WorldWideScience

Sample records for hole doping treatment

  1. Hole transport in pure and doped hematite

    Science.gov (United States)

    Liao, Peilin; Carter, Emily A.

    2012-07-01

    Hematite (α-Fe2O3) is a promising candidate for use in photovoltaic (PV) and photoelectrochemical devices. Its poor conductivity is one major drawback. Doping hematite either p-type or n-type greatly enhances its measured conductivity and is required for potential p-n junctions in PVs. Here, we study hole transport in pure and doped hematite using an electrostatically embedded cluster model with ab initio quantum mechanics (unrestricted Hartree-Fock theory). Consistent with previous work, the model suggests that hole hopping is via oxygen anions for pure hematite. The activation energy for hole mobility is predicted to be at least 0.1 eV higher than the activation energy for electron mobility, consistent with the trend observed in experiments. We examine four dopants—magnesium(II), nickel(II), copper(II), and manganese(II/III) in direct cation substitution sites—to gain insight into the mechanism by which conductivity is improved. The activation energies are used to assess qualitative effects of different dopants. The hole carriers are predicted to be attracted to O anions near the dopants. The magnitude of the trapping effect is similar among the four dopants in their +2 oxidation states. The multivalent character of Mn doping facilitates local hole transport around Mn centers via a low-barrier O-Mn-O pathway, which suggests that higher hole mobility can be achieved with increasing Mn doping concentration, especially when a network of these low-barrier pathways is produced. Our results suggest that the experimentally observed conductivity increase in Mg-, Ni-, and Cu-doped p-type hematite is mostly due to an increase in hole carriers rather than improved mobility, and that Mg-, Ni-, and Cu-doping perform similarly, while the conductivity of Mn-doped hematite might be significantly improved in the high doping concentration limit.

  2. Hole-doped cuprate high temperature superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Chu, C.W.; Deng, L.Z.; Lv, B.

    2015-07-15

    Highlights: • Historical discoveries of hole-doped cuprates and representative milestone work. • Several simple and universal scaling laws of the hole-doped cuprates. • A comprehensive classification list with references for hole-doped cuprates. • Representative physical parameters for selected hole-doped cuprates. - Abstract: Hole-doped cuprate high temperature superconductors have ushered in the modern era of high temperature superconductivity (HTS) and have continued to be at center stage in the field. Extensive studies have been made, many compounds discovered, voluminous data compiled, numerous models proposed, many review articles written, and various prototype devices made and tested with better performance than their nonsuperconducting counterparts. The field is indeed vast. We have therefore decided to focus on the major cuprate materials systems that have laid the foundation of HTS science and technology and present several simple scaling laws that show the systematic and universal simplicity amid the complexity of these material systems, while referring readers interested in the HTS physics and devices to the review articles. Developments in the field are mostly presented in chronological order, sometimes with anecdotes, in an attempt to share some of the moments of excitement and despair in the history of HTS with readers, especially the younger ones.

  3. Hall hole mobility in boron-doped homoepitaxial diamond

    Science.gov (United States)

    Pernot, J.; Volpe, P. N.; Omnès, F.; Muret, P.; Mortet, V.; Haenen, K.; Teraji, T.

    2010-05-01

    Hall hole mobility of boron-doped homoepitaxial (100) diamond samples has been investigated in the temperature range of 100-900 K, both experimentally and theoretically. The temperature dependence of the mobility measured in high-quality and low boron-doped materials was compared with theoretical calculations to determine the phonon-hole coupling constants (deformation potential for acoustic phonons and coupling constant for optical phonons). The maximum hole mobility is found to be close to 2000cm2/Vs at room temperature. For boron-doped material, the hole scattering by neutral boron atoms is shown to be important in diamond due to the high ionization energy of the boron acceptor. The doping dependence of the Hall hole mobility is established for boron-doping levels ranging between 1014 and 1020cm-3 at 300 and 500 K. The physical reasons which make diamond a semiconductor with a higher mobility than other semiconductors of column IV are discussed.

  4. Hole conduction in pure and doped lead bromide crystals

    NARCIS (Netherlands)

    Schoonman, J.

    The conductivity of pure and doped lead bromide was measured in a bromine atmosphere in the temperature region 25–200°C. The defect chemistry of nonstoichiometric lead bromide is presented. The hole mobility was derived from the time dependent change in the conductivity after admission/removal of

  5. Exploring the effect of hole localization on the charge-phonon dynamics of hole doped delafossite.

    Science.gov (United States)

    Mazumder, Nilesh; Mandal, Prasanta; Roy, Rajarshi; Ghorai, Uttam Kumar; Saha, Subhajit; Chattopadhyay, Kalyan Kumar

    2017-09-20

    For weak or moderate doping, electrical measurement is not suitable for detecting changes in the charge localization inside a semiconductor. Here, to investigate the nature of charge-phonon coupling in the presence of gradually delocalized holes within a weak doping regime (~1016 cm-3), we examine the temperature dependent Raman spectra (303-817 K) of prototype hole doped delafossite [Formula: see text] (x  =  0/0.03, y  =  0/0.01). For both [Formula: see text] and [Formula: see text] phonons, negative lineshape asymmetry and relative thermal hardening are distinctly observed upon [Formula: see text] and [Formula: see text] doping. Using Allen formalism, charge density of states at the Fermi level per spin and molecule, and charge delocalization associated to [Formula: see text] plane, are estimated to increase appreciably upon codoping compared to the [Formula: see text]-axis. We delineate the interdependence between charge-phonon coupling constant ([Formula: see text]) and anharmonic phonon lifetime ([Formula: see text]), and deduce that excitation of delocalized holes weakly coupled with phonons of larger [Formula: see text] is the governing feature of observed Fano asymmetry ([Formula: see text]) reversal.

  6. Effective magnetic correlations in hole-doped graphene nanoflakes

    Science.gov (United States)

    Valli, A.; Amaricci, A.; Toschi, A.; Saha-Dasgupta, T.; Held, K.; Capone, M.

    2016-12-01

    The magnetic properties of zigzag graphene nanoflakes (ZGNFs) are investigated within the framework of inhomogeneous dynamical mean-field theory. At half-filling and for realistic values of the local interaction, the ZGNF is in a fully compensated antiferromagnetic (AF) state, which is found to be robust against temperature fluctuations. Introducing charge carriers in the AF background drives the ZGNF metallic and stabilizes a magnetic state with a net uncompensated moment at low temperatures. The change in magnetism is ascribed to the delocalization of the doped holes in the proximity of the edges, which mediate ferromagnetic correlations between the localized magnetic moments. Depending on the hole concentration, the magnetic transition may display a pronounced hysteresis over a wide range of temperatures, indicating the coexistence of magnetic states with different symmetries. This suggests the possibility of achieving electrostatic control of the magnetic state of ZGNFs to realize a switchable spintronic device.

  7. Hole doped Dirac states in silicene by biaxial tensile strain

    KAUST Repository

    Kaloni, Thaneshwor P.

    2013-03-11

    The effects of biaxial tensile strain on the structure, electronic states, and mechanical properties of silicene are studied by ab-initio calculations. Our results show that up to 5% strain the Dirac cone remains essentially at the Fermi level, while higher strain induces hole doped Dirac states because of weakened Si–Si bonds. We demonstrate that the silicene lattice is stable up to 17% strain. It is noted that the buckling first decreases with the strain (up to 10%) and then increases again, which is accompanied by a band gap variation. We also calculate the Grüneisen parameter and demonstrate a strain dependence similar to that of graphene.

  8. Hole-doping of fullerenes and nanotubes by way of intercalation chemistry.

    Science.gov (United States)

    Claves, D

    2007-01-01

    Succeeding to the electron-doping processes of carbon nanostructures, chemical methods devoted to the hole-doping of the latter have significantly developed over the past ten years. Intercalation chemistry remains a top-rated technique in this purpose, among the variety of available chemical doping schemes. A review of the p-type doping of fullerenes and nanotubes by this method is exposed, which also includes a wide range of derived potential applications and prospects regarding the materials thus obtained.

  9. Thermoelectric performance of electron and hole doped PtSb2

    KAUST Repository

    Saeed, Yasir

    2013-04-30

    We investigate the thermoelectric properties of electron and hole doped PtSb2. Our results show that for doping of 0.04 holes per unit cell ( 1.5×1020 cm−3 ) PtSb2 shows a high Seebeck coefficient at room temperature, which can also be achieved at other temperatures by controlling the carrier concentration (both electron and hole). The electrical conductivity becomes temperature independent when the doping exceeds some 0.2 electrons/holes per unit cell. The figure of merit at 800 K in electron and hole doped PtSb2 is comparatively low at 0.13 and 0.21, respectively, but may increase significantly with As alloying due to the likely opening of a band gap and reduction of the lattice thermal conductivity.

  10. Enhancement of the hole injection into regioregular poly(3-hexylthiophene) by molecular doping

    NARCIS (Netherlands)

    Zhang, Y.; Blom, P.W.M.

    2010-01-01

    The hole injection in Schottky barriers formed between p -type doped regioregular poly(3-hexylthiophene-2,5-diyl) (rr-P3HT) and silver (Ag) is investigated. The rr-P3HT is controllably doped using the acceptor 2,3,5,6-Tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ). We demonstrate that only

  11. Pairing symmetries of a hole-doped extended two-orbital model for the pnictides

    Energy Technology Data Exchange (ETDEWEB)

    Nicholson, Andrew D [ORNL; Ge, Weihao [University of Tennessee, Knoxville (UTK) & Oak Ridge National Laboratory (ORNL); Riera, J. A. [Universidad Nacional de Rosario; Daghofer, Maria [ORNL; Moreo, Adriana [ORNL; Dagotto, Elbio R [ORNL

    2012-01-01

    The hole-doped ground state of a recently introduced extended t-U-J two-orbital Hubbard model for the Fe-based superconductors is studied via exact diagonalization methods on small clusters. Similarly as in the previously studied case of electron doping [A. Nicholson et al., Phys. Rev. Lett. 106, 217002 (2011)], upon hole doping it is observed that there are several competing pairing symmetries, including A1g , B1g , and B2g . However, contrary to the electron-doped case, the ground state of the hole-doped state has pseudocrystal momentum k = ( , ) in the unfolded Brillouin zone. In the two Fe-atom per unit cell representation, this indicates that the ground state involves antibonding, rather than bonding, combinations of the orbitals of the two Fe atoms in the unit cell. The lowest state with k = (0,0) has only a slightly higher energy. These results indicate that this simple two-orbital model may be useful to capture some subtle aspects of the hole-doped pnictides, since calculations for the five-orbital model have unveiled a hole pocket centered at M [k = ( , )] in the unfolded Brillouin zone.

  12. Hole states in diamond p-delta-doped field effect transistors

    Energy Technology Data Exchange (ETDEWEB)

    Martinez-Orozco, J C; Rodriguez-Vargas, I [Unidad Academica de Fisica, Universidad Autonoma de Zacatecas, Calzada Solidaridad Esquina con Paseo la Bufa S/N, CP 98060 Zacatecas, ZAC. (Mexico); Mora-Ramos, M E, E-mail: jcmover@correo.unam.m [Facultad de Ciencias, Universidad Autonoma del Estado de Morelos, Av. Universidad 1001, Col. Chamilpa, CP 62209 Cuernavaca, MOR. (Mexico)

    2009-05-01

    The p-delta-doping in diamond allows to create high density two-dimensional hole gases. This technique has already been applied in the design and fabrication of diamond-based field effect transistors. Consequently, the knowledge of the electronic structure is of significant importance to understand the transport properties of diamond p-delta-doped systems. In this work the hole subbands of diamond p-type delta-doped quantum wells are studied within the framework of a local-density Thomas-Fermi-based approach for the band bending profile. The calculation incorporates an independent three-hole-band scheme and considers the effects of the contact potential, the delta-channel to contact distance, and the ionized impurity density.

  13. Chemical hole doping into large-area transition metal dichalcogenide monolayers using boron-based oxidant

    Science.gov (United States)

    Matsuoka, Hirofumi; Kanahashi, Kaito; Tanaka, Naoki; Shoji, Yoshiaki; Li, Lain-Jong; Pu, Jiang; Ito, Hiroshi; Ohta, Hiromichi; Fukushima, Takanori; Takenobu, Taishi

    2018-02-01

    Hole carrier doping into single-crystalline transition metal dichalcogenide (TMDC) films can be achieved with various chemical reagents. However, large-area polycrystalline TMDC monolayers produced by a chemical vapor deposition (CVD) growth method have yet to be chemically doped. Here, we report that a salt of a two-coordinate boron cation, Mes2B+ (Mes: 2,4,6-trimethylphenyl group), with a chemically stable tetrakis(pentafluorophenyl)borate anion, [(C6F5)4B]‑, can serve as an efficient hole-doping reagent for large-area CVD-grown tungsten diselenide (WSe2) films. Upon doping, the sheet resistance of large-area polycrystalline WSe2 monolayers decreased from 90 GΩ/sq to 3.2 kΩ/sq.

  14. Lead Monoxide: Two-Dimensional Ferromagnetic Semiconductor Induced by Hole-Doping

    KAUST Repository

    Wang, Yao

    2017-04-12

    We employ first-principles calculations to demonstrate ferromagnetic ground states for single- and multi-layer lead monoxide (PbO) under hole-doping, originating from a van Hove singularity at the valence band edge. Both the sample thickness and applied strain are found to have huge effects on the electronic and magnetic properties. Multi-layer PbO is an indirect band gap semiconductor, while a direct band gap is realized in the single-layer limit. In hole-doped single-layer PbO, biaxial tensile strain can enhance the stability of the ferromagnetic state.

  15. Prediction of phonon-mediated superconductivity in hole-doped black phosphorus.

    Science.gov (United States)

    Feng, Yanqing; Sun, Hongyi; Sun, Junhui; Lu, Zhibin; You, Yong

    2018-01-10

    We study the conventional electron-phonon mediated superconducting properties of hole-doped black phosphorus by density functional calculations and get quite a large electron-phonon coupling (EPC) constant λ ~ 1.0 with transition temperature T C ~ 10 K, which is comparable to MgB 2 when holes are doped into the degenerate and nearly flat energy bands around the Fermi level. We predict that the softening of low-frequency [Formula: see text] optical mode and its phonon displacement, which breaks the lattice nonsymmorphic symmetry of gliding plane and lifts the band double degeneracy, lead to a large EPC. These factors are favorable for BCS superconductivity.

  16. Effective doublon and hole temperatures in the photo-doped dynamic Hubbard model.

    Science.gov (United States)

    Werner, Philipp; Eckstein, Martin

    2016-03-01

    Hirsch's dynamic Hubbard model describes the effect of orbital expansion with occupancy by coupling the doublon operator to an auxiliary boson. In the Mott insulating phase, empty sites (holes) and doubly occupied orbitals (doublons) become charge carriers on top of the half-filled background. We use the nonequilibrium dynamical mean field method to study the properties of photo-doped doublons and holes in this model in the strongly correlated regime. In particular, we discuss how photodoping leads to doublon and hole populations with different effective temperatures, and we analyze the relaxation behavior as a function of the boson coupling and boson energy. In the polaronic regime, the nontrivial energy exchange between doublons, holes, and bosons can result in a negative temperature distribution for the holes.

  17. Effective doublon and hole temperatures in the photo-doped dynamic Hubbard model

    Directory of Open Access Journals (Sweden)

    Philipp Werner

    2016-03-01

    Full Text Available Hirsch's dynamic Hubbard model describes the effect of orbital expansion with occupancy by coupling the doublon operator to an auxiliary boson. In the Mott insulating phase, empty sites (holes and doubly occupied orbitals (doublons become charge carriers on top of the half-filled background. We use the nonequilibrium dynamical mean field method to study the properties of photo-doped doublons and holes in this model in the strongly correlated regime. In particular, we discuss how photodoping leads to doublon and hole populations with different effective temperatures, and we analyze the relaxation behavior as a function of the boson coupling and boson energy. In the polaronic regime, the nontrivial energy exchange between doublons, holes, and bosons can result in a negative temperature distribution for the holes.

  18. The anomalous optical conductivity in hole-doped cuprate superconductors

    Science.gov (United States)

    Gao, He; Yuan, Feng; Chen, Shaou; Zhao, Huaisong

    2018-02-01

    Based on the renormalized t- J model and self-consistent mean field theory, the doping and energy dependence of optical conductivity and effective electron number in cuprate superconductors are discussed. As the result of the presence of the pseudogap in normal state, the optical conductivity exhibits two main components from underdoping to overdoping, a narrow band peaked around zero energy and a broadband centered in the mid-infrared region which deviates the Drude formula. With increasing the doping concentration, the spectral weight of the optical conductivity suppressed strongly in underdoped region increases quickly, and the peak position of the mid-infrared band moves towards to the lower energy region, then incorporates into the narrow band centered in zero energy in the heavily overdoped region. By virtue of the integral, the effective electron number is obtained, and it increases monotonically from zero energy to mid-infrared characteristic energy with increasing energy, then shows a plateau feature when the energy is larger. In particular, the mid-infrared characteristic energy scales with the pseudogap, reflecting the presence of the mid-infrared band is the result of the pseudogap effect.

  19. Spin-state polarons in lightly-hole-doped LaCoO3.

    Science.gov (United States)

    Podlesnyak, A; Russina, M; Furrer, A; Alfonsov, A; Vavilova, E; Kataev, V; Büchner, B; Strässle, Th; Pomjakushina, E; Conder, K; Khomskii, D I

    2008-12-12

    Inelastic neutron scattering (INS), electron spin resonance (ESR), and nuclear magnetic resonance (NMR) measurements were employed to establish the origin of the strong magnetic signal in lightly-hole-doped La1-xSrxCoO3, x approximately 0.002. Both INS and ESR low temperature spectra show intense excitations with large effective g factors approximately 10-18. NMR data indicate the creation of extended magnetic clusters. From the Q dependence of the INS magnetic intensity, we conclude that the observed anomalies are caused by the formation of octahedrally shaped spin-state polarons comprising seven Co ions. The present INS, ESR, and NMR data give evidence for two regimes in the lightly-hole-doped samples: (i) T35 K dominated by thermally activated magnetic Co3+ ions.

  20. Spin-state polarons in lightly hole-doped LaCoO3

    Energy Technology Data Exchange (ETDEWEB)

    Podlesnyak, Andrey A [ORNL; Russina, Margarita [Hahn-Meitner Institut, Berlin, Germany; Furrer, Albert [Laboratory for Neutron Scattering ETHZ & PSI; Alfonsov, Aleksei [IFW Dresden; Vavilova, Eugenia [IFW Dresden; Kataev, Vladislav [IFW Dresden; Buechner, Bernd [IFW Dresden; Straessle, Thierry [Laboratory for Neutron Scattering ETHZ & PSI; Pomjakushina, Ekaterina [Paul Scherrer Institut, Villigen, Switzerland; Conder, Kazimierz [Paul Scherrer Institut, Villigen, Switzerland; Khomskii, Daniel [Universitat zu Koln, Koln, Germany

    2008-01-01

    Inelastic neutron scattering (INS), electron spin resonance (ESR), and nuclear magnetic resonance (NMR) measurements were employed to establish the origin of the strong magnetic signal in lightly-hole-doped La{sub 1-x}Sr{sub x}CoO{sub 3}, x{approx}0.002. Both INS and ESR low temperature spectra show intense excitations with large effective g factors {approx}10-18. NMR data indicate the creation of extended magnetic clusters. From the Q dependence of the INS magnetic intensity, we conclude that the observed anomalies are caused by the formation of octahedrally shaped spin-state polarons comprising seven Co ions. The present INS, ESR, and NMR data give evidence for two regimes in the lightly-hole-doped samples: (i) T < 35 K dominated by spin polarons; (ii) T > 35 K dominated by thermally activated magnetic Co{sup 3+} ions.

  1. Superconducting and normal state properties of heavily hole-doped diamond synthesized at high pressure

    Directory of Open Access Journals (Sweden)

    V.A. Sidorov, E.A. Ekimov, A.V. Rakhmanina, S.M. Stishov, E.D. Bauer and J.D. Thompson

    2006-01-01

    Full Text Available Diamonds, synthesized at high pressures and high temperatures in the presence of boron, are heavily hole-doped by incorporation of boron into the diamond lattice. These diamonds become superconducting below Tc=2–9 K. Synthesis in the systems B-C and B4C-C at P=9 GPa and T=2500–2800 K result in formation of polycrystalline carbonado-like material, whereas synthesis from B-C-H gives small single crystals and intergrowth plates. Dense superconducting bodies can be prepared by compacting these single crystal particles at P=8 GPa and T=1800 K. Specific heat and resistivity measurements in magnetic fields prove the bulk nature of superconductivity in all pressure-synthesized samples and provide a consistent set of materials parameters that favor a conventional weak-coupling electron–phonon interpretation of the superconducting mechanism at high hole doping. Schottky barrier tunneling conductance spectra, obtained with contacts fabricated at the surface of these hole-doped diamonds, indicate the appearance of superconducting gap below Tc.

  2. Towards low-dimensional hole systems in Be-doped GaAs nanowires

    DEFF Research Database (Denmark)

    Ullah, A. R.; Gluschke, J. G.; Jeppesen, Peter Krogstrup

    2017-01-01

    our development of nanowire transistors featuring Be-doped p-type GaAs nanowires, AuBe alloy contacts and patterned local gate electrodes towards making nanowire-based quantum hole devices. We report on nanowire transistors with traditional substrate back-gates and EBL-defined metal/oxide top......GaAs was central to the development of quantum devices but is rarely used for nanowire-based quantum devices with InAs, InSb and SiGe instead taking the leading role. p-type GaAs nanowires offer a path to studying strongly confined 0D and 1D hole systems with strong spin–orbit effects, motivating...... transistor performance for moderate doping, with conduction freezing out at low temperature for lowly doped nanowires and inability to reach a clear off-state under gating for the highly doped nanowires. Our best devices give on-state conductivity 95 nS, off-state conductivity 2 pS, on-off ratio $\\sim {10...

  3. Origin of a spin-state polaron in lightly hole doped LaCoO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Alfonsov, A; Vavilova, E; Kataev, V; Buechner, B [IFW Dresden, D-01069 Dresden (Germany); Podlesnyak, A; Russina, M [Hahn-Meitner-Institut, D-14109 Berlin (Germany); Furrer, A; Straessle, Th; Pomjakushina, E [Laboratory for Neutron Scattering, ETH Zuerich and PSI, CH-5232 Villigen PSI (Switzerland); Conder, K [Laboratory for Developments and Methods, PSI, CH-5232 Villigen PSI (Switzerland); Khomskii, D I, E-mail: v.kataev@ifw-dresden.d, E-mail: a.alfonsov@ifw-dresden.d [II. Physikalisches Institut, Universitaet zu Koeln, 50937 Koeln (Germany)

    2009-03-01

    We performed electron spin and nuclear magnetic resonance and inelastic neutron scattering measurements of a single crystal of lightly hole-doped La{sub 1}-{sub x}Sr{sub x}CoO{sub 3}, x approx 0.002 in order to establish the origin of a surprisingly strong magnetization due to a very small Sr doping. The data provide experimental evidence for the creation at low temperatures of extended spin clusters with a large spin multiplicity. We argue that the doped hole couples ferromagnetically seven magnetic Co ions yielding a spin-state polaron with a huge local magnetic moment with a strong orbital contribution.

  4. Effect of uniaxial stress on gallium, beryllium, and copper-doped germanium hole population inversion lasers

    Energy Technology Data Exchange (ETDEWEB)

    Chamberlin, Danielle Russell [Univ. of California, Berkeley, CA (United States)

    1998-05-01

    The effects of stress on germanium lasers doped with single, double, and triple acceptors have been investigated. The results can be explained quantitatively with theoretical calculations and can be attributed to specific changes in the energy levels of acceptors in germanium under stress. In contrast to previous measurements, gallium-doped Ge crystals show a decrease in lasing upon uniaxial stress. The decrease seen here is attributed to the decrease in heavy hole effective mass upon application of uniaxial stress, which results in a decreased population inversion. The discrepancy between this work and previous studies can be explained with the low compensation level of the material used here. Because the amount of ionized impurity scattering in low-compensated germanium lasers is small to begin with, the reduction in scattering with uniaxial stress does not play a significant role in changing the laser operation. Beryllium-doped germanium lasers operate based on a different mechanism of population inversion. In this material it is proposed that holes can transfer between bands by giving their energy to a neutral beryllium atom, raising the hole from the ground to a bound excited state. The free hole will then return to zero energy with some probability of entering the other band. The minimum and maximum E/B ratios for lasing change with uniaxial stress because of the change in effective mass and bound excited state energy. These limits have been calculated for the case of 300 bar [100] stress, and match very well with the observed data. This adds further credence to the proposed mechanism for population inversion in this material. In contrast to Be and Ga-doped lasers, copper-doped lasers under uniaxial stress show an increase in the range of E and B where lasing is seen. To understand this change the theoretical limits for population inversion based on both the optical phonon mechanism and the neutral acceptor mechanism have been calculated. The data are

  5. Spin-state polaron in lightly hole doped LaCoO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Alfonsov, A.; Kataev, V.; Buechner, B. [IFW Dresden, D-01171 Dresden (Germany); Vavilova, E. [IFW Dresden, D-01171 Dresden (Germany); Zavoisky Physical Technical Institute, RAS, 420029 Kazan (Russian Federation); Podlesnyak, A.; Russina, M. [Hahn-Meitner-Institut, D-14109 Berlin (Germany); Furrer, A.; Straessle, T. [Laboratory for Neutron Scattering, ETH Zuerich, CH-5232 Villigen (Switzerland); PSI, CH-5232 Villigen PSI (Switzerland); Pomjakushina, E. [Laboratory for Neutron Scattering, ETH Zuerich, CH-5232 Villigen (Switzerland); Laboratory for Developments and Methods, PSI, CH-5232 Villigen (Switzerland); Conder, K. [Laboratory for Developments and Methods, PSI, CH-5232 Villigen (Switzerland); Khomskii, D.I. [II. Physikalisches Institut, Universitaet Koeln, 50937 Koeln (Germany)

    2009-07-01

    LaCoO{sub 3} is nonmagnetic at low temperatures and shows a T-activated magnetism due to a change of the Co{sup 3+} spin state. Surprisingly, a very small Sr{sup 2+} (i.e. hole) doping yields a strong magnetic response already at low T. To establish its nature we performed electron spin- (ESR), nuclear magnetic resonance (NMR) and inelastic neutron scattering (INS) measurements of lightly doped La{sub 1-x}Sr{sub x}CoO{sub 3} single crystals (x{proportional_to}0.002). {sup 59}Co NMR data indicate the formation of extended magnetic clusters distributed over the entire sample volume. Low-T ESR spectra show up multiple lines with large g-factors suggesting that these clusters have a large spin multiplicity with a strong orbital contribution. From the Q-dependence of the INS intensity we conclude that the cluster comprises 7 magnetic Co ions. We propose a mechanism of how already a very light hole doping yields a formation of big spin polarons in LaCoO{sub 3}.

  6. Correlated electron-hole mechanism for molecular doping in organic semiconductors

    Science.gov (United States)

    Li, Jing; D'Avino, Gabriele; Pershin, Anton; Jacquemin, Denis; Duchemin, Ivan; Beljonne, David; Blase, Xavier

    2017-07-01

    The electronic and optical properties of the paradigmatic F4TCNQ-doped pentacene in the low-doping limit are investigated by a combination of state-of-the-art many-body ab initio methods accounting for environmental screening effects, and a carefully parametrized model Hamiltonian. We demonstrate that while the acceptor level lies very deep in the gap, the inclusion of electron-hole interactions strongly stabilizes dopant-semiconductor charge transfer states and, together with spin statistics and structural relaxation effects, rationalize the possibility for room-temperature dopant ionization. Our findings reconcile available experimental data, shedding light on the partial vs. full charge transfer scenario discussed in the literature, and question the relevance of the standard classification in shallow or deep impurity levels prevailing for inorganic semiconductors.

  7. Hole mobility enhancement and p-doping in monolayer WSe2 by gold decoration

    KAUST Repository

    Chen, Chang-Hsiao

    2014-10-28

    Tungsten diselenide (WSe2) is an attractive transition metal dichalcogenide material, since its Fermi energy close to the mid gap makes it an excellent candidate for realizing p-n junction devices and complementary digital logic applications. Doping is one of the most important technologies for controlling the Fermi energy in semiconductors, including 2D materials. Here we present a simple, stable and controllable p-doping technique on a WSe2 monolayer, where a more p-typed WSe2 field effect transistor is realized by electron transfer from the WSe2 to the gold (Au) decorated on the WSe2 surfaces. Related changes in Raman spectroscopy are also reported. The p-doping caused by Au on WSe2 monolayers lowers the channel resistance by orders of magnitude. The effective hole mobility is ~100 (cm2/Vs) and the near ideal subthreshold swing of ~60 mV/decade and high on/off current ratio of >106 are observed. The Au deposited on the WSe2 also serves as a protection layer to prevent a reaction between the WSe2 and the environment, making the doping stable and promising for future scalable fabrication.

  8. Suppression of superconductivity in Pr-doped 123-systems: hole localization and hole clustering concepts in CuO2 planes

    Directory of Open Access Journals (Sweden)

    V Daadmehr

    2006-09-01

    Full Text Available   Doping Pr in 123-systems gives rise to some anomalies, such as critical Temperature suppression. Here, we show that a modification of hole localization theory based on a geometrical modeling by band percolation theory can put forward as a good explanation for the critical temperature suppression for the whole range of Pr-doping value. In this model the key concept of hole clustering is introduced and shown to have a great role near phase transition point, so we can not ignore it in any modeling or calculation. Also we have provided some experimental evidence which manifests an agreement between simulation based on hole clustering effect and the experimental data.

  9. Tunable magneto-optical effects in hole-doped group-IIIA metal-monochalcogenide monolayers

    Science.gov (United States)

    Feng, Wanxiang; Guo, Guang-Yu; Yao, Yugui

    2017-03-01

    Because of unusual properties and fascinating prospects for next-generation device applications, two-dimensional (2D) materials have attracted enormous attention since graphene was discovered in 2004. Among the 2D materials beyond graphene, group-IIIA metal-monochalcogenide (MX) monolayers (MLs), are receiving increasing interests because their excellent applications on electronics and optoelectronics. Recently, ferromagnetism and half-metallicity have been predicted in hole-doped GaS and GaSe MLs, which promise exciting potentials for semiconductor spintronics. Detection and measurement of spontaneous magnetization in these 2D materials will be essential for their spintronic applications. The magneto-optical (MO) effects not only are a powerful probe of magnetism in 2D materials but also have valuable applications in high-density data-storage technology. Furthermore, anomalous Hall effect is not only an ideal transport probe of itinerant magnetism but also of considerable current interest because of its topological nature. Here we perform a systematic first-principles density functional study on the MO Kerr and Faraday effects as well as such important magnetic and transport properties as magneto-crystalline anisotropy energy (MAE) and anomalous Hall conductivity (AHC) of all hole-doped MX (M = Ga, In; X = S, Se, Te) MLs. In this paper, we report the following important findings: (a) gate-tunable MO effects in MX MLs in a broad range of hole concentration; (b) large Kerr and Faraday rotation angles with Kerr angles comparable to well-known MO 3d-transition-metal multilayers and Faraday angles being among the largest ones reported; (c) tunable MAE and large AHC, making MX MLs suitable for magnetic memory devices current-driven via spin-transfer torque and also promising materials for magnetic field nanosensors with high sensitivity. Superior MO characteristics, together with the other interesting properties, would make MX MLs an excellent family of 2D materials for

  10. Spectral hole lifetimes and spin population relaxation dynamics in neodymium-doped yttrium orthosilicate

    Science.gov (United States)

    Cruzeiro, E. Zambrini; Tiranov, A.; Usmani, I.; Laplane, C.; Lavoie, J.; Ferrier, A.; Goldner, P.; Gisin, N.; Afzelius, M.

    2017-05-01

    We present a detailed study of the lifetime of optical spectral holes due to population storage in Zeeman sublevels of Nd3 +:Y2SiO5 . The lifetime is measured as a function of magnetic field strength and orientation, temperature, and Nd3 + doping concentration. At the lowest temperature of 3 K we find a general trend where the lifetime is short at low field strengths, then increases to a maximum lifetime at a few hundred mT, and then finally decays rapidly for high field strengths. This behavior can be modeled with a relaxation rate dominated by Nd3 +-Nd3 + cross relaxation at low fields and spin lattice relaxation at high magnetic fields. The maximum lifetime depends strongly on both the field strength and orientation, due to the competition between these processes and their different angular dependencies. The cross relaxation limits the maximum lifetime for concentrations as low as 30 ppm of Nd3 + ions. By decreasing the concentration to less than 1 ppm we could completely eliminate the cross relaxation, reaching a lifetime of 3.8 s at 3 K. At higher temperatures the spectral hole lifetime is limited by the magnetic-field-independent Raman and Orbach processes. In addition we show that the cross relaxation rate can be strongly reduced by creating spectrally large holes of the order of the optical inhomogeneous broadening. Our results are important for the development and design of new rare-earth-ion doped crystals for quantum information processing and narrow-band spectral filtering for biological tissue imaging.

  11. Persistent Luminescence Hole-Type Materials by Design: Transition-Metal-Doped Carbon Allotrope and Carbides.

    Science.gov (United States)

    Qu, Bingyan; Zhang, Bo; Wang, Lei; Zhou, Rulong; Zeng, Xiao Cheng; Li, Liang

    2016-03-02

    Electron traps play a crucial role in a wide variety of compounds of persistent luminescence (PL) materials. However, little attention has been placed on the hole-trap-type PL materials. In this study, a novel hole-dominated persistent luminescence (PL) mechanism is predicted. The mechanism is validated in the night pearl diamond (NPD) composed of lonsdaleite with ultralong persistent luminescence (PL) (more than 72 h). The computed band structures suggest that the Fe ion dopant in lonsdaleite is responsible for the luminescence of NPD due to the desired defect levels within the band gap for electronic transition. Other possible impurity defects in lonsdaleite, such as K, Ca, Mg, Zn, or Tl dopants, or C vacancy can also serve as the hole-trap centers to enhance the PL. Among other 3d transition-metal-ion dopants considered, Cr and Mn ions are predicted to give rise to PL property. The predicted PL mechanism via transition-metal doping of lonsdaleite offers an exciting opportunity for engineering new PL materials by design.

  12. Hole transport and photoluminescence in Mg-doped InN

    Energy Technology Data Exchange (ETDEWEB)

    Miller, N.; Ager III, J. W.; Smith III, H. M.; Mayer, M. A.; Yu, K. M.; Haller, E. E.; Walukiewicz, W.; Schaff, W. J.; Gallinat, C.; Koblmuller, G.; Speck, J. S.

    2010-03-24

    Hole conductivity and photoluminescence were studied in Mg-doped InN films grown by molecular beam epitaxy. Because surface electron accumulation interferes with carrier type determination by electrical measurements, the nature of the majority carriers in the bulk of the films was determined using thermopower measurements. Mg concentrations in a"window" from ca. 3 x 1017 to 1 x 1019 cm-3 produce hole-conducting, p-type films as evidenced by a positive Seebeck coecient. This conclusion is supported by electrolyte-based capacitance voltage measurements and by changes in the overall mobility observed by Hall effect, both of which are consistent with a change from surface accumulation on an n-type film to surface inversion on a p-type film. The observed Seebeck coefficients are understood in terms of a parallel conduction model with contributions from surface and bulk regions. In partially compensated films with Mg concentrations below the window region, two peaks are observed in photoluminescence at 672 meV and at 603 meV. They are attributed to band-to-band and band-to-acceptor transitions, respectively, and an acceptor binding energy of ~;;70 meV is deduced. In hole-conducting films with Mg concentrations in the window region, no photoluminescence is observed; this is attributed to electron trapping by deep states which are empty for Fermi levels close to the valence band edge.

  13. Electronic, magnetic and transport properties of transition metal-doped holely C2N-h2D nanoribbons

    Science.gov (United States)

    He, Jing-Jing; Guo, Yan-Dong; Yan, Xiao-Hong; Zeng, Hong-Li

    2018-01-01

    A novel layered two-dimensional graphene-like material C2N-h2D with evenly distributed holes and nitrogen atoms has been synthesized via a bottom-up wet-chemical reaction [Nat. Commun. 6, 6486 (2015)]. The presence of holes provides a ground for further functionalization by doping. By performing a first-principles study, we have doped transition metals at the center of the holes of C2N-h2D nanoribbons and explored their doping effects on electronic, magnetic and transport properties. It is found that the doping can essentially regulate the electronic properties of C2N-h2D nanoribbons. The metallic zigzag ribbon is tuned into a semiconductor for Mn, Fe and Co-doped cases, but half-metal for Ni-doping. This transition is derived from the peculiar band morphology which has a big band gap between the edge state and the higher band, so when the energy of the edge state is reduced by the impurity state, the band gap falls too and crosses the Fermi level. In contrast, the pristine semiconducting armchair C2N-h2D nanoribbon is changed into metallic. Different from the zigzag case, its physical mechanism originates from the hybridization of 3 d orbitals of transition metal atoms and the p orbitals of carbon and nitrogen atoms which introduces several resonant peaks at the Fermi level in the density of states. Furthermore, the magnetic moments of all doped materials are enhanced compared to the pristine structures but decrease as the atomic number of the transition metal atom increases. And the spin polarization of armchair C2N-h2D nanoribbon is increased, while that of the zigzag structure is decreased except the Ni-doped one which is completely spin-polarized suggesting great prospects in the future of spintronics and nanoelectronics.

  14. From Complex Magnetism Ordering to Simple Ferromagnetism in Two-Dimensional LaCrSb{sub 3} by Hole Doping.

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Haijie; Narayan, Awadhesh; Fang, Lei; Calta, Nicholas P.; Shi, Fengyuan; Chung, Duck Young; Wagner, Lucas; Kwok, Wai-Kwong; Kanatzidis, Mercouri G.

    2016-10-11

    Competing orders widely exist in many material systems, such as superconductivity, magnetism, and ferroelectricity; LaCrSb3 is a highly anisotropic magnetic material in which the spins are aligned ferromagnetically in one direction and canted antiferromagnetically in another in the Cr-Sb chains. Hole doping with Sr2+ and Ca2+ in the La site suppresses the antiferromagnetic correlations and transforms the anisotropic magnetic order into a ferromagnetic lattice in all directions. First-principles density functional theory calculations show that the canted magnetic order becomes energetically less favorable compared to the FM order upon hole doping. Doping in the La site is an effective approach to modulate the competing orders in LaCrSb3.

  15. Hole-density evolution of the one-particle spectral function in doped ladders

    Science.gov (United States)

    Martins, George B.; Gazza, Claudio; Dagotto, Elbio

    1999-06-01

    The spectral function A(q,ω) of doped t-J ladders is presented on clusters with up to 2×20 sites at zero temperature applying a recently developed technique that uses up to ~6×106 rung-basis states. Similarities with photoemission results for the two-dimensional cuprates are observed, such as the existence of a gap at (π,0) near half-filling (caused by hole pair formation) and flat bands in its vicinity. These features should be observable in angle-resolved photoemission spectroscopy experiments on ladders. The main result of the paper is the nontrivial evolution of the spectral function from a narrow band at x=0, to a quasinoninteracting band at x>=0.5. It was also observed that the low-energy peaks of a cluster spectra acquire finite linewidths as their energies move away from the chemical potential.

  16. Realization of a Hole-Doped Mott Insulator on a Triangular Silicon Lattice

    Science.gov (United States)

    Ming, Fangfei; Johnston, Steve; Mulugeta, Daniel; Smith, Tyler S.; Vilmercati, Paolo; Lee, Geunseop; Maier, Thomas A.; Snijders, Paul C.; Weitering, Hanno H.

    2017-12-01

    The physics of doped Mott insulators is at the heart of some of the most exotic physical phenomena in materials research including insulator-metal transitions, colossal magnetoresistance, and high-temperature superconductivity in layered perovskite compounds. Advances in this field would greatly benefit from the availability of new material systems with a similar richness of physical phenomena but with fewer chemical and structural complications in comparison to oxides. Using scanning tunneling microscopy and spectroscopy, we show that such a system can be realized on a silicon platform. The adsorption of one-third monolayer of Sn atoms on a Si(111) surface produces a triangular surface lattice with half filled dangling bond orbitals. Modulation hole doping of these dangling bonds unveils clear hallmarks of Mott physics, such as spectral weight transfer and the formation of quasiparticle states at the Fermi level, well-defined Fermi contour segments, and a sharp singularity in the density of states. These observations are remarkably similar to those made in complex oxide materials, including high-temperature superconductors, but highly extraordinary within the realm of conventional s p -bonded semiconductor materials. It suggests that exotic quantum matter phases can be realized and engineered on silicon-based materials platforms.

  17. Treatment of idiopathic macular hole with silicone oil tamponade

    Directory of Open Access Journals (Sweden)

    Ivanovska-Adjievska B

    2012-09-01

    Full Text Available Biljana Ivanovska-Adjievska,1 Salih Boskurt,1 Faruk Semiz,1 Hakan Yuzer,1 Vesna Dimovska-Jordanova21European Eye Hospital, Skopje, Macedonia, 2Clinic for Eye Diseases, University "St Cyril and Methodius", Skopje, MacedoniaPurpose: We analyzed the anatomical and visual outcomes after surgical treatment of idiopathic macular holes with pars plana vitrectomy, internal limiting membrane (ILM peeling using Brilliant Blue dye, and silicone oil tamponade without postoperative posturing.Methods: This was a retrospective interventional study of 10 eyes in eight patients who underwent surgical treatment of idiopathic macular holes using pars plana vitrectomy, ILM peeling using Brilliant Blue dye, and silicone oil tamponade without postoperative posturing. The preoperative staging of macular holes and postoperative anatomic outcomes were assessed using spectral-domain optical coherence tomography.Results: All patients were women with a mean age of 66.86 ± 4.8 years. In two patients, bilateral macular holes were present and both eyes were operated on. Stage 2 macular hole was diagnosed in three eyes, three eyes had stage 3, and four eyes had stage 4 macular holes. Anatomical success and closure of the macular hole was achieved in nine eyes (90% after one operation. In one eye, the macular hole was closed after reoperation. The preoperative mean best-corrected visual acuity (BCVA was 0.15 decimal units (0.8 logMAR units. Until the end of the follow-up period, BCVA was 0.25 decimal units (0.6 logMAR units. Visual acuity was improved in seven patients (70%. In two patients (20%, visual acuity remained at the same level, and in one eye (10%, visual acuity decreased. Postoperatively, all patients reported a significant reduction of metamorphopsia.Conclusion: Initial results after 20G pars plana vitrectomy with peeling of the ILM, use of dye (Brilliant Blue, and tamponade with silicone oil without postoperative posturing gave good anatomical and functional

  18. Effects of magnetization on hole localization and MnO{sub 6} octahedra disorder in hole-doped lanthanum manganese perovskites

    Energy Technology Data Exchange (ETDEWEB)

    Booth, C.H.; Brosha, E.L.; Kwei, G.H. [Los Alamos National Lab., NM (United States); Bridges, F. [Univ. of California, Santa Cruz, CA (United States). Physics Dept.; Neumeier, J.J. [Florida Atlanta Univ., Boca Raton, FL (United States). Physics Dept.

    1998-12-31

    The authors review the distortions of the MnO{sub 6} octahedra reduced by magnetization in hole-doped lanthanum manganese perovskites. The systems they consider include the colossal magnetoresistance (CMR) samples La{sub 1{minus}x}Ca{sub x}MnO{sub 3} (x = 0.21, 0.25, 0.30), La{sub 0.76}Ba{sub 0.33}MnO{sub 3}, and a poorer quality La{sub 0.76}Pb{sub 0.33}MnO{sub 3} sample. They also report preliminary work on three samples of oxygen-doped LaMnO{sub 3+{delta}} and a lanthanum-deficient La{sub 0.9}MnO{sub 3} sample. They find the same exponential relationship between the removal of the distortion and the sample magnetization in the Ba- and Pb-doped CMR samples as was found previously for the Ca doped samples. The MnO{sub 6} distortion in the oxygen-doped materials is found to slightly reduce below the magnetic transition, although much less so than in the CMR samples. Above T{sub C}, the antiferromagnetic LaMnO{sub 3.006} sample shows a softer temperature dependence of the Mn-O bond length distribution broadening. Surprisingly, even this sample shows deviations from thermal (Debye) behavior near T{sub N}, possibly due to FM coupling within MnO planes.

  19. Boron-Doped Graphite for High Work Function Carbon Electrode in Printable Hole-Conductor-Free Mesoscopic Perovskite Solar Cells.

    Science.gov (United States)

    Duan, Miao; Tian, Chengbo; Hu, Yue; Mei, Anyi; Rong, Yaoguang; Xiong, Yuli; Xu, Mi; Sheng, Yusong; Jiang, Pei; Hou, Xiaomeng; Zhu, Xiaotong; Qin, Fei; Han, Hongwei

    2017-09-20

    Work function of carbon electrodes is critical in obtaining high open-circuit voltage as well as high device performance for carbon-based perovskite solar cells. Herein, we propose a novel strategy to upshift work function of carbon electrode by incorporating boron atom into graphite lattice and employ it in printable hole-conductor-free mesoscopic perovskite solar cells. The high-work-function boron-doped carbon electrode facilitates hole extraction from perovskite as verified by photoluminescence. Meanwhile, the carbon electrode is endowed with an improved conductivity because of a higher graphitization carbon of boron-doped graphite. These advantages of the boron-doped carbon electrode result in a low charge transfer resistance at carbon/perovskite interface and an extended carrier recombination lifetime. Together with the merit of both high work function and conductivity, the power conversion efficiency of hole-conductor-free mesoscopic perovskite solar cells is increased from 12.4% for the pristine graphite electrode-based cells to 13.6% for the boron-doped graphite electrode-based cells with an enhanced open-circuit voltage and fill factor.

  20. Spin-Glass Transition and Giant Paramagnetism in Heavily Hole-Doped Bi2Sr2Co2Oy

    Science.gov (United States)

    Hsu, Hung Chang; Lee, Wei-Li; Lin, Jiunn-Yuan; Young, Ben-Li; Kung, Hsiang-Hsi; Huang, Jian; Chou, Fang Cheng

    2014-02-01

    Hole-doped single crystals of misfit-layered cobaltate Bi2-xPbxSr2-zCo2Oy (x = 0-0.61, y = 8.28-8.62, and z = 0.01-0.22) have been successfully grown using the optical floating-zone method. Heavier hole doping has been achieved through both Pb substitution in the Bi site and the more effective Sr vacancy formation. The Co4+ : Co3+ ratio can be raised significantly from its original ˜1 : 1 to 4.5 : 1, as confirmed by iodometric titration. A spin-glass transition temperature of Tg ˜ 70 K is confirmed by ac susceptibility measurement when the Co4+ : Co3+ ratio becomes higher than 2 : 1, presumably owing to the significantly increased probability of triangular geometrical frustration among antiferromagnetically coupled localized Co4+ spins.

  1. Potential Thermoelectric Performance from Optimization of Hole-Doped Bi_{2}Se_{3}

    Directory of Open Access Journals (Sweden)

    David Parker

    2011-10-01

    Full Text Available We present an analysis of the potential thermoelectric performance of hole-doped Bi_{2}Se_{3}, which is commonly considered to show inferior room temperature performance when compared to Bi_{2}Te_{3}. We find that if the lattice thermal conductivity can be reduced by nanostructuring techniques (as have been applied to Bi_{2}Te_{3} in Refs. [W. Xie, X. Tang, Y. Yan, Q. Zhang, and T. M. Tritt, Unique Nanostructures and Enhanced Thermoelectric Performance of Melt-Spun BiSbTe Alloys, Appl. Phys. Lett. 94, 102111 (2009; APPLAB0003-695110.1063/1.3097026B. Poudel et al., High-Thermoelectric Performance of Nanostructured Bismuth Antimony Telluride Bulk Alloys, Science 320, 634 (2008.SCIEAS0036-807510.1126/science.1156446] the material may show optimized ZT values of unity or more in the 300–500 K temperature range and thus be suitable for cooling and moderate temperature waste heat recovery and thermoelectric solar cell applications. Central to this conclusion are the larger band gap and the relatively heavier valence bands of Bi_{2}Se_{3}.

  2. Investigation of plasmon resonance tunneling through subwavelength hole arrays in highly doped conductive ZnO films

    Science.gov (United States)

    Nader, Nima; Vangala, Shivashankar; Hendrickson, Joshua R.; Leedy, Kevin D.; Look, David C.; Guo, Junpeng; Cleary, Justin W.

    2015-11-01

    Experimental results pertaining to plasmon resonance tunneling through a highly conductive zinc oxide (ZnO) layer with subwavelength hole-arrays is investigated in the mid-infrared regime. Gallium-doped ZnO layers are pulsed-laser deposited on a silicon wafer. The ZnO has metallic optical properties with a bulk plasma frequency of 214 THz, which is equivalent to a free space wavelength of 1.4 μm. Hole arrays with different periods and hole shapes are fabricated via a standard photolithography process. Resonant mode tunneling characteristics are experimentally studied for different incident angles and compared with surface plasmon theoretical calculations and finite-difference time-domain simulations. Transmission peaks, higher than the baseline predicted by diffraction theory, are observed in each of the samples at wavelengths that correspond to the excitation of surface plasmon modes.

  3. Investigation of plasmon resonance tunneling through subwavelength hole arrays in highly doped conductive ZnO films

    Energy Technology Data Exchange (ETDEWEB)

    Nader, Nima, E-mail: nima.nader@nist.gov; Vangala, Shivashankar [Solid State Scientific Corporation, 12 Simon St., Nashua, New Hampshire 03060 (United States); Air Force Research Laboratory, Sensors Directorate, 2241 Avionics Circle, Wright Patterson AFB, Ohio 45433 (United States); Hendrickson, Joshua R.; Leedy, Kevin D.; Cleary, Justin W. [Air Force Research Laboratory, Sensors Directorate, 2241 Avionics Circle, Wright Patterson AFB, Ohio 45433 (United States); Look, David C. [Air Force Research Laboratory, Sensors Directorate, 2241 Avionics Circle, Wright Patterson AFB, Ohio 45433 (United States); Wyle Laboratories, Inc., 2601 Mission Point Blvd., Suite 300, Dayton, Ohio 45435 (United States); Semiconductor Research Center, Wright State University, Dayton, Ohio 45435 (United States); Guo, Junpeng [Department of Electrical and Computer Engineering, University of Alabama in Huntsville, 301 Sparkman Drive, Huntsville, Alabama 35899 (United States)

    2015-11-07

    Experimental results pertaining to plasmon resonance tunneling through a highly conductive zinc oxide (ZnO) layer with subwavelength hole-arrays is investigated in the mid-infrared regime. Gallium-doped ZnO layers are pulsed-laser deposited on a silicon wafer. The ZnO has metallic optical properties with a bulk plasma frequency of 214 THz, which is equivalent to a free space wavelength of 1.4 μm. Hole arrays with different periods and hole shapes are fabricated via a standard photolithography process. Resonant mode tunneling characteristics are experimentally studied for different incident angles and compared with surface plasmon theoretical calculations and finite-difference time-domain simulations. Transmission peaks, higher than the baseline predicted by diffraction theory, are observed in each of the samples at wavelengths that correspond to the excitation of surface plasmon modes.

  4. Room temperature d (0) ferromagnetism in hole doped Y2O3: widening the choice of host to tailor DMS.

    Science.gov (United States)

    Chakraborty, Brahmananda; Ramaniah, Lavanya M

    2016-08-24

    Transition metal-free-ferromagnetism in diluted magnetic semiconductors (DMS) is of much current interest in view of the search for more efficient DMS materials for spintronics applications. Our DFT results predict for the first time, that impurities from group1A (Li(+), Na(+), K(+)) doped on Y2O3 can induce a magnetic signature with a magnetic moment around 2.0 μ B per defect at hole concentrations around 1.63  ×  10(21) cm(-3), which is one order less than the critical hole density of ZnO with ferromagnetic coupling large enough to promote room temperature ferromagnetism. The induction of room temperature ferromagnetism by hole doping with an impurity atom from group 1A, which injects two holes per defect in the system, implies that the recommendation of three holes per defect given in the literature, which puts a restriction on the choice of host material and the impurity, is not a necessary criterion for hole induced room temperature ferromagnetism. DFT simulations with the generalized gradient approximation (GGA), confirmed by the more sophisticated hybrid functional, Heyd-Scuseria-Ernzerhof (HSE06), predict that the magnetic moment is mostly contributed by O atoms surrounding the impurity atom and the magnetic moment scale up with impurity concentration which is a positive indicator for practical applications. We quantitatively and extensively demonstrate through the analysis of the density of states and ferromagnetic coupling that the Stoner criterion is satisfied by pushing the Fermi level inside the valence band to activate room temperature ferromagnetism. The stability of the structure and the persistence of ferromagnetism at room temperature were demonstrated by ab initio MD simulations and computation of Curie temperature through the mean field approximation. This study widens the choice of host oxides to tailor DMS for spintronics applications.

  5. Quantum-Dot Light-Emitting Diodes with Nitrogen-Doped Carbon Nanodot Hole Transport and Electronic Energy Transfer Layer

    Science.gov (United States)

    Park, Young Ran; Jeong, Hu Young; Seo, Young Soo; Choi, Won Kook; Hong, Young Joon

    2017-04-01

    Electroluminescence efficiency is crucial for the application of quantum-dot light-emitting diodes (QD-LEDs) in practical devices. We demonstrate that nitrogen-doped carbon nanodot (N-CD) interlayer improves electrical and luminescent properties of QD-LEDs. The N-CDs were prepared by solution-based bottom up synthesis and were inserted as a hole transport layer (HTL) between other multilayer HTL heterojunction and the red-QD layer. The QD-LEDs with N-CD interlayer represented superior electrical rectification and electroluminescent efficiency than those without the N-CD interlayer. The insertion of N-CD layer was found to provoke the Förster resonance energy transfer (FRET) from N-CD to QD layer, as confirmed by time-integrated and -resolved photoluminescence spectroscopy. Moreover, hole-only devices (HODs) with N-CD interlayer presented high hole transport capability, and ultraviolet photoelectron spectroscopy also revealed that the N-CD interlayer reduced the highest hole barrier height. Thus, more balanced carrier injection with sufficient hole carrier transport feasibly lead to the superior electrical and electroluminescent properties of the QD-LEDs with N-CD interlayer. We further studied effect of N-CD interlayer thickness on electrical and luminescent performances for high-brightness QD-LEDs. The ability of the N-CD interlayer to improve both the electrical and luminescent characteristics of the QD-LEDs would be readily exploited as an emerging photoactive material for high-efficiency optoelectronic devices.

  6. Formation of Single-Holed Cobalt/N-Doped Carbon Hollow Particles with Enhanced Electrocatalytic Activity toward Oxygen Reduction Reaction in Alkaline Media.

    Science.gov (United States)

    Guan, Bu Yuan; Yu, Le; Lou, Xiong Wen David

    2017-10-01

    Design and construction of metal-organic framework (MOF) composite precursors have recently been considered as a promising strategy for the preparation of different structured metal/carbon-based functional materials. Here, an MOF composite-assisted strategy to synthesize single-holed cobalt/N-doped carbon hollow particles is reported. The yolk-shell polystyrene@zeolitic imidazolate framework-67 (PS@ZIF-67) composite precursors are first synthesized, followed by a controlled pyrolysis to obtain cobalt/N-doped carbon hollow particles with a large single hole on each shell. Moreover, the MOF-coating approach reported in this work can be extended to prepare various core-shell ZIF-67 composites with different structures and compositions. Benefiting from the structural and compositional advantages, the as-derived single-holed cobalt/N-doped carbon hollow particles manifest superior electrocatalytic oxygen reduction performance with high activity and excellent durability.

  7. Complex quantum transport in a modulation doped strained Ge quantum well heterostructure with a high mobility 2D hole gas

    Science.gov (United States)

    Morrison, C.; Casteleiro, C.; Leadley, D. R.; Myronov, M.

    2016-09-01

    The complex quantum transport of a strained Ge quantum well (QW) modulation doped heterostructure with two types of mobile carriers has been observed. The two dimensional hole gas (2DHG) in the Ge QW exhibits an exceptionally high mobility of 780 000 cm2/Vs at temperatures below 10 K. Through analysis of Shubnikov de-Haas oscillations in the magnetoresistance of this 2DHG below 2 K, the hole effective mass is found to be 0.065 m0. Anomalous conductance peaks are observed at higher fields which deviate from standard Shubnikov de-Haas and quantum Hall effect behaviour due to conduction via multiple carrier types. Despite this complex behaviour, analysis using a transport model with two conductive channels explains this behaviour and allows key physical parameters such as the carrier effective mass, transport, and quantum lifetimes and conductivity of the electrically active layers to be extracted. This finding is important for electronic device applications, since inclusion of highly doped interlayers which are electrically active, for enhancement of, for example, room temperature carrier mobility, does not prevent analysis of quantum transport in a QW.

  8. Phosphorus doped graphene by inductively coupled plasma and triphenylphosphine treatments

    Energy Technology Data Exchange (ETDEWEB)

    Shin, Dong-Wook, E-mail: shindong37@skku.edu; Kim, Tae Sung; Yoo, Ji-Beom, E-mail: jbyoo@skku.edu

    2016-10-15

    Highlights: • Substitution doping is a promising method for opening the energy band gap of graphene. • Substitution doping with phosphorus in the graphene lattice has numerous advantage such as high band gap, low formation energy, and high net charge density compared to nitrogen. • V{sub dirac} of Inductively coupled plasma (ICP) and triphenylphosphine (TPP) treated graphene was −57 V, which provided clear evidence of n-type doping. • Substitutional doping of graphene with phosphorus is verified by the XPS spectra of P 2p core level and EELS mapping of phosphorus. • The chemical bonding between P and graphene is very stable for a long time in air (2 months). - Abstract: Graphene is considered a host material for various applications in next-generation electronic devices. However, despite its excellent properties, one of the most important issues to be solved as an electronic material is the creation of an energy band gap. Substitution doping is a promising method for opening the energy band gap of graphene. Herein, we demonstrate the substitutional doping of graphene with phosphorus using inductively coupled plasma (ICP) and triphenylphosphine (TPP) treatments. The electrical transfer characteristics of the phosphorus doped graphene field effect transistor (GFET) have a V{sub dirac} of ∼ − 54 V. The chemical bonding between P and C was clearly observed in XPS spectra, and uniform distribution of phosphorus within graphene domains was confirmed by EELS mapping. The capability for substitutional doping of graphene with phosphorus can significantly promote the development of graphene based electronic devices.

  9. Temperature-dependent anisotropic resistivity in electron, hole and isoelectron - doped BaFe2As2 superconductors

    Science.gov (United States)

    Tanatar, M. A.

    2012-02-01

    Anisotropic electrical resistivity, ρ(T), was studied in iron-arsenide superconductors, obtained by doping the parent BaFe2As2 compound on three different sites: (1) electron donor transition metal (Co,Ni,Rh,Pd) substitution of Fe [1,2]; (2) hole donor K substitution of Ba [3]; (3) isoelectron P substitution of As. For all three types of dopants a range of T-linear behavior is found at the optimal doping in both the in-plane and the inter-plane ρ(T) above Tc. At some higher temperature this range of T-linear resistivity is capped by a slope-changing anomaly, which, by comparison with NMR, magnetic susceptibility and Hall effect measurements, can be identified with the onset of carrier activation over the pseudogap [1]. The doping-evolution of anisotropic temperature dependent ρ(T) and of the pseudogap are quite different for three types of doping. A three-dimensional T-H phase diagram summarizing our results will be presented. Furthermore, potential correlation of the anisotropic normal state transport and anisotropic superconducting state heat transport will be discussed. [4pt] In collaboration with N. Ni, A. Thaler, S.L.Bud'ko, P.C. Canfield, R. Prozorov, Bing Shen, Hai-Hu Wen, K. Hashimoto, S. Kasahara, T. Terashima, T. Shibauchi and Y. Matsuda. [4pt] [1] M.A.Tanatar et al. PRB 82, 134528 (2010)[0pt] [2] M.A.Tanatar et al. PRB 84, 014519 (2011)[0pt] [3] M.A.Tanatar et al. arXiv:1106.0533

  10. Hole-doping effect on the magnetic state of delafossite oxide CuCrO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Okuda, T; Beppu, Y; Fujii, Y; Kishimoto, T; Uto, K; Onoe, T; Jufuku, N; Hidaka, S; Terada, N [Department of Nano-Structures and Advanced Materials, Kagoshima University, 1-21-40 Korimoto, Kagoshima 890-0065 (Japan); Miyasaka, S, E-mail: okuda@eee.kagoshima-u.ac.j [Department of Physics, Osaka University, 1-1, Machikaneyama, Toyonaka, Osaka 560-0043 (Japan)

    2009-03-01

    We investigated the substitution effects of Mg{sup 2+}, Ca{sup 2+}, and Al{sup 3+} for Cr{sup 3+} on the magnetic, transport and thermal properties of delafossite oxide CuCrO{sub 2}, which possesses a quasi-2D Heisenberg triangular antiferromagnetic (AF) lattice. Magnetization and specific heat measurements indicated that AF ordering is promoted by the substitution of nonmagnetic Mg{sup 2+} for Cr{sup 3+} (S = 3/2), despite the fact that a spin vacancy is introduced in a 120 deg. spin structure at the Cr sites. These results suggest that the residual magnetic frustration is partially broken by spin fluctuations, which are enhanced through the interaction between the itinerant hole introduced by Mg doping and the localized spin at the Cr site.

  11. Stable and null current hysteresis perovskite solar cells based nitrogen doped graphene oxide nanoribbons hole transport layer

    Science.gov (United States)

    Kim, Jeongmo; Mat Teridi, Mohd Asri; Mohd Yusoff, Abd. Rashid Bin; Jang, Jin

    2016-06-01

    Perovskite solar cells are becoming one of the leading technologies to reduce our dependency on traditional power sources. However, the frequently used component poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) has several shortcomings, such as an easily corroded indium-tin-oxide (ITO) interface at elevated temperatures and induced electrical inhomogeneity. Herein, we propose solution-processed nitrogen-doped graphene oxide nanoribbons (NGONRs) as a hole transport layer (HTL) in perovskite solar cells, replacing the conducting polymer PEDOT:PSS. The conversion efficiency of NGONR-based perovskite solar cells has outperformed a control device constructed using PEDOT:PSS. Moreover, our proposed NGONR-based devices also demonstrate a negligible current hysteresis along with improved stability. This work provides an effective route for substituting PEDOT:PSS as the effective HTL.

  12. Enhanced Performance of Quantum Dot-Based Light-Emitting Diodes with Gold Nanoparticle-Doped Hole Injection Layer

    Science.gov (United States)

    Chen, Fei; Lin, Qingli; Wang, Hongzhe; Wang, Lei; Zhang, Fengjuan; Du, Zuliang; Shen, Huaibin; Li, Lin Song

    2016-08-01

    In this paper, the performance of quantum dot-based light-emitting diodes (QLEDs) comprising ZnCdSe/ZnS core-shell QDs as an emitting layer were enhanced by employing Au-doped poly(3,4-ethylenedioxythiophene)/polystyrene sulfonate (PEDOT:PSS) hole injection layer (HIL). By varying the concentration and dimension of Au nanoparticle (NP) dopants in PEDOT:PSS, the optimal devices were obtained with ~22-nm-sized Au NP dopant at the concentration with an optical density (OD) of 0.21. Highly bright green QLEDs with a maximum external quantum efficiency (EQE) of 8.2 % and a current efficiency of 29.1 cd/A exhibit 80 % improvement compared with devices without Au NP dopants. The improved performance may be attributed to the significant increase in the hole injection rate as a result of the introduction of Au NPs and the good matching between the resonance frequency of the localized surface plasmon resonance (LSPR) generated by the Au NPs and the emission band of QD layer, as well as the suppressed Auger recombination of QD layer due to the LSPR-induced near-field enhanced radiative recombination rate of excitons. These results are helpful for fabricating high-performance QD-based applications, such as full-color displays and solid-state lighting.

  13. Hydroxyethyl cellulose doped with copper(II) phthalocyanine-tetrasulfonic acid tetrasodium salt as an effective dual functional hole-blocking layer for polymer light-emitting diodes

    Science.gov (United States)

    Wu, Cheng-Liang; Chen, Yun

    2017-07-01

    We report a doping method to improve the performance of solution-processed polymer light-emitting diodes (PLEDs). Doping 12 wt% copper(II) phthalocyanine-tetrasulfonated acid tetrasodium salt (TS-CuPc) into hydroxyethyl cellulose (HEC) as a dual functional hole-blocking layer (df-HBL) of multilayer PLED (glass/ITO/PEDOT:PSS/HY-PPV/TS-CuPc-doped HEC/LiF/Al) significantly enhanced maximum luminance, maximum current and power efficiency over that without the df-HBL (10,319 cd/m2, 2.98 cd/A and 1.24 lm/W) to (29,205 cd/m2, 13.27 cd/A and 9.56 lm/W). CV measurements reveal that HEC possesses a powerful hole-blocking capability. Topography and conductivity AFM images show that doping TS-CuPc increases the interfacial contact area and interfacial conductivity, which can overcome the insulating nature of HEC and thus further facilitate electron injection. Enhancements in device performance are attributed to the improved carrier balance and recombination in the presence of df-HBL, confirmed in electron-only and hole-only devices. Moreover, apparently raised open-circuit voltages provide further evidence that enhanced electron injection is indeed realized by the df-HBL. This study demonstrates an effective approach to develop highly efficient PLEDs.

  14. Fabrication of Ni-doped BiVO4 semiconductors with enhanced visible-light photocatalytic performances for wastewater treatment

    Science.gov (United States)

    Regmi, Chhabilal; Kshetri, Yuwaraj K.; Kim, Tae-Ho; Pandey, Ramesh Prasad; Ray, Schindra Kumar; Lee, Soo Wohn

    2017-08-01

    A visible-light-driven Ni-doped BiVO4 photocatalyst was synthesized using a microwave hydrothermal method. The nominal Ni doping amount of 1 wt% provided excellent photoactivity for a variety of water pollutants, such as ibuprofen (pharmaceutical), Escherichia coli (bacteria), and green tides (phytoplankton). Each Ni-doped BiVO4 sample exhibits better performance than pure BiVO4. The degradation of ibuprofen reaches 80% within 90 min, the deactivation of Escherichia coli reaches around 92% within 5 h, and the inactivation of green tide (Chlamydomonas pulsatilla) reaches 70% upon 60 min of the visible light irradiation. The first principle calculation and thermodynamic modeling revealed that Ni doping in the vanadium site gives the most stable configuration of the synthesized samples with the formation of an in-gap energy state and oxygen vacancies. The in-gap energy state and the oxygen vacancies serve as an electron-trapping center that decreases the migration time of the photogenerated carrier and increases the separation efficiency of electron-hole pairs, which are responsible for the observed efficient photocatalytic, anti-bacterial and anti-algal activity of the samples. These properties thus suggest potential applications of Ni-doped BiVO4 as a multifunctional material in the field of wastewater treatment.

  15. Nonlinear dynamics of non-equilibrium holes in p-type modulation-doped GaInNAs/GaAs quantum wells.

    Science.gov (United States)

    Khalil, Hagir Mohammed; Sun, Yun; Balkan, Naci; Amann, Andreas; Sopanen, Markku

    2011-03-02

    Nonlinear charge transport parallel to the layers of p-modulation-doped GaInNAs/GaAs quantum wells (QWs) is studied both theoretically and experimentally. Experimental results show that at low temperature, T = 13 K, the presence of an applied electric field of about 6 kV/cm leads to the heating of the high mobility holes in the GaInNAs QWs, and their real-space transfer (RST) into the low-mobility GaAs barriers. This results in a negative differential mobility and self-generated oscillatory instabilities in the RST regime. We developed an analytical model based upon the coupled nonlinear dynamics of the real-space hole transfer and of the interface potential barrier controlled by space-charge in the doped GaAs layer. Our simulation results predict dc bias-dependent self-generated current oscillations with frequencies in the high microwave range.

  16. Nonlinear dynamics of non-equilibrium holes in p-type modulation-doped GaInNAs/GaAs quantum wells

    Directory of Open Access Journals (Sweden)

    Amann Andreas

    2011-01-01

    Full Text Available Abstract Nonlinear charge transport parallel to the layers of p-modulation-doped GaInNAs/GaAs quantum wells (QWs is studied both theoretically and experimentally. Experimental results show that at low temperature, T = 13 K, the presence of an applied electric field of about 6 kV/cm leads to the heating of the high mobility holes in the GaInNAs QWs, and their real-space transfer (RST into the low-mobility GaAs barriers. This results in a negative differential mobility and self-generated oscillatory instabilities in the RST regime. We developed an analytical model based upon the coupled nonlinear dynamics of the real-space hole transfer and of the interface potential barrier controlled by space-charge in the doped GaAs layer. Our simulation results predict dc bias-dependent self-generated current oscillations with frequencies in the high microwave range.

  17. W-doped TiO2 mesoporous electron transport layer for efficient hole transport material free perovskite solar cells employing carbon counter electrodes

    Science.gov (United States)

    Xiao, Yuqing; Cheng, Nian; Kondamareddy, Kiran Kumar; Wang, Changlei; Liu, Pei; Guo, Shishang; Zhao, Xing-Zhong

    2017-02-01

    Doping of TiO2 by metal elements for the scaffold layer of the perovskite solar cells has been proved to be one of the effective methods to improve the power conversion efficiency. In the present work, we report the impact of doping of TiO2 nanoparticles with different amounts of tungsten (W) on the photovoltaic properties of hole transport material free perovskite solar cells (PSCs) that employ carbon counter electrode. Light doping with W (less than 1000 ppm) improves the power conversion efficiencies (PCEs) of solar cells by promoting the electron conductivity in the TiO2 layer which facilitates electron transfer and collection. With the incorporation of W, average efficiency of PSCs is increased from 9.1% for the un-doped samples to 10.53% for the 1000 ppm W-doped samples, mainly originates from the increase of short circuit current density and fill factor. Our champion cell exhibits an impressive PCE of 12.06% when using the 1000 ppm W-doped TiO2 films.

  18. Electronic and magnetic properties of the (001) surface of hole-doped manganites

    Science.gov (United States)

    Zenia, H.; Gehring, G. A.; Banach, G.; Temmerman, W. M.

    2005-01-01

    The electronic and magnetic properties of ferromagnetic doped manganites are investigated by means of model tight-binding and self-interaction corrected local spin density (SIC-LSD) approximation calculations. It is found that the surface alone by breaking the cubic symmetry induces a difference in the occupation of the two eg orbitals at the surface. We found surface localization of one orbital and hence a change in the Mn valency from four in the bulk to three at the subsurface. Different surface or disordered interface induced localization of the orbitals are considered too with respect to the nature and the strength of the local orbital ordering and magnetic exchange coupling between the surface/interface and the bulklike region. We predict that better tunneling can be achieved in tunnel barriers that favor slightly the occupancy of the Mn eg(3z2-r2) at the interface.

  19. The effect of gap fluctuations on interacting and non-interacting polarization for nano-superconducting grains in electron- and hole-doped cuprates

    Science.gov (United States)

    Afzali, R.; Alizadeh, A.

    2017-12-01

    The behavior of non-interacting and interacting polarization under influence of fluctuations of the superconducting gap with D-wave symmetry and under consideration of the gap dependence on nano- grain size is obtained in terms of the frequency, temperature and the size at zero and finite temperatures for rectangular cuprate nano-superconducting grains. By using Eliashberg equations and applying the relations of the fermionic dispersion for the hole-doped and electron-doped cuprates, we numerically compute the real part of size-dependent polarization for both types of cuprates. We show that the peak of real part of polarization moves to higher frequency by including the additional fluctuating part of gap (or the nano-size effect). Also, we obtain the temperatures for different frequencies, in which the effect of gap fluctuations fades. In the case of size-dependent gap, there is a critical frequency; for frequencies lower (higher) than the critical frequency, the nano-effect weakens (improves) the superconducting state. Moreover, it is concluded that the real part of polarization for hole- doped cuprates in terms of the grain size has more significant amount in comparison with electron-doped ones.

  20. Tensile Strain Effects on the Magneto-transport in Calcium Manganese Oxide Thin Films: Comparison with its Hole-doped Counterpart

    Science.gov (United States)

    Lawson, Bridget; Neubauer, Samuel; Chaudhry, Adeel; Hart, Cacie; Ferrone, Natalie; Houston, David; Yong, Grace; Kolagani, Rajeswari

    Magnetoresistance properties of the epitaxial thin films of doped rare earth manganites are known to be influenced by the effect of bi-axial strain induced by lattice mismatch with the substrate. In hole-doped manganites, the effect of both compressive and tensile strain is qualitatively consistent with the expected changes in unit cell symmetry from cubic to tetragonal, leading to Jahn-Teller strain fields that affect the energy levels of Mn3 + energy levels. Recent work in our laboratory on CaMnO3 thin films has pointed out that tetragonal distortions introduced by tensile lattice mismatch strain may also have the effect of modulating the oxygen content of the films in agreement with theoretical models that propose such coupling between strain and oxygen content. Our research focuses on comparing the magneto-transport properties of hole-doped manganite LaCaMnO3 thin films with that of its electron doped counter parts, in an effort to delineate the effects of oxygen stoichiometry changes on magneto-transport from the effects of Jahn-Teller type strain. Towson University Office of Undergraduate Research, Fisher Endowment Grant and Undergraduate Research Grant from the Fisher College of Science and Mathematics, Seed Funding Grant from the School of Emerging technologies and the NSF Grant ECCS 112856.

  1. Breakdown of single spin-fluid model in the heavily hole-doped superconductor CsFe2As2

    Science.gov (United States)

    Zhao, D.; Li, S. J.; Wang, N. Z.; Li, J.; Song, D. W.; Zheng, L. X.; Nie, L. P.; Luo, X. G.; Wu, T.; Chen, X. H.

    2018-01-01

    Although Fe-based superconductors are correlated electronic systems with multiorbital, previous nuclear magnetic resonance (NMR) measurement suggests that a single spin-fluid model is sufficient to describe its spin behavior. Here, we first observed the breakdown of single spin-fluid model in a heavily hole-doped Fe-based superconductor CsFe2As2 by site-selective NMR measurement. At high-temperature regime, both Knight shift and nuclear spin-lattice relaxation at 133Cs and 75As nuclei exhibit distinct temperature-dependent behavior, suggesting the breakdown of the single spin-fluid model in CsFe2As2 . This is ascribed to the coexistence of both localized and itinerant spin degree of freedom at 3 d orbitals, which is consistent with the orbital-selective Mott phase. With decreasing temperature, the single spin-fluid behavior is recovered below T*˜75 K due to a coherent state among 3 d orbitals. The Kondo liquid scenario is proposed to understand the low-temperature coherent state.

  2. Critical increase in Na-doping facilitates acceptor band movements that yields ~180 meV shallow hole conduction in ZnO bulk crystals

    Science.gov (United States)

    Parmar, Narendra S.; Yim, Haena; Choi, Ji-Won

    2017-03-01

    Stable p-type conduction in ZnO has been a long time obstacle in utilizing its full potential such as in opto-electronic devices. We designed a unique experimental set-up in the laboratory for high Na-doping by thermal diffusion in the bulk ZnO single crystals. SIMS measurement shows that Na concentration increases by 3 orders of magnitude, to ~3 × 1020 cm-3 as doping temperature increases to 1200 °C. Electronic infrared absorption was measured for Na-acceptors. Absorption bands were observed near (0.20-0.24) eV. Absorption bands blue shifted by 0.04 eV when doped at 1200 °C giving rise to shallow acceptor level. NaZn band movements as a function of doping temperature are also seen in Photoluminescence emission (PL), Photoluminescence excitation (PLE) and UV-Vis transmission measurements. Variable temperature Hall measurements show stable p-type conduction with hole binding energy ~0.18 eV in ZnO samples that were Na-doped at 1200 °C.

  3. Hole-spin dynamics in p-doped GaAs/AlGaAs heterostructures; Lochspindynamik in p-dotierten GaAs/AlGaAs-Heterostrukturen

    Energy Technology Data Exchange (ETDEWEB)

    Kugler, Michael

    2012-11-15

    This work investigates the spin dynamics of holes in p-doped GaAs/AlGaAs quantum wells (QW) at low temperatures. To examine the energetic structure of the used samples, PL and PLE-spectroscopy were employed. Time resolved Kerr and Faraday-Rotation (TRKR/FR) and 'Resonant Spin Amplification' (RSA) were used to analyse the spin dynamics. First, the signal formation in TRKR/FR and RSA experiments is discussed taking into account the interconnected charge carrier dynamics and spin dynamics of electrons and holes. An excitation energy dependent sign change of the Kerr signal amplitude could be observed, whose energetic position corresponds to an absorption maximum in PLE experiments. This behavior could be explained by an energy dependent splitting of the spin niveaus, which leads to an energy dependence of the Faraday and Kerr signal. Furthermore, two initialization processes were investigated, which could be used to transfer optically generated spin information into the resident hole spin system. This could be achieved by either applying a magnetic field, or by rapid dephasing of hole spins immediately after excitation. Changes in excitation energy, excitation density or temperature could be used to influence the fast dephasing processes and therefore the initial ratio of hole to electron spins. The complex, interconnected charge carrier and spin dynamics of electrons and holes could be accurately reproduced using a rate equation model. This allowed for the extraction of physically relevant parameters like spin lifetimes and g-factors from RSA and TRKR/FR data. An analytical model that was developed at the Wroclaw University of Technology delivered matching results. In the second part of the experimental work, the dependence of the hole spin lifetime and the hole g-factor on various parameters was analysed. Here, the RSA method could for the first time be applied to two-dimensional hole systems, allowing for new insights into the regime of long lived hole

  4. Effects of disorder on the intrinsically hole-doped iron-based superconductor KC a2F e4A s4F2 by cobalt substitution

    Science.gov (United States)

    Ishida, Junichi; Iimura, Soshi; Hosono, Hideo

    2017-11-01

    In this paper, the effects of cobalt substitution on the transport and electronic properties of the recently discovered iron-based superconductor KC a2F e4A s4F2 , with Tc=33 K , are reported. This material is an unusual superconductor showing intrinsic hole conduction (0.25 holes /F e2 + ). Upon doping of Co, the Tc of KC a2(Fe1-xC ox) 4A s4F2 gradually decreased, and bulk superconductivity disappeared when x ≥0.25 . Conversion of the primary carrier from p type to n type upon Co-doping was clearly confirmed by Hall measurements, and our results are consistent with the change in the calculated Fermi surface. Nevertheless, neither spin density wave (SDW) nor an orthorhombic phase, which are commonly observed for nondoped iron-based superconductors, was observed in the nondoped or electron-doped samples. The electron count in the 3 d orbitals and structural parameters were compared with those of other iron-based superconductors to show that the physical properties can be primarily ascribed to the effects of disorder.

  5. Variational Monte Carlo method for fermionic models combined with tensor networks and applications to the hole-doped two-dimensional Hubbard model

    Science.gov (United States)

    Zhao, Hui-Hai; Ido, Kota; Morita, Satoshi; Imada, Masatoshi

    2017-08-01

    The conventional tensor-network states employ real-space product states as reference wave functions. Here, we propose a many-variable variational Monte Carlo (mVMC) method combined with tensor networks by taking advantages of both to study fermionic models. The variational wave function is composed of a pair product wave function operated by real-space correlation factors and tensor networks. Moreover, we can apply quantum number projections, such as spin, momentum, and lattice symmetry projections, to recover the symmetry of the wave function to further improve the accuracy. We benchmark our method for one- and two-dimensional Hubbard models, which show significant improvement over the results obtained individually either by mVMC or by tensor network. We have applied the present method to a hole-doped Hubbard model on the square lattice, which indicates the stripe charge/spin order coexisting with a weak d -wave superconducting order in the ground state for the doping concentration of less than 0.3, where the stripe oscillation period gets longer with increasing hole concentration. The charge homogeneous and highly superconducting state also exists as a metastable excited state for the doping concentration less than 0.25.

  6. Oxygen hole-doping effects on the spin-chain system Ca2+xY2-xCu5O

    Science.gov (United States)

    Park, K.; Cackowski, T.; Markert, J. T.

    2008-04-01

    The magnetic properties of the low-dimensional spin-chain system Ca2+xY2-xCu5O were studied as a function of oxygen content and Ca-doping. A series of samples with different oxygen contents were prepared by solid state reaction under various oxygen pressures up to 170 atm and characterized by X-ray diffraction and iodometric titration. Oxygen deficiency was observed to be from δ=0.2-0.4 at 0.2 atm to δ≈0.0 at 170 atm oxygen pressure. Oxygen deficiency increases with Ca-doping at fixed oxygen pressure. The temperature dependence of the magnetic moment and of the specific heat are reported here for the x=0.9 sample with various oxygen deficiencies. The effects of oxygen deficiency on magnetic coupling are compared with Ca-doping. Notably, oxygen content plays a much more critical role in the reduction of magnetic interactions in the CuO2 chains than Ca-doping, even for the same hole concentration.

  7. An efficient interconnection unit composed of electron-transporting layer/metal/p-doped hole-transporting layer for tandem organic photovoltaics

    Science.gov (United States)

    Shim, Hyun-Sub; Kim, Sei-Yong; Whan Kim, Ji; Kim, Tae-Min; Lee, Chang-Heon; Kim, Jang-Joo

    2013-05-01

    We report an efficient interconnection unit (ICU) consisting of an electron transporting layer/metal/p-doped hole transporting layer (p-HTL) structure for tandem organic photovoltaic (TOPV) cells. The ICU satisfies all the requirements of optical transparency and low voltage loss and for functioning as an optical spacer. The variation of the short circuit current and open circuit voltage (VOC) of the TOPV cells with increasing thickness of the p-HTL in the ICU followed the theoretical predictions, proving that the ICU does not disturb the electrical characteristics of the TOPV cells up to a p-HTL thickness of 100 nm with minimal VOC loss (˜3%).

  8. Direct comparison of hole doping effects due to cation and to oxygen content on magnetic properties of the spin-chain system Ca2+xY2-xCu5O10-δ

    Science.gov (United States)

    Park, Keeseong; Cackowski, Theodore; Markert, John

    2008-03-01

    A quasi-one dimensional system, Ca2+xY2-xCu5O10-δ (CaYCuO) is studied to compare the magnetic effects of cation doping with those of oxygen deficiency. Hole doping (p) due to cation concentration (x) and oxygen deficiency (δ) in other copper oxides is often observed to obey p = x - 2 δ. CaYCuO has a simple edge shared CuO structure and is hole dopable up to a formal copper valence of 2.4. Various Ca doped CaYCuO specimens were fabricated in different oxygen environments, including high pressure oxygen up to 170 atm. X-ray diffraction and iodometric titration were used to confirm phase and oxygen content. Samples are found to be more oxygen deficient with increasing cation doping. Magnetic moment and specific heat were measured. The antiferromagnetic phase was observed up to x = 1.0 doping for fully oxygenated specimens. N'eel temperatures decreased with increasing cation doping and decreasing oxygen deficiency. The decrease in N'eel temperature is found to be more than expected from hole doping p = x - 2 δ. A new quantity that describes all of the behavior of N'eel temperature, p' = x - (2/3) δ, is proposed.

  9. Improving the efficiency and environmental stability of inverted planar perovskite solar cells via silver-doped nickel oxide hole-transporting layer

    Science.gov (United States)

    Wei, Ying; Yao, Kai; Wang, Xiaofeng; Jiang, Yihua; Liu, Xueyuan; Zhou, Naigen; Li, Fan

    2018-01-01

    In this paper, we demonstrate the high-performance inverted planar heterojunction perovskite solar cells (PeSCs) based on the novel inorganic hole-transporting layer (HTL) of silver (Ag)-doped NiOx (Ag:NiOx). Density-functional theory (DFT) calculation reveals that Ag prefers to occupy the substitutional Ni site (AgNi) and behaves as an acceptor in NiO lattice. Compared with the pristine NiOx films, appropriate Ag doping can increase the optical transparency, work function, electrical conductivity and hole mobility of NiOx films. Moreover, the CH3NH3PbI3 perovskite films grown on Ag:NiOx exhibit better crystallinity, higher coverage and smoother surface with densely packed larger grains than those grown on the pristine NiOx film. Consequently, the Ag:NiOx HTL boosts the efficiency of the inverted planar heterojunction PeSCs from 13.46% (for the pristine NiOx-based device) to 16.86% (for the 2 at.% Ag:NiOx-based device). Furthermore, the environmental stability of PeSCs based on Ag:NiOx HTL is dramatically improved compared to devices based on organic HTLs and pristine NiOx HTLs. This work provides a simple and effective HTL material system for high-efficient and stable PeSCs.

  10. Fabrication of Ni-doped BiVO{sub 4} semiconductors with enhanced visible-light photocatalytic performances for wastewater treatment

    Energy Technology Data Exchange (ETDEWEB)

    Regmi, Chhabilal [Department of Environmental and Biochemical Engineering, Sun Moon University, Chungnam 31460 (Korea, Republic of); Kshetri, Yuwaraj K. [Department of Advanced Materials Engineering, Sun Moon University, Chungnam 31460 (Korea, Republic of); Kim, Tae-Ho [Division of Mechanics and ICT Convergence Engineering, Sun Moon University, Chungnam 31460 (Korea, Republic of); Pandey, Ramesh Prasad [Institute of Biomolecule Reconstruction, Department of BT-Convergent Pharmaceutical Engineering, Sun Moon University, Chungnam 31460 (Korea, Republic of); Ray, Schindra Kumar [Department of Environmental and Biochemical Engineering, Sun Moon University, Chungnam 31460 (Korea, Republic of); Lee, Soo Wohn, E-mail: swlee@sunmoon.ac.kr [Department of Environmental and Biochemical Engineering, Sun Moon University, Chungnam 31460 (Korea, Republic of)

    2017-08-15

    Highlights: • Synthesis of a Ni-doped BiVO{sub 4} semiconductor photocatalyst with reduced band gap energy. • Ni-doped BiVO{sub 4} provided efficient photocatalytic activity for ibuprofen degradation and E. coli and green tide deactivation. • DFT calculation and thermodynamic modeling to understand the underlying mechanism. - Abstract: A visible-light-driven Ni-doped BiVO{sub 4} photocatalyst was synthesized using a microwave hydrothermal method. The nominal Ni doping amount of 1 wt% provided excellent photoactivity for a variety of water pollutants, such as ibuprofen (pharmaceutical), Escherichia coli (bacteria), and green tides (phytoplankton). Each Ni-doped BiVO{sub 4} sample exhibits better performance than pure BiVO{sub 4}. The degradation of ibuprofen reaches 80% within 90 min, the deactivation of Escherichia coli reaches around 92% within 5 h, and the inactivation of green tide (Chlamydomonas pulsatilla) reaches 70% upon 60 min of the visible light irradiation. The first principle calculation and thermodynamic modeling revealed that Ni doping in the vanadium site gives the most stable configuration of the synthesized samples with the formation of an in-gap energy state and oxygen vacancies. The in-gap energy state and the oxygen vacancies serve as an electron-trapping center that decreases the migration time of the photogenerated carrier and increases the separation efficiency of electron-hole pairs, which are responsible for the observed efficient photocatalytic, anti-bacterial and anti-algal activity of the samples. These properties thus suggest potential applications of Ni-doped BiVO{sub 4} as a multifunctional material in the field of wastewater treatment.

  11. Promising wastewater treatment using rare earth-doped nanoferrites

    Energy Technology Data Exchange (ETDEWEB)

    Ahmed, M.A., E-mail: moala47@hotmail.com [Materials Science Lab (1), Physics Department, Faculty of Science, Cairo University, Giza (Egypt); Bishay, Samiha T.; Khafagy, Rasha M. [Physics Department, Girls College for Arts, Science and Education, Ain Shams University, Cairo (Egypt); Saleh, N.M. [Physics Department, Faculty of Science, Western Mountain University (Libya)

    2014-01-15

    Single-phases of the spinel nanoferrites Zn{sub 0.5}Co{sub 0.5}Al{sub 0.5}R{sub 0.04}Fe{sub 1.46}O{sub 4}; R=Sm, Pr, Ce and La, were synthesized using the flash auto combustion method. X-ray diffraction (XRD) results indicated that doping nanoferrites with small concentrations of rare earth elements (RE) allowed their entrance to the spinel lattice. Transmission electron microscope (TEM) images revealed that doping with different RE elements resulted in the formation of different nanometric shapes such as nanospheres and nanowires. Doping with Sm{sup 3+} and Ce{sup 3+} resulted in the formation of nanospheres with average diameter of 14 and 30 nm respectively. In addition to the granular nanospheres, doping with Pr{sup 3+} and La{sup 3+} resulted in the formation of some nanowires with different aspect ratios (average length of ≈100 nm and diameter of ≈9 nm) and (average length of ≈150 nm and outer diameter of ≈22 nm) respectively. At fixed temperature, the Ac conductivity (σ) increased as the RE ionic radius increases except for Ce, due to the role of valance fluctuation from Ce{sup 3+} to Ce{sup 4+} ions. La- and Pr-doped nanoferrites showed the highest ac conductivity values, which is most probably due to the presence of large numbers of nanowires in these two types of ferrites. For all entire samples, the effective magnetic moment (μ{sub eff}) decreased, while the Curie temperature (T{sub C}) increased as the RE ionic radius increases. The synthesized rare earth nanoferrites showed promising results in purifying colored wastewater. La-doped ferrite was capable for up-taking 92% of the dye content, followed by Pr-doped ferrite, which adsorbed 85% of the dye, while Sm- and Ce-doped ferrites showed lower dye removal efficiency of 80% and 72% respectively. High dye uptake shown by La- and Pr-doped ferrites is most probably due to the presence of nanowires and their higher Ac conductivity values. These excellent results were not previously reported

  12. Tight-binding study of the hole subband structure properties of p-type delta-doped quantum wells in Si by using a Thomas-Fermi-Dirac potential

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez-Vargas, I; Madrigal-Melchor, J; Vlaev, S J, E-mail: isaac@planck.reduaz.m [Unidad Academica de Fisica, Universidad Autonoma de Zacatecas, Calzada Solidaridad Esquina Con Paseo La Bufa S/N, 98060 Zacatecas, ZAC. (Mexico)

    2009-05-01

    We present the hole subband structure of p-type delta-doped single, double, multiple and superlattice quantum wells in Si. We use the first neighbors sp{sup 3}s' tight-binding approximation including spin for the hole level structure analysis. The parameters of the tight-binding hamiltonian were taken from Klimeck et al. [Klimeck G, Bowen R C, Boykin T B, Salazar-Lazaro C, Cwik T A and Stoica A 2000 Superlattice. Microst. 27 77], first neighbors parameters that give realiable results for the valence band of Si. The calculations are based on a scheme previously proposed and applied to delta-doped quantum well systems [Vlaev S J and Gaggero-Sager L M 1998 Phys. Rev. B 58 1142]. The scheme relies on the incorporation of the delta-doped quantum well potential in the diagonal terms of the tight-binding hamiltonian. We give a detail description of the delta-doped quantum well structures, this is, we study the hole subband structure behavior as a function of the impurity density, the interwell distance of the doped planes and the superlattice period. We also compare our results with the available theoretical and experimental data, obtaining a reasonable agreement.

  13. Enhanced thermoelectric figure-of-merit ZT for hole-doped Bi2Sr2Co2Oy through Pb substitution

    Science.gov (United States)

    Hsu, H. C.; Lee, W. L.; Wu, K. K.; Kuo, Y. K.; Chen, B. H.; Chou, F. C.

    2012-05-01

    Single crystals of Bi2-xPbxSr2Co2Oy (0 ≤ x ≤ 0.55) have been grown using optical floating-zone method. The chemical compositions were determined using combined electron probe microanalysis and iodometric titration. Physical properties including electrical resistivity (ρ), Seebeck coefficient (S), and thermal conductivity (κ) were measured using single crystal specimens. Successful hole doping through Pb substitution is confirmed through combined iodometry titration, electrical transport, and Seebeck coefficient measurements. Significant reduction on both in-plane resistivity and thermal conductivity was found as a result of Pb substitution to the Bi site. The thermoelectric figure-of-merit ZT for x ˜ 0.55 is raised 20 folds from the undoped sample at room temperature.

  14. La modified TiO{sub 2} photoanode and its effect on DSSC performance: A comparative study of doping and surface treatment on deep and surface charge trapping

    Energy Technology Data Exchange (ETDEWEB)

    Ako, Rajour Tanyi [Faculty of Science, Universiti Brunei Darussalam, Jalan Tungku Link, BE1410, Negara Brunei Darussalam (Brunei Darussalam); Ekanayake, Piyasiri, E-mail: piyasiri.ekanayake@ubd.edu.bn [Faculty of Science, Universiti Brunei Darussalam, Jalan Tungku Link, BE1410, Negara Brunei Darussalam (Brunei Darussalam); Centre for Advanced Material and Energy Sciences (CAMES), Universiti Brunei Darussalam, Jalan Tungku Link, BE1410, Negara Brunei Darussalam (Brunei Darussalam); Tan, Ai Ling [Faculty of Science, Universiti Brunei Darussalam, Jalan Tungku Link, BE1410, Negara Brunei Darussalam (Brunei Darussalam); Young, David James [Faculty of Science, Universiti Brunei Darussalam, Jalan Tungku Link, BE1410, Negara Brunei Darussalam (Brunei Darussalam); Faculty of Science, Health, Education and Engineering, University of the Sunshine Coast, Maroochydore DC, Queensland, 4558 (Australia); Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research - A*STAR, #08-03, 2 Fusionopolis Way, Innovis, 138634 (Singapore)

    2016-04-01

    The effect of Lanthanum ions (La{sup 3+}) on charge trapping in dye-sensitized solar cell (DSSC) photoanodes has been investigated with doped and surface-treated TiO{sub 2} nanoparticles. Doped nanoparticles consisting of 0.5 mol.% Mg and La co-doped TiO{sub 2}, 0.5 mol.% Mg doped TiO{sub 2} and pure TiO{sub 2} were synthesized by the sol gel method. Surface-treated nanoparticles of Mg doped TiO{sub 2} and pure TiO{sub 2} were prepared by ball milling in 0.05 M aqueous La{sup 3+} solution. All materials were analyzed by XRD, XPS and UV–Vis DRS. Cell performance, surface free energy state changes and electron injection efficiency of DSSCs based on these nanoparticles were evaluated using current –voltage measurements, EIS and Incident photon to current conversion efficiency. Doped materials had La and Mg ions incorporated into the TiO{sub 2} lattice, while no lattice changes were observed for the surface-treated materials. Less visible light was absorbed by treated oxides compared with doped oxide samples. The overall power conversion efficiencies (PCE) of DSSC photoanodes based on doped materials were twice those of photoanodes fabricated from treated nanoparticles. Doping establishes deep traps that reduce the recombination of electron–hole (e–h) pairs. Conversely, the presence of absorbed oxygen in treated materials enhances e–h recombination with electrolyte at surface trap sites. - Highlights: • DSSC performance is investigated using photoanodes of doped and La{sup 3+} surface treated TiO{sub 2}. • TiO{sub 2} and Mg–TiO{sub 2} treated with La{sup 3+} absorbed less visible light. • A high concentration of absorbed oxygen on surface treated oxides reduced band bending. • Increased surface free energy in the modified DSSC anodes is caused more by Mg{sup 2+} at Ti{sup 4+} than by La{sup 3+} at the surfaces. • Near surface charge traps due to La{sup 3+} treatment promotes e–h recombination.

  15. Effect of heat treatment on the crystal structure and FTIR spectra of Sm doped cerium dioxide film

    Science.gov (United States)

    Liu, Xiaozhou; Liu, Xiaozhou; Xia, Letian; Chen, Jie; Wang, Xiaoyu

    2017-04-01

    The Sm doped cerium dioxide films were prepared with cerium foils as raw materials by anodization in Sm(NO3)3-Na2C2O4-NH3·H2O-H2O-(CH2OH)2 electrolyte. The anodic Sm doped cerium oxide films were heat treated in 100°C ~ 400°C. The heat treated anodic Sm doped cerium oxide films were characterized with X-ray diffraction (XRD) and Fourier transform infrared (FTIR) techniques respectively. The heat treated anodic Sm doped cerium oxide film at 100°C is the semi crystalline film. As heat treatment temperatures being in 200°C ~ 400°C, the heat treated anodic Sm doped cerium oxide films have a structure of cubic fluorite respectively. The doping of Sm can be achieved well by anodization method and be recognized as replacement doping or caulking doping. The crystal structure of Sm doped cerium dioxide films become more complete with the increase of heat treatment temperature in 200 ~ 400 °C. The doping of Sm can improve the crystallinity of the cerium dioxide film. The presence of adsorbing water, ethylene glycol and CO2 in the heat treated anodic Sm doped cerium oxide film at 100°C. The adsorbing ethylene glycols and water, CO2 in the anodic Sm doped cerium oxide film are removed at 200°C and 300°C respectively.

  16. Characterisation of the hole-acoustic phonon interaction in modulation doped Si/Si sub 1 sub - sub x Ge sub x (0.085<=x<=0.28) heterostructures

    CERN Document Server

    Braithwaite, G

    1999-01-01

    magnetoresistance measurements, the has determined the carrier temperature dependence of the hole-hole scattering rate. It will be shown that by considering the fully self consistent nature of carrier-carrier scattering in the weak localisation regime ('dirty limit'), and by including the effect of carrier-carrier scattering in the 'clean limit', it is possible to calculate the dephasing rates for this system and obtain agreement with the measured experimental data to within an accuracy of +-10%. This is a significant improvement on some of the previous calculations for other 2D systems that have been observed in the literature. This Thesis will also report the preliminary results and analysis of pulsed high electric field measurements where the two dimensional hole gas is expected to interact with optical phonons. The work presented in this Thesis describes the experimental investigation of the two dimensional hole gas - acoustic phonon interaction in non-inverted modulation doped strained Si sub 1 sub - sub...

  17. Non-degenerate n-type doping by hydrazine treatment in metal work function engineered WSe2 field-effect transistor

    Science.gov (United States)

    Lee, Inyeal; Rathi, Servin; Li, Lijun; Lim, Dongsuk; Atif Khan, Muhammad; Kannan, E. S.; Kim, Gil-Ho

    2015-11-01

    We report a facile and highly effective n-doping method using hydrazine solution to realize enhanced electron conduction in a WSe2 field-effect transistor (FET) with three different metal contacts of varying work functions—namely, Ti, Co, and Pt. Before hydrazine treatment, the Ti- and Co-contacted WSe2 FETs show weak ambipolar behaviour with electron dominant transport, whereas in the Pt-contacted WSe2 FETs, the p-type unipolar behaviour was observed with the transport dominated by holes. In the hydrazine treatment, a p-type WSe2 FET (Pt contacted) was converted to n-type with enhanced electron conduction, whereas highly n-doped properties were achieved for both Ti- and Co-contacted WSe2 FETs with on-current increasing by three orders of magnitude for Ti. All n-doped WSe2 FETs exhibited enhanced hysteresis in their transfer characteristics, which opens up the possibility of developing memories using transition metal dichalcogenides.

  18. Communication: Hole localization in Al-doped quartz SiO{sub 2} within ab initio hybrid-functional DFT

    Energy Technology Data Exchange (ETDEWEB)

    Gerosa, Matteo [Department of Energy, Politecnico di Milano, via Ponzio 34/3, 20133 Milano (Italy); Di Valentin, Cristiana; Pacchioni, Gianfranco [Dipartimento di Scienza dei Materiali, Università di Milano-Bicocca, via R. Cozzi 55, 20125 Milan (Italy); Bottani, Carlo Enrico, E-mail: carlo.bottani@polimi.it [Department of Energy, Politecnico di Milano, via Ponzio 34/3, 20133 Milano (Italy); Center for Nano Science and Technology @Polimi, Istituto Italiano di Tecnologia, via Pascoli 70/3, 20133 Milano (Italy); Onida, Giovanni [Dipartimento di Fisica dell’ Universita’ degli Studi di Milano and European Theoretical Spectroscopy Facility (ETSF), Via Celoria 16, 20133 Milan (Italy)

    2015-09-21

    We investigate the long-standing problem of hole localization at the Al impurity in quartz SiO{sub 2}, using a relatively recent DFT hybrid-functional method in which the exchange fraction is obtained ab initio, based on an analogy with the static many-body COHSEX approximation to the electron self-energy. As the amount of the admixed exact exchange in hybrid functionals has been shown to be determinant for properly capturing the hole localization, this problem constitutes a prototypical benchmark for the accuracy of the method, allowing one to assess to what extent self-interaction effects are avoided. We obtain good results in terms of description of the charge localization and structural distortion around the Al center, improving with respect to the more popular B3LYP hybrid-functional approach. We also discuss the accuracy of computed hyperfine parameters, by comparison with previous calculations based on other self-interaction-free methods, as well as experimental values. We discuss and rationalize the limitations of our approach in computing defect-related excitation energies in low-dielectric-constant insulators.

  19. Effect of Rashba Spin-Orbit Interaction on the Stability of Spin-Vortex-Induced Loop Current in Hole-Doped Cuprate Superconductors: A Scenario for the Appearance of Magnetic Field Enhanced Charge Order and Fermi Surface Reconstruction

    Science.gov (United States)

    Morisaki, Tsubasa; Wakaura, Hikaru; Koizumi, Hiroyasu

    2017-10-01

    Rashba type spin-orbit interaction is included in the model Hamiltonian for the spin-vortex-induced loop current (SVILC) mechanism of superconductivity for hole doped cuprate superconductors and its effects are investigated. We assume that a Rashba interaction appears around the small polarons formed by the doped holes in the bulk; its internal electric field is assumed to be in the direction perpendicular to the CuO2 plane and stabilizes the spin polarization lying in the CuO2 plane. We examine 4 × 4, 4 × 6, and 4 × 8 spin-vortex-quartet (SVQ) and perform Monte Carlo simulations to estimate the superconducting transition temperature Tc, where each SVQ is a n × m two dimensional region (in the units of the lattice constant) containing four holes, four spin-vortices, and four SVILCs. We find that the 4 × 6 SVQ is the most stable one among them with the highest Tc; in this case, the hole concentration per Cu atom is x = 0.167, which is close to the optimal doping value x = 0.170, suggesting that the optimal doping may be related to the stabilization of the superconducting state by the Rashba interaction. We also find that the 4 × 8 SVQ becomes more stable than the 4 × 6 SVQ in a current flowing situation; this indicates that the conversion from the 4 × 6 SVQs to 4 × 8 SVQs may occur upon the emergence of a macroscopic current by the application of a magnetic field. This conversion may explain the enhancement of the charge order around x = 0.125 and the Fermi surface reconstruction upon an application of a magnetic field.

  20. Electronic correlations in the hole-doped superconductor RbFe{sub 2}As{sub 2} probed via {sup 75}As NMR

    Energy Technology Data Exchange (ETDEWEB)

    Molatta, S.; Wosnitza, J. [Hochfeld-Magnetlabor Dresden (HLD), Helmholtz-Zentrum Dresden-Rossendorf (Germany); TU Dresden (Germany); DFG, GRK-1621 (Germany); Zhang, Z.; Dmytriieva, D.; Kuehne, H. [Hochfeld-Magnetlabor Dresden (HLD), Helmholtz-Zentrum Dresden-Rossendorf (Germany); Khim, S.; Grafe, H.J. [IFW Dresden (Germany); Wurmehl, S.; Buechner, B. [TU Dresden (Germany); DFG, GRK-1621 (Germany); IFW Dresden (Germany)

    2016-07-01

    We will present latest {sup 75}As NMR data in the normal state of the stoichiometric superconductor RbFe{sub 2}As{sub 2}. This will be put into context to known results for the heavily hole-doped compound KFe{sub 2}As{sub 2}. The static and dynamic magnetic correlations were probed via measurements of the Knight shift and nuclear spin-lattice relaxation rate in a wide temperature range from 0.3 to 300 K. Although neither a magnetic nor a structural transition were observed down to lowest temperatures, the very close proximity of the ground state to a magnetic instability is indicated by a pronounced Curie-Weiss-like behavior of spin fluctuations. At around 100 K, we find a maximum of the Knight shift and a changing exponent of the temperature-dependent relaxation rate. This is phenomenologically similar to the case of KFe{sub 2}As{sub 2} and was proposed to stem from a incoherence-coherence crossover mechanism of electronic correlations.

  1. Effect of thermal treatment in vacuum on Fe-doped SnO{sub 2} powders

    Energy Technology Data Exchange (ETDEWEB)

    Bilovol, V. [Laboratorio de Solidos Amorfos, INTECIN, Facultad de Ingenieria, Universidad de Buenos Aires, Paseo Colon 850, C1063ACV Buenos Aires (Argentina); Mudarra Navarro, A.M.; Rodriguez Torres, C.E. [Departamento de Fisica, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, IFLP-CCT La Plata, CONICET (Argentina); Cabrera, A.F., E-mail: cabrera@fisica.unlp.edu.ar [Departamento de Fisica, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, IFLP-CCT La Plata, CONICET (Argentina)

    2012-08-15

    A sample of 10 at% Fe-doped SnO{sub 2} powder was prepared by mechanical alloying and then thermally treated at 773 K in vacuum. The fit of the diffraction patterns and X-ray absorption spectroscopy measurements revealed that the as milled sample was pure doped rutile. Fe dissolved into SnO{sub 2} was found in Fe{sup 2+}/Fe{sup 3+} ionic valence with mainly paramagnetic behavior. After the thermal treatment all techniques indicate the formation of the ternary Sn{sub 0.36}Fe{sub 2.64}O{sub 4} spinel phase, which is responsible for the observed ferromagnetism.

  2. Molecular Doping of the Hole-Transporting Layer for Efficient, Single-Step Deposited Colloidal Quantum Dot Photovoltaics

    KAUST Repository

    Kirmani, Ahmad R.

    2017-07-31

    Employment of thin perovskite shells and metal halides as surface-passivants for colloidal quantum dots (CQDs) have been important, recent developments in CQD optoelectronics. These have opened the route to single-step deposited high-performing CQD solar cells. These promising architectures employ a QD hole-transporting layer (HTL) whose intrinsically shallow Fermi level (EF) restricts band-bending at maximum power-point during solar cell operation limiting charge collection. Here, we demonstrate a generalized approach to effectively balance band-edge energy levels of the main CQD absorber and charge-transport layer for these high-performance solar cells. Briefly soaking the QD HTL in a solution of the metal-organic p-dopant, molybdenum tris(1-(trifluoroacetyl)-2-(trifluoromethyl)ethane-1,2-dithiolene), effectively deepens its Fermi level, resulting in enhanced band bending at the HTL:absorber junction. This blocks the back-flow of photo-generated electrons, leading to enhanced photocurrent and fill factor compared to undoped devices. We demonstrate 9.0% perovskite-shelled and 9.5% metal-halide-passivated CQD solar cells, both achieving ca. 10% relative enhancements over undoped baselines.

  3. P3HT:PCBM:pentacene inverted polymer solar cells with roughened Al-doped ZnO nanorod array and photoelectrochemical treatment

    Science.gov (United States)

    Lee, Hsin-Ying; Huang, Hung-Lin

    2014-05-01

    In this work, the P3HT:PCBM:pentacene (1:0.8:0.065 by weight) inverted polymer solar cells with roughened Aldoped ZnO (AZO) nanorod array were fabricated. The pentacene doping could modulate the hole mobility and the electron mobility in the active layer. The optimal hole-electron mobility balance ( µh/ µe=1.000) was achieved as the pentacene doping ratio of 0.065. The 100-nm-long AZO nanorod array were formed as the carrier collection layer and the carrier transportation layer of the inverted polymer solar cells using the combination techniques of the laser interference photolithography method and the wet etching process. Because the AZO nanorod array was prepared using the wet etching process, more defects were formed on the sidewall surface of the AZO nanorods. In this work, the photoelectrochemical (PEC) method was used to grow Zn(OH)2 and Al(OH)3 thin layer on the sidewall surface of the AZO nanorods, which could reduce the carrier recombination path in the inverted polymer solar cells. Compared with the P3HT:PCBM:pentacene (1:0.8:0.065) inverted polymer solar cells without PEC treatment, the short circuit current density and the power conversion efficiency of the inverted polymer solar cells with PEC treatment were increased from 14.56 mA/cm2 to 15.85 mA/cm2 and from 5.45% to 6.13%, respectively. The enhancement in the performance of the inverted polymer solar cells with PEC treatment could be attributed to that the PEC treatment could effectively passivate the defects on the surface of the AZO nonorods.

  4. Solvothermal syntheses of Bi and Zn co-doped TiO{sub 2} with enhanced electron-hole separation and efficient photodegradation of gaseous toluene under visible-light

    Energy Technology Data Exchange (ETDEWEB)

    Li, Juan-Juan [Center for Excellence in Regional Atmospheric Environment, and Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021 (China); Cai, Song-Cai [Center for Excellence in Regional Atmospheric Environment, and Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021 (China); University of Chinese Academy of Sciences, Beijing, 100049 (China); Xu, Zhen [Center for Excellence in Regional Atmospheric Environment, and Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021 (China); Chen, Xi [Center for Excellence in Regional Atmospheric Environment, and Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021 (China); University of Chinese Academy of Sciences, Beijing, 100049 (China); Chen, Jin [Center for Excellence in Regional Atmospheric Environment, and Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021 (China); Jia, Hong-Peng, E-mail: hpjia@iue.ac.cn [Center for Excellence in Regional Atmospheric Environment, and Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021 (China); Chen, Jing, E-mail: jing.chen@fjirsm.ac.cn [State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002 (China)

    2017-03-05

    Highlights: • Bi-Zn co-doped TiO{sub 2} catalysts were prepared by solvothermal route. • The incorporation of Bi doping into the TiO{sub 2} generates intermediate energy levels. • Bi and Zn doping showed the enhanced absorption in visible-light region. • Zn dopant acts as a mediator of interfacial charge transfer. • TiBi{sub 1.9%}Zn{sub 1%}O{sub 2} exhibited high photocatalytic degradation for toluene. - Abstract: This study investigated the effects of Bi doped and Bi-Zn co-doped TiO{sub 2} on photodegradation of gaseous toluene. The doped TiO{sub 2} with various concentration of metal was prepared using the solvothermal route and characterized by SEM, XRD, Raman, BET, DRS, XPS, PL and EPR. Their photocatalytic activities under visible-light irradiation were drastically influenced by the dopant content. The results showed that moderate metal doping levels were obviously beneficial for the toluene degradation, while high doping levels suppressed the photocatalytic activity. The photocatalytic degradation of toluene over TiBi{sub 1.9%}O{sub 2} and TiBi{sub 1.9%}Zn{sub 1%}O{sub 2} can reach to 51% and 93%, respectively, which are much higher than 25% of TiO{sub 2}. Bi doping into TiO{sub 2} lattice generates new intermediate energy level of Bi below the CB edge of TiO{sub 2}. The electron excitation from the VB to Bi orbitals results in the decreased band gap, extended absorption of visible-light and thus enhances its photocatalytic efficiency. Zn doping not only further enhances the absorption in this visible-light region, but also Zn dopant exists as the form of ZnO crystallites located on the interfaces of TiO{sub 2} agglomerates and acts as a mediator of interfacial charge transfer to suppress the electron-hole recombination. These synergistic effects are responsible for the enhanced photocatalytic performance.

  5. Sol-gel deposition and plasma treatment of intrinsic, aluminum-doped, and gallium-doped zinc oxide thin films as transparent conductive electrodes

    Science.gov (United States)

    Zhu, Zhaozhao; Mankowski, Trent; Balakrishnan, Kaushik; Shikoh, Ali Sehpar; Touati, Farid; Benammar, Mohieddine A.; Mansuripur, Masud; Falco, Charles M.

    2015-09-01

    Zinc oxide and aluminum/gallium-doped zinc oxide thin films were deposited via sol-gel spin-coating technique. Employing plasma treatment as alternative to post thermal annealing, we found that the morphologies of these thin films have changed and the sheet resistances have been significantly enhanced. These plasma-treated thin films also show very good optical properties, with transmittance above 90% averaged over the visible wavelength range. Our best aluminum/gallium-doped zinc oxide thin films exhibit sheet resistances (Rs) of ~ 200 Ω/sq and ~ 150 Ω/sq, respectively.

  6. [Treatment of patellar fractures with cable through the bone and Kirschner with a hole in the tail].

    Science.gov (United States)

    Sun Xiao-liang; Yang, Guo-jing; Zhang, Lei; Wang, Wei-liang; Xie, Bing-ju

    2015-07-01

    To study clinical effects of a new internal fixation by using a cable through the bone and Kirschner with a hole in the tail, for the treatment of patellar fractures. From May 2012 to July 2013, thirty-four patients with patellar fractures were treated with cable through the bone and Kirschner with a hole in the tail. All the patients had close fracture,including 12 transverse fractures and 22 comminuted fractures. There were 18 males and 16 females, ranging in age from 26 to 81 years old, with an average of (46.0 ± 3.0) years old. After open reduction, two appropriate length of Kirschner with a hole in the tail were driven into the patella as perpendicular to the fracture line or the major fragments as possible. A transverse bone tunnel was then drilled with a Kirschner at one side of the patella. Then the cable, which was successively pulled through the bone tunnel and the hole of Kirschner, was crossed in a figure-eight over the anterior of the patella, tightened and fixated by special instruments. The Kirschner was clipped off on the edge of the hole. If it was a comminuted fracture, another cable was used to fasten the patella with cerclage. Postoperative evaluation was based on Bostman. All the patients were followed up, and the duration ranged from 12 to 26 months, with a mean of (16.0 ± 2.0) months. Fractures healed in all the cases without such complications as infection, loosening of Kirschner and cable loop, and skin irritation. According to the Böstman score system, 33 cases got an excellent result, and 1 good. The cable through the bone and Kirschner with a hole in the tail is a simple, stable and effective method for the treatment of patellar fractures, especially the transverse fractures, with earlier knee exercise and fewer complications.

  7. Oxygen hole-doping effects on the spin-chain system Ca{sub 2+x}Y{sub 2-x}Cu{sub 5}O{sub 10-{delta}}

    Energy Technology Data Exchange (ETDEWEB)

    Park, K. [Department of Physics, University of Texas at Austin, Austin, TX 78712 (United States)], E-mail: kspark@physics.utexas.edu; Cackowski, T. [Department of Physics, University of Texas at Austin, Austin, TX 78712 (United States); Markert, J.T. [Department of Physics, University of Texas at Austin, Austin, TX 78712 (United States)], E-mail: markert@physics.utexas.edu

    2008-04-01

    The magnetic properties of the low-dimensional spin-chain system Ca{sub 2+x}Y{sub 2-x}Cu{sub 5}O{sub 10-{delta}} were studied as a function of oxygen content and Ca-doping. A series of samples with different oxygen contents were prepared by solid state reaction under various oxygen pressures up to 170 atm and characterized by X-ray diffraction and iodometric titration. Oxygen deficiency was observed to be from {delta}=0.2-0.4 at 0.2 atm to {delta}{approx}0.0 at 170 atm oxygen pressure. Oxygen deficiency increases with Ca-doping at fixed oxygen pressure. The temperature dependence of the magnetic moment and of the specific heat are reported here for the x=0.9 sample with various oxygen deficiencies. The effects of oxygen deficiency on magnetic coupling are compared with Ca-doping. Notably, oxygen content plays a much more critical role in the reduction of magnetic interactions in the CuO{sub 2} chains than Ca-doping, even for the same hole concentration.

  8. Magnetotransport property of the hole-doped delafossite CuCr0.97Mg0.03O2 with a Spin-3/2 antiferromagnetic triangular sublattice

    Science.gov (United States)

    Okuda, Tetsuji; Oozono, Satoshi; Kihara, Takumi; Tokunaga, Masashi

    2013-06-01

    The magnetotransport property of a hole-doped delafossite CuCr0.97Mg0.03O2 with a spin-3/2 antiferromagnetic (AF) triangular sublattice was investigated by using a pulsed high magnetic field. A dramatic change of magnetoresistance was observed with a variation of temperature, which indicates that a spin fluctuation due to a competition between the AF and the ferromagnetic Hund's interactions is enhanced at temperatures around the Néel temperatures ( T N). The competition may lead to a partially-disordered state at temperatures below T N which may cause a nontrivial promotion of a 120° Néel state.

  9. Treatment of screw hole defects using bone graft materials: a histologic and biomechanic study.

    Science.gov (United States)

    York, M J; Hutton, W C

    1996-01-01

    We surgically applied compression plates, secured with cortical screws, to the anterolateral surface of each radius in 20 dogs. Five weeks later, the plates and screws were removed. The dogs were then divided into four groups of 5, and each group had the screw holes in the left radii filled with a different form of bone graft material. The screw holes in the right radii received no graft material and served as controls. Five weeks later the dogs were euthanized, and the radii were removed and torqued to failure. All bones failed through a previous screw hole. An analysis of variance comparing all grafted radii to the ungrafted controls revealed no significant difference in torque to failure. This suggests that both grafted and ungrafted screw holes still increase stress at 5 weeks, and any period of protection after plate removal should be longer than 5 weeks. However, histology revealed that the holes filled with graft material had, in every case, more bone in the screw holes than did the holes in the ungrafted controls.

  10. Hole-Transporting Layer Treatment of Planar Hybrid n-Si/PEDOT:PSS Solar Cells with Power Conversion Efficiency up to 14.5%

    Directory of Open Access Journals (Sweden)

    Chenxu Zhang

    2017-01-01

    Full Text Available A systematical investigation was carried out into the effects of the hole-transporting layer treatment of poly(3,4-ethylenedioxythiophene:poly(styrenesulfonate (PEDOT:PSS on the performance of planar hybrid n-Si/PEDOT:PSS solar cells. Triton X-100 and ethylene glycol (EG were chosen to improve the conductivity and surface morphology of the PEDOT:PSS film. It was found that the annealing temperature has a great influence on the PEDOT:PSS material properties and the corresponding device performance. By optimizing the annealing temperature, the conductivity of the PEDOT:PSS film doped with Triton X-100 and EG could be enhanced by a factor of more than three orders. And the corresponding device also shows record power conversion efficiency as high as 14.5% with an open circuit voltage of 0.627 V, a short circuit current of 32.6 mA/cm2, and a fill factor of 70.7%.

  11. Hole pairs in a spin liquid: Influence of electrostatic hole-hole repulsion

    Science.gov (United States)

    Gazza, Claudio; Martins, George B.; Riera, José; Dagotto, Elbio

    1999-01-01

    The stability of hole bound states in the t-J model including short-range Coulomb interactions is analyzed using computational techniques on ladders with up to 2×30 sites. For a nearest-neighbor (NN) hole-hole repulsion, the two-holes bound state is surprisingly robust and breaks only when the repulsion is several times the exchange J. At ~10% hole doping the pairs break only for a NN repulsion as large as V~4J. Pair-pair correlations remain robust in the regime of hole binding. The results support electronic hole-pairing mechanisms on ladders based on holes moving in spin-liquid backgrounds. Implications in two dimensions are also presented. The need for better estimations of the range and strength of the Coulomb interaction in copper oxides is remarked.

  12. Utility of microscope-integrated optical coherence tomography (MIOCT) in the treatment of myopic macular hole retinal detachment.

    Science.gov (United States)

    Kumar, Atul; Kakkar, Prateek; Ravani, Raghav Dinesh; Markan, Ashish

    2017-07-14

    Macular hole-associated retinal detachment in high myopia is described as a final stage in progression of myopic traction maculopathy (MTM).1â€"3 Shimada et al4 described the progressive stages of MTM from macular retinoschisis to serous retinal detachment in high myopia. Stage 4 MTM is characterised as disappearance of retinoschisis with progression to retinal detachment due to macular hole formation. It is hypothesised that vitreoschisis and abnormal vitreo-retinal interface create the premacular tangential traction.5 6 Intraoperative triamcinolone acetonide is used to visualise the residual posterior vitreous cortex (PVC). We hereby describe the utility of microscope-integrated optical coherence tomography (MIOCT) in assisting complete removal of PVC and internal limiting membrane (ILM) peeling with multilayered inverted ILM flap in the treatment of myopic macular hole retinal detachment. MIOCT helped identify vitreoschisis and confirm the position of ILM flaps over the macular hole intraoperatively. © BMJ Publishing Group Ltd (unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

  13. Hafnium-doped hydroxyapatite nanoparticles with ionizing radiation for lung cancer treatment.

    Science.gov (United States)

    Chen, Min-Hua; Hanagata, Nobutaka; Ikoma, Toshiyuki; Huang, Jian-Yuan; Li, Keng-Yuan; Lin, Chun-Pin; Lin, Feng-Huei

    2016-06-01

    Recently, photodynamic therapy (PDT) is one of the new clinical options by generating cytotoxic reactive oxygen species (ROS) to kill cancer cells. However, the optical approach of PDT is limited by tissue penetration depth of visible light. In this study, we propose that a ROS-enhanced nanoparticle, hafnium-doped hydroxyapatite (Hf:HAp), which is a material to yield large quantities of ROS inside the cells when the nanoparticles are bombarded with high penetrating power of ionizing radiation. Hf:HAp nanoparticles are generated by wet chemical precipitation with total doping concentration of 15mol% Hf(4+) relative to Ca(2+) in HAp host material. The results show that the HAp particles could be successfully doped with Hf ions, resulted in the formation of nano-sized rod-like shape and with pH-dependent solubility. The impact of ionizing radiation on Hf:HAp nanoparticles is assessed by using in-vitro and in-vivo model using A549 cell line. The 2',7'-dichlorofluorescein diacetate (DCFH-DA) results reveal that after being exposed to gamma rays, Hf:HAp could significantly lead to the formation of ROS in cells. Both cell viability (WST-1) and cytotoxicity (LDH) assay show the consistent results that A549 lung cancer cell lines are damaged with changes in the cells' ROS level. The in-vivo studies further demonstrate that the tumor growth is inhibited owing to the cells apoptosis when Hf:HAp nanoparticles are bombarded with ionizing radiation. This finding offer a new therapeutic method of interacting with ionizing radiation and demonstrate the potential of Hf:HAp nanoparticles in tumor treatment, such as being used in a palliative treatment after lung surgical procedure. Photodynamic therapy (PDT) is one of the new clinical options by generating cytotoxic reactive oxygen species (ROS) to kill cancer cells. Unfortunately, the approach of PDT is usually limited to the treatment of systemic disease and deeper tumor, due to the limited tissue penetration depth of visible

  14. Effect of Doping Phosphorescent Material and Annealing Treatment on the Performance of Polymer Solar Cells

    Directory of Open Access Journals (Sweden)

    Zixuan Wang

    2013-01-01

    Full Text Available A series of polymer solar cells (PSCs with P3HT:PCBM or P3HT:PCBM:Ir(btpy3 blend films as the active layer were fabricated under the same conditions. Effects of phosphorescent material Ir(btpy3 doping concentration and annealing temperature on the performance of PSCs were investigated. The short-circuit current density (Jsc and open-circuit voltage (Voc are increased by adopting P3HT:PCBM:Ir(btpy3 blend films as the active layer when the cells do not undergo annealing treatment. The increased Jsc should be attributed to the increase of photon harvesting induced by doping phosphorescent material Ir(btpy3 and the effective energy transfer from Ir(btpy3 to P3HT. The effective energy transfer from Ir(btpy3 to P3HT was demonstrated by time-resolved photoluminescence (PL spectra. The increased Voc is due to the photovoltaic effect between Ir(btpy3 and PCBM. The power conversion efficiency (PCE of PSCs with P3HT:PCBM as the active layer is increased from 0.19% to 1.49% by annealing treatment at 140°C for 10 minutes. The PCE of PSCs with P3HT:PCBM:Ir(btpy3 as the active layer is increased from 0.49% to 0.95% by annealing treatment at lower temperature at 100°C for 10 minutes.

  15. Preparation and Characterization of High-Temperature Hole Burning Materials

    National Research Council Canada - National Science Library

    Bommareddi, Rami

    2004-01-01

    .... Hole burning efficiency depends on the glass composition as well. We investigated persistent spectral hole burning studies in europium doped glasses such as sodium borates, silicates, borosilicates, germinates and tellurites...

  16. Minimally Invasive Supraorbital Key-hole Approach for the Treatment of Anterior Cranial Fossa Meningiomas

    Science.gov (United States)

    IACOANGELI, Maurizio; NOCCHI, Niccolò; NASI, Davide; DI RIENZO, Alessandro; DOBRAN, Mauro; GLADI, Maurizio; COLASANTI, Roberto; ALVARO, Lorenzo; POLONARA, Gabriele; SCERRATI, Massimo

    2016-01-01

    The most important target of minimally invasive surgery is to obtain the best therapeutic effect with the least iatrogenic injury. In this background, a pivotal role in contemporary neurosurgery is played by the supraorbital key-hole approach proposed by Perneczky for anterior cranial base surgery. In this article, it is presented as a possible valid alternative to the traditional craniotomies in anterior cranial fossa meningiomas removal. From January 2008 to January 2012 at our department 56 patients underwent anterior cranial base meningiomas removal. Thirty-three patients were submitted to traditional approaches while 23 to supraorbital key-hole technique. A clinical and neuroradiological pre- and postoperative evaluation were performed, with attention to eventual complications, length of surgical procedure, and hospitalization. Compared to traditional approaches the supraorbital key-hole approach was associated neither to a greater range of postoperative complications nor to a longer surgical procedure and hospitalization while permitting the same lesion control. With this technique, minimization of brain exposition and manipulation with reduction of unwanted iatrogenic injuries, neurovascular structures preservation, and a better aesthetic result are possible. The supraorbital key-hole approach according to Perneckzy could represent a valid alternative to traditional approaches in anterior cranial base meningiomas surgery. PMID:26804334

  17. Hydrogen plasma treatment for improved conductivity in amorphous aluminum doped zinc tin oxide thin films

    Directory of Open Access Journals (Sweden)

    M. Morales-Masis

    2014-09-01

    Full Text Available Improving the conductivity of earth-abundant transparent conductive oxides (TCOs remains an important challenge that will facilitate the replacement of indium-based TCOs. Here, we show that a hydrogen (H2-plasma post-deposition treatment improves the conductivity of amorphous aluminum-doped zinc tin oxide while retaining its low optical absorption. We found that the H2-plasma treatment performed at a substrate temperature of 50 °C reduces the resistivity of the films by 57% and increases the absorptance by only 2%. Additionally, the low substrate temperature delays the known formation of tin particles with the plasma and it allows the application of the process to temperature-sensitive substrates.

  18. Hydrogen plasma treatment for improved conductivity in amorphous aluminum doped zinc tin oxide thin films

    Energy Technology Data Exchange (ETDEWEB)

    Morales-Masis, M., E-mail: monica.moralesmasis@epfl.ch; Ding, L.; Dauzou, F. [Photovoltaics and Thin-Film Electronics Laboratory (PVLab), Institute of Microengineering (IMT), Ecole Polytechnique Fédérale de Lausanne - EPFL, Rue de la Maladière 71b, CH-2002 Neuchatel (Switzerland); Jeangros, Q. [Interdisciplinary Centre for Electron Microscopy, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne (Switzerland); Hessler-Wyser, A. [Photovoltaics and Thin-Film Electronics Laboratory (PVLab), Institute of Microengineering (IMT), Ecole Polytechnique Fédérale de Lausanne - EPFL, Rue de la Maladière 71b, CH-2002 Neuchatel (Switzerland); Interdisciplinary Centre for Electron Microscopy, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne (Switzerland); Nicolay, S. [Centre Suisse d’Electronique et de Microtechnique (CSEM) SA, Rue Jaquet-Droz 1, CH-2002 Neuchatel (Switzerland); Ballif, C. [Photovoltaics and Thin-Film Electronics Laboratory (PVLab), Institute of Microengineering (IMT), Ecole Polytechnique Fédérale de Lausanne - EPFL, Rue de la Maladière 71b, CH-2002 Neuchatel (Switzerland); Centre Suisse d’Electronique et de Microtechnique (CSEM) SA, Rue Jaquet-Droz 1, CH-2002 Neuchatel (Switzerland)

    2014-09-01

    Improving the conductivity of earth-abundant transparent conductive oxides (TCOs) remains an important challenge that will facilitate the replacement of indium-based TCOs. Here, we show that a hydrogen (H{sub 2})-plasma post-deposition treatment improves the conductivity of amorphous aluminum-doped zinc tin oxide while retaining its low optical absorption. We found that the H{sub 2}-plasma treatment performed at a substrate temperature of 50 °C reduces the resistivity of the films by 57% and increases the absorptance by only 2%. Additionally, the low substrate temperature delays the known formation of tin particles with the plasma and it allows the application of the process to temperature-sensitive substrates.

  19. Improved characteristics of conventional and inverted polymer photodetectors using phosphonic acid-based self-assembled monolayer treatment for interfacial engineering of Ga-doped ZnO electrodes

    Science.gov (United States)

    Kajii, Hirotake; Mohri, Yoshinori; Okui, Hiyuto; Kondow, Masahiko; Ohmori, Yutaka

    2018-03-01

    The characteristics of conventional and inverted polymer photodetectors based on a blend of a donor, poly(3-hexylthiophene) (P3HT), and an acceptor, fullerene derivative [6,6]phenyl-C61-butyric acid methyl ester (PCBM) using Ga-doped ZnO (GZO) electrodes modified by phosphonic acid-based self-assembled monolayer (SAM) treatment in a short time are investigated. Fluoroalkyl SAM, 1H,1H,2H,2H-perfluorooctane phosphonic acid (FOPA) treatment leads to efficient hole extraction from the active layer. The characteristics of the conventional device with GZO modified by FOPA treatment are almost the same as those with indium tin oxide modified by FOPA. Cs2CO3 and aminoalkyl SAM, 11-aminoundecylphosphonic acid (11-AUPA) treatments suppress the hole injection from GZO to the organic layer. For the inverted devices with GZO cathodes using Cs2CO3 and 11-AUPA, the dark current decreases, which results in the improved photodetector detectivity. An inverted device with both Cs2CO3 and 11-AUPA exhibits incident-photon-to-current conversion efficiency (IPCE) of approximately 65% (80%) at 0 V (‑6 V) under light irradiation (λ = 500 nm), high on/off ratio, and improved durability. Improved open-circuit voltage and IPCE at low voltages are achieved by these treatments, which are related with the improved internal built-in field, the reduction of recombination probability in the vicinity of GZO, and the modified charge collection efficiency.

  20. The magnetic phase diagram of the spin-chain system Ca{sub 2+x}Y{sub 2-x}Cu{sub 5}O{sub 10-{delta}}: Oxygen hole-doping corrections

    Energy Technology Data Exchange (ETDEWEB)

    Park, Keeseong [Department of Physics, University of Texas at Austin, 1 University Station C1600, Austin, TX 78712 (United States)], E-mail: kspark@physics.utexas.edu; Lee, Yong J.; Markert, John T. [Department of Physics, University of Texas at Austin, 1 University Station C1600, Austin, TX 78712 (United States)

    2007-09-01

    Recently, the antiferromagnetic transition temperature in the coupled spin-chain system Ca{sub 2+x}Y{sub 2-x}Cu{sub 5}O{sub 10-{delta}} was found to decrease with increasing x and disappear around x = 1.4 [K. Kubo, S. Kurogi, Y. Koike, T. Nishizaki, N. Kobayashi, Phys. Rev. B 71 (2005) 104413]. We report the results of X-ray diffraction, magnetic susceptibility, heat capacity, and iodometric titration measurements, and find that such behavior corresponds to oxygen-deficient specimens. We propose that the correct phase diagram is a function of both cation doping and oxygen content, with hole concentration p = (x - 2{delta}) per formula unit. We find that the true phase transition occurs just below p = 1.0, corresponding to a hole concentration of 0.20 per copper. For example, for x = 1.00, the single crystals of Kubo et al. (2005) correspond to our polycrystalline specimens with {delta} = 0.37 (p = 0.26), a very large oxygen-defect effect. Such a composition has only a slightly suppressed Neel temperature, while for our fully oxygenated x = 1.00 samples, the antiferromagnetic transition is completely suppressed.

  1. W/Mo co-doped BiVO4 for photocatalytic treatment of polymer-containing wastewater in oilfield

    Science.gov (United States)

    Zhou, Ying; Li, Wei; Wan, Wenchao; Zhang, Ruiyang; Lin, Yuanhua

    2015-06-01

    Polymer flooding is an effective way to enhance oil recovery (EOR). However, the treatment of the oily wastewater becomes an urgent issue. Photocatalysis is a promising approach for this purpose. In this report, W/Mo co-doped BiVO4 particles are synthesized by hydrothermal method. W/Mo co-doping could promote an effective separation of photogenerated carriers reflecting from the 6 times higher photocurrent density compared to pure BiVO4. The photodegradation of partially hydrolyzed polyacrylamide (HPAM) over 0.5 at.% W and 1.5 at.% Mo co-doped BiVO4 is 43% under UV-vis light irradiation for 3 h, which is much higher than that of pure BiVO4 (18%).

  2. Effect of heat treatment on microstructural and optical properties of CBD grown Al-doped ZnO thin films

    Energy Technology Data Exchange (ETDEWEB)

    Chandramohan, R., E-mail: rathinam.chandramohan@gmail.com [Department of Physics, Sree Sevugan Annamalai College, College Road, Devakottai 630303 (India); Vijayan, T.A. [Department of Physics, Sree Sevugan Annamalai College, College Road, Devakottai 630303 (India); Arumugam, S.; Ramalingam, H.B. [Department of Physics, Government Arts College, Udumalpet 642126 (India); Dhanasekaran, V.; Sundaram, K.; Mahalingam, T. [Department of Physics, Alagappa University, Karaikudi 630003 (India)

    2011-02-15

    Research highlights: > Effect of annealing temperature on Al-doped ZnO thin films. > Microstructural properties of Al-doped ZnO thin films. > Optical constants are found to increase with increase of heat treatment. - Abstract: Investigations on the effect of annealing temperature on the structural, optical properties and morphology of Al-doped ZnO thin films deposited on glass substrate by chemical bath deposition have been carried out. X-ray diffraction studies revealed that deposited films are in polycrystalline nature with hexagonal structure along the (0 0 2) crystallographic plane. Microstructural properties of films such as crystallite size, texture coefficient, stacking fault probability and microstrain were calculated from predominant (0 0 2) diffraction lines. The UV-Vis-NIR spectroscopy studies revealed that all the films have high optical transmittance (>60%) in the visible range. The optical band gap values are found to be in the range of 3.25-3.31 eV. Optical constants have been estimated and the values of n and k are found to increase with increase of heat treatment. The films have increased transmittance with increase of heat treatment. Al-doped ZnO thin films fabricated by this simple and economic chemical bath deposition technique without using any carrier gas are found to be good in structural and optical properties which are desirable for photovoltaic applications. Scanning electron microscopic images revealed that the hexagonal shaped grains that occupy the entire surface of the film with its near stoichiometric composition.

  3. Long-Wavelength Infrared Surface Plasmons on Ga-Doped ZnO Films Excited via 2D Hole Arrays for Extraordinary Optical Transmission (Preprint)

    Science.gov (United States)

    2013-10-01

    Branch Aerospace Components & Subsystems Division Nima Nader Esfahani and Shivashankar Vangala Solid State Scientific Corporation David...Hendrickson, Kevin D. Leedy, Junpeng Guo, and Darren Thomson (AFRL/RYD) Nima Nader Esfahani and Shivashankar Vangala (Solid State Scientific Corporation...hole arrays for extraordinary optical transmission Justin W. Cleary*a, Nima Nader Esfahania,b,c, Shivashankar Vangalaa,b, Junpeng Guoa,d,e

  4. Use of seawater for the boron-doped diamond electrochemical treatment of diluted vinasse wastewater.

    Science.gov (United States)

    Daskalaki, V M; Marakas, H; Mantzavinos, D; Katsaounis, A; Gikas, P

    2013-01-01

    Vinasse wastewater of high organic content (COD = 131,000 mg/L) and low biodegradability (BOD5/COD = 0.11) cannot be easily managed and usually require several consecutive treatment steps. The objective of this work was to dilute vinasse wastewater with seawater and then subject them to electrochemical oxidation over boron-doped diamond (BDD) electrodes. The use of seawater is a rational and novel approach for plants close to the seashore since it may achieve the desirable levels of effluent concentration and conductivity without consuming other water resources and extra electrolytes. Experiments were conducted at initial COD values of 830-8,400 mg/L, NaCl concentrations of 34-200 mM and current densities of 70-200 mA/cm(2) for up to 5 hours. The effect of current density and NaCl concentration was marginal on the electrochemical treatment, while the single most important parameter was the initial COD concentration. The order of reaction for COD reduction appears to be 'first' at low effluent concentrations and it decreases to 'zero' at higher concentrations, denoting the importance of the ratio of organics to reactive radicals concentration. Based on COD and total organic carbon data, it is postulated that degradation occurs predominantly through total oxidation (i.e. mineralization) to carbon dioxide and water, which is characteristic of BDD anodes.

  5. Effect of Heat Treatment Under Nitrogen Atmosphere on Sprayed Fluorine Doped In2O3 Thin Films

    Science.gov (United States)

    Beji, Nasreddine; Ajili, Mejda; Turki, Najoua Kamoun

    2016-07-01

    Fluorine-doped indium oxide thin films (In2O3:F) were prepared at 500°C for different fluorine concentrations (0 at.%, 2 at.%, 6 at.% and 10 at.%) using the chemical spray pyrolysis technique. Structure and surface morphology of these films were characterized by x-ray diffraction (XRD) and atomic force microscopy (AFM). XRD analysis revealed that fluorine doped In2O3 thin films exhibit a centered cubic structure with the (400) preferential orientation. The change of the preferential reflection plane from (222) to (400) was found after doping. The doping optimum concentration of thin film crystal structure is obtained witha fluorine ratio equal to 2 at.%. The crystallinity improvement of In2O3:F (2 at.%) film is detected after annealing at 200°C, 300°C, and 400°C in nitrogen gas for 45 min. Transmission and reflection spectra measurements were performed over the wavelength range of 250-2500 nm. The band gap energy increase from 3.10 eV to 3.45 eV was detected after treatment at 400°C. In parallel, the electrical resistivity, deduced from Hall effect measurements, decreases from 428.90 × 10-4 Ω cm to 6.58 × 10-4 Ω cm.

  6. Multifunctional Gadolinium-Doped Mesoporous TiO2 Nanobeads: Photoluminescence, Enhanced Spin Relaxation, and Reactive Oxygen Species Photogeneration, Beneficial for Cancer Diagnosis and Treatment.

    Science.gov (United States)

    Imani, Roghayeh; Dillert, Ralf; Bahnemann, Detlef W; Pazoki, Meysam; Apih, Tomaž; Kononenko, Veno; Repar, Neža; Kralj-Iglič, Veronika; Boschloo, Gerrit; Drobne, Damjana; Edvinsson, Tomas; Iglič, Aleš

    2017-05-01

    Materials with controllable multifunctional abilities for optical imaging (OI) and magnetic resonant imaging (MRI) that also can be used in photodynamic therapy are very interesting for future applications. Mesoporous TiO2 sub-micrometer particles are doped with gadolinium to improve photoluminescence functionality and spin relaxation for MRI, with the added benefit of enhanced generation of reactive oxygen species (ROS). The Gd-doped TiO2 exhibits red emission at 637 nm that is beneficial for OI and significantly improves MRI relaxation times, with a beneficial decrease in spin-lattice and spin-spin relaxation times. Density functional theory calculations show that Gd3+ ions introduce impurity energy levels inside the bandgap of anatase TiO2 , and also create dipoles that are beneficial for charge separation and decreased electron-hole recombination in the doped lattice. The Gd-doped TiO2 nanobeads (NBs) show enhanced ability for ROS monitored via • OH radical photogeneration, in comparison with undoped TiO2 nanobeads and TiO2 P25, for Gd-doping up to 10%. Cellular internalization and biocompatibility of TiO2 @xGd NBs are tested in vitro on MG-63 human osteosarcoma cells, showing full biocompatibility. After photoactivation of the particles, anticancer trace by means of ROS photogeneration is observed just after 3 min irradiation. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. A nitrogen-doped carbon nanotube enhanced polyethersulfone membrane system for water treatment

    Science.gov (United States)

    Phao, Neo; Nxumalo, Edward N.; Mamba, Bhekie B.; Mhlanga, Sabelo D.

    Water quality in South Africa and around the world continues to deteriorate due to contamination by organic, inorganic and microbial substances. While many efforts have been done to address water quality problems, current drinking water treatment technologies remain costly and do not effectively remove pollutants to acceptable levels. In this work nitrogen doped carbon nanotubes/polyethersulfone (N-CNT/PES) blend membranes were synthesized via a modified phase inversion method and assessed for suitability in drinking water treatment. The N-CNTs with outer diameters of 30-45 nm and 3% N content were prepared using a conventional chemical vapour deposition method and functionalized by refluxing in HNO3. The confirmation and degree of functionalization with -OH and -COOH groups was determined using Fourier-transform infrared (FTIR) spectroscopy and zeta potential analysis. FTIR studies confirmed the successful incorporation of functionalized N-CNTs (N-CNTs) in the membrane matrix. Atomic force microscopy (AFM) analysis revealed that the addition of N-CNTs leads to reduced surface roughness, suggesting a good dispersion of the N-CNTs in the matrix. Permeability studies revealed that the addition of N-CNTs to the polyethersulfone (PES) solution increased the water flux of the blend membrane by up to 70%. N-CNT loadings of 0.04 wt% in the blend membranes gave low surface contact angle of 55° and high fluxes. In addition, inclusion of N-CNTs enhanced the mechanical properties of the N-CNT/PES blend membranes. The use of N-CNTs in mixed matrix PES membranes is reported for the first time here. The result already suggests superior compatibility of the N-CNTs with PES compared to undoped CNTs, due to the high surface reactivity of the N-CNTs.

  8. Shelf life stability comparison in air for solution processed pristine PDPP3T polymer and doped spiro-OMeTAD as hole transport layer for perovskite solar cell

    Directory of Open Access Journals (Sweden)

    Ashish Dubey

    2016-06-01

    Full Text Available This data in brief includes forward and reverse scanned current density–voltage (J–V characteristics of perovskite solar cells with PDPP3T and spiro-OMeTAD as HTL, stability testing conditions of perovskite solar cell shelf life in air for both PDPP3T and spiro-OMeTAD as HTL as per the description in Ref. [1], and individual J–V performance parameters acquired with increasing time exposed in ambient air are shown for both type of devices using PDPP3T and spiro-OMeTAD as HTL. The data collected in this study compares the device stability with time for both PDPP3T and spiro-OMeTAD based perovskite solar cells and is directly related to our research article “solution processed pristine PDPP3T polymer as hole transport layer for efficient perovskite solar cells with slower degradation” [2].

  9. Shelf life stability comparison in air for solution processed pristine PDPP3T polymer and doped spiro-OMeTAD as hole transport layer for perovskite solar cell.

    Science.gov (United States)

    Dubey, Ashish; Adhikari, Nirmal; Venkatesan, Swaminathan; Gu, Shaopeng; Khatiwada, Devendra; Wang, Qi; Mohammad, Lal; Kumar, Mukesh; Qiao, Qiquan

    2016-06-01

    This data in brief includes forward and reverse scanned current density-voltage ( J - V ) characteristics of perovskite solar cells with PDPP3T and spiro-OMeTAD as HTL, stability testing conditions of perovskite solar cell shelf life in air for both PDPP3T and spiro-OMeTAD as HTL as per the description in Ref. [1], and individual J - V performance parameters acquired with increasing time exposed in ambient air are shown for both type of devices using PDPP3T and spiro-OMeTAD as HTL. The data collected in this study compares the device stability with time for both PDPP3T and spiro-OMeTAD based perovskite solar cells and is directly related to our research article "solution processed pristine PDPP3T polymer as hole transport layer for efficient perovskite solar cells with slower degradation" [2].

  10. Results of the 2-Year Ocriplasmin for Treatment for Symptomatic Vitreomacular Adhesion Including Macular Hole (OASIS) Randomized Trial.

    Science.gov (United States)

    Dugel, Pravin U; Tolentino, Michael; Feiner, Leonard; Kozma, Petra; Leroy, Annick

    2016-10-01

    The Ocriplasmin for Treatment for Symptomatic Vitreomacular Adhesion Including Macular Hole (OASIS) trial was designed to evaluate the long-term efficacy and safety profile of ocriplasmin for the treatment of symptomatic vitreomacular adhesion (VMA)/vitreomacular traction, including full-thickness macular hole (FTMH). Phase 3b, randomized, sham-controlled, double-masked, multicenter clinical trial. Sample size was 220 subjects (146 ocriplasmin, 74 sham) randomized in a 2:1 ratio to receive intravitreal ocriplasmin 0.125 mg or sham injection. The trial involved 12 visits over 24-months. Inclusion criteria included presence of VMA and best-corrected visual acuity (BCVA) of 20/32 or worse in the study eye. Exclusion criteria included FTMH >400 μm, presence of epiretinal membrane (ERM), and aphakia in the study eye. The primary efficacy end point was the proportion of subjects with pharmacologic VMA resolution at day 28. Secondary efficacy end points were assessed at month 24 and included proportion of subjects with BCVA gain from baseline, nonsurgical FTMH closure, vitrectomy, and Visual Function Questionnaire 25 (VFQ-25) outcomes. The OASIS trial met its primary end point with pharmacologic VMA resolution at day 28 being significantly higher in the ocriplasmin group (41.7%) compared with the sham group (6.2%). The treatment effect was maintained until study end. In the ocriplasmin group, pharmacologic VMA resolution at day 28 was higher in subgroups with the following baseline characteristics compared with the complementary subgroups without them: presence of focal VMA, presence of FTMH, absence of ERM, and phakic lens status. In the ocriplasmin group, 50.5% of subjects had a ≥2-line improvement in BCVA from baseline compared with 39.1% of subjects in the sham group. The nonsurgical FTMH closure rate was 30.0% for the ocriplasmin group compared with 15.4% for the sham group. All other secondary end points also favored ocriplasmin over sham. Regarding safety, most

  11. Effect of fluorine plasma treatment with chemically reduced graphene oxide thin films as hole transport layer in organic solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Youn-Yeol; Kang, Byung Hyun; Lee, Yang Doo; Lee, Sang Bin; Ju, Byeong-Kwon, E-mail: bkju@korea.ac.kr

    2013-12-15

    The inorganic materials such as V{sub 2}O{sub 5}, MoO{sub 3} and WO{sub 3} were investigated to replace PEDOT:PSS as hole transport layer (HTL) in organic electronic devices such as organic solar cells (OSCs) and organic lighting emission diodes. However, these methods require vacuum techniques that are long time process and complex. Here, we report about plasma treatment with SF{sub 6} and CF{sub 4} using reactive ion etching on reduced graphene oxide (rGO) thin films that are obtained using an eco-friendly method with vitamin C. The plasma treated rGO thin films have dipoles since they consist of covalent bonds with fluorine on the surface of rGO. This means it is possible to increase the electrostatic potential energy than bare rGO. Increased potential energy on the surface of rGO films is worth applying organic electronic devices as HTL such as OSCs. Consequently, the power conversion efficiency of OSCs increased more than the rGO films without plasma treatment.

  12. Treatment of gingival hyperpigmentation by erbium-doped:yttrium, aluminum, and garnet laser for esthetic purposes.

    Science.gov (United States)

    Azzeh, Manal M

    2007-01-01

    The normal color of gingiva is pink. Gingival hyperpigmentation is mostly caused by the physiologic deposition of melanin by melanocytes. In "gummy smile" patients, melanin gingival hyperpigmentation causes an esthetic problem and may cause physiologic disturbances. Methods to remove gingival hyperpigmentation vary, but it seems that the most reliable and satisfactory procedure is laser ablation. Six white patients (five females and one male), who complain of having dark-brown to black gingival hyperpigmentation were included in the study. Three of them were smokers. Laser ablation was performed by an erbium-doped:yttrium, aluminum, and garnet (Er:YAG) laser (settings: 250 mJ, 15 Hz, with water and air and using the defocused mode) without using topical or local anesthesia. Each patient required about 20 to 25 minutes for completion of the procedure. After 4 days, another laser ablation (with the same previous settings) was performed to ensure good results. Patients were evaluated a month after completion of treatment and on a semiannual basis. The follow-up period ranged between 6 and 18 months. In all patients, no discomfort, pain, or bleeding complications were found intraoperatively or 4 days postoperatively. Ablated wounds healed almost completely within 4 days. No recurrence of gingival hyperpigmentation was found during the follow-up periods. Achieved results were satisfactory for patients and the operator. Taking into account the advantages of using lasers, it seems to be that the depigmentation of melanin hyperpigmented gingiva by the Er:YAG laser is a reliable and satisfactory procedure. Esthetic results were satisfactory for patients and the operator, and no repigmentation was found during the follow-up period.

  13. Enhanced electrical conductivities of N-doped carbon nanotubes by controlled heat treatment.

    Science.gov (United States)

    Fujisawa, Kazunori; Tojo, Tomohiro; Muramatsu, Hiroyuki; Elías, Ana L; Vega-Díaz, Sofía M; Tristán-López, Ferdinando; Kim, Jin Hee; Hayashi, Takuya; Kim, Yoong Ahm; Endo, Morinobu; Terrones, Mauricio

    2011-10-05

    The thermal stability of nitrogen (N) functionalities on the sidewalls of N-doped multi-walled carbon nanotubes was investigated at temperatures ranging between 1000 °C and 2000 °C. The structural stability of the doped tubes was then correlated with the electrical conductivity both at the bulk and at the individual tube levels. When as-grown tubes were thermally treated at 1000 °C, we observed a very significant decrease in the electrical resistance of the individual nanotubes, from 54 kΩ to 0.5 kΩ, which is attributed to a low N doping level (e.g. 0.78 at% N). We noted that pyridine-type N was first decomposed whereas the substitutional N was stable up to 1500 °C. For nanotubes heat treated to 1800 °C and 2000 °C, the tubes exhibited an improved degree of crystallinity which was confirmed by both the low R value (I(D)/I(G)) in the Raman spectra and the presence of straight graphitic planes observed in TEM images. However, N atoms were not detected in these tubes and caused an increase in their electrical resistivity and resistance. These partially annealed doped tubes with enhanced electrical conductivities could be used in the fabrication of robust and electrically conducting composites, and these results could be extrapolated to N-doped graphene and other nanocarbons.

  14. Facile and highly effective synthesis of controllable lattice sulfur-doped graphene quantum dots via hydrothermal treatment of durian.

    Science.gov (United States)

    Wang, Gang; Guo, Qinglei; Chen, Da; Liu, Zhiduo; Zheng, Xiaohu; Xu, Anli; Yang, Siwei; Ding, Guqiao

    2018-01-19

    Recently, the biomass "bottom-up" approach for the synthesis of graphene quantum dots have attracted broad interest because of the outstanding features, including low-cost, rapid and environmentally friendly nature. However, the low crystalline quality of products, substitutional doping with heteroatoms in lattice and ambiguous reaction mechanism strongly challenge the further development of this technique. Herein, we proposed a facile and effective strategy to prepare controllable sulfur (S) doping in graphene quantum dots, occurring in a lattice substitution manner, by hydrothermal treatment of durian with platinum catalyst. S atoms in graphene quantum dots are demonstrated to exist in the thiophene structure, resulting good optical and chemical stabilities, as well as ultrahigh quantum yield. Detailed mechanism of the hydrothermal reaction progress was investigated. High-efficiency reforming-cyclization provided by platinum was evidenced by the co-existence of diversified sp2 fused heterocyclic compounds and thiophene derivatives. Moreover, we also demonstrated that saccharides in durian with small molecular weight (graphene quantum dots. Due to the desulfurizing process, controllable photoluminescence properties could be achieved in as-prepared graphene quantum dots via tuning doping concentrations.

  15. Silicone Oil Reinjection without Macular Buckling for Treatment of Recurrent Myopic Macular Hole Retinal Detachment after Silicone Oil Removal

    Directory of Open Access Journals (Sweden)

    Hammouda Hamdy Ghoraba

    2014-01-01

    Full Text Available Purpose. To evaluate the efficacy of silicone oil (S.O reinjection without macular buckling for treatment of recurrent myopic macular hole retinal detachment (MHRD after silicone oil removal. Methods. A retrospective consecutive interventional study from medical reports on cases of myopic MHRD. Fifty-three eyes of 51 patients underwent silicone oil removal after successful repair of MHRD were reviewed. The main outcomes were the retinal status after silicone oil removal and management of recurrent cases. Results. The rate of recurrent RD (Re RD after silicone oil removal was 11.3% (6 out of 53 eyes. One case refused any other interference. In the remaining 5 eyes, 4 eyes (80% could be reattached by S.O re-injection and one eye (20% developed Re RD after S.O re-injection. Range of followup after management of recurrence was 5–53 months (mean 18.7 months. Conclusions. This case series concluded that the risk factors for recurrent RD after silicone oil removal from cases of myopic MHRD were high myopia, open flat MH, and large posterior staphyloma. Revision of vitrectomy and S.O re-injection can reattach most of recurrent cases.

  16. CdS nanoparticles sensitization of Al-doped ZnO nanorod array thin film with hydrogen treatment as an ITO/FTO-free photoanode for solar water splitting

    National Research Council Canada - National Science Library

    Hsu, Chih-Hsiung; Chen, Dong-Hwang

    2012-01-01

    Aluminum-doped zinc oxide (AZO) nanorod array thin film with hydrogen treatment possesses the functions of transparent conducting oxide thin film and 1-D nanostructured semiconductor simultaneously...

  17. Probing the Spinning of the Massive Black Hole in the Galactic Center via Pulsar Timing: A Full Relativistic Treatment

    Science.gov (United States)

    Zhang, Fupeng; Saha, Prasenjit

    2017-11-01

    Pulsars around the massive black hole (MBH) in the Galactic center (GC) are expected to be revealed by upcoming facilities (e.g., the Square Kilometer Array). Under a full relativistic framework with the pulsar approximated as a test particle, we investigate the constraints on the spinning of the MBH by monitoring the timing of surrounding pulsars. For GC pulsars orbiting closely around the MBH (e.g., ≲1000 au), we find that full relativistic treatment in modeling accurately their timing signals can be necessary, as the relativistic signals are orders of magnitude larger than the time-of-arrival measurement accuracies. Although usually there are near degeneracies among MBH spin parameters, the constraints on the spinning of the MBH are still very tight. By continuously monitoring a normal pulsar in orbits with a period of ∼2.6 yr and an eccentricity of 0.3–0.9 under a timing precision of 1–5 ms, within ∼8 yr the spin magnitude and the orientations of the GC MBH can be constrained with 2σ error of {10}-3{--}{10}-2 and {10}-1{--}{10}0, respectively. Even for pulsars in orbits similar to the detected star S2/S0-2 or S0-102, we find that the spinning of the MBH can still be constrained within 4–8 yr, with the most significant constraints provided near the pericenter passage. If the proper motion of the pulsars with astrometric accuracy of 10 μas can also be collected along with the timing measurement, then the position, velocity, mass, and distance to the solar system of the MBH can be constrained to ∼10 μas, ∼1 μas yr‑1, ∼ 10 {M}ȯ , and ∼1 pc, respectively.

  18. Effect of Heat Treatment on Optical Properties of Crosslinkable Azo Chromophore Doped in Poly Amic Acid

    Science.gov (United States)

    Hamedi, S.; Gharavi, A.

    2015-11-01

    In this work, we have studied the optical properties of a crosslinkable poly amic acid containing Disperse Red 1. The thin films were cured at 130, 160 and 195 °C. The structural and optical properties of the doped films were investigated by using UV-VIS spectra, and Prism Coupling techniques. The composite crosslinks during poling rendering it totally insoluble. A r33 of 1.5 pm/v was obtained after poling.

  19. Effect of nitrogen doping on the microstructure and visible light photocatalysis of titanate nanotubes by a facile cohydrothermal synthesis via urea treatment

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Cheng-Ching; Hsu, Tzu-Chien, E-mail: tjhsu@facmail.nsysu.edu.tw; Lu, Shan-Yu

    2013-09-01

    A facile one-step cohydrothermal synthesis via urea treatment has been adopted to prepare a series of nitrogen-doped titanate nanotubes with highly efficient visible light photocatalysis of rhodamine B, in an effect to identify the effect of nitrogen doping on the photodegradation efficiency. The morphology and microstructure of the thus-prepared N-doped titanates were characterized by nitrogen adsorption/desorption isotherms, transmission electron microscopy, and scanning electron microscopy. With increasing urea loadings, the N-doped titanates change from a porous multi-layer and nanotube-shaped to a dense and aggregated particle-shaped structure, accompanied with reduced specific surface area and pore volume and enhanced pore diameter. Interstitial linkage to titanate via Ti-O-N and Ti-N-O is confirmed by X-ray photoelectron spectroscopy. Factors governing the photocatalytic degradation such as the specific surface area of the catalyst and the degradation pathway are analyzed, a mechanistic illustration on the photodegradation is provided, and a 3-stage degradation mechanism is identified. The synergistic contribution due to the enhanced deethylation and chromophore cleavage on rhodamine B molecules and the reduced band gap on the catalyst TiO{sub 2} by interstitial nitrogen-doping has been accounted for the high photodegradation efficiency of the N-doped titanate nanotubes.

  20. Black Hole's 1/N Hair

    CERN Document Server

    Dvali, Gia

    2013-01-01

    According to the standard view classically black holes carry no hair, whereas quantum hair is at best exponentially weak. We show that suppression of hair is an artifact of the semi-classical treatment and that in the quantum picture hair appears as an inverse mass-square effect. Such hair is predicted in the microscopic quantum description in which a black hole represents a self-sustained leaky Bose-condensate of N soft gravitons. In this picture the Hawking radiation is the quantum depletion of the condensate. Within this picture we show that quantum black hole physics is fully compatible with continuous global symmetries and that global hair appears with the strength B/N, where B is the global charge swallowed by the black hole. For large charge this hair has dramatic effect on black hole dynamics. Our findings can have interesting astrophysical consequences, such as existence of black holes with large detectable baryonic and leptonic numbers.

  1. Successful closure of treatment-naïve, flat edge (Type II, full-thickness macular hole using inverted internal limiting membrane flap technique

    Directory of Open Access Journals (Sweden)

    Hussain N

    2016-10-01

    Full Text Available Nazimul Hussain,1 Anjli Hussain2 1Department of Ophthalmology, Al Zahra Hospital, 2Al Zahra Medical Center, Dubai, United Arab Emirates Objective: The objective of this study was to present the outcome of the internal limiting membrane (ILM peeling flap technique for a treatment-naïve, flat edge (Type II, full-thickness macular hole (MH. Methods: A 52-year-old man presented with complaints of decreased vision and seeing black spot. He was diagnosed to have a flat edge, full-thickness MH, which was confirmed by optical coherence tomography (OCT. He underwent 23G vitrectomy with brilliant blue G-assisted inverted ILM peeling with an inverted flap over the hole followed by fluid gas exchange. Results: Postoperative follow-up until 3 months showed successful closure of the MH, which was confirmed by OCT. The best-corrected visual acuity improved from baseline 6/60 to 6/12 at the final follow-up. Conclusion: Using the inverted ILM flap technique, a treatment-naïve, flat edge (Type II, full thickness MH achieved successful anatomical and functional outcomes. Keywords: macular hole, inverted ILM, optical coherence tomography

  2. Charge carrier holes and Majorana fermions

    Science.gov (United States)

    Liang, Jingcheng; Lyanda-Geller, Yuli

    2017-05-01

    Understanding Luttinger holes in low dimensions is crucial for numerous spin-dependent phenomena and nanotechnology. In particular, hole quantum wires that are proximity coupled to a superconductor is a promising system for the observation of Majorana fermions. Earlier treatments of confined Luttinger holes ignored a mutual transformation of heavy and light holes at the heteroboundaries. We derive the effective hole Hamiltonian in the ground state. The mutual transformation of holes is crucial for Zeeman and spin-orbit coupling, and results in several spin-orbit terms linear in momentum in hole quantum wires. We discuss the criterion for realizing Majorana modes in charge carrier hole systems. GaAs or InSb hole wires shall exhibit stronger topological superconducting pairing, and provide additional opportunities for its control compared to InSb electron systems.

  3. Coronal Holes

    Directory of Open Access Journals (Sweden)

    Steven R. Cranmer

    2009-09-01

    Full Text Available Coronal holes are the darkest and least active regions of the Sun, as observed both on the solar disk and above the solar limb. Coronal holes are associated with rapidly expanding open magnetic fields and the acceleration of the high-speed solar wind. This paper reviews measurements of the plasma properties in coronal holes and how these measurements are used to reveal details about the physical processes that heat the solar corona and accelerate the solar wind. It is still unknown to what extent the solar wind is fed by flux tubes that remain open (and are energized by footpoint-driven wave-like fluctuations, and to what extent much of the mass and energy is input intermittently from closed loops into the open-field regions. Evidence for both paradigms is summarized in this paper. Special emphasis is also given to spectroscopic and coronagraphic measurements that allow the highly dynamic non-equilibrium evolution of the plasma to be followed as the asymptotic conditions in interplanetary space are established in the extended corona. For example, the importance of kinetic plasma physics and turbulence in coronal holes has been affirmed by surprising measurements from the UVCS instrument on SOHO that heavy ions are heated to hundreds of times the temperatures of protons and electrons. These observations point to specific kinds of collisionless Alfvén wave damping (i.e., ion cyclotron resonance, but complete theoretical models do not yet exist. Despite our incomplete knowledge of the complex multi-scale plasma physics, however, much progress has been made toward the goal of understanding the mechanisms ultimately responsible for producing the observed properties of coronal holes.

  4. Efficacy and safety of erbium-doped yttrium aluminium garnet fractional resurfacing laser for treatment of facial acne scars.

    Science.gov (United States)

    Nirmal, Balakrishnan; Pai, Sathish B; Sripathi, Handattu; Rao, Raghavendra; Prabhu, Smitha; Kudur, Mohan H; Nayak, Sudhir U K

    2013-01-01

    Treatment of acne scars with ablative fractional laser resurfacing has given good improvement. But, data on Indian skin are limited. A study comparing qualitative, quantitative, and subjective assessments is also lacking. Our aim was to assess the improvement of facial acne scars with Erbium-doped Yttrium Aluminium Garnet (Er:YAG) 2940 nm fractional laser resurfacing and its adverse effects in 25 patients at a tertiary care teaching hospital. All 25 patients received four treatment sessions with Er:YAG fractional laser at 1-month interval. The laser parameters were kept constant for each of the four sittings in all patients. Qualitative and quantitative assessments were done using Goodman and Barron grading. Subjective assessment in percentage of improvement was also documented 1 month after each session. Photographs were taken before each treatment session and 1 month after the final session. Two unbiased dermatologists performed independent clinical assessments by comparing the photographs. The kappa statistics was used to monitor the agreement between the dermatologists and patients. Most patients (96%) showed atleast fair improvement. Rolling and superficial box scars showed higher significant improvement when compared with ice pick and deep box scars. Patient's satisfaction of improvement was higher when compared to physician's observations. No serious adverse effects were noted with exacerbation of acne lesions forming the majority. Ablative fractional photothermolysis is both effective and safe treatment for atrophic acne scars in Indian skin.Precise evaluation of acne scar treatment can be done by taking consistent digital photographs.

  5. Removal of organic contaminants from secondary effluent by anodic oxidation with a boron-doped diamond anode as tertiary treatment.

    Science.gov (United States)

    Garcia-Segura, Sergi; Keller, Jürg; Brillas, Enric; Radjenovic, Jelena

    2015-01-01

    Electrochemical advanced oxidation processes (EAOPs) have been widely investigated as promising technologies to remove trace organic contaminants from water, but have rarely been used for the treatment of real waste streams. Anodic oxidation with a boron-doped diamond (BDD) anode was applied for the treatment of secondary effluent from a municipal sewage treatment plant containing 29 target pharmaceuticals and pesticides. The effectiveness of the treatment was assessed from the contaminants decay, dissolved organic carbon and chemical oxygen demand removal. The effect of applied current and pH was evaluated. Almost complete mineralization of effluent organic matter and trace contaminants can be obtained by this EAOP primarily due to the action of hydroxyl radicals formed at the BDD surface. The oxidation of Cl(-) ions present in the wastewater at the BDD anode gave rise to active chlorine species (Cl2/HClO/ClO(-)), which are competitive oxidizing agents yielding chloramines and organohalogen byproducts, quantified as adsorbable organic halogen. However, further anodic oxidation of HClO/ClO(-) species led to the production of ClO3(-) and ClO4(-) ions. The formation of these species hampers the application as a single-stage tertiary treatment, but posterior cathodic reduction of chlorate and perchlorate species may reduce the risks associated to their presence in the environment. Copyright © 2014 Elsevier B.V. All rights reserved.

  6. Successful treatment of facial telangiectasias using a micropulse 1,064-nm neodymium-doped yttrium aluminum garnet laser.

    Science.gov (United States)

    Rose, Amy E; Goldberg, David J

    2013-07-01

    To evaluate the safety and efficacy of a microsecond 1,064-nm neodymium-doped yttrium aluminum garnet (Nd:YAG) laser for the treatment of facial telangiectasias. Subjects ages 35-70 with Fitzpatrick skin types I to III and facial telangiectasias underwent two treatments with a micropulse (0.65 ms) 1,064-nm Nd:YAG laser. Treatments were spaced 30 days apart, with a final evaluation 60 days after the second treatment. Evaluation included digital photography and an assessment of the degree of improvement on a scale from 1 to 5 by the subject and a nontreating investigator. Twenty subjects (18 women, two men) with Fitzpatrick skin type II and III completed the study. The nontreating investigator rated the objective clinical response as total clearance (100% clear) in 10% (n = 2) of subjects, significant clearance (≥50% clear) in 75% (n = 15), and some clearance (0-49% clear) in 15% (n = 3). None of the subjects was rated as having no clearance or worsening. In terms of subjective clearance reported by subjects, 80% (n = 16) reported significant clearance, with the remainder reporting some clearance. No adverse events were reported. The micropulse 1,064-nm Nd:YAG successfully treated facial telangiectasias with a high degree of patient satisfaction, minimal discomfort, and no adverse events. © 2013 by the American Society for Dermatologic Surgery, Inc. Published by Wiley Periodicals, Inc.

  7. Quantum black holes

    CERN Document Server

    Calmet, Xavier; Winstanley, Elizabeth

    2014-01-01

    Written by foremost experts, this short book gives a clear description of the physics of quantum black holes. The reader will learn about quantum black holes in four and higher dimensions, primordial black holes, the production of black holes in high energy particle collisions, Hawking radiation, black holes in models of low scale quantum gravity and quantum gravitational aspects of black holes.

  8. Graphene Oxide by UV-Ozone Treatment as an Efficient Hole Extraction Layer for Highly Efficient and Stable Polymer Solar Cells.

    Science.gov (United States)

    Xia, Yingdong; Pan, Yufeng; Zhang, Haijuan; Qiu, Jian; Zheng, Yiting; Chen, Yonghua; Huang, Wei

    2017-08-09

    The hole extraction layer has a significant impact on the achievement of high-efficiency polymer solar cells (PSCs). Here, we report an efficient approach to direct UV-ozone treatment by larger device performance enhancement employing graphene oxide (GO). The dramatic performance enhancement of PSCs with the P3HT:PCBM blend as an active layer was demonstrated by the UV-ozone treatment of GO for 30 min: best power conversion efficiency (PCE) of 4.18%, fill factor of 0.63, Jsc of 10.94 mA cm-2, and Voc of 0.61 V, which are significantly higher than those of the untreated GO (1.82%) and highly comparable PEDOT:PSS-based PSCs (3.73%). In addition, PSCs with UV-ozone-treated GO showed a longer stability than PSCs with PEDOT:PSS. The significant enhancement of PCEs of PSCs can be attributed to the fact that ozone molecules can oxidize GO into CO2 and leave highly conductive graphene particles. We suggest that this simple UV-ozone treatment can provide an efficient method for highly efficient GO hole extraction in high-performance PSCs.

  9. Comparison of a fractional bipolar radiofrequency device and a fractional erbium-doped glass 1,550-nm device for the treatment of atrophic acne scars: a randomized split-face clinical study.

    Science.gov (United States)

    Rongsaard, Nopnarueporn; Rummaneethorn, Paisal

    2014-01-01

    A fractional erbium-doped glass 1,550-nm and a fractional bipolar radiofrequency (RF) device are effective in the treatment of atrophic acne scars. To compare the clinical effectiveness and side effects of fractional bipolar RF with those of fractional erbium-doped glass in atrophic acne scars treatment. Twenty Thai subjects with atrophic acne scars received three split-face monthly treatments, one side with fractional bipolar RF and the other with fractional erbium-doped glass. Three independent physicians and patients evaluated improvement in acne scars 4 weeks after the last treatment. Side effects were also recorded after each treatment. The study found significant improvement in acne scars after treatment with fractional bipolar RF and with a fractional erbium-doped glass device without a statistically significant difference between the two devices. The side effects of both devices were pain, transient facial erythema, and scab formation. The pain score with fractional erbium-doped glass was higher than that with fractional bipolar RF, but duration of scab shedding was shorter. One case had postinflammatory hyperpigmentation on only the side treated with fractional erbium-doped glass. Fractional bipolar RF and fractional erbium-doped glass have similar effectiveness for the treatment of atrophic acne scars. © 2013 by the American Society for Dermatologic Surgery, Inc. Published by Wiley Periodicals, Inc.

  10. Efficacy and safety of Erbium-doped Yttrium Aluminium Garnet fractional resurfacing laser for treatment of facial acne scars

    Directory of Open Access Journals (Sweden)

    Balakrishnan Nirmal

    2013-01-01

    Full Text Available Background: Treatment of acne scars with ablative fractional laser resurfacing has given good improvement. But, data on Indian skin are limited. A study comparing qualitative, quantitative, and subjective assessments is also lacking. Aim: Our aim was to assess the improvement of facial acne scars with Erbium-doped Yttrium Aluminium Garnet (Er:YAG 2940 nm fractional laser resurfacing and its adverse effects in 25 patients at a tertiary care teaching hospital. Methods: All 25 patients received four treatment sessions with Er:YAG fractional laser at 1-month interval. The laser parameters were kept constant for each of the four sittings in all patients. Qualitative and quantitative assessments were done using Goodman and Barron grading. Subjective assessment in percentage of improvement was also documented 1 month after each session. Photographs were taken before each treatment session and 1 month after the final session. Two unbiased dermatologists performed independent clinical assessments by comparing the photographs. The kappa statistics was used to monitor the agreement between the dermatologists and patients. Results: Most patients (96% showed atleast fair improvement. Rolling and superficial box scars showed higher significant improvement when compared with ice pick and deep box scars. Patient′s satisfaction of improvement was higher when compared to physician′s observations. No serious adverse effects were noted with exacerbation of acne lesions forming the majority. Conclusion: Ablative fractional photothermolysis is both effective and safe treatment for atrophic acne scars in Indian skin.Precise evaluation of acne scar treatment can be done by taking consistent digital photographs.

  11. Removal of organic contaminants from secondary effluent by anodic oxidation with a boron-doped diamond anode as tertiary treatment

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Segura, Sergi, E-mail: sergigarcia@ub.edu [Advanced Water Management Centre, The University of Queensland, Level 4, Gehrmann Bld. (60), St Lucia, QLD 072 (Australia); Laboratori d’Electroquímica dels Materials i del Medi Ambient, Departament de Química Física, Facultat de Química, Universitat de Barcelona, Martí i Franquès 1-11, 08028 Barcelona (Spain); Keller, Jürg [Advanced Water Management Centre, The University of Queensland, Level 4, Gehrmann Bld. (60), St Lucia, QLD 072 (Australia); Brillas, Enric [Laboratori d’Electroquímica dels Materials i del Medi Ambient, Departament de Química Física, Facultat de Química, Universitat de Barcelona, Martí i Franquès 1-11, 08028 Barcelona (Spain); Radjenovic, Jelena, E-mail: j.radjenovic@awmc.uq.edu.au [Advanced Water Management Centre, The University of Queensland, Level 4, Gehrmann Bld. (60), St Lucia, QLD 072 (Australia)

    2015-02-11

    Graphical abstract: - Highlights: • Mineralization of secondary effluent by anodic oxidation with BDD anode. • Complete removal of 29 pharmaceuticals and pesticides at trace level concentrations. • Organochlorine and organobromine byproducts were formed at low μM concentrations. • Chlorine species evolution assessed to evaluate the anodic oxidation applicability. - Abstract: Electrochemical advanced oxidation processes (EAOPs) have been widely investigated as promising technologies to remove trace organic contaminants from water, but have rarely been used for the treatment of real waste streams. Anodic oxidation with a boron-doped diamond (BDD) anode was applied for the treatment of secondary effluent from a municipal sewage treatment plant containing 29 target pharmaceuticals and pesticides. The effectiveness of the treatment was assessed from the contaminants decay, dissolved organic carbon and chemical oxygen demand removal. The effect of applied current and pH was evaluated. Almost complete mineralization of effluent organic matter and trace contaminants can be obtained by this EAOP primarily due to the action of hydroxyl radicals formed at the BDD surface. The oxidation of Cl{sup −} ions present in the wastewater at the BDD anode gave rise to active chlorine species (Cl{sub 2}/HClO/ClO{sup −}), which are competitive oxidizing agents yielding chloramines and organohalogen byproducts, quantified as adsorbable organic halogen. However, further anodic oxidation of HClO/ClO{sup −} species led to the production of ClO{sub 3}{sup −} and ClO{sub 4}{sup −} ions. The formation of these species hampers the application as a single-stage tertiary treatment, but posterior cathodic reduction of chlorate and perchlorate species may reduce the risks associated to their presence in the environment.

  12. Simple InCl3 Doped PEDOT:PSS and UV-Ozone Treatment Strategy: External Quantum Efficiency up to 21% for Solution-Processed Organic Light-Emitting Devices with a Thermally Activated Delayed Fluorescence Emitter.

    Science.gov (United States)

    Zhou, Tao; Xie, Guohua; Gong, Shaolong; Huang, Manli; Luo, Jiajia; Yang, Chuluo

    2017-10-04

    A low-cost and easy-process scheme for solution-processed organic light-emitting devices (OLEDs) was provided to overcome the flaws of poly(styrene sulfonic acid)-doped poly(3,4-ethylenedioxythiphene) (PEDOT:PSS) together with the indium tin oxide anode. The modified PEDOT:PSS with higher work function (5.66 eV) and more efficient hole injecting ability was obtained by simply mixing the aqueous PEDOT:PSS with InCl3 and then consecutive ultraviolet-ozone treatment. The simply structured and solution-processed OLEDs with our modified PEDOT:PSS achieved a very high external quantum efficiency of 21.0% using a classic thermally activated delayed fluorescence emitter, 2,4,5,6-tetrakis(carbazol-9-yl)-1,3-dicyanobenzene. The origin of this great promotion was explored through photoelectron spectroscopy, Fourier transform infrared reflection spectroscopy, and atomic force microscopy, from which we inferred that InCl3 itself, the losing of insulting PSS outer shell, and transformation to quinoid structure of PEDOT chains accounted for this improvement. Our modification method of PEDOT:PSS is beneficial for promoting solution-processed organic semiconducting devices.

  13. Thermoluminescence dependence on the wavelength of monochromatic UV-radiation in Cu-doped KCl and KBr at room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Perez R, A.; Piters, T.; Aceves, R.; Rodriguez M, R.; Perez S, R., E-mail: rperez@cifus.uson.mx [Universidad de Sonora, Departamento de Investigaciones en Fisica, Apdo. Postal 5-088, 83190 Hermosillo, Sonora (Mexico)

    2014-08-15

    Thermoluminescence (Tl) dependence on the UV irradiation wavelengths from 200 to 500 nm in Cu-doped KCl and KBr crystals with different thermal treatment has been analyzed. Spectrum of the Tl intensity of each material show lower intensity at wavelengths longer than 420 nm. The Tl intensity depends on the irradiation wavelength. Structure of the Tl intensity spectrum of each sample is very similar to the structure of its optical absorption spectrum, indicating that at each wavelength, monochromatic radiation is absorbed to produce electronic transitions and electron hole pairs. Thermoluminescence of materials with thermal treatment at high temperature shows electron-hole trapping with less efficiency. The results show that Cu-doped alkali-halide materials are good detectors of a wide range of UV monochromatic radiations and could be used to measure UV radiation doses. (Author)

  14. Sustainable energy recovery in wastewater treatment by microbial fuel cells: stable power generation with nitrogen-doped graphene cathode.

    Science.gov (United States)

    Liu, Yuan; Liu, Hong; Wang, Chuan; Hou, Shuang-Xia; Yang, Nuan

    2013-12-03

    Microbial fuel cells (MFCs) recover energy sustainably in wastewater treatment. Performance of non-noble cathode catalysts with low cost in neutral medium is vital for stable power generation. Nitrogen-doped graphene (NG) as cathode catalyst was observed to exhibit high and durable activity at buffered pH 7.0 during electrochemical measurements and in MFCs with respect to Pt/C counterpart. Electrochemical measurements showed that the oxygen reduction reaction (ORR) on NG possessed sustained activity close to the state-of-art Pt/C in terms of onset potential and electron transfer number. NG-MFCs displayed maximum voltage output of 650 mV and maximum power density of 776 ± 12 mW m(-2), larger than 610 mV and 750 ± 19 mW m(-2) of Pt/C-MFCs, respectively. Furthermore, long-time test lasted over 90 days, during which the maximum power density of NG-MFCs declined by 7.6%, with stability comparable to Pt/C-MFCs. Structure characterization of NG implied that the relatively concentrated acidic oxygen-containing groups improved such long-time stability by repelling the protons due to the same electrostatic force, and thus the C-N active centers for ORR were left undestroyed. These findings demonstrated the competitive advantage of NG to advance the application of MFCs for recovering biomass energy in treatment of wastewater with neutral pH.

  15. Optical properties of Er{sup 3+}-doped strontium barium niobate nanocrystals obtained by thermal treatment in glass

    Energy Technology Data Exchange (ETDEWEB)

    Haro-Gonzalez, P. [Dep. of Fisica Fundamental Experimental, Electronica y Sistemas, Universidad de La Laguna Avda Astrofisico Franscisco Sanchez, 38206 La Laguna, S/C de Tenerife (Spain)], E-mail: patharo@ull.es; Lahoz, F. [Dep. of Fisica Fundamental Experimental, Electronica y Sistemas, Universidad de La Laguna Avda Astrofisico Franscisco Sanchez, 38206 La Laguna, S/C de Tenerife (Spain); Gonzalez-Platas, J. [Dep. of Fisica Fundamental II, Universidad de La Laguna, 38206 La Laguna, S/C de Tenerife (Spain); Caceres, J.M. [Dep. of Edafologia y Geologia, Universidad de La Laguna, 38206 La Laguna, S/C de Tenerife (Spain); Gonzalez-Perez, S. [Dep. of Fisica Fundamental Experimental, Electronica y Sistemas, Universidad de La Laguna Avda Astrofisico Franscisco Sanchez, 38206 La Laguna, S/C de Tenerife (Spain); Marrero-Lopez, D. [Dep. of Quimica Inorganica, Universidad de La Laguna, 38206 La Laguna, S/C de Tenerife (Spain); Capuj, N. [Dep. of Fisica Basica, Universidad de La Laguna, 38206 La Laguna, S/C de Tenerife (Spain); Martin, I.R. [Dep. of Fisica Fundamental Experimental, Electronica y Sistemas, Universidad de La Laguna Avda Astrofisico Franscisco Sanchez, 38206 La Laguna, S/C de Tenerife (Spain)

    2008-05-15

    Measurements of the optical properties of Er{sup 3+} ions in strontium barium niobate glass and glass ceramics have been carried out. The glasses have been fabricated using a melt-quenching method, and the glass ceramic samples have been obtained from the glass precursor by a thermal treatment. The ceramic samples formed by a glassy phase, and a crystalline phase contains nanocrystals of Sr{sub 1-x}Ba{sub x}Nb{sub 2}O{sub 6} (SBN) doped with Er{sup 3+} ions with a mean size of {approx}50 nm, as confirmed with XRD. Green up-conversion emission has been obtained under excitation at 800 nm, and the temporal evolution of this emission has been reported with the purpose of determining the involved up-conversion mechanism. These optical measures have confirmed that the Er{sup 3+} ions have been incorporated into the SBN matrix, after a thermal treatment, which produced an increment of the up-conversion efficiency.

  16. Influence of heat treatment and oxygen doping on the mechanical properties and biocompatibility of titanium-niobium binary alloys.

    Science.gov (United States)

    da Silva, Luciano Monteiro; Claro, Ana Paula Rosifini Alves; Donato, Tatiani Ayako Goto; Arana-Chavez, Victor E; Moraes, João Carlos Silos; Buzalaf, Marília Afonso Rabelo; Grandini, Carlos Roberto

    2011-05-01

    The most commonly used titanium (Ti)-based alloy for biological applications is Ti-6Al-4V, but some studies associate the vanadium (V) with the cytotoxic effects and adverse reactions in tissues, while aluminum (Al) has been associated with neurological disorders. Ti-Nb alloys belong to a new class of Ti-based alloys with no presence of Al and V and with elasticity modulus values that are very attractive for use as a biomaterial. It is well known that the presence of interstitial elements (such as oxygen, for example) changes the mechanical properties of alloys significantly, particularly the elastic properties, the same way that heat treatments can change the microstructure of these alloys. This article presents the effect of heat treatment and oxygen doping in some mechanical properties and the biocompatibility of three alloys of the Ti-Nb system, characterized by density measurements, X-ray diffraction, optical microscopy, Vickers microhardness, in vitro cytotoxicity, and mechanical spectroscopy. © 2011, Copyright the Authors. Artificial Organs © 2011, International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.

  17. [Internal fixation with one-hole microplate for the treatment of collateral ligament injuries of the metacarpophalangeal joint of the thumb combined with fracture].

    Science.gov (United States)

    Wang, Xi-Xun; Sun, De-Tao; Chen, Xu-Hui; Li, Jun; Cui, Yan; Hu, Ji-Chao; Shu, Zheng-Hua; He, Jian; Ding, Chao-Qi; Chen, Bo

    2015-03-01

    To study clinical effects of one-hole microplate internal fixation for the treatment of collateral ligament injuries of the metacarpophalangeal joint of the thumb combined with fracture. Twenty-two patients (16 males, 6 females) with collateral ligament injuries of the metacarpophalangeal joint of the thumb combined fracture were treated with one-hole microplate internal fixation. The age of the patients ranged from 18 to 53 years old with a mean age of 28.5 years old. The duration from injury to surgery ranged from 2 hours to 2 months, and the mean time was 6 days. All the patients had collateral ligament injuries combined with fracture of the metacarpophalangeal joint of the thumb. Thirteen patients had injuries in the right hand and 9 patients had injuries in the left hand. There were 18 cases of closed wound and 4 cases of open wound. Eighteen patients had fresh injuries ( 2 weeks). Sixteen patients had injuries in the ulnar collateral ligament of the thumb combined with fracture, 6 patients had radial collateral ligament injuries of the thumb combined with fracture, 4 cases of which were complicated with injuries of abductor pollicis brevis and the end of the flexor pollicis brevis tender. The size of the avulsed fragment was about 3.0 mm x 4.0 mm to 6.0 mm x 7.0 mm. The incisions of 22 patients healed by first intention. The follow-up periods ranged from 6 months to 5 years old,with an average of 2.5 years old. The thumb function was evaluated by Saetta and other evaluation criteria, and 20 patients got an excellent result and 2 good. The application of one-hole microplate internal fixation in treating collateral ligament injuries with fracture of the metacarpophalangeal joint of the thumb is an effective method.

  18. Photocatalytic performance of Cu-doped TiO2 nanofibers treated by the hydrothermal synthesis and air-thermal treatment

    Science.gov (United States)

    Wu, Ming-Chung; Wu, Po-Yeh; Lin, Ting-Han; Lin, Tz-Feng

    2018-02-01

    Series of transition metal-doped TiO2 (metal/TiO2) is prepared by combining the hydrothermal synthesis and air-thermal treatment without any reduction process. The selected transition metal precursors, including Ag, Au, Co, Cr, Cu, Fe, Ni, Pd, Pt, Y, and Zn, were individually doped into TiO2 nanofibers to evaluate the photocatalytic degradation activity and photocatalytic hydrogen generation. Consider the photocatalytic performance of these synthesized metal/TiO2 under UV-A irradiation, copper doped TiO2 nanofibers (Cu/TiO2 NFs) was chosen for further study due to its extraordinary reactivity. Systematical studies were spread to optimize the doping concentration and the calcination condition for much higher photocatalytic activity Cu/TiO2 NFs. In the photocatalytic degradation test, 0.5 mol%-Cu/TiO2 NFs calcined at 650 °C exhibits the highest activity, which is even higher than commercial TiO2-AEROXIDE® TiO2 P25 under UV-A irradiation. The synthesized 0.5 mol%-Cu/TiO2-650 NFs also have the capability in the photocatalytic hydrogen production. The hydrogen evolution rates are 200 μmol/g·h under UV-A irradiation and 280 μmol/g·h under UV-B irradiation. The density of state calculated by CASTEP for Cu/TiO2 indicates that Cu doping contributes to the states near valence band edge and narrows the band gap. The disclosed process in this study is industrial safe, convenient and cost-effective. We further produce a significant amount of TiO2-based catalysts without any hydrogen reduction treatment.

  19. Drug treatment for high IOP at early stage after vitrectomy for macular hole caused by high myopia

    Directory of Open Access Journals (Sweden)

    Yu-Juan Zhou

    2015-12-01

    Full Text Available AIM:To study the effect of only latanoprost eye drops or combined with other medicines on lowering intraocular pressure(IOPafter early pars plana vitrectomy(PPVfor macular hole without retinal detachment caused by high myopia.METHODS:One hundred and eighty-eight cases(205 eyessuffered from macular hole caused by high myopia without reinal detachment who underwent PPV combined with C3F8 tamponade were studied retrospectively and measured the IOP at 1wk after surgeries. The patients whose IOP was 22~29mmHg were named as group A. Then they were divided randomly into two subgroups, group A1(treated by carteolol eye dropsand subgroup A2(treated by latanoprost eye drops. The patients whose IOP was 30~39mmHg were named as group B. Then they were divided randomly into two subgroups, group B1(treated by both carteolol and brimonidine tartrate eye dropsand subgroup B2(treated by both latanoprost and carteolol eye drops. The patients whose IOP was ≥40mmHg were named as group C and they were all treated by rapid intravenous injection of 20% Mannitol. Meanwhile, they were divided randomly into two subgroups, group C1(treated by carteolol,brimonidine tartrate and brinzolamide eye drops and subgroup C2(treated by carteolol,brimonidine tartrate and latanoprost eye drops. Continuous observation lasted 3d. If IOP dropped to below 21 mmHg, we considered it valid. And then,compare the effectiveness, IOP reduction and the average effective duration. RESULTS:Eighty-nine eyes met the criteria of high IOP and IOP of 70 eyes(78.6%increased within 3d after operations. There were 31 eyes in group A including 14 eyes in group A1 and 17 eyes in group A2.The number of effective cases of the two groups was 5(35.7%and 13(76.5%respectively, the difference was statistically significant(χ2=5.24,P=0.03.The IOP reduction of the two groups were 4.21±1.22mmHg(24%, 8.76±3.03mmHg(29.6%, respectively, and the difference was statistically significant(t=5.73,Pt=2.85,P=0.012.There

  20. Holon Wigner Crystal in a Lightly Doped Kagome Quantum Spin Liquid

    Science.gov (United States)

    Jiang, Hong-Chen; Devereaux, T.; Kivelson, S. A.

    2017-08-01

    We address the problem of a lightly doped spin liquid through a large-scale density-matrix renormalization group study of the t -J model on a kagome lattice with a small but nonzero concentration δ of doped holes. It is now widely accepted that the undoped (δ =0 ) spin-1 /2 Heisenberg antiferromagnet has a spin-liquid ground state. Theoretical arguments have been presented that light doping of such a spin liquid could give rise to a high temperature superconductor or an exotic topological Fermi liquid metal. Instead, we infer that the doped holes form an insulating charge-density wave state with one doped hole per unit cell, i.e., a Wigner crystal. Spin correlations remain short ranged, as in the spin-liquid parent state, from which we infer that the state is a crystal of spinless holons, rather than of holes. Our results may be relevant to kagome lattice herbertsmithite upon doping.

  1. Significant improvement in visible light photocatalytic activity of Fe doped TiO2 using an acid treatment process

    Science.gov (United States)

    Moradi, Vahid; Jun, Martin B. G.; Blackburn, Arthur; Herring, Rodney A.

    2018-01-01

    Transition metal dopants have been used to decrease the band gap energy of TiO2 for visible light photocatalytic purposes. Fe3+ is a good dopant candidate owing to its capability to decrease the band gap energy and enhance the electron/hole trapping. However, in previous studies the photocatalytic activity of Fe-TiO2 was around 40-50% for a reaction time of ∼300 min. Herein, using HRTEM it was found out that the photocatalytic activity of Fe-TiO2 is limited by an amorphous contamination layer on the surface of the Fe-TiO2 nanoparticles. The contamination layer was determined to be composed of iron oxide by XPS surface analysis. The contamination layer was successfully removed using an acid treatment process comprising of HCl solution. Using the cleaned Fe-TiO2 nanoparticles, the photocatalytic activity measured utilizing a solution of 20 mg L-1 methyl orange (MO) was significantly increased from 24% to 98% within 60 min of reaction time under visible light illumination.

  2. PEDOT:PSS/Graphene Nanocomposite Hole-Injection Layer in Polymer Light-Emitting Diodes

    Directory of Open Access Journals (Sweden)

    Chun-Hsuan Lin

    2012-01-01

    Full Text Available We report on effects of doping graphene in poly(3,4-ethylenedioxythiophene: poly(styrene sulfonate, PEDOT:PSS, as a PEDOT:PSS/graphene nanocomposite hole injection layer on the performance enhancement of polymer light-emitting diodes (PLEDs. Graphene oxides were first synthesized and then mixed in the PEDOT:PSS solution with specifically various amounts. Graphenes were reduced in the PEDOT:PSS matrix through thermal reduction. PLED devices with hole-injection nanocomposite layer containing particular doping concentration were fabricated, and the influence of doping concentration on device performance was examined by systematically characterizations of various device properties. Through the graphene doping, the resistance in the hole-injection layer and the turn-on voltage could be effectively reduced that benefited the injection and transport of holes and resulted in a higher overall efficiency. The conductivity of the hole-injection layer was monotonically increased with the increase of doping concentration, performance indices from various aspects, however, did not show the same dependence because faster injected holes might alter not only the balance of holes and electrons but also their combination locations in the light-emitting layer. Results show that optimal doping concentration was the case with 0.03 wt% of graphene oxide.

  3. Highly Conductive PEDOT:PSS Transparent Hole Transporting Layer with Solvent Treatment for High Performance Silicon/Organic Hybrid Solar Cells.

    Science.gov (United States)

    Li, Qingduan; Yang, Jianwei; Chen, Shuangshuang; Zou, Jizhao; Xie, Weiguang; Zeng, Xierong

    2017-08-23

    Efficient Si/organic hybrid solar cells were fabricated with dimethyl sulfoxide (DMSO) and surfactant-doped poly(3,4-ethylenedioxythiophene): polystyrene (PEDOT:PSS). A post-treatment on PEDOT:PSS films with polar solvent was performed to increase the device performance. We found that the performance of hybrid solar cells increase with the polarity of solvent. A high conductivity of 1105 S cm - 1 of PEDOT:PSS was achieved by adopting methanol treatment, and the best efficiency of corresponding hybrid solar cells reaches 12.22%. X-ray photoelectron spectroscopy (XPS) and RAMAN spectroscopy were utilized to conform to component changes of PEDOT:PSS films after solvent treatment. It was found that the removal of the insulator PSS from the film and the conformational changes are the determinants for the device performance enhancement. Electrochemical impedance spectroscopy (EIS) was used to investigate the recombination resistance and capacitance of methanol-treated and untreated hybrid solar cells, indicating that methanol-treated devices had a larger recombination resistance and capacitance. Our findings bring a simple and efficient way for improving the performance of hybrid solar cell.

  4. Highly Conductive PEDOT:PSS Transparent Hole Transporting Layer with Solvent Treatment for High Performance Silicon/Organic Hybrid Solar Cells

    Science.gov (United States)

    Li, Qingduan; Yang, Jianwei; Chen, Shuangshuang; Zou, Jizhao; Xie, Weiguang; Zeng, Xierong

    2017-08-01

    Efficient Si/organic hybrid solar cells were fabricated with dimethyl sulfoxide (DMSO) and surfactant-doped poly(3,4-ethylenedioxythiophene): polystyrene (PEDOT:PSS). A post-treatment on PEDOT:PSS films with polar solvent was performed to increase the device performance. We found that the performance of hybrid solar cells increase with the polarity of solvent. A high conductivity of 1105 S cm- 1 of PEDOT:PSS was achieved by adopting methanol treatment, and the best efficiency of corresponding hybrid solar cells reaches 12.22%. X-ray photoelectron spectroscopy (XPS) and RAMAN spectroscopy were utilized to conform to component changes of PEDOT:PSS films after solvent treatment. It was found that the removal of the insulator PSS from the film and the conformational changes are the determinants for the device performance enhancement. Electrochemical impedance spectroscopy (EIS) was used to investigate the recombination resistance and capacitance of methanol-treated and untreated hybrid solar cells, indicating that methanol-treated devices had a larger recombination resistance and capacitance. Our findings bring a simple and efficient way for improving the performance of hybrid solar cell.

  5. Airplane dopes and doping

    Science.gov (United States)

    Smith, W H

    1919-01-01

    Cellulose acetate and cellulose nitrate are the important constituents of airplane dopes in use at the present time, but planes were treated with other materials in the experimental stages of flying. The above compounds belong to the class of colloids and are of value because they produce a shrinking action on the fabric when drying out of solution, rendering it drum tight. Other colloids possessing the same property have been proposed and tried. In the first stages of the development of dope, however, shrinkage was not considered. The fabric was treated merely to render it waterproof. The first airplanes constructed were covered with cotton fabric stretched as tightly as possible over the winds, fuselage, etc., and flying was possible only in fine weather. The necessity of an airplane which would fly under all weather conditions at once became apparent. Then followed experiments with rubberized fabrics, fabrics treated with glue rendered insoluble by formaldehyde or bichromate, fabrics treated with drying and nondrying oils, shellac, casein, etc. It was found that fabrics treated as above lost their tension in damp weather, and the oil from the motor penetrated the proofing material and weakened the fabric. For the most part the film of material lacked durability. Cellulose nitrate lacquers, however were found to be more satisfactory under varying weather conditions, added less weight to the planes, and were easily applied. On the other hand, they were highly inflammable, and oil from the motor penetrated the film of cellulose nitrate, causing the tension of the fabric to be relaxed.

  6. Influence of screening effect on hydrogen passivation of hole silicon

    CERN Document Server

    Aleksandrov, O V

    2002-01-01

    The simulation of hole silicon passivation during hydrogen diffusion with account of hydrogen-acceptor pairs formation, internal electrical field and screening effect has been carried out. Screening by free carriers of hydrogen and acceptor ions results in shortening their interaction radii and slacking the concentration dependence of hydrogen diffusivity at high level of silicon doping. The consistency of simulated and experimental profiles of holes and hydrogen-acceptor pairs is reached in a broad band of doping levels from 4 x 10 sup 1 sup 4 to 1.2 x 10 sup 2 sup 0 cm sup - sup 3 at the pair binding energy of 0.70-0.79 eV while the radius of the Coulomb interaction of hydrogen and boron ions is equal to 35 A under low doping and decrease with increasing doping level

  7. Effect of Ga doping and point defect on magnetism of ZnO

    Energy Technology Data Exchange (ETDEWEB)

    Hou, Qingyu [College of Science, Inner Mongolia University of Technology, 010051 Hohhot (China); Zhao, Chunwang, E-mail: cwzhao@shmtu.edu.cn [College of Arts and Sciences, Shanghai Maritime University, 201306 Shanghai (China); Jia, Xiaofang; Qu, Lingfeng [College of Science, Inner Mongolia University of Technology, 010051 Hohhot (China)

    2017-02-01

    The combined influence mechanism of Ga doping and Zn vacancy or O vacancy on magnetism of ZnO is studied using the first-principle calculation. The coexistence of Ga doping and Zn vacancy can achieve a Curie temperature higher than room temperature and the Ga doped ZnO system is a p-type diluted degenerate semiconductor with metalized ferromagnetism. The magnetism of the doping system of Ga doping and Zn vacancy is mainly contributed by double-exchange interaction through the holes of Zn vacancy taking carrier as medium. However, the system of Ga doping and O vacancy is non-magnetic. In the coexistence of Ga doping and Zn vacancy or O vacancy, a close relative distance between doping and vacancy will reduce the formation energy of the doping system but increase the easiness of doping and vacancy, as well as enhance the stability of the doping system.

  8. Doped Nanocrystals

    National Research Council Canada - National Science Library

    David J. Norris; Alexander L. Efros; Steven C. Erwin

    2008-01-01

    The critical role that dopants play in semiconductor devices has stimulated research on the properties and the potential applications of semiconductor nanocrystals, or colloidal quantum dots, doped...

  9. Influence of sulfidation treatment on the structure and tribological properties of nitrogen-doped diamond-like carbon films

    Science.gov (United States)

    Zeng, Qun-feng; Dong, Guang-neng; Xie, You-bai

    2008-04-01

    The nitrogen-doped diamond-like carbon (DLC) films were deposited on high speed steel (HSS) substrates in the direct current unbalanced magnetron sputtering system. Sulphurized layer was formed on the surface of DLC films by means of liquid sulfidation in the intermixture of urea and thiourea solution in order to improve the tribological properties of DLC films. The influence of sulfidation treatment on the structure and tribological properties of DLC films was investigated in this work. The structure and wear surface morphology of DLC films were analyzed by Raman spectroscopy, XPS and SEM, respectively. It reveals that the treated films are smooth and uniform; and sulfur atoms are bonded chemically. The treated films have broader distribution of Raman spectra in the range of 1000-1800 cm -1 and higher ID/ IG ratio than the untreated films as a result of the appearance of the crystalline graphite structure after the sulfidation treatment. It is showed that the sp 2 relative content increase in the treated films from the XPS measurement. The Raman results are consistent with the XPS results. The tribological properties of DLC films were investigated using a ball-on-disk rotating friction and wear tester under dry friction conditions. It is found that the sulfidation concentration plays an important part in the tribological properties of the treated DLC films. The results showed the treated films with low sulfidation concentration have a lower friction coefficient (0.1) than the treated films with high sulfidation concentration (0.26) and the untreated films (0.27) under the same friction testing conditions, which can be attributed to both the presence of sulfur-containing materials and the forming of the mechanical alloyed layer on the wear surface. Adding the dry nitrogen to the sliding surface in the testing system helps the friction coefficient of the treated films with low sulfidation concentration to decrease to 0.04 further in this work. On the basis of the

  10. Magnetic properties of doped Mn-Ga alloys made by mechanical milling and heat treatment

    Directory of Open Access Journals (Sweden)

    Daniel R. Brown

    2016-05-01

    Full Text Available Mn-Ga alloys have shown hard magnetic properties, even though these alloys contain no rare-earth metals. However, much work is needed before rare-earth magnets can be replaced. We have examined the magnetic properties of bulk alloys made with partial replacement of both the Mn and Ga elements in the Mn0.8Ga0.2 system. Bulk samples of Mn-Ga-Bi, Mn-Ga-Al, Mn-Fe-Ga and Mn-(FeB-Ga alloys were fabricated and studied using mechanically milling and heat treatments while altering the atomic percentage of the third element between 2.5 and 20 at%. The ternary alloy exhibits all hard magnetic properties at room temperature with large coercivity. Annealed Mn-Ga-X bulk composites exhibit high coercivities up to 16.6 kOe and remanence up to 9.8 emu/g, that is increased by 115% over the binary system.

  11. Magnetic properties of doped Mn-Ga alloys made by mechanical milling and heat treatment

    Energy Technology Data Exchange (ETDEWEB)

    Brown, Daniel R. [Department of Material Science and Engineering, Florida State University, Tallahassee, FL 32304 (United States); National High Magnetic Field Laboratory, Tallahassee, FL 32310 (United States); Han, Ke; Niu, Rongmei [National High Magnetic Field Laboratory, Tallahassee, FL 32310 (United States); Siegrist, Theo; Besara, Tiglet [Department of Material Science and Engineering, Florida State University, Tallahassee, FL 32304 (United States); Department of Chemical Engineering, Florida Agricultural and Mechanical University-Florida State University, Tallahassee, FL 32304 (United States)

    2016-05-15

    Mn-Ga alloys have shown hard magnetic properties, even though these alloys contain no rare-earth metals. However, much work is needed before rare-earth magnets can be replaced. We have examined the magnetic properties of bulk alloys made with partial replacement of both the Mn and Ga elements in the Mn{sub 0.8}Ga{sub 0.2} system. Bulk samples of Mn-Ga-Bi, Mn-Ga-Al, Mn-Fe-Ga and Mn-(FeB)-Ga alloys were fabricated and studied using mechanically milling and heat treatments while altering the atomic percentage of the third element between 2.5 and 20 at%. The ternary alloy exhibits all hard magnetic properties at room temperature with large coercivity. Annealed Mn-Ga-X bulk composites exhibit high coercivities up to 16.6 kOe and remanence up to 9.8 emu/g, that is increased by 115% over the binary system.

  12. Life inside black holes

    OpenAIRE

    Dokuchaev, V. I.

    2012-01-01

    We consider test planet and photon orbits of the third kind inside a black hole, which are stable, periodic and neither come out of the black hole nor terminate at the singularity. Interiors of supermassive black holes may be inhabited by advanced civilizations living on planets with the third-kind orbits. In principle, one can get information from the interiors of black holes by observing their white hole counterparts.

  13. [Idiopathic macular hole: history and status quo review].

    Science.gov (United States)

    Samoylov, A N; Khaibrakhmanov, T R; Fazleeva, G A; Samoylova, P A

    2017-01-01

    The article reviews the literature on one of the topical problems of vitreoretinal surgery - idiopathic macular holes. The history, concept, classification and diagnostics, as well as surgical and alternative treatment methods of macular holes are explored.

  14. X-ray excited luminescence of Ga- and In-doped ZnO microrods by annealing treatment

    Science.gov (United States)

    Li, Qianli; Liu, Xiaolin; Gu, Mu; Huang, Shiming; Zhang, Juannan; Ni, Chen; Liu, Bo; Hu, Yahua; Wu, Qiang; Zhao, Shuning

    2016-10-01

    Ga- and In-doped ZnO microrods were prepared by low temperature hydrothermal process, and the effect of annealing temperature on morphology, crystallization, photoluminescence and X-ray excited luminescence were deeply researched. The results showed that both Ga- and In-doped ZnO microrods were possessed of a good crystalline quality and exhibited an intense visible emission band with a blue-shift under X-ray excitation. This blue-shift of the visible luminescence could be ascribed to the different contributions of the defect emissions, i.e. the increase in the oxygen vacancy (VO) emission and the decrease of the oxygen interstitial (Oi) emission. Moreover, a strong ultraviolet luminescence was also obtained by further hydrogen annealing. It is expected that Ga- and In-doped microrods are promising candidates for development of fast and high-spatial-resolution X-ray imaging detectors.

  15. Treatment of chronic subdural hematomas with subdural evacuating port system placement in the intensive care unit: evolution of practice and comparison with bur hole evacuation in the operating room.

    Science.gov (United States)

    Flint, Alexander C; Chan, Sheila L; Rao, Vivek A; Efron, Allen D; Kalani, Maziyar A; Sheridan, William F

    2017-12-01

    OBJECTIVE The aims of this study were to evaluate a multiyear experience with subdural evacuating port system (SEPS) placement for chronic subdural hematoma (cSDH) in the intensive care unit at a tertiary neurosurgical center and to compare SEPS placement with bur hole evacuation in the operating room. METHODS All cases of cSDH evacuation were captured over a 7-year period at a tertiary neurosurgical center within an integrated health care delivery system. The authors compared the performance characteristics of SEPS and bur hole placement with respect to recurrence rates, change in recurrence rates over time, complications, length of stay, discharge disposition, and mortality rates. RESULTS A total of 371 SEPS cases and 659 bur hole cases were performed (n = 1030). The use of bedside SEPS placement for cSDH treatment increased over the 7-year period, from 14% to 80% of cases. Reoperation within 6 months was higher for the SEPS (15.6%) than for bur hole drainage (9.1%) across the full 7-year period (p = 0.002). This observed overall difference was due to a higher rate of reoperation during the same hospitalization (7.0% for SEPS vs 3.2% for bur hole; p = 0.008). Over time, as the SEPS procedure became more common and modifications of the SEPS technique were introduced, the rate of in-hospital reoperation after SEPS decreased to 3.3% (p = 0.02 for trend), and the difference between SEPS and bur hole recurrence was no longer significant (p = 0.70). Complications were uncommon and were similar between the groups. CONCLUSIONS Overall performance characteristics of bedside SEPS and bur hole drainage in the operating room were similar. Modifications to the SEPS technique over time were associated with a reduced reoperation rate.

  16. Potential use of gallium-doped phosphate-based glass material for periodontitis treatment.

    Science.gov (United States)

    Sahdev, Rohan; Ansari, Tahera I; Higham, Susan M; Valappil, Sabeel P

    2015-07-01

    are biocompatible in a rat model. The findings warrant further investigation and will have important clinical implications in the future treatment and management of periodontitis. © The Author(s) 2015 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.

  17. Zr-doped TiO{sub 2} supported on delaminated clay materials for solar photocatalytic treatment of emerging pollutants

    Energy Technology Data Exchange (ETDEWEB)

    Belver, C., E-mail: carolina.belver@uam.es; Bedia, J.; Rodriguez, J.J.

    2017-01-15

    Highlights: • Novel Zr-doped TiO{sub 2} delaminated clay materials were prepared by a sol-gel process. • Zr is incorporated into the anatase lattice. • Zr-TiO{sub 2} nanoparticles are homogenously distributed over the delaminated clay. • Zr doping enhances the photoactivity by reducing the band gap. • Degradation rates were favored at low concentrations and high radiation intensities. - Abstract: Solar light-active Zr-doped TiO{sub 2} nanoparticles were successfully immobilized on delaminated clay materials by a one-step sol-gel route. Fixing the amount of TiO{sub 2} at 65 wt.%, this work studies the influence of Zr loading (up to 2%) on the photocatalytic activity of the resulting Zr-doped TiO{sub 2}/clay materials. The structural characterization demonstrates that all samples were formed by a delaminated clay with nanostructured anatase assembled on its surface. The Zr dopant was successfully incorporated into the anatase lattice, resulting in a slight deformation of the anatase crystal and the reduction of the band gap. These materials exhibit high surface area with a disordered mesoporous structure formed by TiO{sub 2} particles (15–20 nm) supported on a delaminated clay. They were tested in the solar photodegradation of antipyrine, usually used as an analgesic drug and selected as an example of emerging pollutant. High degradation rates have been obtained at low antipyrine concentrations and high solar irradiation intensities with the Zr-doped TiO{sub 2}/clay catalyst, more effective than the undoped one. This work demonstrates the potential application of the synthesis method for preparing novel and efficient solar-light photocatalysts based on metal-doped anatase and a delaminated clay.

  18. Zr-doped TiO2 supported on delaminated clay materials for solar photocatalytic treatment of emerging pollutants.

    Science.gov (United States)

    Belver, C; Bedia, J; Rodriguez, J J

    2017-01-15

    Solar light-active Zr-doped TiO2 nanoparticles were successfully immobilized on delaminated clay materials by a one-step sol-gel route. Fixing the amount of TiO2 at 65wt.%, this work studies the influence of Zr loading (up to 2%) on the photocatalytic activity of the resulting Zr-doped TiO2/clay materials. The structural characterization demonstrates that all samples were formed by a delaminated clay with nanostructured anatase assembled on its surface. The Zr dopant was successfully incorporated into the anatase lattice, resulting in a slight deformation of the anatase crystal and the reduction of the band gap. These materials exhibit high surface area with a disordered mesoporous structure formed by TiO2 particles (15-20nm) supported on a delaminated clay. They were tested in the solar photodegradation of antipyrine, usually used as an analgesic drug and selected as an example of emerging pollutant. High degradation rates have been obtained at low antipyrine concentrations and high solar irradiation intensities with the Zr-doped TiO2/clay catalyst, more effective than the undoped one. This work demonstrates the potential application of the synthesis method for preparing novel and efficient solar-light photocatalysts based on metal-doped anatase and a delaminated clay. Copyright © 2016 Elsevier B.V. All rights reserved.

  19. Transition of Emission Colours as a Consequence of Heat-Treatment of Carbon Coated Ce3+-Doped YAG Phosphors

    NARCIS (Netherlands)

    Yin, L.J.; Dierre, B.F.P.R.; Sekiguchi, Takashi; van Ommen, J.R.; Hintzen, H.T.J.M.; Cho, Yujin

    2017-01-01

    To modify the luminescence properties of Ce3+-doped Y3Al5O12 (YAG) phosphors, they have been coated with a carbon layer by chemical vapor deposition and subsequently heat-treated at high temperature under N2 atmosphere. Luminescence of the

  20. Electron-enhanced hole injection in blue polyfluorene-based polymer light-emitting diodes

    NARCIS (Netherlands)

    Woudenbergh, T. van; Wildeman, J.; Blom, P.W.M.; Bastiaansen, J.J.A.M.; Langeveld-Voss, B.M.W.

    2004-01-01

    It has recently been reported that, after electrical conditioning, an ohmic hole contact is formed in poly(9,9-dioctylfluorene) (PFO)-based polymer light-emitting diodes (PLED), despite the large hole-injection barrier obtained with a poly(styrene sulfonic acid)-doped

  1. Higher spin black holes

    National Research Council Canada - National Science Library

    Gutperle, Michael; Kraus, Per

    2011-01-01

    .... We find solutions that generalize the BTZ black hole and carry spin-3 charge. The black hole entropy formula yields a result for the asymptotic growth of the partition function at finite spin-3 chemical potential...

  2. [Asthma drugs and doping].

    Science.gov (United States)

    Pillard, F; Rolland, Y; Rivière, D

    1999-11-01

    Some drugs regularly used in the treatment of asthma (beta-agonists and corticosteroids) are registered on the list of drugs forbidden in sport, because they have a doping action. To avoid penalizing asthmatic sportsmen, some beta-agonists (Salbutamol, Salmeterol, Terbutaline) and corticosteroids are allowed only in inhaled form, with written notification from the prescribing physician, a pneumologist or the team doctor. Considering the increase of doping with increasing involvement of physicians, good and up to date notions about the current rules of prescription in asthmatic sportsmen are needed.

  3. A prospective, randomized, double-blind comparison of an ablative fractional 2940-nm erbium-doped yttrium aluminum garnet laser with a nonablative fractional 1550-nm erbium-doped glass laser for the treatment of photoaged Asian skin.

    Science.gov (United States)

    Moon, Hye-Rim; Yun, Woo-Jin; Lee, Ye Jin; Lee, Mi-Woo; Chang, SungEun

    2015-01-01

    As compared with ablative fractional CO2 laser, ablative fractional erbium-doped yttrium aluminum garnet (Er:YAG) laser is considered to be a more suitable treatment option for photoaged skin in Asians due to the lower incidence of postinflammatory hyperpigmentation. To compare the efficacy and safety of ablative fractional Er:YAG laser (ablative fractional resurfacing [AFR]) and nonablative fractional 1550-nm Er:glass laser (non-AFR [NAFR]) in the treatment of photoaging. This was a prospective, randomized, double-blinded comparative study. In three sessions, at four-week intervals, 19 patients received Er:YAG AFR, and 15 patients received Er:glass NAFR. Pigmentation, uneven tone/erythema, wrinkles and overall features of photoaging were scored. Patient satisfaction, adverse effects and pain scores were recorded. Melanin and erythema indexes were measured. Reductions in pigmentation and uneven tone/erythema scores were significantly greater after Er:YAG AFR, while wrinkle score reduction was significantly greater after Er:glass NAFR. Physician and patient assessments for the overall features showed greater improvement in the Er:glass NAFR. Treatment-related pain or adverse events were less in the Er:YAG AFR. Both Er:YAG AFR and Er:glass NAFR are effective and safe and could be used in a complementary manner for treating photoaged Asian skin.

  4. Doping droops.

    Science.gov (United States)

    Chaturvedi, Aditi; Chaturvedi, Harish; Kalra, Juhi; Kalra, Sudhanshu

    2007-01-01

    Drug abuse is a major concern in the athletic world. The misconception among athletes and their coaches is that when an athlete breaks a record it is due to some "magic ingredient" and not because of training, hard work, mental attitude and championship performance. The personal motivation to win in competitive sports has been intensified by national, political, professional and economic incentives. Under this increased pressure athletes have turned to finding this "magic ingredient". Athlete turns to mechanical (exercise, massage), nutritional (vitamins, minerals), pharmacological (medicines) or gene therapies to have an edge over other players. The World Anti-Doping Agency (WADA) has already asked scientists to help find ways to prevent gene therapy from becoming the newest form of doping. The safety of the life of athletes is compromised with all forms of doping techniques, be it a side effect of a drug or a new technique of gene doping.

  5. Monopole black hole skyrmions

    OpenAIRE

    Moss, I.G.; Shiiki, N.; Winstanley, E.

    2000-01-01

    Charged black hole solutions with pion hair are discussed. These can be\\ud used to study monopole black hole catalysis of proton decay.\\ud There also exist\\ud multi-black hole skyrmion solutions with BPS monopole behaviour.

  6. Luminescence properties of Sm{sup 3+} doped YPO{sub 4}: Effect of solvent, heat-treatment, Ca{sup 2+}/W{sup 6+}-co-doping and its hyperthermia application

    Energy Technology Data Exchange (ETDEWEB)

    Dutta, Dimple P.; Ningthoujam, R. S., E-mail: rsn@barc.gov.in; Tyagi, A. K. [Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400085 (India)

    2012-12-15

    Sm{sup 3+} doped YPO{sub 4} spherical nanoparticles are prepared by wet chemical route. Pure YPO{sub 4} shows the tetragonal phase, which is stable up to 900 °C, whereas pure SmPO{sub 4} shows the phase transition from hexagonal to monoclinic when heated above 800 °C. The (2-10 at.%) Sm{sup 3+} doped YPO{sub 4} shows the mixture of phases of tetragonal and hexagonal, which transform to the tetragonal phase above 800 °C. Infra-red study could distinguish confined water in the pore of hexagonal phase from water present on the surface of particles. Luminescence intensities of Sm{sup 3+} at 564, 601 and 645 nm are weak in case of as-prepared samples because of high non-radiative rate arising from the H{sub 2}O molecules present in pores of hexagonal lattice. The intensities increase for samples heated up to 900 °C because of increase of extent of radiative rate. Luminescence lifetime increases with increase of heat-treatment up to 900 °C. When solvent of as-prepared sample was changed from the H{sub 2}O to D{sub 2}O, 5 times enhancement in luminescence intensity is observed, which can be ascribed to the lower vibration energy of D-O over H-O, which is near to Sm{sup 3+}. When Y{sup 3+} and P{sup 5+} ions are substituted by Ca{sup 3+} and W{sup 3+} up to 3 at.%, there is an enhancement of luminescence. In order to use them as bio-labeling in drug delivery for hyperthermia applications, hybrid of Fe{sub 3}O{sub 4}@YPO{sub 4}:7Sm is prepared and heating up to 45 °C is observed under AC magnetic field.

  7. Hole transport in c-plane InGaN-based green laser diodes

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, Yang; Liu, Jianping, E-mail: jpliu2010@sinano.ac.cn; Tian, Aiqin; Zhang, Feng; Feng, Meixin; Hu, Weiwei; Zhang, Shuming; Ikeda, Masao; Li, Deyao; Zhang, Liqun; Yang, Hui [Key Lab of Nanodevices and Applications, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences (CAS), Suzhou 215123 (China); School of Nano Technology and Nano Bionics, University of Science and Technology of China, Suzhou 215123 (China)

    2016-08-29

    Hole transport in c-plane InGaN-based green laser diodes (LDs) has been investigated by both simulations and experiments. It is found that holes can overflow from the green double quantum wells (DQWs) at high current density, which reduces carrier injection efficiency of c-plane InGaN-based green LDs. A heavily silicon-doped layer right below the green DQWs can effectively suppress hole overflow from the green DQWs.

  8. Enhanced Visible-Light Photocatalytic Performance of Nanosized Anatase TiO2 Doped with CdS Quantum Dots for Cancer-Cell Treatment

    Directory of Open Access Journals (Sweden)

    Kangqiang Huang

    2012-01-01

    Full Text Available CdS quantum-dots-(QDs-doped TiO2 nanocomposites were successfully synthesized using the sol-gel technique and characterized by SEM, TEM, XRD, EDS, UV-Vis, and FS. They were then used as a new “photosensitizer” based on photodynamic therapy (PDT for cancer-cell treatment. The photocatalytic activities of CdS-TiO2 on leukemia tumors were investigated by using Cell Counting Kit-8 (CCK-8 assay. The ultrastructural morphology of treated cells was also studied by AFM. The experimental results indicated that an obvious inhibition of tumor growth would be observed in groups treated with CdS-TiO2 nanocomposites, and the PDT efficiency in the presence of CdS-doped TiO2 was significantly higher than that of TiO2, revealing that the photocatalytic activities of TiO2 could be effectively enhanced by the modification of CdS QDs. Additionally, CdS- TiO2 can exhibit a very high photodynamic efficiency of 80.5% at a final concentration of 200 μg/mL under visible-light irradiation. CdS-TiO2 nanocomposites in this case were regarded as a promising application for cancer-cell treatment.

  9. Improved Black Hole Fireworks: Asymmetric Black-Hole-to-White-Hole Tunneling Scenario

    CERN Document Server

    De Lorenzo, Tommaso

    2015-01-01

    A new scenario for gravitational collapse has been recently proposed by Haggard and Rovelli. Presenting the model under the name of black hole fireworks, they claimed that the accumulation of quantum gravitational effects outside the horizon can cause the tunneling of geometry from a black hole to a white hole, allowing a bounce of the collapsing star which can eventually go back to infinity. In this paper we discuss the instabilities of this model and propose a simple minimal modification which eliminates them, as well as other related instabilities discussed in the literature. The new scenario is a time-asymmetric version of the original model with a time-scale for the final explosion that is shorter than m log m in Planck units. Our analysis highlights the importance of irreversibility in gravitational collapse which, in turn, uncovers important issues that cannot be addressed in detail without a full quantum gravity treatment.

  10. Doping dependence of ordered phases and emergent quasiparticles in the doped Hubbard-Holstein model

    Science.gov (United States)

    Mendl, C. B.; Nowadnick, E. A.; Huang, E. W.; Johnston, S.; Moritz, B.; Devereaux, T. P.

    2017-11-01

    We present determinant quantum Monte Carlo simulations of the hole-doped single-band Hubbard-Holstein model on a square lattice, to investigate how quasiparticles emerge when doping a Mott insulator (MI) or a Peierls insulator (PI). The MI regime at large Hubbard interaction U and small relative e-ph coupling strength λ is quickly suppressed upon doping, by drawing spectral weight from the upper Hubbard band and shifting the lower Hubbard band towards the Fermi level, leading to a metallic state with emergent quasiparticles at the Fermi level. On the other hand, the PI regime at large λ and small U persists out to relatively high doping levels. We study the evolution of the d -wave superconducting susceptibility with doping, and find that it increases with lowering temperature in a regime of intermediate values of U and λ .

  11. Effect of structure, size and copper doping on the luminescence properties of ZnS

    Energy Technology Data Exchange (ETDEWEB)

    Kamal, Ch. Satya [Crystal Growth and Nanoscience Research Centre, Government College (A), Rajahmundry, Andhra Pradesh 533 105 (India); Mishra, R.K. [Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Patel, Dinesh K. [Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Casali Center for Applied Chemistry, The Hebrew University of Jerusalem, 9190401 (Israel); Rao, K. Ramachandra, E-mail: drkrcr@gmail.com [Crystal Growth and Nanoscience Research Centre, Government College (A), Rajahmundry, Andhra Pradesh 533 105 (India); Sudarsan, V., E-mail: vsudar@barc.gov.in [Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Vatsa, R.K. [Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400085 (India)

    2016-09-15

    Highlights: • Blue and green emission intensity form ZnS is sensitive to crystallographic form. • For ZnS nanoparticles, emission characteristics are not affected by copper doping. • Cu solubility poor in ZnS nanoparticles compared to corresponding bulk. - Abstract: Luminescence properties of wurtzite and cubic forms of bulk ZnS have been investigated in detail and compared with that of ZnS nanoparticles. Blue emission observed in both hexagonal and cubic forms of undoped bulk ZnS is explained based on electron–hole recombination involving electron in conduction band and hole trapped in Zn{sup 2+} vacancies where as green emission arises due to electron hole recombination from Zn{sup 2+} and S{sup 2−} vacancies. Conversion of wurtzite form to cubic form is associated with relative increase in intensity of green emission due to increased defect concentration brought about by high temperature heat treatment. Copper doping in ZnS, initially leads to formation of both Cu{sub Zn} and Cu{sub i} (interstitial copper) centers, and latter to mainly Cu{sub Zn} centers as revealed by variation in relative intensities of blue and green emission from the samples.

  12. Black holes in binary stars

    NARCIS (Netherlands)

    Wijers, R.A.M.J.

    1996-01-01

    Introduction Distinguishing neutron stars and black holes Optical companions and dynamical masses X-ray signatures of the nature of a compact object Structure and evolution of black-hole binaries High-mass black-hole binaries Low-mass black-hole binaries Low-mass black holes Formation of black holes

  13. Charged cosmological black hole

    Science.gov (United States)

    Moradi, Rahim; Stahl, Clément; Firouzjaee, Javad T.; Xue, She-Sheng

    2017-11-01

    The cosmological black holes are black holes living not in an asymptotically flat universe but in an expanding spacetime. They have a rich dynamics especially for their mass and horizon. In this article, we perform a natural step in investigating this new type of black hole: we consider the possibility of a charged cosmological black hole. We derive the general equations of motion governing its dynamics and report a new analytic solution for the special case of the charged Lematre-Tolman-Bondi equations of motion that describe a charged cosmological black hole. We then study various relevant quantities for the characterization of the black hole, such as the C-function, the effect of the charge on the black hole flux, and the nature of the singularity. We also perform numerical investigations to strengthen our results. Finally, we challenge a model of gamma ray burst within our framework.

  14. Studies of thermal annealing and dope composition on the enhancement of separation performance cellulose acetate membrane for brackish water treatment from Jepara

    Directory of Open Access Journals (Sweden)

    Tutuk Djoko Kusworo

    2014-08-01

    Full Text Available Membrane is an alternative technology of water treatment with filtration principle that is being widely developed and used for water treatment. The main objective of this study was to make an asymmetric membrane using cellulose acetate polymer and study the effect of additive and annealing treatment on the morphology structure and performance of cellulose acetate membranes in brackish water treatment. Asymmetric membranes for brackish water treatment were casted using a casting machine process from dope solutions containing cellulose acetates and acetone as a solvent. Membranes was prepared by phase inversion method  with variation of polyethylene glycol (PEG concentration of 1 and 5 wt% and with thermal annealing at 60 oC in 10 seconds and without thermal annealing behavior. Membrane characterization consists of calculation of membrane flux and rejection with brackish water as a feed from Jepara. The research concluded that asymmetric cellulose acetate membrane can be made by dry/wet phase inversion method. The more added concentration of PEG will be resulted the larger pore of membrane. Meanwhile the higher temperature and the longer time of annealing treatment, the skin layer of membrane become denser. Membrane with the composition of 18 wt% cellulose acetate, 5 wt% PEG, 1 wt% distilled water, with heat treatment at temperature of 60 oC for 10 seconds is obtained optimal performance.

  15. Superconductivity in carrier-doped silicon carbide

    Directory of Open Access Journals (Sweden)

    Takahiro Muranaka, Yoshitake Kikuchi, Taku Yoshizawa, Naoki Shirakawa and Jun Akimitsu

    2008-01-01

    Full Text Available We report growth and characterization of heavily boron-doped 3C-SiC and 6H-SiC and Al-doped 3C-SiC. Both 3C-SiC:B and 6H-SiC:B reveal type-I superconductivity with a critical temperature Tc=1.5 K. On the other hand, Al-doped 3C-SiC (3C-SiC:Al shows type-II superconductivity with Tc=1.4 K. Both SiC:Al and SiC:B exhibit zero resistivity and diamagnetic susceptibility below Tc with effective hole-carrier concentration n higher than 1020 cm−3. We interpret the different superconducting behavior in carrier-doped p-type semiconductors SiC:Al, SiC:B, Si:B and C:B in terms of the different ionization energies of their acceptors.

  16. Fractional Erbium-Doped Yttrium Aluminum Garnet Laser Versus Microneedling in Treatment of Atrophic Acne Scars: A Randomized Split-Face Clinical Study.

    Science.gov (United States)

    Osman, Mai Abdel Raouf; Shokeir, Hisham Ali; Fawzy, Marwa M

    2017-01-01

    Ablative fractional erbium-doped yttrium aluminum garnet (Er:YAG) laser and microneedling have been popularized in recent years and their effectiveness and side effects individually reported. No previous study, however, has directly compared the efficacy and safety between the 2 different treatments. To compare the efficacy and safety of the ablative fractional Er:YAG laser and microneedling for the treatment of atrophic acne scars. Thirty patients with atrophic acne scars were randomly treated in a split-face manner with a fractional Er:YAG laser on one side and microneedling on the other side. All patients received 5 treatments with a 1-month interval. Objective and subjective assessments were obtained at baseline and at 3 months after the final treatment. At the 3-month follow-up, both treatment modalities induced noticeable clinical and histological improvement, with significantly better results in fractional Er:YAG laser versus microneedling (70% vs 30%), respectively (p acne scars, with significantly higher scar response to the fractional Er:YAG laser treatment.

  17. A low-fluence 1064-nm Q-switched neodymium-doped yttrium aluminium garnet laser for the treatment of café-au-lait macules.

    Science.gov (United States)

    Kim, Hyeong-Rae; Ha, Jeong-Min; Park, Min-Soo; Lee, Young; Seo, Young-Joon; Kim, Chang-Deok; Lee, Jeung-Hoon; Im, Myung

    2015-09-01

    Café-au-lait macules (CALMs) are a common pigmentary disorder. Although a variety of laser modalities have been used to treat CALMs, their efficacies vary and dyspigmentation may develop. We evaluated the clinical efficacy and safety of a low-fluence 1064-nm Q-switched neodymium-doped yttrium aluminium garnet (Nd:YAG) laser for the treatment of CALMs. In a preliminary investigation, 6 patients underwent a split-lesion comparative study with 532- and 1064-nm Q-switched Nd:YAG laser treatment. In total, 32 patients with 39 CALMs were enrolled in a subsequent prospective trial to evaluate the treatment with a low-fluence 1064-nm Q-switched Nd:YAG laser. In the preliminary study, the 1064-nm treatment group had a more favorable response and a shorter recovery time. In a subsequent prospective trial of a 1064-nm laser, 74.4% of the lesions showed a clinical response with clearance of ≥50.0%. The treatment regimen was well tolerated; 15.4% of patients experienced adverse events. The study participants were followed for 6 months, and there were no relevant treatment controls in the prospective trial group. Low-fluence 1064-nm Q-switched Nd:YAG laser therapy afforded good clinical improvement for treating CALMs. Copyright © 2015 American Academy of Dermatology, Inc. Published by Elsevier Inc. All rights reserved.

  18. Evaluation of the water-treatment ability of silica-doped titanium dioxide-coated glass plates using a cationic coupling reagent based on a flow analytical system.

    Science.gov (United States)

    Sugita, Tsuyoshi; Mori, Masanobu; Mase, Akinori; Noguchi, Shin-nosuke; Tokutome, Toru; Fujii, Kengo; Hara, Chisato; Katayama, Kenji; Iwamoto, Shinji; Itabashi, Hideyuki

    2015-01-01

    In this study, a photocatalytic plate bound to highly dispersible silica-doped titanium dioxide (SiT) on a trimethoxysilyl-propyldiethylenetriamine (dien)-coated glass plate (dien-plate) was newly synthesized, and was evaluated by a flow analytical (FA) system, which consists of a photocatalytic reactor and a spectrophotometer, to continuously monitor the absorbance of tested chemicals. The method was not required to collect any sample solution at a constant period. The SiT-dien-plate facilitated the photodecomposition of methylene blue (MB) and indigo carmine (InC) in aqueous solutions. Notably, MB was quantitatively photo-decomposed following 18 h of UV-light irradiation, related to the electrostatic adsorption of surface-bound particles. A water-treatment ability of visible-light-responsive vanadium-modified nitrogen/silica co-doped titanium dioxide fixed on the dien-plate was also evaluated by the FA system. It clarified to decompose MB and InC under visible-light irradiation. Finally, the decomposition of a humic substance dissolved from Middle West China peaty soils by the SiT-dien-plate under UV-irradiation was assessed as applying the FA system with a photocatalytic plate.

  19. Stimulated Black Hole Evaporation

    CERN Document Server

    Spaans, Marco

    2016-01-01

    Black holes are extreme expressions of gravity. Their existence is predicted by Einstein's theory of general relativity and is supported by observations. Black holes obey quantum mechanics and evaporate spontaneously. Here it is shown that a mass rate $R_f\\sim 3\\times 10^{-8} (M_0/M)^{1/2}$ $M_0$ yr$^{-1}$ onto the horizon of a black hole with mass $M$ (in units of solar mass $M_0$) stimulates a black hole into rapid evaporation. Specifically, $\\sim 3 M_0$ black holes can emit a large fraction of their mass, and explode, in $M/R_f \\sim 3\\times 10^7 (M/M_0)^{3/2}$ yr. These stimulated black holes radiate a spectral line power $P \\sim 2\\times 10^{39} (M_0/M)^{1/2}$ erg s$^{-1}$, at a wavelength $\\lambda \\sim 3\\times 10^5 (M/M_0)$ cm. This prediction can be observationally verified.

  20. Astrophysical black holes

    CERN Document Server

    Gorini, Vittorio; Moschella, Ugo; Treves, Aldo; Colpi, Monica

    2016-01-01

    Based on graduate school lectures in contemporary relativity and gravitational physics, this book gives a complete and unified picture of the present status of theoretical and observational properties of astrophysical black holes. The chapters are written by internationally recognized specialists. They cover general theoretical aspects of black hole astrophysics, the theory of accretion and ejection of gas and jets, stellar-sized black holes observed in the Milky Way, the formation and evolution of supermassive black holes in galactic centers and quasars as well as their influence on the dynamics in galactic nuclei. The final chapter addresses analytical relativity of black holes supporting theoretical understanding of the coalescence of black holes as well as being of great relevance in identifying gravitational wave signals. With its introductory chapters the book is aimed at advanced graduate and post-graduate students, but it will also be useful for specialists.

  1. Hole crystallization in semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Bonitz, M [Institut fuer Theoretische Physik und Astrophysik, Christian-Albrechts-Universitaet Kiel, 24098 Kiel (Germany); Filinov, V S [Institut fuer Theoretische Physik und Astrophysik, Christian-Albrechts-Universitaet Kiel, 24098 Kiel (Germany); Fortov, V E [Institute for High Energy Density, Russian Academy of Sciences, Izhorskay 13/19, Moscow 127412 (Russian Federation); Levashov, P R [Institute for High Energy Density, Russian Academy of Sciences, Izhorskay 13/19, Moscow 127412 (Russian Federation); Fehske, H [Institut fuer Physik, Universitaet Greifswald, l7487 Greifswald (Germany)

    2006-04-28

    When electrons in a solid are excited to a higher energy band they leave behind a vacancy (hole) in the original band which behaves like a positively charged particle. Here we predict that holes can spontaneously order into a regular lattice in semiconductors with sufficiently flat valence bands. The critical hole to electron effective mass ratio required for this phase transition is found to be of the order of 80.

  2. Hole crystallization in semiconductors

    OpenAIRE

    Bonitz, M.; Filinov, V. S.; Fortov, V. E.; Levashov, P. R.; Fehske, H.

    2005-01-01

    When electrons in a solid are excited to a higher energy band they leave behind a vacancy (hole) in the original band which behaves like a positively charged particle. Here we predict that holes can spontaneously order into a regular lattice in semiconductors with sufficiently flat valence bands. The critical hole to electron effective mass ratio required for this phase transition is found to be of the order of 80.

  3. Asymptotic black holes

    Science.gov (United States)

    Ho, Pei-Ming

    2017-04-01

    Following earlier works on the KMY model of black-hole formation and evaporation, we construct the metric for a matter sphere in gravitational collapse, with the back-reaction of pre-Hawking radiation taken into consideration. The mass distribution and collapsing velocity of the matter sphere are allowed to have an arbitrary radial dependence. We find that a generic gravitational collapse asymptote to a universal configuration which resembles a black hole but without horizon. This approach clarifies several misunderstandings about black-hole formation and evaporation, and provides a new model for black-hole-like objects in the universe.

  4. Design and Optimization of Air-Doped 3-dB Terahertz Fiber Directional Couplers

    DEFF Research Database (Denmark)

    Bao, Hualong; Nielsen, Kristian; Rasmussen, Henrik K.

    2014-01-01

    We present a thorough practical design optimization of broadband low loss, terahertz (THz) photonic crystal fiber directional couplers in which the two cores are mechanically down- doped with a triangular array of air holes.......We present a thorough practical design optimization of broadband low loss, terahertz (THz) photonic crystal fiber directional couplers in which the two cores are mechanically down- doped with a triangular array of air holes....

  5. Activated carbon supported TiO2-photocatalysis doped with Fe ions for continuous treatment of dye wastewater in a dynamic reactor.

    Science.gov (United States)

    Li, Youji; Chen, Jun; Liu, Jianben; Ma, Mingyuan; Chen, Wei; Li, Leiyong

    2010-01-01

    Fe-doped TiO2 coated on activated carbon (Fe-TiO2/AC, FTA) composites were prepared by an improved sol-gel method and characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, X-ray diffractometry, inductively coupled plasma mass spectrometry and BET surface area analysis. Obtained FTA composites were applied to the continuous treatment of dye wastewater in a dynamic reactor. The effects of Fe ion content, catalyst content, UV-lamp power and flowrate of the continuous treatment of dye wastewater on degradation efficiency were analyzed to determine the optimum operating conditions of dye wastewater degradation. Continuous photocatalytic experiments provided interesting results that VIFTA had a high chemical oxygen demand (COD) removal rate compared with TiO2, Fe doped TiO2 (FT) and TiO2 coated on activated carbon (TA). In particular, when using the FTA catalyst with a Fe ion content of 0.33%, the kinetic content (k = 0.0376) of COD removal was more than the sum of both TA (0.0205) and 0.33% FT (0.0166). FTA showed a high photoactivity because of a synergistic effect between Fe ions and AC on TiO2, which is higher than the individual effects of AC or Fe ions on TiO2. Additionally, for the photocatalytic degradation of dye wastewater, the optimum Fe ion content, catalyst content, UV-lamp power and flowrate were 0.33%, 6 g/L, 60 W (two lamps) and 300 mL/hr, respectively. An investigation of catalyst reuse revealed that the 0.33% FTA showed almost no deactivation in photocatalytic degradation of naturally treated wastewater.

  6. High-fluence and high-density treatment of perioral rhytides using a new, fractionated 2,790-nm ablative erbium-doped Yttrium Scandium Gallium Garnet Laser.

    Science.gov (United States)

    Ciocon, David H; Hussain, Mussarat; Goldberg, David J

    2011-06-01

    In this study, we evaluated the safety and efficacy of a novel 2,790-nm erbium-doped yttrium scandium gallium garnet (Er:YSGG) laser system for the treatment of facial photodamage and perioral wrinkles using a single-treatment, high-fluence, high-density protocol. Eleven female participants with Fitzpatrick skin types II to III and facial wrinkles underwent a single full-face fractional ablative treatment with a 2,790-nm Er:YSGG laser. Follow-up visits were completed at 1, 2, and 6 weeks 3 and 6 months. Quartile improvement scale (0-4) and Fitzpatrick wrinkle scores (1-9) were used for the assessments. Based on blinded photographic assessments, the mean difference in Fitzpatrick wrinkle scores for full face wrinkles was 1.5 ± 1.2 (a reduction from 6.6 to 5.1; paired t-test, p = .003). There was also a statistically significant mean reduction of 1.7 ± 1.3 in perioral wrinkle scores (from 6.7 to 5.0; p = .002). No serious adverse events were reported. A novel, fractionated, ablative 2,790-nm Er:YSGG laser can safely and effectively treat photodamage and perioral wrinkles in a single treatment using a high-fluence, high-density protocol. Cutera provided the equipment used in this study and funding to Dr. Goldberg. © 2011 by the American Society for Dermatologic Surgery, Inc.

  7. Picosecond 532-nm neodymium-doped yttrium aluminium garnet laser-a novel and promising modality for the treatment of café-au-lait macules.

    Science.gov (United States)

    Artzi, Ofir; Mehrabi, Joseph N; Koren, Amir; Niv, Roni; Lapidoth, Moshe; Levi, Assi

    2017-11-02

    Café-au-lait macules (CALMs) present as benign hyperpigmented, well-circumscribed spots on the skin for which many patients seek treatment for aesthetic reasons. The objective of this study is to report our experience in treating CALMs using a picosecond 532-nm neodymium-doped yttrium aluminium garnet (PS 532 nm) laser. This is a retrospective case series of 16 patients with CALMs who were treated by a PS 532-nm laser (1-4 treatments, 4-8 weeks apart). Response as seen on clinical photographs was assessed by two independent dermatologists and graded on a scale of 0 (exacerbation) to 5 (95-100% improvement). Patient satisfaction and tolerance were documented at final visit. The results of 15 patients demonstrated significant improvement (average 3.43), and their satisfaction and tolerance levels were high. One patient had no response whatsoever to treatment. The PS 532-nm laser is a promising novel modality for the treatment of CALMs.

  8. Black Hole Dynamic Potentials

    Indian Academy of Sciences (India)

    2016-01-27

    Jan 27, 2016 ... In the following paper, certain black hole dynamic potentials have been developed definitively on the lines of classical thermodynamics. These potentials have been refined in view of the small differences in the equations of the laws of black hole dynamics as given by Bekenstein and those of ...

  9. Black hole levitron

    NARCIS (Netherlands)

    Arsiwalla, X.D.; Verlinde, E.P.

    2010-01-01

    We study the problem of spatially stabilizing four dimensional extremal black holes in background electric/magnetic fields. Whilst looking for stationary stable solutions describing black holes placed in external fields we find that taking a continuum limit of Denef et al.’s multicenter

  10. Black holes matter

    DEFF Research Database (Denmark)

    Kragh, Helge Stjernholm

    2016-01-01

    Review essay, Marcia Bartusiak, Black Hole: How an Idea Abandoned by Newtonians, Hated by Einstein, and Gambled On by Hawking Became Loved (New Haven: Yale University Press, 2015).......Review essay, Marcia Bartusiak, Black Hole: How an Idea Abandoned by Newtonians, Hated by Einstein, and Gambled On by Hawking Became Loved (New Haven: Yale University Press, 2015)....

  11. Black hole Berry phase

    NARCIS (Netherlands)

    de Boer, J.; Papadodimas, K.; Verlinde, E.

    2009-01-01

    Supersymmetric black holes are characterized by a large number of degenerate ground states. We argue that these black holes, like other quantum mechanical systems with such a degeneracy, are subject to a phenomenon which is called the geometric or Berry’s phase: under adiabatic variations of the

  12. Black holes an introduction

    CERN Document Server

    Raine, Derek

    2005-01-01

    This introduction to the fascinating subject of black holes fills a significant gap in the literature which exists between popular, non-mathematical expositions and advanced textbooks at the research level. It is designed for advanced undergraduates and first year postgraduates as a useful stepping-stone to the advanced literature. The book provides an accessible introduction to the exact solutions of Einstein’s vacuum field equations describing spherical and axisymmetric (rotating) black holes. The geometry and physical properties of these spacetimes are explored through the motion of particles and light. The use of different coordinate systems, maximal extensions and Penrose diagrams is explained. The association of the surface area of a black hole with its entropy is discussed and it is shown that with the introduction of quantum mechanics black holes cease to be black and can radiate. This result allows black holes to satisfy the laws of thermodynamics and thus be consistent with the rest of physics.

  13. Black Hole Simulation

    Science.gov (United States)

    1999-01-01

    This graphic shows the computer simulation of a black hole from start to finish. Plasma is falling slowly toward the black hole in a (at the upper left). The plasma has a magnetic field, shown by the white lines. It picks up speed as it falls toward the hole in b (at the upper right), c (lower left) and d (lower right). However, the rotating black hole twists up space itself (and the magnetic field lines) and ejects electromagnetic power along the north and south poles above the black hole. The red and white color shows the immense electromagnetic power output, which eventually will pick up particles and form squirting jets. This simulation was conducted using supercomputers at Japan's National Institute for Fusion Science.

  14. Black hole critical phenomena without black holes

    Indian Academy of Sciences (India)

    Abstract. Studying the threshold of black hole formation via numerical evolution has led to the discovery of fascinating nonlinear phenomena. Power-law mass scaling, aspects of universality, and self-similarity have now been found for a large variety of models. However, questions remain. Here I briefly review critical ...

  15. The Thermodynamics of Black Holes

    National Research Council Canada - National Science Library

    Emparan, Roberto; Tinto, Massimo; Barbero G, J Fernando; Heusler, Markus; Rendall, Alan D; Adamo, Timothy M; Liebling, Steven L; Sasaki, Misao; Poisson, Eric; Wald, Robert M; Postnov, Konstantin A; Amendola, Luca; Shibata, Masaru; Tagoshi, Hideyuki; Reall, Harvey S; Kozameh, Carlos; Palenzuela, Carlos; Yungelson, Lev R; Villaseñor, Eduardo J. S; Appleby, Stephen; Taniguchi, Keisuke; Dhurandhar, Sanjeev V; Bacon, David; Newman, Ezra T; Baker, Tessa; Baldi, Marco; Bartolo, Nicola; Blanchard, Alain; Bonvin, Camille; Borgani, Stefano; Branchini, Enzo; Burrage, Clare; Camera, Stefano; Carbone, Carmelita; Casarini, Luciano; Cropper, Mark; de Rham, Claudia; Di Porto, Cinzia; Ealet, Anne; Ferreira, Pedro G; Finelli, Fabio; García-Bellido, Juan; Giannantonio, Tommaso; Guzzo, Luigi; Heavens, Alan; Heisenberg, Lavinia; Heymans, Catherine; Hoekstra, Henk; Hollenstein, Lukas; Holmes, Rory; Horst, Ole; Jahnke, Knud; Kitching, Thomas D; Koivisto, Tomi; Kunz, Martin; La Vacca, Giuseppe; March, Marisa; Majerotto, Elisabetta; Markovic, Katarina; Marsh, David; Marulli, Federico; Massey, Richard; Mellier, Yannick; Mota, David F; Nunes, Nelson J; Percival, Will; Pettorino, Valeria; Porciani, Cristiano; Quercellini, Claudia; Read, Justin; Rinaldi, Massimiliano; Sapone, Domenico; Scaramella, Roberto; Skordis, Constantinos; Simpson, Fergus; Taylor, Andy; Thomas, Shaun; Trotta, Roberto; Verde, Licia; Vernizzi, Filippo; Vollmer, Adrian; Wang, Yun; Weller, Jochen; Zlosnik, Tom

    ...We review the present status of black hole thermodynamics. Our review includes discussion of classical black hole thermodynamics, Hawking radiation from black holes, the generalized second law, and the issue of entropy bounds...

  16. Hole-ness of point clouds

    Science.gov (United States)

    Gronz, Oliver; Seeger, Manuel; Klaes, Björn; Casper, Markus C.; Ries, Johannes B.

    2015-04-01

    Accurate and dense 3D models of soil surfaces can be used in various ways: They can be used as initial shapes for erosion models. They can be used as benchmark shapes for erosion model outputs. They can be used to derive metrics, such as random roughness... One easy and low-cost method to produce these models is structure from motion (SfM). Using this method, two questions arise: Does the soil moisture, which changes the colour, albedo and reflectivity of the soil, influence the model quality? How can the model quality be evaluated? To answer these questions, a suitable data set has been produced: soil has been placed on a tray and areas with different roughness structures have been formed. For different moisture states - dry, medium, saturated - and two different lighting conditions - direct and indirect - sets of high-resolution images at the same camera positions have been taken. From the six image sets, 3D point clouds have been produced using VisualSfM. The visual inspection of the 3D models showed that all models have different areas, where holes of different sizes occur. But it is obviously a subjective task to determine the model's quality by visual inspection. One typical approach to evaluate model quality objectively is to estimate the point density on a regular, two-dimensional grid: the number of 3D points in each grid cell projected on a plane is calculated. This works well for surfaces that do not show vertical structures. Along vertical structures, many points will be projected on the same grid cell and thus the point density rather depends on the shape of the surface but less on the quality of the model. Another approach has been applied by using the points resulting from Poisson Surface Reconstructions. One of this algorithm's properties is the filling of holes: new points are interpolated inside the holes. Using the original 3D point cloud and the interpolated Poisson point set, two analyses have been performed: For all Poisson points, the

  17. Development of solar-driven electrochemical and photocatalytic water treatment system using a boron-doped diamond electrode and TiO2 photocatalyst.

    Science.gov (United States)

    Ochiai, Tsuyoshi; Nakata, Kazuya; Murakami, Taketoshi; Fujishima, Akira; Yao, Yanyan; Tryk, Donald A; Kubota, Yoshinobu

    2010-02-01

    A high-performance, environmentally friendly water treatment system was developed. The system consists mainly of an electrochemical and a photocatalytic oxidation unit, with a boron-doped diamond (BDD) electrode and TiO(2) photocatalyst, respectively. All electric power for the mechanical systems and the electrolysis was able to be provided by photovoltaic cells. Thus, this system is totally driven by solar energy. The treatment ability of the electrolysis and photocatalysis units was investigated by phenol degradation kinetics. An observed rate constant of 5.1 x 10(-3)dm(3)cm(-2)h(-1) was calculated by pseudo-first-order kinetic analysis for the electrolysis, and a Langmuir-Hinshelwood rate constant of 5.6 microM(-1)min(-1) was calculated by kinetic analysis of the photocatalysis. According to previous reports, these values are sufficient for the mineralization of phenol. In a treatment test of river water samples, large amounts of chemical and biological contaminants were totally wet-incinerated by the system. This system could provide 12L/day of drinking water from the Tama River using only solar energy. Therefore, this system may be useful for supplying drinking water during a disaster. (c) 2009 Elsevier Ltd. All rights reserved.

  18. Effect of the deposition temperature and a hydrogen post-annealing treatment on the structural, electrical, and optical properties of Ga-doped ZnO films

    Science.gov (United States)

    Lee, Min-Jung; Lee, Tae-Il; Lim, Jinhyong; Bang, Jungsik; Lee, Woong; Lee, Taeyoon; Myoung, Jae-Min

    2009-09-01

    The combined effects of the deposition temperature and a hydrogen post-annealing treatment on the structural, electrical, and optical properties of Ga-doped ZnO (GZO) films were investigated as a potential substitute for indium tin oxide transparent conductive oxide (TCO). On the as-deposited films, increasing the deposition temperature initially improved the electrical properties, but a deposition temperature in excess of 423 K resulted in the deterioration of the electrical properties due to the development of ZnGa2O4 and Ga2O3 phases originating from the excessive amount of the Ga dopant. While a post-annealing treatment of the GZO films in hydrogen leveled off the overall properties, improvement in the electrical property was observed only in films initially deposited at room temperature. This is attributed to the excessively high concentration of the dopant Ga released from ZnGa2O4 and Ga2O3 during the post-annealing treatment. It is therefore suggested that in the preparation of TCOs based on GZO films, the concentration of the dopant Ga should be carefully controlled to obtain the optimal properties by suppressing the formation of ZnGa2O4 and Ga2O3 that occurs due to the presence of excess Ga.

  19. Electrochemical treatment of reverse osmosis concentrate on boron-doped electrodes in undivided and divided cell configurations.

    Science.gov (United States)

    Bagastyo, Arseto Y; Batstone, Damien J; Kristiana, Ina; Escher, Beate I; Joll, Cynthia; Radjenovic, Jelena

    2014-08-30

    An undivided electrolytic cell may offer lower electrochlorination through reduction of chlorine/hypochlorite at the cathode. This study investigated the performance of electrooxidation of reverse osmosis concentrate using boron-doped diamond electrodes in membrane-divided and undivided cells. In both cell configurations, similar extents of chemical oxygen demand and dissolved organic carbon removal were obtained. Continuous formation of chlorinated organic compounds was observed regardless of the membrane presence. However, halogenation of the organic matter did not result in a corresponding increase in toxicity (Vibrio fischeri bioassay performed on extracted samples), with toxicity decreasing slightly until 10AhL(-1), and generally remaining near the initial baseline-toxicity equivalent concentration (TEQ) of the raw concentrate (i.e., ∼2mgL(-1)). The exception was a high range toxicity measure in the undivided cell (i.e., TEQ=11mgL(-1) at 2.4AhL(-1)), which rapidly decreased to 4mgL(-1). The discrepancy between the halogenated organic matter and toxicity patterns may be a consequence of volatile and/or polar halogenated by-products formed in oxidation by OH electrogenerated at the anode. The undivided cell exhibited lower energy compared to the divided cell, 0.25kWhgCOD(-1) and 0.34kWhgCOD(-1), respectively, yet it did not demonstrate any improvement regarding by-products formation. Copyright © 2014 Elsevier B.V. All rights reserved.

  20. Antarctic Ozone Hole, 2000

    Science.gov (United States)

    2002-01-01

    Each spring the ozone layer over Antarctica nearly disappears, forming a 'hole' over the entire continent. The hole is created by the interaction of some man-made chemicals-freon, for example-with Antarctica's unique weather patterns and extremely cold temperatures. Ozone in the stratosphere absorbs ultraviolet radiation from the sun, thereby protecting living things. Since the ozone hole was discovered many of the chemicals that destroy ozone have been banned, but they will remain in the atmosphere for decades. In 2000, the ozone hole grew quicker than usual and exceptionally large. By the first week in September the hole was the largest ever-11.4 million square miles. The top image shows the average total column ozone values over Antarctica for September 2000. (Total column ozone is the amount of ozone from the ground to the top of the atmosphere. A relatively typical measurement of 300 Dobson Units is equivalent to a layer of ozone 0.12 inches thick on the Earth's surface. Levels below 220 Dobson Units are considered to be significant ozone depletion.) The record-breaking hole is likely the result of lower than average ozone levels during the Antarctic fall and winter, and exceptionally cold temperatures. In October, however (bottom image), the hole shrank dramatically, much more quickly than usual. By the end of October, the hole was only one-third of it's previous size. In a typical year, the ozone hole does not collapse until the end of November. NASA scientists were surprised by this early shrinking and speculate it is related to the region's weather. Global ozone levels are measured by the Total Ozone Mapping Spectrometer (TOMS). For more information about ozone, read the Earth Observatory's ozone fact sheet, view global ozone data and see these ozone images. Images by Greg Shirah, NASA GSFC Scientific Visualization Studio.

  1. Electrolyte selection and microbial toxicity for electrochemical oxidative water treatment using a boron-doped diamond anode to support site specific contamination incident response.

    Science.gov (United States)

    Phillips, Rebecca B; James, Ryan R; Magnuson, Matthew L

    2018-01-06

    Intentional and unintentional contamination incidents, such as terrorist attacks, natural disasters, and accidental spills, can result in large volumes of contaminated water. These waters may require pre-treatment before disposal and assurances that treated waters will not adversely impact biological processes at wastewater treatment facilities, or receiving waters. Based on recommendations of an industrial workgroup, this study addresses such concerns by studying electrochemical advanced oxidation process (EAOP) pre-treatment for contaminated waters, using a boron-doped diamond (BDD) anode, prior to discharge to wastewater treatment facilities. Reaction conditions were investigated, and microbial toxicity was assessed using the Microtox® toxicity assay and the Nitrification Inhibition test. A range of contaminants were studied including herbicides, pesticides, pharmaceuticals and flame retardants. Resulting toxicities varied with supporting electrolyte from 5% to 92%, often increasing, indicating that microbial toxicity, in addition to parent compound degradation, should be monitored during treatment. These toxicity results are particularly novel because they systematically compare the microbial toxicity effects of a variety of supporting electrolytes, indicating some electrolytes may not be appropriate in certain applications. Further, these results are the first known report of the use of the Nitrification Inhibition test for this application. Overall, these results systematically demonstrate that anodic oxidation using the BDD anode is useful for addressing water contaminated with refractory organic contaminants, while minimizing impacts to wastewater plants or receiving waters accepting EAOP-treated effluent. The results of this study indicate nitrate can be a suitable electrolyte for incident response and, more importantly, serve as a baseline for site specific EAOP usage. Copyright © 2018 Elsevier Ltd. All rights reserved.

  2. Comparison of black hole growth in galaxy mergers with gasoline and ramses

    OpenAIRE

    Gabor, Jared M.; Capelo, Pedro R.; Volonteri, Marta; Bournaud, Frédéric; Bellovary, Jillian; Governato, Fabio; Quinn, Thomas

    2016-01-01

    Supermassive black hole dynamics during galaxy mergers is crucial in determining the rate of black hole mergers and cosmic black hole growth. As simulations achieve higher resolution, it becomes important to assess whether the black hole dynamics is influenced by the treatment of the interstellar medium in different simulation codes. We compare simulations of black hole growth in galaxy mergers with two codes: the smoothed particle hydrodynamics code GASOLINE, and the adaptive mesh refinement...

  3. Scalarized hairy black holes

    Energy Technology Data Exchange (ETDEWEB)

    Kleihaus, Burkhard, E-mail: b.kleihaus@uni-oldenburg.de [Institut für Physik, Universität Oldenburg, Postfach 2503, D-26111 Oldenburg (Germany); Kunz, Jutta [Institut für Physik, Universität Oldenburg, Postfach 2503, D-26111 Oldenburg (Germany); Yazadjiev, Stoytcho [Department of Theoretical Physics, Faculty of Physics, Sofia University, Sofia 1164 (Bulgaria)

    2015-05-11

    In the presence of a complex scalar field scalar–tensor theory allows for scalarized rotating hairy black holes. We exhibit the domain of existence for these scalarized black holes, which is bounded by scalarized rotating boson stars and hairy black holes of General Relativity. We discuss the global properties of these solutions. Like their counterparts in general relativity, their angular momentum may exceed the Kerr bound, and their ergosurfaces may consist of a sphere and a ring, i.e., form an ergo-Saturn.

  4. Scalarized Hairy Black Holes

    CERN Document Server

    Kleihaus, Burkhard; Yazadjiev, Stoytcho

    2015-01-01

    In the presence of a complex scalar field scalar-tensor theory allows for scalarized rotating hairy black holes. We exhibit the domain of existence for these scalarized black holes, which is bounded by scalarized rotating boson stars and ordinary hairy black holes. We discuss the global properties of these solutions. Like their counterparts in general relativity, their angular momentum may exceed the Kerr bound, and their ergosurfaces may consist of a sphere and a ring, i.e., form an ergo-Saturn.

  5. Black hole uncertainties

    CERN Document Server

    Danielsson, U H

    1993-01-01

    In this work the quantum theory of two dimensional dilaton black holes is studied using the Wheeler De Witt equation. The solutions correspond to wave functions of the black hole. It is found that for an observer inside the horizon, there are uncertainty relations for the black hole mass and a parameter in the metric determining the Hawking flux. Only for a particular value of this parameter, can both be known with arbitrary accuracy. In the generic case there is instead a relation which is very similar to the so called string uncertainty relation.

  6. Black holes new horizons

    CERN Document Server

    Hayward, Sean Alan

    2013-01-01

    Black holes, once just fascinating theoretical predictions of how gravity warps space-time according to Einstein's theory, are now generally accepted as astrophysical realities, formed by post-supernova collapse, or as supermassive black holes mysteriously found at the cores of most galaxies, powering active galactic nuclei, the most powerful objects in the universe. Theoretical understanding has progressed in recent decades with a wider realization that local concepts should characterize black holes, rather than the global concepts found in textbooks. In particular, notions such as trapping h

  7. Scalarized hairy black holes

    Directory of Open Access Journals (Sweden)

    Burkhard Kleihaus

    2015-05-01

    Full Text Available In the presence of a complex scalar field scalar–tensor theory allows for scalarized rotating hairy black holes. We exhibit the domain of existence for these scalarized black holes, which is bounded by scalarized rotating boson stars and hairy black holes of General Relativity. We discuss the global properties of these solutions. Like their counterparts in general relativity, their angular momentum may exceed the Kerr bound, and their ergosurfaces may consist of a sphere and a ring, i.e., form an ergo-Saturn.

  8. Structural and electrical characterization of zinc oxide doped with antimony

    Directory of Open Access Journals (Sweden)

    G. Juárez Díaz

    2014-08-01

    Full Text Available In this work we report the results of structural and electrical characterization realized on zinc oxide single crystal samples with (001 orientation, which were doped with antimony. Doping was carried out by antimony thermal diffusion at 1000 °C for periods of 1 and 2 hours under nitrogen environment from a solid source formed by antimony oxide. Electrical characterization by I-V curves and Hall effect shown an increase in acceptor concentration which demonstrates that doping is effective and create holes in zinc oxide samples.

  9. Electronic Strengthening of Graphene by Charge Doping

    Science.gov (United States)

    Si, Chen; Liu, Zheng; Duan, Wenhui; Liu, Feng

    2013-03-01

    Graphene is known as the strongest 2D material in nature, yet we show that moderate charge doping of either electrons or holes can further enhance its ideal strength by up to ~17%, based on first principles calculations. This unusual electronic enhancement, versus conventional structural enhancement, of material's strength is achieved by an intriguing physical mechanism of charge doping counteracting on strain induced enhancement of Kohn anomaly, which leads to an overall stiffening of zone boundary K1 phonon mode whose softening under strain is responsible for graphene failure. Electrons and holes work in the same way due to the high electron-hole symmetry around the Dirac point of graphene, while over doping may weaken the graphene by softening other phonon modes. Our findings uncover another fascinating property of graphene with broad implications in graphene-based electromechanical devices. The work is support by DOE-BES program. C.S. thanks Tsinghua exchange student fund for supporting her visit at U. of Utah. W. D. thanks support by the Ministry of Science and Technology of China

  10. Electrochemical treatment of reverse osmosis concentrate on boron-doped electrodes in undivided and divided cell configurations

    Energy Technology Data Exchange (ETDEWEB)

    Bagastyo, Arseto Y. [Advanced Water Management Centre, The University of Queensland, St Lucia, QLD 4072 (Australia); Department of Environmental Engineering, Institut Teknologi Sepuluh Nopember, Surabaya 60111 (Indonesia); Batstone, Damien J. [Advanced Water Management Centre, The University of Queensland, St Lucia, QLD 4072 (Australia); Kristiana, Ina [Curtin Water Quality Research Centre, Resources and Chemistry Precinct, Department of Chemistry, Curtin University, Bentley, Perth, WA 6102 (Australia); Escher, Beate I. [National Research Centre for Environmental Toxicology (Entox), The University of Queensland, Brisbane, QLD 4108 (Australia); Joll, Cynthia [Curtin Water Quality Research Centre, Resources and Chemistry Precinct, Department of Chemistry, Curtin University, Bentley, Perth, WA 6102 (Australia); Radjenovic, Jelena, E-mail: j.radjenovic@uq.edu.au [Advanced Water Management Centre, The University of Queensland, St Lucia, QLD 4072 (Australia)

    2014-08-30

    Highlights: • 100% of COD and ∼70% of DOC was removed in both cell configurations. • ∼21.7 mg L{sup −1} of AOCl and ∼2.3 mg L{sup −1} of AOBr was formed regardless of the membrane use. • The TEQ was far lower than expected given the high AOCl concentrations. • The undivided cell consumed lower energy compared to the divided cell. - Abstract: An undivided electrolytic cell may offer lower electrochlorination through reduction of chlorine/hypochlorite at the cathode. This study investigated the performance of electrooxidation of reverse osmosis concentrate using boron-doped diamond electrodes in membrane-divided and undivided cells. In both cell configurations, similar extents of chemical oxygen demand and dissolved organic carbon removal were obtained. Continuous formation of chlorinated organic compounds was observed regardless of the membrane presence. However, halogenation of the organic matter did not result in a corresponding increase in toxicity (Vibrio fischeri bioassay performed on extracted samples), with toxicity decreasing slightly until 10 Ah L{sup −1}, and generally remaining near the initial baseline-toxicity equivalent concentration (TEQ) of the raw concentrate (i.e., ∼2 mg L{sup −1}). The exception was a high range toxicity measure in the undivided cell (i.e., TEQ = 11 mg L{sup −1} at 2.4 Ah L{sup −1}), which rapidly decreased to 4 mg L{sup −1}. The discrepancy between the halogenated organic matter and toxicity patterns may be a consequence of volatile and/or polar halogenated by-products formed in oxidation by OH· electrogenerated at the anode. The undivided cell exhibited lower energy compared to the divided cell, 0.25 kWh gCOD{sup −1} and 0.34 kWh gCOD{sup −1}, respectively, yet it did not demonstrate any improvement regarding by-products formation.

  11. Black Hole Shadows of Charged Spinning Black Holes

    OpenAIRE

    Takahashi, Rohta

    2005-01-01

    We propose a method for measuring the black hole charge by imaging a black hole shadow in a galactic center by future interferometers. Even when the black hole is uncharged, it is possible to confirm the charge neutrality by this method. We first derive the analytic formulae of the black hole shadow in an optically thin medium around a charged spinning black hole, and then investigate how contours of the black hole shadow depend on the spin and the charge of the black hole for several inclina...

  12. Black holes with halos

    Science.gov (United States)

    Monten, Ruben; Toldo, Chiara

    2018-02-01

    We present new AdS4 black hole solutions in N =2 gauged supergravity coupled to vector and hypermultiplets. We focus on a particular consistent truncation of M-theory on the homogeneous Sasaki–Einstein seven-manifold M 111, characterized by the presence of one Betti vector multiplet. We numerically construct static and spherically symmetric black holes with electric and magnetic charges, corresponding to M2 and M5 branes wrapping non-contractible cycles of the internal manifold. The novel feature characterizing these nonzero temperature configurations is the presence of a massive vector field halo. Moreover, we verify the first law of black hole mechanics and we study the thermodynamics in the canonical ensemble. We analyze the behavior of the massive vector field condensate across the small-large black hole phase transition and we interpret the process in the dual field theory.

  13. Blue Holes & Hurricanes

    National Research Council Canada - National Science Library

    David Levin

    2017-01-01

    A blue hole in the ocean is a striking sight. Fly over remote areas of the Caribbean Sea and you'll see shallow turquoise water stretching for miles, interrupted only by occasional sand bars and coral reefs...

  14. Illuminating black holes

    Science.gov (United States)

    Barr, Ian A.; Bull, Anne; O'Brien, Eileen; Drillsma-Milgrom, Katy A.; Milgrom, Lionel R.

    2016-07-01

    Two-dimensional shadows formed by illuminating vortices are shown to be visually analogous to the gravitational action of black holes on light and surrounding matter. They could be useful teaching aids demonstrating some of the consequences of general relativity.

  15. Nonsingular black hole

    Science.gov (United States)

    Chamseddine, Ali H.; Mukhanov, Viatcheslav

    2017-03-01

    We consider the Schwarzschild black hole and show how, in a theory with limiting curvature, the physical singularity "inside it" is removed. The resulting spacetime is geodesically complete. The internal structure of this nonsingular black hole is analogous to Russian nesting dolls. Namely, after falling into the black hole of radius rg, an observer, instead of being destroyed at the singularity, gets for a short time into the region with limiting curvature. After that he re-emerges in the near horizon region of a spacetime described by the Schwarzschild metric of a gravitational radius proportional to rg^{1/3}. In the next cycle, after passing the limiting curvature, the observer finds himself within a black hole of even smaller radius proportional to rg^{1/9}, and so on. Finally after a few cycles he will end up in the spacetime where he remains forever at limiting curvature.

  16. Black hole quantum spectrum

    National Research Council Canada - National Science Library

    Corda, Christian

    2013-01-01

    Introducing a black hole (BH) effective temperature, which takes into account both the non-strictly thermal character of Hawking radiation and the countable behavior of emissions of subsequent Hawking quanta, we recently re...

  17. Holographic black hole chemistry

    National Research Council Canada - National Science Library

    Karch, Andreas; Robinson, Brandon

    2015-01-01

    Thermodynamic quantities associated with black holes in Anti-de Sitter space obey an interesting identity when the cosmological constant is included as one of the dynamical variables, the generalized Smarr relation...

  18. Doping location-dependent energy transfer dynamics in Mn-doped CdS/ZnS nanocrystals.

    Science.gov (United States)

    Chen, Hsiang-Yun; Maiti, Sourav; Son, Dong Hee

    2012-01-24

    Dynamics of energy transfer and charge carrier localization in Mn-doped CdS/ZnS core/shell nanocrystals correlated with doping location and concentration are studied via transient absorption measurement of exciton relaxation dynamics. The strong dependence of exciton-Mn energy transfer rate on doping location was directly resolved in the transient bleach recovery and electron intraband absorption data by using layer-by-layer synthesized Mn-doped nanocrystals. With 1.2 nm decrease in doping radius in the ZnS shell, energy transfer rate increases by 6 fold. We identified that hole trapping is the major competing process that inhibits the energy transfer in Mn-doped CdS/ZnS nanocrystals. From the branching ratio of the energy transfer and hole trapping, combined with luminescence quantum yield measurement, we also obtained doping location-dependent radiative relaxation quantum yield of Mn(2+) ions that is as high as 0.95. © 2011 American Chemical Society

  19. Charged Galileon black holes

    Energy Technology Data Exchange (ETDEWEB)

    Babichev, Eugeny; Charmousis, Christos [Laboratoire de Physique Théorique (LPT), Univ. Paris-Sud, CNRS UMR 8627, F-91405 Orsay (France); Hassaine, Mokhtar, E-mail: eugeny.babichev@th.u-psud.fr, E-mail: christos.charmousis@th.u-psud.fr, E-mail: hassaine@inst-mat.utalca.cl [Instituto de Matemática y Física, Universidad de Talca, Casilla 747, Talca (Chile)

    2015-05-01

    We consider an Abelian gauge field coupled to a particular truncation of Horndeski theory. The Galileon field has translation symmetry and couples non minimally both to the metric and the gauge field. When the gauge-scalar coupling is zero the gauge field reduces to a standard Maxwell field. By taking into account the symmetries of the action, we construct charged black hole solutions. Allowing the scalar field to softly break symmetries of spacetime we construct black holes where the scalar field is regular on the black hole event horizon. Some of these solutions can be interpreted as the equivalent of Reissner-Nordstrom black holes of scalar tensor theories with a non trivial scalar field. A self tuning black hole solution found previously is extended to the presence of dyonic charge without affecting whatsoever the self tuning of a large positive cosmological constant. Finally, for a general shift invariant scalar tensor theory we demonstrate that the scalar field Ansatz and method we employ are mathematically compatible with the field equations. This opens up the possibility for novel searches of hairy black holes in a far more general setting of Horndeski theory.

  20. Screening dynamics in doped titanates

    Energy Technology Data Exchange (ETDEWEB)

    Rubensson, J.E.; Luening, J.; Eisebitt, S. [Forschungszentrum Juelich (Germany)] [and others

    1997-04-01

    The time scale for carrier relaxation in semiconductors is on the same order of magnitude as the life time of shallow core hole states (a few femtoseconds). Resonant Inelastic soft X-ray scattering (RIXS) which involves (virtual) excitations of core levels consequently contains information about the time development of the electronic structure on this time scale. In many cases one can treat the scattering in an absorption (SXA) followed-by-emission (SXE) picture, where simply the rates for various processes can be compared with the intermediate core hole state decay rate as an internal {open_quotes}clock{close_quotes}. By variation of x (0 < x < 1) in La{sub x}Sr{sub 1{minus}x}TiO{sub 3}, the amount of Ti d electrons in the system can be controlled. SrTiO{sub 3} (x=0) is an insulator with an empty Ti d band. With increasing x, electrons are doped into the Ti d-band, and LaTiO{sub 3} (x=1) is a Mott Hubbard insulator with a Ti 3d{sup 1} configuration. In this work the authors demonstrate that the rate for Ti 2p core hole screening in La{sub x}Sr{sub 1{minus}x}TiO{sub 3} is doping dependent. The screening rate increases with the availability of Ti 3d electrons, and they estimate it to be 3.8 x 10{sup 13}/sec in La{sub 0.05}Sr{sub 0.95}TiO{sub 3}.

  1. The Thermodynamics of Black Holes

    Directory of Open Access Journals (Sweden)

    Wald Robert M.

    2001-01-01

    Full Text Available We review the present status of black hole thermodynamics. Our review includes discussion of classical black hole thermodynamics, Hawking radiation from black holes, the generalized second law, and the issue of entropy bounds. A brief survey also is given of approaches to the calculation of black hole entropy. We conclude with a discussion of some unresolved open issues.

  2. Exploring plasmonic coupling in hole-cap arrays

    OpenAIRE

    Schmidt, Thomas M.; Maj Frederiksen; Vladimir Bochenkov; Duncan S. Sutherland

    2015-01-01

    Summary The plasmonic coupling between gold caps and holes in thin films was investigated experimentally and through finite-difference time-domain (FDTD) calculations. Sparse colloidal lithography combined with a novel thermal treatment was used to control the vertical spacing between caps and hole arrays and compared to separated arrays of holes or caps. Optical spectroscopy and FDTD simulations reveal strong coupling between the gold caps and both Bloch Wave-surface plasmon polariton (BW-SP...

  3. Coherent quasi-particles-to-incoherent hole-carriers crossover in underdoped cuprates

    OpenAIRE

    Hashimoto, M.; Yoshida, T.; Tanaka, K.; Fujimori, A.; Okusawa, M.; Wakimoto, S.; K. Yamada; Kakeshita, T.; Eisaki, H.; Uchida, S.

    2008-01-01

    In underdoped cuprates, only a portion of the Fermi surface survives as Fermi arcs due to pseudogap opening. In hole-doped La$_{2}$CuO$_4$, we have deduced the "coherence temperature" $T_{coh}$ of quasi-particles on the Fermi arc above which the broadened leading edge position in angle-integrated photoemission spectra is shifted away from the Fermi level and the quasi-particle concept starts to lose its meaning. $T_{coh}$ is found to rapidly increase with hole doping, an opposite behavior to ...

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

    CERN Document Server

    Long Tao; Zhang Guo Yi

    2001-01-01

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

  5. A simple preparation method and characterization of B and N co-doped TiO2 nanotube arrays with enhanced photoelectrochemical performance

    Science.gov (United States)

    Georgieva, J.; Valova, E.; Armyanov, S.; Tatchev, D.; Sotiropoulos, S.; Avramova, I.; Dimitrova, N.; Hubin, A.; Steenhaut, O.

    2017-08-01

    Highly ordered TiO2 nanotube arrays (TNTA) have attracted much attention due to the excellent photocatalytic, optical and electrical properties. However, their absorption range is limited to ultraviolet (UV) spectrum only due to the wide band gap (3.2 eV). One of the strategies to overcome this problem is doping with boron and nitrogen. They are produced via titanium sheet anodization and subsequent electrochemical treatment of titania in an electrolyte containing boric acid. The as-prepared B-TNTA are annealed in N2 atmosphere at 500 °C for 2 h to obtain B,N-TNTA. The samples are characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), UV-vis diffuse reflectance spectroscopy (DRS) and X-ray photoelectron spectroscopy (XPS). The B,N-TNTA consist of uniform and well aligned nanotubes with an average inner diameter of 80-100 nm and a length not exceeding 1 μm. The photocurrent response measurements of undoped TNTA, N-doped and B,N-co-doped samples are performed under UV and visible light (Vis) illumination and a comparison is made. The obtained results show that the B,N-doping leads to remarkable photocurrent enhancement and better photocatalytic activity for methyl orange (MO) degradation due to the synergistic effects of B,N-co-doping and lower electron-hole recombination rates.

  6. Hole induced spin polarons in LaCoO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Alfonsov, A.; Kataev, V.; Buechner, B. [IFW Dresden, D-01171 Dresden (Germany); Vavilova, E. [IFW Dresden, D-01171 Dresden (Germany); Zavoisky Physical Technical Institute, RAS, 420029 Kazan (Russian Federation); Podlesnyak, A. [Oak Ridge National Laboratory, P.O. BOX 2008 MS6494, Oak Ridge, TN 37831-6494 (United States); Khomskii, D.I. [II. Physikalisches Institut, Universitaet Koeln, 50937 Koeln (Germany)

    2010-07-01

    We report a comparative high field electron spin- (ESR), nuclear magnetic resonance (NMR) and static magnetization study of lightly hole-doped samples of La{sub 0.998}Sr{sub 0.002}CoO{sub 3} and La{sub 0.998}Ca{sub 0.002}CoO{sub 3}. We have shown before that small Sr doping of LaCoO{sub 3} yields the spin-state polaron with a big spin value and large spin orbital coupling. The Ca{sup 2+} ion, in contrast to the Sr{sup 2+} ion, has almost the same ionic radii as the La{sup 3+} ion. Therefore, the substitution of Ca for La provides mainly a hole to the system without creating a sizeable crystal field distortion around the substituted Ca ion. This difference enables us to ascertain the roles of the introduced hole and the created crystal field distortion in the formation of the spin polarons. The data obtained on Ca and Sr doped LaCoO{sub 3} samples provide experimental evidence that the introduced hole indeed plays the main role. We discuss a model of the formation of big spin polarons in LaCoO{sub 3} due to a very small hole doping.

  7. Minority carrier diffusion lengths and mobilities in low-doped n-InGaAs for focal plane array applications

    National Research Council Canada - National Science Library

    Walker, Alexandre William; Denhoff, Michael W

    2017-01-01

    The hole diffusion length in n-InGaAs is extracted for two samples of different doping concentrations using a set of long and thin diffused junction diodes separated by various distances on the order...

  8. Black holes and beyond

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2002-02-01

    Belief in the existence of black holes is the ultimate act of faith for a physicist. First suggested by the English clergyman John Michell in the year 1784, the gravitational pull of a black hole is so strong that nothing - not even light - can escape. Gravity might be the weakest of the fundamental forces but black-hole physics is not for the faint-hearted. Black holes present obvious problems for would-be observers because they cannot, by definition, be seen with conventional telescopes - although before the end of the decade gravitational-wave detectors should be able to study collisions between black holes. Until then astronomers can only infer the existence of a black hole from its gravitational influence on other matter, or from the X-rays emitted by gas and dust as they are dragged into the black hole. However, once this material passes through the 'event horizon' that surrounds the black hole, we will never see it again - not even with X-ray specs. Despite these observational problems, most physicists and astronomers believe that black holes do exist. Small black holes a few kilometres across are thought to form when stars weighing more than about two solar masses collapse under the weight of their own gravity, while supermassive black holes weighing millions of solar masses appear to be present at the centre of most galaxies. Moreover, some brave physicists have proposed ways to make black holes - or at least event horizons - in the laboratory. The basic idea behind these 'artificial black holes' is not to compress a large amount of mass into a small volume, but to reduce the speed of light in a moving medium to less than the speed of the medium and so create an event horizon. The parallels with real black holes are not exact but the experiments could shed new light on a variety of phenomena. The first challenge, however, is to get money for the research. One year on from a high-profile meeting on artificial black holes in London, for

  9. ⁶⁴Cu-Doped PdCu@Au Tripods: A Multifunctional Nanomaterial for Positron Emission Tomography and Image-Guided Photothermal Cancer Treatment.

    Science.gov (United States)

    Pang, Bo; Zhao, Yongfeng; Luehmann, Hannah; Yang, Xuan; Detering, Lisa; You, Meng; Zhang, Chao; Zhang, Lei; Li, Zhi-Yuan; Ren, Qiushi; Liu, Yongjian; Xia, Younan

    2016-03-22

    This article reports a facile synthesis of radiolabeled PdCu@Au core-shell tripods for use in positron emission tomography (PET) and image-guided photothermal cancer treatment by directly incorporating radioactive (64)Cu atoms into the crystal lattice. The tripod had a unique morphology determined by the PdCu tripod that served as a template for the coating of Au shell, in addition to well-controlled specific activity and physical dimensions. The Au shell provided the nanostructure with strong absorption in the near-infrared region and effectively prevented the Cu and (64)Cu atoms in the core from oxidization and dissolution. When conjugated with D-Ala1-peptide T-amide (DAPTA), the core-shell tripods showed great enhancement in targeting the C-C chemokine receptor 5 (CCR5), a newly identified theranostic target up-regulated in triple negative breast cancer (TNBC). Specifically, the CCR5-targeted tripods with an arm length of about 45 nm showed 2- and 6-fold increase in tumor-to-blood and tumor-to-muscle uptake ratios, respectively, relative to their nontargeted counterpart in an orthotopic mouse 4T1 TNBC model at 24 h postinjection. The targeting specificity was further validated via a competitive receptor blocking study. We also demonstrated the use of these targeted, radioactive tripods for effective photothermal treatment in the 4T1 tumor model as guided by PET imaging. The efficacy of treatment was confirmed by the significant reduction in tumor metabolic activity revealed through the use of (18)F-fluorodeoxyglucose PET/CT imaging. Taken together, we believe that the (64)Cu-doped PdCu@Au tripods could serve as a multifunctional platform for both PET imaging and image-guided photothermal cancer therapy.

  10. Effect of Cl2 plasma treatment and annealing on vanadium based metal contacts to Si-doped Al0.75Ga0.25N

    Science.gov (United States)

    Lapeyrade, Mickael; Alamé, Sabine; Glaab, Johannes; Mogilatenko, Anna; Unger, Ralph-Stephan; Kuhn, Christian; Wernicke, Tim; Vogt, Patrick; Knauer, Arne; Zeimer, Ute; Einfeldt, Sven; Weyers, Markus; Kneissl, Michael

    2017-09-01

    In order to understand the electrical properties of V/Al/Ni/Au metal contacts to Si-doped Al0.75Ga0.25N layers, X-ray photoelectron spectroscopy analysis was performed on differently treated AlGaN:Si surfaces before metal deposition, and transmission electron microscopy was used to study the semiconductor-metal interface after contact annealing at 900 °C. Cl2 plasma etching of AlGaN increases the aluminum/nitrogen ratio at the surface, and Al oxide or oxynitride is always formed by any surface treatment applied after etching. After contact annealing, a complex interface structure including amorphous AlOx and different metal phases such as Al-Au-Ni, V-Al, and V2N were found. The electrical properties of the contacts were determined by thermionic emission and/or thermionic field emission in the low voltage regime. Nearly ohmic contacts on AlGaN surfaces exposed to a Cl2 plasma were only obtained by annealing the sample at a temperature of 815 °C under N2/NH3 prior to metallization. By this treatment, the oxygen contamination on the surface could be minimized, resulting in a larger semiconductor area to be in direct contact with metal phases such as Al-rich Al-Au-Ni or V-Al and leading to a contact resistivity of 2.5 × 10-2 Ω cm2. This treatment can be used to significantly reduce the operating voltage of current deep ultraviolet light emitting diodes which will increase their wall plug efficiency and lower the thermal stress during their operation.

  11. Effect of combination dope composition and evaporation time on the separation performance of cellulose acetate membrane for demak brackish water treatment

    Directory of Open Access Journals (Sweden)

    Kusworo Tutuk Djoko

    2017-01-01

    Full Text Available The coastal areas in Indonesia often have a problem of clean water lack, because the water is classified as brackish water. Therefore, this research investigated the fabrication of CA membranes using phase inversion method for brackish water treatment. Investigation was conducted to study the effect of combination dope composition and evaporation time on separation performance and morphology of the memrbane. Membrane was fabricated by dry-wet phase inversion technique with variation of polymer concentration 17, 18 and 20 wt% in the total solid and evaporation time of 5, 10 and 15 seconds, respectively. The asymmetric membranes were characterized by permeability test through rejection and flux measurements using brackish water as feed. The experimental results from SEM images analysis showed that all the membranes have a thin small porous layer and thicker sub-structure of larger porous layer formed asymmetric membrane. Moreover, the greater polymer concentration is resulting smaller pore size and smaller membrane porosity. The longer evaporation time was also resulted in denser membrane active layer. The best membrane performance was observed at the composition of 20 wt% CA polymer, 1 wt % polyethylene glycol with the solvent evaporation time of 15 seconds.

  12. Stable Organic Radicals as Hole Injection Dopants for Efficient Optoelectronics.

    Science.gov (United States)

    Bin, Zhengyang; Guo, Haoqing; Liu, Ziyang; Li, Feng; Duan, Lian

    2018-02-07

    Precursors of reactive organic radicals have been widely used as n-dopants in electron-transporting materials to improve electron conductivity and enhance electron injection. However, the utilization of organic radicals in hole counterparts has been ignored. In this work, stable organic radicals have been proved for the first time to be efficient dopants to enhance hole injection. From the absorbance spectra and the ultraviolet photoelectron spectra, we could observe an efficient electron transfer between the organic radical, (4-N-carbazolyl-2,6-dichlorophenyl)bis(2,4,6-trichlorophenyl)methyl (TTM-1Cz), and the widely used hole injection material, 1,4,5,8,9,11-hexaazatriphenylene hexacarbonitrile (HAT-CN). When the unpaired electron of TTM-1Cz is transferred to HAT-CN, it would be oxidized to a TTM-1Cz cation with a newly formed lowest unoccupied molecular orbital which is quite close to the highest occupied molecular orbital (HOMO) of the hole-transporting material (HTM). In this way, the TTM-1Cz cation would promote the electron extraction from the HOMO of the HTM and improve hole injection. Using TTM-1Cz-doped HAT-CN as the hole injection layer, efficient organic light-emitting diodes with extremely low voltages can be attained.

  13. Merging Black Holes

    Science.gov (United States)

    Centrella, John

    2009-01-01

    The final merger of two black holes is expected to be the strongest gravitational wave source for ground-based interferometers such as LIGO, VIRGO, and GEO600, as well as the space-based LISA. Observing these sources with gravitational wave detectors requires that we know the radiation waveforms they emit. And, when the black holes merge in the presence of gas and magnetic fields, various types of electromagnetic signals may also be produced. Since these mergers take place in regions of extreme gravity, we need to solve Einstein's equations of general relativity on a computer. For more than 30 years, scientists have tried to compute black hole mergers using the methods of numerical relativity. The resulting computer codes have been plagued by instabilities, causing them to crash well before the black holes in the binary could complete even a single orbit. Within the past few years, however, this situation has changed dramatically, with a series of remarkable breakthroughs. This talk will focus on new simulations that are revealing the dynamics and waveforms of binary black hole mergers, and their applications in gravitational wave detection, testing general relativity, and astrophysics.

  14. Scanning photocurrent microscopy reveals electron-hole asymmetry in ionic liquid-gated WS{sub 2} transistors

    Energy Technology Data Exchange (ETDEWEB)

    Ubrig, Nicolas, E-mail: nicolas.ubrig@unige.ch; Kuzmenko, Alexey B., E-mail: Alexey.Kuzmenko@unige.ch [DPMC, Université de Genève, 24 quai Ernest Ansermet, CH-1211 Geneva (Switzerland); Jo, Sanghyun; Morpurgo, Alberto F. [DPMC, Université de Genève, 24 quai Ernest Ansermet, CH-1211 Geneva (Switzerland); GAP, Université de Genève, 24 quai Ernest Ansermet, CH-1211 Geneva (Switzerland); Berger, Helmuth [Institut de Physique de la Matière Condendée, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne (Switzerland)

    2014-04-28

    We perform scanning photocurrent microscopy on WS{sub 2} ionic liquid-gated field effect transistors exhibiting high-quality ambipolar transport. By properly biasing the gate electrode, we can invert the sign of the photocurrent showing that the minority photocarriers are either electrons or holes. Both in the electron- and hole-doping regimes the photocurrent decays exponentially as a function of the distance between the illumination spot and the nearest contact, in agreement with a two-terminal Schottky-barrier device model. This allows us to compare the value and the doping dependence of the diffusion length of the minority electrons and holes on a same sample. Interestingly, the diffusion length of the minority carriers is several times larger in the hole accumulation regime than in the electron accumulation regime, pointing out an electron-hole asymmetry in WS{sub 2}.

  15. Entropy spectrum of (1+1) dimensional stringy black holes

    Energy Technology Data Exchange (ETDEWEB)

    Suresh, Jishnu; Kuriakose, V.C. [Cochin University of Science and Technology, Department of Physics, Cochin, Kerala (India)

    2015-05-15

    We explore the entropy spectrum of (1+1) dimensional dilatonic stringy black holes via the adiabatic invariant integral method known as Jiang and Han's method (Phys Lett B 718:584, 2012) and the Bohr-Sommerfeld quantization rule. It is found that the corresponding spectrum depends on black hole parameters like charge, ADM mass, and, more interestingly, on the dilatonic field. We calculate the entropy of the present black hole system via the Euclidean treatment of quantum gravity and study the thermodynamics of the black hole and find that the system does not undergo any phase transition. (orig.)

  16. Black hole gravitohydromagnetics

    CERN Document Server

    Punsly, Brian

    2008-01-01

    Black hole gravitohydromagnetics (GHM) is developed from the rudiments to the frontiers of research in this book. GHM describes plasma interactions that combine the effects of gravity and a strong magnetic field, in the vicinity (ergosphere) of a rapidly rotating black hole. This topic was created in response to the astrophysical quest to understand the central engines of radio loud extragalactic radio sources. The theory describes a "torsional tug of war" between rotating ergospheric plasma and the distant asymptotic plasma that extracts the rotational inertia of the black hole. The recoil from the struggle between electromagnetic and gravitational forces near the event horizon is manifested as a powerful pair of magnetized particle beams (jets) that are ejected at nearly the speed of light. These bipolar jets feed large-scale magnetized plasmoids on scales as large as millions of light years (the radio lobes of extragalactic radio sources). This interaction can initiate jets that transport energy fluxes exc...

  17. Merging Black Holes

    Science.gov (United States)

    Centrella, Joan

    2012-01-01

    The final merger of two black holes is expected to be the strongest source of gravitational waves for both ground-based detectors such as LIGO and VIRGO, as well as future. space-based detectors. Since the merger takes place in the regime of strong dynamical gravity, computing the resulting gravitational waveforms requires solving the full Einstein equations of general relativity on a computer. For many years, numerical codes designed to simulate black hole mergers were plagued by a host of instabilities. However, recent breakthroughs have conquered these instabilities and opened up this field dramatically. This talk will focus on.the resulting 'gold rush' of new results that is revealing the dynamics and waveforms of binary black hole mergers, and their applications in gravitational wave detection, testing general relativity, and astrophysics

  18. Black-hole astrophysics

    Energy Technology Data Exchange (ETDEWEB)

    Bender, P. [Univ. of Colorado, Boulder, CO (United States); Bloom, E. [Stanford Linear Accelerator Center, Menlo Park, CA (United States); Cominsky, L. [Sonoma State Univ., Rohnert Park, CA (United States). Dept. of Physics and Astronomy] [and others

    1995-07-01

    Black-hole astrophysics is not just the investigation of yet another, even if extremely remarkable type of celestial body, but a test of the correctness of the understanding of the very properties of space and time in very strong gravitational fields. Physicists` excitement at this new prospect for testing theories of fundamental processes is matched by that of astronomers at the possibility to discover and study a new and dramatically different kind of astronomical object. Here the authors review the currently known ways that black holes can be identified by their effects on their neighborhood--since, of course, the hole itself does not yield any direct evidence of its existence or information about its properties. The two most important empirical considerations are determination of masses, or lower limits thereof, of unseen companions in binary star systems, and measurement of luminosity fluctuations on very short time scales.

  19. Ozone Hole Over Antarctica

    Science.gov (United States)

    2002-01-01

    These images from the Total Ozone Mapping Spectrometer (TOMS) show the progressive depletion of ozone over Antarctica from 1979 to 1999. This 'ozone hole' has extended to cover an area as large as 10.5 million square miles in September 1998. The previous record of 10.0 million square miles was set in 1996. The Antarctic ozone hole develops each year between late August and early October. Regions with higher levels of ozone are shown in red. NASA and NOAA instruments have been measuring Antarctic ozone levels since the early 1970s. Large regions of depleted ozone began to develop over Antarctica in the early 1980s. Ozone holes of substantial size and depth are likely to continue to form during the next few years, scientists hope to see a reduction in ozone loss as levels of ozone-destroying CFCs (chlorofluorocarbons) are gradually reduced. Credit: Images by Greg Shirah, NASA Goddard Space Flight Center Scientific Visualization Studio

  20. Turbulent black holes.

    Science.gov (United States)

    Yang, Huan; Zimmerman, Aaron; Lehner, Luis

    2015-02-27

    We demonstrate that rapidly spinning black holes can display a new type of nonlinear parametric instability-which is triggered above a certain perturbation amplitude threshold-akin to the onset of turbulence, with possibly observable consequences. This instability transfers from higher temporal and azimuthal spatial frequencies to lower frequencies-a phenomenon reminiscent of the inverse cascade displayed by (2+1)-dimensional fluids. Our finding provides evidence for the onset of transitory turbulence in astrophysical black holes and predicts observable signatures in black hole binaries with high spins. Furthermore, it gives a gravitational description of this behavior which, through the fluid-gravity duality, can potentially shed new light on the remarkable phenomena of turbulence in fluids.

  1. Braneless Black Holes

    Energy Technology Data Exchange (ETDEWEB)

    Rajaraman, Arvind

    2003-06-02

    It is known that the naive version of D-brane theory is inadequate to explain the black hole entropy in the limit in which the Schwarzschild radius becomes larger than all compactification radii. We present evidence that a more consistent description can be given in terms of strings with rescaled tensions. We show that the rescaling can be interpreted as a redshift of the tension of a fundamental string in the gravitational field of the black hole. An interesting connection is found between the string level number and the Rindler energy. Using this connection, we reproduce the entropies of Schwarzschild black holes in arbitrary dimensions in terms of the entropy of a single string at the Hagedorn temperature.

  2. Study of sterilization-treatment in pure and N- doped carbon thin films synthesized by inductively coupled plasma assisted pulsed-DC magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Javid, Amjed [Center for Advanced Plasma Surface Technology (CAPST), NU-SKKU Joint Institute for Plasma Nano-Materials (IPNM), Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Department of Textile Processing, National Textile University, Faisalabad 37610 (Pakistan); Kumar, Manish, E-mail: manishk@skku.edu [Center for Advanced Plasma Surface Technology (CAPST), NU-SKKU Joint Institute for Plasma Nano-Materials (IPNM), Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Han, Jeon Geon, E-mail: hanjg@skku.edu [Center for Advanced Plasma Surface Technology (CAPST), NU-SKKU Joint Institute for Plasma Nano-Materials (IPNM), Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of)

    2017-01-15

    Highlights: • Pure and N-doped nanocrystallie carbon films are synthesized by ICP assisted pulsed DC plasma process. • ICP power induces the increase in average graphitic crystallite size from 4.86 nm to 6.42 nm. • Beneficial role of ICP source assistance to achieve high sputtering throughput (deposition rate ∼55 nm/min). • Post-sterilization electron-transport study shows N-doped carbon films having promising stability. - Abstract: Electrically-conductive nanocrystalline carbon films, having non-toxic and non-immunogenic characteristics, are promising candidates for reusable medical devices. Here, the pure and N- doped nanocrystalline carbon films are deposited by the assistance of inductively coupled plasma (ICP) in an unbalanced facing target pulsed-DC magnetron sputtering process. Through the optical emission spectroscopy study, the role of ICP assistance and N-doping on the reactive components/radicals during the synthesis is presented. The N-doping enhances the three fold bonding configurations by increasing the ionization and energies of the plasma species. Whereas, the ICP addition increases the plasma density to control the deposition rate and film structure. As a result, sputtering-throughput (deposition rate: 31–55 nm/min), electrical resistivity (4–72 Ωcm) and water contact angle (45.12°–54°) are significantly tailored. Electric transport study across the surface microchannel confirms the superiority of N-doped carbon films for sterilization stability over the undoped carbon films.

  3. Characterizing Black Hole Mergers

    Science.gov (United States)

    Baker, John; Boggs, William Darian; Kelly, Bernard

    2010-01-01

    Binary black hole mergers are a promising source of gravitational waves for interferometric gravitational wave detectors. Recent advances in numerical relativity have revealed the predictions of General Relativity for the strong burst of radiation generated in the final moments of binary coalescence. We explore features in the merger radiation which characterize the final moments of merger and ringdown. Interpreting the waveforms in terms of an rotating implicit radiation source allows a unified phenomenological description of the system from inspiral through ringdown. Common features in the waveforms allow quantitative description of the merger signal which may provide insights for observations large-mass black hole binaries.

  4. Magnonic Black Holes

    Science.gov (United States)

    Roldán-Molina, A.; Nunez, Alvaro S.; Duine, R. A.

    2017-02-01

    We show that the interaction between the spin-polarized current and the magnetization dynamics can be used to implement black-hole and white-hole horizons for magnons—the quanta of oscillations in the magnetization direction in magnets. We consider three different systems: easy-plane ferromagnetic metals, isotropic antiferromagnetic metals, and easy-plane magnetic insulators. Based on available experimental data, we estimate that the Hawking temperature can be as large as 1 K. We comment on the implications of magnonic horizons for spin-wave scattering and transport experiments, and for magnon entanglement.

  5. Superfluid Black Holes.

    Science.gov (United States)

    Hennigar, Robie A; Mann, Robert B; Tjoa, Erickson

    2017-01-13

    We present what we believe is the first example of a "λ-line" phase transition in black hole thermodynamics. This is a line of (continuous) second order phase transitions which in the case of liquid ^{4}He marks the onset of superfluidity. The phase transition occurs for a class of asymptotically anti-de Sitter hairy black holes in Lovelock gravity where a real scalar field is conformally coupled to gravity. We discuss the origin of this phase transition and outline the circumstances under which it (or generalizations of it) could occur.

  6. Magnonic Black Holes.

    Science.gov (United States)

    Roldán-Molina, A; Nunez, Alvaro S; Duine, R A

    2017-02-10

    We show that the interaction between the spin-polarized current and the magnetization dynamics can be used to implement black-hole and white-hole horizons for magnons-the quanta of oscillations in the magnetization direction in magnets. We consider three different systems: easy-plane ferromagnetic metals, isotropic antiferromagnetic metals, and easy-plane magnetic insulators. Based on available experimental data, we estimate that the Hawking temperature can be as large as 1 K. We comment on the implications of magnonic horizons for spin-wave scattering and transport experiments, and for magnon entanglement.

  7. Are Black Holes Springy?

    CERN Document Server

    Good, Michael R R

    2014-01-01

    A $(3+1)$-dimensional asymptotically flat Kerr black hole angular speed $\\Omega_+$ can be used to define an effective spring constant, $k=m\\Omega_+^2$. Its maximum value is the Schwarzschild surface gravity, $k = \\kappa $, which rapidly weakens as the black hole spins down and the temperature increases. The Hawking temperature is expressed in terms of the spring constant: $2\\pi T = \\kappa - k$. Hooke's law, in the extremal limit, provides the force $F = 1/4$, which is consistent with the conjecture of maximum force in general relativity.

  8. Doping and defects in YBa2Cu3O7: Results from hybrid density functional theory

    KAUST Repository

    Schwingenschlögl, Udo

    2012-06-21

    Modified orbital occupation and inhomogeneous charge distribution in high-Tc oxide compounds due to doping and/or defects play a huge role for the material properties. To establish insight into the charge redistribution, we address metallic YBa2Cu3O7 in two prototypical configurations: Ca doped (hole doping) and O deficient (electron doping). By means of first principles calculations for fully relaxed structures, we evaluate the orbital occupations. We find that the change of the charge density, in particular in the CuO2 planes, shows a complex spatial pattern instead of the expected uniform (de-)population of the valence states.

  9. Al-bound hole polarons in TiO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Stashans, Arvids, E-mail: arvids@utpl.edu.ec [Grupo de Fisicoquimica de Materiales, Instituto de Quimica Aplicada, Universidad Tecnica Particular de Loja, Apartado 11-01-608, Loja (Ecuador); Bermeo, Sthefano [Grupo de Fisicoquimica de Materiales, Instituto de Quimica Aplicada, Universidad Tecnica Particular de Loja, Apartado 11-01-608, Loja (Ecuador)] [Escuela de Electronica y Telecomunicaciones, Universidad Tecnica Particular de Loja, Apartado 11-01-608, Loja (Ecuador)

    2009-09-18

    Changes in the structural and electronic properties of TiO{sub 2} (anatase and rutile) due to the Al-doping are studied using a quantum-chemical approach based on the Hartree-Fock theory. The formation of hole polarons trapped at oxygen sites near the Al impurity has been discovered and their spatial configuration are discussed. The occurrence of well-localized one-center hole polarons in rutile may influence its photocatalytic activity. Optical absorption energy for this hole center is obtained, 0.4 eV, using the {Delta}SCF approach.

  10. Hydrogenation temperature related inner structures and visible-light-driven photocatalysis of N–F co-doped TiO{sub 2} nanosheets

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Wei, E-mail: wangweinj0603@126.com; Ni, Yaru, E-mail: niyr2000@hotmail.com; Lu, Chunhua, E-mail: lchnjut@163.com; Xu, Zhongzi, E-mail: xzznjut@163.com

    2014-01-30

    A systematic study has been devoted to prepare N–F co-doped anatase TiO{sub 2} nanosheets with further hydrogenation treatment at different temperatures. The hydrogenation temperature plays a significant role in changing the inner structure of TiO{sub 2} from N–F co-doping to the truly hydrogenated characteristic, resulting in various bandgap structures with different light absorption ability and photogenerated electron–hole pair separation efficiency. Moreover, the visible-light-driven photocatalytic activity not only depend on the light absorption ability, but also affected by the amount of defect states significantly. Results indicate that isolated defect state will serve as photogenerated electron–hole pair recombination center, while a large amount of combined defect states will truly reduce the bandgap, enhance the light absorption and the photogenerated electron–hole pair separation efficiency. The photocatalyst hydrogenated at 500 °C, which has a specific bandgap structure, gives the highest ability in the degradation of phenol under the visible light irradiation. This simple investigation is of great significance for the design and preparation of anion modified TiO{sub 2}-based photocatalysts with specific crystal structures to make sufficient use of the visible light for environment protection.

  11. Preparation and characterization of visible-light-driven N-F-Ta tri-doped TiO{sub 2} photocatalysts

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Wei, E-mail: wwnjut@hotmail.com [State Key Laboratory of Materials-Orient Chemical Engineering, College of Materials Science and Engineering, Nanjing University of Technology, Nanjing 210009 (China); Lu, Chunhua, E-mail: lchnjut@163.com [State Key Laboratory of Materials-Orient Chemical Engineering, College of Materials Science and Engineering, Nanjing University of Technology, Nanjing 210009 (China); Ni, Yaru; Su, Mingxing; Huang, Wenjuan; Xu, Zhongzi [State Key Laboratory of Materials-Orient Chemical Engineering, College of Materials Science and Engineering, Nanjing University of Technology, Nanjing 210009 (China)

    2012-09-01

    Highlights: Black-Right-Pointing-Pointer N-F-Ta tri-doping can further improve the visible-light photoactivity of N single doped TiO{sub 2}. Black-Right-Pointing-Pointer There are N 2p-Ta 5d hybridized states which narrow the band gap and reduce the photogenerated electrons and holes recombination rate located in the gap region of TiO{sub 2}. Black-Right-Pointing-Pointer The introduced F atoms enhance the N incorporation which further promote the N 2p-Ta 5d hybridized states. Black-Right-Pointing-Pointer Charge compensation during the doping process is a very important factor. - Abstract: A new strategy to synthesize visible-light-driven N doped and N-F-Ta tri-doped TiO{sub 2} nanocatalysts via a hydrothermal combined with heat treatment method applied in Rhodamine B (RhB) and phenol decomposition was reported. The tri-doped sample gave the highest visible-light photocatalytic activity when the molar ratio of Ta to Ti was 1%. At a low tri-doping level, physicochemical analysis indicated that the synergistic effects of N, F and Ta could effectively increase not only the crystallite surface area but also the light absorption and {center_dot}OH generation ability, which contributed to the enhancement of visible-light photocatalytic activities. EPR and XPS analysis demonstrated that N-Ta interaction induced the charge compensation to form N 2p-Ta 5d hybridized states which improved the separation ability of the photoexcited electron-hole pairs. Still, F incorporation facilitated the incorporation of N which further promoted the N 2p-Ta 5d hybridized states. The N 2p, {pi}*N-O, oxygen vacancy, Ti{sup 3+} and Ta 5d states were also responsible for the band gap narrowing. However, a high tri-doping level would affect the crystal growth and introduce too many defects into the lattice, reducing the visible-light photoactivity.

  12. Almost BPS black holes

    NARCIS (Netherlands)

    Goldstein, K.D.|info:eu-repo/dai/nl/314132376; Katmadas, S.

    2009-01-01

    We study non-BPS black hole solutions to ungauged supergravity with 8 supercharges coupled to vector multiplets in four and five dimensions. We identify a large class of five dimensional non-BPS solutions, which we call ``almost BPS'', that are supersymmetric on local patches and satisfy a first

  13. Nonsingular black hole

    Energy Technology Data Exchange (ETDEWEB)

    Chamseddine, Ali H. [American University of Beirut, Physics Department, Beirut (Lebanon); I.H.E.S., Bures-sur-Yvette (France); Mukhanov, Viatcheslav [Niels Bohr Institute, Niels Bohr International Academy, Copenhagen (Denmark); Ludwig-Maximilians University, Theoretical Physics, Munich (Germany); MPI for Physics, Munich (Germany)

    2017-03-15

    We consider the Schwarzschild black hole and show how, in a theory with limiting curvature, the physical singularity ''inside it'' is removed. The resulting spacetime is geodesically complete. The internal structure of this nonsingular black hole is analogous to Russian nesting dolls. Namely, after falling into the black hole of radius r{sub g}, an observer, instead of being destroyed at the singularity, gets for a short time into the region with limiting curvature. After that he re-emerges in the near horizon region of a spacetime described by the Schwarzschild metric of a gravitational radius proportional to r{sub g}{sup 1/3}. In the next cycle, after passing the limiting curvature, the observer finds himself within a black hole of even smaller radius proportional to r{sub g}{sup 1/9}, and so on. Finally after a few cycles he will end up in the spacetime where he remains forever at limiting curvature. (orig.)

  14. When Black Holes Collide

    Science.gov (United States)

    Baker, John

    2010-01-01

    Among the fascinating phenomena predicted by General Relativity, Einstein's theory of gravity, black holes and gravitational waves, are particularly important in astronomy. Though once viewed as a mathematical oddity, black holes are now recognized as the central engines of many of astronomy's most energetic cataclysms. Gravitational waves, though weakly interacting with ordinary matter, may be observed with new gravitational wave telescopes, opening a new window to the universe. These observations promise a direct view of the strong gravitational dynamics involving dense, often dark objects, such as black holes. The most powerful of these events may be merger of two colliding black holes. Though dark, these mergers may briefly release more energy that all the stars in the visible universe, in gravitational waves. General relativity makes precise predictions for the gravitational-wave signatures of these events, predictions which we can now calculate with the aid of supercomputer simulations. These results provide a foundation for interpreting expect observations in the emerging field of gravitational wave astronomy.

  15. "Holes": Folklore Redux.

    Science.gov (United States)

    Mascia, Elizabeth G.

    2001-01-01

    Demonstrates that a careful reading of the book for young adults, "Holes" by Louis Sachar, reveals how this contemporary story is grounded in folklore, and that it is this debt to folk literature that allows readers to accept an improbable plot. Shows how the story weaves together elements from traditional folk literature and stretches them across…

  16. The Antarctic Ozone Hole.

    Science.gov (United States)

    Stolarski, Richard S.

    1988-01-01

    Discusses the Airborne Antarctic Ozone Experiment (1987) and the findings of the British Antarctic Survey (1985). Proposes two theories for the appearance of the hole in the ozone layer over Antarctica which appears each spring; air pollution and natural atmospheric shifts. Illustrates the mechanics of both. Supports worldwide chlorofluorocarbon…

  17. A structural probe of the doped holes in cuprate superconductors

    NARCIS (Netherlands)

    Abbamonte, P; Rusydi, A; Sawatzky, GA; Logvenov, G; Bozovic, [No Value; Venema, L.C.

    2002-01-01

    An unresolved issue concerning cuprate superconductors is whether the distribution of carriers in the CuO2 plane is uniform or inhomogeneous. Because the carriers comprise a small fraction of the total charge density and may be rapidly fluctuating, modulations are difficult to detect directly. We

  18. Graphene doping methods and device applications.

    Science.gov (United States)

    Oh, Jong Sik; Kim, Kyong Nam; Yeom, Geun Young

    2014-02-01

    Graphene has recently been studied as a promising material to replace and enhance conventional electronic materials in various fields such as electronics, photovoltaics, sensors, etc. However, for the electronic applications of graphene prepared by various techniques such as chemical vapor deposition, chemical exfoliation, mechanical exfoliation, etc., critical limitations are found due to the defects in the graphene in addition to the absence of a semiconducting band gap. For that, many researchers have investigated the doped graphene which is effective to tailor its electronic property and chemical reactivity. This work presents a review of the various graphene doping methods and their device applications. As doping methods, direct synthesis method and post treatment method could be categorized. Because the latter case has been widely investigated and used in various electronic applications, we will focus on the post treatment method. Post treatment method could be further classified into wet and dry doping methods. In the case of wet doping, acid treatment, metal chloride, and organic material coating are the methods used to functionalize graphene by using dip-coating, spin coating, etc. Electron charge transfer achieved from graphene to dopants or from dopants to graphene makes p-type or n-type graphenes, respectively, with sheet resistance reduction effect. In the case of dry doping, it can be further categorized into electrostatic field method, evaporation method, thermal treatment method, plasma treatment method, etc. These doping techniques modify Fermi energy level of graphene and functionalize the property of graphene. Finally, some perspectives and device applications of doped graphene are also briefly discussed.

  19. Quantum aspects of black holes

    CERN Document Server

    2015-01-01

    Beginning with an overview of the theory of black holes by the editor, this book presents a collection of ten chapters by leading physicists dealing with the variety of quantum mechanical and quantum gravitational effects pertinent to black holes. The contributions address topics such as Hawking radiation, the thermodynamics of black holes, the information paradox and firewalls, Monsters, primordial black holes, self-gravitating Bose-Einstein condensates, the formation of small black holes in high energetic collisions of particles, minimal length effects in black holes and small black holes at the Large Hadron Collider. Viewed as a whole the collection provides stimulating reading for researchers and graduate students seeking a summary of the quantum features of black holes.

  20. Direct cost of pars plana vitrectomy for the treatment of macular hole, epiretinal membrane and vitreomacular traction: a bottom-up approach.

    Science.gov (United States)

    Nicod, Elena; Jackson, Timothy L; Grimaccia, Federico; Angelis, Aris; Costen, Marc; Haynes, Richard; Hughes, Edward; Pringle, Edward; Zambarakji, Hadi; Kanavos, Panos

    2016-11-01

    The direct cost to the National Health Service (NHS) in England of pars plana vitrectomy (PPV) is unknown since a bottom-up costing exercise has not been undertaken. Healthcare resource group (HRG) costing relies on a top-down approach. We aimed to quantify the direct cost of intermediate complexity PPV. Five NHS vitreoretinal units prospectively recorded all consumables, equipment and staff salaries during PPV undertaken for vitreomacular traction, epiretinal membrane and macular hole. Out-of-surgery costs between admission and discharge were estimated using a representative accounting method. The average patient time in theatre for 57 PPVs was 72 min. The average in-surgery cost for staff was £297, consumables £619, and equipment £82 (total £997). The average out-of-surgery costs were £260, including nursing and medical staff, other consumables, eye drops and hospitalisation. The total cost was therefore £1634, including 30 % overheads. This cost estimate was an under-estimate because it did not include out-of-theatre consumables or equipment. The average reimbursed HRG tariff was £1701. The cost of undertaking PPV of intermediate complexity is likely to be higher than the reimbursed tariff, except for hospitals with high throughput, where amortisation costs benefit from economies of scale. Although this research was set in England, the methodology may provide a useful template for other countries.

  1. Fabrication of efficient graphene-doped polymer/fullerene bilayer organic solar cells in air using spin coating followed by ultrasonic vibration post treatment

    Science.gov (United States)

    Zabihi, Fatemeh; Chen, Qianli; Xie, Yu; Eslamian, Morteza

    2016-12-01

    In this work, in an attempt to improve the performance and lifetime of organic solar cells, P3HT photon absorbing polymer was doped with graphene (G) nano-sheets, to make light harvesting G-P3HT composite thin film. The composite this film was then employed as the donor of a bilayer organic solar cell with the structure of glass/ITO/PEDOT:PSS/G-P3HT/C60/Al. The reference P3HT:PCBM bulk heterojunction solar cell was also fabricated for comparison. All solution-processed layers were made by spin coating in humid air (Shanghai, China); C60 and Al were deposited by thermal evaporation. An effective mechanical treatment approach developed by the authors, i.e. the application of forced ultrasonic vibration on the wet spun-on films, was used to improve the dispersion of graphene in G-P3HT composite films to obtain a uniform nanostructure. This mechanical method eliminates tedious and expensive chemical steps, currently performed to engineer the structure of organic solar cells. It is evidenced that the G-P3HT composite thin films, post treated by ultrasonic vibration at the optimum vibration duration, possess superior electrical conductivity, charge carrier mobility and density, uniform surface potential distribution, and lower surface roughness, compared to those of P3HT and G-P3HT thin films made without vibration. The results show significant improvement in the power conversion efficiency (PCE) of vibration-treated G-P3HT/C60 cell (PCE = 5.17%, the highest reported for this structure), substantiating the strong positive effect of using graphene and forced vibration for the fabrication of P3HT active layer in the bilayer cell structure.

  2. Black holes thermodynamics, information, and firewalls

    CERN Document Server

    Mann, Robert B

    2015-01-01

    This book reflects the resurgence of interest in the quantum properties of black holes, culminating most recently in controversial discussions about firewalls. On the thermodynamic side, it describes how new developments allowed the inclusion of pressure/volume terms in the first law, leading to a new understanding of black holes as chemical systems, experiencing novel phenomena such as triple points and reentrant phase transitions. On the quantum-information side, the reader learns how basic arguments undergirding quantum complementarity have been shown to be flawed; and how this suggests that a black hole may surround itself with a firewall: a violent and chaotic region of highly excited states. In this thorough and pedagogical treatment, Robert Mann traces these new developments from their roots to our present-day understanding, highlighting their relationships and the challenges they present for quantum gravity.

  3. Black Hole: The Interior Spacetime

    CERN Document Server

    Ong, Yen Chin

    2016-01-01

    The information loss paradox is often discussed from the perspective of the observers who stay outside of a black hole. However, the interior spacetime of a black hole can be rather nontrivial. We discuss the open problems regarding the volume of a black hole, and whether it plays any role in information storage. We also emphasize the importance of resolving the black hole singularity, if one were to resolve the information loss paradox.

  4. Effect of iodine doping in the deposition solution and iodine vapor pressure in the sensitization treatment on the properties of PbSe films

    Science.gov (United States)

    Suh, Youngjoon; Suh, Sang-Hee

    2017-09-01

    Effect of iodine-doping in the deposition solution and iodine vapor pressure during the sensitization process on the morphological, microstructural, electrical, and optical properties of PbSe films was studied. Undoped and iodine-doped PbSe films of polycrystalline particles were coated on thermally oxidized silicon substrates by chemical bath deposition. The PbSe films were oxidized at 380°C for 30 min and then iodinated at different iodine vapor pressures at 380°C for 5 min. When the iodine vapor pressure was below 20 Pa, PbSeO3 was the main phase formed on the surface of PbSe microcrystals for both undoped and iodine-doped films. As the iodine vapor pressure was increased above 20 Pa, Pb3I2O2 and PbI2 phases were formed in both types of films and PbSeO3 disappeared in the undoped film. Only the iodine-doped films showed photo response. The sheet resistance and IR signal-to-noise ratio had maximum values at the iodine vapor pressure of 17.5 Pa in the iodine-doped film. The x-ray diffraction spectra, scanning electron microscopy morphologies, and EDS analyses of the sensitized PbSe films show that the main role of iodine in the sensitization is helping solid-state sintering of PbSe microcrystals which may lead to redistribution of oxygen atoms in the effective atomic sites.

  5. Switching of the hole injection barrier in blue polymer light-emitting diodes

    NARCIS (Netherlands)

    van Woudenbergh, T; Blom, PWM; Heremans, PL; Muccini, M; Hofstraat, H

    2004-01-01

    The contact energy barrier of poly(3,4-ethylenedioxythiophene) doped with poly(styrene sulfonic acid) (PEDOT:PSS) on poly(9,9-dioctylfluorene) (PFO) amounts to 1 eV, resulting in a hole injection current that is reduced by 6-7 orders of magnitude. However, upon electrical addressing it is

  6. Ninth international conference on hole burning, single molecule and related spectroscopies: science and applications (HBSM 2006)

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2006-07-01

    This conference was organized around 9 sessions: -) single molecule, -) quantum optics, -) hole-burning materials and mechanisms, -) single nano-particle spectroscopy, -) dephasing and spectral diffusion, -) microwave photonics, -) biological systems, -) rare earth doped materials, -) novel laser sources. This document gathers only the slides of the presentations.

  7. String physics and black holes

    Energy Technology Data Exchange (ETDEWEB)

    Susskind, L. [Stanford Univ., CA (United States). Dept. of Physics; Uglum, J. [Stanford Univ., CA (United States). Dept. of Physics

    1996-02-01

    In these lectures we review the quantum physics of large Schwarzschild black holes. Hawking`s information paradox, the theory of the stretched horizon and the principle of black hole complementarity are covered. We then discuss how the ideas of black hole complementarity may be realized in string theory. Finally, arguments are given that the world may be a hologram. (orig.).

  8. Copper doped borate dosimeters revisited

    Energy Technology Data Exchange (ETDEWEB)

    Alajerami, Y.S.M. [Department of Physics, Universiti Teknologi Malaysia, 81310 Skudai, Johor (Malaysia); Department of Medical Radiography, Al-Azhar University, Gaza Strip, Palestine (Country Unknown); Hashim, S., E-mail: suhairul@utm.my [Department of Physics, Universiti Teknologi Malaysia, 81310 Skudai, Johor (Malaysia); Oncology Treatment Centre, Sultan Ismail Hospital, 81100 Johor Bahru (Malaysia); Ghoshal, S.K. [Department of Physics, Universiti Teknologi Malaysia, 81310 Skudai, Johor (Malaysia); Bradley, D.A. [Centre for Nuclear and Radiation Physics, Department of Physics, University of Surrey, Guildford GU2 7XH (United Kingdom); Department of Physics, Faculty of Science, University of Malaya, 50603 Kuala Lumpur (Malaysia); Mhareb, M. [Department of Physics, Universiti Teknologi Malaysia, 81310 Skudai, Johor (Malaysia); Saleh, M.A. [Department of Physics, Universiti Teknologi Malaysia, 81310 Skudai, Johor (Malaysia); National Atomic Energy Commission (NATEC), Sana' a (Yemen)

    2014-11-15

    We render a panoramic overview on copper (Cu) doped borate dosimeters. Preparing a dosimeter by mixing specific materials with precise weights and methods is a never-ending quest. The recommended composition is highly decisive for accurate estimation of the absorbed dose, prediction of the biological outcome, determination of the treatment dose for radiation therapy and facilitation of personal monitoring. Based on these principles, the proposed dosimeter must cover a series of dosimetric properties to realize the exact results and assessment. The doped borate dosimeters indeed demonstrate attractive thermoluminescence (TL) features. Several dedicated efforts are attempted to improve the luminescence properties by doping various transition metals or rare-earth elements. The Cu ion being one of the preferred activators shows excellent TL properties as revealed via detail comparison with other dosimeters. Two oxide states of Cu (Cu{sup +} and Cu{sup ++}) with reasonable atomic number allow easy interaction with boron network. Interestingly, the intrinsic luminescent centers of borate lattice are in cross linked with that of Cu{sup +} ions. Thus, the activation of borate dosimeter with Cu ions for the enhancement of the TL sensitivity is recognized. These dosimeters reveal similar glow curves as the standard TLD-100 (LiF:Mg,Ti) one irrespective of the use of modifiers and synthesis techniques. They display high sensitivity, low fading, dose response linearity over wide range and practical minimum detectable dose. Furthermore, the effective atomic number being the most beneficial aspect (equivalent to that of human tissue) of borate dosimeters do not show any change due to Cu ion activations. The past development, major challenges, excitement, applications, recent progress and the future promises of Cu doped borate TL dosimeters are highlighted. - Highlights: • The manuscript gives a panoramic overview on copper doped borate dosimeters. • Cu ions activated

  9. Doping dependence of collective spin states in LaCoO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Alfonsov, A.; Kataev, V.; Buechner, B. [IFW Dresden (Germany); Vavilova, E. [IFW Dresden (Germany); Zavoisky Physical Technical Institute, RAS, Kazan (Russian Federation); Podlesnyak, A. [Oak Ridge National Laboratory, TN (United States); Pomjakushina, E. [ETH Zurich, Paul Scherrer Institut, Villigen (Switzerland)

    2011-07-01

    We have shown recently that a small Sr doping of LaCoO{sub 3} yields the spin-state polaron with a big spin value and substantial spin orbital coupling. The Sr for La substitution provides the hole doping due to different valency of Sr and La. In addition, it gives rise to a distortion of the crystal field around the doped ion due to the mismatch of ionic radii. The present work is aimed to discriminate between the effect of the charge (hole- or electron) doping and the effect of structural distortion. For that we have carried out a comparative high field electron spin- (ESR), nuclear magnetic resonance (NMR) and static magnetization study of lightly doped samples of La{sub 0.998}A{sub 0.002}CoO{sub 3} (A=Sr,Ca,Y,Sn,Ce). We discuss the role of the heterovalent hole- (Sr{sup 2+}, Ca{sup 2+}) and electron doping (Sn{sup 4+}, Ce{sup 4+}) as well as the homovalent doping with Y{sup 3+} (r{sup ion}{sub Y{sup 3+}}<< r{sup ion}{sub La{sup 3+}}) for the formation of the spin-state polaron in LaCoO{sub 3}.

  10. Physicochemical evaluation of bore-hole water from selected fish ...

    African Journals Online (AJOL)

    holes in selected fish farms in the three districts of Edo State, Nigeria. Sample collection, treatment and determination of physical and chemical properties were according to approved standards. The results showed that all the parameters ...

  11. Nonsingular Black Holes

    CERN Document Server

    Olmo, Gonzalo J

    2011-01-01

    We find that if general relativity is modified at the Planck scale by a Ricci-squared term, electrically charged black holes may be nonsingular. These objects concentrate their mass in a microscopic sphere of radius $r_{core}\\approx N_q^{1/2}l_P/3$, where $l_P$ is the Planck length and $N_q$ is the number of electric charges. The singularity is avoided if the mass of the object satisfies the condition $M_0^2\\approx m_P^2 \\alpha_{em}^{3/2} N_q^3/2$, where $m_P$ is the Planck mass and $\\alpha_{em}$ is the fine-structure constant. For astrophysical black holes this amount of charge is so small that their external horizon almost coincides with their Schwarzschild radius. We work within a first-order (Palatini) approach.

  12. The Effect of Acceptor and Donor Doping on Oxygen Vacancy Concentrations in Lead Zirconate Titanate (PZT

    Directory of Open Access Journals (Sweden)

    Christoph Slouka

    2016-11-01

    Full Text Available The different properties of acceptor-doped (hard and donor-doped (soft lead zirconate titanate (PZT ceramics are often attributed to different amounts of oxygen vacancies introduced by the dopant. Acceptor doping is believed to cause high oxygen vacancy concentrations, while donors are expected to strongly suppress their amount. In this study, La3+ donor-doped, Fe3+ acceptor-doped and La3+/Fe3+-co-doped PZT samples were investigated by oxygen tracer exchange and electrochemical impedance spectroscopy in order to analyse the effect of doping on oxygen vacancy concentrations. Relative changes in the tracer diffusion coefficients for different doping and quantitative relations between defect concentrations allowed estimates of oxygen vacancy concentrations. Donor doping does not completely suppress the formation of oxygen vacancies; rather, it concentrates them in the grain boundary region. Acceptor doping enhances the amount of oxygen vacancies but estimates suggest that bulk concentrations are still in the ppm range, even for 1% acceptor doping. Trapped holes might thus considerably contribute to the charge balancing of the acceptor dopants. This could also be of relevance in understanding the properties of hard and soft PZT.

  13. Prisons of light : black holes

    Science.gov (United States)

    Ferguson, Kitty

    What is a black hole? Could we survive a visit to one -- perhaps even venture inside? Have we yet discovered any real black holes? And what do black holes teach us about the mysteries of our Universe? These are just a few of the tantalizing questions examined in this tour-de-force, jargon-free review of one of the most fascinating topics in modern science. In search of the answers, we trace a star from its birth to its death throes, take a hypothetical journey to the border of a black hole and beyond, spend time with some of the world's leading theoretical physicists and astronomers, and take a whimsical look at some of the wild ideas black holes have inspired. Prisons of Light - Black Holes is comprehensive and detailed. Yet Kitty Ferguson's lightness of touch and down-to-earth analogies set this book apart from all others on black holes and make it a wonderfully stimulating and entertaining read.

  14. Study of sterilization-treatment in pure and N- doped carbon thin films synthesized by inductively coupled plasma assisted pulsed-DC magnetron sputtering

    Science.gov (United States)

    Javid, Amjed; Kumar, Manish; Han, Jeon Geon

    2017-01-01

    Electrically-conductive nanocrystalline carbon films, having non-toxic and non-immunogenic characteristics, are promising candidates for reusable medical devices. Here, the pure and N- doped nanocrystalline carbon films are deposited by the assistance of inductively coupled plasma (ICP) in an unbalanced facing target pulsed-DC magnetron sputtering process. Through the optical emission spectroscopy study, the role of ICP assistance and N-doping on the reactive components/radicals during the synthesis is presented. The N-doping enhances the three fold bonding configurations by increasing the ionization and energies of the plasma species. Whereas, the ICP addition increases the plasma density to control the deposition rate and film structure. As a result, sputtering-throughput (deposition rate: 31-55 nm/min), electrical resistivity (4-72 Ωcm) and water contact angle (45.12°-54°) are significantly tailored. Electric transport study across the surface microchannel confirms the superiority of N-doped carbon films for sterilization stability over the undoped carbon films.

  15. Reduction of hydrogen-induced optical losses of plasma-enhanced chemical vapor deposition silicon oxynitride by phosphorus doping and heat treatment

    NARCIS (Netherlands)

    Hussein, M.G.; Worhoff, Kerstin; Sengo, G.; Sengo, G.; Driessen, A.

    2007-01-01

    Plasma enhanced chemical vapor deposition phosphoros-doped silicon oxynitride (SiON) layers with a refractive index of 1.505 were deposited from $N_{2}O$, 2% $SiH_{4}/N_{2}$, and 5% $PH_{3}/Ar$ gaseous mixtures. The $PH_{3}/Ar$ flow rate was varied to investigate the effect of the dopant to the

  16. Structure and functionality of bromine doped graphite.

    Science.gov (United States)

    Hamdan, Rashid; Kemper, A F; Cao, Chao; Cheng, H P

    2013-04-28

    First-principles calculations are used to study the enhanced in-plane conductivity observed experimentally in Br-doped graphite, and to study the effect of external stress on the structure and functionality of such systems. The model used in the numerical calculations is that of stage two doped graphite. The band structure near the Fermi surface of the doped systems with different bromine concentrations is compared to that of pure graphite, and the charge transfer between carbon and bromine atoms is analyzed to understand the conductivity change along different high symmetry directions. Our calculations show that, for large interlayer separation between doped graphite layers, bromine is stable in the molecular form (Br2). However, with increased compression (decreased layer-layer separation) Br2 molecules tend to dissociate. While in both forms, bromine is an electron acceptor. The charge exchange between the graphite layers and Br atoms is higher than that with Br2 molecules. Electron transfer to the Br atoms increases the number of hole carriers in the graphite sheets, resulting in an increase of conductivity.

  17. All-solution processed composite hole transport layer for quantum dot light emitting diode

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Xiaoli [Tianjin Key Laboratory of Low Dimensional Materials Physics and Preparing Technology, School of Science, Tianjin University, Tianjin 300072 (China); Synergetic Innovation Center of Chemical Science and Engineering, Tianjin (China); Dai, Haitao, E-mail: htdai@tju.edu.cn [Tianjin Key Laboratory of Low Dimensional Materials Physics and Preparing Technology, School of Science, Tianjin University, Tianjin 300072 (China); Zhao, Junliang; Wang, Shuguo [Tianjin Key Laboratory of Low Dimensional Materials Physics and Preparing Technology, School of Science, Tianjin University, Tianjin 300072 (China); Sun, Xiaowei [Department of Electrical & Electronic Engineering, South University of Science and Technology of China, Tangchang Road 1088, Shenzhen, Guangdong 518055 (China)

    2016-03-31

    In the present work, poly-TPD and TCTA composite hole transport layer (HTL) was employed in solution processed CdSe/ZnS quantum dot light emitting diodes (QLEDs). As the doping level of TCTA can determine the carriers transport efficiency of HTL, the proper mixing ratio of TCTA and poly-TPD should be found to optimize the performance of composite HTL for QLEDs. The doping of poly-TPD by low TCTA content can make its HOMO level lower and then reduce the energy barrier height from HTL to quantum dots (QDs), whereas the doping of poly-TPD by the concentrated TCTA results in the degraded performance of QLEDs due to its decreased hole transport mobility. By using the optimized composition with poly-TPD:TCTA (3:1) as the hole transport layer, the luminescence of the device exhibits about double enhancement compared with that of poly-TPD based device. The improvement of luminescence is mainly attributed to the lower energy barrier of hole injection. The Förster resonant energy transfer (FRET) mechanism in the devices was investigated through theoretical and experimental analysis and the results indicate that the TCTA doping makes no difference on FRET. Therefore, the charge injection mechanism dominates the improved performance of the devices. - Highlights: • Quantum dot light emitting diodes (QLEDs) were fabricated by all solution method. • The performance of QLEDs was optimized by varying the composite hole transport layer. • The blend HTL could promote hole injection by optimizing HOMO levels. • The energy transfer mechanism was analyzed by studying Förster resonant energy transfer process.

  18. Exploring plasmonic coupling in hole-cap arrays

    Directory of Open Access Journals (Sweden)

    Thomas M. Schmidt

    2015-01-01

    Full Text Available The plasmonic coupling between gold caps and holes in thin films was investigated experimentally and through finite-difference time-domain (FDTD calculations. Sparse colloidal lithography combined with a novel thermal treatment was used to control the vertical spacing between caps and hole arrays and compared to separated arrays of holes or caps. Optical spectroscopy and FDTD simulations reveal strong coupling between the gold caps and both Bloch Wave-surface plasmon polariton (BW-SPP modes and localized surface plasmon resonance (LSPR-type resonances in hole arrays when they are in close proximity. The interesting and complex coupling between caps and hole arrays reveals the details of the field distribution for these simple to fabricate structures.

  19. Exploring plasmonic coupling in hole-cap arrays.

    Science.gov (United States)

    Schmidt, Thomas M; Frederiksen, Maj; Bochenkov, Vladimir; Sutherland, Duncan S

    2015-01-01

    The plasmonic coupling between gold caps and holes in thin films was investigated experimentally and through finite-difference time-domain (FDTD) calculations. Sparse colloidal lithography combined with a novel thermal treatment was used to control the vertical spacing between caps and hole arrays and compared to separated arrays of holes or caps. Optical spectroscopy and FDTD simulations reveal strong coupling between the gold caps and both Bloch Wave-surface plasmon polariton (BW-SPP) modes and localized surface plasmon resonance (LSPR)-type resonances in hole arrays when they are in close proximity. The interesting and complex coupling between caps and hole arrays reveals the details of the field distribution for these simple to fabricate structures.

  20. A simple preparation method and characterization of B and N co-doped TiO{sub 2} nanotube arrays with enhanced photoelectrochemical performance

    Energy Technology Data Exchange (ETDEWEB)

    Georgieva, J., E-mail: jenia@ipc.bas.bg [Rostislaw Kaischew Institute of Physical Chemistry, Bulgarian Academy of Sciences (Bulgaria); Valova, E.; Armyanov, S.; Tatchev, D. [Rostislaw Kaischew Institute of Physical Chemistry, Bulgarian Academy of Sciences (Bulgaria); Sotiropoulos, S. [Department of Chemistry, Aristotle University of Thessaloniki (Greece); Avramova, I. [Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences (Bulgaria); Dimitrova, N. [Rostislaw Kaischew Institute of Physical Chemistry, Bulgarian Academy of Sciences (Bulgaria); Hubin, A.; Steenhaut, O. [Research Group Electrochemical and Surface Engineering (SURF), Vrije Universiteit Brussel (Belgium)

    2017-08-15

    Highlights: • An environment-sparing method for preparation of B,N-co-doped TNTA is realized. • N and B promote additionally the reduction of Ti(IV) to Ti(III) during the crystallization annealing. • N and B dopants are predominantly in interstitial positions. • B,N-TNTA exhibited better photoelectrochemical performance and photoelectrocatalytic degradation of MO. - Abstract: Highly ordered TiO{sub 2} nanotube arrays (TNTA) have attracted much attention due to the excellent photocatalytic, optical and electrical properties. However, their absorption range is limited to ultraviolet (UV) spectrum only due to the wide band gap (3.2 eV). One of the strategies to overcome this problem is doping with boron and nitrogen. They are produced via titanium sheet anodization and subsequent electrochemical treatment of titania in an electrolyte containing boric acid. The as-prepared B-TNTA are annealed in N{sub 2} atmosphere at 500 °C for 2 h to obtain B,N-TNTA. The samples are characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), UV–vis diffuse reflectance spectroscopy (DRS) and X-ray photoelectron spectroscopy (XPS). The B,N-TNTA consist of uniform and well aligned nanotubes with an average inner diameter of 80–100 nm and a length not exceeding 1 μm. The photocurrent response measurements of undoped TNTA, N-doped and B,N-co-doped samples are performed under UV and visible light (Vis) illumination and a comparison is made. The obtained results show that the B,N-doping leads to remarkable photocurrent enhancement and better photocatalytic activity for methyl orange (MO) degradation due to the synergistic effects of B,N-co-doping and lower electron-hole recombination rates.

  1. Doping in competition or doping in sport?

    Science.gov (United States)

    Lippi, Giuseppe; Franchini, Massimo; Guidi, Gian Cesare

    2008-01-01

    Since ancient times, competitive athletes have been familiar with the use of ergogenic aids and they will probably continue to use unfair and harmful substances in future, because their inclination to victory, along with the mirage of glory and money, will probably overcome health and legal risks. We searched PubMed using the term doping over the period 1990 to the present day. We also included non-English journals. By literature searching, it emerges that the phenomenon of doping is complex and multifaceted. It involves a number of causes and factors that do not originate solely in the athletic field, making universality its main feature. It is in fact observed in all ages and levels of competition, and it concerns all sports, even the most unpredictable. The high number of athletes testing positive for anti-doping controls attests that the current strategy might be analytically adequate to unmask most (but not all) doping practices, but it is probably ineffective to prevent athletes to dope and modify this upsetting trend. Growing points As doping parallels the use of medications, food supplements, alcohol and social drugs, a reinforced preventive policy is advisable. The current anti-doping policy should be replaced with a more efficient and practical strategy to identify and monitor abnormal and harmful deviations of the biochemical and haematological profiles.

  2. On Testing the Kerr Metric of the Massive Black Hole in the Galactic Center via Stellar Orbital Motion: Full General Relativistic Treatment

    Science.gov (United States)

    Zhang, Fupeng; Lu, Youjun; Yu, Qingjuan

    2015-08-01

    S-stars, discovered in the vicinity of the massive black hole (MBH) in the Galactic center (GC), are anticipated to provide unique dynamical constraints on the MBH spin and metric, in addition to the mass. In this paper, we develop a fast full general relativistic method to simultaneously constrain the MBH mass, spin, and spin direction by considering both the orbital motion of a star close to the GC MBH and the propagation of photons from the star to a distant observer. Based on the current observations and dynamical model predictions, we assume six example stars with different semimajor axes ({a}{orb}) and eccentricities ({e}{orb}) and numerically calculate their projected trajectories in the sky plane and redshift curves. Two of those stars are set to have orbital configurations similar to that of S0-2/S2 and S0-102. We find that the spin-induced effects on the projected trajectory and redshift curve of a given star, including the leading term by the Lense-Thirring precession and the frame dragging, and the high-order precession due to the quadruple moment, depend on both the absolute value and the direction of the spin. The maximum values of the spin-induced position displacement and the redshift differences of the star over a full orbit may differ by a factor of several to more than one order of magnitude for two cases with significantly different spin directions. The dependence patterns of the position displacements and redshift differences on the spin direction are different, and thus the position and the redshift data are complementary for constraining the MBH spin and its direction. Adopting the Markov Chain Monte Carlo fitting technique, we illustrate that the spin of the GC MBH is likely to be well constrained by using the motion of S0-2/S2 over a period of ˜45 years if the spin is close to one and if the astrometric and spectroscopic precisions can be as high as ({σ }{{p}},{σ }Z)˜ (10 μ {as},1 {km} {{{s}}}-1), which is expected to be realized by

  3. Comparison of two Q-switched lasers and a short-pulse erbium-doped yttrium aluminum garnet laser for treatment of cosmetic tattoos containing titanium and iron in an animal model.

    Science.gov (United States)

    Wang, Chia-Chen; Huang, Chuen-Lin; Yang, An-Hang; Chen, Chih-Kang; Lee, Shao-Chen; Leu, Fur-Jiang

    2010-11-01

    Cosmetic tattoos contain titanium and ferric oxide and darken through reduction after Q-switched laser irradiation. The optimal treatment for removing these pigments remains unknown. To compare the effects of two Q-switched lasers and a short-pulse erbium-doped yttrium aluminum garnet (SP Er:YAG) laser to remove cosmetic tattoos in an animal model. Rats were tattooed using white, flesh-colored, and brown inks (4 bands of each color) on their backs. For each color, one band was left untreated, and one each was treated with a Q-switched neodymium-doped YAG laser, a Q-switched alexandrite laser, and a SP Er:YAG laser every 3 weeks until the pigments were clear. The two Q-switched lasers were equally effective; all three pigments darkened initially and then resolved gradually. Up to 20, 18, and 10 sessions were required to remove white, flesh-colored, and brown tattoos, respectively. Only six sessions were required with the SP Er:YAG laser. Minimal scarring was observed with all lasers. Skin biopsies confirmed pigment granule fragmentation after Q-switched laser treatment and a decrease in the amount of pigment after SP Er:YAG laser treatment. The SP Er:YAG laser was superior to the Q-switched lasers for removing cosmetic tattoos. © 2010 by the American Society for Dermatologic Surgery, Inc.

  4. Photocatalytic degradation of methylene blue on Sn-doped titania nanoparticles synthesized by solution combustion route

    Energy Technology Data Exchange (ETDEWEB)

    Bhange, P.D., E-mail: pallavi.ncl@gmail.com [Department of Chemistry, Shivaji University, Kolhapur 416004, MS (India); Awate, S.V. [Catalysis Division, National Chemical Laboratory, Pune 411008 (India); Gholap, R.S. [Center for Material Characterization, National Chemical Laboratory, Pune 411008 (India); Gokavi, G.S.; Bhange, D.S. [Department of Chemistry, Shivaji University, Kolhapur 416004, MS (India)

    2016-04-15

    Highlights: • Series of Sn-doped titania nanoparticles were prepared by solution combustion synthesis method. • Sn-doped titania nanoparticles were tested for degradation of MB under UV light irradiation. • The maximum Sn doping in the TiO{sub 2} lattice is found to be less than 10%. • The crystallite size decreases with increase in the Sn content. • The doping of Sn into TiO{sub 2} lattice hinders the recombination of electrons and holes thus enhance the photocatalytic activity. - Abstract: Series of tin-doped titania nanoparticles with varying tin content in the range 0–20 mol% have been prepared by solution combustion synthesis route using urea as a fuel. The structure, surface morphology and optical activity of Sn-doped TiO{sub 2} nanoparticles were investigated by various analytical techniques such as powder XRD, SEM, TEM, UV–vis and N{sub 2} adsorption study. The crystalline structures of the various phases were studied by rietveld refinement of the XRD data. The photocatalytic performance of Sn-doped titania nanoparticles were tested for degradation of MB under UV and visible light irradiation. The results reveal that the photocatalytic activity increases with increase in tin content which may be due to decrease in crystallite size with increase in surface area. The doping of Sn into TiO{sub 2} lattice hinders the recombination of electrons and holes thus enhance the quantum efficiency of photocatalytic reaction.

  5. The Electric and Optical Properties of Doped Small Molecular Organic Light-Emitting Devices

    Energy Technology Data Exchange (ETDEWEB)

    Cheon, Kwang-Ohk [Iowa State Univ., Ames, IA (United States)

    2003-01-01

    Organic light-emitting devices (OLEDs) constitute a new and exciting emissive display technology. In general, the basic OLED structure consists of a stack of fluorescent organic layers sandwiched between a transparent conducting-anode and metallic cathode. When an appropriate bias is applied to the device, holes are injected from the anode and electrons from the cathode; some of the recombination events between the holes and electrons result in electroluminescence (EL). Until now, most of the efforts in developing OLEDs have focused on display applications, hence on devices within the visible range. However some organic devices have been developed for ultraviolet or infrared emission. Various aspects of the device physics of doped small molecular OLEDs were described and discussed. The doping layer thickness and concentration were varied systematically to study their effects on device performances, energy transfer, and turn-off dynamics. Low-energy-gap DCM2 guest molecules, in either α-NPD or DPVBi host layers, are optically efficient fluorophores but also generate deep carrier trap-sites. Since their traps reduce the carrier mobility, the current density decreases with increased doping concentration. At the same time, due to efficient energy transfer, the quantum efficiency of the devices is improved by light doping or thin doping thickness, in comparison with the undoped neat devices. However, heavy doping induces concentration quenching effects. Thus, the doping concentration and doping thickness may be optimized for best performance.

  6. FIFA's approach to doping in football

    Science.gov (United States)

    Dvorak, J; Graf‐Baumann, T; D'Hooghe, M; Kirkendall, D; Taennler, H; Saugy, M

    2006-01-01

    Background and objectives FIFA's anti‐doping strategy relies on education and prevention. A worldwide network of physicians guarantees doping control procedures that are straightforward and leave no place for cheating. FIFA actively acknowledges its responsibility to protect players from harm and ensure equal chances for all competitors by stringent doping control regulations, data collection of positive samples, support of research, and collaboration with other organisations. This article aims to outline FIFA's approach to doping in football. Method Description of FIFA's doping control regulations and procedures, statistical analysis of FIFA database on doping control, and comparison with data obtained by WADA accredited laboratories as for 2004. Results Data on positive doping samples per substance and confederation/nation documented at the FIFA medical office from 1994 to 2005 are provided. According to the FIFA database, the incidence of positive cases over the past 11 years was 0.12%, with about 0.42% in 2004 (based on the assumption of 20 750 samples per year) and 0.37% in 2005. Especially important in this regard is the extremely low incidence of the true performance enhancing drugs such as anabolic steroids and stimulants. However, there is a need for more consistent data collection and cross checks among international anti‐doping agencies as well as for further studies on specific substances, methods, and procedures. With regard to general health impairments in players, FIFA suggests that principles of occupational medicine should be considered and treatment with banned substances for purely medical reasons should be permitted to enable players to carry out their profession. At the same time, a firm stand has to be taken against suppression of symptoms by medication with the aim of meeting the ever increasing demands on football players. Conclusion Incidence of doping in football seems to be low, but much closer collaboration and further

  7. Behavior of Random Hole Optical Fibers under Gamma Ray Irradiation and Its Potential Use in Radiation Sensing Applications

    Directory of Open Access Journals (Sweden)

    Anbo Wang

    2007-05-01

    Full Text Available Effects of radiation on sensing and data transmission components are of greatinterest in many applications including homeland security, nuclear power generation, andmilitary. A new type of microstructured optical fiber (MOF called the random hole opticalfiber (RHOF has been recently developed. The RHOFs can be made in many differentforms by varying the core size and the size and extent of porosity in the cladding region.The fibers used in this study possessed an outer diameter of 110 μm and a core ofapproximately 20 μm. The fiber structure contains thousands of air holes surrounding thecore with sizes ranging from less than 100 nm to a few μm. We present the first study ofthe behavior of RHOF under gamma irradiation. We also propose, for the first time to ourknowledge, an ionizing radiation sensor system based on scintillation light from ascintillator phosphor embedded within a holey optical fiber structure. The RHOF radiationresponse was compared to normal single mode and multimode commercial fibers(germanium doped core, pure silica cladding and to those of radiation resistant fibers (puresilica core with fluorine doped cladding fibers. The comparison was done by measuringradiation-induced absorption (RIA in all fiber samples at the 1550 nm wavelength window(1545 ± 25 nm. The study was carried out under a high-intensity gamma ray field from a 60Co source (with an exposure rate of 4x104 rad/hr at an Oak Ridge National Laboratory gamma ray irradiation facility. Linear behavior, at dose values less than 106 rad, was observed in all fiber samples except in the pure silica core fluorine doped cladding fiber which showed RIA saturation at 0.01 dB. RHOF samples demonstrated low RIA (0.02 and 0.005 dB compared to standard germanium doped core pure silica cladding (SMF and MMF fibers. Results also showed the possibility of post-fabrication treatment to improve the radiation resistance of the RHOF fibers.

  8. Thermal BEC Black Holes

    Directory of Open Access Journals (Sweden)

    Roberto Casadio

    2015-10-01

    Full Text Available We review some features of Bose–Einstein condensate (BEC models of black holes obtained by means of the horizon wave function formalism. We consider the Klein–Gordon equation for a toy graviton field coupled to a static matter current in a spherically-symmetric setup. The classical field reproduces the Newtonian potential generated by the matter source, while the corresponding quantum state is given by a coherent superposition of scalar modes with a continuous occupation number. An attractive self-interaction is needed for bound states to form, the case in which one finds that (approximately one mode is allowed, and the system of N bosons can be self-confined in a volume of the size of the Schwarzschild radius. The horizon wave function formalism is then used to show that the radius of such a system corresponds to a proper horizon. The uncertainty in the size of the horizon is related to the typical energy of Hawking modes: it decreases with the increasing of the black hole mass (larger number of gravitons, resulting in agreement with the semiclassical calculations and which does not hold for a single very massive particle. The spectrum of these systems has two components: a discrete ground state of energy m (the bosons forming the black hole and a continuous spectrum with energy ω > m (representing the Hawking radiation and modeled with a Planckian distribution at the expected Hawking temperature. Assuming the main effect of the internal scatterings is the Hawking radiation, the N-particle state can be collectively described by a single-particle wave-function given by a superposition of a total ground state with energy M = Nm and Entropy 2015, 17 6894 a Planckian distribution for E > M at the same Hawking temperature. This can be used to compute the partition function and to find the usual area law for the entropy, with a logarithmic correction related to the Hawking component. The backreaction of modes with ω > m is also shown to reduce

  9. stu Black Holes Unveiled

    CERN Document Server

    Bellucci, S; Marrani, A; Yeranyan, A

    2008-01-01

    The general solutions of the radial attractor flow equations for extremal black holes, both for non-BPS with non-vanishing central charge Z and for Z=0, are obtained for the so-called stu model, the minimal rank-3 N=2 symmetric supergravity in d=4 space-time dimensions. Comparisons with previous results, as well as the fake supergravity (first order) formalism and an analysis of the BPS bound all along the non-BPS attractor flows and of the marginal stability of corresponding D-brane configurations, are given.

  10. stu Black Holes Unveiled

    Science.gov (United States)

    Bellucci, Stefano; Ferrara, Sergio; Marrani, Alessio; Yeranyan, Armen

    2008-12-01

    The general solutions of the radial attractor flow equations for extremal black holes, both for non-BPS with non-vanishing central charge Z and for Z = 0, are obtained for the so-called stu model, the minimal rank-3 N = 2 symmetric supergravity in d = 4 space-time dimensions. Comparisons with previous results, as well as the fake supergravity (first order) formalism and an analysis of the BPS bound all along the non-BPS attractor flows and of the marginal stability of corresponding D-brane configurations, are given.

  11. Black hole squeezers

    Science.gov (United States)

    Su, Daiqin; Ho, C. T. Marco; Mann, Robert B.; Ralph, Timothy C.

    2017-09-01

    We show that the gravitational quasinormal modes (QNMs) of a Schwarzschild black hole play the role of a multimode squeezer that can generate particles. For a minimally coupled scalar field, the QNMs "squeeze" the initial state of the scalar field (even for the vacuum) and produce scalar particles. The maximal squeezing amplitude is inversely proportional to the cube of the imaginary part of the QNM frequency, implying that the particle generation efficiency is higher for lower decaying QNMs. Our results show that the gravitational perturbations can amplify Hawking radiation.

  12. Artificial ozone holes

    CERN Document Server

    Dolya, S N

    2014-01-01

    This article considers an opportunity of disinfecting a part of the Earth surface, occupying a large area of ten thousand square kilometers. The sunlight will cause dissociation of molecular bromine into atoms; each bromine atom kills thirty thousand molecules of ozone. Each bromine plate has a mass of forty milligrams grams and destroys ozone in the area of hundred square meters. Thus, to form the ozone hole over the area of ten thousand square kilometers, it is required to have the total mass of bromine equal to the following four tons.

  13. Artificial black holes

    CERN Document Server

    Visser, Matt; Volovik, Grigory E

    2009-01-01

    Physicists are pondering on the possibility of simulating black holes in the laboratory by means of various "analog models". These analog models, typically based on condensed matter physics, can be used to help us understand general relativity (Einstein's gravity); conversely, abstract techniques developed in general relativity can sometimes be used to help us understand certain aspects of condensed matter physics. This book contains 13 chapters - written by experts in general relativity, particle physics, and condensed matter physics - that explore various aspects of this two-way traffic.

  14. Surfing a Black Hole

    Science.gov (United States)

    2002-10-01

    Star Orbiting Massive Milky Way Centre Approaches to within 17 Light-Hours [1] Summary An international team of astronomers [2], lead by researchers at the Max-Planck Institute for Extraterrestrial Physics (MPE) , has directly observed an otherwise normal star orbiting the supermassive black hole at the center of the Milky Way Galaxy. Ten years of painstaking measurements have been crowned by a series of unique images obtained by the Adaptive Optics (AO) NAOS-CONICA (NACO) instrument [3] on the 8.2-m VLT YEPUN telescope at the ESO Paranal Observatory. It turns out that earlier this year the star approached the central Black Hole to within 17 light-hours - only three times the distance between the Sun and planet Pluto - while travelling at no less than 5000 km/sec . Previous measurements of the velocities of stars near the center of the Milky Way and variable X-ray emission from this area have provided the strongest evidence so far of the existence of a central Black Hole in our home galaxy and, implicitly, that the dark mass concentrations seen in many nuclei of other galaxies probably are also supermassive black holes. However, it has not yet been possible to exclude several alternative configurations. In a break-through paper appearing in the research journal Nature on October 17th, 2002, the present team reports their exciting results, including high-resolution images that allow tracing two-thirds of the orbit of a star designated "S2" . It is currently the closest observable star to the compact radio source and massive black hole candidate "SgrA*" ("Sagittarius A") at the very center of the Milky Way. The orbital period is just over 15 years. The new measurements exclude with high confidence that the central dark mass consists of a cluster of unusual stars or elementary particles, and leave little doubt of the presence of a supermassive black hole at the centre of the galaxy in which we live . PR Photo 23a/02 : NACO image of the central region of the Milky Way

  15. High-pressure and doping studies of the superconducting antiperovskite SrPt3P

    Science.gov (United States)

    Jawdat, BenMaan I.; Lv, Bing; Zhu, Xiyu; Xue, Yuyi; Chu, Ching-wu

    2015-03-01

    We report the results of our investigation of SrPt3P , a recently discovered strong-coupling superconductor with Tc=8.4 K, by application of high physical pressure and by chemical doping. We study hole-doped SrPt3P , which was theoretically predicted to have a higher Tc, resistively, magnetically, and calorimetrically. Here we present the results of these studies and discuss their implications.

  16. Black holes in massive gravity

    CERN Document Server

    Babichev, Eugeny

    2015-01-01

    We review the black hole solutions of the ghost-free massive gravity theory and its bimetric extension and outline the main results on the stability of these solutions against small perturbations. Massive (bi)-gravity accommodates exact black hole solutions, analogous to those of General Relativity. In addition to these solutions, hairy black holes -- solutions with no correspondent in General Relativity -- have been found numerically, whose existence is a natural consequence of the absence of the Birkhoff's theorem in these theories. The existence of extra propagating degrees of freedom, makes the stability properties of these black holes richer and more complex than those of General Relativity. In particular, the bi-Schwarzschild black hole exhibits an unstable spherically symmetric mode, while the bi-Kerr geometry is also generically unstable, both against the spherical mode and against superradiant instabilities. If astrophysical black holes are described by these solutions, the superradiant instability o...

  17. Fe doped TiO{sub 2} photocatalyst for the removal of As(III) under visible radiation and its potential application on the treatment of As-contaminated groundwater

    Energy Technology Data Exchange (ETDEWEB)

    Garza-Arévalo, J.I.; García-Montes, I. [Universidad Autónoma de Nuevo León, UANL, Facultad de Ciencias Químicas, Cd. Universitaria, San Nicolás de los Garza, Nuevo León C.P. 66451, México (Mexico); Reyes, M.Hinojosa [Instituto Potosino de Investigación Científica y Tecnológica, IPICYT, División de Materiales Avanzados, Camino a la Presa San José 2055, Col. Lomas 4a. sección, San Luis Potosí, SLP 78216, México (Mexico); Guzmán-Mar, J.L. [Universidad Autónoma de Nuevo León, UANL, Facultad de Ciencias Químicas, Cd. Universitaria, San Nicolás de los Garza, Nuevo León C.P. 66451, México (Mexico); Rodríguez-González, V. [Instituto Potosino de Investigación Científica y Tecnológica, IPICYT, División de Materiales Avanzados, Camino a la Presa San José 2055, Col. Lomas 4a. sección, San Luis Potosí, SLP 78216, México (Mexico); and others

    2016-01-15

    Highlights: • Incorporation of Fe in TiO{sub 2} lattice extended absorption to visible light region. • TiO{sub 2}–Fe 1.0 in anatase crystalline form was synthesized by sol–gel method. • TiO{sub 2}–Fe 1.0 showed the highest photocatalytic activity for As(III) oxidation. • TiO{sub 2}–Fe 1.0 had the highest adsorption capacity for the removal of generated As(V). • TiO{sub 2}–Fe is a promising material on the treatment of As contaminated groundwater. - Abstract: The Fe doped TiO{sub 2} catalyst was evaluated under visible radiation for As(III) removal. The TiO{sub 2}–Fe was synthesized by sol–gel technique at 0.0, 1.0, 2.5, 5.0 and 10.0 wt% iron doping concentrations. The semiconductors were characterized by X-ray diffraction, diffuse reflectance UV–vis, Raman spectroscopy, nitrogen physisorption, SEM–EDS and potentiometric titration for point of zero charge determination. The photocatalytic oxidation of As(III) was assessed in aqueous suspension contained 5 mg L{sup −1} As(III) at pH 7 with 0.25 g L{sup −1} catalyst loading. The incorporation of iron ions in TiO{sub 2} lattice extended the absorption to visible light region and create surface oxygen vacancies which favor photocatalytic oxidation reaction of As(III) using a small doping amount of Fe (1.0 wt%) in TiO{sub 2} powder. Additionally, TiO{sub 2}–Fe 1.0 showed the highest adsorption capacity for As(V) removal compared to sol–gel TiO{sub 2} and P25 indicating that this catalyst is a promising material for As contaminated groundwater treatment.

  18. Black Holes in Higher Dimensions

    Directory of Open Access Journals (Sweden)

    Reall Harvey S.

    2008-09-01

    Full Text Available We review black-hole solutions of higher-dimensional vacuum gravity and higher-dimensional supergravity theories. The discussion of vacuum gravity is pedagogical, with detailed reviews of Myers–Perry solutions, black rings, and solution-generating techniques. We discuss black-hole solutions of maximal supergravity theories, including black holes in anti-de Sitter space. General results and open problems are discussed throughout.

  19. Small hole polarons in rare-earth titanates

    Energy Technology Data Exchange (ETDEWEB)

    Bjaalie, L.; Moetakef, P.; Cain, T. A.; Janotti, A.; Himmetoglu, B.; Stemmer, S.; Van de Walle, C. G. [Materials Department, University of California Santa Barbara, California 91306-5050 (United States); Ouellette, D. G.; Allen, S. J. [Department of Physics, University of California, Santa Barbara, California 91306-5050 (United States)

    2015-06-08

    We investigate the behavior of hole polarons in rare-earth titanates by combining optical conductivity measurements with first-principles hybrid density functional calculations. Sr-doped GdTiO{sub 3} (Gd{sub 1−x}Sr{sub x}TiO{sub 3}) was grown by molecular beam epitaxy. We show that a feature in the optical conductivity that was previously identified with the Mott-Hubbard gap is actually associated with the excitation of a small polaron. The assignment is based on an excellent match between the experimental spectra and first-principles calculations for polaron excitation mechanisms.

  20. Black holes and the multiverse

    Energy Technology Data Exchange (ETDEWEB)

    Garriga, Jaume [Departament de Fisica Fonamental i Institut de Ciencies del Cosmos, Universitat de Barcelona, Marti i Franques, 1, Barcelona, 08028 Spain (Spain); Vilenkin, Alexander; Zhang, Jun, E-mail: jaume.garriga@ub.edu, E-mail: vilenkin@cosmos.phy.tufts.edu, E-mail: jun.zhang@tufts.edu [Institute of Cosmology, Tufts University, 574 Boston Ave, Medford, MA, 02155 (United States)

    2016-02-01

    Vacuum bubbles may nucleate and expand during the inflationary epoch in the early universe. After inflation ends, the bubbles quickly dissipate their kinetic energy; they come to rest with respect to the Hubble flow and eventually form black holes. The fate of the bubble itself depends on the resulting black hole mass. If the mass is smaller than a certain critical value, the bubble collapses to a singularity. Otherwise, the bubble interior inflates, forming a baby universe, which is connected to the exterior FRW region by a wormhole. A similar black hole formation mechanism operates for spherical domain walls nucleating during inflation. As an illustrative example, we studied the black hole mass spectrum in the domain wall scenario, assuming that domain walls interact with matter only gravitationally. Our results indicate that, depending on the model parameters, black holes produced in this scenario can have significant astrophysical effects and can even serve as dark matter or as seeds for supermassive black holes. The mechanism of black hole formation described in this paper is very generic and has important implications for the global structure of the universe. Baby universes inside super-critical black holes inflate eternally and nucleate bubbles of all vacua allowed by the underlying particle physics. The resulting multiverse has a very non-trivial spacetime structure, with a multitude of eternally inflating regions connected by wormholes. If a black hole population with the predicted mass spectrum is discovered, it could be regarded as evidence for inflation and for the existence of a multiverse.

  1. Thermodynamics of Accelerating Black Holes.

    Science.gov (United States)

    Appels, Michael; Gregory, Ruth; Kubizňák, David

    2016-09-23

    We address a long-standing problem of describing the thermodynamics of an accelerating black hole. We derive a standard first law of black hole thermodynamics, with the usual identification of entropy proportional to the area of the event horizon-even though the event horizon contains a conical singularity. This result not only extends the applicability of black hole thermodynamics to realms previously not anticipated, it also opens a possibility for studying novel properties of an important class of exact radiative solutions of Einstein equations describing accelerated objects. We discuss the thermodynamic volume, stability, and phase structure of these black holes.

  2. Hole dynamics in noble metals

    OpenAIRE

    Campillo, I.; Rubio, A.; Pitarke, J. M.; Goldmann, A.; Echenique, P. M.

    2000-01-01

    We present a detailed analysis of hole dynamics in noble metals (Cu and Au), by means of first-principles many-body calculations. While holes in a free-electron gas are known to live shorter than electrons with the same excitation energy, our results indicate that d-holes in noble metals exhibit longer inelastic lifetimes than excited sp-electrons, in agreement with experiment. The density of states available for d-hole decay is larger than that for the decay of excited electrons; however, th...

  3. Effect of silicon doping on electrical and optical properties of stoichiometric Cu2ZnSnS4 solar cells

    Science.gov (United States)

    Guo, Huafei; Li, Yan; Guo, Xiaohai; Yuan, Ningyi; Ding, Jianning

    2018-02-01

    To enhance the conversion efficiency of CZTS solar cells, both large grains with few defects and high carrier mobility are important. Here, For improving the grain sizes and hole mobility silicon (Si) was doped into the CZTS films. The influence of the Si doping concentration on the CZTS film macro- and microstructures is examined using X-ray diffraction and scanning electron microscopy. In addition, the optical and electrical properties of the CZTS thin films with different Si doping concentrations are examined. Finally, a 2.53% efficiency was obtained while the Si doping concertation is 0.65%.

  4. Quantum conductance staircase of holes in silicon nanosandwiches

    Directory of Open Access Journals (Sweden)

    Nikolay T. Bagraev

    2017-03-01

    Full Text Available The results of studying the quantum conductance staircase of holes in one-dimensional channels obtained by the split-gate method inside silicon nanosandwiches that are the ultra-narrow quantum well confined by the delta barriers heavily doped with boron on the n-type Si (100 surface are reported. Since the silicon quantum wells studied are ultra-narrow (~2 nm and confined by the delta barriers that consist of the negative-U dipole boron centers, the quantized conductance of one-dimensional channels is observed at relatively high temperatures (T>77 K. Further, the current-voltage characteristic of the quantum conductance staircase is studied in relation to the kinetic energy of holes and their sheet density in the quantum wells. The results show that the quantum conductance staircase of holes in p-Si quantum wires is caused by independent contributions of the one-dimensional (1D subbands of the heavy and light holes. In addition, the field-related inhibition of the quantum conductance staircase is demonstrated in the situation when the energy of the field-induced heating of the carriers become comparable to the energy gap between the 1D subbands. The use of the split-gate method made it possible to detect the effect of a drastic increase in the height of the quantum conductance steps when the kinetic energy of holes is increased; this effect is most profound for quantum wires of finite length, which are not described under conditions of a quantum point contact. In the concluding section of this paper we present the findings for the quantum conductance staircase of holes that is caused by the edge channels in the silicon nanosandwiches prepared within frameworks of the Hall geometry. This longitudinal quantum conductance staircase, Gxx, is revealed by the voltage applied to the Hall contacts, with the plateaus and steps that bring into correlation respectively with the odd and even fractional values.

  5. Alternative medicine and doping in sports

    Directory of Open Access Journals (Sweden)

    Benjamin Koh

    2012-01-01

    Full Text Available Athletes are high achievers who may seek creative or unconventional methods to improve performance. The literature indicates that athletes are among the heaviest users of complementary and alternative medicine (CAM and thus may pioneer population trends in CAM use. Unlike non-athletes, athletes may use CAM not just for prevention, treatment or rehabilitation from illness or injuries, but also for performance enhancement. Assuming that athletes’ creative use of anything unconventional is aimed at “legally” improving performance, CAM may be used because it is perceived as more “natural” and erroneously assumed as not potentially doping. This failure to recognise CAMs as pharmacological agents puts athletes at risk of inadvertent doping.The general position of the World Anti-Doping Authority (WADA is one of strict liability, an application of the legal proposition that ignorance is no excuse and the ultimate responsibility is on the athlete to ensure at all times whatever is swallowed, injected or applied to the athlete is both safe and legal for use. This means that a violation occurs whether or not the athlete intentionally or unintentionally, knowingly or unknowingly, used a prohibited substance/method or was negligent or otherwise at fault. Athletes are therefore expected to understand not only what is prohibited, but also what might potentially cause an inadvertent doping violation. Yet, as will be discussed, athlete knowledge on doping is deficient and WADA itself sometimes changes its position on prohibited methods or substances. The situation is further confounded by the conflicting stance of anti-doping experts in the media. These highly publicised disagreements may further portray inconsistencies in anti-doping guidelines and suggest to athletes that what is considered doping is dependent on the dominant political zeitgeist. Taken together, athletes may believe that unless a specific and explicit ruling is made, guidelines are

  6. Alternative medicine and doping in sports.

    Science.gov (United States)

    Koh, Benjamin; Freeman, Lynne; Zaslawski, Christopher

    2012-01-01

    Athletes are high achievers who may seek creative or unconventional methods to improve performance. The literature indicates that athletes are among the heaviest users of complementary and alternative medicine (CAM) and thus may pioneer population trends in CAM use. Unlike non-athletes, athletes may use CAM not just for prevention, treatment or rehabilitation from illness or injuries, but also for performance enhancement. Assuming that athletes' creative use of anything unconventional is aimed at "legally" improving performance, CAM may be used because it is perceived as more "natural" and erroneously assumed as not potentially doping. This failure to recognise CAMs as pharmacological agents puts athletes at risk of inadvertent doping.The general position of the World Anti-Doping Authority (WADA) is one of strict liability, an application of the legal proposition that ignorance is no excuse and the ultimate responsibility is on the athlete to ensure at all times whatever is swallowed, injected or applied to the athlete is both safe and legal for use. This means that a violation occurs whether or not the athlete intentionally or unintentionally, knowingly or unknowingly, used a prohibited substance/method or was negligent or otherwise at fault. Athletes are therefore expected to understand not only what is prohibited, but also what might potentially cause an inadvertent doping violation. Yet, as will be discussed, athlete knowledge on doping is deficient and WADA itself sometimes changes its position on prohibited methods or substances. The situation is further confounded by the conflicting stance of anti-doping experts in the media. These highly publicised disagreements may further portray inconsistencies in anti-doping guidelines and suggest to athletes that what is considered doping is dependent on the dominant political zeitgeist. Taken together, athletes may believe that unless a specific and explicit ruling is made, guidelines are open to interpretation

  7. Metal Doped Manganese Oxide Thin Films for Supercapacitor Application.

    Science.gov (United States)

    Tung, Mai Thanh; Thuy, Hoang Thi Bich; Hang, Le Thi Thu

    2015-09-01

    Co and Fe doped manganese oxide thin films were prepared by anodic deposition at current density of 50 mA cm(-2) using the electrolyte containing manganese sulfate and either cobalt sulfate or ferrous sulfate. Surface morphology and crystal structure of oxides were studied by scanning electron microscope (SEM) and X-ray diffraction (XRD). Chemical composition of materials was analyzed by X-ray energy dispersive spectroscope (EDS), iodometric titration method and complexometric titration method, respectively. Supercapacitive behavior of Co and Fe doped manganese oxide films were characterized by cyclic voltammetry (CV) and impedance spectroscopy (EIS). The results show that the doped manganese oxides are composed of nano fiber-like structure with radius of 5-20 nm and remain amorphous structure after heat treatment at 100 degrees C for 2 hours. The average valence of manganese increases from +3.808 to +3.867 after doping Co and from +3.808 to +3.846 after doping Fe. The doped manganese oxide film electrodes exhibited preferably ideal pseudo-capacitive behavior. The specific capacitance value of deposited manganese oxide reaches a maximum of 175.3 F/g for doping Co and 244.6 F/g for doping Fe. The thin films retained about 84% of the initial capacity even after 500 cycles of charge-discharge test. Doping Co and Fe decreases diffusion and charge transfer resistance of the films. The electric double layer capacitance and capacitor response frequency are increased after doping.

  8. Electrical Properties of Polytypic Mg Doped GaAs Nanowires

    Directory of Open Access Journals (Sweden)

    N. Cifuentes

    2016-01-01

    Full Text Available The electrical transport properties of individual Mg doped GaAs nanowires are investigated. It is shown that Mg can be successfully used as a nontoxic p-type dopant in GaAs nanowires. The doping levels, expanding over two orders of magnitude, and free holes mobility in the NW were obtained by the analysis of field effect transistors transfer curves. The temperature dependence of the electrical resistivity above room temperature shows that the polytypic structure of the NWs strongly modifies the NWs charge transport parameters, like the resistivity activation energy and holes mobility. At lower temperatures the NWs exhibit variable range hopping conduction. Both Mott and Efros-Shklovskii variable range hopping mechanisms were clearly identified in the nanowires.

  9. Comprehensive phase diagram of two-dimensional space charge doped Bi2Sr2CaCu2O8+x.

    Science.gov (United States)

    Sterpetti, Edoardo; Biscaras, Johan; Erb, Andreas; Shukla, Abhay

    2017-12-12

    The phase diagram of hole-doped high critical temperature superconductors as a function of doping and temperature has been intensively studied with chemical variation of doping. Chemical doping can provoke structural changes and disorder, masking intrinsic effects. Alternatively, a field-effect transistor geometry with an electrostatically doped, ultra-thin sample can be used. However, to probe the phase diagram, carrier density modulation beyond 1014 cm-2 and transport measurements performed over a large temperature range are needed. Here we use the space charge doping method to measure transport characteristics from 330 K to low temperature. We extract parameters and characteristic temperatures over a large doping range and establish a comprehensive phase diagram for one-unit-cell-thick BSCCO-2212 as a function of doping, temperature and disorder.

  10. Doping control in sport

    DEFF Research Database (Denmark)

    Overbye, Marie Birch

    2016-01-01

    Doping testing is a key component enforced by anti-doping authorities to detect and deter doping in sport. Policy is developed to protect athletes' right to participate in doping-free sport; and testing is a key tool to secure this right. Accordingly, athletes' responses to anti-doping efforts.......e., the efforts of stakeholders involved in testing) in their own sport both nationally and worldwide. Moreover, it seeks to identify whether specific factors such as previous experience of testing and perceived proximity of doping have an impact on athletes' perceptions of the testing system. The study comprises...... a web-based questionnaire (N = 645; response rate 43%) and uses qualitative findings to elaborate on and explain quantitative results. Results showed that two-thirds of the athletes reported the national testing programme in their sport to be appropriate. A majority of the athletes who had an opinion...

  11. Polarization induced doped transistor

    Science.gov (United States)

    Xing, Huili; Jena, Debdeep; Nomoto, Kazuki; Song, Bo; Zhu, Mingda; Hu, Zongyang

    2016-06-07

    A nitride-based field effect transistor (FET) comprises a compositionally graded and polarization induced doped p-layer underlying at least one gate contact and a compositionally graded and doped n-channel underlying a source contact. The n-channel is converted from the p-layer to the n-channel by ion implantation, a buffer underlies the doped p-layer and the n-channel, and a drain underlies the buffer.

  12. Measurements and characterization of a hole trap in neutron-irradiated silicon

    Energy Technology Data Exchange (ETDEWEB)

    Avset, B.S.

    1996-04-01

    The report describes measurements on a hole trap in neutron irradiated silicon diodes made one high resistivity phosphorus doped floatzone silicon. The hole trap was detected by Deep Level Transient Spectroscopy. This measurement gave a trap activation energy of 0.475 MeV. Other measurements showed that the trap has very small capture cross sections for both holes and electrons (10{sup -18} to 10{sup -20} cm{sup 2}) and that the hole capture cross section is temperature dependent. The energy level position of the trap has been estimated to be between 0.25 and 0.29 eV from the valence band. 25 refs., 21 figs., 4 tabs.

  13. Black holes under external influence £

    Indian Academy of Sciences (India)

    KTF MFF UK

    of the flux of external fields across charged and rotating black holes which are approaching extremal states. Recently this effect has been shown to occur for black hole solutions in string theory. We also discuss black holes surrounded by rings and disks and rotating black holes accelerated by strings. Keywords. Black holes ...

  14. An introduction to spherically symmetric loop quantum gravity black holes

    Energy Technology Data Exchange (ETDEWEB)

    Gambini, Rodolfo [Instituto de Física, Facultad de Ciencias, Iguá 4-225, esq. Mataojo, 11400 Montevideo (Uruguay); Pullin, Jorge [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803-4001 (United States)

    2015-03-26

    We review recent developments in the treatment of spherically symmetric black holes in loop quantum gravity. In particular, we discuss an exact solution to the quantum constraints that represents a black hole and is free of singularities. We show that new observables that are not present in the classical theory arise in the quantum theory. We also discuss Hawking radiation by considering the quantization of a scalar field on the quantum spacetime.

  15. Effect of doping and annealing on the physical properties of ZnO:Mg ...

    Indian Academy of Sciences (India)

    Abstract. Well-dispersed undoped and Mg-doped ZnO nanoparticles with different doping con- centrations at various annealing temperatures are synthesized using basic chemical solution method without any capping agent. To understand the effect of Mg doping and heat treatment on the structure and optical response of ...

  16. Effect of doping and annealing on the physical properties of ZnO: Mg ...

    Indian Academy of Sciences (India)

    Well-dispersed undoped and Mg-doped ZnO nanoparticles with different doping concentrations at various annealing temperatures are synthesized using basic chemical solution method without any capping agent. To understand the effect of Mg doping and heat treatment on the structure and optical response of the ...

  17. Black-Hole Mass Measurements

    DEFF Research Database (Denmark)

    Vestergaard, Marianne

    2004-01-01

    The applicability and apparent uncertainties of the techniques currently available for measuring or estimating black-hole masses in AGNs are briefly summarized.......The applicability and apparent uncertainties of the techniques currently available for measuring or estimating black-hole masses in AGNs are briefly summarized....

  18. Black Holes in Our Universe

    Indian Academy of Sciences (India)

    Black holes are bits of space, or more precisely, 'space-time', from which even light cannot escape, because they are regions of extremely strong gravity. We now know that black holes, es- pecially those that are a million times heavier than our Sun or more, i.e., 'supermassive', are abundant in our universe, occur- ring in the ...

  19. Drilling miniature holes, Part III

    Energy Technology Data Exchange (ETDEWEB)

    Gillespie, L.K.

    1978-07-01

    Miniature components for precision electromechanical mechanisms such as switches, timers, and actuators typically require a number of small holes. Because of the precision required, the workpiece materials, and the geometry of the parts, most of these holes must be produced by conventional drilling techniques. The use of such techniques is tedious and often requires considerable trial and error to prevent drill breakage, minimize hole mislocation and variations in hole diameter. This study of eight commercial drill designs revealed that printed circuit board drills produced better locational and size repeatability than did other drills when centerdrilling was not used. Boring holes 1 mm in dia, or less, as a general rule did not improve hole location in brass or stainless steel. Hole locations of patterns of 0.66-mm holes can be maintained within 25.4-..mu..m diametral positional tolerance if setup misalignments can be eliminated. Size tolerances of +- 3.8 ..mu..m can be maintained under some conditions when drilling flat plates. While these levels of precision are possible with existing off-the-shelf drills, they may not be practical in many cases.

  20. ATLAS simulated black hole event

    CERN Multimedia

    Pequenão, J

    2008-01-01

    The simulated collision event shown is viewed along the beampipe. The event is one in which a microscopic-black-hole was produced in the collision of two protons (not shown). The microscopic-black-hole decayed immediately into many particles. The colors of the tracks show different types of particles emerging from the collision (at the center).

  1. Asymmetric black dyonic holes

    Directory of Open Access Journals (Sweden)

    I. Cabrera-Munguia

    2015-04-01

    Full Text Available A 6-parametric asymptotically flat exact solution, describing a two-body system of asymmetric black dyons, is studied. The system consists of two unequal counterrotating Kerr–Newman black holes, endowed with electric and magnetic charges which are equal but opposite in sign, separated by a massless strut. The Smarr formula is generalized in order to take into account their contribution to the mass. The expressions for the horizon half-length parameters σ1 and σ2, as functions of the Komar parameters and of the coordinate distance, are displayed, and the thermodynamic properties of the two-body system are studied. Furthermore, the seven physical parameters satisfy a simple algebraic relation which can be understood as a dynamical scenario, in which the physical properties of one body are affected by the ones of the other body.

  2. Magnetic fields around black holes

    Science.gov (United States)

    Garofalo, David A. G.

    Active Galactic Nuclei are the most powerful long-lived objects in the universe. They are thought to harbor supermassive black holes that range from 1 million solar masses to 1000 times that value and possibly greater. Theory and observation are converging on a model for these objects that involves the conversion of gravitational potential energy of accreting gas to radiation as well as Poynting flux produced by the interaction of the rotating spacetime and the electromagnetic fields originating in the ionized accretion flow. The presence of black holes in astrophysics is taking center stage, with the output from AGN in various forms such as winds and jets influencing the formation and evolution of the host galaxy. This dissertation addresses some of the basic unanswered questions that plague our current understanding of how rotating black holes interact with their surrounding magnetized accretion disks to produce the enormous observed energy. Two magnetic configurations are examined. The first involves magnetic fields connecting the black hole with the inner accretion disk and the other involves large scale magnetic fields threading the disk and the hole. We study the effects of the former type by establishing the consequences that magnetic torques between the black hole and the inner accretion disk have on the energy dissipation profile. We attempt a plausible explanation to the observed "Deep Minimum" state in the Seyfert galaxy MCG-6- 30-15. For the latter type of magnetic geometry, we study the effects of the strength of the magnetic field threading the black hole within the context of the cherished Blandford & Znajek mechanism for black hole spin energy extraction. We begin by addressing the problem in the non-relativistic regime where we find that the black hole-threading magnetic field is stronger for greater disk thickness, larger magnetic Prandtl number, and for a larger accretion disk. We then study the problem in full relativity where we show that our

  3. When Charged Black Holes Merge

    Science.gov (United States)

    Kohler, Susanna

    2016-08-01

    Most theoretical models assume that black holes arent charged. But a new study shows that mergers of charged black holes could explain a variety of astrophysical phenomena, from fast radio bursts to gamma-ray bursts.No HairThe black hole no hair theorem states that all black holes can be described by just three things: their mass, their spin, and their charge. Masses and spins have been observed and measured, but weve never measured the charge of a black hole and its widely believed that real black holes dont actually have any charge.That said, weve also never shown that black holes dont have charge, or set any upper limits on the charge that they might have. So lets suppose, for a moment, that its possible for a black hole to be charged. How might that affect what we know about the merger of two black holes? A recent theoretical study by Bing Zhang (University of Nevada, Las Vegas) examines this question.Intensity profile of a fast radio burst, a sudden burst of radio emission that lasts only a few milliseconds. [Swinburne Astronomy Productions]Driving TransientsZhangs work envisions a pair of black holes in a binary system. He argues that if just one of the black holes carries charge possibly retained by a rotating magnetosphere then it may be possible for the system to produce an electromagnetic signal that could accompany gravitational waves, such as a fast radio burst or a gamma-ray burst!In Zhangs model, the inspiral of the two black holes generates a global magnetic dipole thats perpendicular to the plane of the binarys orbit. The magnetic flux increases rapidly as the separation between the black holes decreases, generating an increasingly powerful magnetic wind. This wind, in turn, can give rise to a fast radio burst or a gamma-ray burst, depending on the value of the black holes charge.Artists illustration of a short gamma-ray burst, thought to be caused by the merger of two compact objects. [ESO/A. Roquette]Zhang calculates lower limits on the charge

  4. Prisons of Light - Black Holes

    Science.gov (United States)

    Ferguson, Kitty

    1998-05-01

    In this jargon-free review of one of the most fascinating topics in modern science, acclaimed science writer Kitty Ferguson examines the discovery of black holes, their nature, and what they can teach us about the mysteries of the universe. In search of the answers, we trace a star from its birth to its death throes, take a hypothetical journey to the border of a black hole and beyond, spend time with some of the world's leading theoretical physicists and astronomers, and take a whimsical look at some of the wild ideas black holes have inspired. Prisons of Light--Black Holes is comprehensive and detailed. Yet Kitty Ferguson's lightness of touch and down-to-earth analogies set this book apart from all others on black holes and make it a wonderfully stimulating and entertaining read.

  5. String-Corrected Black Holes

    Energy Technology Data Exchange (ETDEWEB)

    Hubeny, V.

    2005-01-12

    We investigate the geometry of four dimensional black hole solutions in the presence of stringy higher curvature corrections to the low energy effective action. For certain supersymmetric two charge black holes these corrections drastically alter the causal structure of the solution, converting seemingly pathological null singularities into timelike singularities hidden behind a finite area horizon. We establish, analytically and numerically, that the string-corrected two-charge black hole metric has the same Penrose diagram as the extremal four-charge black hole. The higher derivative terms lead to another dramatic effect--the gravitational force exerted by a black hole on an inertial observer is no longer purely attractive. The magnitude of this effect is related to the size of the compactification manifold.

  6. Doped spin ladders under magnetic field; Echelles de spins dopees sous champ magnetique

    Energy Technology Data Exchange (ETDEWEB)

    Roux, G

    2007-07-15

    This thesis deals with the physics of doped two-leg ladders which are a quasi one-dimensional and unconventional superconductor. We particularly focus on the properties under magnetic field. Models for strongly correlated electrons on ladders are studied using exact diagonalization and density-matrix renormalization group (DMRG). Results are also enlightened by using the bosonization technique. Taking into account a ring exchange it highlights the relation between the pairing of holes and the spin gap. Its influence on the dynamics of the magnetic fluctuations is also tackled. Afterwards, these excitations are probed by the magnetic field by coupling it to the spin degree of freedom of the electrons through Zeeman effect. We show the existence of doping-dependent magnetization plateaus and also the presence of an inhomogeneous superconducting phase (FFLO phase) associated with an exceeding of the Pauli limit. When a flux passes through the ladder, the magnetic field couples to the charge degree of freedom of the electrons via orbital effect. The diamagnetic response of the doped ladder probes the commensurate phases of the t-J model at low J/t. Algebraic transverse current fluctuations are also found once the field is turned on. Lastly, we report numerical evidences of a molecular superfluid phase in the 3/2-spin attractive Hubbard model: at a density low enough, bound states of four fermions, called quartets, acquire dominant superfluid fluctuations. The observed competition between the superfluid and density fluctuations is connected to the physics of doped ladders. (author)

  7. Doping properties of cadmium-rich arsenic-doped CdTe single crystals: Evidence of metastable AX behavior

    Energy Technology Data Exchange (ETDEWEB)

    Nagaoka, Akira [Department of Materials Science and Engineering, Kyoto University, Kyoto 606-8501, Japan; Materials Science and Engineering and Electrical and Computer Engineering Departments, University of Utah, Salt Lake City, Utah 84112, USA; Kuciauskas, Darius [National Renewable Energy Laboratory (NREL), Golden, Colorado 80401, USA; Scarpulla, Michael A. [Materials Science and Engineering and Electrical and Computer Engineering Departments, University of Utah, Salt Lake City, Utah 84112, USA

    2017-12-04

    Cd-rich composition and group-V element doping are of interest for simultaneously maximizing the hole concentration and minority carrier lifetime in CdTe, but the critical details concerning point defects are not yet fully established. Herein, we report on the properties of arsenic doped CdTe single crystals grown from Cd solvent by the travelling heater method. The photoluminescence spectra and activation energy of 74 +/- 2 meV derived from the temperature-dependent Hall effect are consistent with AsTe as the dominant acceptor. Doping in the 10^16 to 10^17/cm^3 range is achieved for measured As concentrations between 10^16 and 10^20/cm^3 with the highest doping efficiency of 40% occurring near 10^17 As/cm^3. We observe persistent photoconductivity, a hallmark of light-induced metastable configuration changes consistent with AX behavior. Additionally, quenching experiments reveal at least two mechanisms of increased p-type doping in the dark, one decaying over 2-3 weeks and the other persisting for at least 2 months. These results provide essential insights for the application of As-doped CdTe in thin film solar cells.

  8. Are LIGO's Black Holes Made From Smaller Black Holes?

    Science.gov (United States)

    Kohler, Susanna

    2017-05-01

    The recent successes of the Laser Interferometer Gravitational-Wave Observatory (LIGO) has raised hopes that several long-standing questions in black-hole physics will soon be answerable. Besides revealing how the black-hole binary pairs are built, could detections with LIGO also reveal how the black holes themselves form?Isolation or HierarchyThe first detection of gravitational waves, GW150914, was surprising for a number of reasons. One unexpected result was the mass of the two black holes that LIGO saw merging: they were a whopping 29 and 36 solar masses.On the left of this schematic, two first-generation (direct-collapse) black holes form a merging binary. The right illustrates a second-generation hierarchical merger: each black hole in the final merging binary was formed by the merger of two smaller black holes. [Adapted fromGerosa et al., a simultaneously published paper that also explores the problem of hierarchical mergers and reaches similar conclusions]How do black holes of this size form? One possibility is that they form in isolation from the collapse of a single massive star. In an alternative model, they are created through the hierarchical merger of smaller black holes, gradually building up to the size we observed.A team of scientists led by Maya Fishbach (University of Chicago) suggests that we may soon be able to tell whether or not black holes observed by LIGO formed hierarchically. Fishbach and collaborators argue that hierarchical formation leaves a distinctive signature on the spins of the final black holes and that as soon as we have enough merger detections from LIGO, we can use spin measurements to statistically determine if LIGO black holes were formed hierarchically.Spins from Major MergersWhen two black holes merge, both their original spins and the angular momentum of the pair contribute to the spin of the final black hole that results. Fishbach and collaborators calculate the expected distribution of these final spins assuming that

  9. Area spectrum of slowly rotating black holes

    OpenAIRE

    Myung, Yun Soo

    2010-01-01

    We investigate the area spectrum for rotating black holes which are Kerr and BTZ black holes. For slowly rotating black holes, we use the Maggiore's idea combined with Kunstatter's method to derive their area spectra, which are equally spaced.

  10. New entropy formula for Kerr black holes

    OpenAIRE

    Gonzalez, Hernan; Grumiller, Daniel; Merbis, Wout; Wutte, Raphaela

    2017-01-01

    We introduce a new entropy formula for Kerr black holes inspired by recent results for 3-dimensional black holes and cosmologies with soft Heisenberg hair. We show that also Kerr-Taub-NUT black holes obey the same formula.

  11. Luminescence of devitrificated non-doped and Eu,Dy and Tm doped wollastonite crystal in glass; Luminescence de cristaux de devitrivication de wollastonite dans des verres non dopes et dopes en Eu,Dy et Tm

    Energy Technology Data Exchange (ETDEWEB)

    El Marraki, A.; Schvoerer, M.; Bechtel, F. [Univ. Michel de Montaigne-Bordeaux 3, Pessac (France). Centre de Recherche en Phys. Appliquee a l' Archeologie

    2000-10-16

    Wollastonite crystals (CaSiO{sub 3}), ''pure'' or doped with rare earth ions, were grown by a devitrification process of a ternary SiO{sub 2}-Na{sub 2}O-CaO glass. The nature of point defects in these crystals was studied. Concerning the non-doped crystals, two trap centers were revealed by thermoluminescence (TL) and identified by electron spin resonance (ESR) using preheating experiments: one is a hole center HC{sub 1} and the other one an electron center whose main characteristic feature is g = 2.0020. Cathodoluminescence (CL) studies showed an important emission band considered as intrinsic. As for the doped crystals (Eu, Dy, Tm), most CL emission bands were identified. With TL, it is shown that Eu acts in wollastonite crystals as an electron trap and also as an emission centre. (orig.)

  12. Doping-Promoted Solar Water Oxidation on Hematite Photoanodes.

    Science.gov (United States)

    Zhang, Yuchao; Ji, Hongwei; Ma, Wanhong; Chen, Chuncheng; Song, Wenjing; Zhao, Jincai

    2016-07-01

    As one of the most promising materials for solar water oxidation, hematite has attracted intense research interest for four decades. Despite their desirable optical band gap, stability and other attractive features, there are great challenges for the implementation of hematite-based photoelectrochemical cells. In particular, the extremely low electron mobility leads to severe energy loss by electron hole recombination. Elemental doping, i.e., replacing lattice iron with foreign atoms, has been shown to be a practical solution. Here we review the significant progresses in metal and non-metal element doping-promoted hematite solar water oxidation, focusing on the role of dopants in adjusting carrier density, charge collection efficiency and surface water oxidation kinetics. The advantages and salient features of the different doping categories are compared and discussed.

  13. Dyes Degradation with Fe-Doped Titanium Nanotube Photocatalysts Prepared from Spend Steel Slag

    Directory of Open Access Journals (Sweden)

    Chih Ming Ma

    2013-01-01

    Full Text Available TiO2 has been studied most commonly because it has high stability, nontoxicity, high catalytic activity, and high conductivity. Many studies have shown that TiO2 would generate electron-hole pairs illuminated with UV and surround more energy than that before being illuminated. In this study, the titanium nanotube (TNT photocatalysts were prepared to increase the surface area and adsorption capacity. The Fe TNT was also prepared from a slag iron since many slag irons cause waste treatment problems. In this study, a different Fe loading was also assessed since TNT doped with metals can be used to improve the degradation efficiency. Furthermore, five kinds of dye concentration, including 10, 20, 100, 200, and 400 ppm, and five kinds of Fe-doped content, including 0, 0.77, 1.13, 2.24, and 4.50%, were tested. Different kinds of reaction time and dye species were also assessed. In this result, Direct Black 22 was the most difficult to be degraded, although the concentration was decreased or the dose amount was increased. The degradation efficiency of 10 ppm Direct Black 22 was below 40% with 0.04 gL−1 TNT under 365 nm UV irradiation.

  14. Rational hybrid modulation of P, N dual-doped holey graphene for high-performance supercapacitors

    Science.gov (United States)

    Nazarian-Samani, Masoud; Haghighat-Shishavan, Safa; Nazarian-Samani, Mahboobeh; Kim, Myeong-Seong; Cho, Byung-Won; Oh, Si-Hyoung; Kashani-Bozorg, Seyed Farshid; Kim, Kwang-Bum

    2017-12-01

    A P, N dual-doped holey graphene (PNHG) material is prepared by a scalable, facile synthetic approach, using a mixture of glucose, dicyandiamide (DCDA), and phosphoric acid (H3PO4). H3PO4 successfully functions as an "acid catalyst" to encourage the uniform breakage of C=C bonds to create large, localized perforations over the graphene monolith. Further acid treatment and annealing introduce in-plane holes. The correlation between the capacitance of the PNHG and its structural parameters during the fabrication process is comprehensively evaluated. A thermally induced sp2→sp3 transformation occurs at high temperatures because of the substantial loss of graphitic sp2-type carbons, together with a dramatic reduction in capacitance. The target PNHG-400 electrode material delivers exceptionally high gravimetric capacitance (235.5 F g-1 at 0.5 A g-1), remarkable rate capability (84.8% at 70 A g-1), superior capacitance retention (93.2 and 92.7% at 10 and 50 A g-1 over 25000 cycles, respectively), and acceptable volumetric capacitance due to moderate density, when it is used with organic electrolytes in the voltage range between 0 and 3 V. These results suggest a pioneering defect-engineered strategy to fabricate dual-doped holey graphene with valuable structural properties for high-performance electric double layer supercapacitors, which could be used in next-generation energy storage applications.

  15. Annealing effect on the electron spin dynamics in heavily Mn-doped (Ga,Mn)As

    Energy Technology Data Exchange (ETDEWEB)

    Yue, Han; Chen, Lin; Gao, Haixia; Zhao, Jianhua; Zhang, Xinhui [Institute of Semiconductors, Chinese Academy of Sciences, Beijing (China)

    2014-05-15

    A temperature- and photo-excitation-density-dependent electron spin dephasing process has been studied by time-resolved magneto-optical Kerr effect (TR-MOKE) measurements for heavily-doped (Ga,Mn)As after appropriate annealing treatment. Unlike the as-grown (Ga,Mn)As in which s-d scattering is dominant for spin dephasing at low temperature, the exchange scattering induced by Mn ions is efficiently suppressed after annealing. For annealed (Ga,Mn)As, the p-d exchange coupling proves to be important for the electron spin dephasing process. Moreover, the Coulomb scattering arising from the weakly-localized holes and Mn impurities is revealed to play an important role in the electron spin dephasing after annealing. Our results demonstrate that the impurity induced disorder plays a significant role in the electron spin-dephasing process in (Ga,Mn)As when Mn is over doped by as much as 15%, which is a critical issue that needs to be considered to achieve high-quality (Ga,Mn)As thin films with a higher Curie temperature T{sub C} and better functionality.

  16. To dope or not to dope

    DEFF Research Database (Denmark)

    Overbye, Marie Birch; Knudsen, Mette Lykke; Pfister, Gertrud Ursula

    2013-01-01

    tAim: This study aims to examine the circumstances which athletes say affect their (hypothetical) consid-erations of whether to dope or not and explore the differences between athletes of different gender, ageand sport type.Methods: 645 elite athletes (mean age: 22.12; response rate: 43%) represe......tAim: This study aims to examine the circumstances which athletes say affect their (hypothetical) consid-erations of whether to dope or not and explore the differences between athletes of different gender, ageand sport type.Methods: 645 elite athletes (mean age: 22.12; response rate: 43......%) representing 40 sports completed aweb-based questionnaire. Participants were asked to imagine themselves in a situation in which theyhad to decide whether to dope or not to dope and then evaluate how different circumstances would affecttheir decisions.Results: Multiple circumstances had an effect on athletes......’ hypothetical decisions. The most effective deter-rents were related to legal and social sanctions, side-effects and moral considerations. Female athletesand younger athletes evaluated more reasons as deterrents than older, male athletes. When confrontedwith incentives to dope, the type of sport was often...

  17. Percutaneous epidural drainage through a burr hole

    Directory of Open Access Journals (Sweden)

    Priscila M Falsarella

    2016-01-01

    Full Text Available Intracranial extradural collection may cause an increase in intracranial pressure, requiring rapid emergency treatment to reduce morbidity and mortality. We described an alternative CT-guided percutaneous access for extradural collection drainage. We report a case of a patient with previous craniectomy for meningioma ressection who presented to the Emergency Department with symptoms of intracranial hypertension. Brains CT showed a extradural collection with subfalcine herniation. After multidisciplinary discussion a CT-guided percutaneous drainage through previous burr hole was performed. The patient was discharged after 36 hours of admission, without further symptoms. We describe a safe and effective alternative percutaneous access for extradural collection drainage in patients with previous burr hole.

  18. [Doping and sports].

    Science.gov (United States)

    Lippi, G; Guidi, G

    1999-09-01

    Doping is widely known as the use of banned substances and practices by athletes in an attempt to improve sporting performances. The term doping likely derives from "dope", an ancient expression referred to a primitive alcoholic drink that was used as a stimulant in South African ceremonial dances; gradually, the term was extended and finally adopted his current significance. There are at least two essential reasons to support the fight against doping: the potential harmful effects on athletes and the depth corruption of the fair competition. An exhaustive list of banned substances and methods has been drawn by the International Olympic Committee and further accepted by other International Sport Authorities and Federations. This list, regularly updated, is basically divided into doping substances (stimulants, narcotic analgesics, anabolic agents, diuretics, peptide and glycoprotein hormones and analogues), doping methods (blood doping, pharmacological, chemical and physical manipulation) and drugs subjected to certain restrictions (alcohol, marijuana, local anesthetics, corticosteroids and beta-blockers). Although there might be some medical conditions, which could legitimate the need of these substances or methods, there is no place for their use in sport. Thus, an athlete's consume of any of these substances or methods will result in disqualification. Aim of the present review is to provide a synthetic description of both the desirable effects and the potentially harmful consequences of the use of some of the major doping substances and methods.

  19. VTrans Small Culvert Inventory - Access Holes

    Data.gov (United States)

    Vermont Center for Geographic Information — Vermont Agency of Transportation Small Culvert Inventory: Access Holes. This data contains access hole locations along VTrans maintained roadways. The data was...

  20. Black Hole Grabs Starry Snack

    Science.gov (United States)

    2006-01-01

    [figure removed for brevity, see original site] Poster Version This artist's concept shows a supermassive black hole at the center of a remote galaxy digesting the remnants of a star. NASA's Galaxy Evolution Explorer had a 'ringside' seat for this feeding frenzy, using its ultraviolet eyes to study the process from beginning to end. The artist's concept chronicles the star being ripped apart and swallowed by the cosmic beast over time. First, the intact sun-like star (left) ventures too close to the black hole, and its own self-gravity is overwhelmed by the black hole's gravity. The star then stretches apart (middle yellow blob) and eventually breaks into stellar crumbs, some of which swirl into the black hole (cloudy ring at right). This doomed material heats up and radiates light, including ultraviolet light, before disappearing forever into the black hole. The Galaxy Evolution Explorer was able to watch this process unfold by observing changes in ultraviolet light. The area around the black hole appears warped because the gravity of the black hole acts like a lens, twisting and distorting light.

  1. Light-induced charge-transport properties of photorefractive barium-calcium-titanate crystals doped with iron

    Science.gov (United States)

    Veenhuis, H.; Börger, T.; Buse, K.; Kuper, C.; Hesse, H.; Krätzig, E.

    2000-07-01

    Nominally pure and iron doped, as-grown, and thermally annealed photorefractive barium-calcium-titanate crystals of the congruently melting composition Ba0.23Ca0.77TiO3 (BCT) are investigated by holographic and conventional electrical techniques. Refractive-index changes, two-beam-coupling gains, photoconductivities, dark conductivities, and bulk-photovoltaic current densities are measured. As-grown and oxidized crystals are hole conductive and at usual illumination conditions (light wavelength 514.5 nm, light intensity between 0.1 and 1 W/cm2) all measured properties are excellently described by an one-center charge-transport model. The effective electrooptic coefficient r333 is only about 30 pm/V and thus much smaller than the value obtained from interferometric measurements. Two-beam-coupling gains as high as 7 cm-1 are achieved. Doping with iron increases considerably the effective trap density, and bulk-photovoltaic fields of the order of some kilovolts per centimeter are observed in iron-doped crystals. Typical response times of iron-doped, as-grown, or oxidized crystals are about 0.5 s at 1 W/cm2. Reduction yields electron-conductive BCT. The dark storage time increases from 6 min in the as-grown state to 3 h upon a slight reduction treatment, but decreases for strongly reduced samples. The investigation reveals that BCT will become a very promising alternative to barium-titanate crystals (BaTiO3) for many applications.

  2. Atlantic coastal plain geothermal test holes, Virginia: hole completion reports

    Energy Technology Data Exchange (ETDEWEB)

    Cobb, L.B.; Radford, L.; Glascock, M.

    1979-03-01

    A description of the Atlantic Coastal Plain Geothermal Drilling Program and data for the following geothermal test holes drilled in Virginia are summarized: Creeds, Norfolk Naval Base, Langley Air Force Base, Wattsville, Withams, and Atlantic.

  3. Unveiling the edge of time black holes, white holes, wormholes

    CERN Document Server

    Gribbin, John

    1992-01-01

    Acclaimed science writer John Gribbin recounts dramatic stories that have led scientists to believe black holes and their more mysterious kin are not only real, but might actually provide a passage to other universes and travel through time.

  4. Quantum mechanics of black holes.

    Science.gov (United States)

    Witten, Edward

    2012-08-03

    The popular conception of black holes reflects the behavior of the massive black holes found by astronomers and described by classical general relativity. These objects swallow up whatever comes near and emit nothing. Physicists who have tried to understand the behavior of black holes from a quantum mechanical point of view, however, have arrived at quite a different picture. The difference is analogous to the difference between thermodynamics and statistical mechanics. The thermodynamic description is a good approximation for a macroscopic system, but statistical mechanics describes what one will see if one looks more closely.

  5. Orbital resonances around black holes.

    Science.gov (United States)

    Brink, Jeandrew; Geyer, Marisa; Hinderer, Tanja

    2015-02-27

    We compute the length and time scales associated with resonant orbits around Kerr black holes for all orbital and spin parameters. Resonance-induced effects are potentially observable when the Event Horizon Telescope resolves the inner structure of Sgr A*, when space-based gravitational wave detectors record phase shifts in the waveform during the resonant passage of a compact object spiraling into the black hole, or in the frequencies of quasiperiodic oscillations for accreting black holes. The onset of geodesic chaos for non-Kerr spacetimes should occur at the resonance locations quantified here.

  6. Black holes and Higgs stability

    CERN Document Server

    Tetradis, Nikolaos

    2016-09-20

    We study the effect of primordial black holes on the classical rate of nucleation of AdS regions within the standard electroweak vacuum. We find that the energy barrier for transitions to the new vacuum, which characterizes the exponential suppression of the nucleation rate, can be reduced significantly in the black-hole background. A precise analysis is required in order to determine whether the the existence of primordial black holes is compatible with the form of the Higgs potential at high temperature or density in the Standard Model or its extensions.

  7. Oral tranexamic acid enhances the efficacy of low-fluence 1064-nm quality-switched neodymium-doped yttrium aluminum garnet laser treatment for melasma in Koreans: a randomized, prospective trial.

    Science.gov (United States)

    Shin, Jung U; Park, Jihun; Oh, Sang Ho; Lee, Ju Hee

    2013-03-01

    Tranexamic acid (TA) has recently gained in popularity in the treatment of pigmentary disorders. To evaluate the clinical efficacy and safety of oral TA combined with low-fluence 1064-nm quality-switched neodymium-doped yttrium aluminum garnet (QSNY) laser for the treatment of melasma. Forty-eight patients with melasma were enrolled in the study and subsequently divided into two groups: a combination group and a laser treatment group. All patients were treated with two sessions of low-fluence QSNY laser, and patients in the combination group took 8 weeks of oral TA. Two blinded dermatologists evaluated patients using the Modified Melasma Area and Severity Index (mMASI) and a clinical improvement scale. Mean mMASI score 4 weeks after the second treatment decreased significantly in both groups from base line. Based on overall clinical improvement, a greater number of patients scored as grade 3 and more in the combination group; no patients were scored as grade 4 in the laser-alone group. Oral TA may prove a safe and efficient treatment option for melasma in combination with low-fluence QSNY laser therapy. © 2012 by the American Society for Dermatologic Surgery, Inc. Published by Wiley Periodicals, Inc.

  8. Pyrene-Based Blue AIEgen: Enhanced Hole Mobility and Good EL Performance in Solution-Processed OLEDs

    Directory of Open Access Journals (Sweden)

    Jie Yang

    2017-12-01

    Full Text Available Organic luminogens with strong solid-state emission have attracted much attention for their widely practical applications. However, the traditional organic luminogens with planar conformations often suffer from the notorious aggregation-caused quenching (ACQ effect in solid state for the π–π stacking. Here, a highly efficient blue emitter TPE-4Py with an aggregation-induced emission (AIE effect is achieved by combining twisted tetraphenylethene (TPE core and planar pyrene peripheries. When the emitter was spin-coated in non-doped OLEDs with or without a hole-transporting layer, comparable EL performance was achieved, showing the bifunctional property as both an emitter and a hole-transporting layer. Furthermore, its EL efficiency was promoted in doped OLED, even at a high doping concentration (50%, because of its novel AIE effect, with a current efficiency up to 4.9 cd/A at 484 nm.

  9. Heating solar coronal holes

    Science.gov (United States)

    Parker, E. N.

    1991-01-01

    It has been shown that the coronal hole, and the associated high-speed stream in the solar wind, are powered by a heat input of the order of 500,000 ergs/sq cm s, with most of the heat injected in the first 1-2 solar radii, and perhaps 100,000 ergs/sq cm s introduced at distances of several solar radii to provide the high speed of the issuing solar wind. The traditional view has been that this energy is obtained from Alfven waves generated in the subphotospheric convection, which dissipate as they propagate outward, converting the wave energy into heat. This paper reviews the generation of waves and the known wave dissipation mechanisms, to show that the necessary Alfven waves are not produced under the conditions presently understood to exist in the sun, nor would such waves dissipate significantly in the first 1-2 solar radii if they existed. Wave dissipation occurs only over distances of the order of 5 solar radii or more.

  10. Bottom hole blowout preventer

    Energy Technology Data Exchange (ETDEWEB)

    Lineham, D.H.

    1991-04-24

    An automatically controlled ball-valve type bottom-hole blowout preventer is provided for use in drilling oil or gas wells. The blowout preventer of the invention operates under normal drilling conditions in a fully open position with an unrestricted bore. This condition is maintained by a combination of spring and mud flow pressure acting against the upper surfaces of the valve. In the event of a well kick or blowout, pressures from gas or fluid volumes acting against the lower surfaces of the valve force it into the fully closed position. A system of ports and check valves within the blowout preventer forces hydraulic fluid from one chamber to another. The metering effect of these ports determines the rate of closure of the valve, thereby allowing normal running and pulling of the drill string or tubing, without interference to pipe fill-up or drainage, from valve closure. The blowout preventer is placed in a subassembly that is an integral part of the drill string and can be incorporated in a string in any location. 3 figs.

  11. Black hole meiosis

    Science.gov (United States)

    van Herck, Walter; Wyder, Thomas

    2010-04-01

    The enumeration of BPS bound states in string theory needs refinement. Studying partition functions of particles made from D-branes wrapped on algebraic Calabi-Yau 3-folds, and classifying states using split attractor flow trees, we extend the method for computing a refined BPS index, [1]. For certain D-particles, a finite number of microstates, namely polar states, exclusively realized as bound states, determine an entire partition function (elliptic genus). This underlines their crucial importance: one might call them the ‘chromosomes’ of a D-particle or a black hole. As polar states also can be affected by our refinement, previous predictions on elliptic genera are modified. This can be metaphorically interpreted as ‘crossing-over in the meiosis of a D-particle’. Our results improve on [2], provide non-trivial evidence for a strong split attractor flow tree conjecture, and thus suggest that we indeed exhaust the BPS spectrum. In the D-brane description of a bound state, the necessity for refinement results from the fact that tachyonic strings split up constituent states into ‘generic’ and ‘special’ states. These are enumerated separately by topological invariants, which turn out to be partitions of Donaldson-Thomas invariants. As modular predictions provide a check on many of our results, we have compelling evidence that our computations are correct.

  12. Linear polarization Yb3+-doped fiber laser with novel innerclad structures

    NARCIS (Netherlands)

    Martinez-Pinon, F.; Alvarez-Chavez, J.A.; Jaramillo Vigueras, D.; de la Cruz-May, L.; Offerhaus, Herman L.

    2008-01-01

    Results on high radiance Yb3+-doped fiber lasers with novel double innerclad structures (double-D clad and four hole) and polarized output at ≈1090 nm are presented. We have demonstrated >40% of the total output power being polarized, making the fiber laser suitable for LIDAR and second-harmonic

  13. Charge carrier trapping processes in lanthanide doped La-, Gd-, Y-, and LuPO4

    NARCIS (Netherlands)

    Lyu, T.; Dorenbos, P.

    2017-01-01

    Various methods for deliberate design electron and hole trapping materials are explored with a study on double lanthanide doped rare earth ortho phosphates. Cerium acts as recombination center while lanthanide codopants as electron trapping centers in LaPO4:0.005Ce3+,0.005Ln3+. The electron trap

  14. Multimode laser emission from dye-doped hollow polymer optical fibre

    Indian Academy of Sciences (India)

    2014-02-09

    Feb 9, 2014 ... tion of Rh B-doped methyl methacrylate (MMA). Hole in the preform can be achieved by placing a teflon rod on the centre of the glass tube during the polymerization. Final fibre structure with required diameter was obtained by heat drawing process. The diam- eter of the final fibre structure can be controlled ...

  15. Effect of Doping and Pressure on Magnetism and Lattice Structure of Fe-Based Superconductors

    Science.gov (United States)

    2010-04-14

    effect as hole doping (sub- stituting Ba by K). However, later it was found that pressure and/or strain can lead to essentially the same effect12,13...even better, Sr) by a rare earth like La or Yb seems to be chemically natural (cf. superconducting cuprates or colossal magnetoresistance manganites

  16. Design and optimization of mechanically down-doped terahertz fiber directional couplers

    DEFF Research Database (Denmark)

    Bao, Hualong; Nielsen, Kristian; Rasmussen, Henrik K.

    2014-01-01

    We present a thorough practical design optimization of broadband low loss, terahertz (THz) photonic crystal fiber directional couplers in which the two cores are mechanically down-doped with a triangular array of air holes. A figure of merit taking both the 3-dB bandwidth and loss of the coupler...

  17. Numerical and analytical modeling of polarization-dependent gain in erbium-doped fiber amplifiers

    Science.gov (United States)

    Leners, R.; Georges, T.

    1995-10-01

    We present a rate-equation model that accounts for polarization hole burning in erbium-doped fiber amplifiers. This model yields analytical expressions for the polarization sensitivity of the amplifier for arbitrary signal polarization states. We investigate the influence of the birefringence properties of the fiber and calculate the average polarization properties of an amplifier chain. Copyright (c) 1995 Optical Society of America

  18. Erratic Black Hole Regulates Itself

    Science.gov (United States)

    2009-03-01

    New results from NASA's Chandra X-ray Observatory have made a major advance in explaining how a special class of black holes may shut off the high-speed jets they produce. These results suggest that these black holes have a mechanism for regulating the rate at which they grow. Black holes come in many sizes: the supermassive ones, including those in quasars, which weigh in at millions to billions of times the mass of the Sun, and the much smaller stellar-mass black holes which have measured masses in the range of about 7 to 25 times the Sun's mass. Some stellar-mass black holes launch powerful jets of particles and radiation, like seen in quasars, and are called "micro-quasars". The new study looks at a famous micro-quasar in our own Galaxy, and regions close to its event horizon, or point of no return. This system, GRS 1915+105 (GRS 1915 for short), contains a black hole about 14 times the mass of the Sun that is feeding off material from a nearby companion star. As the material swirls toward the black hole, an accretion disk forms. This system shows remarkably unpredictable and complicated variability ranging from timescales of seconds to months, including 14 different patterns of variation. These variations are caused by a poorly understood connection between the disk and the radio jet seen in GRS 1915. Chandra, with its spectrograph, has observed GRS 1915 eleven times since its launch in 1999. These studies reveal that the jet in GRS 1915 may be periodically choked off when a hot wind, seen in X-rays, is driven off the accretion disk around the black hole. The wind is believed to shut down the jet by depriving it of matter that would have otherwise fueled it. Conversely, once the wind dies down, the jet can re-emerge. "We think the jet and wind around this black hole are in a sort of tug of war," said Joseph Neilsen, Harvard graduate student and lead author of the paper appearing in the journal Nature. "Sometimes one is winning and then, for reasons we don

  19. Formation of bioactive N-doped TiO2 on Ti with visible light-induced antibacterial activity using NaOH, hot water, and subsequent ammonia atmospheric heat treatment.

    Science.gov (United States)

    Kawashita, Masakazu; Endo, Naoko; Watanabe, Tomoaki; Miyazaki, Toshiki; Furuya, Maiko; Yokota, Kotoe; Abiko, Yuki; Kanetaka, Hiroyasu; Takahashi, Nobuhiro

    2016-09-01

    Titanium (Ti) treated with NaOH and hot water, and heated in an ammmonia (NH3) gas atmosphere for 1 or 3h exhibited in vitro apatite formation within 7days when soaked in simulated body fluid (SBF). Moreover, the treated Ti decomposed methylene blue and showed excellent bactericidal activity against Escherichia coli under visible light irradiation. The surface treatment resulted in the formation of a fine network of N-doped anatase-type titania (TiO2-xNx) on the Ti surface, which was responsible for both the apatite formation in SBF and the visible light-induced antibacterial activity. These preliminary results highlight the efficacy of our simple method for producing novel bioactive Ti with visible light-induced antibacterial activity, which could be applied to orthopaedic and dental implants without the risk of infection. Copyright © 2016 Elsevier B.V. All rights reserved.

  20. The physics of black holes

    CERN Document Server

    Susskind, Leonard

    1997-01-01

    I will describe profound revolution in our understanding of black holes and their relation to quantum mechanics that has occured over the last few years as a result of a deeper understanding of string theory.

  1. Hole dephasing caused by hole-hole interaction in a multilayered black phosphorus.

    Science.gov (United States)

    Li, Lijun; Khan, Muhammad Atif; Lee, Yoontae; Lee, Inyeal; Yun, Sun Jin; Youn, Doo-Hyeb; Kim, Gil-Ho

    2017-11-01

    We study the magnetotransport of holes in a multilayered black phosphorus in a temperature range of 1.9 to 21.5 K. We observed a negative magnetoresistance at magnetic fields up to 1.5 T. This negative magetoresistance was analyzed by weak localization theory in diffusive regime. At the lowest temperature and the highest carrier density we found a phase coherence length of 48 nm. The linear temperature dependence of the dephasing rate shows that the hole-hole scattering processes with small energy transfer are the dominant contribution in breaking the carrier phase coherence.

  2. Investigation of xFe2O4 (x = Mn, Co) doped hydroxylapatite ferromagnetic biomaterials for the treatment of damaged bone and magnetically targeted drug delivery systems

    Science.gov (United States)

    Anand, Vikas; Singh, K. J.; Kaur, Kulwinder; Bhatia, Gaurav

    2016-05-01

    Magnetically attracted MnFe2O4 and CoFe2O4 doped hydroxylapatite samples have been prepared by using co-precipitation method in the laboratory. Bioactive nature of samples has been confirmed from XRD spectra. Ferromagnetic behavior of samples has been studied by using vibration sample magnetometer. Human osteoblast cell line MG63 has been used to explore the cell viability of samples. Drug carrier ability of samples has been checked with gentamycin as an antibiotic and results show that samples can be used as excellent drug carriers. Drug loaded samples can be easily targeted to specific area due to their attractive nature towards external magnetic field. Our results indicate that prepared samples possess good bioactive as well as ferromagnetic behavior with drug carrier ability and hence, our samples can be potential candidates for the clinical applications.

  3. Clinical reach progress of idiopathic macular hole

    Directory of Open Access Journals (Sweden)

    Hui-Lan Sun

    2017-02-01

    Full Text Available Idiopathic macular hole(IMHis unequivocal inducement lead to limiting full-thickness defect of retinal neurepithelium layerin macular region. It's one of the most important fundus macular degeneration. According to the different causes and the anatomical site, the lesion has a different classification, and its etiology and pathogenesis are diverse and complex. But along with the continuous renewal of ophthalmologic examination instrument and the continuous improvement of surgical technique, treatment of IMH is diversified and treatment effect is more obvious. Not only that, IHM preventive treatment also gradually get used in clinical. In this paper, we reviewed the progress of IMH in terms of the pathogenesis, relative examination, surgical treatment, preoperative prognostic evaluation and so on.

  4. The 2002 Antarctic Ozone Hole

    Science.gov (United States)

    Newman, P. A.; Nash, E. R.; Douglass, A. R.; Kawa, S. R.

    2003-01-01

    Since 1979, the ozone hole has grown from near zero size to over 24 Million km2. This area is most strongly controlled by levels of inorganic chlorine and bromine oncentrations. In addition, dynamical variations modulate the size of the ozone hole by either cooling or warming the polar vortex collar region. We will review the size observations, the size trends, and the interannual variability of the size. Using a simple trajectory model, we will demonstrate the sensitivity of the ozone hole to dynamical forcing, and we will use these observations to discuss the size of the ozone hole during the 2002 Austral spring. We will further show how the Cly decreases in the stratosphere will cause the ozone hole to decrease by 1-1.5% per year. We will also show results from a 3-D chemical transport model (CTM) that has been continuously run since 1999. These CTM results directly show how strong dynamics acts to reduce the size of the ozone hole.

  5. Black Hole Spin Measurement Uncertainty

    Science.gov (United States)

    Salvesen, Greg; Begelman, Mitchell C.

    2018-01-01

    Angular momentum, or spin, is one of only two fundamental properties of astrophysical black holes, and measuring its value has numerous applications. For instance, obtaining reliable spin measurements could constrain the growth history of supermassive black holes and reveal whether relativistic jets are powered by tapping into the black hole spin reservoir. The two well-established techniques for measuring black hole spin can both be applied to X-ray binaries, but are in disagreement for cases of non-maximal spin. This discrepancy must be resolved if either technique is to be deemed robust. We show that the technique based on disc continuum fitting is sensitive to uncertainties regarding the disc atmosphere, which are observationally unconstrained. By incorporating reasonable uncertainties into black hole spin probability density functions, we demonstrate that the spin measured by disc continuum fitting can become highly uncertain. Future work toward understanding how the observed disc continuum is altered by atmospheric physics, particularly magnetic fields, will further strengthen black hole spin measurement techniques.

  6. Evolution of magnetic oxygen states in Sr-doped LaCoO3.

    Science.gov (United States)

    Medling, S; Lee, Y; Zheng, H; Mitchell, J F; Freeland, J W; Harmon, B N; Bridges, F

    2012-10-12

    Magnetism in La(1-x)Sr(x)CoO(3) as a function of doping is investigated with x-ray absorption spectroscopy and x-ray magnetic circular dicrhoism at the O K edge, and corresponding first principles electronic structure calculations. For small x, the spectra are consistent with the formation of ferromagnetic clusters occurring within a nonmagnetic insulating matrix. Sr-induced, magnetic O-hole states form just above E(F) and grow with increasing Sr doping. Density functional calculations for x=0 yield a nonmagnetic ground state with the observed rhombohedral distortion and indicates that doping introduces holes at the Fermi level in magnetic states with significant O 2p and Co t(2g) character for the undistorted pseudocubic structure. Supercell calculations show stronger magnetism on oxygen atoms having more Sr neighbors.

  7. Evolution of Magnetic Oxygen States in Sr-Doped LaCoO3

    Energy Technology Data Exchange (ETDEWEB)

    Medling, S.; Lee, Yuen; Zheng, H.; Mitchell, J.F.; Freeland, J.W.; Harmon, Bruce N.; Bridges, F.

    2012-10-12

    Magnetism in La1-xSrxCoO3 as a function of doping is investigated with x-ray absorption spectroscopy and x-ray magnetic circular dicrhoism at the O K edge, and corresponding first principles electronic structure calculations. For small x, the spectra are consistent with the formation of ferromagnetic clusters occurring within a nonmagnetic insulating matrix. Sr-induced, magnetic O-hole states form just above EF and grow with increasing Sr doping. Density functional calculations for x=0 yield a nonmagnetic ground state with the observed rhombohedral distortion and indicates that doping introduces holes at the Fermi level in magnetic states with significant O 2p and Co t2g character for the undistorted pseudocubic structure. Supercell calculations show stronger magnetism on oxygen atoms having more Sr neighbors.

  8. Accretion, primordial black holes and standard cosmology

    Indian Academy of Sciences (India)

    Primordial black holes evaporate due to Hawking radiation. We find that the evaporation times of primordial black holes increase when accretion of radiation is included. Thus, depending on accretion efficiency, more primordial black holes are existing today, which strengthens the conjecture that the primordial black holes ...

  9. Formation and Coalescence of Electron Solitary Holes

    DEFF Research Database (Denmark)

    Saeki, K.; Michelsen, Poul; Pécseli, H. L.

    1979-01-01

    Electron solitary holes were observed in a magnetized collisionless plasma. These holes were identified as Bernstein-Green-Kruskal equilibria, thus being purely kinetic phenomena. The electron hole does not damp even though its velocity is close to the electron thermal velocity. Two holes attract...

  10. MBE growth of heavily carbon doped GaAsSb on InP for heterojunction bipolar transistor applications

    Science.gov (United States)

    Yarekha, D. A.; Godey, S.; Wallart, X.; Colder, H.; Zaknoune, M.; Mollot, F.

    2007-04-01

    Carbon doped GaAsSb samples have been grown by solid source molecular beam epitaxy using carbon tetrabromide as carbon source. A maximal hole concentration of 4.5×10 20 cm -3 has been obtained with a corresponding mobility of 19 cm 2/V s. For hole concentrations in the 4-8×10 19 cm -3 range, typically used in HBTs, the hole mobility is 45-50 cm 2/V s. We show that 450 °C is the optimal growth temperature at which both high hole concentration and mobility are obtained. An InP/GaAsSb/InP DHBT test structure with a 2×10 19 cm -3 carbon doped base has been realised. The current gain β is about 80 and the emitter-base and base-collector junction ideality factors are 1.15 and 1.05, respectively, indicating good junction properties.

  11. Three-dimensional ruthenium-doped TiO 2 sea urchins for enhanced visible-light-responsive H 2 production

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen-Phan, Thuy-Duong; Luo, Si; Vovchok, Dimitriy; Llorca, Jordi; Sallis, Shawn; Kattel, Shyam; Xu, Wenqian; Piper, Louis F. J.; Polyansky, Dmitry E.; Senanayake, Sanjaya D.; Stacchiola, Dario J.; Rodriguez, José A.

    2016-01-01

    Three-dimensional (3D) monodispersed sea urchin-like Ru-doped rutile TiO2 hierarchical architectures composed of radially aligned, densely-packed TiO2 nanorods have been successfully synthesized via an acid-hydrothermal method at low temperature without the assistance of any structure-directing agent and post annealing treatment. The addition of a minuscule concentration of ruthenium dopants remarkably catalyze the formation of the 3D urchin structure and drive the enhanced photocatalytic H2 production under visible light irradiation, not possible on undoped and bulk rutile TiO2. Increasing ruthenium doping dosage not only increases the surface area up to 166 m2 g-1 but also induces enhanced photo response in the regime of visible and near infrared light. The doping introduces defect impurity levels, i.e. oxygen vacancy and under-coordinated Ti3+, significantly below the conduction band of TiO2, and ruthenium species act as electron donors/acceptors that accelerate the photogenetated hole and electron transfer and efficiently suppress the rapid charge recombination, therefore improving the visible-light-driven activity.

  12. Mg doping of InGaN layers grown by PA-MBE for the fabrication of Schottky barrier photodiodes

    OpenAIRE

    Pereiro, J. (James); Redondo-Cubero, A; Fernandez-Garrido, S.; Rivera, C; Navarro, A.; Muñoz, E; Calleja, E; Gago, R.; Pereiro, Juan

    2010-01-01

    ABSTRACT This work reports on the fabrication of Schottky barrier based Mg-doped (In, Ga)N layers for fluorescence applications. Mg acceptors are used in order to compensate surface and bulk donors that prevent the fabrication of Schottky contacts on unintentionally doped (In, Ga)N layers. Rectifying properties of the contacts exhibited a major improvement when (In, Ga)N:Mg is used. The electrical and optical measurements of the layers showed a hole concentration up to 3?10 19 holes/cm 3 w...

  13. Minority carrier diffusion lengths and mobilities in low-doped n-InGaAs for focal plane array applications

    Science.gov (United States)

    Walker, Alexandre W.; Denhoff, Mike W.

    2017-02-01

    The hole diffusion length in n-InGaAs is extracted for two samples of different doping concentrations using a set of long and thin diffused junction diodes separated by various distances on the order of the diffusion length. The methodology is described, including the ensuing analysis which yields diffusion lengths between 70 - 85 μm at room temperature for doping concentrations in the range of 5 - 9 × 1015 cm-3 . The analysis also provides insight into the minority carrier mobility which is a parameter not commonly reported in the literature. Hole mobilities on the order of 500 - 750 cm2/V·s are reported for the aforementioned doping range, which are comparable albeit longer than the majority hole mobility for the same doping magnitude in p-InGaAs. A radiative recombination coefficient of (0.5+/-0.2)×10-10 cm-3 s -1 is also extracted from the ensuing analysis for an InGaAs thickness of 2.7 μm. Preliminary evidence is also given for both heavy and light hole diffusion. The dark current of InP/InGaAs p-i-n photodetectors with 25 and 15 μm pitches are then calibrated to device simulations and correlated to the extracted diffusion lengths and doping concentrations. An effective Shockley-Read-Hall lifetime of between 90-200 μs provides the best fit to the dark current of these structures.

  14. Rethinking Black Hole Accretion Discs

    Science.gov (United States)

    Salvesen, Greg

    Accretion discs are staples of astrophysics. Tapping into the gravitational potential energy of the accreting material, these discs are highly efficient machines that produce copious radiation and extreme outflows. While interesting in their own right, accretion discs also act as tools to study black holes and directly influence the properties of the Universe. Black hole X-ray binaries are fantastic natural laboratories for studying accretion disc physics and black hole phenomena. Among many of the curious behaviors exhibited by these systems are black hole state transitions -- complicated cycles of dramatic brightening and dimming. Using X-ray observations with high temporal cadence, we show that the evolution of the accretion disc spectrum during black hole state transitions can be described by a variable disc atmospheric structure without invoking a radially truncated disc geometry. The accretion disc spectrum can be a powerful diagnostic for measuring black hole spin if the effects of the disc atmosphere on the emergent spectrum are well-understood; however, properties of the disc atmosphere are largely unconstrained. Using statistical methods, we decompose this black hole spin measurement technique and show that modest uncertainties regarding the disc atmosphere can lead to erroneous spin measurements. The vertical structure of the disc is difficult to constrain due to our ignorance of the contribution to hydrostatic balance by magnetic fields, which are fundamental to the accretion process. Observations of black hole X-ray binaries and the accretion environments near supermassive black holes provide mounting evidence for strong magnetization. Performing numerical simulations of accretion discs in the shearing box approximation, we impose a net vertical magnetic flux that allows us to effectively control the level of disc magnetization. We study how dynamo activity and the properties of turbulence driven by the magnetorotational instability depend on the

  15. Inverted Internal Limiting Membrane Flap For Large Traumatic Macular Holes.

    Science.gov (United States)

    Abou Shousha, Mohsen Ahmed

    2016-01-01

    The aim of the study was to assess the role of inverted internal limiting membrane flap as a treatment option for large traumatic macular holes.This is a prospective noncomparative study in which 12 eyes with large traumatic macular holes (basal diameter of 1300-2800 μm) since 3 to 6 months were subjected to standard 23-gauge vitrectomy with removal of the posterior hyaloid, brilliant blue G (BBG)-assisted internal limiting membrane peeling in a circular fashion keeping it attached to the edge of the hole to create a flap. At the end of the surgery, air fluid exchange was done with inversion of the internal limiting membrane flap inside the macular hole using the soft tipped cannula and sulfur hexafluoride 20% as tamponade. The main follow-up measures are the best corrected visual acuity and the optical coherence tomography for 6 to 9 months.All the included eyes had a closed hole from the first week postoperative and along the follow-up period (6-9 months). The best corrected visual acuity improved from 20/2000 to 20/200 with a median of 20/400 preoperatively to 20/400 to 20/50 with a median of 20/100 at the end of follow-up period.Inverted internal limiting membrane flap is a good adjuvant to standard vitrectomy in the management of large traumatic macular holes that led to the 100% closure rate and improvement of best corrected visual acuity.

  16. Aluminum Doped Parahydrogen Solids

    National Research Council Canada - National Science Library

    Fajardo, Mario

    2001-01-01

    ...) solids doped with large (- 1 %) concentrations of Al atoms. We incorporated into our apparatus a commercially available effusive Al atom source capable of delivering Al atom fluxes in excess of 10(exp 17...

  17. Regular black hole in three dimensions

    OpenAIRE

    Myung, Yun Soo; Yoon, Myungseok

    2008-01-01

    We find a new black hole in three dimensional anti-de Sitter space by introducing an anisotropic perfect fluid inspired by the noncommutative black hole. This is a regular black hole with two horizons. We compare thermodynamics of this black hole with that of non-rotating BTZ black hole. The first-law of thermodynamics is not compatible with the Bekenstein-Hawking entropy.

  18. The geometry of Kerr black holes

    CERN Document Server

    O'Neill, Barrett

    2014-01-01

    This unique monograph by a noted UCLA professor examines in detail the mathematics of Kerr black holes, which possess the properties of mass and angular momentum but carry no electrical charge. Suitable for advanced undergraduates and graduate students of mathematics, physics, and astronomy as well as professional physicists, the self-contained treatment constitutes an introduction to modern techniques in differential geometry. The text begins with a substantial chapter offering background on the mathematics needed for the rest of the book. Subsequent chapters emphasize physical interpretation

  19. Nitrogen-Doped Graphene and its Application in Electrochemical Biosensing

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Ying; Shao, Yuyan; Matson, Dean W.; Li, Jinghong; Lin, Yuehe

    2010-05-05

    Chemical doping with foreign atoms is an effective method to intrinsically modify the properties of host materials. Among them, nitrogen (N) doping plays a critical role in regulating the electronic properties of carbon materials. Recently, graphene as a true 2-dimensional carbon material has shown fascinating applications in bioelectronics and biosensors. In this paper, we report a facile strategy to prepare N-doped graphene by using plasma treatment of pristine graphene synthesized via chemical method. Meanwhile, a possible schematic diagram has been proposed to detail the structure of N-doped graphene. By controlling the exposure time, N percentage in host grapheme can be regulated ranging from 0.11% to 1.35%. Moreover, the as prepared N-doped graphene has displayed high electrocatalytic activity to hydrogen peroxide and further been used for glucose biosensing with concentration as low as 0.01 mM in the presence of interferences.

  20. Magnetic properties in BiFeO{sub 3} doped with Cu and Zn first-principles investigation

    Energy Technology Data Exchange (ETDEWEB)

    Rong, Qing-Yan [School of Physics and Electronics, Hunan University, Changsha 410082 (China); Department of Physics and Mathematics, Hunan Institute of Engineering, Xiangtan 411104 (China); Xiao, Wen-Zhi, E-mail: xiaowenzhi@hnu.edu.cn [School of Physics and Electronics, Hunan University, Changsha 410082 (China); Department of Physics and Mathematics, Hunan Institute of Engineering, Xiangtan 411104 (China); Xiao, Gang [School of Physics and Electronics, Hunan University, Changsha 410082 (China); Department of Physics and Mathematics, Hunan Institute of Engineering, Xiangtan 411104 (China); Hu, Ai-Ming [Department of Physics and Mathematics, Hunan Institute of Engineering, Xiangtan 411104 (China); Wang, Ling-Ling, E-mail: llwang@hnu.edu.cn [School of Physics and Electronics, Hunan University, Changsha 410082 (China)

    2016-07-25

    Based on first-principles spin-polarized density functional theory calculations, the electronic structures, and magnetic properties of Cu and Zn-doped BiFeO{sub 3} are investigated. The calculated formation energies show that Cu prefers to occupy Fe site, while the Zn prefer to occupy Bi site. All the doped BiFeO{sub 3} systems turn out to be favorable for G-type antiferromagnetic arrangement. The substitution of Cu and Zn for Fe produces a magnetic moment of 3.0 and 4.0 μ{sub B} per dopant, respectively. The net magnetic moments are from the broken symmetry of the AFM spin ordering network. For the substitution of Cu and Zn for Bi, the net magnetic moment originates from Cu/Zn itself and hole introduced by Cu/Zn. Two-Cu/Zn-doped cases show various magnetic behaves. If O vacancy is far away from dopants, the O vacancies don't affect the net magnetic moment of the substitution of Cu and Zn for Fe, but have notable effect for Bi site doping. The O vacancies result in metallicity in all doped cases. Our study demonstrates that the nonmagnetic Cu and Zn doping will lead to the diversity and complexity of magnetic properties depending on doping sites, distance between dopants, intrinsic defect, and so on, which could be responsible for the observed various magnetic behaviors in Cu/Zn-doped BiFeO{sub 3} samples. - Highlights: • The Fe site doping produces magnetic moments, due to the breaking of the symmetry. • The Bi site doping produces magnetic moments which originate from unpaired holes. • Different substitutions of Cu/Zn for Fe result in various magnetic properties. • The O vacancies make all the doped samples metallic and affect magnetic properties.

  1. Doping characteristics of Si-doped n-GaN Epilayers grown by low-pressure metal-organic chemical-vapor deposition

    CERN Document Server

    Noh, S K; Park, S E; Lee, I H; Choi, I H; Son, S J; Lim, K Y; Lee, H J

    1998-01-01

    We studied doping behaviors through analysis of the electronic properties of a series of undoped and Si-doped GaN epilayers grown on (0001) sapphire substrates by the low-pressure metal-organic chemical-vapor deposition (LP-MOCVD) technique. The doping efficiency was in the range of 0.4 - 0.8, and an empirical relation expressed as eta = 0.45 log[Si] - 8.1 was obtained. The temperature dependence of carrier concentration showed that the donor activation energy monotonically decreased from 17.6 meV to almost zero as the doping level increased. We suggest that the reduction in the activation energy is related not to autodoped defect centers but to doped Si donors and that the behavior originates from the formation of an impurity band. On the basis of an abrupt change in the compensation ratio from 0.9 to 0.5 by Si-doping, an exceptional difference in the Hall mobility between the undoped and the Si-doped films is explained by a mixed conduction mechanism of electrons and holes.

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

    KAUST Repository

    Awan, Saif Ullah

    2014-10-28

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

  3. Correlations between 1/f noise and thermal treatment of Al-doped ZnO thin films deposited by direct current sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Barhoumi, A., E-mail: amira-barhoumi@yahoo.fr; Guermazi, S. [University of Sfax, Research Unit: PMISI, Faculty of Science Sfax, Route de la Soukra Km 3.5-B.P. n° 1171-3000 Sfax (Tunisia); Leroy, G.; Gest, J.; Carru, J. C. [University Lille North of France, ULCO, UDSMM, 62228 Calais (France); Yang, L. [Hebei Union University, Electrical Engineering, 46 Xinhua Road, Tangshan 063009, Hebei (China); Boughzala, H. [University of Tunis El-Manar, Faculty of Science Tunis,, Laboratory of Crystallochemistry, 1060 Tunis (Tunisia); Duponchel, B. [University Lille North of France, ULCO, UDSMM, 59140 Dunkerque (France)

    2014-05-28

    Al-doped ZnO thin films (AZO) have been deposited on amorphous glass substrates by DC sputtering at different substrate temperatures T{sub s}. X-Ray diffraction results reveal that AZO thin films have a hexagonal wurtzite structure with (002) preferred orientation. (002) peaks indicate that the crystalline structure of the films is oriented with c-axis perpendicular to the substrate. Three-dimensional (3D) atomic force microscopy images of AZO thin films deposited on glass substrate at 200 °C, 300 °C, and 400 °C, respectively, shows the improvement of the crystallinity and the homogeneity of AZO thin films with T{sub s} which is in agreement with the noise measurements. The noise was characterized between 1 Hz and 100 kHz and we have obtained 1/f spectra. The noise is very sensitive to the crystal structure especially to the orientation of the crystallites which is perpendicular to the substrate and to the grain boundaries which generate a high current flow and a sharp increase in noise. Through time, R{sub sh} and [αμ]{sub eff} increase with the modification of the crystallinity of AZO thin films. Study of noise aging shows that the noise is more sensitive than resistivity for all AZO thin films.

  4. Probing the doping mechanisms and electrical properties of Al, Ga and In doped ZnO prepared by spray pyrolysis

    KAUST Repository

    Maller, Robert

    2016-05-24

    The measured structural, optical and electrical properties of Al, Ga and In doped ZnO films deposited using spray pyrolysis are reported over the doping range 0.1 - 3 atomic percent (at. %). Over the entire doping series highly transparent, polycrystalline thin films are prepared. Using the AC Hall effect we probe the electronic properties of our doped films separating the impact of doping on the measured charge carrier concentrations and Hall mobility, with an emphasis on the low doping, < 1 at. %, range. In this doping range highly resistive films are formed and we highlight AC Hall as a reliable and highly reproducible technique for analysing the doping mechanism. The implementation of a simple, post-deposition heat treatment of our AZO films creates typical films with charge carrier concentrations exceeding > 1019 cm-3 and electron mobilities over 10 cm2/Vs. We describe in detail the nature of the defect chemistry and the role of intrinsic defects, particularly traps, and show that despite significant variations in dopant species and grain boundary concentrations that the defect chemistry dominates the electrical characteristics.

  5. Sanctions for doping in sport

    Directory of Open Access Journals (Sweden)

    Mandarić Sanja

    2014-01-01

    Full Text Available Top-level sport imposes new and more demanding physical and psychological pressures, and the desire for competing, winning and selfassertion leads athletes into temptation to use prohibited substances in order to achieve the best possible results. Regardless of the fact that the adverse consequences of prohibited substances are well-known, prestige and the need to dominate sports arenas have led to their use in sports. Doping is one of the biggest issues in sport today, and the fight against it is a strategic objective on both global and national levels. World Anti-Doping Agency, the International Olympic Committee, international sports federations, national anti-doping agencies, national sports federations, as well as governments and their repressive apparatuses are all involved in the fight against doping in sport. This paper points to a different etymology and phenomenology of doping, the beginnings of doping in sport, sports doping scandals as well as the most important international instruments regulating this issue. Also, there is a special reference in this paper to the criminal and misdemeanor sanctions for doping in sport. In Serbia doping in sport is prohibited by the Law on Prevention of Doping in Sports which came into force in 2005 and which prescribes the measures and activities aimed at prevention of doping in sport. In this context, the law provides for the following three criminal offenses: use of doping substances, facilitating the use of doping substances, and unauthorized production and putting on traffic of doping substances. In addition, aiming at curbing the abuse of doping this law also provides for two violations. More frequent and repetitive doping scandals indicate that doping despite long-standing sanctions is still present in sports, which suggests that sanctions alone have not given satisfactory results so far.

  6. Modulation Doped Field-Effect Photodetectors

    Science.gov (United States)

    Romero, Murilo Araujo

    1995-01-01

    The dissertation is concerned with the modeling and characterization of MODFETs (Modulation Doped Field -Effect Transistors) as photodetectors. Analytical derivation revealed that the dominant photodetection mechanism in the devices is the internal photovoltaic effect, caused by hole accumulation in the GaAs layer. The illumination acts as an additional terminal, producing a shift in the gate to source bias point, through which the device can be controlled. The MODFET photoresponse is characterized by a logarithmic dependence on light intensity and extremely high optical gain at low optical power levels. A responsivity in excess of 10^5 A/W was measured. The response speed of currently available devices is limited to the MHz range. Several device structures, designed to extend the electrical bandwidth while preserving gain over conventional photodiodes, are proposed. The experimentally observed negative photoresponse mechanism is explained and the optical control of a MODFET oscillator is demonstrated.

  7. Lectures on Quantum Black Holes

    CERN Document Server

    Dabholkar, Atish

    2012-01-01

    In these notes we describe recent progress in understanding finite size corrections to the black hole entropy. Much of the earlier work concerning quantum black holes has been in the limit of large charges when the area of the even horizon is also large. In recent years there has been substantial progress in understanding the entropy of supersymmetric black holes within string theory going well beyond the large charge limit. It has now become possible to begin exploring finite size effects in perturbation theory in inverse size and even nonperturbatively, with highly nontrivial agreements between thermodynamics and statistical mechanics. Unlike the leading Bekenstein-Hawking entropy which follows from the two-derivative Einstein-Hilbert action, these finite size corrections depend sensitively on the phase under consideration and contain a wealth of information about the details of compactification as well as the spectrum of nonperturbative states in the theory. Finite-size corrections are therefore very inter...

  8. Massive Black Holes and Galaxies

    CERN Multimedia

    CERN. Geneva

    2016-01-01

    Evidence has been accumulating for several decades that many galaxies harbor central mass concentrations that may be in the form of black holes with masses between a few million to a few billion time the mass of the Sun. I will discuss measurements over the last two decades, employing adaptive optics imaging and spectroscopy on large ground-based telescopes that prove the existence of such a massive black hole in the Center of our Milky Way, beyond any reasonable doubt. These data also provide key insights into its properties and environment. Most recently, a tidally disrupting cloud of gas has been discovered on an almost radial orbit that reached its peri-distance of ~2000 Schwarzschild radii in 2014, promising to be a valuable tool for exploring the innermost accretion zone. Future interferometric studies of the Galactic Center Black hole promise to be able to test gravity in its strong field limit.

  9. The black hole quantum atmosphere

    Science.gov (United States)

    Dey, Ramit; Liberati, Stefano; Pranzetti, Daniele

    2017-11-01

    Ever since the discovery of black hole evaporation, the region of origin of the radiated quanta has been a topic of debate. Recently it was argued by Giddings that the Hawking quanta originate from a region well outside the black hole horizon by calculating the effective radius of a radiating body via the Stefan-Boltzmann law. In this paper we try to further explore this issue and end up corroborating this claim, using both a heuristic argument and a detailed study of the stress energy tensor. We show that the Hawking quanta originate from what might be called a quantum atmosphere around the black hole with energy density and fluxes of particles peaked at about 4 MG, running contrary to the popular belief that these originate from the ultra high energy excitations very close to the horizon. This long distance origin of Hawking radiation could have a profound impact on our understanding of the information and transplanckian problems.

  10. Black holes and galaxy formation

    CERN Document Server

    Propst, Raphael J

    2010-01-01

    Galaxies are the basic unit of cosmology. The study of galaxy formation is concerned with the processes that formed a heterogeneous universe from a homogeneous beginning. The physics of galaxy formation is complicated because it deals with the dynamics of stars, thermodynamics of gas and energy production of stars. A black hole is a massive object whose gravitational field is so intense that it prevents any form of matter or radiation to escape. It is hypothesized that the most massive galaxies in the universe- "elliptical galaxies"- grow simultaneously with the supermassive black holes at their centers, giving us much stronger evidence that black holes control galaxy formation. This book reviews new evidence in the field.

  11. Black holes and random matrices

    Science.gov (United States)

    Cotler, Jordan S.; Gur-Ari, Guy; Hanada, Masanori; Polchinski, Joseph; Saad, Phil; Shenker, Stephen H.; Stanford, Douglas; Streicher, Alexandre; Tezuka, Masaki

    2017-05-01

    We argue that the late time behavior of horizon fluctuations in large anti-de Sitter (AdS) black holes is governed by the random matrix dynamics characteristic of quantum chaotic systems. Our main tool is the Sachdev-Ye-Kitaev (SYK) model, which we use as a simple model of a black hole. We use an analytically continued partition function | Z( β + it)|2 as well as correlation functions as diagnostics. Using numerical techniques we establish random matrix behavior at late times. We determine the early time behavior exactly in a double scaling limit, giving us a plausible estimate for the crossover time to random matrix behavior. We use these ideas to formulate a conjecture about general large AdS black holes, like those dual to 4D super-Yang-Mills theory, giving a provisional estimate of the crossover time. We make some preliminary comments about challenges to understanding the late time dynamics from a bulk point of view.

  12. Lee–Wick black holes

    Directory of Open Access Journals (Sweden)

    Cosimo Bambi

    2017-01-01

    Full Text Available We derive and study an approximate static vacuum solution generated by a point-like source in a higher derivative gravitational theory with a pair of complex conjugate ghosts. The gravitational theory is local and characterized by a high derivative operator compatible with Lee–Wick unitarity. In particular, the tree-level two-point function only shows a pair of complex conjugate poles besides the massless spin two graviton. We show that singularity-free black holes exist when the mass of the source M exceeds a critical value Mcrit. For M>Mcrit the spacetime structure is characterized by an outer event horizon and an inner Cauchy horizon, while for M=Mcrit we have an extremal black hole with vanishing Hawking temperature. The evaporation process leads to a remnant that approaches the zero-temperature extremal black hole state in an infinite amount of time.

  13. The black hole quantum atmosphere

    Directory of Open Access Journals (Sweden)

    Ramit Dey

    2017-11-01

    Full Text Available Ever since the discovery of black hole evaporation, the region of origin of the radiated quanta has been a topic of debate. Recently it was argued by Giddings that the Hawking quanta originate from a region well outside the black hole horizon by calculating the effective radius of a radiating body via the Stefan–Boltzmann law. In this paper we try to further explore this issue and end up corroborating this claim, using both a heuristic argument and a detailed study of the stress energy tensor. We show that the Hawking quanta originate from what might be called a quantum atmosphere around the black hole with energy density and fluxes of particles peaked at about 4MG, running contrary to the popular belief that these originate from the ultra high energy excitations very close to the horizon. This long distance origin of Hawking radiation could have a profound impact on our understanding of the information and transplanckian problems.

  14. Holes at High Blowing Ratios

    Directory of Open Access Journals (Sweden)

    Phillip M. Ligrani

    1996-01-01

    Full Text Available Experimental results are presented which describe the development and structure of flow downstream of a single row of holes with compound angle orientations producing film cooling at high blowing ratios. This film cooling configuration is important because similar arrangements are frequently employed on the first stage of rotating blades of operating gas turbine engines. With this configuration, holes are spaced 6d apart in the spanwise direction, with inclination angles of 24 degrees, and angles of orientation of 50.5 degrees. Blowing ratios range from 1.5 to 4.0 and the ratio of injectant to freestream density is near 1.0. Results show that spanwise averaged adiabatic effectiveness, spanwise-averaged iso-energetic Stanton number ratios, surveys of streamwise mean velocity, and surveys of injectant distributions change by important amounts as the blowing ratio increases. This is due to injectant lift-off from the test surface just downstream of the holes.

  15. Enhanced performance of photodetector and photovoltaic based on carrier reflector and back surface field generated by doped graphene

    Science.gov (United States)

    Chang, Che-Wei; Wang, Di-Yan; Tan, Wei-Chun; Huang, I.-Sheng; Wang, I.-Sheng; Chen, Chia-Chun; Yang, Ying-Jay; Chen, Yang-Fang

    2012-08-01

    We report the influence of carrier reflector and back surface field generated by doped graphene on n-ZnO nanoridges/p-silicon photodetectors and silicon solar cells. It is found that the p-type graphene not only acts as an electron blocking layer, but also helps the collection of photogenerated holes. Quite surprisingly, the on/off ratio of the photodetector with the insertion of doped graphene can be increased by up to 40 times. Moreover, we demonstrate that typical silicon solar cells with the doped graphene, the cell efficiency can be enhanced by about 20%. Our approach would expand numerous applications for graphene-based optoelectronic devices.

  16. Macular Hole in Behcet's Disease

    Directory of Open Access Journals (Sweden)

    Shwu-Jiuan Sheu

    2004-11-01

    Full Text Available Behcet's disease is an inflammatory disorder of unknown cause, characterized by recurrent oral aphthous ulcers, genital ulcers, uveitis, and skin lesions. Ocular involvement occurs in 60-80% of patients with Behcet's disease and presents as panuveitis in most cases. Posterior segment involvement may lead to irreversible alterations and significant vision loss. The development of a partial or full-thickness macular hole, though rarely reported, may cause serious vision loss. In this report, we present two cases of macular hole in the worse eye of bilateral cases of Behcet's disease, and discuss the possible mechanisms and management in such cases.

  17. Defect formation and carrier doping in epitaxial films of the infinite layer compound

    Energy Technology Data Exchange (ETDEWEB)

    Feenstra, R.; Pennycook, S.J.; Chisholm, M.F. [Oak Ridge National Lab., TN (United States). Solid State Div.] [and others

    1996-02-01

    The correlation between defect formation and carrier doping in epitaxial films of the infinite layer compound SrCuO{sub 2} has been studied via molecular beam epitaxy controlled layer-by-layer growth experiments, chemically resolved scanning transmission electron microscopy, scanning tunneling microscopy, x-ray diffraction, electrical transport measurements, and post-growth oxidation-reduction annealing. Based on the complementary information provided by these experiments, it is concluded that the carrier doping is dominated by the formation of an electron-doped, Sr and O deficient matrix under mildly oxidizing growth conditions. Hole-doping is induced by extended defects containing excess Sr atoms and may lead to superconductivity after high-temperature oxidation.

  18. Al-doping effects on the photovoltaic performance of inverted polymer solar cells

    Science.gov (United States)

    Yu, Xuan; Shi, Ya-feng; Yu, Xiao-ming; Zhang, Jian-jun; Ge, Ya-ming; Chen, Li-qiao; Pan, Hong-jun

    2016-03-01

    The properties of Al-doped ZnO (AZO) play an important role in the photovoltaic performance of inverted polymer solar cells (PSCs), which is used as electron transport and hole blocking buffer layers. In this work, we study the effects of Al-doping level in AZO on device performance in detail. Results indicate that the device performance intensely depends on the Al-doping level. The AZO thin films with Al-doping atomic percentage of 1.0% possess the best conductivity. The resulting solar cells show the enhanced short current density and the fill factor ( FF) simultaneously, and the power conversion efficiency ( PCE) is improved by 74%, which are attributed to the reduced carrier recombination and the optimized charge transport and extraction between AZO and the active layer.

  19. Electron doped layered nickelates: Spanning the phase diagram of the cuprates

    Energy Technology Data Exchange (ETDEWEB)

    Botana, Antia S.; Pardo, Victor; Norman, Michael R.

    2017-07-01

    Pr4Ni3O8 is an overdoped analog of hole-doped layered cuprates. Here we show via ab initio calculations that Ce-doped Pr4Ni3O8 (Pr3CeNi3O8) has the same electronic structure as the antiferromagnetic insulating phase of parent cuprates.We find that substantial Ce doping should be thermodynamically stable and that other 4+ cations would yield a similar antiferromagnetic insulating state, arguing this configuration is robust for layered nickelates of low-enough valence. The analogies with cuprates at different d fillings suggest that intermediate Ce-doping concentrations near 1/8 should be an appropriate place to search for superconductivity in these low-valence Ni oxides.

  20. Evolution of Hall resistivity and spectral function with doping in the SU(2) theory of cuprates

    Science.gov (United States)

    Morice, C.; Montiel, X.; Pépin, C.

    2017-10-01

    Recent transport experiments in the cuprate superconductors linked the opening of the pseudogap to a change in electronic dispersion [S. Badoux et al., Nature (London) 531, 210 (2015), 10.1038/nature16983]. Transport measurements showed that the carrier density sharply changes from x to 1 +x at the pseudogap critical doping, in accordance with the change from Fermi arcs at low doping to a large hole Fermi surface at high doping. The SU(2) theory of cuprates shows that short-range antiferromagnetic correlations cause the arising of both charge and superconducting orders, which are related by an SU(2) symmetry. The fluctuations associated with this symmetry form a pseudogap phase. Here we derive the renormalized electronic propagator under the SU(2) dome, and calculate the spectral functions and transport quantities of the renormalized bands. We show that their evolution with doping matches both spectral and transport measurements.

  1. Performance Study of CdS/Co-Doped-CdSe Quantum Dot Sensitized Solar Cells

    Directory of Open Access Journals (Sweden)

    Xiaoping Zou

    2014-01-01

    Full Text Available In order to optimize the charge transfer path in quantum dot sensitized solar cells (QDSCs, we employed successive ionic layer adsorption and reaction method to dope CdSe with Co for fabricating CdS/Co-doped-CdSe QDSCs constructed with CdS/Co-doped-CdSe deposited on mesoscopic TiO2 film as photoanode, Pt counter electrode, and sulfide/polysulfide electrolyte. After Co doping, the bandgap of CdSe quantum dot decreases, and the conduction band and valence band all improve, forming a cascade energy level which is more conducive to charge transport inside the solar cell and reducing the recombination of electron-hole thus improving the photocurrent and ultimately improving the power conversion efficiency. This work has not been found in the literature.

  2. Electronic properties of boron and nitrogen doped graphene nanoribbons and its application for graphene electronics

    Energy Technology Data Exchange (ETDEWEB)

    Huang Bing, E-mail: Bing.Huang@nrel.go [Department of Physics, Tsinghua University, Beijing 100084 (China)

    2011-01-24

    On the basis of density functional theory calculations, we have systematically investigated the electronic properties of armchair-edge graphene nanoribbons (GNRs) doped with boron (B) and nitrogen (N) atoms. B (N) atoms could effectively introduce holes (electrons) to GNRs and the system exhibits p- (n-) type semiconducting behavior after B (N) doping. According to the electronic structure calculations, Z-shape GNR-based field effect transistors (FETs) is constructed by selective doping with B or N atoms. Using first-principles quantum transport calculations, we demonstrate that the B-doped p-type GNR-FETs can exhibit high levels of performance, with high ON/OFF ratios and low subthreshold swing. Furthermore, the performance parameters of GNR-FETs could be controlled by the p-type semiconducting channel length.

  3. High-pressure studies on Ba-doped cobalt perovskites by neutron diffraction

    Science.gov (United States)

    Cao, Huibo; Garlea, Vasile; Wang, Fangwei; Dos Santos, Antonio; Cheng, Zhaohua

    2012-02-01

    Cobalt perovskite possess rich structural, magnetic and electrical properties depending on the subtle balance of the interactions among the spin, charge, and orbital degrees of freedom. Divalent hole-doped cobalt perovskites LaA^2+CoO3 exhibit structural phase transitions, metal-insulator transitions, and multi-magnetic phase transitions. High-pressure measurement is believed to mimic the size effects of the doped ions. We performed neutron diffraction experiments on selected Ba-doped LaCoO3 under pressures up to 6.3 GPa at SNAP at Spallation Neutron Source of ORNL. This work focuses on the high-pressure effects of the selected Ba-doped samples and the change of the phase diagram with pressure.

  4. Superconductivity. Quasiparticle mass enhancement approaching optimal doping in a high-T(c) superconductor.

    Science.gov (United States)

    Ramshaw, B J; Sebastian, S E; McDonald, R D; Day, James; Tan, B S; Zhu, Z; Betts, J B; Liang, Ruixing; Bonn, D A; Hardy, W N; Harrison, N

    2015-04-17

    In the quest for superconductors with higher transition temperatures (T(c)), one emerging motif is that electronic interactions favorable for superconductivity can be enhanced by fluctuations of a broken-symmetry phase. Recent experiments have suggested the existence of the requisite broken-symmetry phase in the high-T(c) cuprates, but the impact of such a phase on the ground-state electronic interactions has remained unclear. We used magnetic fields exceeding 90 tesla to access the underlying metallic state of the cuprate YBa2Cu3O(6+δ) over a wide range of doping, and observed magnetic quantum oscillations that reveal a strong enhancement of the quasiparticle effective mass toward optimal doping. This mass enhancement results from increasing electronic interactions approaching optimal doping, and suggests a quantum critical point at a hole doping of p(crit) ≈ 0.18. Copyright © 2015, American Association for the Advancement of Science.

  5. Photocatalytic Water Treatment by Titanium Dioxide: Recent Updates

    Directory of Open Access Journals (Sweden)

    Manoj A. Lazar

    2012-12-01

    Full Text Available Photocatalytic water treatment using nanocrystalline titanium dioxide (NTO is a well-known advanced oxidation process (AOP for environmental remediation. With the in situ generation of electron-hole pairs upon irradiation with light, NTO can mineralize a wide range of organic compounds into harmless end products such as carbon dioxide, water, and inorganic ions. Photocatalytic degradation kinetics of pollutants by NTO is a topic of debate and the mostly reporting Langmuir-Hinshelwood kinetics must accompanied with proper experimental evidences. Different NTO morphologies or surface treatments on NTO can increase the photocatalytic efficiency in degradation reactions. Wisely designed photocatalytic reactors can decrease energy consumption or can avoid post-separation stages in photocatalytic water treatment processes. Doping NTO with metals or non-metals can reduce the band gap of the doped catalyst, enabling light absorption in the visible region. Coupling NTO photocatalysis with other water-treatment technologies can be more beneficial, especially in large-scale treatments. This review describes recent developments in the field of photocatalytic water treatment using NTO.

  6. Blue and white phosphorescent organic light emitting diode performance improvement by confining electrons and holes inside double emitting layers

    Energy Technology Data Exchange (ETDEWEB)

    Tsai, Yu-Sheng; Hong, Lin-Ann; Juang, Fuh-Shyang; Chen, Cheng-Yin

    2014-09-15

    In this research, complex emitting layers (EML) were fabricated using TCTA doping hole-transport material in the front half of a bipolar 26DCzPPy as well as PPT doping electron-transport material in the back half of 26DCzPPy. Blue dopant FIrpic was also mixed inside the complex emitting layer to produce a highly efficient blue phosphorescent organic light emitting diode (OLED). The hole and electron injection and carrier recombination rate were effectively increased. The fabricated complex emitting layers exhibited current efficiency of 42 cd/A and power efficiency of 30 lm/W when the luminance was 1000 cd/m{sup 2}, driving voltage was 4.4 V, and current density was 2.4 mA/cm{sup 2}. A white OLED component was then manufactured by doping red dopant [Os(bpftz){sub 2}(PPh{sub 2}Me){sub 2}] (Os) in proper locations. When the Os dopant was doped in between the complex emitting layers, excitons were effectively confined within, increasing the recombination rate and therefore reducing the color shift. The resulting Commission Internationale de L’Eclairage (CIE) coordinates shifted from 4 to 10 V is (Δx=−0.04, Δy=+0.01). The component had a current efficiency of 35.7 cd/A, a power efficiency of 24 lm/W, driving voltage of 4.6 V and a CIE{sub x,y} of (0.31,0.35) at a luminance of 1000 cd/m{sup 2}, with a maximum luminance of 15,600 cd/m{sup 2} at 10 V. Attaching an outcoupling enhancement film was applied to increase the luminance efficiency to 30 lm/W. - Highlights: • Used the complex double emitting layers. • Respectively doped hole and electron transport material in the bipolar host. • Electrons and holes are effectively confined within EMLs to produce excitons.

  7. [Cardiovascular alterations associated with doping].

    Science.gov (United States)

    Thieme, D; Büttner, A

    2015-05-01

    Doping -the abuse of anabolic-androgenic steroids in particular- is widespread in amateur and recreational sports and does not solely represent a problem of professional sports. Excessive overdose of anabolic steroids is well documented in bodybuilding or powerlifting leading to significant side effects. Cardiovascular damages are most relevant next to adverse endocrine effects.Clinical cases as well as forensic investigations of fatalities or steroid consumption in connection with trafficking of doping agents provide only anecdotal evidence of correlations between side effects and substance abuse. Analytical verification and self-declarations of steroid users have repeatedly confirmed the presumption of weekly dosages between 300 and 2000 mg, extra to the fact that co-administration of therapeutics to treat side-effects represent a routine procedure. Beside the most frequent use of medications used to treat erectile dysfunction or estrogenic side-effects, a substantial number of antihypertensive drugs of various classes, i.e. beta-blockers, diuretics, angiotensin II receptor antagonists, calcium channel blockers, as well as ACE inhibitors were recently confiscated in relevant doping cases. The presumptive correlation between misuse of anabolic steroids and self-treatment of cardiovascular side effects was explicitly confirmed by detailed user statements.Two representative fatalities of bodybuilders were introduced to outline characteristic, often lethal side effects of excessive steroid abuse. Moreover, illustrative autopsy findings of steroid acne, thrombotic occlusion of Ramus interventricularis anterior and signs of cardiac infarctions are presented.A potential steroid abuse should be carefully considered in cases of medical consultations of patients exhibiting apparent constitutional modifications and corresponding adverse effects. Moreover, common self-medications -as frequently applied by steroid consumers- should be taken into therapeutic considerations.

  8. A Bug That Can Dig a Hole in the Stomach!

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 11; Issue 3. A Bug That Can Dig a Hole in the Stomach! - The Discovery that Revolutionized the Treatment of Peptic Ulcer. M E Sandeepa Dipshikha Chakravartty. General Article Volume 11 Issue 3 March 2006 pp 36-40 ...

  9. Facile synthesis of Sm-doped BiFeO{sub 3} nanoparticles for enhanced visible light photocatalytic performance

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Zijun; Chen, Da, E-mail: dchen_80@hotmail.com; Wang, Sen; Zhang, Ning; Qin, Laishun, E-mail: qinlaishun@cjlu.edu.cn; Huang, Yuexiang

    2017-06-15

    Highlights: • Effective Sm doping into BiFeO{sub 3} nanoparticles was obtained by a facile sol-gel route. • Band gap of Sm-doped BiFeO{sub 3} nanoparticles was regulated by the dopant concentration. • Sm-doped BiFeO{sub 3} nanoparticles exhibited superior photocatalytic activities. • The possible photocatalytic mechanism of Sm-doped BiFeO{sub 3} nanospheres was discussed. - Abstract: In this work, the effect of Sm doping on the structural and photocatalytic properties of BiFeO{sub 3} (BFO) was investigated. A series of Sm doped BFO nanoparticles containing different Sm dopant contents (Bi{sub (1−x)}Sm{sub x}FeO{sub 3}, x = 0.00, 0.01, 0.03, 0.05, 0.07, 0.10) were synthesized via a simple sol-gel route. It was revealed that Sm{sup 3+} ions were successfully doped into BFO nanoparticles, and the band gap value was gradually decreased when increasing Sm dopant concentration. The photocatalytic activity of Sm-doped BFO photocatalyst was significantly affected by the Sm doping content. Compared to pure BFO, the Sm-doped BFO samples exhibited much higher photocatalytic activity. The improved photocatalytic activity of Sm-doped BFO could be attributed to the enhanced visible light absorption and the efficient separation of photogenerated electrons and holes derived from Sm dopant trapping level in the Sm-doped BFO samples. In addition, the possible photocatalytic mechanism of Sm-doped BFO photocatalyst was also proposed.

  10. Charge and spin quantum fluctuations in the doped strongly coupled Hubbard model on the honeycomb lattice

    Science.gov (United States)

    Ribeiro, F. G.; Coutinho-Filho, M. D.

    2015-07-01

    Field-theoretic methods are used to investigate the large-U Hubbard model on the honeycomb lattice at half-filling and in the hole-doped regime. Within the framework of a functional-integral approach, we obtain the Lagrangian density associated with the charge and spin degrees of freedom. The Hamiltonian related to the charge degrees of freedom is exactly diagonalized. In the strong-coupling regime, we derive a perturbative low-energy theory suitable to describe the quantum antiferromagnetic phase (AF) as a function of hole doping. At half-filling, we deal with the underlying spin degrees of freedom of the quantum AF Heisenberg model by employing a second-order spin-wave analysis, in which case we have calculated the ground-state energy and the staggered magnetization; the results are in very good agreement with previous studies. Further, in the continuum, we derive a nonlinear σ model with a topological Hopf term that describes the AF-VBS (valence bond solid) competition. Lastly, in the challenging doped regime, our approach allows the derivation of a t -J Hamiltonian, and the analysis of the role played by charge and spin quantum fluctuations on the ground-state energy and, particularly, on the breakdown of the AF order at a critical hole doping; the results are benchmarked against recent Grassmann tensor product state simulations.

  11. Two-particle self-consistent analysis for the electron-hole asymmetry of superconductivity in cuprate superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Ogura, Daisuke; Kuroki, Kazuhiko [Department of Physics, Graduate School of Science, Osaka University, Toyonaka (Japan)

    2017-06-15

    In the hole-doped type cuprate superconductors, it is well-known that the superconducting transition temperature T{sub c} exhibits a dome-like structure against doping. On the other hand, recent experiments unveil that T{sub c} in the electron-doped compounds shows a monotonic increase with decreasing the doping, at least down to a very small doping rate. Our recent study for the three-band d-p model has unveiled that this asymmetric behavior can be explained as a combined effect of the intrinsic electron-hole asymmetry in systems comprising Cu3 d and O2 p orbitals and the band-filling-dependent vertex correction. In the present study, we study another compound Tl{sub 2} Ba{sub 2} CuO{sub 6} to show that this explanation can be applied to other cuprate superconductors with the small d{sub z{sup 2}} orbital mixture. By varying the d-p offset, we also study how the strength of the d-p hybridization controls the spin fluctuation and hence the pairing interaction. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  12. Ulnar shortening osteotomy with a new sliding-hole plate.

    Science.gov (United States)

    Kitzinger, Hugo B; Löw, Steffen; Krimmer, Hermann

    2003-09-01

    Ulnar shortening osteotomy represents a common procedure for surgical treatment of the ulnar impaction syndrome but is still associated with complications like malrotation, angulation, or malunion because of incomplete closure of the osteotomy gap. Therefore, the authors developed a special 7-hole compression plate that allows fixation of the ulna before the osteotomy is carried out to prevent rotation. With this plate, a shortening of up to 10 mm is possible and the compression holes allow closure of the osteotomy gap. The plate has been used in 23 ulnar shortening cases at their center with good results. The authors describe the technique and report their results of ulnar shortening with this device.

  13. Black Holes and Exotic Spinors

    Directory of Open Access Journals (Sweden)

    J. M. Hoff da Silva

    2016-05-01

    Full Text Available Exotic spin structures are non-trivial liftings, of the orthogonal bundle to the spin bundle, on orientable manifolds that admit spin structures according to the celebrated Geroch theorem. Exotic spin structures play a role of paramount importance in different areas of physics, from quantum field theory, in particular at Planck length scales, to gravity, and in cosmological scales. Here, we introduce an in-depth panorama in this field, providing black hole physics as the fount of spacetime exoticness. Black holes are then studied as the generators of a non-trivial topology that also can correspond to some inequivalent spin structure. Moreover, we investigate exotic spinor fields in this context and the way exotic spinor fields branch new physics. We also calculate the tunneling probability of exotic fermions across a Kerr-Sen black hole, showing that the exotic term does affect the tunneling probability, altering the black hole evaporation rate. Finally we show that it complies with the Hawking temperature universal law.

  14. Black Holes in Our Universe

    Indian Academy of Sciences (India)

    Abstract. Current technologies have enabled glimpses at the many facetsof black holes, which we know to be plentiful in our cosmos.A panoramic view of the evidence for them is presented hereacross the large range of masses that they span.

  15. Extremal Higher Spin Black Holes

    NARCIS (Netherlands)

    Bañados, M.; Castro, A.; Faraggi, A.; Jottar, J.I.

    The gauge sector of three-dimensional higher spin gravities can be formulated as a Chern-Simons theory. In this context, a higher spin black hole corresponds to a flat connection with suitable holonomy (smoothness) conditions which are consistent with the properties of a generalized thermal

  16. From Pinholes to Black Holes

    Energy Technology Data Exchange (ETDEWEB)

    Fenimore, Edward E. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2014-10-06

    Pinhole photography has made major contributions to astrophysics through the use of “coded apertures”. Coded apertures were instrumental in locating gamma-ray bursts and proving that they originate in faraway galaxies, some from the birth of black holes from the first stars that formed just after the big bang.

  17. Rotating black hole and quintessence

    CERN Document Server

    Ghosh, Sushant G

    2015-01-01

    We discuss spherically symmetric exact solutions of the Einstein equations for quintessential matter surrounding a black hole (BH), which has additional parameters ($\\alpha$ and $\\omega$) due to the quintessential matter, apart from the mass ($M$). In turn, we employ the Newman\\(-\\)Janis complex transformation to this spherical quintessence BH solution and present a rotating counterpart that is identified, for $\\alpha=-e^2 \

  18. 'Black holes': escaping the void.

    Science.gov (United States)

    Waldron, Sharn

    2013-02-01

    The 'black hole' is a metaphor for a reality in the psyche of many individuals who have experienced complex trauma in infancy and early childhood. The 'black hole' has been created by an absence of the object, the (m)other, so there is no internalized object, no (m)other in the psyche. Rather, there is a 'black hole' where the object should be, but the infant is drawn to it, trapped by it because of an intrinsic, instinctive need for a 'real object', an internalized (m)other. Without this, the infant cannot develop. It is only the presence of a real object that can generate the essential gravity necessary to draw the core of the self that is still in an undeveloped state from deep within the abyss. It is the moving towards a real object, a (m)other, that relativizes the absolute power of the black hole and begins a reformation of its essence within the psyche. © 2013, The Society of Analytical Psychology.

  19. Black Hole Macro-Quantumness

    CERN Document Server

    Dvali, Gia

    2014-01-01

    It is a common wisdom that properties of macroscopic bodies are well described by (semi)classical physics. As we have suggested this wisdom is not applicable to black holes. Despite being macroscopic, black holes are quantum objects. They represent Bose-Einstein condensates of N-soft gravitons at the quantum critical point, where N Bogoliubov modes become gapless. As a result, physics governing arbitrarily-large black holes (e.g., of galactic size) is a quantum physics of the collective Bogoiliubov modes. This fact introduces a new intrinsically-quantum corrections in form of 1/N, as opposed to exp(-N). These corrections are unaccounted by the usual semiclassical expansion in h and cannot be recast in form of a quantum back-reaction to classical metric. Instead the metric itself becomes an approximate entity. These 1/N corrections abolish the presumed properties of black holes, such as non existence of hair, and are the key to nullifying the so-called information paradox.

  20. The olfactory hole-board test in rats: a new paradigm to study aversion and preferences to odors

    Directory of Open Access Journals (Sweden)

    Kerstin eWernecke

    2015-08-01

    Full Text Available Odors of biological relevance (e.g. predator odors, sex odors are known to effectively influence basic survival needs of rodents such as anti-predatory defensiveness and mating behaviors. Research focused on the effects of these odors on rats’ behavior mostly includes multi-trial paradigms where animals experience single odor exposures in subsequent, separated experimental sessions. In the present study, we introduce a modification of the olfactory hole-board test that allows studying the effects of different odors on rats’ behavior within single trials. First, we demonstrated that the corner holes of the hole-board were preferentially visited by rats. The placement of different odors under the corner holes changed this hole preference. We showed that holes with carnivore urine samples were avoided, while corner holes with female rat urine samples were preferred. Furthermore, corner holes with urine samples from a carnivore, herbivore and omnivore were differentially visited indicating that rats can discriminate these odors. To test whether anxiolytic treatment specifically modulate the avoidance of carnivore urine holes, we treated rats with buspirone. Buspirone treatment completely abolished the avoidance of carnivore urine holes. Taken together, our findings indicate that the olfactory hole-board test is a valuable tool for measuring avoidance and preference responses to biologically-relevant odors.

  1. Supersymmetric black holes and Freudenthal duality

    Science.gov (United States)

    Marrani, Alessio; Mandal, Taniya; Tripathy, Prasanta K.

    2017-07-01

    We study the effect of Freudenthal duality on supersymmetric extremal black hole attractors in 𝒩 = 2, D = 4 ungauged supergravity. Freudenthal duality acts on the dyonic black hole charges as an anti-involution which keeps the black hole entropy and the critical points of the effective black hole potential invariant. We analyze its effect on the recently discovered distinct, mutually exclusive phases of axionic supersymmetric black holes, related to the existence of nontrivial involutory constant matrices. In particular, we consider a supersymmetric D0 - D4 - D6 black hole and we explicitly Freudenthal-map it to a supersymmetric D0 - D2 - D4 - D6 black hole. We thus show that the charge representation space of a supersymmetric D0 - D2 - D4 - D6 black hole also contains mutually exclusive domains.

  2. Spin distribution of primordial black holes

    Science.gov (United States)

    Chiba, Takeshi; Yokoyama, Shuichiro

    2017-08-01

    We estimate the spin distribution of primordial black holes based on the recent study of the critical phenomena in the gravitational collapse of a rotating radiation fluid. We find that primordial black holes are mostly slowly rotating.

  3. Implementing black hole as efficient power plant

    CERN Document Server

    Wei, Shao-Wen

    2016-01-01

    Treating the black hole molecules as working substance and considering its phase structure, we study the black hole heat engine by a charged anti-de Sitter black hole. In the reduced temperature-entropy chart, it is found that the work, heat, and efficiency of the engine are independent of the black hole charge. Applying the Rankine cycle with or without a back pressure mechanism to the black hole heat engine, the efficiency is numerically solved. The result shows that the black hole engine working along the Rankine cycle with a back pressure mechanism has a higher efficiency. This provides a novel and efficient mechanism to produce the useful mechanical work with black hole, and such heat engine may act as a possible energy source for the high energy astrophysical phenomena near the black hole.

  4. Mass Inflation in the Loop Black Hole

    CERN Document Server

    Brown, Eric G; Modesto, Leonardo

    2011-01-01

    In classical general relativity the Cauchy horizon within a two-horizon black hole is unstable via a phenomenon known as mass inflation, in which the mass parameter (and the spacetime curvature) of the black hole diverges at the Cauchy horizon. Here we study this effect for loop black holes -- quantum gravitationally corrected black holes from loop quantum gravity -- whose construction alleviates the $r=0$ singularity present in their classical counterparts. We use a simplified model of mass inflation, which makes use of the generalized DTR relation, to conclude that the Cauchy horizon of loop black holes indeed results in a curvature singularity similar to that found in classical black holes. The DTR relation is of particular utility in the loop black hole because it does not directly rely upon Einstein's field equations. We elucidate some of the interesting and counterintuitive properties of the loop black hole, and corroborate our results using an alternate model of mass inflation due to Ori.

  5. Foundations of Black Hole Accretion Disk Theory

    National Research Council Canada - National Science Library

    Abramowicz, Marek A; Fragile, P. Chris

    2013-01-01

    This review covers the main aspects of black hole accretion disk theory. We begin with the view that one of the main goals of the theory is to better understand the nature of black holes themselves...

  6. Sn-doped hematite nanostructures for photoelectrochemical water splitting.

    Science.gov (United States)

    Ling, Yichuan; Wang, Gongming; Wheeler, Damon A; Zhang, Jin Z; Li, Yat

    2011-05-11

    We report on the synthesis and characterization of Sn-doped hematite nanowires and nanocorals as well as their implementation as photoanodes for photoelectrochemical water splitting. The hematite nanowires were prepared on a fluorine-doped tin oxide (FTO) substrate by a hydrothermal method, followed by high temperature sintering in air to incorporate Sn, diffused from the FTO substrate, as a dopant. Sn-doped hematite nanocorals were prepared by the same method, by adding tin(IV) chloride as the Sn precursor. X-ray photoelectron spectroscopy analysis confirms Sn(4+) substitution at Fe(3+) sites in hematite, and Sn-dopant levels increase with sintering temperature. Sn dopant serves as an electron donor and increases the carrier density of hematite nanostructures. The hematite nanowires sintered at 800 °C yielded a pronounced photocurrent density of 1.24 mA/cm(2) at 1.23 V vs RHE, which is the highest value observed for hematite nanowires. In comparison to nanowires, Sn-doped hematite nanocorals exhibit smaller feature sizes and increased surface areas. Significantly, they showed a remarkable photocurrent density of 1.86 mA/cm(2) at 1.23 V vs RHE, which is approximately 1.5 times higher than that of the nanowires. Ultrafast spectroscopy studies revealed that there is significant electron-hole recombination within the first few picoseconds, while Sn doping and the change of surface morphology have no major effect on the ultrafast dynamics of the charge carriers on the picosecond time scales. The enhanced photoactivity in Sn-doped hematite nanostructures should be due to the improved electrical conductivity and increased surface area.

  7. Extremal higher spin black holes

    Energy Technology Data Exchange (ETDEWEB)

    Bañados, Máximo [Instituto de Física, Pontificia Universidad Católica de Chile, Casilla 306, Santiago (Chile); Castro, Alejandra [Institute for Theoretical Physics, University of Amsterdam,Science Park 904, Postbus 94485, Amsterdam, 1090 GL (Netherlands); Faraggi, Alberto [Instituto de Física, Pontificia Universidad Católica de Chile, Casilla 306, Santiago (Chile); Jottar, Juan I. [Institut für Theoretische Physik, ETH Zürich,Zürich, CH-8093 (Switzerland)

    2016-04-13

    The gauge sector of three-dimensional higher spin gravities can be formulated as a Chern-Simons theory. In this context, a higher spin black hole corresponds to a flat connection with suitable holonomy (smoothness) conditions which are consistent with the properties of a generalized thermal ensemble. Building on these ideas, we discuss a definition of black hole extremality which is appropriate to the topological character of 3d higher spin theories. Our definition can be phrased in terms of the Jordan class of the holonomy around a non-contractible (angular) cycle, and we show that it is compatible with the zero-temperature limit of smooth black hole solutions. While this notion of extremality does not require supersymmetry, we exemplify its consequences in the context of sl(3|2)⊕sl(3|2) Chern-Simons theory and show that, as usual, not all extremal solutions preserve supersymmetries. Remarkably, we find in addition that the higher spin setup allows for non-extremal supersymmetric black hole solutions. Furthermore, we discuss our results from the perspective of the holographic duality between sl(3|2)⊕sl(3|2) Chern-Simons theory and two-dimensional CFTs with W{sub (3|2)} symmetry, the simplest higher spin extension of the N=2 super-Virasoro algebra. In particular, we compute W{sub (3|2)} BPS bounds at the full quantum level, and relate their semiclassical limit to extremal black hole or conical defect solutions in the 3d bulk. Along the way, we discuss the role of the spectral flow automorphism and provide a conjecture for the form of the semiclassical BPS bounds in general N=2 two-dimensional CFTs with extended symmetry algebras.

  8. Fermi surface reconstruction and anomalous low-temperature resistivity in electron-doped L a2 -xC exCu O4

    Science.gov (United States)

    Sarkar, Tarapada; Mandal, P. R.; Higgins, J. S.; Zhao, Yi; Yu, Heshan; Jin, Kui; Greene, Richard L.

    2017-10-01

    We report a b -plane Hall-effect and magnetoresistivity measurements on L a2 -xC exCu O4 thin films as a function of doping for magnetic fields up to 14 T and temperatures down to 1.8 K. A dramatic change in the low-temperature (1.8 K) normal-state Hall coefficient is found near a doping Ce =0.14 . This, along with a nonlinear Hall resistance as a function of magnetic field, suggests that the Fermi surface reconstructs at a critical doping of Ce =0.14 . A competing antiferromagnetic phase is the likely cause of this Fermi surface reconstruction. Low-temperature linear-in-T resistivity is found at Ce =0.14 , but anomalously, also at higher doping. We compare our data with similar behavior found in hole-doped cuprates at a doping where the pseudogap ends.

  9. Satellite hole formation during dewetting: experiment and simulation

    CERN Document Server

    Neto, C; Seemann, R; Blossey, R; Becker, J; Grün, G

    2003-01-01

    The dewetting of thin polymer films on solid substrates has been studied extensively in recent years. These films can decay either by nucleation events or by spinodal dewetting, essentially only depending on the interface potential describing the short- and long-range intermolecular interactions between the interfaces and the initial film thickness. Here, we describe experiments and simulations concerned with the decay of polystyrene thin films. The rupture of the film occurs by the formation of a correlated pattern of holes ('satellite holes') along the liquid rims accumulating at the channel borders. The development of this complex film rupture process, which is neither simply spinodal nor nucleation dewetting, can be mimicked precisely by making use of a novel simulation code based on a rigorous mathematical treatment of the thin film equation and on the knowledge of the effective interface potential of the system. The conditions that determine the appearance and the position of the satellite holes around ...

  10. A New Cosmological Model: Black Hole Universe

    OpenAIRE

    Zhang T. X.

    2009-01-01

    A new cosmological model called black hole universe is proposed. According to this model, the universe originated from a hot star-like black hole with several solar masses, and gradually grew up through a supermassive black hole with billion solar masses to the present state with hundred billion-trillion solar masses by accreting ambient mate- rials and merging with other black holes. The entire space is structured with infinite layers hierarchically. The innermost three laye...

  11. Efficient Photoelectrochemical Water Oxidation by Metal-Doped Bismuth Vanadate Photoanode with Iron Oxyhydroxide Electrocatalyst

    Directory of Open Access Journals (Sweden)

    Eun Jin Joo

    2016-01-01

    Full Text Available Intensive attention has been currently focused on the discovery of semiconductor and proficient cocatalysts for eventual applications to the photoelectrochemical water splitting system. A W-Mo-doped BiVO4 semiconductor was prepared by the surfactant-assisted thermal decomposition method on a fluorine-doped tin oxide conductive film. The W-Mo-doped BiVO4 films showed a porous morphology with the grain sizes of about 270 nm. Because the hole diffusion length of BiVO4 is about 100 nm, the W-Mo-doped BiVO4 film in this study is an ideal candidate for the photoelectrochemical water oxidation. Iron oxyhydroxide (FeOOH electrocatalyst was chemically deposited on the W-Mo-doped BiVO4 to investigate the effect of the electrocatalyst on the semiconductor. The W-Mo-doped BiVO4/FeOOH composite electrode showed enhanced activity compared to the pristine W-Mo-doped BiVO4 electrode for water oxidation reaction. The chemical deposition is a promising method for the deposition of FeOOH on semiconductor.

  12. Facile fabrication of visible light induced Bi2O3 nanorod using conventional heat treatment method

    Science.gov (United States)

    Raza, Waseem; Khan, Azam; Alam, Umair; Muneer, M.; Bahnemann, D.

    2016-03-01

    In this paper, a new Bi2O3 based photocatalyst doped with varying concentration of Nb and Mn metal ion was fabricated by conventional heat treatment method and their photocatalytic activity was investigated. The prepared material was characterized by X-ray diffraction (XRD), UV-Visible Spectroscopy, Fourier transform infrared (FTIR) and Scanning Electron Microscopic (SEM) techniques. The XRD analysis of synthesized photocatalyst was found to exhibit characteristic peaks of well crystallized monoclinic α-Bi2O3. The XRD pattern of pure and metal doped Bi2O3 were found to more or less similar. The crystallite size of doped materials were smaller than pure Bi2O3 and size decreases with increasing dopant concentration from 0.5 to 2.0% for Nb & 1.0-3.0% for Mn and remains almost constant at higher dopant concentration. The SEM analysis clearly indicate the formation of nanorod like morphologies. The UV-Vis absorption spectra of synthesized nanorods revealed that the absorption edge shift towards longer wavelength on doping with Nb and Mn metal ions which is beneficial for absorbing more visible light in the solar spectrum. The prepared doped Bi2O3 nanorod showed the excellent photocatalytic activity for degradation of selected organic pollutants, such as Methylene Blue (MB) and Rodaamime B (RhB) under visible light source. The higher activity of doped Bi2O3 nanorod may be attributed to absorption of more visible light leading to generation of higher photogenerated electron hole pairs and efficient separation of photoinduced charge carrier to inhibit the recombination rate.

  13. Growth and electrical transport properties of very high mobility two-dimensional hole gases displaying persistent photoconductivity

    Science.gov (United States)

    Henini, M.; Rodgers, P. J.; Crump, P. A.; Gallagher, B. L.; Hill, G.

    1994-10-01

    We report on the growth by molecular beam epitaxy of modulation-doped GaAs-(Ga,Al)As heterostructures with low-temperature hole mobility exceeding 1.2×106 cm2 V-1 s-1 with carrier concentrations as low as 0.8×1011 cm-2: The highest value observed at such low densities. We also report the first observation of persistent positive photoconductivity in a two-dimensional hole gas. An analysis of the number density and temperature dependence of the mobility leads us to conclude that the mobility is limited by phonon scattering above ˜4 K and interface scattering at lower temperatures.

  14. Enhanced Efficiency of Polymer Light-Emitting Diodes by Dispersing Dehydrated Nanotube Titanic Acid in the Hole-buffer Layer

    Science.gov (United States)

    Qian, L.; Xu, Z.; Teng, F.; Duan, X.-X.; Jin, Z.-S.; Du, Z.-L.; Li, F.-S.; Zheng, M.-J.; Wang, Y.-S.

    2007-06-01

    Efficiency of polymer light-emitting diodes (PLEDs) with poly(2-methoxy-5-(2-ethyl hexyloxy)- p-phenylene vinylene) (MEH-PPV) as an emitting layer was improved if a dehydrated nanotubed titanic acid (DNTA) doped hole-buffer layer polyethylene dioxythiophene (PEDOT) was used. Photoluminescence (PL) and Raman spectra indicated a stronger interaction between DNTA and sulfur atom in thiophene of PEDOT, which suppresses the chemical interaction between vinylene of MEH-PPV and thiophene of PEDOT. The interaction decreases the defect states in an interface region to result in enhancement in device efficiency, even though the hole transporting ability of PEDOT was decreased.

  15. Enhanced Efficiency of Polymer Light-Emitting Diodes by Dispersing Dehydrated Nanotube Titanic Acid in the Hole-buffer Layer

    Energy Technology Data Exchange (ETDEWEB)

    Qian, L., E-mail: qian_lei@126.com; Xu, Z.; Teng, F.; Duan, X.-X. [Beijing Jiaotong University, Institute of Optoelectronic Technology (China); Jin, Z.-S.; Du, Z.-L. [Henan University, Key Laboratory on special functional materials (China); Li, F.-S.; Zheng, M.-J. [State Key Laboratory for Artificial Microstructures and Mesoscopic Physics, Peking University, Department of Physics (China); Wang, Y.-S. [Beijing Jiaotong University, Institute of Optoelectronic Technology (China)

    2007-06-15

    Efficiency of polymer light-emitting diodes (PLEDs) with poly(2-methoxy-5-(2-ethyl hexyloxy)-p-phenylene vinylene) (MEH-PPV) as an emitting layer was improved if a dehydrated nanotubed titanic acid (DNTA) doped hole-buffer layer polyethylene dioxythiophene (PEDOT) was used. Photoluminescence (PL) and Raman spectra indicated a stronger interaction between DNTA and sulfur atom in thiophene of PEDOT, which suppresses the chemical interaction between vinylene of MEH-PPV and thiophene of PEDOT. The interaction decreases the defect states in an interface region to result in enhancement in device efficiency, even though the hole transporting ability of PEDOT was decreased.

  16. Compensating Scientism through "The Black Hole."

    Science.gov (United States)

    Roth, Lane

    The focal image of the film "The Black Hole" functions as a visual metaphor for the sacred, order, unity, and eternal time. The black hole is a symbol that unites the antinomic pairs of conscious/unconscious, water/fire, immersion/emersion, death/rebirth, and hell/heaven. The black hole is further associated with the quest for…

  17. Black Hole Monodromy and Conformal Field Theory

    NARCIS (Netherlands)

    Castro, A.; Lapan, J.M.; Maloney, A.; Rodriguez, M.J.

    2013-01-01

    The analytic structure of solutions to the Klein-Gordon equation in a black hole background, as represented by monodromy data, is intimately related to black hole thermodynamics. It encodes the "hidden conformal symmetry" of a nonextremal black hole, and it explains why features of the inner event

  18. On Quantum Contributions to Black Hole Growth

    NARCIS (Netherlands)

    Spaans, M.

    2013-01-01

    The effects of Wheeler’s quantum foam on black hole growth are explored from an astrophysical per- spective. Quantum fluctuations in the form of mini (10−5 g) black holes can couple to macroscopic black holes and allow the latter to grow exponentially in mass on a time scale of 109 years.

  19. Accretion, primordial black holes and standard cosmology

    Indian Academy of Sciences (India)

    Abstract. Primordial black holes evaporate due to Hawking radiation. We find that the evaporation times of primordial black holes increase when accretion of radiation is included. Thus, depending on accretion efficiency, more primordial black holes are existing today, which strengthens the con- jecture that the primordial ...

  20. On black holes and gravitational waves

    CERN Document Server

    Loinger, Angelo

    2002-01-01

    Black holes and gravitational waves are theoretical entities of today astrophysics. Various observed phenomena have been associated with the concept of black hole ; until now, nobody has detected gravitational waves. The essays contained in this book aim at showing that the concept of black holes arises from a misinterpretation of general relativity and that gravitational waves cannot exist.

  1. Extremal black holes in N=2 supergravity

    NARCIS (Netherlands)

    Katmadas, S.

    2011-01-01

    An explanation for the entropy of black holes has been an outstanding problem in recent decades. A special case where this is possible is that of extremal black holes in N=2 supergravity in four and five dimensions. The best developed case is for black holes preserving some supersymmetry (BPS),

  2. Photoelectrocatalytic degradation of methylene blue using F doped TiO2photoelectrode under visible light irradiation.

    Science.gov (United States)

    Liu, Dong; Tian, Renwen; Wang, Jianqiao; Nie, Er; Piao, Xianqing; Li, Xin; Sun, Zhuo

    2017-10-01

    Photoelectrocatalysis (PEC) has attracted great interest due to cost effectiveness and high efficiency in water treatment. In this study, F doped TiO 2 (F-TiO 2 ) photoelectrodes with honeycomb like morphology were prepared, and the PEC performance was investigated. F-TiO 2 particles that showed enhanced absorption of visible light were synthesized via a sol-gel method. F-TiO 2 particles were anchored onto the surface of F-doped SnO 2 glass by a screen-printing method to prepare the F-TiO 2 photoelectrodes. The PEC performance of the F-TiO 2 photoelectrodes was investigated via the degradation of methylene blue (MB) under visible light irradiation. The results show that the F-TiO 2 photoelectrodes exhibited an excellent PEC performance that was affected by the F doping content, applied bias and solution pH. A maximum decolorization percentage of 97.8% was achieved by the FT-15 photoelectrode, with a 1.4 V bias at pH 9.94 after 4.0 h of visible light irradiation. The high PEC performance of the F-TiO 2 photoelectrodes is mainly ascribed to the efficient separation of electron-hole (e - -h + ) pairs and the creation of active radicals such as hydroxyl radicals (OH). The PEC decolorization kinetic data were analyzed using the first-order kinetic model and the Langmuir-Hinshelwood (L-H) model. The data indicates that the PEC degradation of MB molecules mainly occurred on the surface of the F-TiO 2 photoelectrodes, and the MB molecules were discolored mainly by h + (41.5%) and OH (46.5%). In addition, 8.2% of the MB molecules were discolored by other oxidative species, and 3.8% of the MB molecules were discolored by self-sensitized oxidation. Copyright © 2017 Elsevier Ltd. All rights reserved.

  3. N-Doped Graphene with Low Intrinsic Defect Densities via a Solid Source Doping Technique

    Directory of Open Access Journals (Sweden)

    Bo Liu

    2017-09-01

    Full Text Available N-doped graphene with low intrinsic defect densities was obtained by combining a solid source doping technique and chemical vapor deposition (CVD. The solid source for N-doping was embedded into the copper substrate by NH3 plasma immersion. During the treatment, NH3 plasma radicals not only flattened the Cu substrate such that the root-mean-square roughness value gradually decreased from 51.9 nm to 15.5 nm but also enhanced the nitrogen content in the Cu substrate. The smooth surface of copper enables good control of graphene growth and the decoupling of height fluctuations and ripple effects, which compensate for the Coulomb scattering by nitrogen incorporation. On the other hand, the nitrogen atoms on the pre-treated Cu surface enable nitrogen incorporation with low defect densities, causing less damage to the graphene structure during the process. Most incorporated nitrogen atoms are found in the pyrrolic configuration, with the nitrogen fraction ranging from 1.64% to 3.05%, while the samples exhibit low defect densities, as revealed by Raman spectroscopy. In the top-gated graphene transistor measurement, N-doped graphene exhibits n-type behavior, and the obtained carrier mobilities are greater than 1100 cm2·V−1·s−1. In this study, an efficient and minimally damaging n-doping approach was proposed for graphene nanoelectronic applications.

  4. N-Doped Graphene with Low Intrinsic Defect Densities via a Solid Source Doping Technique.

    Science.gov (United States)

    Liu, Bo; Yang, Chia-Ming; Liu, Zhiwei; Lai, Chao-Sung

    2017-09-30

    N-doped graphene with low intrinsic defect densities was obtained by combining a solid source doping technique and chemical vapor deposition (CVD). The solid source for N-doping was embedded into the copper substrate by NH₃ plasma immersion. During the treatment, NH₃ plasma radicals not only flattened the Cu substrate such that the root-mean-square roughness value gradually decreased from 51.9 nm to 15.5 nm but also enhanced the nitrogen content in the Cu substrate. The smooth surface of copper enables good control of graphene growth and the decoupling of height fluctuations and ripple effects, which compensate for the Coulomb scattering by nitrogen incorporation. On the other hand, the nitrogen atoms on the pre-treated Cu surface enable nitrogen incorporation with low defect densities, causing less damage to the graphene structure during the process. Most incorporated nitrogen atoms are found in the pyrrolic configuration, with the nitrogen fraction ranging from 1.64% to 3.05%, while the samples exhibit low defect densities, as revealed by Raman spectroscopy. In the top-gated graphene transistor measurement, N-doped graphene exhibits n-type behavior, and the obtained carrier mobilities are greater than 1100 cm²·V -1 ·s -1 . In this study, an efficient and minimally damaging n-doping approach was proposed for graphene nanoelectronic applications.

  5. Modulation Doping of Silicon using Aluminium-induced Acceptor States in Silicon Dioxide

    Science.gov (United States)

    König, Dirk; Hiller, Daniel; Gutsch, Sebastian; Zacharias, Margit; Smith, Sean

    2017-01-01

    All electronic, optoelectronic or photovoltaic applications of silicon depend on controlling majority charge carriers via doping with impurity atoms. Nanoscale silicon is omnipresent in fundamental research (quantum dots, nanowires) but also approached in future technology nodes of the microelectronics industry. In general, silicon nanovolumes, irrespective of their intended purpose, suffer from effects that impede conventional doping due to fundamental physical principles such as out-diffusion, statistics of small numbers, quantum- or dielectric confinement. In analogy to the concept of modulation doping, originally invented for III-V semiconductors, we demonstrate a heterostructure modulation doping method for silicon. Our approach utilizes a specific acceptor state of aluminium atoms in silicon dioxide to generate holes as majority carriers in adjacent silicon. By relocating the dopants from silicon to silicon dioxide, Si nanoscale doping problems are circumvented. In addition, the concept of aluminium-induced acceptor states for passivating hole selective tunnelling contacts as required for high-efficiency photovoltaics is presented and corroborated by first carrier lifetime and tunnelling current measurements. PMID:28425460

  6. Chandra Catches "Piranha" Black Holes

    Science.gov (United States)

    2007-07-01

    Supermassive black holes have been discovered to grow more rapidly in young galaxy clusters, according to new results from NASA's Chandra X-ray Observatory. These "fast-track" supermassive black holes can have a big influence on the galaxies and clusters that they live in. Using Chandra, scientists surveyed a sample of clusters and counted the fraction of galaxies with rapidly growing supermassive black holes, known as active galactic nuclei (or AGN). The data show, for the first time, that younger, more distant galaxy clusters contained far more AGN than older, nearby ones. Galaxy clusters are some of the largest structures in the Universe, consisting of many individual galaxies, a few of which contain AGN. Earlier in the history of the universe, these galaxies contained a lot more gas for star formation and black hole growth than galaxies in clusters do today. This fuel allows the young cluster black holes to grow much more rapidly than their counterparts in nearby clusters. Illustration of Active Galactic Nucleus Illustration of Active Galactic Nucleus "The black holes in these early clusters are like piranha in a very well-fed aquarium," said Jason Eastman of Ohio State University (OSU) and first author of this study. "It's not that they beat out each other for food, rather there was so much that all of the piranha were able to really thrive and grow quickly." The team used Chandra to determine the fraction of AGN in four different galaxy clusters at large distances, when the Universe was about 58% of its current age. Then they compared this value to the fraction found in more nearby clusters, those about 82% of the Universe's current age. The result was the more distant clusters contained about 20 times more AGN than the less distant sample. AGN outside clusters are also more common when the Universe is younger, but only by factors of two or three over the same age span. "It's been predicted that there would be fast-track black holes in clusters, but we never

  7. Shapes and Positions of Black Hole Shadows in Accretion Disks and Spin Parameters of Black Holes

    OpenAIRE

    Takahashi, Rohta

    2004-01-01

    Can we determine a spin parameter of a black hole by observation of a black hole shadow in an accretion disk? In order to answer this question, we make a qualitative analysis and a quantitative analysis of a shape and a position of a black hole shadow casted by a rotating black hole on an optically thick accretion disk and its dependence on an angular momentum of a black hole. We have found black hole shadows with a quite similar size and a shape for largely different black hole spin paramete...

  8. The stable problem of the black-hole connected region in the Schwarzschild black hole

    OpenAIRE

    Tian, Guihua

    2005-01-01

    The stability of the Schwarzschild black hole is studied. Using the Painlev\\'{e} coordinate, our region can be defined as the black-hole-connected region(r>2m, see text) of the Schwarzschild black hole or the white-hole-connected region(r>2m, see text) of the Schwarzschild black hole. We study the stable problems of the black-hole-connected region. The conclusions are: (1) in the black-hole-connected region, the initially regular perturbation fields must have real frequency or complex frequen...

  9. Gene doping: the hype and the reality.

    Science.gov (United States)

    Wells, D J

    2008-06-01

    Some spectacular results from genetic manipulation of laboratory rodents and increasing developments in human gene therapy raise the spectre of genetic modification or 'gene doping' in sports. Candidate targets include the induction of muscle hypertrophy through overexpression of specific splice variants of insulin-like growth factor-1 or blockade of the action of myostatin, increasing oxygen delivery by raising the hematocrit through the use of erythropoietin, induction of angiogenesis with vascular endothelial growth factors or related molecules and changes in muscle phenotype through expression of peroxisome-proliferator-activated receptor- delta and associated molecules. Some of these potential genetic enhancements, particularly where the genetic modification and its action are confined to the muscles, may be undetectable using current tests. This had lead to exaggerated predictions that gene doping in athletics will be common within the next few years. However, a review of the methods of gene transfer and the current 'state of the art' in development of genetic treatments for human disease show that the prospects for gene doping remain essentially theoretical at present. Despite this conclusion, it will be important to continue to monitor improvements in the technology and to develop methods of detection, particularly those based on identifying patterns of changes in response to doping as opposed to the detection of specific agents.

  10. High performance unipolar MoTe2 field effect transistors enabled by doping and Al2O3 capping

    Science.gov (United States)

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

    We carry out the first systematic experiment on carrier type modulation of MoTe2 FET in this work. unipolar p- and n-type MoTe2 FETs with 105 and 106 on-off ratios are achieved through rapid thermal annealing (RTA) and Benzyl Viologen (BV) doping respectively. By varying the vacuum level in RTA chamber before annealing and BV dopant concentration, annealing condition, both hole and electron doping concentration can be modulated in a wide range from slight doping to degenerate like doping. Furthermore, Al2O3 is deposited onto the device surfaces for the mobility engineering. Hole and electron mobilities are improved to 62 cm2/Vs and 82 cm2/Vs respectively after Al2O3 capping; they are among the highest carrier mobilities of MoTe2 transistors ever obtained. A lateral homogeneous MoTe2 p-n diode is fabricated combining the electron and hole doping techniques, the device displays excellent diode properties with a high rectification ratio of 104 at 0 gate bias and an ideality factor of 1.2. This work was supported by the Global Research Laboratory and Global Frontier R&D Programs at the Center for Hybrid Interface Materials, both funded by the Ministry of Science, ICT & Future Planning via the National Research Foundation of Korea (NRF).

  11. Plasmonic doped semiconductor nanocrystals: Properties, fabrication, applications and perspectives

    Science.gov (United States)

    Kriegel, Ilka; Scotognella, Francesco; Manna, Liberato

    2017-02-01

    Degenerately doped semiconductor nanocrystals (NCs) are of recent interest to the NC community due to their tunable localized surface plasmon resonances (LSPRs) in the near infrared (NIR). The high level of doping in such materials with carrier densities in the range of 1021cm-3 leads to degeneracy of the doping levels and intense plasmonic absorption in the NIR. The lower carrier density in degenerately doped semiconductor NCs compared to noble metals enables LSPR tuning over a wide spectral range, since even a minor change of the carrier density strongly affects the spectral position of the LSPR. Two classes of degenerate semiconductors are most relevant in this respect: impurity doped semiconductors, such as metal oxides, and vacancy doped semiconductors, such as copper chalcogenides. In the latter it is the density of copper vacancies that controls the carrier concentration, while in the former the introduction of impurity atoms adds carriers to the system. LSPR tuning in vacancy doped semiconductor NCs such as copper chalcogenides occurs by chemically controlling the copper vacancy density. This goes in hand with complex structural modifications of the copper chalcogenide crystal lattice. In contrast the LSPR of degenerately doped metal oxide NCs is modified by varying the doping concentration or by the choice of host and dopant atoms, but also through the addition of capacitive charge carriers to the conduction band of the metal oxide upon post-synthetic treatments, such as by electrochemical- or photodoping. The NIR LSPRs and the option of their spectral fine-tuning make accessible important new features, such as the controlled coupling of the LSPR to other physical signatures or the enhancement of optical signals in the NIR, sensing application by LSPR tracking, energy production from the NIR plasmon resonance or bio-medical applications in the biological window. In this review we highlight the recent advances in the synthesis of various different plasmonic

  12. doped stable clusters a

    Indian Academy of Sciences (India)

    ABHIJIT DUTTA

    2018-01-30

    ., showed that Ru-doped. Rh6 cluster is a better catalyst for the activation of methanol compared to pure Rh6. It may be noted that methanol activation occurs via O–H bond dissociation rather than C–H bond.25 Rhodium nano ...

  13. Doped barium titanate nanoparticles

    Indian Academy of Sciences (India)

    We have synthesized nickel (Ni) and iron (Fe) ion doped BaTiO3 nanoparticles through a chemical route using polyvinyl alcohol (PVA). The concentration of dopant varies from 0 to 2 mole% in the specimens. The results from X-ray diffractograms and transmission electron micrographs show that the particle diameters in the ...

  14. Doped zinc oxide microspheres

    Science.gov (United States)

    Arnold, Jr., Wesley D.; Bond, Walter D.; Lauf, Robert J.

    1993-01-01

    A new composition and method of making same for a doped zinc oxide microsphere and articles made therefrom for use in an electrical surge arrestor which has increased solid content, uniform grain size and is in the form of a gel.

  15. BLOOD DOPING AND RISKS

    Directory of Open Access Journals (Sweden)

    Goran Vasić

    2015-05-01

    Full Text Available Doping is the way in which athletes misuse of chemicals and other types of medical interventions (eg, blood replacement, try to get ahead in the results of other athletes or their performance at the expense of their own health. The aim of this work is the analysis of blood doping and the display of negative consequences that this way of increasing capabilities brings. Method: The methodological work is done descriptively. Results: Even in 1972 at the Stockholm Institute for gymnastics and sport, first Dr. Bjorn Ekblom started having blood doping. Taken from the blood, athletes through centifuge separating red blood cells from blood plasma, which is after a month of storage in the fridge, every athlete back into the bloodstream. Tests aerobic capacity thereafter showed that the concerned athletes can run longer on average for 25% of the treadmill than before. Discussion: Blood doping carries with it serious risks, excessive amount of red cells “thickens the blood,” increased hematocrit, which reduces the heart’s ability to pump blood to the periphery. All this makes it difficult for blood to flow through blood vessels, and there is a great danger that comes to a halt in the circulation, which can cause cardiac arrest, stroke, pulmonary edema, and other complications that can be fatal.

  16. Spectral Hole Burning via Kerr Nonlinearity

    Science.gov (United States)

    Khan, Anwar Ali; Abdul Jabar, M. S.; Jalaluddin, M.; Bacha, Bakht Amin; Iftikhar, Ahmad

    2015-10-01

    Spectral hole burning is investigated in an optical medium in the presence of Doppler broadening and Kerr nonlinearity. The Kerr nonlinearity generates coherent hole burning in the absorption spectrum. The higher order Kerr nonlinearity enhances the typical lamb dip of the hole. Normal dispersion in the hole burning region while Steep anomalous dispersion between the two hole burning regions also enhances with higher order Kerr effect. A large phase shift creates large delay or advancement in the pulse propagation while no distortion is observed in the pulse. These results provide significant steps to improve optical memory, telecom devices, preservation of information and image quality. Supported by Higher Education Commission (HEC) of Pakistan

  17. Black hole thermodynamics with conical defects

    Science.gov (United States)

    Appels, Michael; Gregory, Ruth; Kubizňák, David

    2017-05-01

    Recently we have shown [1] how to formulate a thermodynamic first law for a single (charged) accelerated black hole in AdS space by fixing the conical deficit angles present in the spacetime. Here we show how to generalise this result, formulating thermodynamics for black holes with varying conical deficits. We derive a new potential for the varying tension defects: the thermodynamic length, both for accelerating and static black holes. We discuss possible physical processes in which the tension of a string ending on a black hole might vary, and also map out the thermodynamic phase space of accelerating black holes and explore their critical phenomena.

  18. Black-hole creation in quantum cosmology

    Energy Technology Data Exchange (ETDEWEB)

    Zhong Chao, Wu [Rome, Univ. `La Sapienza` (Italy). International Center for Relativistic Astrophysics]|[Specola Vaticana, Vatican City State (Vatican City State, Holy See)

    1997-11-01

    It is proven that the probability of a black hole created from the de Sitter space-time background, at the Wkb level, is the exponential of one quarter of the sum of the black hole and cosmological horizon areas, or the total entropy of the universe. This is true not only for the spherically symmetric cases of the Schwarzschild or Reissner-Nordstroem black holes, but also for the rotating cases of the Kerr black hole and the rotating charged case of the Newman black hole. The de Sitter metric is the most probable evolution at the Planckian era of the universe.

  19. Soft X-ray angle-resolved photoemission spectroscopy of heavily boron-doped superconducting diamond films

    Directory of Open Access Journals (Sweden)

    T. Yokoya, T. Nakamura, T. Matushita, T. Muro, H. Okazaki, M. Arita, K. Shimada, H. Namatame, M. Taniguchi, Y. Takano, M. Nagao, T. Takenouchi, H. Kawarada and T. Oguchi

    2006-01-01

    Full Text Available We have performed soft X-ray angle-resolved photoemission spectroscopy (SXARPES of microwave plasma-assisted chemical vapor deposition diamond films with different B concentrations in order to study the origin of the metallic behavior of superconducting diamond. SXARPES results clearly show valence band dispersions with a bandwidth of ~23 eV and with a top of the valence band at gamma point in the Brillouin zone, which are consistent with the calculated valence band dispersions of pure diamond. Boron concentration-dependent band dispersions near the Fermi level (EF exhibit a systematic shift of EF, indicating depopulation of electrons due to hole doping. These SXARPES results indicate that diamond bands retain for heavy boron doping and holes in the diamond band are responsible for the metallic states leading to superconductivity at low temperature. A high-resolution photoemission spectroscopy spectrum near EF of a heavily boron-doped diamond superconductor is also presented.

  20. From Black Holes to Quivers

    CERN Document Server

    Manschot, Jan; Sen, Ashoke

    2012-01-01

    Middle cohomology states on the Higgs branch of supersymmetric quiver quantum mechanics - also known as pure Higgs states - have recently emerged as possible microscopic candidates for single-centered black hole micro-states, as they carry zero angular momentum and appear to be robust under wall-crossing. Using the connection between quiver quantum mechanics on the Coulomb branch and the quantum mechanics of multi-centered black holes, we propose a general algorithm for reconstructing the full moduli-dependent cohomology of the moduli space of an arbitrary quiver, in terms of the BPS invariants of the pure Higgs states. We analyze many examples of quivers with loops, including all cyclic Abelian quivers and several examples with two loops or non-Abelian gauge groups, and provide supporting evidence for this proposal. We also develop methods to count pure Higgs states directly.

  1. Black hole with quantum potential

    Directory of Open Access Journals (Sweden)

    Ahmed Farag Ali

    2016-08-01

    Full Text Available In this work, we investigate black hole (BH physics in the context of quantum corrections. These quantum corrections were introduced recently by replacing classical geodesics with quantal (Bohmian trajectories and hence form a quantum Raychaudhuri equation (QRE. From the QRE, we derive a modified Schwarzschild metric, and use that metric to investigate BH singularity and thermodynamics. We find that these quantum corrections change the picture of Hawking radiation greatly when the size of BH approaches the Planck scale. They prevent the BH from total evaporation, predicting the existence of a quantum BH remnant, which may introduce a possible resolution for the catastrophic behavior of Hawking radiation as the BH mass approaches zero. Those corrections also turn the spacelike singularity of the black hole to be timelike, and hence this may ameliorate the information loss problem.

  2. Black hole with quantum potential

    Energy Technology Data Exchange (ETDEWEB)

    Ali, Ahmed Farag, E-mail: ahmed.ali@fsc.bu.edu.eg [Department of Physics, Faculty of Science, Benha University, Benha 13518 (Egypt); Khalil, Mohammed M., E-mail: moh.m.khalil@gmail.com [Department of Electrical Engineering, Alexandria University, Alexandria 12544 (Egypt)

    2016-08-15

    In this work, we investigate black hole (BH) physics in the context of quantum corrections. These quantum corrections were introduced recently by replacing classical geodesics with quantal (Bohmian) trajectories and hence form a quantum Raychaudhuri equation (QRE). From the QRE, we derive a modified Schwarzschild metric, and use that metric to investigate BH singularity and thermodynamics. We find that these quantum corrections change the picture of Hawking radiation greatly when the size of BH approaches the Planck scale. They prevent the BH from total evaporation, predicting the existence of a quantum BH remnant, which may introduce a possible resolution for the catastrophic behavior of Hawking radiation as the BH mass approaches zero. Those corrections also turn the spacelike singularity of the black hole to be timelike, and hence this may ameliorate the information loss problem.

  3. "Twisted" black holes are unphysical

    CERN Document Server

    Gray, Finnian; Schuster, Sebastian; Visser, Matt

    2016-01-01

    So-called "twisted" black holes have recently been proposed by Zhang (1609.09721 [gr-qc]), and further considered by Chen and Jing (1610.00886 [gr-qc]), and more recently by Ong (1610.05757 [gr-qc]). While these spacetimes are certainly Ricci-flat, and so mathematically satisfy the vacuum Einstein equations, they are also merely minor variants on Taub--NUT spacetimes. Consequently they exhibit several unphysical features that make them quite unreasonable as realistic astrophysical objects. Specifically, these "twisted" black holes are not (globally) asymptotically flat. Furthermore, they contain closed timelike curves that are not hidden behind any event horizon --- the most obvious of these closed timelike curves are small azimuthal circles around the rotation axis, but the effect is more general. The entire region outside the horizon is infested with closed timelike curves.

  4. Ultraslow Light Propagation in an Inhomogeneously Broadened Rare-Earth Ion-Doped Crystal

    Science.gov (United States)

    Baldit, E.; Bencheikh, K.; Monnier, P.; Levenson, J. A.; Rouget, V.

    2005-09-01

    We show that coherent population oscillations effect allows us to burn a narrow spectral hole (26 Hz) within the homogeneous absorption line of the optical transition of an erbium ion-doped crystal. The large dispersion of the index of refraction associated with this hole permits us to achieve a group velocity as low as 2.7m/s with a transmission of 40%. We especially benefit from the inhomogeneous absorption broadening of the ions to tune both the transmission coefficient, from 40% to 90%, and the light group velocity from 2.7m/s to 100m/s.

  5. Van der Waals black hole

    Directory of Open Access Journals (Sweden)

    Aruna Rajagopal

    2014-10-01

    Full Text Available In the context of extended phase space, where the negative cosmological constant is treated as a thermodynamic pressure in the first law of black hole thermodynamics, we find an asymptotically AdS metric whose thermodynamics matches exactly that of the Van der Waals fluid. We show that as a solution of Einstein's equations, the corresponding stress energy tensor obeys (at least for certain range of metric parameters all three weak, strong, and dominant energy conditions.

  6. Effects of electron blocking and hole trapping of the red guest emitter materials on hybrid white organic light emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Lin-Ann; Vu, Hoang-Tuan [National Formosa University, Institute of Electro-Optical and Materials Science, Huwei, Yunlin County, Taiwan (China); Juang, Fuh-Shyang, E-mail: fsjuang@seed.net.tw [National Formosa University, Institute of Electro-Optical and Materials Science, Huwei, Yunlin County, Taiwan (China); Lai, Yun-Jr [National Formosa University, Institute of Electro-Optical and Materials Science, Huwei, Yunlin County, Taiwan (China); Yeh, Pei-Hsun [Raystar Optronics, Inc., 5F No. 25, Keya Rd. Daya Township, Taichung County, Taiwan (China); Tsai, Yu-Sheng [National Formosa University, Institute of Electro-Optical and Materials Science, Huwei, Yunlin County, Taiwan (China)

    2013-10-01

    Hybrid white organic light emitting diodes (HWOLEDs) with fluorescence and phosphorescence hybrid structures are studied in this work. HWOLEDs were fabricated with blue/red emitting layers: fluorescent host material doped with sky blue material, and bipolar phosphorescent host emitting material doped with red dopant material. An electron blocking layer is applied that provides hole red guest emitter hole trapping effects, increases the charge carrier injection quantity into the emitting layers and controls the recombination zone (RZ) that helps balance the device color. Spacer layers were also inserted to expand the RZ, increase efficiency and reduce energy quenching along with roll-off effects. The resulting high efficiency warm white OLED device has the lower highest occupied molecule orbital level red guest material, current efficiency of 15.9 cd/A at current density of 20 mA/cm{sup 2}, and Commission Internationale de L'Eclairage coordinates of (0.34, 0.39)

  7. Enhanced photocatalytic activity of α-Bi2O3 with high electron-hole mobility by codoping approach: A first-principles study

    Science.gov (United States)

    Li, Yujie; Yang, Fan; Yu, Ying

    2015-12-01

    To improve the photocatalytic activity of narrow-gap material Bi2O3, efforts need be made to lower the electron-hole recombination rate and widen the response range of visible light. Understanding the related mechanism is vital, which may lead to high electron-hole mobility and suitable band edge. In this paper we have studied the atomic and electronic structure of single metallic atom (Ag, Cu, Pb, Pd, Sn)-doped and nitrogen (N)-metal codoped Bi2O3 with α phase by first principles calculations. The calculation results firstly show that new impurity states appeared in band gap of α-Bi2O3 after single metal doping, especially for the doping of Cu, Ag and Pb, which showed shallow acceptor levels for α-Bi2O3. And the formation energy analysis indicates that Cu doped system was easier to be formed than other doped systems. All of those calculated properties are helpful to enhance the photocatalytic property of α-Bi2O3, which agrees well with experimental results. Interestingly, for anion atom N together with metallic atom (Ag, Cu, Pb, Pd, Sn) codoped α-Bi2O3 systems, it is found that N-2p state had impact on the electronic structure. Holes were demonstrated to be more delocalized in (Cu + N) codoped α-Bi2O3 system, which was responsible for high mobility of holes, then lowering the electron-hole recombination, and finally improving the photocatalytic performance of Bi2O3 significantly.

  8. Opportunity Leaves a Trail of 'Rat' Holes

    Science.gov (United States)

    2004-01-01

    NASA's Mars Exploration Rover Opportunity's rock abrasion tool, known informally as the 'Rat,' has nibbled seven holes into the slope of 'Endurance Crater.' This image from the rover's navigation camera was released previously (PIA06716) without the Rat holes labeled so that viewers could try to find the holes themselves. Here, the holes have been identified. Starting from the uppermost pictured (closest to the crater rim) to the lowest, the Rat hole targets are: 'Tennessee,' 'Cobblehill,' 'Virginia,' 'London,' 'Grindstone,' 'Kettlestone,' and 'Drammensfjorden.' These holes were drilled on sols 138 (June 13, 2004), 143 (June 18), 145 (June 20), 148 (June 23), 151 (June 26), 153 (June 28) and 161 (July 7), respectively. Each hole is 4.5 centimeters (1.8 inches) in diameter.

  9. Collision of two rotating Hayward black holes

    Energy Technology Data Exchange (ETDEWEB)

    Gwak, Bogeun [Sejong University, Department of Physics and Astronomy, Seoul (Korea, Republic of)

    2017-07-15

    We investigate the spin interaction and the gravitational radiation thermally allowed in a head-on collision of two rotating Hayward black holes. The Hayward black hole is a regular black hole in a modified Einstein equation, and hence it can be an appropriate model to describe the extent to which the regularity effect in the near-horizon region affects the interaction and the radiation. If one black hole is assumed to be considerably smaller than the other, the potential of the spin interaction can be analytically obtained and is dependent on the alignment of angular momenta of the black holes. For the collision of massive black holes, the gravitational radiation is numerically obtained as the upper bound by using the laws of thermodynamics. The effect of the Hayward black hole tends to increase the radiation energy, but we can limit the effect by comparing the radiation energy with the gravitational waves GW150914 and GW151226. (orig.)

  10. Plasma electron-hole kinematics: momentum conservation

    CERN Document Server

    Hutchinson, I H

    2016-01-01

    We analyse the kinematic properties of a plasma electron hole: a non-linear self-sustained localized positive electric potential perturbation, trapping electrons, that behaves as a coherent entity. When a hole accelerates or grows in depth, ion and electron plasma momentum is changed both within the hole and outside it, by an energization process we call jetting. We present a comprehensive analytic calculation of the momentum changes of an isolated general one-dimensional hole. The conservation of the total momentum gives the hole's kinematics, determining its velocity evolution. Our results explain many features of the behavior of hole speed observed in numerical simulations, including self-acceleration at formation, and hole pushing and trapping by ion streams.

  11. Reed's Conjecture on hole expansions

    CERN Document Server

    Fouquet, Jean-Luc

    2012-01-01

    In 1998, Reed conjectured that for any graph $G$, $\\chi(G) \\leq \\lceil \\frac{\\omega(G) + \\Delta(G)+1}{2}\\rceil$, where $\\chi(G)$, $\\omega(G)$, and $\\Delta(G)$ respectively denote the chromatic number, the clique number and the maximum degree of $G$. In this paper, we study this conjecture for some {\\em expansions} of graphs, that is graphs obtained with the well known operation {\\em composition} of graphs. We prove that Reed's Conjecture holds for expansions of bipartite graphs, for expansions of odd holes where the minimum chromatic number of the components is even, when some component of the expansion has chromatic number 1 or when a component induces a bipartite graph. Moreover, Reed's Conjecture holds if all components have the same chromatic number, if the components have chromatic number at most 4 and when the odd hole has length 5. Finally, when $G$ is an odd hole expansion, we prove $\\chi(G)\\leq\\lceil\\frac{\\omega(G)+\\Delta(G)+1}{2}\\rceil+1$.

  12. Soft Hair on Black Holes.

    Science.gov (United States)

    Hawking, Stephen W; Perry, Malcolm J; Strominger, Andrew

    2016-06-10

    It has recently been shown that Bondi-van der Burg-Metzner-Sachs supertranslation symmetries imply an infinite number of conservation laws for all gravitational theories in asymptotically Minkowskian spacetimes. These laws require black holes to carry a large amount of soft (i.e., zero-energy) supertranslation hair. The presence of a Maxwell field similarly implies soft electric hair. This Letter gives an explicit description of soft hair in terms of soft gravitons or photons on the black hole horizon, and shows that complete information about their quantum state is stored on a holographic plate at the future boundary of the horizon. Charge conservation is used to give an infinite number of exact relations between the evaporation products of black holes which have different soft hair but are otherwise identical. It is further argued that soft hair which is spatially localized to much less than a Planck length cannot be excited in a physically realizable process, giving an effective number of soft degrees of freedom proportional to the horizon area in Planck units.

  13. Entanglement Entropy of Black Holes

    Directory of Open Access Journals (Sweden)

    Sergey N. Solodukhin

    2011-10-01

    Full Text Available The entanglement entropy is a fundamental quantity, which characterizes the correlations between sub-systems in a larger quantum-mechanical system. For two sub-systems separated by a surface the entanglement entropy is proportional to the area of the surface and depends on the UV cutoff, which regulates the short-distance correlations. The geometrical nature of entanglement-entropy calculation is particularly intriguing when applied to black holes when the entangling surface is the black-hole horizon. I review a variety of aspects of this calculation: the useful mathematical tools such as the geometry of spaces with conical singularities and the heat kernel method, the UV divergences in the entropy and their renormalization, the logarithmic terms in the entanglement entropy in four and six dimensions and their relation to the conformal anomalies. The focus in the review is on the systematic use of the conical singularity method. The relations to other known approaches such as ’t Hooft’s brick-wall model and the Euclidean path integral in the optical metric are discussed in detail. The puzzling behavior of the entanglement entropy due to fields, which non-minimally couple to gravity, is emphasized. The holographic description of the entanglement entropy of the black-hole horizon is illustrated on the two- and four-dimensional examples. Finally, I examine the possibility to interpret the Bekenstein-Hawking entropy entirely as the entanglement entropy.

  14. A conducting nano-filament (CNF) network as a precursor to the origin of superconductivity in electron-doped copper oxides

    OpenAIRE

    Yu, Heshan; He, Ge; Lin, Ziquan; Kusmartseva, Anna; Yua, Jie; Zhu, Beiyi; Yang, Yi-feng; Xiang, Tao; Liang LI; Wang, Junfeng; Kusmartsev, F. V.; Jin, Kui

    2016-01-01

    Emergency of superconductivity at the instabilities of antiferromagnetism has been widely recognized in unconventional superconductors. In copper-oxide superconductors, spin fluctuations play a predominant role in electron pairing with electron dopants yet composite orders veil the nature of superconductivity for hole-doped family. However, in electron-doped copper oxide superconductors (cuprates) the AFM critical end point is still in controversy for different probes, demonstrating high sens...

  15. Optical Characterization of the Hole Polaron in a Series of Diketopyrrolopyrrole Polymers Used for Organic Photovoltaics

    Directory of Open Access Journals (Sweden)

    Evan L. Williams

    2014-12-01

    Full Text Available A strategy that is often used for designing low band gap polymers involves the incorporation of electron-rich (donor and electron-deficient (acceptor conjugated segments within the polymer backbone. In this paper we investigate such a series of Diketopyrrolopyrrole (DPP-based co-polymers. The co-polymers consisted of a DPP unit attached to a phenylene, naphthalene, or anthracene unit. Additionally, polymers utilizing either the thiophene-flanked DPP or the furan-flanked DPP units paired with the naphthalene comonomer were compared. As these polymers have been used as donor materials and subsequent hole transporting materials in organic solar cells, we are specifically interested in characterizing the optical absorption of the hole polaron of these DPP based copolymers. We employ chemical doping, electrochemical doping, and photoinduced absorption (PIA studies to probe the hole polaron absorption spectra. While some donor-acceptor polymers have shown an appreciable capacity to generate free charge carriers upon photoexcitation, no polaron signal was observed in the PIA spectrum of the polymers in this study. The relations between molecular structure and optical properties are discussed.

  16. Electronic dynamics due to exchange interaction with holes in GaAs

    Science.gov (United States)

    Schneider, Hans Christian; Krauß, Michael

    2010-02-01

    We present an investigation of electron-spin dynamics in p-doped bulk GaAs due to the electron-hole exchange interaction, aka the Bir-Aronov-Pikus mechanism. We discuss under which conditions a spin relaxation times for this mechanism is, in principle, accessible to experimental techniques, in particular to 2-photon photoemission, but also Faraday/Kerr effect measurements. We give numerical results for the spin relaxation time for a range of p-doping densities and temperatures. We then go beyond the relaxation time approximation and calculate numerically the spin-dependent electron dynamics by including the spin-flip electron-hole exchange scattering and spin-conserving carrier Coulomb scattering at the level of Boltzmann scattering integrals. We show that the electronic dynamics deviates from the simple spin-relaxation dynamics for electrons excited at high energies where the thermalization does not take place faster than the spin relaxation time. We also present a derivation of the influence of screening on the electron-hole exchange scattering and conclude that it can be neglected for the case of GaAs, but may become important for narrow-gap semiconductors.

  17. Ni-doped (CeO{sub 2−δ})–YSZ mesoarchitectured with nanocrystalline framework: the effect of thermal treatment on structure, surface chemistry and catalytic properties in the partial oxidation of methane (CPOM)

    Energy Technology Data Exchange (ETDEWEB)

    Somacescu, Simona, E-mail: ssimona@icf.ro [Romanian Academy, “Ilie Murgulescu” Institute of Physical Chemistry (Romania); Florea, Mihaela [University of Bucharest, Department of Organic Chemistry, Biochemistry and Catalysis, Faculty of Chemistry (Romania); Osiceanu, Petre; Calderon-Moreno, Jose Maria [Romanian Academy, “Ilie Murgulescu” Institute of Physical Chemistry (Romania); Ghica, Corneliu [National Institute of Materials Physics (Romania); Serra, Jose Manuel [Universidad Politécnica de Valencia - Consejo Superior de Investigaciones Científicas, Instituto de Tecnología Química (Spain)

    2015-11-15

    Ni-doped (CeO{sub 2−δ})–YSZ (5 mol% Ni oxide, 10 mol% ceria) mesoarchitectures (MA) with nanocrystalline framework have been synthesized by an original, facile and cheap approach based on Triton X100 nonionic surfactant as template and water as solvent at a strong basic pH value. Following the hydrothermal treatment under autogenous pressure (∼18 bars), Ni, Ce, Y, and Zr were well ordered as MA with nanocrystalline framework, assuring thermal stability. A comprehensive investigation of structure, texture, morphology, and surface chemistry was performed by means of a variety of complementary techniques (X-Ray Diffraction, XRD; Raman Spectroscopy, RS; Brunauer—Emmett—Teller, BET; Temperature—Programmed Reduction, TPR; Transmission Electron Microscopy, TEM and DF-STEM; X-ray Photoelectron Spectroscopy, XPS; Catalytic activity and selectivity). N{sub 2} sorption measurements highlighted that the mesoporous structure is formed at 600 °C and remains stable at 800 °C. At 900 °C, the MA collapses, favoring the formation of macropores. The XRD and Raman Spectroscopy of all samples showed the presence of a pure, single phase with fluorite-type structure. At 900 °C, an increased tetragonal distortion of the cubic lattice was observed. The surface chemistry probed by XPS exhibits a mixture of oxidation states (Ce{sup 3+} + Ce{sup 4+}) with high percentage of Ce{sup 3+} valence state ∼35 % and (Ni{sup 3+} and Ni{sup 2+}) oxidation states induced by the thermal treatment. These nanoparticles assembled into MA show high stability and selectivity over time in catalytic partial oxidation of methane (CPOM). These promising performances suggest an interesting prospect for introduction as anode within IT-SOFC assemblies.Graphical Abstract.

  18. Improved conversion efficiency in dye-sensitized solar cells based on electrospun Al-doped ZnO nanofiber electrodes prepared by seed layer treatment

    Science.gov (United States)

    Yun, Sining; Lim, Sangwoo

    2011-02-01

    The application of electrospun nanofibers in electronic devices is limited due to their poor adhesion to conductive substrates. To improve this, a seed layer (SD) is introduced on the FTO substrate before the deposition of the electrospun composite nanofibers. This facilitates the release of interfacial tensile stress during calcination and enhances the interfacial adhesion of the AZO nanofiber films with the FTO substrate. Dye-sensitized solar cells (DSSC) based on these AZO nanofiber photoelectrodes have been fabricated and investigated. An energy conversion efficiency ( η) of 0.54-0.55% has been obtained under irradiation of AM 1.5 simulated sunlight (100 mW/cm 2), indicating a massive improvement of η in the AZO nanofiber film DSSCs after SD-treatment of the FTO substrate as compared to those with no treatment. The SD-treatment has been demonstrated to be a simple and facile method to solve the problem of poor adhesion between electrospun nanofibers and the conductive substrate.

  19. Doping Induced Solubility Control

    Science.gov (United States)

    Jacobs, Ian Edward

    Polymeric semiconductors are promising class of materials, which combine many of the electrical properties of inorganic semiconductors with the mechanical flexibility and chemical processability of organic materials. Semiconducting polymers can be deposited from solution over large areas at low cost, and may find applications in displays, photovoltaics, and sensor arrays. Unfortunately, these materials are generally mutually soluble with other organics, preventing solution-based deposition of complex patterned structures using standard photolithographic techniques. Here, we present an entirely new method for patterning conductive polymers utilizing a change in polymer solubility upon p-type doping. Many polymer : molecular dopant systems, including the extensively studied system poly-(3-hexylthiophene) : 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (P3HT : F4TCNQ), are rendered insoluble in a wide range solvents by p-type doping at only a few mol%. By sequentially doping and dedoping films, polymer solubility can be switched on an off at will. We find that doped films can be easily prepared in a two-step process, by first coating the polymer (P3HT), then exposing the film to an orthogonal solvent containing the dopant (F4TCNQ). Dedoping is achieved by means of a chemical reaction that deactivates F4TCNQ, allowing it to be removed by an orthogonal solvent in a single step. This process allows for fully quantitative dedoping, in some cases leaving films with an even lower free carrier density than as cast films by removing intrinsic p-type defects. In addition, we have also identified a photochemical reaction between F4TCNQ and solvents such as tetrahydrofuran (THF), which similarly yields a non-doping product. By immersing films in THF and exposing them to light, this reaction allows for direct, optical patterning of P3HT films. Using laser scanning confocal microscopy (LSCM), we demonstrate direct write topographic patterning of arbitrary structures with in

  20. Plasma electron hole kinematics. II. Hole tracking Particle-In-Cell simulation

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, C.; Hutchinson, I. H. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

    2016-08-15

    The kinematics of a 1-D electron hole is studied using a novel Particle-In-Cell simulation code. A hole tracking technique enables us to follow the trajectory of a fast-moving solitary hole and study quantitatively hole acceleration and coupling to ions. We observe a transient at the initial stage of hole formation when the hole accelerates to several times the cold-ion sound speed. Artificially imposing slow ion speed changes on a fully formed hole causes its velocity to change even when the ion stream speed in the hole frame greatly exceeds the ion thermal speed, so there are no reflected ions. The behavior that we observe in numerical simulations agrees very well with our analytic theory of hole momentum conservation and the effects of “jetting.”.

  1. XFEM Modelling of Multi-holes Plate with Single-row and Staggered Holes Configurations

    Directory of Open Access Journals (Sweden)

    Supar Khairi

    2017-01-01

    Full Text Available Joint efficiency is the key to composite structures assembly design, good structures response is dependent upon multi-holes behavior as subjected to remote loading. Current benchmarking work were following experimental testing series taken from literature on multi-holes problem. Eleven multi-hole configurations were investigated with various pitch and gage distance of staggered holes and non-staggered holes (single-row holes. Various failure modes were exhibited, most staggered holes demonstrates staggered crack path but non-staggered holes series displayed crack path along net-section plane. Stress distribution were carried out and good agreement were exhibited in experimental observation as reported in the respective literature. Consequently, strength prediction work were carried out under quasi-static loading, most showed discrepancy between 8% -31%, better prediction were exhibited in thicker and non-staggered holes plate combinations.

  2. Investigation Performance and Mechanisms of Inverted Polymer Solar Cells by Pentacene Doped P3HT : PCBM

    Directory of Open Access Journals (Sweden)

    Hsin-Ying Lee

    2014-01-01

    Full Text Available The inverted polymer solar cells (PSCs with pentacene-doped P3HT : PCBM absorption layers were fabricated. It was demonstrated that the pentacene doping modulated the electron mobility and the hole mobility in the resulting absorption layer. Furthermore, by varying the doping content, the optimal carrier mobility balance could be obtained. In addition, the pentacene doping led to an improvement in the crystallinity of the resulting films and made an enhancement in the light absorption, which was partly responsible for the performance improvement of the solar cells. Using the space-charge-limited current (SCLC method, it was determined that the balanced carrier mobility (μh/μe=1.000 was nearly achieved when a pentacene doping ratio of 0.065 by weight was doped into the P3HT : PCBM : pentacene absorption layer. Compared with the inverted PSCs without the pentacene doping, the short circuit current density and the power conversion efficiency of the inverted PSCs with the pentacene doping ratio of 0.065 were increased from 9.73 mA/cm2 to 11.26 mA/cm2 and from 3.39% to 4.31%, respectively.

  3. Exploring and rationalising effective n-doping of large area CVD-graphene by NH3.

    Science.gov (United States)

    Bianco, G V; Losurdo, M; Giangregorio, M M; Capezzuto, P; Bruno, G

    2014-02-28

    Despite the large number of papers on the NH3 doping of graphene, the achievement of stable n-doped large area CVD (chemical vapor deposition) graphene, which is intrinsically p-doped, is still challenging. A control of the NH3 chemisorption and of the N-bond configuration is still needed. The feasibility of a room temperature high pressure NH3 treatment of CVD graphene to achieve n-type doping is shown here. We use and correlate data for (a) sheet resistance, R(sh), and the Hall coefficient, R(H), in van der Pauw configuration, acquired in real time during the NH3 doping of CVD-graphene on a glass substrate, (b) optical measurements of the effect of doping on the graphene Van Hove singularity point at 4.6 eV in the dielectric function spectra by spectroscopic ellipsometry, and of (c) N-bond configuration by XPS to better understand and, finally, control the NH3 doping of graphene. The discussion is focused on the thermal and time stability of the n-doping after air exposure. A chemical rationale is provided for the NH3 n-doping based on the interaction of (i) NH3 with intrinsic oxygen functionalities and defects of CVD graphene and of (ii) C-NH2 doping centers with acceptor species present in the air.

  4. The Electric and Optical Properties of Doped Small Molecular Organic Light-Emitting Devices

    CERN Document Server

    Kwang Ohk Cheo

    2003-01-01

    Organic light-emitting devices (OLEDs) constitute a new and exciting emissive display technology. In general, the basic OLED structure consists of a stack of fluorescent organic layers sandwiched between a transparent conducting-anode and metallic cathode. When an appropriate bias is applied to the device, holes are injected from the anode and electrons from the cathode; some of the recombination events between the holes and electrons result in electroluminescence (EL). Until now, most of the efforts in developing OLEDs have focused on display applications, hence on devices within the visible range. However some organic devices have been developed for ultraviolet or infrared emission. Various aspects of the device physics of doped small molecular OLEDs were described and discussed. The doping layer thickness and concentration were varied systematically to study their effects on device performances, energy transfer, and turn-off dynamics. Low-energy-gap DCM2 guest molecules, in either alpha-NPD or DPVBi host l...

  5. Doping the Copper-Oxygen Planes with Electrons: The View with Photoemission

    Energy Technology Data Exchange (ETDEWEB)

    Armitage, Norman P.

    2002-03-07

    The undoped parent compounds of high-temperature cuprate superconductors are known to be antiferromagnetic Mott insulators. As the CuO{sub 2} planes are doped with charge carriers, the antiferromagnetic phase subsides and superconductivity emerges. The symmetry, or the lack thereof, between doping with electrons (n-type) or holes (p-type) has important theoretical implications as most models implicitly assume symmetry. However, most of what we know about these superconductors comes from experiments performed on p-type materials. The much fewer number of measurements from n-type compounds suggest that there may be both commonalities and differences between the two sides of the phase diagram. This issue of electron/hole symmetry has not been seriously discussed, perhaps, because the experimental database of n-type results is very limited.

  6. ERYTHROPOIETIN AS DOPING AGENT

    Directory of Open Access Journals (Sweden)

    Nina Đukanović

    2012-09-01

    Full Text Available Doping is the use of prohibited substances and/or methods that improve the abilities of athletes. Erythropoietin (EPO, the kidney hormone, belongs to a group of substances that are classified as blood doping, and it can be found on the list of banned substances from 1990. year. Its application leads to an increase in the number of red blood cells, which enables better supply of oxygen, and thus improve the aerobic performance of athletes. Because of that, EPO is very popular in sports where the endurance is predominantly required like a marathon, cycling, triathlon, nordic skiing. Erythropoietin can cause some adverse events, primarily to increase blood viscosity, which is associated with a higher risk of various thromboembolic complications. In detection of EPO use two groups of tests are available, through a urine sample (direct method and blood sample (indirect method.

  7. Synthesis of ceramic powder of TiO{sub 2} doped with Zr by the Pechini Method applied in ceramic membranes for water treatment; Sintese de pos ceramicos de TiO{sub 2} dopado com Zr obtido pelo Metodo Pechini aplicados em membranas ceramicas para tramento de agua

    Energy Technology Data Exchange (ETDEWEB)

    Farias, R.F.V.; Fernandes, M.S.M.; Silva, R.S.; Franca, K.B.; Lira, H.L.; Bonifacio, M.A.R., E-mail: raissavenuto@gmail.com, E-mail: maniza-f@hotmail.com, E-mail: raquel.ssb@hotmail.com, E-mail: kepler@labdes.ufcg.edu.br, E-mail: helio.lira@ufcg.edu.br, E-mail: m_aparecidaribeiro@yahoo.com.br [Universidade Federal de Campina Grande (UFCG), PB (Brazil)

    2016-07-01

    This paper describes the synthesis of ceramic powder of TiO2 doped with Zr by the polymeric precursor method, also known as Pechini method applied in ceramic membranes for water treatment. Three compositions were synthesized according to the molar ratio Ti{sub x}-1Zr{sub x}O{sub 2} (x = 0.25, 0.50 and 0.75 moles), calcined at 700° C/1h. The samples were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM) and microbiological analysis. The presence of the doping element was not decisive in the average size of crystallite, which ranged from 5.5 to 11.3 nm. The SEM images showed clusters with uniform surface and granular aspect, it is still possible to see a clearly porous structure formed by clusters of uniform size for all samples. The microbiological analyses of powders have revealed that they have bactericidal properties. (author)

  8. Doping and Public Health

    DEFF Research Database (Denmark)

    Christiansen, Ask Vest

    rad av världens främsta idrottsvetare och dopningsexperter hade mött upp för att presentera papers till en intresserad och engagerad publik. Temat för konferensen var "Doping and Public Health", och den aspekten behandlades också; dock tolkade flera presentatörer temat på sina egna vis, och hela...

  9. Modulation-frequency-controlled change from sub- to superluminal regime in highly doped erbium fibers.

    Science.gov (United States)

    Melle, Sonia; Calderón, Oscar G; Caro, Cesar E; Cabrera-Granado, E; Antón, M A; Carreño, F

    2008-04-15

    We report a change from sub- to superluminal propagation upon increasing the modulation frequency of an amplitude-modulated 1,550 nm signal when propagating through highly doped erbium fibers pumped at 980 nm. We show that the interplay between the pump absorption and the pump-power broadening of the spectral hole induced by coherent population oscillations may drastically affect the fractional advancement or delay of the signal for the considered fibers.

  10. Photoluminescence of p-doped quantum wells with strong spin splitting

    OpenAIRE

    Kossacki, P.; Boukari, H.; Bertolini, M; Ferrand, D.; Cibert, J.; Tatarenko, S.; Gaj, J. A.; Deveaud, B.; Ciulin, V.; Potemski, M.

    2004-01-01

    The spectroscopic properties of a spin polarized two-dimensional hole gas are studied in modulation doped (Cd,Mn)Te quantum wells. The giant Zeeman effect induces a significant spin splitting even at very small values of the applied field. Several methods of measuring the carrier density (Hall effect, filling factors of the Landau levels at high field, various manifestations of Moss-Burstein shifts) are described and calibrated. The value of the spin splitting needed to fully polarize the hol...

  11. Doped Chiral Polymer Metamaterials Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Doped Chiral Polymer Metamaterials (DCPM) with tunable resonance frequencies have been developed by adding plasmonic inclusions into chiral polymers with variable...

  12. Heat Treatment Effect on Eu3+ Doped TeO2-BaO-Bi2O3 Glass Systems with Ag Nanoparticles

    Directory of Open Access Journals (Sweden)

    Tomasz Lewandowski

    2017-01-01

    Full Text Available Glass systems of 73TeO2-4BaO-3Bi2O3-2Eu2O3-xAg (in molar ratio where x = 0, 1, 2, and 3 compositions have been successfully synthesized. Silver nanoparticles were obtained with the employment of heat treatment (HT procedure executed at 350°C. Glass transition temperatures of different compositions have been determined through DSC measurements. XRD results presented characteristic amorphous halo indicating lack of long range order in the samples. FTIR structural studies revealed that glass matrix is mainly composed of TeO3 and TeO4 species and is stable after different applied heat treatment times. X-ray photoelectron spectroscopy (XPS measurements confirmed that in selected samples part of Ag ions changed oxidation state to form Ag0 species. TEM measurements revealed nanoparticles of size in the range of 20–40 nm. UV-vis absorption results demonstrated characteristic transitions of Eu3+ ions. Additionally, UV-vis spectra of samples heat-treated for 6, 12, 24, and 48 hours presented bands related to silver nanoparticles. Photoluminescence (PL studies have been performed with excitation wavelength of λexc=395 nm. Obtained spectra exhibited peaks due to 5D0-7FJ (where J=2,3,4 and 5D1-7FJ (where J=1,2,3 transitions of Eu3+. Moreover, luminescence measurement indicated enhancement of rare earth ions emissions in several of the annealed samples. Increase of emission intensity of about 35% has been observed.

  13. Limits on P: filling in holes vs. falling in holes

    Directory of Open Access Journals (Sweden)

    Peter Svenonius

    2004-01-01

    Full Text Available All Germanic languages make extensive use of verb-particle combinations (known as separable-prefix verbs in the OV languages. I show some basic differences here distinguishing the Scandinavian type from the OV West Germanic languages, with English superficially patterning with Scandinavian but actually manifesting a distinct type. Specifically, I argue that the P projection is split into p and P (in accordance with earlier work, roughly analogous to v and V in the verb phrase. In English, p is always present in PP, and enables P to assign case, if P has an internal argument (as it does in "fall in the hole". The arguments of particle verbs are then arguments of p, external arguments of the particle (as in "throw the rock in". OV West Germanic allows p to be missing completely, thus having a type of unaccusative particle whose inner argument must receive case from the verb (corresponding to "fall the hole in," impossible in English. Scandinavian allows p to be missing, so that there is no external argument of the particle, but provides an alternative source for case for the internal argument (giving examples corresponding to "pour in the glass". Thus English and Scandinavian are different from OV West Germanic in lacking the unaccusative type of particle, while Scandinavian differs from OV West Germanic and English in having an alternative source of case.

  14. Excimer laser doping technique for application in an integrated CdTe imaging device

    CERN Document Server

    Mochizuki, D; Aoki, T; Tomita, Y; Nihashi, T; Hatanaka, Y

    1999-01-01

    CdTe is an attractive semiconductor material for applications in solid-state high-energy X-ray and gamma-ray imaging systems because of its high absorption coefficient, large band gap, good mobility lifetime product of holes and stability at normal atmospheric conditions. We propose a new concept for fabricating an integrated CdTe with monolithic circuit configuration for two-dimensional imaging systems suitable for medical, research or industrial applications and operation at room temperature. A new doping technique has been recently developed that employs excimer laser radiation to diffuse impurity atoms into the semiconductor. Accordingly, heavily doped n- and p-type layers with resistivities less than 1 OMEGA cm can be formed on the high resistive CdTe crystals. We have further extended this technique for doping with spatial pattern. We will present the laser doping technique and various results thus obtained. Spatially patterned doping is demonstrated and we propose the use of these doping techniques for...

  15. Photocatalysis and hydrophilicity of doped TiO2 thin films.

    Science.gov (United States)

    Lee, Young Cheol; Hong, Young Pyo; Lee, Ha Yong; Kim, Hoon; Jung, Young Jin; Ko, Kyung Hyun; Jung, Hyun Seok; Hong, Kug Sun

    2003-11-01

    TiO(2) thin films were prepared using the dip-coating method with a polymeric sol including additives such as Al, W, and Al+W to examine two major properties: photocatalysis and hydrophilicity. W-doped films showed the best photocatalytic efficiency, while Al-doped film was poorer than undoped samples. However, good hydrophilicity in terms of saturation contact angle and surface conversion rate was found in Al- and (Al+W)-mixed-doped films. It was found that deep electron-hole traps and high surface acidity of W-doped TiO(2) thin film were the major factors in high photocatalytic efficiency. In addition, low surface acidities of Al- and (Al+W)-doped films provided better hydrophilicity than W-doped ones. However, the amount of [Ti(3+)] point defects on the surface was another major factor, probably the most important, in getting the best hydrophilicity. Conclusively, it seemed that many parts of the photocatalysis mechanism depend more on bulk-related properties than do those of hydrophilicity, which can be defined as an interfacial (surface) or near-surface-restricted process.

  16. Electronic structure of graphene nanoribbons doped with nitrogen atoms: a theoretical insight.

    Science.gov (United States)

    Torres, A E; Fomine, S

    2015-04-28

    The electronic structure of graphene nanoribbons doped with a graphitic type of nitrogen atoms has been studied using B3LYP, B2PLYP and CAS methods. In all but one case the restricted B3LYP solutions were unstable and the CAS calculations provided evidence for the multiconfigurational nature of the ground state with contributions from two dominant configurations. The relative stability of the doped nanoribbons depends mostly on the mutual position of the dopant atoms and notably less on the position of nitrogen atoms within the nanoribbon. N-graphitic doping affects cationic states much more than anionic ones due the participation of the nitrogen atoms in the stabilization of the positive charge, resulting in a drop in ionization energies (IPs) for N-graphitic doped systems. Nitrogen atoms do not participate in the negative charge stabilization of anionic species and, therefore, the doping does not affect the electron affinities (EAs). The unrestricted B3LYP method is the method of choice for the calculation of IPs and EAs. Restricted B3LYP and B2PLYP produces unreliable results for both IPs and EAs while CAS strongly underestimates the electron affinities. This is also true for the reorganization energies where restricted B3LYP produces qualitatively incorrect results. Doping changes the reorganization energy of the nanoribbons; the hole reorganization energy is generally higher than the corresponding electron reorganization energy due to the participation of nitrogen atoms in the stabilization of the positive charge.

  17. Universality of pseudogap and emergent order in lightly doped Mott insulators

    Science.gov (United States)

    Battisti, I.; Bastiaans, K. M.; Fedoseev, V.; de la Torre, A.; Iliopoulos, N.; Tamai, A.; Hunter, E. C.; Perry, R. S.; Zaanen, J.; Baumberger, F.; Allan, M. P.

    2017-01-01

    It is widely believed that high-temperature superconductivity in the cuprates emerges from doped Mott insulators. When extra carriers are inserted into the parent state, the electrons become mobile but the strong correlations from the Mott state are thought to survive--inhomogeneous electronic order, a mysterious pseudogap and, eventually, superconductivity appear. How the insertion of dopant atoms drives this evolution is not known, nor is whether these phenomena are mere distractions specific to hole-doped cuprates or represent genuine physics of doped Mott insulators. Here we visualize the evolution of the electronic states of (Sr1-xLax)2IrO4, which is an effective spin-1/2 Mott insulator like the cuprates, but is chemically radically different. Using spectroscopic-imaging scanning tunnelling microscopy (SI-STM), we find that for a doping concentration of x ~ 5%, an inhomogeneous, phase-separated state emerges, with the nucleation of pseudogap puddles around clusters of dopant atoms. Within these puddles, we observe the same iconic electronic order that is seen in underdoped cuprates. We investigate the genesis of this state and find evidence at low doping for deeply trapped carriers, leading to fully gapped spectra, which abruptly collapse at a threshold of x ~ 4%. Our results clarify the melting of the Mott state, and establish phase separation and electronic order as generic features of doped Mott insulators.

  18. Hydrothermal Synthesis of Nitrogen-Doped Titanium Dioxide and Evaluation of Its Visible Light Photocatalytic Activity

    Directory of Open Access Journals (Sweden)

    Junjie Qian

    2012-01-01

    Full Text Available Nitrogen-doped titanium dioxide (N-doped TiO2 photocatalyst was synthesized from nanotube titanic acid (denoted as NTA; molecular formula H2Ti2O5·H2O precursor via a hydrothermal route in ammonia solution. As-synthesized N-doped TiO2 catalysts were characterized by means of X-ray diffraction, transmission electron microscopy, diffuse reflectance spectrometry, X-ray photoelectron spectroscopy, electron spin resonance spectrometry and Fourier transform infrared spectrometry. It was found that nanotube ammonium titanate (NAT was produced as an intermediate during the preparation of N-doped TiO2 from NTA, as evidenced by the N1s X-ray photoelectron spectroscopic peak of NH4 + at 401.7 eV. The catalyst showed much higher activities to the degradation of methylene blue and p-chlorophenol under visible light irradiation than Degussa P25. This could be attributed to the enhanced absorption of N-doped TiO2 in visible light region associated with the formation of single-electron-trapped oxygen vacancies and the inhibition of recombination of photo-generated electron-hole pair by doped nitrogen.

  19. Material Exchange Property of Organo Lead Halide Perovskite with Hole-Transporting Materials

    Directory of Open Access Journals (Sweden)

    Seigo Ito

    2015-10-01

    Full Text Available Using X-ray diffraction (XRD, it was confirmed that the deposition of hole-transporting materials (HTM on a CH3NH3PbI3 perovskite layer changed the CH3NH3PbI3 perovskite crystal, which was due to the material exchanging phenomena between the CH3NH3PbI3 perovskite and HTM layers. The solvent for HTM also changed the perovskite crystal. In order to suppress the crystal change, doping by chloride ion, bromide ion and 5-aminovaleric acid was attempted. However, the doping was unable to stabilize the perovskite crystal against HTM deposition. It can be concluded that the CH3NH3PbI3 perovskite crystal is too soft and flexible to stabilize against HTM deposition.

  20. Boosting jet power in black hole spacetimes

    Science.gov (United States)

    Neilsen, David; Lehner, Luis; Palenzuela, Carlos; Hirschmann, Eric W.; Liebling, Steven L.; Motl, Patrick M.; Garrett, Travis

    2011-01-01

    The extraction of rotational energy from a spinning black hole via the Blandford–Znajek mechanism has long been understood as an important component in models to explain energetic jets from compact astrophysical sources. Here we show more generally that the kinetic energy of the black hole, both rotational and translational, can be tapped, thereby producing even more luminous jets powered by the interaction of the black hole with its surrounding plasma. We study the resulting Poynting jet that arises from single boosted black holes and binary black hole systems. In the latter case, we find that increasing the orbital angular momenta of the system and/or the spins of the individual black holes results in an enhanced Poynting flux. PMID:21768341