WorldWideScience

Sample records for s2 subunit insights

  1. Transcriptional profiling of Vero E6 cells over-expressing SARS-CoV S2 subunit: Insights on viral regulation of apoptosis and proliferation

    International Nuclear Information System (INIS)

    Yeung, Y.-S.; Yip, C.-W.; Hon, C.-C.; Chow, Ken Y.C.; Ma, Iris C.M.; Zeng Fanya; Leung, Frederick C.C.

    2008-01-01

    We have previously demonstrated that over-expression of spike protein (S) of severe acute respiratory syndrome coronavirus (SARS-CoV) or its C-terminal subunit (S2) is sufficient to induce apoptosis in vitro. To further investigate the possible roles of S2 in SARS-CoV-induced apoptosis and pathogenesis of SARS, we characterized the host expression profiles induced upon S2 over-expression in Vero E6 cells by oligonucleotide microarray analysis. Possible activation of mitochondrial apoptotic pathway in S2 expressing cells was suggested, as evidenced by the up-regulation of cytochrome c and down-regulation of the Bcl-2 family anti-apoptotic members. Inhibition of Bcl-2-related anti-apoptotic pathway was further supported by the diminution of S2-induced apoptosis in Vero E6 cells over-expressing Bcl-xL. In addition, modulation of CCN E2 and CDKN 1A implied the possible control of cell cycle arrest at G1/S phase. This study is expected to extend our understanding on the pathogenesis of SARS at a molecular level

  2. Adsorption studies of alcohol molecules on monolayer MoS_2 nanosheet—A first-principles insights

    International Nuclear Information System (INIS)

    Nagarajan, V.; Chandiramouli, R.

    2017-01-01

    Highlights: • The adsorption of methanol, ethanol & 1-propanol on MoS_2 nanosheet are studied. • The PDOS & band structure confirms adsorption of alcohol vapors on MoS_2 nanosheet. • The adsorption of 1-propanol vapor on MoS_2 nanosheet is more favorable. • The alcohol molecules adsorption on MoS_2 nanosheet is explored in atomistic level. - Abstract: The electronic and adsorption properties of three different alcohol molecules namely methanol, ethanol and 1-propanol vapors on MoS_2 nanosheet is investigated using DFT method. The structural stability of MoS_2 nanosheet is ascertained with formation energy. The adsorption properties of alcohol molecules on MoS_2 base material is discussed in terms of average energy gap variation, Mulliken charge transfer, energy band gap and adsorption energy. The prominent adsorption sites of methanol, ethanol and 1-propanol vapors on MoS_2 nanosheet are studied in atomistic level. The projected density of states (PDOS) spectrum gives the clear insights on the electronic properties of MoS_2 nanosheet. The PDOS and energy band structure confirmed the adsorption of alcohol vapors on MoS_2 nanosheet. The variation in the band structure and PDOS is noticed upon adsorption of methanol, ethanol and 1-propanol molecules on MoS_2 nanosheet. The PDOS spectrum also reveals the variation in peak maxima owing to transfer of electron between alcohol molecules and MoS_2 base material. The adsorption of 1-propanol vapor on MoS_2 nanosheet is observed to be more favorable than other alcohol molecules. The findings confirm that monolayer MoS_2 nanosheet can be used to detect the presence of alcohol vapors in the environment.

  3. Atomic-scale insight into the origin of pyridine inhibition of MoS2-based hydrotreating catalysts

    DEFF Research Database (Denmark)

    Temel, Burcin; Tuxen, Anders K.; Kibsgaard, Jakob

    2010-01-01

    in earlier IR experiments on high surface alumina-supported MoS2 catalyst. The adsorption sites appear to be very similar to the brim sites involved in hydrogenation reactions in HDS. Thus, the combined STM and DFT results provide new atomic-scale insight into the inhibition effect of basic N......-compounds in HDS and the first direct observation of the adsorption mode of basic N-compounds on the catalytically active MoS2 edges. Our results lend further support to previously reported correlations between inhibiting strength and proton affinity for the N-containing compounds....

  4. Mining Protein Evolution for Insights into Mechanisms of Voltage-Dependent Sodium Channel Auxiliary Subunits.

    Science.gov (United States)

    Molinarolo, Steven; Granata, Daniele; Carnevale, Vincenzo; Ahern, Christopher A

    2018-02-21

    Voltage-gated sodium channel (VGSC) beta (β) subunits have been called the "overachieving" auxiliary ion channel subunit. Indeed, these subunits regulate the trafficking of the sodium channel complex at the plasma membrane and simultaneously tune the voltage-dependent properties of the pore-forming alpha-subunit. It is now known that VGSC β-subunits are capable of similar modulation of multiple isoforms of related voltage-gated potassium channels, suggesting that their abilities extend into the broader voltage-gated channels. The gene family for these single transmembrane immunoglobulin beta-fold proteins extends well beyond the traditional VGSC β1-β4 subunit designation, with deep roots into the cell adhesion protein family and myelin-related proteins - where inherited mutations result in a myriad of electrical signaling disorders. Yet, very little is known about how VGSC β-subunits support protein trafficking pathways, the basis for their modulation of voltage-dependent gating, and, ultimately, their role in shaping neuronal excitability. An evolutionary approach can be useful in yielding new clues to such functions as it provides an unbiased assessment of protein residues, folds, and functions. An approach is described here which indicates the greater emergence of the modern β-subunits roughly 400 million years ago in the early neurons of Bilateria and bony fish, and the unexpected presence of distant homologues in bacteriophages. Recent structural breakthroughs containing α and β eukaryotic sodium channels containing subunits suggest a novel role for a highly conserved polar contact that occurs within the transmembrane segments. Overall, a mixture of approaches will ultimately advance our understanding of the mechanism for β-subunit interactions with voltage-sensor containing ion channels and membrane proteins.

  5. Structural insights into methyltransferase KsgA function in 30S ribosomal subunit biogenesis.

    Science.gov (United States)

    Boehringer, Daniel; O'Farrell, Heather C; Rife, Jason P; Ban, Nenad

    2012-03-23

    The assembly of the ribosomal subunits is facilitated by ribosome biogenesis factors. The universally conserved methyltransferase KsgA modifies two adjacent adenosine residues in the 3'-terminal helix 45 of the 16 S ribosomal RNA (rRNA). KsgA recognizes its substrate adenosine residues only in the context of a near mature 30S subunit and is required for the efficient processing of the rRNA termini during ribosome biogenesis. Here, we present the cryo-EM structure of KsgA bound to a nonmethylated 30S ribosomal subunit. The structure reveals that KsgA binds to the 30S platform with the catalytic N-terminal domain interacting with substrate adenosine residues in helix 45 and the C-terminal domain making extensive contacts to helix 27 and helix 24. KsgA excludes the penultimate rRNA helix 44 from adopting its position in the mature 30S subunit, blocking the formation of the decoding site and subunit joining. We suggest that the activation of methyltransferase activity and subsequent dissociation of KsgA control conformational changes in helix 44 required for final rRNA processing and translation initiation.

  6. Structural Insights into Methyltransferase KsgA Function in 30S Ribosomal Subunit Biogenesis*

    Science.gov (United States)

    Boehringer, Daniel; O'Farrell, Heather C.; Rife, Jason P.; Ban, Nenad

    2012-01-01

    The assembly of the ribosomal subunits is facilitated by ribosome biogenesis factors. The universally conserved methyltransferase KsgA modifies two adjacent adenosine residues in the 3′-terminal helix 45 of the 16 S ribosomal RNA (rRNA). KsgA recognizes its substrate adenosine residues only in the context of a near mature 30S subunit and is required for the efficient processing of the rRNA termini during ribosome biogenesis. Here, we present the cryo-EM structure of KsgA bound to a nonmethylated 30S ribosomal subunit. The structure reveals that KsgA binds to the 30S platform with the catalytic N-terminal domain interacting with substrate adenosine residues in helix 45 and the C-terminal domain making extensive contacts to helix 27 and helix 24. KsgA excludes the penultimate rRNA helix 44 from adopting its position in the mature 30S subunit, blocking the formation of the decoding site and subunit joining. We suggest that the activation of methyltransferase activity and subsequent dissociation of KsgA control conformational changes in helix 44 required for final rRNA processing and translation initiation. PMID:22308031

  7. Enhanced Electrochemical and Thermal Transport Properties of Graphene/MoS2 Heterostructures for Energy Storage: Insights from Multiscale Modeling.

    Science.gov (United States)

    Gong, Feng; Ding, Zhiwei; Fang, Yin; Tong, Chuan-Jia; Xia, Dawei; Lv, Yingying; Wang, Bin; Papavassiliou, Dimitrios V; Liao, Jiaxuan; Wu, Mengqiang

    2018-05-02

    Graphene has been combined with molybdenum disulfide (MoS 2 ) to ameliorate the poor cycling stability and rate performance of MoS 2 in lithium ion batteries, yet the underlying mechanisms remain less explored. Here, we develop multiscale modeling to investigate the enhanced electrochemical and thermal transport properties of graphene/MoS 2 heterostructures (GM-Hs) with a complex morphology. The calculated electronic structures demonstrate the greatly improved electrical conductivity of GM-Hs compared to MoS 2 . Increasing the graphene layers in GM-Hs not only improves the electrical conductivity but also stabilizes the intercalated Li atoms in GM-Hs. It is also found that GM-Hs with three graphene layers could achieve and maintain a high thermal conductivity of 85.5 W/(m·K) at a large temperature range (100-500 K), nearly 6 times that of pure MoS 2 [∼15 W/(m·K)], which may accelerate the heat conduction from electrodes to the ambient. Our quantitative findings may shed light on the enhanced battery performances of various graphene/transition-metal chalcogenide composites in energy storage devices.

  8. Insight into π-hole interactions containing the inorganic heterocyclic compounds S2N2/SN2P2.

    Science.gov (United States)

    Lu, Bo; Zhang, Xueying; Meng, Lingpeng; Zeng, Yanli

    2017-08-01

    Similar to σ-hole interactions, the π-hole interaction has attracted much attention in recent years. According to the positive electrostatic potentials above and below the surface of inorganic heterocyclic compounds S 2 N 2 and three SN 2 P 2 isomers (heterocyclic compounds 1-4), and the negative electrostatic potential outside the X atom of XH 3 (X = N, P, As), S 2 N 2 /SN 2 P 2 ⋯XH 3 (X = N, P, As) complexes were constructed and optimized at the MP2/aug-cc-pVTZ level. The X atom of XH 3 (X = N, P, As) is almost perpendicular to the ring of the heterocyclic compounds. The π-hole interaction energy becomes greater as the trend goes from 1⋯XH 3 to 4⋯XH 3 . These π-hole interactions are weak and belong to "closed-shell" noncovalent interactions. According to the energy decomposition analysis, of the three attractive terms, the dispersion energy contributes more than the electrostatic energy. The polarization effect also plays an important role in the formation of π-hole complexes, with the contrasting phenomena of decreasing electronic density in the π-hole region and increasing electric density outside the X atom of XH 3 (X = N, P, As). Graphical abstract Computed density difference plots for the complexes 3⋯NH 3 (a 1 ), 3⋯PH 3 (b 1 ), 3⋯AsH 3 (c 1 ) and electron density shifts for the complexes 3⋯NH 3 (a 2 ), 3⋯PH 3 (b 2 ),3⋯AsH 3 (c 2 ) on the 0.001 a.u. contour.

  9. Crystal structure of the bacterial luciferase/flavin complex provides insight into the function of the beta subunit.

    Science.gov (United States)

    Campbell, Zachary T; Weichsel, Andrzej; Montfort, William R; Baldwin, Thomas O

    2009-07-07

    Bacterial luciferase from Vibrio harveyi is a heterodimer composed of a catalytic alpha subunit and a homologous but noncatalytic beta subunit. Despite decades of enzymological investigation, structural evidence defining the active center has been elusive. We report here the crystal structure of V. harveyi luciferase bound to flavin mononucleotide (FMN) at 2.3 A. The isoalloxazine ring is coordinated by an unusual cis-Ala-Ala peptide bond. The reactive sulfhydryl group of Cys106 projects toward position C-4a, the site of flavin oxygenation. This structure also provides the first data specifying the conformations of a mobile loop that is crystallographically disordered in both prior crystal structures [(1995) Biochemistry 34, 6581-6586; (1996) J. Biol. Chem. 271, 21956 21968]. This loop appears to be a boundary between solvent and the active center. Within this portion of the protein, a single contact was observed between Phe272 of the alpha subunit, not seen in the previous structures, and Tyr151 of the beta subunit. Substitutions at position 151 on the beta subunit caused reductions in activity and total quantum yield. Several of these mutants were found to have decreased affinity for reduced flavin mononucleotide (FMNH(2)). These findings partially address the long-standing question of how the beta subunit stabilizes the active conformation of the alpha subunit, thereby participating in the catalytic mechanism.

  10. Insights into highly improved solar-driven photocatalytic oxygen evolution over integrated Ag3PO4/MoS2 heterostructures

    Science.gov (United States)

    Cui, Xingkai; Yang, Xiaofei; Xian, Xiaozhai; Tian, Lin; Tang, Hua; Liu, Qinqin

    2018-04-01

    Oxygen evolution has been considered as the rate-determining step in photocatalytic water splitting due to its sluggish four-electron half-reaction rate, the development of oxygen-evolving photocatalysts with well-defined morphologies and superior interfacial contact is highly important for achieving high-performance solar water splitting. Herein, we report the fabrication of Ag3PO4/MoS2 nanocomposites and, for the first time, their use in photocatalytic water splitting into oxygen under LED light illumination. Ag3PO4 nanoparticles were found to be anchored evenly on the surface of MoS2 nanosheets, confirming an efficient hybridization of two semiconductor materials. A maximum oxygen-generating rate of 201.6 mol L-1 g-1 h-1 was determined when 200 mg MoS2 nanosheets were incorporated into Ag3PO4 nanoparticles, which is around 5 times higher than that of bulk Ag3PO4. Obvious enhancements in light-harvesting property, as well as electron-hole separation and charge transportation are revealed by the combination of different characterizations. ESR analysis verified that more active oxygen-containing radicals generate over illuminated Ag3PO4/MoS2 composite photocatalysts rather than irradiated Ag3PO4. The improvement in oxygen evolution performance of Ag3PO4/MoS2 composite photocatalysts is ascribed to wide spectra response in the visible-light region, more efficient charge separation and enhanced oxidation capacity in the valence band (VB). This study provides new insights into the design and development of novel composite photocatalytic materials for solar-to-fuel conversion.

  11. Bonding and magnetic response properties of several toroid structures. Insights of the role of Ni2S2 as a building block from relativistic density functional theory calculations.

    Science.gov (United States)

    Muñoz-Castro, Alvaro

    2011-10-06

    Relativistic density functional calculations were carried out on several nickel toroid mercaptides of the general formula [Ni(μ-SR)(2)](n), with the aim to characterize and analyze their stability and magnetic response properties, in order to gain more insights into their stabilization and size-dependent behavior. The Ni-ligand interaction has been studied by means projected density of states and energy decomposition analysis, which denotes its stabilizing character. The graphical representation of the response to an external magnetic field is applied for the very first time taking into account the spin-orbit term. This map allows one to clearly characterize the magnetic behavior inside and in the closeness of the toroid structure showing the prescence of paratropic ring currents inside the Ni(n) ring, and by contrast, diatropic currents confined in each Ni(2)S(2) motif denoting an aromatic behavior (in terms of magnetic criteria). The calculated data suggests that the Ni(2)S(2) moiety can be regarded as a stable constructing block, which can afford several toroid structures of different nuclearities in agreement with that reported in the experimental literature. In addition, the effects of the relativistic treatment over the magnetic response properties on these lighter compounds are denoted by comparing nonrelativistic, scalar relativistic, and scalar plus spin-orbit relativistic treatments, showing their acting, although nonpronunced, role.

  12. Molecular Insights into the Potential Insecticidal Interaction of β-Dihydroagarofuran Derivatives with the H Subunit of V-ATPase

    Directory of Open Access Journals (Sweden)

    Jielu Wei

    2017-10-01

    Full Text Available Celangulin V (CV, one of dihydroagarofuran sesquiterpene polyesters isolated from Chinese bittersweet (Celastrus angulatus Maxim, is famous natural botanical insecticide. Decades of research suggests that is displays excellent insecticidal activity against some insects, such as Mythimna separata Walker. Recently, it has been validated that the H subunit of V-ATPase is one of the target proteins of the insecticidal dihydroagarofuran sesquiterpene polyesters. As a continuation of the development of new pesticides from these natural products, a series of β-dihydroagarofuran derivatives have been designed and synthesized. The compound JW-3, an insecticidal derivative of CV with a p-fluorobenzyl group, exhibits higher insecticidal activity than CV. In this study, the potential inhibitory effect aused by the interaction of JW-3 with the H subunit of V-ATPase c was verified by confirmatory experiments at the molecular level. Both spectroscopic techniques and isothermal titration calorimetry measurements showed the binding of JW-3 to the subunit H of V-ATPase was specific and spontaneous. In addition, the possible mechanism of action of the compound was discussed. Docking results indicated compound JW-3 could bind well in ‘the interdomain cleft’ of the V-ATPase subunit H by the hydrogen bonding and make conformation of the ligand–protein complex become more stable. All results are the further validations of the hypothesis, that the target protein of insecticidal dihydroagarofuran sesquiterpene polyesters and their β-dihydroagarofuran derivatives is the subunit H of V-ATPase. The results also provide new ideas for developing pesticides acting on V-ATPase of insects.

  13. Structural insights into RipC, a putative citrate lyase β subunit from a Yersinia pestis virulence operon

    International Nuclear Information System (INIS)

    Torres, Rodrigo; Chim, Nicholas; Sankaran, Banumathi; Pujol, Céline; Bliska, James B.; Goulding, Celia W.

    2011-01-01

    Comparison of the 2.45 Å resolution crystal structure of homotrimeric RipC, a putative citrate lyase β subunit from Y. pestis, with structural homologs reveals conserved RipC residues that are implicated in CoA binding. Yersinia pestis remains a threat, with outbreaks of plague occurring in rural areas and its emergence as a weapon of bioterrorism; thus, an improved understanding of its various pathogenicity pathways is warranted. The rip (required for intracellular proliferation) virulence operon is required for Y. pestis survival in interferon-γ-treated macrophages and has been implicated in lowering macrophage-produced nitric oxide levels. RipC, one of three gene products from the rip operon, is annotated as a citrate lyase β subunit. Furthermore, the Y. pestis genome lacks genes that encode citrate lyase α and γ subunits, suggesting a unique functional role of RipC in the Y. pestisrip-mediated survival pathway. Here, the 2.45 Å resolution crystal structure of RipC revealed a homotrimer in which each monomer consists of a (β/α) 8 TIM-barrel fold. Furthermore, the trimeric state was confirmed in solution by size-exclusion chromatography. Through sequence and structure comparisons with homologous proteins, it is proposed that RipC is a putative CoA- or CoA-derivative binding protein

  14. Insight into a conformation of the PNA-PNA duplex with (2‧R,4‧R)- and (2‧R,4‧S)-prolyl-(1S,2S)-2-aminocyclopentanecarboxylic acid backbones

    Science.gov (United States)

    Maitarad, Amphawan; Poomsuk, Nattawee; Vilaivan, Chotima; Vilaivan, Tirayut; Siriwong, Khatcharin

    2018-04-01

    Suitable conformations for peptide nucleic acid (PNA) self-hybrids with (2‧R,4‧R)- and (2‧R,4‧S)-prolyl-(1S,2S)-2-aminocyclopentanecarboxylic acid backbones (namely, acpcPNA and epi-acpcPNA, respectively) were investigated based on molecular dynamics simulations. The results revealed that hybridization of the acpcPNA was observed only in the parallel direction, with a conformation close to the P-type structure. In contrast, self-hybrids of the epi-acpcPNA were formed in the antiparallel and parallel directions; the antiparallel duplex adopted the B-form conformation, and the parallel duplex was between B- and P-forms. The calculated binding energies and the experimental data indicate that the antiparallel epi-acpcPNA self-hybrid was more stable than the parallel duplex.

  15. From two-dimensional graphene oxide to three-dimensional honeycomb-like Ni3S2@graphene oxide composite: insight into structure and electrocatalytic properties

    Science.gov (United States)

    Wei, Xinting; Li, Yueqiang; Xu, Wenli; Zhang, Kaixuan; Yin, Jie; Shi, Shaozhen; Wei, Jiazhen; Di, Fangfang; Guo, Junxue; Wang, Can; Chu, Chaofan; Sui, Ning; Chen, Baoli; Zhang, Yingtian; Hao, Hongguo; Zhang, Xianxi; Zhao, Jinsheng; Zhou, Huawei; Wang, Shuhao

    2017-12-01

    Three-dimensional (3D) graphene composites have drawn increasing attention in energy storage/conversion applications due to their unique structures and properties. Herein, we synthesized 3D honeycomb-like Ni3S2@graphene oxide composite (3D honeycomb-like Ni3S2@GO) by a one-pot hydrothermal method. We found that positive charges of Ni2+ and negative charges of NO3- in Ni(NO3)2 induced a transformation of graphene oxide with smooth surface into graphene oxide with wrinkled surface (w-GO). The w-GO in the mixing solution of Ni(NO3)2/thioacetamide/H2O evolved into 3D honeycomb-like Ni3S2@GO in solvothermal process. The GO effectively inhibited the aggregation of Ni3S2 nanoparticles. Photoelectrochemical cells based on 3D Ni3S2@GO synthesized at 60 mM l-1 Ni(NO3)2 exhibited the best energy conversion efficiency. 3D Ni3S2@GO had smaller charge transfer resistance and larger exchange current density than pure Ni3S2 for iodine reduction reaction. The cyclic stability of 3D honeycomb-like Ni3S2@GO was good in the iodine electrolyte. Results are of great interest for fundamental research and practical applications of 3D GO and its composites in solar water-splitting, artificial photoelectrochemical cells, electrocatalysts and Li-S or Na-S batteries.

  16. Mechanistic Insight into the Stability of HfO2-Coated MoS2 Nanosheet Anodes for Sodium Ion Batteries

    KAUST Repository

    Ahmed, Bilal

    2015-06-01

    It is demonstrated for the first time that surface passivation of 2D nanosheets of MoS2 by an ultrathin and uniform layer of HfO2 can significantly improve the cyclic performance of sodium ion batteries. After 50 charge/discharge cycles, bare MoS2 and HfO2 coated MoS2 electrodes deliver the specific capacity of 435 and 636 mAh g-1, respectively, at current density of 100 mA g-1. These results imply that batteries using HfO2 coated MoS2 anodes retain 91% of the initial capacity; in contrast, bare MoS2 anodes retain only 63%. Also, HfO2 coated MoS2 anodes show one of the highest reported capacity values for MoS2. Cyclic voltammetry and X-ray photoelectron spectroscopy results suggest that HfO2 does not take part in electrochemical reaction. The mechanism of capacity retention with HfO2 coating is explained by ex situ transmission electron microscope imaging and electrical impedance spectroscopy. It is illustrated that HfO2 acts as a passivation layer at the anode/electrolyte interface and prevents structural degradation during charge/discharge process. Moreover, the amorphous nature of HfO2 allows facile diffusion of Na ions. These results clearly show the potential of HfO2 coated MoS2 anodes, which performance is significantly higher than previous reports where bulk MoS2 or composites of MoS2 with carbonaceous materials are used. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Mechanistic Insight into the Stability of HfO2-Coated MoS2 Nanosheet Anodes for Sodium Ion Batteries

    KAUST Repository

    Ahmed, Bilal; Anjum, Dalaver H.; Hedhili, Mohamed N.; Alshareef, Husam N.

    2015-01-01

    It is demonstrated for the first time that surface passivation of 2D nanosheets of MoS2 by an ultrathin and uniform layer of HfO2 can significantly improve the cyclic performance of sodium ion batteries. After 50 charge/discharge cycles, bare MoS2 and HfO2 coated MoS2 electrodes deliver the specific capacity of 435 and 636 mAh g-1, respectively, at current density of 100 mA g-1. These results imply that batteries using HfO2 coated MoS2 anodes retain 91% of the initial capacity; in contrast, bare MoS2 anodes retain only 63%. Also, HfO2 coated MoS2 anodes show one of the highest reported capacity values for MoS2. Cyclic voltammetry and X-ray photoelectron spectroscopy results suggest that HfO2 does not take part in electrochemical reaction. The mechanism of capacity retention with HfO2 coating is explained by ex situ transmission electron microscope imaging and electrical impedance spectroscopy. It is illustrated that HfO2 acts as a passivation layer at the anode/electrolyte interface and prevents structural degradation during charge/discharge process. Moreover, the amorphous nature of HfO2 allows facile diffusion of Na ions. These results clearly show the potential of HfO2 coated MoS2 anodes, which performance is significantly higher than previous reports where bulk MoS2 or composites of MoS2 with carbonaceous materials are used. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Bonding Quandary in the [Cu3S2](3+) Core: Insights from the Analysis of Domain Averaged Fermi Holes and the Local Spin

    Czech Academy of Sciences Publication Activity Database

    Ponec, Robert; Ramos-Córdoba, E.; Salvador, P.

    2013-01-01

    Roč. 117, č. 9 (2013), s. 1975-1982 ISSN 1089-5639 R&D Projects: GA ČR GA203/09/0118 Grant - others:SMCT(ES) MAT2008-04834; SMCT(ES) CTQ2011-23441/BQU; SFPU(ES) AP2008-01231 Institutional support: RVO:67985858 Keywords : Cu3S2 core * dafh analysis * bonding quandary Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.775, year: 2013

  19. The NMR solution structure of Mycobacterium tuberculosis F-ATP synthase subunit ε provides new insight into energy coupling inside the rotary engine.

    Science.gov (United States)

    Joon, Shin; Ragunathan, Priya; Sundararaman, Lavanya; Nartey, Wilson; Kundu, Subhashri; Manimekalai, Malathy S S; Bogdanović, Nebojša; Dick, Thomas; Grüber, Gerhard

    2018-03-01

    Mycobacterium tuberculosis (Mt) F 1 F 0 ATP synthase (α 3 :β 3 :γ:δ:ε:a:b:b':c 9 ) is essential for the viability of growing and nongrowing persister cells of the pathogen. Here, we present the first NMR solution structure of Mtε, revealing an N-terminal β-barrel domain (NTD) and a C-terminal domain (CTD) composed of a helix-loop-helix with helix 1 and -2 being shorter compared to their counterparts in other bacteria. The C-terminal amino acids are oriented toward the NTD, forming a domain-domain interface between the NTD and CTD. The Mtε structure provides a novel mechanistic model of coupling c-ring- and ε rotation via a patch of hydrophobic residues in the NTD and residues of the CTD to the bottom of the catalytic α 3 β 3 -headpiece. To test our model, genome site-directed mutagenesis was employed to introduce amino acid changes in these two parts of the epsilon subunit. Inverted vesicle assays show that these mutations caused an increase in ATP hydrolysis activity and a reduction in ATP synthesis. The structural and enzymatic data are discussed in light of the transition mechanism of a compact and extended state of Mtε, which provides the inhibitory effects of this coupling subunit inside the rotary engine. Finally, the employment of these data with molecular docking shed light into the second binding site of the drug Bedaquiline. Structural data are available in the PDB under the accession number 5YIO. © 2018 Federation of European Biochemical Societies.

  20. New insights into structure-function relationship of the DHPR beta1a subunit in skeletal muscle excitation-contraction coupling using zebrafish 'relaxed' as an expression system

    International Nuclear Information System (INIS)

    Dayal, A.

    2010-01-01

    The paralyzed zebrafish strain relaxed carries a null mutation for the skeletal muscle dihydropyridine receptor (DHPR) [beta]1a subunit. The lack of [beta]1a not only impedes functional [alpha]1S membrane expression but also precludes the skeletal muscle-specific ultrastructural arrangement of DHPRs into tetrads opposite ryanodine receptor (RyR1), coherent with the absence of skeletal muscle excitation-contraction (EC) coupling. With the plethora of experimental approaches feasible with zebrafish model organism and importantly with the [beta]1-null mutation having a monogenetic inheritance and because of the survival of the relaxed larvae for some days, we were able to establish the zebrafish relaxed as an expression system. Linking in vitro to in vivo observations, a clear differentiation between the major functional roles of [beta] subunits in EC coupling was feasible. The skeletal muscle [beta]1a subunit was able to restore all parameters of EC coupling upon expression in relaxed myotubes and larvae. Expression of the phylogenetically closest isoform to [beta]1a, the cardiac/neuronal [beta]2a subunit or the most distant neuronal [beta]M from the housefly in relaxed myotubes and larvae was likewise able to fully restore [alpha]1S triad targeting and facilitate charge movement. However, efficient tetrad formation and thus intact DHPR-RyR1 coupling was exclusively promoted by the [beta]1a isoform. Consequently, we postulated a model according to which [beta]1a acts as a unique allosteric modifier of [alpha]1S conformation crucial for skeletal muscle EC coupling. Therefore, unique structural elements in [beta]1a must be present which endow it with this exclusive property. Earlier, a unique hydrophobic heptad repeat motif (LVV) in the [beta]1a C-terminus was postulated by others to be essential for skeletal muscle EC coupling. We wanted to address the question if the proposed [beta]1a heptad repeat motif could be an active element of the DHPR-RyR1 signal transduction

  1. A cyclic nucleotide-gated channel mutation associated with canine daylight blindness provides insight into a role for the S2 segment tri-Asp motif in channel biogenesis.

    Directory of Open Access Journals (Sweden)

    Naoto Tanaka

    Full Text Available Cone cyclic nucleotide-gated channels are tetramers formed by CNGA3 and CNGB3 subunits; CNGA3 subunits function as homotetrameric channels but CNGB3 exhibits channel function only when co-expressed with CNGA3. An aspartatic acid (Asp to asparagine (Asn missense mutation at position 262 in the canine CNGB3 (D262N subunit results in loss of cone function (daylight blindness, suggesting an important role for this aspartic acid residue in channel biogenesis and/or function. Asp 262 is located in a conserved region of the second transmembrane segment containing three Asp residues designated the Tri-Asp motif. This motif is conserved in all CNG channels. Here we examine mutations in canine CNGA3 homomeric channels using a combination of experimental and computational approaches. Mutations of these conserved Asp residues result in the absence of nucleotide-activated currents in heterologous expression. A fluorescent tag on CNGA3 shows mislocalization of mutant channels. Co-expressing CNGB3 Tri-Asp mutants with wild type CNGA3 results in some functional channels, however, their electrophysiological characterization matches the properties of homomeric CNGA3 channels. This failure to record heteromeric currents suggests that Asp/Asn mutations affect heteromeric subunit assembly. A homology model of S1-S6 of the CNGA3 channel was generated and relaxed in a membrane using molecular dynamics simulations. The model predicts that the Tri-Asp motif is involved in non-specific salt bridge pairings with positive residues of S3/S4. We propose that the D262N mutation in dogs with CNGB3-day blindness results in the loss of these inter-helical interactions altering the electrostatic equilibrium within in the S1-S4 bundle. Because residues analogous to Tri-Asp in the voltage-gated Shaker potassium channel family were implicated in monomer folding, we hypothesize that destabilizing these electrostatic interactions impairs the monomer folding state in D262N mutant CNG

  2. Theoretical insight into the effect of collision energy on the S(3P) + SH( X 2∏) → S2( X 3∑g -) + H(2S) reaction

    Science.gov (United States)

    Shoubao, Gao; Guomeng, Chen; Yuzhi, Song; Qingtian, Meng; Qing, Xu

    2018-01-01

    In this work, the dynamics of reaction S(3P) + SH( X 2∏) → S2( X 3∑g -) + H(2S) has been investigated using quasi-classical trajectories method on a newly constructed accurate double many-body expansion potential energy surface of Song et al. [J. Phys. Chem. A 115, 5274 (2011)]. The integral cross section and the rate constant are obtained. Furthermore, the distribution reflecting vector correlation and the polarization-dependent differential cross section are investigated. The results show a decreasing behavior of the integral cross section as the increasing of the collision energy, and dominate complex forming mechanism at lower energies, as well as the stripping mechanism at higher energies. Those results indicate that the product S2 is sensitively affected by the collision energy.

  3. Dirac particle on S2

    International Nuclear Information System (INIS)

    Ferreira, P.L.; Palladino, B.E.

    1985-01-01

    The problem of a Dirac particle in stationary motion on S 2 - a two dimensional sphere embedded in Euclidean space E 3 - is discussed. It provides a particularly simple case of an exactly solvable constrained Dirac particle whose properties are here studied, with emphasis on its magnetic moment. (Author) [pt

  4. The beta1 subunit of the Na,K-ATPase pump interacts with megalencephalic leucoencephalopathy with subcortical cysts protein 1 (MLC1) in brain astrocytes: new insights into MLC pathogenesis.

    Science.gov (United States)

    Brignone, Maria S; Lanciotti, Angela; Macioce, Pompeo; Macchia, Gianfranco; Gaetani, Matteo; Aloisi, Francesca; Petrucci, Tamara C; Ambrosini, Elena

    2011-01-01

    Megalencephalic leucoencephalopathy with subcortical cysts (MLC) is a rare congenital leucodystrophy caused by mutations in MLC1, a membrane protein of unknown function. MLC1 expression in astrocyte end-feet contacting blood vessels and meninges, along with brain swelling, fluid cysts and myelin vacuolation observed in MLC patients, suggests a possible role for MLC1 in the regulation of fluid and ion homeostasis and cellular volume changes. To identify MLC1 direct interactors and dissect the molecular pathways in which MLC1 is involved, we used NH2-MLC1 domain as a bait to screen a human brain library in a yeast two-hybrid assay. We identified the β1 subunit of the Na,K-ATPase pump as one of the interacting clones and confirmed it by pull-downs, co-fractionation assays and immunofluorescence stainings in human and rat astrocytes in vitro and in brain tissue. By performing ouabain-affinity chromatography on astrocyte and brain extracts, we isolated MLC1 and the whole Na,K-ATPase enzyme in a multiprotein complex that included Kir4.1, syntrophin and dystrobrevin. Because Na,K-ATPase is involved in intracellular osmotic control and volume regulation, we investigated the effect of hypo-osmotic stress on MLC1/Na,K-ATPase relationship in astrocytes. We found that hypo-osmotic conditions increased MLC1 membrane expression and favoured MLC1/Na,K-ATPase-β1 association. Moreover, hypo-osmosis induced astrocyte swelling and the reversible formation of endosome-derived vacuoles, where the two proteins co-localized. These data suggest that through its interaction with Na,K-ATPase, MLC1 is involved in the control of intracellular osmotic conditions and volume regulation in astrocytes, opening new perspectives for understanding the pathological mechanisms of MLC disease.

  5. The Pyridoxal 5′-Phosphate (PLP-Dependent Enzyme Serine Palmitoyltransferase (SPT: Effects of the Small Subunits and Insights from Bacterial Mimics of Human hLCB2a HSAN1 Mutations

    Directory of Open Access Journals (Sweden)

    Ashley E. Beattie

    2013-01-01

    Full Text Available The pyridoxal 5′-phosphate (PLP-dependent enzyme serine palmitoyltransferase (SPT catalyses the first step of de novo sphingolipid biosynthesis. The core human enzyme is a membrane-bound heterodimer composed of two subunits (hLCB1 and hLCB2a/b, and mutations in both hLCB1 (e.g., C133W and C133Y and hLCB2a (e.g., V359M, G382V, and I504F have been identified in patients with hereditary sensory and autonomic neuropathy type I (HSAN1, an inherited disorder that affects sensory and autonomic neurons. These mutations result in substrate promiscuity, leading to formation of neurotoxic deoxysphingolipids found in affected individuals. Here we measure the activities of the hLCB2a mutants in the presence of ssSPTa and ssSPTb and find that all decrease enzyme activity. High resolution structural data of the homodimeric SPT enzyme from the bacterium Sphingomonas paucimobilis (Sp SPT provides a model to understand the impact of the hLCB2a mutations on the mechanism of SPT. The three human hLCB2a HSAN1 mutations map onto Sp SPT (V246M, G268V, and G385F, and these mutant mimics reveal that the amino acid changes have varying impacts; they perturb the PLP cofactor binding, reduce the affinity for both substrates, decrease the enzyme activity, and, in the most severe case, cause the protein to be expressed in an insoluble form.

  6. Highly conserved small subunit residues influence rubisco large subunit catalysis.

    Science.gov (United States)

    Genkov, Todor; Spreitzer, Robert J

    2009-10-30

    The chloroplast enzyme ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) catalyzes the rate-limiting step of photosynthetic CO(2) fixation. With a deeper understanding of its structure-function relationships and competitive inhibition by O(2), it may be possible to engineer an increase in agricultural productivity and renewable energy. The chloroplast-encoded large subunits form the active site, but the nuclear-encoded small subunits can also influence catalytic efficiency and CO(2)/O(2) specificity. To further define the role of the small subunit in Rubisco function, the 10 most conserved residues in all small subunits were substituted with alanine by transformation of a Chlamydomonas reinhardtii mutant that lacks the small subunit gene family. All the mutant strains were able to grow photosynthetically, indicating that none of the residues is essential for function. Three of the substitutions have little or no effect (S16A, P19A, and E92A), one primarily affects holoenzyme stability (L18A), and the remainder affect catalysis with or without some level of associated structural instability (Y32A, E43A, W73A, L78A, P79A, and F81A). Y32A and E43A cause decreases in CO(2)/O(2) specificity. Based on the x-ray crystal structure of Chlamydomonas Rubisco, all but one (Glu-92) of the conserved residues are in contact with large subunits and cluster near the amino- or carboxyl-terminal ends of large subunit alpha-helix 8, which is a structural element of the alpha/beta-barrel active site. Small subunit residues Glu-43 and Trp-73 identify a possible structural connection between active site alpha-helix 8 and the highly variable small subunit loop between beta-strands A and B, which can also influence Rubisco CO(2)/O(2) specificity.

  7. Controlling S2 terminal using FS software

    Science.gov (United States)

    Xue, Zhuhe

    New S2FS software for controlling S2 terminal of Sheshan station has been developed. It works under Field System software. All S2 operation commands are incorporated in a station program. The interface of SWT computer and S2 terminal is RS232 interface. S2FS software is designed by using Shell and C language. It has been used in VSOP experiments.

  8. Thermal conductivity of bulk and monolayer MoS2

    KAUST Repository

    Gandi, Appala

    2016-02-26

    © Copyright EPLA, 2016. We show that the lattice contribution to the thermal conductivity of MoS2 strongly dominates the carrier contribution in a broad temperature range from 300 to 800 K. Since theoretical insight into the lattice contribution is largely missing, though it would be essential for materials design, we solve the Boltzmann transport equation for the phonons self-consistently in order to evaluate the phonon lifetimes. In addition, the length scale for transition between diffusive and ballistic transport is determined. The low out-of-plane thermal conductivity of bulk MoS2 (2.3 Wm-1K-1 at 300 K) is useful for thermoelectric applications. On the other hand, the thermal conductivity of monolayer MoS2 (131 Wm-1K-1 at 300 K) is comparable to that of Si.

  9. Catalytic Subunit 1 of Protein Phosphatase 2A Is a Subunit of the STRIPAK Complex and Governs Fungal Sexual Development.

    Science.gov (United States)

    Beier, Anna; Teichert, Ines; Krisp, Christoph; Wolters, Dirk A; Kück, Ulrich

    2016-06-21

    The generation of complex three-dimensional structures is a key developmental step for most eukaryotic organisms. The details of the molecular machinery controlling this step remain to be determined. An excellent model system to study this general process is the generation of three-dimensional fruiting bodies in filamentous fungi like Sordaria macrospora Fruiting body development is controlled by subunits of the highly conserved striatin-interacting phosphatase and kinase (STRIPAK) complex, which has been described in organisms ranging from yeasts to humans. The highly conserved heterotrimeric protein phosphatase PP2A is a subunit of STRIPAK. Here, catalytic subunit 1 of PP2A was functionally characterized. The Δpp2Ac1 strain is sterile, unable to undergo hyphal fusion, and devoid of ascogonial septation. Further, PP2Ac1, together with STRIPAK subunit PRO22, governs vegetative and stress-related growth. We revealed in vitro catalytic activity of wild-type PP2Ac1, and our in vivo analysis showed that inactive PP2Ac1 blocks the complementation of the sterile deletion strain. Tandem affinity purification, followed by mass spectrometry and yeast two-hybrid analysis, verified that PP2Ac1 is a subunit of STRIPAK. Further, these data indicate links between the STRIPAK complex and other developmental signaling pathways, implying the presence of a large interconnected signaling network that controls eukaryotic developmental processes. The insights gained in our study can be transferred to higher eukaryotes and will be important for understanding eukaryotic cellular development in general. The striatin-interacting phosphatase and kinase (STRIPAK) complex is highly conserved from yeasts to humans and is an important regulator of numerous eukaryotic developmental processes, such as cellular signaling and cell development. Although functional insights into the STRIPAK complex are accumulating, the detailed molecular mechanisms of single subunits are only partially understood

  10. Morphology-controlled synthesis of MoS2 nanostructures with different lithium storage properties

    International Nuclear Information System (INIS)

    Wang, Xiwen; Zhang, Zhian; Chen, Yaqiong; Qu, Yaohui; Lai, Yanqing; Li, Jie

    2014-01-01

    Highlights: • MoS 2 nanospheres, nanoribbons and nanoparticles were prepared by hydrothermal method. • The surfactant and temperature control the shape and crystal structure of MoS 2 . • MoS 2 nanospheres exhibit the excellent lithium storage property. - Abstract: A one-step hydrothermal process was employed to prepare a series of MoS 2 nanostructures via simply altering the surfactant as soft template and hydrothermal reaction temperature. Three kinds of MoS 2 nanostructures (three-dimensional (3D) hierarchical nanospheres, one-dimensional (1D) nanoribbons, and large aggregated nanoparticles) were successfully achieved and investigated well by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), and Brunauer–Emmett–Teller analysis (BET). Electrochemical tests reveal that these MoS 2 samples could deliver high initial discharge capacities (higher than 1050.0 mA h g −1 ), but various cycling performances. The hierarchical MoS 2 nanospheres assembled by sheet-like subunits show the highest specific capacity of 1355.1 mA h g −1 , and 66.8% of which can be retained after 50 cycles. The good lithium storage property of hierarchical MoS 2 nanospheres can be attributed to the higher electrolyte/MoS 2 contact area and stable 3D layered structure

  11. Crystal Structure of the Oxazolidinone Antibiotic Linezolid Bound to the 50S Ribosomal Subunit

    Energy Technology Data Exchange (ETDEWEB)

    Ippolito,J.; Kanyo, Z.; Wang, D.; Franceschi, F.; Moore, P.; Steitz, T.; Duffy, E.

    2008-01-01

    The oxazolidinone antibacterials target the 50S subunit of prokaryotic ribosomes. To gain insight into their mechanism of action, the crystal structure of the canonical oxazolidinone, linezolid, has been determined bound to the Haloarcula marismortui 50S subunit. Linezolid binds the 50S A-site, near the catalytic center, which suggests that inhibition involves competition with incoming A-site substrates. These results provide a structural basis for the discovery of improved oxazolidinones active against emerging drug-resistant clinical strains.

  12. Characterization of fimbrial subunits from Bordetella species

    NARCIS (Netherlands)

    Mooi, F.R.; Heide, H.G.J. van der; Avest, A.R. ter; Welinder, K.G.; Livey, I.; Zeijst, B.A.M. van der; Gaastra, W.

    Using antisera raised against serotype 2 and 3 fimbrial subunits from Bordetella pertussis, serologically related polypeptides were detected in Bordetella bronchiseptica, Bordetella parapertussis and Bordetella avium strains. The two B. pertussis fimbrial subunits, and three of the serologically

  13. Charging effect at grain boundaries of MoS2

    Science.gov (United States)

    Yan, Chenhui; Dong, Xi; Li, Connie H.; Li, Lian

    2018-05-01

    Grain boundaries (GBs) are inherent extended defects in chemical vapor deposited (CVD) transition metal dichalcogenide (TMD) films. Characterization of the atomic structure and electronic properties of these GBs is crucial for understanding and controlling the properties of TMDs via defect engineering. Here, we report the atomic and electronic structure of GBs in CVD grown MoS2 on epitaxial graphene/SiC(0001). Using scanning tunneling microscopy/spectroscopy, we find that GBs mostly consist of arrays of dislocation cores, where the presence of mid-gap states shifts both conduction and valence band edges by up to 1 eV. Our findings demonstrate the first charging effect near GBs in CVD grown MoS2, providing insights into the significant impact GBs can have on materials properties.

  14. Bacterial cellulose biosynthesis: diversity of operons, subunits, products and functions

    Science.gov (United States)

    Römling, Ute; Galperin, Michael Y.

    2015-01-01

    Summary Recent studies of bacterial cellulose biosynthesis, including structural characterization of a functional cellulose synthase complex, provided the first mechanistic insight into this fascinating process. In most studied bacteria, just two subunits, BcsA and BcsB, are necessary and sufficient for the formation of the polysaccharide chain in vitro. Other subunits – which differ among various taxa – affect the enzymatic activity and product yield in vivo by modulating expression of biosynthesis apparatus, export of the nascent β-D-glucan polymer to the cell surface, and the organization of cellulose fibers into a higher-order structure. These auxiliary subunits play key roles in determining the quantity and structure of the resulting biofilm, which is particularly important for interactions of bacteria with higher organisms that lead to rhizosphere colonization and modulate virulence of cellulose-producing bacterial pathogens inside and outside of host cells. Here we review the organization of four principal types of cellulose synthase operons found in various bacterial genomes, identify additional bcs genes that encode likely components of the cellulose biosynthesis and secretion machinery, and propose a unified nomenclature for these genes and subunits. We also discuss the role of cellulose as a key component of biofilms formed by a variety of free-living and pathogenic bacteria and, for the latter, in the choice between acute infection and persistence in the host. PMID:26077867

  15. Regulation of KV channel voltage-dependent activation by transmembrane β subunits

    Directory of Open Access Journals (Sweden)

    Xiaohui eSun

    2012-04-01

    Full Text Available Voltage-activated K+ (KV channels are important for shaping action potentials and maintaining resting membrane potential in excitable cells. KV channels contain a central pore-gate domain (PGD surrounded by four voltage-sensing domains (VSD. The VSDs will change conformation in response to alterations of the membrane potential thereby inducing the opening of the PGD. Many KV channels are heteromeric protein complexes containing auxiliary β subunits. These β subunits modulate channel expression and activity to increase functional diversity and render tissue specific phenotypes. This review focuses on the KV β subunits that contain transmembrane (TM segments including the KCNE family and the β subunits of large conductance, Ca2+- and voltage-activated K+ (BK channels. These TM β subunits affect the voltage-dependent activation of KV α subunits. Experimental and computational studies have described the structural location of these β subunits in the channel complexes and the biophysical effects on VSD activation, PGD opening and VSD-PGD coupling. These results reveal some common characteristics and mechanistic insights into KV channel modulation by TM β subunits.

  16. Efficient expression of functional (α6β22β3 AChRs in Xenopus oocytes from free subunits using slightly modified α6 subunits.

    Directory of Open Access Journals (Sweden)

    Carson Kai-Kwong Ley

    Full Text Available Human (α6β2(α4β2β3 nicotinic acetylcholine receptors (AChRs are essential for addiction to nicotine and a target for drug development for smoking cessation. Expressing this complex AChR is difficult, but has been achieved using subunit concatamers. In order to determine what limits expression of α6* AChRs and to efficiently express α6* AChRs using free subunits, we investigated expression of the simpler (α6β22β3 AChR. The concatameric form of this AChR assembles well, but is transported to the cell surface inefficiently. Various chimeras of α6 with the closely related α3 subunit increased expression efficiency with free subunits and produced pharmacologically equivalent functional AChRs. A chimera in which the large cytoplasmic domain of α6 was replaced with that of α3 increased assembly with β2 subunits and transport of AChRs to the oocyte surface. Another chimera replacing the unique methionine 211 of α6 with leucine found at this position in transmembrane domain 1 of α3 and other α subunits increased assembly of mature subunits containing β3 subunits within oocytes. Combining both α3 sequences in an α6 chimera increased expression of functional (α6β22β3 AChRs to 12-fold more than with concatamers. This is pragmatically useful, and provides insights on features of α6 subunit structure that limit its expression in transfected cells.

  17. Architecture of the large subunit of the mammalian mitochondrial ribosome.

    Science.gov (United States)

    Greber, Basil J; Boehringer, Daniel; Leitner, Alexander; Bieri, Philipp; Voigts-Hoffmann, Felix; Erzberger, Jan P; Leibundgut, Marc; Aebersold, Ruedi; Ban, Nenad

    2014-01-23

    Mitochondrial ribosomes synthesize a number of highly hydrophobic proteins encoded on the genome of mitochondria, the organelles in eukaryotic cells that are responsible for energy conversion by oxidative phosphorylation. The ribosomes in mammalian mitochondria have undergone massive structural changes throughout their evolution, including ribosomal RNA shortening and acquisition of mitochondria-specific ribosomal proteins. Here we present the three-dimensional structure of the 39S large subunit of the porcine mitochondrial ribosome determined by cryo-electron microscopy at 4.9 Å resolution. The structure, combined with data from chemical crosslinking and mass spectrometry experiments, reveals the unique features of the 39S subunit at near-atomic resolution and provides detailed insight into the architecture of the polypeptide exit site. This region of the mitochondrial ribosome has been considerably remodelled compared to its bacterial counterpart, providing a specialized platform for the synthesis and membrane insertion of the highly hydrophobic protein components of the respiratory chain.

  18. Catalytic Subunit 1 of Protein Phosphatase 2A Is a Subunit of the STRIPAK Complex and Governs Fungal Sexual Development

    Directory of Open Access Journals (Sweden)

    Anna Beier

    2016-06-01

    Full Text Available The generation of complex three-dimensional structures is a key developmental step for most eukaryotic organisms. The details of the molecular machinery controlling this step remain to be determined. An excellent model system to study this general process is the generation of three-dimensional fruiting bodies in filamentous fungi like Sordaria macrospora. Fruiting body development is controlled by subunits of the highly conserved striatin-interacting phosphatase and kinase (STRIPAK complex, which has been described in organisms ranging from yeasts to humans. The highly conserved heterotrimeric protein phosphatase PP2A is a subunit of STRIPAK. Here, catalytic subunit 1 of PP2A was functionally characterized. The Δpp2Ac1 strain is sterile, unable to undergo hyphal fusion, and devoid of ascogonial septation. Further, PP2Ac1, together with STRIPAK subunit PRO22, governs vegetative and stress-related growth. We revealed in vitro catalytic activity of wild-type PP2Ac1, and our in vivo analysis showed that inactive PP2Ac1 blocks the complementation of the sterile deletion strain. Tandem affinity purification, followed by mass spectrometry and yeast two-hybrid analysis, verified that PP2Ac1 is a subunit of STRIPAK. Further, these data indicate links between the STRIPAK complex and other developmental signaling pathways, implying the presence of a large interconnected signaling network that controls eukaryotic developmental processes. The insights gained in our study can be transferred to higher eukaryotes and will be important for understanding eukaryotic cellular development in general.

  19. Crystal structure of the P pilus rod subunit PapA.

    Directory of Open Access Journals (Sweden)

    Denis Verger

    2007-05-01

    Full Text Available P pili are important adhesive fibres involved in kidney infection by uropathogenic Escherichia coli strains. P pili are assembled by the conserved chaperone-usher pathway, which involves the PapD chaperone and the PapC usher. During pilus assembly, subunits are incorporated into the growing fiber via the donor-strand exchange (DSE mechanism, whereby the chaperone's G1 beta-strand that complements the incomplete immunoglobulin-fold of each subunit is displaced by the N-terminal extension (Nte of an incoming subunit. P pili comprise a helical rod, a tip fibrillum, and an adhesin at the distal end. PapA is the rod subunit and is assembled into a superhelical right-handed structure. Here, we have solved the structure of a ternary complex of PapD bound to PapA through donor-strand complementation, itself bound to another PapA subunit through DSE. This structure provides insight into the structural basis of the DSE reaction involving this important pilus subunit. Using gel filtration chromatography and electron microscopy on a number of PapA Nte mutants, we establish that PapA differs in its mode of assembly compared with other Pap subunits, involving a much larger Nte that encompasses not only the DSE region of the Nte but also the region N-terminal to it.

  20. Magic Clusters of MoS2 by Edge S2 Interdimer Spacing Modulation.

    Science.gov (United States)

    Ryou, Junga; Kim, Yong-Sung

    2018-05-17

    Edge atomic and electronic structures of S-saturated Mo-edge triangular MoS 2 nanoclusters are investigated using density functional theory calculations. The edge electrons described by the S 2 -p x p x π* (S 2 -Π x ) and Mo-d xy orbitals are found to interplay to pin the S 2 -Π x Fermi wavenumber at k F = 2/5 as the nanocluster size increases, and correspondingly, the ×5 Peierls edge S 2 interdimer spacing modulation is induced. For the particular sizes of N = 5 n - 2 and 5 n, where N is the number of Mo atoms at one edge representing the nanocluster size and n is a positive integer, the effective ×5 interdimer spacing modulation stabilizes the nanoclusters, which are identified here to be the magic S-saturated Mo-edge triangular MoS 2 nanoclusters. With the S 2 -Π x Peierls gap, the MoS 2 nanoclusters become far-edge S 2 -Π x semiconducting and subedge Mo-d xy metallic as N → ∞.

  1. Subunit Stoichiometry of Human Muscle Chloride Channels

    OpenAIRE

    Fahlke, Christoph; Knittle, Timothy; Gurnett, Christina A.; Campbell, Kevin P.; George, Alfred L.

    1997-01-01

    Voltage-gated Cl? channels belonging to the ClC family appear to function as homomultimers, but the number of subunits needed to form a functional channel is controversial. To determine subunit stoichiometry, we constructed dimeric human skeletal muscle Cl? channels in which one subunit was tagged by a mutation (D136G) that causes profound changes in voltage-dependent gating. Sucrose-density gradient centrifugation experiments indicate that both monomeric and dimeric hClC-1 channels in their ...

  2. Interlocking Friction Governs the Mechanical Fracture of Bilayer MoS2.

    Science.gov (United States)

    Jung, Gang Seob; Wang, Shanshan; Qin, Zhao; Martin-Martinez, Francisco J; Warner, Jamie H; Buehler, Markus J

    2018-04-24

    A molybdenum disulfide (MoS 2 ) layered system is a two-dimensional (2D) material, which is expected to provide the next generation of electronic devices together with graphene and other 2D materials. Due to its significance for future electronics applications, gaining a deep insight into the fundamental mechanisms upon MoS 2 fracture is crucial to prevent mechanical failure toward reliable applications. Here, we report direct experimental observation and atomic modeling of the complex failure behaviors of bilayer MoS 2 originating from highly variable interlayer frictions, elucidated with in situ transmission electron microscopy and large-scale reactive molecular dynamics simulations. Our results provide a systematic understanding of the effects that different stacking and loading conditions have on the failure mechanisms and crack-tip behaviors in the bilayer MoS 2 systems. Our findings unveil essential properties in fracture of this 2D material and provide mechanistic insight into its mechanical failure.

  3. An Investigation on the He−(1s2s2 2S Resonance in Debye Plasmas

    Directory of Open Access Journals (Sweden)

    Arijit Ghoshal

    2017-01-01

    Full Text Available The effect of Debye plasma on the 1 s 2 s 2 2 S resonance states in the scattering of electron from helium atom has been investigated within the framework of the stabilization method. The interactions among the charged particles in Debye plasma have been modelled by Debye–Huckel potential. The 1 s 2 s excited state of the helium atom has been treated as consisting of a H e + ionic core plus an electron moving around. The interaction between the core and the electron has then been modelled by a model potential. It has been found that the background plasma environment significantly affects the resonance states. To the best of our knowledge, such an investigation of 1 s 2 s 2 2 S resonance states of the electron–helium system embedded in Debye plasma environment is the first reported in the literature.

  4. Role of the Rubisco Small Subunit

    Energy Technology Data Exchange (ETDEWEB)

    Spreitzer, Robert Joseph [Univ. of Nebraska, Lincoln, NE (United States)

    2016-11-05

    Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) catalyzes the rate-limiting step of CO2 fixation in photosynthesis. However, it is a slow enzyme, and O2 competes with CO2 at the active site. Oxygenation initiates the photorespiratory pathway, which also results in the loss of CO2. If carboxylation could be increased or oxygenation decreased, an increase in net CO2 fixation would be realized. Because Rubisco provides the primary means by which carbon enters all life on earth, there is much interest in engineering Rubisco to increase the production of food and renewable energy. Rubisco is located in the chloroplasts of plants, and it is comprised of two subunits. Much is known about the chloroplast-gene-encoded large subunit (rbcL gene), which contains the active site, but much less is known about the role of the nuclear-gene-encoded small subunit in Rubisco function (rbcS gene). Both subunits are coded by multiple genes in plants, which makes genetic engineering difficult. In the eukaryotic, green alga Chlamydomonas reinhardtii, it has been possible to eliminate all the Rubisco genes. These Rubisco-less mutants can be maintained by providing acetate as an alternative carbon source. In this project, focus has been placed on determining whether the small subunit might be a better genetic-engineering target for improving Rubisco. Analysis of a variable-loop structure (βA-βB loop) of the small subunit by genetic selection, directed mutagenesis, and construction of chimeras has shown that the small subunit can influence CO2/O2 specificity. X-ray crystal structures of engineered chimeric-loop enzymes have indicated that additional residues and regions of the small subunit may also contribute to Rubisco function. Structural dynamics of the small-subunit carboxyl terminus was also investigated. Alanine-scanning mutagenesis of the most-conserved small-subunit residues has identified a

  5. The beta subunit of casein kinase II

    DEFF Research Database (Denmark)

    Boldyreff, B; Piontek, K; Schmidt-Spaniol, I

    1991-01-01

    cDNAs encoding the beta subunit of pig and mouse CKII were isolated. The porcine cDNA was expressed as a fusion protein in Escherichia coli and used for the production of anti-CKII-beta subunit specific antibodies....

  6. 28 CFR 51.6 - Political subunits.

    Science.gov (United States)

    2010-07-01

    ... 28 Judicial Administration 2 2010-07-01 2010-07-01 false Political subunits. 51.6 Section 51.6 Judicial Administration DEPARTMENT OF JUSTICE (CONTINUED) PROCEDURES FOR THE ADMINISTRATION OF SECTION 5 OF THE VOTING RIGHTS ACT OF 1965, AS AMENDED General Provisions § 51.6 Political subunits. All political...

  7. ASIC subunit ratio and differential surface trafficking in the brain.

    Science.gov (United States)

    Wu, Junjun; Xu, Yuanyuan; Jiang, Yu-Qing; Xu, Jiangping; Hu, Youjia; Zha, Xiang-ming

    2016-01-08

    Acid-sensing ion channels (ASICs) are key mediators of acidosis-induced responses in neurons. However, little is known about the relative abundance of different ASIC subunits in the brain. Such data are fundamental for interpreting the relative contribution of ASIC1a homomers and 1a/2 heteromers to acid signaling, and essential for designing therapeutic interventions to target these channels. We used a simple biochemical approach and semi-quantitatively determined the molar ratio of ASIC1a and 2 subunits in mouse brain. Further, we investigated differential surface trafficking of ASIC1a, ASIC2a, and ASIC2b. ASIC1a subunits outnumber the sum of ASIC2a and ASIC2b. There is a region-specific variation in ASIC2a and 2b expression, with cerebellum and striatum expressing predominantly 2b and 2a, respectively. Further, we performed surface biotinylation and found that surface ASIC1a and ASIC2a ratio correlates with their total expression. In contrast, ASIC2b exhibits little surface presence in the brain. This result is consistent with increased co-localization of ASIC2b with an ER marker in 3T3 cells. Our data are the first semi-quantitative determination of relative subunit ratio of various ASICs in the brain. The differential surface trafficking of ASICs suggests that the main functional ASICs in the brain are ASIC1a homomers and 1a/2a heteromers. This finding provides important insights into the relative contribution of various ASIC complexes to acid signaling in neurons.

  8. AdS2 holographic dictionary

    International Nuclear Information System (INIS)

    Cvetič, Mirjam; Papadimitriou, Ioannis

    2016-01-01

    We construct the holographic dictionary for both running and constant dilaton solutions of the two dimensional Einstein-Maxwell-Dilaton theory that is obtained by a circle reduction from Einstein-Hilbert gravity with negative cosmological constant in three dimensions. This specific model ensures that the dual theory has a well defined ultraviolet completion in terms of a two dimensional conformal field theory, but our results apply qualitatively to a wider class of two dimensional dilaton gravity theories. For each type of solutions we perform holographic renormalization, compute the exact renormalized one-point functions in the presence of arbitrary sources, and derive the asymptotic symmetries and the corresponding conserved charges. In both cases we find that the scalar operator dual to the dilaton plays a crucial role in the description of the dynamics. Its source gives rise to a matter conformal anomaly for the running dilaton solutions, while its expectation value is the only non trivial observable for constant dilaton solutions. The role of this operator has been largely overlooked in the literature. We further show that the only non trivial conserved charges for running dilaton solutions are the mass and the electric charge, while for constant dilaton solutions only the electric charge is non zero. However, by uplifting the solutions to three dimensions we show that constant dilaton solutions can support non trivial extended symmetry algebras, including the one found by Compère, Song and Strominger http://dx.doi.org/10.1007/JHEP05(2013)152, in agreement with the results of Castro and Song http://arxiv.org/abs/1411.1948. Finally, we demonstrate that any solution of this specific dilaton gravity model can be uplifted to a family of asymptotically AdS 2 ×S 2 or conformally AdS 2 ×S 2 solutions of the STU model in four dimensions, including non extremal black holes. The four dimensional solutions obtained by uplifting the running dilaton solutions coincide

  9. Dicyclohexylammonium (S-2-azido-3-phenylpropanoate

    Directory of Open Access Journals (Sweden)

    Sebastian J. Petrik

    2012-07-01

    Full Text Available The asymmetric unit of the title compound, C12H24N+·C9H8N3O2−, consists of two dicyclohexylammonium cations linked to two (S-2-azido-3-phenylpropanoate anions by four short N—H...O hydrogen bonds with N...O distances in the range 2.712 (3–2.765 (3 Å. The dicyclohexylammonium cations and the aryl and carboxylate groups of the anion are related by a pseudo-inversion centre, with overall crystallographic inversion symmetry for the structure broken by the chirality of the α-C atoms of the anions.

  10. A study on the electronic and interfacial structures of monolayer ReS2-metal contacts.

    Science.gov (United States)

    Wang, Jin; Yang, Guofeng; Sun, Rui; Yan, Pengfei; Lu, Yanan; Xue, Junjun; Chen, Guoqing

    2017-10-11

    In this paper, we perform a systematic and rigorous study to evaluate the Ohmic nature of the top-contact formed by the monolayer ReS 2 (mReS 2 ) and metals (gold, silver, platinum, nickel, titanium, and scandium) by means of first-principles density functional theory calculations. We investigate the potential barrier, charge transfer and atomic orbital overlap at the mReS 2 -metal interface in consideration of van der Waals forces to understand how efficiently carriers could be injected from the metal contact to the mReS 2 channel. ReS 2 is physisorbed on Au and Ag, which leads to little perturbation of its electronic structures and forms a larger Schottky contact and a higher tunnel barrier at the interface. ReS 2 is chemisorbed on Ti and Sc, where the bonding strongly perturbs the electronic structures and is found to be purely Ohmic. The bonding of ReS 2 on Pt and Ni lies between these two extreme cases, demonstrating an intermediate behavior. These findings not only provide an insight into the mReS 2 -metal interfaces but may also prove to be instrumental in the future design of ReS 2 -based devices with good performance.

  11. -MoS2 Lateral Heterojunctions

    KAUST Repository

    Li, Ming-yang

    2018-02-28

    2D layered heterostructures have attracted intensive interests due to their unique optical, transport, and interfacial properties. The laterally stitched heterojunction based on dissimilar 2D transition metal dichalcogenides forms an intrinsic p–n junction without the necessity of applying an external voltage. However, no scalable processes are reported to construct the devices with such lateral heterostructures. Here, a scalable strategy, two-step and location-selective chemical vapor deposition, is reported to synthesize self-aligned WSe2–MoS2 monolayer lateral heterojunction arrays and demonstrates their light-emitting devices. The proposed fabrication process enables the growth of high-quality interfaces and the first successful observation of electroluminescence at the WSe2–MoS2 lateral heterojunction. The electroluminescence study has confirmed the type-I alignment at the interface rather than commonly believed type-II alignment. This self-aligned growth process paves the way for constructing various 2D lateral heterostructures in a scalable manner, practically important for integrated 2D circuit applications.

  12. The alpha2-delta protein: an auxiliary subunit of voltage-dependent calcium channels as a recognized drug target.

    Science.gov (United States)

    Thorpe, Andrew J; Offord, James

    2010-07-01

    Currently, there are two drugs on the market, gabapentin (Neurontin) and pregabalin (Lyrica), that are proposed to exert their therapeutic effect through binding to the alpha2-delta subunit of voltage-sensitive calcium channels. This activity was unexpected, as the alpha2-delta subunit had previously been considered not to be a pharmacological target. In this review, the role of the alpha2-delta subunits is discussed and the mechanism of action of the alpha2-delta ligands in vitro and in vivo is summarized. Finally, new insights into the mechanism of drugs that bind to this protein are discussed.

  13. Eukaryotic RNA polymerase subunit RPB8 is a new relative of the OB family.

    Science.gov (United States)

    Krapp, S; Kelly, G; Reischl, J; Weinzierl, R O; Matthews, S

    1998-02-01

    RNA polymerase II subunit RPB8 is an essential subunit that is highly conserved throughout eukaryotic evolution and is present in all three types of nuclear RNA polymerases. We report the first high resolution structural insight into eukaryotic RNA polymerase architecture with the solution structure of RPB8 from Saccharomyces cerevisiae. It consists of an eight stranded, antiparallel beta-barrel, four short helical regions and a large, unstructured omega-loop. The strands are connected in classic Greek-key fashion. The overall topology is unusual and contains a striking C2 rotational symmetry. Furthermore, it is most likely a novel associate of the oligonucleotide/oligosaccharide (OB) binding protein class.

  14. Infrared realization of dS2 in AdS2

    Science.gov (United States)

    Anninos, Dionysios; Hofman, Diego M.

    2018-04-01

    We describe a two-dimensional geometry that smoothly interpolates between an asymptotically AdS2 geometry and the static patch of dS2. We find this ‘centaur’ geometry to be a solution of dilaton gravity with a specific class of potentials for the dilaton. We interpret the centaur geometry as a thermal state in the putative quantum mechanics dual to the AdS2 evolved with the global Hamiltonian. We compute the thermodynamic properties and observe that the centaur state has finite entropy and positive specific heat. The static patch is the infrared part of the centaur geometry. We discuss boundary observables sensitive to the static patch region.

  15. Acetylcholine Receptor: Complex of Homologous Subunits

    Science.gov (United States)

    Raftery, Michael A.; Hunkapiller, Michael W.; Strader, Catherine D.; Hood, Leroy E.

    1980-06-01

    The acetylcholine receptor from the electric ray Torpedo californica is composed of five subunits; two are identical and the other three are structurally related to them. Microsequence analysis of the four polypeptides demonstrates amino acid homology among the subunits. Further sequence analysis of both membrane-bound and Triton-solubilized, chromatographically purified receptor gave the stoichiometry of the four subunits (40,000:50,000:60,000:65,000 daltons) as 2:1:1:1, indicating that this protein is a pentameric complex with a molecular weight of 255,000 daltons. Genealogical analysis suggests that divergence from a common ancestral gene occurred early in the evolution of the receptor. This shared ancestry argues that each of the four subunits plays a functional role in the receptor's physiological action.

  16. Positive modulation of delta-subunit containing GABAA receptors in mouse neurons

    DEFF Research Database (Denmark)

    Vardya, Irina; Hoestgaard-Jensen, Kirsten; Nieto-Gonzalez, Jose Luis

    2012-01-01

    δ-subunit containing extrasynaptic GABA(A) receptors are potential targets for modifying neuronal activity in a range of brain disorders. With the aim of gaining more insight in synaptic and extrasynaptic inhibition, we used a new positive modulator, AA29504, of δ-subunit containing GABA(A) recep......δ-subunit containing extrasynaptic GABA(A) receptors are potential targets for modifying neuronal activity in a range of brain disorders. With the aim of gaining more insight in synaptic and extrasynaptic inhibition, we used a new positive modulator, AA29504, of δ-subunit containing GABA......(A) receptors in mouse neurons in vitro and in vivo. Whole-cell patch-clamp recordings were carried out in the dentate gyrus in mouse brain slices. In granule cells, AA29504 (1 μM) caused a 4.2-fold potentiation of a tonic current induced by THIP (1 μM), while interneurons showed a potentiation of 2.6-fold......-free environment using Ca²⁺ imaging in cultured neurons, AA29504 showed GABA(A) receptor agonism in the absence of agonist. Finally, AA29504 exerted dose-dependent stress-reducing and anxiolytic effects in mice in vivo. We propose that AA29504 potentiates δ-containing GABA(A) receptors to enhance tonic inhibition...

  17. The Subunit Principle in Scar Face Revision.

    Science.gov (United States)

    Elshahat, Ahmed; Lashin, Riham

    2017-06-01

    Facial scaring is considered one of the most difficult cosmetic problems for any plastic surgeon to solve. The condition is more difficult if the direction of the scar is not parallel to relaxed skin tension lines. Attempts to manage this difficult situation included revisions using geometric designs, Z plasties or W plasties to camouflage the straight line visible scaring. The use of long-lasting resorbable sutures was tried too. Recently, the use of botulinum toxin during revision improved the results. Fractional CO2 lasers, microfat grafts, and platelet-rich plasma were added to the armamentarium. The scar is least visible if placed in the junction between the facial subunits. The aim of this study is to investigate the use of the subunit principle to improve the results of scar revision. Four patients were included in this study. Tissue expansion of the intact part of the subunit allowed shifting the scar to the junction between the affected subunit and the adjacent one. Tissue expansion, delivery of the expanders, and advancement of the flaps were successful in all patients. The fact that this is a 2-stage procedure and sacrifices some of the intact skin from the affected facial subunit, makes this technique reserved to patients with ugly facial scars who are ambitious to improve their appearance.

  18. One step hydrothermal synthesis of 3D CoS2@MoS2-NG for high performance supercapacitors.

    Science.gov (United States)

    Meng, Qi; Chen, Yizhi; Zhu, Wenkun; Zhang, Ling; Yang, Xiaoyong; Duan, Tao

    2018-05-03

    A three-dimensional (3D) MoS 2 coated CoS 2 -nitrogen doped graphene (NG) (CoS 2 @MoS 2 -NG) hybrid has been synthesized by a one step hydrothermal method as supercapacitor (SC) electrode material for the first time. Such a composite consists of NG embedded with stacked CoS 2 @MoS 2 sheets. With a 3D skeleton, it prevents the agglomeration of CoS 2 @MoS 2 nanoparticles, resulting in sound conductivity, rich porous structures and a large surface area. The results indicate that CoS 2 @MoS 2 -NG has higher specific capacitance (198 F g -1 at 1 A g -1 ), better rate performance (with about 56.57% from 1 to 16 A g -1 ) and an improved cycle stability (with about 96.97% after 1000 cycles). It is an ideal candidate for SC electrode materials.

  19. Molecular cloning and analysis of zebrafish voltage-gated sodium channel beta subunit genes: implications for the evolution of electrical signaling in vertebrates

    Directory of Open Access Journals (Sweden)

    Zhong Tao P

    2007-07-01

    Full Text Available Abstract Background Action potential generation in excitable cells such as myocytes and neurons critically depends on voltage-gated sodium channels. In mammals, sodium channels exist as macromolecular complexes that include a pore-forming alpha subunit and 1 or more modulatory beta subunits. Although alpha subunit genes have been cloned from diverse metazoans including flies, jellyfish, and humans, beta subunits have not previously been identified in any non-mammalian species. To gain further insight into the evolution of electrical signaling in vertebrates, we investigated beta subunit genes in the teleost Danio rerio (zebrafish. Results We identified and cloned single zebrafish gene homologs for beta1-beta3 (zbeta1-zbeta3 and duplicate genes for beta4 (zbeta4.1, zbeta4.2. Sodium channel beta subunit loci are similarly organized in fish and mammalian genomes. Unlike their mammalian counterparts, zbeta1 and zbeta2 subunit genes display extensive alternative splicing. Zebrafish beta subunit genes and their splice variants are differentially-expressed in excitable tissues, indicating tissue-specific regulation of zbeta1-4 expression and splicing. Co-expression of the genes encoding zbeta1 and the zebrafish sodium channel alpha subunit Nav1.5 in Chinese Hamster Ovary cells increased sodium current and altered channel gating, demonstrating functional interactions between zebrafish alpha and beta subunits. Analysis of the synteny and phylogeny of mammalian, teleost, amphibian, and avian beta subunit and related genes indicated that all extant vertebrate beta subunits are orthologous, that beta2/beta4 and beta1/beta3 share common ancestry, and that beta subunits are closely related to other proteins sharing the V-type immunoglobulin domain structure. Vertebrate sodium channel beta subunit genes were not identified in the genomes of invertebrate chordates and are unrelated to known subunits of the para sodium channel in Drosophila. Conclusion The

  20. Schottky Barrier Height of Pd/MoS2 Contact by Large Area Photoemission Spectroscopy.

    Science.gov (United States)

    Dong, Hong; Gong, Cheng; Addou, Rafik; McDonnell, Stephen; Azcatl, Angelica; Qin, Xiaoye; Wang, Weichao; Wang, Weihua; Hinkle, Christopher L; Wallace, Robert M

    2017-11-08

    MoS 2 , as a model transition metal dichalcogenide, is viewed as a potential channel material in future nanoelectronic and optoelectronic devices. Minimizing the contact resistance of the metal/MoS 2 junction is critical to realizing the potential of MoS 2 -based devices. In this work, the Schottky barrier height (SBH) and the band structure of high work function Pd metal on MoS 2 have been studied by in situ X-ray photoelectron spectroscopy (XPS). The analytical spot diameter of the XPS spectrometer is about 400 μm, and the XPS signal is proportional to the detection area, so the influence of defect-mediated parallel conduction paths on the SBH does not affect the measurement. The charge redistribution by Pd on MoS 2 is detected by XPS characterization, which gives insight into metal contact physics to MoS 2 and suggests that interface engineering is necessary to lower the contact resistance for the future generation electronic applications.

  1. Observation of Room-Temperature Magnetoresistance in Monolayer MoS2 by Ferromagnetic Gating.

    Science.gov (United States)

    Jie, Wenjing; Yang, Zhibin; Zhang, Fan; Bai, Gongxun; Leung, Chi Wah; Hao, Jianhua

    2017-07-25

    Room-temperature magnetoresistance (MR) effect is observed in heterostructures of wafer-scale MoS 2 layers and ferromagnetic dielectric CoFe 2 O 4 (CFO) thin films. Through the ferromagnetic gating, an MR ratio of -12.7% is experimentally achieved in monolayer MoS 2 under 90 kOe magnetic field at room temperature (RT). The observed MR ratio is much higher than that in previously reported nonmagnetic metal coupled with ferromagnetic insulator, which generally exhibited MR ratio of less than 1%. The enhanced MR is attributed to the spin accumulation at the heterostructure interface and spin injection to the MoS 2 layers by the strong spin-orbit coupling effect. The injected spin can contribute to the spin current and give rise to the MR by changing the resistance of MoS 2 layers. Furthermore, the MR effect decreases as the thickness of MoS 2 increases, and the MR ratio becomes negligible in MoS 2 with thickness more than 10 layers. Besides, it is interesting to find a magnetic field direction dependent spin Hall magnetoresistance that stems from a combination of the spin Hall and the inverse spin Hall effects. Our research provides an insight into exploring RT MR in monolayer materials, which should be helpful for developing ultrathin magnetic storage devices in the atomically thin limit.

  2. The modulation of Schottky barriers of metal-MoS2 contacts via BN-MoS2 heterostructures.

    Science.gov (United States)

    Su, Jie; Feng, Liping; Zhang, Yan; Liu, Zhengtang

    2016-06-22

    Using first-principles calculations within density functional theory, we systematically studied the effect of BN-MoS2 heterostructure on the Schottky barriers of metal-MoS2 contacts. Two types of FETs are designed according to the area of the BN-MoS2 heterostructure. Results show that the vertical and lateral Schottky barriers in all the studied contacts, irrespective of the work function of the metal, are significantly reduced or even vanish when the BN-MoS2 heterostructure substitutes the monolayer MoS2. Only the n-type lateral Schottky barrier of Au/BN-MoS2 contact relates to the area of the BN-MoS2 heterostructure. Notably, the Pt-MoS2 contact with n-type character is transformed into a p-type contact upon substituting the monolayer MoS2 by a BN-MoS2 heterostructure. These changes of the contact natures are ascribed to the variation of Fermi level pinning, work function and charge distribution. Analysis demonstrates that the Fermi level pinning effects are significantly weakened for metal/BN-MoS2 contacts because no gap states dominated by MoS2 are formed, in contrast to those of metal-MoS2 contacts. Although additional BN layers reduce the interlayer interaction and the work function of the metal, the Schottky barriers of metal/BN-MoS2 contacts still do not obey the Schottky-Mott rule. Moreover, different from metal-MoS2 contacts, the charges transfer from electrodes to the monolayer MoS2, resulting in an increment of the work function of these metals in metal/BN-MoS2 contacts. These findings may prove to be instrumental in the future design of new MoS2-based FETs with ohmic contact or p-type character.

  3. AdS2 models in an embedding superspace

    International Nuclear Information System (INIS)

    McKeon, D.G.C.; Sherry, T.N.

    2003-01-01

    An embedding superspace, whose bosonic part is the flat (2+1)-dimensional embedding space for AdS 2 , is introduced. Superfields and several supersymmetric models are examined in the embedded AdS 2 superspace

  4. Electron microscopy studies on MoS2 nanocrystals

    DEFF Research Database (Denmark)

    Hansen, Lars Pilsgaard

    Industrial-style MoS2-based hydrotreating catalysts are studied using electron microscopy. The MoS2 nanostructures are imaged with single-atom sensitivity to reveal the catalytically important edge structures. Furthermore, the in-situ formation of MoS2 crystals is imaged for the first time....

  5. Immunochemical aspects of crotoxim and its subunits

    International Nuclear Information System (INIS)

    Nakazone, A.K.

    1979-01-01

    Crotamine and crotoxin with the subunits - phospholipase A and crotapotin - were obtained by purification from Crotalus durissus terrificus venom. Interaction studies of the subunits using crotalic antiserum, indicated that: crotoxin is formed of crotapotin and phospholipase A with the molar ratio of 1 to 1; using crotapotin 125 I the presence of a soluble complex was shown with the same antiserum. Immunological precipitation reactions demonstrated that crotapotin is antigenic: crotapotin and phospholipase A presented similar antigenic determinants; crotoxin antiserum reacted with each one of the submits; when the subunits are mixed to form synthetic crotoxin some antigenic determinants are masked in the process of interaction. Crotamine, interacted with crotapotin 1:1, without hidden antigenic determinants crotapotin antigenic site seems to be formed by, at least, one lysine. Enzimatical activity of phospholipase A apreared to be dependent on some reaction conditions when its arginine residues are blocked. Tyrosines of phospholipase A are more susceptible to labelling with 131 I than crotapotin. Gama irradiation of aqueous solutions of the subunits produced modifications in the ultraviolet spectra. A decrease of the enzymatic activity occured as a function of radiation dosis. Immunological activities of crotapotin and phospholipase A were not altered [pt

  6. Involvement of proteasomal subunits zeta and iota in RNA degradation.

    Science.gov (United States)

    Petit, F; Jarrousse, A S; Dahlmann, B; Sobek, A; Hendil, K B; Buri, J; Briand, Y; Schmid, H P

    1997-01-01

    We have identified two distinct subunits of 20 S proteasomes that are associated with RNase activity. Proteasome subunits zeta and iota, eluted from two-dimensional Western blots, hydrolysed tobacco mosaic virus RNA, whereas none of the other subunits degraded this substrate under the same conditions. Additionally, proteasomes were dissociated by 6 M urea, and subunit zeta, containing the highest RNase activity, was isolated by anion-exchange chromatography and gel filtration. Purified subunit zeta migrated as a single spot on two-dimensional PAGE with a molecular mass of approx. 28 kDa. Addition of anti-(subunit zeta) antibodies led to the co-precipitation of this proteasome subunit and nuclease activity. This is the first evidence that proteasomal alpha-type subunits are associated with an enzymic activity, and our results provide further evidence that proteasomes may be involved in cellular RNA metabolism. PMID:9337855

  7. Gold nanoparticles on MoS2 layered crystal flakes

    International Nuclear Information System (INIS)

    Cao, Wei; Pankratov, Vladimir; Huttula, Marko; Shi, Xinying; Saukko, Sami; Huang, Zhongjia; Zhang, Meng

    2015-01-01

    Inorganic layered crystal MoS 2 is considered as one of the most promising and efficient semiconductor materials for future transistors, photoelectronics, and electrocatalysis. To boost MoS 2 -based material applications, one direction is to grow physically and chemically reactive nanoparticles onto MoS 2 . Here we report on a simple route to synthesis crystalized MoS 2 –Au complexes. The gold nanoparticles were grown on MoS 2 flakes through a wet method in the oxygen free environment at room temperature. Nanoparticles with diameters varying from 9 nm to 429 nm were controlled by the molar ratios of MoS 2 and HAuCl 4 precursors. MoS 2 host flakes keep intrinsic honeycomb layered structures and the Au nanoparticles cubic-center crystal microstructures. From product chemical states analysis, the synthesis was found driven by redox reactions between the sulphide and the chloroauric acid. Photoluminescence measurement showed that introducing Au nanoparticles onto MoS 2 stacks substantially prompted excitonic transitions of stacks, as an analogy for doping Si wafers with dopants. Such composites may have potential applications in wide ranges similar as the doped Si. - Highlights: • The Au nanoparticles were decorated on MoS 2 in oxygen free ambiences via a wet method. • The Au nanoparticles are size-controllable and crystalized. • Chemical reaction scheme was clarified. • The MoS 2 –Au complexes have strong photoluminescent properties

  8. Cr doping induced negative transverse magnetoresistance in C d3A s2 thin films

    Science.gov (United States)

    Liu, Yanwen; Tiwari, Rajarshi; Narayan, Awadhesh; Jin, Zhao; Yuan, Xiang; Zhang, Cheng; Chen, Feng; Li, Liang; Xia, Zhengcai; Sanvito, Stefano; Zhou, Peng; Xiu, Faxian

    2018-02-01

    The magnetoresistance of a material conveys various dynamic information about charge and spin carriers, inspiring both fundamental studies in physics and practical applications such as magnetic sensors, data storage, and spintronic devices. Magnetic impurities play a crucial role in the magnetoresistance as they induce exotic states of matter such as the quantum anomalous Hall effect in topological insulators and tunable ferromagnetic phases in dilute magnetic semiconductors. However, magnetically doped topological Dirac semimetals are hitherto lacking. Here, we report a systematic study of Cr-doped C d3A s2 thin films grown by molecular-beam epitaxy. With the Cr doping, C d3A s2 thin films exhibit unexpected negative transverse magnetoresistance and strong quantum oscillations, bearing a trivial Berry's phase and an enhanced effective mass. More importantly, with ionic gating the magnetoresistance of Cr-doped C d3A s2 thin films can be drastically tuned from negative to positive, demonstrating the strong correlation between electrons and the localized spins of the Cr impurities, which we interpret through the formation of magnetic polarons. Such a negative magnetoresistance under perpendicular magnetic field and its gate tunability have not been observed previously in the Dirac semimetal C d3A s2 . The Cr-induced topological phase transition and the formation of magnetic polarons in C d3A s2 provide insights into the magnetic interaction in Dirac semimetals as well as their potential applications in spintronics.

  9. Anomalous photoluminescence thermal quenching of sandwiched single layer MoS_2

    KAUST Repository

    Tangi, Malleswararao; Shakfa, Mohammad Khaled; Mishra, Pawan; Li, Ming-Yang; Chiu, Ming-Hui; Ng, Tien Khee; Li, Lain-Jong; Ooi, Boon S.

    2017-01-01

    We report an unusual thermal quenching of the micro-photoluminescence (µ-PL) intensity for a sandwiched single-layer (SL) MoS2. For this study, MoS2 layers were chemical vapor deposited on molecular beam epitaxial grown In0.15Al0.85N lattice matched templates. Later, to accomplish air-stable sandwiched SL-MoS2, a thin In0.15Al0.85N cap layer was deposited on the MoS2/In0.15Al0.85N heterostructure. We confirm that the sandwiched MoS2 is a single layer from optical and structural analyses using µ-Raman spectroscopy and scanning transmission electron microscopy, respectively. By using high-resolution X-ray photoelectron spectroscopy, no structural phase transition of MoS2 is noticed. The recombination processes of bound and free excitons were analyzed by the power-dependent µ-PL studies at 77 K and room temperature (RT). The temperature-dependent micro photoluminescence (TDPL) measurements were carried out in the temperature range of 77 – 400 K. As temperature increases, a significant red-shift is observed for the free-exciton PL peak, revealing the delocalization of carriers. Further, we observe unconventional negative thermal quenching behavior, the enhancement of the µ-PL intensity with increasing temperatures up to 300K, which is explained by carrier hopping transitions that take place between shallow localized states to the band-edges. Thus, this study renders a fundamental insight into understanding the anomalous thermal quenching of µ-PL intensity of sandwiched SL-MoS2.

  10. Anomalous photoluminescence thermal quenching of sandwiched single layer MoS_2

    KAUST Repository

    Tangi, Malleswararao

    2017-09-22

    We report an unusual thermal quenching of the micro-photoluminescence (µ-PL) intensity for a sandwiched single-layer (SL) MoS2. For this study, MoS2 layers were chemical vapor deposited on molecular beam epitaxial grown In0.15Al0.85N lattice matched templates. Later, to accomplish air-stable sandwiched SL-MoS2, a thin In0.15Al0.85N cap layer was deposited on the MoS2/In0.15Al0.85N heterostructure. We confirm that the sandwiched MoS2 is a single layer from optical and structural analyses using µ-Raman spectroscopy and scanning transmission electron microscopy, respectively. By using high-resolution X-ray photoelectron spectroscopy, no structural phase transition of MoS2 is noticed. The recombination processes of bound and free excitons were analyzed by the power-dependent µ-PL studies at 77 K and room temperature (RT). The temperature-dependent micro photoluminescence (TDPL) measurements were carried out in the temperature range of 77 – 400 K. As temperature increases, a significant red-shift is observed for the free-exciton PL peak, revealing the delocalization of carriers. Further, we observe unconventional negative thermal quenching behavior, the enhancement of the µ-PL intensity with increasing temperatures up to 300K, which is explained by carrier hopping transitions that take place between shallow localized states to the band-edges. Thus, this study renders a fundamental insight into understanding the anomalous thermal quenching of µ-PL intensity of sandwiched SL-MoS2.

  11. Africa Insight

    African Journals Online (AJOL)

    Africa Insight is a quarterly, peer-reviewed journal of the Africa Institute of South Africa. It is accredited by the South African National Department of Higher Education and Training (DHET) and is indexed in the International Bibliography of Social Science (IBSS). It is a multi-disciplinary journal primarily focusing on African ...

  12. S = -1 and S = -2 few-body hypernuclei

    International Nuclear Information System (INIS)

    Gibson, B.F.

    1997-01-01

    The S = -1 and S = -2 few-body bound states are the focus of this discussion. Implications for the understanding of the baryon-baryon interaction are examined. Octet-octet coupling effects not found in conventional, non-strange nuclei are highlighted. TJNAF wave function tests for the S = -1 sector are noted. The need to identify S = -2 hypernuclei to explore the S = -2 strong interaction and to test model predictions is emphasized

  13. Faceted MoS2 nanotubes and nanoflowers

    International Nuclear Information System (INIS)

    Deepak, Francis Leonard; Mayoral, Alvaro; Yacaman, Miguel Jose

    2009-01-01

    A simple synthesis of novel faceted MoS 2 nanotubes (NTs) and nanoflowers (NFs) starting from molybdenum oxide and thiourea as the sulphur source is reported. The MoS 2 nanotubes with the faceted morphology have not been observed before. Further the as-synthesized MoS 2 nanotubes have high internal surface area. The nanostructures have been characterized by a variety of electron microscopy techniques. It is expected that these MoS 2 nanostrutures will find important applications in energy storage, catalysis and field emission.

  14. Muscular subunits transplantation for facial reanimation

    Directory of Open Access Journals (Sweden)

    Hazan André Salo Buslik

    2006-01-01

    Full Text Available PURPOSE: To present an alternative technique for reconstruction of musculocutaneous damages in the face transferring innervated subsegments(subunits of the latissimus dorsi flap for replacement of various facial mimetic muscles. METHODS: One clinical case of trauma with skin and mimetic muscles damage is described as an example of the technique. The treatment was performed with microsurgical transfer of latissimus dorsi muscle subunits. Each subunit present shape and dimensions of the respective mimetic muscles replaced. The origin, insertions and force vectors for the mimicmuscle lost were considered. Each subsegment has its own arterial and venous supply with a motor nerve component for the muscular unit. RESULTS: Pre and one year postoperative photos registration of static and dynamic mimic aspects, as well as digital electromyography digital data of the patients were compared. The transplanted muscular units presented myoeletric activity, fulfilling both the functional and cosmetic aspect. CONCLUSION: This technique seems to be a promising way to deal with the complex musculocutaneous losses of the face as well as facial palsy.

  15. Influvac, a trivalent inactivated subunit influenza vaccine.

    Science.gov (United States)

    Zuccotti, Gian Vincenzo; Fabiano, Valentina

    2011-01-01

    Influenza represents a major sanitary and socio-economic burden and vaccination is universally considered the most effective strategy for preventing the disease and its complications. Traditional influenza vaccines have been on the market since the late 1940s, with million of doses administered annually worldwide, and demonstrated a substantial efficacy and safety. The trivalent inactivated subunit vaccine has been available for more than 25 years and has been studied in healthy children, adults and the elderly and in people affected by underlying chronic medical conditions. We describe vaccine technology focusing on subunit vaccine production procedures and mode of action and provide updated information on efficacy and safety available data. A review of efficacy and safety data in healthy subjects and in high risk populations from major sponsor- and investigator-driven studies. The vaccine showed a good immunogenicity and a favorable safety profile in all target groups. In the panorama of actually available influenza vaccines, trivalent inactivated subunit vaccine represents a well-established tool for preventing flu and the associated complications.

  16. Soybean glycinin subunits: Characterization of physicochemical and adhesion properties.

    Science.gov (United States)

    Mo, Xiaoqun; Zhong, Zhikai; Wang, Donghai; Sun, Xiuzhi

    2006-10-04

    Soybean proteins have shown great potential for applications as renewable and environmentally friendly adhesives. The objective of this work was to study physicochemical and adhesion properties of soy glycinin subunits. Soybean glycinin was extracted from soybean flour and then fractionated into acidic and basic subunits with an estimated purity of 90 and 85%, respectively. Amino acid composition of glycinin subunits was determined. The high hydrophobic amino acid content is a major contributor to the solubility behavior and water resistance of the basic subunits. Acidic subunits and glycinin had similar solubility profiles, showing more than 80% solubility at pH 2.0-4.0 or 6.5-12.0, whereas basic subunits had considerably lower solubility with the minimum at pH 4.5-8.0. Thermal analysis using a differential scanning calorimeter suggested that basic subunits form new oligomeric structures with higher thermal stability than glycinin but no highly ordered structures present in isolated acidic subunits. The wet strength of basic subunits was 160% more than that of acidic subunits prepared at their respective isoelectric points (pI) and cured at 130 degrees C. Both pH and the curing temperature significantly affected adhesive performance. High-adhesion water resistance was usually observed for adhesives from protein prepared at their pI values and cured at elevated temperatures. Basic subunits are responsible for the water resistance of glycinin and are a good starting material for the development of water-resistant adhesives.

  17. Topotactic synthesis of a new BiS2-based superconductor Bi2(O,F)S2

    OpenAIRE

    Okada, Tomoyuki; Ogino, Hiraku; Shimoyama, Jun-ichi; Kishio, Kohji

    2015-01-01

    A new BiS2-based superconductor Bi2(O,F)S2 was discovered. This is a layered compound consisting of alternate stacking structure of rock-salt-type BiS2 superconducting layer and fluorite-type Bi(O,F) blocking layer. Bi2(O,F)S2 was obtained as the main phase by topotactic fluorination of undoped Bi2OS2 using XeF2, which is the first topotactic synthesis of an electron-doped superconductor via reductive fluorination. With increasing F-content, a- and c-axis length increased and decreased, respe...

  18. Topotactic synthesis of a new BiS2-based superconductor Bi2(O,F)S2

    Science.gov (United States)

    Okada, Tomoyuki; Ogino, Hiraku; Shimoyama, Jun-ichi; Kishio, Kohji

    2015-02-01

    A new BiS2-based superconductor, Bi2(O,F)S2, was discovered. It is a layered compound consisting of alternately stacked structure of rock-salt-type BiS2 superconducting layers and fluorite-type Bi(O,F) blocking layers. Bi2(O,F)S2 was obtained as the main phase by topotactic fluorination of undoped Bi2OS2 using XeF2. This is the first topotactic synthesis of an electron-doped superconductor via reductive fluorination. With increasing F-content, a- and c-axis lengths increased and decreased, respectively, and Tc increased to 5.1 K.

  19. Magnetoresistance in Co/2D MoS2/Co and Ni/2D MoS2/Ni junctions.

    Science.gov (United States)

    Zhang, Han; Ye, Meng; Wang, Yangyang; Quhe, Ruge; Pan, Yuanyuan; Guo, Ying; Song, Zhigang; Yang, Jinbo; Guo, Wanlin; Lu, Jing

    2016-06-28

    Semiconducting single-layer (SL) and few-layer MoS2 have a flat surface, free of dangling bonds. Using density functional theory coupled with non-equilibrium Green's function method, we investigate the spin-polarized transport properties of Co/2D MoS2/Co and Ni/2D MoS2/Ni junctions with MoS2 layer numbers of N = 1, 3, and 5. Well-defined interfaces are formed between MoS2 and metal electrodes. The junctions with a SL MoS2 spacer are almost metallic owing to the strong coupling between MoS2 and the ferromagnets, while those are tunneling with a few layer MoS2 spacer. Both large magnetoresistance and tunneling magnetoresistance are found when fcc or hcp Co is used as an electrode. Therefore, flat single- and few-layer MoS2 can serve as an effective nonmagnetic spacer in a magnetoresistance or tunneling magnetoresistance device with a well-defined interface.

  20. Intercalation of Si between MoS2 layers

    Directory of Open Access Journals (Sweden)

    Rik van Bremen

    2017-09-01

    Full Text Available We report a combined experimental and theoretical study of the growth of sub-monolayer amounts of silicon (Si on molybdenum disulfide (MoS2. At room temperature and low deposition rates we have found compelling evidence that the deposited Si atoms intercalate between the MoS2 layers. Our evidence relies on several experimental observations: (1 Upon the deposition of Si on pristine MoS2 the morphology of the surface transforms from a smooth surface to a hill-and-valley surface. The lattice constant of the hill-and-valley structure amounts to 3.16 Å, which is exactly the lattice constant of pristine MoS2. (2 The transitions from hills to valleys are not abrupt, as one would expect for epitaxial islands growing on-top of a substrate, but very gradual. (3 I(V scanning tunneling spectroscopy spectra recorded at the hills and valleys reveal no noteworthy differences. (4 Spatial maps of dI/dz reveal that the surface exhibits a uniform work function and a lattice constant of 3.16 Å. (5 X-ray photo-electron spectroscopy measurements reveal that sputtering of the MoS2/Si substrate does not lead to a decrease, but an increase of the relative Si signal. Based on these experimental observations we have to conclude that deposited Si atoms do not reside on the MoS2 surface, but rather intercalate between the MoS2 layers. Our conclusion that Si intercalates upon the deposition on MoS2 is at variance with the interpretation by Chiappe et al. (Adv. Mater. 2014, 26, 2096–2101 that silicon forms a highly strained epitaxial layer on MoS2. Finally, density functional theory calculations indicate that silicene clusters encapsulated by MoS2 are stable.

  1. Functional divergence of chloroplast Cpn60α subunits during Arabidopsis embryo development.

    Directory of Open Access Journals (Sweden)

    Xiaolong Ke

    2017-09-01

    Full Text Available Chaperonins are a class of molecular chaperones that assist in the folding and assembly of a wide range of substrates. In plants, chloroplast chaperonins are composed of two different types of subunits, Cpn60α and Cpn60β, and duplication of Cpn60α and Cpn60β genes occurs in a high proportion of plants. However, the importance of multiple Cpn60α and Cpn60β genes in plants is poorly understood. In this study, we found that loss-of-function of CPNA2 (AtCpn60α2, a gene encoding the minor Cpn60α subunit in Arabidopsis thaliana, resulted in arrested embryo development at the globular stage, whereas the other AtCpn60α gene encoding the dominant Cpn60α subunit, CPNA1 (AtCpn60α1, mainly affected embryonic cotyledon development at the torpedo stage and thereafter. Further studies demonstrated that CPNA2 can form a functional chaperonin with CPNB2 (AtCpn60β2 and CPNB3 (AtCpn60β3, while the functional partners of CPNA1 are CPNB1 (AtCpn60β1 and CPNB2. We also revealed that the functional chaperonin containing CPNA2 could assist the folding of a specific substrate, KASI (β-ketoacyl-[acyl carrier protein] synthase I, and that the KASI protein level was remarkably reduced due to loss-of-function of CPNA2. Furthermore, the reduction in the KASI protein level was shown to be the possible cause for the arrest of cpna2 embryos. Our findings indicate that the two Cpn60α subunits in Arabidopsis play different roles during embryo development through forming distinct chaperonins with specific AtCpn60β to assist the folding of particular substrates, thus providing novel insights into functional divergence of Cpn60α subunits in plants.

  2. Tunable Electrical and Optical Characteristics in Monolayer Graphene and Few-Layer MoS2 Heterostructure Devices.

    Science.gov (United States)

    Rathi, Servin; Lee, Inyeal; Lim, Dongsuk; Wang, Jianwei; Ochiai, Yuichi; Aoki, Nobuyuki; Watanabe, Kenji; Taniguchi, Takashi; Lee, Gwan-Hyoung; Yu, Young-Jun; Kim, Philip; Kim, Gil-Ho

    2015-08-12

    Lateral and vertical two-dimensional heterostructure devices, in particular graphene-MoS2, have attracted profound interest as they offer additional functionalities over normal two-dimensional devices. Here, we have carried out electrical and optical characterization of graphene-MoS2 heterostructure. The few-layer MoS2 devices with metal electrode at one end and monolayer graphene electrode at the other end show nonlinearity in drain current with drain voltage sweep due to asymmetrical Schottky barrier height at the contacts and can be modulated with an external gate field. The doping effect of MoS2 on graphene was observed as double Dirac points in the transfer characteristics of the graphene field-effect transistor (FET) with a few-layer MoS2 overlapping the middle part of the channel, whereas the underlapping of graphene have negligible effect on MoS2 FET characteristics, which showed typical n-type behavior. The heterostructure also exhibits a strongest optical response for 520 nm wavelength, which decreases with higher wavelengths. Another distinct feature observed in the heterostructure is the peak in the photocurrent around zero gate voltage. This peak is distinguished from conventional MoS2 FETs, which show a continuous increase in photocurrent with back-gate voltage. These results offer significant insight and further enhance the understanding of the graphene-MoS2 heterostructure.

  3. The interface of the ferromagnetic metal CoS2 and the nonmagnetic semiconductor FeS2

    KAUST Repository

    Nazir, S.; Schwingenschlö gl, Udo

    2010-01-01

    semiconductor shows a metallic character. The CoS2 stays close to half-metallicity at the interface, while the FeS2 becomes metallic. The magnetic moment of the Co atoms at the interface slightly decreases as compared to the bulk value and a small moment

  4. Design lateral heterostructure of monolayer ZrS2 and HfS2 from first principles calculations

    Science.gov (United States)

    Yuan, Junhui; Yu, Niannian; Wang, Jiafu; Xue, Kan-Hao; Miao, Xiangshui

    2018-04-01

    The successful fabrication of two-dimensional lateral heterostructures (LHS's) has opened up unprecedented opportunities in material science and device physics. It is therefore highly desirable to search for more suitable materials to create such heterostructures for next-generation devices. Here, we investigate a novel lateral heterostructure composed of monolayer ZrS2 and HfS2 based on density functional theory. The phonon dispersion and ab initio molecular dynamics analysis indicate its good kinetic and thermodynamic stability. Remarkably, we find that these lateral heterostructures exhibit an indirect to direct bandgap transition, in contrast to the intrinsic indirect bandgap nature of ZrS2 and HfS2. The type-II alignment and chemical bonding across the interline have also been revealed. The tensile strain is proved to be an efficient way to modulate the band structure. Finally, we further discuss other three stable lateral heterostructures: (ZrSe2)2(HfSe2)2 LHS, (ZrS2)2(ZrSe2)2 LHS and (HfS2)2(HfSe2)2 LHS. Generally, the lateral heterostructures of monolayer ZrS2 and HfS2 are of excellent electrical properties, and may find potential applications for future electronic devices.

  5. Enhancement of photovoltaic response in multilayer MoS2 induced by plasma doping.

    Science.gov (United States)

    Wi, Sungjin; Kim, Hyunsoo; Chen, Mikai; Nam, Hongsuk; Guo, L Jay; Meyhofer, Edgar; Liang, Xiaogan

    2014-05-27

    Layered transition-metal dichalcogenides hold promise for making ultrathin-film photovoltaic devices with a combination of excellent photovoltaic performance, superior flexibility, long lifetime, and low manufacturing cost. Engineering the proper band structures of such layered materials is essential to realize such potential. Here, we present a plasma-assisted doping approach for significantly improving the photovoltaic response in multilayer MoS2. In this work, we fabricated and characterized photovoltaic devices with a vertically stacked indium tin oxide electrode/multilayer MoS2/metal electrode structure. Utilizing a plasma-induced p-doping approach, we are able to form p-n junctions in MoS2 layers that facilitate the collection of photogenerated carriers, enhance the photovoltages, and decrease reverse dark currents. Using plasma-assisted doping processes, we have demonstrated MoS2-based photovoltaic devices exhibiting very high short-circuit photocurrent density values up to 20.9 mA/cm(2) and reasonably good power-conversion efficiencies up to 2.8% under AM1.5G illumination, as well as high external quantum efficiencies. We believe that this work provides important scientific insights for leveraging the optoelectronic properties of emerging atomically layered two-dimensional materials for photovoltaic and other optoelectronic applications.

  6. Gold Dispersion and Activation on the Basal Plane of Single-Layer MoS2

    KAUST Repository

    Merida, Cindy S.; Le, Duy; Echeverrí a, Elena M.; Nguyen, Ariana E.; Rawal, Takat B; Naghibi Alvillar, Sahar; Kandyba, Viktor; Al-Mahboob, Abdullah; Losovyj, Yaroslav B.; Katsiev, Khabiboulakh; Valentin, Michael D.; Huang, Chun-Yu; Gomez, Michael J.; Lu, I-Hsi; Guan, Alison; Barinov, Alexei; Rahman, Talat S; Dowben, Peter A.; Bartels, Ludwig

    2017-01-01

    Gold islands are typically associated with high binding affinity to adsorbates and catalytic activity. Here we present the growth of such dispersed nanoscale gold islands on single layer MoS2, prepared on an inert SiO2/Si support by chemical vapor deposition (CVD). This study offers a combination of growth process development, optical characterization, photoelectron spectroscopy at sub-micron spatial resolution, and advanced density functional theory modeling for detailed insight into the electronic interaction between gold and single-layer MoS2. In particular, we find the gold density of states in Au/MoS2/SiO2/Si to be far less well-defined than Au islands on other 2-dimensional materials such as graphene, for which we also provide data. We attribute this effect to the presence of heterogeneous Au adatom/MoS2-support interactions within the nanometer-scale gold cluster. As a consequence, theory predicts that CO will exhibit adsorption energies in excess of 1 eV at the Au cluster edges, where the local density of states is dominated by Au 5dz2 symmetry.

  7. Gold Dispersion and Activation on the Basal Plane of Single-Layer MoS2

    KAUST Repository

    Merida, Cindy S.

    2017-12-09

    Gold islands are typically associated with high binding affinity to adsorbates and catalytic activity. Here we present the growth of such dispersed nanoscale gold islands on single layer MoS2, prepared on an inert SiO2/Si support by chemical vapor deposition (CVD). This study offers a combination of growth process development, optical characterization, photoelectron spectroscopy at sub-micron spatial resolution, and advanced density functional theory modeling for detailed insight into the electronic interaction between gold and single-layer MoS2. In particular, we find the gold density of states in Au/MoS2/SiO2/Si to be far less well-defined than Au islands on other 2-dimensional materials such as graphene, for which we also provide data. We attribute this effect to the presence of heterogeneous Au adatom/MoS2-support interactions within the nanometer-scale gold cluster. As a consequence, theory predicts that CO will exhibit adsorption energies in excess of 1 eV at the Au cluster edges, where the local density of states is dominated by Au 5dz2 symmetry.

  8. Emergence of topological and topological crystalline phases in TlBiS2 and TlSbS2

    KAUST Repository

    Zhang, Qingyun; Cheng, Yingchun; Schwingenschlö gl, Udo

    2015-01-01

    Using first-principles calculations, we investigate the band structure evolution and topological phase transitions in TlBiS2 and TlSbS2 under hydrostatic pressure as well as uniaxial and biaxial strain. The phase transitions are identified by parity analysis and by calculating the surface states. Zero, one, and four Dirac cones are found for the (111) surfaces of both TlBiS2 and TlSbS2 when the pressure grows, which confirms trivial-nontrivial-trivial phase transitions. The Dirac cones at the (M) over bar points are anisotropic with large out-of-plane component. TlBiS2 shows normal, topological, and topological crystalline insulator phases under hydrostatic pressure, thus being the first compound to exhibit a phase transition from a topological to a topological crystalline insulator.

  9. Emergence of topological and topological crystalline phases in TlBiS2 and TlSbS2

    KAUST Repository

    Zhang, Qingyun

    2015-02-11

    Using first-principles calculations, we investigate the band structure evolution and topological phase transitions in TlBiS2 and TlSbS2 under hydrostatic pressure as well as uniaxial and biaxial strain. The phase transitions are identified by parity analysis and by calculating the surface states. Zero, one, and four Dirac cones are found for the (111) surfaces of both TlBiS2 and TlSbS2 when the pressure grows, which confirms trivial-nontrivial-trivial phase transitions. The Dirac cones at the (M) over bar points are anisotropic with large out-of-plane component. TlBiS2 shows normal, topological, and topological crystalline insulator phases under hydrostatic pressure, thus being the first compound to exhibit a phase transition from a topological to a topological crystalline insulator.

  10. Soft chemistry routes to GeS2 nanoparticles

    Science.gov (United States)

    Courthéoux, Laurence; Mathiaud, Romain; Ribes, Michel; Pradel, Annie

    2018-04-01

    Spherical GeS2 particles are prepared by a low temperature liquid route with TEOG as germanium precursor and either H2S or thioacetamide (TAA) as sulfur precursors. The size and agglomeration of the particles change depending upon the temperature and nature of the solvent. Most synthesis lead to preparing amorphous GeS2. When the reaction kinetic is slowed down by using TAA at 25 °C, the obtained GeS2 product presents a larger order in the range of few Å as proven by Raman spectroscopy, even though it is still an amorphous compound as suggested by X-Ray diffraction and TEM experiments.

  11. Discovery of gaseous S2 in Io's Pele plume.

    Science.gov (United States)

    Spencer, J R; Jessup, K L; McGrath, M A; Ballester, G E; Yelle, R

    2000-05-19

    Spectroscopy of Io's Pele plume against Jupiter by the Hubble Space Telescope in October 1999 revealed absorption due to S2 gas, with a column density of 1.0 +/- 0.2 x 10(16) per square centimeter, and probably also SO(2) gas with a column density of 7 +/- 3 x 10(16) per square centimeter. This SO2/S2 ratio (3 to 12) is expected from equilibration with silicate magmas near the quartz-fayalite-magnetite or wüstite-magnetite buffers. Condensed S3 and S4, probable coloring agents in Pele's red plume deposits, may form by polymerization of the S2, which is unstable to ultraviolet photolysis. Diffuse red deposits near other Io volcanoes suggest that venting and polymerization of S2 gas is a widespread feature of Io volcanism.

  12. Electronic structure of shandite Co3Sn2S2

    Science.gov (United States)

    Dedkov, Y. S.; Holder, M.; Molodtsov, S. L.; Rosner, H.

    2008-03-01

    The electronic structure of shandite Co3Sn2S2 was determined by photoelectron spectroscopy and compared with ab initio band structure calculations. Presented results give evidence that this compound has half-metallic ferromagnetic properties.

  13. Charge density study of two FeS2 polymorphs

    DEFF Research Database (Denmark)

    Schmøkel, Mette Stokkebro; Jørgensen, Mads Ry Vogel; Bjerg, Lasse

    Experimental charge density studies of inorganic solids have proven to be a difficult task due to systematic errors related to data collection such as absorption and extinction; however, the use of synchrotron radiation has the potential to minimize these problems. [1] One of the pioneering...... experimental electron density studies of an inorganic solid containing a transition metal was presented by Stevens et al. [2] who investigated the effect of crystal-field splitting of the partially filled iron d-orbitals in the pyrite structure of FeS2. Other studies of various FeS2 structures, including...... pyrite, has been performed by Gibbs et al. [3], however, these are all based on theoretical calculations rather than experiment. In the current study we revisit FeS2 through an experimental charge density study of the two low-spin iron FeS2 structures, pyrite and marcasite. High-quality, low...

  14. Monolayer MoS2 heterojunction solar cells

    KAUST Repository

    Tsai, Menglin

    2014-08-26

    We realized photovoltaic operation in large-scale MoS2 monolayers by the formation of a type-II heterojunction with p-Si. The MoS 2 monolayer introduces a built-in electric field near the interface between MoS2 and p-Si to help photogenerated carrier separation. Such a heterojunction photovoltaic device achieves a power conversion efficiency of 5.23%, which is the highest efficiency among all monolayer transition-metal dichalcogenide-based solar cells. The demonstrated results of monolayer MoS 2/Si-based solar cells hold the promise for integration of 2D materials with commercially available Si-based electronics in highly efficient devices. © 2014 American Chemical Society.

  15. Human aldolase B subunit-specific radioimmunoassay

    International Nuclear Information System (INIS)

    Asaka, M.; Alpert, E.

    1983-01-01

    A radioimmunoassay was developed for the direct quantification of aldolase B in human serum and tissues. The method is a double-antibody radioimmunoassay technique using radioiodinated aldolase B homopolymer as ligand, chicken antibodies to aldolase B and rabbit antibodies to chicken IgG. This radioimmunoassay was shown to be specific for the aldolase B subunit, with no cross-reactivity with either human aldolase A subunit or homopolymeric human aldolase C (C 4 ). The lowest measurable amount by this method was 2 ng/ml. Aldolase B is predominantly found in normal liver tissue, with relatively-high aldolase B levels also observed in kidney. Aldolase B levels in the serum obtained from 11 normal subjects ranged from 23 to 38 ng/ml, with a mean of 28.5 +- 9.2 (S.D.) ng/ml. Almost all of patients with hepatitis had serum aldolase B levels greater than 30 ng/ml. In cancer patients, serum aldolase B was slightly elevated in patients with metastatic liver cancer and primary lever cell carcinoma, whereas no elevation of serum aldolase B was shown in patients without liver metastasis. (Auth.)

  16. Thermochemical study of MoS2 oxidation

    International Nuclear Information System (INIS)

    Filimonov, D.S.; Topor, N.D.; Kesler, Ya.A.

    1990-01-01

    Thermochemical studies of oxidation processes of metallic molybdenum, sulfur, molybdenum disulfide under different conditions in microcalorimeter are conducted. Values of thermal effects which are used to calculate standard formation enthalpy of MoS 2 and which correlate well are obtained. Δ f H 0 (MoS 2 ,298.15 K) recommended value constitutes (-223.0±16.7) kJ/mol

  17. Crystal structure of new AsS2 compound

    International Nuclear Information System (INIS)

    Bolotina, N. B.; Brazhkin, V. V.; Dyuzheva, T. I.; Lityagina, L. M.; Kulikova, L. F.; Nikolaev, N. A.; Verin, I. A.

    2013-01-01

    AsS 2 single crystals have been obtained for the first time from an As 2 S 3 melt at pressures above 6 GPa and temperatures above 800 K in the As 2 S 3 → AsS + AsS 2 reaction. The monoclinic structure of the new high-pressure phase is solved by X-ray diffraction analysis and compared to the structure of high-pressure AsS phase, which was studied previously.

  18. Tunneling in BP-MoS2 heterostructure

    Science.gov (United States)

    Liu, Xiaochi; Qu, Deshun; Kim, Changsik; Ahmed, Faisal; Yoo, Won Jong

    Tunnel field effect transistor (TFET) is considered to be a leading option for achieving SS mV/dec. In this work, black phosphorus (BP) and molybdenum disulfide (MoS2) heterojunction devices are fabricated. We find that thin BP flake and MoS2 form normal p-n junctions, tunneling phenomena can be observed when BP thickness increases to certain level. PEO:CsClO4 is applied on the surface of the device together with a side gate electrode patterned together with source and drain electrodes. The Fermi level of MoS2 on top of BP layer can be modulated by the side gating, and this enables to vary the MoS2-BP tunnel diode property from off-state to on-state. Since tunneling is the working mechanism of MoS2-BP junction, and PEO:CsClO4\\ possesses ultra high dielectric constant and small equivalent oxide thickness (EOT), a low SS of 55 mV/dec is obtained from MoS2-BP TFET. This work was supported by the Global Research Laboratory and Global Frontier R&D Programs at the Center for Hybrid Interface Materials, both funded by the Ministry of Science, ICT & Future Planning via the National Research Foundation of Korea (NRF).

  19. Subunit stoichiometry of the chloroplast photosystem I complex

    International Nuclear Information System (INIS)

    Bruce, B.D.; Malkin, R.

    1988-01-01

    A native photosystem I (PS I) complex and a PS I core complex depleted of antenna subunits has been isolated from the uniformly 14 C-labeled aquatic higher plant, Lemna. These complexes have been analyzed for their subunit stoichiometry by quantitative sodium dodecyl sulfate-polyacrylamide gel electrophoresis methods. The results for both preparations indicate that one copy of each high molecular mass subunit is present per PS I complex and that a single copy of most low molecular mass subunits is also present. These results suggest that iron-sulfur center X, an early PS I electron acceptor proposed to bind to the high molecular mass subunits, contains a single [4Fe-4S] cluster which is bound to a dimeric structure of high molecular mass subunits, each providing 2 cysteine residues to coordinate this cluster

  20. Transcriptional regulators of Na, K-ATPase subunits

    OpenAIRE

    Zhiqin eLi; Sigrid A Langhans

    2015-01-01

    The Na,K-ATPase classically serves as an ion pump creating an electrochemical gradient across the plasma membrane that is essential for transepithelial transport, nutrient uptake and membrane potential. In addition, Na,K-ATPase also functions as a receptor, a signal transducer and a cell adhesion molecule. With such diverse roles, it is understandable that the Na,K-ATPase subunits, the catalytic alpha-subunit, the beta-subunit and the FXYD proteins, are controlled extensively during developme...

  1. Large-scale synthesis of NbS2 nanosheets with controlled orientation on graphene by ambient pressure CVD.

    Science.gov (United States)

    Ge, Wanyin; Kawahara, Kenji; Tsuji, Masaharu; Ago, Hiroki

    2013-07-07

    We report ambient pressure chemical vapor deposition (CVD) growth of single-crystalline NbS2 nanosheets with controlled orientation. On Si and SiO2 substrates, NbS2 nanosheets grow almost perpendicular to the substrate surface. However, when we apply transferred CVD graphene on SiO2 as a substrate, NbS2 sheets grow laterally lying on the graphene. The NbS2 sheets show the triangular and hexagonal shapes with a thickness of about 20-200 nm and several micrometres in the lateral dimension. Analyses based on X-ray diffraction and Raman spectroscopy indicate that the NbS2 nanosheets are single crystalline 3R-type with a rhombohedral structure of R3m space group. Our findings on the formation of highly aligned NbS2 nanosheets on graphene give new insight into the formation mechanism of NbS2 and would contribute to the templated growth of various layered materials.

  2. Activating basal-plane catalytic activity of two-dimensional MoS2 monolayer with remote hydrogen plasma

    KAUST Repository

    Cheng, Chia-Chin

    2016-09-10

    Two-dimensional layered transition metal dichalcogenide (TMD) materials such as Molybdenum disufide (MoS2) have been recognized as one of the low-cost and efficient electrocatalysts for hydrogen evolution reaction (HER). The crystal edges that account for a small percentage of the surface area, rather than the basal planes, of MoS2 monolayer have been confirmed as their active catalytic sites. As a result, extensive efforts have been developing in activating the basal planes of MoS2 for enhancing their HER activity. Here, we report a simple and efficient approach-using a remote hydrogen-plasma process-to creating S-vacancies on the basal plane of monolayer crystalline MoS2; this process can generate high density of S-vacancies while mainly maintaining the morphology and structure of MoS2 monolayer. The density of S-vacancies (defects) on MoS2 monolayers resulted from the remote hydrogen-plasma process can be tuned and play a critical role in HER, as evidenced in the results of our spectroscopic and electrical measurements. The H2-plasma treated MoS2 also provides an excellent platform for systematic and fundamental study of defect-property relationships in TMDs, which provides insights for future applications including electrical, optical and magnetic devices. © 2016 Elsevier Ltd.

  3. The interface of the ferromagnetic metal CoS2 and the nonmagnetic semiconductor FeS2

    KAUST Repository

    Nazir, S.

    2010-11-05

    The electronic and magnetic properties of the cubic pyriteCoS2/FeS2interface are studied using the all-electron full-potential linearized augmented plane wave method. We find that this contact between a ferromagneticmetal and a nonmagnetic semiconductor shows a metallic character. The CoS2 stays close to half-metallicity at the interface, while the FeS2 becomes metallic. The magnetic moment of the Co atoms at the interface slightly decreases as compared to the bulk value and a small moment is induced on the Fe atoms. Furthermore, at the interfaceferromagnetic ordering is found to be energetically favorable as compared to antiferromagnetic ordering.

  4. Intricate Resonant Raman Response in Anisotropic ReS2.

    Science.gov (United States)

    McCreary, Amber; Simpson, Jeffrey R; Wang, Yuanxi; Rhodes, Daniel; Fujisawa, Kazunori; Balicas, Luis; Dubey, Madan; Crespi, Vincent H; Terrones, Mauricio; Hight Walker, Angela R

    2017-10-11

    The strong in-plane anisotropy of rhenium disulfide (ReS 2 ) offers an additional physical parameter that can be tuned for advanced applications such as logic circuits, thin-film polarizers, and polarization-sensitive photodetectors. ReS 2 also presents advantages for optoelectronics, as it is both a direct-gap semiconductor for few-layer thicknesses (unlike MoS 2 or WS 2 ) and stable in air (unlike black phosphorus). Raman spectroscopy is one of the most powerful characterization techniques to nondestructively and sensitively probe the fundamental photophysics of a 2D material. Here, we perform a thorough study of the resonant Raman response of the 18 first-order phonons in ReS 2 at various layer thicknesses and crystal orientations. Remarkably, we discover that, as opposed to a general increase in intensity of all of the Raman modes at excitonic transitions, each of the 18 modes behave differently relative to each other as a function of laser excitation, layer thickness, and orientation in a manner that highlights the importance of electron-phonon coupling in ReS 2 . In addition, we correct an unrecognized error in the calculation of the optical interference enhancement of the Raman signal of transition metal dichalcogenides on SiO 2 /Si substrates that has propagated through various reports. For ReS 2 , this correction is critical to properly assessing the resonant Raman behavior. We also implemented a perturbation approach to calculate frequency-dependent Raman intensities based on first-principles and demonstrate that, despite the neglect of excitonic effects, useful trends in the Raman intensities of monolayer and bulk ReS 2 at different laser energies can be accurately captured. Finally, the phonon dispersion calculated from first-principles is used to address the possible origins of unexplained peaks observed in the Raman spectra, such as infrared-active modes, defects, and second-order processes.

  5. Structural basis of subunit selectivity for competitive NMDA receptor antagonists with preference for GluN2A over GluN2B subunits

    Energy Technology Data Exchange (ETDEWEB)

    Lind, Genevieve E.; Mou, Tung-Chung; Tamborini, Lucia; Pomper, Martin G.; De Micheli, Carlo; Conti, Paola; Pinto, Andrea; Hansen, Kasper B. (JHU); (Milan); (Montana)

    2017-07-31

    NMDA-type glutamate receptors are ligand-gated ion channels that contribute to excitatory neurotransmission in the central nervous system (CNS). Most NMDA receptors comprise two glycine-binding GluN1 and two glutamate-binding GluN2 subunits (GluN2A–D). We describe highly potent (S)-5-[(R)-2-amino-2-carboxyethyl]-4,5-dihydro-1H-pyrazole-3-carboxylic acid (ACEPC) competitive GluN2 antagonists, of which ST3 has a binding affinity of 52 nM at GluN1/2A and 782 nM at GluN1/2B receptors. This 15-fold preference of ST3 for GluN1/2A over GluN1/2B is improved compared with NVP-AAM077, a widely used GluN2A-selective antagonist, which we show has 11-fold preference for GluN1/2A over GluN1/2B. Crystal structures of the GluN1/2A agonist binding domain (ABD) heterodimer with bound ACEPC antagonists reveal a binding mode in which the ligands occupy a cavity that extends toward the subunit interface between GluN1 and GluN2A ABDs. Mutational analyses show that the GluN2A preference of ST3 is primarily mediated by four nonconserved residues that are not directly contacting the ligand, but positioned within 12 Å of the glutamate binding site. Two of these residues influence the cavity occupied by ST3 in a manner that results in favorable binding to GluN2A, but occludes binding to GluN2B. Thus, we reveal opportunities for the design of subunit-selective competitive NMDA receptor antagonists by identifying a cavity for ligand binding in which variations exist between GluN2A and GluN2B subunits. This structural insight suggests that subunit selectivity of glutamate-site antagonists can be mediated by mechanisms in addition to direct contributions of contact residues to binding affinity.

  6. Two-dimensional MoS2 electromechanical actuators

    Science.gov (United States)

    Hung, Nguyen T.; Nugraha, Ahmad R. T.; Saito, Riichiro

    2018-02-01

    We investigate the electromechanical properties of two-dimensional MoS2 monolayers with 1H, 1T, and 1T‧ structures as a function of charge doping by using density functional theory. We find isotropic elastic moduli in the 1H and 1T structures, while the 1T‧ structure exhibits an anisotropic elastic modulus. Moreover, the 1T structure is shown to have a negative Poisson’s ratio, while Poisson’s ratios of the 1H and 1T‧ are positive. By charge doping, the monolayer MoS2 shows a reversible strain and work density per cycle ranging from  -0.68% to 2.67% and from 4.4 to 36.9 MJ m-3, respectively, making them suitable for applications in electromechanical actuators. We also examine the stress generated in the MoS2 monolayers and we find that 1T and 1T‧ MoS2 monolayers have relatively better performance than 1H MoS2 monolayer. We argue that such excellent electromechanical performance originate from the electrical conductivity of the metallic 1T and semimetallic 1T‧ structures and also from their high Young’s modulus of about 150-200 GPa.

  7. Association of ω with the C-terminal region of β' subunit is essential for assembly of RNA polymerase in Mycobacterium tuberculosis.

    Science.gov (United States)

    Mao, Chunyou; Zhu, Yan; Lu, Pei; Feng, Lipeng; Chen, Shiyun; Hu, Yangbo

    2018-04-09

    a mycobacterial specific ω loop that plays a role in this function was also characterized. Our study provides fresh insights for further characterizing the roles of bacterial ω subunit. Copyright © 2018 American Society for Microbiology.

  8. Synthesis of porous CuInS2 crystals

    International Nuclear Information System (INIS)

    Akaki, Yoji; Matsubara, Takanori; Ohno, Yuki; Momiki, Takanori; Ide, Kazuki

    2009-01-01

    CuInS 2 crystals were grown from starting materials CuCl 2 .2H 2 O, InCl 3 .4H 2 O and thiourea with ethylene glycol solution, that were placed into a flask, heated, and refluxed for 1 hour. The diffraction peaks only from CuInS 2 phase appear for all the samples. The morphology of CuInS 2 crystal was porous, and the porous crystals exist in two kinds. One kind was flower-like crystals which complexly lack the flakes, another one was sphere-like crystals existed with a number of the poles. The sizes of sphere-like porous crystals were approximately 1.0 μm. The specific surface area of the samples grown at 180 C and 600 rpm estimated approximately 30 m 2 /g. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  9. Plasmons on the edge of MoS2 nanostructures

    DEFF Research Database (Denmark)

    Andersen, Kirsten; Jacobsen, Karsten Wedel; Thygesen, Kristian Sommer

    2014-01-01

    Using ab initio calculations we predict the existence of one-dimensional (1D), atomically confined plasmons at the edges of a zigzag MoS2 nanoribbon. The strongest plasmon originates from a metallic edge state localized on the sulfur dimers decorating the Mo edge of the ribbon. A detailed analysis...... of the dielectric function reveals that the observed deviations from the ideal 1D plasmon behavior result from single-particle transitions between the metallic edge state and the valence and conduction bands of the MoS2 sheet. The Mo and S edges of the ribbon are clearly distinguishable in calculated spatially...... resolved electron energy loss spectrum owing to the different plasmonic properties of the two edges. The edge plasmons could potentially be utilized for tuning the photocatalytic activity of MoS2 nanoparticles....

  10. Ultrafast photocurrents in monolayer MoS2

    Science.gov (United States)

    Parzinger, Eric; Wurstbauer, Ursula; Holleitner, Alexander W.

    Two-dimensional transition metal dichalcogenides such as MoS2 have emerged as interesting materials for optoelectronic devices. In particular, the ultrafast dynamics and lifetimes of photoexcited charge carriers have attracted great interest during the last years. We investigate the photocurrent response of monolayer MoS2 on a picosecond time scale utilizing a recently developed pump-probe spectroscopy technique based on coplanar striplines. We discuss the ultrafast dynamics within MoS2 including photo-thermoelectric currents and the impact of built-in fields due to Schottky barriers as well as the Fermi level pinning at the contact region. We acknowledge support by the ERC via Project 'NanoREAL', the DFG via excellence cluster 'Nanosystems Initiative Munich' (NIM), and through the TUM International Graduate School of Science and Engineering (IGSSE) and BaCaTeC.

  11. Single-layer MoS2 electronics.

    Science.gov (United States)

    Lembke, Dominik; Bertolazzi, Simone; Kis, Andras

    2015-01-20

    CONSPECTUS: Atomic crystals of two-dimensional materials consisting of single sheets extracted from layered materials are gaining increasing attention. The most well-known material from this group is graphene, a single layer of graphite that can be extracted from the bulk material or grown on a suitable substrate. Its discovery has given rise to intense research effort culminating in the 2010 Nobel Prize in physics awarded to Andre Geim and Konstantin Novoselov. Graphene however represents only the proverbial tip of the iceberg, and increasing attention of researchers is now turning towards the veritable zoo of so-called "other 2D materials". They have properties complementary to graphene, which in its pristine form lacks a bandgap: MoS2, for example, is a semiconductor, while NbSe2 is a superconductor. They could hold the key to important practical applications and new scientific discoveries in the two-dimensional limit. This family of materials has been studied since the 1960s, but most of the research focused on their tribological applications: MoS2 is best known today as a high-performance dry lubricant for ultrahigh-vacuum applications and in car engines. The realization that single layers of MoS2 and related materials could also be used in functional electronic devices where they could offer advantages compared with silicon or graphene created a renewed interest in these materials. MoS2 is currently gaining the most attention because the material is easily available in the form of a mineral, molybdenite, but other 2D transition metal dichalcogenide (TMD) semiconductors are expected to have qualitatively similar properties. In this Account, we describe recent progress in the area of single-layer MoS2-based devices for electronic circuits. We will start with MoS2 transistors, which showed for the first time that devices based on MoS2 and related TMDs could have electrical properties on the same level as other, more established semiconducting materials. This

  12. Electrical characteristics of multilayer MoS2 FET's with MoS2/graphene heterojunction contacts.

    Science.gov (United States)

    Kwak, Joon Young; Hwang, Jeonghyun; Calderon, Brian; Alsalman, Hussain; Munoz, Nini; Schutter, Brian; Spencer, Michael G

    2014-08-13

    The electrical properties of multilayer MoS2/graphene heterojunction transistors are investigated. Temperature-dependent I-V measurements indicate the concentration of unintentional donors in exfoliated MoS2 to be 3.57 × 10(11) cm(-2), while the ionized donor concentration is determined as 3.61 × 10(10) cm(-2). The temperature-dependent measurements also reveal two dominant donor levels, one at 0.27 eV below the conduction band and another located at 0.05 eV below the conduction band. The I-V characteristics are asymmetric with drain bias voltage and dependent on the junction used for the source or drain contact. I-V characteristics of the device are consistent with a long channel one-dimensional field-effect transistor model with Schottky contact. Utilizing devices, which have both graphene/MoS2 and Ti/MoS2 contacts, the Schottky barrier heights of both interfaces are measured. The charge transport mechanism in both junctions was determined to be either thermionic-field emission or field emission depending on bias voltage and temperature. On the basis of a thermionic field emission model, the barrier height at the graphene/MoS2 interface was determined to be 0.23 eV, while the barrier height at the Ti/MoS2 interface was 0.40 eV. The value of Ti/MoS2 barrier is higher than previously reported values, which did not include the effects of thermionic field emission.

  13. Liposome-Based Adjuvants for Subunit Vaccines: Formulation Strategies for Subunit Antigens and Immunostimulators

    DEFF Research Database (Denmark)

    Schmidt, Signe Tandrup; Foged, Camilla; Korsholm, Karen Smith

    2016-01-01

    be classified into delivery systems or immunostimulators. Liposomes are versatile delivery systems for antigens, and they can carefully be customized towards desired immune profiles by combining them with immunostimulators and optimizing their composition, physicochemical properties and antigen-loading mode......The development of subunit vaccines has become very attractive in recent years due to their superior safety profiles as compared to traditional vaccines based on live attenuated or whole inactivated pathogens, and there is an unmet medical need for improved vaccines and vaccines against pathogens...... of immunostimulators and antigens, respectively, into liposomes, and the choice of immunostimulator should ideally be based on knowledge regarding the specific PRR expression profile of the target APCs. Here, we review state-of-the-art formulation approaches employed for the inclusion of immunostimulators and subunit...

  14. ReaxFF Reactive Force-Field Study of Molybdenum Disulfide (MoS2).

    Science.gov (United States)

    Ostadhossein, Alireza; Rahnamoun, Ali; Wang, Yuanxi; Zhao, Peng; Zhang, Sulin; Crespi, Vincent H; van Duin, Adri C T

    2017-02-02

    Two-dimensional layers of molybdenum disulfide, MoS 2 , have been recognized as promising materials for nanoelectronics due to their exceptional electronic and optical properties. Here we develop a new ReaxFF reactive potential that can accurately describe the thermodynamic and structural properties of MoS 2 sheets, guided by extensive density functional theory simulations. This potential is then applied to the formation energies of five different types of vacancies, various vacancy migration barriers, and the transition barrier between the semiconducting 2H and metallic 1T phases. The energetics of ripplocations, a recently observed defect in van der Waals layers, is examined, and the interplay between these defects and sulfur vacancies is studied. As strain engineering of MoS 2 sheets is an effective way to manipulate the sheets' electronic and optical properties, the new ReaxFF description can provide valuable insights into morphological changes that occur under various loading conditions and defect distributions, thus allowing one to tailor the electronic properties of these 2D crystals.

  15. Impact of Microstructure on MoS2 Oxidation and Friction.

    Science.gov (United States)

    Curry, John F; Wilson, Mark A; Luftman, Henry S; Strandwitz, Nicholas C; Argibay, Nicolas; Chandross, Michael; Sidebottom, Mark A; Krick, Brandon A

    2017-08-23

    This work demonstrates the role of microstructure in the friction and oxidation behavior of the lamellar solid lubricant molybdenum disulfide (MoS 2 ). We report on systematic investigations of oxidation and friction for two MoS 2 films with distinctively different microstructures-amorphous and planar/highly-ordered-before and after exposure to atomic oxygen (AO) and high-temperature (250 °C) molecular oxygen. A combination of experimental tribology, molecular dynamics simulations, X-ray photoelectron spectroscopy (XPS), and high-sensitivity low-energy ion scattering (HS-LEIS) was used to reveal new insights about the links between structure and properties of these widely utilized low-friction materials. Initially, ordered MoS 2 films showed a surprising resistance to both atomic and molecular oxygens (even at elevated temperature), retaining characteristic low friction after exposure to extreme oxidative environments. XPS shows comparable oxidation of both coatings via AO; however, monolayer resolved compositional depth profiles from HS-LEIS reveal that the microstructure of the ordered coatings limits oxidation to the first atomic layer.

  16. Stabilizing the discrete vortex of topological charge S=2

    International Nuclear Information System (INIS)

    Kevrekidis, P.G.; Frantzeskakis, D.J.

    2005-01-01

    We study the instability of the discrete vortex with topological charge S=2 in a prototypical lattice model and observe its mediation through the central lattice site. Motivated by this finding, we analyze the model with the central site being inert. We identify analytically and observe numerically the existence of a range of linearly stable discrete vortices with S=2 in the latter model. The range of stability is comparable to that of the recently observed experimentally S=1 discrete vortex, suggesting the potential for observation of such higher charge discrete vortices

  17. Conduction quantization in monolayer MoS2

    Science.gov (United States)

    Li, T. S.

    2016-10-01

    We study the ballistic conduction of a monolayer MoS2 subject to a spatially modulated magnetic field by using the Landauer-Buttiker formalism. The band structure depends sensitively on the field strength, and its change has profound influence on the electron conduction. The conductance is found to demonstrate multi-step behavior due to the discrete number of conduction channels. The sharp peak and rectangular structures of the conductance are stretched out as temperature increases, due to the thermal broadening of the derivative of the Fermi-Dirac distribution function. Finally, quantum behavior in the conductance of MoS2 can be observed at temperatures below 10 K.

  18. Lithium insertion mechanism in SnS2

    International Nuclear Information System (INIS)

    Lefebvre-Devos, I.; Olivier-Fourcade, J.; Jumas, J.C.; Lavela, P.

    2000-01-01

    We study lithium insertion in SnS 2 by means of 119 Sn Moessbauer spectroscopy, x-ray absorption spectroscopy at Sn L I,III , and S K edges, and theoretical electronic structures (calculated in the density-functional theory framework). An insertion mechanism is derived according to the Li amount. It shows the influence of the SnS 2 -layered structure on the Sn reduction, particularly the possibility of an intermediate oxidation state between Sn IV and Sn II , which is not observed during Li insertion in three-dimensional sulfides

  19. Thermal decomposition studies of CuInS2

    Institute of Scientific and Technical Information of China (English)

    Sunil H. CHAKI

    2008-01-01

    Single crystals of copper indium disulphide (CuInS2) have been successfully grown by the chemical vapour transport (CVT) technique using iodine as the transporting agent. Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) were carried out for the CVT grown CuInS2 single crystals. It was revealed that the crystals are thermally stable between the ambient temperature (300 K) and 845 K and that the decomposi-tion occurs sequentially in three steps. The kinetic para-meters, e.g., activation energy, order of reaction, and frequency factor were evaluated using non-mechanistic equations for thermal decomposition.

  20. Raman scattering in orthorhombic CuInS2 nanocrystals

    International Nuclear Information System (INIS)

    Dzhagan, V.M.; Valakh, M.Ya.; Litvinchuk, A.P.; Kruszynska, M.; Kolny-Olesiak, J.; Himcinschi, C.; Zahn, D.R.T.

    2014-01-01

    We report the results of non-resonant and resonant Raman scattering in orthorhombic nanocrystalline CuInS 2 semiconductor, supported by density functional first principle lattice dynamics calculations. A larger number of dominant phonon modes in comparison with standard tetragonal CuInS 2 phases is shown to be associated with peculiarities of cation sublattice ordering and is the ''fingerprint'' of the corresponding structural polymorph. Good overall agreement is found between theoretical and experimental phonon mode frequencies. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  1. Liposome-Based Adjuvants for Subunit Vaccines: Formulation Strategies for Subunit Antigens and Immunostimulators

    Directory of Open Access Journals (Sweden)

    Signe Tandrup Schmidt

    2016-03-01

    Full Text Available The development of subunit vaccines has become very attractive in recent years due to their superior safety profiles as compared to traditional vaccines based on live attenuated or whole inactivated pathogens, and there is an unmet medical need for improved vaccines and vaccines against pathogens for which no effective vaccines exist. The subunit vaccine technology exploits pathogen subunits as antigens, e.g., recombinant proteins or synthetic peptides, allowing for highly specific immune responses against the pathogens. However, such antigens are usually not sufficiently immunogenic to induce protective immunity, and they are often combined with adjuvants to ensure robust immune responses. Adjuvants are capable of enhancing and/or modulating immune responses by exposing antigens to antigen-presenting cells (APCs concomitantly with conferring immune activation signals. Few adjuvant systems have been licensed for use in human vaccines, and they mainly stimulate humoral immunity. Thus, there is an unmet demand for the development of safe and efficient adjuvant systems that can also stimulate cell-mediated immunity (CMI. Adjuvants constitute a heterogeneous group of compounds, which can broadly be classified into delivery systems or immunostimulators. Liposomes are versatile delivery systems for antigens, and they can carefully be customized towards desired immune profiles by combining them with immunostimulators and optimizing their composition, physicochemical properties and antigen-loading mode. Immunostimulators represent highly diverse classes of molecules, e.g., lipids, nucleic acids, proteins and peptides, and they are ligands for pattern-recognition receptors (PRRs, which are differentially expressed on APC subsets. Different formulation strategies might thus be required for incorporation of immunostimulators and antigens, respectively, into liposomes, and the choice of immunostimulator should ideally be based on knowledge regarding the

  2. Myristoylated α subunits of guanine nucleotide-binding regulatory proteins

    International Nuclear Information System (INIS)

    Buss, J.E.; Mumby, S.M.; Casey, P.J.; Gilman, A.G.; Sefton, B.M.

    1987-01-01

    Antisera directed against specific subunits of guanine nucleotide-binding regulatory proteins (G proteins) were used to immunoprecipitate these polypeptides from metabolically labeled cells. This technique detects, in extracts of a human astrocytoma cell line, the α subunits of G/sub s/ (stimulatory) (α 45 and α 52 ), a 41-kDa subunit of G/sub i/ (inhibitory) (α 41 ), a 40-kDa protein (α 40 ), and the 36-kDa β subunit. No protein that comigrated with the α subunit of G 0 (unknown function) (α 39 ) was detected. In cells grown in the presence of [ 3 H]myristic acid, α 41 and α 40 contained 3 H label, while the β subunit did not. Chemical analysis of lipids attached covalently to purified α 41 and α 39 from bovine brain also revealed myristic acid. Similar analysis of brain G protein β and γ subunits and of G/sub t/ (Transducin) subunits (α, β, and γ) failed to reveal fatty acids. The fatty acid associated with α 41 , α 40 , and α 39 was stable to treatment with base, suggesting that the lipid is linked to the polypeptide via an amide bond. These GTP binding proteins are thus identified as members of a select group of proteins that contains myristic acid covalently attached to the peptide backbone. Myristate may play an important role in stabilizing interactions of G proteins with phospholipid or with membrane-bound proteins

  3. Development of a Subunit Vaccine for Contagious Bovine ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    Their work has set the stage for commercial development of a sub-unit vaccine. ... The sub-unit vaccine will be cost-effective, easy to produce, and safe. How it will make a ... IDRC invites applications for the IDRC Doctoral Research Awards.

  4. Aspergillus oryzae S2 alpha-amylase production under solid state fermentation: optimization of culture conditions.

    Science.gov (United States)

    Sahnoun, Mouna; Kriaa, Mouna; Elgharbi, Fatma; Ayadi, Dorra-Zouari; Bejar, Samir; Kammoun, Radhouane

    2015-04-01

    Aspergillus oryzae S2 was assayed for alpha-amylase production under solid state fermentation (SSF). In addition to AmyA and AmyB already produced in monitored submerged culture, the strain was noted to produce new AmyB oligomeric forms, in particular a dominant tetrameric form named AmyC. The latter was purified to homogeneity through fractional acetone precipitation and size exclusion chromatography. SDS-PAGE and native PAGE analyses revealed that, purified AmyC was an approximately 172 kDa tetramer of four 42 kDa subunits. AmyC was also noted to display the same NH2-terminal amino acid sequence residues and approximately the same physico-chemical properties of AmyA and AmyB, to exhibit maximum activity at pH 5.6 and 60 °C, and to produce maltose and maltotriose as major starch hydrolysis end-products. Soyabean meal was the best substitute to yeast extract compared to fish powder waste and wheat gluten waste. AmyC production was optimized under SSF using statistical design methodology. Moisture content of 76.25%, C/N substrate ratio of 0.62, and inoculum size of 10(6.87) spores allowed maximum activity of 22118.34 U/g of dried substrate, which was 33 times higher than the one obtained before the application of the central composite design (CCD). Copyright © 2015 Elsevier B.V. All rights reserved.

  5. Studies on the subunits of human glycoprotein hormones in relation to reproduction

    International Nuclear Information System (INIS)

    Hagen, C.

    1977-01-01

    In this review summarising present knowledge of the biological and immunological activity of the subunits of human glycoprotein hormones, the specificity of the α-subunit and β-subunit radioimmunoassays are discussed. The crossreaction studies performed with the α-subunit radioimmunoassays are aummarised in one table while those with the β-subunit radioimmunoassays are presented in a second table. (JIW)

  6. INTRINSIC REGULATION OF HEMOGLOBIN EXPRESSION BY VARIABLE SUBUNIT INTERFACE STRENGTHS

    Science.gov (United States)

    Manning, James M.; Popowicz, Anthony M.; Padovan, Julio C.; Chait, Brian T.; Manning, Lois R.

    2012-01-01

    SUMMARY The expression of the six types of human hemoglobin subunits over time is currently considered to be regulated mainly by transcription factors that bind to upstream control regions of the gene (the “extrinsic” component of regulation). Here we describe how subunit pairing and further assembly to tetramers in the liganded state is influenced by the affinity of subunits for one another (the “intrinsic” component of regulation). The adult hemoglobin dimers have the strongest subunit interfaces and the embryonic hemoglobins are the weakest with fetal hemoglobins of intermediate strength, corresponding to the temporal order of their expression. These variable subunit binding strengths and the attenuating effects of acetylation contribute to the differences with which these hemoglobin types form functional O2-binding tetramers consistent with gene switching. PMID:22129306

  7. Anionic construction of the SLq,s(2) algebra

    International Nuclear Information System (INIS)

    Matheus-Valle, J.L.; Monteiro, M.R.

    1993-01-01

    Considering anionic oscillators in a two-dimensional lattice, the quantum semi-group sl (q,s ) (2) is realized by means of a generalized Schwinger construction. It is found that the parameter q of the algebra is connected to the statistical parameter, whereas the s parameter is related to a s-deformed oscillator introduced at each point of the lattice. (author)

  8. Hydrophobic Ice Confined between Graphene and MoS2

    NARCIS (Netherlands)

    Bampoulis, Pantelis; Teernstra, V.J.; Lohse, Detlef; Zandvliet, Henricus J.W.; Poelsema, Bene

    2016-01-01

    The structure and nature of water confined between hydrophobic molybdenum disulfide (MoS2) and graphene (Gr) are investigated at room temperature by means of atomic force microscopy. We find the formation of two-dimensional (2D) crystalline ice layers. In contrast to the hexagonal ice “bilayers” of

  9. Magnetoresistance in molybdenite (MoS2) crystals

    International Nuclear Information System (INIS)

    Chakraborty, B.R.; Dutta, A.K.

    1975-01-01

    The principal magnetoresistance ratios of molybdenite (MoS 2 ), the naturally occurring semiconducting crystal, have been investigated at magnetic fields ranging from 4.5 KOe and within the temperature range 300 0 K to 700 0 K. Unlike some previous observations, magnetoresistance has been found to be negative. (author)

  10. High pressure synthesis of BiS2

    DEFF Research Database (Denmark)

    Søndergaard-Pedersen, Simone; Nielsen, Morten Bormann; Bremholm, Martin

    crystal structures and electrical properties.1,2 Up until now, the most sulfur rich phase in the Bi-S phase diagram was Bi2S3.3 For BiS2 the Bi atoms have anisotropic charge distribution and more complex structures are expected when comparing the layered structures of transition metal dichalcogenides....... The possibilities of using high pressure synthesis to discover new phases in the Bi-S binary system were investigated as early as the 1960’s.4 The research led to discovery of a compound with BiS2 stoichiometry, but no structure solution of BiS2 was reported. A reason behind making this new phase is to study...... the physical properties since the related compound Bi2S3 is known to be a thermoelectric material.5 In this research the BiS2 compound was synthesized by a high pressure and high temperature method using a multi-anvil large volume press and the structure was solved by single crystal diffraction. The structure...

  11. Plasma-assisted synthesis of MoS2

    Science.gov (United States)

    Campbell, Philip M.; Perini, Christopher J.; Chiu, Johannes; Gupta, Atul; Ray, Hunter S.; Chen, Hang; Wenzel, Kevin; Snyder, Eric; Wagner, Brent K.; Ready, Jud; Vogel, Eric M.

    2018-03-01

    There has been significant interest in transition metal dichalcogenides (TMDs), including MoS2, in recent years due to their potential application in novel electronic and optical devices. While synthesis methods have been developed for large-area films of MoS2, many of these techniques require synthesis temperatures of 800 °C or higher. As a result of the thermal budget, direct synthesis requiring high temperatures is incompatible with many integrated circuit processes as well as flexible substrates. This work explores several methods of plasma-assisted synthesis of MoS2 as a way to lower the synthesis temperature. The first approach used is conversion of a naturally oxidized molybdenum thin film to MoS2 using H2S plasma. Conversion is demonstrated at temperatures as low as 400 °C, and the conversion is enabled by hydrogen radicals which reduce the oxidized molybdenum films. The second method is a vapor phase reaction incorporating thermally evaporated MoO3 exposed to a direct H2S plasma, similar to chemical vapor deposition (CVD) synthesis of MoS2. Synthesis at 400 °C results in formation of super-stoichiometric MoS2 in a beam-interrupted growth process. A final growth method relies on a cyclical process in which a small amount of Mo is sputtered onto the substrate and is subsequently sulfurized in a H2S plasma. Similar results could be realized using an atomic layer deposition (ALD) process to deposit the Mo film. Compared to high temperature synthesis methods, the lower temperature samples are lower quality, potentially due to poor crystallinity or higher defect density in the films. Temperature-dependent conductivity measurements are consistent with hopping conduction in the plasma-assisted synthetic MoS2, suggesting a high degree of disorder in the low-temperature films. Optimization of the plasma-assisted synthesis process for slower growth rate and better stoichiometry is expected to lead to high quality films at low growth temperature.

  12. Atomic Scale Simulation on the Anti-Pressure and Friction Reduction Mechanisms of MoS2 Monolayer

    Directory of Open Access Journals (Sweden)

    Yang Liu

    2018-04-01

    Full Text Available MoS2 nanosheets can be used as solid lubricants or additives of lubricating oils to reduce friction and resist wear. However, the atomic scale mechanism still needs to be illustrated. Herein, molecular simulations on the indentation and scratching process of MoS2 monolayer supported by Pt(111 surface were conducted to study the anti-pressure and friction reduction mechanisms of the MoS2 monolayer. Three deformation stages of Pt-supported MoS2 monolayer were found during the indentation process: elastic deformation, plastic deformation and finally, complete rupture. The MoS2 monolayer showed an excellent friction reduction effect at the first two stages, as a result of enhanced load bearing capacity and reduced deformation degree of the substrate. Unlike graphene, rupture of the Pt-supported MoS2 monolayer was related primarily to out-of-plane compression of the monolayer. These results provide a new insight into the relationship between the mechanical properties and lubrication properties of 2D materials.

  13. Virtual half-metallicity at the CoS2/FeS2 interface induced by strain

    KAUST Repository

    Nazir, Safdar

    2013-01-01

    Spin polarized ab initio calculations based on density functional theory are performed to investigate the electronic and magnetic properties of the interface between the ferromagnetic metal CoS2 and the nonmagnetic semiconductor FeS2. Relaxation of the interface structure is taken into account by atomic force minimization. We find that both Co and Fe are close to half-metallicity at the interface. Tensile strain is shown to strongly enhance the spin polarization so that a virtually half-metallic interface can be achieved, for comparably moderate strain. © 2012 The Royal Society of Chemistry.

  14. Stability of Sulphur Dimers (S2) in Cometary Ices

    International Nuclear Information System (INIS)

    Mousis, O.; Ronnet, T.; Ozgurel, O.; Pauzat, F.; Markovits, A.; Ellinger, Y.; Lunine, J. I.; Luspay-Kuti, A.

    2017-01-01

    S 2 has been observed for decades in comets, including comet 67P/Churyumov–Gerasimenko. Despite the fact that this molecule appears ubiquitous in these bodies, the nature of its source remains unknown. In this study, we assume that S 2 is formed by irradiation (photolysis and/or radiolysis) of S-bearing molecules embedded in the icy grain precursors of comets and that the cosmic ray flux simultaneously creates voids in ices within which the produced molecules can accumulate. We investigate the stability of S 2 molecules in such cavities, assuming that the surrounding ice is made of H 2 S or H 2 O. We show that the stabilization energy of S 2 molecules in such voids is close to that of the H 2 O ice binding energy, implying that they can only leave the icy matrix when this latter sublimates. Because S 2 has a short lifetime in the vapor phase, we derive that its formation in grains via irradiation must occur only in low-density environments such as the ISM or the upper layers of the protosolar nebula, where the local temperature is extremely low. In the first case, comets would have agglomerated from icy grains that remained pristine when entering the nebula. In the second case, comets would have agglomerated from icy grains condensed in the protosolar nebula and that would have been efficiently irradiated during their turbulent transport toward the upper layers of the disk. Both scenarios are found consistent with the presence of molecular oxygen in comets.

  15. The S2 UAS, a Modular Platform for Atmospheric Science

    Science.gov (United States)

    Elston, J. S.; Stachura, M.; Bland, G.

    2017-12-01

    Black Swift Technologies, LLC (BST) developed and refined the S2 in partnership with NASA. The S2 is a novel small Unmanned Aircraft System (sUAS) specifically designed to meet the needs of atmospheric and earth observing scientific field campaigns. This tightly integrated system consists of an airframe, avionics, and sensors designed to measure atmospheric parameters (e.g., temperature, pressure, humidity, and 3D winds) and well as carry up to 2.3kg (5lbs) of additional payload. At the core of the sensing suite is a custom designed multi-hole-probe being developed to provide accurate measurements in u, v and w while remaining simple to integrate as well as low-cost. The S2 relies on the commercially-available SwiftCore Flight Management System (FMS), which has been proven in the field to provide a cost-effective, powerful, and easy-to-operate solution to meet the demanding requirements of nomadic scientific field campaigns. The airframe capabilities are currently being expanded to achieve high altitude flights through strong winds and damaging airborne particulates. Additionally, the well-documented power and data interfaces of the S2 will be employed to integrate the sensors required for the measurement of soil moisture content, atmospheric volcanic phenomenon, fire weather, as well as provide satellite calibration via multispectral cameras. Extensive flight testing has been planned to validate the S2 system's ability to operate in difficult terrain including mountainside takeoff and recovery and flights up to 6000m above sea level.

  16. Synthesis and Characterization of the Quaternary Thio-aluminogermanates A(AlS2)(GeS2) (A = Na, K)

    KAUST Repository

    Al-Bloushi, Mohammed; Davaasuren, Bambar; Emwas, Abdul-Hamid M.; Rothenberger, Alexander

    2015-01-01

    The quaternary thioaluminogermanates Na(AlS2)(GeS2) (1) and K(AlS2)(GeS2) (2) crystallize in the tetragonal space group I4/mcm (no. 140) with unit cell parameters a = 7.4274(11) Å, c = 5.8560(12) Å for Na(AlS2)(GeS2) and a = 7.8826(2) Å, c = 5

  17. Comparitive study of fluorescence lifetime quenching of rhodamine 6G by MoS2 and Au-MoS2

    Science.gov (United States)

    Shakya, Jyoti; Kasana, Parath; Mohanty, T.

    2018-04-01

    Time resolved fluorescence study of Rhodamine 6G (R6G) in the presence of Molybdenum disulfide (MoS2) nanosheets and gold doped MoS2 (Au-MoS2) have been carried out and discussed. We have analyzed the fluorescence decay curves of R6G and it is observed that Au-MoS2 is a better fluorescence lifetime quencher as compare to MoS2 nanosheets. Also, the energy transfer efficiency and energy transfer rate from R6G to MoS2 and Au-MoS2 has been calculated and found higher for Au-MoS2.

  18. Prospects of zero Schottky barrier height in a graphene-inserted MoS2-metal interface

    Science.gov (United States)

    Chanana, Anuja; Mahapatra, Santanu

    2016-01-01

    A low Schottky barrier height (SBH) at source/drain contact is essential for achieving high drive current in atomic layer MoS2-channel-based field effect transistors. Approaches such as choosing metals with appropriate work functions and chemical doping are employed previously to improve the carrier injection from the contact electrodes to the channel and to mitigate the SBH between the MoS2 and metal. Recent experiments demonstrate significant SBH reduction when graphene layer is inserted between metal slab (Ti and Ni) and MoS2. However, the physical or chemical origin of this phenomenon is not yet clearly understood. In this work, density functional theory simulations are performed, employing pseudopotentials with very high basis sets to get insights of the charge transfer between metal and monolayer MoS2 through the inserted graphene layer. Our atomistic simulations on 16 different interfaces involving five different metals (Ti, Ag, Ru, Au, and Pt) reveal that (i) such a decrease in SBH is not consistent among various metals, rather an increase in SBH is observed in case of Au and Pt; (ii) unlike MoS2-metal interface, the projected dispersion of MoS2 remains preserved in any MoS2-graphene-metal system with shift in the bands on the energy axis. (iii) A proper choice of metal (e.g., Ru) may exhibit ohmic nature in a graphene-inserted MoS2-metal contact. These understandings would provide a direction in developing high-performance transistors involving heteroatomic layers as contact electrodes.

  19. Holographic description of AdS2 black holes

    International Nuclear Information System (INIS)

    Castro, Alejandra; Larsen, Finn; Grumiller, Daniel; McNees, Robert

    2008-01-01

    We develop the holographic renormalization of AdS 2 gravity systematically. We find that a bulk Maxwell term necessitates a boundary mass term for the gauge field and verify that this unusual term is invariant under gauge transformations that preserve the boundary conditions. We determine the energy-momentum tensor and the central charge, recovering recent results by Hartman and Strominger. We show that our expressions are consistent with dimensional reduction of the AdS 3 energy-momentum tensor and the Brown-Henneaux central charge. As an application of our results we interpret the entropy of AdS 2 black holes as the ground state entropy of a dual CFT.

  20. Central charge for AdS2 quantum gravity

    International Nuclear Information System (INIS)

    Hartman, Thomas; Strominger, Andrew

    2009-01-01

    Two-dimensional Maxwell-dilaton quantum gravity on AdS 2 with radius l and a constant electric field E is studied. In conformal gauge, this is equivalent to a CFT on a strip. In order to maintain consistent boundary conditions, the usual conformal diffeomorphisms must be accompanied by a certain U(1) gauge transformation. The resulting conformal transformations are generated by a twisted stress tensor, which has a central charge c = 3kE 2 l 4 /4 where k is the level of the U(1) current. This is an AdS 2 analog of the Brown-Henneaux formula c = 3l/2G for the central charge of quantum gravity on AdS 3 .

  1. Open strings on AdS2 branes

    International Nuclear Information System (INIS)

    Lee, Peter; Ooguri, Hirosi.; Park, Jongwon; Tannenhauser, Jonathan

    2001-01-01

    We study the spectrum of open strings on AdS 2 branes in AdS 3 in an NS-NS background, using the SL(2,R) WZW model. When the brane carries no fundamental string charge, the open string spectrum is the holomorphic square root of the spectrum of closed strings in AdS 3 . It contains short and long strings, and is invariant under spectral flow. When the brane carries fundamental string charge, the open string spectrum again contains short and long strings in all winding sectors. However, branes with fundamental string charge break half the spectral flow symmetry. This has different implications for short and long strings. As the fundamental string charge increases, the brane approaches the boundary of AdS 3 . In this limit, the induced electric field on the worldvolume reaches its critical value, producing noncommutative open string theory on AdS 2

  2. Ultra-wideband spectral analysis using S2 technology

    International Nuclear Information System (INIS)

    Krishna Mohan, R.; Chang, T.; Tian, M.; Bekker, S.; Olson, A.; Ostrander, C.; Khallaayoun, A.; Dollinger, C.; Babbitt, W.R.; Cole, Z.; Reibel, R.R.; Merkel, K.D.; Sun, Y.; Cone, R.; Schlottau, F.; Wagner, K.H.

    2007-01-01

    This paper outlines the efforts to develop an ultra-wideband spectrum analyzer that takes advantage of the broad spectral response and fine spectral resolution (∼25 kHz) of spatial-spectral (S2) materials. The S2 material can process the full spectrum of broadband microwave transmissions, with adjustable time apertures (down to 100 μs) and fast update rates (up to 1 kHz). A cryogenically cooled Tm:YAG crystal that operates on microwave signals modulated onto a stabilized optical carrier at 793 nm is used as the core for the spectrum analyzer. Efforts to develop novel component technologies that enhance the performance of the system and meet the application requirements are discussed, including an end-to-end device model for parameter optimization. We discuss the characterization of new ultra-wide bandwidth S2 materials. Detection and post-processing module development including the implementation of a novel spectral recovery algorithm using field programmable gate array technology (FPGA) is also discussed

  3. Highly sensitive MoS2 photodetectors with graphene contacts

    Science.gov (United States)

    Han, Peize; St. Marie, Luke; Wang, Qing X.; Quirk, Nicholas; El Fatimy, Abdel; Ishigami, Masahiro; Barbara, Paola

    2018-05-01

    Two-dimensional materials such as graphene and transition metal dichalcogenides (TMDs) are ideal candidates to create ultra-thin electronics suitable for flexible substrates. Although optoelectronic devices based on TMDs have demonstrated remarkable performance, scalability is still a significant issue. Most devices are created using techniques that are not suitable for mass production, such as mechanical exfoliation of monolayer flakes and patterning by electron-beam lithography. Here we show that large-area MoS2 grown by chemical vapor deposition and patterned by photolithography yields highly sensitive photodetectors, with record shot-noise-limited detectivities of 8.7 × 1014 Jones in ambient condition and even higher when sealed with a protective layer. These detectivity values are higher than the highest values reported for photodetectors based on exfoliated MoS2. We study MoS2 devices with gold electrodes and graphene electrodes. The devices with graphene electrodes have a tunable band alignment and are especially attractive for scalable ultra-thin flexible optoelectronics.

  4. Ultra-wideband spectral analysis using S2 technology

    Energy Technology Data Exchange (ETDEWEB)

    Krishna Mohan, R. [Spectrum Lab, Montana State University, Bozeman, MT 59717 (United States)]. E-mail: krishna@spectrum.montana.edu; Chang, T. [Spectrum Lab, Montana State University, Bozeman, MT 59717 (United States); Tian, M. [Spectrum Lab, Montana State University, Bozeman, MT 59717 (United States); Department of Physics, Montana State University, Bozeman, MT 59717 (United States); Bekker, S. [Spectrum Lab, Montana State University, Bozeman, MT 59717 (United States); Olson, A. [Spectrum Lab, Montana State University, Bozeman, MT 59717 (United States); Ostrander, C. [Spectrum Lab, Montana State University, Bozeman, MT 59717 (United States); Khallaayoun, A. [Spectrum Lab, Montana State University, Bozeman, MT 59717 (United States); Dollinger, C. [Spectrum Lab, Montana State University, Bozeman, MT 59717 (United States); Babbitt, W.R. [Spectrum Lab, Montana State University, Bozeman, MT 59717 (United States); Department of Physics, Montana State University, Bozeman, MT 59717 (United States); Cole, Z. [Spectrum Lab, Montana State University, Bozeman, MT 59717 (United States); S2 Corporation, Bozeman, MT 59718 (United States); Reibel, R.R. [Spectrum Lab, Montana State University, Bozeman, MT 59717 (United States); S2 Corporation, Bozeman, MT 59718 (United States); Merkel, K.D. [Spectrum Lab, Montana State University, Bozeman, MT 59717 (United States); S2 Corporation, Bozeman, MT 59718 (United States); Sun, Y. [Department of Physics, Montana State University, Bozeman, MT 59717 (United States); Cone, R. [Department of Physics, Montana State University, Bozeman, MT 59717 (United States); Schlottau, F. [University of Colorado, Boulder, CO 80309 (United States); Wagner, K.H. [University of Colorado, Boulder, CO 80309 (United States)

    2007-11-15

    This paper outlines the efforts to develop an ultra-wideband spectrum analyzer that takes advantage of the broad spectral response and fine spectral resolution ({approx}25 kHz) of spatial-spectral (S2) materials. The S2 material can process the full spectrum of broadband microwave transmissions, with adjustable time apertures (down to 100 {mu}s) and fast update rates (up to 1 kHz). A cryogenically cooled Tm:YAG crystal that operates on microwave signals modulated onto a stabilized optical carrier at 793 nm is used as the core for the spectrum analyzer. Efforts to develop novel component technologies that enhance the performance of the system and meet the application requirements are discussed, including an end-to-end device model for parameter optimization. We discuss the characterization of new ultra-wide bandwidth S2 materials. Detection and post-processing module development including the implementation of a novel spectral recovery algorithm using field programmable gate array technology (FPGA) is also discussed.

  5. Band structural properties of MoS2 (molybdenite)

    International Nuclear Information System (INIS)

    Gupta, V.P.

    1980-01-01

    Semiconductivity and superconductivity in MoS 2 (molybdenite) can be understood in terms of the band structure of MoS 2 . The band structural properties of MoS 2 are presented here. The energy dependence of nsub(eff) and epsilon(infinity)sub(eff) is investigated. Using calculated values of nsub(eff) and epsilon(infinity)sub(eff), the Penn gap has been determined. The value thus obtained is shown to be in good agreement with the reflectivity data and also with the value obtained from the band structure. The Ravindra and Srivastava formula has been shown to give values for the isobaric temperature gradient of Esub(G)[(deltaEsub(G)/deltaT)sub(P)], which are in agreement with the experimental data, and the contribution to (deltaEsub(G)/deltaT)sub(P) due to the electron lattice interaction has been evaluated. In addition, the electronic polarizability has been calculated using a modified Lorentz-Lorenz relation. (author)

  6. S2p core level spectroscopy of short chain oligothiophenes

    Science.gov (United States)

    Baseggio, O.; Toffoli, D.; Stener, M.; Fronzoni, G.; de Simone, M.; Grazioli, C.; Coreno, M.; Guarnaccio, A.; Santagata, A.; D'Auria, M.

    2017-12-01

    The Near-Edge X-ray-Absorption Fine-Structure (NEXAFS) and X-ray Photoemission Spectroscopy (XPS) of short-chain oligothiophenes (thiophene, 2,2'-bithiophene, and 2,2':5',2″-terthiophene) in the gas phase have been measured in the sulfur L2,3-edge region. The assignment of the spectral features is based on the relativistic two-component zeroth-order regular approximation time dependent density functional theory approach. The calculations allow us to estimate both the contribution of the spin-orbit splitting and of the molecular-field splitting to the sulfur binding energies and give results in good agreement with the experimental measurements. The deconvolution of the calculated S2p NEXAFS spectra into the two manifolds of excited states converging to the LIII and LII edges facilitates the attribution of the spectral structures. The main S2p NEXAFS features are preserved along the series both as concerns the energy positions and the nature of the transitions. This behaviour suggests that the electronic and geometrical environment of the sulfur atom in the three oligomers is relatively unaffected by the increasing chain length. This trend is also observed in the XPS spectra. The relatively simple structure of S2p NEXAFS spectra along the series reflects the localized nature of the virtual states involved in the core excitation process.

  7. The light subunit of system bo,+ is fully functional in the absence of the heavy subunit

    OpenAIRE

    Reig, Núria; Chillarón, Josep; Bartoccioni, Paola; Fernández, Esperanza; Bendahan, Annie; Zorzano, Antonio; Kanner, Baruch; Palacín, Manuel; Bertran, Joan

    2002-01-01

    The heteromeric amino acid transporters are composed of a type II glycoprotein and a non-glycosylated polytopic membrane protein. System bo,+ exchanges dibasic for neutral amino acids. It is composed of rBAT and bo,+AT, the latter being the polytopic membrane subunit. Mutations in either of them cause malfunction of the system, leading to cystinuria. bo,+AT-reconstituted systems from HeLa or MDCK cells catalysed transport of arginine that was totally dependent on the presence of one of the bo...

  8. Local structure in (MnS)2x(CuInS2)1-x alloys

    International Nuclear Information System (INIS)

    Pietnoczka, A.; Bacewicz, R.; Schorr, S.

    2006-01-01

    Local structure around Mn atoms in (MnS) 2x (CuInS 2 ) 1-x alloys for x≤0.09 has been determined using near-edge and extended X-ray absorption fine structure (XANES and EXAFS) measured at the Mn K-edge. We found that for the Mn concentration up to 9 at% Mn atoms substitute preferentially for indium in the chalcopyrite lattice. The Mn-S bond length is 2.43±0.015 Aa, and is about 2% shorter than the In-S bond length. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (Abstract Copyright [2006], Wiley Periodicals, Inc.)

  9. TiS2 and ZrS2 single- and double-wall nanotubes: first-principles study.

    Science.gov (United States)

    Bandura, Andrei V; Evarestov, Robert A

    2014-02-15

    Hybrid density functional theory has been applied for investigations of the electronic and atomic structure of bulk phases, nanolayers, and nanotubes based on titanium and zirconium disulfides. Calculations have been performed on the basis of the localized atomic functions by means of the CRYSTAL-2009 computer code. The full optimization of all atomic positions in the regarded systems has been made to study the atomic relaxation and to determine the most favorable structures. The different layered and isotropic bulk phases have been considered as the possible precursors of the nanotubes. Calculations on single-walled TiS2 and ZrS2 nanotubes confirmed that the nanotubes obtained by rolling up the hexagonal crystalline layers with octahedral 1T morphology are the most stable. The strain energy of TiS2 and ZrS2 nanotubes is small, does not depend on the tube chirality, and approximately obeys to D(-2) law (D is nanotube diameter) of the classical elasticity theory. It is greater than the strain energy of the similar TiO2 and ZrO2 nanotubes; however, the formation energy of the disulfide nanotubes is considerably less than the formation energy of the dioxide nanotubes. The distance and interaction energy between the single-wall components of the double-wall nanotubes is proved to be close to the distance and interaction energy between layers in the layered crystals. Analysis of the relaxed nanotube shape using radial coordinate of the metal atoms demonstrates a small but noticeable deviation from completely cylindrical cross-section of the external walls in the armchair-like double-wall nanotubes. Copyright © 2013 Wiley Periodicals, Inc.

  10. Synthesis And Electrochemical Characteristics Of Mechanically Alloyed Anode Materials SnS2 For Li/SnS2 Cells

    Directory of Open Access Journals (Sweden)

    Hong J.H.

    2015-06-01

    Full Text Available With the increasing demand for efficient and economic energy storage, tin disulfide (SnS2, as one of the most attractive anode candidates for the next generation high-energy rechargeable Li-ion battery, have been paid more and more attention because of its high theoretical energy density and cost effectiveness. In this study, a new, simple and effective process, mechanical alloying (MA, has been developed for preparing fine anode material tin disulfides, in which ammonium chloride (AC, referred to as process control agents (PCAs, were used to prevent excessive cold-welding and accelerate the synthesis rates to some extent. Meanwhile, in order to decrease the mean size of SnS2 powder particles and improve the contact areas between the active materials, wet milling process was also conducted with normal hexane (NH as a solvent PCA. The prepared powders were both characterized by X-ray diffraction, Field emission-scanning electron microscopeand particle size analyzer. Finally, electrochemical measurements for Li/SnS2 cells were takenat room temperature, using a two-electrode cell assembled in an argon-filled glove box and the electrolyte of 1M LiPF6 in a mixture of ethylene carbonate(EC/dimethylcarbonate (DMC/ethylene methyl carbonate (EMC (volume ratio of 1:1:1.

  11. Synthesis and Characterization of the Quaternary Thio-aluminogermanates A(AlS2)(GeS2) (A = Na, K)

    KAUST Repository

    Al-Bloushi, Mohammed

    2015-05-27

    The quaternary thioaluminogermanates Na(AlS2)(GeS2) (1) and K(AlS2)(GeS2) (2) crystallize in the tetragonal space group I4/mcm (no. 140) with unit cell parameters a = 7.4274(11) Å, c = 5.8560(12) Å for Na(AlS2)(GeS2) and a = 7.8826(2) Å, c = 5.8642(4) Å for K(AlS2)(GeS2). The crystal structure comprises of one-dimensional [(AlS2)(GeS2)]- anionic chains with Al and Ge sharing the tetrahedral site. The alkali metal cations fill the square antiprismatic voids between chains. Both 1 and 2 are semiconductors with bandgap of around 3.6 eV and 3.5 eV, respectively. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Genetic analysis of the cytoplasmic dynein subunit families.

    Science.gov (United States)

    Pfister, K Kevin; Shah, Paresh R; Hummerich, Holger; Russ, Andreas; Cotton, James; Annuar, Azlina Ahmad; King, Stephen M; Fisher, Elizabeth M C

    2006-01-01

    Cytoplasmic dyneins, the principal microtubule minus-end-directed motor proteins of the cell, are involved in many essential cellular processes. The major form of this enzyme is a complex of at least six protein subunits, and in mammals all but one of the subunits are encoded by at least two genes. Here we review current knowledge concerning the subunits, their interactions, and their functional roles as derived from biochemical and genetic analyses. We also carried out extensive database searches to look for new genes and to clarify anomalies in the databases. Our analysis documents evolutionary relationships among the dynein subunits of mammals and other model organisms, and sheds new light on the role of this diverse group of proteins, highlighting the existence of two cytoplasmic dynein complexes with distinct cellular roles.

  13. Genetic analysis of the cytoplasmic dynein subunit families.

    Directory of Open Access Journals (Sweden)

    K Kevin Pfister

    2006-01-01

    Full Text Available Cytoplasmic dyneins, the principal microtubule minus-end-directed motor proteins of the cell, are involved in many essential cellular processes. The major form of this enzyme is a complex of at least six protein subunits, and in mammals all but one of the subunits are encoded by at least two genes. Here we review current knowledge concerning the subunits, their interactions, and their functional roles as derived from biochemical and genetic analyses. We also carried out extensive database searches to look for new genes and to clarify anomalies in the databases. Our analysis documents evolutionary relationships among the dynein subunits of mammals and other model organisms, and sheds new light on the role of this diverse group of proteins, highlighting the existence of two cytoplasmic dynein complexes with distinct cellular roles.

  14. Atomic and electronic structure of MoS2 nanoparticles

    DEFF Research Database (Denmark)

    Bollinger, Mikkel; Jacobsen, Karsten Wedel; Nørskov, Jens Kehlet

    2003-01-01

    Using density-functional theory (DFT) we present a detailed theoretical study of MoS2 nanoparticles. We focus on the edge structures, and a number of different edge terminations are investigated. Several, but not all, of these configurations have one-dimensional metallic states localized at the e...... and the composition of the gas phase. Using the Tersoff-Hamann formalism, scanning-tunneling microscopy (STM) images of the edges are simulated for direct comparison with recent STM experiments. In this way we identify the experimentally observed edge structure....

  15. Spatially inhomogeneous barrier height in graphene/MoS2 Schottky junctions

    Science.gov (United States)

    Tomer, Dushyant; Rajput, Shivani; Li, Lian

    Graphene interfaced with a semiconductor forms a Schottky junction with rectifying properties. In this study, graphene Schottky junctions are fabricated by transferring CVD monolayer graphene on mechanically exfoliated MoS2 multilayers. The forward bias current-voltage characteristics are measured in the temperature range of 210-300 K. An increase in the zero bias barrier height and decrease in the ideality factor are observed with increasing temperature. Such behavior is attributed to Schottky barrier inhomogeneities possibly due to graphene ripples and ridges at the junction interface as suggested by atomic force microscopy. Assuming a Gaussian distribution of the barrier height, mean barrier of 0.97+/-0.10 eV is found for the graphene MoS2 junction. Our findings provide significant insight on the barrier height inhomogeneities in graphene/two dimensional semiconductor Schottky junctions. U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering Award No. DEFG02-07ER46228.

  16. Strain-Dependent Edge Structures in MoS2 Layers.

    Science.gov (United States)

    Tinoco, Miguel; Maduro, Luigi; Masaki, Mukai; Okunishi, Eiji; Conesa-Boj, Sonia

    2017-11-08

    Edge structures are low-dimensional defects unavoidable in layered materials of the transition metal dichalcogenides (TMD) family. Among the various types of such structures, the armchair (AC) and zigzag (ZZ) edge types are the most common. It has been predicted that the presence of intrinsic strain localized along these edges structures can have direct implications for the customization of their electronic properties. However, pinning down the relation between local structure and electronic properties at these edges is challenging. Here, we quantify the local strain field that arises at the edges of MoS 2 flakes by combining aberration-corrected transmission electron microscopy (TEM) with the geometrical-phase analysis (GPA) method. We also provide further insight on the possible effects of such edge strain on the resulting electronic behavior by means of electron energy loss spectroscopy (EELS) measurements. Our results reveal that the two-dominant edge structures, ZZ and AC, induce the formation of different amounts of localized strain fields. We also show that by varying the free edge curvature from concave to convex, compressive strain turns into tensile strain. These results pave the way toward the customization of edge structures in MoS 2 , which can be used to engineer the properties of layered materials and thus contribute to the optimization of the next generation of atomic-scale electronic devices built upon them.

  17. Transcriptional regulators of Na, K-ATPase subunits

    Directory of Open Access Journals (Sweden)

    Zhiqin eLi

    2015-10-01

    Full Text Available The Na,K-ATPase classically serves as an ion pump creating an electrochemical gradient across the plasma membrane that is essential for transepithelial transport, nutrient uptake and membrane potential. In addition, Na,K-ATPase also functions as a receptor, a signal transducer and a cell adhesion molecule. With such diverse roles, it is understandable that the Na,K-ATPase subunits, the catalytic alpha-subunit, the beta-subunit and the FXYD proteins, are controlled extensively during development and to accommodate physiological needs. The spatial and temporal expression of Na,K-ATPase is partially regulated at the transcriptional level. Numerous transcription factors, hormones, growth factors, lipids and extracellular stimuli modulate the transcription of the Na,K-ATPase subunits. Moreover, epigenetic mechanisms also contribute to the regulation of Na,K-ATPase expression. With the ever growing knowledge about diseases associated with the malfunction of Na,K-ATPase, this review aims at summarizing the best-characterized transcription regulators that modulate Na,K-ATPase subunit levels. As abnormal expression of Na,K-ATPase subunits have been observed in many carcinoma, we will also discuss transcription factors that are associated with epithelial-to-mesenchymal transition, a crucial step in the progression of many tumors to malignant disease.

  18. Role of hydrogen in the chemical vapor deposition growth of MoS2 atomic layers

    Science.gov (United States)

    Li, Xiao; Li, Xinming; Zang, Xiaobei; Zhu, Miao; He, Yijia; Wang, Kunlin; Xie, Dan; Zhu, Hongwei

    2015-04-01

    Hydrogen plays a crucial role in the chemical vapor deposition (CVD) growth of graphene. Here, we have revealed the roles of hydrogen in the two-step CVD growth of MoS2. Our study demonstrates that hydrogen acts as the following: (i) an inhibitor of the thermal-induced etching effect in the continuous film growth process; and (ii) a promoter of the desulfurization reaction by decreasing the S/Mo atomic ratio and the oxidation reaction of the obtained MoSx (0 desulfurization reaction by decreasing the S/Mo atomic ratio and the oxidation reaction of the obtained MoSx (0 < x < 2) films. A high hydrogen content of more than 100% in argon forms nano-sized circle-like defects and damages the continuity and uniformity of the film. Continuous MoS2 films with a high crystallinity and a nearly perfect S/Mo atomic ratio were finally obtained after sulfurization annealing with a hydrogen content in the range of 20%-80%. This insightful understanding reveals the crucial roles of hydrogen in the CVD growth of MoS2 and paves the way for the controllable synthesis of two-dimensional materials. Electronic supplementary information (ESI) available: Low-magnification optical images; Raman spectra of 0% and 5% H2 samples; AFM characterization; Schematic of the film before and after sulfurization annealing; Schematic illustrations of two typical Raman-active phonon modes (E12g, A1g); Raman (mapping) spectra for 40% and 80% H2 samples before and after sulfurization annealing; PL spectra. See DOI: 10.1039/c5nr00904a

  19. Critical gravity on AdS2 spacetimes

    International Nuclear Information System (INIS)

    Myung, Yun Soo; Kim, Yong-Wan; Park, Young-Jai

    2011-01-01

    We study the critical gravity in two-dimensional anti-de Sitter (AdS 2 ) spacetimes, which was obtained from the cosmological topologically massive gravity (TMG Λ ) in three dimensions by using the Kaluza-Klein dimensional reduction. We perform the perturbation analysis around AdS 2 , which may correspond to the near-horizon geometry of the extremal Banados, Teitelboim, and Zanelli (BTZ) black hole obtained from the TMG Λ with identification upon uplifting three dimensions. A massive propagating scalar mode δF satisfies the second-order differential equation away from the critical point of K=l, whose solution is given by the Bessel functions. On the other hand, δF satisfies the fourth-order equation at the critical point. We exactly solve the fourth-order equation, and compare it with the log gravity in two dimensions. Consequently, the critical gravity in two dimensions could not be described by a massless scalar δF ml and its logarithmic partner δF log 4th .

  20. Facile one-pot synthesis of CoS_2-MoS_2/CNTs as efficient electrocatalyst for hydrogen evolution reaction

    International Nuclear Information System (INIS)

    Liu, Yan-Ru; Hu, Wen-Hui; Li, Xiao; Dong, Bin; Shang, Xiao; Han, Guan-Qun; Chai, Yong-Ming; Liu, Yun-Qi; Liu, Chen-Guang

    2016-01-01

    Highlights: • Ternary hybrid CoS_2-MoS_2/CNTs electrocatalysts have been prepared. • CNTs as support may provide good conductivity and low the agglomeration of MoS_2. • CoS_2 with intrinsic metallic conductivity may enhance the activity for HER. • Ternary CoS_2-MoS_2/CNTs have the better activity and stability for HER. - Abstract: Ternary hybrid cobalt disulfide-molybdenum disulfides supported on carbon nanotubes (CoS_2-MoS_2/CNTs) electrocatalysts have been prepared via a simple hydrothermal method. CNTs as support may provide good conductivity and low the agglomeration of layered MoS_2 structure. CoS_2 with intrinsic metallic conductivity may enhance the activity of the ternary hybrid electrocatalysts for hydrogen evolution reaction (HER). X-ray diffraction (XRD) data confirm the formation of ternary hybrid nanocomposites composed of CNTs, CoS_2 and amorphous MoS_2. Scanning electron microscopy (SEM) images show that strong combination between MoS_2, CNTs and regular orthohexagonal CoS_2 has been obtained. The dispersion of each component is good and no obvious agglomeration can be observed. It is found that compared with CoS_2/CNTs and MoS_2/CNTs, the ternary CoS_2-MoS_2/CNTs have the better activity for HER with a low onset potential of 70 mV (vs. RHE) and a small Talel slope of 67 mV dec"−"1, and are extremely stable after 1000 cycles. In addition, the optimal doping ratio of Co to Mo is 2:1, which have better HER activity. It is proved that the introduction of carbon materials and Co atoms could improve the performances of MoS_2-based electrocatalysts for HER.

  1. The essential role of AMPA receptor GluR2 subunit RNA editing in the normal and diseased brain

    Directory of Open Access Journals (Sweden)

    Amanda Lorraine Wright

    2012-04-01

    Full Text Available AMPA receptors are comprised of different combinations of GluR1-GluR4 (also known as GluA1-GluA4 and GluR-A to GluR-D subunits. The GluR2 subunit is subject to Q/R site RNA editing by the ADAR2 enzyme, which converts a codon for glutamine (Q, present in the GluR2 gene, to a codon for arginine (R found in the mRNA. AMPA receptors are calcium (Ca2+-permeable if they contain the unedited GluR2(Q subunit or if they lack the GluR2 subunit. While most AMPA receptors in the brain contain the edited GluR2(R subunit and are therefore Ca2+-impermeable, recent evidence suggests that Ca2+-permeable GluR2-lacking AMPA receptors are important in synaptic plasticity and learning. However, the presence of Ca2+-permeable AMPA receptors containing unedited GluR2 leads to excitotoxic cell loss. Recent studies have indicated that RNA editing of GluR2 is deregulated in diseases, such as amyotrophic lateral sclerosis (ALS, as well in acute neurodegenerative conditions, such as ischemia. More recently, studies have investigated the regulation of RNA editing and possible causes for its deregulation during disease. In this review, we will explore the role of GluR2 RNA editing in the healthy and diseased brain and outline new insights into the mechanisms that control this process.

  2. Strain engineering in monolayer WS2, MoS2, and the WS2/MoS2 heterostructure

    KAUST Repository

    He, Xin; Li, Hai; Zhu, Zhiyong; Dai, Zhenyu; Yang, Yang; Yang, Peng; Zhang, Qiang; Li, Peng; Schwingenschlö gl, Udo; Zhang, Xixiang

    2016-01-01

    Mechanically exfoliated monolayers of WS2, MoS2 and their van der Waals heterostructure were fabricated on flexible substrate so that uniaxial tensile strain can be applied to the two-dimensional samples. The modification of the band structure under strain was investigated by micro-photoluminescence spectroscopy at room temperature as well as by first-principles calculations. Exciton and trion emissions were observed in both WS2 and the heterostructure at room temperature, and were redshifted by strain, indicating potential for applications in flexible electronics and optoelectronics.

  3. Strain engineering in monolayer WS2, MoS2, and the WS2/MoS2 heterostructure

    KAUST Repository

    He, Xin

    2016-10-27

    Mechanically exfoliated monolayers of WS2, MoS2 and their van der Waals heterostructure were fabricated on flexible substrate so that uniaxial tensile strain can be applied to the two-dimensional samples. The modification of the band structure under strain was investigated by micro-photoluminescence spectroscopy at room temperature as well as by first-principles calculations. Exciton and trion emissions were observed in both WS2 and the heterostructure at room temperature, and were redshifted by strain, indicating potential for applications in flexible electronics and optoelectronics.

  4. FeS2-doped MoS2 nanoflower with the dominant 1T-MoS2 phase as an excellent electrocatalyst for high-performance hydrogen evolution

    International Nuclear Information System (INIS)

    Zhao, Xue; Ma, Xiao; Lu, Qingqing; Li, Qun; Han, Ce; Xing, Zhicai; Yang, Xiurong

    2017-01-01

    Well-established methods to improve the hydrogen evolution reaction (HER) performances include, but are not limited to, tailoring the morphology and electronic structure of transition metal dichalcogenides (TMDs), and doping of earth abundant chemicals such as iron pyrite FeS 2 into existing TMDs. In this work, MoS 2 nanoflowers with the majority being octahedral MoS 2 (1T-MoS 2 ) and doped with FeS 2 were prepared and applied to HER. The as-prepared catalysts were characterized by X-ray absorption fine structure at the K-edge of Mo, S, and Fe to probe the local electronic structures. The resulting nanomaterial was identified to be FeS 2 doped MoS 2 nanoflower (denoted as Fe-MoS 2 NF) with 66% 1T-MoS 2 which was the metallic phase and could drastically boost the HER properties. The Fe-MoS 2 NF exhibited high HER performance with a Tafel slope of 82 mV dec −1 and it needs 136 mV to achieve a current density of 10 mA cm −2 . The synthesis of Fe-MoS 2 NF with refined morphology and active electronic structure is expected to open a new era for improving the catalytic activity and stability of MoS 2 .

  5. Leptin and insulin engage specific PI3K subunits in hypothalamic SF1 neurons

    Directory of Open Access Journals (Sweden)

    Jong-Woo Sohn

    2016-08-01

    Full Text Available Objective: The ventromedial hypothalamic nucleus (VMH regulates energy balance and glucose homeostasis. Leptin and insulin exert metabolic effects via their cognate receptors expressed by the steroidogenic factor 1 (SF1 neurons within the VMH. However, detailed cellular mechanisms involved in the regulation of these neurons by leptin and insulin remain to be identified. Methods: We utilized genetically-modified mouse models and performed patch-clamp electrophysiology experiments to resolve this issue. Results: We identified distinct populations of leptin-activated and leptin-inhibited SF1 neurons. In contrast, insulin uniformly inhibited SF1 neurons. Notably, we found that leptin-activated, leptin-inhibited, and insulin-inhibited SF1 neurons are distinct subpopulations within the VMH. Leptin depolarization of SF1 neuron also required the PI3K p110β catalytic subunit. This effect was mediated by the putative transient receptor potential C (TRPC channel. On the other hand, hyperpolarizing responses of SF1 neurons by leptin and insulin required either of the p110α or p110β catalytic subunits, and were mediated by the putative ATP-sensitive K+ (KATP channel. Conclusions: Our results demonstrate that specific PI3K catalytic subunits are responsible for the acute effects of leptin and insulin on VMH SF1 neurons, and provide insights into the cellular mechanisms of leptin and insulin action on VMH SF1 neurons that regulate energy balance and glucose homeostasis. Author Video: Author Video Watch what authors say about their articles Keywords: Cellular mechanism, Conditional knockout mouse, Patch clamp technique, Functional heterogeneity, Homeostasis

  6. An investigation of AdS2 backreaction and holography

    International Nuclear Information System (INIS)

    Engelsöy, Julius; Mertens, Thomas G.; Verlinde, Herman

    2016-01-01

    We investigate a dilaton gravity model in AdS 2 proposed by Almheiri and Polchinski http://dx.doi.org/10.1007/JHEP11(2015)014 and develop a 1d effective description in terms of a dynamical boundary time with a Schwarzian derivative action. We show that the effective model is equivalent to a 1d version of Liouville theory, and investigate its dynamics and symmetries via a standard canonical framework. We include the coupling to arbitrary conformal matter and analyze the effective action in the presence of possible sources. We compute commutators of local operators at large time separation, and match the result with the time shift due to a gravitational shockwave interaction. We study a black hole evaporation process and comment on the role of entropy in this model.

  7. Fine Grained Chaos in AdS_{2} Gravity.

    Science.gov (United States)

    Haehl, Felix M; Rozali, Moshe

    2018-03-23

    Quantum chaos can be characterized by an exponential growth of the thermal out-of-time-order four-point function up to a scrambling time u[over ^]_{*}. We discuss generalizations of this statement for certain higher-point correlation functions. For concreteness, we study the Schwarzian theory of a one-dimensional time reparametrization mode, which describes two-dimensional anti-de Sitter space (AdS_{2}) gravity and the low-energy dynamics of the Sachdev-Ye-Kitaev model. We identify a particular set of 2k-point functions, characterized as being both "maximally braided" and "k-out of time order," which exhibit exponential growth until progressively longer time scales u[over ^]_{*}^{(k)}∼(k-1)u[over ^]_{*}. We suggest an interpretation as scrambling of increasingly fine grained measures of quantum information, which correspondingly take progressively longer time to reach their thermal values.

  8. Fine Grained Chaos in AdS2 Gravity

    Science.gov (United States)

    Haehl, Felix M.; Rozali, Moshe

    2018-03-01

    Quantum chaos can be characterized by an exponential growth of the thermal out-of-time-order four-point function up to a scrambling time u^*. We discuss generalizations of this statement for certain higher-point correlation functions. For concreteness, we study the Schwarzian theory of a one-dimensional time reparametrization mode, which describes two-dimensional anti-de Sitter space (AdS2 ) gravity and the low-energy dynamics of the Sachdev-Ye-Kitaev model. We identify a particular set of 2 k -point functions, characterized as being both "maximally braided" and "k -out of time order," which exhibit exponential growth until progressively longer time scales u^*(k)˜(k -1 )u^*. We suggest an interpretation as scrambling of increasingly fine grained measures of quantum information, which correspondingly take progressively longer time to reach their thermal values.

  9. Pituitary glycoprotein hormone a-subunit secretion by cirrhotic patients

    Directory of Open Access Journals (Sweden)

    Oliveira M.C.

    1999-01-01

    Full Text Available Secretion of the a-subunit of pituitary glycoprotein hormones usually follows the secretion of intact gonadotropins and is increased in gonadal failure and decreased in isolated gonadotropin deficiency. The aim of the present study was to determine the levels of the a-subunit in the serum of patients with cirrhosis of the liver and to compare the results obtained for eugonadal cirrhotic patients with those obtained for cirrhotic patients with hypogonadotropic hypogonadism. Forty-seven of 63 patients with cirrhosis (74.6% presented hypogonadism (which was central in 45 cases and primary in 2, 7 were eugonadal, and 9 women were in normal menopause. The serum a-subunit was measured by the fluorimetric method using monoclonal antibodies. Cross-reactivity with LH, TSH, FSH and hCG was 6.5, 1.2, 4.3 and 1.1%, respectively, with an intra-assay coefficient of variation (CV of less than 5% and an interassay CV of 5%, and sensitivity limit of 4 ng/l. The serum a-subunit concentration ranged from 36 to 6253 ng/l, with a median of 273 ng/l. The median was 251 ng/l for patients with central hypogonadism and 198 ng/l for eugonadal patients. The correlation between the a-subunit and basal LH levels was significant both in the total sample (r = 0.48, P<0.01 and in the cirrhotic patients with central hypogonadism (r = 0.33, P = 0.02. Among men with central hypogonadism there was a negative correlation between a-subunit levels and total testosterone levels (r = 0.54, P<0.01 as well as free testosterone levels (r = -0.53, P<0.01. In conclusion, although the a-subunit levels are correlated with LH levels, at present they cannot be used as markers for hypogonadism in patients with cirrhosis of the liver.

  10. OBTAINING AND PROPERTIES OF AgInS2 FILMS

    Directory of Open Access Journals (Sweden)

    M. A. Abdullaev

    2016-01-01

    Full Text Available Aim. The aim is to obtain AgInS2 films and study their electrical and optical properties.Methods. The samples of thin AgInS2 films for measurement were obtained by the method of magnetron sputtering with direct current. The structure, phase and elemental composition were studied using DRON-2 X-ray diffractometer (СuKа - radiation and the microscope LEO-1450 with EDS attachment for X-ray microanalysis. The optical transmittance and absorption were examined using MDR-2 monochromator in the wavelength range of 400-800 nm with the Keitley electrometer and FD-10G; we applied the spectral resolution of ± 1 meV. The electrical conductivity, Hall effect was measured by the four-point probe method with indium ohmic contacts. Measurements were carried out in the temperature range of 77-400 K.Findings. We obtained indium disulfide and silver films with the thickness of up to 1 μm on quartz substrates by magnetron sputtering. It is shown that increasing the substrate temperature to about 450 0С allows to obtain single phase film with a chalcopyrite structure with a band gap of 1.88 eV and high absorption coefficient (>104см-1.Conclusions. The possibility of obtaining films in a wide range of the electrical resistance and variation of the electrical parameters at constant stoichiometry is of interest for efficient technologies of phototransduction.

  11. The first transmembrane domain (TM1) of β2-subunit binds to the transmembrane domain S1 of α-subunit in BK potassium channels

    Science.gov (United States)

    Morera, Francisco J.; Alioua, Abderrahmane; Kundu, Pallob; Salazar, Marcelo; Gonzalez, Carlos; Martinez, Agustin D.; Stefani, Enrico; Toro, Ligia; Latorre, Ramon

    2012-01-01

    The BK channel is one of the most broadly expressed ion channels in mammals. In many tissues, the BK channel pore-forming α-subunit is associated to an auxiliary β-subunit that modulates the voltage- and Ca2+-dependent activation of the channel. Structural components present in β-subunits that are important for the physical association with the α-subunit are yet unknown. Here, we show through co-immunoprecipitation that the intracellular C-terminus, the second transmembrane domain (TM2) and the extracellular loop of the β2-subunit are dispensable for association with the α-subunit pointing transmembrane domain 1 (TM1) as responsible for the interaction. Indeed, the TOXCAT assay for transmembrane protein–protein interactions demonstrated for the first time that TM1 of the β2-subunit physically binds to the transmembrane S1 domain of the α-subunit. PMID:22710124

  12. Probing the functional subunits of the tonoplast H+-ATPase

    International Nuclear Information System (INIS)

    Randall, S.K.; Lai, S.; Sze, H.

    1986-01-01

    The tonoplast ATPase of oat roots is composed of at least three polypeptides of 72, 60, and 16 kDa. The 16 kDA polypeptide covalently binds N,N'-dicyclohexylcarbodiimide and is postulated to be a component of the proton channel. Initial studies to identify other subunits indicate that both the 72 and 60 kDa subunits covalently bind 14 C]-7-chloro-4-nitrobenzo-2-oxa-1,3-diazole and [ 14 C]N-ethylamleimide, inhibitors of the tonoplast ATPase. ATP prevents binding of these inhibitors suggesting that both the 72 and 60 kDa subunits are involved in substrate binding. Polyclonal antibody has been made to the 72 kDa subunit. Western blot analysis of tonoplast vesicles reveals single reactive polypeptide (72 kDa). The antibody shows no cross-reactivity towards either the mitochondrial F 1 -ATPase or the plasma membrane ATPase. This antibody specifically inhibits ATP hydrolysis and ATP-dependent H + pumping in native tonoplast vesicles. The authors conclude that the 72 kDa subunit is intimately associated with the catalytic (or ATP-binding) site

  13. High-Resolution Tracking Asymmetric Lithium Insertion and Extraction and Local Structure Ordering in SnS2.

    Science.gov (United States)

    Gao, Peng; Wang, Liping; Zhang, Yu-Yang; Huang, Yuan; Liao, Lei; Sutter, Peter; Liu, Kaihui; Yu, Dapeng; Wang, En-Ge

    2016-09-14

    In the rechargeable lithium ion batteries, the rate capability and energy efficiency are largely governed by the lithium ion transport dynamics and phase transition pathways in electrodes. Real-time and atomic-scale tracking of fully reversible lithium insertion and extraction processes in electrodes, which would ultimately lead to mechanistic understanding of how the electrodes function and why they fail, is highly desirable but very challenging. Here, we track lithium insertion and extraction in the van der Waals interactions dominated SnS2 by in situ high-resolution TEM method. We find that the lithium insertion occurs via a fast two-phase reaction to form expanded and defective LiSnS2, while the lithium extraction initially involves heterogeneous nucleation of intermediate superstructure Li0.5SnS2 domains with a 1-4 nm size. Density functional theory calculations indicate that the Li0.5SnS2 is kinetically favored and structurally stable. The asymmetric reaction pathways may supply enlightening insights into the mechanistic understanding of the underlying electrochemistry in the layered electrode materials and also suggest possible alternatives to the accepted explanation of the origins of voltage hysteresis in the intercalation electrode materials.

  14. Efficient visible-light photocatalytic and enhanced photocorrosion inhibition of Ag2WO4 decorated MoS2 nanosheets

    Science.gov (United States)

    Thangavel, Sakthivel; Thangavel, Srinivas; Raghavan, Nivea; Alagu, Raja; Venugopal, Gunasekaran

    2017-11-01

    The use of two-dimensional nanomaterials as co-catalysts in the photodegradation of toxic compounds using light irradiation is an attractive ecofriendly process. In this study, we prepared a novel MoS2/Ag2WO4 nanohybrid via a one-step hydrothermal approach and the photocatalytic properties were investigated by the degradation of methyl-orange under stimulated irradiation. The nanohybrid exhibits enhanced efficiency in dye degradation compared to the bare Ag2WO4 nanorods; the same has been evidently confirmed with UV-visible spectra and total organic carbon removal analysis. The pseudo-first order rate constant of the nanohybrid is nearly 1.8 fold higher than that of the bare Ag2WO4 nanorods. With the aid of classical radical quenching and photoluminescence spectral analysis, a reasonable mechanism has been derived for the addition of MoS2 to nanohybrids to enhance the photocatalytic efficiency. MoS2 prevents photocorrosion of Ag2WO4 and also diminishes the number of photogenerated electron-hole recombination. Our findings could provide new insights in understanding the mechanism of the MoS2/Ag2WO4 nanohybrid as an efficient photocatalyst suitable for waste-water treatment and remedial applications.

  15. Spectroscopy, microscopy and theoretical study of NO adsorption on MoS2 and Co-Mo-S hydrotreating catalysts

    DEFF Research Database (Denmark)

    Topsøe, Nan-Yu; Tuxen, Anders Kyrme; Hinnemann, Berit

    2011-01-01

    nfrared (IR) spectroscopy using NO as a probe molecule has been one of the important methods for characterizing hydrotreating catalysts, since this technique provides information on the nature and quantity of active edge sites of these catalysts. However, due to the strong adsorption of NO, which......) calculations, we present new atomic-scale insight into the nature of NO adsorption on MoS2 and Co-Mo-S nanoclusters. The DFT calculations and STM experiments show that NO does not adsorb at fully sulfided MoS2 edges not containing hydrogen. However, typical sulfided catalysts will have hydrogen present...... NO as a probe molecule to obtain detailed atomic-scale information on hydrotreating catalysts and the origins of activity differences. (C) 2011 Published by Elsevier Inc....

  16. Role of regulatory subunits and protein kinase inhibitor (PKI) in determining nuclear localization and activity of the catalytic subunit of protein kinase A.

    Science.gov (United States)

    Wiley, J C; Wailes, L A; Idzerda, R L; McKnight, G S

    1999-03-05

    Regulation of protein kinase A by subcellular localization may be critical to target catalytic subunits to specific substrates. We employed epitope-tagged catalytic subunit to correlate subcellular localization and gene-inducing activity in the presence of regulatory subunit or protein kinase inhibitor (PKI). Transiently expressed catalytic subunit distributed throughout the cell and induced gene expression. Co-expression of regulatory subunit or PKI blocked gene induction and prevented nuclear accumulation. A mutant PKI lacking the nuclear export signal blocked gene induction but not nuclear accumulation, demonstrating that nuclear export is not essential to inhibit gene induction. When the catalytic subunit was targeted to the nucleus with a nuclear localization signal, it was not sequestered in the cytoplasm by regulatory subunit, although its activity was completely inhibited. PKI redistributed the nuclear catalytic subunit to the cytoplasm and blocked gene induction, demonstrating that the nuclear export signal of PKI can override a strong nuclear localization signal. With increasing PKI, the export process appeared to saturate, resulting in the return of catalytic subunit to the nucleus. These results demonstrate that both the regulatory subunit and PKI are able to completely inhibit the gene-inducing activity of the catalytic subunit even when the catalytic subunit is forced to concentrate in the nuclear compartment.

  17. Novel subunit structure observed for noncooperative hemoglobin from Urechis caupo.

    Science.gov (United States)

    Kolatkar, P R; Meador, W E; Stanfield, R L; Hackert, M L

    1988-03-05

    Tetrameric hemoglobin from the "fat innkeeper" worm Urechis caupo possesses a novel subunit arrangement having an "inside out" quaternary structure in that the G/H helices are located on the outer surface of the tetramer. A 5-A resolution crystal structure reveals that although the individual subunits are beta-like, having a distinct D helix and the general myoglobin fold, the subunit contacts are very different from those previously observed for hemoglobins. Furthermore, the hemoglobin from U. caupo is also quite different from the unusual hemoglobin tetramer from clam which also has its G/H helices on the outer surface but with the hemes in close proximity through E-F helical contacts (Royer, W. E., Jr., Love, W. E., and Fenderson, F. F. (1985) Nature 316, 277-280).

  18. Dynamic properties of motor proteins with two subunits

    International Nuclear Information System (INIS)

    Kolomeisky, Anatoly B; III, Hubert Phillips

    2005-01-01

    The dynamics of motor protein molecules consisting of two subunits is investigated using simple discrete stochastic models. Exact steady-state analytical expressions are obtained for velocities and dispersions for any number of intermediate states and conformations between the corresponding binding states of proteins. These models enable us to provide a detailed description and comparison of two different mechanisms of the motion of motor proteins along the linear tracks: the hand-over-hand mechanism, when the motion of subunits alternate; and the inchworm mechanism, when one subunit is always trailing another one. It is shown that the proteins in the hand-over-hand mechanism move faster and fluctuate more than the molecules in the inchworm mechanism. The effect of external forces on dynamic properties of motor proteins is also discussed. Finally, a quantitative method, based on experimental observations for single motor proteins, is proposed for distinguishing between two mechanisms of motion

  19. CSNAP Is a Stoichiometric Subunit of the COP9 Signalosome

    Directory of Open Access Journals (Sweden)

    Shelly Rozen

    2015-10-01

    Full Text Available The highly conserved COP9 signalosome (CSN complex is a key regulator of all cullin-RING-ubiquitin ligases (CRLs, the largest family of E3 ubiquitin ligases. Until now, it was accepted that the CSN is composed of eight canonical components. Here, we report the discovery of an additional integral and stoichiometric subunit that had thus far evaded detection, and we named it CSNAP (CSN acidic protein. We show that CSNAP binds CSN3, CSN5, and CSN6, and its incorporation into the CSN complex is mediated through the C-terminal region involving conserved aromatic residues. Moreover, depletion of this small protein leads to reduced proliferation and a flattened and enlarged morphology. Finally, on the basis of sequence and structural properties shared by both CSNAP and DSS1, a component of the related 19S lid proteasome complex, we propose that CSNAP, the ninth CSN subunit, is the missing paralogous subunit of DSS1.

  20. Cholera Toxin B: One Subunit with Many Pharmaceutical Applications

    Directory of Open Access Journals (Sweden)

    Keegan J. Baldauf

    2015-03-01

    Full Text Available Cholera, a waterborne acute diarrheal disease caused by Vibrio cholerae, remains prevalent in underdeveloped countries and is a serious health threat to those living in unsanitary conditions. The major virulence factor is cholera toxin (CT, which consists of two subunits: the A subunit (CTA and the B subunit (CTB. CTB is a 55 kD homopentameric, non-toxic protein binding to the GM1 ganglioside on mammalian cells with high affinity. Currently, recombinantly produced CTB is used as a component of an internationally licensed oral cholera vaccine, as the protein induces potent humoral immunity that can neutralize CT in the gut. Additionally, recent studies have revealed that CTB administration leads to the induction of anti-inflammatory mechanisms in vivo. This review will cover the potential of CTB as an immunomodulatory and anti-inflammatory agent. We will also summarize various recombinant expression systems available for recombinant CTB bioproduction.

  1. Thermostable Subunit Vaccines for Pulmonary Delivery: How Close Are We?

    DEFF Research Database (Denmark)

    Foged, Camilla

    2016-01-01

    , such as influenza, tuberculosis, and Ebola, for which no good universal vaccines exist. At least two pharmaceutical improvements are expected to help filling this gap: i) The development of thermostable vaccine dosage forms, and ii) the full exploitation of the adjuvant technology for subunit vaccines to potentiate...... strong immune responses. This review highlights the status and recent advances in formulation and pulmonary delivery of thermostable human subunit vaccines. Such vaccines are very appealing from compliance, distribution and immunological point of view: Being non-invasive, inhalable vaccines are self...... immunity. Here, I review state of the art and perspectives in formulation design and processing methods for powder-based subunit vaccines intended for pulmonary administration, and present dry powder inhaler technologies suitable for translating these vaccines into clinical trials....

  2. Search for the H Dibaryon (S = -2) Using Diffraction Dissociation

    Energy Technology Data Exchange (ETDEWEB)

    Ecklund, K.

    2005-04-05

    The observed hadrons are understood as bound states of three quarks (baryons) or of quarks and antiquarks (mesons). To date no six quark bound state other than the loosely bound deuteron has been observed. Quantum Chromodynamics permits other color-singlet bound states of quarks, and a number of phenomenological models extended from the baryon (q{sup 3}) and meson (q{bar q}) sectors predict bound six quark states (q{sup 6}). The most probable candidate is the H dibaryon, composed of two each of the lightest three quarks (udsuds), with quantum numbers J{sup P} = 0{sup +}, I = 0 and S = -2. Its mass would likely be between the deuteron mass and twice the {Lambda} (uds) mass. This dissertation describes a search for the H dibaryon conducted in a neutral beam at the Brookhaven National Laboratory's Alternating Gradient Synchrotron. In the experiment a 24.1 GeV/c proton beam struck a 1.35 interaction length platinum target producing a collimated neutral beam (62 {mu}sr at 65 mrad from the incident proton direction) which propagated through a 18 m vacuum decay tank before entering a double arm spectrometer. Approximately 20 m from the production target a 10 cm (0.15 interaction length) long active scintillator dissociator was placed in the beam.

  3. Thermoluminescence kinetics of pyrite (FeS2)

    International Nuclear Information System (INIS)

    Silverman, A.N; Levy, P.W.; Kierstead, J.A.

    1990-01-01

    Thermoluminescence of pyrite (FeS 2 ) has been investigated to study the kinetics of single peak glow curves. The material used normally exhibits one large and four small peaks. However a glow curve can be obtained with only the large single peak that is suitable for testing thermoluminescence kinetics. Glow curves from aliquots of a single natural pyrite crystal studied in detail contain two low intensity thermoluminescence (TL) peaks at ∼90 degree and ∼250 degree C, and two chemiluminescence (CL) peaks at ∼350 degree and ∼430 degree C. The CL peaks are largely removable by initially heating the sample chamber under vacuum, pumping through liquid nitrogen traps, and recording glow curves immediately after helium is introduced, procedures which reduce system contaminants that react with pyrite. The shape, the variation of the temperature of the peak maximum (T max ) with dose, and the retrapping to recombination cross section ratio σ of the large 250 degree C peak are better described by the general one trap (GOT) kinetic equation, the basic equation from which the 1st and 2nd order kinetic equations are obtained as special cases (see text), than by the 1st and 2nd order equations. 12 refs., 7 figs

  4. Proofs that Develop Insight

    Science.gov (United States)

    Weber, Keith

    2010-01-01

    Many mathematics educators have noted that mathematicians do not only read proofs to gain conviction but also to obtain insight. The goal of this article is to discuss what this insight is from mathematicians' perspective. Based on interviews with nine research-active mathematicians, two sources of insight are discussed. The first is reading a…

  5. Mediator Complex Subunits MED2, MED5, MED16, and MED23 Genetically Interact in the Regulation of Phenylpropanoid Biosynthesis.

    Science.gov (United States)

    Dolan, Whitney L; Dilkes, Brian P; Stout, Jake M; Bonawitz, Nicholas D; Chapple, Clint

    2017-12-01

    The phenylpropanoid pathway is a major global carbon sink and is important for plant fitness and the engineering of bioenergy feedstocks. In Arabidopsis thaliana , disruption of two subunits of the transcriptional regulatory Mediator complex, MED5a and MED5b, results in an increase in phenylpropanoid accumulation. By contrast, the semidominant MED5b mutation reduced epidermal fluorescence4-3 ( ref4-3 ) results in dwarfism and constitutively repressed phenylpropanoid accumulation. Here, we report the results of a forward genetic screen for suppressors of ref4-3. We identified 13 independent lines that restore growth and/or phenylpropanoid accumulation in the ref4-3 background. Two of the suppressors restore growth without restoring soluble phenylpropanoid accumulation, indicating that the growth and metabolic phenotypes of the ref4-3 mutant can be genetically disentangled. Whole-genome sequencing revealed that all but one of the suppressors carry mutations in MED5b or other Mediator subunits. RNA-seq analysis showed that the ref4-3 mutation causes widespread changes in gene expression, including the upregulation of negative regulators of the phenylpropanoid pathway, and that the suppressors reverse many of these changes. Together, our data highlight the interdependence of individual Mediator subunits and provide greater insight into the transcriptional regulation of phenylpropanoid biosynthesis by the Mediator complex. © 2017 American Society of Plant Biologists. All rights reserved.

  6. Characterization of the 1S-2S transition in antihydrogen.

    Science.gov (United States)

    Ahmadi, M; Alves, B X R; Baker, C J; Bertsche, W; Capra, A; Carruth, C; Cesar, C L; Charlton, M; Cohen, S; Collister, R; Eriksson, S; Evans, A; Evetts, N; Fajans, J; Friesen, T; Fujiwara, M C; Gill, D R; Hangst, J S; Hardy, W N; Hayden, M E; Isaac, C A; Johnson, M A; Jones, J M; Jones, S A; Jonsell, S; Khramov, A; Knapp, P; Kurchaninov, L; Madsen, N; Maxwell, D; McKenna, J T K; Menary, S; Momose, T; Munich, J J; Olchanski, K; Olin, A; Pusa, P; Rasmussen, C Ø; Robicheaux, F; Sacramento, R L; Sameed, M; Sarid, E; Silveira, D M; Stutter, G; So, C; Tharp, T D; Thompson, R I; van der Werf, D P; Wurtele, J S

    2018-05-01

    In 1928, Dirac published an equation 1 that combined quantum mechanics and special relativity. Negative-energy solutions to this equation, rather than being unphysical as initially thought, represented a class of hitherto unobserved and unimagined particles-antimatter. The existence of particles of antimatter was confirmed with the discovery of the positron 2 (or anti-electron) by Anderson in 1932, but it is still unknown why matter, rather than antimatter, survived after the Big Bang. As a result, experimental studies of antimatter 3-7 , including tests of fundamental symmetries such as charge-parity and charge-parity-time, and searches for evidence of primordial antimatter, such as antihelium nuclei, have high priority in contemporary physics research. The fundamental role of the hydrogen atom in the evolution of the Universe and in the historical development of our understanding of quantum physics makes its antimatter counterpart-the antihydrogen atom-of particular interest. Current standard-model physics requires that hydrogen and antihydrogen have the same energy levels and spectral lines. The laser-driven 1S-2S transition was recently observed 8 in antihydrogen. Here we characterize one of the hyperfine components of this transition using magnetically trapped atoms of antihydrogen and compare it to model calculations for hydrogen in our apparatus. We find that the shape of the spectral line agrees very well with that expected for hydrogen and that the resonance frequency agrees with that in hydrogen to about 5 kilohertz out of 2.5 × 10 15 hertz. This is consistent with charge-parity-time invariance at a relative precision of 2 × 10 -12 -two orders of magnitude more precise than the previous determination 8 -corresponding to an absolute energy sensitivity of 2 × 10 -20 GeV.

  7. A first principle Comparative study of electronic and optical properties of 1H –MoS2 and 2H –MoS2

    International Nuclear Information System (INIS)

    Kumar, Ashok; Ahluwalia, P.K.

    2012-01-01

    First principle calculations of electronic and optical properties of monolayer MoS 2 , so called 1H –MoS 2 , is performed which has emerged as a new direct band gap semiconductor. Before calculations of the properties of 1H –MoS 2 , we have calculated structural parameters, electronic properties (electronic band structure and electronic density of states) and frequency dependent optical response (real and imaginary part of dielectric function, energy loss function, absorption and reflectance spectra) of 2H –MoS 2 and compared with existing experimental results and found that our calculated results are in very good agreements with experimental results. To compare the dielectric functions of bulk (2H –MoS 2 ) and monolayer (1H –MoS 2 ) phases we have further extended these calculations to the single layer MoS 2 (1H –MoS 2 ) which is analogous to graphene. Structural parameters of 1H –MoS 2 are found very close to its bulk 2H –MoS 2 . We find direct electronic band gap at ‘K’ high symmetry point as compared to indirect band gap in its bulk 2H – MoS2. Our calculated dielectric function for 1H – MoS2 shows structure at nearly same energy positions as compared to 2H – MoS2 with additional structure at 3.8 eV. Also additional well defined energy loss peaks revealing the plasmonic resonances at 15.7 eV and 16.0 eV for E vector perpendicular and parallel to c axis respectively for 1H – MoS2 have been found, which are the signatures of surface plasmons at these energies. -- Highlights: ► Structural parameters of 2H-MoS2 and 1H-MoS2 are nearly identical. ► States around the Fermi energy are mainly due to the metal d states. ► Strong hybridization between Mo-d and S-p states below the Fermi energy has been found. ► Optical spectra of 2H-MoS2 finds very good agreements with experimental optical spectra. ► The band gap is found to be direct for 1H-MoS2 as compared to indirect for 2H-MoS2.

  8. The acceleration intermediate phase (NiS and Ni3S2) evolution by nanocrystallization in Li/NiS2 thermal batteries with high specific capacity

    Science.gov (United States)

    Jin, Chuanyu; Zhou, Lingping; Fu, Licai; Zhu, Jiajun; Li, Deyi; Yang, Wulin

    2017-06-01

    The intermediate phase of NiS2 is thought to be a bottleneck currently to improve the overall performance of Li/NiS2 thermal batteries because of its low conductivity and close formation enthalpy between NiS2 and the intermediate phase (NiS, Ni3S2, etc). For improving the discharge performances of Li/NiS2 thermal batteries, the nano NiS2 with an average size of 85 ± 5 nm is designated as a cathode material. The electrochemical measurements show that the specific capacity of nano NiS2 cathode is higher than micro NiS2. The nano NiS2 cathode exhibits excellent electrochemical performances with high specific capacities of 794 and 654 mAh g-1 at current density of 0.1 and 0.5 A cm-2 under a cut-off voltage of 0.5 V, respectively. These results show that the rapid intermediate phase evolution from the nanocrystallization can obviously enhance use efficiency of NiS2 and improve discharge performances of thermal batteries.

  9. Evaluation of subunit vaccines against feline immunodeficiency virus infection

    NARCIS (Netherlands)

    Horzinek, M.C.; Verschoor, E.J.; Willemse, M.J.; Stam, J.G.; Vliet, A.L.W. van; Pouwels, H.; Chalmers, S.K.; Sondermeijer, P.J.; Hesselink, W.; Ronde, A. de

    1996-01-01

    Subunit vaccines prepared against feline immunodeficiency virus (FIV) infection were evaluated in two trials. First, cats were immunized with bacterial expression products of an envelope fragment that contained the V3 neutralization domain of the FIV surface protein fused to either galactokinase

  10. Partial agonists and subunit selectivity at NMDA receptors

    DEFF Research Database (Denmark)

    Risgaard, Rune; Hansen, Kasper Bø; Clausen, Rasmus Prætorius

    2010-01-01

    Subunit-selective ligands for glutamate receptors remains an area of interest as glutamate is the major excitatory neurotransmitter in the brain and involved in a number of diseased states in the central nervous system (CNS). Few subtype-selective ligands are known, especially among the N...

  11. Therapeutic potential of Mediator complex subunits in metabolic diseases.

    Science.gov (United States)

    Ranjan, Amol; Ansari, Suraiya A

    2018-01-01

    The multisubunit Mediator is an evolutionary conserved transcriptional coregulatory complex in eukaryotes. It is needed for the transcriptional regulation of gene expression in general as well as in a gene specific manner. Mediator complex subunits interact with different transcription factors as well as components of RNA Pol II transcription initiation complex and in doing so act as a bridge between gene specific transcription factors and general Pol II transcription machinery. Specific interaction of various Mediator subunits with nuclear receptors (NRs) and other transcription factors involved in metabolism has been reported in different studies. Evidences indicate that ligand-activated NRs recruit Mediator complex for RNA Pol II-dependent gene transcription. These NRs have been explored as therapeutic targets in different metabolic diseases; however, they show side-effects as targets due to their overlapping involvement in different signaling pathways. Here we discuss the interaction of various Mediator subunits with transcription factors involved in metabolism and whether specific interaction of these transcription factors with Mediator subunits could be potentially utilized as therapeutic strategy in a variety of metabolic diseases. Copyright © 2017 Elsevier B.V. and Société Française de Biochimie et Biologie Moléculaire (SFBBM). All rights reserved.

  12. α-4 subunit of nicotinic acetylcholine receptor polymorphisms exhibit ...

    African Journals Online (AJOL)

    Background: Smoking behavior is influenced by both genetic and environmental factors. Nicotine is the major addictive substance in cigarettes. Nicotinic acetylcholine receptors (nAChRs) are thought to play an important role in nicotine addiction of smokers. One of the genes, α-4 subunit of nicotinic acetylcholine receptor ...

  13. Structural interaction of novel dendrimer and subunits with water

    African Journals Online (AJOL)

    Preferred Customer

    interaction study with solvents are essential [4-6] and several subunits are used for .... slowed down the viscous flow with higher excess limiting viscosities of the 2,4,6- ..... Practical Organic Chemistry, 5th ed.; Wiley: New York; 1989; p 300. 14.

  14. Moessbauer spectroscopic studies of hemoglobin and its isolated subunits

    International Nuclear Information System (INIS)

    Hoy, G.R.; Cook, D.C.; Berger, R.L.; Friedman, F.K.

    1986-01-01

    Samples of 90% enriched 57Fe hemoglobin and its isolated subunits have been prepared. Moessbauer spectroscopic measurements have been made on three such samples. Sample one contained contributions of oxyhemoglobin, deoxyhemoglobin, and carbonmonoxyhemoglobin. This sample was studied from a temperature of 90 K down to 230 mK. Measurements were also made at 4.2 K using a small applied magnetic field of 1.0 T. In general, the measured quadrupole splittings and isomer shifts for each component agreed with previous measurements on single component samples in the literature, and thus demonstrated that chemically enriched hemoglobin has not been altered. The second and third samples were isolated alpha and beta subunits, respectively. We have found measurable Moessbauer spectral differences between the HbO 2 sites in the alpha subunit sample and the beta subunit sample. The measured Moessbauer spectral areas indicate that the iron ion has the largest mean-square displacement at the deoxy Hb sites as compared to that at the oxy- and carbonmonoxy Hb sites. The mean-square displacement at the HbO 2 sites is the smallest

  15. N terminus of Swr1 binds to histone H2AZ and provides a platform for subunit assembly in the chromatin remodeling complex.

    Science.gov (United States)

    Wu, Wei-Hua; Wu, Chwen-Huey; Ladurner, Andreas; Mizuguchi, Gaku; Wei, Debbie; Xiao, Hua; Luk, Ed; Ranjan, Anand; Wu, Carl

    2009-03-06

    Variant histone H2AZ-containing nucleosomes are involved in the regulation of gene expression. In Saccharomyces cerevisiae, chromatin deposition of histone H2AZ is mediated by the fourteen-subunit SWR1 complex, which catalyzes ATP-dependent exchange of nucleosomal histone H2A for H2AZ. Previous work defined the role of seven SWR1 subunits (Swr1 ATPase, Swc2, Swc3, Arp6, Swc5, Yaf9, and Swc6) in maintaining complex integrity and H2AZ histone replacement activity. Here we examined the function of three additional SWR1 subunits, bromodomain containing Bdf1, actin-related protein Arp4 and Swc7, by analyzing affinity-purified mutant SWR1 complexes. We observed that depletion of Arp4 (arp4-td) substantially impaired the association of Bdf1, Yaf9, and Swc4. In contrast, loss of either Bdf1 or Swc7 had minimal effects on overall complex integrity. Furthermore, the basic H2AZ histone replacement activity of SWR1 in vitro required Arp4, but not Bdf1 or Swc7. Thus, three out of fourteen SWR1 subunits, Bdf1, Swc7, and previously noted Swc3, appear to have roles auxiliary to the basic histone replacement activity. The N-terminal region of the Swr1 ATPase subunit is necessary and sufficient to direct association of Bdf1 and Swc7, as well as Arp4, Act1, Yaf9 and Swc4. This same region contains an additional H2AZ-H2B specific binding site, distinct from the previously identified Swc2 subunit. These findings suggest that one SWR1 enzyme might be capable of binding two H2AZ-H2B dimers, and provide further insight on the hierarchy and interdependency of molecular interactions within the SWR1 complex.

  16. Stable MoS2 Field-Effect Transistors Using TiO2 Interfacial Layer at Metal/MoS2 Contact

    KAUST Repository

    Park, Woojin

    2017-09-07

    Molybdenum disulphide (MoS2) is an emerging 2-dimensional (2D) semiconductor for electronic devices. However, unstable and low performance of MoS2 FETs is an important concern. In this study, inserting an atomic layer deposition (ALD) titanium dioxide (TiO2) interfacial layer between contact metal and MoS2 channel is suggested to achieve more stable performances. The reduced threshold voltage (VTH) shift and reduced series resistance (RSD) were simultaneously achieved.

  17. Effect of high and low molecular weight glutenin subunits, and subunits of gliadin on physicochemical parameters of different wheat genotypes

    Directory of Open Access Journals (Sweden)

    Mariana Souza Costa

    2013-02-01

    Full Text Available Identification of functional properties of wheat flour by specific tests allows genotypes with appropriate characteristics to be selected for specific industrial uses. The objective of wheat breeding programs is to improve the quality of germplasm bank in order to be able to develop wheat with suitable gluten strength and extensibility for bread making. The aim of this study was to evaluate 16 wheat genotypes by correlating both glutenin subunits of high and low molecular weight and gliadin subunits with the physicochemical characteristics of the grain. Protein content, sedimentation volume, sedimentation index, and falling number values were analyzed after the grains were milled. Hectoliter weight and mass of 1000 seeds were also determined. The glutenin and gliadin subunits were separated using polyacrylamide gel in the presence of sodium dodecyl sulfate. The data were evaluated using variance analysis, Pearson's correlation, principal component analysis, and cluster analysis. The IPR 85, IPR Catuara TM, T 091015, and T 091069 genotypes stood out from the others, which indicate their possibly superior grain quality with higher sedimentation volume, higher sedimentation index, and higher mass of 1000 seeds; these genotypes possessed the subunits 1 (Glu-A1, 5 + 10 (Glu-D1, c (Glu-A3, and b (Glu-B3, with exception of T 091069 genotype that possessed the g allele instead of b in the Glu-B3.

  18. Comparison of sequences of hypervariable region (HVR subunit S-1 gene of field isolate I-37 infectious bronchitis virus with Connecticut serotype

    Directory of Open Access Journals (Sweden)

    N.L.P Indi Dharmayanti

    2003-06-01

    Full Text Available Infectious Bronchitis is a contagious and acute respiratory disease in chickens caused by infectious bronchitis virus (IBV.Antigenic differences in IBV are associated with changes in the sequence of the spike glycoprotein (S. The subunit S1 which demonstrates more sequence variability than S-2 have been identified as hypervariable region (HVR-1 and 2. There were several IB virus field isolates included I-37 have been identified in Indonesia by serum neutralization method. However, gene sequence variation in HVR subunit S-1 had not yet been identified. Isolate I-37 was close to the serotype Connecticut 46 (Conn 46. The aim of this study is to identify sequence variation of HVR subunit S-1 gene of isolate I-37 produced by Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR and sequencing. Several procedures were carried out in the study including virus titration, propagation and was concentrated from the allantoic fluid infected with IBV. Then, RNA was extracted for RTPCR. urther the product was sequnced and its homology with IBV references from GenBank was compared by GenMac version 8.0. Result showed that isolate I-37 produced 515 bp of amplification product. Isolate I-37 and Conn 46 are same serotype, yet their HVR subunit S-1 nucleotides and amino acids (protein differ by 6.9% and 15.6% respectively. It might be concluded that isolate I-37 was variant of Conn 46.

  19. Structurally Deformed MoS2 for Electrochemically Stable, Thermally Resistant, and Highly Efficient Hydrogen Evolution Reaction

    KAUST Repository

    Chen, Yen-Chang; Lu, Ang-Yu; Lu, Ping; Yang, Xiulin; Jiang, Chang-Ming; Mariano, Marina; Kaehr, Brian; Lin, Oliver; Taylor, André ; Sharp, Ian D.; Li, Lain-Jong; Chou, Stanley S.; Tung, Vincent

    2017-01-01

    The emerging molybdenum disulfide (MoS2) offers intriguing possibilities for realizing a transformative new catalyst for driving the hydrogen evolution reaction (HER). However, the trade-off between catalytic activity and long-term stability represents a formidable challenge and has not been extensively addressed. This study reports that metastable and temperature-sensitive chemically exfoliated MoS2 (ce-MoS2) can be made into electrochemically stable (5000 cycles), and thermally robust (300 °C) while maintaining synthetic scalability and excellent catalytic activity through physical-transformation into 3D structurally deformed nanostructures. The dimensional transition enabled by a high throughput electrohydrodynamic process provides highly accessible, and electrochemically active surface area and facilitates efficient transport across various interfaces. Meanwhile, the hierarchically strained morphology is found to improve electronic coupling between active sites and current collecting substrates without the need for selective engineering the electronically heterogeneous interfaces. Specifically, the synergistic combination of high strain load stemmed from capillarity-induced-self-crumpling and sulfur (S) vacancies intrinsic to chemical exfoliation enables simultaneous modulation of active site density and intrinsic HER activity regardless of continuous operation or elevated temperature. These results provide new insights into how catalytic activity, electrochemical-, and thermal stability can be concurrently enhanced through the physical transformation that is reminiscent of nature, in which properties of biological materials emerge from evolved dimensional transitions.

  20. Structurally Deformed MoS2 for Electrochemically Stable, Thermally Resistant, and Highly Efficient Hydrogen Evolution Reaction

    KAUST Repository

    Chen, Yen-Chang

    2017-10-12

    The emerging molybdenum disulfide (MoS2) offers intriguing possibilities for realizing a transformative new catalyst for driving the hydrogen evolution reaction (HER). However, the trade-off between catalytic activity and long-term stability represents a formidable challenge and has not been extensively addressed. This study reports that metastable and temperature-sensitive chemically exfoliated MoS2 (ce-MoS2) can be made into electrochemically stable (5000 cycles), and thermally robust (300 °C) while maintaining synthetic scalability and excellent catalytic activity through physical-transformation into 3D structurally deformed nanostructures. The dimensional transition enabled by a high throughput electrohydrodynamic process provides highly accessible, and electrochemically active surface area and facilitates efficient transport across various interfaces. Meanwhile, the hierarchically strained morphology is found to improve electronic coupling between active sites and current collecting substrates without the need for selective engineering the electronically heterogeneous interfaces. Specifically, the synergistic combination of high strain load stemmed from capillarity-induced-self-crumpling and sulfur (S) vacancies intrinsic to chemical exfoliation enables simultaneous modulation of active site density and intrinsic HER activity regardless of continuous operation or elevated temperature. These results provide new insights into how catalytic activity, electrochemical-, and thermal stability can be concurrently enhanced through the physical transformation that is reminiscent of nature, in which properties of biological materials emerge from evolved dimensional transitions.

  1. 2D molybdenum disulphide (2D-MoS2) modified electrodes explored towards the oxygen reduction reaction

    Science.gov (United States)

    Rowley-Neale, Samuel J.; Fearn, Jamie M.; Brownson, Dale A. C.; Smith, Graham C.; Ji, Xiaobo; Banks, Craig E.

    2016-08-01

    Two-dimensional molybdenum disulphide nanosheets (2D-MoS2) have proven to be an effective electrocatalyst, with particular attention being focused on their use towards increasing the efficiency of the reactions associated with hydrogen fuel cells. Whilst the majority of research has focused on the Hydrogen Evolution Reaction (HER), herein we explore the use of 2D-MoS2 as a potential electrocatalyst for the much less researched Oxygen Reduction Reaction (ORR). We stray from literature conventions and perform experiments in 0.1 M H2SO4 acidic electrolyte for the first time, evaluating the electrochemical performance of the ORR with 2D-MoS2 electrically wired/immobilised upon several carbon based electrodes (namely; Boron Doped Diamond (BDD), Edge Plane Pyrolytic Graphite (EPPG), Glassy Carbon (GC) and Screen-Printed Electrodes (SPE)) whilst exploring a range of 2D-MoS2 coverages/masses. Consequently, the findings of this study are highly applicable to real world fuel cell applications. We show that significant improvements in ORR activity can be achieved through the careful selection of the underlying/supporting carbon materials that electrically wire the 2D-MoS2 and utilisation of an optimal mass of 2D-MoS2. The ORR onset is observed to be reduced to ca. +0.10 V for EPPG, GC and SPEs at 2D-MoS2 (1524 ng cm-2 modification), which is far closer to Pt at +0.46 V compared to bare/unmodified EPPG, GC and SPE counterparts. This report is the first to demonstrate such beneficial electrochemical responses in acidic conditions using a 2D-MoS2 based electrocatalyst material on a carbon-based substrate (SPEs in this case). Investigation of the beneficial reaction mechanism reveals the ORR to occur via a 4 electron process in specific conditions; elsewhere a 2 electron process is observed. This work offers valuable insights for those wishing to design, fabricate and/or electrochemically test 2D-nanosheet materials towards the ORR.Two-dimensional molybdenum disulphide nanosheets

  2. Highly Enhanced Gas Adsorption Properties in Vertically Aligned MoS2 Layers.

    Science.gov (United States)

    Cho, Soo-Yeon; Kim, Seon Joon; Lee, Youhan; Kim, Jong-Seon; Jung, Woo-Bin; Yoo, Hae-Wook; Kim, Jihan; Jung, Hee-Tae

    2015-09-22

    In this work, we demonstrate that gas adsorption is significantly higher in edge sites of vertically aligned MoS2 compared to that of the conventional basal plane exposed MoS2 films. To compare the effect of the alignment of MoS2 on the gas adsorption properties, we synthesized three distinct MoS2 films with different alignment directions ((1) horizontally aligned MoS2 (basal plane exposed), (2) mixture of horizontally aligned MoS2 and vertically aligned layers (basal and edge exposed), and (3) vertically aligned MoS2 (edge exposed)) by using rapid sulfurization method of CVD process. Vertically aligned MoS2 film shows about 5-fold enhanced sensitivity to NO2 gas molecules compared to horizontally aligned MoS2 film. Vertically aligned MoS2 has superior resistance variation compared to horizontally aligned MoS2 even with same surface area exposed to identical concentration of gas molecules. We found that electrical response to target gas molecules correlates directly with the density of the exposed edge sites of MoS2 due to high adsorption of gas molecules onto edge sites of vertically aligned MoS2. Density functional theory (DFT) calculations corroborate the experimental results as stronger NO2 binding energies are computed for multiple configurations near the edge sites of MoS2, which verifies that electrical response to target gas molecules (NO2) correlates directly with the density of the exposed edge sites of MoS2 due to high adsorption of gas molecules onto edge sites of vertically aligned MoS2. We believe that this observation extends to other 2D TMD materials as well as MoS2 and can be applied to significantly enhance the gas sensor performance in these materials.

  3. Improved wavelengths for the 1s2s3S1-1s2p3P0,2 transitions in helium-like Si12+

    International Nuclear Information System (INIS)

    Armour, I.A.; Myers, E.G.; Silver, J.D.; Traebert, E.; Oxford Univ.

    1979-01-01

    The wavelengths of the 1s2s 3 S 1 -1s2p 3 P 0 , 2 transitions in He-like Si 12+ have been remaesured to be 87.86 +- 0.01 nm and 81.48 +- 0.01 nm. The use of Rydberg lines for the calibration of fast beam spectra is discussed. (orig.)

  4. Electrophysiology and Beyond: Multiple roles of Na+ channel β subunits in development and disease

    Science.gov (United States)

    Patino, Gustavo A.; Isom, Lori L.

    2010-01-01

    Voltage-gated Na+ channel (VGSC) β subunits are not “auxiliary.” These multifunctional molecules not only modulate Na+ current (INa), but also function as cell adhesion molecules (CAMs) – playing roles in aggregation, migration, invasion, neurite outgrowth, and axonal fasciculation. β subunits are integral members of VGSC signaling complexes at nodes of Ranvier, axon initial segments, and cardiac intercalated disks, regulating action potential propagation through critical intermolecular and cell-cell communication events. At least in vitro, many β subunit cell adhesive functions occur both in the presence and absence of pore-forming VGSC α subunits, and in vivo β subunits are expressed in excitable as well as non-excitable cells, thus β subunits may play important functional roles on their own, in the absence of α subunits. VGSC β1 subunits are essential for life and appear to be especially important during brain development. Mutations in β subunit genes result in a variety of human neurological and cardiovascular diseases. Moreover, some cancer cells exhibit alterations in β subunit expression during metastasis. In short, these proteins, originally thought of as merely accessory to α subunits, are critical players in their own right in human health and disease. Here we discuss the role of VGSC β subunits in the nervous system. PMID:20600605

  5. Characterization of the interaction between the cohesin subunits Rad21 and SA1/2.

    Directory of Open Access Journals (Sweden)

    Nenggang Zhang

    Full Text Available The cohesin complex is responsible for the fidelity of chromosomal segregation during mitosis. It consists of four core subunits, namely Rad21/Mcd1/Scc1, Smc1, Smc3, and one of the yeast Scc3 orthologs SA1 or SA2. Sister chromatid cohesion is generated during DNA replication and maintained until the onset of anaphase. Among the many proposed models of the cohesin complex, the 'core' cohesin subunits Smc1, Smc3, and Rad21 are almost universally displayed as tripartite ring. However, other than its supportive role in the cohesin ring, little is known about the fourth core subunit SA1/SA2. To gain deeper insight into the function of SA1/SA2 in the cohesin complex, we have mapped the interactive regions of SA2 and Rad21 in vitro and ex vivo. Whereas SA2 interacts with Rad21 through a broad region (301-750 aa, Rad21 binds to SA proteins through two SA-binding motifs on Rad21, namely N-terminal (NT and middle part (MP SA-binding motif, located at 60-81 aa of the N-terminus and 383-392 aa of the MP of Rad21, respectively. The MP SA-binding motif is a 10 amino acid, α-helical motif. Deletion of these 10 amino acids or mutation of three conserved amino acids (L(385, F(389, and T(390 in this α-helical motif significantly hinders Rad21 from physically interacting with SA1/2. Besides the MP SA-binding motif, the NT SA-binding motif is also important for SA1/2 interaction. Although mutations on both SA-binding motifs disrupt Rad21-SA1/2 interaction, they had no apparent effect on the Smc1-Smc3-Rad21 interaction. However, the Rad21-Rad21 dimerization was reduced by the mutations, indicating potential involvement of the two SA-binding motifs in the formation of the two-ring handcuff for chromosomal cohesion. Furthermore, mutant Rad21 proteins failed to significantly rescue precocious chromosome separation caused by depletion of endogenous Rad21 in mitotic cells, further indicating the physiological significance of the two SA-binding motifs of Rad21.

  6. In Search of Insight.

    Science.gov (United States)

    Kaplan, Craig A.; Simon, Herbert A.

    1990-01-01

    Attaining the insight needed to solve the Mutilated Checkerboard problem, which requires discovery of an effective problem representation (EPR), is described. Performance on insight problems can be predicted from the availability of generators and constraints in the search for an EPR. Data for 23 undergraduates were analyzed. (TJH)

  7. Protein kinase A regulatory subunit distribution in medulloblastoma

    International Nuclear Information System (INIS)

    Mucignat-Caretta, Carla; Denaro, Luca; Redaelli, Marco; D'Avella, Domenico; Caretta, Antonio

    2010-01-01

    Previous studies showed a differential distribution of the four regulatory subunits of cAMP-dependent protein kinases inside the brain, that changed in rodent gliomas: therefore, the distribution of these proteins inside the brain can give information on the functional state of the cells. Our goal was to examine human brain tumors to provide evidence for a differential distribution of protein kinase A in different tumors. The distribution of detergent insoluble regulatory (R1 and R2) and catalytic subunits of cAMP dependent kinases was examined in pediatric brain tumors by immunohistochemistry and fluorescent cAMP analogues binding. R2 is organized in large single dots in medulloblastomas, while it has a different appearance in other tumors. Fluorescent cAMP labelling was observed only in medulloblastoma. A different distribution of cAMP dependent protein kinases has been observed in medulloblastoma

  8. Testing experimental subunit furunculosis vaccines for rainbow trout

    DEFF Research Database (Denmark)

    Marana, Moonika H.; Chettri, Jiwan Kumar; Skov, Jakob

    2016-01-01

    Aeromonas salmonicida subsp. salmonicida (AS) is the etiological agent of typical furunculosis in salmonid fish. The disease causes bacterial septicemia and is a major fish health problem in salmonid aquaculture worldwide, inducing high morbidity and mortality. In this study we vaccinated rainbow...... trout with subunit vaccines containing protein antigens that were selected based on an in silico antigen discovery approach. Thus, the proteome of AS strain A449 was analyzed by an antigen discovery platform and its proteins consequently ranked by their predicted ability to evoke protective immune...... response against AS. Fourteen proteins were prepared in 3 different experimental subunit vaccine combinations and used to vaccinate rainbow trout by intraperitoneal (i.p.) injection. We tested the proteins for their ability to elicit antibody production and protection. Thus, fish were exposed to virulent...

  9. Mapping of the Mouse Actin Capping Protein Beta Subunit Gene

    Directory of Open Access Journals (Sweden)

    Cooper John A

    2000-07-01

    Full Text Available Abstract Background Capping protein (CP, a heterodimer of α and β subunits, is found in all eukaryotes. CP binds to the barbed ends of actin filaments in vitro and controls actin assembly and cell motility in vivo. Vertebrates have three isoforms of CPβ produced by alternatively splicing from one gene; lower organisms have one gene and one isoform. Results We isolated genomic clones corresponding to the β subunit of mouse CP and identified its chromosomal location by interspecies backcross mapping. Conclusions The CPβ gene (Cappb1 mapped to Chromosome 4 between Cdc42 and D4Mit312. Three mouse mutations, snubnose, curly tail, and cribriform degeneration, map in the vicinity of the β gene.

  10. Adsorption of DNA/RNA nucleobases onto single-layer MoS2 and Li-Doped MoS2: A dispersion-corrected DFT study

    Science.gov (United States)

    Sadeghi, Meisam; Jahanshahi, Mohsen; Ghorbanzadeh, Morteza; Najafpour, Ghasem

    2018-03-01

    The kind of sensing platform in nano biosensor plays an important role in nucleic acid sequence detection. It has been demonstrated that graphene does not have an intrinsic band gap; therefore, transition metal dichalcogenides (TMDs) are desirable materials for electronic base detection. In the present work, a comparative study of the adsorption of the DNA/RNA nucleobases [Adenine (A), Cytosine (C) Guanine (G), Thymine (T) and Uracil (U)] onto the single-layer molybdenum disulfide (MoS2) and Li-doped MoS2 (Li-MoS2) as a sensing surfaces was investigated by using Dispersion-corrected Density Functional Theory (D-DFT) calculations and different measure of equilibrium distances, charge transfers and binding energies for the various nucleobases were calculated. The results revealed that the interactions between the nucleobases and the MoS2 can be strongly enhanced by introducing metal atom, due to significant charge transfer from the Li atom to the MoS2 when Lithium is placed on top of the MoS2. Furthermore, the binding energies of the five nucleobases were in the range of -0.734 to -0.816 eV for MoS2 and -1.47 to -1.80 eV for the Li-MoS2. Also, nucleobases were adsorbed onto MoS2 sheets via the van der Waals (vdW) force. This high affinity and the renewable properties of the biosensing platform demonstrated that Li-MoS2 nanosheet is biocompatible and suitable for nucleic acid analysis.

  11. Chloride channels in the plasma membrane of a foetal Drosophila cell line, S2

    DEFF Research Database (Denmark)

    Asmild, Margit; Willumsen, Niels J.

    2000-01-01

    S2 cells, Cl- Channels, Expression system, Drosophila, Inward rectifier, Outward rectifier, Patch clamp......S2 cells, Cl- Channels, Expression system, Drosophila, Inward rectifier, Outward rectifier, Patch clamp...

  12. Deep-level transient spectroscopy of TiO2/CuInS2 heterojunctions

    NARCIS (Netherlands)

    Nanu, M.; Boulch, F.; Schoonman, J.; Goossens, A.

    2005-01-01

    Deep-level transient spectroscopy (DLTS) has been used to measure the concentration and energy position of deep electronic states in CuInS2. Flat TiO2?CuInS2 heterojunctions as well as TiO2-CuInS2 nanocomposites have been investigated. Subband-gap electronic states in CuInS2 films are mostly due to

  13. Cryo-EM Structure of the Archaeal 50S Ribosomal Subunit in Complex with Initiation Factor 6 and Implications for Ribosome Evolution

    Science.gov (United States)

    Greber, Basil J.; Boehringer, Daniel; Godinic-Mikulcic, Vlatka; Crnkovic, Ana; Ibba, Michael; Weygand-Durasevic, Ivana; Ban, Nenad

    2013-01-01

    Translation of mRNA into proteins by the ribosome is universally conserved in all cellular life. The composition and complexity of the translation machinery differ markedly between the three domains of life. Organisms from the domain Archaea show an intermediate level of complexity, sharing several additional components of the translation machinery with eukaryotes that are absent in bacteria. One of these translation factors is initiation factor 6 (IF6), which associates with the large ribosomal subunit. We have reconstructed the 50S ribosomal subunit from the archaeon Methanothermobacter thermautotrophicus in complex with archaeal IF6 at 6.6 Å resolution using cryo-electron microscopy (EM). The structure provides detailed architectural insights into the 50S ribosomal subunit from a methanogenic archaeon through identification of the rRNA expansion segments and ribosomal proteins that are shared between this archaeal ribosome and eukaryotic ribosomes but are mostly absent in bacteria and in some archaeal lineages. Furthermore, the structure reveals that, in spite of highly divergent evolutionary trajectories of the ribosomal particle and the acquisition of novel functions of IF6 in eukaryotes, the molecular binding of IF6 on the ribosome is conserved between eukaryotes and archaea. The structure also provides a snapshot of the reductive evolution of the archaeal ribosome and offers new insights into the evolution of the translation system in archaea. PMID:22306461

  14. Global Proteome Analysis Identifies Active Immunoproteasome Subunits in Human Platelets*

    Science.gov (United States)

    Klockenbusch, Cordula; Walsh, Geraldine M.; Brown, Lyda M.; Hoffman, Michael D.; Ignatchenko, Vladimir; Kislinger, Thomas; Kast, Juergen

    2014-01-01

    The discovery of new functions for platelets, particularly in inflammation and immunity, has expanded the role of these anucleate cell fragments beyond their primary hemostatic function. Here, four in-depth human platelet proteomic data sets were generated to explore potential new functions for platelets based on their protein content and this led to the identification of 2559 high confidence proteins. During a more detailed analysis, consistently high expression of the proteasome was discovered, and the composition and function of this complex, whose role in platelets has not been thoroughly investigated, was examined. Data set mining resulted in identification of nearly all members of the 26S proteasome in one or more data sets, except the β5 subunit. However, β5i, a component of the immunoproteasome, was identified. Biochemical analyses confirmed the presence of all catalytically active subunits of the standard 20S proteasome and immunoproteasome in human platelets, including β5, which was predominantly found in its precursor form. It was demonstrated that these components were assembled into the proteasome complex and that standard proteasome as well as immunoproteasome subunits were constitutively active in platelets. These findings suggest potential new roles for platelets in the immune system. For example, the immunoproteasome may be involved in major histocompatibility complex I (MHC I) peptide generation, as the MHC I machinery was also identified in our data sets. PMID:25146974

  15. Global proteome analysis identifies active immunoproteasome subunits in human platelets.

    Science.gov (United States)

    Klockenbusch, Cordula; Walsh, Geraldine M; Brown, Lyda M; Hoffman, Michael D; Ignatchenko, Vladimir; Kislinger, Thomas; Kast, Juergen

    2014-12-01

    The discovery of new functions for platelets, particularly in inflammation and immunity, has expanded the role of these anucleate cell fragments beyond their primary hemostatic function. Here, four in-depth human platelet proteomic data sets were generated to explore potential new functions for platelets based on their protein content and this led to the identification of 2559 high confidence proteins. During a more detailed analysis, consistently high expression of the proteasome was discovered, and the composition and function of this complex, whose role in platelets has not been thoroughly investigated, was examined. Data set mining resulted in identification of nearly all members of the 26S proteasome in one or more data sets, except the β5 subunit. However, β5i, a component of the immunoproteasome, was identified. Biochemical analyses confirmed the presence of all catalytically active subunits of the standard 20S proteasome and immunoproteasome in human platelets, including β5, which was predominantly found in its precursor form. It was demonstrated that these components were assembled into the proteasome complex and that standard proteasome as well as immunoproteasome subunits were constitutively active in platelets. These findings suggest potential new roles for platelets in the immune system. For example, the immunoproteasome may be involved in major histocompatibility complex I (MHC I) peptide generation, as the MHC I machinery was also identified in our data sets. © 2014 by The American Society for Biochemistry and Molecular Biology, Inc.

  16. Radioimmunoassay of TSH subunits in thyroid diseases and endocrine opthalmopahty

    International Nuclear Information System (INIS)

    Eder, W.

    1982-01-01

    Highly sensitive radioimmunoassays of hTSH sub-units were developed. The hormone preparations were labelled with 125-iodine according to a modified chloramine -T method, and purified by chromatography using biogel P6 and P60. Rabbit antisera were used as antibodies. Separation of the antibody-bound and of the free antigens was carried out via the double antibody method. The antiserum required for this purpose was obtained from a goat. The sensitivity of the assay was influenced by changing the protein content of the buffer, the incubation volume, the tracer amounts, the incubation time and the incubation temperature. For hTSH-α, the lowest detectable limit was found to be 50 pg/ml, for hTSH-#betta# 20 pg/ml. Thus, the sub-units could be determined for 98% of the patients under review. The #betta#-TSH radioimmunoassay is largely specific, TSH cross-reacts to a degree of 5%. The computerized evoluation was carried out by means of Spline approximation using the Siemens 4004 computer. Precision and accurateness are in compliance with generally accpted criteria. The serum levels of α and #betta# sub-units showed no discordancy with regard to TSH. In all groups of patients examined, the levels of the hormone-specific #betta#-chain were found to be exclusively dependent upon the actual thyroid activity. (orig.) [de

  17. Rendering high charge density of states in ionic liquid-gated MoS 2 transistors

    NARCIS (Netherlands)

    Lee, Y.; Lee, J.; Kim, S.; Park, H.S.

    2014-01-01

    We investigated high charge density of states (DOS) in the bandgap of MoS2 nanosheets with variable temperature measurements on ionic liquid-gated MoS2 transistors. The thermally activated charge transport indicates that the electrical current in the two-dimensional MoS 2 nanosheets under high

  18. The cytochrome oxidase subunit I and subunit III genes in Oenothera mitochondria are transcribed from identical promoter sequences

    Science.gov (United States)

    Hiesel, Rudolf; Schobel, Werner; Schuster, Wolfgang; Brennicke, Axel

    1987-01-01

    Two loci encoding subunit III of the cytochrome oxidase (COX) in Oenothera mitochondria have been identified from a cDNA library of mitochondrial transcripts. A 657-bp sequence block upstream from the open reading frame is also present in the two copies of the COX subunit I gene and is presumably involved in homologous sequence rearrangement. The proximal points of sequence rearrangements are located 3 bp upstream from the COX I and 1139 bp upstream from the COX III initiation codons. The 5'-termini of both COX I and COX III mRNAs have been mapped in this common sequence confining the promoter region for the Oenothera mitochondrial COX I and COX III genes to the homologous sequence block. ImagesFig. 5. PMID:15981332

  19. Edge passivation induced single-edge ferromagnetism of zigzag MoS_2 nanoribbons

    International Nuclear Information System (INIS)

    Wang, Rui; Sun, Hui; Ma, Ben; Hu, Jingguo; Pan, Jing

    2017-01-01

    We performed density functional theory study on electronic structure, magnetic properties and stability of zigzag MoS_2 nanoribbons (ZMoS_2NRs) with and without oxygen (O) passivation. The bare ZMoS_2NRs are magnetic metal with ferromagnetic edge states, edge passivation decreases their magnetism because of the decrease of edge unsaturated electrons. Obviously, the electronic structure and magnetic properties of ZMoS_2NRs greatly depend on edge states. When both edges are passivated by O atoms, ZMoS_2NRs are nonmagnetic metals. When either edge is passivated by O atoms, the systems exhibit single-edge ferromagnetism and magnetism concentrates on the non-passivated edge. Edge passivation can not only tune the magnetism of ZMoS_2NRs, but also enhance their stability by eliminating dangling bonds. These interesting findings on ZMoS_2NRs may open the possibility of their application in nanodevices and spintronics. - Highlights: • Edge passivation for tuning magnetism of zigzag MoS_2 nanoribbons (ZMoS_2NRs) is proposed. • Edge passivation can tune ZMoS_2NRs from nonmagnetic metal to ferromagnetic metal. • When either edge is passivated, the systems exhibit single-edge ferromagnetic states. • These findings may inspire great interest in the community of ZMoS_2NRs and motivate numerous experimental researches.

  20. High conductivity graphene-like MoS2/polyaniline nanocomposites and its application in supercapacitor

    International Nuclear Information System (INIS)

    Wang, Jin; Wu, Zongchao; Hu, Kunhong; Chen, Xiangying; Yin, Huabing

    2015-01-01

    Highlights: • A facile synthesis method of MoS 2 /PANI intercalated nanocomposites is developed. • There is synergistic effect between PANI and MoS 2 layer in the MoS 2 /PANI composites. • Intercalation is benefit for electrons transportation and conductivity increase. • The well-defined MoS 2 /PANI have good specific capacitances and long cyclic life. - Abstract: High conductivity nanocomposites of molybdenum disulfide (MoS 2 )/polyaniline (PANI) were prepared via direct intercalation of aniline monomer and doped with dodecyl benzene sulfonic acid (DBSA). The intercalated interaction between PANI and MoS 2 improves the conductivity and thermal stability of MoS 2 /PANI nanocomposites with the increasing fraction of MoS 2 . The conductivity and maximum weight loss velocity temperature of PANI/MoS 2 -38 sample are 2.38 S cm −1 and 353 °C, respectively. This architecture is also advantageous for enhancing the capacitance properties and cyclic stabilities of MoS 2 /PANI electrodes. In comparison to the specific capacitance of 131 F/g and 42% retained capacitance over 600 cycles of PANI electrode, the MoS 2 /PANI-38 electrode provides a specific capacitance up to 390 F/g and 86% retained capacitance over 1000 cycles. Thus it provides an improved capacitance method which synergistically combines pseudocapacitance and double-layer capacitance for supercapacitor electrodes

  1. Identification and characterization of the donkey CSN1S2 I and II cDNAs

    Directory of Open Access Journals (Sweden)

    Davide Nicodemo

    2010-04-01

    Full Text Available The αs2 casein, encoded by the CSN1S2 gene, is one of the three Calcium sensitive caseins present in the milk of ruminants of zootechnical interest and in the milk of Equidae species (horse and donkey. In the present study, we cloned, sequenced and analysed two different donkey CSN1S2 cDNAs that we called CSN1S2 I and CSN1S2 II. The first, which spans over a fragment of 1016 nt, is constituted by 19 exons and encodes for a predicted protein (called αs2-I of 221 aminoacids; the second, of which we determined the entire sequence (16 exons, encodes for a predicted peptide (called αs2-II of 168 aminoacids. Alternative splicing and genetic markers are reported for both genes.

  2. Tailored MoS2 nanorods: a simple microwave assisted synthesis

    Science.gov (United States)

    Reshmi, S.; Akshaya, M. V.; Satpati, Biswarup; Roy, Anupam; Basu, Palash Kumar; Bhattacharjee, K.

    2017-11-01

    We report here the synthesis of MoS2 nanostructures by a simple liquid phase exfoliation of MoS2 powder in organic solvents followed by microwave treatment. The probe sonication and the microwave treatment play an important role in rolling and curling of the MoS2 nanosheets to give rise to MoS2 spheres and rod/tube like-structures with diameter approximately 150-200 nm. The MoS2 nanorods formed in this fashion are hollow inside with a wall thickness of 15-20 nm and the length of the nanorods is found in the order of several micrometers. Synthesis of such tailored MoS2 nanorods by liquid phase exfoliation is not yet reported. Our observations suggest the 2H phase of bulk MoS2 remains preserved in the nanostructures with high crystalline quality.

  3. Cryo-EM structure of the archaeal 50S ribosomal subunit in complex with initiation factor 6 and implications for ribosome evolution

    DEFF Research Database (Denmark)

    Greber, Basil J; Boehringer, Daniel; Godinic-Mikulcic, Vlatka

    2012-01-01

    additional components of the translation machinery with eukaryotes that are absent in bacteria. One of these translation factors is initiation factor 6 (IF6), which associates with the large ribosomal subunit. We have reconstructed the 50S ribosomal subunit from the archaeon Methanothermobacter...... between this archaeal ribosome and eukaryotic ribosomes but are mostly absent in bacteria and in some archaeal lineages. Furthermore, the structure reveals that, in spite of highly divergent evolutionary trajectories of the ribosomal particle and the acquisition of novel functions of IF6 in eukaryotes......, the molecular binding of IF6 on the ribosome is conserved between eukaryotes and archaea. The structure also provides a snapshot of the reductive evolution of the archaeal ribosome and offers new insights into the evolution of the translation system in archaea....

  4. Stable MoS2 Field-Effect Transistors Using TiO2 Interfacial Layer at Metal/MoS2 Contact

    KAUST Repository

    Park, Woojin; Min, Jung-Wook; Shaikh, Sohail F.; Hussain, Muhammad Mustafa

    2017-01-01

    dioxide (TiO2) interfacial layer between contact metal and MoS2 channel is suggested to achieve more stable performances. The reduced threshold voltage (VTH) shift and reduced series resistance (RSD) were simultaneously achieved.

  5. Functional mapping of the fission yeast DNA polymerase δ B-subunit Cdc1 by site-directed and random pentapeptide insertion mutagenesis

    Directory of Open Access Journals (Sweden)

    Gray Fiona C

    2009-08-01

    Full Text Available Abstract Background DNA polymerase δ plays an essential role in chromosomal DNA replication in eukaryotic cells, being responsible for synthesising the bulk of the lagging strand. In fission yeast, Pol δ is a heterotetrameric enzyme comprising four evolutionarily well-conserved proteins: the catalytic subunit Pol3 and three smaller subunits Cdc1, Cdc27 and Cdm1. Pol3 binds directly to the B-subunit, Cdc1, which in turn binds the C-subunit, Cdc27. Human Pol δ comprises the same four subunits, and the crystal structure was recently reported of a complex of human p50 and the N-terminal domain of p66, the human orthologues of Cdc1 and Cdc27, respectively. Results To gain insights into the structure and function of Cdc1, random and directed mutagenesis techniques were used to create a collection of thirty alleles encoding mutant Cdc1 proteins. Each allele was tested for function in fission yeast and for binding of the altered protein to Pol3 and Cdc27 using the two-hybrid system. Additionally, the locations of the amino acid changes in each protein were mapped onto the three-dimensional structure of human p50. The results obtained from these studies identify amino acid residues and regions within the Cdc1 protein that are essential for interaction with Pol3 and Cdc27 and for in vivo function. Mutations specifically defective in Pol3-Cdc1 interactions allow the identification of a possible Pol3 binding surface on Cdc1. Conclusion In the absence of a three-dimensional structure of the entire Pol δ complex, the results of this study highlight regions in Cdc1 that are vital for protein function in vivo and provide valuable clues to possible protein-protein interaction surfaces on the Cdc1 protein that will be important targets for further study.

  6. Structure-function analysis and genetic interactions of the SmG, SmE, and SmF subunits of the yeast Sm protein ring.

    Science.gov (United States)

    Schwer, Beate; Kruchten, Joshua; Shuman, Stewart

    2016-09-01

    A seven-subunit Sm protein ring forms a core scaffold of the U1, U2, U4, and U5 snRNPs that direct pre-mRNA splicing. Using human snRNP structures to guide mutagenesis in Saccharomyces cerevisiae, we gained new insights into structure-function relationships of the SmG, SmE, and SmF subunits. An alanine scan of 19 conserved amino acids of these three proteins, comprising the Sm RNA binding sites or inter-subunit interfaces, revealed that, with the exception of Arg74 in SmF, none are essential for yeast growth. Yet, for SmG, SmE, and SmF, as for many components of the yeast spliceosome, the effects of perturbing protein-RNA and protein-protein interactions are masked by built-in functional redundancies of the splicing machine. For example, tests for genetic interactions with non-Sm splicing factors showed that many benign mutations of SmG, SmE, and SmF (and of SmB and SmD3) were synthetically lethal with null alleles of U2 snRNP subunits Lea1 and Msl1. Tests of pairwise combinations of SmG, SmE, SmF, SmB, and SmD3 alleles highlighted the inherent redundancies within the Sm ring, whereby simultaneous mutations of the RNA binding sites of any two of the Sm subunits are lethal. Our results suggest that six intact RNA binding sites in the Sm ring suffice for function but five sites may not. © 2016 Schwer et al.; Published by Cold Spring Harbor Laboratory Press for the RNA Society.

  7. Structure–function analysis and genetic interactions of the SmG, SmE, and SmF subunits of the yeast Sm protein ring

    Science.gov (United States)

    Schwer, Beate; Kruchten, Joshua; Shuman, Stewart

    2016-01-01

    A seven-subunit Sm protein ring forms a core scaffold of the U1, U2, U4, and U5 snRNPs that direct pre-mRNA splicing. Using human snRNP structures to guide mutagenesis in Saccharomyces cerevisiae, we gained new insights into structure–function relationships of the SmG, SmE, and SmF subunits. An alanine scan of 19 conserved amino acids of these three proteins, comprising the Sm RNA binding sites or inter-subunit interfaces, revealed that, with the exception of Arg74 in SmF, none are essential for yeast growth. Yet, for SmG, SmE, and SmF, as for many components of the yeast spliceosome, the effects of perturbing protein–RNA and protein–protein interactions are masked by built-in functional redundancies of the splicing machine. For example, tests for genetic interactions with non-Sm splicing factors showed that many benign mutations of SmG, SmE, and SmF (and of SmB and SmD3) were synthetically lethal with null alleles of U2 snRNP subunits Lea1 and Msl1. Tests of pairwise combinations of SmG, SmE, SmF, SmB, and SmD3 alleles highlighted the inherent redundancies within the Sm ring, whereby simultaneous mutations of the RNA binding sites of any two of the Sm subunits are lethal. Our results suggest that six intact RNA binding sites in the Sm ring suffice for function but five sites may not. PMID:27417296

  8. Magnetism by interfacial hybridization and p-type doping of MoS2 in Fe4N/MoS2 superlattices: A first-principles study

    KAUST Repository

    Feng, Nan

    2014-03-26

    Magnetic and electronic properties of Fe4N(111)/MoS 2(√3 × √3) superlattices are investigated by first-principles calculations, considering two models: (I) FeIFe II-S and (II) N-S interfaces, each with six stacking configurations. In model I, strong interfacial hybridization between FeI/Fe II and S results in magnetism of monolayer MoS2, with a magnetic moment of 0.33 μB for Mo located on top of Fe I. For model II, no magnetism is induced due to weak N-S interfacial bonding, and the semiconducting nature of monolayer MoS2 is preserved. Charge transfer between MoS2 and N results in p-type MoS2 with Schottky barrier heights of 0.5-0.6 eV. Our results demonstrate that the interfacial geometry and hybridization can be used to tune the magnetism and doping in Fe4N(111)/MoS2(√3 × √3) superlattices. © 2014 American Chemical Society.

  9. Magnetism by interfacial hybridization and p-type doping of MoS2 in Fe4N/MoS2 superlattices: A first-principles study

    KAUST Repository

    Feng, Nan; Mi, Wenbo; Cheng, Yingchun; Guo, Zaibing; Schwingenschlö gl, Udo; Bai, Haili

    2014-01-01

    Magnetic and electronic properties of Fe4N(111)/MoS 2(√3 × √3) superlattices are investigated by first-principles calculations, considering two models: (I) FeIFe II-S and (II) N-S interfaces, each with six stacking configurations. In model I, strong interfacial hybridization between FeI/Fe II and S results in magnetism of monolayer MoS2, with a magnetic moment of 0.33 μB for Mo located on top of Fe I. For model II, no magnetism is induced due to weak N-S interfacial bonding, and the semiconducting nature of monolayer MoS2 is preserved. Charge transfer between MoS2 and N results in p-type MoS2 with Schottky barrier heights of 0.5-0.6 eV. Our results demonstrate that the interfacial geometry and hybridization can be used to tune the magnetism and doping in Fe4N(111)/MoS2(√3 × √3) superlattices. © 2014 American Chemical Society.

  10. Shake-up transitions in S 2p, S 2s and F 1s photoionization of the SF6 molecule

    International Nuclear Information System (INIS)

    Decleva, P; Fronzoni, G; Kivimaeki, A; Alvarez Ruiz, J; Svensson, S

    2009-01-01

    Shake-up transitions occurring upon core photoionization in the SF 6 molecule have been studied experimentally and theoretically. The S 2p, S 2s and F 1s shake-up satellite photoelectron spectra were measured using Al Ka radiation at 1487 eV photon energy. They have been interpreted with the aid of ab initio configuration interaction calculations in the sudden-limit approximation. For the S 2p spectrum, conjugate shake-up transitions were also calculated. Clear evidence of conjugate processes is observed in the S 2p shake-up spectrum measured at 230 eV photon energy. The experimental and theoretical S 2p and S 2s shake-up spectra show very similar structures mainly due to orbital relaxation involving S 3s and 3p participation. For the calculation of the F 1s shake-up spectrum, the symmetry lowering of the molecule in the final states was considered, resulting in a good agreement with the experiment.

  11. Confocal absorption spectral imaging of MoS2: optical transitions depending on the atomic thickness of intrinsic and chemically doped MoS2.

    Science.gov (United States)

    Dhakal, Krishna P; Duong, Dinh Loc; Lee, Jubok; Nam, Honggi; Kim, Minsu; Kan, Min; Lee, Young Hee; Kim, Jeongyong

    2014-11-07

    We performed a nanoscale confocal absorption spectral imaging to obtain the full absorption spectra (over the range 1.5-3.2 eV) within regions having different numbers of layers and studied the variation of optical transition depending on the atomic thickness of the MoS2 film. Three distinct absorption bands corresponding to A and B excitons and a high-energy background (BG) peak at 2.84 eV displayed a gradual redshift as the MoS2 film thickness increased from the monolayer, to the bilayer, to the bulk MoS2 and this shift was attributed to the reduction of the gap energy in the Brillouin zone at the K-point as the atomic thickness increased. We also performed n-type chemical doping of MoS2 films using reduced benzyl viologen (BV) and the confocal absorption spectra modified by the doping showed a strong dependence on the atomic thickness: A and B exciton peaks were greatly quenched in the monolayer MoS2 while much less effect was shown in larger thickness and the BG peak either showed very small quenching for 1 L MoS2 or remained constant for larger thicknesses. Our results indicate that confocal absorption spectral imaging can provide comprehensive information on optical transitions of microscopic size intrinsic and doped two-dimensional layered materials.

  12. Magnetism by interfacial hybridization and p-type doping of MoS(2) in Fe(4)N/MoS(2) superlattices: a first-principles study.

    Science.gov (United States)

    Feng, Nan; Mi, Wenbo; Cheng, Yingchun; Guo, Zaibing; Schwingenschlögl, Udo; Bai, Haili

    2014-03-26

    Magnetic and electronic properties of Fe4N(111)/MoS2(√3 × √3) superlattices are investigated by first-principles calculations, considering two models: (I) Fe(I)Fe(II)-S and (II) N-S interfaces, each with six stacking configurations. In model I, strong interfacial hybridization between Fe(I)/Fe(II) and S results in magnetism of monolayer MoS2, with a magnetic moment of 0.33 μB for Mo located on top of Fe(I). For model II, no magnetism is induced due to weak N-S interfacial bonding, and the semiconducting nature of monolayer MoS2 is preserved. Charge transfer between MoS2 and N results in p-type MoS2 with Schottky barrier heights of 0.5-0.6 eV. Our results demonstrate that the interfacial geometry and hybridization can be used to tune the magnetism and doping in Fe4N(111)/MoS2(√3 × √3) superlattices.

  13. Energy, fine structure, and hyperfine structure of the core-excited states 1s2s2pnp 5P (n = 2-5) and 1s2p2mp 5S (m = 2-5) for Li- ion

    International Nuclear Information System (INIS)

    Wang, Z.B.; Gou, B.C.; Chen, F.

    2006-01-01

    The relativistic energies, the oscillator strength, and the lifetimes of high-lying core-excited states 1s2s2pnp 5 P (n=2-5) and 1s2p 2 mp 5 S 0 (m=2-5) of Li - ion are calculated with the saddle-point variational method and restricted variation method. The fine structure and the hyperfine structure of the core-excited states for this system are also explored. The results are compared with other theoretical and experimental data in the literature. The energy obtained in this work are much lower than the others previously published whereas the wavelengths and radiative life-times are in agreement

  14. Electron impact excitation-autoionisation of the (2s2)1S, (2p2)1D and (2s2p)1P autoionising states of helium

    International Nuclear Information System (INIS)

    Samardzic, O.; Hurn, J.A.; Weigold, E.; Brunger, M.J.

    1994-01-01

    The electron impact excitation of the (2s 2 ) 1 S, (2p 2 ) 1 D and (2s2p) 1 P autoionising states of helium and their subsequent radiationless decay was studied by observation of the ejected electrons. The present work was carried out at an incident energy of 94.6 eV and for ejected electron scattering angles in the range 25-135 deg C. The lineshapes observed in the present ejected electron spectra are analysed using the Shore-Balashov parametrisation. As part of the analysis procedure, numerically rigorous confidence limits were determined for the derived parameters. No previous experimental or theoretical work has been undertaken at the incident energy of the present investigation but, where possible, the resulting parameters are qualitatively compared against the 80 eV results of other experiments and theory. 37 refs., 4 figs

  15. Oxidation of atomically thin MoS2 on SiO2

    Science.gov (United States)

    Yamamoto, Mahito; Cullen, William; Einstein, Theodore; Fuhrer, Michael

    2013-03-01

    Surface oxidation of MoS2 markedly affects its electronic, optical, and tribological properties. However, oxidative reactivity of atomically thin MoS2 has yet to be addressed. Here, we investigate oxidation of atomic layers of MoS2 using atomic force microscopy and Raman spectroscopy. MoS2 is mechanically exfoliated onto SiO2 and oxidized in Ar/O2 or Ar/O3 (ozone) at 100-450 °C. MoS2 is much more reactive to O2 than an analogous atomic membrane of graphene and monolayer MoS2 is completely etched very rapidly upon O2 treatment above 300 °C. Thicker MoS2 (> 15 nm) transforms into MoO3 after oxidation at 400 °C, which is confirmed by a Raman peak at 820 cm-1. However, few-layer MoS2 oxidized below 400 °C exhibits no MoO3 Raman mode but etch pits are formed, similar to graphene. We find atomic layers of MoS2 shows larger reactivity to O3 than to O2 and monolayer MoS2 transforms chemically upon O3 treatment even below 100 °C. Work supported by the U. of Maryland NSF-MRSEC under Grant No. DMR 05-20741.

  16. Synthesis of Epitaxial Single-Layer MoS2 on Au(111).

    Science.gov (United States)

    Grønborg, Signe S; Ulstrup, Søren; Bianchi, Marco; Dendzik, Maciej; Sanders, Charlotte E; Lauritsen, Jeppe V; Hofmann, Philip; Miwa, Jill A

    2015-09-08

    We present a method for synthesizing large area epitaxial single-layer MoS2 on the Au(111) surface in ultrahigh vacuum. Using scanning tunneling microscopy and low energy electron diffraction, the evolution of the growth is followed from nanoscale single-layer MoS2 islands to a continuous MoS2 layer. An exceptionally good control over the MoS2 coverage is maintained using an approach based on cycles of Mo evaporation and sulfurization to first nucleate the MoS2 nanoislands and then gradually increase their size. During this growth process the native herringbone reconstruction of Au(111) is lifted as shown by low energy electron diffraction measurements. Within the MoS2 islands, we identify domains rotated by 60° that lead to atomically sharp line defects at domain boundaries. As the MoS2 coverage approaches the limit of a complete single layer, the formation of bilayer MoS2 islands is initiated. Angle-resolved photoemission spectroscopy measurements of both single and bilayer MoS2 samples show a dramatic change in their band structure around the center of the Brillouin zone. Brief exposure to air after removing the MoS2 layer from vacuum is not found to affect its quality.

  17. Exfoliated MoS2 nanosheets as efficient catalysts for electrochemical hydrogen evolution

    International Nuclear Information System (INIS)

    Ji, Shanshan; Yang, Zhe; Zhang, Chao; Liu, Zhenyan; Tjiu, Weng Weei; Phang, In Yee; Zhang, Zheng; Pan, Jisheng; Liu, Tianxi

    2013-01-01

    Graphical abstract: An efficient electrocatalyst for hydrogen evolution has been developed based on exfoliation of bulk MoS 2 crystals via a direct dispersion and ultrasonication method. Drop-casting method is used to fabricate the exfoliated MoS 2 nanosheets modified glass carbon electrode (E-MoS 2 /GCE) with various loadings. The E-MoS 2 /GCE with electrode loading of 48 μg cm −1 exhibits high catalytic activity for hydrogen evolution with a low overpotential (−0.12 V) and a high current density (1.26 mA cm −2 , at η = 150 mV). -- Highlights: • Two-dimensional MoS 2 nanosheets have been obtained by exfoliation of bulk MoS 2 crystals. • Exfoliated MoS 2 nanosheets show high electrocatalytic activity for H 2 production. • This study provides a new approach for renewable and economic H 2 production. -- Abstract: An efficient electrocatalyst for hydrogen evolution has been developed based on liquid exfoliation of bulk MoS 2 via a direct dispersion and ultrasonication method. Transmission electron microscopy and atomic force microscopy measurements show that the exfoliated MoS 2 consists of two-dimensional nanosheets. The exfoliated MoS 2 nanosheets modified glass carbon electrode (E-MoS 2 /GCE) with various loadings is fabricated via a drop-casting method. The electrocatalytic activity of E-MoS 2 /GCE toward hydrogen evolution reaction is examined using linear sweep voltammetry. It is shown that the E-MoS 2 /GCE with an electrode loading of 48 μg cm −2 exhibits a high catalytic activity for hydrogen evolution with a low overpotential (−0.12 V) and a high current density (1.26 mA cm −2 , at η = 150 mV)

  18. Early continuous white noise exposure alters l-alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptor subunit glutamate receptor 2 and gamma-aminobutyric acid type a receptor subunit beta3 protein expression in rat auditory cortex.

    Science.gov (United States)

    Xu, Jinghong; Yu, Liping; Zhang, Jiping; Cai, Rui; Sun, Xinde

    2010-02-15

    Auditory experience during the postnatal critical period is essential for the normal maturation of auditory function. Previous studies have shown that rearing infant rat pups under conditions of continuous moderate-level noise delayed the emergence of adult-like topographic representational order and the refinement of response selectivity in the primary auditory cortex (A1) beyond normal developmental benchmarks and indefinitely blocked the closure of a brief, critical-period window. To gain insight into the molecular mechanisms of these physiological changes after noise rearing, we studied expression of the AMPA receptor subunit GluR2 and GABA(A) receptor subunit beta3 in the auditory cortex after noise rearing. Our results show that continuous moderate-level noise rearing during the early stages of development decreases the expression levels of GluR2 and GABA(A)beta3. Furthermore, noise rearing also induced a significant decrease in the level of GABA(A) receptors relative to AMPA receptors. However, in adult rats, noise rearing did not have significant effects on GluR2 and GABA(A)beta3 expression or the ratio between the two units. These changes could have a role in the cellular mechanisms involved in the delayed maturation of auditory receptive field structure and topographic organization of A1 after noise rearing. Copyright 2009 Wiley-Liss, Inc.

  19. Managing brain extracellular K+ during neuronal activity: The physiological role of the Na+/K+-ATPase subunit isoforms

    Directory of Open Access Journals (Sweden)

    Brian Roland eLarsen

    2016-04-01

    Full Text Available AbstractDuring neuronal activity in the brain, extracellular K+ rises and is subsequently removed to prevent a widespread depolarization. One of the key players in regulating extracellular K+ is the Na+/K+-ATPase, although the relative involvement and physiological impact of the different subunit isoform compositions of the Na+/K+-ATPase remain unresolved. The various cell types in the brain serve a certain temporal contribution in the face of network activity; astrocytes respond directly to the immediate release of K+ from neurons, whereas the neurons themselves become the primary K+ absorbers as activity ends. The kinetic characteristics of the catalytic α subunit isoforms of the Na+/K+-ATPase are, partly, determined by the accessory β subunit with which they combine. The isoform combinations expressed by astrocytes and neurons, respectively, appear to be in line with the kinetic characteristics required to fulfill their distinct physiological roles in clearance of K+ from the extracellular space in the face of neuronal activity.Understanding the nature, impact and effects of the various Na+/K+-ATPase isoform combinations in K+ management in the central nervous system might reveal insights into pathological conditions such as epilepsy, migraine, and spreading depolarization following cerebral ischemia. In addition, particular neurological diseases occur as a result of mutations in the α2- (familial hemiplegic migraine type 2 and α3 isoforms (rapid-onset dystonia parkinsonism/alternating hemiplegia of childhood. This review addresses aspects of the Na+/K+-ATPase in the regulation of extracellular K+ in the central nervous system as well as the related pathophysiology. Understanding the physiological setting in non-pathological tissue would provide a better understanding of the pathological events occurring during disease.

  20. Molecular cloning of the human casein kinase II α subunit

    International Nuclear Information System (INIS)

    Meisner, H.; Heller-Harrison, R.; Buxton, J.; Czech, M.P.

    1989-01-01

    A human cDNA encoding the α subunit of casein kinase II and a partial cDNA encoding the rat homologue were isolated by using a Drosophila casein kinase II cDNA probe. The 2.2-kb human cDNA contains a 1.2-kb open reading frame, 150 nucleotides of 5' leader, and 850 nucleotides of 3' noncoding region. Except for the first 7 deduced amino acids that are missing in the rat cDNA, the 328 amino acids beginning with the amino terminus are identical between human and rat. The Drosophila enzyme sequence is 90% identical with the human casein kinase II sequence, and there is only a single amino acid difference between the published partial bovine sequence and the human sequence. In addition, the C-terminus of the human cDNA has an extra 53 amino acids not present in Drosophila. Northern analysis of rat and human RNA showed predominant bands of 5.5, 3.1, and 1.8 kb. In rat tissues, brain and spleen had the highest levels of casein kinase II α subunit specific RNA, while skeletal muscle showed the lowest. Southern analysis of human cultured cell and tissue genomic DNA using the full-length cDNA probe revealed two bands with restriction enzymes that have no recognition sites within the cDNA and three to six bands with enzymes having single internal sites. These results are consistent with the possibility that two genes encode the α subunits

  1. Covalent dimerization of ribulose bisphosphate carboxylase subunits by UV radiation

    Energy Technology Data Exchange (ETDEWEB)

    Ferreira, R.M.B. [Universidade Tecnica, Lisbon (Portugal). Inst. Superior de Agronomia]|[Universidade Nova de Lisboa, Oeiras (Portugal). Instituto de Tecnologia Quimica e Biologica; Franco, E.; Teixeira, A.R.N. [Universidade Tecnica, Lisbon (Portugal). Inst. Superior de Agronomia

    1996-08-15

    The effect of UV radiation (UV-A, UV-B and UV-C) on ribulose bisphosphate carboxylase from a variety of plant species was examined. The exposition of plant leaves or the pure enzyme to UV radiation produced a UV-dependent accumulation of a 65 kDa polypeptide (P65). Different approaches were utilized to elucidate the origin and structure of P65: electrophoretic and fluorographic analyses of {sup 35}S-labelled ribulose biphosphate carboxylase exposed to UV radiation and immunological experiments using antibodies specific for P65, for the large and small subunits of ribulose biphosphate carboxylase and for high-molecular-mass aggregates of the enzyme. These studies revealed that P65 is a dimer, formed by the covalent, non-disulphide linkage of one small subunit with one large subunit of ribulose biphosphate carboxylase. For short periods of time (<1 h), the amount of P65 formed increased with the duration of the exposure to the UV radiation and with the energy of the radiation applied. Prolonged exposure to UV radiation (1-6 h) resulted in the formation of high-molecular-mass aggregates of ribulose biphosphate carboxylase. Formation of P65 was shown to depend on the native state of the protein, was stimulated by inhibitors of enzyme activity, and was inhibited by activators of enzyme activity. A UV-independent accumulation of P65 was also achieved by the in vitro incubation of plant crude extracts. However, the UV-dependent and the UV-independent formation of P65 seemed to occur by distinct molecular mechanisms. The UV-dependent accumulation of P65 was immunologically detected in all species examined, including Lemna minor, Arum italicum, Brassica oleracea, Triticum aestivum, Zea mays, Pisum sativum and Phaseolus vulgaris, suggesting that it may constitute a universal response to UV radiation, common to all photosynthetic tissues. (Author).

  2. Covalent dimerization of ribulose bisphosphate carboxylase subunits by UV radiation

    International Nuclear Information System (INIS)

    Ferreira, R.M.B.; Universidade Nova de Lisboa, Oeiras; Franco, E.; Teixeira, A.R.N.

    1996-01-01

    The effect of UV radiation (UV-A, UV-B and UV-C) on ribulose bisphosphate carboxylase from a variety of plant species was examined. The exposition of plant leaves or the pure enzyme to UV radiation produced a UV-dependent accumulation of a 65 kDa polypeptide (P65). Different approaches were utilized to elucidate the origin and structure of P65: electrophoretic and fluorographic analyses of 35 S-labelled ribulose biphosphate carboxylase exposed to UV radiation and immunological experiments using antibodies specific for P65, for the large and small subunits of ribulose biphosphate carboxylase and for high-molecular-mass aggregates of the enzyme. These studies revealed that P65 is a dimer, formed by the covalent, non-disulphide linkage of one small subunit with one large subunit of ribulose biphosphate carboxylase. For short periods of time (<1 h), the amount of P65 formed increased with the duration of the exposure to the UV radiation and with the energy of the radiation applied. Prolonged exposure to UV radiation (1-6 h) resulted in the formation of high-molecular-mass aggregates of ribulose biphosphate carboxylase. Formation of P65 was shown to depend on the native state of the protein, was stimulated by inhibitors of enzyme activity, and was inhibited by activators of enzyme activity. A UV-independent accumulation of P65 was also achieved by the in vitro incubation of plant crude extracts. However, the UV-dependent and the UV-independent formation of P65 seemed to occur by distinct molecular mechanisms. The UV-dependent accumulation of P65 was immunologically detected in all species examined, including Lemna minor, Arum italicum, Brassica oleracea, Triticum aestivum, Zea mays, Pisum sativum and Phaseolus vulgaris, suggesting that it may constitute a universal response to UV radiation, common to all photosynthetic tissues. (Author)

  3. Flexible Connectors between Capsomer Subunits that Regulate Capsid Assembly.

    Science.gov (United States)

    Hasek, Mary L; Maurer, Joshua B; Hendrix, Roger W; Duda, Robert L

    2017-08-04

    Viruses build icosahedral capsids of specific size and shape by regulating the spatial arrangement of the hexameric and pentameric protein capsomers in the growing shell during assembly. In the T=7 capsids of Escherichia coli bacteriophage HK97 and other phages, 60 capsomers are hexons, while the rest are pentons that are correctly positioned during assembly. Assembly of the HK97 capsid to the correct size and shape has been shown to depend on specific ionic contacts between capsomers. We now describe additional ionic interactions within capsomers that also regulate assembly. Each is between the long hairpin, the "E-loop," that extends from one subunit to the adjacent subunit within the same capsomer. Glutamate E153 on the E-loop and arginine R210 on the adjacent subunit's backbone alpha-helix form salt bridges in hexamers and pentamers. Mutations that disrupt these salt bridges were lethal for virus production, because the mutant proteins assembled into tubes or sheets instead of capsids. X-ray structures show that the E153-R210 links are flexible and maintained during maturation despite radical changes in capsomer shape. The E153-R210 links appear to form early in assembly to enable capsomers to make programmed changes in their shape during assembly. The links also prevent flattening of capsomers and premature maturation. Mutant phenotypes and modeling support an assembly model in which flexible E153-R210 links mediate capsomer shape changes that control where pentons are placed to create normal-sized capsids. The E-loop may be conserved in other systems in order to play similar roles in regulating assembly. Copyright © 2017 Elsevier Ltd. All rights reserved.

  4. Sex Hormone Receptor Expression in the Human Vocal Fold Subunits.

    Science.gov (United States)

    Kirgezen, Tolga; Sunter, Ahmet Volkan; Yigit, Ozgur; Huq, Gulben Erdem

    2017-07-01

    The study aimed to evaluate the existence of sex hormone receptors in the subunits of vocal fold. This is a cadaver study. The androgen, estrogen, and progesterone receptors were examined in the epithelium (EP), superficial layer of the lamina propria (SLP), vocal ligament (VL), and macula flava (MF) of the vocal folds from 42 human cadavers (21 male, 21 female) by immunohistochemical methods. Their staining ratios were scored and statistically compared. The androgen receptor score was significantly higher for the MF than for the EP and SLP (P vocal fold, mostly in the MF and VLs. Copyright © 2017 The Voice Foundation. Published by Elsevier Inc. All rights reserved.

  5. Prognostic significance of cytosolic pS2 content in ovarian tumors

    International Nuclear Information System (INIS)

    Raigoso, P.; Allende, T.; Zeidan, N.; Llana, B.; Bernardo, L.; Roiz, C.; Tejuca, S.; Vazquez, J.; Lamelas, M.L.

    2002-01-01

    Aim: pS2 is an estrogen regulated peptide which has been associated with a good prognosis an with a more favorable response to treatment in breast cancer patients. In ovarian tumors, the expression of pS2 was demonstrated at both mRNA and protein levels. In addition, it has been showed significant association of pS2 with mucinous differentiation or well differentiation grade of the tumors. However, it is little know about the prognostic significance of the pS2 content in ovarian carcinomas. The aims of the present work were to analyze the cytosolic pS2 content in benign and malignant ovarian tumors, its relationship with clinico-pathologic parameters, steroid receptor status, and prognostic significance. Material and Methods: We analysed the cytosolic concentrations of pS2 in 91 specimen ovarian tissues by an immunoradiometric assay (ELSA-pS2, CIS, France). The tissues were 8 normal ovaries, 43 benign tumors and 40 malignant ovarian tumors. The same ovarian tissues processed to pS2 were analyzed to Estrogen (ER) and Progesterone (PgR) Receptor status. These steroid receptors were quantified biochemically following commercial ELISA method (ABBOTT Diagnostics, Germany). The relationship between cytosolic content and clinico-pathologic factors was examined by the Mann-Whitney or Kruskall-Wallis test. Correlation between steroid receptors and pS2 content was calculated with the Spearman test. Survival curves were calculated using the Kaplan-Meier method and compared by the log-rank test. Differences were considered significant at 5% probability level. Results: pS2 could be detected in 30 cases (32.9%) with values ranged from 0.04 to 89 ng/mg prt. Only one normal ovary showed detectable levels of pS2 and there were not differences in cytosolic content between benign and malignant ovarian tumors. The pS2 levels were only associated to mucinous differentiation in both benign and malignant ovarian tumors (p=0.029 and p=0.015, respectively). Significantly higher

  6. N-linked glycans are required on epithelial Na+ channel subunits for maturation and surface expression.

    Science.gov (United States)

    Kashlan, Ossama B; Kinlough, Carol L; Myerburg, Michael M; Shi, Shujie; Chen, Jingxin; Blobner, Brandon M; Buck, Teresa M; Brodsky, Jeffrey L; Hughey, Rebecca P; Kleyman, Thomas R

    2018-03-01

    Epithelial Na + channel (ENaC) subunits undergo N-linked glycosylation in the endoplasmic reticulum where they assemble into an αβγ complex. Six, 13, and 5 consensus sites (Asn-X-Ser/Thr) for N-glycosylation reside in the extracellular domains of the mouse α-, β-, and γ-subunits, respectively. Because the importance of ENaC N-linked glycans has not been fully addressed, we examined the effect of preventing N-glycosylation of specific subunits on channel function, expression, maturation, and folding. Heterologous expression in Xenopus oocytes or Fischer rat thyroid cells with αβγ-ENaC lacking N-linked glycans on a single subunit reduced ENaC activity as well as the inhibitory response to extracellular Na + . The lack of N-linked glycans on the β-subunit also precluded channel activation by trypsin. However, channel activation by shear stress was N-linked glycan independent, regardless of which subunit was modified. We also discovered that the lack of N-linked glycans on any one subunit reduced the total and surface levels of cognate subunits. The lack of N-linked glycans on the β-subunit had the largest effect on total levels, with the lack of N-linked glycans on the γ- and α-subunits having intermediate and modest effects, respectively. Finally, channels with wild-type β-subunits were more sensitive to limited trypsin proteolysis than channels lacking N-linked glycans on the β-subunit. Our results indicate that N-linked glycans on each subunit are required for proper folding, maturation, surface expression, and function of the channel.

  7. Many-body effects in valleytronics: direct measurement of valley lifetimes in single-layer MoS2.

    Science.gov (United States)

    Mai, Cong; Barrette, Andrew; Yu, Yifei; Semenov, Yuriy G; Kim, Ki Wook; Cao, Linyou; Gundogdu, Kenan

    2014-01-08

    Single layer MoS2 is an ideal material for the emerging field of "valleytronics" in which charge carrier momentum can be finely controlled by optical excitation. This system is also known to exhibit strong many-body interactions as observed by tightly bound excitons and trions. Here we report direct measurements of valley relaxation dynamics in single layer MoS2, by using ultrafast transient absorption spectroscopy. Our results show that strong Coulomb interactions significantly impact valley population dynamics. Initial excitation by circularly polarized light creates electron-hole pairs within the K-valley. These excitons coherently couple to dark intervalley excitonic states, which facilitate fast electron valley depolarization. Hole valley relaxation is delayed up to about 10 ps due to nondegeneracy of the valence band spin states. Intervalley biexciton formation reveals the hole valley relaxation dynamics. We observe that biexcitons form with more than an order of magnitude larger binding energy compared to conventional semiconductors. These measurements provide significant insight into valley specific processes in 2D semiconductors. Hence they could be used to suggest routes to design semiconducting materials that enable control of valley polarization.

  8. Binding mechanism and dynamic conformational change of C subunit of PKA with different pathways.

    Science.gov (United States)

    Chu, Wen-Ting; Chu, Xiakun; Wang, Jin

    2017-09-19

    The catalytic subunit of PKA (PKAc) exhibits three major conformational states (open, intermediate, and closed) during the biocatalysis process. Both ATP and substrate/inhibitor can effectively induce the conformational changes of PKAc from open to closed states. Aiming to explore the mechanism of this allosteric regulation, we developed a coarse-grained model and analyzed the dynamics of conformational changes of PKAc during binding by performing molecular dynamics simulations for apo PKAc, binary PKAc (PKAc with ATP, PKAc with PKI), and ternary PKAc (PKAc with ATP and PKI). Our results suggest a mixed binding mechanism of induced fit and conformational selection, with the induced fit dominant. The ligands can drive the movements of Gly-rich loop as well as some regions distal to the active site in PKAc and stabilize them at complex state. In addition, there are two parallel pathways (pathway with PKAc-ATP as an intermediate and pathway PKAc-PKI as an intermediate) during the transition from open to closed states. By molecular dynamics simulations and rate constant analyses, we find that the pathway through PKAc-ATP intermediate is the main binding route from open to closed state because of the fact that the bound PKI will hamper ATP from successful binding and significantly increase the barrier for the second binding subprocess. These findings will provide fundamental insights of the mechanisms of PKAc conformational change upon binding.

  9. First-principle study of hydrogenation on monolayer MoS2

    International Nuclear Information System (INIS)

    Xu, Yong; Li, Yin; Chen, Xi; Zhang, Ru; Zhang, Chunfang; Lu, Pengfei

    2016-01-01

    The structural and electronic properties of hydrogenation on 1H-MoS 2 and 1T-MoS 2 have been systematically explored by using density functional theory (DFT) calculations. Our calculated results indicate an energetically favorable chemical interaction between H and MoS 2 monolayer for H adsorption when increasing concentration of H atoms. For 1H-MoS 2 , single H atom adsorption creates midgap approaching the Fermi level which increases the n-type carrier concentration effectively. As a consequence, its electrical conductivity is expected to increase significantly. For 1T-MoS 2 , H atoms adsorption can lead to the opening of a direct gap of 0.13 eV compared to the metallic pristine 1T-MoS 2 .

  10. Construction of MoS2/Si nanowire array heterojunction for ultrahigh-sensitivity gas sensor

    Science.gov (United States)

    Wu, Di; Lou, Zhenhua; Wang, Yuange; Xu, Tingting; Shi, Zhifeng; Xu, Junmin; Tian, Yongtao; Li, Xinjian

    2017-10-01

    Few-layer MoS2 thin films were synthesized by a two-step thermal decomposition process. In addition, MoS2/Si nanowire array (SiNWA) heterojunctions exhibiting excellent gas sensing properties were constructed and investigated. Further analysis reveals that such MoS2/SiNWA heterojunction devices are highly sensitive to nitric oxide (NO) gas under reverse voltages at room temperature (RT). The gas sensor demonstrated a minimum detection limit of 10 ppb, which represents the lowest value obtained for MoS2-based sensors, as well as an ultrahigh response of 3518% (50 ppm NO, ˜50% RH), with good repeatability and selectivity of the MoS2/SiNWA heterojunction. The sensing mechanisms were also discussed. The performance of the MoS2/SiNWA heterojunction gas sensors is superior to previous results, revealing that they have great potential in applications relating to highly sensitive gas sensors.

  11. Enhanced monolayer MoS2/InP heterostructure solar cells by graphene quantum dots

    Science.gov (United States)

    Wang, Peng; Lin, Shisheng; Ding, Guqiao; Li, Xiaoqiang; Wu, Zhiqian; Zhang, Shengjiao; Xu, Zhijuan; Xu, Sen; Lu, Yanghua; Xu, Wenli; Zheng, Zheyang

    2016-04-01

    We demonstrate significantly improved photovoltaic response of monolayer molybdenum disulfide (MoS2)/indium phosphide (InP) van der Waals heterostructure induced by graphene quantum dots (GQDs). Raman and photoluminescence measurements indicate that effective charge transfer takes place between GQDs and MoS2, which results in n-type doping of MoS2. The doping effect increases the barrier height at the MoS2/InP heterojunction, thus the averaged power conversion efficiency of MoS2/InP solar cells is improved from 2.1% to 4.1%. The light induced doping by GQD provides a feasible way for developing more efficient MoS2 based heterostructure solar cells.

  12. Enhanced photoresponse of monolayer molybdenum disulfide (MoS2) based on microcavity structure

    Science.gov (United States)

    Lu, Yanan; Yang, Guofeng; Wang, Fuxue; Lu, Naiyan

    2018-05-01

    There is an increasing interest in using monolayer molybdenum disulfide (MoS2) for optoelectronic devices because of its inherent direct band gap characteristics. However, the weak absorption of monolayer MoS2 restricts its applications, novel concepts need to be developed to address the weakness. In this work, monolayer MoS2 monolithically integrates with plane microcavity structure, which is formed by the top and bottom chirped distributed Bragg reflector (DBR), is demonstrated to improve the absorption of MoS2. The optical absorption is 17-fold enhanced, reaching values over 70% at work wavelength. Moreover, the monolayer MoS2-based photodetector device with microcavity presents a significantly increased photoresponse, demonstrating its promising prospects in MoS2-based optoelectronic devices.

  13. Spin transport properties of partially edge-hydrogenated MoS2 nanoribbon heterostructure

    International Nuclear Information System (INIS)

    Peng, Li; Yao, Kailun; Zhu, Sicong; Ni, Yun; Zu, Fengxia; Wang, Shuling; Guo, Bin; Tian, Yong

    2014-01-01

    We report ab initio calculations of electronic transport properties of heterostructure based on MoS 2 nanoribbons. The heterostructure consists of edge hydrogen-passivated and non-passivated zigzag MoS 2 nanoribbons (ZMoS 2 NR-H/ZMoS 2 NR). Our calculations show that the heterostructure has half-metallic behavior which is independent of the nanoribbon width. The opening of spin channels of the heterostructure depends on the matching of particular electronic orbitals in the Mo-dominated edges of ZMoS 2 NR-H and ZMoS 2 NR. Perfect spin filter effect appears at small bias voltages, and large negative differential resistance and rectifying effects are also observed in the heterostructure.

  14. Synthesis, characterization and photocatalytic performance of chemically exfoliated MoS2

    Science.gov (United States)

    Prabhakar Vattikuti, S. V.; Shim, Jaesool

    2018-03-01

    Two-dimensional (2D) layered structure transition metal dichalcogenides (TMDs) has gained huge attention and importance for photocatalytic energy conversion because of their unique properties. Molybdenum disulfide (MoS2) nanosheets were synthesized via one-pot method and exfoliated in (dimethylformamide) DMF solution. Subsequent exfoliated MoS2 nanosheets (e-MoS2) were used as photocatalysts for degradation of Rhodamine B (RhB) pollutant under solar light irradiation. The e-MoS2 nanosheets exhibited excellent photocatalytic activity than that of pristine MoS2, owing to high specific surface area with enormous active sites and light absorption capacity. In addition, e-MoS2 demonstrated remarkable photocatalytic stability.

  15. Impact and Origin of Interface States in MOS Capacitor with Monolayer MoS2 and HfO2 High-k Dielectric.

    Science.gov (United States)

    Xia, Pengkun; Feng, Xuewei; Ng, Rui Jie; Wang, Shijie; Chi, Dongzhi; Li, Cequn; He, Zhubing; Liu, Xinke; Ang, Kah-Wee

    2017-01-13

    Two-dimensional layered semiconductors such as molybdenum disulfide (MoS 2 ) at the quantum limit are promising material for nanoelectronics and optoelectronics applications. Understanding the interface properties between the atomically thin MoS 2 channel and gate dielectric is fundamentally important for enhancing the carrier transport properties. Here, we investigate the frequency dispersion mechanism in a metal-oxide-semiconductor capacitor (MOSCAP) with a monolayer MoS 2 and an ultra-thin HfO 2 high-k gate dielectric. We show that the existence of sulfur vacancies at the MoS 2 -HfO 2 interface is responsible for the generation of interface states with a density (D it ) reaching ~7.03 × 10 11  cm -2  eV -1 . This is evidenced by a deficit S:Mo ratio of ~1.96 using X-ray photoelectron spectroscopy (XPS) analysis, which deviates from its ideal stoichiometric value. First-principles calculations within the density-functional theory framework further confirms the presence of trap states due to sulfur deficiency, which exist within the MoS 2 bandgap. This corroborates to a voltage-dependent frequency dispersion of ~11.5% at weak accumulation which decreases monotonically to ~9.0% at strong accumulation as the Fermi level moves away from the mid-gap trap states. Further reduction in D it could be achieved by thermally diffusing S atoms to the MoS 2 -HfO 2 interface to annihilate the vacancies. This work provides an insight into the interface properties for enabling the development of MoS 2 devices with carrier transport enhancement.

  16. Isoforms of U1-70k control subunit dynamics in the human spliceosomal U1 snRNP.

    Directory of Open Access Journals (Sweden)

    Helena Hernández

    2009-09-01

    Full Text Available Most human protein-encoding genes contain multiple exons that are spliced together, frequently in alternative arrangements, by the spliceosome. It is established that U1 snRNP is an essential component of the spliceosome, in human consisting of RNA and ten proteins, several of which are post-translationally modified and exist as multiple isoforms. Unresolved and challenging to investigate are the effects of these post translational modifications on the dynamics, interactions and stability of the particle. Using mass spectrometry we investigate the composition and dynamics of the native human U1 snRNP and compare native and recombinant complexes to isolate the effects of various subunits and isoforms on the overall stability. Our data reveal differential incorporation of four protein isoforms and dynamic interactions of subunits U1-A, U1-C and Sm-B/B'. Results also show that unstructured post-translationally modified C-terminal tails are responsible for the dynamics of Sm-B/B' and U1-C and that their interactions with the Sm core are controlled by binding to different U1-70k isoforms and their phosphorylation status in vivo. These results therefore provide the important functional link between proteomics and structure as well as insight into the dynamic quaternary structure of the native U1 snRNP important for its function.

  17. Piperlongumine selectively suppresses ABC-DLBCL through inhibition of NF-κB p65 subunit nuclear import

    Energy Technology Data Exchange (ETDEWEB)

    Niu, Mingshan [Blood Diseases Institute, Xuzhou Medical College, Xuzhou, Jiangsu (China); Jiangsu Key Laboratory of Bone Marrow Stem Cell, Xuzhou Medical College, Xuzhou, Jiangsu (China); Department of Hematology, Affiliated Hospital of Xuzhou Medical College, Xuzhou, Jiangsu (China); Shen, Yangling; Xu, Xiaoyu [Blood Diseases Institute, Xuzhou Medical College, Xuzhou, Jiangsu (China); Jiangsu Key Laboratory of Bone Marrow Stem Cell, Xuzhou Medical College, Xuzhou, Jiangsu (China); Yao, Yao; Fu, Chunling [Blood Diseases Institute, Xuzhou Medical College, Xuzhou, Jiangsu (China); Jiangsu Key Laboratory of Bone Marrow Stem Cell, Xuzhou Medical College, Xuzhou, Jiangsu (China); Department of Hematology, Affiliated Hospital of Xuzhou Medical College, Xuzhou, Jiangsu (China); Yan, Zhiling [Department of Hematology, Affiliated Hospital of Xuzhou Medical College, Xuzhou, Jiangsu (China); Wu, Qingyun [Blood Diseases Institute, Xuzhou Medical College, Xuzhou, Jiangsu (China); Jiangsu Key Laboratory of Bone Marrow Stem Cell, Xuzhou Medical College, Xuzhou, Jiangsu (China); Department of Hematology, Affiliated Hospital of Xuzhou Medical College, Xuzhou, Jiangsu (China); Cao, Jiang; Sang, Wei [Department of Hematology, Affiliated Hospital of Xuzhou Medical College, Xuzhou, Jiangsu (China); Zeng, Lingyu [Blood Diseases Institute, Xuzhou Medical College, Xuzhou, Jiangsu (China); Jiangsu Key Laboratory of Bone Marrow Stem Cell, Xuzhou Medical College, Xuzhou, Jiangsu (China); Department of Hematology, Affiliated Hospital of Xuzhou Medical College, Xuzhou, Jiangsu (China); Li, Zhenyu [Department of Hematology, Affiliated Hospital of Xuzhou Medical College, Xuzhou, Jiangsu (China); Liu, Xuejiao, E-mail: liuxuejiao0923@126.com [Insititute of Nervous System Diseases, Xuzhou Medical College, Xuzhou, Jiangsu (China); and others

    2015-07-10

    Constitutive NF-κB activation is required for survival of activated B cell-like subtype of diffuse large B cell lymphoma (ABC-DLBCL). However, current NF-κB targeting strategies lack cancer cell specificity. Here, we identified a novel inhibitor, piperlongumine, features direct binding to NF-κB p65 subunit and suppression of p65 nuclear import. This was accompanied by NF-κB reporter activity suppression and NF-κB target gene downregulation. Moreover, mutation of Cys{sup 38} to Ser in p65 abolished this effect of piperlongumine on inhibition of p65 nuclear import. Furthermore, we show that piperlongumine selectively inhibited proliferation and induced apoptosis of ABC-DLBCL cells. Most notably, it has been reported that piperlongumine did not affect normal cells even at high doses and was nontoxic to animals. Hence, our current study provides new insight into piperlongumine's mechanism of action and novel approach to ABC-DLBCL target therapy. - Highlights: • Current NF-κB targeting strategies lack cancer cell specificity. • Piperlongumine inhibits NF-κB p65 subunit nuclear import via directly binding to p65. • Piperlongumine selectively inhibits proliferation of ABC-DLBCL cells. • This study provides a novel approach to ABC-DLBCL target therapy.

  18. Piperlongumine selectively suppresses ABC-DLBCL through inhibition of NF-κB p65 subunit nuclear import

    International Nuclear Information System (INIS)

    Niu, Mingshan; Shen, Yangling; Xu, Xiaoyu; Yao, Yao; Fu, Chunling; Yan, Zhiling; Wu, Qingyun; Cao, Jiang; Sang, Wei; Zeng, Lingyu; Li, Zhenyu; Liu, Xuejiao

    2015-01-01

    Constitutive NF-κB activation is required for survival of activated B cell-like subtype of diffuse large B cell lymphoma (ABC-DLBCL). However, current NF-κB targeting strategies lack cancer cell specificity. Here, we identified a novel inhibitor, piperlongumine, features direct binding to NF-κB p65 subunit and suppression of p65 nuclear import. This was accompanied by NF-κB reporter activity suppression and NF-κB target gene downregulation. Moreover, mutation of Cys 38 to Ser in p65 abolished this effect of piperlongumine on inhibition of p65 nuclear import. Furthermore, we show that piperlongumine selectively inhibited proliferation and induced apoptosis of ABC-DLBCL cells. Most notably, it has been reported that piperlongumine did not affect normal cells even at high doses and was nontoxic to animals. Hence, our current study provides new insight into piperlongumine's mechanism of action and novel approach to ABC-DLBCL target therapy. - Highlights: • Current NF-κB targeting strategies lack cancer cell specificity. • Piperlongumine inhibits NF-κB p65 subunit nuclear import via directly binding to p65. • Piperlongumine selectively inhibits proliferation of ABC-DLBCL cells. • This study provides a novel approach to ABC-DLBCL target therapy

  19. New families of conservative systems on $S^2$ possessing an integral of fourth degree in momenta

    OpenAIRE

    Selivanova, Elena N.

    1997-01-01

    There is a well-known example of integrable conservative system on $S^2$, the case of Kovalevskaya in the dynamics of a rigid body, possessing an integral of fourth degree in momenta. Goryachev proposed a one-parameter family of examples of conservative systems on $S^2$ possessing an integral of fourth degree in momenta which includes the case of Kovalevskaya. In this paper we proposed new examples of conservative systems on $S^2$ possessing an integral of fourth degree in momenta.

  20. Study on the performance of MoS2 modified PTFE composites by molding process

    Science.gov (United States)

    Ma, Weiqiang; Hou, Genliang; Bi, Song; Li, Ping; Li, Penghui

    2017-10-01

    MoS2 filled PTFE composites were prepared by cold pressing and sintering molding. The compressive and creep properties of composite materials were analyzed by controlling the size of molded composites during molding. The results show that the composites have the best compressive and creep resistance when the molding pressure is 55 MPa in the MoS2 composites with 15% mass fraction, which is a practical reference for the preparation of MoS2-modified PTFE composites.

  1. Enhanced photocatalytic activity and synthesis of ZnO nanorods/MoS2 composites

    Science.gov (United States)

    Li, Hui; Shen, Hao; Duan, Libing; Liu, Ruidi; Li, Qiang; Zhang, Qian; Zhao, Xiaoru

    2018-05-01

    A stable and recyclable organic degradation catalyst based on MoS2 functionalized ZnO nanorods was introduced. ZnO nanorods were synthesized on the glass substrates (2 cm*2 cm) by sol-gel method and hydrothermal method and functionalized with MoS2 via an argon flow annealing method. The structure and morphology of the as-prepared samples were characterized by XRD, SEM and TEM. Results showed that a small amount of MoS2 was successfully wrapped on the surfaces of ZnO nanorods. XPS analyses showed the existence of Zn-S between ZnO and MoS2, indicating that the MoS2 was combined with ZnO through chemical bonds and formed the ZnO/MoS2 heterostructure. PL results revealed that ZnO/MoS2 had lower fluorescence spectra indicating an electron transport channel between ZnO and MoS2 which separated electrons and holes. Photocatalytic experiment showed that ZnO/MoS2 composites showed a better photodegradation performance of Rhodamine B (RhB) after functionalized with MoS2 under the UV light irradiation which could be attributed to the separation and transfer of photogenerated electrons and holes between ZnO and MoS2. Meanwhile, the high active adsorption sites on the edges of MoS2 also accelerated the degradation process. Furthermore, the scavengers were used to investigate the major active species and results indicated that h+ was the major reactive species for the degradation.

  2. TaS2 nanosheet-based room-temperature dosage meter for nitric oxide

    Directory of Open Access Journals (Sweden)

    Qiyuan He

    2014-09-01

    Full Text Available A miniature dosage meter for toxic gas is developed based on TaS2 nanosheets, which is capable of indicating the toxic dosage of trace level NO at room temperature. The TaS2 film-based chemiresistor shows an irreversible current response against the exposure of NO. The unique non-recovery characteristic makes the TaS2 film-based device an ideal indicator of total dosage of chronicle exposure.

  3. Unexpected optical limiting properties from MoS2 nanosheets modified by a semiconductive polymer.

    Science.gov (United States)

    Zhao, Min; Chang, Meng-Jie; Wang, Qiang; Zhu, Zhen-Tong; Zhai, Xin-Ping; Zirak, Mohammad; Moshfegh, Alireza Z; Song, Ying-Lin; Zhang, Hao-Li

    2015-08-07

    Direct solvent exfoliation of bulk MoS2 with the assistance of poly(3-hexylthiophene) (P3HT) produces a novel two-dimensional organic/inorganic semiconductor hetero-junction. The obtained P3HT-MoS2 nanohybrid exhibits unexpected optical limiting properties in contrast to the saturated absorption behavior of both P3HT and MoS2, showing potential in future photoelectric applications.

  4. Cloning, purification, and functional characterization of Carocin S2, a ribonuclease bacteriocin produced by Pectobacterium carotovorum

    Directory of Open Access Journals (Sweden)

    Tzeng Kuo-Ching

    2011-05-01

    Full Text Available Abstract Background Most isolates of Pectobacterium carotovorum subsp. carotovorum (Pcc produce bacteriocins. In this study, we have determined that Pcc strain F-rif-18 has a chromosomal gene encoding the low-molecular-weight bacteriocin, Carocin S2, and that this bacteriocin inhibits the growth of a closely related strain. Carocin S2 is inducible by ultraviolet radiation but not by mutagenic agents such as mitomycin C. Results A carocin S2-defective mutant, TF1-2, was obtained by Tn5 insertional mutagenesis using F-rif-18. A 5706-bp DNA fragment was detected by Southern blotting, selected from a genomic DNA library, and cloned to the vector, pMS2KI. Two adjacent complete open reading frames within pMS2KI were sequenced, characterized, and identified as caroS2K and caroS2I, which respectively encode the killing protein and immunity protein. Notably, carocin S2 could be expressed not only in the mutant TF1-2 but also in Escherichia coli DH5α after entry of the plasmid pMS2KI. Furthermore, the C-terminal domain of CaroS2K was homologous to the nuclease domains of colicin D and klebicin D. Moreover, SDS-PAGE analysis showed that the relative mass of CaroS2K was 85 kDa and that of CaroS2I was 10 kDa. Conclusion This study shown that another nuclease type of bacteriocin was found in Pectobacterium carotovorum. This new type of bacteriocin, Carocin S2, has the ribonuclease activity of CaroS2K and the immunity protein activity of CaroS2I.

  5. Ganoderma-Like MoS2 /NiS2 with Single Platinum Atoms Doping as an Efficient and Stable Hydrogen Evolution Reaction Catalyst.

    Science.gov (United States)

    Guan, Yongxin; Feng, Yangyang; Wan, Jing; Yang, Xiaohui; Fang, Ling; Gu, Xiao; Liu, Ruirui; Huang, Zhengyong; Li, Jian; Luo, Jun; Li, Changming; Wang, Yu

    2018-05-27

    Herein, a unique ganoderma-like MoS 2 /NiS 2 hetero-nanostructure with isolated Pt atoms anchored is reported. This novel ganoderma-like heterostructure can not only efficiently disperse and confine the few-layer MoS 2 nanosheets to fully expose the edge sites of MoS 2 , and provide more opportunity to capture the Pt atoms, but also tune the electronic structure to modify the catalytic activity. Because of the favorable dispersibility and exposed large specific surface area, single Pt atoms can be easily anchored on MoS 2 nanosheets with ultrahigh loading of 1.8 at% (the highest is 1.3 at% to date). Owing to the ganoderma-like structure and platinum atoms doping, this catalyst shows Pt-like catalytic activity for the hydrogen evolution reaction with an ultralow overpotential of 34 mV and excellent durability of only 2% increase in overpotential for 72 h under the constant current density of 10 mA cm -2 . © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. A tunnelling study on polymer/1T-LixTaS2 layered nanocomposites

    International Nuclear Information System (INIS)

    Enomoto, Hiroyuki; Takai, Hiroyuki; Ozaki, Hajime; Lerner, Michael M

    2004-01-01

    Electronic structures near the Fermi level of polymer/1T-Li x TaS 2 layered nanocomposites have been studied by tunnelling spectroscopy. Polymer/1T-Li x TaS 2 layered nanocomposites were synthesized by using the exfoliation-adsorption technique. Single crystals of 1T-TaS 2 were used as host materials. Poly(ethylene oxide) (PEO) and poly(ethylenimine) (PEI) with different molecular weights were adopted as guest intercalants. Powder x-ray diffraction patterns showed that all samples of the polymer/1T-Li x TaS 2 layered nanocomposites contain organic polymer between all individual 1T-TaS 2 sheets. Although 1T-TaS 2 single crystal is well known to show quite unique temperature dependences of the resistivity due to the charge density wave (CDW), the resistivities of all polymer/1T-Li x TaS 2 nanocomposites showed semiconductor-like temperature dependences. The tunnelling spectra of polymer/1T-Li x TaS 2 nanocomposites revealed that the CDW gap disappears in the density of states near the Fermi level of polymer/1T-Li x TaS 2 nanocomposites and their electronic structures show a metallic behaviour

  7. Analysis of optical and electronic properties of MoS2 for optoelectronics and FET applications

    Science.gov (United States)

    Ullah, Muhammad S.; Yousuf, Abdul Hamid Bin; Es-Sakhi, Azzedin D.; Chowdhury, Masud H.

    2018-04-01

    Molybdenum disulfide (MoS2) is considered as a promising alternative to conventional semiconductor materials that used in the IC industry because of its novel properties. In this paper, we explore the optical and electronic properties of MoS2 for photodetector and transistors applications. This simulation is done using `DFT materials properties simulator'. Our findings show that mono- and multi-layer MoS2 is suitable for conventional and tunnel FET applications due to direct and indirect band-gap respectively. The bulk MoS2 crystal, which are composed of stacked layers have indirect bandgap and mono-layer MoS2 crystal form direct bandgap at the K-point of Brillouin zone. Indirect bandgap of bulk MoS2 crystal implies that phonons need to be involved in band-to-band tunneling (BTBT) process. Degenerately doped semiconductor, which is basically spinning the Fermi level, changing the DOS profile, and thinning the indirect bandgap that allow tunneling from valence band to conduction band. The optical properties of MoS2 is explored in terms of Absorption coefficient, extinction coefficient and refractive index. Our results shows that a MoS2 based photodetector can be fabricate to detect light in the visible range (below 500nm). It is also observed that the MoS2 is most sensitive for the light of wavelength 450nm.

  8. Superconductivity in palladium-doped 2H-TaS2

    Science.gov (United States)

    Zhou, M. H.; Li, X. C.; Dong, C.

    2018-06-01

    A series of Pd x TaS2 (0.01 ≤ x ≤ 0.08) samples were prepared and characterized via scanning electron microscope, x-ray powder diffraction, resistivity, magnetization and specific heat measurements. The lattice parameter c associated with the interlayer distance increases monotonically with the Pd content while the parameter a remains essentially constant. The crystal structure of Pd0.08TaS2 has been determined and refined by Rietveld refinement. Pd0.08TaS2 is hexagonal (space group: P31c) with lattice parameters a = 3.3151(1) Å, c = 12.1497(9) Å. The superconducting transition temperature T c (0.8 K) of TaS2 can be dramatically enhanced by Pd doping, and the maximum T c of 4.2 K, about five times the T c of pure TaS2, is obtained in Pd0.04TaS2. We have determined the superconducting parameters of Pd0.04TaS2, and found that the enhancement of T c can be attributed to the increase of density of states at the Fermi level. The charge density wave (CDW) of TaS2 is gradually suppressed with Pd doping and disappears in Pd0.06TaS2. This suggests that there is a competitive interplay between superconductivity and CDW in this system.

  9. Interfacial chemical reactions between MoS2 lubricants and bearing materials

    Science.gov (United States)

    Zabinski, J. S.; Tatarchuk, B. J.

    1989-01-01

    XPS and conversion-electron Moessbauer spectroscopy (CEMS) were used to examine iron that was deposited on the basal plane of MoS2 single crystals and subjected to vacuum annealing, oxidizing, and reducing environments. Iron either intercalated into the MoS2 structure or formed oriented iron sulfides, depending on the level of excess S in the MoS2 structure. CEMS data demonstrated that iron sulfide crystal structures preferentially aligned with respect to the MoS2 basal plane, and that alignment (and potentially adhesion) could be varied by appropriate high-temperature annealing procedures.

  10. Sequential structural and optical evolution of MoS2 by chemical synthesis and exfoliation

    Science.gov (United States)

    Kim, Ju Hwan; Kim, Jungkil; Oh, Si Duck; Kim, Sung; Choi, Suk-Ho

    2015-06-01

    Various types of MoS2 structures are successfully obtained by using economical and facile sequential synthesis and exfoliation methods. Spherically-shaped lumps of multilayer (ML) MoS2 are prepared by using a conventional hydrothermal method and were subsequently 1st-exfoliated in hydrazine while being kept in autoclave to be unrolled and separated into five-to-six-layer MoS2 pieces of several-hundred nm in size. The MoS2 MLs are 2nd-exfoliated in sodium naphthalenide under an Ar ambient to finally produce bilayer MoS2 crystals of ~100 nm. The sequential exfoliation processes downsize MoS2 laterally and reduce its number of layers. The three types of MoS2 allotropes exhibit particular optical properties corresponding to their structural differences. These results suggest that two-dimensional MoS2 crystals can be prepared by employing only chemical techniques without starting from high-pressure-synthesized bulk MoS2 crystals.

  11. A charged residue at the subunit interface of PCNA promotes trimer formation by destabilizing alternate subunit interactions

    International Nuclear Information System (INIS)

    Freudenthal, Bret D.; Gakhar, Lokesh; Ramaswamy, S.; Washington, M. Todd

    2009-01-01

    Eukaryotic proliferating cell nuclear antigen (PCNA), an essential accessory factor in DNA replication and repair, is a ring-shaped homotrimer. A novel nontrimeric structure of E113G-mutant PCNA protein is reported, which shows that this protein forms alternate subunit interactions. It is concluded that the charged side chain of Glu113 promotes normal trimer formation by destabilizing these alternate subunit interactions. Eukaryotic proliferating cell nuclear antigen (PCNA) is an essential replication accessory factor that interacts with a variety of proteins involved in DNA replication and repair. Each monomer of PCNA has an N-terminal domain A and a C-terminal domain B. In the structure of the wild-type PCNA protein, domain A of one monomer interacts with domain B of a neighboring monomer to form a ring-shaped trimer. Glu113 is a conserved residue at the subunit interface in domain A. Two distinct X-ray crystal structures have been determined of a mutant form of PCNA with a substitution at this position (E113G) that has previously been studied because of its effect on translesion synthesis. The first structure was the expected ring-shaped trimer. The second structure was an unanticipated nontrimeric form of the protein. In this nontrimeric form, domain A of one PCNA monomer interacts with domain A of a neighboring monomer, while domain B of this monomer interacts with domain B of a different neighboring monomer. The B–B interface is stabilized by an antiparallel β-sheet and appears to be structurally similar to the A–B interface observed in the trimeric form of PCNA. The A–A interface, in contrast, is primarily stabilized by hydrophobic interactions. Because the E113G substitution is located on this hydrophobic surface, the A–A interface should be less favorable in the case of the wild-type protein. This suggests that the side chain of Glu113 promotes trimer formation by destabilizing these possible alternate subunit interactions

  12. Determinants of RNA polymerase alpha subunit for interaction with beta, beta', and sigma subunits: hydroxyl-radical protein footprinting.

    OpenAIRE

    Heyduk, T; Heyduk, E; Severinov, K; Tang, H; Ebright, R H

    1996-01-01

    Escherichia coli RNA polymerase (RNAP) alpha subunit serves as the initiator for RNAP assembly, which proceeds according to the pathway 2 alpha-->alpha 2-->alpha 2 beta-->alpha 2 beta beta'-->alpha 2 beta beta' sigma. In this work, we have used hydroxyl-radical protein footprinting to define determinants of alpha for interaction with beta, beta', and sigma. Our results indicate that amino acids 30-75 of alpha are protected from hydroxyl-radical-mediated proteolysis upon interaction with beta ...

  13. Heterotrimeric G protein subunits are located on rat liver endosomes

    Directory of Open Access Journals (Sweden)

    Van Dyke Rebecca W

    2004-01-01

    Full Text Available Abstract Background Rat liver endosomes contain activated insulin receptors and downstream signal transduction molecules. We undertook these studies to determine whether endosomes also contain heterotrimeric G proteins that may be involved in signal transduction from G protein-coupled receptors. Results By Western blotting Gsα, Giα1,2, Giα3 and Gβ were enriched in both canalicular (CM and basolateral (BLM membranes but also readily detectable on three types of purified rat liver endosomes in the order recycling receptor compartment (RRC > compartment for uncoupling of receptor and ligand (CURL > multivesicular bodies (MVB >> purified secondary lysosomes. Western blotting with antibodies to Na, K-ATPase and to other proteins associated with plasma membranes and intracellular organelles indicated this was not due to contamination of endosome preparations by CM or BLM. Adenylate cyclase (AC was also identified on purified CM, BLM, RRC, CURL and MVB. Percoll gradient fractionation of liver postnuclear supernatants demonstrated co-occurrence of endosomes and heterotrimeric G protein subunits in fractions with little plasma membrane markers. By confocal microscopy, punctate staining for Gsα, Giα3 and Gβ corresponded to punctate areas of endocytosed Texas red-dextran in hepatocytes from control and cholera toxin-treated livers. Conclusion We conclude that heterotrimeric G protein subunits as well as AC likely traffic into hepatocytes on endosome membranes, possibly generating downstream signals spatially separate from signalling generated at the plasma membrane, analogous to the role(s of internalized insulin receptors.

  14. Fungal mediator tail subunits contain classical transcriptional activation domains.

    Science.gov (United States)

    Liu, Zhongle; Myers, Lawrence C

    2015-04-01

    Classical activation domains within DNA-bound eukaryotic transcription factors make weak interactions with coactivator complexes, such as Mediator, to stimulate transcription. How these interactions stimulate transcription, however, is unknown. The activation of reporter genes by artificial fusion of Mediator subunits to DNA binding domains that bind to their promoters has been cited as evidence that the primary role of activators is simply to recruit Mediator. We have identified potent classical transcriptional activation domains in the C termini of several tail module subunits of Saccharomyces cerevisiae, Candida albicans, and Candida dubliniensis Mediator, while their N-terminal domains are necessary and sufficient for their incorporation into Mediator but do not possess the ability to activate transcription when fused to a DNA binding domain. This suggests that Mediator fusion proteins actually are functioning in a manner similar to that of a classical DNA-bound activator rather than just recruiting Mediator. Our finding that deletion of the activation domains of S. cerevisiae Med2 and Med3, as well as C. dubliniensis Tlo1 (a Med2 ortholog), impairs the induction of certain genes shows these domains function at native promoters. Activation domains within coactivators are likely an important feature of these complexes and one that may have been uniquely leveraged by a common fungal pathogen. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

  15. Thermostable cross-protective subunit vaccine against Brucella species.

    Science.gov (United States)

    Cherwonogrodzky, John W; Barabé, Nicole D; Grigat, Michelle L; Lee, William E; Poirier, Robert T; Jager, Scott J; Berger, Bradley J

    2014-12-01

    A subunit vaccine candidate was produced from Brucella suis 145 (biovar 4; expressing both the A antigen of Brucella abortus and the M antigen of Brucella melitensis). The preparation consisted mostly of polysaccharide (PS; >90% [wt/wt]; both cell-associated PS and exo-PS were combined) and a small amount of protein (1 to 3%) with no apparent nucleic acids. Vaccinated mice were protected (these had a statistically significant reduction in bacterial colonization compared to that of unvaccinated controls) when challenged with representative strains of three Brucella species most pathogenic for humans, i.e., B. abortus, B. melitensis, and B. suis. As little as 1 ng of the vaccine, without added adjuvant, protected mice against B. suis 145 infection (5 × 10(5) CFU), and a single injection of 1 μg of this subunit vaccine protected mice from B. suis 145 challenge for at least 14 months. A single immunization induced a serum IgG response to Brucella antigens that remained elevated for up to 9 weeks. The use of heat (i.e., boiling-water bath, autoclaving) in the vaccine preparation showed that it was thermostable. This method also ensured safety and security. The vaccine produced was immunogenic and highly protective against multiple strains of Brucella and represents a promising candidate for further evaluation. Copyright © 2014, American Society for Microbiology. All Rights Reserved.

  16. Binding of ATP by pertussis toxin and isolated toxin subunits

    International Nuclear Information System (INIS)

    Hausman, S.Z.; Manclark, C.R.; Burns, D.L.

    1990-01-01

    The binding of ATP to pertussis toxin and its components, the A subunit and B oligomer, was investigated. Whereas, radiolabeled ATP bound to the B oligomer and pertussis toxin, no binding to the A subunit was observed. The binding of [ 3 H]ATP to pertussis toxin and the B oligomer was inhibited by nucleotides. The relative effectiveness of the nucleotides was shown to be ATP > GTP > CTP > TTP for pertussis toxin and ATP > GTP > TTP > CTP for the B oligomer. Phosphate ions inhibited the binding of [ 3 H]ATP to pertussis toxin in a competitive manner; however, the presence of phosphate ions was essential for binding of ATP to the B oligomer. The toxin substrate, NAD, did not affect the binding of [ 3 H]ATP to pertussis toxin, although the glycoprotein fetuin significantly decreased binding. These results suggest that the binding site for ATP is located on the B oligomer and is distinct from the enzymatically active site but may be located near the eukaryotic receptor binding site

  17. Binding of ATP by pertussis toxin and isolated toxin subunits

    Energy Technology Data Exchange (ETDEWEB)

    Hausman, S.Z.; Manclark, C.R.; Burns, D.L. (Center for Biologics Evaluation and Research, Bethesda, MD (USA))

    1990-07-03

    The binding of ATP to pertussis toxin and its components, the A subunit and B oligomer, was investigated. Whereas, radiolabeled ATP bound to the B oligomer and pertussis toxin, no binding to the A subunit was observed. The binding of ({sup 3}H)ATP to pertussis toxin and the B oligomer was inhibited by nucleotides. The relative effectiveness of the nucleotides was shown to be ATP > GTP > CTP > TTP for pertussis toxin and ATP > GTP > TTP > CTP for the B oligomer. Phosphate ions inhibited the binding of ({sup 3}H)ATP to pertussis toxin in a competitive manner; however, the presence of phosphate ions was essential for binding of ATP to the B oligomer. The toxin substrate, NAD, did not affect the binding of ({sup 3}H)ATP to pertussis toxin, although the glycoprotein fetuin significantly decreased binding. These results suggest that the binding site for ATP is located on the B oligomer and is distinct from the enzymatically active site but may be located near the eukaryotic receptor binding site.

  18. Role of the beta subunit of casein kinase-2 on the stability and specificity of the recombinant reconstituted holoenzyme

    DEFF Research Database (Denmark)

    Meggio, F; Boldyreff, B; Marin, O

    1992-01-01

    Recombinant human alpha subunit from casein kinase-2 (CK-2) was subjected, either alone or in combination with recombinant human beta subunit, to high temperature, tryptic digestion and urea treatment. In all three cases, it was shown that the presence of the beta subunit could drastically reduce...... the autophosphorylation site. It is suggested that the acidic domain of the beta subunit, encompassing residues 55-71, plays a role in the interactions between the beta and alpha subunits....

  19. Dreaming and insight

    Science.gov (United States)

    Edwards, Christopher L.; Ruby, Perrine M.; Malinowski, Josie E.; Bennett, Paul D.; Blagrove, Mark T.

    2013-01-01

    This paper addresses claims that dreams can be a source of personal insight. Whereas there has been anecdotal backing for such claims, there is now tangential support from findings of the facilitative effect of sleep on cognitive insight, and of REM sleep in particular on emotional memory consolidation. Furthermore, the presence in dreams of metaphorical representations of waking life indicates the possibility of novel insight as an emergent feature of such metaphorical mappings. In order to assess whether personal insight can occur as a result of the consideration of dream content, 11 dream group discussion sessions were conducted which followed the Ullman Dream Appreciation technique, one session for each of 11 participants (10 females, 1 male; mean age = 19.2 years). Self-ratings of deepened self-perception and personal gains from participation in the group sessions showed that the Ullman technique is an effective procedure for establishing connections between dream content and recent waking life experiences, although wake life sources were found for only 14% of dream report text. The mean Exploration-Insight score on the Gains from Dream Interpretation questionnaire was very high and comparable to outcomes from the well-established Hill (1996) therapist-led dream interpretation method. This score was associated between-subjects with pre-group positive Attitude Toward Dreams (ATD). The need to distinguish “aha” experiences as a result of discovering a waking life source for part of a dream, from “aha” experiences of personal insight as a result of considering dream content, is discussed. Difficulties are described in designing a control condition to which the dream report condition can be compared. PMID:24550849

  20. OpenGL Insights

    CERN Document Server

    Cozzi, Patrick

    2012-01-01

    Get Real-World Insight from Experienced Professionals in the OpenGL Community With OpenGL, OpenGL ES, and WebGL, real-time rendering is becoming available everywhere, from AAA games to mobile phones to web pages. Assembling contributions from experienced developers, vendors, researchers, and educators, OpenGL Insights presents real-world techniques for intermediate and advanced OpenGL, OpenGL ES, and WebGL developers. Go Beyond the Basics The book thoroughly covers a range of topics, including OpenGL 4.2 and recent extensions. It explains how to optimize for mobile devices, explores the design

  1. World energy insight 2011

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2011-11-15

    The World Energy Insight 2011 is the official publication of the World Energy Council. It includes interviews, articles and case studies from a distinguished panel of World Energy Council Officers, CEOs, government ministers, academics and opinion formers from all areas of the energy sector and provides perspectives from around the globe. Government, industry and NGO's offer both policy and technology perspectives. The insights within this publication add to the work that WEC is doing to provide the forum for energy leaders, along with the on-going WEC studies and programmes on Energy Policies, 2050 Energy Scenarios, Energy Resources & Technologies, Energy for Urban Innovation, Rules Of Energy Trade and Global Energy Access.

  2. MoS2-modified ZnO quantum dots nanocomposite: Synthesis and ultrafast humidity response

    International Nuclear Information System (INIS)

    Ze, Lu; Yueqiu, Gong; Xujun, Li; Yong, Zhang

    2017-01-01

    Highlights: • MoS 2 @ZnO QDs composite structure was synthesized by two-steps methods. • Ultrafast humidity sensing response is achieved by MoS 2 @ZnO QDs humidity sensor. • Sensor performs excellent cycle stability from 11% to 95% RH. • Humidity sensor could detect wide humidity range (11–95%). - Abstract: In this work, ZnO quantum dots (QDs), layered MoS 2 and MoS 2 -modified ZnO QDs (MoS 2 @ZnO QDs) nanocomposite were synthesized and then applied as humidity sensor. The crystal structure, morphology and element distribution of ZnO QDs, MoS 2 and MoS 2 @ZnO QDs were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and energy dispersive X-ray spectrometry, respectively. The humidity sensing characteristics of the MoS 2 and MoS 2 @ZnO QDs against various relative humidity were measured at room temperature. The results show that the MoS 2 @ZnO QDs sensor exhibits high sensitivity with an impedance variation of three or four orders of magnitude to relative humidity range of 11–95% and it exhibits a short response-recovery time (1 s for adsorption and 20 s for desorption) and excellent repeatability. The mechanisms of the excellent performance for humidity sensing of MoS 2 @ZnO QDs sensor were discussed based on its impedance properties. Our work could offer guidelines to design higher performance especially ultrafast humidity response sensor utilizing the nanocomposite structure with two dimensional material and QDs.

  3. Satukirjan tuottaminen S2 lapsille suomenkielen opetuksen tukemiseen : päiväkoti-ikäisten S2 lasten suomenkielen kehittyminen

    OpenAIRE

    Ketonummi, Taika

    2015-01-01

    Kasvavan maahanmuuton vuoksi yhä useammassa päiväkodissa on Suomi toisena kielenä (S2) lapsia. Monissa paikoissa haasteeksi onkin noussut näiden suomenkielen oppimisen tukeminen Sain kehittämistehtäväni Salon kaupungin Anisten päiväkodista, jossa minulta toivottiin materiaaleja S2 lasten suomenkielen opettamiseen. Tuotin yhteistyössä päiväkodin kanssa satukirjan, joka sisältää neljä arkipäivän aiheisiin liittyvää satua: aamun herätys, aamupala, ulkoleikki sekä iltapesu ja nukkumaan meno. ...

  4. Characterisation by nuclear magnetic resonance of the β catalytic subunit of the chloroplastic coupling factor

    International Nuclear Information System (INIS)

    Andre, Francois

    1986-09-01

    This academic work addressed the use of nuclear magnetic resonance (NMR) for the structural and dynamic study of the catalytic sub-unit of the extrinsic section of a membrane complex, the chloroplastic H+-ATPase. This work included the development of a protocol of preparation and quantitative purification of β subunits isolated from the CF1 for the elaboration of a concentrated sample for NMR, and then the study of the β subunit by using proton NMR

  5. Antibodies to the α-subunit of insulin receptor from eggs of immunized hens

    International Nuclear Information System (INIS)

    Song, C.; Yu, J.; Bai, D.H.; Hester, P.Y.; Kim, K.

    1985-01-01

    Simple methods for the generation, purification, and assay of antibodies to the α-subunit of insulin receptor from eggs of immunized hen have been described. Chicken antibodies against the α-subunit inhibit insulin binding to the receptor and stimulate glucose oxidation as well as autophosphorylation of the β-subunit. Thus the properties of chicken antibodies are very similar to those of antibodies found in human autoimmune diseases and different from rabbit antibodies obtained against the same antigen

  6. Cloning and sequencing of the casein kinase 2 alpha subunit from Zea mays

    DEFF Research Database (Denmark)

    Dobrowolska, G; Boldyreff, B; Issinger, O G

    1991-01-01

    The nucleotide sequence of the cDNA coding for the alpha subunit of casein kinase 2 of Zea mays has been determined. The cDNA clone contains an open reading frame of 996 nucleotides encoding a polypeptide comprising 332 amino acids. The primary amino acid sequence exhibits 75% identity to the alpha...... subunit and 71% identity to the alpha' subunit of human casein kinase 2....

  7. Compensatory expression of human -Acetylglucosaminyl-1-phosphotransferase subunits in mucolipidosis type III gamma

    OpenAIRE

    Pohl , Sandra; Tiede , Stephan; Castrichini , Monica; Cantz , Michael; Gieselmann , Volkmar; Braulke , Thomas

    2009-01-01

    Abstract The N-Acetylglucosaminyl-1-phosphotransferase plays a key role in the generation of mannose 6-phosphate (M6P) recognition markers essential for efficient transport of lysosomal hydrolases to lysosomes. The phosphotransferase is composed of six subunits (?2, ?2, ?2). The ?- and ?-subunits are catalytically active and encoded by a single gene, GNPTAB, whereas the ?-subunit encoded by GNPTG is proposed to recognize conformational structures common to lysosomal enzymes. Defects in GN...

  8. Subunits of the Snf1 kinase heterotrimer show interdependence for association and activity.

    Science.gov (United States)

    Elbing, Karin; Rubenstein, Eric M; McCartney, Rhonda R; Schmidt, Martin C

    2006-09-08

    The Snf1 kinase and its mammalian orthologue, the AMP-activated protein kinase (AMPK), function as heterotrimers composed of a catalytic alpha-subunit and two non-catalytic subunits, beta and gamma. The beta-subunit is thought to hold the complex together and control subcellular localization whereas the gamma-subunit plays a regulatory role by binding to and blocking the function of an auto-inhibitory domain (AID) present in the alpha-subunit. In addition, catalytic activity requires phosphorylation by a distinct upstream kinase. In yeast, any one of three Snf1-activating kinases, Sak1, Tos3, or Elm1, can fulfill this role. We have previously shown that Sak1 is the only Snf1-activating kinase that forms a stable complex with Snf1. Here we show that the formation of the Sak1.Snf1 complex requires the beta- and gamma-subunits in vivo. However, formation of the Sak1.Snf1 complex is not necessary for glucose-regulated phosphorylation of the Snf1 activation loop. Snf1 kinase purified from cells lacking the beta-subunits do not contain any gamma-subunit, indicating that the Snf1 kinase does not form a stable alphagamma dimer in vivo. In vitro kinase assays using purified full-length and truncated Snf1 proteins demonstrate that the kinase domain, which lacks the AID, is significantly more active than the full-length Snf1 protein. Addition of purified beta- and gamma-subunits could stimulate the kinase activity of the full-length alpha-subunit but only when all three subunits were present, suggesting an interdependence of all three subunits for assembly of a functional complex.

  9. The testis-specific Cα2 subunit of PKA is kinetically indistinguishable from the common Cα1 subunit of PKA

    Directory of Open Access Journals (Sweden)

    Herberg Friedrich W

    2011-08-01

    Full Text Available Abstract Background The two variants of the α-form of the catalytic (C subunit of protein kinase A (PKA, designated Cα1 and Cα2, are encoded by the PRKACA gene. Whereas Cα1 is ubiquitous, Cα2 expression is restricted to the sperm cell. Cα1 and Cα2 are encoded with different N-terminal domains. In Cα1 but not Cα2 the N-terminal end introduces three sites for posttranslational modifications which include myristylation at Gly1, Asp-specific deamidation at Asn2 and autophosphorylation at Ser10. Previous reports have implicated specific biological features correlating with these modifications on Cα1. Since Cα2 is not modified in the same way as Cα1 we tested if they have distinct biochemical activities that may be reflected in different biological properties. Results We show that Cα2 interacts with the two major forms of the regulatory subunit (R of PKA, RI and RII, to form cAMP-sensitive PKAI and PKAII holoenzymes both in vitro and in vivo as is also the case with Cα1. Moreover, using Surface Plasmon Resonance (SPR, we show that the interaction patterns of the physiological inhibitors RI, RII and PKI were comparable for Cα2 and Cα1. This is also the case for their potency to inhibit catalytic activities of Cα2 and Cα1. Conclusion We conclude that the regulatory complexes formed with either Cα1 or Cα2, respectively, are indistinguishable.

  10. The NH2-terminal php domain of the alpha subunit of the Escherichia coli replicase binds the epsilon proofreading subunit.

    Science.gov (United States)

    Wieczorek, Anna; McHenry, Charles S

    2006-05-05

    The alpha subunit of the replicase of all bacteria contains a php domain, initially identified by its similarity to histidinol phosphatase but of otherwise unknown function (Aravind, L., and Koonin, E. V. (1998) Nucleic Acids Res. 26, 3746-3752). Deletion of 60 residues from the NH2 terminus of the alpha php domain destroys epsilon binding. The minimal 255-residue php domain, estimated by sequence alignment with homolog YcdX, is insufficient for epsilon binding. However, a 320-residue segment including sequences that immediately precede the polymerase domain binds epsilon with the same affinity as the 1160-residue full-length alpha subunit. A subset of mutations of a conserved acidic residue (Asp43 in Escherichia coli alpha) present in the php domain of all bacterial replicases resulted in defects in epsilon binding. Using sequence alignments, we show that the prototypical gram+ Pol C, which contains the polymerase and proofreading activities within the same polypeptide chain, has an epsilon-like sequence inserted in a surface loop near the center of the homologous YcdX protein. These findings suggest that the php domain serves as a platform to enable coordination of proofreading and polymerase activities during chromosomal replication.

  11. Distinct forms of the β subunit of GTP-binding regulatory proteins identified by molecular cloning

    International Nuclear Information System (INIS)

    Fong, H.K.W.; Amatruda, T.T. III; Birren, B.W.; Simon, M.I.

    1987-01-01

    Two distinct β subunits of guanine nucleotide-binding regulatory proteins have been identified by cDNA cloning and are referred to as β 1 and β 1 subunits. The bovine transducin β subunit (β 1 ) has been cloned previously. The author now isolated and analyzed cDNA clones that encode the β 2 subunit from bovine adrenal, bovine brain, and a human myeloid leukemia cell line, HL-60. The 340-residue M/sub r/ 37,329 Β 2 protein is 90% identical with β 1 in predicted amino acid sequence, and it is also organized as a series of repetitive homologous segments. The major mRNA that encodes the bovine β 2 subunit is 1.7 kilobases in length. It is expressed at lower levels than β 1 subunit mRNA in all tissues examined. The β 1 and β 2 messages are expressed in cloned human cell lines. Hybridization of cDNA probes to bovine DNA showed that β 1 and β 2 are encoded by separate genes. The amino acid sequences for the bovine and human β 2 subunit are identical, as are the amino acid sequences for the bovine and human β 1 subunit. This evolutionary conservation suggests that the two β subunits have different roles in the signal transduction process

  12. Translation activity of chimeric ribosomes composed of Escherichia coli and Bacillus subtilis or Geobacillus stearothermophilus subunits

    Directory of Open Access Journals (Sweden)

    Sayaka Tsuji

    2017-07-01

    Full Text Available Ribosome composition, consisting of rRNA and ribosomal proteins, is highly conserved among a broad range of organisms. However, biochemical studies focusing on ribosomal subunit exchangeability between organisms remain limited. In this study, we show that chimeric ribosomes, composed of Escherichia coli and Bacillus subtilis or E. coli and Geobacillus stearothermophilus subunits, are active for β-galactosidase translation in a highly purified E. coli translation system. Activities of the chimeric ribosomes showed only a modest decrease when using E. coli 30 S subunits, indicating functional conservation of the 50 S subunit between these bacterial species.

  13. Specific radioimmunoassay of HCG and its α and β subunits: methods and results

    International Nuclear Information System (INIS)

    Reuter, A.M.; Schoonbrood, J.; Franchimont, P.

    1976-01-01

    To create antisera that are specific for the radioimmunoassay of HCG and its subunits, the antisera are neutralized by incubation with LH or HCG. For each RIA system the inhibition curves of HCG and its subunits LH, FSH, TSH and STH are obtained. The 125 I labelled hormones HCG, α and β subunits and LH were chromatographed over a Sephadex G 100 column. Serum of menopausal and pregnant women were chromatographed in the same way and the fractions subjected to RIA. HCG and its subunits were determined by RIA in the sera of patients with different kinds of cancer

  14. Immunochemical analysis of Micrococcus lysodeikticus (luteus) F1-ATPase and its subunits.

    Science.gov (United States)

    Urban, C; Salton, M R

    1983-08-31

    The F1-ATPase from Micrococcus lysodeikticus has been purified to 95% protein homogeneity in this laboratory and as all other bacterial F1S, possesses five distinct subunits with molecular weights ranging from 60 000 to 10 000 (Huberman, M. and Salton, M.R.J. (1979) Biochim. Biophys. Acta 547, 230-240). In this communication, we demonstrate the immunochemical reactivities of antibodies to native and SDS-dissociated subunits with the native and dissociated F1-ATPase and show that: (1) the antibodies generated to the native or SDS-dissociated subunits react with the native molecule; (2) all of the subunits comprising the F1 are antigenically unique as determined by crossed immunoelectrophoresis and the Ouchterlony double-diffusion techniques; (3) antibodies to the SDS-denatured individual delta- and epsilon-subunits can be used to destabilize the interaction of these specific subunits with the rest of the native F1; and (4) all subunit antibodies as well as anti-native F1 were found to inhibit ATPase activity to varying degrees, the strongest inhibition being seen with antibodies to the total F1 and anti-alpha- and anti-beta-subunit antibodies. The interaction of specific subunit antibodies may provide a new and novel way to study further and characterize the catalytic portions of F1-ATPases and in general may offer an additional method for the examination of multimeric proteins.

  15. Novel field-effect schottky barrier transistors based on graphene-MoS 2 heterojunctions

    KAUST Repository

    Tian, He; Tan, Zhen; Wu, Can; Wang, Xiaomu; Mohammad, Mohammad Ali; Xie, Dan; Yang, Yi; Wang, Jing; Li, Lain-Jong; Xu, Jun; Ren, Tian-Ling

    2014-01-01

    0.5-20 cm2/V.s). Here, we report a novel field-effect Schottky barrier transistors (FESBT) based on graphene-MoS2 heterojunction (GMH), where the characteristics of high mobility from graphene and high on-off ratio from MoS2 are properly balanced

  16. A Route to Permanent Valley Polarization in Monolayer MoS2

    KAUST Repository

    Singh, Nirpendra

    2016-10-24

    Realization of permanent valley polarization in Cr-doped monolayer MoS2 is found to be unfeasible because of extended moment formation. Introduction of an additional hole is suggested as a viable solution. V-doped monolayer MoS2 is demonstrated to sustain permanent valley polarization and therefore can serve as a prototype material for valleytronics.

  17. Few-layer MoS2 as nitrogen protective barrier

    Science.gov (United States)

    Akbali, B.; Yanilmaz, A.; Tomak, A.; Tongay, S.; Çelebi, C.; Sahin, H.

    2017-10-01

    We report experimental and theoretical investigations of the observed barrier behavior of few-layer MoS2 against nitrogenation. Owing to its low-strength shearing, low friction coefficient, and high lubricity, MoS2 exhibits the demeanor of a natural N-resistant coating material. Raman spectroscopy is done to determine the coating capability of MoS2 on graphene. Surface morphology of our MoS2/graphene heterostructure is characterized by using optical microscopy, scanning electron microscopy, and atomic force microscopy. In addition, density functional theory-based calculations are performed to understand the energy barrier performance of MoS2 against nitrogenation. The penetration of nitrogen atoms through a defect-free MoS2 layer is prevented by a very high vertical diffusion barrier, indicating that MoS2 can serve as a protective layer for the nitrogenation of graphene. Our experimental and theoretical results show that MoS2 material can be used both as an efficient nanocoating material and as a nanoscale mask for selective nitrogenation of graphene layer.

  18. Hydrothermal synthesis of flower-like MoS2 nanospheres for electrochemical supercapacitors.

    Science.gov (United States)

    Zhou, Xiaoping; Xu, Bin; Lin, Zhengfeng; Shu, Dong; Ma, Lin

    2014-09-01

    Flower-like MoS2 nanospheres were synthesized by a hydrothermal route. The structure and surface morphology of the as-prepared MoS2 was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The supercapacitive behavior of MoS2 in 1 M KCl electrolyte was studied by means of cyclic voltammetry (CV), constant current charge-discharge cycling (CD) and electrochemical impedance spectroscopy (EIS). The XRD results indicate that the as-prepared MoS2 has good crystallinity. SEM images show that the MoS2 nanospheres have uniform sizes with mean diameter about 300 nm. Many nanosheets growing on the surface make the MoS2 nanospheres to be a flower-like structure. The specific capacitance of MoS2 is 122 F x g(-1) at 1 A x g(-1) or 114 F x g(-1) at 2 mv s(-1). All the experimental results indicate that MoS2 is a promising electrode material for electrochemical supercapacitors.

  19. Resilient carbon encapsulation of iron pyrite (FeS2) cathodes in lithium ion batteries

    Science.gov (United States)

    Yoder, Tara S.; Tussing, Matthew; Cloud, Jacqueline E.; Yang, Yongan

    2015-01-01

    Converting iron pyrite (FeS2) from a non-cyclable to a cyclable cathode material for lithium ion batteries has been an ongoing challenge in recent years. Herein we report a promising mitigation strategy: wet-chemistry based conformal encapsulation of synthetic FeS2 nanocrystals in a resilient carbon (RC) matrix (FeS2@RC). The FeS2@RC composite was fabricated by dispersing autoclave-synthesized FeS2 nanocrystals in an aqueous glucose solution, polymerizing the glucose in a hydrothermal reactor, and finally heating the polymer/FeS2 composite in a tube furnace to partially carbonize the polymer. The FeS2@RC electrodes showed superior cyclability compared with the FeS2 electrodes, that is, 25% versus 1% of retention at the 20th cycle. Based on electrochemical analysis, XRD study, and SEM characterization, the performance enhancement was attributed to RC's ability to accommodate volume fluctuation, enhance charge transfer, alleviate detrimental side reactions, and suppress loss of the active material. Furthermore, the remaining issues associated with the current system were identified and future research directions were proposed.

  20. Liquid-Phase Co-Exfoliated Graphene/MoS2 Nanocomposite for Methanol Gas Sensing.

    Science.gov (United States)

    Zhang, Shao-Lin; Yue, Hongyan; Liang, Xishuang; Yang, Woo-Chul

    2015-10-01

    We developed an efficient method to co-exfoliate graphite and MoS2 to fabricate graphene/MoS2 nanocomposite. The size, morphology, and crystal structure of the graphene/MoS2 nanocomposite were carefully examined. The as-prepared graphene/MoS2 nanocomposite was fabricated into thin film sensor by a facile drop casting method and tested with methanol gas in various concentrations. The sensitivity, response time, and repeatability of the graphene/MoS2 nanocomposite sensor towards methanol gas were systematically investigated. A pure MoS2 based thin film sensor was also prepared and compared with the nanocomposite sensor to better understand the synergetic effect in the sensing performance. Our research demonstrated that compositing MoS2 with graphene could overcome the shortcoming of MoS2 as a sensor material and bring in a promising gas-sensing performance with a quicker response/recovery time and an enhanced sensitivity. Moreover, this composited material with a distinct structure and an excellent electronic property is expected to have potential application in various fields, such as optoelectronic.

  1. Research progress in photolectric materials of CuFeS2

    Science.gov (United States)

    Jing, Mingxing; Li, Jing; Liu, Kegao

    2018-03-01

    CuFeS2 as a photoelectric material, there are many advantages, such as high optical absorption coefficient, direct gap semiconductor, thermal stability, no photo-recession effect and so on. Because of its low price, abundant reserves and non-toxic, CuFeS2 has attracted extensive attention of scientists.Preparation method of thin film solar cells are included that Electrodeposition, sputtering, thermal evaporation, thermal spraying method, co-reduction method.In this paper, the development of CuFeS2 thin films prepared by co-reduction method and co-reduction method is introduced.In this paper, the structure and development of solar cells, advantages of CuFeS2 as solar cell material, the structure and photoelectric properties and magnetic properties of CuFeS2, preparation process analysis of CuFeS2 thin film, research and development of CuFeS2 in solar cells is included herein. Finally, the development trend of CuFeS2 optoelectronic materials is analyzed and further research directions are proposed.

  2. MoS2 coated hollow carbon spheres for anodes of lithium ion batteries

    International Nuclear Information System (INIS)

    Zhang, Yufei; Wang, Ye; Shi, Wenhui; Yang, Huiying; Yang, Jun; Huang, Wei; Dong, Xiaochen

    2016-01-01

    With the assistance of resorcinol–formaldehyde, MoS 2 coated hollow carbon spheres (C@MoS 2 ) were synthesized through a facile hydrothermal route followed by heat and alkali treatments. The measurements indicate that the hollow carbon spheres with an average diameter of 300 nm and shell thickness of 20 nm. And the hollow core are uniformly covered by ultrathin MoS 2 nanosheets with a length increased to 400 nm. The unique hollow structure and the synergistic effect between carbon layer and MoS 2 nanosheets significantly enhance the rate capability and electrochemical stability of C@MoS 2 spheres as anode material of lithium-ion battery. The synthesized C@MoS 2 delivered a capacity of 750 mAh g −1 at a current density of 100 mA g −1 . More importantly, the C@MoS 2 maintained a reversible capacity of 533 mAh g −1 even at a high current density of 1000 mA g −1 . The study indicated that MoS 2 coated hollow carbon spheres can be promising anode material for next generation high-performance lithium-ion batteries. (paper)

  3. S2Biom database with logistical components of the biomass value chain

    NARCIS (Netherlands)

    Annevelink, E.; Groot, de H.L.E.; Shah, N.; Giarola, S.; Pantaleo, M.; Anttila, P.; Vis, Martijn; Raa, te Rik; Berg, van den Douwe; Gabrielle, B.

    2015-01-01

    The S2Biom project (www.s2biom.eu) - Delivery of sustainable supply of non-food biomass to support
    a resource-efficient Bioeconomy in Europe - supports sustainable delivery chains of non-food biomass feedstock.
    This poses a logistical challenge because the quality and handling

  4. Structural and optical properties of Zn doped CuInS 2 thin films

    Indian Academy of Sciences (India)

    Copper indium sulphide (CIS) films were deposited by spray pyrolysis onto glass ... The effects of Zn (0–5%)molecular weight compared with CuInS2 Source and ... candidates for use as doped acceptors to fabricate CuInS2-based solar cells.

  5. The Interface between Gd and Monolayer MoS2: A First-Principles Study

    KAUST Repository

    Zhang, Xuejing; Mi, Wenbo; Wang, Xiaocha; Cheng, Yingchun; Schwingenschlö gl, Udo

    2014-01-01

    We analyze the electronic structure of interfaces between two-, four- and six-layer Gd(0001) and monolayer MoS2 by first-principles calculations. Strong chemical bonds shift the Fermi energy of MoS2 upwards into the conduction band. At the surface

  6. Synthesis of MoS 2 Inorganic Fullerene-like Nanoparticles by a ...

    African Journals Online (AJOL)

    MoS2 nanoparticles with fullerene-like structure (IF-MoS2) were successfully obtained at heating temperature higher than 840 °C by a chemical vapour deposition method usingMoO3 and sulfur powders as raw materials. The synthesized samples were characterized by XRD, SEM, TEM, EDX and Raman spectrometry, ...

  7. Magnetic MoS2 on multiwalled carbon nanotubes for sulfide sensing.

    Science.gov (United States)

    Li, Chunxiang; Zhang, Dan; Wang, Jiankang; Hu, Pingan; Jiang, Zhaohua

    2017-07-04

    A novel hybrid metallic cobalt insided in multiwalled carbon nanotubles/molybdenum disulfide (Co@CNT/MoS 2 ) modified glass carbon electrode (GCE) was fabricated with a adhesive of Nafion suspension and used as chemical sensors for sulfide detection. Single-layered MoS 2 was coated on CNTs through magnetic traction force between paramagnetic monolayer MoS 2 and Co particles in CNTs. Co particles faciliated the collection of paramagnetic monolayer MoS 2 exfoliated from bulk MoS 2 in solution. Amperometric analysis, cycle voltammetry, cathodic stripping analysis and linear sweep voltammetry results showed the Co@CNT/MoS 2 modified GCE exhibited excellent electrochemical activity to sulfide in buffer solutions, but amperometric analysis was found to be more sensitive than the other methods. The amperometric response result indicated the Co@CNT/MoS 2 -modified GCE electrode was an excellent electrochemical sensor for detecting S 2- with a detection limit of 7.6 nM and sensitivity of 0.23 mA/μM. The proposed electrode was used for the determination of sulfide levels in hydrogen sulfide-pretreated fruits, and the method was also verified with recovery studies. Copyright © 2017 Elsevier B.V. All rights reserved.

  8. Atomic-scale structure of single-layer MoS2 nanoclusters

    DEFF Research Database (Denmark)

    Helveg, S.; Lauritsen, J. V.; Lægsgaard, E.

    2000-01-01

    We have studied using scanning tunneling microscopy (STM) the atomic-scale realm of molybdenum disulfide (MoS2) nanoclusters, which are of interest as a model system in hydrodesulfurization catalysis. The STM gives the first real space images of the shape and edge structure of single-layer MoS2...

  9. Non-stoichiometry of MoS2 phase prepared by sputtering

    International Nuclear Information System (INIS)

    Ito, T.; Nakajima, K.

    1978-01-01

    The lattice parameters and S/Mo atomic ratio in sputtered MoS 2 films have been examined as a function of sputtering conditions, especially the vacuum pressure in the chamber. It was found that the deposited films had a defect MoS 2 structure ranging from 1.6 to 2 in S/Mo ratio, depending on the pressure. (author)

  10. Alternative-splicing in the exon-10 region of GABA(A receptor beta(2 subunit gene: relationships between novel isoforms and psychotic disorders.

    Directory of Open Access Journals (Sweden)

    Cunyou Zhao

    Full Text Available BACKGROUND: Non-coding single nucleotide polymorphisms (SNPs in GABRB2, the gene for beta(2-subunit of gamma-aminobutyric acid type A (GABA(A receptor, have been associated with schizophrenia (SCZ and quantitatively correlated to mRNA expression and alternative splicing. METHODS AND FINDINGS: Expression of the Exon 10 region of GABRB2 from minigene constructs revealed this region to be an "alternative splicing hotspot" that readily gave rise to differently spliced isoforms depending on intron sequences. This led to a search in human brain cDNA libraries, and the discovery of two novel isoforms, beta(2S1 and beta(2S2, bearing variations in the neighborhood of Exon-10. Quantitative real-time PCR analysis of postmortem brain samples showed increased beta(2S1 expression and decreased beta(2S2 expression in both SCZ and bipolar disorder (BPD compared to controls. Disease-control differences were significantly correlated with SNP rs187269 in BPD males for both beta(2S1 and beta(2S2 expressions, and significantly correlated with SNPs rs2546620 and rs187269 in SCZ males for beta(2S2 expression. Moreover, site-directed mutagenesis indicated that Thr(365, a potential phosphorylation site in Exon-10, played a key role in determining the time profile of the ATP-dependent electrophysiological current run-down. CONCLUSION: This study therefore provided experimental evidence for the importance of non-coding sequences in the Exon-10 region in GABRB2 with respect to beta(2-subunit splicing diversity and the etiologies of SCZ and BPD.

  11. Global China Insights

    NARCIS (Netherlands)

    Segers, Rien; Fischer, Ingrid

    Journal in which the Groningen Confucius Institute (GCI) shares different perspectives on China and provides insights into China from as many different aspects as possible. GCI aims to provide a full view of real China to the readers as well as featuring international and comprehensive perspectives,

  12. Global China Insights

    NARCIS (Netherlands)

    Segers, Rien; Havinga, Marieke; Fischer, Ingrid

    2013-01-01

    Journal in which the Groningen Confucius Institute (GCI) shares different perspectives on China and provides insights into China from as many different aspects as possible. GCI aims to provide a full view of real China to the readers as well as featuring international and comprehensive perspectives,

  13. Africa Insight: Submissions

    African Journals Online (AJOL)

    Author Guidelines. Africa Insight is a quarterly, peer-reviewed journal of the Africa Institute of South Africa (AISA). It is accredited by the Department of Higher ... Abstract: All articles should be accompanied by an abstract of between 100 and 125 words stating the main research problem, major findings and conclusion(s).

  14. Effect of HMM Glutenin Subunits on Wheat Quality Attributes

    Directory of Open Access Journals (Sweden)

    Daniela Horvat

    2009-01-01

    Full Text Available Glutenin is a group of polymeric gluten proteins. Glutenin molecules consist of glutenin subunits linked together with disulphide bonds and having higher (HMM-GS and lower (LMM-GS molecular mass. The main objective of this study is the evaluation of the influence of HMM-GS on flour processing properties. Seven bread wheat genotypes with contrasting quality attributes and different HMM-GS composition were analyzed during three years. The composition and quantity of HMM-GS were determined by SDS-PAGE and RP-HPLC, respectively. The quality diversity among genotypes was estimated by the analysis of wheat grain, and flour and bread quality parameters. The presence of HMM glutenin subunits 1 and 2* at Glu-A1 and the subunits 5+10 at Glu-D1 loci, as well as a higher proportion of total HMM-GS, had a positive effect on wheat quality. Cluster analysis of the three groups of data (genotype and HMM-GS, flour and bread quality, and dough rheology yielded the same hierarchical structure for the first top three levels, and similarity of the corresponding dendrograms was proved by the principal eigenvalues of the corresponding Euclidian distance matrices. The obtained similarity in classification based on essentially different types of measurements reflects strong natural association between genetic data, product quality and physical properties. Principal component analysis (PCA was applied to effectively reduce large data set into lower dimensions of latent variables amenable for the analysis. PCA analysis of the total set of data (15 variables revealed a very strong interrelationship between the variables. The first three PCA components accounted for 96 % of the total variance, which was significant to the level of 0.05 and was considered as the level of experimental error. These data imply that the quality of wheat cultivars can be contributed to HMM-GS data and should be taken into account in breeding programs assisted by computer models with the aim to

  15. Enhancement of photocatalytic property on ZnS/MoS2 composite under visible light irradiation

    Directory of Open Access Journals (Sweden)

    Cheng Jiushan

    2017-01-01

    Full Text Available In this paper, the composite ZnS/MoS2 was obtained via two steps including solvothermal methods. The as-synthesized sample was characterized by X-ray diffraction (XRD, scanning electron microscopy (SEM and UV-Vis. diffuse reflectance spectra (DRS. The photocatalytic activity of the product was evaluated through photocatalytic degradation of Rhodamine B (Rh B under UV-Vis. light irradiation; the electrical conductivity of ZnS/MoS2 composites was significantly improved compared to ZnS, MoS2, respectively. The results showed that the ZnS/MoS2 composite photocatalyst possesses better photocatalytic activity in degrading Rh B than the single ZnS or the single MoS2. The better photocatalytic properties may be due to the synergetic effect of two semiconductors, because of which electrons and holes were separated effectively. And its specific microstructure played an active role in evaluating photocatalytic performance.

  16. Electronic structure and transport properties of zigzag MoS2 nanoribbons

    Science.gov (United States)

    Sharma, Uma Shankar; Shah, Rashmi; Mishra, Pankaj Kumar

    2018-05-01

    In present study, electronic and transport properties of the 8zigzag MoS2 nanoribbons (8ZMoS2NRs) are investigated using ab-initio density functional theory [DFT]. The calculations were performed using nonequilibrium Green's function (NEGF) formalism based on DFT as implemented in the TranSiesta code. Results show that the defect can introduces few extra states into the energy gap, which lead nanoribbons to reveal a metallic characteristic. The voltage-current (VI) graph of 8ZMoS2NRs show a threshold current increases after introducing Mo defect in the devices. when introducing a Mo vacancy under low biases, the current will be suppressed—whereas under high biases, the current through the defected 8ZMoS2NRs will increases rapidly, due to the other channel being opened, that make possibility of 8ZMoS2NRs application in electronic devices such as voltage regulation.

  17. Chemical formation and spectroscopy of S2 in a free jet expansion

    Science.gov (United States)

    Heaven, M.; Miller, Terry A.; Bondybey, V. E.

    1984-01-01

    H2S seeded in a free jet expansion of Ar is photolyzed by an ArF laser. The liberated free radical fragments react to form S2 molecules, cooled rotationally by the jet to ≲20 K. A detailed rotational analysis of the laser induced fluorescence spectrum of the 2-3, B-X band of S2 reveals localized perturbations due to the B″ 3Πu state of S2. A deperturbation analysis for both 32S2 and 32S34S spectra yields, in conjunction with recent work by Patino and Barrow, values for the rotational constant, spin-orbit coupling constant, and Te for B″ 3ΠuS2.

  18. Magnetic and electrical properties in BaNiS2-type solid solutions

    International Nuclear Information System (INIS)

    Irizawa, Akinori; Yoshimura, Kazuyoshi; Kosuge, Koji

    2000-01-01

    The magnetic and electrical properties are reported in the new solid solutions BaCo 1-x Cu x S 2 and BaNi 1-x Fe x S 2 . Both compounds show spin-glass-like behavior, although the type of spin frustrations is different with each other. BaCo 1-x Cu x S 2 shows a competition type spin-glass behavior with reentrant phenomenon from antiferromagnetic to spin-glass at low temperatures. BaNi 1-x Fe x S 2 shows a dilute type spin-glass behavior together with super-paramagnetic properties. The temperature variation of 57 Fe Moessbauer spectra in BaNi 0.8 Fe 0.2 S 2 is explicable in a framework of cluster-glass. (author)

  19. Analysis of the Genome and Chromium Metabolism-Related Genes of Serratia sp. S2.

    Science.gov (United States)

    Dong, Lanlan; Zhou, Simin; He, Yuan; Jia, Yan; Bai, Qunhua; Deng, Peng; Gao, Jieying; Li, Yingli; Xiao, Hong

    2018-05-01

    This study is to investigate the genome sequence of Serratia sp. S2. The genomic DNA of Serratia sp. S2 was extracted and the sequencing library was constructed. The sequencing was carried out by Illumina 2000 and complete genomic sequences were obtained. Gene function annotation and bioinformatics analysis were performed by comparing with the known databases. The genome size of Serratia sp. S2 was 5,604,115 bp and the G+C content was 57.61%. There were 5373 protein coding genes, and 3732, 3614, and 3942 genes were respectively annotated into the GO, KEGG, and COG databases. There were 12 genes related to chromium metabolism in the Serratia sp. S2 genome. The whole genome sequence of Serratia sp. S2 is submitted to the GenBank database with gene accession number of LNRP00000000. Our findings may provide theoretical basis for the subsequent development of new biotechnology to repair environmental chromium pollution.

  20. [Poor insight and psychosis].

    Science.gov (United States)

    Giotakos, O

    2017-01-01

    A variety of phenomena might be considered as reflecting impaired insight in psychosis, like failure to recognize signs, symptoms or disease, failure to derive appropriate cognitive representations, despite recognition of the disease, and misattribution of the source or cause of the disease. The unawareness of tardive dyskinesia symptoms in schizophrenic patients points that self-awareness deficits in schizophrenia may be domain specific. Poor insight is an independent phenomenological and a prevalent feature in psychotic disorders in general, and in schizophrenia in particular, but we don't know yet if delusions in schizophrenia are the result of an entirely normal attempt to account for abnormal perceptual experiences or a product of abnormal experience but of normal reasoning. The theoretical approaches regarding impaired insight include the disturbed perceptual input, the impaired linkage between thought and emotion and the breakdown of the process of self-monitoring and error checking. The inability to distinguish between internally and externally generated mental events has been described by the metarepresentation theory. This theory includes the awareness of ones' goals, which leads to disorders of willed action, the awareness of intention, which leads to movement disorders, and the awareness of intentions of others, which leads to paranoid delusions. The theory of metarepresentation implies mainly output mechanisms, like the frontal cortex, while the input mechanism implies posterior brain systems, including the parietal lobe. There are many similarities between the disturbances of awareness seen in schizophrenia and those seen as a result of known neurological impairment. Neuropsychological models of impaired insight typically attribute the disturbance to any of a variety of core deficits in the processing of information. In this respect, lack of insight is on conceptual par with alogia, apraxia or aphasia in reflecting disturbed cognitive processing. In

  1. Electronic structures of ReS2, ReSe2 and TcS2 in the real and the hypothetical undistorted structures

    NARCIS (Netherlands)

    Fang, CM; Wiegers, GA; Haas, C; deGroot, RA

    1997-01-01

    The transition-metal dichalcogenides ReX2 (X = Sor Se) and TcS2 with a d(3) electron configuration have distorted; CdCl2 and Cd(OH)(2) structures, respectively, with the Re(Tc) atoms in each layer forming parallelogram-shaped connected clusters (diamond chain). Ab-initio band-structure calculations

  2. Growth, structure and stability of sputter-deposited MoS2 thin films

    Directory of Open Access Journals (Sweden)

    Reinhard Kaindl

    2017-05-01

    Full Text Available Molybdenum disulphide (MoS2 thin films have received increasing interest as device-active layers in low-dimensional electronics and also as novel catalysts in electrochemical processes such as the hydrogen evolution reaction (HER in electrochemical water splitting. For both types of applications, industrially scalable fabrication methods with good control over the MoS2 film properties are crucial. Here, we investigate scalable physical vapour deposition (PVD of MoS2 films by magnetron sputtering. MoS2 films with thicknesses from ≈10 to ≈1000 nm were deposited on SiO2/Si and reticulated vitreous carbon (RVC substrates. Samples deposited at room temperature (RT and at 400 °C were compared. The deposited MoS2 was characterized by macro- and microscopic X-ray, electron beam and light scattering, scanning and spectroscopic methods as well as electrical device characterization. We find that room-temperature-deposited MoS2 films are amorphous, of smooth surface morphology and easily degraded upon moderate laser-induced annealing in ambient conditions. In contrast, films deposited at 400 °C are nano-crystalline, show a nano-grained surface morphology and are comparatively stable against laser-induced degradation. Interestingly, results from electrical transport measurements indicate an unexpected metallic-like conduction character of the studied PVD MoS2 films, independent of deposition temperature. Possible reasons for these unusual electrical properties of our PVD MoS2 thin films are discussed. A potential application for such conductive nanostructured MoS2 films could be as catalytically active electrodes in (photo-electrocatalysis and initial electrochemical measurements suggest directions for future work on our PVD MoS2 films.

  3. Evaluating Mechanical Properties of Few Layers MoS2 Nanosheets-Polymer Composites

    Directory of Open Access Journals (Sweden)

    Muhammad Bilal Khan

    2017-01-01

    Full Text Available The reinforcement effects of liquid exfoliated molybdenum disulphide (MoS2 nanosheets, dispersed in polystyrene (PS matrix, are evaluated here. The range of composites (0~0.002 volume fraction (Vf MoS2-PS is prepared via solution casting. Size selected MoS2 nanosheets (3~4 layers, with a lateral dimension L 0.5~1 µm, have improved Young’s modulus up to 0.8 GPa for 0.0002 Vf MoS2-PS as compared to 0.2 GPa observed for PS only. The ultimate tensile strength (UTS is improved considerably (~×3 with a minute addition of MoS2 nanosheets (0.00002 Vf. The MoS2 nanosheets lateral dimension and number of layers are approximated using atomic force microscopy (AFM. The composites formation is confirmed using X-ray diffraction (XRD and scanning electron microscopy (SEM. Theoretical predicted results (Halpin-Tsai model are well below the experimental findings, especially at lower concentrations. Only at maximum concentrations, the experimental and theoretical results coincide. The high aspect ratio of MoS2 nanosheets, homogeneous dispersion inside polymer, and their probable planar orientation are the possible reasons for the effective stress transfer, resulting in enhanced mechanical characteristics. Moreover, the micro-Vickers hardness (HV of the MoS2-PS is also improved from 19 (PS to 23 (0.002 Vf MoS2-PS as MoS2 nanosheets inclusion may hinder the deformation more effectively.

  4. Determination of hCG-alpha subunit in threatened pregnancy

    International Nuclear Information System (INIS)

    Talas, M.; Pohanka, J.; Fingerova, H.; Janouskova, M.; Krikal, Z.; Prasilova, J.; Zupkova, H.

    1987-01-01

    Radioimmunoassay of the hCG-alpha subunit was made using an antibody anti hCG-alpha serum, highly purified hCG-alpha for 125 I-labelling and the standard hCG-alpha. Sera of healthy pregnant women sampled throughout the whole pregnancies were used to determine x-bar±S.D. of hCG-alpha for 14-day intervals. Included in the study were groups of women with high risk of premature labor, late toxemia of pregnancy, twins and fetal hypotrophy. It was shown that increased hCG-alpha is found in pregnant women in whom signs of late toxemia of pregnancy are combined with high risk of premature labor, or with twin pregnancies, while in those with fetal hypotrophy hCG-alpha is within normal limits. (author). 3 figs., 7 refs

  5. Chaperonin Structure - The Large Multi-Subunit Protein Complex

    Directory of Open Access Journals (Sweden)

    Irena Roterman

    2009-03-01

    Full Text Available The multi sub-unit protein structure representing the chaperonins group is analyzed with respect to its hydrophobicity distribution. The proteins of this group assist protein folding supported by ATP. The specific axial symmetry GroEL structure (two rings of seven units stacked back to back - 524 aa each and the GroES (single ring of seven units - 97 aa each polypeptide chains are analyzed using the hydrophobicity distribution expressed as excess/deficiency all over the molecule to search for structure-to-function relationships. The empirically observed distribution of hydrophobic residues is confronted with the theoretical one representing the idealized hydrophobic core with hydrophilic residues exposure on the surface. The observed discrepancy between these two distributions seems to be aim-oriented, determining the structure-to-function relation. The hydrophobic force field structure generated by the chaperonin capsule is presented. Its possible influence on substrate folding is suggested.

  6. Glycine Receptor α2 Subunit Activation Promotes Cortical Interneuron Migration

    Directory of Open Access Journals (Sweden)

    Ariel Avila

    2013-08-01

    Full Text Available Glycine receptors (GlyRs are detected in the developing CNS before synaptogenesis, but their function remains elusive. This study demonstrates that functional GlyRs are expressed by embryonic cortical interneurons in vivo. Furthermore, genetic disruption of these receptors leads to interneuron migration defects. We discovered that extrasynaptic activation of GlyRs containing the α2 subunit in cortical interneurons by endogenous glycine activates voltage-gated calcium channels and promotes calcium influx, which further modulates actomyosin contractility to fine-tune nuclear translocation during migration. Taken together, our data highlight the molecular events triggered by GlyR α2 activation that control cortical tangential migration during embryogenesis.

  7. New light on the Kr-(4p55s2) Feshbach resonances: high-resolution electron scattering experiments and B-spline R-matrix calculations

    International Nuclear Information System (INIS)

    Hoffmann, T H; Ruf, M-W; Hotop, H; Zatsarinny, O; Bartschat, K; Allan, M

    2010-01-01

    In a joint experimental and theoretical effort, we carried out a detailed study of electron scattering from Kr atoms in the energy range of the low-lying Kr - (4p 5 5s 2 ) Feshbach resonances. Absolute angle-differential cross sections for elastic electron scattering were measured over the energy range 9.3-10.3 eV with an energy width of about 13 meV at scattering angles between 10 deg. and 180 deg. Using several sets of elastic scattering phase shifts, a detailed analysis of the sharp Kr - (4p 5 5s 2 2 P 3/2 ) resonance was carried out, resulting in a resonance width of Γ 3/2 3.6(2) meV. By direct comparison with the position of the Ar - (3p 5 4s 2 2 P 3/2 ) resonance, the energy for the Kr - (4p 5 5s 2 2 P 3/2 ) resonance was determined as E 3/2 = 9.489(3) eV. A Fano-type fit of the higher lying Kr - (4p 5 5s 2 2 P 1/2 ) resonance yielded the resonance parameters Γ 1/2 = 33(5) meV and E 1/2 = 10.126(4) eV. In order to obtain additional insights, B-spline R-matrix calculations were performed for both the elastic and the inelastic cross sections above the threshold for 4p 5 5s excitation. They provide the total and angle-differential cross sections for excitation of long-lived and short-lived levels of the 4p 5 5s configuration in Kr and branching ratios for the decay of the Kr - (4p 5 5s 2 2 P 1/2 ) resonance into the three available exit channels. The results are compared with selected experimental data.

  8. The subunit structure of the extracellular hemoglobin of Biomphalaria glabrata

    International Nuclear Information System (INIS)

    Arndt, Marcio H.L.; Naves, Cristiani F.; Xavier, Luciana P.; Santoro, Marcelo M.

    1997-01-01

    Full text. The hemoglobin of Biomphalaria glabrata was purified to homogeneity by a two step purification protocol using a gel filtration column (Superose 6 HR/Pharmacia ) followed by an anion exchange chromatography (MONO-Q Sepharose/Pharmacia). The dissociation products were analysed by a 5 - 15 % Polyacrylamide gel electrophoresis containing Sodium Dodecyl Sulfate (SDS-PAGE) giving a band of 270 K Daltons and a band of 180 K Daltons after reduction with β-mercaptoethanol. The same profile was obtained in a 3.5 % Agarose gel electrophoresis containing SDS (SDS-AGE) showing additional bands of higher molecular weight. These bands were proposed to be monomers, dimers and trimers and, after reduction in a Bidimensional SDS-AGE, the proposed monomers and dimers were decomposed in two and four bands that were interpreted as 1 - 4 chains. The hemoglobin was digested by four different proteases ( Thrombin, Trypsin, Chymotrypsin and Subtilisin ) showing several equivalent fragments with molecular weights multiples of its minimum molecular weight ( 17.7 K Daltons). The circular dichroism spectrum of the protein showed a characteristic high α-helix content. We proposed that this hemoglobin is a pentamer of approx. 360 K Daltons subunits each formed by two 180 K Daltons chains linked in pairs by disulfide bridges and each of these chains comprises ten Heme binding domains. These data were compared to other Planorbidae extracellular hemoglobins. Up to now, the quaternary structure of this hemoglobin (shape and disposition of the subunits) is unknown. It is intended to elucidate its structure by Small Angle X-Ray Scattering in Brazilian National Laboratory of Synchrotron Light (LNLS). (author)

  9. Differential regulation of thyrotropin subunit apoprotein and carbohydrate biosynthesis by thyroid hormone

    International Nuclear Information System (INIS)

    Taylor, T.; Weintraub, B.D.

    1985-01-01

    The regulation of TSH apoprotein and carbohydrate biosynthesis by thyroid hormone was studied by incubating pituitaries from normal and hypothyroid (3 weeks post-thyroidectomy) rats in medium containing [ 14 C]alanine and [ 3 H] glucosamine. After 6 h, samples were sequentially treated with anti-TSH beta to precipitate TSH and free TSH beta, anti-LH beta to clear the sample of LH and free LH beta, then anti-LH alpha to precipitate free alpha-subunit. Total proteins were acid precipitated. All precipitates were subjected to electrophoresis on sodium dodecyl sulfate-polyacrylamide gels, which were then sliced and assayed by scintillation spectrometry. In hypothyroid pituitaries plus medium, [ 14 C]alanine incorporation in combined and free beta-subunits was 26 times normal and considerably greater than the 3.4-fold increase seen in total protein; combined and free alpha-subunits showed no specific increase in apoprotein synthesis. [ 3 H]Glucosamine incorporation in combined alpha- and beta-subunits in hypothyroid samples was 13 and 21 times normal, respectively, and was greater than the 1.9-fold increase in total protein; free alpha-subunit showed no specific increase in carbohydrate synthesis. The glucosamine to alanine ratio, reflecting relative glycosylation of newly synthesized molecules, was increased in hypothyroidism for combined alpha-subunits, but not for combined beta-subunits, free alpha-subunits, or total proteins. In summary, short term hypothyroidism selectively stimulated TSH beta apoprotein synthesis and carbohydrate synthesis of combined alpha- and beta-subunits. Hypothyroidism also increased the relative glycosylation of combined alpha-subunit. Thus, thyroid hormone deficiency appears to alter the rate-limiting step in TSH assembly (i.e. beta-subunit synthesis) as well as the carbohydrate structure of TSH, which may play important roles in its biological function

  10. Copolymer semiconductors comprising thiazolothiazole or benzobisthiazole, or benzobisoxazole electron acceptor subunits, and electron donor subunits, and their uses in transistors and solar cells

    Science.gov (United States)

    Jenekhe, Samson A; Subramaniyan, Selvam; Ahmed, Eilaf; Xin, Hao; Kim, Felix Sunjoo

    2014-10-28

    The inventions disclosed, described, and/or claimed herein relate to copolymers comprising copolymers comprising electron accepting A subunits that comprise thiazolothiazole, benzobisthiazole, or benzobisoxazoles rings, and electron donating subunits that comprise certain heterocyclic groups. The copolymers are useful for manufacturing organic electronic devices, including transistors and solar cells. The invention also relates to certain synthetic precursors of the copolymers. Methods for making the copolymers and the derivative electronic devices are also described.

  11. Roles of the β subunit hinge domain in ATP synthase F1 sector: Hydrophobic network formed by introduced βPhe174 inhibits subunit rotation

    International Nuclear Information System (INIS)

    Nakanishi-Matsui, Mayumi; Kashiwagi, Sachiko; Kojima, Masaki; Nonaka, Takamasa; Futai, Masamitsu

    2010-01-01

    The ATP synthase β subunit hinge domain (βPhe148 ∼ βGly186, P-loop/α-helixB/loop/β-sheet4, Escherichia coli residue numbering) dramatically changes in conformation upon nucleotide binding. We previously reported that F 1 with the βSer174 to Phe mutation in the domain lowered the γ subunit rotation speed, and thus decreased the ATPase activity [M. Nakanishi-Matsui, S. Kashiwagi, T. Ubukata, A. Iwamoto-Kihara, Y. Wada, M. Futai, Rotational catalysis of Escherichia coli ATP synthase F 1 sector. Stochastic fluctuation and a key domain of the β subunit, J. Biol. Chem. 282 (2007) 20698-20704.]. Homology modeling indicates that the amino acid replacement induces a hydrophobic network, in which the βMet159, βIle163, and βAla167 residues of the β subunit are involved together with the mutant βPhe174. The network is expected to stabilize the conformation of β DP (nucleotide-bound form of the β subunit), resulting in increased activation energy for transition to β E (empty β subunit). The modeling further predicts that replacement of βMet159 with Ala or Ile weakens the hydrophobic network. As expected, these two mutations experimentally suppressed the ATPase activities as well as subunit rotation of βS174F. Furthermore, the rotation rate decreased with the increase of the strength in the hydrophobic network. These results indicate that the smooth conformational change of the β subunit hinge domain is pertinent for the rotational catalysis.

  12. Metallic CoS2 nanowire electrodes for high cycling performance supercapacitors

    Science.gov (United States)

    Ren, Ren; Faber, Matthew S.; Dziedzic, Rafal; Wen, Zhenhai; Jin, Song; Mao, Shun; Chen, Junhong

    2015-12-01

    We report metallic cobalt pyrite (CoS2) nanowires (NWs) prepared directly on current collecting electrodes, e.g., carbon cloth or graphite disc, for high-performance supercapacitors. These CoS2 NWs have a variety of advantages for supercapacitor applications. Because the metallic CoS2 NWs are synthesized directly on the current collector, the good electrical connection enables efficient charge transfer between the active CoS2 materials and the current collector. In addition, the open spaces between the sea urchin structure NWs lead to a large accessible surface area and afford rapid mass transport. Moreover, the robust CoS2 NW structure results in high stability of the active materials during long-term operation. Electrochemical characterization reveals that the CoS2 NWs enable large specific capacitance (828.2 F g-1 at a scan rate of 0.01 V s-1) and excellent long term cycling stability (0-2.5% capacity loss after 4250 cycles at 5 A g-1) for pseudocapacitors. This example of metallic CoS2 NWs for supercapacitor applications expands the opportunities for transition metal sulfide-based nanostructures in emerging energy storage applications.

  13. Ultra-broadband nonlinear saturable absorption of high-yield MoS2 nanosheets

    Science.gov (United States)

    Wei, Rongfei; Zhang, Hang; Hu, Zhongliang; Qiao, Tian; He, Xin; Guo, Qiangbing; Tian, Xiangling; Chen, Zhi; Qiu, Jianrong

    2016-07-01

    High-yield MoS2 nanosheets with strong nonlinear optical (NLO) responses in a broad near-infrared range were synthesized by a facile hydrothermal method. The observation of saturable absorption, which was excited by the light with photon energy smaller than the gap energy of MoS2, can be attributed to the enhancement of the hybridization between the Mo d-orbital and S p-orbital by the oxygen incorporation into MoS2. High-yield MoS2 nanosheets with high modulation depth and large saturable intensity generated a stable, passively Q-switched fiber laser pulse at 1.56 μm. The high output power of 1.08 mW can be attained under a very low pump power of 30.87 mW. Compared to recently reported passively Q-switched fiber lasers utilizing exfoliated MoS2 nanosheets, the efficiency of the laser for our passive Q-switching operation is larger and reaches 3.50%. This research may extend the understanding on the NLO properties of MoS2 and indicate the feasibility of the high-yield MoS2 nanosheets to passively Q-switched fiber laser effectively at low pump strengths.

  14. Enhanced photoresponse characteristics of transistors using CVD-grown MoS2/WS2 heterostructures

    Science.gov (United States)

    Shan, Junjie; Li, Jinhua; Chu, Xueying; Xu, Mingze; Jin, Fangjun; Fang, Xuan; Wei, Zhipeng; Wang, Xiaohua

    2018-06-01

    Semiconductor heterostructures based on transition metal dichalcogenides provide a broad platform to research two-dimensional nanomaterials and design atomically thin devices for fundamental and applied interests. The MoS2/WS2 heterostructure was prepared on SiO2/Si substrate by chemical vapor deposition (CVD) in our research. And the optical properties of the heterostructure was characterized by Raman and photoluminescence (PL) spectroscopy. The similar 2 orders of magnitude decrease of PL intensity in MoS2/WS2 heterostructures was tested, which is attribute to the electrical and optical modulation effects are connected with the interfacial charge transfer between MoS2 and WS2 films. Using MoS2/WS2 heterostructure as channel material of the phototransistor, we demonstrated over 50 folds enhanced photoresponsivity of multilayer MoS2 field-effect transistor. The results indicate that the MoS2/WS2 films can be a promising heterostructure material to enhance the photoresponse characteristics of MoS2-based phototransistors.

  15. Controlled p-doping of black phosphorus by integration of MoS2 nanoparticles

    Science.gov (United States)

    Jeon, Sumin; Kim, Minwoo; Jia, Jingyuan; Park, Jin-Hong; Lee, Sungjoo; Song, Young Jae

    2018-05-01

    Black phosphorus (BP), a new family of two dimensional (2D) layered materials, is an attractive material for future electronic, photonic and chemical sensing devices, thanks to its high carrier density and a direct bandgap of 0.3-2.0 eV, depending on the number of layers. Controllability over the properties of BP by electrical or chemical modulations is one of the critical requirements for future various device applications. Herein, we report a new doping method of BP by integration of density-controlled monolayer MoS2 nanoparticles (NPs). MoS2 NPs with different density were synthesized by chemical vapor deposition (CVD) and transferred onto a few-layer BP channel, which induced a p-doping effect. Scanning electron microscopy (SEM) confirmed the size and distribution of MoS2 NPs with different density. Raman and X-ray photoelectron spectroscopy (XPS) were measured to confirm the oxidation on the edge of MoS2 NPs and a doping effect of MoS2 NPs on a BP channel. The doping mechanism was explained by a charge transfer by work function differences between BP and MoS2 NPs, which was confirmed by Kelvin probe force microscopy (KPFM) and electrical measurements. The hole concentration of BP was controlled with different densities of MoS2 NPs in a range of 1012-1013 cm-2.

  16. Hydrogen-induced structural transition in single layer ReS2

    Science.gov (United States)

    Yagmurcukardes, M.; Bacaksiz, C.; Senger, R. T.; Sahin, H.

    2017-09-01

    By performing density functional theory-based calculations, we investigate how structural, electronic and mechanical properties of single layer ReS2 can be tuned upon hydrogenation of its surfaces. It is found that a stable, fully hydrogenated structure can be obtained by formation of strong S-H bonds. The optimized atomic structure of ReS2H2 is considerably different than that of the monolayer ReS2 which has a distorted-1T phase. By performing phonon dispersion calculations, we also predict that the Re2-dimerized 1T structure (called 1T {{}\\text{R{{\\text{e}}2}}} ) of the ReS2H2 is dynamically stable. Unlike the bare ReS2 the 1T {{}\\text{R{{\\text{e}}2}}} -ReS2H2 structure which is formed by breaking the Re4 clusters into separated Re2 dimers, is an indirect-gap semiconductor. Furthermore, mechanical properties of the 1T {{}\\text{R{{\\text{e}}2}}} phase in terms of elastic constants, in-plane stiffness (C) and Poisson ratio (ν) are investigated. It is found that full hydrogenation not only enhances the flexibility of the single layer ReS2 crystal but also increases anisotropy of the elastic constants.

  17. Doping effect on monolayer MoS2 for visible light dye degradation - A DFT study

    Science.gov (United States)

    Cheriyan, Silpa; Balamurgan, D.; Sriram, S.

    2018-04-01

    The electronic and optical properties of, Nitrogen (N), Cobalt (Co), and Co-N co-doped monolayers of MoS2 has been studied by using density functional theory (DFT) for visible light photocatalytic activity. From the calculations, it has been observed that the band gap of monolayer MoS2 has been reduced while doping. However, the band gaps of pristine and N doped MoS2 monolayers only falls in the visible region while for Co and Co-N co-doped systems, the band gap shifted to IR region. The optical calculation also confirms the results. The formation energy values of the doped system reaveal that MoS2 monolayer drops its stability while doping. To evaluate the photocatalytic response, band edge potentials of pristine and N-MoS2 are calculated, and the observed results show that compared to N-doped MoS2 monolayer, pure MoS2 is highly suitable for visible light photocatalytic dye degradation.

  18. MoS2 @HKUST-1 Flower-Like Nanohybrids for Efficient Hydrogen Evolution Reactions.

    Science.gov (United States)

    Wang, Chengli; Su, Yingchun; Zhao, Xiaole; Tong, Shanshan; Han, Xiaojun

    2018-01-24

    A novel MoS 2 -based flower-like nanohybrid for hydrogen evolution was fabricated through coating the Cu-containing metal-organic framework (HKUST-1) onto MoS 2 nanosheets. It is the first time that MoS 2 @HKUST-1 nanohybrids have been reported for the enhanced electrochemical performance of HER. The morphologies and components of the MoS 2 @HKUST-1 flower-like nanohybrids were characterized by scanning electron microscopy, X-ray diffraction analysis and Fourier transform infrared spectroscopy. Compared with pure MoS 2 , the MoS 2 @HKUST-1 hybrids exhibit enhanced performance on hydrogen evolution reaction with an onset potential of -99 mV, a smaller Tafel slope of 69 mV dec -1 , and a Faradaic efficiency of nearly 100 %. The MoS 2 @HKUST-1 flower-like nanohybrids exhibit excellent stability in acidic media. This design opens new possibilities to effectively synthesize non-noble metal catalysts with high performance for the hydrogen evolution reaction (HER). © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Unravelling merging behaviors and electrostatic properties of CVD-grown monolayer MoS2 domains

    International Nuclear Information System (INIS)

    Hao, Song; Yang, Bingchu; Gao, Yongli

    2016-01-01

    The presence of grain boundaries is inevitable for chemical vapor deposition (CVD)-grown MoS 2 domains owing to various merging behaviors, which greatly limits its potential applications in novel electronic and optoelectronic devices. It is therefore of great significance to unravel the merging behaviors of the synthesized polygon shape MoS 2 domains. Here we provide systematic investigations of merging behaviors and electrostatic properties of CVD-grown polycrystalline MoS 2 crystals by multiple means. Morphological results exhibit various polygon shape features, ascribed to polycrystalline crystals merged with triangle shape MoS 2 single crystals. The thickness of triangle and polygon shape MoS 2 crystals is identical manifested by Raman intensity and peak position mappings. Three merging behaviors are proposed to illustrate the formation mechanisms of observed various polygon shaped MoS 2 crystals. The combined photoemission electron microscopy and kelvin probe force microscopy results reveal that the surface potential of perfect merged crystals is identical, which has an important implication for fabricating MoS 2 -based devices.

  20. Supercapacitive properties of hydrothermally synthesized sphere like MoS2 nanostructures

    International Nuclear Information System (INIS)

    Krishnamoorthy, Karthikeyan; Veerasubramani, Ganesh Kumar; Radhakrishnan, Sivaprakasam; Kim, Sang Jae

    2014-01-01

    Highlights: • MoS 2 nanostructures were synthesized by hydrothermal method. • Randomly stacked MoS 2 was obtained. • FE-SEM studies show the sphere like morphology of MoS 2 . • Specific capacitance of 92.85 F/g was achieved using charge–discharge analysis. • MoS 2 electrode shows capacitance retention of about 93.8% after 1000 cycles. - Abstract: In this communication, we have investigated the supercapacitive behaviour of MoS 2 nanostructures prepared by a facile one-pot hydrothermal approach using ammonium heptamolybdate and thiourea as starting materials. The X-ray diffraction study revealed the formation of randomly stacked layers of MoS 2 . The field-emission scanning electron microscope studies suggested the formation of sphere like MoS 2 nanostructures and a plausible mechanism for the formation of the obtained structure is discussed. The cyclic voltammetry study shows the typical rectangular shaped curves with a specific capacitance of 106 F/g at a scan rate of 5 mV/s. Galvanostatic charge–discharge measurements suggested the maximum specific capacitance of about 92.85 F/g at discharge current density of 0.5 mA/cm 2 . Cyclic stability tests revealed the capacitance retention of about 93.8% after 1000 cycles suggesting a good cyclic capacity of the prepared MoS 2 . The electrochemical impedance spectroscopic results such as Nyquist and Bode phase angle plots suggested that the hydrothermally synthesized MoS 2 nanostructures will be a suitable candidate for electrochemical supercapacitor applications

  1. Fabrication and evaluation of atmospheric plasma spraying WC-Co-Cu-MoS2 composite coatings

    International Nuclear Information System (INIS)

    Yuan Jianhui; Zhu Yingchun; Zheng Xuebing; Ji Heng; Yang Tao

    2011-01-01

    Research highlights: → Protective WC-Co-based coatings containing solid lubricant Cu and MoS 2 used in wear applications were investigated in this study. → It was found that the MoS 2 composition in the feed powder was kept in WC-Co-Cu-MoS 2 coatings, and the decomposition and decarburization of WC in APS process were improved. → Combining the wear resistance of WC with the lubricating properties of Cu and MoS 2 has an extremely beneficial effect on improving the tribological performance of the resulting coating. - Abstract: Protective WC-Co-based coatings containing solid lubricant Cu and MoS 2 used in wear applications were investigated in this study. These coatings were deposited on mild steel substrates by atmospheric plasma spraying (APS). The feedstock powders were prepared by mechanically mixing the solid lubricant powders and WC-Co powder, followed by sintering and crushing the mixtures to avoid different particle flighting trajectories at plasma. The tribological properties of the coatings against stainless steel balls were examined by ball-on-disk (BOD) tribometer under normal atmospheric condition. The microstructure of the coatings was studied by optical microscope, scanning electron microscope and X-ray diffraction. It was found that the MoS 2 composition in the feed powder was kept in WC-Co-Cu-MoS 2 coatings, and the decomposition and decarburization of WC in APS process were improved, which were attributed to the protection of Cu around them. The friction and wear behaviors of all the WC-Co-Cu-MoS 2 coatings were superior to that of WC-Co coating. Such behavior was associated to different wear mechanisms operating for WC-Co coating and the WC-Co-Cu-MoS 2 coatings.

  2. Investigation of the optical properties of MoS2 thin films using spectroscopic ellipsometry

    International Nuclear Information System (INIS)

    Yim, Chanyoung; O'Brien, Maria; Winters, Sinéad; McEvoy, Niall; Mirza, Inam; Lunney, James G.; Duesberg, Georg S.

    2014-01-01

    Spectroscopic ellipsometry (SE) characterization of layered transition metal dichalcogenide (TMD) thin films grown by vapor phase sulfurization is reported. By developing an optical dispersion model, the extinction coefficient and refractive index, as well as the thickness of molybdenum disulfide (MoS 2 ) films, were extracted. In addition, the optical band gap was obtained from SE and showed a clear dependence on the MoS 2 film thickness, with thinner films having a larger band gap energy. These results are consistent with theory and observations made on MoS 2 flakes prepared by exfoliation, showing the viability of vapor phase derived TMDs for optical applications

  3. Topological Phase Diagrams of Bulk and Monolayer TiS2−xTex

    KAUST Repository

    Zhu, Zhiyong; Cheng, Yingchun; Schwingenschlö gl, Udo

    2013-01-01

    With the use of ab initio calculations, the topological phase diagrams of bulk and monolayer TiS2−xTex are established. Whereas bulk TiS2−xTex shows two strong topological phases [1;(000)] and [1;(001)] for 0.44S2−xTex is a unique system for studying topological phases in three and two dimensions simultaneously.

  4. Intercalation of organic molecules into SnS2 single crystals

    International Nuclear Information System (INIS)

    Toh, M.L.; Tan, K.J.; Wei, F.X.; Zhang, K.K.; Jiang, H.; Kloc, C.

    2013-01-01

    SnS 2 is a layered semiconductor with a van der Waals gap separating the covalently bonded layers. In this study, post-synthesis intercalation of donor organic amine molecules, such as ethylenediamine (en), into tin disulfide and secondary intercalation of p-phenylenediamine (PPD) and 1, 5-naphthalenediamine (NDA) into SnS 2e n have been verified with X-ray diffraction. PPD and NDA did not intercalate directly even during prolonged annealing but replaced en readily if en was already present in the van der Waals gap. The c-lattice dilation is proportional to the intercalant size. Unit cell lattices of intercalated products were determined from the positions of the X-ray diffraction peaks. Optical images taken during the intercalation showed that intercalation progressed from the periphery towards the interior of the crystal. TEM diffraction patterns in the [0 0 1] direction of SnS 2 after intercalation revealed defects and stacking mismatches among the SnS 2 layers caused by the intercalation. UV–Vis absorption studies showed a red shift in the band edge of the SnS 2 material after intercalation. The band edge was 2.2 eV for pristine SnS 2 ; after intercalation with en or PPD, the absorbance spectra band edges shifted to approximately 0.7 eV or 0.5 eV, respectively. - Graphical Abstract: SnS 2 single crystals were intercalated with organic amine molecules such as ethylenediamine, phenylenediamine and naphthalenediamine. Absorption studies showed red shift of band edge after intercalation, which was consistent with optical observations. X-ray diffraction indicated lattice dilation in the c-lattice of SnS 2 after intercalation. Highlights: ► Organic molecules intercalated inhomogenously between covalently bonded SnS 2 layers. ► Ethylenediamine (en) intercalate directly into SnS 2 . ► Phenylenediamine (PPD) and naphthalenediamine (NDA) can be intercalated into SnS 2 secondary. ► In a secondary intercalation the bonds between layers are weakened by direct

  5. Topological surface Fermi arcs in magnetic Weyl semimetal Co$_3$Sn$_2$S$_2$

    OpenAIRE

    Xu, Qiunan; Liu, Enke; Shi, Wujun; Muechler, Lukas; Felser, Claudia; Sun, Yan

    2017-01-01

    Very recently, the half-metallic compound Co$_3$Sn$_2$S$_2$ was predicted to be a magnetic WSM with Weyl points only 60 meV above the Fermi level ($E_F$). Owing to the low charge carrier density and large Berry curvature induced, Co$_3$Sn$_2$S$_2$ possesses both a large anomalous Hall conductivity (AHC) and a large anomalous Hall angle (AHA), which provide strong evidence for the existence of Weyl points in Co$_3$Sn$_2$S$_2$. In this work, we theoretically studied the surface topological feat...

  6. Topological Phase Diagrams of Bulk and Monolayer TiS2−xTex

    KAUST Repository

    Zhu, Zhiyong

    2013-02-12

    With the use of ab initio calculations, the topological phase diagrams of bulk and monolayer TiS2−xTex are established. Whereas bulk TiS2−xTex shows two strong topological phases [1;(000)] and [1;(001)] for 0.44S2−xTex is a unique system for studying topological phases in three and two dimensions simultaneously.

  7. Functional regulation of Pb-Ti/MoS_2 composite coatings for environmentally adaptive solid lubrication

    International Nuclear Information System (INIS)

    Ren, Siming; Li, Hao; Cui, Mingjun; Wang, Liping; Pu, Jibin

    2017-01-01

    Highlights: • Co-doped Pb-Ti/MoS_2 composite coatings were successfully fabricated by unbalanced magnetron sputtering system. • Co-doped Pb-Ti/MoS_2 composite coatings showed lower friction coefficient and longer wear life in both humid and vacuum environments than that of single-doped ones. • The wear behaviours of Pb-Ti/MoS_2 composite coatings with the increase of Pb content is in accordance with the variation in H/E ratio that higher H/E is corresponding to the lower wear rate of coating. - Abstract: The lubrication of molybdenum disulfide coatings has commonly been limited by the application environments, for instance, the crystal MoS_2 are easily affected by water to form MoO_3 that causes a higher friction coefficient and short lifetime. Therefore, to improve the tribolgical performance of MoS_2 in high humidity condition, the co-doped Pb-Ti/MoS_2 composite coatings are deposited by unbalanced magnetron sputtering system. The design of the co-doping elements in MoS_2-based coatings can not only maintain the characteristic of low humidity-sensitivity as the Ti/MoS_2 coating but also improve the mechanical properties and tribological performance of coatings as a comparison with single-doped ones. Moreover, the ultra-low friction coefficient with a minimum value of 0.006 under the vacuum condition is achieved for Pb-Ti/MoS_2 composite coating containing about 4.6 at.% Pb, depending on the densification structure of coating. Intriguingly, the wear behaviours of Pb-Ti/MoS_2 composite coatings are in accordance with the variation in H/E (hardness to the elastic modulus) ratio that the coating with higher H/E exhibits lower wear rate. These results demonstrate that the lubricating properties of MoS_2 coatings in both humid environment and vacuum condition can be achieved through the Pb and Ti co-doped, which is of great significant for developing MoS_2 coatings as the environmentally adaptive lubricants.

  8. Synthesis of coaxial nanotubes of MoS2 and carbon

    International Nuclear Information System (INIS)

    Reza, C.; Perez, M.; Santiago, P.

    2002-01-01

    The di chalcogenides WS 2 and MoS 2 by their tubular properties were combined. It was synthesized coaxial structures of MoS 2 with C with the purpose to studying the possible structural changes of the MoS 2 nano tubes at was submitted to a propylene gas flux as carbon precursor in a thermal treatment. Studies of structural characterization by Transmission Electron Microscopy (Tem) were realized. The theoretical simulation of the structure was realized using an algorithm type multilayer. The possibility of the nano tubes are applied to gas storage as can be the hydrogen arouse interest by the energy production. (Author)

  9. World energy insight 2011

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2011-11-15

    The World Energy Insight 2011 is the official publication of the World Energy Council. It includes interviews, articles and case studies from a distinguished panel of World Energy Council Officers, CEOs, government ministers, academics and opinion formers from all areas of the energy sector and provides perspectives from around the globe. Government, industry and NGO's offer both policy and technology perspectives. The insights within this publication add to the work that WEC is doing to provide the forum for energy leaders, along with the on-going WEC studies and programmes on Energy Policies, 2050 Energy Scenarios, Energy Resources & Technologies, Energy for Urban Innovation, Rules Of Energy Trade and Global Energy Access.

  10. The politics of insight

    OpenAIRE

    Salvi, Carola; Cristofori, Irene; Grafman, Jordan; Beeman, Mark

    2016-01-01

    Previous studies showed that liberals and conservatives differ in cognitive style. Liberals are more flexible, and tolerant of complexity and novelty, whereas conservatives are more rigid, are more resistant to change, and prefer clear answers. We administered a set of compound remote associate problems, a task extensively used to differentiate problem-solving styles (via insight or analysis). Using this task, several researches have proven that self-reports, which differentiate between insig...

  11. HPC Insights, Fall 2011

    Science.gov (United States)

    2011-01-01

    Power 6 ( Davinci ) systems. We have also made use of the Air Force Research Laboratory DSRC Altix (Hawk) and the Engineer Research and Development...the design and development of high performance gas turbine combustion systems both as a pretest analysis tool to predict static and dynamic...application while gaining insight into MATLAB’s value as an engineering tool . I would like to thank the MHPCC and the Akamai Workforce Initiative

  12. Regulated appearance of NMDA receptor subunits and channel functions during in vitro neuronal differentiation

    NARCIS (Netherlands)

    Jelitai, Márta; Schlett, Katalin; Varju, Patrícia; Eisel, Ulrich; Madarász, Emília

    The schedule of NMDA receptor subunit expression and the appearance of functional NMDA-gated ion channels were investigated during the retinoic acid (RA) induced neuronal differentiation of NE-4C, a p53-deficient mouse neuroectodermal progenitor cell line. NR2A. NR2B, and NR2D subunit transcripts

  13. Differential expression of BK channel isoforms and beta-subunits in rat neuro-vascular tissues

    DEFF Research Database (Denmark)

    Poulsen, Asser Nyander; Wulf, Helle; Hay-Schmidt, Anders

    2009-01-01

    We investigated the expression of splice variants and beta-subunits of the BK channel (big conductance Ca(2+)-activated K(+) channel, Slo1, MaxiK, K(Ca)1.1) in rat cerebral blood vessels, meninges, trigeminal ganglion among other tissues. An alpha-subunit splice variant X1(+24) was found expresse...

  14. Differential antibiotic sensitivity determined by the large ribosomal subunit in thermophilic archaea.

    OpenAIRE

    Ruggero, D; Londei, P

    1996-01-01

    Hybrid ribosomes obtained by mixing the ribosomal subunits of the extremely thermophilic archaea Sulfolobus solfataricus and Desulfurococcus mobilis were tested for their sensitivity to selected antibiotics. It is shown that structural differences in the large ribosomal subunits determine qualitatively and quantitatively the patterns of response to alpha-sarcin and paromomycin in these species.

  15. Isolation and characterization of recombinant human casein kinase II subunits alpha and beta from bacteria

    DEFF Research Database (Denmark)

    Grankowski, N; Boldyreff, B; Issinger, O G

    1991-01-01

    cDNA encoding the casein kinase II (CKII) subunits alpha and beta of human origin were expressed in Escherichia coli using expression vector pT7-7. Significant expression was obtained with E. coli BL21(DE3). The CKII subunits accounted for approximately 30% of the bacterial protein; however, most...

  16. A-Raf kinase is a new interacting partner of protein kinase CK2 beta subunit

    DEFF Research Database (Denmark)

    Boldyreff, B; Issinger, O G

    1997-01-01

    In a search for protein kinase CK2 beta subunit binding proteins using the two-hybrid system, more than 1000 positive clones were isolated. Beside clones for the alpha' and beta subunit of CK2, there were clones coding for a so far unknown protein, whose partial cDNA sequence was already deposited...

  17. Purification of the alpha and beta subunits of phosphorylase kinase for structural studies

    International Nuclear Information System (INIS)

    Sotiroudis, T.G.; Heilmeyer, L.M.G. Jr.; Crabb, J.W.

    1987-01-01

    Structural analysis of the alpha (Mr, 132,000) and beta (Mr, 113,000) subunits of phosphorylase kinase may provide clues to their yet unknown functions however purification remains problematic. Preparative RP-HPLC procedures yield inconveniently large, dilute solutions and concentration steps are required prior to subunit modification and fragmentation. Concentration of the β subunit usually results in significant losses due to insolubility. Using preparative SDS-polyacrylamide gel electrophoresis, they have purified the α, 7 , and β subunits from rabbit muscle phosphorylase kinase in a soluble and concentrated form suitable for structural studies. Phosphorylase kinase labelled with fluorescein isothiocyanate in the α and α' subunits and fully 14 C-S-carboxymethylated was fractionated on a 5% acrylamide Laemmli slab gel. The subunit bands were visualized by fluorescence and by SDS precipitation then excised and electroeluted in the presence of SDS using an ELUTRAP device. From 4.5 mg of enzyme applied to a 4.5 mm thick gel about 70% of the α subunit and about 90% of the β subunit were typically recovered in less than 1 ml with overnight elution

  18. The politics of insight.

    Science.gov (United States)

    Salvi, Carola; Cristofori, Irene; Grafman, Jordan; Beeman, Mark

    2016-01-01

    Previous studies showed that liberals and conservatives differ in cognitive style. Liberals are more flexible, and tolerant of complexity and novelty, whereas conservatives are more rigid, are more resistant to change, and prefer clear answers. We administered a set of compound remote associate problems, a task extensively used to differentiate problem-solving styles (via insight or analysis). Using this task, several researches have proven that self-reports, which differentiate between insight and analytic problem-solving, are reliable and are associated with two different neural circuits. In our research we found that participants self-identifying with distinct political orientations demonstrated differences in problem-solving strategy. Liberals solved significantly more problems via insight instead of in a step-by-step analytic fashion. Our findings extend previous observations that self-identified political orientations reflect differences in cognitive styles. More specifically, we show that type of political orientation is associated with problem-solving strategy. The data converge with previous neurobehavioural and cognitive studies indicating a link between cognitive style and the psychological mechanisms that mediate political beliefs.

  19. The politics of insight

    Science.gov (United States)

    Salvi, Carola; Cristofori, Irene; Grafman, Jordan; Beeman, Mark

    2016-01-01

    Previous studies showed that liberals and conservatives differ in cognitive style. Liberals are more flexible, and tolerant of complexity and novelty, whereas conservatives are more rigid, are more resistant to change, and prefer clear answers. We administered a set of compound remote associate problems, a task extensively used to differentiate problem-solving styles (via insight or analysis). Using this task, several researches have proven that self-reports, which differentiate between insight and analytic problem-solving, are reliable and are associated with two different neural circuits. In our research we found that participants self-identifying with distinct political orientations demonstrated differences in problem-solving strategy. Liberals solved significantly more problems via insight instead of in a step-by-step analytic fashion. Our findings extend previous observations that self-identified political orientations reflect differences in cognitive styles. More specifically, we show that type of political orientation is associated with problem-solving strategy. The data converge with previous neurobehavioural and cognitive studies indicating a link between cognitive style and the psychological mechanisms that mediate political beliefs. PMID:26810954

  20. Fine structure and ionization energy of the 1s2s2p 4P state of the helium negative ion He-.

    Science.gov (United States)

    Wang, Liming; Li, Chun; Yan, Zong-Chao; Drake, G W F

    2014-12-31

    The fine structure and ionization energy of the 1s2s2p (4)P state of the helium negative ion He(-) are calculated in Hylleraas coordinates, including relativistic and QED corrections up to O(α(4)mc(2)), O((μ/M)α(4)mc(2)), O(α(5)mc(2)), and O((μ/M)α(5)mc(2)). Higher order corrections are estimated for the ionization energy. A comparison is made with other calculations and experiments. We find that the present results for the fine structure splittings agree with experiment very well. However, the calculated ionization energy deviates from the experimental result by about 1 standard deviation. The estimated theoretical uncertainty in the ionization energy is much less than the experimental accuracy.

  1. Solid solutions of thallium in TlGaSe2, TlGaS2, and TlInS2

    International Nuclear Information System (INIS)

    Voroshilov, Yu. V.; Potorii, M.V.; Shevchenko, S.V.

    1986-01-01

    The authors study the nature of the dissolution of thallium in ternary phases. They have synthesized alloys of the stoichiometric compositions TlGaS 2 , TlGaSe 2 , and T1InS 2 , and their solid solutions, maximally enriched in thallium, the compositions of which were Tl /SUB 1.34/ GA /SUB 0.89/ S 2 , Tl /SUB 1.31/ Ga /SUB 0.90/ Se 2 , and Tl /SUB 1.15/ In /SUB 0.95/ S /SUB 2./ . Samples were synthesized from the elemental components of the following purities: gallium of V4 grade; indium of V4 grade; thallium of T1000 grade; selenium of special purity 22-4 grade, and sulfur of special purity garde. The compositions were checked by x-ray-phase-(DRON-0.5) and microstructural-analyses with simultaneous determination of the density and microhardness of the samples. It is found that the lattic parameter increases and the increase in the density and microhardness points to strengthening of the structure during the formation of the solid solutions

  2. CMOS-compatible batch processing of monolayer MoS2 MOSFETs

    Science.gov (United States)

    Xiong, Kuanchen; Kim, Hyun; Marstell, Roderick J.; Göritz, Alexander; Wipf, Christian; Li, Lei; Park, Ji-Hoon; Luo, Xi; Wietstruck, Matthias; Madjar, Asher; Strandwitz, Nicholas C.; Kaynak, Mehmet; Lee, Young Hee; Hwang, James C. M.

    2018-04-01

    Thousands of high-performance 2D metal-oxide-semiconductor field effect transistors (MOSFETs) were fabricated on wafer-scale chemical vapor deposited MoS2 with fully-CMOS-compatible processes such as photolithography and aluminum metallurgy. The yield was greater than 50% in terms of effective gate control with less-than-10 V threshold voltage, even for MOSFETs having deep-submicron gate length. The large number of fabricated MOSFETs allowed statistics to be gathered and the main yield limiter to be attributed to the weak adhesion between the transferred MoS2 and the substrate. With cut-off frequencies approaching the gigahertz range, the performances of the MOSFETs were comparable to that of state-of-the-art MoS2 MOSFETs, whether the MoS2 was grown by a thin-film process or exfoliated from a bulk crystal.

  3. Structural and electronic phase transitions of ThS2 from first-principles calculations

    International Nuclear Information System (INIS)

    Guo, Yongliang; Wang, Changying; Qiu, Wujie; Ke, Xuezhi

    2016-01-01

    Performed a systematic study using first-principles methods of the pressure-induced structural and electronic phase transitions in ThS_2, which may play an important role in the next generation nuclear energy fuel technology.

  4. Quantum transport through MoS2 constrictions defined by photodoping

    Science.gov (United States)

    Epping, Alexander; Banszerus, Luca; Güttinger, Johannes; Krückeberg, Luisa; Watanabe, Kenji; Taniguchi, Takashi; Hassler, Fabian; Beschoten, Bernd; Stampfer, Christoph

    2018-05-01

    We present a device scheme to explore mesoscopic transport through molybdenum disulfide (MoS2) constrictions using photodoping. The devices are based on van-der-Waals heterostructures where few-layer MoS2 flakes are partially encapsulated by hexagonal boron nitride (hBN) and covered by a few-layer graphene flake to fabricate electrical contacts. Since the as-fabricated devices are insulating at low temperatures, we use photo-induced remote doping in the hBN substrate to create free charge carriers in the MoS2 layer. On top of the device, we place additional metal structures, which define the shape of the constriction and act as shadow masks during photodoping of the underlying MoS2/hBN heterostructure. Low temperature two- and four-terminal transport measurements show evidence of quantum confinement effects.

  5. Role of interlayer coupling in ultra thin MoS2

    KAUST Repository

    Cheng, Yingchun; Zhu, Zhiyong; Schwingenschlö gl, Udo

    2012-01-01

    The effects of interlayer coupling on the vibrational and electronic properties of ultra thin MoS 2 were studied by ab initio calculations. For smaller slab thickness, the interlayer distance is significantly elongated because of reduced interlayer

  6. NEW THIO S2- ADDUCTS WITH ANTIMONY (III AND V HALIDE: SYNTHESIS AND INFRARED STUDY

    Directory of Open Access Journals (Sweden)

    HASSAN ALLOUCH

    2013-12-01

    Full Text Available Five new S2- adducts with SbIII and SbV halides have been synthesized and studied by infrared. Discrete structures have been suggested, the environment around the antimony being tetrahedral, trigonal bipyramidal or octahedral.

  7. Quantum criticality and duality in the Sachdev-Ye-Kitaev/AdS2 chain

    Science.gov (United States)

    Jian, Shao-Kai; Xian, Zhuo-Yu; Yao, Hong

    2018-05-01

    We show that the quantum critical point (QCP) between a diffusive metal and ferromagnetic (or antiferromagnetic) phases in the SYK chain has a gravitational description corresponding to the double-trace deformation in an AdS2 chain. Specifically, by studying a double-trace deformation of a Z2 scalar in an AdS2 chain where the Z2 scalar is dual to the order parameter in the SYK chain, we find that the susceptibility and renormalization group equation describing the QCP in the SYK chain can be exactly reproduced in the holographic model. Our results suggest that the infrared geometry in the gravity theory dual to the diffusive metal of the SYK chain is also an AdS2 chain. We further show that the transition in SYK model captures universal information about double-trace deformation in generic black holes with near horizon AdS2 space-time.

  8. Study of solid lubrication with MoS2 coating in the presence of ...

    Indian Academy of Sciences (India)

    Molybdenum disulphide (MoS2) based solid lubricant mixtures con- taining zirconia and ... age during relative movement and to reduce friction and wear. ..... In this hexagonal structure the bonds between the carbon atoms in a layer are strong.

  9. Polytypism and unexpected strong interlayer coupling in two-dimensional layered ReS2

    Science.gov (United States)

    Qiao, Xiao-Fen; Wu, Jiang-Bin; Zhou, Linwei; Qiao, Jingsi; Shi, Wei; Chen, Tao; Zhang, Xin; Zhang, Jun; Ji, Wei; Tan, Ping-Heng

    2016-04-01

    Anisotropic two-dimensional (2D) van der Waals (vdW) layered materials, with both scientific interest and application potential, offer one more dimension than isotropic 2D materials to tune their physical properties. Various physical properties of 2D multi-layer materials are modulated by varying their stacking orders owing to significant interlayer vdW coupling. Multilayer rhenium disulfide (ReS2), a representative anisotropic 2D material, was expected to be randomly stacked and lack interlayer coupling. Here, we demonstrate two stable stacking orders, namely isotropic-like (IS) and anisotropic-like (AI) N layer (NL, N > 1) ReS2 are revealed by ultralow- and high-frequency Raman spectroscopy, photoluminescence and first-principles density functional theory calculation. Two interlayer shear modes are observed in AI-NL-ReS2 while only one shear mode appears in IS-NL-ReS2, suggesting anisotropic- and isotropic-like stacking orders in IS- and AI-NL-ReS2, respectively. This explicit difference in the observed frequencies identifies an unexpected strong interlayer coupling in IS- and AI-NL-ReS2. Quantitatively, the force constants of them are found to be around 55-90% of those of multilayer MoS2. The revealed strong interlayer coupling and polytypism in multi-layer ReS2 may stimulate future studies on engineering physical properties of other anisotropic 2D materials by stacking orders.Anisotropic two-dimensional (2D) van der Waals (vdW) layered materials, with both scientific interest and application potential, offer one more dimension than isotropic 2D materials to tune their physical properties. Various physical properties of 2D multi-layer materials are modulated by varying their stacking orders owing to significant interlayer vdW coupling. Multilayer rhenium disulfide (ReS2), a representative anisotropic 2D material, was expected to be randomly stacked and lack interlayer coupling. Here, we demonstrate two stable stacking orders, namely isotropic-like (IS) and

  10. Genetic polymorphism of CSN1S2 in South African dairy goat ...

    African Journals Online (AJOL)

    Rulien

    2016-12-24

    Dec 24, 2016 ... variation for αs2-casein in the South African goat populations ... of Pretoria's experimental farm (Saanens) and commercial goat farms in the provinces of Gauteng. (Toggenburg), North West (British Alpine and Toggenburg), ...

  11. Large theoretical thermoelectric power factor of suspended single-layer MoS2

    International Nuclear Information System (INIS)

    Babaei, Hasan; Khodadadi, J. M.; Sinha, Sanjiv

    2014-01-01

    We have calculated the semi-classical thermoelectric power factor of suspended single-layer (SL)- MoS 2 utilizing electron relaxation times derived from ab initio calculations. Measurements of the thermoelectric power factor of SL-MoS 2 on substrates reveal poor power factors. In contrast, we find the thermoelectric power factor of suspended SL-MoS 2 to peak at ∼2.8 × 10 4 μW/m K 2 at 300 K, at an electron concentration of 10 12 cm −2 . This figure is higher than that in bulk Bi 2 Te 3 , for example. Given its relatively high thermal conductivity, suspended SL-MoS 2 may hold promise for in-plane thin-film Peltier coolers, provided reasonable mobilities can be realized

  12. Low cost, Lightweight, FeS2-Based Photovoltaic Devices by On Demand Ink Jet Printing

    Data.gov (United States)

    National Aeronautics and Space Administration — This research projects seeks to develop novel synthesis for iron pyrite, FeS2, nanocrystals and nanorods. The synthesis of the material includes investigating the...

  13. Strongly luminescent monolayered MoS2 prepared by effective ultrasound exfoliation.

    Science.gov (United States)

    Štengl, Václav; Henych, Jiří

    2013-04-21

    Intense ultrasound in a pressurized batch reactor was used for preparation of monolayered MoS2 nanosheets from natural mineral molybdenite. Exfoliation of bulk MoS2 using ultrasound is an attractive route to large-scale preparation of monolayered crystals. To evaluate the quality of delamination, methods like X-ray diffraction, Raman spectroscopy and microscopic techniques (TEM and AFM) were employed. From single- or few-layered products obtained from intense sonication, MoS2 quantum dots (MoSQDs) were prepared by a one-pot reaction by refluxing exfoliated nanosheets of MoS2 in ethylene glycol under atmospheric pressure. The synthesised MoSQDs were characterised by photoluminescence spectroscopy and laser-scattering particle size analysis. Our easy preparation leads to very strongly green luminescing quantum dots.

  14. Two-dimensional Si nanosheets with local hexagonal structure on a MoS(2) surface.

    Science.gov (United States)

    Chiappe, Daniele; Scalise, Emilio; Cinquanta, Eugenio; Grazianetti, Carlo; van den Broek, Bas; Fanciulli, Marco; Houssa, Michel; Molle, Alessandro

    2014-04-02

    The structural and electronic properties of a Si nanosheet (NS) grown onto a MoS2 substrate by means of molecular beam epitaxy are assessed. Epitaxially grown Si is shown to adapt to the trigonal prismatic surface lattice of MoS2 by forming two-dimensional nanodomains. The Si layer structure is distinguished from the underlying MoS2 surface structure. The local electronic properties of the Si nanosheet are dictated by the atomistic arrangement of the layer and unlike the MoS2 hosting substrate they are qualified by a gap-less density of states. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Room temperature ferromagnetism in Fe-doped semiconductor ZrS2 single crystals

    Science.gov (United States)

    Muhammad, Zahir; Lv, Haifeng; Wu, Chuanqiang; Habib, Muhammad; Rehman, Zia ur; Khan, Rashid; Chen, Shuangming; Wu, Xiaojun; Song, Li

    2018-04-01

    Two dimensional (2D) layered magnetic materials have obtained much attention due to their intriguing properties with a potential application in the field of spintronics. Herein, room-temperature ferromagnetism with 0.2 emu g‑1 magnetic moment is realized in Fe-doped ZrS2 single crystals of millimeter size, in comparison with diamagnetic behaviour in ZrS2. The electron paramagnetic resonance spectroscopy reveals that 5.2wt% Fe-doping ZrS2 crystal exhibit high spin value of g-factor about 3.57 at room temperature also confirmed this evidence, due to the unpaired electrons created by doped Fe atoms. First principle static electronic and magnetic calculations further confirm the increased stability of long range ferromagnetic ordering and enhanced magnetic moment in Fe-doped ZrS2, originating from the Fe spin polarized electron near the Fermi level.

  16. Accuracy of S2 Alar-Iliac Screw Placement Under Robotic Guidance.

    Science.gov (United States)

    Laratta, Joseph L; Shillingford, Jamal N; Lombardi, Joseph M; Alrabaa, Rami G; Benkli, Barlas; Fischer, Charla; Lenke, Lawrence G; Lehman, Ronald A

    Case series. To determine the safety and feasibility of S2 alar-iliac (S2AI) screw placement under robotic guidance. Similar to standard iliac fixation, S2AI screws aid in achieving fixation across the sacropelvic junction and decreasing S1 screw strain. Fortunately, the S2AI technique minimizes prominent instrumentation and the need for offset connectors to the fusion construct. Herein, we present an analysis of the largest series of robotic-guided S2AI screws in the literature without any significant author conflicts of interest with the robotics industry. Twenty-three consecutive patients who underwent spinopelvic fixation with 46 S2AI screws under robotic guidance were analyzed from 2015 to 2016. Screws were placed by two senior spine surgeons, along with various fellow or resident surgical assistants, using a proprietary robotic guidance system (Renaissance; Mazor Robotics Ltd., Caesara, Israel). Screw position and accuracy was assessed on intraoperative CT O-arm scans and analyzed using three-dimensional interactive viewing and manipulation of the images. The average caudal angle in the sagittal plane was 31.0° ± 10.0°. The average horizontal angle in the axial plane using the posterior superior iliac spine as a reference was 42.8° ± 6.6°. The average S1 screw to S2AI screw angle was 11.3° ± 9.9°. Two violations of the iliac cortex were noted, with an average breach distance of 7.9 ± 4.8 mm. One breach was posterior (2.2%) and one was anterior (2.2%). The overall robotic S2AI screw accuracy rate was 95.7%. There were no intraoperative neurologic, vascular, or visceral complications related to the placement of the S2AI screws. Spinopelvic fixation achieved using a bone-mounted miniature robotic-guided S2AI screw insertion technique is safe and reliable. Despite two breaches, no complications related to the placement of the S2AI screws occurred in this series. Level IV, therapeutic. Copyright © 2017 Scoliosis Research Society. Published by Elsevier

  17. Large Current Modulation and Spin-Dependent Tunneling of Vertical Graphene/MoS$_{2}$ Heterostructures

    OpenAIRE

    Myoung, Nojoon; Seo, Kyungchul; Lee, Seung Joo; Ihm, Gukhyung

    2013-01-01

    Vertical graphene heterostructures have been introduced as an alternative architecture for electronic devices by using quantum tunneling. Here, we present that the current on/off ratio of vertical graphene field-effect transistors is enhanced by using an armchair graphene nanoribbon as an electrode. Moreover, we report spin-dependent tunneling current of the graphene/MoS2 heterostructures. When an atomically thin MoS2 layer sandwiched between graphene electrodes becomes magnetic, Dirac fermio...

  18. Exciton-dominant Electroluminescence from a Diode of Monolayer MoS2

    Science.gov (United States)

    2014-05-14

    injected electrons and holes, is a reliable technique to study exciton recombination processes in monolayer MoS2, including val- ley and spin excitation...temperature. After superimposing a white light scattering image of the de - vice, we find that the electroluminescence is localized at the edge of the...We find the emerged feature (labeled NX) peaks at 550 nm with energy of 2.255 eV. In low dimensional system, like monolayer MoS2, Coulomb interactions

  19. Atomic-Monolayer MoS2 Band-to-Band Tunneling Field-Effect Transistor

    KAUST Repository

    Lan, Yann Wen

    2016-09-05

    The experimental observation of band-to-band tunneling in novel tunneling field-effect transistors utilizing a monolayer of MoS2 as the conducting channel is demonstrated. Our results indicate that the strong gate-coupling efficiency enabled by two-dimensional materials, such as monolayer MoS2, results in the direct manifestation of a band-to-band tunneling current and an ambipolar transport.

  20. Electronic and magnetic properties of MoS2 nanoribbons with sulfur line vacancy defects

    International Nuclear Information System (INIS)

    Han, Yang; Zhou, Jian; Dong, Jinming

    2015-01-01

    Highlights: • We performed DFT calculations on Sulfur line defects embedded MoS 2 . • The defects induced bond strains are larger in the zigzag (ZZ) edge ones. • The ZZ ones are metals, having two degenerate ground states FM and AFM. • The armchair ones are nonmagnetic semiconductors. • The defects can induce some defect states in the electronic structures. - Abstract: Motivated by the recent experimental result that single sulfur vacancies in monolayer MoS 2 are mobile under the electron beam and easily agglomerate into the sulfur line vacancy defects [Physical Review B 88, 035301(2013)] , the structural, electronic and magnetic properties of one dimensional zigzag (ZZ) and armchair (AC) edge MoS 2 nanoribbons with single or double staggered sulfur line vacancy defects (hereafter, abbreviated as SV or DV, respectively), parallel to their edges, have been investigated systematically by density functional theory calculations. It is very interesting to find that the bond strains induced by the sulfur line vacancy defect can cause a much larger out-of plane distortions in the ZZ edge MoS 2 nanoribbon than in the AC edge counterpart. Besides, the defective ZZ edge MoS 2 nanoribbons with SV or DV are both metals, having their two respective degenerate ground states with the same energy, among which one is ferromagnetic (FM “ + +”) and the other is antiferromagnetic (AFM “ + −”). But the AC edge MoS 2 nanoribbons with SV or DV are both nonmagnetic semiconductors, having very different gap values. Finally, the sulfur line vacancy defects would induce some defect states in the electronic structures of the defective MoS 2 nanoribbons. All these important results could provide a new route of tuning the electronic properties of MoS 2 nanoribbons and its derivatives for their promising applications in nanoelectronics and optoelectronics

  1. Improving the Stability of High-Performance Multilayer MoS2 Field-Effect Transistors.

    Science.gov (United States)

    Liu, Na; Baek, Jongyeol; Kim, Seung Min; Hong, Seongin; Hong, Young Ki; Kim, Yang Soo; Kim, Hyun-Suk; Kim, Sunkook; Park, Jozeph

    2017-12-13

    In this study, we propose a method for improving the stability of multilayer MoS 2 field-effect transistors (FETs) by O 2 plasma treatment and Al 2 O 3 passivation while sustaining the high performance of bulk MoS 2 FET. The MoS 2 FETs were exposed to O 2 plasma for 30 s before Al 2 O 3 encapsulation to achieve a relatively small hysteresis and high electrical performance. A MoO x layer formed during the plasma treatment was found between MoS 2 and the top passivation layer. The MoO x interlayer prevents the generation of excess electron carriers in the channel, owing to Al 2 O 3 passivation, thereby minimizing the shift in the threshold voltage (V th ) and increase of the off-current leakage. However, prolonged exposure of the MoS 2 surface to O 2 plasma (90 and 120 s) was found to introduce excess oxygen into the MoO x interlayer, leading to more pronounced hysteresis and a high off-current. The stable MoS 2 FETs were also subjected to gate-bias stress tests under different conditions. The MoS 2 transistors exhibited negligible decline in performance under positive bias stress, positive bias illumination stress, and negative bias stress, but large negative shifts in V th were observed under negative bias illumination stress, which is attributed to the presence of sulfur vacancies. This simple approach can be applied to other transition metal dichalcogenide materials to understand their FET properties and reliability, and the resulting high-performance hysteresis-free MoS 2 transistors are expected to open up new opportunities for the development of sophisticated electronic applications.

  2. Grain size effect of monolayer MoS2 transistors characterized by second harmonic generation mapping

    KAUST Repository

    Lin, Chih-Pin

    2015-08-27

    We investigated different CVD-synthesized MoS2 films, aiming to correlate the device characteristics with the grain size. The grain size of MoS2 can be precisely characterized through nondestructive second harmonic generation mapping based on the degree of inversion symmetry. The devices with larger grains at the channel region show improved on/off current ratio, which can be explained by the less carrier scattering caused by the grain boundaries.

  3. The XXX spin s quantum chain and the alternating s1, s2 chain with boundaries

    International Nuclear Information System (INIS)

    Doikou, Anastasia

    2002-01-01

    The integrable XXX spin s quantum chain and the alternating s 1 , s 2 (s 1 -s 2 =1/2) chain with boundaries are considered. The scattering of their excitations with the boundaries via the Bethe ansatz method is studied, and the exact boundary S matrices are computed in the limit s,s 1,2 →∞. Moreover, the connection of these models with the SU(2) Principal Chiral, WZW and the RSOS models is discussed

  4. What are System Dynamics Insights?

    OpenAIRE

    Stave, K.; Zimmermann, N. S.; Kim, H.

    2016-01-01

    This paper explores the concept of system dynamics insights. In our field, the term “insight” is generally understood to mean dynamic insight, that is, a deep understanding about the relationship between structure and behavior. We argue this is only one aspect of the range of insights possible from system dynamics activities, and describe a broader range of potential system dynamics insights. We also propose an initial framework for discussion that relates different types of system dynamics a...

  5. Submitochondrial distributions and stabilities of subunits 4, 5, and 6 of yeast cytochrome oxidase in assembly defective mutants.

    Science.gov (United States)

    Glerum, D M; Tzagoloff, A

    1997-08-04

    The concentration and submitochondrial distribution of the subunit polypeptides of cytochrome oxidase have been studied in wild type yeast and in different mutants impaired in assembly of this respiratory complex. All the subunit polypeptides of the enzyme are associated with mitochondrial membranes of wild type cells, except for a small fraction of subunits 4 and 6 that is recovered in the soluble protein fraction of mitochondria. Cytochrome oxidase mutants consistently display a severe reduction in the steady-state concentration of subunit 1 due to its increased turnover. As a consequence, most of subunit 4, which normally is associated with subunit 1, is found in the soluble fraction. A similar shift from membrane-bound to soluble subunit 6 is seen in mutants blocked in expression of subunit 5a. In contrast, null mutations in COX6 coding for subunit 6 promote loss of subunit 5a. The absence of subunit 5a in the cox6 mutant is the result of proteolytic degradation rather than regulation of its expression by subunit 6. The possible role of the ATP-dependent proteases Rca1p and Afg3p in proteolysis of subunits 1 and 5a has been assessed in strains with combined mutations in COX6, RCA1, and/or AFG3. Immunochemical assays indicate that another protease(s) must be responsible for most of the proteolytic loss of these proteins.

  6. Persistence of the mitochondrial permeability transition in the absence of subunit c of human ATP synthase.

    Science.gov (United States)

    He, Jiuya; Ford, Holly C; Carroll, Joe; Ding, Shujing; Fearnley, Ian M; Walker, John E

    2017-03-28

    The permeability transition in human mitochondria refers to the opening of a nonspecific channel, known as the permeability transition pore (PTP), in the inner membrane. Opening can be triggered by calcium ions, leading to swelling of the organelle, disruption of the inner membrane, and ATP synthesis, followed by cell death. Recent proposals suggest that the pore is associated with the ATP synthase complex and specifically with the ring of c-subunits that constitute the membrane domain of the enzyme's rotor. The c-subunit is produced from three nuclear genes, ATP5G1 , ATP5G2 , and ATP5G3 , encoding identical copies of the mature protein with different mitochondrial-targeting sequences that are removed during their import into the organelle. To investigate the involvement of the c-subunit in the PTP, we generated a clonal cell, HAP1-A12, from near-haploid human cells, in which ATP5G1 , ATP5G2 , and ATP5G3 were disrupted. The HAP1-A12 cells are incapable of producing the c-subunit, but they preserve the characteristic properties of the PTP. Therefore, the c-subunit does not provide the PTP. The mitochondria in HAP1-A12 cells assemble a vestigial ATP synthase, with intact F 1 -catalytic and peripheral stalk domains and the supernumerary subunits e, f, and g, but lacking membrane subunits ATP6 and ATP8. The same vestigial complex plus associated c-subunits was characterized from human 143B ρ 0 cells, which cannot make the subunits ATP6 and ATP8, but retain the PTP. Therefore, none of the membrane subunits of the ATP synthase that are involved directly in transmembrane proton translocation is involved in forming the PTP.

  7. Topographic antigenic determinants recognized by monoclonal antibodies on human choriogonadotropin beta-subunit

    International Nuclear Information System (INIS)

    Bidart, J.M.; Troalen, F.; Salesse, R.; Bousfield, G.R.; Bohuon, C.J.; Bellet, D.H.

    1987-01-01

    We describe a first attempt to study the antibody-combining sites recognized by monoclonal antibodies raised against the beta-subunit of human choriogonadotropin (hCG). Two groups of antibodies were first defined by their ability to recognize only the free beta-subunit or the free and combined subunit. Antibodies FBT-11 and FBT-11-L bind only to hCG beta-subunit but not to hCG, whereas antibodies FBT-10 and D1E8 bind to both the beta-subunit and the hormone. In both cases, the antigenic determinants were localized to the core of the protein (residues 1-112), indicating the weak immunogenicity of the specific carboxyl-terminal extension of hCG-beta. Nine synthetic peptides spanning different regions of hCG-beta and lutropin-beta were assessed for their capacity to inhibit antibody binding. A synthetic peptide inclusive of the NH2-terminal region (residues 1-7) of the hCG beta-subunit was found to inhibit binding to the radiolabeled subunit of a monoclonal antibody specific for free hCG-beta (FBT-11). Further delineation of the antigenic site recognized by this antibody provided evidence for the involvement of fragment 82-92. Moreover, monoclonal antibody FBT-11 inhibited the recombination of hCG-beta to hCG-alpha, indicating that its antigenic determinant might be located nearby or in the hCG-beta portion interacting with the alpha-subunit. Binding of monoclonal antibody FBT-10, corresponding to the second antigenic determinant, was weakly inhibited by fragment 82-105 and did not impair the recombination of the hCG beta-subunit to the hCG alpha-subunit. Its combining site appeared to be located in a region of the intact native choriogonadotropin present at the surface of the hormone-receptor complex

  8. Photoelectrochemical-type sunlight photodetector based on MoS2/graphene heterostructure

    International Nuclear Information System (INIS)

    Huang, Zongyu; Han, Weijia; Chander, D Sathish; Qi, Xiang; Zhang, Han; Tang, Hongli; Ren, Long

    2015-01-01

    We have fabricated a novel sunlight photo-detector based on a MoS 2 /graphene heterostructure. The MoS 2 /graphene heterostructure was prepared by a facile hydrothermal method along with a subsequent annealing process followed by a substrate-induced high selective nucleation and growth mechanism. The microstructures and morphologies of the two-dimensional MoS 2 /graphene heterostructure can be experimentally confirmed by x-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and a UV–vis absorption spectrometer. Photoresponse investigations performed by a photoelectrochemical (PEC) measurement system indicate that the synthesized MoS 2 /graphene heterostructure shows superior photoresponse activities under the illumination of sunlight in contrast with bare MoS 2 and graphene. The improved photoresponsivity can be attributed to the enhanced light absorption, strong light–matter interaction and the extremely efficient charge separation of the heterostructure. The structure and performances of the MoS 2 /graphene heterostructure suggest promising applications in the field of photonics and optoelectronics. (paper)

  9. MoS2 solid-lubricating film fabricated by atomic layer deposition on Si substrate

    Science.gov (United States)

    Huang, Yazhou; Liu, Lei; Lv, Jun; Yang, Junjie; Sha, Jingjie; Chen, Yunfei

    2018-04-01

    How to reduce friction for improving efficiency in the usage of energy is a constant challenge. Layered material like MoS2 has long been recognized as an effective surface lubricant. Due to low interfacial shear strengths, MoS2 is endowed with nominal frictional coefficient. In this work, MoS2 solid-lubricating film was directly grown by atomic layer deposition (ALD) on Si substrate using MoCl5 and H2S. Various methods were used to observe the grown MoS2 film. Moreover, nanotribological properties of the film were observed by an atomic force microscope (AFM). Results show that MoS2 film can effectively reduce the friction force by about 30-45% under different loads, indicating the huge application value of the film as a solid lubricant. Besides the interlayer-interfaces-sliding, the smaller capillary is another reason why the grown MoS2 film has smaller friction force than that of Si.

  10. Graphene/MoS2 hybrid technology for large-scale two-dimensional electronics.

    Science.gov (United States)

    Yu, Lili; Lee, Yi-Hsien; Ling, Xi; Santos, Elton J G; Shin, Yong Cheol; Lin, Yuxuan; Dubey, Madan; Kaxiras, Efthimios; Kong, Jing; Wang, Han; Palacios, Tomás

    2014-06-11

    Two-dimensional (2D) materials have generated great interest in the past few years as a new toolbox for electronics. This family of materials includes, among others, metallic graphene, semiconducting transition metal dichalcogenides (such as MoS2), and insulating boron nitride. These materials and their heterostructures offer excellent mechanical flexibility, optical transparency, and favorable transport properties for realizing electronic, sensing, and optical systems on arbitrary surfaces. In this paper, we demonstrate a novel technology for constructing large-scale electronic systems based on graphene/molybdenum disulfide (MoS2) heterostructures grown by chemical vapor deposition. We have fabricated high-performance devices and circuits based on this heterostructure, where MoS2 is used as the transistor channel and graphene as contact electrodes and circuit interconnects. We provide a systematic comparison of the graphene/MoS2 heterojunction contact to more traditional MoS2-metal junctions, as well as a theoretical investigation, using density functional theory, of the origin of the Schottky barrier height. The tunability of the graphene work function with electrostatic doping significantly improves the ohmic contact to MoS2. These high-performance large-scale devices and circuits based on this 2D heterostructure pave the way for practical flexible transparent electronics.

  11. Two-dimensional MoS2: A promising building block for biosensors.

    Science.gov (United States)

    Gan, Xiaorong; Zhao, Huimin; Quan, Xie

    2017-03-15

    Recently, two-dimensional (2D) layered nanomaterials have trigged intensive interest due to the intriguing physicochemical properties that stem from a quantum size effect connected with their ultra-thin structure. In particular, 2D molybdenum disulfide (MoS 2 ), as an emerging class of stable inorganic graphene analogs with intrinsic finite bandgap, would possibly complement or even surpass graphene in electronics and optoelectronics fields. In this review, we first discuss the historical development of ultrathin 2D nanomaterials. Then, we are concerned with 2D MoS 2 including its structure-property relationships, synthesis methods, characterization for the layer thickness, and biosensor applications over the past five years. Thereinto, we are highlighting recent advances in 2D MoS 2 -based biosensors, especially emphasize the preparation of sensing elements, roles of 2D MoS 2 , and assay strategies. Finally, on the basis of the current achievements on 2D MoS 2 and other ultrathin layered nanomaterials, perspectives on the challenges and opportunities for the exploration of 2D MoS 2 -based biosensors are put forward. Copyright © 2016 Elsevier B.V. All rights reserved.

  12. Synthesis of Monolayer MoS2 by Chemical Vapor Deposition

    Science.gov (United States)

    Withanage, Sajeevi; Lopez, Mike; Dumas, Kenneth; Jung, Yeonwoong; Khondaker, Saiful

    Finite and layer-tunable band gap of transition metal dichalcogenides (TMDs) including molybdenum disulfide (MoS2) are highlighted over the zero band gap graphene in various semiconductor applications. Weak interlayer Van der Waal bonding of bulk MoS2 allows to cleave few to single layer MoS2 using top-down methods such as mechanical and chemical exfoliation, however few micron size of these flakes limit MoS2 applications to fundamental research. Bottom-up approaches including the sulfurization of molybdenum (Mo) thin films and co-evaporation of Mo and sulfur precursors received the attention due to their potential to synthesize large area. We synthesized monolayer MoS2 on Si/SiO2 substrates by atmospheric pressure Chemical Vapor Deposition (CVD) methods using sulfur and molybdenum trioxide (MoO3) as precursors. Several growth conditions were tested including precursor amounts, growth temperature, growth time and flow rate. Raman, photoluminescence (PL) and atomic force microscopy (AFM) confirmed monolayer islands merging to create large area were observed with grain sizes up to 70 μm without using any seeds or seeding promoters. These studies provide in-depth knowledge to synthesize high quality large area MoS2 for prospective electronics applications.

  13. Apoptotic activity and gene responses in Drosophila melanogaster S2 cells, induced by azadirachtin A.

    Science.gov (United States)

    Xu, Lin; Li, Sheng; Ran, Xueqin; Liu, Chang; Lin, Rutao; Wang, Jiafu

    2016-09-01

    Azadirachtin has been used as an antifeedant and growth disruption agent for many insect species. Previous investigations have reported the apoptotic effects of azadirachtin on some insect cells, but the molecular mechanisms are still not clear. This study investigated the underlying molecular mechanisms for the apoptotic effects induced by azadirachtin on Drosophila melanogaster S2 cells in vitro. The results of the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide assay demonstrated that azadirachtin exhibited significant cytotoxicity to S2 cells in a time- and dose-dependent manner. The changes in cellular morphology and the DNA fragmentation demonstrated that azadirachtin induced remarkable apoptosis of S2 cells. Expression levels of 276 genes were found to be significantly changed in S2 cells after exposure to azadirachtin, as detected by Drosophila genome array. Among these genes, calmodulin (CaM) was the most highly upregulated gene. Azadirachtin was further demonstrated to trigger intracellular Ca(2+) release in S2 cells. The genes related to the apoptosis pathway, determined from chip data, were validated by the real-time quantitative polymerase chain reaction method. The results showed that azadirachtin-mediated intracellular Ca(2+) release was the primary event that triggered apoptosis in Drosophila S2 cells through both pathways of the Ca(2+) -CaM and EcR/Usp signalling cascade. © 2015 Society of Chemical Industry. © 2015 Society of Chemical Industry.

  14. Functionalization of liquid-exfoliated two-dimensional 2H-MoS2.

    Science.gov (United States)

    Backes, Claudia; Berner, Nina C; Chen, Xin; Lafargue, Paul; LaPlace, Pierre; Freeley, Mark; Duesberg, Georg S; Coleman, Jonathan N; McDonald, Aidan R

    2015-02-23

    Layered two-dimensional (2D) inorganic transition-metal dichalchogenides (TMDs) have attracted great interest as a result of their potential application in optoelectronics, catalysis, and medicine. However, methods to functionalize and process such 2D TMDs remain scarce. We have established a facile route towards functionalized layered MoS2 . We found that the reaction of liquid-exfoliated 2D MoS2 , with M(OAc)2 salts (M=Ni, Cu, Zn; OAc=acetate) yielded functionalized MoS2 -M(OAc)2 materials. Importantly, this method furnished the 2H-polytype of MoS2 which is a semiconductor. X-ray photoelectron spectroscopy (XPS), diffuse reflectance infrared Fourier transform spectroscopy (DRIFT-IR), and thermogravimetric analysis (TGA) provide strong evidence for the coordination of MoS2 surface sulfur atoms to the M(OAc)2 salt. Interestingly, functionalization of 2H-MoS2 allows for its dispersion/processing in more conventional laboratory solvents. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. MoS2 nanosheet functionalized with Cu nanoparticles and its application for glucose detection

    International Nuclear Information System (INIS)

    Huang, Jingwei; Dong, Zhengping; Li, Yanrong; Li, Jing; Tang, Weijie; Yang, Haidong; Wang, Jia; Bao, Yun; Jin, Jun; Li, Rong

    2013-01-01

    Graphical abstract: - Highlights: • First report on decorating MoS 2 nanosheet with Cu nanoparticles by chemical reduction. • Cu nanoparticles were uniformly decorated on MoS 2 nanosheet. • Glucose biosensor based on copper nanoparticles-MoS 2 nanosheet hybrid is fabricated. • The biosensor exhibits high sensitivity. - Abstract: For the first time, Cu nanoparticles were evenly decorated on MoS 2 nanosheet by chemical reduction. The as-prepared Cu-MoS 2 hybrid was characterized by atomic force microscope (AFM), Raman spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD) and then used to fabricate a non-enzymatic glucose sensor. The performance of our sensor was investigated by cyclic voltammetry and amperometric measurement in alkaline media. Electrochemical tests showed that Cu-MoS 2 hybrid exhibited synergistic electrocatalytic activity on the oxidation of glucose with a high sensitivity of 1055 μA mM −1 cm −2 and a linear range up to 4 mM

  16. Composition of the mitochondrial electron transport chain in acanthamoeba castellanii: structural and evolutionary insights.

    Science.gov (United States)

    Gawryluk, Ryan M R; Chisholm, Kenneth A; Pinto, Devanand M; Gray, Michael W

    2012-11-01

    The mitochondrion, derived in evolution from an α-proteobacterial progenitor, plays a key metabolic role in eukaryotes. Mitochondria house the electron transport chain (ETC) that couples oxidation of organic substrates and electron transfer to proton pumping and synthesis of ATP. The ETC comprises several multiprotein enzyme complexes, all of which have counterparts in bacteria. However, mitochondrial ETC assemblies from animals, plants and fungi are generally more complex than their bacterial counterparts, with a number of 'supernumerary' subunits appearing early in eukaryotic evolution. Little is known, however, about the ETC of unicellular eukaryotes (protists), which are key to understanding the evolution of mitochondria and the ETC. We present an analysis of the ETC proteome from Acanthamoeba castellanii, an ecologically, medically and evolutionarily important member of Amoebozoa (sister to Opisthokonta). Data obtained from tandem mass spectrometric (MS/MS) analyses of purified mitochondria as well as ETC complexes isolated via blue native polyacrylamide gel electrophoresis are combined with the results of bioinformatic queries of sequence databases. Our bioinformatic analyses have identified most of the ETC subunits found in other eukaryotes, confirming and extending previous observations. The assignment of proteins as ETC subunits by MS/MS provides important insights into the primary structures of ETC proteins and makes possible, through the use of sensitive profile-based similarity searches, the identification of novel constituents of the ETC along with the annotation of highly divergent but phylogenetically conserved ETC subunits. © 2012 Elsevier B.V. All rights reserved.

  17. In situ carbon encapsulation of vertical MoS2 arrays with SnO2 for durable high rate lithium storage: dominant pseudocapacitive behavior.

    Science.gov (United States)

    Li, Mengjiao; Deng, Qinglin; Wang, Junyong; Jiang, Kai; Hu, Zhigao; Chu, Junhao

    2018-01-03

    Improving the conductivity and charge transfer kinetics is favourable for innovation of sustainable energy devices such as metal oxide/sulfide-based electrodes. Herein, with an intercalation pseudocapacitance effect, an in situ polymerization-carbonization process for novel carbon-sealed vertical MoS 2 -SnO 2 anchored on graphene aerogel (C@MoS 2 -SnO 2 @Gr) has enabled excellent rate performance and durability of the anode of lithium ion batteries to be achieved. The integrated carbon layer and graphene matrix provide a bicontinuous conductive network for efficient electron/ion diffusion pathways. The charge transfer kinetics could be enhanced by the synergistic effects between vertical MoS 2 nanosheets and well-dispersed SnO 2 particles. Based on the crystal surface matching, the ameliorated electric contact between MoS 2 and SnO 2 can promote the extraction of Li + from Li 2 O and restrain the serious aggregation of Li x Sn. As a result, the improved reversibility leads to a higher initial coulombic efficiency (ICE) of 80% (0.1 A g -1 current density) compared to that of other materials. In particular, with the dominating surface capacitive process, the C@MoS 2 -SnO 2 @Gr electrode delivers a stable capacity of 680 mA h g -1 at 2.5 A g -1 for 2000 cycles. Quantitative insight into the origin of the boosted kinetics demonstrated the high pseudocapacitance contribution (above 90%) which leads to the durable high rate Li ion storage.

  18. P-MoS2 / n-CdS thin film heterojunction

    International Nuclear Information System (INIS)

    El Maliki, H.; Gourmelon, E.; Bernede, J.C.; Pouzet, J.; Mebarki, M.; Khelil, A.; Zoaeter, M.

    1999-01-01

    Full text.Layered transition metal dichacolgenides such as MoS 2 are semiconductors that can be good candidates for solar energy conversion. Photo-electrochemical cells based on single crystals have achieved and efficiency of 17% (1). However, up to day, no solid rectifying contact has been put in evidence in the case of MoS 2 thin films.. Recently we have shown that such high crystalline quality MoS 2 films can be obtained onto textured tungsten slides. This allowed to try to grow sandwich rectifying structures. The bottom electrode will be W, MoS 2 being p-type, the n type film used was CdS and the upper electrode was indium. W foils textured along the (h00) direction were used as substrate and bottom electrode. The use of a W (textured) substrate induces the texturation of the MoS 2 films along the (001) direction when after evaporation of the constituents the films were annealed at T=1073 K for half an hour under argon atmosphere. Upon the MoS 2 a CdS thin film was deposited by chemical bath deposition (CBD). CdS thin films were prepared classically from a solution of cadmium sulfate, thiourea in hydrazine and ammonia. Ammonia was used adjust the solution pH to a value between 9 and 10. Bath temperature has been held constant at 343 K. Thin deposit films of CdS were yellow colored. They were constituted of an homogenous and adherent layer with a thickness of about 100 nm. It has been shown by x-ray diffraction the they were crystallized in their hexagonal structure. At least an indium film was deposited in order to achieve the structure M/MoS 2 p/CdSn/M. In order to check the equality of the W/MoS 2 contact, W/MoS 2 /W samples were also carried out by sputtering deposition of the tungsten upper electrode (300 nm thick). The thickness of the MoS 2 layers was about 500 nm. The J-V characteristics of a W/MoS 2 /W sample are ohmic. Moreover the resistance deduced from the slope ΔV/ΔI increases when the temperature decreases, which shows that there is not any

  19. Subunit association as the stabilizing determinant for archaeal methionine adenosyltransferases.

    Science.gov (United States)

    Garrido, Francisco; Alfonso, Carlos; Taylor, John C; Markham, George D; Pajares, María A

    2009-07-01

    Archaea contain a class of methionine adenosyltransferases (MATs) that exhibit substantially higher stability than their mesophilic counterparts. Their sequences are highly divergent, but preserve the essential active site motifs of the family. We have investigated the origin of this increased stability using chemical denaturation experiments on Methanococcus jannaschii MAT (Mj-MAT) and mutants containing single tryptophans in place of tyrosine residues. The results from fluorescence, circular dichroism, hydrodynamic, and enzyme activity measurements showed that the higher stability of Mj-MAT derives largely from a tighter association of its subunits in the dimer. Local fluorescence changes, interpreted using secondary structure predictions, further identify the least stable structural elements as the C-terminal ends of beta-strands E2 and E6, and the N-terminus of E3. Dimer dissociation however requires a wider perturbation of the molecule. Additional analysis was initially hindered by the lack of crystal structures for archaeal MATs, a limitation that we overcame by construction of a 3D-homology model of Mj-MAT. This model predicts preservation of the chain topology and three-domain organization typical of this family, locates the least stable structural elements at the flat contact surface between monomers, and shows that alterations in all three domains are required for dimer dissociation.

  20. The Regulation of NF-κB Subunits by Phosphorylation

    Directory of Open Access Journals (Sweden)

    Frank Christian

    2016-03-01

    Full Text Available The NF-κB transcription factor is the master regulator of the inflammatory response and is essential for the homeostasis of the immune system. NF-κB regulates the transcription of genes that control inflammation, immune cell development, cell cycle, proliferation, and cell death. The fundamental role that NF-κB plays in key physiological processes makes it an important factor in determining health and disease. The importance of NF-κB in tissue homeostasis and immunity has frustrated therapeutic approaches aimed at inhibiting NF-κB activation. However, significant research efforts have revealed the crucial contribution of NF-κB phosphorylation to controlling NF-κB directed transactivation. Importantly, NF-κB phosphorylation controls transcription in a gene-specific manner, offering new opportunities to selectively target NF-κB for therapeutic benefit. This review will focus on the phosphorylation of the NF-κB subunits and the impact on NF-κB function.

  1. DNA binding properties of the small cascade subunit Csa5.

    Directory of Open Access Journals (Sweden)

    Michael Daume

    Full Text Available CRISPR-Cas systems provide immunity against viral attacks in archaeal and bacterial cells. Type I systems employ a Cas protein complex termed Cascade, which utilizes small CRISPR RNAs to detect and degrade the exogenic DNA. A small sequence motif, the PAM, marks the foreign substrates. Previously, a recombinant type I-A Cascade complex from the archaeon Thermoproteus tenax was shown to target and degrade DNA in vitro, dependent on a native PAM sequence. Here, we present the biochemical analysis of the small subunit, Csa5, of this Cascade complex. T. tenax Csa5 preferentially bound ssDNA and mutants that showed decreased ssDNA-binding and reduced Cascade-mediated DNA cleavage were identified. Csa5 oligomerization prevented DNA binding. Specific recognition of the PAM sequence was not observed. Phylogenetic analyses identified Csa5 as a universal member of type I-A systems and revealed three distinct groups. A potential role of Csa5 in R-loop stabilization is discussed.

  2. Editing modifies the GABA(A) receptor subunit alpha3

    DEFF Research Database (Denmark)

    Ohlson, Johan; Pedersen, Jakob Skou; Haussler, David

    2007-01-01

    Adenosine to inosine (A-to-I) pre-mRNA editing by the ADAR enzyme family has the potential to increase the variety of the proteome. This editing by adenosine deamination is essential in mammals for a functional brain. To detect novel substrates for A-to-I editing we have used an experimental method...... to find selectively edited sites and combined it with bioinformatic techniques that find stem-loop structures suitable for editing. We present here the first verified editing candidate detected by this screening procedure. We show that Gabra-3, which codes for the alpha3 subunit of the GABA(A) receptor......, is a substrate for editing by both ADAR1 and ADAR2. Editing of the Gabra-3 mRNA recodes an isoleucine to a methionine. The extent of editing is low at birth but increases with age, reaching close to 100% in the adult brain. We therefore propose that editing of the Gabra-3 mRNA is important for normal brain...

  3. Vaccine profile of herpes zoster (HZ/su) subunit vaccine.

    Science.gov (United States)

    Cunningham, Anthony L; Heineman, Thomas

    2017-07-01

    Herpes zoster (HZ) causes an often severe and painful rash in older people and may be complicated by prolonged pain (postherpetic neuralgia; PHN) and by dissemination in immune-compromised patients. HZ results from reactivation of latent varicella-zoster virus (VZV) infection, often associated with age-related or other causes of decreased T cell immunity. A live attenuated vaccine boosts this immunity and provides partial protection against HZ, but this decreases with age and declines over 8 years. Areas covered: A new HZ subunit (HZ/su) vaccine combines a key surface VZV glycoprotein (E) with a T cell-boosting adjuvant system (AS01 B ) and is administered by two intramuscular injections two months apart. Expert commentary: HZ/su showed excellent efficacy of ~90% in immunocompetent adults ≥50 and ≥70 years of age, respectively, in the ZOE-50 and ZOE-70 phase III controlled trials. Efficacy was unaffected by advancing age and persisted for >3 years. Approximately 9.5% of subjects had severe, but transient (1-2 days) injection site pain, swelling or redness. Compliance with both vaccine doses was high (95%). The vaccine will have a major impact on HZ management. Phase I-II trials showed safety and immunogenicity in severely immunocompromised patients. Phase III trial results are expected soon.

  4. Design of a hyperstable 60-subunit protein icosahedron

    Science.gov (United States)

    Hsia, Yang; Bale, Jacob B.; Gonen, Shane; Shi, Dan; Sheffler, William; Fong, Kimberly K.; Nattermann, Una; Xu, Chunfu; Huang, Po-Ssu; Ravichandran, Rashmi; Yi, Sue; Davis, Trisha N.; Gonen, Tamir; King, Neil P.; Baker, David

    2016-07-01

    The icosahedron is the largest of the Platonic solids, and icosahedral protein structures are widely used in biological systems for packaging and transport. There has been considerable interest in repurposing such structures for applications ranging from targeted delivery to multivalent immunogen presentation. The ability to design proteins that self-assemble into precisely specified, highly ordered icosahedral structures would open the door to a new generation of protein containers with properties custom-tailored to specific applications. Here we describe the computational design of a 25-nanometre icosahedral nanocage that self-assembles from trimeric protein building blocks. The designed protein was produced in Escherichia coli, and found by electron microscopy to assemble into a homogenous population of icosahedral particles nearly identical to the design model. The particles are stable in 6.7 molar guanidine hydrochloride at up to 80 degrees Celsius, and undergo extremely abrupt, but reversible, disassembly between 2 molar and 2.25 molar guanidinium thiocyanate. The icosahedron is robust to genetic fusions: one or two copies of green fluorescent protein (GFP) can be fused to each of the 60 subunits to create highly fluorescent ‘standard candles’ for use in light microscopy, and a designed protein pentamer can be placed in the centre of each of the 20 pentameric faces to modulate the size of the entrance/exit channels of the cage. Such robust and customizable nanocages should have considerable utility in targeted drug delivery, vaccine design and synthetic biology.

  5. Fc receptor gamma subunit polymorphisms and systemic lupus erythematosus

    International Nuclear Information System (INIS)

    Al-Ansari, Aliya; Ollier, W.E.; Gonzalez-Gay, Miguel A.; Gul, Ahmet; Inanac, Murat; Ordi, Jose; Teh, Lee-Suan; Hajeer, Ali H.

    2004-01-01

    To investigate the possible association between Fc receptor gamma polymorphisms and systemic lupus erythematosus (SLE). We have investigated the full FcR gamma gene for polymorphisms using polymerase chain reaction (PCR)-single strand confirmational polymorphisms and DNA sequencing .The polymorphisms identified were genotype using PCR-restriction fragment length polymorphism. Systemic lupus erythematosus cases and controls were available from 3 ethnic groups: Turkish, Spanish and Caucasian. The study was conducted in the year 2001 at the Arthritis Research Campaign, Epidemiology Unit, Manchester University Medical School, Manchester, United Kingdom. Five single nucleotide polymorphisms were identified, 2 in the promoter, one in intron 4 and, 2 in the 3'UTR. Four of the 5 single nucleotide polymorphisms (SNPs) were relatively common and investigated in the 3 populations. Allele and genotype frequencies of all 4 investigated SNPs were not statistically different cases and controls. fc receptor gamma gene does not appear to contribute to SLE susceptibility. The identified polymorphisms may be useful in investigating other diseases where receptors containing the FcR gamma subunit contribute to the pathology. (author)

  6. Rapid water disinfection using vertically aligned MoS_2 nanofilms and visible light

    International Nuclear Information System (INIS)

    Liu, Chong; Kong, Desheng; Hsu, Po-Chun; Yuan, Hongtao; Lee, Hyun-Wook

    2016-01-01

    Here, solar energy is readily available in most climates and can be used for water purification. However, solar disinfection of drinking water (SODIS) mostly relies on ultraviolet light, which represents only 4% of total solar energy, and this leads to slow treatment speed. The development of new materials that can harvest visible light for water disinfection, and speed up solar water purification, is therefore highly desirable. Here, we show that few-layered vertically aligned MoS_2 (FLV-MoS_2) films can be used to harvest the whole spectrum of visible light (~ 50% of solar energy) and achieve highly efficient water disinfection. The bandgap of MoS_2 was increased from 1.3 eV to 1.55 eV by decreasing the domain size, which allowed the FLV-MoS_2 to generate reactive oxygen species (ROS) for bacterial inactivation in water. The FLV-MoS_2 showed ~15 times better log inactivation efficiency of indicator bacteria compared to bulk MoS_2, and much faster inactivation of bacteria under both visible light and sunlight illumination compared to widely used TiO_2. Moreover, by using a 5 nm copper film on top of the FLV-MoS_2 as a catalyst to facilitate electron-hole pair separation and promote the generation of ROS, the disinfection rate was further increased 6 fold. With our approach, we achieved water disinfection of >99.999% inactivation of bacteria in 20 minutes with a small amount of material (1.6 mg/L) under simulated visible light.

  7. Rapid water disinfection using vertically aligned MoS2 nanofilms and visible light

    International Nuclear Information System (INIS)

    Liu, Chong; Kong, Desheng; Hsu, Po-Chun; Yuan, Hongtao; Lee, Hyun-Wook

    2016-01-01

    In most climates, solar energy is readily available and can be used for water purification. But, solar disinfection of drinking water mostly relies on ultraviolet light, which represents only 4% of the total solar energy, and this leads to a slow treatment speed. Therefore, the development of new materials that can harvest visible light for water disinfection, and so speed up solar water purification, is highly desirable. Here we show that few-layered vertically aligned MoS_2 (FLV-MoS_2) films can be used to harvest the whole spectrum of visible light (~50% of solar energy) and achieve highly efficient water disinfection. The bandgap of MoS_2 was increased from 1.3 to 1.55 eV by decreasing the domain size, which allowed the FLV-MoS_2 to generate reactive oxygen species (ROS) for bacterial inactivation in the water. The FLV-MoS_2 showed a ~15 times better log inactivation efficiency of the indicator bacteria compared with that of bulk MoS_2, and a much faster inactivation of bacteria under both visible light and sunlight illumination compared with the widely used TiO_2. Moreover, by using a 5 nm copper film on top of the FLV-MoS_2 as a catalyst to facilitate electron–hole pair separation and promote the generation of ROS, the disinfection rate was increased a further sixfold. Here, we achieved water disinfection of >99.999% inactivation of bacteria in 20 min with a small amount of material (1.6 mg l–1) under simulated visible light.

  8. Three-Dimensional Tubular MoS2/PANI Hybrid Electrode for High Rate Performance Supercapacitor.

    Science.gov (United States)

    Ren, Lijun; Zhang, Gaini; Yan, Zhe; Kang, Liping; Xu, Hua; Shi, Feng; Lei, Zhibin; Liu, Zong-Huai

    2015-12-30

    By using three-dimensional (3D) tubular molybdenum disulfide (MoS2) as both an active material in electrochemical reaction and a framework to provide more paths for insertion and extraction of ions, PANI nanowire arrays with a diameter of 10-20 nm can be controllably grown on both the external and internal surface of 3D tubular MoS2 by in situ oxidative polymerization of aniline monomers and 3D tubular MoS2/PANI hybrid materials with different amounts of PANI are prepared. A controllable growth of PANI nanowire arrays on the tubular MoS2 surface provides an opportunity to optimize the capacitive performance of the obtained electrodes. When the loading amount of PANI is 60%, the obtained MoS2/PANI-60 hybrid electrode not only shows a high specific capacitance of 552 F/g at a current density of 0.5 A/g, but also gives excellent rate capability of 82% from 0.5 to 30 A/g. The remarkable rate performance can be mainly attributed to the architecture with synergistic effect between 3D tubular MoS2 and PANI nanowire arrays. Moreover, the MoS2/PANI-60 based symmetric supercapacitor also exhibits the excellent rate performance and good cycling stability. The specific capacitance based on the total mass of the two electrodes is 124 F/g at a current density of 1 A/g and 79% of its initial capacitance is remained after 6000 cycles. The 3D tubular structure provides a good and favorable method for improving the capacitance retention of PANI electrode.

  9. Effect of MoS2 on hydrogenation storage properties of LiBH4

    International Nuclear Information System (INIS)

    Liang, Dan; Han, Shumin; Wang, Jiasheng; Zhang, Wei; Zhao, Xin; Zhao, Ziyang

    2014-01-01

    The hydrogen storage properties of LiBH 4 ball milled with 20 wt% MoS 2 have been investigated. It shows that the LiBH 4 doped with MoS 2 exhibits favorable hydrogenation and dehydrogenation properties in terms of decomposition temperature and hydriding/dehydriding reversibility. The sample with MoS 2 starts to release hydrogen at 230 °C and has a decrease of 80 °C in contrast with pristine LiBH 4 . Furthermore, for the second cycle, the LiBH 4 with MoS 2 maintains a reversible hydrogen storage capacity of about 8.0 wt% which is almost identical with the first cycle under 5 MPa at 550 °C. Analyzed by the XRD and the FTIR results, LiBH 4 can be regenerated after re-hydrogenation under a relatively mild condition by adding MoS 2 . The improvement of the hydrogenation and dehydrogenation properties mainly results from the formation of Li 2 S and MoB 2 during ball milling. -- Graphical abstract: Hydrogen absorption curves of LiBH 4 doped with MoS 2 for five cycles at 400 °C. Highlights: • The hydrogen absorption capacity is nearly the same for 5 cycles at 400 °C. • The sample with MoS 2 starts to release hydrogen at 230 °C. • The coexistence of MoB 2 and Li 2 S catalyzes the decomposition of LiBH 4

  10. Opto-electronic characterization of polycrystalline CuInS2 and Cu(In,Ga)S2 absorber layers by photoluminescence

    International Nuclear Information System (INIS)

    Heidemann, Florian

    2011-01-01

    Photoluminescence (PL) is an established method to characterize the optoelectronic properties of solar cell absorber layers. With the help of Planck's generalized law it is in principle possible to determine the quasi-Fermi level splitting - which is the upper limit of the open circuit voltage V oc - and the absorption coefficient of a solar cell before its actual completion. For large-scale measurements (mm/cm regime) this is valid for absorber layers with lateral homogeneous properties, however it is not directly transferable to polycrystalline semiconductors due to laterally fluctuating opto-electronic and structural parameters. The lateral fluctuations in opto-electronic properties of polycrystalline Cu(In 1-ξ Ga ξ )S 2 have been analyzed (e.g. with respect to fluctuations in quasi-Fermi level splitting, optical band-gap and sub band-gap absorbance) by measuring laterally and spectrally resolved PL on the μm-scale and providing the transition towards macroscopic PL measurements on the mm-scale. To give a comprehensive characterization, surface roughness and optical properties have been studied and methods for feature extraction have been applied. On the microscopic scale variations in the quasi-Fermi level splitting Δ x,y E Fnp of about 38 meV (CuInS 2 ) and 53 meV (Cu(In,Ga)S 2 ) have been found. From local absorbance spectra extracted from PL measurements on Cu(In,Ga)S 2 fluctuations in the optical band-gap E opt with a full width at half maximum of FWHM E opt ∼80 meV could be extracted, whereas band-gap fluctuations in CuInS 2 are found to be negligible. Thus band-gap fluctuations seem to be mainly caused by a varying gallium (Ga) content. Furthermore, regions with higher E opt and with it a potential higher Ga content, show a higher quasi-Fermi level splitting. As a major limiting factor for the local quasi-Fermi level splitting E Fnp the local density of deep defects could be identified. Due to low luminescence yields of Cu(In 1-ξ Ga ξ )S 2 under

  11. Structural characterization of recombinant crustacyanin subunits from the lobster Homarus americanus

    International Nuclear Information System (INIS)

    Ferrari, Michele; Folli, Claudia; Pincolini, Elisa; McClintock, Timothy S.; Rössle, Manfred; Berni, Rodolfo; Cianci, Michele

    2012-01-01

    The two recombinant apo subunits H1 and H2 from H. americanus have been structurally characterized. Reconstitution studies with astaxanthin reproduced the bathochromic shift of 85–95 nm typical of the natural crustacyanin subunits. Crustacean crustacyanin proteins are linked to the production and modification of carapace colour, with direct implications for fitness and survival. Here, the structural and functional properties of the two recombinant crustacyanin subunits H 1 and H 2 from the American lobster Homarus americanus are reported. The two subunits are structurally highly similar to the corresponding natural apo crustacyanin CRTC and CRTA subunits from the European lobster H. gammarus. Reconstitution studies of the recombinant crustacyanin proteins H 1 and H 2 with astaxanthin reproduced the bathochromic shift of 85–95 nm typical of the natural crustacyanin subunits from H. gammarus in complex with astaxanthin. Moreover, correlations between the presence of crustacyanin genes in crustacean species and the resulting carapace colours with the spectral properties of the subunits in complex with astaxanthin confirmed this genotype–phenotype linkage

  12. Self-subunit swapping occurs in another gene type of cobalt nitrile hydratase.

    Directory of Open Access Journals (Sweden)

    Yi Liu

    Full Text Available Self-subunit swapping is one of the post-translational maturation of the cobalt-containing nitrile hydratase (Co-NHase family of enzymes. All of these NHases possess a gene organization of , which allows the activator protein to easily form a mediatory complex with the α-subunit of the NHase after translation. Here, we discovered that the incorporation of cobalt into another type of Co-NHase, with a gene organization of , was also dependent on self-subunit swapping. We successfully isolated a recombinant NHase activator protein (P14K of Pseudomonas putida NRRL-18668 by adding a Strep-tag N-terminal to the P14K gene. P14K was found to form a complex [α(StrepP14K(2] with the α-subunit of the NHase. The incorporation of cobalt into the NHase of P. putida was confirmed to be dependent on the α-subunit substitution between the cobalt-containing α(StrepP14K(2 and the cobalt-free NHase. Cobalt was inserted into cobalt-free α(StrepP14K(2 but not into cobalt-free NHase, suggesting that P14K functions not only as a self-subunit swapping chaperone but also as a metallochaperone. In addition, NHase from P. putida was also expressed by a mutant gene that was designed with a order. Our findings expand the general features of self-subunit swapping maturation.

  13. Voltage-Gated Sodium Channel β1/β1B Subunits Regulate Cardiac Physiology and Pathophysiology

    Directory of Open Access Journals (Sweden)

    Nnamdi Edokobi

    2018-04-01

    Full Text Available Cardiac myocyte contraction is initiated by a set of intricately orchestrated electrical impulses, collectively known as action potentials (APs. Voltage-gated sodium channels (NaVs are responsible for the upstroke and propagation of APs in excitable cells, including cardiomyocytes. NaVs consist of a single, pore-forming α subunit and two different β subunits. The β subunits are multifunctional cell adhesion molecules and channel modulators that have cell type and subcellular domain specific functional effects. Variants in SCN1B, the gene encoding the Nav-β1 and -β1B subunits, are linked to atrial and ventricular arrhythmias, e.g., Brugada syndrome, as well as to the early infantile epileptic encephalopathy Dravet syndrome, all of which put patients at risk for sudden death. Evidence over the past two decades has demonstrated that Nav-β1/β1B subunits play critical roles in cardiac myocyte physiology, in which they regulate tetrodotoxin-resistant and -sensitive sodium currents, potassium currents, and calcium handling, and that Nav-β1/β1B subunit dysfunction generates substrates for arrhythmias. This review will highlight the role of Nav-β1/β1B subunits in cardiac physiology and pathophysiology.

  14. Thioaluminogermanate M(AlS2)(GeS2)4 (M = Na, Ag, Cu): Synthesis, Crystal Structures, Characterization, Ion-Exchange and Solid-State 27Al and 23Na NMR Spectroscopy

    KAUST Repository

    Alahmary, Fatimah S.

    2018-03-14

    The new thioaluminogermanate Na(AlS2)(GeS2)4 (1) was successfully synthesized by a direct combination reaction. The compound crystallizes in the monoclinic space group P21/n (no. 14) with unit cell parameters a = 6.803(3) Å, b = 38.207(2) Å, c = 6.947(4) Å, and β = 119.17(3)°. The crystal structure is composed of a [(AlS2)(GeS2)4]− 3D polyanionic network, in which Al and Ge atoms share the atomic positions and Na cations occupy the channels and voids formed by the connection of (Ge/Al)S4 tetrahedra. The title compound shows a cation-exchange property with monovalent Ag+ and Cu+ ions at room temperature in solvent media, resulting in the formation of the isostructural compounds Ag(AlS2)(GeS2)4 (2) and Cu(AlS2)(GeS2)4 (3), respectively. The ion-exchange products Ag(AlS2)(GeS2)4 (2) and Cu(AlS2)(GeS2)4 (3) show higher air stability and narrower bandgap energies compared to those of the parent compound Na(AlS2)(GeS2)4 (1).

  15. Thioaluminogermanate M(AlS2)(GeS2)4 (M = Na, Ag, Cu): Synthesis, Crystal Structures, Characterization, Ion-Exchange and Solid-State 27Al and 23Na NMR Spectroscopy

    KAUST Repository

    Alahmary, Fatimah S.; Davaasuren, Bambar; Emwas, Abdul-Hamid M.; Rothenberger, Alexander

    2018-01-01

    The new thioaluminogermanate Na(AlS2)(GeS2)4 (1) was successfully synthesized by a direct combination reaction. The compound crystallizes in the monoclinic space group P21/n (no. 14) with unit cell parameters a = 6.803(3) Å, b = 38.207(2) Å, c = 6.947(4) Å, and β = 119.17(3)°. The crystal structure is composed of a [(AlS2)(GeS2)4]− 3D polyanionic network, in which Al and Ge atoms share the atomic positions and Na cations occupy the channels and voids formed by the connection of (Ge/Al)S4 tetrahedra. The title compound shows a cation-exchange property with monovalent Ag+ and Cu+ ions at room temperature in solvent media, resulting in the formation of the isostructural compounds Ag(AlS2)(GeS2)4 (2) and Cu(AlS2)(GeS2)4 (3), respectively. The ion-exchange products Ag(AlS2)(GeS2)4 (2) and Cu(AlS2)(GeS2)4 (3) show higher air stability and narrower bandgap energies compared to those of the parent compound Na(AlS2)(GeS2)4 (1).

  16. Scalable Patterning of MoS2 Nanoribbons by Micromolding in Capillaries.

    Science.gov (United States)

    Hung, Yu-Han; Lu, Ang-Yu; Chang, Yung-Huang; Huang, Jing-Kai; Chang, Jeng-Kuei; Li, Lain-Jong; Su, Ching-Yuan

    2016-08-17

    In this study, we report a facile approach to prepare dense arrays of MoS2 nanoribbons by combining procedures of micromolding in capillaries (MIMIC) and thermolysis of thiosalts ((NH4)2MoS4) as the printing ink. The obtained MoS2 nanoribbons had a thickness reaching as low as 3.9 nm, a width ranging from 157 to 465 nm, and a length up to 2 cm. MoS2 nanoribbons with an extremely high aspect ratio (length/width) of ∼7.4 × 10(8) were achieved. The MoS2 pattern can be printed on versatile substrates, such as SiO2/Si, sapphire, Au film, FTO/glass, and graphene-coated glass. The degree of crystallinity of the as-prepared MoS2 was discovered to be adjustable by varying the temperature through postannealing. The high-temperature thermolysis (1000 °C) results in high-quality conductive samples, and field-effect transistors based on the patterned MoS2 nanoribbons were demonstrated and characterized, where the carrier mobility was comparable to that of thin-film MoS2. In contrast, the low-temperature-treated samples (170 °C) result in a unique nanocrystalline MoSx structure (x ≈ 2.5), where the abundant and exposed edge sites were obtained from highly dense arrays of nanoribbon structures by this MIMIC patterning method. The patterned MoSx was revealed to have superior electrocatalytic efficiency (an overpotential of ∼211 mV at 10 mA/cm(2) and a Tafel slope of 43 mV/dec) in the hydrogen evolution reaction (HER) when compared to the thin-film MoS2. The report introduces a new concept for rapidly fabricating cost-effective and high-density MoS2/MoSx nanostructures on versatile substrates, which may pave the way for potential applications in nanoelectronics/optoelectronics and frontier energy materials.

  17. Scalable Patterning of MoS2Nanoribbons by Micromolding in Capillaries

    KAUST Repository

    Hung, Yu-Han

    2016-07-27

    In this study, we report a facile approach to prepare dense arrays of MoS2 nanoribbons by combining procedures of micromolding in capillaries (MIMIC) and thermolysis of thiosalts ((NH4)2MoS4) as the printing ink. The obtained MoS2 nanoribbons had a thickness reaching as low as 3.9 nm, a width ranging from 157 to 465 nm, and a length up to 2 cm. MoS2 nanoribbons with an extremely high aspect ratio (length/width) of ∼7.4 × 108 were achieved. The MoS2 pattern can be printed on versatile substrates, such as SiO2/Si, sapphire, Au film, FTO/glass, and graphene-coated glass. The degree of crystallinity of the as-prepared MoS2 was discovered to be adjustable by varying the temperature through postannealing. The high-temperature thermolysis (1000 °C) results in high-quality conductive samples, and field-effect transistors based on the patterned MoS2 nanoribbons were demonstrated and characterized, where the carrier mobility was comparable to that of thin-film MoS2. In contrast, the low-temperature-treated samples (170 °C) result in a unique nanocrystalline MoSx structure (x ≈ 2.5), where the abundant and exposed edge sites were obtained from highly dense arrays of nanoribbon structures by this MIMIC patterning method. The patterned MoSx was revealed to have superior electrocatalytic efficiency (an overpotential of ∼211 mV at 10 mA/cm2 and a Tafel slope of 43 mV/dec) in the hydrogen evolution reaction (HER) when compared to the thin-film MoS2. The report introduces a new concept for rapidly fabricating cost-effective and high-density MoS2/MoSx nanostructures on versatile substrates, which may pave the way for potential applications in nanoelectronics/optoelectronics and frontier energy materials. © 2016 American Chemical Society.

  18. Global regulatory roles of the cAMP/PKA pathway revealed by phenotypic, transcriptomic and phosphoproteomic analyses in a null mutant of the PKA catalytic subunit in Candida albicans.

    Science.gov (United States)

    Cao, Chengjun; Wu, Mei; Bing, Jian; Tao, Li; Ding, Xuefen; Liu, Xiaoyun; Huang, Guanghua

    2017-07-01

    The conserved cAMP-dependent protein kinase (PKA) plays critical roles in the regulation of morphological transitions and virulence in the human fungal pathogen Candida albicans. It has long been thought that the PKA catalytic subunit is essential for cell viability in this fungus. Paradoxically, the single adenylyl cyclase-encoding gene, CYR1, which is required for the production of cAMP in C. albicans, is not essential for cell growth. Here, a double mutant of TPK1 and TPK2 (tpk2/tpk2 tpk1/tpk1, t2t1), which encode two isoforms of the PKA catalytic subunit was successfully generated, suggesting that this subunit is not essential for cell viability. Inactivation of the PKA catalytic subunit blocked filamentation and dramatically attenuated white-to-opaque switching, but promoted sexual mating. Comparative transcriptomic analyses demonstrated that the t2t1 and cyr1/cyr1 mutants exhibited similar global gene expression profiles. Compared with the WT strain, the general transcriptional activity and metabolism were significantly decreased in both the t2t1 and cyr1/cyr1 mutants. Using combined phosphoproteomic and bioinformatic analyses, we identified 181 potential PKA phosphorylation targets, which represent 148 unique proteins involved in a wide spectrum of biological processes. The study sheds new insights into the global regulatory features of the cAMP/PKA pathway in C. albicans. © 2017 John Wiley & Sons Ltd.

  19. Recent advances in MoS2 nanostructured materials for energy and environmental applications - A review

    Science.gov (United States)

    Theerthagiri, J.; Senthil, R. A.; Senthilkumar, B.; Reddy Polu, Anji; Madhavan, J.; Ashokkumar, Muthupandian

    2017-08-01

    Molybdenum disulfide (MoS2), a layered transition metal dichalcogenide with an analogous structure to graphene, has attracted enormous attention worldwide owing to its use in a variety of applications such as energy storage, energy conversion, environmental remediation and sensors. MoS2 and graphene have almost similar functional properties such as high charge carrier transport, high wear resistance and good mechanical strength and friction. However, MoS2 is advantageous over graphene due to its low-cost, abundancy, tailorable morphologies and tuneable band gap with good visible light absorption properties. In this review, we have focussed mainly on recent advances in MoS2 nanostructured materials for the applications in the broad area of energy and environment. Special attention has been paid to their applications in dye-sensitized solar cells, supercapacitor, Li-ion battery, hydrogen evolution reaction, photocatalysis for the degradation of organic pollutants, chemical/bio sensors and gas sensors. Finally, the challenges to design MoS2 nanostructures suitable for energy and environmental applications are also highlighted.

  20. MoS2-InGaZnO Heterojunction Phototransistors with Broad Spectral Responsivity.

    Science.gov (United States)

    Yang, Jaehyun; Kwak, Hyena; Lee, Youngbin; Kang, Yu-Seon; Cho, Mann-Ho; Cho, Jeong Ho; Kim, Yong-Hoon; Jeong, Seong-Jun; Park, Seongjun; Lee, Hoo-Jeong; Kim, Hyoungsub

    2016-04-06

    We introduce an amorphous indium-gallium-zinc-oxide (a-IGZO) heterostructure phototransistor consisting of solution-based synthetic molybdenum disulfide (few-layered MoS2, with a band gap of ∼1.7 eV) and sputter-deposited a-IGZO (with a band gap of ∼3.0 eV) films as a novel sensing element with a broad spectral responsivity. The MoS2 and a-IGZO films serve as a visible light-absorbing layer and a high mobility channel layer, respectively. Spectroscopic measurements reveal that appropriate band alignment at the heterojunction provides effective transfer of the visible light-induced electrons generated in the few-layered MoS2 film to the underlying a-IGZO channel layer with a high carrier mobility. The photoresponse characteristics of the a-IGZO transistor are extended to cover most of the visible range by forming a heterojunction phototransistor that harnesses a visible light responding MoS2 film with a small band gap prepared through a large-area synthetic route. The MoS2-IGZO heterojunction phototransistors exhibit a photoresponsivity of approximately 1.7 A/W at a wavelength of 520 nm (an optical power of 1 μW) with excellent time-dependent photoresponse dynamics.

  1. Novel field-effect schottky barrier transistors based on graphene-MoS 2 heterojunctions

    KAUST Repository

    Tian, He

    2014-08-11

    Recently, two-dimensional materials such as molybdenum disulphide (MoS 2) have been demonstrated to realize field effect transistors (FET) with a large current on-off ratio. However, the carrier mobility in backgate MoS2 FET is rather low (typically 0.5-20 cm2/V.s). Here, we report a novel field-effect Schottky barrier transistors (FESBT) based on graphene-MoS2 heterojunction (GMH), where the characteristics of high mobility from graphene and high on-off ratio from MoS2 are properly balanced in the novel transistors. Large modulation on the device current (on/off ratio of 105) is achieved by adjusting the backgate (through 300 nm SiO2) voltage to modulate the graphene-MoS2 Schottky barrier. Moreover, the field effective mobility of the FESBT is up to 58.7 cm2/V.s. Our theoretical analysis shows that if the thickness of oxide is further reduced, a subthreshold swing (SS) of 40 mV/decade can be maintained within three orders of drain current at room temperature. This provides an opportunity to overcome the limitation of 60 mV/decade for conventional CMOS devices. The FESBT implemented with a high on-off ratio, a relatively high mobility and a low subthreshold promises low-voltage and low-power applications for future electronics.

  2. Friction and wear mechanisms in MoS2/Sb2O3/Au nanocomposite coatings

    International Nuclear Information System (INIS)

    Scharf, T.W.; Kotula, P.G.; Prasad, S.V.

    2010-01-01

    Fundamental phenomena governing the tribological mechanisms in sputter deposited amorphous MoS 2 /Sb 2 O 3 /Au nanocomposite coatings are reported. In dry environments the nanocomposite has the same low friction coefficient as pure MoS 2 (∼0.007). However, unlike pure MoS 2 coatings, which wear through in air (50% relative humidity), the composite coatings showed minimal wear, with wear factors of ∼1.2-1.4 x 10 -7 mm 3 Nm -1 in both dry nitrogen and air. The coatings exhibited non-Amontonian friction behavior, with the friction coefficient decreasing with increasing Hertzian contact stress. Cross-sectional transmission electron microscopy of wear surfaces revealed that frictional contact resulted in an amorphous to crystalline transformation in MoS 2 with 2H-basal (0 0 0 2) planes aligned parallel to the direction of sliding. In air the wear surface and subsurface regions exhibited islands of Au. The mating transfer films were also comprised of (0 0 0 2)-oriented basal planes of MoS 2 , resulting in predominantly self-mated 'basal on basal' interfacial sliding and, thus, low friction and wear.

  3. Oxidation of MoS2 by thermal and hyperthermal atomic oxygen

    International Nuclear Information System (INIS)

    Cross, J.B.; Martin, J.A.; Pope, L.E.; Koontz, S.L.

    1989-01-01

    The present study shows that, at 1.5 eV O-atom translational energy, SO 2 is generated and outgases from an anhydrous MoS 2 surface with a reactivity nearly that of kapton. The reaction of atomic oxygen with MoS 2 has little or no translational energy barrier; i.e., thermally generated atomic oxygen reacts as readily as that having 1.5 eV of translational energy. It is also shown that water present in the flowing afterglow apparatus used to study thermal O-atom reactivity formed sulfates on the MoS 2 surface and that the sulfate is most likely in the form of sulfuric acid. These results imply that water dumps or outgasing in low earth orbit have the potential of forming sulfuric acid covered surfaces on MoS 2 lubricants. Friction measurements show a high initial friction coefficient (0.2) for O-atom exposed MoS 2 surfaces which drops to the normal low value (0.05) after several cycles of operation

  4. Interpretation of the photoelectron spectra of FeS(2)(-) by a multiconfiguration computational approach.

    Science.gov (United States)

    Clima, Sergiu; Hendrickx, Marc F A

    2007-11-01

    The ground states of FeS(2) and FeS(2)(-), and several low-lying excited electronic states of FeS(2) that are responsible for the FeS(2)(-) photoelectron spectrum, are calculated. At the B3LYP level an open, quasi-linear [SFeS](-) conformation is found as the most stable structure, which is confirmed at the ab initio CASPT2 computational level. Both the neutral and the anionic unsaturated complexes possess high-spin electronic ground states. For the first time a complete assignment of the photoelectron spectrum of FeS(2)(-) is proposed. The lowest energy band in this spectrum is ascribed to an electron detachment from the two highest-lying 3dpi antibonding orbitals (with respect to the iron-sulfur bonding) of iron. The next-lowest experimental band corresponds to an electron removal from nonbonding, nearly pure sulfur orbitals. The two highest bands in the spectra are assigned as electron detachments from pi and sigma bonding mainly sulfur orbitals.

  5. Effect of interfaces on electron transport properties of MoS2-Au Contacts

    Science.gov (United States)

    Aminpour, Maral; Hapala, Prokop; Le, Duy; Jelinek, Pavel; Rahman, Talat S.; Rahman's Group Collaboration; Nanosurf Lab Collaboration

    2014-03-01

    Single layer MoS2 is a promising material for future electronic devices such as transistors since it has good transport characteristics with mobility greater than 200 cm-1V-1s-1 and on-off current ratios up to 108. However, before MoS2 can become a mainstream electronic material for the semiconductor industry, the design of low resistive metal-semiconductor junctions as contacts of the electronic devices needs to be addressed and studied systematically. We have examined the effect of Au contacts on the electronic transport properties of single layer MoS2 using density functional theory in combination with the non-equilibrium Green's function method. The Schottky barrier between Au contact and MoS2, transmission spectra, and I-V curves will be reported and discussed as a function of MoS2 and Au interfaces of varying geometry. This work is supported in part by the US Department of Energy under grant DE-FG02-07ER15842.

  6. Doping of two-dimensional MoS2 by high energy ion implantation

    Science.gov (United States)

    Xu, Kang; Zhao, Yuda; Lin, Ziyuan; Long, Yan; Wang, Yi; Chan, Mansun; Chai, Yang

    2017-12-01

    Two-dimensional (2D) materials have been demonstrated to be promising candidates for next generation electronic circuits. Analogues to conventional Si-based semiconductors, p- and n-doping of 2D materials are essential for building complementary circuits. Controllable and effective doping strategies require large tunability of the doping level and negligible structural damage to ultrathin 2D materials. In this work, we demonstrate a doping method utilizing a conventional high-energy ion-implantation machine. Before the implantation, a Polymethylmethacrylate (PMMA) protective layer is used to decelerate the dopant ions and minimize the structural damage to MoS2, thus aggregating the dopants inside MoS2 flakes. By optimizing the implantation energy and fluence, phosphorus dopants are incorporated into MoS2 flakes. Our Raman and high-resolution transmission electron microscopy (HRTEM) results show that only negligibly structural damage is introduced to the MoS2 lattice during the implantation. P-doping effect by the incorporation of p+ is demonstrated by Photoluminescence (PL) and electrical characterizations. Thin PMMA protection layer leads to large kinetic damage but also a more significant doping effect. Also, MoS2 with large thickness shows less kinetic damage. This doping method makes use of existing infrastructures in the semiconductor industry and can be extended to other 2D materials and dopant species as well.

  7. Enhanced Gas Separation through Nanoconfined Ionic Liquid in Laminated MoS2 Membrane.

    Science.gov (United States)

    Chen, Danke; Ying, Wen; Guo, Yi; Ying, Yulong; Peng, Xinsheng

    2017-12-20

    Two-dimensional (2D) materials-based membranes show great potential for gas separation. Herein an ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF 4 ]), was confined in the 2D channels of MoS 2 -laminated membranes via an infiltration process. Compared with the corresponding bulk [BMIM][BF 4 ], nanoconfined [BMIM][BF 4 ] shows an obvious incremental increase in freezing point and a shift of vibration bands. The resulting MoS 2 -supported ionic liquid membrane (MoS 2 SILM) exhibits excellent CO 2 separation performance with high CO 2 permeance (47.88 GPU) and superb selectivity for CO 2 /N 2 (131.42), CO 2 /CH 4 (43.52), and CO 2 /H 2 (14.95), which is much better than that of neat [BMIM][BF 4 ] and [BMIM][BF 4 ]-based membranes. The outstanding performance of MoS 2 SILMs is attributed to the nanoconfined [BMIM][BF 4 ], which enables fast transport of CO 2 . Long-term operation also reveals the durability and stability of the prepared MoS 2 SILMs. The method of confining ILs in the 2D nanochannels of 2D materials may pave a new way for CO 2 capture and separation.

  8. Chemisorption-induced n-doping of MoS2 by oxygen

    International Nuclear Information System (INIS)

    Qi, Long; Wang, Ying; Wu, Yihong; Shen, Lei

    2016-01-01

    Both chemisorption and physisorption affect the electronic properties of two-dimensional materials, such as MoS 2 , but it remains a challenge to probe their respective roles experimentally. Through repeated in-situ electrical measurements of few-layer MoS 2 field-effect transistors in an ultrahigh vacuum system with well-controlled oxygen partial pressure (6 × 10 −8 mbar–3 × 10 −7 mbar), we were able to study the effect of chemisorption on surface defects separately from physically adsorbed oxygen molecules. It is found that chemisorption of oxygen results in n-doping in the channel but negligible effect on mobility and on/off ratio of the MoS 2 transistors. These results are in disagreement with the previous reports on p-doping and degradation of the device's performance when both chemisorption and physisorption are present. Through the analysis of adsorption-desorption kinetics and the first-principles calculations of electronic properties, we show that the experimentally observed n-doping effect originates from dissociative adsorption of oxygen at the surface defects of MoS 2 , which lowers the conduction band edge locally and makes the MoS 2 channel more n-type-like as compared to the as-fabricated devices

  9. Preparation of nanostructured and nanosheets of MoS2 oxide using oxidation method.

    Science.gov (United States)

    Amini, Majed; Ramazani S A, Ahmad; Faghihi, Morteza; Fattahpour, Seyyedfaridoddin

    2017-11-01

    Molybdenum disulfide (MoS 2 ), a two-dimensional transition metal has a 2D layered structure and has recently attracted attention due to its novel catalytic properties. In this study, MoS 2 has been successfully intercalated using chemical and physical intercalation techniques, while enhancing its surface properties. The final intercalated MoS 2 is of many interests because of its low-dimensional and potential properties in in-situ catalysis. In this research, we report different methods to intercalate the layers of MoS 2 successfully using acid-treatment, ultrasonication, oxidation and thermal shocking. The other goal of this study is to form SO bonds mainly because of expected enhanced in-situ catalytic operations. The intercalated MoS 2 is further characterized using analyses such as Fourier Transform Infrared Spectroscopy (FTIR), Raman, Contact Angle, X-ray diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM), Energy Dispersive X-Ray Microanalysis (EDAX), Transmission electron microscopy (TEM), and BET. Copyright © 2017. Published by Elsevier B.V.

  10. Unraveling the Raman Enhancement Mechanism on 1T'-Phase ReS2 Nanosheets.

    Science.gov (United States)

    Miao, Peng; Qin, Jing-Kai; Shen, Yunfeng; Su, Huimin; Dai, Junfeng; Song, Bo; Du, Yunchen; Sun, Mengtao; Zhang, Wei; Wang, Hsing-Lin; Xu, Cheng-Yan; Xu, Ping

    2018-04-01

    2D transition metal dichalcogenides materials are explored as potential surface-enhanced Raman spectroscopy substrates. Herein, a systematic study of the Raman enhancement mechanism on distorted 1T (1T') rhenium disulfide (ReS 2 ) nanosheets is demonstrated. Combined Raman and photoluminescence studies with the introduction of an Al 2 O 3 dielectric layer unambiguously reveal that Raman enhancement on ReS 2 materials is from a charge transfer process rather than from an energy transfer process, and Raman enhancement is inversely proportional while the photoluminescence quenching effect is proportional to the layer number (thickness) of ReS 2 nanosheets. On monolayer ReS 2 film, a strong resonance-enhanced Raman scattering effect dependent on the laser excitation energy is detected, and a detection limit as low as 10 -9 m can be reached from the studied dye molecules such as rhodamine 6G and methylene blue. Such a high enhancement factor achieved through enhanced charge interaction between target molecule and substrate suggests that with careful consideration of the layer-number-dependent feature and excitation-energy-related resonance effect, ReS 2 is a promising Raman enhancement platform for sensing applications. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Determination of band offsets at GaN/single-layer MoS2 heterojunction

    KAUST Repository

    Tangi, Malleswararao

    2016-07-25

    We report the band alignment parameters of the GaN/single-layer (SL) MoS2 heterostructure where the GaN thin layer is grown by molecular beam epitaxy on CVD deposited SL-MoS2/c-sapphire. We confirm that the MoS2 is an SL by measuring the separation and position of room temperature micro-Raman E1 2g and A1 g modes, absorbance, and micro-photoluminescence bandgap studies. This is in good agreement with HRTEM cross-sectional analysis. The determination of band offset parameters at the GaN/SL-MoS2 heterojunction is carried out by high-resolution X-ray photoelectron spectroscopy accompanying with electronic bandgap values of SL-MoS2 and GaN. The valence band and conduction band offset values are, respectively, measured to be 1.86 ± 0.08 and 0.56 ± 0.1 eV with type II band alignment. The determination of these unprecedented band offset parameters opens up a way to integrate 3D group III nitride materials with 2D transition metal dichalcogenide layers for designing and modeling of their heterojunction based electronic and photonic devices.

  12. Symmetrical synergy of hybrid CoS2-WS2 electrocatalysts for hydrogen evolution reaction

    KAUST Repository

    Zhou, Xiaofeng; Yang, Xiulin; Li, Henan; Hedhili, Mohamed N.; Huang, Kuo-Wei; Li, Lain-Jong; Zhang, Wenjing

    2017-01-01

    A highly active and stable hybrid electrocatalyst 3D hierarchical CoS2 nanosheets incorporated with WS2 (CoS2@WS2) has been developed via a one-step sulfurization method for the first time, where the contents of WS2 can be adjusted easily. We first prove the addition of small amounts of WS2 enhances the hydrogen evolution reaction (HER) performance of CoS2, and vise versa. In other words, we validated the symmetric synergy for HER between the Co- and W-based sulfide hybrid catalysts. In addition, we confirmed that the formation of nanointerfaces of Co-S-W between CoS2 and WS2 was responsible for the excellent HER activity (an overpotential of -97.2 mV at -10 mA/cm2, a small Tafel slope of 66.0 mV/dec, and prominent electrochemical stability) of hybrid electrocatalyst CoS2@WS2.

  13. Photoresponse properties of large area MoS2 metal–semiconductor–metal photodetectors

    Science.gov (United States)

    Ko, Tsung-Shine; Huang, Yu-Jen; Lin, Der-Yuh; Lin, Chia-Feng; Hong, Bo-Syun; Chen, Hone-Zern

    2018-04-01

    In this study, a large-area molybdenum disulfide (MoS2) thin film was obtained by low pressure thermal sulfurization. Raman scattering spectrum shows that the peaks at 374 and 403 cm‑1 are from the MoS2 thin film. XRD result reveals peaks at 33 and 58.5° indicating MoS2(100) and (110) crystal planes. By using gold (Au), silver (Ag), and aluminum (Al) as contact materials on the MoS2 thin film, photoresponsivity results indicate that Ag is a suitable material for obtaining a high responsivity for a high-performance photodetector (PD). Photocurrent mapping measurements also reveal that Ag contacts have the best carrier transport characteristic with carrier diffusion length of 101 µm among these contacts. Furthermore, we investigated metal–semiconductor–metal MoS2 thin film PDs with interdigitated fingers of 300, 400, 500, and 600 µm contact widths, which showed that the large contact widths could produce a high photoresponse for PD application owing to low resistance.

  14. Preparation and tribological properties of MoS2/graphene oxide composites

    Science.gov (United States)

    Song, Haojie; Wang, Biao; Zhou, Qiang; Xiao, Jiaxuan; Jia, Xiaohua

    2017-10-01

    A hydrothermal route is developed for the synthesis of MoS2/graphene oxide (GO) composites based on the hydrothermal reduction of Na2MoO4 and GO sheets with L-cysteine. The MoS2/GO composites in improving friction and wear of the sunshine oil on sliding steel surfaces under low or high applied load were demonstrated. In tests with sliding steel surfaces, the sunshine oil that contains small amounts of MoS2/GO composites exhibited the lowest specific friction coefficient and wear rate under all of the sliding conditions. Scanning electron microscopy and energy dispersive spectrometer performed to analyze the wear scar surfaces after friction confirmed that the outstanding lubrication performance of MoS2/GO composites could be attributed to their good dispersion stability and extremely thin laminated structure, which allow the MoS2/GO composites to easily enter the contact area, thereby preventing the rough surfaces from coming into direct contact.

  15. High performance MoS2 TFT using graphene contact first process

    Directory of Open Access Journals (Sweden)

    Chih-Shiang Chang Chien

    2017-08-01

    Full Text Available An ohmic contact of graphene/MoS2 heterostructure is determined by using ultraviolet photoelectron spectroscopy (UPS. Since graphene shows a great potential to replace metal contact, a direct comparison of Cr/Au contact and graphene contact on the MoS2 thin film transistor (TFT is made. Different from metal contacts, the work function of graphene can be modulated. As a result, the subthreshold swing can be improved. And when VgS2 TFT, a new method using graphene contact first and MoS2 layer last process that can avoid PMMA residue and high processing temperature is applied. MoS2 TFT using this method shows on/off current ratio up to 6×106 order of magnitude, high mobility of 116 cm2/V-sec, and subthreshold swing of only 0.515 V/dec.

  16. Functionalized NbS2 as cathode for Li- and Na-ion batteries

    KAUST Repository

    Zhu, Jiajie

    2017-07-27

    Cathodes of Li- and Na-ion batteries usually have capacities <200 mAh/g, significantly less than the anodes. Two-dimensional materials can overcome this limitation but suffer from low voltages. In this context, we investigate NbS2 functionalized by O, F, and Cl as a cathode material by first-principles calculations, considering both the conversion and intercalation mechanisms. NbS2O2 shows a higher voltage than NbS2 for both Li and Na, but the voltage decreases drastically for increasing ion coverage. Even higher voltages and favorable dependences on the ion coverage are achieved by F and Cl functionalization. We obtain NbS2F2 and NbS2Cl2 energy densities of 1223 mW h/g and 823 mW h/g for lithiation and 1086 mW h/g and 835 mW h/g for sodiation, respectively. These values are higher than those for most state-of-the-art cathode materials (∼600 mW h/g). In addition, low diffusion barriers enable high cycling rates.

  17. Optically active charge transfer in hybrids of Alq3 nanoparticles and MoS2 monolayer

    Science.gov (United States)

    Ghimire, Ganesh; Dhakal, Krishna P.; Neupane, Guru P.; Jo, Seong Gi; Kim, Hyun; Seo, Changwon; Lee, Young Hee; Joo, Jinsoo; Kim, Jeongyong

    2017-05-01

    Organic/inorganic hybrid structures have been widely studied because of their enhanced physical and chemical properties. Monolayers of transition metal dichalcogenides (1L-TMDs) and organic nanoparticles can provide a hybridization configuration between zero- and two-dimensional systems with the advantages of convenient preparation and strong interface interaction. Here, we present such a hybrid system made by dispersing π-conjugated organic (tris (8-hydroxyquinoline) aluminum(III)) (Alq3) nanoparticles (NPs) on 1L-MoS2. Hybrids of Alq3 NP/1L-MoS2 exhibited a two-fold increase in the photoluminescence of Alq3 NPs on 1L-MoS2 and the n-doping effect of 1L-MoS2, and these spectral and electronic modifications were attributed to the charge transfer between Alq3 NPs and 1L-MoS2. Our results suggested that a hybrid of organic NPs/1L-TMD can offer a convenient platform to study the interface interactions between organic and inorganic nano objects and to engineer optoelectronic devices with enhanced performance.

  18. Synthesis and characterization of KCu3S2 microstructures through a composite-hydroxide mediated method

    International Nuclear Information System (INIS)

    Huang Linyong; Liu Jing; Zuo Zhiyuan; Liu Hong; Liu Duo; Wang Jiyang; Boughton, Robert I.

    2010-01-01

    Graphical abstract: Display Omitted Research highlights: → One of the ternary K-Cu-S compounds, KCu 3 S 2 microbelts and nanobelts were synthesized by using a composite-hydroxide mediated (CHM) approach with the absence of any organic surfactants. → X-ray powder diffraction results indicate that the belts possess a monoclinic KCu 3 S 2 crystalline structure. → Scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM) were used to obtain detailed characterization of the microstructure and nanostructure of this material. → A growth mechanism of KCu 3 S 2 microbelts was proposed. → Measurements of the UV-vis absorption spectrum have been performed, and the results reveal that this material is semiconducting with a bandgap of 1.459 eV. - Abstract: KCu 3 S 2 microslabs and microbelts have been synthesized using a composite-hydroxide mediated (CHM) approach without the presence of an organic surfactant. X-ray powder diffraction results indicate that the belts possess a monoclinic KCu 3 S 2 crystalline structure. Scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM) were used to obtain detailed characterization of the microstructure and nanostructure of this material. Measurements of the UV-vis absorption spectrum have been performed, and the results reveal that this material is semiconducting with a bandgap of 1.459 eV.

  19. Temperature dependence of Ni3S2 nanostructures with high electrochemical performance

    Science.gov (United States)

    Wang, Y. L.; Wei, X. Q.; Li, M. B.; Hou, P. Y.; Xu, X. J.

    2018-04-01

    Different Ni3S2 nanostructures have been successfully synthesized at different temperatures by a facile and efficient solvothermal method. The Ni3S2 nanostructures with three-dimensional (3D) nanosheets array and silkworm eggs-like morphologies were obtained by adjusting the reaction temperature. A large number of 3D nanosheets are interconnected to form an open network structure with porous of Ni3S2 at 180 °C, and electrochemical tests showed that the special structure exhibited the outstanding specific capacitance (1357 F g -1 at 1 A g-1) and excellent cycling stability (maintained 91% after 3000 cycles). In comparison, the performance of Ni3S2 silkworm eggs-like structure is not very perfect. This may be due to the fact that the 3D nanosheets with porous structure can improve the electrochemical performance by shortening effectively the diffusion path of electrolyte ions and increasing the active sites during charging and discharging. Among them, the reaction temperature is the main factor to control the formation of the 3D nanosheets array. These results indicated the Ni3S2 nanosheets promising applications as high-performance supercapacitor electrode materials.

  20. Attapulgite-CeO2/MoS2 ternary nanocomposite for photocatalytic oxidative desulfurization

    Science.gov (United States)

    Li, Xiazhang; Zhang, Zuosong; Yao, Chao; Lu, Xiaowang; Zhao, Xiaobing; Ni, Chaoying

    2016-02-01

    Novel attapulgite(ATP)-CeO2/MoS2 ternary nanocomposites were synthesized by microwave assisted assembly method. The structures of the nanocomposites were characterized by XRD, FT-IR, UV-vis, XPS and in situ TEM. The photocatalytic activities of ATP-CeO2/MoS2 composites were investigated by degradating dibenzothiophene (DBT) in gasoline under visible light irradiation. The effect of the mass ratio of CeO2 to MoS2 on photocatalytic activity was investigated. The results indicate that the three-dimensional network structure is firmly constructed by ATP skeleton, CeO2 particles and MoS2 nanosheet which effectively increase the surface area of the composites and promote the separation of electrons and holes by resulting electronic transmission channels of multi-channel in space. The degradation rate of DBT can reach 95% under 3 h irradiation when the mass ratio of CeO2/MoS2 is 4/10. A plausible mechanism for the photocatalytic oxidative desulfurization of this nanocomposite is put forward.

  1. Measurement of the 1S-2S frequency in atomic hydrogen

    International Nuclear Information System (INIS)

    Hildum, E.A.

    1986-01-01

    A first precise measurement of the 1S-2S energy interval in atomic hydrogen was obtained by observing the 1S-2S transition in an atomic beam by pulsed Doppler-free two-photon spectroscopy and using an interferometrically calibrated line of 130 Te 2 at 486 nm as the references. The measured 1S-2S frequency is 2,466,061 395.6(4.9)MHz. With the calculated 1S Lamb shift, the 1S-2S frequency yields a value for the Rydberg constant, R/sub ∞/ = 109,737.314 92(22) cm -1 , which is not in good agreement with the most recent previously measured value, 109,737.315 44(11) cm -1 , obtained by S.R. Amin et al. It is, however, in good agreement with a previous Rydberg value, 109,737.315 04(32) cm -1 , measured by J.E.M. Goldsmith. If the Rydberg constant is taken as given, the 1S-2S frequency determines a value for the 1S Lamb shift. With Amin's Rydberg, the measured Lamb shift is 8161.0(5.4) MHz, in poor agreement with the theoretical value of 8149.43(8) MHz. With Goldsmith's Rydberg, the measurement Lamb shift is 8151.0(8.7) MHz, in good agreement with theory

  2. Serotonin-S2 and dopamine-D2 receptors are the same size in membranes

    International Nuclear Information System (INIS)

    Brann, M.R.

    1985-01-01

    Target size analysis was used to compare the sizes of serotonin-S2 and dopamine-D2 receptors in rat brain membranes. The sizes of these receptors were standardized by comparison with the muscarinic receptor, a receptor of known size. The number of serotonin-S2 receptors labeled with (3H)ketanserin or (3H)spiperone in frontal cortex decreased as an exponential function of radiation dose, and receptor affinity was not affected. The number of dopamine-D2 receptors labeled with (3H)spiperone in striatum also decreased as an exponential function of radiation dose, and D2 and S2 receptors were equally sensitive to radiation. In both striatum and frontal cortex, the number of muscarinic receptors labeled with (3H)QNB decreased as an exponential function of radiation dose, and were much less sensitive to radiation than S2 and D2 receptors. These data indicate that in rat brain membranes, S2 and D2 receptors are of similar size, and both molecules are much larger than the muscarinic receptor

  3. Negative Differential Transconductance in a MoS2 /WSe2 Heterojunction Field Effect Transistor

    Science.gov (United States)

    Zubair, Ahmad; Nourbakhsh, Amirhasan; Dresselhaus, Mildred; de Gendt, Stefan; Palacios, Tomas

    2015-03-01

    In this work, we demonstrate the negative transconductance in heterojunction transistors made of two-dimensional materials for the first time. Negative transconductance plays a key role in multi-valued logic/memory and frequency multiplication circuits. The simpler fabrication method of stacked van der Waals heterostructures compared to the conventional bulk semiconductors and large area CVD growth of the layered 2D materials systems makes it a prime candidate for scalable novel applications of their heterostructures. Vertically stacked MoS2/WSe2 heterostructures are fabricated by mechanical exfoliation and an in-house dry transfer process. A two-step process of e-beam lithography and metal deposition (Au on MoS2, and Pd on WSe2) were performed to fabricate n-type MoS2 and ambipolar WSe2 FET. The transfer characteristics on the non-overlapping regions shows the expected characteristics of the n-type, MoS2 FET and ambipolar WSe2 FET. At the same time, the transfer characteristics of the overlapping region between MoS2 and WSe2 show negative differential transconductance. With proper scaling and careful optimization this negative differential transconductance will lead to novel applications.

  4. Chemical Doping Effects in Multilayer MoS2 and its Application in Complementary Inverter.

    Science.gov (United States)

    Yoo, Hocheon; Hong, Seongin; On, Sungmin; Ahn, Hyungju; Lee, Han-Koo; Hong, Young Ki; Kim, Sunkook; Kim, Jae-Joon

    2018-06-19

    Multilayer MoS2 has been gaining interests as a new semiconducting material for flexible displays, memory devices, chemical/bio sensors, and photodetectors. However, conventional multilayer MoS2 devices have exhibited limited performances due to the Schottky barrier (SB) and defects. Here, we demonstrate PDPP3T doping effects in multilayer MoS2, which results in improved electrical characteristics (~3.2X mobility compared to the baseline and a high current on/off ratio of 106). Synchrotron-based study using X-ray photoelectron spectroscopy (XPS) and grazing-incidence wide-angle X-ray diffraction (GIWAXD) provides mechanisms that align the edge-on crystallites (97.5 %) of the PDPP3T as well as a larger interaction with MoS2 that leads to dipole and charge transfer effects (at annealing temperature of 300 °C), which support the observed enhancement of the electrical characteristics. Furthermore, we demonstrate a hybrid CMOS inverter using the PDPP3T-doped MoS2 and organic DNTT transistors as n- and p-channels, respectively. The proposed hybrid inverter offers an ultra-high voltage gain of ~205 V/V.

  5. Symmetrical synergy of hybrid CoS2-WS2 electrocatalysts for hydrogen evolution reaction

    KAUST Repository

    Zhou, Xiaofeng

    2017-06-05

    A highly active and stable hybrid electrocatalyst 3D hierarchical CoS2 nanosheets incorporated with WS2 (CoS2@WS2) has been developed via a one-step sulfurization method for the first time, where the contents of WS2 can be adjusted easily. We first prove the addition of small amounts of WS2 enhances the hydrogen evolution reaction (HER) performance of CoS2, and vise versa. In other words, we validated the symmetric synergy for HER between the Co- and W-based sulfide hybrid catalysts. In addition, we confirmed that the formation of nanointerfaces of Co-S-W between CoS2 and WS2 was responsible for the excellent HER activity (an overpotential of -97.2 mV at -10 mA/cm2, a small Tafel slope of 66.0 mV/dec, and prominent electrochemical stability) of hybrid electrocatalyst CoS2@WS2.

  6. Induction of Chirality in Two-Dimensional Nanomaterials: Chiral 2D MoS2 Nanostructures.

    Science.gov (United States)

    Purcell-Milton, Finn; McKenna, Robert; Brennan, Lorcan J; Cullen, Conor P; Guillemeney, Lilian; Tepliakov, Nikita V; Baimuratov, Anvar S; Rukhlenko, Ivan D; Perova, Tatiana S; Duesberg, Georg S; Baranov, Alexander V; Fedorov, Anatoly V; Gun'ko, Yurii K

    2018-02-27

    Two-dimensional (2D) nanomaterials have been intensively investigated due to their interesting properties and range of potential applications. Although most research has focused on graphene, atomic layered transition metal dichalcogenides (TMDs) and particularly MoS 2 have gathered much deserved attention recently. Here, we report the induction of chirality into 2D chiral nanomaterials by carrying out liquid exfoliation of MoS 2 in the presence of chiral ligands (cysteine and penicillamine) in water. This processing resulted in exfoliated chiral 2D MoS 2 nanosheets showing strong circular dichroism signals, which were far past the onset of the original chiral ligand signals. Using theoretical modeling, we demonstrated that the chiral nature of MoS 2 nanosheets is related to the presence of chiral ligands causing preferential folding of the MoS 2 sheets. There was an excellent match between the theoretically calculated and experimental spectra. We believe that, due to their high aspect ratio planar morphology, chiral 2D nanomaterials could offer great opportunities for the development of chiroptical sensors, materials, and devices for valleytronics and other potential applications. In addition, chirality plays a key role in many chemical and biological systems, with chiral molecules and materials critical for the further development of biopharmaceuticals and fine chemicals, and this research therefore should have a strong impact on relevant areas of science and technology such as nanobiotechnology, nanomedicine, and nanotoxicology.

  7. Biomining of MoS2 with Peptide-based Smart Biomaterials.

    Science.gov (United States)

    Cetinel, Sibel; Shen, Wei-Zheng; Aminpour, Maral; Bhomkar, Prasanna; Wang, Feng; Borujeny, Elham Rafie; Sharma, Kumakshi; Nayebi, Niloofar; Montemagno, Carlo

    2018-02-20

    Biomining of valuable metals using a target specific approach promises increased purification yields and decreased cost. Target specificity can be implemented with proteins/peptides, the biological molecules, responsible from various structural and functional pathways in living organisms by virtue of their specific recognition abilities towards both organic and inorganic materials. Phage display libraries are used to identify peptide biomolecules capable of specifically recognizing and binding organic/inorganic materials of interest with high affinities. Using combinatorial approaches, these molecular recognition elements can be converted into smart hybrid biomaterials and harnessed for biotechnological applications. Herein, we used a commercially available phage-display library to identify peptides with specific binding affinity to molybdenite (MoS 2 ) and used them to decorate magnetic NPs. These peptide-coupled NPs could capture MoS 2 under a variety of environmental conditions. The same batch of NPs could be re-used multiple times to harvest MoS 2 , clearly suggesting that this hybrid material was robust and recyclable. The advantages of this smart hybrid biomaterial with respect to its MoS 2 -binding specificity, robust performance under environmentally challenging conditions and its recyclability suggests its potential application in harvesting MoS 2 from tailing ponds and downstream mining processes.

  8. Structure and tribological properties of MoS2 low friction thin films

    Directory of Open Access Journals (Sweden)

    Paradecka Agnieszka

    2017-01-01

    Full Text Available The main aim of the studies was the deposition of the AlCrN film, covered by molybdenum disulphide (MoS2 – based lubricant, on the austenitic steel substrate. The AlCrN and MoS2 layers were deposited by PVD lateral rotating ARC-cathodes (LARC and magnetron sputtering technology on the X6CrNiMoTi17-12-2 respectively. Structural characterizations of the MoS2 thin films have been carried out using SEM (scanning electron microscopy and AFM (atomic force microscopy to determine the surface topography as well as HRTEM (high-resolution transmission electron microscopy and Raman spectroscopy for structural investigations. The tribological wear relationships using ball-on-disc test were specified for surface layers, determining the friction co-efficient and mass loss of the investigated surfaces. Tests of the coatings’ adhesion to the substrate material were made using the scratch test. HRTEM investigation shows an amorphous character of the MoS2 layer. In sliding dry friction conditions, the friction co-efficient for the investigated elements is set in the range between 0.4-0.5. The investigated coating reveals high wear resistance. The coating demonstrated a dense cross-sectional morphology as well as good adhesion to the substrate. The good properties of the PVD AlCrN+MoS2 coatings make them suitable in various engineering and industrial applications.

  9. Epitaxial growth of ReS2(001) thin film via deposited-Re sulfurization

    Science.gov (United States)

    Urakami, Noriyuki; Okuda, Tetsuya; Hashimoto, Yoshio

    2018-02-01

    In this paper, we present the formation of large-size rhenium disulfide (ReS2) films via the sulfurization of Re films deposited on sapphire substrates. The effects of sulfurization temperature and pressure on the crystal quality were investigated. A [001]-oriented single crystal of ReS2 films with 6 × 10 mm2 area was realized. By sulfurizing Re films at 1100 °C, ReS2 films with well-defined sharp interfaces to c-plane sapphire substrates could be formed. Below and above the sulfurization temperature of 1100 °C, incomplete sulfurization and film degradation were observed. The twofold symmetry of the monocrystalline in-plane structure composed of Re-Re bonds along with Re-S bonds pointed to a distorted 1T structure, indicating that this structure is the most stable atomic arrangement for ReS2. For a S/Re compositional ratio equal to or slightly lower than 2.0, characteristic Raman vibrational modes with the narrowest line widths were observed. The typical absorption peak of ReS2 can be detected at 1.5 eV.

  10. Photon wavelength dependent valley photocurrent in multilayer MoS2

    Science.gov (United States)

    Guan, Hongming; Tang, Ning; Xu, Xiaolong; Shang, LiangLiang; Huang, Wei; Fu, Lei; Fang, Xianfa; Yu, Jiachen; Zhang, Caifeng; Zhang, Xiaoyue; Dai, Lun; Chen, Yonghai; Ge, Weikun; Shen, Bo

    2017-12-01

    The degree of freedom (DOF) of the K (K') valley in transition-metal dichalcogenides, especially molybdenum disulfide (MoS2), offers an opportunity for next-generation valleytronics devices. In this work, the K (K') valley DOF of multilayer MoS2 is studied by means of the photon wavelength dependent circular photogalvanic effect (CPGE) at room temperature upon a strong external out-of-plane electric field induced by an ionic liquid (IL) gate, which breaks the spatial-inversion symmetry. It is demonstrated that only on resonant excitations in the K (K') valley can the valley-related CPGE signals in multilayer MoS2 with an IL gate be detected, indicating that the valley contrast is indeed regenerated between the K and K' valleys when the electric field is applied. As expected, it can also be seen that the K (K') valley DOF in multilayer MoS2 can be modulated by the external electric field. The observation of photon wavelength dependent valley photocurrent in multilayer MoS2, with the help of better Ohmic contacts, may pave a way for optoelectronic applications of valleytronics in the future.

  11. Probing the biocompatibility of MoS2 nanosheets by cytotoxicity assay and electrical impedance spectroscopy

    Science.gov (United States)

    Shah, Pratikkumar; Narayanan, Tharangattu N.; Li, Chen-Zhong; Alwarappan, Subbiah

    2015-08-01

    Transition metal dichalgogenides such as MoS2 have recently emerged as hot two-dimensional (2D) materials due to their superior electronic and catalytic properties. Recently, we have reported the usefulness of MoS2 nanosheets toward the electrochemical detection of neurotransmitters and glucose (Narayanan et al 2014 Nanotechnology 25 335702). Furthermore, there are reports available in the literature that demonstrate the usefulness of MoS2 nanosheets for biosensing and energy storage applications (Zhu et al 2013 J. Am. Chem. Soc. 135 5998-6001 Pumera and Loo 2014 Trends Anal. Chem. 61 49-53 Lee et al 2014 Sci. Rep. 4 7352; Stephenson et al 2014 Energy Environ. Sci. 7 209-31). Understanding the cytotoxic effect of any material is very important prior to employing them for any in vivo biological applications such as implantable sensors, chips, or carriers for drug delivery and cell imaging purposes. Herein, we report the cytotoxicity of the MoS2 nanosheets based on the cytotoxic assay results and electrical impedance analysis using rat pheochromocytoma cells (PC12) and rat adrenal medulla endothelial cells (RAMEC). Our results indicated that the MoS2 nanosheets synthesized in our work are safe 2D nanosheets for futuristic biomedical applications.

  12. Determination of band offsets at GaN/single-layer MoS2 heterojunction

    KAUST Repository

    Tangi, Malleswararao; Mishra, Pawan; Ng, Tien Khee; Hedhili, Mohamed N.; Janjua, Bilal; Alias, Mohd Sharizal; Anjum, Dalaver H.; Tseng, Chien-Chih; Shi, Yumeng; Joyce, Hannah J.; Li, Lain-Jong; Ooi, Boon S.

    2016-01-01

    We report the band alignment parameters of the GaN/single-layer (SL) MoS2 heterostructure where the GaN thin layer is grown by molecular beam epitaxy on CVD deposited SL-MoS2/c-sapphire. We confirm that the MoS2 is an SL by measuring the separation and position of room temperature micro-Raman E1 2g and A1 g modes, absorbance, and micro-photoluminescence bandgap studies. This is in good agreement with HRTEM cross-sectional analysis. The determination of band offset parameters at the GaN/SL-MoS2 heterojunction is carried out by high-resolution X-ray photoelectron spectroscopy accompanying with electronic bandgap values of SL-MoS2 and GaN. The valence band and conduction band offset values are, respectively, measured to be 1.86 ± 0.08 and 0.56 ± 0.1 eV with type II band alignment. The determination of these unprecedented band offset parameters opens up a way to integrate 3D group III nitride materials with 2D transition metal dichalcogenide layers for designing and modeling of their heterojunction based electronic and photonic devices.

  13. Micro-dressing of a carbon nanotube array with MoS2 gauze

    Science.gov (United States)

    Lim, Sharon Xiaodai; Woo, Kah Whye; Ng, Junju; Lu, Junpeng; Kwang, Siu Yi; Zhang, Zheng; Tok, Eng Soon; Sow, Chorng-Haur

    2015-10-01

    Few-layer MoS2 film has been successfully assembled over an array of CNTs. Using different focused laser beams with different wavelengths, site selective patterning of either the MoS2 film or the supporting CNT array is achieved. This paves the way for applications and investigations into the fundamental properties of the hybrid MoS2/CNT material with a controlled architecture. Through Raman mapping, straining and electron doping of the MoS2 film as a result of interaction with the supporting CNT array are detected. The role of the MoS2 film was further emphasized with a lower work function being detected from Ultra-violet Photoelectron Spectrsocopy (UPS) measurements of the hybrid material, compared to the CNT array. The effect of the changes in the work function was illustrated through the optoelectronic behavior of the hybrid material. At 0 V, 3.49 nA of current is measured upon illuminating the sample with a broad laser beam emitting laser light with a wavelength of 532 nm. With a strong response to external irradiation of different wavelengths, and changes to the power of the excitation source, the hybrid material has shown potential for applications in optoelectronic devices.

  14. Rheological and tribological behaviour of lubricating oils containing platelet MoS2 nanoparticles

    Science.gov (United States)

    Wan, Qingming; Jin, Yi; Sun, Pengcheng; Ding, Yulong

    2014-05-01

    This work concerns rheological and frictional behaviour of lubricating oils containing platelet molybdenum disulfide (MoS2) nanoparticles (average diameter 50 nm; single layer thickness 3 nm). Stable nano-MoS2 lubricants were formulated and measured for their rheological behaviour and tribological performance. Rheological experiments showed that the nano-MoS2 oils were non-Newtonian following the Bingham plastic fluid model. The viscosity data fitted the classic Hinch-Leal (H-L) model if an agglomeration factor of 1.72 was introduced. Tribological experiments indicated that the use of MoS2 nanoparticles could enhance significantly the tribological performance of the base lubricating oil (reduced frictional coefficient, reduced surface wear and increased stability). Scanning electron microscopy, laser confocal microscope and x-ray energy dispersive spectroscopy analyses suggested that the reduced frictional coefficient and surface wear be associated with surface patching effects. Such patching effects were shown to depend on the concentration of MoS2 nanoparticles, and an effective patching required a concentration over approximately 1 wt%. The increased stability could be attributed to the enhanced heat transfer and lubricating oil film strength due to the presence of nanoparticles.

  15. Functionalized NbS2 as cathode for Li- and Na-ion batteries

    KAUST Repository

    Zhu, Jiajie; Alshareef, Husam N.; Schwingenschlö gl, Udo

    2017-01-01

    Cathodes of Li- and Na-ion batteries usually have capacities <200 mAh/g, significantly less than the anodes. Two-dimensional materials can overcome this limitation but suffer from low voltages. In this context, we investigate NbS2 functionalized by O, F, and Cl as a cathode material by first-principles calculations, considering both the conversion and intercalation mechanisms. NbS2O2 shows a higher voltage than NbS2 for both Li and Na, but the voltage decreases drastically for increasing ion coverage. Even higher voltages and favorable dependences on the ion coverage are achieved by F and Cl functionalization. We obtain NbS2F2 and NbS2Cl2 energy densities of 1223 mW h/g and 823 mW h/g for lithiation and 1086 mW h/g and 835 mW h/g for sodiation, respectively. These values are higher than those for most state-of-the-art cathode materials (∼600 mW h/g). In addition, low diffusion barriers enable high cycling rates.

  16. Novel Field-Effect Schottky Barrier Transistors Based on Graphene-MoS2 Heterojunctions

    Science.gov (United States)

    Tian, He; Tan, Zhen; Wu, Can; Wang, Xiaomu; Mohammad, Mohammad Ali; Xie, Dan; Yang, Yi; Wang, Jing; Li, Lain-Jong; Xu, Jun; Ren, Tian-Ling

    2014-01-01

    Recently, two-dimensional materials such as molybdenum disulphide (MoS2) have been demonstrated to realize field effect transistors (FET) with a large current on-off ratio. However, the carrier mobility in backgate MoS2 FET is rather low (typically 0.5–20 cm2/V·s). Here, we report a novel field-effect Schottky barrier transistors (FESBT) based on graphene-MoS2 heterojunction (GMH), where the characteristics of high mobility from graphene and high on-off ratio from MoS2 are properly balanced in the novel transistors. Large modulation on the device current (on/off ratio of 105) is achieved by adjusting the backgate (through 300 nm SiO2) voltage to modulate the graphene-MoS2 Schottky barrier. Moreover, the field effective mobility of the FESBT is up to 58.7 cm2/V·s. Our theoretical analysis shows that if the thickness of oxide is further reduced, a subthreshold swing (SS) of 40 mV/decade can be maintained within three orders of drain current at room temperature. This provides an opportunity to overcome the limitation of 60 mV/decade for conventional CMOS devices. The FESBT implemented with a high on-off ratio, a relatively high mobility and a low subthreshold promises low-voltage and low-power applications for future electronics. PMID:25109609

  17. Three human alcohol dehydrogenase subunits: cDNA structure and molecular and evolutionary divergence

    International Nuclear Information System (INIS)

    Ikuta, T.; Szeto, S.; Yoshida, A.

    1986-01-01

    Class I human alcohol dehydrogenase (ADH; alcohol:NAD + oxidoreductase, EC 1.1.1.1) consists of several homo- and heterodimers of α, β, and γ subunits that are governed by the ADH1, ADH2, and ADH3 loci. The authors previously cloned a full length of cDNA for the β subunit, and the complete sequence of 374 amino acid residues was established. cDNAs for the α and γ subunits were cloned and characterized. A human liver cDNA library, constructed in phage λgt11, was screened by using a synthetic oligonucleotide probe that was matched to the γ but not to the β sequence. Clone pUCADHγ21 and clone pUCADHα15L differed from β cDNA with respect to restriction sites and hybridization with the nucleotide probe. Clone pUCADHγ21 contained an insertion of 1.5 kilobase pairs (kbp) and encodes 374 amino acid residues compatible with the reported amino acid sequence of the γ subunit. Clone pUCADHα15L contained an insertion of 2.4 kbp and included nucleotide sequences that encode 374 amino acid residues for another subunit, the γ subunit. In addition, this clone contained the sequences that encode the COOH-terminal part of the β subunit at its extended 5' region. The amino acid sequences and coding regions of the cDNAs of the three subunits are very similar. A high degree of resemblance is observed also in their 3' noncoding regions. However, distinctive differences exist in the vicinity of the Zn-binding cysteine residue at position 46. Based on the cDNA sequences and the deduced amino acid sequences of the three subunits, their structural and evolutionary relationships are discussed

  18. Regulated appearance of NMDA receptor subunits and channel functions during in vitro neuronal differentiation.

    Science.gov (United States)

    Jelitai, Márta; Schlett, Katalin; Varju, Patrícia; Eisel, Ulrich; Madarász, Emília

    2002-04-01

    The schedule of NMDA receptor subunit expression and the appearance of functional NMDA-gated ion channels were investigated during the retinoic acid (RA) induced neuronal differentiation of NE-4C, a p53-deficient mouse neuroectodermal progenitor cell line. NR2A, NR2B, and NR2D subunit transcripts were present in both nondifferentiated and neuronally differentiated cultures, while NR2C subunits were expressed only transiently, during the early period of neural differentiation. Several splice variants of NR1 were detected in noninduced progenitors and in RA-induced cells, except the N1 exon containing transcripts that appeared after the fourth day of induction, when neuronal processes were already formed. NR1 and NR2A subunit proteins were detected both in nondifferentiated progenitor cells and in neurons, while the mature form of NR2B subunit protein appeared only at the time of neuronal process elongation. Despite the early presence of NR1 and NR2A subunits, NMDA-evoked responses could be detected in NE-4C neurons only after the sixth day of induction, coinciding in time with the expression of the mature NR2B subunit. The formation of functional NMDA receptors also coincided with the appearance of synapsin I and synaptophysin. The lag period between the production of the subunits and the onset of channel function suggests that subunits capable of channel formation cannot form functional NMDA receptors until a certain stage of neuronal commitment. Thus, the in vitro neurogenesis by NE-4C cells provides a suitable tool to investigate some inherent regulatory processes involved in the initial maturation of NMDA receptor complexes. Copyright 2002 Wiley Periodicals, Inc.

  19. Effect of glutenin subunits on the baking quality of Brazilian wheat genotypes

    OpenAIRE

    Costa, Mariana Souza; Scholz, Maria Brígida dos Santos; Miranda, Martha Zavariz; Franco, Célia Maria Landi

    2017-01-01

    ABSTRACT This study aimed to evaluate the effect of the high and low molecular weight glutenin subunits on the grain traits of sixteen Brazilian wheat genotypes. Grain hardness index, milling traits, physicochemical and rheological properties of the flour, and specific volume and firmness of the bread were evaluated. Physicochemical properties of the flour were not influenced by glutenin subunits. Genotypes with subunits at the Glu-B1 (17+18 or 7+8), Glu-D1 (5+10), and Glu-A3 (b) were associa...

  20. Inhibition of herpesvirus and influenza virus replication by blocking polymerase subunit interactions.

    Science.gov (United States)

    Palù, Giorgio; Loregian, Arianna

    2013-09-01

    Protein-protein interactions (PPIs) play a key role in many biological processes, including virus replication in the host cell. Since most of the PPIs are functionally essential, a possible strategy to inhibit virus replication is based on the disruption of viral protein complexes by peptides or small molecules that interfere with subunit interactions. In particular, an attractive target for antiviral drugs is the binding between the subunits of essential viral enzymes. This review describes the development of new antiviral compounds that inhibit herpesvirus and influenza virus replication by blocking interactions between subunit proteins of their polymerase complexes. Copyright © 2013 Elsevier B.V. All rights reserved.

  1. Synthesis of porous CuInS2 crystals using a stirrer

    International Nuclear Information System (INIS)

    Akaki, Yoji; Ohno, Yuki; Momiki, Takanori

    2013-01-01

    Porous CuInS 2 crystals were grown from starting materials CuCl 2 .2H 2 O, InCl 3 .4H 2 O and thiorea with ethylene glycol solution, that were placed into a flask, heated, and refluxed for 1 hour. The diffraction peaks only from CuInS 2 phase appear for all the samples. The morphology of CuInS 2 crystal was porous, and the porous crystals exist in two kinds. One kind was flower-like crystals which complexly lack the flakes, another one was sphere-like crystals existed with a number of the poles. The specific surface area of the samples grown by stirring starting materials with In to Cu ratio of 4.3 for 30 minutes was found approximately to be 55 m 2 /g. (copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  2. High-Sensitivity, Highly Transparent, Gel-Gated MoS2 Phototransistor on Biodegradable Nanopaper

    KAUST Repository

    Zhang, Qing

    2016-06-21

    Transition metal dichalcogenides hold great promise for a variety of novel electrical, optical and mechanical devices and applications. Among them, molybdenum disulphide (MoS2) is gaining increasing attention as the gate dielectric and semiconductive channel for high-perfomance field effect transistors. Here we report on the first MoS2 phototransistor built on flexible, transparent and biodegradable substrate with electrolyte gate dielectric. We have carried out systematic studies on its electrical and optoelectronic properties. The MoS2 phototransistor exhibited excellent photo responsivity of ~1.5 kA/W, about two times higher compared to typical back-gated devices reported in previous studies. The device is highly transparent at the same time with an average optical transmittance of 82%. Successful fabrication of phototransistors on flexible cellulose nanopaper with excellent performance and transparency suggests that it is feasible to achieve an ecofriendly, biodegradable phototransistor with great photoresponsivity, broad spectral range and durable flexibility.

  3. Efficient spin injection and giant magnetoresistance in Fe / MoS 2 / Fe junctions

    KAUST Repository

    Dolui, Kapildeb

    2014-07-02

    We demonstrate giant magnetoresistance in Fe/MoS2/Fe junctions by means of ab initio transport calculations. We show that junctions incorporating either a monolayer or a bilayer of MoS2 are metallic and that Fe acts as an efficient spin injector into MoS2 with an efficiency of about 45%. This is the result of the strong coupling between the Fe and S atoms at the interface. For junctions of greater thickness, a maximum magnetoresistance of ∼300% is obtained, which remains robust with the applied bias as long as transport is in the tunneling limit. A general recipe for improving the magnetoresistance in spin valves incorporating layered transition metal dichalcogenides is proposed. © 2014 American Physical Society.

  4. Research Update: Spin transfer torques in permalloy on monolayer MoS2

    Directory of Open Access Journals (Sweden)

    Wei Zhang

    2016-03-01

    Full Text Available We observe current induced spin transfer torque resonance in permalloy (Py grown on monolayer MoS2. By passing rf current through the Py/MoS2 bilayer, field-like and damping-like torques are induced which excite the ferromagnetic resonance of Py. The signals are detected via a homodyne voltage from anisotropic magnetoresistance of Py. In comparison to other bilayer systems with strong spin-orbit torques, the monolayer MoS2 cannot provide bulk spin Hall effects and thus indicates the purely interfacial nature of the spin transfer torques. Therefore our results indicate the potential of two-dimensional transition-metal dichalcogenide for the use of interfacial spin-orbitronics applications.

  5. Edge structures and properties of triangular antidots in single-layer MoS2

    KAUST Repository

    Gan, Li Yong; Cheng, Yingchun; Schwingenschlö gl, Udo; Yao, Yingbang; Zhao, Yong; Zhang, Xixiang; Huang, Wei

    2016-01-01

    Density functional theory and experiments are employed to shed light on the edge structures of antidots in O etched single-layer MoS2. The equilibrium morphology is found to be the zigzag Mo edge with each Mo atom bonded to two O atoms, in a wide range of O chemical potentials. Scanning electron microscopy shows that the orientation of the created triangular antidots is opposite to the triangular shape of the single-layer MoS2 samples, in agreement with the theoretical predictions. Furthermore, edges induced by O etching turn out to be p-doped, suggesting an effective strategy to realize p-type MoS2 devices. Published by AIP Publishing.

  6. Probing the interlayer coupling of twisted bilayer MoS2 using photoluminescence spectroscopy.

    Science.gov (United States)

    Huang, Shengxi; Ling, Xi; Liang, Liangbo; Kong, Jing; Terrones, Humberto; Meunier, Vincent; Dresselhaus, Mildred S

    2014-10-08

    Two-dimensional molybdenum disulfide (MoS2) is a promising material for optoelectronic devices due to its strong photoluminescence emission. In this work, the photoluminescence of twisted bilayer MoS2 is investigated, revealing a tunability of the interlayer coupling of bilayer MoS2. It is found that the photoluminescence intensity ratio of the trion and exciton reaches its maximum value for the twisted angle 0° or 60°, while for the twisted angle 30° or 90° the situation is the opposite. This is mainly attributed to the change of the trion binding energy. The first-principles density functional theory analysis further confirms the change of the interlayer coupling with the twisted angle, which interprets our experimental results.

  7. Edge structures and properties of triangular antidots in single-layer MoS2

    KAUST Repository

    Gan, Li Yong

    2016-08-30

    Density functional theory and experiments are employed to shed light on the edge structures of antidots in O etched single-layer MoS2. The equilibrium morphology is found to be the zigzag Mo edge with each Mo atom bonded to two O atoms, in a wide range of O chemical potentials. Scanning electron microscopy shows that the orientation of the created triangular antidots is opposite to the triangular shape of the single-layer MoS2 samples, in agreement with the theoretical predictions. Furthermore, edges induced by O etching turn out to be p-doped, suggesting an effective strategy to realize p-type MoS2 devices. Published by AIP Publishing.

  8. Kinetics of Ni3S2 sulfide dissolution in solutions of sulfuric and hydrochloric acids

    Science.gov (United States)

    Palant, A. A.; Bryukvin, V. A.; Vinetskaya, T. N.; Makarenkova, T. A.

    2008-02-01

    The kinetics of Ni3S2 sulfide (heazlewoodite) dissolution in solutions of hydrochloric and sulfuric acids is studied. The process under study in the temperature range of 30 90°C is found to occur in a kinetic regime and is controlled by the corresponding chemical reactions of the Ni3S2 decomposition by solutions of inorganic acids ( E a = 67 92 kJ/mol, or 16 22 kcal/mol). The only exception is the Ni3S2-HCl system at elevated temperatures (60 90°C). In this case, the apparent activation energy decreases sharply to 8.8 kJ/mol (2.1 kcal/mol), which is explained by the catalytic effect of gaseous chlorine formed under these conditions. The studies performed are related to the physicochemical substantiation of the hydrometallurgical processing of the copper-nickel converter mattes produced in the industrial cycle of the Norilsk Mining Company.

  9. Dielectric Losses and Charge Transfer in Antimony-Doped TlGaS2 Single Crystal

    Science.gov (United States)

    Asadov, S. M.; Mustafaeva, S. N.

    2018-03-01

    Effect of semimetallic antimony (0.5 mol % Sb) on the dielectric properties and ac-conductivity of TlGaS2-based single crystals grown by the Bridgman-Stockbarger method has been studied. The experimental results on the frequency dispersion of dielectric coefficients and the conductivity of TlGa0.995Sb0.005S2 single crystals allowed the revealing of the dielectric loss nature, the charge transfer mechanism, and the estimation of the parameters of the states localized in the energy gap. The antimony-doping of the TlGaS2 single crystal leads to an increase in the density of states near the Fermi level and a decrease in the average time and average distance of hopes.

  10. Physicochemical properties of discontinuous S2-glass fiber reinforced resin composite.

    Science.gov (United States)

    Huang, Qiting; Qin, Wei; Garoushi, Sufyan; He, Jingwei; Lin, Zhengmei; Liu, Fang; Vallittu, Pekka K; Lassila, Lippo V J

    2018-01-30

    The objective of this study was to investigate several physicochemical properties of an experimental discontinuous S2-glass fiber-reinforced resin composite. The experimental composite was prepared by mixing 10 wt% of discontinuous S2-glass fibers with 27.5 wt% of resin matrix and 62.5 wt% of particulate fillers. Flexural strength (FS) and modulus (FM), fracture toughness (FT), work of fracture (WOF), double bond conversion (DC), Vickers hardness, volume shrinkage (VS) and fiber length distribution were determined. These were compared with two commercial resin composites. The experimental composite showed the highest FS, WOF and FT compared with two control composites. The DC of the experimental composite was comparable with controls. No significant difference was observed in VS between the three tested composites. The use of discontinuous glass fiber fillers with polymer matrix and particulate fillers yielded improved physical properties and substantial improvement was associated with the use of S2-glass fiber.

  11. High-Sensitivity, Highly Transparent, Gel-Gated MoS2 Phototransistor on Biodegradable Nanopaper

    KAUST Repository

    Zhang, Qing; Bao, Wenzhong; Gong, Amy; Gong, Tao; Ma, Dakang; Wan, Jiayu; Dai, Jiaqi; Munday, J; He, Jr-Hau; Hu, Liangbing; Zhang, Daihua

    2016-01-01

    Transition metal dichalcogenides hold great promise for a variety of novel electrical, optical and mechanical devices and applications. Among them, molybdenum disulphide (MoS2) is gaining increasing attention as the gate dielectric and semiconductive channel for high-perfomance field effect transistors. Here we report on the first MoS2 phototransistor built on flexible, transparent and biodegradable substrate with electrolyte gate dielectric. We have carried out systematic studies on its electrical and optoelectronic properties. The MoS2 phototransistor exhibited excellent photo responsivity of ~1.5 kA/W, about two times higher compared to typical back-gated devices reported in previous studies. The device is highly transparent at the same time with an average optical transmittance of 82%. Successful fabrication of phototransistors on flexible cellulose nanopaper with excellent performance and transparency suggests that it is feasible to achieve an ecofriendly, biodegradable phototransistor with great photoresponsivity, broad spectral range and durable flexibility.

  12. Metallization and superconductivity in Ca-intercalated bilayer MoS2

    Science.gov (United States)

    Szczȱśniak, R.; Durajski, A. P.; Jarosik, M. W.

    2017-12-01

    A two-dimensional molybdenum disulfide (MoS2) has attracted significant interest recently due to its outstanding physical, chemical and optoelectronic properties. In this paper, using the first-principles calculations, the dynamical stability, electronic structure and superconducting properties of Ca-intercalated bilayer MoS2 are investigated. The calculated electron-phonon coupling constant implies that the stable form of investigated system is a strong-coupling superconductor (λ = 1.05) with a low value of critical temperature (TC = 13.3 K). Moreover, results obtained within the framework of the isotropic Migdal-Eliashberg formalism proved that Ca-intercalated bilayer MoS2 exhibits behavior that goes beyond the scope of the conventional BCS theory.

  13. Electronic and Optical Properties of TiS_2 Determined from Generalized Gradient Approximation Study

    International Nuclear Information System (INIS)

    El-Kouch, Hamza; Farh, Larbi El; Sayah, Jamal; Challioui, Allal

    2015-01-01

    The electronic and optical properties of TiS_2 are studied by using an ab-initio calculation within the frame of density functional theory. A linearized and augmented plane wave basis set with the generalized gradient approximation as proposed by Perdew et al. is used for the energy exchange-correlation determination. The results show a metallic character of TiS_2, and the plots of total and partial densities of states of TiS_2 show the metallic character of the bonds and a strong hybridization between the states d of Ti and p of S below the Fermi energy. The optical properties of the material such as real and imaginary parts of dielectric constant (ϵ(ω) = ϵ_1(ω) + iϵ_2(ω)), refractive index n(ω), optical reflectivity R(ω), for E//x and E//z are performed for the energy range of 0–14 eV. (paper)

  14. Magnetic field dependence of electronic properties of MoS2 quantum dots with different edges

    Science.gov (United States)

    Chen, Qiao; Li, L. L.; Peeters, F. M.

    2018-02-01

    Using the tight-binding approach, we investigate the energy spectrum of square, triangular, and hexagonal MoS2 quantum dots (QDs) in the presence of a perpendicular magnetic field. Novel edge states emerge in MoS2 QDs, which are distributed over the whole edge which we call ring states. The ring states are robust in the presence of spin-orbit coupling (SOC). The corresponding energy levels of the ring states oscillate as a function of the perpendicular magnetic field which are related to Aharonov-Bohm oscillations. Oscillations in the magnetic field dependence of the energy levels and the peaks in the magneto-optical spectrum emerge (disappear) as the ring states are formed (collapsed). The period and the amplitude of the oscillation decrease with the size of the MoS2 QDs.

  15. Methyl Butanoate Adsorption on MoS2 Surface: A Density Functional Theory Investigation

    Directory of Open Access Journals (Sweden)

    Prabowo Wahyu Aji Eko

    2018-01-01

    Full Text Available Methyl butanoate is one of the compound which is obtained from triglyceride molecule. It has hydrocarbon components and hence may produce hydrocarbon through hydrodeoxygenation (HDO or decarbonylation (DCO processes. The first step to uncover the underlying mechanism of HDO or DCO is to find the active site of methyl butanoate adsorption over the catalyst. This study attempts to investigate the active site of methyl butanoate adsorption on MoS2 surface. Stable bonding configuration for methyl butanoate adsorption on MoS2 is investigated by using density functional theory (DFT. This investigation consists of geometry optimisation and adsorption energy calculations. The stable configuration of methyl butanoate adsorption on MoS2 surface is found to be on top of Mo atom in Mo-edge surface.

  16. High performance and transparent multilayer MoS2 transistors: Tuning Schottky barrier characteristics

    Directory of Open Access Journals (Sweden)

    Young Ki Hong

    2016-05-01

    Full Text Available Various strategies and mechanisms have been suggested for investigating a Schottky contact behavior in molybdenum disulfide (MoS2 thin-film transistor (TFT, which are still in much debate and controversy. As one of promising breakthrough for transparent electronics with a high device performance, we have realized MoS2 TFTs with source/drain electrodes consisting of transparent bi-layers of a conducting oxide over a thin film of low work function metal. Intercalation of a low work function metal layer, such as aluminum, between MoS2 and transparent source/drain electrodes makes it possible to optimize the Schottky contact characteristics, resulting in about 24-fold and 3 orders of magnitude enhancement of the field-effect mobility and on-off current ratio, respectively, as well as transmittance of 87.4 % in the visible wavelength range.

  17. The Interface between Gd and Monolayer MoS2: A First-Principles Study

    KAUST Repository

    Zhang, Xuejing

    2014-12-08

    We analyze the electronic structure of interfaces between two-, four- and six-layer Gd(0001) and monolayer MoS2 by first-principles calculations. Strong chemical bonds shift the Fermi energy of MoS2 upwards into the conduction band. At the surface and interface the Gd f states shift to lower energy and new surface/interface Gd d states appear at the Fermi energy, which are strongly hybridized with the Mo 4d states and thus lead to a high spin-polarization (ferromagnetically ordered Mo magnetic moments of 0.15 μB). Gd therefore is an interesting candidate for spin injection into monolayer MoS2.

  18. Effect of ion irradiation on nanoscale TiS2 systems with suppressed Titania phase

    International Nuclear Information System (INIS)

    Hazarika, Saurabh J; Mohanta, Dambarudhar; Tripathi, A; Kanjilal, D.

    2016-01-01

    Titanium disulfide (TiS 2 ), being an important of the transition metal dichalcogenide, (TMDC) family, has drawn numerous interest owing to exhibition of tunable band gap as well as high carrier mobility. In this work, we highlight preparation of TiS 2 nanopowder with minimal TiO 2 content and also demonstrate modified properties upon swift heavy ion irradiation on TiS 2 nanoparticles dispersed PVA films. Different properties of the irradiated samples have been characterized through diffraction, microscopic and spectroscopic techniques. As a result of irradiation, due to agglomeration of particles, the grain size is found to increase. We could also observe a red shift after irradiation with increasing fluence, leading to easy flow of electron from valence to conduction band, which shows that conduction of electrons is more in case of irradiated films compared to the pristine one and thus there may be a possibility of using the irradiated samples in various optoelectronic devices. (paper)

  19. Edge structures and properties of triangular antidots in single-layer MoS2

    International Nuclear Information System (INIS)

    Gan, Li-Yong; Cheng, Yingchun; Huang, Wei; Schwingenschlögl, Udo; Yao, Yingbang; Zhao, Yong; Zhang, Xi-xiang

    2016-01-01

    Density functional theory and experiments are employed to shed light on the edge structures of antidots in O etched single-layer MoS 2 . The equilibrium morphology is found to be the zigzag Mo edge with each Mo atom bonded to two O atoms, in a wide range of O chemical potentials. Scanning electron microscopy shows that the orientation of the created triangular antidots is opposite to the triangular shape of the single-layer MoS 2 samples, in agreement with the theoretical predictions. Furthermore, edges induced by O etching turn out to be p-doped, suggesting an effective strategy to realize p-type MoS 2 devices.

  20. Electronic and magnetic properties of SnS2 monolayer doped with non-magnetic elements

    Science.gov (United States)

    Xiao, Wen-Zhi; Xiao, Gang; Rong, Qing-Yan; Wang, Ling-Ling

    2018-05-01

    We performed a systematic study of the electronic structures and magnetic properties of SnS2 monolayer doped with non-magnetic elements in groups IA, IIA and IIIA based on the first-principles methods. The doped systems exhibit half-metallic and metallic natures depending on the doping elements. The formation of magnetic moment is attributable to the cooperative effect of the Hund's rule coupling and hole concentration. The spin polarization can be stabilized and enhanced through confining the delocalized impurity states by biaxial tensile strain in hole-doped SnS2 monolayer. Both the double-exchange and p-p exchange mechanisms are simultaneously responsible for the ferromagnetic ground state in those hole-doped materials. Our results demonstrate that spin polarization can be induced and controlled in SnS2 monolayers by non-magnetic doping and tensile strain.

  1. Aqueous Synthesis of ZnSe/ZnS-2-R-Benzothiazole Nanocrystals with White Emission

    Directory of Open Access Journals (Sweden)

    Ying-Fan Liu

    2016-01-01

    Full Text Available We prepared water-soluble white light-emitting ZnSe/ZnS-2-R-benzothiazole nanocrystals (NCs, R = 2-hydroxy-5-(2,5-dimethyl-thienyl-phenyl. The penicillamine (Pen capped ZnSe/ZnS NCs were firstly prepared with high photoluminescence quantum yields (PL QY of 40%. Then they bond to 2-R-benzothiazole molecules, resulting in white light-emitting ZnSe/ZnS-2-R-benzothiazole NCs with QY of 75% over a 375 to 650 nm range of emission, which can be applied to white light-emitting diodes. The ZnSe/ZnS-2-R-benzothiazole NCs with two emission bands at around 451 and 557 nm were discussed and the possible mechanism of the interaction of ZnSe/ZnS NCs with 2-R-benzothiazole was also proposed.

  2. Room temperature synthesis of ReS2 through aqueous perrhenate sulfidation

    Science.gov (United States)

    Borowiec, Joanna; Gillin, William P.; Willis, Maureen A. C.; Boi, Filippo S.; He, Y.; Wen, J. Q.; Wang, S. L.; Schulz, Leander

    2018-02-01

    In this study, a direct sulfidation reaction of ammonium perrhenate (NH4ReO4) leading to a synthesis of rhenium disulfide (ReS2) is demonstrated. These findings reveal the first example of a simplistic bottom-up approach to the chemical synthesis of crystalline ReS2. The reaction presented here takes place at room temperature, in an ambient and solvent-free environment and without the necessity of a catalyst. The atomic composition and structure of the as-synthesized product were characterized using several analysis techniques including energy dispersive x-ray spectroscopy, x-ray photoelectron spectroscopy, x-ray diffraction, transmission electron microscopy, Raman spectroscopy, thermogravimetric analysis and differential scanning calorimetry. The results indicated the formation of a lower symmetry (1Tʹ) ReS2 with a low degree of layer stacking.

  3. Stretching and breaking of monolayer MoS2—an atomistic simulation

    International Nuclear Information System (INIS)

    Lorenz, Tommy; Joswig, Jan-Ole; Seifert, Gotthard

    2014-01-01

    We report on the simulation of the nanoindentation process of monolayer MoS 2 using molecular-dynamics simulations and a density-functional based tight-binding method. A circular sheet of MoS 2 with clamped boundaries was indented by a slowly moved tip, which deformed and finally pierced the layer. We found the Young’s modulus of monolayer MoS 2 to be 262 GPa, which is in good agreement with experimental observations. Furthermore, the energetic and structural behavior during the indentation process was analyzed. Elasticity theory supplies the necessary equations to explain the experiment. Thereby, the nature of the linear term in the force-deflection relation is discussed. (letter)

  4. Is MoS2 a robust material for 2D electronics?

    International Nuclear Information System (INIS)

    Lorenz, Tommy; Joswig, Jan-Ole; Seifert, Gotthard; Ghorbani-Asl, Mahdi; Heine, Thomas

    2014-01-01

    A nanoindentation computer experiment has been carried out by means of Born–Oppenheimer molecular-dynamics simulations employing the density-functional based tight-binding method. A free-standing MoS 2 sheet, fixed at a circular support, was indented by a stiff, sharp tip. During this process, the strain on the nanolayer is locally different, with maximum values in the vicinity of the tip. All studied electronic properties—the band gap, the projected density of states, the atomic charges and the quantum conductance through the layer—vary only slightly before they change significantly when the MoS 2 sheet finally is pierced. After strong local deformation due to the indentation process, the electronic conductance in our model still is 80% of its original value. Thus, the electronic structure of single-layer MoS 2 is rather robust upon local deformation. (paper)

  5. Insight in seasonal affective disorder.

    Science.gov (United States)

    Ghaemi, S N; Sachs, G S; Baldassano, C F; Truman, C J

    1997-01-01

    Lack of insight complicates the evaluation and treatment of patients with psychotic and affective disorders. No studies of insight in seasonal affective disorder (SAD) have been reported. Thirty patients with SAD diagnosed by the Structured Clinical Interview for DSM-III-R but no other axis I conditions were treated short-term with light-therapy. Insight was measured with the Scale to Assess Unawareness of Mental Disorder (SUMD) as modified by the authors to assess the self-report of insight into depressive symptoms. Increasing scores (1 to 5) indicated increasing unawareness of illness (i.e., less insight). SAD patients displayed a moderate amount of insight when depressed (mean SUMD score, 2.5). When recovered, they showed no significant change in insight into past depressive symptoms (mean SUMD score, 2.8). Greater insight into current depressive symptoms correlated with more depressive symptoms on the Hamilton Rating Scale for Depression score ([HRSD] r = .35, P depressive symptoms that does not change after recovery, a result in agreement with studies of insight in psychosis and mania. Further, in SAD, increased severity of illness may be associated with increased insight into depressive symptoms, consistent with the hypothesis of depressive realism.

  6. OPTOELECTRONIC PROPERTIES OF CdS – AgInS2 SOLAR CELLS

    Directory of Open Access Journals (Sweden)

    M. A. Abdullaev

    2016-01-01

    Full Text Available Aim. To conduct experimental studies of optoelectronic properties of CdS - AgInS2 solar cells.Methods. AgInS2 films for solar cell CdS-AgInS2 were obtained by magnetron sputtering of crystalline targets derived from bulk ingots. Cadmium sulfide layers were deposited on the AgInS2 films by an electrochemical method in cadmium salts solution, thiourea and ammonia. AgInS2 bulk crystals were obtained in two stages: a direct fusion of the primary components (99,999 in a stoichiometric ratio, followed by directional solidification in a vertical furnace; re-synthesis has been performed on a staggered basis by heating the obtained ingots at temperatures close to the melting points of elements in the two-zone horizontal furnace.Findings. The paper presents the results of experimental studies of the electrical properties and photosensitivity of CdS-AgInS2 film heterojunction obtained by the magnetron. We measured the current-voltage characteristics and quantum efficiency of photoconversion at temperatures up to 250-356 K. We also identified the short circuit current of up to 25 mA/cm2 and open circuit voltage of 0.38 V.Conclusions. The study of the properties of solar cells in recent years has an important place. The results presented in the work would contribute to more efficient conversion of solar energy into electricity.

  7. In situ preparation of NiS2/CoS2 composite electrocatalytic materials on conductive glass substrates with electronic modulation for high-performance counter electrodes of dye-sensitized solar cells

    Science.gov (United States)

    Li, Faxin; Wang, Jiali; Zheng, Li; Zhao, Yaqiang; Huang, Niu; Sun, Panpan; Fang, Liang; Wang, Lei; Sun, Xiaohua

    2018-04-01

    The electrocatalytic composite materials of honeycomb structure NiS2 nanosheets loaded with metallic CoS2 nanoparticles are in situ prepared on F doped SnO2 conductive glass (FTO) substrates used as counter electrodes of DSSCs through chemical bath deposition (CBD) and sulfidizing process. Single crystalline NiS2 honeycomb structure array lay a foundation for the large surface area of NiS2/CoS2 composite CEs. The formed NiS2/CoS2 nanointerface modulates electronic structure of composite CEs from the synergetic interactions between CoS2 nanoparticles and NiS2 nanosheets, which dramatically improves the electrocatalytic activity of NiS2/CoS2 composite CEs; Metallic CoS2 nanoparticles covering NiS2 nanosheets electrodes adjusts the electrodes' structure and then reduces the series resistance (Rs) and the Nernst diffusion resistance (Zw) of counter electrodes. The improvement of these areas greatly enhances the electrocatalytic performance of CEs and the short circuit current density (Jsc) and Fill factor (FF) of DSSCs. Impressively, the DSSC based on NiS2/CoS2-0.1 CE shows the best photovoltaic performance with photovoltaic conversion efficiency of 8.22%, which is 24.36% higher than that (6.61%) of the DSSC with Pt CE. And the NiS2/CoS2-0.1 CE also displays a good stability in the iodine based electrolyte. This work indicates that rational construction of composite electrocatalytic materials paves an avenue for high-performance counter electrodes of DSSCs.

  8. Carbon Domains on MoS2/TiO2 System via Catalytic Acetylene Oligomerization: Synthesis, Structure, and Surface Properties

    Directory of Open Access Journals (Sweden)

    Sara Cravanzola

    2017-11-01

    Full Text Available Carbon domains have been obtained at the surface of a MoS2/TiO2 (Evonik, P25 system via oligomerization and cyclotrimerization reactions involved in the interaction of the photoactive material with acetylene. Firstly, MoS2 nanosheets have been synthesized at the surface of TiO2, via sulfidation of a molybdenum oxide precursor with H2S (bottom-up method. Secondly, the morphology and the structure, the optical and the vibrational properties of the obtained materials, for each step of the synthesis procedure, have been investigated by microscopy and spectroscopy methods. In particular, transmission electron microscopy images provide a simple tool to highlight the effectiveness of the sulfidation process, thus showing 1L, 2L, and stacked MoS2 nanosheets anchored to the surface of TiO2 nanoparticles. Lastly, in-situ FTIR spectroscopy investigation gives insights into the nature of the oligomerized species, showing that the formation of both polyenic and aromatic systems can be taken into account, being their formation promoted by both Ti and Mo catalytic sites. This finding gives an opportunity for the assembly of extended polyenic, polyaromatic, or mixed domains firmly attached at the surface of photoactive materials. The presented approach, somehow different from the carbon adding or doping processes of TiO2, is of potential interest for the advanced green chemistry and energy conversion/transport applications.

  9. 3D architecture constructed via the confined growth of MoS2 nanosheets in nanoporous carbon derived from metal-organic frameworks for efficient hydrogen production.

    Science.gov (United States)

    Liu, Yun; Zhou, Xiaoli; Ding, Tao; Wang, Chunde; Yang, Qing

    2015-11-21

    The design and synthesis of robust, high-performance and low-cost three-dimensional (3D) hierarchical structured materials for the electrochemical reduction of water to generate hydrogen is of great significance for practical water splitting applications. In this study, we develop an in situ space-confined method to synthesize an MoS2-based 3D hierarchical structure, in which the MoS2 nanosheets grow in the confined nanopores of metal-organic frameworks (MOFs)-derived 3D carbons as electrocatalysts for efficient hydrogen production. Benefiting from its unique structure, which has more exposed active sites and enhanced conductivity, the as-prepared MoS2/3D nanoporous carbon (3D-NPC) composite exhibits remarkable electrocatalytic activity for the hydrogen evolution reaction (HER) with a small onset overpotential of ∼0.16 V, large cathodic currents, small Tafel slope of 51 mV per decade and good durability. We anticipate that this in situ confined growth provides new insights into the construction of high performance catalysts for energy storage and conversion.

  10. Supersymmetric AdS3, AdS2 and bubble solutions

    International Nuclear Information System (INIS)

    Gauntlett, Jerome P.; Waldram, Daniel; Kim, Nakwoo

    2007-01-01

    We present new supersymmetric AdS 3 solutions of type IIB supergravity and AdS 2 solutions of D = 11 supergravity. The former are dual to conformal field theories in two dimensions with N = (0, 2) supersymmetry while the latter are dual to conformal quantum mechanics with two supercharges. Our construction also includes AdS 2 solutions of D = 11 supergravity that have non-compact internal spaces which are dual to three-dimensional N = 2 superconformal field theories coupled to point-like defects. We also present some new bubble-type solutions, corresponding to BPS states in conformal theories, that preserve four supersymmetries

  11. Spectroscopic Signatures for Interlayer Coupling in MoS2-WSe2 van der Waals Stacking

    Science.gov (United States)

    2014-09-07

    K. Direct Imaging of Band Profile in Single Layer MoS2 on Graphite: Quasiparticle Energy Gap, Metallic Edge States, and Edge Band Bending. Nano Lett...1403.6455v1. 51. Shi, H.; Pan, H.; Zhang, Y.-W.; Yakobson, B. I. Quasiparticle Band Structures and Optical Properties of Strained Mono- layer MoS2 and WS2...Phys. Rev. B 2013, 87, 155304. 52. Liang, Y.; Huang, S.; Soklaski, R.; Yang, L. Quasiparticle Band-edge Energy and Band Offsets of Monolayer of

  12. S2 synthetic acceleration scheme for the one-dimensional S/sub n/ equations

    International Nuclear Information System (INIS)

    Lorence, L.J. Jr.; Larsen, E.W.; Morel, J.E.

    1986-01-01

    The authors have developed an S 2 synthetic acceleration method for the one-dimensional S/sub n/ equations with linear-discontinuous (LD) spatial differencing, and implemented it in a new version of the ONETRAN code. As in the diffusion-synthetic acceleration (DSA) of Morel, both the zeroth and first moments of the scattering source are accelerated. This is done by using the S 2 equations with Gauss quadrature rather than the diffusion equation as the low-order operator in the synthetic acceleration scheme

  13. Achieving Ohmic Contact for High-quality MoS2 Devices on Hexagonal Boron Nitride

    Science.gov (United States)

    Cui, Xu

    MoS2, among many other transition metal dichalcogenides (TMDCs), holds great promise for future applications in nano-electronics, opto-electronics and mechanical devices due to its ultra-thin nature, flexibility, sizable band-gap, and unique spin-valley coupled physics. However, there are two main challenges that hinder careful study of this material. Firstly, it is hard to achieve Ohmic contacts to mono-layer MoS2, particularly at low temperatures (T) and low carrier densities. Secondly, materials' low quality and impurities introduced during the fabrication significantly limit the electron mobility of mono- and few-layer MoS2 to be substantially below theoretically predicted limits, which has hampered efforts to observe its novel quantum transport behaviours. Traditional low work function metals doesn't necessary provide good electron injection to thin MoS2 due to metal oxidation, Fermi level pinning, etc. To address the first challenge, we tried multiple contact schemes and found that mono-layer hexagonal boron nitride (h-BN) and cobalt (Co) provide robust Ohmic contact. The mono-layer spacer serves two advantageous purposes: it strongly interacts with the transition metal, reducing its work function by over 1 eV; and breaks the metal-TMDCs interaction to eliminate the interfacial states that cause Fermi level pinning. We measure a flat-band Schottky barrier of 16 meV, which makes thin tunnel barriers upon doping the channels, and thus achieve low-T contact resistance of 3 kohm.um at a carrier density of 5.3x10. 12/cm. 2. Similar to graphene, eliminating all potential sources of disorder and scattering is the key to achieving high performance in MoS2 devices. We developed a van der Waals heterostructure device platform where MoS2 layers are fully encapsulated within h-BN and electrically contacted in a multi-terminal geometry using gate-tunable graphene electrodes. The h-BN-encapsulation provides excellent protection from environmental factors, resulting in

  14. Rotationally Commensurate Growth of MoS2 on Epitaxial Graphene

    Science.gov (United States)

    2015-11-13

    October 11, 2015 Accepted: November 13, 2015 A rtic le www.acsnano.org © XXXX American Chemical Society A DOI: 10.1021/acsnano.5b06398 ACS Nano XXXX ...interface between EG and MoS2 is highlighted in red. ACS Nano Article DOI: 10.1021/acsnano.5b06398 ACS Nano XXXX , XXX, XXX−XXX B The as-grown MoS2/EG...orientations. ACS Nano Article DOI: 10.1021/acsnano.5b06398 ACS Nano XXXX , XXX, XXX−XXX C nature of EG give rise to the inversion of the relative DOS at

  15. Role of interlayer coupling in ultra thin MoS2

    KAUST Repository

    Cheng, Yingchun

    2012-01-01

    The effects of interlayer coupling on the vibrational and electronic properties of ultra thin MoS 2 were studied by ab initio calculations. For smaller slab thickness, the interlayer distance is significantly elongated because of reduced interlayer coupling. This explains the anomalous thickness dependence of the lattice vibrations observed by Lee et al. (ACS Nano, 2010, 4, 2695). The absence of interlayer coupling in mono-layer MoS 2 induces a transition from direct to indirect band gap behaviour. Our results demonstrate a strong interplay between the intralayer chemical bonding and the interlayer van-der-Waals interaction. This journal is © 2012 The Royal Society of Chemistry.

  16. Scanning tunneling spectroscopy of MoS2 monolayer in presence of ethanol gas

    Science.gov (United States)

    Hosseini, Seyed Ali; Iraji zad, Azam; Berahman, Masoud; Aghakhani Mahyari, Farzaneh; Shokouh, Seyed Hossein Hosseini

    2018-04-01

    Due to high surface to volume ratio and tunable band gap, two dimensional (2D) layered materials such as MoS2, is good candidate for gas sensing applications. This research mainly focuses on variation of Density of States (DOS) of MoS2 monolayes caused by ethanol adsorption. The nanosheets are synthesized by liquid exfoliation, and then using Scanning Tunneling Spectroscopy (STS) and Density Functional Theory (DFT), local electronic characteristic such as DOS and band gap in non-vacuum condition are analyzed. The results show that ethanol adsorption enhances DOS and deform orbitals near the valence and conduction bands that increase transport of carriers on the sheet.

  17. In situ catalytic growth of large-area multilayered graphene/MoS2 heterostructures

    OpenAIRE

    Fu, Wei; Du, Fei-Hu; Su, Juan; Li, Xin-Hao; Wei, Xiao; Ye, Tian-Nan; Wang, Kai-Xue; Chen, Jie-Sheng

    2014-01-01

    Stacking various two-dimensional atomic crystals on top of each other is a feasible approach to create unique multilayered heterostructures with desired properties. Herein for the first time, we present a controlled preparation of large-area graphene/MoS2 heterostructures via a simple heating procedure on Mo-oleate complex coated sodium sulfate under N2 atmosphere. Through a direct in situ catalytic reaction, graphene layer has been uniformly grown on the MoS2 film formed by the reaction of M...

  18. Thiol-modified MoS2 nanosheets as a functional layer for electrical bistable devices

    Science.gov (United States)

    Li, Guan; Tan, Fenxue; Lv, Bokun; Wu, Mengying; Wang, Ruiqi; Lu, Yue; Li, Xu; Li, Zhiqiang; Teng, Feng

    2018-01-01

    Molybdenum disulfide nanosheets have been synthesized by one-pot method using 1-ODT as sulfur source and surfactant. The structure, morphology and optical properties of samples were investigated by XRD, FTIR, Abs spectrum and TEM patterns. The XRD pattern indicated that the as-obtained MoS2 belong to hexagonal system. The as-obtained MoS2 nanosheets blending with PVK could be used to fabricate an electrically bistable devices through a simple spin-coating method and the device exhibited an obvious electrical bistability properties. The charge transport mechanism of the device was discussed based on the filamentary switching models.

  19. Protein Kinase A Regulatory Subunits in Human Adipose Tissue

    Science.gov (United States)

    Mantovani, Giovanna; Bondioni, Sara; Alberti, Luisella; Gilardini, Luisa; Invitti, Cecilia; Corbetta, Sabrina; Zappa, Marco A.; Ferrero, Stefano; Lania, Andrea G.; Bosari, Silvano; Beck-Peccoz, Paolo; Spada, Anna

    2009-01-01

    OBJECTIVE—In human adipocytes, the cAMP-dependent pathway mediates signals originating from β-adrenergic activation, thus playing a key role in the regulation of important metabolic processes, i.e., lipolysis and thermogenesis. Cyclic AMP effects are mainly mediated by protein kinase A (PKA), whose R2B regulatory isoform is the most expressed in mouse adipose tissue, where it protects against diet-induced obesity and fatty liver development. The aim of the study was to investigate possible differences in R2B expression, PKA activity, and lipolysis in adipose tissues from obese and nonobese subjects. RESEARCH DESIGN AND METHODS—The expression of the different PKA regulatory subunits was evaluated by immunohistochemistry, Western blot, and real-time PCR in subcutaneous and visceral adipose tissue samples from 20 nonobese and 67 obese patients. PKA activity and glycerol release were evaluated in total protein extract and adipocytes isolated from fresh tissue samples, respectively. RESULTS—Expression techniques showed that R2B was the most abundant regulatory protein, both at mRNA and protein level. Interestingly, R2B mRNA levels were significantly lower in both subcutaneous and visceral adipose tissues from obese than nonobese patients and negatively correlated with BMI, waist circumference, insulin levels, and homeostasis model assessment of insulin resistance. Moreover, both basal and stimulated PKA activity and glycerol release were significantly lower in visceral adipose tissue from obese patients then nonobese subjects. CONCLUSIONS—Our results first indicate that, in human adipose tissue, there are important BMI-related differences in R2B expression and PKA activation, which might be included among the multiple determinants involved in the different lipolytic response to β-adrenergic activation in obesity. PMID:19095761

  20. P. berghei telomerase subunit TERT is essential for parasite survival.

    Directory of Open Access Journals (Sweden)

    Agnieszka A Religa

    Full Text Available Telomeres define the ends of chromosomes protecting eukaryotic cells from chromosome instability and eventual cell death. The complex regulation of telomeres involves various proteins including telomerase, which is a specialized ribonucleoprotein responsible for telomere maintenance. Telomeres of chromosomes of malaria parasites are kept at a constant length during blood stage proliferation. The 7-bp telomere repeat sequence is universal across different Plasmodium species (GGGTTT/CA, though the average telomere length varies. The catalytic subunit of telomerase, telomerase reverse transcriptase (TERT, is present in all sequenced Plasmodium species and is approximately three times larger than other eukaryotic TERTs. The Plasmodium RNA component of TERT has recently been identified in silico. A strategy to delete the gene encoding TERT via double cross-over (DXO homologous recombination was undertaken to study the telomerase function in P. berghei. Expression of both TERT and the RNA component (TR in P. berghei blood stages was analysed by Western blotting and Northern analysis. Average telomere length was measured in several Plasmodium species using Telomere Restriction Fragment (TRF analysis. TERT and TR were detected in blood stages and an average telomere length of ∼ 950 bp established. Deletion of the tert gene was performed using standard transfection methodologies and we show the presence of tert- mutants in the transfected parasite populations. Cloning of tert- mutants has been attempted multiple times without success. Thorough analysis of the transfected parasite populations and the parasite obtained from extensive parasite cloning from these populations provide evidence for a so called delayed death phenotype as observed in different organisms lacking TERT. The findings indicate that TERT is essential for P. berghei cell survival. The study extends our current knowledge on telomere biology in malaria parasites and validates further