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Sample records for small polaron transport

  1. Polaronic transport in polysilanes

    Czech Academy of Sciences Publication Activity Database

    Nešpůrek, Stanislav; Nožár, Juraj; Kadashchuk, A.; Fishchuk, I. I.

    2009-01-01

    Roč. 193, č. 1 (2009), s. 1-4 ISSN 1742-6588. [International Conference on Electron Dynamics in Semiconductors, Optoelectronics and Nanostructures /16./. Montpellier, 24.08.2009-28.08.2009] R&D Projects: GA AV ČR IAA100100622; GA AV ČR KAN400720701 Institutional research plan: CEZ:AV0Z40500505 Keywords : polaronic transport * polysilanes * charge carrier mobility Subject RIV: CD - Macromolecular Chemistry

  2. Effect of defects on the small polaron formation and transport properties of hematite from first-principles calculations.

    Science.gov (United States)

    Smart, Tyler J; Ping, Yuan

    2017-10-04

    Hematite (α-Fe 2 O 3 ) is a promising candidate as a photoanode material for solar-to-fuel conversion due to its favorable band gap for visible light absorption, its stability in an aqueous environment and its relatively low cost in comparison to other prospective materials. However, the small polaron transport nature in α-Fe 2 O 3 results in low carrier mobility and conductivity, significantly lowering its efficiency from the theoretical limit. Experimentally, it has been found that the incorporation of oxygen vacancies and other dopants, such as Sn, into the material appreciably enhances its photo-to-current efficiency. Yet no quantitative explanation has been provided to understand the role of oxygen vacancy or Sn-doping in hematite. We employed density functional theory to probe the small polaron formation in oxygen deficient hematite, N-doped as well as Sn-doped hematite. We computed the charged defect formation energies, the small polaron formation energy and hopping activation energies to understand the effect of defects on carrier concentration and mobility. This work provides us with a fundamental understanding regarding the role of defects on small polaron formation and transport properties in hematite, offering key insights into the design of new dopants to further improve the efficiency of transition metal oxides for solar-to-fuel conversion.

  3. Small polaron hopping in magnetic semiconductors

    International Nuclear Information System (INIS)

    Emin, D.; Liu, N.L.H.

    1978-01-01

    In a number of magnetic insulators it has been hypothesized that the charge carriers form small polarons. The transfer of an electron between magnetic sites and how the magnetic nature of the material affects the rate which characterizes small-polaron hops between magnetic sites were studied. The basic transfer processes are addressed from a many-electron point in which the itinerant electron is treated as indistinguishable from those which contribute unpaired spins at the magnetic sites

  4. Small polarons and c-axis transport in highly anisotropic metals

    International Nuclear Information System (INIS)

    Ho, A.F.; Schofield, A.J.

    2002-09-01

    Motivated by the anomalous c-axis transport properties of the quasi two-dimensional metal, Sr 2 RuO 4 , and some of its relatives, we have studied the interlayer hopping of single electrons that are coupled strongly to c-axis bosons. We find a c-axis resistivity that reflects the in-plane electronic scattering in the low and very high temperature limits (relative to the characteristic temperature of the boson T boson ). For temperatures near the T boson , a broad maximum in the resistivity can appear for sufficiently strong electron-boson coupling. This feature may account for the observed 'metallic to non-metallic crossover' seen in these layered oxides, where the boson may be a phonon. (author)

  5. Small polarons in 2D perovskites

    KAUST Repository

    Cortecchia, Daniele

    2017-11-02

    We demonstrate that white light luminescence in two-dimensional (2D) perovskites stems from photoinduced formation of small polarons confined at specific sites of the inorganic framework in the form of self-trapped electrons and holes. We discuss their application in white light emitting devices and X-ray scintillators.

  6. Small polarons in 2D perovskites

    KAUST Repository

    Cortecchia, Daniele; Yin, Jun; Birowosuto, Muhammad D.; Lo, Shu-Zee A.; Gurzadyan, Gagik G.; Bruno, Annalisa; Bredas, Jean-Luc; Soci, Cesare

    2017-01-01

    We demonstrate that white light luminescence in two-dimensional (2D) perovskites stems from photoinduced formation of small polarons confined at specific sites of the inorganic framework in the form of self-trapped electrons and holes. We discuss their application in white light emitting devices and X-ray scintillators.

  7. Thermoelectric power of small polarons in magnetic semiconductors

    International Nuclear Information System (INIS)

    Liu, N.H.; Emin, D.

    1984-01-01

    The thermoelectric power (Seebeck coefficient) α of a small polaron in both ferromagnetic and antiferromagnetic semiconductors and insulators is calculated for the first time. In particular, we obtain the contribution to the Seebeck coefficient arising from exchange interactions between the severely localized carrier (i.e., small polaron) of charge q and the spins of the host lattice. In essence, we study the heat transported along with a carrier. This heat, the Peltier heat, Pi, is related to the Seebeck coefficient by the Kelvin relation: Pi = qTα, where T is the temperature. The heat per carrier is simply the product of the temperature and the change of the entropy of the system when a small polaron is added to it. The magnetic contribution to the Seebeck coefficient is therefore directly related to the change of the magnetic entropy of the system upon introduction of a charge carrier. We explicitly treat the intrasite and intersite exchange interactions between a small polaron and the spins of a spin-1/2 system. These magnetic interactions produce two competing contributions to the Seebeck coefficient. First, adding the carrier tends to provide extra spin freedom (e.g., spin up or spin down of the carrier). This effect augments the entropy of the system, thereby producing a positive contribution to the Peltier heat. Second, however, the additional exchange between the carrier and the sites about it enhances the exchange binding among these sites. This generally reduces the energetically allowable spin configurations. The concomitant reduction of the system's entropy provides a negative contribution to the Peltier heat. At the highest of temperatures, when kT exceeds the intrasite exchange energy, the first effect dominates. Then, the Peltier heat is simply augmented by kT ln2

  8. Small-polaron formation and motion in magnetic semiconductors

    International Nuclear Information System (INIS)

    Emin, D.

    1979-01-01

    The fundamental physical processes associated with small-polaron formation are described with various magnetic semi-conductors being cited as examples. Attention is then directed toward the mechanisms of charge transfer and small-polaron hopping motion in magnetic semiconductors

  9. Peltier heat of a small polaron in a magnetic semiconductor

    International Nuclear Information System (INIS)

    Liu, N.H.; Emin, D.

    1985-01-01

    For the first time the heat transported with a small polaron in both antiferromagnetic and ferromagnetic semiconductors is calculated. This heat, the Peltier heat, π, is obtained from the change of the entropy of the total system upon introduction of a charge carrier. We explicitly consider both the intrasite and intersite exchange interactions between a small polaron and the interacting spins of a spin-1/2 magnet. There are two competing magnetic contributions to the Peltier heat. First, adding the carrier increases the spin entropy of the system. This provides a positive contribution to π. Second, the exchange between the carrier and the sites about it enhances the exchange binding between these sites. This reduces the energetically allowable spin configurations and provides a negative contribution to π. At extremely high temperatures when kT exceeds the intrasite exchange energy, the first effect dominates. Then π is simply augmented by kT ln 2. However, well below the magnetic transition temperature the second effect dominates. In the experimentally accessible range between these limits both effects are comparable and sizable. The net magnetic contribution to the Peltier heat rises with temperature. Thus, a carrier's interactions with its magnetic environment produces a significant and distinctive contribution to its Peltier heat

  10. Peltier heat of a small polaron in a magnetic semiconductor

    International Nuclear Information System (INIS)

    Liu, N.L.H.; Emin, D.

    1984-01-01

    The heat transported with a small polaron in both antiferromagnetic and ferromagnetic semiconductors is calculated. This heat, the Peltier heat, π, is obtained from the change of the entropy of the total system upon introduction of a charge carrier. We explicitly consider both the intrasite and intersite exchange interactions between a small polaron and the interacting spins of a spin-1/2 magnet. There are two competing magnetic contributions to the Peltier heat. First, adding the carrier increases the spin entropy of the system. This provides a positive contribution to π. Second, the exchange between the carrier and the sites about it enhances the exchange binding between these sites. This reduces the energetically allowable spin configurations and provides a negative contribution to π. At extremely high temperature when kT exceeds the intrasite exchange energy, the first effect dominates. Then π is simply augmented by kTln2. However, well below the magnetic transition temperature the second effect dominates. In the experimentally accessible range between these limits both effects are comparable and sizable. The net magnetic contribution to the Peltier heat rises with temperature. Thus, a carrier's interactions with its magnetic environment produces a significant and distinctive contribution to its Peltier heat

  11. Problems of linear electron (polaron) transport theory in semiconductors

    CERN Document Server

    Klinger, M I

    1979-01-01

    Problems of Linear Electron (Polaron) Transport Theory in Semiconductors summarizes and discusses the development of areas in electron transport theory in semiconductors, with emphasis on the fundamental aspects of the theory and the essential physical nature of the transport processes. The book is organized into three parts. Part I focuses on some general topics in the theory of transport phenomena: the general dynamical theory of linear transport in dissipative systems (Kubo formulae) and the phenomenological theory. Part II deals with the theory of polaron transport in a crystalline semicon

  12. O{sup -} bound small polarons in oxide materials

    Energy Technology Data Exchange (ETDEWEB)

    Schirmer, O F [Department of Physics, University of Osnabrueck, D-49076 Osnabrueck (Germany)

    2006-11-01

    Holes bound to acceptor defects in oxide crystals are often localized by lattice distortion at just one of the equivalent oxygen ligands of the defect. Such holes thus form small polarons in symmetric clusters of a few oxygen ions. An overview on mainly the optical manifestations of those clusters is given. The article is essentially divided into two parts: the first one covers the basic features of the phenomena and their explanations, exemplified by several paradigmatic defects; in the second part numerous oxide materials are presented which exhibit bound small polaron optical properties. The first part starts with summaries on the production of bound hole polarons and the identification of their structure. It is demonstrated why they show strong, wide absorption bands, usually visible, based on polaron stabilization energies of typically 1 eV. The basic absorption process is detailed with a fictitious two-well system. Clusters with four, six and twelve equivalent ions are realized in various oxide compounds. In these cases several degenerate optically excited polaron states occur, leading to characteristic final state resonance splittings. The peak energies of the absorption bands as well as the sign of the transfer energy depend on the topology of the clusters. A special section is devoted to the distinction between interpolaron and intrapolaron optical transitions. The latter are usually comparatively weak. The oxide compounds exhibiting bound hole small polaron absorptions include the alkaline earth oxides (e.g. MgO), BeO and ZnO, the perovskites BaTiO{sub 3} and KTaO{sub 3}, quartz, the sillenites (e.g. Bi{sub 12}TiO{sub 20}), Al{sub 2}O{sub 3}, LiNbO{sub 3}, topaz and various other materials. There are indications that the magnetic crystals NiO, doped with Li, and LaMnO{sub 3}, doped with Sr, also show optical features caused by bound hole polarons. Beyond being elementary paradigms for the properties of small polarons in general, the defect species treated

  13. Small-polaron model of light atom diffusion

    International Nuclear Information System (INIS)

    Emin, D.

    1977-01-01

    A number of researchers have treated the diffusion of light interstitials in metals in strict analogy with the theory for the hopping diffusion of electrons in low-mobility insulators. In other words, these authors view the diffusion of light atoms as simply being an example of small-polaron hopping motion. In this paper the motion of a small polaron is introduced, and the mechanism of its motion is described. The experimental results are then succinctly presented. Next the physical assumptions implicit in the theory are compared with the situation which is believed to characterize the existence and motion of light interstitial atoms in metals. Concomitantly, the modifications of the small-polaron theory required in applying it to light atom diffusion are ennumerated

  14. Photoelectron spectroscopy on the charge reorganization energy and small polaron binding energy of molecular film

    Energy Technology Data Exchange (ETDEWEB)

    Kera, Satoshi, E-mail: kera@ims.ac.jp [Institute for Molecular Science, Myodaiji, Okazaki 444-8585 (Japan); Department of Nanomaterial Science, Graduate School of Advanced Integration Science, Chiba University, Inage-ku, Chiba 263-8522 (Japan); Ueno, Nobuo [Department of Nanomaterial Science, Graduate School of Advanced Integration Science, Chiba University, Inage-ku, Chiba 263-8522 (Japan)

    2015-10-01

    Understanding of electron-phonon coupling as well as intermolecular interaction is required to discuss the mobility of charge carrier in functional molecular solids. This article summarizes recent progress in direct measurements of valence hole-vibration coupling in ultrathin films of organic semiconductors by using ultraviolet photoelectron spectroscopy (UPS). The experimental study of hole-vibration coupling of the highest occupied molecular orbital (HOMO) state in ordered monolayer film by UPS is essential to comprehend hole-hopping transport and small-polaron related transport in organic semiconductors. Only careful measurements can attain the high-resolution spectra and provide key parameters in hole-transport dynamics, namely the charge reorganization energy and small polaron binding energy. Analyses methods of the UPS HOMO fine feature and resulting charge reorganization energy and small polaron binding energy are described for pentacene and perfluoropentacene films. Difference between thin-film and gas-phase results is discussed by using newly measured high-quality gas-phase spectra of pentacene. Methodology for achieving high-resolution UPS measurements for molecular films is also described.

  15. Mechanism of small-polaron formation in the biferroic YCrO{sub 3} doped with calcium

    Energy Technology Data Exchange (ETDEWEB)

    Duran, A., E-mail: dural@cnyn.unam.mx [Universidad Nacional Autonoma de Mexico, Centro de Nanociencias y Nanotecnologia, Apartado Postal 41, C.P. 22800, Ensenada, B.C. (Mexico); Verdin, E. [Universidad de Sonora, Departamento de Fisica, Apartado Postal 1626, Hermosillo, Sonora C.P. 8300 (Mexico); Escamilla, R.; Morales, F.; Escudero, R. [Universidad Nacional Autonoma de Mexico, Instituto de Investigaciones en Materiales, Apartado Postal 70-360, Mexico D.F. 04510 (Mexico)

    2012-04-16

    Highlights: Black-Right-Pointing-Pointer The Ca doped in the YCrO3 matrix was analyzed by means of complete structural, magnetic and electric properties. Black-Right-Pointing-Pointer E{sub act} deduced by Arrhenius' Law suggests small-polarons as conduction mechanisms in pristine and doped sample. Black-Right-Pointing-Pointer Local non-centrosymmetry in pristine sample is proposed as responsible of small polarons formation. Black-Right-Pointing-Pointer A mechanism of formation of small polarons is proposed supported by experimental evidence. Black-Right-Pointing-Pointer The structural distortion caused by the Ca doped in the YCrO3 matrix is harmful to the Ferroic properties. - Abstract: The effects of Ca substitutions on the structure, magnetism and electrical properties of YCrO{sub 3} ceramics are investigated by X-ray diffraction, magnetic susceptibility and electrical conductivity measurements. The cell volume decrease occurs through the change from Cr(III) to Cr(IV) as a result of the charge compensation of the Ca doping. No changes are observed in the antiferromagnetic transition temperature while strong changes are observed in the transport measurements due to Ca content. The increase of the electrical conductivity as well as the decrease of the activation energy is caused by the formation of the small-polarons localized in the O-Cr-O lattice distortion. The origin of small-polarons in the undoped sample is different in nature from the calcium doped. 'Local non-centrosymmetry' is the source of the small-polaron formation in undoped sample, while the change from Cr(III) to Cr(IV) through the charge compensation of Ca(II) in the Y(III) site is the source of small-polarons formations. The decrease of the average bond length Cr-O as well as effective moments in the paramagnetic state and the increase of the electrical conductivity are clear evidence that the Ca doping induces localized polarons, which in turn, these quasiparticles move from site to

  16. Transport through a vibrating quantum dot: Polaronic effects

    International Nuclear Information System (INIS)

    Koch, T; Alvermann, A; Fehske, H; Loos, J; Bishop, A R

    2010-01-01

    We present a Green's function based treatment of the effects of electron-phonon coupling on transport through a molecular quantum dot in the quantum limit. Thereby we combine an incomplete variational Lang-Firsov approach with a perturbative calculation of the electron-phonon self energy in the framework of generalised Matsubara Green functions and a Landauer-type transport description. Calculating the ground-state energy, the dot single-particle spectral function and the linear conductance at finite carrier density, we study the low-temperature transport properties of the vibrating quantum dot sandwiched between metallic leads in the whole electron-phonon coupling strength regime. We discuss corrections to the concept of an anti-adiabatic dot polaron and show how a deformable quantum dot can act as a molecular switch.

  17. Small polaron conduction in lead modified lanthanum ferrite ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Bhargav, K.K.; Ram, S.; Majumder, S.B., E-mail: subhasish@matsc.iitkgp.ernet.in

    2015-07-25

    Highlights: • La{sub 0.8}Pb{sub 0.2}FeO{sub 3} (ε{sub r} ∼ 30,000) shows higher dielectric constant than LaFeO{sub 3} (∼14,000). • Lower A-site dopant content, the dielectric maxima shift to higher temperature. • The frequency dependence of ε{sub r} and tan δ vs. temperature exhibit CDC like behavior. • R{sub g} and R{sub gb} of Pb modified LaFeO{sub 3} follow small polaron hopping conduction model. - Abstract: In the present work we have illustrated the physics of the electrical characteristics of nanocrystalline La{sub 1−x}Pb{sub x}FeO{sub 3,} (0 ⩽ x ⩽ 0.2) powder prepared using auto-combustion synthesis. The effect of lead doping on the dielectric, impedance and ac conductivity characteristics of lanthanum ferrite has systematically been investigated. The synthesized powders were phase pure and crystallized into centro-symmetric Pnma space group. As compared to pure LaFeO{sub 3} ceramics (dielectric constant ∼ 14,000), the dielectric constant is grossly increased (∼30,000) in Pb doped LaFeO{sub 3}. The temperature dependence of dielectric constant of 10.0 at.% Pb doped LaFeO{sub 3} exhibits dielectric maxima similar to that observed in ferroelectric ceramics with non-centrosymmetric point group. For La{sub 0.8}Pb{sub 0.2}FeO{sub 3} ceramics, the frequency dependence of the dielectric constant and loss tangent at various temperatures (300–450 K) exhibit typical colossal dielectric constant (CDC) like behavior. From the impedance spectroscopy we have estimated the grain and grain boundary resistance and capacitance of Pb doped LaFeO{sub 3} that follow a small polaron hopping conduction model. Long range movement of the charge carriers govern the CDC behavior.

  18. Effects of compositional defects on small polaron hopping in micas.

    Science.gov (United States)

    Rosso, Kevin M; Ilton, Eugene S

    2005-06-22

    Hartree-Fock calculations and electron transfer (ET) theory were used to model the effects of compositional defects on ET in the brucite-like octahedral sheet of mica. ET was modeled as an Fe(IIIII) valence interchange reaction across shared octahedral edges of the M2-M2 iron sublattice. The model entails the hopping of localized electrons and small polaron behavior. Hartree-Fock calculations indicate that substitution of F for structural OH bridges increases the reorganization energy lambda, decreases the electronic coupling matrix element V(AB), and thereby substantially decreases the hopping rate. The lambda increase arises from modification of the metal-ligand bond force constants, and the V(AB) decrease arises from reduction of superexchange interaction through anion bridges. Deprotonation of an OH bridge, consistent with a possible mechanism of maintaining charge neutrality during net oxidation, yields a net increase in the ET rate. Although substitution of Al or Mg for Fe in M1 sites distorts the structure of adjacent Fe-occupied M2 sites, the distortion has little net impact on ET rates through these M2 sites. Hence the main effect of Al or Mg substitution for Fe, should it occur in the M2 sublattice, is to block ET pathways. Collectively, these findings pave the way for larger-scale oxidation/reduction models to be constructed for realistic, compositionally diverse micas.

  19. Implications of the formation of small polarons in Li2O2 for Li-air batteries

    Science.gov (United States)

    Kang, Joongoo; Jung, Yoon Seok; Wei, Su-Huai; Dillon, Anne C.

    2012-01-01

    Lithium-air batteries (LABs) are an intriguing next-generation technology due to their high theoretical energy density of ˜11 kWh/kg. However, LABs are hindered by both poor rate capability and significant polarization in cell voltage, primarily due to the formation of Li2O2 in the air cathode. Here, by employing hybrid density functional theory, we show that the formation of small polarons in Li2O2 limits electron transport. Consequently, the low electron mobility μ = 10-10-10-9 cm2/V s contributes to both the poor rate capability and the polarization that limit the LAB power and energy densities. The self-trapping of electrons in the small polarons arises from the molecular nature of the conduction band states of Li2O2 and the strong spin polarization of the O 2p state. Our understanding of the polaronic electron transport in Li2O2 suggests that designing alternative carrier conduction paths for the cathode reaction could significantly improve the performance of LABs at high current densities.

  20. First-principles supercell calculations of small polarons with proper account for long-range polarization effects

    Science.gov (United States)

    Kokott, Sebastian; Levchenko, Sergey V.; Rinke, Patrick; Scheffler, Matthias

    2018-03-01

    We present a density functional theory (DFT) based supercell approach for modeling small polarons with proper account for the long-range elastic response of the material. Our analysis of the supercell dependence of the polaron properties (e.g., atomic structure, binding energy, and the polaron level) reveals long-range electrostatic effects and the electron–phonon (el–ph) interaction as the two main contributors. We develop a correction scheme for DFT polaron calculations that significantly reduces the dependence of polaron properties on the DFT exchange-correlation functional and the size of the supercell in the limit of strong el–ph coupling. Using our correction approach, we present accurate all-electron full-potential DFT results for small polarons in rocksalt MgO and rutile TiO2.

  1. Inapplicability of small-polaron model for the explanation of infrared absorption spectrum in acetanilide.

    Science.gov (United States)

    Zeković, Slobodan; Ivić, Zoran

    2009-01-01

    The applicability of small-polaron model for the interpretation of infrared absorption spectrum in acetanilide has been critically reexamined. It is shown that the energy difference between the normal and anomalous peak, calculated by means of small-polaron theory, displays pronounced temperature dependence which is in drastic contradiction with experiment. It is demonstrated that self-trapped states, which are recently suggested to explain theoretically the experimental absorption spectrum in protein, cannot cause the appearance of the peaks in absorption spectrum for acetanilide.

  2. Small polaron hopping conduction mechanism in LiFePO4 glass and crystal

    Science.gov (United States)

    Banday, Azeem; Murugavel, Sevi

    2017-01-01

    The optimization of a cathode material is the most important criterion of lithium ion battery technology, which decides the power density. In order to improve the rate capability, a cathode material must possess high electronic and ionic conductivities. Therefore, it is important to understand the charge transport mechanism in such an advanced cathode material in its intrinsic state before modifying it by various means. In this work, we report the thermal, structural, and electrical conductivity studies on lithium iron phosphate, LiFePO4, both in its polycrystalline (LFPC) and glassy (LFPG) counterpart states. The vibrational spectroscopic measurements reveal the characteristic vibrational modes, which are the intrinsic part of LFPC, whereas in LFPG, the phonon modes become broader and overlap with each other due to the lattice disorder. The electrical conductivity measurements reveal that LFPG exhibits a higher polaronic conductivity of 1.6 orders than the LFPC sample. The temperature dependent dc conductivity has been analyzed with the Mott model of polarons and reveals the origin of enhanced polaronic conductivity in LFPG. Based on the analysis, the enhanced polaronic conductivity in LFPG has been attributed to the combined effect of reduced hopping length, decreased activation energy, and enhanced polaron concentration.

  3. Formation time of a small electron polaron in LiNbO3: measurements and interpretation

    International Nuclear Information System (INIS)

    Qiu, Yong; Ucer, K.B.; Williams, R.T.

    2005-01-01

    Infrared optical absorption attributed to the electron polaron on a non-defective site in LiNbO 3 and KNbO 3 has previously been observed using pulsed electron and laser techniques. With subpicosecond laser excitation and spectroscopy, it is possible to measure a rise time of the infrared absorption, which may be interpreted as the time for a band-state conduction electron to cool by phonon scattering, collapse its wavefunction around a site made attractive by thermal disorder, and relax vibrationally to a small polaron. This is a process which is of fundamental interest, involving dynamics of self-localization from band states and vibrational relaxation of a localized electron in an otherwise non-defective lattice. For example, Gavartin and Shluger have recently performed calculations on the role of thermal fluctuations in self-trapping of holes in MgO. We report initial measurements on the rise time of infrared absorption at 0.95 eV (Mg-perturbed polaron) in LiNbO 3 :Mg to be τ R ∼230 fs at T=20 K and τ R ∼110 fs at T=296 K. We discuss 2 stages that together may account for the delay and its temperature dependence: free-electron cooling and vibrational relaxation of a ''defect'' (small polaron) in a host. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  4. Effect of base-pair inhomogeneities on charge transport along the DNA molecule, mediated by twist and radial polarons

    International Nuclear Information System (INIS)

    Palmero, F; Archilla, J F R; Hennig, D; Romero, F R

    2004-01-01

    Some recent results for a three-dimensional, semi-classical, tight-binding model for DNA show that there are two types of polarons, namely radial and twist polarons, which can transport charge along the DNA molecule. However, the existence of two types of base pairs in real DNA makes it crucial to find out if charge transport also exists in DNA chains with different base pairs. In this paper, we address this problem in its simple case, a homogeneous chain except for a single different base pair, which we call a base-pair inhomogeneity, and its effect on charge transport. Radial polarons experience either reflection or trapping. However, twist polarons are good candidates for charge transport along real DNA. This transport is also very robust with respect to weak parametric and diagonal disorder

  5. Small polaron formation and motion of holes in a-SiO2

    International Nuclear Information System (INIS)

    Hughes, R.C.; Emin, D.

    1978-01-01

    X-ray generated holes in SiO 2 are observed to be reduced to low mobility in times of the order of vibrational periods, 10 -12 s. The temperature dependence, electric field dependence and magnitude of this mobility for times up to about 100 ns are consistent with those of hole-like small polarons. The circumstances which favor the occurrence of rapid small polaron formation are a large effective mass (narrow valence band), the presence of the long-range hole-lattice interaction characteristic of an ionic material and the presence of disorder, all of which are found in amorphous SiO 2 . An alternative explanation involving trapping requires an extremely large localized state density and fortuitous temperature and field dependences of the hopping rates

  6. Dynamics of the optically-induced properties of a small-polaronic glass

    International Nuclear Information System (INIS)

    Emin, D.

    1979-01-01

    The relaxation and recombination of an electronic excitation created by the absorption of a super-band-gap photon is considered for a system in which excitons and charge carriers find it energetically favorable to self-trap. The notions of a barrier to self-trapping, a short-range repulsion between electrons and holes, and the electromodulation of the small-polaron absorption band play a central role in this discussion. The results are consistent with experiments on chalcogenide glasses

  7. Transport and ordering of polarons in CER manganites PrCaMnO

    International Nuclear Information System (INIS)

    Schramm, S; Hoffmann, J; Jooss, Ch

    2008-01-01

    The temperature-dependent resistivity and the colossal resistance effect induced by strong electric fields of the small-band Pr 1-x Ca x MnO 3 (PCMO) manganites are analysed with respect to the influence of the Ca doping, post-annealing, the prehistory of the electric stimulation, and the physical dimensions of the sample. Despite the phase separation between charge and orbital ordered and disordered phases, PCMO reveals the properties of a homogeneous medium with a conductivity governed by the hopping of small polarons if the electric field is not too strong. In contrast, high electric fields induce a structural transition which gives rise to a glassy behaviour in the transient regime. In the low resistance state the small activation energy of charge carrier hopping implies a transition to large polaron hopping

  8. A new DFT approach to model small polarons in oxides with proper account for long-range polarization

    Science.gov (United States)

    Kokott, Sebastian; Levchenko, Sergey V.; Scheffler, Matthias; Theory Department Team

    In this work, we address two important challenges in the DFT description of small polarons (excess charges localized within one unit cell): sensitivity to the errors in exchange-correlation (XC) treatment and finite-size effects in supercell calculations. The polaron properties are obtained using a modified neutral potential-energy surface (PES). Using the hybrid HSE functional and considering the whole range 0 Deutsche Forschungsgemeinschaft).

  9. Non-canonical distribution and non-equilibrium transport beyond weak system-bath coupling regime: A polaron transformation approach

    Science.gov (United States)

    Xu, Dazhi; Cao, Jianshu

    2016-08-01

    The concept of polaron, emerged from condense matter physics, describes the dynamical interaction of moving particle with its surrounding bosonic modes. This concept has been developed into a useful method to treat open quantum systems with a complete range of system-bath coupling strength. Especially, the polaron transformation approach shows its validity in the intermediate coupling regime, in which the Redfield equation or Fermi's golden rule will fail. In the polaron frame, the equilibrium distribution carried out by perturbative expansion presents a deviation from the canonical distribution, which is beyond the usual weak coupling assumption in thermodynamics. A polaron transformed Redfield equation (PTRE) not only reproduces the dissipative quantum dynamics but also provides an accurate and efficient way to calculate the non-equilibrium steady states. Applications of the PTRE approach to problems such as exciton diffusion, heat transport and light-harvesting energy transfer are presented.

  10. Anisotropic small-polaron hopping in W:BiVO4 single crystals

    International Nuclear Information System (INIS)

    Rettie, Alexander J. E.; Chemelewski, William D.; Zhou, Jianshi; Lindemuth, Jeffrey; McCloy, John S.; Marshall, Luke G.; Emin, David; Mullins, C. Buddie

    2015-01-01

    DC electrical conductivity, Seebeck and Hall coefficients are measured between 300 and 450 K on single crystals of monoclinic bismuth vanadate that are doped n-type with 0.3% tungsten donors (W:BiVO 4 ). Strongly activated small-polaron hopping is implied by the activation energies of the Arrhenius conductivities (about 300 meV) greatly exceeding the energies characterizing the falls of the Seebeck coefficients' magnitudes with increasing temperature (about 50 meV). Small-polaron hopping is further evidenced by the measured Hall mobility in the ab-plane (10 −1  cm 2  V −1  s −1 at 300 K) being larger and much less strongly activated than the deduced drift mobility (about 5 × 10 −5  cm 2  V −1  s −1 at 300 K). The conductivity and n-type Seebeck coefficient is found to be anisotropic with the conductivity larger and the Seebeck coefficient's magnitude smaller and less temperature dependent for motion within the ab-plane than that in the c-direction. These anisotropies are addressed by considering highly anisotropic next-nearest-neighbor (≈5 Å) transfers in addition to the somewhat shorter (≈4 Å), nearly isotropic nearest-neighbor transfers

  11. Full-counting statistics of energy transport of molecular junctions in the polaronic regime

    International Nuclear Information System (INIS)

    Tang, Gaomin; Yu, Zhizhou; Wang, Jian

    2017-01-01

    We investigate the full-counting statistics (FCS) of energy transport carried by electrons in molecular junctions for the Anderson–Holstein model in the polaronic regime. Using the two-time quantum measurement scheme, the generating function (GF) for the energy transport is derived and expressed as a Fredholm determinant in terms of Keldysh nonequilibrium Green’s function in the time domain. Dressed tunneling approximation is used in decoupling the phonon cloud operator in the polaronic regime. This formalism enables us to analyze the time evolution of energy transport dynamics after a sudden switch-on of the coupling between the dot and the leads towards the stationary state. The steady state energy current cumulant GF in the long time limit is obtained in the energy domain as well. Universal relations for steady state energy current FCS are derived under a finite temperature gradient with zero bias and this enabled us to express the equilibrium energy current cumulant by a linear combination of lower order cumulants. The behaviors of energy current cumulants in steady state under temperature gradient and external bias are numerically studied and explained. The transient dynamics of energy current cumulants is numerically calculated and analyzed. Universal scaling of normalized transient energy cumulants is found under both temperature gradient and external bias. (paper)

  12. Appearance of small polaron hopping conduction in iron modified cobalt lithium bismuth borate glasses

    Energy Technology Data Exchange (ETDEWEB)

    Dahiya, M. S.; Khasa, S., E-mail: skhasa@yahoo.com; Yadav, Arti [Physics Department, Deenbandhu Chhotu Ram University of Science and Technology, Murthal, India-131039 (India); Agarwal, A. [Applied Physics Department, Guru Jambheshwara University of Science and Technology, Hisar, India-125001 (India)

    2016-05-23

    Lithium bismuth borate glasses containing different amounts of cobalt and iron oxides having chemical composition xFe{sub 2}O{sub 3}•(20-x)CoO•30Li{sub 2}O•10Bi{sub 2}O{sub 3}•40B{sub 2}O{sub 3} (x = 0, 5, 10, 15 and 20 mol% abbreviated as CFLBB1-5 respectively) prepared via melt quench technique have been investigated for their dc electrical conductivity. The amorphous nature of prepared glasses has been confirmed through X-ray diffraction measurements. The dc electrical conductivity has been analyzed by applying Mott’s small polaron hopping model. Activation energies corresponding to lower and higher temperature region have been evaluated. The iron ion concentration (N), mean spacing between iron ions (R) and polaron radius (R{sub p}) has been evaluated using the values of phonon radius (R{sub ph}) and Debye temperature (θ{sub D}). The glass sample without iron (CFLBB1) shows ionic conductivity but the incorporation of iron in the glass matrix results in the appearance of electronic conductivity.

  13. Raman and optical spectroscopic studies of small-to-large polaron crossover in the perovskite manganese oxides

    International Nuclear Information System (INIS)

    Yoon, S.; Liu, H.L.; Schollerer, G.; Cooper, S.L.; Han, P.D.; Payne, D.A.; Cheong, S.; Fisk, Z.

    1998-01-01

    We present an optical reflectance and Raman-scattering study of the A 1-x A ' x MnO 3 system as a function of temperature and doping (0.2≤x≤0.5). The metal-semiconductor transition in the A 1-x A ' x MnO 3 system is characterized by a change from a diffusive electronic Raman-scattering response in the high-temperature paramagnetic phase, to a flat continuum scattering response in the low-temperature ferromagnetic phase. We interpret this change in the scattering response as a crossover from a small-polaron-dominated regime at high temperatures to a large-polaron-dominated low-temperature regime. Interestingly, we observe evidence for the coexistence of large and small polarons in the low-temperature ferromagnetic phase. We contrast these results with those obtained for EuB 6 , which is a low-T c magnetic semiconductor with similar properties to the manganites, but with a substantially reduced carrier density and polaron energy. copyright 1998 The American Physical Society

  14. Direct observation of anisotropic small-hole polarons in an orthorhombic structure of BiV O4 films

    Science.gov (United States)

    Chaudhuri, A.; Mandal, L.; Chi, X.; Yang, M.; Scott, M. C.; Motapothula, M.; Yu, X. J.; Yang, P.; Shao-Horn, Y.; Venkatesan, T.; Wee, A. T. S.; Rusydi, A.

    2018-05-01

    Here, we report an anisotropic small-hole polaron in an orthorhombic structure of BiV O4 films grown by pulsed-laser deposition on yttrium-doped zirconium oxide substrate. The polaronic state and electronic structure of BiV O4 films are revealed using a combination of polarization-dependent x-ray absorption spectroscopy at V L3 ,2 edges, spectroscopic ellipsometry, x-ray photoemission spectroscopies, and high-resolution x-ray diffraction with the support of first-principles calculations. We find that in the orthorhombic phase, which is slightly different from the conventional pucherite structure, the unoccupied V 3d orbitals and charge inhomogeneities lead to an anisotropic small-hole polaron state. Our result shows the importance of the interplay of charge and lattice for the formation of a hole polaronic state, which has a significant impact in the electrical conductivity of BiV O4 , hence its potential use as a photoanode for water splitting.

  15. The effect of correlations on the non-ohmic behavior of the small-polaron hopping conductivity in 1D and 3D disordered systems

    International Nuclear Information System (INIS)

    Dimakogianni, M; Triberis, G P

    2010-01-01

    According to percolation theory the investigation of charge transport in disordered systems is equivalent to the study of the possibility of the passage of the carriers through a random network of impedances which interconnect the different lattice sites. When the site energies are not the same, the energy of a site affects the incoming as well as the outgoing impedances connected to the given site and this gives rise to correlations between neighboring impedances. This new condition characterizes the transport process and imposes the evaluation of the average number of sites accessible by a bond from a given site for all possible configurations of sites that satisfy the percolation condition. The generalized molecular crystal model, appropriate for the study of small-polaron hopping transport in disordered systems, and the Kubo formula permit the evaluation of these impedances. Taking correlations into account, theoretical percolation considerations applicable to one-dimensional and three-dimensional disordered systems, lead to analytical expressions for the temperature and electric field dependence of the DC conductivity at high (multi-phonon-assisted hopping) and low (few-phonon-assisted hopping) temperatures. The theoretical analysis reveals the effect of correlations on the non-ohmic behavior of the small-polaron hopping conductivity and permits the evaluation of the maximum hopping distance. Quantitative estimates of this effect are presented comparing the theoretical results, including correlations with those ignoring them, previously reported, applying them to recent experimental data for a wide temperature range and from low up to moderate electric fields.

  16. The polaron problem and the Boltzmann equation

    International Nuclear Information System (INIS)

    Devreese, J.

    1979-01-01

    A mobility theory for the Feynman polaron is developed. It is shown that the Boltzmann equation for polarons is valid for weak coupling and not too high electric fields. The analytical results indicate that for E → 0 the relaxation time approximation is valid. A comparison is made of three methods to calculate the mobility in a linear electron transport theory. An approximation to the Kubo formula, a mobility calculation using path integrals by Feynman and a calculation based on the displaced Maxwell distribution function are considered. The three methods lead to equivalent results in the weak scattering and small electric field limit

  17. Charge Transport in 4 nm Molecular Wires with Interrupted Conjugation: Combined Experimental and Computational Evidence for Thermally Assisted Polaron Tunneling.

    Science.gov (United States)

    Taherinia, Davood; Smith, Christopher E; Ghosh, Soumen; Odoh, Samuel O; Balhorn, Luke; Gagliardi, Laura; Cramer, Christopher J; Frisbie, C Daniel

    2016-04-26

    We report the synthesis, transport measurements, and electronic structure of conjugation-broken oligophenyleneimine (CB-OPI 6) molecular wires with lengths of ∼4 nm. The wires were grown from Au surfaces using stepwise aryl imine condensation reactions between 1,4-diaminobenzene and terephthalaldehyde (1,4-benzenedicarbaldehyde). Saturated spacers (conjugation breakers) were introduced into the molecular backbone by replacing the aromatic diamine with trans-1,4-diaminocyclohexane at specific steps during the growth processes. FT-IR and ellipsometry were used to follow the imination reactions on Au surfaces. Surface coverages (∼4 molecules/nm(2)) and electronic structures of the wires were determined by cyclic voltammetry and UV-vis spectroscopy, respectively. The current-voltage (I-V) characteristics of the wires were acquired using conducting probe atomic force microscopy (CP-AFM) in which an Au-coated AFM probe was brought into contact with the wires to form metal-molecule-metal junctions with contact areas of ∼50 nm(2). The low bias resistance increased with the number of saturated spacers, but was not sensitive to the position of the spacer within the wire. Temperature dependent measurements of resistance were consistent with a localized charge (polaron) hopping mechanism in all of the wires. Activation energies were in the range of 0.18-0.26 eV (4.2-6.0 kcal/mol) with the highest belonging to the fully conjugated OPI 6 wire and the lowest to the CB3,5-OPI 6 wire (the wire with two saturated spacers). For the two other wires with a single conjugation breaker, CB3-OPI 6 and CB5-OPI 6, activation energies of 0.20 eV (4.6 kcal/mol) and 0.21 eV (4.8 kcal/mol) were found, respectively. Computational studies using density functional theory confirmed the polaronic nature of charge carriers but predicted that the semiclassical activation energy of hopping should be higher for CB-OPI molecular wires than for the OPI 6 wire. To reconcile the experimental and

  18. Electron small polarons and their mobility in iron (oxyhydr)oxide nanoparticles

    DEFF Research Database (Denmark)

    Katz, Jordan E; Zhang, Xiaoyi; Attenkofer, Klaus

    2012-01-01

    Electron mobility within iron (oxyhydr)oxides enables charge transfer between widely separated surface sites. There is increasing evidence that this internal conduction influences the rates of interfacial reactions and the outcomes of redox-driven phase transformations of environmental interest....... To determine the links between crystal structure and charge-transport efficiency, we used pump-probe spectroscopy to study the dynamics of electrons introduced into iron(III) (oxyhydr)oxide nanoparticles via ultrafast interfacial electron transfer. Using time-resolved x-ray spectroscopy and ab initio...

  19. Polarons induced electronic transport, dielectric relaxation and magnetodielectric coupling in spin frustrated Ba{sub 2}FeWO{sub 6}

    Energy Technology Data Exchange (ETDEWEB)

    Pezhumkattil Palakkal, Jasnamol [Academy of Scientific and Innovative Research (AcSIR), CSIR—National Institute for Interdisciplinary Science and Technology (CSIR-NIIST) Campus, Trivandrum 695 019 (India); Materials Science and Technology Division, National Institute for Interdisciplinary Science and Technology, CSIR, Trivandrum 695 019 (India); Lekshmi, P. Neenu; Thomas, Senoy [Materials Science and Technology Division, National Institute for Interdisciplinary Science and Technology, CSIR, Trivandrum 695 019 (India); Valant, Matjaz [Materials Research Laboratory, University of Nova Gorica, Nova Gorica 5000 (Slovenia); Suresh, K.G. [Department of Physics, Indian Institute of Technology Bombay, Mumbai 400 076 (India); Varma, Manoj Raama, E-mail: manoj@niist.res.in [Academy of Scientific and Innovative Research (AcSIR), CSIR—National Institute for Interdisciplinary Science and Technology (CSIR-NIIST) Campus, Trivandrum 695 019 (India); Materials Science and Technology Division, National Institute for Interdisciplinary Science and Technology, CSIR, Trivandrum 695 019 (India)

    2016-04-15

    Highlights: • Ordered double perovskite Ba{sub 2}FeWO{sub 6} synthesized in reducing atmosphere possess a tetragonal I4/m crystal structure with mixed valent Fe/W cations. • Ba{sub 2}FeWO{sub 6} has an antiferromagnetic structure with T{sub N} at 19 K. • Insulating Ba{sub 2}FeWO{sub 6} shows different conducting mechanisms at different temperature regions and dielectric relaxation. • The polarons invoked by the mixed valence state of cations and their disordered arrangements are solely responsible for the various physical phenomena observed in Ba{sub 2}FeWO{sub 6}. - Abstract: Mixed valent double perovskite Ba{sub 2}FeWO{sub 6}, with tetragonal crystal structure, synthesized in a highly controlled reducing atmosphere, shows antiferromagnetic transition at T{sub N} = 19 K. A cluster glass-like transition is observed around 30 K arising from the competing interactions between inhomogeneous magnetic states. The structural distortion leads to the formation of polarons that are not contributing to DC conduction below charge ordering temperature, T{sub CO} = 279 K. Above T{sub CO}, small polarons will start to hop by exploiting thermal energy and participate in the conduction mechanism. The polarons are also responsible for the dielectric relaxor behavior, in which the dielectric relaxation time follows non-linearity in temperature as proposed by Fulcher. The material also exhibits a small room temperature magnetoresistance of 1.7% at 90 kOe. An intrinsic magnetodielectric coupling of ∼4% near room temperature and at lower temperatures, as well as an extrinsic magnetodielectric coupling change from +4% to −6% at around 210 K are reported.

  20. Interplay of cross-plane polaronic transport and resistive switching in Pt–Pr0.67Ca0.33MnO3–Pt heterostructures

    International Nuclear Information System (INIS)

    Scherff, M; Hoffmann, J; Meyer, B; Danz, Th; Jooss, Ch

    2013-01-01

    The identification of the cross-plane electric transport mechanisms in different resistance states of metal–oxide sandwich structures is essential for gaining insights into the mechanisms of resistive switching (RS). Here, we present a systematic study of cross-plane electric transport properties of Pr 0.67 Ca 0.33 MnO 3 (PCMO) thin films sandwiched by precious Pt metal electrodes. We observe three different transport regimes: ohmic, nonlinear and RS. The nonlinear regime is associated with colossal magneto-resistance (CMR) and colossal electro-resistance (CER) effects. In contrast to RS, the CMR and CER are volatile resistance effects which persist only during application of strong magnetic or electric fields and they are restricted to low temperatures. At low current densities, the device resistance is dominated by small polaron hopping transport of the PCMO film. At higher electric current densities near the switching threshold, the interface resistance starts to dominate and remarkably also exhibits thermally activated transport properties. Our studies also shed light onto the interplay of colossal resistance effects and RS: at low temperatures, RS can be only induced by reduction of the PCMO resistivity through CMR and CER. This clearly demonstrates the key role of the current density for controlling the amplitude of non-volatile resistive changes. Conversely, the CMR can be used as a probe for the switching induced changes in disorder and correlations. At small switching amplitudes, we observe slight changes in polaron activation energy which can be attributed to changes at the interface. If the switching amplitude exceeds 1000% and more, the CMR effect in the device can be reversibly changed. This indicates persistent changes in electronic or lattice structure of large regions within the PCMO film. (paper)

  1. Polaron interaction energies in reduced tungsten trioxide

    International Nuclear Information System (INIS)

    Iguchi, E.; Salje, E.; Tilley, R.J.D.

    1981-01-01

    Consideration of the properties of reduced tungsten trioxide suggest that the mobile charge carriers are polarons. As it is uncertain how the presence of polarons will influence the microstructures of the crystallographic shear (CS) planes present in reduced tungsten trioxide we have calculated both the polaron-CS plane and polaron-polaron interaction energy for a variety of circumstances. Three CS plane geometries were considered, (102), (103), and (001) CS plane arrays, and the nominal compositions of the crystals ranged from WO 2 70 to WO 3 0 . The polarons were assumed to have radii from 0.6 to 1.0 nm and the polaron-CS plane electrostatic interaction was assumed to be screened. The results suggest that for the most part the total interaction energy is small and is unlikely to be of major importance in controlling the microstructures found in CS planes. However, at very high polaron densities the interaction energy could be appreciable and may have some influence on the existence range of CS phases

  2. Electric field control of the small-polaron hopping conduction in spatial confined Pr0.7(Ca0.6Sr0.40.3MnO3/PMN-PT heterostructure

    Directory of Open Access Journals (Sweden)

    Hao Kuang

    2017-05-01

    Full Text Available The electric field dependent high-temperature small-polaron hopping conduction was investigated in patterned Pr0.7(Ca0.6Sr0.40.3MnO3 strips. The small-polaronic activation energy EA and the carrier localization were found to decrease with the reduction of the strip size. Meanwhile, a similar dependence on the strip size was also obtained for the calculated small-polaron coupling constants, which could be related to the strain relaxation in strips. These results indicate that the spatial confinement prefers to delocalize the carrier and reduce the electron-phonon interaction. Furthermore, opposite variation trends of EA under negative and positive electric field were found in the strips with small size, which could be attributed to the enhancement of polarization effect induced by the reduction of strip size.

  3. Polarons in advanced materials

    CERN Document Server

    Alexandrov, Alexandre Sergeevich

    2008-01-01

    Polarons in Advanced Materials will lead the reader from single-polaron problems to multi-polaron systems and finally to a description of many interesting phenomena in high-temperature superconductors, ferromagnetic oxides, conducting polymers and molecular nanowires. The book divides naturally into four parts. Part I introduces a single polaron and describes recent achievements in analytical and numerical studies of polaron properties in different electron-phonon models. Part II and Part III describe multi-polaron physics, and Part IV describes many key physical properties of high-temperature superconductors, colossal magnetoresistance oxides, conducting polymers and molecular nanowires, which were understood with polarons and bipolarons. The book is written in the form of self-consistent reviews authored by well-established researchers actively working in the field and will benefit scientists and postgraduate students with a background in condensed matter physics and materials sciences.

  4. Small polaron hopping conduction in samples of ceramic La1.4Sr1.6Mn2O7.06

    International Nuclear Information System (INIS)

    Nakatsugawa, H.; Iguchi, E.; Jung, W.H.; Munakata, F.

    1999-01-01

    The ceramic sample of La 1.4 Sr 1.6 Mn 2 O 7.06 exhibits the metal-insulator transition and a negative magnetoresistance in the vicinity of the Curie temperature (T C ∼ 100 K). The dc magnetic susceptibility between 100 K and 280 K is nearly constant and decreases gradually with increasing temperature above 280 K. The measurements of dc resistivity and the thermoelectric power indicate that small polaron hopping conduction takes place at T > 280 K. The spin ordering due to the two-dimensional d x 2 -y 2 state occurring at T > 280 K is directly related to the hopping conduction above 280 K, although the spin ordering due to the one-dimensional d 3z 2 -r 2 state takes place at T > T C . The two-dimensional d x 2 -y 2 state extending within the MnO 2 sheets starts to narrow and leads to the carrier localisation at 280 K. The effective number of holes in this sample estimated from the thermoelectric power is considerably smaller than the nominal value. This indicates that the small polaron hopping conduction takes place predominantly within the in-plane MnO 2 sheets. A discussion is given of the experimental results of the ceramic sample of La 2/3 Ca 1/3 MnO 2.98 . Copyright (1999) CSIRO Australia

  5. Determining a hopping polaron's bandwidth from its Seebeck coefficient: Measuring the disorder energy of a non-crystalline semiconductor

    International Nuclear Information System (INIS)

    Emin, David

    2016-01-01

    Charge carriers that execute multi-phonon hopping generally interact strongly enough with phonons to form polarons. A polaron's sluggish motion is linked to slowly shifting atomic displacements that severely reduce the intrinsic width of its transport band. Here a means to estimate hopping polarons' bandwidths from Seebeck-coefficient measurements is described. The magnitudes of semiconductors' Seebeck coefficients are usually quite large (>k/|q| = 86 μV/K) near room temperature. However, in accord with the third law of thermodynamics, Seebeck coefficients must vanish at absolute zero. Here, the transition of the Seebeck coefficient of hopping polarons to its low-temperature regime is investigated. The temperature and sharpness of this transition depend on the concentration of carriers and on the width of their transport band. This feature provides a means of estimating the width of a polaron's transport band. Since the intrinsic broadening of polaron bands is very small, less than the characteristic phonon energy, the net widths of polaron transport bands in disordered semiconductors approach the energetic disorder experienced by their hopping carriers, their disorder energy

  6. Small transport aircraft technology

    Science.gov (United States)

    Williams, L. J.

    1983-01-01

    Information on commuter airline trends and aircraft developments is provided to upgrade the preliminary findings of a NASA-formed small transport aircraft technology (STAT) team, established to determine whether the agency's research and development programs could help commuter aircraft manufacturers solve technical problems related to passenger acceptance and use of 19- to 50-passenger aircraft. The results and conclusions of the full set of completed STAT studies are presented. These studies were performed by five airplane manufacturers, five engine manufacturers, and two propeller manufacturers. Those portions of NASA's overall aeronautics research and development programs which are applicable to commuter aircraft design are summarized. Areas of technology that might beneficially be expanded or initiated to aid the US commuter aircraft manufacturers in the evolution of improved aircraft for the market are suggested.

  7. Polaron crossover in molecular solids

    International Nuclear Information System (INIS)

    Zoli, Marco; Das, A N

    2004-01-01

    An analytical variational method is applied to the molecular Holstein Hamiltonian in which the dispersive features of the dimension dependent phonon spectrum are taken into account by a force constant approach. The crossover between a large and a small size polaron is monitored, in one, two and three dimensions and for different values of the adiabatic parameter, through the behaviour of the effective mass as a function of the electron-phonon coupling. By increasing the strength of the intermolecular forces the crossover becomes smoother and occurs at higher e-ph couplings. These effects are more evident in three dimensions. We show that our modified Lang-Firsov method starts to capture the occurrence of a polaron self-trapping transition when the electron energies become of order of the phonon energies. The self-trapping event persists in the fully adiabatic regime. At the crossover we estimate polaron effective masses of order ∼ 5-40 times the bare band mass according to the dimensionality and the value of the adiabatic parameter. Modified Lang-Firsov polaron masses are substantially reduced in two and three dimensions. There is no self-trapping in the antiadiabatic regime

  8. Polarons in acetanilide

    Science.gov (United States)

    Scott, Alwyn C.; Bigio, Irving J.; Johnston, Clifford T.

    1989-06-01

    The best available data are presented of the integrated intensity of the 1650-cm-1 band in crystalline acetanilide as a function of temperature. A concise theory of polaron states is presented and used to interpret the data.

  9. Big magnetoresistance: magnetic polarons

    International Nuclear Information System (INIS)

    Teresa, J.M. de; Ibarra, M.R.

    1997-01-01

    By using several macro and microscopic experimental techniques we have given evidence for magnetoresistance in manganese oxides caused by the effect of the magnetic field on the magnetic polarons. (Author) 3 refs

  10. Effects of hole self-trapping by polarons on transport and negative bias illumination stress in amorphous-IGZO

    Science.gov (United States)

    de Jamblinne de Meux, A.; Pourtois, G.; Genoe, J.; Heremans, P.

    2018-04-01

    The effects of hole injection in amorphous indium-gallium-zinc-oxide (a-IGZO) are analyzed by means of first-principles calculations. The injection of holes in the valence band tail states leads to their capture as a polaron, with high self-trapping energies (from 0.44 to 1.15 eV). Once formed, they mediate the formation of peroxides and remain localized close to the hole injection source due to the presence of a large diffusion energy barrier (of at least 0.6 eV). Their diffusion mechanism can be mediated by the presence of hydrogen. The capture of these holes is correlated with the low off-current observed for a-IGZO transistors, as well as with the difficulty to obtain a p-type conductivity. The results further support the formation of peroxides as being the root cause of Negative Bias Illumination Stress (NBIS). The strong self-trapping substantially reduces the injection of holes from the contact and limits the creation of peroxides from a direct hole injection. In the presence of light, the concentration of holes substantially rises and mediates the creation of peroxides, responsible for NBIS.

  11. Crossover from Polaronic to Magnetically Phase-Separated Behavior in La1-xSrxCoO3

    Science.gov (United States)

    Phelan, D.; El Khatib, S.; Wang, S.; Barker, J.; Zhao, J.; Zheng, H.; Mitchell, J. F.; Leighton, C.

    2013-03-01

    Dilute hole-doping in La1-xSrxCoO3 leads to the formation of ``spin-state polarons'' where a non-zero spin-state is stabilized on the nearest Co3+ ions surrounding a hole. Here, we discuss the development of electronic/magnetic properties of this system from non-magnetic x=0, through the regime of spin-state polarons, and into the region where longer-range spin correlations and phase separation develop. We present magnetometry, transport, heat capacity, and small-angle neutron scattering (SANS) on single crystals. Magnetometry indicates a crossover with x from Langevin-like behavior (polaronic) to a state with a freezing temperature and finite coercivity. Fascinating correlations with this behavior are seen in transport measurements, the evolution from polaronic to clustered states being accompanied by a crossover from Mott variable range hopping to intercluster hopping. SANS data shows Lorentzian scattering from short-range ferromagnetic clusters first emerging around x = 0.03 with correlation lengths of order two unit cells. We argue that this system provides a unique opportunity to understand in detail the crossover from polaronic to truly phase-separated states.

  12. Polaronic transport and thermoelectricity in Fe1 -xCoxSb2S4 (x =0 , 0.1, and 0.2)

    Science.gov (United States)

    Liu, Yu; Kang, Chang-Jong; Stavitski, Eli; Du, Qianheng; Attenkofer, Klaus; Kotliar, G.; Petrovic, C.

    2018-04-01

    We report a study of Co-doped berthierite Fe1 -xCoxSb2S4 (x =0 , 0.1, and 0.2). The alloy series of Fe1 -xCoxSb2S4 crystallize in an orthorhombic structure with the Pnma space group, similar to FeSb2, and show semiconducting behavior. The large discrepancy between activation energy for conductivity, Eρ (146 ˜270 meV ), and thermopower, ES (47 ˜108 meV ), indicates the polaronic transport mechanism. Bulk magnetization and heat-capacity measurements of pure FeSb2S4 (x =0 ) exhibit a broad antiferromagnetic transition (TN=46 K ) followed by an additional weak transition (T*=50 K ). Transition temperatures (TN and T*) slightly decrease with increasing Co content x . This is also reflected in the thermal conductivity measurement, indicating strong spin-lattice coupling. Fe1 -xCoxSb2S4 shows relatively high value of thermopower (up to ˜624 μ V K-1 at 300 K) and thermal conductivity much lower when compared to FeSb2, a feature desired for potential applications based on FeSb2 materials.

  13. Diagrams in the polaron model

    International Nuclear Information System (INIS)

    Smondyrev, M.A.

    1985-01-01

    The perturbation theory for the polaron energy is systematically treated on the diagrammatic basis. Feynman diagrams being constructed allow to calculate the polaron energy up to the third order in powers of the coupling constant. Similar calculations are performed for the average number of virtual phonons

  14. Continual integration method in the polaron model

    International Nuclear Information System (INIS)

    Kochetov, E.A.; Kuleshov, S.P.; Smondyrev, M.A.

    1981-01-01

    The article is devoted to the investigation of a polaron system on the base of a variational approach formulated on the language of continuum integration. The variational method generalizing the Feynman one for the case of the system pulse different from zero has been formulated. The polaron state has been investigated at zero temperature. A problem of the bound state of two polarons exchanging quanta of a scalar field as well as a problem of polaron scattering with an external field in the Born approximation have been considered. Thermodynamics of the polaron system has been investigated, namely, high-temperature expansions for mean energy and effective polaron mass have been studied [ru

  15. Polaron variable range hopping in TiO2-δ(-0.04=<δ=<0.2) thin films

    International Nuclear Information System (INIS)

    Heluani, S.P.; Comedi, D.; Villafuerte, M.; Juarez, G.

    2007-01-01

    The mechanisms of electrical conduction in TiO 2-δ (-0.04= 2 +Ar gas atmospheres where changes in δ and film structure had been achieved by varying the O 2 flow rate and the substrate temperature. The electrical transport properties of these samples were investigated by measuring the conductivity as a function of temperature between 17K and room temperature. At the temperature range between 200 and 290K the best fit to the experimental data was obtained assuming a dependence characteristic of adiabatic variable range hopping. At lower temperature the activation energy for the conductivity tends to zero. The results suggest that the conduction mechanism is adiabatic small polaron hopping, which switches to conduction in a polaron band at low temperatures

  16. Frequency and temperature dependence of the electrical conductivity of KTaO3; Li and PbTiO3; La, Cu: Indication of a low temperature polaron mechanism

    International Nuclear Information System (INIS)

    Levstik, A.; Filipic, C.; Bidault, O.; Maglione, M.

    2008-01-01

    Recently, the concept of polarons has again been at the focus of solid-state research, as it can constitute the basis for understanding the high-temperature superconductivity or the colossal magnetoresistance of materials. More than a decade ago there were some indications that polarons play an important role in explaining low temperature maxima in imaginary part of the dielectric constant ε '' (T) in ABO 3 perovskites. In the present work we report the ac electrical conductivities of KTaO 3 ; Li and PbTiO 3 ; La, Cu and their frequency and temperature dependence. The real part of the complex ac conductivity was found to follow the universal dielectric response σ ' ∝ν s . A detailed theoretical analysis of the temperature dependence of the parameter s revealed that, at low temperatures, the tunnelling of small polarons is the dominating charge transport mechanism in ABO 3 perovskites

  17. Polaron-mediated surface reconstruction in the reduced Rutile TiO2 (110) surface

    Science.gov (United States)

    Reticcioli, Michele; Setvin, Martin; Hao, Xianfeng; Diebold, Ulrike; Franchini, Cesare

    The role of polarons is of key importance for the understanding of the fundamental properties and functionalities of TiO2. We use density functional theory with an on-site Coulomb interaction and molecular dynamics to study the formation and dynamics of small polarons in the reduced rutile (110) surface. We show that excess electrons donated by oxygen-vacancies (VO) form mobile small polarons that hop easily in subsurface and surface Ti-sites. The polaron formation becomes more favorable by increasing the VO concentration level (up to 20%) due to the progressively lower energy cost needed to distort the lattice. However, at higher VO concentration the shortening of the averaged polaron-polaron distance leads to an increased Coulomb repulsion among the trapped charges at the Ti-sites, which weakens this trend. This instability is overtaken by means of a structural 1 × 2 surface reconstruction, characterized by a distinctively more favorable polaron distribution. The calculations are validated by a direct comparison with experimental AFM and STM data. Our study identifies a fundamentally novel mechanism to drive surface reconstructions and resolves a long standing issue on the origin of the reconstruction in rutile (110) surface.

  18. Ground state energy of a polaron in a superlattice

    International Nuclear Information System (INIS)

    Mensah, S.Y.; Allotey, F.K.A.; Nkrumah, G.; Mensah, N.G.

    2000-10-01

    The ground state energy of a polaron in a superlattice was calculated using the double-time Green functions. The effective mass of the polaron along the planes perpendicular to the superlattice axis was also calculated. The dependence of the ground state energy and the effective mass along the planes perpendicular to the superlattice axis on the electron-phonon coupling constant α and on the superlattice parameters (i.e. the superlattice period d and the bandwidth Δ) were studied. It was observed that if an infinite square well potential is assumed, the ground state energy of the polaron decreases (i.e. becomes more negative) with increasing α and d, but increases with increasing Δ. For small values of α, the polaron ground state energy varies slowly with Δ, becoming approximately constant for large Δ. The effective mass along the planes perpendicular to the superlattice axis was found to be approximately equal to the mass of an electron for all typical values of α, d and Δ. (author)

  19. Transport in a small aspect ratio torus

    International Nuclear Information System (INIS)

    White, R.B.; Gates, D.A.; Mynick, H.E.

    2005-01-01

    Transport theory in toroidal devices often assumes large aspect ratio and also assumes the poloidal field is small compared to the toroidal field. These assumptions result in transport which in the low collision rate limit is dominated by banana orbits, giving the largest collisionless excursion of a particle from an initial flux surface. However in a small aspect ratio device the gyro radius may be larger than the banana excursion, resulting in significant deviations from the standard neoclassical predictions. In this paper we report numerical simulation of diffusion in low and high beta low aspect ratio equilibria. We also sketch an analytic theory. The diffusion, which we refer to as omniclassical, is a combination of neoclassical and properly averaged classical effects, and can be two or three times the neoclassical value. Good agreement of the analytic theory with numerical simulations is obtained. (author)

  20. Excitonic and Polaronic Properties of 2D Hybrid Organic–Inorganic Perovskites

    KAUST Repository

    Yin, Jun

    2017-01-20

    We theoretically characterize the unusual white-light emission properties of two-dimensional (2D) hybrid organic inorganic perovskites with an APbX(4) structure (where A is a bidentate organic cation and X = Cl, Br). In addition to band structure calculations including corrections due to spin orbit couplings and electron hole interactions, a computationally intensive molecular cluster approach is exploited to describe the excitonic and polaronic properties of these 2D perovskites at the atomistic level. Upon adding or removing an electron from the neutral systems, we find that strongly localized small polarons form in the 2D clusters. The polaron charge density is distributed over just lattice sites, which is consistent with the calculated large polaron binding energies, on the order of similar to 0.4-1.2 eV.

  1. Small Transport Aircraft Technology /STAT/ Propulsion Study

    Science.gov (United States)

    Heldenbrand, R. W.; Baerst, C. F.; Rowse, J. H.

    1980-01-01

    The NASA Small Transport Aircraft Technology (STAT) Propulsion Study was established to identify technology requirements and define the research and development required for new commuter aircraft. Interim results of the studies defined mission and design characteristics for 30- and 50-passenger aircraft. Sensitivities were defined that relate changes in engine specific fuel consumption (SFC), weight, and cost (including maintenance) to changes in the aircraft direct operating cost (DOC), takeoff gross weight, and empty weight. A comparison of performance and economic characteristics is presented between aircraft powered by 1980 production engines and those powered by a 1990 advanced technology baseline engine.

  2. Optical Detection of Polarons in High - Tc Cuprate

    International Nuclear Information System (INIS)

    Calvani, P.; Capizzi, M.; Lupi, S.; Maselli, P.; Paolone, A.; Roy LURE, P.; Berger, H.

    1995-01-01

    The optical conductivity σ (ω) of slightly e-doped single-crystals of (Nd,Gd) 2 CuO 4-y shows local modes in the far-infrared as well as a broad infrared absorption centered at ∼ 0.1 eV (d-band). This latter shows a fine structure, in agreement with recent calculations of Alexandrov et al., which is made up by intense overtones of the local modes observed in the far-infrared. Similar polaronic structures are shown to exist in the normal metallic phase of Nd 2-x Ce x CuO 4-y and even in the σ (ω ) of YBCO crystals, measured by different authors. The present observations provide evidence for the existence of small polarons in all materials with a Cu-O plane

  3. Large polarons in lead halide perovskites

    OpenAIRE

    Miyata, Kiyoshi; Meggiolaro, Daniele; Trinh, M. Tuan; Joshi, Prakriti P.; Mosconi, Edoardo; Jones, Skyler C.; De Angelis, Filippo; Zhu, X.-Y.

    2017-01-01

    Lead halide perovskites show marked defect tolerance responsible for their excellent optoelectronic properties. These properties might be explained by the formation of large polarons, but how they are formed and whether organic cations are essential remain open questions. We provide a direct time domain view of large polaron formation in single-crystal lead bromide perovskites CH3NH3PbBr3 and CsPbBr3. We found that large polaron forms predominantly from the deformation of the PbBr3 ? framewor...

  4. Optimizing sealed transports of small ornamental fish

    Directory of Open Access Journals (Sweden)

    Rui Esteves da Silva

    2014-06-01

    Full Text Available This is a report on multiple simulated long-term transports of small ornamental fish inside plastic bags. The species involved were Diplodus sargus, Gobius paganellus, Gobiusculus flavescens, Lepadogaster lepadogaster and Lipophrys pholis. The objective of such simulations was moving the maximum bioload possible while ensuring 100% survivorship, ultimately resulting in savings for the end-receiver. Transports were simulated over 24, 48 and 72 hours, with increasing animal bioloads per bag. Half of the trials were performed with “regular” saltwater while the other half involved seawater buffered with Amquel ®, sodium carbonate and sodium bicarbonate, with the objective of keeping ammonia low and pH similar to initial baseline values. At the end of each trial, temperature, dissolved oxygen, pH and ammonia were analized and the survival rate calculated and recorded. L. lepadogaster endured the highest bioloads at 100% survivorship (i.e. up to 30 g / L, which is not surprising given the intertidal nature of this species. D. sargus exhibited mortalities with bioloads as low as 3,23 g / L, which echoes its predominantly pelagic nature and relatively lesser ability to endure confinement. The three remaining species showed varying degrees of tolerance to increasing bioloads in transport: L. pholis, also an intertidal species, handled up to 20 g/L over 72 hours, while G. paganellus handled up to 7 g/L over 72 hours, and G. flavescens (a predominantly pelagic species could deal with no more than 6 g/L up to 72 hours.

  5. Polaron-Driven Surface Reconstructions

    Directory of Open Access Journals (Sweden)

    Michele Reticcioli

    2017-09-01

    Full Text Available Geometric and electronic surface reconstructions determine the physical and chemical properties of surfaces and, consequently, their functionality in applications. The reconstruction of a surface minimizes its surface free energy in otherwise thermodynamically unstable situations, typically caused by dangling bonds, lattice stress, or a divergent surface potential, and it is achieved by a cooperative modification of the atomic and electronic structure. Here, we combined first-principles calculations and surface techniques (scanning tunneling microscopy, non-contact atomic force microscopy, scanning tunneling spectroscopy to report that the repulsion between negatively charged polaronic quasiparticles, formed by the interaction between excess electrons and the lattice phonon field, plays a key role in surface reconstructions. As a paradigmatic example, we explain the (1×1 to (1×2 transition in rutile TiO_{2}(110.

  6. Stability and Polaronic Motion of Self-Trapped Holes in Silver Halides

    DEFF Research Database (Denmark)

    Loftager, Simon; Garcia-Fernandez, P.; Aramburu, J. A.

    2016-01-01

    Polarons and their associated transport properties are a field of great current interest both in chemistry and physics. To further our understanding of these quasi-particles, we have carried out first-principles calculations of self-trapped holes (STHs) in the model compounds AgCl and AgBr, for w......Polarons and their associated transport properties are a field of great current interest both in chemistry and physics. To further our understanding of these quasi-particles, we have carried out first-principles calculations of self-trapped holes (STHs) in the model compounds AgCl and Ag...

  7. Transportable high sensitivity small sample radiometric calorimeter

    International Nuclear Information System (INIS)

    Wetzel, J.R.; Biddle, R.S.; Cordova, B.S.; Sampson, T.E.; Dye, H.R.; McDow, J.G.

    1998-01-01

    A new small-sample, high-sensitivity transportable radiometric calorimeter, which can be operated in different modes, contains an electrical calibration method, and can be used to develop secondary standards, will be described in this presentation. The data taken from preliminary tests will be presented to indicate the precision and accuracy of the instrument. The calorimeter and temperature-controlled bath, at present, require only a 30-in. by 20-in. tabletop area. The calorimeter is operated from a laptop computer system using unique measurement module capable of monitoring all necessary calorimeter signals. The calorimeter can be operated in the normal calorimeter equilibration mode, as a comparison instrument, using twin chambers and an external electrical calibration method. The sample chamber is 0.75 in (1.9 cm) in diameter by 2.5 in. (6.35 cm) long. This size will accommodate most 238 Pu heat standards manufactured in the past. The power range runs from 0.001 W to <20 W. The high end is only limited by sample size

  8. Dynamics of photogenerated polarons and polaron pairs in P3HT thin films

    Czech Academy of Sciences Publication Activity Database

    Menšík, Miroslav; Pfleger, Jiří; Toman, Petr

    2017-01-01

    Roč. 677, 1 June (2017), s. 87-91 ISSN 0009-2614 R&D Projects: GA MŠk(CZ) LO1507 Institutional support: RVO:61389013 Keywords : poly(3-hexyl thiophene) * transient absorption spectroscopy * polaron and polaron pairs Subject RIV: CD - Macromolecular Chemistry OBOR OECD: Polymer science Impact factor: 1.815, year: 2016

  9. Giant Optical Polarization Rotation Induced by Spin-Orbit Coupling in Polarons

    Science.gov (United States)

    Casals, Blai; Cichelero, Rafael; García Fernández, Pablo; Junquera, Javier; Pesquera, David; Campoy-Quiles, Mariano; Infante, Ingrid C.; Sánchez, Florencio; Fontcuberta, Josep; Herranz, Gervasi

    2016-07-01

    We have uncovered a giant gyrotropic magneto-optical response for doped ferromagnetic manganite La2 /3Ca1 /3MnO3 around the near room-temperature paramagnetic-to-ferromagnetic transition. At odds with current wisdom, where this response is usually assumed to be fundamentally fixed by the electronic band structure, we point to the presence of small polarons as the driving force for this unexpected phenomenon. We explain the observed properties by the intricate interplay of mobility, Jahn-Teller effect, and spin-orbit coupling of small polarons. As magnetic polarons are ubiquitously inherent to many strongly correlated systems, our results provide an original, general pathway towards the generation of magnetic-responsive gigantic gyrotropic responses that may open novel avenues for magnetoelectric coupling beyond the conventional modulation of magnetization.

  10. 76 FR 27935 - Small Business Size Standards: Transportation and Warehousing

    Science.gov (United States)

    2011-05-13

    ... assistance, SBA establishes small business definitions (referred to as size standards) for private sector... SMALL BUSINESS ADMINISTRATION 13 CFR Part 121 RIN 3245-AG08 Small Business Size Standards: Transportation and Warehousing AGENCY: U.S. Small Business Administration. ACTION: Proposed rule. SUMMARY: The U...

  11. Large polarons in lead halide perovskites

    Science.gov (United States)

    Miyata, Kiyoshi; Meggiolaro, Daniele; Trinh, M. Tuan; Joshi, Prakriti P.; Mosconi, Edoardo; Jones, Skyler C.; De Angelis, Filippo; Zhu, X.-Y.

    2017-01-01

    Lead halide perovskites show marked defect tolerance responsible for their excellent optoelectronic properties. These properties might be explained by the formation of large polarons, but how they are formed and whether organic cations are essential remain open questions. We provide a direct time domain view of large polaron formation in single-crystal lead bromide perovskites CH3NH3PbBr3 and CsPbBr3. We found that large polaron forms predominantly from the deformation of the PbBr3− frameworks, irrespective of the cation type. The difference lies in the polaron formation time, which, in CH3NH3PbBr3 (0.3 ps), is less than half of that in CsPbBr3 (0.7 ps). First-principles calculations confirm large polaron formation, identify the Pb-Br-Pb deformation modes as responsible, and explain quantitatively the rate difference between CH3NH3PbBr3 and CsPbBr3. The findings reveal the general advantage of the soft [PbX3]− sublattice in charge carrier protection and suggest that there is likely no mechanistic limitations in using all-inorganic or mixed-cation lead halide perovskites to overcome instability problems and to tune the balance between charge carrier protection and mobility. PMID:28819647

  12. Importance of polaron effects for charge carrier mobility above and ...

    Indian Academy of Sciences (India)

    Orifjon Ganiev

    2017-05-30

    May 30, 2017 ... sizes and effective masses are large polarons. According ... nating metallic and insulating domains with mobile ... The mobile polaronic carriers are con- ..... [51] T Kondo, Y Hamaya, A D Palczewski, T Takeuchi, J S Wen,.

  13. Polaron as the extended particle model

    International Nuclear Information System (INIS)

    Kochetov, E.A.; Kuleshov, S.P.; Smondyrev, M.A.

    1977-01-01

    The polaron (a moving electron with concomitant lattice distortion) mass and energy are calculated. The problem of finding the Green function in the polaron model is solved. A number of the simplest approximations corresponding to the approximation in the picture of straight-line paths is considered. The case of strong coupling requires more detailed study of the particle motion in the effective field, caused by the significant polarization of vacuum near the particle. As a consequence, a more complex approximation of functional integrals is required. A variation method is used in this case. The bound state of a polaron interacting not only with photons, but also with some external classical field is investigated as well. A classical potential is considered as an example

  14. Importance of polaron effects for charge carrier mobility above and ...

    Indian Academy of Sciences (India)

    It is shown that the scattering of polaronic charge carriers and bosonic Cooper pairs at acoustic and optical phonons are responsible for the charge carrier mobility above and below the PG temperature. We show that the energy scales of the binding energies of large polarons and polaronic Cooper pairs can be identified by ...

  15. Polaron in the dilute critical Bose condensate

    Science.gov (United States)

    Pastukhov, Volodymyr

    2018-05-01

    The properties of an impurity immersed in a dilute D-dimensional Bose gas at temperatures close to its second-order phase transition point are considered. Particularly by means of the 1/N-expansion, we calculate the leading-order polaron energy and the damping rate in the limit of vanishing boson–boson interaction. It is shown that the perturbative effective mass and the quasiparticle residue diverge logarithmically in the long-length limit, signalling the non-analytic behavior of the impurity spectrum and pole-free structure of the polaron Green’s function in the infrared region, respectively.

  16. Evidence for polaron conduction in nanostructured manganese ferrite

    International Nuclear Information System (INIS)

    Gopalan, E Veena; Anantharaman, M R; Malini, K A; Saravanan, S; Kumar, D Sakthi; Yoshida, Yasuhiko

    2008-01-01

    Nanoparticles of manganese ferrite were prepared by the chemical co-precipitation technique. The dielectric parameters, namely, real and imaginary dielectric permittivity (ε' and ε-prime), ac conductivity (σ ac ) and dielectric loss tangent (tanδ), were measured in the frequency range of 100 kHz-8 MHz at different temperatures. The variations of dielectric dispersion (ε') and dielectric absorption (ε-prime) with frequency and temperature were also investigated. The variation of dielectric permittivity with frequency and temperature followed the Maxwell-Wagner model based on interfacial polarization in consonance with Koops phenomenological theory. The dielectric loss tangent and hence ε-prime exhibited a relaxation at certain frequencies and at relatively higher temperatures. The dispersion of dielectric permittivity and broadening of the dielectric absorption suggest the possibility of a distribution of relaxation time and the existence of multiple equilibrium states in manganese ferrite. The activation energy estimated from the dielectric relaxation is found to be high and is characteristic of polaron conduction in the nanosized manganese ferrite. The ac conductivity followed a power law dependence σ ac = Bω n typical of charge transport assisted by a hopping or tunnelling process. The observed minimum in the temperature dependence of the frequency exponent n strongly suggests that tunnelling of the large polarons is the dominant transport process

  17. Sediment transport and channel morphology of small, forested streams.

    Science.gov (United States)

    Marwan A. Hassan; Michael Church; Thomas E. Lisle; Francesco Brardinoni; Lee Benda; Gordon E. Grant

    2005-01-01

    This paper reviews sediment transport and channel morphology in small, forested streams in the Pacific Northwest region of North America to assess current knowledge of channel stability and morphology relevant to riparian management practices around small streams. Small channels are defined as ones in which morphology and hydraulics may be significantly influenced by...

  18. Chiral plaquette polaron theory of cuprate superconductivity

    Science.gov (United States)

    Tahir-Kheli, Jamil; Goddard, William A., III

    2007-07-01

    Ab initio density functional calculations on explicitly doped La2-xSrxCuO4 find that doping creates localized holes in out-of-plane orbitals. A model for cuprate superconductivity is developed based on the assumption that doping leads to the formation of holes on a four-site Cu plaquette composed of the out-of-plane A1 orbitals apical Opz , planar Cud3z2-r2 , and planar Opσ . This is in contrast to the assumption of hole doping into planar Cudx2-y2 and Opσ orbitals as in the t-J model. Allowing these holes to interact with the d9 spin background leads to chiral polarons with either a clockwise or anticlockwise charge current. When the polaron plaquettes percolate through the crystal at x≈0.05 for La2-xSrxCuO4 , a Cudx2-y2 and planar Opσ band is formed. The computed percolation doping of x≈0.05 equals the observed transition to the “metallic” and superconducting phase for La2-xSrxCuO4 . Spin exchange Coulomb repulsion with chiral polarons leads to d -wave superconducting pairing. The equivalent of the Debye energy in phonon superconductivity is the maximum energy separation between a chiral polaron and its time-reversed partner. This energy separation is on the order of the antiferromagnetic spin coupling energy, Jdd˜0.1eV , suggesting a higher critical temperature. An additive skew-scattering contribution to the Hall effect is induced by chiral polarons and leads to a temperature dependent Hall effect that fits the measured values for La2-xSrxCuO4 . The integrated imaginary susceptibility, observed by neutron spin scattering, satisfies ω/T scaling due to chirality and spin-flip scattering of polarons along with a uniform distribution of polaron energy splittings. The derived functional form is compatible with experiments. The static spin structure factor for chiral spin coupling of the polarons to the undoped antiferromagnetic Cud9 spins is computed for classical spins on large two-dimensional lattices and is found to be incommensurate with a

  19. Polaron scattering by an external field

    International Nuclear Information System (INIS)

    Kochetov, E.A.

    1980-01-01

    The problem of polaron scattering by an external field is studied. The problem is solved using the stationary scattering theory formalism based on two operators: the G Green function operator and the T scattering operator. The dependence of the scattering amplitude on the quasi particle structure is studied. The variation approach is used for estimation of the ground energy level

  20. Explanation for the temperature dependence of plasma frequencies in SrTiO3 using mixed-polaron theory

    International Nuclear Information System (INIS)

    Eagles, D.M.; Georgiev, M.; Petrova, P.C.

    1996-01-01

    A theory of mixed polarons is used to interpret the published experimental results of Gervais et al. on temperature-dependent plasma frequencies in Nb-doped SrTiO 3 . For given polaron masses before mixing, the appropriate average mixed-polaron mass at any temperature T depends on two quantities, δ and b, which are measures of the separation between the bottoms of large and nearly small polaron bands before mixing and of a mixing matrix element; δ and b are assumed to have arbitrary linear dependences on T, probably related to a T dependence of the bare mass, and a term quadratic in T is included in δ, determined from the T dependence of large-polaron binding energies. Including a constraint on the ratio δ/|b| at low T from known masses from specific-heat data, satisfactory agreement is obtained with masses determined from plasma frequencies. This gives further support for the theory of mixed polarons in SrTiO 3 in addition to that already published. copyright 1996 The American Physical Society

  1. Quantum vibrational polarons: Crystalline acetanilide revisited

    Science.gov (United States)

    Hamm, Peter; Edler, Julian

    2006-03-01

    We discuss a refined theoretical description of the peculiar spectroscopy of crystalline acetanilide (ACN). Acetanilide is a molecular crystal with quasi-one-dimensional chains of hydrogen-bonded units, which is often regarded as a model system for the vibrational spectroscopy of proteins. In linear spectroscopy, the CO stretching (amide I) band of ACN features a double-peak structure, the lower of which shows a pronounced temperature dependence which has been discussed in the context of polaron theory. In nonlinear spectroscopy, both of these peaks respond distinctly differently. The lower-frequency band exhibits the anharmonicity expected from polaron theory, while the higher-frequency band responds as if it were quasiharmonic. We have recently related the response of the higher-frequency band to that of a free exciton [J. Edler and P. Hamm, J. Chem. Phys. 117, 2415 (2002)]. However, as discussed in the present paper, the free exciton is not an eigenstate of the full quantum version of the Holstein polaron Hamiltonian, which is commonly used to describe these phenomena. In order to resolve this issue, we present a numerically exact solution of the Holstein polaron Hamiltonian in one dimension (1D) and 3D. In 1D, we find that the commonly used displaced oscillator picture remains qualitatively correct, even for relatively large exciton coupling. However, the result is not in agreement with the experiment, as it fails to explain the free-exciton band. In contrast, when taking into account the 3D nature of crystalline acetanilide, certain parameter regimes exist where the displaced oscillator picture breaks down and states appear in the spectrum that indeed exhibit the characteristics of a free exciton. The appearance of these states is a speciality of vibrational polarons, whose source of exciton coupling is transition dipole coupling which is expected to have opposite signs of interchain and intrachain coupling.

  2. Spin-polaron theory of high-Tc superconductivity: I, spin polarons and high-Tc pairing

    International Nuclear Information System (INIS)

    Wood, R.F.

    1993-06-01

    The concept of a spin polaron is introduced and contrasted with the more familiar ionic polaron picture. A brief review of aspects of ionic bipolaronic superconductivity is given with particular emphasis on the real-space pairing and true Bose condensation characteristics. The formation energy of spin polarons is then calculated in analogy with ionic polarons. The spin-flip energy of a Cu spin in an antiferromagnetically aligned CuO 2 plane is discussed. It is shown that the introduction of holes into the CuO 2 planes will always lead to the destruction of long-range AF ordering due to the formation of spin polarons. The pairing of two spin polarons can be expected because of the reestablishment of local (short-range) AF ordering; the magnitude of the pairing energy is estimated using a simplified model. The paper closes with a brief discussion of the formal theory of spin polarons

  3. Free water transport, small pore transport and the osmotic pressure gradient

    NARCIS (Netherlands)

    Parikova, Alena; Smit, Watske; Zweers, Machteld M.; Struijk, Dirk G.; Krediet, Raymond T.

    2008-01-01

    BACKGROUND: Water transport in peritoneal dialysis (PD) patients occurs through the small pores and water channels, the latter allowing free water transport (FWT). The osmotic gradient is known to be one of the major determinants of water transport. The objective of the study was to analyse the

  4. Magnetic polarons in a nonequilibrium polariton condensate

    Science.gov (United States)

    Mietki, Paweł; Matuszewski, Michał

    2017-09-01

    We consider a condensate of exciton polaritons in a diluted magnetic semiconductor microcavity. Such a system may exhibit magnetic self-trapping in the case of sufficiently strong coupling between polaritons and magnetic ions embedded in the semiconductor. We investigate the effect of the nonequilibrium nature of exciton polaritons on the physics of the resulting self-trapped magnetic polarons. We find that multiple polarons can exist at the same time, and we derive a critical condition for self-trapping that is different from the one predicted previously in the equilibrium case. Using the Bogoliubov-de Gennes approximation, we calculate the excitation spectrum and provide a physical explanation in terms of the effective magnetic attraction between polaritons, mediated by the ion subsystem.

  5. Magnon Polarons in the Spin Seebeck Effect.

    Science.gov (United States)

    Kikkawa, Takashi; Shen, Ka; Flebus, Benedetta; Duine, Rembert A; Uchida, Ken-Ichi; Qiu, Zhiyong; Bauer, Gerrit E W; Saitoh, Eiji

    2016-11-11

    Sharp structures in the magnetic field-dependent spin Seebeck effect (SSE) voltages of Pt/Y_{3}Fe_{5}O_{12} at low temperatures are attributed to the magnon-phonon interaction. Experimental results are well reproduced by a Boltzmann theory that includes magnetoelastic coupling. The SSE anomalies coincide with magnetic fields tuned to the threshold of magnon-polaron formation. The effect gives insight into the relative quality of the lattice and magnetization dynamics.

  6. Diagrammatic Monte Carlo study of Fröhlich polaron dispersion in two and three dimensions

    Science.gov (United States)

    Hahn, Thomas; Klimin, Sergei; Tempere, Jacques; Devreese, Jozef T.; Franchini, Cesare

    2018-04-01

    We present results for the solution of the large polaron Fröhlich Hamiltonian in 3 dimensions (3D) and 2 dimensions (2D) obtained via the diagrammatic Monte Carlo (DMC) method. Our implementation is based on the approach by Mishchenko [A. S. Mishchenko et al., Phys. Rev. B 62, 6317 (2000), 10.1103/PhysRevB.62.6317]. Polaron ground state energies and effective polaron masses are successfully benchmarked with data obtained using Feynman's path integral formalism. By comparing 3D and 2D data, we verify the analytically exact scaling relations for energies and effective masses from 3 D →2 D , which provides a stringent test for the quality of DMC predictions. The accuracy of our results is further proven by providing values for the exactly known coefficients in weak- and strong-coupling expansions. Moreover, we compute polaron dispersion curves which are validated with analytically known lower and upper limits in the small-coupling regime and verify the first-order expansion results for larger couplings, thus disproving previous critiques on the apparent incompatibility of DMC with analytical results and furnishing useful reference for a wide range of coupling strengths.

  7. Strong-coupling polaron effect in quantum dots

    International Nuclear Information System (INIS)

    Zhu Kadi; Gu Shiwei

    1993-11-01

    Strong-coupling polaron in a parabolic quantum dot is investigated by the Landau-Pekar variational treatment. The polaron binding energy and the average number of virtual phonons around the electron as a function of the effective confinement length of the quantum dot are obtained in Gaussian function approximation. It is shown that both the polaron binding energy and the average number of virtual phonons around the electron decrease by increasing the effective confinement length. The results indicate that the polaronic effects are more pronounced in quantum dots than those in two-dimensional and three-dimensional cases. (author). 15 refs, 4 figs

  8. Finite temperature dynamics of a Holstein polaron: The thermo-field dynamics approach

    Science.gov (United States)

    Chen, Lipeng; Zhao, Yang

    2017-12-01

    Combining the multiple Davydov D2 Ansatz with the method of thermo-field dynamics, we study finite temperature dynamics of a Holstein polaron on a lattice. It has been demonstrated, using the hierarchy equations of motion method as a benchmark, that our approach provides an efficient, robust description of finite temperature dynamics of the Holstein polaron in the simultaneous presence of diagonal and off-diagonal exciton-phonon coupling. The method of thermo-field dynamics handles temperature effects in the Hilbert space with key numerical advantages over other treatments of finite-temperature dynamics based on quantum master equations in the Liouville space or wave function propagation with Monte Carlo importance sampling. While for weak to moderate diagonal coupling temperature increases inhibit polaron mobility, it is found that off-diagonal coupling induces phonon-assisted transport that dominates at high temperatures. Results on the mean square displacements show that band-like transport features dominate the diagonal coupling cases, and there exists a crossover from band-like to hopping transport with increasing temperature when including off-diagonal coupling. As a proof of concept, our theory provides a unified treatment of coherent and incoherent transport in molecular crystals and is applicable to any temperature.

  9. The Effects of Different Electron-Phonon Couplings on the Spectral and Transport Properties of Small Molecule Single-Crystal Organic Semiconductors

    Directory of Open Access Journals (Sweden)

    Carmine Antonio Perroni

    2014-03-01

    Full Text Available Spectral and transport properties of small molecule single-crystal organic semiconductors have been theoretically analyzed focusing on oligoacenes, in particular on the series from naphthalene to rubrene and pentacene, aiming to show that the inclusion of different electron-phonon couplings is of paramount importance to interpret accurately the properties of prototype organic semiconductors. While in the case of rubrene, the coupling between charge carriers and low frequency inter-molecular modes is sufficient for a satisfactory description of spectral and transport properties, the inclusion of electron coupling to both low-frequency inter-molecular and high-frequency intra-molecular vibrational modes is needed to account for the temperature dependence of transport properties in smaller oligoacenes. For rubrene, a very accurate analysis in the relevant experimental configuration has allowed for the clarification of the origin of the temperature-dependent mobility observed in these organic semiconductors. With increasing temperature, the chemical potential moves into the tail of the density of states corresponding to localized states, but this is not enough to drive the system into an insulating state. The mobility along different crystallographic directions has been calculated, including vertex corrections that give rise to a transport lifetime one order of magnitude smaller than the spectral lifetime of the states involved in the transport mechanism. The mobility always exhibits a power-law behavior as a function of temperature, in agreement with experiments in rubrene. In systems gated with polarizable dielectrics, the electron coupling to interface vibrational modes of the gate has to be included in addition to the intrinsic electron-phonon interaction. While the intrinsic bulk electron-phonon interaction affects the behavior of mobility in the coherent regime below room temperature, the coupling with interface modes is dominant for the

  10. Peritoneal fluid transport in CAPD patients with different transport rates of small solutes.

    Science.gov (United States)

    Sobiecka, Danuta; Waniewski, Jacek; Weryński, Andrzej; Lindholm, Bengt

    2004-01-01

    Continuous ambulatory peritoneal dialysis (CAPD) patients with high peritoneal solute transport rate often have inadequate peritoneal fluid transport. It is not known whether this inadequate fluid transport is due solely to a too rapid fall of osmotic pressure, or if the decreased effectiveness of fluid transport is also a contributing factor. To analyze fluid transport parameters and the effectiveness of dialysis fluid osmotic pressure in the induction of fluid flow in CAPD patients with different small solute transport rates. 44 CAPD patients were placed in low (n = 6), low-average (n = 13), high-average (n = 19), and high (n = 6) transport groups according to a modified peritoneal equilibration test (PET). The study involved a 6-hour peritoneal dialysis dwell with 2 L 3.86% glucose dialysis fluid for each patient. Radioisotopically labeled serum albumin was added as a volume marker.The fluid transport parameters (osmotic conductance and fluid absorption rate) were estimated using three mathematical models of fluid transport: (1) Pyle model (model P), which describes ultrafiltration rate as an exponential function of time; (2) model OS, which is based on the linear relationship of ultrafiltration rate and overall osmolality gradient between dialysis fluid and blood; and (3) model G, which is based on the linear relationship between ultrafiltration rate and glucose concentration gradient between dialysis fluid and blood. Diffusive mass transport coefficients (K(BD)) for glucose, urea, creatinine, potassium, and sodium were estimated using the modified Babb-Randerson-Farrell model. The high transport group had significantly lower dialysate volume and glucose and osmolality gradients between dialysate and blood, but significantly higher K(BD) for small solutes compared with the other transport groups. Osmotic conductance, fluid absorption rate, and initial ultrafiltration rate did not differ among the transport groups for model OS and model P. Model G yielded

  11. One dimensional polaron effects and current inhomogeneities in sequential phonon emission

    Energy Technology Data Exchange (ETDEWEB)

    Hellman, E.S.; Harris, J.S.; Hanna, C.; Laughlin, R.B.

    1985-07-01

    We have constructed a physical model to explain the tunneling current oscillations reported by Hickmott et al., for GaAs/AlGaAs heterostructures in high magnetic fields. We propose that the periodic structure observed is due to space charge which builds up in the undepleted layer when electrons enter it with energy just below the phonon emission threshold. Such electrons interact with the lattice to form polarons whose energy is pinned to the phonon energy, and thus has a very small group velocity. The polaron effect is strongly enhanced by the confinement of the electrons by the strong magnetic field. We infer from the current-voltage data that most of the tunneling current flows through a small area of the sample. The combined model gives reasonable quantitative agreement with experiment. 6 refs., 6 figs.

  12. One dimensional polaron effects and current inhomogeneities in sequential phonon emission

    International Nuclear Information System (INIS)

    Hellman, E.S.; Harris, J.S.; Hanna, C.; Laughlin, R.B.

    1985-07-01

    We have constructed a physical model to explain the tunneling current oscillations reported by Hickmott et al., for GaAs/AlGaAs heterostructures in high magnetic fields. We propose that the periodic structure observed is due to space charge which builds up in the undepleted layer when electrons enter it with energy just below the phonon emission threshold. Such electrons interact with the lattice to form polarons whose energy is pinned to the phonon energy, and thus has a very small group velocity. The polaron effect is strongly enhanced by the confinement of the electrons by the strong magnetic field. We infer from the current-voltage data that most of the tunneling current flows through a small area of the sample. The combined model gives reasonable quantitative agreement with experiment. 6 refs., 6 figs

  13. Charge transport in organic crystals

    Energy Technology Data Exchange (ETDEWEB)

    Ortmann, Frank

    2009-07-01

    The understanding of charge transport is one of the central goals in the research on semiconducting crystals. For organic crystals this is particularly complicated due to the strength of the electron-phonon interaction which requires the description of a seamless transition between the limiting cases of a coherent band-transport mechanism and incoherent hopping. In this thesis, charge transport phenomena in organic crystals are studied by theoretical means. A theory for charge transport in organic crystals is developed which covers the whole temperature range from low T, where it reproduces an expression from the Boltzmann equation for band transport, via elevated T, where it generalizes Holstein's small-polaron theory to finite bandwidths, up to high T, for which a temperature dependence equal to Marcus' electron-transfer theory is obtained. Thereby, coherent band transport and thermally induced hopping are treated on equal footing while simultaneously treating the electron-phonon interaction non-perturbatively. By avoiding the approximation of narrow polaron bands the theory allows for the description of large and small polarons and serves as a starting point for computational studies. The theoretical description is completed by using ab initio material parameters for the selected crystals under study. These material parameters are taken from density functional theory calculations for durene, naphthalene, and guanine crystals. Besides the analysis of the transport mechanism, special focus is put on the study of the relationship between mobility anisotropy and structure of the crystals. This study is supported by a 3D-visualization method for the transport channels in such crystals which has been derived in this thesis. (orig.)

  14. Neutron diffuse scattering in magnetite due to molecular polarons

    International Nuclear Information System (INIS)

    Yamada, Y.; Wakabayashi, N.; Nicklow, R.M.

    1980-01-01

    A detailed neutron diffuse scattering study has been carried out in order to verify a model which describes the property of valence fluctuations in magnetite above T/sub V/. This model assumes the existence of a complex which is composed of two excess electrons and a local displacement mode of oxygens within the fcc primitive cell. The complex is called a molecular polaron. It is assumed that at sufficiently high temperatures there is a random distribution of molecular polarons, which are fluctuating independently by making hopping motions through the crystal or by dissociating into smaller polarons. The lifetime of each molecular polaron is assumed to be long enough to induce an instantaneous strain field around it. Based on this model, the neutron diffuse scattering cross section due to randomly distributed dressed molecular polarons has been calculated. A precise measurement of the quasielastic scattering of neutrons has been carried out at 150 K. The observed results definitely show the characteristics which are predicted by the model calculation and, thus, give evidence for the existence of the proposed molecular polarons. From this standpoint, the Verwey transition of magnetite may be viewed as the cooperative ordering process of dressed molecular polarons. Possible extensions of the model to describe the ordering and the dynamical behavior of the molecular polarons are discussed

  15. Polaron binding energy in polymers: poly[methyl(phenyl)silylene

    Czech Academy of Sciences Publication Activity Database

    Nožár, Juraj; Nešpůrek, Stanislav; Šebera, Jakub

    2012-01-01

    Roč. 18, č. 2 (2012), s. 623-629 ISSN 1610-2940 R&D Projects: GA AV ČR KAN400720701 Institutional research plan: CEZ:AV0Z40500505 Keywords : polaron * polaron binding energy * polysilane Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.984, year: 2012

  16. Soliton and polaron generation in polyacetylene

    International Nuclear Information System (INIS)

    Su, Zhao-bin; Yu, Lu.

    1984-07-01

    The nonradiative decay of an e-h pair into soliton pair and that of an electron (hole) into polaron as well as the photoproduction of soliton pairs are considered using the lattice relaxation theory of multiphonon processes generalized to include the self-consistency of the multi-electron states with the lattice symmetry breaking. The selection rule which forbids the direct process of photogeneration for neutral pair is derived from the symmetry arguments. The branching ratio of the photogenerated neutral to charged soliton pairs is estimated. The recent related experiments are discussed. (author)

  17. Spectrally resolved hyperfine interactions between polaron and nuclear spins in organic light emitting diodes: Magneto-electroluminescence studies

    Energy Technology Data Exchange (ETDEWEB)

    Crooker, S. A.; Kelley, M. R.; Martinez, N. J. D.; Nie, W.; Mohite, A.; Nayyar, I. H.; Tretiak, S.; Smith, D. L. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Liu, F.; Ruden, P. P. [University of Minnesota, Minneapolis, Minnesota 55455 (United States)

    2014-10-13

    We use spectrally resolved magneto-electroluminescence (EL) measurements to study the energy dependence of hyperfine interactions between polaron and nuclear spins in organic light-emitting diodes. Using layered devices that generate bright exciplex emission, we show that the increase in EL emission intensity I due to small applied magnetic fields of order 100 mT is markedly larger at the high-energy blue end of the EL spectrum (ΔI/I ∼ 11%) than at the low-energy red end (∼4%). Concurrently, the widths of the magneto-EL curves increase monotonically from blue to red, revealing an increasing hyperfine coupling between polarons and nuclei and directly providing insight into the energy-dependent spatial extent and localization of polarons.

  18. Properties of a Bound Polaron under a Perpendicular Magnetic Field

    International Nuclear Information System (INIS)

    Liu Jia; Chen Ziyu; Xiao Jinglin; Huo Shufen

    2007-01-01

    We investigate the influence of a perpendicular magnetic field on a bound polaron near the interface of a polar-polar semiconductor with Rashba effect. The external magnetic field strongly changes the ground state binding energy of the polaron and the Rashba spin-orbit (SO) interaction originating from the inversion asymmetry in the heterostructure splits the ground state binding energy of the bound polaron. In this paper, we have shown how the ground state binding energy will be with the change of the external magnetic field, the location of a single impurity, the wave vector of the electron and the electron areal density, taking into account the SO coupling. Due to the presence of the phonons, whose energy gives negative contribution to the polaron's, the spin-splitting states of the bound polaron are more stable, and we find that in the condition of week magnetic field, the Zeeaman effect can be neglected.

  19. Weak coupling polaron and Landau-Zener scenario: Qubits modeling

    Science.gov (United States)

    Jipdi, M. N.; Tchoffo, M.; Fokou, I. F.; Fai, L. C.; Ateuafack, M. E.

    2017-06-01

    The paper presents a weak coupling polaron in a spherical dot with magnetic impurities and investigates conditions for which the system mimics a qubit. Particularly, the work focuses on the Landau-Zener (LZ) scenario undergone by the polaron and derives transition coefficients (transition probabilities) as well as selection rules for polaron's transitions. It is proven that, the magnetic impurities drive the polaron to a two-state superposition leading to a qubit structure. We also showed that the symmetry deficiency induced by the magnetic impurities (strong magnetic field) yields to the banishment of transition coefficients with non-stacking states. However, the transition coefficients revived for large confinement frequency (or weak magnetic field) with the orbital quantum numbers escorting transitions. The polaron is then shown to map a qubit independently of the number of relevant states with the transition coefficients lifted as LZ probabilities and given as a function of the electron-phonon coupling constant (Fröhlich constant).

  20. DFT+U study of polaronic conduction in Li2O2 and Li2CO3

    DEFF Research Database (Denmark)

    García Lastra, Juan Maria; Myrdal, J.S.G.; Christensen, Rune

    2013-01-01

    The main discharge products formed at the cathode of nonaqueous Li-air batteries are known to be Li2O2 and residual Li2CO3. Recent experiments indicate that the charge transport through these materials is the main limiting factor for the battery performance. It has been also shown...... that the performance of the battery decreases drastically when the amount of Li2CO3 at the cathode increases with respect to Li2O2. In this work, we study the formation and transport of hole and electron polarons in Li2O2 and Li2CO3 using density functional theory (DFT) within the PBE+U approximation. For both...... materials, we find that the formation of polarons (both hole and electron) is stabilized with respect to the delocalized states for all physically relevant values of U. We find a much higher mobility for hole polarons than for the electron polarons, and we show that the poor charge transport in Li2CO3...

  1. Magnetic Polarons in Anisotropic Quantum Dots

    Science.gov (United States)

    Oszwaldowski, Rafal; Petukhov, Andre; Zutic, Igor

    2010-03-01

    Tunability of confinement in magnetically-doped quantum dots (QDs) allows to tailor magnetism to an extent not available in bulk semiconductors. Versatile control of magnetic ordering, along with piezomagnetism, has been predicted even at a fixed number of carriers [1]. Recent experiments on colloidal QDs revealed strongly bound magnetic polarons (MPs) [2]. Previous studies of MPs in bulk semiconductors showed that the mean-field theory predicts a spurious magnetic phase transition, which is removed by taking into account spin fluctuations [3]. Here we present our theoretical results for MPs forming in QDs with pronounced magnetic anisotropy, which influences the spin fluctuations. We apply our findings to explain some peculiarities of the magnetic behavior of type-II ZnSe/(Zn,Mn)Te QDs, where magnetic polarons are found to persist to at least 200K [4]. Supported by ONR, AFOSR, and NSF-ECCS CAREER. [4pt] [1] R. M. Abolfath, A. G. Petukhov, and I. Zutic, Phys. Rev. Lett. 101, 207202 (2008); I. Zutic and A. G. Petukhov, Nature Mater.4, 623 (2009). [0pt] [2] R. Beaulac et al., Science 325, 973 (2009). [0pt] [3] T. Dietl and J. Spalek, Phys. Rev. Lett. 48, 355 (1982). [0pt] [4] I. R. Sellers, R. Oszwaldowski, et al., preprint; I. R. Sellers et al., Phys. Rev. Lett. 100, 136405 (2008).

  2. Size dependent polaronic conduction in hematite

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, Monika; Banday, Azeem; Murugavel, Sevi [Department of Physics and Astrophysics, University of Delhi, Delhi – 110 007 (India)

    2016-05-23

    Lithium Ion Batteries have been attracted as the major renewable energy source for all portable electronic devices because of its advantages like superior energy density, high theoretical capacity, high specific energy, stable cycling and less memory effects. Recently, α-Fe{sub 2}O{sub 3} has been considered as a potential anode material due to high specific capacity, low cost, high abundance and environmental benignity. We have synthesized α-Fe{sub 2}O{sub 3} with various sizes by using the ball milling and sol-gel procedure. Here, we report the dc conductivity measurement for the crystallite size ranging from 15 nm to 50 nm. It has been observed that the enhancement in the polaronic conductivity nearly two orders in magnitude while reducing the crystallite size from bulk into nano scale level. The enhancement in the conductivity is due to the augmented to compressive strain developed in the material which leads to pronounced decrease in the hopping length of polarons. Thus, nanocrystaline α-Fe{sub 2}O{sub 3} may be a better alternative anode material for lithium ion batteries than earlier reported systems.

  3. Size dependent polaronic conduction in hematite

    International Nuclear Information System (INIS)

    Sharma, Monika; Banday, Azeem; Murugavel, Sevi

    2016-01-01

    Lithium Ion Batteries have been attracted as the major renewable energy source for all portable electronic devices because of its advantages like superior energy density, high theoretical capacity, high specific energy, stable cycling and less memory effects. Recently, α-Fe_2O_3 has been considered as a potential anode material due to high specific capacity, low cost, high abundance and environmental benignity. We have synthesized α-Fe_2O_3 with various sizes by using the ball milling and sol-gel procedure. Here, we report the dc conductivity measurement for the crystallite size ranging from 15 nm to 50 nm. It has been observed that the enhancement in the polaronic conductivity nearly two orders in magnitude while reducing the crystallite size from bulk into nano scale level. The enhancement in the conductivity is due to the augmented to compressive strain developed in the material which leads to pronounced decrease in the hopping length of polarons. Thus, nanocrystaline α-Fe_2O_3 may be a better alternative anode material for lithium ion batteries than earlier reported systems.

  4. Heavy-flavour transport: from large to small systems

    Energy Technology Data Exchange (ETDEWEB)

    Beraudo, A.; De Pace, A.; Monteno, M.; Nardi, M.; Prino, F.

    2016-12-15

    Predictions for heavy-flavour production in relativistic heavy-ion experiments provided by the POWLANG transport setup, including now also an in-medium hadronization model, are displayed, After showing some representative findings for the Au-Au and Pb-Pb cases, a special focus will be devoted to the results obtained in the small systems formed in proton(deuteron)-nucleus collisions, where recent experimental data suggest the possible formation of a medium featuring a collective behaviour.

  5. The Bogolubov Representation of the Polaron Model and Its Completely Integrable RPA-Approximation

    International Nuclear Information System (INIS)

    Bogolubov, Nikolai N. Jr.; Prykarpatsky, Yarema A.; Ghazaryan, Anna A.

    2009-12-01

    The polaron model in ionic crystal is studied in the N. Bogolubov representation using a special RPA-approximation. A new exactly solvable approximated polaron model is derived and described in detail. Its free energy at finite temperature is calculated analytically. The polaron free energy in the constant magnetic field at finite temperature is also discussed. Based on the structure of the N. Bogolubov unitary transformed polaron Hamiltonian a very important new result is stated: the full polaron model is exactly solvable. (author)

  6. Screening effect on the polaron by surface plasmons

    Science.gov (United States)

    Xu, Xiaoying; Xu, Xiaoshan; Seal, Katyayani; Guo, Hangwen; Shen, Jian; Low Dimensional Materials Physics, Oak Ridge National Lab Team; University of Tennessee Team; Physics Department, Fudan University Team

    2011-03-01

    Surface plasmons occur when the conduction electrons at a metal/dielectric interface resonantly interact with external electromagnetic fields. While surface plasmons in vicinity of a polaron in the dielectric material, a strong screening effect on polaron characteristics is introduced. In this work, we observed the reduction of polarons in multiferroic LuFe2O4, which is mainly contributed by surface plasmons. Research sponsored by the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory, managed by UT-Battelle, LLC, for the U. S. Department of Energy.

  7. Bi-Polaron Condensation in High Tc Superconductors

    International Nuclear Information System (INIS)

    Ranninger, J.

    1995-01-01

    On the basis of optical measurements-, photoemission-, EXAFS- and neutron scattering-experiments we conclude that itinerant valence electrons coexist with localized bi-polarons.Entering the metallic phase upon chemical doping, a charge transfer between the two electronic subsystems is triggered off. We show that as the temperature is lowered towards Tc this process leads to a delocalization of bi-polarons due to a precursor effect of superfluidity of those bi-polarons. Upon entering the superconducting phase, these bipolarons ultimately condense into a superfluid state which is expected to largely determine the superconducting properties of high Tc materials. (authors)

  8. Method of T-products in polaron theory

    International Nuclear Information System (INIS)

    Bogolubov, N.N. Jr.; Kurbatov, A.M.; Kireev, A.N.

    1985-11-01

    T-products method is used for the investigation of equilibrium thermodynamic properties of Frohlich's model in polaron theory. Polaron free energy at finite temperatures is calculated on the basis of Bogolubov's variational principle. A trial function is chosen in the most general form corresponding to arbitrary number of oscillators harmonically interacting with electron. The upper bound to the polaron ground state energy in limiting case of weak interaction and low temperatures is obtained and investigated in detail. It is shown that the result becomes more exact by increasing the number of oscillators. (author)

  9. Multiphonon generation during photodissociation of slow Landau-Pekar polarons

    International Nuclear Information System (INIS)

    Myasnikov, E. N.; Myasnikova, A. E.; Mastropas, Z. P.

    2006-01-01

    The spectra of the low-temperature photodissociation (photoionization) of Landau-Pekar polarons are calculated using the theory of quantum-coherent states and a new method of variation with respect to the parameters of phonon vacuum deformation. It is shown that the final polaron states upon photodissociation may have different numbers of phonons produced in a single dissociation event and different momenta of charge carriers. The spectrum of optical absorption related to the photodissociation of polarons exhibits a superposition of bands corresponding to various numbers of phonons formed as a result of dissociation of a single polaron. Due to a large width of the energy region corresponding to the final states of charge carriers, the halfwidth of each band is on the order of the energy of polaron coupling and is much greater than the phonon energy. For this reason, the individual phonon bands exhibit strong overlap. The very broad and, probably, structureless band formed as a result of the superposition of all these components begins at an energy equal to the sum of the polaron coupling energy (E p ) and the phonon energy. This band has a maximum at a frequency of about 5.6E p /ℎ and a halfwidth on the order of 5.6E p /ℎ at a unit effective mass (m* = m e ) of band electrons. For an effective charge carrier mass within m* = (1-3)m e , the energy of the polaron band maximum can be estimated as 5E p with an error of about 10%, and the halfwidth falls within 3.4E p 1/2 p . The multiphonon character of this band is related to a decay of the phonon condensate after the escape of charge carrier from a polaron. Such polarons are likely to be observed in the spectra of complex metal oxides, including high-temperature superconductors. Examples of such polaron bands in the reported absorption and photoconductivity spectra of nonstoichiometric cuprates, manganites, nickelates, and titanates are presented. A theory of the formation of Landau-Pekar polarons with the

  10. Influence of quasi-particle density over polaron mobility in armchair graphene nanoribbons.

    Science.gov (United States)

    Silva, Gesiel Gomes; da Cunha, Wiliam Ferreira; de Sousa Junior, Rafael Timóteo; Almeida Fonseca, Antonio Luciano; Ribeiro Júnior, Luiz Antônio; E Silva, Geraldo Magela

    2018-06-20

    An important aspect concerning the performance of armchair graphene nanoribbons (AGNRs) as materials for conceiving electronic devices is related to the mobility of charge carriers in these systems. When several polarons are considered in the system, a quasi-particle wave function can be affected by that of its neighbor provided the two are close enough. As the overlap may affect the transport of the carrier, the question concerning how the density of polarons affect its mobility arises. In this work, we investigate such dependence for semiconducting AGNRs in the scope of nonadiabatic molecular dynamics. Our results unambiguously show an impact of the density on both the stability and average velocity of the quasi-particles. We have found a phase transition between regimes where increasing density stops inhibiting and starts promoting mobility; densities higher than 7 polarons per 45 Å present increasing mean velocity with increasing density. We have also established three different regions relating electric field and average velocity. For the lowest electric field regime, surpassing the aforementioned threshold results in overcoming the 0.3 Å fs-1 limit, thus representing a transition between subsonic and supersonic regimes. For the highest of the electric fields, density effects alone are responsible for a stunning difference of 1.5 Å fs-1 in the mean carrier velocity.

  11. Energy Migration in Organic Thin Films--From Excitons to Polarons

    Science.gov (United States)

    Mullenbach, Tyler K.

    The rise of organic photovoltaic devices (OPVs) and organic light-emitting devices has generated interest in the physics governing exciton and polaron dynamics in thin films. Energy transfer has been well studied in dilute solutions, but there are emergent properties in thin films and greater complications due to complex morphologies which must be better understood. Despite the intense interest in energy transport in thin films, experimental limitations have slowed discoveries. Here, a new perspective of OPV operation is presented where photovoltage, instead of photocurrent, plays the fundamental role. By exploiting this new vantage point the first method of measuring the diffusion length (LD) of dark (non-luminescent) excitons is developed, a novel photodetector is invented, and the ability to watch exciton arrival, in real-time, at the donor-acceptor heterojunction is presented. Using an enhanced understanding of exciton migration in thin films, paradigms for enhancing LD by molecular modifications are discovered, and the first exciton gate is experimentally and theoretically demonstrated. Generation of polarons from exciton dissociation represents a second phase of energy migration in OPVs that remains understudied. Current approaches are capable of measuring the rate of charge carrier recombination only at open-circuit. To enable a better understanding of polaron dynamics in thin films, two new approaches are presented which are capable of measuring both the charge carrier recombination and transit rates at any OPV operating voltage. These techniques pave the way for a more complete understanding of charge carrier kinetics in molecular thin films.

  12. 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.

  13. Urea transporter proteins as targets for small-molecule diuretics.

    Science.gov (United States)

    Esteva-Font, Cristina; Anderson, Marc O; Verkman, Alan S

    2015-02-01

    Conventional diuretics such as furosemide and thiazides target salt transporters in kidney tubules, but urea transporters (UTs) have emerged as alternative targets. UTs are a family of transmembrane channels expressed in a variety of mammalian tissues, in particular the kidney. UT knockout mice and humans with UT mutations exhibit reduced maximal urinary osmolality, demonstrating that UTs are necessary for the concentration of urine. Small-molecule screening has identified potent and selective inhibitors of UT-A, the UT protein expressed in renal tubule epithelial cells, and UT-B, the UT protein expressed in vasa recta endothelial cells. Data from UT knockout mice and from rodents administered UT inhibitors support the diuretic action of UT inhibition. The kidney-specific expression of UT-A1, together with high selectivity of the small-molecule inhibitors, means that off-target effects of such small-molecule drugs should be minimal. This Review summarizes the structure, expression and function of UTs, and looks at the evidence supporting the validity of UTs as targets for the development of salt-sparing diuretics with a unique mechanism of action. UT-targeted inhibitors may be useful alone or in combination with conventional diuretics for therapy of various oedemas and hyponatraemias, potentially including those refractory to treatment with current diuretics.

  14. Quasi-one-dimensional polaronic states due to the preferential reduction in the Li sub 1 sub + sub x V sub 3 O sub 8 insertion electrode

    CERN Document Server

    Onoda, M

    2003-01-01

    The structural and electronic properties of the Li sub 1 sub + sub x V sub 3 O sub 8 insertion electrode, where 0 sup 0.1 with nearly stoichiometric oxygen atoms, small polarons exist without carrier-creation energy at high temperatures, while at low temperatures the conduction may be of variable-range hopping (VRH) type. For x > 0.2, one-dimensional magnetic properties appear due to sizable exchange couplings and order-disorder effects of additional Li ions may lead to significant change of transport properties. For the intermediate composition 0 < x sup<= 0.1, strong randomness of the Li doping and the congenital oxygen deficiency cause VRH states even at high temperatures.

  15. Electromagnetic fields in small systems from a multiphase transport model

    Science.gov (United States)

    Zhao, Xin-Li; Ma, Yu-Gang; Ma, Guo-Liang

    2018-02-01

    We calculate the electromagnetic fields generated in small systems by using a multiphase transport (AMPT) model. Compared to A +A collisions, we find that the absolute electric and magnetic fields are not small in p +Au and d +Au collisions at energies available at the BNL Relativistic Heavy Ion Collider and in p +Pb collisions at energies available at the CERN Large Hadron Collider. We study the centrality dependencies and the spatial distributions of electromagnetic fields. We further investigate the azimuthal fluctuations of the magnetic field and its correlation with the fluctuating geometry using event-by-event simulations. We find that the azimuthal correlation 〈" close="〉cos(ϕα+ϕβ-2 ΨRP)〉">cos2 (ΨB-Ψ2) between the magnetic field direction and the second-harmonic participant plane is almost zero in small systems with high multiplicities, but not in those with low multiplicities. This indicates that the charge azimuthal correlation is not a valid probe to study the chiral magnetic effect (CME) in small systems with high multiplicities. However, we suggest searching for possible CME effects in small systems with low multiplicities.

  16. Semiclassical and quantum polarons in crystalline acetanilide

    Science.gov (United States)

    Hamm, P.; Tsironis, G. P.

    2007-08-01

    Crystalline acetanilide is a an organic solid with peptide bond structure similar to that of proteins. Two states appear in the amide I spectral region having drastically different properties: one is strongly temperature dependent and disappears at high temperatures while the other is stable at all temperatures. Experimental and theoretical work over the past twenty five years has assigned the former to a selftrapped state while the latter to an extended free exciton state. In this article we review the experimental and theoretical developments on acetanilide paying particular attention to issues that are still pending. Although the interpretation of the states is experimentally sound, we find that specific theoretical comprehension is still lacking. Among the issues that that appear not well understood is the effective dimensionality of the selftrapped polaron and free exciton states.

  17. Small Aircraft Transportation System, Higher Volume Operations Concept: Normal Operations

    Science.gov (United States)

    Abbott, Terence S.; Jones, Kenneth M.; Consiglio, Maria C.; Williams, Daniel M.; Adams, Catherine A.

    2004-01-01

    This document defines the Small Aircraft Transportation System (SATS), Higher Volume Operations (HVO) concept for normal conditions. In this concept, a block of airspace would be established around designated non-towered, non-radar airports during periods of poor weather. Within this new airspace, pilots would take responsibility for separation assurance between their aircraft and other similarly equipped aircraft. Using onboard equipment and procedures, they would then approach and land at the airport. Departures would be handled in a similar fashion. The details for this operational concept are provided in this document.

  18. Small Aircraft Transportation System Higher Volume Operations Concept

    Science.gov (United States)

    Abbott, Terence S.; Consiglio, Maria C.; Baxley, Brian T.; Williams, Daniel M.; Jones, Kenneth M.; Adams, Catherine A.

    2006-01-01

    This document defines the Small Aircraft Transportation System (SATS) Higher Volume Operations concept. The general philosophy underlying this concept is the establishment of a newly defined area of flight operations called a Self-Controlled Area (SCA). Within the SCA, pilots would take responsibility for separation assurance between their aircraft and other similarly equipped aircraft. This document also provides details for a number of off-nominal and emergency procedures which address situations that could be expected to occur in a future SCA. The details for this operational concept along with a description of candidate aircraft systems to support this concept are provided.

  19. Influence of impurities on the polaron effective mass

    International Nuclear Information System (INIS)

    Lima, R.A.T. de.

    1975-01-01

    Using the Green Function formalism, it is verified the Rodriguez's model for the effective mass of the polaron at finite temperature in the presence of 'traps'. Some aspects of this model were discussed. (M.W.O.) [pt

  20. Polaron self-localization in white-light emitting hybrid perovskites

    KAUST Repository

    Cortecchia, Daniele

    2017-02-03

    Two-dimensional (2D) perovskites with the general formula APbX are attracting increasing interest as solution processable, white-light emissive materials. Recent studies have shown that their broadband emission is related to the formation of intra-gap colour centres. Here, we provide an in-depth description of the charge localization sites underlying the generation of such radiative centres and their corresponding decay dynamics, highlighting the formation of small polarons trapped within their lattice distortion field. Using a combination of spectroscopic techniques and first-principles calculations to study the white-light emitting 2D perovskites (EDBE)PbCl and (EDBE)PbBr, we infer the formation of Pb , Pb, and X (where X = Cl or Br) species confined within the inorganic perovskite framework. Due to strong Coulombic interactions, these species retain their original excitonic character and form self-trapped polaron-excitons acting as radiative colour centres. These findings are expected to be relevant for a broad class of white-light emitting perovskites with large polaron relaxation energy.

  1. Holstein polaron in a valley-degenerate two-dimensional semiconductor.

    Science.gov (United States)

    Kang, Mingu; Jung, Sung Won; Shin, Woo Jong; Sohn, Yeongsup; Ryu, Sae Hee; Kim, Timur K; Hoesch, Moritz; Kim, Keun Su

    2018-05-28

    Two-dimensional (2D) crystals have emerged as a class of materials with tunable carrier density 1 . Carrier doping to 2D semiconductors can be used to modulate many-body interactions 2 and to explore novel composite particles. The Holstein polaron is a small composite particle of an electron that carries a cloud of self-induced lattice deformation (or phonons) 3-5 , which has been proposed to play a key role in high-temperature superconductivity 6 and carrier mobility in devices 7 . Here we report the discovery of Holstein polarons in a surface-doped layered semiconductor, MoS 2 , in which a puzzling 2D superconducting dome with the critical temperature of 12 K was found recently 8-11 . Using a high-resolution band mapping of charge carriers, we found strong band renormalizations collectively identified as a hitherto unobserved spectral function of Holstein polarons 12-18 . The short-range nature of electron-phonon (e-ph) coupling in MoS 2 can be explained by its valley degeneracy, which enables strong intervalley coupling mediated by acoustic phonons. The coupling strength is found to increase gradually along the superconducting dome up to the intermediate regime, which suggests a bipolaronic pairing in the 2D superconductivity.

  2. Specific lysosomal transport of small neutral amino acids

    International Nuclear Information System (INIS)

    Pisoni, R.L.; Flickinger, K.S.; Thoene, J.G.; Christensen, H.N.

    1986-01-01

    Studies of amino acid exodus from lysosomes have allowed us previously to describe transport systems specific for cystine and another for cationic amino acids in fibroblast lysosomes. They are now able to study amino acid uptake into highly purified fibroblast lysosomes obtained by separating crude granular fraction on gradients formed by centrifugation in 35% isoosmotic Percoll solutions. Analog inhibition and saturation studies indicate that L-[ 14 C]proline (50 μM) uptake by fibroblast lysosomes at 37 0 C in 50 mM citrate/tris pH 7.0 buffer containing 0.25 M sucrose is mediated by two transport systems, one largely specific for L-proline and the other for which transport is shared with small neutral amino acids such as alanine, serine and threonine. At 7 mM, L-proline inhibits L-[ 14 C]proline uptake almost completely, whereas ala, ser, val, thr, gly, N-methylalanine and sarcosine inhibit proline uptake by 50-65%. The system shared by alanine, serine and threonine is further characterized by these amino acids strongly inhibiting the uptakes of each other. Lysosomal proline transport is selective for the L-isomer of the amino acid, and is scarcely inhibited by 7 mM arg, glu, asp, leu, phe, his, met, (methylamino) isobutyrate, betaine or N,N-dimethylglycine. Cis or trans-4-hydroxy-L-proline inhibit proline uptake only slightly. In sharp contrast to the fibroblast plasma membrane in which Na + is required for most proline and alanine transport, lysosomal uptake of these amino acids occurs independently of Na +

  3. Tracking polaron generation in electrochemically doped polyaniline thin films

    Science.gov (United States)

    Kalagi, S. S.; Patil, P. S.

    2018-04-01

    Electrochemically deposited polyaniline films on ITO substrates have been studied for their optical properties. π-π*transitions inducing the formation of polarons and bipolarons have been studied from the optical spectra. The generation of these quasiparticles and the corresponding quantum of energy stored has been analysed and calculated from the experimental data. The evolution of polaron with increased levels of protonation has been identified and the necessary energy required for the transitions have been explained with the help of band structure diagram.

  4. 78 FR 70617 - Notice of Funding Availability for the Small Business Transportation Resource Center Program

    Science.gov (United States)

    2013-11-26

    ... assistance, business training programs, business assessment, management training, counseling, marketing and... assessment of the regional small business transportation community needs. (B) General Management & Technical... improve the management of their own small business to expand their transportation- related contracts and...

  5. Analysis of Small Aircraft as a Transportation System

    Science.gov (United States)

    Dollyhigh, Samuel M.; Yackovetsky, Robert E. (Technical Monitor)

    2002-01-01

    An analysis was conducted to examine the market viability of small aircraft as a transportation mode in competition with automobile and scheduled commercial air travel by estimating the pool of users that would potentially switch to on-demand air travel due to cost/time savings. The basis for the analysis model was the Integrated Air Transportation System Evaluation Tool (IATSET) which was developed under contract to NASA by the Logistics Management Institute. IATSET is a macroeconomic model that predicts at a National level the mode choice between automobile, scheduled air, and on-demand air travel based on the value of a travelers time and monetary cost of the trip. A number of modifications are detailed to the original IATSET to better model the changing small aircraft environment. The potential trip market was modeled for the Eclipse 500 operated as a corporate jet and as an air taxi for the business travel market. The Cirrus 20R and a $80K single engine piston aircraft (based on automobile manufacturing technology) are evaluated in the pleasure and personal business travel market.

  6. Spin-polarons and high-Tc superconductivity

    International Nuclear Information System (INIS)

    Wood, R.F.

    1994-03-01

    The spin-polaron concept is introduced in analogy to ionic and electronic polarons and the assumptions underlying the author's approach to spin-polaron mediated high-T c superconductivity are discussed. Elementary considerations about the spin-polaron formation energy are reviewed and the possible origin of the pairing mechanism illustrated schematically. The electronic structure of the CuO 2 planes is treated from the standpoint of antiferromagnetic band calculations that lead directly to the picture of holes predominantly on the oxygen sublattice in a Mott-Hubbard/charge transfer insulator. Assuming the holes to be described in a Bloch representation but with the effective mass renormalized by spin-polaron formation, equations for the superconducting gap, Δ, and transition temperature, T c , are developed and the symmetry of Δ discussed. After further simplifications, T c is calculated as a function of the carrier concentration, x. It is shown that the calculated behavior of T c (x) follows the experimental results closely and leads to a natural explanation of the effects of under- and over-doping. The paper concludes with a few remarks about the evidence for the carriers being fermions (polarons) or bosons (bipolarons)

  7. Transportable, small high-pressure preservation vessel for cells

    International Nuclear Information System (INIS)

    Kamimura, N; Sotome, S; Shimizu, A; Nakajima, K; Yoshimura, Y

    2010-01-01

    We have previously reported that the survival rate of astrocytes increases under high-pressure conditions at 4 0 C. However, pressure vessels generally have numerous problems for use in cell preservation and transportation: (1) they cannot be readily separated from the pressurizing pump in the pressurized state; (2) they are typically heavy and expensive due the use of materials such as stainless steel; and (3) it is difficult to regulate pressurization rate with hand pumps. Therefore, we developed a transportable high-pressure system suitable for cell preservation under high-pressure conditions. This high-pressure vessel has the following characteristics: (1) it can be easily separated from the pressurizing pump due to the use of a cock-type stop valve; (2) it is small and compact, is made of PEEK and weighs less than 200 g; and (3) pressurization rate is regulated by an electric pump instead of a hand pump. Using this transportable high-pressure vessel for cell preservation, we found that astrocytes can survive for 4 days at 1.6 MPa and 4 0 C.

  8. Hole polaron-polaron interaction in transition metal oxides and its limit to p-type doping

    Science.gov (United States)

    Chen, Shiyou; Wang, Lin-Wang

    2014-03-01

    Traditionally the origin of the poor p-type conductivity in some transition metal oxides (TMOs) was attributed to the limited hole concentration: the charge-compensating donor defects, such as oxygen vacancies and cation interstitials, can form spontaneously as the Fermi energy shifts down to near the valence band maximum. Besides the thermodynamic limit to the hole concentration, the limit to the hole mobility can be another possible reason, e.g., the hole carrier can form self-trapped polarons with very low carrier mobility. Although isolated hole polarons had been found in some TMOs, the polaron-polaron interaction is not well-studied. Here we show that in TMOs such as TiO2 and V2O5, the hole polarons prefer to bind with each other to form bipolarons, which are more stable than free hole carriers or separated polarons. This pushes the hole states upward into the conduction band and traps the holes. The rise of the Fermi energy suppresses the spontaneous formation of the charge-compensating donor defects, so the conventional mechanism becomes ineffective. Since it can happen in the impurity-free TMO lattices, independent of any extrinsic dopant, it acts as an intrinsic and general limit to the p-type conductivity in these TMOs. This material is based upon work performed by the JCAP, a US DOE Energy Innovation Hub, the NSFC (No. 61106087 and 91233121) and special funds for major state basic research (No. 2012CB921401).

  9. Fundamental models of electronic transport in amorphous semiconductors

    International Nuclear Information System (INIS)

    Emin, D.

    1982-01-01

    Significant fundamental questions lie at the heart of our understanding of the electronic and optical properties of semiconducting and insulating glasses. In this article the principal features of the Mott-CFO model and the small-polaron model are described. While the Mott-CFO model seems to apply to the high-mobility electron transport in glassy SiO 2 and Cd 2 As 3 it does not appear applicable to the most frequently studied chalocogenide glasses. Furthermore, the Mott-CFO model does not account for as basic a feature as the sign of the Hall effect. On the other hand, the small-polaron model accounts for the observed d.c. conductivity, Peltier heat and Hall mobility in a very simple and direct manner

  10. Electrical transport properties of V2O5 thin films obtained by thermal annealing of layers grown by RF magnetron sputtering at room temperature

    International Nuclear Information System (INIS)

    Giannetta, H.M.R.; Calaza, C.; Lamas, D.G.; Fonseca, L.; Fraigi, L.

    2015-01-01

    The present study investigates the main electrical transport mechanism in V 2 O 5 thin films deposited by RF magnetron sputtering on the basis of the Mott's small polaron hopping model. The material under test was obtained at room temperature from a V 2 O 5 target and then oxidized at high temperature under air atmosphere to obtain the desired V 2 O 5 phase. The dependence of the electrical conductivity of the V 2 O 5 thin films with temperature was analyzed using the Mott's small polarons hopping transport model under the Schnakenberg form. Model results suggest a polaron binding energy W H = 0.1682 eV, with a structural disorder energy W D = 0.2241 eV and an optical phonon frequency ν 0 = 0.468 × 10 13 s −1 . These results are in agreement with data reported in literature for single crystal V 2 O 5 . However, the carrier mobility μ = 1.5019 × 10 −5 cm 2 /Vs computed in the non-adiabatic regime is significantly smaller than that of the single crystal, suggesting a strong electron–phonon coupling in the V 2 O 5 thin films obtained with the proposed deposition method. - Highlights: • A two-stage deposition method compatible with lift-off patterning is proposed. • V 2 O 5 films are deposited by RF magnetron sputtering and then annealed in air. • Films are analyzed by SEM and its pure phase nature is confirmed by XRD. • Electrical conductivity was fitted using Mott's model for small polarons. • Fit derived parameters confirm charge transport through small-polarons hopping

  11. Electrical transport properties of V{sub 2}O{sub 5} thin films obtained by thermal annealing of layers grown by RF magnetron sputtering at room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Giannetta, H.M.R., E-mail: hgiann@inti.gov.ar [Centro de Micro y Nano Electrónica del Bicentenario (CMNB), Instituto Nacional de Tecnología Industrial (INTI), San Martín, Buenos Aires (Argentina); Universidad Tecnológica Nacional (UTN) — Facultad Regional Buenos Aires (FRBA) (Argentina); Calaza, C. [Instituto de Microelectrónica de Barcelona, Centro Nacional de Microelectrónica (IMB-CNM, CSIC), Campus UAB, Bellaterra, 08193 Barcelona (Spain); Lamas, D.G. [Universidad Nacional del Comahue CONICET-CITEFA — Laboratorio de Caracterización de Materiales, Facultad de Ingeniería, Neuquen (Argentina); Fonseca, L. [Instituto de Microelectrónica de Barcelona, Centro Nacional de Microelectrónica (IMB-CNM, CSIC), Campus UAB, Bellaterra, 08193 Barcelona (Spain); Fraigi, L. [Centro de Micro y Nano Electrónica del Bicentenario (CMNB), Instituto Nacional de Tecnología Industrial (INTI), San Martín, Buenos Aires (Argentina); Universidad Tecnológica Nacional (UTN) — Facultad Regional Buenos Aires (FRBA) (Argentina)

    2015-08-31

    The present study investigates the main electrical transport mechanism in V{sub 2}O{sub 5} thin films deposited by RF magnetron sputtering on the basis of the Mott's small polaron hopping model. The material under test was obtained at room temperature from a V{sub 2}O{sub 5} target and then oxidized at high temperature under air atmosphere to obtain the desired V{sub 2}O{sub 5} phase. The dependence of the electrical conductivity of the V{sub 2}O{sub 5} thin films with temperature was analyzed using the Mott's small polarons hopping transport model under the Schnakenberg form. Model results suggest a polaron binding energy W{sub H} = 0.1682 eV, with a structural disorder energy W{sub D} = 0.2241 eV and an optical phonon frequency ν{sub 0} = 0.468 × 10{sup 13}s{sup −1}. These results are in agreement with data reported in literature for single crystal V{sub 2}O{sub 5}. However, the carrier mobility μ = 1.5019 × 10{sup −5} cm{sup 2}/Vs computed in the non-adiabatic regime is significantly smaller than that of the single crystal, suggesting a strong electron–phonon coupling in the V{sub 2}O{sub 5} thin films obtained with the proposed deposition method. - Highlights: • A two-stage deposition method compatible with lift-off patterning is proposed. • V{sub 2}O{sub 5} films are deposited by RF magnetron sputtering and then annealed in air. • Films are analyzed by SEM and its pure phase nature is confirmed by XRD. • Electrical conductivity was fitted using Mott's model for small polarons. • Fit derived parameters confirm charge transport through small-polarons hopping.

  12. The contribution of free water transport and small pore transport to the total fluid removal in peritoneal dialysis

    NARCIS (Netherlands)

    Parikova, Alena; Smit, Watske; Struijk, Dirk G.; Zweers, Machteld M.; Krediet, Raymond T.

    2005-01-01

    BACKGROUND: Water transport in peritoneal dialysis (PD) patients is across the small pores and water channels, the latter allowing free water transport. The objective of the study was to investigate the contribution of each transport route on transcapillary ultrafiltration (TCUF). METHODS: Standard

  13. Polaron Self-localization in White-light Emitting Hybrid Perovskites

    OpenAIRE

    Cortecchia, Daniele; Yin, Jun; Bruno, Annalisa; Lo, Shu-Zee Alencious; Gurzadyan, Gagik G.; Mhaisalkar, Subodh; Brédas, Jean-Luc; Soci, Cesare

    2016-01-01

    Two-dimensional (2D) perovskites with general formula $APbX_4$ are attracting increasing interest as solution processable, white-light emissive materials. Recent studies have shown that their broadband emission is related to the formation of intra-gap color centers; however, the nature and dynamics of the emissive species have remained elusive. Here we show that the broadband photoluminescence of the 2D perovskites $(EDBE)PbCl_4$ and $(EDBE)PbBr_4$ stems from the localization of small polaron...

  14. Logarithmic corrections in a quantization rule. The polaron spectrum

    International Nuclear Information System (INIS)

    Karasev, M.V.; Pereskokov, A.V.

    1994-01-01

    A nonlinear integrodifferential equation that arises in polaron theory is considered. The integral nonlinearity is given by a convolution with the Coulomb potential. Radially symmetric solutions are sought. In the semiclassical limit, an equation for the self-consistent potential is found and studied. The potential has a logarithmic singularity at the origin, and also a turning point at 1. The phase shifts at these points are determined. The quantization rule that takes into account the logarithmic corrections gives a simple asymptotic formula for the polaron spectrum. Global semiclassical solutions of the original nonlinear equation are constructed. 18 refs., 1 tab

  15. Polaronic and dressed molecular states in orbital Feshbach resonances

    Science.gov (United States)

    Xu, Junjun; Qi, Ran

    2018-04-01

    We consider the impurity problem in an orbital Feshbach resonance (OFR), with a single excited clock state | e ↑⟩ atom immersed in a Fermi sea of electronic ground state | g ↓⟩. We calculate the polaron effective mass and quasi-particle residue, as well as the polaron to molecule transition. By including one particle-hole excitation in the molecular state, we find significant correction to the transition point. This transition point moves toward the BCS side for increasing particle densities, which suggests that the corresponding many-body physics is similar to a narrow resonance.

  16. A self-consistent theory of the magnetic polaron

    International Nuclear Information System (INIS)

    Marvakov, D.I.; Kuzemsky, A.L.; Vlahov, J.P.

    1984-10-01

    A finite temperature self-consistent theory of magnetic polaron in the s-f model of ferromagnetic semiconductors is developed. The calculations are based on the novel approach of the thermodynamic two-time Green function methods. This approach consists in the introduction of the ''irreducible'' Green functions (IGF) and derivation of the exact Dyson equation and exact self-energy operator. It is shown that IGF method gives a unified and natural approach for a calculation of the magnetic polaron states by taking explicitly into account the damping effects and finite lifetime. (author)

  17. Al-bound hole polarons in TiO2

    International Nuclear Information System (INIS)

    Stashans, Arvids; Bermeo, Sthefano

    2009-01-01

    Changes in the structural and electronic properties of TiO 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 ΔSCF approach.

  18. 77 FR 10943 - Small Business Size Standards: Transportation and Warehousing

    Science.gov (United States)

    2012-02-24

    ... 14.0 Transportation. 485510 Charter Bus Industry 7.0 14.0 485991 Special Needs Transportation... NAICS Sector 48-49. That represents 0.7 percent of total firms in industries in that Sector that have... Limousine Service 14.0 485410 School and Employee Bus 14.0 Transportation. 485510 Charter Bus Industry 14.0...

  19. Spin fluctuation and small polaron conduction dominated electrical ...

    Indian Academy of Sciences (India)

    Administrator

    temperature regime (20 K < T < 53 K), shows a minima near 53 K and increases with T ... Manganite nanoparticles; resistivity; spin fluctuation; electron–phonon interaction; electron– ... the low-doped regime because of the series of structural,.

  20. Oregon department of transportation small business group twice-monthly payments pilot project : summary report.

    Science.gov (United States)

    2008-07-01

    Oregon Department of Transportation (ODOT) recently completed a pilot study on small business payment practices. In the study, three pilot projects were tested where payments to small business contractors were changed from a monthly payment to twice-...

  1. Trapping, self-trapping and the polaron family

    International Nuclear Information System (INIS)

    Stoneham, A M; Gavartin, J; Shluger, A L; Kimmel, A V; Ramo, D Munoz; Roennow, H M; Aeppli, G; Renner, C

    2007-01-01

    The earliest ideas of the polaron recognized that the coupling of an electron to ionic vibrations would affect its apparent mass and could effectively immobilize the carrier (self-trapping). We discuss how these basic ideas have been generalized to recognize new materials and new phenomena. First, there is an interplay between self-trapping and trapping associated with defects or with fluctuations in an amorphous solid. In high dielectric constant oxides, like HfO 2 , this leads to oxygen vacancies having as many as five charge states. In colossal magnetoresistance manganites, this interplay makes possible the scanning tunnelling microscopy (STM) observation of polarons. Second, excitons can self-trap and, by doing so, localize energy in ways that can modify the material properties. Third, new materials introduce new features, with polaron-related ideas emerging for uranium dioxide, gate dielectric oxides, Jahn-Teller systems, semiconducting polymers and biological systems. The phonon modes that initiate self-trapping can be quite different from the longitudinal optic modes usually assumed to dominate. Fourth, there are new phenomena, like possible magnetism in simple oxides, or with the evolution of short-lived polarons, like muons or excitons. The central idea remains that of a particle whose properties are modified by polarizing or deforming its host solid, sometimes profoundly. However, some of the simpler standard assumptions can give a limited, indeed misleading, description of real systems, with qualitative inconsistencies. We discuss representative cases for which theory and experiment can be compared in detail

  2. Localized polarons and doorway vibrons in finite quantum structures

    Czech Academy of Sciences Publication Activity Database

    Fehske, H.; Wellein, G.; Loos, Jan; Bishop, A. R.

    2008-01-01

    Roč. 77, č. 8 (2008), 085117/1-085117/6 ISSN 1098-0121 Institutional research plan: CEZ:AV0Z10100521 Keywords : quantum dots * electron - phonon interaction * polarons Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.322, year: 2008

  3. Polaron effects on the dc- and ac-tunneling characteristics of molecular Josephson junctions

    Science.gov (United States)

    Wu, B. H.; Cao, J. C.; Timm, C.

    2012-07-01

    We study the interplay of polaronic effect and superconductivity in transport through molecular Josephson junctions. The tunneling rates of electrons are dominated by vibronic replicas of the superconducting gap, which show up as prominent features in the differential conductance for the dc and ac current. For relatively large molecule-lead coupling, a features that appears when the Josephson frequency matches the vibron frequency can be identified with an over-the-gap structure observed by Marchenkov [Nat. Nanotech. 1748-338710.1038/nnano.2007.2182, 481 (2007)]. However, we are more concerned with the weak-coupling limit, where resonant tunneling through the molecular level dominates. We find that certain features involving both Andreev reflection and vibron emission show an unusual shift of the bias voltage V at their maximum with the gate voltage Vg as V˜(2/3)Vg. Moreover, due to the polaronic effect, the ac Josephson current shows a phase shift of π when the bias eV is increased by one vibronic energy quantum ℏωv. This distinctive even-odd effect is explained in terms of the different sign of the coupling to vibrons of electrons and of Andreev-reflected holes.

  4. Production and cost of harvesting, processing, and transporting small-diameter (< 5 inches) trees for energy

    Science.gov (United States)

    Fei Pan; Han-Sup Han; Leonard R. Johnson; William J. Elliot

    2008-01-01

    Dense, small-diameter stands generally require thinning from below to improve fire-tolerance. The resulting forest biomass can be used for energy production. The cost of harvesting, processing, and transporting small-diameter trees often exceeds revenues due to high costs associated with harvesting and transportation and low market values for forest biomass....

  5. 14 CFR 135.397 - Small transport category airplane performance operating limitations.

    Science.gov (United States)

    2010-01-01

    ... 14 Aeronautics and Space 3 2010-01-01 2010-01-01 false Small transport category airplane... PERSONS ON BOARD SUCH AIRCRAFT Airplane Performance Operating Limitations § 135.397 Small transport category airplane performance operating limitations. (a) No person may operate a reciprocating engine...

  6. Understanding Transportation Choice of Families with Small Children in Oslo

    OpenAIRE

    Miller, Scott Thomas

    2011-01-01

    This qualitative study took place in the Oslo area and focused on the transportation mode choices of parents with children in day care. Understanding why parents choose a certain mode of transport was the main objective of this research. Answers to the question of why were looked at in the context of theories stemming from urban planning, sociology, psychology amongst others. The findings show that while geographical distances did have the largest impact on how people travelled around work h...

  7. Kinetics of transmembrane transport of small molecules into electropermeabilized cells.

    Science.gov (United States)

    Pucihar, Gorazd; Kotnik, Tadej; Miklavcic, Damijan; Teissié, Justin

    2008-09-15

    The transport of propidium iodide into electropermeabilized Chinese hamster ovary cells was monitored with a photomultiplier tube during and after the electric pulse. The influence of pulse amplitude and duration on the transport kinetics was investigated with time resolutions from 200 ns to 4 ms in intervals from 400 micros to 8 s. The transport became detectable as early as 60 micros after the start of the pulse, continued for tens of seconds after the pulse, and was faster and larger for higher pulse amplitudes and/or longer pulse durations. With fixed pulse parameters, transport into confluent monolayers of cells was slower than transport into suspended cells. Different time courses of fluorescence increase were observed during and at various times after the pulse, reflecting different transport mechanisms and ongoing membrane resealing. The data were compared to theoretical predictions of the Nernst-Planck equation. After a delay of 60 micros, the time course of fluorescence during the pulse was approximately linear, supporting a mainly electrophoretic solution of the Nernst-Planck equation. The time course after the pulse agreed with diffusional solution of the Nernst-Planck equation if the membrane resealing was assumed to consist of three distinct components, with time constants in the range of tens of microseconds, hundreds of microseconds, and tens of seconds, respectively.

  8. Correlation between excited d-orbital electron lifetime in polaron dynamics and coloration of WO3 upon ultraviolet exposure

    Science.gov (United States)

    Lee, Young-Ahn; Han, Seung-Ik; Rhee, Hanju; Seo, Hyungtak

    2018-05-01

    Polarons have been suggested to explain the mechanism of the coloration of WO3 induced by UV light. However, despite the many experimental results that support small polarons as a key mechanism, direct observation of the carrier dynamics of polarons have yet to be reported. Here, we investigate the correlation between the electronic structure and the coloration of WO3 upon exposure to UV light in 5% H2/N2 gas and, more importantly, reveal photon-induced excited d-electron generation/relaxation via the W5+ oxidation state. The WO3 is fabricated by radio-frequency magnetron sputtering. X-ray diffraction patterns show that prepared WO3 is amorphous. Optical bandgap of 3.1 eV is measured by UV-vis before and after UV light. The results of Fourier transform infrared and Raman exhibit pristine WO3 is formed with surface H2O. The colored WO3 shows reduced state of W5+ state (34.3 eV) by using X-ray photoelectron spectroscopy. The valence band maximum of WO3 after UV light in H2 is shifted from mid gap to shallow donor by using ultraviolet photoelectron spectroscopy. During the exploration of the carrier dynamics, pump (700 nm)-probe (1000 nm) spectroscopy at the femtosecond scale was used. The results indicated that electron-phonon relaxation of UV-irradiated WO3, which is the origin of the polaron-induced local surface plasmonic effect, is dominant, resulting in slow decay (within a few picoseconds); in contrast, pristine WO3 shows fast decay (less than a picosecond). Accordingly, the long photoinduced carrier relaxation is ascribed to the prolonged hot-carrier lifetime in reduced oxides resulting in a greater number of free d-electrons and, therefore, more interactions with the W5+ sub-gap states.

  9. Polarons and Mobile Impurities Near a Quantum Phase Transition

    Science.gov (United States)

    Shadkhoo, Shahriar

    This dissertation aims at improving the current understanding of the physics of mobile impurities in highly correlated liquid-like phases of matter. Impurity problems pose challenging and intricate questions in different realms of many-body physics. For instance, the problem of ''solvation'' of charged solutes in polar solvents, has been the subject of longstanding debates among chemical physicists. The significant role of quantum fluctuations of the solvent, as well as the break down of linear response theory, render the ordinary treatments intractable. Inspired by this complicated problem, we first attempt to understand the role of non-specific quantum fluctuations in the solvation process. To this end, we calculate the dynamic structure factor of a model polar liquid, using the classical Molecular Dynamics (MD) simulations. We verify the failure of linear response approximation in the vicinity of a hydrated electron, by comparing the outcomes of MD simulations with the predictions of linear response theory. This nonlinear behavior is associated with the pronounced peaks of the structure factor, which reflect the strong fluctuations of the local modes. A cavity picture is constructed based on heuristic arguments, which suggests that the electron, along with the surrounding polarization cloud, behave like a frozen sphere, for which the linear response theory is broken inside and valid outside. The inverse radius of the spherical region serves as a UV momentum cutoff for the linear response approximation to be applicable. The problem of mobile impurities in polar liquids can be also addressed in the framework of the ''polaron'' problem. Polaron is a quasiparticle that typically acquires an extended state at weak couplings, and crossovers to a self-trapped state at strong couplings. Using the analytical fits to the numerically obtained charge-charge structure factor, a phenomenological approach is proposed within the Leggett's influence functional formalism, which

  10. Bound magnetic polaron in a semimagnetic double quantum well

    Science.gov (United States)

    Kalpana, P.; Jayakumar, K.

    2017-09-01

    The effect of different combinations of the concentration of Mn2+ ion in the Quantum well Cd1-xinMnxin Te and the barrier Cd1-xoutMnxout Te on the Bound Magnetic Polaron (BMP) in a Diluted Magnetic Semiconductors (DMS) Double Quantum Well (DQW) has been investigated. The Schrodinger equation is solved variationally in the effective mass approximation through which the Spin Polaronic Shift (SPS) due to the formation of BMP has been estimated for various locations of the donor impurity in the DQW. The results show that the effect of the increase of Mn2+ ion composition with different combinations on SPS is predominant for On Centre Well (OCW) impurity when compared to all other impurity locations when there is no application of magnetic field (γ = 0), γ being a dimensionless parameter for the magnetic field, and the same is predominant for On Centre Barrier (OCB) impurity with the application of external magnetic field (γ = 0.15).

  11. Transport cross section for small-angle scattering

    International Nuclear Information System (INIS)

    D'yakonov, M.I.; Khaetskii, A.V.

    1991-01-01

    Classical mechanics is valid for describing potential scattering under the conditions (1) λ much-lt α and (2) U much-gt ℎυ/α, where λ is the de Broglie wavelength, α is the characteristic size of the scatterer, U is the characteristic value of the potential energy, and υ is the velocity of the scattered particle. The second of these conditions means that the typical value of the classical scattering angle is far larger than the diffraction angle λ/α. In this paper the authors show that this second condition need not hold in a derivation of the transport cross section. In other words, provided that the condition λ much-lt α holds, it is always possible to calculate the transport cross section from the expressions of classical mechanics, even in the region U approx-lt ℎυ/α, where the scattering is diffractive,and the differential cross section is greatly different from the classical cross section. The transport cross section is found from the classical expression even in the anticlassical case U much-lt ℎυ/α, where the Born approximation can be used

  12. Electron localization, polarons and clustered states in manganites

    International Nuclear Information System (INIS)

    Mannella, N.

    2004-01-01

    Full text: A recent multi-spectroscopic study of prototypical colossal magnetoresistance (CMR) compounds La 1-x Sr x MnO 3 (LSMO, x = 0.3, 0.4) using photoemission (PE), x-ray absorption (XAS), x-ray emission (XES) and extended x-ray absorption e structure (EXAFS) has exposed a dramatic change in the electronic structure on crossing the ferromagnetic-to-paramagnetic transition temperature (T C ). In particular, this investigation revealed an increase of the Mn magnetic moment by ca. 1 Bohr magneton and charge transfer to the Mn atom on crossing T C concomitant with the presence of Jahn-Teller distortions, thus providing direct evidence of lattice polaron formation. These results thus challenge the belief of some authors that the LSMO compounds are canonical double-exchange (DE) systems in which polaron formation is unimportant, and thus help to unify the theoretical description of the CMR oxides. The relationship of these data to other recent work suggesting electron localization, polarons and phase separation, along with additional measurements of magnetic susceptibility indicating the formation of ferromagnetic clusters in the metallic paramagnetic state above T C will be discussed

  13. Absolute instability of polaron mode in semiconductor magnetoplasma

    Science.gov (United States)

    Paliwal, Ayushi; Dubey, Swati; Ghosh, S.

    2018-01-01

    Using coupled mode theory under hydrodynamic regime, a compact dispersion relation is derived for polaron mode in semiconductor magnetoplasma. The propagation and amplification characteristics of the wave are explored in detail. The analysis deals with the behaviour of anomalous threshold and amplification derived from dispersion relation, as function of external parameters like doping concentration and applied magnetic field. The results of this investigation are hoped to be useful in understanding electron-longitudinal optical phonon interplay in polar n-type semiconductor plasmas under the influence of coupled collective cyclotron excitations. The best results in terms of smaller threshold and higher gain of polaron mode could be achieved by choosing moderate doping concentration in the medium at higher magnetic field. For numerical appreciation of the results, relevant data of III-V n-GaAs compound semiconductor at 77 K is used. Present study provides a qualitative picture of polaron mode in magnetized n-type polar semiconductor medium duly shined by a CO2 laser.

  14. Transport-diffusion comparisons for small core LMFBR disruptive accidents

    International Nuclear Information System (INIS)

    Tomlinson, E.T.

    1977-11-01

    A number of numerical experiments were performed to assess the validity of diffusion theory for calculating the reactivity state of various small core LMFBR disrupted geometries. The disrupted configurations correspond, in general, to various configurations predicted by SAS3A for transient undercooling (TUC) and transient overpower (TOP) accidents for homogeneous cores and to the ZPPR-7 configurations for heterogeneous core. In all TUC cases diffusion theory was shown to be inadequate for the calculation of reactivity changes during core disassembly

  15. Mechanisms of calcium transport in small intestine. Final report

    International Nuclear Information System (INIS)

    DeLuca, H.F.

    1982-01-01

    The vitamin D hormone, 1,25-dihydroxyvitamin D 3 , was demonstrated to be the prime hormonal agent regulating intestinal absorption of divalent cations. Production of the vitamin D hormone is, in turn, regulated by parathyroid hormone, low dietary calcium, low plasma phosphorus, and is suppressed by 1,25-dihydroxyvitamin D 3 , by high plasma phosphorus, high plasma calcium, and the absence of parathyroid hormone. A variety of analogs of the vitamin D hormone were prepared. In addition, the preparation of radiolabeled vitamin D hormone was accomplished using chemical synthesis, and this highly radioactive substance was found to localize in the nuclei of the intestinal villus cells that promote intestinal absorption of calcium. A receptor for the vitamin D hormone was also located, and the general mechanism of response to the vitamin D hormone included the binding to a receptor molecule, transfer to the nucleus, transcription of specific genes followed by translation to transport proteins. Methods were developed for the discovery of the appropriate gene products that play a role in calcium transport

  16. Defect chemistry of ''BaCuO2''. Pt. 2. Transport properties and nature of defects

    International Nuclear Information System (INIS)

    Chiodelli, G.; Consiglio Nazionale delle Ricerche, Pavia; Anselmi-Tamburini, U.; Consiglio Nazionale delle Ricerche, Pavia; Arimondi, M.; Consiglio Nazionale delle Ricerche, Pavia; Spinolo, G.; Consiglio Nazionale delle Ricerche, Pavia; Flor, G.; Consiglio Nazionale delle Ricerche, Pavia

    1995-01-01

    The charge transport properties of ''BaCuO 2 '' with 88:90 (Ba:Cu) cation ratio were characterized by thermopower, electrical conductivity and ionic transport number measurements in a wide range of temperature and oxygen partial pressure conditions. The nature of carriers is always represented by small polarons due to self-trapping of the electronic holes generated by the oxygen non-stoichiometry equilibrium. Some anomalies in carrier mobility as a function of temperature are shown not to be related to incomplete ionization of oxygen atoms on interstitial sites (orig.)

  17. Electronic and vibrational hopping transport in boron carbides

    International Nuclear Information System (INIS)

    Emin, D.

    1991-01-01

    General concepts of hopping-type transport and localization are reviewed. Disorder, electronic correlations and atomic displacements, effects ignored in electronic band structure calculations, foster localization of electronic charge carriers. Examples are given that illustrate the efficacy of these effects in producing localization. This introduction is followed by a brief discussion of the relation between hopping-type transport and localization. The fundamentals of the formation, localization, and hopping transport of small polarons and/or bipolarons is then described. Electronic transport in boron carbides is presented as an example of the adiabatic hopping of small bipolarons. Finally, the notion of vibrational hopping is introduced. The high-temperature thermal diffusion in boron carbides is presented as a potential application of this idea

  18. Non-contact transportation system of small objects using Ultrasonic Waveguides

    International Nuclear Information System (INIS)

    Nakamura, K; Koyama, D

    2012-01-01

    A transportation system for small object or fluid without contact is investigated being based on ultrasonic levitation. Small objects are suspended against gravity at the nodal points in ultrasonic pressure field due to the sound radiation force generated as the gradient of the energy density of the field. In this study, the trapped object is transported in the horizontal plane by introducing the spatial shift of the standing waves by the switching the lateral modes or travelling waves. The goal of the study is to establish a technology which can provide a total system with the flexibility in composing various transportation paths. Methods for linear/rotary stepping motions and continuous linear transportation are explained in this report. All the transportation tracks are composed of a bending vibrator and a reflector. The design for these acoustic cavity/waveguide is discussed.

  19. Analysis of the Sodium Recirculation Theory of Solute Coupled Water Transport in Small Intestine

    DEFF Research Database (Denmark)

    Larsen, E. H.; Sørensen, Jens Nørkær; Sørensen, J. B.

    2002-01-01

    Our previous mathematical model of solute-coupled water transport through the intestinal epithelium is extended for dealing with electrolytes rather than electroneutral solutes. A 3Na+-2K+ pump in the lateral membranes provides the energy-requiring step for driving transjunctional and translateral......, computations predict that the concentration differences between lis and bathing solutions are small for all three ions. Nevertheless, the diffusion fluxes of the ions out of lis significantly exceed their mass transports. It is concluded that isotonic transport requires recirculation of all three ions....... The computed sodium recirculation flux that is required for isotonic transport corresponds to that estimated in experiments on toad small intestine. This result is shown to be robust and independent of whether the apical entrance mechanism for the sodium ion is a channel, a SGLT1 transporter driving inward...

  20. Small substrate transport and mechanism of a molybdate ATP binding cassette transporter in a lipid environment.

    Science.gov (United States)

    Rice, Austin J; Harrison, Alistair; Alvarez, Frances J D; Davidson, Amy L; Pinkett, Heather W

    2014-05-23

    Embedded in the plasma membrane of all bacteria, ATP binding cassette (ABC) importers facilitate the uptake of several vital nutrients and cofactors. The ABC transporter, MolBC-A, imports molybdate by passing substrate from the binding protein MolA to a membrane-spanning translocation pathway of MolB. To understand the mechanism of transport in the biological membrane as a whole, the effects of the lipid bilayer on transport needed to be addressed. Continuous wave-electron paramagnetic resonance and in vivo molybdate uptake studies were used to test the impact of the lipid environment on the mechanism and function of MolBC-A. Working with the bacterium Haemophilus influenzae, we found that MolBC-A functions as a low affinity molybdate transporter in its native environment. In periods of high extracellular molybdate concentration, H. influenzae makes use of parallel molybdate transport systems (MolBC-A and ModBC-A) to take up a greater amount of molybdate than a strain with ModBC-A alone. In addition, the movement of the translocation pathway in response to nucleotide binding and hydrolysis in a lipid environment is conserved when compared with in-detergent analysis. However, electron paramagnetic resonance spectroscopy indicates that a lipid environment restricts the flexibility of the MolBC translocation pathway. By combining continuous wave-electron paramagnetic resonance spectroscopy and substrate uptake studies, we reveal details of molybdate transport and the logistics of uptake systems that employ multiple transporters for the same substrate, offering insight into the mechanisms of nutrient uptake in bacteria. © 2014 by The American Society for Biochemistry and Molecular Biology, Inc.

  1. Asymptotic dependence of Gross–Tulub polaron ground-state energy in the strong coupling region

    Directory of Open Access Journals (Sweden)

    N.I. Kashirina

    2017-12-01

    Full Text Available The properties of translationally invariant polaron functional have been investigated in the region of strong and extremely strong coupling. It has been shown that the Gross–Tulub polaron functional obtained earlier using the methods of field theory was derived only for the region , where is the Fröhlich constant of the electron-phonon coupling. Various representations of exact and approximate polaron functionals have been considered. Asymptotic dependences of the polaron energy have been obtained using a functional extending the Gross–Tulub functional to the region of extremely strong coupling. The asymptotic dependence of polaron energies for an extremely strong coupling are (for the one-parameter variational function fk, and (for a two-parameter function . It has been shown that the virial theorem 1:3:4 holds for the two-parameter function . Minimization of the approximate functional obtained by expanding the exact Gross–Tulub functional in a series on leads to a quadratic dependence of the polaron energy. This approximation is justified for . For a two-parameter function , the corresponding dependence has the form . However, the use of approximate functionals, in contrast to the strict variational procedure, when the exact polaron functional varies, does not guarantee obtaining the upper limit for the polaron energy.

  2. Effect of interchain coupling on the excited polaron in conjugated polymers

    International Nuclear Information System (INIS)

    Li, Xiao-xue; Chen, Gang

    2017-01-01

    Based on the one-dimensional extended Su–Schrieffer–Heeger model, we theoretically investigate the effect of interchain coupling on the formation and polarization of the single-excited state of polaron in conjugated polymers. It is found that there exists a turnover value of the coupling strength, over which the excited polaron could not be formed in either of the two coupled chains. Instead, a polaron-like particle is localized at the center of each chain. In addition, we also find that the reverse polarization of the excited polaron could be enhanced for some cases in polymer when the interchain coupling becomes strong until it exceeds the critical value. - Highlights: • Effect of interchain coupling on the single-excited state of polaron is studied. • When coupling strength exceeds critical value, the excited polaron is dissociated. • Soliton pair could be dissociated into polaron-like particle with strong coupling. • Reverse polarization of excited polaron is enhanced by weak interchain coupling. • Reverse polarization is obtained more easily in solid film of polymer molecules.

  3. Effect of interchain coupling on the excited polaron in conjugated polymers

    Energy Technology Data Exchange (ETDEWEB)

    Li, Xiao-xue, E-mail: sps_lixx@ujn.edu.cn; Chen, Gang, E-mail: ss_cheng@ujn.edu.cn

    2017-02-05

    Based on the one-dimensional extended Su–Schrieffer–Heeger model, we theoretically investigate the effect of interchain coupling on the formation and polarization of the single-excited state of polaron in conjugated polymers. It is found that there exists a turnover value of the coupling strength, over which the excited polaron could not be formed in either of the two coupled chains. Instead, a polaron-like particle is localized at the center of each chain. In addition, we also find that the reverse polarization of the excited polaron could be enhanced for some cases in polymer when the interchain coupling becomes strong until it exceeds the critical value. - Highlights: • Effect of interchain coupling on the single-excited state of polaron is studied. • When coupling strength exceeds critical value, the excited polaron is dissociated. • Soliton pair could be dissociated into polaron-like particle with strong coupling. • Reverse polarization of excited polaron is enhanced by weak interchain coupling. • Reverse polarization is obtained more easily in solid film of polymer molecules.

  4. Repulsive polarons and itinerant ferromagnetism in strongly polarized Fermi gases

    DEFF Research Database (Denmark)

    Massignan, Pietro; Bruun, Georg

    2011-01-01

    We analyze the properties of a single impurity immersed in a Fermi sea. At positive energy and scattering lengths, we show that the system possesses a well-defined but metastable excitation, the repulsive polaron, and we calculate its energy, quasiparticle residue and effective mass. From...... polarized (ferromagnetic) domains are then examined for a binary mixture of atoms with a general mass ratio. Our results indicate that mass imbalance lowers the critical interaction strength for phase-separation, but that very short quasiparticle decay times will complicate the experimental observation...

  5. Quantum transition and decoherence of levitating polaron on helium film thickness under an electromagnetic field

    Science.gov (United States)

    Kenfack, S. C.; Fotue, A. J.; Fobasso, M. F. C.; Djomou, J.-R. D.; Tiotsop, M.; Ngouana, K. S. L.; Fai, L. C.

    2017-12-01

    We have studied the transition probability and decoherence time of levitating polaron in helium film thickness. By using a variational method of Pekar type, the ground and the first excited states of polaron are calculated above the liquid-helium film placed on the polar substrate. It is shown that the polaron transits from the ground to the excited state in the presence of an external electromagnetic field in the plane. We have seen that, in the helium film, the effects of the magnetic and electric fields on the polaron are opposite. It is also shown that the energy, transition probability and decoherence time of the polaron depend sensitively on the helium film thickness. We found that decoherence time decreases as a function of increasing electron-phonon coupling strength and the helium film thickness. It is seen that the film thickness can be considered as a new confinement in our system and can be adjusted in order to reduce decoherence.

  6. Observation of Spin-Polarons in a strongly interacting Fermi liquid

    Science.gov (United States)

    Zwierlein, Martin

    2009-03-01

    We have observed spin-polarons in a highly imbalanced mixture of fermionic atoms using tomographic RF spectroscopy. Feshbach resonances allow to freely tune the interactions between the two spin states involved. A single spin down atom immersed in a Fermi sea of spin up atoms can do one of two things: For strong attraction, it can form a molecule with exactly one spin up partner, but for weaker interaction it will spread its attraction and surround itself with a collection of majority atoms. This spin down atom ``dressed'' with a spin up cloud constitutes the spin-polaron. We have observed a striking spectroscopic signature of this quasi-particle for various interaction strengths, a narrow peak in the spin down spectrum that emerges above a broad background. The narrow width signals a long lifetime of the spin-polaron, much longer than the collision rate with spin up atoms, as it must be for a proper quasi-particle. The peak position allows to directly measure the polaron energy. The broad pedestal at high energies reveals physics at short distances and is thus ``molecule-like'': It is exactly matched by the spin up spectra. The comparison with the area under the polaron peak allows to directly obtain the quasi-particle weight Z. We observe a smooth transition from polarons to molecules. At a critical interaction strength of 1/kFa = 0.7, the polaron peak vanishes and spin up and spin down spectra exactly match, signalling the formation of molecules. This is the same critical interaction strength found earlier to separate a normal Fermi mixture from a superfluid molecular Bose-Einstein condensate. The spin-polarons determine the low-temperature phase diagram of imbalanced Fermi mixtures. In principle, polarons can interact with each other and should, at low enough temperatures, form a superfluid of p-wave pairs. We will present a first indication for interactions between polarons.

  7. Observation of semiconductor to metallic transition and polaron hopping in double perovskite Pr{sub 2}CoTiO{sub 6} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Mahato, Dev K., E-mail: drdevkumar@yahoo.com [Department of Physics, National Institute of Technology Patna, Patna 800005 (India); Sinha, T.P. [Department of Physics, Bose Institute, 93/1, APC Road, Kolkata 700009 (India)

    2017-05-01

    This paper describes semiconductor to metal transition and polaron conduction in double perovskite Pr{sub 2}CoTiO{sub 6} (PCTO) ceramics. The XRD pattern recorded at room temperature confirmed the pure phase, single crystalline structure. The semicircle arc in the impedance plot at each temperature can be attributed to the grain boundary contribution, indicating one dominating response in the measurement frequency range. The semiconductor to metallic transition was also confirmed by the variation of grain boundary resistance (R{sub gb}) with temperature. The activation energy estimated from the imaginary part of electrical modulus and impedance are found to be the characteristic of polaron conduction in PCTO. Ac conductivity followed power law dependence σ{sub ac} = Bω{sup n}. The observed variation of the exponent ‘n’ with temperature suggests the typical of charge transport assisted by a hopping process. The observed minimum in the temperature dependence of frequency exponent ‘n’ strongly suggests that the large polaron tunneling is the dominant transport process.

  8. Nonlinear Transport in Organic Thin Film Transistors with Soluble Small Molecule Semiconductor.

    Science.gov (United States)

    Kim, Hyeok; Song, Dong-Seok; Kwon, Jin-Hyuk; Jung, Ji-Hoon; Kim, Do-Kyung; Kim, SeonMin; Kang, In Man; Park, Jonghoo; Tae, Heung-Sik; Battaglini, Nicolas; Lang, Philippe; Horowitz, Gilles; Bae, Jin-Hyuk

    2016-03-01

    Nonlinear transport is intensively explained through Poole-Frenkel (PF) transport mechanism in organic thin film transistors with solution-processed small molecules, which is, 6,13-bis(triisopropylsilylethynyl) (TIPS) pentacene. We outline a detailed electrical study that identifies the source to drain field dependent mobility. Devices with diverse channel lengths enable the extensive exhibition of field dependent mobility due to thermal activation of carriers among traps.

  9. Shock absorbing evaluation of the rigid polyurethane foam and styrofoam applied to a small transportation package

    International Nuclear Information System (INIS)

    Seo, K.S.; Lee, J.C.; Bang, K.S.; Han, H.S.; Chung, S.H.; Choi, B.I.; Ha, J.H.

    2004-01-01

    The package design objectives for the drop condition are to maintain the integrity of the structural material by reducing the impact force. There are two kinds of the shock absorbing materials such as rigid polyurethane foam (PU) and Styrofoam (EPS: Expanded Poly Styrene). These materials are generally used in small transportation packages. The stress-strain curves were obtained by the compression tests until the PU and EPS reached their lock-up strain. This paper describes that, in the case of a small transportation package of a cylindrical shape, the shock absorbing effects were evaluated by utilizing the compression properties of the PU and EPS foam

  10. Evaluating the transport in small-world and scale-free networks

    International Nuclear Information System (INIS)

    Juárez-López, R.; Obregón-Quintana, B.; Hernández-Pérez, R.; Reyes-Ramírez, I.; Guzmán-Vargas, L.

    2014-01-01

    We present a study of some properties of transport in small-world and scale-free networks. Particularly, we compare two types of transport: subject to friction (electrical case) and in the absence of friction (maximum flow). We found that in clustered networks based on the Watts–Strogatz (WS) model, for both transport types the small-world configurations exhibit the best trade-off between local and global levels. For non-clustered WS networks the local transport is independent of the rewiring parameter, while the transport improves globally. Moreover, we analyzed both transport types in scale-free networks considering tendencies in the assortative or disassortative mixing of nodes. We construct the distribution of the conductance G and flow F to evaluate the effects of the assortative (disassortative) mixing, finding that for scale-free networks, as we introduce different levels of the degree–degree correlations, the power-law decay in the conductances is altered, while for the flow, the power-law tail remains unchanged. In addition, we analyze the effect on the conductance and the flow of the minimum degree and the shortest path between the source and destination nodes, finding notable differences between these two types of transport

  11. Direct detection of SERCA calcium transport and small-molecule inhibition in giant unilamellar vesicles

    International Nuclear Information System (INIS)

    Bian, Tengfei; Autry, Joseph M.; Casemore, Denise; Li, Ji; Thomas, David D.; He, Gaohong; Xing, Chengguo

    2016-01-01

    We have developed a charge-mediated fusion method to reconstitute the sarco/endoplasmic reticulum Ca 2+ -ATPase (SERCA) in giant unilamellar vesicles (GUV). Intracellular Ca 2+ transport by SERCA controls key processes in human cells such as proliferation, signaling, and contraction. Small-molecule effectors of SERCA are urgently needed as therapeutics for Ca 2+ dysregulation in human diseases including cancer, diabetes, and heart failure. Here we report the development of a method for efficiently reconstituting SERCA in GUV, and we describe a streamlined protocol based on optimized parameters (e.g., lipid components, SERCA preparation, and activity assay requirements). ATP-dependent Ca 2+ transport by SERCA in single GUV was detected directly using confocal fluorescence microscopy with the Ca 2+ indicator Fluo-5F. The GUV reconstitution system was validated for functional screening of Ca 2+ transport using thapsigargin (TG), a small-molecule inhibitor of SERCA currently in clinical trials as a prostate cancer prodrug. The GUV system overcomes the problem of inhibitory Ca 2+ accumulation for SERCA in native and reconstituted small unilamellar vesicles (SUV). We propose that charge-mediated fusion provides a widely-applicable method for GUV reconstitution of clinically-important membrane transport proteins. We conclude that GUV reconstitution is a technological advancement for evaluating small-molecule effectors of SERCA.

  12. The analysis by several neutron transport methods of a small PWR model problem

    International Nuclear Information System (INIS)

    Halsall, M.J.

    1980-09-01

    A small model problem in x-y co-ordinate geometry is specified in detail to permit readers to make their own calculations. The problem is analysed using diffusion theory, differential and integral transport methods and a Monte Carlo code, and a best estimate eigenvalue is deduced. (author)

  13. 75 FR 3517 - Notice of Funding Availability for the Small Business Transportation Resource Center Program

    Science.gov (United States)

    2010-01-21

    ..., business assessment, management training, counseling, technical assistance, marketing and outreach, and the... necessary to improve the management of their own small business to expand their transportation-related..., bonding assistance, business counseling, management assistance and direct referrals to DOT agencies at the...

  14. Human Enteroids as a Model of Upper Small Intestinal Ion Transport Physiology and Pathophysiology

    NARCIS (Netherlands)

    J. Foulke-Abel (Jennifer); J. In (Julie); Yin, J. (Jianyi); N.C. Zachos (Nicholas C.); O. Kovbasnjuk (Olga); M.K. Estes (Mary K.); H.R. de Jonge (Hugo); M. Donowitz (Mark)

    2016-01-01

    textabstractBackground & Aims Human intestinal crypt-derived enteroids are a model of intestinal ion transport that require validation by comparison with cell culture and animal models. We used human small intestinal enteroids to study neutral Na+ absorption and stimulated fluid and anion secretion

  15. Interfacial area transport of bubbly flow in a small diameter pipe

    International Nuclear Information System (INIS)

    Hibiki, Takashi; Takamasa, Tomoji; Ishii, Mamoru

    2001-01-01

    In relation to the development of the interfacial area transport equation, this study focused on modeling of the interfacial area transport mechanism of vertical adiabatic air-water bubbly flows in a relatively small diameter pipe where the bubble size-to-pipe diameter ratio was relatively high and the radial motion of bubbles was restricted by the presence of the pipe wall. The sink term of the interfacial area concentration was modeled by considering wake entrainment as a possible bubble coalescence mechanism, whereas the source term was neglected by assuming negligibly small bubble breakup for low liquid velocity conditions based on visual observation. One-dimensional interfacial area transport equation with the derived sink term was evaluated by using five datasets of vertical adiabatic air-water bubbly flows measured in a 9.0 mm-diameter pipe (superficial gas velocity: 0.013-0.052 m/s, superficial liquid velocity: 0.58-1.0 m/s). The modeled interfacial area transport equation could reproduce the proper trend of the axial interfacial area transport and predict the measured interfacial area concentrations within an average relative deviation of ±11.1%. It was recognized that the present model would be promising for predicting the interfacial area transport of the examined bubbly flows. (author)

  16. The Small Protein SgrT Controls Transport Activity of the Glucose-Specific Phosphotransferase System.

    Science.gov (United States)

    Lloyd, Chelsea R; Park, Seongjin; Fei, Jingyi; Vanderpool, Carin K

    2017-06-01

    The bacterial small RNA (sRNA) SgrS has been a fruitful model for discovery of novel RNA-based regulatory mechanisms and new facets of bacterial physiology and metabolism. SgrS is one of only a few characterized dual-function sRNAs. SgrS can control gene expression posttranscriptionally via sRNA-mRNA base-pairing interactions. Its second function is coding for the small protein SgrT. Previous work demonstrated that both functions contribute to relief of growth inhibition caused by glucose-phosphate stress, a condition characterized by disrupted glycolytic flux and accumulation of sugar phosphates. The base-pairing activity of SgrS has been the subject of numerous studies, but the activity of SgrT is less well characterized. Here, we provide evidence that SgrT acts to specifically inhibit the transport activity of the major glucose permease PtsG. Superresolution microscopy demonstrated that SgrT localizes to the cell membrane in a PtsG-dependent manner. Mutational analysis determined that residues in the N-terminal domain of PtsG are important for conferring sensitivity to SgrT-mediated inhibition of transport activity. Growth assays support a model in which SgrT-mediated inhibition of PtsG transport activity reduces accumulation of nonmetabolizable sugar phosphates and promotes utilization of alternative carbon sources by modulating carbon catabolite repression. The results of this study expand our understanding of a basic and well-studied biological problem, namely, how cells coordinate carbohydrate transport and metabolism. Further, this work highlights the complex activities that can be carried out by sRNAs and small proteins in bacteria. IMPORTANCE Sequencing, annotation and investigation of hundreds of bacterial genomes have identified vast numbers of small RNAs and small proteins, the majority of which have no known function. In this study, we explore the function of a small protein that acts in tandem with a well-characterized small RNA during metabolic

  17. Mobility balance in the light-emitting layer governs the polaron accumulation and operational stability of organic light-emitting diodes

    Science.gov (United States)

    Kim, Jae-Min; Lee, Chang-Heon; Kim, Jang-Joo

    2017-11-01

    Organic light-emitting diode (OLED) displays are lighter and more flexible, have a wider color gamut, and consume less power than conventional displays. Stable materials and the structural design of the device are important for OLED longevity. Control of charge transport and accumulation in the device is particularly important because the interaction of excitons and polarons results in material degradation. This research investigated the charge dynamics of OLEDs experimentally and by drift-diffusion modeling. Parallel capacitance-voltage measurements of devices provided knowledge of charge behavior at different driving voltages. A comparison of exciplex-forming co-host and single host structures established that the mobility balance in the emitting layers determined the amount of accumulated polarons in those layers. Consequently, an exciplex-forming co-host provides a superior structure in terms of device lifetime and efficiency because of its well-balanced mobility. Minimizing polaron accumulation is key to achieving long OLED device lifetimes. This is a crucial aspect of device physics that must be considered in the device design structure.

  18. A polaronic model of superconductivity in doped fulleride systems

    International Nuclear Information System (INIS)

    Tiwari, S.C.

    2007-01-01

    Full text: A polaronic model of superconductivity in doped fulleride systems is presented. The normal and anomalous one-particle Green's functions are derived for a system with strong electron phonon coupling. The study of collapse of the electron band and the phonon vacuum is presented within the mean-field approximation. Self consistent equation for the superconducting order parameter is derived using Green's function technique and following Lang and Firsov transformations. Expressions for specific heat, density of states, free energy and critical field based on this model have been derived. The theory is applied to explain the experimental results in the systems K 3 C 60 and Rb 3 C 6 O. These results are in good agreement with the available experimental data. (authors)

  19. Study of spin-polaron formation in 1D systems

    Energy Technology Data Exchange (ETDEWEB)

    Arredondo, Y.; Navarro, O. [Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, Apartado Postal 70-360, 04510 México D.F. (Mexico); Vallejo, E. [Facultad de Ingeniería Mecánica y Eléctrica, Universidad Autónoma de Coahuila, Carretera Torreón-Matamoros Km. 7.5 Ciudad Universitaria, 27276 Torreón, Coahuila (Mexico)

    2014-05-15

    We study numerically the formation of spin-polarons in low-dimensional systems. We consider a ferromagnetic Kondo lattice model with Hund coupling J{sub H} and localized spins interacting antiferromagnetically with coupling constant J. We investigate the ground state phase diagram as a function of the exchange couplings J{sub H} and J and as a function of the band filling, since it has been observed that doping either on the ferromagnetic or antiferromagnetic regime lead to formation of magnetic domains [1]. We explore the quasi-particle formation and phase separation using the density-matrix renormalization group method, which is a highly efficient method to investigate quasi-one-dimensional strongly correlated systems.

  20. Study of spin-polaron formation in 1D systems

    International Nuclear Information System (INIS)

    Arredondo, Y.; Navarro, O.; Vallejo, E.

    2014-01-01

    We study numerically the formation of spin-polarons in low-dimensional systems. We consider a ferromagnetic Kondo lattice model with Hund coupling J H and localized spins interacting antiferromagnetically with coupling constant J. We investigate the ground state phase diagram as a function of the exchange couplings J H and J and as a function of the band filling, since it has been observed that doping either on the ferromagnetic or antiferromagnetic regime lead to formation of magnetic domains [1]. We explore the quasi-particle formation and phase separation using the density-matrix renormalization group method, which is a highly efficient method to investigate quasi-one-dimensional strongly correlated systems

  1. Proton impurity in the neutron matter: a nuclear polaron problem

    Energy Technology Data Exchange (ETDEWEB)

    Kutschera, M [Institute of Nuclear Physics, Cracow (Poland); Wojcik, W [Politechnika Krakowska, Cracow (Poland)

    1992-10-01

    We study interactions of a proton impurity with density oscillations of the neutron matter in a Debye approximation. The proton-phonon coupling is of the deformation-potential type at long wavelengths. It is weak at low density and increases with the neutron matter density. We calculate the proton`s effective mass perturbatively for a weak coupling, and use a canonical transformation technique for stronger couplings. The proton`s effective mass grows significantly with density, and at higher densities the proton impurity can be localized. This behaviour is similar to that of the polaron in solids. We obtain properties of the localized proton in the strong coupling regime from variational calculations, treating the neutron in the Thomas-Fermi approximation. (author). 14 refs, 8 figs.

  2. Effects of taurine on plasma glucose concentration and active glucose transport in the small intestine.

    Science.gov (United States)

    Tsuchiya, Yo; Kawamata, Koichi

    2017-11-01

    Taurine lowers blood glucose levels and improves hyperglycemia. However, its effects on glucose transport in the small intestine have not been investigated. Here, we elucidated the effect of taurine on glucose absorption in the small intestine. In the oral glucose tolerance test, addition of 10 mmol/L taurine suppressed the increase in hepatic portal glucose concentrations. To investigate whether the suppressive effect of taurine occurs via down-regulation of active glucose transport in the small intestine, we performed an assay using the everted sac of the rat jejunum. Addition of taurine to the mucosal side of the jejunum suppressed active glucose transport via sodium-glucose cotransporter 1 (SGLT1). After elimination of chloride ions from the mucosal solution, taurine did not show suppressive effects on active glucose transport. These results suggest that taurine suppressed the increase in hepatic portal glucose concentrations via suppression of SGLT1 activity in the rat jejunum, depending on chloride ions. © 2017 Japanese Society of Animal Science.

  3. Polaron-electron assisted giant dielectric dispersion in SrZrO{sub 3} high-k dielectric

    Energy Technology Data Exchange (ETDEWEB)

    Borkar, Hitesh; Barvat, Arun; Pal, Prabir; Kumar, Ashok, E-mail: ashok553@nplindia.org [CSIR-National Physical Laboratory, Dr. K. S. Krishnan Marg, New Delhi 110012 (India); Academy of Scientific and Innovative Research (AcSIR), CSIR-National Physical Laboratory (CSIR-NPL) Campus, Dr. K S Krishnan Marg, New Delhi 110012 (India); Shukla, A. K. [CSIR-National Physical Laboratory, Dr. K. S. Krishnan Marg, New Delhi 110012 (India); Pulikkotil, J. J. [CSIR-National Physical Laboratory, Dr. K. S. Krishnan Marg, New Delhi 110012 (India); Academy of Scientific and Innovative Research (AcSIR), CSIR-National Physical Laboratory (CSIR-NPL) Campus, Dr. K S Krishnan Marg, New Delhi 110012 (India); Computation and Networking Facility, CSIR-National Physical Laboratory, New Delhi 110012 (India)

    2016-06-07

    The SrZrO{sub 3} is a well known high-k dielectric constant (∼22) and high optical bandgap (∼5.8 eV) material and one of the potential candidates for future generation nanoelectronic logic elements (8 nm node technology) beyond silicon. Its dielectric behavior is fairly robust and frequency independent till 470 K; however, it suffers a strong small-polaron based electronic phase transition (T{sub e}) linking 650 to 750 K. The impedance spectroscopy measurements revealed the presence of conducting grains and grain boundaries at elevated temperature which provide energetic mobile charge carriers with activation energy in the range of 0.7 to 1.2 eV supporting the oxygen ions and proton conduction. X-ray photoemission spectroscopy measurements suggest the presence of weak non-stoichiometric O{sup 2−} anions and hydroxyl species bound to different sites at the surface and bulk. These thermally activated charge carriers at elevated temperature significantly contribute to the polaronic based dielectric anomaly and conductivity. Our dielectric anomaly supports pseudo phase transition due to high degree of change in ZrO{sub 6} octahedral angle in the temperature range of 650–750 K, where electron density and phonon vibration affect the dielectric and conductivity properties.

  4. The Air Transportation Policy of Small States: Meeting the Challenges of Globalization

    Science.gov (United States)

    Antoniou, Andreas

    2001-01-01

    The air transport policies of small states are currently at a crossroad. Policy makers in these countries are facing a difficult dilemma: either follow the general trend of liberalization and pay the high cost of the resulting restructuring or maintain the existing regulatory and ownership structures at the risk of isolation thus undermining the viability and sustainability of their air transport sector and their economies in general. This paper proposes to explore the broad issues raised by this difficult dilemma, to outline its special significance in the context of small states and to delineate the options opened to the economic policymakers; in these states. After a brief note on the method of research, we sketch the main elements of the international air transport industry in which the airlines of small states are called upon to act. We then propose to review the main features of the analytical framework of this debate as it pertains to the special circumstances of these states. Then we focus on the challenges facing the airlines of Small States, while the next section proposes a number of the alternative policy options open to the policy makers in these states. The main conclusions are drawn in the final section.

  5. Polaron self-localization in white-light emitting hybrid perovskites

    KAUST Repository

    Cortecchia, Daniele; Yin, Jun; Bruno, Annalisa; Lo, Shu Zee Alencious; Gurzadyan, Gagik G.; Mhaisalkar, Subodh; Bredas, Jean-Luc; Soci, Cesare

    2017-01-01

    within the inorganic perovskite framework. Due to strong Coulombic interactions, these species retain their original excitonic character and form self-trapped polaron-excitons acting as radiative colour centres. These findings are expected to be relevant

  6. Excitonic and Polaronic Properties of 2D Hybrid Organic–Inorganic Perovskites

    KAUST Repository

    Yin, Jun; Li, Hong; Cortecchia, Daniele; Soci, Cesare; Bredas, Jean-Luc

    2017-01-01

    calculations including corrections due to spin orbit couplings and electron hole interactions, a computationally intensive molecular cluster approach is exploited to describe the excitonic and polaronic properties of these 2D perovskites at the atomistic level

  7. Linear and non-linear infrared response of one-dimensional vibrational Holstein polarons in the anti-adiabatic limit: Optical and acoustical phonon models

    Science.gov (United States)

    Falvo, Cyril

    2018-02-01

    The theory of linear and non-linear infrared response of vibrational Holstein polarons in one-dimensional lattices is presented in order to identify the spectral signatures of self-trapping phenomena. Using a canonical transformation, the optical response is computed from the small polaron point of view which is valid in the anti-adiabatic limit. Two types of phonon baths are considered: optical phonons and acoustical phonons, and simple expressions are derived for the infrared response. It is shown that for the case of optical phonons, the linear response can directly probe the polaron density of states. The model is used to interpret the experimental spectrum of crystalline acetanilide in the C=O range. For the case of acoustical phonons, it is shown that two bound states can be observed in the two-dimensional infrared spectrum at low temperature. At high temperature, analysis of the time-dependence of the two-dimensional infrared spectrum indicates that bath mediated correlations slow down spectral diffusion. The model is used to interpret the experimental linear-spectroscopy of model α-helix and β-sheet polypeptides. This work shows that the Davydov Hamiltonian cannot explain the observations in the NH stretching range.

  8. Comparative analysis of magnetic resonance in the polaron pair recombination and the triplet exciton-polaron quenching models

    Science.gov (United States)

    Mkhitaryan, V. V.; Danilović, D.; Hippola, C.; Raikh, M. E.; Shinar, J.

    2018-01-01

    We present a comparative theoretical study of magnetic resonance within the polaron pair recombination (PPR) and the triplet exciton-polaron quenching (TPQ) models. Both models have been invoked to interpret the photoluminescence detected magnetic resonance (PLDMR) results in π -conjugated materials and devices. We show that resonance line shapes calculated within the two models differ dramatically in several regards. First, in the PPR model, the line shape exhibits unusual behavior upon increasing the microwave power: it evolves from fully positive at weak power to fully negative at strong power. In contrast, in the TPQ model, the PLDMR is completely positive, showing a monotonic saturation. Second, the two models predict different dependencies of the resonance signal on the photoexcitation power, PL. At low PL, the resonance amplitude Δ I /I is ∝PL within the PPR model, while it is ∝PL2 crossing over to PL3 within the TPQ model. On the physical level, the differences stem from different underlying spin dynamics. Most prominently, a negative resonance within the PPR model has its origin in the microwave-induced spin-Dicke effect, leading to the resonant quenching of photoluminescence. The spin-Dicke effect results from the spin-selective recombination, leading to a highly correlated precession of the on-resonance pair partners under the strong microwave power. This effect is not relevant for TPQ mechanism, where the strong zero-field splitting renders the majority of triplets off resonance. On the technical level, the analytical evaluation of the line shapes for the two models is enabled by the fact that these shapes can be expressed via the eigenvalues of a complex Hamiltonian. This bypasses the necessity of solving the much larger complex linear system of the stochastic Liouville equations. Our findings pave the way towards a reliable discrimination between the two mechanisms via cw PLDMR.

  9. Improved Cost Management at Small and Medium Sized Road Transport Companies: Case Hungary

    Directory of Open Access Journals (Sweden)

    Zoltan Bokor

    2015-10-01

    Full Text Available Small and medium sized road freight transport companies located in Hungary are facing strong competition on the logistics market. An advanced cost management system supporting decisions on capacity allocations or pricing may be a competitive advantage for them and indirectly for the whole economy as well. Still, they generally apply simple, traditional cost calculation regimes, potentially sufficient in case of a homogeneous service portfolio. Nevertheless, road haulage companies with heterogeneous service structures may witness information distortions when using traditional costing methods. So it might be recommended for them to introduce better costing principles. To support an improved transport costing, a multi-level full cost allocation model has been set up and tested in this paper. The research results have pointed out that such a methodological development accompanied by the extension of the data collection mechanism can contribute to making the cost management systems of road freight transport companies more effective.

  10. Early vertebrate origin and diversification of small transmembrane regulators of cellular ion transport.

    Science.gov (United States)

    Pirkmajer, Sergej; Kirchner, Henriette; Lundell, Leonidas S; Zelenin, Pavel V; Zierath, Juleen R; Makarova, Kira S; Wolf, Yuri I; Chibalin, Alexander V

    2017-07-15

    Small transmembrane proteins such as FXYDs, which interact with Na + ,K + -ATPase, and the micropeptides that interact with sarco/endoplasmic reticulum Ca 2+ -ATPase play fundamental roles in regulation of ion transport in vertebrates. Uncertain evolutionary origins and phylogenetic relationships among these regulators of ion transport have led to inconsistencies in their classification across vertebrate species, thus hampering comparative studies of their functions. We discovered the first FXYD homologue in sea lamprey, a basal jawless vertebrate, which suggests small transmembrane regulators of ion transport emerged early in the vertebrate lineage. We also identified 13 gene subfamilies of FXYDs and propose a revised, phylogeny-based FXYD classification that is consistent across vertebrate species. These findings provide an improved framework for investigating physiological and pathophysiological functions of small transmembrane regulators of ion transport. Small transmembrane proteins are important for regulation of cellular ion transport. The most prominent among these are members of the FXYD family (FXYD1-12), which regulate Na + ,K + -ATPase, and phospholamban, sarcolipin, myoregulin and DWORF, which regulate the sarco/endoplasmic reticulum Ca 2+ -ATPase (SERCA). FXYDs and regulators of SERCA are present in fishes, as well as terrestrial vertebrates; however, their evolutionary origins and phylogenetic relationships are obscure, thus hampering comparative physiological studies. Here we discovered that sea lamprey (Petromyzon marinus), a representative of extant jawless vertebrates (Cyclostomata), expresses an FXYD homologue, which strongly suggests that FXYDs predate the emergence of fishes and other jawed vertebrates (Gnathostomata). Using a combination of sequence-based phylogenetic analysis and conservation of local chromosome context, we determined that FXYDs markedly diversified in the lineages leading to cartilaginous fishes (Chondrichthyes) and bony

  11. Cycling as a Smart and Green Mode of Transport in Small Touristic Cities

    Directory of Open Access Journals (Sweden)

    Paraskevi Karanikola

    2018-01-01

    Full Text Available Cycling as a mode of transport is a low-cost, health-improving way to travel and offers environmental benefits for the cities that promote it. It is only recently, though, with concerns over climate change, pollution, congestion, and obesity among others, that have cities throughout the world have begun to implement policies to promote cycling. In Greece, however, the use of the bicycle is limited. In Preveza, a small touristic city in Northwestern Greece where the use of the bicycle is prominent when compared to other Greek cities, there are efforts to promote cycling. Through the aid of a structured questionnaire, the residents evaluated the suitability of the city for cycling, the existing infrastructure, appropriate education, and behavior of cyclists and drivers. More than half of the residents use bicycles as their transportation and stated that bicycles are an inexpensive way of transport in the city and had the opinion that the state should encourage bicycle use by supporting subvention in bicycle acquisition. Two-thirds of the residents evaluated the cycling facilities of their city as adequate, but unsafe for young cyclists who do not follow the rules of transport. Adult cyclists, in contrast, were more loyal to the code, but stated that drivers did not respect their presence on the roads. This research provides important information on the perceived shortcomings of cycling as a transport mode in Preveza that may be of interest to towns/cities with similar characteristics.

  12. Small Molecule Membrane Transporters in the Mammalian Podocyte: A Pathogenic and Therapeutic Target

    Directory of Open Access Journals (Sweden)

    Cristina Zennaro

    2014-11-01

    Full Text Available The intriguingly complex glomerular podocyte has been a recent object of intense study. Researchers have sought to understand its role in the pathogenesis of common proteinuric diseases such as minimal change disease and focal segmental glomerular sclerosis. In particular, considerable effort has been directed towards the anatomic and functional barrier to macromolecular filtration provided by the secondary foot processes, but little attention has been paid to the potential of podocytes to handle plasma proteins beyond the specialization of the slit diaphragm. Renal membrane transporters in the proximal tubule have been extensively studied for decades, particularly in relation to drug metabolism and elimination. Recently, uptake and efflux transporters for small organic molecules have also been found in the glomerular podocyte, and we and others have found that these transporters can engage not only common pharmaceuticals but also injurious endogenous and exogenous agents. We have also found that the activity of podocyte transporters can be manipulated to inhibit pathogen uptake and efflux. It is conceivable that podocyte transporters may play a role in disease pathogenesis and may be a target for future drug development.

  13. The Small-Angle Neutron Scattering Data Analysis of the Phospholipid Transport Nanosystem Structure

    Science.gov (United States)

    Zemlyanaya, E. V.; Kiselev, M. A.; Zhabitskaya, E. I.; Aksenov, V. L.; Ipatova, O. M.; Ivankov, O. I.

    2018-05-01

    The small-angle neutron scattering technique (SANS) is employed for investigation of structure of the phospholipid transport nanosystem (PTNS) elaborated in the V.N.Orekhovich Institute of Biomedical Chemistry (Moscow, Russia). The SANS spectra have been measured at the YuMO small-angle spectrometer of IBR-2 reactor (Joint Institute of Nuclear Research, Dubna, Russia). Basic characteristics of polydispersed population of PTNS unilamellar vesicles (average radius of vesicles, polydispersity, thickness of membrane, etc.) have been determined in three cases of the PTNS concentrations in D2O: 5%, 10%, and 25%. Numerical analysis is based on the separated form factors method (SFF). The results are discussed in comparison with the results of analysis of the small-angle X-ray scattering spectra collected at the Kurchatov Synchrotron Radiation Source of the National Research Center “Kurchatov Institute” (Moscow, Russia).

  14. Synthesis, transport and dielectric properties of polyaniline/Co3O4 ...

    Indian Academy of Sciences (India)

    TECS

    Synthesis, transport and dielectric properties of polyaniline/Co3O4 composites ... Initial increment in conductivity is due to extended chain length of polyaniline where polarons possess .... Figure 3 displays the scanning electron micrograph of.

  15. Strong-coupling Bose polarons out of equilibrium: Dynamical renormalization-group approach

    Science.gov (United States)

    Grusdt, Fabian; Seetharam, Kushal; Shchadilova, Yulia; Demler, Eugene

    2018-03-01

    When a mobile impurity interacts with a surrounding bath of bosons, it forms a polaron. Numerous methods have been developed to calculate how the energy and the effective mass of the polaron are renormalized by the medium for equilibrium situations. Here, we address the much less studied nonequilibrium regime and investigate how polarons form dynamically in time. To this end, we develop a time-dependent renormalization-group approach which allows calculations of all dynamical properties of the system and takes into account the effects of quantum fluctuations in the polaron cloud. We apply this method to calculate trajectories of polarons following a sudden quench of the impurity-boson interaction strength, revealing how the polaronic cloud around the impurity forms in time. Such trajectories provide additional information about the polaron's properties which are challenging to extract directly from the spectral function measured experimentally using ultracold atoms. At strong couplings, our calculations predict the appearance of trajectories where the impurity wavers back at intermediate times as a result of quantum fluctuations. Our method is applicable to a broader class of nonequilibrium problems. As a check, we also apply it to calculate the spectral function and find good agreement with experimental results. At very strong couplings, we predict that quantum fluctuations lead to the appearance of a dark continuum with strongly suppressed spectral weight at low energies. While our calculations start from an effective Fröhlich Hamiltonian describing impurities in a three-dimensional Bose-Einstein condensate, we also calculate the effects of additional terms in the Hamiltonian beyond the Fröhlich paradigm. We demonstrate that the main effect of these additional terms on the attractive side of a Feshbach resonance is to renormalize the coupling strength of the effective Fröhlich model.

  16. The pairing theory of polarons in real- and impulse spaces

    International Nuclear Information System (INIS)

    Dzhumanov, S.; Abboudy, S.; Baratov, A.A.

    1995-07-01

    A consistent pairing theory of carriers in real- and impulse spaces is developed. The pairing of different free (F), delocalized (D) and self-trapped (S) carriers in real-space, leading to the formation of various bipolaronic states are considered within the continuum model and adiabatic approximation taking into account the combined effect of the short- and long-range components of electron-lattice interaction with and without electron correlation. The formation possibility of D- and S-bipolarons as a function of ε ∞ /ε 0 are shown. The pairing scenarios of carriers in k-space leading to the formation of different bipolarons (including also Cooper pairs dynamic bipolarons) are considered within the generalized BCS-like model taking into account the combined phonon and polaron-bag mediated processes. It is shown that the pure BCS pairing picture is the particular case of the general BCS-like one. The possible relevance of the obtained results to high-T c superconductors is discussed in details in the framework of a novel two-stage Fermi-Bose-liquid scenarios of superconductivity which is caused by single particle and pair condensation of an attracting bipolarons. (author). 51 refs, 6 figs

  17. Electronic contributions to the transport properties and specific heat of solid UO2: an empirical, self-consistent analysis

    International Nuclear Information System (INIS)

    Hyland, G.J.; Ralph, J.

    1982-07-01

    From an empirical, self-consistent analysis of new high temperature data on the thermo-electric Seebeck coefficient and d.c. electrical conductivity, the value of the free energy controlling the equilibrium of the thermally induced reaction, 2U 4+ reversible U 3+ + U 5+ is determined (treating the U 3+ and U 5+ as small polarons) and used to calculate the contribution of the process to the high temperature thermal conductivity and specific heat of UO 2 . It is found that the transport properties can be completely accounted for in this way, but not the anomalous rise in specific heat - the origin of which remains obscure. (U.K.)

  18. Acoustic Levitation Transportation of Small Objects Using a Ring-type Vibrator

    Science.gov (United States)

    Thomas, Gilles P. L.; Andrade, Marco A. B.; Adamowski, Julio C.; Silva, Eḿílio C. N.

    A new device for noncontact transportation of small solid objects is presented here. Ultrasonic flexural vibrations are generated along the ring shaped vibrator using two Langevin transducers and by using a reflector parallel to the vibrator, small particles are trapped at the nodal points of the resulting acoustic standing wave. The particles are then moved by generating a traveling wave along the vibrator, which can be done by modulating the vibration amplitude of the transducers. The working principle of the traveling wave along the vibrator has been modeled by the superposition of two orthogonal standing waves, and the position of the particles can be predicted by using finite element analysis of the vibrator and the resulting acoustic field. A prototype consisting of a 3 mm thick, 220 mm long, 50 mm wide and 52 mm radius aluminum ring-type vibrator and a reflector of the same length and width was built and small polystyrene spheres have been successfully transported along the straight parts of the vibrator.

  19. The Small Aircraft Transportation System for America: A Case in Public Infrastructure Change

    Science.gov (United States)

    Bowen, Brent D.

    2000-01-01

    The National Aeronautics and Space Administration (NASA), U.S. Department of Transportation, Federal Aviation Administration, industry stakeholders, and academia, have joined forces to pursue the NASA National General Aviation Roadmap leading to a Small Aircraft Transportation System (SATS). This strategic undertaking has a 25-year goal to bring next-generation technologies and improve travel between remote communities and transportation centers in urban areas by utilizing the nation's 5,400 public-use general aviation airports. To facilitate this initiative, a comprehensive upgrade of public infrastructure must be planned, coordinated, and implemented within the framework of the national air transportation system. The Nebraska NASA EPSCoR Program has proposed to deliver research support in key public infrastructure areas in coordination with the General Aviation Program Office at the NASA Langley Research Center. Ultimately, SATS may permit tripling aviation system throughput capacity by tapping the underutilized general aviation facilities to achieve the national goal of doorstep-to-destination travel at four times the speed of highways for the nation's suburban, rural, and remote communities.

  20. Influence of Mg doping on the behaviour of polaronic light-induced absorption in LiNbO3

    International Nuclear Information System (INIS)

    Conradi, D.; Merschjann, C.; Schoke, B.; Imlau, M.; Corradi, G.; Polgar, K.

    2008-01-01

    Transient light-induced absorption changes α li (t), caused by optically generated small polarons, are investigated in LiNbO 3 :Mg below and above the optical-damage-resistance threshold (ODRT). The lifetime of α li (t) is reduced by three orders of magnitude above the ODRT while a significantly enhanced amplitude α max li is observed in the infrared. Our observations are in full accordance with the predictions of microscopic models for the ODRT, namely the removal of Nb Li antisite defects upon incorporation of Mg ions, and an enhanced dark conductivity. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (Abstract Copyright [2008], Wiley Periodicals, Inc.)

  1. Point-to-Point! Validation of the Small Aircraft Transportation System Higher Volume Operations Concept

    Science.gov (United States)

    Williams, Daniel M.

    2006-01-01

    Described is the research process that NASA researchers used to validate the Small Aircraft Transportation System (SATS) Higher Volume Operations (HVO) concept. The four phase building-block validation and verification process included multiple elements ranging from formal analysis of HVO procedures to flight test, to full-system architecture prototype that was successfully shown to the public at the June 2005 SATS Technical Demonstration in Danville, VA. Presented are significant results of each of the four research phases that extend early results presented at ICAS 2004. HVO study results have been incorporated into the development of the Next Generation Air Transportation System (NGATS) vision and offer a validated concept to provide a significant portion of the 3X capacity improvement sought after in the United States National Airspace System (NAS).

  2. Polaron binding energy and effective mass in the GaAs film

    International Nuclear Information System (INIS)

    Wu Zhenhua; Yan Liangxing; Tian Qiang; Li Hua; Liu Bingcan

    2012-01-01

    The binding energy and effective mass of a polaron in a GaAs film deposited on the Al 0.3 Ga 0.7 As substrate are studied theoretically by using the fractional-dimensional space approach. Our calculations show that the polaron binding energy and mass shift decrease monotonously with increasing the film thickness. For the film thicknesses with L w ≤ 70Å and the substrate thicknesses with L b ≤ 200Å, the different values of the substrate thickness influence the polaron binding energy and mass shift in the GaAs film. The polaron binding energy and mass shift increase monotonously with increasing the substrate thickness. For the film thickness with L w ≥ 70Å or the substrate thicknesses with L b ≤ 200Å, the different values of the substrate thickness have no significant influence on the polaron binding energy and mass shift in the GaAs film deposited on the Al 0.3 Ga 0.7 As substrate.

  3. Observation of Spin Polarons in a Tunable Fermi Liquid of Ultracold Atoms

    Science.gov (United States)

    Zwierlein, Martin

    2009-05-01

    We have observed spin polarons, dressed spin down impurities in a spin up Fermi sea of ultracold atoms via tomographic RF spectroscopy. Feshbach resonances allow to freely tune the interactions between the two spin states involved. A single spin down atom immersed in a Fermi sea of spin up atoms can do one of two things: For strong attraction, it can form a molecule with exactly one spin up partner, but for weaker interaction it will spread its attraction and surround itself with a collection of majority atoms. This spin down atom dressed with a spin up cloud constitutes the spin- or Fermi polaron. We have observed a striking spectroscopic signature of this quasi-particle for various interaction strengths, a narrow peak in the spin down spectrum that emerges above a broad background. The spectra allow us to directly measure the polaron energy and the quasi-particle residue Z. The polarons are found to be only weakly interacting with each other, and can thus be identified with the quasi-particles of Landau's Fermi liquid theory. At a critical interaction strength, we observe a transition from spin one-half polarons to spin zero molecules. At this point the Fermi liquid undergoes a phase transition into a superfluid Bose liquid.

  4. Gross–Tulub polaron functional in the region of intermediate and strong coupling

    Directory of Open Access Journals (Sweden)

    N.I. Kashirina

    2017-10-01

    Full Text Available Properties of the polaron functional obtained as a result of averaging the Fröhlich Hamiltonian on the translation-invariant function have been investigated. The polaron functional can be represented in two different forms. It has been shown that the functional of translationally invariant Gross–Tulub polaron cannot be applied in the strong coupling region, where the real part of the complex quantity takes negative values. The function coincides in its structure with the dynamic susceptibility of degenerate electron gas. The necessary condition for obtaining correct results is investigation of the region of admissible values of the Gross–Tulub functional depending on properties of the function , variational parameters, and the electron-phonon interaction parameter α (Fröhlich coupling constant. A simple and exact formula for the recoil energy of the translationally invariant polaron has been derived, which makes it possible to extend the range of admissible values of the parameters of the electron-phonon interaction to the region of extremely strong coupling (α > 10, where . Numerical investigation of different forms of polaron functionals obtained using the field theory methods has been carried out.

  5. Synchronization and Control of Halo-Chaos in Beam Transport Network with Small World Topology

    International Nuclear Information System (INIS)

    Liu Qiang; Fang Jinqing; Li Yong

    2007-01-01

    The synchronous conditions of two kinds of the small-world (SW) network are studied. The small world topology can affect on dynamical behaviors of the beam transport network (BTN) largely, if the BTN is constructed with the SW topology, the global linear coupling and special linear feedback can realize the synchronization control of beam halo-chaos as well as periodic state in the BTN with the SW topology, respectively. This important result can provide an effective way for the experimental study and the engineering design of the BTN in the high-current accelerator driven radioactive clean nuclear power systems, and may have potential use in prospective applications for halo-chaos secure communication.

  6. Possibility of observation of polaron normal modes at the far-infrared spectrum of acetanilide and related organics

    Science.gov (United States)

    Kalosakas, G.; Aubry, S.; Tsironis, G. P.

    1998-10-01

    We use a stationary and normal mode analysis of the semiclassical Holstein model in order to connect the low-frequency linear polaron modes to low-lying far-infrared lines of the acetanilide spectrum and through parameter fitting we comment on the validity of the polaron results in this system.

  7. Transportation Limitation Access to the Small Islands (Case Study: Banggai Laut Regency)

    Science.gov (United States)

    Sunarti, S.

    2018-02-01

    Indonesia is as an archipelago and maritime country, the large number of Islands owned and scattered in all directions makes a challenge for the Government in equitable development. Development in Indonesia has not been spread evenly and tends to focus on the big island, while the smaller islands are still far behind and lack of government attention. One of them is the lack of infrastructure especially the access to the small islands. Among the small islands in Indonesia with minimal maritime infrastructure or transportation is Banggai Laut Regency, Central Sulawesi Province. This Regency is a new regency that separate itself from its previous regency that is Banggai Kepulauan Regency in about 4 years ago. For the development of the Banggai Laut Regency, access to reach that regency is quite difficult. Therefore, the aim of this research is to find infrastructure development strategy to support the development of Banggai Laut Regency. The research method used was the concurrent model mixed method. Data collection method was done with primary data through field observation and interview, secondary data through literature and document review. Analytical techniques used are qualitative descriptive and Map Overlay techniques using GIS to describe the characteristics of study areas and spatial relationships between islands. The results of this research conclude that the Banggai Laut Regency requires infrastructure development particularly maritime transportation to enhance accessibility of the community headed to Banggi Laut Regency or headed to another island from the Banggai Laut Regency.

  8. Sediment transport to and from small impoundments in northeast Kansas, March 2009 through September 2011

    Science.gov (United States)

    Foster, Guy M.; Lee, Casey J.; Ziegler, Andrew C.

    2012-01-01

    The U.S. Geological Survey, in cooperation with the Kansas Water Office, investigated sediment transport to and from three small impoundments (average surface area of 0.1 to 0.8 square miles) in northeast Kansas during March 2009 through September 2011. Streamgages and continuous turbidity sensors were operated upstream and downstream from Atchison County, Banner Creek, and Centralia Lakes to study the effect of varied watershed characteristics and agricultural practices on sediment transport in small watersheds in northeast Kansas. Atchison County Lake is located in a predominantly agricultural basin of row crops, with wide riparian buffers along streams, a substantial amount of tile drainage, and numerous small impoundments (less than 0.05 square miles; hereafter referred to as “ponds”). Banner Creek Lake is a predominantly grassland basin with numerous small ponds located in the watershed, and wide riparian buffers along streams. Centralia Lake is a predominantly agricultural basin of row crops with few ponds, few riparian buffers along streams, and minimal tile drainage. Upstream from Atchison County, Banner Creek, and Centralia Lakes 24, 38, and 32 percent, respectively, of the total load was transported during less than 0.1 percent (approximately 0.9 days) of the time. Despite less streamflow in 2011, larger sediment loads during that year indicate that not all storm events transport the same amount of sediment; larger, extreme storms during the spring may transport much larger sediment loads in small Kansas watersheds. Annual sediment yields were 360, 400, and 970 tons per square mile per year at Atchison County, Banner, and Centralia Lake watersheds, respectively, which were less than estimated yields for this area of Kansas (between 2,000 and 5,000 tons per square mile per year). Although Centralia and Atchison County Lakes had similar percentages of agricultural land use, mean annual sediment yields upstream from Centralia Lake were about 2.7 times

  9. Transport Mechanisms in Organic Thin-Film Transistors

    Science.gov (United States)

    Fung, A. W. P.

    1996-03-01

    Recent success in fabricating field-effect transistors with polycrystalline α-sexithiophene (α-6T) has allowed us to study charge transport in this organic semiconductor. The appealing structural property that the oligomer chains are seated almost perpendicular to the substrate provides a model π-conjugated system which we find exhibits band transport at low temperatures. We observe a behavioral transition around 50K which is consistent with the metal-insulator transition in Holstein's small-polaron theory. The fact that we can observe intrinsic behavior means that the ambient-temperature mobility obtained in these transistors is optimal for α-6T. Agreement with the Holstein theory provides us with a prescription for rational design of materials for organic transistor applications. Work done in collaboration with L. Torsi, A. Dodabalapur, L. J. Rothberg and H. E. Katz.

  10. Tokamak electron heat transport by direct numerical simulation of small scale turbulence

    International Nuclear Information System (INIS)

    Labit, B.

    2002-10-01

    In a fusion machine, understanding plasma turbulence, which causes a degradation of the measured energy confinement time, would constitute a major progress in this field. In tokamaks, the measured ion and electron thermal conductivities are of comparable magnitude. The possible sources of turbulence are the temperature and density gradients occurring in a fusion plasma. Whereas the heat losses in the ion channel are reasonably well understood, the origin of the electron losses is more uncertain. In addition to the radial velocity associated to the fluctuations of the electric field, electrons are more affected than ions by the magnetic field fluctuations. In experiments, the confinement time can be conveniently expressed in terms of dimensionless parameters. Although still somewhat too imprecise, these scaling laws exhibit strong dependencies on the normalized pressure β or the normalized Larmor radius, ρ * . The present thesis assesses whether a tridimensional, electromagnetic, nonlinear fluid model of plasma turbulence driven by a specific instability can reproduce the dependence of the experimental electron heat losses on the dimensionless parameters β and ρ * . The investigated interchange instability is the Electron Temperature Gradient driven one (ETG). The model is built by using the set of Braginskii equations. The developed simulation code is global in the sense that a fixed heat flux is imposed at the inner boundary, leaving the gradients free to evolve. From the nonlinear simulations, we have put in light three characteristics for the ETG turbulence: the turbulent transport is essentially electrostatic; the potential and pressure fluctuations form radially elongated cells called streamers; the transport level is very low compared to the experimental values. The thermal transport dependence study has shown a very small role of the normalized pressure, which is in contradiction with the Ohkama's formula. On the other hand, the crucial role of the

  11. Modulation of small intestinal phosphate transporter by dietary supplements of mineral phosphorus and phytase in broilers.

    Science.gov (United States)

    Huber, Korinna; Zeller, Ellen; Rodehutscord, Markus

    2015-05-01

    Dietary phosphorus (P) is known as a main modulator of phosphate (Pi) transporter expression. The effect of supplemented mineral P with or without phytase on protein expression of two sodium-dependent Pi (NaPi) transporters and a calcium channel was studied in the small intestine of broilers. Thirty-six broilers were randomly assigned to six different diets at 15 days of age. Two levels of total P (tP, adjusted by monocalcium phosphate (MCP) supplementation), 0.39% (BD-) and 0.47% (BD+) were fed until day 25; and at each tP level, three levels of phytase were used with 0, 500, and 12,500 FTU/kg of an E. coli phytase. Mucosa samples from jejunum and ileum were taken and apical membranes were isolated by MgCl2 precipitation. Protein expression of NaPi IIb, NaPi type III (PiT1) and the calcium channel TRPV6 were semiquantitatively measured by Western blotting and jejunal mucosal phytase activity by measurement of Pi release. The jejunal NaPi IIb transporter was expressed with two distinct bands, which were modulated differently by diet. NaPi IIb Band1 increased (P phytase supplementation but was not affected by MCP supplementation. This inverse modulation of Band1 and Band2 was significantly related to the amount of net absorbed P with higher expression of Band1 at higher amounts of net absorbed P. In addition, a second Pi transporter, PiT1, was detected in which ileal expression decreased (P phytase supplementation. The expression of the calcium channel TRPV6 was increased in BD+ groups. A trend for an interaction between MCP and phytase supplementation on mucosal phytase activity was observed (P = 0.079) with a decrease in activity when BD+ with 12,500 FTU/kg phytase was fed. Chicken intestinal epithelial cells responded to dietary supplemented phytase and MCP by changing the Pi transporter expression in apical membranes. In conclusion, availability of Pi is most likely the key modulator of transporter protein expression. However, a contribution of lower inositol

  12. Polaron effects on nonlinear optical rectification in asymmetrical Gaussian potential quantum wells with applied electric fields

    International Nuclear Information System (INIS)

    Wu, Jinghe; Guo, Kangxian; Liu, Guanghui

    2014-01-01

    Polaron effects on nonlinear optical rectification in asymmetrical Gaussian potential quantum wells are studied by the effective mass approximation and the perturbation theory. The numerical results show that nonlinear optical rectification coefficients are strongly dependent on the barrier hight V 0 of the Gaussian potential quantum wells, the range L of the confinement potential and the electric field F. Besides, the numerical results show that no matter how V 0 , L and F change, taking into consideration polaron effects, the optical rectification coefficients χ 0 (2) get greatly enhanced.

  13. Quantum Monte Carlo simulations of the Fermi-polaron problem and bosons with Gaussian interactions

    Energy Technology Data Exchange (ETDEWEB)

    Kroiss, Peter Michael

    2017-02-01

    This thesis deals with the application of current Quantum Monte Carlo algorithms to many-body systems of fermionic and bosonic species. The first part applies the diagrammatic Monte Carlo method to the Fermi polaron problem, a system of an impurity interacting resonantly with a homogeneous Fermi bath. It is numerically shown that the three particle-hole diagrams do not contribute significantly to the final answer in a quasi-two-dimensional setup, thus demonstrating a nearly perfect destructive interference of contributions in subspaces with higher-order particle-hole lines. Consequently, for strong-enough confinement in the third direction, the transition between the polaron and the molecule ground state is found to be in good agreement with the pure two-dimensional case and agrees very well with the one found by the wave-function approach in the two-particle-hole subspace. In three-dimensional Fermi-polaron systems with mass imbalance of impurity and bath atoms, polaron energy and quasiparticle residue can be accurately determined over a broad range of impurity masses. Furthermore, the spectral function of an imbalanced polaron demonstrates the stability of the quasiparticle and also allows us to locate the repulsive polaron as an excited state. The quantitative exactness of two-particle-hole wave functions is investigated, resulting in a relative lowering of polaronic energies in the mass-imbalance phase diagram. Tan's contact coefficient for the mass-balanced polaron system is found to be in good agreement with variational methods. Mass-imbalanced systems can be studied experimentally by ultracold atom mixtures such as {sup 6}Li-{sup 40}K. In the second part of the thesis, the ground state of a two-dimensional system of Bose particles of spin zero, interacting via a repulsive Gaussian-Core potential, is investigated by means of path integral Monte Carlo simulations. The quantum phase diagram is qualitatively identical to that of two-dimensional Yukawa

  14. 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.

  15. DFT+U study of self-trapping, trapping, and mobility of oxygen-type hole polarons in barium stannate

    Science.gov (United States)

    Geneste, Grégory; Amadon, Bernard; Torrent, Marc; Dezanneau, Guilhem

    2017-10-01

    The charge-transfer insulating perovskite oxides currently used as fuel cell electrolytes undergo, at high temperature, an oxidation reaction 1/2 O2(g ) +VO••→OOX+2 h• , that produces oxygen-type holes. Understanding the nature and mobility of these oxygen-type holes is an important step to improve the performance of devices, but presents a theoretical challenge since, in their localized form, they cannot be captured by standard density functional theory. Here, we employ the DFT+U formalism with a Hubbard correction on the p orbitals of oxygen to investigate several properties of these holes, in the particular case of BaSnO3. We describe the small oxygen-type hole polarons, the self-trapping at their origin, and their trapping by trivalent dopants (Ga, Sc, In, Lu, Y, Gd, La). Strong similarities with protonic defects are observed concerning the evolution of the trapping energy with ionic radius of the dopant. Moreover, we show that long-range diffusion of holes is a complex phenomenon, that proceeds by a succession of several mechanisms. However, the standard implementation of DFT+U within the projector augmented-wave (PAW) formalism leads to use very large, unphysical values of U for the O-p orbital. We propose here a slightly modified DFT+U scheme, that takes into account the fact that the O-p is truncated in usual DFT+U implementation in PAW. This scheme yields more physical values of U than the ones traditionally used in the literature, and describes well the properties of the hole polaron.

  16. Small-sized linear accelerator of 2.5 MeV electrons with a local radiation shield for custom examination of freight transported by motor transport

    International Nuclear Information System (INIS)

    Baklanov, A.V.; Gavrish, Yu.N.; Klinov, A.P.; Krest'yaninov, A.S.; Nikolaev, V.M.; Fomin, L.P.; Linkenbach, H.A.; Geus, G.; Knospel, W.

    2001-01-01

    A new development of a small-sized linear accelerator of 2.5 MeV electrons with a local radiation protection is described. The accelerator is intended for movable facilities of radiation custom of the freight transported by motor transport. Main constructive solutions, mass and dimension characteristics and results of preliminary tests of the accelerator parameters and characteristics of radiation protection are presented [ru

  17. Fingerprints of spin-orbital polarons and of their disorder in the photoemission spectra of doped Mott insulators with orbital degeneracy

    Science.gov (United States)

    Avella, Adolfo; Oleś, Andrzej M.; Horsch, Peter

    2018-04-01

    We explore the effects of disordered charged defects on the electronic excitations observed in the photoemission spectra of doped transition metal oxides in the Mott insulating regime by the example of the R1 -xCaxVO3 perovskites, where R = La, ⋯, Lu. A fundamental characteristic of these vanadium d2 compounds with partly filled t2 g valence orbitals is the persistence of spin and orbital order up to high doping, in contrast to the loss of magnetic order in high-Tc cuprates at low defect concentration. We study the disordered electronic structure of such doped Mott-Hubbard insulators within the unrestricted Hartree-Fock approximation and, as a result, manage to explain the spectral features that occur in photoemission and inverse photoemission. In particular, (i) the atomic multiplet excitations in the inverse photoemission spectra and the various defect-related states and satellites are qualitatively well reproduced, (ii) a robust Mott gap survives up to large doping, and (iii) we show that the defect states inside the Mott gap develop a soft gap at the Fermi energy. The soft defect-states gap, which separates the highest occupied from the lowest unoccupied states, can be characterized by a shape and a scale parameter extracted from a Weibull statistical sampling of the density of states near the chemical potential. These parameters provide a criterion and a comprehensive schematization for the insulator-metal transition in disordered systems. Our results provide clear indications that doped holes are bound to charged defects and form small spin-orbital polarons whose internal kinetic energy is responsible for the opening of the soft defect-states gap. We show that this kinetic gap survives disorder fluctuations of defects and is amplified by the long-range electron-electron interactions, whereas we observe a Coulomb singularity in the atomic limit. The small size of spin-orbital polarons is inferred by an analysis of the inverse participation ratio and by

  18. Tracking of Short Distance Transport Pathways in Biological Tissues by Ultra-Small Nanoparticles

    Science.gov (United States)

    Segmehl, Jana S.; Lauria, Alessandro; Keplinger, Tobias; Berg, John K.; Burgert, Ingo

    2018-03-01

    In this work, ultra-small europium-doped HfO2 nanoparticles were infiltrated into native wood and used as trackers for studying penetrability and diffusion pathways in the hierarchical wood structure. The high electron density, laser induced luminescence, and crystallinity of these particles allowed for a complementary detection of the particles in the cellular tissue. Confocal Raman microscopy and high-resolution synchrotron scanning wide-angle X-ray scattering (WAXS) measurements were used to detect the infiltrated particles in the native wood cell walls. This approach allows for simultaneously obtaining chemical information of the probed biological tissue and the spatial distribution of the integrated particles. The in-depth information about particle distribution in the complex wood structure can be used for revealing transport pathways in plant tissues, but also for gaining better understanding of modification treatments of plant scaffolds aiming at novel functionalized materials.

  19. A coupled model of transport-reaction-mechanics with trapping. Part I - Small strain analysis

    Science.gov (United States)

    Salvadori, A.; McMeeking, R.; Grazioli, D.; Magri, M.

    2018-05-01

    A fully coupled model for mass and heat transport, mechanics, and chemical reactions with trapping is proposed. It is rooted in non-equilibrium rational thermodynamics and assumes that displacements and strains are small. Balance laws for mass, linear and angular momentum, energy, and entropy are stated. Thermodynamic restrictions are identified, based on an additive strain decomposition and on the definition of the Helmholtz free energy. Constitutive theory and chemical kinetics are studied in order to finally write the governing equations for the multi-physics problem. The field equations are solved numerically with the finite element method, stemming from a three-fields variational formulation. Three case-studies on vacancies redistribution in metals, hydrogen embrittlement, and the charge-discharge of active particles in Li-ion batteries demonstrate the features and the potential of the proposed model.

  20. Small Aircraft Transportation System, Higher Volume Operations Concept: Off-Nominal Operations

    Science.gov (United States)

    Abbott, Terence S.; Consiglio, Maria C.; Baxley, Brian T.; Williams, Daniel M.; Conway, Sheila R.

    2005-01-01

    This document expands the Small Aircraft Transportation System, (SATS) Higher Volume Operations (HVO) concept to include off-nominal conditions. The general philosophy underlying the HVO concept is the establishment of a newly defined area of flight operations called a Self-Controlled Area (SCA). During periods of poor weather, a block of airspace would be established around designated non-towered, non-radar airports. Aircraft flying enroute to a SATS airport would be on a standard instrument flight rules flight clearance with Air Traffic Control providing separation services. Within the SCA, pilots would take responsibility for separation assurance between their aircraft and other similarly equipped aircraft. Previous work developed the procedures for normal HVO operations. This document provides details for off-nominal and emergency procedures for situations that could be expected to occur in a future SCA.

  1. Optimization of Intracellular Transportation of Gene Therapeutic DNA in Small Cell Lung Cancer (Ph.d.)

    DEFF Research Database (Denmark)

    Cramer, Frederik

    2013-01-01

    Small cell lung cancer (SCLC) is a highly malignant disease characterized as being very aggressive and metastasizing at a rapid pace. The malevolent pace of SCLC cell migration results in almost three out of four SCLC patients having disseminated SCLC at the time of diagnosis. Unfortunately...... has to be able to repeated systemic delivery of gene therapy to cancer cells in a both safe and efficient way. Non-viral delivery vectors fulfill many of these requirements except the latter. It is currently very difficult to systemically transport sufficient amounts of therapeutic DNA, by a non......-viral delivery system, to the nuclei of the SCLC cells. As a result, the gene therapy expression obtained is too low to have any clinical relevance. We have at the Department of Radiation Biology developed a transcriptionally targeting suicide gene therapy system which is built on a double stranded DNA plasmid...

  2. Clinical course teaching in transport of critically ill patients: Small group methods

    Directory of Open Access Journals (Sweden)

    Mohammad Taghi Beigmohammadi

    2016-10-01

    Full Text Available Critically ill patient transfer is potentially risky and may be lead to morbidity and mortality. Physicians' skill is very important for safe transport. We want to evaluate the effect of clinical course teaching on the promotion of physicians' abilities in the transport of critically ill patients. In an interventional study, 320 interns, male and female, were taught about patient transfer in two groups include in one day clinical course as the small group system (n=160 and other group the lecture base learning (n=160. In the clinical course, each participant under observation of an anesthesiologist in the operation room and ICU was acquainted with mask ventilation, intubation and learned to work with a defibrillator, infusion pump, portable ventilator and pulse oximeter. In lecture group, the anesthesiologist explained the topics by video and dummy. At the end of education course, the interns’ abilities were evaluated based on checklist method and scored by the project colleague in all educational items. Three hundred twenty interns, 122 males, and 198 females; were enrolled, two groups. The clinical course training caused improvements in the interns’ knowledge and abilities in intubation and use of the defibrillator and portable ventilator vs.lecture group significantly (P<0.005. The males were better than females in laryngoscopy, but the progress of the females was significantly better than males (P=0.003. The rate of adverse events was reduced significantly after clinical course teaching (P=0.041 Clinical course teaching could promote interns' clinical competencies in the transport of critically ill patients.

  3. Effects of system-bath coupling on a photosynthetic heat engine: A polaron master-equation approach

    Science.gov (United States)

    Qin, M.; Shen, H. Z.; Zhao, X. L.; Yi, X. X.

    2017-07-01

    Stimulated by suggestions of quantum effects in energy transport in photosynthesis, the fundamental principles responsible for the near-unit efficiency of the conversion of solar to chemical energy became active again in recent years. Under natural conditions, the formation of stable charge-separation states in bacteria and plant reaction centers is strongly affected by the coupling of electronic degrees of freedom to a wide range of vibrational motions. These inspire and motivate us to explore the effects of the environment on the operation of such complexes. In this paper, we apply the polaron master equation, which offers the possibilities to interpolate between weak and strong system-bath coupling, to study how system-bath couplings affect the exciton-transfer processes in the Photosystem II reaction center described by a quantum heat engine (QHE) model over a wide parameter range. The effects of bath correlation and temperature, together with the combined effects of these factors are also discussed in detail. We interpret these results in terms of noise-assisted transport effect and dynamical localization, which correspond to two mechanisms underpinning the transfer process in photosynthetic complexes: One is resonance energy transfer and the other is the dynamical localization effect captured by the polaron master equation. The effects of system-bath coupling and bath correlation are incorporated in the effective system-bath coupling strength determining whether noise-assisted transport effect or dynamical localization dominates the dynamics and temperature modulates the balance of the two mechanisms. Furthermore, these two mechanisms can be attributed to one physical origin: bath-induced fluctuations. The two mechanisms are manifestations of the dual role played by bath-induced fluctuations depending on the range of parameters. The origin and role of coherence are also discussed. It is the constructive interplay between noise and coherent dynamics, rather

  4. The Small Aircraft Transportation System (SATS), Higher Volume Operations (HVO) Off-Nominal Operations

    Science.gov (United States)

    Baxley, B.; Williams, D.; Consiglio, M.; Conway, S.; Adams, C.; Abbott, T.

    2005-01-01

    The ability to conduct concurrent, multiple aircraft operations in poor weather, at virtually any airport, offers an important opportunity for a significant increase in the rate of flight operations, a major improvement in passenger convenience, and the potential to foster growth of charter operations at small airports. The Small Aircraft Transportation System, (SATS) Higher Volume Operations (HVO) concept is designed to increase traffic flow at any of the 3400 nonradar, non-towered airports in the United States where operations are currently restricted to one-in/one-out procedural separation during Instrument Meteorological Conditions (IMC). The concept's key feature is pilots maintain their own separation from other aircraft using procedures, aircraft flight data sent via air-to-air datalink, cockpit displays, and on-board software. This is done within the Self-Controlled Area (SCA), an area of flight operations established during poor visibility or low ceilings around an airport without Air Traffic Control (ATC) services. The research described in this paper expands the HVO concept to include most off-nominal situations that could be expected to occur in a future SATS environment. The situations were categorized into routine off-nominal operations, procedural deviations, equipment malfunctions, and aircraft emergencies. The combination of normal and off-nominal HVO procedures provides evidence for an operational concept that is safe, requires little ground infrastructure, and enables concurrent flight operations in poor weather.

  5. Quantitative measurements of magnetic polaron binding on acceptors in CdMnTe alloys

    Science.gov (United States)

    Nhung, Tran Hong; Planel, R.

    1983-03-01

    The acceptor binding energy is measured as a function of Temperature and composition in Cd1-x Mnx Te alloys, by time resolved spectroscopy. The Bound magnetic polaron effect is measured and compared with a theory accouting for magnetic saturation and fluctuations.

  6. Impact of morphology on polaron delocalization in a semicrystalline conjugated polymer

    KAUST Repository

    Steyrleuthner, Robert; Zhang, Yuexing; Zhang, Lei; Kraffert, Felix; Cherniawski, Benjamin P.; Bittl, Robert; Briseno, Alejandro L.; Bredas, Jean-Luc; Behrends, Jan

    2016-01-01

    We investigate the delocalization of holes in the semicrystalline conjugated polymer poly(2,5-bis(3-alkylthiophene-2-yl)thieno[3,2-b]thiophene) (PBTTT) by directly measuring the hyperfine coupling between photogenerated polarons and bound nuclear

  7. Decay of Polarons and Molecules in a Strongly Polarized Fermi Gas

    DEFF Research Database (Denmark)

    Bruun, Georg; Massignan, P.

    2010-01-01

    , and that it vanishes much faster than the energy difference between the two states, thereby confirming the first order nature of the polaron-molecule transition. In the regime where each state is metastable, we find quasiparticle lifetimes which are much longer than what is expected for a usual Fermi liquid. Our...

  8. Effect of doping Ca on polaron hopping in LaSr 2 Mn 2 O 7

    Indian Academy of Sciences (India)

    ... Lecture Workshops · Refresher Courses · Symposia · Live Streaming. Home; Journals; Pramana – Journal of Physics; Volume 58; Issue 5-6. Effect of doping Ca on polaron hopping in LaSr2Mn2O7. S N Bhatia Osama A Yassin. Colossal Magnetoresistance & Other Materials Volume 58 Issue 5-6 May-June 2002 pp 1061- ...

  9. A new polaronic order-disorder phase transition in magnetite as observed through μSR

    International Nuclear Information System (INIS)

    Boekema, C.; Lichti, R.L.; Denison, A.B.; Brabers, V.A.M.; Cooke, D.W.; Heffner, R.H.; Hutson, R.L.; Schillaci, M.E.

    1986-01-01

    Recent μSr measurements on the Mott-Wigner glass magnetite, as a function of temperature and external magnetic field have shown the existence of two inequivalent magnetic sites below T A = 247 K. These data are being interpreted in terms of the onset or destruction of local order manifested as local atomic correlations (molecular polarons). (orig.)

  10. Time Domain View of Liquid-like Screening and Large Polaron Formation in Lead Halide Perovskites

    Science.gov (United States)

    Joshi, Prakriti Pradhan; Miyata, Kiyoshi; Trinh, M. Tuan; Zhu, Xiaoyang

    The structural softness and dynamic disorder of lead halide perovskites contributes to their remarkable optoelectronic properties through efficient charge screening and large polaron formation. Here we provide a direct time-domain view of the liquid-like structural dynamics and polaron formation in single crystal CH3NH3PbBr3 and CsPbBr3 using femtosecond optical Kerr effect spectroscopy in conjunction with transient reflectance spectroscopy. We investigate structural dynamics as function of pump energy, which enables us to examine the dynamics in the absence and presence of charge carriers. In the absence of charge carriers, structural dynamics are dominated by over-damped picosecond motions of the inorganic PbBr3- sub-lattice and these motions are strongly coupled to band-gap electronic transitions. Carrier injection from across-gap optical excitation triggers additional 0.26 ps dynamics in CH3NH3PbBr3 that can be attributed to the formation of large polarons. In comparison, large polaron formation is slower in CsPbBr3 with a time constant of 0.6 ps. We discuss how such dynamic screening protects charge carriers in lead halide perovskites. US Department of Energy, Office of Science - Basic Energy Sciences.

  11. Disorder-tuned charge transport in organic semiconductors

    Science.gov (United States)

    Xu, Feng; Qiu, Dong; Yan, Dadong

    2013-02-01

    We propose that the polaron transport in organic semiconductors is remarkably tuned by the fluctuation of polarization energy. The tuning effect of energetic fluctuation not only causes a continuous transition from non-Arrhenius to Arrhenius temperature activated charge transport with increasing moderate disorder strengths but also results in a band-like conduction in the low disorder regime which benefits from the enhanced mobilities in shallow trap states. As a result, a unified description of polaron transport is obtained for a set of typical organic semiconductors.

  12. An ab initio model of electron transport in hematite (a-Fe2O3) basal planes

    International Nuclear Information System (INIS)

    Rosso, Kevin M.; Smith, Dayle MA; Dupuis, Michel

    2003-01-01

    Transport of conduction electrons through basal planes of the hematite lattice was modeled as a valence alternation of iron cations using ab initio molecular orbital calculations and electron transfer theory. A cluster approach was successfully implemented to compute electron transfer rate-controlling quantities such as the reorganization energy and electronic coupling matrix element. Localization of a conduction electron at an iron lattice site is accompanied by large iron/oxygen bond length increases that give rise to a large inner-sphere component of the reorganization energy. The interaction between the reactant and product electronic states in the crossing?point configuration is substantial and leads to an adiabatic electron transfer system. Electron transfer is predicted to possess a small positive activation energy that turns out to be in excellent agreement with values deduced from conductivity measurements. Measured electron mobility can be explained in terms of nearest neighbor electron hops without significant contribution from iron atoms further away. Comparison of the predicted maximum polaron binding energy with the predicted half bandwidth indicates compliance with the small polaron condition. Therefore the localized electron treatment is appropriate to describe electron transport in this system

  13. Polaronic Nonmetal-Correlated Metal Crossover System β'-CuxV2O5 with Anharmonic Copper Oscillation and Thermoelectric Conversion Performance

    Science.gov (United States)

    Onoda, Masashige; Sato, Takuma

    2017-12-01

    The crystal structures and electronic properties of β'CuxV2O5 are explored through measurements of X-ray four-circle diffraction, electrical resistivity, thermoelectric power, thermal conductivity, magnetization, and electron paramagnetic resonance. For various compositions with 0.243 ≤ x ≤ 0.587, the crystal structures are redetermined through the anharmonic approach of the copper displacement factors, where the anharmonicity is reduced with increasing Cu concentration. The electron transport for x ≤ 0.45 is nonmetallic due to polaron hopping and the random potential of Cu ions, while for x = 0.60, a correlated Fermi-liquid state appears with a Wilson ratio of 1.3 and a Kadowaki-Woods ratio close to the universal value for heavy-fermion systems. At around x = 0.50, the polaronic bandwidth may broaden so that the Hubbard subbands caused by the electron correlation will overlap. The nonmetallic composition in the proximity of the nonmetal-metal crossover shows a dimensionless thermoelectric power factor of 10-2 at 300 K, partly due to the anharmonic copper oscillation.

  14. Big data analytics — A review of data-mining models for small and medium enterprises in the transportation sector.

    OpenAIRE

    Selamat, Siti Aishah Mohd; Prakoonwit, Simant; Sahandi, Reza; Khan, W.; Ramachandran, M.

    2018-01-01

    The need for small and medium enterprises (SMEs) to adopt data analytics has reached a critical point, given the surge of data implied by the advancement of technology. Despite data mining (DM) being widely used in the transportation sector, it is staggering to note that there are minimal research case studies being done on the application of DM by SMEs, specifically in the transportation sector. From the extensive review conducted, the three most common DM models used by large enterprises in...

  15. Preliminary study on performance of a coupled hydrodynamic and sediment transport model on small domain

    Science.gov (United States)

    Rasyif, Teuku M.; Kato, Shigeru; Syamsidik, Okabe, Takumi

    2017-10-01

    Numerical simulation is one of the useful tools to analyze natural phenomena in the earth such as the tsunami disaster. Several numerical models can simulate the tsunami wave from its generation, propagation, and inundation. However, most tsunami models do not include the sediment transport module. The tsunami wave actually induces a lot of sediment during the propagation in the coastal area. In the case of Indian Ocean Tsunami in 2004, massive morphological changes were caused by the tsunami waves around Sumatra coast. In Aceh, some areas eroded by the tsunami wave were living place for a local community. It is indispensable for the resident in the coastal area to estimate the risk of morphological changes due to a tsunami wave. Therefore, a model that can investigate the morphological changes due tsunami wave is necessary. The result of this model can be used to consider a countermeasure for tsunami wave impact in the coastal area, such as land-use management and planning. The COMCOT-SED model had been developed by several researchers. This model combines the hydrodynamic module and the sediment module. The aim of this study is to get general information about performance of the COMCOT-SED model and to modify the model for more accurate results. Firstly, the model was demonstrated in the ideal condition to confirm the model validity. Then, we evaluated the model performance comparing the model results and the laboratory experiment data which was conducted by other researcher. The authors found that the results of water level and bottom profile by the original model in the ideal condition are not suitable. The model modification will give us more suitable results. The modified model will be applied to simulate the tsunami wave and sediment transport in the small area.

  16. Simulations of charge transport in organic compounds

    Energy Technology Data Exchange (ETDEWEB)

    Vehoff, Thorsten

    2010-05-05

    We study the charge transport properties of organic liquid crystals, i.e. hexabenzocoronene and carbazole macrocycle, and single crystals, i.e. rubrene, indolocarbazole and benzothiophene derivatives (BTBT, BBBT). The aim is to find structure-property relationships linking the chemical structure as well as the morphology with the bulk charge carrier mobility of the compounds. To this end, molecular dynamics (MD) simulations are performed yielding realistic equilibrated morphologies. Partial charges and molecular orbitals are calculated based on single molecules in vacuum using quantum chemical methods. The molecular orbitals are then mapped onto the molecular positions and orientations, which allows calculation of the transfer integrals between nearest neighbors using the molecular orbital overlap method. Thus we obtain realistic transfer integral distributions and their autocorrelations. In case of organic crystals the differences between two descriptions of charge transport, namely semi-classical dynamics (SCD) in the small polaron limit and kinetic Monte Carlo (KMC) based on Marcus rates, are studied. The liquid crystals are investigated solely in the hopping limit. To simulate the charge dynamics using KMC, the centers of mass of the molecules are mapped onto lattice sites and the transfer integrals are used to compute the hopping rates. In the small polaron limit, where the electronic wave function is spread over a limited number of neighboring molecules, the Schroedinger equation is solved numerically using a semi-classical approach. The carbazole macrocycles form columnar structures arranged on a hexagonal lattice with side chains facing inwards, so columns can closely approach each other allowing inter-columnar and thus three-dimensional transport. We are able to show that, on the time-scales of charge transport, static disorder due to slow side chain motions is the main factor determining the mobility. The high mobility of rubrene is explained by two main

  17. The Small Aircraft Transportation System (SATS), Higher Volume Operations (HVO) Concept and Research

    Science.gov (United States)

    Baxley, B.; Williams, D.; Consiglio, M.; Adams, C.; Abbott, T.

    2005-01-01

    The ability to conduct concurrent, multiple aircraft operations in poor weather at virtually any airport offers an important opportunity for a significant increase in the rate of flight operations, a major improvement in passenger convenience, and the potential to foster growth of operations at small airports. The Small Aircraft Transportation System, (SATS) Higher Volume Operations (HVO) concept is designed to increase capacity at the 3400 non-radar, non-towered airports in the United States where operations are currently restricted to one-in/one-out procedural separation during low visibility or ceilings. The concept s key feature is that pilots maintain their own separation from other aircraft using air-to-air datalink and on-board software within the Self-Controlled Area (SCA), an area of flight operations established during poor visibility and low ceilings around an airport without Air Traffic Control (ATC) services. While pilots self-separate within the SCA, an Airport Management Module (AMM) located at the airport assigns arriving pilots their sequence based on aircraft performance, position, winds, missed approach requirements, and ATC intent. The HVO design uses distributed decision-making, safe procedures, attempts to minimize pilot and controller workload, and integrates with today's ATC environment. The HVO procedures have pilots make their own flight path decisions when flying in Instrument Metrological Conditions (IMC) while meeting these requirements. This paper summarizes the HVO concept and procedures, presents a summary of the research conducted and results, and outlines areas where future HVO research is required. More information about SATS HVO can be found at http://ntrs.nasa.gov.

  18. Gluon transport equation in the small angle approximation and the onset of Bose–Einstein condensation

    International Nuclear Information System (INIS)

    Blaizot, Jean-Paul; Liao, Jinfeng; McLerran, Larry

    2014-01-01

    To understand the evolution of a dense system of gluons, such as those produced in the early stages of ultra-relativistic heavy ion collisions, is an important and challenging problem. We describe the approach to thermal equilibrium using the small angle approximation for gluon scattering in a Boltzmann equation that includes the effects of Bose statistics. The role of Bose statistical factors in amplifying the rapid growth of the population of the soft modes is essential. With these factors properly taken into account, one finds that elastic scattering alone provides an efficient mechanism for populating soft modes, and in fact leads to rapid infrared local thermalization. Furthermore, recent developments suggest that high initial overpopulation plays a key role and may lead to dynamical Bose–Einstein condensation. The kinetics of condensation is an interesting problem in itself. By solving the transport equation for initial conditions with a large enough initial phase-space density the equilibrium state contains a Bose condensate, and we present numerical evidence that such over-occupied systems reach the onset of Bose–Einstein condensation in a finite time. It is also found that the approach to condensation is characterized by a scaling behavior. Finally we discuss a number of extensions of the present study

  19. Gluon transport equation in the small angle approximation and the onset of Bose–Einstein condensation

    Energy Technology Data Exchange (ETDEWEB)

    Blaizot, Jean-Paul [Institut de Physique Théorique, CNRS/URA 2306, CEA Saclay, F-91191 Gif-sur-Yvette (France); Liao, Jinfeng [Physics Dept. and CEEM, Indiana University, 2401 N Milo B. Sampson Lane, Bloomington, IN 47408 (United States); RIKEN BNL Research Center, Bldg. 510A, Brookhaven National Laboratory, Upton, NY 11973 (United States); McLerran, Larry [Physics Dept., Bldg. 510A, Brookhaven National Laboratory, Upton, NY 11973 (United States); RIKEN BNL Research Center, Bldg. 510A, Brookhaven National Laboratory, Upton, NY 11973 (United States); Physics Department, China Central Normal University, Wuhan (China)

    2014-11-15

    To understand the evolution of a dense system of gluons, such as those produced in the early stages of ultra-relativistic heavy ion collisions, is an important and challenging problem. We describe the approach to thermal equilibrium using the small angle approximation for gluon scattering in a Boltzmann equation that includes the effects of Bose statistics. The role of Bose statistical factors in amplifying the rapid growth of the population of the soft modes is essential. With these factors properly taken into account, one finds that elastic scattering alone provides an efficient mechanism for populating soft modes, and in fact leads to rapid infrared local thermalization. Furthermore, recent developments suggest that high initial overpopulation plays a key role and may lead to dynamical Bose–Einstein condensation. The kinetics of condensation is an interesting problem in itself. By solving the transport equation for initial conditions with a large enough initial phase-space density the equilibrium state contains a Bose condensate, and we present numerical evidence that such over-occupied systems reach the onset of Bose–Einstein condensation in a finite time. It is also found that the approach to condensation is characterized by a scaling behavior. Finally we discuss a number of extensions of the present study.

  20. Preliminary Validation of the Small Aircraft Transportation System Higher Volume Operations (SATS HVO) Concept

    Science.gov (United States)

    Williams, Daniel; Consiglio, Maria; Murdoch, Jennifer; Adams, Catherine

    2004-01-01

    This document provides a preliminary validation of the Small Aircraft Transportation System (SATS) Higher Volume Operations (HVO) concept for normal conditions. Initial results reveal that the concept provides reduced air traffic delays when compared to current operations without increasing pilot workload. Characteristic to the SATS HVO concept is the establishment of a newly defined area of flight operations called a Self-Controlled Area (SCA) which would be activated by air traffic control (ATC) around designated non-towered, non-radar airports. During periods of poor visibility, SATS pilots would take responsibility for separation assurance between their aircraft and other similarly equipped aircraft in the SCA. Using onboard equipment and simple instrument flight procedures, they would then be better able to approach and land at the airport or depart from it. This concept would also require a new, ground-based automation system, typically located at the airport that would provide appropriate sequencing information to the arriving aircraft. Further validation of the SATS HVO concept is required and is the subject of ongoing research and subsequent publications.

  1. Criticality coefficient calculation for a small PWR using Monte Carlo Transport Code

    Energy Technology Data Exchange (ETDEWEB)

    Trombetta, Debora M.; Su, Jian, E-mail: dtrombetta@nuclear.ufrj.br, E-mail: sujian@nuclear.ufrj.br [Coordenacao dos Programas de Pos-Graduacao em Engenharia (COPPE/UFRJ), Rio de Janeiro, RJ (Brazil); Chirayath, Sunil S., E-mail: sunilsc@tamu.edu [Department of Nuclear Engineering and Nuclear Security Science and Policy Institute, Texas A and M University, TX (United States)

    2015-07-01

    Computational models of reactors are increasingly used to predict nuclear reactor physics parameters responsible for reactivity changes which could lead to accidents and losses. In this work, preliminary results for criticality coefficient calculation using the Monte Carlo transport code MCNPX were presented for a small PWR. The computational modeling developed consists of the core with fuel elements, radial reflectors, and control rods inside a pressure vessel. Three different geometries were simulated, a single fuel pin, a fuel assembly and the core, with the aim to compare the criticality coefficients among themselves.The criticality coefficients calculated were: Doppler Temperature Coefficient, Coolant Temperature Coefficient, Coolant Void Coefficient, Power Coefficient, and Control Rod Worth. The coefficient values calculated by the MCNP code were compared with literature results, showing good agreement with reference data, which validate the computational model developed and allow it to be used to perform more complex studies. Criticality Coefficient values for the three simulations done had little discrepancy for almost all coefficients investigated, the only exception was the Power Coefficient. Preliminary results presented show that simple modelling as a fuel assembly can describe changes at almost all the criticality coefficients, avoiding the need of a complex core simulation. (author)

  2. Zero-Magnetic-Field Spin Splitting of Polaron's Ground State Energy Induced by Rashba Spin-Orbit Interaction

    International Nuclear Information System (INIS)

    Liu Jia; Xiao Jingling

    2006-01-01

    We study theoretically the ground state energy of a polaron near the interface of a polar-polar semiconductor by considering the Rashba spin-orbit (SO) coupling with the Lee-Low-Pines intermediate coupling method. Our numerical results show that the Rashba SO interaction originating from the inversion asymmetry in the heterostructure splits the ground state energy of the polaron. The electron areal density and vector dependence of the ratio of the SO interaction to the total ground state energy or other energy composition are obvious. One can see that even without any external magnetic field, the ground state energy can be split by the Rashba SO interaction, and this split is not a single but a complex one. Since the presents of the phonons, whose energy gives negative contribution to the polaron's, the spin-splitting states of the polaron are more stable than electron's.

  3. 78 FR 26684 - Notice of Funding Availability for the Small Business Transportation Resource Center Program

    Science.gov (United States)

    2013-05-07

    ... of 20 hours of individual or group counseling sessions to small businesses per month. (D) Planning... technical assistance, business training programs, business assessment, management training, counseling... activities such as information dissemination, small business counseling, and technical assistance with small...

  4. 78 FR 4973 - Notice of Funding Availability for the Small Business Transportation Resource Center Program

    Science.gov (United States)

    2013-01-23

    ... individual or group counseling sessions to small businesses per month. (D) Planning Committee 1. Establish a... training programs, business assessment, management training, counseling, marketing and outreach, and the... dissemination, small business counseling, and technical assistance with small businesses currently doing...

  5. 77 FR 36034 - Notice of Funding Availability for the Small Business Transportation Resource Center Program

    Science.gov (United States)

    2012-06-15

    ... hours of individual or group counseling sessions to small businesses per month. (D) Planning Committee 1... programs, business assessment, management training, counseling, marketing and outreach, and the... dissemination, small business counseling, and technical assistance with small businesses currently doing...

  6. Bayesian estimation of the hydraulic and solute transport properties of a small-scale unsaturated soil column

    NARCIS (Netherlands)

    Moreira, Paulo H S; Van Genuchten, Martinus Th; Orlande, Helcio R B; Cotta, Renato M.

    2016-01-01

    In this study the hydraulic and solute transport properties of an unsaturated soil were estimated simultaneously from a relatively simple small-scale laboratory column infiltration/outflow experiment. As governing equations we used the Richards equation for variably saturated flow and a physical

  7. Borreliacidal activity of Borrelia metal transporter A (BmtA binding small molecules by manganese transport inhibition

    Directory of Open Access Journals (Sweden)

    Wagh D

    2015-02-01

    Full Text Available Dhananjay Wagh,* Venkata Raveendra Pothineni,* Mohammed Inayathullah, Song Liu, Kwang-Min Kim, Jayakumar Rajadas Biomaterials and Advanced Drug Delivery Laboratory, Stanford Cardiovascular Pharmacology Division, Cardiovascular Institute, Stanford University School of Medicine, Palo Alto, CA, USA *These authors contributed equally to this work  Abstract: Borrelia burgdorferi, the causative agent of Lyme disease, utilizes manganese (Mn for its various metabolic needs. We hypothesized that blocking Mn transporter could be a possible approach to inhibit metabolic activity of this pathogen and eliminate the infection. We used a combination of in silico protein structure prediction together with molecular docking to target the Borrelia metal transporter A (BmtA, a single known Mn transporter in Borrelia and screened libraries of FDA approved compounds that could potentially bind to the predicted BmtA structure with high affinity. Tricyclic antihistamines such as loratadine, desloratadine, and 3-hydroxydesloratadine as well as yohimbine and tadalafil demonstrated a tight binding to the in silico folded BmtA transporter. We, then, tested borreliacidal activity and dose response of the shortlisted compounds from this screen using a series of in vitro assays. Amongst the probed compounds, desloratadine exhibited potent borreliacidal activity in vitro at and above 78 µg/mL (250 µM. Borrelia treated with lethal doses of desloratadine exhibited a significant loss of intracellular Mn specifically and a severe structural damage to the bacterial cell wall. Our results support the possibility of developing a novel, targeted therapy to treat Lyme disease by targeting specific metabolic needs of Borrelia.  Keywords: Lyme disease, BmtA, Borrelia burgdorferi, desloratadine, Bac Titer-Glo assay

  8. Hall effect driven by non-collinear magnetic polarons in diluted magnetic semiconductors

    Science.gov (United States)

    Denisov, K. S.; Averkiev, N. S.

    2018-04-01

    In this letter, we develop the theory of Hall effect driven by non-collinear magnetic textures (topological Hall effect—THE) in diluted magnetic semiconductors (DMSs). We show that a carrier spin-orbit interaction induces a chiral magnetic ordering inside a bound magnetic polaron (BMP). The inner structure of non-collinear BMP is controlled by the type of spin-orbit coupling, allowing us to create skyrmion- (Rashba) or antiskyrmion-like (Dresselhaus) configurations. The asymmetric scattering of itinerant carriers on polarons leads to the Hall response which exists in weak external magnetic fields and at low temperatures. We point out that DMS-based systems allow one to investigate experimentally the dependence of THE both on a carrier spin polarization and on a non-collinear magnetic texture shape.

  9. Effect of thermodynamic fluctuations of magnetization on the bound magnetic polaron state in ferromagnetic semiconductors

    International Nuclear Information System (INIS)

    Bednarski, Henryk; Spałek, Józef

    2014-01-01

    We extend the theory of the bound magnetic polaron (BMP) in diluted paramagnetic semiconductors to the situation with a ferromagnetic phase transition. This is achieved by including the classical Gaussian fluctuations of magnetization from the quartic (non-Gaussian) term in the effective Ginzburg–Landau Hamiltonian for the spins. Within this approach, we find a ferromagnetically ordered state within the BMP in the temperature range well above the Curie temperature for the host magnetic semiconductor. Numerical results are compared directly with the recently available experimental data for the ferromagnetic semiconductor GdN. The agreement is excellent, given the simplicity of our model, and is because the polaron size (≃1.4 nm) encompasses a relatively large but finite number (N≈400) of quasiclassical spins S=7/2 coming from Gd 3+ ions. The presence of BMP invalidates the notion of critical temperature and thus makes the incorporation of classical Gaussian fluctuations sufficient to realistically describe the situation. (paper)

  10. Impact of morphology on polaron delocalization in a semicrystalline conjugated polymer

    KAUST Repository

    Steyrleuthner, Robert

    2016-12-20

    We investigate the delocalization of holes in the semicrystalline conjugated polymer poly(2,5-bis(3-alkylthiophene-2-yl)thieno[3,2-b]thiophene) (PBTTT) by directly measuring the hyperfine coupling between photogenerated polarons and bound nuclear spins using electron nuclear double resonance spectroscopy. An extrapolation of the corresponding oligomer spectra reveals that charges tend to delocalize over 4.0-4.8 nm with delocalization strongly dependent on molecular order and crystallinity of the PBTTT polymer thin films. Density functional theory calculations of hyperfine couplings confirm that long-range corrected functionals appropriately describe the change in coupling strength with increasing oligomer size and agree well with the experimentally measured polymer limit. Our discussion presents general guidelines illustrating the various pitfalls and opportunities when deducing polaron localization lengths from hyperfine coupling spectra of conjugated polymers.

  11. Two Impurities in a Bose-Einstein Condensate: From Yukawa to Efimov Attracted Polarons

    Science.gov (United States)

    Naidon, Pascal

    2018-04-01

    The well-known Yukawa and Efimov potentials are two different mediated interaction potentials. The first one arises in quantum field theory from the exchange of virtual particles. The second one is mediated by a real particle resonantly interacting with two other particles. This Letter shows how two impurities immersed in a Bose-Einstein condensate can exhibit both phenomena. For a weak attraction with the condensate, the two impurities form two polarons that interact through a weak Yukawa attraction mediated by virtual excitations. For a resonant attraction with the condensate, the exchanged excitation becomes a real boson and the mediated interaction changes to a strong Efimov attraction that can bind the two polarons. The resulting bipolarons turn into in-medium Efimov trimers made of the two impurities and one boson. Evidence of this physics could be seen in ultracold mixtures of atoms.

  12. Kinetic Monte Carlo Study of Ambipolar Lithium Ion and Electron-Polaron Diffusion into Nanostructured TiO2

    International Nuclear Information System (INIS)

    Yu, Jianguo; Sushko, Maria L.; Kerisit, Sebastien N.; Rosso, Kevin M.; Liu, Jun

    2012-01-01

    Nanostructured titania (TiO2) polymorphs have proved to be promising electrode materials for next generation lithium-ion batteries. However, there is still a lack of understanding of the fundamental microscopic processes that control charge transport in these materials. Here we present microscopic simulations of the collective dynamics of lithium-ion (Li+) and charge compensating electron polarons (e-) in rutile TiO2 nanoparticles in contact with idealized conductive matrix and electrolyte. Kinetic Monte Carlo simulations are used, parameterized by molecular dynamics-based predictions of activation energy barriers for Li+ and e- diffusion. Simulations reveal the central role of electrostatic coupling between Li+ and e- on their collective drift diffusion at the nanoscale. They also demonstrate that high contact area between conductive matrix and rutile nanoparticles leads to undesirable coupling-induced surface saturation effects during Li+ insertion, which limits the overall capacity and conductivity of the material. These results help provide guidelines for design of nanostructured electrode materials with improved electrochemical performance.

  13. Second order approximation for optical polaron in the strong coupling case

    International Nuclear Information System (INIS)

    Bogolubov, N.N. Jr.

    1993-11-01

    Here we propose a method of construction second order approximation for ground state energy for class of model Hamiltonian with linear type interaction on Bose operators in strong coupling case. For the application of the above method we have considered polaron model and propose construction set of nonlinear differential equations for definition ground state energy in strong coupling case. We have considered also radial symmetry case. (author). 10 refs

  14. Generalized formula for electron emission taking account of the polaron effect

    Science.gov (United States)

    Barengolts, Yu A.; Beril, S. I.; Barengolts, S. A.

    2018-01-01

    A generalized formula is derived for the electron emission current as a function of temperature, field, and electron work function in a metal-dielectric system that takes account of the quantum nature of the image forces. In deriving the formula, the Fermi-Dirac distribution for electrons in a metal and the quantum potential of the image obtained in the context of electron polaron theory are used.

  15. Quantum fluctuations of D5d polarons on C60 molecules

    International Nuclear Information System (INIS)

    Wang Chui-Lin; Wang Wenzheng; Liu Yuliang; Su Zhaobin; Yu Lu.

    1994-06-01

    The dynamic Jahn-Teller splitting of the six equivalent D 5d polarons due to quantum fluctuations is studied in the framework of the Bogoliubov-de Gennes formalism. The tunneling induced level splittings are determined to be 2 T 1u + 2 T 2u and 1 A g + 1 H g for C 1- 60 and C -2 60 , respectively, which should give rise to observable effects in experiments. (author). 17 refs, 2 tabs

  16. The role of hydrostatic pressure and temperature on bound polaron in semiconductor quantum dot

    International Nuclear Information System (INIS)

    El Moussaouy, A.; Ouchani, N.

    2014-01-01

    We studied theoretically the effects of hydrostatic pressure and temperature on the binding energy of shallow hydrogenic impurity in a cylindrical quantum dot (QD) using a variational approach within the effective mass approximation. The hydrostatic stress was applied along the QD growth axis. The interactions between the charge carriers and confined longitudinal optical (LO) phonon modes are taken into account. The numerical computation for GaAs/Ga 1−x Al x As QD has shown that the binding energy with and without the polaronic correction depends on the location of the impurity and the pressure effect and it is more pronounced for impurities in the QD center. Both the binding energy and the polaronic contribution increase linearly with increasing stress. For each pressure value, these energies are also found to decrease as the temperature increases. The results obtained show that in experimental studies of optical and electronic properties of QDs, the effects of pressure, temperature and polaronic correction on donor impurity binding energy should be taken into consideration

  17. DFT +U Modeling of Hole Polarons in Organic Lead Halide Perovskites

    Science.gov (United States)

    Welch, Eric; Erhart, Paul; Scolfaro, Luisa; Zakhidov, Alex

    Due to the ever present drive towards improved efficiencies in solar cell technology, new and improved materials are emerging rapidly. Organic halide perovskites are a promising prospect, yet a fundamental understanding of the organic perovskite structure and electronic properties is missing. Particularly, explanations of certain physical phenomena, specifically a low recombination rate and high mobility of charge carriers still remain controversial. We theoretically investigate possible formation of hole polarons adopting methodology used for oxide perovskites. The perovskite studied here is the ABX3structure, with A being an organic cation, B lead and C a halogen; the combinations studied allow for A1,xA2 , 1 - xBX1,xX2 , 3 - xwhere the alloy convention is used to show mixtures of the organic cations and/or the halogens. Two organic cations, methylammonium and formamidinium, and three halogens, iodine, chlorine and bromine are studied. Electronic structures and polaron behavior is studied through first principle density functional theory (DFT) calculations using the Vienna Ab Initio Simulation Package (VASP). Local density approximation (LDA) pseudopotentials are used and a +U Hubbard correction of 8 eV is added; this method was shown to work with oxide perovskites. It is shown that a localized state is realized with the Hubbard correction in systems with an electron removed, residing in the band gap of each different structure. Thus, hole polarons are expected to be seen in these perovskites.

  18. Structural correlations in the generation of polaron pairs in low-bandgap polymers for photovoltaics

    Science.gov (United States)

    Tautz, Raphael; da Como, Enrico; Limmer, Thomas; Feldmann, Jochen; Egelhaaf, Hans-Joachim; von Hauff, Elizabeth; Lemaur, Vincent; Beljonne, David; Yilmaz, Seyfullah; Dumsch, Ines; Allard, Sybille; Scherf, Ullrich

    2012-07-01

    Polymeric semiconductors are materials where unique optical and electronic properties often originate from a tailored chemical structure. This allows for synthesizing conjugated macromolecules with ad hoc functionalities for organic electronics. In photovoltaics, donor-acceptor co-polymers, with moieties of different electron affinity alternating on the chain, have attracted considerable interest. The low bandgap offers optimal light-harvesting characteristics and has inspired work towards record power conversion efficiencies. Here we show for the first time how the chemical structure of donor and acceptor moieties controls the photogeneration of polaron pairs. We show that co-polymers with strong acceptors show large yields of polaron pair formation up to 24% of the initial photoexcitations as compared with a homopolymer (η=8%). π-conjugated spacers, separating the donor and acceptor centre of masses, have the beneficial role of increasing the recombination time. The results provide useful input into the understanding of polaron pair photogeneration in low-bandgap co-polymers for photovoltaics.

  19. A probabilistic risk-analysis of the transport of small radioactive material type B packages in France

    International Nuclear Information System (INIS)

    Hubert, P.; Pages, P.

    1982-01-01

    The assessment of the accidental risk due to the road transportation of a small package containing γ-ray emitters is performed in France. Analyzing records of road transportation accidents, modeling the package behaviour and estimating the importance of the involved population are the three main steps of the study. The interest of such an anlysis relies on the relative simplicity of the model and the availability of statistical data. This allows modelling of the whole process and study of the various sensitivities. It is also of pratical interest when assessing the cost-effectiveness of some safety/protection measures

  20. 75 FR 42181 - Notice of Funding Availability for the Small Business Transportation Resource Center Program

    Science.gov (United States)

    2010-07-20

    ... of 20 hours of individual or group counseling sessions to small businesses per month. (D) Planning... training programs, such as, business assessment, management training, counseling, technical assistance... business counseling, and technical assistance with small businesses currently doing business with public...

  1. 75 FR 23319 - Notice of Funding Availability for the Small Business Transportation Resource Center Program

    Science.gov (United States)

    2010-05-03

    ... contracts and subcontracts portfolio. 3. Provide a minimum of 20 hours of individual or group counseling... programs, such as, business assessment, management training, counseling, technical assistance, marketing... dissemination, small business counseling, and technical assistance with small businesses currently doing...

  2. 76 FR 30990 - Notice of Funding Availability for the Small Business Transportation Resource Center Program

    Science.gov (United States)

    2011-05-27

    ... training programs, such as, business assessment, management training, counseling, technical assistance, marketing and outreach, and the dissemination of information, to encourage and assist small businesses to..., including management and technical services, that will enable small disadvantaged businesses to take...

  3. Environmental Impact of Tourism and Air Transport on the Sustainable Development of Small Island Developing States

    Science.gov (United States)

    1999-01-01

    The United Nations General Assembly recognized that many small island developing countries were confronted with compelling factors such as their smallness in size, susceptibility and vulnerability to natural disasters, remoteness of access and geogra...

  4. 77 FR 42790 - Notice of Funding Availability for the Small Business Transportation Resource Center Program

    Science.gov (United States)

    2012-07-20

    ... subcontracts portfolio. 3. Provide a minimum of 20 hours of individual or group counseling sessions to small..., business assessment, management training, counseling, marketing and outreach, and the dissemination of... dissemination, small business counseling, and technical assistance with small businesses currently doing...

  5. Phosphate transport in pig proximal small intestines during postnatal development: lack of modulation by calcitriol.

    Science.gov (United States)

    Schröder, B; Hattenhauer, O; Breves, G

    1998-04-01

    The role of calcitriol in the intestinal absorption of inorganic phosphate (Pi) during postnatal development was studied in newborn [6 weeks pp) control piglets (con) and piglets suffering from inherited calcitriol deficiency (def). In addition, a number of def piglets were treated with vitamin D3 (def-D3). Regardless of age, plasma calcitriol concentrations in def piglets were unphysiologically low (16-21 pg/ml) and differed significantly from those in respective con animals (60-69 pg/ml) and vitamin D3-treated def piglets (50-56 pg/ml). However, newborn and suckling def piglets had normal Ca (approximately 3.0 mmol/liter) and Pi (approximately 2.8 mmol/liter) plasma levels. Def piglets became hypocalcemic (1.9 mmol/liter) and hypophosphatemic (1.9 mmol/liter) between 4-6 weeks pp. Treatment with vitamin D3 significantly increased plasma Ca (3.2 mmol/liter) and Pi (2.7 mmol/liter) levels in weaned def animals. Regardless of calcitriol status, net Pi flux rates (active Pi absorption, as determined with the in vitro Ussing-chamber technique) from the upper small intestines was maximal at birth [170-224 nmol/(cm2 x h)] and decreased by approximately 80% during the first week of life before remaining constant [30-50 nmol/(cm2 x h)] during the following development. In weaned def piglets, net Pi flux rates were significantly lower by about 80% compared with those in con animals. Treatment of def piglets with vitamin D3 had no effect in newborn and suckling animals but reconstituted net Pi flux rates to normal values at weaning age. Age-dependent and calcitriol-mediated changes in net Pi flux rates were paralleled by respective maximum velocity values of Na+-dependent Pi uptake across the brush border membrane of the enterocytes (newborn piglets, 1.9-2.2 nmol/(mg protein 10 sec); suckling piglets, 0.4-0.6 nmol/(mg protein x 10 sec); weaned piglets, 0.7, 0.3, and 0.7 nmol/(mg protein x 10 sec) in con, def, and def-D3 animals, respectively). These findings suggest that

  6. First-Principles Modeling of Polaron Formation in TiO2 Polymorphs.

    Science.gov (United States)

    Elmaslmane, A R; Watkins, M B; McKenna, K P

    2018-06-21

    We present a computationally efficient and predictive methodology for modeling the formation and properties of electron and hole polarons in solids. Through a nonempirical and self-consistent optimization of the fraction of Hartree-Fock exchange (α) in a hybrid functional, we ensure the generalized Koopmans' condition is satisfied and self-interaction error is minimized. The approach is applied to model polaron formation in known stable and metastable phases of TiO 2 including anatase, rutile, brookite, TiO 2 (H), TiO 2 (R), and TiO 2 (B). Electron polarons are predicted to form in rutile, TiO 2 (H), and TiO 2 (R) (with trapping energies ranging from -0.02 eV to -0.35 eV). In rutile the electron localizes on a single Ti ion, whereas in TiO 2 (H) and TiO 2 (R) the electron is distributed across two neighboring Ti sites. Hole polarons are predicted to form in anatase, brookite, TiO 2 (H), TiO 2 (R), and TiO 2 (B) (with trapping energies ranging from -0.16 eV to -0.52 eV). In anatase, brookite, and TiO 2 (B) holes localize on a single O ion, whereas in TiO 2 (H) and TiO 2 (R) holes can also be distributed across two O sites. We find that the optimized α has a degree of transferability across the phases, with α = 0.115 describing all phases well. We also note the approach yields accurate band gaps, with anatase, rutile, and brookite within six percent of experimental values. We conclude our study with a comparison of the alignment of polaron charge transition levels across the different phases. Since the approach we describe is only two to three times more expensive than a standard density functional theory calculation, it is ideally suited to model charge trapping at complex defects (such as surfaces and interfaces) in a range of materials relevant for technological applications but previously inaccessible to predictive modeling.

  7. Overview: Small Aircraft Transportation System Airborne Remote Sensing Fuel Droplet Evaporation

    Science.gov (United States)

    Bowen, Brent (Editor); Holmes, Bruce; Gogos, George; Narayanan, Ram; Smith, Russell; Woods, Sara

    2004-01-01

    , Codes, and Strategic Enterprises. During the first year of funding, Nebraska established open and frequent lines of communication with university affairs officers and other key personnel at all NASA Centers and Enterprises, and facilitated the development of collaborations between and among junior faculty in the state and NASA researchers. As a result, Nebraska initiated a major research cluster, the Small Aircraft Transportation System Nebraska Implementation Template.

  8. CD147: a small molecule transporter ancillary protein at the crossroad of multiple hallmarks of cancer and metabolic reprogramming.

    Science.gov (United States)

    Kendrick, Agnieszka A; Schafer, Johnathon; Dzieciatkowska, Monika; Nemkov, Travis; D'Alessandro, Angelo; Neelakantan, Deepika; Ford, Heide L; Pearson, Chad G; Weekes, Colin D; Hansen, Kirk C; Eisenmesser, Elan Z

    2017-01-24

    Increased expression of CD147 in pancreatic cancer has been proposed to play a critical role in cancer progression via CD147 chaperone function for lactate monocarboxylate transporters (MCTs). Here, we show for the first time that CD147 interacts with membrane transporters beyond MCTs and exhibits a protective role for several of its interacting partners. CD147 prevents its interacting partner's proteasome-dependent degradation and incorrect plasma membrane localization through the CD147 transmembrane (TM) region. The interactions with transmembrane small molecule and ion transporters identified here indicate a central role of CD147 in pancreatic cancer metabolic reprogramming, particularly with respect to amino acid anabolism and calcium signaling. Importantly, CD147 genetic ablation prevents pancreatic cancer cell proliferation and tumor growth in vitro and in vivo in conjunction with metabolic rewiring towards amino acid anabolism, thus paving the way for future combined pharmacological treatments.

  9. Bayesian estimation of the hydraulic and solute transport properties of a small-scale unsaturated soil column

    Directory of Open Access Journals (Sweden)

    Moreira Paulo H. S.

    2016-03-01

    Full Text Available In this study the hydraulic and solute transport properties of an unsaturated soil were estimated simultaneously from a relatively simple small-scale laboratory column infiltration/outflow experiment. As governing equations we used the Richards equation for variably saturated flow and a physical non-equilibrium dual-porosity type formulation for solute transport. A Bayesian parameter estimation approach was used in which the unknown parameters were estimated with the Markov Chain Monte Carlo (MCMC method through implementation of the Metropolis-Hastings algorithm. Sensitivity coefficients were examined in order to determine the most meaningful measurements for identifying the unknown hydraulic and transport parameters. Results obtained using the measured pressure head and solute concentration data collected during the unsaturated soil column experiment revealed the robustness of the proposed approach.

  10. Modeling of a Small Transportation Company’s Start-up with Limited Data during Economic Recession

    OpenAIRE

    Fang, Xiaoping; Ansell, Jonathan; Chen, Weiya

    2014-01-01

    This paper presents a modeling method for analyzing a small transportation company’s start-up and growth during a global economic crisis which had an impact on in China which is designed to help the owners make better investment and operating decisions with limited data. Since there is limited data, simple regression model and binary regression model failed to generate satisfactory results, so an additive periodic time series model was built to forecast business orders and income. Since the t...

  11. 75 FR 79072 - Notice of Funding Availability for the Small Business Transportation Resource Center Program

    Science.gov (United States)

    2010-12-17

    ... hours of individual or group counseling sessions to small businesses per month. (D) Planning Committee 1..., such as, business assessment, management training, counseling, technical assistance, marketing and... counseling, and technical assistance with small businesses currently doing business with public and private...

  12. Growth of embryo and gene expression of nutrient transporters in the small intestine of the domestic pigeon (Columba livia)*

    Science.gov (United States)

    Chen, Ming-xia; Li, Xiang-guang; Yang, Jun-xian; Gao, Chun-qi; Wang, Bin; Wang, Xiu-qi; Yan, Hui-chao

    2015-01-01

    The objective of this study was to investigate the relationship between gene expression of nutrient (amino acid, peptide, sodium and proton) transporters in the small intestine and embryonic growth in domestic pigeons (Columba livia). One hundred and twenty-five fertilized eggs were randomly assigned into five groups and were incubated under optimal conditions (temperature of 38.1 °C and relative humidity of 55%). Twenty embryos/birds from each group were sacrificed by cervical dislocation on embryonic day (E) 9, 11, 13, 15 and day of hatch (DOH). The eggs, embryos (without yolk sac), and organs (head, brain, heart, liver, lungs, kidney, gizzard, small intestine, legs, and thorax) were dissected, cleaned, and weighed. Small intestine samples were collected for RNA isolation. The mRNA abundance of intestinal nutrient transporters was evaluated by real-time reverse transcription-polymerase chain reaction (RT-PCR). We classified these ten organs into four types according to the changes in relative weight during embryonic development. In addition, the gene expression of nutrient transporters was differentially regulated by embryonic day. The mRNA abundances of b0,+AT, EAAT3, y+LAT2, PepT1, LAT4, NHE2, and NHE3 increased linearly with age, whereas mRNA abundances of CAT1, CAT2, LAT1, EAAT2, SNAT1, and SNAT2 were increased to higher levels on E9 or E11 and then decreased to lower levels until DOH. The results of correlation analysis showed that the gene expressions of b0,+AT, EAAT3, PepT1, LAT4, NHE2, NHE3, and y+LAT2 had positive correlations with body weight (0.71

  13. Growth of embryo and gene expression of nutrient transporters in the small intestine of the domestic pigeon (Columba livia).

    Science.gov (United States)

    Chen, Ming-xia; Li, Xiang-guang; Yang, Jun-xian; Gao, Chun-qi; Wang, Bin; Wang, Xiu-qi; Yan, Hui-chao

    2015-06-01

    The objective of this study was to investigate the relationship between gene expression of nutrient (amino acid, peptide, sodium and proton) transporters in the small intestine and embryonic growth in domestic pigeons (Columba livia). One hundred and twenty-five fertilized eggs were randomly assigned into five groups and were incubated under optimal conditions (temperature of 38.1 °C and relative humidity of 55%). Twenty embryos/birds from each group were sacrificed by cervical dislocation on embryonic day (E) 9, 11, 13, 15 and day of hatch (DOH). The eggs, embryos (without yolk sac), and organs (head, brain, heart, liver, lungs, kidney, gizzard, small intestine, legs, and thorax) were dissected, cleaned, and weighed. Small intestine samples were collected for RNA isolation. The mRNA abundance of intestinal nutrient transporters was evaluated by real-time reverse transcription-polymerase chain reaction (RT-PCR). We classified these ten organs into four types according to the changes in relative weight during embryonic development. In addition, the gene expression of nutrient transporters was differentially regulated by embryonic day. The mRNA abundances of b(0,+)AT, EAAT3, y(+)LAT2, PepT1, LAT4, NHE2, and NHE3 increased linearly with age, whereas mRNA abundances of CAT1, CAT2, LAT1, EAAT2, SNAT1, and SNAT2 were increased to higher levels on E9 or E11 and then decreased to lower levels until DOH. The results of correlation analysis showed that the gene expressions of b(0,+)AT, EAAT3, PepT1, LAT4, NHE2, NHE3, and y(+)LAT2 had positive correlations with body weight (0.71

  14. 78 FR 13148 - Notice of Funding Availability for the Small Business Transportation Resource Center Program

    Science.gov (United States)

    2013-02-26

    ... financial and technical assistance, business training programs, business assessment, management training... business'' will refer to: 8(a), small disadvantaged businesses (SDB), disadvantaged business enterprises... as Disadvantaged Business Enterprises (DBE) and the development of programs to encourage, stimulate...

  15. 78 FR 41817 - Notice of Funding Availability for the Small Business Transportation Resource Center Program

    Science.gov (United States)

    2013-07-11

    ... and technical assistance, business training programs, business assessment, management training... business'' will refer to: 8(a), small disadvantaged businesses (SDB), disadvantaged business enterprises... 49 parts 23 and or 26 as Disadvantaged Business Enterprises (DBE) and the development of programs to...

  16. Demonstration of global supply chains with intermodal transportation and decision support for small and medium business.

    Science.gov (United States)

    2009-08-14

    The globalization has exposed all companies, large or small, to global competition : and cooperation. The US furniture industry is not an exception in this process. Table 1 : provides an overall picture of the evolvement of the US residential furnitu...

  17. Redesigning Main Streets in Small Communities: The Viagra of Transportation Investment

    Science.gov (United States)

    1998-09-16

    The national Main Street movement is building momentum. Over 1,200 small : communities across America have rediscovered their Main Streets with impressive : investment in time, energy and money. The tangible measures of return include: : economic gro...

  18. Vibronic effects and destruction of exciton coherence in optical spectra of J-aggregates: A variational polaron transformation approach

    Energy Technology Data Exchange (ETDEWEB)

    Bloemsma, E.A.; Silvis, M.H.; Stradomska, A.; Knoester, J., E-mail: j.knoester@rug.nl

    2016-12-20

    Using a symmetry adapted polaron transformation of the Holstein Hamiltonian, we study the interplay of electronic excitation-vibration couplings, resonance excitation transfer interactions, and temperature in the linear absorption spectra of molecular J-aggregates. Semi-analytical expressions for the spectra are derived and compared with results obtained from direct numerical diagonalization of the Hamiltonian in the two-particle basis set representation. At zero temperature, we show that our polaron transformation reproduces both the collective (exciton) and single-molecule (vibrational) optical response associated with the appropriate standard perturbation limits. Specifically, for the molecular dimer excellent agreement with the spectra from the two-particle approach for the entire range of model parameters is obtained. This is in marked contrast to commonly used polaron transformations. Upon increasing the temperature, the spectra show a transition from the collective to the individual molecular features, which results from the thermal destruction of the exciton coherence.

  19. Polaron Hopping in Nano-scale Poly(dA–Poly(dT DNA

    Directory of Open Access Journals (Sweden)

    Singh Mahi

    2010-01-01

    Full Text Available Abstract We investigate the current–voltage relationship and the temperature-dependent conductance of nano-scale samples of poly(dA–poly(dT DNA molecules. A polaron hopping model has been used to calculate the I–V characteristic of nano-scale samples of DNA. This model agrees with the data for current versus voltage at temperatures greater than 100 K. The quantities G 0 , i 0 , and T 1d are determined empirically, and the conductivity is estimated for samples of poly(dA–poly(dT.

  20. The ground state energy of a bound polaron in the presence of a magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Zorkani, I [International Centre for Theoretical Physics, Trieste (Italy); Belhissi, R [Faculte des Sciences Dhar Mahraz, Fes (Morocco). Dept. de Physique

    1995-09-01

    A theoretical calculation for the ground state energy of a bound polaron as a function of the magnetic field is presented. The theory is based on a variational approach using a trial wave function proposed by Devreese et al. in the absence of the magnetic field. It was shown that his function is adequate for all electron - phonon coupling {alpha} and all parameter {gamma}{sub 0} which is the ratio between the L.O. phonon energy and the Colombian one. Analytical results are obtained in the weak coupling limit. (author). 27 refs, 4 figs, 1 tab.

  1. Inelastic scattering in a local polaron model with quadratic coupling to bosons

    DEFF Research Database (Denmark)

    Olsen, Thomas

    2009-01-01

    We calculate the inelastic scattering probabilities in the wide band limit of a local polaron model with quadratic coupling to bosons. The central object is a two-particle Green's function which is calculated exactly using a purely algebraic approach. Compared with the usual linear interaction term...... a quadratic interaction term gives higher probabilities for inelastic scattering involving a large number of bosons. As an application we consider the problem hot-electron-mediated energy transfer at surfaces and use the delta self-consistent field extension of density-functional theory to calculate...

  2. A variational study of the self-trapped magnetic polaron formation in double-exchange model

    International Nuclear Information System (INIS)

    Liu Tao; Feng Mang; Wang Kelin

    2005-01-01

    We study the formation of self-trapped magnetic polaron (STMP) in an antiferro/ferromagnetic double-exchange model semi-analytically by variational solutions. It is shown that the Jahn-Teller effect is not essential to the STMP formation and the STMP forms in the antiferromagnetic material within the region of the order of the lattice constant. We also confirm that no ground state STMP exists in the ferromagnetic background, but the ground state bound MP could appear due to the impurity potential

  3. Nonequilibrium transport through molecular junctions in the quantum regime

    Czech Academy of Sciences Publication Activity Database

    Koch, T.; Loos, Jan; Alvermann, A.; Fehske, H.

    2011-01-01

    Roč. 84, č. 12 (2011), 125131/1-125131/16 ISSN 1098-0121 Institutional research plan: CEZ:AV0Z10100521 Keywords : the ory of electron ic transport * scattering mechanisms * polarons and electron -phonon interactions * quantum dots Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.691, year: 2011

  4. Breakdown of the lattice polaron picture in La0.7Ca0.3MnO3 single crystals

    International Nuclear Information System (INIS)

    Chun, S. H.; Salamon, M. B.; Tomioka, Y.; Tokura, Y.

    2000-01-01

    When heated through the magnetic transition at T C , La 0.7 Ca 0.3 MnO 3 changes from a band metal to a polaronic insulator. The Hall constant R H , through its activated behavior and sign anomaly, provides key evidence for polaronic behavior. We use R H and the Hall mobility to demonstrate the breakdown of the polaron phase. Above 1.4T C , the polaron picture holds in detail, while below, the activation energies of both R H and the mobility deviate strongly from their polaronic values. These changes reflect the presence of metallic, ferromagnetic fluctuations, in the volume of which the Hall effect develops additional contributions tied to quantal phases. (c) 2000 The American Physical Society

  5. Modeling of a Small Transportation Company’s Start-Up with Limited Data during Economic Recession

    Directory of Open Access Journals (Sweden)

    Xiaoping Fang

    2013-01-01

    Full Text Available This paper presents a modeling method for analyzing a small transportation company’s start-up and growth during a global economic crisis which had an impact on China which is designed to help the owners make better investment and operating decisions with limited data. Since there is limited data, simple regression model and binary regression model failed to generate satisfactory results, so an additive periodic time series model was built to forecast business orders and income. Since the transportation market is segmented by business type and transportation distance, a polynomial model and logistic curve model were constructed to forecast the growth trend of each segmented transportation market, and the seasonal influence function was fitted by seasonal ratio method. Although both of the models produced satisfactory results and showed very nearly the same of goodness-of-fit in the sample, the logistic model presented better forecasting performance out of the sample therefore closer to the reality. Additionally, by checking the development trajectory of the case company’s business and the financial crisis in 2008, the modeling and analysis suggest that the sample company is affected by national macroeconomic factors such as GDP and import & export, and this effect comes with a time lag of one to two years.

  6. Small scale variability of transport and composition of dissolved organic matter in the subsoil

    Science.gov (United States)

    Leinemann, T.; Mikutta, R.; Kalbitz, K.; Guggenberger, G.

    2016-12-01

    Dissolved organic matter (DOM) is the most mobile fraction of carbon in the soil and connects the carbon-rich topsoil with the subsoil where translocated OM may get stabilized. The water flux in soil is highly heterogeneous, both temporarily and spatially. We, therefore, hypothesize that at high flow velocities, DOM can bypass possible mineral binding sites and microorganisms, thus leading to less degraded DOM under high flow velocities. To address this question, we investigated water and DOM fluxes in situ using segmented suction plates (4 x 4 segments on 24 x 24 cm) installed into three soil observatories at three depths (10 cm, 50 cm, and 150 cm) in a Dystric Cambisol under Beech (Fagus sylvatica) near Hannover, Germany. To follow the transport of carbon from the litter layer through the soil, an in situ 13C-labelling experiment has been conducted in January 2015. Concentration of dissolved organic carbon (DOC) and DOM composition was analyzed using high temperature combustion and photometric methods. The amount of transported DOC decreased by ca. 80 % from 10 to 50 cm depth and by 40 % from 50 to 150 cm depth. Different flow patterns existed at the centimeter scale, which were stable over time for individual suction plate segments. The specific UV280 nm absorbance of DOM decreased with increasing soil depth. This indicates a selective loss of aromatic compounds. The influence of different flow regimes on the DOM quality became apparent in the subsoil samples (>50 cm depth) showing a correlation of increasing UV280 nm absorbance with increasing water flux. The 13C-labelling experiment showed that after 10 month just 0.3 % of the DOC in 150 cm depth was derived from fresh litter. The transport of leaf litter carbon seemed to be controlled by the flow regime as the DO13C ratio and the water flux correlated positively. This can be an indication for the importance of preferential flow on carbon transport to the subsoil.

  7. ANALYSIS OF PROCESS OF PROCUREMENT OF TRANSPORTATION EQUIPMENT OF A SMALL COMPANY

    Directory of Open Access Journals (Sweden)

    Cleverson Faber de Assis

    2018-03-01

    Full Text Available The case study presented here is to analyze the costs of purchase, hire or simple hiring of freight to carry out the transport of a manufacturer of insulated panels in the Greater São Paulo. The survey showed, as main objective, the comparison and evaluation of maintenance costs of the vehicle fleet in the case of own equipment the equipment rental value if the option is outsourcing the fleet. Justified the study, because transport is an extremely important activity within the company's logistics operation in question. The transport operation must be operated with the greatest possible efficiency, since it has a direct impact on product costs. The method used was the absorption costing, identifying all costs per vehicle. This method is based on the allocation of direct costs to the object according to their consumption. The methodology ranked as the purpose was exploratory and descriptive. As for the means they were used bibliographical research, document and case study. The approach to the problem was quantitative. With the presented results was simulated an investment plan, showing the advantages and disadvantages of each scenario presented above.

  8. A note on conservative transport in anisotropic, heterogeneous porous media in the presence of small-amplitude transients

    Science.gov (United States)

    Naff, R.L.

    1998-01-01

    The late-time macrodispersion coefficients are obtained for the case of flow in the presence of a small-scale deterministic transient in a three-dimensional anisotropic, heterogeneous medium. The transient is assumed to affect only the velocity component transverse to the mean flow direction and to take the form of a periodic function. For the case of a highly stratified medium, these late-time macrodispersion coefficients behave largely as the standard coefficients used in the transport equation. Only in the event that the medium is isotropic is it probable that significant deviations from the standard coefficients would occur.

  9. 78 FR 13143 - Notice of Funding Availability for the Small Business Transportation Resource Center Program

    Science.gov (United States)

    2013-02-26

    ... financial and technical assistance, business training programs, business assessment, management training... business'' will refer to: 8(a), small disadvantaged businesses (SDB), disadvantaged business enterprises... 49 parts 23 and or 26 as Disadvantaged Business Enterprises (DBE) and the development of programs to...

  10. Impact of the electron-transport layer on the performance of solution-processed small-molecule organic solar cells.

    Science.gov (United States)

    Long, Guankui; Wan, Xiangjian; Kan, Bin; Hu, Zhicheng; Yang, Xuan; Zhang, Yi; Zhang, Mingtao; Wu, Hongbing; Huang, Fei; Su, Shijian; Cao, Yong; Chen, Yongsheng

    2014-08-01

    Although the performance of polymer solar cells has been improved significantly recently through careful optimization with different interlayers for the same materials, more improvement is needed in this respect for small-molecule-based solar cells, particularly for the electron-transport layers (ETLs). In this work, three different solution-processed ETLs, PFN, ZnO nanoparticles, and LiF, were investigated and compared in the performance of small-molecule-based devices, and power conversion efficiencies (PCEs) of 8.32, 7.30, and 7.38% were achieved, respectively. The mechanism for the ETL-induced enhancement has been studied, and different ETLs have a significantly different impact on the device performance. The clearly improved performance of PFN is attributed to the combination of reduced bimolecular recombination and increased effective photon absorption in the active layer. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Quantitative Modeling of Membrane Transport and Anisogamy by Small Groups Within a Large-Enrollment Organismal Biology Course

    Directory of Open Access Journals (Sweden)

    Eric S. Haag

    2016-12-01

    Full Text Available Quantitative modeling is not a standard part of undergraduate biology education, yet is routine in the physical sciences. Because of the obvious biophysical aspects, classes in anatomy and physiology offer an opportunity to introduce modeling approaches to the introductory curriculum. Here, we describe two in-class exercises for small groups working within a large-enrollment introductory course in organismal biology. Both build and derive biological insights from quantitative models, implemented using spreadsheets. One exercise models the evolution of anisogamy (i.e., small sperm and large eggs from an initial state of isogamy. Groups of four students work on Excel spreadsheets (from one to four laptops per group. The other exercise uses an online simulator to generate data related to membrane transport of a solute, and a cloud-based spreadsheet to analyze them. We provide tips for implementing these exercises gleaned from two years of experience.

  12. Transportation

    National Research Council Canada - National Science Library

    Adams, James; Carr, Ron; Chebl, Maroun; Coleman, Robert; Costantini, William; Cox, Robert; Dial, William; Jenkins, Robert; McGovern, James; Mueller, Peter

    2006-01-01

    ...., trains, ships, etc.) and maximizing intermodal efficiency. A healthy balance must be achieved between the flow of international commerce and security requirements regardless of transportation mode...

  13. Prediction of Repair Work Duration for Gas Transport Systems Based on Small Data Samples

    DEFF Research Database (Denmark)

    Lesnykh, Valery; Litvin, Yuri; Kozin, Igor

    2016-01-01

    Prediction of the duration of a repair and maintenance project of a gas transport system is an important part of planning activities. There exist numerous sources of uncertainties that may result in time overruns possibly leading to multiple negative consequences. Our experience in planning...... this work suggests that accepting the stochastic nature of the project duration is a constructive step towards the preparedness to contingencies and defining penalties for repair companies. To support this approach, one needs to construct probability distributions of the durations of the projects...

  14. Singlet and triplet polaron relaxation in doubly charged self-assembled quantum dots

    International Nuclear Information System (INIS)

    Grange, T; Zibik, E A; Ferreira, R; Bastard, G; Carpenter, B A; Phillips, P J; Stehr, D; Winnerl, S; Helm, M; Steer, M J; Hopkinson, M; Cockburn, J W; Skolnick, M S; Wilson, L R

    2007-01-01

    Polaron relaxation in self-assembled InAs/GaAs quantum dot samples containing 2 electrons per dot is studied using far-infrared, time-resolved pump-probe measurements for transitions between the s-like ground and p-like first excited conduction band states. Spin-flip transitions between singlet and triplet states are observed experimentally in the decay of the absorption bleaching, which shows a clear biexponential dependence. The initial fast decay (∼30 ps) is associated with the singlet polaron decay, while the decay component with the longer time constant (∼5 ns) corresponds to the excited state triplet lifetime. The results are explained by considering the intrinsic Dresselhaus spin-orbit interaction, which induces spin-flip transitions by acoustic phonon emission or phonon anharmonicity. We have calculated the spin-flip decay times, and good agreement is obtained between the experiment and the simulation of the pump-probe signal. Our results demonstrate the importance of spin-mixing effects for intraband energy relaxation in InAs/GaAs quantum dots

  15. Non-relativistic Limit of a Dirac Polaron in Relativistic Quantum Electrodynamics

    CERN Document Server

    Arai, A

    2006-01-01

    A quantum system of a Dirac particle interacting with the quantum radiation field is considered in the case where no external potentials exist. Then the total momentum of the system is conserved and the total Hamiltonian is unitarily equivalent to the direct integral $\\int_{{\\bf R}^3}^\\oplus\\overline{H({\\bf p})}d{\\bf p}$ of a family of self-adjoint operators $\\overline{H({\\bf p})}$ acting in the Hilbert space $\\oplus^4{\\cal F}_{\\rm rad}$, where ${\\cal F}_{\\rm rad}$ is the Hilbert space of the quantum radiation field. The fibre operator $\\overline{H({\\bf p})}$ is called the Hamiltonian of the Dirac polaron with total momentum ${\\bf p} \\in {\\bf R}^3$. The main result of this paper is concerned with the non-relativistic (scaling) limit of $\\overline{H({\\bf p})}$. It is proven that the non-relativistic limit of $\\overline{H({\\bf p})}$ yields a self-adjoint extension of a Hamiltonian of a polaron with spin $1/2$ in non-relativistic quantum electrodynamics.

  16. Density functional theory + U modeling of polarons in organohalide lead perovskites

    Directory of Open Access Journals (Sweden)

    Eric Welch

    2016-12-01

    Full Text Available We investigate the possible formation of polarons in four organic perovskites (CH3NH3PbI3, CH3NH3PbBr3, CH3NH3PbCl3, and CH3NH3PbI2Cl1 using a density functional theory (DFT calculations with local potentials and hybrid functionals. We show that DFT+U method with U = 8 eV predicts a correct band-gap and matches the forces on ions from hybrid calculations. We then use the DFT + U approach to study the effect of polarons, i.e. to search the configuration space and locate the lowest energy localized band gap state self-trapped hole (STH. STH configurations were found for three pure halides and one mixed halide system. Spin orbit coupling (SOC was also taken into account and the results may be found in the supplementary material. This study focuses on the +U method; however, SOC corrections added to the DFT+U calculations also resulted in STH states in all four systems.

  17. Madelung and Hubbard interactions in polaron band model of doped organic semiconductors

    Science.gov (United States)

    Png, Rui-Qi; Ang, Mervin C.Y.; Teo, Meng-How; Choo, Kim-Kian; Tang, Cindy Guanyu; Belaineh, Dagmawi; Chua, Lay-Lay; Ho, Peter K.H.

    2016-01-01

    The standard polaron band model of doped organic semiconductors predicts that density-of-states shift into the π–π* gap to give a partially filled polaron band that pins the Fermi level. This picture neglects both Madelung and Hubbard interactions. Here we show using ultrahigh workfunction hole-doped model triarylamine–fluorene copolymers that Hubbard interaction strongly splits the singly-occupied molecular orbital from its empty counterpart, while Madelung (Coulomb) interactions with counter-anions and other carriers markedly shift energies of the frontier orbitals. These interactions lower the singly-occupied molecular orbital band below the valence band edge and give rise to an empty low-lying counterpart band. The Fermi level, and hence workfunction, is determined by conjunction of the bottom edge of this empty band and the top edge of the valence band. Calculations are consistent with the observed Fermi-level downshift with counter-anion size and the observed dependence of workfunction on doping level in the strongly doped regime. PMID:27582355

  18. Multi-impurity polarons in a dilute Bose-Einstein condensate

    International Nuclear Information System (INIS)

    Santamore, D H; Timmermans, Eddy

    2011-01-01

    We describe the ground state of a large, dilute, neutral atom Bose-Einstein condensate (BEC) doped with N strongly coupled mutually indistinguishable, bosonic neutral atoms (referred to as ‘impurity’) in the polaron regime where the BEC density response to the impurity atoms remains significantly smaller than the average density of the surrounding BEC. We find that N impurity atoms with N ≠ 1 can self-localize at a lower value of the impurity-boson interaction strength than a single impurity atom. When the ‘bare’ short-range impurity-impurity repulsion does not play a significant role, the self-localization of multiple bosonic impurity atoms into the same single particle orbital (which we call co-self-localization) is the nucleation process of the phase separation transition. When the short-range impurity-impurity repulsion successfully competes with co-self-localization, the system may form a stable liquid of self-localized single impurity polarons. (paper)

  19. Observation of magnetic polarons in the magnetoresistive pyrochlore Lu2V2O7

    International Nuclear Information System (INIS)

    Storchak, Vyacheslav G; Brewer, Jess H; Eshchenko, Dmitry G; Mengyan, Patrick W; Zhou Haidong; Wiebe, Christopher R

    2013-01-01

    Materials that exhibit colossal magnetoresistance (CMR) have attracted much attention due to their potential technological applications. One particularly interesting model for the magnetoresistance of low-carrier-density ferromagnets involves mediation by magnetic polarons (MP)—electrons localized in nanoscale ferromagnetic ‘droplets’ by their exchange interaction. However, MP have not previously been directly detected and their size has been difficult to determine from macroscopic measurements. In order to provide this crucial information, we have carried out muon spin rotation measurements on the magnetoresistive semiconductor Lu 2 V 2 O 7 in the temperature range from 2 to 300 K and in magnetic fields up to 7 T. Magnetic polarons with characteristic radius R ≈ 0.4 nm are detected below about 100 K, where Lu 2 V 2 O 7 exhibits CMR; at higher temperature, where the magnetoresistance vanishes, these MP also disappear. This observation confirms the MP-mediated model of CMR and reveals the microscopic size of the MP in magnetoresistive pyrochlores. (paper)

  20. Small-bubble transport and splitting dynamics in a symmetric bifurcation

    KAUST Repository

    Qamar, Adnan; Warnez, Matthew; Valassis, Doug T.; Guetzko, Megan E.; Bull, Joseph L.

    2017-01-01

    Simulations of small bubbles traveling through symmetric bifurcations are conducted to garner information pertinent to gas embolotherapy, a potential cancer treatment. Gas embolotherapy procedures use intra-arterial bubbles to occlude tumor blood supply. As bubbles pass through bifurcations in the blood stream nonhomogeneous splitting and undesirable bioeffects may occur. To aid development of gas embolotherapy techniques, a volume of fluid method is used to model the splitting process of gas bubbles passing through artery and arteriole bifurcations. The model reproduces the variety of splitting behaviors observed experimentally, including the bubble reversal phenomenon. Splitting homogeneity and maximum shear stress along the vessel walls is predicted over a variety of physical parameters. Small bubbles, having initial length less than twice the vessel diameter, were found unlikely to split in the presence of gravitational asymmetry. Maximum shear stresses were found to decrease exponentially with increasing Reynolds number. Vortex-induced shearing near the bifurcation is identified as a possible mechanism for endothelial cell damage.

  1. Small-bubble transport and splitting dynamics in a symmetric bifurcation

    KAUST Repository

    Qamar, Adnan

    2017-06-28

    Simulations of small bubbles traveling through symmetric bifurcations are conducted to garner information pertinent to gas embolotherapy, a potential cancer treatment. Gas embolotherapy procedures use intra-arterial bubbles to occlude tumor blood supply. As bubbles pass through bifurcations in the blood stream nonhomogeneous splitting and undesirable bioeffects may occur. To aid development of gas embolotherapy techniques, a volume of fluid method is used to model the splitting process of gas bubbles passing through artery and arteriole bifurcations. The model reproduces the variety of splitting behaviors observed experimentally, including the bubble reversal phenomenon. Splitting homogeneity and maximum shear stress along the vessel walls is predicted over a variety of physical parameters. Small bubbles, having initial length less than twice the vessel diameter, were found unlikely to split in the presence of gravitational asymmetry. Maximum shear stresses were found to decrease exponentially with increasing Reynolds number. Vortex-induced shearing near the bifurcation is identified as a possible mechanism for endothelial cell damage.

  2. Small-bubble transport and splitting dynamics in a symmetric bifurcation.

    Science.gov (United States)

    Qamar, Adnan; Warnez, Matthew; Valassis, Doug T; Guetzko, Megan E; Bull, Joseph L

    2017-08-01

    Simulations of small bubbles traveling through symmetric bifurcations are conducted to garner information pertinent to gas embolotherapy, a potential cancer treatment. Gas embolotherapy procedures use intra-arterial bubbles to occlude tumor blood supply. As bubbles pass through bifurcations in the blood stream nonhomogeneous splitting and undesirable bioeffects may occur. To aid development of gas embolotherapy techniques, a volume of fluid method is used to model the splitting process of gas bubbles passing through artery and arteriole bifurcations. The model reproduces the variety of splitting behaviors observed experimentally, including the bubble reversal phenomenon. Splitting homogeneity and maximum shear stress along the vessel walls is predicted over a variety of physical parameters. Small bubbles, having initial length less than twice the vessel diameter, were found unlikely to split in the presence of gravitational asymmetry. Maximum shear stresses were found to decrease exponentially with increasing Reynolds number. Vortex-induced shearing near the bifurcation is identified as a possible mechanism for endothelial cell damage.

  3. Transportation

    International Nuclear Information System (INIS)

    Anon.

    1998-01-01

    Here is the decree of the thirtieth of July 1998 relative to road transportation, to trade and brokerage of wastes. It requires to firms which carry out a road transportation as well as to traders and to brokers of wastes to declare their operations to the prefect. The declaration has to be renewed every five years. (O.M.)

  4. Pick-up, transport and release of a molecular cargo using a small-molecule robotic arm

    Science.gov (United States)

    Kassem, Salma; Lee, Alan T. L.; Leigh, David A.; Markevicius, Augustinas; Solà, Jordi

    2016-02-01

    Modern-day factory assembly lines often feature robots that pick up, reposition and connect components in a programmed manner. The idea of manipulating molecular fragments in a similar way has to date only been explored using biological building blocks (specifically DNA). Here, we report on a wholly artificial small-molecule robotic arm capable of selectively transporting a molecular cargo in either direction between two spatially distinct, chemically similar, sites on a molecular platform. The arm picks up/releases a 3-mercaptopropanehydrazide cargo by formation/breakage of a disulfide bond, while dynamic hydrazone chemistry controls the cargo binding to the platform. Transport is controlled by selectively inducing conformational and configurational changes within an embedded hydrazone rotary switch that steers the robotic arm. In a three-stage operation, 79-85% of 3-mercaptopropanehydrazide molecules are transported in either (chosen) direction between the two platform sites, without the cargo at any time fully dissociating from the machine nor exchanging with other molecules in the bulk.

  5. Gene expression of transporters and phase I/II metabolic enzymes in murine small intestine during fasting

    Directory of Open Access Journals (Sweden)

    van der Meijde Jolanda

    2007-08-01

    Full Text Available Abstract Background Fasting has dramatic effects on small intestinal transport function. However, little is known on expression of intestinal transport and phase I/II metabolism genes during fasting and the role the fatty acid-activated transcription factor PPARα may play herein. We therefore investigated the effects of fasting on expression of these genes using Affymetrix GeneChip MOE430A arrays and quantitative RT-PCR. Results After 24 hours of fasting, expression levels of 33 of the 253 analyzed transporter and phase I/II metabolism genes were changed. Upregulated genes were involved in transport of energy-yielding molecules in processes such as glycogenolysis (G6pt1 and mitochondrial and peroxisomal oxidation of fatty acids (Cact, Mrs3/4, Fatp2, Cyp4a10, Cyp4b1. Other induced genes were responsible for the inactivation of the neurotransmitter serotonin (Sert, Sult1d1, Dtd, Papst2, formation of eicosanoids (Cyp2j6, Cyp4a10, Cyp4b1, or for secretion of cholesterol (Abca1 and Abcg8. Cyp3a11, typically known because of its drug metabolizing capacity, was also increased. Fasting had no pronounced effect on expression of phase II metabolic enzymes, except for glutathione S-transferases which were down-regulated. Time course studies revealed that some genes were acutely regulated, whereas expression of other genes was only affected after prolonged fasting. Finally, we identified 8 genes that were PPARα-dependently upregulated upon fasting. Conclusion We have characterized the response to fasting on expression of transporters and phase I/II metabolic enzymes in murine small intestine. Differentially expressed genes are involved in a variety of processes, which functionally can be summarized as a increased oxidation of fat and xenobiotics, b increased cholesterol secretion, c increased susceptibility to electrophilic stressors, and d reduced intestinal motility. This knowledge increases our understanding of gut physiology, and may be of relevance

  6. Impact of electro-magnetic stabilization, small- scale turbulence and multi-scale interactions on heat transport in JET

    Science.gov (United States)

    Mantica, Paola

    2016-10-01

    Heat transport experiments in JET, based on ICRH heat flux scans and temperature modulation, have confirmed the importance of two transport mechanisms that are often neglected in modeling experimental results, but are crucial to reach agreement between theory and experiment and may be significant in ITER. The first mechanism is the stabilizing effect of the total pressure gradient (including fast ions) on ITG driven ion heat transport. Such stabilization is found in non-linear gyro-kinetic electro-magnetic simulations using GENE and GYRO, and is the explanation for the observed loss of ion stiffness in the core of high NBI-power JET plasmas. The effect was recently observed also in JET plasmas with dominant ICRH heating and small rotation, due to ICRH fast ions, which is promising for ITER. Such mechanism dominates over ExB flow shear in the core and needs to be included in quasi-linear models to increase their ability to capture the relevant physics. The second mechanism is the capability of small- scale ETG instabilities to carry a significant fraction of electron heat. A decrease in Te peaking is observed when decreasing Zeff Te/Ti, which cannot be ascribed to TEMs but is in line with ETGs. Non-linear GENE single-scale simulations of ETGs and ITG/TEMs show that the ITG/TEM electron heat flux is not enough to match experiment. TEM stiffness is also much lower than measured. In the ETG single scale simulations the external flow shear is used to saturate the ETG streamers. Multi-scale simulations are ongoing, in which the ion zonal flows are the main saturating mechanism for ETGs. These costly simulations should provide the final answer on the importance of ETG-driven electron heat flux in JET. with JET contributors [F.Romanelli, Proc.25thIAEA FEC]. Supported by EUROfusion Grant 633053.

  7. Preliminary investigation of the transport of small plastic litter along a vegetated riverbank

    Science.gov (United States)

    Liu, Da; Valyrakis, Manousos

    2017-04-01

    Plastics are widely used in consumer products, due to its low cost, low weight and high durability compared to other types of materials. Contamination of marine ecosystems due to plastics (including microplastics) is a challenge that has received a lot of attention due to the significant risks it poses for the environment and human health. Plastics find their way to the ocean from land via the river system. Studying and obtaining a better understanding of the mechanisms contributing to the fate of plastic litter is therefore important in proactively devising methods to reduce their quantity or produce designs to trap plastic pollutants and prevent them from entering the ocean through estuaries. In this context, it is a common observation of hydraulic practitioners and field geomorphologists, that plastic litter can be trapped within riparian vegetation patches along streams or canals, which can be washed away in periods of high flows. To this goal this study aims to use a series of purpose specific physical experiments to examine the mechanisms of dispersion of plastic litter along the water surface of a channel with simulated riparian vegetation. The set of experiments are conducted in a recirculating flume with rigid riverbank and riparian vegetation modeled by a large number of acrylic rods, placed on the top of the riverbank section. Six different sizes of pieces of Styrofoam are used to simulate plastic litter. These are released from different locations upstream and in the vicinity of the riparian vegetation for various configurations (linear, staggered and random) of characteristic solid density. The trajectory of the plastic litter is recorded with a camera offering a top view of the arrangement. From the analysis of this a variety of results are obtained including transport metrics (including transport velocity and time to trapping) and litter-trapping location. The relation between the size of the litter, the vegetation configuration and the traveling

  8. Multiphonon contribution to the polaron formation in cuprates with strong electron correlations and strong electron-phonon interaction

    Science.gov (United States)

    Ovchinnikov, Sergey G.; Makarov, Ilya A.; Kozlov, Peter A.

    2017-03-01

    In this work dependences of the electron band structure and spectral function in the HTSC cuprates on magnitude of electron-phonon interaction (EPI) and temperature are investigated. We use three-band p-d model with diagonal and offdiagonal EPI with breathing and buckling phonon mode in the frameworks of polaronic version of the generalized tight binding (GTB) method. The polaronic quasiparticle excitation in the system with EPI within this approach is formed by a hybridization of the local multiphonon Franck-Condon excitations with lower and upper Hubbard bands. Increasing EPI leads to transfer of spectral weight to high-energy multiphonon excitations and broadening of the spectral function. Temperature effects are taken into account by occupation numbers of local excited polaronic states and variations in the magnitude of spin-spin correlation functions. Increasing the temperature results in band structure reconstruction, spectral weight redistribution, broadening of the spectral function peak at the top of the valence band and the decreasing of the peak intensity. The effect of EPI with two phonon modes on the polaron spectral function is discussed.

  9. Shallow trapping vs. deep polarons in a hybrid lead halide perovskite, CH3NH3PbI3.

    Science.gov (United States)

    Kang, Byungkyun; Biswas, Koushik

    2017-10-18

    There has been considerable speculation over the nature of charge carriers in organic-inorganic hybrid perovskites, i.e., whether they are free and band-like, or they are prone to self-trapping via short range deformation potentials. Unusually long minority-carrier diffusion lengths and moderate-to-low mobilities, together with relatively few deep defects add to their intrigue. Here we implement density functional methods to investigate the room-temperature, tetragonal phase of CH 3 NH 3 PbI 3 . We compare charge localization behavior at shallow levels and associated lattice relaxation versus those at deep polaronic states. The shallow level originates from screened Coulomb interaction between the perturbed host and an excited electron or hole. The host lattice has a tendency towards forming these shallow traps where the electron or hole is localized not too far from the band edge. In contrast, there is a considerable potential barrier that must be overcome in order to initiate polaronic hole trapping. The formation of a hole polaron (I 2 - center) involves strong lattice relaxation, including large off-center displacement of the organic cation, CH 3 NH 3 + . This type of deep polaron is energetically unfavorable, and active shallow traps are expected to shape the carrier dynamics in this material.

  10. Transport of particles, drops, and small organisms in density stratified fluids

    Science.gov (United States)

    Ardekani, Arezoo M.; Doostmohammadi, Amin; Desai, Nikhil

    2017-10-01

    Sedimenting particles and motile organisms are ubiquitously found in oceans and lakes, where density stratification naturally occurs due to temperature or salinity gradients. We explore the effects of stratification on the fundamental hydrodynamics of settling particles, rising drops, and small organisms. The results of our direct numerical simulations of the sedimentation of particles show that the presence of vertical density gradients in the water column can substantially affect the settling dynamics of a particle, interaction between a pair of particles, and settling rates and microstructure of suspension of particles. We show that elongation of particles affects both the settling orientation and the settling rate of particles in stratified fluids, which will have direct consequences on the vertical flux of particulate matter and carbon flux in the ocean. We further demonstrate an unexpected effect of buoyancy, potentially affecting a broad range of processes at pycnoclines in oceans and lakes. In particular, stratification has a major effect on the flow field, energy expenditure, and nutrient uptake of small organisms. In addition, the role of stratification in pattern formation of bioconvection plumes of algal cells and in biogenic mixing is investigated. In particular, the numerical approach allows for considering the effects of background turbulence and hydrodynamic perturbations produced by swimming organisms, shedding light on the contribution of organisms in the mixing process in aqueous environments.

  11. Transportation

    National Research Council Canada - National Science Library

    Allshouse, Michael; Armstrong, Frederick Henry; Burns, Stephen; Courts, Michael; Denn, Douglas; Fortunato, Paul; Gettings, Daniel; Hansen, David; Hoffman, D. W; Jones, Robert

    2007-01-01

    .... The ability of the global transportation industry to rapidly move passengers and products from one corner of the globe to another continues to amaze even those wise to the dynamics of such operations...

  12. Transport, dissociation and rotation of small self-interstitial atom clusters in tungsten

    International Nuclear Information System (INIS)

    Zhou, W.H.; Zhang, C.G.; Li, Y.G.; Zeng, Z.

    2014-01-01

    Numerical calculations have been performed to study the thermal motion of self-interstitial atom (SIA) clusters in tungsten (W). Molecular dynamics simulations show that SIA clusters exhibit a fast one-dimensional (1D) motion along the close packed 〈1 1 1〉 direction accompanied by a significant mass transport in this direction. A low frequency vibration mode is identified and considered to assist the motion of SIAs. The migration energy of SIA clusters are weakly dependent on their size in the average value of 0.019 eV, which is due to the strong interaction between SIAs revealed by calculating the potential energy curve of artificially moving the SIAs along 〈1 1 1〉 direction as well as nudged elastic band (NEB) method. The rotation process of SIA cluster is studied by activation–relaxation technique and the results show that SIA cluster presents complex rotation process. Our results on the motion SIA cluster may provide updated understanding on the performance decay of materials related to SIA defects

  13. Parton Theory of Magnetic Polarons: Mesonic Resonances and Signatures in Dynamics

    Science.gov (United States)

    Grusdt, F.; Kánasz-Nagy, M.; Bohrdt, A.; Chiu, C. S.; Ji, G.; Greiner, M.; Greif, D.; Demler, E.

    2018-01-01

    When a mobile hole is moving in an antiferromagnet it distorts the surrounding Néel order and forms a magnetic polaron. Such interplay between hole motion and antiferromagnetism is believed to be at the heart of high-temperature superconductivity in cuprates. In this article, we study a single hole described by the t -Jz model with Ising interactions between the spins in two dimensions. This situation can be experimentally realized in quantum gas microscopes with Mott insulators of Rydberg-dressed bosons or fermions, or using polar molecules. We work at strong couplings, where hole hopping is much larger than couplings between the spins. In this regime we find strong theoretical evidence that magnetic polarons can be understood as bound states of two partons, a spinon and a holon carrying spin and charge quantum numbers, respectively. Starting from first principles, we introduce a microscopic parton description which is benchmarked by comparison with results from advanced numerical simulations. Using this parton theory, we predict a series of excited states that are invisible in the spectral function and correspond to rotational excitations of the spinon-holon pair. This is reminiscent of mesonic resonances observed in high-energy physics, which can be understood as rotating quark-antiquark pairs carrying orbital angular momentum. Moreover, we apply the strong-coupling parton theory to study far-from-equilibrium dynamics of magnetic polarons observable in current experiments with ultracold atoms. Our work supports earlier ideas that partons in a confining phase of matter represent a useful paradigm in condensed-matter physics and in the context of high-temperature superconductivity in particular. While direct observations of spinons and holons in real space are impossible in traditional solid-state experiments, quantum gas microscopes provide a new experimental toolbox. We show that, using this platform, direct observations of partons in and out of equilibrium are

  14. Small-scale sediment transport patterns and bedform morphodynamics: New insights from high resolution multibeam bathymetry

    Science.gov (United States)

    Barnard, Patrick L.; Erikson, Li H.; Rubin, David M.; Kvitek, Rikk G.

    2011-01-01

    New multibeam echosounder and processing technologies yield sub-meter-scale bathymetric resolution, revealing striking details of bedform morphology that are shaped by complex boundary-layer flow dynamics at a range of spatial and temporal scales. An inertially aided post processed kinematic (IAPPK) technique generates a smoothed best estimate trajectory (SBET) solution to tie the vessel motion-related effects of each sounding directly to the ellipsoid, significantly reducing artifacts commonly found in multibeam data, increasing point density, and sharpening seafloor features. The new technique was applied to a large bedform field in 20–30 m water depths in central San Francisco Bay, California (USA), revealing bedforms that suggest boundary-layer flow deflection by the crests where 12-m-wavelength, 0.2-m-amplitude bedforms are superimposed on 60-m-wavelength, 1-m-amplitude bedforms, with crests that often were strongly oblique (approaching 90°) to the larger features on the lee side, and near-parallel on the stoss side. During one survey in April 2008, superimposed bedform crests were continuous between the crests of the larger features, indicating that flow detachment in the lee of the larger bedforms is not always a dominant process. Assessment of bedform crest peakedness, asymmetry, and small-scale bedform evolution between surveys indicates the impact of different flow regimes on the entire bedform field. This paper presents unique fine-scale imagery of compound and superimposed bedforms, which is used to (1) assess the physical forcing and evolution of a bedform field in San Francisco Bay, and (2) in conjunction with numerical modeling, gain a better fundamental understanding of boundary-layer flow dynamics that result in the observed superimposed bedform orientation.

  15. Varying the charge of small cations in liquid water: Structural, transport, and thermodynamical properties

    Science.gov (United States)

    Martelli, Fausto; Vuilleumier, Rodolphe; Simonin, Jean-Pierre; Spezia, Riccardo

    2012-10-01

    In this work, we show how increasing the charge of small cations affects the structural, thermodynamical, and dynamical properties of these ions in liquid water. We have studied the case of lanthanoid and actinoid ions, for which we have recently developed accurate polarizable force fields, and the ionic radius is in the 0.995-1.250 Å range, and explored the valency range from 0 to 4+. We found that the ion charge strongly structures the neighboring water molecules and that, in this range of charges, the hydration enthalpies exhibit a quadratic dependence with respect to the charge, in line with the Born model. The diffusion process follows two main regimes: a hydrodynamical regime for neutral or low charges, and a dielectric friction regime for high charges in which the contraction of the ionic radius along the series of elements causes a decrease of the diffusion coefficient. This latter behavior can be qualitatively described by theoretical models, such as the Zwanzig and the solvated ion models. However, these models need be modified in order to obtain agreement with the observed behavior in the full charge range. We have thus modified the solvated ion model by introducing a dependence of the bare ion radius as a function of the ionic charge. Besides agreement between theory and simulation this modification allows one to obtain an empirical unified model. Thus, by analyzing the contributions to the drag coefficient from the viscous and the dielectric terms, we are able to explain the transition from a regime in which the effect of viscosity dominates to one in which dielectric friction governs the motion of ions with radii of ca. 1 Å.

  16. Formation of spin-polarons in the ferromagnetic Kondo lattice model away from half-filling

    International Nuclear Information System (INIS)

    Arredondo, Y; Navarro, O; Vallejo, E; Avignon, M

    2012-01-01

    Even though realistic one-dimensional experiments in the field of half-metallic semiconductors are not at hand yet, we are interested in the underlying fundamental physics. In this regard we study a one-dimensional ferromagnetic Kondo lattice model, a model in which a conduction band is coupled ferromagnetically to a background of localized d moments with coupling constant J H , and investigate the T = 0 phase diagram as a function of the antiferromagnetic interaction J between the localized moments and the band-filling n, since it has been observed that doping of the compounds has led to formation of magnetic domains. We explore the spin-polaron formation by looking at the nearest-neighbour correlation functions in the spin and charge regimes for which we use the density matrix renormalization group method, which is a highly efficient method to investigate quasi-one-dimensional strongly correlated systems. (paper)

  17. Many-polaron theory for superconductivity and charge-density waves in a strongly coupled electron-phonon system with quasi-two-dimensionality: An interpolation between the adiabatic limit and the inverse-adiabatic limit

    International Nuclear Information System (INIS)

    Nasu, K.

    1987-01-01

    The phase diagram of a two-dimensional N-site N-electron system (N>>1) with site-diagonal electron-phonon (e-ph) coupling is studied in the context of polaron theory, so as to clarify the competition between the superconducting (SC) state and the charge-density wave (CDW) state. The Fermi surface of noninteracting electrons is assumed to be a complete circle with no nesting-type instability in the case of weak e-ph coupling, so as to focus on such a strong coupling that even the standard ''strong-coupling theory'' for superconductivity breaks down. Phonon clouds moving with electrons as well as a frozen phonon are taken into account by a variational method, combined with a mean-field theory. It covers the whole region of three basic parameters characterizing the system: the intersite transfer energy of electron T, the e-ph coupling energy S, and the phonon energy ω. The resultant phase diagram is given in a triangular coordinate space spanned by T, S, and ω. In the adiabatic region ω >(T,S) near the ω vertex of the triangle, on the other hand, each electron becomes a small polaron, and the SC state is always more stable than the CDW state, because the retardation effect is absent

  18. Influence of convection on the diffusive transport and sieving of water and small solutes across the peritoneal membrane.

    Science.gov (United States)

    Asghar, Ramzana B; Diskin, Ann M; Spanel, Patrik; Smith, David; Davies, Simon J

    2005-02-01

    The three-pore model of peritoneal membrane physiology predicts sieving of small solutes as a result of the presence of a water-exclusive pathway. The purpose of this study was to measure the diffusive and convective components of small solute transport, including water, under differing convection. Triplicate studies were performed in eight stable individuals using 2-L exchanges of bicarbonate buffered 1.36 or 3.86% glucose and icodextrin. Diffusion of water was estimated by establishing an artificial gradient of deuterated water (HDO) between blood/body water and the dialysate. (125)RISA (radio-iodinated serum albumin) was used as an intraperitoneal volume marker to determine the net ultrafiltration and reabsorption of fluid. The mass transfer area coefficient (MTAC) for HDO and solutes was estimated using the Garred and Waniewski equations. The MTAC of HDO calculated for 1.36% glucose and icodextrin were similar (36.8 versus 39.7 ml/min; P = 0.3), whereas for other solutes, values obtained using icodextrin were consistently higher (P solutes is a reflection of their sieving. The increase in the MTAC of water and urea associated with an increase in convection is most likely due to increased mixing within the interstitium.

  19. Effects of Polaron and Quantum Confinement on the Nonlinear Optical Properties in a GaAs/Ga1-xAlxAs Quantum Well Wire

    Directory of Open Access Journals (Sweden)

    L. Caroline Sugirtham

    2014-01-01

    Full Text Available The binding energy of a polaron confined in a GaAs/Ga1-xAlxAs quantum well wire is calculated within the framework of the variational technique and Lee-Low Pines approach. The polaron-induced photoionization cross section as a function of normalized photon energy for a on-centre donor impurity in the quantum wire is investigated. The oscillator strength with the geometrical effect is studied taking into account the polaron effects in a GaAs/Ga0.8Al0.2As quantum well wire. The effect of polaron on the third-order susceptibility of third harmonic generation is studied. Our theoretical results are shown to be in good agreement with previous investigations.

  20. Double path integral method for obtaining the mobility of the one-dimensional charge transport in molecular chain.

    Science.gov (United States)

    Yoo-Kong, Sikarin; Liewrian, Watchara

    2015-12-01

    We report on a theoretical investigation concerning the polaronic effect on the transport properties of a charge carrier in a one-dimensional molecular chain. Our technique is based on the Feynman's path integral approach. Analytical expressions for the frequency-dependent mobility and effective mass of the carrier are obtained as functions of electron-phonon coupling. The result exhibits the crossover from a nearly free particle to a heavily trapped particle. We find that the mobility depends on temperature and decreases exponentially with increasing temperature at low temperature. It exhibits large polaronic-like behaviour in the case of weak electron-phonon coupling. These results agree with the phase transition (A.S. Mishchenko et al., Phys. Rev. Lett. 114, 146401 (2015)) of transport phenomena related to polaron motion in the molecular chain.

  1. Transportation

    Science.gov (United States)

    2007-01-01

    Faculty ii INDUSTRY TRAVEL Domestic Assistant Deputy Under Secretary of Defense (Transportation Policy), Washington, DC Department of...developed between the railroad and trucking industries. Railroads: Today’s seven Class I freight railroad systems move 42% of the nation’s intercity ...has been successfully employed in London to reduce congestion and observed by this industry study during its travels . It is currently being

  2. Monte Carlo tests of small-world architecture for coarse-grained networks of the United States railroad and highway transportation systems

    Science.gov (United States)

    Aldrich, Preston R.; El-Zabet, Jermeen; Hassan, Seerat; Briguglio, Joseph; Aliaj, Enela; Radcliffe, Maria; Mirza, Taha; Comar, Timothy; Nadolski, Jeremy; Huebner, Cynthia D.

    2015-11-01

    Several studies have shown that human transportation networks exhibit small-world structure, meaning they have high local clustering and are easily traversed. However, some have concluded this without statistical evaluations, and others have compared observed structure to globally random rather than planar models. Here, we use Monte Carlo randomizations to test US transportation infrastructure data for small-worldness. Coarse-grained network models were generated from GIS data wherein nodes represent the 3105 contiguous US counties and weighted edges represent the number of highway or railroad links between counties; thus, we focus on linkage topologies and not geodesic distances. We compared railroad and highway transportation networks with a simple planar network based on county edge-sharing, and with networks that were globally randomized and those that were randomized while preserving their planarity. We conclude that terrestrial transportation networks have small-world architecture, as it is classically defined relative to global randomizations. However, this topological structure is sufficiently explained by the planarity of the graphs, and in fact the topological patterns established by the transportation links actually serve to reduce the amount of small-world structure.

  3. Transport and fluxes of terrestrial polycyclic aromatic hydrocarbons in a small mountain river and submarine canyon system.

    Science.gov (United States)

    Lin, Bing-Sian; Lee, Chon-Lin; Brimblecombe, Peter; Liu, James T

    2016-08-01

    Polycyclic aromatic hydrocarbon (PAH) concentrations in the Gaoping River were investigated in the wet and dry seasons. PAH characteristics allowed us to trace the particulate matter transported in a river-sea system containing a small mountain river, continental shelf, and submarine canyon. PAH signatures of the Gaoping River showed that particles were rapidly transported from the high mountain to the Gaoping coastal areas in the wet season, even arriving at the deep ocean via the Gaoping Submarine Canyon. By contrast, in the dry season, the particles were delivered quite slowly and included mostly pyrogenic contaminants. The annual riverine flux estimates for PAHs were 2241 kg in the Gaoping river-sea system. Only 18.0 kg were associated with the dissolved phase; the rest was bound onto particles. The fluxes caused by typhoons and their effects accounted for 20.2% of the dissolved and 68.4% of the particulate PAH fluxes from the river. Normalized partition coefficients for organic carbon suggested that PAHs were rigid on the particles. Distinct source characteristics were evident for PAHs on riverine suspended particles and coastal surface sediments: the particles in the wet season (as background signals) were similar to petrogenic sources, whereas the particles in the dry season had characteristics of coal burning and vehicular emissions. The sediments in the northwestern shelf were similar to pyrogenic sources (including vehicular emissions and coal and biomass burning), whereas the sediments in the canyon and southeastern shelf arose from mixed sources, although some diesel signature was also evident. Copyright © 2016 Elsevier Ltd. All rights reserved.

  4. Phonon-affected steady-state transport through molecular quantum dots

    Czech Academy of Sciences Publication Activity Database

    Koch, T.; Fehske, H.; Loos, Jan

    T151, č. 1 (2012), 1-10 ISSN 0031-8949 Institutional research plan: CEZ:AV0Z10100521 Keywords : the ory of electron ic transport * scattering mechanisms * polarons and electron -phonon interactions Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.032, year: 2012

  5. Polaronic and bipolaronic structures in the adiabatic Hubbard-Holstein model involving 2 electrons and its extensions

    International Nuclear Information System (INIS)

    Proville, L.

    1998-01-01

    This thesis brings its contribution to the bipolaronic theory which might explain the origin of superconductivity at high temperature. A polaron is a quasiparticle made up of a localized electron and a deformation in the crystal structure. 2 electrons in singlet states localized on the same site form a bipolaron. Whenever the Coulomb repulsion between the 2 electrons is too strong bipolaron turns into 2 no bound polarons. We study the existence and the mobility of bipolarons. We describe the electron-phonon interaction by the Holstein term and the Coulomb repulsion by the Hubbard term. 2 assumptions are made: - the local electron-phonon interaction is strong and opposes the Coulomb repulsion between Hubbard type electrons - the system is close to the adiabatic limit. The system is reduced to 2 electrons in order to allow an exact treatment and the investigation of some bipolaronic bound states. At 2-dimensions the existence of bipolarons requires a very strong coupling which forbids any classical mobility. In some cases an important tunneling effect appears and we show that mobile bipolarons exist in a particular parameter range. Near the adiabatic limit we prove that polaronic and bipolaronic structures exist for a great number of electrons. (A.C.)

  6. Large polaron tunneling, magnetic and impedance analysis of magnesium ferrite nanocrystallite

    Energy Technology Data Exchange (ETDEWEB)

    Mahato, Dev K., E-mail: drdevkumar@yahoo.com [Department of Physics, National Institute of Technology Patna, Patna 800 005 (India); Majumder, Sumit [Department of Physics, Jadavpur University, Kolkata 700032 (India); Surface Physics and Material Science Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700 064 (India); Banerjee, S. [Surface Physics and Material Science Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700 064 (India)

    2017-08-15

    Graphical abstract: The diffraction peaks corresponding to the planes (111), (220), (311), (222), (400), (422), (511), (440), (620), (533) and (444) provide a clear evidence for the formation of spinel structure of the ferrites. The lattice parameter ‘a’ determined as 8.392 Å matches well with JCPDS (73-2410) file for MgFe{sub 2}O{sub 4.} The volume of the unit cell is 591.012 Å{sup 3}. The crystallite size of the synthesized powder estimated from X-ray peak broadening of (311) highest intensity diffraction peak using Scherer formula was 56.4 nm. - Highlights: • Both the grain and grain boundaries contribution to conductivity of the Mg-ferrite has been observed. • Polydispersive nature of the material is checked using Cole – Cole relation. • The ac conductivity of magnesium ferrite followed σ{sub ac} ∝ ω{sup n} dependence. • The variation of the exponent ‘n’ with temperature suggests that overlapping large polaron tunnelling is the dominant conduction mechanism. • The superparamagnetic behavior of this Mg-ferrite has been observed for sample S1 annealed at 500 °C. - Abstract: Single phase MgFe{sub 2}O{sub 4} (MFO) ferrite was prepared through sol-gel auto-combustion route. The Rietveld analysis of X-ray patterns reveals that our samples are single phase. The increase in average particle size with annealing temperature and formation of nanoparticle agglomerates is observed in MgFe{sub 2}O{sub 4}. The structural morphology of the nanoparticles is studied using Scanning Electron Microscopy (SEM). Formation of spinel structure is confirmed using Fourier transform infrared spectroscopy (FTIR). The Zero-Field-Cooled (ZFC) and Field-Cooled (FC) magnetization measurements show the maximum irreversibility at 700 °C annealing temperature. The formation of a maximum at blocking temperature, T{sub B}∼ 180 K for sample annealed at 500 °C in the ZFC curve shows the superparamagnetic behavior of the sample. The increase of saturation magnetism (M

  7. Investigation on structural, magneto-transport, magnetic and thermal properties of La{sub 0.8}Ca{sub 0.2−x}Ba{sub x}MnO{sub 3} (0 ⩽ x ⩽ 0.2) manganites

    Energy Technology Data Exchange (ETDEWEB)

    Manjunatha, S.O. [Department of Physics, Manipal Institute of Technology, Manipal University, Manipal 576104 (India); Rao, Ashok, E-mail: ashokanu_rao@rediffmail.com [Department of Physics, Manipal Institute of Technology, Manipal University, Manipal 576104 (India); Subhashini [Material Processing Laboratory, Department of Physics, National Institute of Technology Karnataka, Surathkal 575025 (India); Okram, G.S. [UGC-DAE Consortium for Scientific Research, Khandwa Road, Indore 452 001, MP (India)

    2015-08-15

    Highlights: • Ba-doped compounds follow small polaron hopping model in high temperature range. • Ba-doping introduces structural phase transformation. • MR (%) decreases with Ba-doping, however T{sub MI} and T{sub C} increase with doping. • High temperature TEP data follows SPH model. • At low temperatures, electron–magnon scattering play role in thermal transport. - Abstract: A systematic study on the structural, electrical, magnetic and thermo-electric properties of La{sub 0.8}Ba{sub x}Ca{sub 0.2−x}MnO{sub 3} (0 ⩽ x ⩽ 0.2) manganites is carried out in the present work. The samples have been prepared using solid state reaction technique. All the samples are single phased. It is seen that Ba-doping introduces a structural phase transformation viz. from rhombohedral to cubic system. Electric and magnetic studies respectively show that the metal–insulator transition temperature, T{sub MI} and Curie temperature, T{sub C} increase with Ba-content. Magneto-resistance (MR) data shows that it decreases with Ba-doping. Analyses of the electrical transport data in metallic region i.e. T < T{sub MI} shows that the electrical transport is governed predominantly by electron–electron scattering process. On the other hand, the adiabatic small polaron hopping (ASPH) model is appropriate in the high-temperature insulating range viz. T > T{sub MI}. We have used the electrical resistivity data in the entire temperature range (50–300 K) and analyzed using the phenomenological percolation model which is based on the phase segregation mechanism. We have analyzed the Seebeck coefficient data which reveals that the small polaron hopping mechanism is operative in high temperature regime and the low temperature region is examined by taking into account the impurity, electron–magnon scattering, and spin wave fluctuation terms. It is established that the electron–magnon scattering is dominating for the thermoelectric transport below T{sub MI}.

  8. Bound magnetic polaron in Zn-rich cobalt-doped ZnSe nanowires

    Science.gov (United States)

    Hou, Lipeng; Pan, Longfei; Liang, Bianbian; Liu, Yuting; Zhang, Li; Bukhtiar, Arfan; Shi, Lijie; Liu, Ruibin; Zou, Bingsuo

    2018-02-01

    The micro-luminescence spectra of the diluted magnetic semiconductor (DMS) can reflect the spin-exciton interaction and related relaxation process. Here the micro-photoluminescence (micro-PL) spectra and PL lifetime measurements have been done on an individual ferromagnetic (FM)-coupled cobalt (Co) doped zinc selenide (ZnSe) nanowire. There occurs a double-peak profile in its near bandedge emission spectrum: the first peak is from free exciton (FX) and the second comes from magnetic polaron (MP). In their temperature dependent PL spectra, the MP emission peak demonstrates obviously temperature-independent behavior, in contrast to the behaviors of FX and reported exciton MP in nanobelt. It is found that in this Co(II) doped ZnSe nanowires, this MP’s temperature-independent emission is related to the coupling between exciton and a FM nanocluster (↑↑↓). The nanocluster is likely due to the interaction of Se vacancies of the wide bandgap semiconductors with the antiferromagnetic (AFM) arrangement transition metal (TM) ions in these Se-deficient Co doped ZnSe nanowires. These results reflect that the AFM coupling TM ions pair can give rise to FM behavior with the involvement of positive charge defect, also indicating that the micro-luminescence detection can be used to study the magnetic coupling in DMS.

  9. Effects of polarons on static polarizabilities and second order hyperpolarizabilities of conjugated polymers

    International Nuclear Information System (INIS)

    Wang Ya-Dong; Meng Yan; Di Bing; Wang Shu-Ling; An Zhong

    2010-01-01

    According to the one-dimensional tight-binding Su—Schrieffer—Heeger model, we have investigated the effects of charged polarons on the static polarizability, α xx , and the second order hyperpolarizabilities, γ xxxx , of conjugated polymers. Our results are consistent qualitatively with previous ab initio and semi-empirical calculations. The origin of the universal growth is discussed using a local-view formalism that is based on the local atomic charge derivatives. Furthermore, combining the Su-Schrieffer-Heeger model and the extended Hubbard model, we have investigated systematically the effects of electron-electron interactions on α xx and γ xxxx of charged polymer chains. For a fixed value of the nearest-neighbour interaction V, the values of α xx and γ xxxx increase as the on-site Coulomb interaction U increases for U c and decrease with U for U > U c , where U c is a critical value of U at which the static polarizability or the second order hyperpolarizability reaches a maximal value of α max or γ max . It is found that the effect of the e-e interaction on the value of α xx is dependent on the ratio between U and V for either a short or a long charged polymer. Whereas, that effect on the value of γ xxxx is sensitive both to the ratio of U to V and to the size of the molecule. (rapid communication)

  10. Faraday rotation by the undisturbed bulk and by photoinduced giant polarons in EuTe

    Science.gov (United States)

    Henriques, A. B.; Usachev, P. A.

    2017-11-01

    A quantum mechanical model is developed for the Faraday effect in europium telluride, for photons of energy within the transparency gap. The model is based on the well known band edge electronic energy states in EuTe. A concise expression for the Verdet constant is obtained, determined by few parameters already available in the literature. The Verdet constant adopted here, defined by the ratio between the Faraday rotation angle and the magnetization, is in effect temperature independent. Its dependence on the photon energy and applied magnetic field is in excellent agreement with published results. Below 3 T the Verdet constant is also nearly independent on field, but above 3 T at low temperatures it increases due to the band gap redshift. The model is used to calculate the photoinduced Faraday rotation associated with photoinduced giant magnetic polarons in EuTe. The theoretical photoinduced Faraday rotation excitation describes quite well the main features seen experimentally. Due to the common band-edge electronic energy structure, the model reported here could be extended to all other europium chalcogenides.

  11. Disentangling overlapping high-field EPR spectra of organic radicals: Identification of light-induced polarons in the record fullerene-free solar cell blend PBDB-T:ITIC

    Science.gov (United States)

    Van Landeghem, Melissa; Maes, Wouter; Goovaerts, Etienne; Van Doorslaer, Sabine

    2018-03-01

    We present a combined high-field EPR and DFT study of light-induced radicals in the bulk heterojunction blend of PBDB-T:ITIC, currently one of the highest efficiency non-fullerene donor:acceptor combinations in organic photovoltaics. We demonstrate two different approaches for disentangling the strongly overlapping high-field EPR spectra of the positive and negative polarons after charge separation: (1) relaxation-filtered field-swept EPR based on the difference in T1 spin-relaxation times and (2) field-swept EDNMR-induced EPR by exploiting the presence of 14N hyperfine couplings in only one of the radical species, the small molecule acceptor radical. The approach is validated by light-induced EPR spectra on related blends and the spectral assignment is underpinned by DFT computations. The broader applicability of the spectral disentangling methods is discussed.

  12. Disentangling overlapping high-field EPR spectra of organic radicals: Identification of light-induced polarons in the record fullerene-free solar cell blend PBDB-T:ITIC.

    Science.gov (United States)

    Van Landeghem, Melissa; Maes, Wouter; Goovaerts, Etienne; Van Doorslaer, Sabine

    2018-03-01

    We present a combined high-field EPR and DFT study of light-induced radicals in the bulk heterojunction blend of PBDB-T:ITIC, currently one of the highest efficiency non-fullerene donor:acceptor combinations in organic photovoltaics. We demonstrate two different approaches for disentangling the strongly overlapping high-field EPR spectra of the positive and negative polarons after charge separation: (1) relaxation-filtered field-swept EPR based on the difference in T 1 spin-relaxation times and (2) field-swept EDNMR-induced EPR by exploiting the presence of 14 N hyperfine couplings in only one of the radical species, the small molecule acceptor radical. The approach is validated by light-induced EPR spectra on related blends and the spectral assignment is underpinned by DFT computations. The broader applicability of the spectral disentangling methods is discussed. Copyright © 2018 Elsevier Inc. All rights reserved.

  13. Small scale laboratory studies of flow and transport phenomena in pores and fractures: Phase II. Progress report, 3rd year continuation proposal, and work plan

    Energy Technology Data Exchange (ETDEWEB)

    Wilson, J.L.

    1994-05-01

    Small scale laboratory experiments, equipped with an ability to actually observe behavior on the pore level using microscopy, provide an economical and easily understood scientific tool to help us validate concepts and assumptions about the transport of contaminants, and offers the propensity to discover heretofore unrecognized phenomena or behavior. The main technique employs etched glass micromodels, composed of two etched glass plates, sintered together, to form a two dimensional network of three dimensional pores. Flow and transport behavior is observed on a pore or pore network level, and recorder on film and video tape. This technique is coupled with related column studies. These techniques have been used to study multiphase flow, colloid transport and most recently bacteria transport. The project has recently moved to the Bacteria Transport Subprogram, and efforts have been redirected to support that Subprogram and its collaborative field experiment. We proposed to study bacteria transport factors of relevance to the field experiment, using micromodels and other laboratory techniques. Factors that may be addressed include bacteria characteristics (eg, hydrophobicity), pore size and shape, permeability heterogeneity, surface chemistry (eg, iron oxide coatings), surface chemistry heterogeneity, active versus resting cell bacteria, and mixed bacteria populations. In other work we will continue to examine the effects of fluid-fluid interfaces on bacteria transport, and develop a new assay for bacteria hydrophobicity. Finally we will collaborate on characterization of the field site, and the design, operation, and interpretation of the field experiment.

  14. Theory of super-para-electric large polaron for gigantic photo-enhancements of dielectric constant and electronic conductivity in SrTiO3

    International Nuclear Information System (INIS)

    Yu Qiu; Nasu, Keiichiro

    2005-01-01

    In connection with the recent experimental discoveries on gigantic photoenhancements of the electronic conductivity and the quasi-static dielectric susceptibility in SrTiO 3 , we theoretically study a photo-generation mechanism of a charged ferroelectric domain in this quantum dielectric. The photo-generated electron, being quite itinerant in the 3d band of Ti 4+ , is assumed to couple weakly but quadratically with soft-anharmonic T 1u phonons in this quantum dielectric. The photo-generated electron is also assumed to couple strongly but linearly with the breathing type high energy phonons. Using a tight binding model for electron, we will show that these two types of electron-phonon couplings result in two types of polarons, a 'super-para-electric (SPE) large polaron' with a quasi-global parity violation, and an 'off-centre type self-trapped polaron' with only a local parity violation. We will also show that this SPE large polaron is nothing else but a singly charged (e - ) and conductive ferroelectric (or SPE) domain with a quasi macroscopic size. This polaron or domain is also shown to have a high mobility and a large quasi-static dielectric susceptibility

  15. The small intestinal epithelia of beef steers differentially express sugar transporter messenger ribonucleic acid in response to abomasal versus ruminal infusion of starch hydrolysate.

    Science.gov (United States)

    Liao, S F; Harmon, D L; Vanzant, E S; McLeod, K R; Boling, J A; Matthews, J C

    2010-01-01

    In mammals, the absorption of monosaccharides from small intestinal lumen involves at least 3 sugar transporters (SugT): sodium-dependent glucose transporter 1 (SGLT1; gene SLC5A1) transports glucose and galactose, whereas glucose transporter (GLUT) 5 (GLUT5; gene SLC2A5) transports fructose, across the apical membrane of enterocytes. In contrast, GLUT2 (gene SLC2A2) transports all of these sugars across basolateral and apical membranes. To compare the distribution patterns and sensitivity with nutritional regulation of these 3 SugT mRNA in beef cattle small intestinal tissue, 18 ruminally and abomasally catheterized Angus steers (BW approximately 260 kg) were assigned to water (control), ruminal cornstarch (partially hydrolyzed by alpha-amylase; SH), or abomasal SH infusion treatments (n = 6) and fed an alfalfa-cube-based diet at 1.3 x NE(m) requirement. The SH infusions amounted to 20% of ME intake. After 14- or 16-d of infusion, steers were killed; duodenal, jejunal, and ileal epithelia harvested; and total RNA extracted. The relative amount of SugT mRNA in epithelia was determined using real-time reverse transcription-PCR quantification methods. Basal expression of GLUT2 and SGLT1 mRNA was greater (P content of GLUT5 mRNA was greater (P content of GLUT5 mRNA in small intestinal epithelia was not affected (P > or = 0.16) by either SH infusion treatment. In contrast, GLUT2 and SGLT1 mRNA content in the ileal epithelium was increased (P content also was increased (P = 0.07) by 64% after ruminal SH infusion. These results demonstrate that the ileum of beef cattle small intestine adapts to an increased luminal supply of glucose by increasing SGLT1 and GLUT2 mRNA content, whereas increased ruminal SH supply results in duodenal upregulation of SGLT1 mRNA content. These adaptive responses of GLUT2 and SGLT1 mRNA to abomasal or ruminal SH infusion suggest that beef cattle can adapt to increase their carbohydrate assimilation through small intestinal epithelia, assuming

  16. Tight Binding methods in quantum transport through molecules and small devices: from the coherent to the incoherent description

    Energy Technology Data Exchange (ETDEWEB)

    Pastawaski, Horacio M. [Universidad Nacional de Cordoba, Cordoba (Argentina); Medina, Ernesto [Instituto Venezolano de Investigaciones Cientificas, Caracas (Venezuela)

    2001-03-01

    We discuss the steady-state electronic transport in solid-state and molecular devices in the quantum regime. The decimation technique allows a comprehensive description of the electronic structure. Such a method is used, in conjunction with the generalizations of Landauer's tunneling formalism, to describe a wide range of transport regimes. We analyze mesoscopic and semiclassical metallic transport, the metal-insulator transition, and the resonant tunneling regime. The effects of decoherence on transport is discussed in terms of the D' Amato-Pastawski model. A brief presentation of the time dependent phenomena is also included. [Spanish] Se discuten el transporte, en el estado estacionario, en dispositivos moleculares y de estado solido en el regimen cuantico. La tecnica de decimacion permite una descripcion completa de la estructura electronica. Tal metodo, en conjunto con la generalizacion del formalismo de Landauer, puede ser usado para describir un rango amplio de regimenes de transporte. Se analizan el transporte mesoscopico y semiclasico en el regimen metalico, la transicion metal-aislante, y el regimen de tunel resonante. Los efectos de decoherencia en el transporte son tratados en terminos de modelos de D'amato-Pastawski. Finalmente se incluye una breve presentacion de fenomenos dependientes del tiempo.

  17. Multiyear ice transport and small scale sea ice deformation near the Alaska coast measured by air-deployable Ice Trackers

    Science.gov (United States)

    Mahoney, A. R.; Kasper, J.; Winsor, P.

    2015-12-01

    Highly complex patterns of ice motion and deformation were captured by fifteen satellite-telemetered GPS buoys (known as Ice Trackers) deployed near Barrow, Alaska, in spring 2015. Two pentagonal clusters of buoys were deployed on pack ice by helicopter in the Beaufort Sea between 20 and 80 km offshore. During deployment, ice motion in the study region was effectively zero, but two days later the buoys captured a rapid transport event in which multiyear ice from the Beaufort Sea was flushed into the Chukchi Sea. During this event, westward ice motion began in the Chukchi Sea and propagated eastward. This created new openings in the ice and led to rapid elongation of the clusters as the westernmost buoys accelerated away from their neighbors to the east. The buoys tracked ice velocities of over 1.5 ms-1, with fastest motion occurring closest to the coast indicating strong current shear. Three days later, ice motion reversed and the two clusters became intermingled, rendering divergence calculations based on the area enclosed by clusters invalid. The data show no detectable difference in velocity between first year and multiyear ice floes, but Lagrangian timeseries of SAR imagery centered on each buoy show that first year ice underwent significant small-scale deformation during the event. The five remaining buoys were deployed by local residents on prominent ridges embedded in the landfast ice within 16 km of Barrow in order to track the fate of such features after they detached from the coast. Break-up of the landfast ice took place over a period of several days and, although the buoys each initially followed a similar eastward trajectory around Point Barrow into the Beaufort Sea, they rapidly dispersed over an area more than 50 km across. With rapid environmental and socio-economic change in the Arctic, understanding the complexity of nearshore ice motion is increasingly important for predict future changes in the ice and the tracking ice-related hazards

  18. Electronic and magnetic phase separation in EuB6. Fluctuation spectroscopy and nonlinear transport

    International Nuclear Information System (INIS)

    Amyan, Adham

    2013-01-01

    The main topics of this thesis are electrical, stationary, and time-resolved transport measurements on EuB 6 as well as the further development of measuring methods and analysis procedures of the fluctuation spectroscopy. The first part of this thesis was dedicated to the further development of the already known measuring methods under application of a fast data-acquisition card. The second part deals with the electrical transport properties of EuB 6 and the understanding of the coupling between charge and magnetic degrees of freedom. By means of resistance and nonlinear-transport measurements as well as fluctuation spectroscopy hypotheses of other scientists were systematically verified as well as new knowledge obtained. The magnetoresistance was studied as function of the temperature in small external magnetic fields between 1 mT and 700 mT. Measurements of the third harmonic resistance as function of the temperature show maxima at T MI and T C . Electrical-resistance fluctuations were measured without external magnetic field between 5 and 100 K as well in presence of a magnetic field between 18 K and 32 K. At constant temperature measurements of the spectral power density in external magnetic fields were performed in the temperature range from 18 K to 32 K. Highly resolving measurements of the thermal expansion coefficient showed a very strong coupling of the magnetic (polaronic) degrees of freedom to the crystal lattice.

  19. Charge transport in micas: The kinetics of FeII/III electron transfer in the octahedral sheet

    International Nuclear Information System (INIS)

    Rosso, Kevin M.; Ilton, Eugene S.

    2003-01-01

    The two principal FeII/III electron exchange reactions underlying charge transport in the octahedral sheet of ideal end-member annite were modeled using a combination of ab initio calculations and Marcus electron transfer theory. A small polaron model was applied which yielded electron hopping activation energies that agree well with the limited available experimental data. A small ab initio cluster model successfully reproduced several important structural, energetic, and magnetic characteristics of the M1 and M2 Fe sites in the annite octahedral sheet. The cluster enabled calculation of the internal reorganization energy and electronic coupling matrix elements for the M2-M2 and M1-M2 electron transfer reactions. The M2-M2 electron transfer is symmetric with a predicted forward/reverse electron hopping rate of 106 s-1. The M1-M2 electron transfers are asymmetric due to the higher ionization potential by 0.46 eV of FeII in the M1 site. The electronic coupling matrix elements for these reactions are predicted to be small and of similar magnitude, suggesting the possibility that the coupling is essentially direction independent amongst hopping directions in the octahedral sheet. M1 Fe sites are predicted to be efficient electron traps and charge transport should occur by nearest-neighbor electron hops along the M2 Fe sublattice

  20. Anisotropic transport in the quasi-one-dimensional semiconductor Li{sub 0.33}MoO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Moshfeghyeganeh, S.; Cote, A. N.; Cohn, J. L., E-mail: cohn@physics.miami.edu [Department of Physics, University of Miami, Coral Gables, Florida 33124 (United States); Neumeier, J. J. [Department of Physics, Montana State University, Bozeman, Montana 59717 (United States)

    2016-03-07

    Transport measurements (electrical resistivity, Seebeck coefficient, and thermal conductivity) in the temperature range 80–500 K are presented for single crystals of the quasi-one-dimensional (Q1D) semiconductor Li{sub 0.33}MoO{sub 3}. Opposite signs are observed for the Seebeck coefficient along the trinclinic a and c axes, with S{sub c} − S{sub a} ≃ 250 μV/K near room temperature and ≃100 μV/K at 380 K. The thermal conductivity at room temperature in the a-c planes was ∼2 W/m K and ∼10 times smaller along b*. A weak structural anomaly at T{sub s} ≈ 355 K, identified in the temperature-dependent lattice constants, coincides with anomalies in the electrical properties. Analysis of the electronic transport at T > T{sub s} favors an intrinsic semiconductor picture for transport along the most conducting Q1D axis and small-polaronic transport along the other directions, providing insight into the origin of the Seebeck anisotropy.

  1. Effect of different conductivity between the spin polarons on spin injection in a ferromagnet/organic semiconductor system

    International Nuclear Information System (INIS)

    Mi Yilin; Zhang Ming; Yan Hui

    2008-01-01

    Spin injection across ferromagnet/organic semiconductor system with finite width of the layers was studied theoretically considering spin-dependent conductivity in the organic-semiconductor. It was found that the spin injection efficiency is directly dependent on the difference between the conductivity of the up-spin and down-spin polarons in the spin-injected organic system. Furthermore, the finite width of the structure, interfacial electrochemical-potential and conductivity mismatch have great influence on the spin injection process across ferromagnet/organic semiconductor interface

  2. SCORCH - a zero dimensional plasma evolution and transport code for use in small and large tokamak systems

    International Nuclear Information System (INIS)

    Clancy, B.E.; Cook, J.L.

    1984-12-01

    The zero-dimensional code SCORCH determines number density and temperature evolution in plasmas using concepts derived from the Hinton and Hazeltine transport theory. The code uses the previously reported ADL-1 data library

  3. Mechanisms of calcium transport in small intestine. Overall review of the contract, September 1, 1972--March 1, 1976

    Energy Technology Data Exchange (ETDEWEB)

    DeLuca, H.F.

    1976-01-01

    Progress is reported in the following areas of research: role of high molecular weight protein in calcium transport in vitamin D deficient chicks; subcellular localization of 1,25-(OH)/sub 2/D/sub 3/; receptor proteins for 1,25-(OH)/sub 2/D/sub 3/; effects of high calcium diet, strontium diet, EHDP, and parathyroidectomy on intestinal calcium transport in chicks; effects of analogs of 1,25-(OH)/sub 2/D/sub 3/ on intestinal calcium transport; discrimination by chicks against vitamin D/sub 2/ compounds by metabolism; effects of extract of Solanum malacoxylan on intestinal calcium absorption in nephrectomized rats; and role of vitamin D in phosphate transport reactions in the intestine. (HLW)

  4. Carrier transport in amorphous silicon utilizing picosecond photoconductivity

    Science.gov (United States)

    Johnson, A. M.

    1981-08-01

    The development of a high-speed electronic measurement capability permitted the direct observation of the transient photoresponse of amorphous silicon (a-Si) with a time resolution of approximately 10ps. This technique was used to measure the initial mobility of photogenerated (2.1eV) free carriers in three types of a-Si having widely different densities of structural defects (i.e., as prepared by: (1) RF glow discharge (a-Si:H); (2) chemical vapor deposition; and (3) evaporation in ultra-high vacuum). In all three types of a-Si, the same initial mobility of approximately 1 cu cm/Vs at room temperature was found. This result tends to confirm the often-made suggestion that the free carrier mobility is determined by the influence of shallow states associated with the disorder in the random atomic network, and is an intrinsic property of a-Si which is unaffected by the method of preparation. The rate of decay of the photocurrent correlates with the density of structural defects and varies from 4ps to 200ps for the three types of a-Si investigated. The initial mobility of a-Si:H was found to be thermally activated. The possible application of extended state transport controlled by multiple trapping and small polaron formation is discussed.

  5. The Ship Tethered Aerostat Remote Sensing System (STARRS): Observations of Small-Scale Surface Lateral Transport During the LAgrangian Submesoscale ExpeRiment (LASER)

    Science.gov (United States)

    Carlson, D. F.; Novelli, G.; Guigand, C.; Özgökmen, T.; Fox-Kemper, B.; Molemaker, M. J.

    2016-02-01

    The Consortium for Advanced Research on the Transport of Hydrocarbon in the Environment (CARTHE) will carry out the LAgrangian Submesoscale ExpeRiment (LASER) to study the role of small-scale processes in the transport and dispersion of oil and passive tracers. The Ship-Tethered Aerostat Remote Sensing System (STARRS) will observe small-scale surface dispersion in the open ocean. STARRS is built around a high-lift-capacity (30 kg) helium-filled aerostat. STARRS is equipped with a high resolution digital camera. An integrated GNSS receiver and inertial navigation system permit direct geo-rectification of the imagery. Consortium for Advanced Research on the Transport of Hydrocarbon in the Environment (CARTHE) will carry out the LAgrangian Submesoscale ExpeRiment (LASER) to study the role of small-scale processes in the transport and dispersion of oil and passive tracers. The Ship-Tethered Aerostat Remote Sensing System (STARRS) was developed to produce observational estimates of small-scale surface dispersion in the open ocean. STARRS is built around a high-lift-capacity (30 kg) helium-filled aerostat. STARRS is equipped with a high resolution digital camera. An integrated GNSS receiver and inertial navigation system permit direct geo-rectification of the imagery. Thousands of drift cards deployed in the field of view of STARRS and tracked over time provide the first observational estimates of small-scale (1-500 m) surface dispersion in the open ocean. The STARRS imagery will be combined with GPS-tracked surface drifter trajectories, shipboard observations, and aerial surveys of sea surface temperature in the DeSoto Canyon. In addition to obvious applications to oil spill modelling, the STARRS observations will provide essential benchmarks for high resolution numerical modelsDrift cards deployed in the field of view of STARRS and tracked over time provide the first observational estimates of small-scale (1-100 m) surface dispersion in the open ocean. The STARRS

  6. Synthesis, in vitro and in vivo small-animal SPECT evaluation of novel technetium labeled bile acid analogues to study (altered) hepatic transporter function

    International Nuclear Information System (INIS)

    Neyt, Sara; Vliegen, Maarten; Verreet, Bjorn; De Lombaerde, Stef; Braeckman, Kim; Vanhove, Christian; Huisman, Maarten Thomas; Dumolyn, Caroline; Kersemans, Ken; Hulpia, Fabian; Van Calenbergh, Serge; Mannens, Geert; De Vos, Filip

    2016-01-01

    Introduction: Hepatobiliary transport mechanisms are crucial for the excretion of substrate toxic compounds. Drugs can inhibit these transporters, which can lead to drug–drug interactions causing toxicity. Therefore, it is important to assess this early during the development of new drug candidates. The aim of the current study is the (radio)synthesis, in vitro and in vivo evaluation of a technetium labeled chenodeoxycholic and cholic acid analogue: [ 99m Tc]-DTPA-CDCA and [ 99m ]Tc-DTPA-CA, respectively, as biomarker for disturbed transporter functionality. Methods: [99mTc]-DTPA-CDCA([ 99m Tc]-3a) and [99mTc]-DTPA-CA ([ 99m Tc]-3b) were synthesized and evaluated in vitro and in vivo. Uptake of both tracers was investigated in NTCP, OCT1, OATP1B1, OATP1B3 transfected cell lines. K m and V max values were determined and compared to [ 99m Tc]-mebrofenin ([ 99m Tc]-MEB). Efflux was investigated by means of CTRL, MRP2 and BSEP transfected inside-out vesicles. Metabolite analysis was performed using pooled human liver S9. Wild type (n = 3) and rifampicin treated (n = 3) mice were intravenously injected with 37 MBq of tracer. After dynamic small-animal SPECT and short CT acquisitions, time–activity curves of heart, liver, gallbladder and intestines were obtained. Results: We demonstrated that OATP1B1 and OATP1B3 are the involved uptake transporters of both compounds. Both tracers show a higher affinity compared to [ 99m Tc]-MEB, but are in a similar range as endogenous bile acids for OATP1B1 and OATP1B3. [ 99m Tc]-3a shows higher affinities compared to [ 99m Tc]-3b. V max values were lower compared to [ 99m Tc]-MEB, but in the same range as endogenous bile acids. MRP2 was identified as efflux transporter. Less than 7% of both radiotracers was metabolized in the liver. In vitro results were confirmed by in vivo results. Uptake in the liver and efflux to gallbladder + intestines and urinary bladder of both tracers was observed. Transport was inhibited by rifampicin

  7. Protein Restriction with Amino Acid-Balanced Diets Shrinks Circulating Pool Size of Amino Acid by Decreasing Expression of Specific Transporters in the Small Intestine.

    Directory of Open Access Journals (Sweden)

    Kai Qiu

    Full Text Available Dietary protein restriction is not only beneficial to health and longevity in humans, but also protects against air pollution and minimizes feeding cost in livestock production. However, its impact on amino acid (AA absorption and metabolism is not quite understood. Therefore, the study aimed to explore the effect of protein restriction on nitrogen balance, circulating AA pool size, and AA absorption using a pig model. In Exp.1, 72 gilts weighting 29.9 ± 1.5 kg were allocated to 1 of the 3 diets containing 14, 16, or 18% CP for a 28-d trial. Growth (n = 24, nitrogen balance (n = 6, and the expression of small intestinal AA and peptide transporters (n = 6 were evaluated. In Exp.2, 12 barrows weighting 22.7 ± 1.3 kg were surgically fitted with catheters in the portal and jejunal veins as well as the carotid artery and assigned to a diet containing 14 or 18% CP. A series of blood samples were collected before and after feeding for determining the pool size of circulating AA and AA absorption in the portal vein, respectively. Protein restriction did not sacrifice body weight gain and protein retention, since nitrogen digestibility was increased as dietary protein content reduced. However, the pool size of circulating AA except for lysine and threonine, and most AA flux through the portal vein were reduced in pigs fed the low protein diet. Meanwhile, the expression of peptide transporter 1 (PepT-1 was stimulated, but the expression of the neutral and cationic AA transporter systems was depressed. These results evidenced that protein restriction with essential AA-balanced diets, decreased AA absorption and reduced circulating AA pool size. Increased expression of small intestinal peptide transporter PepT-1 could not compensate for the depressed expression of jejunal AA transporters for AA absorption.

  8. Effect of Förster-mediated triplet-polaron quenching and triplet-triplet annihilation on the efficiency roll-off of organic light-emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Eersel, H. van [Simbeyond B.V., P.O. Box 513, NL-5600 MB Eindhoven (Netherlands); Bobbert, P. A.; Janssen, R. A. J.; Coehoorn, R., E-mail: r.coehoorn@tue.nl [Department of Applied Physics and Institute for Complex Molecular Systems, Eindhoven University of Technology, P.O. Box 513, NL-5600 MB Eindhoven (Netherlands)

    2016-04-28

    We report the results of a systematic study of the interplay of triplet-polaron quenching (TPQ) and triplet-triplet annihilation (TTA) on the efficiency roll-off of organic light-emitting diodes (OLEDs) with increasing current density. First, we focus on OLEDs based on the green phosphorescent emitter tris[2-phenylpyridine]iridium(III) (Ir(ppy){sub 3}) and the red phosphorescent dye platinum octaethylporphyrin. It is found that the experimental data can be reproduced using kinetic Monte Carlo (kMC) simulations within which TPQ and TTA are due to a nearest-neighbor (NN) interaction, or due to a more long-range Förster-type process. Furthermore, we find a subtle interplay between TPQ and TTA: decreasing the contribution of one process can increase the contribution of the other process, so that the roll-off is not significantly reduced. Furthermore, we find that just analyzing the shape of the roll-off is insufficient for determining the relative role of TPQ and TTA. Subsequently, we investigate the wider validity of this picture using kMC simulations for idealized but realistic symmetric OLEDs, with an emissive layer containing a small concentration of phosphorescent dye molecules in a matrix material. Whereas for NN-interactions the roll-off can be reduced when the dye molecules act as shallow hole and electron traps, we find that such an approach becomes counterproductive for long-range TTA and TPQ. Developing well-founded OLED design rules will thus require that more quantitative information is available on the rate and detailed mechanism of the TPQ and TTA processes.

  9. High Levels of Dietary Supplement Vitamins A, C and E are Absorbed in the Small Intestine and Protect Nutrient Transport Against Chronic Gamma Irradiation

    Science.gov (United States)

    Azzam, Edouard I.; Ferraris, Ronaldo P.; Howell, Roger W.

    2015-01-01

    We examined nutrient transport in the intestines of mice exposed to chronic low-LET 137Cs gamma rays. The mice were whole-body irradiated for 3 days at dose rates of 0, 0.13 and 0.20 Gy/h, for total dose delivery of 0, 9.6 or 14.4 Gy, respectively. The mice were fed either a control diet or a diet supplemented with high levels of vitamins A, C and E. Our results showed that nutrient transport was perturbed by the chronic irradiation conditions. However, no apparent alteration of the macroscopic intestinal structures of the small intestine were observed up to day 10 after initiating irradiation. Jejunal fructose uptake measured in vitro was strongly affected by the chronic irradiation, whereas uptake of proline, carnosine and the bile acid taurocholate in the ileum was less affected. D-glucose transport did not appear to be inhibited significantly by either 9.6 or 14.4 Gy exposure. In the 14.4 Gy irradiated groups, the diet supplemented with high levels of vitamins A, C and E increased intestinal transport of fructose compared to the control diet (day 10; t test, P = 0.032), which correlated with elevated levels of vitamins A, C and E in the plasma and jejunal enterocytes. Our earlier studies with mice exposed acutely to 137Cs gamma rays demonstrated significant protection for transport of fructose, glucose, proline and carnosine. Taken together, these results suggest that high levels of vitamins A, C and E dietary supplements help preserve intestinal nutrient transport when intestines are irradiated chronically or acutely with low-LET gamma rays. PMID:26484399

  10. Electronic and magnetic phase separation in EuB{sub 6}. Fluctuation spectroscopy and nonlinear transport; Elektronische und magnetische Phasenseparation in EuB{sub 6}. Fluktuationsspektroskopie und nichtlinearer Transport

    Energy Technology Data Exchange (ETDEWEB)

    Amyan, Adham

    2013-07-09

    The main topics of this thesis are electrical, stationary, and time-resolved transport measurements on EuB{sub 6} as well as the further development of measuring methods and analysis procedures of the fluctuation spectroscopy. The first part of this thesis was dedicated to the further development of the already known measuring methods under application of a fast data-acquisition card. The second part deals with the electrical transport properties of EuB{sub 6} and the understanding of the coupling between charge and magnetic degrees of freedom. By means of resistance and nonlinear-transport measurements as well as fluctuation spectroscopy hypotheses of other scientists were systematically verified as well as new knowledge obtained. The magnetoresistance was studied as function of the temperature in small external magnetic fields between 1 mT and 700 mT. Measurements of the third harmonic resistance as function of the temperature show maxima at T{sub MI} and T{sub C}. Electrical-resistance fluctuations were measured without external magnetic field between 5 and 100 K as well in presence of a magnetic field between 18 K and 32 K. At constant temperature measurements of the spectral power density in external magnetic fields were performed in the temperature range from 18 K to 32 K. Highly resolving measurements of the thermal expansion coefficient showed a very strong coupling of the magnetic (polaronic) degrees of freedom to the crystal lattice.

  11. Electrical transport and giant magnetoresistance in La{sub 0.62}Er{sub 0.05}Ba{sub 0.33}Fe{sub x}Mn{sub 1−x}O{sub 3} (x = 0.00, and 0.15) manganites

    Energy Technology Data Exchange (ETDEWEB)

    Abassi, Mounira, E-mail: manoura881@outlook.fr [Laboratoire de la Matière Condensée et des Nanosciences, Département de Physique, Faculté des Sciences de Monastir, 5019 (Tunisia); Mohamed, Za; Dhahri, J. [Laboratoire de la Matière Condensée et des Nanosciences, Département de Physique, Faculté des Sciences de Monastir, 5019 (Tunisia); Hlil, E.K. [Institut Néel, CNRS et Université Joseph Fourier, BP 166, F-38042 Grenoble cedex 9 (France)

    2015-08-05

    Highlights: • The samples exhibit PM–FM phase transition. • The electrical transport is investigated. • Low temperature minimum resistivity is observed. - Abstract: We have investigated the influence of fer (Fe) doping on the magneto-electrical properties of polycrystalline samples La{sub 0.62}Er{sub 0.05}Ba{sub 0.33}Fe{sub x}Mn{sub 1−x}O{sub 3} (x = 0.00, 0.10 and 0.15), prepared through conventional solid state ceramics route. Comparison of experimental data with the theoretical models shows that in the metal–ferromagnetic region, the electrical behavior of the three samples is quite well described by a theory based on electron–phonon, electron–electron, electron–magnon and Kondo-like spin dependent scattering. For the high temperature paramagnetic insulating regime, the adiabatic small polaron hopping (SPH) model is found to fit well the experimental curves.

  12. Redirected charge transport arising from diazonium grafting of carbon coated LiFePO4.

    Science.gov (United States)

    Madec, L; Seid, K A; Badot, J-C; Humbert, B; Moreau, P; Dubrunfaut, O; Lestriez, B; Guyomard, D; Gaubicher, J

    2014-11-07

    The morphological and the electrical properties of carbon coated LiFePO4 (LFPC) active material functionalized by 4-ethynylbenzene tetrafluoroboratediazonium salt were investigated. For this purpose, FTIR, Raman, XPS, High Resolution Transmission Electron Microscopy (HRTEM) and Broadband Dielectric Spectroscopy (BDS) were considered. Electronic conductivities of LFPC samples at room temperature were found to decrease in a large frequency range upon simple immersion in polar solvents and to decrease further upon functionalization. Due to their high dipole moment, strongly physisorbed molecules detected by XPS likely add barriers to electron hopping. Significant alteration of the carbon coating conductivity was only observed, however, upon functionalization. This effect is most presumably associated with an increase in the sp(3) content determined by Raman spectroscopy, which is a strong indication of the formation of a covalent bond between the organic layer and the carbon coating. In this case, the electron flux appears to be redirected and relayed by short-range (intra chain) and long-range (inter chain) electron transport through molecular oligomers anchored at the LFPC surface. The latter are controlled by tunnelling and slightly activated hopping, which enable higher conductivity at low temperature (T < 250 K). Alteration of the electron transport within the carbon coating also allows detection of a relaxation phenomenon that corresponds to small polaron hopping in bulk LiFePO4. XPS and HRTEM images allow a clear correlation of these findings with the island type oligomeric structure of grafted molecules.

  13. Method for delivery of small molecules and proteins across the cell wall of algae using molecular transporters

    Science.gov (United States)

    Geihe, Erika; Trantow, Brian; Wender, Paul; Hyman, Joel M.; Parvin, Bahram

    2017-11-14

    The introduction of tools to study, control or expand the inner-workings of algae has been slow to develop. Provided are embodiments of a molecular method based on guanidinium-rich molecular transporters (GR-MoTrs) for bringing molecular cargos into algal cells. The methods of the disclosure have been shown to work in wild-type algae that have an intact cell wall. Developed using Chlamydomonas reinhardtii, this method is also successful with less studied algae, including Neochloris oleoabundans and Scenedesmus dimorphus, thus providing a new and versatile tool for algal research and modification. The method of delivering a cargo compound to an algal cell comprises contacting an algal cell with a guanidinium-rich delivery vehicle comprising a guanidinium-rich molecular transporter (GR-MoTr) linked to a cargo compound desired to be delivered to the algal cell, whereby the guanidinium-rich molecular transporter can traverse the algal cell wall, thereby delivering the cargo compound to the algal cell.

  14. Simulation of electron transport in GaAs/AlAs superlattices with a small number of periods for the THz frequency range

    International Nuclear Information System (INIS)

    Pavelyev, D. G.; Vasilev, A. P.; Kozlov, V. A.; Koschurinov, Yu. I.; Obolenskaya, E. S.; Obolensky, S. V.; Ustinov, V. M.

    2016-01-01

    The electron transport in superlattices based on GaAs/AlAs heterostructures with a small number of periods (6 periods) is calculated by the Monte Carlo method. These superlattices are used in terahertz diodes for the frequency stabilization of quantum cascade lasers in the range up to 4.7 THz. The band structure of superlattices with different numbers of AlAs monolayers is considered and their current–voltage characteristics are calculated. The calculated current–voltage characteristics are compared with the experimental data. The possibility of the efficient application of these superlattices in the THz frequency range is established both theoretically and experimentally.

  15. Late stage crystallization and healing during spin-coating enhance carrier transport in small-molecule organic semiconductors

    KAUST Repository

    Chou, Kang Wei; Khan, Hadayat Ullah; Niazi, Muhammad Rizwan; Yan, Buyi; Li, Ruipeng; Payne, Marcia M.; Anthony, John Edward; Smilgies, Detlef Matthias; Amassian, Aram

    2014-01-01

    Spin-coating is currently the most widely used solution processing method in organic electronics. Here, we report, for the first time, a direct investigation of the formation process of the small-molecule organic semiconductor (OSC) 6,13-bis

  16. High Expression of UGT1A1/1A6 in Monkey Small Intestine: Comparison of Protein Expression Levels of Cytochromes P450, UDP-Glucuronosyltransferases, and Transporters in Small Intestine of Cynomolgus Monkey and Human.

    Science.gov (United States)

    Akazawa, Takanori; Uchida, Yasuo; Miyauchi, Eisuke; Tachikawa, Masanori; Ohtsuki, Sumio; Terasaki, Tetsuya

    2018-01-02

    Cynomolgus monkeys have been widely used for the prediction of drug absorption in humans. The purpose of this study was to clarify the regional protein expression levels of cytochromes P450 (CYPs), UDP-glucuronosyltransferases (UGTs), and transporters in small intestine of cynomolgus monkey using liquid chromatography-tandem mass spectrometry, and to compare them with the corresponding levels in human. UGT1A1 in jejunum and ileum were >4.57- and >3.11-fold and UGT1A6 in jejunum and ileum were >16.1- and >8.57-fold, respectively, more highly expressed in monkey than in human. Also, jejunal expression of monkey CYP3A8 (homologue of human CYP3A4) was >3.34-fold higher than that of human CYP3A4. Among apical drug efflux transporters, BCRP showed the most abundant expression in monkey and human, and the expression levels of BCRP in monkey and human were >1.74- and >1.25-fold greater than those of P-gp and >2.76- and >4.50-fold greater than those of MRP2, respectively. These findings should be helpful to understand species differences of the functions of CYPs, UGTs, and transporters between monkey and human. The UGT1A1/1A6 data would be especially important because it is difficult to identify isoforms responsible for species differences of intestinal glucuronidation by means of functional studies due to overlapping substrate specificity.

  17. Structure and transport properties of coherently strained La{sub 2/3}Ca{sub 1/3}MnO{sub 3}/SrTiO{sub 3} superlattices

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Yafeng [Walther-Meissner-Institut, Bayerische Akademie der Wissenschaften, Walther-Meissner Str. 8, 85748 Garching (Germany); Northwest Institute for Nonferrous Metal Research, P.O. Box 51, Xi' an, Shaanxi 710016 (China); Klein, J.; Herbstritt, F.; Philipp, J.B.; Marx, A.; Alff, L.; Gross, R. [Walther-Meissner-Institut, Bayerische Akademie der Wissenschaften, Walther-Meissner Str. 8, 85748 Garching (Germany); Zhang, H. [Engineering Center of Electronic Information Materials and Devices, University of Electronic Science and Technology of China, Chengdu, Sichuan 610054 (China)

    2005-07-01

    We have prepared high quality, coherently strained La{sub 2/3}Ca{sub 1/3}MnO{sub 3}/SrTiO{sub 3} superlattices with different modulation periods by laser molecular beam epitaxy on (001) SrTiO{sub 3} and NdGaO{sub 3} substrates. A detailed structural characterization was performed by high-angle X-ray diffraction (HAXRD) and low-angle X-ray reflectivity (LAXRR). All superlattices are very flat, show excellent structural coherence and very small mosaic spread (0.02 ). The in-plane coherency strain was varied by changing the thickness ratio of the constituent layers allowing for a systematic variation of the resulting tetragonal distortion of LCMO. The c-axis lattice parameter of LCMO could be continuously changed from 3.87 Aa to 3.79 Aa. The interface roughness was analyzed by offset low-angle X-ray reflectivity and low-angle rocking curve measurements. It was found to be of the order of one unit cell with a significant part of the roughness being vertically correlated. The strain induced tetragonal distortion of LCMO was found to cause strong reduction of the paramagnetic to ferromagnetic transition temperature from about 260 to 120 K and an increase of resistivity. The transport properties in the paramagnetic regime could be well described by a small polaron hopping model. The lattice distortions were found to result in a significant increase of the polaron trapping energy. Our results show that coherently strain superlattices are an interesting model system for the systematic study of the effect of lattice distortions on the magnetic and electronic properties of the doped manganites. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  18. Interrelation of transport properties, defect structure and spin state of Ni3+ in La1.2Sr0.8Ni0.9Fe0.1O4+δ

    Science.gov (United States)

    Gilev, A. R.; Kiselev, E. A.; Zakharov, D. M.; Cherepanov, V. A.

    2017-10-01

    The total conductivity, Seebeck coefficient and oxygen non-stoichiometry for La1.2Sr0.8Ni0.9Fe0.1O4+δ have been measured vs temperature and oxygen partial pressure P(O2). The measurements were carried out at 800, 850, 900 and 950 °C within the P(O2) range of 10-5-0.21 atm. La1.2Sr0.8Ni0.9Fe0.1O4+δ was shown to be oxygen deficient in all temperature and P(O2) ranges studied. The calculated values of the partial molar enthalpy of oxygen depend very slightly on oxygen content (δ), indicating that La1.2Sr0.8Ni0.9Fe0.1O4+δ with the oxygen deficiency can be considered an ideal solution. The model of point defect equilibria in La1.2Sr0.8Ni0.9Fe0.1O4+δ has been proposed and fitted to experimental dependencies. Subsequent joint analysis of the defect structure and transport properties revealed that electron holes can coexist in both localized and quasi-delocalized states in the oxide: the former corresponded to high-spin state Ni3+ and the latter - to low-spin state Ni3+. The mobilities of localized electron holes were shown to be significantly lower in comparison to quasi-delocalized ones. The behavior of localized electron holes was explained in terms of a small polaron conduction mechanism; in contrast, quasi-delocalized electron holes were described in terms of a band conduction approach. The small polaron conduction mechanism was shown to be predominant in the Sr- and Fe-co-doped lanthanum nickelate.

  19. Mechanisms of calcium transport in small intestine. Overall review of the contract, September 1, 1972--March 1, 1975

    International Nuclear Information System (INIS)

    DeLuca, H.F.

    1975-01-01

    During the past three years considerable advance has been registered in our understanding of the mechanism of intestinal calcium transport, which is activated in response to 1,25-(OH) 2 D 3 , the active form of the vitamin in the system. In brush borders isolated from vitamin D-deficient chicks, a 200,000 molecular weight protein has been found by disc gel electrophoresis which is not present in chicks given vitamin D. This protein does not bind calcium and does not possess calcium dependent adenosine triphosphatase activity. Following the administration of 1,25-(OH) 2 D 3 to the deficient chicks this protein disappears from the disc gel profiles and a protein of molecular weight 220,000 appears in the gel profiles. This protein has been isolated and shown to possess calcium adenosine triphosphatase activity, alkaline phosphatase activity and it binds calcium. Work is progressing on the purification of these proteins with the ultimate aim of discerning what role they have in intestinal calcium transport. (U.S.)

  20. A disordered polaron model for polarized fluorescence excitation spectra of LH1 and LH2 bacteriochlorophyll antenna aggregates

    International Nuclear Information System (INIS)

    Trinkunas, Gediminas; Freiberg, Arvi

    2006-01-01

    Excitonic polarons in antenna complexes are subject to static lattice disorder. A model has been developed to analyze polarized fluorescence excitation spectra of circular light-harvesting complexes from purple photosynthetic bacteria containing bacteriochlorophyll as the main photoactive pigment that includes both diagonal (energetic) and off-diagonal (structural) disorders. Essential differences of disorder realizations seem to exist between the core LH1 and peripheral LH2 complexes from the bacterium Rhodobacter sphaeroides. The disorder in LH1 appears to be dominated by the structural disorder, while that in LH2, by energetic one. These differences may be due to relatively bigger size of the LH1 complex and, consequently, with its enhanced structural flexibility

  1. Electromagnetic-field dependence of the internal excited state of the polaron and the qubit in quantum dot with thickness

    Science.gov (United States)

    Bai, Xu-Fang; Xin, Wei; Yin, Hong-Wu; Eerdunchaolu

    2017-06-01

    The electromagnetic-field dependence of the ground and the first excited-state (GFES) energy eigenvalues and eigenfunctions of the strong-coupling polaron in a quantum dot (QD) was studied for various QD thicknesses by using the variational method of the Pekar type (VMPT). On this basis, we construct a qubit in the quantum dot (QQD) by taking a two-level structure of the polaron as the carrier. The results of numerical calculations indicate that the oscillation period of the qubit, {itT}{in0}, increases with increasing the thickness of the quantum dot (TQD) {itL}, but decreases with increasing the cyclotron frequency of the magnetic field (CFMF) ω{in{itc}}, electric-field strength {itF}, and electron-phonon coupling strength (EPCS) α. The probability density of the qubit |Ψ({itρ}, {itz}, {itt})|{su2} presents a normal distribution of the electronic transverse coordinate ρ, significantly influenced by the TQD and effective radius of the quantum dot (ERQD) {itR}{in0}, and shows a periodic oscillation with variations in the electronic longitudinal coordinate {itz}, polar angle φ and time {itt}. The decoherence time τ and the quality factor {itQ} of the free rotation increase with increasing the CFMF ω{in{itc}}, dispersion coefficient η, and EPCS α, but decrease with increasing the electric-field strength {itF}, TQD {itL}, and ERQD {itR}{in0}. The TQD is an important parameter of the qubit. Theoretically, the target, which is to regulate the oscillation period, decoherence time and quality factor of the free rotation of the qubit, can be achieved by designing different TQDs and regulating the strength of the electromagnetic field.

  2. The Impact of Molecular p-Doping on Charge Transport in High-Mobility Small-Molecule/Polymer Blend Organic Transistors

    KAUST Repository

    Paterson, Alexandra F.

    2017-12-27

    Molecular doping is a powerful tool with the potential to resolve many of the issues currently preventing organic thin-film transistor (OTFT) commercialization. However, the addition of dopant molecules into organic semiconductors often disrupts the host lattice, introducing defects and harming electrical transport. New dopant-based systems that overcome practical utilization issues, while still reaping the electrical performance benefits, would therefore be extremely valuable. Here, the impact of p-doping on the charge transport in blends consisting of the small-molecule 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT), the polymer indacenodithiophene-benzothiadiazole (C16IDT-BT), and the molecular dopant C60F48 is investigated. Electrical field-effect measurements indicate that p-doping not only enhances the average saturation mobility from 1.4 to 7.8 cm2 V−1 s−1 over 50 devices (maximum values from around 4 to 13 cm2 V−1 s−1), but also improves bias–stress stability, contact resistance, threshold voltage, and the overall device-to-device performance variation. Importantly, materials characterization using X-ray diffraction, X-ray photoemission spectroscopy, and ultraviolet photoemission spectroscopy, combined with charge transport modeling, reveal that effective doping is achieved without perturbing the microstructure of the polycrystalline semiconductor film. This work highlights the remarkable potential of ternary organic blends as a simple platform for OTFTs to achieve all the benefits of doping, with none of the drawbacks.

  3. The Impact of Molecular p-Doping on Charge Transport in High-Mobility Small-Molecule/Polymer Blend Organic Transistors

    KAUST Repository

    Paterson, Alexandra F.; Lin, Yen-Hung; Mottram, Alexander D.; Fei, Zhuping; Niazi, Muhammad Rizwan; Kirmani, Ahmad R.; Amassian, Aram; Solomeshch, Olga; Tessler, Nir; Heeney, Martin; Anthopoulos, Thomas D.

    2017-01-01

    Molecular doping is a powerful tool with the potential to resolve many of the issues currently preventing organic thin-film transistor (OTFT) commercialization. However, the addition of dopant molecules into organic semiconductors often disrupts the host lattice, introducing defects and harming electrical transport. New dopant-based systems that overcome practical utilization issues, while still reaping the electrical performance benefits, would therefore be extremely valuable. Here, the impact of p-doping on the charge transport in blends consisting of the small-molecule 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT), the polymer indacenodithiophene-benzothiadiazole (C16IDT-BT), and the molecular dopant C60F48 is investigated. Electrical field-effect measurements indicate that p-doping not only enhances the average saturation mobility from 1.4 to 7.8 cm2 V−1 s−1 over 50 devices (maximum values from around 4 to 13 cm2 V−1 s−1), but also improves bias–stress stability, contact resistance, threshold voltage, and the overall device-to-device performance variation. Importantly, materials characterization using X-ray diffraction, X-ray photoemission spectroscopy, and ultraviolet photoemission spectroscopy, combined with charge transport modeling, reveal that effective doping is achieved without perturbing the microstructure of the polycrystalline semiconductor film. This work highlights the remarkable potential of ternary organic blends as a simple platform for OTFTs to achieve all the benefits of doping, with none of the drawbacks.

  4. Recent advances in small molecular, non-polymeric organic hole transporting materials for solid-state DSSC

    Directory of Open Access Journals (Sweden)

    Bui Thanh-Tuan

    2013-10-01

    Full Text Available Issue from thin-film technologies, dye-sensitized solar cells have become one of the most promising technologies in the field of renewable energies. Their success is not only due to their low weight, the possibility of making large flexible surfaces, but also to their photovoltaic efficiency which are found to be more and more significant (>12% with a liquid electrolyte, >7% with a solid organic hole conductor. This short review highlights recent advances in the characteristics and use of low-molecular-weight glass-forming organic materials as hole transporters in all solid-state dye-sensitized solar cells. These materials must feature specific physical and chemical properties that will ensure both the operation of a photovoltaic cell and the easy implementation. This review is an english extended version based on our recent article published in Matériaux & Techniques 101, 102 (2013.

  5. Dealing with water deficit in Atta ant colonies: large ants scout for water while small ants transport it

    Directory of Open Access Journals (Sweden)

    Antonio Carlos Da-Silva

    2012-07-01

    Leafcutter ants (Atta sexdens rubropilosa (Forel 1908 have an elaborate social organization, complete with caste divisions. Activities carried out by specialist groups contribute to the overall success and survival of the colony when it is confronted with environmental challenges such as dehydration. Ants detect variations in humidity inside the nest and react by activating several types of behavior that enhance water uptake and decrease water loss, but it is not clear whether or not a single caste collects water regardless of the cost of bringing this resource back to the colony. Accordingly, we investigated water collection activities in three colonies of Atta sexdens rubropilosa experimentally exposed to water stress. Specifically, we analyzed whether or not the same ant caste foraged for water, regardless of the absolute energetic cost (distance of transporting this resource back to the colony. Our experimental design offered water sources at 0 m, 1 m and 10 m from the nest. We studied the body size of ants near the water sources from the initial offer of water (time  =  0 to 120 min, and tested for specialization. We observed a reduction in the average size and variance of ants that corroborated the specialization hypothesis. Although the temporal course of specialization changed with distance, the final outcome was similar among distances. Thus, we conclude that, for this species, a specialist (our use of the word “specialist” does not mean exclusive task force is responsible for collecting water, regardless of the cost of transporting water back to the colony.

  6. Transcriptional Responses of Escherichia coli to a Small-Molecule Inhibitor of LolCDE, an Essential Component of the Lipoprotein Transport Pathway

    Science.gov (United States)

    Lorenz, Christian; Dougherty, Thomas J.

    2016-01-01

    ABSTRACT In Gram-negative bacteria, a dedicated machinery consisting of LolABCDE components targets lipoproteins to the outer membrane. We used a previously identified small-molecule inhibitor of the LolCDE complex of Escherichia coli to assess the global transcriptional consequences of interference with lipoprotein transport. Exposure of E. coli to the LolCDE inhibitor at concentrations leading to minimal and significant growth inhibition, followed by transcriptome sequencing, identified a small group of genes whose transcript levels were decreased and a larger group whose mRNA levels increased 10- to 100-fold compared to those of untreated cells. The majority of the genes whose mRNA concentrations were reduced were part of the flagellar assembly pathway, which contains an essential lipoprotein component. Most of the genes whose transcript levels were elevated encode proteins involved in selected cell stress pathways. Many of these genes are involved with envelope stress responses induced by the mislocalization of outer membrane lipoproteins. Although several of the genes whose RNAs were induced have previously been shown to be associated with the general perturbation of the cell envelope by antibiotics, a small subset was affected only by LolCDE inhibition. Findings from this work suggest that the efficiency of the Lol system function may be coupled to a specific monitoring system, which could be exploited in the development of reporter constructs suitable for use for screening for additional inhibitors of lipoprotein trafficking. IMPORTANCE Inhibition of the lipoprotein transport pathway leads to E. coli death and subsequent lysis. Early significant changes in the levels of RNA for a subset of genes identified to be associated with some periplasmic and envelope stress responses were observed. Together these findings suggest that disruption of this key pathway can have a severe impact on balanced outer membrane synthesis sufficient to affect viability. PMID

  7. Transcriptional Responses of Escherichia coli to a Small-Molecule Inhibitor of LolCDE, an Essential Component of the Lipoprotein Transport Pathway.

    Science.gov (United States)

    Lorenz, Christian; Dougherty, Thomas J; Lory, Stephen

    2016-12-01

    In Gram-negative bacteria, a dedicated machinery consisting of LolABCDE components targets lipoproteins to the outer membrane. We used a previously identified small-molecule inhibitor of the LolCDE complex of Escherichia coli to assess the global transcriptional consequences of interference with lipoprotein transport. Exposure of E. coli to the LolCDE inhibitor at concentrations leading to minimal and significant growth inhibition, followed by transcriptome sequencing, identified a small group of genes whose transcript levels were decreased and a larger group whose mRNA levels increased 10- to 100-fold compared to those of untreated cells. The majority of the genes whose mRNA concentrations were reduced were part of the flagellar assembly pathway, which contains an essential lipoprotein component. Most of the genes whose transcript levels were elevated encode proteins involved in selected cell stress pathways. Many of these genes are involved with envelope stress responses induced by the mislocalization of outer membrane lipoproteins. Although several of the genes whose RNAs were induced have previously been shown to be associated with the general perturbation of the cell envelope by antibiotics, a small subset was affected only by LolCDE inhibition. Findings from this work suggest that the efficiency of the Lol system function may be coupled to a specific monitoring system, which could be exploited in the development of reporter constructs suitable for use for screening for additional inhibitors of lipoprotein trafficking. Inhibition of the lipoprotein transport pathway leads to E. coli death and subsequent lysis. Early significant changes in the levels of RNA for a subset of genes identified to be associated with some periplasmic and envelope stress responses were observed. Together these findings suggest that disruption of this key pathway can have a severe impact on balanced outer membrane synthesis sufficient to affect viability. Copyright © 2016 Lorenz et al.

  8. [Relationships among health-promoting activities, going out and perceived transportation problems of elderly people living in a small town far from the nearest train station].

    Science.gov (United States)

    Yoshimoto, T; Kawata, C

    1999-03-01

    To estimate the change in health-promoting activities among elderly people affected by community organizing environments, we examined the relationships among health-promoting activity, going out and perceived transportation problems. A questionnaire was sent to 567 men and women aged 60 years old and over living in a small town in Kanagawa prefecture between July 27 and August 12 in 1995. The questionnaire consisted of 42 items concerning health, social ability of daily living (including the desire to participate in social activities), attitude toward health-promoting activities, and perceived transportation problems. A total of 397 people responded and the answers from 368 people were analyzed after excluding responses from those unable to go out by themselves and those who seldom went out. Single regression analysis and multiregression analysis were used with the sum of responses for each question representing factors related to health-promoting behavior. A probability level of 5 percent was considered significant. The reliability of the data was examined with Cronbach's coefficient alpha. Coefficients of determination for health promoting behavior were 42% in men and 48% in women. In both men and women, age, social ability of daily living and attitudes toward health-promoting behavior were related to health-promoting activity. In women, more actively going out was related to more active health-promoting activity. Higher perception of transportation problems had a negative effect on going out. In men, neither of these factors had any relationship with health-promoting activity. In men, poorer health conditions were related to more active health-promoting activity, but in women, there was no relationship between those factors. These results show that there are gender differences in the relationships among the factors related to health-promoting activities in elderly people. In women, a higher perception of transportation problems restrained actively going out and

  9. Charge and energy transports via poly-phenylacetylene based dendrimers

    Science.gov (United States)

    Shin, Yongwoo; Li, Minghai; Lin, Xi

    2010-03-01

    Poly-Phenylacetylene (PPA) is widely used in photoconductivity, photoluminescence, and light harvesting applications. In this work, we investigate the charge and exciton transport energetics and mechanisms in the PPA-based dendrimers using our recently developed adapted Su-Schrieffer-Heeger (SSH) model Hamiltonians and ab initio Hartree-Fock (HF) calculations. We found both doping and photo-excitation lead to the formation of optical phonon dressed pi electron states, namely the self-localized polarons, in the energy gap. Independent from their origins, these polarons can be self-trapped at multiple lattice locations along the PPA chain, and migrate from one to the next with an activation barrier of ˜0.006 eV, slightly higher than the corresponding barrier found in trans-polyacetylene. The PPA-based dendrimers can be constructed via the meta-positions of phenyl rings. In this case, we found the dendrimer junctions form attractive potential wells for both polarons and excitons, and the width and height of these junction potential wells can be controlled by the geometry of the dendrimers.

  10. Development and demonstration of prototype transportation equipment for emplacing HL vitrified waste canisters into small diameter bored horizontal disposal cells

    International Nuclear Information System (INIS)

    Seidler, Wolf K.; Bosgiraud, Jean-Michel; Londe, Louis

    2008-01-01

    Over a period of 4 and years the National Radioactive Waste Management Agency (Andra), working with a variety of Contractors mostly specializing in nuclear orientated mechanical applications, successfully designed, fabricated and demonstrated 2 very different prototype high level waste transport systems. The first system, based on air cushion technology, was developed primarily for very heavy loads (17 to 45 tonnes). The results of this work are described in a separate presentation (Paper 21) at this Conference. The second system, developed by Andra within the framework of the ESDRED Project, generally referred to as the 'Pushing Robot System' for vitrified waste canisters, is the subject of this paper. The 'Pushing Robot System' is a part of the French national disposal concept that is described in Andra's 'Dossier 2005'. The latter is a public document that can be viewed on Andra's web site (www.andra.fr). The 'Pushing Robot System' system is designed for the deep geological disposal (in clay formations) of 'C' type vitrified waste canisters. In its entirety the system provides for the transport, emplacement and, if necessary, the retrieval of those canisters. Nothing in the design of the Andra emplacement equipment would preclude its utilization in horizontal openings in other types of geological settings. Over a period of some 8 years Andra has developed the 'Pushing Robot System' in 3 phases. Initially there was only the 'Conceptual Design' (Phase 1) which was incorporated in the Dossier 2005. This was followed by Phase 2 i.e. the design and fabrication of a simplified full scale prototype system henceforth referred to a P1, which includes a Pushing Robot, a Dummy Canister and a Test Bench. P1 details were also incorporated in the Dossier 2005. Finally, during Phase 3, a second more comprehensive full scale prototype system P2 has been designed and is being assembled and tested this month. This system includes a Transport Shuttle, a Transfer Shielding Cask, a

  11. Techno-economic prospects of small-scale membrane reactors in a future hydrogen-fuelled transportation sector

    International Nuclear Information System (INIS)

    Sjardin, M.; Damen, K.J.; Faaij, A.P.C.

    2006-01-01

    The membrane reactor is a novel technology for the production of hydrogen from natural gas. It promises economic small-scale hydrogen production, e.g. at refuelling stations and has the potential of inexpensive CO 2 separation. Four configurations of the membrane reactor have been modelled with Aspen plus to determine its thermodynamic and economic prospects. Overall energy efficiency is 84% HHV without H 2 compression (78% with compression up to 482bar). The modelling results also indicate that by using a sweep gas, the membrane reactor can produce a reformer exit stream consisting mainly of CO 2 and H 2 O (>90% mol ) suited for CO 2 sequestration after water removal with an efficiency loss of only 1% pt . Reforming with a 2MW membrane reactor (250 unit production volume) costs 14$/GJ H 2 including compression, which is more expensive than conventional steam reforming+compression (12$/GJ). It does, however, promise a cheap method of CO 2 separation, 14$/t CO 2 captured, due to the high purity of the exit stream. The well-to-wheel chain of the membrane reactor has been compared to centralised steam reforming to assess the trade-off between production scale and the construction of a hydrogen and a CO 2 distribution infrastructure. If the scale of centralised hydrogen production is below 40MW, the trade-off could be favourable for the membrane reactor with small-scale CO 2 capture (18$/GJ including H 2 storage, dispensing and CO 2 sequestration for 40MW SMR versus 19$/GJ for MR). The membrane reactor might become competitive with conventional steam reforming provided that thin membranes can be combined with high stability and a cheap manufacturing method for the membrane tubes. Thin membranes, industrial utility prices and larger production volumes (i.e. technological learning) might reduce the levelised hydrogen cost of the membrane reactor at the refuelling station to less than 14$/GJ including CO 2 sequestration cost, below that of large-scale H 2 production with

  12. Minimum Transendothelial Electrical Resistance Thresholds for the Study of Small and Large Molecule Drug Transport in a Human in Vitro Blood-Brain Barrier Model.

    Science.gov (United States)

    Mantle, Jennifer L; Min, Lie; Lee, Kelvin H

    2016-12-05

    A human cell-based in vitro model that can accurately predict drug penetration into the brain as well as metrics to assess these in vitro models are valuable for the development of new therapeutics. Here, human induced pluripotent stem cells (hPSCs) are differentiated into a polarized monolayer that express blood-brain barrier (BBB)-specific proteins and have transendothelial electrical resistance (TEER) values greater than 2500 Ω·cm 2 . By assessing the permeabilities of several known drugs, a benchmarking system to evaluate brain permeability of drugs was established. Furthermore, relationships between TEER and permeability to both small and large molecules were established, demonstrating that different minimum TEER thresholds must be achieved to study the brain transport of these two classes of drugs. This work demonstrates that this hPSC-derived BBB model exhibits an in vivo-like phenotype, and the benchmarks established here are useful for assessing functionality of other in vitro BBB models.

  13. Power maximization method for land-transportable fully passive lead–bismuth cooled small modular reactor systems

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Jaehyun, E-mail: chojh@kaeri.re.kr [Korea Atomic Energy Research Institute, 1405 Daedeok-daero, Yuseong-gu, Daejeon 305-353 (Korea, Republic of); Shin, Yong-Hoon; Hwang, Il Soon [Seoul National University, Sillim-dong, Gwanak-gu, Seoul 151-742 (Korea, Republic of)

    2015-08-15

    Highlights: • The power maximization method for LBE natural circulation cooled SMRs was developed. • The two powers in view of neutronics and thermal-hydraulics were considered. • The limitations for designing of LBE natural circulation cooled SMRs were summarized. • The necessary conditions for safety shutdown in accidents were developed. • The maximized power in the case study is 206 MW thermal. - Abstract: Although current pressurized water reactors (PWRs) have significantly contributed to global energy supply, PWR technology has not been considered a trustworthy energy solution owing to its problems of spent nuclear fuels (SNFs), nuclear safety, and nuclear economy. In order to overcome these problems, a lead–bismuth eutectic (LBE) fully passive cooling small modular reactor (SMR) system is suggested. This technology can not only provide the solution for the problems of SNFs through the transmutation feature of the LBE coolant, but also strengthen safety and economy through the concept of natural circulation cooling SMRs. It is necessary to maximize the advantages, namely safety and economy, of this type of nuclear power plants for broader applications in the future. Accordingly, the objective of this study is to maximize the reactor core power while satisfying the limitations of shipping size, materials endurance, and criticality of a long-burning core as well as safety under beyond design basis events. To achieve these objectives, the design limitations of natural circulating LBE-cooling SMRs are derived. Then, the power maximization method is developed based on obtaining the design limitations. The results of this study are expected to contribute to the effectiveness of the reactor design stage by providing insights to designers, as well as by formulating methods for the power maximization of other types of SMRs.

  14. Small-scale sediment transport patterns and bedform morphodynamics: New insights from high-resolution multibeam bathymetry

    Science.gov (United States)

    Barnard, P.L.; Erikson, L.H.; Kvitek, R.G.

    2011-01-01

    New multibeam echosounder and processing technologies yield sub-meter-scale bathymetric resolution, revealing striking details of bedform morphology that are shaped by complex boundary-layer flow dynamics at a range of spatial and temporal scales. An inertially aided post processed kinematic (IAPPK) technique generates a smoothed best estimate trajectory (SBET) solution to tie the vessel motion-related effects of each sounding directly to the ellipsoid, significantly reducing artifacts commonly found in multibeam data, increasing point density, and sharpening seafloor features. The new technique was applied to a large bedform field in 20-30 m water depths in central San Francisco Bay, California (USA), revealing bedforms that suggest boundary-layer flow deflection by the crests where 12-m-wavelength, 0.2-m-amplitude bedforms are superimposed on 60-m-wavelength, 1-m-amplitude bedforms, with crests that often were strongly oblique (approaching 90??) to the larger features on the lee side, and near-parallel on the stoss side. During one survey in April 2008, superimposed bedform crests were continuous between the crests of the larger features, indicating that flow detachment in the lee of the larger bedforms is not always a dominant process. Assessment of bedform crest peakedness, asymmetry, and small-scale bedform evolution between surveys indicates the impact of different flow regimes on the entire bedform field. This paper presents unique fine-scale imagery of compound and superimposed bedforms, which is used to (1) assess the physical forcing and evolution of a bedform field in San Francisco Bay, and (2) in conjunction with numerical modeling, gain a better fundamental understanding of boundary-layer flow dynamics that result in the observed superimposed bedform orientation. ?? 2011 Springer-Verlag (outside the USA).

  15. Late stage crystallization and healing during spin-coating enhance carrier transport in small-molecule organic semiconductors

    KAUST Repository

    Chou, Kang Wei

    2014-01-01

    Spin-coating is currently the most widely used solution processing method in organic electronics. Here, we report, for the first time, a direct investigation of the formation process of the small-molecule organic semiconductor (OSC) 6,13-bis(triisopropylsilylethynyl) (TIPS)-pentacene during spin-coating in the context of an organic thin film transistor (OTFT) application. The solution thinning and thin film formation were monitored in situ by optical reflectometry and grazing incidence wide angle X-ray scattering, respectively, both of which were performed during spin-coating. We find that OSC thin film formation is akin to a quenching process, marked by a deposition rate of ∼100 nm s-1, nearly three orders of magnitude faster than drop-casting. This is then followed by a more gradual crystallization and healing step which depends upon the spinning speed. We associate this to further crystallization and healing of defects by residency of the residual solvent trapped inside the kinetically trapped film. The residency time of the trapped solvent is extended to several seconds by slowing the rotational speed of the substrate and is credited with improving the carrier mobility by nearly two orders of magnitude. Based on this insight, we deliberately slow down the solvent evaporation further and increase the carrier mobility by an additional order of magnitude. These results demonstrate how spin-coating conditions can be used as a handle over the crystallinity of organic semiconductors otherwise quenched during initial formation only to recrystallize and heal during extended interaction with the trapped solvent. This journal is © the Partner Organisations 2014.

  16. Revealing the Value of “Green” and the Small Group with a Big Heart in Transportation Mode Choice

    Directory of Open Access Journals (Sweden)

    David Gaker

    2013-07-01

    Full Text Available To address issues of climate change, people are more and more being presented with the greenhouse gas emissions associated with their alternatives. Statements of pounds or kilograms of CO2 are showing up in trip planners, car advertisements, and even restaurant menus under the assumption that this information influences behavior. This research contributes to the literature that investigates how travelers respond to such information. Our objective is to better understand the “value of green” or how much travelers are willing to pay in money in order to reduce the CO2 associated with their travel. As with previous work, we designed and conducted a mode choice experiment using methods that have long been used to study value of time. The contributions of this paper are twofold. First, we employ revealed preference data, whereas previous studies have been based on stated preferences. Second, we provide new insight on how the value of green is distributed in the population. Whereas previous work has specified heterogeneity either systematically or with a continuous distribution, we find that a latent class choice model specification better fits the data and also is attractive behaviorally. The best fitting latent class model has two classes: one large class (76% of the sample who are not willing to spend any time or money to reduce their CO2 and a second class (24% of the sample who value reducing their CO2 at a very high rate of $2.68 per pound of reduction—our so-called small group with a big heart. We reanalyzed three datasets that we had previously collected and found considerable robustness of this two class result.

  17. The coupling of runoff and dissolved organic matter transport: Insights from in situ fluorescence measurements in small streams and large rivers

    Science.gov (United States)

    Pellerin, B. A.; Bergamaschi, B. A.; Downing, B. D.; Saraceno, J.; Shanley, J. B.; Aiken, G.; Murdoch, P. S.

    2011-12-01

    Understanding dissolved organic matter (DOM) dynamics in streams and rivers can help characterize mercury transport, assess causes of drinking water issues, and lead to improved understanding of watershed source areas and carbon loads to downstream ecosystems. However, traditional sampling approaches that collect discrete concentration data at weekly to monthly intervals often fail to adequately capture hydrological pulses ranging from early snowmelt periods to short-duration rainfall events. Continuous measurements of chromophoric dissolved organic matter fluorescence (FDOM) in rivers and streams now provide an opportunity to more accurately quantify DOM loads and processes in aquatic ecosystems at a range of scales. In this study, we used continuous FDOM data from in situ sensors along with discharge data to assess the coupling of FDOM transport and runoff in small streams and large rivers. Results from headwater catchments in New England and California show that FDOM is tightly coupled with runoff, supporting strong linkages between watershed flow paths and DOM concentrations in streams. Results also show that the magnitude of FDOM response relative to runoff varies seasonally, with highest concentrations during autumn rainfall events (after leaf fall) and lower concentrations during peak snowmelt for equivalent runoff. In large river basins, FDOM dynamics are also coupled with runoff and exhibit the same seasonal variability in the magnitude of FDOM response relative to discharge. However, the peaks in FDOM typically lag runoff by several days, reflecting the influence of a variety of factors such as water residence times, reservoir releases, and connectivity to organic matter-rich riparian floodplains and wetlands. Our results show that in situ FDOM data will be important for understanding the coupling of runoff and DOM across multiple scales and could serve a critical role in monitoring, assessment and decision-making in both small and large watersheds.

  18. Research into 2D Dynamics and Control of Small Oscillations of a Cross-Beam during Transportation by Two Overhead Cranes

    Directory of Open Access Journals (Sweden)

    Alexander V. Perig

    2017-01-01

    Full Text Available A new mathematical model of a 3DOF 2D mechanical system “transported cross-beam, two moving bridge cranes” has been proposed. Small system oscillations have been derived through the introduction of Lagrange equations. The numerical estimation of 3DOF system motion has been carried out with equation-based Modelica language. The present article uses the Lagrange method and numerical and optimization methods, realized with JModelica.org and Optimica freeware. The absolute swaying of the cross-beam with respect to the displacement of the two moving bridge cranes was estimated. The phase portraits of the 3DOF system for linear and angular coordinates were presented. An open loop optimal control problem was posed for the motion of the bridge cranes. A “bang-bang” control strategy was implemented for the derivation of an optimal control solution, which enables the travel of two bridge cranes at a prescribed distance for minimum time and minimum swaying of a heavy cross-beam. The derived results of the numerical simulation can be easily practically realized by crane operators with good agreement with simple engineering estimations. The proposed control strategy enables synchronous motion of two bridge cranes with a cross-beam that practically solves the posed problem of unwanted excessive oscillations of a heavy cross-beam during transportation.

  19. Evaluating Molecular Properties Involved in Transport of Small Molecules in Stratum Corneum: A Quantitative Structure-Activity Relationship for Skin Permeability

    Directory of Open Access Journals (Sweden)

    Chen-Peng Chen

    2018-04-01

    Full Text Available The skin permeability (Kp defines the rate of a chemical penetrating across the stratum corneum. This value is widely used to quantitatively describe the transport of molecules in the outermost layer of epidermal skin and indicate the significance of skin absorption. This study defined a Kp quantitative structure-activity relationship (QSAR based on 106 chemical substances of Kp measured using human skin and interpreted the molecular interactions underlying transport behavior of small molecules in the stratum corneum. The Kp QSAR developed in this study identified four molecular descriptors that described the molecular cyclicity in the molecule reflecting local geometrical environments, topological distances between pairs of oxygen and chlorine atoms, lipophilicity, and similarity to antineoplastics in molecular properties. This Kp QSAR considered the octanol-water partition coefficient to be a direct influence on transdermal movement of molecules. Moreover, the Kp QSAR identified a sub-domain of molecular properties initially defined to describe the antineoplastic resemblance of a compound as a significant factor in affecting transdermal permeation of solutes. This finding suggests that the influence of molecular size on the chemical’s skin-permeating capability should be interpreted with other relevant physicochemical properties rather than being represented by molecular weight alone.

  20. Evaluating Molecular Properties Involved in Transport of Small Molecules in Stratum Corneum: A Quantitative Structure-Activity Relationship for Skin Permeability.

    Science.gov (United States)

    Chen, Chen-Peng; Chen, Chan-Cheng; Huang, Chia-Wen; Chang, Yen-Ching

    2018-04-15

    The skin permeability ( Kp ) defines the rate of a chemical penetrating across the stratum corneum. This value is widely used to quantitatively describe the transport of molecules in the outermost layer of epidermal skin and indicate the significance of skin absorption. This study defined a Kp quantitative structure-activity relationship (QSAR) based on 106 chemical substances of Kp measured using human skin and interpreted the molecular interactions underlying transport behavior of small molecules in the stratum corneum. The Kp QSAR developed in this study identified four molecular descriptors that described the molecular cyclicity in the molecule reflecting local geometrical environments, topological distances between pairs of oxygen and chlorine atoms, lipophilicity, and similarity to antineoplastics in molecular properties. This Kp QSAR considered the octanol-water partition coefficient to be a direct influence on transdermal movement of molecules. Moreover, the Kp QSAR identified a sub-domain of molecular properties initially defined to describe the antineoplastic resemblance of a compound as a significant factor in affecting transdermal permeation of solutes. This finding suggests that the influence of molecular size on the chemical's skin-permeating capability should be interpreted with other relevant physicochemical properties rather than being represented by molecular weight alone.

  1. Enhancement of charge transport properties of small molecule semiconductors by controlling fluorine substitution and effects on photovoltaic properties of organic solar cells and perovskite solar cells.

    Science.gov (United States)

    Yun, Jae Hoon; Park, Sungmin; Heo, Jin Hyuck; Lee, Hyo-Sang; Yoon, Seongwon; Kang, Jinback; Im, Sang Hyuk; Kim, Hyunjung; Lee, Wonmok; Kim, BongSoo; Ko, Min Jae; Chung, Dae Sung; Son, Hae Jung

    2016-11-01

    We prepared a series of small molecules based on 7,7'-(4,4-bis(2-ethylhexyl)-4 H -silolo[3,2- b :4,5- b ']dithiophene-2,6-diyl)bis(4-(5'-hexyl-[2,2'-bithiophene]-5-yl)benzo[ c ][1,2,5]thiadiazole) with different fluorine substitution patterns ( 0F-4F ). Depending on symmetricity and numbers of fluorine atoms incorporated in the benzo[ c ][1,2,5]thiadiazole unit, they show very different optical and morphological properties in a film. 2F and 4F , which featured symmetric and even-numbered fluorine substitution patterns, display improved molecular packing structures and higher crystalline properties in a film compared with 1F and 3F and thus, 2F achieved the highest OTFT mobility, which is followed by 4F . In the bulk heterojunction solar cell fabricated with PC 71 BM, 2F achieves the highest photovoltaic performance with an 8.14% efficiency and 0F shows the lowest efficiency of 1.28%. Moreover, the planar-type perovskite solar cell (PSC) prepared with 2F as a dopant-free hole transport material shows a high power conversion efficiency of 14.5% due to its high charge transporting properties, which were significantly improved compared with the corresponding PSC device obtained from 0F (8.5%). From the studies, it is demonstrated that low variation in the local dipole moment and the narrow distribution of 2F conformers make intermolecular interactions favorable, which may effectively drive crystal formations in the solid state and thus, higher charge transport properties compared with 1F and 3F .

  2. Advances in the Synthesis of Small Molecules as Hole Transport Materials for Lead Halide Perovskite Solar Cells.

    Science.gov (United States)

    Rodríguez-Seco, Cristina; Cabau, Lydia; Vidal-Ferran, Anton; Palomares, Emilio

    2018-04-17

    Over hundreds of new organic semiconductor molecules have been synthesized as hole transport materials (HTMs) for perovskite solar cells. However, to date, the well-known N 2 , N 2 , N 2' , N 2' , N 7 , N 7 , N 7' , octakis-(4-methoxyphenyl)-9,9-spirobi-[9,9'-spirobi[9 H-fluorene]-2,2',7,7'-tetramine (spiro-OMeTAD) is still the best choice for the best perovskite device performance. Nevertheless, there is a consensus that spiro-OMeTAD by itself is not stable enough for long-term stable devices, and its market price makes its use in large-scale production costly. Novel synthetic routes for new HTMs have to be sought that can be carried out in fewer synthetic steps and can be easily scaled up for commercial purposes. On the one hand, synthetic chemists have taken, as a first approach, the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of the spiro-OMeTAD molecule as a reference to synthesize molecules with similar energy levels, although these HOMO and LUMO energy levels often have been measured indirectly in solution using cyclic voltammetry. On the other hand, the "spiro" chemical core has also been studied as a structural motif for novel HTMs. However, only a few molecules incorporated as HTMs in complete functional perovskite solar cells have been capable of matching the performance of the best-performing perovskite solar cells made using spiro-OMeTAD. In this Account, we describe the advances in the synthesis of HTMs that have been tested in perovskite solar cells. The comparison of solar cell efficiencies is of course very challenging because the solar cell preparation conditions may differ from laboratory to laboratory. To extract valuable information about the HTM molecular structure-device function relationship, we describe those examples that always have used spiro-OMeTAD as a control device and have always used identical experimental conditions (e.g., the use of the same chemical dopant for the HTM or

  3. Bipolar polaron pair recombination in P3HT/PCBM solar cells

    DEFF Research Database (Denmark)

    Kupijai, Alexander J.; Behringer, Konstantin M.; Corazza, Michael

    2015-01-01

    . However, in organic devices the nature of the dominant spin-dependent processes is still subject to considerable debate. Using multi-frequency pulsed electrically detected magnetic resonance (pEDMR), we show that the spin-dependent response of P3HT/PCBM solar cells at low temperatures is governed...... of the electron spin on charge transport which can be exploited in spintronic devices or to improve solar cell eciencies. Magnetic resonance techniques are particularly helpful to elucidate the microscopic structure of paramagnetic states in semiconductors as well as the transport processes they are involved in...

  4. f-f Magnetic polaron Wigner glass and anomalous superconductivity in U sub 1 sub - sub x Th sub x Be sub 1 sub 3

    CERN Document Server

    Kasuya, T

    2000-01-01

    Mechanisms of the anomalous properties in the heavy fermion superconductor UBe sub 1 sub 3 and its alloys, in particular for the Th dopings, are studied in detail based on the fundamental electronic states to be consistent with all the crucial experimental results. As the reference systems for the magnetic polaron formation, Ce monopnictides, as well as USb and UTe, are mentioned. From detailed systematic studies of the dilute alloy systems, it is postulated that the 5f states in UBe sub 1 sub 3 split into the well-localized core 5f GAMMA sup 2 sub 7 singlet state and other delocalized 5f states situated around the Fermi energy forming the f-f magnetic polarons through the strong intra-atomic ferromagnetic f-f exchange interaction. The accompanied lattice polarons are also shown to play important roles. In the p-d band states, the f-f exchange interaction and the intersite p-f mixing interactions for the p-f Kondo state are of nearly equal strengths causing a rich variety of delicately balanced states. For th...

  5. Quantitation of dopamine transporter blockade by methylphenidate: first in vivo investigation using [123I]FP-CIT and a dedicated small animal SPECT

    International Nuclear Information System (INIS)

    Nikolaus, Susanne; Wirrwar, Andreas; Antke, Christina; Arkian, Shahram; Mueller, Hans-Wilhelm; Larisch, Rolf; Schramm, Nils

    2005-01-01

    The aim of this study was to investigate the feasibility of assessing dopamine transporter binding after treatment with methylphenidate in the rat using a recently developed high-resolution small animal single-photon emission computed tomograph (TierSPECT) and [ 123 I]FP-CIT. [ 123 I]FP-CIT was administered intravenously 1 h after intraperitoneal injection of methylphenidate (10 mg/kg) or vehicle. Animals underwent scanning 2 h after radioligand administration. The striatum was identified by superimposition of [ 123 I]FP-CIT scans with bone metabolism and perfusion scans obtained with 99m Tc-DPD and 99m Tc-tetrofosmin, respectively. As these tracers do not pass the blood-brain barrier, their distribution permits the identification of extracerebral anatomical landmarks such as the orbitae and the harderian glands. The cerebellum was identified by superimposing [ 123 I]FP-CIT scans with images of brain perfusion obtained with 99m Tc-HMPAO. Methylphenidate-treated animals and vehicle-treated animals yielded striatal equilibrium ratios (V '' 3 ) of 0.24±0.26 (mean ± SD) and 1.09±0.42, respectively (ttest, two-tailed, p '' 3 values amounted to 0.05±0.28 (methylphenidate) and 0.3±0.39 (saline, p=0.176). This first in vivo study of rat dopamine transporter binding after pre-treatment with methylphenidate showed a mean reduction of 78% in striatal [ 123 I]FP-CIT accumulation. The results can be interpreted in terms of a pharmacological blockade in the rat striatum and show that in vivo quantitation of dopamine transporter binding is feasible with [ 123 I]FP-CIT and the TierSPECT. This may be of future relevance for in vivo investigations on rat models of attention deficit/hyperactivity disorder. Furthermore, our findings suggest that investigations in other animal models, e.g. of Parkinson's and Huntington's disease, may be feasible using SPECT radioligands and small animal imaging systems. (orig.)

  6. Quantitation of dopamine transporter blockade by methylphenidate: first in vivo investigation using [{sup 123}I]FP-CIT and a dedicated small animal SPECT

    Energy Technology Data Exchange (ETDEWEB)

    Nikolaus, Susanne; Wirrwar, Andreas; Antke, Christina; Arkian, Shahram; Mueller, Hans-Wilhelm; Larisch, Rolf [Heinrich-Heine University, Clinic of Nuclear Medicine, Duesseldorf (Germany); Schramm, Nils [Research Center Juelich, Central Laboratory for Electronics, Juelich (Germany)

    2005-03-01

    The aim of this study was to investigate the feasibility of assessing dopamine transporter binding after treatment with methylphenidate in the rat using a recently developed high-resolution small animal single-photon emission computed tomograph (TierSPECT) and [{sup 123}I]FP-CIT. [{sup 123}I]FP-CIT was administered intravenously 1 h after intraperitoneal injection of methylphenidate (10 mg/kg) or vehicle. Animals underwent scanning 2 h after radioligand administration. The striatum was identified by superimposition of [{sup 123}I]FP-CIT scans with bone metabolism and perfusion scans obtained with {sup 99m}Tc-DPD and {sup 99m}Tc-tetrofosmin, respectively. As these tracers do not pass the blood-brain barrier, their distribution permits the identification of extracerebral anatomical landmarks such as the orbitae and the harderian glands. The cerebellum was identified by superimposing [{sup 123}I]FP-CIT scans with images of brain perfusion obtained with {sup 99m}Tc-HMPAO. Methylphenidate-treated animals and vehicle-treated animals yielded striatal equilibrium ratios (V''{sub 3}) of 0.24{+-}0.26 (mean {+-} SD) and 1.09{+-}0.42, respectively (ttest, two-tailed, p<0.0001). Cortical V''{sub 3} values amounted to 0.05{+-}0.28 (methylphenidate) and 0.3{+-}0.39 (saline, p=0.176). This first in vivo study of rat dopamine transporter binding after pre-treatment with methylphenidate showed a mean reduction of 78% in striatal [{sup 123}I]FP-CIT accumulation. The results can be interpreted in terms of a pharmacological blockade in the rat striatum and show that in vivo quantitation of dopamine transporter binding is feasible with [{sup 123}I]FP-CIT and the TierSPECT. This may be of future relevance for in vivo investigations on rat models of attention deficit/hyperactivity disorder. Furthermore, our findings suggest that investigations in other animal models, e.g. of Parkinson's and Huntington's disease, may be feasible using SPECT radioligands and

  7. Geomorphic change and sediment transport during a small artificial flood in a transformed post-dam delta: The Colorado River delta, United States and Mexico

    Science.gov (United States)

    Mueller, Erich R.; Schmidt, John C.; Topping, David J.; Shafroth, Patrick B.; Rodríguez-Burgueño, Jesús Eliana; Ramírez-Hernández, Jorge; Grams, Paul E.

    2017-01-01

    The Colorado River delta is a dramatically transformed landscape. Major changes to river hydrology and morpho-dynamics began following completion of Hoover Dam in 1936. Today, the Colorado River has an intermittent and/or ephemeral channel in much of its former delta. Initial incision of the river channel in the upstream ∼50 km of the delta occurred in the early 1940s in response to spillway releases from Hoover Dam under conditions of drastically reduced sediment supply. A period of relative quiescence followed, until the filling of upstream reservoirs precipitated a resurgence of flows to the delta in the 1980s and 1990s. Flow releases during extreme upper basin snowmelt in the 1980s, flood flows from the Gila River basin in 1993, and a series of ever-decreasing peak flows in the late 1990s and early 2000s further incised the upstream channel and caused considerable channel migration throughout the river corridor. These variable magnitude post-dam floods shaped the modern river geomorphology. In 2014, an experimental pulse-flow release aimed at rejuvenating the riparian ecosystem and understanding hydrologic dynamics flowed more than 100 km through the length of the delta’s river corridor. This small artificial flood caused localized meter-scale scour and fill of the streambed, but did not cause further incision or significant bank erosion because of its small magnitude. Suspended-sand-transport rates were initially relatively high immediately downstream from the Morelos Dam release point, but decreasing discharge from infiltration losses combined with channel widening downstream caused a rapid downstream reduction in suspended-sand-transport rates. A zone of enhanced transport occurred downstream from the southern U.S.-Mexico border where gradient increased, but effectively no geomorphic change occurred beyond a point 65 km downstream from Morelos Dam. Thus, while the pulse flow connected with the modern estuary, deltaic sedimentary processes were not

  8. Differential cross section study of fragment production, at small angle, in relativistic heavy ion collisions. Application at a calculation of heavy ion beam transport in the matter

    International Nuclear Information System (INIS)

    Morel, P.

    1992-02-01

    Relativistic heavy ion collisions present the opportunity of creating in laboratory small volumes of hot, dense nuclear matter. On the experimental point of view, the collision events are characterized by a great number of fragments, especially in the direction of the projectile. The first part is devoted to a survey of relativistic heavy ion physics. Then, we present two experimental set-ups which permit, in particular, the analyse of light fragment production at small angles. We present experimental results concerning light projectiles on Ca, Nb, Pb targets, with energies from 200 A.MeV up to 600 A.MeV. Different aspects of the collision are put in evidence. Momentum and charge differential cross section are extrapolated to other projectile/target systems; that is used in a transport calculation of Ne ions in a target of biological interest (water), with a collimator. We show that nuclear fragmentation produces a dispersion in the spatial and energy distributions, and that one light fragments have a range greater than the projectile range. That last point causes a distortion of the Bragg curve, and that distortion must be taken into account for the application of heavy ions to radiotherapy problems. 95 figs., 8 tabs

  9. Intrinsic Charge Transport in Organic Field-Effect Transistors

    Science.gov (United States)

    Podzorov, Vitaly

    2005-03-01

    Organic field-effect transistors (OFETs) are essential components of modern electronics. Despite the rapid progress of organic electronics, understanding of fundamental aspects of the charge transport in organic devices is still lacking. Recently, the OFETs based on highly ordered organic crystals have been fabricated with innovative techniques that preserve the high quality of single-crystal organic surfaces. This technological progress facilitated the study of transport mechanisms in organic semiconductors [1-4]. It has been demonstrated that the intrinsic polaronic transport, not dominated by disorder, with a remarkably high mobility of ``holes'' μ = 20 cm^2/Vs can be achieved in these devices at room temperature [4]. The signatures of the intrinsic polaronic transport are the anisotropy of the carrier mobility and an increase of μ with cooling. These and other aspects of the charge transport in organic single-crystal FETs will be discussed. Co-authors are Etienne Menard, University of Illinois at Urbana Champaign; Valery Kiryukhin, Rutgers University; John Rogers, University of Illinois at Urbana Champaign; Michael Gershenson, Rutgers University. [1] V. Podzorov et al., Appl. Phys. Lett. 82, 1739 (2003); ibid. 83, 3504 (2003). [2] V. C. Sundar et al., Science 303, 1644 (2004). [3] R. W. I. de Boer et al., Phys. Stat. Sol. (a) 201, 1302 (2004). [4] V. Podzorov et al., Phys. Rev. Lett. 93, 086602 (2004).

  10. Ba doped Fe3O4 nanocrystals: Magnetic field and temperature tuning dielectric and electrical transport

    Science.gov (United States)

    Dutta, Papia; Mandal, S. K.; Nath, A.

    2018-05-01

    Nanocrystalline BaFe2O4 has been prepared through low temperature pyrophoric reaction method. The structural, dielectric and electrical transport properties of BaFe2O4 are investigated in detail. AC electrical properties have been studied over the wide range of frequencies with applied dc magnetic fields and temperatures. The value of impedance is found to increase with increase in magnetic field attributing the magnetostriction property of the sample. The observed value of magneto-impedance and magnetodielectric is found to ∼32% and ∼33% at room temperature. Nyquist plots have been fitted using resistance-capacitor circuits at different magnetic fields and temperatures showing the dominant role of grain and grain boundaries of the sample. Metal-semiconductor transition ∼403 K has been discussed in terms of delocalized and localized charge carrier.We have estimated activation energy using Arrhenius relation indicating temperature dependent electrical relaxation process in the system. Ac conductivity follow a Jonscher’s single power law indicating the large and small polaronic hopping conduction mechanism in the system.

  11. Effect of sulfur addition on the transport properties of semiconducting iron phosphate glasses

    Energy Technology Data Exchange (ETDEWEB)

    El-Desoky, M.M. [Physics Department, Faculty of Science, Suez Canal University, Suez (Egypt); Ibrahim, F.A. [Department of Physics, Faculty of Education, Suez Canal University, Al-Arish (Egypt); Hassaan, M.Y. [Department of Physics, Faculty of Science, Al-Azhar University, Nasr City, 11884 Cairo (Egypt)

    2011-08-15

    The present paper focuses on a quantitative analysis of the metallic and semiconducting behavior of electrical resistivity in La{sub 0.91}Rb{sub 0.06}Mn{sub 0.94}O{sub 3} manganites. The contribution of inherent low-frequency acoustic phonons as well as high-frequency optical phonons, to the electron-phonon resistivity is estimated following Bloch-Gruneisen model. The computed phonon resistivity is compared with that of reported metallic resistivity, accordingly {rho}diff. [{rho}exp. - {l_brace}{rho}0 + {rho}e-ph (={rho}ac + {rho}op){r_brace}] have been analysed through electron-electron scattering. Also, the difference can be varies linearly with T{sup 4.5} in accordance with the electron-magnon scattering in the double exchange process. The results reveal important aspects transport mechanism as well as point out that it is not only dominated by electron-phonon scattering, but also by electron-electron and electron-magnon scattering process. Alternatively, in high temperature regime (T {>=} T{sub P}) the semiconducting nature is discussed with Mott's variable range hopping (VRH) and small polaron conduction (SPC) model. (authors)

  12. Effect of sulfur addition on the transport properties of semiconducting iron phosphate glasses

    International Nuclear Information System (INIS)

    El-Desoky, M.M.; Ibrahim, F.A.; Hassaan, M.Y.

    2011-01-01

    The present paper focuses on a quantitative analysis of the metallic and semiconducting behavior of electrical resistivity in La 0.91 Rb 0.06 Mn 0.94 O 3 manganites. The contribution of inherent low-frequency acoustic phonons as well as high-frequency optical phonons, to the electron-phonon resistivity is estimated following Bloch-Gruneisen model. The computed phonon resistivity is compared with that of reported metallic resistivity, accordingly ρdiff. [ρexp. - {ρ0 + ρe-ph (=ρac + ρop)}] have been analysed through electron-electron scattering. Also, the difference can be varies linearly with T 4.5 in accordance with the electron-magnon scattering in the double exchange process. The results reveal important aspects transport mechanism as well as point out that it is not only dominated by electron-phonon scattering, but also by electron-electron and electron-magnon scattering process. Alternatively, in high temperature regime (T ≥ T P ) the semiconducting nature is discussed with Mott's variable range hopping (VRH) and small polaron conduction (SPC) model. (authors)

  13. Segmental dependent transport of low permeability compounds along the small intestine due to P-glycoprotein: the role of efflux transport in the oral absorption of BCS class III drugs.

    Science.gov (United States)

    Dahan, Arik; Amidon, Gordon L

    2009-01-01

    The purpose of this study was to investigate the role of P-gp efflux in the in vivo intestinal absorption process of BCS class III P-gp substrates, i.e. high-solubility low-permeability drugs. The in vivo permeability of two H (2)-antagonists, cimetidine and famotidine, was determined by the single-pass intestinal perfusion model in different regions of the rat small intestine, in the presence or absence of the P-gp inhibitor verapamil. The apical to basolateral (AP-BL) and the BL-AP transport of the compounds in the presence or absence of various efflux transporters inhibitors (verapamil, erythromycin, quinidine, MK-571 and fumitremorgin C) was investigated across Caco-2 cell monolayers. P-gp expression levels in the different intestinal segments were confirmed by immunoblotting. Cimetidine and famotidine exhibited segmental dependent permeability through the gut wall, with decreased P(eff) in the distal ileum in comparison to the proximal regions of the intestine. Coperfusion of verapamil with the drugs significantly increased the permeability in the ileum, while no significant change in the jejunal permeability was observed. Both drugs exhibited significantly greater BL-AP than AP-BL Caco-2 permeability, indicative of net mucosal secretion. Concentration dependent decrease of this secretion was obtained by the P-gp inhibitors verapamil, erythromycin and quinidine, while no effect was evident by the MRP2 inhibitor MK-571 and the BCRP inhibitor FTC, indicating that P-gp is the transporter mediates the intestinal efflux of cimetidine and famotidine. P-gp levels throughout the intestine were inversely related to the in vivo permeability of the drugs from the different segments. The data demonstrate that for these high-solubility low-permeability P-gp substrates, P-gp limits in vivo intestinal absorption in the distal segments of the small intestine; however P-gp plays a minimal role in the proximal intestinal segments due to significant lower P-gp expression levels

  14. Electronic transport properties of hot-pressed B/sub 6/Si

    International Nuclear Information System (INIS)

    Wood, C.; Emin, D.; Feigelson, R.S.; Mackinnon, I.D.R.

    1987-01-01

    Measurements of the electrical conductivity, Seebeck coefficient and Hall mobility from --300 K to --1300 K have been carried out on multiphase hotpressed samples of the nominal composition B/sub 6/Si. In all samples the conductivity and the p-type Seebeck coefficient both increase smoothly with increasing temperature. By themselves, these facts suggest small-polaronic hopping between inequivalent sites. The measured Hall mobilities are always low, but vary in sign. A possible explanation is offered for this anomalous behavior

  15. Transport of radiolabelled glycoprotein to cell surface and lysosome-like bodies of absorptive cells in cultured small-intestinal tissue from normal subjects and patients with a lysosomal storage disease

    International Nuclear Information System (INIS)

    Ginsel, L.A.; Onderwater, J.J.M.; Daems, W.T.

    1979-01-01

    The transport of 3 H-fucose and 3 H-glucosamine-labelled glycoproteins in the absorptive cells of cultured human small-intestinal tissue was investigated with light- and electron-microscopical autoradiography. The findings showed that these glycoproteins were completed in the Golgi apparatus and transported in small vesicular structures to the apical cytoplasm of these cells. Since this material arrived in the cell coat on the microvilli and in the lysosome-like bodies simultaneously, a crinophagic function of these organelles in the regulation of the transport or secretion of cell-coat material was supported. In the absorptive cells of patients with fucosidosis or Hunter's type of lysosomal storage disease, a similar transport of cell-coat material to the lysosome-like bodies and a congenital defect of a lysosomal hydrolase normally involved in the degradation of cell-coat material, can explain the accumulation of this material in the dense bodies. (orig.) [de

  16. VTrans Small Culvert Inventory - Culverts

    Data.gov (United States)

    Vermont Center for Geographic Information — Vermont Agency of Transportation Small Culvert Inventory: Culverts. This data contains small culverts locations along VTrans maintained roadways. The data was...

  17. Feature of polaronic charge carriers in polysilanes: Experimental and theoretical approach

    Czech Academy of Sciences Publication Activity Database

    Nešpůrek, Stanislav; Kochalska, Anna; Nožár, Juraj; Kadashchuk, A.; Fishchuk, I. I.; Sworakowski, J.; Kajzar, F.

    2010-01-01

    Roč. 521, - (2010), s. 72-83 ISSN 1542-1406. [International Conference on Frontiers of Polymers and Advanced Materials /10./. Santiago, 27.09.2009-02.10.2009] R&D Projects: GA AV ČR IAA100100622; GA AV ČR KAN400720701 Institutional research plan: CEZ:AV0Z40500505 Keywords : binding energy * charge mobility * hopping transport Subject RIV: CD - Macromolecular Chemistry Impact factor: 0.543, year: 2010

  18. Tokamak electron heat transport by direct numerical simulation of small scale turbulence; Transport de chaleur electronique dans un tokamak par simulation numerique directe d'une turbulence de petite echelle

    Energy Technology Data Exchange (ETDEWEB)

    Labit, B

    2002-10-01

    In a fusion machine, understanding plasma turbulence, which causes a degradation of the measured energy confinement time, would constitute a major progress in this field. In tokamaks, the measured ion and electron thermal conductivities are of comparable magnitude. The possible sources of turbulence are the temperature and density gradients occurring in a fusion plasma. Whereas the heat losses in the ion channel are reasonably well understood, the origin of the electron losses is more uncertain. In addition to the radial velocity associated to the fluctuations of the electric field, electrons are more affected than ions by the magnetic field fluctuations. In experiments, the confinement time can be conveniently expressed in terms of dimensionless parameters. Although still somewhat too imprecise, these scaling laws exhibit strong dependencies on the normalized pressure {beta} or the normalized Larmor radius, {rho}{sub *}. The present thesis assesses whether a tridimensional, electromagnetic, nonlinear fluid model of plasma turbulence driven by a specific instability can reproduce the dependence of the experimental electron heat losses on the dimensionless parameters {beta} and {rho}{sub *}. The investigated interchange instability is the Electron Temperature Gradient driven one (ETG). The model is built by using the set of Braginskii equations. The developed simulation code is global in the sense that a fixed heat flux is imposed at the inner boundary, leaving the gradients free to evolve. From the nonlinear simulations, we have put in light three characteristics for the ETG turbulence: the turbulent transport is essentially electrostatic; the potential and pressure fluctuations form radially elongated cells called streamers; the transport level is very low compared to the experimental values. The thermal transport dependence study has shown a very small role of the normalized pressure, which is in contradiction with the Ohkama's formula. On the other hand

  19. Exploring Polaronic, Excitonic Structures and Luminescence in Cs4PbBr6/CsPbBr3.

    Science.gov (United States)

    Kang, Byungkyun; Biswas, Koushik

    2018-02-15

    Among the important family of halide perovskites, one particular case of all-inorganic, 0-D Cs 4 PbBr 6 and 3-D CsPbBr 3 -based nanostructures and thin films is witnessing intense activity due to ultrafast luminescence with high quantum yield. To understand their emissive behavior, we use hybrid density functional calculations to first compare the ground-state electronic structure of the two prospective compounds. The dispersive band edges of CsPbBr 3 do not support self-trapped carriers, which agrees with reports of weak exciton binding energy and high photocurrent. The larger gap 0-D material Cs 4 PbBr 6 , however, reveals polaronic and excitonic features. We show that those lattice-coupled carriers are likely responsible for observed ultraviolet emission around ∼375 nm, reported in bulk Cs 4 PbBr 6 and Cs 4 PbBr 6 /CsPbBr 3 composites. Ionization potential calculations and estimates of type-I band alignment support the notion of quantum confinement leading to fast, green emission from CsPbBr 3 nanostructures embedded in Cs 4 PbBr 6 .

  20. Eclipse Phase of Herpes Simplex Virus Type 1 Infection: Efficient Dynein-Mediated Capsid Transport without the Small Capsid Protein VP26

    Science.gov (United States)

    Döhner, Katinka; Radtke, Kerstin; Schmidt, Simone; Sodeik, Beate

    2006-01-01

    Cytoplasmic dynein,together with its cofactor dynactin, transports incoming herpes simplex virus type 1 (HSV-1) capsids along microtubules (MT) to the MT-organizing center (MTOC). From the MTOC, capsids move further to the nuclear pore, where the viral genome is released into the nucleoplasm. The small capsid protein VP26 can interact with the dynein light chains Tctex1 (DYNLT1) and rp3 (DYNLT3) and may recruit dynein to the capsid. Therefore, we analyzed nuclear targeting of incoming HSV1-ΔVP26 capsids devoid of VP26 and of HSV1-GFPVP26 capsids expressing a GFPVP26 fusion instead of VP26. To compare the cell entry of different strains, we characterized the inocula with respect to infectivity, viral genome content, protein composition, and particle composition. Preparations with a low particle-to-PFU ratio showed efficient nuclear targeting and were considered to be of higher quality than those containing many defective particles, which were unable to induce plaque formation. When cells were infected with HSV-1 wild type, HSV1-ΔVP26, or HSV1-GFPVP26, viral capsids were transported along MT to the nucleus. Moreover, when dynein function was inhibited by overexpression of the dynactin subunit dynamitin, fewer capsids of HSV-1 wild type, HSV1-ΔVP26, and HSV1-GFPVP26 arrived at the nucleus. Thus, even in the absence of the potential viral dynein receptor VP26, HSV-1 used MT and dynein for efficient nuclear targeting. These data suggest that besides VP26, HSV-1 encodes other receptors for dynein or dynactin. PMID:16873277

  1. Effect of egg weight on composition, embryonic growth, and expression of amino acid transporter genes in yolk sac membranes and small intestines of the domestic pigeon (Columba livia).

    Science.gov (United States)

    Chen, M X; Li, X G; Yan, H C; Wang, X Q; Gao, C Q

    2016-06-01

    The objective of this study was to investigate the effect of egg weight on the composition of the egg, the growth of the embryo, and the expression of amino acid transporter genes in the yolk sac membranes and small intestines of the domestic pigeon (Columba livia). A total of 240 fertilized eggs were collected and divided into two groups based on the weight of the eggs, light (LE) and heavy (HE). The composition of 20 eggs from each group was measured, and the remaining eggs were weighed and placed in an incubator. On embryonic days (E) 9, 11, 13, and 15 and day of hatch (DOH), 15 embryos/hatchlings from each group were measured for embryonic growth, and samples were collected. The HE had heavier yolk and albumen weights than the LE (P < 0.01). Compared with the LE, the HE had heavier yolk-free embryonic body and yolk sac weights from E13 to DOH (P < 0.05). Additionally, the HE had larger yolk sac membrane weights from E13 to E15 (P < 0.05) and had more residual yolk sac content on DOH than those of the LE (P < 0.01). The yolk absorption was greater for the HE than for the LE from E11 to E13 (P < 0.05). Furthermore, the abundance of CAT2 and PepT1 mRNA in the yolk sac membranes was greater in the HE than in the LE on E13 (P < 0.05). Compared with the LE, the gene expression of EAAT2 in the intestine on E13 was greater in the HE, whereas the expression of EAAT3 was lower in the HE (P < 0.05). Taken together, our results suggest that egg weight influenced the composition of the eggs, embryonic development, and expression of amino acid transporter genes in the yolk sac membranes and small intestines of pigeon embryos. © 2016 Poultry Science Association Inc.

  2. Magnetic, Electrical Transport and Impedance Spectroscopy Studies on Ti Substituted La0.67Sr0.33MnO3 Ceramics

    International Nuclear Information System (INIS)

    Zalita, Z.; Halim, S.A.; Lim, K.P.; Talib, Z.A.; Hishamuddin, Z.; Walter, C.P.

    2009-01-01

    La 0.67 Sr 0.33 Mn 1-x Ti x O 3 samples with x = 0.0, 0.2, 0.4 and 0.6 have been prepared using the conventional solid-state reaction method. The structure, magnetic and electrical transport properties as well as the impedance spectroscopy of the samples were investigated. The powder XRD analysis showed that all samples were single phase with rhombohedral perovskite structure. The magnetization curve suggests that the Ti substituted samples exhibit weak ferromagnetic behaviour. The highest magnetoresistance (MR) value was obtained for sample x = 0.2 at temperature 200 K and field 1 T, which was 32.5 %. Low field magnetoresistance (LFMR) effect was observed for the x = 0.0 sample. The metal-like resistivity curve for the x = 0.0 sample was best fitted with ρ = ρo + ρ2T2 equation, indicating the grain boundary effects and electron-electron scattering process contribution. Semiconductor-like transport behaviour was observed for the Ti substituted samples and can be fitted by variable range hopping (VRH) and small polaron hopping (SPH) mechanisms. The activation energy of the samples increased when the Ti composition increased. An equivalent circuit was proposed for the impedance plot with a series of two parallel RC circuits. The grain, grain boundary and electrode resistance values increased with Ti composition due to the reduction of the Mn 3+ / Mn 4+ ratio. (author)

  3. Solitons and polarons in quasi-one dimensional conducting polymers and related materials

    International Nuclear Information System (INIS)

    Campbell, D.K.

    1983-01-01

    In recent years it has become increasingly appreciated that fundamentally nonlinear excitations - solitons - play an essential role in an incredible variety of natural systems. These solitons, which frequently exhibit remarkable stability under interactions and perturbations, often dominate the transport, response, or structural properties of the systems in which they occur. In this article, we present an introduction to the solitons that occur in quasi-one-dimensional conducting polymers (synmetals) and related systems. The relevance of this subject to molecular electronic devices is twofold. First, many of these materials have molecular structures similar to possible prototype molecular switches. Second, to understand in detail how a molecular electronic device could work, it is essential to have a broad perspective on the nature of possible excitations in a variety of natural and synthetic molecular materials. 51 references

  4. Charge transport in organic semiconductors.

    Science.gov (United States)

    Bässler, Heinz; Köhler, Anna

    2012-01-01

    Modern optoelectronic devices, such as light-emitting diodes, field-effect transistors and organic solar cells require well controlled motion of charges for their efficient operation. The understanding of the processes that determine charge transport is therefore of paramount importance for designing materials with improved structure-property relationships. Before discussing different regimes of charge transport in organic semiconductors, we present a brief introduction into the conceptual framework in which we interpret the relevant photophysical processes. That is, we compare a molecular picture of electronic excitations against the Su-Schrieffer-Heeger semiconductor band model. After a brief description of experimental techniques needed to measure charge mobilities, we then elaborate on the parameters controlling charge transport in technologically relevant materials. Thus, we consider the influences of electronic coupling between molecular units, disorder, polaronic effects and space charge. A particular focus is given to the recent progress made in understanding charge transport on short time scales and short length scales. The mechanism for charge injection is briefly addressed towards the end of this chapter.

  5. Three-dimensional hole transport in nickel oxide by alloying with MgO or ZnO

    Science.gov (United States)

    Alidoust, Nima; Carter, Emily A.

    2015-11-01

    It has been shown previously that the movement of a hole in nickel oxide is confined to two dimensions, along a single ferromagnetic plane. Such confinement may hamper hole transport when NiO is used as a p-type transparent conductor in various solar energy conversion technologies. Here, we use the small polaron model, along with unrestricted Hartree-Fock and complete active space self-consistent field calculations to show that forming substitutional MxNi1-xO alloys with M = Mg or Zn reduces the barrier for movement of a hole away from the ferromagnetic plane to which it is confined. Such reduction occurs for hole transfer alongside one or two M ions that have been substituted for Ni ions. Furthermore, the Mg and Zn ions do not trap holes on O sites in their vicinity, and NiO's transparency is preserved upon forming the alloys. Thus, forming MxNi1-xO alloys with M = Mg or Zn may enhance NiO's potential as a p-type transparent conducting oxide, by disrupting the two-dimensional confinement of holes in pure NiO.

  6. Excitonic polarons in quasi-one-dimensional LH1 and LH2 bacteriochlorophyll a antenna aggregates from photosynthetic bacteria: A wavelength-dependent selective spectroscopy study

    International Nuclear Information System (INIS)

    Freiberg, Arvi; Raetsep, Margus; Timpmann, Kou; Trinkunas, Gediminas

    2009-01-01

    Spectral characteristics of the optically excited states in the ring-shaped quasi-one-dimensional aggregates comprising 18 and 32 tightly coupled bacteriochlorophyll a molecules have been investigated using selective spectroscopy methods and theoretical modelling of the data. Distinguished by the lowest electronic transition energies in the LH2 and LH1 antenna complexes these aggregates govern the functionally important ultrafast funneling of solar excitation energy in the photosynthetic membranes of purple bacteria. It was found by using a sophisticated differential fluorescence line narrowing method that exciton-phonon coupling in terms of the dimensionless Huang-Rhys factor is strong in these systems, justifying an excitonic polaron theoretical approach for the data analysis. Although we reached this qualitative conclusion already previously, in this work essential dependence of the exciton-phonon coupling strength and reorganization energy on excitation wavelength as well as on excitation light fluence has been established. We then show that these results corroborate with the properties of excitonic polarons in diagonally disordered ensembles of the aggregates. Furthermore, the weighted density of states of the phonon modes, which is an important characteristic of dynamical systems interacting with their surroundings, was derived. Its shape, being similar for all studied circular aggregates, deviates significantly from a reference profile describing local response of a protein to the Q y electronic transition in a single bacteriochlorophyll a molecule. Similarities of the data for regular and B800 deficient mutant LH2 complexes indicate that the B800 pigments have no direct influence on the electronic states of the B850 aggregate system. Consistent set of model parameters was determined, unambiguously implying that excitonic polarons, rather than bare excitons are proper lowest-energy optical excitations in the LH1 and LH2 antenna complexes

  7. Excitonic polarons in quasi-one-dimensional LH1 and LH2 bacteriochlorophyll a antenna aggregates from photosynthetic bacteria: A wavelength-dependent selective spectroscopy study

    Energy Technology Data Exchange (ETDEWEB)

    Freiberg, Arvi [Institute of Physics, University of Tartu, Riia 142, 51014 Tartu (Estonia); Institute of Molecular and Cell Biology, University of Tartu, Riia 23, 51010 Tartu (Estonia)], E-mail: arvi.freiberg@ut.ee; Raetsep, Margus; Timpmann, Kou [Institute of Physics, University of Tartu, Riia 142, 51014 Tartu (Estonia); Trinkunas, Gediminas [Insitute of Physics, Savanoriu pr. 231, LT-02300 Vilnius (Lithuania)

    2009-02-23

    Spectral characteristics of the optically excited states in the ring-shaped quasi-one-dimensional aggregates comprising 18 and 32 tightly coupled bacteriochlorophyll a molecules have been investigated using selective spectroscopy methods and theoretical modelling of the data. Distinguished by the lowest electronic transition energies in the LH2 and LH1 antenna complexes these aggregates govern the functionally important ultrafast funneling of solar excitation energy in the photosynthetic membranes of purple bacteria. It was found by using a sophisticated differential fluorescence line narrowing method that exciton-phonon coupling in terms of the dimensionless Huang-Rhys factor is strong in these systems, justifying an excitonic polaron theoretical approach for the data analysis. Although we reached this qualitative conclusion already previously, in this work essential dependence of the exciton-phonon coupling strength and reorganization energy on excitation wavelength as well as on excitation light fluence has been established. We then show that these results corroborate with the properties of excitonic polarons in diagonally disordered ensembles of the aggregates. Furthermore, the weighted density of states of the phonon modes, which is an important characteristic of dynamical systems interacting with their surroundings, was derived. Its shape, being similar for all studied circular aggregates, deviates significantly from a reference profile describing local response of a protein to the Q{sub y} electronic transition in a single bacteriochlorophyll a molecule. Similarities of the data for regular and B800 deficient mutant LH2 complexes indicate that the B800 pigments have no direct influence on the electronic states of the B850 aggregate system. Consistent set of model parameters was determined, unambiguously implying that excitonic polarons, rather than bare excitons are proper lowest-energy optical excitations in the LH1 and LH2 antenna complexes.

  8. Status report on the Small Secure Transportable Autonomous Reactor (SSTAR) /Lead-cooled Fast Reactor (LFR) and supporting research and development.

    Energy Technology Data Exchange (ETDEWEB)

    Sienicki, J. J.; Moisseytsev, A.; Yang, W. S.; Wade, D. C.; Nikiforova, A.; Hanania, P.; Ryu, H. J.; Kulesza, K. P.; Kim, S. J.; Halsey, W. G.; Smith, C. F.; Brown, N. W.; Greenspan, E.; de Caro, M.; Li, N.; Hosemann, P.; Zhang, J.; Yu, H.; Nuclear Engineering Division; LLNL; LANL; Massachusetts Inst. of Tech.; Ecole des Mines de Paris; Oregon State Univ.; Univ.of California at Berkley

    2008-06-23

    This report provides an update on development of a pre-conceptual design for the Small Secure Transportable Autonomous Reactor (SSTAR) Lead-Cooled Fast Reactor (LFR) plant concept and supporting research and development activities. SSTAR is a small, 20 MWe (45 MWt), natural circulation, fast reactor plant for international deployment concept incorporating proliferation resistance for deployment in non-fuel cycle states and developing nations, fissile self-sufficiency for efficient utilization of uranium resources, autonomous load following making it suitable for small or immature grid applications, and a high degree of passive safety further supporting deployment in developing nations. In FY 2006, improvements have been made at ANL to the pre-conceptual design of both the reactor system and the energy converter which incorporates a supercritical carbon dioxide Brayton cycle providing higher plant efficiency (44 %) and improved economic competitiveness. The supercritical CO2 Brayton cycle technology is also applicable to Sodium-Cooled Fast Reactors providing the same benefits. One key accomplishment has been the development of a control strategy for automatic control of the supercritical CO2 Brayton cycle in principle enabling autonomous load following over the full power range between nominal and essentially zero power. Under autonomous load following operation, the reactor core power adjusts itself to equal the heat removal from the reactor system to the power converter through the large reactivity feedback of the fast spectrum core without the need for motion of control rods, while the automatic control of the power converter matches the heat removal from the reactor to the grid load. The report includes early calculations for an international benchmarking problem for a LBE-cooled, nitride-fueled fast reactor core organized by the IAEA as part of a Coordinated Research Project on Small Reactors without Onsite Refueling; the calculations use the same neutronics

  9. Theory of quantum transport at nanoscale an introduction

    CERN Document Server

    Ryndyk, Dmitry A

    2016-01-01

    This book is an introduction to a rapidly developing field of modern theoretical physics – the theory of quantum transport at nanoscale. The theoretical methods considered in the book are in the basis of our understanding of charge, spin and heat transport in nanostructures and nanostructured materials and are widely used in nanoelectronics, molecular electronics, spin-dependent electronics (spintronics) and bio-electronics. The book is based on lectures for graduate and post-graduate students at the University of Regensburg and the Technische Universität Dresden (TU Dresden). The first part is devoted to the basic concepts of quantum transport: Landauer-Büttiker method and matrix Green function formalism for coherent transport, Tunneling (Transfer) Hamiltonian and master equation methods for tunneling, Coulomb blockade, vibrons and polarons. The results in this part are obtained as possible without sophisticated techniques, such as nonequilibrium Green functions, which are considered in detail in the...

  10. Polaronic effects on the off-center donor impurity in AlAs/GaAs/SiO2 spherical core/shell quantum dots

    Science.gov (United States)

    El Haouari, M.; Feddi, E.; Dujardin, F.; Restrepo, R. L.; Mora-Ramos, M. E.; Duque, C. A.

    2017-11-01

    The ground state of a conduction electron coupled to an off-center impurity donor in a AlAS/GaAs spherical core/shell quantum dot is investigated theoretically. The image-charge effect and the influence of the electron-polar-LO-phonon interaction are considered. The electron-impurity binding energy is calculated via a variational procedure and is reported both as a function of the shell width and of the radial position of the donor atom. The polaronic effects on this quantity are particularly discussed.

  11. River transport of mercury from artisanal and small-scale gold mining and risks for dietary mercury exposure in Madre de Dios, Peru.

    Science.gov (United States)

    Diringer, Sarah E; Feingold, Beth J; Ortiz, Ernesto J; Gallis, John A; Araújo-Flores, Julio M; Berky, Axel; Pan, William K Y; Hsu-Kim, Heileen

    2015-02-01

    Artisanal and small-scale gold mining (ASGM) is a major contributor to deforestation and the largest anthropogenic source of atmospheric mercury worldwide. Despite significant information on the direct health impacts of mercury to ASGM miners, the impact of mercury contamination on downstream communities has not been well characterized, particularly in Peru's Madre de Dios region. In this area, ASGM has increased significantly since 2000 and has led to substantial political and social controversy. This research examined the spatial distribution and transport of mercury through the Madre de Dios River with distance from ASGM activity. This study also characterized risks for dietary mercury exposure to local residents who depend on fish from the river. River sediment, suspended solids from the water column, and fish samples were collected in 2013 at 62 sites near 17 communities over a 560 km stretch of the Madre de Dios River and its major tributaries. In areas downstream of known ASGM activity, mercury concentrations in sediment, suspended solids, and fish within the Madre de Dios River were elevated relative to locations upstream of mining. Fish tissue mercury concentrations were observed at levels representing a public health threat, with greater than one-third of carnivorous fish exceeding the international health standard of 0.5 mg kg(-1). This study demonstrates that communities located hundreds of kilometers downstream of ASGM activity, including children and indigenous populations who may not be involved in mining, are at risk of dietary mercury exposure that exceed acceptable body burdens. This report represents the first systematic study of the region to aid policy decision-making related to ASGM activities in Peru.

  12. Electron beam induced electronic transport in alkyl amine-intercalated VOx nanotubes

    International Nuclear Information System (INIS)

    O'Dwyer, C.; Lavayen, V.; Clavijo-Cedeno, C.; Torres, C.M.S.

    2008-01-01

    The electron beam induced electronic transport in primary alkyl amine-intercalated V 2 O 5 nanotubes is investigated where the organic amine molecules are employed as molecular conductive wires to an aminosilanized substrate surface and contacted to Au interdigitated electrode contacts. The results demonstrate that the high conductivity of the nanotubes is related to the non-resonant tunnelling through the amine molecules and a reduced polaron hopping conduction through the vanadium oxide itself. Both nanotube networks and individual nanotubes exhibit similarly high conductivities where the minority carrier transport is bias dependent and nanotube diameter invariant. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  13. Transport-entropy correlations in La0.7Ca0.3MnO3 manganite

    International Nuclear Information System (INIS)

    Debnath, J.C.; Strydom, A.M.

    2014-01-01

    An investigation of the magnetic entropy change ΔS M and resistivity ρ, and the relation between them, for La 0.7 Ca 0.3 MnO 3 (LCMO) material has been presented. By using an equation of the form ΔS M =−α∫ 0 H [(δln(ρ))/(δT) ] H dH (α=9.98 emu/g), which relates magnetic order to transport behavior of the compounds, we measure the magnetic entropy change ΔS M from the resistivity measurement, where the resistivity results agree quite well with the fitting parameter α=9.98 emu/g in the intermediate temperature range. This result reveals the predominant role of magnetic polarons on the magnetoresistive property of manganites. It is obvious that magnetic disorder, characterized by ΔS M , affects the magnetic polarons, while the magnetic polarons influence the electronic transport properties, which may be the underlying reason for a salient ΔS M −ρ relation. It also provides an alternative method to determine magnetic entropy change on the basis of resistive measurements

  14. A new method for finding the minimum free energy pathway of ions and small molecule transportation through protein based on 3D-RISM theory and the string method

    Science.gov (United States)

    Yoshida, Norio

    2018-05-01

    A new method for finding the minimum free energy pathway (MFEP) of ions and small molecule transportation through a protein based on the three-dimensional reference interaction site model (3D-RISM) theory combined with the string method has been proposed. The 3D-RISM theory produces the distribution function, or the potential of mean force (PMF), for transporting substances around the given protein structures. By applying the string method to the PMF surface, one can readily determine the MFEP on the PMF surface. The method has been applied to consider the Na+ conduction pathway of channelrhodopsin as an example.

  15. FOB-SH: Fragment orbital-based surface hopping for charge carrier transport in organic and biological molecules and materials

    Science.gov (United States)

    Spencer, J.; Gajdos, F.; Blumberger, J.

    2016-08-01

    We introduce a fragment orbital-based fewest switches surface hopping method, FOB-SH, designed to efficiently simulate charge carrier transport in strongly fluctuating condensed phase systems such as organic semiconductors and biomolecules. The charge carrier wavefunction is expanded and the electronic Hamiltonian constructed in a set of singly occupied molecular orbitals of the molecular sites that mediate the charge transfer. Diagonal elements of the electronic Hamiltonian (site energies) are obtained from a force field, whereas the off-diagonal or electronic coupling matrix elements are obtained using our recently developed analytic overlap method. We derive a general expression for the exact forces on the adiabatic ground and excited electronic state surfaces from the nuclear gradients of the charge localized electronic states. Applications to electron hole transfer in a model ethylene dimer and through a chain of ten model ethylenes validate our implementation and demonstrate its computational efficiency. On the larger system, we calculate the qualitative behaviour of charge mobility with change in temperature T for different regimes of the intermolecular electronic coupling. For small couplings, FOB-SH predicts a crossover from a thermally activated regime at low temperatures to a band-like transport regime at higher temperatures. For higher electronic couplings, the thermally activated regime disappears and the mobility decreases according to a power law. This is interpreted by a gradual loss in probability for resonance between the sites as the temperature increases. The polaron hopping model solved for the same system gives a qualitatively different result and underestimates the mobility decay at higher temperatures. Taken together, the FOB-SH methodology introduced here shows promise for a realistic investigation of charge carrier transport in complex organic, aqueous, and biological systems.

  16. FOB-SH: Fragment orbital-based surface hopping for charge carrier transport in organic and biological molecules and materials

    Energy Technology Data Exchange (ETDEWEB)

    Spencer, J.; Gajdos, F.; Blumberger, J., E-mail: j.blumberger@ucl.ac.uk [Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT (United Kingdom)

    2016-08-14

    We introduce a fragment orbital-based fewest switches surface hopping method, FOB-SH, designed to efficiently simulate charge carrier transport in strongly fluctuating condensed phase systems such as organic semiconductors and biomolecules. The charge carrier wavefunction is expanded and the electronic Hamiltonian constructed in a set of singly occupied molecular orbitals of the molecular sites that mediate the charge transfer. Diagonal elements of the electronic Hamiltonian (site energies) are obtained from a force field, whereas the off-diagonal or electronic coupling matrix elements are obtained using our recently developed analytic overlap method. We derive a general expression for the exact forces on the adiabatic ground and excited electronic state surfaces from the nuclear gradients of the charge localized electronic states. Applications to electron hole transfer in a model ethylene dimer and through a chain of ten model ethylenes validate our implementation and demonstrate its computational efficiency. On the larger system, we calculate the qualitative behaviour of charge mobility with change in temperature T for different regimes of the intermolecular electronic coupling. For small couplings, FOB-SH predicts a crossover from a thermally activated regime at low temperatures to a band-like transport regime at higher temperatures. For higher electronic couplings, the thermally activated regime disappears and the mobility decreases according to a power law. This is interpreted by a gradual loss in probability for resonance between the sites as the temperature increases. The polaron hopping model solved for the same system gives a qualitatively different result and underestimates the mobility decay at higher temperatures. Taken together, the FOB-SH methodology introduced here shows promise for a realistic investigation of charge carrier transport in complex organic, aqueous, and biological systems.

  17. Multiple efflux pumps are involved in the transepithelial transport of colchicine: combined effect of p-glycoprotein and multidrug resistance-associated protein 2 leads to decreased intestinal absorption throughout the entire small intestine.

    Science.gov (United States)

    Dahan, Arik; Sabit, Hairat; Amidon, Gordon L

    2009-10-01

    The purpose of this study was to thoroughly characterize the efflux transporters involved in the intestinal permeability of the oral microtubule polymerization inhibitor colchicine and to evaluate the role of these transporters in limiting its oral absorption. The effects of P-glycoprotein (P-gp), multidrug resistance-associated protein 2 (MRP2), and breast cancer resistance protein (BCRP) inhibitors on colchicine bidirectional permeability were studied across Caco-2 cell monolayers, inhibiting one versus multiple transporters simultaneously. Colchicine permeability was then investigated in different regions of the rat small intestine by in situ single-pass perfusion. Correlation with the P-gp/MRP2 expression level throughout different intestinal segments was investigated by immunoblotting. P-gp inhibitors [N-(4-[2-(1,2,3,4-tetrahydro-6,7-dimethoxy-2-isoquinolinyl)ethyl]-phenyl)-9,10-dihydro-5-methoxy-9-oxo-4-acridine carboxamide (GF120918), verapamil, and quinidine], and MRP2 inhibitors [3-[[3-[2-(7-chloroquinolin-2-yl)vinyl]phenyl]-(2-dimethylcarbamoylethylsulfanyl)methylsulfanyl] propionic acid (MK571), indomethacin, and p-aminohippuric acid (p-AH)] significantly increased apical (AP)-basolateral (BL) and decreased BL-AP Caco-2 transport in a concentration-dependent manner. No effect was obtained by the BCRP inhibitors fumitremorgin C (FTC) and pantoprazole. P-gp/MRP2 inhibitors combinations greatly reduced colchicine mucosal secretion, including complete abolishment of efflux (GF120918/MK571). Colchicine displayed low (versus metoprolol) and constant permeability along the rat small-intestine. GF120918 significantly increased colchicine permeability in the ileum with no effect in the jejunum, whereas MK571 augmented jejunal permeability without changing the ileal transport. The GF120918/MK571 combination caused an effect similar to that of MK571 alone in the jejunum and to that of GF120918 alone in the ileum. P-gp expression followed a gradient increasing from

  18. Transport Statistics - Transport - UNECE

    Science.gov (United States)

    Sustainable Energy Statistics Trade Transport Themes UNECE and the SDGs Climate Change Gender Ideas 4 Change UNECE Weekly Videos UNECE Transport Areas of Work Transport Statistics Transport Transport Statistics About us Terms of Reference Meetings and Events Meetings Working Party on Transport Statistics (WP.6

  19. Sediment Transport

    DEFF Research Database (Denmark)

    Liu, Zhou

    Flow and sediment transport are important in relation to several engineering topics, e.g. erosion around structures, backfilling of dredged channels and nearshore morphological change. The purpose of the present book is to describe both the basic hydrodynamics and the basic sediment transport...... mechanics. Chapter 1 deals with fundamentals in fluid mechanics with emphasis on bed shear stress by currents, while chapter 3 discusses wave boundary layer theory. They are both written with a view to sediment transport. Sediment transport in rivers, cross-shore and longshore are dealt with in chapters 2......, 4 and 5, respectively. It is not the intention of the book to give a broad review of the literature on this very wide topic. The book tries to pick up information which is of engineering importance. An obstacle to the study of sedimentation is the scale effect in model tests. Whenever small...

  20. Transport of trans-tiliroside (kaempferol-3-β-D-(6"-p-coumaroyl-glucopyranoside) and related flavonoids across Caco-2 cells, as a model of absorption and metabolism in the small intestine.

    Science.gov (United States)

    Luo, Zijun; Morgan, Michael R A; Day, Andrea J

    2015-01-01

    1. Absorption and metabolism of tiliroside (kaempferol 3-β-D-(6"-p-coumaroyl)-glucopyranoside) and its related compounds kaempferol, kaempferol-3-glucoside and p-coumaric acid were investigated in the small intestinal Caco-2 cell model. Apparent permeation (Papp) was determined as 0.62 × 10(-6) cm/s, 3.1 × 10(-6) cm/s, 0 and 22.8 × 10(-6) cm/s, respectively. 2. Mechanistic study showed that the transportation of tiliroside, kaempferol-3-glucoside and p-coumaric acid in Caco-2 model were transporter(s) involved, while transportation of kaempferol was solely by passive diffusion mechanism. 3. Efflux transporters, multi-drug-resistance-associated protein-2 (MRP2), were shown to play a role in limiting the uptake of tiliroside. Inhibitors of MRP2, (MK571 and rifampicin) and co-incubation with kaempferol (10 μM), increased transfer from the apical to the basolateral side by three to five fold. 4. Metabolites of kaempferol-3-glucoside and p-coumaric acid were not detected in the current Caco-2 model, while tiliroside was metabolised to a limited extent, with two tiliroside mono-glucuronides identified; and kaempferol was metabolised to a higher extent, with three mono-glucuronides and two mono-sulfates identified. 5. In conclusion, tiliroside was metabolised and transported across Caco-2 cell membrane to a limited extent. Transportation could be increased by applying MRP2 inhibitors or co-incubation with kaempferol. It is proposed that tiliroside can be absorbed by human; future pharmacokinetics studies are warranted in order to determine the usefulness of tiliroside as a bioactive agent.

  1. Studies on structural, dielectric, and transport properties of Ni{sub 0.65}Zn{sub 0.35}Fe{sub 2}O{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Pradhan, Dhiren K.; Misra, Pankaj; Sahoo, Satyaprakash; Katiyar, Ram S., E-mail: rkatiyar@hpcf.upr.edu [Department of Physics and Institute of Functional Nanomaterials, University of Puerto Rico, San Juan 00936, Puerto Rico (United States); Puli, Venkata S. [Department of Physics and Engineering Physics, Tulane University, New Orleans, Louisiana 70118 (United States); Pradhan, Dillip K. [Department of Physics, National Institute of Technology, Rourkela 769008 (India)

    2014-06-28

    We report the crystal structure, dielectric, transport, and magnetic properties of Ni{sub 0.65}Zn{sub 0.35}Fe{sub 2}O{sub 4}. Rietveld refinement results of X-ray diffraction patterns confirm the phase formation of the material with cubic crystal structure (Fd3{sup ¯}m). The frequency dependent ac conductivity behavior obeys the Jonscher's power law and is explained using the jump relaxation model. The observed behavior of temperature dependent bulk conductivity is attributed to the variable-range hopping of localized polarons. The correlation of polaron conduction and high permittivity behavior of NZFO is established on the basis of long range and short range conduction mechanisms. The complex impedance spectra clearly show the contribution of both grain and grain boundary effect on the electrical properties.

  2. Polaron effects on the linear and the nonlinear optical absorption coefficients and refractive index changes in cylindrical quantum dots with applied magnetic field

    International Nuclear Information System (INIS)

    Wu Qingjie; Guo Kangxian; Liu Guanghui; Wu Jinghe

    2013-01-01

    Polaron effects on the linear and the nonlinear optical absorption coefficients and refractive index changes in cylindrical quantum dots with the radial parabolic potential and the z-direction linear potential with applied magnetic field are theoretically investigated. The optical absorption coefficients and refractive index changes are presented by using the compact-density-matrix approach and iterative method. Numerical calculations are presented for GaAs/AlGaAs. It is found that taking into account the electron-LO-phonon interaction, not only are the linear, the nonlinear and the total optical absorption coefficients and refractive index changes enhanced, but also the total optical absorption coefficients are more sensitive to the incident optical intensity. It is also found that no matter whether the electron-LO-phonon interaction is considered or not, the absorption coefficients and refractive index changes above are strongly dependent on the radial frequency, the magnetic field and the linear potential coefficient.

  3. Taurine uptake by human retinal pigment epithelium: implications for the transport of small solutes between the choroid and the outer retina.

    Science.gov (United States)

    Hillenkamp, Jost; Hussain, Ali A; Jackson, Timothy L; Cunningham, Joanna R; Marshall, John

    2004-12-01

    To characterize the Michaelis-Menten kinetics of the taurine transporter (TT) in retinal pigment epithelium (RPE) freshly isolated from human donor eyes. To identify the rate limiting compartment in the pathway of taurine delivery from the choroidal blood supply to the outer retina composed by Bruch's-choroid (BC) and the RPE in the human older age group. In human donor samples (4 melanoma-affected eyes, and 14 control eyes; age range, 62-93 years), radiochemical techniques were used to determine the RPE taurine accumulation at various exogenous concentrations. The transport capability of human RPE was obtained from a kinetic analysis of the high-affinity carrier over a substrate concentration of 1 to 60 microM taurine. Uptake of taurine into human RPE at a taurine concentration of 1 microM was independent of donor age (P > 0.05) and averaged at 2.83 +/- 0.27 (SEM) pmol/10 minutes per 6-mm trephine. Taurine transport by human RPE was mediated by a high-affinity carrier of K(m) 50 microM and V(max) of 267 pmol/10 minutes per 5-mm disc. In human donor RPE, uptake of taurine remained viable in the age range 62 to 93 years. Taurine transport rates in the RPE were lower than across the isolated BC complex, and thus the data suggest that the former compartment houses the rate-limiting step in the delivery of taurine to the outer retina.

  4. Transport of the photodynamic therapy agent 5-aminolevulinic acid by distinct H+-coupled nutrient carriers coexpressed in the small intestine.

    Science.gov (United States)

    Anderson, Catriona M H; Jevons, Mark; Thangaraju, Muthusamy; Edwards, Noel; Conlon, Nichola J; Woods, Steven; Ganapathy, Vadivel; Thwaites, David T

    2010-01-01

    5-Aminolevulinic acid (ALA) is a prodrug used in photodynamic therapy, fluorescent diagnosis, and fluorescent-guided resection because it leads to accumulation of the photosensitizer protoporphyrin IX (PpIX) in tumor tissues. ALA has good oral bioavailability, but high oral doses are required to obtain selective PpIX accumulation in colonic tumors because accumulation is also observed in normal gut mucosa. Structural similarities between ALA and GABA led us to test the hypothesis that the H(+)-coupled amino acid transporter PAT1 (SLC36A1) will contribute to luminal ALA uptake. Radiolabel uptake and electrophysiological measurements identified PAT1-mediated H(+)-coupled ALA symport after heterologous expression in Xenopus oocytes. The selectivity of the nontransported inhibitors 5-hydroxytryptophan and 4-aminomethylbenzoic acid for, respectively, PAT1 and the H(+)-coupled di/tripeptide transporter PepT1 (SLC15A1) were examined. 5-Hydroxytryptophan selectively inhibited PAT1-mediated amino acid uptake across the brush-border membrane of the human intestinal (Caco-2) epithelium whereas 4-aminomethylbenzoic acid selectively inhibited PepT1-mediated dipeptide uptake. The inhibitory effects of 5-hydroxytryptophan and 4-aminomethylbenzoic acid were additive, demonstrating that both PAT1 and PepT1 contribute to intestinal transport of ALA. This is the first demonstration of overlap in substrate specificity between these distinct transporters for amino acids and dipeptides. PAT1 and PepT1 expression was monitored by reverse transcriptase-polymerase chain reaction using paired samples of normal and cancer tissue from human colon. mRNA for both transporters was detected. PepT1 mRNA was increased 2.3-fold in cancer tissues. Thus, increased PepT1 expression in colonic cancer could contribute to the increased PpIX accumulation observed. Selective inhibition of PAT1 could enhance PpIX loading in tumor tissue relative to that in normal tissue.

  5. Electron-phonon interaction in quantum transport through quantum dots and molecular systems

    Science.gov (United States)

    Ojeda, J. H.; Duque, C. A.; Laroze, D.

    2016-12-01

    The quantum transport and effects of decoherence properties are studied in quantum dots systems and finite homogeneous chains of aromatic molecules connected to two semi-infinite leads. We study these systems based on the tight-binding approach through Green's function technique within a real space renormalization and polaron transformation schemes. In particular, we calculate the transmission probability following the Landauer-Büttiker formalism, the I - V characteristics and the noise power of current fluctuations taken into account the decoherence. Our results may explain the inelastic effects through nanoscopic systems.

  6. Effect of feeding soybean meal and differently processed peas on intestinal morphology and functional glucose transport in the small intestine of broilers.

    Science.gov (United States)

    Röhe, I; Boroojeni, F Goodarzi; Zentek, J

    2017-09-01

    Peas are locally grown legumes being rich in protein and starch. However, the broad usage of peas as a feed component in poultry nutrition is limited to anti-nutritional factors, which might impair gut morphology and function. This study investigated the effect of feeding raw or differently processed peas compared with feeding a soybean meal-based control diet (C) on intestinal morphology and nutrient transport in broilers. A total of 360 day-old broiler chicks were fed with one of the following diets: The C diet, and 3 diets containing raw peas (RP), fermented peas (FP) and enzymatically pre-digested peas (EP), each supplying 30% of dietary crude protein. After 35 d, jejunal samples of broilers were taken for analyzing histomorphological parameters, active glucose transport in Ussing chambers and the expression of genes related to glucose absorption, intestinal permeability and cell maturation. Villus length (P = 0.017) and crypt depth (P = 0.009) of EP-fed broilers were shorter compared to birds received C. The villus surface area was larger in broilers fed C compared to those fed with the pea-containing feed (P = 0.005). Glucose transport was higher for broilers fed C in comparison to birds fed with the EP diet (P = 0.044). The sodium-dependent glucose co-transporter 1 (SGLT-1) expression was down-regulated in RP (P = 0.028) and FP (P = 0.015) fed broilers. Correlation analyses show that jejunal villus length negatively correlates with the previously published number of jejunal intraepithelial T cells (P = 0.014) and that jejunal glucose transport was negatively correlated with the occurrence of jejunal intraepithelial leukocytes (P = 0.041). To conclude, the feeding of raw and processed pea containing diets compared to a soybean based diet reduced the jejunal mucosal surface area of broilers, which on average was accompanied by lower glucose transport capacities. These morphological and functional alterations were associated with observed mucosal immune

  7. Muonium formation via charge transport in solids and liquids

    International Nuclear Information System (INIS)

    Storchak, Vyacheslav G.; Brewer, Jess H.; Cox, Stephen F.J.

    1997-01-01

    We review our recent experimental studies on delayed muonium formation in insulators and semiconductors. This involves the positive muon capturing one of the excess electrons liberated in its own ionization track and competes with recombination or escape of the electrons. The muon is generally found to thermalise well 'downstream' from the center of the electron distribution, so that the transport mechanism of the electrons is a crucial factor. This is discussed in terms of the different tendencies to localization (as polarons in solids or in bubbles in liquids) vs. band-like propagation. Studies of Van der Waals cryocrystals and cryoliquids are reviewed and some preliminary results reported for sapphire and silicon. Transport distances and times are determined from the variation of μSR signal amplitudes with applied electric and magnetic fields, respectively, enabling the development of a new technique for measuring electron mobilities on a microscopic scale

  8. Long-term excess fat and/or fructose ingestion causes changes in small artery K+ transporter expression and function with effects on blood pressure

    DEFF Research Database (Denmark)

    Olsen, A. K.; Salomonsson, M.; Sørensen, C. M.

    + channels, Na/K-ATPase, and voltage-gated Ca2+ channels are crucial determinants of resistance artery tone. Only scarce information is available on the role of K+ transporters in pathophysiological mechanisms induced by long-term feeding of laboratory rats with either high-fat, high-fructose or high-fat/high-fructose...... diet. HYPOTHESIS: A 28-week diet consisting of high-fat or high-fructose, or both, will lead to changes in K+ transporter expression and function, which will be linked with changes in blood pressure, arterial smooth muscle function, endothelial function and passive structural/mechanical properties....... METHODS: Male Sprague Dawley rats (4 weeks) were randomized into 4 diet groups receiving a diet with normal chow (CTR, N=19), high-fat chow (60% saturated fat, FAT, N=18), high-fructose (10% in drinking water; FRUC, N=15), or a combination of fat/fructose (FAT/FRUC, N=15) for 28 weeks. Systolic blood...

  9. Low-Protein Diet Supplemented with Keto Acids Is Associated with Suppression of Small-Solute Peritoneal Transport Rate in Peritoneal Dialysis Patients

    Directory of Open Access Journals (Sweden)

    Na Jiang

    2011-01-01

    Full Text Available Objective. We investigate whether low-protein diet would show benefits in suppressing peritoneal transport rate in peritoneal dialysis (PD patients. Methods. This is a supplemented analysis of our previously published trial, which randomized 60 PD patients to receive low- (LP: dietary protein intake of 0.6–0.8 g/kg/d, keto-acid-supplemented low- (sLP: 0.6–0.8 g/kg/d with 0.12 g/kg/d of keto acids, or high- (HP: 1.0–1.2 g/kg/d protein diet and lasted for one year. In this study, the variations of peritoneal transport rate were assessed. Results. While baseline D/Pcr (dialysate-to-plasma concentration ratio for creatinine at 4 hour and D/D0glu (dialysate glucose at 4 hour to baseline dialysate glucose concentration ratio were similar, D/Pcr in group sLP was lower, and D/D0glu was higher than those in the other two groups (P<0.05 at 12th month. D/D0glu increased (P<0.05, and D/Pcr tended to decrease, (P=0.071 in group sLP. Conclusions. Low-protein diet with keto acids may benefit PD patients by maintaining peritoneum at a lower transport rate.

  10. Low-protein diet supplemented with keto acids is associated with suppression of small-solute peritoneal transport rate in peritoneal dialysis patients.

    Science.gov (United States)

    Jiang, Na; Qian, Jiaqi; Lin, Aiwu; Fang, Wei; Zhang, Weiming; Cao, Liou; Wang, Qin; Ni, Zhaohui; Yao, Qiang

    2011-01-01

    Objective. We investigate whether low-protein diet would show benefits in suppressing peritoneal transport rate in peritoneal dialysis (PD) patients. Methods. This is a supplemented analysis of our previously published trial, which randomized 60 PD patients to receive low- (LP: dietary protein intake of 0.6-0.8 g/kg/d), keto-acid-supplemented low- (sLP: 0.6-0.8 g/kg/d with 0.12 g/kg/d of keto acids), or high- (HP: 1.0-1.2 g/kg/d) protein diet and lasted for one year. In this study, the variations of peritoneal transport rate were assessed. Results. While baseline D/P(cr) (dialysate-to-plasma concentration ratio for creatinine at 4 hour) and D/D0(glu) (dialysate glucose at 4 hour to baseline dialysate glucose concentration ratio) were similar, D/P(cr) in group sLP was lower, and D/D0(glu) was higher than those in the other two groups (P diet with keto acids may benefit PD patients by maintaining peritoneum at a lower transport rate.

  11. Oxygen Transport Membranes

    Energy Technology Data Exchange (ETDEWEB)

    S. Bandopadhyay

    2008-08-30

    small polaron conduction mechanism. Scanning transmission electron microscopy (STEM) and electron energy loss spectroscopy (EELS) were used to develop strategies to detect and characterize vacancy creation, dopant segregations and defect association in the oxygen conducting membrane material. The pO{sub 2} and temperature dependence of the conductivity, non-stoichiometry and thermal-expansion behavior of compositions with increasing complexity of substitution on the perovskite A and B sites were studied. Studies with the perovskite structure show anomalous behavior at low oxygen partial pressures (<10{sup -5} atm). The anomalies are due to non-equilibrium effects and can be avoided by using very strict criteria for the attainment of equilibrium. The slowness of the oxygen equilibration kinetics arises from two different mechanisms. In the first, a two phase region occurs between an oxygen vacancy ordered phase such as brownmillerite SrFeO{sub 2.5} and perovskite SrFeO{sub 3-x}. The slow kinetics is associated with crossing the two phase region. The width of the miscibility gap decreases with increasing temperature and consequently the effect is less pronounced at higher temperature. The preferred kinetic pathway to reduction of perovskite ferrites when the vacancy concentration corresponds to the formation of significant concentrations of Fe{sup 2+} is via the formation of a Ruddlesden-Popper (RP) phases as clearly observed in the case of La{sub 0.5}Sr{sub 0.5}FeO{sub 3-x} where LaSrFeO{sub 4} is found together with Fe. In more complex compositions, such as LSFTO, iron or iron rich phases are observed locally with no evidence for the presence of discrete RP phase. Fracture strength of tubular perovskite membranes was determined in air and in reducing atmospheric conditions. The strength of the membrane decreased with temperature and severity of reducing conditions although the strength distribution (Weibull parameter, m) was relatively unaltered. Surface and volume

  12. Study on the electrical transport properties of La{sub 2/3}Ba{sub 1/3}MnO{sub 3}:Ag{sub 0.04}/LaAlO{sub 3} (001) films

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Xiang, E-mail: lxjim@126.com; Zhao, Shuang; Zhang, Shao-Chun

    2017-01-01

    La{sub 2/3}Ba{sub 1/3}MnO{sub 3}: wt%Ag{sub x} (LBMO:Ag{sub x}, x=0.04) films were prepared on single crystalline (001)-orientated LaAlO{sub 3} substrates by pulsed laser deposition technique. All the samples show along the (00l) orientation in rhombohedral structure with R3c space group. The surface roughness (Ra), insulator-metal transition temperature (Tp) and resistivity at Tp (ρ{sub Tp}) of the LBMO:Ag{sub 0.04} films reached optimal values of 3.29 nm, 288 K and 0.033 Ω cm at 740 °C, respectively. The improvement of electrical transport properties in the films are attributed to the optimal growth temperature and Ag-doping improve the microstructure of the surfaces, grain boundaries (GBs) in connectivity and better crystallization. In addition, the electrical conduction behaviors can be well fitted with the grain/domain boundary, electron–electron and magnon scattering mechanisms in the ferromagnetic metallic region (Tsmall polaron hopping mechanism in the paramagnetic insulating region (T>Tp).

  13. The Study of Turbulent Fluctuation Characteristics in a Small Rotary Engine with a Peripheral Port Based on the Improved Delayed Detached Eddy Simulation Shear-Stress Transport (IDDES-SST Method

    Directory of Open Access Journals (Sweden)

    Yan Zhang

    2018-03-01

    Full Text Available In this paper, an improved delayed detached eddy simulation method combined with shear-stress transport (SST model was used to study the three-dimensional turbulent characteristics in a small rotary engine with a peripheral port. The turbulent characteristics including instantaneous velocity, turbulent fluctuation, coherent structure and velocity circulation were analysed based on a dynamic model of the small rotary engine. Three sets of conclusions on the basis of computational results were obtained. First, it was found that large-scale vortex structures with high intensity were distributed in the center of the chamber in the intake process and broke into lots of small vortex structures in the compression process. Second, flow stability in the X direction decreased from the leading to the trailing in the small rotary engine. The fluctuation velocity of the Y direction showed the paraboloid feature and its peak position moved from the mid-back to the middle of the chamber during the operation process. Third, during the intake process, two vortices occurred in the cross section parallel to the covers and were located at the leading and trailing of the cross section, respectively. Compared to the intake process, more vortices occur at cross sections which were far away from the central section during the compression process.

  14. Influence of the centrifugal force and parallel dynamics on the toroidal momentum transport due to small scale turbulence in a tokamak

    International Nuclear Information System (INIS)

    Peeters, A. G.; Camenen, Y.; Casson, F. J.; Hornsby, W. A.; Snodin, A. P.; Strintzi, D.; Angioni, C.

    2009-01-01

    The paper derives the gyro-kinetic equation in the comoving frame of a toroidally rotating plasma, including both the Coriolis drift effect [A. G. Peeters et al., Phys. Rev. Lett. 98, 265003 (2007)] as well as the centrifugal force. The relation with the laboratory frame is discussed. A low field side gyro-fluid model is derived from the gyro-kinetic equation and applied to the description of parallel momentum transport. The model includes the effects of the Coriolis and centrifugal force as well as the parallel dynamics. The latter physics effect allows for a consistent description of both the Coriolis drift effect as well as the ExB shear effect [R. R. Dominguez and G. M. Staebler, Phys. Fluids B 5, 3876 (1993)] on the momentum transport. Strong plasma rotation as well as parallel dynamics reduce the Coriolis (inward) pinch of momentum and can lead to a sign reversal generating an outward pinch velocity. Also, the ExB shear effect is, in a similar manner, reduced by the parallel dynamics and stronger rotation.

  15. Experimental manifestations of the Nb.sup.4+./sup.-O.sup.-./sup. polaronic excitons in KTa.sub.0.988./sub.Nb.sub.0.012./sub.O.sub.3./sub..

    Czech Academy of Sciences Publication Activity Database

    Yusupov, R.V.; Gracheva, I.N.; Rodionov, A.A.; Syrnikov, P. P.; Gubaev, A. I.; Dejneka, Alexandr; Jastrabík, Lubomír; Trepakov, V.A.; Salakhov, M.K.

    2011-01-01

    Roč. 84, č. 17 (2011), 174118/1-174118/7 ISSN 1098-0121 R&D Projects: GA MŠk(CZ) 1M06002 Institutional research plan: CEZ:AV0Z10100522 Keywords : photoinduced EPR * Nb 4+ -O - polaronic excitons * KTa 0.988 Nb 0.012 O 3 Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.691, year: 2011

  16. Molecular-weight dependence of interchain polaron delocalization and exciton bandwidth in high-mobility conjugated polymers

    DEFF Research Database (Denmark)

    Chang, J.F.; Clark, J.; Zhao, N.

    2006-01-01

    delocalization with increasing conjugation length and crystalline quality. From comparative studies of field-effect transistor characteristics, film morphology, and optical properties our study provides a microscopic understanding of the factors which limit the charge transport in P3HT to field-effect mobilities......Interchain interactions have a profound effect on the optical as well as charge transport properties of conjugated polymer thin films. In contrast to oligomeric model systems in solution-deposited polymer thin films the study of such effects is complicated by the complex microstructure. We present...

  17. Feasibility study of a microwave or far-infrared scattering experiment to measure small scale turbulence and anomalous transport in J.E.T

    International Nuclear Information System (INIS)

    Koechlin, F.; Olivain, J.; Gresillon, D.; Truc, A.

    1981-03-01

    In the first part, we make a rapid review of what can be expected as low frequency turbulence in J.E.T. This is to define the parameters of the density fluctuations which can be expected. A method to deduce the anomalous transport is described. In the second part, the physical problems of measuring these parameters by microwave or far-infrared scattering are outlined. In the third part, a preliminary study of a microwave scattering experiment at lambda approximately 1.3 mm is made. In the fourth part, a F.I.R. laser experiment at 10.6 μm is also proposed to perform the same measurements. In this last case, an estimation of the thermal nature of the plasma emission could be made, in order to eventually extend the diagnostic to the ion temperature measurement

  18. Low-Protein Diet Supplemented with Keto Acids Is Associated with Suppression of Small-Solute Peritoneal Transport Rate in Peritoneal Dialysis Patients

    OpenAIRE

    Jiang, Na; Qian, Jiaqi; Lin, Aiwu; Fang, Wei; Zhang, Weiming; Cao, Liou; Wang, Qin; Ni, Zhaohui; Yao, Qiang

    2011-01-01

    Objective. We investigate whether low-protein diet would show benefits in suppressing peritoneal transport rate in peritoneal dialysis (PD) patients. Methods. This is a supplemented analysis of our previously published trial, which randomized 60 PD patients to receive low- (LP: dietary protein intake of 0.6–0.8 g/kg/d), keto-acid-supplemented low- (sLP: 0.6–0.8 g/kg/d with 0.12 g/kg/d of keto acids), or high- (HP: 1.0–1.2 g/kg/d) protein diet and lasted for one year. In this study, the variat...

  19. Justified requirements in private transportation and a recommendation for improving the efficiency of household energy utilisation through the use of small ecologically-friendly or 'ultralight' vehicles for mass private transportation in the 21st century

    International Nuclear Information System (INIS)

    Juravic, T.

    1999-01-01

    Needs and ownership are sociobiologically manifested in the alter-ego of a Homo sapiens where the natural progression of events (a household being the fundamental microlevel) and the social order, i.e. globalisation, are based on ownership and needs as sacred rights, and for this reason universal values like energy conservation end up as the waste of the mindless worship of consumption. Justified needs are phenomena of a consumerist (egocentric, pragmatic, voluntary) social conscience and instinctive behaviour - an unpredictable cause resulting from freedom being the foundation of the quality of life, socio-economic and political changes but are mutually exclusive to understanding (expressing and gaining deeper and richer knowledge). Inbuilt limits and/or control of consumption, which are already used in household appliances with aforeset processes (goals) for unknown consumers, to achieve large energy savings in 'routine' functions are more effective than attempts to prevent mistakes (lack of user knowledge through repression). A private vehicle, as a symbol of the freedom and quality of life, is a mechanism for achieving 'justified' needs and presents another means of household energy utilisation. The consumer's desires regarding private transportation are not sufficiently reconciled with intelligent microprocessors (expert systems), which achieve (the most) optimal behaviour in the process of transportation. This detailed consideration (as part of investigating the technical system) cannot be examined on a strictly logical or scientific basis, as it only proposes a method of co-agreement (not co-reponsability) of manufacturers and consumers and an alternative logical way of thinking, or organisation of the interaction between vehicles and traffic in order to form a judgement of really justifiable needs, and to achieve a robotic private vehicle, transportation and traffic. The goal of this consideration is to establish the DIVISION of energy with the help of

  20. Spot 42 Small RNA Regulates Arabinose-Inducible araBAD Promoter Activity by Repressing Synthesis of the High-Affinity Low-Capacity Arabinose Transporter

    Science.gov (United States)

    Chen, Jiandong

    2016-01-01

    ABSTRACT The l-arabinose-inducible araBAD promoter (PBAD) enables tightly controlled and tunable expression of genes of interest in a broad range of bacterial species. It has been used successfully to study bacterial sRNA regulation, where PBAD drives expression of target mRNA translational fusions. Here we report that in Escherichia coli, Spot 42 sRNA regulates PBAD promoter activity by affecting arabinose uptake. We demonstrate that Spot 42 sRNA represses araF, a gene encoding the AraF subunit of the high-affinity low-capacity arabinose transporter AraFGH, through direct base-pairing interactions. We further show that endogenous Spot 42 sRNA is sufficient to repress araF expression under various growth conditions. Finally, we demonstrate this posttranscriptional repression has a biological consequence, decreasing the induction of PBAD at low levels of arabinose. This problem can be circumvented using strategies reported previously for avoiding all-or-none induction behavior, such as through constitutive expression of the low-affinity high-capacity arabinose transporter AraE or induction with a higher concentration of inducers. This work adds araF to the set of Spot 42-regulated genes, in agreement with previous studies suggesting that Spot 42, itself negatively regulated by the cyclic AMP (cAMP) receptor protein-cAMP complex, reinforces the catabolite repression network. IMPORTANCE The bacterial arabinose-inducible system is widely used for titratable control of gene expression. We demonstrate here that a posttranscriptional mechanism mediated by Spot 42 sRNA contributes to the functionality of the PBAD system at subsaturating inducer concentrations by affecting inducer uptake. Our finding extends the inputs into the known transcriptional control for the PBAD system and has implications for improving its usage for tunable gene expression. PMID:27849174

  1. Modeling chemical accumulation in sediment of small waterbodies accounting for sediment transport and water-sediment exchange processes over long periods.

    Science.gov (United States)

    Patterson, David Albert; Strehmel, Alexander; Erzgräber, Beate; Hammel, Klaus

    2017-12-01

    In a recent scientific opinion of the European Food Safety Authority it is argued that the accumulation of plant protection products in sediments over long time periods may be an environmentally significant process. Therefore, the European Food Safety Authority proposed a calculation to account for plant protection product accumulation. This calculation, however, considers plant protection product degradation within sediment as the only dissipation route, and does not account for sediment dynamics or back-diffusion into the water column. The hydraulic model Hydrologic Engineering Center-River Analysis System (HEC-RAS; US Army Corps of Engineers) was parameterized to assess sediment transport and deposition dynamics within the FOrum for Co-ordination of pesticide fate models and their USe (FOCUS) scenarios in simulations spanning 20 yr. The results show that only 10 to 50% of incoming sediment would be deposited. The remaining portion of sediment particles is transported across the downstream boundary. For a generic plant protection product substance this resulted in deposition of only 20 to 50% of incoming plant protection product substance. In a separate analysis, the FOCUS TOXSWA model was utilized to examine the relative importance of degradation versus back-diffusion as loss processes from the sediment compartment for a diverse range of generic plant protection products. In simulations spanning 20 yr, it was shown that back-diffusion was generally the dominant dissipation process. The results of the present study show that sediment dynamics and back-diffusion should be considered when calculating long-term plant protection product accumulation in sediment. Neglecting these may lead to a systematic overestimation of accumulation. Environ Toxicol Chem 2017;36:3223-3231. © 2017 SETAC. © 2017 SETAC.

  2. Paleoclassical transport explains electron transport barriers in RTP and TEXTOR

    NARCIS (Netherlands)

    Hogeweij, G. M. D.; Callen, J.D.

    2008-01-01

    The recently developed paleoclassical transport model sets the minimum level of electron thermal transport in a tokamak. This transport level has proven to be in good agreement with experimental observations in many cases when fluctuation-induced anomalous transport is small, i.e. in (near-) ohmic

  3. Polaronic and bipolaronic structures in the adiabatic Hubbard-Hostein model involving 2 electrons and in its extensions; Structures polaroniques et bipolaroniques dans le modele de hostein hubbard adiabatique a deux electrons et ses extensions

    Energy Technology Data Exchange (ETDEWEB)

    Proville, L

    1998-03-30

    This thesis brings its contribution to the bipolaronic theory which might explain the origin of superconductivity at high temperature. A polaron is a quasiparticle made up of a localized electron and a deformation in the crystal structure. 2 electrons in singlet states localized on the same site form a bipolaron. Whenever the Coulomb repulsion between the 2 electrons is too strong bipolaron turns into 2 no bound polarons. We study the existence and the mobility of bipolarons. We describe the electron-phonon interaction by the Holstein term and the Coulomb repulsion by the Hubbard term. 2 assumptions are made: - the local electron-phonon interaction is strong and opposes the Coulomb repulsion between Hubbard type electrons - the system is close to the adiabatic limit. The system is reduced to 2 electrons in order to allow an exact treatment and the investigation of some bipolaronic bound states. At 2-dimensions the existence of bipolarons requires a very strong coupling which forbids any classical mobility. In some cases an important tunneling effect appears and we show that mobile bipolarons exist in a particular parameter range. Near the adiabatic limit we prove that polaronic and bipolaronic structures exist for a great number of electrons. (A.C.) 33 refs.

  4. Exploratory clinical trial of (4S)-4-(3-[18F]fluoropropyl)-L-glutamate for imaging xC- transporter using positron emission tomography in patients with non-small cell lung or breast cancer.

    Science.gov (United States)

    Baek, Sora; Choi, Chang-Min; Ahn, Sei Hyun; Lee, Jong Won; Gong, Gyungyub; Ryu, Jin-Sook; Oh, Seung Jun; Bacher-Stier, Claudia; Fels, Lüder; Koglin, Norman; Hultsch, Christina; Schatz, Christoph A; Dinkelborg, Ludger M; Mittra, Erik S; Gambhir, Sanjiv S; Moon, Dae Hyuk

    2012-10-01

    (4S)-4-(3-[(18)F]fluoropropyl)-l-glutamate (BAY 94-9392, alias [(18)F]FSPG) is a new tracer to image x(C)(-) transporter activity with positron emission tomography (PET). We aimed to explore the tumor detection rate of [(18)F]FSPG in patients relative to 2-[(18)F]fluoro-2-deoxyglucose ([(18)F]FDG). The correlation of [(18)F]FSPG uptake with immunohistochemical expression of x(C)(-) transporter and CD44, which stabilizes the xCT subunit of system x(C)(-), was also analyzed. Patients with non-small cell lung cancer (NSCLC, n = 10) or breast cancer (n = 5) who had a positive [(18)F]FDG uptake were included in this exploratory study. PET images were acquired following injection of approximately 300 MBq [(18)F]FSPG. Immunohistochemistry was done using xCT- and CD44-specific antibody. [(18)F]FSPG PET showed high uptake in the kidney and pancreas with rapid blood clearance. [(18)F]FSPG identified all 10 NSCLC and three of the five breast cancer lesions that were confirmed by pathology. [(18)F]FSPG detected 59 of 67 (88%) [(18)F]FDG lesions in NSCLC, and 30 of 73 (41%) in breast cancer. Seven lesions were additionally detected only on [(18)F]FSPG in NSCLC. The tumor-to-blood pool standardized uptake value (SUV) ratio was not significantly different from that of [(18)F]FDG in NSCLC; however, in breast cancer, it was significantly lower (P < 0.05). The maximum SUV of [(18)F]FSPG correlated significantly with the intensity of immunohistochemical staining of x(C)(-) transporter and CD44 (P < 0.01). [(18)F]FSPG seems to be a promising tracer with a relatively high cancer detection rate in patients with NSCLC. [(18)F]FSPG PET may assess x(C)(-) transporter activity in patients with cancer.

  5. The effects of optical phonon on the binding energy of bound polaron in a wurtzite ZnO/MgxZn1−xO quantum well

    International Nuclear Information System (INIS)

    Zhao, Feng-Qi; Guo, Zi-Zheng; Zhu, Jun

    2014-01-01

    An improved Lee-Low-Pines intermediate coupling method is used to study the energies and binding energies of bound polarons in a wurtzite ZnO/Mg x Zn 1−x O quantum well. The contributions from different branches of long-wave optical phonons, i.e., confined optical phonons, interface optical phonons, and half-space optical phonons are considered. In addition to electron-phonon interaction, the impurity-phonon interaction, and the anisotropy of material parameters, such as phonon frequency, electron effective mass, and dielectric constant, are also included in our computation. Ground-state energies, binding energies and detailed phonon contributions from various phonons as functions of well width, impurity position and composition are presented. Our result suggests that total phonon contribution to ground state and binding energies in the studied wurtzite ZnO/Mg 0.3 Zn 0.7 O quantum wells varies between 28–23 meV and 62–45 meV, respectively, which are much larger than the corresponding values (about 3.2–1.8 meV and 1.6–0.3 meV) in GaAs/Al 0.3 Ga 0.7 As quantum wells. For a narrower quantum well, the phonon contribution mainly comes from interface and half-space phonons, for a wider quantum well, most of phonon contribution originates from confined phonons. The contribution from all the phonon modes to binding energies increases slowly either when impurity moves far away from the well center in the z direction or with the increase in magnesium composition (x). It is found that different phonons have different influences on the binding energies of bound polarons. Furthermore, the phonon contributions to binding energies as functions of well width, impurity position, and composition are very different from one another. In general, the electron-optical phonon interaction and the impurity center-optical phonon interaction play an important role in electronic states of ZnO-based quantum wells and cannot be neglected.

  6. A Density Functional Theory Study of the Ionic and Electronic Transport Mechanisms in LiFeBO3 Battery Electrodes

    DEFF Research Database (Denmark)

    Loftager, Simon; García Lastra, Juan Maria; Vegge, Tejs

    2016-01-01

    electrochemical effects can be explained by an intrinsically low Li-ion and electron/hole-polaron mobility in Li0.5FeBO3 due to high activation barriers for both the ionic and electronic transport. These studies include the effects of the experimentally reported commensurate modulation. We have also investigated...... with the formation of intermediate phases is linked to the intrinsically poor properties of the Li0.5FeBO3 phase rather than to the presence of interfaces between different phases....

  7. Transport properties of Pb-doped Bi4Sr3Ca3Cu4Ox semiconducting glasses and glass-ceramic superconductors

    International Nuclear Information System (INIS)

    Chatterjee, S.; Banerjee, S.; Mollah, S.; Chaudhuri, B.K.

    1996-01-01

    Electrical conductivity and thermoelectric power (TEP) of the as-quenched and annealed (at 500 degree C for 10 h and 840 degree C for 24 h) Bi 4-n Pb n Sr 3 Ca 3 Cu 4 O x (x = 0 endash 1.0) glasses have been measured. The dc conductivity data of the as-quenched and the partially annealed (at 500 degree C) glasses can be explained by considering the small-polaron hopping conduction mechanism which is found to change from the nonadiabatic to the adiabatic regime with annealing the glasses at 500 degree C. This change over is due to the presence of microcrystals in the partially annealed glasses as observed from x-ray-diffraction and scanning electron microscopic studies. This adiabatic behavior is also visualized even for some as-quenched glasses having a very small amount of the more conducting microcrystalline phase. All the 840 degree C annealed glasses are superconductors with T c between 110 and 115 K. The Seebeck coefficient (S) of the partially annealed glass system is found to be positive and increases linearly with temperature. The S values of the corresponding glass-ceramic superconductors showing broad peaks around T c . A change over in the values of S from positive (below ∼290 K) to negative (above ∼290 K) indicates the coexistence of both electrons and holes in these superconductors. The TEP data can be fitted with both the two-band model of Forro et al. [Solid State Commun. 73, 501 (1990)] and the Nagaosa-Lee model [Phys. Rev. Lett. 64, 2450 (1990)]. Therefore, the bosonic contribution in the transport properties of these superconductors, as suggested by the Nagaosa-Lee model, is supported. copyright 1996 The American Physical Society

  8. Propagation effect on photoluminescence of spin-aligned high-density exciton magnetic polarons in Cd{sub 0.8}Mn{sub 0.2}Te

    Energy Technology Data Exchange (ETDEWEB)

    Nagata, M.; Hirase, T.; Miyajima, K., E-mail: miyajima@rs.tus.ac.jp

    2017-04-15

    Characteristics of photoluminescence (PL) originating from high-density exciton magnetic polarons (HD-EMPs) for Cd{sub 0.8}Mn{sub 0.2}Te were investigated. The PL appeared only under selective excitation of the localized excitons, and the intensity increased superlinearly with the excitation density. Directivity of the PL was revealed. Therefore, it is concluded that the superlinear increase in the PL intensity resulted from a light amplification process owing to the stimulated emission. In addition, the existence of birefringence that originates from a uniaxial gradation of the Mn ion concentrations was revealed. The degree of circular polarization (DOCP) of the PL is important to obtain the spin alignment state of the HD-EMPs. The initial DOCPs of the PL were examined by removing a variation of the polarization during propagation inside the sample. As a result, it was found that the initial DOCPs of the PL were almost constant for the photon energy. The obtained initial DOCPs exhibited different values for right- and left-circularly polarized excitations, which resulted from different mechanisms of the spin alignment of the HD-EMPs.

  9. Monte Carlo study of efficiency roll-off of phosphorescent organic light-emitting diodes: Evidence for dominant role of triplet-polaron quenching

    Energy Technology Data Exchange (ETDEWEB)

    Eersel, H. van, E-mail: h.v.eersel@tue.nl; Coehoorn, R. [Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven (Netherlands); Philips Research Laboratories, High Tech Campus 4, 5656 AE Eindhoven (Netherlands); Bobbert, P. A.; Janssen, R. A. J. [Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven (Netherlands)

    2014-10-06

    We present an advanced molecular-scale organic light-emitting diode (OLED) model, integrating both electronic and excitonic processes. Using this model, we can reproduce the measured efficiency roll-off for prototypical phosphorescent OLED stacks based on the green dye tris[2-phenylpyridine]iridium (Ir(ppy){sub 3}) and the red dye octaethylporphine platinum (PtOEP) and study the cause of the roll-off as function of the current density. Both the voltage versus current density characteristics and roll-off agree well with experimental data. Surprisingly, the results of the simulations lead us to conclude that, contrary to what is often assumed, not triplet-triplet annihilation but triplet-polaron quenching is the dominant mechanism causing the roll-off under realistic operating conditions. Simulations for devices with an optimized recombination profile, achieved by carefully tuning the dye trap depth, show that it will be possible to fabricate OLEDs with a drastically reduced roll-off. It is envisaged that J{sub 90}, the current density at which the efficiency is reduced to 90%, can be increased by almost one order of magnitude as compared to the experimental state-of-the-art.

  10. Monte Carlo study of efficiency roll-off of phosphorescent organic light-emitting diodes: Evidence for dominant role of triplet-polaron quenching

    International Nuclear Information System (INIS)

    Eersel, H. van; Coehoorn, R.; Bobbert, P. A.; Janssen, R. A. J.

    2014-01-01

    We present an advanced molecular-scale organic light-emitting diode (OLED) model, integrating both electronic and excitonic processes. Using this model, we can reproduce the measured efficiency roll-off for prototypical phosphorescent OLED stacks based on the green dye tris[2-phenylpyridine]iridium (Ir(ppy) 3 ) and the red dye octaethylporphine platinum (PtOEP) and study the cause of the roll-off as function of the current density. Both the voltage versus current density characteristics and roll-off agree well with experimental data. Surprisingly, the results of the simulations lead us to conclude that, contrary to what is often assumed, not triplet-triplet annihilation but triplet-polaron quenching is the dominant mechanism causing the roll-off under realistic operating conditions. Simulations for devices with an optimized recombination profile, achieved by carefully tuning the dye trap depth, show that it will be possible to fabricate OLEDs with a drastically reduced roll-off. It is envisaged that J 90 , the current density at which the efficiency is reduced to 90%, can be increased by almost one order of magnitude as compared to the experimental state-of-the-art.

  11. The FDG uptake and glucose transporter(GLUT-1) expression of the mediastinal nodes in the non-small cell lung cancer

    International Nuclear Information System (INIS)

    Baik, Hee Jong; Jung, Jin Haeng

    2000-12-01

    The aim of this study was to understand the mechanism of FDG uptake in the mediastinal nodes, and improve the accuracy of mediastinal staging of non-small cell lung cancer by PET. To evaluate factors determining the FDG uptake in mediastinal nodes, FDG-PET was performed preoperatively, and mediastinal dissection with pulmonary resection was done in 20 LSCLC patients. The GLUT-1 expression was studied by immunohistochemistry of paraffin-section from the mediastinal nodes(n=50, true positive 11, true negative 23, false positive 11, false negative 5) using the antiGLUT-1 antibody. The staining intensity of tumor(grade 0-4), percentage of tumor, level of follicular hyperplasia(grade 1-4), and staining intensity of follicle was also studied. The staining intensity of true positive nodes was higher than that of false negative group(Mann-Whitney test, P=0.07) in the metastased nodes. The level of follicular hyperplasia of false positive nodes was higher than that of true negative nodes in non-metastased nodes(P=0.02). This finding indicates that FN interpretation of mediastinal nodes by FDG-PET might be associated with low uptake of FDG due to low expression of GLUT-1, and that FP might be associated with high level of follicular hyperplasia as a reactive change to inflammatory and/or immune reaction

  12. Solute transport dynamics in small, shallow groundwater-dominated agricultural catchments: insights from a high-frequency, multisolute 10 yr-long monitoring study

    Directory of Open Access Journals (Sweden)

    A. H. Aubert

    2013-04-01

    stocking period and the dominant process that limits transport to the stream, i.e. the connectivity of the stocking compartment. This mechanistic classification can be applied to any chemical solute to help assess its origin, storage or production location and transfer mechanism in similar catchments.

  13. Flow behaviour, suspended sediment transport and transmission losses in a small (sub-bank-full) flow event in an Australian desert stream

    Science.gov (United States)

    Dunkerley, David; Brown, Kate

    1999-08-01

    The behaviour of a discrete sub-bank-full flow event in a small desert stream in western NSW, Australia, is analysed from direct observation and sediment sampling during the flow event and from later channel surveys. The flow event, the result of an isolated afternoon thunderstorm, had a peak discharge of 9 m3/s at an upstream station. Transmission loss totally consumed the flow over the following 7·6 km. Suspended sediment concentration was highest at the flow front (not the discharge peak) and declined linearly with the log of time since passage of the flow front, regardless of discharge variation. The transmission loss responsible for the waning and eventual cessation of flow occurred at a mean rate of 13.2% per km. This is quite rapid, and is more than twice the corresponding figure for bank-full flows estimated by Dunkerley (1992) on the same stream system. It is proposed that transmission losses in ephemeral streams of the kind studied may be minimized in flows near bank-full stage, and be higher in both sub-bank-full and overbank flows. Factors contributing to enhanced flow loss in the sub-bank-full flow studied included abstractions of flow to pools, scour holes and other low points along the channel, and overflow abstractions into channel filaments that did not rejoin the main flow. On the other hand, losses were curtailed by the shallow depth of banks wetted and by extensive mud drapes that were set down over sand bars and other porous channel materials during the flow. Thus, in contrast with the relatively regular pattern of transmission loss inferred from large floods, losses from low flows exhibit marked spatial variability and depend to a considerable extent on streamwise variations in channel geometry, in addition to the depth and porosity of channel perimeter sediments.

  14. Human peptide transporters

    DEFF Research Database (Denmark)

    Nielsen, Carsten Uhd; Brodin, Birger; Jørgensen, Flemming Steen

    2002-01-01

    Peptide transporters are epithelial solute carriers. Their functional role has been characterised in the small intestine and proximal tubules, where they are involved in absorption of dietary peptides and peptide reabsorption, respectively. Currently, two peptide transporters, PepT1 and PepT2, wh...

  15. Research using small tokamaks

    International Nuclear Information System (INIS)

    1993-01-01

    This document consists of a collection of papers presented at the IAEA Technical Committee Meeting on Research Using Small Tokamaks. It contains 22 papers on a wide variety of research aspects, including diagnostics, design, transport, equilibrium, stability, and confinement. Some of these papers are devoted to other concepts (stellarators, compact tori). Refs, figs and tabs

  16. Optical transition energy of magneto-polaron in a GaAs{sub 0.9}P{sub 0.1}/GaAs{sub 0.6}P{sub 0.4} quantum dot

    Energy Technology Data Exchange (ETDEWEB)

    Vinolin, Ada [Dept. of Physics, Madurai Kamaraj University College, Alagarkoil Road, Madurai-625002. India (India); Peter, A. John, E-mail: a.john.peter@gmail.com [Dept. of Physics, Govt. Arts College, Melur-625106. Madurai. India (India)

    2015-06-24

    Magneto-LO-polaron in a cylindrical GaAs{sub 0.9} P{sub 0.1} / GaAs{sub 0.6} P{sub 0.4} quantum dot is investigated taking into consideration of geometrical confinement effect. The effects of phonon on the exciton binding energy and the interband emission energy as a function of dot radius are found. The calculations are performed within the single band effective mass approximation using the variational method based on the Lee-Low-Pine LLP transformation.

  17. Suppression of roll-off characteristics of organic light-emitting diodes by narrowing current injection/transport area to 50 nm

    Energy Technology Data Exchange (ETDEWEB)

    Hayashi, Kyohei, E-mail: k-hayashi@bioorg.rcast.u-tokyo.ac.jp; Inoue, Munetomo; Yoshida, Kou [Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395 (Japan); Nakanotani, Hajime [Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395 (Japan); JST, ERATO, Adachi Molecular Exciton Engineering Project, c/o OPERA, Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395 (Japan); Innovative Organic Device Laboratory, Institute of Systems, Information Technologies and Nanotechnologies (ISIT), 744 Motooka, Nishi, Fukuoka 819-0395 (Japan); Mikhnenko, Oleksandr; Nguyen, Thuc-Quyen, E-mail: quyen@chem.ucsb.edu, E-mail: adachi@cstf.kyushu-u.ac.jp [Center for Polymers and Organic Solids, University of California, Santa Barbara, California 93106-9510 (United States); Adachi, Chihaya, E-mail: quyen@chem.ucsb.edu, E-mail: adachi@cstf.kyushu-u.ac.jp [Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395 (Japan); JST, ERATO, Adachi Molecular Exciton Engineering Project, c/o OPERA, Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395 (Japan); Innovative Organic Device Laboratory, Institute of Systems, Information Technologies and Nanotechnologies (ISIT), 744 Motooka, Nishi, Fukuoka 819-0395 (Japan); International Institute for Carbon Neutral Energy Research (WPI-I2CNER), Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395 (Japan)

    2015-03-02

    Using e-beam nanolithography, the current injection/transport area in organic light-emitting diodes (OLEDs) was confined into a narrow linear structure with a minimum width of 50 nm. This caused suppression of Joule heating and partial separation of polarons and excitons, so the charge density where the electroluminescent efficiency decays to the half of the initial value (J{sub 0}) was significantly improved. A device with a narrow current injection width of 50 nm exhibited a J{sub 0} that was almost two orders of magnitude higher compared with that of the unpatterned OLED.

  18. Structural, Transport and Electrochemical Properties of LiFePO4 Substituted in Lithium and Iron Sublattices (Al, Zr, W, Mn, Co and Ni)

    Science.gov (United States)

    Molenda, Janina; Kulka, Andrzej; Milewska, Anna; Zając, Wojciech; Świerczek, Konrad

    2013-01-01

    LiFePO4 is considered to be one of the most promising cathode materials for lithium ion batteries for electric vehicle (EV) application. However, there are still a number of unsolved issues regarding the influence of Li and Fe-site substitution on the physicochemical properties of LiFePO4. This is a review-type article, presenting results of our group, related to the possibility of the chemical modification of phosphoolivine by introduction of cation dopants in Li and Fe sublattices. Along with a synthetic review of previous papers, a large number of new results are included. The possibility of substitution of Li+ by Al3+, Zr4+, W6+ and its influence on the physicochemical properties of LiFePO4 was investigated by means of XRD, SEM/EDS, electrical conductivity and Seebeck coefficient measurements. The range of solid solution formation in Li1−3xAlxFePO4, Li1−4xZrxFePO4 and Li1−6xWxFePO4 materials was found to be very narrow. Transport properties of the synthesized materials were found to be rather weakly dependent on the chemical composition. The battery performance of selected olivines was tested by cyclic voltammetry (CV). In the case of LiFe1−yMyPO4 (M = Mn, Co and Ni), solid solution formation was observed over a large range of y (0 0.25 leads to considerably lower values of σ. The activated character of electrical conductivity with a rather weak temperature dependence of the Seebeck coefficient suggests a small polaron-type conduction mechanism. The electrochemical properties of LiFe1−yMyPO4 strongly depend on the Fe substitution level. PMID:28809235

  19. Structural, Transport and Electrochemical Properties of LiFePO4 Substituted in Lithium and Iron Sublattices (Al, Zr, W, Mn, Co and Ni

    Directory of Open Access Journals (Sweden)

    Konrad Świerczek

    2013-04-01

    Full Text Available LiFePO4 is considered to be one of the most promising cathode materials for lithium ion batteries for electric vehicle (EV application. However, there are still a number of unsolved issues regarding the influence of Li and Fe-site substitution on the physicochemical properties of LiFePO4. This is a review-type article, presenting results of our group, related to the possibility of the chemical modification of phosphoolivine by introduction of cation dopants in Li and Fe sublattices. Along with a synthetic review of previous papers, a large number of new results are included. The possibility of substitution of Li+ by Al3+, Zr4+, W6+ and its influence on the physicochemical properties of LiFePO4 was investigated by means of XRD, SEM/EDS, electrical conductivity and Seebeck coefficient measurements. The range of solid solution formation in Li1−3xAlxFePO4, Li1−4xZrxFePO4 and Li1−6xWxFePO4 materials was found to be very narrow. Transport properties of the synthesized materials were found to be rather weakly dependent on the chemical composition. The battery performance of selected olivines was tested by cyclic voltammetry (CV. In the case of LiFe1−yMyPO4 (M = Mn, Co and Ni, solid solution formation was observed over a large range of y (0 0.25 leads to considerably lower values of σ. The activated character of electrical conductivity with a rather weak temperature dependence of the Seebeck coefficient suggests a small polaron-type conduction mechanism. The electrochemical properties of LiFe1−yMyPO4 strongly depend on the Fe substitution level.

  20. Small transport aircraft technology propeller study

    Science.gov (United States)

    Black, B. M.; Magliozzi, B.; Rohrbach, C.

    1983-01-01

    A study to define potential benefits of advanced technology propeller for 1985-1990 STAT commuter airplanes was completed. Two baselines, a Convair, 30 passenger, 0.47 Mach number airplane and a Lockheed, 50 passenger, 0.70 Mach number airplane, were selected from NASA-Ames sponsored airframe contracts. Parametric performance, noise level, weight and cost trends for propellers with varying number of blades, activity factor, camber and diameter incorporating blade sweep, tip proplets, advanced composite materials, advanced airfoils, advanced prevision synchrophasing and counter-rotation are presented. The resulting DOC, fuel burned, empty weight and acquisition cost benefits are presented for resizings of the two baseline airplanes. Six-bladed propeller having advanced composite blades, advanced airfoils, tip proplets and advanced prevision synchrophasers provided the maximum DOC improvements for both airplanes. DOC and fuel burned were reduced by 8.3% and 17.0% respectively for the Convair airplane and by 24.9% and 41.2% respectively for the Lockheed airplane. The larger reductions arose from a baseline definition with very heavy fuselage acoustic treatment. An alternate baseline, with a cabin noise 13dB in excess of the objective, was also studied.

  1. Small Data

    NARCIS (Netherlands)

    S. Pemberton (Steven)

    2014-01-01

    htmlabstractThe term “Open Data” often goes hand in hand with the term “Big Data”, where large data sets get released allowing for analysis, but the Cinderella of the Open Data ball is Small Data, small amounts of data, nonetheless possibly essential, that are too small to be put in some database or

  2. Photophysical properties of novel small acceptor molecules and their application in hybrid small-molecular/polymeric organic solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Inal, Sahika; Castellani, Mauro; Neher, Dieter [Universitaet Potsdam, Institut fuer Physik und Astronomie, Potsdam-Golm (Germany); Sellinger, Alan [Institute of Materials Research and Engineering, Singapore (Singapore)

    2009-07-01

    Recent experimental investigations revealed that the photovoltaic properties of our devices are related to the balance between recombination and field-induced dissociation of interfacial excited states such as exciplexes or geminate polaron pairs. This balance was shown to be affected by the nanomorphology at the heterojunction. We have analyzed the photophysical properties of a new materials couple comprising an electron-donating PPV copolymer and a vinazene-based small molecule acceptor. Steady state and time-resolved photoluminescence (PL) spectroscopy in solution and in the solid state showed the formation of excimers within the acceptor. The associated long-range diffusion promise efficient energy harvesting at the heterojunction. On the other hand, blends of the PPV-derivative and the small molecule revealed strong exciplex formation. Therefore, bilayered hybrid small-molecular/polymeric solar cells have been fabricated by consequently spin-coating the macromolecular donor and the small molecule acceptor from two different solvents. The bilayer architecture limits recombination processes enabling high FFs of around 44% and a technologically important open circuit voltage of 1Volt.

  3. Transport properties of La 1- xSr xCoO 3- δ films (0.15⩽ x⩽0.5)

    Science.gov (United States)

    Prokhorov, G.; Kaminsky, G. G.; Kravchenko, I. I.; Lee, Y. P.

    2002-11-01

    The magnetic and transport properties of La 1- xSr xCoO 3 films prepared by laser ablation have been investigated. The metal-insulator transition was observed in the films with decreasing Sr 2+ concentration (if x⩽0.25). Analysis of the experimental results revealed that the transport of carriers in the metallic state is governed by electron-electron scattering if the nature of a small energy gap in the spectrum of electron excitations is taken into account. An oxygen deficiency in the aged La 0.5Sr 0.5CoO 3- δ film leads not only to a change in the Co 3+/Co 4+ ratio, but also to a structural disorder in the Co-O-Co conduction channel due to the accumulated oxygen vacancies. A growth of the resistivity with decreasing temperature for the aged La 0.5Sr 0.5CoO 3- δ film is explained in the framework of the Coulomb-interaction model. Analysis of ρ( T) data shows that the transport of carriers at high temperatures (above the temperature of magnetic transition) in the insulating state ( x⩽0.25) is governed by the Mott-like variable-range hopping (VRH) rather than motion of the lattice polarons. However, the VRH model needs to be modified for compounds of this type. The ρ( T) dependence is fairly described based on the two parallel-resistor model in the low-temperature range, where one resistor corresponds to the ferromagnetic metal-cluster network and the other to the insulating matrix (IM). Two mechanisms of magnetoresistance (MR) are involved in the investigated films. In the metallic state ( x>0.25) the MR is provided by a change in the electron scattering rate, influenced by the magnetic field. This process is reflected in the MR temperature dependence as a small peak at the Curie temperature. In the insulating state ( x⩽0.25) the phase separation into the ferromagnetic metallic clusters and the IM is formed and an applied magnetic field induces a growth of the ferromagnetic metallic phase that can be possibly described by the double-exchange mechanism.

  4. Impact of D2O/H2O Solvent Exchange on the Emission of HgTe and CdTe Quantum Dots: Polaron and Energy Transfer Effects.

    Science.gov (United States)

    Wen, Qiannan; Kershaw, Stephen V; Kalytchuk, Sergii; Zhovtiuk, Olga; Reckmeier, Claas; Vasilevskiy, Mikhail I; Rogach, Andrey L

    2016-04-26

    We have studied light emission kinetics and analyzed carrier recombination channels in HgTe quantum dots that were initially grown in H2O. When the solvent is replaced by D2O, the nonradiative recombination rate changes highlight the role of the vibrational degrees of freedom in the medium surrounding the dots, including both solvent and ligands. The contributing energy loss mechanisms have been evaluated by developing quantitative models for the nonradiative recombination via (i) polaron states formed by strong coupling of ligand vibration modes to a surface trap state (nonresonant channel) and (ii) resonant energy transfer to vibration modes in the solvent. We conclude that channel (i) is more important than (ii) for HgTe dots in either solution. When some of these modes are removed from the relevant spectral range by the H2O to D2O replacement, the polaron effect becomes weaker and the nonradiative lifetime increases. Comparisons with CdTe quantum dots (QDs) served as a reference where the resonant energy loss (ii) a priori was not a factor, also confirmed by our experiments. The solvent exchange (H2O to D2O), however, is found to slightly increase the overall quantum yield of CdTe samples, probably by increasing the fraction of bright dots in the ensemble. The fundamental study reported here can serve as the foundation for the design and optimization principles of narrow bandgap quantum dots aimed at applications in long wavelength colloidal materials for infrared light emitting diodes and photodetectors.

  5. Small Data

    OpenAIRE

    Pemberton, Steven

    2014-01-01

    htmlabstractThe term “Open Data” often goes hand in hand with the term “Big Data”, where large data sets get released allowing for analysis, but the Cinderella of the Open Data ball is Small Data, small amounts of data, nonetheless possibly essential, that are too small to be put in some database or online dataset to be put to use. RDFa is a technology that allows Cinderella to go to the ball.

  6. Radiation Transport

    Energy Technology Data Exchange (ETDEWEB)

    Urbatsch, Todd James [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2015-06-15

    We present an overview of radiation transport, covering terminology, blackbody raditation, opacities, Boltzmann transport theory, approximations to the transport equation. Next we introduce several transport methods. We present a section on Caseology, observing transport boundary layers. We briefly broach topics of software development, including verification and validation, and we close with a section on high energy-density experiments that highlight and support radiation transport.

  7. Chamber transport

    International Nuclear Information System (INIS)

    Olson, Craig L.

    2001-01-01

    Heavy ion beam transport through the containment chamber plays a crucial role in all heavy ion fusion (HIF) scenarios. Here, several parameters are used to characterize the operating space for HIF beams; transport modes are assessed in relation to evolving target/accelerator requirements; results of recent relevant experiments and simulations of HIF transport are summarized; and relevant instabilities are reviewed. All transport options still exist, including (1) vacuum ballistic transport, (2) neutralized ballistic transport, and (3) channel-like transport. Presently, the European HIF program favors vacuum ballistic transport, while the US HIF program favors neutralized ballistic transport with channel-like transport as an alternate approach. Further transport research is needed to clearly guide selection of the most attractive, integrated HIF system

  8. Small hydro

    International Nuclear Information System (INIS)

    Bennett, K.; Tung, T.

    1995-01-01

    A small hydro plant in Canada is defined as any project between 1 MW and 15 MW but the international standard is 10 MW. The global market for small hydro development was considered good. There are some 1000 to 2000 MW of generating capacity being added each year. In Canada, growth potential is considered small, primarily in remote areas, but significant growth is anticipated in Eastern Europe, Africa and Asia. Canada with its expertise in engineering, manufacturing and development is considered to have a good chance to take advantage of these growing markets

  9. Transport Nuclear Liability Insurance

    International Nuclear Information System (INIS)

    Folens, M.

    2006-01-01

    Although transport of nuclear substances represents only a very small part of the global transport of dangerous goods, it takes place every day all over the world and it is part of our daily life. Transport of nuclear material takes also place at every stage of the nuclear fuel cycle; radioactive materials are carried out all over the world by all major modes of transport: sea, air, road and rail. Despite the large number of nuclear transports, they are not considered as posing a serious risk. A major nuclear incident is almost always associated with the operating of fixed installations such as nuclear power plants; just think about Three Mile Island and Chernobyl. This perception is strengthened by the absence so far of serious accidents in the nuclear transport sector and this finding is in fact proof of the very safe conditions of nuclear transport. But accidents can never be excluded entirely and in some cases damages could be as large as those caused by fixed installations. This means that protection of the interests of possible victims should also be covered in a correct way. That is why the special nuclear liability regime has also been developed to cover damage caused by a nuclear transport accident. As stated by Patrick Reyners, the prime motivation for originally adopting a special nuclear regime was the harmonisation of national legislation and that nowhere more than in the field of international transport operations is such harmonisation felt desirable . The international legal regime has been developed along two tracks, one based on the mode of transport and the other based on the notion of dangerous goods. The linkage between those two tracks is of permanent concern and the mode of transport is the key element to determine which international instrument should be applicable. The purpose of this paper is to briefly introduce the financial security provided by the insurance industry to cover the international nuclear liability regime for nuclear

  10. Comparative Study of Magnetic Ordering and Electrical Transport in Bulk and Nano-Grained Nd{sub 0.67}Sr{sub 0.33}MnO{sub 3} Manganites

    Energy Technology Data Exchange (ETDEWEB)

    Arun, B. [Materials Science and Technology Division, CSIR-National Institute for Interdisciplinary Science and Technology, Trivandrum (India); Academy of Scientific and Innovative Research (AcSIR), CSIR, Trivandrum (India); Suneesh, M.V. [Materials Science and Technology Division, CSIR-National Institute for Interdisciplinary Science and Technology, Trivandrum (India); Vasundhara, M., E-mail: vasu.mutta@gmail.com [Materials Science and Technology Division, CSIR-National Institute for Interdisciplinary Science and Technology, Trivandrum (India)

    2016-11-15

    We have prepared bulk and nano-sized Nd{sub 0.67}Sr{sub 0.33}MnO{sub 3} manganites by solid state and low-temperature mild solgel methods respectively. Both the compounds crystallized into an orthorhombic structure with Pbnm space group confirmed from Rietveld refinement of X-ray powder diffraction patterns. Nano-grained compound shows an average particle size of 22 nm with broad grain size distribution revealed from the Transmission electron micrographs. It appeared that the long range ferromagnetic order becomes unstable upon the reduction of the samples dimension down to nano meter scale. DC magnetization and AC susceptibility results showed frustration of spins in nano-grained compound and thereby it could lead to a cluster glass-like behaviour. Temperature dependence of electrical resistivity under different magnetic fields shows the broad maxima at higher temperatures and a low temperature upturn in both the compounds, however, the latter is more prominent in the nano grained compound. Combination of Kondo effect with electron and phonon interactions govern the low temperature resistivity and a small polaron hopping mechanism dominates at high temperatures for both the compounds. The magnetoresistance is understood by the effect of spin polarized tunneling through the grain boundary. The experimental results revealed that the reduction in particle size influences severely on the magnetic, electrical and magneto transport properties. - Highlights: • Long range ferromagnetic ordered state become unstable in case of nano compound. • It shows broad magnetic transition and cluster glass nature. • Kondo effect with electron-phonon interactions dominate the resistivity at low temperature.

  11. Role of Li2O2@Li2CO3 Interfaces on Charge Transport in Nonaqueous Li−Air Batteries

    DEFF Research Database (Denmark)

    Mekonnen, Yedilfana Setarge; García Lastra, Juan Maria; Hummelshøj, Jens S.

    2015-01-01

    The formation and oxidation of the main discharge product in nonaqueous secondary Li−O2 batteries, that is, Li2O2, has been studied intensively, but less attention has been given to the formation of cathode−electrolyte interfaces, which can significantly influence the performance of the Li−O2...... battery. Here we apply density functional theory with the Hubbard U correction (DFT+U) and nonequilibrium Green’s function (NEGF) methods to investigate the role of Li2O2@Li2CO3 interface layers on the ionic and electronic transport properties at the oxygen electrode. We show that, for example, lithium...... vacancies accumulate at the peroxide part of the interface during charge, reducing the coherent electron transport by two to three orders of magnitude compared with pristine Li2O2. During discharge, Li2O2@Li2CO3 interfaces may, however, provide an alternative in-plane channel for fast electron polaron...

  12. Transport phenomena

    International Nuclear Information System (INIS)

    Kirczenow, G.; Marro, J.

    1974-01-01

    Some simple remarks on the basis of transport theory. - Entropy, dynamics and scattering theory. - Response, relaxation and fluctuation. - Fluctuating hydrodynamics and renormalization of susceptibilities and transport coefficients. - Irreversibility of the transport equations. - Ergodic theory and statistical mechanics. - Correlation functions in Heisenberg magnets. - On the Enskog hard-sphere kinetic eqquation and the transport phenomena of dense simple gases. - What can one learn from Lorentz models. - Conductivity in a magnetic field. - Transport properties in gases in presence of external fields. - Transport properties of dilute gases with internal structure. (orig.) [de

  13. Native Small Airways Secrete Bicarbonate

    OpenAIRE

    Shamsuddin, A. K. M.; Quinton, Paul M.

    2014-01-01

    Since the discovery of Cl− impermeability in cystic fibrosis (CF) and the cloning of the responsible channel, CF pathology has been widely attributed to a defect in epithelial Cl− transport. However, loss of bicarbonate (HCO3−) transport also plays a major, possibly more critical role in CF pathogenesis. Even though HCO3− transport is severely affected in the native pancreas, liver, and intestines in CF, we know very little about HCO3− secretion in small airways, the principle site of morbidi...

  14. Neurotransmitter transporters

    DEFF Research Database (Denmark)

    Gether, Ulrik; Andersen, Peter H; Larsson, Orla M

    2006-01-01

    The concentration of neurotransmitters in the extracellular space is tightly controlled by distinct classes of membrane transport proteins. This review focuses on the molecular function of two major classes of neurotransmitter transporter that are present in the cell membrane of neurons and....... Recent research has provided substantial insight into the structure and function of these transporters. In particular, the recent crystallizations of bacterial homologs are of the utmost importance, enabling the first reliable structural models of the mammalian neurotransmitter transporters...

  15. Analysis of Proton Transport Experiments.

    Science.gov (United States)

    1980-09-05

    which can inhibit transport, may grow . The abrupt loss of transport at higher currents in the small channel suggests this possibility. Future experiments... Unicorn Park Drive Woburn, MA 01801 Attn: H. Linnerud 1 copy Lawrence Livermore Laboratory P. 0. Box 808 Livermore, CA 94550 Attn: R. J. Briggs 1 copy R

  16. Sustainable Transportation

    DEFF Research Database (Denmark)

    Hall, Ralph P.; Gudmundsson, Henrik; Marsden, Greg

    2014-01-01

    The transportation system is the backbone of economic and social progress and the means by which humans access goods and services and connect with one another. Yet, as the scale of transportation activities has grown worldwide, so too have the negative environmental, social, and economic impacts...... that relate to the construction and maintenance of transportation infrastructure and the operation or use of the different transportation modes. The concept of sustainable transportation emerged in response to these concerns as part of the broader notion of sustainable development. Given the transportation...... sector’s significant contribution to global challenges such as climate change, it is often said that sustainable development cannot be achieved without sustainable transportation....

  17. Environmental assessment of freight transportation

    Energy Technology Data Exchange (ETDEWEB)

    Flodstroem, E. [MariTerm AB, Goeteborg (Sweden)

    1998-04-01

    This report is a short version in English of two reports in Swedish: KFB report 1994:6 `Environmental effects of change of transport mode for goods transportation` and `Combining of transport models` which was performed as a commission for the Swedish environmental protection agency. The aim of both studies is to investigate the environmental effects of political measures to transfer goods from one transport mode to another. To be able to calculate the environmental effects a method to follow the transport chains has been developed. By defining the transport chains with a main transport mode it has been possible to relate the emissions to the different modes. The main results are that the transferable volumes are limited and even if a maximum volume is transferred, the positive environmental effects are small compared to the effects of measures to reduce the emissions from the vehicles 3 refs, 22 figs, 34 tabs

  18. Transcellular transport of calcium

    Energy Technology Data Exchange (ETDEWEB)

    Terepka, A R; Coleman, J R; Armbrecht, H J; Gunter, T E

    1976-01-01

    Studies of two calcium transporting epithelia, embryonic chick chorioallantoic membrane and the small intestine of rat and chick, have strongly suggested that the transfer of calcium across a cell involves processes distinctly different from intracellular calcium ion regulation. In the proposed model, transcellular calcium transport is considered as a specialized process developed only by certain cells in those tissues charged with bulk transfer of calcium. The overall effect of the endocytotic mechanism is bulk calcium movement across a cell, protection of mitochondria from exposure to high concentrations of calcium, and the avoidance of wide and potentially toxic fluctuations in cytosol ionic calcium levels. (MFB)

  19. Magneto-transport and thermoelectric properties of La0.8-xBixCa0.2MnO3 manganites

    International Nuclear Information System (INIS)

    Manjunatha, S.O.; Rao, Ashok

    2015-01-01

    In the present work, we report the studies on the magneto-transport and thermoelectric properties of La 0.8-x Bi x Ca 0.2 MnO 3 (x = 0.00, 0.05, 0.10) manganites. The samples were prepared using the conventional solid state reaction method. Structural characterization has done using XRD. Rietveld refinement technique has confirmed the single phase formation of the samples with no impurity peaks observed within experimental limits. SEM micrograph confirms the formation of grains with good intimacy. The cell parameters and the unit cell volume is observed to decrease with increasing Bi concentration. It is attributed to the smaller ionic size of Bi compare to La. Magneto-resistance of the samples are measured using standard four probe technique. The Metal-Insulator transition (TMI) is found to decrease upon doping with overall increase in the resistivity. The observed effect is due to the fact that the Ca ions possibly increases the tendency of screening of 6s 2 orbital of Bi 3+ ions. As orientation of the 6s 2 lone pair toward a surrounding anion (O 2- ) produces a local distortion and as a result, the movement of eg electrons through the Mn-O-Mn bridges, is severely reduced. Resistance of the samples is observed to reduce on application of magnetic field of 8Tesla due to the fact that the magnetic field induces spin alignment and suppress the spin fluctuation resulting in large decrease in resistance. Thermopower measurement shows that all the samples are exhibiting the anomaly of phase transition from metal like behavior in low temperature to insulator like behavior at high temperature. As the temperature increases from 5K the pristine sample exhibit a small positive and nearly constant value of S till 172K. Then the value of S start to increase sharply and reaches a maximum value of ≈41μV/K at 234K and decreases rather sharply on further increase in temperature. The analysis of thermoelectric power data confirmed the validity of small polaron type conduction

  20. Nuclear transport

    International Nuclear Information System (INIS)

    Anon.

    2003-01-01

    During january and february 2003, a unique event concerning nuclear transport was reported and rated 1 on the INES scale. This event concerns the absence of a maintenance operation on a shipping cask. This shipping cask was used for several years for nuclear transport inside La-hague site before being re-assigned to transport on public thoroughfare. The re-assignment of the cask should have been preceded and conditioned by a maintenance operation whose purpose is to check the efficiency of its radiation shield. During this period 2 on-site inspections concerning the transport of nuclear materials were performed. (A.C.)

  1. Ocean transportation

    National Research Council Canada - National Science Library

    Frankel, Ernst G; Marcus, Henry S

    1973-01-01

    .... This analysis starts with a review of ocean transportation demand and supply including projections of ship capacity demand and world shipbuilding capacity under various economic and political assumptions...

  2. Rural Public Transportation: An Instructional Module.

    Science.gov (United States)

    Hayden, Linda

    A concept-based introduction to rural public transportation is provided in this instructional module for undergraduate and graduate transportation-related courses for disciplines such as engineering, business, sociology, and technology. Rural public transportation involves systems in rural and small urban areas with populations under 50,000…

  3. Magneto-transport properties of La{sub 0.75}Ca{sub 0.15}Sr{sub 0.1}MnO{sub 3} with YBa{sub 2}Cu{sub 3}O{sub 7–δ} addition

    Energy Technology Data Exchange (ETDEWEB)

    Zghal, E. [Laboratoire de Physique des Matériaux, Université de Sfax, Faculté des Sciences de Sfax, B. P. 1171, 3000 Sfax (Tunisia); Koubaa, M., E-mail: mohamedkoubaa@yahoo.fr [Laboratoire de Physique des Matériaux, Université de Sfax, Faculté des Sciences de Sfax, B. P. 1171, 3000 Sfax (Tunisia); Berthet, P. [Institut de Chimie Moléculaire et Matériaux d’Orsay, Bâtiment 410 Université Paris-Sud XI, 15 rue Georges Clémenceau, 91405 Orsay Cedex (France); Sicard, L. [ITODYS, Université Paris Diderot, CNRS UMR 7086, 15 rue Jean Antoine de Baïf, 75205 Paris (France); Cheikhrouhou-Koubaa, W. [Laboratoire de Physique des Matériaux, Université de Sfax, Faculté des Sciences de Sfax, B. P. 1171, 3000 Sfax (Tunisia); Decorse-Pascanut, C. [Institut de Chimie Moléculaire et Matériaux d’Orsay, Bâtiment 410 Université Paris-Sud XI, 15 rue Georges Clémenceau, 91405 Orsay Cedex (France); Cheikhrouhou, A. [Laboratoire de Physique des Matériaux, Université de Sfax, Faculté des Sciences de Sfax, B. P. 1171, 3000 Sfax (Tunisia); and others

    2016-09-15

    We report the structural, magnetic, electrical and magentoresistance properties of (La{sub 0.75}Ca{sub 0.15}Sr{sub 0.1}MnO{sub 3}){sub 1−x}(YBa{sub 2}Cu{sub 3}O{sub 7−δ}){sub x} (with x=0, 0.025, 0.05, 0.075, 0.1, 0.2, and 0.3) composites synthesized through sol–gel method. The powder X-ray diffraction patterns indicate no evidence of reaction between La{sub 0.75}Ca{sub 0.15}Sr{sub 0.1}MnO{sub 3} (LCSMO) and YBa{sub 2}Cu{sub 3}O{sub 7−δ} (YBCO). The addition of YBCO induces a reduction of the total magnetization while the Curie temperature remains almost constant (∼312 K). The behavior of the electrical resistivity evolves differently depending on the doping level. Above the paramagnetic–insulating transition temperature the resistivity data were best-fitted by using the adiabatic small polaron and variable range hopping models. Ferromagnetic–metallic regime in the composites seems to emanate from the electron–phonon or/and electron–magnon scattering processes. With increasing the YBCO doping content (until x=0.1), the positive magnetoresistance (MR) of YBCO phase dominates the negative MR of LCSMO one, which gives rise to the decreasing of MR of the composites. - Highlights: • LCSMO compound possess an orthorhombic-distorted structure (Pbnm space group). • YBCO crystallizes in orthorhombic structure (Pmmm space group). • Resistivity increases with increasing YBCO content in LCSMO/YBCO composites. • A detailed analysis of the transport mechanisms. • Coexistence of positive and negative MR in the composites.

  4. Small talk

    Directory of Open Access Journals (Sweden)

    Ryszard Przybylski

    2016-12-01

    Full Text Available The poem Small talk conjures up a communicative situation in which the main character, a newcomer from Poland, answers conventional questions related to their country. Bearing in mind the fact that this poem is set during a military dictatorship, superficial interest in his homeland may trigger a feeling of impatience. This is at least the impression formed if we adopt the perspective defined within the romantic tradition, and when taking into account the conventional poetry of martial law in Poland. Nevertheless, Barańczak retains an ironic distance towards such communicative situations and, as a consequence, does not create poetry that meets most readersʼ expectations. His poetic imperative for verbal art to be the expression of mistrust remains valid.

  5. Small Composers

    DEFF Research Database (Denmark)

    Holgersen, Sven-Erik; Bruun, Peter; Tjagvad, Mette

    2018-01-01

    the study: What expectations do the class teacher and the professional musicians have to the creative practice, i.e. to the collaboration and to the musical outcome? To which extent do the collaborating partners share a common understanding of the aim, content and method of the workshop? How do the roles......The present chapter discusses roles and responsibilities of the collaborating partners in a creative music workshop called Small Composers. The aim is to be attentive to a number of potential alterations implicated by the collaborating partners’ different backgrounds. The following questions guided...... and responsibilities of the collaborating partners become visible through the practice? How do the professional identities of the teacher and the musicians become visible and what are the implications for the workshop as a musical community of practice?...

  6. Stochastic models of intracellular transport

    KAUST Repository

    Bressloff, Paul C.

    2013-01-09

    The interior of a living cell is a crowded, heterogenuous, fluctuating environment. Hence, a major challenge in modeling intracellular transport is to analyze stochastic processes within complex environments. Broadly speaking, there are two basic mechanisms for intracellular transport: passive diffusion and motor-driven active transport. Diffusive transport can be formulated in terms of the motion of an overdamped Brownian particle. On the other hand, active transport requires chemical energy, usually in the form of adenosine triphosphate hydrolysis, and can be direction specific, allowing biomolecules to be transported long distances; this is particularly important in neurons due to their complex geometry. In this review a wide range of analytical methods and models of intracellular transport is presented. In the case of diffusive transport, narrow escape problems, diffusion to a small target, confined and single-file diffusion, homogenization theory, and fractional diffusion are considered. In the case of active transport, Brownian ratchets, random walk models, exclusion processes, random intermittent search processes, quasi-steady-state reduction methods, and mean-field approximations are considered. Applications include receptor trafficking, axonal transport, membrane diffusion, nuclear transport, protein-DNA interactions, virus trafficking, and the self-organization of subcellular structures. © 2013 American Physical Society.

  7. Neutron transport

    International Nuclear Information System (INIS)

    Berthoud, Georges; Ducros, Gerard; Feron, Damien; Guerin, Yannick; Latge, Christian; Limoge, Yves; Santarini, Gerard; Seiler, Jean-Marie; Vernaz, Etienne; Coste-Delclaux, Mireille; M'Backe Diop, Cheikh; Nicolas, Anne; Andrieux, Catherine; Archier, Pascal; Baudron, Anne-Marie; Bernard, David; Biaise, Patrick; Blanc-Tranchant, Patrick; Bonin, Bernard; Bouland, Olivier; Bourganel, Stephane; Calvin, Christophe; Chiron, Maurice; Damian, Frederic; Dumonteil, Eric; Fausser, Clement; Fougeras, Philippe; Gabriel, Franck; Gagnier, Emmanuel; Gallo, Daniele; Hudelot, Jean-Pascal; Hugot, Francois-Xavier; Dat Huynh, Tan; Jouanne, Cedric; Lautard, Jean-Jacques; Laye, Frederic; Lee, Yi-Kang; Lenain, Richard; Leray, Sylvie; Litaize, Olivier; Magnaud, Christine; Malvagi, Fausto; Mijuin, Dominique; Mounier, Claude; Naury, Sylvie; Nicolas, Anne; Noguere, Gilles; Palau, Jean-Marc; Le Pallec, Jean-Charles; Peneliau, Yannick; Petit, Odile; Poinot-Salanon, Christine; Raepsaet, Xavier; Reuss, Paul; Richebois, Edwige; Roque, Benedicte; Royer, Eric; Saint-Jean, Cyrille de; Santamarina, Alain; Serot, Olivier; Soldevila, Michel; Tommasi, Jean; Trama, Jean-Christophe; Tsilanizara, Aime; Behar, Christophe; Provitina, Olivier; Lecomte, Michael; Forestier, Alain; Bender, Alexandra; Parisot, Jean-Francois; Finot, Pierre

    2013-10-01

    This bibliographical note presents a reference book which addresses the study of neutron transport in matter, the study of conditions for a chain reaction and the study of modifications of matter composition due to nuclear reactions. This book presents the main nuclear data, their measurement, assessment and processing, and the spallation. It proposes an overview of methods applied for the study of neutron transport: basic equations and their derived forms, deterministic methods and Monte Carlo method of resolution of the Boltzmann equation, methods of resolution of generalized Bateman equations, methods of time resolution of space kinetics coupled equations. It presents the main calculation codes, discusses the qualification and experimental aspects, and gives an overview of neutron transport applications: neutron transport calculation of reactors, neutron transport coupled with other disciplines, physics of fuel cycle, criticality

  8. Transport Phenomena in Gel

    Directory of Open Access Journals (Sweden)

    Masayuki Tokita

    2016-05-01

    Full Text Available Gel becomes an important class of soft materials since it can be seen in a wide variety of the chemical and the biological systems. The unique properties of gel arise from the structure, namely, the three-dimensional polymer network that is swollen by a huge amount of solvent. Despite the small volume fraction of the polymer network, which is usually only a few percent or less, gel shows the typical properties that belong to solids such as the elasticity. Gel is, therefore, regarded as a dilute solid because its elasticity is much smaller than that of typical solids. Because of the diluted structure, small molecules can pass along the open space of the polymer network. In addition to the viscous resistance of gel fluid, however, the substance experiences resistance due to the polymer network of gel during the transport process. It is, therefore, of importance to study the diffusion of the small molecules in gel as well as the flow of gel fluid itself through the polymer network of gel. It may be natural to assume that the effects of the resistance due to the polymer network of gel depends strongly on the network structure. Therefore, detailed study on the transport processes in and through gel may open a new insight into the relationship between the structure and the transport properties of gel. The two typical transport processes in and through gel, that is, the diffusion of small molecules due to the thermal fluctuations and the flow of gel fluid that is caused by the mechanical pressure gradient will be reviewed.

  9. Animal Transports

    Directory of Open Access Journals (Sweden)

    Diana Ludrovcová

    2016-08-01

    Full Text Available Purpose and Originality: The research is aimed to the animal transports issue, from two points of view – first is the animal cruelty and second is the policy and economic consideration. The goal is to acquaint the readers with the transports risks and its cruelty and evaluation of the economic, political aspects for he involved countries. The study is oriented on more points of view, what is rare in works with a similar theme. Method: This paper examines many issues and examinations from different authors and subsequently summarized the findings with authors own knowledge to one expanded unit. Results: Results proves, that livestock transports have negative impact on animal´s health, environment. Number of transported animals is rising every year. Society: Research familiarize the society with the animal transports, cruelty against animals during them, and influence of transports on some countries, their economy, policy. People get better informed and can form their own opinion on this topic. They may start acting, undertaking some steps to improve the present situation, what could help a lot to animals and environment. Limitations / further research: Future research could show progress and improvement of transports, quality of food supply and economics.

  10. Water Transport Mediated by Other Membrane Proteins.

    Science.gov (United States)

    Huang, Boyue; Wang, Hongkai; Yang, Baoxue

    2017-01-01

    Water transport through membrane is so intricate that there are still some debates. (Aquaporins) AQPs are entirely accepted to allow water transmembrane movement depending on osmotic gradient. Cotransporters and uniporters , however, are also concerned in water homeotatsis. Urea transporter B (UT-B) has a single-channel water permeability that is similar to AQP1. Cystic fibrosis transmembrane conductance regulator (CFTR ) was initially thought as a water channel but now not believed to transport water directly. By cotranporters, water is transported by water osmosis coupling with substrates, which explains how water is transported across the isolated small intestine. This chapter provides information about water transport mediated by other membrane proteins except AQPs .

  11. Thermal transport in cuprates, cobaltates, and manganites

    International Nuclear Information System (INIS)

    Berggold, K.

    2006-09-01

    The subject of this thesis is the investigation of the thermal transport properties of three classes of transition-metal oxides: Cuprates, cobaltates, and manganites. The layered cuprates R 2 CuO 4 with R=La, Pr, Nd, Sm, Eu, and Gd show an anomalous thermal conductivity κ. Two maxima of κ are observed as a function of temperature for a heat current within the CuO 2 planes, whereas for a heat current perpendicular to the CuO 2 planes only a conventional phononic low-temperature maximum of κ is present. Evidence is provided that the high-temperature maximum is caused by heat-carrying excitations on the CuO 2 square lattice. Moreover, it is shown that the complex low-temperature and magnetic-field behavior of κ in Nd 2 CuO 4 is most likely caused by additional phonon scattering rather than by heat-carrying Nd magnons, as it was proposed in the literature. In the cobaltates RCoO 3 with R=La, Pr, Nd, and Eu, a temperature-induced spin-state transition of the Co 3+ ions occurs. It is shown that the additional lattice disorder caused by the random distribution of populated higher spin states causes a large suppression of the thermal conductivity of LaCoO 3 for T>25 K. The effect is much weaker in PrCoO 3 and NdCoO 3 due to the increased spin gap. A quantitative analysis of the responsible mechanisms based on EuCoO 3 as a reference compound is provided. A main result is that the static disorder is sufficient to explain the suppression of κ. No dynamical Jahn-Teller distortion, as proposed in the literature, is necessary to enhance the scattering strength. Below 25 K, k is mainly determined by resonant phonon scattering on paramagnetic impurity levels, e.g. caused by oxygen non-stoichiometry. Such a suppression of the thermal conductivity by resonant scattering processes is e.g. known from Holmium ethylsulfate. This effect is most pronounced in LaCoO 3 , presumably due to magnetic polaron formation. In the doped compounds La 1-x Sr x CoO 3 with 0≤x≤0.25, a large

  12. Thermal transport in cuprates, cobaltates, and manganites

    Energy Technology Data Exchange (ETDEWEB)

    Berggold, K.

    2006-09-15

    The subject of this thesis is the investigation of the thermal transport properties of three classes of transition-metal oxides: Cuprates, cobaltates, and manganites. The layered cuprates R{sub 2}CuO{sub 4} with R=La, Pr, Nd, Sm, Eu, and Gd show an anomalous thermal conductivity {kappa}. Two maxima of {kappa} are observed as a function of temperature for a heat current within the CuO{sub 2} planes, whereas for a heat current perpendicular to the CuO{sub 2} planes only a conventional phononic low-temperature maximum of {kappa} is present. Evidence is provided that the high-temperature maximum is caused by heat-carrying excitations on the CuO{sub 2} square lattice. Moreover, it is shown that the complex low-temperature and magnetic-field behavior of {kappa} in Nd{sub 2}CuO{sub 4} is most likely caused by additional phonon scattering rather than by heat-carrying Nd magnons, as it was proposed in the literature. In the cobaltates RCoO{sub 3} with R=La, Pr, Nd, and Eu, a temperature-induced spin-state transition of the Co{sup 3+} ions occurs. It is shown that the additional lattice disorder caused by the random distribution of populated higher spin states causes a large suppression of the thermal conductivity of LaCoO{sub 3} for T>25 K. The effect is much weaker in PrCoO{sub 3} and NdCoO{sub 3} due to the increased spin gap. A quantitative analysis of the responsible mechanisms based on EuCoO{sub 3} as a reference compound is provided. A main result is that the static disorder is sufficient to explain the suppression of {kappa}. No dynamical Jahn-Teller distortion, as proposed in the literature, is necessary to enhance the scattering strength. Below 25 K, k is mainly determined by resonant phonon scattering on paramagnetic impurity levels, e.g. caused by oxygen non-stoichiometry. Such a suppression of the thermal conductivity by resonant scattering processes is e.g. known from Holmium ethylsulfate. This effect is most pronounced in LaCoO{sub 3}, presumably due to

  13. Ocean transportation

    National Research Council Canada - National Science Library

    Frankel, Ernst G; Marcus, Henry S

    1973-01-01

    .... The discussion of technology considers the ocean transportation system as a whole, and the composite subsystems such as hull, outfit, propulsion, cargo handling, automation, and control and interface technology...

  14. Ocean transportation

    National Research Council Canada - National Science Library

    Frankel, Ernst G; Marcus, Henry S

    1973-01-01

    .... In ocean transportation economics we present investment and operating costs as well as the results of a study of financing of shipping. Similarly, a discussion of government aid to shipping is presented.

  15. Nicaragua - Transportation

    Data.gov (United States)

    Millennium Challenge Corporation — The evaluation examines impacts of the Transportation Project in three ways. First, we calculate economic rates of return associated with reduced user costs for each...

  16. Inventory theory, mode choice and network structure in freight transport

    NARCIS (Netherlands)

    Combes, F.; Tavasszy, L.A.

    2016-01-01

    In passenger transport, hub-and-spoke networks allow the transportation of small passenger flows with competitive frequencies, in a way that direct line networks cannot. Equivalently, in freight transport, it can be expected that small shipper-receiver flows of high added value commodities transit

  17. RF transport

    International Nuclear Information System (INIS)

    Choroba, Stefan

    2013-01-01

    This paper deals with the techniques of transport of high-power radiofrequency (RF) power from a RF power source to the cavities of an accelerator. Since the theory of electromagnetic waves in waveguides and of waveguide components is very well explained in a number of excellent text books it will limit itself on special waveguide distributions and on a number of, although not complete list of, special problems which sometimes occur in RF power transportation systems. (author)

  18. Public transport

    OpenAIRE

    Lethbridge, Jane

    2008-01-01

    Public transport plays an essential role in enabling people from low income and other disadvantaged groups to access employment and services. It also contributes to the development of social networks and social capital, by helping people to visit friends and relatives and take part in community and other social activities. Public policy makers have begun to recognise that adequate public transport provision can play an important role in reducing social exclusion. [Taken from introductory para...

  19. Magnetic and electronic properties of La3 M O7 and possible polaron formation in hole-doped La3 M O7 (M   =  Ru and Os)

    International Nuclear Information System (INIS)

    Gao, Bin; Weng, Yakui; Zhang, Jun-Jie; Zhang, Huimin; Zhang, Yang; Dong, Shuai

    2017-01-01

    Oxides with 4 d /5 d transition metal ions are physically interesting for their particular crystalline structures as well as the spin–orbit coupled electronic structures. Recent experiments revealed a series of 4 d /5 d transition metal oxides R 3 M O 7 (R : rare earth; M : 4 d /5 d transition metal) with unique quasi-one-dimensional M chains. Here first-principles calculations have been performed to study the electronic structures of La 3 OsO 7 and La 3 RuO 7 . Our study confirm both of them to be Mott insulating antiferromagnets with identical magnetic order. The reduced magnetic moments, which are much smaller than the expected value for ideal high-spin state (3 t 2g orbitals occupied), are attributed to the strong p   −   d hybridization with oxygen ions, instead of the spin–orbit coupling. The Ca-doping to La 3 OsO 7 and La 3 RuO 7 can not only modulate the nominal carrier density but also affect the orbital order as well as the local distortions. The Coulombic attraction and particular orbital order would prefer to form polarons, which might explain the puzzling insulating behavior of doped 5 d transition metal oxides. In addition, our calculations predict that the Ca-doping can trigger ferromagnetism in La 3 RuO 7 but not in La 3 OsO 7 . (paper)

  20. Pressure-induced colossal piezoresistance effect and the collapse of the polaronic state in the bilayer manganite (La0.4Pr0.6)1.2Sr1.8Mn2O7

    International Nuclear Information System (INIS)

    Thiyagarajan, R; Manivannan, N; Arumugam, S; Esakki Muthu, S; Tamilselvan, N R; Yoshino, H; Murata, K; Sekar, C; Apostu, M O; Suryanarayanan, R; Revcolevschi, A

    2012-01-01

    We have investigated the effect of hydrostatic pressure as a function of temperature on the resistivity of a single crystal of the bilayer manganite (La 0.4 Pr 0.6 ) 1.2 Sr 1.8 Mn 2 O 7 . Whereas a strong insulating behaviour is observed at all temperatures at ambient pressure, a clear transition into a metallic-like behaviour is induced when the sample is subjected to a pressure (P) of ∼1.0 GPa at T 6 in the low temperature region at moderate pressures is observed. When the pressure is increased further (5.5 GPa), the high temperature polaronic state disappears and a metallic behaviour is observed. The insulator to metal transition temperature exponentially increases with pressure and the distinct peak in the resistivity that is observed at 1.0 GPa almost vanishes for P > 7.0 GPa. A modification in the orbital occupation of the e g electron between 3d x 2 -y 2 and 3d z 2 -r 2 states, as proposed earlier, leading to a ferromagnetic double-exchange phenomenon, can qualitatively account for our data. (paper)