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Sample records for 1d zigzag chain

  1. Hierarchical looping of zigzag nucleosome chains in metaphase chromosomes.

    PubMed

    Grigoryev, Sergei A; Bascom, Gavin; Buckwalter, Jenna M; Schubert, Michael B; Woodcock, Christopher L; Schlick, Tamar

    2016-02-02

    The architecture of higher-order chromatin in eukaryotic cell nuclei is largely unknown. Here, we use electron microscopy-assisted nucleosome interaction capture (EMANIC) cross-linking experiments in combination with mesoscale chromatin modeling of 96-nucleosome arrays to investigate the internal organization of condensed chromatin in interphase cell nuclei and metaphase chromosomes at nucleosomal resolution. The combined data suggest a novel hierarchical looping model for chromatin higher-order folding, similar to rope flaking used in mountain climbing and rappelling. Not only does such packing help to avoid tangling and self-crossing, it also facilitates rope unraveling. Hierarchical looping is characterized by an increased frequency of higher-order internucleosome contacts for metaphase chromosomes compared with chromatin fibers in vitro and interphase chromatin, with preservation of a dominant two-start zigzag organization associated with the 30-nm fiber. Moreover, the strong dependence of looping on linker histone concentration suggests a hierarchical self-association mechanism of relaxed nucleosome zigzag chains rather than longitudinal compaction as seen in 30-nm fibers. Specifically, concentrations lower than one linker histone per nucleosome promote self-associations and formation of these looped networks of zigzag fibers. The combined experimental and modeling evidence for condensed metaphase chromatin as hierarchical loops and bundles of relaxed zigzag nucleosomal chains rather than randomly coiled threads or straight and stiff helical fibers reconciles aspects of other models for higher-order chromatin structure; it constitutes not only an efficient storage form for the genomic material, consistent with other genome-wide chromosome conformation studies that emphasize looping, but also a convenient organization for local DNA unraveling and genome access.

  2. Hierarchical looping of zigzag nucleosome chains in metaphase chromosomes

    PubMed Central

    Grigoryev, Sergei A.; Bascom, Gavin; Buckwalter, Jenna M.; Schubert, Michael B.; Woodcock, Christopher L.; Schlick, Tamar

    2016-01-01

    The architecture of higher-order chromatin in eukaryotic cell nuclei is largely unknown. Here, we use electron microscopy-assisted nucleosome interaction capture (EMANIC) cross-linking experiments in combination with mesoscale chromatin modeling of 96-nucleosome arrays to investigate the internal organization of condensed chromatin in interphase cell nuclei and metaphase chromosomes at nucleosomal resolution. The combined data suggest a novel hierarchical looping model for chromatin higher-order folding, similar to rope flaking used in mountain climbing and rappelling. Not only does such packing help to avoid tangling and self-crossing, it also facilitates rope unraveling. Hierarchical looping is characterized by an increased frequency of higher-order internucleosome contacts for metaphase chromosomes compared with chromatin fibers in vitro and interphase chromatin, with preservation of a dominant two-start zigzag organization associated with the 30-nm fiber. Moreover, the strong dependence of looping on linker histone concentration suggests a hierarchical self-association mechanism of relaxed nucleosome zigzag chains rather than longitudinal compaction as seen in 30-nm fibers. Specifically, concentrations lower than one linker histone per nucleosome promote self-associations and formation of these looped networks of zigzag fibers. The combined experimental and modeling evidence for condensed metaphase chromatin as hierarchical loops and bundles of relaxed zigzag nucleosomal chains rather than randomly coiled threads or straight and stiff helical fibers reconciles aspects of other models for higher-order chromatin structure; it constitutes not only an efficient storage form for the genomic material, consistent with other genome-wide chromosome conformation studies that emphasize looping, but also a convenient organization for local DNA unraveling and genome access. PMID:26787893

  3. Heat Capacity of 1D Molecular Chains

    NASA Astrophysics Data System (ADS)

    Bagatskii, M. I.; Barabashko, M. S.; Sumarokov, V. V.; Jeżowski, A.; Stachowiak, P.

    2017-04-01

    The heat capacity of 1D chains of nitrogen and methane molecules (adsorbed in the outer grooves of bundles of closed-cap single-walled carbon nanotubes) has been studied in the temperature ranges 2-40 and 2-60 K, respectively. The temperature dependence of the heat capacity of 1D chains of nitrogen molecules below 3 K is close to a linear. It was found that the rotational heat capacity of methane molecules is a significant part of the total heat capacity of the chains throughout the whole investigated temperature range, whereas in the case of nitrogen, the librations are significant only above 15 K. The dependence of the heat capacity for methane below 10 K indicates the presence of a Schottky anomaly caused by the tunneling between the lowest energy levels of the CH4 molecule rotational spectra. Characteristic features observed in the temperature dependence of the heat capacity of 1D methane crystals are also discussed.

  4. Pressure-induced zigzag phosphorus chain and superconductivity in boron monophosphide

    PubMed Central

    Zhang, Xinyu; Qin, Jiaqian; Liu, Hanyu; Zhang, Shiliang; Ma, Mingzhen; Luo, Wei; Liu, Riping; Ahuja, Rajeev

    2015-01-01

    We report on the prediction of the zinc-blende structure BP into a novel C2/m phase from 113 to 208 GPa which possesses zigzag phosphorus chain structure, followed by another P42/mnm structure above 208 GPa above using the particle-swarm search method. Strong electron-phonon coupling λ in compressed BP is found, in particular for C2/m phase with the zigzag phosphorus chain, which has the highest λ (0.56–0.61) value among them, leading to its high superconducting critical temperature Tc (9.4 K–11.5 K), which is comparable with the 4.5 K to 13 K value of black phosphorus phase I (orthorhombic, Cmca). This is the first system in the boron phosphides which shows superconductivity from the present theoretical calculations. Our results show that pressure-induced zigzag phosphorus chain in BP exhibit higher superconducting temperature TC, opening a new route to search and design new superconductor materials with zigzag phosphorus chains. PMID:25737341

  5. Effects of Quantum Spin-1 /2 Impurities on the Magnetic Properties of Zigzag Spin Chains

    NASA Astrophysics Data System (ADS)

    Karmakar, Koushik; Skoulatos, Markos; Prando, Giacomo; Roessli, Bertran; Stuhr, Uwe; Hammerath, Franziska; Rüegg, Christian; Singh, Surjeet

    2017-03-01

    We investigate the effect of Co2 + (spin-1 /2 ) impurities on the magnetic ground state and low-lying spin excitations of the quasione-dimensional spin-1 /2 antiferromagnet SrCuO2 by means of neutron scattering, muon spin spectroscopy, and bulk (ac and dc) magnetic susceptibilities. We found that dilute Co doping induces an Ising-like anisotropy and enhances the magnetic ordering temperature rather significantly, but preserves the gapless nature of the spin excitations. These results are in apparent contradiction with the recent studies of Ni (spin-1) doped SrCuO2 . Low-temperature magnetic behavior of the Co-doped zigzag chains in SrCuO2 reveals the presence of a weak geometrical spin frustration.

  6. Effects of Quantum Spin-1/2 Impurities on the Magnetic Properties of Zigzag Spin Chains.

    PubMed

    Karmakar, Koushik; Skoulatos, Markos; Prando, Giacomo; Roessli, Bertran; Stuhr, Uwe; Hammerath, Franziska; Rüegg, Christian; Singh, Surjeet

    2017-03-10

    We investigate the effect of Co^{2+} (spin-1/2) impurities on the magnetic ground state and low-lying spin excitations of the quasione-dimensional spin-1/2 antiferromagnet SrCuO_{2} by means of neutron scattering, muon spin spectroscopy, and bulk (ac and dc) magnetic susceptibilities. We found that dilute Co doping induces an Ising-like anisotropy and enhances the magnetic ordering temperature rather significantly, but preserves the gapless nature of the spin excitations. These results are in apparent contradiction with the recent studies of Ni (spin-1) doped SrCuO_{2}. Low-temperature magnetic behavior of the Co-doped zigzag chains in SrCuO_{2} reveals the presence of a weak geometrical spin frustration.

  7. Antisymmetric Spin-Orbit Coupling in a d-p Model on a Zigzag Chain

    DOE PAGES

    Sugita, Yusuke; Hayami, Satoru; Motome, Yukitoshi

    2015-12-29

    In this paper, we theoretically investigate how an antisymmetric spin-orbit coupling emerges in electrons moving on lattice structures which are centrosymmetric but break the spatial inversion symme- try at atomic positions. We construct an effective d-p model on the simplest lattice structure, a zigzag chain of edge-sharing octahedra, with taking into account the crystalline electric field, the spin-orbit coupling, and on-site and inter-site d-p hybridizations. We show that an effective antisymmetric spin-orbit coupling arises in the sublattice-dependent form, which results in a hidden spin polarization in the band structure. Finally, we explicitly derive the effective antisymmetric spin-orbit coupling for dmore » electrons, which not only explains the hidden spin polarization but also indicates how to enhance it.« less

  8. Antisymmetric Spin-Orbit Coupling in a d-p Model on a Zigzag Chain

    SciTech Connect

    Sugita, Yusuke; Hayami, Satoru; Motome, Yukitoshi

    2015-12-29

    In this paper, we theoretically investigate how an antisymmetric spin-orbit coupling emerges in electrons moving on lattice structures which are centrosymmetric but break the spatial inversion symme- try at atomic positions. We construct an effective d-p model on the simplest lattice structure, a zigzag chain of edge-sharing octahedra, with taking into account the crystalline electric field, the spin-orbit coupling, and on-site and inter-site d-p hybridizations. We show that an effective antisymmetric spin-orbit coupling arises in the sublattice-dependent form, which results in a hidden spin polarization in the band structure. Finally, we explicitly derive the effective antisymmetric spin-orbit coupling for d electrons, which not only explains the hidden spin polarization but also indicates how to enhance it.

  9. Spin currents and filtering behavior in zigzag graphene nanoribbons with adsorbed molybdenum chains

    NASA Astrophysics Data System (ADS)

    García-Fuente, A.; Gallego, L. J.; Vega, A.

    2015-04-01

    By means of density-functional-theoretic calculations, we investigated the structural, electronic and transport properties of hydrogen-passivated zigzag graphene nanoribbons (ZGNRs) on which a one-atom-thick Mo chain was adsorbed (with or without one or two missing atoms), or in which the passivating hydrogen atoms were replaced by Mo atoms. Mo-passivated ZGNRs proved to be nonmagnetic. ZGNRs with an adsorbed defect-free Mo chain were most stable with the Mo atoms forming dimers above edge bay sites, which suppressed the magnetic moments of the C atoms in that half of the ribbon; around the Fermi level of these systems, each spin component had a transmission channel via the Mo spz band and one had an additional channel created by polarization of the ZGNR π* band, leading to a net spin current. The absence of an Mo dimer from an Mo chain adsorbed at the ZGNR edge made the system a perfect spin filter at low voltage bias by suppressing the Mo spz band channels. Thus this last kind of hybrid system is a potential spin valve.

  10. Spin-stripe phase in a frustrated zigzag spin-1/2 chain

    PubMed Central

    Pregelj, M.; Zorko, A.; Zaharko, O.; Nojiri, H.; Berger, H.; Chapon, L. C.; Arčon, D.

    2015-01-01

    Motifs of periodic modulations are encountered in a variety of natural systems, where at least two rival states are present. In strongly correlated electron systems, such behaviour has typically been associated with competition between short- and long-range interactions, for example, between exchange and dipole–dipole interactions in the case of ferromagnetic thin films. Here we show that spin-stripe textures may develop also in antiferromagnets, where long-range dipole–dipole magnetic interactions are absent. A comprehensive analysis of magnetic susceptibility, high-field magnetization, specific heat and neutron diffraction measurements unveils β-TeVO4 as a nearly perfect realization of a frustrated (zigzag) ferromagnetic spin-1/2 chain. Notably, a narrow spin-stripe phase develops at elevated magnetic fields due to weak frustrated short-range interchain exchange interactions, possibly assisted by the symmetry-allowed electric polarization. This concept provides an alternative route for the stripe formation in strongly correlated electron systems and may help understanding of other widespread, yet still elusive, stripe-related phenomena. PMID:26068618

  11. Site-Selective Antimony Doping in Arsenic Zigzag Chains of 112-Type Ca1-xLaxFeAs2

    NASA Astrophysics Data System (ADS)

    Ota, Hiromi; Kudo, Kazutaka; Kimura, Takumi; Kitahama, Yutaka; Mizukami, Tasuku; Ioka, Satoshi; Nohara, Minoru

    2017-02-01

    Single crystal X-ray diffraction studies were performed for the Sb-doped 112-type iron-based superconductor Ca1-xLaxFeAs2 with the superconducting transition temperature Tc of 47 K. Doped Sb preferably substituted not for As(1) in the FeAs layers but for As(2) in the layers of As zigzag chains. Structural reasons for Tc enhancement by Sb doping were discussed.

  12. Cyanide-bridged Fe(III)-Co(II) bis double zigzag chains with a slow relaxation of the magnetisation.

    PubMed

    Toma, Luminita Marilena; Lescouëzec, Rodrigue; Lloret, Francesc; Julve, Miguel; Vaissermann, Jacqueline; Verdaguer, Michel

    2003-08-07

    Reaction of [Fe(III)(bipy)(CN)4]- with fully solvated M(II) cations [M = Co (1) and Mn (2)] produces the isostructural bis double zigzag chains [[Fe(III)(bipy)(CN)4]2M(II)(H2O)] x MeCN x (1/2)H2O; 1 exhibits intrachain ferromagnetic and interchain antiferromagnetic couplings, slow magnetic relaxation and hysteresis effects.

  13. Homometallic ferrimagnetism in the zig-zag chain compound Na2Cu5Si4O14

    NASA Astrophysics Data System (ADS)

    Reis, M. S.; Dos Santos, A. Moreira; Amaral, V. S.; Brandão, P.; Rocha, J.

    2006-06-01

    The structure of Na2Cu5Si4O14 is comprised of zig-zag chains of alternating Cu edge-sharing dimers and trimers, with different magnetic ground states, allowing the occurrence of homometallic ferrimagnetism. The magnetic susceptibility data are consistent with that of a ferrimagnetic chain compound, and are predicted using a model that considers interactions intra-trimers (related to the exchange integral J1=-224.9K ), intra-dimer (J3=40.22K) , and inter dimer-trimer (J2=-8.01K) . The magnetic interaction between the antiferromagnetic trimer and ferromagnetic dimer is in accordance with the Goodenough rules applied to the Cu-O topology. A three-dimensional antiferromagnetic ordering is observed below TN=8K , corresponding to the magnetic ordering between chains. In addition, since TN˜θp there is not a significant degree of frustration in the chain ordering.

  14. Comparative Study on Effects of Armchair and Zigzag Graphene Electrodes on Ballistic Transport through C Atomic Chain

    NASA Astrophysics Data System (ADS)

    Ambavale, S. K.; Sharma, A. C.

    2011-07-01

    We performed theoretical investigations on electronic transport through carbon atomic chain (CAC) attached to relaxed armchair graphene (ACG) and zigzag graphene (ZZG) electrodes with the use of scattering state formalism implemented in PWSCF code of Quantum Espresso package. Our computed results show that the equilibrium conductance of CAC attached to ZZG-electrodes tends to zero over a wide energy range covering Fermi energy. Similar behavior of conductance is not seen when ZZG electrodes are replaced by ACG electrodes. CAC connected to ACG electrode is found better conducting as compared to CAC connected to ZZG electrode.

  15. Nanojet-induced modes in 1D chains of microspheres

    NASA Astrophysics Data System (ADS)

    Kapitonov, A. M.; Astratov, V. N.

    2007-02-01

    We report on the light transport phenomena in linear chains composed of several tens of touching spherical microcavities. A new optical mode type, namely nanojet-induced modes (NIMs) is observed. These modes result from the optical coupling of microspheres acting as a series of micro-lenses, which periodically focus propagating wave into photonic nanojets. Theoretically, formation of periodic nanojets has been predicted in Z. Chen et al., Opt. Lett. 31, 389 (2006). The chains were produced by means of the self-assembly directed by micro-flows of water suspension of polystyrene microspheres. The mean size of spheres was varied in the 2-10 micron range. To couple light to NIMs we used built-in emission sources formed by several locally excited dye-doped microcavities from the same chain. Conversion of modes emitted by the light source into the NIMs results in losses of several dB per sphere in the vicinity (first few tens of spheres) of such sources. At longer distances we found an attenuation rate as small as 0.5 dB per sphere that reveals low intrinsic propagation loss for NIMs. The NIMs have potential applications for coupling and guiding of light in compact arrays of spherical cavities with extremely high quality (Q) whispering gallery modes.

  16. Co-assembly of Zn(SPh){sub 2} and organic linkers into helical and zig-zag polymer chains

    SciTech Connect

    Liu Yi; Yu Lingmin; Loo, Say Chye Joachim; Blair, Richard G.; Zhang Qichun

    2012-07-15

    Two novel one-dimensional coordination polymers, single helicate [Zn(SPh){sub 2}(TPyTA)(EG)]{sub n} (EG=ethylene glycol) (1) and zig-zag structure [Zn(SPh){sub 2}(BPyVB)]{sub n} (2), were synthesized under solvothermal conditions at 150 Degree-Sign C or room temperature by the co-assembly of Zn(SPh){sub 2} and organic linkers such as 2,4,6-tri(4-pyridyl)-1,3,5-triazine (TPyTA) and 1,3-bis(trans-4-pyridylvinyl)benzene (BPyVB). X-ray crystallography study reveals that both polymers 1 and 2 crystallize in space group P2{sub 1}/c of the monoclinic system. The solid-state UV-vis absorption spectra show that 1 and 2 have maxium absorption onsets at 400 nm and 420 nm, respectively. TGA analysis indicates that 1 and 2 are stable up to 110 Degree-Sign C and 210 Degree-Sign C. - Graphical abstract: Two novel one-dimensional coordination polymers, single helicate [Zn(SPh){sub 2}(TPyTA)(EG)]{sub n} (1) and zig-zag structure [Zn(SPh){sub 2}(BPyVB)]{sub n} (2), were synthesized. Solid-state UV-vis absorptions show that 1 and 2 have maxium absorption onsets at 400 nm and 420 nm, respectively. TGA analysis indicates that 1 and 2 are stable up to 110 Degree-Sign C and 210 Degree-Sign C. Highlights: Black-Right-Pointing-Pointer Two novel one-dimensional coordination polymers have been synthesized. Black-Right-Pointing-Pointer TPyTA results in helical structures in 1 while BPyVB leads to zig-zag chains in 2. Black-Right-Pointing-Pointer Solid-state UV-vis absorption spectra and TGA analysis of the title polymers were studied.

  17. Theoretical Investigation of the Interfaces and Mechanisms of Induced Spin Polarization of 1D Narrow Zigzag Graphene- and h-BN Nanoribbons on a SrO-Terminated LSMO(001) Surface.

    PubMed

    Avramov, Paul; Kuzubov, Alexander A; Kuklin, Artem V; Lee, Hyosun; Kovaleva, Evgenia A; Sakai, Seiji; Entani, Shiro; Naramoto, Hiroshi; Sorokin, Pavel B

    2017-01-26

    The structure of the interfaces and the mechanisms of induced spin polarization of 1D infinite and finite narrow graphene- and h-BN zigzag nanoribbons placed on a SrO-terminated La1-xSrxMnO3 (LSMO) (001) surface were studied using density functional theory (DFT) electronic structure calculations. It was found that the π-conjugated nanofragments are bonded to the LSMO(001) surface by weak disperse interactions. The types of coordination of the fragments, the strength of bonding, and the rate of spin polarization depend upon the nature of the fragments. Infinite and finite graphene narrow zigzag nanoribbons are characterized by the lift of the spin degeneracy and strong spin polarization caused by interface-induced structural asymmetry and oxygen-mediated indirect exchange interactions with Mn ions of LSMO support. Spin polarization changes the semiconducting nature of infinite graphene nanoribbons to half-metallic state with visible spin-up density of states at the Fermi level. The h-BN nanoribbon binding energy is weaker than graphene nanoribbon ones with noticeably shorter interlayer distance. The asymmetry effect and indirect exchange interactions cause spin polarization of h-BN nanoribbon as well with formation of embedded states inside the band gap. The results show a possibility to use one-atom thick nanofragments to design LSMO-based heterostructures for spintronic nanodevices with h-BN as an inert spacer to develop different potential barriers.

  18. A novel coordination polymer containing both interdigitated 1D chains and interpenetrated 2D grids.

    PubMed

    Ayyappan, Ponnaiyan; Evans, Owen R; Lin, Wenbin

    2002-07-01

    A hydro(solvo)thermal reaction between zinc perchlorate and ethyl ester of a new pyridinecarboxylate bridging ligand of approximately 17.6 A in length yields a unique coordination polymer which contains both interdigitated infinite 1D chains and interpenetrated 2D rhombohedral grids [Zn(2.5)(L)(4)(mu(3)-OH)] x (H(2)O)(5), 1, where L is 3-[[4-(4-pyridylethenyl)phenyl]ethenyl]benzoate. The 1D chains contain mu(3)-bridged hydroxy groups and have a [Zn(4)(mu(3)-OH)(2)(L)(6)] stoichiometry, while the 2D grids have a Zn(L)(2) formula and diagonal distances of 31.7 and 25.2 A. Crystal data for 1: monoclinic space group P2/c, a = 15.686(2) A, b = 12.6103(16) A, c = 38.999(5) A, beta = 98.397(2) degrees, and Z = 4.

  19. Magnetic properties driven by local structure in quasi-1D Ising chain system cobaltate system

    NASA Astrophysics Data System (ADS)

    Kim, Bongjae; Kim, Beom Hyun; Kim, Kyoo; Choi, Hong Chul; Park, Sang-Yeon; Jeong, Y.-H.; Min, B. I.

    2012-02-01

    Using ab-initio band structure method and the microscopic model calculation, the origins of the large orbital magnetic moment and unique magnetic anisotropy in the quasi-1D magnetic cobaltate, α-CoV2O6, is investigated. Unique crystal electric field effect in α-CoV2O6 is combined with the strong spin-orbit coupling, results in intriguing magnetic properties of the system. Based on the estimated strengths of the intra- and the inter-chain exchange interaction, experimentally found 1/3 magnetization plateau in the MH curve can be attributed to spin-flop mechanism. Origin of the reduced magnetic entropy behavior is found to be the strong uniaxial magnetic anisotropy in the quasi-1D Ising chain system.

  20. Self-assembled 1D magnetic Ising chains: epitaxial islands of Co/Ru(0001)

    NASA Astrophysics Data System (ADS)

    Li, Dongqi; Yu, Chengtao; Pearson, John; Bader, Samuel

    2002-03-01

    We have self-assembled magnetic Co dot chains via epitaxial island decoration of grooved Ru(0001) to create a model 1D system. Co wedge-like structures of 0-60 nm thick were deposited onto flat and grooved Ru(0001) substrates via molecular beam epitaxy at 350¢ªC and characterized ex-situ with atomic force and the magnetic force microscopy (MFM), and magneto-optic Kerr effect. The grooved substrate has a saw-tooth profile with spacing of order of 1 um, due to residual polishing scratches / step bunching. Co forms strain-induced, quasi-hexagonal dots of 70-500 nm in diameter and 1-20 nm high, depending on nominal dosage. On grooved substrate, the dots self align into chains along the groove near the top and bottom of the saw-tooth structure.[1] The dots are ferromagnetically coupled along the chain and exhibit magnetic single-domains with in-plane uniaxial anisotropy along the grooves. The inter-dot magnetic pair correlation was deduced from the MFM images of the dot-chains, and can be understood in terms of the classic 1D Ising model. * Work supported by DOE BES-MS under #W-31-109-ENG-38. 1. Chengtao Yu, Dongqi Li, J. Pearson, and S.D. Bader, Appl. Phys. Lett. 78, 1228 (2001); ibid. 79, 3848 (2001).

  1. Enumeration of four-connected three-dimensional nets. II. Conversion of edges of three-connected 2D nets into zigzag chains.

    PubMed

    Han; Smith

    1999-03-01

    Four-connected three-dimensional (3D) nets were systematically enumerated by converting some horizontal edges of a vertical stack of three-connected two-dimensional (2D) nets into vertical zigzag chains. 77 out of 131 2D nets were selected for enumeration, and different arrangements of zigzag edges and horizontal edges were investigated. This yielded 138 3D nets of which 19 are represented by known structures: cristobalite; tridymite; MAPO-39 (International Zeolite Association Structure Commission code ATN); svyatoslavite; Li-A(BW) (ABW); cancrinite (CAN); AlPO-31 (ATO); MAPO-36 (ATS); BaFe(2)O(4); 'nepheline hydrate' (JBW); bikitaite (BIK); KBGe(2)O(6); CsAlSi(5)O(12) (CAS); UiO-6 (OSI); Theta-1 (TON); ZSM-12 (MTW); ZSM-23 (MTT); AlPO-53C; and CIT-5 (CFI).

  2. Spin-liquid ground state in the frustrated J1-J2 zigzag chain system BaTb2O4

    DOE PAGES

    Aczel, A. A.; Li, L.; Garlea, V. O.; ...

    2015-07-13

    We have investigated polycrystalline samples of the zigzag chain system BaTb2O4 with magnetic susceptibility, heat capacity, neutron powder diffraction, and muon spin relaxation measurements. No magnetic transitions are observed in the bulk measurements, while neutron diffraction reveals low-temperature, short-range, intrachain magnetic correlations between Tb3+ ions. Muon spin relaxation measurements indicate that these correlations are dynamic, as the technique detects no signatures of static magnetism down to 0.095 K. Altogether these findings provide strong evidence for a spin liquid ground state in BaTb2O4.

  3. FractionalSzExcitation and Its Boundstate for theS=1/2 Antiferromagnetic Zigzag Spin Chain in a Magnetic Field

    NASA Astrophysics Data System (ADS)

    Okunishi, Kouichi; Tonegawa, Takashi

    2005-01-01

    We demonstrate that domain-wall type excitations carrying the fractional magnetization $S^z=\\pm1/3$ and their bound state describe the low-energy physics around the 1/3 plateau of the antiferromagnetic zigzag spin chain in the strongly frustrated region. In particular we discuss the relevance of such domain-wall excitations to the characteristic properties of the magnetization curves: the 1/3 plateau accompanying the spontaneous symmetry breaking of the translation, the cusp singularities above and/or below the plateau, and the even-odd effect in the magnetization curve.

  4. Formation of Gd coordination polymer with 1D chains mediated by Bronsted acidic ionic liquids

    NASA Astrophysics Data System (ADS)

    Luo, Qianqian; Han, Ying; Lin, Hechun; Zhang, Yuanyuan; Duan, Chungang; Peng, Hui

    2017-03-01

    One dimensional coordination polymer Gd[(SO4)(NO3)(C2H6SO)2] (1) is prepared through the mediation of Bronsted acid ionic liquid, which crystallized in the monoclinic space of C2/c. In this polymer, adjacent Gd atoms are linked by two SO42- ions to generate a 1-D chain, and all oxygen atoms in SO42- groups are connected to three nearest Gd atoms in μ3:η1:η1:η2 fashion. Gd, S and N from SO42- and NO3- are precisely coplanar. The planar is coordinated by a pair of DMSO molecules, which is parallel and linked by hydrogen bonding to form a three-dimensional supramolecular network. Magnetic susceptibility measurement of 1 reveals weak antiferromagnetic interactions between the Gd (III) ions. It exhibits relatively large magneto-caloric effect with -ΔSm=28.8 J Kg-1 K-1 for ΔH=7 T.

  5. A novel cryogenic magnetic refrigerant metal-organic framework based on 1D gadolinium(III) chain

    NASA Astrophysics Data System (ADS)

    Tang, Qun; Li, Peng-Fei; Zou, Zhi-Ming; Liu, Zheng; Liu, Shu-Xia

    2017-02-01

    A metal-organic framework (MOF) based on gadolinium ion (Gd3+) and tricarboxylate ligand, [Gd(BTPCA)(H2O)]·2DMF·3H2O (Gd-BTPCA) (H3BTPCA =1,1‧,1‧-(benzene-1,3,5-triyl)tripiperidine-4-carboxylic acid; DMF=dimethylformamide), was synthesized and structurally characterized. The adjacent Gd3+ ions are intraconnected by the carboxylate groups of the BTPCA3- ligands to form a 1D Gd3+ ion chain. The 1D Gd3+ ion chains are interconnected by the BTPCA3- ligands, giving rise to a 3D framework with 1D open channel. The magnetic studies indicate that Gd-BTPCA exhibits weak ferromagnetic interactions, and acts as a cryogenic magnetic refrigerant having the magnetic entropy change (-ΔSm) of 20.40 J kg-1 K-1 for ΔH =7 T at 3 K.

  6. Topological defect formation in 1D and 2D spin chains realized by network of optical parametric oscillators

    NASA Astrophysics Data System (ADS)

    Hamerly, Ryan; Inaba, Kensuke; Inagaki, Takahiro; Takesue, Hiroki; Yamamoto, Yoshihisa; Mabuchi, Hideo

    2016-09-01

    A network of optical parametric oscillators (OPOs) is used to simulate classical Ising and XY spin chains. The collective nonlinear dynamics of this network, driven by quantum noise rather than thermal fluctuations, seeks out the Ising/XY ground state as the system transitions from below to above the lasing threshold. We study the behavior of this “Ising machine” for three canonical problems: a 1D ferromagnetic spin chain, a 2D square lattice and problems where next-nearest-neighbor couplings give rise to frustration. If the pump turn-on time is finite, topological defects form (domain walls for the Ising model, winding number and vortices for XY) and their density can be predicted from a numerical model involving a linear “growth stage” and a nonlinear “saturation stage”. These predictions are compared against recent data for a 10,000-spin 1D Ising machine.

  7. Multiple mobility edges in a 1D Aubry chain with Hubbard interaction in presence of electric field: Controlled electron transport

    NASA Astrophysics Data System (ADS)

    Saha, Srilekha; Maiti, Santanu K.; Karmakar, S. N.

    2016-09-01

    Electronic behavior of a 1D Aubry chain with Hubbard interaction is critically analyzed in presence of electric field. Multiple energy bands are generated as a result of Hubbard correlation and Aubry potential, and, within these bands localized states are developed under the application of electric field. Within a tight-binding framework we compute electronic transmission probability and average density of states using Green's function approach where the interaction parameter is treated under Hartree-Fock mean field scheme. From our analysis we find that selective transmission can be obtained by tuning injecting electron energy, and thus, the present model can be utilized as a controlled switching device.

  8. Crystal structures of bovine CD1d reveal altered αGalCer presentation and a restricted A' pocket unable to bind long-chain glycolipids.

    PubMed

    Wang, Jing; Guillaume, Joren; Pauwels, Nora; Van Calenbergh, Serge; Van Rhijn, Ildiko; Zajonc, Dirk M

    2012-01-01

    NKT cells play important roles in immune surveillance. They rapidly respond to pathogens by detecting microbial glycolipids when presented by the non-classical MHC I homolog CD1d. Previously, ruminants were considered to lack NKT cells due to the lack of a functional CD1D gene. However, recent data suggest that cattle express CD1d with unknown function. In an attempt to characterize the function of bovine CD1d, we assessed the lipid binding properties of recombinant Bos taurus CD1d (boCD1d) in vitro. BoCD1d is able to bind glycosphingolipids (GSLs) with fatty acid chain lengths of C₁₈, while GSLs with fatty acids of C₂₄ do not bind. Crystal structures of boCD1d bound to a short-chain C₁₂-di-sulfatide antigen, as well as short-chain C₁₆-αGalCer revealed that the Á pocket of boCD1d is restricted in size compared to that of both mouse and human CD1d, explaining the inability of long chain GSL's to bind to boCD1d. Moreover, while di-sulfatide is presented similarly compared to the presentation of sulfatide by mouse CD1d, αGalCer is presented differently at the cell surface, due to an amino acid Asp151Asn substitution that results in loss of intimate contacts between the αGalCer headgroup and CD1d. The altered αGalCer presentation by boCD1d also explains its lack of cross-activation of mouse iNKT cells and raises the interesting question of the nature and function of bovine lipid-reactive T cells.

  9. Crystal Structures of Bovine CD1d Reveal Altered αGalCer Presentation and a Restricted A’ Pocket Unable to Bind Long-Chain Glycolipids

    PubMed Central

    Wang, Jing; Guillaume, Joren; Pauwels, Nora; Van Calenbergh, Serge; Van Rhijn, Ildiko; Zajonc, Dirk M.

    2012-01-01

    NKT cells play important roles in immune surveillance. They rapidly respond to pathogens by detecting microbial glycolipids when presented by the non-classical MHC I homolog CD1d. Previously, ruminants were considered to lack NKT cells due to the lack of a functional CD1D gene. However, recent data suggest that cattle express CD1d with unknown function. In an attempt to characterize the function of bovine CD1d, we assessed the lipid binding properties of recombinant Bos taurus CD1d (boCD1d) in vitro. BoCD1d is able to bind glycosphingolipids (GSLs) with fatty acid chain lengths of C18, while GSLs with fatty acids of C24 do not bind. Crystal structures of boCD1d bound to a short-chain C12-di-sulfatide antigen, as well as short-chain C16-αGalCer revealed that the Á pocket of boCD1d is restricted in size compared to that of both mouse and human CD1d, explaining the inability of long chain GSL’s to bind to boCD1d. Moreover, while di-sulfatide is presented similarly compared to the presentation of sulfatide by mouse CD1d, αGalCer is presented differently at the cell surface, due to an amino acid Asp151Asn substitution that results in loss of intimate contacts between the αGalCer headgroup and CD1d. The altered αGalCer presentation by boCD1d also explains its lack of cross-activation of mouse iNKT cells and raises the interesting question of the nature and function of bovine lipid-reactive T cells. PMID:23110152

  10. Characterizing gapped phases of a 1D spin chain with on-site and spatial symmetries

    NASA Astrophysics Data System (ADS)

    West, Colin; Prakash, Abhishodh; Wei, Tzu-Chieh

    We investigate the phase diagram of a spin-1 chain whose Hamiltonian is invariant under translation, lattice inversion and a global A4 symmetry in the spin degrees of freedom. The classification scheme by Chen, Gu, and Wen allows us to enumerate all possible phases under the given symmetry. Then, we determine which of these phases actually occur in the two-parameter Hamiltonian. Using numerical methods proposed by Pollmann and Turner (2012) we determine the characteristic projective parameters for the Symmetry Protected Topological (SPT) phases. In addition, we present a method for determining the projective commutation parameter in these phases. The resulting phase diagram is rich and contains at least nine different SPT phases. This work was supported in part by the National Science Foundation.

  11. Two unprecedented 1D coordination polymer chains based on tetranuclear copper(II) building blocks

    SciTech Connect

    Li Gaijuan; Xing Yan Song Shuyan; Xu Ning; Liu Xianchun; Su Zhongmin

    2008-09-15

    The reaction of copper(II) sulfate with pyridine in DMF or methanol yield two unprecedented Cu(II) coordination polymers {l_brace}[Cu{sub 4}({mu}{sub 4}-O)(py){sub 4}(SO{sub 4}){sub 4}][{mu}-Cu(py)(DMF){sub 2}]{r_brace}{sub n}(1) and {l_brace}[Cu{sub 4}({mu}{sub 4}-O)(py){sub 4}(SO{sub 4}){sub 4}][{mu}-Cu(py){sub 4}]{r_brace}{sub n}(2), respectively. Single-crystal X-ray diffraction indicated that compound 1 crystallizes in the monoclinic system, space group p2(1)/n, a=14.542(5) A, b=16.359(5) A, c=18.951(5) A, {beta}=92.047(5){sup o}, V=4505(2) A{sup 3}, Z=4 while 2 is monoclinic C2/c, a=23.078(5) A, b=10.214(5) A, c=23.142(5) A, {beta}=115.471(5){sup o}, V=4925(3) A{sup 3}, Z=4. Both of the two compounds consist of tetrahedral tetranuclear [Cu{sub 4}({mu}{sub 4}-O)(py){sub 4}(SO{sub 4}){sub 4}] clusters that are bridged by pentacoordinated Cu atom for 1 or hexacoordinated Cu atoms for 2 through the sulfate oxygen to form the infinite one-dimensional polymer chains. - Graphical abstract: Two unprecedented Cu(II) coordination polymers have been prepared by using solvothermal method; they consist of tetrahedral tetranuclear clusters that are bridged by unique Cu(II) atom through the sulfate oxygen to form the infinite one-dimensional polymer chains (a) for complex 1 and (b) for complex 2.

  12. The role of solitons in charge and energy transfer in 1D molecular chains

    NASA Astrophysics Data System (ADS)

    Ivić , Zoran

    1998-03-01

    The idea that polarons and solitons could play the crucial role in the transport processes in biological structures, has been critically reexamined on the basis of the general theory of self-trapping phenomena. The criteria which enable one to determine conditions for the existence and stability of polarons and solitons and to determine their character, in dependence of the values of the basic physical parameters of the system, were formulated. Validity of the so-called Davydov's soliton model was discussed on the basis of these criteria. It was found that the original Davydov's proposal, based upon the idea of the soliton creation due to the single excitation (particle, vibron, etc.) self-trapping, cannot explain the intramolecular energy transfer in α-helix and acetanilide. However, Davydov theory is flexible enough to describe the single electron transfer in some systems (α-helix and acetanilide for example). In the many-particle systems, dressing effect, due to the quantum nature of phonons, may cause the creation of the bound states of the several excitons in the molecular chain. The possibility of creation of the soliton states of this type is discussed for the simple Fröhlich's one-dimensional model. The regions of the system parameter space where different mechanisms dominate the behaviour of such entities are characterized.

  13. Two-step spin transition in a 1D Fe(II) 1,2,4-triazole chain compound.

    PubMed

    Dîrtu, Marinela M; Schmit, France; Naik, Anil D; Rusu, Ionela; Rotaru, Aurelian; Rackwitz, Sergej; Wolny, Juliusz A; Schünemann, Volker; Spinu, Leonard; Garcia, Yann

    2015-04-07

    A thermochromic 1D spin crossover coordination (SCO) polymer [Fe(βAlatrz)3](BF4)2⋅2 H2O (1⋅2 H2O), whose precursor βAlatrz, (1,2,4-triazol-4-yl-propionate) has been tailored from a β-amino acid ester is investigated in detail by a set of superconducting quantum interference device (SQUID), (57)Fe Mössbauer, differential scanning calorimetry, infrared, and Raman measurements. An hysteretic abrupt two-step spin crossover (T1/2(↓) = 230 K and T1/2(↑) = 235 K, and T1/2(↓) = 172 K and T1/2(↑) = 188 K, respectively) is registered for the first time for a 1,2,4-triazole-based Fe(II) 1D coordination polymer. The two-step SCO configuration is observed in a 1:2 ratio of low-spin/high-spin in the intermediate phase for a 1D chain. The origin of the stepwise transition was attributed to a distribution of chains of different lengths in 1⋅2 H2O after First Order Reversal Curves (FORC) analyses. A detailed DFT analysis allowed us to propose the normal mode assignment of the Raman peaks in the low-spin and high-spin states of 1⋅2 H2O. Vibrational spectra of 1⋅2 H2O reveal that the BF4(-) anions and water molecules play no significant role on the vibrational properties of the [Fe(βAlatrz)3](2+) polymeric chains, although non-coordinated water molecules have a dramatic influence on the emergence of a step in the spin transition curve. The dehydrated material [Fe(βAlatrz)3](BF4)2 (1) reveals indeed a significantly different magnetic behavior with a one-step SCO which was also investigated.

  14. Functional CD1d and/or NKT cell invariant chain transcript in horse, pig, African elephant and guinea pig, but not in ruminants

    PubMed Central

    Looringh van Beeck, Frank A.; Reinink, Peter; Hermsen, Roel; Zajonc, Dirk M.; Laven, Marielle J.; Fun, Axel; Troskie, Milana; Schoemaker, Nico J.; Morar, Darshana; Lenstra, Johannes A.; Vervelde, Lonneke; Rutten, Victor P.M.G.; van Eden, Willem; Van Rhijn, Ildiko

    2009-01-01

    CD1d-restricted invariant natural killer T cells (NKT cells) have been well characterized in humans and mice, but it is unknown whether they are present in other species. Here we describe the invariant TCR α chain and the full length CD1d transcript of pig and horse. Molecular modeling predicts that porcine (po) invariant TCR α chain/poCD1d/α-GalCer and equine (eq) invariant TCR α chain/eqCD1d/α-GalCer form complexes that are highly homologous to the human complex. Since a prerequisite for the presence of NKT cells is the expression of CD1d protein, we performed searches for CD1D genes and CD1d transcripts in multiple species. Previously, cattle and guinea pig have been suggested to lack CD1D genes. The CD1D genes of European taurine cattle (Bos taurus) are known to be pseudogenes because of disrupting mutations in the start codon and in the donor splice site of the first intron. Here we show that the same mutations are found in six other ruminants: African buffalo, sheep, bushbuck, bongo, N’Dama cattle, and roe deer. In contrast, intact CD1d transcripts were found in guinea pig, African elephant, horse, rabbit, and pig. Despite the discovery of a highly homologous NKT/CD1d system in pig and horse, our data suggest that functional CD1D and CD1d-restricted NKT cells are not universally present in mammals. PMID:19185921

  15. Structural variation from heterometallic cluster-based 1D chain to heterometallic tetranuclear cluster: Syntheses, structures and magnetic properties

    SciTech Connect

    Zhang, Shu-Hua; Zhao, Ru-Xia; Li, He-Ping; Ge, Cheng-Min; Li, Gui; Huang, Qiu-Ping; Zou, Hua-Hong

    2014-08-15

    Using the solvothermal method, we present the comparative preparation of ([Co{sub 3}Na(dmaep){sub 3}(ehbd)(N{sub 3}){sub 3}]·DMF){sub n} (1) and [Co{sub 2}Na{sub 2}(hmbd){sub 4}(N{sub 3}){sub 2}(DMF){sub 2}] (2), where Hehbd is 3-ethoxy-2-hydroxy-benzaldehyde, Hhmbd is 3-methoxy-2-hydroxy-benzaldehyde, and Hdmaep is 2-dimethylaminomethyl-6-ethoxy-phenol, which was synthesized by an in-situ reaction. Complexes 1 and 2 were characterized by elemental analysis, IR spectroscopy, and X-ray single-crystal diffraction. Complex 1 is a novel heterometallic cluster-based 1-D chain and 2 is a heterometallic tetranuclear cluster. The (Co{sub 3}{sup II}Na) and (Co{sub 2}{sup II}Na{sub 2}) cores display dominant ferromagnetic interaction from the nature of the binding modes through μ{sub 1,1,1}-N{sub 3}{sup –} (end-on, EO). - Graphical abstract: Two novel cobalt complexes have been prepared. Compound 1 consists of tetranuclear (Co{sub 3}{sup II}Na) units, which further formed a 1-D chain. Compound 2 is heterometallic tetranuclear cluster. Two complexes display dominant ferromagnetic interaction. - Highlights: • Two new heterometallic complexes have been synthesized by solvothermal method. • The stereospecific blockade of the ligands in the synthesis system seems to be the most important synthetic parameter. • The magnetism studies show that 1 and 2 exhibit ferromagnetic interactions. • Complex 1 shows slowing down of magnetization and not blocking of magnetization.

  16. New Mononuclear Cu(II) Complexes and 1D Chains with 4-Amino-4H-1,2,4-triazole

    PubMed Central

    Dîrtu, Marinela M.; Boland, Yves; Gillard, Damien; Tinant, Bernard; Robeyns, Koen; Safin, Damir A.; Devlin, Eamonn; Sanakis, Yiannis; Garcia, Yann

    2013-01-01

    The crystal structures of two mononuclear Cu(II) NH2trz complexes [Cu(NH2trz)4(H2O)](AsF6)2 (I) and [Cu(NH2trz)4(H2O)](PF6)2 (II) as well as two coordination polymers [Cu(μ2-NH2trz)2Cl]Cl·H2O (III) and [Cu(μ2-NH2trz)2Cl] (SiF6)0.5·1.5H2O (IV) are presented. Cationic 1D chains with bridging bis-monodentate μ2-coordinated NH2trz and bridging μ2-coordinated chloride ligands are present in III and IV. In these coordination polymers, the Cu(II) ions are strongly antiferromagnetically coupled with J = −128.4 cm−1 for III and J = −143 cm−1 for IV (H = −J∑SiSi+1), due to the nature of the bridges between spin centers. Inter-chain interactions present in the crystal structures were taken into consideration, as well as g factors, which were determined experimentally, for the quantitative modeling of their magnetic properties. PMID:24300095

  17. Synthesis of zigzag-chain and cyclic-octanuclear calcium complexes and hexanuclear bulky aryl-phosphate sodium complexes with ortho-amide groups: structural transformation involving a network of inter- and intramolecular hydrogen bonds.

    PubMed

    Onoda, Akira; Yamada, Yusuke; Okamura, Taka-aki; Doi, Mototsugu; Yamamoto, Hitoshi; Ueyama, Norikazu

    2002-02-13

    Three new polynuclear Ca(II)- and Na(I) phosphate complexes with two strategically oriented bulky amide groups, 2,6-(PhCONH)(2)C(6)H(3)OPO(3)H(2), were synthesized, including one with a zigzag-chain, [Ca(II)[O(3)POC(6)H(3)-2,6-(NHCOPh)(2)](H(2)O)(4)(EtOH)](n), a cyclic-octanuclear form, [Ca(II)(8)[O(3)POC(6)H(3)-2,6-(NHCOPh)(2)](8)(O=CHNMe(2))(8)(H(2)O)(12)], and a hexanuclear complex, (NHEt(3))[Na(3)[O(3)POC(6)H(3)-2,6-(NHCOPh)(2)](2)(H(2)O)(MeOH)(7)]. X-ray crystallography revealed that all have an unsymmetric ligand position due to the bulky amide groups. A dynamic transformation of the Ca(II) zigzag-chain structure to the cyclic-octanuclear complex was induced by changing coordination of DMF molecules, which caused a reorganization of the intermolecular/intramolecular hydrogen bond network.

  18. Spin coupling in zigzag Wigner crystals.

    SciTech Connect

    Klironomos, A. D.; Meyer, J. S.; Hikihara, T.; Matveev, K. A.; Materials Science Division; Ohio State Univ.; Hokkaido Univ.

    2007-08-01

    We consider interacting electrons in a quantum wire in the case of a shallow confining potential and low electron density. In a certain range of densities, the electrons form a two-row (zigzag) Wigner crystal whose spin properties are determined by nearest and next-nearest neighbor exchange as well as by three- and four-particle ring exchange processes. The phase diagram of the resulting zigzag spin chain has regions of complete spin polarization and partial spin polarization in addition to a number of unpolarized phases, including antiferromagnetism and dimer order as well as a novel phase generated by the four-particle ring exchange.

  19. Quantum soliton in 1D Heisenberg spin chains with Dzyaloshinsky-Moriya and next-nearest-neighbor interactions

    NASA Astrophysics Data System (ADS)

    Djoufack, Z. I.; Tala-Tebue, E.; Nguenang, J. P.; Kenfack-Jiotsa, A.

    2016-10-01

    We report in this work, an analytical study of quantum soliton in 1D Heisenberg spin chains with Dzyaloshinsky-Moriya Interaction (DMI) and Next-Nearest-Neighbor Interactions (NNNI). By means of the time-dependent Hartree approximation and the semi-discrete multiple-scale method, the equation of motion for the single-boson wave function is reduced to the nonlinear Schrödinger equation. It comes from this present study that the spectrum of the frequencies increases, its periodicity changes, in the presence of NNNI. The antisymmetric feature of the DMI was probed from the dispersion curve while changing the sign of the parameter controlling it. Five regions were identified in the dispersion spectrum, when the NNNI are taken into account instead of three as in the opposite case. In each of these regions, the quantum model can exhibit quantum stationary localized and stable bright or dark soliton solutions. In each region, we could set up quantum localized n-boson Hartree states as well as the analytical expression of their energy level, respectively. The accuracy of the analytical studies is confirmed by the excellent agreement with the numerical calculations, and it certifies the stability of the stationary quantum localized solitons solutions exhibited in each region. In addition, we found that the intensity of the localization of quantum localized n-boson Hartree states increases when the NNNI are considered. We also realized that the intensity of Hartree n-boson states corresponding to quantum discrete soliton states depend on the wave vector.

  20. Quantum soliton in 1D Heisenberg spin chains with Dzyaloshinsky-Moriya and next-nearest-neighbor interactions.

    PubMed

    Djoufack, Z I; Tala-Tebue, E; Nguenang, J P; Kenfack-Jiotsa, A

    2016-10-01

    We report in this work, an analytical study of quantum soliton in 1D Heisenberg spin chains with Dzyaloshinsky-Moriya Interaction (DMI) and Next-Nearest-Neighbor Interactions (NNNI). By means of the time-dependent Hartree approximation and the semi-discrete multiple-scale method, the equation of motion for the single-boson wave function is reduced to the nonlinear Schrödinger equation. It comes from this present study that the spectrum of the frequencies increases, its periodicity changes, in the presence of NNNI. The antisymmetric feature of the DMI was probed from the dispersion curve while changing the sign of the parameter controlling it. Five regions were identified in the dispersion spectrum, when the NNNI are taken into account instead of three as in the opposite case. In each of these regions, the quantum model can exhibit quantum stationary localized and stable bright or dark soliton solutions. In each region, we could set up quantum localized n-boson Hartree states as well as the analytical expression of their energy level, respectively. The accuracy of the analytical studies is confirmed by the excellent agreement with the numerical calculations, and it certifies the stability of the stationary quantum localized solitons solutions exhibited in each region. In addition, we found that the intensity of the localization of quantum localized n-boson Hartree states increases when the NNNI are considered. We also realized that the intensity of Hartree n-boson states corresponding to quantum discrete soliton states depend on the wave vector.

  1. Power law behavior of the zigzag transition in Yukawa clusters

    SciTech Connect

    Sheridan, T. E.; Magyar, Andrew L.

    2010-11-15

    We provide direct experimental evidence that the width of a Yukawa cluster exhibits power law behavior during the one-dimensional (1D) to two-dimensional (2D) zigzag transition. Configurations of small dusty (complex) plasma clusters confined in a biharmonic potential well are characterized as the well anisotropy is varied. When the anisotropy is large the particles are in a 1D straight-line configuration. As the anisotropy is decreased the cluster undergoes a zigzag transition to a 2D configuration. The measured dependence of cluster width on anisotropy follows a power law. A second transition from the zigzag to an elliptical configuration is also observed. The results are in very good agreement with a model of identical particles interacting through a Yukawa potential.

  2. Spin Gap in the Zigzag Spin-1/2 Chain Cuprate Sr0.9Ca0.1CuO2

    NASA Astrophysics Data System (ADS)

    Hammerath, F.; Nishimoto, S.; Grafe, H.-J.; Wolter, A. U. B.; Kataev, V.; Ribeiro, P.; Hess, C.; Drechsler, S.-L.; Büchner, B.

    2011-07-01

    We report a comparative study of Cu63 nuclear magnetic resonance spin lattice relaxation rates T1-1 on undoped SrCuO2 and Ca-doped Sr0.9Ca0.1CuO2 spin chain compounds. A temperature independent T1-1 is observed for SrCuO2 as expected for an S=1/2 Heisenberg chain. Surprisingly, we observe an exponential decrease of T1-1 for T<90K in the Ca-doped sample evidencing the opening of a spin gap. The data analysis within the J1-J2 Heisenberg model employing density-matrix renormalization group calculations suggests an impurity driven small alternation of the J2-exchange coupling as a possible cause of the spin gap.

  3. Supramolecular open-framework based on 1-D iron phosphate-diphosphate chains assembled through hydrogen bonding

    SciTech Connect

    Salvado, Miguel A.; Pertierra, Pilar; Trobajo, Camino; Garcia, Jose R.

    2008-05-15

    Fe(H{sub 2}PO{sub 4})(H{sub 2}P{sub 2}O{sub 7}).C{sub 5}H{sub 5}N, a new iron(III) phosphate with an open-framework has been synthesized hydrothermally using pyridine as organic template. The crystal structure was solved ab initio using conventional powder X-ray diffraction data. The unit cell is orthorhombic, a=9.5075(2), b=10.1079(1), c=13.3195(2) A, space group P2{sub 1}2{sub 1}2{sub 1}, Z=4. The structure consists of FeO{sub 6} octahedra joined by H{sub 2}PO{sub 4} and H{sub 2}P{sub 2}O{sub 7} groups forming linear chains interconnected by hydrogen bonding to give rise to a supramolecular framework enclosing tunnels in which the pyridine molecules reside. - Graphical abstract: The low temperature hydrothermal synthesis offers many possibilities in the preparation of new materials with mixed octahedral-tetrahedral open-frameworks. Fe(H{sub 2}PO{sub 4})(H{sub 2}P{sub 2}O{sub 7}).C{sub 5}H{sub 5}N is constituted by linear chains of FeO{sub 6} octahedra joined through of both dihydrogenphosphate and dihydrogendiphosphate bridges, interconnected by hydrogen bonds, originating channels where the pyridine molecules are located.

  4. A novel 1D chain of azido bridged copper(II) with a salen-type di-Schiff base ligand

    NASA Astrophysics Data System (ADS)

    Biswas, Saptarshi; Ghosh, Ashutosh

    2012-07-01

    One new complex of Cu(II), [(CuL)2Cu3(N3)6]n (1) has been synthesized by reacting the "ligand complex", [CuL] with copper acetate and sodium azide (NaN3) in methanol-water where the di-Schiff base ligand H2L = N,N‧-bis(α-methylsalicylidene)-1,3-propanediamine. The X-ray single crystal structural analysis shows that complex 1 consists of an incomplete face-sharing double cube of four Cu(II) ions with the formula of [(CuL)2Cu2(N3)2]2+ which are connected by [Cu(N3)4]2- unit to form a novel 1D chain.

  5. Synthesis and characterization of a 1D chain-like Cu{sub 6} substituted sandwich-type phosphotungstate with pendant dinuclear Cu–azido complexes

    SciTech Connect

    Li, Yan-Ying; Zhao, Jun-Wei; Wei, Qi; Yang, Bai-Feng; Yang, Guo-Yu

    2014-02-15

    A novel Cu–azido complex modified hexa-Cu{sup II} substituted sandwich-type phosphotungstate [Cu(en){sub 2}]([Cu{sub 2}(en){sub 2}(μ-1,1-N{sub 3}){sub 2}(H{sub 2}O)]{sub 2}[Cu{sub 6}(en){sub 2}(H{sub 2}O){sub 2}(B-α-PW{sub 9}O{sub 34}){sub 2}])·6H{sub 2}O (1) (en=ethylene-diamine) has been prepared under hydrothermal conditions and structurally characterized by elemental analyses, IR spectra, powder X-ray diffraction (PXRD) and single-crystal X-ray diffraction. 1 displays a beautiful 1-D chain architecture constructed from sandwich-type [Cu{sub 2}(en){sub 2}(μ-1,1-N{sub 3}){sub 2}(H{sub 2}O)]{sub 2}[Cu{sub 6}(en){sub 2}(H{sub 2}O){sub 2}(B-α-PW{sub 9}O{sub 34}){sub 2}]{sup 2−} units and [Cu(en){sub 2}]{sup 2+} linkers. To our knowledge, 1 represents the first hexa-Cu{sup II} sandwiched phosphotungstate with supporting Cu–azido complexes. - Graphical abstract: The first hexa-Cu{sup II} sandwiched phosphotungstate with supporting Cu–azido complexes has been prepared and characterized. Display Omitted - Highlights: • Hexa-copper-substituted phosphotungstate. • Cu–azido complexes modified hexa-Cu{sup II} substituted sandwich-type polyoxometalate. • 1-D chain architecture built by hexa-copper-substituted polyoxotungstate units.

  6. Spin-liquid ground state in the frustrated J1-J2 zigzag chain system BaTb2O4

    SciTech Connect

    Aczel, A. A.; Li, L.; Garlea, V. O.; Yan, J. -Q.; Weickert, F.; Zapf, V. S.; Movshovich, R.; Jaime, M.; Baker, P. J.; Keppens, V.; Mandrus, D.

    2015-07-13

    We have investigated polycrystalline samples of the zigzag chain system BaTb2O4 with magnetic susceptibility, heat capacity, neutron powder diffraction, and muon spin relaxation measurements. No magnetic transitions are observed in the bulk measurements, while neutron diffraction reveals low-temperature, short-range, intrachain magnetic correlations between Tb3+ ions. Muon spin relaxation measurements indicate that these correlations are dynamic, as the technique detects no signatures of static magnetism down to 0.095 K. Altogether these findings provide strong evidence for a spin liquid ground state in BaTb2O4.

  7. o-, m-, and p-Pyridyl isomer effects on construction of 1D loop-and-chains: Silver(I) coordination polymers with Y-type tridentate ligands

    NASA Astrophysics Data System (ADS)

    Kim, Jeong Gyun; Cho, Yoonjung; Lee, Haeri; Lee, Young-A.; Jung, Ok-Sang

    2016-10-01

    Self-assembly of silver(I) hexafluorophosphate with unique Y-type tridentate ligands (2,6-bis[(2-picolinoyloxy-5-methylphenyl)methyl]-p-tolylpicolinate (o-L), 2-nicotinoyloxy- (m-L), and 2-isonicotinoyloxy- (p-L)) produces single crystals consisting of 1D loop-and-chain coordination polymers of [Ag(o-L)](PF6)·Me2CO·CHCl3, [Ag(m-L)](PF6)·Me2CO, and [Ag3(p-L)2](PF6)3·2H2O·2C2H5OH·4CH2Cl2 with quite different trigonal prismatic, trigonal, and linear silver(I) coordination geometry, respectively. Coordinating ability of the three ligands for AgPF6 is in the order of p-L > o-L > m-L. The solvate molecules of [Ag(o-L)](PF6)·Me2CO·CHCl3 can be removed, and be replaced reversibly in the order of acetone ≫ chloroform ≈ dichloromethane ≫ benzene, without destruction of its skeleton.

  8. Self-assembly of silver(I) coordination polymers from aminopyrimidyl derivatives and malonate acid: From 1D chain to 2D layer

    NASA Astrophysics Data System (ADS)

    Sun, Di; Zhang, Na; Xu, Qin-Juan; Luo, Geng-Geng; Huang, Rong-Bin; Zheng, Lan-Sun

    2010-04-01

    Two new silver(I) coordination polymers (CPs) of the formula [Ag 2(dmapym) 4(mal)·H 2O] n ( 1) and [Ag 3(apym) 3(mal)NO 3] n ( 2) (dmapym = 2-amino-4,6-dimethylprimidine, apym = 2-aminopyrimidine, H 2mal = malonate) have been synthesized by reactions of AgNO 3 and 2-aminopyrimidyl ligands with malonate under the ammoniacal condition. Both complexes have been characterized by element analysis, IR and single-crystal X-ray diffraction. The monodentate dmapym and tridentate mal ligands link Ag(I) ions to give complex 1 a one-dimensional (1D) H-shaped chain structure. The complex 2 is a two-dimensional (2D) double sheet structure constructed by (4, 4) single sheet. Additionally, the hydrogen-bonding and C-H⋯π interactions also direct the self-assembly of supramolecular architectures. The photoluminescence properties of the 1 and 2 were investigated in the solid state at room temperature.

  9. Molecular cable-like 1-D iodic spiral chains covered with triple helices stabilized in guest-included chiral porous framework.

    PubMed

    Tadokoro, Makoto; Tanaka, Yasuko; Noguchi, Khoichiro; Sugaya, Tomoaki; Isoda, Kyosuke

    2012-07-21

    The supramolecular crystal {[Pr(DMFA)](3)[Ni(II)(Hbim)(3)](2)I}(n) with intricate chiral networks of [Ni(II)(Hbim)(3)](-) molecules is reported. It includes a cationic architecture as a guest, constructed from chiral nanotubes that penetrate I(-) chains with spiral channels wrapped by triple helices. The I(-) chains have AC conductivity in crystals like a molecular cable.

  10. Molecular tectonics: self-complementary supramolecular Se...N synthons directing assembly of 1D silver chains into 3D porous molecular architectures.

    PubMed

    Zhou, Ai-Ju; Zheng, Shao-Liang; Fang, Yue; Tong, Ming-Liang

    2005-06-27

    Reaction of 2,1,3-benzoselenadiazole (bsd) with AgNO3 results in the formation of a novel model example of a Se...N synthon directed molecular network of different polymorphs at different temperatures. Alpha-[Ag(bsd)2(NO3)] x 0.5bsd formed at ambient temperature, has a 3D porous molecular network constructed with monomeric [Ag(bsd)2(NO3)] motif, and has 1D channels that are encapsulated with 1D arrays of two-fold-disordered dimeric (bsd)2 guests aggregated by the self-complementary nonbonded Se...N interactions. This is the first molecular net directed by supramolecular Se...N synthons. The second polymorph, beta-[Ag(bsd)2(NO3)] x 0.5bsd, formed from an analogous reaction at 50 degrees C, contains a similar 3D molecular network constructed with tetrameric [Ag4(bsd)8(NO3)4] motif and 1D arrays of well-ordered dimeric (bsd)2 guests are encapsulated in the channels. Such ordered (bsd)2 dimers provide an excellent simplified dimeric model for MO calculations of intermolecular nonbonded Se...N interactions.

  11. Electronic structures of reconstructed zigzag silicene nanoribbons

    SciTech Connect

    Ding, Yi E-mail: wangyanli-04@tsinghua.org.cn; Wang, Yanli E-mail: wangyanli-04@tsinghua.org.cn

    2014-02-24

    Edge states and magnetism are crucial for spintronic applications of nanoribbons. Here, using first-principles calculations, we explore structural stabilities and electronic properties of zigzag silicene nanoribbons (ZSiNRs) with Klein and pentagon-heptagon reconstructions. Comparing to unreconstructed zigzag edges, deformed bare pentagon-heptagon ones are favored under H-poor conditions, while H-rich surroundings stabilize di-hydrogenated Klein edges. These Klein edges have analogous magnetism to zigzag ones, which also possess the electric-field-induced half-metallicity of nanoribbons. Moreover, diverse magnetic states can be achieved by asymmetric Klein and zigzag edges into ZSiNRs, which could be transformed from antiferromagnetic-semiconductors to bipolar spin-gapless-semiconductors and ferromagnetic-metals depending on edge hydrogenations.

  12. Non-native side chain IR probe in peptides: ab initio computation and 1D and 2D IR spectral simulation.

    PubMed

    Zheng, Michael L; Zheng, David C; Wang, Jianping

    2010-02-18

    Infrared frequency region of 2000-2600 cm(-1) (i.e., ca. 4-5 microm in wavelength) is a well-known open spectral window for peptides and proteins. In this work, six unnatural amino acids (unAAs) were designed to have characteristic absorption bands located in this region. Key chemical groups that served as side chains in these unAAs are C[triple bond]C, Phe-C[triple bond]C, N=C=O, N=C=S, P-H, and Si-H, respectively. Cysteine (a natural AA having S-H in side chain) was also studied for comparison. The anharmonic vibrational properties, including frequencies, anharmonicities, and intermode couplings, were examined using the density functional theory. Broadband linear infrared (IR) and two-dimensional (2D) IR spectra were simulated for each molecule. It is found that all of the side chain modes have significant overtone diagonal anharmonicities. All have moderate transition dipole strengths except the C[triple bond]C and S-H stretching modes, in comparison with the C=O stretching mode. In each case, a collection of 2D IR cross peaks were predicted to appear due to the presence of the side chain groups, whose strengths are closely related to the intramolecular anharmonic interactions, and to the transition dipole strengths of the coupled vibrators. Further, potential energy distribution analysis and high-order anharmonic constant computation showed that these IR probes possess a varying degree of mode localization. The results suggest that these IR probes are potentially useful in complementing the well-studied amide-I mode, to investigate structures and dynamics of peptides and proteins.

  13. Effects of magnetic site disorder of the 1-D Ising spin chain compounds Ca3(Co,Mn)2O6 with dilute doping

    NASA Astrophysics Data System (ADS)

    Casas, Brian; Lampen, Paula; Phan, Manh-Huong; Srikanth, Hariharan; Kovak, Jozef; Skorvanek, Ivan

    2015-03-01

    The spin chain compound Ca3Co2O6 has been extensively studied due to a number of unusual properties originating from geometrically frustrated Ising-like spin chains arranged in a triangular lattice. These quasi one dimensional structures provide an ideal environment to study dilute magnetic disorder in spin-glass like systems. Disorder controlled via chemical doping has been observed to weaken the spin glass behavior and disrupt a number of metamagnetic transitions found in pristine Ca3Co2O6. We report a systematic study of the effects of dilute Mn doping (x = 0.05 - 0.50) in Ca3Co2-xMnxO6 synthesized via a sol-gel method. Detailed AC and DC magnetization measurements performed on a SQUID magnetometer reveal the suppression of the step-like metamagnetic transitions by a doping of x = 0.25. The relaxation time is found to decrease with increasing Mn content, showing the destruction of the spin-glass like behavior. Our observations yield new insight into the role of site disorder on the glassy behavior in spin chain systems. Research was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Award No. DE-FG02-07ER46438.

  14. Structural Modulation from 1D Chain to 3D Framework: Improved Thermostability, Insensitivity, and Energies of Two Nitrogen-Rich Energetic Coordination Polymers.

    PubMed

    Guo, Zhaoqi; Wu, Yunlong; Deng, Chongqing; Yang, Guoping; Zhang, Jiangong; Sun, Zhihua; Ma, Haixia; Gao, Chao; An, Zhongwei

    2016-11-07

    Two new energetic coordination polymers (CPs) [Pb(BT)(H2O)3]n (1) and [Pb3(DOBT)3(H2O)2]n·(4H2O)n (2) with 1D and 3D structures were synthesized by employing two rational designed ligands, 1H,1'H-5,5'-bitetrazole (H2BT) and 1H,1'H-[5,5'-bitetrazole]-1,1'-diol ligands (DHBT), respectively. Thermal analyses and sensitivity tests show that the 3D architecture reinforces the network of 2 which has higher thermal stability and lower sensitivity than that of 1. Through oxygen-bomb combustion calorimetry the molar enthalpy of formation of 2 is derived to be much higher than that of 1 as well as the reported CPs. Herein, more importantly, the heats of detonation (ΔHdet) were calculated according to the decomposition products of TG-DSC-MS-FTIR simultaneous analyses for the first time. The calculated results show that ΔHdet of 2 is 23% higher than that of 1. This research demonstrates that 3D energetic CP with outstanding energetic properties can be obtained through efficient and reasonable design.

  15. Dynamics and supramolecular organization of the 1D spin transition polymeric chain compound [Fe(NH2trz)3](NO3)2. Muon spin relaxation.

    PubMed

    Garcia, Yann; Campbell, Stewart J; Lord, James S; Boland, Yves; Ksenofontov, Vadim; Gütlich, Philipp

    2007-09-27

    The thermal spin transition that occurs in the polymeric chain compound [Fe(NH(2)trz)3](NO3)2 above room temperature has been investigated by zero-field muon spin relaxation (microSR) over the temperature range approximately 8-402 K. The depolarization curves are best described by a Lorentzian and a Gaussian line that represent fast and slow components, respectively. The spin transition is associated with a hysteresis loop of width DeltaT = 34 K (T1/2 upward arrow = 346 K and T1/2 downward arrow = 312 K) that has been delineated by the temperature variation of the initial asymmetry parameter, in good agreement with previously published magnetic measurements. Zero-field and applied field (20-2000 Oe) microSR measurements show the presence of diamagnetic muon species and paramagnetic muonium radical species (A = 753 +/- 77 MHz) over the entire temperature range. Fast dynamics have been revealed in the high-spin state of [Fe(NH(2)trz)3](NO3)2 with the presence of a Gaussian relaxation mode that is mostly due to the dipolar interaction with static nuclear moments. This situation, where the muonium radicals are totally decoupled and not able to sense paramagnetic fluctuations, implies that the high-spin dynamics fall outside the muon time scale. Insights to the origin of the cooperative effects associated with the spin transition of [Fe(NH(2)trz)3](NO3)2 through muon implantation are presented.

  16. 1D μ-glycine-briged copper (II) chain in complex [Cu(μ-Gly)Im(ClO4)]n and ferromagnetic interactions among copper (II)

    NASA Astrophysics Data System (ADS)

    Pan, Lu; Lv, Xue-Chuan; Luo, Guan-Hua; Gao, Xiao-Han; Tan, Zhi-Cheng

    2016-12-01

    Complex [Cu(μ-Gly)Im(ClO4)]n(Im = imidazole, and Gly = glycine) with μ-glycine-briged copper (II) chain, containing six-coordination distorted elongated octahedron, was synthesized and characterized. The complex belongs to space group P 21/c measured by X-ray single crystal diffraction. In the cluster, each Cu2+ ion are six-coordination by one nitrogen atom and two oxygen atoms of glycine, one nitrogen atoms of imidazole, and two of oxygen atoms of two perchlorate. Each Cu2+ ion has an N2O4 donor set, which forms the distorted elongated octahedron due to the Jahn-Teller (JT) effect. The magnetic and thermodynamic properties were researched. Magnetic susceptibilities of the complex showed that ferromagnetic interactions occurred between the Cu (II) atoms. The Curie-Weiss constant C = 0.565 cm3 K·mol-1 and the Weiss constant θ = 1.0585 K were given by the Curie-Weiss law The ferromagnetic nature of the interaction could be deduced as the exchange pathway of Cusbnd Osbnd Csbnd Osbnd Cu, which involved an equatorial position at one copper (II) ion and an axial position of the nearest copper (II). The complex decomposed from 511 to 538 K as two steps.

  17. Crossed Andreev reflection in a zigzag graphene nanoribbon-superconductor junction

    NASA Astrophysics Data System (ADS)

    Wang, J.; Liu, S.

    2012-01-01

    We investigate the crossed Andreev reflection (CAR) in a zigzag graphene nanoribbon/superconductor/nanoribbon junction. It is shown that when the zigzag chain number of the ribbon is even and only the zero-energy mode is involved in transport either the elastic cotunneling or the local Andreev reflection could be entirely suppressed by using a gate voltage whereas a sizable CAR is achieved. When one of the ribbon leads is magnetized not only is the CAR exclusive, but also the spin state of the CAR transmission is nonlocally controllable. The physical origin is the peculiar valley selection rule in the even zigzag graphene nanoribbon. The ideal Cooper-pair splitting in the proposed device holds for all applied bias in the superconducting energy gap.

  18. Half-metallic zigzag carbon nanotube dots.

    PubMed

    Hod, Oded; Scuseria, Gustavo E

    2008-11-25

    A comprehensive first-principles theoretical study of the electronic properties and half-metallic nature of finite zigzag carbon nanotubes is presented. Unlike previous reports, we find that all nanotubes studied present a spin-polarized ground state, where opposite spins are localized at the two zigzag edges in a long-range antiferromagnetic-type configuration. Relative stability analysis of the different spin states indicates that, for the shorter segments, spin-ordering should be present even at room temperature. The energy gap between the highest occupied and the lowest unoccupied molecular orbitals of the finite systems is found to be inversely proportional to the nanotube's segment lengths, suggesting a route to control their electronic properties. Similar to the case of zigzag graphene nanoribbons, half-metallic behavior is obtained under the influence of an external axial electric field.

  19. Strain-induced topological phase transition at zigzag edges of monolayer transition-metal dichalcogenides

    NASA Astrophysics Data System (ADS)

    Li, Linhu; Castro, Eduardo V.; Sacramento, Pedro D.

    2016-11-01

    The effect of strain in zigzag ribbons of monolayer transition-metal dichalcogenides with induced superconductivity is studied using a minimal three-band tight-binding model. The unstrained system shows a topological phase with Majorana zero modes localized at the boundaries of the one-dimensional (1D) zigzag edges. By direct inspection of the spectrum and wave functions we examine the evolution of the topological phase as an in-plane, uniaxial deformation is imposed. It is found that strain shifts the energy of 1D edge states, thus causing a topological phase transition which eliminates the Majorana modes. For realistic parameter values, we show that the effect of strain can be changed from completely destructive—in which case a small built-in strain is enough to destroy the topological phase—to a situation where strain becomes an effective tuning parameter which can be used to manipulate Majorana zero modes. These two regimes are accessible by increasing the value of the applied Zeeman field within realistic values. We also study how strain effects are affected by the chemical potential, showing, in particular, how unwanted effects can be minimized. Finally, as a cross-check of the obtained results, we reveal the connection between 1D Majorana zero modes in the zigzag edge and the multiband Berry phase, which serves as a topological invariant of this system.

  20. New coordination polymers from 1D chain, 2D layer to 3D framework constructed from 1,2-phenylenediacetic acid and 1,3-bis(4-pyridyl)propane flexible ligands

    SciTech Connect

    Xin Lingyun; Liu Guangzhen; Wang Liya

    2011-06-15

    The hydrothermal reactions of Cd, Zn, or Cu(II) acetate salts with H{sub 2}PHDA and BPP flexible ligands afford three new coordination polymers, including [Cd(PHDA)(BPP)(H{sub 2}O)]{sub n}(1), [Zn(PHDA)(BPP)]{sub n}(2), and [Cu{sub 2}(PHDA){sub 2}(BPP)]{sub n}(3) (H{sub 2}PHDA=1,2-phenylenediacetic acid, BPP=1,3-bis(4-pyridyl)propane). The single-crystal X-ray diffractions reveal that all three complexes feature various metal carboxylate subunits extended further by the BPP ligands to form a diverse range of structures, displaying a remarked structural sensitivity to metal(II) cation. Complex 1 containing PHDA-bridged binuclear cadmium generates 1D double-stranded chain, complex 2 results in 2D{yields}2D interpenetrated (4,4) grids, and complex 3 displays a 3D self-penetrated framework with 4{sup 8}6{sup 6}8 rob topology. In addition, fluorescent analyses show that both 1 and 2 exhibit intense blue-violet photoluminescence in the solid state. - Graphical Abstract: We show diverse supramolecular frameworks based on the same ligands (PHDA and BPP) and different metal acetate salts including 1D double-stranded chain, 2D {yields} 2D twofold interpenetrated layer, and 3D self-penetration networks. Highlights: > Three metal(II = 2 /* ROMAN ) coordination polymers were synthesized using H{sub 2}PHDA and BPP. > The diversity of structures show a remarked sensitivity to metal(II) center. > Complexes show the enhancement of fluorescence compared to that of free ligand.

  1. Zigzag turning preference of freely crawling cells.

    PubMed

    Yang, Taeseok Daniel; Park, Jin-Sung; Choi, Youngwoon; Choi, Wonshik; Ko, Tae-Wook; Lee, Kyoung J

    2011-01-01

    The coordinated motion of a cell is fundamental to many important biological processes such as development, wound healing, and phagocytosis. For eukaryotic cells, such as amoebae or animal cells, the cell motility is based on crawling and involves a complex set of internal biochemical events. A recent study reported very interesting crawling behavior of single cell amoeba: in the absence of an external cue, free amoebae move randomly with a noisy, yet, discernible sequence of 'run-and-turns' analogous to the 'run-and-tumbles' of swimming bacteria. Interestingly, amoeboid trajectories favor zigzag turns. In other words, the cells bias their crawling by making a turn in the opposite direction to a previous turn. This property enhances the long range directional persistence of the moving trajectories. This study proposes that such a zigzag crawling behavior can be a general property of any crawling cells by demonstrating that 1) microglia, which are the immune cells of the brain, and 2) a simple rule-based model cell, which incorporates the actual biochemistry and mechanics behind cell crawling, both exhibit similar type of crawling behavior. Almost all legged animals walk by alternating their feet. Similarly, all crawling cells appear to move forward by alternating the direction of their movement, even though the regularity and degree of zigzag preference vary from one type to the other.

  2. Boron nitride zigzag nanoribbons: optimal thermoelectric systems.

    PubMed

    Zberecki, K; Swirkowicz, R; Barnaś, J

    2015-09-14

    Conventional and spin related thermoelectric effects in zigzag boron nitride nanoribbons are studied theoretically within the Density Functional Theory (DFT) approach. Nanoribbons with edges passivated with hydrogen, as well as those with bare edges are analyzed. It is shown that one spin channel in the nanoribbons of 0HB-0HN and 2HB-1HN types becomes nonconductive slightly above the Fermi level, and therefore such nanoribbons reveal remarkable spin related thermoelectric phenomena and are promising materials for thermoelectric nanodevices. Thermoelectricity in BN nanoribbons of other types is less efficient and therefore these materials are less interesting for applications.

  3. Zigzag laser with reduced optical distortion

    DOEpatents

    Albrecht, Georg F.; Comaskey, Brian; Sutton, Steven B.

    1994-01-01

    The architecture of the present invention has been driven by the need to solve the beam quality problems inherent in Brewster's angle tipped slab lasers. The entrance and exit faces of a solid state slab laser are cut perpendicular with respect to the pump face, thus intrinsically eliminating distortion caused by the unpumped Brewster's angled faces. For a given zigzag angle, the residual distortions inherent in the remaining unpumped or lightly pumped ends may be reduced further by tailoring the pump intensity at these ends.

  4. Zigzag laser with reduced optical distortion

    DOEpatents

    Albrecht, G.F.; Comaskey, B.; Sutton, S.B.

    1994-04-19

    The architecture of the present invention has been driven by the need to solve the beam quality problems inherent in Brewster's angle tipped slab lasers. The entrance and exit faces of a solid state slab laser are cut perpendicular with respect to the pump face, thus intrinsically eliminating distortion caused by the unpumped Brewster's angled faces. For a given zigzag angle, the residual distortions inherent in the remaining unpumped or lightly pumped ends may be reduced further by tailoring the pump intensity at these ends. 11 figures.

  5. Circular zig-zag scan video format

    SciTech Connect

    Peterson, C.G.; Simmons, C.M.

    1991-03-21

    This invention is comprised of a circular, zig-zag scan for use with vidicon tubes. A sine wave is generated, rectified and its fourth root extracted. The fourth root, and its inverse, are used to generate horizontal ramp and sync signals. The fourth root is also used to generate a vertical sync signal, and the vertical sync signal, along with the horizontal sync signal, are used to generate the vertical ramp signal. Cathode blanking and preamplifier clamp signals are also obtained from the vertical sync signal.

  6. Stability analysis of zigzag boron nitride nanoribbons

    SciTech Connect

    Rai, Hari Mohan Late, Ravikiran; Saxena, Shailendra K.; Kumar, Rajesh; Sagdeo, Pankaj R.; Jaiswal, Neeraj K.; Srivastava, Pankaj

    2015-05-15

    We have explored the structural stability of bare and hydrogenated zigzag boron nitride nanoribbons (ZBNNRs). In order to investigate the structural stability, we calculate the cohesive energy for bare, one-edge and both edges H-terminated ZBNNRs with different widths. It is found that the ZBNNRs with width Nz=8 are energetically more favorable than the lower-width counterparts (Nz<8). Bare ZBNNRs have been found energetically most stable as compared to the edge terminated ribbons. Our analysis reveals that the structural stability is a function of ribbon-width and it is not affected significantly by the type of edge-passivation (one-edge or both-edges)

  7. The electronic transport behavior of hybridized zigzag graphene and boron nitride nanoribbons

    SciTech Connect

    Zhou, Yuhong; Zhang, Jianbing; Miao, Xiangshui; Zhang, Daoli; Ye, Cong

    2014-03-21

    In this present work, we have investigated the electronic transport properties of the hybridized structure constructed by the zigzag graphene and boron-nitride (BN) nanoribbons (Z-B{sub n}N{sub m}C{sub p}, n + m + p = 16) through employing nonequilibrium Green's functions in combination with the density-functional theory. The results demonstrate that the electronic transport properties of the hybridized Z-B{sub n}N{sub m}C{sub p} nanoribbons are strongly dependent on the width of boron-nitride or graphene nanoribbons. When the numbers of n and m are not equal, the negative differential resistance behavior is observed, which can be modulated by varying the width of BN nanoribbons. The conductance of the hybridized Z-B{sub n}N{sub m}C{sub p} nanoribbons with odd numbers of zigzag carbon chains also increases by the width of BN nanoribbons.

  8. Spin current pumped by a rotating magnetic field in zigzag graphene nanoribbons

    NASA Astrophysics Data System (ADS)

    Wang, J.; Chan, K. S.

    2010-10-01

    We study electron spin resonance in zigzag graphene nanoribbons by applying a rotating magnetic field on the system without any bias. By using the nonequilibrium Green's function technique, the spin-resolved pumped current is explicitly derived in a rotating reference frame. The pumped spin current density increases with the system size and the intensity of the transverse rotating magnetic field. For graphene nanoribbons with an even number of zigzag chains, there is a nonzero pumped charge current in addition to the pumped spin current owing to the broken spatial inversion symmetry of the system, but its magnitude is much smaller than the spin current. The short-ranged static disorder from either impurities or defects in the ribbon can depress the spin current greatly due to the localization effect, whereas the long-ranged disorder from charge impurities can avoid inter-valley scattering so that the spin current can survive in the strong disorder for the single-energy mode.

  9. Electric gating induced bandgaps and enhanced Seebeck effect in zigzag bilayer graphene ribbons

    NASA Astrophysics Data System (ADS)

    Vu, Thanh-Tra; Tran, Van-Truong

    2016-08-01

    We theoretically investigate the effect of a transverse electric field generated by side gates and a vertical electric field generated by top/back gates on energy bands and transport properties of zigzag bilayer graphene ribbons (Bernal stacking). Using atomistic tight binding calculations and Green’s function formalism we demonstrate that a bandgap is opened when either field is applied and even enlarged under simultaneous influence of the two fields. Interestingly, although vertical electric fields are widely used to control the bandgap in bilayer graphene, here we show that transverse fields exhibit a more positive effect in terms of modulating a larger range of bandgap and retaining good electrical conductance. The Seebeck effect is also demonstrated to be enhanced strongly—by about 13 times for a zigzag bilayer graphene ribbon with 16 chain lines. These results may motivate new designs of devices made of bilayer graphene ribbons using electric gates.

  10. Charge transport in a zigzag silicene nanoribbon

    NASA Astrophysics Data System (ADS)

    Mehrotra, Nakul; Kumar, Niraj; Sen, Arijit

    2013-02-01

    Nanoscale transport properties of a zigzag silicene nanoribbon (zSiNR) are studied using first-principles calculations based on the non-equilibrium Green's function approach. Our theoretical analysis demonstrates how the scattering wavefunctions in the device region can shed light on the conductance behavior of a nanoelectronic device, made up of 3-zSiNR, spanning the width of three hexagons. The lowering of conductance at 100 mV bias is due mainly to the dominant character of the lowest unoccupied molecular orbital (LUMO) in the transmission profile. A zSiNR, having higher conductance than germanene, can thus be a potential candidate for silicon-based nanoelectronic devices due to its rich optoelectronic properties.

  11. How a zigzag carbon nanotube grows.

    PubMed

    Yuan, Qinghong; Ding, Feng

    2015-05-11

    Owing to the unique structure of zigzag (ZZ) carbon nanotubes (CNTs), their ring-by-ring growth behavior is different from that of chiral or armchair (AC) CNTs, on the rims of which kinks serve as active sites for carbon attachment. Through first-principle calculations, we found that, because of the high energy barrier of initiating a new carbon ring at the rim of a ZZ CNT, the growth rate of a ZZ CNT is proportional to its diameter and significantly (10-1000 times) slower than that of other CNTs. This study successfully explained the broad experimental observation of the lacking of ZZ CNTs in CNT samples and completed the theory of CNT growth.

  12. Crystal orbital study on the double walls made of nanotubes encapsulated inside zigzag carbon nanotubes

    SciTech Connect

    Zhao, Xin; Qiao, Weiye; Li, Yuliang; Huang, Yuanhe

    2015-01-15

    The structure stabilities and electronic properties are investigated by using ab initio self-consistent-field crystal orbital method based on density functional theory for the one-dimensional (1D) double-wall nanotubes made of n-gon SiO{sub 2} nanotubes encapsulated inside zigzag carbon nanotubes. It is found that formation of the combined systems is energetically favorable when the distance between the two constituents is around the Van der Waals scope. The obtained band structures show that all the combined systems are semiconductors with nonzero energy gaps. The frontier energy bands (the highest occupied band and the lowest unoccupied band) of double-wall nanotubes are mainly derived from the corresponding carbon nanotubes. The mobilities of charge carriers are calculated to be within the range of 10{sup 2}–10{sup 4} cm{sup 2} V{sup −1} s{sup −1} for the hybrid double-wall nanotubes. Young’s moduli are also calculated for the combined systems. For the comparison, geometrical and electronic properties of n-gon SiO{sub 2} nanotubes are also calculated and discussed. - Graphical abstract: Structures and band structures of the optimum 1D Double walls nanotubes. The optimized structures are 3-gon SiO2@(15,0), 5-gon SiO2@(17,0), 6-gon SiO2@(18,0) and 7-gon SiO2@(19,0). - Highlights: • The structure and electronic properties of the 1D n-gon SiO{sub 2}@(m,0)s are studied using SCF-CO method. • The encapsulation of 1D n-gon SiO{sub 2} tubes inside zigzag carbon nanotubes can be energetically favorable. • The 1D n-gon SiO{sub 2}@(m,0)s are all semiconductors. • The mobility of charge carriers and Young’s moduli are calculated.

  13. Performance of zigzag corrugated furrows in Bolivia

    NASA Astrophysics Data System (ADS)

    Roldán Cañas, J.; Chipana, R.; Moreno-Pérez, M. F.; Chipana, G.

    2012-04-01

    In Bolivia, irrigation area is estimated in more than 250000 ha, being surface irrigation the most common method. In highland areas (Altiplano) and in interandean valleys, traditional and ancestral irrigation systems such as flood irrigation, contour furrows, zigzag corrugated furrows, suka kollus and irrigation by kanis, are the most important. In the case of very steep terrains and shallow soils, the zigzag corrugated irrigation method is very frequent. This irrigation method has been used for a long time but their low application efficiency and the shortage of water justify this work devoted to their characterization and to study their performance. The experimental study was conducted southeast of the city of La Paz in the community of Cebollino located at 2600 meters above sea level. Furrow characteristics vary in function of crop type and soil slope, so that the larger the slope the greater the separation between furrows. In our case, the crop chosen was the lettuce and the experimental plot had an area of 800 m2 with a slope ranging between 14 and 18%. Blocks of corrugated furrows were identified and experimental measures were made during each irrigation, once per week, in the central blocks to avoid border effects. To determine advance curves 15 stations were used spaced 18 m. At each station, advance and recession time and infiltration depth were measured. Inlet and outlet flow were controlled each 5 min. To calculate the reference evapotranspiration, the Hargraves-Samani equation was used. Due to the very high terrain slopes, the advance curve takes a linear form rather than the typical exponential form. This hinders the proper calculation of the parameters of the Kostiakov-Lewis equation used to determine the infiltrated depth values. The inlet flow range, along irrigation events, between 0.01 and 0.085 L/s due to the uncontrolled use of water in fields located upstream. The large variability of inflow flow difficult irrigation management especially in

  14. Electronic and magnetic properties of armchair and zigzag graphene nanoribbons.

    PubMed

    Owens, Frank J

    2008-05-21

    The electronic properties, band gap, and ionization potential of zigzag and armchair graphene nanoribbons are calculated as a function of the number of carbon atoms in the ribbon employing density functional theory at the B3LYP6-31G* level. In armchair ribbons, the ionization potential and band gap show a gradual decrease with length. For zigzag ribbons, the dependence of the band gap and ionization potential on ribbon length is different depending on whether the ribbon has an unpaired electron or not. It is also found that boron and nitrogen zigzag and armchair doped graphene nanoribbons have a triplet ground state and could be ferromagnetic.

  15. One-dimensional sawtooth and zigzag lattices for ultracold atoms

    PubMed Central

    Zhang, Ting; Jo, Gyu-Boong

    2015-01-01

    We describe tunable optical sawtooth and zigzag lattices for ultracold atoms. Making use of the superlattice generated by commensurate wavelengths of light beams, tunable geometries including zigzag and sawtooth configurations can be realised. We provide an experimentally feasible method to fully control inter- (t) and intra- (t′) unit-cell tunnelling in zigzag and sawtooth lattices. We analyse the conversion of the lattice geometry from zigzag to sawtooth, and show that a nearly flat band is attainable in the sawtooth configuration by means of tuning the lattice parameters. The bandwidth of the first excited band can be reduced up to 2% of the ground bandwidth for a wide range of lattice setting. A nearly flat band available in a tunable sawtooth lattice would offer a versatile platform for the study of interaction-driven quantum many-body states with ultracold atoms. PMID:26530007

  16. Transport properties of zigzag graphene nanoribbon decorated with copper clusters

    SciTech Connect

    Berahman, M.; Sheikhi, M. H.

    2014-09-07

    Using non-equilibrium green function with density functional theory, the present study investigates the transport properties of decorated zigzag graphene nanoribbon with a copper cluster. We have represented the decoration of zigzag graphene nanoribbon with single copper atom and cluster containing two and three copper atoms. In all the cases, copper atoms tend to occupy the edge state. In addition, we have shown that copper can alter the current-voltage characteristic of zigzag graphene nanoribbon and create new fluctuations and negative differential resistance. These alternations are made due to discontinuity in the combination of orbitals along the graphene nanoribbon. Decoration alters these discontinuities and creates more visible fluctuations. However, in low bias voltages, the changes are similar in all the cases. The study demonstrates that in the decorated zigzag graphene nanoribbon, the edge states are the main states for transporting electron from one electrode to another.

  17. Zigzag Assembly of Carbon Nanotubes inside Au Microtrenches.

    PubMed

    Cao, Anyuan; Ajayan, Pulickel M

    2004-05-20

    We report the self-assembly of zigzag patterns consisting of aligned carbon nanotubes inside Au microtrenches by chemical vapor deposition using ferrocene/xylene solution as the precursor. The zigzag nanotubes have uniform size and constant interpattern distance, which can be controlled by simply changing the width of the Au trenches. We demonstrated the tunable length and orientation of nanotubes during self-assembly, leading to a predictable motion of zigzag patterns. A growth model was proposed for the zigzag assembly of nanotubes, including the formation and subsequent splitting of an amorphous carbon layer on the pattern top. Rows of nanotube micropatterns regularly distributed along the Au trench are potential candidates as integrated arrays of thermal or mechanical detectors and actuators.

  18. Zigzag phosphorene nanoribbons: one-dimensional resonant channels in two-dimensional atomic crystals

    PubMed Central

    Páez, Carlos J; Pereira, Ana L C; Schulz, Peter A

    2016-01-01

    We theoretically investigate phosphorene zigzag nanoribbons as a platform for constriction engineering. In the presence of a constriction at one of the edges, quantum confinement of edge-protected states reveals conductance peaks, if the edge is uncoupled from the other edge. If the constriction is narrow enough to promote coupling between edges, it gives rise to Fano-like resonances as well as antiresonances in the transmission spectrum. These effects are shown to mimic an atomic chain like behavior in a two dimensional atomic crystal. PMID:28144546

  19. Unraveling metamaterial properties in zigzag-base folded sheets

    PubMed Central

    Eidini, Maryam; Paulino, Glaucio H.

    2015-01-01

    Creating complex spatial objects from a flat sheet of material using origami folding techniques has attracted attention in science and engineering. In the present work, we use the geometric properties of partially folded zigzag strips to better describe the kinematics of known zigzag/herringbone-base folded sheet metamaterials such as Miura-ori. Inspired by the kinematics of a one–degree of freedom zigzag strip, we introduce a class of cellular folded mechanical metamaterials comprising different scales of zigzag strips. This class of patterns combines origami folding techniques with kirigami. Using analytical and numerical models, we study the key mechanical properties of the folded materials. We show that our class of patterns, by expanding on the design space of Miura-ori, is appropriate for a wide range of applications from mechanical metamaterials to deployable structures at small and large scales. We further show that, depending on the geometry, these materials exhibit either negative or positive in-plane Poisson’s ratios. By introducing a class of zigzag-base materials in the current study, we unify the concept of in-plane Poisson’s ratio for similar materials in the literature and extend it to the class of zigzag-base folded sheet materials. PMID:26601253

  20. Unraveling metamaterial properties in zigzag-base folded sheets.

    PubMed

    Eidini, Maryam; Paulino, Glaucio H

    2015-09-01

    Creating complex spatial objects from a flat sheet of material using origami folding techniques has attracted attention in science and engineering. In the present work, we use the geometric properties of partially folded zigzag strips to better describe the kinematics of known zigzag/herringbone-base folded sheet metamaterials such as Miura-ori. Inspired by the kinematics of a one-degree of freedom zigzag strip, we introduce a class of cellular folded mechanical metamaterials comprising different scales of zigzag strips. This class of patterns combines origami folding techniques with kirigami. Using analytical and numerical models, we study the key mechanical properties of the folded materials. We show that our class of patterns, by expanding on the design space of Miura-ori, is appropriate for a wide range of applications from mechanical metamaterials to deployable structures at small and large scales. We further show that, depending on the geometry, these materials exhibit either negative or positive in-plane Poisson's ratios. By introducing a class of zigzag-base materials in the current study, we unify the concept of in-plane Poisson's ratio for similar materials in the literature and extend it to the class of zigzag-base folded sheet materials.

  1. Encapsulated discrete octameric water cluster, 1D water tape, and 3D water aggregate network in diverse MOFs based on bisimidazolium ligands

    NASA Astrophysics Data System (ADS)

    Shi, Ruo-Bing; Pi, Min; Jiang, Shuang-Shuang; Wang, Yuan-Yuan; Jin, Chuan-Ming

    2014-08-01

    Four new metal-organic frameworks, [Zn(2-mBIM)2(SO3CF3)2·(H2O)4] (1), [Zn(BMIE)(1,4-BDC)]·(H2O)3 (2), [Cd(BIM)2(OH)(H2O)2(PF6)]·(H2O)4 (3), and [Cd(PA-BIM)2 (ClO4)2]·11.33H2O (4) (2-mBIM = bis(2-methylimidazol-1-yl)methane, BMIE = 1,2-bis[1-(2-methylimidazole)-diethoxy]ethane, BIM = bis(imidazol-1-yl)methane, and PA-BIM = 1,1-bis [(2-phenylazo)imidazol-1-yl]methane) have been prepared and structurally characterized. Complex 1 exhibits an infinite 1D cationic beaded-chain structure, which encapsulated discrete octameric water clusters that are comprised of a chair-like hexameric water cluster with two extra water molecules dangling on two diagonal vertices of the chair. Complex 2 forms a 1D infinite zigzag metal-organic chain structure with a 1D T4(0)A(4) water tape. Complexes 3 show a 2D grid-like sheet structure with the 1D water tape T4(0)A(0)2(0) motif. Complex 4 is a porous 3D MOF with tetrahedron-coordinated Cd(II) centers and trans-conformation PA-BIM ligands. These holes are occupied by a fascinating three-dimensional water clathrate network, which consists of cage-shaped structural tetradecameric water cluster (H2O)14 units and six independent bridged water molecules. The results suggest that the bisimidazolium ligands and anions play crucial roles in the formation of the different host structures and different guest water aggregations. Additionally, the thermal stabilities and photoluminescence spectra of the complexes have been discussed.

  2. Magnetic moment and magnetic anisotropy of linear and zigzag 4d and 5d transition metal nanowires: First-principles calculations

    NASA Astrophysics Data System (ADS)

    Tung, J. C.; Guo, G. Y.

    2010-03-01

    An extensive ab initio study of the physical properties of both linear and zigzag atomic chains of all 4d and 5d transition metals (TMs) within the generalized gradient approximation by using the accurate projector-augmented wave method, has been carried out. The atomic structures of equilibrium and metastable states were theoretically determined. All the TM linear chains are found to be unstable against the corresponding zigzag structures. All the TM chains, except Nb, Ag, and La, have a stable (or metastable) magnetic state in either the linear or zigzag or both structures. Magnetic states appear also in the sufficiently stretched Nb and La linear chains and in the largely compressed Y and La chains. The spin magnetic moments in the Mo, Tc, Ru, Rh, W, Re chains could be large (≥1.0μB/atom) . Structural transformation from the linear to zigzag chains could suppress the magnetism already in the linear chain, induce the magnetism in the zigzag structure, and also cause a change in the magnetic state (ferromagnetic to antiferromagnetic or vice verse). The calculations including the spin-orbit coupling reveal that the orbital moments in the Zr, Tc, Ru, Rh, Pd, Hf, Ta, W, Re, Os, Ir, and Pt chains could be rather large (≥0.1μB/atom) . Importantly, large magnetic anisotropy energy (≥1.0meV/atom) is found in most of the magnetic TM chains, suggesting that these nanowires could have fascinating applications in ultrahigh-density magnetic memories and hard disks. In particular, giant magnetic anisotropy energy (≥10.0meV/atom) could appear in the Ru, Re, Rh, and Ir chains. Furthermore, the magnetic anisotropy energy in several elongated linear chains could be as large as 40.0 meV/atom. A spin-reorientation transition occurs in the Ru, Ir, Ta, Zr, La, Ta, and Ir linear chains when they are elongated. Remarkably, all the 5d as well as Tc and Pd chains show the colossal magnetic anisotropy (i.e., it is impossible to rotate magnetization into certain directions

  3. Antiferromagnetic S=1/2 Spin Chain Driven by p-Orbital Ordering in CsO2

    NASA Astrophysics Data System (ADS)

    Riyadi, Syarif; Zhang, Baomin; de Groot, Robert A.; Caretta, Antonio; van Loosdrecht, Paul H. M.; Palstra, Thomas T. M.; Blake, Graeme R.

    2012-05-01

    We demonstrate, using a combination of experiment and density functional theory, that orbital ordering drives the formation of a one-dimensional (1D) S=1/2 antiferromagnetic spin chain in the 3D rocksalt structure of cesium superoxide (CsO2). The magnetic superoxide anion (O2-) exhibits degeneracy of its 2p-derived molecular orbitals, which is lifted by a structural distortion on cooling. A spin chain is then formed by zigzag ordering of the half-filled superoxide orbitals, promoting a superexchange pathway mediated by the pz orbitals of Cs+ along only one crystal direction. This scenario is analogous to the 3d-orbital-driven spin chain found in the perovskite KCuF3 and is the first example of an inorganic quantum spin system with unpaired p electrons.

  4. Iris Segmentation and Normalization Algorithm Based on Zigzag Collarette

    NASA Astrophysics Data System (ADS)

    Rizky Faundra, M.; Ratna Sulistyaningrum, Dwi

    2017-01-01

    In this paper, we proposed iris segmentation and normalization algorithm based on the zigzag collarette. First of all, iris images are processed by using Canny Edge Detection to detect pupil edge, then finding the center and the radius of the pupil with the Hough Transform Circle. Next, isolate important part in iris based zigzag collarette area. Finally, Daugman Rubber Sheet Model applied to get the fixed dimensions or normalization iris by transforming cartesian into polar format and thresholding technique to remove eyelid and eyelash. This experiment will be conducted with a grayscale eye image data taken from a database of iris-Chinese Academy of Sciences Institute of Automation (CASIA). Data iris taken is the data reliable and widely used to study the iris biometrics. The result show that specific threshold level is 0.3 have better accuracy than other, so the present algorithm can be used to segmentation and normalization zigzag collarette with accuracy is 98.88%

  5. A Refined Zigzag Beam Theory for Composite and Sandwich Beams

    NASA Technical Reports Server (NTRS)

    Tessler, Alexander; Sciuva, Marco Di; Gherlone, Marco

    2009-01-01

    A new refined theory for laminated composite and sandwich beams that contains the kinematics of the Timoshenko Beam Theory as a proper baseline subset is presented. This variationally consistent theory is derived from the virtual work principle and employs a novel piecewise linear zigzag function that provides a more realistic representation of the deformation states of transverse-shear flexible beams than other similar theories. This new zigzag function is unique in that it vanishes at the top and bottom bounding surfaces of a beam. The formulation does not enforce continuity of the transverse shear stress across the beam s cross-section, yet is robust. Two major shortcomings that are inherent in the previous zigzag theories, shear-force inconsistency and difficulties in simulating clamped boundary conditions, and that have greatly limited the utility of these previous theories are discussed in detail. An approach that has successfully resolved these shortcomings is presented herein. Exact solutions for simply supported and cantilevered beams subjected to static loads are derived and the improved modelling capability of the new zigzag beam theory is demonstrated. In particular, extensive results for thick beams with highly heterogeneous material lay-ups are discussed and compared with corresponding results obtained from elasticity solutions, two other zigzag theories, and high-fidelity finite element analyses. Comparisons with the baseline Timoshenko Beam Theory are also presented. The comparisons clearly show the improved accuracy of the new, refined zigzag theory presented herein over similar existing theories. This new theory can be readily extended to plate and shell structures, and should be useful for obtaining relatively low-cost, accurate estimates of structural response needed to design an important class of high-performance aerospace structures.

  6. Stiff Monatomic Gold Wires with a Spinning Zigzag Geometry

    SciTech Connect

    Sanchez-Portal, D.; Artacho, E.; Junquera, J.; Soler, J.M.; Ordejon, P.; Garcia, A.

    1999-11-01

    Using first-principles density-functional calculations, gold monatomic wires are found to exhibit a zigzag shape which remains under tension, becoming linear just before breaking. At room temperature they are found to spin, which explains the extremely long apparent interatomic distances shown by electron microscopy. The zigzag structure is stable if the tension is relieved, the wire holding its chainlike shape even as a free-standing cluster. This unexpected metallic-wire stiffness stems from the transverse quantization in the wire, as shown in a simple free electron model. {copyright} {ital 1999} {ital The American Physical Society }

  7. From 1D chain to 3D network: a new family of inorganic-organic hybrid semiconductors MO3(L)(x) (M = Mo, W; L = organic linker) built on perovskite-like structure modules.

    PubMed

    Zhang, Xiao; Hejazi, Mehdi; Thiagarajan, Suraj J; Woerner, William R; Banerjee, Debasis; Emge, Thomas J; Xu, Wenqian; Teat, Simon J; Gong, Qihan; Safari, Ahmad; Yang, Ronggui; Parise, John B; Li, Jing

    2013-11-20

    MO3 (M = Mo, W) or VI-VI binary compounds are important semiconducting oxides that show great promise for a variety of applications. In an effort to tune and enhance their properties in a systematic manner we have applied a designing strategy to deliberately introduce organic linker molecules in these perovskite-like crystal lattices. This approach has led to a wealth of new hybrid structures built on one-dimensional (1D) and two-dimensional (2D) VI-VI modules. The hybrid semiconductors exhibit a number of greatly improved properties and new functionality, including broad band gap tunability, negative thermal expansion, largely reduced thermal conductivity, and significantly enhanced dielectric constant compared to their MO3 parent phases.

  8. Stress Waves and Characteristics of Zigzag and Armchair Silicene Nanoribbons

    PubMed Central

    Fan, Yu-Cheng; Fang, Te-Hua; Chen, Tao-Hsing

    2016-01-01

    The mechanical properties of silicene nanostructures subject to tensile loading were studied via a molecular dynamics (MD) simulation. The effects of temperature on Young’s modulus and the fracture strain of silicene with armchair and zigzag types were examined. The maximum in-plane stress and the corresponding critical strain of the armchair and the zigzag silicene sheets at 300 K were 8.85 and 10.62, and 0.187 and 0.244 N/m, respectively. The in-plane stresses of the silicene sheet in the armchair direction at the temperatures of 300, 400, 500, and 600 K were 8.85, 8.50, 8.26, and 7.79 N/m, respectively. The in-plane stresses of the silicene sheet in the zigzag direction at the temperatures of 300, 400, 500, and 600 K were 10.62, 9.92, 9.64, and 9.27 N/m, respectively. The improved mechanical properties can be calculated in a silicene sheet yielded in the zigzag direction compared with the tensile loading in the armchair direction. The wrinklons and waves were observed at the shear band across the center zone of the silicene sheet. These results provide useful information about the mechanical and fracture behaviors of silicene for engineering applications.

  9. A pure inorganic 1D chain based on {Mo8O28} clusters and Mn(II) ions: [Mn(H2O)2Mo8O28 ] n 6 n -

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaofen; Yan, Yonghong; Wu, Lizhou; Yu, Chengxin; Dong, Xinbo; Hu, Huaiming; Xue, Ganglin

    2016-01-01

    A new pure inorganic polymer, (NH4)6n[Mn(H2O)2Mo8O28)]n(H2O)2n(1), has been synthesized and characterized by elemental analyses, IR spectrum, UV-vis absorption spectra, TG-DSC and electrochemical studies. In 1, [Mo8O28]8- anions act as tetradentate ligands and are alternately linked by Mn(H2O)2 2 + ions into a one-dimensional chain structure. It is interesting that 1 represents the first example of pure inorganic-inorganic hybrid based on octamolybdate and transition metal ions. Moreover, it was indicated that 1 had definite catalytic activities on the probe reaction of benzyl alcohol oxidation to benzaldehyde with H2O2.

  10. Refined Zigzag Theory for Homogeneous, Laminated Composite, and Sandwich Plates: A Homogeneous Limit Methodology for Zigzag Function Selection

    NASA Technical Reports Server (NTRS)

    Tessler, Alexander; DiSciuva, Marco; Gherlone, marco

    2010-01-01

    The Refined Zigzag Theory (RZT) for homogeneous, laminated composite, and sandwich plates is presented from a multi-scale formalism starting with the inplane displacement field expressed as a superposition of coarse and fine contributions. The coarse kinematic field is that of first-order shear-deformation theory, whereas the fine kinematic field has a piecewise-linear zigzag distribution through the thickness. The condition of limiting homogeneity of transverse-shear properties is proposed and yields four distinct sets of zigzag functions. By examining elastostatic solutions for highly heterogeneous sandwich plates, the best-performing zigzag functions are identified. The RZT predictive capabilities to model homogeneous and highly heterogeneous sandwich plates are critically assessed, demonstrating its superior efficiency, accuracy ; and a wide range of applicability. The present theory, which is derived from the virtual work principle, is well-suited for developing computationally efficient CO-continuous finite elements, and is thus appropriate for the analysis and design of high-performance load-bearing aerospace structures.

  11. Width-dependent structural stability and magnetic properties of monolayer zigzag MoS2 nanoribbons

    NASA Astrophysics Data System (ADS)

    Wen, Yan-Ni; Gao, Peng-Fei; Chen, Xi; Xia, Ming-Gang; Zhang, Yang; Zhang, Sheng-Li

    2017-01-01

    First-principles study based on density functional theory has been employed to investigate width-dependent structural stability and magnetic properties of monolayer zigzag MoS2 nanoribbons (ZZ-MoS2 NRs). The width N = 4-6 (the numbers of zigzag Mo-S chains along the ribbon length) are considered. The results show that all studied ZZ-MoS2 NRs are less stable than two-dimensional MoS2 monolayer, exhibiting that a broader width ribbon behaves better structural stability and an inversely proportional relationship between the structural stability (or the ribbon with) and boundary S-Mo interaction. Electronic states imply that all ZZ-MoS2 NRs exhibit magnetic properties, regardless of their widths. Total magnetic moment increases with the increasing width N, which is mainly ascribed to the decreasing S-Mo interaction of the two zigzag edges. In order to confirm this reason, a uniaxial tension strain is applied to ZZ-MoS2 NRs. It has been found that, with the increasing tension strain, the bond length of boundary S-Mo increases, at the same time, the magnetic moment increases also. Our results suggest the rational applications of ZZ-MoS2 NRs in nanoelectronics and spintronics.

  12. Discrete hexamer water clusters and 2D water layer trapped in three luminescent Ag/tetramethylpyrazine/benzene-dicarboxylate hosts: 1D chain, 2D layer and 3D network

    NASA Astrophysics Data System (ADS)

    Mei, Hong-Xin; Zhang, Ting; Huang, Hua-Qi; Huang, Rong-Bin; Zheng, Lan-Sun

    2016-03-01

    Three mix-ligand Ag(I) coordination compounds, namely, {[Ag10(tpyz) 5(L1) 5(H2 O)2].(H2 O)4}n (1, tpyz = 2,3,4,5-tetramethylpyrazine, H2 L1 = phthalic acid), [Ag4(tpyz) 2(L2) 2(H2 O)].(H2 O)5}n (2, H2 L2 = isophthalic acid) {[Ag2(tpyz) 2(L3) (H2 O)4].(H2 O)8}n (3, H2 L3 = terephthalic acid), have been synthesized and characterized by elemental analysis, IR, PXRD and X-ray single-crystal diffraction. 1 exhibits a 2D layer which can be simplified as a (4,4) net. 2 is a 3D network which can be simplified as a (3,3)-connected 2-nodal net with a point symbol of {102.12}{102}. 3 consists of linear [Ag(tpyz) (H2 O)2]n chain. Of particular interest, discrete hexamer water clusters were observed in 1 and 2, while a 2D L10(6) water layer exists in 3. The results suggest that the benzene dicarboxylates play pivotal roles in the formation of the different host architectures as well as different water aggregations. Moreover, thermogravimetric analysis (TGA) and emissive behaviors of these compounds were investigated.

  13. Ab initio characterization of the quantum linear-zigzag transition using density matrix renormalization group calculations

    NASA Astrophysics Data System (ADS)

    Silvi, Pietro; Calarco, Tommaso; Morigi, Giovanna; Montangero, Simone

    2014-03-01

    Ions of the same charge inside confining potentials can form crystalline structures which can be controlled by means of the ion density and of the external trap parameters. In particular, a linear chain of trapped ions exhibits a transition to a zigzag equilibrium configuration, which is controlled by the strength of the transverse confinement. Studying this phase transition in the quantum regime is a challenging problem, even when employing numerical methods to simulate microscopically quantum many-body systems. Here we present a compact analytical treatment to map the original long-range problem into a short-range quantum field theory on a lattice. We provide a complete numerical architecture, based on the density matrix renormalization group, to address the effective quantum ϕ4 model. This technique is instrumental in giving a complete characterization of the phase diagram, as well as pinpointing the universality class of the criticality.

  14. Atomic Structure of Clathrin: A β Propeller Terminal Domain Joins an α Zigzag Linker

    PubMed Central

    ter Haar, Ernst; Musacchio, Andrea; Harrison, Stephen C.; Kirchhausen, Tomas

    2015-01-01

    Summary Clathrin triskelions form the lattice that organizes recruitment of proteins to coated pits and helps drive vesiculation of the lipid bilayer. We report the crystal structure at 2.6 Å resolution of a 55 kDa N-terminal fragment from the 190 kDa clathrin heavy chain. The structure comprises the globular “terminal domain” and the linker that joins it to the end of a triskelion leg. The terminal domain is a seven-blade β propeller, a structure well adapted to interaction with multiple partners, such as the AP-1 and AP-2 sorting adaptor complexes and the nonvisual arrestins. The linker is an α-helical zigzag emanating from the propeller domain. We propose that this simple motif may extend into the rest of the clathrin leg. PMID:9827808

  15. Characteristics of Li diffusion on silicene and zigzag nanoribbon

    NASA Astrophysics Data System (ADS)

    Yan-Hua, Guo; Jue-Xian, Cao; Bo, Xu

    2016-01-01

    We perform a density functional study on the adsorption and diffusion of Li atoms on silicene sheet and zigzag nanoribbons. Our results show that the diffusion energy barrier of Li adatoms on silicene sheet is 0.25 eV, which is much lower than on graphene and Si bulk. The diffusion barriers along the axis of zigzag silicene nanoribbon range from 0.1 to 0.25 eV due to an edge effect, while the diffusion energy barrier is about 0.5 eV for a Li adatom to enter into a silicene nanoribbon. Our calculations indicate that using silicene nanoribbons as anodes is favorable for a Li-ion battery. Project supported by the National Natural Science Foundation of China (Grant Nos. 11074212 and 11204123) and the Natural Science Foundation of Jiangsu province, China (Grant No. BK20130945).

  16. Stiff monatomic gold wires with a spinning zigzag geometry

    NASA Astrophysics Data System (ADS)

    Soler, José M.; Sánchez-Portal, Daniel; Artacho, Emilio; Junquera, Javier; Ordejón, García, Alberto

    2000-03-01

    We have recently studied( D. Sánchez-Portal, E. Artacho, J. Junquera, P. Ordejón, A. Garcí)a, J. Soler, Phys. Rev. Lett 83, 3884 (1999). the structure and elastical properties of gold monatomic wires by means of first principles density functional calculations. The wires are found to exhibit a zigzag shape which remains under tension, becoming linear just before breaking. At room temperature they are found to spin, what explains the extremely long apparent interatomic distances shown by electron microscopy. The zigzag structure is stable if the tension is relieved, the wire holding its chainlike shape even as a free-standing cluster. This unexpected metallic-wire stiffness stems from the transverse quantization in the wire, as shown in a simple free electron model.

  17. Perfect spin filtering effect in ultrasmall helical zigzag graphene nanoribbons

    NASA Astrophysics Data System (ADS)

    Zhang, Zi-Yue

    2017-02-01

    The spin-polarized transport properties of helical zigzag graphene nanoribbons (ZGNRs) are investigated by first-principles calculations. It is found that although all helical ZGNRs have similar density of states and edge states, they show obviously different transport characteristics depending on the curling manners. ZGNRs curled along zigzag orientation exhibit perfect spin filtering effect with a large spin-split gap near the Fermi level, while ZGNRs curled along armchair orientation behave as conventional conductors for both two spin channels. The spin filtering effect will be weakened with the increase of either ribbon width or curling diameter. The results suggest that ultrasmall helical ZGNRs have important potential applications in spintronics and flexible electronics.

  18. Giant edge state splitting at atomically precise graphene zigzag edges

    PubMed Central

    Wang, Shiyong; Talirz, Leopold; Pignedoli, Carlo A.; Feng, Xinliang; Müllen, Klaus; Fasel, Roman; Ruffieux, Pascal

    2016-01-01

    Zigzag edges of graphene nanostructures host localized electronic states that are predicted to be spin-polarized. However, these edge states are highly susceptible to edge roughness and interaction with a supporting substrate, complicating the study of their intrinsic electronic and magnetic structure. Here, we focus on atomically precise graphene nanoribbons whose two short zigzag edges host exactly one localized electron each. Using the tip of a scanning tunnelling microscope, the graphene nanoribbons are transferred from the metallic growth substrate onto insulating islands of NaCl in order to decouple their electronic structure from the metal. The absence of charge transfer and hybridization with the substrate is confirmed by scanning tunnelling spectroscopy, which reveals a pair of occupied/unoccupied edge states. Their large energy splitting of 1.9 eV is in accordance with ab initio many-body perturbation theory calculations and reflects the dominant role of electron–electron interactions in these localized states. PMID:27181701

  19. Nematic liquid crystals on sinusoidal channels: the zigzag instability

    NASA Astrophysics Data System (ADS)

    Silvestre, Nuno M.; Romero-Enrique, Jose M.; Telo da Gama, Margarida M.

    2017-01-01

    Substrates which are chemically or topographically patterned induce a variety of liquid crystal textures. The response of the liquid crystal to competing surface orientations, typical of patterned substrates, is determined by the anisotropy of the elastic constants and the interplay of the relevant lengths scales, such as the correlation length and the surface geometrical parameters. Transitions between different textures, usually with different symmetries, may occur under a wide range of conditions. We use the Landau-de Gennes free energy to investigate the texture of nematics in sinusoidal channels with parallel anchoring bounded by nematic-air interfaces that favour perpendicular (hometropic) anchoring. In micron size channels 5CB was observed to exhibit a non-trivial texture characterized by a disclination line, within the channel, which is broken into a zigzag pattern. Our calculations reveal that when the elastic anisotropy of the nematic does not favour twist distortions the defect is a straight disclination line that runs along the channel, which breaks into a zigzag pattern with a characteristic period, when the twist elastic constant becomes sufficiently small when compared to the splay and bend constants. The transition occurs through a twist instability that drives the defect line to rotate from its original position. The interplay between the energetically favourable twist distortions that induce the defect rotation and the liquid crystal anchoring at the surfaces leads to the zigzag pattern. We investigate in detail the dependence of the periodicity of the zigzag pattern on the geometrical parameters of the sinusoidal channels, which in line with the experimental results is found to be non-linear.

  20. Nematic liquid crystals on sinusoidal channels: the zigzag instability.

    PubMed

    Silvestre, Nuno M; Romero-Enrique, Jose M; Telo da Gama, Margarida M

    2017-01-11

    Substrates which are chemically or topographically patterned induce a variety of liquid crystal textures. The response of the liquid crystal to competing surface orientations, typical of patterned substrates, is determined by the anisotropy of the elastic constants and the interplay of the relevant lengths scales, such as the correlation length and the surface geometrical parameters. Transitions between different textures, usually with different symmetries, may occur under a wide range of conditions. We use the Landau-de Gennes free energy to investigate the texture of nematics in sinusoidal channels with parallel anchoring bounded by nematic-air interfaces that favour perpendicular (hometropic) anchoring. In micron size channels 5CB was observed to exhibit a non-trivial texture characterized by a disclination line, within the channel, which is broken into a zigzag pattern. Our calculations reveal that when the elastic anisotropy of the nematic does not favour twist distortions the defect is a straight disclination line that runs along the channel, which breaks into a zigzag pattern with a characteristic period, when the twist elastic constant becomes sufficiently small when compared to the splay and bend constants. The transition occurs through a twist instability that drives the defect line to rotate from its original position. The interplay between the energetically favourable twist distortions that induce the defect rotation and the liquid crystal anchoring at the surfaces leads to the zigzag pattern. We investigate in detail the dependence of the periodicity of the zigzag pattern on the geometrical parameters of the sinusoidal channels, which in line with the experimental results is found to be non-linear.

  1. Refined Zigzag Theory for Laminated Composite and Sandwich Plates

    NASA Technical Reports Server (NTRS)

    Tessler, Alexander; DiSciuva, Marco; Gherlone, Marco

    2009-01-01

    A refined zigzag theory is presented for laminated-composite and sandwich plates that includes the kinematics of first-order shear deformation theory as its baseline. The theory is variationally consistent and is derived from the virtual work principle. Novel piecewise-linear zigzag functions that provide a more realistic representation of the deformation states of transverse-shear-flexible plates than other similar theories are used. The formulation does not enforce full continuity of the transverse shear stresses across the plate s thickness, yet is robust. Transverse-shear correction factors are not required to yield accurate results. The theory is devoid of the shortcomings inherent in the previous zigzag theories including shear-force inconsistency and difficulties in simulating clamped boundary conditions, which have greatly limited the accuracy of these theories. This new theory requires only C(sup 0)-continuous kinematic approximations and is perfectly suited for developing computationally efficient finite elements. The theory should be useful for obtaining relatively efficient, accurate estimates of structural response needed to design high-performance load-bearing aerospace structures.

  2. Contact wire zigzag value detection in the electrified railway

    NASA Astrophysics Data System (ADS)

    Gao, Xiaorong

    2001-05-01

    One of the main reasons for result the pantograph-catenary system fault in electrified railway is the contact wire zigzag value exceeding quota. In this paper, an infrared LED based photoelectric detecting system which is directly installed in the electric locomotives is presented and the method of dynamic measuring of the contact wire bias is realized. The system designed which consists of IR-LED and corresponding photo-detectors, encoder, signal transmission channel insulating from high to low voltage side, decoder and data processing device is described in details. It is shown that the zigzag value examining sensors are mounted on the head of pantograph, each neighbor unit get interval distance of 10 mm and there are 120 units altogether. The signals are output when the overhead line slipping over the slide's surface of the pantograph. The experimental results of the zigzag value obtained from the field test are reported and it has been practically proved that measuring error < 0.5%. The results are of important significance for the dynamic performance analysis as well as fault diagnosis for the pantograph- catenary system.

  3. Severe Hypertriglyceridemia in Glut1D on Ketogenic Diet.

    PubMed

    Klepper, Joerg; Leiendecker, Baerbel; Heussinger, Nicole; Lausch, Ekkehart; Bosch, Friedrich

    2016-04-01

    High-fat ketogenic diets are the only treatment available for Glut1 deficiency (Glut1D). Here, we describe an 8-year-old girl with classical Glut1D responsive to a 3:1 ketogenic diet and ethosuximide. After 3 years on the diet a gradual increase of blood lipids was followed by rapid, severe asymptomatic hypertriglyceridemia (1,910 mg/dL). Serum lipid apheresis was required to determine liver, renal, and pancreatic function. A combination of medium chain triglyceride-oil and a reduction of the ketogenic diet to 1:1 ratio normalized triglyceride levels within days but triggered severe myoclonic seizures requiring comedication with sultiam. Severe hypertriglyceridemia in children with Glut1D on ketogenic diets may be underdiagnosed and harmful. In contrast to congenital hypertriglyceridemias, children with Glut1D may be treated effectively by dietary adjustments alone.

  4. Parity conservation in electron-phonon scattering in zigzag graphene nanoribbon

    SciTech Connect

    Chu, Yanbiao; Gautreau, Pierre; Basaran, Cemal

    2014-09-15

    In contrast with carbon nanotubes, the absence of translational symmetry (or periodical boundary condition) in the restricted direction of zigzag graphene nanoribbon removes the selection rule of subband number conservation. However, zigzag graphene nanoribbons with even dimers do have the inversion symmetry. We, therefore, propose a selection rule of parity conservation for electron-phonon interactions. The electron-phonon scattering matrix in zigzag graphene nanoribbons is developed using the tight-binging model within the deformation potential approximation.

  5. Parity conservation in electron-phonon scattering in zigzag graphene nanoribbon

    NASA Astrophysics Data System (ADS)

    Chu, Yanbiao; Gautreau, Pierre; Basaran, Cemal

    2014-09-01

    In contrast with carbon nanotubes, the absence of translational symmetry (or periodical boundary condition) in the restricted direction of zigzag graphene nanoribbon removes the selection rule of subband number conservation. However, zigzag graphene nanoribbons with even dimers do have the inversion symmetry. We, therefore, propose a selection rule of parity conservation for electron-phonon interactions. The electron-phonon scattering matrix in zigzag graphene nanoribbons is developed using the tight-binging model within the deformation potential approximation.

  6. Optimizing the thermoelectric performance of zigzag and chiral carbon nanotubes

    PubMed Central

    2012-01-01

    Using nonequilibrium molecular dynamics simulations and nonequilibrium Green's function method, we investigate the thermoelectric properties of a series of zigzag and chiral carbon nanotubes which exhibit interesting diameter and chirality dependence. Our calculated results indicate that these carbon nanotubes could have higher ZT values at appropriate carrier concentration and operating temperature. Moreover, their thermoelectric performance can be significantly enhanced via isotope substitution, isoelectronic impurities, and hydrogen adsorption. It is thus reasonable to expect that carbon nanotubes may be promising candidates for high-performance thermoelectric materials. PMID:22325623

  7. Catalytic Performance of a New 1D Cu(II) Coordination Polymer {Cu(NO₃)(H₂O)}(HTae)(4,4'-Bpy) for Knoevenagel Condensation.

    PubMed

    Larrea, Edurne S; Fernández de Luis, Roberto; Arriortua, María I

    2016-12-01

    The {Cu(NO₃)(H₂O)}(HTae)(4,4'-Bpy) (H₂Tae = 1,1,2,2-tetraacetylethane, 4,4'-Bpy = 4,4'-Dipyridyl) 1D coordination polymer has been obtained by slow evaporation. The crystal structure consists of parallel and oblique {Cu(HTae)(4,4'-Bpy)} zig-zag metal-organic chains stacked along the [100] crystallographic direction. Copper(II) ions are in octahedral coordination environment linked to two nitrogen atoms of two bridging 4,4'-Bpy and to two oxygen atoms of one HTae molecule in the equatorial plane. The occupation of the axial positions varies from one copper atom to another, with different combinations of water molecules and nitrate anions, giving rise to a commensurate super-structure. By means of the thermal removal of water molecules, copper coordinatively unsaturated centres are obtained. These open metal sites could act as Lewis acid active sites in several heterogeneous catalytic reactions. The dehydrated compound, CuHTaeBpy_HT, has been tested as a heterogeneous recoverable catalyst for Knoevenagel condensation reactions. The catalyst is active and heterogeneous for the condensation of aldehydes with malononitrile at 60 °C using a molar ratio catalyst:substrate of 3 % and toluene as solvent. The catalyst suffers a partial loss of activity when reusing it, but can be reused at least four times.

  8. Formation of helical ion chains

    NASA Astrophysics Data System (ADS)

    Nigmatullin, R.; del Campo, A.; De Chiara, G.; Morigi, G.; Plenio, M. B.; Retzker, A.

    2016-01-01

    We study the nonequilibrium dynamics of the linear-to-zigzag structural phase transition exhibited by an ion chain confined in a trap with periodic boundary conditions. The transition is driven by reducing the transverse confinement at a finite quench rate, which can be accurately controlled. This results in the formation of zigzag domains oriented along different transverse planes. The twists between different domains can be stabilized by the topology of the trap, and under laser cooling the system has a chance to relax to a helical chain with nonzero winding number. Molecular dynamics simulations are used to obtain a large sample of possible trajectories for different quench rates. The scaling of the average winding number with different quench rates is compared to the prediction of the Kibble-Zurek theory, and a good quantitative agreement is found.

  9. Tuning Charge and Spin Excitations in Zigzag Edge Nanographene Ribbons

    PubMed Central

    Dutta, Sudipta; Wakabayashi, Katsunori

    2012-01-01

    Graphene and its quasi-one-dimensional counterpart, graphene nanoribbons, present an ideal platform for tweaking their unique electronic, magnetic and mechanical properties by various means for potential next-generation device applications. However, such tweaking requires knowledge of the electron-electron interactions that play a crucial role in these confined geometries. Here, we have investigated the magnetic and conducting properties of zigzag edge graphene nanoribbons (ZGNRs) using the many-body configuration interaction (CI) method on the basis of the Hubbard Hamiltonian. For the half-filled case, the many-body ground state shows a ferromagnetic spin-spin correlation along the zigzag edge, which supports the picture obtained from one-electron theory. However, hole doping reduces the spin and charge excitation gap, making the ground state conducting and magnetic. We also provide a two-state model that explains the low-lying charge and spin excitation spectrum of ZGNRs. An experimental setup to confirm the hole-mediated conducting and magnetic states is discussed. PMID:22816042

  10. Unusual electronic properties of clean and disordered zigzag graphene nanoribbons.

    PubMed

    Luck, J M; Avishai, Y

    2015-01-21

    We revisit the problem of electron transport in clean and disordered zigzag graphene nanoribbons, and expose numerous hitherto unknown peculiar properties of these systems at zero energy, where both sublattices decouple because of chiral symmetry. For clean ribbons, we give a quantitative description of the unusual power-law dispersion of the central energy bands and of its main consequences, including the strong divergence of the density of states near zero energy, and the vanishing of the transverse localization length of the corresponding edge states. In the presence of off-diagonal disorder, which respects the lattice chiral symmetry, all zero-energy localization properties are found to be anomalous. Recasting the problem in terms of coupled Brownian motions enables us to derive numerous asymptotic results by analytical means. In particular the typical conductance gN of a disordered sample of width N and length L is shown to decay as exp(-CNw√L), for arbitrary values of the disorder strength w, while the relative variance of ln gN approaches a non-trivial constant KN. The dependence of the constants CN and KN on the ribbon width N is predicted. From the mere viewpoint of the transfer-matrix formalism, zigzag ribbons provide a case study with many unusual features. The transfer matrix describing propagation through one unit cell of a clean ribbon is not diagonalizable at zero energy. In the disordered case, we encounter non-trivial random matrix products such that all Lyapunov exponents vanish identically.

  11. Crystal orbital study on the double walls made of nanotubes encapsulated inside zigzag carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Zhao, Xin; Qiao, Weiye; Li, Yuliang; Huang, Yuanhe

    2015-01-01

    The structure stabilities and electronic properties are investigated by using ab initio self-consistent-field crystal orbital method based on density functional theory for the one-dimensional (1D) double-wall nanotubes made of n-gon SiO2 nanotubes encapsulated inside zigzag carbon nanotubes. It is found that formation of the combined systems is energetically favorable when the distance between the two constituents is around the Van der Waals scope. The obtained band structures show that all the combined systems are semiconductors with nonzero energy gaps. The frontier energy bands (the highest occupied band and the lowest unoccupied band) of double-wall nanotubes are mainly derived from the corresponding carbon nanotubes. The mobilities of charge carriers are calculated to be within the range of 102-104 cm2 V-1 s-1 for the hybrid double-wall nanotubes. Young's moduli are also calculated for the combined systems. For the comparison, geometrical and electronic properties of n-gon SiO2 nanotubes are also calculated and discussed.

  12. Enhanced Li Adsorption and Diffusion on MoS2 Zigzag Nanoribbons by Edge Effects: A Computational Study.

    PubMed

    Li, Yafei; Wu, Dihua; Zhou, Zhen; Cabrera, Carlos R; Chen, Zhongfang

    2012-08-16

    By means of density functional theory computations, we systematically investigated the adsorption and diffusion of Li on the 2-D MoS2 nanosheets and 1-D zigzag MoS2 nanoribbons (ZMoS2NRs), in comparison with MoS2 bulk. Although the Li mobility can be significantly facilitated in MoS2 nanosheets, their decreased Li binding energies make them less attractive for cathode applications. Because of the presence of unique edge states, ZMoS2NRs have a remarkably enhanced binding interaction with Li without sacrificing the Li mobility, and thus are promising as cathode materials of Li-ion batteries with a high power density and fast charge/discharge rates.

  13. Energy band modulation of graphane by hydrogen-vacancy chains: A first-principles study

    SciTech Connect

    Wu, Bi-Ru; Yang, Chih-Kai

    2014-08-15

    We investigated a variety of configurations of hydrogen-vacancy chains in graphane by first-principles density functional calculation. We found that graphane with two zigzag H-vacancy chains segregated by one or more H chain is generally a nonmagnetic conductor or has a negligible band gap. However, the same structure is turned into a semiconductor and generates a magnetic moment if either one or both of the vacancy chains are blocked by isolated H atoms. If H-vacancy chains are continuously distributed, the structure is similar to a zigzag graphene nanoribbon embedded in graphane. It was also found that the embedded zigzag graphene nanoribbon is antiferromagnetic, and isolated H atoms left in the 2-chain nanoribbon can tune the band gap and generate net magnetic moments. Similar effects are also obtained if bare carbon atoms are present outside the nanoribbon. These results are useful for designing graphene-based nanoelectronic circuits.

  14. Fracture resistance of zigzag single walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Lu, Qiang; Bhattacharya, Baidurya

    2006-03-01

    Carbon nanotubes (CNTs) are known to possess extraordinary strength, stiffness and ductility properties. Their fracture resistance is an important issue from the perspective of durability and reliability of CNT-based materials and devices. According to existing studies, brittle fracture is one of the important failure modes of single-walled carbon nanotube (SWNT) failure due to mechanical loading. However, based on the authors' knowledge, the fracture resistance of CNTs has not been quantified so far. In this paper, the fracture resistance of zigzag SWNTs with preexisting defects is calculated using fracture mechanics concepts based on atomistic simulations. The interatomic forces are modelled with a modified Morse potential; the Anderson thermostat is used for temperature control. The problem of unstable crack growth at finite temperature, presumably caused by the lattice trapping effect, is circumvented by computing the strain energy release rate through a series of displacement-controlled tensile loading of SWNTs (applied through moving the outermost layer of atoms at one end at constant strain rate of 9.4 × 10-4 ps-1) with pre-existing crack-like defects of various lengths. The strain energy release rate, G, is computed for (17, 0), (28, 0) and (35, 0) SWNTs (each with aspect ratio 4) with pre-existing cracks up to 29.5 Å long. The fracture resistance, Gc, is determined as a function of crack length for each tube at three different temperatures (1, 300 and 500 K). A significant dependence of Gc on crack length is observed, reminiscent of the rising R curve behaviour of metals at the macroscale: for the zigzag nanotubes Gc increases with crack length at small length, and tends to reach a constant value if the tube diameter is large enough. We suspect that the lattice trapping effect plays the role of crack tip plasticity at the atomic scale. For example, at 300 K, Gc for the (35, 0) tube with aspect ratio 4 converges to 6 J m-2 as the crack length exceeds 20

  15. Modified Heisenberg model for the zig-zag structure in multiferroic RMn{sub 2}O{sub 5}

    SciTech Connect

    Bahoosh, Safa Golrokh; Wesselinowa, Julia M.; Trimper, Steffen

    2015-08-28

    The class of RMn{sub 2}O{sub 5} (R = Ho, Tb, Y, Eu) compounds offers multiferroic properties where the refined magnetic zig-zag order breaks the inversion symmetry. Varying the temperature, the system undergoes a magnetic and a subsequent ferroelectric phase transition where the ferroelectricity is magnetically induced. We propose a modified anisotropic Heisenberg model that can be used as a tractable analytical model studying the properties of those antiferromagnetic zig-zag spin chains. Based on a finite temperature Green's function method, it is shown that the polarization is induced solely by different exchange couplings of the two different Mn{sup 4+} and Mn{sup 3+} magnetic ions. We calculate the excitation energy of the spin system for finite temperatures, which for its part determines the temperature dependent magnetization and polarization. The ferroelectric phase transition is manifested as a kink in the excitation energy. The variation of the polarization by an external magnetic field depends strongly on the direction of that field. Whereas, the polarization in b-direction increases with an external magnetic field as well in b-direction it can be switched for strong fields in a-direction. The results based on that modified Heisenberg model are in qualitative agreement with experimental data.

  16. Even-odd effect on the edge states for zigzag phosphorene nanoribbons under a perpendicular electric field

    NASA Astrophysics Data System (ADS)

    Zhou, Benliang; Zhou, Benhu; Zhou, Xiaoying; Zhou, Guanghui

    2017-02-01

    We study the variation of electronic property for zigzag-edge phosphorene nanoribbons (ZPNRs) under a perpendicular electric field (PEF). Using the tight-binding Hamiltonian combined with the surface lattice Green’s function (GF) approach, we show that the response of edge states to PEF for a N-ZPNR with even- or odd-N (number of zigzag chains) is qualitatively different. The field opens a gap between two edge bands near the Fermi energy for even-N ribbons, but for odd-N ones where the two edge bands are always nearly degenerated. This difference is originally from that the Stark-effect-induced energies at the upper and lower edges for even- and odd-N ZPNRs are different due to the peculiar lattice structure of phosphorene. In consequence, the electronic densities are more localized at the edges driven by the field for even-N ZPNRs but not for odd-N ones. This even-odd effect is also reflected in conductance, which indicates that the odd-N ZPNRs may be more suitable for the usage of field-effect transistor.

  17. Magneto-electronic and optical properties of zigzag silicene nanoribbons

    NASA Astrophysics Data System (ADS)

    Shyu, Feng-Lin

    2017-03-01

    The tight-binding model including the spin-orbit coupling (SOC) is used to study electronic and optical properties of zigzag silicene nanoribbons (ZSiNRs) in magnetic and electric fields. The SOC affects the low-energy bands and induces new selection rules leading to richer optical spectra. Except an increase in bandgaps, perpendicular magnetic field further exhibits spin-polarized Landau levels, in which electron's probability density of band-edge states distributes like a standing-wave. Landau levels could enhance the DOS and increases absorption frequency and strength. Perpendicular electric field (Fz) increases bandgap and thus absorption frequency, but it does not change band symmetry, edge-states, and selection rules. Moreover, Fz enhances the split of spin-polarized states inducing more absorption peaks. Parallel electric field (Fx) leads to an overlap between conduction and valence bands and destroys band symmetry and Landau levels. Consequently, Fx exhibits new selection rules and enriches absorption spectra.

  18. Zig-zag twins and helical phase transformations.

    PubMed

    Ganor, Yaniv; Dumitrică, Traian; Feng, Fan; James, Richard D

    2016-04-28

    We demonstrate the large bending deformation induced by an array of permanent magnets (applied field ∼0.02 T) designed to minimize poles in the bent state of the crystal. Planar cantilevers of NiMnGa (5M modulated martensite) ferromagnetic shape memory alloy deform into an arched shape according to theory, with a zig-zag microstructure that complies with the kinematic and magnetic compatibility between adjacent twin variants. A general theory of bent and twisted states is given, applicable to both twinning and austenite/martensite transformations. Some of these configurations achieve order-of-magnitude amplification of rotation and axial strain. We investigate also atomistic analogues of these bent and twisted configurations with perfect interfaces between phases. These mechanisms of large deformation, induced by small magnetic fields or temperature changes, have potential application to the development of new actuation technologies for micro-robotic systems.

  19. Towards intrinsic magnetism of graphene sheets with irregular zigzag edges.

    PubMed

    Chen, Lianlian; Guo, Liwei; Li, Zhilin; Zhang, Han; Lin, Jingjing; Huang, Jiao; Jin, Shifeng; Chen, Xiaolong

    2013-01-01

    The magnetism of graphene has remained divergent and controversial due to absence of reliable experimental results. Here we show the intrinsic magnetism of graphene edge states revealed based on unidirectional aligned graphene sheets derived from completely carbonized SiC crystals. It is found that ferromagnetism, antiferromagnetism and diamagnetism along with a probable superconductivity exist in the graphene with irregular zigzag edges. A phase diagram is constructed to show the evolution of the magnetism. The ferromagnetic ordering curie-temperature of the fundamental magnetic order unit (FMOU) is 820 ± 80 K. The antiferromagnetic ordering Neel temperature of the FMOUs belonging to different sublattices is about 54 ± 2 K. The diamagnetism is similar to that of graphite and can be well described by the Kotosonov's equation. Our experimental results provide new evidences to clarify the controversial experimental phenomena observed in graphene and contribute to a deeper insight into the nature of magnetism in graphene based system.

  20. Novel Design for Centrifugal Countercurrent Chromatography: I. Zigzag Toroidal Column

    PubMed Central

    Yang, Yi; Aisa, Haji Akber; Ito, Yoichiro

    2009-01-01

    The toroidal coil using an equilateral triangular core has improved both retention of the stationary phase and peak resolution of the conventional toroidal coil in centrifugal countercurrent chromatography. To further improve the retention of stationary phase and peak resolution, a novel zigzag toroidal coil was designed and the performance of the system was evaluated at various flow rates. The results indicated that both retention of stationary phase and peak resolution were improved as the flow rate was decreased. Modification of the tubing by pressing at given intervals with a pair of pliers improved the peak resolution without increasing the column pressure. All these separations were performed under low column pressure indicating the separation can be further improved by increasing the column length and/or revolution speed without damaging the separation column. PMID:20046954

  1. Magnetic edge-state excitons in zigzag graphene nanoribbons.

    PubMed

    Yang, Li; Cohen, Marvin L; Louie, Steven G

    2008-10-31

    We present first-principles calculations of the optical properties of zigzag-edged graphene nanoribbons (ZGNRs) employing the GW-Bethe-Salpeter equation approach with the spin interaction included. Optical response of the ZGNRs is found to be dominated by magnetic edge-state-derived excitons with large binding energy. The absorption spectrum is composed of a characteristic series of exciton states, providing a possible signature for identifying the ZGNRs. The edge-state excitons are charge-transfer excitations with the excited electron and hole located on opposite edges; they moreover induce a spin transfer across the ribbon, resulting in a photoreduction of the magnetic ordering. These novel characteristics are potentially useful in the applications.

  2. The opposite induced magnetic moment in narrow zigzag graphene nanoribbons

    NASA Astrophysics Data System (ADS)

    Liu, Hong; Hu, Bian; Liu, Na

    2016-11-01

    Based on the analysis of band structure and edge states on zigzag graphene nanoribbons (ZGNRs), we can study theoretically the origination of two minimal quantum conductance. At the two energy points - 0.20 eV and 0.15 eV corresponding to the two dips of quantum conductance, the spin-polarized quantum conductance is about 45%. Furthermore, the two types of edge-localized carriers in the opposite transport directions along the two opposite edge sides form the quantum internal loop current, which can generate one big magnetic moment. At these two energy points - 0.17 eV and 0.15 eV the two induced magnetic moments are in opposite signals.

  3. Evaluation of zigzag furrow irrigation in Andean communities

    NASA Astrophysics Data System (ADS)

    Roldán Cañas, José; Chipana, Gladys; Chipana, René; Fátima Moreno Pérez, María

    2014-05-01

    It is estimated that the area under irrigation in Bolivia represents 9.7% of the cultivated area, ie 253,100 ha. Traditional surface irrigation is the main system used in Bolivia. Currently, 40,000 ha are irrigated in the La Paz Department. The largest irrigated surface and the areas that produce most food in the Department are located in the eastern and western mountain ranges. However, the region's abrupt terrain makes it impossible to use conventional surface irrigation methods. . As a result, farmers in the inter-Andean valleys have used other surface irrigation methods intensively for hundreds of years like zigzag furrow. In this study, we conducted field trials in the rural community of Cebollullo of the municipality of Palca of La Paz Department. Cebollullo is located at an altitude of 2,780 m above sea level. Its geographic coordinates are 16°41'90.1"S to 16°43'12"S latitude and 67°52'13"W to 67°59'15"W longitude. The irrigated area is characterized by its steep slopes and zigzag corrugated furrow irrigation method is used. The main objective of this study is to evaluate the performance of zigzag furrow irrigation in this community. The study plot has an area of 728 m2 and the average slope is 16.46%. For irrigation evaluation, the data of a middle furrow were taken to avoid boundary effects. Irrigation events recorded during the crop development were 21, with irrigation frequency of 2 to 3 days, of which 10 events were evaluated weekly. Due to the low flow rates used for irrigation, the inflow and outflow measurement of the furrows was made volumetrically. These flow measurements were made at five-minute intervals during irrigation. The zigzag corrugated irrigation method uses low flow discharges in order to decrease the rate of irrigation allowing infiltration of required volume by the crops and reducing soil erosion. Application efficiencies in the study plot ranged between 7.55% and 30.31%, with losses by surface runoff from 45.90% to 85.83% and

  4. Zigzag stacks and m-regular linear stacks.

    PubMed

    Chen, William Y C; Guo, Qiang-Hui; Sun, Lisa H; Wang, Jian

    2014-12-01

    The contact map of a protein fold is a graph that represents the patterns of contacts in the fold. It is known that the contact map can be decomposed into stacks and queues. RNA secondary structures are special stacks in which the degree of each vertex is at most one and each arc has length of at least two. Waterman and Smith derived a formula for the number of RNA secondary structures of length n with exactly k arcs. Höner zu Siederdissen et al. developed a folding algorithm for extended RNA secondary structures in which each vertex has maximum degree two. An equation for the generating function of extended RNA secondary structures was obtained by Müller and Nebel by using a context-free grammar approach, which leads to an asymptotic formula. In this article, we consider m-regular linear stacks, where each arc has length at least m and the degree of each vertex is bounded by two. Extended RNA secondary structures are exactly 2-regular linear stacks. For any m ≥ 2, we obtain an equation for the generating function of the m-regular linear stacks. For given m, we deduce a recurrence relation and an asymptotic formula for the number of m-regular linear stacks on n vertices. To establish the equation, we use the reduction operation of Chen, Deng, and Du to transform an m-regular linear stack to an m-reduced zigzag (or alternating) stack. Then we find an equation for m-reduced zigzag stacks leading to an equation for m-regular linear stacks.

  5. Ground states of the Ising model on an anisotropic triangular lattice: stripes and zigzags.

    PubMed

    Dublenych, Yu I

    2013-10-09

    A complete solution of the ground-state problem for the Ising model on an anisotropic triangular lattice with the nearest-neighbor interactions in a magnetic field is presented. It is shown that this problem can be reduced to the ground-state problem for an infinite chain with the interactions up to the second neighbors. In addition to the known ground-state structures (which correspond to full-dimensional regions in the parameter space of the model), new structures are found (at the boundaries of these regions), in particular, zigzagging stripes similar to those observed experimentally in colloidal monolayers. Though the number of parameters is relatively large (four), all the ground-state structures of the model are constructed and analyzed and therefore the paper can be considered as an example of a complete solution of a ground-state problem for classical spin or lattice-gas models. The paper can also help to verify the correctness of some results obtained previously by other authors and concerning the ground states of the model under consideration.

  6. Dual-channel current valve in a three terminal zigzag graphene nanoribbon junction

    NASA Astrophysics Data System (ADS)

    Zhang, L.

    2017-02-01

    We theoretically propose a dual-channel current valve based on a three terminal zigzag graphene nanoribbon (ZGNR) junction driven by three asymmetric time-dependent pumping potentials. By means of the Keldysh Green’s function method, we show that two asymmetric charge currents can be pumped in the different left-right terminals of the device at a zero bias, which mainly stems from the single photon-assisted pumping approximation and the valley valve effect in a ZGNR p-n junction. The ON and OFF states of pumped charge currents are crucially dependent on the even-odd chain widths of the three electrodes, the pumping frequency, the lattice potential and the Fermi level. Two-tunneling spin valves are also considered to spatially separate and detect 100% polarized spin currents owing to the combined spin pump effect and the valley selective transport in a three terminal ZGNR ferromagnetic junction. Our investigations might be helpful to control the spatial and spin degrees of freedom of electrons in graphene pumping devices.

  7. Dual-channel current valve in a three terminal zigzag graphene nanoribbon junction.

    PubMed

    Zhang, L

    2017-02-08

    We theoretically propose a dual-channel current valve based on a three terminal zigzag graphene nanoribbon (ZGNR) junction driven by three asymmetric time-dependent pumping potentials. By means of the Keldysh Green's function method, we show that two asymmetric charge currents can be pumped in the different left-right terminals of the device at a zero bias, which mainly stems from the single photon-assisted pumping approximation and the valley valve effect in a ZGNR p-n junction. The ON and OFF states of pumped charge currents are crucially dependent on the even-odd chain widths of the three electrodes, the pumping frequency, the lattice potential and the Fermi level. Two-tunneling spin valves are also considered to spatially separate and detect 100% polarized spin currents owing to the combined spin pump effect and the valley selective transport in a three terminal ZGNR ferromagnetic junction. Our investigations might be helpful to control the spatial and spin degrees of freedom of electrons in graphene pumping devices.

  8. A rational route to SCM materials based on a 1-D cobalt selenocyanato coordination polymer.

    PubMed

    Boeckmann, Jan; Näther, Christian

    2011-07-07

    Thermal annealing of a discrete complex with terminal SeCN anions and monodentate coligands enforces the formation of a 1D cobalt selenocyanato coordination polymer that shows slow relaxation of the magnetization. Therefore, this approach offers a rational route to 1D materials that might show single chain magnetic behaviour.

  9. Electronic, bonding, and optical properties of 1d [CuCN]n (n = 1-10) chains, 2d [CuCN]n (n = 2-10) nanorings, and 3d [Cun (CN)n ]m (n = 4, m = 2, 3; n = 10, m = 2) tubes studied by DFT/TD-DFT methods.

    PubMed

    Tsipis, Athanassios C; Stalikas, Alexandros V

    2015-06-30

    The electronic, bonding, and photophysical properties of one-dimensional [CuCN](n) (n = 1-10) chains, 2-D [CuCN](n) (n = 2-10) nanorings, and 3-D [Cu(n)(CN)(n)](m) (n = 4, m = 2, 3; n = 10, m = 2) tubes are investigated by means of a multitude of computational methodologies using density functional theory (DFT) and time-dependent-density-functional theory (TD-DFT) methods. The calculations revealed that the 2-D [CuCN](n) (n = 2-10) nanorings are more stable than the respective 1-D [CuCN](n) (n = 2-10) linear chains. The 2-D [CuCN](n) (n = 2-10) nanorings are predicted to form 3-D [Cun (CN)(n)](m) (n = 4, m = 2, 3; n = 10, m = 2) tubes supported by weak stacking interactions, which are clearly visualized as broad regions in real space by the 3D plots of the reduced density gradient. The bonding mechanism in the 1-D [CuCN](n) (n = 1-10) chains, 2-D [CuCN](n) (n = 2-10) nanorings, and 3-D [Cu(n)(CN)(n)](m) (n = 4, m = 2, 3; n = 10, m = 2) tubes are easily recognized by a multitude of electronic structure calculation approaches. Particular emphasis was given on the photophysical properties (absorption and emission spectra) of the [CuCN](n) chains, nanorings, and tubes which were simulated by TD-DFT calculations. The absorption and emission bands in the simulated TD-DFT absorption and emission spectra have thoroughly been analyzed and assignments of the contributing principal electronic transitions associated to individual excitations have been made.

  10. Optimization of the nanotwin-induced zigzag surface of copper by electromigration.

    PubMed

    Chen, Hsin-Ping; Huang, Chun-Wei; Wang, Chun-Wen; Wu, Wen-Wei; Liao, Chien-Neng; Chen, Lih-Juann; Tu, King-Ning

    2016-02-07

    By adding nanotwins to Cu, the surface electromigration (EM) slows down. The atomic mobility of the surface step-edges is retarded by the triple points where a twin meets a free surface to form a zigzag-type surface. We observed that EM can alter the zigzag surface structure to optimize the reduction of EM, according to Le Chatelier's principle. Statistically, the optimal alternation is to change an arbitrary (111)/(hkl) zigzag pair to a pair having a very low index (hkl) plane, especially the (200) plane. Using in situ ultrahigh vacuum and high-resolution transmission electron microscopy, we examined the effects of different zigzag surfaces on the rate of EM. The calculated rate of surface EM can be decreased by a factor of ten.

  11. Optical properties of two-dimensional zigzag and armchair graphyne nanoribbon semiconductor.

    PubMed

    Asadpour, Mohamad; Jafari, Mahmoud; Asadpour, Milad; Jafari, Maryam

    2015-03-15

    Optical properties of zigzag and armchair graphyne nanoribbon (GNR) sheet were investigated. Effect of increasing the width of nanoribbon on optical properties and optical band gap in particular was also studied. Calculations were based on density functional theory (DFT) and the results showed that these structures were semiconductors with the optical band gap of about 1-3.5 eV; this value was higher than for the armchair than zigzag structures. With increasing the width of the ribbons, optical band gap decreased in both structures and maximum electron energy loss spectroscopy (EELS) and dielectric constant increased for the zigzag and armchair structures. Moreover, for the armchair structure, maximum optical reflectivity versus GNR width was a linear function, while it showed a teeth behavior for the zigzag structure.

  12. Bond Operator Mean Field Approach to the Magnetization Plateaux in Quantum Antiferromagnets —Application to the S=1/2 Coupled Dimerized Zigzag Heisenberg Chains—

    NASA Astrophysics Data System (ADS)

    Hida, Kazuo; Shiino, Masaru; Chen, Wei

    2004-06-01

    The magnetization plateaux in two dimensionally coupled S=1/2 dimerized zigzag Heisenberg chains are investigated by means of the bond operator mean field approximation. In the absence of the interchain coupling, this model is known to have a plateau at half of the saturation magnetization accompanied by the spontaneous translational symmetry breakdown. The parameter regime in which the plateau appears is reproduced well within the present approximation. In the presence of the interchain coupling, this plateau is shown to be suppressed. This result is also supported by the numerical diagonalization calculation.

  13. Optimization of the nanotwin-induced zigzag surface of copper by electromigration

    NASA Astrophysics Data System (ADS)

    Chen, Hsin-Ping; Huang, Chun-Wei; Wang, Chun-Wen; Wu, Wen-Wei; Liao, Chien-Neng; Chen, Lih-Juann; Tu, King-Ning

    2016-01-01

    By adding nanotwins to Cu, the surface electromigration (EM) slows down. The atomic mobility of the surface step-edges is retarded by the triple points where a twin meets a free surface to form a zigzag-type surface. We observed that EM can alter the zigzag surface structure to optimize the reduction of EM, according to Le Chatelier's principle. Statistically, the optimal alternation is to change an arbitrary (111)/(hkl) zigzag pair to a pair having a very low index (hkl) plane, especially the (200) plane. Using in situ ultrahigh vacuum and high-resolution transmission electron microscopy, we examined the effects of different zigzag surfaces on the rate of EM. The calculated rate of surface EM can be decreased by a factor of ten.By adding nanotwins to Cu, the surface electromigration (EM) slows down. The atomic mobility of the surface step-edges is retarded by the triple points where a twin meets a free surface to form a zigzag-type surface. We observed that EM can alter the zigzag surface structure to optimize the reduction of EM, according to Le Chatelier's principle. Statistically, the optimal alternation is to change an arbitrary (111)/(hkl) zigzag pair to a pair having a very low index (hkl) plane, especially the (200) plane. Using in situ ultrahigh vacuum and high-resolution transmission electron microscopy, we examined the effects of different zigzag surfaces on the rate of EM. The calculated rate of surface EM can be decreased by a factor of ten. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr05418d

  14. Method for fabricating zig-zag slabs for solid state lasers

    NASA Technical Reports Server (NTRS)

    Sridharan, Arun Kumar (Inventor); Saraf, Shailendhar (Inventor); Byer, Robert L. (Inventor)

    2006-01-01

    A method for batch manufacturing of slabs for zig-zag lasers including steps of bonding two non-active media to either side of an active medium to form a sandwich, dicing the sandwich to provide slices, rendering two surfaces of each slice into total-internal-reflection (TIR) surfaces, and then dicing the slices perpendicular to the TIR surfaces to provide a plurality of zig-zag slabs.

  15. Entanglement, excitations, and correlation effects in narrow zigzag graphene nanoribbons

    NASA Astrophysics Data System (ADS)

    Hagymási, I.; Legeza, Ö.

    2016-10-01

    We investigate the low-lying excitation spectrum and ground-state properties of narrow graphene nanoribbons with zigzag edge configurations. Nanoribbons of comparable widths have been synthesized very recently [P. Ruffieux et al., Nature (London) 531, 489 (2016)], 10.1038/nature17151, and their descriptions require more sophisticated methods since in this regime conventional methods, like mean-field or density-functional theory with local-density approximation, fail to capture the enhanced quantum fluctuations. Using the unbiased density-matrix renormalization-group algorithm, we calculate the charge gaps with high accuracy for different widths and interaction strengths and compare them with mean-field results. It turns out that the gaps are much smaller in the former case due to the proper treatment of quantum fluctuations. Applying the elements of quantum information theory, we also reveal the entanglement structure inside a ribbon and examine the spectrum of subsystem density matrices to understand the origin of entanglement. We examine the possibility of magnetic ordering and the effect of magnetic field. Our findings are relevant for understanding the gap values in different recent experiments and the deviations between them.

  16. Intrinsic half metallicity in lithium terminated zigzag graphene nanoribbons

    NASA Astrophysics Data System (ADS)

    Tyagi, Neha; Jaiswal, Neeraj K.; Sharma, Varun; Jha, Kamal K.; Srivastava, Pankaj

    2017-01-01

    Half-metallic materials are the prime requisite for future spintronic devices. In present work, the possibility of half-metallic characteristic has been investigated in Li terminated zigzag graphene nanoribbons (ZGNR) using density functional theory. Two different configurations: (i) both edges Li termination (Li-both edges) and (ii) one edge Li termination (Li-one edge), have been examined in the present study. The calculated binding energy (ranging from -3.19 eV to -4.96 eV) confirms that both the considered configurations are energetically viable to obtain. All the considered structures settled in antiferromagnetic ground state which is more stable than that of spin compensated state. Further, it is revealed that upto 100% spin polarization can be achieved (without application of any external electric field) in ZGNR with Li-one edge. Moreover, the observed half-metallicity is found to be independent of the ribbon width and therefore pledges for applications in novel spin filtering devices.

  17. Engineering spin exchange in nonbipartite graphene zigzag edges

    NASA Astrophysics Data System (ADS)

    Ortiz, R.; Lado, J. L.; Melle-Franco, M.; Fernández-Rossier, J.

    2016-09-01

    The rules that govern spin exchange interaction in pristine graphene nanostructures are constrained by the bipartite character of the lattice, so that the sign of the exchange is determined by whether magnetic moments are on the same sublattice or not. The synthesis of graphene ribbons with perfect zigzag edges and a fluoranthene group with a pentagon ring, a defect that breaks the bipartite nature of the honeycomb lattice, has been recently demonstrated. Here we address how the electronic and spin properties of these structures are modified by such defects, both for indirect exchange interactions as well as the emergent edge magnetism, studied both with density functional theory and mean-field Hubbard model calculations. In all instances we find that the local breakdown of the bipartite nature at the defect reverts the sign of the otherwise ferromagnetic correlations along the edge, introducing a locally antiferromagnetic intraedge coupling and, for narrow ribbons, also revert the antiferromagnetic interedge interactions that are normally found in pristine ribbons. Our findings show that these pentagon defects are a resource that permits us to engineer the spin exchange interactions in graphene-based nanostructures.

  18. Half-metallicity in aluminum-doped zigzag silicene nanoribbons

    NASA Astrophysics Data System (ADS)

    Dong, Yao-Jun; Wang, Xue-Feng; Vasilopoulos, P.; Zhai, Ming-Xing; Wu, Xue-Mei

    2014-03-01

    The spin-dependent electronic structures of aluminum-(Al) doped zigzag silicene nanoribbons (ZSiNRs) are investigated by first-principles calculations. When ZSiNRs are substitutionally doped by a single Al atom on different sites in every three primitive cells, they become half-metallic in some cases, a property that can be used in spintronic devices. More interestingly, spin-down electrons can be transported at the Fermi energy when the Al atom is placed on the sub-edge site. In contrast, spin-up electrons can be transported at the Fermi energy when the ZSiNRs are doped on sites near their centre. The magnetic moment on the edge is considerably suppressed if the Al atom is doped on edge or near-edge sites. Similar results are obtained for a phosphorus-(P) and boron-(B) doped ZSiNR. When two or more Si atoms are replaced by Al atoms, in general the half-metallic behaviour is replaced by a metallic, spin gapless semiconducting or semiconducting one. When a line of six Si atoms, along the ribbon's width, are replaced by Al atoms, the spin resolution of the band structure is suppressed and the system becomes nonmagnetic.

  19. Electronic structure and magnetic properties of zigzag blue phosphorene nanoribbons

    SciTech Connect

    Hu, Tao; Hong, Jisang

    2015-08-07

    We investigated the electronic structure and magnetism of zigzag blue phosphorene nanoribbons (ZBPNRs) using first principles density functional theory calculations by changing the widths of ZBPNRs from 1.5 to 5 nm. In addition, the effect of H and O passivation was explored as well. The ZBPNRs displayed intra-edge antiferromagnetic ground state with a semiconducting band gap of ∼0.35 eV; and this was insensitive to the edge structure relaxation effect. However, the edge magnetism of ZBPNRs disappeared with H-passivation. Moreover, the band gap of H-passivated ZBPNRs was greatly enhanced because the calculated band gap was ∼1.77 eV, and this was almost the same as that of two-dimensional blue phosphorene layer. For O-passivated ZBPNRs, we also found an intra-edge antiferromagnetic state. Besides, both unpassivated and O-passivated ZBPNRs preserved almost the same band gap. We predict that the electronic band structure and magnetic properties can be controlled by means of passivation. Moreover, the edge magnetism can be also modulated by the strain. Nonetheless, the intrinsic physical properties are size independent. This feature can be an advantage for device applications because it may not be necessary to precisely control the width of the nanoribbon.

  20. Ferroelectric surface induced electron doping in a zigzag graphene nanoribbon

    NASA Astrophysics Data System (ADS)

    Belletti, G. D.; Dalosto, S. D.; Tinte, S.

    2016-11-01

    The interface between a zigzag graphene nanoribbon (zGNR) and the ferroelectric PbTiO3 (0 0 1) surface is studied through first-principles calculations. We investigate how the electric polarization normal to the surface tunes the zGNR electronic and magnetic properties. A ferroelectric single-domain configuration with polarization up and down is considered including explicitly a bottom metallic electrode. Our results show how not only the ferroelectric polarization direction determines the doping in zGNR—the downward polarization induces a p-type doping in a planar zGNR whereas the upward polarization keeps it intrinsic—but also the features of the clean ferroelectric surface, such as the atomic relaxation and the electronic distribution. Interestingly, the surface ferroelectric polarization, besides tuning the carrier type as it does in graphene, also closes the zGNR band gap which can be understood in terms of the weakening of the local magnetic moment of the edge carbon atoms as the polarization increases. The zGNR antiferromagnetic ground state is preserved without breaking the α-β degeneracy.

  1. Edge magnetization in Bernal-stacked trilayer zigzag graphene nanoribbons

    NASA Astrophysics Data System (ADS)

    Pérez, Juan Antonio Casao

    2016-06-01

    We have used a tight-binding Hamiltonian of an ABA-stacked trilayer zigzag graphene nanoribbon with β-alignment edges to study the edge magnetizations. Our model includes the effect of the intralayer next-nearest-neighbor hopping, the interlayer hopping responsible for the trigonal warping and the interaction between electrons, which is considered by a single band Hubbard model in the mean field approximation. Firstly, in the neutral system we analyzed the two magnetic states in which both edge magnetizations reach their maximum value; the first one is characterized by an intralayer ferromagnetic coupling between the magnetizations at opposite edges, whereas in the second state that coupling is antiferromagnetic. The band structure, the location of the edge-state bands and the local density of states resolved in spin are calculated in order to understand the origins of the edge magnetizations. We have also introduced an electron doping so that the number of electrons in the ribbon unit cell is higher than in neutral case. As a consequence, we have obtained magnetization steps and charge accumulation at the edges of the sample, which are caused by the edge-state flat bands.

  2. Optimization of linear zigzag insert metastructures for low-frequency vibration attenuation using genetic algorithms

    NASA Astrophysics Data System (ADS)

    Abdeljaber, Osama; Avci, Onur; Kiranyaz, Serkan; Inman, Daniel J.

    2017-02-01

    Vibration suppression remains a crucial issue in the design of structures and machines. Recent studies have shown that with the use of metamaterial inspired structures (or metastructures), considerable vibration attenuation can be achieved. Optimization of the internal geometry of metastructures maximizes the suppression performance. Zigzag inserts have been reported to be efficient for vibration attenuation. It has also been reported that the geometric parameters of the inserts affect the vibration suppression performance in a complex manner. In an attempt to find out the most efficient parameters, an optimization study has been conducted on the linear zigzag inserts and is presented here. The research reported in this paper aims at developing an automated method for determining the geometry of zigzag inserts through optimization. This genetic algorithm based optimization process searches for optimal zigzag designs which are properly tuned to suppress vibrations when inserted in a specific host structure (cantilever beam). The inserts adopted in this study consist of a cantilever zigzag structure with a mass attached to its unsupported tip. Numerical simulations are carried out to demonstrate the efficiency of the proposed zigzag optimization approach.

  3. EMODEL_1D v. 1.0

    SciTech Connect

    Aldridge, David F.

    2016-07-06

    Program EMODEL_1D is an electromagnetic earth model construction utility designed to generate a three-dimensional (3D) uniformly-gridded representation of one-dimensional (1D) layered earth model. Each layer is characterized by the isotropic EM properties electric permittivity ?, magnetic permeability ?, and current conductivity ?. Moreover, individual layers of the model may possess a linear increase/decrease of any or all of these properties with depth.

  4. Nonlocal order parameters for the 1D Hubbard model.

    PubMed

    Montorsi, Arianna; Roncaglia, Marco

    2012-12-07

    We characterize the Mott-insulator and Luther-Emery phases of the 1D Hubbard model through correlators that measure the parity of spin and charge strings along the chain. These nonlocal quantities order in the corresponding gapped phases and vanish at the critical point U(c)=0, thus configuring as hidden order parameters. The Mott insulator consists of bound doublon-holon pairs, which in the Luther-Emery phase turn into electron pairs with opposite spins, both unbinding at U(c). The behavior of the parity correlators is captured by an effective free spinless fermion model.

  5. Nonlocal Order Parameters for the 1D Hubbard Model

    NASA Astrophysics Data System (ADS)

    Montorsi, Arianna; Roncaglia, Marco

    2012-12-01

    We characterize the Mott-insulator and Luther-Emery phases of the 1D Hubbard model through correlators that measure the parity of spin and charge strings along the chain. These nonlocal quantities order in the corresponding gapped phases and vanish at the critical point Uc=0, thus configuring as hidden order parameters. The Mott insulator consists of bound doublon-holon pairs, which in the Luther-Emery phase turn into electron pairs with opposite spins, both unbinding at Uc. The behavior of the parity correlators is captured by an effective free spinless fermion model.

  6. Ab initio study of H2O and water-chain-induced properties of carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Agrawal, B. K.; Singh, V.; Pathak, A.; Srivastava, R.

    2007-05-01

    We perform an ab initio study of the motion of the nano sized water dimer through a single-walled carbon nanotube (SWCNT), the stability of an encapsulated one-dimensional (1D) water chain inside SWCNT, and the H2O -induced structural, energetic, electronic, and optical properties of the SWCNTs. The adsorption of the water molecules is caused by the dispersion forces, i.e., the van der Waals (vdW) interactions. Thus, the role of the vdW interactions in the estimation of the BE for the weakly bound adsorbates cannot be ignored as has been done in several earlier publications. We find that a single H2O molecule or single water dimer or a 1D chain of water dimers is trapped inside the medium-sized (6,6) carbon nanotube placed in vacuum. However, the H2O molecule or water dimer may be transmitted in case the tube is surrounded by water or water vapor at high vapor pressure at high temperatures. On the other hand, a chain of single H2O molecules or more number of the encapsulated H2O molecules is very weakly coupled to the wide (10,10) carbon nanotube and can, thus, easily transmit through the carbon nanotube in agreement with the recent experiments. Further, appreciable adsorption both inside and on the surface of the (10,10) carbon nanotube is predicted in concurrence with the experiments. The small (medium-sized) diameter tubes will adsorb strongly (accommodate) the water molecules outside (inside) the nanotubes. The H2O adsorption converts the conducting small-diameter zigzag (5,0) tube into a semiconductor. Further, the adsorption reduces the band gap of the semiconducting achiral zigzag (10,0) nanotube but increases the band gap of a chiral semiconducting (4,2) tube. The adsorbed H2O molecules increase the electrical conductivity in agreement with the experiment. The overall peak structure in the optical absorption for the pristine tube is not altered significantly by the adsorption except for small alterations in the energy locations and the relative intensities

  7. Dinuclear and 1D iron(III) Schiff base complexes bridged by 4-salicylideneamino-1,2,4-triazolate: X-ray structures and magnetic properties.

    PubMed

    Herchel, Radovan; Pavelek, Lubomír; Trávníček, Zdeněk

    2011-11-28

    Four new iron(III) complexes were obtained by the reaction of 4-salicylideneamino-1,2,4-triazole (Hsaltrz) and selected dinuclear μ-oxo-bridged iron(III) Schiff base complexes [{FeL(4)}(2)(μ-O)], where L(4) represents a terminal tetradentate dianionic Schiff-base ligand. X-ray structural analysis revealed a novel bridging mode of κN,κO of the saltrz ligand to form dinuclear complexes [{Fe(salen)(μ-saltrz)}(2)]·CH(3)OH (1) (H(2)salen = N,N'-ethylenebis(salicylimine)) and [{Fe(salpn)(μ-saltrz)}(2)] (2) (H(2)salpn = N,N'-1,2-propylenbis(salicylimine)), whereas one-dimensional (1D) zig-zag chains were formed in the case of [{Fe(salch)(μ-saltrz)}·0.5CH(3)OH](n) (3) (H(2)salch = N,N'-cyclohexanebis(salicylimine)) and [Fe(salophen)(μ-saltrz)](n) (4) (H(2)salophen = N,N'-o-phenylenebis(salicylimine)). It was also shown that the rigidity of the terminal ligand L(4) can be considered as the key factor for the molecular dimensionality of the products. The thorough magnetic analysis based on SQUID experiments, including the isotropic exchange and the zero-field splitting of both temperature and field dependent data, was performed for dimeric (1 and 2) and also for polymeric compounds (3 and 4) and revealed weak antiferromagnetic exchange mediated by the saltrz anions with much larger D-parameter (|D|≫|J|).

  8. Potent neutralizing anti-CD1d antibody reduces lung cytokine release in primate asthma model

    PubMed Central

    Nambiar, Jonathan; Clarke, Adam W; Shim, Doris; Mabon, David; Tian, Chen; Windloch, Karolina; Buhmann, Chris; Corazon, Beau; Lindgren, Matilda; Pollard, Matthew; Domagala, Teresa; Poulton, Lynn; Doyle, Anthony G

    2015-01-01

    CD1d is a receptor on antigen-presenting cells involved in triggering cell populations, particularly natural killer T (NKT) cells, to release high levels of cytokines. NKT cells are implicated in asthma pathology and blockade of the CD1d/NKT cell pathway may have therapeutic potential. We developed a potent anti-human CD1d antibody (NIB.2) that possesses high affinity for human and cynomolgus macaque CD1d (KD ∼100 pM) and strong neutralizing activity in human primary cell-based assays (IC50 typically <100 pM). By epitope mapping experiments, we showed that NIB.2 binds to CD1d in close proximity to the interface of CD1d and the Type 1 NKT cell receptor β-chain. Together with data showing that NIB.2 inhibited stimulation via CD1d loaded with different glycolipids, this supports a mechanism whereby NIB.2 inhibits NKT cell activation by inhibiting Type 1 NKT cell receptor β-chain interactions with CD1d, independent of the lipid antigen in the CD1d antigen-binding cleft. The strong in vitro potency of NIB.2 was reflected in vivo in an Ascaris suum cynomolgus macaque asthma model. Compared with vehicle control, NIB.2 treatment significantly reduced bronchoalveolar lavage (BAL) levels of Ascaris-induced cytokines IL-5, IL-8 and IL-1 receptor antagonist, and significantly reduced baseline levels of GM-CSF, IL-6, IL-15, IL-12/23p40, MIP-1α, MIP-1β, and VEGF. At a cellular population level NIB.2 also reduced numbers of BAL lymphocytes and macrophages, and blood eosinophils and basophils. We demonstrate that anti-CD1d antibody blockade of the CD1d/NKT pathway modulates inflammatory parameters in vivo in a primate inflammation model, with therapeutic potential for diseases where the local cytokine milieu is critical. PMID:25751125

  9. Potent neutralizing anti-CD1d antibody reduces lung cytokine release in primate asthma model.

    PubMed

    Nambiar, Jonathan; Clarke, Adam W; Shim, Doris; Mabon, David; Tian, Chen; Windloch, Karolina; Buhmann, Chris; Corazon, Beau; Lindgren, Matilda; Pollard, Matthew; Domagala, Teresa; Poulton, Lynn; Doyle, Anthony G

    2015-01-01

    CD1d is a receptor on antigen-presenting cells involved in triggering cell populations, particularly natural killer T (NKT) cells, to release high levels of cytokines. NKT cells are implicated in asthma pathology and blockade of the CD1d/NKT cell pathway may have therapeutic potential. We developed a potent anti-human CD1d antibody (NIB.2) that possesses high affinity for human and cynomolgus macaque CD1d (KD ∼100 pM) and strong neutralizing activity in human primary cell-based assays (IC50 typically <100 pM). By epitope mapping experiments, we showed that NIB.2 binds to CD1d in close proximity to the interface of CD1d and the Type 1 NKT cell receptor β-chain. Together with data showing that NIB.2 inhibited stimulation via CD1d loaded with different glycolipids, this supports a mechanism whereby NIB.2 inhibits NKT cell activation by inhibiting Type 1 NKT cell receptor β-chain interactions with CD1d, independent of the lipid antigen in the CD1d antigen-binding cleft. The strong in vitro potency of NIB.2 was reflected in vivo in an Ascaris suum cynomolgus macaque asthma model. Compared with vehicle control, NIB.2 treatment significantly reduced bronchoalveolar lavage (BAL) levels of Ascaris-induced cytokines IL-5, IL-8 and IL-1 receptor antagonist, and significantly reduced baseline levels of GM-CSF, IL-6, IL-15, IL-12/23p40, MIP-1α, MIP-1β, and VEGF. At a cellular population level NIB.2 also reduced numbers of BAL lymphocytes and macrophages, and blood eosinophils and basophils. We demonstrate that anti-CD1d antibody blockade of the CD1d/NKT pathway modulates inflammatory parameters in vivo in a primate inflammation model, with therapeutic potential for diseases where the local cytokine milieu is critical.

  10. Upstream Design and 1D-CAE

    NASA Astrophysics Data System (ADS)

    Sawada, Hiroyuki

    Recently, engineering design environment of Japan is changing variously. Manufacturing companies are being challenged to design and bring out products that meet the diverse demands of customers and are competitive against those produced by rising countries(1). In order to keep and strengthen the competitiveness of Japanese companies, it is necessary to create new added values as well as conventional ones. It is well known that design at the early stages has a great influence on the final design solution. Therefore, design support tools for the upstream design is necessary for creating new added values. We have established a research society for 1D-CAE (1 Dimensional Computer Aided Engineering)(2), which is a general term for idea, methodology and tools applicable for the upstream design support, and discuss the concept and definition of 1D-CAE. This paper reports our discussion about 1D-CAE.

  11. Helical Floquet Channels in 1D Lattices

    NASA Astrophysics Data System (ADS)

    Budich, Jan Carl; Hu, Ying; Zoller, Peter

    2017-03-01

    We show how dispersionless channels exhibiting perfect spin-momentum locking can arise in a 1D lattice model. While such spectra are forbidden by fermion doubling in static 1D systems, here we demonstrate their appearance in the stroboscopic dynamics of a periodically driven system. Remarkably, this phenomenon does not rely on any adiabatic assumptions, in contrast to the well known Thouless pump and related models of adiabatic spin pumps. The proposed setup is shown to be experimentally feasible with state-of-the-art techniques used to control ultracold alkaline earth atoms in optical lattices.

  12. Application of the Refined Zigzag Theory to the Modeling of Delaminations in Laminated Composites

    NASA Technical Reports Server (NTRS)

    Groh, Rainer M. J.; Weaver, Paul M.; Tessler, Alexander

    2015-01-01

    The Refined Zigzag Theory is applied to the modeling of delaminations in laminated composites. The commonly used cohesive zone approach is adapted for use within a continuum mechanics model, and then used to predict the onset and propagation of delamination in five cross-ply composite beams. The resin-rich area between individual composite plies is modeled explicitly using thin, discrete layers with isotropic material properties. A damage model is applied to these resin-rich layers to enable tracking of delamination propagation. The displacement jump across the damaged interfacial resin layer is captured using the zigzag function of the Refined Zigzag Theory. The overall model predicts the initiation of delamination to within 8% compared to experimental results and the load drop after propagation is represented accurately.

  13. Simulation of the wavefront distortion and beam quality for a high-power zigzag slab laser

    NASA Astrophysics Data System (ADS)

    Shin, Jae Sung; Cha, Yong-Ho; Cha, Byung Heon; Lee, Hyeon Cheor; Kim, Hyun Tae; Lee, Jung Hwan

    2016-12-01

    A simulation method of the beam quality for a high-power zigzag slab laser has been developed. This method can predict the wavefront distortion and beam quality for various optical arrangements and optimize the design effectively. A Nd:YAG zigzag slab laser amplifier was designed as an application. The optimized design shows a beam quality of 1.20 corresponding to the minimized wavefront distortion with a peak-to-valley of 0.568 μm and root mean square of 0.115 μm even under high-power operation with a total pump power of 14 kW. Although there are some effects other than the optical design error that incur wavefront distortions, this method can help to determine the first optical design of the zigzag slab laser without the need for many experimental studies.

  14. The spin-dependent transport properties of zigzag α-graphyne nanoribbons and new device design

    PubMed Central

    Ni, Yun; Wang, Xia; Tao, Wei; Zhu, Si-Cong; Yao, Kai-Lun

    2016-01-01

    By performing first-principle quantum transport calculations, we studied the electronic and transport properties of zigzag α-graphyne nanoribbons in different magnetic configurations. We designed the device based on zigzag α-graphyne nanoribbon and studied the spin-dependent transport properties, whose current-voltage curves show obvious spin-polarization and conductance plateaus. The interesting transport behaviours can be explained by the transport spectra under different magnetic configurations, which basically depends on the symmetry matching of the electrodes’ bandstructures. Simultaneously, spin Seebeck effect is also found in the device. Thus, according to the transport behaviours, zigzag α-graphyne nanoribbons can be used as a dual spin filter diode, a molecule signal converter and a spin caloritronics device, which indicates that α-graphyne is a promising candidate for the future application in spintronics. PMID:27180808

  15. Zigzag order and phase competition in expanded Kitaev-Heisenberg model on honeycomb lattice

    NASA Astrophysics Data System (ADS)

    Yao, Xiaoyan

    2015-07-01

    The Kitaev-Heisenberg model on the honeycomb lattice is investigated in two cases: (I) with the Kitaev interaction between the nearest neighbors, and (II) with the Kitaev interaction between the next nearest neighbors. In the full parameter range, the ground states are searched by Monte Carlo simulation and identified by evaluating the correlation functions. The energies of different phases are calculated and compared with the simulated result to show the phase competition. It is observed from both energy calculation and the density of states that the zigzag order shows a symmetric behavior to the stripy phase in the pure Kitaev-Heisenberg model. By considering more interactions in both cases, the energy of zigzag order can be reduced lower than the energies of other states. Thus the zigzag phase may be stabilized in more parameter region and even extended to the whole parameter range.

  16. Geometrical Nonlinear Analysis of Composite Structures by Zigzag Theory—A Review

    NASA Astrophysics Data System (ADS)

    Shirbhate, N. J.; Tungikar, V. B.

    2010-10-01

    Advances in manufacturing technologies of composites leads to its uses as main load carrying structures which essentially need to be thick structures. Thus it is becoming increasingly important to predict accurately interlaminar variations of stresses and displacements along thickness of the composites. A review of the recent development of finite element methods for geometrical nonlinear analysis of composite structures specifically using zigzag theory is presented in this paper. The literature review is devoted to the recently developed finite elements, theories based on zigzag function for carrying out geometrical nonlinear analysis of composite structures. The future research is summarized finally.

  17. Adatom-induced local reconstructions in zigzag silicene nanoribbons: Spin semiconducting properties and large spin thermopowers

    NASA Astrophysics Data System (ADS)

    Yang, X. F.; Zou, X. L.; Kuang, Y. W.; Shao, Z. G.; Zhang, J.; Hong, X. K.; Zhang, D. B.; Feng, J. F.; Chen, X. S.; Liu, Y. S.

    2017-01-01

    Using first-principles methods, we have investigated magnetic properties and thermospin effects of zigzag silicene nanoribbons (ZSiNRs) absorbed by a single Si atom. After a relaxation, a steady dumbbell-like structure is formed, which induces a weaker antiferromagnetic (AFM) coupling between two zigzag edges. Therefore, a band gap is opened, meanwhile the adsorbed ZSiNRs show a spin semiconducting property. A large spin thermopower and weak charge thermopower in adsorbed ZSiNR-based devices can be simultaneously achieved, which is attributed to a nearly perfect mirror symmetry of spin-up and spin-down transmission spectra relative to the Fermi level.

  18. Analysis of the rotational structure in the high-resolution infrared spectra of trans-hexatriene-1,1-d2 and -cis-1-d1

    NASA Astrophysics Data System (ADS)

    Craig, Norman C.; Fuson, Hannah A.; Tian, Hengfeng; Blake, Thomas A.

    2012-09-01

    Mixtures of trans-hexatriene-1,1-d2, -cis-1-d1, and -trans-1-d1 have been synthesized. Anharmonic frequencies and harmonic intensities were predicted with the B3LYP/cc-pVTZ model for the out-of-plane (a″) modes of the three isotopologues. Assignments are proposed for most of the a″ vibrational modes above 500 cm-1. Ground state (GS) rotational constants have been determined for the 1,1-d2 and cis-1-d1 species from the analysis of rotational structure of C-type bands in the high-resolution (0.0015 cm-1) infrared spectra in a mixture of the three isotopologues. The GS constants for the 1,1-d2 species are A0 = 0.8018850(6), B0 = 0.0418540(6), and C0 = 0.0397997(4) cm-1. The GS constants for the cis-1-d1 species are A0 = 0.809388(1), B0 = 0.043532(2), and C0 = 0.041320(1) cm-1. Small inertial defects confirm planarity for both species. These ground state rotational constants are intended for use in determining a semiexperimental equilibrium structure and evaluating the influence of chain length on π-electron delocalization in polyenes.

  19. TCTEX1D2 mutations underlie Jeune asphyxiating thoracic dystrophy with impaired retrograde intraflagellar transport

    PubMed Central

    Schmidts, Miriam; Hou, Yuqing; Cortés, Claudio R.; Mans, Dorus A.; Huber, Celine; Boldt, Karsten; Patel, Mitali; van Reeuwijk, Jeroen; Plaza, Jean-Marc; van Beersum, Sylvia E. C.; Yap, Zhi Min; Letteboer, Stef J. F.; Taylor, S. Paige; Herridge, Warren; Johnson, Colin A.; Scambler, Peter J.; Ueffing, Marius; Kayserili, Hulya; Krakow, Deborah; King, Stephen M.; Beales, Philip L.; Al-Gazali, Lihadh; Wicking, Carol; Cormier-Daire, Valerie; Roepman, Ronald; Mitchison, Hannah M.; Witman, George B.; Al-Turki, Saeed; Anderson, Carl; Anney, Richard; Antony, Dinu; Asimit, Jennifer; Ayub, Mohammad; Barrett, Jeff; Barroso, Inês; Bentham, Jamie; Bhattacharya, Shoumo; Blackwood, Douglas; Bobrow, Martin; Bochukova, Elena; Bolton, Patrick; Boustred, Chris; Breen, Gerome; Brion, Marie-Jo; Brown, Andrew; Calissano, Mattia; Carss, Keren; Chatterjee, Krishna; Chen, Lu; Cirak, Sebhattin; Clapham, Peter; Clement, Gail; Coates, Guy; Collier, David; Cosgrove, Catherine; Cox, Tony; Craddock, Nick; Crooks, Lucy; Curran, Sarah; Daly, Allan; Danecek, Petr; Smith, George Davey; Day-Williams, Aaron; Day, Ian; Durbin, Richard; Edkins, Sarah; Ellis, Peter; Evans, David; Farooqi, I. Sadaf; Fatemifar, Ghazaleh; Fitzpatrick, David; Flicek, Paul; Floyd, Jamie; Foley, A. Reghan; Franklin, Chris; Futema, Marta; Gallagher, Louise; Gaunt, Tom; Geschwind, Daniel; Greenwood, Celia; Grozeva, Detelina; Guo, Xiaosen; Gurling, Hugh; Hart, Deborah; Hendricks, Audrey; Holmans, Peter; Huang, Jie; Humphries, Steve E.; Hurles, Matt; Hysi, Pirro; Jackson, David; Jamshidi, Yalda; Jewell, David; Chris, Joyce; Kaye, Jane; Keane, Thomas; Kemp, John; Kennedy, Karen; Kent, Alastair; Kolb-Kokocinski, Anja; Lachance, Genevieve; Langford, Cordelia; Lee, Irene; Li, Rui; Li, Yingrui; Ryan, Liu; Lönnqvist, Jouko; Lopes, Margarida; MacArthur, Daniel G.; Massimo, Mangino; Marchini, Jonathan; Maslen, John; McCarthy, Shane; McGuffin, Peter; McIntosh, Andrew; McKechanie, Andrew; McQuillin, Andrew; Memari, Yasin; Metrustry, Sarah; Min, Josine; Moayyeri, Alireza; Morris, James; Muddyman, Dawn; Muntoni, Francesco; Northstone, Kate; O'Donovan, Michael; O'Rahilly, Stephen; Onoufriadis, Alexandros; Oualkacha, Karim; Owen, Michael; Palotie, Aarno; Panoutsopoulou, Kalliope; Parker, Victoria; Parr, Jeremy; Paternoster, Lavinia; Paunio, Tiina; Payne, Felicity; Perry, John; Pietilainen, Olli; Plagnol, Vincent; Quail, Michael A.; Quaye, Lydia; Raymond, Lucy; Rehnström, Karola; Brent Richards, J.; Ring, Sue; Ritchie, Graham R S; Savage, David B.; Schoenmakers, Nadia; Semple, Robert K.; Serra, Eva; Shihab, Hashem; Shin, So-Youn; Skuse, David; Small, Kerrin; Smee, Carol; Soler, Artigas María; Soranzo, Nicole; Southam, Lorraine; Spector, Tim; St Pourcain, Beate; St. Clair, David; Stalker, Jim; Surdulescu, Gabriela; Suvisaari, Jaana; Tachmazidou, Ioanna; Tian, Jing; Timpson, Nic; Tobin, Martin; Valdes, Ana; van Kogelenberg, Margriet; Vijayarangakannan, Parthiban; Wain, Louise; Walter, Klaudia; Wang, Jun; Ward, Kirsten; Wheeler, Ellie; Whittall, Ros; Williams, Hywel; Williamson, Kathy; Wilson, Scott G.; Wong, Kim; Whyte, Tamieka; ChangJiang, Xu; Zeggini, Eleftheria; Zhang, Feng; Zheng, Hou-Feng

    2015-01-01

    The analysis of individuals with ciliary chondrodysplasias can shed light on sensitive mechanisms controlling ciliogenesis and cell signalling that are essential to embryonic development and survival. Here we identify TCTEX1D2 mutations causing Jeune asphyxiating thoracic dystrophy with partially penetrant inheritance. Loss of TCTEX1D2 impairs retrograde intraflagellar transport (IFT) in humans and the protist Chlamydomonas, accompanied by destabilization of the retrograde IFT dynein motor. We thus define TCTEX1D2 as an integral component of the evolutionarily conserved retrograde IFT machinery. In complex with several IFT dynein light chains, it is required for correct vertebrate skeletal formation but may be functionally redundant under certain conditions. PMID:26044572

  20. Calibration of a 1D/1D urban flood model using 1D/2D model results in the absence of field data.

    PubMed

    Leandro, J; Djordjević, S; Chen, A S; Savić, D A; Stanić, M

    2011-01-01

    Recently increased flood events have been prompting researchers to improve existing coupled flood-models such as one-dimensional (1D)/1D and 1D/two-dimensional (2D) models. While 1D/1D models simulate sewer and surface networks using a one-dimensional approach, 1D/2D models represent the surface network by a two-dimensional surface grid. However their application raises two issues to urban flood modellers: (1) stormwater systems planning/emergency or risk analysis demands for fast models, and the 1D/2D computational time is prohibitive, (2) and the recognized lack of field data (e.g. Hunter et al. (2008)) causes difficulties for the calibration/validation of 1D/1D models. In this paper we propose to overcome these issues by calibrating a 1D/1D model with the results of a 1D/2D model. The flood-inundation results show that: (1) 1D/2D results can be used to calibrate faster 1D/1D models, (2) the 1D/1D model is able to map the 1D/2D flood maximum extent well, and the flooding limits satisfactorily in each time-step, (3) the 1D/1D model major differences are the instantaneous flow propagation and overestimation of the flood-depths within surface-ponds, (4) the agreement in the volume surcharged by both models is a necessary condition for the 1D surface-network validation and (5) the agreement of the manholes discharge shapes measures the fitness of the calibrated 1D surface-network.

  1. Glass-based 1-D dielectric microcavities

    NASA Astrophysics Data System (ADS)

    Chiasera, Alessandro; Scotognella, Francesco; Valligatla, Sreeramulu; Varas, Stefano; Jasieniak, Jacek; Criante, Luigino; Lukowiak, Anna; Ristic, Davor; Gonçalves, Rogeria Rocha; Taccheo, Stefano; Ivanda, Mile; Righini, Giancarlo C.; Ramponi, Roberta; Martucci, Alessandro; Ferrari, Maurizio

    2016-11-01

    We have developed a reliable RF sputtering techniques allowing to fabricate glass-based one dimensional microcavities, with high quality factor. This property is strongly related to the modification of the density of states due to the confinement of the gain medium in a photonic band gap structure. In this short review we present some of the more recent results obtained by our team exploiting these 1D microcavities. In particular we present: (1) Er3+ luminescence enhancement of the 4I13/2 → 4I15/2 transition; (2) broad band filters based on disordered 1-D photonic structures; (3) threshold defect-mode lasing action in a hybrid structure.

  2. Centrosome Positioning in 1D Cell Migration

    NASA Astrophysics Data System (ADS)

    Adlerz, Katrina; Aranda-Espinoza, Helim

    During cell migration, the positioning of the centrosome and nucleus define a cell's polarity. For a cell migrating on a two-dimensional substrate the centrosome is positioned in front of the nucleus. Under one-dimensional confinement, however, the centrosome is positioned behind the nucleus in 60% of cells. It is known that the centrosome is positioned by CDC42 and dynein for cells moving on a 2D substrate in a wound-healing assay. It is currently unknown, however, if this is also true for cells moving under 1D confinement, where the centrosome position is often reversed. Therefore, centrosome positioning was studied in cells migrating under 1D confinement, which mimics cells migrating through 3D matrices. 3 to 5 μm fibronectin lines were stamped onto a glass substrate and cells with fluorescently labeled nuclei and centrosomes migrated on the lines. Our results show that when a cell changes directions the centrosome position is maintained. That is, when the centrosome is between the nucleus and the cell's trailing edge and the cell changes direction, the centrosome will be translocated across the nucleus to the back of the cell again. A dynein inhibitor did have an influence on centrosome positioning in 1D migration and change of directions.

  3. Ab initio study of semiconductor atoms impurities in zigzag edge (10,0) carbon nanotubes

    SciTech Connect

    Muttaqien, Fahdzi Suprijadi

    2015-04-16

    The substitutional impurities in zigzag edge (10,0) carbon nanotubes have been studied by using first principles calculations. Silicon (Si), gallium (Ga), and arsenic (As) atom have been chosen as semiconductor based-atom for replacing carbon atoms in CNT’s surface. The silicon atom changes the energy gap of pristine zigzag (10,0) CNT, it is 0.19 eV more narrow than that of pristine CNT. Geometrically, the silicon atom creates sp{sup 3} bond with three adjacent carbon atoms, where the tetrahedral form of its sp{sup 3} bond is consisted of free unoccupied state. The silicon atom does not induce magnetism to zigzag CNT. Due to gallium (Ga) and arsenic (As) atom substitution, the zigzag CNT becomes metallic and has magnetic moment of 1 µ{sub B}. The valance and conduction band are crossed each other, then the energy gap is vanished. The electronic properties of GaAs-doped CNT are dominantly affected by gallium atom and its magnetic properties are dominantly affected by arsenic atom. These results prove that the CNT with desired properties can be obtained with substitutional impurities without any giving structural defect.

  4. Mechanism of stabilization and magnetization of impurity-doped zigzag graphene nanoribbons

    NASA Astrophysics Data System (ADS)

    Uchida, Yuuki; Gomi, Shun-ichi; Matsuyama, Haruyuki; Akaishi, Akira; Nakamura, Jun

    2016-12-01

    Doping is an efficient way to modify the electronic structure of graphene. Although there have been a considerable number of studies on the electronic structure of impurity-doped graphene, every study has suggested a different interpretation of the appearance of impurity levels of dopants located near the so-called zigzag edge of graphene nanoribbons (GNRs). Here, we propose a charge transfer model that satisfactorily explains the change in electronic structure upon N(B) doping of zigzag GNR (ZGNR). The structural stability and electronic structure of the doped ZGNR have been investigated using first-principles calculations based on the density functional theory. The formation energy of doping increases as a function of the distance between the N(B) atom and the zigzag edge, and two tendencies are observed depending on whether the dopant is an odd or even number of sites away from the zigzag edge. Such peculiar behavior of the formation energy can be successfully explained by charge transfer between the so-called edge state localized at the edge and the 2p-state of the dopant. Such an electron (hole) transfer leads to the compensation (disappearance) of the local spin-magnetic moment at one side of the ZGNR, manifesting in the ferromagnetic ground state of ZGNR.

  5. Synthesis and characterization of silver nanowires with zigzag morphology in N, N-dimethylformamide

    NASA Astrophysics Data System (ADS)

    He, Xin; Zhao, Xiujian; Chen, Yunxia; Feng, Jinyang; Sun, Zhenya

    2007-08-01

    Zigzag silver nanowires with a uniform diameter of 20±5 nm were prepared by reducing silver nitrate (AgNO 3) with N, N-dimethylformamide (DMF) in the presence of tetrabutyl titanate (TBT) and acetylacetone (AcAc) at 373 K for 18 h. X-ray and selected area electron diffraction (XRD and SAED) patterns reveal that the prepared product is made of pure silver with face centered cubic structure. Transmission electron microscopy (TEM) investigations suggest that the amount of silver nanowires is enhanced with increase in reaction time, and the end-to-end assemblies of silver nanorods are observed during the reaction process. After 18 h reaction, silver nanowires with zigzag morphology are obtained. In this paper, a possible growth process of silver nanowires with this interesting shape is described. Silver nanoparticles with small sizes were obtained by reducing Ag + ions with DMF, providing seeds for homogeneous growth of silver nanorods. With the extending reaction time, the synthesized silver nanorods were connected in an end-to-end manner, and the interface between the connections of two nanorods gradually disappeared. The final product shows zigzag morphology with various angles. The angles between two connecting straight parts of zigzag nanowires exhibit an alterable range of 74-151°. These silver nanowires show tremendous potential applications in future nanoscale electronic circuits.

  6. Communication: Origin of the difference between carbon nanotube armchair and zigzag ends

    SciTech Connect

    Li, Yunguo Ahuja, Rajeev; Larsson, J. Andreas

    2014-03-07

    In this work, we have found that the difference between armchair and zigzag ends of carbon nanotubes (CNTs) does not pertain at close study for individual bonds and thus alternative strategies need to be developed to reach the ultimate goals in selective growth. Based on first-principles simulations, the difference between binding strengths for CNTs of different chirality was investigated using hydrogen dissociation energies at their passivated ends. When all H atoms are removed collectively we find the well-known difference: that armchair bonds are much weaker than zigzag ones, which is typically seen for both CNT ends and graphene edges. However, when individual H atoms are removed we find almost no difference in hydrogen dissociation energies, small difference in bond lengths, which by association means small difference in C–C and M–C binding energies. We show convincingly that the difference in binding energy between armchair and zigzag ends is due to a fragment stabilization effect that is only manifested when all (or several neighbouring) bonds are broken. This is because at armchair ends/edges neighbouring dangling bonds can pair-up to form C≡C triple bonds that constitute a considerable stabilization effect compared to the isolated dangling bonds at zigzag ends/edges. Consequently, in many processes, e.g., catalytic growth where bonds are normally created/broken sequentially, not collectively, the difference between armchair and zigzag ends/edges cannot be used to discriminate growth of one type over the other to achieve chiral selective growth. Strategies are discussed to realize chirality selective growth in the light of the results presented, including addition of C{sub 2}-fragments to favor armchair tubes.

  7. A 1-D dusty plasma photonic crystal

    SciTech Connect

    Mitu, M. L.; Ticoş, C. M.; Toader, D.; Banu, N.; Scurtu, A.

    2013-09-21

    It is demonstrated numerically that a 1-D plasma crystal made of micron size cylindrical dust particles can, in principle, work as a photonic crystal for terahertz waves. The dust rods are parallel to each other and arranged in a linear string forming a periodic structure of dielectric-plasma regions. The dispersion equation is found by solving the waves equation with the boundary conditions at the dust-plasma interface and taking into account the dielectric permittivity of the dust material and plasma. The wavelength of the electromagnetic waves is in the range of a few hundred microns, close to the interparticle separation distance. The band gaps of the 1-D plasma crystal are numerically found for different types of dust materials, separation distances between the dust rods and rod diameters. The distance between levitated dust rods forming a string in rf plasma is shown experimentally to vary over a relatively wide range, from 650 μm to about 1350 μm, depending on the rf power fed into the discharge.

  8. Tctex1d2 Is a Negative Regulator of GLUT4 Translocation and Glucose Uptake.

    PubMed

    Shimoda, Yoko; Okada, Shuichi; Yamada, Eijiro; Pessin, Jeffrey E; Yamada, Masanobu

    2015-10-01

    Tctex1d2 (Tctex1 domain containing 2) is an open reading frame that encodes for a functionally unknown protein that contains a Tctex1 domain found in dynein light chain family members. Examination of gene expression during adipogenesis demonstrated a marked increase in Tctex1d2 protein expression that was essentially undetectable in preadipocytes and markedly induced during 3T3-L1 adipocyte differentiation. Tctex1d2 overexpression significantly inhibited insulin-stimulated glucose transporter 4 (GLUT4) translocation and 2-deoxyglucose uptake. In contrast, Tctex1d2 knockdown significantly increased insulin-stimulated GLUT4 translocation and 2-deoxyglucose uptake. However, acute insulin stimulation (up to 30 min) in 3T3-L1 adipocytes with overexpression or knockdown of Tctex1d2 had no effect on Akt phosphorylation, a critical signal transduction target required for GLUT4 translocation. Although overexpression of Tctex1d2 had no significant effect on GLUT4 internalization, Tctex1d2 was found to associate with syntaxin 4 in an insulin-dependent manner and inhibit Doc2b binding to syntaxin 4. In addition, glucose-dependent insulinotropic polypeptide rescued the Tctex1d2 inhibition of insulin-stimulated GLUT4 translocation by suppressing the Tctex1d2-syntaxin 4 interaction and increasing Doc2b-Synatxin4 interactions. Taking these results together, we hypothesized that Tctex1d2 is a novel syntaxin 4 binding protein that functions as a negative regulator of GLUT4 plasma membrane translocation through inhibition of the Doc2b-syntaxin 4 interaction.

  9. 1D-VAR Retrieval Using Superchannels

    NASA Technical Reports Server (NTRS)

    Liu, Xu; Zhou, Daniel; Larar, Allen; Smith, William L.; Schluessel, Peter; Mango, Stephen; SaintGermain, Karen

    2008-01-01

    Since modern ultra-spectral remote sensors have thousands of channels, it is difficult to include all of them in a 1D-var retrieval system. We will describe a physical inversion algorithm, which includes all available channels for the atmospheric temperature, moisture, cloud, and surface parameter retrievals. Both the forward model and the inversion algorithm compress the channel radiances into super channels. These super channels are obtained by projecting the radiance spectra onto a set of pre-calculated eigenvectors. The forward model provides both super channel properties and jacobian in EOF space directly. For ultra-spectral sensors such as Infrared Atmospheric Sounding Interferometer (IASI) and the NPOESS Airborne Sounder Testbed Interferometer (NAST), a compression ratio of more than 80 can be achieved, leading to a significant reduction in computations involved in an inversion process. Results will be shown applying the algorithm to real IASI and NAST data.

  10. First-principles prediction of a low energy edge-reconstruction for zigzag phosphorene nanoribbons

    NASA Astrophysics Data System (ADS)

    Shi, XiZhi; He, ChaoYu; OuYang, Tao; Zhang, ChunXiao; Tang, Chao; Zhong, JianXin

    2017-02-01

    Based on first-principles calculations, a new-type of edge reconstruction with remarkable stability is predicted for zigzag phosphorene nanoribbons. Such a new-type of edge reconstruction is named as θ-edge according to its θ-like configuration, in which all edge atoms are fully self-passivated with a coordination number of 3. In ZZ nanoribbons, θ-edge is energetically more stable than the bare case and as stable as the previously proposed ZZ‧-o reconstruction. In ZZ54 nanoribbons, θ-edge is energetically more stable than the metastable Δ-edge spontaneously formed in normal VASP optimization, and it is the most stable one among all these edge reconstructions. Further investigation shows that zigzag phosphorene nanoribbons with θ-edge are semiconductors with band gaps varying inversely with ribbon width.

  11. Which nanowire couples better electrically to a metal contact: Armchair or zigzag nanotube?

    NASA Technical Reports Server (NTRS)

    Anantram, M. P.; Biegel, Bryan (Technical Monitor)

    2001-01-01

    The fundamental question of how chirality affects tile electronic coupling of a nanotube to metal contacts is important for tile application of nanotubes as nanowires. We show that metallic-zigzag nanotubes are superior to armchair nanotubes as nanowires, by modeling the metal-nanotube interface. More specifically, we show that as a function of coupling strength, the total electron transmission of armchair nanotubes increases and tends to be pinned close to unity for a metal with Fermi wave vector close to that of gold. In contrast, the transmission probability of zigzag nanotubes increases to the maximum possible value of two. The origin of these effects lies in the details of the wave function, which is explained.

  12. Perfect Spin-filtering in graphene monolayer-bilayer superlattice with zigzag boundaries

    PubMed Central

    Yu, Hang; Liu, Jun-Feng

    2016-01-01

    We show that the spontaneous magnetization is formed at the zigzag boundary between monolayer and bilayer graphene by the self-consistent calculation based on Hubbard model. In a monolayer- bilayer graphene superlattice with zigzag boundaries, it is surprising that nearly 100% spin polarization is achieved in the energy window around the Dirac point, no matter the magnetization configuration at two boundaries is parallel or antiparallel. The reason is that the low-energy transport is only influenced by the magnetization at one edge, but not by that at the other. The underlying physics is unveiled by the spin-split band structure and the distribution of the wave-function pertaining to the lowest (highest) subband of electron (hole). PMID:27140666

  13. Zigzag line defects and manipulation of colloids in a nematic liquid crystal in microwrinkle grooves

    PubMed Central

    Ohzono, Takuya; Fukuda, Jun-ichi

    2012-01-01

    Spatially confined liquid crystals exhibit non-uniform alignment, often accompanied by self-organised topological defects of non-trivial shape in response to imposed boundary conditions and geometry. Here we show that a nematic liquid crystal, when confined in a sinusoidal microwrinkle groove, exhibits a new periodic arrangement of twist deformations and a zigzag line defect. This periodic ordering results from the inherent liquid crystal elastic anisotropy and the antagonistic boundary conditions at the flat liquid crystal–air and the curved liquid crystal–groove interfaces. The periodic structure can be tuned by controlling the groove geometry and the molecular chirality, which demonstrates the importance of boundary conditions and introduced asymmetry for the engineering of topological defects. Moreover, the kinks in the zigzag defects can trap small particles, which may afford a new method for manipulation of colloids. Our system, which uses easily fabricated microwrinkle grooves, provides a new microfabrication method based on the arrangement of controllable defects. PMID:22426222

  14. Magnetic structure and Magnetic transport Properties of Graphene Nanoribbons With Sawtooth Zigzag Edges

    NASA Astrophysics Data System (ADS)

    Wang, D.; Zhang, Z.; Zhu, Z.; Liang, B.

    2014-12-01

    The magnetic structure and magnetic transport properties of hydrogen-passivated sawtooth zigzag-edge graphene nanoribbons (STGNRs) are investigated theoretically. It is found that all-sized ground-state STGNRs are ferromagnetic and always feature magnetic semiconductor properties, whose spin splitting energy gap Eg changes periodically with the width of STGNRs. More importantly, for the STGNR based device, the dual spin-filtering effect with the perfect (100%) spin polarization and high-performance dual spin diode effect with a rectification ratio about 1010 can be predicted. Particularly, a highly effective spin-valve device is likely to be realized, which displays a giant magnetoresistace (MR) approaching 1010%, which is three orders magnitude higher than the value predicted based on the zigzag graphene nanoribbons and six orders magnitude higher than previously reported experimental values for the MgO tunnel junction. Our findings suggest that STGNRs might hold a significant promise for developing spintronic devices.

  15. First-principles study of carrier-induced ferromagnetism in bilayer and multilayer zigzag graphene nanoribbons

    NASA Astrophysics Data System (ADS)

    Sawada, Keisuke; Ishii, Fumiyuki; Saito, Mineo

    2014-04-01

    We studied magnetism in bilayer and multilayer zigzag graphene nanoribbons (ZGNRs) through first-principles density functional theory calculations. We found that the magnetic ground state of bilayer ZGNRs is the C-type antiferromagnetic (AFM) state, which is the AFM order between intraplane-edge carbon atoms and ferromagnetic (FM) order between interplane edge carbon atoms. In the cases of infinitely stacked multilayer ZGNRs, i.e., zigzag graphite nanoribbons, the C-type AFM state is also the most stable. By carrier doping, we found that the magnetic ground state changed from the C-AFM state to the FM state and, thus, realized two-dimensional FM surface (edge) states of graphite with a metallic conductivity.

  16. Optical properties of fluorescent zigzag graphene quantum dots derived from multi-walled carbon nanotubes

    SciTech Connect

    Chen, Wei; Li, Fushan Wu, Chaoxing; Guo, Tailiang

    2014-02-10

    Graphene quantum dots (GQDs), which are edge-bound nanometer-size graphene pieces, have fascinating electronic and optical properties due to their quantum confinement and edge effect. In this paper, GQDs were synthesized by using acid treatment and chemical exfoliation of multi-walled carbon nanotubes (MWCNTs). The structure of the GQDs was investigated by transmission electron microscope. The GQDs have a uniform size distribution, zigzag edge structure and two-dimensional morphology. The results indicated that the GQDs have bright blue emission upon UV excitation. The highly fluorescent GQDs exhibited high water solubility and good stability. It is shown that the acid treatment of MWCNTs leads to the formation of the functional group in zigzag sites, which results in the pH-dependent fluorescence of the GQDs.

  17. Controlled Formation of Zigzag and Armchair Edges in Graphene Nanoribbons by Joule Heating

    SciTech Connect

    Sumpter, Bobby G; Dresselhaus, M; Terrones Maldonado, Mauricio; Meunier, Vincent; Romo Herrera, Jose M; Jia, Xiaoting; Hofmann, Mario; Campos-Delgado, Jessica; Reina, Alfonso; Kong, Jing; Hsieh, Ya-Ping; Son, Hyungbin

    2009-01-01

    We demonstrate and monitor an efficient edge reconstruction process, at the atomic scale, for graphite nanoribbons by Joule heating inside an integrated transmission electron microscope equipped with a scanning tunneling stage STM (TEM-STM system). During Joule annealing, sharp edges and step-edge arrays are formed, mostly with either zigzag or armchair edge configurations. Their formation is driven by both thermal and electric field related mechanisms. Model calculations show that the dominant annealing mechanisms involve point defect annealing and edge reconstruction. Joule heating is thus shown to provide an effective way to produce clean zigzag and armchair edges, which could be useful for both fundamental studies of edge reactivity, magnetism, and could provide a route for increasing carrier mobility and for the development of future electronics applications.

  18. Analysis of Rotational Structure in the High-Resolution Infrared Spectra of the TRANS-HEXATRIENE-1,1-D2 and -CIS-1-D1 Species

    NASA Astrophysics Data System (ADS)

    Craig, Norman C.; Fuson, Hannah A.; Tian, Hengfeng; Blake, Thomas A.

    2011-06-01

    Hexatriene-1,1-D2 with some admixture of the cis-1-D1 and trans-1-D1 species was synthesized by reaction of 2,4-pentadienal and (methyl-D3)-triphenylphosphonium iodide (Wittig reagent). The trans isomer was isolated by preparative gas chromatography, and the high-resolution (0.0015 Cm-1) infrared spectrum was recorded on a Bruker IFS 125HR instrument. The rotational structure in two C-type bands for the 1,1-D2 species was analyzed. For this species the bands at 902.043 and 721.864 Cm-1 yielded composite ground state rotational constants of A0 = 0.801882(1), B0 = 0.041850(2), and C0 = 0.039804(1) Cm-1. For the cis-1-D1 species the C-type band at 803.018 Cm-1 gave A0 = 0.809384(2), B0 = 0.043530(3), and C0 = 0.041321(2) Cm-1. By iodine-catalyzed isomerization, we have obtained some of the much less favored cis isomer and hope to obtain microwave spectra for its three deuterium-substituted species. The rotational constants reported here contribute to data needed for determining a semi-experimental structure for trans-hexatriene, which should show that the structural consequences of pi-electron delocalization increase with the chain length of polyenes.

  19. 75 FR 27411 - Airworthiness Directives; Turbomeca Arriel 1B, 1D, 1D1, and 1S1 Turboshaft Engines

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-05-17

    ... (that incorporate Turbomeca Modification (mod) TU 148), Arriel 1D, 1D1, and 1S1 turboshaft engines that do not incorporate mod TU 347. That AD also requires initial and repetitive replacements of 2nd stage... incorporate mod TU 148), 1D, 1D1, and 1S1 turboshaft engines that do not incorporate mod TU 347. We...

  20. High resolution scanning tunneling microscopy of a 1D coordination polymer with imidazole-based N,N,O ligands on HOPG.

    PubMed

    Fischer, Nina V; Mitra, Utpal; Warnick, Karl-Georg; Dremov, Viacheslav; Stocker, Michael; Wölfle, Thorsten; Hieringer, Wolfgang; Heinemann, Frank W; Burzlaff, Nicolai; Görling, Andreas; Müller, Paul

    2014-09-08

    Novel κ(3) -N,N,O ligands tend to form 1D coordination polymer strands. Deposition of 1D structures on highly oriented pyrolytic graphite (HOPG) was achieved from diluted solutions and polymer strands have been studied on HOPG by AFM/STM. Single strands were mapped by STM and their electronic properties were subsequently characterized by current imaging tunneling spectroscopy (CITS). Periodic density functional calculations simulating a polymer strand deposited on a HOPG surface are in agreement with the zig-zag structure indicated by experimental findings. Both the observed periodicity and the Zn-Zn distances can be reproduced in the simulations. Van der Waals interactions were found to play a major role for the geometry of the isolated polymer strand, for the adsorption geometry on HOPG, as well as for the adsorption energy.

  1. Zigzag Generalized Lévy Walk: the In Vivo Search Strategy of Immunocytes

    PubMed Central

    Li, Hui; Qi, Shuhong; Jin, Honglin; Qi, Zhongyang; Zhang, Zhihong; Fu, Ling; Luo, Qingming

    2015-01-01

    Immune responses are based on the coordinated searching behaviors of immunocytes that are aimed at tracking down specific targets. The search efficiency of immunocytes significantly affects the speed of initiation and development of immune responses. Previous studies have shown that not only the intermittent walk but also the zigzag turning preference of immunocytes contributes to the search efficiency. However, among existing models describing immunocytes' search strategy, none has captured both features. Here we propose a zigzag generalized Lévy walk model to describe the search strategy of immunocytes more accurately and comprehensively by considering both the intermittent and the zigzag-turning walk features. Based on the analysis of the searching behaviors of typical immune cell types, dendritic cells and leukocytes, in their native physiological environment, we demonstrate that the model can describe the in vivo search strategy of immunocytes well. Furthermore, by analyzing the search efficiency, we find that this type of search strategy enables immunocytes to capture rare targets in approximately half the time than the previously proposed generalized Lévy walk. This study sheds new light on the fundamental mechanisms that drive the efficient initiation and development of immune responses and in turn may lead to the development of novel therapeutic approaches for diseases ranging from infection to cancer. PMID:26379792

  2. Thermally induced spin-dependent current based on Zigzag Germanene Nanoribbons

    NASA Astrophysics Data System (ADS)

    Majidi, Danial; Faez, Rahim

    2017-02-01

    In this paper, using first principle calculation and non-equilibrium Green's function, the thermally induced spin current in Hydrogen terminated Zigzag-edge Germanene Nanoribbon (ZGeNR-H) is investigated. In this model, because of the difference between the source and the drain temperature of ZGeNR device, the spin up and spin down currents flow in the opposite direction with two different threshold temperatures (Tth). Hence, a pure spin polarized current which belongs to spin down is obtained. It is shown that, for temperatures above the threshold temperature spin down current increases with the increasing temperature up to 75 K and then decreases. But spin up current rises steadily and in the high temperature we can obtain polarized spin up current. In addition, we show an acceptable spin current around the room temperature for ZGeNR. The transmission peaks in ZGeNR which are closer to the Fermi level rather than Zigzag Graphene Nanoribbon (ZGNRS) which causes ZGeNR to have spin current at higher temperatures. Finally, it is indicated that by tuning the back gate voltage, the spin current can be completely modulated and polarized. Simulation results verify the Zigzag Germanene Nanoribbon as a promising candidate for spin caloritronics devices, which can be applied in future low power consumption technology.

  3. Refinement of Timoshenko Beam Theory for Composite and Sandwich Beams Using Zigzag Kinematics

    NASA Technical Reports Server (NTRS)

    Tessler, Alexander; DiSciuva, Marco; Gherlone, Marco

    2007-01-01

    A new refined theory for laminated-composite and sandwich beams that contains the kinematics of the Timoshenko Beam Theory as a proper baseline subset is presented. This variationally consistent theory is derived from the virtual work principle and employs a novel piecewise linear zigzag function that provides a more realistic representation of the deformation states of transverse shear flexible beams than other similar theories. This new zigzag function is unique in that it vanishes at the top and bottom bounding surfaces of a beam. The formulation does not enforce continuity of the transverse shear stress across the beam s cross-section, yet is robust. Two major shortcomings that are inherent in the previous zigzag theories, shear-force inconsistency and difficulties in simulating clamped boundary conditions, and that have greatly limited the utility of these previous theories are discussed in detail. An approach that has successfully resolved these shortcomings is presented herein. This new theory can be readily extended to plate and shell structures, and should be useful for obtaining accurate estimates of structural response of laminated composites.

  4. High power tube solid-state laser with zigzag propagation of pump and laser beam

    NASA Astrophysics Data System (ADS)

    Savich, Michael

    2015-02-01

    A novel resonator and pumping design with zigzag propagation of pumping and laser beams permits to design an improved tube Solid State Laser (SSL), solving the problem of short absorption path to produce a high power laser beam (100 - 1000kW). The novel design provides an amplifier module and laser oscillator. The tube-shaped SSL includes a gain element fiber-optically coupled to a pumping source. The fiber optic coupling facilitates light entry at compound Brewster's angle of incidence into the laser gain element and uses internal reflection to follow a "zigzag" path in a generally spiral direction along the length of the tube. Optics are arranged for zigzag propagation of the laser beam, while the cryogenic cooling system is traditional. The novel method of lasing uses advantages of cylindrical geometry to reach the high volume of gain medium with compactness and structural rigidity, attain high pump density and uniformity, and reach a low threshold without excessive increase of the temperature of the crystal. The design minimizes thermal lensing and stress effects, and provides high gain amplification, high power extraction from lasing medium, high pumping and lasing efficiency and a high beam quality.

  5. Design, synthesis, and functional activity of labeled CD1d glycolipid agonists.

    PubMed

    Jervis, Peter J; Polzella, Paolo; Wojno, Justyna; Jukes, John-Paul; Ghadbane, Hemza; Garcia Diaz, Yoel R; Besra, Gurdyal S; Cerundolo, Vincenzo; Cox, Liam R

    2013-04-17

    Invariant natural killer T cells (iNKT cells) are restricted by CD1d molecules and activated upon CD1d-mediated presentation of glycolipids to T cell receptors (TCRs) located on the surface of the cell. Because the cytokine response profile is governed by the structure of the glycolipid, we sought a method for labeling various glycolipids to study their in vivo behavior. The prototypical CD1d agonist, α-galactosyl ceramide (α-GalCer) 1, instigates a powerful immune response and the generation of a wide range of cytokines when it is presented to iNKT cell TCRs by CD1d molecules. Analysis of crystal structures of the TCR-α-GalCer-CD1d ternary complex identified the α-methylene unit in the fatty acid side chain, and more specifically the pro-S hydrogen at this position, as a site for incorporating a label. We postulated that modifying the glycolipid in this way would exert a minimal impact on the TCR-glycolipid-CD1d ternary complex, allowing the labeled molecule to function as a good mimic for the CD1d agonist under investigation. To test this hypothesis, the synthesis of a biotinylated version of the CD1d agonist threitol ceramide (ThrCer) was targeted. Both diastereoisomers, epimeric at the label tethering site, were prepared, and functional experiments confirmed the importance of substituting the pro-S, and not the pro-R, hydrogen with the label for optimal activity. Significantly, functional experiments revealed that biotinylated ThrCer (S)-10 displayed behavior comparable to that of ThrCer 5 itself and also confirmed that the biotin residue is available for streptavidin and antibiotin antibody recognition. A second CD1d agonist, namely α-GalCer C20:2 4, was modified in a similar way, this time with a fluorescent label. The labeled α-GalCer C20:2 analogue (11) again displayed functional behavior comparable to that of its unlabeled substrate, supporting the notion that the α-methylene unit in the fatty acid amide chain should be a suitable site for attaching

  6. Design, Synthesis, and Functional Activity of Labeled CD1d Glycolipid Agonists

    PubMed Central

    2013-01-01

    Invariant natural killer T cells (iNKT cells) are restricted by CD1d molecules and activated upon CD1d-mediated presentation of glycolipids to T cell receptors (TCRs) located on the surface of the cell. Because the cytokine response profile is governed by the structure of the glycolipid, we sought a method for labeling various glycolipids to study their in vivo behavior. The prototypical CD1d agonist, α-galactosyl ceramide (α-GalCer) 1, instigates a powerful immune response and the generation of a wide range of cytokines when it is presented to iNKT cell TCRs by CD1d molecules. Analysis of crystal structures of the TCR−α-GalCer–CD1d ternary complex identified the α-methylene unit in the fatty acid side chain, and more specifically the pro-S hydrogen at this position, as a site for incorporating a label. We postulated that modifying the glycolipid in this way would exert a minimal impact on the TCR–glycolipid–CD1d ternary complex, allowing the labeled molecule to function as a good mimic for the CD1d agonist under investigation. To test this hypothesis, the synthesis of a biotinylated version of the CD1d agonist threitol ceramide (ThrCer) was targeted. Both diastereoisomers, epimeric at the label tethering site, were prepared, and functional experiments confirmed the importance of substituting the pro-S, and not the pro-R, hydrogen with the label for optimal activity. Significantly, functional experiments revealed that biotinylated ThrCer (S)-10 displayed behavior comparable to that of ThrCer 5 itself and also confirmed that the biotin residue is available for streptavidin and antibiotin antibody recognition. A second CD1d agonist, namely α-GalCer C20:2 4, was modified in a similar way, this time with a fluorescent label. The labeled α-GalCer C20:2 analogue (11) again displayed functional behavior comparable to that of its unlabeled substrate, supporting the notion that the α-methylene unit in the fatty acid amide chain should be a suitable site for

  7. Synthesis and characterization of 1D iron(II) spin crossover coordination polymers with hysteresis.

    PubMed

    Bauer, Wolfgang; Lochenie, Charles; Weber, Birgit

    2014-02-07

    Purposeful ligand design was used for the synthesis of eight new 1D iron(II) spin crossover coordination polymers aiming for cooperative spin transitions with hysteresis. The results from magnetic measurements and X-ray structure analysis show that the combination of rigid linkers and a hydrogen bond network between the 1D chains is a promising tool to reach this goal. Five of the eight new samples show a cooperative spin transition with hysteresis with up to 43 K wide hysteresis loops.

  8. On the origin of multi-step spin transition behaviour in 1D nanoparticles

    NASA Astrophysics Data System (ADS)

    Chiruta, Daniel; Jureschi, Catalin-Maricel; Linares, Jorge; Dahoo, Pierre Richard; Garcia, Yann; Rotaru, Aurelian

    2015-09-01

    To investigate the spin state switching mechanism in spin crossover (SCO) nanoparticles, a special attention is given to three-step thermally induced SCO behavior in 1D chains. An additional term is included in the standard Ising-like Hamiltonian to account for the border interaction between SCO molecules and its local environment. It is shown that this additional interaction, together with the short range interaction, drives the multi-steps thermal hysteretic behavior in 1D SCO systems. The relation between a polymeric matrix and this particular multi-step SCO phenomenon is discussed accordingly. Finally, the environmental influence on the SCO system's size is analyzed as well.

  9. Crystal structure of 7,8,9,10-tetra­hydro­benzo[b]naphtho­[2,1-d]furan

    PubMed Central

    Wu, Zhongyuan; Reetz, Manfred T.; Harms, Klaus

    2016-01-01

    In the title compound, C16H14O, the cyclo­hexene ring has a half-chair conformation. The mean plane, calculated through all non-H atoms of the mol­ecule, except for the central CH2 atoms of the cyclo­hexene ring, which deviate by 0.340 (3) and −0.369 (3) Å from this mean plane, has an r.m.s. deviation of 0.012 Å. In the crystal, there are C—H⋯π contacts present, resulting in the formation of zigzag chains propagating along the [010] direction. PMID:26870597

  10. 1D-1D Coulomb drag in a 6 Million Mobility Bi-layer Heterostructure

    NASA Astrophysics Data System (ADS)

    Bilodeau, Simon; Laroche, Dominique; Xia, Jian-Sheng; Lilly, Mike; Reno, John; Pfeiffer, Loren; West, Ken; Gervais, Guillaume

    We report Coulomb drag measurements in vertically-coupled quantum wires. The wires are fabricated in GaAs/AlGaAs bilayer heterostructures grown from two different MBE chambers: one at Sandia National Laboratories (1.2M mobility), and the other at Princeton University (6M mobility). The previously observed positive and negative drag signals are seen in both types of devices, demonstrating the robustness of the result. However, attempts to determine the temperature dependence of the drag signal in the 1D regime proved challenging in the higher mobility heterostructure (Princeton), in part because of difficulties in aligning the wires within the same transverse subband configuration. Nevertheless, this work, performed at the Microkelvin laboratory of the University of Florida, is an important proof-of-concept for future investigations of the temperature dependence of the 1D-1D drag signal down to a few mK. Such an experiment could confirm the Luttinger charge density wave interlocking predicted to occur in the wires. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL8500.

  11. Adiabatic quantum state transfer in tight-binding chains using periodic driving fields

    NASA Astrophysics Data System (ADS)

    Longhi, S.

    2014-09-01

    A method for high-fidelity coherent adiabatic transport in a zig-zag tight-binding chain, based on application of two external periodic driving fields, is theoretically proposed. The method turns out to be robust against imperfections and disorder of the static lattice Hamiltonian, is tolerant to next-nearest neighborhood interactions, and enables coherent transport in long chains without the need for a local control and timing of the trapping potential.

  12. Simulations of Edge Effect in 1D Spin Crossover Compounds by Atom-Phonon Coupling Model

    NASA Astrophysics Data System (ADS)

    Linares, J.; Chiruta, D.; Jureschi, C. M.; Alayli, Y.; Turcu, C. O.; Dahoo, P. R.

    2016-08-01

    We used the atom-phonon coupling model to explain and illustrate the behaviour of a linear nano-chain of molecules. The analysis of the system's behaviour was performed using Free Energy method, and by applying Monte Carlo Metropolis (MCM) method which take into account the phonon contribution. In particular we tested both the MCM algorithm and the dynamic-matrix method and we expose how the thermal behaviour of a 1D spin crossover system varies as a function of different factors. Furthermore we blocked the edge atoms of the chain in its high spin state to study the effect on the system's behaviour.

  13. Zigzag faceting and width refinement of graphene nanoribbons and nanoperforations via catalyzed edge-annealing on Cu(111)

    NASA Astrophysics Data System (ADS)

    Safron, Nathaniel S.; Choi, Jonathan W.; Kim, Myungwoong; Shin, Naechul; Gopalan, Padma; Arnold, Michael S.

    2015-12-01

    Top-down subtractive lithography has previously been used to pattern graphene nanostructures which lack ideal properties due to (1) limited resolution and (2) disordered edges. Here, we introduce a method to convert such disordered edges into relatively smooth zigzag edges via annealing on a Cu(111) substrate at ~950 °C. The Cu catalyzes the re-arrangement of graphene edge atoms to energetically favorable sites, inducing zigzag edge faceting. The dimensions of the graphene nanostructures can be increased, decreased, or held constant during the annealing by tuning the relative balance between growth and etching reactions, described by a fundamental growth rate equation. To demonstrate the flexibility of this method, we lithographically pattern graphene nanoribbons with zigzag or armchair orientations, or alternatively perforate graphene with circular holes, and then anneal these nanostructures to realize zigzag edge termination in each case, with nanostructure feature size tailored from 8 to 80 nm. The annealed nanostructures have smoother zigzag edges (~40% reduction in 1σ line edge roughness), and Raman spectroscopy confirms that they have lower edge disorder than top-down patterned samples.

  14. Effect of vertical-strain-induced symmetry breaking on transport properties of zigzag graphene nanoribbons

    NASA Astrophysics Data System (ADS)

    Zou, Dongqing; Zhao, Wenkai; Fang, Changfeng; Cui, Bin; Liu, Desheng

    2017-02-01

    Using density functional theory combined with nonequilibrium Green's function formalism, we investigate the transport properties of zigzag graphene nanoribbons (ZGNRs) under vertical strain. Our calculations show that localized state induced by vertical strain will inhibit the electronic transport of the systems at zero bias, but at nonzero bias, the localized state can enhance the electronic transport behavior if ZGNRs are symmetry with respect to the mid-plane between two edges. This is because the localized state produces an asymmetry electron density distribution which break the current suppression. These findings may be useful for the application of strain-induced ZGNR based molecular devices.

  15. Effect of edge vacancies on localized states in a semi-infinite zigzag graphene sheet

    NASA Astrophysics Data System (ADS)

    Glebov, A. A.; Katkov, V. L.; Osipov, V. A.

    2016-12-01

    The effect of vacancies on the robustness of zero-energy edge electronic states in zigzag-type graphene layer is studied at different concentrations and distributions of defects. All calculations are performed by using the Green's function method and the tight-binding approximation. It is found that the arrangement of defects plays a crucial role in the destruction of the edge states. We have specified a critical distance between edge vacancies when their mutual influence becomes significant and affects markedly the density of electronic states at graphene edge.

  16. The electronic and magnetic properties of corrugated zigzag graphene nanoribbons with divacancy defects

    NASA Astrophysics Data System (ADS)

    Tan, Xiao-Dong; Liao, Xiao-Ping; Sun, Litao

    2017-01-01

    We investigate the electronic and magnetic properties of the corrugated zigzag graphene nanoribbons (ZGNRs) with divacancy defects by means of the first principle calculations. We show that the magnitude of corrugation in the defective ZGNR determines whether the system is in the antiferromagnetic state, in the ferromagnetic state, or in the nonmagnetic state. Correspondingly, the mutual transition between the semiconductor and the metal can also be realized in this structure. Moreover, for semiconductors the energy gap displays oscillating behaviors as the magnitude of corrugation increases. These results are identified as being useful in manufacturing flexible devices.

  17. Aharanov-Bohm effect for the edge states of zigzag carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Sasaki, K.; Suzuki, M.; Saito, R.

    2008-01-01

    Two delocalized states of metallic zigzag carbon nanotubes near the Dirac point can be localized by the Aharanov-Bohm magnetic field around 20T . The dependence of the localization on the length and diameter of the nanotubes shows that the localization-delocalization transition can be observed for 2nm diameter tube. The mechanism of the localization is explained in terms of the deformation-induced gauge field, which shows a topological nature of the localization. The transition from the delocalized states to the localized states can be observed by scanning tunneling microscopy and spectroscopy. A similarity between the transition and the spin Hall effect is discussed.

  18. Edge modes in zigzag and armchair ribbons of monolayer MoS2.

    PubMed

    Rostami, Habib; Asgari, Reza; Guinea, Francisco

    2016-12-14

    We explore the electronic structure, orbital character and topological aspect of a monolayer MoS2 nanoribbon using tight-binding (TB) and low-energy ([Formula: see text]) models. We obtain a mid-gap edge mode in the zigzag ribbon of monolayer MoS2, which can be traced back to the topological properties of the bulk band structure. Monolayer MoS2 can be considered as a valley Hall insulator. The boundary conditions at armchair edges mix the valleys on the edges, and a gap is induced in the edge modes. The spin-orbit coupling in the valence band reduces the hybridization of the bulk states.

  19. Electronic thermal conductivity of armchair graphene nanoribbons and zigzag carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Mousavi, Hamze; Khodadadi, Jabbar; Kurdestany, Jamshid Moradi; Grabowski, Marek

    2017-01-01

    Through the Green's function formalism and tight-binding Hamiltonian model calculations, the temperature dependent electronic thermal conductivity (TC) for different diameters of zigzag carbon nanotubes and their corresponding unzipped armchair graphene nanoribbons is calculated. All functional temperature dependencies bear crossovers, for which, at higher temperatures, nanotubes have a slightly higher TC than their derived nanoribbons, while below that crossover, both systems exhibit a significant coincidence over a moderate range of lower temperatures. Noticeably, TC decreases with increasing the width or diameter of the corresponding systems. Also, at low temperatures TC is proportional to the density of states around the Fermi level, and thus increasing for metal or semiconductors of narrower gap cases.

  20. Effect of edge vacancies on localized states in semi-infinite zigzag graphene sheet

    NASA Astrophysics Data System (ADS)

    Glebov, A. A.; Katkov, V. L.; Osipov, V. A.

    2016-12-01

    The effect of vacancies on the robustness of zero-energy edge electronic states in zigzag-type graphene layer is studied at different concentrations and distributions of defects. All calculations are performed by using the Green's function method and the tight-binding approximation. It is found that the arrangement of defects plays a crucial role in the destruction of the edge states. We have specified a critical distance between edge vacancies when their mutual influence becomes significant and affects markedly the density of electronic states at graphene edge.

  1. The modification of benzene adsorption on zigzag single-wall carbon nanotubes by carboxylation

    NASA Astrophysics Data System (ADS)

    Hamadanian, Masood; Tavangar, Zahra; Naseh, Sara

    2016-12-01

    In this work, the adsorption of benzene molecule on (10,0) functionalized zigzag single-wall carbon nanotubes was studied using density functional theory. Geometric structures, adsorption energies and electronic properties of five supercells were investigated. It was found that the carboxylation causes a notable increment in the adsorption capability of SWCNT in uptaking benzene as a pollutant molecule. The highest absorbency was achieved when benzene molecule had interaction with both SWCNT and COOH functional group through π-π interaction and hydrogen bonding.

  2. Focusing and directional beaming effects of airborne sound through a planar lens with zigzag slits

    SciTech Connect

    Tang, Kun; Qiu, Chunyin Lu, Jiuyang; Ke, Manzhu; Liu, Zhengyou

    2015-01-14

    Based on the Huygens-Fresnel principle, we design a planar lens to efficiently realize the interconversion between the point-like sound source and Gaussian beam in ambient air. The lens is constructed by a planar plate perforated elaborately with a nonuniform array of zigzag slits, where the slit exits act as subwavelength-sized secondary sources carrying desired sound responses. The experiments operated at audible regime agree well with the theoretical predictions. This compact device could be useful in daily life applications, such as for medical and detection purposes.

  3. Pure spin current induced by adiabatic quantum pumping in zigzag-edged graphene nanoribbons

    SciTech Connect

    Souma, Satofumi Ogawa, Matsuto

    2014-05-05

    We show theoretically that pure spin current can be generated in zigzag edged graphene nanoribbons through the adiabatic pumping by edge selective pumping potentials. The origin of such pure spin current is the spin splitting of the edge localized states, which are oppositely spin polarized at opposite edges. In the proposed device, each edge of the ribbon is covered by two independent time-periodic local gate potentials with a definite phase difference, inducing the edge spin polarized current. When the pumping phase difference is opposite in sign between two edges, the total charge currents is zero and the pure edge spin current is generated.

  4. A density functional theory-based finite element method to study the vibrational characteristics of zigzag phosphorene nanotubes

    NASA Astrophysics Data System (ADS)

    Shahnazari, A.; Ansari, R.; Rouhi, S.

    2017-04-01

    In this paper, the vibrational characteristics of zigzag phosphorene nanotubes are investigated by using a three-dimensional finite element model. The beam elements are used to simulate the P-P bonds in the structure of the phosphorene nanotubes. The elastic properties of the beam elements are computed from the similarity of energy terms in the molecular and structural mechanics. Besides, mass elements are located at the place of the atoms. Considering the zigzag phosphorene nanotubes with different diameters, it is shown that the effect of the diameter on the first natural frequencies of the nanotubes can be neglected. However, this effect increases for higher modes. Besides, at the same diameter, the zigzag phosphorene nanotubes with larger aspect ratios (length/diameter) have smaller frequencies.

  5. Zigzagging causility model of EPR correlations and on the interpretation of quantum mechanics

    SciTech Connect

    de Beauregard, O.C.

    1988-09-01

    Being formalized inside the S-matrix scheme, the zigzagging causility model of EPR correlations has full Lorentz and CPT invariance. EPR correlations, proper or reversed, and Wheeler's smoky dragon metaphor are respectively pictured in a spacetime or in the momentum-energy space, as V-shaped, anti LAMBDA-shaped, or C-shaped ABC zigzags, with a summation at B over virtual states absolute value B>

  6. Geometric effects on mixing performance in a novel passive micromixer with trapezoidal-zigzag channels

    NASA Astrophysics Data System (ADS)

    Le The, Hai; Ta, Bao Quoc; Le Thanh, Hoa; Dong, Tao; Nguyen Thoi, Trung; Karlsen, Frank

    2015-09-01

    A novel passive micromixer, called a trapezoidal-zigzag micromixer (TZM), is reported. A TZM is composed of trapezoidal channels in a zigzag and split-recombine arrangement that enables multiple mixing mechanisms, including splitting-recombining, twisting, transversal flows, vortices, and chaotic advection. The effects of geometric parameters of the TZM on mixing performance are systematically investigated by the Taguchi method and numerical simulations in COMSOL Multiphysics. The number of mixing units, the slope angle of the trapezoidal channel, the height of the constriction element, and the width ratio between the middle-trapezoidal channel and the side-trapezoidal channel are the four parameters under study. The mixing performance of the TZM is investigated at three different Reynolds number (Re) values of 0.5, 5, and 50. The results showed that a TZM with six mixing units, a trapezoidal slope angle of 75°, a constricting height of 100 µm, and a width ratio of 0.5 has the highest mixing efficiency. This optimal TZM has a mixing efficiency greater than 85% for Re values from 0.1 to 80. In particular, for Re  ⩽  0.9 and Re  ⩾  20, the mixing efficiency of the optimal TZM is greater than 90%. The proposed TZM has a higher mixing efficiency and a smaller footprint than previously reported micromixers.

  7. A single bubble path transition from spiral to zigzag in dilute surfactant solution

    NASA Astrophysics Data System (ADS)

    Tagawa, Yoshiyuki; Kawaguchi, Wataru; Funakubo, Ami; Takagi, Shu; Matsumoto, Yoichiro

    2007-11-01

    The surfactant effect on a single bubble motion is so important that it changes whole bubbly flow structures. One of the surfactant key effects is to decrease bubble rise velocity. This phenomenon is described as Marangoni effect which is quantitatively investigated by many experiments and numerical calculations of straight rising bubbles. Some other previous researches studied a bubble trajectory transition from a zigzag trajectory to spiral in super purified water (Mougin et al. 2002). However, the surfactant effect on this 3D motion bubbles is not enough investigated. To investigate it in detail, we measured trajectories of single bubbles rising in a tank of 1300mm height filled with dilute surfactant solution. We observed a bubble motion transition from spiral to zigzag, which is just reverse transition of trajectories in super purified water. Considering our other measurement results of bubble trajectories in super purified water, those in different surfactant solution, and a profile of bubble rise velocity, we think this interesting result is explained by surfactant concentration on a bubble surface. We will discuss its mechanism in detail in our presentation.

  8. Polarization effects in active Fresnel rhomb zig-zag slab amplifier

    SciTech Connect

    Bikmatov, R.G.; Chernyak, V.M.; Ignat`ev, L.P.; Kuznetsov, V.G.; Pergament, M.I.; Smirnov, R.V.; Sokolov, V.I.; Hunt, J.T.; Manes, K.

    1997-01-27

    The concept to use a slab as active element, working in zig-zag geometry, and also as Fresnel rhomb, seems to be rather attractive. However, in this case different depolarization effects in active element arc of crucial importance. We have carried out the estimations of depolarization effects arising both due to mechanical loading of an active element at its fastening and due to thermooptical distortions. To check up these rigid requirements to depolarization (0.1 % - 0.01 %) careful measurements of depolarization effects and their sources are being carried out. Mechanical loading gives one of the main contributions in depolarization at fastening of active element. Using model experiments with glass Fresnel rhomb under mechanical loading we have measured depolarization effects. It is proposed to use additional glass plate to compensate beam depolarization in zig-zag slab. The received results allow to expect successful use of the slab amplifier as a Fresnel rhomb providing rather high quality of optical material of active clement.

  9. Tuning spin polarization and spin transport of zigzag graphene nanoribbons by line defects.

    PubMed

    Tang, G P; Zhang, Z H; Deng, X Q; Fan, Z Q; Zhu, H L

    2015-01-07

    From first-principles methods, the spin-dependent electronic properties of zigzag-edged graphene nanoribbons (ZGNRs) with a line defect (558-defect) are investigated systematically and compared to those of the pristine ZGNR. Results show that the line defect possesses an obvious tuning effect on the spin-polarization of the edge carbon atoms of the defective ZGNRs, and the spin-polarization and spin-transport are sensitive to the position of line defects. The defective ZGNRs can realize a transition from antiferromagnetism (AFM) to ferrimagnetism and ferromagnetism (FM) via changing the position of line defects from the center to the zigzag edge of ZGNRs. More importantly, when the line defect is located at the one edge, the defective ZGNRs exhibit the long-range magnetic ordering at edges with a high Curie temperature up to 276 K, and the defective ZGNR system can generate a high-performance spin-filter effect in the large bias range, 0.0-0.5 V. Such a sensitive modulation for the spin-polarization and spin-transport holds great promise for applications of the graphene-based systems in nano-scale spintronic devices.

  10. First-principles study on electron transport through BN-dimer embedded zigzag carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Egami, Yoshiyuki; Akera, Hiroshi

    2017-04-01

    First-principles calculations are performed for electron transmission through a metallic zigzag carbon nanotube with substitutional BN dimers parallel to the nanotube axis. The transmission coefficient is calculated in the energy range (around the charge neutrality point) in which there exist two degenerate subbands for each spin. Wave functions in the circumferential direction of one of the degenerate subbands can be chosen so as to have nodes at the position of a carbon dimer parallel to the nanotube axis. It is shown that the transmission probability of an incident wave with such wave-function nodes depends crucially on positions of BN dimers relative to the nodes. By placing each of dimers at one of the nodes, the transmission probability is substantially enhanced and is well described by the Born approximation in spite of spatially extended scattering potential due to ionized B and N. This suggests that the arrangement in the circumferential direction of various impurities influences transport through metallic zigzag carbon nanotubes.

  11. Peculiar half-metallic state in zigzag nanoribbons of MoS2: Spin filtering

    NASA Astrophysics Data System (ADS)

    Khoeini, F.; Shakouri, Kh.; Peeters, F. M.

    2016-09-01

    Layered structures of molybdenum disulfide (MoS2) belong to a new class of two-dimensional (2D) semiconductor materials in which monolayers exhibit a direct band gap in their electronic spectrum. This band gap has recently been shown to vanish due to the presence of metallic edge modes when MoS2 monolayers are terminated by zigzag edges on both sides. Here, we demonstrate that a zigzag nanoribbon of MoS2, when exposed to an external exchange field in combination with a transverse electric field, has the potential to exhibit a peculiar half-metallic nature and thereby allows electrons of only one spin direction to move. The peculiarity of such spin-selective conductors originates from a spin switch near the gap-closing region, so the allowed spin orientation can be controlled by means of an external gate voltage. It is shown that the induced half-metallic phase is resistant to random fluctuations of the exchange field as well as the presence of edge vacancies.

  12. Nematic and smectic ordering in a system of two-dimensional hard zigzag particles.

    PubMed

    Varga, Szabolcs; Gurin, Péter; Armas-Pérez, Julio C; Quintana-H, Jacqueline

    2009-11-14

    The orientational and positional ordering of the two-dimensional system of hard zigzag particles has been investigated by means of Onsager theory. Analytical results are obtained for the transition densities of the isotropic-nematic and the nematic-smectic phase transitions. It is shown that the stability of the nematic and smectic phases is very sensitive to the molecular shape. In the hard needle limit, only the isotropic-nematic phase transition takes place, while increasing the tail length and the bent angle between the central core and the tails destabilizes the nematic phase. On the other hand the stability of the smectic phase is due to the increasing excluded area cost with bent angle and the tail length. The zigzag particles pack in a layered structure such that they are tilted and form semi-ideal gas in the layers to push the high cost excluded area regions into the interstitial regions. The predictions of Onsager theory are in good agreement with MC simulation data.

  13. Electric field effect on (6,0) zigzag single-walled aluminum nitride nanotube.

    PubMed

    Baei, Mohammad T; Peyghan, Ali Ahmadi; Moghimi, Masoumeh

    2012-09-01

    Structural, electronic, and electrical responses of the H-capped (6,0) zigzag single-walled aluminum nitride nanotube was studied under the parallel and transverse electric fields with strengths 0-140 × 10(-4) a.u. by using density functional calculations. Geometry optimizations were carried out at the B3LYP/6-31G* level of theory using a locally modified version of the GAMESS electronic structure program. The dipole moments, atomic charge variations, and total energy of the (6,0) zigzag AlNNT show increases with increase in the applied external electric field strengths. The length, tip diameters, electronic spatial extent, and molecular volume of the nanotube do not significantly change with increasing electric field strength. The energy gap of the nanotube decreases with increases of the electric field strength and its reactivity is increased. Increase of the ionization potential, electron affinity, chemical potential, electrophilicity, and HOMO and LUMO in the nanotube with increase of the applied parallel electric field strengths shows that the parallel field has a much stronger interaction with the nanotube with respect to the transverse electric field strengths. Analysis of the parameters indicates that the properties of AlNNTs can be controlled by the proper external electric field.

  14. Quasi-1D physics in metal-organic frameworks: MIL-47(V) from first principles

    PubMed Central

    Jaeken, Jan W; De Baerdemacker, Stijn; Lejaeghere, Kurt; Van Speybroeck, Veronique

    2014-01-01

    Summary The geometric and electronic structure of the MIL-47(V) metal-organic framework (MOF) is investigated by using ab initio density functional theory (DFT) calculations. Special focus is placed on the relation between the spin configuration and the properties of the MOF. The ground state is found to be antiferromagnetic, with an equilibrium volume of 1554.70 Å3. The transition pressure of the pressure-induced large-pore-to-narrow-pore phase transition is calculated to be 82 MPa and 124 MPa for systems with ferromagnetic and antiferromagnetic chains, respectively. For a mixed system, the transition pressure is found to be a weighted average of the ferromagnetic and antiferromagnetic transition pressures. Mapping DFT energies onto a simple-spin Hamiltonian shows both the intra- and inter-chain coupling to be antiferromagnetic, with the latter coupling constant being two orders of magnitude smaller than the former, suggesting the MIL-47(V) to present quasi-1D behavior. The electronic structure of the different spin configurations is investigated and it shows that the band gap position varies strongly with the spin configuration. The valence and conduction bands show a clear V d-character. In addition, these bands are flat in directions orthogonal to VO6 chains, while showing dispersion along the the direction of the VO6 chains, similar as for other quasi-1D materials. PMID:25383285

  15. Nonlinear electrical conductivity in a 1D granular medium

    NASA Astrophysics Data System (ADS)

    Falcon, E.; Castaing, B.; Creyssels, M.

    2004-04-01

    We report on observations of the electrical transport within a chain of metallic beads (slightly oxidized) under an applied stress. A transition from an insulating to a conductive state is observed as the applied current is increased. The voltage-current ( U- I) characteristics are nonlinear and hysteretic, and saturate to a low voltage per contact (0.4 V). Our 1D experiment allows us to understand phenomena (such as the “Branly effect”) related to this conduction transition by focusing on the nature of the contacts instead of the structure of the granular network. We show that this transition comes from an electro-thermal coupling in the vicinity of the microcontacts between each bead - the current flowing through these contact points generates their local heating which leads to an increase of their contact areas, and thus enhances their conduction. This current-induced temperature rise (up to 1050 ^{circ}C) results in the microsoldering of the contact points (even for voltages as low as 0.4 V). Based on this self-regulated temperature mechanism, an analytical expression for the nonlinear U- I back trajectory is derived, and is found to be in very good agreement with the experiments. In addition, we can determine the microcontact temperature with no adjustable parameters. Finally, the stress dependence of the resistance is found to be strongly non-hertzian due to the presence of the surface films. This dependence cannot be usually distinguished from the one due to the disorder of the granular contact network in 2D or 3D experiments.

  16. Brady 1D seismic velocity model ambient noise prelim

    SciTech Connect

    Mellors, Robert J.

    2013-10-25

    Preliminary 1D seismic velocity model derived from ambient noise correlation. 28 Green's functions filtered between 4-10 Hz for Vp, Vs, and Qs were calculated. 1D model estimated for each path. The final model is a median of the individual models. Resolution is best for the top 1 km. Poorly constrained with increasing depth.

  17. First principle study of structural, electronic and magnetic properties of zigzag boron nitride nanoribbon: Role of vacancies

    SciTech Connect

    Kumar, Arun; Bahadur, Amar; Mishra, Madhukar; Vasudeva, Neena

    2015-05-15

    We study the effect of vacancies on the structural, electronic and magnetic properties of zigzag boron nitride nanoribbon (ZBNNR) by using first principle calculations. We find that the shift of the vacancies with respect to the ribbon edges causes change in the structural geometry, electronic structure and magnetization of ZBNNR. These vacancies also produce band gap modulation and consequently results the magnetization of ZBNNR.

  18. Molecular tectonics: from 1-D interwoven racemic chains to quadruple-stranded helices.

    PubMed

    Lin, Mei-Jin; Jouaiti, Abdelaziz; Kyritsakas, Nathalie; Hosseini, Mir Wais

    2010-01-07

    The combination of two positional isomers tectons 1 and 2, based on a racemic 1,1'-spirobi(indane) scaffold bearing two pyridine units, with HgCl(2) affords doubly interwoven and quadruple-stranded helical architectures, respectively.

  19. Spin electronic manipulation based on zigzag-edgegraphene nanojunction with a line defect

    NASA Astrophysics Data System (ADS)

    Li, Haidong; Zheng, Lili; Li, Ruixue

    2017-01-01

    We investigate the transport of spin electron through the zigzag-edge graphene nanojunction with a line defect. When the magnetization is zero, the conductance spectra exhibits a well-defined insulating band around the point far away from Dirac point. And the width of the insulating band is exactly equal to the energy splitting between the lowest conduction band of the left lead and the new state of the device region. For the parallel configuration, with the enhancement of the magnetization, the conductance value will be reduced by half around the Dirac point. For the antiparallel configuration, the width of the well-defined insulating band becomes larger with the rising of the magnetization.

  20. Structural and Electronic Properties of Zigzag Graphene Nanoribbons on Si(001) Substrates

    NASA Astrophysics Data System (ADS)

    Li, Jing; Yang, Shen-Yuan; Li, Shu-Shen

    2015-02-01

    We study the adsorption of zigzag graphene nanoribbons (GNRs) on Si(001) substrates using the first-principles density functional theory, exploring the effects of the interface interaction on the structural and electronic properties of both GNRs and the substrate. By comparing the adsorption structures predicted by the local density approximation, the generalized gradient approximation, and the DFT-D2 approach, we confirm that both edge and inner C atoms of GNRs can form covalent bonds with the substrate. The GNR/substrate interaction destroys the antiferromagnetic coupling of the edge states in GNRs. The charge transfer from the substrate to GNRs exhibits a complicated pattern and is mainly localized near the C-Si bonds. We also observe a strong perturbation of the surface states and a surface reconstruction transition induced by the GNR adsorption.

  1. Solution of the antiferromagnetic Ising model with multisite interaction on a zigzag ladder.

    PubMed

    Jurčišinová, E; Jurčišin, M

    2014-09-01

    We consider the antiferromagnetic spin-1/2 Ising model with multisite interaction in an external magnetic field on an infinite zigzag ladder. The model is solved exactly by using the transfer matrix method. Using the exact expression for the total magnetization per site, the magnetic properties of the model are investigated in detail. The model exhibits the formation of magnetization plateaus for low temperatures, and it is shown that their properties depend strongly on the strength of the multisite interaction. All possible ground states of the model are found and discussed. The existence of nontrivial singular ground states is proven and exact explicit expressions for them are found. The macroscopic degeneracy of the ground states is investigated and discussed.

  2. Modulation instability in a zigzag array of nonlinear waveguides with alternating positive and negative refractive indices

    SciTech Connect

    Dovgiy, A A

    2014-12-31

    The modulation instability is analytically investigated in a zigzag array of tunnel-coupled optical waveguides with alternating refractive indices and Kerr nonlinearity. Particular solutions to a system of coupled nonlinear equations are found. They describe the propagation of electromagnetic waves that are uniform along the waveguide and their instability is studied. It is shown that the coupling coefficient between the waveguides, which are non-nearest neighbours, has a significant effect on the instability of the waves in question. When the coupling coefficient exceeds a certain threshold, the modulation instability disappears regardless of the radiation power. The influence of the ratio of the wave amplitudes in adjacent waveguides to the instability of the particular solutions is studied. Different variants of the nonlinear response in waveguides are considered. The studies performed present a new unusual type of the modulation instability in nonlinear periodic systems. (metamaterials)

  3. Triplet p-wave pairing correlation in low-doped zigzag graphene nanoribbons

    NASA Astrophysics Data System (ADS)

    Ma, Tianxing; Yang, Fan; Huang, Zhongbing; Lin, Hai-Qing

    2017-02-01

    We reveal an edge spin triplet p–wave superconducting pairing correlation in slightly doped zigzag graphene nanoribbons. By employing a method that combines random-phase approximation, the finite-temperature determinant quantum Monte Carlo approach, and the ground-state constrained-path quantum Monte Carlo method, it is shown that such a spin-triplet pairing is mediated by the ferromagnetic fluctuations caused by the flat band at the edge. The spin susceptibility and effective pairing interactions at the edge strongly increase as the on-site Coulomb interaction increases, indicating the importance of electron-electron correlations. It is also found that the doping-dependent ground-state p-wave pairing correlation bears some similarity to the famous superconducting dome in the phase diagram of a high-temperature superconductor, while the spin correlation at the edge is weakened as the system is doped away from half filling.

  4. Effects of edge magnetism on the Kohn anomalies of zigzag graphene nanoribbons.

    PubMed

    Culchac, F J; Capaz, Rodrigo B

    2016-02-12

    The effects of edge magnetism on the Kohn anomaly (KA) of the G-band phonons of zigzag graphene nanoribbons (ZGNRs) are studied using a combination of the tight-binding and mean-field Hubbard models. We show that the opening of an energy gap, induced by magnetic ordering, significantly changes the KA effects, particularly for narrow ribbons in which the gap is larger than the phonon energy. Therefore, the G-band phonon frequency and lifetime are altered for a magnetically-ordered edge state with respect to an unpolarized edge state. The effects of temperature, ZGNR width, doping and transverse electric fields are systematically investigated. We propose using this effect to probe the magnetic order of edge states in graphene nanoribbons using Raman spectroscopy.

  5. Two-dimensional thermography image retrieval from zig-zag scanned data with TZ-SCAN

    NASA Astrophysics Data System (ADS)

    Okumura, Hiroshi; Yamasaki, Ryohei; Arai, Kohei

    2008-10-01

    TZ-SCAN is a simple and low cost thermal imaging device which consists of a single point radiation thermometer on a tripod with a pan-tilt rotator, a DC motor controller board with a USB interface, and a laptop computer for rotator control, data acquisition, and data processing. TZ-SCAN acquires a series of zig-zag scanned data and stores the data as CSV file. A 2-D thermal distribution image can be retrieved by using the second quefrency peak calculated from TZ-SCAN data. An experiment is conducted to confirm the validity of the thermal retrieval algorithm. The experimental result shows efficient accuracy for 2-D thermal distribution image retrieval.

  6. Edge modes in zigzag and armchair ribbons of monolayer MoS2

    NASA Astrophysics Data System (ADS)

    Rostami, Habib; Asgari, Reza; Guinea, Francisco

    2016-12-01

    We explore the electronic structure, orbital character and topological aspect of a monolayer MoS2 nanoribbon using tight-binding (TB) and low-energy (\\boldsymbol{k}\\centerdot \\boldsymbol{p} ) models. We obtain a mid-gap edge mode in the zigzag ribbon of monolayer MoS2, which can be traced back to the topological properties of the bulk band structure. Monolayer MoS2 can be considered as a valley Hall insulator. The boundary conditions at armchair edges mix the valleys on the edges, and a gap is induced in the edge modes. The spin-orbit coupling in the valence band reduces the hybridization of the bulk states.

  7. Width and defect effects on the electronic transport of zigzag MoS2 nanoribbons

    NASA Astrophysics Data System (ADS)

    An, Yipeng; Zhang, Mengjun; Da, Haixia; Fu, Zhaoming; Jiao, Zhaoyong; Liu, Zhiyong

    2016-06-01

    Using first-principles methods, we investigate the electronic transport properties of zigzag MoS2 nanoribbons (Z-MoS2NRs). The current-voltage (I-V) curves of Z-MoS2NRs show a negative differential resistive (NDR) effect, and are independent of nanoribbon width. The current flowing through the nanoribbon is mainly along the Mo-edge, with two different local current channels (Mo  →  Mo hop current and S  →  Mo  →  S bond current). The current will be suppressed when introducing a Mo vacancy-defect at the Mo-edge under low biases—while, under high biases, the current through the defected Z-MoS2NRs will increase a little, due to the other S-edge channel being opened.

  8. Non-equilibrium tunneling in zigzag graphene nanoribbon break-junction results in spin filtering

    NASA Astrophysics Data System (ADS)

    Jiang, Liming; Qiu, Wanzhi; Sharafat Hossain, Md; Al-Dirini, Feras; Evans, Robin; Skafidas, Efstratios

    2016-02-01

    Spintronic devices promise new faster and lower energy-consumption electronic systems. Graphene, a versatile material and candidate for next generation electronics, is known to possess interesting spintronic properties. In this paper, by utilizing density functional theory and non-equilibrium green function formalism, we show that Fano resonance can be generated by introducing a break junction in a zigzag graphene nanoribbon (ZGNR). Using this effect, we propose a new spin filtering device that can be used for spin injection. Our theoretical results indicate that the proposed device could achieve high spin filtering efficiency (over 90%) at practical fabrication geometries. Furthermore, our results indicate that the ZGNR break junction lattice configuration can dramatically affect spin filtering efficiency and thus needs to be considered when fabricating real devices. Our device can be fabricated on top of spin transport channel and provides good integration between spin injection and spin transport.

  9. Zigzag Connected Autotransformer-Based 24-pulse AC-DC Converter

    NASA Astrophysics Data System (ADS)

    Xiao-qiang, Chen; Hao, Qiu

    2015-02-01

    In this paper, a zigzag connected autotransformer-based 24-pulse AC-DC converter is designed, modeled and simulated to feed direct torque controlled induction motor drives. Winding arrangements and parameters of the autotransformer and interphase reactor are given. Moreover, the design procedure of the autotransformer is modified to make it suitable for retrofit applications. Simulation results indicate that the system is capable of eliminating up to 21st harmonics in the ac mains current. The effect of load variation and load character is also studied to demonstrate the performance and effectiveness of the proposed 24-pulse converters. A set of power quality indices at ac mains and dc side are presented to compare the performance of 6-, 12- and 24-pulse converters.

  10. Triplet p-wave pairing correlation in low-doped zigzag graphene nanoribbons

    PubMed Central

    Ma, Tianxing; Yang, Fan; Huang, Zhongbing; Lin, Hai-Qing

    2017-01-01

    We reveal an edge spin triplet p–wave superconducting pairing correlation in slightly doped zigzag graphene nanoribbons. By employing a method that combines random-phase approximation, the finite-temperature determinant quantum Monte Carlo approach, and the ground-state constrained-path quantum Monte Carlo method, it is shown that such a spin-triplet pairing is mediated by the ferromagnetic fluctuations caused by the flat band at the edge. The spin susceptibility and effective pairing interactions at the edge strongly increase as the on-site Coulomb interaction increases, indicating the importance of electron-electron correlations. It is also found that the doping-dependent ground-state p-wave pairing correlation bears some similarity to the famous superconducting dome in the phase diagram of a high-temperature superconductor, while the spin correlation at the edge is weakened as the system is doped away from half filling. PMID:28186185

  11. All-in-one 4-telescope beam combination with a zig-zag array of waveguides

    NASA Astrophysics Data System (ADS)

    Diener, Romina; Minardi, Stefano; Tepper, Jan; Nolte, Stefan; Labadie, Lucas

    2016-08-01

    In this work we propose a new geometry of discrete beam combiners (DBC) for spectrally-resolved stellar interferometry which overcomes limitations of previous designs. The new beam combiner is based on an array of coupled waveguides arranged in zig-zag pattern. It has been numerically optimized for the combination of 4 telescopes and engineered to operate in the L-band. We manufactured a first sample by direct laser writing in Gallium Lanthanum Sulfide glass, a highly transmissive material in the mid-infrared (550 nm to 10 μm). Initial near-field characterization of the fabricated sample at a wavelength of 3.4 μm are encouraging, but highlighted the necessity of a better control of the polarization dispersion of individual waveguides, as well as induced stresses from manufacturing process.

  12. Cubic Zig-Zag Enrichment of the Classical Kirchhoff Kinematics for Laminated and Sandwich Plates

    NASA Technical Reports Server (NTRS)

    Nemeth, Michael P.

    2012-01-01

    A detailed anaylsis and examples are presented that show how to enrich the kinematics of classical Kirchhoff plate theory by appending them with a set of continuous piecewise-cubic functions. This analysis is used to obtain functions that contain the effects of laminate heterogeneity and asymmetry on the variations of the inplane displacements and transverse shearing stresses, for use with a {3, 0} plate theory in which these distributions are specified apriori. The functions used for the enrichment are based on the improved zig-zag plate theory presented recently by Tessler, Di Scuva, and Gherlone. With the approach presented herein, the inplane displacements are represented by a set of continuous piecewise-cubic functions, and the transverse shearing stresses and strains are represented by a set of piecewise-quadratic functions that are discontinuous at the ply interfaces.

  13. Non-equilibrium tunneling in zigzag graphene nanoribbon break-junction results in spin filtering

    SciTech Connect

    Jiang, Liming; Qiu, Wanzhi; Sharafat Hossain, Md; Al-Dirini, Feras; Skafidas, Efstratios; Evans, Robin

    2016-02-07

    Spintronic devices promise new faster and lower energy-consumption electronic systems. Graphene, a versatile material and candidate for next generation electronics, is known to possess interesting spintronic properties. In this paper, by utilizing density functional theory and non-equilibrium green function formalism, we show that Fano resonance can be generated by introducing a break junction in a zigzag graphene nanoribbon (ZGNR). Using this effect, we propose a new spin filtering device that can be used for spin injection. Our theoretical results indicate that the proposed device could achieve high spin filtering efficiency (over 90%) at practical fabrication geometries. Furthermore, our results indicate that the ZGNR break junction lattice configuration can dramatically affect spin filtering efficiency and thus needs to be considered when fabricating real devices. Our device can be fabricated on top of spin transport channel and provides good integration between spin injection and spin transport.

  14. Ab-initio study of structural, electronic, and transport properties of zigzag GaP nanotubes.

    PubMed

    Srivastava, Anurag; Jain, Sumit Kumar; Khare, Purnima Swarup

    2014-03-01

    Stability and electronic properties of zigzag (3 ≤ n ≤ 16) gallium phosphide nanotubes (GaP NTs) have been analyzed by employing a systematic ab-intio approach based on density functional theory using generalized gradient approximation with revised Perdew Burke Ernzerhoff type parameterization. Diameter dependence of bond length, buckling, binding energy, and band gap has been investigated and the analysis shows that the bond length and buckling decreases with increasing diameter of the tube, highest binding energy of (16, 0) confirms this as the most stable amongst all the NTs taken into consideration. The present GaP NTs shows direct band gap and it increases with diameter of the tubes. Using a two probe model for (4, 0) NT the I-V relationship shows an exponential increase in current on applying bias voltage beyond 1.73 volt.

  15. Tailoring graphene magnetism by zigzag triangular holes: A first-principles thermodynamics study

    DOE PAGES

    Khan, Muhammad Ejaz; Zhang, P.; Sun, Yi -Yang; ...

    2016-03-30

    In this study, we discuss the thermodynamic stability and magnetic property of zigzag triangular holes (ZTHs) in graphene based on the results of first-principles density functional theory calculations. We find that ZTHs with hydrogen-passivated edges in mixed sp2/sp3 configurations (z211) could be readily available at experimental thermodynamic conditions, but ZTHs with 100% sp2 hydrogen-passivation (z1) could be limitedly available at high temperature and ultra-high vacuum conditions. Graphene magnetization near the ZTHs strongly depends on the type and the size of the triangles. While metallic z1 ZTHs exhibit characteristic edge magnetism due to the same-sublattice engineering, semiconducting z211 ZTHs do showmore » characteristic corner magnetism when the size is small < 2 nm. Our findings could be useful for experimentally tailoring metal-free carbon magnetism by simply fabricating triangular holes in graphene.« less

  16. Prediction of Composite Laminate Strength Properties Using a Refined Zigzag Plate Element

    NASA Technical Reports Server (NTRS)

    Barut, Atila; Madenci, Erdogan; Tessler, Alexander

    2013-01-01

    This study presents an approach that uses the refined zigzag element, RZE(exp2,2) in conjunction with progressive failure criteria to predict the ultimate strength of composite laminates based on only ply-level strength properties. The methodology involves four major steps: (1) Determination of accurate stress and strain fields under complex loading conditions using RZE(exp2,2)-based finite element analysis, (2) Determination of failure locations and failure modes using the commonly accepted Hashin's failure criteria, (3) Recursive degradation of the material stiffness, and (4) Non-linear incremental finite element analysis to obtain stress redistribution until global failure. The validity of this approach is established by considering the published test data and predictions for (1) strength of laminates under various off-axis loading, (2) strength of laminates with a hole under compression, and (3) strength of laminates with a hole under tension.

  17. Spontaneous nucleation of structural defects in inhomogeneous ion chains

    NASA Astrophysics Data System (ADS)

    De Chiara, Gabriele; del Campo, Adolfo; Morigi, Giovanna; Plenio, Martin B.; Retzker, Alex

    2010-11-01

    Structural defects in ion crystals can be formed during a linear quench of the transverse trapping frequency across the mechanical instability from a linear chain to a zigzag structure. The density of defects after the sweep can be conveniently described by the Kibble-Zurek mechanism (KZM). In particular, the number of kinks in the zigzag ordering can be derived from a time-dependent Ginzburg-Landau equation for the order parameter, here the zigzag transverse size, under the assumption that the ions are continuously laser cooled. In a linear Paul trap, the transition becomes inhomogeneous, since the charge density is larger in the center and more rarefied at the edges. During the linear quench, the mechanical instability is first crossed in the center of the chain, and a front, at which the mechanical instability is crossed during the quench, is identified that propagates along the chain from the center to the edges. If the velocity of this front is smaller than the sound velocity, the dynamics become adiabatic even in the thermodynamic limit and no defect is produced. Otherwise, the nucleation of kinks is reduced with respect to the case in which the charges are homogeneously distributed, leading to a new scaling of the density of kinks with the quenching rate. The analytical predictions are verified numerically by integrating the Langevin equations of motion of the ions, in the presence of a time-dependent transverse confinement. We argue that the non-equilibrium dynamics of an ion chain in a Paul trap constitutes an ideal scenario to test the inhomogeneous extension of the KZM, which lacks experimental evidence to date.

  18. Interaction of environmental contaminants with zebrafish organic anion transporting polypeptide, Oatp1d1 (Slco1d1)

    SciTech Connect

    Popovic, Marta; Zaja, Roko; Fent, Karl; Smital, Tvrtko

    2014-10-01

    Polyspecific transporters from the organic anion transporting polypeptide (OATP/Oatp) superfamily mediate the uptake of a wide range of compounds. In zebrafish, Oatp1d1 transports conjugated steroid hormones and cortisol. It is predominantly expressed in the liver, brain and testes. In this study we have characterized the transport of xenobiotics by the zebrafish Oatp1d1 transporter. We developed a novel assay for assessing Oatp1d1 interactors using the fluorescent probe Lucifer yellow and transient transfection in HEK293 cells. Our data showed that numerous environmental contaminants interact with zebrafish Oatp1d1. Oatp1d1 mediated the transport of diclofenac with very high affinity, followed by high affinity towards perfluorooctanesulfonic acid (PFOS), nonylphenol, gemfibrozil and 17α-ethinylestradiol; moderate affinity towards carbaryl, diazinon and caffeine; and low affinity towards metolachlor. Importantly, many environmental chemicals acted as strong inhibitors of Oatp1d1. A strong inhibition of Oatp1d1 transport activity was found by perfluorooctanoic acid (PFOA), chlorpyrifos-methyl, estrone (E1) and 17β-estradiol (E2), followed by moderate to low inhibition by diethyl phthalate, bisphenol A, 7-acetyl-1,1,3,4,4,6-hexamethyl-1,2,3,4 tetrahydronapthalene and clofibrate. In this study we identified Oatp1d1 as a first Solute Carrier (SLC) transporter involved in the transport of a wide range of xenobiotics in fish. Considering that Oatps in zebrafish have not been characterized before, our work on zebrafish Oatp1d1 offers important new insights on the understanding of uptake processes of environmental contaminants, and contributes to the better characterization of zebrafish as a model species. - Highlights: • We optimized a novel assay for determination of Oatp1d1 interactors • Oatp1d1 is the first SLC characterized fish xenobiotic transporter • PFOS, nonylphenol, diclofenac, EE2, caffeine are high affinity Oatp1d1substrates • PFOA, chlorpyrifos

  19. D1/D5 dopamine receptors modulate spatial memory formation.

    PubMed

    da Silva, Weber C N; Köhler, Cristiano C; Radiske, Andressa; Cammarota, Martín

    2012-02-01

    We investigated the effect of the intra-CA1 administration of the D1/D5 receptor antagonist SCH23390 and the D1/D5 receptor agonist SKF38393 on spatial memory in the water maze. When given immediately, but not 3h after training, SCH23390 hindered long-term spatial memory formation without affecting non-spatial memory or the normal functionality of the hippocampus. On the contrary, post-training infusion of SKF38393 enhanced retention and facilitated the spontaneous recovery of the original spatial preference after reversal learning. Our findings demonstrate that hippocampal D1/D5 receptors play an essential role in spatial memory processing.

  20. Metal-insulator transition in the hollandite K2V8O16 with a frustrated zigzag ladder probed by V51 NMR

    NASA Astrophysics Data System (ADS)

    Shimizu, Yasuhiro; Okai, Katsunori; Itoh, Masayuki; Isobe, Masahiro; Yamaura, Jun-Ichi; Yamauchi, Touru; Ueda, Yutaka

    2011-04-01

    We report the experimental results of V51 NMR measurements on the hollandite K2V8O16 consisting of a frustrated zigzag ladder with the orbital degrees of freedom. The metal-insulator transition is found to involve the spin-singlet formation by the V51 Knight shift K, the nuclear spin-lattice relaxation rate 1/T1, and the spin-echo decay rate 1/T2 measurements. In the insulating state, the anisotropic electric-field gradient supports the dxy orbital order with the spin singlet along the chain. The dxy orbital is magnetically most active in the metallic state, as observed by the anisotropic Knight shift, which suggests the strong electron correlation in the dxy band. Despite the large enhancement of the spin susceptibility, no apparent spin correlation is developed in the frustrated metallic state. Pressure suppresses the electron correlation continuously, as highlighted in the decrease of the metal-insulator transition and the spin susceptibility keeping the largest dxy contribution in the metallic state. A robust spin-singlet insulating phase with the large spin gap and paramagnetic spins appears above 1 GPa, which suggests a competition of the charge-orbital ordering pattern.

  1. TBC1D24 genotype–phenotype correlation

    PubMed Central

    Balestrini, Simona; Milh, Mathieu; Castiglioni, Claudia; Lüthy, Kevin; Finelli, Mattea J.; Verstreken, Patrik; Cardon, Aaron; Stražišar, Barbara Gnidovec; Holder, J. Lloyd; Lesca, Gaetan; Mancardi, Maria M.; Poulat, Anne L.; Repetto, Gabriela M.; Banka, Siddharth; Bilo, Leonilda; Birkeland, Laura E.; Bosch, Friedrich; Brockmann, Knut; Cross, J. Helen; Doummar, Diane; Félix, Temis M.; Giuliano, Fabienne; Hori, Mutsuki; Hüning, Irina; Kayserili, Hulia; Kini, Usha; Lees, Melissa M.; Meenakshi, Girish; Mewasingh, Leena; Pagnamenta, Alistair T.; Peluso, Silvio; Mey, Antje; Rice, Gregory M.; Rosenfeld, Jill A.; Taylor, Jenny C.; Troester, Matthew M.; Stanley, Christine M.; Ville, Dorothee; Walkiewicz, Magdalena; Falace, Antonio; Fassio, Anna; Lemke, Johannes R.; Biskup, Saskia; Tardif, Jessica; Ajeawung, Norbert F.; Tolun, Aslihan; Corbett, Mark; Gecz, Jozef; Afawi, Zaid; Howell, Katherine B.; Oliver, Karen L.; Berkovic, Samuel F.; Scheffer, Ingrid E.; de Falco, Fabrizio A.; Oliver, Peter L.; Striano, Pasquale; Zara, Federico

    2016-01-01

    Objective: To evaluate the phenotypic spectrum associated with mutations in TBC1D24. Methods: We acquired new clinical, EEG, and neuroimaging data of 11 previously unreported and 37 published patients. TBC1D24 mutations, identified through various sequencing methods, can be found online (http://lovd.nl/TBC1D24). Results: Forty-eight patients were included (28 men, 20 women, average age 21 years) from 30 independent families. Eighteen patients (38%) had myoclonic epilepsies. The other patients carried diagnoses of focal (25%), multifocal (2%), generalized (4%), and unclassified epilepsy (6%), and early-onset epileptic encephalopathy (25%). Most patients had drug-resistant epilepsy. We detail EEG, neuroimaging, developmental, and cognitive features, treatment responsiveness, and physical examination. In silico evaluation revealed 7 different highly conserved motifs, with the most common pathogenic mutation located in the first. Neuronal outgrowth assays showed that some TBC1D24 mutations, associated with the most severe TBC1D24-associated disorders, are not necessarily the most disruptive to this gene function. Conclusions: TBC1D24-related epilepsy syndromes show marked phenotypic pleiotropy, with multisystem involvement and severity spectrum ranging from isolated deafness (not studied here), benign myoclonic epilepsy restricted to childhood with complete seizure control and normal intellect, to early-onset epileptic encephalopathy with severe developmental delay and early death. There is no distinct correlation with mutation type or location yet, but patterns are emerging. Given the phenotypic breadth observed, TBC1D24 mutation screening is indicated in a wide variety of epilepsies. A TBC1D24 consortium was formed to develop further research on this gene and its associated phenotypes. PMID:27281533

  2. Falling chains

    NASA Astrophysics Data System (ADS)

    Wong, Chun Wa; Yasui, Kosuke

    2006-06-01

    The one-dimensional fall of a folded chain with one end suspended from a rigid support and a chain falling from a resting heap on a table is studied. Because their Lagrangians contain no explicit time dependence, the falling chains are conservative systems. Their equations of motion are shown to contain a term that enforces energy conservation when masses are transferred between subchains. We show that Cayley's 1857 energy nonconserving solution for a chain falling from a resting heap is incorrect because it neglects the energy gained when a link leaves a subchain. The maximum chain tension measured by Calkin and March for the falling folded chain is given a simple if rough interpretation. Other aspects of the falling folded chain are briefly discussed.

  3. Controlling Orientational Order in 1-D Assemblies of Multivalent Triangular Prisms.

    PubMed

    Kohlstedt, Kevin L; Olvera de la Cruz, Monica; Schatz, George C

    2013-01-03

    Multivalent nanostructures are becoming an increasingly important player in the self-assembly of supramolecular lattices. Understanding the role that shape plays in the coordination of the assemblies is crucial for the functional response of the material. We develop a simple design rule for the assembly of multivalent Au triangular nanoprisms into 1-D ordered arrays based on both the length of the valent DNA and the aspect ratio of the prism. Using MD simulations, we describe an order parameter that captures the short-range order of the assembly controlled by the design parameters. The order parameter shows that even short chains (N = 4) of prisms have a high degree of orientational order that transitions to no orientational order when the DNA length is similar to the prism length. Unlike isotropic polyvalent assemblies, we find that the highly oriented chains of prisms lose orientational order in discrete steps during melting as the prisms in the arrays dissociate.

  4. Rab28 is a TBC1D1/TBC1D4 substrate involved in GLUT4 trafficking.

    PubMed

    Zhou, Zhou; Menzel, Franziska; Benninghoff, Tim; Chadt, Alexandra; Du, Chen; Holman, Geoffrey D; Al-Hasani, Hadi

    2017-01-01

    The Rab-GTPase-activating proteins (GAPs) TBC1D1 and TBC1D4 play important roles in the insulin-stimulated translocation of the glucose transporter GLUT4 from intracellular vesicles to the plasma membrane in muscle cells and adipocytes. We identified Rab28 as a substrate for the GAP domains of both TBC1D1 and TBC1D4 in vitro. Rab28 is expressed in adipose cells and skeletal muscle, and its GTP-binding state is acutely regulated by insulin. We found that in intact isolated mouse skeletal muscle, siRNA-mediated knockdown of Rab28 decreases basal glucose uptake. Conversely, in primary rat adipose cells, overexpression of Rab28-Q72L, a constitutively active mutant, increases basal cell surface levels of an epitope-tagged HA-GLUT4. Our results indicate that Rab28 is a novel GTPase involved in the intracellular retention of GLUT4 in insulin target cells.

  5. Zig-Zag Thermal-Chemical 3-D Instabilities in the Mantle Wedge: Numerical Study

    NASA Astrophysics Data System (ADS)

    Zhu, G.; Gerya, T. V.; Arcay, D.; Yuen, D. A.

    2008-12-01

    To understand the plume initiation and propagation it is important to understand whether small-scale convection is occurring under the back-arc in the Low Viscosity Wedge(LVW) and its implication on the island-arc volcanism. Honda et al. [Honda and Saito, 2003; Honda, et al., 2007]) already deployed small- scale convection in the Low Viscosity Wedge (LVW) above a subducting slab with kinematically imposed velocity boundary condition. They have suggested that a roll (finger)-like pattern of hot and cold anomalies emerges in the mantle wedge above the subducting slab. Here, we perform three-dimensional coupled petrological-thermomechanical numerical simulations of intraoceanic one-sided subduction with spontaneously bending retreating slab characterized by weak hydrated upper interface by using multigrid approach combined with characteristics-based marker-in-cell method with conservative finite difference schemes[Gerya and Yuen, 2003a], to investigate the 3D instabilities above the slab and lateral variation along the arc. Our results show that water released from subducting slab through dehydration reactions may lower the viscosity of the mantle. It allows the existence of wave-like small-scale convection in the LVW, which is shown as roll-like structure in 2D petrological-thermomechanical numerical experiments [Gorczyk et al., 2006] using in-situ rock properties computed on the basis of Gibbs free energy minimization. However, in our 3D cases, the rolls aligning with the arc mainly occur earlier , while zig-zag small-scale thermal-chemical instabilities may episodically form above the slab at later stages, which is different from the aligning finger-like pattern in purely thermal models (Honda et al,2003;2007). Also in contrast to thermal convection chemically buoyant hydrated plumes rising from the slab in our models are actually colder then the mantle wedge [Gerya and Yuen 2003b] which also strongly modify both the convection pattern and the seismic structure in

  6. Polar discontinuities and 1D interfaces in monolayered materials

    NASA Astrophysics Data System (ADS)

    Martinez-Gordillo, Rafael; Pruneda, Miguel

    2015-12-01

    Interfaces are the birthplace of a multitude of fascinating discoveries in fundamental science, and have enabled modern electronic devices, from transistors, to lasers, capacitors or solar cells. These interfaces between bulk materials are always bi-dimensional (2D) 'surfaces'. However the advent of graphene and other 2D crystals opened up a world of possibilities, as in this case the interfaces become one-dimensional (1D) lines. Although the properties of 1D nanoribbons have been extensively discussed in the last few years, 1D interfaces within infinite 2D systems had remained mostly unexplored until very recently. These include grain boundaries in polycrystalline samples, or interfaces in hybrid 2D sheets composed by segregated domains of different materials (as for example graphene/BN hybrids, or chemically different transition metal dichalcogenides). As for their 2D counterparts, some of these 1D interfaces exhibit polar characteristics, and can give rise to fascinating new physical properties. Here, recent experimental discoveries and theoretical predictions on the polar discontinuities that arise at these 1D interfaces will be reviewed, and the perspectives of this new research topic, discussed.

  7. Ion-sensing properties of 1D vanadium pentoxide nanostructures

    PubMed Central

    2012-01-01

    The application of one-dimensional (1D) V2O5·nH2O nanostructures as pH sensing material was evaluated. 1D V2O5·nH2O nanostructures were obtained by a hydrothermal method with systematic control of morphology forming different nanostructures: nanoribbons, nanowires and nanorods. Deposited onto Au-covered substrates, 1D V2O5·nH2O nanostructures were employed as gate material in pH sensors based on separative extended gate FET as an alternative to provide FET isolation from the chemical environment. 1D V2O5·nH2O nanostructures showed pH sensitivity around the expected theoretical value. Due to high pH sensing properties, flexibility and low cost, further applications of 1D V2O5·nH2O nanostructures comprise enzyme FET-based biosensors using immobilized enzymes. PMID:22709724

  8. Experimental study and modeling of atomic-scale friction in zigzag and armchair lattice orientations of MoS2

    PubMed Central

    Li, Meng; Shi, Jialin; Liu, Lianqing; Yu, Peng; Xi, Ning; Wang, Yuechao

    2016-01-01

    Abstract Physical properties of two-dimensional materials, such as graphene, black phosphorus, molybdenum disulfide (MoS2) and tungsten disulfide, exhibit significant dependence on their lattice orientations, especially for zigzag and armchair lattice orientations. Understanding of the atomic probe motion on surfaces with different orientations helps in the study of anisotropic materials. Unfortunately, there is no comprehensive model that can describe the probe motion mechanism. In this paper, we report a tribological study of MoS2 in zigzag and armchair orientations. We observed a characteristic power spectrum and friction force values. To explain our results, we developed a modified, two-dimensional, stick-slip Tomlinson model that allows simulation of the probe motion on MoS2 surfaces by combining the motion in the Mo layer and S layer. Our model fits well with the experimental data and provides a theoretical basis for tribological studies of two-dimensional materials. PMID:27877869

  9. Zig-zag networks of self-excited periodic oscillations in a tunnel diode and a fiber-ring laser

    NASA Astrophysics Data System (ADS)

    Francke, Ricardo E.; Pöschel, Thorsten; Gallas, Jason A. C.

    2013-04-01

    We report numerical evidence showing that periodic oscillations can produce unexpected and wide-ranging zig-zag parameter networks embedded in chaos in the control space of nonlinear systems. Such networks interconnect shrimplike windows of stable oscillations and are illustrated here for a tunnel diode, for an erbium-doped fiber-ring laser, and for the Hénon map, a proxy of certain CO2 lasers. Networks in maps can be studied without the need for solving differential equations. Tuning parameters along zig-zag networks allows one to continuously modify wave patterns without changing their chaotic or periodic nature. In addition, we report convenient parameter ranges where such networks can be detected experimentally.

  10. Bandgaps of zigzag finite-length nanotubes ab initio calculations: ground state degeneracy and single-electron spectra

    NASA Astrophysics Data System (ADS)

    Mestechkin, Mikhail; Zubkov, Vladimir

    2005-05-01

    Different versions of ab initio quantum chemical models (cluster and periodic boundary conditions approximations) have been used to analyze the effect of finite length and the partial filling of the highest occupied orbital on the band-gaps of carbon nanotubes. In agreement with the previous calculations in the tight-binding approximation and pi-electron open shell model, it has been shown that the ground state of the nanotube with the zigzag structure is triplet. It has been confirmed that these tubes exhibit metallic or semiconductor properties with a very narrow half-filled conduction band. The band-gap is of order few tens of eV, and it is estimated that approximately 0.1-0.2% of pi-electrons belong to the conduction band of finite zigzag nanotubes. The triplet state is predicted to be the ground state of finite-length carbon nanotubes.

  11. Tuning Magnetism and Electronic Phase Transitions by Strain and Electric Field in Zigzag MoS2 Nanoribbons.

    PubMed

    Kou, Liangzhi; Tang, Chun; Zhang, Yi; Heine, Thomas; Chen, Changfeng; Frauenheim, Thomas

    2012-10-18

    Effective modulation of physical properties via external control may open various potential nanoelectronic applications of single-layer MoS2 nanoribbons (MoS2NRs). We show by first-principles calculations that the magnetic and electronic properties of zigzag MoS2NRs exhibit sensitive response to applied strain and electric field. Tensile strain in the zigzag direction produces reversible modulation of magnetic moments and electronic phase transitions among metallic, half-metallic, and semiconducting states, which stem from the energy-level shifts induced by an internal electric polarization and the competing covalent/ionic interactions. A simultaneously applied electric field further enhances or suppresses the strain-induced modulations depending on the direction of the electric field relative to the internal polarization. These findings suggest a robust and efficient approach to modulating the properties of MoS2NRs by a combination of strain engineering and electric field tuning.

  12. The growth model and electronic properties of single- and double-walled zigzag silicon nanotubes: Depending on the structures

    NASA Astrophysics Data System (ADS)

    Lin, Xiang; Lu, Junzhe; Liu, Jing; Tang, Yuchao; Zhu, Hengjiang

    2017-02-01

    The growth model and electronic properties of the capped zigzag single- and double-walled silicon nanotubes (SWSiNTs and DWSiNTs) are studied with the Density Functional Theory (DFT) method. Particularly, the morphologies of the silicon nanotubes (SiNTs) and the layer-by-layer growth process are explored. Capping of SiNTs is explained well in terms of pentagons. It seems that pentagons or heptagons play apivotal role during the SiNTs growth. Moreover, the structures of the finite SWSiNTs and DWSiNTs are studied. Finally, the infinite SWSiNTs and DWSiNTs can be set up with the repeat unit cells based on the periodic trait of the corresponding finite SiNTs. All of the zigzag SWSiNTs and DWSiNTs have a narrow band gap.

  13. Zig-zag networks of self-excited periodic oscillations in a tunnel diode and a fiber-ring laser.

    PubMed

    Francke, Ricardo E; Pöschel, Thorsten; Gallas, Jason A C

    2013-04-01

    We report numerical evidence showing that periodic oscillations can produce unexpected and wide-ranging zig-zag parameter networks embedded in chaos in the control space of nonlinear systems. Such networks interconnect shrimplike windows of stable oscillations and are illustrated here for a tunnel diode, for an erbium-doped fiber-ring laser, and for the Hénon map, a proxy of certain CO(2) lasers. Networks in maps can be studied without the need for solving differential equations. Tuning parameters along zig-zag networks allows one to continuously modify wave patterns without changing their chaotic or periodic nature. In addition, we report convenient parameter ranges where such networks can be detected experimentally.

  14. A density-functional-theory-based finite element model to study the mechanical properties of zigzag phosphorene nanotubes

    NASA Astrophysics Data System (ADS)

    Ansari, R.; Shahnazari, A.; Rouhi, S.

    2017-04-01

    In this paper, the density functional theory calculations are used to obtain the elastic properties of zigzag phosphorene nanotubes. Besides, based on the similarity between phosphorene nanotubes and a space-frame structure, a three-dimensional finite element model is proposed in which the atomic bonds are simulated by beam elements. The results of density functional theory are employed to compute the properties of the beam elements. Finally, using the proposed finite element model, the elastic modulus of the zigzag phosphorene nanotubes is computed. It is shown that phosphorene nanotubes with larger radii have larger Young's modulus. Comparing the results of finite element model with those of density functional theory, it is concluded that the proposed model can predict the elastic modulus of phosphorene nanotubes with a good accuracy.

  15. Designing of spin-filtering devices in zigzag graphene nanoribbons heterojunctions by asymmetric hydrogenation and B-N doping

    SciTech Connect

    Zhang, Dan; Zhang, Xiaojiao; Ouyang, Fangping; Li, Mingjun; Xu, Hui; Long, Mengqiu

    2015-01-07

    Using nonequilibrium Green's function in combination with the spin-polarized density functional theory, the spin-dependent transport properties of boron and nitrogen doped zigzag graphene nanoribbons (ZGNRs) heterojunctions with single or double edge-saturated hydrogen have been investigated. Our results show that the perfect spin-filtering effect (100%), rectifying behavior and negative differential resistance can be realized in the ZGNRs-based systems. And the corresponding physical analysis has been given.

  16. Pitch-based pattern splitting for 1D layout

    NASA Astrophysics Data System (ADS)

    Nakayama, Ryo; Ishii, Hiroyuki; Mikami, Koji; Tsujita, Koichiro; Yaegashi, Hidetami; Oyama, Kenichi; Smayling, Michael C.; Axelrad, Valery

    2015-07-01

    The pattern splitting algorithm for 1D Gridded-Design-Rules layout (1D layout) for sub-10 nm node logic devices is shown. It is performed with integer linear programming (ILP) based on the conflict graph created from a grid map for each designated pitch. The relation between the number of times for patterning and the minimum pitch is shown systematically with a sample pattern of contact layer for each node. From the result, the number of times for patterning for 1D layout is fewer than that for conventional 2D layout. Moreover, an experimental result including SMO and total integrated process with hole repair technique is presented with the sample pattern of contact layer whose pattern density is relatively high among critical layers (fin, gate, local interconnect, contact, and metal).

  17. Flexible Photodetectors Based on 1D Inorganic Nanostructures

    PubMed Central

    Lou, Zheng

    2015-01-01

    Flexible photodetectors with excellent flexibility, high mechanical stability and good detectivity, have attracted great research interest in recent years. 1D inorganic nanostructures provide a number of opportunities and capabilities for use in flexible photodetectors as they have unique geometry, good transparency, outstanding mechanical flexibility, and excellent electronic/optoelectronic properties. This article offers a comprehensive review of several types of flexible photodetectors based on 1D nanostructures from the past ten years, including flexible ultraviolet, visible, and infrared photodetectors. High‐performance organic‐inorganic hybrid photodetectors, as well as devices with 1D nanowire (NW) arrays, are also reviewed. Finally, new concepts of flexible photodetectors including piezophototronic, stretchable and self‐powered photodetectors are examined to showcase the future research in this exciting field. PMID:27774404

  18. PC-1D installation manual and user's guide

    SciTech Connect

    Basore, P.A.

    1991-05-01

    PC-1D is a software package for personal computers that uses finite-element analysis to solve the fully-coupled two-carrier semiconductor transport equations in one dimension. This program is particularly useful for analyzing the performance of optoelectronic devices such as solar cells, but can be applied to any bipolar device whose carrier flows are primarily one-dimensional. This User's Guide provides the information necessary to install PC-1D, define a problem for solution, solve the problem, and examine the results. Example problems are presented which illustrate these steps. The physical models and numerical methods utilized are presented in detail. This document supports version 3.1 of PC-1D, which incorporates faster numerical algorithms with better convergence properties than previous versions of the program. 51 refs., 17 figs., 5 tabs.

  19. Cantilevered single walled boron nitride nanotube based nanomechanical resonators of zigzag and armchair forms

    NASA Astrophysics Data System (ADS)

    Panchal, Mitesh B.; Upadhyay, S. H.

    2013-05-01

    In this paper, the dynamic response analysis of single walled boron nitride nanotubes (SWBNNTs) has been done using a finite element method (FEM). To this end, different types of zigzag and armchair layups of SWBNNTs are considered with cantilever configuration to analyze the mass detection application, as a SWBNNT based nanomechanical resonator. Using three dimensional elastic beams and point masses, single walled boron nitride nanotubes are approximated as atomistic finite element models. Implementing the finite element simulation approach, the resonant frequency of cantilevered nanotubes obtained and observed the shifts in it mainly due to an additional nanoscale mass to the nanotube tip. The effect on resonant frequency shift due to dimensional variation in terms of length as well as diameter is explored by considering different aspect ratios of nanotubes. The effect of intermediate landing positions of added mass on resonant frequency shift is also analyzed by considering excitations of different modes of vibration. Also, the effect of chiralities compared for resonant frequency variations to check the effect on sensitivity due to different forms of SWBNNTs. The present approach is found to be effectual in terms of dealing different chiralities, boundary conditions and consideration of added mass to analyze the dynamic behavior of cantilevered SWBNNT based nanomechanical resonators. The simulation results are compared with the analytical results based on continuum mechanics and found in good agreement as one of the toolkits for systematic analysis approach for novel design of SWBNNT based nanomechanical resonators for wide range of applications.

  20. Magneto-induced tunability of thermo-spin current in deformed zigzag graphene nanoribbons

    SciTech Connect

    Adinehloo, Davoud Fathipour, Morteza

    2015-12-21

    The aim of this report is to unfold how the thermo-electric spin-polarized current in a transverse-biased zigzag graphene nanoribbon changes in the presence of uniaxial deformations and uniform perpendicular magnetic field. Employing the two-parameter Hubbard model along with the non-equilibrium Green's function formalism, we found that both uniaxial strain and magnetic field can significantly modulate the bandgap, local distribution of edge states, and the critical transverse electric field needed to achieve the half-metallic phase in the ribbon. Our analysis shows a significant enhancement of the maximum attainable spin-polarized current as functions of both source temperature and contacts temperature difference, with increasing the magnetic field or applying any magnitude of compressive strain. Furthermore, it is shown that the magneto-resistance ratio of the device, can be drastically tuned via strain engineering, reaching values as high as 2 × 10{sup 4}% for compressive strains of 5% magnitude.

  1. Effect of random edge-vacancy disorder in zigzag graphene nanoribbons

    NASA Astrophysics Data System (ADS)

    Baldwin, J. P. C.; Hancock, Y.

    2016-10-01

    The magnetic and coherent transport properties of small-width zigzag graphene nanoribbons (ZGNRs) with monohydrogen edge passivation are investigated as a function of random edge-vacancy disorder and ribbon length. Results from noninteracting tight-binding models with (i) nearest and (ii) up to third nearest neighbor hopping are compared against those obtained from an extended mean-field Hubbard model for edge-defected ZGNRs (length = 48.02 Å and width = 9.24 Å ). Through ensemble averaging, a persistent magnetism and Hubbard-U (i.e., spin-generated) conductance gap is found irrespective of the extent of random edge-vacancy disorder. At longer device lengths (up to 144.1 Å ) and at high disorder (42.5%), gaps open in the noninteracting model systems, whereas the gap in the Hubbard-calculated systems becomes spin dependent. In all cases, the conductance gaps increase as a function of increasing system length, although the gaps in the Hubbard systems remain smaller due to increased robustness against edge disorder. The continuance of the magnetic state and gap robustness in the ensemble-averaged Hubbard results indicates a complex interplay between the kinetics, disorder, system size, and spin interaction. Such findings may serve to reinform previous studies that have used noninteracting models to investigate disorder in ZGNRs.

  2. Zigzag nanoribbons of two-dimensional silicene-like crystals: magnetic, topological and thermoelectric properties.

    PubMed

    Wierzbicki, Michał; Barnaś, Józef; Swirkowicz, Renata

    2015-12-09

    The effects of electron-electron and spin-orbit interactions on the ground-state magnetic configuration and on the corresponding thermoelectric and spin thermoelectric properties in zigzag nanoribbons of two-dimensional hexagonal crystals are analysed theoretically. The thermoelectric properties of quasi-stable magnetic states are also considered. Of particular interest is the influence of Coulomb and spin-orbit interactions on the topological edge states and on the transition between the topological insulator and conventional gap insulator states. It is shown that the interplay of both interactions also has a significant impact on the transport and thermoelectric characteristics of the nanoribbons. The spin-orbit interaction also determines the in-plane magnetic easy axis. The thermoelectric properties of nanoribbons with in-plane magnetic moments are compared to those of nanoribbons with edge magnetic moments oriented perpendicularly to their plane. Nanoribbons with ferromagnetic alignment of the edge moments are shown to reveal spin thermoelectricity in addition to the conventional one.

  3. Inducing half-metallicity with enhanced stability in zigzag graphene nanoribbons via fluorine passivation

    NASA Astrophysics Data System (ADS)

    Jaiswal, Neeraj K.; Tyagi, Neha; Kumar, Amit; Srivastava, Pankaj

    2017-02-01

    Half metals are the primary ingredients for the realization of novel spintronic devices. In the present work, by employing density functional theory based first-principles calculation, we predict half metallic behavior in fluorine passivated zigzag graphene nanoribbons (F-ZGNR). Four different structures have been investigated viz. one edge F passivated ZGNR (F-ZGNR-1), both edges F passivated ZGNR (F-ZGNR-2), F passivation on alternate sites in first configuration (alt-1) and F passivation on alternate sites in second configuration (alt-2). Interestingly, it is noticed that F passivation is analogous to H passivation (pristine), however, F-ZGNR are reckoned energetically more stable than pristine ones. An spin induced band gap is noticed for all F-ZGNR irrespective of their widths although its magnitude is slightly less than the pristine counterparts. With an external transverse electric field, ribbons undergo semiconducting to half metallic transformation. The observed half metallic character with enhanced stability present F-ZGNR as a better candidate than pristine ZGNR towards the realization of upcoming spintronic devices.

  4. First-principles study of line-defect-embedded zigzag graphene nanoribbons: electronic and magnetic properties.

    PubMed

    Guan, Zhaoyong; Si, Chen; Hu, Shuanglin; Duan, Wenhui

    2016-04-28

    Based on first-principles calculations, we present the electronic and magnetic properties of a class of line defect-embedded zigzag graphene nanoribbons, with one edge saturated by two hydrogen atoms per carbon atom and the other edge terminated by only one hydrogen atom. Such edge-modified nanoribbons without line defects are found to be typical bipolar magnetic semiconductors (BMS). In contrast, when the line defect is introduced into the ribbons, the ground state is ferromagnetic, and the resulting nanoribbons can be tuned to spin-polarized metal, metal with Dirac point, or half-metal by varying the position of the line defect, owing to the defect-induced self-doping of the BMS. Specifically, when the line defect is far away from the edges of the ribbon, the system shows half-metallicity. We further confirm the structural and magnetic stability at room temperature by first-principles molecular dynamics simulations. Our findings reveal the possibility of building metal-free electronic/spintronic devices with magnetic/half-metallic graphene nanoribbons.

  5. Controllable spin polarization and spin filtering in a zigzag silicene nanoribbon

    SciTech Connect

    Farokhnezhad, Mohsen Esmaeilzadeh, Mahdi Pournaghavi, Nezhat; Ahmadi, Somaieh

    2015-05-07

    Using non-equilibrium Green's function, we study the spin-dependent electron transport properties in a zigzag silicene nanoribbon. To produce and control spin polarization, it is assumed that two ferromagnetic strips are deposited on the both edges of the silicene nanoribbon and an electric field is perpendicularly applied to the nanoribbon plane. The spin polarization is studied for both parallel and anti-parallel configurations of exchange magnetic fields induced by the ferromagnetic strips. We find that complete spin polarization can take place in the presence of perpendicular electric field for anti-parallel configuration and the nanoribbon can work as a perfect spin filter. The spin direction of transmitted electrons can be easily changed from up to down and vice versa by reversing the electric field direction. For parallel configuration, perfect spin filtering can occur even in the absence of electric field. In this case, the spin direction can be changed by changing the electron energy. Finally, we investigate the effects of nonmagnetic Anderson disorder on spin dependent conductance and find that the perfect spin filtering properties of nanoribbon are destroyed by strong disorder, but the nanoribbon retains these properties in the presence of weak disorder.

  6. Electronic and magnetic properties of zigzag silicene nanoribbons with Stone–Wales defects

    SciTech Connect

    Dong, Haixia; Fang, Dangqi; Gong, Baihua; Zhang, Yang; Zhang, Erhu; Zhang, Shengli

    2015-02-14

    The structural, electronic, and magnetic properties of zigzag silicene nanoribbons (ZSiNRs) with Stone–Wales (SW) defects were investigated using first-principles calculations. We found that two types of SW defects (named SW-Ι and SW-ΙΙ) exist in ZSiNRs. The SW defect was found to be the most stable at the edge of the ZSiNR, independently of the defect orientation, even more stable than it is in an infinite silicene sheet. In addition, the ZSiNRs can transition from semiconductor to metal or half-metal by modifying the SW defect location and concentration. For the same defect concentration, the band structures influenced by the SW-Ι defect are more distinct than those influenced by the SW-ΙΙ when the SW defect is at the edge. The present study suggests the possibility of tuning the electronic properties of ZSiNRs using the SW defects and might motivate their potential application in nanoelectronics and spintronics.

  7. Preserving the edge magnetism of zigzag graphene nanoribbons by ethylene termination: insight by Clar's rule.

    PubMed

    Li, Yafei; Zhou, Zhen; Cabrera, Carlos R; Chen, Zhongfang

    2013-01-01

    By means of density functional theory computations, we demonstrated that C2H4 is the ideal terminal group for zigzag graphene nanoribbons (zGNRs) in terms of preserving the edge magnetism with experimental feasibility. The C2H4 terminated zGNRs (C2H4-zGNRs) with pure sp(2) coordinated edges can be stabilized at rather mild experimental conditions, and meanwhile reproduce the electronic and magnetic properties of those hydrogen terminated zGNRs. Interestingly, the electronic structures and relative stability of C2H4-zGNRs with different edge configurations can be well interpreted by employing the Clar's rule. The multiple edge hyperconjugation interactions are responsible for the enhanced stability of the sp(2) coordinated edges of C2H4-zGNRs. Moreover, we demonstrated that even pure sp(2) termination is not a guarantee for edge magnetism, for example, C2H2 termination can couple to the π-electron system of zGNRs, and destroy the magnetism. Our studies would pave the way for the application of zGNRs in spintronics.

  8. Wortmannin-induced vacuole fusion enhances amyloplast dynamics in Arabidopsis zigzag1 hypocotyls

    PubMed Central

    Alvarez, Ashley Ann; Han, Sang Won; Toyota, Masatsugu; Brillada, Carla; Zheng, Jiameng; Gilroy, Simon

    2016-01-01

    Gravitropism in Arabidopsis shoots depends on the sedimentation of amyloplasts in the endodermis, and a complex interplay between the vacuole and F-actin. Gravity response is inhibited in zigzag-1 (zig-1), a mutant allele of VTI11, which encodes a SNARE protein involved in vacuole fusion. zig-1 seedlings have fragmented vacuoles that fuse after treatment with wortmannin, an inhibitor of phosphatidylinositol 3-kinase, and underscore a role of phosphoinositides in vacuole fusion. Using live-cell imaging with a vertical stage microscope, we determined that young endodermal cells below the apical hook that are smaller than 70 μm in length are the graviperceptive cells in dark-grown hypocotyls. This result was confirmed by local wortmannin application to the top of zig-1 hypocotyls, which enhanced shoot gravitropism in zig-1 mutants. Live-cell imaging of zig-1 hypocotyl endodermal cells indicated that amyloplasts are trapped between juxtaposed vacuoles and their movement is severely restricted. Wortmannin-induced fusion of vacuoles in zig-1 seedlings increased the formation of transvacuolar strands, enhanced amyloplast sedimentation and partially suppressed the agravitropic phenotype of zig-1 seedlings. Hypergravity conditions at 10 g were not sufficient to displace amyloplasts in zig-1, suggesting the existence of a physical tether between the vacuole and amyloplasts. Our results overall suggest that vacuole membrane remodeling may be involved in regulating the association of vacuoles and amyloplasts during graviperception. PMID:27816929

  9. Analytical and experimental investigation of flexible longitudinal zigzag structures for enhanced multi-directional energy harvesting

    NASA Astrophysics Data System (ADS)

    Zhou, Shengxi; Hobeck, Jared D.; Cao, Junyi; Inman, Daniel J.

    2017-03-01

    This paper makes a complete investigation of flexible longitudinal zigzag (FLZ) energy harvesters for the purpose of enhancing energy harvesting from low-frequency and low-amplitude excitation. A general theoretical model of the FLZ energy harvesters with large joint block mass is proposed. In order to verify the accuracy of the theoretical model, both experimental results and finite element analysis via ANSYS software are presented. Results show that the theoretical model can successfully predict the dynamic response and the output power of the FLZ energy harvesters. Both theoretical and experimental results demonstrate that the proposed energy harvesters can effectively harvest vibration energy even when the direction of excitation relative to the harvester varies from 0° to 90°. Under the low excitation level of 0.18 m s‑2, the experimental maximum output power of a FLZ energy harvester with five beams was found to be 1.016 mW. Finally, the results indicate that the proposed structure is capable of effective energy conversion across a large range of excitation angles at low-frequency and low-amplitude excitations, which makes it suitable for a wide range of working conditions.

  10. Fundamental insights into the electronic structure of zigzag MoS2 nanoribbons.

    PubMed

    Yu, Shansheng; Zheng, Weitao

    2016-02-14

    The structural and electronic properties of zigzag MoS2 nanoribbons are investigated using first-principles density functional theory. Our models are motivated by the experimental observations, in which both Mo edges are terminated by S atoms. Our calculations show that the edge can introduce some extra states into the energy gap, which lead nanoribbons to exhibit a metallic characteristic. Such extra states around the Fermi level are flat or dispersed. Through detailed analyses, we identify and discriminate them based on the major contributors. By applying an external transverse electric field, Eext the extra states around the Fermi level can shift apparently, especially for those attributed to Mo-edge atoms. It can be explained by the charge redistribution in the MoS2 nanoribbons due to Eext. In addition, the nanoribbon can be changed from metal to an n/p-type semiconductor according to different edge hydrogenation. After full edge hydrogenation, we observe a characteristic of anti-bonding orbitals between H and S atoms at the Mo-edge. Interestingly, the energy of anti-bonding orbitals and electric conductivity of nanoribbons can be tailored by Eext. The results suggest a strategy controlling the performance of MoS2 for hydrogen evolution.

  11. Tunable magnetic states on the zigzag edges of hydrogenated and halogenated group-IV nanoribbons

    NASA Astrophysics Data System (ADS)

    Wang, Tzu-Cheng; Hsu, Chia-Hsiu; Huang, Zhi-Quan; Chuang, Feng-Chuan; Su, Wan-Sheng; Guo, Guang-Yu

    2016-12-01

    The magnetic and electronic properties of hydrogenated and halogenated group-IV zigzag nanoribbons (ZNRs) are investigated by first-principles density functional calculations. Fascinatingly, we find that all the ZNRs have magnetic edges with a rich variety of electronic and magnetic properties tunable by selecting the parent and passivating elements as well as controlling the magnetization direction and external strain. In particular, the electric property of the edge band structure can be tuned from the conducting to insulating with a band gap up to 0.7 eV. The last controllability would allow us to develop magnetic on-off nano-switches. Furthermore, ZNRs such as SiI, Ge, GeI and SnH, have fully spin-polarized metallic edge states and thus are promising materials for spintronics. The calculated magnetocrystalline anisotropy energy can be as large as ~9 meV/edge-site, being 2×103 time greater than that of bulk Ni and Fe (~5 μeV/atom), and thus has great potential for high density magneto-electric data-storage devices. Finally, the calculated exchange coupling strength and thus magnetic transition temperature increases as the applied strain goes from ‑5% to 5%. Our findings thus show that these ZNRs would have exciting applications in next-generation electronic and spintronic nano-devices.

  12. Tunable magnetic states on the zigzag edges of hydrogenated and halogenated group-IV nanoribbons

    PubMed Central

    Wang, Tzu-Cheng; Hsu, Chia-Hsiu; Huang, Zhi-Quan; Chuang, Feng-Chuan; Su, Wan-Sheng; Guo, Guang-Yu

    2016-01-01

    The magnetic and electronic properties of hydrogenated and halogenated group-IV zigzag nanoribbons (ZNRs) are investigated by first-principles density functional calculations. Fascinatingly, we find that all the ZNRs have magnetic edges with a rich variety of electronic and magnetic properties tunable by selecting the parent and passivating elements as well as controlling the magnetization direction and external strain. In particular, the electric property of the edge band structure can be tuned from the conducting to insulating with a band gap up to 0.7 eV. The last controllability would allow us to develop magnetic on-off nano-switches. Furthermore, ZNRs such as SiI, Ge, GeI and SnH, have fully spin-polarized metallic edge states and thus are promising materials for spintronics. The calculated magnetocrystalline anisotropy energy can be as large as ~9 meV/edge-site, being 2×103 time greater than that of bulk Ni and Fe (~5 μeV/atom), and thus has great potential for high density magneto-electric data-storage devices. Finally, the calculated exchange coupling strength and thus magnetic transition temperature increases as the applied strain goes from −5% to 5%. Our findings thus show that these ZNRs would have exciting applications in next-generation electronic and spintronic nano-devices. PMID:27982055

  13. Tailoring graphene magnetism by zigzag triangular holes: A first-principles thermodynamics study

    SciTech Connect

    Khan, Muhammad Ejaz; Zhang, P.; Sun, Yi -Yang; Zhang, S. B.; Kim, Yong -Hyun

    2016-03-30

    In this study, we discuss the thermodynamic stability and magnetic property of zigzag triangular holes (ZTHs) in graphene based on the results of first-principles density functional theory calculations. We find that ZTHs with hydrogen-passivated edges in mixed sp2/sp3 configurations (z211) could be readily available at experimental thermodynamic conditions, but ZTHs with 100% sp2 hydrogen-passivation (z1) could be limitedly available at high temperature and ultra-high vacuum conditions. Graphene magnetization near the ZTHs strongly depends on the type and the size of the triangles. While metallic z1 ZTHs exhibit characteristic edge magnetism due to the same-sublattice engineering, semiconducting z211 ZTHs do show characteristic corner magnetism when the size is small < 2 nm. Our findings could be useful for experimentally tailoring metal-free carbon magnetism by simply fabricating triangular holes in graphene.

  14. Prospects of asymmetrically H-terminated zigzag germanene nanoribbons for spintronic application

    NASA Astrophysics Data System (ADS)

    Sharma, Varun; Srivastava, Pankaj; Jaiswal, Neeraj K.

    2017-02-01

    First-principles investigations have been performed to explore the spin based electronic and transport properties of asymmetrically H-terminated zigzag germanene nanoribbons (2Hsbnd H ZGeNR). Investigations reveal a significant formation energy difference (ΔEF = EF(2H-H) - EF(H-H) ∼ -0.49 eV), highlighting more energetic stability for asymmetric edge termination compared to symmetric edge termination, irrespective of the ribbon width. Further, magnetic moment analysis and total energy calculations were performed to unveil that these structures have a magnetic ground state with preferred ferromagnetic (FM) coupling. The calculated E-k structures project a unique bipolar semiconducting behaviour for 2Hsbnd H ZGeNR which is contrast to H-terminated ZGeNR. Half-metallic transformation has also been revealed via suitable p-type or n-type doping for these structures. Finally, transport calculations were performed to highlight the selective contributions of spin-down (spin-up) electrons in the I-V characteristics of the doped 2Hsbnd H ZGeNR, suggesting their vitality for spintronic device applications.

  15. Metal enhanced fluorescence improved protein and DNA detection by zigzag Ag nanorod arrays.

    PubMed

    Ji, Xiaofan; Xiao, Chenyu; Lau, Wai-Fung; Li, Jianping; Fu, Junxue

    2016-08-15

    As metal nano-arrays show great potential on metal enhanced fluorescence (MEF) than random nanostructures, MEF of Ag zigzag nanorod (ZNR) arrays made by oblique angle deposition has been studied for biomolecule-protein interaction and DNA hybridization. By changing the folding number and the deposition substrate temperature, a 14-fold enhancement factor (EF) is obtained for biotin-neutravidin detection. The optimal folding number is decided as Z=7, owing to the high scattering intensity of Ag ZNRs. The substrate temperature T=25°C and 0°C slightly alters the morphology of Ag ZNRs but has no big difference in EF. Further, Ag ZNRs deposited on a layer of Ag film have been introduced to the DNA hybridization and a significant signal enhancement has been observed through the fluorescence microscope. Through a detailed quantitative EF analysis, which excludes the enhancing effect from the increased surface area of ZNRs and only considers the contribution of MEF, an EF of 28 is achieved for the hybridization of two single-stranded oligonucleotides with 33 bases. Furthermore, a limit of detection is determined as 0.01pM. We believe that the Ag ZNR arrays can serve as a universal and sensitive bio-detection platform.

  16. Anisotropic thermoelectric behavior in armchair and zigzag mono- and fewlayer MoS2 in thermoelectric generator applications

    NASA Astrophysics Data System (ADS)

    Arab, Abbas; Li, Qiliang

    2015-09-01

    In this work, we have studied thermoelectric properties of monolayer and fewlayer MoS2 in both armchair and zigzag orientations. Density functional theory (DFT) using non-equilibrium Green’s function (NEGF) method has been implemented to calculate the transmission spectra of mono- and fewlayer MoS2 in armchair and zigzag directions. Phonon transmission spectra are calculated based on parameterization of Stillinger-Weber potential. Thermoelectric figure of merit, ZT, is calculated using these electronic and phonon transmission spectra. In general, a thermoelectric generator is composed of thermocouples made of both n-type and p-type legs. Based on our calculations, monolayer MoS2 in armchair orientation is found to have the highest ZT value for both p-type and n-type legs compared to all other armchair and zigzag structures. We have proposed a thermoelectric generator based on monolayer MoS2 in armchair orientation. Moreover, we have studied the effect of various dopant species on thermoelectric current of our proposed generator. Further, we have compared output current of our proposed generator with those of Silicon thin films. Results indicate that thermoelectric current of MoS2 armchair monolayer is several orders of magnitude higher than that of Silicon thin films.

  17. Realizing semiconductor-half-metal transition in zigzag graphene nanoribbons supported on hybrid fluorographene-graphane nanoribbons.

    PubMed

    Tang, Shaobin; Cao, Xinrui

    2014-11-14

    Hydrogenation and fluorination provide promising applications for tuning the properties of graphene-based nanomaterials. Using first-principles calculations, we investigate the electronic and magnetic properties of zigzag graphene nanoribbons (ZGNRs) supported on hydrogenated and fluorinated ZGNRs. Our results indicate that the support of zigzag graphane nanoribbon with its full width has less impact on the electronic and magnetic properties of ZGNRs, whereas the ZGNRs supported on fluorographene nanoribbons can be tuned to metal with almost degenerated ferro- and anti-ferromagnetic states due to the intrinsic polarization of substrate. The ZGNRs supported on zigzag hybrid fluorographene-graphane nanoribbons are spin-polarized half-semiconductors with distinct band gaps for spin-up and spin-down channels. Interestingly, in the absence of an external electric field, the spin-polarized band gaps of supported ZGNRs can be well modulated in the opposite direction by changing the ratio of fluorination to hydrogenation concentration in hybrid substrates. Furthermore, the ZGNRs supported on hybrid nanoribbons exhibit the half-semiconducting to half-metallic behavior transition as the interlayer spacing is gradually reduced, which is realized more easily for the hybrid support with a relatively wide fluorographene moiety compared to its narrow counterpart. Present results provide a novel way for designing substrate-supported graphene spintronic devices.

  18. Anisotropic thermoelectric behavior in armchair and zigzag mono- and fewlayer MoS2 in thermoelectric generator applications

    PubMed Central

    Arab, Abbas; Li, Qiliang

    2015-01-01

    In this work, we have studied thermoelectric properties of monolayer and fewlayer MoS2 in both armchair and zigzag orientations. Density functional theory (DFT) using non-equilibrium Green’s function (NEGF) method has been implemented to calculate the transmission spectra of mono- and fewlayer MoS2 in armchair and zigzag directions. Phonon transmission spectra are calculated based on parameterization of Stillinger-Weber potential. Thermoelectric figure of merit, ZT, is calculated using these electronic and phonon transmission spectra. In general, a thermoelectric generator is composed of thermocouples made of both n-type and p-type legs. Based on our calculations, monolayer MoS2 in armchair orientation is found to have the highest ZT value for both p-type and n-type legs compared to all other armchair and zigzag structures. We have proposed a thermoelectric generator based on monolayer MoS2 in armchair orientation. Moreover, we have studied the effect of various dopant species on thermoelectric current of our proposed generator. Further, we have compared output current of our proposed generator with those of Silicon thin films. Results indicate that thermoelectric current of MoS2 armchair monolayer is several orders of magnitude higher than that of Silicon thin films. PMID:26333948

  19. Anisotropic thermoelectric behavior in armchair and zigzag mono- and fewlayer MoS2 in thermoelectric generator applications.

    PubMed

    Arab, Abbas; Li, Qiliang

    2015-09-03

    In this work, we have studied thermoelectric properties of monolayer and fewlayer MoS2 in both armchair and zigzag orientations. Density functional theory (DFT) using non-equilibrium Green's function (NEGF) method has been implemented to calculate the transmission spectra of mono- and fewlayer MoS2 in armchair and zigzag directions. Phonon transmission spectra are calculated based on parameterization of Stillinger-Weber potential. Thermoelectric figure of merit, ZT, is calculated using these electronic and phonon transmission spectra. In general, a thermoelectric generator is composed of thermocouples made of both n-type and p-type legs. Based on our calculations, monolayer MoS2 in armchair orientation is found to have the highest ZT value for both p-type and n-type legs compared to all other armchair and zigzag structures. We have proposed a thermoelectric generator based on monolayer MoS2 in armchair orientation. Moreover, we have studied the effect of various dopant species on thermoelectric current of our proposed generator. Further, we have compared output current of our proposed generator with those of Silicon thin films. Results indicate that thermoelectric current of MoS2 armchair monolayer is several orders of magnitude higher than that of Silicon thin films.

  20. GIS-BASED 1-D DIFFUSIVE WAVE OVERLAND FLOW MODEL

    SciTech Connect

    KALYANAPU, ALFRED; MCPHERSON, TIMOTHY N.; BURIAN, STEVEN J.

    2007-01-17

    This paper presents a GIS-based 1-d distributed overland flow model and summarizes an application to simulate a flood event. The model estimates infiltration using the Green-Ampt approach and routes excess rainfall using the 1-d diffusive wave approximation. The model was designed to use readily available topographic, soils, and land use/land cover data and rainfall predictions from a meteorological model. An assessment of model performance was performed for a small catchment and a large watershed, both in urban environments. Simulated runoff hydrographs were compared to observations for a selected set of validation events. Results confirmed the model provides reasonable predictions in a short period of time.

  1. Non-cooperative Brownian donkeys: A solvable 1D model

    NASA Astrophysics Data System (ADS)

    Jiménez de Cisneros, B.; Reimann, P.; Parrondo, J. M. R.

    2003-12-01

    A paradigmatic 1D model for Brownian motion in a spatially symmetric, periodic system is tackled analytically. Upon application of an external static force F the system's response is an average current which is positive for F < 0 and negative for F > 0 (absolute negative mobility). Under suitable conditions, the system approaches 100% efficiency when working against the external force F.

  2. Magnetic tetrastability in a spin chain

    NASA Astrophysics Data System (ADS)

    Pianet, Vivien; Urdampilleta, Matias; Colin, Thierry; Clérac, Rodolphe; Coulon, Claude

    2016-08-01

    Bistability in magnetism is extensively used, in particular for information storage. Here an alternative approach using tetrastable magnetic domains in one-dimensional (1D) spin systems is presented. Using numerical and analytical calculations, we show that a spin chain with a canting angle of π/4 possesses four energy-equivalent states. We discuss the static properties of this canted 1D system such as the profile and the energy of the domain walls as they govern the dynamics of the magnetization. The realization of this π/4 canted spin chain could enable the encoding of the information on four bits, which is a potential alternative toward the increase of storage density.

  3. Plasmonic Excitations of 1D Metal-Dielectric Interfaces in 2D Systems: 1D Surface Plasmon Polaritons

    NASA Astrophysics Data System (ADS)

    Mason, Daniel R.; Menabde, Sergey G.; Yu, Sunkyu; Park, Namkyoo

    2014-04-01

    Surface plasmon-polariton (SPP) excitations of metal-dielectric interfaces are a fundamental light-matter interaction which has attracted interest as a route to spatial confinement of light far beyond that offered by conventional dielectric optical devices. Conventionally, SPPs have been studied in noble-metal structures, where the SPPs are intrinsically bound to a 2D metal-dielectric interface. Meanwhile, recent advances in the growth of hybrid 2D crystals, which comprise laterally connected domains of distinct atomically thin materials, provide the first realistic platform on which a 2D metal-dielectric system with a truly 1D metal-dielectric interface can be achieved. Here we show for the first time that 1D metal-dielectric interfaces support a fundamental 1D plasmonic mode (1DSPP) which exhibits cutoff behavior that provides dramatically improved light confinement in 2D systems. The 1DSPP constitutes a new basic category of plasmon as the missing 1D member of the plasmon family: 3D bulk plasmon, 2DSPP, 1DSPP, and 0D localized SP.

  4. Second-order nonlinear optical response of zigzag BN single-walled nanotubes

    NASA Astrophysics Data System (ADS)

    Margulis, Vl. A.; Muryumin, E. E.; Gaiduk, E. A.

    2010-12-01

    A theory based on the two-band tight-binding approximation for π electrons is developed to describe the second-order nonlinear optical (NLO) properties of arrays of uniformly sized and well-aligned boron-nitride single-walled nanotubes (BN-SWNTs) with a zigzag achiral structure. It is assumed that the coherent light beam at frequency ω , incident upon the nanotube sample, is linearly polarized along the symmetry axis of the nanotubes. The long-axis NLO susceptibility χ(2)(ω) of those nanotubes is calculated within the independent nanotube approximation and in neglecting local-field effects. Using the perturbation-theory formalism in the crystal-momentum representation, we derive an explicit analytic expression for the χ(2)(ω) and apply it to study three distinct second-order NLO effects possible in the BN-SWNTs due to their noncentrosymmetric structure—namely, second-harmonic generation (SHG), linear electro-optical (LEO) effect, and nonlinear optical rectification (NOR). The theory is illustrated by numerical model calculations of the SHG, LEO, and NOR susceptibility spectra for several representative BN-SWNT ensembles consisting of large-diameter nanotubes. The calculated SHG spectra are found to be dominated by the highly peaked 2ω resonance at half the band-gap energy of the BN-SWNTs, where the absorption of light is negligible. Distinct features are also found in the LEO and NOR susceptibility spectra, e.g., a sudden switching of the susceptibility from a positive peak value to a negative peak one in the near vicinity of the fundamental absorption edge. A fairly large magnitude of those susceptibilities, reaching the order of 10-7esu under off-resonant conditions and up to 10-6esu in the resonant case, suggests that BN-SWNTs are a promising material for various electro-optical device applications.

  5. TCTEX1D4, a novel protein phosphatase 1 interactor: connecting the phosphatase to the microtubule network

    PubMed Central

    Korrodi-Gregório, Luís; Vieira, Sandra I.; Esteves, Sara L. C.; Silva, Joana V.; Freitas, Maria João; Brauns, Ann-Kristin; Luers, Georg; Abrantes, Joana; Esteves, Pedro J.; da Cruz e Silva, Odete A. B.; Fardilha, Margarida; da Cruz e Silva, Edgar F.

    2013-01-01

    Summary Reversible phosphorylation plays an important role as a mechanism of intracellular control in eukaryotes. PPP1, a major eukaryotic Ser/Thr-protein phosphatase, acquires its specificity by interacting with different protein regulators, also known as PPP1 interacting proteins (PIPs). In the present work we characterized a physiologically relevant PIP in testis. Using a yeast two-hybrid screen with a human testis cDNA library, we identified a novel PIP of PPP1CC2 isoform, the T-complex testis expressed protein 1 domain containing 4 (TCTEX1D4) that has recently been described as a Tctex1 dynein light chain family member. The overlay assays confirm that TCTEX1D4 interacts with the different spliced isoforms of PPP1CC. Also, the binding domain occurs in the N-terminus, where a consensus PPP1 binding motif (PPP1BM) RVSF is present. The distribution of TCTEX1D4 in testis suggests its involvement in distinct functions, such as TGFβ signaling at the blood–testis barrier and acrosome cap formation. Immunofluorescence in human ejaculated sperm shows that TCTEX1D4 is present in the flagellum and in the acrosome region of the head. Moreover, TCTEX1D4 and PPP1 co-localize in the microtubule organizing center (MTOC) and microtubules in cell cultures. Importantly, the TCTEX1D4 PPP1BM seems to be relevant for complex formation, for PPP1 retention in the MTOC and movement along microtubules. These novel results open new avenues to possible roles of this dynein, together with PPP1. In essence TCTEX1D4/PPP1C complex appears to be involved in microtubule dynamics, sperm motility, acrosome reaction and in the regulation of the blood–testis barrier. PMID:23789093

  6. Morphodynamics and sediment tracers in 1-D (MAST-1D): 1-D sediment transport that includes exchange with an off-channel sediment reservoir

    NASA Astrophysics Data System (ADS)

    Lauer, J. Wesley; Viparelli, Enrica; Piégay, Hervé

    2016-07-01

    Bed material transported in geomorphically active gravel bed rivers often has a local source at nearby eroding banks and ends up sequestered in bars not far downstream. However, most 1-D numerical models for gravel transport assume that gravel originates from and deposits on the channel bed. In this paper, we present a 1-D framework for simulating morphodynamic evolution of bed elevation and size distribution in a gravel-bed river that actively exchanges sediment with its floodplain, which is represented as an off-channel sediment reservoir. The model is based on the idea that sediment enters the channel at eroding banks whose elevation depends on total floodplain sediment storage and on the average elevation of the floodplain relative to the channel bed. Lateral erosion of these banks occurs at a specified rate that can represent either net channel migration or channel widening. Transfer of material out of the channel depends on a typical bar thickness and a specified lateral exchange rate due either to net channel migration or narrowing. The model is implemented using an object oriented framework that allows users to explore relationships between bank supply, bed structure, and lateral change rates. It is applied to a ∼50-km reach of the Ain River, France, that experienced significant reduction in sediment supply due to dam construction during the 20th century. Results are strongly sensitive to lateral exchange rates, showing that in this reach, the supply of sand and gravel at eroding banks and the sequestration of gravel in point bars can have strong influence on overall reach-scale sediment budgets.

  7. 1D Josephson quantum interference grids: diffraction patterns and dynamics

    NASA Astrophysics Data System (ADS)

    Lucci, M.; Badoni, D.; Corato, V.; Merlo, V.; Ottaviani, I.; Salina, G.; Cirillo, M.; Ustinov, A. V.; Winkler, D.

    2016-02-01

    We investigate the magnetic response of transmission lines with embedded Josephson junctions and thus generating a 1D underdamped array. The measured multi-junction interference patterns are compared with the theoretical predictions for Josephson supercurrent modulations when an external magnetic field couples both to the inter-junction loops and to the junctions themselves. The results provide a striking example of the analogy between Josephson phase modulation and 1D optical diffraction grid. The Fiske resonances in the current-voltage characteristics with voltage spacing {Φ0}≤ft(\\frac{{\\bar{c}}}{2L}\\right) , where L is the total physical length of the array, {Φ0} the magnetic flux quantum and \\bar{c} the speed of light in the transmission line, demonstrate that the discrete line supports stable dynamic patterns generated by the ac Josephson effect interacting with the cavity modes of the line.

  8. 1-D Numerical Analysis of ABCC Engine Performance

    NASA Technical Reports Server (NTRS)

    Holden, Richard

    1999-01-01

    ABCC engine combines air breathing and rocket engine into a single engine to increase the specific impulse over an entire flight trajectory. Except for the heat source, the basic operation of the ABCC is similar to the basic operation of the RBCC engine. The ABCC is intended to have a higher specific impulse than the RBCC for single stage Earth to orbit vehicle. Computational fluid dynamics (CFD) is a useful tool for the analysis of complex transport processes in various components in ABCC propulsion system. The objective of the present research was to develop a transient 1-D numerical model using conservation of mass, linear momentum, and energy equations that could be used to predict flow behavior throughout a generic ABCC engine following a flight path. At specific points during the development of the 1-D numerical model a myriad of tests were performed to prove the program produced consistent, realistic numbers that follow compressible flow theory for various inlet conditions.

  9. Ultrahigh-Q nanocavity with 1D photonic gap.

    PubMed

    Notomi, M; Kuramochi, E; Taniyama, H

    2008-07-21

    Recently, various wavelength-sized cavities with theoretical Q values of approximately 10(8) have been reported, however, they all employ 2D or 3D photonic band gaps to realize strong light confinement. Here we numerically demonstrate that ultrahigh-Q (2.0x10(8)) and wavelength-sized (V(eff) approximately 1.4(lambda/n)3) cavities can be achieved by employing only 1D periodicity.

  10. Nonreciprocity of edge modes in 1D magnonic crystal

    NASA Astrophysics Data System (ADS)

    Lisenkov, I.; Kalyabin, D.; Osokin, S.; Klos, J. W.; Krawczyk, M.; Nikitov, S.

    2015-03-01

    Spin waves propagation in 1D magnonic crystals is investigated theoretically. Mathematical model based on plane wave expansion method is applied to different types of magnonic crystals, namely bi-component magnonic crystal with symmetric/asymmetric boundaries and ferromagnetic film with periodically corrugated top surface. It is shown that edge modes in magnonic crystals may exhibit nonreciprocal behaviour at much lower frequencies than in homogeneous films.

  11. The stability of 1-D soliton in transverse direction

    NASA Astrophysics Data System (ADS)

    Verma, Deepa; Bera, Ratan Kumar; Das, Amita; Kaw, Predhiman

    2016-12-01

    The complete characterization of the exact 1-D solitary wave solutions (both stationary and propagating) for light plasma coupled system have been studied extensively in the parameter space of light frequency and the group speed [Poornakala et al., Phys. Plasmas 9(5), 1820 (2002)]. It has been shown in 1-D that solutions with single light wave peak and paired structures are stable and hence long lived. However, solutions having multiple peaks of light wave are unstable due to Raman scattering instability [Saxena et al., Phys. Plasmas 14, 072307 (2007)]. Here, we have shown with the help of 2-D fluid simulation that single peak and paired solutions too get destabilized by the transverse filamentation instability. The numerical growth rates obtained from simulations is seen to compare well with the analytical values. It is also shown that multiple peaks solitons first undergo the regular 1-D forward Raman scattering instability. Subsequently, they undergo a distinct second phase of destabilization through transverse filamentation instability. This is evident from the structure as well as the plot of the perturbed energy which shows a second phase of growth after saturating initially. The growth rate of the filamentation instability being comparatively slower than the forward Raman instability this phase comes quite late and is clearly distinguishable.

  12. Examining Prebiotic Chemistry Using O(^1D) Insertion Reactions

    NASA Astrophysics Data System (ADS)

    Hays, Brian M.; Laas, Jacob C.; Weaver, Susanna L. Widicus

    2013-06-01

    Aminomethanol, methanediol, and methoxymethanol are all prebiotic molecules expected to form via photo-driven grain surface chemistry in the interstellar medium (ISM). These molecules are expected to be precursors for larger, biologically-relevant molecules in the ISM such as sugars and amino acids. These three molecules have not yet been detected in the ISM because of the lack of available rotational spectra. A high resolution (sub)millimeter spectrometer coupled to a molecular source is being used to study these molecules using O(^1D) insertion reactions. The O(^1D) chemistry is initiated using an excimer laser, and the products of the insertion reactions are adiabatically cooled using a supersonic expansion. Experimental parameters are being optimized by examination of methanol formed from O(^1D) insertion into methane. Theoretical studies of the structure and reaction energies for aminomethanol, methanediol, and methoxymethanol have been conducted to guide the laboratory studies once the methanol experiment has been optimized. The results of the calculations and initial experimental results will be presented.

  13. Development of 1D Liner Compression Code for IDL

    NASA Astrophysics Data System (ADS)

    Shimazu, Akihisa; Slough, John; Pancotti, Anthony

    2015-11-01

    A 1D liner compression code is developed to model liner implosion dynamics in the Inductively Driven Liner Experiment (IDL) where FRC plasmoid is compressed via inductively-driven metal liners. The driver circuit, magnetic field, joule heating, and liner dynamics calculations are performed at each time step in sequence to couple these effects in the code. To obtain more realistic magnetic field results for a given drive coil geometry, 2D and 3D effects are incorporated into the 1D field calculation through use of correction factor table lookup approach. Commercial low-frequency electromagnetic fields solver, ANSYS Maxwell 3D, is used to solve the magnetic field profile for static liner condition at various liner radius in order to derive correction factors for the 1D field calculation in the code. The liner dynamics results from the code is verified to be in good agreement with the results from commercial explicit dynamics solver, ANSYS Explicit Dynamics, and previous liner experiment. The developed code is used to optimize the capacitor bank and driver coil design for better energy transfer and coupling. FRC gain calculations are also performed using the liner compression data from the code for the conceptual design of the reactor sized system for fusion energy gains.

  14. Enhancing Solar Cell Efficiencies through 1-D Nanostructures

    PubMed Central

    2009-01-01

    The current global energy problem can be attributed to insufficient fossil fuel supplies and excessive greenhouse gas emissions resulting from increasing fossil fuel consumption. The huge demand for clean energy potentially can be met by solar-to-electricity conversions. The large-scale use of solar energy is not occurring due to the high cost and inadequate efficiencies of existing solar cells. Nanostructured materials have offered new opportunities to design more efficient solar cells, particularly one-dimensional (1-D) nanomaterials for enhancing solar cell efficiencies. These 1-D nanostructures, including nanotubes, nanowires, and nanorods, offer significant opportunities to improve efficiencies of solar cells by facilitating photon absorption, electron transport, and electron collection; however, tremendous challenges must be conquered before the large-scale commercialization of such cells. This review specifically focuses on the use of 1-D nanostructures for enhancing solar cell efficiencies. Other nanostructured solar cells or solar cells based on bulk materials are not covered in this review. Major topics addressed include dye-sensitized solar cells, quantum-dot-sensitized solar cells, and p-n junction solar cells.

  15. Quantum transport behavior of Ni-based dinuclear complexes in presence of zigzag graphene nanoribbon as electrode

    NASA Astrophysics Data System (ADS)

    Sarkar, Sunandan; Pramanik, Anup; Sarkar, Pranab

    2016-10-01

    Quantum transport properties of some Ni-based dinuclear complexes with different polydentate organic ligands have been studied by applying abinitio density functional theory along with nonequilibrium Green's function formulations. It is demonstrated that these materials are capable of showing multifunctional spin dependent properties by the influence of edge states of zigzag edged graphene nanoribbons. The current-voltage characteristics of these materials show spin dependent negative differential resistance behavior, spin filtering effect, and also voltage rectifying property. Proper tuning of these materials can alter these effects which may be utilized in various spintronic devices.

  16. Optimization of magneto-resistive response of ion-irradiated exchange biased films through zigzag arrangement of magnetization

    SciTech Connect

    Trützschler, Julia; Sentosun, Kadir; McCord, Jeffrey; Langer, Manuel; Fassbender, Jürgen; Mönch, Ingolf; Mattheis, Roland

    2014-03-14

    Exchange coupled ferromagnetic-antiferromagnetic Ni{sub 81}Fe{sub 19}/Ir{sub 23}Mn{sub 77} films with a zigzag alignment of magnetization are prepared by local ion irradiation. The anisotropic magneto-resistive behavior of the magnetic thin film structures is correlated to the magnetic structure and modeled. A unique uniaxial field sensitivity along the net magnetization alignment is obtained through the orthogonally modulated and magnetic domain wall stabilized magnetic ground state. Controlling local thin film magnetization distributions and, thus, the overall magnetization response opens unique ways to tailor the magneto-resistive sensitivity of functional magnetic thin film devices.

  17. Natural Outbreak of BVDV-1d-Induced Mucosal Disease Lacking Intestinal Lesions.

    PubMed

    Bianchi, M V; Konradt, G; de Souza, S O; Bassuino, D M; Silveira, S; Mósena, A C S; Canal, C W; Pavarini, S P; Driemeier, D

    2017-03-01

    Bovine viral diarrhea virus (BVDV) belongs to the Pestivirus genus, which is further divided into subgenotypes (1a-1u and 2a-c). When persistent infection occurs, the calf will be immunotolerant to BVDV and possibly develop mucosal disease. This study describes an outbreak of BVDV-1d-induced mucosal disease lacking intestinal lesions. Eleven calves presented with anorexia, sialorrhea, lameness, recumbency, and death. Three calves were necropsied, showing ulceration of the interdigital skin and the oral and nasal mucosa; linear ulcers in the tongue, esophagus, and rumen; and rounded ulcers in the abomasum. Microscopically, mucosa and skin had superficial necrosis, with single-cell necrosis and vacuolation in epithelial cells, and severe parakeratosis. Immunohistochemistry (IHC) showed BVDV antigen in the cytoplasm of epithelial cells in skin and mucosa. All 11 dead calves were positive upon reverse transcription-polymerase chain reaction (RT-PCR) for the detection of Pestivirus along with another 11 live calves from the herd, which were positive again by RT-PCR and IHC after a 4-week interval. Sequencing of the 5' untranslated region and N-terminal protease showed that viruses from these 22 calves were homologous and of subgenotype BVDV-1d. Cytopathic BVDV was isolated from 8 of 11 dead calves, but only noncytopathic BVDV was isolated from the 11 live animals. The findings indicate that this was an outbreak of mucosal disease caused by BVDV-1d, with high morbidity, and lesions restricted to the upper alimentary system and skin and absent from intestine. Thus, the epidemiological and pathological features in this form of mucosal disease may be similar to vesicular diseases, including foot and mouth disease.

  18. Application of WinSRFR4 program to zigzag corrugated furrow irrigation in Bolivia

    NASA Astrophysics Data System (ADS)

    Roldán Cañas, José; Moreno Perez, Maria Fatima; Garcia Moreno, Francisco Javier; Chipana, Rene

    2013-04-01

    Program WinSRFR4, developed by the Agricultural Research Service-U.S. Department of Agriculture, is used to perform surface irrigation evaluations, to establish appropriate irrigation parameters to get better irrigation efficiencies, to execute irrigation simulations and so to set several alternatives to the design of an irrigation. This paper aims to adapt WinSRFR4 program to zigzag corrugated furrow irrigation performed in the Andean regions of Bolivia. These irrigations are quite peculiar as they are carried out in areas with steep slope and with very low flow rates to avoid the risk of erosion. Besides of this, the flow rates are quite variable during the irrigation application. The greater length of the furrows is drawn on contours performing small jumps between consecutive contours. Available data are taken for seven irrigations for different periods of lettuce crop growth. First, a model that fits irrigations executed has been searched. For this, we have conducted a series of tests with the program WinSRFR4, being necessary to carry some simplifications given the peculiarity of this type of irrigation. The procedure consisted in determining the advance curves during irrigation. Later, the parameters of the Kostiakov - Lewis equation have been calculated by the method of Walker and Elliot. Although the furrow longitudinal profile was available, a mean slope was used at the time of establishing the model. WinSRFR provides a model of analyzed irrigation with a coefficient of determination ranged from R2 = 0.3520 to R2 = 0.9095. Finally, the errors obtained in the mass balances are between 2% and 14%. The model showed that application efficiencies ranged between 9% and 35%, rather poor, while runoff coefficients varied between 47% and 91%. Not too much importance is given to the fact that runoff occurs because runoff water is used in plots located at a lower level Irrigation simulations have been carried out using WinSRFR by changing the operation variables

  19. Extended-Range Ultrarefractive 1D Photonic Crystal Prisms

    NASA Technical Reports Server (NTRS)

    Ting, David Z.

    2007-01-01

    A proposal has been made to exploit the special wavelength-dispersive characteristics of devices of the type described in One-Dimensional Photonic Crystal Superprisms (NPO-30232) NASA Tech Briefs, Vol. 29, No. 4 (April 2005), page 10a. A photonic crystal is an optical component that has a periodic structure comprising two dielectric materials with high dielectric contrast (e.g., a semiconductor and air), with geometrical feature sizes comparable to or smaller than light wavelengths of interest. Experimental superprisms have been realized as photonic crystals having three-dimensional (3D) structures comprising regions of amorphous Si alternating with regions of SiO2, fabricated in a complex process that included sputtering. A photonic crystal of the type to be exploited according to the present proposal is said to be one-dimensional (1D) because its contrasting dielectric materials would be stacked in parallel planar layers; in other words, there would be spatial periodicity in one dimension only. The processes of designing and fabricating 1D photonic crystal superprisms would be simpler and, hence, would cost less than do those for 3D photonic crystal superprisms. As in 3D structures, 1D photonic crystals may be used in applications such as wavelength-division multiplexing. In the extended-range configuration, it is also suitable for spectrometry applications. As an engineered structure or artificially engineered material, a photonic crystal can exhibit optical properties not commonly found in natural substances. Prior research had revealed several classes of photonic crystal structures for which the propagation of electromagnetic radiation is forbidden in certain frequency ranges, denoted photonic bandgaps. It had also been found that in narrow frequency bands just outside the photonic bandgaps, the angular wavelength dispersion of electromagnetic waves propagating in photonic crystal superprisms is much stronger than is the angular wavelength dispersion obtained

  20. Dispersion relations for circular single and double dusty plasma chains

    SciTech Connect

    Tkachenko, D. V.; Misko, V. R.; Sheridan, T. E.

    2011-10-15

    We derive dispersion relations for a system of identical particles confined in a two-dimensional annular harmonic well and which interact through a Yukawa potential, e.g., a dusty plasma ring. When the particles are in a single chain (i.e., a one-dimensional ring), we find a longitudinal acoustic mode and a transverse optical mode which show approximate agreement with the dispersion relation for a straight configuration for large radii of the ring. When the radius decreases, the dispersion relations modify: there appears an anticrossing of the modes near the crossing point resulting in a frequency gap between the lower and upper branches of the modified dispersion relations. For the double chain (i.e., a two-dimensional zigzag configuration), the dispersion relation has four branches: longitudinal acoustic and optical and transverse acoustic and optical.

  1. ESO science data product standard for 1D spectral products

    NASA Astrophysics Data System (ADS)

    Micol, Alberto; Arnaboldi, Magda; Delmotte, Nausicaa A. R.; Mascetti, Laura; Retzlaff, Joerg

    2016-07-01

    The ESO Phase 3 process allows the upload, validation, storage, and publication of reduced data through the ESO Science Archive Facility. Since its introduction, 2 million data products have been archived and published; 80% of them are one-dimensional extracted and calibrated spectra. Central to Phase3 is the ESO science data product standard that defines metadata and data format of any product. This contribution describes the ESO data standard for 1d-spectra, its adoption by the reduction pipelines of selected instrument modes for in-house generation of reduced spectra, the enhanced archive legacy value. Archive usage statistics are provided.

  2. Deconvolution/identification techniques for 1-D transient signals

    SciTech Connect

    Goodman, D.M.

    1990-10-01

    This paper discusses a variety of nonparametric deconvolution and identification techniques that we have developed for application to 1-D transient signal problems. These methods are time-domain techniques that use direct methods for matrix inversion. Therefore, they are not appropriate for large data'' problems. These techniques involve various regularization methods and permit the use of certain kinds of a priori information in estimating the unknown. These techniques have been implemented in a package using standard FORTRAN that should make the package readily transportable to most computers. This paper is also meant to be an instruction manual for the package. 25 refs., 17 figs., 1 tab.

  3. Breakdown of 1D water wires inside charged carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Pant, Shashank

    2016-11-01

    Using molecular dynamics approach we investigated the structure and dynamics of water confined inside pristine and charged 6,6 carbon nanotubes (CNTs). This study reports the breakdown of 1D water wires and the emergence of triangular faced water on incorporating charges in 6,6 CNTs. Incorporation of charges results in high potential barriers to flipping of water molecules due to the formation of large number of hydrogen bonds. The PMF analyses show the presence of ∼2 kcal/mol barrier for the movement of water inside pristine CNT and almost negligible barrier in charged CNTs.

  4. Spatial coherence of polaritons in a 1D channel

    SciTech Connect

    Savenko, I. G.; Iorsh, I. V.; Kaliteevski, M. A.; Shelykh, I. A.

    2013-01-15

    We analyze time evolution of spatial coherence of a polariton ensemble in a quantum wire (1D channel) under constant uniform resonant pumping. Using the theoretical approach based on the Lindblad equation for a one-particle density matrix, which takes into account the polariton-phonon and excitonexciton interactions, we study the behavior of the first-order coherence function g{sup 1} for various pump intensities and temperatures in the range of 1-20 K. Bistability and hysteresis in the dependence of the first-order coherence function on the pump intensity is demonstrated.

  5. Nanofluidic sustainable energy conversion using a 1D nanofluidic network.

    PubMed

    Kim, Sang Hui; Kwak, Seungmin; Han, Sung Il; Chun, Dong Won; Lee, Kyu Hyoung; Kim, Jinseok; Lee, Jeong Hoon

    2014-05-01

    We propose a 1-dimensional (1D) nanofluidic energy conversion device by implementing a surface-patterned Nafion membrane for the direct energy conversion of the pressure to electrical power. By implementing a -200-nm-thick nano-bridge with a 5-nm pore size between two microfluidic channels, we acquired an effective streaming potential of 307 mV and output power of 94 pW with 0.1 mM KCI under pressure difference of 45 MPa. The experimental results show both the effects of applied pressure differences and buffer concentrations on the effective streaming potential, and are consistent with the analytical prediction.

  6. 1-D blood flow modelling in a running human body.

    PubMed

    Szabó, Viktor; Halász, Gábor

    2017-04-10

    In this paper an attempt was made to simulate blood flow in a mobile human arterial network, specifically, in a running human subject. In order to simulate the effect of motion, a previously published immobile 1-D model was modified by including an inertial force term into the momentum equation. To calculate inertial force, gait analysis was performed at different levels of speed. Our results show that motion has a significant effect on the amplitudes of the blood pressure and flow rate but the average values are not effected significantly.

  7. Chain Sampling

    DTIC Science & Technology

    1972-08-01

    35609 Advanced Techniques Branch Plans and Programs Analysis Division Directorate for Product Assurance U. S. Army Missile Command Redstone Arsenal...Ray Heathcock Advanced Techniques Branch Plans and Programs Analysis Division Directorate for Product Assurance U. S. Army Missile Command...for Product Assurance has established a rather unique computer program for handling a variety of chain sampling schemes and is available for

  8. Synthesis, crystal structure, and properties of a 1-D terbium-substituted monolacunary Keggin-type polyoxotungstate.

    PubMed

    Ma, Pengtao; Si, Yanan; Wan, Rong; Zhang, Shaowei; Wang, Jingping; Niu, Jingyang

    2015-03-05

    A new 1-D linear chainlike terbium-substituted polyoxometalate [Tb(H2O)2(α-PW11O39)](4-) (1) has been synthesized in aqueous solution and characterized by elemental analysis, inductively coupled plasma atomic emission spectrometry (ICP-AES), X-ray powder diffraction (XRPD), IR spectrum, thermal analysis, electrospray ionization mass spectrometry (ESI-MS), and X-ray single-crystal diffraction. X-ray structural analysis reveals that 1 displays a 1-D linear chain containing [Tb(H2O)2(α-PW11O39)](4-) moieties. The Tb(III) cation incorporated into the monolacunary Keggin-type [α-PW11O39](7-) unit resides in a distorted monocapped triangular prismatic geometry and acts as a linker to join two adjacent [α-PW11O39](7-) units to form a 1-D chain structure. Solid-state photoluminescent property of 1 has been investigated at room temperature and the photoluminescent emission mainly results from the synergistic effect of the Tb(III) cation and the Na7[α-PW11O39] precursor. The ESI-MS spectrum of 1 confirms that the polyanion [Tb(H2O)(HPW11O39)](3-) is stable in aqueous solution.

  9. Differential Recognition of CD1d-[alpha]-Galactosyl Ceramide by the V[beta]8.2 and V[beta]7 Semi-invariant NKT T Cell Receptors

    SciTech Connect

    Pellicci, Daniel G.; Patel, Onisha; Kjer-Nielsen, Lars; Pang, Siew Siew; Sullivan, Lucy C.; Kyparissoudis, Konstantinos; Brooks, Andrew G.; Reid, Hugh H.; Gras, Stephanie; Lucet, Isabelle S.; Koh, Ruide; Smyth, Mark J.; Mallevaey, Thierry; Matsuda, Jennifer L.; Gapin, Laurent; McCluskey, James; Godfrey, Dale I.; Rossjohn, Jamie; PMCI-A; Monash; UCHSC; Melbourne

    2009-09-02

    The semi-invariant natural killer T cell receptor (NKT TCR) recognizes CD1d-lipid antigens. Although the TCR{alpha} chain is typically invariant, the {beta} chain expression is more diverse, where three V{beta} chains are commonly expressed in mice. We report the structures of V{alpha}14-V{beta}8.2 and V{alpha}14-V{beta}7 NKT TCRs in complex with CD1d-{alpha}-galactosylceramide ({alpha}-GalCer) and the 2.5 {angstrom} structure of the human NKT TCR-CD1d-{alpha}-GalCer complex. Both V{beta}8.2 and V{beta}7 NKT TCRs and the human NKT TCR ligated CD1d-{alpha}-GalCer in a similar manner, highlighting the evolutionarily conserved interaction. However, differences within the V{beta} domains of the V{beta}8.2 and V{beta}7 NKT TCR-CD1d complexes resulted in altered TCR{beta}-CD1d-mediated contacts and modulated recognition mediated by the invariant {alpha} chain. Mutagenesis studies revealed the differing contributions of V{beta}8.2 and V{beta}7 residues within the CDR2{beta} loop in mediating contacts with CD1d. Collectively we provide a structural basis for the differential NKT TCR V{beta} usage in NKT cells.

  10. Blood flow quantification using 1D CFD parameter identification

    NASA Astrophysics Data System (ADS)

    Brosig, Richard; Kowarschik, Markus; Maday, Peter; Katouzian, Amin; Demirci, Stefanie; Navab, Nassir

    2014-03-01

    Patient-specific measurements of cerebral blood flow provide valuable diagnostic information concerning cerebrovascular diseases rather than visually driven qualitative evaluation. In this paper, we present a quantitative method to estimate blood flow parameters with high temporal resolution from digital subtraction angiography (DSA) image sequences. Using a 3D DSA dataset and a 2D+t DSA sequence, the proposed algorithm employs a 1D Computational Fluid Dynamics (CFD) model for estimation of time-dependent flow values along a cerebral vessel, combined with an additional Advection Diffusion Equation (ADE) for contrast agent propagation. The CFD system, followed by the ADE, is solved with a finite volume approximation, which ensures the conservation of mass. Instead of defining a new imaging protocol to obtain relevant data, our cost function optimizes the bolus arrival time (BAT) of the contrast agent in 2D+t DSA sequences. The visual determination of BAT is common clinical practice and can be easily derived from and be compared to values, generated by a 1D-CFD simulation. Using this strategy, we ensure that our proposed method fits best to clinical practice and does not require any changes to the medical work flow. Synthetic experiments show that the recovered flow estimates match the ground truth values with less than 12% error in the mean flow rates.

  11. Tunability and Sensing Properties of Plasmonic/1D Photonic Crystal

    NASA Astrophysics Data System (ADS)

    Shaban, Mohamed; Ahmed, Ashour M.; Abdel-Rahman, Ehab; Hamdy, Hany

    2017-02-01

    Gold/one-dimensional photonic crystal (Au/1D-PC) is fabricated and applied for sensitive sensing of glucose and different chemical molecules of various refractive indices. The Au layer thickness is optimized to produce surface plasmon resonance (SPR) at the right edge of the photonic band gap (PBG). As the Au deposition time increased to 60 sec, the PBG width is increased from 46 to 86 nm in correlation with the behavior of the SPR. The selectivity of the optimized Au/1D-PC sensor is tested upon the increase of the environmental refractive index of the detected molecules. The resonance wavelength and the PBG edges increased linearly and the transmitted intensity increased nonlinearly as the environment refractive index increased. The SPR splits to two modes during the detection of chloroform molecules based on the localized capacitive coupling of Au particles. Also, this structure shows high sensitivity at different glucose concentrations. The PBG and SPR are shifted to longer wavelengths, and PBG width is decreased linearly with a rate of 16.04 Å/(μg/mm3) as the glucose concentration increased. The proposed structure merits; operation at room temperature, compact size, and easy fabrication; suggest that the proposed structure can be efficiently used for the biomedical and chemical application.

  12. Tunability and Sensing Properties of Plasmonic/1D Photonic Crystal

    PubMed Central

    Shaban, Mohamed; Ahmed, Ashour M.; Abdel-Rahman, Ehab; Hamdy, Hany

    2017-01-01

    Gold/one-dimensional photonic crystal (Au/1D-PC) is fabricated and applied for sensitive sensing of glucose and different chemical molecules of various refractive indices. The Au layer thickness is optimized to produce surface plasmon resonance (SPR) at the right edge of the photonic band gap (PBG). As the Au deposition time increased to 60 sec, the PBG width is increased from 46 to 86 nm in correlation with the behavior of the SPR. The selectivity of the optimized Au/1D-PC sensor is tested upon the increase of the environmental refractive index of the detected molecules. The resonance wavelength and the PBG edges increased linearly and the transmitted intensity increased nonlinearly as the environment refractive index increased. The SPR splits to two modes during the detection of chloroform molecules based on the localized capacitive coupling of Au particles. Also, this structure shows high sensitivity at different glucose concentrations. The PBG and SPR are shifted to longer wavelengths, and PBG width is decreased linearly with a rate of 16.04 Å/(μg/mm3) as the glucose concentration increased. The proposed structure merits; operation at room temperature, compact size, and easy fabrication; suggest that the proposed structure can be efficiently used for the biomedical and chemical application. PMID:28176799

  13. Engineered atom-light interactions in 1D photonic crystals

    NASA Astrophysics Data System (ADS)

    Martin, Michael J.; Hung, Chen-Lung; Yu, Su-Peng; Goban, Akihisa; Muniz, Juan A.; Hood, Jonathan D.; Norte, Richard; McClung, Andrew C.; Meenehan, Sean M.; Cohen, Justin D.; Lee, Jae Hoon; Peng, Lucas; Painter, Oskar; Kimble, H. Jeff

    2014-05-01

    Nano- and microscale optical systems offer efficient and scalable quantum interfaces through enhanced atom-field coupling in both resonators and continuous waveguides. Beyond these conventional topologies, new opportunities emerge from the integration of ultracold atomic systems with nanoscale photonic crystals. One-dimensional photonic crystal waveguides can be engineered for both stable trapping configurations and strong atom-photon interactions, enabling novel cavity QED and quantum many-body systems, as well as distributed quantum networks. We present the experimental realization of such a nanophotonic quantum interface based on a nanoscale photonic crystal waveguide, demonstrating a fractional waveguide coupling of Γ1 D /Γ' of 0 . 32 +/- 0 . 08 , where Γ1 D (Γ') is the atomic emission rate into the guided (all other) mode(s). We also discuss progress towards intra-waveguide trapping of ultracold Cs. This work was supported by the IQIM, an NSF Physics Frontiers Center with support from the Moore Foundation, the DARPA ORCHID program, the AFOSR QuMPASS MURI, the DoD NSSEFF program, NSF, and the Kavli Nanoscience Institute (KNI) at Caltech.

  14. Constitutive modeling and control of 1D smart composite structures

    NASA Astrophysics Data System (ADS)

    Briggs, Jonathan P.; Ostrowski, James P.; Ponte-Castaneda, Pedro

    1998-07-01

    Homogenization techniques for determining effective properties of composite materials may provide advantages for control of stiffness and strain in systems using hysteretic smart actuators embedded in a soft matrix. In this paper, a homogenized model of a 1D composite structure comprised of shape memory alloys and a rubber-like matrix is presented. With proportional and proportional/integral feedback, using current as the input state and global strain as an error state, implementation scenarios include the use of tractions on the boundaries and a nonlinear constitutive law for the matrix. The result is a simple model which captures the nonlinear behavior of the smart composite material system and is amenable to experiments with various control paradigms. The success of this approach in the context of the 1D model suggests that the homogenization method may prove useful in investigating control of more general smart structures. Applications of such materials could include active rehabilitation aids, e.g. wrist braces, as well as swimming/undulating robots, or adaptive molds for manufacturing processes.

  15. Tunability and Sensing Properties of Plasmonic/1D Photonic Crystal.

    PubMed

    Shaban, Mohamed; Ahmed, Ashour M; Abdel-Rahman, Ehab; Hamdy, Hany

    2017-02-08

    Gold/one-dimensional photonic crystal (Au/1D-PC) is fabricated and applied for sensitive sensing of glucose and different chemical molecules of various refractive indices. The Au layer thickness is optimized to produce surface plasmon resonance (SPR) at the right edge of the photonic band gap (PBG). As the Au deposition time increased to 60 sec, the PBG width is increased from 46 to 86 nm in correlation with the behavior of the SPR. The selectivity of the optimized Au/1D-PC sensor is tested upon the increase of the environmental refractive index of the detected molecules. The resonance wavelength and the PBG edges increased linearly and the transmitted intensity increased nonlinearly as the environment refractive index increased. The SPR splits to two modes during the detection of chloroform molecules based on the localized capacitive coupling of Au particles. Also, this structure shows high sensitivity at different glucose concentrations. The PBG and SPR are shifted to longer wavelengths, and PBG width is decreased linearly with a rate of 16.04 Å/(μg/mm(3)) as the glucose concentration increased. The proposed structure merits; operation at room temperature, compact size, and easy fabrication; suggest that the proposed structure can be efficiently used for the biomedical and chemical application.

  16. Influence of zigzag edges on the Ruderman-Kittel-Kasuya-Yosida interaction between magnetic impurities in graphene nanoribbons

    SciTech Connect

    Akbari-Sharbaf, A. Cottam, M. G.

    2014-11-21

    Localized magnetic impurity centres in graphene can interact through the π-electrons, leading to an effective Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction. A RKKY-type study is presented for graphene ribbons with zigzag edges. Specifically investigations of how the edges modify the interaction between two localized magnetic moments are made by using a tight-binding Hamiltonian to describe the hopping of the π-electrons between adjacent sites and a contact term for interactions with the localized moments. In terms of a Green's function formalism for the excitation spectrum, which comprises modified bulk modes and two different types of localized edge modes, explicit analytical expressions are obtained for the RKKY interaction for any two magnetic sites on the graphene ribbon. The results enable us to determine the RKKY contributions that arise individually from the bulk-like modes and from the two types of edge modes in the zigzag geometry. The importance of these contributions varies depending on the proximity of the magnetic impurities to each other and to an edge.

  17. Comparative study on performance of a zigzag printed circuit heat exchanger with various channel shapes and configurations

    NASA Astrophysics Data System (ADS)

    Lee, Sang-Moon; Kim, Kwang-Yong

    2013-07-01

    Comparative study has been performed with various channel cross-sectional shapes and channel configurations of a zigzag printed circuit heat exchanger (PCHE), which has been considered as a heat exchanging device for the gas turbine based generation systems. Three-dimensional Reynolds-averaged Navier-Stokes equations and heat transfer equations are solved to analyze conjugate heat transfer in the zigzag channels. The shear stress transport model with a low Reynolds number wall treatment is used as a turbulence closure. The global Nusselt number, Colburn j-factor, effectiveness, and friction factor are used to estimate the thermal-hydraulic performance of the PCHE. Four different shapes of channel cross section (semicircular, rectangular, trapezoidal, and circular) and four different channel configurations are tested to determine their effects on thermal-hydraulic performance. The rectangular channel shows the best thermal performance but the worst hydraulic performance, while the circular channel shows the worst thermal performance. The Colburn j-factor and friction factor are found to be inversely proportional to the Reynolds number in cold channels, while the effectiveness and global Nusselt number are proportional to the Reynolds number.

  18. Reactions of HO2 with carbon monoxide and nitric oxide and of O/1 D/ with water.

    NASA Technical Reports Server (NTRS)

    Simonaitis, R.; Heicklen, J.

    1973-01-01

    Investigation of the reactions of the hydroperoxyl radical with carbon monoxide and nitric oxide in a static system, and reexamination of the reaction of O(1 D) with water. The HO2 radicals were generated by the photolysis of N2O at 2139 A in the presence of excess H2O or H2 and smaller amounts of CO and O2. The O(1 D) atoms produced from the photolysis of N2O react with H2O or with H2 to give OH radicals in the case of H2O or OH radicals and H atoms in the case of H2. With H2O, two OH radicals are produced for each O(1 D) removed at low pressures, but the OH yield drops as the pressure is raised. This drop is attributed to an insertion reaction which removes from 10 to 30% of the O(1 D) atoms at about 650 torr of H2O at 200 F. The OH radicals generated can react with either CO or H2 to produce H atoms, which then add to O2 to produce HO2. In the absence of NO, the HO2 radicals could react by two routes, while with NO present NO2 is produced in a long chain process.

  19. Heat transfer and pressure drop correlations of microchannel heat exchangers with S-shaped and zigzag fins for carbon dioxide cycles

    SciTech Connect

    Ngo, Tri Lam; Kato, Yasuyoshi; Nikitin, Konstantin; Ishizuka, Takao

    2007-11-15

    A new microchannel heat exchanger (MCHE) with S-shaped fins was developed using the three-dimensional computational fluid dynamics (3D CFD) FLUENT code. The MCHE provided 6-7 times lower pressure drop while maintaining heat-transfer performance that was almost equivalent to that of a conventional MCHE with zigzag fins. This study was done to confirm the simulation results of thermal-hydraulic performance using a supercritical carbon dioxide loop, and to propose empirical correlations of Nusselt numbers and pressure-drop factors for a new MCHE with S-shaped fins and a conventional one with zigzag fins. This study is also intended to confirm the independence of Pr obtained in the previous study by widely varying Pr from 0.75 to 2.2. Experimental results show that the pressure-drop factor of the MCHEs with S-shaped fins is 4-5 times less than that of MCHE with zigzag fins, although Nu is 24-34% less, depending on the Re within its range. The Nusselt number correlations are expressed, respectively as Nu{sub S-shaped} {sub fins} = 0.1740 Re{sup 0.593}Pr{sup 0.430} and Nu{sub zigzag} {sub fins} = 0.1696 Re{sup 0.629}Pr{sup 0.317} for the MCHE with S-shaped and zigzag fins, and their pressure-drop factors are given as f{sub S-shaped} {sub fins} = 0.4545 Re{sup -0.340} and f{sub zigzag} {sub fins} = 0.1924 Re{sup -0.091}. The Nu correlation of the MCHE with S-shaped fins reproduces the experimental data of overall heat transfer coefficients with a standard deviation (1 sigma) of {+-}2.3%, although it is {+-}3.0% for the MCHE with zigzag fins. The calculated pressure drops obtained from pressure-drop factor correlations agree with the experimental data within a standard deviation of {+-}16.6% and {+-}13.5% for the MCHEs with S-shaped and zigzag fins, respectively. (author)

  20. Zigzag-Shaped Superlattices on the Basis of Graphene Nanoribbons: Structure and Electronic Properties

    NASA Astrophysics Data System (ADS)

    Saroka, V. A.; Batrakov, K. G.

    2016-09-01

    The paper focuses on superlattices consisting of two coplanar fragments of one-layer graphene nanoribbons that have different width and are connected at an angle. Classification of such superlattices was carried out; their electronic properties were studied using the tight-binding method. It was demonstrated that in superlattices consisting of two fragments of graphene nanoribbons with armchair edges connected at an angle of 60°, the band gap can be regulated by the number of dimeric carbon atom chains of one of the fragments. In that case one can observe a periodic dependence of the band gap on the number of chains with a characteristic period equal to three dimeric chains. The number of dimeric chains of the second superlattice fragment regulates the average band gap value near which the periodic oscillations occur, as well as the amplitude of those oscillations. Therefore, one can accomplish a sufficiently precise band gap tuning for such structures. Such tuning can find its wide application in the booming carbon nanoelectronics industry when creating generators, amplifiers and sensors in the nanochains.

  1. The Extended Family of CD1d-Restricted NKT Cells: Sifting through a Mixed Bag of TCRs, Antigens, and Functions

    PubMed Central

    Macho-Fernandez, Elodie; Brigl, Manfred

    2015-01-01

    Natural killer T (NKT) cells comprise a family of specialized T cells that recognize lipid antigens presented by CD1d. Based on their T cell receptor (TCR) usage and antigen specificities, CD1d-restricted NKT cells have been divided into two main subsets: type I NKT cells that use a canonical invariant TCR α-chain and recognize α-galactosylceramide (α-GalCer), and type II NKT cells that use a more diverse αβ TCR repertoire and do not recognize α-GalCer. In addition, α-GalCer-reactive NKT cells that use non-canonical αβ TCRs and CD1d-restricted T cells that use γδ or δ/αβ TCRs have recently been identified, revealing further diversity among CD1d-restricted T cells. Importantly, in addition to their distinct antigen specificities, functional differences are beginning to emerge between the different members of the CD1d-restricted T cell family. In this review, while using type I NKT cells as comparison, we will focus on type II NKT cells and the other non-invariant CD1d-restricted T cell subsets, and discuss our current understanding of the antigens they recognize, the formation of stimulatory CD1d/antigen complexes, the modes of TCR-mediated antigen recognition, and the mechanisms and consequences of their activation that underlie their function in antimicrobial responses, anti-tumor immunity, and autoimmunity. PMID:26284062

  2. Chain Gang

    NASA Technical Reports Server (NTRS)

    2006-01-01

    6 August 2006 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a chain of clustered and battered craters. These were formed by secondary impact. That is, somewhere to the south (beyond the bottom of this image), a large impact crater formed. When this occurred, material ejected from the crater was thrown tens to hundreds of kilometers away. This material then impacted the martian surface, forming clusters and chains of smaller craters.

    Location near: 15.8oN, 35.6oW Image width: 3 km (1.9 mi) Illumination from: upper left Season: Northern Spring

  3. Self-assembly of 1-D n-type nanostructures based on naphthalene diimide-appended dipeptides.

    PubMed

    Shao, Hui; Nguyen, Tuan; Romano, Natalie C; Modarelli, David A; Parquette, Jon R

    2009-11-18

    n-Type 1D nanostructures are formed from the beta-sheet assembly of dipeptides bearing a 1,4,5,8-naphthalenetetracarboxylic acid diimide (NDI) side chain into either helical nanofibers or twisted nanoribbons. Amyloid-like 1-D helical nanofibers and twisted nanoribbons assemble in an aqueous solution depending on the placement of the NDI group. beta-Sheet-type hydrogen bonding and pi-pi association play important roles in directing the assembly process. A delicate balance between electrostatic repulsion and hydrophobic interactions is critical for self-assembly. Fluorescence lifetime and anisotropy experiments indicate that the nature of the intermolecular organization and packing within the nanostructures critically impacts intermolecular energy migration pi-electron delocalization.

  4. Single‐Layered Hybrid Materials Based on 1D Associated Metalorganic Nanoribbons for Controlled Release of Pheromones

    PubMed Central

    Moreno, José María; Navarro, Ismael; Díaz, Urbano; Primo, Jaime

    2016-01-01

    Abstract A new family of stable layered organic–inorganic materials has been prepared, in one‐step solvothermal process. They are based on an ordered nickel cluster‐type nanoribbons separated from each other by specific alkyl (heptyl‐ or dodecyl‐) arylic mono‐carboxylate moieties acting as molecular spacers, perpendicular to the 1D inorganic chains. These organic spacers contain hydrocarbon tails with different length which control the separation level between inorganic 1D sub‐units, inhibiting the 3D growth of conventional DUT‐8‐type metal–organic frameworks (MOFs). The lamellar nature of the materials formed was studied and confirmed by different characterization techniques, showing the structural location of individual organic and inorganic building units. They have been successfully used as a long‐lasting biodegradable and water‐proof materials for controlled release of chemicals, such as pheromones for sustainable treatment of insect plagues. PMID:27444798

  5. A series of novel 1D coordination polymers constructed from metal?quinolone complex fragments linked by aromatic dicarboxylate ligands

    NASA Astrophysics Data System (ADS)

    He, Jiang-Hong; Xiao, Dong-Rong; Yan, Shi-Wei; Sun, Dian-Zhen; Chen, Hai-Yan; Wang, Xin; Yang, Juan; Ye, Zhong-Li; Yuan, Ruo; Wang, En-Bo

    2012-08-01

    Self-assembly of quinolones with metal salts in the presence of aromatic dicarboxylate ligands affords a series of novel 1D metal-quinolone complexes, namely [Mn(Hppa)(oba)]·3H2O (1), [Co(Hppa)(oba)]·3.25H2O (2), [Zn(Hppa)(sdba)]·1.5H2O (3), [Mn(Hcf)(bpda)(H2O)]·2H2O (4), [Mn(Hppa)2(bpdc)] (5) and [Mn(Hlome)2(bpdc)]·4H2O (6) (Hppa = Pipemidic acid, Hcf = ciprofloxacin, Hlome = lomefloxacin). The structures of compounds 1-3 consist of novel polymeric chains spanning two different directions, which display an intriguing 1D → 3D inclined polycatenation of supramolecular ladders. Compound 4 exhibits a chain compound formed from the interconnection of [Mn2(Hcf)2(μ-CO2)2] dimers with bpda ligands. Compounds 5 and 6 are similar chain compounds constructed from [Mn(Hppa)2] (or [Mn(Hlome)2]) fragments linked by bpdc ligands. The magnetic properties of 4 have been studied, which indicate the existence of antiferromagnetic interactions. Furthermore, the luminescent properties of compound 3 are discussed.

  6. Axion string dynamics I: 2+1D

    NASA Astrophysics Data System (ADS)

    Fleury, Leesa M.; Moore, Guy D.

    2016-05-01

    If the axion exists and if the initial axion field value is uncorrelated at causally disconnected points, then it should be possible to predict the efficiency of cosmological axion production, relating the axionic dark matter density to the axion mass. The main obstacle to making this prediction is correctly treating the axion string cores. We develop a new algorithm for treating the axionic string cores correctly in 2+1 dimensions. When the axionic string cores are given their full physical string tension, axion production is about twice as efficient as in previous simulations. We argue that the string network in 2+1 dimensions should behave very differently than in 3+1 dimensions, so this result cannot be simply carried over to the physical case. We outline how to extend our method to 3+1D axion string dynamics.

  7. 1-D ELECTRO-OPTIC BEAM STEERING DEVICE.

    PubMed

    Wang, Wei-Chih; Tsui, Chi Leung

    2011-06-05

    In this paper, we present the design and fabrication of a 1D beam steering device based on planar electro-optic thermal-plastic prisms and a collimator lens array. With the elimination of moving parts, the proposed device is able to overcome the mechanical limitations of present scanning devices, such as fatigue and low operating frequency, while maintaining a small system footprint (~0.5mm×0.5mm). From experimental data, our prototype device is able to achieve a maximum deflection angle of 5.6° for a single stage prism design and 29.2° for a cascaded three prisms stage design. The lens array shows a 4µm collimated beam diameter.

  8. Combinatorial approach to exactly solve the 1D Ising model

    NASA Astrophysics Data System (ADS)

    Seth, Swarnadeep

    2017-01-01

    The Ising model is a well known statistical model which can be solved exactly by various methods. The most familiar one is the transfer matrix method. Sometimes it can be difficult to approach the open boundary case rather than periodic boundary ones in higher dimensions. But physically it is more intuitive to study the open boundary case, as it gives a closer view of the real system. We have introduced a new method called the pairing method to determine the exact partition function for the simplest case, a 1D Ising lattice. This method simplifies the problem's complexities and reduces it to a pure combinatorial problem. The study also reveals that it is possible to apply this pairing method in the case of a 2D square lattice. The obtained results agree perfectly with the values in the literature and this new approach provides an algorithmic insight to deal with such problems.

  9. Statistical analysis of 1D HRR target features

    NASA Astrophysics Data System (ADS)

    Gross, David C.; Schmitz, James L.; Williams, Robert L.

    2000-08-01

    Automatic target recognition (ATR) and feature-aided tracking (FAT) algorithms that use one-dimensional (1-D) high range resolution (HRR) profiles require unique or distinguishable target features. This paper explores the use of statistical measures to quantify the separability and stability of ground target features found in HRR profiles. Measures of stability, such as the mean and variance, can be used to determine the stability of a target feature as a function of the target aspect and elevation angle. Statistical measures of feature predictability and separability, such as the Fisher and Bhattacharyya measures, demonstrate the capability to adequately predict the desired target feature over a specified aspect angular region. These statistical measures for separability and stability are explained in detail and their usefulness is demonstrated with measured HRR data.

  10. Axion string dynamics I: 2+1D

    SciTech Connect

    Fleury, Leesa M.; Moore, Guy D.

    2016-05-03

    If the axion exists and if the initial axion field value is uncorrelated at causally disconnected points, then it should be possible to predict the efficiency of cosmological axion production, relating the axionic dark matter density to the axion mass. The main obstacle to making this prediction is correctly treating the axion string cores. We develop a new algorithm for treating the axionic string cores correctly in 2+1 dimensions. When the axionic string cores are given their full physical string tension, axion production is about twice as efficient as in previous simulations. We argue that the string network in 2+1 dimensions should behave very differently than in 3+1 dimensions, so this result cannot be simply carried over to the physical case. We outline how to extend our method to 3+1D axion string dynamics.

  11. Effective theory of black holes in the 1/D expansion

    NASA Astrophysics Data System (ADS)

    Emparan, Roberto; Shiromizu, Tetsuya; Suzuki, Ryotaku; Tanabe, Kentaro; Tanaka, Takahiro

    2015-06-01

    The gravitational field of a black hole is strongly localized near its horizon when the number of dimensions D is very large. In this limit, we can effectively replace the black hole with a surface in a background geometry (e.g. Minkowski or Anti-deSitter space). The Einstein equations determine the effective equations that this `black hole surface' (or membrane) must satisfy. We obtain them up to next-to-leading order in 1/ D for static black holes of the Einstein-(A)dS theory. To leading order, and also to next order in Minkowski backgrounds, the equations of the effective theory are the same as soap-film equations, possibly up to a redshift factor. In particular, the Schwarzschild black hole is recovered as a spherical soap bubble. Less trivially, we find solutions for `black droplets', i.e. black holes localized at the boundary of AdS, and for non-uniform black strings.

  12. Uniform Propagation of Chaos for Kac's 1D Particle System

    NASA Astrophysics Data System (ADS)

    Cortez, Roberto

    2016-12-01

    In this paper we study Kac's 1D particle system, consisting of the velocities of N particles colliding at constant rate and randomly exchanging energies. We prove uniform (in time) propagation of chaos in Wasserstein distance with explicit polynomial rates in N, for both the squared (i.e., the energy) and non-squared particle system. These rates are of order N^{-1/3} (almost, in the non-squared case), assuming that the initial distribution of the limit nonlinear equation has finite moments of sufficiently high order (4+ɛ is enough when using the 2-Wasserstein distance). The proof relies on a convenient parametrization of the collision recently introduced by Hauray, as well as on a coupling technique developed by Cortez and Fontbona.

  13. 1-D ELECTRO-OPTIC BEAM STEERING DEVICE

    PubMed Central

    Wang, Wei-Chih; Tsui, Chi Leung

    2011-01-01

    In this paper, we present the design and fabrication of a 1D beam steering device based on planar electro-optic thermal-plastic prisms and a collimator lens array. With the elimination of moving parts, the proposed device is able to overcome the mechanical limitations of present scanning devices, such as fatigue and low operating frequency, while maintaining a small system footprint (~0.5mm×0.5mm). From experimental data, our prototype device is able to achieve a maximum deflection angle of 5.6° for a single stage prism design and 29.2° for a cascaded three prisms stage design. The lens array shows a 4µm collimated beam diameter. PMID:22199458

  14. Etude des chaines de spins par les methodes de la theorie quantique des champs

    NASA Astrophysics Data System (ADS)

    Allen, Dave

    Notre etude porte sur la chaine de spins en zigzag avec dimerisation dans le cas des spins 1/2 et 1. L'echelle de spin ordinaire et la chaine en zigzag simple en sont des cas particuliers. Dans la limite continue, ces systemes sont decrits par des modeles Wess-Zumino-Witten couples. Afin de pouvoir calculer les fonctions de correlation, nous exposons differentes equivalences quantiques permettant de simplifier les calculs. Dans le cas de chaines de spin 1/2, nous demontrons l'equivalence avec un modele de type Gross-Neveu, en fonction de fermions de Majorana; ces fermions decrivent alors les excitations elementaires du systeme. Nous exposons une vision classique de ces excitations afin de voir les mecanismes de confinement des spinons. Dans le cas de chaines de spin 1, l'etude est plus complexe. Nous pouvons decrire le systeme a l'aide de modeles sine-Gordon perturbes par de nombreuses interactions. En se limitant aux plus importantes, nous pouvons expliquer le comportement du gap en fonction du couplage interchaine observe numeriquement.

  15. Lanczos diagonalizations of the 1-D Peierls-Hubbard model

    SciTech Connect

    Loh, E.Y.; Campbell, D.K.; Gammel, J.T.

    1989-01-01

    In studies of interacting electrons in reduced dimensions'' one is trapped between the Scylla of exponential growth of the number of states in any exact many-body basis and the Charybdis of the failure of mean-field theories to capture adequately the effects of interactions. In the present article we focus on one technique -- the Lanczos method -- which, at least in the case of the 1-D Peierls-Hubbard model, appears to allow us to sail the narrow channel between these two hazards. In contrast to Quantum Monte Carlo methods, which circumvent the exponential growth of states by statistical techniques and importance sampling, the Lanczos approach attacks this problem head-on by diagonalizing the full Hamiltonian. Given the restrictions of present computers, this approach is thus limited to studying finite clusters of roughly 12--14 sites. Fortunately, in one dimension, such clusters are usually sufficient for extracting many of the properties of the infinite system provided that one makes full use of the ability to vary the boundary conditions. In this article we shall apply the Lanczos methodology and novel phase randomization'' techniques to study the 1-D Peierls-Hubbard model, with particular emphasis on the optical absorption properties, including the spectrum of absorptions as a function of photon energy. Despite the discreteness of the eigenstates in our finite clusters, we are able to obtain optical spectra that, in cases where independent tests can be made, agree well with the known exact results for the infinite system. Thus we feel that this combination of techniques represents an important and viable means of studying many interesting novel materials involving strongly correlated electrons. 26 refs., 6 figs.

  16. Evaluating 1d Seismic Models of the Lunar Interior

    NASA Astrophysics Data System (ADS)

    Yao, Y.; Thorne, M. S.; Weber, R. C.; Schmerr, N. C.

    2012-12-01

    A four station seismic network was established on the Moon from 1969 to 1977 as part of the Apollo Lunar Surface Experiment Package (ALSEP). A total of nine 1D seismic velocity models were generated using a variety of different techniques. In spite of the fact that these models were generated from the same data set, significant differences exist between them. We evaluate these models by comparing predicted travel-times to published catalogs of lunar events. We generate synthetic waveform predictions for 1D lunar models using a modified version of the Green's Function of the Earth by Minor Integration (GEMINI) technique. Our results demonstrate that the mean square errors between predicted and measured P-wave travel times are smaller than those for S-wave travel times in all cases. Moreover, models fit travel times for artificial and meteoroid impacts better than for shallow and deep moonquakes. Overall, models presented by Nakamura [Nakamura, 1983] and Garcia et al. [Garcia et al., 2011] predicted the observed travel times better than all other models and were comparable in their explanation of travel-times. Nevertheless, significant waveform differences exist between these models. In particular, the seismic velocity structure of the lunar crust and regolith strongly affect the waveform characteristics predicted by these models. Further complexity is added by possible mantle discontinuity structure that exists in a subset of these models. We show synthetic waveform predictions for these models demonstrating the role that crustal structure has in generating long duration seismic coda inherent in the lunar waveforms.

  17. Tuning heat transport in trapped-ion chains across a structural phase transition

    NASA Astrophysics Data System (ADS)

    Ruiz, A.; Alonso, D.; Plenio, M. B.; del Campo, A.

    2014-06-01

    We analyze the heat transport in an ion chain that is confined in a strongly anisotropic Paul trap. To drive a heat current across the chain different pairs of counterpropagating laser beams are applied to the ions on the edges. The lasers behave as heat reservoirs operating at different temperatures, and a nonequilibrium heat flow can be sustained. The control of the spatial distribution of the ions in the chain by variation of the trapping frequencies makes ion chains an ideal testbed to study heat transport properties in finite open systems of low dimensionality with tunable nonlinearities. We explore heat transport across a structural phase transition between the linear and zigzag configurations, identifying the condition for optimal heat transport.

  18. New Family of Cerium Halide Based Materials: CeX 3 ·ROH Compounds Containing Planes, Chains, and Tetradecanuclear Rings

    SciTech Connect

    Vaughn, Shae Anne; Chakoumakos, Bryan C.; Custelcean, Radu; Ramey, Joanne O.; Smith, Mark D.; Boatner, Lynn A.; zur Loye, Hans-Conrad

    2012-10-15

    Six members of a new family of cerium-halide-based materials with promising scintillation behavior have been synthesized in single crystal form, and their crystal structures were determined. S p e c i fi c a l l y , t h e s e n e w c o m p o u n d s a r e [(CeCl3)7(BuOH)16(H2O)2] (BuOH)2 (1), (CeBr3)14(BuOH)36 (2), [(CeCl3)7(1-PrOH)16(H2O)2] (1-PrOH)2 (3), [(CeBr3)7(1- PrOH)18] (1-PrOH)2 (4), [(CeCl3)6(iBuOH)15] (iBuOH)2 (5), and CeCl3(sec-BuOH)2(H2O) (6). Additionally, the scintillation ability of compound 1 was established. The structures of these cerium-halide-based materials consist of catenated tetradecanuclear rings that arrange themselves into three distinct structural motifs which contain the largest lanthanide-based ring structures reported to date; the different motifs are obtained by involving specific alcohols during synthesis. Specifically, n-butanol and n-propanol lead to 1-D chains of tetradecanuclear rings, and iso-butanol leads to 2-D parquet-patterned sheets of rectangular tetradecanuclear rings, while sec-butanol results in a zigzag 1-D chain structure. One of the compounds, [(CeCl3)6(iBuOH)15] (iBuOH)2, has been shown to scintillate with a light yield of up to 1920 photons/MeV, and due to the presence of protons, it should be capable of detecting high energy neutrons without the necessity of prior thermalization. Furthermore, it also appears to be the first cerium-based compound that scintillates in spite of the fact that water coordinates to two of the Ce(III) centers within the structure.

  19. Binding Strength and Dynamics of Invariant Natural Killer Cell T Cell Receptor/CD1d-Glycosphingolipid Interaction on Living Cells by Single Molecule Force Spectroscopy*

    PubMed Central

    Bozna, Bianca L.; Polzella, Paolo; Rankl, Christian; Zhu, Rong; Salio, Mariolina; Shepherd, Dawn; Duman, Memed; Cerundolo, Vincenzo; Hinterdorfer, Peter

    2011-01-01

    Invariant natural killer T (iNKT) cells are a population of T lymphocytes that play an important role in regulating immunity to infection and tumors by recognizing endogenous and exogenous CD1d-bound lipid molecules. Using soluble iNKT T cell receptor (TCR) molecules, we applied single molecule force spectroscopy for the investigation of the iNKT TCR affinity for human CD1d molecules loaded with glycolipids differing in the length of the phytosphingosine chain using either recombinant CD1d molecules or lipid-pulsed THP1 cells. In both settings, the dissociation of the iNKT TCR from human CD1d molecules loaded with the lipid containing the longer phytosphingosine chain required higher unbinding forces compared with the shorter phytosphingosine lipid. Our findings are discussed in the context of previous results obtained by surface plasmon resonance measurements. We present new insights into the energy landscape and the kinetic rate constants of the iNKT TCR/human CD1d-glycosphingolipid interaction and emphasize the unique potential of single molecule force spectroscopy on living cells. PMID:21454514

  20. Binding strength and dynamics of invariant natural killer cell T cell receptor/CD1d-glycosphingolipid interaction on living cells by single molecule force spectroscopy.

    PubMed

    Bozna, Bianca L; Polzella, Paolo; Rankl, Christian; Zhu, Rong; Salio, Mariolina; Shepherd, Dawn; Duman, Memed; Cerundolo, Vincenzo; Hinterdorfer, Peter

    2011-05-06

    Invariant natural killer T (iNKT) cells are a population of T lymphocytes that play an important role in regulating immunity to infection and tumors by recognizing endogenous and exogenous CD1d-bound lipid molecules. Using soluble iNKT T cell receptor (TCR) molecules, we applied single molecule force spectroscopy for the investigation of the iNKT TCR affinity for human CD1d molecules loaded with glycolipids differing in the length of the phytosphingosine chain using either recombinant CD1d molecules or lipid-pulsed THP1 cells. In both settings, the dissociation of the iNKT TCR from human CD1d molecules loaded with the lipid containing the longer phytosphingosine chain required higher unbinding forces compared with the shorter phytosphingosine lipid. Our findings are discussed in the context of previous results obtained by surface plasmon resonance measurements. We present new insights into the energy landscape and the kinetic rate constants of the iNKT TCR/human CD1d-glycosphingolipid interaction and emphasize the unique potential of single molecule force spectroscopy on living cells.

  1. The complex metal-rich boride Ti{sub 1+x}Rh{sub 2-x+y}Ir{sub 3-y}B{sub 3} (x=0.68, y=1.06) with a new structure type containing B{sub 4} zigzag fragments: Synthesis, crystal chemistry and theoretical calculations

    SciTech Connect

    Goerens, Christian; Fokwa, Boniface P.T.

    2012-08-15

    Polycrystalline samples and single crystals of the new complex boride Ti{sub 1+x}Rh{sub 2-x+y}Ir{sub 3-y}B{sub 3} (x=0.68; y=1.06) were synthesized by arc-melting the elements in a water-cooled copper crucible under an argon atmosphere and characterized by X-Ray diffraction as well as EDX measurements. The crystal structure was refined on the basis of single crystal data. The new phase, which represents a new structure type containing trans zigzag B{sub 4} fragments as well as isolated boron atoms crystallizes in the orthorhombic space group Pbam (Nr. 55) with the lattice parameters a=8.620(1) A, b=14.995(2) A and c=3.234(1) A. First-principles density functional theory calculations using the Vienna ab-initio simulation package (VASP) were performed on an appropriate structural model (using a supercell approach) and the experimental crystallographic data could be reproduced accurately. Based on this model, the density of states and crystal orbital Hamilton population (for bonding analysis) were calculated, using the linear muffin-tin orbital atomic sphere approximation (LMTO-ASA) method. According to these calculations, this metal-rich compound should be metallic, as expected. Furthermore, very strong boron-boron interactions are observed in the trans zigzag B{sub 4} fragment, which induce a clear differentiation of two types of metal-boron contacts with different strength. The observed three-dimensional metal-metal interaction is in good agreement with the predicted metallic behavior. - graphical abstract: The structure of Ti{sub 1.68(2)}Rh{sub 2.38(6)}Ir{sub 1.94(4)} B{sub 3}, a new structure type containing planar trans zigzag B{sub 4} units, is another example which illustrates the tendency of metal-rich borides to form B-B bonds with increasing boron content. Beside the B{sub 4} fragment it exhibits one-dimensional chains of titanium atoms and hold one-dimensional strings of face-sharing empty tetrahedral and square pyramidal clusters (see figure). Highlights

  2. CD1d Expression in Paneth Cells and Rat Exocrine Pancreas Revealed by Novel Monoclonal Antibodies Which Differentially Affect NKT Cell Activation

    PubMed Central

    Monzon-Casanova, Elisa; Steiniger, Birte; Schweigle, Stefanie; Clemen, Holger; Zdzieblo, Daniela; Starick, Lisa; Müller, Ingrid; Wang, Chyung-Ru; Rhost, Sara; Cardell, Susanna; Pyz, Elwira; Herrmann, Thomas

    2010-01-01

    Background CD1d is a nonpolymorphic MHC class I-like molecule which presents nonpeptide ligands, e.g. glycolipids, to NKT cells. These cells are known to have multiple effects on innate and adaptive immune responses and on the development of pathological conditions. In order to analyze CD1d expression and function in the rat, the first rat CD1d-specific monoclonal antibodies (mAbs) were generated. Methodology/Principal Findings Two mAbs, WTH-1 and WTH-2, were generated which bound equally well to cell surface-expressed rat and mouse CD1d. Their non-overlapping epitopes were mapped to the CD1d heavy chain. Flow cytometry and immunohistological analyses revealed a nearly identical degree and pattern of CD1d expression for hematopoieitic cells of both species. Notable is also the detection of CD1d protein in mouse and rat Paneth cells as well as the extremely high CD1d expression in acinar exocrine cells of the rat pancreas and the expression of CD4 on rat marginal zone B cells. Both mAbs blocked α-galactosylceramide recognition by primary rat and mouse NKT cells. Interestingly, the two mAbs differed in their impact on the activation of various autoreactive T cell hybridomas, including the XV19.2 hybridoma whose activation was enhanced by the WTH-1 mAb. Conclusions/Significance The two novel monoclonal antibodies described in this study, allowed the analysis of CD1d expression and CD1d-restricted T cell responses in the rat for the first time. Moreover, they provided new insights into mechanisms of CD1d-restricted antigen recognition. While CD1d expression by hematopoietic cells of mice and rats was extremely similar, CD1d protein was detected at not yet described sites of non-lymphatic tissues such as the rat exocrine pancreas and Paneth cells. The latter is of special relevance given the recently reported defects of Paneth cells in CD1d−/− mice, which resulted in an altered composition of the gut flora. PMID:20927351

  3. Evaluation of the Transport of Natural Radioactive Materials in Large Lysimeters Using Hydrus-1D

    NASA Astrophysics Data System (ADS)

    Pontedeiro, E.; Cipriani, M.; van Genuchten, M.; Simunek, J.

    2007-12-01

    The mining industry in Brazil often uses raw materials that contain relatively high concentrations of naturally occurring radioactive materials (referred to as NORM). Ores of relatively low grade typically are used to produce refined metals of high purity (e.g., Nb, Ta, Sn, and Au) using pyrometallurgic processes. The final waste is a slag rich in natural radioactive contaminants (the U and Th decay series), which are then usually deposited in industrial landfills. To study the long-term fate and transport of radionuclides leached from the NORM wastes, several large (3 m deep) lysimeters were constructed at the Pocos de Caldas Laboratory of the Brazilian Nuclear Energy Commision (CNEN). The lysimeters were packed with surface soils and slags from one of the mining sites in South East Brazil. Main purpose of our lysimeter experiments was to follow the dissolution and transport of radionuclides from the slags under natural climatic conditions. Leaching rates and radionuclide concentrations of the effluent were observed during a three-year time period. A variety of physical and chemical properties of the soils and slags (including laboratory batch equilibrium sorption values) were also determined. The data were analyzed using several computer software packages, including the STANMOD code for analytical modeling of decay chain transport during steady flow, the HYDRUS-1D code for variably-saturated flow and the transport of multiple solutes, and the HP1 code for a more comprehensive analysis of the geochemistry involved. In this presentation we describe the experimental setup and provide preliminary results of the theoretical analyses, especially those using HYDRUS-1D.

  4. Transport properties of bare and hydrogenated zigzag silicene nanoribbons: Negative differential resistances and perfect spin-filtering effects

    SciTech Connect

    Yang, X. F.; Liu, Y. S. Feng, J. F.; Wang, X. F.; Zhang, C. W.; Chi, F.

    2014-09-28

    Ab initio calculations are performed to investigate the spin-polarized transport properties of the bare and hydrogenated zigzag silicene nanoribbons (ZSiNRs). The results show that the ZSiNRs with symmetric (asymmetric) edges prefer the ferromagnetic (antiferromagnetic) as their ground states with the semiconductor properties, while the accordingly antiferromagnetic (ferromagnetic) states exhibit the metallic behaviors. These facts result in a giant magnetoresistance behavior between the ferromagnetic and antiferromagnetic states in the low bias-voltage regime. Moreover, in the ferromagnetic ZSiNRs with asymmetric edges, a perfect spin-filtering effect with 100% positive electric current polarization can be achieved by altering the bias voltage. In addition, we also find that the negative differential resistances prefer the metastable states. The findings here indicate that the asymmetric and symmetric ZSiNRs are promising materials for spintronic applications.

  5. Edge contact dependent spin transport for n-type doping zigzag-graphene with asymmetric edge hydrogenation

    PubMed Central

    Deng, Xiaoqing; Zhang, Zhenhua; Tang, Guiping; Fan, Zhiqiang; Zhu, Huali; Yang, Changhu

    2014-01-01

    Spin transport features of the n-type doping zigzag graphene nanoribbons (ZGNRs) with an edge contact are investigated by first principle methods, where ZGNRs are C–H2 bonded at one edge while C–H bonded at the other to form an asymmetric edge hydrogenation. The results show that a perfect spin filtering effect (100%) in such ZGNR nanojunctions can be achieved in a very large bias region for the unchanged spin states regardless of bias polarities, and the nanojunction with a contact of two C–H2 bonded edges has larger spin polarized current than that with a contact of two C–H bonded edges. The transmission pathways and the projected density of states (PDOS) demonstrate that the edge of C-H2 bonds play a crucial role for the spin magnetism and spin-dependent transport properties. Moreover, the negative differential resistance (NDR) effect is also observed in the spin-polarized current. PMID:24509476

  6. Designing and building nanowires: directed nanocrystal self-assembly into radically branched and zigzag PbS nanowires

    NASA Astrophysics Data System (ADS)

    Xu, Fan; Ma, Xin; Gerlein, L. Felipe; Cloutier, Sylvain G.

    2011-07-01

    Lead sulfide nanowires with controllable optoelectronic properties would be promising building blocks for various applications. Here, we report the hot colloidal synthesis of radically branched and zigzag nanowires through self-attachment of star-shaped and octahedral nanocrystals in the presence of multiple surfactants. We obtained high-quality single-crystal nanowires with uniform diameter along the entire length, and the size of the nanowire can be tuned by tailoring the reaction parameters. This slow oriented attachment provides a better understanding of the intricacies of this complex nanocrystal assembly process. Meanwhile, these self-assembled nanowire structures have appealing lateral conformations with narrow side arms or highly faceted edges, where strong quantum confinement can occur. Consequently, the single-crystal nanowire structures exhibit strong photoluminescence in the near-infrared region with a large blue-shift compared to the bulk material.

  7. Intrinsic spin dependent and ferromagnetic stability on edge saturated zigzag graphene-like carbon-nitride nanoribbons

    SciTech Connect

    Zhang, Shuai; Li, Chong E-mail: jiayu@zzu.edu.cn; Li, S. F.; Sun, Q.; Jia, Yu E-mail: jiayu@zzu.edu.cn; Guo, Z. X.

    2014-04-28

    Using first-principles calculations, we have investigated the electronic and magnetic properties of zigzag graphene-like carbon-nitride nanoribbons (Zg-CNNRs) with mono- and dihydrogen-terminated edges asymmetrically. The results demonstrate that spin-down channel completely dominates the states adjacent Fermi level, which is an intrinsic feature and can be accounted for the valence band maximum derived from the nonbonding N-(p{sub x},p{sub y}) orbitals, instead of the bonding C/N-p{sub z} π state. Importantly, ferromagnetic ordering is found to be preferred and the magnetism is entirely localized on the N sites of saturated edge due to its stronger electronegativity. Additionally, various edge saturations are further proposed to try to enhance the ferromagnetic ordering and to manipulate the magnetism distributions of Zg-CNNRs.

  8. Sensitivity analysis of multi-layered C-axis inclined zigzag zinc oxide thin-film resonators as viscosity sensors.

    PubMed

    Zhang, Haifeng; Bao, Yuanye

    2014-03-01

    This paper presents a theoretical analysis of a new zigzag C-axis inclined multi-layer ZnO thin-film bulk acoustic wave resonator (FBAR) as a viscosity sensor to monitor the lubrication performance of engine oil and other liquids. Free vibration and forced vibration for the FBAR loaded with liquids are analyzed. Equations necessary to calculate the sensitivity are derived. The numerical analysis shows that as the number of layers increases, the absolute sensitivity increases as well. The influences on the sensitivity of C-axis inclined angle, Q-factor, and thickness are also investigated. The results provide a foundation for further design of multi-layer FBAR viscosity sensors.

  9. Magnetic Relaxation and Coercivity of Finite-size Single Chain Magnets

    NASA Astrophysics Data System (ADS)

    Gredig, Thomas; Byrne, Matthew; Vindigni, Alessandro

    2015-03-01

    The magnetic coercivity of hysteresis loops for iron phthalocyanine thin films depends on the iron chain length and the measurement sweep speed below 5 K. The average one-dimensional (1D) iron chain length in samples is controlled during deposition. These 1D iron chains can be tuned over one order of magnitude with the shortest chain having 100 elements. We show that the coercivity strongly increases with the average length of the iron chains, which self-assemble parallel to the substrate surface. Magnetic relaxation and sweep speed data suggest spin dynamics play an important role. Implementing Glauber dynamics with a finite-sized 1D Ising model provides qualitative agreement with experimental data. This suggests that iron phthalocyanine thin films act as single chain magnets and provide a solid test system for tunable finite-sized magnetic chains. This research has been supported with the NSF-DMR 0847552 grant.

  10. Dynamic decoupling in the presence of 1D random walk

    NASA Astrophysics Data System (ADS)

    Chakrabarti, Arnab; Chakraborty, Ipsita; Bhattacharyya, Rangeet

    2016-05-01

    In the recent past, many dynamic decoupling sequences have been proposed for the suppression of decoherence of spins connected to thermal baths of various natures. Dynamic decoupling schemes for suppressing decoherence due to Gaussian diffusion have also been developed. In this work, we study the relative performances of dynamic decoupling schemes in the presence of a non-stationary Gaussian noise such as a 1D random walk. Frequency domain analysis is not suitable to determine the performances of various dynamic decoupling schemes in suppressing decoherence due to such a process. Thus, in this work, we follow a time domain calculation to arrive at the following conclusions: in the presence of such a noise, we show that (i) the traditional Carr-Purcell-Meiboom-Gill (CPMG) sequence outperforms Uhrig’s dynamic decoupling scheme, (ii) CPMG remains the optimal sequence for suppression of decoherence due to random walk in the presence of an external field gradient. Later, the theoretical predictions are experimentally verified by using nuclear magnetic resonance spectroscopy on spin 1/2 particles diffusing in a liquid medium.

  11. 1-D Modeling of Massive Particle Injection (MPI) in Tokamaks

    NASA Astrophysics Data System (ADS)

    Wu, W.; Parks, P. B.; Izzo, V. A.

    2008-11-01

    A 1-D Fast Current Quench (FCQ) model is developed to study current evolution and runaway electron suppression under massive density increase. The model consists of coupled toroidal electric field and energy equations, and it is solved numerically for DIII-D and ITER operating conditions. Simulation results suggest that fast shutdown by D2 liquid jet/pellet injection is in principle achievable for the desired plasma cooling time (˜15 ms for DIII-D and ˜50 ms for ITER) under ˜150x or higher densification. The current density and pressure profile are practically unaltered during the initial phase of jet propagation when dilution cooling dominates. With subsequent radiation cooling, the densified discharge enters the strongly collisional regime where Pfirsch-Schluter thermal diffusion can inhibit current contraction on the magnetic axis. Often the 1/1 kink instability, addressed by Kadomtsev's magnetic reconnection model, can be prevented. Our results are compared with NIMROD simulations in which the plasma is suddenly densified by ˜100x and experiences instantaneous dilution cooling, allowing for use of actual (lower) Lundquist numbers.

  12. Energy eigenfunctions of the 1D Gross-Pitaevskii equation

    NASA Astrophysics Data System (ADS)

    Marojević, Želimir; Göklü, Ertan; Lämmerzahl, Claus

    2013-08-01

    We developed a new and powerful algorithm by which numerical solutions for excited states in a gravito-optical surface trap have been obtained. They represent solutions in the regime of strong nonlinearities of the Gross-Pitaevskii equation. In this context we also briefly review several approaches which allow, in principle, for calculating excited state solutions. It turns out that without modifications these are not applicable to strongly nonlinear Gross-Pitaevskii equations. The importance of studying excited states of Bose-Einstein condensates is also underlined by a recent experiment of Bücker et al. in which vibrational state inversion of a Bose-Einstein condensate has been achieved by transferring the entire population of the condensate to the first excited state. Here we focus on demonstrating the applicability of our algorithm for three different potentials by means of numerical results for the energy eigenstates and eigenvalues of the 1D Gross-Pitaevskii-equation. We compare the numerically found solutions and find out that they completely agree with the case of known analytical solutions.

  13. 1-D Numerical Analysis of RBCC Engine Performance

    NASA Technical Reports Server (NTRS)

    Han, Samuel S.

    1998-01-01

    An RBCC engine combines air breathing and rocket engines into a single engine to increase the specific impulse over an entire flight trajectory. Considerable research pertaining to RBCC propulsion was performed during the 1960's and these engines were revisited recently as a candidate propulsion system for either a single-stage-to-orbit (SSTO) or two-stage-to-orbit (TSTO) launch vehicle. There are a variety of RBCC configurations that had been evaluated and new designs are currently under development. However, the basic configuration of all RBCC systems is built around the ejector scramjet engine originally developed for the hypersonic airplane. In this configuration, a rocket engine plays as an ejector in the air-augmented initial acceleration mode, as a fuel injector in scramjet mode and the rocket in all rocket mode for orbital insertion. Computational fluid dynamics (CFD) is a useful tool for the analysis of complex transport processes in various components in RBCC propulsion systems. The objective of the present research was to develop a transient 1-D numerical model that could be used to predict flow behavior throughout a generic RBCC engine following a flight path.

  14. Control and imaging of O(1D2) precession.

    PubMed

    Wu, Shiou-Min; Radenovic, Dragana Č; van der Zande, Wim J; Groenenboom, Gerrit C; Parker, David H; Vallance, Claire; Zare, Richard N

    2011-01-01

    Larmor precession of a quantum mechanical angular momentum vector about an applied magnetic field forms the basis for a range of magnetic resonance techniques, including nuclear magnetic resonance spectroscopy and magnetic resonance imaging. We have used a polarized laser pump-probe scheme with velocity-map imaging detection to visualize, for the first time, the precessional motion of a quantum mechanical angular momentum vector. Photodissociation of O(2) at 157 nm provides a clean source of fast-moving O((1)D(2)) atoms, with their electronic angular momentum vector strongly aligned perpendicular to the recoil direction. In the presence of an external magnetic field, the distribution of atomic angular momenta precesses about the field direction, and polarization-sensitive images of the atomic scattering distribution recorded as a function of field strength yield 'time-lapse-photography' style movies of the precessional motion. We present movies recorded in various experimental geometries, and discuss potential consequences and applications in atmospheric chemistry and reaction dynamics.

  15. Cavitation Influence in 1D Part-load Vortex Models

    NASA Astrophysics Data System (ADS)

    Dörfler, P. K.

    2016-11-01

    Residual swirl in the draft tube of Francis turbines may cause annoying low- frequency pulsation of pressure and power output, in particular during part-load operation. A 1D analytical model for these dynamic phenomena would enable simulation by some conventional method for computing hydraulic transients. The proper structure of such a model has implications for the prediction of prototype behaviour based on laboratory tests. The source of excitation as well as the dynamic transmission behaviour of the draft tube flow may both be described either by lumped or distributed parameters. The distributed version contains more information and, due to limited possibilities of identification, some data must be estimated. The distributed cavitation compliance is an example for this dilemma. In recent publications, the customary assumption of a constant wave speed has produced dubious results. The paper presents a more realistic model for distributed compressibility. The measured influence of the Thoma number is applied with the local cavitation factor. This concept is less sensitive to modelling errors and explains both the Thoma and Froude number influence. The possible effect of the normally unknown non-condensable gas content in the vortex cavity is shortly commented. Its measurement in future tests is recommended. It is also recommended to check the available analytical vortex models for possible dispersion effects.

  16. Exchange anisotropy as mechanism for spin-stripe formation in frustrated spin chains

    NASA Astrophysics Data System (ADS)

    Pregelj, M.; Zaharko, O.; Herak, M.; Gomilšek, M.; Zorko, A.; Chapon, L. C.; Bourdarot, F.; Berger, H.; Arčon, D.

    2016-08-01

    We investigate the spin-stripe mechanism responsible for the peculiar nanometer modulation of the incommensurate magnetic order that emerges between the vector-chiral and the spin-density-wave phase in the frustrated zigzag spin-1/2 chain compound β -TeVO4 . A combination of magnetic-torque, neutron-diffraction, and spherical-neutron-polarimetry measurements is employed to determine the complex magnetic structures of all three ordered phases. Based on these results, we develop a simple phenomenological model, which exposes the exchange anisotropy as the key ingredient for the spin-stripe formation in frustrated spin systems.

  17. Spatio-temporal stability of 1D Kerr cavity solitons

    NASA Astrophysics Data System (ADS)

    Gelens, L.; Parra-Rivas, P.; Leo, F.; Gomila, D.; Matias, Manuel A.; Coen, S.

    2014-05-01

    The Lugiato-Lefever equation (LLE) has been extensively studied since its derivation in 1987, when this meanfield model was introduced to describe nonlinear optical cavities. The LLE was originally derived to describe a ring cavity or a Fabry-Perot resonator with a transverse spatial extension and partially filled with a nonlinear medium but it has also been shown to be applicable to other types of cavities, such as fiber resonators and microresonators. Depending on the parameters used, the LLE can present a monostable or bistable input-output response curve. A large number of theoretical studies have been done in the monostable regime, but the bistable regime has remained widely unexplored. One of the reasons for this was that previous experimental setups were not able to works in such regimes of the parameter space. Nowadays the possibility of reaching such parameter regimes experimentally has renewed the interest in the LLE. In this contribution, we present an in-depth theoretical study of the different dynamical regimes that can appear in parameter space, focusing on the dynamics of localized solutions, also known as cavity solitons (CSs). We show that time-periodic oscillations of a 1D CS appear naturally in a broad region of parameter space. More than this oscillatory regime, which has been recently demonstrated experimentally,1 we theoretically report on several kinds of chaotic dynamics. We show that the existence of CSs and their dynamics is related with the spatial dynamics of the system and with the presence of a codimension-2 point known as a Fold-Hopf bifurcation point. These dynamical regimes can become accessible by using devices such as microresonators, for instance widely used for creating optical frequency combs.

  18. Restrained dark U (1 )d at low energies

    NASA Astrophysics Data System (ADS)

    Correia, Fagner C.; Fajfer, Svjetlana

    2016-12-01

    We investigate a spontaneously broken U (1 )d gauge symmetry with a muon-specific dark Higgs. Our first goal is to verify how the presence of a new dark Higgs, ϕ , and a dark gauge boson, V , can simultaneously face the anomalies from the muon magnetic moment and the proton charge radius. Second, by assuming that V must decay to an electron-positron pair, we explore the corresponding parameter space determined with the low-energy constraints coming from K →μ X , electron (g -2 )e, K →μ νμe+e-, K →μ νμμ+μ-, and τ →ντμ νμe+e-. We focus on the scenario where the V mass is below ˜2 mμ and the ϕ mass runs from few MeV to 250 MeV, with V -photon mixing of the order ˜O (10-3). Among weak process at low energies, we check the influence of the new light vector on kaon decays as well as on the scattering e+e-→μ+μ-e+e- and discuss the impact of the dark Higgs on e+e-→μ+μ-μ+μ-. Finally, we consider contributions of the V -photon mixing in the decays π0→γ e+e-, η →γ e+e-, ρ →π e+e-, K*→K e+e-, and ϕ (1020 )→η e+e-.

  19. A new general 1-D vadose zone flow solution method

    NASA Astrophysics Data System (ADS)

    Ogden, Fred L.; Lai, Wencong; Steinke, Robert C.; Zhu, Jianting; Talbot, Cary A.; Wilson, John L.

    2015-06-01

    We have developed an alternative to the one-dimensional partial differential equation (PDE) attributed to Richards (1931) that describes unsaturated porous media flow in homogeneous soil layers. Our solution is a set of three ordinary differential equations (ODEs) derived from unsaturated flux and mass conservation principles. We used a hodograph transformation, the Method of Lines, and a finite water-content discretization to produce ODEs that accurately simulate infiltration, falling slugs, and groundwater table dynamic effects on vadose zone fluxes. This formulation, which we refer to as "finite water-content", simulates sharp fronts and is guaranteed to conserve mass using a finite-volume solution. Our ODE solution method is explicitly integrable, does not require iterations and therefore has no convergence limits and is computationally efficient. The method accepts boundary fluxes including arbitrary precipitation, bare soil evaporation, and evapotranspiration. The method can simulate heterogeneous soils using layers. Results are presented in terms of fluxes and water content profiles. Comparing our method against analytical solutions, laboratory data, and the Hydrus-1D solver, we find that predictive performance of our finite water-content ODE method is comparable to or in some cases exceeds that of the solution of Richards' equation, with or without a shallow water table. The presented ODE method is transformative in that it offers accuracy comparable to the Richards (1931) PDE numerical solution, without the numerical complexity, in a form that is robust, continuous, and suitable for use in large watershed and land-atmosphere simulation models, including regional-scale models of coupled climate and hydrology.

  20. Modeling shear band interaction in 1D torsion

    NASA Astrophysics Data System (ADS)

    Partom, Yehuda; Hanina, Erez

    2017-01-01

    When two shear bands are being formed at close distance from each other they interact, and further development of one of them may be quenched down. As a result there should be a minimum distance between shear bands. In the literature there are at least three analytical models for this minimum distance. Predictions of these models do not generally agree with each other and with test results. Recently we developed a 1D numerical scheme to predict the formation of shear bands in a torsion test of a thin walled pipe. We validated our code by reproducing results of the pioneering experiments of Marchand and Duffy, and then used it to investigate the mechanics of shear localization and shear band formation. We describe our shear band code in a separate publication, and here we use it only as a tool to investigate the interaction between two neighboring shear bands during the process of their formation. We trigger the formation of shear bands by specifying two perturbations of the initial strength. We vary the perturbations in terms of their amplitude and/or their width. Usually, the stronger perturbation triggers a faster developing shear band, which then prevails and quenches the development of the other shear band. We change the distance between the two shear bands and find, that up to a certain distance one of the shear bands becomes fully developed, and the other stays only partially developed. Beyond this distance the two shear bands are both fully developed. Finally, we check the influence of certain material and loading parameters on the interaction between the two shear bands, and compare the results to predictions of the analytical models from the literature.

  1. SCCRO3 (DCUN1D3) Antagonizes the Neddylation and Oncogenic Activity of SCCRO (DCUN1D1)*

    PubMed Central

    Huang, Guochang; Stock, Cameron; Bommeljé, Claire C.; Weeda, Víola B.; Shah, Kushyup; Bains, Sarina; Buss, Elizabeth; Shaha, Manish; Rechler, Willi; Ramanathan, Suresh Y.; Singh, Bhuvanesh

    2014-01-01

    The activity of cullin-RING type ubiquitination E3 ligases is regulated by neddylation, a process analogous to ubiquitination that culminates in covalent attachment of the ubiquitin-like protein Nedd8 to cullins. As a component of the E3 for neddylation, SCCRO/DCUN1D1 plays a key regulatory role in neddylation and, consequently, cullin-RING ligase activity. The essential contribution of SCCRO to neddylation is to promote nuclear translocation of the cullin-ROC1 complex. The presence of a myristoyl sequence in SCCRO3, one of four SCCRO paralogues present in humans that localizes to the membrane, raises questions about its function in neddylation. We found that although SCCRO3 binds to CAND1, cullins, and ROC1, it does not efficiently bind to Ubc12, promote cullin neddylation, or conform to the reaction processivity paradigms, suggesting that SCCRO3 does not have E3 activity. Expression of SCCRO3 inhibits SCCRO-promoted neddylation by sequestering cullins to the membrane, thereby blocking its nuclear translocation. Moreover, SCCRO3 inhibits SCCRO transforming activity. The inhibitory effects of SCCRO3 on SCCRO-promoted neddylation and transformation require both an intact myristoyl sequence and PONY domain, confirming that membrane localization and binding to cullins are required for in vivo functions. Taken together, our findings suggest that SCCRO3 functions as a tumor suppressor by antagonizing the neddylation activity of SCCRO. PMID:25349211

  2. Resolution-optimized NMR measurement of (1)D(CH), (1)D(CC) and (2)D(CH) residual dipolar couplings in nucleic acid bases.

    PubMed

    Boisbouvier, Jérôme; Bryce, David L; O'neil-Cabello, Erin; Nikonowicz, Edward P; Bax, Ad

    2004-11-01

    New methods are described for accurate measurement of multiple residual dipolar couplings in nucleic acid bases. The methods use TROSY-type pulse sequences for optimizing resolution and sensitivity, and rely on the E.COSY principle to measure the relatively small two-bond (2)D(CH) couplings at high precision. Measurements are demonstrated for a 24-nt stem-loop RNA sequence, uniformly enriched in (13)C, and aligned in Pf1. The recently described pseudo-3D method is used to provide homonuclear (1)H-(1)H decoupling, which minimizes cross-correlation effects and optimizes resolution. Up to seven (1)H-(13)C and (13)C-(13)C couplings are measured for pyrimidines (U and C), including (1)D(C5H5), (1)D(C6H6), (2)D(C5H6), (2)D(C6H5), (1)D(C5C4), (1)D(C5C6), and (2)D(C4H5). For adenine, four base couplings ((1)D(C2H2), (1)D(C8H8), (1)D(C4C5), and (1)D(C5C6)) are readily measured whereas for guanine only three couplings are accessible at high relative accuracy ((1)D(C8H8), (1)D(C4C5), and (1)D(C5C6)). Only three dipolar couplings are linearly independent in planar structures such as nucleic acid bases, permitting cross validation of the data and evaluation of their accuracies. For the vast majority of dipolar couplings, the error is found to be less than +/-3% of their possible range, indicating that the measurement accuracy is not limiting when using these couplings as restraints in structure calculations. Reported isotropic values of the one- and two-bond J couplings cluster very tightly for each type of nucleotide.

  3. New approach for designing single-chain magnets: organization of chains via hydrogen bonding between nucleobases.

    PubMed

    Zhang, Wei-Xiong; Shiga, Takuya; Miyasaka, Hitoshi; Yamashita, Masahiro

    2012-04-25

    Two one-dimensional (1D) manganese complexes, [Mn(2)(naphtmen)(2)(L)](ClO(4))·2Et(2)O·2MeOH·H(2)O (1) and [Mn(2)(naphtmen)(2)(HL)](ClO(4))(2)·MeOH (2), were synthesized by using a bridging ligand with a nucleobase moiety, 6-amino-9-β-carboxyethylpurine, and a salen-type manganese(III) dinuclear complex, [Mn(2)(naphtmen)(2)(H(2)O)(2)](ClO(4))(2) (naphtmen(2-) = N,N'-(1,1,2,2-tetramethylethylene)bis(naphthylideneiminato) dianion). In 1 and 2, the carboxylate-bridged Mn(III) dinuclear units are alternately linked by two kinds of weak Mn···O interactions into 1D chains. As a result, canted antiferromagnetic and ferromagnetic interactions are alternately present along the chains, leading to a 1D chain with non-cancellation of anisotropic spins. Since the chains connected via H-bonds between nucleobase moieties are magnetically isolated, both 1 and 2 act as single-chain magnets (SCMs). More importantly, this result shows the smaller canting angles hinder long-range ordering in favor of SCM dynamics.

  4. Correlation between inter-spin interaction and molecular dynamics of organic radicals in organic 1D nanochannels

    SciTech Connect

    Kobayashi, Hirokazu

    2015-12-31

    One-dimensional (1D) molecular chains of 4-substituted-2,2,6,6-tetramethyl-1-piperidinyloxyl (4-X-TEMPO) radicals were constructed in the crystalline 1D nanochannels of 2,4,6-tris(4-chlorophenoxy)-1,3,5-triazine (CLPOT) used as a template. The ESR spectra of CLPOT inclusion compounds (ICs) using 4-X-TEMPO were examined on the basis of spectral simulation using EasySpin program package for simulating and fitting ESR spectra. The ESR spectra of [(CLPOT){sub 2}-(TEMPO){sub 1.0}] IC were isotropic in the total range of temperatures. The peak-to-peak line width (ΔB{sub pp}) became monotonically narrower from 2.8 to 1.3 mT with increase in temperature in the range of 4.2–298 K. The effect of the rotational diffusion motion of TEMPO radicals in the CLPOT nanochannels for the inter-spin interaction of the [(CLPOT){sub 2}-(TEMPO){sub 1.0}] IC was found to be smaller than the case of [(TPP){sub 2}−(TEMPO){sub 1.0}] IC (TPP = tris(o-phenylenedioxy)cyclotriphosphazene) reported in our previous study. The ΔB{sub pp} of the [(CLPOT){sub 2}-(TEMPO){sub 1.0}] IC in the whole range of temperatures was much narrower than the estimation to be based on the Van Vleck’s formula for the second moment of the rigid lattice model where the electron spin can be considered as fixed; 11 mT of Gaussian line-width component. This suggests the possibility of exchange narrowing in the 1D organic-radical chains of the [(CLPOT){sub 2}-(TEMPO){sub 1.0}] IC. On the other hand, the ESR spectra of [(CLPOT){sub 2}-(MeO-TEMPO){sub 0.41}] IC (MeO-TEMPO = 4-methoxy-TEMPO) were reproduced by a superposition of major broad isotropic adsorption line and minor temperature-dependent modulated triplet component. This suggests that the IC has the part of 1D organic-radical chains and MeO-TEMPO molecules isolated in the CLPOT nanochannels.

  5. Engineering 1D Quantum Stripes from Superlattices of 2D Layered Materials.

    PubMed

    Gruenewald, John H; Kim, Jungho; Kim, Heung Sik; Johnson, Jared M; Hwang, Jinwoo; Souri, Maryam; Terzic, Jasminka; Chang, Seo Hyoung; Said, Ayman; Brill, Joseph W; Cao, Gang; Kee, Hae-Young; Seo, Sung S Ambrose

    2017-01-01

    Dimensional tunability from two dimensions to one dimension is demonstrated for the first time using an artificial superlattice method in synthesizing 1D stripes from 2D layered materials. The 1D confinement of layered Sr2 IrO4 induces distinct 1D quantum-confined electronic states, as observed from optical spectroscopy and resonant inelastic X-ray scattering. This 1D superlattice approach is generalizable to a wide range of layered materials.

  6. Clathrin heavy chain, light chain interactions.

    PubMed Central

    Winkler, F K; Stanley, K K

    1983-01-01

    Purified pig brain clathrin can be reversibly dissociated and separated into heavy chain trimers and light chains in the presence of non-denaturing concentrations of the chaotrope thiocyanate. The isolated heavy chain trimers reassemble into regular polygonal cage structures in the absence of light chains. The light chain fraction can be further resolved into its two components L alpha and L beta which give different one-dimensional peptide maps. Radiolabelled light chains bind with high affinity (KD < 10(-10) M) to heavy chain trimers, to heavy chain cages and to a 110,000 mol. wt. tryptic fragment of the heavy chain. Both light chains compete with each other and with light chains from other sources for the same binding sites on heavy chains and c.d. spectroscopy shows that the two pig brain light chains possess very similar structures. We conclude that light chains from different sources, despite some heterogeneity, have a highly conserved, high affinity binding site on the heavy chain but are not essential for the formation of regular cage structures. Images Fig. 1. Fig. 2. Fig. 3. Fig. 4. Fig. 8. PMID:10872336

  7. Preliminary abatement device evaluation: 1D-2D KGM cyclone design

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Cyclones are predominately used in controlling cotton gin particulate matter (PM) emissions. The most commonly used cyclone designs are the 2D-2D and 1D-3D; however other designs such as the 1D-2D KGM have or are currently being used. A 1D-2D cyclone has a barrel length equal to the barrel diamete...

  8. Large Area Synthesis of 1D-MoSe2 Using Molecular Beam Epitaxy.

    PubMed

    Poh, Sock Mui; Tan, Sherman J R; Zhao, Xiaoxu; Chen, Zhongxin; Abdelwahab, Ibrahim; Fu, Deyi; Xu, Hai; Bao, Yang; Zhou, Wu; Loh, Kian Ping

    2017-01-23

    Large area synthesis of 1D-MoSe2 nanoribbons on both insulating and conducting substrates via molecular beam epitaxy is presented. Dimensional controlled growth of 2D, 1D-MoSe2 , and 1D-2D-MoSe2 hybrid heterostructure is achieved by tuning the growth temperature or Mo:Se precursor ratio.

  9. PPM1D exerts its oncogenic properties in human pancreatic cancer through multiple mechanisms.

    PubMed

    Wu, Bo; Guo, Bo-Min; Kang, Jie; Deng, Xian-Zhao; Fan, You-Ben; Zhang, Xiao-Ping; Ai, Kai-Xing

    2016-03-01

    Protein phosphatase, Mg(2+)/Mn(2+) dependent, 1D (PPM1D) is emerging as an oncogene by virtue of its negative control on several tumor suppressor pathways. However, the clinical significance of PPM1D in pancreatic cancer (PC) has not been defined. In this study, we determined PPM1D expression in human PC tissues and cell lines and their irrespective noncancerous controls. We subsequently investigated the functional role of PPM1D in the migration, invasion, and apoptosis of MIA PaCa-2 and PANC-1 PC cells in vitro and explored the signaling pathways involved. Furthermore, we examined the role of PPM1D in PC tumorigenesis in vivo. Our results showed that PPM1D is overexpressed in human PC tissues and cell lines and significantly correlated with tumor growth and metastasis. PPM1D promotes PC cell migration and invasion via potentiation of the Wnt/β-catenin pathway through downregulation of apoptosis-stimulating of p53 protein 2 (ASPP2). In contrast to PPM1D, our results showed that ASPP2 is downregulated in PC tissues. Additionally, PPM1D suppresses PC cell apoptosis via inhibition of the p38 MAPK/p53 pathway through both dephosphorylation of p38 MAPK and downregulation of ASPP2. Furthermore, PPM1D promotes PC tumor growth in vivo. Our results demonstrated that PPM1D is an oncogene in PC.

  10. Synthesis, characterization and comparison of polyaniline 1D-structure controlled by poly(L-lactide) and poly(D-lactide)

    NASA Astrophysics Data System (ADS)

    Gu, Zhou-Jie; Shen, Qing

    2016-01-01

    1D-structural polyaniline (PANI) was controllably synthesized by utilizing the poly(L-lactide) (PLLA) and poly(D-lactide) (PDLA) as controllers. FESEM images showed that the morphology of 1D-structural PANI controlled by PDLA likes a joint obviously unlike PLLA controlled vertebra structure reported previously. To set the ratio of ANI/PLLA (ml/g) at 0.45/0.135, 0.45/0.270 and 0.45/0.540, the formed PANI 1D structure was changed in the cross-section as four round leaves, four non-round leaves and four sharp leaves, respectively. FTIR and XRD analysis indicated that the PLLA and PDLA both were doped in PANI chains while the PLLA was strongly in the electrons delocalization than that of the PDLA due probably to the L-type stronger in crystal polymorphism than that of the D-type.

  11. Triheptanoin for glucose transporter type I deficiency (G1D): Modulation of human ictogenesis, cerebral metabolic rate and cognitive indices by a food supplement

    PubMed Central

    Pascual, Juan M.; Liu, Peiying; Mao, Deng; Kelly, Dorothy; Hernandez, Ana; Sheng, Min; Good, Levi B.; Ma, Qian; Marin-Valencia, Isaac; Zhang, Xuchen; Park, Jason Y.; Hynan, Linda S.; Stavinoha, Peter; Roe, Charles R.; Lu, Hanzhang

    2015-01-01

    Objective G1D is commonly associated with electrographic spike-wave and - less-noticeably – with absence seizures. The G1D syndrome has long been attributed to energy (i.e., ATP-synthetic) failure, as have experimental, toxic-rodent epilepsies to impaired brain metabolism and tricarboxylic acid (TCA) cycle intermediate depletion. Indeed, a (seldom-acknowledged) function of glucose and other substrates is the generation of brain TCAs via carbon-donor reactions collectively named anaplerosis. However, TCAs are preserved in murine G1D. This renders inferences about energy failure premature and suggests a different hypothesis, also grounded on our findings, that consumption of alternate TCA precursors is stimulated, potentially detracting from other functions. Second, common ketogenic diets can ameliorate G1D seizures, but lead to a therapeutically-counterintuitive reduction in blood glucose available to the brain, and they can prove ineffective in 1/3 of cases. While developing G1D treatments, all of this motivated us to: a) uphold (rather than attenuate) the residual brain glucose flux that all G1D patients possess; and b) stimulate the TCA cycle, including anaplerosis. Therefore, we tested the medium-chain triglyceride triheptanoin, a widely-used medical food supplement that can fulfill both of these metabolic roles. The rationale is that ketone bodies derived from ketogenic diets are not anaplerotic, in contrast with triheptanoin metabolites, as we have shown in the G1D mouse brain. Design We supplemented the regular diet of a case series of G1D patients with food-grade triheptanoin. First we confirmed that, despite their frequent electroencephalographic (EEG) presence as spike-waves, most seizures are rarely visible, such that perceptions by patients or others are inadequate for treatment evaluation. Thus, we used EEG, quantitative neuropsychological, blood analytical, and MRI cerebral metabolic rate measurements as main outcomes. Setting Academic and

  12. The alpha(1D)-adrenergic receptor directly regulates arterial blood pressure via vasoconstriction.

    PubMed

    Tanoue, Akito; Nasa, Yoshihisa; Koshimizu, Takaaki; Shinoura, Hitomi; Oshikawa, Sayuri; Kawai, Takayuki; Sunada, Sachie; Takeo, Satoshi; Tsujimoto, Gozoh

    2002-03-01

    To investigate the physiological role of the alpha(1D)-adrenergic receptor (alpha(1D)-AR) subtype, we created mice lacking the alpha(1D)-AR (alpha(1D)(-/-)) by gene targeting and characterized their cardiovascular function. In alpha(1D)-/- mice, the RT-PCR did not detect any transcript of the alpha(1D)-AR in any tissue examined, and there was no apparent upregulation of other alpha(1)-AR subtypes. Radioligand binding studies showed that alpha(1)-AR binding capacity in the aorta was lost, while that in the heart was unaltered in alpha(1D)-/- mice. Non-anesthetized alpha(1D)-/- mice maintained significantly lower basal systolic and mean arterial blood pressure conditions, relative to wild-type mice, and they showed no significant change in heart rate or in cardiac function, as assessed by echocardiogram. Besides hypotension, the pressor responses to phenylephrine and norepinephrine were decreased by 30-40% in alpha(1D)-/- mice. Furthermore, the contractile response of the aorta and the pressor response of isolated perfused mesenteric arterial beds to alpha(1)-AR stimulation were markedly reduced in alpha(1D)-/- mice. We conclude that the alpha(1D)-AR participates directly in sympathetic regulation of systemic blood pressure by vasoconstriction.

  13. Perfect mirror transport protocol with higher dimensional quantum chains.

    PubMed

    Paz-Silva, Gerardo A; Rebić, Stojan; Twamley, Jason; Duty, Tim

    2009-01-16

    A globally controlled scheme for quantum transport is proposed. The scheme works on a 1D chain of nearest neighbor coupled systems of qudits (finite dimension), or qunats (continuous variable), taking any arbitrary initial quantum state of the chain and producing a final quantum state, which is perfectly spatially mirrored about the midpoint of the chain. As a particular novel application, the method can be used to transport continuous variable quantum states. A physical realization is proposed where it is shown how the quantum states of the microwave fields held in a chain of driven superconducting coplanar waveguides can experience quantum mirror transport when coupled by switchable Cooper pair boxes.

  14. Magnetic ordering in the frustrated J1 - J2 Ising chain candidate BaNd2O4

    DOE PAGES

    Aczel, Adam A.; Li, Ling; Garlea, Vasile O.; ...

    2014-10-06

    The AR2O4 family (R = rare earth) has recently been attracting interest as a new series of frustrated magnets, with the magnetic R atoms forming zigzag chains running along the c axis. In this paper, we have investigated polycrystalline BaNd2O4 with a combination of magnetization, heat-capacity, and neutron powder diffraction measurements. Magnetic Bragg peaks are observed below TN = 1.7 K, and they can be indexed with a propagation vector of k = (0,1/2,1/2). The signal from magnetic diffraction is well described by long-range ordering of only one of the two types of Nd zigzag chains, with collinear up-up-down-down intrachainmore » spin configurations (double Néel state). Furthermore, low-temperature magnetization and heat-capacity measurements reveal two magnetic-field-induced spin transitions at 2.75 and 4 T for T = 0.46 K. The high-field phase is paramagnetic, while the intermediate-field state may arise from a spin transition of the long-range ordered Nd chains. Finally, one possible candidate for the field-induced ordered state corresponds to an up-up-down intrachain spin configuration, as predicted for a classical J1-J2 Ising chain with a double Néel ground state in zero field.« less

  15. Electronic properties of zigzag, armchair and their hybrid quantum dots of graphene and boron-nitride with and without substitution: A DFT study

    NASA Astrophysics Data System (ADS)

    Yamijala, Sharma S. R. K. C.; Bandyopadhyay, Arkamita; Pati, Swapan K.

    2014-05-01

    Spin-polarized density functional theory calculations have been performed on armchair graphene quantum dots and boron-nitride quantum dots (AG/BNQDs) and the effect of carbon/boron-nitride substitution on the electronic properties of these AG/BNQDs has been investigated. As a first step to consider more realistic quantum dots, quantum dots which are a combination of zigzag QDs and armchair QDs have been considered. Effect of substitution on these hybrid quantum dots has been explored for both GQDs and BNQDs and such results have been compared and contrasted with the results of substituted AG/BNQDs and their zigzag analogs. Our work suggests that the edge substitution can play an important tool while tuning the electronic properties of quantum dots.

  16. Structure and electronic properties of the double-wall nanotubes constructed from SiO2 nanotubes encapsulated inside zigzag carbon nanotubes.

    PubMed

    Qiao, Weiye; Bai, Hongcun; Zhu, Ying; Huang, Yuanhe

    2012-05-09

    This paper presents ab initio self-consistent field crystal orbital calculations on the structures, stabilities, elastic and electronic properties of the double-wall nanotubes made of SiO(2) nanotubes encapsulated inside zigzag carbon nanotubes based on density functional theory. It is found that formation of the combined systems is energetically favorable when the nearest distance between the two constituents is in the area of the van der Waals effect. The obtained band structures show that all the combined systems are semiconductors with nonzero energy gaps. Based on the deformation potential theory and effective mass approximation, the mobilities of charge carriers are calculated to be in the range of 10(2)-10(4) cm(2) V(-1) s(-1), the same order of magnitude as those of the corresponding zigzag carbon nanotubes. The Young's moduli are also calculated for the combined systems.

  17. Investigating Zigzag Film Growth Behaviors in Layer-by-Layer Self-Assembly of Small Molecules through a High-Gravity Technique.

    PubMed

    Cheng, Mengjiao; Jiang, Chao; Luo, Caijun; Zhang, Yajun; Shi, Feng

    2015-08-26

    The zigzag film growth behavior in the layer-by-layer (LbL) assembly method is a ubiquitous phenomenon for which the growth mechanism was rarely investigated, especially for small molecules. To interpret the zigzag increasing manner, we hypothesized that the desorption kinetics of small molecules was dominant for the film growth behavior and demonstrated this hypotheis by introducing the high-gravity technique into the LbL assembly of a typical polyelectrolyte/small molecule system of polyethylenimine (PEI) and meso-tetra(4-carboxyphenyl)porphine (Por). The results showed that the high-gravity technique remarkably accelerated the desorption process of Por; the high-gravity LbL assembly provides a good platform to reveal the desorption kinetics of Por, which is tedious to study in conventional situation. We found that as much as 50 min is required for Por molecules to reach desorption equilibrium from the substrate to the bulk PEI solution for the conventional dipping method; however, the process could be accelerated and require only 100 s if a high-gravity field is used. Nonequilibrated desorption at 10 min for normal dipping and at 30 s for high-gravity-field-assisted assembly both exhibited a zigzag film growth, but after reaching desorption equilibrium at 100 s under a high-gravity field, film growth began to cycle between assembly and complete disassembly instead of LbL assembly. For the first time we have proven that the high-gravity technique can also accelerate the desorption process and demonstrated the desorption-dependent mechanism of small molecules for zigzag film growth behaviors.

  18. Chemical vapor deposition synthesis of near-zigzag single-walled carbon nanotubes with stable tube-catalyst interface

    PubMed Central

    Zhao, Qiuchen; Xu, Ziwei; Hu, Yue; Ding, Feng; Zhang, Jin

    2016-01-01

    Chemical vapor deposition (CVD) growth is regarded as the most promising method for realizing structure-specific single-walled carbon nanotube (SWNT) growth. In the past 20 years, many efforts dedicated to chirality-selective SWNT growth using various strategies have been reported. However, normal CVD growth under constant conditions could not fully optimize the chirality because the randomly formed cap structure allows the nucleation of all types of SWNTs and the chirality of an SWNT is unlikely to be changed during the following elongation process. We report a new CVD process that allows temperature to be periodically changed to vary SWNT chirality multiple times during elongation to build up the energetically preferred SWNT-catalyst interface. With this strategy, SWNTs with small helix angles (less than 10°), which are predicted to have lower interfacial formation energy than others, are enriched up to ~72%. Kinetic analysis of the process suggests a multiple redistribution feature whereby a large chiral angle SWNT tends to reach the near-zigzag chirality step by step with a small chiral angle change at each step, and hence, we named this method “tandem plate CVD.” This method opens a door to synthesizing chirality-selective SWNTs by rational catalyst design. PMID:27386532

  19. Wave Function Parity Loss Used to Mitigate Thermal Broadening in Spin-orbit Coupled Zigzag Graphene Analogues

    NASA Astrophysics Data System (ADS)

    Sadi, Mohammad Abdullah; Liang, Gengchiau

    2017-01-01

    Carrier transport through a graphene zigzag nanoribbon (ZNR) is possible to be blocked by a p-n profile implemented along its transport direction. However, we found that in cases of analogous materials with significant intrinsic spin-orbit coupling (SOC), i.e. silicene and germanene, such a profile on ZNR of these materials allows transmission mostly through spin-orbit coupled energy window due to the loss of the parity of wave functions at different energies caused by SOC. Next, a p-i-n scheme on germanene ZNR is proposed to simultaneously permit edge transmission and decimate bulk transmission. The transmission spectrum is shown to mitigate the effect of thermal broadening on germanene and silicene ZNR based spin-separators by improving spin polarization yield by 400% and 785%, respectively, at 300 K. The importance of proper gate voltage and position for such performance is further elucidated. Finally, the modulation the current output of the proposed U-shape p-i-n device while maintaining its spin polarization is discussed.

  20. Molecular dynamics study of radiation damage and microstructure evolution of zigzag single-walled carbon nanotubes under carbon ion incidence

    NASA Astrophysics Data System (ADS)

    Li, Huan; Tang, Xiaobin; Chen, Feida; Huang, Hai; Liu, Jian; Chen, Da

    2016-07-01

    The radiation damage and microstructure evolution of different zigzag single-walled carbon nanotubes (SWCNTs) were investigated under incident carbon ion by molecular dynamics (MD) simulations. The radiation damage of SWCNTs under incident carbon ion with energy ranging from 25 eV to 1 keV at 300 K showed many differences at different incident sites, and the defect production increased to the maximum value with the increase in incident ion energy, and slightly decreased but stayed fairly stable within the majority of the energy range. The maximum damage of SWCNTs appeared when the incident ion energy reached 200 eV and the level of damage was directly proportional to incident ion fluence. The radiation damage was also studied at 100 K and 700 K and the defect production decreased distinctly with rising temperature because radiation-induced defects would anneal and recombine by saturating dangling bonds and reconstructing carbon network at the higher temperature. Furthermore, the stability of a large-diameter tube surpassed that of a thin one under the same radiation environments.

  1. Theoretical study on the oxidation of zigzag silicon carbide nanotubes (SiCNTs) by singlet O2

    NASA Astrophysics Data System (ADS)

    Wang, Hong; Liu, Wei; Zhao, Jing-xiang

    2012-11-01

    Singlet O2 produced upon photoexcitation is a very important oxidative reagent. The study on its reaction with nanotube might be useful not only to evaluate the stability of the nanotube upon air exposure and sunlight, but also to modify the properties of the nanotube. Considering the unique properties and wide applications of silicon carbide nanotube (SiCNT), in this paper, we performed extensive density functional theory (DFT) calculations to study the oxidation of a series of zigzag (n,0) SiCNTs (n=6 to 12) by singlet O2. It is found that the reaction process contains two steps, namely, (i) [2+2] cycloaddition of a singlet O2 to the Si-C bond, followed by (ii) the dissociation of the O-O bond, leading to the formation of an epoxide configuration with a highly exothermicity (>4.00 eV). Compared with pure SiCNT, the cycloaddition of singlet O2 on tube leads to the decrease of the band gap, while the formation of the stable epoxy structure render band gap increase. Our results indicate that the SiCNT is more prone to be degraded after exposure to air and sunlight.

  2. Zig-zag magnetic ordering in honeycomb-layered Na3Co2SbO6

    NASA Astrophysics Data System (ADS)

    Wong, Cheryl; Avdeev, Maxim; Ling, Chris D.

    2016-11-01

    Na3Co2SbO6 is a layered oxide with a hexagonal O3-type structure, in which CdI2-type edge-sharing MO6 octahedral layers are intercalated by Na. The MO6 octahedral layer in turn adopts a honeycomb ordering pattern of magnetic (S=3/2) Co2+ sites surrounding isolated non-magnetic Sb5+ sites. Magnetic susceptibility measurements show that Na3Co2SbO6 orders antiferromagnetically below TN=8.3 K, with an effective magnetic moment of 5.22 μB (indicating a strong orbital contribution above the expected spin-only value of 3.87μB). While a honeycomb arrangement of magnetic cations could, in principle, support a co-operative long-range-ordered magnetic structure in which all nearest neighbors are antiferromagnetic with respect to one another, symmetry analysis of low-temperature neutron powder diffraction data shows that it instead adopts a partially frustrated 'zig-zag' ordering in which 2/3 of nearest-neighbor interactions are ferromagnetic and 1/3 are antiferromagnetic. The low Néel temperature and Weiss constant of θ = 2.2 K underlines the presence of significant frustration of the expected strong superexchange interactions among Co2+.

  3. Effects of line defects on spin-dependent electronic transport of zigzag MoS{sub 2} nanoribbons

    SciTech Connect

    Li, Xin-Mei; Yang, Kai-Wei; Zhang, Dan; Ding, Jia-Feng; Xu, Hui; Long, Meng-Qiu; Cui, Li-Ling

    2016-01-15

    The nonlinear spin-dependent transport properties in zigzag molybdenum-disulfide nanoribbons (ZMNRs) with line defects are investigated systematically using nonequilibrium Green’s function method combined with density functional theory. The results show that the line defects can enhance the electronic transfer ability of ZMNRs. The types and locations of the line defects are found critical in determining the spin polarization and the current-voltage (I-V) characteristics of the line defected ZMNRs. For the same defect type, the total currents of the ribbons with the line defects in the centers are lager than those on the edges. And for the same location, the total currents of the systems with the sulfur (S) line defect are larger than the according systems with the molybdenum (Mo) line defect. All the considered systems present magnetism properties. And in the S line defected systems, the spin reversal behaviors can be observed. In both the spin-up and spin-down states of the Mo line defected systems, there are obvious negative differential resistance behaviors. The mechanisms are proposed for these phenomena.

  4. Spin-dependent Seebeck Effect, Thermal Colossal Magnetoresistance and Negative Differential Thermoelectric Resistance in Zigzag Silicene Nanoribbon Heterojunciton

    NASA Astrophysics Data System (ADS)

    Fu, Hua-Hua; Wu, Dan-Dan; Zhang, Zu-Quan; Gu, Lei

    2015-05-01

    Spin-dependent Seebeck effect (SDSE) is one of hot topics in spin caloritronics, which examine the relationships between spin and heat transport in materials. Meanwhile, it is still a huge challenge to obtain thermally induced spin current nearly without thermal electron current. Here, we construct a hydrogen-terminated zigzag silicene nanoribbon heterojunction, and find that by applying a temperature difference between the source and the drain, spin-up and spin-down currents are generated and flow in opposite directions with nearly equal magnitudes, indicating that the thermal spin current dominates the carrier transport while the thermal electron current is much suppressed. By modulating the temperature, a pure thermal spin current can be achieved. Moreover, a thermoelectric rectifier and a negative differential thermoelectric resistance can be obtained in the thermal electron current. Through the analysis of the spin-dependent transport characteristics, a phase diagram containing various spin caloritronic phenomena is provided. In addition, a thermal magnetoresistance, which can reach infinity, is also obtained. Our results put forward an effective route to obtain a spin caloritronic material which can be applied in future low-power-consumption technology.

  5. Spin-dependent Seebeck Effect, Thermal Colossal Magnetoresistance and Negative Differential Thermoelectric Resistance in Zigzag Silicene Nanoribbon Heterojunciton

    PubMed Central

    Fu, Hua-Hua; Wu, Dan-Dan; Zhang, Zu-Quan; Gu, Lei

    2015-01-01

    Spin-dependent Seebeck effect (SDSE) is one of hot topics in spin caloritronics, which examine the relationships between spin and heat transport in materials. Meanwhile, it is still a huge challenge to obtain thermally induced spin current nearly without thermal electron current. Here, we construct a hydrogen-terminated zigzag silicene nanoribbon heterojunction, and find that by applying a temperature difference between the source and the drain, spin-up and spin-down currents are generated and flow in opposite directions with nearly equal magnitudes, indicating that the thermal spin current dominates the carrier transport while the thermal electron current is much suppressed. By modulating the temperature, a pure thermal spin current can be achieved. Moreover, a thermoelectric rectifier and a negative differential thermoelectric resistance can be obtained in the thermal electron current. Through the analysis of the spin-dependent transport characteristics, a phase diagram containing various spin caloritronic phenomena is provided. In addition, a thermal magnetoresistance, which can reach infinity, is also obtained. Our results put forward an effective route to obtain a spin caloritronic material which can be applied in future low-power-consumption technology. PMID:26000658

  6. Spin-dependent Seebeck Effect, Thermal Colossal Magnetoresistance and Negative Differential Thermoelectric Resistance in Zigzag Silicene Nanoribbon Heterojunciton.

    PubMed

    Fu, Hua-Hua; Wu, Dan-Dan; Zhang, Zu-Quan; Gu, Lei

    2015-05-22

    Spin-dependent Seebeck effect (SDSE) is one of hot topics in spin caloritronics, which examine the relationships between spin and heat transport in materials. Meanwhile, it is still a huge challenge to obtain thermally induced spin current nearly without thermal electron current. Here, we construct a hydrogen-terminated zigzag silicene nanoribbon heterojunction, and find that by applying a temperature difference between the source and the drain, spin-up and spin-down currents are generated and flow in opposite directions with nearly equal magnitudes, indicating that the thermal spin current dominates the carrier transport while the thermal electron current is much suppressed. By modulating the temperature, a pure thermal spin current can be achieved. Moreover, a thermoelectric rectifier and a negative differential thermoelectric resistance can be obtained in the thermal electron current. Through the analysis of the spin-dependent transport characteristics, a phase diagram containing various spin caloritronic phenomena is provided. In addition, a thermal magnetoresistance, which can reach infinity, is also obtained. Our results put forward an effective route to obtain a spin caloritronic material which can be applied in future low-power-consumption technology.

  7. Half-metallic ferromagnetism in Mn-doped zigzag AlN nanoribbon from first-principles

    NASA Astrophysics Data System (ADS)

    Aghili, S.; Beiranvand, R.; Elahi, S. M.; Abolhasani, M. R.

    2016-12-01

    Based on first-principles calculations, we investigate the effect of Mn impurity on the electronic and magnetic properties of H-terminated zigzag AlN nanoribbons (ZAlNNRs), using the band structure results obtained through the full potential linearized augmented plane wave method within the density functional theory. The calculated results show that the H-terminated ZAlNNR is semiconducting and non magnetic material with a direct band gap of about 2.78 eV. Density of state analyses shows that the top of the valence band is mainly contributed by N atoms, while just beside the conduction band the whole DOS is mainly contributed by Al atoms. The main result is a transition from non-magnetic semiconducting character to half-metallic features upon doping. The Mn-doped ZAlNNR shows complete (100%) spin polarization at the Fermi level and the charge transport is totally originated from Manganese spin up electrons in the nanoribbon. These results propose potential application for the development of AlN nanoribbon-based in magneto-electronic devices.

  8. Chromatin conformation in living cells: support for a zig-zag model of the 30 nm chromatin fiber

    NASA Technical Reports Server (NTRS)

    Rydberg, B.; Holley, W. R.; Mian, I. S.; Chatterjee, A.

    1998-01-01

    A new method was used to probe the conformation of chromatin in living mammalian cells. The method employs ionizing radiation and is based on the concept that such radiation induces correlated breaks in DNA strands that are in spatial proximity. Human dermal fibroblasts in G0 phase of the cell cycle and Chinese hamster ovary cells in mitosis were irradiated by X-rays or accelerated ions. Following lysis of the cells, DNA fragments induced by correlated breaks were end-labeled and separated according to size on denaturing polyacrylamide gels. A characteristic peak was obtained for a fragment size of 78 bases, which is the size that corresponds to one turn of DNA around the nucleosome. Additional peaks between 175 and 450 bases reflect the relative position of nearest-neighbor nucleosomes. Theoretical calculations that simulate the indirect and direct effect of radiation on DNA demonstrate that the fragment size distributions are closely related to the chromatin structure model used. Comparison of the experimental data with theoretical results support a zig-zag model of the chromatin fiber rather than a simple helical model. Thus, radiation-induced damage analysis can provide information on chromatin structure in the living cell. Copyright 1998 Academic Press.

  9. A Multi-scale Refined Zigzag Theory for Multilayered Composite and Sandwich Plates with Improved Transverse Shear Stresses

    NASA Technical Reports Server (NTRS)

    Iurlaro, Luigi; Gherlone, Marco; Di Sciuva, Marco; Tessler, Alexander

    2013-01-01

    The Refined Zigzag Theory (RZT) enables accurate predictions of the in-plane displacements, strains, and stresses. The transverse shear stresses obtained from constitutive equations are layer-wise constant. Although these transverse shear stresses are generally accurate in the average, layer-wise sense, they are nevertheless discontinuous at layer interfaces, and thus they violate the requisite interlaminar continuity of transverse stresses. Recently, Tessler applied Reissner's mixed variational theorem and RZT kinematic assumptions to derive an accurate and efficient shear-deformation theory for homogeneous, laminated composite, and sandwich beams, called RZT(m), where "m" stands for "mixed". Herein, the RZT(m) for beams is extended to plate analysis, where two alternative assumptions for the transverse shear stresses field are examined: the first follows Tessler's formulation, whereas the second is based on Murakami's polynomial approach. Results for elasto-static simply supported and cantilever plates demonstrate that Tessler's formulation results in a powerful and efficient structural theory that is well-suited for the analysis of multilayered composite and sandwich panels.

  10. Volumetric image reconstruction in a dental panoramic imaging system with a limited-angle zigzag scan geometry

    NASA Astrophysics Data System (ADS)

    Hong, Daeki; Cho, Hyosung; Lee, Seonhwa; Oh, Jieun; Lee, Minsik; Kim, Hyojeong; Je, Uikyu; Park, Yeonok; Choi, Sungil; Koo, Yangseo; Cho, Heemoon

    2013-01-01

    As a continuation of our dental imaging R&D, we have proposed a novel idea that is capable of implementing cost-effective, low-dose, volumetric image reconstruction directly onto a dental panoramic imaging system. In the proposed geometry, a linear-type panoramic detector is rotated 90° from the orientation for panoramic imaging and scanned along a limited-angle zigzag trajectory in the axial direction to cover the whole imaging volume thickness. We used an effective reconstruction algorithm based on the total-variation (TV) minimization approach for the proposed geometry and performed systematic simulation work to demonstrate the viability of our proposed approach and its effectiveness for three-dimensional (3D) dental X-ray imaging. We have successfully reconstructed images of substantially high image accuracy from the proposed geometry and evaluated the reconstruction quality by using an image similarity metric, the universal-quality index (UQI). We expect the proposed method to be applicable to developing a cost-effective, low-dose, all-in-one dental X-ray imaging system.

  11. Wave Function Parity Loss Used to Mitigate Thermal Broadening in Spin-orbit Coupled Zigzag Graphene Analogues

    PubMed Central

    Sadi, Mohammad Abdullah; Liang, Gengchiau

    2017-01-01

    Carrier transport through a graphene zigzag nanoribbon (ZNR) is possible to be blocked by a p-n profile implemented along its transport direction. However, we found that in cases of analogous materials with significant intrinsic spin-orbit coupling (SOC), i.e. silicene and germanene, such a profile on ZNR of these materials allows transmission mostly through spin-orbit coupled energy window due to the loss of the parity of wave functions at different energies caused by SOC. Next, a p-i-n scheme on germanene ZNR is proposed to simultaneously permit edge transmission and decimate bulk transmission. The transmission spectrum is shown to mitigate the effect of thermal broadening on germanene and silicene ZNR based spin-separators by improving spin polarization yield by 400% and 785%, respectively, at 300 K. The importance of proper gate voltage and position for such performance is further elucidated. Finally, the modulation the current output of the proposed U-shape p-i-n device while maintaining its spin polarization is discussed. PMID:28091616

  12. Quantitative and qualitative characterization of zigzag spatiotemporal chaos in a system of amplitude equations for nematic electroconvection.

    PubMed

    Oprea, Iuliana; Triandaf, Ioana; Dangelmayr, Gerhard; Schwartz, Ira B

    2007-06-01

    It has been suggested by experimentalists that a weakly nonlinear analysis of the recently introduced equations of motion for the nematic electroconvection by M. Treiber and L. Kramer [Phys. Rev. E 58, 1973 (1998)] has the potential to reproduce the dynamics of the zigzag-type extended spatiotemporal chaos and localized solutions observed near onset in experiments [M. Dennin, D. S. Cannell, and G. Ahlers, Phys. Rev. E 57, 638 (1998); J. T. Gleeson (private communication)]. In this paper, we study a complex spatiotemporal pattern, identified as spatiotemporal chaos, that bifurcates at the onset from a spatially uniform solution of a system of globally coupled complex Ginzburg-Landau equations governing the weakly nonlinear evolution of four traveling wave envelopes. The Ginzburg-Landau system can be derived directly from the weak electrolyte model for electroconvection in nematic liquid crystals when the primary instability is a Hopf bifurcation to oblique traveling rolls. The chaotic nature of the pattern and the resemblance to the observed experimental spatiotemporal chaos in the electroconvection of nematic liquid crystals are confirmed through a combination of techniques including the Karhunen-Loeve decomposition, time-series analysis of the amplitudes of the dominant modes, statistical descriptions, and normal form theory, showing good agreement between theory and experiments.

  13. Electronic properties of pure and p-type doped hexagonal sheets and zigzag nanoribbons of InP

    NASA Astrophysics Data System (ADS)

    Longo, R. C.; Carrete, J.; Alemany, M. M. G.; Gallego, L. J.

    2013-02-01

    Unlike graphene, a hexagonal InP sheet (HInPS) cannot be obtained by mechanical exfoliation from the native bulk InP, which crystallizes in the zinc blende structure under ambient conditions. However, by ab initio density functional theory calculations we found that a slightly buckled HInPS is stable both in pristine form and when doped with Zn atoms; the same occurred for hydrogen-passivated zigzag InP nanoribbons (ZInPNRs), quasi-one-dimensional versions of the quasi-two-dimensional material. We investigated the electronic properties of both nanostructures, in the latter case also in the presence of an external transverse electric field, and the results are compared with those of hypothetical planar HInPS and ZInPNRs. The band gaps of planar ZInPNRs were found to be tunable by the choice of strength of this field, and to show an asymmetric behavior under weak electric fields, by which the gap can either be increased or decreased depending on their direction; however, this effect is absent from slightly buckled ZInPNRs. The binding energies of the acceptor impurity states of Zn-doped HInPS and ZInPNRs were found to be similar and much larger than that of Zn-doped bulk InP. These latter findings show that the reduction of the dimensionality of these materials limits the presence of free carriers.

  14. Comparison of noncovalent interactions of zigzag and armchair carbon nanotubes with heterocyclic and aromatic compounds: Imidazole and benzene, imidazophenazines, and tetracene

    NASA Astrophysics Data System (ADS)

    Zarudnev, Eugene S.; Stepanian, Stepan G.; Adamowicz, Ludwik; Leontiev, Victor S.; Karachevtsev, Victor A.

    2017-02-01

    We study non-covalent functionalization of SWCNT by linear heterocyclic compounds such as imidazophenazine (F1) and its derivatives (F2-F4). MP2 and DFT/M05-2X quantum-chemical methods are used to determine the structures and the interaction energies of complexes formed by F1-F4 with the zigzag(10,10) and armchair(6,6) nanotubes. The calculations show that for small diameter nanotubes the binding energies with zigzag nanotubes are stronger than with armchair nanotubes. But above the diameter of 1.4 nm the interaction energies for the armchair nanotubes become larger than for the zigzag nanotubes. Experimental measurements demonstrates that the ratio of the integral intensity of the resonance Raman bands assigned to the RBM modes of semiconducting nanotubes to the integral intensity of the metallic nanotubes increases for supernatant of SWCNT:F4 (1,2,3-triazole-[4,5-d]-phenazine) hybrids solved in 1-Methyl-2-pyrrolidone as compared to this ratio in sediment samples. It demonstrates that the linear heterocyclic compounds can be used for separating SWCNTs with different electron-conduction types.

  15. Negative differential resistance and bias-modulated metal-to-insulator transition in zigzag C2N-h2D nanoribbon

    PubMed Central

    He, Jing-Jing; Guo, Yan-Dong; Yan, Xiao-Hong

    2017-01-01

    Motivated by the fabrication of layered two-dimensional material C2N-h2D [Nat. Commun. 6, 6486 (2015)], we cut the single-layer C2N-h2D into a zigzag nanoribbon and perform a theoretical study. The results indicate that the band structure changes from semiconducting to metallic and a negative differential resistance effect occurs in the I-V curve. Interestingly, the current can be reduced to zero and this insulator-like state can be maintained as the bias increases. We find this unique property is originated from a peculiar band morphology, with only two subbands appearing around the Fermi level while others being far away. Furthermore the width and symmetry of the zigzag C2N-h2D nanoribbon can be used to tune the transport properties, such as cut-off bias and the maximum current. We also explore the electron transport property of an aperiodic model composed of two nanoribbons with different widths and obtain the same conclusion. This mechanism can be extended to other systems, e.g., hybrid BCN nanoribbons. Our discoveries suggest that the zigzag C2N-h2D nanoribbon has great potential in nanoelectronics applications. PMID:28382947

  16. XPB Induces C1D Expression to Counteract UV-Induced Apoptosis

    PubMed Central

    Li, Guang; Liu, Juhong; Abu-Asab, Mones; Masabumi, Shibuya; Maru, Yoshiro

    2010-01-01

    Although C1D has been shown to be involved in DNA double-strand breaks repair, how C1D expression was induced and the mechanism(s) by which C1D facilitates DNA repair in mammalian cells remain poorly understood. We and others have previously shown that expression of XPB protein efficiently compensated the UV-irradiation sensitive phenotype of 27-1 cells which lacks functional XPB. To further explore XPB-regulated genes that could be involved in UV-induced DNA repair, Differential Display analysis of mRNA level from CHO-9, 27-1 and 27-1 complemented with wild-type XPB were performed and C1D gene was identified as one of the major genes whose expression was significantly up-regulated by restoring XPB function. We found that XPB is essential to induce C1D transcription after UV-irradiation. The increase of C1D expression effectively compensates the UV-induced proteolysis of C1D and thus maintains cellular C1D level to cope with DNA damage inflicted by UV-irradiation. We further showed that although insufficient to rescue 27-1 cells from UV-induced apoptosis by itself, C1D facilitates XPB DNA repair through direct interaction with XPB. Our findings provided direct evidence that C1D is associated with DNA repair complex and may promote repair of UV-induced DNA damage. PMID:20530579

  17. Helical structures in vertically aligned dust particle chains in a complex plasma.

    PubMed

    Hyde, Truell W; Kong, Jie; Matthews, Lorin S

    2013-05-01

    Self-assembly of structures from vertically aligned, charged dust particle bundles within a glass box placed on the lower, powered electrode of a Gaseous Electronics Conference rf reference cell were produced and examined experimentally. Self-organized formation of one-dimensional vertical chains, two-dimensional zigzag structures, and three-dimensional helical structures of triangular, quadrangular, pentagonal, hexagonal, and heptagonal symmetries are shown to occur. System evolution is shown to progress from a one-dimensional chain structure, through a zigzag transition to a two-dimensional, spindlelike structure, and then to various three-dimensional, helical structures exhibiting multiple symmetries. Stable configurations are found to be dependent upon the system confinement, γ(2)=(ω(0h)/ω(0v))(2) (where ω(0h,v) are the horizontal and vertical dust resonance frequencies), the total number of particles within a bundle, and the rf power. For clusters having fixed numbers of particles, the rf power at which structural phase transitions occur is repeatable and exhibits no observable hysteresis. The critical conditions for these structural phase transitions as well as the basic symmetry exhibited by the one-, two-, and three-dimensional structures that subsequently develop are in good agreement with the theoretically predicted configurations of minimum energy determined employing molecular dynamics simulations for charged dust particles confined in a prolate, spheroidal potential as presented theoretically by Kamimura and Ishihara [Kamimura and Ishihara, Phys. Rev. E 85, 016406 (2012)].

  18. Tandem repeats modify the structure of the canine CD1D gene.

    PubMed

    Looringh van Beeck, F A; Leegwater, P A J; Herrmann, T; Broere, F; Rutten, V P M G; Willemse, T; Van Rhijn, I

    2013-06-01

    Among the CD1 proteins that present lipid antigens to T cells, CD1d is the only one that stimulates a population of T cells with an invariant T-cell receptor known as NKT cells. Sequencing of a 722 nucleotide gap in the dog (Canis lupus familiaris) genome revealed that the canine CD1D gene lacks a sequence homologous to exon 2 of human CD1D, coding for the start codon and signal peptide. Also, the canine CD1D gene contains three different short tandem repeats that disrupt the expected gene structure. Because canine CD1D cDNA lacks sequences homologous to human exon 2 and 3, the functionality of canine CD1d protein may be affected, and this could have consequences for the development and activation of canine NKT cells.

  19. Examination of 1D Solar Cell Model Limitations Using 3D SPICE Modeling: Preprint

    SciTech Connect

    McMahon, W. E.; Olson, J. M.; Geisz, J. F.; Friedman, D. J.

    2012-06-01

    To examine the limitations of one-dimensional (1D) solar cell modeling, 3D SPICE-based modeling is used to examine in detail the validity of the 1D assumptions as a function of sheet resistance for a model cell. The internal voltages and current densities produced by this modeling give additional insight into the differences between the 1D and 3D models.

  20. Tunable Design of Structural Colors Produced by Pseudo-1D Photonic Crystals of Graphene Oxide.

    PubMed

    Tong, Liping; Qi, Wei; Wang, Mengfan; Huang, Renliang; Su, Rongxin; He, Zhimin

    2016-07-01

    It is broadly observed that graphene oxide (GO) films appear transparent with a thickness of about several nanometers, whereas they appear dark brown or almost black with thickness of more than 1 μm. The basic color mechanism of GO film on a sub-micrometer scale, however, is not well understood. This study reports on GO pseudo-1D photonic crystals (p1D-PhCs) exhibiting tunable structural colors in the visible wavelength range owing to its 1D Bragg nanostructures. Striking structural colors of GO p1D-PhCs could be tuned by simply changing either the volume or concentration of the aqueous GO dispersion during vacuum filtration. Moreover, the quantitative relationship between thickness and reflection wavelength of GO p1D-PhCs has been revealed, thereby providing a theoretical basis to rationally design structural colors of GO p1D-PhCs. The spectral response of GO p1D-PhCs to humidity is also obtained clearly showing the wavelength shift of GO p1D-PhCs at differently relative humidity values and thus encouraging the integration of structural color printing and the humidity-responsive property of GO p1D-PhCs to develop a visible and fast-responsive anti-counterfeiting label. The results pave the way for a variety of potential applications of GO in optics, structural color printing, sensing, and anti-counterfeiting.

  1. Controlled Self-Assembly of Cyclophane Amphiphiles: From 1D Nanofibers to Ultrathin 2D Topological Structures

    SciTech Connect

    Cai, Zhengxu; Li, Lianwei; Lo, Wai-Yip; Zhao, Donglin; Wu, Qinghe; Zhang, Na; Su, Yu-An; Chen, Wei; Yu, Luping

    2016-07-05

    A novel series of amphiphilic TC-PEG molecules were designed and synthesized based on the orthogonal cyclophane unit. These molecules were able to self-assemble from 1D nanofibers and nanobelts to 2D ultrathin nanosheets (3 nm thick) in a controlled way by tuning the length of PEG side chains. The special structure of the cyclophane moiety allowed control in construction of nanostructures through programmed noncovalent interactions (hydrophobic hydrophilic interaction and pi-pi interaction). The self-assembled nanostructures were characterized by combining real space imaging (TEM, SEM, and AFM) and reciprocal space scattering (GIWAXS) techniques. This unique supramolecular system may provide a new strategy for the design of materials with tunable nanomorphology and functionality.

  2. Giant Fluctuations of Local Magnetoresistance of Organic Spin Valves and the Non-Hermitian 1D Anderson Model

    NASA Astrophysics Data System (ADS)

    Roundy, R. C.; Nemirovsky, D.; Kagalovsky, V.; Raikh, M. E.

    2014-06-01

    Motivated by recent experiments, where the tunnel magnetoresitance (TMR) of a spin valve was measured locally, we theoretically study the distribution of TMR along the surface of magnetized electrodes. We show that, even in the absence of interfacial effects (like hybridization due to donor and acceptor molecules), this distribution is very broad, and the portion of area with negative TMR is appreciable even if on average the TMR is positive. The origin of the local sign reversal is quantum interference of subsequent spin-rotation amplitudes in the course of incoherent transport of carriers between the source and the drain. We find the distribution of local TMR exactly by drawing upon formal similarity between evolution of spinors in time and of the reflection coefficient along a 1D chain in the Anderson model. The results obtained are confirmed by the numerical simulations.

  3. Observation of ferromagnetic and antiferromagnetic coupling in 1-D and 2-D extended structures of copper(II) terephthalates

    SciTech Connect

    Deakin, L.; Arif, A.M.; Miller, J.S.

    1999-11-01

    The reaction between CuCl{sub 2}{center{underscore}dot}2H{sub 2}O and disodium terephthalate, Na{sub 2}tp, in aqueous solution simultaneously produces chain, bis(aqua)[{mu}-(terephthalato-{kappa}O:{kappa}O{prime})]copper(II), monohydrate, Cutp(OH{sub 2}){sub 2}{center{underscore}dot}H{sub 2}O (1), and layered, bis(aqua)[{mu}-(terephthalato-{kappa}O)]copper(II), Cutp(OH{sub 2}){sub 2} (2), structured materials. 1 (C{sub 8}H{sub 10}CuO{sub 7}) belongs to the orthorhombic P2{sub 1}2{sub 1}2 space group [a = 6.3015(4) {angstrom}, b = 6.8743(4) {angstrom}, c = 22.9972(14) {angstrom}, and Z = 4] and incorporates tp in a bridging bis-monodentate binding mode and Cu(II) in a tetragonally elongated octahedron. 2 (C{sub 8}H{sub 10}CuO{sub 6}) which belongs to the orthorhombic Pmc2{sub 1} space group [a = 10.7421(8) {angstrom}, b = 7.2339(10) {angstrom}, c = 5.7143(13) {angstrom}, and Z = 2] incorporates tp in a mono-bidentate binding mode and Cu(II) in a distorted square pyramid. 1 and 2 exhibit axial X-band powder EPR spectra with G{sub {perpendicular}} = 2.08, g{sub {parallel}} = 2.29 (1) and g{sub {perpendicular}} = 2.07, g{sub {parallel}} = 2.29 (2) at 300 K. 1 obeys the Curie-Weiss law at high temperatures ({theta} = {minus}7.2 K) and at low temperatures behaves as 1-D magnetic chains with an exchange-coupling constant of J/k{sub B} = {minus}9.15 K (H = {minus}2JS{sub 1}{center{underscore}dot}S{sub 2}). This material displays a spontaneous moment below 2 K under small applied magnetic fields, consistent with the presence of spin canting. 2 exhibits ferromagnetic interactions with {theta} = +0.8 K. Along the 1-D chain where coordinated water forms the bridge between metal centers, the coupling between Cu(II) is J/k{sub B} = +0.6 K. The fit of the magnetic susceptibility for 2 using a molecular field correction, which takes into consideration antiferromagnetic interactions between chains via the tp ligand, yields J{prime}/k{sub B} = {minus}0.13 K.

  4. Health supply chain management.

    PubMed

    Zimmerman, Rolf; Gallagher, Pat

    2010-01-01

    This chapter gives an educational overview of: * The actual application of supply chain practice and disciplines required for service delivery improvement within the current health environment. * A rationale for the application of Supply Chain Management (SCM) approaches to the Health sector. * The tools and methods available for supply chain analysis and benchmarking. * Key supply chain success factors.

  5. Therapeutic implications of CD1d expression and tumor-infiltrating macrophages in pediatric medulloblastomas.

    PubMed

    Teo, Wan-Yee; Elghetany, M Tarek; Shen, Jianhe; Man, Tsz-Kwong; Li, Xiaonan; Chintagumpala, Murali; Su, Jack Meng Fen; Dauser, Robert; Whitehead, William; Adesina, Adekunle M; Lau, Ching C

    2014-11-01

    Immunobiology of medulloblastoma (MB), the most common malignant brain tumor in children, is poorly understood. Although tumor cells in some MBs were recently shown to express CD1d and be susceptible to Vα24-invariant natural killer T (NKT)-cell cytotoxicity, the clinical relevance of CD1d expression in MB patients remains unknown. We investigated the expression of CD1d in pediatric MBs and correlated with molecular and clinical characteristics. Specifically, we explored if NKT cell therapy can be targeted at a subset of pediatric MBs with poorer prognosis. Particularly, infantile MBs have a worse outcome because radiotherapy is delayed to avoid neurocognitive sequelae. Immunohistochemistry for CD1d was performed on a screening set of 38 primary pediatric MBs. Gene expression of the membrane form of M2 macrophage marker, CD163, was studied in an expanded cohort of 60 tumors. Outcome data was collected prospectively. Thirteen of 38 MBs (34.2 %) expressed CD1d on immunohistochemistry. CD1d was expressed mainly on MB tumor cells, and on some tumor-associated macrophages. Majority (18/22, 82 %) of non sonic-hedgehog/Wingless-activated MBs (group 3 and 4) were CD1d-negative (p = 0.05). A subset of infantile MBs (4/9, 44.4 %) expressed CD1d. Macrophages infiltrating MB expressed CD163 apart from CD1d. Molecular subtypes demonstrated statistical differences in CD163 expression, SHH-tumors were the most enriched (p = 0.006). Molecular and clinical subtypes of pediatric MB exhibit distinct differences in CD1d expression, which have important therapeutic implications. High CD1d expression in infantile MBs offers potential new immunotherapeutic treatment with NKT cell therapy in infants, where treatment is suboptimal due delayed radiotherapy.

  6. Mapping of the serotonin 5-HT{sub 1D{alpha}} autoreceptor gene (HTR1D) on chromosome 1 using a silent polymorphism in the coding region

    SciTech Connect

    Ozaki, N.; Lappalainen, J.; Linnoila, M.

    1995-04-24

    Serotonin (5-HT){sub ID} receptors are 5-HT release-regulating autoreceptors in the human brain. Abnormalities in brain 5-HT function have been hypothesized in the pathophysiology of various psychiatric disorders, including obsessive-compulsive disorder, autism, mood disorders, eating disorders, impulsive violent behavior, and alcoholism. Thus, mutations occurring in 5-HT autoreceptors may cause or increase the vulnerability to any of these conditions. 5-HT{sub 1D{alpha}} and 5-HT{sub 1D{Beta}} subtypes have been previously localized to chromosomes 1p36.3-p34.3 and 6q13, respectively, using rodent-human hybrids and in situ localization. In this communication, we report the detection of a 5-HT{sub 1D{alpha}} receptor gene polymorphism by single strand conformation polymorphism (SSCP) analysis of the coding sequence. The polymorphism was used for fine scale linkage mapping of 5-HT{sub 1D{alpha}} on chromosome 1. This polymorphism should also be useful for linkage studies in populations and in families. Our analysis also demonstrates that functionally significant coding sequence variants of the 5-HT{sub 1D{alpha}} are probably not abundant either among alcoholics or in the general population. 14 refs., 1 fig., 1 tab.

  7. Electronic-to-vibrational energy transfer efficiency in the O/1 D/-N2 and O/1 D/-CO systems

    NASA Technical Reports Server (NTRS)

    Slanger, T. G.; Black, G.

    1974-01-01

    With the aid of a molecular resonance fluorescence technique, which utilizes optical pumping from the v = 1 level of the ground state of CO by A 1 Pi-X 1 Sigma radiation, a study is made of the efficiency of E-V transfer from O(1 D) to CO. O(1 D) is generated at a known rate by O2 photodissociation at 1470 A in an intermittent mode, and the small modulation of the fluorescent signal associated with CO (v = 1) above the normal thermal background is interpreted in terms of E-V transfer efficiency. The CO (v = 1) lifetime in this system is determined mainly by resonance trapping of the IR fundamental band, and is found to be up to ten times longer than the natural radiative lifetime. For CO, (40 plus or minus 8)% of the O(1 D) energy is converted into vibrational energy. By observing the effect of N2 on the CO (v = 1) fluorescent intensity and lifetime, it is possible to obtain the E-V transfer efficiency for the system O(1 D)-N2 relative to that for O(1 D)-CO. The results indicate that the efficiency for N2 is (83 plus or minus 10)% of that for CO.

  8. Comments about the use of a Zig-Zag transformer to reduce the neutral current created by unbalanced nonlinear loads

    SciTech Connect

    Beverly, L.; Hance, R.; Kristalinski, A.; Visser, A.

    1993-09-01

    The subject of AC line currents with high harmonic content and the potential for overloaded neutral wires caused by the non-linear loading of electronic power supplies has become one of the most popular and at the same time a very complex topic among electrical engineers. Different solutions are offered for this problem. Some examples are specially designed K-rated AC distribution transformers, delta connected primary windings, and L-C tuned filters. All of the above methods have some limitations. For instance, a K-rated transformer does not eliminate harmonics, but transmits them into the feeder. Neutral currents that flow from various loads to the K-rated transformer are still very high. These K-rated transformers are more expensive and are larger in physical size than conventional transformers. The delta connected primary of a power distribution transformer can only eliminate triplen harmonics for balanced loads. Neutral currents caused by the loads are not eliminated. The primary side circuit breaker may also not protect a transformer against overcurrents because the circuit breaker will not see the triplen harmonic current that is circulating in the primary of the transformer. L-C filters can create undesirable resonances, which will lead to an increase in harmonic currents. Another solution is to use a number of small Zig-Zag transformers to reduce the neutral current. This is attractive for the following reasons: relatively low cost, simplicity, ease of installation on existing distribution systems, ability to keep neutral currents local thus eliminating the need for larger neutral wires, and the ability to improve the fundamental load current balance as well.

  9. High performance current and spin diode of atomic carbon chain between transversely symmetric ribbon electrodes

    PubMed Central

    Dong, Yao-Jun; Wang, Xue-Feng; Yang, Shuo-Wang; Wu, Xue-Mei

    2014-01-01

    We demonstrate that giant current and high spin rectification ratios can be achieved in atomic carbon chain devices connected between two symmetric ferromagnetic zigzag-graphene-nanoribbon electrodes. The spin dependent transport simulation is carried out by density functional theory combined with the non-equilibrium Green's function method. It is found that the transverse symmetries of the electronic wave functions in the nanoribbons and the carbon chain are critical to the spin transport modes. In the parallel magnetization configuration of two electrodes, pure spin current is observed in both linear and nonlinear regions. However, in the antiparallel configuration, the spin-up (down) current is prohibited under the positive (negative) voltage bias, which results in a spin rectification ratio of order 104. When edge carbon atoms are substituted with boron atoms to suppress the edge magnetization in one of the electrodes, we obtain a diode with current rectification ratio over 106. PMID:25142376

  10. Closed Circular Chains

    ERIC Educational Resources Information Center

    Caglayan, Günhan

    2016-01-01

    A Steiner chain is defined as the sequence of n circles that are all tangent to two given non-intersecting circles. A closed chain, in particular, is one in which every circle in the sequence is tangent to the previous and next circles of the chain. In a closed Steiner chain the first and the "n"th circles of the chain are also tangent…

  11. Frustrated spin chain physics near the Majumdar-Ghosh point in szenicsite Cu3(MoO4)(OH)4

    NASA Astrophysics Data System (ADS)

    Lebernegg, Stefan; Janson, Oleg; Rousochatzakis, Ioannis; Nishimoto, Satoshi; Rosner, Helge; Tsirlin, Alexander A.

    2017-01-01

    In this joint experimental and theoretical work magnetic properties of the Cu2 + mineral szenicsite Cu3(MoO4) (OH) 4 are investigated. This compound features isolated triple chains in its crystal structure, where the central chain involves an edge-sharing geometry of the CuO4 plaquettes, while the two side chains feature a corner-sharing zigzag geometry. The magnetism of the side chains can be described in terms of antiferromagnetic dimers with a coupling larger than 200 K. The central chain was found to be a realization of the frustrated antiferromagnetic J1-J2 chain model with J1≃68 K and a sizable second-neighbor coupling J2. The central and side chains are nearly decoupled owing to interchain frustration. Therefore, the low-temperature behavior of szenicsite should be entirely determined by the physics of the central frustrated J1-J2 chain. Our heat-capacity measurements reveal an accumulation of magnetic entropy at low temperatures and suggest a proximity of the system to the Majumdar-Ghosh point of the antiferromagnetic J1-J2 spin chain, J2/J1=0.5 .

  12. X(3872) as a {sup 1}D{sub 2} charmonium state

    SciTech Connect

    Kalashnikova, Yu. S.; Nefediev, A. V.

    2010-11-01

    The {sup 1}D{sub 2} charmonium assignment for the X(3872) meson is considered, as prompted by a recent result from the BABAR Collaboration, favoring 2{sup -+} quantum numbers for X. It is shown that established properties of X(3872) are in a drastic conflict with the {sup 1}D{sub 2} cc assignment.

  13. Four 1-D metal-organic polymers self-assembled from semi-flexible benzimidazole-based ligand: Syntheses, structures and fluorescent properties

    NASA Astrophysics Data System (ADS)

    Zhou, Chun-lin; Wang, Shi-min; Liu, Sai-nan; Yu, Tian-tian; Li, Rui-ying; Xu, Hong; Liu, Zhong-yi; Sun, Huan; Cheng, Jia-jia; Li, Jin-peng; Hou, Hong-wei; Chang, Jun-biao

    2016-08-01

    Four one-dimensional (1-D) metal-organic polymers based on methylene-bis(1,1‧-benzimidazole)(mbbz), namely, {[Hg(mbbz)(SCN)2]·1/3H2O}n (1), [Co(mbbz)(Cl)2]n (2), {[Co(mbbz)(SO4)]·CH3OH}n (3) and {[Zn(mbbz)(SO4)]·CH3OH}n (4) have been successfully synthesized and structurally characterized. Single-crystal X-ray diffraction reveals that polymers 1 and 2 exhibit interesting 1-D double helical chain structures, while polymers 3 and 4 are 1-D double chain structures due to the bridging effect of mbbz ligands and sulfate anions. These polymers containing the mbbz-based ligand have a high degree of dependence on the corresponding counter anions. Furthermore, the fluorescence properties of the four polymers were also investigated in the solid state, showing the fluorescence signal changes in comparing with that of free ligand mbbz.

  14. Syntheses, crystal structures and properties of two 1-D cadmium(II) coordination polymers based on 1,1'-(1,3-propanediyl)bis-1H-benzimidazole

    SciTech Connect

    Yang Huaixia; Meng Xiangru; Liu Yun; Hou Hongwei Fan Yaoting; Shen Xiaoqing

    2008-09-15

    The combination of framework-builders 1,1'-(1,3-propanediyl)bis-1H-benzimidazole (pbbm), Cd(II) ion and framework-regulator ClO{sub 4}{sup -} or SO{sub 4}{sup 2-} provides two new coordination polymers [Cd(pbbm){sub 2}(ClO{sub 4}){sub 2}]{sub n}(1) and {l_brace}[Cd(pbbm)SO{sub 4}(H{sub 2}O){sub 2}].CH{sub 3}OH{r_brace}{sub n}(2). Both of them display 1-D chain framework, but their detailed structures are clearly different from each other. 1 displays a 1-D ribbon of rings framework, 2 features an interesting infinite 1-D looped chain structure composed of two kinds of rings, the smaller 8-membered ring and the larger 20-membered ring. The antimicrobial activities of the two polymers were tested by the agar diffusion method and the results indicated that they exhibited antimicrobial activities against bacterial strands. The measurement of the non-isothermal kinetics of the thermal decomposition of 2 reveals that there are at least three steps that occur in its decomposition process. - Graphical abstract: Two new Cd(II)-containing complexes have been synthesized and characterized by single-crystal X-ray diffraction. The antimicrobial activity and the non-isothermal kinetics of the thermal decomposition of the polymers were also investigated. Display Omitted.

  15. The organic anion transport polypeptide 1d1 (Oatp1d1) mediates hepatocellular uptake of phalloidin and microcystin into skate liver

    SciTech Connect

    Meier-Abt, F.; Hammann-Haenni, A.; Stieger, B.; Ballatori, N.; Boyer, J.L. . E-mail: james.boyer@yale.edu

    2007-02-01

    Organic anion transporting polypeptides (rodent Oatp; human OATP) mediate cellular uptake of numerous organic compounds including xenobiotic toxins into mammalian hepatocytes. In the little skate Leucoraja erinacea a liver-specific Oatp (Oatp1d1, also called sOatp) has been identified and suggested to represent an evolutionarily ancient precursor of the mammalian liver OATP1B1 (human), Oatp1b2 (rat), and OATP1B3 (human). The present study tested whether Oatp1d1 shares functional transport activity of the xenobiotic oligopeptide toxins phalloidin and microcystin with the mammalian liver Oatps/OATPs. The phalloidin analogue [{sup 3}H]-demethylphalloin was taken up into skate hepatocytes with high affinity (Km {approx} 0.4 {mu}M), and uptake could be inhibited by phalloidin and a variety of typical Oatp/OATP substrates such as bromosulfophthalein, bile salts, estrone-3-sulfate, cyclosporine A and high concentrations of microcystin-LR (Ki {approx} 150 {mu}M). When expressed in Xenopus laevis oocytes Oatp1d1 increased uptake of demethylphalloin (Km {approx} 2.2 {mu}M) and microcystin-LR (Km {approx} 27 {mu}M) 2- to 3-fold over water-injected oocytes, whereas the alternative skate liver organic anion transporter, the dimeric Ost{alpha}/{beta}, exhibited no phalloidin and only minor microcystin-LR transport. Also, the closest mammalian Oatp1d1 orthologue, the human brain and testis OATP1C1, did not show any phalloidin transport activity. These results demonstrate that the evolutionarily ancient Oatp1d1 is able to mediate uptake of cyclic oligopeptide toxins into skate liver. The findings support the notion that Oatp1d1 is a precursor of the liver-specific mammalian Oatps/OATPs and that its transport properties are closely associated with certain forms of toxic liver injury such as for example protein phosphatase inhibition by the water-borne toxin microcystin.

  16. Non-thermal distribution of O(1D) atoms in the night-time thermosphere

    NASA Technical Reports Server (NTRS)

    Yee, Jeng-Hwa

    1988-01-01

    The 6300 A O(1D-3P) emission has been used for many years to remotely monitor the thermospheric temperature from the Doppler width of its line profile. The O(1D) atoms in the nighttime thermosphere are initially produced by the dissociative recombination of O2(+) ions with kinetic energy much greater than the thermal energy of the ambient neutrals. The validity of the technique to monitor neutral ambient temperature by measuring O(1D) 6300 A emission depends on the degree of thermalization of the O(1D) atoms. The object of this study is to calculate the velocity distribution of the O(1D) atoms and to examine the effect of nonthermal distribution on the nighttime thermospheric neutral temperature determined.

  17. Electronic properties and STM images of vacancy clusters and chains in functionalized silicene and germanene

    NASA Astrophysics Data System (ADS)

    Jamdagni, Pooja; Kumar, Ashok; Sharma, Munish; Thakur, Anil; Ahluwalia, P. K.

    2017-01-01

    Electronic properties and STM topographical images of X (=F, H, O) functionalized silicene and germanene have been investigated by introducing various kind of vacancy clusters and chain patterns in monolayers within density functional theory (DFT) framework. The relative ease of formation of vacancy clusters and chain patterns is found to be energetically most favorable in hydrogenated silicene and germanene. F- and H-functionalized silicene and germanene are direct bandgap semiconducting with bandgap ranging between 0.1-1.9 eV, while O-functionalized monolayers are metallic in nature. By introducing various vacancy clusters and chain patterns in both silicene and germanene, the electronic and magnetic properties get modified in significant manner e.g. F- and H-functionalized silicene and germanene with hexagonal and rectangle vacancy clusters are non-magnetic semiconductors with modified bandgap values while pentagonal and triangle vacancy clusters induce metallicity and magnetic character in monolayers; hexagonal vacancy chain patterns induce direct-to-indirect gap transition while zigzag vacancy chain patterns retain direct bandgap nature of monolayers. Calculated STM topographical images show distinctly different characteristics for various type of vacancy clusters and chain patterns which may be used as electronic fingerprints to identify various vacancy patterns in silicene and germanene created during the process of functionalization.

  18. Laser amplifier chain

    DOEpatents

    Hackel, Richard P.

    1992-01-01

    A laser amplifier chain has a plurality of laser amplifiers arranged in a chain to sequentially amplify a low-power signal beam to produce a significantly higher-power output beam. Overall efficiency of such a chain is improved if high-gain, low efficiency amplifiers are placed on the upstream side of the chain where only a very small fraction of the total pumped power is received by the chain and low-gain, high-efficiency amplifiers are placed on the downstream side where a majority of pumping energy is received by the chain.

  19. Laser amplifier chain

    DOEpatents

    Hackel, R.P.

    1992-10-20

    A laser amplifier chain has a plurality of laser amplifiers arranged in a chain to sequentially amplify a low-power signal beam to produce a significantly higher-power output beam. Overall efficiency of such a chain is improved if high-gain, low efficiency amplifiers are placed on the upstream side of the chain where only a very small fraction of the total pumped power is received by the chain and low-gain, high-efficiency amplifiers are placed on the downstream side where a majority of pumping energy is received by the chain. 6 figs.

  20. The FC-1D: The profitable alternative Flying Circus Commercial Aviation Group

    NASA Technical Reports Server (NTRS)

    Meza, Victor J.; Alvarez, Jaime; Harrington, Brook; Lujan, Michael A.; Mitlyng, David; Saroughian, Andy; Silva, Alex; Teale, Tim

    1994-01-01

    The FC-1D was designed as an advanced solution for a low cost commercial transport meeting or exceeding all of the 1993/1994 AIAA/Lockheed request for proposal requirements. The driving philosophy behind the design of the FC-1D was the reduction of airline direct operating costs. Every effort was made during the design process to have the customer in mind. The Flying Circus Commercial Aviation Group targeted reductions in drag, fuel consumption, manufacturing costs, and maintenance costs. Flying Circus emphasized cost reduction throughout the entire design program. Drag reduction was achieved by implementation of the aft nacelle wing configuration to reduce cruise drag and increase cruise speeds. To reduce induced drag, rather than increasing the wing span of the FC-1D, spiroids were included in the efficient wing design. Profile and friction drag are reduced by using riblets in place of paint around the fuselage and empennage of the FC-1D. Choosing a single aisle configuration enabled the Flying Circus to optimize the fuselage diameter. Thus, reducing fuselage drag while gaining high structural efficiency. To further reduce fuel consumption a weight reduction program was conducted through the use of composite materials. An additional quality of the FC-1D is its design for low cost manufacturing and assembly. As a result of this design attribute, the FC-1D will have fewer parts which reduces weight as well as maintenance and assembly costs. The FC-1D is affordable and effective, the apex of commercial transport design.

  1. Structure and Catalytic Mechanism of Human Steroid 5-Reductase (AKR1D1)

    SciTech Connect

    Costanzo, L.; Drury, J; Christianson, D; Penning, T

    2009-01-01

    Human steroid 5{beta}-reductase (aldo-keto reductase (AKR) 1D1) catalyzes reduction of {Delta}{sup 4}-ene double bonds in steroid hormones and bile acid precursors. We have reported the structures of an AKR1D1-NADP{sup +} binary complex, and AKR1D1-NADP{sup +}-cortisone, AKR1D1-NADP{sup +}-progesterone and AKR1D1-NADP{sup +}-testosterone ternary complexes at high resolutions. Recently, structures of AKR1D1-NADP{sup +}-5{beta}-dihydroprogesterone complexes showed that the product is bound unproductively. Two quite different mechanisms of steroid double bond reduction have since been proposed. However, site-directed mutagenesis supports only one mechanism. In this mechanism, the 4-pro-R hydride is transferred from the re-face of the nicotinamide ring to C5 of the steroid substrate. E120, a unique substitution in the AKR catalytic tetrad, permits a deeper penetration of the steroid substrate into the active site to promote optimal reactant positioning. It participates with Y58 to create a 'superacidic' oxyanion hole for polarization of the C3 ketone. A role for K87 in the proton relay proposed using the AKR1D1-NADP{sup +}-5{beta}-dihydroprogesterone structure is not supported.

  2. Unusual Transformation from a Solvent-Stabilized 1D Coordination Polymer to a Metal-Organic Framework (MOF)-Like Cross-Linked 3D Coordination Polymer.

    PubMed

    Lee, Seung-Chul; Choi, Eun-Young; Lee, Sang-Beom; Kim, Sang-Wook; Kwon, O-Pil

    2015-10-26

    An unusual 1D-to-3D transformation of a coordination polymer based on organic linkers containing highly polar push-pull π-conjugated side chains is reported. The coordination polymers are synthesized from zinc nitrate and an organic linker, namely, 2,5-bis{4-[1-(4-nitrophenyl)pyrrolidin-2-yl]butoxy}terephthalic acid, which possesses highly polar (4-nitrophenyl)pyrrolidine groups, with high dipole moments of about 7 D. The coordination polymers exhibit an unusual transformation from a soluble, solvent-stabilized 1D coordination polymer into an insoluble, metal-organic framework (MOF)-like 3D coordination polymer. The coordination polymer exhibits good film-forming ability, and the MOF-like films are insoluble in conventional organic solvents.

  3. Isostructural 1D coordination polymers of Zn(II), Cd(II) and Cu(II) with phenylpropynoic acid and DABCO as organic linkers

    NASA Astrophysics Data System (ADS)

    Saravanakumar, Rajendran; Varghese, Babu; Sankararaman, Sethuraman

    2014-11-01

    Using phenylpropynoic acid (PPA) and 1,4-diazabicyclo[2.2.2]octane (DABCO) as organic spacers, isostructural coordination polymers of Zn(II), Cd(II) and Cu(II) were synthesized by solvothermal method and structurally characterized using single crystal XRD, powder XRD, 13C CP-MAS NMR spectroscopy. Single crystal XRD data revealed four PPA units coordinating with two metal ions forming a paddle wheel secondary building unit (SBU). The paddle wheel units are connected through coordination of DABCO nitrogen to the metal centers from the axial positions leading to the formation of the 1D coordination polymers along the c axis. Intermolecular π stacking and Csbnd H…π interactions between the adjacent polymer chains convert the 1D coordination polymer into an interesting 3D network with the Csbnd H…π bonds running along the crystallographic a and b axes. Thermal and nitrogen adsorption studies of these coordination polymers are reported.

  4. Design and synthesis of new 1D and 2D R-isophthalic acid-based coordination polymers (R = hydrogen or bromine).

    PubMed

    Zhang, Ren; Gong, Qihan; Emge, Thomas J; Banerjee, Debasis; Li, Jing

    2013-01-01

    Three new R-isophthalic acid-based (R = H or Br) coordination polymers have been designed and synthesized. By changing the N-containing ligand in the system, we are able to tune the dimensionality of coordination polymers from one-dimension (1D) to two-dimensions (2D) with the same basic building unit. Also, different metal ions can be incorporated into the same structures. Compound 1 [Cu(bipa)(py)2]·0.5(H2O) (H2bipa = 5-bromoisophthalic acid; py = pyridine) and compound 2 [Co(bipa)(py)2] are 1D chain structures. Compound 3 [Cu8(ipa)8(bpe)8]·2(bpe)·4(H2O) (bpe=1,2-bis(4-pyridyl)ethane) is a 2D layered structure.

  5. Instability and charge density wave of metallic quantum chains on a silicon surface

    SciTech Connect

    Yeom, H.W.; Takeda, S.; Rotenberg, E.; Matsuda, I.; Horikoshi, K.; Schaefer, J.; Lee, C.M.; Kevan, S.D.; Ohta, T.; Nagao, T.; Hasegawa, S.

    1999-06-14

    Self-assembled indium linear chains on the Si(111) surface are found to exhibit instability of the metallic phase and 1D charge density wave (CDW). The room-temperature metallic phase of these chains undergoes a temperature-induced, reversible transition into a semiconducting phase. The 1D CDW along the chains is observed directly in real space by scanning tunneling microscopy at low temperature. The Fermi contours of the metallic phase measured by angle-resolved photoemission exhibit a perfect nesting predicting precisely the CDW periodicity.

  6. On the Current Drive Capability of Low Dimensional Semiconductors: 1D versus 2D

    NASA Astrophysics Data System (ADS)

    Zhu, Y.; Appenzeller, J.

    2015-10-01

    Low-dimensional electronic systems are at the heart of many scaling approaches currently pursuit for electronic applications. Here, we present a comparative study between an array of one-dimensional (1D) channels and its two-dimensional (2D) counterpart in terms of current drive capability. Our findings from analytical expressions derived in this article reveal that under certain conditions an array of 1D channels can outperform a 2D field-effect transistor because of the added degree of freedom to adjust the threshold voltage in an array of 1D devices.

  7. On the Current Drive Capability of Low Dimensional Semiconductors: 1D versus 2D.

    PubMed

    Zhu, Y; Appenzeller, J

    2015-12-01

    Low-dimensional electronic systems are at the heart of many scaling approaches currently pursuit for electronic applications. Here, we present a comparative study between an array of one-dimensional (1D) channels and its two-dimensional (2D) counterpart in terms of current drive capability. Our findings from analytical expressions derived in this article reveal that under certain conditions an array of 1D channels can outperform a 2D field-effect transistor because of the added degree of freedom to adjust the threshold voltage in an array of 1D devices.

  8. GaAs solar cell photoresponse modeling using PC-1D V2.1

    NASA Technical Reports Server (NTRS)

    Huber, D. A.; Olsen, L. C.; Dunham, G.; Addis, F. W.

    1991-01-01

    Photoresponse data of high efficiency GaAs solar cells were analyzed using PC-1D V2.1. The approach required to use PC-1D for photoresponse data analysis, and the physical insights gained from performing the analysis are discussed. In particular, the effect of Al(x)Ga(1-x)As heteroface quality was modeled. Photoresponse or spectral quantum efficiency is an important tool in characterizing material quality and predicting cell performance. The strength of the photoresponse measurement lies in the ability to precisely fit the experimental data with a physical model. PC-1D provides a flexible platform for calculations based on these physical models.

  9. On the current drive capability of low dimensional semiconductors: 1D versus 2D

    SciTech Connect

    Zhu, Y.; Appenzeller, J.

    2015-10-29

    Low-dimensional electronic systems are at the heart of many scaling approaches currently pursuit for electronic applications. Here, we present a comparative study between an array of one-dimensional (1D) channels and its two-dimensional (2D) counterpart in terms of current drive capability. Lastly, our findings from analytical expressions derived in this article reveal that under certain conditions an array of 1D channels can outperform a 2D field-effect transistor because of the added degree of freedom to adjust the threshold voltage in an array of 1D devices.

  10. Chiral spin liquids in arrays of spin chains

    NASA Astrophysics Data System (ADS)

    Gorohovsky, Gregory; Pereira, Rodrigo G.; Sela, Eran

    2015-06-01

    We describe a coupled-chain construction for chiral spin liquids in two-dimensional spin systems. Starting from a one-dimensional zigzag spin chain and imposing SU(2) symmetry in the framework of non-Abelian bosonization, we first show that our approach faithfully describes the low-energy physics of an exactly solvable model with a three-spin interaction. Generalizing the construction to the two-dimensional case, we obtain a theory that incorporates the universal properties of the chiral spin liquid predicted by Kalmeyer and Laughlin: charge-neutral edge states, gapped spin-1/2 bulk excitations, and ground-state degeneracy on the torus signaling the topological order of this quantum state. In addition, we show that the chiral spin liquid phase is more easily stabilized in frustrated lattices containing corner-sharing triangles, such as the extended kagome lattice, than in the triangular lattice. Our field-theoretical approach invites generalizations to more exotic chiral spin liquids and may be used to assess the existence of the chiral spin liquid as the ground state of specific lattice systems.

  11. Ubiquitination and degradation of the hominoid-specific oncoprotein TBC1D3 is regulated by protein palmitoylation

    SciTech Connect

    Kong, Chen; Lange, Jeffrey J.; Samovski, Dmitri; Su, Xiong; Liu, Jialiu; Sundaresan, Sinju; Stahl, Philip D.

    2013-05-03

    Highlights: •Hominoid-specific oncogene TBC1D3 is targeted to plasma membrane by palmitoylation. •TBC1D3 is palmitoylated on two cysteine residues: 318 and 325. •TBC1D3 palmitoylation governs growth factors-induced TBC1D3 degradation. •Post-translational modifications may regulate oncogenic properties of TBC1D3. -- Abstract: Expression of the hominoid-specific oncoprotein TBC1D3 promotes enhanced cell growth and proliferation by increased activation of signal transduction through several growth factors. Recently we documented the role of CUL7 E3 ligase in growth factors-induced ubiquitination and degradation of TBC1D3. Here we expanded our study to discover additional molecular mechanisms that control TBC1D3 protein turnover. We report that TBC1D3 is palmitoylated on two cysteine residues: 318 and 325. The expression of double palmitoylation mutant TBC1D3:C318/325S resulted in protein mislocalization and enhanced growth factors-induced TBC1D3 degradation. Moreover, ubiquitination of TBC1D3 via CUL7 E3 ligase complex was increased by mutating the palmitoylation sites, suggesting that depalmitoylation of TBC1D3 makes the protein more available for ubiquitination and degradation. The results reported here provide novel insights into the molecular mechanisms that govern TBC1D3 protein degradation. Dysregulation of these mechanisms in vivo could potentially result in aberrant TBC1D3 expression and promote oncogenesis.

  12. Quantum and semi-classical transport in RTDs using NEMO 1-D

    NASA Technical Reports Server (NTRS)

    Klimeck, G.; Stout, P.; Bowen, R. C.

    2003-01-01

    NEMO 1-D has been developed primarily for the simulation of resonant tunneling diodes, and quantitative and predictive agreements with experimental high performance, high current density devices have been achieved in the past.

  13. Vorticity and Λ polarization in event-by-event (3+1)D viscous hydrodynamics

    NASA Astrophysics Data System (ADS)

    Pang, Long-Gang; Fang, Ren-Hong; Petersen, Hannah; Wang, Qun; Wang, Xin-Nian

    2017-01-01

    We visualized the vortical fluid in fluctuating QGP using (3+1)D viscous hydrodynamics, computed the spin distribution and correlation of hyperons and estimated the polarization splitting between Λ and .

  14. Quasi-one dimensional (Q1D) nanostructures: Synthesis, integration and device application

    NASA Astrophysics Data System (ADS)

    Chien, Chung-Jen

    Quasi-one-dimensional (Q1D) nanostructures such as nanotubes and nanowires have been widely regarded as the potential building blocks for nanoscale electronic, optoelectronic and sensing devices. In this work, the content can be divided into three categories: Nano-material synthesis and characterizations, alignment and integration, physical properties and application. The dissertation consists of seven chapters as following. Chapter 1 will give an introduction to low dimensional nano-materials. Chapter 2 explains the mechanism how Q1D nanostructure grows. Chapter 3 describes the methods how we horizontally and vertically align the Q1D nanostructure. Chapter 4 and 5 are the electrical and optical device characterization respectively. Chapter 6 demonstrates the integration of Q1D nanostructures and the device application. The last chapter will discuss the future work and conclusion of the thesis.

  15. Ruthenium and osmium complexes of hemilabile chiral monophosphinite ligands derived from 1D-pinitol or 1D-chiro-inositol as catalysts for asymmetric hydrogenation reactions.

    PubMed

    Slade, Angela T; Lensink, Cornelis; Falshaw, Andrew; Clark, George R; Wright, L James

    2014-12-07

    The monophosphinite ligands, 1D-1,2;5,6-di-O-cyclopentylidene-3-O-methyl-4-O-diphenylphosphino-chiro-inositol (D-P1), 1D-1,2;5,6-di-O-isopropylidene-3-O-methyl-4-O-diphenylphosphino-chiro-inositol (D-P2), 1D-1,2;5,6-di-O-cyclohexylidene-3-O-methyl-4-O-diphenylphosphino-chiro-inositol (D-P3), and 1D-1,2;5,6-di-O-cyclopentylidene-3-O-ethyl-4-O-diphenylphosphino-chiro-inositol (D-P4), can be conveniently prepared from the chiral natural products 1D-pinitol or 1D-chiro-inositol. On treatment of toluene solutions of RuCl2(PPh3)3 with two mole equivalents of the ligands D-PY (Y = 1-4) the complexes RuCl2(D-P1)2 (1), RuCl2(D-P2)2 (4), RuCl2(D-P3)2 (5), or RuCl2(D-P4)2 (6), respectively, are formed. Similarly, treatment of OsCl2(PPh3)3 with D-P1 gives OsCl2(D-P1)2 (7). The single crystal X-ray structure determination of 1 reveals that each D-P1 ligand coordinates to ruthenium through phosphorus and the oxygen atom of the methoxyl group. Treatment of 1 with excess LiBr or LiI results in metathesis of the chloride ligands and RuBr2(D-P1)2 (2) or RuI2(D-P1)2 (3), respectively, are formed. Exposure of a solution of 1 to carbon monoxide results in the very rapid formation of RuCl2(CO)2(D-P1)2 (8), thereby demonstrating the ease with which the oxygen donors are displaced from the metal and hence the hemilabile nature of the two bidentate D-P1 ligands in 1. Preliminary studies indicate that 1-7 act as catalysts for the asymmetric hydrogenation reactions of acetophenone and 3-quinuclidinone to give the corresponding alcohols in generally high conversions but low enantiomeric excesses.

  16. Actinometric measurement of j(O3-O(1D)) using a luminol detector

    NASA Technical Reports Server (NTRS)

    Bairai, Solomon T.; Stedman, Donald H.

    1992-01-01

    The photolysis frequency of ozone to singlet D oxygen atoms has been measured by means of a chemical actinometer using a luminol based detector. The instrument measures j(O3-O(1D)) with a precision of 10 percent. The data collected in winter and spring of 1991 is in agreement with model predictions and previously measured values. Data from a global solar radiometer can be used to estimate the effects of local cloudiness on j(O3-O(1D)).

  17. Structural resistance of chemically modified 1-D nanostructured titanates in inorganic acid environment

    SciTech Connect

    Marinkovic, Bojan A.; Fredholm, Yann C.; Morgado, Edisson

    2010-10-15

    Sodium containing one-dimensional nanostructured layered titanates (1-D NSLT) were produced both from commercial anatase powder and Brazilian natural rutile mineral sands by alkali hydrothermal process. The 1-D NSLT were chemically modified with proton, cobalt or iron via ionic exchange and all products were additionally submitted to intensive inorganic acid aging (pH = 0.5) for 28 days. The morphology and crystal structure transformations of chemically modified 1-D NSLT were followed by transmission electron microscopy, powder X-ray diffraction, selected area electron diffraction and energy dispersive spectroscopy. It was found that the original sodium rich 1-D NSLT and cobalt substituted 1-D NSLT were completely converted to rutile nanoparticles, while the protonated form was transformed in a 70%-30% (by weight) anatase-rutile nanoparticles mixture, very similar to that of the well-known TiO{sub 2}-photocatalyst P25 (Degussa). The iron substituted 1-D NSLT presented better acid resistance as 13% of the original structure and morphology remained, the rest being converted in rutile. A significant amount of remaining 1-D NSLT was also observed after the acid treatment of the product obtained from rutile sand. The results showed that phase transformation of NSLT into titanium dioxide polymorph in inorganic acid conditions were controllable by varying the exchanged cations. Finally, the possibility to transform, through acid aging, 1-D NSLT obtained from Brazilian natural rutile sand into TiO{sub 2}-polymorphs was demonstrated for the first time to the best of authors' knowledge, opening path for producing TiO{sub 2}-nanoproducts with different morphologies through a simple process and from a low cost precursor.

  18. 1D-Var assimilation of TMI and SSM/I observations in rainy areas

    NASA Astrophysics Data System (ADS)

    Moreau, E.; Lopez, P.; Bauer, P.

    2003-04-01

    The assimilation of observations related to cloud and precipitation has become a very important issue for most operational weather services including ECMWF. A 1D-Var method was developed by Marécal and Mahfouf (2000) for correcting individual profiles of the model's control variables in order to decrease the discrepancies that often exist between the simulated surface rainfall rates and corresponding retrievals obtained from TMI or SSM/I microwave measurements. Instead of performing the 1D-Var on surface rainfall rates that are derived from multi-channel microwave brightness temperatures (BTs) thanks to various algorithms, the 1D-Var calculations have been applied to the BTs directly. The multiple sensitivities of the BTs to the vertically integrated amounts of rain water and cloud water should provide a stronger constraint on the 1D-Var minimization. Another advantage of this method could result from the better knowledge of the errors on observed BTs than on derived rainfall rates. The potential of applying 1D-Var directly to TMI and SSM/I microwave brightness temperatures has been investigated in this study and its results have been compared with the 1D-Var with derived rainfall rates. Results are presented for a pacific super-typhoon and for a north-atlantic extratropical front. A comparison of the retrieved rain profiles using both methods with rain information deduced from the TRMM precipitation radar (PR) is also presented. Additional direct comparisons with the PR reflectivities will be shown by A. Benedetti (2003). Following the work by Marécal and Mahfouf (2002), indirect "1D-Var + 4D-Var" assimilation experiments will be performed. In this approach, the temperature and humidity increments provided by the 1D-Var are first converted into total column water vapour pseudo-observations that are in turn assimilated in ECMWF's 4D-Var system.

  19. Coherent Synchrotron Radiation and Space Charge for a 1-D Bunch on an Arbitrary Planar Orbit

    SciTech Connect

    Warnock, R.L.; /SLAC

    2008-01-08

    Realistic modeling of coherent synchrotron radiation (CSR) and the space charge force in single-pass systems and rings usually requires at least a two-dimensional (2-D) description of the charge/current density of the bunch. Since that leads to costly computations, one often resorts to a 1-D model of the bunch for first explorations. This paper provides several improvements to previous 1-D theories, eliminating unnecessary approximations and physical restrictions.

  20. Energy dependent 3-body loss in out-of-equilibrium 1D Bose gases

    NASA Astrophysics Data System (ADS)

    Zundel, Laura; Xia, Lin; Wilson, Joshua; Riou, Jean-Felix; Weiss, David

    2015-05-01

    We measure the three-body loss of out-of-equilibrium one-dimensional (1D) Bose gases and find that it depends strongly on the average energy of the distribution. The theory of three-body loss in 1D gas experiments is incomplete due to the challenge of calculating how correlations evolve. We present an empirical model based on energy dependent correlations and show that it reproduces the data.

  1. Epigenetic activation of a cryptic TBC1D16 transcript enhances melanoma progression by targeting EGFR

    PubMed Central

    Vizoso, Miguel; Ferreira, Humberto J; Lopez-Serra, Paula; Javier Carmona, F; Martínez-Cardús, Anna; Girotti, Maria Romina; Villanueva, Alberto; Guil, Sonia; Moutinho, Catia; Liz, Julia; Portela, Anna; Heyn, Holger; Moran, Sebastian; Vidal, August; Martinez-Iniesta, Maria; Manzano, Jose L; Fernandez-Figueras, Maria Teresa; Elez, Elena; Muñoz-Couselo, Eva; Botella-Estrada, Rafael; Berrocal, Alfonso; Pontén, Fredrik; van den Oord, Joost; Gallagher, William M; Frederick, Dennie T; Flaherty, Keith T; McDermott, Ultan; Lorigan, Paul; Marais, Richard; Esteller, Manel

    2016-01-01

    Metastasis is responsible for most cancer-related deaths, and, among common tumor types, melanoma is one with great potential to metastasize. Here we study the contribution of epigenetic changes to the dissemination process by analyzing the changes that occur at the DNA methylation level between primary cancer cells and metastases. We found a hypomethylation event that reactivates a cryptic transcript of the Rab GTPase activating protein TBC1D16 (TBC1D16-47 kDa; referred to hereafter as TBC1D16-47KD) to be a characteristic feature of the metastatic cascade. This short isoform of TBC1D16 exacerbates melanoma growth and metastasis both in vitro and in vivo. By combining immunoprecipitation and mass spectrometry, we identified RAB5C as a new TBC1D16 target and showed that it regulates EGFR in melanoma cells. We also found that epigenetic reactivation of TBC1D16-47KD is associated with poor clinical outcome in melanoma, while conferring greater sensitivity to BRAF and MEK inhibitors. PMID:26030178

  2. Controlled Growth of 1D MoSe2 Nanoribbons with Spatially Modulated Edge States.

    PubMed

    Cheng, Fang; Xu, Hai; Xu, Wentao; Zhou, Pinjia; Martin, Jens; Loh, Kian Ping

    2017-02-08

    Two-dimensional (2D) transition metal dichalcogenides (TMDCs) possess interesting one-dimensional (1D) properties at its edges and inversion domain boundaries, where properties markedly different from the 2D basal plane, such as 1D metallicity and charge density waves, can be observed. Although 2D TMDCs crystals are widely grown by chemical vapor deposition (CVD), the fabrication of 1D TMDCs ribbons is challenging due to the difficulty to confine growth in only one dimension. Here we report the controlled growth of MoSe2 nanoribbons with an aspect ratio >100 by using prepatterned Se reconstructions on Au(100). Using scanning tunneling microscope and spectroscopy (STM/STS), the atomic and electronic structure of MoSe2 nanoribbons are studied. The ultranarrow ribbons show metallic behavior, while wider ribbons show a crossover from metallic to semiconducting behavior going from the edge to the center of the ribbon. The observed conductance modulations of the ultranarrow ribbons are attributed to 1D Moiré pattern. Remarkably, it shows a different periodicity compared with the 2D Moiré pattern in wider ribbons indicating that the 1D system is softened due to the high ratio of edge to basal plane bonds. Further, we demonstrated that the nanoribbons are stable against ambient conditions, which suggests that 1D TMDCs can be exploited for further applications.

  3. The structure of nanocomposite 1D cationic conductor crystal@SWNT.

    PubMed

    Kiselev, N A; Kumskov, A S; Zakalyukin, R M; Vasiliev, A L; Chernisheva, M V; Eliseev, A A; Krestinin, A V; Freitag, B; Hutchison, J L

    2012-06-01

    Nanocomposites consisting of one-dimensional (1D) crystals of the cationic conductors CuI, CuBr and AgBr inside single-walled carbon nanotubes, mainly (n, 0), were obtained using the capillary technique. 1D crystal structure models were proposed based on the high resolution transmission electron microscopy performed on a FEI Titan 80-300 at 80 kV with aberration correction. According to the models and image simulations there are two modifications of 1D crystal: hexagonal close-packed bromine (iodine) anion sublattice (growth direction <001>) and 1D crystal cubic structure (growth direction <112>) compressed transversely to the nanotube (D(m) ∼1.33 nm) axis. Tentatively this kind of 1D crystal can be considered as monoclinic. One modification of the anion sublattice reversibly transforms into the other inside the nanotube, probably initiated by electron beam heating. As demonstrated by micrographs, copper or silver cations can occupy octahedral positions or are statistically distributed across two tetrahedral positions. A 1DAgBr@SWNT (18, 0; 19, 0) pseudoperiodic 'lattice distortion' is revealed resulting from convolution of the nanotube wall function image with 1D cubic crystal function image.

  4. PPM1D controls nucleolar formation by up-regulating phosphorylation of nucleophosmin

    PubMed Central

    Kozakai, Yuuki; Kamada, Rui; Furuta, Junya; Kiyota, Yuhei; Chuman, Yoshiro; Sakaguchi, Kazuyasu

    2016-01-01

    An increase of nucleolar number and size has made nucleoli essential markers for cytology and tumour development. However, the underlying basis for their structural integrity and abundance remains unclear. Protein phosphatase PPM1D was found to be up-regulated in different carcinomas including breast cancers. Here, we demonstrate for the first time that PPM1D regulates nucleolar formation via inducing an increased phosphorylation of the nucleolar protein NPM. We show that PPM1D overexpression induces an increase in the nucleolar number regardless of p53 status. We also demonstrated that specific sequential phosphorylation of NPM is important for nucleolar formation and that PPM1D is a novel upstream regulator of this phosphorylation pathway. These results enhance our understanding of the molecular mechanisms that govern nucleoli formation by demonstrating that PPM1D regulates nucleolar formation by regulating NPM phosphorylation status through a novel signalling pathway, PPM1D-CDC25C-CDK1-PLK1. PMID:27619510

  5. A spin-Seebeck diode with a negative differential spin-Seebeck effect in a hydrogen-terminated zigzag silicene nanoribbon heterojunction.

    PubMed

    Fu, Hua-Hua; Gu, Lei; Wu, Dan-Dan

    2016-05-14

    The spin-Seebeck effect (SSE), the central topic of spin caloritronics, provides a new direction for future low power consumption technology. To realize device applications of SSE, a spin-Seebeck diode (SSD) with a negative differential SSE is very desirable. To this end, we constructed a spin caloritronics device that was composed of a ferromagnetic double-single-hydrogen-terminated zigzag silicene nanoribbon (ZSiNR-H2-H) and an antiferromagnetic double-double-hydrogen-terminated zigzag silicene nanoribbon (ZSiNR-H2-H2). By using ab initio calculations combined with nonequilibrium Green's function technique, we found that thermally driven spin current through the heterojunction featured the SSD effect and negative differential SSE. The former originates from the asymmetrical thermal-driven conducting electrons and holes, and the latter ascribes to the thermal spin compensation effect. Their physical mechanisms are much different from the previous ones mainly relying on the spin-wave excitations in the interface between metals and magnetic insulators, supporting our study that puts forward a new route to realize the SSD with a negative differential SSE.

  6. Liquid crystalline and solid phases for a system of hard zigzag particles with Lennard-Jones sites in two-dimensions

    NASA Astrophysics Data System (ADS)

    Lechuga-Sanabria, Fidelmar; Chapela, Gustavo A.; Quintana-H, Jacqueline

    2013-10-01

    The map of low and high density phases of an idealized system, the infinitely hard zigzag line model with two Lennard-Jones (LJ) sites is presented. LJ sites are added to a previous model composed of the infinitely hard zigzag line shape particles, R.A. Perusqía, J. Peón, J. Quintana, Physica A 345 (1) (2005) 130-142. The attractions and the molecular volume added to this system through the LJ sites create a more realistic model and, as a consequence, a richer phase behavior is obtained. Although the volume of the LJ sites is quite small it is enough to produce solid phases, absent in the original model. On the other hand the smectic phase that was present in the hard system was not found in this case. Two molecular conformations are chosen to provide a comparison with the previous model. The isothermal-isobaric is used to establish the thermodynamic regions of the different molecular self aggregations and to compare them to already published results.

  7. Gushing metal chain

    NASA Astrophysics Data System (ADS)

    Belyaev, Alexander; Sukhanov, Alexander; Tsvetkov, Alexander

    2016-03-01

    This article addresses the problem in which a chain falls from a glass from some height. This phenomenon demonstrates a paradoxical rise of the chain over the glass. To explain this effect, an initial hypothesis and an appropriate theory are proposed for calculating the steady fall parameters of the chain. For this purpose, the modified Cayley's problem of falling chain given its rise due to the centrifugal force of upward inertia is solved. Results show that the lift caused by an increase in linear density at the part of chain where it is being bent (the upper part) is due to the convergence of the chain balls to one another. The experiments confirm the obtained estimates of the lifting chain.

  8. Kinetics of O(1D) + H2O and O(1D) + H2: absolute rate coefficients and O(3P) yields between 227 and 453 K.

    PubMed

    Vranckx, Stijn; Peeters, Jozef; Carl, Shaun

    2010-08-28

    The rate coefficients for the crucial atmospheric reactions of O((1)D) with H(2)O and H(2), k(1) and k(2), were measured over a wide temperature range using O((1)D) detection based on the chemiluminescence reaction of O((1)D) with C(2)H. Analyzing the decays of the chemiluminescence intensities yielded a value for k(1)(T) of (1.70 x 10(-10)exp[36 K/T]) cm(3) s(-1). Multiplying or dividing k(1)(T) by a factor f(T) = 1.04 exp(5.59(|1 K/T- 1/287|)), gives the 95% confidence limits; our new determination, in good agreement with previous studies, further reduces the uncertainty in k(1). An extended study of k(2) yielded a temperature independent rate constant of (1.35 +/- 0.05) x 10(-10) cm(3) s(-1). This precise value, based on an extended set of determinations with very low scatter, is significantly larger than the current recommendations, as were two other recent k(2) determinations. Secondly, the fractions of O((1)D) quenched to O((3)P) by H(2)O and H(2), k(1b)/k(1) and k(2b)/k(2), were precisely determined from fits to chemiluminescence decays. A temperature-independent value for k(1b)/k(1) of 0.010 +/- 0.003 was found. For the quenching fraction k(2b)/k(2) a value of 0.007 +/- 0.007 was obtained at room temperature. Both determinations are significantly smaller than values and upper limits from previous studies.

  9. Synthesis, structure and magnetic properties of 5-(4-Sulfophenylazo) salicylate-bridged 1D coordination polymers containing linear trinuclear metal clusters

    NASA Astrophysics Data System (ADS)

    Liu, Hong; Song, Li-jun; Ju, Zhan-feng; Li, Wei; Zhang, Jie

    2008-03-01

    Three new trinuclear metal complexes with an azobenzene-containing ligand [M 3(Sasa) 2(Py) 2(H 2O) 8] (Na 2HSasa = 5-(4-Sulfophenylazo) salicylic acid disodium salt; Py = pyridine; M = Cu, Co, Zn), are synthesized through the interface diffusion and structurally characterized by single crystal X-ray diffraction, XRPD analysis and spectral methods. The metal ions in distorted octahedral coordination environments are connected by Sasa ligands to form 1D coordination polymer chain containing the linear trinuclear units with single syn-anti carboxylate bridges. The extensive hydrogen bonding interactions hold these chains together into 3D supramolecular network. Weak antiferromagnetic interactions between adjacent metal ions with J = -1.85 cm -1 and J = -2.81 cm -1 dominate the magnetic properties of Cu(II) and Co(II) complexes, separately.

  10. Magnetic relaxation of 1D coordination polymers (X)₂[Mn(acacen)Fe(CN)₆], X = Ph₄P⁺, Et₄N⁺.

    PubMed

    Rams, Michał; Peresypkina, Eugenia V; Mironov, Vladimir S; Wernsdorfer, Wolfgang; Vostrikova, Kira E

    2014-10-06

    Substitution of the organic cation X in the 1D polymer, (X)2[Mn(acacen)Fe(CN)6], leads to an essential change in magnetic behavior. Due to the presence of more voluminous Ph4P(+) cations, the polyanion has a more geometrically distorted chain skeleton and, as a consequence, enhanced single chain magnet (SCM) characteristics compared to those for Et4N(+). The Arrhenius relaxation energy barriers, the exchange interaction constant and the zero-field splitting anisotropy of Mn(III) are determined from the analysis of magnetic measurements. The discussion is supported with ligand field calculations for [Fe(CN)6](3-) that unveils the significant anisotropy of Fe magnetic moments.

  11. Addimer chain structures: Metastable precursors to island formation on Ge Si(0 0 1)-(2 × n) alloyed surface

    NASA Astrophysics Data System (ADS)

    Solis, Kyle J.; Williams, Lance R.; Swartzentruber, B. S.; Han, Sang M.

    2007-01-01

    We have identified addimer chain structures as metastable precursors to compact epitaxial islands on the (2 × n) reconstructed SiGe wetting layer, using polarity-switching scanning tunneling microscopy (STM). These chain structures are comprised of 2-12 addimers residing in the troughs of neighboring substrate dimer rows. The chain structures extend along equivalent <1 3 0> directions across the substrate dimer rows in a zigzag fashion, giving rise to kinked and straight segments. We measure a kink-to-straight ratio of nearly 2:1. This ratio corresponds to a free energy difference of 17 ± 4 meV, favoring the formation of kinked segments. The chain structures convert to compact epitaxial islands at elevated temperatures (⩾90 °C). This conversion suggests that the chain structures are a precursor for compact island formation on the SiGe wetting layer. We digitally process filled- and empty-state STM images to distinguish chain structures from compact islands. By monitoring the populations of both species over time, the chain-to-island conversion rates are measured at substrate temperatures ranging from 90 to 150 °C. The activation energy for the conversion process is measured to be 0.7 ± 0.2 eV with a corresponding pre-exponential factor of 5 × 10 4±2 s -1.

  12. Chain Ends and the Ultimate Tensile Strength of Polyethylene Fibers

    NASA Astrophysics Data System (ADS)

    O'Connor, Thomas C.; Robbins, Mark O.

    Determining the tensile yield mechanisms of oriented polymer fibers remains a challenging problem in polymer mechanics. By maximizing the alignment and crystallinity of polyethylene (PE) fibers, tensile strengths σ ~ 6 - 7 GPa have been achieved. While impressive, first-principal calculations predict carbon backbone bonds would allow strengths four times higher (σ ~ 20 GPa) before breaking. The reduction in strength is caused by crystal defects like chain ends, which allow fibers to yield by chain slip in addition to bond breaking. We use large scale molecular dynamics (MD) simulations to determine the tensile yield mechanism of orthorhombic PE crystals with finite chains spanning 102 -104 carbons in length. The yield stress σy saturates for long chains at ~ 6 . 3 GPa, agreeing well with experiments. Chains do not break but always yield by slip, after nucleation of 1D dislocations at chain ends. Dislocations are accurately described by a Frenkel-Kontorova model, parametrized by the mechanical properties of an ideal crystal. We compute a dislocation core size ξ = 25 . 24 Å and determine the high and low strain rate limits of σy. Our results suggest characterizing such 1D dislocations is an efficient method for predicting fiber strength. This research was performed within the Center for Materials in Extreme Dynamic Environments (CMEDE) under the Hopkins Extreme Materials Institute at Johns Hopkins University. Financial support was provided by Grant W911NF-12-2-0022.

  13. Benchmarks and models for 1-D radiation transport in stochastic participating media

    SciTech Connect

    Miller, David Scott

    2000-08-01

    Benchmark calculations for radiation transport coupled to a material temperature equation in a 1-D slab and 1-D spherical geometry binary random media are presented. The mixing statistics are taken to be homogeneous Markov statistics in the 1-D slab but only approximately Markov statistics in the 1-D sphere. The material chunk sizes are described by Poisson distribution functions. The material opacities are first taken to be constant and then allowed to vary as a strong function of material temperature. Benchmark values and variances for time evolution of the ensemble average of material temperature energy density and radiation transmission are computed via a Monte Carlo type method. These benchmarks are used as a basis for comparison with three other approximate methods of solution. One of these approximate methods is simple atomic mix. The second approximate model is an adaptation of what is commonly called the Levermore-Pomraning model and which is referred to here as the standard model. It is shown that recasting the temperature coupling as a type of effective scattering can be useful in formulating the third approximate model, an adaptation of a model due to Su and Pomraning which attempts to account for the effects of scattering in a stochastic context. This last adaptation shows consistent improvement over both the atomic mix and standard models when used in the 1-D slab geometry but shows limited improvement in the 1-D spherical geometry. Benchmark values are also computed for radiation transmission from the 1-D sphere without material heating present. This is to evaluate the performance of the standard model on this geometry--something which has never been done before. All of the various tests demonstrate the importance of stochastic structure on the solution. Also demonstrated are the range of usefulness and limitations of a simple atomic mix formulation.

  14. The autophagy machinery restrains iNKT cell activation through CD1D1 internalization.

    PubMed

    Keller, Christian W; Loi, Monica; Ewert, Svenja; Quast, Isaak; Theiler, Romina; Gannagé, Monique; Münz, Christian; De Libero, Gennaro; Freigang, Stefan; Lünemann, Jan D

    2017-03-15

    Invariant natural killer T (iNKT) cells are innate T cells with powerful immune regulatory functions that recognize glycolipid antigens presented by the CD1D protein. While iNKT-cell-activating glycolipids are currently being explored for their efficacy to improve immunotherapy against infectious diseases and cancer, little is known about the mechanisms that control CD1D antigen presentation and iNKT cell activation in vivo. CD1D molecules survey endocytic pathways to bind lipid antigens in MHC class II containing compartments (MIICs) before recycling to the plasma membrane. Autophagosomes intersect with MIICs and autophagy-related proteins are known to support antigen loading for increased CD4(+) T cell immunity. Here, we report that mice with dendritic cell (DC)-specific deletion of the essential autophagy gene Atg5 showed better CD1D1-restricted glycolipid presentation in vivo. These effects led to enhanced iNKT cell cytokine production upon antigen recognition and lower bacterial loads during Sphingomonas paucimobilis infection. Enhanced iNKT cell activation was independent of receptor-mediated glycolipid uptake or costimulatory signals. Instead, loss of Atg5 in DCs impaired clathrin-dependent internalization of CD1D1 molecules via the adaptor protein complex 2 (AP2) and, thus, increased surface expression of stimulatory CD1D1-glycolipid complexes. These findings indicate that the autophagic machinery assists in the recruitment of AP2 to CD1D1 molecules resulting in attenuated iNKT cell activation, in contrast to the supporting role of macroautophagy in CD4(+) T cell stimulation.

  15. Benchmarks and models for 1-D radiation transport in stochastic participating media

    NASA Astrophysics Data System (ADS)

    Miller, David Scott

    Benchmark calculations for radiation transport coupled to a material temperature equation in a 1-D slab and 1-D spherical geometry binary random media are presented. The mixing statistics are taken to be homogeneous Markov statistics in the 1-D slab but only approximately Markov statistics in the 1-D sphere. The material chunk sizes are described by Poisson distribution functions. The material opacities are first taken to be constant and then allowed to vary as a strong function of material temperature. Benchmark values and variances for time evolution of the ensemble average of material temperature energy density and radiation transmission are computed via a Monte Carlo type method. These benchmarks are used as a basis for comparison with three other approximate methods of solution. One of these approximate methods is simple atomic mix. The second approximate model is an adaptation of what is commonly called the Levermore-Pomraning model and which is referred to here as the standard model. It is shown that recasting the temperature coupling as a type of effective scattering can be useful in formulating the third approximate model, an adaptation of a model due to Su and Pomraning which attempts to account for the effects of scattering in a stochastic context. This last adaptation shows consistent improvement over both the atomic mix and standard models when used in the 1-D slab geometry but shows limited improvement in the 1-D spherical geometry. Benchmark values are also computed for radiation transmission from the 1-D sphere without material heating present. This is to evaluate the performance of the standard model on this geometry-something which has never been done before. All of the various tests demonstrate the importance of stochastic structure on the solution. Also demonstrated are the range of usefulness and limitations of a simple atomic mix formulation.

  16. Synthesis, crystal structures, magnetic and luminescent properties of unique 1D p-ferrocenylbenzoate-bridged lanthanide complexes

    SciTech Connect

    Yan, P.F.; Zhang, F.M.; Li, G.M.; Zhang, J.W.; Sun, W.B.; Suda, M.; Einaga, Y.

    2009-07-15

    Treatments of p-ferrocenylbenzoate [p-NaOOCH{sub 4}C{sub 6}Fc, Fc=(eta{sup 5}-C{sub 5}H{sub 5})Fe(eta{sup 5}-C{sub 5}H{sub 4})] with Ln(NO{sub 3}){sub 3}.nH{sub 2}O afford seven p-ferrocenylbenzoate lanthanide complexes {l_brace}[Ln(OOCH{sub 4}C{sub 6}Fc){sub 2}(mu{sub 2}-OOCH{sub 4}C{sub 6}Fc){sub 2}(H{sub 2}O){sub 2}](H{sub 3}O){r_brace}{sub n} [Ln=Ce (1), Pr (2), Sm (3), Eu (4), Gd (5), Tb (6) and Dy (7)]. X-ray crystallographic analysis reveals that the isomorphous complexes {l_brace}[Ce(OOCH{sub 4}C{sub 6}Fc){sub 2}(mu{sub 2}-OOCH{sub 4}C{sub 6}Fc){sub 2}(H{sub 2}O){sub 2}](H{sub 3}O){r_brace}{sub n} (1) and {l_brace}[Pr(OOCH{sub 4}C{sub 6}Fc){sub 2}(mu{sub 2}-OOCH{sub 4}C{sub 6}Fc){sub 2}(H{sub 2}O){sub 2}](H{sub 3}O){r_brace}{sub n} (2) form a unique 1D double-bridged infinite chain structure bridged by mu{sub 2}-OOCH{sub 4}C{sub 6}Fc groups. Each Ln(III) ion adopts a dodecahedron coordination environment with eight coordinated oxygen atoms from two terminal monodentate coordinated FcC{sub 6}H{sub 4}COO{sup -} units, two terminal monodentate coordinated H{sub 2}O molecules and four mu{sub 2}-{sup -}OOCH{sub 4}C{sub 6}Fc units. The luminescent spectra reveal that only 4 and 6 exhibit characteristic emissions of lanthanide ions, Eu(III) and Tb(III) ions, respectively. The variable-temperature magnetic properties of 5 and 7 suggest that a ferromagnetic coupling between spin carriers may exist in 5. - Graphical abstract: Seven p-ferrocenylbenzoate lanthanide coordination polymers were synthesized. Given is the perspective view of a unique 1D double-bridged infinite chain structure of 1, excitation and emission spectra of 6 and plots of chi{sub m}T vs. T and chi{sub m}{sup -1} vs. T of 5.

  17. The influence of interchain coupling on intramolecular oscillation mobility in coupled macromolecular chains: The case of coplanar parallel chains

    NASA Astrophysics Data System (ADS)

    Čevizović, D.; Petković, S.; Galović, S.; Chizhov, A.; Reshetnyak, A.

    2015-10-01

    We enlarge our results from the study of the hopping mechanism of the oscillation excitation transport in 1D model of one biologica-likel macromolecular chain to the case of a system composed from two 1D parallel macromolecular chains with consideration of the properties of intramolecular oscillation excitations. We suppose, that due to the exciton interaction with thermal oscillation (generated by mechanical phonon subsystem) of structural elements (consisting of the peptide group) of the chains, the exciton becomes by self trapped and forms the polaron state. We suggest a model which generalizes the modified Holstein polaron model to the case of two macromolecular chains and find that because of the interchain coupling, the exciton energy band is splitted into two subbands. The hopping process of exciton migration along the macromolecular chains is studied in dependence of system parameters and temperature. We pay an special attention to the temperature range (near T = 300 K) in which living cells operate. It is found that for the certain values of the system parameters there exists the abrupt change of the exciton migration nature from practically free (light) exciton motion to an immobile (heavy, dressed by phonon cloud) quasiparticle We discuss an application of the obtained results to the exciton transport both within deoxyribonucleic acid molecule and in the 2D polymer films organized from such macromolecular chains.

  18. Marriage of exact enumeration and 1/d expansion methods: Lattice model of dilute polymers

    NASA Astrophysics Data System (ADS)

    Nemirovsky, A. M.; Freed, Karl F.; Ishinabe, Takao; Douglas, Jack F.

    1992-06-01

    We consider the properties of a self-avoiding polymer chain with nearestneighbor contact energy ɛ on a d-dimensional hypercubic lattice. General theoretical arguments enable us to prescribe the exact analytic form of the n-segment chain partition function C n ,and unknown coefficients for chains of up to 11 segments are determined using exact enumeration data in d=2-6. This exact form provides the main ingredient to produce a large- n expansion in d -1of the chain free energy through fifth order with the full dependence on the contact energy retained. The ɛ-dependent chain connectivity constant and free energy amplitude are evaluated within the d -1expansion to O(d -5). Our general formulation includes for the first time self-avoiding walks, neighboravoiding walks, theta, and collapsed chains as particular limiting cases.

  19. Epitaxial 1D electron transport layers for high-performance perovskite solar cells.

    PubMed

    Han, Gill Sang; Chung, Hyun Suk; Kim, Dong Hoe; Kim, Byeong Jo; Lee, Jin-Wook; Park, Nam-Gyu; Cho, In Sun; Lee, Jung-Kun; Lee, Sangwook; Jung, Hyun Suk

    2015-10-07

    We demonstrate high-performance perovskite solar cells with excellent electron transport properties using a one-dimensional (1D) electron transport layer (ETL). The 1D array-based ETL is comprised of 1D SnO2 nanowires (NWs) array grown on a F:SnO2 transparent conducting oxide substrate and rutile TiO2 nanoshells epitaxially grown on the surface of the 1D SnO2 NWs. The optimized devices show more than 95% internal quantum yield at 750 nm, and a power conversion efficiency (PCE) of 14.2%. The high quantum yield is attributed to dramatically enhanced electron transport in the epitaxial TiO2 layer, compared to that in conventional nanoparticle-based mesoporous TiO2 (mp-TiO2) layers. In addition, the open space in the 1D array-based ETL increases the prevalence of uniform TiO2/perovskite junctions, leading to reproducible device performance with a high fill factor. This work offers a method to achieve reproducible, high-efficiency perovskite solar cells with high-speed electron transport.

  20. Usher Syndrome 1D and Nonsyndromic Autosomal Recessive Deafness DFNB12 Are Caused by Allelic Mutations of the Novel Cadherin-Like Gene CDH23

    PubMed Central

    Bork, Julie M.; Peters, Linda M.; Riazuddin, Saima; Bernstein, Steve L.; Ahmed, Zubair M.; Ness, Seth L.; Polomeno, Robert; Ramesh, Arabandi; Schloss, Melvin; Srisailpathy, C. R. Srikumari; Wayne, Sigrid; Bellman, Susan; Desmukh, Dilip; Ahmed, Zahoor; Khan, Shaheen N.; Kaloustian, Vazken M. Der; Li, X. Cindy; Lalwani, Anil; Riazuddin, Sheikh; Bitner-Glindzicz, Maria; Nance, Walter E.; Liu, Xue-Zhong; Wistow, Graeme; Smith, Richard J. H.; Griffith, Andrew J.; Wilcox, Edward R.; Friedman, Thomas B.; Morell, Robert J.

    2001-01-01

    Genes causing nonsyndromic autosomal recessive deafness (DFNB12) and deafness associated with retinitis pigmentosa and vestibular dysfunction (USH1D) were previously mapped to overlapping regions of chromosome 10q21-q22. Seven highly consanguineous families segregating nonsyndromic autosomal recessive deafness were analyzed to refine the DFNB12 locus. In a single family, a critical region was defined between D10S1694 and D10S1737, ∼0.55 cM apart. Eighteen candidate genes in the region were sequenced. Mutations in a novel cadherin-like gene, CDH23, were found both in families with DFNB12 and in families with USH1D. Six missense mutations were found in five families with DFNB12, and two nonsense and two frameshift mutations were found in four families with USH1D. A northern blot analysis of CDH23 showed a 9.5-kb transcript expressed primarily in the retina. CDH23 is also expressed in the cochlea, as is demonstrated by polymerase chain reaction amplification from cochlear cDNA. PMID:11090341

  1. A New Carbon Allotrope with Six-Fold Helical Chains in all-sp2 Bonding Networks

    PubMed Central

    Wang, Jian-Tao; Chen, Changfeng; Wang, Enge; Kawazoe, Yoshiyuki

    2014-01-01

    Using a recently developed approach to constructing covalent network structures from linear carbyne, we identify by ab initio calculations a new carbon allotrope in () symmetry that comprises six-fold helical chains with alternating sp2-type single and double bonds along the chains that are connected via zigzag benzene rings. This 6-fold carbene is characterized as a three-dimensional three-connected chiral crystalline modification of graphite. Phonon and electronic band calculations indicate that this new structure is dynamically stable and is a semiconductor with a band gap of 0.47 eV, in contrast to the semimetallic nature of graphite. Simulated x-ray diffraction patterns of the 6-fold carbene provide an excellent match to the previously unexplained distinct diffraction peak of a new carbon allotrope found in recent detonation experiments. These results establish a new carbon phase and offer insights into its outstanding structural and electronic properties. PMID:24614093

  2. Chain entanglements. I. Theory

    NASA Astrophysics Data System (ADS)

    Fixman, Marshall

    1988-09-01

    A model of concentrated polymer solution dynamics is described. The forces in a linear generalized Langevin equation for the motion of a probe chain are derived on the assumption that all relaxation of the forces is due to motion of the surrounding matrix. Vicinal chain displacements are classified as viscoelastic deformation, reptation, and minor residual fluctuations. The latter provide a torsional relaxation of the primitive path that minimizes the significance of transverse forces on the probe chain. All displacements of vicinal segments are assumed proportional to the forces that they exert on the probe chain. In response to an external force, the displacement of the probe chain relative to a laboratory frame is increased by viscoelastic deformation of the matrix, but reptative diffusion relative to the deforming matrix is slowed down. The net effect on translational diffusion is negligible if the probe and vicinal chains have the same chain length N, but the friction constant for reptative motion is increased by a factor N1-xs. xs=1/2 if Gaussian conformational statistics applies during the disengagement process, while xs =0.6 if excluded volume statistics applies. The translational friction constant is βp ˜N2, as in reptation theory, but the viscosity is η˜N4-xs . The persistence of entanglements during the translational diffusion of the probe chain across many radii of gyration is rationalized pictorially in terms of correlated reptative motion of the probe and vicinal chains.

  3. Supply chain planning classification

    NASA Astrophysics Data System (ADS)

    Hvolby, Hans-Henrik; Trienekens, Jacques; Bonde, Hans

    2001-10-01

    Industry experience a need to shift in focus from internal production planning towards planning in the supply network. In this respect customer oriented thinking becomes almost a common good amongst companies in the supply network. An increase in the use of information technology is needed to enable companies to better tune their production planning with customers and suppliers. Information technology opportunities and supply chain planning systems facilitate companies to monitor and control their supplier network. In spite if these developments, most links in today's supply chains make individual plans, because the real demand information is not available throughout the chain. The current systems and processes of the supply chains are not designed to meet the requirements now placed upon them. For long term relationships with suppliers and customers, an integrated decision-making process is needed in order to obtain a satisfactory result for all parties. Especially when customized production and short lead-time is in focus. An effective value chain makes inventory available and visible among the value chain members, minimizes response time and optimizes total inventory value held throughout the chain. In this paper a supply chain planning classification grid is presented based current manufacturing classifications and supply chain planning initiatives.

  4. Dynamical Analysis and Big Bang Bifurcations of 1D and 2D Gompertz's Growth Functions

    NASA Astrophysics Data System (ADS)

    Rocha, J. Leonel; Taha, Abdel-Kaddous; Fournier-Prunaret, D.

    In this paper, we study the dynamics and bifurcation properties of a three-parameter family of 1D Gompertz's growth functions, which are defined by the population size functions of the Gompertz logistic growth equation. The dynamical behavior is complex leading to a diversified bifurcation structure, leading to the big bang bifurcations of the so-called “box-within-a-box” fractal type. We provide and discuss sufficient conditions for the existence of these bifurcation cascades for 1D Gompertz's growth functions. Moreover, this work concerns the description of some bifurcation properties of a Hénon's map type embedding: a “continuous” embedding of 1D Gompertz's growth functions into a 2D diffeomorphism. More particularly, properties that characterize the big bang bifurcations are considered in relation with this coupling of two population size functions, varying the embedding parameter. The existence of communication areas of crossroad area type or swallowtails are identified for this 2D diffeomorphism.

  5. A comparison of 1D and 2D LSTM architectures for the recognition of handwritten Arabic

    NASA Astrophysics Data System (ADS)

    Yousefi, Mohammad Reza; Soheili, Mohammad Reza; Breuel, Thomas M.; Stricker, Didier

    2015-01-01

    In this paper, we present an Arabic handwriting recognition method based on recurrent neural network. We use the Long Short Term Memory (LSTM) architecture, that have proven successful in different printed and handwritten OCR tasks. Applications of LSTM for handwriting recognition employ the two-dimensional architecture to deal with the variations in both vertical and horizontal axis. However, we show that using a simple pre-processing step that normalizes the position and baseline of letters, we can make use of 1D LSTM, which is faster in learning and convergence, and yet achieve superior performance. In a series of experiments on IFN/ENIT database for Arabic handwriting recognition, we demonstrate that our proposed pipeline can outperform 2D LSTM networks. Furthermore, we provide comparisons with 1D LSTM networks trained with manually crafted features to show that the automatically learned features in a globally trained 1D LSTM network with our normalization step can even outperform such systems.

  6. Defective transient endogenous spleen colony formation in S1/S1d mice.

    PubMed

    Wiktor-Jedrzejczak, W; Ahmed, A; Sharkis, S J; McKee, A; Sell, K W

    1979-04-01

    WCB6F1 mice of the genotype S1/S1d did not form transient 5-day endogenous spleen colonies following midlethal irradiation, either spontaneously or in response to postirradiation bleeding. Their hematologically normal (+/+) littermates produced colonies equivalent in number and morphologic type to a normal strain (D2B6F1), as evaluated by both macroscopic and microscopic criteria. Bone marrow cells from S1/S1d mice, when transplanted into lethally irradiated +/+ mice, were able to generate equivalent numbers of transient endogenous spleen colonies (TE-CFUs), as compared to that obtained when syngeneic +/+ marrow cells were injected into lethally irradiated +/+ recipients. A defective growth of an early class of hematopoietic progenitor cells, resulting in the clinical course of the S1/S1d anemia is suggested and confirms previous reports on the microenvironmental nature of this abnormality.

  7. Collective mode damping and viscosity in a 1D unitary Fermi gas

    NASA Astrophysics Data System (ADS)

    Punk, M.; Zwerger, W.

    2006-08-01

    We calculate the damping of the Bogoliubov Anderson mode in a one-dimensional (1D) two-component attractive Fermi gas for arbitrary coupling strength within a quantum hydrodynamic approach. Using the Bethe-ansatz solution of the 1D BCS-BEC crossover problem, we derive analytic results for the viscosity covering the full range from a Luther Emery liquid of weakly bound pairs to a Lieb Liniger gas of strongly bound bosonic dimers. At the unitarity point, the system is a Tonks Girardeau gas with a universal constant αζ = 0.38 in the viscosity ζ = αζplanck n for T = 0. For the trapped case, we calculate the Q-factor of the breathing mode and show that the damping provides a sensitive measure of temperature in 1D Fermi gases.

  8. TBC1D24 Mutation Causes Autosomal Dominant Non-Syndromic Hearing Loss

    PubMed Central

    Azaiez, Hela; Booth, Kevin T.; Bu, Fengxiao; Huygen, Patrick; Shibata, Seiji; Shearer, A. Eliot; Kolbe, Diana; Meyer, Nicole; Black-Ziegelbein, E. Ann; Smith, Richard J.H.

    2014-01-01

    Hereditary hearing loss (HHL) is extremely heterogeneous. Over 70 genes have been identified to date, and with the advent of massively parallel sequencing, the pace of novel gene discovery has accelerated. In a family segregating progressive autosomal dominant non-syndromic hearing loss (ADNSHL) we used OtoSCOPE® to exclude mutations in known deafness genes and then performed segregation mapping and whole exome sequencing (WES) to identify a unique variant, p.Ser178Leu, in TBC1D24 that segregates with the hearing loss phenotype. TBC1D24 encodes a GTPase-activating protein expressed in the cochlea. Ser178 is highly conserved across vertebrates and its change is predicted to be damaging. Other variants in TBC1D24 have been associated with a panoply of clinical symptoms including autosomal recessive NSHL (ARNSHL), syndromic hearing impairment associated with onychodystrophy, osteodystrophy, mental retardation and seizures (DOORS syndrome), and a wide range of epileptic disorders. PMID:24729539

  9. Peptide conjugates for directing the morphology and assembly of 1D nanoparticle superstructures.

    PubMed

    Zhang, Chen; Song, Chengyi; Fry, H Christopher; Rosi, Nathaniel L

    2014-01-20

    Designed peptide conjugates molecules are used to direct the synthesis and assembly of gold nanoparticles into complex 1D nanoparticle superstructures with various morphologies. Four peptide conjugates, each based on the gold-binding peptide (AYSSGAPPMPPF; PEPAu ), are prepared: C12H23O-AYSSGAPPMPP (1), C12H23O-AYSSGAPPMPPF (2), C12H23O-AYSSGAPPMPPFF (3), and C12H23O-AYSSGAPPMPPFFF (4). The affect that C-terminal hydrophobic F residues have on both the soft-assembly of the peptide conjugates and the resulting assembly of gold nanoparticle superstructures is examined. It is shown that the addition of two C-terminal F residues (3) leads to thick, branched 1D gold nanoparticle superstructures, whereas the addition of three C-terminal F residues (4) leads to bundling of thin 1D nanoparticle superstructures.

  10. A User's Guide to AMR1D: An Instructional Adaptive Mesh Refinement Code for Unstructured Grids

    NASA Technical Reports Server (NTRS)

    deFainchtein, Rosalinda

    1996-01-01

    This report documents the code AMR1D, which is currently posted on the World Wide Web (http://sdcd.gsfc.nasa.gov/ESS/exchange/contrib/de-fainchtein/adaptive _mesh_refinement.html). AMR1D is a one-dimensional finite element fluid-dynamics solver, capable of adaptive mesh refinement (AMR). It was written as an instructional tool for AMR on unstructured mesh codes. It is meant to illustrate the minimum requirements for AMR on more than one dimension. For that purpose, it uses the same type of data structure that would be necessary on a two-dimensional AMR code (loosely following the algorithm described by Lohner).

  11. Entangling strings of neutral atoms in 1D atomic pipeline structures.

    PubMed

    Dorner, U; Fedichev, P; Jaksch, D; Lewenstein, M; Zoller, P

    2003-08-15

    We study a string of neutral atoms with nearest neighbor interaction in a 1D beam splitter configuration, where the longitudinal motion is controlled by a moving optical lattice potential. The dynamics of the atoms crossing the beam splitter maps to a 1D spin model with controllable time dependent parameters, which allows the creation of maximally entangled states of atoms by crossing a quantum phase transition. Furthermore, we show that this system realizes protected quantum memory, and we discuss the implementation of one- and two-qubit gates in this setup.

  12. DOPEX-1D2C: A one-dimensional, two-constraint radiation shield optimization code

    NASA Technical Reports Server (NTRS)

    Lahti, G. P.

    1973-01-01

    A one-dimensional, two-constraint radiation sheild weight optimization procedure and a computer program, DOPEX-1D2C, is described. The DOPEX-1D2C uses the steepest descent method to alter a set of initial (input) thicknesses of a spherical shield configuration to achieve a minimum weight while simultaneously satisfying two dose-rate constraints. The code assumes an exponential dose-shield thickness relation with parameters specified by the user. Code input instruction, a FORTRAN-4 listing, and a sample problem are given. Typical computer time required to optimize a seven-layer shield is less than 1/2 minute on an IBM 7094.

  13. Column Testing and 1D Reactive Transport Modeling to Evaluate Uranium Plume Persistence Processes

    SciTech Connect

    Johnson, Raymond H.; Morrison, Stan; Morris, Sarah; Tigar, Aaron; Dam, William; Dayvault, Jalena

    2016-04-26

    Motivation for Study: Natural flushing of contaminants at various U.S. Department of Energy Office of Legacy Management sites is not proceeding as quickly as predicted (plume persistence) Objectives: Help determine natural flushing rates using column tests. Use 1D reactive transport modeling to better understand the major processes that are creating plume persistence Approach: Core samples from under a former mill tailings area Tailings have been removed. Column leaching using lab-prepared water similar to nearby Gunnison River water. 1D reactive transport modeling to evaluate processes

  14. Symmetry Violations in Partially Oxidized One-Dimensional (1D) Transition Metal Polymers. Metal-Ligand-Metal (M-L-M) Bridged Systems

    NASA Astrophysics Data System (ADS)

    Böhm, Michael C.

    1984-09-01

    The band structure of the metal-ligand-metal (M-L-M) bridged quasi one-dimensional (1D) cyclopentadienylmanganese polymer, MnCp 1, has been studied in the unoxidized state and in a partly oxidized modification with one electron removed from each second MnCp fragment. The tight-binding approach is based on a semiempirical self-consistent-field (SCF) Hartree-Fock (HF) crystal orbital (CO) model of the INDO-type (intermediate neglect of differential overlap) combined with a statistical averaging procedure which has its origin in the grand canonical ensemble. The latter approximation allows for an efficient investigation of violations of the translation symmetries in the oxidized 1D material. The oxidation process in 1 is both ligand- and metal-centered (Mn 3d-2 states). The mean-field minimum corresponds to a charge density wave (CDW) solution with inequivalent Mn sites within the employed repeat-units. The symmetry adapted solution with electronically identical 3d centers is a maximum in the variational space. The coupling of this electronic instability to geometrical deformations is also analyzed. The ligand amplitudes encountered in the hole-state wave function prevent extremely large charge separations between the 3d centers which are found in ID systems without bridging moieties (e.g. Ni(CN)2-5 chain). The symmetry reduction in oxidized 1 is compared with violations of spatial symmetries in finite transition metal derivatives and simple solids. The stabilization of the valence bond-type (VB) solution is physically rationalized (i.e. left-right correlations between the 3d centers). The computational results derived for 1 are generalized to oxidized transition metal chains with band occupancies that are simple fractions of the number of stacking units and to 1D systems that deviate from this relation. The entropy-influence for temperatures T ≠ 0 is shortly discussed (stabilization of domain or cluster structures).

  15. C Fe chains due to segregated carbon impurities on Fe(1 0 0)

    NASA Astrophysics Data System (ADS)

    Fujii, Jun; Panaccione, Giancarlo; Vobornik, Ivana; Rossi, Giorgio; Trimarchi, Giancarlo; Binggeli, Nadia

    2006-09-01

    Bulk carbon impurities segregate at the Fe(1 0 0) surface and, upon thermal annealing, can form metastable surface phases with local and long range order and peculiar electronic properties. We present a surface science study of C-segregated Fe(1 0 0) with scanning tunneling microscopy, angle resolved photoemission, and ab initio calculations of the surface structure and electron states. In particular the c(3√2 × √2) structure, observed for 0.67 atomic layers of C segregated at the iron surface, is found to be due to self-organized carbon stripes made of zig-zag chains. The strong hybridization between C and Fe was observed in ARPES spectra.

  16. Sonochemical synthesis of 0D, 1D, and 2D zinc oxide nanostructures in ionic liquids and their photocatalytic activity.

    PubMed

    Alammar, Tarek; Mudring, Anja-Verena

    2011-12-16

    Ultrasound synthesis of zinc oxide from zinc acetate and sodium hydroxide in ionic liquids (ILs) is a fast, facile, and effective, yet highly morphology- and size-selective route to zinc oxide nanostructures of various dimensionalities. No additional organic solvents, water, surfactants, or templating agents are required. Depending on the synthetic conditions, the selective manufacturing of 0D, 1D, and 2D ZnO nanostructures is possible: Whereas the formation of rodlike structures is typically favored, ZnO nanoparticles can be obtained either under strongly basic conditions or by use of ILs with a long alkyl chain, such as 1-n-alkyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([C(n)mim][Tf(2)N]; n>8). A short ultrasound irradiation time favors the formation of ZnO nanosheets. Prolonged irradiation leads to the conversion of the ZnO nanosheets into nanorods. In contrast, ionothermal synthesis (conventional heating) does not allow for morphology tuning by variation of the IL or other synthesis conditions, as the longer reaction times required lead always to the formation of well-developed hexagonal nanocrystals with prismatic tips. The ZnO nanostructures synthesized by using ultrasound were efficient photocatalysts in the photodegradation of methyl orange. The photoactivity was observed to be as high as 95 % for ZnO nanoparticles obtained in [C(10)mim][Tf(2)N].

  17. Scale up tools in reactive extrusion and compounding processes. Could 1D-computer modeling be helpful?

    NASA Astrophysics Data System (ADS)

    Pradel, J.-L.; David, C.; Quinebèche, S.; Blondel, P.

    2014-05-01

    Industrial scale-up (or scale down) in Compounding and Reactive Extrusion processes is one of the most critical R&D challenges. Indeed, most of High Performances Polymers are obtained within a reactive compounding involving chemistry: free radical grafting, in situ compatibilization, rheology control... but also side reactions: oxidation, branching, chain scission... As described by basic Arrhenius and kinetics laws, the competition between all chemical reactions depends on residence time distribution and temperature. Then, to ensure the best possible scale up methodology, we need tools to match thermal history of the formulation along the screws from a lab scale twin screw extruder to an industrial one. This paper proposes a comparison between standard scale-up laws and the use of Computer modeling Software such as Ludovic® applied and compared to experimental data. Scaling data from a compounding line to another one, applying general rules (for example at constant specific mechanical energy), shows differences between experimental and computed data, and error depends on the screw speed range. For more accurate prediction, 1D-Computer Modeling could be used to optimize the process conditions to ensure the best scale-up product, especially in temperature sensitive reactive extrusion processes. When the product temperature along the screws is the key, Ludovic® software could help to compute the temperature profile along the screws and extrapolate conditions, even screw profile, on industrial extruders.

  18. Synthesis and magnetic properties of new tellurate compounds Na4MTeO6 (M = Co and Ni) with a ferromagnetic spin-chain structure.

    PubMed

    He, Zhangzhen; Guo, Wenbin; Cui, Meiyan; Tang, Yingying

    2017-03-31

    New tellurate compounds Na4MTeO6 (M = Co and Ni) were synthesized by a conventional high-temperature solid-state reaction. The title compounds crystallize in the monoclinic system of a space group P2/c and the triclinic system of a space group P1[combining macron], respectively. Both compounds exhibit a zigzag spin-chain structure, in which Na4CoTeO6 shows uniform chains built by Co(2+) ions and Na4NiTeO6 shows alternating chains built by Ni(2+) ions. Magnetic measurements confirm that Na4CoTeO6 and Na4NiTeO6 possess an antiferromagnetic ordering at TN = ∼3 K and ∼6.5 K, respectively, while a metamagnetic transition can be observed in the magnetization curve with an increasing field at 2 K.

  19. Building dictionaries of 1D and 3D motifs by mining the Unaligned 1D sequences of 17 archaeal and bacterial genomes.

    PubMed

    Rigoutsos, I; Gao, Y; Floratos, A; Parida, L

    1999-01-01

    We have used the Teiresias algorithm to carry out unsupervised pattern discovery in a database containing the unaligned ORFs from the 17 publicly available complete archaeal and bacterial genomes and build a 1D dictionary of motifs. These motifs which we refer to as seqlets account for and cover 97.88% of this genomic input at the level of amino acid positions. Each of the seqlets in this 1D dictionary was located among the sequences in Release 38.0 of the Protein Data Bank and the structural fragments corresponding to each seqlet's instances were identified and aligned in three dimensions: those of the seqlets that resulted in RMSD errors below a pre-selected threshold of 2.5 Angstroms were entered in a 3D dictionary of structurally conserved seqlets. These two dictionaries can be thought of as cross-indices that facilitate the tackling of tasks such as automated functional annotation of genomic sequences, local homology identification, local structure characterization, comparative genomics, etc.

  20. Ab initio quantum transport in atomic carbon chains

    NASA Astrophysics Data System (ADS)

    Botello-Méndez, Andrés R.; Charlier, Jean-Christophe; Banhart, Florian; NAPS Team; Carbyne Collaboration

    2015-03-01

    Carbyne, the sp-hybridized phase of carbon, is still a missing link in the family of carbon allotropes. Recently, detailed electrical measurements and first-principles electronic transport calculations have been performed on monoatomic carbon chains. When the 1D system is under strain, the current-voltage curves exhibit a semiconducting behavior, which corresponds to the polyyne structure of the atomic chain with alternating single and triple bonds. Conversely, when the chain is unstrained, the ohmic behavior is observed in agreement with the metallic cumulene structure with double bonds, confirming recent theoretical predictions, namely that a metal-insulator transition can be induced by adjusting the strain. The key role of the contacting leads is also scrutinized by ab initio quantum conductance calculations, explaining the rectifying behavior measured in monoatomic carbon chains in a non-symmetric contact configuration.

  1. Epitaxial 1D electron transport layers for high-performance perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Han, Gill Sang; Chung, Hyun Suk; Kim, Dong Hoe; Kim, Byeong Jo; Lee, Jin-Wook; Park, Nam-Gyu; Cho, In Sun; Lee, Jung-Kun; Lee, Sangwook; Jung, Hyun Suk

    2015-09-01

    We demonstrate high-performance perovskite solar cells with excellent electron transport properties using a one-dimensional (1D) electron transport layer (ETL). The 1D array-based ETL is comprised of 1D SnO2 nanowires (NWs) array grown on a F:SnO2 transparent conducting oxide substrate and rutile TiO2 nanoshells epitaxially grown on the surface of the 1D SnO2 NWs. The optimized devices show more than 95% internal quantum yield at 750 nm, and a power conversion efficiency (PCE) of 14.2%. The high quantum yield is attributed to dramatically enhanced electron transport in the epitaxial TiO2 layer, compared to that in conventional nanoparticle-based mesoporous TiO2 (mp-TiO2) layers. In addition, the open space in the 1D array-based ETL increases the prevalence of uniform TiO2/perovskite junctions, leading to reproducible device performance with a high fill factor. This work offers a method to achieve reproducible, high-efficiency perovskite solar cells with high-speed electron transport.We demonstrate high-performance perovskite solar cells with excellent electron transport properties using a one-dimensional (1D) electron transport layer (ETL). The 1D array-based ETL is comprised of 1D SnO2 nanowires (NWs) array grown on a F:SnO2 transparent conducting oxide substrate and rutile TiO2 nanoshells epitaxially grown on the surface of the 1D SnO2 NWs. The optimized devices show more than 95% internal quantum yield at 750 nm, and a power conversion efficiency (PCE) of 14.2%. The high quantum yield is attributed to dramatically enhanced electron transport in the epitaxial TiO2 layer, compared to that in conventional nanoparticle-based mesoporous TiO2 (mp-TiO2) layers. In addition, the open space in the 1D array-based ETL increases the prevalence of uniform TiO2/perovskite junctions, leading to reproducible device performance with a high fill factor. This work offers a method to achieve reproducible, high-efficiency perovskite solar cells with high-speed electron transport

  2. Complexin cross-links pre-fusion SNAREs into a zig-zag array: a structure-based model for complexin clamping

    PubMed Central

    Kümmel, Daniel; Krishnakumar, Shyam S.; Radoff, Daniel T.; Li, Feng; Giraudo, Claudio G.; Pincet, Frederic; Rothman, James E.; Reinisch, Karin M.

    2011-01-01

    Summary Complexin prevents SNAREs from releasing neurotransmitters until an action potential arrives at the synapse. To understand the mechanism for this inhibition, we determined the structure of complexin bound to a mimetic of a pre-fusion SNAREpin lacking the portion of the v-SNARE which zippers last to trigger fusion. The “central helix” of complexin is anchored to one SNARE complex while its “accessory helix” extends away at ~45° and bridges to a second complex, occupying the vacant v-SNARE binding site to inhibit fusion. That the accessory helix competes with the v-SNARE for t-SNARE binding was expected, but surprisingly, the interaction occurs inter-molecularly. Thus complexin organizes the SNAREs into a zig-zag topology which, when interposed between the vesicle and plasma membranes, is incompatible with fusion. PMID:21785414

  3. Quasi-continuous-wave, laser-diode-end-pumped Yb:YAG zigzag slab oscillator with high brightness at room temperature

    NASA Astrophysics Data System (ADS)

    Jiang, Hao; Chen, Xiaoming; Xu, Liu; Gao, Qingsong; Hu, Hao; Wu, Yingchen; Xu, Xiaoxiao

    2017-02-01

    An experimental demonstration of a quasi-continuous-wave, laser-diode (LD)-end-pumped Yb:YAG zigzag slab oscillator with a high efficiency and power at room temperature has been presented. An image-inverting resonator was used in the slab laser to avoid beam excursion to the slab end and laser power instability. The emitted laser had an average power of 330 W at 1030 nm when the average pump power was 712 W at 940 nm with a repetition rate of 10 Hz and a pulse duration of 10 ms, which corresponded to an optical conversion efficiency of 46.3% and a slope efficiency of 56.0%.

  4. Density functional theory investigation of interaction of zigzag (7,0) single-walled carbon nanotube with Watson-Crick DNA base pairs

    NASA Astrophysics Data System (ADS)

    Shukla, Manoj K.; Dubey, Madan; Zakar, Eugene; Namburu, Raju; Leszczynski, Jerzy

    2010-08-01

    A first-principles investigation of interaction of DNA base pairs on the outer surface of zigzag (7,0) single-walled carbon nanotube (CNT) was carried out at the M05-2X/6-31G(d) level of geometry optimization and BSSE corrected interaction energy calculation using the same theoretical level and the 6-311G(d,p), cc-pVDZ and cc-pVTZ basis sets. Study revealed that CNT forms complexes of similar strength with both base pairs. Electron density maps suggest that complexes are characterized by stacking interaction through coupling of π-charge clouds of base pairs and CNT. BSSE corrected interaction energies and density of states calculations indicated the weak nature of interaction between base pairs and CNT.

  5. The effect of buckling on I–V characteristics of symmetric and asymmetric zigzag germanene nanoribbons: a first-principle calculation

    NASA Astrophysics Data System (ADS)

    Arjmand, T.; Bagheri Tagani, M.; Rahimpour Soleimani, H.

    2017-03-01

    In this paper, we consider zigzag-edge germanene nanoribbons with small buckling and even (symmetric) or odd (asymmetric) widths. Although the band structures of these two type structures are the same, they are noticeably different in terms of conductivity and current. In previous works on silicene, the role of buckling to dominate the effect of symmetry has been ignored and just the buckling changes of the symmetry space group from σ to C 2 are shown. In this case, buckling is the main factor responsible for differences in conductivity and current. Fluorine, hydroxyl, and hydrogen are used to passivate the nanoribbon edges. Results show that the current and conductivity are strongly dependent on the kinds of substitutional atoms/groups used to passivate the structure. It is found that symmetry breaking is not the only effective factor in the creation of current—buckling and backscattering are also important.

  6. Electric field effect on the zigzag (6,0) single-wall BC2N nanotube for use in nano-electronic circuits.

    PubMed

    Baei, Mohammad T; Peyghan, Ali Ahmadi; Moghimi, Masoumeh; Hashemian, Saeede

    2013-01-01

    We have analyzed the effect of external electric field on the zigzag (6,0) single-wall BC2N nanotube using density functional theory calculations. Analysis of the structural parameters indicates that the nanotube is resistant against the external electric field strengths. Analysis of the electronic structure of the nanotube indicates that the applied parallel electric field strengths have a much stronger interaction with the nanotube with respect to the transverse electric field strengths and the nanotube is easier to modulate by the applied parallel electric field. Our results show that the properties of the nanotube can be controlled by the proper external electric field for use in nano-electronic circuits.

  7. Organisation and ordering of 1D porphyrin polymers synthesised by on-surface Glaser coupling.

    PubMed

    Saywell, Alex; Browning, Abigail S; Rahe, Philipp; Anderson, Harry L; Beton, Peter H

    2016-08-16

    One-dimensional polymer chains consisting of π-conjugated porphyrin units are formed via Glaser coupling on a Ag(111) surface. Scanning probe microscopy reveals the covalent structure of the products and their ordering. The conformational flexibility within the chains is investigated via a comparision of room temperature and cryogenic measurements.

  8. A light-induced spin crossover actuated single-chain magnet

    NASA Astrophysics Data System (ADS)

    Liu, Tao; Zheng, Hui; Kang, Soonchul; Shiota, Yoshihito; Hayami, Shinya; Mito, Masaki; Sato, Osamu; Yoshizawa, Kazunari; Kanegawa, Shinji; Duan, Chunying

    2013-11-01

    Both spin-crossover complexes and molecular nanomagnets display bistable magnetic states, potentially behaving as elementary binary units for information storage. It is a challenge to introduce spin-crossover units into molecular nanomagnets to switch the bistable state of the nanomagnets through external stimuli-tuned spin crossover. Here we report an iron(II) spin-crossover unit and paramagnetic iron(III) ions that are incorporated into a well-isolated double-zigzag chain. The chain exhibits thermally induced reversible spin-crossover and light-induced excited spin-state trapping at the iron(II) sites. Single-chain magnet behaviour is actuated accompanying the synergy between light-induced excited spin-state trapping at the iron(II) sites and ferromagnetic interactions between the photoinduced high-spin iron(II) and low-spin iron(III) ions in the chain. The result provides a strategy to switch the bistable state of molecular nanomagnets using external stimuli such as light and heat, with the potential to erase and write information at a molecular level.

  9. Quasiparticle band structure of infinite hydrogen fluoride and hydrogen chloride chains.

    PubMed

    Buth, Christian

    2006-10-21

    We study the quasiparticle band structure of isolated, infinite (HF)(infinity) and (HCl)(infinity) bent (zigzag) chains and examine the effect of the crystal field on the energy levels of the constituent monomers. The chains are one of the simplest but realistic models of the corresponding three-dimensional crystalline solids. To describe the isolated monomers and the chains, we set out from the Hartree-Fock approximation, harnessing the advanced Green's function methods local molecular orbital algebraic diagrammatic construction (ADC) scheme and local crystal orbital ADC (CO-ADC) in a strict second order approximation, ADC(2,2) and CO-ADC(2,2), respectively, to account for electron correlations. The configuration space of the periodic correlation calculations is found to converge rapidly only requiring nearest-neighbor contributions to be regarded. Although electron correlations cause a pronounced shift of the quasiparticle band structure of the chains with respect to the Hartree-Fock result, the bandwidth essentially remains unaltered in contrast to, e.g., covalently bound compounds.

  10. Chain Reaction Polymerization.

    ERIC Educational Resources Information Center

    McGrath, James E.

    1981-01-01

    The salient features and importance of chain-reaction polymerization are discussed, including such topics as the thermodynamics of polymerization, free-radical polymerization kinetics, radical polymerization processes, copolymers, and free-radical chain, anionic, cationic, coordination, and ring-opening polymerizations. (JN)

  11. Critical Chain Exercises

    ERIC Educational Resources Information Center

    Doyle, John Kevin

    2010-01-01

    Critical Chains project management focuses on holding buffers at the project level vs. task level, and managing buffers as a project resource. A number of studies have shown that Critical Chain project management can significantly improve organizational schedule fidelity (i.e., improve the proportion of projects delivered on time) and reduce…

  12. Antigen-Induced Increases in Pulmonary Mast Cell Progenitor Numbers Depend on IL-9 and CD1d-Restricted NKT Cells1

    PubMed Central

    Jones, Tatiana G.; Hallgren, Jenny; Humbles, Alison; Burwell, Timothy; Finkelman, Fred D.; Alcaide, Pilar; Austen, K. Frank; Gurish, Michael F.

    2009-01-01

    Pulmonary mast cell progenitor (MCp) numbers increase dramatically in sensitized and aerosolized Ag-challenged mice. This increase depends on CD4+ T cells, as no MCp increase occurs in the lungs of sensitized wild-type (WT) mice after mAb depletion of CD4+ but not CD8+ cells before aerosol Ag challenge. Neither the genetic absence of IL-4, IL-4Rα chain, STAT-6, IFN-γ, or IL-12p40 nor mAb blockade of IFN-γ, IL-3, IL-4, IL-5, IL-6, IL-10, IL-13, IL-17A, IL-12p40, or IL-12p40Rβ1 before Ag challenge in WT mice reduces the pulmonary MCp increase. However, sensitized and Ag-challenged IL-9-deficient mice and sensitized WT mice given mAb to IL-9 just before Ag challenge show significant reductions in elicited lung MCp/106 mononuclear cells of 47 and 66%, respectively. CD1d-deficient mice and WT mice receiving anti-CD1d before Ag challenge also show significant reductions of 65 and 59%, respectively, in elicited lung MCp/106 mononuclear cells, revealing an additional requirement for MCp recruitment. However, in Jα18-deficient mice, which lack only type 1 or invariant NKT cells, the increase in the numbers of lung MCp with Ag challenge was intact, indicating that their recruitment must be mediated by type 2 NKT cells. Furthermore, anti-CD1d treatment of IL-9-deficient mice or anti-IL-9 treatment of CD1d-deficient mice does not further reduce the significant partial impairment of MCp recruitment occurring with a single deficiency. These findings implicate type 2 NKT cells and IL-9 as central regulators that function in the same pathway mediating the Ag-induced increase in numbers of pulmonary MCp. PMID:19783672

  13. On the extrema of a nonconvex functional with double-well potential in 1D

    NASA Astrophysics Data System (ADS)

    Gao, David Yang; Lu, Xiaojun

    2016-06-01

    This paper mainly investigates the extrema of a nonconvex functional with double-well potential in 1D through the approach of nonlinear differential equations. Based on the canonical duality method, the corresponding Euler-Lagrange equation with Neumann boundary condition can be converted into a cubic dual algebraic equation, which will help find the local extrema for the primal problem.

  14. Structural and mechanistic insights into regulation of the retromer coat by TBC1d5

    PubMed Central

    Jia, Da; Zhang, Jin-San; Li, Fang; Wang, Jing; Deng, Zhihui; White, Mark A.; Osborne, Douglas G.; Phillips-Krawczak, Christine; Gomez, Timothy S.; Li, Haiying; Singla, Amika; Burstein, Ezra; Billadeau, Daniel D.; Rosen, Michael K.

    2016-01-01

    Retromer is a membrane coat complex that is recruited to endosomes by the small GTPase Rab7 and sorting nexin 3. The timing of this interaction and consequent endosomal dynamics are thought to be regulated by the guanine nucleotide cycle of Rab7. Here we demonstrate that TBC1d5, a GTPase-activating protein (GAP) for Rab7, is a high-affinity ligand of the retromer cargo selective complex VPS26/VPS29/VPS35. The crystal structure of the TBC1d5 GAP domain bound to VPS29 and complementary biochemical and cellular data show that a loop from TBC1d5 binds to a conserved hydrophobic pocket on VPS29 opposite the VPS29–VPS35 interface. Additional data suggest that a distinct loop of the GAP domain may contact VPS35. Loss of TBC1d5 causes defective retromer-dependent trafficking of receptors. Our findings illustrate how retromer recruits a GAP, which is likely to be involved in the timing of Rab7 inactivation leading to membrane uncoating, with important consequences for receptor trafficking. PMID:27827364

  15. Recent developments in testing techniques for elastic mechanical properties of 1-D nanomaterials.

    PubMed

    Wang, Weidong; Li, Shuai; Zhang, Hongti; Lu, Yang

    2015-01-01

    One-dimensional (1-D) nanomaterials exhibit great potentials in their applications to functional materials, nano-devices and systems owing to their excellent properties. In the past decade, considerable studies have been done, with new patents being developed, on these 1-D building blocks for for their mechanical properties, especially elastic properties, which provide a solid foundation for the design of nanoelectromechanical systems (NEMS) and predictions of reliability and longevity for their devices. This paper reviews some of the recent investigations on techniques as well as patents available for the quantitative characterization of the elastic behaviors of various 1-D nanomaterials, with particular focus on on-chip testing system. The review begins with an overview of major testing methods for 1-D nanostructures' elastic properties, including nanoindentation testing, AFM (atomic force microscopy) testing, in situ SEM (scanning electron microscopy) testing, in situ TEM (transmission electron microscopy) testing and the testing system on the basis of MEMS (micro-electro-mechanical systems) technology, followed by advantages and challenges of each testing approach. This review also focuses on the MEMS-based testing apparatus, which can be actuated and measured inside SEM and TEM with ease, allowing users to highly magnify the continuous images of the specimen while measuring load electronically and independently. The combination of on-chip technologies and the in situ electron microscopy is expected to be a potential testing technique for nanomechanics. Finally, details are presented on the key challenges and possible solutions in the implementation of the testing techniques referred above.

  16. Combustion synthesis as a novel method for production of 1-D SiC nanostructures.

    PubMed

    Huczko, Andrzej; Bystrzejewski, Michał; Lange, Hubert; Fabianowska, Agnieszka; Cudziło, Stanisław; Panas, Andrzej; Szala, Mateusz

    2005-09-01

    1-D nanostructures of cubic phase silicon carbide (beta-SiC) were efficiently produced by combustion synthesis of mixtures containing Si-containing compounds and halocarbons in a calorimetric bomb. The influence of the operating parameters on 1-D SiC formation yield was studied. The heat release, the heating rate, and the chamber pressure increase were monitored during the process. The composition and structural features of the products were characterized by elemental analysis, X-ray diffraction, differential thermal analysis/ thermogravimetric technique, Raman spectroscopy, scanning and transmission electron microscopy, and energy-dispersive X-ray spectrometry. This self-induced growth process can produce SiC nanofibers and nanotubes ca. 20-100 nm in diameter with the aspect ratio higher than 1000. Bulk scale Raman studies showed the product to be comprised of mostly cubic polytype of SiC and that finite size effects are present. We believe that the nucleation mechanism involving radical gaseous species is responsible for 1-D nanostructures growth. The present study has enlarged the family of nanofibers and nanotubes available and offers a possible, new general route to 1-D crystalline materials.

  17. A South American Prehistoric Mitogenome: Context, Continuity, and the Origin of Haplogroup C1d

    PubMed Central

    Sans, Mónica; Figueiro, Gonzalo; Hughes, Cris E.; Lindo, John; Hidalgo, Pedro C.; Malhi, Ripan S.

    2015-01-01

    Based on mitochondrial DNA (mtDNA), it has been estimated that at least 15 founder haplogroups peopled the Americas. Subhaplogroup C1d3 was defined based on the mitogenome of a living individual from Uruguay that carried a lineage previously identified in hypervariable region I sequences from ancient and modern Uruguayan individuals. When complete mitogenomes were studied, additional substitutions were found in the coding region of the mitochondrial genome. Using a complete ancient mitogenome and three modern mitogenomes, we aim to clarify the ancestral state of subhaplogroup C1d3 and to better understand the peopling of the region of the Río de la Plata basin, as well as of the builders of the mounds from which the ancient individuals were recovered. The ancient mitogenome, belonging to a female dated to 1,610±46 years before present, was identical to the mitogenome of one of the modern individuals. All individuals share the mutations defining subhaplogroup C1d3. We estimated an age of 8,974 (5,748–12,261) years for the most recent common ancestor of C1d3, in agreement with the initial peopling of the geographic region. No individuals belonging to the defined lineage were found outside of Uruguay, which raises questions regarding the mobility of the prehistoric inhabitants of the country. Moreover, the present study shows the continuity of Native lineages over at least 6,000 years. PMID:26509686

  18. Millimeter and Submillimeter Studies of O(^1D) Insertion Reactions to Form Molecules of Astrophysical Interest

    NASA Astrophysics Data System (ADS)

    Hays, Brian; Wehres, Nadine; Deprince, Bridget Alligood; Roy, Althea A. M.; Laas, Jacob; Widicus Weaver, Susanna L.

    2015-06-01

    While both the number of detected interstellar molecules and their chemical complexity continue to increase, understanding of the processes leading to their formation is lacking. Our research group combines laboratory spectroscopy, observational astronomy, and astrochemical modeling for an interdisciplinary examination of the chemistry of star and planet formation. This talk will focus on our laboratory studies of O(^1D) insertion reactions with organic molecules to produce molecules of astrophysical interest. By employing these reactions in a supersonic expansion, we are able to produce interstellar organic reaction intermediates that are unstable under terrestrial conditions; we then probe the products using millimeter and submillimeter spectroscopy. We benchmarked this setup using the well-studied O(^1D) + methane reaction to form methanol. After optimizing methanol production, we moved on to study the O(^1D) + ethylene reaction to form vinyl alcohol (CH_2CHOH), and the O(^1D) + methyl amine reaction to form aminomethanol (NH_2CH_2OH). Vinyl alcohol measurements have now been extended up to 450 GHz, and the associated spectral analysis is complete. A possible detection of aminomethanol has also been made, and continued spectral studies and analysis are underway. We will present the results from these experiments and discuss future applications of these molecular and spectroscopic techniques.

  19. Characterization of 5-HT1D receptor binding sites in post-mortem human brain cortex.

    PubMed Central

    Martial, J; de Montigny, C; Cecyre, D; Quirion, R

    1991-01-01

    The present study provides further evidence for the presence of serotonin1D (5-HT1D) receptors in post-mortem human brain. Receptor binding parameters in temporal cortex homogenates were assessed using [3H]5-HT in the presence of 100 nM 8-OH-DPAT, 1 microM propranolol and 1 microM mesulergine to prevent labelling of the 5-HT1A, 5-HT1B and 5-HT1C sites, respectively. Under these conditions, [3H]5-HT apparently bound to a class of high affinity (Kd = 5.0 +/- 1.0 nM) low capacity (Bmax = 96 +/- 23 fmol/mg protein) sites. In competition experiments, 5-HT and 5-carboxyamidotryptamine (5-CT), as well as ergotamine, lysergic acid, sumatriptan and RU-24969 exhibited high affinity for these sites. This pharmacological profile is concordant with the ligand selectivity pattern reported for 5-HT1D receptors in other species and thus provides further evidence for its existence in human temporal cortex. In addition, the competition profile of some ligands, particularly of unlabelled 5-HT, 5-CT and ergotamine, revealed the existence of a lower affinity binding site. The latter suggests receptor heterogeneity or the presence of a lower affinity state of 5-HT1D receptors. PMID:1911737

  20. Sensitivity of quantum yield for O(/sup 1/D) production from ozone photolysis

    SciTech Connect

    Wuebbles, D.J.; Tarp, R.L.

    1980-06-01

    Recent laboratory studies have indicated that the quantum yield for O(/sup 1/D) production from photolysis of ozone may be less than unity at wavelengths shorter than 300 nm (below the fall off region). Previously it had been assumed that the quantum yield was unity at these wavelengths. Based on the recent work of Brock and Watson (who measured the quantum yield at 266 nm), the effect of assuming a quantum yield of 0.9 for O(/sup 1/D) production at wavelengths less than 300 nm in the LLL 1-d model was tested. Since measurements of the quantum yield fall off at longer wavelength also assume unity quantum yield below the fall off region, we also multiplied the O(/sup 1/D) quantum yield through this region by 0.9. The remaining quantum yield from the photolysis reaction is assumed to produce O(/sup 3/P) at all wavelengths so that the total quantum yield is unity.