a phase III trial it failed to achieve clinical endpoints and revealed neurotoxicity. Limitations of Cintredekin Besudotox include its short half-life, which demanded frequent or continued administration, and binding to IL4R/IL13R, present in normal brain cells. These shortcomings were overcome by our therapeutic Ad, thus representing a significant advance in the development of targeted therapeutics for GBM.

  6. Sputtering deposition of P-type SnO films with SnO₂ target in hydrogen-containing atmosphere.

    Science.gov (United States)

    Hsu, Po-Ching; Hsu, Chao-Jui; Chang, Ching-Hsiang; Tsai, Shiao-Po; Chen, Wei-Chung; Hsieh, Hsing-Hung; Wu, Chung-Chih

    2014-08-27

    In this work, we had investigated sputtering deposition of p-type SnO using the widely used and robust SnO2 target in a hydrogen-containing reducing atmosphere. The effects of the hydrogen-containing sputtering gas on structures, compositions, optical, and electrical properties of deposited SnOx films were studied. Results show that polycrystalline and SnO-dominant films could be readily obtained by carefully controlling the hydrogen gas ratio in the sputtering gas and the extent of reduction reaction. P-type conductivity was unambiguously observed for SnO-dominant films with traceable Sn components, exhibiting a p-type Hall mobility of up to ∼3 cm(2) V(-1) s(-1). P-type SnO thin-film transistors using such SnO-dominant films were also demonstrated.

  7. Ambipolar Organic Phototransistors with p-Type/n-Type Conjugated Polymer Bulk Heterojunction Light-Sensing Layers

    KAUST Repository

    Nam, Sungho

    2016-11-18

    Ambipolar organic phototransistors with sensing channel layers, featuring p-type and n-type conjugated polymer bulk heterojunctions, exhibit outstanding light-sensing characteristics in both p-channel and n-channel sensing operation modes.

  8. Surface modifications caused by a swift heavy ion irradiation on crystalline p-type gallium antimonide

    Energy Technology Data Exchange (ETDEWEB)

    Jadhav, Vidya, E-mail: vj1510@yahoo.com

    2015-09-01

    Surface modifications caused by a swift heavy ion irradiation on crystalline p-type gallium antimonide crystal have been reported. Single crystal, 1 0 0〉 orientations and ∼500 μm thick p-type GaSb samples with carrier concentration of 3.30 × 10{sup 17} cm{sup −3} were irradiated at 100 MeV Fe{sup 7+} ions. We have used 15UD Pelletron facilities at IUAC with varying fluences of 5 × 10{sup 10}–1 × 10{sup 14} ions cm{sup −2}. The effects of irradiation on these samples have been investigated using, spectroscopic ellipsometry, atomic force microscopy and ultraviolet–visible–NIR spectroscopy techniques. Ellipsometry parameters, psi (Ψ) and delta (Δ) for the unirradiated sample and samples irradiated with different fluences were recorded. The data were fit to a three phase model to determine the refractive index and extinction coefficient. The refractive index and extinction coefficient for various fluences in ultraviolet, visible, and infrared, regimes were evaluated. Atomic force microscopy has been used to study these surface modifications. In order to have more statistical information about the surface, we have plotted the height structure histogram for all the samples. For unirradiated sample, we observed the Gaussian fitting. This result indicates the more ordered height structure symmetry. Whereas for the sample irradiated with the fluence of 1 × 10{sup 13}, 5 × 10{sup 13} and 1 × 10{sup 14} ions cm{sup −2}, we observed the scattered data. The width of the histogram for samples irradiated up to the fluence of 1 × 10{sup 13} ion cm{sup −2} was found to be almost same however it decreased at higher fluence. UV reflectance spectra of the sample irradiated with increasing fluences exhibit three peaks at 292, 500 and 617 nm represent the high energy GaSb; E{sub 1}, E{sub 1} + Δ and E{sub 2} band gaps in all irradiated samples.

  9. Few-Layer MoS₂ p-Type Devices Enabled by Selective Doping Using Low Energy Phosphorus Implantation.

    Science.gov (United States)

    Nipane, Ankur; Karmakar, Debjani; Kaushik, Naveen; Karande, Shruti; Lodha, Saurabh

    2016-02-23

    P-type doping of MoS2 has proved to be a significant bottleneck in the realization of fundamental devices such as p-n junction diodes and p-type transistors due to its intrinsic n-type behavior. We report a CMOS compatible, controllable and area selective phosphorus plasma immersion ion implantation (PIII) process for p-type doping of MoS2. Physical characterization using SIMS, AFM, XRD and Raman techniques was used to identify process conditions with reduced lattice defects as well as low surface damage and etching, 4X lower than previous plasma based doping reports for MoS2. A wide range of nondegenerate to degenerate p-type doping is demonstrated in MoS2 field effect transistors exhibiting dominant hole transport. Nearly ideal and air stable, lateral homogeneous p-n junction diodes with a gate-tunable rectification ratio as high as 2 × 10(4) are demonstrated using area selective doping. Comparison of XPS data from unimplanted and implanted MoS2 layers shows a shift of 0.67 eV toward lower binding energies for Mo and S peaks indicating p-type doping. First-principles calculations using density functional theory techniques confirm p-type doping due to charge transfer originating from substitutional as well as physisorbed phosphorus in top few layers of MoS2. Pre-existing sulfur vacancies are shown to enhance the doping level significantly.

  10. High performance p-type NiOx thin-film transistor by Sn doping

    Science.gov (United States)

    Lin, Tengda; Li, Xiuling; Jang, Jin

    2016-06-01

    Major obstacles towards power efficient complementary electronics employing oxide thin-film transistors (TFTs) lie in the lack of equivalent well performing p-channel devices. Here, we report a significant performance enhancement of solution-processed p-type nickel oxide (NiOx) TFTs by introducing Sn dopant. The Sn-doped NiOx (Sn-NiOx) TFTs annealed at 280 °C demonstrate substantially improved electrical performances with the increase in the on/off current ratio (Ion/Ioff) by ˜100 times, field-effect mobility (μlin) by ˜3 times, and the decrease in subthreshold swing by half, comparing with those of pristine NiOx TFTs. X-ray photoelectron spectroscopy and X-ray diffraction results confirm that Sn atoms tend to substitute Ni sites and induce more amorphous phase. A decrease in density of states in the gap of NiOx by Sn doping and the shift of Fermi level (EF) into the midgap lead to the improvements of TFT performances. As a result, Sn-NiOx can be a promising material for the next-generation, oxide-based electronics.

  11. p-Type CuYO{sub 2} as hydrogen photocathode

    Energy Technology Data Exchange (ETDEWEB)

    Trari, M.; Bouguelia, A.; Bessekhouad, Y. [Laboratoire de Stockage et de Valorisation des Energies Renouvelables, BP 32 El-Alia 16311, Algiers (Algeria)

    2006-01-23

    A new photochemical system based on a CuYO{sub 2} dispersion in aqueous S{sup 2-} or SO{sub 3}{sup 2-} solution as hole scavengers is proposed. The delafossite CuYO{sub 2}, doped with calcium, is a low p-type semiconductor with a hole mobility of 7.3x10{sup -7}m{sup 2}V{sup -1}s{sup -1}. The band gap is 3.50eV and the transition is directly allowed. The valence band edge, located at 5.23eV below vacuum, is made up from Cu-3d type typical of delafossite oxides. The flat band potential V{sub fb} (+0.17V{sub sce}) lies below the H{sub 2}O/H{sub 2} potential permitting a spontaneous H{sub 2}-formation under band gap illumination in aqueous S{sup 2-} or SO{sub 3}{sup 2-} electrolytes. p-CuYO{sub 2} loaded with n-Cu{sub 2}O exhibited a higher performance with a H{sub 2} evolution rate of 0.4cm{sup 3}h{sup -1} in 0.1MS{sup 2-} (pH 13.4). The decrease of photoactivity over time is due to the formation of yellow polysulfides S{sub n}{sup 2-} which compete with H{sub 2}O in the reduction process. (author)

  12. Robust p-type doping of copper oxide using nitrogen implantation

    Science.gov (United States)

    Jorge, Marina; Polyakov, Stanislav M.; Cooil, Simon; Schenk, Alex K.; Edmonds, Mark; Thomsen, Lars; Mazzola, Federico; Wells, Justin W.

    2017-07-01

    We demonstrate robust p-type doping of Cu2O using low/medium energy ion implantation. Samples are made by controlled oxidation of annealed Cu metal foils, which results in Cu2O with levels of doping close to intrinsic. Samples are then implanted with nitrogen ions using a kinetic energy in the few keV range. Using this method, we are able to produce very high levels of doping, as evidenced by a 350 meV shift in the Fermi level towards the VB maximum. The robustness of the nitrogen implanted samples are tested by exposing them to atmospheric contaminants, and elevated temperatures. The samples are found to survive an increase in temperature of many hundreds of degrees. The robustness of the samples, combined with the fact that the materials used are safe, abundant and non-toxic and that the methods used for the growth of Cu2O and N+ implantation are simple and cheap to implement industrially, underlines the potential of Cu2O:N for affordable intermediate band photovoltaics.

  13. Plasmodium P-Type Cyclin CYC3 Modulates Endomitotic Growth during Oocyst Development in Mosquitoes.

    Science.gov (United States)

    Roques, Magali; Wall, Richard J; Douglass, Alexander P; Ramaprasad, Abhinay; Ferguson, David J P; Kaindama, Mbinda L; Brusini, Lorenzo; Joshi, Nimitray; Rchiad, Zineb; Brady, Declan; Guttery, David S; Wheatley, Sally P; Yamano, Hiroyuki; Holder, Anthony A; Pain, Arnab; Wickstead, Bill; Tewari, Rita

    2015-11-01

    Cell-cycle progression and cell division in eukaryotes are governed in part by the cyclin family and their regulation of cyclin-dependent kinases (CDKs). Cyclins are very well characterised in model systems such as yeast and human cells, but surprisingly little is known about their number and role in Plasmodium, the unicellular protozoan parasite that causes malaria. Malaria parasite cell division and proliferation differs from that of many eukaryotes. During its life cycle it undergoes two types of mitosis: endomitosis in asexual stages and an extremely rapid mitotic process during male gametogenesis. Both schizogony (producing merozoites) in host liver and red blood cells, and sporogony (producing sporozoites) in the mosquito vector, are endomitotic with repeated nuclear replication, without chromosome condensation, before cell division. The role of specific cyclins during Plasmodium cell proliferation was unknown. We show here that the Plasmodium genome contains only three cyclin genes, representing an unusual repertoire of cyclin classes. Expression and reverse genetic analyses of the single Plant (P)-type cyclin, CYC3, in the rodent malaria parasite, Plasmodium berghei, revealed a cytoplasmic and nuclear location of the GFP-tagged protein throughout the lifecycle. Deletion of cyc3 resulted in defects in size, number and growth of oocysts, with abnormalities in budding and sporozoite formation. Furthermore, global transcript analysis of the cyc3-deleted and wild type parasites at gametocyte and ookinete stages identified differentially expressed genes required for signalling, invasion and oocyst development. Collectively these data suggest that cyc3 modulates oocyst endomitotic development in Plasmodium berghei.

  14. Design of P-Type Cladding Layers for Tunnel-Injected UVA Light Emitting Diodes

    CERN Document Server

    Zhang, Yuewei; Akyol, Fatih; Allerman, Andrew A; Moseley, Michael W; Armstrong, Andrew M; Rajan, Siddharth

    2016-01-01

    We discuss the engineering of p-AlGaN cladding layers for achieving efficient tunnel-injected III-Nitride ultraviolet light emitting diodes (UV LEDs) in the UV-A spectral range. We show that capacitance-voltage measurements can be used to estimate the compensation and doping in p-AlGaN layers located between the multi-quantum well region and the tunnel junction layer. By increasing the p-type doping concentration to overcome the background compensation, on-wafer external quantum efficiency and wall-plug efficiency of 3.37% and 1.62% were achieved for tunnel-injected UV LEDs emitting at 325 nm. We also show that interband tunneling hole injection can be used to realize UV LEDs without any acceptor doping. The work discussed here provides new understanding of hole doping and transport in AlGaN-based UV LEDs, and demonstrates the excellent performance of tunnel-injected LEDs for the UV-A wavelength range.

  15. P-type Planet–Planet Scattering: Kepler Close Binary Configurations

    Science.gov (United States)

    Gong, Yan-Xiang

    2017-01-01

    A hydrodynamical simulation shows that a circumbinary planet will migrate inward to the edge of the disk cavity. If multiple planets form in a circumbinary disk, successive migration will lead to planet–planet scattering (PPS). PPS of Kepler-like circumbinary planets is discussed in this paper. The aim of this paper is to answer how PPS affects the formation of these planets. We find that a close binary has a significant influence on the scattering process. If PPS occurs near the unstable boundary of a binary, about 10% of the systems can be completely destroyed after PPS. In more than 90% of the systems, there is only one planet left. Unlike the eccentricity distribution produced by PPS in a single star system, the surviving planets generally have low eccentricities if PPS take place near the location of the currently found circumbinary planets. In addition, the ejected planets are generally the innermost of two initial planets. The above results depend on the initial positions of the two planets. If the initial positions of the planets are moved away from the binary, the evolution tends toward statistics similar to those around single stars. In this process, the competition between the planet–planet force and the planet-binary force makes the eccentricity distribution of surviving planets diverse. These new features of P-type PPS will deepen our understanding of the formation of these circumbinary planets.

  16. TSC measurements on proton-irradiated p-type Si-sensors

    Energy Technology Data Exchange (ETDEWEB)

    Donegani, Elena; Fretwurst, Eckhart; Garutti, Erika; Junkes, Alexandra [University of Hamburg (Germany)

    2016-07-01

    Thin n{sup +}p Si sensors are potential candidates for coping with neutron equivalent fluences up to 2.10{sup 16} n{sub eq}/cm{sup 2} and an ionizing dose in the order of a few MGy, which are expected e.g. for the HL-LHC upgrade. The aim of the present work is to provide experimental data on radiation-induced defects in order to: firstly, get a deeper understanding of the properties of hadron induced defects, and secondly develop a radiation damage model based on microscopic measurements. Therefore, the outcomes of Thermally Stimulated Current measurements on 200 μm thick Float-Zone (FZ) and Magnetic Czochralski (MCz) diodes will be shown, as a results of irradiation with 23 MeV protons and isothermal annealing. The samples were irradiated in the fluence range (0.3-1).10{sup 14} n{sub eq}/cm{sup 2}, so that the maximal temperature at which the TSC signal is still sharply distinguishable from the dark current is 200 K. In particular, special focus will be given to the defect introduction rate and to the issue of boron removal in p-type silicon. Annealing studies allow to distinguish which defects mainly contribute to the leakage current and which to the space charge, and thus correlate microscopic defects properties with macroscopic sensor properties.

  17. Plasmodium P-Type Cyclin CYC3 Modulates Endomitotic Growth during Oocyst Development in Mosquitoes

    KAUST Repository

    Roques, Magali

    2015-11-13

    Cell-cycle progression and cell division in eukaryotes are governed in part by the cyclin family and their regulation of cyclin-dependent kinases (CDKs). Cyclins are very well characterised in model systems such as yeast and human cells, but surprisingly little is known about their number and role in Plasmodium, the unicellular protozoan parasite that causes malaria. Malaria parasite cell division and proliferation differs from that of many eukaryotes. During its life cycle it undergoes two types of mitosis: endomitosis in asexual stages and an extremely rapid mitotic process during male gametogenesis. Both schizogony (producing merozoites) in host liver and red blood cells, and sporogony (producing sporozoites) in the mosquito vector, are endomitotic with repeated nuclear replication, without chromosome condensation, before cell division. The role of specific cyclins during Plasmodium cell proliferation was unknown. We show here that the Plasmodium genome contains only three cyclin genes, representing an unusual repertoire of cyclin classes. Expression and reverse genetic analyses of the single Plant (P)-type cyclin, CYC3, in the rodent malaria parasite, Plasmodium berghei, revealed a cytoplasmic and nuclear location of the GFP-tagged protein throughout the lifecycle. Deletion of cyc3 resulted in defects in size, number and growth of oocysts, with abnormalities in budding and sporozoite formation. Furthermore, global transcript analysis of the cyc3-deleted and wild type parasites at gametocyte and ookinete stages identified differentially expressed genes required for signalling, invasion and oocyst development. Collectively these data suggest that cyc3 modulates oocyst endomitotic development in Plasmodium berghei.

  18. p-Type hydrogen sensing with Al- and V-doped TiO2 nanostructures

    Science.gov (United States)

    Li, Zhaohui; Ding, Dongyan; Ning, Congqin

    2013-01-01

    Doping with other elements is one of the efficient ways to modify the physical and chemical properties of TiO2 nanomaterials. In the present work, anatase TiO2 nanofilms doped with Al and V elements were fabricated through anodic oxidation of Ti6Al4V alloy and further annealing treatment. Hydrogen sensing behavior of the crystallized Ti-Al-V-O nanofilms at various working temperatures was investigated through exposure to 1,000 ppm H2. Different from n-type hydrogen sensing characteristics of undoped TiO2 nanotubes, the Al- and V-doped nanofilms presented a p-type hydrogen sensing behavior by showing increased resistance upon exposure to the hydrogen-containing atmosphere. The Ti-Al-V-O nanofilm annealed at 450°C was mainly composed of anatase phase, which was sensitive to hydrogen-containing atmosphere only at elevated temperatures. Annealing of the Ti-Al-V-O nanofilm at 550°C could increase the content of anatase phase in the oxide nanofilm and thus resulted in a good sensitivity and resistance recovery at both room temperature and elevated temperatures. The TiO2 nanofilms doped with Al and V elements shows great potential for use as a robust semiconducting hydrogen sensor.

  19. Porous silicon damage enhanced phosphorus and aluminium gettering of p-type Czochralski silicon

    Energy Technology Data Exchange (ETDEWEB)

    Hassen, M. [Institut National de Recherche Scientifique et Technique, Laboratoire de Photovoltaique et des Semiconducteurs, PB 95 2050 Hammam-Lif (Tunisia); Ben Jaballah, A. [Institut National de Recherche Scientifique et Technique, Laboratoire de Photovoltaique et des Semiconducteurs, PB 95 2050 Hammam-Lif (Tunisia)]. E-mail: gadour2003@yahoo.fr; Hajji, M. [Institut National de Recherche Scientifique et Technique, Laboratoire de Photovoltaique et des Semiconducteurs, PB 95 2050 Hammam-Lif (Tunisia); Rahmouni, H. [Laboratoire de Physique des Semiconducteurs et des Composants Electroniques, Faculte des Sciences de Monastir, Rue de Kairouan, 5000 Monastir (Tunisia); Selmi, A. [Laboratoire de Physique des Semiconducteurs et des Composants Electroniques, Faculte des Sciences de Monastir, Rue de Kairouan, 5000 Monastir (Tunisia); Ezzaouia, H. [Institut National de Recherche Scientifique et Technique, Laboratoire de Photovoltaique et des Semiconducteurs, PB 95 2050 Hammam-Lif (Tunisia)

    2005-12-05

    In this work, porous silicon damage (PSD) is presented as a simple sequence for efficient external purification techniques. The method consists of using thin nanoporous p-type silicon on both sides of the silicon substrates with randomly hemispherical voids. Then, two main sample types are processed. In the first type, thin aluminium layers ({>=}1 {mu}m) are thermally evaporated followed by photo-thermal annealing treatments in N{sub 2} atmosphere at one of several temperatures ranging between 600 and 800 deg. C. In the second type, phosphorus is continually diffused in N{sub 2}/O{sub 2} ambient in a solid phase from POCl{sub 3} solution during heating at one of several temperatures ranging between 750 and 1000 deg. C for 1 h. Hall Effect and Van Der Pauw methods prove the existence of an optimum temperature in the case of phosphorus gettering at 900 deg. C yielding a Hall mobility of about 982 cm{sup 2} V{sup -1} s{sup -1}. However, in the case of aluminium gettering, there is no gettering limit in the as mentioned temperature range. Metal/Si Schottky diodes are elaborated to clarify these improvements. In this study, we demonstrate that enhanced metal solubility model cannot explain the gettering effect. The solid solubility of aluminium is higher than that of P atoms in silicon; however, the device yield confirms the effectiveness of phosphorus as compared to aluminium.

  20. P-type InGaAsP coolers for integrated optic devices

    Science.gov (United States)

    Vashaee, Daryoosh; LaBounty, Christopher J.; Fang, Xiaofeng; Zeng, Gehong; Abraham, Patrick; Bowers, John E.; Shakouri, Ali

    2001-05-01

    Single stage thin film coolers based on thermoelectric and thermionic cooling in p-type InGaAsP superlattice structures have been fabricated. Devices with different sizes and at various ambient temperatures have been characterized. Experimental results showed 0.5 degree centigrade cooling below the ambient temperature at 25C. This cooling over 1 4mu2m thick superlattice barrier corresponds to cooling power densities on the order of 200 W/cm2. The device cools by a factor of two better at higher temperatures (70C). This is due to the reduction of the superlattice thermal conductivity and the broadening of the electronic distribution function at higher temperatures. 150x150 micrometers 2 devices provide largest cooling at room temperature while the optimum device size shrinks as the temperature increases. Simulations results that take into account finite thermal resistance of the InP substrate, the effect of the contact resistance, heat generation in the wire-bonds and metallic pads on top of the device predict accurately the optimum cooling of these micro refrigerators. By eliminating the major parasitic sources of heating (Joule heating in the substrate, heat conduction through the side contact and reducing the contact resistance to 5x7-7 ohm-cm2) simulations show that, ultimately, one can achieve 15 degree(s)C cooling (10's of kW/cm2 cooling power) with single stage p-InGaAsP thin film coolers.

  1. Structural change and power factor enhancement of thermoelectric p-type films

    Energy Technology Data Exchange (ETDEWEB)

    Rothe, Katrin; Leipner, Hartmut; Heyroth, Frank [Interdisziplinaeres Zentrum fuer Materialwissenschaften, Martin-Luther-Universitaet 06099 Halle (Germany); Stordeur, Matthias; Engers, Bernd [angaris GmbH, Heinrich-Damerow-Str. 1, 06120 Halle (Germany)

    2008-07-01

    By sputter-deposition thin films of the thermoelectric effective p-type compound semiconductor (Bi{sub 0.15}Sb{sub 0.85}){sub 2}Te{sub 3} were prepared. For the first time a distinct increase of the electrical conductivity s was observed after heating of the as-deposited films and afterwards cooling. For the enlightenment of this typical behavior, which seems to be similar found for phase change materials consisting of (Ge, Sb, Te)-alloys, also the Seebeck (S) and the Hall coefficient were measured. It was established that the increase of the electrical conductivity is not connected with an expected decrease of the Seebeck coefficient, because the charge carrier density is reduced but at the same time the hole mobility is increasing. Corresponding analytical investigations by XRD, EDX, and REM shows that besides a grain growth in the polycrystalline films a Te-rich phase appears after the heat treatment. The increase of the electrical conductivity at nearly unchanged Seebeck coefficient can be exploited for the enhancement of the film power factor (S{sup 2}s). This is important for the efficiency of thermoelectric thin films devices as miniaturized coolers, generators, and sensors. Nevertheless for a quantitative interpretation of the presented new experimental results further investigations and theoretical considerations are required.

  2. Ferromagnetic ordering of Cr and Fe doped p-type diamond: An ab initio study

    Energy Technology Data Exchange (ETDEWEB)

    Benecha, E. M. [Department of Physics, University of South Africa, P.O Box 392, UNISA 0003, Pretoria (South Africa); Lombardi, E. B. [College of Graduate Studies, University of South Africa, P.O Box 392, UNISA 0003, Pretoria (South Africa)

    2014-02-21

    Ferromagnetic ordering of transition metal dopants in semiconductors holds the prospect of combining the capabilities of semiconductors and magnetic systems in single hybrid devices for spintronic applications. Various semiconductors have so far been considered for spintronic applications, but low Curie temperatures have hindered room temperature applications. We report ab initio DFT calculations on the stability and magnetic properties of Fe and Cr impurities in diamond, and show that their ground state magnetic ordering and stabilization energies depend strongly on the charge state and type of co-doping. We predict that divacancy Cr{sup +2} and substitutional Fe{sup +1} order ferromagnetically in p-type diamond, with magnetic stabilization energies (and magnetic moment per impurity ion) of 16.9 meV (2.5 μ{sub B}) and 33.3 meV (1.0 μ{sub B}), respectively. These magnetic stabilization energies are much larger than what has been achieved in other semiconductors at comparable impurity concentrations, including the archetypal dilute magnetic semiconductor GaAs:Mn. In addition, substitutional Fe{sup +1} exhibits a strong half-metallic character, with the Fermi level crossing bands in only the spin down channel. These results, combined with diamond’s extreme properties, demonstrate that Cr or Fe dopedp-type diamond may successfully be considered in the search for room temperature spintronic materials.

  3. High-throughput search of ternary chalcogenides for p-type transparent electrodes

    Science.gov (United States)

    Shi, Jingming; Cerqueira, Tiago F. T.; Cui, Wenwen; Nogueira, Fernando; Botti, Silvana; Marques, Miguel A. L.

    2017-01-01

    Delafossite crystals are fascinating ternary oxides that have demonstrated transparent conductivity and ambipolar doping. Here we use a high-throughput approach based on density functional theory to find delafossite and related layered phases of composition ABX2, where A and B are elements of the periodic table, and X is a chalcogen (O, S, Se, and Te). From the 15 624 compounds studied in the trigonal delafossite prototype structure, 285 are within 50 meV/atom from the convex hull of stability. These compounds are further investigated using global structural prediction methods to obtain their lowest-energy crystal structure. We find 79 systems not present in the materials project database that are thermodynamically stable and crystallize in the delafossite or in closely related structures. These novel phases are then characterized by calculating their band gaps and hole effective masses. This characterization unveils a large diversity of properties, ranging from normal metals, magnetic metals, and some candidate compounds for p-type transparent electrodes. PMID:28266587

  4. Enhanced thermoelectric figure of merit of p-type half-Heuslers.

    Science.gov (United States)

    Yan, Xiao; Joshi, Giri; Liu, Weishu; Lan, Yucheng; Wang, Hui; Lee, Sangyeop; Simonson, J W; Poon, S J; Tritt, T M; Chen, Gang; Ren, Z F

    2011-02-01

    Half-Heuslers would be important thermoelectric materials due to their high temperature stability and abundance if their dimensionless thermoelectric figure of merit (ZT) could be made high enough. The highest peak ZT of a p-type half-Heusler has been so far reported about 0.5 due to the high thermal conductivity. Through a nanocomposite approach using ball milling and hot pressing, we have achieved a peak ZT of 0.8 at 700 °C, which is about 60% higher than the best reported 0.5 and might be good enough for consideration for waste heat recovery in car exhaust systems. The improvement comes from a simultaneous increase in Seebeck coefficient and a significant decrease in thermal conductivity due to nanostructures. The samples were made by first forming alloyed ingots using arc melting and then creating nanopowders by ball milling the ingots and finally obtaining dense bulk by hot pressing. Further improvement in ZT is expected when average grain sizes are made smaller than 100 nm.

  5. Results with p-type pixel sensors with different geometries for the HL-LHC

    Energy Technology Data Exchange (ETDEWEB)

    Allport, P.P. [Department of Physics, University of Liverpool, Oxford Road, Liverpool, L69 7ZE (United Kingdom); Bates, R.; Butter, C. [Department of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ (United Kingdom); Casse, G. [Department of Physics, University of Liverpool, Oxford Road, Liverpool, L69 7ZE (United Kingdom); Dervan, P.J., E-mail: Paul.Dervan@cern.ch [Department of Physics, University of Liverpool, Oxford Road, Liverpool, L69 7ZE (United Kingdom); Forshaw, D.; Tsurin, I. [Department of Physics, University of Liverpool, Oxford Road, Liverpool, L69 7ZE (United Kingdom)

    2013-12-11

    Pixel detectors will be extensively used for the four innermost layers of the upgraded ATLAS experiment at the future High Luminosity LHC (HL-LHC) at CERN. The total area of pixel sensors will be over 5 m{sup 2}. The silicon sensors that will instrument the pixel volume will have to face several technology challenges. They will have to withstand doses up to 2×10{sup 16} n{sub eq}cm{sup −2}, to have a reduced inactive area at the edge of the sensors still being able to hold 1000 V bias voltage and to be relatively low cost considering the large area to be covered. N-side readout on p-type bulk is the most promising technology for satisfying the various requirements. Several sensor types have been produced in the UK, conceived for various readout systems, for studying the properties of n-in-p and n-in-n sensors before and after irradiation with test beam and laboratory measurements. The status of these studies is presented here.

  6. Interstitial oxygen as a source of p-type conductivity in hexagonal manganites

    Science.gov (United States)

    Skjærvø, Sandra H.; Wefring, Espen T.; Nesdal, Silje K.; Gaukås, Nikolai H.; Olsen, Gerhard H.; Glaum, Julia; Tybell, Thomas; Selbach, Sverre M.

    2016-12-01

    Hexagonal manganites, h-RMnO3 (R=Sc, Y, Ho-Lu), have been intensively studied for their multiferroic properties, magnetoelectric coupling, topological defects and electrically conducting domain walls. Although point defects strongly affect the conductivity of transition metal oxides, the defect chemistry of h-RMnO3 has received little attention. We use a combination of experiments and first principles electronic structure calculations to elucidate the effect of interstitial oxygen anions, Oi, on the electrical and structural properties of h-YMnO3. Enthalpy stabilized interstitial oxygen anions are shown to be the main source of p-type electronic conductivity, without reducing the spontaneous ferroelectric polarization. A low energy barrier interstitialcy mechanism is inferred from Density Functional Theory calculations to be the microscopic migration path of Oi. Since the Oi content governs the concentration of charge carrier holes, controlling the thermal and atmospheric history provides a simple and fully reversible way of tuning the electrical properties of h-RMnO3.

  7. Orientation Effects in Ballistic High-Strained P-type Si Nanowire FETs

    Directory of Open Access Journals (Sweden)

    Hong Yu

    2009-04-01

    Full Text Available In order to design and optimize high-sensitivity silicon nanowire-field-effect transistor (SiNW FET pressure sensors, this paper investigates the effects of channel orientations and the uniaxial stress on the ballistic hole transport properties of a strongly quantized SiNW FET placed near the high stress regions of the pressure sensors. A discrete stress-dependent six-band k.p method is used for subband structure calculation, coupled to a two-dimensional Poisson solver for electrostatics. A semi-classical ballistic FET model is then used to evaluate the ballistic current-voltage characteristics of SiNW FETs with and without strain. Our results presented here indicate that [110] is the optimum orientation for the p-type SiNW FETs and sensors. For the ultra-scaled 2.2 nm square SiNW, due to the limit of strong quantum confinement, the effect of the uniaxial stress on the magnitude of ballistic drive current is too small to be considered, except for the [100] orientation. However, for larger 5 nm square SiNW transistors with various transport orientations, the uniaxial tensile stress obviously alters the ballistic performance, while the uniaxial compressive stress slightly changes the ballistic hole current. Furthermore, the competition of injection velocity and carrier density related to the effective hole masses is found to play a critical role in determining the performance of the nanotransistors.

  8. High-Performance p-Type Black Phosphorus Transistor with Scandium Contact.

    Science.gov (United States)

    Li, Ling; Engel, Michael; Farmer, Damon B; Han, Shu-Jen; Wong, H-S Philip

    2016-04-26

    A record high current density of 580 μA/μm is achieved for long-channel, few-layer black phosphorus transistors with scandium contacts after 400 K vacuum annealing. The annealing effectively improves the on-state current and Ion/Ioff ratio by 1 order of magnitude and the subthreshold swing by ∼2.5×, whereas Al2O3 capping significantly degrades transistor performances, resulting in 5× lower on-state current and 3× lower Ion/Ioff ratio. The influences of moisture on black phosphorus metal contacts are elucidated by analyzing the hysteresis of 3-20 nm thick black phosphorus transistors with scandium and gold contacts under different conditions: as-fabricated, after vacuum annealing, and after Al2O3 capping. The optimal black phosphorus film thickness for transistors with scandium contacts is found to be ∼10 nm. Moreover, p-type performance is shown in all transistors with scandium contacts, suggesting that the Fermi level is pinned closer to the valence band regardless of the flake thickness.

  9. Extraction of interface state density and resistivity of suspended p-type silicon nanobridges

    Institute of Scientific and Technical Information of China (English)

    Zhang Jiahong; Liu Qingquan; Ge Yixian; Gu Fang; Li Min; Mao Xiaoli; Cao Hongxia

    2013-01-01

    The evaluation of the influence of the bending deformation of silicon nanobridges on their electrical properties is crucial for sensing and actuating applications.A combined theory/experimental approach for determining the resistivity and the density of interface states of the bending silicon nanobridges is presented.The suspended p-type silicon nanobridge test structures were fabricated from silicon-on-insulator wafers by using a standard CMOS lithography and anisotropic wet etching release process.After that,we measured the resistance of a set of silicon nanobridges versus their length and width under different bias voltages.In conjunction with a theoretical model,we have finally extracted both the interface state density of and resistivity suspended silicon nanobridges under different bending deformations,and found that the resistivity of silicon nanobridges without bending was 9.45 mΩ·cm and the corresponding interface charge density was around 1.7445 × 1013 cm-2.The bending deformation due to the bias voltage slightly changed the resistivity of the silicon nanobridge,however,it significantly changed the distribution of interface state charges,which strongly depends on the intensity of the stress induced by bending deformation.

  10. High-throughput search of ternary chalcogenides for p-type transparent electrodes

    Science.gov (United States)

    Shi, Jingming; Cerqueira, Tiago F. T.; Cui, Wenwen; Nogueira, Fernando; Botti, Silvana; Marques, Miguel A. L.

    2017-03-01

    Delafossite crystals are fascinating ternary oxides that have demonstrated transparent conductivity and ambipolar doping. Here we use a high-throughput approach based on density functional theory to find delafossite and related layered phases of composition ABX2, where A and B are elements of the periodic table, and X is a chalcogen (O, S, Se, and Te). From the 15 624 compounds studied in the trigonal delafossite prototype structure, 285 are within 50 meV/atom from the convex hull of stability. These compounds are further investigated using global structural prediction methods to obtain their lowest-energy crystal structure. We find 79 systems not present in the materials project database that are thermodynamically stable and crystallize in the delafossite or in closely related structures. These novel phases are then characterized by calculating their band gaps and hole effective masses. This characterization unveils a large diversity of properties, ranging from normal metals, magnetic metals, and some candidate compounds for p-type transparent electrodes.

  11. Growth of antimony doped P-type zinc oxide nanowires for optoelectronics

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Zhong Lin; Pradel, Ken

    2016-09-27

    In a method of growing p-type nanowires, a nanowire growth solution of zinc nitrate (Zn(NO.sub.3).sub.2), hexamethylenetetramine (HMTA) and polyethylenemine (800 M.sub.w PEI) is prepared. A dopant solution to the growth solution, the dopant solution including an equal molar ration of sodium hydroxide (NaOH), glycolic acid (C.sub.2H.sub.4O.sub.3) and antimony acetate (Sb(CH.sub.3COO).sub.3) in water is prepared. The dopant solution and the growth solution combine to generate a resulting solution that includes antimony to zinc in a ratio of between 0.2% molar to 2.0% molar, the resulting solution having a top surface. An ammonia solution is added to the resulting solution. A ZnO seed layer is applied to a substrate and the substrate is placed into the top surface of the resulting solution with the ZnO seed layer facing downwardly for a predetermined time until Sb-doped ZnO nanowires having a length of at least 5 .mu.m have grown from the ZnO seed layer.

  12. Realization of Cu-Doped p-Type ZnO Thin Films by Molecular Beam Epitaxy.

    Science.gov (United States)

    Suja, Mohammad; Bashar, Sunayna B; Morshed, Muhammad M; Liu, Jianlin

    2015-04-29

    Cu-doped p-type ZnO films are grown on c-sapphire substrates by plasma-assisted molecular beam epitaxy. Photoluminescence (PL) experiments reveal a shallow acceptor state at 0.15 eV above the valence band edge. Hall effect results indicate that a growth condition window is found for the formation of p-type ZnO thin films, and the best conductivity is achieved with a high hole concentration of 1.54 × 10(18) cm(-3), a low resistivity of 0.6 Ω cm, and a moderate mobility of 6.65 cm(2) V(-1) s(-1) at room temperature. Metal oxide semiconductor capacitor devices have been fabricated on the Cu-doped ZnO films, and the characteristics of capacitance-voltage measurements demonstrate that the Cu-doped ZnO thin films under proper growth conditions are p-type. Seebeck measurements on these Cu-doped ZnO samples lead to positive Seebeck coefficients and further confirm the p-type conductivity. Other measurements such as X-ray diffraction, X-ray photoelectron, Raman, and absorption spectroscopies are also performed to elucidate the structural and optical characteristics of the Cu-doped p-type ZnO films. The p-type conductivity is explained to originate from Cu substitution of Zn with a valency of +1 state. However, all p-type samples are converted to n-type over time, which is mostly due to the carrier compensation from extrinsic defects of ZnO.

  13. P-type thin films transistors with solution-deposited lead sulfide films as semiconductor

    Energy Technology Data Exchange (ETDEWEB)

    Carrillo-Castillo, A.; Salas-Villasenor, A.; Mejia, I. [Department of Materials Science and Engineering, The University of Texas at Dallas. 800 West Campbell Rd, Richardson, TX 75083 (United States); Aguirre-Tostado, S. [Centro de Investigacion en Materiales Avanzados, S. C. Alianza Norte 202, Parque de Investigacion e Innovacion Tecnologica, Apodaca, Nuevo Leon, C.P. 666000 (Mexico); Gnade, B.E. [Department of Materials Science and Engineering, University of Texas at Dallas. 800 West Campbell Rd, Richardson, TX 75083 (United States); Quevedo-Lopez, M.A., E-mail: mxq071000@utdallas.edu [Department of Materials Science and Engineering, University of Texas at Dallas. 800 West Campbell Rd, Richardson, TX 75083 (United States)

    2012-01-31

    In this paper we demonstrate p-type thin film transistors fabricated with lead sulfide (PbS) as semiconductor deposited by chemical bath deposition methods. Crystallinity and morphology of the resulting PbS films were characterized using X-ray diffraction, atomic force microscopy and scanning electron microscopy. Devices were fabricated using photolithographic processes in a bottom gate configuration with Au as source and drain top contacts. Field effect mobility for as-fabricated devices was {approx} 0.09 cm{sup 2} V{sup -1} s{sup -1} whereas the mobility for devices annealed at 150 Degree-Sign C/h in forming gas increased up to {approx} 0.14 cm{sup 2} V{sup -1} s{sup -1}. Besides the thermal annealing, the entire fabrications process was maintained below 100 Degree-Sign C. The electrical performance of the PbS-thin film transistors was studied before and after the 150 Degree-Sign C anneal as well as a function of the PbS active layer thicknesses. - Highlights: Black-Right-Pointing-Pointer Thin film transistors with PbS as semiconductor deposited by chemical bath deposition. Black-Right-Pointing-Pointer Photolithography-based thin film transistors with PbS films at low temperatures. Black-Right-Pointing-Pointer Electron mobility for anneal-PbS devices of {approx} 0.14 cm{sup 2} V{sup -1} s{sup -1}. Black-Right-Pointing-Pointer Highest mobility reported in thin film transistors with PbS as the semiconductor.

  14. Plasmodium P-Type Cyclin CYC3 Modulates Endomitotic Growth during Oocyst Development in Mosquitoes.

    Directory of Open Access Journals (Sweden)

    Magali Roques

    2015-11-01

    Full Text Available Cell-cycle progression and cell division in eukaryotes are governed in part by the cyclin family and their regulation of cyclin-dependent kinases (CDKs. Cyclins are very well characterised in model systems such as yeast and human cells, but surprisingly little is known about their number and role in Plasmodium, the unicellular protozoan parasite that causes malaria. Malaria parasite cell division and proliferation differs from that of many eukaryotes. During its life cycle it undergoes two types of mitosis: endomitosis in asexual stages and an extremely rapid mitotic process during male gametogenesis. Both schizogony (producing merozoites in host liver and red blood cells, and sporogony (producing sporozoites in the mosquito vector, are endomitotic with repeated nuclear replication, without chromosome condensation, before cell division. The role of specific cyclins during Plasmodium cell proliferation was unknown. We show here that the Plasmodium genome contains only three cyclin genes, representing an unusual repertoire of cyclin classes. Expression and reverse genetic analyses of the single Plant (P-type cyclin, CYC3, in the rodent malaria parasite, Plasmodium berghei, revealed a cytoplasmic and nuclear location of the GFP-tagged protein throughout the lifecycle. Deletion of cyc3 resulted in defects in size, number and growth of oocysts, with abnormalities in budding and sporozoite formation. Furthermore, global transcript analysis of the cyc3-deleted and wild type parasites at gametocyte and ookinete stages identified differentially expressed genes required for signalling, invasion and oocyst development. Collectively these data suggest that cyc3 modulates oocyst endomitotic development in Plasmodium berghei.

  15. Electron spin relaxation in p-type GaAs quantum wells

    Science.gov (United States)

    Zhou, Y.; Jiang, J. H.; Wu, M. W.

    2009-11-01

    We investigate electron spin relaxation in p-type GaAs quantum wells from a fully microscopic kinetic spin Bloch equation approach, with all the relevant scatterings, such as electron-impurity, electron-phonon, electron-electron Coulomb, electron-hole Coulomb and electron-hole exchange (the Bir-Aronov-Pikus (BAP) mechanism) scatterings, explicitly included. Via this approach, we examine the relative importance of the D'yakonov-Perel' (DP) and BAP mechanisms in wide ranges of temperature, hole density, excitation density and impurity density, and present a phase-diagram-like picture showing the parameter regime where the DP or BAP mechanism is more important. It is discovered that in the impurity-free case the temperature regime where the BAP mechanism is more efficient than the DP one is around the hole Fermi temperature for high hole density, regardless of excitation density. However, in the high impurity density case with the impurity density identical to the hole density, this regime is roughly from the electron Fermi temperature to the hole Fermi temperature. Moreover, we predict that for the impurity-free case, in the regime where the DP mechanism dominates the spin relaxation at all temperatures, the temperature dependence of the spin relaxation time (SRT) presents a peak around the hole Fermi temperature, which originates from the electron-hole Coulomb scattering. We also predict that at low temperature, the hole-density dependence of the electron SRT exhibits a double-peak structure in the impurity-free case, whereas it shows first a peak and then a valley in the case of identical impurity and hole densities. These intriguing behaviors are due to the contribution from holes in high subbands.

  16. Fabrication and simulation of single crystal p-type Si nanowire using SOI technology

    Energy Technology Data Exchange (ETDEWEB)

    Dehzangi, Arash, E-mail: arashd53@hotmail.com [Institute of Microengineering and Nanoelectronics (IMEN), Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor (Malaysia); Larki, Farhad [Institute of Microengineering and Nanoelectronics (IMEN), Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor (Malaysia); Naseri, Mahmud G. [Department of Physics, Faculty of Science, Malayer University, Malayer, Hamedan (Iran, Islamic Republic of); Navasery, Manizheh [Department of Physics, Faculty of Science, Universiti Putra Malaysia, 43400 Serdang, Selangor (Malaysia); Majlis, Burhanuddin Y.; Razip Wee, Mohd F. [Institute of Microengineering and Nanoelectronics (IMEN), Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor (Malaysia); Halimah, M.K. [Department of Physics, Faculty of Science, Universiti Putra Malaysia, 43400 Serdang, Selangor (Malaysia); Islam, Md. Shabiul; Md Ali, Sawal H. [Institute of Microengineering and Nanoelectronics (IMEN), Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor (Malaysia); Saion, Elias [Department of Physics, Faculty of Science, Universiti Putra Malaysia, 43400 Serdang, Selangor (Malaysia)

    2015-04-15

    Highlights: • Single crystal silicon nanowire is fabricated on Si on insulator substrate, using atomic force microscope (AFM) nanolithography and KOH + IPA chemical wet etching. • Some of major parameters in fabrication process, such as writing speed and applied voltage along with KOH etching depth are investigated, and then the I–V characteristic of Si nanowires is measured. • For better understanding of the charge transmission through the nanowire, 3D-TCAD simulation is performed to simulate the Si nanowires with the same size of the fabricated ones, and variation of majority and minority carriers, hole quasi-Fermi level and generation/recombination rate are investigated. - Abstract: Si nanowires (SiNWs) as building blocks for nanostructured materials and nanoelectronics have attracted much attention due to their major role in device fabrication. In the present work a top-down fabrication approach as atomic force microscope (AFM) nanolithography was performed on Si on insulator (SOI) substrate to fabricate a single crystal p-type SiNW. To draw oxide patterns on top of the SOI substrate local anodic oxidation was carried out by AFM in contact mode. After the oxidation procedure, an optimized solution of 30 wt.% KOH with 10 vol.% IPA for wet etching at 63 °C was applied to extract the nanostructure. The fabricated SiNW had 70–85 nm full width at half maximum width, 90 nm thickness and 4 μm length. The SiNW was simulated using Sentaurus 3D software with the exact same size of the fabricated device. I–V characterization of the SiNW was measured and compared with simulation results. Using simulation results variation of carrier's concentrations, valence band edge energy and recombination generation rate for different applied voltage were investigated.

  17. Enzyme-linked immunosorbent assay for detection of immunoglobulin G antibodies to Escherichia coli Vero cytotoxin 1.

    Science.gov (United States)

    Karmali, M A; Petric, M; Winkler, M; Bielaszewska, M; Brunton, J; van de Kar, N; Morooka, T; Nair, G B; Richardson, S E; Arbus, G S

    1994-06-01

    The frequency of Vero cytotoxin 1 (VT1)-neutralizing antibody (NAb) in serum specimens from 790 age-stratified (0 to 70 years) control individuals from Toronto was 61 of 790 (7.7%), with a peak of 19% in the 20- to 30-year-old age group and a second peak of 16.7% in the 60- to 70-year-old age group. A total of 568 serum specimens, including 538 from the 790 Toronto control subjects, 21 from patients from three outbreaks of VT-producing Escherichia coli (VTEC) infection, and 9 known VT1-NAb-positive serum specimens from patients with hemolytic-uremic syndrome (HUS), were then tested for the presence of anti-VT1 immunoglobulin G (IgG) by an enzyme-linked immunosorbent assay (ELISA). The mean ELISA values of 522 VT1-NAb-negative serum specimens and 46 VT1-NAb-positive serum specimens were 0.09 +/- 0.06 (range, 0 to 0.56) and 0.78 +/- 0.66 (range, 0.16 to 2.91), respectively (P < 0.001; Student's t test). With a breakpoint of 0.21 (mean ELISA value of the VT1-NAb-negative sera + 2 standard deviations), the sensitivity, specificity, positive predictive value, and negative predictive value of the VT1 IgG ELISA compared with those of the VT1-NAb assay were, respectively, 95.7, 98.7, 86.3, and 99.6%. There were nine discrepant serum specimens, of which seven were anti-VT1 IgG positive and VT1-NAb negative and two were anti-VT1 IgG negative and VT1-NAb positive. The ELISA was also used for testing 238 control serum specimens from The Netherlands, Japan, and India and acute- and convalescent-phase serum specimens from 42 Toronto patients with HUS. The frequencies of anti-VT1 IgG (with VT1-NAb frequencies in parantheses) in control sera from the Netherlands, Japan, and India were 6% (3%), 1.1% (0%), and 12% (10%), respectively, with no age clustering. The frequencies of anti-VT1 IgG seropositivity in HUS patients were 5 of 14 (35.7%) in patients with unknown toxin exposure, 2 of 22 (9.1%) in individuals with known exposure to VT1 plus VT2 or VT1 alone, and 0 of 6 (0%) in

  18. Meta-analysis of the relationship between cytotoxin-associated gene-A and ischemic stroke subtypes

    Institute of Scientific and Technical Information of China (English)

    Xu Yang; Xiaoli Zhao; Yongjun Gao; Zhidong Zheng; Jilai Li; Xinyi Li; Xiaoyuan Niu; Yingying Su

    2011-01-01

    OBJECTIVE:To assess the role of cytotoxin-associated gene-A (CagA) positive strains of Helicobacterpylori (Hp)in ischemic stroke (IS)subtypes.DATA SOURCES:A computer-based online search of PubMed,EMBASE,the Cochrane Collaboration database,the CNKI database and the VIP database,from January 1997 to July 2010,was performed to find relevant studies.DATA SELECTION:Case-control studies relevant to CagA with IS and IS subtypes were selected.Data regarding related factors in the case group and control group were acquired using the same approach.All patients had been diagnosed as exhibiting IS using skull CT or MRI,and were etiologically typed according to the 1993 TOAST diagnosis criteria.Two investigators independently performed the same search and study selection.Meta-analyses were then performed for the selected studies using RevMan 5.0 software (Cochrane Collaboration) after strict screening.Heterogeneity tests,sensitivity analyses and publication bias assessments were then conducted.MAIN OUTCOME MEASURES:Relationship of CagA with IS and IS subtypes.RESULTS:Eight studies were selected,involving data from 879 patients with IS,and 849 healthy controls.Five out of eight of the selected studies were related to large artery atherosclerosis (461patients with IS and 497 health controls).The results of our meta-analysis revealed a significant association between prior infection with CagA-positive strains and increased risk of IS (odds ratio (OR) = 2.31,95% confidence interval (CI):1.89 2.82,P<0.01).In addition,we found an association between infection with CagA-negative strains and IS (OR = 0.57,95%C/:0.47 0.70,P<0.01).CagA positive and negative strains were found to correlate with large artery atherosclerosis (CagA-positive strains:OR = 2.87,95%CI:2.19-3.77,P < 0.01;CagA-negative strains:OR = 0.51,95%CI:0.39-0.67,P< 0.01).Because of the diversity of etiological factors in the case-control study,we conducted further analyses after correcting for confounding factors

  19. Inorganic p-Type Semiconductors: Their Applications and Progress in Dye-Sensitized Solar Cells and Perovskite Solar Cells

    Directory of Open Access Journals (Sweden)

    Ming-Hsien Li

    2016-04-01

    Full Text Available Considering the increasing global demand for energy and the harmful ecological impact of conventional energy sources, it is obvious that development of clean and renewable energy is a necessity. Since the Sun is our only external energy source, harnessing its energy, which is clean, non-hazardous and infinite, satisfies the main objectives of all alternative energy strategies. With attractive features, i.e., good performance, low-cost potential, simple processibility, a wide range of applications from portable power generation to power-windows, photoelectrochemical solar cells like dye-sensitized solar cells (DSCs represent one of the promising methods for future large-scale power production directly from sunlight. While the sensitization of n-type semiconductors (n-SC has been intensively studied, the use of p-type semiconductor (p-SC, e.g., the sensitization of wide bandgap p-SC and hole transport materials with p-SC have also been attracting great attention. Recently, it has been proved that the p-type inorganic semiconductor as a charge selective material or a charge transport material in organometallic lead halide perovskite solar cells (PSCs shows a significant impact on solar cell performance. Therefore the study of p-type semiconductors is important to rationally design efficient DSCs and PSCs. In this review, recent published works on p-type DSCs and PSCs incorporated with an inorganic p-type semiconductor and our perspectives on this topic are discussed.

  20. Precipitation of Cu and Ni in n- and p-type Czochralski-grown silicon characterized by photoluminescence imaging

    Science.gov (United States)

    Sun, Chang; Nguyen, Hieu T.; Rougieux, Fiacre E.; Macdonald, Daniel

    2017-02-01

    Photoluminescence (PL) images and micro-PL maps were taken on Cu- or Ni-doped monocrystalline silicon wafers, to investigate the distribution of the metal precipitates. Several n-type and p-type wafers were used in which Cu or Ni were introduced in the starting melt of the ingots and precipitated during the ingot cooling (as opposed to surface contamination). The micro-PL mapping allowed investigation of the metal precipitates with a higher spatial resolution. Markedly different precipitation patterns were observed in n- and p-type samples: in both Cu- and Ni-doped n-type samples, circular central regions and edge regions were observed. In these regions, particles were distributed randomly and homogeneously. In the p-type Cu-doped and Ni-doped samples, by contrast, the precipitates occurred in lines along orientations. The difference in the precipitation behaviour in n- and p-type samples is conjectured to be caused by different concentrations of self-interstitials and vacancies remaining in the crystal during the ingot cooling: there are more vacancies in the n-type ingots but more interstitials in the p-type ingots. The dopant effects on the intrinsic point defect concentrations in silicon crystals and possible precipitation mechanisms are discussed based on the findings in this work and the literature.

  1. Comparison of ferromagnetism in n- and p-type magnetic semiconductor thin films of ZnCoO

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Y.H., E-mail: yuhua@phys.ncku.edu.t [Department of Physics, National Cheng Kung University, No. 1, Ta-Shuei Road, Tainan 70101, Taiwan (China); Lee, J.C.; Min, J.F. [Department of Physics, National Cheng Kung University, No. 1, Ta-Shuei Road, Tainan 70101, Taiwan (China); Su, C.W. [Department of Applied Physics, National Chiayi University, Chiayi 60004, Taiwan (China)

    2011-07-15

    Both n- and p-type diluted magnetic semiconductor ZnCoO are made by magnetron co-sputtering with, respectively, dopants of Al and dual dopants of Al and N. The two sputtering targets are compound ZnCoO with 5% weight of Co and pure metal Al. Sputtering gases for n- and p-type films are pure Ar and N{sub 2}, respectively. These films are magnetic at room temperature and possess free electron- and hole-concentration of 5.34x10{sup 20} and 5.27x10{sup 13} cm{sup -3}. Only the n-type film exhibits anomalous Hall-effect signals. Magnetic properties of these two types of films are compared and discussed based on measurements of microstructure and magneto-transport properties. - Research highlights: n-type ZnCoO:Al and p-type ZnCoO:(Al, N) films are made and are both ferromagnetic at room temperature. Signal of anomalous Hall-effect (AHE) is clearly observed only for n-type film but not for p-type film. Photoluminescence (PL) spectrum shows a peak attributed to shallow acceptor band of N. Ferromagnetic exchange coupling between magnetic ions in n-type film is through spin polarized free electrons. Ferromagnetism in p-type film is not attributed to the free hole-carriers mediation but to the overlap of BMP.

  2. A subcytotoxic dose of subtilase cytotoxin prevents lipopolysaccharide-induced inflammatory responses, depending on its capacity to induce the unfolded protein response.

    Science.gov (United States)

    Harama, Daisuke; Koyama, Kensuke; Mukai, Mai; Shimokawa, Naomi; Miyata, Masanori; Nakamura, Yuki; Ohnuma, Yuko; Ogawa, Hideoki; Matsuoka, Shuji; Paton, Adrienne W; Paton, James C; Kitamura, Masanori; Nakao, Atsuhito

    2009-07-15

    Subtilase cytotoxin (SubAB) is the prototype of a newly identified family of AB(5) cytotoxins produced by Shiga toxigenic Escherichia coli. SubAB specifically cleaves the essential endoplasmic reticulum (ER) chaperone BiP (GRP78), resulting in the activation of ER stress-induced unfolded protein response (UPR). We have recently shown that the UPR following ER stress can suppress cellular responses to inflammatory stimuli during the later phase, in association with inhibition of NF-kappaB activation. These findings prompted us to hypothesize that SubAB, as a selective UPR inducer, might have beneficial effects on inflammation-associated pathology via a UPR-dependent inhibition of NF-kappaB activation. The pretreatment of a mouse macrophage cell line, RAW264.7, with a subcytotoxic dose of SubAB-triggered UPR and inhibited LPS-induced MCP-1 and TNF-alpha production associated with inhibition of NF-kappaB activation. SubA(A272)B, a SubAB active site mutant that cannot induce UPR, did not show such effects. In addition, pretreatment with a sublethal dose of SubAB, but not SubA(A272)B, protected the mice from LPS-induced endotoxic lethality associated with reduced serum MCP-1 and TNF-alpha levels and also prevented the development of experimental arthritis induced by LPS in mice. Collectively, although SubAB has been identified originally as a toxin associated with the pathogenesis of hemolytic uremic syndrome, the unique ability of SubAB to selectively induce the UPR may have the potential to prevent LPS-associated inflammatory pathology under subcytotoxic conditions.

  3. Subtilase cytotoxin-encoding subAB2 variants in verotoxin-producing Escherichia coli strains isolated from goats and sheep.

    Science.gov (United States)

    Orden, José A; Domínguez-Bernal, Gustavo; de la Fuente, Ricardo; Carrión, Javier

    2016-04-01

    Subtilase cytotoxin (SubAB) is a cytotoxin which might contribute to the virulence of verotoxin-producing Escherichia coli (VTEC) strains in humans. Three variants of SubAB encoding genes have been described (subAB1, subAB2-1, and subAB2-2) and it has been suggested that the strains positive for two variants of subAB may be more pathogenic for humans. In this study, 188 subAB2-positive VTEC strains isolated from goats and sheep were investigated for the presence of the subAB2-1 and subAB2-2 variants by PCR. Eighty-one of the 132 (61.4%) caprine strains and 36 of the 56 (64.3%) ovine strains possessed the subAB2-1 variant and all ovine and caprine strains, except one, were positive for the subAB2-2 variant. The results of this study show for first time that the subAB2-1 and subAB2-2 variants are found in caprine subAB2-positive VTEC strains and confirm that both subAB2 variants are detected in ovine subAB2-positive VTEC strains. Since no significant difference in the presence of both subAB2 variants was found among strains belonging to serotypes associated with severe illness in humans and strains not belonging to these serotypes, the occurrence of two subAB2 variants seems not to be associated with a higher risk of severe disease in humans.

  4. Photoelectrochemical hydrogen-evolution over p-type chalcopyrite CuInSe{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Djellal, L. [Laboratoire des Solutions Solides, Faculte de Physique, (USTHB) BP 32 El Alia 16111, Algiers (Algeria); Omeiri, S.; Bouguelia, A. [Laboratoire de Stockage et de Valorisation des Energies Renouvelables, Faculte de Chimie, (USTHB) BP 32 El Alia 16111, Algiers (Algeria); Trari, M. [Laboratoire de Stockage et de Valorisation des Energies Renouvelables, Faculte de Chimie, (USTHB) BP 32 El Alia 16111, Algiers (Algeria)], E-mail: mtrari@caramail.com

    2009-05-12

    Photocatalytic H{sub 2}-production has been realized over active CuInSe{sub 2}, synthesized by the fusion technique. The material crystallizes in the chalcopyrite structure and exhibits p-type conductivity ascribed to copper deficiency. An optical gap of 0.95 eV was determined from the reflectance diffuse spectrum. The electrical conductivity follows an Arrhenius-type law with activation energy of 23 meV in conformity with polaron hopping. The slope and the intercept of the Mott-Schottky plot gave a holes density N{sub A} of 5.9 x 10{sup 18} cm{sup -3} and a flat band potential of -0.36V{sub SCE}, in perfect agreement with the photo-onset potential V{sub on} (-0.35V{sub SCE}). Hence, the conduction band, located at -1.29V{sub SCE}, allows a spontaneous H{sub 2} liberation upon visible light. In aqueous solutions, the material is stabilized by hole consumption involving X{sup 2-} species (=S{sup 2-} and SO{sub 3}{sup 2-}). H{sub 2} formation would become thermodynamically easy in alkaline media and the best photoactivity was obtained in thiosulfate electrolyte (10{sup -2} M S{sub 2}O{sub 3}{sup 2-}, 0.5 M KOH) with an evolution rate of 0.009 ml mg{sup -1} h{sup -1}. The light induced electron transfer through the interface involves two steps mechanism where S{sub 2}O{sub 3}{sup 2-} is oxidized to SO{sub 3}{sup 2-} and SO{sub 4}{sup 2-} by successive reactions. Such results are corroborated by the semi logarithmic plots and photocurrent-photopotential characteristics. The influence of pH was studied with S{sub 2}O{sub 3}{sup 2-} The tendency towards saturation for prolonged irradiation is attributed to competitive reductions of the end products S{sub n}{sup 2-} and S{sub 2}O{sub 6}{sup 2-} with water and to the yellow color of polysulfide S{sub n}{sup 2-}.

  5. Comparison of p-type commercial electron diodes for in vivo dosimetry.

    Science.gov (United States)

    Marre, D; Marinello, G

    2004-01-01

    This paper compares the characteristics of three types of commercial p-type electron diodes specially designed for in vivo dosimetry (Scanditronix EDD2, Sun Nuclear QED 111200-0 and PTW T60010E diodes coupled with a Therados DPD510 dosimeter) in electron fields with energies from 4.5 to 21 MeV, and in conditions similar to those encountered in radiotherapy. In addition to the diodes, a NACP plane parallel ionization chamber and film dosimeters have been used in the experiments. The influence of beam direction on the diode responses (directional effect) was investigated. It was found to be the greatest for the lowest electron beam energy. At 12 MeV and an incidence of +/- 30 degrees, the variation was found to be less than 1% for the Scanditronix and Sun Nuclear diodes and less than 3% for the PTW one. The three diodes exhibited a variation in sensitivity with dose-per-pulse of less than 1% over the range 0.18-0.43 mGy/pulse. The temperature dependence was also studied. The response was linear for the three diodes between 22.2 and 40 degrees C and the sensitivity variations with temperature were (0.25+/-0.01)%/degree C, (0.28+/-0.01)%/degree C, and (0.02 +/-0.01)%/degree C for Scanditronix, Sun Nuclear, and PTW diodes, respectively. Finally the perturbation to the irradiation field induced by the presence of diodes placed at the surface of a homogeneous phantom was investigated and found to be significant, both at the surface and at the depth of maximum dose (several tens of percent) for all three diode types. There is an increase of dose right underneath the diode (close to the surface) and a dose shadow at the depth of maximum. The study shows that electron diodes can be used for in vivo dosimetry provided their characteristics are carefully established before use and taken into consideration at the time of interpretation of the results.

  6. Lifetime and DLTS studies of interstitial Fe in p-type Si

    Energy Technology Data Exchange (ETDEWEB)

    Syre, M.; Holt, A. [Institute for Energy Technology (IFE), Solar Energy Department, P.O. Box 40, 2027 Kjeller (Norway); Monakov, E. [University of Oslo (UiO), Department of Physics, Blindern P.O. Box 1048, 0316 Oslo (Norway); Institute for Energy Technology (IFE), Solar Energy Department, P.O. Box 40, 2027 Kjeller (Norway); Svensson, B.G. [University of Oslo (UiO), Department of Physics, Blindern P.O. Box 1048, 0316 Oslo (Norway)

    2011-03-15

    Fe is one of the most prominent metallic impurities in solar-grade Si. In this work we have investigated the kinetics of in-diffusion and formation of the interstitial fraction (Fe{sub i}). P-type Cz-Si with a resistivity of 10 {omega}-cm has been intentionally contaminated with Fe by in-diffusion from a surface layer of FeCl{sub 3} at 700 C followed by cooling with a rate of {proportional_to} 3.3 K/s. The concentration of Fe{sub i} has been measured both by microwave photo conductance decay ({mu}-PCD) and deep level transient spectroscopy (DLTS). In the {mu}-PCD measurements, the Fe{sub i} concentration has been determined using the ef- fect of light-induced splitting of the iron-boron pairs (FeB), while in the DLTS measurements Fe{sub i} has been monitored by the donor electronic state at 0.43 eV above the valence band. We have observed a linear dependence between the minority carrier lifetime ({tau}) and the inverse Fe{sub i} concentration. This confirms Fe{sub i} as the dominating recombination centre. In the present investigations we use a material relevant for solar cells with a resistivity of 10 {omega}-cm. We have found that the concentration of interstitial iron decreases with increasing time for in-diffusion of Fe, provided identical cooling condition. This decreasing con- centration of Fe{sub i} is believed to be due to formation of more iron precipitates that serve as sinks for fast diffusing Fe{sub i}. A high temperature anneal at 1000 C for 1 minute followed by fast cooling ({proportional_to} 33 K/s) results in dissolution of the precipitates and freezing Fe into interstitial positions, where the concentration of Fe{sub i} increases with increasing in-diffusion time. (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  7. Boric acid solution concentration influencing p-type emitter formation in n-type crystalline Si solar cells

    Science.gov (United States)

    Singha, Bandana; Singh Solanki, Chetan

    2016-09-01

    Boric acid (BA) is a spin on dopant (BSoD) source which is used to form p+ emitters in n-type c-Si solar cells. High purity boric acid powder (99.99% pure) when mixed with deionized (DI) water can result in high quality p-type emitter with less amount of surface defects. In this work, we have used different concentrations of boric acid solution concentrations to fabricate p-type emitters with sheet resistance values < 90 Ω/□. The corresponding junction depths for the same are less than 500 nm as measured by SIMS analysis. Boron rich layer (BRL), which is considered as detrimental in emitter performance is found to be minimal for BA solution concentration less than 2% and hence useful for p-type emitter formation.

  8. Modeling of normal incidence absorption in p-type GaAs/AlGaAs quantum well infrared detectors

    Science.gov (United States)

    Brown, Gail J.; Szmulowicz, Frank

    1995-04-01

    The absorption of infrared radiation at normal incidence in p-type GaAs/AlGaAs quantum wells, unlike in n-type, is fundamentally allowed. We have measured and theoretically modeled the bound-to-continuum absorption in these p-type materials. The infrared absorption coefficient was calculated are based on the electronic structure, wave functions and optical matrix elements obtained from an 8 X 8 envelope-function approximation (EFA) calculation. The 8 X 8 EFA Hamiltonian incorporates the coupling between the heavy, light, spin-orbit, and conduction bands. In calculating the continuum states for bound-to- continuum intersubband absorption, we do not enclose the well in an artificial box with infinite walls. A comparison of the theoretical absorption and measured photoresponse results verified the accuracy of our model and provided a basis for optimizing the design of p-type quantum wells for infrared detection.

  9. Fabrication of p-type ZnO nanofibers by electrospinning for field-effect and rectifying devices

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Shuai; Liu, Shu-Liang; Liu, Ling-Zhi; Liu, Yi-Chen [College of Physics, Qingdao University, Qingdao 266071 (China); Long, Yun-Ze, E-mail: yunze.long@163.com [College of Physics, Qingdao University, Qingdao 266071 (China); Key Laboratory of Photonics Materials and Technology in Universities of Shandong (Qingdao University), Qingdao 266071 (China); State Key Laboratory Cultivation Base of New Fiber Materials and Modern Textile, Qingdao University, Qingdao 266071 (China); Collaborative Innovation Center for Marine Biomass Fibers, Materials and Textiles of Shandong Province, Qingdao 266071 (China); Zhang, Hong-Di; Zhang, Jun-Cheng; Han, Wen-Peng [College of Physics, Qingdao University, Qingdao 266071 (China); Key Laboratory of Photonics Materials and Technology in Universities of Shandong (Qingdao University), Qingdao 266071 (China)

    2014-01-27

    Ce-doped p-type ZnO nanofibers were synthesized by electrospinning and followed calcinations. The surface morphology, elementary composition, and crystal structure of the nanofibers were investigated. The field effect curve confirms that the resultant Ce-doped ZnO nanofibers are p-type semiconductor. A p-n heterojunction device consisting of Ce-doped p-type ZnO nanofibers and n-type indium tin oxide (ITO) thin film was fabricated on a piece of quartz substrate. The current-voltage (I-V) characteristic of the p-n heterojunction device shows typical rectifying diode behavior. The turn-on voltage appears at about 7 V under the forward bias and the reverse current is impassable.

  10. In silico identification and characterization of the ion transport specificity for P-type ATPases in the Mycobacterium tuberculosis complex

    Directory of Open Access Journals (Sweden)

    Novoa-Aponte Lorena

    2012-10-01

    Full Text Available Abstract Background P-type ATPases hydrolyze ATP and release energy that is used in the transport of ions against electrochemical gradients across plasma membranes, making these proteins essential for cell viability. Currently, the distribution and function of these ion transporters in mycobacteria are poorly understood. Results In this study, probabilistic profiles were constructed based on hidden Markov models to identify and classify P-type ATPases in the Mycobacterium tuberculosis complex (MTBC according to the type of ion transported across the plasma membrane. Topology, hydrophobicity profiles and conserved motifs were analyzed to correlate amino acid sequences of P-type ATPases and ion transport specificity. Twelve candidate P-type ATPases annotated in the M. tuberculosis H37Rv proteome were identified in all members of the MTBC, and probabilistic profiles classified them into one of the following three groups: heavy metal cation transporters, alkaline and alkaline earth metal cation transporters, and the beta subunit of a prokaryotic potassium pump. Interestingly, counterparts of the non-catalytic beta subunits of Hydrogen/Potassium and Sodium/Potassium P-type ATPases were not found. Conclusions The high content of heavy metal transporters found in the MTBC suggests that they could play an important role in the ability of M. tuberculosis to survive inside macrophages, where tubercle bacilli face high levels of toxic metals. Finally, the results obtained in this work provide a starting point for experimental studies that may elucidate the ion specificity of the MTBC P-type ATPases and their role in mycobacterial infections.

  11. Simulation of Enhancement Mode GaN HEMTs with Threshold > 5 V using P-type Buffer

    CERN Document Server

    Bajaj, Sanyam; Krishnamoorthy, Sriram; Hung, Ting-Hsiang; Rajan, Siddharth

    2015-01-01

    A high threshold voltage enhancement-mode GaN HEMT with p-type doped buffer is discussed and simulated. Analytical expressions are derived to explain the role of buffer capacitance in designing and enhancing threshold voltage. Simulations of the proposed device with p-type buffer show threshold voltages above 5 V, and a positive shift in threshold voltage as the oxide capacitance is reduced, thus enabling threshold voltage tunability over an unprecedented range for GaN-based HEMTs. The electric field profiles, breakdown performance, on-resistance and delay tradeoffs in the proposed pGaN back HEMT device are also discussed.

  12. Proton Pumping and Slippage Dynamics of a Eukaryotic P-Type ATPase Studied at the Single-Molecule Level

    DEFF Research Database (Denmark)

    Veshaguri, Salome

    In all eukaryotes the plasma membrane potential and secondary transport systems are energized by P-type ATPases whose regulation however remains poorly understood. Here we monitored at the single-molecule level the activity of the prototypic proton pumping P-type ATPase Arabidopsis thaliana isoform......-intuitively increased the time spent pumping. Allosteric regulation by pH gradients affected the time spent pumping and the leakage probability but surprisingly not the intrinsic pumping rate. Interestingly, ATP dilution decreased the ATP hydrolysis rates in bulk while single molecule data revealed that intrinsic...

  13. Enhanced p-type conductivity and band gap narrowing in heavily Al doped NiO thin films deposited by RF magnetron sputtering.

    Science.gov (United States)

    Nandy, S; Maiti, U N; Ghosh, C K; Chattopadhyay, K K

    2009-03-18

    Stoichiometric NiO, a Mott-Hubbard insulator at room temperature, shows p-type electrical conduction due to the introduction of Ni(2+) vacancies (V(Ni)('')) and self-doping of Ni(3+) ions in the presence of excess oxygen. The electrical conductivity of this important material is low and not sufficient for active device fabrication. Al doped NiO thin films were synthesized by radio frequency (RF) magnetron sputtering on glass substrates at a substrate temperature of 250 °C in an oxygen + argon atmosphere in order to enhance the p-type electrical conductivity. X-ray diffraction studies confirmed the correct phase formation and also oriented growth of NiO thin films. Al doping was confirmed by x-ray photoelectron spectroscopic studies. The structural, electrical and optical properties of the films were investigated as a function of Al doping (0-4 wt%) in the target. The room temperature electrical conductivity increased from 0.01-0.32 S cm (-1) for 0-4% Al doping. With increasing Al doping, above the Mott critical carrier density, energy band gap shrinkage was observed. This was explained by the shift of the band edges due to the existence of exchange and correlation energies amongst the electron-electron and hole-hole systems and also by the interaction between the impurity quasi-particle system.

  14. The P-type ATPase CATP-1 is a novel regulator of C. elegans developmental timing that acts independently of its predicted pump function.

    Science.gov (United States)

    Ruaud, Anne-Françoise; Bessereau, Jean-Louis

    2007-03-01

    During postembryonic stages, metazoans synchronize the development of a large number of cells, tissues and organs by mechanisms that remain largely unknown. In Caenorhabditis elegans larvae, an invariant cell lineage is tightly coordinated with four successive molts, thus defining a genetically tractable system to analyze the mechanisms underlying developmental synchronization. Illegitimate activation of nicotinic acetylcholine receptors (nAChRs) by the nicotinic agonist dimethylphenylpiperazinium (DMPP) during the second larval stage (L2) of C. elegans causes a lethal heterochronic phenotype. DMPP exposure delays cell division and differentiation without affecting the molt cycle, hence resulting in deadly exposure of a defective cuticle to the surrounding environment. In a screen for DMPP-resistant mutants, we identified catp-1 as a gene coding for a predicted cation-transporting P-type ATPase expressed in the epidermis. Larval development was specifically slowed down at the L2 stage in catp-1 mutants compared with wild-type animals and was not further delayed after exposure to DMPP. We demonstrate that CATP-1 interacts with the insulin/IGF and Ras-MAPK pathways to control several postembryonic developmental events. Interestingly, these developmental functions can be fulfilled independently of the predicted cation-transporter activity of CATP-1, as pump-dead engineered variants of CATP-1 can rescue most catp-1-mutant defects. These results obtained in vivo provide further evidence for the recently proposed pump-independent scaffolding functions of P-type ATPases in the modulation of intracellular signaling.

  15. Structure, properties, and bonding of ZrTe (MnP type), a low-symmetry, high-temperature modification of ZrTe (WC type).

    Science.gov (United States)

    Orlygsson, G; Harbrecht, B

    2001-05-09

    ZrTe (MnP) was synthesized by high-temperature methods at 1570 K in Ta ampules. The structure of the telluride was determined by means of single-crystal X-ray diffraction to be orthorhombic, Pnma (No. 62), Z = 4, Pearson Symbol oP8, a = 739.15(15) pm, b = 377.23(8) pm, c = 694.34(14) pm. The orthorhombic MnP type structure is a distorted variant of the NiAs type structure with pronounced metal-metal zigzag chains. Zigzag chains are typical for phases with a d(2) metal atom electron configuration. According to extended Hückel calculations, the homonuclear interactions in the zigzag chains make up for 2/3 of the Zr-Zr interactions in ZrTe (MnP) and contribute decisively to the stability of the structure. The emergence of the distorted MnP type structure instead of the high-symmetry NiAs type ZrTe at high temperatures can be understood as the result of an optimization of homonuclear Zr-Zr interactions arising from states close to the Fermi level. The hexagonal WC type ZrTe transforms above 1438 +/- 5 K into ZrTe (MnP) (DeltaH = 8.3 +/- 1.0 kJ mol(-1)). The phase transition is reversible, although at room-temperature the reverse reaction is kinetically inhibited. Zr5Te4 and Zr5Te6 are the phases next to ZrTe. ZrTe (MnP) exhibits temperature-independent paramagnetic properties (chi(mol) = 0.14 x 10(-3) cm(3) mol(-1)), as typical for a metallic conductor. Resistivity measurements on ZrTe (MnP) imply metallic behavior.

  16. Electrical band-gap narrowing in n- and p-type heavily doped silicon at 300 K

    Science.gov (United States)

    Van Cong, H.; Brunet, S.

    1986-09-01

    Based on previous results band-gap narrowing in heavily doped silicon at 300 K is investigated and expressed in terms of impurity size-and-doping effects. The results obtained for n- and p-type heavily doped silicon are compared with other theories and experiments.

  17. Sodium and potassium doped P-type ZnO films by sol-gel spin-coating technique

    Science.gov (United States)

    Au, Benedict Wen-Cheun; Chan, Kah-Yoong

    2017-07-01

    Zinc oxide (ZnO) is a promising material in a variety of applications including sensors, transistors and solar cells. Many researchers studied N-type ZnO films and reported enhanced properties. On the other hand, P-type ZnO films were rarely attempted due to the self-compensation effect. Success in achieving P-type ZnO films is important as it will pave the way for more advanced complementary devices. In this work, P-type sodium and potassium doped ZnO films were fabricated on glass substrates with doping concentration between 0 and 25 at.%. The influences of doping concentration on surface morphology, structural, optical and electrical properties were investigated using atomic force microscopy, X-ray diffraction spectroscopy, energy-dispersive X-ray spectroscopy, ultraviolet-visible (UV-Vis) spectrophotometer, photoluminescence spectroscopy and Hall-effect electrical transport measurement system. The distinctive behavior of P-type ZnO films with different doping concentrations will be discussed.

  18. Study of p-type ZnO and MgZnO Thin Films for Solid State Lighting

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Jianlin [Univ. of California, Riverside, CA (United States)

    2015-07-31

    This project on study of p-type ZnO and MgZnO thin films for solid state lighting was carried out by research group of Prof. Jianlin Liu of UCR during the four-year period between August 2011 and July 2015. Tremendous progress has been made on the proposed research. This final report summarizes the important findings.

  19. Ab initio studies on n-type and p-type Li4Ti5O12

    Institute of Scientific and Technical Information of China (English)

    Zhong Zhi-Yong; Nie Zheng-Xin; Du Yan-Lan; Ouyang Chu-Ying; Shi Si-Qi; Lei Min-Sheng

    2009-01-01

    This paper studies the structure and electronic properties of Li4Ti5O12, as anode material for lithium ion batteries,from first principles calculations. The results suggest that there are two kinds of unit cell of Li4Ti5O12: n-type and p-type. The two unit cells have different structures and electronic properties: the n-type with two 16d site Li ions is metallic by electron, while the p-type with three 16d Li ions is metallic by hole. However, the Li4Ti5O12 is an insulator.It is very interesting that one n-type cell and two p-type cells constitute one Li4Ti5O12 supercell which is insulating.The results show that the intercalation potential obtained with a p-type unit cell with one additional electron is quite close to the experimental value of 1.5 V.

  20. INTERACT

    DEFF Research Database (Denmark)

    Jochum, Elizabeth; Borggreen, Gunhild; Murphey, TD

    This paper considers the impact of visual art and performance on robotics and human-computer interaction and outlines a research project that combines puppetry and live performance with robotics. Kinesics—communication through movement—is the foundation of many theatre and performance traditions...... interaction between a human operator and an artificial actor or agent. We can apply insights from puppetry to develop culturally-aware robots. Here we describe the development of a robotic marionette theatre wherein robotic controllers assume the role of human puppeteers. The system has been built, tested...

  1. First-principles study of p-type ZnO by S-Na co-doping

    Science.gov (United States)

    Tan, Xingyi; Li, Qiang; Zhu, Yongdan

    2017-08-01

    Using the first-principles method based on the density functional theory, the formation energy, electronic structures of S-Na co-doping in ZnO were calculated. The calculated results show that NaZn-SO have smaller formation energy than Nain-SO in energy ranges from -3.10 to 0 eV of {μ }{{O}}, indicating that it opens up a new opportunity for growth the p-type ZnO. The band structure shows that the NaZn system is a p-type direct-band-gap semiconductor material and the calculated band gap (0.84 eV) is larger than pure ZnO (0.74 eV). The NaZn-SO system is also a p-type semiconductor material with a direct band gap (0.80 eV). The influence of S-Na co-doping in ZnO on p-type conductivity is also discussed. The effective masses of NaZn-SO are larger than effective masses of NaZn and the NaZn-SO have more hole carriers than NaZn, meaning the hole in the NaZn-SO system may have a better carrier transfer character. So we inferred that NaZn-SO should be a candidate of p-type conduction. Project supported by the Natural Science Foundation of Hubei Province, China (Nos. 2014CFB342, 2014CFB619) and the Doctoral Foundation for Scientific Research of Hubei University for Nationalities (No. MY2013B020).

  2. Realization of stable p-type ZnO thin films using Li-N dual acceptors

    Energy Technology Data Exchange (ETDEWEB)

    Rao, T. Prasada, E-mail: prasadview@gmail.com [Advanced Materials Laboratory, Department of Physics, National Institute of Technology, Tiruchirappalli- 620 015 (India); Kumar, M.C. Santhosh, E-mail: santhoshmc@nitt.edu [Advanced Materials Laboratory, Department of Physics, National Institute of Technology, Tiruchirappalli- 620 015 (India)

    2011-09-01

    Highlights: > We have presented a promising Li-N dual acceptor doping method to realize p-type ZnO films via spray pyrolysis. > The influence of concentration of Li-N on the structural, electrical, and optical properties of p-type ZnO:(Li, N) films were investigated in detail. > It is found that (Li, N):ZnO films deposited on glass substrate show the preferential orientation of (002) plane. > The Hall Effect measurements exhibited p-type behaviour on (Li, N):ZnO thin films and the stability of the samples were verified by aging studies. - Abstract: Lithium and nitrogen dual acceptors-doped p-type ZnO thin films have been prepared using spray pyrolysis technique. The influence of dual acceptor (Li, N) doping on the structural, electrical, and optical properties of (Li, N):ZnO films are investigated in detail. The (Li, N):ZnO films exhibit good crystallinity with a preferred c-axis orientation. From AFM studies, it is found that the surface roughness of the thin films increases with the increase of doping percentage. The Hall Effect measurements showed p-type conductivity. The Hall measurements have been performed periodically up to seven months and it is observed that the films show p-type conductivity throughout the period of observation. The samples with Li:N ratio of 8:8 mol% showed the lowest resistivity of 35.78 {Omega} cm, while sample with Li:N ratio of 6:6 mol% showed highest carrier concentration. The PL spectra of (Li, N):ZnO films show a strong UV emission at room temperature. Furthermore, PL spectra show low intensity in deep level transition, indicating a low density of native defects. This indicates that the formation of intrinsic defects is effectively suppressed by dual acceptor (Li, N) doping in ZnO thin films. The chemical bonding states of N and Li in the films were examined by XPS analysis.

  3. Perovskite Sr-doped LaCrO3 as a new p-type transparent conducting oxide

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Hongliang; Du, Yingge; Papadogianni, Alexandra; Bierwagen, Oliver; Sallis, Shawn; Piper, Louis F. J.; Bowden, Mark E.; Shutthanandan, V.; Sushko, Petr; Chambers, Scott A.

    2015-09-16

    Transparent conducting oxides (TCOs) constitute a unique class of materials which combine the seemingly mutually exclusive properties of electrical conductivity and optical transparency in a single material. TCOs are useful for a wide range of applications including solar cells, displays, light emitting diodes and transparent electronics. Simple post-transition metal oxides such as ZnO, In2O3 and SnO2 are wide gap insulators in which the ionic character generates an oxygen 2p-derived valence band (VB) and a metal s-derived conduction band (CB), resulting in large optical band gaps (>3.0 eV) and excellent n-type conductivity when donor doped. In contrast, the development of efficient p-type TCOs remains a global materials challenge. Converting n-type oxides to p-type analogs by acceptor doping is extremely difficult and these materials display poor conductivity.

  4. P-type Cu2O/SnO bilayer thin film transistors processed at low temperatures

    KAUST Repository

    Al-Jawhari, Hala A.

    2013-10-09

    P-type Cu2O/SnO bilayer thin film transistors (TFTs) with tunable performance were fabricated using room temperature sputtered copper and tin oxides. Using Cu2O film as capping layer on top of a SnO film to control its stoichiometry, we have optimized the performance of the resulting bilayer transistor. A transistor with 10 nm/15 nm Cu2O to SnO thickness ratio (25 nm total thickness) showed the best performance using a maximum process temperature of 170 C. The bilayer transistor exhibited p-type behavior with field-effect mobility, on-to-off current ratio, and threshold voltage of 0.66 cm2 V-1 s-1, 1.5×10 2, and -5.2 V, respectively. The advantages of the bilayer structure relative to single layer transistor are discussed. © 2013 American Chemical Society.

  5. Growth of nitrogen-doped p-type ZnO thin films prepared by atomic layer epitaxy

    Institute of Scientific and Technical Information of China (English)

    LEE Chongmu; LIM Jongmin; PARK Suyoung; KIM Hyounwoo

    2006-01-01

    Nitrogen-doped, p-type ZnO thin films were grown successfully on sapphire (0001) substrates by using atomic layer epitaxy (ALE). Zn(C2H5)2[Diethylzinc,DEZn], H2O and NH3 were used as a zinc precursor, an oxidant and a doping source gas, respectively. The lowest electrical resistivity of the p-type ZnO films grown by ALE and annealed at 1000 ℃ in an oxygen atmosphere for 1 h was 18.3 Ω·m with a hole concentration of 3.71×1017cm-3 . Low temperature-photoluminescence analysis and time-dependent Hall measurement results support that the nitrogen-doped ZnO after annealing is ap-type semiconductor.

  6. Search for Pauli exclusion principle violating atomic transitions and electron decay with a p-type point contact germanium detector

    Energy Technology Data Exchange (ETDEWEB)

    Abgrall, N.; Arnquist, I. J.; Avignone, F. T.; Barabash, A. S.; Bertrand, F. E.; Bradley, A. W.; Brudanin, V.; Busch, M.; Buuck, M.; Caldwell, A. S.; Chan, Y. -D.; Christofferson, C. D.; Chu, P. -H.; Cuesta, C.; Detwiler, J. A.; Dunagan, C.; Efremenko, Yu.; Ejiri, H.; Elliott, S. R.; Finnerty, P. S.; Galindo-Uribarri, A.; Gilliss, T.; Giovanetti, G. K.; Goett, J.; Green, M. P.; Gruszko, J.; Guinn, I. S.; Guiseppe, V. E.; Henning, R.; Hoppe, E. W.; Howard, S.; Howe, M. A.; Jasinski, B. R.; Keeter, K. J.; Kidd, M. F.; Konovalov, S. I.; Kouzes, R. T.; LaFerriere, B. D.; Leon, J.; MacMullin, J.; Martin, R. D.; Massarczyk, R.; Meijer, S. J.; Mertens, S.; Orrell, J. L.; O’Shaughnessy, C.; Poon, A. W. P.; Radford, D. C.; Rager, J.; Rielage, K.; Robertson, R. G. H.; Romero-Romero, E.; Shanks, B.; Shirchenko, M.; Suriano, A. M.; Tedeschi, D.; Trimble, J. E.; Varner, R. L.; Vasilyev, S.; Vetter, K.; Vorren, K.; White, B. R.; Wilkerson, J. F.; Wiseman, C.; Xu, W.; Yakushev, E.; Yu, C. -H.; Yumatov, V.; Zhitnikov, I.

    2016-11-11

    A search for Pauli-exclusion-principle-violating K electron transitions was performed using 89.5 kg-d of data collected with a p-type point contact high-purity germanium detector operated at the Kimballton Underground Research Facility. A lower limit on the transition lifetime of s at 90% C.L. was set by looking for a peak at 10.6 keV resulting from the X-ray and Auger electrons present following the transition. A similar analysis was done to look for the decay of atomic K-shell electrons into neutrinos, resulting in a lower limit of s at 90% C.L. It is estimated that the Majorana Demonstrator, a 44 kg array of p-type point contact detectors that will search for the neutrinoless double-beta decay of Ge, could improve upon these exclusion limits by an order of magnitude after three years of operation.

  7. First results on charge collection efficiency of heavily irradiated microstrip sensors fabricated on oxygenated p-type silicon

    Energy Technology Data Exchange (ETDEWEB)

    Casse, G. E-mail: gcasse@hep.ph.liv.ac.uk; Allport, P.P.; Marti i Garcia, S.; Lozano, M.; Turner, P.R

    2004-02-01

    Heavy hadron irradiation leads to type inversion of n-type silicon detectors. After type inversion, the charge collected at low bias voltages by silicon microstrip detectors is higher when read out from the n-side compared to p-side read out. The n-side read out has been successfully used in combination with oxygen-enriched n-type silicon substrate to maximise the radiation hardness of microstrip detectors. Alternatively, the n-side read out can be implemented on p-type substrates reducing the complexity of fabrication. Miniature silicon microstrip detectors made on standard and oxygen-enriched p-type substrate have been produced. The charge collection properties of such detectors with and without oxygenation are here compared for the first time after severe charged hadron irradiation.

  8. Increased Photoconductivity Lifetime in GaAs Nanowires by Controlled n-Type and p-Type Doping.

    Science.gov (United States)

    Boland, Jessica L; Casadei, Alberto; Tütüncüoglu, Gözde; Matteini, Federico; Davies, Christopher L; Jabeen, Fauzia; Joyce, Hannah J; Herz, Laura M; Fontcuberta I Morral, Anna; Johnston, Michael B

    2016-04-26

    Controlled doping of GaAs nanowires is crucial for the development of nanowire-based electronic and optoelectronic devices. Here, we present a noncontact method based on time-resolved terahertz photoconductivity for assessing n- and p-type doping efficiency in nanowires. Using this technique, we measure extrinsic electron and hole concentrations in excess of 10(18) cm(-3) for GaAs nanowires with n-type and p-type doped shells. Furthermore, we show that controlled doping can significantly increase the photoconductivity lifetime of GaAs nanowires by over an order of magnitude: from 0.13 ns in undoped nanowires to 3.8 and 2.5 ns in n-doped and p-doped nanowires, respectively. Thus, controlled doping can be used to reduce the effects of parasitic surface recombination in optoelectronic nanowire devices, which is promising for nanowire devices, such as solar cells and nanowire lasers.

  9. P-type polymer-based Ag2S atomic switch for “tug of war” operation

    Science.gov (United States)

    Lutz, Carolin; Hasegawa, Tsuyoshi; Tsuchiya, Takashi; Adelsberger, Christoph; Hayakawa, Ryoma; Chikyow, Toyohiro

    2017-06-01

    The Ag2S gap-type atomic switch based “tug of war” device is a promising element for building a new type of CMOS free neuromorphic computer-hardware. Since Ag+ cations are reduced during operation of the device, it was thought that the gap-material should be a n-type polymer. In this study, we revealed that the polymer bithiophene-oligoethyleneoxide (BTOE) doped poly(ethylene oxide) (PEO), which was used as gap-material in the first demonstration of the “tug of war”, is a p-type polymer. For this we used impedance spectroscopy and transistor measurements. We elaborate on how the electrochemical processes in the “tug of war” devices could be explained in the case of p-type conductive gap-materials.

  10. Kondo screening in two-dimensional p -type transition-metal dichalcogenides

    Science.gov (United States)

    Phillips, Michael; Aji, Vivek

    2017-02-01

    Systems with strong spin-orbit coupling support a number of new phases of matter and novel phenomena. This work focuses on the interplay of spin-orbit coupling and interactions in yielding correlated phenomena in two-dimensional transition-metal dichalcogenides. In particular we explore the physics of Kondo screening resulting from the lack of centrosymmetry, large spin splitting, and spin valley locking in hole-doped systems. The key ingredients are (i) valley-dependent spin-momentum locking perpendicular to the two-dimensional crystal, (ii) a single nondegenerate Fermi surface per valley, and (iii) nontrivial Berry curvature associated with the low-energy bands. The resulting Kondo resonance has a finite-triplet component and nontrivial momentum space structure which facilitates new approaches to both probing and manipulating the correlated state. Using a variational wave function and the numerical renormalization group approaches we study the nature of the Kondo resonance both in the absence and presence of circularly polarized light. The latter induces an imbalance in the population of the two valleys leading to novel magnetic phenomena in the correlated state.

  11. Ultrasonic study of point defects in electron-irradiated p-type silicon

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, W.L.

    1987-01-01

    The mechanisms of interaction of ultrasonic waves with point defects in crystals are reviewed, and a perturbation approach is introduced that leads to general expressions for the resonance and relaxation strengths in terms of matrix elements of the ultrasonic perturbation. These expressions provide the basis for a discussion of the polarization dependence of resonance and relaxation. Selection rules for cubic crystals are presented. An exploratory ultrasonic study is performed on electron-irradiated B-doped and Al-doped silicon. Neutral substitutional boron is detected before irradiation, as expected from previous ultrasonic studies on unirradiated silicon. This defect produces both resonance and relaxation. Similar effects are observed for substitutional aluminum. After irradiation, a relaxation is observed when the sample is exposed to 0.18-0.39 eV light. By comparison with previous EPR results, this relaxation is identified as the singly positively charged state of the vacancy, V/sup +/. Preliminary results on the relaxation time and strength of V/sup +/ suggest that it may have several populated vibronic levels. Another relaxation is observed in irradiated Al-doped silicon when the sample is exposed to white light. From its annealing behavior and dopant dependence, it is identified as a nonequilibrium charge state of interstitial aluminum.

  12. Interactions

    DEFF Research Database (Denmark)

    The main theme of this anthology is the unique interaction between mathematics, physics and philosophy during the beginning of the 20th century. Seminal theories of modern physics and new fundamental mathematical structures were discovered or formed in this period. Significant physicists...... such as Lorentz and Einstein as well as mathematicians such as Poincare, Minkowski, Hilbert and Weyl contributed to this development. They created the new physical theories and the mathematical disciplines that play such paramount roles in their mathematical formulations. These physicists and mathematicians were...

  13. Effects of air-annealing on the electrical properties of p-type tin monoxide thin-film transistors

    Science.gov (United States)

    Cho, In-Tak; U, Myeonghun; Song, Sang-Hun; Lee, Jong-Ho; Kwon, Hyuck-In

    2014-04-01

    We have investigated the effects of air-annealing on the electrical performance of the p-type tin oxide thin-film transistors (TFTs). The air-annealing of the tin oxide thin-film was made using a mini furnace at various temperatures. From the x-ray photoelectron spectroscopy (XPS) and x-ray diffraction (XRD) data, it is demonstrated that the phase of tin oxide partially transforms from SnO to SnO2 with an air-annealing process, and it accelerates as the annealing temperature increases. The electrical performance of the p-type tin oxide TFT with a channel thickness of 25 nm exhibits much improved electrical performance when air-annealed at 230 °C for 1 h, but a decrease of the on-current is observed with an ambipolar operation in 260 and 290 °C air-annealed devices. Based on the XPS, XRD, and Hall measurement data, the reduced hole concentration inside the channel due to the recombination with electrons from SnO2 is believed to be the reason for the electrical performance improvement in 230 °C air-annealed p-type tin oxide TFTs, and a partial formation of n-type SnO2 channel is considered as the plausible reason for the ambipolar operation in tin oxide TFTs with high annealing temperatures. Our experimental results show that there is an optimum air-annealing temperature which can improve the electrical performance in p-type tin oxide TFTs.

  14. Radioisotope space power generator. Annual report, July 1, 1975--September 30, 1976. [TPM-217 P-type selenides

    Energy Technology Data Exchange (ETDEWEB)

    Elsner, N.B.; Chin, J.; Staley, H.G.; Steeger, E.J.; Gantzel, P.K.

    1977-09-01

    TPM-217 P-type selenide usefulness in thermoelectric converters depends on its dimensional, electrical and thermal stability at high temperature and its compatibility with other converter component materials in a low pressure environment. Experimental efforts have been directed at determining: the vaporization behavior at 900/sup 0/C, the partial pressures of vaporizing species versus temperature, vapor suppression coatings, thermal expansion, dimensional stability, and the high temperature compatibility of TPM-217 with proposed end cap materials.

  15. Optical characteristics of p-type GaAs-based semiconductors towards applications in photoemission infrared detectors

    Science.gov (United States)

    Lao, Y. F.; Perera, A. G. U.; Wang, H. L.; Zhao, J. H.; Jin, Y. J.; Zhang, D. H.

    2016-03-01

    Free-carrier effects in a p-type semiconductor including the intra-valence-band and inter-valence-band optical transitions are primarily responsible for its optical characteristics in infrared. Attention has been paid to the inter-valence-band transitions for the development of internal photoemission (IPE) mid-wave infrared (MWIR) photodetectors. The hole transition from the heavy-hole (HH) band to the spin-orbit split-off (SO) band has demonstrated potential applications for 3-5 μm detection without the need of cooling. However, the forbidden SO-HH transition at the Γ point (corresponding to a transition energy Δ0, which is the split-off gap between the HH and SO bands) creates a sharp drop around 3.6 μm in the spectral response of p-type GaAs/AlGaAs detectors. Here, we report a study on the optical characteristics of p-type GaAs-based semiconductors, including compressively strained InGaAs and GaAsSb, and a dilute magnetic semiconductor, GaMnAs. A model-independent fitting algorithm was used to derive the dielectric function from experimental reflection and transmission spectra. Results show that distinct absorption dip at Δ0 is observable in p-type InGaAs and GaAsSb, while GaMnAs displays enhanced absorption without degradation around Δ0. This implies the promise of using GaMnAs to develop MWIR IPE detectors. Discussions on the optical characteristics correlating with the valence-band structure and free-hole effects are presented.

  16. Compensation of native donor doping in ScN: Carrier concentration control and p-type ScN

    Science.gov (United States)

    Saha, Bivas; Garbrecht, Magnus; Perez-Taborda, Jaime A.; Fawey, Mohammed H.; Koh, Yee Rui; Shakouri, Ali; Martin-Gonzalez, Marisol; Hultman, Lars; Sands, Timothy D.

    2017-06-01

    Scandium nitride (ScN) is an emerging indirect bandgap rocksalt semiconductor that has attracted significant attention in recent years for its potential applications in thermoelectric energy conversion devices, as a semiconducting component in epitaxial metal/semiconductor superlattices and as a substrate material for high quality GaN growth. Due to the presence of oxygen impurities and native defects such as nitrogen vacancies, sputter-deposited ScN thin-films are highly degenerate n-type semiconductors with carrier concentrations in the (1-6) × 1020 cm-3 range. In this letter, we show that magnesium nitride (MgxNy) acts as an efficient hole dopant in ScN and reduces the n-type carrier concentration, turning ScN into a p-type semiconductor at high doping levels. Employing a combination of high-resolution X-ray diffraction, transmission electron microscopy, and room temperature optical and temperature dependent electrical measurements, we demonstrate that p-type Sc1-xMgxN thin-film alloys (a) are substitutional solid solutions without MgxNy precipitation, phase segregation, or secondary phase formation within the studied compositional region, (b) exhibit a maximum hole-concentration of 2.2 × 1020 cm-3 and a hole mobility of 21 cm2/Vs, (c) do not show any defect states inside the direct gap of ScN, thus retaining their basic electronic structure, and (d) exhibit alloy scattering dominating hole conduction at high temperatures. These results demonstrate MgxNy doped p-type ScN and compare well with our previous reports on p-type ScN with manganese nitride (MnxNy) doping.

  17. Thermal Stability of P-Type BiSbTe Alloys Prepared by Melt Spinning and Rapid Sintering

    Directory of Open Access Journals (Sweden)

    Yun Zheng

    2017-06-01

    Full Text Available P-type BiSbTe alloys have been widely implemented in waste heat recovery from low-grade heat sources below 600 K, which may involve assorted environments and conditions, such as long-term service, high-temperature exposure (generally 473–573 K and mechanical forces. It is important to evaluate the service performance of these materials in order to prevent possible failures in advance and extend the life cycle. In this study, p-type Bi0.5Sb1.5Te3 commercial zone-melting (ZM ingots were processed by melt spinning and subsequent plasma-activated sintering (MS-PAS, and were then subjected to vacuum-annealing at 473 and 573 K, respectively, for one week. The results show that MS-PAS samples exhibit excellent thermal stability when annealed at 473 K. However, thermal annealing at 573 K for MS-PAS specimens leads to the distinct sublimation of the element Te, which degrades the hole concentration remarkably and results in inferior thermoelectric performance. Furthermore, MS-PAS samples annealed at 473 K demonstrate a slight enhancement in flexural and compressive strengths, probably due to the reduction of residual stress induced during the sintering process. The current work guides the reliable application of p-type Bi0.5Sb1.5Te3 compounds prepared by the MS-PAS technique.

  18. Properties and local environment of p-type and photoluminescent rare earths implanted into ZnO single crystals

    CERN Document Server

    Rita, EMC; Wahl, U; Soares, JC

    This thesis presents an experimental study of the local environment of p-type and Rare- Earth dopants implanted in ZnO single-crystals (SCs). Various nuclear and bulk property techniques were combined in the following evaluations: Implantation damage annealing was evaluated in ZnO SCs implanted with Fe, Sr and Ca. P-type dopants Cu and Ag implanted ZnO SCs were studied revealing that the solubility of Cu in substituting Zn is considerably higher than that of Ag. These results are discussed within the scope of the ZnO p-type doping problematic with these elements. Experimental proofs of the As “anti-site” behavior in ZnO were for the first time attained, i.e., the majority of As atoms are substitutional at the Zn site (SZn), possibly surrounded by two Zn vacancies (VZn). This reinforces the theoretical prediction that As acts as an acceptor in ZnO via the AsZn-2VZn complex formation. The co-doping of ZnO SC with In (donor) and As (acceptor) was addressed. The most striking result is the possible In-As “p...

  19. S-Type and P-Type Habitability in Stellar Binary Systems: A Comprehensive Approach. I. Method and Applications

    CERN Document Server

    Cuntz, Manfred

    2013-01-01

    A comprehensive approach is provided to the study of both S-type and P-type habitability in stellar binary systems, which in principle can also be expanded to systems of higher order. P-type orbits occur when the planet orbits both binary components, whereas in case of S-type orbits the planet orbits only one of the binary components with the second component considered a perturbator. The selected approach encapsulates a variety of different aspects, which include: (1) The consideration of a joint constraint including orbital stability and a habitable environment for a putative system planet through the stellar radiative energy fluxes ("radiative habitable zone"; RHZ) needs to be met. (2) The treatment of conservative, general and extended zones of habitability for the various systems as defined for the Solar System and beyond. (3) The providing of a combined formalism for the assessment of both S-type and P-type habitability; in particular, mathematical criteria are presented for which kind of system S-type ...

  20. S-Type and P-Type Habitability in Stellar Binary Systems: A Comprehensive Approach. II. Elliptical Orbits

    CERN Document Server

    Cuntz, Manfred

    2014-01-01

    In the first paper of this series, a comprehensive approach has been provided for the study of S-type and P-type habitable regions in stellar binary systems, which was, however, restricted to circular orbits of the stellar components. Fortunately, a modest modification of the method also allows for the consideration of elliptical orbits, which of course entails a much broader range of applicability. This augmented method is presented here, and numerous applications are conveyed. In alignment with Paper I, the selected approach considers a variety of aspects, which comprise the consideration of a joint constraint including orbital stability and a habitable region for a putative system planet through the stellar radiative energy fluxes (radiative habitable zone; RHZ). The devised method is based on a combined formalism for the assessment of both S-type and P-type habitability; in particular, mathematical criteria are deduced for which kinds of systems S-type and P-type habitable zones are realized. If the RHZs ...

  1. Raman spectra of p-type transparent semiconducting Cr{sub 2}O{sub 3}:Mg

    Energy Technology Data Exchange (ETDEWEB)

    Fleischer, Karsten, E-mail: fleisck@tcd.ie; Caffrey, David; Farrell, Leo; Norton, Emma; Mullarkey, Daragh; Arca, Elisabetta; Shvets, Igor V.

    2015-11-02

    We present an analysis of the Raman spectra of p-type transparent conducting Cr{sub 2}O{sub 3}:Mg grown by various techniques including spray pyrolysis, pulsed laser deposition, molecular beam epitaxy and reactive magnetron sputtering. The best performing films show a distinct broad range Raman signature related to defect-induced vibrational modes not seen in stoichiometric, undoped material. Our comparative study demonstrates that Raman spectroscopy can quantify unwanted dopant clustering in the material at high Mg concentrations, while also being sensitive to the Mg incorporation site. By correlating the Raman signature to the electrical properties of the films, growth processes can be optimised to give the best conducting films and the local defect structure for effective p-type doping can be studied. - Highlights: • Mg doping in Cr{sub 2}O{sub 3} can lead to dopant clustering in MgCr{sub 2}O{sub 4} phase. • Post-annealing in oxygen can dissolve these clusters improving doping. • High oxygen pressures during growth can prevent dopant clustering. • Raman spectroscopy is a powerful tool to assist growth optimization in p-type oxides.

  2. Fabrication of p-type ZnSe:Sb nanowires for high-performance ultraviolet light photodetector application.

    Science.gov (United States)

    Nie, Biao; Luo, Lin-Bao; Chen, Jing-Jing; Hu, Ji-Gang; Wu, Chun-Yan; Wang, Li; Yu, Yong-Qiang; Zhu, Zhi-Feng; Jie, Jian-Sheng

    2013-03-08

    p-type ZnSe nanowires (NWs) with tunable electrical conductivity were fabricated on a large scale by evaporating a mixed powder composed of ZnSe and Sb in different ratios. According to the structural characterization, the Sb-doped ZnSe NWs are of single crystalline form and grow along the [001] direction. The presence of Sb in the ZnSe NWs was confirmed by XPS spectra. Electrical measurement of a single ZnSe:Sb NW based back-gate metal-oxide field-effect-transistor reveals that all the doped NWs exhibit typical p-type conduction characteristics, and the conductivity can be tuned over eight orders of magnitude, from 6.36 × 10(-7) S cm(-1) for the undoped sample to ∼37.33 S cm(-1) for the heavily doped sample. A crossed p-n nano-heterojunction photodetector made from the as-doped nanostructures displays pronounced rectification behavior, with a rectification ratio as high as 10(3) at ±5 V. Remarkably, it exhibits high sensitivity to ultraviolet light illumination with good reproducibility and quick photoresponse. Finally, the work mechanism of such a p-n junction based photodetector was elucidated. The generality of the above result suggests that the as-doped p-type ZnSe NWs will find wide application in future optoelectronics devices.

  3. Piezoresistive effect in p-type 3C-SiC at high temperatures characterized using Joule heating.

    Science.gov (United States)

    Phan, Hoang-Phuong; Dinh, Toan; Kozeki, Takahiro; Qamar, Afzaal; Namazu, Takahiro; Dimitrijev, Sima; Nguyen, Nam-Trung; Dao, Dzung Viet

    2016-06-28

    Cubic silicon carbide is a promising material for Micro Electro Mechanical Systems (MEMS) applications in harsh environ-ments and bioapplications thanks to its large band gap, chemical inertness, excellent corrosion tolerance and capability of growth on a Si substrate. This paper reports the piezoresistive effect of p-type single crystalline 3C-SiC characterized at high temperatures, using an in situ measurement method. The experimental results show that the highly doped p-type 3C-SiC possesses a relatively stable gauge factor of approximately 25 to 28 at temperatures varying from 300 K to 573 K. The in situ method proposed in this study also demonstrated that, the combination of the piezoresistive and thermoresistive effects can increase the gauge factor of p-type 3C-SiC to approximately 20% at 573 K. The increase in gauge factor based on the combination of these phenomena could enhance the sensitivity of SiC based MEMS mechanical sensors.

  4. Piezoresistive effect in p-type 3C-SiC at high temperatures characterized using Joule heating

    Science.gov (United States)

    Phan, Hoang-Phuong; Dinh, Toan; Kozeki, Takahiro; Qamar, Afzaal; Namazu, Takahiro; Dimitrijev, Sima; Nguyen, Nam-Trung; Dao, Dzung Viet

    2016-06-01

    Cubic silicon carbide is a promising material for Micro Electro Mechanical Systems (MEMS) applications in harsh environ-ments and bioapplications thanks to its large band gap, chemical inertness, excellent corrosion tolerance and capability of growth on a Si substrate. This paper reports the piezoresistive effect of p-type single crystalline 3C-SiC characterized at high temperatures, using an in situ measurement method. The experimental results show that the highly doped p-type 3C-SiC possesses a relatively stable gauge factor of approximately 25 to 28 at temperatures varying from 300 K to 573 K. The in situ method proposed in this study also demonstrated that, the combination of the piezoresistive and thermoresistive effects can increase the gauge factor of p-type 3C-SiC to approximately 20% at 573 K. The increase in gauge factor based on the combination of these phenomena could enhance the sensitivity of SiC based MEMS mechanical sensors.

  5. Thermal Stability of P-Type BiSbTe Alloys Prepared by Melt Spinning and Rapid Sintering.

    Science.gov (United States)

    Zheng, Yun; Tan, Gangjian; Luo, Yubo; Su, Xianli; Yan, Yonggao; Tang, Xinfeng

    2017-06-06

    P-type BiSbTe alloys have been widely implemented in waste heat recovery from low-grade heat sources below 600 K, which may involve assorted environments and conditions, such as long-term service, high-temperature exposure (generally 473-573 K) and mechanical forces. It is important to evaluate the service performance of these materials in order to prevent possible failures in advance and extend the life cycle. In this study, p-type Bi0.5Sb1.5Te₃ commercial zone-melting (ZM) ingots were processed by melt spinning and subsequent plasma-activated sintering (MS-PAS), and were then subjected to vacuum-annealing at 473 and 573 K, respectively, for one week. The results show that MS-PAS samples exhibit excellent thermal stability when annealed at 473 K. However, thermal annealing at 573 K for MS-PAS specimens leads to the distinct sublimation of the element Te, which degrades the hole concentration remarkably and results in inferior thermoelectric performance. Furthermore, MS-PAS samples annealed at 473 K demonstrate a slight enhancement in flexural and compressive strengths, probably due to the reduction of residual stress induced during the sintering process. The current work guides the reliable application of p-type Bi0.5Sb1.5Te₃ compounds prepared by the MS-PAS technique.

  6. Comparative chemical genomics reveal that the spiroindolone antimalarial KAE609 (Cipargamin) is a P-type ATPase inhibitor

    Science.gov (United States)

    Goldgof, Gregory M.; Durrant, Jacob D.; Ottilie, Sabine; Vigil, Edgar; Allen, Kenneth E.; Gunawan, Felicia; Kostylev, Maxim; Henderson, Kiersten A.; Yang, Jennifer; Schenken, Jake; LaMonte, Gregory M.; Manary, Micah J.; Murao, Ayako; Nachon, Marie; Stanhope, Rebecca; Prescott, Maximo; McNamara, Case W.; Slayman, Carolyn W.; Amaro, Rommie E.; Suzuki, Yo; Winzeler, Elizabeth A.

    2016-01-01

    The spiroindolones, a new class of antimalarial medicines discovered in a cellular screen, are rendered less active by mutations in a parasite P-type ATPase, PfATP4. We show here that S. cerevisiae also acquires mutations in a gene encoding a P-type ATPase (ScPMA1) after exposure to spiroindolones and that these mutations are sufficient for resistance. KAE609 resistance mutations in ScPMA1 do not confer resistance to unrelated antimicrobials, but do confer cross sensitivity to the alkyl-lysophospholipid edelfosine, which is known to displace ScPma1p from the plasma membrane. Using an in vitro cell-free assay, we demonstrate that KAE609 directly inhibits ScPma1p ATPase activity. KAE609 also increases cytoplasmic hydrogen ion concentrations in yeast cells. Computer docking into a ScPma1p homology model identifies a binding mode that supports genetic resistance determinants and in vitro experimental structure-activity relationships in both P. falciparum and S. cerevisiae. This model also suggests a shared binding site with the dihydroisoquinolones antimalarials. Our data support a model in which KAE609 exerts its antimalarial activity by directly interfering with P-type ATPase activity. PMID:27291296

  7. Fabrication of p-type conductivity in SnO{sub 2} thin films through Ga doping

    Energy Technology Data Exchange (ETDEWEB)

    Tsay, Chien-Yie, E-mail: cytsay@fcu.edu.tw; Liang, Shan-Chien

    2015-02-15

    Highlights: • P-type Ga-doped SnO{sub 2} semiconductor films were prepared by sol-gel spin coating. • Optical bandgaps of the SnO{sub 2}:Ga films are narrower than that of the SnO{sub 2} film. • SnO{sub 2}:Ga films exhibited p-type conductivity as Ga doping content higher than 10%. • A p-n heterojunction composed of p-type SnO{sub 2}:Ga and n-type ZnO:Al was fabricated. - Abstract: P-type transparent tin oxide (SnO{sub 2}) based semiconductor thin films were deposited onto alkali-free glass substrates by a sol-gel spin-coating method using gallium (Ga) as acceptor dopant. In this study, we investigated the influence of Ga doping concentration ([Ga]/[Sn] + [Ga] = 0%, 5%, 10%, 15%, and 20%) on the structural, optical and electrical properties of SnO{sub 2} thin films. XRD analysis results showed that dried Ga-doped SnO{sub 2} (SnO{sub 2}:Ga) sol-gel films annealed in oxygen ambient at 520 °C for 1 h exhibited only the tetragonal rutile phase. The average optical transmittance of as-prepared thin film samples was higher than 87.0% in the visible light region; the optical band gap energy slightly decreased from 3.92 eV to 3.83 eV with increases in Ga doping content. Hall effect measurement showed that the nature of conductivity of SnO{sub 2}:Ga thin films changed from n-type to p-type when the Ga doping level was 10%, and when it was at 15%, Ga-doped SnO{sub 2} thin films exhibited the highest mean hole concentration of 1.70 × 10{sup 18} cm{sup -3}. Furthermore, a transparent p-SnO{sub 2}:Ga (Ga doping level of 15%)/n-ZnO:Al (Al doping level of 2%) heterojunction was fabricated on alkali-free glass. The I-V curve measurement for the p-n heterojunction diode showed a typical rectifying characteristic with a forward turn-on voltage of 0.65 V.

  8. Study of p-type AlN-doped SnO2 thin films and its transparent devices

    Science.gov (United States)

    Wu, Y. J.; Liu, Y. S.; Hsieh, C. Y.; Lee, P. M.; Wei, Y. S.; Liao, C. H.; Liu, C. Y.

    2015-02-01

    The electrical properties of transparent Al-doped tin oxide (SnO2), N-doped SnO2, and AlN-doped SnO2 thin films were studied. The Al-doped tin oxide (SnO2) thin films all show n-type conduction regardless the annealing condition. The n-type conduction of the as-deposited N-doped SnO2, and AlN-doped SnO2 thin films could be converted to p-type conduction by annealing the films at an elevated temperature of 450 °C. XPS analysis verified that the substitution of N ions in the O ion sites in the annealed N-doped SnO2 and AlN-doped SnO2 thin films were responsible for the n-p conduction transition. The conduction of the annealed N-doped SnO2 and AlN-doped SnO2 thin films could be converted back to n-type conduction by thermally annealing the films at higher temperature, over 450 °C. The p-n conduction transition is related with the outgassing of N ions in the p-type N-doped SnO2 and AlN-doped SnO2 thin films. Remarkably, we found that the Al content can retard the outgassing of N ions in the p-type N-doped SnO2 and AlN-doped SnO2 thin films and prolong the p-n conduction transition temperature above 600 °C. XPS analysis revealed that the formation of the Snsbnd Nsbnd Al bond improved the stability of the N ions in the AlN-doped SnO2 thin films. I-V curve of the p-type AlN-doped SnO2/n-type fluorine-doped SnO2 junction exhibited clear p-n junction characteristics, a low leakage current under the revised bias (1.13 × 10-5 A at -5 V), and a low turn-on voltage (3.24 V). p-Type AlN-doped SnO2/n-type fluorine-doped SnO2 junction exhibited excellent transmittance (over 90%) in the visible region (470-750 nm).

  9. The impact of meteorology on the occurrence of waterborne outbreaks of vero cytotoxin-producing Escherichia coli (VTEC): a logistic regression approach.

    Science.gov (United States)

    O'Dwyer, Jean; Morris Downes, Margaret; Adley, Catherine C

    2016-02-01

    This study analyses the relationship between meteorological phenomena and outbreaks of waterborne-transmitted vero cytotoxin-producing Escherichia coli (VTEC) in the Republic of Ireland over an 8-year period (2005-2012). Data pertaining to the notification of waterborne VTEC outbreaks were extracted from the Computerised Infectious Disease Reporting system, which is administered through the national Health Protection Surveillance Centre as part of the Health Service Executive. Rainfall and temperature data were obtained from the national meteorological office and categorised as cumulative rainfall, heavy rainfall events in the previous 7 days, and mean temperature. Regression analysis was performed using logistic regression (LR) analysis. The LR model was significant (p < 0.001), with all independent variables: cumulative rainfall, heavy rainfall and mean temperature making a statistically significant contribution to the model. The study has found that rainfall, particularly heavy rainfall in the preceding 7 days of an outbreak, is a strong statistical indicator of a waterborne outbreak and that temperature also impacts waterborne VTEC outbreak occurrence.

  10. Ex vivo detection of primary leukemia cells resistant to granule cytotoxin-induced cell death: a rapid isolation method to study granzyme-B-mediated cell death.

    Science.gov (United States)

    Grüllich, Carsten; Friske, Viktoria; Finke, Jürgen

    2008-09-01

    Cytotoxic T lymphocytes and natural killer cells (CTL/NK) induce cell death in leukemia cells by the granzyme B (grB)-dependent granule cytotoxin (GC) pathway. Resistance to GC may be involved in immune evasion of leukemia cells. The delivery of active grB into the cytoplasma is dependent on the presence of perforin (PFN) and grB complexes. We developed a rapid method for the isolation of GC to investigate GC-mediated cell death in primary leukemia cells. We isolated GC containing grB, grB complexes and PFN by detergent free hypotonic lysis of the human NK cell leukemia line YT. The GC induce grB-mediated, caspase-dependent apoptosis in live cells. The human leukemia cell lines KG-1, U937, K562 (myeloid leukemia), Jurkat, Daudi, and BV173 (lymphoblastic leukemia) treated with GC internalized grB and underwent cell death. In primary leukemia cells analyzed ex vivo, we found GC-resistant leukemia cells in three out of seven patients with acute myeloid leukemia and one out of six patients with acute lymphoblastic leukemia. We conclude that our method is fast (approximately 1 h) and yields active GC that induce grB-dependent cell death. Furthermore, resistance to GC can be observed in acute leukemias and may be an important mechanism contributing to leukemia cell immune evasion.

  11. Identification of the newly identified subtilase cytotoxin-encoding gene (subAB2-2) among clinical Shiga toxin-producing Escherichia coli isolates.

    Science.gov (United States)

    Son, Hoang Minh; Duc, Hoang Minh; Honjoh, Ken-Ichi; Miyamoto, Takahisa

    2015-12-01

    Subtilase cytotoxin (SubAB) is an important virulence factor of eae-negative Shiga toxin-producing Escherichia coli (STEC). Three variants of SubAB-encoding genes have been reported in the literature; however, the newly described subAB variant (subAB2-2) was found only in STEC strains from deer meat, sheep, and some wild animals. In this study, subAB variants were detected by PCR and DNA sequencing in 5 out of 12 (41.6%) eae-negative STEC strains isolated from patients. Most subAB-positive STEC strains (80%) harbored the subAB1 gene. The subAB2-2 gene was detected for the first time in the clinical STEC O128:H2 strain. Other virulence genes including stx1a, stx1c, stx2b, ehxA, and tia were also detected in this strain. The DNA sequence analyses of the subAB1 and subAB2-2 genes of the clinical STEC strains showed 99% and 100% identity to those of the reference strains 98NK2 and LM27558stx2, respectively. This is the first report on the detection of the subAB2-2 gene in a clinical STEC isolate.

  12. Comparison of in vivo efficacy of hypoxic cytotoxin tirapazamine and hypoxic cell radiosensitizer KU-2285 in combination with single and fractionated irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Shibata, Toru; Shibamoto, Yuta; Sasai, Keisuke; Oya, Natsuo; Murata, Rumi; Takagi, Takehisa; Hiraoka, Masahiro [Kyoto Univ. (Japan). Chest Disease Research Inst.; Abe, Mitsuyuki

    1996-01-01

    Development of strategies to eradicate radioresistant hypoxic cells would be of great benefit for clinical radiotherapy. In the present study, the in vivo effects of promising hypoxic cytotoxin, tirapazamine (3-amino-1,2,4-benzotriazine 1,4-di-N-oxide), were examined in comparison with those of KU-2285, one of the best hypoxic cell radiosensitizers, in combination with both single and fractionated irradiation. The tumor response was assessed by the standard in vivo-in vitro clonogenic assay using SCCVII tumors in C3H mice and EMT-6/KU tumors in Balb/c mice with different characteristics of tumor hypoxia. With single-dose irradiation (18 Gy), both tirapazamine and KU-2285 showed significant enhancement of cell killing in a dose-dependent manner, but tirapazamine was more effective for SCCVII tumors with acutely hypoxic cells, while KU-2285 was more effective for EMT-6/KU tumors predominantly with chronically hypoxic cells. In fractionated irradiation regimens (4 fractions of 5 Gy at 12 h intervals), tirapazamine showed more marked combined effects at 10 and 20 mg/kg than KU-2285 at 100-200 mg/kg in both SCCVII and EMT-6/KU tumors. We concluded that the effectiveness of KU-2285 and tirapazamine was correlated with the nature of tumor hypoxia with single-dose irradiation, whereas tirapazamine appeared more potent than KU-2285 with fractionated irradiation. These findings suggest the potential usefulness of tirapazamine in clinical fractionated radiotherapy. (author).

  13. Intraphagosomal peroxynitrite as a macrophage-derived cytotoxin against internalized Trypanosoma cruzi: consequences for oxidative killing and role of microbial peroxiredoxins in infectivity.

    Science.gov (United States)

    Alvarez, María Noel; Peluffo, Gonzalo; Piacenza, Lucía; Radi, Rafael

    2011-02-25

    Macrophage-derived radicals generated by the NADPH oxidase complex and inducible nitric-oxide synthase (iNOS) participate in cytotoxic mechanisms against microorganisms. Nitric oxide ((•)NO) plays a central role in the control of acute infection by Trypanosoma cruzi, the causative agent of Chagas disease, and we have proposed that much of its action relies on macrophage-derived peroxynitrite (ONOO(-) + ONOOH) formation, a strong oxidant arising from the reaction of (•)NO with superoxide radical (O(2)(-)). Herein, we have shown that internalization of T. cruzi trypomastigotes by macrophages triggers the assembly of the NADPH oxidase complex to yield O(2)(-) during a 60-90-min period. This does not interfere with IFN-γ-dependent iNOS induction and a sustained (•)NO production (∼24 h). The major mechanism for infection control via reactive species formation occurred when (•)NO and O(2)() were produced simultaneously, generating intraphagosomal peroxynitrite levels compatible with microbial killing. Moreover, biochemical and ultrastructural analysis confirmed cellular oxidative damage and morphological disruption in internalized parasites. Overexpression of cytosolic tryparedoxin peroxidase in T. cruzi neutralized macrophage-derived peroxynitrite-dependent cytotoxicity to parasites and favored the infection in an animal model. Collectively, the data provide, for the first time, direct support for the action of peroxynitrite as an intraphagosomal cytotoxin against pathogens and the premise that microbial peroxiredoxins facilitate infectivity via decomposition of macrophage-derived peroxynitrite.

  14. Purification and partial amino acid sequences of a new presynaplic toxin and a cytotoxin from venom of pit veper Agkistrodon blomhoffii brevicaudus

    Institute of Scientific and Technical Information of China (English)

    吉永华; 陆丽芳; 徐科; Hiroyuki Hattori; Susumu Terakawa

    1995-01-01

    The technique of the reverse-phase performance liquid chromatography (RP-HPLC) was employed to separate and purify the toxic proteins from the venom of Agkistrodon blomhoffii brevicaudus collected in China 3 toxic proteins marked as AgTx-1, AgTx-2 and AgTx-3 consisting of about 122 amino acid residues were screened The toxicities (LD50,) of the AgTx-1, AgTx-2 and AgTx-3 were 0.075, 0.51 and 6.6 mg per kg weight of mice respectively. Toxicological experiment in the chick biventer cervicis nerve-muscle preparation showed that the acetylcholine (Ach) sensitivity of the preparation was unchanged after the total failure of the indirect contraction caused by AgTx-1 and AgTx-2. suggesting that they were presynaptic blockers, namely β-type of snake toxins. However, the amplitude of indirect contraction of the preparation was gradually reduced due to its incomplete relaxation caused by AgTx-3, indicating that it should belong to the category of cytotoxins. The partial amino acid sequences of 3 toxins have been

  15. Growth and electrical properties of high-quality Mg-doped P-type A10.2Ga0.8N films

    Institute of Scientific and Technical Information of China (English)

    Zhou Xiaowei; Li Peixian; Xu Shengrui; Hao Yue

    2009-01-01

    The growth of high-performance Mg-doped p-type AlxGa1-xN(X=0.2)using metal-organic chemical vapor deposition is reported.The influence of growth conditions(growth temperature,magnesium flow,and thermal annealing temperature)on the electrical properties of Mg-doped p-type AlxGa1-xN(X=0.2)has been investigated.Using the optimized conditions,we obtained a minimum p-type resistivity of 0.71 Ωcm for p-type AlGaN with 20% Al fraction.

  16. Reduction of deep levels generated by ion implantation into n- and p-type 4H-SiC

    Science.gov (United States)

    Kawahara, Koutarou; Suda, Jun; Pensl, Gerhard; Kimoto, Tsunenobu

    2010-08-01

    The authors have investigated effects of thermal oxidation on deep levels in the whole energy range of the band gap of 4H-SiC by deep level transient spectroscopy. The deep levels are generated by ion implantation. The dominant defects in n-type samples after ion implantation and high-temperature annealing at 1700 °C are IN3 (Z1/2: EC-0.63 eV) and IN9 (EH6/7: EC-1.5 eV) in low-dose-implanted samples, and IN8 (EC-1.2 eV) in high-dose-implanted samples. These defects can remarkably be reduced by thermal oxidation at 1150 °C. In p-type samples, however, IP8 (HK4: EV+1.4 eV) survives and additional defects such as IP4 (HK0: EV+0.72 eV) appear after thermal oxidation in low-dose-implanted samples. In high-dose-implanted p-type samples, three dominant levels, IP5 (HK2: EV+0.85 eV), IP6 (EV+1.0 eV), and IP7 (HK3: EV+1.3 eV), are remarkably reduced by oxidation at 1150 °C. The dominant defect IP4 observed in p-type 4H-SiC after thermal oxidation can be reduced by subsequent annealing in Ar at 1400 °C. These phenomena are explained by a model that excess interstitials are generated at the oxidizing interface, which diffuse into the bulk region.

  17. P-type ZnO films by phosphorus doping using plasma immersion ion-implantation technique

    Science.gov (United States)

    Nagar, S.; Chakrabarti, S.

    2013-03-01

    ZnO has been a subject of intense research in the optoelectronics community owing to its wide bandgap (3.3eV) and large exciton binding energy (60meV). However, difficulty in doping it p-type posts a hindrance in fabricating ZnO-based devices. In order to make p-type ZnO films, phosphorus implantation, using plasma immersion ion-implantation technique (2kV, 900W, 10μs pulse width) for 30 seconds, was performed on ZnO thin film deposited by RF Magnetron Sputtering (Sample A). The implanted samples were subsequently rapid thermal annealed at 700°C and 1000°C (Samples B and C) in oxygen environment for 30 seconds. Low temperature (8K) photoluminescence spectra reveal dominant donor-bound exciton (D°X) peak at 3.36eV for samples A and B. However, for Sample B the peaks around 3.31eV and 3.22eV corresponding to the free electron-acceptor (FA) and donor to acceptor pair peaks (DAP) are also observed. A dominant peak around 3.35eV, corresponding to acceptor bound exciton (A°X) peak, is detected for Sample C along with the presence of FA and DAP peaks around 3.31eV and 3.22eV. Moreover, the deep level peak around 2.5eV is higher for Sample B which may be due to implantation and acceptor related defects. However, for Sample C, the deep level peaks are very weak compared to the near band edge peaks confirming that these peaks are mainly due to intrinsic defects and not related to acceptors. These results clearly show us a promising way to achieve p-type ZnO films using phosphorus doping.

  18. Nitrogen-monoxide gas-sensing properties of transparent p-type copper-oxide nanorod arrays

    Energy Technology Data Exchange (ETDEWEB)

    Park, Soojeong; Kim, Hyojin; Kim, Dojin [Chungnam National University, Daejeon (Korea, Republic of)

    2015-01-15

    We report the nitrogen-monoxide (NO) gas-sensing properties of transparent p-type copper-oxide (CuO) nanorod arrays synthesized by using the hydrothermal method with a CuO nanoparticle seed layer deposited on a glass substrate via sputtering process. We synthesized polycrystalline CuO nanorods measuring 200 to 300 nm in length and 20 to 30 nm in diameter for three controlled molarity ratios of 1:1, 1:2 and 1:4 between copper nitrate trihydrate [Cu(NO{sub 2}){sub 2}·3H{sub 2}O] and hexamethylenetetramine (C{sub 6}H{sub 12}N{sub 4}). The crystal structures and morphologies of the synthesized CuO nanorod arrays were examined using grazing incidence X-ray diffraction and scanning electron microscopy. The gas-sensing measurements for NO gas in dry air indicated that the CuO nanorodarray-based gas sensors synthesized under hydrothermal condition at a molarity ratio of 1:2 showed the best gas sensing response to NO gas. These CuO nanorod-array gas sensors exhibited a highly sensitive response to NO gas, with a maximum sensitivity of about 650% for 10 ppm NO in dry air at an operating temperature of 100 .deg. C. These transparent p-type CuO nanorod-array gas sensors have shown a reversible and reliable response to NO gas over a range of operating temperatures. These results indicate certain potential use of p-type oxide semiconductor CuO nanorods as sensing materials for several types of gas sensors, including p - n junction gas sensors.

  19. Primary defect transformations in high-resistivity p-type silicon irradiated with electrons at cryogenic temperatures

    CERN Document Server

    Makarenko, L F; Korshunov, F P; Murin, L I; Moll, M

    2009-01-01

    It has been revealed that self-interstitials formed under low intensity electron irradiationin high resistivity p-type silicon can be retained frozen up to room temperature. Low thermal mobility of the self-interstitials suggests that Frenkelpair sinsilicon can be stable at temperatures of about or higher than 100K. A broad DLTS peak with activation energy of 0.14–0.17eV can be identified as related to Frenkel pairs. This peak anneals out at temperatures of 120 140K. Experimental evidences are presented that be coming more mobile under forwardcurrent injection the self-interstitials change their charge state to a less positive one.

  20. Thermoelectric properties of p-type Bi-Sb-Te compositionally graded thermoelectric materials with different barriers

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    In order to find more suitable materials as barriers and to improve the thermoelectric properties, p-type (BiSb)2Te3 (0.85, 0.9) two segments compositionally graded thermoelectric materials (CGTM) with different barriers were fabricated by conventional hot pressure method. Metals Fe, Co, Cu and Al were used as barriers between two segments. The effects of different barriers on thermoelectric properties of CGTM were investigated. The results show that metal Fe is more stable and suitable as the barrier.

  1. Growth and characterization of Czochralski-grown n and p-type GaAs for space solar cell substrates

    Science.gov (United States)

    Chen, R. T.

    1983-01-01

    Progress in LEC (liquid encapsulated Czochralski) crystal growth techniques for producing high-quality, 3-inch-diameter, n- and p-type GaAs crystals suitable for solar cell applications is described. The LEC crystals with low dislocation densities and background impurities, high electrical mobilities, good dopant uniformity, and long diffusion lengths were reproducibly grown through control of the material synthesis, growth and doping conditions. The capability for producing these large-area, high-quality substrates should positively impact the manufacturability of highly efficiency, low cost, radiation-hard GaAs solar cells.

  2. The influence of substrate and annealing temperatures on electrical properties of p-type ZnO films

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, C.Y. [Department of Mathematics and Physics, Shanghai Institute of technology, 120 Cao Bao Road, Shanghai 200235 (China)], E-mail: zhang_canyun@sit.edu.cn

    2009-01-15

    In this study, p-type ZnO films with excellent electrical properties were prepared by ultrasonic spray pyrolysis (USP) combining with a N-Al codoping technique. The influence of the substrate temperature and annealing temperature on electrical properties of ZnO films was investigated. The growth and doping process of ZnO films was explored by thermogravimetry, differential scanning calorimetry and mass spectrum (TG-DSC-MS) measurements. It is suggested that the variation of electrical properties of ZnO films with the substrate temperature and annealing temperature results from the removal of H element out of the films.

  3. Crystallization of P-type ATPases by the High Lipid-Detergent (HiLiDe) Method

    DEFF Research Database (Denmark)

    Sitsel, Oleg; Wang, Kaituo; Liu, Xiangyu;

    2016-01-01

    Determining structures of membrane proteins remains a significant challenge. A technique utilizing high lipid-detergent concentrations ("HiLiDe") circumvents the major bottlenecks of current membrane protein crystallization methods. During HiLiDe, the protein-lipid-detergent ratio is varied...... in a controlled way in order to yield initial crystal hits, which may be subsequently optimized by variation of the crystallization conditions and/or utilizing secondary detergents. HiLiDe preserves the advantages of classical lipid-based methods, yet is compatible with both the vapor diffusion and batch...... crystallization techniques. The method has been applied with particular success to P-type ATPases....

  4. Crystallization of P-type ATPases by the High Lipid-Detergent (HiLiDe) Method.

    Science.gov (United States)

    Sitsel, Oleg; Wang, Kaituo; Liu, Xiangyu; Gourdon, Pontus

    2016-01-01

    Determining structures of membrane proteins remains a significant challenge. A technique utilizing high lipid-detergent concentrations ("HiLiDe") circumvents the major bottlenecks of current membrane protein crystallization methods. During HiLiDe, the protein-lipid-detergent ratio is varied in a controlled way in order to yield initial crystal hits, which may be subsequently optimized by variation of the crystallization conditions and/or utilizing secondary detergents. HiLiDe preserves the advantages of classical lipid-based methods, yet is compatible with both the vapor diffusion and batch crystallization techniques. The method has been applied with particular success to P-type ATPases.

  5. Prediction and theoretical characterization of p-type organic semiconductor crystals for field-effect transistor applications.

    Science.gov (United States)

    Atahan-Evrenk, Sule; Aspuru-Guzik, Alán

    2014-01-01

    The theoretical prediction and characterization of the solid-state structure of organic semiconductors has tremendous potential for the discovery of new high performance materials. To date, the theoretical analysis mostly relied on the availability of crystal structures obtained through X-ray diffraction. However, the theoretical prediction of the crystal structures of organic semiconductor molecules remains a challenge. This review highlights some of the recent advances in the determination of structure-property relationships of the known organic semiconductor single-crystals and summarizes a few available studies on the prediction of the crystal structures of p-type organic semiconductors for transistor applications.

  6. Differentiation of Bulk and Surface Events in p-type Point-Contact Germanium Detectors for Light WIMP Searches

    CERN Document Server

    Li, H B

    2013-01-01

    The p-type point-contact germanium detectors are novel techniques offering kg-scale radiation sensors with sub-keV sensitivities. They have been used for light Dark Matter WIMPs searches and may have potential applications in neutrino physics. There are, however, anomalous surface behaviour which needs to be characterized and understood. We describe the methods and results of a research program whose goals are to identify the bulk and surface events via software pulse shape analysis techniques, and to devise calibration schemes to evaluate the selection efficiency factors. Efficiencies-corrected background spectra from the low-background facility at Kuo-Sheng Neutrino Laboratory are derived.

  7. Two-dimensional ferromagnet/semiconductor transition metal dichalcogenide contacts: p-type Schottky barrier and spin-injection control

    KAUST Repository

    Gan, Liyong

    2013-09-26

    We study the ferromagnet/semiconductor contacts formed by transition metal dichalcogenide monolayers, focusing on semiconducting MoS2 and WS2 and ferromagnetic VS2. We investigate the degree of p-type doping and demonstrate tuning of the Schottky barrier height by vertical compressive pressure. An analytical model is presented for the barrier heights that accurately describes the numerical findings and is expected to be of general validity for all transition metal dichalcogenide metal/semiconductor contacts. Furthermore, magnetic proximity effects induce a 100% spin polarization at the Fermi level in the semiconductor where the spin splitting increases up to 0.70 eV for increasing pressure.

  8. Comparative studies on p-type CuI grown on glass and copper substrate by SILAR method

    Energy Technology Data Exchange (ETDEWEB)

    Dhere, Sunetra L.; Latthe, Sanjay S. [Air Glass Laboratory, Department of Physics, Shivaji University, Kolhapur 416 004, Maharashtra (India); Kappenstein, Charles [University of Poitiers, Laboratory of Catalysis in Organic Chemistry, LA CCO, UMR CNRS 6503, Poitiers-86000 (France); Mukherjee, S.K. [Fuel Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai - 400085, Maharashtra India (India); Rao, A. Venkateswara, E-mail: avrao2012@gmail.com [Air Glass Laboratory, Department of Physics, Shivaji University, Kolhapur 416 004, Maharashtra (India)

    2010-04-01

    Depending upon the method of synthesis and the nature of substrate surface, there is variation in the physico-chemical properties of the material. Cuprous iodide films are deposited at room temperature on the glass and copper substrates by a simple SILAR method and the obtained results are compared. The p-type material with optical band gap 2.88 eV is found to be possessing face-centered cubic crystal structure with lattice parameter 6.134 A. We observed irregular particles for the CuI film on the glass substrate while patterned arrays of micro-rods with cabbage like tips on copper substrate, for the same preparative conditions. Also, the material deposited on copper is showing superhydrophobic nature (contact angle {approx}156{sup o}) while that on glass it is hydrophilic (contact angle {approx}88{sup o}). We have characterized the thin films by X-ray diffraction, scanning electron microscopy, surface roughness and contact angle measurement, thermoelectric power measurement and optical studies. This hydrophobic, p-type material with wide band gap will be helpful in the development of optoelectronic devices.

  9. Binary Oxide p-n Heterojunction Piezoelectric Nanogenerators with an Electrochemically Deposited High p-Type Cu2O Layer.

    Science.gov (United States)

    Baek, Seung Ki; Kwak, Sung Soo; Kim, Joo Sung; Kim, Sang Woo; Cho, Hyung Koun

    2016-08-31

    The high performance of ZnO-based piezoelectric nanogenerators (NGs) has been limited due to the potential screening from intrinsic electron carriers in ZnO. We have demonstrated a novel approach to greatly improve piezoelectric power generation by electrodepositing a high-quality p-type Cu2O layer between the piezoelectric semiconducting film and the metal electrode. The p-n heterojunction using only oxides suppresses the screening effect by forming an intrinsic depletion region, and thus sufficiently enhances the piezoelectric potential, compared to the pristine ZnO piezoelectric NG. Interestingly, a Sb-doped Cu2O layer has high mobility and low surface trap states. Thus, this doped layer is an attractive p-type material to significantly improve piezoelectric performance. Our results revealed that p-n junction NGs consisting of Au/ZnO/Cu2O/indium tin oxide with a Cu2O:Sb (cuprous oxide with a small amount of antimony) layer of sufficient thickness (3 μm) exhibit an extraordinarily high piezoelectric potential of 0.9 V and a maximum output current density of 3.1 μA/cm(2).

  10. Effect of gate dielectrics on the performance of p-type Cu2O TFTs processed at room temperature

    KAUST Repository

    Al-Jawhari, Hala A.

    2013-12-01

    Single-phase Cu2O films with p-type semiconducting properties were successfully deposited by reactive DC magnetron sputtering at room temperature followed by post annealing process at 200°C. Subsequently, such films were used to fabricate bottom gate p-channel Cu2O thin film transistors (TFTs). The effect of using high-κ SrTiO3 (STO) as a gate dielectric on the Cu2O TFT performance was investigated. The results were then compared to our baseline process which uses a 220 nm aluminum titanium oxide (ATO) dielectric deposited on a glass substrate coated with a 200 nm indium tin oxide (ITO) gate electrode. We found that with a 150 nm thick STO, the Cu2O TFTs exhibited a p-type behavior with a field-effect mobility of 0.54 cm2.V-1.s-1, an on/off ratio of around 44, threshold voltage equaling -0.62 V and a sub threshold swing of 1.64 V/dec. These values were obtained at a low operating voltage of -2V. The advantages of using STO as a gate dielectric relative to ATO are discussed. © (2014) Trans Tech Publications, Switzerland.

  11. Search for Pauli Exclusion Principle Violating Atomic Transitions and Electron Decay with a P-type Point Contact Germanium Detector

    CERN Document Server

    Abgrall, N; Avignone, F T; Barabash, A S; Bertrand, F E; Bradley, A W; Brudanin, V; Busch, M; Buuck, M; Caldwell, A S; Chan, Y-D; Christofferson, C D; Chu, P -H; Cuesta, C; Detwiler, J A; Dunagan, C; Efremenko, Yu; Ejiri, H; Elliott, S R; Finnerty, P S; Galindo-Uribarri, A; Gilliss, T; Giovanetti, G K; Goett, J; Green, M P; Gruszko, J; Guinn, I S; Guiseppe, V E; Henning, R; Hoppe, E W; Howard, S; Howe, M A; Jasinski, B R; Keeter, K J; Kidd, M F; Konovalov, S I; Kouzes, R T; LaFerriere, B D; Leon, J; MacMullin, J; Martin, R D; Massarczyk, R; Meijer, S J; Mertens, S; Orrell, J L; O'Shaughnessy, C; Poon, A W P; Radford, D C; Rager, J; Rielage, K; Robertson, R G H; Romero-Romero, E; Shanks, B; Shirchenko, M; Suriano, A M; Tedeschi, D; Trimble, J E; Varner, R L; Vasilyev, S; Vetter, K; Vorren, K; White, B R; Wilkerson, J F; Wiseman, C; Xu, W; Yakushev, E; Yu, C -H; Yumatov, V; Zhitnikov, I

    2016-01-01

    A search for Pauli-exclusion-principle-violating K-alpha electron transitions was performed using 89.5 kg-d of data collected with a p-type point contact high-purity germanium detector operated at the Kimballton Underground Research Facility. A lower limit on the transition lifetime of 5.8x10^30 seconds at 90% C.L. was set by looking for a peak at 10.6 keV resulting from the x-ray and Auger electrons present following the transition. A similar analysis was done to look for the decay of atomic K-shell electrons into neutrinos, resulting in a lower limit of 6.8x10^30 seconds at 90 C.L. It is estimated that the MAJORANA DEMONSTRATOR, a 44 kg array of p-type point contact detectors that will search for the neutrinoless double-beta decay of 76-Ge, could improve upon these exclusion limits by an order of magnitude after three years of operation.

  12. Comparative studies on p-type CuI grown on glass and copper substrate by SILAR method

    Science.gov (United States)

    Dhere, Sunetra L.; Latthe, Sanjay S.; Kappenstein, Charles; Mukherjee, S. K.; Rao, A. Venkateswara

    2010-04-01

    Depending upon the method of synthesis and the nature of substrate surface, there is variation in the physico-chemical properties of the material. Cuprous iodide films are deposited at room temperature on the glass and copper substrates by a simple SILAR method and the obtained results are compared. The p-type material with optical band gap 2.88 eV is found to be possessing face-centered cubic crystal structure with lattice parameter 6.134 Å. We observed irregular particles for the CuI film on the glass substrate while patterned arrays of micro-rods with cabbage like tips on copper substrate, for the same preparative conditions. Also, the material deposited on copper is showing superhydrophobic nature (contact angle ˜156°) while that on glass it is hydrophilic (contact angle ˜88°). We have characterized the thin films by X-ray diffraction, scanning electron microscopy, surface roughness and contact angle measurement, thermoelectric power measurement and optical studies. This hydrophobic, p-type material with wide band gap will be helpful in the development of optoelectronic devices.

  13. Improving the radiation hardness properties of silicon detectors using oxygenated n-type and p-type silicon

    CERN Document Server

    Casse, G L; Hanlon, M

    2000-01-01

    The degradation of the electrical properties of silicon detectors exposed to 24 GeV/c protons were studied using pad diodes made from different silicon materials. Standard high-grade p-type and n-type substrates and oxygenated n-type substrates have been used. The diodes were studied in terms of reverse current (I/sub r/) and full depletion voltage (V/sub fd/) as a function of fluence. The oxygenated devices from different suppliers with a variety of starting materials and techniques, all show a consistent improvement of the degradation rate of V/sub fd/ and CCE compared to un- oxygenated substrate devices. Radiation damage of n-type detectors introduces stable defects acting as effective p-type doping and leads to the change of the conductivity type of the silicon bulk (type inversion) at a neutron equivalent fluence of a few 10/sup 13/ cm/sup -2/. The diode junction after inversion migrates from the original side to the back plane of the detector. The migration of the junction is avoided using silicon detec...

  14. P-stop isolation study of irradiated n-in-p type silicon strip sensors for harsh radiation environment

    CERN Document Server

    AUTHOR|(CDS)2084505

    2015-01-01

    In order to determine the most radiation hard silicon sensors for the CMS Experiment after the Phase II Upgrade in 2023 a comprehensive study of silicon sensors after a fluence of up to $1.5\\times10^{15} n_{eq}/cm^{2}$ corresponding to $3000 fb^{-1}$ after the HL-LHC era has been carried out. The results led to the decision that the future Outer Tracker (20~cm${<}R{<}$110~cm) of CMS will consist of n-in-p type sensors. This technology is more radiation hard but also the manufacturing is more challenging compared to p-in-n type sensors due to additional process steps in order to suppress the accumulation of electrons between the readout strips. One possible isolation technique of adjacent strips is the p-stop structure which is a p-type material implantation with a certain pattern for each individual strip. However, electrical breakdown and charge collection studies indicate that the process parameters of the p-stop structure have to be carefully calibrated in order to achieve a sufficient strip isolatio...

  15. High performance printed N and P-type OTFTs enabling digital and analog complementary circuits on flexible plastic substrate

    Science.gov (United States)

    Jacob, S.; Abdinia, S.; Benwadih, M.; Bablet, J.; Chartier, I.; Gwoziecki, R.; Cantatore, E.; van Roermund, A. H. M.; Maddiona, L.; Tramontana, F.; Maiellaro, G.; Mariucci, L.; Rapisarda, M.; Palmisano, G.; Coppard, R.

    2013-06-01

    This paper presents a printed organic complementary technology on flexible plastic substrate with high performance N and P-type Organic Thin Film Transistors (OTFTs), based on small-molecule organic semiconductors in solution. Challenges related to the integration of both OTFT types in a common complementary flow are addressed, showing the importance of surface treatments. Stability on single devices and on an elementary complementary digital circuit (ring oscillator) is studied, demonstrating that a robust and reliable flow with high electrical performances can be established for printed organic devices. These devices are used to manufacture several analog and digital building blocks. The design is carried out using a model specifically developed for this technology, and taking into account the parametric variability. High-frequency measurements of printed envelope detectors show improved speed performance, resulting from the high mobility of the OTFTs. In addition, a compact dynamic flip-flop and a low-offset comparator are demonstrated, thanks to availability of both n-type and p-type OTFTs in the technology. Measurement results are in good agreement with the simulations. The circuits presented establish a complete library of building blocks for the realization of a printed RFID tag.

  16. Perovskite LaRhO{sub 3} as a p-type active layer in oxide photovoltaics

    Energy Technology Data Exchange (ETDEWEB)

    Nakamura, Masao, E-mail: masao.nakamura@riken.jp; Krockenberger, Yoshiharu [RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198 (Japan); Fujioka, Jun [Department of Applied Physics and Quantum-Phase Electronics Center (QPEC), University of Tokyo, Tokyo 113-8656 (Japan); Kawasaki, Masashi; Tokura, Yoshinori [RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198 (Japan); Department of Applied Physics and Quantum-Phase Electronics Center (QPEC), University of Tokyo, Tokyo 113-8656 (Japan)

    2015-02-16

    Perovskite-type transition-metal oxides have a wide variety of physical properties and triggered intensive research on functional devices in the form of heteroepitaxial junctions. However, there is a missing component that is a p-type conventional band semiconductor. LaRhO{sub 3} (LRO) is one of very few promising candidates having its bandgap between filled t{sub 2g} and empty e{sub g} of Rh in low-spin state, but there has been no report on the synthesis of large-size single crystals or thin films. Here, we report on the junction properties of single-crystalline thin films of LRO grown on (110) oriented Nb-doped SrTiO{sub 3} substrates. The external quantum efficiency of the photo-electron conversion exceeds 1% in the visible-light region due to the wide depletion layer and long diffusion length of minority carriers in LRO. Clear indication of p-type band semiconducting character in a perovskite oxide of LRO will pave a way to explore oxide electronics of perovskite heterostructures.

  17. The synthesis and characterization of Ag-N dual-doped p-type ZnO: experiment and theory.

    Science.gov (United States)

    Duan, Li; Wang, Pei; Yu, Xiaochen; Han, Xiao; Chen, Yongnan; Zhao, Peng; Li, Donglin; Yao, Ran

    2014-03-07

    Ag-N dual-doped ZnO films have been fabricated by a chemical bath deposition method. The p-type conductivity of the dual-doped ZnO:(Ag, N) is stable over a long period of time, and the hole concentration in the ZnO:(Ag, N) is much higher than that in mono-doped ZnO:Ag or ZnO:N. We found that this is because AgZn-NO complex acceptors can be formed in ZnO:(Ag, N). First-principles calculations show that the complex acceptors generate a fully occupied band above the valance band maximum, so the acceptor levels become shallower and the hole concentration is increased. Furthermore, the binding energy of the Ag-N complex in ZnO is negative, so ZnO:(Ag, N) can be stable. These results indicate that the Ag-N dual-doping may be expected to be a potential route to achieving high-quality p-type ZnO for use in a variety of devices.

  18. Performances of miniature microstrip detectors made on oxygen enriched p-type substrates after very high proton irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Casse, G. [Oliver Lodge Laboratory, Department of Physics, University of Liverpool, P.O. Box 147, Liverpool L69 3BX (United Kingdom)]. E-mail: gcasse@hep.ph.liv.ac.uk; Allport, P.P. [Oliver Lodge Laboratory, Department of Physics, University of Liverpool, P.O. Box 147, Liverpool L69 3BX (United Kingdom); Marti i Garcia, S. [IFIC CSIC, Edificio Institutos de Investigacion Apartado de Correos 22085 E-46071, Valencia-Spain (Spain); Lozano, M. [IMB-CNM (CSIC), Campus Universidad Autonoma de Barcelona, 08193 Bellaterra, Barcelona (Spain); Turner, P.R. [Oliver Lodge Laboratory, Department of Physics, University of Liverpool, P.O. Box 147, Liverpool L69 3BX (United Kingdom)

    2004-12-11

    Silicon microstrip detectors with n-type implant read-out strips on FZ p-type bulk (n-in-p) show superior charge collection properties, after heavy irradiation, to the more standard p-strips in n-type silicon (p-in-n). It is also well established that oxygen-enriched n-type silicon substrates show better performance, in terms of degradation of the full depletion voltage after charged hadron irradiation, than the standard FZ silicon used for high energy physics detectors. Silicon microstrip detectors combining both the advantages of oxygenation and of n-strip read-out (n-in-n) have achieved high radiation tolerance to charged hadrons. The manufacturing of n-in-n detectors though requires double-sided processing, resulting in more complicated and expensive devices than standard p-in-n. A cheaper single-sided option, that still combines these advantages, is to use n-in-p devices. P-type FZ wafers have been oxygen-enriched by high temperature diffusion from an oxide layer and successfully used to process miniature (1x1 cm{sup 2}) microstrip detectors. These detectors have been irradiated with 24 GeV/c protons in the CERN/PS T7 irradiation area up to {approx}7.5x10{sup 15} cm{sup -2}. We report results with these irradiated detectors in terms of the charge collection efficiency as a function of the applied bias voltage.

  19. Performances of miniature microstrip detectors made on oxygen enriched p-type substrates after very high proton irradiation

    Science.gov (United States)

    Casse, G.; Allport, P. P.; Martí i Garcia, S.; Lozano, M.; Turner, P. R.

    2004-12-01

    Silicon microstrip detectors with n-type implant read-out strips on FZ p-type bulk (n-in-p) show superior charge collection properties, after heavy irradiation, to the more standard p-strips in n-type silicon (p-in-n). It is also well established that oxygen-enriched n-type silicon substrates show better performance, in terms of degradation of the full depletion voltage after charged hadron irradiation, than the standard FZ silicon used for high energy physics detectors. Silicon microstrip detectors combining both the advantages of oxygenation and of n-strip read-out (n-in-n) have achieved high radiation tolerance to charged hadrons. The manufacturing of n-in-n detectors though requires double-sided processing, resulting in more complicated and expensive devices than standard p-in-n. A cheaper single-sided option, that still combines these advantages, is to use n-in-p devices. P-type FZ wafers have been oxygen-enriched by high temperature diffusion from an oxide layer and succesfully used to process miniature (1×1 cm 2) microstrip detectors. These detectors have been irradiated with 24 GeV/c protons in the CERN/PS T7 irradiation area up to ˜7.5×10 15 cm -2. We report results with these irradiated detectors in terms of the charge collection efficiency as a function of the applied bias voltage.

  20. Characterization of a heavy metal translocating P-type ATPase gene from an environmental heavy metal resistance Enterobacter sp. isolate.

    Science.gov (United States)

    Chien, Chih-Ching; Huang, Chia-Hsuan; Lin, Yi-Wei

    2013-03-01

    Heavy metals are common contaminants found in polluted areas. We have identified a heavy metal translocating P-type ATPase gene (hmtp) via fosmid library and in vitro transposon mutagenesis from an Enterobacter sp. isolate. This gene is believed to participate in the bacterium's heavy metal resistance traits. The complete gene was identified, cloned, and expressed in a suitable Escherichia coli host cell. E. coli W3110, RW3110 (zntA::Km), GG48 (ΔzitB::Cm zntA::Km), and GG51 (ΔzitB::Cm) were used to study the possible effects of this gene for heavy metal (cadmium and zinc in particular) resistance. Among the E. coli strains tested, RW3110 and GG48 showed more sensitivity to cadmium and zinc compared to the wild-type E. coli W3110 and strain GG51. Therefore, strains RW3110 and GG48 were chosen for the reference hosts for further evaluation of the gene's effect. The results showed that expression of this heavy metal translocating P-type ATPase gene could increase the ability for zinc and cadmium resistance in the tested microorganisms.

  1. Chemical Vapor Deposition Growth of Degenerate p-Type Mo-Doped ReS2 Films and Their Homojunction.

    Science.gov (United States)

    Qin, Jing-Kai; Shao, Wen-Zhu; Xu, Cheng-Yan; Li, Yang; Ren, Dan-Dan; Song, Xiao-Guo; Zhen, Liang

    2017-05-10

    Substitutional doping of transition metal dichalcogenide two-dimensional materials has proven to be effective in tuning their intrinsic properties, such as band gap, transport characteristics, and magnetism. In this study, we realized substitutional doping of monolayer rhenium disulfide (ReS2) with Mo via chemical vapor deposition. Scanning transmission electron microscopy demonstrated that Mo atoms are successfully doped into ReS2 by substitutionally replacing Re atoms in the lattice. Electrical measurements revealed the degenerate p-type semiconductor behavior of Mo-doped ReS2 field effect transistors, in agreement with density functional theory calculations. The p-n diode device based on a doped ReS2 and ReS2 homojunction exhibited gate-tunable current rectification behaviors, and the maximum rectification ratio could reach up to 150 at Vd = -2/+2 V. The successful synthesis of p-type ReS2 in this study could largely promote its application in novel electronic and optoelectronic devices.

  2. Search for Pauli exclusion principle violating atomic transitions and electron decay with a p-type point contact germanium detector

    Energy Technology Data Exchange (ETDEWEB)

    Abgrall, N.; Bradley, A.W.; Chan, Y.D.; Mertens, S.; Poon, A.W.P. [Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA (United States); Arnquist, I.J.; Hoppe, E.W.; Kouzes, R.T.; LaFerriere, B.D.; Orrell, J.L. [Pacific Northwest National Laboratory, Richland, WA (United States); Avignone, F.T. [Oak Ridge National Laboratory, Oak Ridge, TN (United States); University of South Carolina, Department of Physics and Astronomy, Columbia, SC (United States); Barabash, A.S.; Konovalov, S.I.; Yumatov, V. [National Research Center ' ' Kurchatov Institute' ' Institute for Theoretical and Experimental Physics, Moscow (Russian Federation); Bertrand, F.E.; Galindo-Uribarri, A.; Radford, D.C.; Varner, R.L.; White, B.R.; Yu, C.H. [Oak Ridge National Laboratory, Oak Ridge, TN (United States); Brudanin, V.; Shirchenko, M.; Vasilyev, S.; Yakushev, E.; Zhitnikov, I. [Joint Institute for Nuclear Research, Dubna (Russian Federation); Busch, M. [Duke University, Department of Physics, Durham, NC (United States); Triangle Universities Nuclear Laboratory, Durham, NC (United States); Buuck, M.; Cuesta, C.; Detwiler, J.A.; Gruszko, J.; Guinn, I.S.; Leon, J.; Robertson, R.G.H. [University of Washington, Department of Physics, Center for Experimental Nuclear Physics and Astrophysics, Seattle, WA (United States); Caldwell, A.S.; Christofferson, C.D.; Dunagan, C.; Howard, S.; Suriano, A.M. [South Dakota School of Mines and Technology, Rapid City, SD (United States); Chu, P.H.; Elliott, S.R.; Goett, J.; Massarczyk, R.; Rielage, K. [Los Alamos National Laboratory, Los Alamos, NM (United States); Efremenko, Yu. [University of Tennessee, Department of Physics and Astronomy, Knoxville, TN (United States); Ejiri, H. [Osaka University, Research Center for Nuclear Physics, Ibaraki, Osaka (Japan); Finnerty, P.S.; Gilliss, T.; Giovanetti, G.K.; Henning, R.; Howe, M.A.; MacMullin, J.; Meijer, S.J.; O' Shaughnessy, C.; Rager, J.; Shanks, B.; Trimble, J.E.; Vorren, K.; Xu, W. [Triangle Universities Nuclear Laboratory, Durham, NC (United States); University of North Carolina, Department of Physics and Astronomy, Chapel Hill, NC (United States); Green, M.P. [North Carolina State University, Department of Physics, Raleigh, NC (United States); Oak Ridge National Laboratory, Oak Ridge, TN (United States); Triangle Universities Nuclear Laboratory, Durham, NC (United States); Guiseppe, V.E.; Tedeschi, D.; Wiseman, C. [University of South Carolina, Department of Physics and Astronomy, Columbia, SC (United States); Jasinski, B.R. [University of South Dakota, Department of Physics, Vermillion, SD (United States); Keeter, K.J. [Black Hills State University, Department of Physics, Spearfish, SD (United States); Kidd, M.F. [Tennessee Tech University, Cookeville, TN (United States); Martin, R.D. [Queen' s University, Department of Physics, Engineering Physics and Astronomy, Kingston, ON (Canada); Romero-Romero, E. [Oak Ridge National Laboratory, Oak Ridge, TN (United States); University of Tennessee, Department of Physics and Astronomy, Knoxville, TN (United States); Vetter, K. [Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA (United States); University of California, Department of Nuclear Engineering, Berkeley, CA (United States); Wilkerson, J.F. [Oak Ridge National Laboratory, Oak Ridge, TN (United States); Triangle Universities Nuclear Laboratory, Durham, NC (United States); University of North Carolina, Department of Physics and Astronomy, Chapel Hill, NC (United States)

    2016-11-15

    A search for Pauli-exclusion-principle-violating K{sub α} electron transitions was performed using 89.5 kg-d of data collected with a p-type point contact high-purity germanium detector operated at the Kimballton Underground Research Facility. A lower limit on the transition lifetime of 5.8 x 10{sup 30} s at 90% C.L. was set by looking for a peak at 10.6 keV resulting from the X-ray and Auger electrons present following the transition. A similar analysis was done to look for the decay of atomic K-shell electrons into neutrinos, resulting in a lower limit of 6.8 x 10{sup 30} s at 90% C.L. It is estimated that the Majorana Demonstrator, a 44 kg array of p-type point contact detectors that will search for the neutrinoless double-beta decay of {sup 76}Ge, could improve upon these exclusion limits by an order of magnitude after three years of operation. (orig.)

  3. Novel p-Type Conductive Semiconductor Nanocrystalline Film as the Back Electrode for High-Performance Thin Film Solar Cells.

    Science.gov (United States)

    Zhang, Ming-Jian; Lin, Qinxian; Yang, Xiaoyang; Mei, Zongwei; Liang, Jun; Lin, Yuan; Pan, Feng

    2016-02-10

    Thin film solar cells, due to the low cost, high efficiency, long-term stability, and consumer applications, have been widely applied for harvesting green energy. All of these thin film solar cells generally adopt various metal thin films as the back electrode, like Mo, Au, Ni, Ag, Al, graphite, and so forth. When they contact with p-type layer, it always produces a Schottky contact with a high contact potential barrier, which greatly affects the cell performance. In this work, we report for the first time to find an appropriate p-type conductive semiconductor film, digenite Cu9S5 nanocrystalline film, as the back electrode for CdTe solar cells as the model device. Its low sheet resistance (16.6 Ω/sq) could compare to that of the commercial TCO films (6-30 Ω/sq), like FTO, ITO, and AZO. Different from the traditonal metal back electrode, it produces a successive gradient-doping region by the controllable Cu diffusion, which greatly reduces the contact potential barrier. Remarkably, it achieved a comparable power conversion efficiency (PCE, 11.3%) with the traditional metal back electrode (Cu/Au thin films, 11.4%) in CdTe cells and a higher PCE (13.8%) with the help of the Au assistant film. We believe it could also act as the back electrode for other thin film solar cells (α-Si, CuInS2, CIGSe, CZTS, etc.), for their performance improvement.

  4. Structural studies of P-type ATPase–ligand complexes using an X-ray free-electron laser

    Energy Technology Data Exchange (ETDEWEB)

    Bublitz, Maike; Nass, Karol; Drachmann, Nikolaj D.; Markvardsen, Anders J.; Gutmann, Matthias J.; Barends, Thomas R. M.; Mattle, Daniel; Shoeman, Robert L.; Doak, R. Bruce; Boutet, Sébastien; Messerschmidt, Marc; Seibert, Marvin M.; Williams, Garth J.; Foucar, Lutz; Reinhard, Linda; Sitsel, Oleg; Gregersen, Jonas L.; Clausen, Johannes D.; Boesen, Thomas; Gotfryd, Kamil; Wang, Kai-Tuo; Olesen, Claus; Møller, Jesper V.; Nissen, Poul; Schlichting, Ilme

    2015-06-11

    Membrane proteins are key players in biological systems, mediating signalling events and the specific transport ofe.g.ions and metabolites. Consequently, membrane proteins are targeted by a large number of currently approved drugs. Understanding their functions and molecular mechanisms is greatly dependent on structural information, not least on complexes with functionally or medically important ligands. Structure determination, however, is hampered by the difficulty of obtaining well diffracting, macroscopic crystals. Here, the feasibility of X-ray free-electron-laser-based serial femtosecond crystallography (SFX) for the structure determination of membrane protein–ligand complexes using microcrystals of various native-source and recombinant P-type ATPase complexes is demonstrated. The data reveal the binding sites of a variety of ligands, including lipids and inhibitors such as the hallmark P-type ATPase inhibitor orthovanadate. By analyzing the resolution dependence of ligand densities and overall model qualities, SFX data quality metrics as well as suitable refinement procedures are discussed. Even at relatively low resolution and multiplicity, the identification of ligands can be demonstrated. This makes SFX a useful tool for ligand screening and thus for unravelling the molecular mechanisms of biologically active proteins.

  5. Structural studies of P-type ATPase–ligand complexes using an X-ray free-electron laser

    Directory of Open Access Journals (Sweden)

    Maike Bublitz

    2015-07-01

    Full Text Available Membrane proteins are key players in biological systems, mediating signalling events and the specific transport of e.g. ions and metabolites. Consequently, membrane proteins are targeted by a large number of currently approved drugs. Understanding their functions and molecular mechanisms is greatly dependent on structural information, not least on complexes with functionally or medically important ligands. Structure determination, however, is hampered by the difficulty of obtaining well diffracting, macroscopic crystals. Here, the feasibility of X-ray free-electron-laser-based serial femtosecond crystallography (SFX for the structure determination of membrane protein–ligand complexes using microcrystals of various native-source and recombinant P-type ATPase complexes is demonstrated. The data reveal the binding sites of a variety of ligands, including lipids and inhibitors such as the hallmark P-type ATPase inhibitor orthovanadate. By analyzing the resolution dependence of ligand densities and overall model qualities, SFX data quality metrics as well as suitable refinement procedures are discussed. Even at relatively low resolution and multiplicity, the identification of ligands can be demonstrated. This makes SFX a useful tool for ligand screening and thus for unravelling the molecular mechanisms of biologically active proteins.

  6. Chemical fabrication of p-type Cu{sub 2}O transparent thin film using molecular precursor method

    Energy Technology Data Exchange (ETDEWEB)

    Nagai, Hiroki [Research Institute of Science and Technology, Kogakuin University, 2665-1 Nakano, Hachioji, Tokyo 192-0015 (Japan); Suzuki, Tatsuya [Department of Applied Chemistry and Chemical Engineering, Graduate School of Kogakuin University, 2665-1 Nakano, Hachioji, Tokyo 192-0015 (Japan); Hara, Hiroki; Mochizuki, Chihiro; Takano, Ichiro; Honda, Tohru [Research Institute of Science and Technology, Kogakuin University, 2665-1 Nakano, Hachioji, Tokyo 192-0015 (Japan); Sato, Mitsunobu, E-mail: lccsato@cc.kogakuin.ac.jp [Research Institute of Science and Technology, Kogakuin University, 2665-1 Nakano, Hachioji, Tokyo 192-0015 (Japan)

    2012-11-15

    A transparent p-type Cu{sub 2}O thin film of 50 nm thickness was successfully fabricated by means of a solution-based process involving the thermal reaction of molecular precursor films spin-coated on a Na-free glass substrate. The precursor solution was prepared by the reaction of an isolated Cu{sup 2+} complex of ethylenediamine-N, N, N Prime , N Prime -tetraacetic acid with dibutylamine in ethanol. The Cu{sub 2}O thin films resulting from heat treatment of the precursor film at 450 Degree-Sign C for 10 min in Ar gas at a flow rate of 1.0 L min{sup -1} were characterized by X-ray diffraction which indicated a precise cubic lattice cell parameter of a = 0.4265(2) nm, with a crystallite size of 8(2) nm. X-ray photoelectron spectroscopy peaks, attributable to the O 1s and Cu 2p{sub 3/2} level of the Cu{sub 2}O film were found at 532.6 eV and 932.4 eV, respectively. An average grain size of the deposited Cu{sub 2}O particles of ca. 200 nm was observed via field-emission scanning electron microscopy. The optical band edge evaluated from the absorption spectrum of the Cu{sub 2}O transparent thin film was 2.3 eV, assuming a direct-transition semiconductor. Hall Effect measurements of the thin film indicated that the single-phase Cu{sub 2}O thin film is a typical p-type semiconductor, with a hole concentration of 1.7 Multiplication-Sign 10{sup 16} cm{sup -3} and hole mobility of 4.8 cm{sup 2} V{sup -1} s{sup -1} at ambient temperature. The activation energy from the valence band to the acceptor level determined from an Arrhenius plot was 0.34 eV. The adhesion strength of the thin film on the Na-free glass substrate was also determined as a critical load (Lc1) of 2.0 N by means of a scratch test. The method described is the first example of fabrication and characterization of a p-type Cu{sub 2}O transparent thin film by a wet process. -- Graphical abstract: The p-type Cu{sub 2}O transparent thin film was facilely fabricated on a Na-free grass substrate by a solution based

  7. Cytotoxin and Pyrogenic Toxin Superantigen Gene Profiles of Staphylococcus aureus Associated with Subclinical Mastitis in Dairy Cows and Relationships with Macrorestriction Genomic Profiles

    Science.gov (United States)

    Fueyo, J. M.; Mendoza, M. C.; Rodicio, M. R.; Muñiz, J.; Alvarez, M. A.; Martín, M. C.

    2005-01-01

    A set of 84 Staphylococcus aureus isolates collected from the milk of cows with subclinical mastitis in Asturias (a cattle region of Spain) and six control strains were tested for sequences of genes encoding hemolysins (hla, hlb, hld, hlg, and hlg-2), leukotoxins (lukPV, lukM, and lukED), toxic shock syndrome toxin (tst), and enterotoxins (sea to see, seg to ser, and seu) by conventional and multiplex PCR. It was found that 84, 83, 11, and 39 isolates carried some type of hl, luk, tst, or se gene, respectively, which were arranged in 14 exotoxin genotypes. All of the isolates were negative for lukPV, hlg, sea, sed, see, sej, sek, sep, seq, and ser. Two gene groupings could be related with pathogenicity islands—[lukED, seg, sei, sem, sen, seo ± seu] with Saβ-1 and [tst, sec, sel] with SaPIbov, present in 45 and 13.1% of the isolates, respectively—while 11.9% of them carried both islands. Only one contained seb (together with υSaβ-1), and another contained seh (together with lukED). The isolates were also analyzed by pulsed-field gel electrophoresis performed with SmaI. Thirty-nine SmaI profiles (similarity coefficient [S] = 0.94 to 0.21) were differentiated; 12, 1, and 10 of these, respectively, were generated by isolates presumptively carrying Saβ-1, SaPIbov, or both. Five SmaI profiles (S ≥ 0.8) formed a cluster, which contained 20 and 10 isolates carrying one (υSaβ-1) or both islands. These data show the high frequency of genes encoding cytotoxins and pyrogenic toxin superantigens, their relationship with pathogenicity islands, and their distribution among a diversity of genetic types of S. aureus related to subclinical mastitis. PMID:15750096

  8. The novel hypoxic cytotoxin, TX-2098 has antitumor effect in pancreatic cancer; possible mechanism through inhibiting VEGF and hypoxia inducible factor-1α targeted gene expression.

    Science.gov (United States)

    Miyake, Kotaro; Nishioka, Masanori; Imura, Satoru; Batmunkh, Erdenebulgan; Uto, Yoshihiro; Nagasawa, Hideko; Hori, Hitoshi; Shimada, Mitsuo

    2012-08-01

    Tumor hypoxia has been considered to be a potential therapeutic target, because hypoxia is a common feature of solid tumors and is associated with their malignant phenotype. In the present study, we investigated the antitumor effect of a novel hypoxic cytotoxin, 3-[2-hydroxyethyl(methyl)amino]-2-quinoxalinecarbonitrile 1,4-dioxide (TX-2098) in inhibiting the expression of hypoxia inducible factor-1α (HIF-1α), and consequently vascular endothelial cell growth factor (VEGF) expression in pancreatic cancer. The antitumor effects of TX-2098 under hypoxia were tested against various human pancreatic cancer cell lines using WST-8 assay. VEGF protein induced pancreatic cancer was determined on cell-free supernatant by ELISA. Moreover, nude mice bearing subcutaneously (s.c.) or orthotopically implanted human SUIT-2 were treated with TX-2098. Tumor volume, survival and expression of HIF-1 and associated molecules were evaluated in treatment versus control groups. In vitro, TX-2098 inhibited the proliferation of various pancreatic cancer cell lines. In s.c model, tumors from nude mice injected with pancreatic cancer cells and treated with TX-2098 showed significant reductions in volume (P<0.01 versus control). Quantitative real-time reverse transcription-PCR analysis revealed that TX-2098 significantly inhibited mRNA expression of the HIF-1 associated molecules, VEGF, glucose transporter 1 and Aldolase A (P<0.01 versus control). These treatments also prolong the survival in orthotopic models. These results suggest that the effect of TX-2098 in pancreatic cancer might be correlated with the expression of VEGF and HIF-1 targeted molecules.

  9. Activation of the Akt-NF-kappaB pathway by subtilase cytotoxin through the ATF6 branch of the unfolded protein response.

    Science.gov (United States)

    Yamazaki, Hiroaki; Hiramatsu, Nobuhiko; Hayakawa, Kunihiro; Tagawa, Yasuhiro; Okamura, Maro; Ogata, Ryouji; Huang, Tao; Nakajima, Shotaro; Yao, Jian; Paton, Adrienne W; Paton, James C; Kitamura, Masanori

    2009-07-15

    Shiga toxin has the potential to induce expression of inflammation-associated genes, although the underlying mechanisms are not well understood. We examined the effects of subtilase cytotoxin (SubAB), an AB(5) toxin produced by some Shiga toxigenic Escherichia coli, on the activation of NF-kappaB. SubAB is known to be a protease which selectively degrades GRP78/Bip. Treatment of NRK-52E cells with SubAB caused rapid cleavage of GRP78. Following the degradation of GRP78, transient activation of NF-kappaB was observed with a peak at 6-12 h; the activation subsided within 24 h despite the continuous absence of intact GRP78. The activation of NF-kappaB was preceded by transient phosphorylation of Akt. Treatment of the cells with a selective inhibitor of Akt1/2 or an inhibitor of PI3K attenuated SubAB-induced NF-kappaB activation, suggesting that activation of Akt is an event upstream of NF-kappaB. Degradation of GRP78 caused the unfolded protein response (UPR), and inducers of the UPR mimicked the stimulatory effects of SubAB on Akt and NF-kappaB. SubAB triggered the three major branches of the UPR including the IRE1-XBP1, PERK, and ATF6 pathways. Dominant-negative inhibition of IRE1alpha, XBP1, or PERK did not attenuate activation of NF-kappaB by SubAB. In contrast, genetic and pharmacological inhibition of ATF6 significantly suppressed SubAB-triggered Akt phosphorylation and NF-kappaB activation. These results suggested that loss of GRP78 by SubAB leads to transient phosphorylation of Akt and consequent activation of NF-kappaB through the ATF6 branch of the UPR.

  10. Pseudomonas aeruginosa ExoT Induces Atypical Anoikis Apoptosis in Target Host Cells by Transforming Crk Adaptor Protein into a Cytotoxin.

    Science.gov (United States)

    Wood, Stephen; Goldufsky, Josef; Shafikhani, Sasha H

    2015-05-01

    Previously, we demonstrated that Pseudomonas aeruginosa ExoT induces potent apoptosis in host epithelial cells in a manner that primarily depends on its ADP-ribosyltransferase domain (ADPRT) activity. However, the mechanism underlying ExoT/ADPRT-induced apoptosis remains undetermined. We now report that ExoT/ADPRT disrupts focal adhesion sites, activates p38β and JNK, and interferes with integrin-mediated survival signaling; causing atypical anoikis. We show that ExoT/ADPRT-induced anoikis is mediated by the Crk adaptor protein. We found that Crk-/- knockout cells are significantly more resistant to ExoT-induced apoptosis, while Crk-/- cells complemented with Crk are rendered sensitive to ExoT-induced apoptosis. Moreover, a dominant negative (DN) mutant form of Crk phenocopies ExoT-induced apoptosis both kinetically and mechanistically. Crk is generally believed to be a component of focal adhesion (FA) and its role in cellular survival remains controversial in that it has been found to be either pro-survival or pro-apoptosis. Our data demonstrate that although Crk is recruited to FA sites, its function is likely not required for FA assembly or for survival per se. However, when modified by ExoT or by mutagenesis, it can be transformed into a cytotoxin that induces anoikis by disrupting FA sites and interfering with integrin survival signaling. To our knowledge, this is the first example whereby a bacterial toxin exerts its cytotoxicity by subverting the function of an innocuous host cellular protein and turning it against the host cell.

  11. Biochemical and pharmacological characterization of a toxic fraction and its cytotoxin-like component isolated from Russell's viper (Daboia russelii russelii) venom.

    Science.gov (United States)

    Thakur, Rupamoni; Chattopadhyay, Pronobesh; Mukherjee, Ashis K

    2015-02-01

    The pathophysiological significance of a toxic fraction (GF-VI DEAE-II) isolated from Russell's viper venom (RVV) is characterized. GF-VI DEAE-II represents 1.6% of the total RVV protein and it comprises of a 27.6kDa minor component (RP-I) (0.04%, w/w) and a major 6.6kDa non-enzymatic peptide (1.11%, w/w), named Rusvitoxin. The LC-MS/MS analysis of RP-I showed its identity to snake venom serine proteases, whereas Rusvitoxin demonstrated its close identity with snake venom three finger toxins, cytotoxins and cardiotoxins particularly from Naja sp. GF-VI DEAE-II was found to be non-cytotoxic to the tested mammalian cancer cells and non-hemolytic; nevertheless, it demonstrated α-fibrin(ogen)ase activity and in vivo toxicity in BALB/c mice with an LD50 (i.p.) of 2.3mg/kg. GF-VI DEAE-II induced lethargy and hind-leg paralysis in mice within 10min of i.p. injection. GF-VI DEAE-II induced hyperfibrinogenomia, and significantly altered (p<0.05) the plasma levels of factor X, pro- and anti-inflammatory cytokines viz. TNF-α, IL-6 and IL-10 in treated mice. Histological observations of tissues and biochemical properties of serum from GF-VI DEAE-II-treated mice suggested multiple organ dysfunctions. Conversely, Rusvitoxin at a dose of 5mg/kg did not induce toxicity in BALB/c mice. At 1:15 (antigen: antivenom, w/w) ratio, commercially polyvalent and monovalent antivenoms neutralized more than 80% of the fibrinolytic and anticoagulant activities of GF-VI DEAE-II. The present study suggests the significant role of GF-VI DEAE-II in RVV-induced pathogenesis in victim/prey.

  12. Targeting urokinase and the transferrin receptor with novel, anti-mitotic N-alkylisatin cytotoxin conjugates causes selective cancer cell death and reduces tumor growth.

    Science.gov (United States)

    Vine, K L; Indira Chandran, V; Locke, J M; Matesic, L; Lee, J; Skropeta, D; Bremner, J B; Ranson, M

    2012-01-01

    Tumor-specific delivery of ligand-directed prodrugs can increase the therapeutic window of chemotherapeutics by maintaining efficacy whilst decreasing toxic side effects. We have previously described a series of synthetic N-alkylated isatin cytotoxins that destabilize microtubules and induce apoptosis with 10-fold greater potency than conventional anti-mitotics in vitro. Here, we report the characterization, in vitro cytotoxicity and in vivo efficacy of a lead compound, 5,7-dibromo-N-(p-hydroxymethylbenzyl)isatin (N-AI) conjugated via an esterase-labile linker (N-AIE) to two proven targeting ligands, transferrin (Tf) and plasminogen activator inhibitor type 2 (PAI-2/serpinB2). N-AI was released from N-AIE and the targeting ligands Tf/PAI-2 in an esterase-dependent manner at 37 C and both Tf- and PAI-2-N-AIE conjugates were stable at physiological pH. Human cancer cell lines which vary in their expression levels of Tf receptor (TfR/CD71) and PAI-2 target, receptor bound urokinase (uPA) selectively internalized the conjugates. Tf-N-AIE was up to 24 times more active than the free drug and showed clear selectivity patterns based on TfR levels. PAI-2-N-AIE showed equivalent activity compared to the parent drug and strong selectivity patterns for uPA levels. In preliminary in vivo experiments, the PAI-2- and Tf-N-AIE conjugates were efficacious at 1/20(th) and 1/10(th) of the dose of the free N-AI, respectively, in a metastatic, orthotopic human breast tumor xenograft mouse model. Thus, this strategy specifically delivers and concentrates a novel class of isatin-based, tubulin destabilizing agents to tumors in vivo and warrants further detailed preclinical investigation.

  13. Relationship between the cytotoxin-associated gene-A status of H pylori strains and cerebral infarction in European Caucasians and Chinese Han: A meta-analysis

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    AIM: To study the relationship between the cytotoxin associated gene-A (CagA) status of H pylori strains and cerebral infarction among European Caucasians and Chinese Han by conducting a meta-analysis. METHODS: Ten case-control studies, with data on a total of 907 cases and 966 controls, were retrieved and considered; disqualified studies were excluded. The included studies were then tested for heterogeneity, and a meta-analysis was performed. RESULTS: The combined data revealed CagA-bearing strains of H pylori which cause chronic infection are associated with an increased risk of cerebral infarction (OR=2.66,95% CI:2. 17-3.26),but no such relationship was found with CagA-negative strains (OR =0.74,95% CI:0.49-1.10) in the overall population. We performed subgroup analyses, dividing the overall population into European Caucasians and Chinese Hart subgroups, and analyzed the studies according to their subgroup classification. Through the subgroup analysis, an association between cerebral infarction and CagA bearing strains was found in both subgroups (OR=2.60,95% CI:1.93-3.49 in Chinese Han; OR=2.71,95% CI:2.05-3.59 in European Caucasians),but no significant association was found between cerebral infarction and CagA-negative strains (OR=0.81,95% CI:0.45-1.48 in Chinese Han; OR=0.64,95% CI:0.37-1.09 in European Caucasians). CONCLUSION: These results suggest CagA-bearing strains of Hpylori are significantly associated with susceptibility to cerebral infarction in Chinese Han and European Caucasians, but that CagA-negative strains are not a definite predisposing factor in either subgroup. The magnitude of this association with cerebral infarction needs to be confirmed by prospective studies and combined studies of H pylori eradication.

  14. Orthogonal assembly of a designed ankyrin repeat protein-cytotoxin conjugate with a clickable serum albumin module for half-life extension.

    Science.gov (United States)

    Simon, Manuel; Frey, Raphael; Zangemeister-Wittke, Uwe; Plückthun, Andreas

    2013-11-20

    The generation of drug conjugates for safe and effective tumor targeting requires binding proteins tolerant to functionalization by rational engineering. Here, we show that Designed Ankyrin Repeat Proteins (DARPins), a novel class of binding proteins not derived from antibodies, can be used as building blocks for facile orthogonal assembly of bioconjugates for tumor targeting with tailored properties. DARPin Ec1, which targets the Epithelial Cell Adhesion Molecule (EpCAM), was genetically modified with a C-terminal cysteine for conjugation of the small molecule cytotoxin monomethylauristatin F (MMAF). In addition, it was N-terminally functionalized by metabolic introduction of the non-natural amino acid azidohomoalanine to enable linkage of site-specifically dibenzocyclooctyne-modified mouse serum albumin (MSA) for half-life extension using Cu(I)-free click chemistry. The conjugate MSA-Ec1-MMAF was assembled to obtain high yields of a pure and stable drug conjugate as confirmed by various analytical methods and in functional assays. The orthogonality of the assembly led to a defined reaction product and preserved the functional properties of all modules, including EpCAM-specific binding and internalization, FcRn binding mediated by MSA, and cytotoxic potency. Linkage of MMAF to the DARPin increased receptor-specific uptake of the drug while decreasing nonspecific uptake, and further coupling of the conjugate to MSA enhanced this effect. In mice, albumin conjugation increased the serum half-life from 11 min to 17.4 h, resulting in a more than 22-fold increase in the area-under-the-curve (AUC). Our data demonstrate the promise of the DARPin format for facile modular assembly of drug conjugates with improved pharmacokinetic performance for tumor targeting.

  15. Reevaluation of the Premier Clostridium difficile toxin A and B immunoassay with comparison to glutamate dehydrogenase common antigen testing evaluating Bartels cytotoxin and Prodesse ProGastro Cd polymerase chain reaction as confirmatory procedures.

    Science.gov (United States)

    Doing, Kirk M; Hintz, Marilyn S; Keefe, Calvin; Horne, Sarah; LeVasseur, Shelby; Kulikowski, Martha L

    2010-02-01

    Enzyme immunoassays are currently the most common tests used in the clinical laboratory for the detection of Clostridium difficile toxins; however, significant problems with their performance have recently been described. We prospectively reevaluated the Meridian Premier C. difficile toxin A/B assay with direct comparison to a 2-step algorithm that screened for C. difficile common antigen and compared cytotoxin and real-time polymerase chain reaction (PCR) as confirmatory procedures. The Premier assay lacked sufficient sensitivity, missing 25% of true-positive samples. PCR was the most sensitive method and the only procedure that allowed same day testing and reporting.

  16. the versatility of the Helicobacter pylori vacuolating cytotoxin vacA in signal transduction and molecular crosstalk.

    Science.gov (United States)

    Backert, Steffen; Tegtmeyer, Nicole

    2010-01-01

    By modulating important properties of eukaryotic cells, many bacterial protein toxins highjack host signalling pathways to create a suitable niche for the pathogen to colonize and persist. Helicobacter pylori VacA is paradigm of pore-forming toxins which contributes to the pathogenesis of peptic ulceration. Several cellular receptors have been described for VacA, which exert different effects on epithelial and immune cells. The crystal structure of VacA p55 subunit might be important for elucidating details of receptor interaction and pore formation. Here we discuss the multiple signalling activities of this important toxin and the molecular crosstalk between VacA and other virulence factors.

  17. Low p-type contact resistance by field-emission tunneling in highly Mg-doped GaN

    Science.gov (United States)

    Okumura, Hironori; Martin, Denis; Grandjean, Nicolas

    2016-12-01

    Mg-doped GaN with a net acceptor concentration (NA-ND) in the high 1019 cm-3 range was grown using ammonia molecular-beam epitaxy. Electrical properties of NiO contact on this heavily doped p-type GaN were investigated. A potential-barrier height of 0.24 eV was extracted from the relationship between NA-ND and the specific contact resistivity (ρc). We found that there is an optimum NA-ND value of 5 × 1019 cm-3 for which ρc is as low as 2 × 10-5 Ω cm2. This low ρc is ascribed to hole tunneling through the potential barrier at the NiO/p+-GaN interface, which is well accounted for by the field-emission model.

  18. Expression of a prokaryotic P-type ATPase in E. coli Plasma Membranes and Purification by Ni2+-affinity chromatography

    Directory of Open Access Journals (Sweden)

    Geisler Markus

    1998-01-01

    Full Text Available In order to characterize the P-type ATPase from Synechocystis 6803 [Geisler (1993 et al. J. Mol. Biol. 234, 1284] and to facilitate its purification, we expressed an N-terminal 6xHis-tagged version of the ATPase in an ATPase deficient E. coli strain. The expressed ATPase was immunodetected as a dominant band of about 97 kDa localized to the E. coli plasma membranes representing about 20-25% of the membrane protein. The purification of the Synecho-cystis 6xHis-ATPase by single-step Ni-affinity chromatography under native and denaturating conditions is described. ATPase activity and the formation of phosphointermediates verify the full function of the enzyme: the ATPase is inhibited by vanadate (IC50= 119 &mgr;M and the formation of phosphorylated enzyme intermediates shown by acidic PAGE depends on calcium, indicating that the Synechocystis P-ATPase functions as a calcium pump.

  19. Effect of Y (Yttrium) Filling Fraction on Thermoelectric Properties of p-type Yy Fex Co4-x Sb12

    Institute of Scientific and Technical Information of China (English)

    TANG Xinfeng; SONG Bo; ZHANG Qingjie

    2006-01-01

    Yttrium-filled skutterndites YyFex Co4-x Sb12 ( y= 0-0.40) were syrthesized. The effect of Y filling fraction on thermoelectric properties of YyFexCo4-xSb12 was investigated. All samples showed p-type conduct. The electrical conductivity decreased with increasing filling fraction y . The Seebeck coefficient increased with increasing temperature. The lattice thermal conductivity decreased with increasing filling fraction y and showed the minimum value at a certain filling fraction y = 0.3. The effect of different filling atoms M( M: Ba, Ce, Y) on the lattice thermal conductivity of MyFex Co4- x Sb12 was discussed. The maximum ZT value of 0.7 was obtained for Y0.08 Fe0.7 Co3.3 Sb12 at 750 K.

  20. Effect of Etching Time on Optical and Thermal Properties of p-Type Porous Silicon Prepared by Electrical Anodisation Method

    Directory of Open Access Journals (Sweden)

    Kasra Behzad

    2012-01-01

    Full Text Available The porous silicon (PSi layers were formed on p-type silicon (Si wafer. The six samples were anodised electrically with 30 mA/cm2 fixed current density for different etching times. The structural, optical, and thermal properties of porous silicon on silicon substrates were investigated by photoluminescence (PL, photoacoustic spectroscopy (PAS, and UV-Vis-NIR spectrophotometer. The thickness and porosity of the layers were measured using the gravimetric method. The band gap of the samples was measured through the photoluminescence (PL peak and absorption spectra, then they were compared. It shows that band gap value increases by raising the porosity. Photoacoustic spectroscopy (PAS was carried out for measuring the thermal diffusivity (TD of the samples.

  1. Very low surface recombination velocities on p-type silicon wafers passivated with a dielectric with fixed negative charge

    Energy Technology Data Exchange (ETDEWEB)

    Agostinelli, G.; Delabie, A.; Dekkers, H.F.W.; De Wolf, S.; Beaucarne, G. [IMEC vzw, Kapeldreef 75, Leuven (Belgium); Vitanov, P.; Alexieva, Z. [CL SENES, Sofia (Bulgaria)

    2006-11-23

    Surface recombination velocities as low as 10cm/s have been obtained by treated atomic layer deposition (ALD) of Al{sub 2}O{sub 3} layers on p-type CZ silicon wafers. Low surface recombination is achieved by means of field induced surface passivation due to a high density of negative charges stored at the interface. In comparison to a diffused back surface field, an external field source allows for higher band bending, that is, a better performance. While this process yields state of the art results, it is not suited for large-scale production. Preliminary results on an industrially viable, alternative process based on a pseudo-binary system containing Al{sub 2}O{sub 3} are presented, too. With this process, surface recombination velocities of 500-1000cm/s have been attained on mc-Si wafers. (author)

  2. Reliability tests of electroless barriers against copper diffusion under bias-temperature stress with n- and p-type substrates

    Science.gov (United States)

    Ueno, Kazuyoshi; Fujishima, Shota; Yamashita, Makoto; Mitsumori, Akiyoshi

    2016-05-01

    To investigate the similarity and difference of substrate conduction type in the time-dependent dielectric breakdown (TDDB) tests for the barrier integrity against Cu diffusion under bias-temperature stress (BTS), the TDDB reliability of electroless NiB and CoWP/NiB was determined by metal oxide semiconductor (MOS) structures on n-type Si (n-Si) substrates, and the test results were compared with those using p-type Si (p-Si) substrates. The TDDB results and mechanism were observed to be qualitatively the same as Cu diffusion for both conduction types. However, the TDDB lifetime using p-Si was found to be potentially shorter because of the reverse bias conditions than that using n-Si under the forward bias conditions.

  3. Large-Scale Surfactant-Free Synthesis of p-Type SnTe Nanoparticles for Thermoelectric Applications

    Directory of Open Access Journals (Sweden)

    Guang Han

    2017-02-01

    Full Text Available A facile one-pot aqueous solution method has been developed for the fast and straightforward synthesis of SnTe nanoparticles in more than ten gram quantities per batch. The synthesis involves boiling an alkaline Na2SnO2 solution and a NaHTe solution for short time scales, in which the NaOH concentration and reaction duration play vital roles in controlling the phase purity and particle size, respectively. Spark plasma sintering of the SnTe nanoparticles produces nanostructured compacts that have a comparable thermoelectric performance to bulk counterparts synthesised by more time- and energy-intensive methods. This approach, combining an energy-efficient, surfactant-free solution synthesis with spark plasma sintering, provides a simple, rapid, and inexpensive route to p-type SnTe nanostructured materials.

  4. Identifying individual n- and p-type ZnO nanowires by the output voltage sign of piezoelectric nanogenerator

    Energy Technology Data Exchange (ETDEWEB)

    Lin, S S; Song, J H; Wang, Z L [School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332 (United States); Lu, Y F, E-mail: zlwang@gatech.ed [State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou, 310027 (China)

    2009-09-09

    Based on a comparative study between the piezoelectric outputs of n-type nanowires (NWs) and n-core/p-shell NWs along with the previous study (Lu et al 2009 Nano. Lett. 9 1223), we demonstrate a one-step technique for identifying the conductivity type of individual ZnO nanowires (NWs) based on the output of a piezoelectric nanogenerator without destroying the sample. A negative piezoelectric output voltage indicates an NW is n-type and it appears after the tip scans across the center of the NW, while a positive output voltage reveals p-type conductivity and it appears before the tip scans across the central line of the NW. This atomic force microscopy based technique is reliable for statistically mapping the majority carrier type in ZnO NWs arrays. The technique may also be applied to other wurtzite semiconductors, such as GaN, CdS and ZnS.

  5. Characterization of micro-strip detectors made with high resistivity n- and p-type Czochralski silicon

    Energy Technology Data Exchange (ETDEWEB)

    Macchiolo, A. [INFN and Universita degli Studi di Florence (Italy)]. E-mail: Anna.Macchiolo@fi.infn.it; Borrello, L. [INFN and Universita degli Studi di Pisa (Italy); Boscardin, M. [ITC-IRST Trento, Povo, Trento (Italy); Bruzzi, M. [INFN and Universita degli Studi di Florence (Italy); Creanza, D. [INFN and Dipartimento Interateneo di Fisica, Bari (Italy); Dalla Betta, G.-F. [ITC-IRST Trento, Povo, Trento (Italy); DePalma, M. [INFN and Dipartimento Interateneo di Fisica, Bari (Italy); Focardi, E. [INFN and Universita degli Studi di Florence (Italy); Manna, N. [INFN and Dipartimento Interateneo di Fisica, Bari (Italy); Menichelli, D. [INFN and Universita degli Studi di Florence (Italy); Messineo, A. [INFN and Universita degli Studi di Pisa (Italy); Piemonte, C. [ITC-IRST Trento, Povo, Trento (Italy); Radicci, V. [INFN and Dipartimento Interateneo di Fisica, Bari (Italy); Ronchin, S. [ITC-IRST Trento, Povo, Trento (Italy); Scaringella, M. [INFN and Universita degli Studi di Florence (Italy); Segneri, G. [INFN and Universita degli Studi di Pisa (Italy); Sentenac, D. [INFN and Universita degli Studi di Pisa (Italy); Zorzi, N. [ITC-IRST Trento, Povo, Trento (Italy)

    2007-04-01

    The results of the pre- and post-irradiation characterization of n- and p-type magnetic Czochralski silicon micro-strip sensors are reported. This work has been carried out within the INFN funded SMART project aimed at the development of radiation-hard semiconductor detectors for the luminosity upgrade of the large Hadron collider (LHC). The detectors have been fabricated at ITC-IRST (Trento, Italy) on 4 in wafers and the layout contains 10 mini-sensors. The devices have been irradiated with 24 GeV/c and 26 MeV protons in two different irradiation campaigns up to an equivalent fluence of 3.4x10{sup 15} 1-MeV n/cm{sup 2}. The post-irradiation results show an improved radiation hardness of the magnetic Czochralski mini-sensors with respect to the reference float-zone sample.

  6. Identifying individual n- and p-type ZnO nanowires by the output voltage sign of piezoelectric nanogenerator

    KAUST Repository

    Lin, S S

    2009-08-18

    Based on a comparative study between the piezoelectric outputs of n-type nanowires (NWs) and n-core/p-shell NWs along with the previous study (Lu et al 2009 Nano. Lett. 9 1223), we demonstrate a one-step technique for identifying the conductivity type of individual ZnO nanowires (NWs) based on the output of a piezoelectric nanogenerator without destroying the sample. A negative piezoelectric output voltage indicates an NW is n-type and it appears after the tip scans across the center of the NW, while a positive output voltage reveals p-type conductivity and it appears before the tip scans across the central line of the NW. This atomic force microscopy based technique is reliable for statistically mapping the majority carrier type in ZnO NWs arrays. The technique may also be applied to other wurtzite semiconductors, such as GaN, CdS and ZnS. © 2009 IOP Publishing Ltd.

  7. Understanding the effect of $n$-type and $p$-type doping in the channel of graphene nanoribbon transistor

    Indian Academy of Sciences (India)

    SUDHANSHU CHOUDHARY; VIKRAM SINGH

    2016-09-01

    In this paper, device performance of graphene nanoribbon field effect transistor (GNRFET) with different doping concentrations in different parts of the channel is reported. The study is performed by using atomistic simulations based on self-consistent solution of Schrodinger’s and Poisson’s equation within the non-equilibrium Green’s function formalism. The transfer and output characteristics suggest that device performance with $n$-type doping in the channel is better with smaller supply voltage compared to higher supply voltage. On increasing the $n$-type doping concentration, we obtained better on-current and output characteristics in comparison with undoped and $p$-type doped channel GNRFET. Further, we introduced step-doping profile in the graphene nanoribbon (GNR) channel and found that the device gives better on-current and good saturation condition when compared to undoped or uniformly-doped channel.

  8. The fabrication of Na doped p-type Zn1- x Mg x O films by pulsed laser deposition

    Science.gov (United States)

    Zhang, L. Q.; Zhang, Y. Z.; Ye, Z. Z.; Lin, S. S.; Lu, B.; He, H. P.; Chen, L. X.; Lu, J. G.; Jiang, J.; Wu, K. W.; Huang, J. Y.; Zhu, L. P.

    2012-01-01

    P-type Zn1- x Mg x O (0≤ x≤0.25) films are obtained through Na doping, as confirmed by repeated Hall-effect measurements and rectification behavior of p-Zn0.81Mg0.19O:Na/ n-Zn0.8Mg0.2O:Al quasi-homojunctions. The absorption and photoluminescence spectra indicate the band gap shifts to higher energy in linearly proportional to Mg content. Critically, X-ray diffraction (XRD) patterns reveal that the strain induced by Na doping can be counteracted through an appropriate content of Mg alloying. Both XRD data and Hall-effect data imply that the solubility of Na acceptor should be enhanced by alloying with Mg. The X-ray photoelectron spectrum (XPS) result indicates the existence of Na. Microstructure structure of the film is confirmed by high-resolution transmission electron microscope.

  9. Primary defect transformations in high-resistivity p-type silicon irradiated with electrons at cryogenic temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Makarenko, L.F., E-mail: makarenko@bsu.b [Department of Applied Mathematics and Computer Science, Belarusian State University, Independence Ave. 4, 220030 Minsk (Belarus); Lastovski, S.B.; Korshunov, F.P.; Murin, L.I. [Scientific-Practical Materials Research Centre of NAS of Belarus, Minsk (Belarus); Moll, M. [CERN, Geneva (Switzerland)

    2009-12-15

    It has been revealed that self-interstitials formed under low intensity electron irradiation in high resistivity p-type silicon can be retained frozen up to room temperature. Low thermal mobility of the self-interstitials suggests that Frenkel pairs in silicon can be stable at temperatures of about or higher than 100 K. A broad DLTS peak with activation energy of 0.14-0.17 eV can be identified as related to Frenkel pairs. This peak anneals out at temperatures of 120-140 K. Experimental evidences are presented that becoming more mobile under forward current injection the self-interstitials change their charge state to a less positive one.

  10. Selective growth of n-type nanoparticles on p-type semiconductors for Z-scheme photocatalysis.

    Science.gov (United States)

    Miyauchi, Masahiro; Nukui, Yuuya; Atarashi, Daiki; Sakai, Etsuo

    2013-10-09

    Nanoparticles of an n-type WO3 semiconductor were segregated on the surface of p-type CaFe2O4 particles by a heterogeneous nucleation process under controlled hydrothermal conditions. By use of this approach, WO3 nanoparticles were selectively deposited on the surface of CaFe2O4, resulting in a significant increase in the photocatalytic reaction rate of the WO3/CaFe2O4 composite for the decomposition of gaseous acetaldehyde under visible-light irradiation. The high visible-light activity of the WO3/CaFe2O4 composite was due to efficient charge recombination through the junctions that formed between the two semiconductors.

  11. Design and analysis of nanowire p-type MOSFET coaxially having silicon core and germanium peripheral channel

    Science.gov (United States)

    Yu, Eunseon; Cho, Seongjae

    2016-11-01

    In this work, a nanowire p-type metal-oxide-semiconductor field-effect transistor (PMOSFET) coaxially having a Si core and a Ge peripheral channel is designed and characterized by device simulations. Owing to the high hole mobility of Ge, the device can be utilized for high-speed CMOS integrated circuits, with the effective confinement of mobile holes in Ge by the large valence band offset between Si and Ge. Source/drain doping concentrations and the ratio between the Si core and Ge channel thicknesses are determined. On the basis of the design results, the channel length is aggressively scaled down by evaluating the primary DC parameters in order to confirm device scalability and low-power applicability in sub-10-nm technology nodes.

  12. Energy and angular anisotropy optimisation of a p-type diode for in vivo dosimetry in photon-beam radiotherapy.

    Science.gov (United States)

    Greene, Simon; Price, Robert A

    2005-01-01

    We present simulation work using the Monte Carlo code MCNPX that shows that there is a possibility of improving the silicon p-type diode as a radiation dosemeter, by altering the construction of the diode. Altering the diode die thickness can reduce the inherent angular anisotropy of the diode, with little effect on its energy response. Conversely, the contact material and geometry have a large impact on the energy response with little effect on the inherent angular anisotropy. By correct choice of contact material, the typical over-response -100 keV relative to the response at 60Co energy can be reduced from approximately 20 to 4. It is expected that further enhancements may be made with different geometries and materials.

  13. Electronic structure of p type Delta doped systems; Estructura electronica de sistemas dopadas con Delta de tipo p

    Energy Technology Data Exchange (ETDEWEB)

    Gaggero S, L.M.; Perez A, R. [Departamento de Fisica de los Materiales, Universidad Nacional de Educacion a Distancia, Senda del Rey s/n, 28040 Madrid (Spain)

    1998-12-31

    We summarize of the results obtained for the electronic structure of quantum wells that consist in an atomic layer doped with impurities of p type. The calculations are made within the frame worth of the wrapper function approach to independent bands and with potentials of Hartree. We study the cases reported experimentally (Be in GaAs and B in Si). We present the levels of energy, the wave functions and the rate of the electronic population between the different subbands, as well as the dependence of these magnitudes with the density of impurities in the layer. The participation of the bans of heavy holes is analysed, light and split-off band in the total electronic population. The effect of the temperature is discussed and we give a possible qualitative explanation of the experimental optical properties. (Author)

  14. Multistrip synthetic single-crystal-diamond photodiode based on a p-type/intrinsic/Schottky metal transverse configuration

    Science.gov (United States)

    Ciancaglioni, I.; Marinelli, Marco; Milani, E.; Prestopino, G.; Verona, C.; Verona-Rinati, G.; Angelone, M.; Pillon, M.; Dolbnya, I.; Sawhney, K.; Tartoni, N.

    2011-04-01

    A synthetic multistrip single-crystal-diamond detector based on a p-type/intrinsic diamond/Schottky metal transverse configuration, operating at zero-bias voltage, was developed. The device was characterized at the Diamond Light Source synchrotron in Harwell (UK) under monochromatic high-flux X-ray beams from 6 to 20 keV and a micro-focused 10 keV beam with a spot size of ~3 μm. No significant pixel-to-pixel variation of both spectral responsivity and time response, high spatial resolution and good signal uniformity along each strip were found, suggesting the tested device structure as a promising sensor for X-ray and UV radiation imaging.

  15. Investigations of nanoreactors on the basis of p-type porous silicon: Electron structure and phase composition

    Energy Technology Data Exchange (ETDEWEB)

    Lenshin, A.S. [Voronezh State University, Solid State Physics and Nanostructures Department, Universitetskaya pl. 1, Voronezh 394006 (Russian Federation); Kashkarov, V.M., E-mail: kash@phys.vsu.ru [Voronezh State University, Solid State Physics and Nanostructures Department, Universitetskaya pl. 1, Voronezh 394006 (Russian Federation); Spivak, Yu. M. [SPbGETU ' LETI' , Department of Microelectronics (Russian Federation); Moshnikov, V.A., E-mail: vamoshnikov@mail.ru [SPbGETU ' LETI' , Department of Microelectronics (Russian Federation)

    2012-08-15

    Investigations of the electron structure and phase composition of the surface layers in porous silicon with a developed system of nanopores were made with the use of ultrasoft X-ray spectroscopy and X-ray photoelectron spectroscopy. The samples of porous silicon were obtained on the substrates with p-type conductivity under different modes of electrochemical etching. Porous surface layer represents a system of weakly connected pores oriented mainly perpendicular to the surface of silicon wafer. The mean transverse pore dimension is of {approx}50 nm. Silicon dioxide and sub-oxide were found in porous layer. We assume that these phases cover pores surface thus providing a possibility of the use of the structures as nanoreactors. -- Highlights: Black-Right-Pointing-Pointer Nanoporous silicon layers were obtained. Black-Right-Pointing-Pointer A system of weakly connected pores was detected. Black-Right-Pointing-Pointer Electron structure and phase composition of the surface layers in porous silicon were investigated.

  16. High temperature thermoelectric properties of p-type skutterudites BaxYbyCo4-zFezSb12

    KAUST Repository

    Dong, Y.

    2012-01-01

    Several polycrystalline p-type skutterudites with compositions Ba xYb yCo 4-zFe zSb 12, with varying filler concentrations x and y, and z = 1 to 2, were synthesized by reacting the constituents and subsequent solid state annealing, followed by densification by hot-pressing. Their thermoelectric properties were evaluated from 300 to 820 K. The Yb filling fraction increased with Fe content while the amount of Fe substitution had little influence on the Ba filling fraction. High purity specimens were obtained when the Fe content was low. Bipolar conduction contributed to the thermal conductivity at elevated temperatures. A maximum ZT value of 0.7 was obtained at 750 K for the specimen with the highest Fe content and filling fraction. The potential for thermoelectric applications is also discussed. © 2012 American Institute of Physics.

  17. P型多系统萎缩的MRI表现%MRI Features of Multiple System Atrophy P Type

    Institute of Scientific and Technical Information of China (English)

    邝岚琼; 王小宜; 邢妩; 廖伟华; 谢芳芳; 那伟

    2012-01-01

    Objective To analyze the MRI features of the multiple system atrophy ( MSA) P,in order to provide ima-geology basis for clinical diagnosis. Materials and Methods MRI findings in 9 patients with MSA P type( parkinsonism in dominant multiple system atrophy) in XiangYa Hospital were analyzed retrospectively. Results Of 9 patients, 6 had abnormal findings in putamen, 4 had putamen atrophy, 2 had the long T2 signal of the putamen edge ( fissure sign) , and 3 had the putamen diffuse little long T1 & T2 signals, and 4 had the very long T, & very short T2 signals in outer back of putamen. Moreover, among these 6 patients, there was one case merely featured in the putamen atrophy and one in the very long T1 & very short T2 signal in the outer back of putamen, and the other 4 cases were found the abnormal changes in a variety of core shell overlap there. There were 5 cases of brain stem abnormalities, one with cross sign, and four with the whole brain stem atrophy (two were found the little long T1 & T2 signal concerning symmetry of the cerebellum feet). Hemisphere abnormalities were found in 3 cases, 3 cases of them were the atrophy of both bilateral frontal temporal parietal oc-cipitals, 2 cases atrophy of bilateral frontal lobes. Cerebellar hemisphere atrophy was found in two cases. Cross sign was found in late MSA P type,and FLAIR sequences facilitate the detection of abnormal signal. Conclusion MRI facilitates the clinical diagnosis of MSA P type.%目的 分析P型多系统萎缩(multiple system atrophy,MSA)的MRI特征,为临床诊断提供影像学依据.资料与方法 回顾性分析经临床诊断为MSA-P型9例患者的常规MRI资料.结果 9例中,6例壳核有异常发现,其中壳核萎缩4例,壳核边缘长T2信号(裂隙征)2例,壳核弥漫性稍长T1、稍长T2信号3例,壳核后外侧极长T1、极短T2信号4例.6例中,单纯表现为壳核萎缩及壳核后外侧极长T1、极短T2信号各1例,余4例为多种壳核异常改变重叠出现.5例脑

  18. Purification, crystallization and preliminary X-ray structural studies of a 7.2 kDa cytotoxin isolated from the venom of Daboia russelli russelli of the Viperidae family

    Energy Technology Data Exchange (ETDEWEB)

    Roy Choudhury, Subhasree [Department of Physiology, University of Calcutta, 92 Acharya Prafulla Chandra Road, Kolkata 700 009 (India); Gomes, Aparna [New Drug Development Division, Indian Institute Of Chemical Biology, 4 Raja S. C. Mallick Road, Kolkata 700 032 (India); Gomes, Antony [Department of Physiology, University of Calcutta, 92 Acharya Prafulla Chandra Road, Kolkata 700 009 (India); Dattagupta, Jiban K.; Sen, Udayaditya, E-mail: udayaditya.sen@saha.ac.in [Crystallography and Molecular Biology Division, Saha Institute of Nuclear Physics, 1/AF Bidhan Nagar, Kolkata 700 064 (India); Department of Physiology, University of Calcutta, 92 Acharya Prafulla Chandra Road, Kolkata 700 009 (India)

    2006-03-01

    A cytotoxin from Indian Russell’s viper (D. russelli russelli) venom having multifunctional activity has been crystallized in space group P4{sub 1}. Larger crystals diffracted to 1.5 Å but were found to be twinned; preliminary data were therefore collected (2.93 Å) from a smaller crystal. A cytotoxin (MW 7.2 kDa) from Indian Russell’s viper (Daboia russelli russelli) venom possessing antiproliferative activity, cardiotoxicity, neurotoxicity and myotoxicity has been purified, characterized and crystallized. The crystals belong to the tetragonal space group P4{sub 1}, with unit-cell parameters a = b = 47.94, c = 50.2 Å. Larger crystals, which diffracted to 1.5 Å, were found to be twinned; diffraction data were therefore collected to 2.93 Å resolution using a smaller crystal. Molecular-replacement calculations identified two molecules of the protein in the asymmetric unit, which is in accordance with the calculated V{sub M} value.

  19. In situ monitoring of stacking fault formation and its carrier lifetime mediation in p-type 4H-SiC

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Bin, E-mail: chenbinmse@gmail.com; Chen, Jun; Yao, Yuanzhao; Sekiguchi, Takashi [National Institute for Materials Science, Tsukuba, Ibaraki 305-0044 (Japan); Matsuhata, Hirofumi; Okumura, Hajime [National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8568 (Japan)

    2014-07-28

    Using the fine control of an electron beam (e-beam) in scanning electron microscopy with the capabilities of both electrical and optical imaging, the stacking fault (SF) formation together with its tuning of carrier lifetime was in situ monitored and investigated in p-type 4H-SiC homoepitaxial films. The SFs were formed through engineering basal plane dislocations with the energy supplied by the e-beam. The e-beam intensity required for the SF formation in the p-type films was ∼100 times higher than that in the n-type ones. The SFs reduced the minority-carrier lifetime in the p-type films, which was opposite to that observed in the n-type case. The reason for the peculiar SF behavior in the p-type 4H-SiC is discussed with the cathodoluminescence results.

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

    National Research Council Canada - National Science Library

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

    2015-01-01

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

  1. Effective surface passivation of p-type crystalline silicon with silicon oxides formed by light-induced anodisation

    Energy Technology Data Exchange (ETDEWEB)

    Cui, Jie, E-mail: j.cui@unsw.edu.au [School of Photovoltaic and Renewable Energy Engineering, The University of New South Wales, Sydney 2052 (Australia); Grant, Nicholas [Centre for Sustainable Energy Systems, Australian National University, Canberra, A.C.T. 0200 (Australia); Lennon, Alison [School of Photovoltaic and Renewable Energy Engineering, The University of New South Wales, Sydney 2052 (Australia)

    2014-12-30

    Highlights: • The surface passivation by anodic SiO{sub 2} formed by light-induced anodisation is investigated. • The anodic SiO{sub 2} grows lower temperatures with shorter growth times. After annealing in oxygen and then forming gas the effective minority carrier lifetime is increased to 150 μs. • It shows a very low positive Q{sub eff} of 3.4 × 10{sup 11} cm{sup −2}, a moderate D{sub it} of 6 × 10{sup 11} eV{sup −1} cm{sup −2}. • It has a very low leakage current density suggesting its application in solar cell as a functional dielectric. - Abstract: Electronic surface passivation of p-type crystalline silicon by anodic silicon dioxide (SiO{sub 2}) was investigated. The anodic SiO{sub 2} was grown by light-induced anodisation (LIA) in diluted sulphuric acid at room temperature, a process that is significantly less-expensive than thermal oxidation which is widely-used in silicon solar cell fabrication. After annealing in oxygen and then forming gas at 400 °C for 30 min, the effective minority carrier lifetime of 3–5 Ω cm, boron-doped Czochralski silicon wafers with a phosphorus-doped 80 Ω/□ emitter and a LIA anodic SiO{sub 2} formed on the p-type surface was increased by two orders of magnitude to 150 μs. Capacitance–voltage measurements demonstrated a very low positive charge density of 3.4 × 10{sup 11} cm{sup −2} and a moderate density of interface states of 6 × 10{sup 11} eV{sup −1} cm{sup −2}. This corresponded to a silicon surface recombination velocity of 62 cm s{sup −1}, which is comparable with values reported for other anodic SiO{sub 2} films, which required higher temperatures and longer growth times, and significantly lower than oxides grown by chemical vapour deposition techniques. Additionally, a very low leakage current density of 3.5 × 10{sup −10} and 1.6 × 10{sup −9} A cm{sup −2} at 1 and −1 V, respectively, was measured for LIA SiO{sub 2} suggesting its potential application as insulation layer in

  2. Investigation of Landau level spin reversal in (110) oriented p-type GaAs quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    Isik, Nebile

    2009-09-01

    In this thesis, the Landau level crossing or anticrossing of hole levels has been investigated in p-type GaAs 400 Aa wide quantum wells. In magneto-transport measurements, this is evidenced with the presence of an anomalous peak in the longitudinal resistance measurements at {nu}=1. In the transversal resistance measurements, no signature of this anomalous peak is observed. By increasing the hole density in the quantum well by applying a top gate voltage, the position of the anomalous peak shifts to higher magnetic fields. At very high densities, anomalous peak disappears. By applying a back gate voltage, the electric field in the quantum well is tuned. A consequence is that the geometry of the quantum well is tuned from square to triangular. The anomalous peak position is shown to depend also on the back gate voltage applied. Temperature dependence of the peak height is consistent with thermal activation energy gap ({delta}/2= 135 {mu}eV). The activation energy gap as a function of the magnetic field has a parabolic like dependence, with the minimum of 135 {mu}eV at 4 T. The peak magnitude is observed to decrease with increasing temperature. An additional peak is observed at {nu}=2 minimum. This additional peak at {nu}=2 might be due to the higher Landau level crossing. The p-type quantum wells have been investigated by photoluminescence spectroscopy, as a function of the magnetic field. The polarization of the emitted light has been analyzed in order to distinguish between the transitions related to spin of electron {+-} 1/2 and spin of hole -+ 3/2. The transition energies of the lowest electron Landau levels with spin {+-} 1/2 and hole Landau levels with spin -+ 3/2 versus magnetic field show crossing at 4 T. The heavy hole Landau levels with spins {+-} 3/2 are obtained by the substraction of transition energies from the sum of lowest electron Landau level energy and the energy gap of GaAs. The heavy hole Landau levels show a crossing at 4 T. However, due to the

  3. Optical and Electrical Effects of p-type μc-SiOx:H in Thin-Film Silicon Solar Cells on Various Front Textures

    Directory of Open Access Journals (Sweden)

    Chao Zhang

    2014-01-01

    Full Text Available p-type hydrogenated microcrystalline silicon oxide (µc-SiOx:H was developed and implemented as a contact layer in hydrogenated amorphous silicon (a-Si:H single junction solar cells. Higher transparency, sufficient electrical conductivity, low ohmic contact to sputtered ZnO:Al, and tunable refractive index make p-type µc-SiOx:H a promising alternative to the commonly used p-type hydrogenated microcrystalline silicon (µc-Si:H contact layers. In this work, p-type µc-SiOx:H layers were fabricated with a conductivity of up to 10−2 S/cm and a Raman crystallinity of above 60%. Furthermore, we present p-type µc-SiOx:H films with a broad range of optical properties (2.1 eV < band gap E04<2.8 eV and 1.6 < refractive index n<2.6. These properties can be tuned by adapting deposition parameters, for example, the CO2/SiH4 deposition gas ratio. A conversion efficiency improvement of a-Si:H solar cells is achieved by applying p-type µc-SiOx:H contact layer compared to the standard p-type µc-Si:H contact layer. As another aspect, the influence of the front side texture on a-Si:H p-i-n solar cells with different p-type contact layers, µc-Si:H and µc-SiOx:H, is investigated. Furthermore, we discuss the correlation between the decrease of Voc and the cell surface area derived from AFM measurements.

  4. The novel hypoxic cytotoxin, TX-2098 has antitumor effect in pancreatic cancer; possible mechanism through inhibiting VEGF and hypoxia inducible factor-1{alpha} targeted gene expression

    Energy Technology Data Exchange (ETDEWEB)

    Miyake, Kotaro, E-mail: hif.panc@gmail.com [Department of Surgery, Institute of Health Biosciences, The University of Tokushima Graduate School, Tokushima 770-8503 (Japan); Nishioka, Masanori; Imura, Satoru; Batmunkh, Erdenebulgan [Department of Surgery, Institute of Health Biosciences, The University of Tokushima Graduate School, Tokushima 770-8503 (Japan); Uto, Yoshihiro [Department of Biological Science and Technology, Institute of Socio Technosciences, The University of Tokushima Graduate School, Tokushima 770-8503 (Japan); Nagasawa, Hideko [Laboratory of Pharmaceutical and Medicinal Chemistry, Gifu Pharmaceutical University, Gifu 501-1196 (Japan); Hori, Hitoshi [Department of Biological Science and Technology, Institute of Socio Technosciences, The University of Tokushima Graduate School, Tokushima 770-8503 (Japan); Shimada, Mitsuo [Department of Surgery, Institute of Health Biosciences, The University of Tokushima Graduate School, Tokushima 770-8503 (Japan)

    2012-08-01

    Tumor hypoxia has been considered to be a potential therapeutic target, because hypoxia is a common feature of solid tumors and is associated with their malignant phenotype. In the present study, we investigated the antitumor effect of a novel hypoxic cytotoxin, 3-[2-hydroxyethyl(methyl)amino]-2-quinoxalinecarbonitrile 1,4-dioxide (TX-2098) in inhibiting the expression of hypoxia inducible factor-1{alpha} (HIF-1{alpha}), and consequently vascular endothelial cell growth factor (VEGF) expression in pancreatic cancer. The antitumor effects of TX-2098 under hypoxia were tested against various human pancreatic cancer cell lines using WST-8 assay. VEGF protein induced pancreatic cancer was determined on cell-free supernatant by ELISA. Moreover, nude mice bearing subcutaneously (s.c.) or orthotopically implanted human SUIT-2 were treated with TX-2098. Tumor volume, survival and expression of HIF-1 and associated molecules were evaluated in treatment versus control groups. In vitro, TX-2098 inhibited the proliferation of various pancreatic cancer cell lines. In s.c model, tumors from nude mice injected with pancreatic cancer cells and treated with TX-2098 showed significant reductions in volume (P < 0.01 versus control). Quantitative real-time reverse transcription-PCR analysis revealed that TX-2098 significantly inhibited mRNA expression of the HIF-1 associated molecules, VEGF, glucose transporter 1 and Aldolase A (P < 0.01 versus control). These treatments also prolong the survival in orthotopic models. These results suggest that the effect of TX-2098 in pancreatic cancer might be correlated with the expression of VEGF and HIF-1 targeted molecules. -- Highlights: Black-Right-Pointing-Pointer We designed and synthesized novel hypoxic cytoxin, TX-2098. Black-Right-Pointing-Pointer TX-2098 inhibited the proliferation of human pancreatic cancer cells than TPZ. Black-Right-Pointing-Pointer TX-2098 reduced VEGF protein level than TPZ. Black-Right-Pointing-Pointer TX-2098

  5. Correlation Between the Raman Crystallinity of p-Type Micro-Crystalline Silicon Layer and Open Circuit Voltage of n-i-p Solar Cells.

    Science.gov (United States)

    Jung, Junhee; Kim, Sunbo; Park, Jinjoo; Shin, Chonghoon; Pham, Duy Phong; Kim, Jiwoong; Chung, Sungyoun; Lee, Youngseok; Yi, Junsin

    2015-10-01

    This article mainly discusses the difference between p-i-n and n-i-p type solar cells. Their structural difference has an effect on cell performance, such as open circuit voltage and fill factor. Although the deposition conditions are the same for both p-i-n and n-i-p cases, the substrate layers for depositing p-type microcrystalline silicon layers differ. In n-i-p cells, the substrate layer is p-type amorphous silicon oxide layer; whereas, in p-i-n cells, the substrate layer is ZnO:Al. The interfacial change leads to a 12% difference in the crystallinity of the p-type microcrystalline silicon layers. When the p-type microcrystalline silicon layer's crystallinity was not sufficient to activate an internal electric field, the open circuit voltage and fill factor decreased 0.075 V and 7.36%, respectively. We analyzed this problem by comparing the Raman spectra, electrical conductivity, activation energy and solar cell performance. By adjusting the thickness of the p-type microcrystalline silicon layer, we increased the open circuit voltage of the n-i-p cell from 0.835 to 0.91 V.

  6. Thermal stability of Ni/Ti/Al ohmic contacts to p-type 4H-SiC

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Hailong; Shen, Huajun, E-mail: shenhuajun@ime.ac.cn; Tang, Yidan; Bai, Yun; Liu, Xinyu [Microwave Device and IC Department, Institute of Microelectronics of Chinese Academy of Sciences, Beijing 100029 (China); Zhang, Xufang [School of Physical Science and Technology, Lanzhou University, Lanzhou 730000 (China); Wu, Yudong; Liu, Kean [Zhuzhou CSR Times Electric Co., Ltd, ZhuZhou 412001 (China)

    2015-01-14

    Low resistivity Ni/Ti/Al ohmic contacts on p-type 4H-SiC epilayer were developed, and their thermal stabilities were also experimentally investigated through high temperature storage at 600 °C for 100 h. The contact resistance of the Al/Ti/Ni/SiC contacts degraded in different degrees, and the contact morphology deteriorated with the increases of the average surface roughness and interface voids. X-ray spectra showed that Ni{sub 2}Si and Ti{sub 3}SiC{sub 2}, which were formed during ohmic contact annealing and contributed to low contact resistivity, were stable under high temperature storage. The existence of the TiAl{sub 3} and NiAl{sub 3} intermetallic phases was helpful to prevent Al agglomeration on the interface and make the contacts thermally stable. Auger electron spectroscopy indicated that the incorporation of oxygen at the surface and interface led to the oxidation of Al or Ti resulting in increased contact resistance. Also, the formation of these oxides roughened the surface and interface. The temperature-dependence of the specific contact resistance indicated that a thermionic field emission mechanism dominates the current transport for contacts before and after the thermal treatment. It suggests that the Ni/Ti/Al composite ohmic contacts are promising for SiC devices to be used in high temperature applications.

  7. The Properties of Sprayed Nanostructured P-Type CuI Films for Dye-Sensitized Solar Cells Application

    Directory of Open Access Journals (Sweden)

    M. N. Amalina

    2012-01-01

    Full Text Available In our experiments, we provide a new approach for depositing CuI (inorganic compound thin films using the mister atomizer technique. The CuI solution was sprayed into fine droplets using argon as a carrier gas at different solution concentrations. The solution sprayed was 50 ml for all samples with substrate temperature constant at 50°C during the deposition process. The result shows that the CuI thin film properties strongly depend on its precursor concentration. The structural properties were characterized by XRD with strong (111 orientation shows for all the CuI thin films. FESEM images revealed that all the CuI thin films deposited were uniform with the existence of nanostructured CuI particle. The EDX measurement confirms the existence of Cu:I in the films. The nanostructured CuI will improve the penetration of p-type between the mesoporous matrix of TiO2 thin film. Promising conductivity value of about 10° S cm−1 was obtained for CuI thin films deposited by this new deposition method. Low transmittance of below 50% was observed for all CuI thin films. The band gap energy obtained here was between 2.82 eV and 2.92 eV which is much smaller than the reported band gap which is 3.1 eV.

  8. Transition from negative to positive photoconductivity in p -type P b1 -xE uxTe films

    Science.gov (United States)

    Pirralho, M. J. P.; Peres, M. L.; Soares, D. A. W.; Braga, P. C. O.; Pena, F. S.; Fornari, C. I.; Rappl, P. H. O.; Abramof, E.

    2017-02-01

    We investigated the photoconductivity effect in p -type P b1 -xE uxTe films for x =0.01 , 0.02, 0.03, 0.05, and 0.06 at T =300 K . The measurements revealed a clear transition from negative to positive photoconductivity as the Eu content x is increased at room temperature. This transition is related to the metal-insulator transition that occurs due to the disorder originated from the introduction of Eu atoms and it is an Anderson transition. Our investigation found that, from the potential application point of view, the sample x =0.06 is more suitable, i.e., it presents an almost noise-free signal and the higher photoconductivity amplitude response. The photoconductive amplitude response for the sample with x =0.06 was investigated further in the temperature range of 77-300 K and, surprisingly, multiple additional transitions were observed with amplitudes that reached around 200 times the original value before illumination. We show that this anomalous behavior is a consequence of the generation and recombination rates between the bands and the 4 f level and a defect level located inside the band gap.

  9. Combinatorial discovery through a distributed outreach program: investigation of the photoelectrolysis activity of p-type Fe, Cr, Al oxides.

    Science.gov (United States)

    Rowley, John G; Do, Thanh D; Cleary, David A; Parkinson, B A

    2014-06-25

    We report the identification of a semiconducting p-type oxide containing iron, aluminum, and chromium (Fe2-x-yCrxAlyO3) with previously unreported photoelectrolysis activity that was discovered by an undergraduate scientist participating in the Solar Hydrogen Activity research Kit (SHArK) program. The SHArK program is a distributed combinatorial science outreach program designed to provide a simple and inexpensive way for high school and undergraduate students to participate in the search for metal oxide materials that are active for the photoelectrolysis of water. The identified Fe2-x-yCrxAlyO3 photoelectrolysis material possesses many properties that make it a promising candidate for further optimization for potential application in a photoelectrolysis device. In addition to being composed of earth abundant elements, the FeCrAl oxide material has a band gap of 1.8 eV. Current-potential measurements for Fe2-x-yCrxAlyO3 showed an open circuit photovoltage of nearly 1 V; however, the absorbed photon conversion efficiency for hydrogen evolution was low (2.4 × 10(-4) at 530 nm) albeit without any deposited hydrogen evolution catalyst. X-ray diffraction of the pyrolyzed polycrystalline thin Fe2-x-yCrxAlyO3 film on fluorine-doped tin oxide substrates shows a hexagonal phase (hematite structure) and scanning electron microscope images show morphology consisting of small crystallites.

  10. Low temperature acetone detection by p-type nano-titania thin film: Equivalent circuit model and sensing mechanism

    Science.gov (United States)

    Bhowmik, B.; Dutta, K.; Hazra, A.; Bhattacharyya, P.

    2014-09-01

    Undoped nanocrystalline anatase p-type TiO2 thin film was deposited by sol-gel method on thermally oxidized p-Si (2-5 Ω cm, ) substrates. The thin film was characterized by X-ray Diffraction (XRD) and Field Emission Scanning Electron Microscopy (FESEM) to confirm the formation of nanocrystalline anatase titania and to determine the crystallite size (∼7 nm). The resistive sensor structure was fabricated employing two lateral Pd electrodes on top of the TiO2 sensing layer. The developed sensor was tested in the temperature range of 50-200 °C for the detection of low ppm acetone (0.5-50 ppm). The maximum response of ∼115% was obtained at 150 °C with response/recovery time of 14 s/22 s at 50 ppm acetone (in air). Moreover, the sensors were capable of detecting acetone as low as 0.5 ppm with acceptable response magnitude. As titania acetone sensors are mostly n-TiO2 based, the acetone sensing mechanism for p-TiO2 is yet to be established authentically. To address the issue, an equivalent circuit model, based on the corresponding band diagram of nanocrystalline p-TiO2 with Pd electrode, was developed to describe the electron transfer mechanism through grain, grain boundary and Pd electrode under the influence of acetone vapor.

  11. High performance p-type segmented leg of misfit-layered cobaltite and half-Heusler alloy

    DEFF Research Database (Denmark)

    Le, Thanh Hung; Van Nong, Ngo; Snyder, Gerald Jeffrey;

    2015-01-01

    In this study, a segmented p-type leg of doped misfit-layered cobaltite Ca2.8Lu0.15Ag0.05Co4O9+δ and half-Heusler Ti0.3Zr0.35Hf0.35CoSb0.8Sn0.2 alloy was fabricated and characterized. The thermoelectric properties of single components, segmented leg, and the electrical contact resistance...... of the joint part were measured as a function of temperature. The output power generation characteristics of segmented legs were characterized in air under various temperature gradients, DT, with the hot side temperature up to 1153 K. At ΔT ≈756 K, the maximum conversion efficiency reached a value of ∼5......%, which is about 65% of that expected from the materials without parasitic losses. The long-term stability investigation for two weeks at the hot and cold side temperatures of 1153/397 K shows that the segmented leg has good durability as a result of stable and low electrical resistance contacts. 2015...

  12. A New Method for the Quick Determination of S-Type and P-Type Habitable Zones in Binary Systems

    Science.gov (United States)

    Wang, Zhaopeng; Cuntz, Manfred

    2017-01-01

    More than 3500 exoplanets have been confirmed nowadays, including a very large number of planets discovered by the Kepler mission. Additional exoplanets are expected to be found by ongoing missions as, e.g., K2 as well as future missions such as TESS. Exoplanets, especially terrestrial planets, located in stellar habitable zones are drawing great attention from the community and the public at large due to their potential for hosting alien life - a prospect that makes the adequate determination of stellar habitable zones an important goal of exoplanetary research. In the local Galactic neighborhood, binary systems occur relatively frequently. Thus, it is the aim of my presentation to offer a method for the quick determination for the existence of habitable zones in binaries. Therefore, fitting formulas for binary habitable zones regarding both S-type and P-type star-planet configurations are provided. Based on previous work in the literature, a joint constraint regarding radiative habitable zones and planetary orbital stability limits is used. Models of stellar habitable zones utilize updated computations for planetary climate models as given by Kopparapu et al. (2013, 2014) [ApJ 765, 131; ApJL 787, L29]. Cases studies showing the quality of the fit formulas, as well as applications to observed systems, are presented as well.

  13. The electrical properties of photodiodes based on nanostructure gallium doped cadmium oxide/p-type silicon junctions

    Science.gov (United States)

    Çavaş, M.; Yakuphanoğlu, F.; Karataş, Ş.

    2017-01-01

    Gallium doped cadmium-oxide (CdO: Ga) thin films were successfully deposited by sol-gel spin coating method on p-type Si substrate. The electrical properties of the photodiode based on nanostructure Ga doped n-CdO/p-Si junctions were investigated. The current-voltage (I-V) characteristics of the structure were investigated under various light intensity and dark. It was observed that generated photocurrent of the Au/n-CdO/p-Si junctions depended on light intensity. The capacitance-voltage and conductance-voltage measurements were carried out for this diode in the frequency range between 100 and 1000 kHz at room temperature by steps of 100 kHz. The capacitance decreased with increasing frequency due to a continuous distribution of the interface states. These results suggested that the Au/n-CdO/p-Si Schottky junctions could be utilized as a photosensor. Furthermore, the voltage and frequency dependence of series resistance were calculated from the C-V and G/ω-V measurements and plotted as functions of voltage and frequency. The distribution profile of R S -V gave a peak in the depletion region at low frequencies and disappeared with increasing frequencies.

  14. Effect of doping concentration on the conductivity and optical properties of p-type ZnO thin films

    Energy Technology Data Exchange (ETDEWEB)

    Pathak, Trilok Kumar [Semiconductor Research Lab, Department of Physics, Gurukula Kangri University, Haridwar (India); Kumar, Vinod, E-mail: vinod.phy@gmail.com [Department of Physics, University of the Free State, Bloemfontein (South Africa); Swart, H.C., E-mail: swarthc@ufs.ac.za [Department of Physics, University of the Free State, Bloemfontein (South Africa); Purohit, L.P., E-mail: proflppurohitphys@gmail.com [Semiconductor Research Lab, Department of Physics, Gurukula Kangri University, Haridwar (India)

    2016-01-01

    Nitrogen doped ZnO (NZO) thin films were synthesized on glass substrates by the sol–gel and spin coating method. Zinc acetate dihydrates and ammonium acetate were used as precursors for zinc and nitrogen, respectively. X-ray diffraction study showed that the thin films have a hexagonal wurtzite structure corresponding (002) peak for undoped and doped ZnO thin films. The transmittance of the films was above 80% and the band gap of the film varies from 3.21±0.03 eV for undoped and doped ZnO. The minimum resistivity of NZO thin films was obtained as 0.473 Ω cm for the 4 at% of nitrogen (N) doping with a mobility of 1.995 cm{sup 2}/V s. The NZO thin films showed p-type conductivity at 2 and 3 at% of N doping. The AC conductivity measurements that were carried out in the frequency range 10 kHz to 0.1 MHz showed localized conduction in the NZO thin films. These highly transparent ZnO films can be used as a possible window layer in solar cells.

  15. Screening of inorganic wide-bandgap p-type semiconductors for high performance hole transport layers in organic photovoltaic devices

    Science.gov (United States)

    Ginley, David; Zakutayev, Andriy; Garcia, Andreas; Widjonarko, Nicodemus; Ndione, Paul; Sigdel, Ajaya; Parilla, Phillip; Olson, Dana; Perkins, John; Berry, Joseph

    2011-03-01

    We will report on the development of novel inorganic hole transport layers (HTL) for organic photovoltaics (OPV). All the studied materials belong to the general class of wide-bandgap p-type oxide semiconductors. Potential candidates suitable for HTL applications include SnO, NiO, Cu2O (and related CuAlO2, CuCrO2, SrCu2O4 etc) and Co3O4 (and related ZnCo2O4, NiCo2O4, MgCo2O4 etc.). Materials have been optimized by high-throughput combinatorial approaches. The thin films were deposited by RF sputtering and pulsed laser deposition at ambient and elevated temperatures. Performance of the inorganic HTLs and that of the reference organic PEDOT:PSS HTL were compared by measuring the power conversion efficiencies and spectral responses of the P3HT/PCBM- and PCDTBT/PCBM-based OPV devices. Preliminary results indicate that Co3O4-based HTLs have performance comparable to that of our previously reported NiOs and PEDOT:PSS HTLs, leading to a power conversion efficiency of about 4 percent. The effect of composition and work function of the ternary materials on their performance in OPV devices is under investigation.

  16. Electrical Detection of the Helical Spin Texture in a p-type Topological Insulator Sb2Te3

    Science.gov (United States)

    Li, C. H.; van ‘T Erve, O. M. J.; Li, Y. Y.; Li, L.; Jonker, B. T.

    2016-07-01

    The surface states of 3D topological insulators (TIs) exhibit a helical spin texture with spin locked at right angles with momentum. The chirality of this spin texture is expected to invert crossing the Dirac point, a property that has been experimentally observed by optical probes. Here, we directly determine the chirality below the Dirac point by electrically detecting spin-momentum locking in surface states of a p-type TI, Sb2Te3. A current flowing in the Sb2Te3 surface states generates a net spin polarization due to spin-momentum locking, which is electrically detected as a voltage on an Fe/Al2O3 tunnel barrier detector. Measurements of this voltage as a function of current direction and detector magnetization indicate that hole spin-momentum locking follows the right-hand rule, opposite that of electron, providing direct confirmation that the chirality is indeed inverted below Dirac point. The spin signal is linear with current, and exhibits a temperature dependence consistent with the semiconducting nature of the TI film and freeze-out of bulk conduction below 100 K. Our results demonstrate that the chirality of the helical spin texture of TI surface states can be determined electrically, an enabling step in the electrical manipulation of spins in next generation TI-based quantum devices.

  17. Fabrication and Characterization of p-Type SnO Thin Film with High c-Axis Preferred Orientation

    Science.gov (United States)

    Pei, Yanli; Liu, Wuguang; Shi, Jingtao; Chen, Zimin; Wang, Gang

    2016-11-01

    p-Type tin monoxide (SnO) thin films with high c-axis preferred orientation have been fabricated on quartz substrate via electron-beam evaporation at 280°C. Subsequently, rapid thermal annealing (RTA) was performed in N2 atmosphere at 400°C to 800°C. Their structural, chemical, optical, and electrical properties were investigated by x-ray diffraction analysis, ultraviolet-visible spectroscopy, scanning electron microscopy, x-ray photoelectron spectroscopy, and Hall-effect measurements. The c-axis-oriented films of Sn-rich SnO presented excellent thermal stability up to RTA at 700°C. Both the crystallization and the hole Hall mobility were enhanced with increasing RTA temperature, with Hall mobility of 16 cm2 V-1 s-1 being obtained after RTA at 700°C. It was considered that the presence of defects and low scattering from grain boundaries contributed to this high Hall mobility. RTA annealing temperature above 700°C induced chemical reaction between SnO and the quartz substrate, with a change of the film to amorphous state with Sn4+ formation.

  18. Persistent Hydrogen Production by the Photo-Assisted Microbial Electrolysis Cell Using a p-Type Polyaniline Nanofiber Cathode.

    Science.gov (United States)

    Jeon, Yongwon; Kim, Sunghyun

    2016-12-08

    A microbial electrolysis cell, though considered as a promising, environmentally friendly technology for hydrogen production, suffers from concomitant production of methane. The high hydrogen/methane ratio at the initial operation stage decreases with time. Here we report for the first time the photoassisted microbial electrolysis cell (MEC) for persistent hydrogen production using polyaniline nanofibers as a cathode. Under 0.8 V external bias and laboratory fluorescent light illumination in a single-chamber MEC, continuous hydrogen production from acetate at a rate of 1.78 mH2 (3)  m(-3)  d(-1) with 79.2 % overall hydrogen recovery was achieved with negligible methane formation for six months. Energy efficiencies based on input electricity as well as input electricity plus substrate were 182 and 66.2 %, respectively. This was attributed to the p-type-semiconductor characteristics of polyaniline nanofibers in which photoexcited electrons are used to reduce protons at the surface and holes are reduced with electrons originating from acetate oxidation at the anode. This method can be extended to microbial wastewater treatment for hydrogen production. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Low specific contact resistance on epitaxial p-type 4H-SiC with a step-bunching surface

    Institute of Scientific and Technical Information of China (English)

    韩超; 张玉明; 宋庆文; 汤晓燕; 张义门; 郭辉; 王悦湖

    2015-01-01

    This paper reports the performances of Ti/Al based ohmic contacts fabricated on highly doped p-type 4H-SiC epitaxial layer which has a severe step-bunching surface. Different contact schemes are investigated based on the Al:Ti composition with no more than 50 at.%Al. The specific contact resistance (SCR) is obtained to be as low as 2.6 × 10−6Ω·cm2 for the bilayered Ti(100 nm)/Al(100 nm) contact treated with 3 min rapid thermal annealing (RTA) at 1000◦C. The microstructure analyses examined by physical and chemical characterization techniques reveal an alloy-assisted ohmic contact formation mechanism, i.e., a high degree of alloying plays a decisive role in forming the interfacial ternary Ti3SiC2 dominating the ohmic behavior of the Ti/Al based contact. Furthermore, a globally covered Ti3SiC2 layer with (0001)-oriented texture can be formed, regardless of the surface step bunching as well as its structural evolution during the metallization annealing.

  20. Tuning the surface Fermi level on p-type gallium nitride nanowires for efficient overall water splitting.

    Science.gov (United States)

    Kibria, M G; Zhao, S; Chowdhury, F A; Wang, Q; Nguyen, H P T; Trudeau, M L; Guo, H; Mi, Z

    2014-04-30

    Solar water splitting is one of the key steps in artificial photosynthesis for future carbon-neutral, storable and sustainable source of energy. Here we show that one of the major obstacles for achieving efficient and stable overall water splitting over the emerging nanostructured photocatalyst is directly related to the uncontrolled surface charge properties. By tuning the Fermi level on the nonpolar surfaces of gallium nitride nanowire arrays, we demonstrate that the quantum efficiency can be enhanced by more than two orders of magnitude. The internal quantum efficiency and activity on p-type gallium nitride nanowires can reach ~51% and ~4.0 mol hydrogen h(-1) g(-1), respectively. The nanowires remain virtually unchanged after over 50,000 μmol gas (hydrogen and oxygen) is produced, which is more than 10,000 times the amount of photocatalyst itself (~4.6 μmol). The essential role of Fermi-level tuning in balancing redox reactions and in enhancing the efficiency and stability is also elucidated.

  1. High hole mobility p-type GaN with low residual hydrogen concentration prepared by pulsed sputtering

    Science.gov (United States)

    Arakawa, Yasuaki; Ueno, Kohei; Kobayashi, Atsushi; Ohta, Jitsuo; Fujioka, Hiroshi

    2016-08-01

    We have grown Mg-doped GaN films with low residual hydrogen concentration using a low-temperature pulsed sputtering deposition (PSD) process. The growth system is inherently hydrogen-free, allowing us to obtain high-purity Mg-doped GaN films with residual hydrogen concentrations below 5 × 1016 cm-3, which is the detection limit of secondary ion mass spectroscopy. In the Mg profile, no memory effect or serious dopant diffusion was detected. The as-deposited Mg-doped GaN films showed clear p-type conductivity at room temperature (RT) without thermal activation. The GaN film doped with a low concentration of Mg (7.9 × 1017 cm-3) deposited by PSD showed hole mobilities of 34 and 62 cm2 V-1 s-1 at RT and 175 K, respectively, which are as high as those of films grown by a state-of-the-art metal-organic chemical vapor deposition apparatus. These results indicate that PSD is a powerful tool for the fabrication of GaN-based vertical power devices.

  2. Study of nanoparticles TiO2 thin films on p-type silicon substrate using different alcoholic solvents

    Science.gov (United States)

    Muaz, A. K. M.; Hashim, U.; Arshad, M. K. Md.; Ruslinda, A. R.; Ayub, R. M.; Gopinath, Subash C. B.; Voon, C. H.; Liu, Wei-Wen; Foo, K. L.

    2016-07-01

    In this paper, sol-gel method spin coating technique is adopted to prepare nanoparticles titanium dioxide (TiO2) thin films. The prepared TiO2 sol was synthesized using titanium butoxide act as a precursor and subjected to deposited on the p-type silicon oxide (p-SiO2) and glass slide substrates under room temperature. The effect of different alcoholic solvents of methanol and ethanol on the structural, morphological, optical and electrical properties were systematically investigated. The coated TiO2 thin films were annealed in furnace at 773 K for 1 h. The structural properties of the TiO2 films were examined with X-ray Diffraction (XRD). From the XRD analysis, both solvents showing good crystallinity with anatase phase were the predominant structure. Atomic Force Microscopy (AFM) was employed to study the morphological of the thin films. The optical properties were investigated by Ultraviolet-visible (UV-Vis) spectroscopy were found that ethanol as a solvent give a higher optical transmittance if compare to the methanol solvent. The electrical properties of the nanoparticles TiO2 thin films were measured using two-point-probe technique.

  3. Enhancement of photocathodic stability of p-type copper(I) oxide electrodes by surface etching treatment

    Energy Technology Data Exchange (ETDEWEB)

    Amano, Fumiaki, E-mail: amano@kitakyu-u.ac.jp [Catalysis Research Center, Hokkaido University, Sapporo 001-0021 (Japan); Graduate School of Environmental Science, Hokkaido University, Sapporo 060-0810 (Japan); Department of Chemical and Environmental Engineering, The University of Kitakyushu, Kitakyushu 808-0135 (Japan); Ebina, Toshihiro [Graduate School of Environmental Science, Hokkaido University, Sapporo 060-0810 (Japan); Ohtani, Bunsho [Catalysis Research Center, Hokkaido University, Sapporo 001-0021 (Japan); Graduate School of Environmental Science, Hokkaido University, Sapporo 060-0810 (Japan)

    2014-01-01

    The photoelectrochemical properties of electrodeposited p-type copper(I) oxide (Cu{sub 2}O) films were investigated using methyl viologen (MV{sup 2+}) as an electron acceptor. The pristine Cu{sub 2}O films were deactivated during the photocathodic reaction as a result of self-reduction, whereas the (111)-oriented Cu{sub 2}O films treated in an aqueous solution containing hexamethylenetetramine at pH 5 and 90 °C exhibited stable photocurrent for MV{sup 2+} reduction into the cation radical. Scanning electron microscope images showed that the treated films contained smaller crystal grains than untreated ones. X-ray photoelectron spectroscopy revealed that the treatment etched the thin layer of copper(II) oxide from the Cu{sub 2}O polycrystalline surface. Etching of the film surface enhanced the stability and steady-state photocurrent for photocathodic reduction of MV{sup 2+}, suggesting that the crystalline composition and structures exposed on the outermost surface of Cu{sub 2}O polycrystalline films have a considerable influence on the selectivity for the photocathodic reaction over self-reduction. - Highlights: • Photoelectrochemical reduction of methyl viologen by (111)-oriented Cu{sub 2}O thin films • Cu{sub 2}O films are etched using an aqueous solution containing hexamethylenetetramine. • Etching decreases crystal grain size and removes the thin layer of CuO. • Etching enhances the stability of Cu{sub 2}O photoelectrodes.

  4. Limits on the use of cobalt sulfide as anode of p-type dye-sensitized solar cells

    Science.gov (United States)

    Bonomo, Matteo; Congiu, Mirko; De Marco, Maria Letizia; Dowling, Denis P.; Di Carlo, Aldo; Graeff, Carlos F. O.; Dini, Danilo

    2017-06-01

    Thin films of cobalt sulfide (CoS) of thickness l  traditional platinized fluorine-doped indium oxide (Pt-FTO) due to the lower cost of the starting materials (Co salts) and the easier procedure of deposition onto large area substrates. The latter process was carried out via direct precipitation of CoS from aqueous solutions. The photoconversion efficiency (η) of the corresponding device was 0.07%. This value is about 35% less than the efficiency that is obtained with the analogous p-DSC employing the Pt-FTO anode (η  =  0.11). Unlike p-DSCs based on Pt-FTO anodes, the photoelectrochemical cells employing CoS electrodes showed that this anodic material was not able to sustain the photocurrent densities generated by P1-sensitized NiO at a given photopotential. Illumination of the p-DSCs with CoS anodes and P1-sensitized NiO cathodes actually induced the reverse bias of the photoelectrochemical cell with CoS behaving like a p-type semiconductor with no degeneracy. Dedicated to Professor Roberto Federici on the occasion of his retirement.

  5. P-type AlAs/[GaAs/AlAs] Semiconductor/Superlattice DBR Grown by MBE

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A p-type AlAs(70.2 nm)/16.5 period [GaAs(3 nm)/AlAs(0.7 nm)] semiconductor/superlatice distributed Bragg reflector (DBR) has been grown on n+-GaAs(100) substrate by V80H molecular beam epitaxy system. Experimental reflection spectrum shows that its central wavelength is 820 nm, with the peak reflectivity for 10-pair DBR of as high as 96 %, and the reflection bandwidth of as wide as 90 nm. We formed a 20×20 μm2 square mesa to measure the series resistance using wet chemical etching. From the measurement result, the series resistance of about 50 Ω is obtained at a moderate doping (3×1018 cm-3). Finally, the dependence of the resistance of the DBR on the temperature is analyzed. From the experimental result, it is found that the mechanism of the low series resistance of this kind of DBR may increase the tunneling current in the semiconductor/superlattice mirror structure, which will result in a decrease in series resistance.

  6. Thomas-Fermi approximation in two p-type delta-doped quantum wells in GaAs an Si

    Energy Technology Data Exchange (ETDEWEB)

    Gaggero-Sager, L. M. [Universidad Autonoma de Zacatecas, Zacatecas (Mexico); M' Peko, J. C.; Perez Alvarez, R. [Universidad de La Habana, Ciudad Habana (Cuba)

    2001-04-01

    Thomas-Fermi calculations of the hole subband structure in two coupled p-type d-doped GaAs and Si quantum wells are carried out as a function of the impurity concentration and the distance l between them. A simple formula is obtained for the potential as a function of these two magnitudes by both types of systems. The numerical results for a double Be-{delta}-doped GaAs (double B-{delta}-doped Si) quantum well show that the energy levels degenerate for l{>=}300 A(l{>=}200 A) for an impurity concentration of 1 x 10{sup 1}3 cm{sup -2}. [Spanish] Presentamos calculos de la estructura de subbandas de huecos, utilizando la aproximacion de Thomas-Fermi para dos pozos cuanticos d-dopados tipo p en GaAs y Si, como funcion de la concentracion de impurezas y de la distancia l entre ambos para los dos tipos de sistemas. Los resultados numericos muestran que para un pozo doble de B-{delta}-dopado GaAs (pozo doble de B-{delta}-dopado Si) con una concentracion de 1 x 10{sup 1}3 cm{sup -2} los niveles estan degenerados para l{>=}300 A(l{>=}200 A).

  7. Ultrafast Dynamics of Hole Injection and Recombination in Organometal Halide Perovskite Using Nickel Oxide as p-Type Contact Electrode.

    Science.gov (United States)

    Corani, Alice; Li, Ming-Hsien; Shen, Po-Shen; Chen, Peter; Guo, Tzung-Fang; El Nahhas, Amal; Zheng, Kaibo; Yartsev, Arkady; Sundström, Villy; Ponseca, Carlito S

    2016-04-01

    There is a mounting effort to use nickel oxide (NiO) as p-type selective electrode for organometal halide perovskite-based solar cells. Recently, an overall power conversion efficiency using this hole acceptor has reached 18%. However, ultrafast spectroscopic investigations on the mechanism of charge injection as well as recombination dynamics have yet to be studied and understood. Using time-resolved terahertz spectroscopy, we show that hole transfer is complete on the subpicosecond time scale, driven by the favorable band alignment between the valence bands of perovskite and NiO nanoparticles (NiO(np)). Recombination time between holes injected into NiO(np) and mobile electrons in the perovskite material is shown to be hundreds of picoseconds to a few nanoseconds. Because of the low conductivity of NiO(np), holes are pinned at the interface, and it is electrons that determine the recombination rate. This recombination competes with charge collection and therefore must be minimized. Doping NiO to promote higher mobility of holes is desirable in order to prevent back recombination.

  8. P-type poly-Si prepared by low-temperature aluminum-induced crystallization and doping for solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Matsumoto, Yasuhiro; Yu, Zhenrui; Morales-Acevedo, Arturo [CINVESTAV-IPN, Mexico, D.F. (Mexico)

    2000-07-01

    P-type poly-Si thin films prepared by low temperature aluminum-induced crystallization and doping are reported. The starting material was boron-doped a-Si:H prepared by PECVD on glass substrates. Aluminum layers with different thickness were evaporated on a-Si:H surface and conventional thermal annealing was performed at temperatures ranging from 300 to 550 Celsius degrees. XRD, SIMS, and Hall effect measurements were carried out to characterize the annealed Al could be crystallized at temperature as low as 300 Celsius degrees in 60 minutes. This material has high carrier concentration as well as high Hall mobility and can be used as a p-layer of seed layer for thin film poly-Si solar cells. The technique reported here is compatible with PECVD process. [Spanish] Se informa sobre la preparacion de peliculas delgadas tipo P y Poli-Si mediante la cristalizacion inducida de aluminio a baja temperatura y el dopado. El material inicial era de boro dopado y a-Si:H preparado PECVD sobre substratos de vidrio. Se evaporaron capas de aluminio de diferente espesor sobre una superficie de a-Si:H y se llevo a cabo un destemplado termico convencional a temperaturas que varian entre 300 y 500 grados Celsius. Se llevaron a cabo mediciones de XRB, SIMS y del efecto Hall para caracterizar el aluminio destemplado para que pudiera ser cristalizado a temperaturas tan bajas como 300 grados Celsius en 60 minutos. Este material tiene una alta concentracion portadora asi como una alta movilidad Hall y puede usarse como una capa de semilla para celdas solares de pelicula delgada Poli-Si. La tecnica reportada aqui es compatible con el proceso PECVD.

  9. Theoretical luminescence spectra in p-type quantum wells and superlattices based on InGaAsN

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Thiago Freire de; Rodrigues, Sara Cristina Pinto [Universidade Federal Rural de Pernambuco (UFRPE), Recife, PE (Brazil). Dept. de Fisica; Silva Junior, Eronides Felisberto da [Universidade Federal de Pernambuco (UFPE), Recife, PE (Brazil). Dept. de Fisica; Sipahi, Guilherme Matos [Universidade de Sao Paulo (IFSC/USP), Sao Carlos, SP (Brazil). Inst. de Fisica; Scolfaro, Luisa Maria Ribeiro [Texas State University, San Marcos, TX (United States), Dept. of Physics

    2012-07-01

    Full text: In the past few years, the dilute nitride system, InGaAsN, is proposed as a good candidate for several device applications. InGaAsN is considered a promising material for laser devices working at 1:3 or 1:5{mu}m and high-efficiency multijunction solar cells. Incorporation of In and N into GaAs result in a strong redshift of the emission wavelength. Besides, the strain can be minimized since the opposite effect of In and N on the lattice constant enables lattice matching of InGaAsN on GaAs. However, despite their great potential for applications, the understanding of their physical properties is rather incomplete. In particular, the dominant mechanisms of light emission in these alloys and their dependence on the nitrogen composition are not well established. Such information is crucial not only for a better understanding of the optical properties of the nitrogen containing III-V alloys, but also for a better technological control of alloy formation and optimization light emission efficiency. Another point concerns to investigation in p-type doping in InGaAsN. This is of great importance since, for example, can improve the transport in HBT (Heterojunction Bipolar Transistors) devices. In this work we report on theoretical luminescence spectra calculations for p-doped GaAs/InGaAsN quantum wells and superlattices. The calculations are performed within the k-vector.p-vector method by solving the full 8 x 8 Kane Hamiltonian, generalized to treat different materials. Strain effects due the lattice mismatch between InGaAsN and GaAs are taken into account. By varying the acceptor concentration we analyze the effect of exchange-correlation, which plays an important role in profile potential and electronic transition. These results can explain several important aspects about optical properties in these systems. (author)

  10. Fine tuning of fluorene-based dye structures for high-efficiency p-type dye-sensitized solar cells.

    Science.gov (United States)

    Liu, Zonghao; Li, Wenhui; Topa, Sanjida; Xu, Xiaobao; Zeng, Xianwei; Zhao, Zhixin; Wang, Mingkui; Chen, Wei; Wang, Feng; Cheng, Yi-Bing; He, Hongshan

    2014-07-09

    We report on an experimental study of three organic push-pull dyes (coded as zzx-op1, zzx-op1-2, and zzx-op1-3) featuring one, two, and three fluorene units as spacers between donors and acceptors for p-type dye-sensitized solar cells (p-DSSC). The results show increasing the number of spacer units leads to obvious increases of the absorption intensity between 300 nm and 420 nm, a subtle increase in hole driving force, and almost the same hole injection rate from dyes to NiO nanoparticles. Under optimized conditions, the zzx-op1-2 dye with two fluorene spacer units outperforms other two dyes in p-DSSC. It exhibits an unprecedented photocurrent density of 7.57 mA cm(-2) under full sun illumination (simulated AM 1.5G light illumination, 100 mW cm(-2)) when the I(-)/I3(-) redox couple and commercial NiO nanoparticles were used as an electrolyte and a semiconductor, respectively. The cells exhibited excellent long-term stability. Theoretical calculations, impedance spectroscopy, and transient photovoltage decay measurements reveal that the zzx-op1-2 exhibits lower photocurrent losses, longer hole lifetime, and higher photogenerated hole density than zzx-op1 and zzx-op1-3. A dye packing model was proposed to reveal the impact of dye aggregation on the overall photovoltaic performance. Our results suggest that the structural engineering of organic dyes is important to enhance the photovoltaic performance of p-DSSC.

  11. Low specific contact resistance on epitaxial p-type 4H-SiC with a step-bunching surface

    Science.gov (United States)

    Han, Chao; Zhang, Yu-Ming; Song, Qing-Wen; Tang, Xiao-Yan; Zhang, Yi-Men; Guo, Hui; Wang, Yue-Hu

    2015-11-01

    This paper reports the performances of Ti/Al based ohmic contacts fabricated on highly doped p-type 4H-SiC epitaxial layer which has a severe step-bunching surface. Different contact schemes are investigated based on the Al:Ti composition with no more than 50 at.% Al. The specific contact resistance (SCR) is obtained to be as low as 2.6 × 10-6 Ω·cm2 for the bilayered Ti(100 nm)/Al(100 nm) contact treated with 3 min rapid thermal annealing (RTA) at 1000 °C. The microstructure analyses examined by physical and chemical characterization techniques reveal an alloy-assisted ohmic contact formation mechanism, i.e., a high degree of alloying plays a decisive role in forming the interfacial ternary Ti3SiC2 dominating the ohmic behavior of the Ti/Al based contact. Furthermore, a globally covered Ti3SiC2 layer with (0001)-oriented texture can be formed, regardless of the surface step bunching as well as its structural evolution during the metallization annealing. Project supported by the Key Specific Projects of Ministry of Education of China (Grant No. 625010101), the National Natural Science Foundation of China (Grant No. 61234006), the Natural Science Foundation of ShaanXi Province, China (Grant No. 2013JQ8012), the Doctoral Fund of Ministry of Education of China (Grant No. 20130203120017), and the Specific Project of the Core Devices, China (Grant No. 2013ZX0100100-004).

  12. Hadron-therapy beam monitoring: Towards a new generation of ultra-thin p-type silicon strip detectors

    Energy Technology Data Exchange (ETDEWEB)

    Bouterfa, M.; Aouadi, K. [Inst. of Information and Communication Technologies, Electronics and Applied Mathematics ICTEAM, Universite Catholique de Louvain, 1348 Louvain-la-Neuve (Belgium); Bertrand, D. [Particle Therapy Dept., Ion Beam Application IBA, 1348 Louvain-la-Neuve (Belgium); Olbrechts, B.; Delamare, R. [Inst. of Information and Communication Technologies, Electronics and Applied Mathematics ICTEAM, Universite Catholique de Louvain, 1348 Louvain-la-Neuve (Belgium); Raskin, J. P.; Gil, E. C. [Institut de Recherche en Mathematique et Physique IRMP, Universite Catholique de Louvain, 1348 Louvain-la-Neuve (Belgium); Flandre, D. [Inst. of Information and Communication Technologies, Electronics and Applied Mathematics ICTEAM, Universite Catholique de Louvain, 1348 Louvain-la-Neuve (Belgium)

    2011-07-01

    Hadron-therapy has gained increasing interest for cancer treatment especially within the last decade. System commissioning and quality assurance procedures impose to monitor the particle beam using 2D dose measurements. Nowadays, several monitoring systems exist for hadron-therapy but all show a relatively high influence on the beam properties: indeed, most devices consist of several layers of materials that degrade the beam through scattering and energy losses. For precise treatment purposes, ultra-thin silicon strip detectors are investigated in order to reduce this beam scattering. We assess the beam size increase provoked by the Multiple Coulomb Scattering when passing through Si, to derive a target thickness. Monte-Carlo based simulations show a characteristic scattering opening angle lower than 1 mrad for thicknesses below 20 {mu}m. We then evaluated the fabrication process feasibility. We successfully thinned down silicon wafers to thicknesses lower than 10 {mu}m over areas of several cm{sup 2}. Strip detectors are presently being processed and they will tentatively be thinned down to 20 {mu}m. Moreover, two-dimensional TCAD simulations were carried out to investigate the beam detector performances on p-type Si substrates. Additionally, thick and thin substrates have been compared thanks to electrical simulations. Reducing the pitch between the strips increases breakdown voltage, whereas leakage current is quite insensitive to strips geometrical configuration. The samples are to be characterized as soon as possible in one of the IBA hadron-therapy facilities. For hadron-therapy, this would represent a considerable step forward in terms of treatment precision. (authors)

  13. Role of the P-Type ATPases, ATP7A and ATP7B in brain copper homeostasis

    Directory of Open Access Journals (Sweden)

    Jonathon eTelianidis

    2013-08-01

    Full Text Available Over the past two decades there have been significant advances in our understanding of copper homeostasis and the pathological consequences of copper dysregulation. Cumulative evidence is revealing a complex regulatory network of proteins and pathways that maintain copper homeostasis. The recognition of copper dysregulation as a key pathological feature in prominent neurodegenerative disorders such as Alzheimer’s, Parkinson’s and prion diseases has led to increased research focus on the mechanisms controlling copper homeostasis in the brain. The copper-transporting P-Type ATPases (copper-ATPases, ATP7A and ATP7B, are critical components of the copper regulatory network. Our understanding of the biochemistry and cell biology of these complex proteins has grown significantly since their discovery in 1993. They are large polytopic transmembrane proteins with six copper-binding motifs within the cytoplasmic N-terminal domain, eight transmembrane domains and highly conserved catalytic domains. These proteins catalyze ATP-dependent copper transport across cell membranes for the metallation of many essential cuproenzymes, as well as for the removal of excess cellular copper to prevent copper toxicity. A key functional aspect of these copper transporters is their copper-responsive trafficking between the trans-Golgi network and the cell periphery. ATP7A- and ATP7B-deficiency, due to genetic mutation, underlie the inherited copper transport disorders, Menkes and Wilson diseases, respectively. Their importance in maintaining brain copper homeostasis is underscored by the severe neuropathological deficits in these disorders. Herein we will review and update our current knowledge of these copper transporters in the brain and the central nervous system, their distribution and regulation, their role in normal brain copper homeostasis and how their absence or dysfunction contributes to disturbances in copper homeostasis and neurodegeneration.

  14. p-Type Transparent Conducting Oxide/n-Type Semiconductor Heterojunctions for Efficient and Stable Solar Water Oxidation.

    Science.gov (United States)

    Chen, Le; Yang, Jinhui; Klaus, Shannon; Lee, Lyman J; Woods-Robinson, Rachel; Ma, Jie; Lum, Yanwei; Cooper, Jason K; Toma, Francesca M; Wang, Lin-Wang; Sharp, Ian D; Bell, Alexis T; Ager, Joel W

    2015-08-05

    Achieving stable operation of photoanodes used as components of solar water splitting devices is critical to realizing the promise of this renewable energy technology. It is shown that p-type transparent conducting oxides (p-TCOs) can function both as a selective hole contact and corrosion protection layer for photoanodes used in light-driven water oxidation. Using NiCo2O4 as the p-TCO and n-type Si as a prototypical light absorber, a rectifying heterojunction capable of light driven water oxidation was created. By placing the charge separating junction in the Si using a np(+) structure and by incorporating a highly active heterogeneous Ni-Fe oxygen evolution catalyst, efficient light-driven water oxidation can be achieved. In this structure, oxygen evolution under AM1.5G illumination occurs at 0.95 V vs RHE, and the current density at the reversible potential for water oxidation (1.23 V vs RHE) is >25 mA cm(-2). Stable operation was confirmed by observing a constant current density over 72 h and by sensitive measurements of corrosion products in the electrolyte. In situ Raman spectroscopy was employed to investigate structural transformation of NiCo2O4 during electrochemical oxidation. The interface between the light absorber and p-TCO is crucial to produce selective hole conduction to the surface under illumination. For example, annealing to produce more crystalline NiCo2O4 produces only small changes in its hole conductivity, while a thicker SiOx layer is formed at the n-Si/p-NiCo2O4 interface, greatly reducing the PEC performance. The generality of the p-TCO protection approach is demonstrated by multihour, stable, water oxidation with n-InP/p-NiCo2O4 heterojunction photoanodes.

  15. Pristine and Al-doped hematite printed films as photoanodes of p-type dye-sensitized solar cells

    Science.gov (United States)

    Congiu, Mirko; De Marco, Maria L.; Bonomo, Matteo; Nunes-Neto, Oswaldo; Dini, Danilo; Graeff, Carlos F. O.

    2017-01-01

    We hereby propose a non-expensive method for the deposition of pure and Al-doped hematite photoanodes in the configuration of thin films for the application of dye-sensitized solar cells (DSSC). The electrodes have been prepared from hematite nanoparticles that were obtained by thermal degradation of a chemical precursor. The particles have been used in the preparation of a paste, suitable for both screen printing and doctor blade deposition. The paste was then spread on fluorine-doped tin oxide (FTO) to obtain porous hematite electrodes. The electrodes have been sensitized using N3 and D5 dyes and were characterized through current/voltage curves under simulated sun light (1 sun, AM 1.5) with a Pt counter electrode. Al-doping of hematite showed interesting changes in the physical and electrochemical characteristics of sensitized photoanodes since we could notice the growth of AlFe2O4 (hercynite) as a secondary crystal phase into the oxides obtained by firing the mixtures of two chemical precursors at different molar ratios. Pure and Al-doped hematite electrodes have been used in a complete n-type DSSCs. The kinetics of charge transfer through the interface dye/electrolyte was studied and compared to that of a typical p-type DSSC based on NiO photocathodes sensitized with erythrosine B. The results suggest a potential application of both Fe2O3 and Fe2O3/AlFe2O4 as photoanodes of a tandem DSSC.

  16. Role of the P-Type ATPases, ATP7A and ATP7B in brain copper homeostasis.

    Science.gov (United States)

    Telianidis, Jonathon; Hung, Ya Hui; Materia, Stephanie; Fontaine, Sharon La

    2013-01-01

    Over the past two decades there have been significant advances in our understanding of copper homeostasis and the pathological consequences of copper dysregulation. Cumulative evidence is revealing a complex regulatory network of proteins and pathways that maintain copper homeostasis. The recognition of copper dysregulation as a key pathological feature in prominent neurodegenerative disorders such as Alzheimer's, Parkinson's, and prion diseases has led to increased research focus on the mechanisms controlling copper homeostasis in the brain. The copper-transporting P-type ATPases (copper-ATPases), ATP7A and ATP7B, are critical components of the copper regulatory network. Our understanding of the biochemistry and cell biology of these complex proteins has grown significantly since their discovery in 1993. They are large polytopic transmembrane proteins with six copper-binding motifs within the cytoplasmic N-terminal domain, eight transmembrane domains, and highly conserved catalytic domains. These proteins catalyze ATP-dependent copper transport across cell membranes for the metallation of many essential cuproenzymes, as well as for the removal of excess cellular copper to prevent copper toxicity. A key functional aspect of these copper transporters is their copper-responsive trafficking between the trans-Golgi network and the cell periphery. ATP7A- and ATP7B-deficiency, due to genetic mutation, underlie the inherited copper transport disorders, Menkes and Wilson diseases, respectively. Their importance in maintaining brain copper homeostasis is underscored by the severe neuropathological deficits in these disorders. Herein we will review and update our current knowledge of these copper transporters in the brain and the central nervous system, their distribution and regulation, their role in normal brain copper homeostasis, and how their absence or dysfunction contributes to disturbances in copper homeostasis and neurodegeneration.

  17. Evolution of the P-type II ATPase gene family in the fungi and presence of structural genomic changes among isolates of Glomus intraradices

    Directory of Open Access Journals (Sweden)

    Sanders Ian R

    2006-03-01

    Full Text Available Abstract Background The P-type II ATPase gene family encodes proteins with an important role in adaptation of the cell to variation in external K+, Ca2+ and Na2+ concentrations. The presence of P-type II gene subfamilies that are specific for certain kingdoms has been reported but was sometimes contradicted by discovery of previously unknown homologous sequences in newly sequenced genomes. Members of this gene family have been sampled in all of the fungal phyla except the arbuscular mycorrhizal fungi (AMF; phylum Glomeromycota, which are known to play a key-role in terrestrial ecosystems and to be genetically highly variable within populations. Here we used highly degenerate primers on AMF genomic DNA to increase the sampling of fungal P-Type II ATPases and to test previous predictions about their evolution. In parallel, homologous sequences of the P-type II ATPases have been used to determine the nature and amount of polymorphism that is present at these loci among isolates of Glomus intraradices harvested from the same field. Results In this study, four P-type II ATPase sub-families have been isolated from three AMF species. We show that, contrary to previous predictions, P-type IIC ATPases are present in all basal fungal taxa. Additionally, P-Type IIE ATPases should no longer be considered as exclusive to the Ascomycota and the Basidiomycota, since we also demonstrate their presence in the Zygomycota. Finally, a comparison of homologous sequences encoding P-type IID ATPases showed unexpectedly that indel mutations among coding regions, as well as specific gene duplications occur among AMF individuals within the same field. Conclusion On the basis of these results we suggest that the diversification of P-Type IIC and E ATPases followed the diversification of the extant fungal phyla with independent events of gene gains and losses. Consistent with recent findings on the human genome, but at a much smaller geographic scale, we provided evidence

  18. Characterization and Stability of Na-doped p-type ZnO Thin Films Preparation by Reactive DC Magnetron Sputtering

    Institute of Scientific and Technical Information of China (English)

    JI Zhen-guo; LIU Fang; HE Hai-yan; HAN Wei-zhi

    2009-01-01

    Na-doped p-type ZnO thin films have been realized by DC reactive magnetron sputtering with a set of metal-Zn targets doped with various Na contents and under different substrate temperatures,respectively.Hall effect measurement,field-emission SEM,X-ray diffraction and optical transmission were carried out to investigate the effects of Na content and substrate temperature on the properties of p-type films. Results indicate that all the Na-doped ZnO films are strongly (002) oriented,and have an average transmittance ~85% in the visible region.Na-doped p-type ZnO films with good structural,electrical,and optical properties can only be obtained at an intermediate amount of Na content and under appropriate substrate temperature.At the optimal condition,the Na-doped p-type ZnO has the lowest resistivity of 13.8Ω· cm with the carrier concentration as high as 1.07×10~(18) cm~(-3).The stability of the Na-doped p-type ZnO is also studied in this paper and it is found that the electrical properties keep stable in a period of one month.

  19. Hot-wire chemical vapor deposition prepared aluminum doped p-type microcrystalline silicon carbide window layers for thin film silicon solar cells

    Science.gov (United States)

    Chen, Tao; Köhler, Florian; Heidt, Anna; Carius, Reinhard; Finger, Friedhelm

    2014-01-01

    Al-doped p-type microcrystalline silicon carbide (µc-SiC:H) thin films were deposited by hot-wire chemical vapor deposition at substrate temperatures below 400 °C. Monomethylsilane (MMS) highly diluted in hydrogen was used as the SiC source in favor of SiC deposition in a stoichiometric form. Aluminum (Al) introduced from trimethylaluminum (TMAl) was used as the p-type dopant. The material property of Al-doped p-type µc-SiC:H thin films deposited with different deposition pressure and filament temperature was investigated in this work. Such µc-SiC:H material is of mainly cubic (3C) SiC polytype. For certain conditions, like high deposition pressure and high filament temperature, additional hexagonal phase and/or stacking faults can be observed. P-type µc-SiC:H thin films with optical band gap E04 ranging from 2.0 to 2.8 eV and dark conductivity ranging from 10-5 to 0.1 S/cm can be prepared. Such transparent and conductive p-type µc-SiC:H thin films were applied in thin film silicon solar cells as the window layer, resulting in an improved quantum efficiency at wavelengths below 480 nm.

  20. Bacterial Cytotoxins Target Rho GTPases

    Science.gov (United States)

    Schmidt, Gudula; Aktories, Klaus

    1998-06-01

    Low molecular mass GTPases of the Rho family, which are involved in the regulation of the actin cytoskeleton and in various signal transduction processes, are the eukaryotic targets of bacterial protein toxins. The toxins covalently modify Rho proteins by ADP ribosylation, glucosylation, and deamidation, thereby inactivating and activating the GTPases.

  1. n- and p-type transport in (110) GaAs substrates, single- and double-cleave structures

    Energy Technology Data Exchange (ETDEWEB)

    Roth, S.F.

    2007-06-06

    In this work low-dimensional systems based on GaAs/AlGaAs are investigated with either holes (p-type) in two-dimensional (2D) systems or electrons (n-type) in one-dimensional (1D) systems as charge carriers. Two-dimensional hole systems (2DHS) are grown with molecular beam epitaxy both on (110) wafers and (1 anti 10) facets with the cleaved-edge overgrowth (CEO) method. We use Si as an acceptor by modulating the growth conditions to fabricate the 2DHS in single-interface heterojunction quantum wells. The mobility of the structures reaches up to 7.0 x 10{sup 5} cm{sup 2}/Vs along the [1 anti 10]-direction and 4.1 x 10{sup 5} cm{sup 2}/Vs along the [001]-direction at a hole density of 1.2 x 10{sup 11} cm{sup -2}. Effective values for anisotropic effective hole masses and scattering times are obtained. Inversion asymmetry induced spin splitting results in different spin densities, which yield beatings of the Shubnikov-de Haas oscillations at low temperatures. In a perpendicular magnetic field the 2DHS is quantized into Landau levels, which depend nonlinearly on B due to a strong mixing of light- and heavy-holes. When the Landau levels anticross on the (110) facet, additional peaks appear within minima of the quantum Hall effect. Thermal activation measurements demonstrate a B-dependent energy gap consistent with such an anticrossing. In the second part of the thesis an electron quantum wire is fabricated with twofold cleaved-edge overgrowth. A variation of the conduction band energy in the substrate layers can directly transfer a potential modulation to the adjacent quantum wire. The concept of a transfer potential applied to a narrow two-dimensional system is demonstrated as a first step. Finally, in narrow quantum well samples a simple vertical quantum wire is successfully demonstrated and contacted at each end with n{sup +}-GaAs layers via two-dimensional (2D) leads. We characterize the 2D lead density and mobility for both cleave facets with four

  2. P-type nitrogen-doped ZnO nanostructures with controlled shape and doping level by facile microwave synthesis.

    Science.gov (United States)

    Herring, Natalie P; Panchakarla, Leela S; El-Shall, M Samy

    2014-03-04

    We report herein the development of a facile microwave irradiation (MWI) method for the synthesis of high-quality N-doped ZnO nanostructures with controlled morphology and doping level. We present two different approaches for the MWI-assisted synthesis of N-doped ZnO nanostructures. In the first approach, N-doping of Zn-poor ZnO prepared using zinc peroxide (ZnO2) as a precursor is carried out under MWI in the presence of urea as a nitrogen source and oleylamine (OAm) as a capping agent for the shape control of the resulting N-doped ZnO nanostructures. Our approach utilizes the MWI process for the decomposition of ZnO2, where the rapid transfer of energy directly to ZnO2 can cause an instantaneous internal temperature rise and, thus, the activation energy for the ZnO2 decomposition is essentially decreased as compared to the decomposition under conductive heating. In the second synthesis method, a one-step synthesis of N-doped ZnO nanostructures is achieved by the rapid decomposition of zinc acetate in a mixture of urea and OAm under MWI. We demonstrate, for the first time, that MWI decomposition of zinc acetate in a mixture of OAm and urea results in the formation of N-doped nanostructures with controlled shape and N-doping level. We report a direct correlation between the intensity of the Raman scattering bands in N-doped ZnO and the concentration of urea used in the synthesis. Electrochemical measurements demonstrate the successful synthesis of stable p-type N-doped ZnO nanostructures using the one-step MWI synthesis and, therefore, allow us to investigate, for the first time, the relationship between the doping level and morphology of the ZnO nanostructures. The results provide strong evidence for the control of the electrical behavior and the nanostructured shapes of ZnO nanoparticles using the facile MWI synthesis method developed in this work.

  3. Fabrication and photoelectric properties of La-doped p-type ZnO nanofibers and crossed p-n homojunctions by electrospinning.

    Science.gov (United States)

    Zhang, H D; Yu, M; Zhang, J C; Sheng, C H; Yan, X; Han, W P; Liu, Y C; Chen, S; Shen, G Z; Long, Y Z

    2015-06-21

    La-doped p-type ZnO nanofibers were successfully synthesized by electrospinning, followed by calcination. The microstructure and morphology of the La-doped ZnO nanofibers were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The field effect curve of individual nanofibers confirms that the resulting La-doped ZnO fibers are p-type semiconductors. The doping mechanism is discussed. Furthermore, crossed p-n homojunction nanofibers were also prepared based on electrospun La-doped p-type ZnO and n-type pure ZnO fibers. The current-voltage curve shows the typical rectifying characteristic of a p-n homojunction device. The turn-on voltage appears at about 2.5 V under the forward bias and the reverse current is impassable.

  4. Fabrication and photoelectric properties of La-doped p-type ZnO nanofibers and crossed p-n homojunctions by electrospinning

    Science.gov (United States)

    Zhang, H. D.; Yu, M.; Zhang, J. C.; Sheng, C. H.; Yan, X.; Han, W. P.; Liu, Y. C.; Chen, S.; Shen, G. Z.; Long, Y. Z.

    2015-06-01

    La-doped p-type ZnO nanofibers were successfully synthesized by electrospinning, followed by calcination. The microstructure and morphology of the La-doped ZnO nanofibers were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The field effect curve of individual nanofibers confirms that the resulting La-doped ZnO fibers are p-type semiconductors. The doping mechanism is discussed. Furthermore, crossed p-n homojunction nanofibers were also prepared based on electrospun La-doped p-type ZnO and n-type pure ZnO fibers. The current-voltage curve shows the typical rectifying characteristic of a p-n homojunction device. The turn-on voltage appears at about 2.5 V under the forward bias and the reverse current is impassable.

  5. Very low surface recombination velocity on p-type c-Si by high-rate plasma-deposited aluminum oxide

    Science.gov (United States)

    Saint-Cast, Pierre; Kania, Daniel; Hofmann, Marc; Benick, Jan; Rentsch, Jochen; Preu, Ralf

    2009-10-01

    Aluminum oxide layers can provide excellent passivation for lowly and highly doped p-type silicon surfaces. Fixed negative charges induce an accumulation layer at the p-type silicon interface, resulting in very effective field-effect passivation. This paper presents highly negatively charged (Qox=-2.1×1012 cm-2) aluminum oxide layers produced using an inline plasma-enhanced chemical vapor deposition system, leading to very low effective recombination velocities (˜10 cm s-1) on low-resistivity p-type substrates. A minimum static deposition rate (100 nm min-1) at least one order of magnitude higher than atomic layer deposition was achieved on a large carrier surfaces (˜1 m2) without significantly reducing the resultant passivation quality.

  6. Design of ``push-pull'' p-type quinoid-based organic dyes with near-IR absorption: A density function theory study

    Science.gov (United States)

    Yang, Zhenqing; Li, Juan; Liu, Yun; Zhang, Wansong

    2017-04-01

    Based on an experimentally synthesized p-type dye QT-1, we screened and designed a series of quinoid-based "push-pull" dyes SPL401 - SPL407 by modifying the π-conjugated linker for ptype dye-sensitized solar cells (p-type DSSC). Further, we systematically calculated their electronic and optical properties by using the density functional theory (DFT) and the time-dependent DFT (TDDFT). The results indicate that compared to QT-1, SPL406 and SPL407, which have not only smaller energy gaps, higher oscillator strength f increased by 70% and 80%, and 141 nm and 110 nm redshifts, respectively, but also a broader absorption spectrum covering the entire visible range to the near-IR region of 1200 nm, may be the most promising candidates among SPL401 - SPL407 for p-type organic sensitizers.

  7. Origin of p-type conductivity of Sb-doped ZnO nanorods and the local structure around Sb ions

    Energy Technology Data Exchange (ETDEWEB)

    Liang, J. K.; Su, H. L., E-mail: suhlnju@hotmail.com, E-mail: ycwu@hfut.edu.cn, E-mail: jcahuang@mail.ncku.edu.tw; Wu, Y. C., E-mail: suhlnju@hotmail.com, E-mail: ycwu@hfut.edu.cn, E-mail: jcahuang@mail.ncku.edu.tw [School of Materials Science and Engineering and Anhui Provincial Key Laboratory of Advanced Functional Materials and Devices, Hefei University of Technology, Hefei 230009, Anhui (China); Chuang, P. Y.; Kuo, C. L.; Huang, S. Y. [Department of Physics, National Cheng Kung University, Tainan 701, Taiwan (China); Chan, T. S. [National Synchrotron Radiation Research Center, Hsinchu 300, Taiwan (China); Huang, J. C. A., E-mail: suhlnju@hotmail.com, E-mail: ycwu@hfut.edu.cn, E-mail: jcahuang@mail.ncku.edu.tw [Department of Physics, National Cheng Kung University, Tainan 701, Taiwan (China); Advanced Optoelectronic Technology Center and Center for Micro/Nano Science and Technology, National Cheng Kung University, Tainan 701, Taiwan (China); Taiwan Consortium of Emergent Crystalline Materials, Ministry of Science and Technology, Taipei 106, Taiwan (China)

    2015-05-25

    To probe the origin of p-type conductivity in Sb-doped ZnO, a careful and detailed synchrotron radiation study was performed. The extended X-ray absorption fine structure and X-ray photoelectron spectroscopy investigations provided the evidence for the formation of the complex defects comprising substitution Sb ions at Zn sites (Sb{sub Zn}) and Zn vacancies within the Sb-doped ZnO lattice. Such complex defects result in the increases of Sb-O coordination number and the Sb valence and thereby lead to the p-type conductivity of Sb-doped ZnO. The back-gate field-effect-transistors based on single nanorod of Sb-doped ZnO were constructed, and the stable p-type conduction behavior was confirmed.

  8. a-Si:H/c-Si heterojunction front- and back contacts for silicon solar cells with p-type base

    Energy Technology Data Exchange (ETDEWEB)

    Rostan, Philipp Johannes

    2010-07-01

    This thesis reports on low temperature amorphous silicon back and front contacts for high-efficiency crystalline silicon solar cells with a p-type base. The back contact uses a sequence of intrinsic amorphous (i-a-Si:H) and boron doped microcrystalline (p-{mu}c-Si:H) silicon layers fabricated by Plasma Enhanced Chemical Vapor Deposition (PECVD) and a magnetron sputtered ZnO:Al layer. The back contact is finished by evaporating Al onto the ZnO:Al and altogether prepared at a maximum temperature of 220 C. Analysis of the electronic transport of mobile charge carriers at the back contact shows that the two high-efficiency requirements low back contact series resistance and high quality c-Si surface passivation are in strong contradiction to each other, thus difficult to achieve at the same time. The preparation of resistance- and effective lifetime samples allows one to investigate both requirements independently. Analysis of the majority charge carrier transport on complete Al/ZnO:Al/a-Si:H/c-Si back contact structures derives the resistive properties. Measurements of the effective minority carrier lifetime on a-Si:H coated wafers determines the back contact surface passivation quality. Both high-efficiency solar cell requirements together are analyzed in complete photovoltaic devices where the back contact series resistance mainly affects the fill factor and the back contact passivation quality mainly affects the open circuit voltage. The best cell equipped with a diffused emitter with random texture and a full-area a-Si:H/c-Si back contact has an independently confirmed efficiency {eta} = 21.0 % with an open circuit voltage V{sub oc} = 681 mV and a fill factor FF = 78.7 % on an area of 1 cm{sup 2}. An alternative concept that uses a simplified a-Si:H layer sequence combined with Al-point contacts yields a confirmed efficiency {eta} = 19.3 % with an open circuit voltage V{sub oc} = 655 mV and a fill factor FF = 79.5 % on an area of 2 cm{sup 2}. Analysis of the

  9. a-Si:H/c-Si heterojunction front- and back contacts for silicon solar cells with p-type base

    Energy Technology Data Exchange (ETDEWEB)

    Rostan, Philipp Johannes

    2010-07-01

    This thesis reports on low temperature amorphous silicon back and front contacts for high-efficiency crystalline silicon solar cells with a p-type base. The back contact uses a sequence of intrinsic amorphous (i-a-Si:H) and boron doped microcrystalline (p-{mu}c-Si:H) silicon layers fabricated by Plasma Enhanced Chemical Vapor Deposition (PECVD) and a magnetron sputtered ZnO:Al layer. The back contact is finished by evaporating Al onto the ZnO:Al and altogether prepared at a maximum temperature of 220 C. Analysis of the electronic transport of mobile charge carriers at the back contact shows that the two high-efficiency requirements low back contact series resistance and high quality c-Si surface passivation are in strong contradiction to each other, thus difficult to achieve at the same time. The preparation of resistance- and effective lifetime samples allows one to investigate both requirements independently. Analysis of the majority charge carrier transport on complete Al/ZnO:Al/a-Si:H/c-Si back contact structures derives the resistive properties. Measurements of the effective minority carrier lifetime on a-Si:H coated wafers determines the back contact surface passivation quality. Both high-efficiency solar cell requirements together are analyzed in complete photovoltaic devices where the back contact series resistance mainly affects the fill factor and the back contact passivation quality mainly affects the open circuit voltage. The best cell equipped with a diffused emitter with random texture and a full-area a-Si:H/c-Si back contact has an independently confirmed efficiency {eta} = 21.0 % with an open circuit voltage V{sub oc} = 681 mV and a fill factor FF = 78.7 % on an area of 1 cm{sup 2}. An alternative concept that uses a simplified a-Si:H layer sequence combined with Al-point contacts yields a confirmed efficiency {eta} = 19.3 % with an open circuit voltage V{sub oc} = 655 mV and a fill factor FF = 79.5 % on an area of 2 cm{sup 2}. Analysis of the

  10. Impact of common metallurgical impurities on ms-Si solar cell efficiency. P-type versus n-type doped ingots

    Energy Technology Data Exchange (ETDEWEB)

    Geerligs, L.J.; Manshanden, P. [ECN Solar Energy, Petten (Netherlands); Solheim, I.; Ovrelid, E.J.; Waernes, A.N. [Sintef materials technology, Trondheim (Norway)

    2006-09-15

    Silicon solar cells based on n-type silicon wafers are less sensitive to carrier lifetime degradation due to several common metal impurities than p-base cells. The theoretical and experimental indications for this have recently received considerable attention. This paper compares p-type and n-type cells purposely contaminated with relatively high levels of impurities, processed by industrial techniques. The impurities considered are Al, Ti, and Fe, which are the dominant impurities in metallurgical silicon and natural quartz. The work also preliminary addresses the question whether the optimal wafer resistivity is the same for n-type as for p-type base mc-Si cells.

  11. Enhancement of the thermoelectric performance of p-type layered oxide Ca3Co4O9+ through heavy doping and metallic nanoinclusions

    DEFF Research Database (Denmark)

    Van Nong, Ngo; Pryds, Nini; Linderoth, Søren

    2011-01-01

    An effective way to improve the thermoelectric performance (ZT) of layered structured oxide materials by carefully choosing heavy ion doping and introducing metallic nanoinclusions is proposed. A p-type oxide material with remarkable highly improved ZT is successfully fabricated using this approach...

  12. p-Type Semiconducting Nickel Oxide as an Efficiency-Enhancing Anode Interfacial Layer in Polymer Bulk-Heterojunction Solar Cells

    National Research Council Canada - National Science Library

    Michael D. Irwin; D. Bruce Buchholz; Alexander W. Hains; Robert P. H. Chang; Tobin J. Marks

    2008-01-01

    To minimize interfacial power losses, thin (5-80 nm) layers of NiO, a p-type oxide semiconductor, are inserted between the active organic layer, poly(3-hexylthiophene) (P3HT) + [6,6]-phenyl-C₆₁...

  13. Cellular function and pathological role of ATP13A2 and related P-type transport ATPases in Parkinson's disease and other neurological disorders.

    Science.gov (United States)

    van Veen, Sarah; Sørensen, Danny M; Holemans, Tine; Holen, Henrik W; Palmgren, Michael G; Vangheluwe, Peter

    2014-01-01

    Mutations in ATP13A2 lead to Kufor-Rakeb syndrome, a parkinsonism with dementia. ATP13A2 belongs to the P-type transport ATPases, a large family of primary active transporters that exert vital cellular functions. However, the cellular function and transported substrate of ATP13A2 remain unknown. To discuss the role of ATP13A2 in neurodegeneration, we first provide a short description of the architecture and transport mechanism of P-type transport ATPases. Then, we briefly highlight key P-type ATPases involved in neuronal disorders such as the copper transporters ATP7A (Menkes disease), ATP7B (Wilson disease), the Na(+)/K(+)-ATPases ATP1A2 (familial hemiplegic migraine) and ATP1A3 (rapid-onset dystonia parkinsonism). Finally, we review the recent literature of ATP13A2 and discuss ATP13A2's putative cellular function in the light of what is known concerning the functions of other, better-studied P-type ATPases. We critically review the available data concerning the role of ATP13A2 in heavy metal transport and propose a possible alternative hypothesis that ATP13A2 might be a flippase. As a flippase, ATP13A2 may transport an organic molecule, such as a lipid or a peptide, from one membrane leaflet to the other. A flippase might control local lipid dynamics during vesicle formation and membrane fusion events.

  14. Cellular function and pathological role of ATP13A2 and related P-type transport ATPases in Parkinson's disease and other neurological disorders

    DEFF Research Database (Denmark)

    van Veen, Sarah; Sørensen, Danny M.; Holemans, Tine

    2014-01-01

    Mutations in ATP13A2 lead to Kufor-Rakeb syndrome, a parkinsonism with dementia. ATP13A2 belongs to the P-type transport ATPases, a large family of primary active transporters that exert vital cellular functions. However, the cellular function and transported substrate of ATP13A2 remain unknown. ...

  15. Fabrication of p-Type ZnO:N Films by Oxidizing Zn3N2 Films in Oxygen Plasma at Low Temperature

    Directory of Open Access Journals (Sweden)

    Yuping Jin

    2017-02-01

    Full Text Available The oxygen vacancy (VO is known as the main compensation center in p-type ZnO, which leads to the difficulty of fabricating high-quality p-type ZnO. To reduce the oxygen vacancies, we oxidized Zn3N2 films in oxygen plasma and successfully prepared p-type ZnO:N films at temperatures ranging from room temperature to 300 °C. The films were characterized by X-ray diffraction (XRD, non-Rutherford backscattering (non-RBS spectroscopy, X-ray photoelectron spectroscopy, photoluminescence spectrum, and Hall Effect. The results show that the nitrogen atoms successfully substitute the oxygen sites in the ZnO:N films. The film prepared at room temperature exhibits the highest hole concentration of 6.22 × 1018 cm−3, and the lowest resistivity of 39.47 Ω∙cm. In all ZnO:N films, the VO defects are reduced significantly. At 200 °C, the film holds the lowest value of VO defects and the strongest UV emission. These results imply that oxygen plasma is very efficient in reducing VO defects in p-type ZnO:N films, and could greatly reduce the reaction temperature. This method is significant for the development of ZnO-based optoelectronic devices.

  16. Cellular function and pathological role of ATP13A2 and related P-type transport ATPases in Parkinson’s disease and other neurological disorders

    Directory of Open Access Journals (Sweden)

    Sarah evan Veen

    2014-05-01

    Full Text Available Mutations in ATP13A2 lead to Kufor-Rakeb syndrome, a parkinsonism with dementia. ATP13A2 belongs to the P-type transport ATPases, a large family of primary active transporters that exert vital cellular functions. However, the cellular function and transported substrate of ATP13A2 remain unknown. To discuss the role of ATP13A2 in neurodegeneration, we first provide a short description of the architecture and transport mechanism of P-type transport ATPases. Then, we briefly highlight key P-type ATPases involved in neuronal disorders such as the copper transporters ATP7A (Menkes disease, ATP7B (Wilson disease, the Na+/K+-ATPases ATP1A2 (familial hemiplegic migraine and ATP1A3 (rapid-onset dystonia parkinsonism. Finally, we review the recent literature of ATP13A2 and discuss ATP13A2’s putative cellular function in the light of what is known concerning the functions of other, better-studied P-type ATPases. We critically review the available data concerning the role of ATP13A2 in heavy metal transport and propose a possible alternative hypothesis that ATP13A2 might be a flippase. As a flippase, ATP13A2 may transport an organic molecule, such as a lipid or a peptide, from one membrane leaflet to the other. A flippase might control local lipid dynamics during vesicle formation and membrane fusion events.

  17. Sensitive optical bio-sensing of p-type WSe2 hybridized with fluorescent dye attached DNA by doping and de-doping effects

    Science.gov (United States)

    Han, Kyu Hyun; Kim, Jun Young; Jo, Seong Gi; Seo, Changwon; Kim, Jeongyong; Joo, Jinsoo

    2017-10-01

    Layered transition metal dichalcogenides, such as MoS2, WSe2 and WS2, are exciting two-dimensional (2D) materials because they possess tunable optical and electrical properties that depend on the number of layers. In this study, the nanoscale photoluminescence (PL) characteristics of the p-type WSe2 monolayer, and WSe2 layers hybridized with the fluorescent dye Cy3 attached to probe-DNA (Cy3/p-DNA), have been investigated as a function of the concentration of Cy3/DNA by using high-resolution laser confocal microscopy. With increasing concentration of Cy3/p-DNA, the measured PL intensity decreases and its peak is red-shifted, suggesting that the WSe2 layer has been p-type doped with Cy3/p-DNA. Then, the PL intensity of the WSe2/Cy3/p-DNA hybrid system increases and the peak is blue-shifted through hybridization with relatively small amounts of target-DNA (t-DNA) (50–100 nM). This effect originates from charge and energy transfer from the Cy3/DNA to the WSe2. For t-DNA detection, our systems using p-type WSe2 have the merit in terms of the increase of PL intensity. The p-type WSe2 monolayers can be a promising nanoscale 2D material for sensitive optical bio-sensing based on the doping and de-doping responses to biomaterials.

  18. Formation and annealing of metastable (interstitial oxygen)-(interstitial carbon) complexes in n- and p-type silicon

    CERN Document Server

    Makarenko, L F; Lastovskii, S B; Murin, L I; Moll, M; Pintilie, I

    2014-01-01

    It is shown experimentally that, in contrast to the stable configuration of (interstitial carbon)-(interstitial oxygen) complexes (CiOi), the corresponding metastable configuration (CiOi{*}) cannot be found in n-Si based structures by the method of capacitance spectroscopy. The rates of transformation CiOi{*} -> CiOi are practically the same for both n- and p-Si with a concentration of charge carriers of no higher than 10(13) cm(-3). It is established that the probabilities of the simultaneous formation of stable and metastable configurations of the complex under study in the case of the addition of an atom of interstitial carbon to an atom of interstitial oxygen is close to 50\\%. This is caused by the orientation dependence of the interaction potential of an atom of interstitial oxygen with an interstitial carbon atom, which diffuses to this oxygen atom.

  19. Effect of Ba Filling Fraction on Thermoelectric Properties of p-type BayFe1.6Co2.4Sb12

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Effects of Ba filling fraction on the thermoelectric properties of p-type filled skutterudite compounds BayFe1.6Co2.4Sb12(y=0-0.63) were investigated.BayFe1.6Co2.4Sb12 showed p-type conduction.The hall coefficient (RH) and seebeck coefficient(α) increased with increasing Ba filling fraction.But hole concentration (p) and electrical conductivity (σ) decreased.While Ba filling fraction was about 0.4,the lattice thermal conductivity (κL) reached the minimum value.The results show that effect of Ba rattling on phonon scattering is the strongest as Sb-icosahedron partial voids are filled by Ba.A maximum dimensionless thermoelectric figure of merit (ZT) value of 0.7 was obtained for Ba0.38Fe1.6Co2.4 Sb12 at 750K.

  20. Adjustable hydrazine modulation of single-wall carbon nanotube network field effect transistors from p-type to n-type

    Science.gov (United States)

    Dai, Ruixuan; Xie, Dan; Xu, Jianlong; Sun, Yilin; Sun, MengXing; Zhang, Cheng; Li, Xian

    2016-11-01

    Single-wall carbon nanotube (SWCNT) network field effect transistors (FETs), which show decent p-type electronic properties, have been fabricated. The use of hydrazine as an aqueous solution and a strong n-type dopant for the SWCNTs is demonstrated in this paper. The electrical properties are obviously tuned by hydrazine treatment at different concentrations on the surface of the SWCNT network FETs. The transport behavior of SWCNTs can be modulated from p-type to n-type, demonstrating the controllable and adjustable doping effect of hydrazine. With a higher concentration of hydrazine, more electrons can be transferred from the hydrazine molecules to the SWCNT network films, thus resulting in a change of threshold voltage, carrier mobility and on-current. By cleaning the device, the hydrazine doping effects vanish, which indicates that the doping effects of hydrazine are reversible. Through x-ray photoelectron spectroscopy (XPS) characterization, the doping effects of hydrazine have also been studied.

  1. Reactive ion etching (RIE) induced p- to n-type conversion in extrinsically doped p-type HgCdTe

    Energy Technology Data Exchange (ETDEWEB)

    Musca, C.A.; Smith, E.P.G.; Siliquini, J.F.; Dell, J.M.; Antoszewski, J.; Faraone, L. [Univ. of Western Australia, Nedlands, Western Australia (Australia). Dept. of Electrical and Electronic Engineering; Piotrowski, J. [Vigo System Ltd., Warsaw (Poland)

    1998-12-31

    Mercury annealing of reactive ion etching (RIE) induced p- to n-type conversion in extrinsically doped p-type epitaxial layers of HgCdTe (x = 0.31) has been used to reconvert n-type conversion sustained during RIE processing. For the RIE processing conditions used (400 mT, CH{sub 4}/H{sub 2}, 90 W) p- to n-type conversion was observed using laser beam induced current (LBIC) measurements. After a sealed tube mercury anneal at 200 C for 17 hours, LBIC measurements clearly indicated no n-type converted region remained. Subsequent Hall measurements confirmed that the material consisted of a p-type layer, with electrical properties equivalent to that of the initial as-grown wafer (N{sub A}-N{sub D} = 2 {times} 10{sup 16} cm{sup {minus}3}, {mu} = 350 cm{sup 2}.V{sup {minus}1}.s{sup {minus}1}).

  2. Cellular function and pathological role of ATP13A2 and related P-type transport ATPases in Parkinson's disease and other neurological disorders

    DEFF Research Database (Denmark)

    van Veen, Sarah; Sørensen, Danny M.; Holemans, Tine;

    2014-01-01

    . To discuss the role of ATP13A2 in neurodegeneration, we first provide a short description of the architecture and transport mechanism of P-type transport ATPases. Then, we briefly highlight key P-type ATPases involved in neuronal disorders such as the copper transporters ATP7A (Menkes disease), ATP7B (Wilson...... disease), the Na+/K+-ATPases ATP1A2 (familial hemiplegic migraine) and ATP1A3 (rapid-onset dystonia parkinsonism). Finally, we review the recent literature of ATP13A2 and discuss ATP13A2's putative cellular function in the light of what is known concerning the functions of other, better-studied P...

  3. Gas doping ratio effects on p-type hydrogenated nanocrystalline silicon thin films grown by hot-wire chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Luo, P.Q. [Solar Energy Institute, Department of Physics, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240 (China)], E-mail: robt@sjtu.edu.cn; Zhou, Z.B. [Solar Energy Institute, Department of Physics, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240 (China)], E-mail: zbzhou@sjtu.edu.cn; Chan, K.Y. [Thin Film Laboratory, Faculty of Engineering, Multimedia University, Jalan Multimedia, Cyberjaya 63100, Selangor (Malaysia); Tang, D.Y.; Cui, R.Q.; Dou, X.M. [Solar Energy Institute, Department of Physics, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240 (China)

    2008-12-30

    Hydrogenated nanocrystalline silicon (nc-Si:H) grown by hot-wire chemical vapor deposition (HWCVD) has recently drawn significant attention in the area of thin-film large area optoelectronics due to possibility of high deposition rate. We report on the effects of diborane (B{sub 2}H{sub 6}) doping ratio on the microstructural and optoelectrical properties of the p-type nc-Si:H thin films grown by HWCVD at low substrate temperature of 200 deg. C and with high hydrogen dilution ratio of 98.8%. An attempt has been made to elucidate the boron doping mechanism of the p-type nc-Si:H thin films deposited by HWCVD and the correlation between the B{sub 2}H{sub 6} doping ratio, crystalline volume fraction, optical band gap and dark conductivity.

  4. A Win-Win Effect for Both the Ferromagnetism and the Dopability of p-Type Doping in ZnO:(Cu+N)

    Science.gov (United States)

    Wei, Ling; Zhang, Wei-Feng

    2013-08-01

    We investigate the electronic structures and magnetic properties of ZnO doped with N, Cu, and (Cu+N) by using a first principles method and considering the strong correlation effect. It is interesting to compare these three systems. ZnO:N has weak p-type doping and unstable ferromagnetism, while ZnO:Cu becomes insulating due to the Jahn—Teller effect. Cu and N codoping can not only greatly improve the dopability of p-type doping accompanying the Jahn—Teller fading, but also enhance the ferromagnetism at the same time. The calculation results indicate that there is a win-win effect between N and Cu dopants in the ZnO:(Cu+N) system, which could possibly find applications in spintronics besides optoelectronics.

  5. Hybrid p-type ZnO film and n-type ZnO nanorod p-n homo-junction for efficient photovoltaic applications

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jong Hyun; Lee, Jun Seok; Lee, Sang Hyo; Nam, Hye Won [Novel Functional Materials and Device Lab, Department of Physics, Hanyang University, Seoul 133-791 (Korea, Republic of); Hong, Jin Pyo, E-mail: jphong@hanyang.ac.k [Novel Functional Materials and Device Lab, Department of Physics, Hanyang University, Seoul 133-791 (Korea, Republic of); Cha, Seoung Nam; Park, Young Jun; Kim, Jong Min [Samsung Advanced Institute of Technology, P.O. Box 11, 1 Suwon 440-600 (Korea, Republic of)

    2010-09-01

    Simple hybrid p-n homo-junctions using p-type ZnO thin films and n-type nanorods grown on fluorine tin oxide (FTO) substrates for photovoltaic applications are described. The ZnO nanorods (1.5 {mu}m) were synthesized via an aqueous solution method with zinc nitrate hexahydrate and hexamethylenetetramine on ZnO seed layers. The 10-nm-thick ZnO seed layers showed n-type conductivity on FTO substrates and were deposited with a sputtering-based method. After synthesizing ZnO nanorods, aluminum-nitride co-doped p-type ZnO films (200 nm) were efficiently grown using pre-activated nitrogen (N) plasma sources with an inductively-coupled dual-target co-sputtering system. The structural and electrical properties of hybrid p-n homo-junctions were investigated by scanning electron microscopy, transmittance spectrophotometry, and I-V measurements.

  6. DLTS study of deep centers created by Ar-ion bombardment in n- and p-type MBE AlGaAs

    Science.gov (United States)

    Kaniewska, M.; Sadowski, J.; Guziewicz, M.

    2004-07-01

    The thermal emission rate of dominant traps in molecular beam epitaxial n- and p-type AlGaAs subjected to Ar-ion beam etching has been studied by deep level transient spectroscopy. Emission signatures were determined and compared with results obtained by other authors for irradiation induced and grown-in defects in GaAs and AlGaAs. The most significant result of this study is the observation that the process-induced defects in n- as well as p-type AlGaAs exhibit emission signatures, which are characteristic of native defects found in GaAs. The effect is discussed in terms of a compensation effect and related band bending.

  7. Efros-Shklovskii type variable range hopping conduction and magnetoresistance in p-type CuGa3Te5

    Science.gov (United States)

    Wasim, S. M.; Essaleh, L.; Marín, G.; Rincón, C.; Amhil, S.; Galibert, J.

    2017-07-01

    Variable range hopping conduction of Efros and Shklovskii type when a Coulomb gap appears at the Fermi level due to repulsive interaction of the holes, is observed in two different temperature regions in the ordered defect compound CuGa3Te5. Since this type of electrical conduction appears over a very wide temperature range between 4 and 150 K, not reported before in elemental II-VI, and I-III-VI2 compound semiconductors, three different methods were employed to analyze the data to confirm this behavior. This is also supported from the study of the variation of impurity band hole mobility with temperature. Other hopping parameters are estimated. The logarithmic variation of the positive magnetoresistance at different temperatures in the two regions varies as B2 and B1/5 above and below the critical field Bc, that separates the low and high magnetic field regions. This is in complete agreement with the theory of Efros and Shklovskii. The temperature dependence of the corresponding slope as T- 3/2 and T- 3/5 is also consistent with the proposed models.

  8. Single ZnO nanowire/p-type GaN heterojunctions for photovoltaic devices and UV light-emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Bie, Ya-Qing; Liao, Zhi-Min; Wang, Peng-Wei; Zhou, Yang-Bo; Han, Xiao-Bing; Ye, Yu; Zhao, Qing; Wu, Xiao-Song; Dai, Lun; Xu, Jun; Sang, Li-Wen; Deng, Jun-Jing; Laurent, K.; Yu, Da-Peng [State Key Laboratory for Mesoscopic Physics, Department of Physics, Peking University, Beijing 100871 (China); Leprince-Wang, Y. [Laboratoire de Physique des Materiaux Divises et Interfaces (LPMDI), CNRS-UMR 8108, Universite Paris-Est., Marne la Vallee Cedex 2, 77454, (France)

    2010-10-08

    We fabricate heterojunctions consisting of a single n-type ZnO nanowire and a p-type GaN film. The photovoltaic effect of heterojunctions exhibits open-circuit voltages ranging from 2 to 2.7 V, and a maximum output power reaching 80 nW. Light-emitting diodes with UV electroluminescence based on the heterojunctions are demonstrated. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  9. Design of n - and p -type oxide thermoelectrics in LaNiO3/SrTiO3(001 ) superlattices exploiting interface polarity

    Science.gov (United States)

    Geisler, Benjamin; Blanca-Romero, Ariadna; Pentcheva, Rossitza

    2017-03-01

    We investigate the structural, electronic, transport, and thermoelectric properties of LaNiO3/SrTiO3(001 ) superlattices containing either exclusively n - or p -type interfaces or coupled interfaces of opposite polarity by using density functional theory calculations with an on-site Coulomb repulsion term. The results show that significant octahedral tilts are induced in the SrTiO3 part of the superlattice. Moreover, the La-Sr distances and Ni-O out-of-plane bond lengths at the interfaces exhibit a distinct variation by about 7 % with the sign of the electrostatic doping. In contrast to the much studied LaAlO3/SrTiO3 system, the charge mismatch at the interfaces is exclusively accommodated within the LaNiO3 layers, whereas the interface polarity leads to a band offset and to the formation of an electric field within the coupled superlattice. Features of the electronic structure indicate an orbital-selective quantization of quantum well states. The potential- and confinement-induced multiband splitting results in complex cylindrical Fermi surfaces with a tendency towards nesting that depends on the interface polarity. The analysis of the thermoelectric response reveals a particularly large positive Seebeck coefficient (135 μ V /K) and a high figure of merit (0.35) for room-temperature cross-plane transport in the p -type superlattice that is attributed to the participation of the SrTiO3 valence band. Superlattices with either n - or p -type interfaces show cross-plane Seebeck coefficients of opposite sign and thus emerge as a platform to construct an oxide-based thermoelectric generator with structurally and electronically compatible n - and p -type oxide thermoelectrics.

  10. Completely transparent ohmic electrode on p-type AlGaN for UV LEDs with core-shell Cu@alloy nanosilk network (Conference Presentation)

    Science.gov (United States)

    Cai, Duanjun; Wang, Huachun; Huang, Youyang; Wu, Chenping; Chen, Xiaohong; Gao, Na; Wei, Tongbo T.; Wang, Junxi; Li, Shuping; Kang, Junyong

    2016-09-01

    Metal nanowire networks hold a great promise, which have been supposed the only alternative to ITO as transparent electrodes for their excellent performance in touch screen, LED and solar cell. It is well known that the difficulty in making transparent ohmic electrode to p-type high-Al-content AlGaN conducting layer has highly constrained the further development of UV LEDs. On the IWN-2014, we reported the ohmic contact to n, p-GaN with direct graphene 3D-coated Cu nanosilk network and the fabrication of complete blue LED. On the ICNS-2015, we reported the ohmic contact to n-type AlGaN conducting layer with Cu@alloy nanosilk network. Here, we further demonstrate the latest results that a novel technique is proposed for fabricating transparent ohmic electrode to high-Al-content AlGaN p-type conducting layer in UV LEDs using Cu@alloy core-shell nanosilk network. The superfine copper nanowires (16 nm) was synthesized for coating various metals such as Ni, Zn, V or Ti with different work functions. The transmittance showed a high transparency (> 90%) over a broad wavelength range from 200 to 3000 nm. By thermal annealing, ohmic contact was achieved on p-type Al0.5Ga0.5N layer with Cu@Ni nanosilk network, showing clearly linear I-V curve. By skipping the p-type GaN cladding layer, complete UV LED chip was fabricated and successfully lit with bright emission at 276 nm.

  11. Change in the electrical conductivity of SnO{sub 2} crystal from n-type to p-type conductivity

    Energy Technology Data Exchange (ETDEWEB)

    Villamagua, Luis, E-mail: luis.villamagua@tyndall.ie [Grupo de Fisicoquímica de Materiales, Universidad Técnica Particular de Loja, Apartado 11-01-608, Loja (Ecuador); Dipartimento di Ingegneria per l’Ambiente e il Territorio e Ingegneria Chimica, Università della Calabria, 87036 Rende (CS) (Italy); Stashans, Arvids [Grupo de Fisicoquímica de Materiales, Universidad Técnica Particular de Loja, Apartado 11-01-608, Loja (Ecuador); Lee, Po-Ming; Liu, Yen-Shuo; Liu, Cheng-Yi [Department of Chemical and Materials Engineering, National Central University, Jhong-Li, Taiwan (China); Carini, Manuela [Dipartimento di Ingegneria per l’Ambiente e il Territorio e Ingegneria Chimica, Università della Calabria, 87036 Rende (CS) (Italy)

    2015-05-01

    Highlights: • Switch from n-type to p-type conductivity in SnO{sub 2} has been studied. • Computational DFT + U method where used. • X-ray diffraction and X-ray photoelectron spectroscopy where used. • Al- and N-codoped SnO{sub 2} compound shows stable p-type conductivity. • Low resistivity (3.657 × 10{sup −1} Ω cm) has been obtained. • High carrier concentration (4.858 × 10{sup 19} cm{sup −3}) has been obtained. - Abstract: The long-sought fully transparent technology will not come true if the n region of the p–n junction does not get as well developed as its p counterpart. Both experimental and theoretical efforts have to be used to study and discover phenomena occurring at the microscopic level in SnO{sub 2} systems. In the present paper, using the DFT + U approach as a main tool and the Vienna ab initio Simulation Package (VASP) we reproduce both intrinsic n-type as well as p-type conductivity in concordance to results observed in real samples of SnO{sub 2} material. Initially, an oxygen vacancy (1.56 mol% concentration) combined with a tin-interstitial (1.56 mol% concentration) scheme was used to achieve the n-type electrical conductivity. Later, to attain the p-type conductivity, crystal already possessing n-type conductivity, was codoped with nitrogen (1.56 mol% concentration) and aluminium (12.48 mol% concentration) impurities. Detailed explanation of structural changes endured by the geometry of the crystal as well as the changes in its electrical properties has been obtained. Our experimental data to a very good extent matches with the results found in the DFT + U modelling.

  12. Boosting the photocurrent density of p-type solar cells based on organometal halide perovskite-sensitized mesoporous NiO photocathodes.

    Science.gov (United States)

    Wang, Huan; Zeng, Xianwei; Huang, Zhanfeng; Zhang, Wenjun; Qiao, Xianfeng; Hu, Bin; Zou, Xiaoping; Wang, Mingkui; Cheng, Yi-Bing; Chen, Wei

    2014-08-13

    The p-n tandem design of a sensitized solar cell is a novel concept holding the potential to overcome the efficiency limitation of conventional single-junction sensitized solar cells. Significant improvement of the photocurrent density (Jsc) of the p-type half-cell is a prerequisite for the realization of a highly efficient p-n tandem cell in the future. This study has demonstrated effective photocathodes based on novel organometal halide perovskite-sensitized mesoporous NiO in liquid-electrolyte-based p-type solar cells. An acceptably high Jsc up to 9.47 mA cm(-2) and efficiency up to 0.71% have been achieved on the basis of the CH3NH3PbI3/NiO solar cell at 100 mW cm(-2) light intensity, which are significantly higher than those of any previously reported liquid-electrolyte-based p-type solar cells based on sensitizers of organic dyes or inorganic quantum dots. The dense blocking layer made by spray pyrolysis of nickel acetylacetonate holds the key to determining the current flow direction of the solar cells. High hole injection efficiency at the perovskite/NiO interface and high hole collection efficiency through the mesoporous NiO network have been proved by time-resolved photoluminescence and transient photocurrent/photovoltage decay measurements. The limitation of these p-type solar cells primarily rests with the adverse light absorption by the NiO mesoporous film; the secondary limitation arises from the highly viscous ethyl acetate-based electrolyte, which is helpful for the solar cell stability but hinders fluent diffusion into the pore channels, giving rise to a nonlinear dependence of Jsc on the light intensity.

  13. XANES and IR spectroscopy study of the electronic structure and chemical composition of porous silicon on n- and p-type substrates

    Energy Technology Data Exchange (ETDEWEB)

    Lenshin, A. S., E-mail: lenshinas@phys.vsu.ru; Kashkarov, V. M.; Seredin, P. V. [Voronezh State University (Russian Federation); Spivak, Yu. M.; Moshnikov, V. A. [LETI St. Petersburg State Electrotechnical University (Russian Federation)

    2011-09-15

    The differences in the electronic structure and composition of porous silicon samples obtained under identical conditions of electrochemical etching on the most commonly used n- and p-type substrates with different conductivities are demonstrated by X-ray absorption near-edge spectroscopy (XANES) and Fourier transform IR spectroscopy (FTIR) methods. It is shown that significantly higher oxidation and saturation with hydrogen is observed for the porous layer on n-type substrates.

  14. The low resistive and transparent Al-doped SnO{sub 2} films: p-type conductivity, nanostructures and photoluminescence

    Energy Technology Data Exchange (ETDEWEB)

    Benouis, C.E. [Department of Material Technology, Physics Faculty, USTOMB University, BP1505 Oran (Algeria); Benhaliliba, M., E-mail: mbenhaliliba@gmail.com [Department of Material Technology, Physics Faculty, USTOMB University, BP1505 Oran (Algeria); Mouffak, Z. [Department of Electrical and Computer Engineering California State University, Fresno, CA (United States); Avila-Garcia, A. [Cinvestav-IPN, Dept. Ingeniería Eléctrica-SEES, Apdo. Postal 14-740, 07000 México, D.F. (Mexico); Tiburcio-Silver, A. [ITT-DIE, Apdo, Postal 20, Metepec 3, 52176 Estado de Mexico (Mexico); Ortega Lopez, M.; Romano Trujillo, R. [Centro de Investigación en Dispositivos Semiconductores, Instituto de Ciencias-BUAP, 14 Sur y Av. San Claudio, C.U. Puebla, Pue. (Mexico); Ocak, Y.S. [Dicle University, Education Faculty, Science Department, 21280 Diyarbakir (Turkey)

    2014-08-01

    Highlights: • Low resistive and high transparency Al doped SnO{sub 2} films. • Films are deposited onto ITO substrate by spray pyrolysis. • Nanostructured films are revealed. • p-Type conductivity is exhibited. • Photoluminescence of films is studied. - Abstract: In this work, we study the crystalline structure, surface morphology, transmittance, optical bandgap and n/p type inversion of tin oxide (SnO{sub 2}). The Nanostructured films of Al-doped SnO{sub 2} were successfully produced onto ITO-coated glass substrates via the spray pyrolysis method at a deposition temperature of 300 °C. A (1 0 1) and (2 1 1)-oriented tetragonal crystal structure was confirmed by X-ray patterns; and grain sizes varied within the range 8−42 nm. The films were polycrystalline, showing a high transparency in the visible (VIS) and infrared (IR) spectra. The optical bandgap was estimated to be around 3.4 eV. The atomic force microscopy (AFM) analysis showed the nanostructures consisting of nanotips, nanopatches, nanopits and nanobubbles. The samples exhibited high conductivity that ranged from 0.55 to 10{sup 4} (S/cm) at ambient and showed an inversion from n to p-type as well as a degenerate semiconductor characters with a bulk concentration reaching 1.7 x 10{sup 19} cm{sup −3}. The photoluminescence measurements reveal the detection of violet, green and yellow emissions.

  15. Fabrication and electrical characterization of Al/DNA-CTMA/ p-type a-Si:H photodiode based on DNA-CTMA biomaterial

    Science.gov (United States)

    Siva Pratap Reddy, M.; Puneetha, Peddathimula; Lee, Young-Woong; Jeong, Seong-Hoon; Park, Chinho

    2017-01-01

    In this work, a deoxyribonucleic acid-cetyltrimethylammonium chloride (DNA-CTMA) biomaterial based p-type hydrogenated amorphous silicon ( a-Si:H) photodiode (PD) is fabricated and its electrical characteristics are investigated. The Al/DNA-CTMA/ p-type a-Si:H PD parameters are studied using current-voltage ( I-V), capacitancevoltage-frequency ( C-V-f) and conductance-voltage-frequency ( G/ω-V-f) measurements. The barrier height and the ideality factor of the diode are found to be 0.78 eV and 1.9, respectively. The electrical and photoconductivity properties of the diode are analyzed by using dark I-V and transient photocurrent techniques. The C-V-f and G/ω-V-f measurements indicate that the capacitance and conductance of the diode depend on the voltage and frequency, respectively. The experimental results reveal that the decreases in capacitance and the increases in conductance with an increase in frequency can be explained on the basis of interface states ( N SS ). Series resistance ( R S ) measurements are performed on the diode and discussed here. The obtained electrical parameters confirm that the Al/DNA-CTMA/ p-type a-Si:H PD can be used as an optical sensor for the development of commercial applications that are environmentally benign. [Figure not available: see fulltext.

  16. Improvement in the Photocurrent of Inverted Organic Solar Cells Using MoO(x)-Doped TAPC as a P-Type Optical Spacer.

    Science.gov (United States)

    Song, Jiyun; Song, Hyung-Jun; Kim, Jun Young; Lee, Yeonkyung; Park, Myeongjin; Kwon, Yongwon; Ko, Youngjun; Lee, Changhee

    2016-05-01

    In this work, we demonstrate enhancement in the short-circuit current of inverted organic photovoltaic cells (OPVs) using a p-type optical spacer. The p-type optical spacer, which consists of molybdenum oxide (MoO(x))-doped 1,1-bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC), shows improved transmittance at visible light with high electrical conductivity. The electrical field distribution of incident light at the active layer of OPVs can be controlled by tuning the thickness of the optical spacer in the OPVs. Specifically, the incorporation of the 20-nm optical spacer layer in the OPV leads to enhanced spectral response of the device in the wavelength range of 400-600 nm, which is consistent with the combined results of improved optical absorption and better charge transport characteristics. As a result, the OPV with a 20-nm p-type optical spacer shows improvement in the short-circuit current compared with a device with 10 nm of embedded MoO(x).

  17. Broadband All-Polymer Phototransistors with Nanostructured Bulk Heterojunction Layers of NIR-Sensing n-Type and Visible Light-Sensing p-Type Polymers.

    Science.gov (United States)

    Han, Hyemi; Nam, Sungho; Seo, Jooyeok; Lee, Chulyeon; Kim, Hwajeong; Bradley, Donal D C; Ha, Chang-Sik; Kim, Youngkyoo

    2015-11-13

    We report 'broadband light-sensing' all-polymer phototransistors with the nanostructured bulk heterojunction (BHJ) layers of visible (VIS) light-sensing electron-donating (p-type) polymer and near infrared (NIR) light-sensing electron-accepting (n-type) polymer. Poly[{2,5-bis-(2-ethylhexyl)-3,6-bis-(thien-2-yl)-pyrrolo[3,4-c]pyrrole-1,4-diyl}-co-{2,2'-(2,1,3-benzothiadiazole)]-5,5'-diyl}] (PEHTPPD-BT), which is synthesized via Suzuki coupling and employed as the n-type polymer, shows strong optical absorption in the NIR region (up to 1100 nm) in the presence of weak absorption in the VIS range (400~600 nm). To strengthen the VIS absorption, poly(3-hexylthiophene) (P3HT) is introduced as the p-type polymer. All-polymer phototransistors with the BHJ (P3HT:PEHTPPD-BT) layers, featuring a peculiar nano-domain morphology, exhibit typical p-type transistor characteristics and efficiently detect broadband (VIS~NIR) lights. The maximum corrected responsivity (without contribution of dark current) reaches up to 85~88% (VIS) and 26~40% (NIR) of theoretical responsivity. The charge separation process between P3HT and PEHTPPD-BT components in the highest occupied molecular orbital is proposed as a major working mechanism for the effective NIR sensing.

  18. Improvement in thermoelectric power factor of mechanically alloyed p-type SiGe by incorporation of TiB2

    Science.gov (United States)

    Ahmad, Sajid; Dubey, K.; Bhattacharya, Shovit; Basu, Ranita; Bhatt, Ranu; Bohra, A. K.; Singh, Ajay; Aswal, D. K.; Gupta, S. K.

    2016-05-01

    Nearly 60% of the world's useful energy is wasted as heat and recovering a fraction of this waste heat by converting it as useful electrical power is an important area of research[1]. Thermoelectric power generators (TEG) are solid state devices which converts heat into electricity. TEG consists of n and p-type thermoelements connected electrically in series and thermally in parallel[2]. Silicon germanium (SiGe) alloy is one of the conventional high temperature thermoelectric materials and is being used in radio-isotopes based thermoelectric power generators for deep space exploration programs.Temperature (T) dependence of thermoelectric (TE) properties of p-type SiGe and p-type SiGe-x wt.%TiB2 (x=6,8,10%) nanocomposite materials has been studied with in the temperature range of 300 K to 1100 K. It is observed that there is an improvement in the power factor (α2/ρ) of SiGe alloy on addition of TiB2 upto 8 wt.% that is mainly due to increase in the Seebeck coefficient (α) and electrical conductivity (σ) of the alloy.

  19. Preparation of p-type NiO films by reactive sputtering and their application to CdTe solar cells

    Science.gov (United States)

    Ishikawa, Ryousuke; Furuya, Yasuaki; Araki, Ryouichi; Nomoto, Takahiro; Ogawa, Yohei; Hosono, Aikyo; Okamoto, Tamotsu; Tsuboi, Nozomu

    2016-02-01

    Transparent p-type NiO films were prepared by reactive sputtering using the facing-target system under Ar-diluted O2 gas at Tsub of 30 and 200 °C. The increasing intensity of dominant X-ray diffraction (XRD) peaks indicates improvements in the crystallinity of NiO films upon Cu doping. In spite of the crystallographic and optical changes after Cu-doping, the electrical properties of Cu-doped NiO films were slightly improved. Upon Ag-doping at 30 °C under low O2 concentration, on the other hand, the intensity of the dominant (111) XRD peaks was suppressed and p-type conductivity increased from ˜10-3 to ˜10-1 S cm-1. Finally, our Ag-doped NiO films were applied as the back contact of CdTe solar cells. CdTe solar cells with a glass/ITO/CdS/CdTe/NiO structure exhibited an efficiency of 6.4%, suggesting the high potential of using p-type NiO for the back-contact film in thin-film solar cells.

  20. Enhanced emission from mid-infrared AlInSb light-emitting diodes with p-type contact grid geometry

    Energy Technology Data Exchange (ETDEWEB)

    Meriggi, Laura, E-mail: l.meriggi.1@research.gla.ac.uk; Ding, Ying; Thayne, Iain G.; Sorel, Marc [Electronic and Nanoscale Engineering, School of Engineering, University of Glasgow, Glasgow G12 8LT (United Kingdom); Steer, Matthew J. [Electronic and Nanoscale Engineering, School of Engineering, University of Glasgow, Glasgow G12 8LT (United Kingdom); Quantum Device Solutions, The West of Scotland Science Park, Block 7 Kelvin Campus, Glasgow G20 0TH (United Kingdom); MacGregor, Calum [Quantum Device Solutions, The West of Scotland Science Park, Block 7 Kelvin Campus, Glasgow G20 0TH (United Kingdom); Ironside, Charles N. [Department of Imaging and Applied Physics, Curtin University, Perth, Western Australia 6845 (Australia)

    2015-02-14

    We report on the impact of lateral current spreading on light emission from aluminium indium antimonide (AlInSb) mid-infrared p-i-n light-emitting diodes (LEDs) grown by molecular beam epitaxy on a GaAs substrate. Due to the high effective mass of holes in Al{sub x}In{sub 1−x}Sb, the resistivity of p-type material determines the 3-D distribution of current flow in the devices. This work shows that maximum light emission, as measured by electroluminescence, and 3-times wall-plug efficiency improvement were obtained at room temperature from devices with a p-type contact grid geometry with a spacing of twice the current spreading length in the p-type material, which was measured by spatially resolved photocurrent. The LED with the optimal contact geometry exhibits improved performance at high injection current levels thanks to the more uniform carrier distribution across the device area.