WorldWideScience

Sample records for carrier density

  1. Carrier-Density-Dependent Lattice Stability in InSb

    International Nuclear Information System (INIS)

    The ultrafast decay of the x-ray diffraction intensity following laser excitation of an InSb crystal has been utilized to observe carrier dependent changes in the potential energy surface. For the first time, an abrupt carrier dependent onset for potential energy surface softening and the appearance of accelerated atomic disordering for a very high average carrier density have been observed. Inertial dynamics dominate the early stages of crystal disordering for a wide range of carrier densities between the onset of crystal softening and the appearance of accelerated atomic disordering

  2. Analytical carrier density and quantum capacitance for graphene

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Lingfei; Wang, Wei; Xu, Guangwei; Ji, Zhuoyu; Lu, Nianduan, E-mail: lunianduan@ime.ac.cn; Li, Ling, E-mail: lingli@ime.ac.cn; Liu, Ming [Key Laboratory of Microelectronics Devices and Integrated Technology, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029 (China); Laboratory of Nanofabrication and Novel Device Integration, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029 (China)

    2016-01-04

    A disorder based analytical carrier density for graphene is presented here. The carrier density, a basic property of all semiconductors, is obtained based on exponential distribution describing the potential fluctuations induced by impurities and shows good agreement with numerical results. The quantum capacitance is subsequently derived from the carrier density, with a good agreement with experimental measurements. A method for extracting the gate coupling function is also proposed, which relates the internal surface potential with the external applied gate voltage. The essential properties of graphene device physics, such as the temperature, material disorder, and surface potential dependences, are captured in these analytical equations.

  3. Carrier Density and Plasma Frequency of Aluminum Nanofilms

    Institute of Scientific and Technical Information of China (English)

    Hao DU; Jun GONG; Chao SUN; Rongfang HUANG; Lishi WEN; W.Y.Cheung; S.P.Wong

    2003-01-01

    In this work, the prerequisite and mode of electromagnetic response of Al nanofilms to electromagnetic wave field was suggested.Reflectance, transmittance in infrared region and carrier density of the films was measured. With the carrier density of the films, the dependence of their plasma frequencies on the film thickness was obtained. On the other hand, the dependence of absorptance on the frequency of electromagnetic wave field was set up by using the measured reflectance and transmittance,which provided plasma frequency-film thickness relation as well. Similarity of both plasma frequency-film thickness relations proved plasma resonance as a mode of electromagnetic response in Al nanofilms.

  4. Tuning carrier density at complex oxide interface with metallic overlayer

    Science.gov (United States)

    Zhou, Y.; Shi, Y. J.; Jiang, S. W.; Yue, F. J.; Wang, P.; Ding, H. F.; Wu, D.

    2016-06-01

    We have systematically investigated the electronic transport properties of the LaAlO3/SrTiO3 interfaces with several different metal capping layers. The sheet carrier density can be tuned in a wide range by the metallic overlayer without changing the carrier mobility. The sheet carrier density variation is found to be linearly dependent on the size of metal work function. This behavior is explained by the mechanism of the charge transfer between the oxide interface and the metal overlayer across the LaAlO3 layer. Our results confirm the existence of a built-in electric field in LaAlO3 film with an estimated value of 67.7 eV/Å. Since the metallic overlayer is essential for devices, the present phenomena must be considered for future applications.

  5. Graphene, a material for high temperature devices; intrinsic carrier density, carrier drift velocity, and lattice energy

    CERN Document Server

    Yin, Yan; Wang, Li; Jin, Kuijuan; Wang, Wenzhong

    2016-01-01

    Heat has always been a killing matter for traditional semiconductor machines. The underlining physical reason is that the intrinsic carrier density of a device made from a traditional semiconductor material increases very fast with a rising temperature. Once reaching a temperature, the density surpasses the chemical doping or gating effect, any p-n junction or transistor made from the semiconductor will fail to function. Here, we measure the intrinsic Fermi level (|E_F|=2.93k_B*T) or intrinsic carrier density (n_in=3.87*10^6 cm^-2 K^-2*T^2), carrier drift velocity, and G mode phonon energy of graphene devices and their temperature dependencies up to 2400 K. Our results show intrinsic carrier density of graphene is an order of magnitude less sensitive to temperature than those of Si or Ge, and reveal the great potentials of graphene as a material for high temperature devices. We also observe a linear decline of saturation drift velocity with increasing temperature, and identify the temperature coefficients of ...

  6. Manipulation of Carrier Density near Ferroelectric/Semiconductor Interfaces

    Science.gov (United States)

    Kesim, Mehmet; Misirlioglu, I. Burc; Mantese, Joseph; Alpay, S. Pamir

    Switchable polarization of a ferroelectric (FE) opens up the opportunity to control the charge density and transport characteristics at the FE/metal and FE/semiconductor (SC) heterointerfaces. Carrier manipulation near such regions can be used in high density non-volatile memories, switchable diodes, and photovoltaic devices. FEs can be utilized as gate oxides in a metal oxide field-effect transistor configuration for non-volatile memory applications with lower gate voltages compared to that of transistors with linear dielectrics. The channel conductance can be modulated reversibly, for instance, by tuning the magnitude and spatial distribution of polarization in the FE. In this study, we show that FE heterostructures can be used to manipulate the conductivity of a FE/SC interface. We employ a non-linear thermodynamic model based on Landau-Ginzburg-Devonshire (LGD) theory to obtain the equilibrium polarization of heterostructures. The carriers along the heterostructures are mapped through coupling the LGD equation with the Maxwell equations and Fermi - Dirac distribution of charged carriers/ionized dopants in the FE and SC. We consider various configurations including FE/SC/paraelectric and FE/SC/FE stacks to investigate the carrier distribution and band bending near such interfaces. The resulting properties are explained through the phase transition characteristics and domain structure of the stacks.

  7. Carrier density driven lasing dynamics in ZnO nanowires

    CERN Document Server

    Wille, Marcel; Michalsky, Tom; Röder, Robert; Ronning, Carsten; Schmidt-Grund, Rüdiger; Grundmann, Marius

    2016-01-01

    We report on the temporal lasing dynamics of high quality ZnO nanowires using time-resolved micro-photoluminescence technique. The temperature dependence of the lasing characteristics and of the corresponding decay constants demonstrate the formation of an electron-hole plasma to be the underlying gain mechanism in the considered temperature range from 10 K to 300 K. We found that the temperature dependent emission onset-time ($t_{\\text{on}}$) strongly depends on the excitation power and becomes smallest in the lasing regime, with values below 5 ps. Furthermore, the observed red shift of the dominating lasing modes in time is qualitatively discussed in terms of the carrier density induced change of the refractive index dispersion after the excitation laser pulse. This theory is supported by extending an existing model for the calculation of the carrier density dependent complex refractive index for different temperatures. This model coincides with the experimental observations and reliably describes the evolu...

  8. Carrier density modulation in graphene underneath Ni electrode

    OpenAIRE

    Moriyama, T.; Nagashio, K.; Nishimura, T; Toriumi, A.

    2013-01-01

    We investigate the transport properties of graphene underneath metal to reveal whether the carrier density in graphene underneath source/drain electrodes in graphene field-effect transistors is fixed. The resistance of the graphene/Ni double-layered structure has shown a graphene-like back-gate bias dependence. In other words, the electrical properties of graphene are not significantly affected by its contact with Ni. This unexpected result may be ascribed to resist residuals at the metal/gra...

  9. Charge carrier density in Li-intercalated graphene

    KAUST Repository

    Kaloni, Thaneshwor P.

    2012-05-01

    The electronic structures of bulk C 6Li, Li-intercalated free-standing bilayer graphene, and Li-intercalated bilayer and trilayer graphene on SiC(0 0 0 1) are studied using density functional theory. Our estimate of Young\\'s modulus suggests that Li-intercalation increases the intrinsic stiffness. For decreasing Li-C interaction, the Dirac point shifts to the Fermi level and the associated band splitting vanishes. For Li-intercalated bilayer graphene on SiC(0 0 0 1) the splitting at the Dirac point is tiny. It is also very small at the two Dirac points of Li-intercalated trilayer graphene on SiC(0 0 0 1). For all the systems under study, a large enhancement of the charge carrier density is achieved by Li intercalation. © 2012 Elsevier B.V. All rights reserved.

  10. Carrier density driven lasing dynamics in ZnO nanowires.

    Science.gov (United States)

    Wille, Marcel; Sturm, Chris; Michalsky, Tom; Röder, Robert; Ronning, Carsten; Schmidt-Grund, Rüdiger; Grundmann, Marius

    2016-06-01

    We report on the temporal lasing dynamics of high quality ZnO nanowires using the time-resolved micro-photoluminescence technique. The temperature dependence of the lasing characteristics and of the corresponding decay constants demonstrate the formation of an electron-hole plasma to be the underlying gain mechanism in the considered temperature range from 10 K to 300 K. We found that the temperature-dependent emission onset-time ([Formula: see text]) strongly depends on the excitation power and becomes smallest in the lasing regime, with values below 5 ps. Furthermore, the observed red shift of the dominating lasing modes in time is qualitatively discussed in terms of the carrier density induced change of the refractive index dispersion after the excitation laser pulse. This theory is supported by extending an existing model for the calculation of the carrier density dependent complex refractive index for different temperatures. This model coincides with the experimental observations and reliably describes the evolution of the refractive index after the excitation laser pulse.

  11. Carrier density driven lasing dynamics in ZnO nanowires

    Science.gov (United States)

    Wille, Marcel; Sturm, Chris; Michalsky, Tom; Röder, Robert; Ronning, Carsten; Schmidt-Grund, Rüdiger; Grundmann, Marius

    2016-06-01

    We report on the temporal lasing dynamics of high quality ZnO nanowires using the time-resolved micro-photoluminescence technique. The temperature dependence of the lasing characteristics and of the corresponding decay constants demonstrate the formation of an electron–hole plasma to be the underlying gain mechanism in the considered temperature range from 10 K to 300 K. We found that the temperature-dependent emission onset-time ({t}{{on}}) strongly depends on the excitation power and becomes smallest in the lasing regime, with values below 5 ps. Furthermore, the observed red shift of the dominating lasing modes in time is qualitatively discussed in terms of the carrier density induced change of the refractive index dispersion after the excitation laser pulse. This theory is supported by extending an existing model for the calculation of the carrier density dependent complex refractive index for different temperatures. This model coincides with the experimental observations and reliably describes the evolution of the refractive index after the excitation laser pulse.

  12. γ radiation caused graphene defects and increased carrier density

    Institute of Scientific and Technical Information of China (English)

    Han Mai-xing; Ji Zhuo-Yu; Shang Li-Wei; Chen Ying-Ping; Wang Hong; Liu Xin; Li Dong-Mei; Liu Ming

    2011-01-01

    We report on a micro-Raman investigation of inducing defects in mono-layer,bi-layer and tri-layer graphene by γ ray radiation.It is found that the radiation exposure results in two-dimensional(2D)and G band position evolution with the layer number increasing and D and D' bands rising,suggesting the presence of defects and related crystal lattice deformation in graphene.Bi-layer graphene is more stable than mono-and tri-layer graphene,indicating that the former is a better candidate in the application of radiation environments.Also,the DC electrical property of the mono-layer graphene device shows that the defects increase the carrier density.

  13. Analytical formulas for carrier density and Fermi energy in semiconductors with a tight-binding band

    International Nuclear Information System (INIS)

    Analytical formulas for evaluating the relation of carrier density and Fermi energy for semiconductors with a tight-binding band have been proposed. The series expansions for a carrier density with fast convergency have been obtained by means of a Bessel function. A simple and analytical formula for Fermi energy has been derived with the help of the Gauss integration method. The results of the proposed formulas are in good agreement with accurate numerical solutions. The formulas have been successfully used in the calculation of carrier density and Fermi energy in a miniband superlattice system. Their accuracy is in the order of 10−5. (paper)

  14. Lithium-ion-based solid electrolyte tuning of the carrier density in graphene

    Science.gov (United States)

    Zhao, Jialin; Wang, Meng; Li, Hui; Zhang, Xuefu; You, Lixing; Qiao, Shan; Gao, Bo; Xie, Xiaoming; Jiang, Mianheng

    2016-01-01

    We have developed a technique to tune the carrier density in graphene using a lithium-ion-based solid electrolyte. We demonstrate that the solid electrolyte can be used as both a substrate to support graphene and a back gate. It can induce a change in the carrier density as large as 1 × 1014 cm−2, which is much larger than that induced with oxide-film dielectrics, and it is comparable with that induced by liquid electrolytes. Gate modulation of the carrier density is still visible at 150 K, which is lower than the glass transition temperature of most liquid gating electrolytes. PMID:27698413

  15. Electron density and carriers of the diffuse interstellar bands

    OpenAIRE

    Gnacinski, P.; Sikorski, J. K.; Galazutdinov, G. A.

    2007-01-01

    We have used the ionisation equilibrium equation to derive the electron density in interstellar clouds in the direction to 13 stars. A linear relation was found, that allows the determination of the electron density from the Mg I and Mg II column densities in diffuse clouds. The comparison of normalised equivalent width of 12 DIBs with the electron density shows that the DIBs equivalent width do not change with electron density varying in the range ne=0.01-2.5 cm^-3. Therefore the DIBs carrie...

  16. Investigating thermal donors in n-type Cz silicon with carrier density imaging

    Directory of Open Access Journals (Sweden)

    Yu Hu

    2012-09-01

    Full Text Available A new method to map the thermal donor concentration in silicon wafers using carrier density imaging is presented. A map of the thermal donor concentration is extracted with high resolution from free carrier density images of a silicon wafer before and after growth of thermal donors. For comparison, free carrier density mapping is also performed using the resistivity method together with linear interpolation. Both methods reveal the same distribution of thermal donors indicating that the carrier density imaging technique can be used to map thermal donor concentration. The interstitial oxygen concentration can also be extracted using the new method in combination with Wijaranakula's model. As part of this work, the lifetime at medium injection level is correlated to the concentration of thermal donors in the as-grown silicon wafer. The recombination rate is found to depend strongly on the thermal donor concentration except in the P-band region.

  17. Tuning carrier density across Dirac point in epitaxial graphene on SiC by corona discharge

    OpenAIRE

    Lartsev, Arseniy; Yager, Thomas; Bergsten, T.; Tzalenchuk, A.; Janssen, Tjbm; Yakimova, R.; Lara-Avila, Samuel; Kubatkin, Sergey

    2014-01-01

    We demonstrate reversible carrier density control across the Dirac point (Delta n similar to 10(13) cm(-2)) in epitaxial graphene on SiC (SiC/G) via high electrostatic potential gating with ions produced by corona discharge. The method is attractive for applications where graphene with a fixed carrier density is needed, such as quantum metrology, and more generally as a simple method of gating 2DEGs formed at semiconductor interfaces and in topological insulators.

  18. Tuning carrier density across Dirac point in epitaxial graphene on SiC by corona discharge

    Science.gov (United States)

    Lartsev, Arseniy; Yager, Tom; Bergsten, Tobias; Tzalenchuk, Alexander; Janssen, T. J. B. M.; Yakimova, Rositza; Lara-Avila, Samuel; Kubatkin, Sergey

    2014-08-01

    We demonstrate reversible carrier density control across the Dirac point (Δn ˜ 1013 cm-2) in epitaxial graphene on SiC (SiC/G) via high electrostatic potential gating with ions produced by corona discharge. The method is attractive for applications where graphene with a fixed carrier density is needed, such as quantum metrology, and more generally as a simple method of gating 2DEGs formed at semiconductor interfaces and in topological insulators.

  19. Tuning carrier density across Dirac point in epitaxial graphene on SiC by corona discharge

    Energy Technology Data Exchange (ETDEWEB)

    Lartsev, Arseniy; Yager, Tom; Lara-Avila, Samuel, E-mail: samuel.lara@chalmers.se; Kubatkin, Sergey [Department of Microtechnology and Nanoscience, Chalmers University of Technology, S-41296 Göteborg (Sweden); Bergsten, Tobias [SP Technical Research Institute of Sweden, S-50115 Borås (Sweden); Tzalenchuk, Alexander [National Physical Laboratory, Teddington TW110LW (United Kingdom); Royal Holloway, University of London, Egham TW20 0EX (United Kingdom); Janssen, T. J. B. M [National Physical Laboratory, Teddington TW110LW (United Kingdom); Yakimova, Rositza [Department of Physics, Chemistry and Biology (IFM), Linköping University, S-58183 Linköping (Sweden)

    2014-08-11

    We demonstrate reversible carrier density control across the Dirac point (Δn ∼ 10{sup 13 }cm{sup −2}) in epitaxial graphene on SiC (SiC/G) via high electrostatic potential gating with ions produced by corona discharge. The method is attractive for applications where graphene with a fixed carrier density is needed, such as quantum metrology, and more generally as a simple method of gating 2DEGs formed at semiconductor interfaces and in topological insulators.

  20. Evolution of the magnetic anisotropy with carrier density in hydrogenated (Ga,Mn)As

    OpenAIRE

    Thevenard, Laura; Largeau, Ludovic; Mauguin, Olivia; Lemaître, Aristide; Khazen, Khashayar; Von Bardeleben, Jürgen

    2007-01-01

    26 pages The magnetic properties of (Ga,Mn)As thin films depend on both the Mn doping level and the carrier concentration. Using a post growth hydrogenation process we show that it is possible to decrease the hole density from 1.1021 cm-3 to

  1. Determination of charge carrier mobility in doped low density polyethylene using DC transients

    DEFF Research Database (Denmark)

    Khalil, M.Salah; Henk, Peter O; Henriksen, Mogens

    1989-01-01

    Charge carrier mobility was determined for plain and doped low-density polyethylene (LDPE) using DC transient currents. Barium titanate was used as a strongly polar dopant and titanium dioxide as a semiconductor dopant. The values of the mobility obtained were on the order of 10-10 cm2 v-1 s-1...... by a factor of five. Charge trapping and space charge formation were modified by the introduction of titanium dioxide...

  2. Relationship between defect density and charge carrier transport in amorphous and microcrystalline silicon

    OpenAIRE

    Astakhov, O.; Carius, R.; F. Finger; Petrusenko, Y.; Borysenko, V.; Barankov, D.

    2009-01-01

    The influence of dangling-bond defects and the position of the Fermi level on the charge carrier transport properties in undoped and phosphorous doped thin-film silicon with structure compositions all the way from highly crystalline to amorphous is investigated. The dangling-bond density is varied reproducibly over several orders of magnitude by electron bombardment and subsequent annealing. The defects are investigated by electron-spin-resonance and photoconductivity spectroscopies. Comparin...

  3. Structure, ionic conductivity and mobile carrier density in fast ionic conducting chalcogenide glasses

    Energy Technology Data Exchange (ETDEWEB)

    Yao, Wenlong [Iowa State Univ., Ames, IA (United States)

    2006-01-01

    This thesis consists of six sections. The first section gives the basic research background on the ionic conduction mechanism in glass, polarization in the glass, and the method of determining the mobile carrier density in glass. The proposed work is also included in this section. The second section is a paper that characterizes the structure of MI + M2S + (0.1 Ga2S3 + 0.9 GeS2) (M = Li, Na, K and Cs) glasses using Raman and IR spectroscopy. Since the ionic radius plays an important role in determining the ionic conductivity in glasses, the glass forming range for the addition of different alkalis into the basic glass forming system 0.1 Ga2S3 + 0.9 GeS2 was studied. The study found that the change of the alkali radius for the same nominal composition causes significant structure change to the glasses. The third section is a paper that investigates the ionic conductivity of MI + M2S + (0.1Ga2S3 + 0.9 GeS2) (M = Li, Na, K and Cs) glasses system. Corresponding to the compositional changes in these fast ionic conducting glasses, the ionic conductivity shows changes due to the induced structural changes. The ionic radius effect on the ionic conductivity in these glasses was investigated. The fourth section is a paper that examines the mobile carrier density based upon the measurements of space charge polarization. For the first time, the charge carrier number density in fast ionic conducting chalcogenide glasses was determined. The experimental impedance data were fitted using equivalent circuits and the obtained parameters were used to determine the mobile carrier density. The influence of mobile carrier density and mobility on the ionic conductivity was separated. The fifth section is a paper that studies the structures of low-alkali-content Na2S + B2S3 (x ≤ 0.2) glasses by neutron and synchrotron x-ray diffraction

  4. Structure, ionic Conductivity and mobile Carrier Density in Fast Ionic Conducting Chalcogenide Glasses

    International Nuclear Information System (INIS)

    This thesis consists of six sections. The first section gives the basic research background on the ionic conduction mechanism in glass, polarization in the glass, and the method of determining the mobile carrier density in glass. The proposed work is also included in this section. The second section is a paper that characterizes the structure of MI + M2S + (0.1 Ga2S3 + 0.9 GeS2) (M = Li, Na, K and Cs) glasses using Raman and IR spectroscopy. Since the ionic radius plays an important role in determining the ionic conductivity in glasses, the glass forming range for the addition of different alkalis into the basic glass forming system 0.1 Ga2S3 + 0.9 GeS2 was studied. The study found that the change of the alkali radius for the same nominal composition causes significant structure change to the glasses. The third section is a paper that investigates the ionic conductivity of MI + M2S + (0.1Ga2S3 + 0.9 GeS2) (M = Li, Na, K and Cs) glasses system. Corresponding to the compositional changes in these fast ionic conducting glasses, the ionic conductivity shows changes due to the induced structural changes. The ionic radius effect on the ionic conductivity in these glasses was investigated. The fourth section is a paper that examines the mobile carrier density based upon the measurements of space charge polarization. For the first time, the charge carrier number density in fast ionic conducting chalcogenide glasses was determined. The experimental impedance data were fitted using equivalent circuits and the obtained parameters were used to determine the mobile carrier density. The influence of mobile carrier density and mobility on the ionic conductivity was separated. The fifth section is a paper that studies the structures of low-alkali-content Na2S + B2S3 (x (le) 0.2) glasses by neutron and synchrotron x-ray diffraction. Similar results were obtained both in neutron and synchrotron x-ray diffraction experiments. The results provide direct structural evidence that doping

  5. Superconductivity in a two-band system with a low carrier density

    International Nuclear Information System (INIS)

    The paper investigates thermodynamic properties of two-zone system with low density of carriers in the vicinity of superconducting transition temperature Tc, taking into account various pairings of carriers. Bell-shaped dependence of Tc on electron concentration is derived and a possibility of occurrence of high-temperature superconductivity is shown. Absolute, CS - CN, and relative, (CS - CN)/CN jumps of electron heat capacity is calculated in the point T=Tc and concentration dependence of these values is studied. The theory allows to derive small, (CS - CN)/CN S - CN)/CN > 1.43 value. Favorable conditions for experimental observation of the bent, depending on chemical potential μ(T) in the point T=Tc, are established. 35 refs., 4 figs

  6. Magnetotransport in the low carrier density ferromagnet EuB6

    International Nuclear Information System (INIS)

    We present a magnetotransport study of the low-carrier density ferromagnet EuB6. This semimetallic compound, which undergoes two ferromagnetic transitions at Tl=15.3 K and Tc=12.5 K, exhibits close to Tl a colossal magnetoresistivity (CMR). We quantitatively compare our data to recent theoretical work, which, however, fails to explain our observations. We attribute this disagreement with theory to the unique type of magnetic polaron formation in EuB6. (c) 2000 American Institute of Physics

  7. Study of energy eigenvalues and density of states of carriers in a triangular quantum wire

    Science.gov (United States)

    Deyasi, Arpan; Bhattacharyya, S.; Das, N. R.

    2012-10-01

    Energy eigenvalues and density of states of carriers in a finite barrier triangular quantum wire embedded inside a rectangular quantum wire are numerically investigated using finite difference technique (FD-Q). Time-independent Schrödinger's equation is solved with appropriate boundary conditions for computation of lowest three eigenstates. The wire is made of lower bandgap GaAs material surrounded by wider bandgap AlxGa1-xAs, and the analysis is carried out by taking into consideration of the conduction band discontinuity and effective mass mismatch at the boundaries. The eigenvalues and the density of states are plotted as function of wire dimension and mole fraction (x). The results are also compared with those obtained using rectangular quantum wire.

  8. Low trap-state density and long carrier diffusion in organolead trihalide perovskite single crystals

    KAUST Repository

    Shi, Dong

    2015-01-29

    The fundamental properties and ultimate performance limits of organolead trihalide MAPbX3(MA = CH3NH3 +; X = Br- or I- ) perovskites remain obscured by extensive disorder in polycrystalline MAPbX3 films. We report an antisolvent vapor-assisted crystallization approach that enables us to create sizable crack-free MAPbX3 single crystals with volumes exceeding 100 cubic millimeters. These large single crystals enabled a detailed characterization of their optical and charge transport characteristics.We observed exceptionally low trap-state densities on the order of 109 to 1010 per cubic centimeter in MAPbX3 single crystals (comparable to the best photovoltaic-quality silicon) and charge carrier diffusion lengths exceeding 10 micrometers. These results were validated with density functional theory calculations.

  9. Enhanced carrier density in Nb-doped SrTiO3 thermoelectrics

    KAUST Repository

    Ozdogan, K.

    2012-03-08

    We study epitaxial SrTiO3 interfaced with Nb-doped SrTi1-x Nb x O3 (x = 0, 0.125, 0.25, 0.375, and 0.5) by full-potential density functional theory. From the electronic band structures obtained by our ab-initio calculations we determine the dependence of the induced metallicity on the Nb concentration. We obtain a monotonous increase of the carrier density with the Nb concentration. The results are confirmed by experiments for SrTi0.88Nb0.12O3 and SrTi0.8Nb0.2O3, demonstrating the predictive power and limitations of our theoretical approach. We also show that the Seebeck coefficient decreases monotonously with increasing temperature.

  10. Imaging the local density of free charge carriers in doped InAs nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Hauer, Benedikt; Taubner, Thomas [I. Institute of Physics (1A), RWTH Aachen Univerity, Sommerfeldstrasse 14, 52074 Aachen (Germany); Sladek, Kamil; Haas, Fabian; Schaepers, Thomas; Hardtdegen, Hilde [Peter Gruenberg Institute (PGI-9), Forschungszentrum Juelich, 52425 Juelich (Germany)

    2013-07-01

    Semiconductor nanowires are promising candidates for future nanoelectronic devices. While the bottom-up approach for their growth could simplify the device fabrication, their quantitative characterization remains challenging. We use scattering-type scanning near-field optical microscopy (s-SNOM) to investigate the local density of free electrons in Si-doped InAs nanowires grown by selective-area metalorganic vapor phase epitaxy (SA-MOVPE). In s-SNOM the evanescent electric field at the apex of an illuminated tip is used to probe a sample at a strongly sub-wavelength resolution. This method is highly sensitive to variations in the sample permittivity around Re(ε) ∼ -2. The use of tunable mid-infrared lasers therefore allows addressing the plasma frequency of free charge carriers in highly doped nanowires. Here, we demonstrate that the sensitivity of s-SNOM is sufficient to detect a slight unintended variation in the carrier concentration during the growth process. Furthermore, using model calculations, we give an estimate of the local density of free electrons.

  11. Carrier-carrier and carrier-phonon scattering in the low-density and low-temperature regime for resonantly pumped semiconductor quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Lorke, M.; Jahnke, F. [Institute for Theoretical Physics, University of Bremen (Germany); Gartner, P. [Institute for Theoretical Physics, University of Bremen (Germany); National Institute for Materials Physics, POB MG-7, Bucharest-Magurele (Romania); Seebeck, J.

    2009-02-15

    We study carrier relaxation due to Coulomb scattering and interaction with LO-phonons in semiconductor quantum dots at low temperatures. Scattering for different relaxation process are evaluated for various carrier distributions that correspond to stages of the typical relaxation kinetics after optical excitation with a weak pulse, generating on average less than one electron per quantum dot. Even when the spacing of the quantum dot energy levels does not match the LO-phonon energy, we.nd that carrier-LO-phonon scattering, in addition to electronelectron and electron-hole interaction, provides efficient carrier relaxation. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  12. Carrier-Density-Dependent Electron Spin Relaxation in GaAs/AlGaAs Multi Quantum Wells

    Institute of Scientific and Technical Information of China (English)

    SHOU Qian; WU Yu; LIU Lu-Ning; WEN Jin-Hui; LAI Tian-Shu; LIN Wei-Zhu

    2005-01-01

    @@ The carrier-density-dependent electron spin relaxation processes in GaAs/AlGaAs multi quantum wells are investigated by a femtosecond pump probe experiment. The spin relaxation time presents two distinguishable trends with the increasing excitation density. It increases from 60ps to 70ps with carrier densities from 1 × 1017 cm-3to 5 × 1017 cm-3 and gradually saturates up to ~80ps at 4 × 1018 cm-3. The experimental results are attributed to the combined competition between collision intensification and scattering potential screening and provide a good experimental confirmation for the theoretical D'yakonov-Perel' mechanism descriptions.

  13. Measuring the mobility of single crystalline wires and its dependence on temperature and carrier density

    Energy Technology Data Exchange (ETDEWEB)

    Amorim, Cleber A; Berengue, Olivia M; Kamimura, Hanay; Chiquito, Adenilson J [NanO LaB-Departamento de Fisica, Universidade Federal de Sao Carlos, CEP 13565-905, CP 676, Sao Carlos, Sao Paulo (Brazil); Leite, Edson R, E-mail: amorim@df.ufscar.br [Laboratorio Interdisciplinar de EletroquImica e Ceramicas, Departamento de Quimica, Universidade Federal de Sao Carlos, CEP 13565-905, CP 676, Sao Carlos, Sao Paulo (Brazil)

    2011-05-25

    Kinetic transport parameters are fundamental for the development of electronic nanodevices. We present new results for the temperature dependence of mobility and carrier density in single crystalline In{sub 2}O{sub 3} samples and the method of extraction of these parameters which can be extended to similar systems. The data were obtained using a conventional Hall geometry and were quantitatively described by the semiconductor transport theory characterizing the electron transport as being controlled by the variable range hopping mechanism. A comprehensive analysis is provided showing the contribution of ionized impurities (low temperatures) and acoustic phonon (high temperatures) scattering mechanisms to the electron mobility. The approach presented here avoids common errors in kinetic parameter extraction from field effect data, serving as a versatile platform for direct investigation of any nanoscale electronic materials.

  14. Tunable one-dimensional electron gas carrier densities at nanostructured oxide interfaces

    Science.gov (United States)

    Zhuang, Houlong L.; Zhang, Lipeng; Xu, Haixuan; Kent, P. R. C.; Ganesh, P.; Cooper, Valentino R.

    2016-05-01

    The emergence of two-dimensional metallic states at the LaAlO3/SrTiO3 (LAO/STO) heterostructure interface is known to occur at a critical thickness of four LAO layers. This insulator to-metal transition can be explained through the “polar catastrophe” mechanism arising from the divergence of the electrostatic potential at the LAO surface. Here, we demonstrate that nanostructuring can be effective in reducing or eliminating this critical thickness. Employing a modified “polar catastrophe” model, we demonstrate that the nanowire heterostructure electrostatic potential diverges more rapidly as a function of layer thickness than in a regular heterostructure. Our first-principles calculations indicate that for nanowire heterostructures a robust one-dimensional electron gas (1DEG) can be induced, consistent with recent experimental observations of 1D conductivity at LAO/STO steps. Similar to LAO/STO 2DEGs, we predict that the 1D charge density decays laterally within a few unit cells away from the nanowire; thus providing a mechanism for tuning the carrier dimensionality between 1D and 2D conductivity. Our work provides insight into the creation and manipulation of charge density at an oxide heterostructure interface and therefore may be beneficial for future nanoelectronic devices and for the engineering of novel quantum phases.

  15. Change of carrier density at the pseudogap critical point of a cuprate superconductor.

    Science.gov (United States)

    Badoux, S; Tabis, W; Laliberté, F; Grissonnanche, G; Vignolle, B; Vignolles, D; Béard, J; Bonn, D A; Hardy, W N; Liang, R; Doiron-Leyraud, N; Taillefer, Louis; Proust, Cyril

    2016-03-10

    The pseudogap is a partial gap in the electronic density of states that opens in the normal (non-superconducting) state of cuprate superconductors and whose origin is a long-standing puzzle. Its connection to the Mott insulator phase at low doping (hole concentration, p) remains ambiguous and its relation to the charge order that reconstructs the Fermi surface at intermediate doping is still unclear. Here we use measurements of the Hall coefficient in magnetic fields up to 88 tesla to show that Fermi-surface reconstruction by charge order in the cuprate YBa2Cu3Oy ends sharply at a critical doping p = 0.16 that is distinctly lower than the pseudogap critical point p* = 0.19 (ref. 11). This shows that the pseudogap and charge order are separate phenomena. We find that the change in carrier density n from n = 1 + p in the conventional metal at high doping (ref. 12) to n = p at low doping (ref. 13) starts at the pseudogap critical point. This shows that the pseudogap and the antiferromagnetic Mott insulator are linked.

  16. Dynamical co-existence of excitons and free carriers in perovskite probed by density-resolved fluorescent spectroscopic method

    CERN Document Server

    Wang, Wei; Wang, Xiangyuan; Lv, Yanping; Wang, Shufeng; Wang, Kai; Shi, Yantao; Xiao, Lixin; Chen, Zhijian; Gong, Qihuang

    2016-01-01

    Using transient fluorescent spectra at time-zero, we develop a density-resolved fluorescent spectroscopic method for investigating photoproducts in CH3NH3PbI3 perovskite and related photophysics. The density dependent dynamical co-existence of excitons and free carriers over a wide density range is experimentally observed for the first time. The exciton binding energy (EB) and the effective mass of electron-hole pair can be estimated based on such co-existence. No ionic polarization is found contributing to photophysical behavior. It also solves the conflict between the large experimentally measured EB and the small predicted values. The spectroscopic method also helps to detect the true free carrier density under continuous illumination without the interference of ionic conductivity. Our methods and results profoundly enrich the study and understanding of the photophysics in perovskite materials for photovoltaic applications.

  17. Thickness dependent charge transfer states and dark carriers density in vacuum deposited small molecule organic photocell

    Science.gov (United States)

    Shekhar, Himanshu; Tzabari, Lior; Solomeshch, Olga; Tessler, Nir

    2016-10-01

    We have investigated the influence of the active layer thickness on the balance of the internal mechanisms affecting the efficiency of copper phthalocyanine - fullerene (C60) based vacuum deposited bulk heterojunction organic photocell. We fabricated a range of devices for which we varied the thickness of the active layer from 40 to 120 nm and assessed their performance using optical and electrical characterization techniques. As reported previously for phthalocyanine:C60, the performance of the device is highly dependent on the active layer thickness and of all the thicknesses we tried, the 40 nm thin active layer device showed the best solar cell characteristic parameters. Using the transfer matrix based optical model, which includes interference effects, we calculated the optical power absorbed in the active layers for the entire absorption band, and we found that this cannot explain the trend with thickness. Measurement of the cell quantum efficiency as a function of light intensity showed that the relative weight of the device internal processes changes when going from 40 nm to 120 nm thick active layer. Electrical modeling of the device, which takes different internal processes into account, allowed to quantify the changes in the processes affecting the generation - recombination balance. Sub gap external quantum efficiency and morphological analysis of the surface of the films agree with the model's result. We found that as the thickness grows the density of charge transfer states and of dark carriers goes up and the uniformity in the vertical direction is reduced.

  18. Superconductivity in transparent zinc-doped In2O3 films having low carrier density

    Directory of Open Access Journals (Sweden)

    Kazumasa Makise, Nobuhito Kokubo, Satoshi Takada, Takashi Yamaguti, Syunsuke Ogura, Kazumasa Yamada, Bunjyu Shinozaki, Koki Yano, Kazuyoshi Inoue and Hiroaki Nakamura

    2008-01-01

    Full Text Available Thin polycrystalline zinc-doped indium oxide (In2O3–ZnO films were prepared by post-annealing amorphous films with various weight concentrations x of ZnO in the range 0≤x ≤0.06. We have studied the dependences of the resistivity ρ and Hall coefficient on temperature T and magnetic field H in the range 0.5≤T ≤300 K, H≤6 Tfor 350 nm films annealed in air. Films with 0≤x≤0.03 show the superconducting resistive transition. The transition temperature Tc is below 3.3 K and the carrier density n is about 1025–1026 m−3. The annealed In2O3–ZnO films were examined by transmission electron microscopy and x-ray diffraction analysis revealing that the crystallinity of the films depends on the annealing time. We studied the upper critical magnetic field Hc2 (T for the film with x = 0.01. From the slope of dHc2 /dT, we obtain the coherence length ξ (0 ≈ 10 nm at T = 0 K and a coefficient of electronic heat capacity that is small compared with those of other oxide materials.

  19. Charge carrier Density Imaging / IR lifetime mapping of Si wafers by Lock-In Thermography

    NARCIS (Netherlands)

    Van der Tempel, L.

    2012-01-01

    ABSTRACT Minority carrier lifetime imaging by lock-in thermography of passivated silicon wafers for photovoltaic cells has been developed for the public Pieken in de Delta project geZONd. CONCLUSIONS Minority carrier lifetime imaging by lock-in thermography of passivatedsilicon wafers is released t

  20. Influence of optical interference and carrier lifetime on the short circuit current density of organic bulk heterojunction solar cells

    Institute of Scientific and Technical Information of China (English)

    You Hai-Long; Zhang Chun-Fu

    2009-01-01

    Based on simple analytical equations, short circuit current density (Jsc) of the organic bulk heterojunction solar cells has been calculated. It is found that the optical interference effect plays a very important role in the determination of JSC;and obvious oscillatory behaviour of Jsc was observed as a function of thickness. At the same time, the influence of JSC only increases the carrier lifetime on JSC also cannot be neglected. When the carrier lifetime is relatively short, at the initial stage and then decreases rapidly with the increase of active layer thickness. However, for a relatively long carrier lifetime, the exciton dissociation probability must be considered, and Jsc behaves wave-like with the increase of active layer thickness. The validity of this model is confirmed by the experimental results.

  1. High-density carrier-accumulated and electrically stable oxide thin-film transistors from ion-gel gate dielectric

    Science.gov (United States)

    Fujii, Mami N.; Ishikawa, Yasuaki; Miwa, Kazumoto; Okada, Hiromi; Uraoka, Yukiharu; Ono, Shimpei

    2015-12-01

    The use of indium-gallium-zinc oxide (IGZO) has paved the way for high-resolution uniform displays or integrated circuits with transparent and flexible devices. However, achieving highly reliable devices that use IGZO for low-temperature processes remains a technological challenge. We propose the use of IGZO thin-film transistors (TFTs) with an ionic-liquid gate dielectric in order to achieve high-density carrier-accumulated IGZO TFTs with high reliability, and we discuss a distinctive mechanism for the degradation of this organic-inorganic hybrid device under long-term electrical stress. Our results demonstrated that an ionic liquid or gel gate dielectric provides highly reliable and low-voltage operation with IGZO TFTs. Furthermore, high-density carrier accumulation helps improve the TFT characteristics and reliability, and it is highly relevant to the electronic phase control of oxide materials and the degradation mechanism for organic-inorganic hybrid devices.

  2. Tuning the conductivity threshold and carrier density of two-dimensional electron gas at oxide interfaces through interface engineering

    Directory of Open Access Journals (Sweden)

    H. J. Harsan Ma

    2015-08-01

    Full Text Available The two-dimensional electron gas (2DEG formed at the perovskite oxides heterostructures is of great interest because of its potential applications in oxides electronics and nanoscale multifunctional devices. A canonical example is the 2DEG at the interface between a polar oxide LaAlO3 (LAO and non-polar SrTiO3 (STO. Here, the LAO polar oxide can be regarded as the modulating or doping layer and is expected to define the electronic properties of 2DEG at the LAO/STO interface. However, to practically implement the 2DEG in electronics and device design, desired properties such as tunable 2D carrier density are necessary. Here, we report the tuning of conductivity threshold, carrier density and electronic properties of 2DEG in LAO/STO heterostructures by insertion of a La0.5Sr0.5TiO3 (LSTO layer of varying thicknesses, and thus modulating the amount of polarization of the oxide over layers. Our experimental result shows an enhancement of carrier density up to a value of about five times higher than that observed at the LAO/STO interface. A complete thickness dependent metal-insulator phase diagram is obtained by varying the thickness of LAO and LSTO providing an estimate for the critical thickness needed for the metallic phase. The observations are discussed in terms of electronic reconstruction induced by polar oxides.

  3. Variation of carrier concentration and interface trap density in 8MeV electron irradiated c-Si solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Bhat, Sathyanarayana, E-mail: asharao76@gmail.com; Rao, Asha, E-mail: asharao76@gmail.com [Department of Physics, Mangalore Institute of Technology and Engineering, Moodabidri, Mangalore-574225 (India); Krishnan, Sheeja [Department of Physics, Sri Devi Institute of Technology, Kenjar, Mangalore-574142 (India); Sanjeev, Ganesh [Microtron Centre, Department of Physics, Mangalore University, Mangalagangothri-574199 (India); Suresh, E. P. [Solar Panel Division, ISRO Satellite Centre, Bangalore-560017 (India)

    2014-04-24

    The capacitance and conductance measurements were carried out for c-Si solar cells, irradiated with 8 MeV electrons with doses ranging from 5kGy – 100kGy in order to investigate the anomalous degradation of the cells in the radiation harsh environments. Capacitance – Voltage measurements indicate that there is a slight reduction in the carrier concentration upon electron irradiation due to the creation of radiation induced defects. The conductance measurement results reveal that the interface state densities and the trap time constant increases with electron dose due to displacement damages in c-Si solar cells.

  4. Enhance Carrier Density Distributions between Double Quantum Wells Violet Ingan Laser Diode by Using Alingan as a Blocking Layer

    Energy Technology Data Exchange (ETDEWEB)

    Abdullah, Rafid A; Ibrahim, Kamarulazizi, E-mail: rafid_alabdali@yahoo.com, E-mail: kamarul@usm.my [Nano-Optoelectronics Research and Technology Laboratory (N.O.R), School of Physics, Universiti Sains Malaysia, 11800 Penang (Malaysia)

    2011-02-15

    Enhancement of carrier (electron and hole) density distributions between double quantum wells (QWs) violet InGaN laser diode (LD) has numerically been obtained by using quaternary AlInGaN as a blocking layer (BL) instead of conventional ternary AlGaN BL. Simulation results indicate that the quaternary BL has a higher refractive index and optical intensity inside the active region than the ternary BL which leads to reducing the threshold current of the LD from 16.42 mA with ternary BL to 13.67 mA with quaternary BL.

  5. Anomalous enhancement of the sheet carrier density beyond the classic limit on a SrTiO3 surface

    Science.gov (United States)

    Kumar, Neeraj; Kitoh, Ai; Inoue, Isao H.

    2016-05-01

    Electrostatic carrier accumulation on an insulating (100) surface of SrTiO3 by fabricating a field effect transistor with Parylene-C (6 nm)/HfO2 (20 nm) bilayer gate insulator has revealed a mystifying phenomenon: sheet carrier density is about 10 times as large as ( is the sheet capacitance of the gate insulator, VG is the gate voltage, and e is the elementary charge). The channel is so clean to exhibit small subthreshod swing of 170 mV/decade and large mobility of 11 cm2/Vs for of 1 × 1014 cm‑2 at room temperature. Since does not depend on either VG nor time duration, beyond is solely ascribed to negative charge compressibility of the carriers, which was in general considered as due to exchange interactions among electrons in the small limit. However, the observed is too large to be naively understood by the framework. Alternative ideas are proposed in this work.

  6. Ionic Wind Phenomenon and Charge Carrier Mobility in Very High Density Argon Corona Discharge Plasma

    Science.gov (United States)

    Nur, M.; Bonifaci, N.; Denat, A.

    2014-04-01

    Wind ions phenomenon has been observed in the high density argon corona discharge plasma. Corona discharge plasma was produced by point to plane electrodes and high voltage DC. Light emission from the recombination process was observed visually. The light emission proper follow the electric field lines that occur between point and plane electrodes. By using saturation current, the mobilities of non-thermal electrons and ions have been obtained in argon gas and liquid with variation of density from 2,5 1021 to 2 1022 cm-3. In the case of ions, we found that the behaviour of the apparent mobility inversely proportional to the density or follow the Langevin variation law. For non-thermal electron, mobility decreases and approximately follows a variation of Langevin type until the density <= 0,25 the critical density of argon.

  7. High charge carrier density at the NaTaO3/SrTiO3 hetero-interface

    KAUST Repository

    Nazir, Safdar

    2011-08-05

    The formation of a (quasi) two-dimensional electron gas between the band insulators NaTaO3 and SrTiO3 is studied by means of the full-potential linearized augmented plane-wave method of density functional theory. Optimization of the atomic positions points to only small changes in the chemical bonding at the interface. Both the p-type (NaO)−/(TiO2)0 and n-type (TaO2)+/(SrO)0 interfaces are found to be metallic with high charge carrier densities. The effects of O vacancies are discussed. Spin-polarized calculations point to the formation of isolated O 2pmagnetic moments, located in the metallic region of the p-type interface.

  8. Investigations of the drift mobility of carriers and density of states in nanocrystalline CdS thin films

    Science.gov (United States)

    Singh, Baljinder; Singh, Janpreet; Kaur, Jagdish; Moudgil, R. K.; Tripathi, S. K.

    2016-06-01

    Nanocrystalline Cadmium Sulfide (nc-CdS) thin films have been prepared on well-cleaned glass substrate at room temperature (300 K) by thermal evaporation technique using inert gas condensation (IGC) method. X-ray diffraction (XRD) analysis reveals that the films crystallize in hexagonal structure with preferred orientation along [002] direction. Scanning electron microscope (SEM) and Transmission electron microscope (TEM) studies reveal that grains are spherical in shape and uniformly distributed over the glass substrates. The optical band gap of the film is estimated from the transmittance spectra. Electrical parameters such as Hall coefficient, carrier type, carrier concentration, resistivity and mobility are determined using Hall measurements at 300 K. Transit time and mobility are estimated from Time of Flight (TOF) transient photocurrent technique in gap cell configuration. The measured values of electron drift mobility from TOF and Hall measurements are of the same order. Constant Photocurrent Method in ac-mode (ac-CPM) is used to measure the absorption spectra in low absorption region. By applying derivative method, we have converted the measured absorption data into a density of states (DOS) distribution in the lower part of the energy gap. The value of Urbach energy, steepness parameter and density of defect states have been calculated from the absorption and DOS spectra.

  9. Optical gas sensing responses in transparent conducting oxides with large free carrier density

    Science.gov (United States)

    Ohodnicki, P. R.; Andio, M.; Wang, C.

    2014-07-01

    Inherent advantages of optical-based sensing devices motivate a need for materials with useful optical responses that can be utilized as thin film functional sensor layers. Transparent conducting metal oxides with large electrical conductivities as typified by Al-doped ZnO (AZO) display attractive properties for high temperature optical gas sensing through strong optical transduction of responses conventionally monitored through changes in measured electrical resistivity. An enhanced optical sensing response in the near-infrared and ultraviolet/visible wavelength ranges is demonstrated experimentally and linked with characteristic modifications to the dielectric constant due to a relatively high concentration of free charge carriers. The impact of light scattering on the magnitude and wavelength dependence of the sensing response is also discussed highlighting the potential for tuning the optical sensing response by controlling the surface roughness of a continuous film or the average particle size of a nanoparticle-based film. The physics underpinning the optical sensing response for AZO films on planar substrates yields significant insight into the measured sensing response for optical fiber-based evanescent wave absorption spectroscopy sensors employing an AZO sensing layer. The physics of optical gas sensing discussed here provides a pathway towards development of sensing materials for extreme temperature optical gas sensing applications. As one example, preliminary results are presented for a Nb-doped TiO2 film with sufficient stability and relatively large sensing responses at sensing temperatures greater than 500 °C.

  10. Magnetotransport of the low-carrier density one-dimensional =1/2 antiferromagnet Yb4As3

    Indian Academy of Sciences (India)

    P Gegenwart; H Aoki; T Cichorek; J Custers; M Jaime; A Ochiai; F Steglich

    2002-05-01

    The transport properties of the semimetallic quasi-one-dimensional = 1/2 antiferromagnet Yb4As3 have been studied by performing low-temperature ( ≥ 0.02 K) and high magnetic-field ( ≤ 60 T) measurements of the electrical resistivity ρ(, ). For ≳ 2 K a `heavy-fermion’-like behavior ρ() = 2 with huge and nearly field-independent coefficient ≈ 3 cm/K2 is observed, whereas at lower temperatures ρ() deviates from this behavior and slightly increases to the lowest . In > 0 and ≲ 6 K the resistivity shows an anomalous magnetic-history dependence together with an unusual relaxation behavior. In the isothermal resistivity Shubnikov–de Haas (SdH) oscillations, arising from a low-density system of mobile As-4 holes, with a frequency of 25 T have been recorded. From the - and -dependence of the SdH oscillations an effective carrier mass of (0.275 ± 0.005) 0 and a charge-carrier mean-free path of 215 Å are determined. Furthermore, in ≥ 15 T, the system is near the quantum limit and spin-splitting effects are observed.

  11. Diffuse Surface Scattering and Quantum Size Effects in the Surface Plasmon Resonances of Low Carrier Density Nanocrystals

    CERN Document Server

    Monreal, R Carmina; Apell, S Peter

    2016-01-01

    The detailed understanding of the physical parameters that determine Localized Surface Plasmon Resonances (LSPRs) is essential to develop new applications for plasmonics. A relatively new area of research has been opened by the identification of LSPRs in low carrier density systems obtained by doping semiconductor quantum dots. We investigate theoretically how diffuse surface scattering of electrons in combination with the effect of quantization due to size (QSE) impact the evolution of the LSPRs with the size of these nanosystems. Two key parameters are the length $R_0$ giving the strength of the QSE and the velocity $\\beta_T$ of the electronic excitations entering in the length scale for diffuse surface scattering. While the QSE itself only produces a blueshift in energy of the LSPRs, the diffuse surface scattering mechanism gives to both energy and linewidth an oscillatory-damped behavior as a function of size, with characteristic lengths that depend on material parameters. Thus, the evolution of the LSPRs...

  12. Understanding droop effect by analysis on carrier density dependence in InGaN/GaN multiple-quantum-well light-emitting diodes

    Science.gov (United States)

    Liu, Wei; Zhao, Degang; Jiang, Desheng; Chen, Ping; Liu, Zongshun; Zhu, Jianjun; Yang, Jing; He, Xiaoguang; Li, Xiaojing; Li, Xiang; Liang, Feng; Liu, Jianping; Zhang, Liqun; Yang, Hui; Zhang, Yuantao; Du, Guotong

    2016-08-01

    The droop behaviors of two InGaN/GaN multiple-quantum-well blue-green light-emitting diodes grown on c-plane sapphires with different In content are investigated. The higher-In-content sample exhibits a lower efficiency, followed by a more significant droop as current increases in comparison with the lower-In-content diode. However, it is found that for both samples their efficiency reduction trend with increasing carrier density is nearly the same. Combining with the recombination rate equations, an analysis reveals that at the same injection current level, the carrier density in the higher-In-content quantum wells which have stronger polarization effect is larger due to the smaller bimolecular recombination coefficient, resulting in a more significant droop with current. Therefore, a study on the dependence of efficiency on carrier density can provide a clear elucidation to the physical mechanism of the efficiency droop behavior.

  13. Stability of low-carrier-density topological-insulator Bi{sub 2}Se{sub 3} thin films and effect of capping layers

    Energy Technology Data Exchange (ETDEWEB)

    Salehi, Maryam [Department of Materials Science and Engineering, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854 (United States); Brahlek, Matthew; Koirala, Nikesh; Moon, Jisoo; Oh, Seongshik, E-mail: ohsean@physics.rutgers.edu [Department of Physics and Astronomy, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854 (United States); Wu, Liang; Armitage, N. P. [Department of Physics and Astronomy, The Institute for Quantum Matter, The Johns Hopkins University, Baltimore, Maryland 21218 (United States)

    2015-09-01

    Although over the past number of years there have been many advances in the materials aspects of topological insulators (TIs), one of the ongoing challenges with these materials is the protection of them against aging. In particular, the recent development of low-carrier-density bulk-insulating Bi{sub 2}Se{sub 3} thin films and their sensitivity to air demands reliable capping layers to stabilize their electronic properties. Here, we study the stability of the low-carrier-density Bi{sub 2}Se{sub 3} thin films in air with and without various capping layers using DC and THz probes. Without any capping layers, the carrier density increases by ∼150% over a week and by ∼280% over 9 months. In situ-deposited Se and ex situ-deposited poly(methyl methacrylate) suppress the aging effect to ∼27% and ∼88%, respectively, over 9 months. The combination of effective capping layers and low-carrier-density TI films will open up new opportunities in topological insulators.

  14. Electrical transport properties of amorphous Zn-doped In2O3 films in a wide region of carrier density

    International Nuclear Information System (INIS)

    We have systematically investigated the temperature dependence of resistivity p and Hall mobility μ of amorphous Zn-doped In2O3 films (350 nm) in the temperature range 2.0 to 300 K. We prepared film specimens with carrier density n ∼ (2 x 1017 - 6 x 1020/cm3) and p ∼ (3 - 4000)μΩcm (300 K) by changing the gas pressure of oxygen during DC-magnetron sputtering. The μ(n) shows the convex characteristic with a broad peak near n ∼ 3 x 1020cm3, taking the value μ ≅ 50cm2/Vs. In the low n region, it has been found that the μ seems to change as μ ∝ n1/3 . For films with n ≥ 5 x 1019/cm3, the p(T) shows the metallic behavior between ∼ 20 K and 300 K. On the other hand, for films with n ≤ 1019/cm3, p(T) essentially shows the insulating behavior at whole temperatures. From the analysis of the p(T) in the expression of p(T) = p0 exp(A/Tn) at low temperatures, we obtained that the data is well explained by n = 1/2 for dirty films. The estimated electron mean free path l(4 K) deviates from the linear dependence of l ∝ n to decease abruptly near l ∼ 0.2 - 0.4 nm corresponding to the average distance between In and In (or oxygen).

  15. Charge Carrier Density and signal induced in a CVD diamond detector from NIF DT neutrons, x-rays, and electrons

    Energy Technology Data Exchange (ETDEWEB)

    Dauffy, L S; Koch, J A

    2005-10-20

    This report investigates the use of x-rays and electrons to excite a CVD polycrystalline diamond detector during a double pulse experiment to levels corresponding to those expected during a successful (1D clean burn) and a typical failed ignition (2D fizzle) shot at the National Ignition Facility, NIF. The monitoring of a failed ignition shot is the main goal of the diagnostic, but nevertheless, the study of a successful ignition shot is also important. A first large neutron pulse is followed by a smaller pulse (a factor of 1000 smaller in intensity) after 50 to 300 ns. The charge carrier densities produced during a successful and failed ignition shot are about 10{sup 15} e-h+/cm{sup 3} and 2.6* 10{sup 12} e-h+/cm{sup 3} respectively, which is lower than the 10{sup 16} e-h+/cm{sup 3} needed to saturate the diamond wafer due to charge recombination. The charge carrier density and the signal induced in the diamond detector are calculated as a function of the incident x-ray and electron energy, flux, and detector dimensions. For available thicknesses of polycrystalline CVD diamond detectors (250 {micro}m to 1000 {micro}m), a flux of over 10{sup 11} x-rays/cm{sup 2} (with x-ray energies varying from 6 keV to about 10 keV) or 10{sup 9} {beta}/cm{sup 2} (corresponding to 400 pC per electron pulse, E{sub {beta}} > 800 keV) is necessary to excite the detector to sufficient levels to simulate a successful ignition's 14 MeV peak. Failed ignition levels would require lower fluxes, over 10{sup 8} x-rays/cm{sup 2} (6 to 10 keV) or 10{sup 6} {beta}/cm{sup 2} (1 pC per electron pulse, E{sub {beta}} > 800 keV). The incident pulse must be delivered on the detector surface in several nanoseconds. The second pulse requires fluxes down by a factor of 1000. Several possible x-ray beam facilities are investigated: (1) the LBNL Advanced Light Source, (2) the Stanford SLAC and SPEAR, (3) the BNL National Synchrotron Light Source, (4) the ANL Advanced Photon Source, (5) the LLNL Janus

  16. Tuning superior solar cell performance of carrier mobility and absorption in perovskite CH3NH3GeCl3: A density functional calculations

    Science.gov (United States)

    Zhao, Yu-Qing; Wu, Li-Juan; Liu, Biao; Wang, Ling-Zhi; He, Peng-Bin; Cai, Meng-Qiu

    2016-05-01

    The solar cell based on hybrid organic-inorganic halide perovskite has received considerable attention. One of the most important issues in the pursuit of further developments in this area is to obtain both a high carrier mobility and an excellent ability of light adsorption. In this paper, we investigate the electronic structure and electronic effective masses of the new non-toxic material CH3NH3GeCl3 by first-principle calculations. The results show that the absorption efficiency of CH3NH3GeCl3 is more superior to that of CH3NH3PbI3 in short wavelength region. We trace this result to the ferroelectricity caused by the more serious octahedral GeCl6- distortion. We also discover a new relationship between the carrier effective masses anisotropy and the anisotropy of electronic density of states along three principal directions. Moreover, while applied the isotropic compressive pressure, the absorption efficiency and carrier mobility of CH3NH3GeCl3 in orthorhombic phase are improved greatly due to changes of electronic structure. We speculate that these are general results of tuning of the carrier mobility by controlling the band gap and the electronic occupation along different directions, to obtain both a high carrier mobility and an excellent ability of light adsorption.

  17. High-density lipoprotein as a potential carrier for delivery of a lipophilic antitumoral drug into hepatoma cells

    Institute of Scientific and Technical Information of China (English)

    Bin Lou; Xue-Ling Liao; Man-Ping Wu; Pei-Fang Cheng; Chun-Yan Yin; Zheng Fei

    2005-01-01

    AIM: To investigate the possibility of recombinant highdensity lipoprotein (rHDL) being a carrier for delivering antitumoral drug to hepatoma cells.METHODS: Recombinant complex of HDL and aclacinomycin(rHDL-ACM) was prepared by cosonication of apoproteins from HDL (Apo HDL) and ACM as well as phosphatidylcholine.Characteristics of the rHDL-ACM were elucidated by electrophoretic mobility, including the size of particles,morphology and entrapment efficiency. Binding activity of rHDL-ACM to human hepatoma cells was determined by competition assay in the presence of excess native HDL. The cytotoxicity of rHDL-ACM was assessed by MTT method.RESULTS: The density range of rHDL-ACM was 1.063-1.210g/mL, and the same as that of native HDL. The purity of all rHDL-ACM preparations was more than 92%.Encapsulated efficiencies of rHDL-ACM were more than90%. rHDL-ACM particles were typical sphere model of lipoproteins and heterogeneous in particle size. The average diameter was 31.26±5.62 nm by measure of 110rHDL-ACM particles in the range of diameter of lipoproteins.rHDL-ACM could bind on SMMC-7721 cells, and such binding could be competed against in the presence of excess native HDL. rHDL-ACM had same binding capacity as native HDL. The cellular uptake of rHDL-ACM by SMMC-7721 hepatoma cells was significantly higher than that of free ACM at the concentration range of 0.5-10 μg/mL(P<0.01). Cytotoxicity of rHDL-ACM to SMMC-7721 cells was significantly higher than that of free ACM at concentration range of less than 5 μg/mL (P<0.01) and IC50 of rHDL-ACM was lower than IC50 of free ACM(1.68 nmol/L vs3 nmol/L). Compared to L02 hepatocytes,a normal liver cell line, the cellular uptake of rHDL-ACM by SMMC-7721 cells was significantly higher (P<0.01) and in a dose-dependent manner at the concentration range of 0.5-10 μg/mL. Cytotoxicity of the rHDL-ACM to SMMC-7721 cells was significantly higher than that to L02 cells at concentration range of 1-7.5 μg/mL (P<0.01). IC50 for

  18. Effective suppression of efficiency droop in GaN-based light-emitting diodes: role of significant reduction of carrier density and built-in field

    Science.gov (United States)

    Yoo, Yang-Seok; Na, Jong-Ho; Son, Sung Jin; Cho, Yong-Hoon

    2016-01-01

    A critical issue in GaN-based high power light-emitting diodes (LEDs) is how to suppress the efficiency droop problem occurred at high current injection while improving overall quantum efficiency, especially in conventional c-plane InGaN/GaN quantum well (QW), without using complicated bandgap engineering or unconventional materials and structures. Although increasing thickness of each QW may decrease carrier density in QWs, formation of additional strain and defects as well as increased built-in field effect due to enlarged QW thickness are unavoidable. Here, we propose a facile and effective method for not only reducing efficiency droop but also improving quantum efficiency by utilizing c-plane InGaN/GaN QWs having thinner barriers and increased QW number while keeping the same single well thickness and total active layer thickness. As the barrier thickness decreases and the QW number increases, both internal electric field and carrier density within QWs are simultaneously reduced without degradation of material quality. Furthermore, we found overall improved efficiency and reduced efficiency droop, which was attributed to the decrease of the built-in field and to less influence by non-radiative recombination processes at high carrier density. This simple and effective approach can be extended further for high power ultraviolet, green, and red LEDs. PMID:27756916

  19. Carrier-density dependence of photoluminescence from localized states in InGaN/GaN quantum wells in nanocolumns and a thin film

    Energy Technology Data Exchange (ETDEWEB)

    Shimosako, N., E-mail: n-shimosako@sophia.jp; Inose, Y.; Satoh, H.; Kinjo, K.; Nakaoka, T.; Oto, T. [Department of Engineering and Applied Sciences, Sophia University, 7-1 Kioi-cho, Chiyoda-ku, Tokyo 102-8554 (Japan); Kishino, K.; Ema, K. [Department of Engineering and Applied Sciences, Sophia University, 7-1 Kioi-cho, Chiyoda-ku, Tokyo 102-8554 (Japan); Sophia Nanotechnology Research Center, Sophia University, 7-1 Kioi-cho, Chiyoda-ku, Tokyo 102-8554 (Japan)

    2015-11-07

    We have measured and analyzed the carrier-density dependence of photoluminescence (PL) spectra and the PL efficiency of InGaN/GaN multiple quantum wells in nanocolumns and in a thin film over a wide excitation range. The localized states parameters, such as the tailing parameter, density and size of the localized states, and the mobility edge density are estimated. The spectral change and reduction of PL efficiency are explained by filling of the localized states and population into the extended states around the mobility edge density. We have also found that the nanocolumns have a narrower distribution of the localized states and a higher PL efficiency than those of the film sample although the In composition of the nanocolumns is higher than that of the film.

  20. Enhanced sheet carrier densities in polarization controlled AlInN/AlN/GaN/InGaN field-effect transistor on Si (111)

    Energy Technology Data Exchange (ETDEWEB)

    Hennig, J., E-mail: jonas.hennig@ovgu.de; Dadgar, A.; Witte, H.; Bläsing, J.; Lesnik, A.; Strittmatter, A.; Krost, A. [Otto-von-Guericke-Universität Magdeburg, Universitätsplatz 2, 39106 Magdeburg (Germany)

    2015-07-15

    We report on GaN based field-effect transistor (FET) structures exhibiting sheet carrier densities of n = 2.9 10{sup 13} cm{sup −2} for high-power transistor applications. By grading the indium-content of InGaN layers grown prior to a conventional GaN/AlN/AlInN FET structure control of the channel width at the GaN/AlN interface is obtained. The composition of the InGaN layer was graded from nominally x{sub In} = 30 % to pure GaN just below the AlN/AlInN interface. Simulations reveal the impact of the additional InGaN layer on the potential well width which controls the sheet carrier density within the channel region of the devices. Benchmarking the In{sub x}Ga{sub 1−x}N/GaN/AlN/Al{sub 0.87}In{sub 0.13}N based FETs against GaN/AlN/AlInN FET reference structures we found increased maximum current densities of I{sub SD} = 1300 mA/mm (560 mA/mm). In addition, the InGaN layer helps to achieve broader transconductance profiles as well as reduced leakage currents.

  1. Enhanced sheet carrier densities in polarization controlled AlInN/AlN/GaN/InGaN field-effect transistor on Si (111

    Directory of Open Access Journals (Sweden)

    J. Hennig

    2015-07-01

    Full Text Available We report on GaN based field-effect transistor (FET structures exhibiting sheet carrier densities of n = 2.9 1013 cm−2 for high-power transistor applications. By grading the indium-content of InGaN layers grown prior to a conventional GaN/AlN/AlInN FET structure control of the channel width at the GaN/AlN interface is obtained. The composition of the InGaN layer was graded from nominally xIn = 30 % to pure GaN just below the AlN/AlInN interface. Simulations reveal the impact of the additional InGaN layer on the potential well width which controls the sheet carrier density within the channel region of the devices. Benchmarking the InxGa1−xN/GaN/AlN/Al0.87In0.13N based FETs against GaN/AlN/AlInN FET reference structures we found increased maximum current densities of ISD = 1300 mA/mm (560 mA/mm. In addition, the InGaN layer helps to achieve broader transconductance profiles as well as reduced leakage currents.

  2. Enhanced sheet carrier densities in polarization controlled AlInN/AlN/GaN/InGaN field-effect transistor on Si (111)

    International Nuclear Information System (INIS)

    We report on GaN based field-effect transistor (FET) structures exhibiting sheet carrier densities of n = 2.9 1013 cm−2 for high-power transistor applications. By grading the indium-content of InGaN layers grown prior to a conventional GaN/AlN/AlInN FET structure control of the channel width at the GaN/AlN interface is obtained. The composition of the InGaN layer was graded from nominally xIn = 30 % to pure GaN just below the AlN/AlInN interface. Simulations reveal the impact of the additional InGaN layer on the potential well width which controls the sheet carrier density within the channel region of the devices. Benchmarking the InxGa1−xN/GaN/AlN/Al0.87In0.13N based FETs against GaN/AlN/AlInN FET reference structures we found increased maximum current densities of ISD = 1300 mA/mm (560 mA/mm). In addition, the InGaN layer helps to achieve broader transconductance profiles as well as reduced leakage currents

  3. Hall effect in the low charge-carrier density ferromagnet UCo{sub 0.5}Sb{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Tran, V.H.; Troc, R.; Bukowski, Z. [W. Trzebiatowski Institute for Low Temperature and Structure Research, Polish Academy of Sciences, P.O. Box 1410, 50-950 Wroclaw (Poland); Paschen, S.; Steglich, F. [Max-Planck Institut fuer Chemische Physik fester Stoffe, 01187 Dresden (Germany)

    2006-01-01

    The Hall coefficient R {sub H} of ferromagnetic UCo{sub 0.5}Sb{sub 2} (T {sub C}=64.5 K) has been measured on a single crystal in the temperature range 2-300 K and in magnetic fields up to 7 T. The values of the normal R{sub 0} and anomalous R{sub s} coefficients were estimated by comparing R{sub H}(B) with magnetisation M (B) data. The charge carrier concentration is found to decrease rapidly when the system undergoes a transition to the ferromagnetic ordered state. The charge mobility appears to fall down by as much as two orders of magnitude for temperatures from 20 K to 2 K. We ascribe this behaviour to an enormous decrease of the carrier collision time. The temperature dependencies of the Hall mean free path and mobility can be consistently interpreted within the 2D-weak localization feature. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  4. A quantitative discussion on band-gap energy and carrier density of CdO in terms of temperature and oxygen partial pressure

    International Nuclear Information System (INIS)

    Calculations relative to the band-gap energy shift and carrier spatial density in cadmium oxide are performed in terms of the oxygen partial pressure and substrate temperature relative to the deposition process in the crystal growth of the above material, starting from the consideration of the Fermi energy of an exciton gas. In particular, the band-gap shift experienced by cadmium oxide in terms of the corresponding partial pressure of oxygen is considered as well as the electron spatial density as a function of the pressure in question. Influence of temperature is discussed by estimating the average rate of variation of the band-gap shift versus temperature. In addition, the sensitivity of the above-mentioned shift to temperature is studied by means of a suitable parameter

  5. Correlation between Curie temperature and carrier density of electron-doped EuO - is there an intrinsic limit on TC

    International Nuclear Information System (INIS)

    The ferromagnetic semiconductor europium oxide exhibits a multitude of giant properties, such as metal-to-insulator transitions, a colossal magneto-resistance, and very pronounced magneto-optic effects. The recently demonstrated spin-polarization of >90 % in the ferromagnetic state and its excellent electronic compatibility with Si make it an interesting candidate for semiconductor based spintronics. Nevertheless the low Curie temperature (TC) of 69 K of undoped EuO is a major obstacle for the use of this outstanding material in commercial spintronic applications. By electron doping EuO with donor impurities, TC can substantially be increased exploiting an additional exchange interaction that is mediated via the conduction electrons. Here we report on measurements of TC and the carrier densities by Hall effect on La and Gd doped EuO films grown over a wide range of doping concentrations and growth conditions. The experiments show that only a small fraction of the introduced impurities actually act as donors even for optimized growth parameters. Furthermore we found a strong correlation between Curie temperatures and carrier densities.

  6. Local charge neutrality condition, Fermi level and majority carrier density of a semiconductor with multiple localized multi-level intrinsic/impurity defects

    Institute of Scientific and Technical Information of China (English)

    Ken K. Chin

    2011-01-01

    For semiconductors with localized intrinsic/impurity defects,intentionally doped or unintentionally incorporated,that have multiple transition energy levels among charge states,the general formulation of the local charge neutrality condition is given for the determination of the Fermi level and the majority carrier density.A graphical method is used to illustrate the solution of the problem.Relations among the transition energy levels of the multi-level defect are derived using the graphical method.Numerical examples are given for p-doping of the CdTe thin film used in solar panels and semi-insulating Si to illustrate the relevance and importance of the issues discussed in this work.

  7. Investigation of charges carrier density in phosphorus and boron doped SiNx:H layers for crystalline silicon solar cells

    International Nuclear Information System (INIS)

    Highlights: ► We investigate the properties of phosphorus and boron-doped silicon nitride films. ► Phosphorus-doped layers yield higher lifetimes than undoped ones. ► The fixed charges density decreases when increasing the films phosphorus content. ► Boron-doped films feature very low lifetimes. ► These doped layers are of particular interest for crystalline silicon solar cells. -- Abstract: Dielectric layers are of major importance in crystalline silicon solar cells processing, especially as anti-reflection coatings and for surface passivation purposes. In this paper we investigate the fixed charge densities (Qfix) and the effective lifetimes (τeff) of phosphorus (P) and boron (B) doped silicon nitride layers deposited by plasma-enhanced chemical vapour deposition. P-doped layers exhibit a higher τeff than standard undoped layers. In contrast, B-doped layers exhibit lower τeff. A strong Qfix decrease is to be seen when increasing the P content within the film. Based on numerical simulations we also demonstrate that the passivation obtained with P- and B-doped layers are limited by the interface states rather than by the fixed charges

  8. Carrier dynamics analysis for efficiency droop in GaN-based light-emitting diodes with different defect densities using time-resolved electroluminescence

    International Nuclear Information System (INIS)

    We developed a direct experimental approach for investigating the correlation between efficiency droop and recombination rate variation under current injection conditions by using time-resolved electroluminescence (EL) technique. We applied this approach to understand the droop phenomenon of GaN-based light-emitting diodes grown on patterned sapphire substrates (LED-on-PAT) and planar sapphire substrates (LED-on-PLA). Because of lower dislocation density and current leakage in LED-on-PAT compared to LED-on-PLA, it was found that the effective carrier density injected into quantum wells (QWs) in LED-on-PAT was higher than that of the LED-on-PLA under the same current injection conditions, based on the analysis of spectral broadening of EL spectra with varying current injection and photoluminescence experiments under resonant and non-resonant excitation conditions. The efficiency droop in LED-on-PAT was found to be much more severe than that of LED-on-PLA, despite the higher overall quantum efficiency of LED-on-PAT. From the time-resolved EL analysis, we could separate radiative and non-radiative recombination contributions and directly observe (i) the decrease and saturation of radiative recombination time and (ii) the increase and following decrease in behavior of non-radiative recombination time with increasing current injection level, showing a strong correlation between efficiency droop and recombination rate variation. (paper)

  9. Radionuclide carriers

    International Nuclear Information System (INIS)

    A new carrier for radionuclide technetium 99m has been prepared for scintiscanning purposes. The new preparate consists of physiologically acceptable water-insoluble Tcsup(99m)-carrier containing from 0.2 to 0.8 weight percent of stannic ion as reductor, bound to an anionic starch derivative with about 1-20% of phosphate substituents. (EG)

  10. Investigation of carrier density and mobility in microcrystalline silicon alloys using Hall effect and thermopower measurements; Untersuchung der Ladungstraegerkonzentration und -beweglichkeit in mikrokristallinen Siliziumlegierungen mit Hall-Effekt und Thermokraft

    Energy Technology Data Exchange (ETDEWEB)

    Sellmer, Christian

    2012-08-31

    The electronic properties of amorphous and microcrystalline silicon layers in thin-film solar cells significantly affect the efficiency of solar cells. An important property of the individual layer is the electronic transport, which is described by the variables conductivity, photoconductivity, mobility, and carrier concentration. In the past, individual characterization methods were typically used to determine the electronic properties. Using the combination of Hall effect, conductivity, and thermoelectric power measurements additional variables can be derived, such as the effective density of states at the valence and conduction band edge, making a more detailed description of the material possible. To systematically study the electronic properties - in particular carrier mobility and carrier concentration - various series of silicon films are prepared for this work including microcrystalline silicon layers of different doping and crystallinity and a series of silicon films where the Fermi level is moved by irradiation with high energy electrons on one and the same sample. The results show that the transition from amorphous to microcrystalline transport is relatively abrupt. If the electron transport takes place in only amorphous regions, it is marked by the sign anomaly of the Hall effect. If a continuous crystalline path exists, the electronic properties are dominated by the crystalline volume fraction. The results of the measurements of silicon layers are compared with those of microcrystalline silicon carbide samples. Silicon carbide is especially interesting for future applications in thin-film solar cells due to high transparency and high conductivity. It is shown that the effective density of states at the valence and conduction band edge as a function of temperature in p- and n-type microcrystalline silicon and silicon carbide samples largely coincide with those of crystalline silicon or silicon carbide. A square root shaped profile of the density of

  11. Aircraft Carriers

    DEFF Research Database (Denmark)

    Nødskov, Kim; Kværnø, Ole

    in Asia and will balance the carrier acquisitions of the United States, the United Kingdom, Russia and India. China’s current military strategy is predominantly defensive, its offensive elements being mainly focused on Taiwan. If China decides to acquire a large carrier with offensive capabilities......, then the country will also acquire the capability to project military power into the region beyond Taiwan, which it does not possess today. In this way, China will have the military capability to permit a change of strategy from the mainly defensive, mainland, Taiwan-based strategy to a more assertive strategy...... to acquire a carrier, they can either buy one or build it themselves. The easiest way would be to buy a carrier, and if that is the chosen option, then Russia would be the most likely country to build it. Technologically, it will be a major challenge for them to build one themselves and it is likely...

  12. Preconception Carrier Screening

    Science.gov (United States)

    ... Events Advocacy For Patients About ACOG Preconception Carrier Screening Home For Patients Search FAQs Preconception Carrier Screening ... Screening FAQ179, August 2012 PDF Format Preconception Carrier Screening Pregnancy What is preconception carrier screening? What is ...

  13. Dopant selection for control of charge carrier density and mobility in amorphous indium oxide thin-film transistors: Comparison between Si- and W-dopants

    Energy Technology Data Exchange (ETDEWEB)

    Mitoma, Nobuhiko, E-mail: MITOMA.Nobuhiko@nims.go.jp, E-mail: TSUKAGOSHI.Kazuhito@nims.go.jp; Kizu, Takio; Lin, Meng-Fang; Tsukagoshi, Kazuhito, E-mail: MITOMA.Nobuhiko@nims.go.jp, E-mail: TSUKAGOSHI.Kazuhito@nims.go.jp [International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science (NIMS), Tsukuba, Ibaraki 305-0044 (Japan); Aikawa, Shinya [International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science (NIMS), Tsukuba, Ibaraki 305-0044 (Japan); Research Institute for Science and Technology, Kogakuin University, Hachioji, Tokyo 192-0015 (Japan); Ou-Yang, Wei [International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science (NIMS), Tsukuba, Ibaraki 305-0044 (Japan); Department of Physics, Engineering Research Center for Nanophotonics and Advanced Instrument, Ministry of Education, East China Normal University, 3663 North Zhongshan Road, Shanghai 200062 (China); Gao, Xu [International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science (NIMS), Tsukuba, Ibaraki 305-0044 (Japan); Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Institute of Functional Nano and Soft Materials (FUNSOM), Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215123 (China); Fujiwara, Akihiko [Research and Utilization Division, Japan Synchrotron Radiation Research Institute/SPring-8, Sayo, Hyogo 679-5198 (Japan); Nabatame, Toshihide [MANA Foundry and MANA Advanced Device Materials Group, National Institute for Materials Science (NIMS), Tsukuba, Ibaraki 305-0044 (Japan)

    2015-01-26

    The dependence of oxygen vacancy suppression on dopant species in amorphous indium oxide (a-InO{sub x}) thin film transistors (TFTs) is reported. In a-InO{sub x} TFTs incorporating equivalent atom densities of Si- and W-dopants, absorption of oxygen in the host a-InO{sub x} matrix was found to depend on difference of Gibbs free energy of the dopants for oxidation. For fully oxidized films, the extracted channel conductivity was higher in the a-InO{sub x} TFTs containing dopants of small ionic radius. This can be explained by a reduction in the ionic scattering cross sectional area caused by charge screening effects.

  14. What Is Carrier Screening?

    Science.gov (United States)

    ... you want to learn. Search form Search Carrier screening You are here Home Testing & Services Testing for ... help you make the decision. What Is Carrier Screening? Carrier screening checks if a person is a " ...

  15. Optoelectronic characterization of carrier extraction in a hot carrier photovoltaic cell structure

    Science.gov (United States)

    Dimmock, James A. R.; Kauer, Matthias; Smith, Katherine; Liu, Huiyun; Stavrinou, Paul N.; Ekins-Daukes, Nicholas J.

    2016-07-01

    A hot carrier photovoltaic cell requires extraction of electrons on a timescale faster than they can lose energy to the lattice. We optically and optoelectronically characterize two resonant tunneling structures, showing their compatability with hot carrier photovoltaic operation, demonstrating structural and carrier extraction properties necessary for such a device. In particular we use time resolved and temperature dependent photoluminescence to determine extraction timescales and energy levels in the structures and demonstrate fast carrier extraction by tunneling. We also show that such devices are capable of extracting photo-generated electrons at high carrier densities, with an open circuit voltage in excess of 1 V.

  16. Fabrication of TiO2-NTs and TiO2-NTs covered honeycomb lattice and investigation of carrier densities in I-/I3- electrolyte by electrochemical impedance spectroscopy

    Science.gov (United States)

    Baran, Evrim; Yazıcı, Birgül

    2015-12-01

    The TiO2 nanotubes (NTs) were produced by one-step (1S) and two-step (2S) anodization technique. Effects of various anodization potential and times on the growth of TiO2-NTs were investigated by using Field Emission-Scanning Electron Microscopy (FE-SEM). The crystal structure of the electrodes was determined with X-ray powder diffractometry (XRD). The most suitable potential and time for TiO2-NTs obtained by both of anodization methods were found to be 21 V and 4 h. XRD results indicated that 2S anodization technique provided better crystallinity. The electrochemical behaviors of the electrodes in acetonitrile electrolyte contained I-/I3- were examined by utilizing electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV) techniques. Electrochemical results showed that 2S anodization technique increases the carrier densities (ND) value of TiO2-NTs, and flat band potential is shifted by 50 mV to more negative values.

  17. Asymmetric Carrier Random PWM

    DEFF Research Database (Denmark)

    Mathe, Laszlo; Lungeanu, Florin; Rasmussen, Peter Omand;

    2010-01-01

    This paper presents a new fixed carrier frequency random PWM method, where a new type of carrier wave is proposed for modulation. Based on the measurements, it is shown that the spread effect of the discrete components from the motor current spectra is very effective independent of the modulation...

  18. Peptide-Carrier Conjugation

    DEFF Research Database (Denmark)

    Hansen, Paul Robert

    2015-01-01

    To produce antibodies against synthetic peptides it is necessary to couple them to a protein carrier. This chapter provides a nonspecialist overview of peptide-carrier conjugation. Furthermore, a protocol for coupling cysteine-containing peptides to bovine serum albumin is outlined....

  19. Charge-carrier relaxation dynamics in highly ordered poly( p -phenylene vinylene): Effects of carrier bimolecular recombination and trapping

    Science.gov (United States)

    Soci, Cesare; Moses, Daniel; Xu, Qing-Hua; Heeger, Alan J.

    2005-12-01

    We have studied the charge-carrier relaxation dynamics in highly ordered poly( p -phenylene vinylene) over a broad time range using fast (t>100ps) transient photoconductivity measurements. The carrier density was also monitored (t>100fs) by means of photoinduced absorption probed at the infrared active vibrational modes. We find that promptly upon charge-carrier photogeneration, the initial polaron dynamics is governed by bimolecular recombination, while later in the subnanosecond time regime carrier trapping gives rise to an exponential decay of the photocurrent. The more sensitive transient photocurrent measurements indicate that in the low excitation regime, when the density of photocarriers is comparable to that of the trapping states (˜1016cm-3) , carrier hopping between traps along with transport via extended states determines the carrier relaxation, a mechanism that is manifested by a long-lived photocurrent “tail.” This photocurrent tail is reduced by lowering the temperature and/or by increasing the excitation density. Based on these data, we develop a comprehensive kinetic model that takes into account the bipolar charge transport, the free-carrier bimolecular recombination, the carrier trapping, and the carrier recombination involving free and trapped carriers.

  20. Carrier lifetimes in thin-film photovoltaics

    Science.gov (United States)

    Baek, Dohyun

    2015-09-01

    The carrier lifetimes in thin-film solar cells are reviewed and discussed. Shockley-Read-Hall recombination is dominant at low carrier density, Auger recombination is dominant under a high injection condition and high carrier density, and surface recombination is dominant under any conditions. Because the surface photovoltage technique is insensitive to the surface condition, it is useful for bulk lifetime measurements. The photoconductance decay technique measures the effective recombination lifetime. The time-resolved photoluminescence technique is very useful for measuring thin-film semiconductor or solar-cell materials lifetime, because the sample is thin, other techniques are not suitable for measuring the lifetime. Many papers have provided time-resolved photoluminescence (TRPL) lifetimes for copper-indium-gallium-selenide (CIGS) and CdTe thin-film solar cell. The TRPL lifetime strongly depends on open-circuit voltage and conversion efficiency; however, the TRPL life time is insensitive to the short-circuit current.

  1. Carrier Statistics and Quantum Capacitance Models of Graphene Nanoscroll

    Directory of Open Access Journals (Sweden)

    M. Khaledian

    2014-01-01

    schematic perfect scroll-like Archimedes spiral. The DOS model was derived at first, while it was later applied to compute the carrier concentration and quantum capacitance model. Furthermore, the carrier concentration and quantum capacitance were modeled for both degenerate and nondegenerate regimes, along with examining the effect of structural parameters and chirality number on the density of state and carrier concentration. Latterly, the temperature effect on the quantum capacitance was studied too.

  2. Photoinduced Transformation between Charge Carrier and Spin Carrier in Polymers

    Institute of Scientific and Technical Information of China (English)

    MEI Yuan; ZHAO Chang; SUN Xin

    2006-01-01

    By dynamical simulations, we show a transforming process between neutral soliton (spin carrier) and charged soliton (charge carrier) in polymers via photo-excitation, taking a polaron as the transitional bridge. It is photoinduced transformation between spin carrier and charge carrier. In this way, we demonstrate an access for polymers to be applied to spintronics.

  3. The value of energy carriers

    NARCIS (Netherlands)

    Gool, W. van

    1987-01-01

    The value of energy carriers can be described thermodynamically by the amount of heat (enthalpy method) or work (exergy or availability method) that can be obtained from the carriers. Prices for energy carriers are used in economics to express their values. The prices for energy carriers are often r

  4. Duchenne muscular dystrophy carriers

    International Nuclear Information System (INIS)

    By means of magnetic resonance imaging (MRI), the proton spin-lattice relaxation times (T1 values) of the skeletal muscles were measured in Duchenne muscular dystrophy (DMD) carriers and normal controls. The bound water fraction (BWF) was calculated from the T1 values obtained, according to the fast proton diffusion model. In the DMD carriers, T1 values of the gluteus maximus and quadriceps femoris muscles were significantly higher, and BWFs of these muscles were significantly lower than in normal control. Degenerative muscular changes accompanied by interstitial edema were presumed responsible for this abnormality. No correlation was observed between the muscle T1 and serum creatine kinase values. The present study showed that MRI could be a useful method for studying the dynamic state of water in both normal and pathological skeletal muscles. Its possible utility for DMD carrier detection was discussed briefly. (orig.)

  5. The value of energy carriers

    OpenAIRE

    Gool, W. van

    1987-01-01

    The value of energy carriers can be described thermodynamically by the amount of heat (enthalpy method) or work (exergy or availability method) that can be obtained from the carriers. Prices for energy carriers are used in economics to express their values. The prices for energy carriers are often related to their enthalpies when other properties and conditions are equivalent. However, it has been suggested that the exergy of the energy carriers is the proper quantity to establish their value...

  6. Carrier localization in gallium nitride

    Energy Technology Data Exchange (ETDEWEB)

    Wetzel, C. [Lawrence Berkeley National Lab., CA (United States)][California Univ., Berkeley, CA (United States); Walukiewicz, W. [Lawrence Berkeley National Lab., CA (United States); Haller, E.E. [Lawrence Berkeley National Lab., CA (United States)][California Univ., Berkeley, CA (United States)] [and others

    1996-09-01

    In wide bandgap GaN, a large number of interesting and important scientific questions remain to be answered. For example, the large free electron concentration reaching 10{sup 19} to 10{sup 20} cm{sup - 3} in nominally undoped material are ascribed to intrinsic defects because no chemical impurity has been found at such high concentrations. According to theoretical models, a nitrogen vacancy acts as a donor but its formation energy is very large in n-type materials, making this suggestion controversial. We have investigated the nature of this yet unidentified donor at large hydrostatic pressure. Results from infrared reflection and Raman scattering indicate strong evidence for localization of free carriers by large pressures. The carrier density is drastically decreased by two orders of magnitude between 20 and 30 GPa. Several techniques provide independent evidence for results in earlier reports and present the first quantitative analysis. A possible interpretation of this effect in terms of the resonant donor level is presented.

  7. Information and Its Carriers.

    Science.gov (United States)

    Herrmann, F.; And Others

    1985-01-01

    Describes: (1) the structure of a data transmission source, carrier, and receiver; (2) a quantitative measure for the amount of data, followed by some quantitative examples of data transmission processes; (3) the concept of data current; (4) data containers; and (5) how this information can be used to structure physics courses. (JN)

  8. Screening-induced carrier transport in silicene

    International Nuclear Information System (INIS)

    Based on the Boltzmann transport equation in the MRT approximation, we present a theory to investigate low-field carrier transport in dual-gated silicene FETs by taking into account screened charged impurity scattering, which is the most likely scattering mechanism limiting the conductivity. Static RPA dielectric screening is also included in the conductivity calculation to study temperature-dependent silicene transport. It is found that both calculated conductivity and band gap not only depend strongly on carrier sheet density, but also depend strongly on effective offset density. More importantly, screening-induced metal-insulator-transition phenomena in buckled silicene can be observed theoretically, which is similar to that obtained in monolayer graphene. (paper)

  9. Heat to electricity conversion by cold carrier emissive energy harvesters

    International Nuclear Information System (INIS)

    This paper suggests a method to convert heat to electricity by the use of devices called cold carrier emissive energy harvesters (cold carrier EEHs). The working principle of such converters is explained and theoretical power densities and efficiencies are calculated for ideal devices. Cold carrier EEHs are based on the same device structure as hot carrier solar cells, but works in an opposite way. Whereas a hot carrier solar cell receives net radiation from the sun and converts some of this radiative heat flow into electricity, a cold carrier EEH sustains a net outflux of radiation to the surroundings while converting some of the energy supplied to it into electricity. It is shown that the most basic type of cold carrier EEHs have the same theoretical efficiency as the ideal emissive energy harvesters described earlier by Byrnes et al. In the present work, it is also shown that if the emission from the cold carrier EEH originates from electron transitions across an energy gap where a difference in the chemical potential of the electrons above and below the energy gap is sustained, power densities slightly higher than those given by Byrnes et al. can be achieved

  10. Heat to electricity conversion by cold carrier emissive energy harvesters

    Energy Technology Data Exchange (ETDEWEB)

    Strandberg, Rune [Department of Engineering Sciences, University of Agder, Jon Lilletuns vei 9, 4879 Grimstad (Norway)

    2015-12-07

    This paper suggests a method to convert heat to electricity by the use of devices called cold carrier emissive energy harvesters (cold carrier EEHs). The working principle of such converters is explained and theoretical power densities and efficiencies are calculated for ideal devices. Cold carrier EEHs are based on the same device structure as hot carrier solar cells, but works in an opposite way. Whereas a hot carrier solar cell receives net radiation from the sun and converts some of this radiative heat flow into electricity, a cold carrier EEH sustains a net outflux of radiation to the surroundings while converting some of the energy supplied to it into electricity. It is shown that the most basic type of cold carrier EEHs have the same theoretical efficiency as the ideal emissive energy harvesters described earlier by Byrnes et al. In the present work, it is also shown that if the emission from the cold carrier EEH originates from electron transitions across an energy gap where a difference in the chemical potential of the electrons above and below the energy gap is sustained, power densities slightly higher than those given by Byrnes et al. can be achieved.

  11. Intestinal solute carriers

    DEFF Research Database (Denmark)

    Steffansen, Bente; Nielsen, Carsten Uhd; Brodin, Birger;

    2004-01-01

    membrane transporters in the small intestine in order to increase oral bioavailabilities of drug or prodrug, the major influence on in vivo pharmacokinetics is suggested to be dose-dependent increase in bioavailability as well as prolonged blood circulation due to large capacity facilitated absorption......A large amount of absorptive intestinal membrane transporters play an important part in absorption and distribution of several nutrients, drugs and prodrugs. The present paper gives a general overview on intestinal solute carriers as well as on trends and strategies for targeting drugs and....../or prodrugs to these carriers in order to increasing oral bioavailability and distribution. A number of absorptive intestinal transporters are described in terms of gene and protein classification, driving forces, substrate specificities and cellular localization. When targeting absorptive large capacity...

  12. Hungarian students’ carrier aspirations

    Directory of Open Access Journals (Sweden)

    A.S. Gubik

    2014-06-01

    Full Text Available The article analyzes the students’ carrier aspiration, right after their graduation and five years after their studies. It examines the differences arising from the students’ family business background and their most important social variables (gender, age. Then the study highlights the effects of study field on the students’ intention. The direct effect of education on starting an enterprise is undiscovered in the literature, the paper deals with the influence of availability and services use, offered by higher institutions.

  13. Carrier transport uphill. I. General

    DEFF Research Database (Denmark)

    Rosenberg, T; Wilbrandt, W

    1963-01-01

    A quantitative treatment of a carrier pump operating with two carrier forms C and Z is presented. Asymmetric metabolic reactions are assumed to transform Z into C on one and C into Z on the other side of the membrane, establishing a carrier cycle. The kinetical consequences of this mechanism...

  14. Carrier dynamics and gain spectra at room-temperature in epitaxial ZNO thin films

    DEFF Research Database (Denmark)

    Yu, Ping; Hvam, Jørn Märcher; Wong, K. S.;

    1999-01-01

    Carrier dynamics of epitaxial ZnO thin film was investigated using a frequency up-conversion tehcnique. At lower carrier densities, the decay time of free exciton recombination was measured to be 24 ps. Rapid decay times of a few picoseconds were observed at higher carrier densities, which show a...... transition of two dynamic processes. The comparison of calculated gain spectrum and experimental data gave evidence that the transition is form exciton-exciton scattering to the recombination of electron hole plasma....

  15. Charge carrier coherence and Hall effect in organic semiconductors

    Science.gov (United States)

    Yi, H. T.; Gartstein, Y. N.; Podzorov, V.

    2016-03-01

    Hall effect measurements are important for elucidating the fundamental charge transport mechanisms and intrinsic mobility in organic semiconductors. However, Hall effect studies frequently reveal an unconventional behavior that cannot be readily explained with the simple band-semiconductor Hall effect model. Here, we develop an analytical model of Hall effect in organic field-effect transistors in a regime of coexisting band and hopping carriers. The model, which is supported by the experiments, is based on a partial Hall voltage compensation effect, occurring because hopping carriers respond to the transverse Hall electric field and drift in the direction opposite to the Lorentz force acting on band carriers. We show that this can lead in particular to an underdeveloped Hall effect observed in organic semiconductors with substantial off-diagonal thermal disorder. Our model captures the main features of Hall effect in a variety of organic semiconductors and provides an analytical description of Hall mobility, carrier density and carrier coherence factor.

  16. Experimental and ab initio ultrafast carrier dynamics in plasmonic nanoparticles

    CERN Document Server

    Brown, Ana M; Narang, Prineha; Schwartzberg, Adam M; Goddard, William A; Atwater, Harry A

    2016-01-01

    Ultrafast pump-probe measurements of plasmonic nanostructures probe the non-equilibrium behavior of excited carriers, which involves several competing effects obscured in typical empirical analyses. Here we present pump-probe measurements of plasmonic nanoparticles along with a complete theoretical description based on first-principles calculations of carrier dynamics and optical response, free of any fitting parameters. We account for detailed electronic-structure effects in the density of states, excited carrier distributions, electron-phonon coupling, and dielectric functions which allow us to avoid effective electron temperature approximations. Using this calculation method, we obtain excellent quantitative agreement with spectral and temporal features in transient-absorption measurements. In both our experiments and calculations, we identify the two major contributions of the initial response with distinct signatures: short-lived highly non-thermal excited carriers and longer-lived thermalizing carriers.

  17. Nonequilibrium carrier dynamics in transition metal dichalcogenide semiconductors

    Science.gov (United States)

    Steinhoff, A.; Florian, M.; Rösner, M.; Lorke, M.; Wehling, T. O.; Gies, C.; Jahnke, F.

    2016-09-01

    When exploring new materials for their potential in (opto)electronic device applications, it is important to understand the role of various carrier interaction and scattering processes. In atomically thin transition metal dichalcogenide semiconductors, the Coulomb interaction is known to be much stronger than in quantum wells of conventional semiconductors like GaAs, as witnessed by the 50 times larger exciton binding energy. The question arises, whether this directly translates into equivalently faster carrier-carrier Coulomb scattering of excited carriers. Here we show that a combination of ab initio band-structure and many-body theory predicts Coulomb-mediated carrier relaxation on a sub-100 fs time scale for a wide range of excitation densities, which is less than an order of magnitude faster than in quantum wells.

  18. Unified description of charge-carrier mobilities in disordered semiconducting polymers

    NARCIS (Netherlands)

    Pasveer, WF; Cottaar, J; Tanase, C; Coehoorn, R; Bobbert, PA; Blom, PWM; de Leeuw, DM; Michels, MAJ

    2005-01-01

    From a numerical solution of the master equation for hopping transport in a disordered energy landscape with a Gaussian density of states, we determine the dependence of the charge-carrier mobility on temperature, carrier density, and electric field. Experimental current-voltage characteristics in d

  19. Maintainable substrate carrier for electroplating

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Chen-An; Abas, Emmanuel Chua; Divino, Edmundo Anida; Ermita, Jake Randal G.; Capulong, Jose Francisco S.; Castillo, Arnold Villamor; Ma, Diana Xiaobing

    2016-08-02

    One embodiment relates to a substrate carrier for use in electroplating a plurality of substrates. The carrier includes a non-conductive carrier body on which the substrates are placed and conductive lines embedded within the carrier body. A plurality of conductive clip attachment parts are attached in a permanent manner to the conductive lines embedded within the carrier body. A plurality of contact clips are attached in a removable manner to the clip attachment parts. The contact clips hold the substrates in place and conductively connecting the substrates with the conductive lines. Other embodiments, aspects and features are also disclosed.

  20. HOT CARRIER SENSITIVITY OF MOSFET's EXPOSED TO SYNCHROTRON-LIGHT

    OpenAIRE

    Przyrembel, G.; Mahnkopf, R.; Wagemann, H.

    1988-01-01

    The influence of synchrotron-light irradiation for p- and n-channel MOSFET's on their sensitivity to hot carrier degradation was investigated. The radiation induces additional interface states and a positive oxide charge. Annealing at 450°C reduces the interface state density to its initial value but not the oxide charge. A hot carrier stress can compensate this remaining charge by trapping electrons. This effect produces an enhanced shift of the threshold voltage compared to non-irradiated d...

  1. Tracking Ultrafast Carrier Dynamics in Single Semiconductor Nanowire Heterostructures

    Directory of Open Access Journals (Sweden)

    Taylor A.J.

    2013-03-01

    Full Text Available An understanding of non-equilibrium carrier dynamics in silicon (Si nanowires (NWs and NW heterostructures is very important due to their many nanophotonic and nanoelectronics applications. Here, we describe the first measurements of ultrafast carrier dynamics and diffusion in single heterostructured Si nanowires, obtained using ultrafast optical microscopy. By isolating individual nanowires, we avoid complications resulting from the broad size and alignment distribution in nanowire ensembles, allowing us to directly probe ultrafast carrier dynamics in these quasi-one-dimensional systems. Spatially-resolved pump-probe spectroscopy demonstrates the influence of surface-mediated mechanisms on carrier dynamics in a single NW, while polarization-resolved femtosecond pump-probe spectroscopy reveals a clear anisotropy in carrier lifetimes measured parallel and perpendicular to the NW axis, due to density-dependent Auger recombination. Furthermore, separating the pump and probe spots along the NW axis enabled us to track space and time dependent carrier diffusion in radial and axial NW heterostructures. These results enable us to reveal the influence of radial and axial interfaces on carrier dynamics and charge transport in these quasi-one-dimensional nanosystems, which can then be used to tailor carrier relaxation in a single nanowire heterostructure for a given application.

  2. Photo-generated carriers lose energy during extraction from polymer-fullerene solar cells

    KAUST Repository

    Melianas, Armantas

    2015-11-05

    In photovoltaic devices, the photo-generated charge carriers are typically assumed to be in thermal equilibrium with the lattice. In conventional materials, this assumption is experimentally justified as carrier thermalization completes before any significant carrier transport has occurred. Here, we demonstrate by unifying time-resolved optical and electrical experiments and Monte Carlo simulations over an exceptionally wide dynamic range that in the case of organic photovoltaic devices, this assumption is invalid. As the photo-generated carriers are transported to the electrodes, a substantial amount of their energy is lost by continuous thermalization in the disorder broadened density of states. Since thermalization occurs downward in energy, carrier motion is boosted by this process, leading to a time-dependent carrier mobility as confirmed by direct experiments. We identify the time and distance scales relevant for carrier extraction and show that the photo-generated carriers are extracted from the operating device before reaching thermal equilibrium.

  3. Autonomous component carrier selection

    DEFF Research Database (Denmark)

    Garcia, Luis Guilherme Uzeda; Pedersen, Klaus; Mogensen, Preben

    2009-01-01

    in local areas, basing our study case on LTE-Advanced. We present extensive network simulation results to demonstrate that a simple and robust interference management scheme, called autonomous component carrier selection allows each cell to select the most attractive frequency configuration; improving......Low-power base stations such as e.g. Femto-cells are one of the candidates for high data rate provisioning in local areas, such as residences, apartment complexes, business offices and outdoor hotspot scenarios. Unfortunately, the benefits are not without new challenges in terms of interference...... management and efficient system operation. Due to the expected large number of user-deployed cells, centralized network planning becomes unpractical and new scalable alternatives must be sought. In this article, we propose a fully distributed and scalable solution to the interference management problem...

  4. Stacking dependence of carrier transport properties in multilayered black phosphorous

    Science.gov (United States)

    Sengupta, A.; Audiffred, M.; Heine, T.; Niehaus, T. A.

    2016-02-01

    We present the effect of different stacking orders on carrier transport properties of multi-layer black phosphorous. We consider three different stacking orders AAA, ABA and ACA, with increasing number of layers (from 2 to 6 layers). We employ a hierarchical approach in density functional theory (DFT), with structural simulations performed with generalized gradient approximation (GGA) and the bandstructure, carrier effective masses and optical properties evaluated with the meta-generalized gradient approximation (MGGA). The carrier transmission in the various black phosphorous sheets was carried out with the non-equilibrium green’s function (NEGF) approach. The results show that ACA stacking has the highest electron and hole transmission probabilities. The results show tunability for a wide range of band-gaps, carrier effective masses and transmission with a great promise for lattice engineering (stacking order and layers) in black phosphorous.

  5. Nonequilibrium carrier dynamics in transition metal dichalcogenide semiconductors

    Science.gov (United States)

    Steinhoff, A.; Florian, M.; Rösner, M.; Lorke, M.; Wehling, T. O.; Gies, C.; Jahnke, F.

    2016-09-01

    When exploring new materials for their potential in (opto)electronic device applications, it is important to understand the role of various carrier interaction and scattering processes. In atomically thin transition metal dichalcogenide semiconductors, the Coulomb interaction is known to be much stronger than in quantum wells of conventional semiconductors like GaAs, as witnessed by the 50 times larger exciton binding energy. The question arises, whether this directly translates into equivalently faster carrier–carrier Coulomb scattering of excited carriers. Here we show that a combination of ab initio band-structure and many-body theory predicts Coulomb-mediated carrier relaxation on a sub-100 fs time scale for a wide range of excitation densities, which is less than an order of magnitude faster than in quantum wells.

  6. Stacking dependence of carrier transport properties in multilayered black phosphorous.

    Science.gov (United States)

    Sengupta, A; Audiffred, M; Heine, T; Niehaus, T A

    2016-02-24

    We present the effect of different stacking orders on carrier transport properties of multi-layer black phosphorous. We consider three different stacking orders AAA, ABA and ACA, with increasing number of layers (from 2 to 6 layers). We employ a hierarchical approach in density functional theory (DFT), with structural simulations performed with generalized gradient approximation (GGA) and the bandstructure, carrier effective masses and optical properties evaluated with the meta-generalized gradient approximation (MGGA). The carrier transmission in the various black phosphorous sheets was carried out with the non-equilibrium green's function (NEGF) approach. The results show that ACA stacking has the highest electron and hole transmission probabilities. The results show tunability for a wide range of band-gaps, carrier effective masses and transmission with a great promise for lattice engineering (stacking order and layers) in black phosphorous. PMID:26809017

  7. 载气对炭/炭复合材料沉积速率、体密度和微观结构的影响%Effect of carrier gases on densification rate, bulk density and microstructure of carbon/carbon composites

    Institute of Scientific and Technical Information of China (English)

    侯振华; 郝名扬; 罗瑞盈; 向巧; 杨威; 商海东; 许怀哲

    2015-01-01

    分别采用H2和CO2作为载气,CH4为前躯体,通过等温化学气相渗积制备炭/炭复合材料,通过偏光显微镜、拉曼光谱、X射线衍射和透射电镜对材料微观结构表征以及渗积过程密度变化,研究载气对沉积速率、体密度和微观结构的影响规律。结果表明:在渗积前50 h,CH4-H2体系的沉积速率明显大于CH4-CO2体系,但在其余渗积时间里,CH4-H2体系的沉积速率小于CH4-CO2体系。当载气从H2变成CO2时,复合材料的体密度从1.626 g/cm3增加到1.723 g/cm3,最大径向密度梯度从0.074 g/cm3减小到0.056 g/cm3。同时,基体炭从纯的粗糙体炭转变为杂化粗糙体炭含有过度生长锥,且平均石墨化度从62.7%下降到50.8%。这些显著的变化是由于CO2的氧化作用降低了表面沉积速率,却没有降低孔内沉积速率,同时大量的缺陷形成于层状石墨烯结构中导致形成过度生长锥,降低了热解炭织构。%Effect of carrier gases( H2 and CO2 ) on the densification rate, bulk density and microstructure of carbon/carbon com-posites fabricated by isothermalchemical vapor infiltration from methane ( CH4 ) was investigated. In the initial 50 h, the densifica-tion rate obtained from CH4-H2 is obviously higher than that from CH4-CO2 , while the densification rate from CH4-H2 is lower than that from CH4-CO2 with a further increase of infiltration time. When the carrier gas is switched from H2 to CO2 , the average bulk density of the compositeincreases from 1. 626 to 1. 723 g/cm3 , the maximum radial density gradient decreases from 0. 074 to 0. 056 g/cm3 , the matrix changes from the pure rough laminar to hybrid rough laminar pyrocarbon with overgrowth cones, and the average degree of graphitization reduces from 62. 7% to 50. 8%. These significant changes are caused by the fact that CO2 can ef-fectively reduce the surface deposition rate but does not inhibit the in-pore infiltration, and thatdefects are formed in the deposits by a

  8. The growth limits of the low cost carrier model

    NARCIS (Netherlands)

    J.G. de Wit; J. Zuidberg

    2012-01-01

    Today, many low cost carriers (LCCs) continue to enjoy rapid growth and still have a fair number of new aircraft on order. There are signs however that the market for LCCs is limited, owing to increasing route density problems, primarily in Europe but seemingly also in North America: the fact that a

  9. Nanostructured Lipid Carriers: A potential drug carrier for cancer chemotherapy

    Directory of Open Access Journals (Sweden)

    Selvamuthukumar Subramanian

    2012-11-01

    Full Text Available Abstract Nanotechnology having developed exponentially, the aim has been on therapeutic undertaking, particularly for cancerous disease chemotherapy. Nanostructured lipid carriers have attracted expanding scientific and commercial vigilance in the last couple of years as alternate carriers for the pharmaceutical consignment, particularly anticancer pharmaceuticals. Shortcomings often came across with anticancer mixtures, such as poor solubility, normal tissue toxicity, poor specificity and steadiness, as well as the high incidence rate of pharmaceutical resistance and the rapid degradation, need of large-scale output procedures, a fast release of the pharmaceutical from its carrier scheme, steadiness troubles, the residues of the organic solvents utilized in the output method and the toxicity from the polymer with esteem to the carrier scheme are anticipated to be overcome through use of the Nanostructured Lipid Carrier. In this review the benefits, types, drug release modulations, steadiness and output techniques of NLCs are discussed. In supplement, the function of NLC in cancer chemotherapy is presented and hotspots in research are emphasized. It is foreseen that, in the beside future, nanostructured lipid carriers will be further advanced to consign cytotoxic anticancer compounds in a more efficient, exact and protected manner.

  10. Basic Stand Alone Carrier Line Items PUF

    Data.gov (United States)

    U.S. Department of Health & Human Services — This release contains the Basic Stand Alone (BSA) Carrier Line Items Public Use Files (PUF) with information from Medicare Carrier claims. The CMS BSA Carrier Line...

  11. Ultrafast carrier dynamics in InGaN/GaN multiple quantum wells

    DEFF Research Database (Denmark)

    Porte, Henrik; Turchinovich, Dmitry; Cooke, David;

    We studied the THz conductivity of InGaN/GaN multiple quantum wells (MQWs)by time-resolved terahertz spectroscopy. A nonexponential carrier density decay is observed due to the restoration of a built-in piezoelectric field. Terahertz conductivity spectra show a nonmetallic behavior of the carriers....

  12. Unified Description of Charge-Carrier Mobilities in Disordered Semiconducting Polymers

    NARCIS (Netherlands)

    Pasveer, W.F.; Cottaar, J.; Tanase, C.; Coehoorn, R.; Bobbert, P.A.; Blom, P.W.M.; De Leeuw, D.M.; Michels, M.A.J.

    2005-01-01

    From a numerically exact solution of the Master equation for hoppingtransport in a disordered energy landscape with a Gaussian densityof states, we determine the dependence on temperature, carrier density, and electric field of the charge carrier mobility. Experimentalspace-charge limited currents i

  13. Renewable energy carriers: Hydrogen or liquid air/nitrogen?

    International Nuclear Information System (INIS)

    The world's energy demand is met mainly by the fossil fuels today. The use of such fuels, however, causes serious environmental issues, including global warming, ozone layer depletion and acid rains. A sustainable solution to the issues is to replace the fossil fuels with renewable ones. Implementing such a solution, however, requires overcoming a number of technological barriers including low energy density, intermittent supply and mobility of the renewable energy sources. A potential approach to overcoming these barriers is to use an appropriate energy carrier, which can store, transport and distribute energy. The work to be reported in this paper aims to assess and compare a chemical energy carrier, hydrogen, with a physical energy carrier, liquid air/nitrogen, and discuss potential applications of the physical carrier. The ocean energy is used as an example of the renewable energy sources in the work. The assessment and comparison are carried out in terms of the overall efficiency, including production, storage/transportation and energy extraction. The environmental impact, waste heat recovery and safety issues are also considered. It is found that the physical energy carrier may be a better alternative to the chemical energy carrier under some circumstances, particularly when there are waste heat sources.

  14. Strong Asymmetric Charge Carrier Dependence in Inelastic Electron Tunneling Spectroscopy of Graphene Phonons.

    Science.gov (United States)

    Natterer, Fabian D; Zhao, Yue; Wyrick, Jonathan; Chan, Yang-Hao; Ruan, Wen-Ying; Chou, Mei-Yin; Watanabe, Kenji; Taniguchi, Takashi; Zhitenev, Nikolai B; Stroscio, Joseph A

    2015-06-19

    The observation of phonons in graphene by inelastic electron tunneling spectroscopy has been met with limited success in previous measurements arising from weak signals and other spectral features which inhibit a clear distinction between phonons and miscellaneous excitations. Utilizing a back-gated graphene device that allows adjusting the global charge carrier density, we introduce an averaging method where individual tunneling spectra at varying charge carrier density are combined into one representative spectrum. This method improves the signal for inelastic transitions while it suppresses dispersive spectral features. We thereby map the total graphene phonon density of states, in good agreement with density functional calculations. Unexpectedly, an abrupt change in the phonon intensity is observed when the graphene charge carrier type is switched through a variation of the back-gate electrode potential. This sudden variation in phonon intensity is asymmetric in the carrier type, depending on the sign of the tunneling bias.

  15. Inhomogeneous and nonstationary Hall states of the CDW with quantized normal carriers

    OpenAIRE

    Brazovskii, Serguei

    2015-01-01

    We suggest a theory for a deformable and sliding charge density wave (CDW) in the Hall bar geometry for the quantum limit when the carriers in remnant small pockets are concentrated at lowest Landau levels (LL) forming a fractionally ($\

  16. Widely Tunable Infrared Antennas Using Free Carrier Refraction.

    Science.gov (United States)

    Lewi, Tomer; Iyer, Prasad P; Butakov, Nikita A; Mikhailovsky, Alexander A; Schuller, Jon A

    2015-12-01

    We demonstrate tuning of infrared Mie resonances by varying the carrier concentration in doped semiconductor antennas. We fabricate spherical silicon and germanium particles of varying sizes and doping concentrations. Single-particle infrared spectra reveal electric and magnetic dipole, quadrupole, and hexapole resonances. We subsequently demonstrate doping-dependent frequency shifts that follow simple Drude models, culminating in the emergence of plasmonic resonances at high doping levels and long wavelengths. These findings demonstrate the potential for actively tuning infrared Mie resonances by optically or electrically modulating charge carrier densities, thus providing an excellent platform for tunable metamaterials.

  17. Time-delayed behaviors of transient four-wave mixing signal intensity in inverted semiconductor with carrier-injection pumping

    Science.gov (United States)

    Hu, Zhenhua; Gao, Shen; Xiang, Bowen

    2016-01-01

    An analytical expression of transient four-wave mixing (TFWM) in inverted semiconductor with carrier-injection pumping was derived from both the density matrix equation and the complex stochastic stationary statistical method of incoherent light. Numerical analysis showed that the TFWM decayed decay is towards the limit of extreme homogeneous and inhomogeneous broadenings in atoms and the decaying time is inversely proportional to half the power of the net carrier densities for a low carrier-density injection and other high carrier-density injection, while it obeys an usual exponential decay with other decaying time that is inversely proportional to half the power of the net carrier density or it obeys an unusual exponential decay with the decaying time that is inversely proportional to a third power of the net carrier density for a moderate carrier-density injection. The results can be applied to studying ultrafast carrier dephasing in the inverted semiconductors such as semiconductor laser amplifier and semiconductor optical amplifier.

  18. Investigation of Cu2ZnSnS4 thin-film solar cells with carrier concentration gradient

    Science.gov (United States)

    Xu, Jiaxiong

    2016-11-01

    To investigate the effect of carrier concentration gradient on Cu2ZnSnS4 (CZTS) thin-film solar cells, the properties of CZTS solar cells were studied by numerical method. The photovoltaic performances of carrier concentration gradient CZTS solar cells were calculated by the solutions of Poisson's equation, continuity equation, and current density equation using AFors-Het v2.4 program. The carrier concentration gradient was changed to analyze its effect. Compared with CZTS solar cells without carrier concentration gradient, the photovoltaic performances of CZTS solar cells can be enhanced by using carrier concentration gradient absorber. The carrier concentration gradient can extend the distribution region of built-in electric field, which is beneficial to the drift of photo-generated carriers. However, the carrier concentration gradient also affects the recombination and series resistances of solar cells. When the defect density of CZTS layer is high, the photo-generated carriers are affected significantly by recombination, resulting in slight effect of carrier concentration gradient. Therefore, the defect density should be reduced to enhance the effect of carrier concentration gradient on improving conversion efficiency of CZTS thin-film solar cells.

  19. Straddle carrier radiation portal monitoring

    Science.gov (United States)

    Andersen, Eric S.; Samuel, Todd J.; Mullen, O. Dennis

    2005-05-01

    U.S. Customs and Border Protection (CBP) is the primary enforcement agency protecting the nation"s ports of entry. CBP is enhancing its capability to interdict the illicit import of nuclear and radiological materials and devices that may be used by terrorists. Pacific Northwest National Laboratory (PNNL) is providing scientific and technical support to CBP in their goal to enable rapid deployment of nuclear and radiation detection systems at U. S. ports of entry to monitor 100% of the incoming international traffic and cargo while not adversely impacting the operations or throughput of the ports. The U.S. ports of entry include the following vectors: land border crossings, seaports, airports, rail crossings, and mail and express consignment courier facilities. U.S. Customs and Border Protection (CBP) determined that a screening solution was needed for Seaport cargo containers being transported by Straddle Carriers (straddle carriers). A stationary Radiation Portal Monitor (RPM) for Straddle Carriers (SCRPM) is needed so that cargo containers can be scanned while in transit under a Straddle Carrier. The Straddle Carrier Portal operational impacts were minimized by conducting a time-motion study at the Port, and adaptation of a Remotely Operated RPM (RO-RPM) booth concept that uses logical lighting schemes for traffic control, cameras, Optical Character Recognition, and wireless technology.

  20. Impact of carriers in oral absorption

    DEFF Research Database (Denmark)

    Gram, Luise Kvisgaard; Rist, Gerda Marie; Lennernäs, Hans;

    2009-01-01

    Carriers may mediate the permeation across enterocytes for drug substances being organic anions. Carrier mediated permeation for the organic anions estrone-3-sulfate (ES) and glipizide across Caco-2 cells were investigated kinetically, and interactions on involved carriers evaluated. Initial......(APP) was not described by carrier kinetics. However, glipizide is affecting exsorption for ES, due to interactions on basolateral carrier. The study confirms that estrone-3-sulfate can be used to characterize anionic carrier kinetics. Furthermore it is suggested that estrone-3-sulfate may be used to identify compounds...... which may interact on anionic carriers....

  1. Road density

    Data.gov (United States)

    U.S. Environmental Protection Agency — Road density is generally highly correlated with amount of developed land cover. High road densities usually indicate high levels of ecological disturbance. More...

  2. Nanofaceting as a stamp for periodic graphene charge carrier modulations

    Science.gov (United States)

    Vondráček, M.; Kalita, D.; Kučera, M.; Fekete, L.; Kopeček, J.; Lančok, J.; Coraux, J.; Bouchiat, V.; Honolka, J.

    2016-04-01

    The exceptional electronic properties of monatomic thin graphene sheets triggered numerous original transport concepts, pushing quantum physics into the realm of device technology for electronics, optoelectronics and thermoelectrics. At the conceptual pivot point is the particular two-dimensional massless Dirac fermion character of graphene charge carriers and its volitional modification by intrinsic or extrinsic means. Here, interfaces between different electronic and structural graphene modifications promise exciting physics and functionality, in particular when fabricated with atomic precision. In this study we show that quasiperiodic modulations of doping levels can be imprinted down to the nanoscale in monolayer graphene sheets. Vicinal copper surfaces allow to alternate graphene carrier densities by several 1013 carriers per cm2 along a specific copper high-symmetry direction. The process is triggered by a self-assembled copper faceting process during high-temperature graphene chemical vapor deposition, which defines interfaces between different graphene doping levels at the atomic level.

  3. Hot carrier-assisted intrinsic photoresponse in graphene.

    Science.gov (United States)

    Gabor, Nathaniel M; Song, Justin C W; Ma, Qiong; Nair, Nityan L; Taychatanapat, Thiti; Watanabe, Kenji; Taniguchi, Takashi; Levitov, Leonid S; Jarillo-Herrero, Pablo

    2011-11-01

    We report on the intrinsic optoelectronic response of high-quality dual-gated monolayer and bilayer graphene p-n junction devices. Local laser excitation (of wavelength 850 nanometers) at the p-n interface leads to striking six-fold photovoltage patterns as a function of bottom- and top-gate voltages. These patterns, together with the measured spatial and density dependence of the photoresponse, provide strong evidence that nonlocal hot carrier transport, rather than the photovoltaic effect, dominates the intrinsic photoresponse in graphene. This regime, which features a long-lived and spatially distributed hot carrier population, may offer a path to hot carrier-assisted thermoelectric technologies for efficient solar energy harvesting.

  4. Theory of Carrier Phase Ambiguity Resolution

    Institute of Scientific and Technical Information of China (English)

    P. J. G. Teunissen

    2003-01-01

    Carrier phase ambiguity resolution is the key to high precision Global Navigation Satellite System(GNSS) positioning and navigation. It applies to a great variety of current and future models of GPS, modernized GPS and Galileo. A proper handling of carrier phase ambiguity resolution requires a proper understanding of the underlying theory of integer inference. In this contribution a brief review is given of the probabilistic theory of integer ambiguity estimation. We describe the concept of ambiguity pull-in regions, introduce the class of admissible integer estimators, determine their probability mass functions and show how their variability solution. The theory is worked out in more detail for integer least-squares and integer bootstrapping. It is shown that the integer least-squares principle maximizes the probability of correct integer estimation. Sharp and easy-to-compute bounds are given for both the ambiguity success rate and the baseline's probability of concentration. Finally the probability density function of the ambiguity residuals is determined. This allows one for the first time to formulate rigorous tests for the integerness of the parameters.

  5. Carrier sense data highway system

    Science.gov (United States)

    Frankel, Robert

    1984-02-14

    A data transmission system includes a transmission medium which has a certain propagation delay time over its length. A number of data stations are successively coupled to the transmission medium for communicating with one another. Each of the data stations includes a transmitter for originating signals, each signal beginning with a carrier of a duration which is at least the propagation delay time of the transmission medium. Each data station also includes a receiver which receives other signals from other data stations and inhibits operation of the transmitter at the same data station when a carrier of another signal is received.

  6. Near-infrared free carrier absorption in heavily doped silicon

    Energy Technology Data Exchange (ETDEWEB)

    Baker-Finch, Simeon C., E-mail: simeon.bakerfinch@gmail.com [School of Engineering, Australian National University, Canberra, ACT 0200 (Australia); PV Lighthouse, Coledale, NSW 2515 (Australia); McIntosh, Keith R. [PV Lighthouse, Coledale, NSW 2515 (Australia); Yan, Di; Fong, Kean Chern; Kho, Teng C. [School of Engineering, Australian National University, Canberra, ACT 0200 (Australia)

    2014-08-14

    Free carrier absorption in heavily doped silicon can have a significant impact on devices operating in the infrared. In the near infrared, the free carrier absorption process can compete with band to band absorption processes, thereby reducing the number of available photons to optoelectronic devices such as solar cells. In this work, we fabricate 18 heavily doped regions by phosphorus and boron diffusion into planar polished silicon wafers; the simple sample structure facilitates accurate and precise measurement of the free carrier absorptance. We measure and model reflectance and transmittance dispersion to arrive at a parameterisation for the free carrier absorption coefficient that applies in the wavelength range between 1000 and 1500 nm, and the range of dopant densities between ∼10{sup 18} and 3 × 10{sup 20} cm{sup −3}. Our measurements indicate that previously published parameterisations underestimate the free carrier absorptance in phosphorus diffusions. On the other hand, published parameterisations are generally consistent with our measurements and model for boron diffusions. Our new model is the first to be assigned uncertainty and is well-suited to routine device analysis.

  7. Hot carrier degradation in semiconductor devices

    CERN Document Server

    2015-01-01

    This book provides readers with a variety of tools to address the challenges posed by hot carrier degradation, one of today’s most complicated reliability issues in semiconductor devices.  Coverage includes an explanation of carrier transport within devices and book-keeping of how they acquire energy (“become hot”), interaction of an ensemble of colder and hotter carriers with defect precursors, which eventually leads to the creation of a defect, and a description of how these defects interact with the device, degrading its performance. • Describes the intricacies of hot carrier degradation in modern semiconductor technologies; • Covers the entire hot carrier degradation phenomenon, including topics such as characterization, carrier transport, carrier-defect interaction, technological impact, circuit impact, etc.; • Enables detailed understanding of carrier transport, interaction of the carrier ensemble with the defect precursors, and an accurate assessment of how the newly created defects imp...

  8. Lung density

    DEFF Research Database (Denmark)

    Garnett, E S; Webber, C E; Coates, G;

    1977-01-01

    The density of a defined volume of the human lung can be measured in vivo by a new noninvasive technique. A beam of gamma-rays is directed at the lung and, by measuring the scattered gamma-rays, lung density is calculated. The density in the lower lobe of the right lung in normal man during quiet...... breathing in the sitting position ranged from 0.25 to 0.37 g.cm-3. Subnormal values were found in patients with emphsema. In patients with pulmonary congestion and edema, lung density values ranged from 0.33 to 0.93 g.cm-3. The lung density measurement correlated well with the findings in chest radiographs...... but the lung density values were more sensitive indices. This was particularly evident in serial observations of individual patients....

  9. Hypernormal Densities

    OpenAIRE

    Giacomini, Raffaella; Gottschling, Andreas; Haefke, Christian; White, Halbert

    2002-01-01

    We derive a new family of probability densities that have the property of closed-form integrability. This flexible family finds a variety of applications, of which we illustrate density forecasting from models of the AR-ARCH class for U.S. inflation. We find that the hypernormal distribution for the model's disturbances leads to better density forecasts than the ones produced under the assumption that the disturbances are Normal or Student's t.

  10. Carrier dynamics and efficiency droop in AlGaN epilayers with different Al content

    Energy Technology Data Exchange (ETDEWEB)

    Tamulaitis, Gintautas; Mickevicius, Juras; Dobrovolskas, Darius; Kuokstis, Edmundas [Semiconductor Physics Department and Institute of Applied Research, Vilnius University, Sauletekio 9-III, 10222 Vilnius (Lithuania); Shur, Michael S. [Department of ECE and CIE, Rensselaer Polytechnic Institute, 110 Eighth Street, Troy, NY 12180 (United States); Shatalov, Max; Yang, Jinwei; Gaska, Remis [Sensor Electronic Technology Inc., 1195 Atlas Road, Columbia, SC 29209 (United States)

    2012-07-15

    Carrier dynamics and emission efficiency droop in AlGaN epilayers containing different Al content were studied under pulsed (30 ps) and quasi-steady-state photoexcitation. Samples with Al content ranging from 17% to 50% but having similar carrier lifetimes (50-80 ps) were selected for the study. Considerable heating of nonequilibrium carriers at room temperature was observed. Carrier redistribution down to deeper localized states is demonstrated. It is shown that the temperature decay is faster than the decay of localized carriers, which determine the photoluminescence decay kinetics at later stages of the decay. The efficiency droop onsets at lower excitation power densities in the samples with higher Al content presumably having higher density of nonradiative recombination centers and higher density of localized states. The results are in favour of the assumption that the droop in these epilayers is caused by saturation of the localized states and hopping of less localized carriers to the centers of nonradiative recombination. The effect might be enhanced by carrier heating (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  11. Optical modulation by carrier depletion in a silicon PIN diode.

    Science.gov (United States)

    Marris-Morini, Delphine; Le Roux, Xavier; Vivien, Laurent; Cassan, Eric; Pascal, Daniel; Halbwax, Mathieu; Maine, Sylvain; Laval, Suzanne; Fédéli, Jean Marc; Damlencourt, Jean François

    2006-10-30

    Experimental results for refractive index variation induced by depletion in a silicon structure integrated in a PIN diode are reported. Thermal effect has been dissociated from the electrical contribution due to carrier density variation induced by a reverse bias voltage. A figure of merit V(pi)L(pi) of 3.1 V.cm has been obtained at 1.55mum. Numerical simulations show a good agreement between experimental and theoretical index variations. PMID:19529496

  12. Densities, Spectral Densities and Modality

    OpenAIRE

    Davies, PL Laurie; Kovac, A.

    2002-01-01

    This paper considers the problem of specifying a simple approximating density function for a given data set (x1,…,xn). Simplicity is measured by the number of modes but several different definitions of approximation are introduced. The taut string method is used to control the numbers of modes and to produce candidate approximating densities. Refinements are introduced that improve the local adaptivity of the procedures and the method is extended to spectral densities.

  13. Fatigue reliability for LNG carrier

    Institute of Scientific and Technical Information of China (English)

    Xiao Taoyun; Zhang Qin; Jin Wulei; Xu Shuai

    2011-01-01

    The procedure of reliability-based fatigue analysis of liquefied natural gas (LNG) carrier of membrane type under wave loads is presented. The stress responses of the hotspots in regular waves with different wave heading angles and wave lengths are evaluated by global ship finite element method (FEM). Based on the probabilistic distribution function of hotspots' short-term stress-range using spectral-based analysis, Weibull distribution is adopted and discussed for fitting the long-term probabilistic distribution of stress-range. Based on linear cumulative damage theory, fatigue damage is characterized by an S-N relationship, and limit state function is established. Structural fatigue damage behavior of several typical hotspots of LNG middle ship section is clarified and reliability analysis is performed. It is believed that the presented results and conclusions can be of use in calibration for practical design and initial fatigue safety evaluation for membrane type LNG carrier.

  14. Gemini surfactants as gene carriers

    Directory of Open Access Journals (Sweden)

    Teresa Piskorska

    2010-03-01

    Full Text Available Gemini surfactants are a new class of amphiphilic compounds built from two classic surfactant moieties bound together by a special spacer group. These compounds appear to be excellent for creating complexes with DNA and are effective in mediating transfection. Thanks to their construction, DNA carrier molecules built from gemini surfactants are able to deliver genes to cells of almost any DNA molecule size, unattainable when using viral gene delivery systems. Moreover, they are much safer for living organisms.

  15. Intrinsic carrier mobility extraction based on a new quasi-analytical model for graphene field-effect transistors

    Science.gov (United States)

    Wang, Shaoqing; Jin, Zhi; Muhammad, Asif; Peng, Songang; Huang, Xinnan; Zhang, Dayong; Shi, Jingyuan

    2016-10-01

    The most common method of mobility extraction for graphene field-effect transistors is proposed by Kim. Kim’s method assumes a constant mobility independent of carrier density and gets the mobility by fitting the transfer curves. However, carrier mobility changes with the carrier density, leading to the inaccuracy of Kim’s method. In our paper, a new and more accurate method is proposed to extract mobility by fitting the output curves at a constant gate voltage. The output curves are fitted using several kinds of current-voltage models. Besides the models in the literature, we present a modified model, which takes into account not only the quantum capacitance, contact resistance, but also a modified drift velocity-field relationship. Comparing with the other models, this new model can fit better with our experimental data. The dependence of carrier intrinsic mobility on carrier density is obtained based on this model.

  16. Preventative maintenance of straddle carriers

    Directory of Open Access Journals (Sweden)

    Si Li

    2015-02-01

    Full Text Available Background: Robotic vehicles such as straddle carriers represent a popular form of cargo handling amongst container terminal operators.Objectives: The purpose of this industry-driven study is to model preventative maintenance (PM influences on the operational effectiveness of straddle carriers.Method: The study employs historical data consisting of 21 273 work orders covering a 27-month period. Two models are developed, both of which forecast influences of PM regimes for different types of carrier.Results: The findings of the study suggest that the reliability of the straddle fleet decreases with increased intervals of PM services. The study also finds that three factors – namely resources, number of new straddles, and the number of new lifting work centres – influence the performances of straddles.Conclusion: The authors argue that this collaborative research exercise makes a significant contribution to existing supply chain management literature, particularly in the area of operations efficiency. The study also serves as an avenue to enhance relevant management practice.

  17. Responsible implementation of expanded carrier screening

    Science.gov (United States)

    Henneman, Lidewij; Borry, Pascal; Chokoshvili, Davit; Cornel, Martina C; van El, Carla G; Forzano, Francesca; Hall, Alison; Howard, Heidi C; Janssens, Sandra; Kayserili, Hülya; Lakeman, Phillis; Lucassen, Anneke; Metcalfe, Sylvia A; Vidmar, Lovro; de Wert, Guido; Dondorp, Wybo J; Peterlin, Borut

    2016-01-01

    This document of the European Society of Human Genetics contains recommendations regarding responsible implementation of expanded carrier screening. Carrier screening is defined here as the detection of carrier status of recessive diseases in couples or persons who do not have an a priori increased risk of being a carrier based on their or their partners' personal or family history. Expanded carrier screening offers carrier screening for multiple autosomal and X-linked recessive disorders, facilitated by new genetic testing technologies, and allows testing of individuals regardless of ancestry or geographic origin. Carrier screening aims to identify couples who have an increased risk of having an affected child in order to facilitate informed reproductive decision making. In previous decades, carrier screening was typically performed for one or few relatively common recessive disorders associated with significant morbidity, reduced life-expectancy and often because of a considerable higher carrier frequency in a specific population for certain diseases. New genetic testing technologies enable the expansion of screening to multiple conditions, genes or sequence variants. Expanded carrier screening panels that have been introduced to date have been advertised and offered to health care professionals and the public on a commercial basis. This document discusses the challenges that expanded carrier screening might pose in the context of the lessons learnt from decades of population-based carrier screening and in the context of existing screening criteria. It aims to contribute to the public and professional discussion and to arrive at better clinical and laboratory practice guidelines. PMID:26980105

  18. Spacelab carrier complement thermal design and performance

    Science.gov (United States)

    Bancroft, S.; Key, R.; Kittredge, S.

    1992-01-01

    The present discussion of the Spacelab carrier complement, which encompasses a Module Carrier, a Module-Pallet Carrier, and a Multiplexer/Demultiplexer Pallet, gives attention to both active and passive thermal performance capabilities, and presents ground testing and analytical results obtained to date. An account is given of the prospective use of a Spacelab Multipurpose Experiment Support Structure.

  19. 7 CFR 33.4 - Carrier.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Carrier. 33.4 Section 33.4 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... ISSUED UNDER AUTHORITY OF THE EXPORT APPLE ACT Definitions § 33.4 Carrier. Carrier means any common...

  20. Carbon phosphide monolayers with superior carrier mobility

    Science.gov (United States)

    Wang, Gaoxue; Pandey, Ravindra; Karna, Shashi P.

    2016-04-01

    Two dimensional (2D) materials with a finite band gap and high carrier mobility are sought after materials from both fundamental and technological perspectives. In this paper, we present the results based on the particle swarm optimization method and density functional theory which predict three geometrically different phases of the carbon phosphide (CP) monolayer consisting of sp2 hybridized C atoms and sp3 hybridized P atoms in hexagonal networks. Two of the phases, referred to as α-CP and β-CP with puckered or buckled surfaces are semiconducting with highly anisotropic electronic and mechanical properties. More remarkably, they have the lightest electrons and holes among the known 2D semiconductors, yielding superior carrier mobility. The γ-CP has a distorted hexagonal network and exhibits a semi-metallic behavior with Dirac cones. These theoretical findings suggest that the binary CP monolayer is a yet unexplored 2D material holding great promise for applications in high-performance electronics and optoelectronics.Two dimensional (2D) materials with a finite band gap and high carrier mobility are sought after materials from both fundamental and technological perspectives. In this paper, we present the results based on the particle swarm optimization method and density functional theory which predict three geometrically different phases of the carbon phosphide (CP) monolayer consisting of sp2 hybridized C atoms and sp3 hybridized P atoms in hexagonal networks. Two of the phases, referred to as α-CP and β-CP with puckered or buckled surfaces are semiconducting with highly anisotropic electronic and mechanical properties. More remarkably, they have the lightest electrons and holes among the known 2D semiconductors, yielding superior carrier mobility. The γ-CP has a distorted hexagonal network and exhibits a semi-metallic behavior with Dirac cones. These theoretical findings suggest that the binary CP monolayer is a yet unexplored 2D material holding great

  1. Mathematical analysis of the Photovoltage Decay (PVD) method for minority carrier lifetime measurements

    Science.gov (United States)

    Vonroos, O. H.

    1982-01-01

    When the diffusion length of minority carriers becomes comparable with or larger than the thickness of a p-n junction solar cell, the characteristic decay of the photon-generated voltage results from a mixture of contributions with different time constants. The minority carrier recombination lifetime tau and the time constant l(2)/D, where l is essentially the thickness of the cell and D the minority carrier diffusion length, determine the signal as a function of time. It is shown that for ordinary solar cells (n(+)-p junctions), particularly when the diffusion length L of the minority carriers is larger than the cell thickness l, the excess carrier density decays according to exp (-t/tau-pi(2)Dt/4l(2)), tau being the lifetime. Therefore, tau can be readily determined by the photovoltage decay method once D and L are known.

  2. Six-wave mixing induced by free-carrier plasma in silicon nanowire waveguides

    CERN Document Server

    Zhou, Heng; Huang, Shu-Wei; Zhou, Linjie; Qiu, Kun; Wong, Chee Wei

    2016-01-01

    Nonlinear wave mixing in mesoscopic silicon structures is a fundamental nonlinear process with broad impact and applications. Silicon nanowire waveguides, in particular, have large third-order Kerr nonlinearity, enabling salient and abundant four-wave-mixing dynamics and functionalities. Besides the Kerr effect, in silicon waveguides two-photon absorption generates high free-carrier densities, with corresponding fifth-order nonlinearity in the forms of free-carrier dispersion and free-carrier absorption. However, whether these fifth-order free-carrier nonlinear effects can lead to six-wave-mixing dynamics still remains an open question until now. Here we report the demonstration of free-carrier-induced six-wave mixing in silicon nanowires. Unique features, including inverse detuning dependence of six-wave-mixing efficiency and its higher sensitivity to pump power, are originally observed and verfied by analytical prediction and numerical modeling. Additionally, asymmetric sideband generation is observed for d...

  3. Arithmetic density

    CERN Document Server

    Garay, Mauricio

    2012-01-01

    Arithmetic class are closed subsets of the euclidean space which generalise arithmetical conditions encoutered in dynamical systems, such as diophantine conditions or Bruno type conditions. I prove density estimates for such sets using Dani-Kleinbock-Margulis techniques.

  4. 49 CFR 376.22 - Exemption for private carrier leasing and leasing between authorized carriers.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 5 2010-10-01 2010-10-01 false Exemption for private carrier leasing and leasing... MOTOR CARRIER SAFETY REGULATIONS LEASE AND INTERCHANGE OF VEHICLES Exemptions for the Leasing Regulations § 376.22 Exemption for private carrier leasing and leasing between authorized carriers....

  5. Effect of carrier relaxation lifetime on the performance of InAs/InP quantum-dash lasers

    KAUST Repository

    Khan, Mohammed Zahed Mustafa

    2011-12-01

    The effect of carrier relaxation process into the quantum dash (Qdash) ground state (GS) is examined theoretically by carrier-photon rate equation model incorporating the inhomogeneous broadening. Increase in the relaxation time and the inhomogeneous broadening degrades the threshold current density. Moreover, our results show that a relaxation time of less than 2 ps gives optimum laser performance. © 2011 IEEE.

  6. Carrier synchronization for STBC OFDM systems

    Institute of Scientific and Technical Information of China (English)

    Cai Jueping; Song Wentao; Li Zan; Ge Jianhua

    2005-01-01

    All-digital carrier synchronization strategies and algorithms for space-time block coding (STBC) orthogonal frequency division multiplexing (OFDM) are proposed in this paper. In our scheme, the continuous pilots (CP) are saved, and the complexity of carrier synchronization is reduced significantly by dividing the process into three steps. The coarse carrier synchronization and the fine carrier synchronization algorithms are investigated and analyzed in detail. Simulations show that the carrier can be locked into tracking mode quickly, and the residual frequency error satisfies the system requirement in both stationary and mobile environments.

  7. Low Bone Density

    Science.gov (United States)

    ... Density Exam/Testing › Low Bone Density Low Bone Density Low bone density is when your bone density ... people with normal bone density. Detecting Low Bone Density A bone density test will determine whether you ...

  8. A new look at gravel pack carrier fluid properties

    Energy Technology Data Exchange (ETDEWEB)

    Scheuerman, R.F.

    1984-02-01

    For gravel pack carrier fluids, less viscosity is needed downhole than for suspending and pumping high gravel loadings on the surface. To achieve this dual viscosity need, breakers are added to degrade the viscosifying polymers. Unfortunately, viscosity breakback criteria are not well defined. In addition to the type and concentration of breaker and temperature, the apparent viscosity breakback time of a polymer solution also depends on the shear rate at which the viscosity is measured. As a result, industry breakback data generally disagree because of the variety of instruments and shear rates used to measure viscosity. This paper discusses two new viscosity breakback criteria for gravel packing carrier fluids: The time for the apparent viscosity at 0.03 sec/sup -1/ to decrease to 1000 cp, and start of compaction of the settled gravel bed. These criteria correlate well with fluid performance and apply to slurries with different initial viscosities (including crosslinked gels), brine densities, and gravel sizes. Data useful for formulating gravel pack carrier fluids are also presented. Although this paper does not define optimum downhole carrier fluid properties, the new criteria reflect downhole conditions better than most previous criteria. They should give better correlation with model studies and field experience, and, in turn, lead to a better understanding of the requirements for optimum downhole performance.

  9. Low loss and high speed silicon optical modulator based on a lateral carrier depletion structure.

    Science.gov (United States)

    Marris-Morini, Delphine; Vivien, Laurent; Fédéli, Jean Marc; Cassan, Eric; Lyan, Philippe; Laval, Suzanne

    2008-01-01

    A high speed and low loss silicon optical modulator based on carrier depletion has been made using an original structure consisting of a p-doped slit embedded in the intrinsic region of a lateral pin diode. This design allows a good overlap between the optical mode and carrier density variations. Insertion loss of 5 dB has been measured with a contrast ratio of 14 dB for a 3 dB bandwidth of 10 GHz. PMID:18521165

  10. Carrier-independent ferromagnetism and giant anomalous Hall effect in magnetic topological insulator

    OpenAIRE

    Chang, Cui-Zu; Zhang, Jin-song; Liu, Min-Hao; Zhang, Zuo-Cheng; Feng, Xiao; Li, Kang; Wang, Li-Li; Chen, Xi; Dai, Xi; Fang, Zhong; Qi, Xiao-Liang; Zhang, Shou-Cheng; Wang, Yayu; He, Ke; Ma, Xu-Cun

    2011-01-01

    Breaking the time-reversal symmetry of a topological insulator (TI) by ferromagnetism can induce exotic magnetoelectric phenomena such as quantized anomalous Hall (QAH) effect. Experimental observation of QAH effect in a magnetically doped TI requires ferromagnetism not relying on the charge carriers. We have realized the ferromagnetism independent of both polarity and density of carriers in Cr-doped BixSb2-xTe3 thin films grown by molecular beam epitaxy. Meanwhile, the anomalous Hall effect ...

  11. Stochastic Ordering based Carrier-to-Interference Ratio Analysis for the Shotgun Cellular Systems

    CERN Document Server

    Madhusudhanan, Prasanna; Youjian,; Liu,; Brown, Timothy X; Baker, Kenneth R

    2011-01-01

    A simple analytical tool based on stochastic ordering is developed to compare the distributions of carrier-to-interference ratio at the mobile station of two cellular systems where the base stations are distributed randomly according to certain non-homogeneous Poisson point processes. The comparison is conveniently done by studying only the base station densities without having to solve for the distributions of the carrier-to-interference ratio, that are often hard to obtain.

  12. Genetic determinants of mammographic density

    International Nuclear Information System (INIS)

    Changes in breast density are highly correlated with steroid hormone exposure. In a cross-sectional study of 396 Caucasian and African-American women, we evaluated whether polymorphisms in genes involved in steroid hormone biosynthesis and metabolism, CYP17 (T27C), COMT (Val158Met), 17HSDB1 (Ser312Gly) and 3HSDB1 (Asn367Thr), predict mammographic density. We also evaluated whether associations vary by menopausal and hormone replacement therapy status. We found no strong consistent relationships between polymorphisms in these genes and breast density. African-American women homozygous for the Thr allele of 3HSDB1 had increased density (the absolute difference versus the Asn/Asn genotype was +19.7%; P trend = 0.02), while Caucasian homozygous women had decreased density (-5.1%; P trend = 0.04). Among premenopausal women, carriers of the Ser allele had (not significantly) greater density (versus Gly/Gly genotype: +7.1%; P trend = 0.07). In addition, among current users of hormone replacement therapy, we observed that women with the low-activity Met/Met genotype of COMT had greater breast density (versus the Val/Val genotype: +11.7%; P trend = 0.01). Additional large studies evaluating these and other candidate breast cancer genes will be required to determine what proportion, if any, of the interindividual differences in breast density are due to underlying genetic variation in genes involved in steroid hormone biosynthesis or metabolism

  13. BER Performance of IEEE 802.11ad for Single Carrier and Multi Carrier

    Directory of Open Access Journals (Sweden)

    Abhishek Kumar Gupta

    2012-05-01

    Full Text Available In present scenario 802.11n is one of the fastest standards which is widely popular. It provides a theoretical maximum of 450 megabits per second (Mbps, with a typical throughput of 100Mbps. As we know, there is high demand for higher speed due to an increasing of high definition (HD video on smart phone usage and home entertainment. As 802.11n is not able to provide the required speed needed for these uses, thus there is need for technologies which can meet therequirement. IEEE 802.11ad is one of such standards which meet the requirement needed for the above. IEEE 802.11ad standard operates at 60 GHz frequency, promise to deliver from 1 to 7 Gbps. 60 GHz band is one of the largest unlicensed bandwidth with availability of at least 5 GHz of continuous bandwidth worldwide. In this paper we have tested the IEEE 802.11ad system model Bits Error Rate (BER for different modulation technique under several coding scheme for both Single Carrier and Multi Carriers. In this model the modulation technique mainly used are Binary Phase Shift Keying (BPSK, Quaternary Phase Shift Keying (QPSK, 16-Quadrature Amplitude Modulation (QAM, 64-Quadrature Amplitude Modulation (QAM and the coding scheme used is Low Density Parity Check (LDPC code with different code rate.

  14. Carrier frequencies, holomorphy and unwinding

    CERN Document Server

    Coifman, Ronald R; Wu, Hau-tieng

    2016-01-01

    We prove that functions of intrinsic-mode type (a classical models for signals) behave essentially like holomorphic functions: adding a pure carrier frequency $e^{int}$ ensures that the anti-holomorphic part is much smaller than the holomorphic part $ \\| P_{-}(f)\\|_{L^2} \\ll \\|P_{+}(f)\\|_{L^2}.$ This enables us to use techniques from complex analysis, in particular the \\textit{unwinding series}. We study its stability and convergence properties and show that the unwinding series can stabilize and show that the unwinding series can provide a high resolution time-frequency representation, which is robust to noise.

  15. Biocheese: A Food Probiotic Carrier

    Directory of Open Access Journals (Sweden)

    J. M. Castro

    2015-01-01

    Full Text Available This review describes some aspects related to the technological barriers encountered in the development and stability of probiotic cheeses. Aspects concerning the viability of probiotic cultures in this matrix are discussed and the potential of cheese as a biofunctional food carrier is analyzed, outlying some points related to health and safety. In general, the manufacture of probiotic cheese should have little change when compared with the elaboration of cheese in the traditional way. The physicochemical and technological parameters influencing the quality of these products have also to be measured so as to obtain a process optimization.

  16. Wuestite - a solar energy carrier

    Energy Technology Data Exchange (ETDEWEB)

    Weidenkaff, A.; Nueesch, P.; Wokaun, A. [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Reller, A. [Hamburg Univ., Hamburg (Germany)

    1997-06-01

    Hydrogen is produced when Wuestite (Fe{sub 1-y}O) is oxidised by water. This reaction is part of a two-step thermochemical metal oxide cycle for the storage of solar energy in the form of chemical energy carriers, characterised by a high chemical potential. The reaction was studied in a tubular furnace with on-line gas analysis and further characterised in detail by DTA und high-temperature X-ray powder diffraction. The influence of non-stoichiometry, morphology and temperature on the mechanism and kinetics of the water-splitting reaction was determined. (author) 3 figs., tabs., 3 refs.

  17. Distinguishing between plasmon-induced and photo-excited carriers in a device geometry (Presentation Recording)

    Science.gov (United States)

    Zhao, Hangqi; Zheng, Bob Y.; Manjavacas, Alejandro; McClain, Michael J.; Nordlander, Peter; Halas, Naomi J.

    2015-09-01

    The use of surface plasmons, charge density oscillations of conduction electrons of metallic nanostructures, could drastically alter how sunlight is converted into electricity or fuels by increasing the efficiency of light-harvesting devices through enhanced light-matter interactions. Surface plasmons can decay directly into energetic electron-hole pairs, or "hot" carriers, which can be used for photocurrent generation or photocatalysis. However, little has been understood about the fundamental mechanisms behind plasmonic carrier generation. Here we use metallic nano-wire based hot carrier devices on a wide-bandgap semiconductor substrate to show that plasmonic hot carrier generation is proportional to field intensity enhancement instead of bulk material absorption. We also show that interband carrier generation results in less energetic carriers than plasmon-induced generation, and a plasmon is required to inject electrons over a large energy barrier. Finite Difference Time Domain (FDTD) method is used for theoretical calculations, which match well with experimental results. This work points to a clear route to increasing the efficiency of plasmonic hot carrier devices and drastically simplifies the theoretical framework for understanding the mechanisms of hot carrier generation.

  18. Ultrafast Hot Carrier Scattering and Generation from Surface Plasmons in Noble Metals

    Science.gov (United States)

    Bernardi, Marco; Mustafa, Jamal; Neaton, Jeffrey B.; Louie, Steven G.

    2015-03-01

    Non-equilibrium ``hot''carriers in materials are challenging to study experimentally as they thermalize at subpicosecond time and nanometer length scale. Recent experiments employed hot carriers generated by light absorption or surface plasmon annihilation in noble metals (e.g., Au and Ag) for catalysis and solar cells. The energy distribution and transport of the generated hot carriers play a key role in these experiments. We present ab initio calculations of the energy distribution of hot carriers generated by surface plasmons in noble metals, and the relaxation time and mean free path of the hot carriers along different crystal directions within 5 eV of the Fermi energy. Our calculations show the interplay of the noble metal s and d bands in determining the damping rate of the plasmon and the mean free path of the hot carriers. The trends we find as a function of surface plasmon momentum and frequency allow us to define optimal experimental conditions for hot carrier generation and extraction. Our approach combines density functional theory, GW, and electron-phonon calculations. Our work provides microscopic insight into hot carriers in noble metals, and their ultrafast dynamics in the presence of surface plasmons.

  19. Ultrafast Carrier Relaxation in InN Nanowires Grown by Reactive Vapor Transport

    Directory of Open Access Journals (Sweden)

    Zervos Matthew

    2008-01-01

    Full Text Available Abstract We have studied femtosecond carrier dynamics in InN nanowires grown by reactive vapor transport. Transient differential absorption measurements have been employed to investigate the relaxation dynamics of photogenerated carriers near and above the optical absorption edge of InN NWs where an interplay of state filling, photoinduced absorption, and band-gap renormalization have been observed. The interface between states filled by free carriers intrinsic to the InN NWs and empty states has been determined to be at 1.35 eV using CW optical transmission measurements. Transient absorption measurements determined the absorption edge at higher energy due to the additional injected photogenerated carriers following femtosecond pulse excitation. The non-degenerate white light pump-probe measurements revealed that relaxation of the photogenerated carriers occurs on a single picosecond timescale which appears to be carrier density dependent. This fast relaxation is attributed to the capture of the photogenerated carriers by defect/surface related states. Furthermore, intensity dependent measurements revealed fast energy transfer from the hot photogenerated carriers to the lattice with the onset of increased temperature occurring at approximately 2 ps after pulse excitation.

  20. Shifting densities

    OpenAIRE

    Mille, Matthieu

    2000-01-01

    In this paper, the author adopt a time-geography approach to examine the temporal variation of urban density by analysing spatial load changes at different times of the day at the communal and community level. The evolution of means of transport coupled with the abandon of the notion of direct proximity to the urban dwelling place provide the basis for this new approach to the study of urban densities. The shift towards spatial specialisation within cities has lead to radical changes in the f...

  1. Carrier detection in xeroderma pigmentosum

    International Nuclear Information System (INIS)

    We were able to detect clinically normal carriers of xeroderma pigmentosum (XP) genes with coded samples of either peripheral blood lymphocytes or skin fibroblasts, using a cytogenetic assay shown previously to detect individuals with cancer-prone genetic disorders. Metaphase cells of phytohemagglutinin-stimulated T-lymphocytes from eight individuals who are obligate heterozygotes for XP were compared with those from nine normal controls at 1.3, 2.3, and 3.3 h after x-irradiation (58 R) during the G2 phase of the cell cycle. Lymphocytes from the XP heterozygotes had twofold higher frequencies of chromatid breaks or chromatid gaps than normal (P less than 10(-5)) when fixed at 2.3 or 3.3 h after irradiation. Lymphocytes from six XP homozygotes had frequencies of breaks and gaps threefold higher than normal. Skin fibroblasts from an additional obligate XP heterozygote, when fixed approximately 2 h after x-irradiation (68 R), had a twofold higher frequency of chromatid breaks and a fourfold higher frequency of gaps than fibroblasts from a normal control. This frequency of aberrations in cells from the XP heterozygote was approximately half that observed in the XP homozygote. The elevated frequencies of chromatid breaks and gaps after G2 phase x-irradiation may provide the basis of a test for identifying carriers of the XP gene(s) within known XP families

  2. Silicon ball grid array chip carrier

    Science.gov (United States)

    Palmer, David W.; Gassman, Richard A.; Chu, Dahwey

    2000-01-01

    A ball-grid-array integrated circuit (IC) chip carrier formed from a silicon substrate is disclosed. The silicon ball-grid-array chip carrier is of particular use with ICs having peripheral bond pads which can be reconfigured to a ball-grid-array. The use of a semiconductor substrate such as silicon for forming the ball-grid-array chip carrier allows the chip carrier to be fabricated on an IC process line with, at least in part, standard IC processes. Additionally, the silicon chip carrier can include components such as transistors, resistors, capacitors, inductors and sensors to form a "smart" chip carrier which can provide added functionality and testability to one or more ICs mounted on the chip carrier. Types of functionality that can be provided on the "smart" chip carrier include boundary-scan cells, built-in test structures, signal conditioning circuitry, power conditioning circuitry, and a reconfiguration capability. The "smart" chip carrier can also be used to form specialized or application-specific ICs (ASICs) from conventional ICs. Types of sensors that can be included on the silicon ball-grid-array chip carrier include temperature sensors, pressure sensors, stress sensors, inertia or acceleration sensors, and/or chemical sensors. These sensors can be fabricated by IC processes and can include microelectromechanical (MEM) devices.

  3. Carrier-dependent magnetic anisotropy of Gd-adsorbed graphene

    Science.gov (United States)

    Lu, Yuan; Zhou, Tie-ge; Shao, Bin; Zuo, Xu; Feng, Min

    2016-05-01

    Using first-principles calculation based on density functional theory, we study the magnetic anisotropy of Gd-adsorbed graphene and its dependence on carrier accumulation. We show that carrier accumulation not only impacts the magnitude of magnetic anisotropy but also switches its sign. Hole accumulation enhances the perpendicular anisotropy up to ˜16 meV per Gd atom, while electron accumulation switches the anisotropy from perpendicular to in-plane direction. Moreover, we find that the first order perturbation of spin-orbit coupling interaction induces a pseudo-gap at Γ for the perpendicular magnetization, which leads to the the anomalous magnetic anisotropy for the neutral composite. Our findings pave the way for magneto-electric materials based on rare-earth-decorated graphene for voltage-controlled spintronics.

  4. Carrier-dependent magnetic anisotropy of Gd-adsorbed graphene

    Directory of Open Access Journals (Sweden)

    Yuan Lu

    2016-05-01

    Full Text Available Using first-principles calculation based on density functional theory, we study the magnetic anisotropy of Gd-adsorbed graphene and its dependence on carrier accumulation. We show that carrier accumulation not only impacts the magnitude of magnetic anisotropy but also switches its sign. Hole accumulation enhances the perpendicular anisotropy up to ∼16 meV per Gd atom, while electron accumulation switches the anisotropy from perpendicular to in-plane direction. Moreover, we find that the first order perturbation of spin-orbit coupling interaction induces a pseudo-gap at Γ for the perpendicular magnetization, which leads to the the anomalous magnetic anisotropy for the neutral composite. Our findings pave the way for magneto-electric materials based on rare-earth-decorated graphene for voltage-controlled spintronics.

  5. Differential Analysis of the Nasal Microbiome of Pig Carriers or Non-Carriers of Staphylococcus aureus

    DEFF Research Database (Denmark)

    Espinosa-Gongora, Carmen; Larsen, Niels; Schonning, Kristian;

    2016-01-01

    pathogen in animal carriers. The aim of this study was to determine whether the nasal microbiome of pig S. aureus carriers differs from that of non-carriers. The V3-V5 region of the 16S rRNA gene was sequenced from nasal swabs of 44 S. aureus carriers and 56 non-carriers using the 454 GS FLX titanium...... microbiome of pigs that are not colonized with S. aureus harbours several species/taxa that are significantly less abundant in pig carriers, suggesting that the nasal microbiota may play a role in the individual predisposition to S. aureus nasal carriage in pigs. Further research is warranted to isolate...

  6. Carriers of the astronomical 2175 ? extinction feature

    Energy Technology Data Exchange (ETDEWEB)

    Bradley, J; Dai, Z; Ernie, R; Browning, N; Graham, G; Weber, P; Smith, J; Hutcheon, I; Ishii, H; Bajt, S; Floss, C; Stadermann, F

    2004-07-20

    The 2175 {angstrom} extinction feature is by far the strongest spectral signature of interstellar dust observed by astronomers. Forty years after its discovery the origin of the feature and the nature of the carrier remain controversial. The feature is enigmatic because although its central wavelength is almost invariant its bandwidth varies strongly from one sightline to another, suggesting multiple carriers or a single carrier with variable properties. Using a monochromated transmission electron microscope and valence electron energy-loss spectroscopy we have detected a 5.7 eV (2175 {angstrom}) feature in submicrometer-sized interstellar grains within interplanetary dust particles (IDPs) collected in the stratosphere. The carriers are organic carbon and amorphous silicates that are abundant and closely associated with one another both in IDPs and in the interstellar medium. Multiple carriers rather than a single carrier may explain the invariant central wavelength and variable bandwidth of the astronomical 2175 {angstrom} feature.

  7. Ultrafast carriers dynamics in filled-skutterudites

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Liang; Xu, Xianfan, E-mail: xxu@purdue.edu [School of Mechanical Engineering and Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907 (United States); Salvador, James R. [Chemical and Materials Systems Laboratory, GM Global R and D, Warren, Michigan 48090 (United States)

    2015-06-08

    Carrier dynamics of filled-skutterudites, an important class of thermoelectric materials, is investigated using ultrafast optical spectroscopy. By tuning the wavelength of the probe laser, charge transfers at different electronic energy levels are interrogated. Analysis based on the Kramers-Kronig relation explains the complex spectroscopy data, which is mainly due to band filling caused by photo-excited carriers and free carrier absorption. The relaxation time of hot carriers is found to be about 0.4–0.6 ps, depending on the electronic energy level, and the characteristic time for carrier-phonon equilibrium is about 0.95 ps. These studies of carrier dynamics, which fundamentally determines the transport properties of thermoelectric material, can provide guidance for the design of materials.

  8. Ultrafast carriers dynamics in filled-skutterudites

    Science.gov (United States)

    Guo, Liang; Xu, Xianfan; Salvador, James R.

    2015-06-01

    Carrier dynamics of filled-skutterudites, an important class of thermoelectric materials, is investigated using ultrafast optical spectroscopy. By tuning the wavelength of the probe laser, charge transfers at different electronic energy levels are interrogated. Analysis based on the Kramers-Kronig relation explains the complex spectroscopy data, which is mainly due to band filling caused by photo-excited carriers and free carrier absorption. The relaxation time of hot carriers is found to be about 0.4-0.6 ps, depending on the electronic energy level, and the characteristic time for carrier-phonon equilibrium is about 0.95 ps. These studies of carrier dynamics, which fundamentally determines the transport properties of thermoelectric material, can provide guidance for the design of materials.

  9. Global Telecommunications Services: Strategies of Major Carriers

    OpenAIRE

    Jerry Mccreary; William R. Boulton; Chetan Sankar

    1993-01-01

    The globalization of telecommunications markets is of primary concern for today’s large telecommunications carriers. International business telecommunications is growing at a rate twice that of domestic traffic. Multi-national customers with offices around the world are demanding integrated solutions to their telecommunications needs. As telecommunication carriers respond to these customers’ needs, the carriers are beginning to expand outside their national boundaries. This paper identifi...

  10. Secure quantum carriers for quantum state sharing

    OpenAIRE

    Karimipour, Vahid; Marvian, Milad

    2010-01-01

    We develop the concept of quantum carrier and show that messages can be uploaded and downloaded from this carrier and while in transit, these messages are hidden from external agents. We explain in detail the working of the quantum carrier for different communication tasks, including quantum key distribution, classical secret and quantum state sharing among a set of $n$ players according to general threshold schemes. The security of the protocol is discussed and it is shown that only the legi...

  11. Heterozygote advantage in Tay-Sachs carriers?

    OpenAIRE

    Spyropoulos, B; Moens, P B; Davidson, J.; Lowden, J. A.

    1981-01-01

    Chi-square analyses of new data as well as data previously reported by Myrianthopoulos have shown that grandparents of Tay-Sachs carriers die from proportionally the same causes as grandparents of noncarriers. It is unlikely that there is any advantage to being a Tay-Sachs carrier insofar as resistance to tuberculosis is concerned. Our results are further evidence to support Fraikor's claim that the high carrier frequency of the allele in Ashkenazi Jews is probably caused by a combination of ...

  12. Carriers by chemical vapor deposition

    Science.gov (United States)

    Mronga, Norbert; Adel, J.; Czech, Erwin

    1990-07-01

    Printed materials are affecting people's lives in a variety of ways and to a constantly increasing extent, both in the private and in the business spheres. In particular, the predicted reduction of printed materials resulting from electronic data processing - the so-called "paperless electronic office" - has not occured, indeed quite the reverse. In recent years electrophotographic reprography has established itself successfully as a competitor to conventional printing processes. In the office a photocopier is now a part of the standard equipment. Because of BASF's traditional intensive involvement with pigments and colored printing inks its interest in new technologies in these areas is especially great. BASF has therefore been engaged in research on carriers for some years now.

  13. The Kinetics of Carrier Transport Inhibition

    DEFF Research Database (Denmark)

    Rosenberg, T.; Wilbrandt, Robert Walter

    1962-01-01

    The kinetical treatment of enzymatic carrier transports as given in previous communications has been extended to conditions of inhibition. Various possible types of inhibitors have been considered differing in the site of attack (enzyme or carrier), in the mode of action (competing with the subst......The kinetical treatment of enzymatic carrier transports as given in previous communications has been extended to conditions of inhibition. Various possible types of inhibitors have been considered differing in the site of attack (enzyme or carrier), in the mode of action (competing...

  14. CARRIER/CASK HANDLING SYSTEM DESCRIPTION DOCUMENT

    Energy Technology Data Exchange (ETDEWEB)

    E.F. Loros

    2000-06-23

    The Carrier/Cask Handling System receives casks on railcars and legal-weight trucks (LWTs) (transporters) that transport loaded casks and empty overpacks to the Monitored Geologic Repository (MGR) from the Carrier/Cask Transport System. Casks that come to the MGR on heavy-haul trucks (HHTs) are transferred onto railcars before being brought into the Carrier/Cask Handling System. The system is the interfacing system between the railcars and LWTs and the Assembly Transfer System (ATS) and Canister Transfer System (CTS). The Carrier/Cask Handling System removes loaded casks from the cask transporters and transfers the casks to a transfer cart for either the ATS or CTS, as appropriate, based on cask contents. The Carrier/Cask Handling System receives the returned empty casks from the ATS and CTS and mounts the casks back onto the transporters for reshipment. If necessary, the Carrier/Cask Handling System can also mount loaded casks back onto the transporters and remove empty casks from the transporters. The Carrier/Cask Handling System receives overpacks from the ATS loaded with canisters that have been cut open and emptied and mounts the overpacks back onto the transporters for disposal. If necessary, the Carrier/Cask Handling System can also mount empty overpacks back onto the transporters and remove loaded overpacks from them. The Carrier/Cask Handling System is located within the Carrier Bay of the Waste Handling Building System. The system consists of cranes, hoists, manipulators, and supporting equipment. The Carrier/Cask Handling System is designed with the tooling and fixtures necessary for handling a variety of casks. The Carrier/Cask Handling System performance and reliability are sufficient to support the shipping and emplacement schedules for the MGR. The Carrier/Cask Handling System interfaces with the Carrier/Cask Transport System, ATS, and CTS as noted above. The Carrier/Cask Handling System interfaces with the Waste Handling Building System for building

  15. Spontaneous Charge Carrier Localization in Extended One-Dimensional Systems

    Science.gov (United States)

    Vlček, Vojtěch; Eisenberg, Helen R.; Steinle-Neumann, Gerd; Neuhauser, Daniel; Rabani, Eran; Baer, Roi

    2016-05-01

    Charge carrier localization in extended atomic systems has been described previously as being driven by disorder, point defects, or distortions of the ionic lattice. Here we show for the first time by means of first-principles computations that charge carriers can spontaneously localize due to a purely electronic effect in otherwise perfectly ordered structures. Optimally tuned range-separated density functional theory and many-body perturbation calculations within the G W approximation reveal that in trans-polyacetylene and polythiophene the hole density localizes on a length scale of several nanometers. This is due to exchange-induced translational symmetry breaking of the charge density. Ionization potentials, optical absorption peaks, excitonic binding energies, and the optimally tuned range parameter itself all become independent of polymer length as it exceeds the critical localization length. Moreover, we find that lattice disorder and the formation of a polaron result from the charge localization in contrast to the traditional view that lattice distortions precede charge localization. Our results can explain experimental findings that polarons in conjugated polymers form instantaneously after exposure to ultrafast light pulses.

  16. Dynamics of Below-Band-Gap Carrier in Highly Excited GaN

    Institute of Scientific and Technical Information of China (English)

    郭冰; 黄锦圣; 叶志镇; 江红星; 林景瑜

    2003-01-01

    Femtosecond time-resolved reflectivity was used to investigate below-band-gap (3.1 eV) carrier dynamics in a nominally undoped GaN epilayer under high excitation. A 2.5-ps rising process can be observed in the transient trace. This shot rising time results from the hot phonon effects which can cause a delayed energy relaxation of the initial photocarriers toward the band edge. From the density dependence of the carrier dynamics, the Mott density was estimated to be 1.51-1.56 × 1019 cm-3. Below the Mott density, the initial probed carrier dynamics was explained to the effect of acoustic phonon-assisted tunnelling for localized states, where a significant excitation density dependence of the tunnelling probability was observed due to the optically induced bandtail extension to lower energies. Above the Mott density, the measured carrier dynamics reflected the relaxation of an electron-hole plasma, in which a distinct fast decay component of 2.3 ps was observed due to the onset of nonlinear relaxation processes such Auger recombination.

  17. Carrier-carrier relaxation kinetics in quantum well semiconductor structures with nonparabolic energy bands

    DEFF Research Database (Denmark)

    Dery, H.; Tromborg, Bjarne; Eisenstein, G.

    2003-01-01

    We describe carrier-carrier scattering dynamics in an inverted quantum well structure including the nonparabolic nature of the valance band. A solution of the semiconductor Bloch equations yields strong evidence to a large change in the temporal evolution of the carrier distributions compared...

  18. A novel model of photo-carrier screening effect on the GaN-based p-i-n ultraviolet detector

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The photo-carrier density in the depletion region of the GaN-based p-i-n ultraviolet(UV) detector is calculated by solving the photo-carrier continuity equation,and the photo-carrier screening electric field is calculated according to Poisson’s equation.Using the numerical calculation method,a novel model of photo-carrier screening effect is presented.Then the influence of photo-carrier screening effect on the distribution of photo-carrier density in the depletion region of p-i-n detector is discussed.The influence of incident power,bias voltage and carrier life time on the photo-carrier screening effect is also analyzed.It is concluded that the influence of photo-carrier screening effect on the performance of GaN-based p-i-n UV detector is non-monotone,the maximum of carrier drift velocity and the minimum of response time can be realized by adjusting the applied voltage.Besides,the incident light duration has strong impact on the photo-carrier screening effect.

  19. Dynamics of carrier recombination in a semiconductor laser structure

    Energy Technology Data Exchange (ETDEWEB)

    Dzhioev, R. I., E-mail: dzhioev@orient.ioffe.ru; Kavokin, K. V.; Kusrayev, Yu. G.; Poletaev, N. K. [Russian Academy of Sciences, Ioffe Physical–Technical Institute (Russian Federation)

    2015-11-15

    Carrier-recombination dynamics is studied by the method of optical orientation at room temperature in the active layer of a laser diode structure. The dependence of the degree of electron-spin orientation on the excitation density is attributed to saturation of the nonradiative-recombination channel. The time of electron capture at recombination centers is determined to be τ{sub e} = 5 × 10{sup –9} s. The temperature of nonequilibrium electrons heated by a He–Ne laser is estimated.

  20. Inert carrier drying and coating process

    International Nuclear Information System (INIS)

    An inert carrier process is described for drying radioactive (particularly low level) waste material and for incorporating the dry material into a binder matrix from which the dried material will not be leached. Experimental details, and examples of the carrier and binder materials, are given. (U.K.)

  1. 14 CFR Section 04 - Air Carrier Groupings

    Science.gov (United States)

    2010-01-01

    ... Aeronautics and Space OFFICE OF THE SECRETARY, DEPARTMENT OF TRANSPORTATION (AVIATION PROCEEDINGS) ECONOMIC... upon their level of operations and the nature of these operations. In order to determine the level of... carrier's level of operations passes the upper or lower limit of its currently assigned carrier...

  2. Providing resilience for carrier ethernet multicast traffic

    DEFF Research Database (Denmark)

    Ruepp, Sarah Renée; Wessing, Henrik; Zhang, Jiang;

    2009-01-01

    This paper presents an overview of the Carrier Ethernet technology with specific focus on resilience. In particular, we detail how multicast traffic, which is essential for e.g. IPTV can be protected. We present Carrier Ethernet resilience methods for linear and ring networks and show by simulation...

  3. Space telemetry degradation due to Manchester data asymmetry induced carrier tracking phase error

    Science.gov (United States)

    Nguyen, Tien M.

    1991-01-01

    The deleterious effects that the Manchester (or Bi-phi) data asymmetry has on the performance of phase-modulated residual carrier communication systems are analyzed. Expressions for the power spectral density of an asymmetric Manchester data stream, the interference-to-carrier signal power ratio (I/C), and the error probability performance are derived. Since data asymmetry can cause undesired spectral components at the carrier frequency, the I/C ratio is given as a function of both the data asymmetry and the telemetry modulation index. Also presented are the data asymmetry and asymmetry-induced carrier tracking loop and the system bit-error rate to various parameters of the models.

  4. Modeling of Carrier Dynamics in Electroabsorption Modulators

    DEFF Research Database (Denmark)

    Højfeldt, Sune

    2002-01-01

    and a phenomenological model for the carrier sweep-out dynamics, we investigate all-optical wavelength conversion, all-optical signal regeneration, and all-optical demultiplexing. A detailed drift-diffusion type model for the sweerp-out of photo-excited carriers in electroabsorption modulators is presented. We use...... the model to calclulate absorption spectra and steady-state carrier distributions in different modulator structures. This allows us to investigate a number of important properties of electroabsorption modulators, such as the electroabsorption effect and th saturation properties. We also investigate...... the influence that carrier recapture has on the device properties, and we discuss the recapture process on a more fundamental level. The model is also used to investigate in detail the carrier sweep-out process in electroabsorption modulators. We investigate how the intrinsic-region width, the separate...

  5. Selection of Carrier Waveforms for PWM Inverter

    Institute of Scientific and Technical Information of China (English)

    陈国呈; 屈克庆; 许春雨; 孙承波

    2003-01-01

    In this paper the influence of different carrier waveforms upon the output characteristics of PWM inverter is described in detail. When a triangular carrier waveform is used in hard-switching PWM inverters, harmonics exist in the neighborhood of the output frequency of the inverter output voltage and current due to the dead time. The triangular carrier waveform used in soft-switching PWM inverter will cause difficulties in controlling resonance-trigger time, higher loss in the resonant circuit, and less utilization of the DC bus voltage. If a sawtooth carrier is used in hard-switching PWM inverter, there will be severe distortion in the current waveform. When sawtooth carriers with alternate positive and negative slopes are used in soft-switching PWM inverters, the resonancetrigger time is easy to control, and distortion in the output voltage and current caused by the dead time will not appear.

  6. Methanol as an energy carrier

    Energy Technology Data Exchange (ETDEWEB)

    Biedermann, P.; Grube, T.; Hoehlein, B. (eds.)

    2006-07-01

    For the future, a strongly growing energy demand is expected in the transport sector worldwide. Economically efficient oil production will run through a maximum in the next decade. Higher fuel prices and an environmentally desirable reduction of emissions will increase the pressure for reducing fuel consumption and emissions in road traffic. These criteria show the urgent necessity of structural changes in the fuel market. Due to its advantages concerning industrial-scale production, storage and global availability, methanol has the short- to medium-term potential for gaining increased significance as a substitution product in the energy market. Methanol can be produced both from fossil energy sources and from biomass or waste materials through the process steps of synthesis gas generation with subsequent methanol synthesis. Methanol has the potential to be used in an environmentally friendly manner in gasoline/methanol mixtures for flexible fuel vehicles with internal combustion engines and in diesel engines with pure methanol. Furthermore, it can be used in fuel cell vehicles with on-board hydrogen production in direct methanol fuel cell drives, and in stationary systems for electricity and heat generation as well as for hydrogen production. Finally, in portable applications it serves as an energy carrier for electric power generation. In this book, the processes for the production and use of methanol are presented and evaluated, markets and future options are discussed and issues of safety and environmental impacts are addressed by a team of well-known authors. (orig.)

  7. Effects of carrier-carrier scattering on population inversion in graphene under pulse photoexcitation

    Science.gov (United States)

    Satou, Akira; Ryzhii, Victor; Otsuji, Taiichi

    2015-01-01

    We study the carrier relaxation dynamics in intrinsic graphene after pulse photoexcitation and reveal effects of intraband carrier-carrier scattering on population inversion in the terahertz region, by conducting simulation based on the quasi-classical Boltzmann equation. It is demonstrated that by changing the dielectric constant of the surrounding materials the rate of carrier-carrier scattering can be controlled and the relaxation dynamics differs for cases with low and high dielectric constants. It is also found that the Pauli blocking of photogeneration in case of the pulse photoexcitation causes decrease in the photocarrier concentration and thus weakening of population inversion with higher dielectric constant.

  8. Charge carrier dynamics in thin film solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Strothkaemper, Christian

    2013-06-24

    This work investigates the charge carrier dynamics in three different technological approaches within the class of thin film solar cells: radial heterojunctions, the dye solar cell, and microcrystalline CuInSe{sub 2}, focusing on charge transport and separation at the electrode, and the relaxation of photogenerated charge carriers due to recombination and energy dissipation to the phonon system. This work relies mostly on optical-pump terahertz-probe (OPTP) spectroscopy, followed by transient absorption (TA) and two-photon photoemission (2PPE). The charge separation in ZnO-electrode/In{sub 2}S{sub 3}-absorber core/shell nanorods, which represent a model system of a radial heterojunction, is analyzed by OPTP. It is concluded, that the dynamics in the absorber are determined by multiple trapping, which leads to a dispersive charge transport to the electrode that lasts over hundreds of picoseconds. The high trap density on the order of 10{sup 19}/cm{sup 3} is detrimental for the injection yield, which exhibits a decrease with increasing shell thickness. The heterogeneous electron transfer from a series of model dyes into ZnO proceeds on a time-scale of 200 fs. However, the photoconductivity builds up just on a 2-10 ps timescale, and 2PPE reveals that injected electrons are meanwhile localized spatially and energetically at the interface. It is concluded that the injection proceeds through adsorbate induced interface states. This is an important result because the back reaction from long lived interface states can be expected to be much faster than from bulk states. While the charge transport in stoichiometric CuInSe{sub 2} thin films is indicative of free charge carriers, CuInSe{sub 2} with a solar cell grade composition (Cu-poor) exhibits signs of carrier localization. This detrimental effect is attributed to a high density of charged defects and a high degree of compensation, which together create a spatially fluctuating potential that inhibits charge transport. On

  9. Hot carrier and hot phonon coupling during ultrafast relaxation of photoexcited electrons in graphene

    Energy Technology Data Exchange (ETDEWEB)

    Iglesias, J. M.; Martín, M. J.; Pascual, E.; Rengel, R., E-mail: raulr@usal.es [Department of Applied Physics, University of Salamanca, Salamanca 37008 (Spain)

    2016-01-25

    We study, by means of a Monte Carlo simulator, the hot phonon effect on the relaxation dynamics in photoexcited graphene and its quantitative impact as compared with considering an equilibrium phonon distribution. Our multi-particle approach indicates that neglecting the hot phonon effect significantly underestimates the relaxation times in photoexcited graphene. The hot phonon effect is more important for a higher energy of the excitation pulse and photocarrier densities between 1 and 3 × 10{sup 12 }cm{sup −2}. Acoustic intervalley phonons play a non-negligible role, and emitted phonons with wavelengths limited up by a maximum (determined by the carrier concentration) induce a slower carrier cooling rate. Intrinsic phonon heating is damped in graphene on a substrate due to the additional cooling pathways, with the hot phonon effect showing a strong inverse dependence with the carrier density.

  10. Fourier-transform-based model for carrier transport in semiconductor heterostructures: Longitudinal optical phonon scattering

    Science.gov (United States)

    Lü, X.; Schrottke, L.; Grahn, H. T.

    2016-06-01

    We present scattering rates for electrons at longitudinal optical phonons within a model completely formulated in the Fourier domain. The total intersubband scattering rates are obtained by averaging over the intrasubband electron distributions. The rates consist of the Fourier components of the electron wave functions and a contribution depending only on the intersubband energies and the intrasubband carrier distributions. The energy-dependent part can be reproduced by a rational function, which allows for the separation of the scattering rates into a dipole-like contribution, an overlap-like contribution, and a contribution which can be neglected for low and intermediate carrier densities of the initial subband. For a balance between accuracy and computation time, the number of Fourier components can be adjusted. This approach facilitates an efficient design of complex heterostructures with realistic, temperature- and carrier density-dependent rates.

  11. Renewable Hydrogen Carrier — Carbohydrate: Constructing the Carbon-Neutral Carbohydrate Economy

    OpenAIRE

    Y.-H. Percival Zhang; Mielenz, Jonathan R.

    2011-01-01

    The hydrogen economy presents an appealing energy future but its implementation must solve numerous problems ranging from low-cost sustainable production, high-density storage, costly infrastructure, to eliminating safety concern. The use of renewable carbohydrate as a high-density hydrogen carrier and energy source for hydrogen production is possible due to emerging cell-free synthetic biology technology—cell-free synthetic pathway biotransformation (SyPaB). Assembly of numerous enzymes and ...

  12. Renewable Hydrogen Carrier — Carbohydrate: Constructing the Carbon-Neutral Carbohydrate Economy

    OpenAIRE

    Y.-H. Percival Zhang; Mielenz, Jonathan R.

    2011-01-01

    The hydrogen economy presents an appealing energy future but its implementation must solve numerous problems ranging from low-cost sustainable production, high-density storage, costly infrastructure, to eliminating safety concern. The use of renewable carbohydrate as a high-density hydrogen carrier and energy source for hydrogen production is possible due to emerging cell-free synthetic biology technology–cell-free synthetic pathway biotransformation (SyPaB). Assembly of numerous enzymes and ...

  13. Carrier scattering in metals and semiconductors

    CERN Document Server

    Gantmakher, VF

    1987-01-01

    The transport properties of solids, as well as the many optical phenomena in them are determined by the scattering of current carriers. ``Carrier Scattering in Metals and Semiconductors'' elucidates the state of the art in the research on the scattering mechanisms for current carriers in metals and semiconductors and describes experiments in which these mechanisms are most dramatically manifested.The selection and organization of the material is in a form to prepare the reader to reason independently and to deal just as independently with available theoretical results and experimental

  14. High capacity carrier ethernet transport networks

    DEFF Research Database (Denmark)

    Rasmussen, Anders; Zhang, Jiang; Yu, Hao;

    2009-01-01

    Ethernet as a transport technology has, up to now, lacked the features such as network layer architecture, customer separation and manageability that carriers require for wide-scale deployment. However, with the advent of PBB-TE and T-MPLS, it is now possible to use Ethernet as a transport...... OAM functions, survivability and the increased bandwidth requirements of carrier class systems. This article provides an overview of PBB-TE and T-MPLS and demonstrates how IPTV services can be realized in the framework of Carrier Ethernet. In addition we provide a case study on performing bit error...

  15. ISRAEL’S NATIONAL WATER CARRIER

    OpenAIRE

    Nathan Cohen

    2008-01-01

    The National Water Carrier of Israel (Ha Movil Ha' Artzi). It is the main water project of Israel and its main task is to transfer water from the rainy north to the center and to the arid south. The National Water Carrier connects the Sea of Galilee with Israel's water system. The original goal was to provide irrigation water to Negev. Today 80% of the water is utilized for Israel's domestic consumption. Most of the water works in Israel are combined with the National Water Carrier for about...

  16. 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.

  17. Injection deep level transient spectroscopy: An improved method for measuring capture rates of hot carriers in semiconductors

    International Nuclear Information System (INIS)

    An improved method for measuring the cross sections for carrier trapping at defects in semiconductors is described. This method, a variation of deep level transient spectroscopy (DLTS) used with bipolar transistors, is applied to hot carrier trapping at vacancy-oxygen, carbon-oxygen, and three charge states of divacancy centers (V2) in n- and p-type silicon. Unlike standard DLTS, we fill traps by injecting carriers into the depletion region of a bipolar transistor diode using a pulse of forward bias current applied to the adjacent diode. We show that this technique is capable of accurately measuring a wide range of capture cross sections at varying electric fields due to the control of the carrier density it provides. Because this technique can be applied to a variety of carrier energy distributions, it should be valuable in modeling the effect of radiation-induced generation-recombination currents in bipolar devices

  18. Injection deep level transient spectroscopy: An improved method for measuring capture rates of hot carriers in semiconductors

    Science.gov (United States)

    Fleming, R. M.; Seager, C. H.; Lang, D. V.; Campbell, J. M.

    2015-07-01

    An improved method for measuring the cross sections for carrier trapping at defects in semiconductors is described. This method, a variation of deep level transient spectroscopy (DLTS) used with bipolar transistors, is applied to hot carrier trapping at vacancy-oxygen, carbon-oxygen, and three charge states of divacancy centers (V2) in n- and p-type silicon. Unlike standard DLTS, we fill traps by injecting carriers into the depletion region of a bipolar transistor diode using a pulse of forward bias current applied to the adjacent diode. We show that this technique is capable of accurately measuring a wide range of capture cross sections at varying electric fields due to the control of the carrier density it provides. Because this technique can be applied to a variety of carrier energy distributions, it should be valuable in modeling the effect of radiation-induced generation-recombination currents in bipolar devices.

  19. Injection deep level transient spectroscopy: An improved method for measuring capture rates of hot carriers in semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Fleming, R. M.; Seager, C. H.; Lang, D. V.; Campbell, J. M. [Sandia National Laboratories, Albuquerque, New Mexico 87185-1415 (United States)

    2015-07-07

    An improved method for measuring the cross sections for carrier trapping at defects in semiconductors is described. This method, a variation of deep level transient spectroscopy (DLTS) used with bipolar transistors, is applied to hot carrier trapping at vacancy-oxygen, carbon-oxygen, and three charge states of divacancy centers (V{sub 2}) in n- and p-type silicon. Unlike standard DLTS, we fill traps by injecting carriers into the depletion region of a bipolar transistor diode using a pulse of forward bias current applied to the adjacent diode. We show that this technique is capable of accurately measuring a wide range of capture cross sections at varying electric fields due to the control of the carrier density it provides. Because this technique can be applied to a variety of carrier energy distributions, it should be valuable in modeling the effect of radiation-induced generation-recombination currents in bipolar devices.

  20. Intraoral radiation carrier for edentulous patients

    International Nuclear Information System (INIS)

    The principles of fabricating an intraoral radioactive carrier have been described to treat malignant diseases of the oral cavity. The prosthesis provides consistent direction and fixation of the radioactive source into the same location

  1. Intraoral radiation carrier for edentulous patients

    Energy Technology Data Exchange (ETDEWEB)

    Sela, M.; Taicher, S.

    1983-12-01

    The principles of fabricating an intraoral radioactive carrier have been described to treat malignant diseases of the oral cavity. The prosthesis provides consistent direction and fixation of the radioactive source into the same location.

  2. Simulation of dual transponder carrier ranging measurements

    Institute of Scientific and Technical Information of China (English)

    Xiang-yu ZHAO; Xiao-jun JIN; Zhong-he JIN

    2009-01-01

    The most dominant error source for microwave ranging is the frequency instability of the oscillator that generates the carrier phase signal. The oscillator noise is very difficult to filter due to its extremely low frequency. A dual transponder carrier ranging method can effectively minimize the oscillator noise by combing the reference phase and the to-and-fro measurement phase from the same single oscillator. This method does not require an accurate time tagging system, since it extracts phases on the same satellite. This paper analyzes the dual transponder carrier ranging system by simulation of the phase measurements with comprehensive error models. Both frequency domain and time domain noise transfer characteristics were simulated to compare them with dual one-way ranging. The simulation results in the two domains conformed to each other and demonstrated that a high level of accuracy can also be achieved by use of the dual transponder carrier ranging system, with relatively simple instruments.

  3. Physician Fee Schedule Carrier Specific Files

    Data.gov (United States)

    U.S. Department of Health & Human Services — The Centers for Medicare and Medicaid Services (CMS) has condensed all 56 Physician Fee Schedule (PFS) carrier specific pricing files into one zip file. It is...

  4. Evaluating multicast resilience in carrier ethernet

    DEFF Research Database (Denmark)

    Ruepp, Sarah Renée; Wessing, Henrik; Zhang, Jiang;

    2010-01-01

    This paper gives an overview of the Carrier Ethernet technology with specific focus on resilience. In particular, we show how multicast traffic, which is essential for IPTV can be protected. We detail the ackground for resilience mechanisms and their control and e present Carrier Ethernet resilie...... resilience methods for linear nd ring networks. By simulation we show that the vailability of a multicast connection can be significantly increased by applying protection methods....

  5. Preparation and application of magnetic microsphere carriers

    Institute of Scientific and Technical Information of China (English)

    ZHANG Bo; XING Jianmin; LIU Huizhou

    2007-01-01

    Magnetic microsphere carriers have received considerable attention,primarily because of their wide applications in the fields of biomedicine and bioengineering.In this paper,preparation methods,surface modification and application of magnetic carriers are reviewed.Emphasis will be placed on recent biological and biomedical developments and trends such as enzyme immobilization,cell isolation,protein purification,target drugs and DNA separation.

  6. Influence of Carrier Transport on Diffraction Efficiency of Steady-State Photocarrier Grating

    Science.gov (United States)

    Sun, Q. M.; Wang, Y. F.; Gao, C. M.; Cui, H.

    2015-06-01

    A two-dimensional theoretical model of a diffractive steady-state photocarrier grating (SSPCG) has been developed. The carrier diffusion equation with a spatially periodic excitation source was solved, and an analytical expression of the carrier density distribution was obtained. Based on the band-filling theory and the Kramers-Kronig relation, the carrier-induced refractive index change of SSPCG was estimated, and the refractive index profile was determined. The diffraction efficiency of the SSPCG was calculated by multilevel rigorous coupled-wave analysis. Simulations were carried out to investigate the influence of the carrier transport properties on the diffraction efficiency of the SSPCG. The results show that a semiconductor material with a longer lifetime and a smaller diffusivity will have a higher diffraction efficiency. The spatial amplitude of the carrier density and the grating strength of the SSPCG are closely related to the grating period. For an InP-based SSPCG, the diffraction efficiency of the transmitted wave reaches its maximum value (25 %) when the grating provides a phase shift. The theoretical analysis and conclusions are helpful for material selection and experimental parameter determination of a diffractive SSPCG.

  7. Carrier induced epitopic suppression of antibody responses induced by virus-like particles is a dynamic phenomenon caused by carrier-specific antibodies.

    Science.gov (United States)

    Jegerlehner, Andrea; Wiesel, Melanie; Dietmeier, Klaus; Zabel, Franziska; Gatto, Dominique; Saudan, Philippe; Bachmann, Martin F

    2010-07-26

    Pre-existing immunity against vaccine carrier proteins has been reported to inhibit the immune response against antigens conjugated to the same carrier by a process termed carrier induced epitopic suppression (CIES). Hence understanding the phenomenon of CIES is of major importance for the development of conjugate vaccines. Virus-like particles (VLPs) are a novel class of potent immunological carriers which have been successfully used to enhance the antibody response to virtually any conjugated antigen. In the present study we investigated the impact of a pre-existing VLP-specific immune response on the development of antibody responses against a conjugated model peptide after primary, secondary and tertiary immunization. Although VLP-specific immune responses led to reduced peptide-specific antibody titers, we showed that CIES against peptide-VLP conjugates could be overcome by high coupling densities, repeated injections and/or higher doses of conjugate vaccine. Furthermore we dissected VLP-specific immunity by adoptively transferring VLP-specific antibodies, B-cells or T(helper) cells separately into naïve mice and found that the observed CIES against peptide-VLP conjugates was mainly mediated by carrier-specific antibodies.

  8. Transport-reaction model for defect and carrier behavior within displacement cascades in gallium arsenide

    Energy Technology Data Exchange (ETDEWEB)

    Wampler, William R.; Myers, Samuel Maxwell,

    2014-02-01

    A model is presented for recombination of charge carriers at displacement damage in gallium arsenide, which includes clustering of the defects in atomic displacement cascades produced by neutron or ion irradiation. The carrier recombination model is based on an atomistic description of capture and emission of carriers by the defects with time evolution resulting from the migration and reaction of the defects. The physics and equations on which the model is based are presented, along with details of the numerical methods used for their solution. The model uses a continuum description of diffusion, field-drift and reaction of carriers and defects within a representative spherically symmetric cluster. The initial radial defect profiles within the cluster were chosen through pair-correlation-function analysis of the spatial distribution of defects obtained from the binary-collision code MARLOWE, using recoil energies for fission neutrons. Charging of the defects can produce high electric fields within the cluster which may influence transport and reaction of carriers and defects, and which may enhance carrier recombination through band-to-trap tunneling. Properties of the defects are discussed and values for their parameters are given, many of which were obtained from density functional theory. The model provides a basis for predicting the transient response of III-V heterojunction bipolar transistors to pulsed neutron irradiation.

  9. Application of mathematical modeling-based algorithms to 'off-carrier' cobalt-60 irradiation processes

    International Nuclear Information System (INIS)

    The irradiation of materials and products 'off carrier' has historically been performed using a 'drop-and-read' methodology whereby the radioisotope source is raised and lowered repeatedly until the desired absorbed dose is achieved. This approach is time consuming from both a manpower and process perspective. Static irradiation-based processes can also be costly because of the need for repeated experimental verification of target dose delivery. In our paper we address the methods used for predicting Ethicon Endo Surgery's (EES's) off-carrier absorbed dose distributions. The scenarios described herein are complex due to the fact that the on-carrier process stream exhibits a wide range of densities and dose rates. The levels of observed complexity are attributed to the 'just-in-time' production strategy and its related requirements as they apply to the programming of EES's cobalt-60 irradiators. Validation of off-carrier processing methodologies requires sophisticated parametric-based systems utilizing mathematical algorithms that predict off-carrier absorbed dose rate relative to the on-carrier process stream components. Irradiation process simulation is achieved using a point kernel computer modeling approach, coupled with database generation and maintenance. Dose prediction capabilities are validated via routine and transfer standard dosimetry

  10. Impact of energy filtering and carrier localization on the thermoelectric properties of granular semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Narducci, Dario, E-mail: dario.narducci@unimib.it [Department of Materials Science, University of Milano Bicocca, via Cozzi 53, 20125 Milano (Italy); Consorzio DeltaTi Research (Italy); Selezneva, Ekaterina [Department of Materials Science, University of Milano Bicocca, via Cozzi 53, 20125 Milano (Italy); Cerofolini, Gianfranco [Department of Materials Science, University of Milano Bicocca, via Cozzi 53, 20125 Milano (Italy); Consorzio DeltaTi Research (Italy); Frabboni, Stefano; Ottaviani, Giampiero [Department of Physics, University of Modena and Reggio Emilia, via Campi 213, 41100 Modena (Italy)

    2012-09-15

    Energy filtering has been widely considered as a suitable tool to increase the thermoelectric performances of several classes of materials. In its essence, energy filtering provides a way to increase the Seebeck coefficient by introducing a strongly energy-dependent scattering mechanism. Under certain conditions, however, potential barriers may lead to carrier localization, that may also affect the thermoelectric properties of a material. A model is proposed, actually showing that randomly distributed potential barriers (as those found, e.g., in polycrystalline films) may lead to the simultaneous occurrence of energy filtering and carrier localization. Localization is shown to cause a decrease of the actual carrier density that, along with the quantum tunneling of carriers, may result in an unexpected increase of the power factor with the doping level. The model is corroborated toward experimental data gathered by several authors on degenerate polycrystalline silicon and lead telluride. - Graphical abstract: In heavily doped semiconductors potential barriers may lead to both carrier energy filtering and localization. This may lead to an enhancement of the thermoelectric properties of the material, resulting in an unexpected increase of the power factor with the doping level. Highlights: Black-Right-Pointing-Pointer Potential barriers are shown to lead to carrier localization in thermoelectric materials. Black-Right-Pointing-Pointer Evidence is put forward of the formation of a mobility edge. Black-Right-Pointing-Pointer Energy filtering and localization may explain the enhancement of power factor in degenerate semiconductors.

  11. Ultrafast carrier dynamics and the role of grain boundaries in polycrystalline silicon thin films grown by molecular beam epitaxy

    Science.gov (United States)

    Titova, Lyubov V.; Cocker, Tyler L.; Xu, Sijia; Baribeau, Jean-Marc; Wu, Xiaohua; Lockwood, David J.; Hegmann, Frank A.

    2016-10-01

    We have used time-resolved terahertz spectroscopy to study microscopic photoconductivity and ultrafast photoexcited carrier dynamics in thin, pure, non-hydrogenated silicon films grown by molecular beam epitaxy on quartz substrates at temperatures ranging from 335 °C to 572 °C. By controlling the growth temperature, thin silicon films ranging from completely amorphous to polycrystalline with minimal amorphous phase can be achieved. Film morphology, in turn, determines its photoconductive properties: in the amorphous phase, carriers are trapped in bandtail states on sub-picosecond time scales, while the carriers excited in crystalline grains remain free for tens of picoseconds. We also find that in polycrystalline silicon the photoexcited carrier mobility is carrier-density-dependent, with higher carrier densities mitigating the effects of grain boundaries on inter-grain transport. In a film grown at the highest temperature of 572 °C, the morphology changes along the growth direction from polycrystalline with needles of single crystals in the bulk of the film to small crystallites interspersed with amorphous silicon at the top of the film. Depth profiling using different excitation wavelengths shows corresponding differences in the photoconductivity: the photoexcited carrier lifetime and mobility are higher in the first 100-150 nm from the substrate, suggesting that thinner, low-temperature grown polycrystalline silicon films are preferable for photovoltaic applications.

  12. Effect of an intersection of carbon nanotubes on the carrier accumulation under an external electric field

    Science.gov (United States)

    Kochi, Taketo; Okada, Susumu

    2016-08-01

    We studied the electronic structure of semiconducting carbon nanotube (CNT) thin films, in which CNTs intersect each other, under an external electric field, using first-principles total-energy calculations within the framework of the density functional theory. Our calculations show that the distribution of accumulated carriers strongly depends on the CNT species, their mutual arrangement with respect to the electrode, and carrier concentrations. Under particular conditions, an induced electric field between the CNTs is opposite to the applied field. We also showed that the quantum capacitance of the CNT thin films depends on the arrangement of the CNTs relative to the electrode.

  13. Magnetic-Phase Dependence of the Spin Carrier Mean Free Path in Graphene Nanoribbons

    Science.gov (United States)

    Li, Jing; Niquet, Yann-Michel; Delerue, Christophe

    2016-06-01

    We show theoretically that the intrinsic (phonon-limited) carrier mobility in graphene nanoribbons is considerably influenced by the presence of spin-polarized edge states. When the coupling between opposite edges switches from antiferromagnetic to ferromagnetic with increasing carrier density, the current becomes spin polarized and the mean free path rises from 10 nm to micrometers. In the ferromagnetic state, the current flows through one majority-spin channel which is ballistic over micrometers and several minority-spin channels with mean free paths as low as 1 nm. These features predicted in technology-relevant conditions could be nicely exploited in spintronic devices.

  14. Electron-phonon coupling modification and carrier mobility enhancement in poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate) films by ultraviolet irradiation

    International Nuclear Information System (INIS)

    The effect of ultraviolet irradiation on the electrical property of poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate) (PEDOT:PSS) films was examined. It is shown that the carrier mobility increases while the carrier density does not change substantially. The carrier mobility in PEDOT:PSS samples exhibits strong temperature dependence, indicating the dominance of tunneling (hopping) at low (high) temperatures. The results demonstrate that changes in the chemical structure may lead to the modification of the electron-phonon coupling, thus increasing the carrier mobility in PEDOT:PSS

  15. Differential Analysis of the Nasal Microbiome of Pig Carriers or Non-Carriers of Staphylococcus aureus.

    Science.gov (United States)

    Espinosa-Gongora, Carmen; Larsen, Niels; Schønning, Kristian; Fredholm, Merete; Guardabassi, Luca

    2016-01-01

    Staphylococcus aureus is presently regarded as an emerging zoonotic agent due to the spread of specific methicillin-resistant S. aureus (MRSA) clones in pig farms. Studying the microbiota can be useful for the identification of bacteria that antagonize such opportunistic veterinary and zoonotic pathogen in animal carriers. The aim of this study was to determine whether the nasal microbiome of pig S. aureus carriers differs from that of non-carriers. The V3-V5 region of the 16S rRNA gene was sequenced from nasal swabs of 44 S. aureus carriers and 56 non-carriers using the 454 GS FLX titanium system. Carriers and non-carriers were selected on the basis of quantitative longitudinal data on S. aureus carriage in 600 pigs sampled at 20 Danish herds included in two previous studies in Denmark. Raw sequences were analysed with the BION meta package and the resulting abundance matrix was analysed using the DESeq2 package in R to identify operational taxonomic units (OTUs) with differential abundance between S. aureus carriers and non-carriers. Twenty OTUs were significantly associated to non-carriers, including species with known probiotic potential and antimicrobial effect such as lactic acid-producing isolates described among Leuconostoc spp. and some members of the Lachnospiraceae family, which is known for butyrate production. Further 5 OTUs were significantly associated to carriage, including known pathogenic bacteria such as Pasteurella multocida and Klebsiella spp. Our results show that the nasal microbiome of pigs that are not colonized with S. aureus harbours several species/taxa that are significantly less abundant in pig carriers, suggesting that the nasal microbiota may play a role in the individual predisposition to S. aureus nasal carriage in pigs. Further research is warranted to isolate these bacteria and assess their possible antagonistic effect on S. aureus for the pursuit of new strategies to control MRSA in pig farming. PMID:27509169

  16. Differential Analysis of the Nasal Microbiome of Pig Carriers or Non-Carriers of Staphylococcus aureus

    Science.gov (United States)

    Espinosa-Gongora, Carmen; Larsen, Niels; Schønning, Kristian; Fredholm, Merete; Guardabassi, Luca

    2016-01-01

    Staphylococcus aureus is presently regarded as an emerging zoonotic agent due to the spread of specific methicillin-resistant S. aureus (MRSA) clones in pig farms. Studying the microbiota can be useful for the identification of bacteria that antagonize such opportunistic veterinary and zoonotic pathogen in animal carriers. The aim of this study was to determine whether the nasal microbiome of pig S. aureus carriers differs from that of non-carriers. The V3-V5 region of the 16S rRNA gene was sequenced from nasal swabs of 44 S. aureus carriers and 56 non-carriers using the 454 GS FLX titanium system. Carriers and non-carriers were selected on the basis of quantitative longitudinal data on S. aureus carriage in 600 pigs sampled at 20 Danish herds included in two previous studies in Denmark. Raw sequences were analysed with the BION meta package and the resulting abundance matrix was analysed using the DESeq2 package in R to identify operational taxonomic units (OTUs) with differential abundance between S. aureus carriers and non-carriers. Twenty OTUs were significantly associated to non-carriers, including species with known probiotic potential and antimicrobial effect such as lactic acid-producing isolates described among Leuconostoc spp. and some members of the Lachnospiraceae family, which is known for butyrate production. Further 5 OTUs were significantly associated to carriage, including known pathogenic bacteria such as Pasteurella multocida and Klebsiella spp. Our results show that the nasal microbiome of pigs that are not colonized with S. aureus harbours several species/taxa that are significantly less abundant in pig carriers, suggesting that the nasal microbiota may play a role in the individual predisposition to S. aureus nasal carriage in pigs. Further research is warranted to isolate these bacteria and assess their possible antagonistic effect on S. aureus for the pursuit of new strategies to control MRSA in pig farming. PMID:27509169

  17. 49 CFR 1139.22 - Revenue data for study carriers.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 8 2010-10-01 2010-10-01 false Revenue data for study carriers. 1139.22 Section... BOARD, DEPARTMENT OF TRANSPORTATION RULES OF PRACTICE PROCEDURES IN MOTOR CARRIER REVENUE PROCEEDINGS Intercity Bus Industry § 1139.22 Revenue data for study carriers. The study carriers, as identified...

  18. Charge carrier transport in liquid crystals

    International Nuclear Information System (INIS)

    The materials exhibiting charge carrier mobility ranging from 10−3 to 0.1 cm2/Vs, i.e., between those of amorphous and crystalline materials, had been missing before the 1990s when the electronic conduction in liquid crystals was discovered. Since then, various liquid crystalline materials including discotic and calamitic liquid crystals have been studied in order to clarify their charge carrier transport properties in liquid crystalline mesophases. In this article, the historical background of the discovery of electronic conduction in liquid crystals, intrinsic and extrinsic conductions, unique properties of the charge carrier transport, the effect of molecular alignment on it, and the conduction mechanism in liquid crystalline mesophases are shortly described on the basis of the experimental and theoretical studies accumulated in these two decades, noting that the missing materials were liquid crystals. - Highlights: • Liquid crystals exhibit charge mobility ranging from 10–3 to 0.1 cm2/Vs. • Electronic (intrinsic) and ionic (extrinsic) conductions in liquid crystals • Unique charge carrier transport properties in liquid crystals • Effect of molecular alignment in mesophases on charge carrier transport • Conduction mechanism in smectic liquid crystals

  19. Extracting hot carriers from photoexcited semiconductor nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Xiaoyang

    2014-12-10

    This research program addresses a fundamental question related to the use of nanomaterials in solar energy -- namely, whether semiconductor nanocrystals (NCs) can help surpass the efficiency limits, the so-called “Shockley-Queisser” limit, in conventional solar cells. In these cells, absorption of photons with energies above the semiconductor bandgap generates “hot” charge carriers that quickly “cool” to the band edges before they can be utilized to do work; this sets the solar cell efficiency at a limit of ~31%. If instead, all of the energy of the hot carriers could be captured, solar-to-electric power conversion efficiencies could be increased, theoretically, to as high as 66%. A potential route to capture this energy is to utilize semiconductor nanocrystals. In these materials, the quasi-continuous conduction and valence bands of the bulk semiconductor become discretized due to confinement of the charge carriers. Consequently, the energy spacing between the electronic levels can be much larger than the highest phonon frequency of the lattice, creating a “phonon bottleneck” wherein hot-carrier relaxation is possible via slower multiphonon emission. For example, hot-electron lifetimes as long as ~1 ns have been observed in NCs grown by molecular beam epitaxy. In colloidal NCs, long lifetimes have been demonstrated through careful design of the nanocrystal interfaces. Due to their ability to slow electronic relaxation, semiconductor NCs can in principle enable extraction of hot carriers before they cool to the band edges, leading to more efficient solar cells.

  20. Dedicated Carrier Deployment in Heterogeneous Networks with Inter-site Carrier Aggregation

    DEFF Research Database (Denmark)

    Wang, Hua; Rosa, Claudio; Pedersen, Klaus I.

    2013-01-01

    ) or picos with dedicated carrier deployment. Collaborative inter-site carrier aggregation (CA) is proposed in scenarios with macro+RRH deployment to make an efficient use of the fragmented spectrum from multiple cells. While in scenarios with macro+pico deployment, UEs can only connect to either...

  1. Hiding secret data into a carrier image

    Directory of Open Access Journals (Sweden)

    Ovidiu COSMA

    2012-06-01

    Full Text Available The object of steganography is embedding hidden information in an appropriate multimedia carrier, e.g., image, audio, or video. There are several known methods of solving this problem, which operate either in the space domain or in the frequency domain, and are distinguished by the following characteristics: payload, robustness and strength. The payload is the amount of secret data that can be embedded in the carrier without inducing suspicious artefacts, robustness indicates the degree in which the secret data is affected by the normal processing of the carrier e.g., compression, and the strength indicate how easy the presence of hidden data can be detected by steganalysis techniques. This paper presents a new method of hiding secret data into a digital image compressed by a technique based on the Discrete Wavelet Transform (DWT [2] and the Set Partitioning In Hierarchical Trees (SPIHT subband coding algorithm [6]. The proposed method admits huge payloads and has considerable strength.

  2. Hot Carrier extraction with plasmonic broadband absorbers

    CERN Document Server

    Ng, Charlene; Dligatch, Svetlana; Roberts, Ann; Davis, Timothy J; Mulvaney, Paul; Gomez, Daniel E

    2016-01-01

    Hot charge carrier extraction from metallic nanostructures is a very promising approach for applications in photo-catalysis, photovoltaics and photodetection. One limitation is that many metallic nanostructures support a single plasmon resonance thus restricting the light-to-charge-carrier activity to a spectral band. Here we demonstrate that a monolayer of plasmonic nanoparticles can be assembled on a multi-stack layered configuration to achieve broad-band, near-unit light absorption, which is spatially localised on the nanoparticle layer. We show that this enhanced light absorbance leads to $\\sim$ 40-fold increases in the photon-to-electron conversion efficiency by the plasmonic nanostructures. We developed a model that successfully captures the essential physics of the plasmonic hot-electron charge generation and separation in these structures. This model also allowed us to establish that efficient hot carrier extraction is limited to spectral regions where the photons possessing energies higher than the S...

  3. Development of radioisotope labeled polymeric carriers

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Seung Jin; Jeong, Jea Min; Hwang, Hyun Jeong [Ewha Womans University, Seoul (Korea)

    2000-04-01

    This research was performed with the aim of developing polymeric radioisotope or drug carriers for obtaining efficient diagnostic therapeutic efficacy. As polymers, polyethylene oxides, polylactides, polycaprolactone were chosen to prepare the devices including micelle system, microemulsion, nanospheres. In addition, anticancer drug loaded polylactide microparticulates were fabricated as a regional chemotherapeutics for the treatment of cancer. Technetium or radioactive iodine was labeled to the polymeric carriers via ligands such as DTPA and HPP, respectively. Labeling efficiency was above 90% and stable enough up to 24 hours. Moreover, injected polymer carriers demonstrated higher blood maintenance and bone uptake than Tin colloid, a control. These results suggested that radioisotope carrying polymeric particulate are promising tools for diagnosing blood vessels or bones. Besides, anticancer drug loaded particulates demonstrated appropriate maintenance of therapeutic concentration and localization. Therefore it was proposed that this therapeutic system may be potential as a cancer therapy modality. 20 refs., 24 figs.,5 tabs. (Author)

  4. Tuning Many-Body Interactions in Graphene: The Effects of Doping on Excitons and Carrier Lifetimes

    Science.gov (United States)

    Mak, Kin Fai; da Jornada, Felipe H.; He, Keliang; Deslippe, Jack; Petrone, Nicholas; Hone, James; Shan, Jie; Louie, Steven G.; Heinz, Tony F.

    2014-05-01

    The optical properties of graphene are strongly affected by electron-electron (e-e) and electron-hole (e-h) interactions. Here we tune these many-body interactions through varying the density of free charge carriers. Measurements from the infrared to the ultraviolet reveal significant changes in the optical conductivity of graphene for both electron and hole doping. The shift, broadening, and modification in shape of the saddle-point exciton resonance reflect strong screening of the many-body interactions by the carriers, as well as changes in quasiparticle lifetimes. Ab initio calculations by the GW Bethe-Salpeter equation method, which take into account the modification of both the repulsive e-e and the attractive e-h interactions, provide excellent agreement with experiment. Understanding the optical properties and high-energy carrier dynamics of graphene over a wide range of doping is crucial for both fundamental graphene physics and for emerging applications of graphene in photonics.

  5. Measuring Charge Carrier Diffusion in Coupled Colloidal Quantum Dot Solids

    KAUST Repository

    Zhitomirsky, David

    2013-06-25

    Colloidal quantum dots (CQDs) are attractive materials for inexpensive, room-temperature-, and solution-processed optoelectronic devices. A high carrier diffusion length is desirable for many CQD device applications. In this work we develop two new experimental methods to investigate charge carrier diffusion in coupled CQD solids under charge-neutral, i.e., undepleted, conditions. The methods take advantage of the quantum-size-effect tunability of our materials, utilizing a smaller-bandgap population of quantum dots as a reporter system. We develop analytical models of diffusion in 1D and 3D structures that allow direct extraction of diffusion length from convenient parametric plots and purely optical measurements. We measure several CQD solids fabricated using a number of distinct methods and having significantly different doping and surface ligand treatments. We find that CQD materials recently reported to achieve a certified power conversion efficiency of 7% with hybrid organic-inorganic passivation have a diffusion length of 80 ± 10 nm. The model further allows us to extract the lifetime, trap density, mobility, and diffusion coefficient independently in each material system. This work will facilitate further progress in extending the diffusion length, ultimately leading to high-quality CQD solid semiconducting materials and improved CQD optoelectronic devices, including CQD solar cells. © 2013 American Chemical Society.

  6. Hot-carrier effects in MOS devices

    CERN Document Server

    Takeda, Eiji; Miura-Hamada, Akemi

    1995-01-01

    The exploding number of uses for ultrafast, ultrasmall integrated circuits has increased the importance of hot-carrier effects in manufacturing as well as for other technological applications. They are rapidly movingout of the research lab and into the real world.This book is derived from Dr. Takedas book in Japanese, Hot-Carrier Effects, (published in 1987 by Nikkei Business Publishers). However, the new book is much more than a translation. Takedas original work was a starting point for developing this much more complete and fundamental text on this increasingly important topic. The new work

  7. Line broadening caused by Coulomb carrier-carrier correlations and dynamics of carrier capture and emission in quantum dots

    DEFF Research Database (Denmark)

    Uskov, Alexander V; Magnúsdóttir, Ingibjörg; Tromborg, Bjarne;

    2001-01-01

    Mechanisms of pure dephasing in quantum dots due to Coulomb correlations and the dynamics of carrier capture and emission are suggested, and a phenomenological model for the dephasing is developed. It is shown that, if the rates of these capture and emission processes are sufficiently high, signi......, significant homogeneous line broadening of the order of several meV can result....

  8. Spatially dispersive dynamical response of hot carriers in doped graphene

    Science.gov (United States)

    Kukhtaruk, S. M.; Kochelap, V. A.; Sokolov, V. N.; Kim, K. W.

    2016-05-01

    We study theoretically wave-vector and frequency dispersion of the complex dynamic conductivity tensor (DCT), σlm(k , ω), of doped monolayer graphene under a strong dc electric field. For a general analysis, we consider the weak ac field of arbitrary configuration given by two independent vectors, the ac field polarization and the wave vector k. The high-field transport and linear response to the ac field are described on the base of the Boltzmann kinetic equation. We show that the real part of DCT, calculated in the collisionless regime, is not zero due to dissipation of the ac wave, whose energy is absorbed by the resonant Dirac quasiparticles effectively interacting with the wave. The role of the kinematic resonance at ω =vF | k | (vF is the Fermi velocity) is studied in detail taking into account deviation from the linear energy spectrum and screening by the charge carriers. The isopower-density curves and distributions of angle between the ac current density and field vectors are presented as a map which provides clear graphic representation of the DCT anisotropy. Also, the map shows certain ac field configurations corresponding to a negative power density, thereby it indicates regions of terahertz frequency for possible electrical (drift) instability in the graphene system.

  9. Free Carrier Distribution Criterion in Quantum Dot Lasers

    Directory of Open Access Journals (Sweden)

    HIFSA SHAHID

    2016-07-01

    Full Text Available The spontaneous emission spectra of a 1.28?m InAs/GaAs QD (Quantum Dot Fabry-Perot laser device has been measured under continuous wave operation at a fixed junction temperature of 300K. At low carrier densities, empirically observed static peak wavelength position and a fixed spectral shape of the spontaneous emission spectra are indicative of the random-like population distribution rather than a global Fermi level in the system. A theoretical model based on the Monte-Carlo method has been shown to have good agreement with the empirical results. In addition the evolutions of spontaneous emission spectral shapes are also explained in terms of many body effects.

  10. Carrier mobility, band tails and defects in microcrystalline silicon

    Science.gov (United States)

    Reynolds, Steve

    2010-11-01

    The development of microcrystalline silicon thin films and devices is briefly reviewed. Transport mechanisms, and the attendant key parameters of carrier mobility, band-tail width and defect density, are linked to film structure and composition. In particular we discuss the wide (but systematic) variations in time-of-flight mobility and its unusual field-dependence. While microcrystalline silicon remains an inferior semiconductor to single-crystal silicon, we propose, and support by means of a computer model, that present device-grade material may be of sufficient quality to justify re-examining whether useful thin-film bipolar devices might be developed. These could find application as more sensitive photo-detectors, and as current drivers in organic LED displays and logic circuits.

  11. The Photophysics of the Carrier of Extended Red Emission

    CERN Document Server

    Smith, T L; Smith, Tracy L.; Witt, Adolf N.

    2001-01-01

    Interstellar dust contains a component which reveals its presence by emitting a broad, unstructured band of light in the 540 to 950 nm wavelength range, referred to as Extended Red Emission (ERE). The presence of interstellar dust and ultraviolet photons are two necessary conditions for ERE to occur. This is the basis for suggestions which attribute ERE to an interstellar dust component capable of photoluminescence. In this study, we have collected all published ERE observations with absolute-calibrated spectra for interstellar environments, where the density of ultraviolet photons can be estimated reliably. In each case, we determined the band-integrated ERE intensity, the wavelength of peak emission in the ERE band, and the efficiency with which absorbed ultraviolet photons are contributing to the ERE. The data show that radiation is not only driving the ERE, as expected for a photoluminescence process, but is modifying the ERE carrier as manifested by a systematic increase in the ERE band's peak wavelength...

  12. Advanced two-way satellite frequency transfer by carrier-phase and carrier-frequency measurements

    Science.gov (United States)

    Fujieda, Miho; Gotoh, Tadahiro; Amagai, Jun

    2016-06-01

    Carrier-phase measurement is one of the ways to improve the measurement resolution of two-way satellite frequency transfer. We introduce two possible methods for carrier-phase measurement: direct carrier-phase detection identified by Two-Way Carrier-Phase (TWCP) and the use of carrier-frequency information identified by Two-Way Carrier Frequency (TWCF). We performed the former using an arbitrary waveform generator and an analog-to-digital sampler and the latter using a conventional modem. The TWCF measurement using the modem had a resolution of 10-13 and the result agreed with that obtained by GPS carrier-phase frequency transfer in a 1500 km baseline. The measurement accuracy may have been limited by the poor frequency resolution of the modem; however, the TWCF measurement was able to improve the stability of conventional two-way satellite frequency transfer. Additionally, we show that the TWCP measurement system has the potential to achieve a frequency stability of 10-17.

  13. Effects of Disorder on Carrier Transport in Cu2 SnS3

    Science.gov (United States)

    Baranowski, Lauryn L.; McLaughlin, Kevin; Zawadzki, Pawel; Lany, Stephan; Norman, Andrew; Hempel, Hannes; Eichberger, Rainer; Unold, Thomas; Toberer, Eric S.; Zakutayev, Andriy

    2015-10-01

    Cu2SnS3 is a promising absorber material that has attracted significant interest in recent years. However, similar to Cu2 ZnSn (S ,Se )4 (CZTS), Cu2 SnS3 displays cation disorder, which complicates the scientific understanding and technological applications of these materials. In this work, we use postdeposition annealing to convert disordered Cu2 SnS3 thin films to the ordered structure. After annealing, we observe crystal structure changes and detect improvements in the majority carrier (hole) transport. However, when the minority carrier (electron) transport is investigated by using optical-pump terahertz-probe spectroscopy, minimal differences are observed in the lifetimes of the photoexcited charge carriers in the ordered and disordered Cu2 SnS3 . By combining the experimental data with theoretical results from first-principles calculations and Monte Carlo simulations, we are able to conclude that even ostensibly "ordered" Cu2 SnS3 displays minority carrier transport properties corresponding to the disordered structure. Transmission electron microscopy investigations reveal only a very low density of planar defects (stacking faults and/or twins) in the annealed film, suggesting that these imperfections can dominate minority carrier transport even at low levels. The results of this study highlight some of the challenges in the development of Cu2 SnS3 -based photovoltaics and have implications for other disordered multinary semiconductors such as CZTS.

  14. Carrier dynamics and terahertz photoconductivity of doped silicon measured by femtosecond pump-terahertz probe spectroscopy

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The carrier dynamics and terahertz photoconductivity in the n-type silicon (n-Si) as well as in the p-type Silicon (p-Si) have been investigated by using femtosecond pump-terahertz probe technique. The measurements show that the relative change of terahertz transmission of p-Si at low pump power is slightly smaller than that of n-Si,due to the lower carrier density induced by the recombination of original holes in the p-type material and the photogenerated electrons. At high pump power,the bigger change of terahertz transmission of p-Si originates from the greater mobility of the carriers compared to n-Si. The transient photoconductivities are calculated and fit well with the Drude-Smith model,showing that the mobility of the photogenerated carriers decreases with the increasing pump power. The obtained results indicate that femtosecond pump-terahertz probe technique is a promising method to investigate the carrier dynamics of semiconductors.

  15. Polyester Dendrimers: Smart Carriers for Drug Delivery

    Directory of Open Access Journals (Sweden)

    Jean–d’Amour K. Twibanire

    2014-01-01

    Full Text Available Polyester dendrimers have been shown to be outstanding candidates for biomedical applications. Compared to traditional polymeric drug vehicles, these biodegradable dendrimers show excellent advantages especially as drug delivery systems because they are non-toxic. Here, advances on polyester dendrimers as smart carriers for drug delivery applications have been surveyed. Both covalent and non-covalent incorporation of drugs are discussed.

  16. Towards 100 gigabit carrier ethernet transport networks

    DEFF Research Database (Denmark)

    Rasmussen, Anders; Zhang, Jiang; Yu, Hao;

    2010-01-01

    Ethernet as a transport technology has, up to now, lacked the features such as network layer architecture, customer separation and manageability that carriers require for wide-scale deployment. However, with the advent of PBB-TE and TMPLS, it is now possible to use Ethernet as a transport...

  17. A new lubricant carrier for metal forming

    DEFF Research Database (Denmark)

    Arentoft, Mogens; Bay, Niels; Tang, Peter Torben;

    2009-01-01

    A lubricant carrier for metal forming processes is developed. Surfaces with pores of micrometer size for entrapping lubricant are generated by electrochemical deposition of an alloy, consisting of two immiscible metals, of which one metal subsequently is etched away leaving 5 mu m layers with a s...... extrusion at high reduction and excessive stroke comparing with conventionally lubrication using phosphate coating and soap....

  18. Polyester Dendrimers: Smart Carriers for Drug Delivery

    OpenAIRE

    Jean–d’Amour K. Twibanire; T. Bruce Grindley

    2014-01-01

    Polyester dendrimers have been shown to be outstanding candidates for biomedical applications. Compared to traditional polymeric drug vehicles, these biodegradable dendrimers show excellent advantages especially as drug delivery systems because they are non-toxic. Here, advances on polyester dendrimers as smart carriers for drug delivery applications have been surveyed. Both covalent and non-covalent incorporation of drugs are discussed.

  19. Dextran: A promising macromolecular drug carrier

    Directory of Open Access Journals (Sweden)

    Dhaneshwar Suneela

    2006-01-01

    Full Text Available Over the past three decades intensive efforts have been made to design novel systems able to deliver the drug more effectively to the target site. The ongoing intense search for novel and innovative drug delivery systems is predominantly a consequence of the well-established fact that the conventional dosage forms are not sufficiently effective in conveying the drug compound to its site of action and once in the target area, in releasing the active agent over a desired period of time. The potential use of macromolecular prodrugs as a means of achieving targeted drug delivery has attracted considerable interest in recent years. Macromolecules such as antibodies, lipoproteins, lectins, proteins, polypeptides, polysaccharides, natural as well as synthetic polymers offer potential applicabilities as high molecular weight carriers for various therapeutically active compounds. Dextrans serve as one of the most promising macromolecular carrier candidates for a wide variety of therapeutic agents due to their excellent physico-chemical properties and physiological acceptance. The present contribution attempts to review various features of the dextran carrier like its source, structural and physico-chemical characteristics, pharmacokinetic fate and its applications as macromolecular carrier with special emphasis on dextran prodrugs.

  20. Itaconic acid carrier ampholytes for isoelectric focusing.

    Science.gov (United States)

    Brenna, O

    1977-04-11

    Commercial carrier ampholytes, obtained by coupling polyethylene polyamines to acrylic acid, exhibit a conductivity minimum in the pH range 5.5-6.5 owing to the lack of appropriate pK values of the polyamine in this pH region. By replacing acrylic with itaconic acid, it has been possible to effect substantial improvements in the pH range 5.5-6.5 as itaconic acid has a pK2 value of 5.45. Upon coupling, the pK of the gramma-carboxyl group remains virtually unaltered. With itoconic acid carrier ampholytes it has been possible to improve the conductivity in the pH range 5.5-6.5 by as much as 400% compared with conventional carrier ampholytes. It is suggected that the commercial products should be supplemented with itaconic acid carrier ampholytes in order to obtain a more uniform conductivity and buffering capacity in the pH range 3-10.

  1. 7 CFR 35.4 - Carrier.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Carrier. 35.4 Section 35.4 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing Practices), DEPARTMENT OF AGRICULTURE COMMODITY STANDARDS AND STANDARD CONTAINER REGULATIONS EXPORT...

  2. Current fluctuation of electron and hole carriers in multilayer WSe{sub 2} field effect transistors

    Energy Technology Data Exchange (ETDEWEB)

    Ko, Seung-Pil; Shin, Jong Mok; Jang, Ho-Kyun; Jin, Jun Eon; Kim, Gyu-Tae, E-mail: gtkim@korea.ac.kr [School of Electrical Engineering, Korea University, Seoul 02481 (Korea, Republic of); Kim, Yong Jin; Kim, Young Keun [Department of Materials Science and Engineering, Korea University, Seoul 02481 (Korea, Republic of); Shin, Minju [School of Electrical Engineering, Korea University, Seoul 02481 (Korea, Republic of); IMEP-LAHC, Grenoble INP-MINATEC, 3 Parvis Louis Neel, 38016 Grenoble (France)

    2015-12-14

    Two-dimensional materials have outstanding scalability due to their structural and electrical properties for the logic devices. Here, we report the current fluctuation in multilayer WSe{sub 2} field effect transistors (FETs). In order to demonstrate the impact on carrier types, n-type and p-type WSe{sub 2} FETs are fabricated with different work function metals. Each device has similar electrical characteristics except for the threshold voltage. In the low frequency noise analysis, drain current power spectral density (S{sub I}) is inversely proportional to frequency, indicating typical 1/f noise behaviors. The curves of the normalized drain current power spectral density (NS{sub I}) as a function of drain current at the 10 Hz of frequency indicate that our devices follow the carrier number fluctuation with correlated mobility fluctuation model. This means that current fluctuation depends on the trapping-detrapping motion of the charge carriers near the channel interface. No significant difference is observed in the current fluctuation according to the charge carrier type, electrons and holes that occurred in the junction and channel region.

  3. Enhanced attached growth of microalgae Scenedesmus. LX1 through ambient bacterial pre-coating of cotton fiber carriers.

    Science.gov (United States)

    Zhuang, Lin-Lan; Azimi, Yaldah; Yu, Dawei; Wang, Wen-Long; Wu, Yin-Hu; Dao, Guo-Hua; Hu, Hong-Ying

    2016-10-01

    The role of bacteria/extracellular polymeric substances (EPS) coated carriers on attached microalgae growth in suspended-solid phase photobioreactor (sspBR) was assessed in this study. The results showed that pre-coating cotton with ambient bacteria and their EPS improved the attached microalgal growth by as much as 230% in terms of attached microalgae density. Additionally, the single cell dry weight, chemical composition and oxygen evolving activity of attached microalgae were significantly affected by the presence of bacteria/EPS coating on the cotton carriers. The protein content of microalgae cells cultivated in the ssPBRs with carriers coated by bacteria and sterilized bacteria were on average 26% and 15% more than uncoated carriers, respectively. Through absorbing and immobilizing nutrients from the bulk medium, the bacteria/EPS coating provided the attached microalgae with nitrogen/phosphorus for protein synthesis, especially during the late stages of batch cultivation. PMID:27416514

  4. Spectral hole-burning and carrier-heating dynamics in InGaAs quantum-dot amplifiers

    DEFF Research Database (Denmark)

    Borri, Paola; Langbein, Wolfgang Werner; Hvam, Jørn Märcher;

    2000-01-01

    The ultrafast gain and index dynamics in a set of InAs-InGaAs-GaAs quantum-dot (QD) amplifiers are measured at room temperature with femtosecond resolution. The role of spectral hole-burning (SHB) and carrier heating (CH) in the recovery of gain compression is investigated in detail. An ultrafast...... recovery of the spectral hole within ~100 fs is measured, comparable to bulk and quantum-well amplifiers, which is contradicting a carrier relaxation bottleneck in electrically pumped QD devices. The CH dynamics in the QD is quantitatively compared with results on an InGaAsP bulk amplifier. Reduced CH for...... both gain and refractive index dynamics of the QD devices is found, which is a promising prerequisite for high-speed applications. This reduction is attributed to reduced free-carrier absorption-induced heating caused by the small carrier density necessary to provide amplification in these low...

  5. Excitation dependent Raman studies of self-seeded grown InN nanoparticles with different carrier concentration.

    Science.gov (United States)

    Madapu, Kishore K; Polaki, S R; Dhara, Sandip

    2016-07-21

    High quality InN nanoparticles are grown using an atmospheric chemical vapour deposition technique via a self-seeded catalytic approach in the temperature range of 580-650 °C. In this temperature region, the nucleation barrier of InN is overcome by seeding low density In nanoparticles prior to introduction of reactive NH3. Samples with increasing carrier densities are grown, with the help of increasing growth temperature, to understand the role of carrier density in the optical phonon structure. Near-resonance Raman spectra show completely different phonon pictures compared to those for the off-resonance spectra. A Raman forbidden mode of B1(high), because of the possible breakdown of selection rules in the near-resonance conditions, is invoked for the first time. The intensity and frequency of this mode strongly depend on the carrier concentration in the sample. In off-resonance conditions, the A1(LO) mode for the sample with higher carrier concentration is dominated by Fano interference rather than plasmon-phonon coupling. Variation of the intensity of the B1(high) mode is correlated with a band filling effect, which is substantiated by the luminescence studies of the InN samples with different carrier concentrations. PMID:27345503

  6. Effective g-factors of carriers in inverted InAs/GaSb bilayers

    Energy Technology Data Exchange (ETDEWEB)

    Mu, Xiaoyang [International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871 (China); Collaborative Innovation Center of Quantum Matter, Beijing 100871 (China); Sullivan, Gerard [Teledyne Scientific and Imaging, Thousand Oaks, California 91630 (United States); Du, Rui-Rui [International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871 (China); Collaborative Innovation Center of Quantum Matter, Beijing 100871 (China); Department of Physics and Astronomy, Rice University, Houston, Texas 77251-1892 (United States)

    2016-01-04

    We perform tilt-field transport experiment on inverted InAs/GaSb, which hosts quantum spin Hall insulator. By means of coincidence method, Landau level (LL) spectra of electron and hole carriers are systematically studied at different carrier densities tuned by gate voltages. When Fermi level stays in the conduction band, we observe LL crossing and anti-crossing behaviors at odd and even filling factors, respectively, with a corresponding g-factor of 11.5. It remains nearly constant for varying filling factors and electron densities. On the contrary, for GaSb holes, only a small Zeeman splitting is observed even at large tilt angles, indicating a g-factor of less than 3.

  7. Effective g-factors of carriers in inverted InAs/GaSb bilayers

    Science.gov (United States)

    Mu, Xiaoyang; Sullivan, Gerard; Du, Rui-Rui

    2016-01-01

    We perform tilt-field transport experiment on inverted InAs/GaSb, which hosts quantum spin Hall insulator. By means of coincidence method, Landau level (LL) spectra of electron and hole carriers are systematically studied at different carrier densities tuned by gate voltages. When Fermi level stays in the conduction band, we observe LL crossing and anti-crossing behaviors at odd and even filling factors, respectively, with a corresponding g-factor of 11.5. It remains nearly constant for varying filling factors and electron densities. On the contrary, for GaSb holes, only a small Zeeman splitting is observed even at large tilt angles, indicating a g-factor of less than 3.

  8. Lower frequency of Gaucher disease carriers among Tay-Sachs disease carriers.

    Science.gov (United States)

    Peleg, L; Frisch, A; Goldman, B; Karpaty, M; Narinsky, R; Bronstein, S; Frydman, M

    1998-01-01

    The heterozygote frequency of Gaucher disease (GD) and Tay-Sachs disease (TSD) is distinctly high among Ashkenazi Jews (1:29 for TSD and 1:16 for GD). Two main theories have been suggested to explain this high occurrence: a founder effect with subsequent genetic drift, and a selective advantage of heterozygotes. We compared the frequency of the GD most common mutation (1226A-->G) among carriers of the common TSD mutation (+1277 TATC) with the frequency of this mutation in the general Ashkenazi population. The frequency of GD carriers among 308 TSD heterozygotes was 1:28 which is about half the expected (P = 0.03). These results indicate that carriers of both diseases do not possess additional evolutionary advantage over single mutation carriers. A reasonable interpretation of these findings is that one or both mutations have arisen relatively recently in different regions of Europe and have not yet reached genetic equilibrium. PMID:9781065

  9. PAPR Reduction in OFDM Systems with Large Number of Sub-Carriers by Carrier Interferometry Approaches

    Institute of Scientific and Technical Information of China (English)

    HE Jian-hui; QUAN Zi-yi; MEN Ai-dong

    2004-01-01

    High Peak-to-Average Power Ratio (PAPR) is one of the major drawbacks of Orthogonal Frequency Division Multiplexing ( OFDM) systems. This paper presents the structures of the particular bit sequences leading to the maximum PAPR (PAPRmax) in Carrier-Interferometry OFDM (CI/OFDM) and Pseudo Orthogonal Carrier-Interferometry OFDM (PO-CI/OFDM) systems for Binary Phase Shift Keying (BPSK) modulation. Furthermore, the simulation and analysis of PAPRmax and PAPR cumulative distribution in CI/OFDM and PO-CI/OFDM systems with 2048 sub-carriers are presented in this paper. The results show that the PAPR of OFDM system with large number of sub-carriers reduced evidently via CI approaches.

  10. Photoconductor-metal contact at higher densities.

    Science.gov (United States)

    Dussel, G. A.; Boer, K. W.; Stirn, R. J.

    1973-01-01

    The formation of space charge in the barrier region is discussed. This region extends to a distance, x-sub o, equal to 200 A plus twice the mean free path of majority carriers. The conventional transport equation can be used only for x greater than x-sub o, and the carrier density at x-sub o represents a boundary condition for the bulk. Its change as a function of applied voltage, temperature, and light intensity in photoconducting CdS is discussed. The time dependence of the space-charge formation in the region between 0 and x-sub o is analyzed. It is shown under which conditions the individuality of the metal contact is observable.

  11. Carrier-interleaved orthogonal multi-electrode multi-carrier resistivity-measurement tool

    Science.gov (United States)

    Cai, Yu; Sha, Shuang

    2016-09-01

    This paper proposes a new carrier-interleaved orthogonal multi-electrode multi-carrier resistivity-measurement tool used in a cylindrical borehole environment during oil-based mud drilling processes. The new tool is an orthogonal frequency division multiplexing access-based contactless multi-measurand detection tool. The tool can measure formation resistivity in different azimuthal angles and elevational depths. It can measure many more measurands simultaneously in a specified bandwidth than the legacy frequency division multiplexing multi-measurand tool without a channel-select filter while avoiding inter-carrier interference. The paper also shows that formation resistivity is not sensitive to frequency in certain frequency bands. The average resistivity collected from N subcarriers can increase the measurement of the signal-to-noise ratio (SNR) by N times given no amplitude clipping in the current-injection electrode. If the clipping limit is taken into account, with the phase rotation of each single carrier, the amplitude peak-to-average ratio can be reduced by 3 times, and the SNR can achieve a 9/N times gain over the single-carrier system. The carrier-interleaving technique is also introduced to counter the carrier frequency offset (CFO) effect, where the CFO will cause inter-pad interference. A qualitative analysis and simulations demonstrate that block-interleaving performs better than tone-interleaving when coping with a large CFO. The theoretical analysis also suggests that increasing the subcarrier number can increase the measurement speed or enhance elevational resolution without sacrificing receiver performance. The complex orthogonal multi-pad multi-carrier resistivity logging tool, in which all subcarriers are complex signals, can provide a larger available subcarrier pool than other types of transceivers.

  12. Band gap tunning in BN-doped graphene systems with high carrier mobility

    KAUST Repository

    Kaloni, T. P.

    2014-02-17

    Using density functional theory, we present a comparative study of the electronic properties of BN-doped graphene monolayer, bilayer, trilayer, and multilayer systems. In addition, we address a superlattice of pristine and BN-doped graphene. Five doping levels between 12.5% and 75% are considered, for which we obtain band gaps from 0.02 eV to 2.43 eV. We demonstrate a low effective mass of the charge carriers.

  13. Band gap tunning in BN-doped graphene systems with high carrier mobility

    International Nuclear Information System (INIS)

    Using density functional theory, we present a comparative study of the electronic properties of BN-doped graphene monolayer, bilayer, trilayer, and multilayer systems. In addition, we address a superlattice of pristine and BN-doped graphene. Five doping levels between 12.5% and 75% are considered, for which we obtain band gaps from 0.02 eV to 2.43 eV. We demonstrate a low effective mass of the charge carriers

  14. Benchmark and gap analysis of current mask carriers vs future requirements: example of the carrier contamination

    Science.gov (United States)

    Fontaine, H.; Davenet, M.; Cheung, D.; Hoellein, I.; Richsteiger, P.; Dejaune, P.; Torsy, A.

    2007-02-01

    In the frame of the European Medea+ 2T302 MUSCLE project, an extensive mask carriers benchmark was carried out in order to evaluate whether some containers answer to the 65nm technology needs. Ten different containers, currently used or expected in the future all along the mask supply chain (blank, maskhouse and fab carriers) were selected at different steps of their life cycle (new, aged, aged & cleaned). The most critical parameters identified for analysis versus future technologies were: automation, particle contamination, chemical contamination (organic outgassing, ionic contamination), cleanability, ESD, airtightness and purgeability. Furthermore, experimental protocols corresponding to suitable methods were then developed and implemented to test each criterion. The benchmark results are presented giving a "state of the art" of mask carriers currently available and allowing a gap analysis for the tested parameters related to future needs. This approach is detailed through the particular case of carrier contamination measurements. Finally, this benchmark / gap analysis leads to propose advisable mask carrier specifications (and the test protocols associated) on various key parameters which can also be taken as guidelines for a standardization perspective for the 65nm technology. This also indicates that none of tested carriers fulfills all the specifications proposed.

  15. Charge density glass from fictions to facts

    International Nuclear Information System (INIS)

    Thirty years ago Fukuyama [J. Phys. Soc. Jpn. 45 (1978) 1474] predicted a transition from charge density wave (CDW) state to the charge density glass (CDG) at a finite temperature as the consequence of the competition between the uniform commensurability pinning and the random impurity pinning. We present strong evidence that the CDG phase indeed exists as a generic feature of density wave systems. However, it arises from the competition of the random impurity pinning and the electrostatic intra-CDW interaction which tends to establish a uniform phase at low temperature. The glass transition occurs at the temperature at which the free carriers cannot efficiently screen the phase distortions. The characteristic length scale of the disorder, i.e. the size of the phase coherent domains, governs the glass properties

  16. Origin of charge density at LaAlO3-on-SrTiO3 heterointerfacespossibility of intrinsic doping

    Energy Technology Data Exchange (ETDEWEB)

    Siemons, W.

    2010-04-29

    As discovered by Ohtomo et al., a large sheet charge density with high mobility exists at the interface between SrTiO{sub 3} and LaAlO{sub 3}. Based on transport, spectroscopic and oxygen-annealing experiments, we conclude that extrinsic defects in the form of oxygen vacancies introduced by the pulsed laser deposition process used by all researchers to date to make these samples is the source of the large carrier densities. Annealing experiments show a limiting carrier density. We also present a model that explains the high mobility based on carrier redistribution due to an increased dielectric constant.

  17. 48 CFR 1615.470 - Carrier investment of FEHB funds.

    Science.gov (United States)

    2010-10-01

    ... CONTRACTING BY NEGOTIATION Contract Pricing 1615.470 Carrier investment of FEHB funds. (a) Except for contracts based on a combination of cost and price analysis (community-rated), the carrier is required...

  18. Carrier cultures of simian foamy virus.

    Science.gov (United States)

    Clarke, J K; Samuels, J; Dermott, E; Gay, F W

    1970-05-01

    The production of cultures of HEp-2 and BHK-21 cells persistently infected with a type 1 simian foamy virus is described. After infection, HEp-2 cells showed no structural changes, whereas BHK-21 cells lost their normal spindle shape and showed mitochondrial damage, and some cells contained many lysosomes. Thin sections also showed that a few BHK-21 cells contained virus particles in low concentration, and infectious virus could be isolated from both the cells and the supernatant fluid. No virus was seen in thin sections of HEp-2 cells, although infectious virus in low titer could be recovered intermittently from lysed cells. Both carrier cultures were immune to challenge with homologous virus and antigen could be detected in over 90% of the cells even after growth for 9 weeks in the presence of virus-neutralizing serum. The distribution of antigen in carrier cultures of both cell types is described and compared with that seen in cytocidal infections. PMID:4986851

  19. Carrier synchronization and detection of polyphase signals.

    Science.gov (United States)

    Lindsey, W. C.; Simon, M. K.

    1972-01-01

    Digital communication networks used for the distribution of high-speed digital information are currently the subject of design studies for many civil and military applications. This paper presents results that are useful in such studies as well as in network planning. In particular, the paper is concerned with the problems of carrier synchronization and noisy reference detection of polyphase signals. Reconstruction of coherent references for the detection of polyphase signals is considered and analyzed for three carrier reconstruction loops, namely, Nth power (multiply-and-divide) loops, generalized Costas (I-Q) loops, and extensions of data-aided (modulation wipeoff) loops. General expressions for the error probability are developed when the reconstructed reference signals are noisy.

  20. Superconductivity in carrier-doped silicon carbide

    Directory of Open Access Journals (Sweden)

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

    2008-01-01

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

  1. Terahertz transport dynamics of graphene charge carriers

    DEFF Research Database (Denmark)

    Buron, Jonas Christian Due

    The electronic transport dynamics of graphene charge carriers at femtosecond (10-15 s) to picosecond (10-12 s) time scales are investigated using terahertz (1012 Hz) time-domain spectroscopy (THz-TDS). The technique uses sub-picosecond pulses of electromagnetic radiation to gauge the electrodynamic...... response of thin conducting films at up to multi-terahertz frequencies. In this thesis THz-TDS is applied towards two main goals; (1) investigation of the fundamental carrier transport dynamics in graphene at femtosecond to picosecond timescales and (2) application of terahertz time-domain spectroscopy...... to rapid and non-contact electrical characterization of large-area graphene, relevant for industrial integration. We show that THz-TDS is an accurate and reliable probe of graphene sheet conductance, and that the technique provides insight into fundamental aspects of the nanoscopic nature of conduction...

  2. Experimental distribution of entanglement with separable carriers.

    Science.gov (United States)

    Fedrizzi, A; Zuppardo, M; Gillett, G G; Broome, M A; Almeida, M P; Paternostro, M; White, A G; Paterek, T

    2013-12-01

    The key requirement for quantum networking is the distribution of entanglement between nodes. Surprisingly, entanglement can be generated across a network without direct transfer-or communication-of entanglement. In contrast to information gain, which cannot exceed the communicated information, the entanglement gain is bounded by the communicated quantum discord, a more general measure of quantum correlation that includes but is not limited to entanglement. Here, we experimentally entangle two communicating parties sharing three initially separable photonic qubits by exchange of a carrier photon that is unentangled with either party at all times. We show that distributing entanglement with separable carriers is resilient to noise and in some cases becomes the only way of distributing entanglement through noisy environments.

  3. Protection switching for carrier ethernet multicast

    DEFF Research Database (Denmark)

    Ruepp, Sarah Renée; Wessing, Henrik; Berger, Michael Stübert

    2010-01-01

    This paper addresses network survivability for IPTV multicast transport in Carrier Ethernet networks. The impact of link failures is investigated and suggestions for intelligent multicast resilience schemes are proposed. In particular, functions of the multicast tree are integrated with the Carri...... recovery path length, recovery time, number of branch nodes and operational complexity. The integrated approach therefore shows significant potential to increase the QoE for IPTV users in case of network failures and recovery actions....

  4. Nanogel Carrier Design for Targeted Drug Delivery

    OpenAIRE

    Eckmann, D.M.; Composto, R. J.; Tsourkas, A; Muzykantov, V. R.

    2014-01-01

    Polymer-based nanogel formulations offer features attractive for drug delivery, including ease of synthesis, controllable swelling and viscoelasticity as well as drug loading and release characteristics, passive and active targeting, and the ability to formulate nanogel carriers that can respond to biological stimuli. These unique features and low toxicity make the nanogels a favorable option for vascular drug targeting. In this review, we address key chemical and biological aspects of nanoge...

  5. Software defined networking: meeting carrier grade requirements

    OpenAIRE

    Staessens, Dimitri; Sharma, Sachin; Colle, Didier; Pickavet, Mario; Demeester, Piet

    2011-01-01

    Software Defined Networking is a networking paradigm which allows network operators to manage networking elements using software running on an external server. This is accomplished by a split in the architecture between the forwarding element and the control element. Two technologies which allow this split for packet networks are ForCES and Openflow. We present energy efficiency and resilience aspects of carrier grade networks which can be met by Openflow. We implement flow restoration and ru...

  6. Atlas V Aft Bulkhead Carrier Rideshare System

    OpenAIRE

    Willcox, Maj Travis

    2012-01-01

    This paper gives the background and details of the Atlas V Aft Bulkhead Carrier to be flown on the National Recoinnassance Office Launch 36 with the Operationally Unique Technologies Satellite Auxiliary Payload. The CubeSats included are from a number of labs, universities and government entities for the purpose of technology demonstration, science experimentation and operational proof of concepts. This mission will pave the way for rideshare on NRO missions and other Atlas V launches.

  7. The solute carrier 6 family of transporters

    DEFF Research Database (Denmark)

    Bröer, Stefan; Gether, Ulrik

    2012-01-01

    The solute carrier 6 (SLC6) family of the human genome comprises transporters for neurotransmitters, amino acids, osmolytes and energy metabolites. Members of this family play critical roles in neurotransmission, cellular and whole body homeostasis. Malfunction or altered expression...... of these transporters is associated with a variety of diseases. Pharmacological inhibition of the neurotransmitter transporters in this family is an important strategy in the management of neurological and psychiatric disorders. This review provides an overview of the biochemical and pharmacological properties...

  8. Photoinduced carrier annihilation in silicon pn junction

    Science.gov (United States)

    Sameshima, Toshiyuki; Motoki, Takayuki; Yasuda, Keisuke; Nakamura, Tomohiko; Hasumi, Masahiko; Mizuno, Toshihisa

    2015-08-01

    We report analysis of the photo-induced minority carrier effective lifetime (τeff) in a p+n junction formed on the top surfaces of a n-type silicon substrate by ion implantation of boron and phosphorus atoms at the top and bottom surfaces followed by activation by microwave heating. Bias voltages were applied to the p+ boron-doped surface with n+ phosphorus-doped surface kept at 0 V. The values of τeff were lower than 1 × 10-5 s under the reverse-bias condition. On the other hand, τeff markedly increased to 1.4 × 10-4 s as the forward-bias voltage increased to 0.7 V and then it leveled off when continuous-wave 635 nm light was illuminated at 0.74 mW/cm2 on the p+ surface. The carrier annihilation velocity S\\text{p + } at the p+ surface region was numerically estimated from the experimental τeff. S\\text{p + } ranged from 4000 to 7200 cm/s under the reverse-bias condition when the carrier annihilation velocity S\\text{n + } at the n+ surface region was assumed to be a constant value of 100 cm/s. S\\text{p + } markedly decreased to 265 cm/s as the forward-bias voltage increased to 0.7 V.

  9. Temperature-dependent minority carrier lifetime of crystalline silicon wafers passivated by high quality amorphous silicon oxide

    Science.gov (United States)

    Inaba, Masahiro; Todoroki, Soichiro; Nakada, Kazuyoshi; Miyajima, Shinsuke

    2016-04-01

    We investigated the effects of annealing on the temperature-dependent minority carrier lifetime of a crystalline silicon wafer passivated by hydrogenated amorphous silicon oxide. The annealing significantly affects the lifetime and its temperature dependence. Our device simulations clearly indicate that valence band offset significantly affects the temperature dependence. We also found a slight increase in the interface defect density after annealing.

  10. The Influence of Oxide Charge on Carrier Mobility in HfO2/TiN Gate Silicon MOSFETs

    NARCIS (Netherlands)

    Hurley, Paul K.; Negara, Adi; Hemert, van Tom; Cherkaoui, Karim

    2009-01-01

    In this work we will provide the results of an investigation into electron and hole mobility at high inversion charge density (6 to 8x1012 cm-2) in TiN/HfO2/SiOx/Si MOSFETs. We examine the influence of oxide charge on carrier mobility by using temperature bias stress to deliberately increase the den

  11. 14 CFR 252.3 - Smoking ban: air carriers.

    Science.gov (United States)

    2010-01-01

    ... 14 Aeronautics and Space 4 2010-01-01 2010-01-01 false Smoking ban: air carriers. 252.3 Section... PROCEEDINGS) ECONOMIC REGULATIONS SMOKING ABOARD AIRCRAFT § 252.3 Smoking ban: air carriers. Air carriers shall prohibit smoking on all scheduled passenger flights....

  12. 14 CFR 252.5 - Smoking ban: foreign air carriers.

    Science.gov (United States)

    2010-01-01

    ... 14 Aeronautics and Space 4 2010-01-01 2010-01-01 false Smoking ban: foreign air carriers. 252.5... PROCEEDINGS) ECONOMIC REGULATIONS SMOKING ABOARD AIRCRAFT § 252.5 Smoking ban: foreign air carriers. (a) Foreign air carriers shall prohibit smoking on all scheduled passenger flight segments: (1) Between...

  13. Legionella pneumophila Secretes a Mitochondrial Carrier Protein during Infection

    OpenAIRE

    Pavel Dolezal; Margareta Aili; Janette Tong; Jhih-Hang Jiang; Marobbio, Carlo M.T.; Sau Fung Lee; Ralf Schuelein; Simon Belluzzo; Eva Binova; Aurelie Mousnier; Gad Frankel; Giulia Giannuzzi; Ferdinando Palmieri; Kipros Gabriel; Thomas Naderer

    2012-01-01

    Author Summary Mitochondrial carrier proteins evolved during endosymbiosis to transport substrates across the mitochondrial inner membrane. As such the proteins are associated exclusively with eukaryotic organisms. Despite this, we identified putative mitochondrial carrier proteins in the genomes of different intracellular bacterial pathogens, including Legionella pneumophila, the causative agent of Legionnaire's disease. We named the mitochondrial carrier protein from L. pneumophila LncP and...

  14. Terahertz carrier dynamics in graphene and graphene nanostructures

    DEFF Research Database (Denmark)

    Jensen, Søren A.; Turchinovich, Dmitry; Tielrooij, Klaas Jan;

    2014-01-01

    Photoexcited charge carriers in 2D graphene and in 1D graphene nanostructures were studied with optical pump-THz probe spectroscopy. We find efficient hot-carrier multiplication in 2D graphene, and predominantly free carrier early time response in 1D nanostructures. © 2014 OSA....

  15. Time Resolved Studies of Carrier Dynamics in III -v Heterojunction Semiconductors.

    Science.gov (United States)

    Westland, Duncan James

    Available from UMI in association with The British Library. Requires signed TDF. Picosecond time-resolution photoluminescence spectroscopy has been used to study transient processes in Ga _{.47}In_{.53 }As/InP multiple quantum wells (MQWs), and in bulk Ga_{.47}In _{.53}As and GaSb. To facilitate the experimental studies, apparatus was constructed to allow the detection of transient luminescence with 3ps time resolution. A frequency upconversion technique was employed. Relaxation of energetic carriers in bulk Ga _{.47}In_{.53 }As by optic phonons has been investigated, and, at carrier densities ~3 times 10^{18}cm ^{-3} is found to be a considerably slower process than simple theory predicts. The discrepancy is resolved by the inclusion of a non-equilibrium population of longitudinal optic phonons in the theoretical description. Slow energy loss is also observed in a 154A MQW under similar conditions, but carriers are found to relax more quickly in a 14A MQW with a comparable repeat period. The theory of non-equilibrium mode occupation is modified to describe the case of a MQW and is found to agree with experiment. Carrier relaxation in GaSb is studied and the importance of occupation of the L _6 conduction band valley in this material is demonstrated. The ambipolar diffusion of a photoexcited carrier plasma through an InP capping layer was investigated using an optical time-of-flight technique. This experiment also enables the efficiency of carrier capture by a Ga _{.47}In_{.53 }As quantum well to be determined. A capture time of 4ps was found.

  16. Joint Iterative Carrier Synchronization and Signal Detection for Dual Carrier 448 Gb/s PDM 16-QAM

    DEFF Research Database (Denmark)

    Zibar, Darko; Carvalho, Luis; Estaran Tolosa, Jose Manuel;

    2013-01-01

    Soft decision driven joint carrier synchronization and signal detection, employing expectation maximization, is experimentally demonstrated. Employing soft decisions offers an improvement of 0.5 dB compared to hard decision digital PLL based carrier synchronization and demodulation....

  17. Literature review of the passenger airline business models: Full service carrier, low-cost carrier and charter airlines

    NARCIS (Netherlands)

    Carmona Benitez, R.B.; Lodewijks, G.

    2008-01-01

    The deregulation and liberalization of the air transportation industry have developed three main passenger business models: full service carriers, low-cost carriers, and charter airlines. Deregulation removed regulated fares and routes increasing competition and yields. Airlines business models main

  18. Laboratory Density Functionals

    OpenAIRE

    Giraud, B. G.

    2007-01-01

    We compare several definitions of the density of a self-bound system, such as a nucleus, in relation with its center-of-mass zero-point motion. A trivial deconvolution relates the internal density to the density defined in the laboratory frame. This result is useful for the practical definition of density functionals.

  19. Velocity Saturation of Hot Carriers in Two-Dimensional Transistors

    Science.gov (United States)

    Bird, Jonathan

    Two-dimensional (2D) materials, including graphene and transition-metal dichalcogenides, have emerged in recent years as possible ``channel-replacement'' materials for use in future generations of post-CMOS devices. Realizing the full potential of these materials requires strategies to maximize their current-carrying capacity, while minimizing Joule losses to its environment. A major source of dissipation for hot carriers in any semiconductor is spontaneous optical-phonon emission, resulting in saturation of the drift velocity. In this presentation, I discuss the results of studies of velocity saturation in both graphene and molybdenum-disulphide transistors, emphasizing how this phenomenon impacts resulting transistor operation. While in graphene the large intrinsic optical-phonon energies promise high saturation velocities, experiments to date have revealed a significant degradation of the drift velocity that arises from the loss of energy from hot carriers to the underlying substrate. I discuss here how this problem can be overcome by implementing a strategy of nanosecond electrical pulsing [H. Ramamoorthy et al., Nano Lett., under review], as a means to drive graphene's hot carriers much faster than substrate heating can occur. In this way we achieve saturation velocities that approach the Fermi velocity near the Dirac point, and which exceed those reported for suspended graphene and for devices fabricated on boron nitride substrates. Corresponding current densities reach those found in carbon nanotubes, and in graphene-on-diamond transistors. In this sense we are able to ``free'' graphene from the influence of its substrate, revealing a pathway to achieve the superior electrical performance promised by this material. Velocity saturation is also found to be important for the operation of monolayer molybdenum-disulphide transistors, where it limits the drain current observed in saturation [G. He et al., Nano Lett. 15, 5052 (2015)]. The implications of these

  20. Carrier Transport Mechanism in Single Crystalline Organic Semiconductor Thin Film Elucidated by Visualized Carrier Motion.

    Science.gov (United States)

    Matsubara, Kohei; Abe, Kentaro; Manaka, Takaaki; Iwamoto, Mitsumasa

    2016-04-01

    Time-resolved microscopic second harmonic generation (TRM-SHG) measurement was conducted to evaluate temperature dependence of the anisotropic carrier transport process in 6,13-Bis(triisopropylsilylethynyl) (TIPS) pentacene single crystalline domains for two orthogonal directions. Enhancement of the electric field induced SHG (EFI-SHG) signal at the electrode edge at low temperature suggests the presence of potential drop in the injection process. We directly evaluated temperature dependence of the carrier mobility by taking into account the potential drop, and concluded that the Marcus theory is appropriate to interpret the carrier transport in anisotropic TIPS pentacene thin film. TRM-SHG method is a facile and effective way to directly visualize transport process in anisotropic materials and to evaluate injection and transport processes simultaneously. PMID:27451638

  1. Probing ultrafast carrier dynamics, nonlinear absorption and refraction in core–shell silicon nanowires

    Indian Academy of Sciences (India)

    Sunil Kumar; M Khorasaninejad; M M Adachi; K S Karim; S S Saini; A K Sood

    2012-09-01

    We investigate the relaxation dynamics of photogenerated carriers in silicon nanowires consisting of a crystalline core and a surrounding amorphous shell, using femtosecond time resolved differential reflectivity and transmission spectroscopy at 3.15 eV and 1.57 eV photon energies. The complex behaviour of the differential transmission and reflectivity transients is the mixed contributions from the crystalline core and the amorphous silicon on the nanowire surface and the substrate where competing effects of state-filling and photoinduced absorption govern the carrier dynamics. Faster relaxation rates are observed on increasing the photogenerated carrier density. Independent experimental results on crystalline silicon-on-sapphire (SOS) help us in separating the contributions from the carrier dynamics in crystalline core and the amorphous regions in the nanowire samples. Further, single-beam z-scan nonlinear transmission experiments at 1.57 eV in both open- and close-aperture configurations yield two-photon absorption coefficient (∼3 cm/GW) and nonlinear refraction coefficient (−2.5 × 10−4 cm2 /GW).

  2. A self-consistent first-principle based approach to model carrier mobility in organic materials

    International Nuclear Information System (INIS)

    Transport through thin organic amorphous films, utilized in OLEDs and OPVs, has been a challenge to model by using ab-initio methods. Charge carrier mobility depends strongly on the disorder strength and reorganization energy, both of which are significantly affected by the details in environment of each molecule. Here we present a multi-scale approach to describe carrier mobility in which the materials morphology is generated using DEPOSIT, a Monte Carlo based atomistic simulation approach, or, alternatively by molecular dynamics calculations performed with GROMACS. From this morphology we extract the material specific hopping rates, as well as the on-site energies using a fully self-consistent embedding approach to compute the electronic structure parameters, which are then used in an analytic expression for the carrier mobility. We apply this strategy to compute the carrier mobility for a set of widely studied molecules and obtain good agreement between experiment and theory varying over several orders of magnitude in the mobility without any freely adjustable parameters. The work focuses on the quantum mechanical step of the multi-scale workflow, explains the concept along with the recently published workflow optimization, which combines density functional with semi-empirical tight binding approaches. This is followed by discussion on the analytic formula and its agreement with established percolation fits as well as kinetic Monte Carlo numerical approaches. Finally, we skatch an unified multi-disciplinary approach that integrates materials science simulation and high performance computing, developed within EU project MMM@HPC

  3. Increase of Carrier-to-Noise Ratio in GPS Receivers Caused by Continuous-Wave Interference

    Directory of Open Access Journals (Sweden)

    J. Li

    2016-09-01

    Full Text Available The increased use of personal private devices (PPDs is drawing greater attention to the effects of continuous-wave interference (CWI on the performance of global positioning system (GPS receivers. The effective carrier-to-noise density ratio (C/N0, an essential index of GNSS receiver performance, is studied in this paper. Receiver tracking performance deteriorates in the presence of interference. Hence, the effective C/N0, which measures tracking performance, decreases. However, simulations and bench tests have shown that the effective C/N0 may increase in the presence of CWI. The reason is that a sinusoidal signal is induced by the CWI in the correlator and may be tracked by the carrier tracking loop. Thus, the effective carrier power depends on the power of the signal induced by the CWI, and the effective C/N0 increases with the power of the CWI. The filtering of the CWI in the carrier tracking loop correlator and its effect on the phase locked loop (PLL tracking performance are analyzed. A mathematical model of the effect of the CWI on the effective C/N0 is derived. Simulation results show that the proposed model is more accurate than existing models, especially when the jam-to-signal ratio (JSR is greater than 30 dBc.

  4. Carrier extraction dynamics from Ge/Si quantum wells in Si solar cells

    International Nuclear Information System (INIS)

    To address the carrier extraction mechanism that determines the fundamental characteristics, such as current density, open circuit voltage, and fill factor in nanostructure-based solar cells, we performed photoluminescence (PL) decay measurements of the Ge/Si quantum wells (QWs) in crystalline-silicon (c-Si) solar cells. We found that the PL decay time of Ge/Si QWs depends on the temperature and the applied electric field; this dependence reflects the carrier separation characteristics of electron–hole pairs in Ge/Si QWs. Above ∼ 40 K, the electron–hole pairs are rapidly separated by the thermal excitation and the built-in electric field of c-Si solar cells. In contrast, at 20 K the PL decay time remains almost unchanged for an applied electric field of up to ± 1 V. These results indicate that the electrons confined in the type-II band offsets could be thermally excited and then extracted by an applied electric field. - Highlights: • Carrier extraction mechanism in nanostructure-based solar cells • Photoluminescence dynamics in Ge/Si quantum wells in Si solar cells • Carrier separation characteristics of electron-hole pairs in type-II Ge/Si QWs

  5. A self-consistent first-principle based approach to model carrier mobility in organic materials

    Energy Technology Data Exchange (ETDEWEB)

    Meded, Velimir; Friederich, Pascal; Symalla, Franz; Neumann, Tobias; Danilov, Denis; Wenzel, Wolfgang [Institute of Nanotechnology, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany)

    2015-12-31

    Transport through thin organic amorphous films, utilized in OLEDs and OPVs, has been a challenge to model by using ab-initio methods. Charge carrier mobility depends strongly on the disorder strength and reorganization energy, both of which are significantly affected by the details in environment of each molecule. Here we present a multi-scale approach to describe carrier mobility in which the materials morphology is generated using DEPOSIT, a Monte Carlo based atomistic simulation approach, or, alternatively by molecular dynamics calculations performed with GROMACS. From this morphology we extract the material specific hopping rates, as well as the on-site energies using a fully self-consistent embedding approach to compute the electronic structure parameters, which are then used in an analytic expression for the carrier mobility. We apply this strategy to compute the carrier mobility for a set of widely studied molecules and obtain good agreement between experiment and theory varying over several orders of magnitude in the mobility without any freely adjustable parameters. The work focuses on the quantum mechanical step of the multi-scale workflow, explains the concept along with the recently published workflow optimization, which combines density functional with semi-empirical tight binding approaches. This is followed by discussion on the analytic formula and its agreement with established percolation fits as well as kinetic Monte Carlo numerical approaches. Finally, we skatch an unified multi-disciplinary approach that integrates materials science simulation and high performance computing, developed within EU project MMM@HPC.

  6. Ionic liquid based lithium battery electrolytes: charge carriers and interactions derived by density functional theory calculations.

    Science.gov (United States)

    Angenendt, Knut; Johansson, Patrik

    2011-06-23

    The solvation of lithium salts in ionic liquids (ILs) leads to the creation of a lithium ion carrying species quite different from those found in traditional nonaqueous lithium battery electrolytes. The most striking differences are that these species are composed only of ions and in general negatively charged. In many IL-based electrolytes, the dominant species are triplets, and the charge, stability, and size of the triplets have a large impact on the total ion conductivity, the lithium ion mobility, and also the lithium ion delivery at the electrode. As an inherent advantage, the triplets can be altered by selecting lithium salts and ionic liquids with different anions. Thus, within certain limits, the lithium ion carrying species can even be tailored toward distinct important properties for battery application. Here, we show by DFT calculations that the resulting charge carrying species from combinations of ionic liquids and lithium salts and also some resulting electrolyte properties can be predicted. PMID:21591707

  7. Charge carrier density dependence of the hole mobility in poly(p-phenylene vinylene)

    NARCIS (Netherlands)

    Tanase, C; Blom, PWM; de Leeuw, DM; Meijer, EJ

    2004-01-01

    The hole transport in various poly(p-phenylene vinylene) (PPV) derivatives has been investigated in field-effect transistors (FETs) and light-emitting diodes (LEDs) as a function of temperature and applied bias. The discrepancy between the experimental hole mobilities extracted from FETs and LEDs ba

  8. Carbon-neutral fuels and energy carriers

    CERN Document Server

    Muradov, Nazim Z

    2011-01-01

    Concerns over an unstable energy supply and the adverse environmental impact of carbonaceous fuels have triggered considerable efforts worldwide to find carbon-free or low-carbon alternatives to conventional fossil fuels. Carbon-Neutral Fuels and Energy Carriers emphasizes the vital role of carbon-neutral energy sources, transportation fuels, and associated technologies for establishing a sustainable energy future. Each chapter draws on the insight of world-renowned experts in such diverse fields as photochemistry and electrochemistry, solar and nuclear energy, biofuels and synthetic fuels, ca

  9. Car Carrier 5.800 TPM

    OpenAIRE

    López de Rojas, Carmen

    2012-01-01

    Tipo de Buque: Car Carrier. Capacidad de carga: carga 1: 3000 coches sin trailers. Carga 2: Carga combinada para 1500 ml de trailers y coches en el resto de las cubiertas del buque no ocupadas por los trailers. Peso muerto 5800 TPM. Capacidad de conductores: 100 personas en camarotes dobles. Sociedad de clasificación: Det Norske Veritas. Reglamentos: Solas, Marpol, Convenio de líneas de carga. Velocidad: 19 nudos al 85% MCR en pruebas. Autonomía: 4500 millas al 80% MCR y 15% al margen de mar....

  10. 76 FR 5424 - Motor Carrier Safety Advisory Committee; Request for Nominations

    Science.gov (United States)

    2011-01-31

    ... Federal Motor Carrier Safety Administration Motor Carrier Safety Advisory Committee; Request for Nominations AGENCY: Federal Motor Carrier Safety Administration (FMCSA), DOT. ACTION: Request for Nominations to the Motor Carrier Safety Advisory Committee (MCSAC). SUMMARY: The FMCSA solicits nominations...

  11. Growth of monolithic full-color GaN-based LED with intermediate carrier blocking layers

    Science.gov (United States)

    El-Ghoroury, Hussein S.; Yeh, Milton; Chen, J. C.; Li, X.; Chuang, Chih-Li

    2016-07-01

    Specially designed intermediate carrier blocking layers (ICBLs) in multi-active regions of III-nitride LEDs were shown to be effective in controlling the carrier injection distribution across the active regions. In principle, the majority of carriers, both holes and electrons, can be guided into targeted quantum wells and recombine to generate light of specific wavelengths at controlled current-densities. Accordingly we proposed and demonstrated a novel monolithic InGaN-based LED to achieve three primary colors of light from one device at selected current densities. This LED structure, which has three different sets of quantum wells separated with ICBLs for three primary red-green-blue (RGB) colors, was grown by metal-organic chemical vapor deposition (MOCVD). Results show that this LED can emit light ranging from 460 to 650 nm to cover the entire visible spectrum. The emission wavelength starts at 650 nm and then decreases to 460 nm or lower as the injection current increases. In addition to three primary colors, many other colors can be obtained by color mixing techniques. To the best of our knowledge, this is the first demonstration of monolithic full-color LED grown by a simple growth technique without using re-growth process.

  12. A charge carrier transport model for donor-acceptor blend layers

    International Nuclear Information System (INIS)

    Highly efficient organic solar cells typically comprise donor-acceptor blend layers facilitating effective splitting of excitons. However, the charge carrier mobility in the blends can be substantially smaller than in neat materials, hampering the device performance. Currently, available mobility models do not describe the transport in blend layers entirely. Here, we investigate hole transport in a model blend system consisting of the small molecule donor zinc phthalocyanine (ZnPc) and the acceptor fullerene C60 in different mixing ratios. The blend layer is sandwiched between p-doped organic injection layers, which prevent minority charge carrier injection and enable exploiting diffusion currents for the characterization of exponential tail states from a thickness variation of the blend layer using numerical drift-diffusion simulations. Trap-assisted recombination must be considered to correctly model the conductivity behavior of the devices, which are influenced by local electron currents in the active layer, even though the active layer is sandwiched in between p-doped contacts. We find that the density of deep tail states is largest in the devices with 1:1 mixing ratio (Et = 0.14 eV, Nt = 1.2 × 1018 cm−3) directing towards lattice disorder as the transport limiting process. A combined field and charge carrier density dependent mobility model are developed for this blend layer

  13. Illumination dependent carrier dynamics of CH3NH3PbBr3 perovskite

    Science.gov (United States)

    Chen, Sheng; Wen, Xiaoming; Huang, Shujuan; Sheng, Rui; Green, Martin A.; Ho-Baillie, Anita

    2015-12-01

    The excellent light harvesting properties and potentially low cost fabrication of organometal halide perovskites have attracted great attention in their application as solar cell device. Apart from the general advantages of organic-inorganic perovskite, CH3NH3PbBr3 has a larger bandgap (~2.3eV) suitable to be the top cell in a tandem solar device. Here we use steady-state and time-resolved photoluminescence (PL) techniques to investigate the photophysical behaviour of CH3NH3PbBr3 perovskite including its carrier dynamics under continuous illumination. Samples were studied under different illumination conditions and the following observations were made: (1) defect assisted recombination is dominant under low excitation under nano-second scale measurement, (2) bimolecular and Auger recombinations dominate under high excitation under the minute timescale measurement, (3) the magnitude PL decay traces decrease over time under continuous excitation. We propose that both the density of photo-generated free carriers and the density of mobile ions have an impact on the carrier dynamic of CH3NH3PbBr3. This finding provides insights into the photophysical properties of perovskite materials.

  14. Theory of anisotropic diamagnetism, local moment magnetization and carrier spin-polarization in Pb1-EuTe

    Indian Academy of Sciences (India)

    R C Patnaik; R K Das; R L Hota; G S Tripathi

    2001-10-01

    We present theoretical analyses of anisotropic lattice diamagnetism, magnetization due to magnetic ions and carrier spin-polarization in the diluted magnetic semiconductor, Pb1-EuTe. The lattice diamagnetism results from orbital susceptibility due to inter band effects and spin-orbit contributions. The spin-orbit contribution is found to be dominant. However, both the contributions show pronounced anisotropy. With increase inx, the diamagnetism decreases. We consider contributions from randomly distributed isolated magnetic ions and clusters of pairs and triads for the local moment magnetization. The isolated magnetic-ion contribution is the dominant one. We calculate the magnetization for two typical magnetic ion concentrations: = 0.03 and = 0.06. Temperature dependence of the magnetization is also considered. Apart from lattice and localized magnetic ions, the carrier contribution to the spin-density is also calculated for a carrier density of = 1018 cm-3. The relative spin-density of carriers increases with increase in the magnetic field strength and magnetic ion concentration. The agreement with experiment where available is reasonably good.

  15. Generalized Carrier to Interference Ratio Analysis for the Shotgun Cellular System

    CERN Document Server

    Madhusudhanan, Prasanna; Liu, Youjian; Brown, Timothy X; Baker, Kenneth

    2010-01-01

    In this paper, the performance of cellular systems in which the base-stations (BS) are randomly placed (so-called shotgun cellular system, SCS) is studied. Previous results for a uniform 2-dimensional distribution of BS are generalized to non-uniform placement of BS in any dimension. The carrier-to-interference ratio (CIR) and the carrier-to-interference-plus-noise ratio (CINR) are analyzed for dense and sparse BS density cellular systems, respectively. A semi-analytical expression for the tail probability of the CIR is derived. Additionally, a tool for comparing the CIR performances of two SCSs based on BS densities is presented. With these results, we completely characterize the performance of a SCS with an arbitrary BS density function. Next, a SCS affected by random shadow fading is shown to be equivalent to another SCS without shadow fading and a different BS density function, and hence the performance of a uniform l-D SCS is independent of shadow fading. Thus, for a sparse uniform l-D SCS, the effect of...

  16. Interplay between carrier and cationic defect concentration in ferromagnetism of anatase Ti1-xTaxO2 thin films

    Directory of Open Access Journals (Sweden)

    A. Roy Barman

    2012-03-01

    Full Text Available Thin films of Ta incorporated TiO2 grown by pulsed laser deposition under specific growth conditions show room temperature ferromagnetism. Ta introduces carriers and concomitantly cationic defects, the combination of which leads to ferromagnetism. In this paper, we report on the dependence of the carrier and cationic defect density (compensation on various parameters such as oxygen growth pressure, temperature and Ta concentration. Most likely, the Ti vacancies act as magnetic centers and the free electrons help with the exchange leading to ferromagnetism via Ruderman-Kittel-Kasuya-Yosida mechanism.

  17. Information carriers and (reading them through) information theory in quantum chemistry.

    Science.gov (United States)

    Geerlings, Paul; Borgoo, Alex

    2011-01-21

    This Perspective discusses the reduction of the electronic wave function via the second-order reduced density matrix to the electron density ρ(r), which is the key ingredient in density functional theory (DFT) as a basic carrier of information. Simplifying further, the 1-normalized density function turns out to contain essentially the same information as ρ(r) and is even of preferred use as an information carrier when discussing the periodic properties along Mendeleev's table where essentially the valence electrons are at stake. The Kullback-Leibler information deficiency turns out to be the most interesting choice to obtain information on the differences in ρ(r) or σ(r) between two systems. To put it otherwise: when looking for the construction of a functional F(AB) = F[ζ(A)(r),ζ(B)(r)] for extracting differences in information from an information carrier ζ(r) (i.e. ρ(r), σ(r)) for two systems A and B the Kullback-Leibler information measure ΔS is a particularly adequate choice. Examples are given, varying from atoms, to molecules and molecular interactions. Quantum similarity of atoms indicates that the shape function based KL information deficiency is the most appropriate tool to retrieve periodicity in the Periodic Table. The dissimilarity of enantiomers for which different information measures are presented at global and local (i.e. molecular and atomic) level leads to an extension of Mezey's holographic density theorem and shows numerical evidence that in a chiral molecule the whole molecule is pervaded by chirality. Finally Kullback-Leibler information profiles are discussed for intra- and intermolecular proton transfer reactions and a simple S(N)2 reaction indicating that the theoretical information profile can be used as a companion to the energy based Hammond postulate to discuss the early or late transition state character of a reaction. All in all this Perspective's answer is positive to the question of whether an even simpler carrier of

  18. Direct Density Derivative Estimation.

    Science.gov (United States)

    Sasaki, Hiroaki; Noh, Yung-Kyun; Niu, Gang; Sugiyama, Masashi

    2016-06-01

    Estimating the derivatives of probability density functions is an essential step in statistical data analysis. A naive approach to estimate the derivatives is to first perform density estimation and then compute its derivatives. However, this approach can be unreliable because a good density estimator does not necessarily mean a good density derivative estimator. To cope with this problem, in this letter, we propose a novel method that directly estimates density derivatives without going through density estimation. The proposed method provides computationally efficient estimation for the derivatives of any order on multidimensional data with a hyperparameter tuning method and achieves the optimal parametric convergence rate. We further discuss an extension of the proposed method by applying regularized multitask learning and a general framework for density derivative estimation based on Bregman divergences. Applications of the proposed method to nonparametric Kullback-Leibler divergence approximation and bandwidth matrix selection in kernel density estimation are also explored. PMID:27140943

  19. Future Road Density

    Data.gov (United States)

    U.S. Environmental Protection Agency — Road density is generally highly correlated with amount of developed land cover. High road densities usually indicate high levels of ecological disturbance. More...

  20. Localized charge carriers in graphene nanodevices

    Energy Technology Data Exchange (ETDEWEB)

    Bischoff, D., E-mail: dominikb@phys.ethz.ch; Varlet, A.; Simonet, P.; Eich, M.; Overweg, H. C.; Ihn, T.; Ensslin, K. [Solid State Physics Laboratory, ETH Zurich, 8093 Zurich (Switzerland)

    2015-09-15

    Graphene—two-dimensional carbon—is a material with unique mechanical, optical, chemical, and electronic properties. Its use in a wide range of applications was therefore suggested. From an electronic point of view, nanostructured graphene is of great interest due to the potential opening of a band gap, applications in quantum devices, and investigations of physical phenomena. Narrow graphene stripes called “nanoribbons” show clearly different electronical transport properties than micron-sized graphene devices. The conductivity is generally reduced and around the charge neutrality point, the conductance is nearly completely suppressed. While various mechanisms can lead to this observed suppression of conductance, disordered edges resulting in localized charge carriers are likely the main cause in a large number of experiments. Localized charge carriers manifest themselves in transport experiments by the appearance of Coulomb blockade diamonds. This review focuses on the mechanisms responsible for this charge localization, on interpreting the transport details, and on discussing the consequences for physics and applications. Effects such as multiple coupled sites of localized charge, cotunneling processes, and excited states are discussed. Also, different geometries of quantum devices are compared. Finally, an outlook is provided, where open questions are addressed.

  1. Information Geometric Density Estimation

    OpenAIRE

    Sun, Ke; Marchand-Maillet, Stéphane

    2014-01-01

    We investigate kernel density estimation where the kernel function varies from point to point. Density estimation in the input space means to find a set of coordinates on a statistical manifold. This novel perspective helps to combine efforts from information geometry and machine learning to spawn a family of density estimators. We present example models with simulations. We discuss the principle and theory of such density estimation.

  2. Evaluating Density Forecasts

    OpenAIRE

    Francis X. Diebold; Todd A. Gunther; Anthony S. Tay

    1997-01-01

    The authors propose methods for evaluating and improving density forecasts. They focus primarily on methods that are applicable regardless of the particular user's loss function, though they take explicit account of the relationships between density forecasts, action choices, and the corresponding expected loss throughout. They illustrate the methods with a detailed series of examples, and they discuss extensions to improving and combining suboptimal density forecasts, multistep-ahead density...

  3. Influence of carrier on the performance of dry powder inhalers.

    Science.gov (United States)

    Saint-Lorant, G; Leterme, P; Gayot, A; Flament, M P

    2007-04-01

    The aim of this work is to study carriers which can become alternatives to monohydrate lactose in dry powder inhalers and to consider particle parameters that influence adhesion between drug and carrier in dry powder inhalers. Different forms of mannitol, lactose and maltitol were mixed with either terbutaline sulphate or formoterol fumarate. The blends were submitted to different adhesion tests where drug detachment from the carrier was obtained either through mechanical vibration or by aspiration. Parameters like particle shape, roughness, amorphous content and cristalline form may affect interactions between drug and carrier. In our case, crystallized forms of the carrier offered lower adhesion but better release of the active ingredient than spray-dried forms. The crystallized mannitol produced maximal fine particle dose. The blends of the mannitols and the two active ingredients gave different results. The two techniques used to assess the adhesion of drugs to carrier particles provide complementary information about drug/carrier interactions and detachment. The mechanical sieving allows to assess blend stability and the air-jet sieving makes it possible to determine how easily the drug separates from carrier. For the drugs tested, the results of fine particle doses are in agreement with the Alpine air-jet sieve results. The tests used are helpful for the choice of a new carrier in the field of the development of new carriers for dry powder inhalers. PMID:17113733

  4. 47 CFR 69.105 - Carrier common line for non-price cap local exchange carriers.

    Science.gov (United States)

    2010-10-01

    ... residential and single-line business lines multiplied by the difference between the residential and single-line business End User Common Line rate cap and the lesser of $6.50 or the non-price cap local exchange... 47 Telecommunication 3 2010-10-01 2010-10-01 false Carrier common line for non-price cap...

  5. Crowding and Density

    Science.gov (United States)

    Design and Environment, 1972

    1972-01-01

    Three-part report pinpointing problems and uncovering solutions for the dual concepts of density (ratio of people to space) and crowding (psychological response to density). Section one, A Primer on Crowding,'' reviews new psychological and social findings; section two, Density in the Suburbs,'' shows conflict between status quo and increased…

  6. Use of alternative carrier materials in AOAC Official Method 2008.05, efficacy of liquid sporicides against spores of Bacillus subtilis on a hard, nonporous surface, quantitative three-step method.

    Science.gov (United States)

    Tomasino, Stephen F; Rastogi, Vipin K; Wallace, Lalena; Smith, Lisa S; Hamilton, Martin A; Pines, Rebecca M

    2010-01-01

    The quantitative Three-Step Method (TSM) for testing the efficacy of liquid sporicides against spores of Bacillus subtilis on a hard, nonporous surface (glass) was adopted as AOAC Official Method 2008.05 in May 2008. The TSM uses 5 x 5 x 1 mm coupons (carriers) upon which spores have been inoculated and which are introduced into liquid sporicidal agent contained in a microcentrifuge tube. Following exposure of inoculated carriers and neutralization, spores are removed from carriers in three fractions (gentle washing, fraction A; sonication, fraction B; and gentle agitation, fraction C). Liquid from each fraction is serially diluted and plated on a recovery medium for spore enumeration. The counts are summed over the three fractions to provide the density (viable spores per carrier), which is log10-transformed to arrive at the log density. The log reduction is calculated by subtracting the mean log density for treated carriers from the mean log density for control carriers. This paper presents a single-laboratory investigation conducted to evaluate the applicability of using two porous carrier materials (ceramic tile and untreated pine wood) and one alternative nonporous material (stainless steel). Glass carriers were included in the study as the reference material. Inoculated carriers were evaluated against three commercially available liquid sporicides (sodium hypochlorite, a combination of peracetic acid and hydrogen peroxide, and glutaraldehyde), each at two levels of presumed efficacy (medium and high) to provide data for assessing the responsiveness of the TSM. Three coupons of each material were evaluated across three replications at each level; three replications of a control were required. Even though all carriers were inoculated with approximately the same number of spores, the observed counts of recovered spores were consistently higher for the nonporous carriers. For control carriers, the mean log densities for the four materials ranged from 6.63 for

  7. Field Effect and Strongly Localized Carriers in the Metal-Insulator Transition Material VO(2).

    Science.gov (United States)

    Martens, K; Jeong, J W; Aetukuri, N; Rettner, C; Shukla, N; Freeman, E; Esfahani, D N; Peeters, F M; Topuria, T; Rice, P M; Volodin, A; Douhard, B; Vandervorst, W; Samant, M G; Datta, S; Parkin, S S P

    2015-11-01

    The intrinsic field effect, the change in surface conductance with an applied transverse electric field, of prototypal strongly correlated VO(2) has remained elusive. Here we report its measurement enabled by epitaxial VO(2) and atomic layer deposited high-κ dielectrics. Oxygen migration, joule heating, and the linked field-induced phase transition are precluded. The field effect can be understood in terms of field-induced carriers with densities up to ∼5×10(13)  cm(-2) which are trongly localized, as shown by their low, thermally activated mobility (∼1×10(-3)  cm(2)/V s at 300 K). These carriers show behavior consistent with that of Holstein polarons and strongly impact the (opto)electronics of VO(2). PMID:26588400

  8. Torrefaction of woody and agro biomasses as energy carriers for European markets

    Energy Technology Data Exchange (ETDEWEB)

    Wilen, C. [VTT Technical Research Centre of Finland, Espoo (Finland)], email: carl.wilen@vtt.fi

    2012-07-01

    New large scale bioenergy carriers are coming to the industrial demonstration phase, such as torrefaction and pyrolysis technologies. Torrefied wood pellets (TOP pellets) will give high energy volumetric density and properties similar to coal in large scale utility boilers. Torrefaction offer an interesting opportunity to replace fossil fuels by co-firing TOP pellets in coal fired pulverized combustion (PC) boilers. The production units can operate in standalone mode or integrated to industrial CHP or forest industry fluidised bed boilers. There are currently more than 950 saw, paper and pulp mills in Europe. They offer attractive business options for energy carrier investment based on existing raw material and forest residue logistics. This project creates good understanding of TOP pellet production, properties, potential uses, and competitiveness and European business opportunities. The project also aims at introducing and promoting Finnish solutions for these markets.

  9. Influence of free carriers on exciton ground states in quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    Klochikhin, A.A. [Ioffe Physical Technical Institute, 194021 St. Petersburg (Russian Federation); Nuclear Physics Institute, 350000 St. Petersburg (Russian Federation); Kochereshko, V.P., E-mail: vladimir.kochereshko@mail.ioffe.ru [Ioffe Physical Technical Institute, 194021 St. Petersburg (Russian Federation); Spin Optics Laboratory, St. Petersburg State University, 198904 St. Petersburg (Russian Federation); Tatarenko, S. [CEA-CNRS Group “Nanophysique et Semiconducteurs”, Institut Néel, CNRS and Universite Joseph Fourier, 25 Avenue des Martyrs, 38042 Grenoble (France)

    2014-10-15

    The influence of free carriers on the ground state of the exciton at zero magnetic field in a quasi-two-dimensional quantum well that contains a gas of free electrons is considered in the framework of the random phase approximation. The effects of the exciton–charge-density interaction and the inelastic scattering processes due to the electron–electron exchange interaction are taken into account. The effect of phase-space filling is considered using an approximate approach. The results of the calculation are compared with the experimental data. - Highlights: • We discussed the effect of free carriers on the exciton ground state in quantum wells. • The processes of exciton–electron scattering become the most important for excitons in doped QWs. • The direct Coulomb scattering can be neglected. • The most important becomes the exchange inelastic exciton–electron scattering.

  10. Bimodal behaviour of charge carriers in graphene induced by electric double layer

    Science.gov (United States)

    Tsai, Sing-Jyun; Yang, Ruey-Jen

    2016-07-01

    A theoretical investigation is performed into the electronic properties of graphene in the presence of liquid as a function of the contact area ratio. It is shown that the electric double layer (EDL) formed at the interface of the graphene and the liquid causes an overlap of the conduction bands and valance bands and increases the density of state (DOS) at the Fermi energy (EF). In other words, a greater number of charge carriers are induced for transport and the graphene changes from a semiconductor to a semimetal. In addition, it is shown that the dependence of the DOS at EF on the contact area ratio has a bimodal distribution which responses to the experimental observation, a pinnacle curve. The maximum number of induced carriers is expected to occur at contact area ratios of 40% and 60%. In general, the present results indicate that modulating the EDL provides an effective means of tuning the electronic properties of graphene in the presence of liquid.

  11. DYNAMIC RESPONSE ANALYSIS OF CARRIER-BASED AIRCRAFT DURING LANDING

    Institute of Scientific and Technical Information of China (English)

    段萍萍; 聂宏; 魏小辉

    2013-01-01

    In view of the complexity of landing on the deck of aircraft carrier ,a systematic model ,composed of six-degree-of-freedom mathematic model of carrier-based aircraft ,four-degree-of-freedom model of landing gears and six-degree-of-freedom mathematic model of carrier , is established in the Matlab-Simulink environment , with damping function of landing gears and dynamic characteristics of tires being considered .The model ,where the car-rier movement is introduced ,is applicable for any abnormal landing condition .Moreover ,the equations of motion and relevant parameter are also derived .The dynamic response of aircraft is calculated via the variable step-size Runge-Kuta algorithm .The effect of attitude angles of aircraft and carrier movement during the process of landing is illustrated in details .The analytical results can provide some reference for carrier-based aircraft design and main-tenance .

  12. Characteristics of participants in a gestational carrier program.

    Science.gov (United States)

    Braverman, A M; Corson, S L

    1992-08-01

    Genetic parents and gestational carriers in our gestational carrier program were evaluated by psychodiagnostic interview and by the Minnesota Multiphasic Personality Interview-2 (MMPI-2), a widely used objective psychological test, to identify psychopathology and describe personality characteristics. Overall, participants exhibited no overt psychopathology. Personality differences were found between gestational carriers and genetic mothers and genetic fathers and mothers. Clinical interviews revealed that gestational carriers tended to be the dominant partner in the relationship, were motivated by a wish to help an infertile couple, enjoyed being pregnant, showed narcissistic needs, and expressed a wish for secondary financial gain. The majority of gestational carriers stated that they had considered becoming a traditional surrogate but felt they could not surrender a child that was genetically theirs. These results indicate that there is not any predisposing psychopathology which attracts participants to the gestational carrier program.

  13. Probability densities and Lévy densities

    DEFF Research Database (Denmark)

    Barndorff-Nielsen, Ole Eiler

    For positive Lévy processes (i.e. subordinators) formulae are derived that express the probability density or the distribution function in terms of power series in time t. The applicability of the results to finance and to turbulence is briefly indicated.......For positive Lévy processes (i.e. subordinators) formulae are derived that express the probability density or the distribution function in terms of power series in time t. The applicability of the results to finance and to turbulence is briefly indicated....

  14. A Silicon Micromachined Gyroscope Driven by the Rotating Carrier Self

    Institute of Scientific and Technical Information of China (English)

    Fuxue Zhang; Xu Mao; Yu Liu; Nan Zhang; Wei Zhang

    2006-01-01

    This paper reported a silicon micromachined gyroscope which is driven by the rotating carrier's angular velocity, the silicon was manufactured by anisotropy etching. The design, fabrication and packing of the sensing element were introduced in the paper. The imitation experimentation and performance test have certificated that the principle of the gyroscope is correct and the gyroscope can be used to sense yawing or pitching angular velocity of the rotating carrier, and the angular velocity of the rotating carrier itself.

  15. Exploring Quaternized Hydroxyethylcellulose as Potential Gene Carriers

    Institute of Scientific and Technical Information of China (English)

    丁菲; 尤俊; 翁小成; 周金平; 章晓联; 周翔; 张俐娜

    2012-01-01

    Cationic polysaccharides have been receiving more attentions and used as nonviral gene delivery vectors. In this paper, quaternized hydroxyethylcellulose (QHEC) derivatives were studied as gene carriers for their efficient DNA binding abilities. All QHECs could form stable QHEC/DNA complexes and resist the degradation of DNase I. And the dynamic light scatter (DLS) results showed that all QHEC/DNA complexes could form compact particles. These QHEC/DNA complexes exhibited effective transfeetion abilities in comparison to the naked DNA. The cytotox- icities of QHEC and QHEC/DNA complexes were also evaluated in four cell lines which were relatively low com- pared with 25 kDa bPEI. All results indicated that these quaternized hydroxyethylcelluloses could be used as poten- tial gene delivery vectors.

  16. Microemulsions as carriers for therapeutic molecules.

    Science.gov (United States)

    Mehta, Surinder K; Kaur, Gurpreet

    2010-01-01

    The thrust for finding newer drug delivery systems for exiting therapeutic molecules has opened a wide window for colloidal systems. Due to the presence of different domains of variable polarity in the microemulsion systems, they show a huge potential to be used as drug delivery vehicles for a variety of drugs. The use of microemulsion as drug delivery vehicles through a number of routes has engaged a large number of research groups in this area. Microemulsion media finds several applications ranging from drug delivery to drug nanoparticle templating due to its ability to enhance solubility, stability and bioavailability. This review on patent articles recounts the patent literature dealing with different kind of microemulsion carriers used via different routes, solubility and permeability enhancement and its use as a template for nanoparticle synthesis. PMID:19807681

  17. Hot carrier injection degradation under dynamic stress

    Institute of Scientific and Technical Information of China (English)

    Ma Xiao-Hua; Cao Yan-Rong; Hao Yue; Zhang Yue

    2011-01-01

    In this paper, we have studied hot carrier injection (HCI) under alternant stress. Under different stress modes, different degradations are obtained from the experiment results. The different alternate stresses can reduce or enhance the HC effect, which mainly depends on the latter condition of the stress cycle. In the stress mode A (DC stress with electron injection), the degradation keeps increasing. In the stress modes B (DC stress and then stress with the smallest gate injection) and C (DC stress and then stress with hole injection under Vg=0V and Vd = 1.8 V), recovery appears in the second stress period. And in the stress mode D (DC stress and then stress with hole injection under Vg = -1.8 V and Vd = 1.8 V), as the traps filled in by holes can be smaller or greater than the generated interface states, the continued degradation or recovery in different stress periods can be obtained.

  18. Blind Estimation of Multiple Carrier Frequency Offsets

    CERN Document Server

    Yu, Yuanning; Poor, H Vincent; Koivunen, Visa

    2007-01-01

    Multiple carrier-frequency offsets (CFO) arise in a distributed antenna system, where data are transmitted simultaneously from multiple antennas. In such systems the received signal contains multiple CFOs due to mismatch between the local oscillators of transmitters and receiver. This results in a time-varying rotation of the data constellation, which needs to be compensated for at the receiver before symbol recovery. This paper proposes a new approach for blind CFO estimation and symbol recovery. The received base-band signal is over-sampled, and its polyphase components are used to formulate a virtual Multiple-Input Multiple-Output (MIMO) problem. By applying blind MIMO system estimation techniques, the system response is estimated and used to subsequently transform the multiple CFOs estimation problem into many independent single CFO estimation problems. Furthermore, an initial estimate of the CFO is obtained from the phase of the MIMO system response. The Cramer-Rao Lower bound is also derived, and the la...

  19. Take advantage of your insurance carrier

    Energy Technology Data Exchange (ETDEWEB)

    Carlow, S.M.

    1990-02-01

    The primary objective of the developer of an independent energy facility is to make a profit through the sale of electricity and steam. The most effective way to achieve this objective is to design, build and operate a facility in a way that maximizes its availability and efficiency without increasing expenses. A property carrier has a range of insurance products and engineering services designed not only to transfer risk but to increase availability and efficiency and reduce the cost of operating and maintaining a facility. The independent energy producer can benefit by taking full advantage of traditional and specialty insurance products as well as engineering services that are available today. There is a whole range of insurance products that apply during the various stages of pre-construction, construction, testing and commercial operation, and these are described.

  20. Carrier Aggregation for LTE-Advanced

    DEFF Research Database (Denmark)

    Pedersen, Klaus Ingemann; Frederiksen, Frank; Rosa, Claudio;

    2011-01-01

    aggregated. This paper presents a summary of the supported CA scenarios as well as an overview of the CA functionality for LTE-Advanced with special emphasis on the basic concept, control mechanisms, and performance aspects. The discussion includes definitions of the new terms primary cell (PCell) and......Carrier aggregation (CA) is one of the key features for LTE-Advanced. By means of CA, users gain access to a total bandwidth of up to 100 MHz in order to meet the IMT-Advanced requirements. The system bandwidth may be contiguous, or composed of several non-contiguous bandwidth chunks, which are...... secondary cell (SCell), mechanisms for activation and deactivation of CCs, and the new cross-CC scheduling functionality for improved control channel optimizations. We also demonstrate how CA can be used as an enabler for simple yet effective frequency domain interference management schemes. In particular...

  1. A Systems View of the Differences between APOE ε4 Carriers and Non-carriers in Alzheimer's Disease.

    Science.gov (United States)

    Jiang, Shan; Tang, Ling; Zhao, Na; Yang, Wanling; Qiu, Yu; Chen, Hong-Zhuan

    2016-01-01

    APOE ε4 is the strongest genetic risk factor for late-onset Alzheimer's disease (AD) and accounts for 50-65% of late-onset AD. Late-onset AD patients carrying or not carrying APOE ε4 manifest many clinico-pathological distinctions. Thus, we applied a weighted gene co-expression network analysis to identify specific co-expression modules in AD based on APOE ε4 stratification. Two specific modules were identified in AD APOE ε4 carriers and one module was identified in non-carriers. The hub genes of one module of AD APOE ε4 carriers were ISOC1, ENO3, GDF10, GNB3, XPO4, ACLY and MATN2. The other module of AD APOE ε4 carriers consisted of 10 hub genes including ANO3, ARPP21, HPCA, RASD2, PCP4 and ADORA2A. The module of AD APOE ε4 non-carriers consisted of 16 hub genes including DUSP5, TNFRSF18, ZNF331, DNAJB5 and RIN1. The module of AD APOE ε4 carriers including ISOC1 and ENO3 and the module of non-carriers contained the most highly connected hub gene clusters. mRNA expression of the genes in the cluster of the ISOC1 and ENO3 module of carriers was shown to be correlated in a time-dependent manner under APOE ε4 treatment but not under APOE ε3 treatment. In contrast, mRNA expression of the genes in the cluster of non-carriers' module was correlated under APOE ε3 treatment but not under APOE ε4 treatment. The modules of carriers demonstrated genetic bases and were mainly enriched in hereditary disorders and neurological diseases, energy metabolism-associated signaling and G protein-coupled receptor-associated pathways. The module including ISOC1 and ENO3 harbored two conserved promoter motifs in its hub gene cluster that could be regulated by common transcription factors and miRNAs. The module of non-carriers was mainly enriched in neurological, immunological and cardiovascular diseases and was correlated with Parkinson's disease. These data demonstrate that AD in APOE ε4 carriers involves more genetic factors and particular biological processes, whereas AD

  2. Fertility preservation in BRCA mutation carriers.

    Science.gov (United States)

    Revelli, Alberto; Salvagno, Francesca; Delle Piane, Luisa; Casano, Simona; Evangelista, Francesca; Pittatore, Giulia; Razzano, Alessandra; Marchino, Gian L; Gennarelli, Gianluca; Benedetto, Chiara

    2016-10-01

    According to enhanced long-term survival rates of these patients, interest in fertility preservation for young women facing gonadotoxic therapies is increasing. Women who carry a mutation in the BRCA1 or BRCA2 gene have a specifically increased lifetime risk of developing breast and tubo-ovarian cancer. Moreover, they are at high risk of undergoing premature infertility due to the medical interventions that are often performed in order to reduce cancer risk or treat an already existing malignancy. Fertility issues are relevant for healthy BRCA mutation carriers, whose family-planning decisions are often influenced by the need of prophylactic bilateral salpingo-oophorectomy at young age. In BRCA mutation carriers who have a breast cancer at young age, the oncostatic treatment is associated with a significant ovarian toxicity linked to chemotherapy as well as to the long lasting hormonotherapy and to the need of delaying pregnancy for several years. Prompt counselling about different fertility preservation options should be offered to all young girls and women at high risk of ovarian insufficiency and infertility. Validated techniques to preserve fertility include oocyte and embryo cryopreservation, while experimental techniques include ovarian suppression with GnRH-analogs during chemotherapy and ovarian tissue cryopreservation. The choice of the best strategy depends on age, type of chemotherapy, partner status, cancer type, time available for fertility preservation intervention and the risk of ovarian metastasis. All available options should be offered and can be performed alone or in combination. A crucial point is to avoid a significant delay to cancer treatment. PMID:26997146

  3. Obstacle avoidance and path planning for carrier aircraft launching

    Directory of Open Access Journals (Sweden)

    Wu Yu

    2015-06-01

    Full Text Available Launching safety and efficiency are important indexes to measure the fighting capacity of carrier. The study on path planning for taxi of carrier aircraft launching under actual deck environment is of great significance. In actual deck scheduling, manual command is applied to taxi of carrier aircraft, which has negative effects on the safety of staff and carrier aircraft launching. In consideration of both the safety and efficiency of carrier aircraft launching, the key elements of the problem are abstracted based on the analysis of deck environment, carrier aircraft maneuver performance and task requirements. According to the problem description, the mathematical model is established including various constraints. The carrier aircraft and the obstacles are reasonably simplified as circle and polygons respectively. What’s more, the proposed collision detection model reduces the calculations. Aimed at the features of model, the theory of model predictive control (MPC is applied to the path search. Then a dynamic weight heuristic function is designed and a dynamic multistep optimization algorithm is proposed. Taking the Nimitz-class aircraft carrier as an example, the paths from parking place to catapult are planned, which indicate the rationality of the model and the effectiveness of the algorithm by comparing the planning results under different simulation environments. The main contribution of research is the establishment of obstacle avoidance and path planning model. In addition, it provides the solution of model and technological foundations for comprehensive command and real-time decision-making of the carrier aircraft.

  4. Joint Iterative Carrier Synchronization and Signal Detection Employing Expectation Maximization

    DEFF Research Database (Denmark)

    Zibar, Darko; de Carvalho, Luis Henrique Hecker; Estaran Tolosa, Jose Manuel;

    2014-01-01

    In this paper, joint estimation of carrier frequency, phase, signal means and noise variance, in a maximum likelihood sense, is performed iteratively by employing expectation maximization. The parameter estimation is soft decision driven and allows joint carrier synchronization and data detection...... and nonlinear phase noise, compared to digital phase-locked loop (PLL) followed by hard decisions. Additionally, soft decision driven joint carrier synchronization and detection offers an improvement of 0.5 dB in terms of input power compared to hard decision digital PLL based carrier synchronization...

  5. Origin of Charge Density at LaAlO3 on SrTiO3 Heterointerfaces: Possibility of Intrinsic Doping

    Science.gov (United States)

    Siemons, Wolter; Koster, Gertjan; Yamamoto, Hideki; Harrison, Walter A.; Lucovsky, Gerald; Geballe, Theodore H.; Blank, Dave H. A.; Beasley, Malcolm R.

    2007-05-01

    As discovered by Ohtomo and Hwang, a large sheet charge density with high mobility exists at the interface between SrTiO3 and LaAlO3. Based on transport, spectroscopic, and oxygen-annealing experiments, we conclude that extrinsic defects in the form of oxygen vacancies introduced by the pulsed laser deposition process used by all researchers to date to make these samples is the source of the large carrier densities. Annealing experiments show a limiting carrier density. We also present a model that explains the high mobility based on carrier redistribution due to an increased dielectric constant.

  6. Trapping of the Enoyl-Acyl Carrier Protein Reductase-Acyl Carrier Protein Interaction.

    Science.gov (United States)

    Tallorin, Lorillee; Finzel, Kara; Nguyen, Quynh G; Beld, Joris; La Clair, James J; Burkart, Michael D

    2016-03-30

    An ideal target for metabolic engineering, fatty acid biosynthesis remains poorly understood on a molecular level. These carrier protein-dependent pathways require fundamental protein-protein interactions to guide reactivity and processivity, and their control has become one of the major hurdles in successfully adapting these biological machines. Our laboratory has developed methods to prepare acyl carrier proteins (ACPs) loaded with substrate mimetics and cross-linkers to visualize and trap interactions with partner enzymes, and we continue to expand the tools for studying these pathways. We now describe application of the slow-onset, tight-binding inhibitor triclosan to explore the interactions between the type II fatty acid ACP from Escherichia coli, AcpP, and its corresponding enoyl-ACP reductase, FabI. We show that the AcpP-triclosan complex demonstrates nM binding, inhibits in vitro activity, and can be used to isolate FabI in complex proteomes. PMID:26938266

  7. Fractures as Carriers for Colloid and Nano-Particles

    Science.gov (United States)

    Weisbrod, N.; Cohen, M.; Tang, X.; Zvikelsky, O.; Meron, H.

    2013-12-01

    One of the major questions in studies in which transport of colloids and nano particles (NPs) is being explored is whether or not they will be mobile on large scales and in large conduits such as fractures and cracks. While many studies explore the migration on a small scale and mostly in ideal porous media, less is known about this topic on larger scales and in fractured rocks or cracked soils. Fractures are likely to be favorable carriers for colloids and NPs due to their large aperture, enabling relatively high flow velocity and smaller tortuosity of the flow path. Transport of various colloids including microspheres, clay particles and viruses, as well as colloid-facilitated transport of lead and cesium was explored in a naturally discrete fractured chalk cores. Preliminary work exploring the transport of NZVIs and TiO2 NPs is being carried out through these cores as well. Our results indicate very high recovery of large microspheres (0.2 and 1 micron) and lower recovery of the small spheres (0.02 micron). It was observed that clay particles, with similar surface properties and sizes to that of the microspheres, show significantly lower recoveries (50 vs over 90%), probably due to the high density of clay particles in respect to the microspheres (2.65 vs. 1.05 g/cm3). High recovery of bacteriophages was also observed, but they exhibit some differences in respect to microspheres with similar properties. In all cases, including the 0.02 micron colloids exhibiting lower recovery rates, arrival times were earlier than that of the bromide that was used as a reference. It was found that colloid-facilitated transport played a major role in the migration of lead and cesium through the fracture. In practice, lead was found to be mobile only in a colloidal form. The on-going work on NP transport through fractures is still in a preliminary phase. Nevertheless, TiO2 recovery was found to be very low. In conclusion, it was observed that in many cases fractures are favorable

  8. Charge carrier recombination in the ITO/PEDOT:PSS/MEH-PPV/Al photodetector

    Directory of Open Access Journals (Sweden)

    Petrović Jovana P.

    2009-01-01

    Full Text Available In this paper we investigate charge carrier recombination processes in polymer based photodetector ITO/PEDOT:PSS/MEH-PPV/Al. The major carriers are the hole polarons created by the photoexcitation in the active MEH-PPV film. The model used in this paper is based on the continuity equation and drift-diffusion equation for hole polarons. We assume the Poole-Frenkel expression for field dependence of the hole polaron mobility. The internal quantum efficiency dependence on incident photon flux density, incident light wavelength and applied electric field is included in the model. The simulated photocurrent density spectra for two different, assumed, recombination mechanisms, linear (monomolecular and square (bimolecular is compared with our experimental results. The bimolecular recombination mechanism applied in our model is assumed to be of Langevin type. The agreement between the measured and the calculated data unambiguously indicate that the hole polaron recombination mechanism in the MEH-PPV film is bimolecular with bimolecular rate constant depending on the external electric field. For the established recombination mechanism the theoretical prediction of the photocurrent density spectra shows excellent agreement with the measured spectra in wide range of inverse bias voltages (from 0 to -8 V.

  9. Enhancing light absorption within the carrier transport length in quantum junction solar cells.

    Science.gov (United States)

    Fu, Yulan; Hara, Yukihiro; Miller, Christopher W; Lopez, Rene

    2015-09-10

    Colloidal quantum dot (CQD) solar cells have attracted tremendous attention because of their tunable absorption spectrum window and potentially low processing cost. Recently reported quantum junction solar cells represent a promising approach to building a rectifying photovoltaic device that employs CQD layers on each side of the p-n junction. However, the ultimate efficiency of CQD solar cells is still highly limited by their high trap state density in both p- and n-type CQDs. By modeling photonic structures to enhance the light absorption within the carrier transport length and by ensuring that the carrier generation and collection efficiencies were both augmented, our work shows that overall device current density could be improved. We utilized a two-dimensional numerical model to calculate the characteristics of patterned CQD solar cells based on a simple grating structure. Our calculation predicts a short circuit current density as high as 31  mA/cm2, a value nearly 1.5 times larger than that of the conventional flat design, showing the great potential value of patterned quantum junction solar cells. PMID:26368966

  10. A Systems View of the Differences between APOE ε4 Carriers and Non-carriers in Alzheimer’s Disease

    Science.gov (United States)

    Jiang, Shan; Tang, Ling; Zhao, Na; Yang, Wanling; Qiu, Yu; Chen, Hong-Zhuan

    2016-01-01

    APOE ε4 is the strongest genetic risk factor for late-onset Alzheimer’s disease (AD) and accounts for 50–65% of late-onset AD. Late-onset AD patients carrying or not carrying APOE ε4 manifest many clinico-pathological distinctions. Thus, we applied a weighted gene co-expression network analysis to identify specific co-expression modules in AD based on APOE ε4 stratification. Two specific modules were identified in AD APOE ε4 carriers and one module was identified in non-carriers. The hub genes of one module of AD APOE ε4 carriers were ISOC1, ENO3, GDF10, GNB3, XPO4, ACLY and MATN2. The other module of AD APOE ε4 carriers consisted of 10 hub genes including ANO3, ARPP21, HPCA, RASD2, PCP4 and ADORA2A. The module of AD APOE ε4 non-carriers consisted of 16 hub genes including DUSP5, TNFRSF18, ZNF331, DNAJB5 and RIN1. The module of AD APOE ε4 carriers including ISOC1 and ENO3 and the module of non-carriers contained the most highly connected hub gene clusters. mRNA expression of the genes in the cluster of the ISOC1 and ENO3 module of carriers was shown to be correlated in a time-dependent manner under APOE ε4 treatment but not under APOE ε3 treatment. In contrast, mRNA expression of the genes in the cluster of non-carriers’ module was correlated under APOE ε3 treatment but not under APOE ε4 treatment. The modules of carriers demonstrated genetic bases and were mainly enriched in hereditary disorders and neurological diseases, energy metabolism-associated signaling and G protein-coupled receptor-associated pathways. The module including ISOC1 and ENO3 harbored two conserved promoter motifs in its hub gene cluster that could be regulated by common transcription factors and miRNAs. The module of non-carriers was mainly enriched in neurological, immunological and cardiovascular diseases and was correlated with Parkinson’s disease. These data demonstrate that AD in APOE ε4 carriers involves more genetic factors and particular biological processes

  11. CARRIER PREPARATION BUILDING MATERIALS HANDLING SYSTEM DESCRIPTION DOCUMENT

    Energy Technology Data Exchange (ETDEWEB)

    E.F. Loros

    2000-06-28

    The Carrier Preparation Building Materials Handling System receives rail and truck shipping casks from the Carrier/Cask Transport System, and inspects and prepares the shipping casks for return to the Carrier/Cask Transport System. Carrier preparation operations for carriers/casks received at the surface repository include performing a radiation survey of the carrier and cask, removing/retracting the personnel barrier, measuring the cask temperature, removing/retracting the impact limiters, removing the cask tie-downs (if any), and installing the cask trunnions (if any). The shipping operations for carriers/casks leaving the surface repository include removing the cask trunnions (if any), installing the cask tie-downs (if any), installing the impact limiters, performing a radiation survey of the cask, and installing the personnel barrier. There are four parallel carrier/cask preparation lines installed in the Carrier Preparation Building with two preparation bays in each line, each of which can accommodate carrier/cask shipping and receiving. The lines are operated concurrently to handle the waste shipping throughputs and to allow system maintenance operations. One remotely operated overhead bridge crane and one remotely operated manipulator is provided for each pair of carrier/cask preparation lines servicing four preparation bays. Remotely operated support equipment includes a manipulator and tooling and fixtures for removing and installing personnel barriers, impact limiters, cask trunnions, and cask tie-downs. Remote handling equipment is designed to facilitate maintenance, dose reduction, and replacement of interchangeable components where appropriate. Semi-automatic, manual, and backup control methods support normal, abnormal, and recovery operations. Laydown areas and equipment are included as required for transportation system components (e.g., personnel barriers and impact limiters), fixtures, and tooling to support abnormal and recovery operations. The

  12. Porous glass carrier for immobilization of brewer's yeast. Kobo koteika tantai to shite no takoshitsu garasu

    Energy Technology Data Exchange (ETDEWEB)

    Kashihara, T. (Kirin Brewery Co. Ltd., Tokyo (Japan))

    1993-07-01

    In this article, merits of porous glass carrier for immobilization are stated as an example of application of vital reaction catalyst for immobilization to the brewing field and furthermore the features of the brewing system of immobilization of yeast for beer brewing (super brew system, SBS) which utilizes the above carrier are outlined. The biggest merit of utilizing immobilized yeast for beer brewing is that increased efficiency of the brewing can be attained, but usable carriers for immobilization whose safety has been confirmed are very few. Since the latter half of 1980's, DEAE cellulose, porous glass and ceramics have been used as the carriers appropriate for the scale of practical brewing. Porous glass carriers have many functions including high percentage of water absorption and capability of holding microorganisms in high density. The number of fungus bodies to be carried with the porous glass is less than that of calcium alginate which is not appropriate for scaling-up for practical brewing. In SBS, fermentation can be made efficiently and in a well balanced manner. 15 refs., 5 figs., 4 tabs.

  13. The construction of an in vitro three-dimensional hematopoietic microenvironment for mouse bone marrow cells employing porous carriers.

    Science.gov (United States)

    Tomimori, Y; Takagi, M; Yoshida, T

    2000-10-01

    Spatial development of mouse bone marrow cellsemploying porous carriers was investigated in order todesign a bioreactor with a three-dimensionalhematopoietic microenvironment. Three types of porouscarriers were used for examining the spatialdevelopment of anchorage-dependent primary stromalcells as feeder cells. Stromal cells were found tospread well at a high density on a polyester nonwovendisc carrier (Fibra cel (FC)) under a scanningelectron microscope, while cells on porous cellulosebeads (Microcube (MC), 500 mum pore diameter)spread at a low density; cells on another type ofcellulose porous beads (CPB, 100 mum pore diameter)were globular. Mouse bone marrow cells wereinoculated to dishes containing three types of porouscarriers which shared more than 30% of the bottomsurface in a dish. The concentration of stromal cellsin the well containing FC was lower than that on theother two carriers. However, the weekly output oftotal hematopoietic cell (suspension cells) increasedbetween day 21 and 28 in the culture using FC while itdecreased monotonously in the cultures by use of theother two carriers. The proportion of progenitorcells (BFU-E, CFU-GM) in the total hematopoietic cellpopulation, after showing an initial decrease,increased after 1 week in the culture using FC whilethe proportion decreased monotonously to zero in thecultures using MC and CPB. PMID:19003386

  14. Quasi phase matching for high order harmonic generation induced by the carrier-envelope phase

    OpenAIRE

    Faccio, Daniele; Serrat, Carles; Cela, Jose M.; Di Trapani, Albert Farres Paolo; Biegert, Jens

    2009-01-01

    We report a novel quasi-phase matching technique for high-order harmonic generation in low-density gases. Numerical simulations show that in few-optical cycle pulsed Bessel beams it is possible to control the pulse envelope and phase velocities which in turn allows to control the carrier-envelope phase during propagation. The resulting oscillations in the peak intensity allow to phase-match the high-order harmonic generation process with a nearly two decade enhancement in the XUV power spectrum.

  15. 14 CFR 255.5 - Contracts with participating carriers.

    Science.gov (United States)

    2010-01-01

    ... (AVIATION PROCEEDINGS) ECONOMIC REGULATIONS AIRLINE COMPUTER RESERVATIONS SYSTEMS § 255.5 Contracts with participating carriers. (a) No system may require a carrier to maintain any particular level of participation or buy any enhancements in its system on the basis of participation levels or enhancements selected...

  16. 27 CFR 26.117 - Action by carrier.

    Science.gov (United States)

    2010-04-01

    ... OF THE TREASURY LIQUORS LIQUORS AND ARTICLES FROM PUERTO RICO AND THE VIRGIN ISLANDS Taxpayment of Liquors and Articles in Puerto Rico Procedure at Port of Arrival § 26.117 Action by carrier. The carrier of the merchandise specified on the Form 487B shall, at the time of unlading at the port of...

  17. Characterization of the "Escherichia Coli" Acyl Carrier Protein Phosphodiesterase

    Science.gov (United States)

    Thomas, Jacob

    2009-01-01

    Acyl carrier protein (ACP) is a small essential protein that functions as a carrier of the acyl intermediates of fatty acid synthesis. ACP requires the posttranslational attachment of a 4'phosphopantetheine functional group, derived from CoA, in order to perform its metabolic function. A Mn[superscript 2+] dependent enzymatic activity that removes…

  18. Quality of service modeling and analysis for carrier ethernet

    NARCIS (Netherlands)

    Malhotra, R.

    2008-01-01

    Today, Ethernet is moving into the mainstream evolving into a carrier grade technology. Termed as Carrier Ethernet it is expected to overcome most of the shortcomings of native Ethernet. It is envisioned to carry services end-to-end serving corporate data networking and broadband access demands as w

  19. Carriers of foot-and-mouth disease virus: a review

    NARCIS (Netherlands)

    Moonen, P.; Schrijver, R.

    2000-01-01

    This review describes current knowledge about persistent foot-and-mouth disease virus (FMDV) infections, the available methods to detect carrier animals, the properties of persisting virus, the immunological mechanisms, and the risk of transmission. In particular, knowledge about the carrier state,

  20. Modeling of carrier dynamics in quantum-well electroabsorption modulators

    DEFF Research Database (Denmark)

    Højfeldt, Sune; Mørk, Jesper

    2002-01-01

    various design parameters have on the device properties, in particular how they affect the carrier dynamics and the corresponding field dynamics. A number of different types of results are presented. We calculate absorption spectra and steady-state field screening due to carrier pile-up at the separate...

  1. Cardiac involvement in carriers of Duchenne and Becker muscular dystrophy

    NARCIS (Netherlands)

    Hoogerwaard, EM; van der Wouw, PA; Wilde, AAM; Bakker, E; Ippel, PF; Oosterwijk, JC; Majoor-Krakauer, DF; van Essen, AJ; Leschot, NJ; de Visser, M

    1999-01-01

    A cross-sectional study in a cohort of DNA proven carriers of Duchenne (DMD) and Becker (BMD) muscular dystrophy was undertaken with the following objectives: (1) to estimate the frequency of electrocardiographic (ECG) and echocardiographic abnormalities; (2) to establish the proportion of carriers

  2. Spread Spectrum Modulation by Using Asymmetric-Carrier Random PWM

    DEFF Research Database (Denmark)

    Mathe, Laszlo; Lungeanu, Florin; Sera, Dezso;

    2012-01-01

    This paper presents a new fixed carrier frequency random PWM method, where a new type of carrier wave is proposed for modulation. Based on simulations and experimental measurements, it is shown that the spread effect of the discrete components from the motor current spectra and acoustic spectra...

  3. 5 CFR 890.505 - Recurring premium payments to carriers.

    Science.gov (United States)

    2010-01-01

    ... § 890.505 Recurring premium payments to carriers. The procedures for payment of premiums, contingency reserve, and interest distribution to FEHB Program carriers shall be those contained in 48 CFR subpart... 5 Administrative Personnel 2 2010-01-01 2010-01-01 false Recurring premium payments to...

  4. AQUASOMES: A NOVEL CARRIER FOR DRUG DELIVERY

    Directory of Open Access Journals (Sweden)

    Vishal Sutariya

    2012-03-01

    Full Text Available Nanobiopharmaceutics involves delivery of biopharmaceutical product through different biomaterials like multifunctional nanoparticles, quantum dots, aquasomes, superparamagnetic iron oxide crystals, and liposomes dendrimers. Nanotechnology has emerged fields of biomedical research in the last few decades the presents context is an attempt to present the brief information about nanobiotechnological applications. Aquasomes are nanoparticulate carrier system but instead of being simple nanoparticles these arse three layered self assembled structures, comprised of a solid phase nanocrystalline core coated with oligomeric film to which biochemically active molecules are adsorbed with or without modification. Aquasomes are spherical 60–300 nm particles used for drug and antigen delivery. Aquasomes discovery comprises a principle from microbiology, food chemistry, biophysics and many discoveries including solid phase synthesis, supramolecular chemistry, molecular shape change and self assembly. Three types of core materials are mainly used for producing aquasomes: tin oxide, nanocrystalline carbon ceramics (diamonds and brushite (calcium phosphate dihydrate. Calcium phosphate is the core of interest, owing to its natural presence in the body. The brushite is unstable and converts to hydroxyapatite upon prolong storage. Hydroxyapatite seems, therefore, a better core for the preparation of aquasomes. It is widely used for the preparation of implants for drug delivery. The solid core provides the structural stability, while the carbohydrate coating protects against dehydration and stabilizes the biochemically active molecules. This property of maintaining the conformational integrity of bioactive molecules has led to the proposal that aquasomes have potential as a carrier system for delivery of peptide, protein, hormones, antigens and genes to specific sites. Aquasome deliver their content through specific targeting, molecular sheiling and slow

  5. Carrier redistribution between different potential sites in semipolar (202¯1) InGaN quantum wells studied by near-field photoluminescence

    KAUST Repository

    Marcinkevičius, S.

    2014-09-15

    © 2014 AIP Publishing LLC. Scanning near-field photoluminescence (PL) spectroscopy at different excitation powers was applied to study nanoscale properties of carrier localization and recombination in semipolar (202¯1) InGaN quantum wells (QWs) emitting in violet, blue, and green-yellow spectral regions. With increased excitation power, an untypical PL peak energy shift to lower energies was observed. The shift was attributed to carrier density dependent carrier redistribution between nm-scale sites of different potentials. Near-field PL scans showed that in (202¯1) QWs the in-plane carrier diffusion is modest, and the recombination properties are uniform, which is advantageous for photonic applications.

  6. Adaptive kernel density estimation

    OpenAIRE

    Philippe Van Kerm

    2003-01-01

    This insert describes the module akdensity. akdensity extends the official kdensity that estimates density functions by the kernel method. The extensions are of two types: akdensity allows the use of an "adaptive kernel" approach with varying, rather than fixed, bandwidths; and akdensity estimates pointwise variability bands around the estimated density functions. Copyright 2003 by Stata Corporation.

  7. MEASUREMENT OF WHEAT DENSITY

    Institute of Scientific and Technical Information of China (English)

    冯跟胜; 党金春; 等

    1995-01-01

    A method used for on line determining the change of wheat density with a automatic watering machine in a lqarge flour mill has been studied.The results show that the higher distinguishing ability is obtained when using 241Am as a γ-ray source for measuring the wheat density than using 137Cs.

  8. Growth of Semi-Insulating GaN Using N2 as Nucleation Layer Carrier Gas Combining with an Optimized Annealing Time

    Institute of Scientific and Technical Information of China (English)

    ZHOU Zhong-Tang; XING Zhi-Gang; GUO Li-Wei; CHEN Hong; ZHOU Jun-Ming

    2007-01-01

    Semi-insulating (SI) GaN is grown using N2 as the nucleation layer (NL) carrier gas combined with an optimized annealing time by metalorganic chemical vapour deposition. Influence of using H2 and N2 as the NL carrier gas is investigated in our experiment. It is found that the sheet resistance of unintentionally doped GaN can be increased from 104Ω/sq to 10Ω Q/sq by changing the NL carrier gas from H2 to N2 while keeping the other growth parameters to be constant, however crystal quality and roughness of the film are degraded unambiguously. This situation can be improved by optimizing the NL annealing time. The high resistance of GaN grown on NL using N2 as the carrier gas is due to higher density of threading dislocations caused by the higher density of nucleation islands and small statistic diameter grain compared to the one using H2 as carrier gas. Annealing the NL for an optimized annealing time can decrease the density of threading dislocation and improve the film roughness and interface of AlGaN/GaN without degrading the sheet resistance of as-grown GaN significantly. High-quality SI GaN is grown after optimizing the annealing time, and AlGaN/GaN high electron mobility transistors are also prepared.

  9. Imaging ballistic carrier trajectories in graphene using scanning gate microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Morikawa, Sei; Masubuchi, Satoru [Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro, Tokyo 153-8505 (Japan); Dou, Ziwei; Wang, Shu-Wei; Smith, Charles G.; Connolly, Malcolm R., E-mail: mrc61@cam.ac.uk [Cavendish Laboratory, Department of Physics, University of Cambridge, Cambridge CB3 0HE (United Kingdom); Watanabe, Kenji; Taniguchi, Takashi [National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044 (Japan); Machida, Tomoki, E-mail: tmachida@iis.u-tokyo.ac.jp [Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro, Tokyo 153-8505 (Japan); Institute for Nano Quantum Information Electronics, University of Tokyo, 4-6-1 Komaba, Meguro, Tokyo 153-8505 (Japan)

    2015-12-14

    We use scanning gate microscopy to map out the trajectories of ballistic carriers in high-mobility graphene encapsulated by hexagonal boron nitride and subject to a weak magnetic field. We employ a magnetic focusing geometry to image carriers that emerge ballistically from an injector, follow a cyclotron path due to the Lorentz force from an applied magnetic field, and land on an adjacent collector probe. The local electric field generated by the scanning tip in the vicinity of the carriers deflects their trajectories, modifying the proportion of carriers focused into the collector. By measuring the voltage at the collector while scanning the tip, we are able to obtain images with arcs that are consistent with the expected cyclotron motion. We also demonstrate that the tip can be used to redirect misaligned carriers back to the collector.

  10. Bombarding Cancer: Biolistic Delivery of therapeutics using Porous Si Carriers

    Science.gov (United States)

    Zilony, Neta; Tzur-Balter, Adi; Segal, Ester; Shefi, Orit

    2013-08-01

    A new paradigm for an effective delivery of therapeutics into cancer cells is presented. Degradable porous silicon carriers, which are tailored to carry and release a model anti-cancer drug, are biolistically bombarded into in-vitro cancerous targets. We demonstrate the ability to launch these highly porous microparticles by a pneumatic capillary gene gun, which is conventionally used to deliver cargos by heavy metal carriers. By optimizing the gun parameters e.g., the accelerating gas pressure, we have successfully delivered the porous carriers, to reach deep targets and to cross a skin barrier in a highly spatial resolution. Our study reveals significant cytotoxicity towards the target human breast carcinoma cells following the delivery of drug-loaded carriers, while administrating empty particles results in no effect on cell viability. The unique combination of biolistics with the temporal control of payload release from porous carriers presents a powerful and non-conventional platform for designing new therapeutic strategies.

  11. Carrier-dependent temporal processing in an auditory interneuron.

    Science.gov (United States)

    Sabourin, Patrick; Gottlieb, Heather; Pollack, Gerald S

    2008-05-01

    Signal processing in the auditory interneuron Omega Neuron 1 (ON1) of the cricket Teleogryllus oceanicus was compared at high- and low-carrier frequencies in three different experimental paradigms. First, integration time, which corresponds to the time it takes for a neuron to reach threshold when stimulated at the minimum effective intensity, was found to be significantly shorter at high-carrier frequency than at low-carrier frequency. Second, phase locking to sinusoidally amplitude modulated signals was more efficient at high frequency, especially at high modulation rates and low modulation depths. Finally, we examined the efficiency with which ON1 detects gaps in a constant tone. As reflected by the decrease in firing rate in the vicinity of the gap, ON1 is better at detecting gaps at low-carrier frequency. Following a gap, firing rate increases beyond the pre-gap level. This "rebound" phenomenon is similar for low- and high-carrier frequencies.

  12. Symmetry energy and density

    CERN Document Server

    Trautmann, Wolfgang; Russotto, Paolo

    2016-01-01

    The nuclear equation-of-state is a topic of highest current interest in nuclear structure and reactions as well as in astrophysics. In particular, the equation-of-state of asymmetric matter and the symmetry energy representing the difference between the energy densities of neutron matter and of symmetric nuclear matter are not sufficiently well constrained at present. The density dependence of the symmetry energy is conventionally expressed in the form of the slope parameter L describing the derivative with respect to density of the symmetry energy at saturation. Results deduced from nuclear structure and heavy-ion reaction data are distributed around a mean value L=60 MeV. Recent studies have more thoroughly investigated the density range that a particular observable is predominantly sensitive to. Two thirds of the saturation density is a value typical for the information contained in nuclear-structure data. Higher values exceeding saturation have been shown to be probed with meson production and collective ...

  13. Learning Grasp Affordance Densities

    DEFF Research Database (Denmark)

    Detry, Renaud; Kraft, Dirk; Kroemer, Oliver;

    2011-01-01

    We address the issue of learning and representing object grasp affordance models. We model grasp affordances with continuous probability density functions (grasp densities) which link object-relative grasp poses to their success probability. The underlying function representation is nonparametric...... these and records their outcomes. When a satisfactory number of grasp data is available, an importance-sampling algorithm turns these into a grasp density. We evaluate our method in a largely autonomous learning experiment run on three objects of distinct shapes. The experiment shows how learning increases success...... and relies on kernel density estimation to provide a continuous model. Grasp densities are learned and refined from exploration, by letting a robot “play” with an object in a sequence of graspand-drop actions: The robot uses visual cues to generate a set of grasp hypotheses; it then executes...

  14. Carrier thermalization under stimulated emission in In0.17Ga0.83N epilayer at room temperature

    International Nuclear Information System (INIS)

    We elucidate a strong room temperature stimulated emission (SE) of In0.17Ga0.83N epilayer grown by molecular beam epitaxy under the subpicosecond pulse excitation. The SE peak at 428 nm emerges on the higher energy side of the spontaneous emission in photoluminescence spectra when the excitation density exceeds the threshold of ∼3.68 mJ/cm2. Nondegenerate transient differential reflectivity measurements show that a multi-stage carrier thermalization from excited states to localized edge states and stimulated emission dominate the decay processes of photogenerated carriers under various excitation densities. Our results indicate that the existence of phonon bottleneck effect could result in a slow thermalization process in the InGaN material even under the condition of stimulated emission

  15. Suppressed carrier scattering in CdS-encapsulated PbS nanocrystal films.

    Science.gov (United States)

    Moroz, Pavel; Kholmicheva, Natalia; Mellott, Bryan; Liyanage, Geethika; Rijal, Upendra; Bastola, Ebin; Huband, Kyla; Khon, Elena; McBride, Keith; Zamkov, Mikhail

    2013-08-27

    One of the key challenges facing the realization of functional nanocrystal devices concerns the development of techniques for depositing colloidal nanocrystals into electrically coupled nanoparticle solids. This work compares several alternative strategies for the assembly of such films using an all-optical approach to the characterization of electron transport phenomena. By measuring excited carrier lifetimes in either ligand-linked or matrix-encapsulated PbS nanocrystal films containing a tunable fraction of insulating ZnS domains, we uniquely distinguish the dynamics of charge scattering on defects from other processes of exciton dissociation. The measured times are subsequently used to estimate the diffusion length and the carrier mobility for each film type within the hopping transport regime. It is demonstrated that nanocrystal films encapsulated into semiconductor matrices exhibit a lower probability of charge scattering than that of nanocrystal solids cross-linked with either 3-mercaptopropionic acid or 1,2-ethanedithiol molecular linkers. The suppression of carrier scattering in matrix-encapsulated nanocrystal films is attributed to a relatively low density of surface defects at nanocrystal/matrix interfaces.

  16. Electronic properties and carrier mobilities of 6,6,12-graphyne nanoribbons

    International Nuclear Information System (INIS)

    Structures, stabilities, electronic properties and carrier mobilities of 6,6,12-graphyne nanoribbons (GyNRs) with armchair and zigzag edges are investigated using the self-consistent field crystal orbital method based on density functional theory. It is found that the 1D GyNRs are more stable than the 2D 6,6,12-graphyne sheet in the view of the Gibbs free energy. The stabilities of these GyNRs decrease as their widths increase. The calculated band structures show that all these GyNRs are semiconductors and that dependence of band gaps on the ribbon width is different from different types of the GyNRs. The carrier mobility was calculated based on the deformation theory and effective mass approach. It is found that the carrier mobilities of these GyNRs can reach the order of 105 cm2 V –1s–1 at room temperature and are comparable to those of graphene NRs. Moreover, change of the mobilities with change of the ribbon width is quite different from different types of the GyNRs

  17. Production of Solid sustainable Energy Carriers from biomass by means of TORrefaction (SECTOR)

    Energy Technology Data Exchange (ETDEWEB)

    Witt, Janet; Bienert, Kathrin [DBFZ Deutsches Biomasseforschungszentrum gemeinnuetzige GmbH, Leipzig (Germany). Bereich Bioenergiesysteme; Zwart, Robin; Kiel, Jaap; Englisch, Martin; Wojcik, Magdalena

    2012-07-01

    SECTOR is a large-scale European project with a strong consortium of over 20 partners from industry and science. The project is focussed on the further development of torrefaction-based technologies for the production of solid bioenergy carriers up to pilot-plant scale and beyond, and on supporting the market introduction of torrefaction-based bioenergy carriers as a commodity renewable solid fuel. The torrefaction of biomass materials is considered to be a very promising technology for the promotion of the large-scale implementation of bioenergy. During torrefaction biomass is heated up in the absence of oxygen to a temperature of 250-320 C. By combining torrefaction with pelletisation or briquetting, biomass materials can be converted into a high-energy-density commodity solid fuel or bioenergy carrier with improved behaviour in (long-distance) transport, handling and storage, and also with superior properties in many major end-use applications. Torrefaction has the potential to provide a significant contribution to an enlarged raw material portfolio for biomass fuel production inside Europe by including both agricultural and forestry biomass. In this way, the SECTOR project is expected to shorten the time-to-market of torrefaction technology and to promote market introduction within stringent sustainability boundary conditions. The European Union provides funding for this project within the Seventh Framework Programme. The project has a duration of 42 months and started in January 2012. (orig.)

  18. Dynamics of photoexcited carrier relaxation and recombination in CdTe/CdS thin films

    Energy Technology Data Exchange (ETDEWEB)

    Levi, D.H.; Fluegel, B.D.; Ahrenkiel, R.K. [National Renewable Energy Lab., Golden, CO (United States)] [and others

    1996-05-01

    Efficiency-limiting defects in photovoltaic devices are readily probed by time-resolved spectroscopy. This paper presents the first direct optical measurements of the relaxation and recombination pathways of photoexcited carriers in the CdS window layer of CdTe/CdS polycrystalline thin films. Femtosecond time-resolved pump/probe measurements indicate the possible existence of a two-phase CdS/CdSTe layer, rather than a continuously graded alloy layer at the CdTe/CdS interface. Complementary time-resolved photoluminescence (PL) measurements show that the photoexcited carriers are rapidly captured by deep-level defects. The temporal and density-dependent properties of the photoluminescence prove that the large Stokes shift of the PL relative to the band edge is due to strong phonon coupling to deep-level defects in CdS. The authors suggest that modifications in the CdS processing may enhance carrier collection efficiency in the blue spectral region.

  19. Accumulated-carrier screening effect based investigation for pixellated CdZnTe radiation detector

    International Nuclear Information System (INIS)

    Using the pixellated CdZnTe detector,the radiation imaging experiment for the Rh target X-ray source was accomplished. The experimental results indicate that the response signals of the anode pixels, which distribute over the center irradiated area,are completely shut-off when the tube Jantage is 45 kV and the tube current increases to 20 μA. Moreover, the non-response pixel area expands with the increase of the tube current, and the total event count of the CdZnTe detector reduces obviously. Furthermore, the inner electric potential and electric field distributions of the pixellated CdZnTe detector were simulated based on the Poisson equation. The simulation results reveal that the accumulation of the hole carriers, which results from the extremely low drift ability of the hole carrier, leads to a relatively high space-charge-density area in the CdZnTe bulk when the irradiated photon flux increases to 5 x 105 mm-2·s-1. And thus, the induced signal screen effect of the anode pixels in the center irradiated area is mainly attributed to the distorted electric field which makes electron carriers drift toward the high potential area in the CdZnTe crystal instead of the pixel anodes. (authors)

  20. Ab initio charge-carrier mobility model for amorphous molecular semiconductors

    Science.gov (United States)

    Massé, Andrea; Friederich, Pascal; Symalla, Franz; Liu, Feilong; Nitsche, Robert; Coehoorn, Reinder; Wenzel, Wolfgang; Bobbert, Peter A.

    2016-05-01

    Accurate charge-carrier mobility models of amorphous organic molecular semiconductors are essential to describe the electrical properties of devices based on these materials. The disordered nature of these semiconductors leads to percolative charge transport with a large characteristic length scale, posing a challenge to the development of such models from ab initio simulations. Here, we develop an ab initio mobility model using a four-step procedure. First, the amorphous morphology together with its energy disorder and intermolecular charge-transfer integrals are obtained from ab initio simulations in a small box. Next, the ab initio information is used to set up a stochastic model for the morphology and transfer integrals. This stochastic model is then employed to generate a large simulation box with modeled morphology and transfer integrals, which can fully capture the percolative charge transport. Finally, the charge-carrier mobility in this simulation box is calculated by solving a master equation, yielding a mobility function depending on temperature, carrier concentration, and electric field. We demonstrate the procedure for hole transport in two important molecular semiconductors, α -NPD and TCTA. In contrast to a previous study, we conclude that spatial correlations in the energy disorder are unimportant for α -NPD. We apply our mobility model to two types of hole-only α -NPD devices and find that the experimental temperature-dependent current density-voltage characteristics of all devices can be well described by only slightly decreasing the simulated energy disorder strength.

  1. Carrier localization effect in polarized InGaN multiple quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    Zukauskas, A.; Kazlauskas, K.; Tamulaitis, G.; Mickevicius, J.; Jursenas, S.; Kurilcik, G.; Miasojedovas, S. [Institute of Materials Science and Applied Research, Vilnius University, Sauletekio al. 9, Build. III, 10222 Vilnius (Lithuania); Springis, M.; Tale, I. [Institute of Solid State Physics, University of Latvia, Kengaraga iela 8, Riga 1063 (Latvia); Cheng, Yung-Chen; Wang, Hsiang-Chen; Huang, Chi-Feng; Yang, C.C. [Graduate Institute of Electro-Optical Engineering, National Taiwan University, 1 Roosevelt Road, Sec. 4, Taipei (Taiwan)

    2005-05-01

    Carrier localization effects in polarized InGaN/GaN multiple quantum wells (MQWs) were investigated as a function of well width, d, and In content, x. Using photoreflectance (PR), photoluminescence (PL), PL excitation (PLE), selective excitation of PL, PL excitation power, and time-resolved PL spectroscopy, the dominance of the localization effect against the built-in field effect on carrier recombination dynamics in In{sub x}Ga{sub 1-x}N MQWs of different well width (d = 2.0-4.0 nm, x {approx} 0.15) and In content (x {approx} 0.22-0.27, d = 2.5 nm) was revealed. Based on the modeling of the PL spectra by Monte Carlo simulation of exciton hopping and the spectroscopic reference provided by PR, increased In content and well width were found to increase the band potential fluctuations and carrier localization depth. The density of localized states deduced from the simulation was found to be in a fair agreement with the PLE data. The built-in field strength in InGaN QWs containing 15% of In was estimated to be of 0.5 MV/cm. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  2. Enhancement of the critical current of intrinsic Josephson junctions by carrier injection

    Science.gov (United States)

    Kizilaslan, O.; Simsek, Y.; Aksan, M. A.; Koval, Y.; Müller, P.

    2015-08-01

    We present a study of the doping effect by carrier injection of high-Tc superconducting Bi-based whiskers. The current was injected in the c-axis direction, i.e., perpendicular to the superconducting planes. Superconducting properties were investigated systematically as a function of the doping level. The doping level of one and the same sample was changed by current injection in very small steps from an underdoped state up to a slightly overdoped state. We have observed that Tc versus log (jc) exhibits a dome-shaped characteristic, which can be fitted by a parabola. As Tc versus carrier concentration has a parabolic form, too, it can be concluded that the critical current density jc increases exponentially with the doping level. The electron-trapping mechanism is interpreted in the framework of Phillips’ microscopic theory. In addition, the Joule heating effect in the intrinsic Josephson junction (IJJ) was controlled by carrier injection, and the effect of the non-equilibrium quasiparticle on the I-V curves of the IJJs was also discussed.

  3. Electronic properties and carrier mobilities of 6,6,12-graphyne nanoribbons

    Energy Technology Data Exchange (ETDEWEB)

    Ding, Heyu; Huang, Yuanhe, E-mail: yuanhe@bnu.edu.cn [College of Chemistry, Beijing Normal University, Beijing, 100875 (China); Bai, Hongcun [Key Laboratory of Energy Sources and Chemical Engineering, Ningxia University, Yinchuan, Ningxia 750021 (China)

    2015-07-15

    Structures, stabilities, electronic properties and carrier mobilities of 6,6,12-graphyne nanoribbons (GyNRs) with armchair and zigzag edges are investigated using the self-consistent field crystal orbital method based on density functional theory. It is found that the 1D GyNRs are more stable than the 2D 6,6,12-graphyne sheet in the view of the Gibbs free energy. The stabilities of these GyNRs decrease as their widths increase. The calculated band structures show that all these GyNRs are semiconductors and that dependence of band gaps on the ribbon width is different from different types of the GyNRs. The carrier mobility was calculated based on the deformation theory and effective mass approach. It is found that the carrier mobilities of these GyNRs can reach the order of 10{sup 5} cm{sup 2} V {sup –1}s{sup –1} at room temperature and are comparable to those of graphene NRs. Moreover, change of the mobilities with change of the ribbon width is quite different from different types of the GyNRs.

  4. Electronic properties and carrier mobilities of 6,6,12-graphyne nanoribbons

    Directory of Open Access Journals (Sweden)

    Heyu Ding

    2015-07-01

    Full Text Available Structures, stabilities, electronic properties and carrier mobilities of 6,6,12-graphyne nanoribbons (GyNRs with armchair and zigzag edges are investigated using the self-consistent field crystal orbital method based on density functional theory. It is found that the 1D GyNRs are more stable than the 2D 6,6,12-graphyne sheet in the view of the Gibbs free energy. The stabilities of these GyNRs decrease as their widths increase. The calculated band structures show that all these GyNRs are semiconductors and that dependence of band gaps on the ribbon width is different from different types of the GyNRs. The carrier mobility was calculated based on the deformation theory and effective mass approach. It is found that the carrier mobilities of these GyNRs can reach the order of 105 cm2 V –1s–1 at room temperature and are comparable to those of graphene NRs. Moreover, change of the mobilities with change of the ribbon width is quite different from different types of the GyNRs.

  5. Long-Lived Hot Carriers in III-V Nanowires.

    Science.gov (United States)

    Tedeschi, D; De Luca, M; Fonseka, H A; Gao, Q; Mura, F; Tan, H H; Rubini, S; Martelli, F; Jagadish, C; Capizzi, M; Polimeni, A

    2016-05-11

    Heat management mechanisms play a pivotal role in driving the design of nanowire (NW)-based devices. In particular, the rate at which charge carriers cool down after an external excitation is crucial for the efficiency of solar cells, lasers, and high-speed transistors. Here, we investigate the thermalization properties of photogenerated carriers by continuous-wave (cw) photoluminescence (PL) in InP and GaAs NWs. A quantitative analysis of the PL spectra recorded up to 310 K shows that carriers can thermalize at a temperature much higher than that of the lattice. We find that the mismatch between carrier and lattice temperature, ΔT, increases exponentially with lattice temperature and depends inversely on the NW diameter. ΔT is instead independent of other NW characteristics, such as crystal structure (wurtzite vs zincblende), chemical composition (InP vs GaAs), shape (tapered vs columnar NWs), and growth method (vapor-liquid-solid vs selective-area growth). Remarkably, carrier temperatures as high as 500 K are reached at the lattice temperature of 310 K in NWs with ∼70 nm diameter. While a population of nonequilibrium carriers, usually referred to as "hot carriers", is routinely generated by high-power laser pulses and detected by ultrafast spectroscopy, it is quite remarkable that it can be observed in cw PL measurements, when a steady-state population of carriers is established. Time-resolved PL measurements show that even in the thinnest NWs carriers have enough time (∼1 ns) after photoexcitation to interact with phonons and thus to release their excess energy. Nevertheless, the inability of carriers to reach a full thermal equilibrium with the lattice points to inhibited phonon emission primarily caused by the large surface-to-volume ratio of small diameter NWs. PMID:27104870

  6. Electromigration of carrier-free radionuclides. 13

    International Nuclear Information System (INIS)

    Using a special type of on line electromigration measurements of γ-emitting radionuclides in homogeneous aqueous electrolytes free of supporting materials the electromigration behaviour of the carrier-free 241Am-Am(III) in inert electrolytes, μ = 0.1 (ClO4-), T = 298.1(1) K, was studied. Basing on experimental dependencies of the overall ion mobilities of 241Am-Am(III) on pH between pH 5.5 and 12.9 the stoichiometric hydrolysis constants pβ3 = 28.8(9) and pK1 = 6.9(2) were obtained. For K4 a limitation of pK4 > 13.9(3) was possible, because no formation of anionic hydrolysis products in solutions pH 241Am-Am(III) degrees in the range pH 5.5 - 3 from +6.85(15) up to +5.50(15) · 10-4 cm2s-1V-1. Dependencies of this effect on overall ionic strength, inert electrolyte anion, and temperature of the electrolytes were studied in detail both in acidic and neutral solutions. (author)

  7. European retrievable carrier Eureca servicing by Hermes

    Science.gov (United States)

    Kerstein, L.; Dettmer, J.; Rath, W.

    1987-09-01

    It has been demonstrated that HERMES with a cargo bay configuration as depicted in figure 1 (5 m length, 3 m diam.) with Handling and Positioning Aid (HPA) and HERMES Robotic Arm (HERA) is capable to service a small platform like EURECA, which is an NSTS quarter payload. Only 1/3 of the HERMES cargo bay volume and payload mass is required for the accommodation of the payload Orbital Replaceable Units. By implementing two additional hydrazine tanks refuelling can be avoided for a two-years EURECA mission. The overall servicing configuration is described as follows: The European Retrievable Carrier EURECA-B is mechanically attached through its -y-side sill trunnion to the HERMES berthing port. The HERMES cargo bay doors with radiators are opened and oriented to earth. The HERMES Robotic Arm is equipped with a Module Service Tool (MST) ready for Orbital Replaceable Unit (ORU) exchange. The HERMES berthing port is located at the rear side of the cargo bay in order to achieve best visibility, clearance and accessibility of the HERMES Robotic Arm operation within the cargo bay and the EURECA payload area. The EURECA solar arrays and antennas remain deployed. During the servicing operation, power will be provided by the fully deployed solar arrays. In order to minimize the plume impingement effect, the solar array edge is directed to the HERMES wing.

  8. POLYURETHANE COMPOSITES AS DRUG CARRIERS:: RELEASE PATTERNS

    Directory of Open Access Journals (Sweden)

    M. V. Grigoreva

    2013-10-01

    Full Text Available Biodegradable polyurethanes attract interest of those developing composite materials for biomedical applications. One of their features is their ability to serve as carriers, or matrixes, for medicines and other bioactive compounds to produce a therapeutic effect in body through targeted and/or prolonged delivery of these compounds in the process of their controlled release from matrix. The review presents polyurethane composites as matrices for a number of drugs. The relation between structure of the composites and their degradability both in vitro and in vivo and the dependence of drug release kinetics on physicochemical properties of polyurethane matrix are highlighted. The release of drugs (cefazolin, naltrexone and piroxicam from the composites based on cross-linked polyurethanes (synthesized from laprols, Mw between 1,500 and 2,000 Da and toluylene diisocyanate demonstrated more or less the same pattern (about 10 days in vitro and three to five days in vivo. In contrast, the composites with dioxydine based on a linear polyurethanes (synthesized from oligotetramethilene glycol, Mw 1,000 Da, diphenylmethane-4,4’-diisocyanate and 1,4-butanediol retained their antimicrobial activity at least 30 days. They also showed a significantly higher breaking strength as compared to that of the composites based on cross-linked polyurethanes.

  9. Drug Carrier for Photodynamic Cancer Therapy

    Directory of Open Access Journals (Sweden)

    Tilahun Ayane Debele

    2015-09-01

    Full Text Available Photodynamic therapy (PDT is a non-invasive combinatorial therapeutic modality using light, photosensitizer (PS, and oxygen used for the treatment of cancer and other diseases. When PSs in cells are exposed to specific wavelengths of light, they are transformed from the singlet ground state (S0 to an excited singlet state (S1–Sn, followed by intersystem crossing to an excited triplet state (T1. The energy transferred from T1 to biological substrates and molecular oxygen, via type I and II reactions, generates reactive oxygen species, (1O2, H2O2, O2*, HO*, which causes cellular damage that leads to tumor cell death through necrosis or apoptosis. The solubility, selectivity, and targeting of photosensitizers are important factors that must be considered in PDT. Nano-formulating PSs with organic and inorganic nanoparticles poses as potential strategy to satisfy the requirements of an ideal PDT system. In this review, we summarize several organic and inorganic PS carriers that have been studied to enhance the efficacy of photodynamic therapy against cancer.

  10. Efficient carrier relaxation and fast carrier recombination of N-polar InGaN/GaN light emitting diodes

    International Nuclear Information System (INIS)

    Based on quantum efficiency and time-resolved electroluminescence measurements, the effects of carrier localization and quantum-confined Stark effect (QCSE) on carrier transport and recombination dynamics of Ga- and N-polar InGaN/GaN light-emitting diodes (LEDs) are reported. The N-polar LED exhibits shorter ns-scale response, rising, delay, and recombination times than the Ga-polar one does. Stronger carrier localization and the combined effects of suppressed QCSE and electric field and lower potential barrier acting upon the forward bias in an N-polar LED provide the advantages of more efficient carrier relaxation and faster carrier recombination. By optimizing growth conditions to enhance the radiative recombination, the advantages of more efficient carrier relaxation and faster carrier recombination in a competitive performance N-polar LED can be realized for applications of high-speed flash LEDs. The research results provide important information for carrier transport and recombination dynamics of an N-polar InGaN/GaN LED

  11. Multi-carrier Equalization by Restoration of RedundancY (MERRY) for Adaptive Channel Shortening in Multi-carrier Systems

    OpenAIRE

    Samir Abd Elghafar; Salaheldin M. Diab; Sallam, Bassiouny M.; Moawad I. Dessouky; El-Sayed M. El-Rabaie; Fathi E. Abd El-Samie

    2013-01-01

    This paper proposes a new blind adaptive channel shortening approach for multi-carrier systems. Theperformance of the discrete Fourier transform-DMT (DFT-DMT) system is investigated with the proposedDST-DMT system over the standard carrier serving area (CSA) loop1. Enhanced bit rates demonstratedand less complexity also involved by the simulationof the DST-DMT system.

  12. Efficient carrier relaxation and fast carrier recombination of N-polar InGaN/GaN light emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Shih-Wei, E-mail: swfeng@nuk.edu.tw; Liao, Po-Hsun [Department of Applied Physics, National University of Kaohsiung, No. 700, Kaohsiung University Rd., Nan Tzu Dist., 811 Kaohsiung, Taiwan (China); Leung, Benjamin; Han, Jung [Department of Electrical Engineering, Yale University, New Haven, Connecticut 06520 (United States); Yang, Fann-Wei [Department of Electronic Engineering, Southern Taiwan University of Science and Technology, Tainan, Taiwan (China); Wang, Hsiang-Chen [Graduate Institute of Opto-Mechatronics and Advanced Institute of Manufacturing with High-Tech Innovations (AIM-HI), National Chung Cheng University, Chia-Yi, Taiwan (China)

    2015-07-28

    Based on quantum efficiency and time-resolved electroluminescence measurements, the effects of carrier localization and quantum-confined Stark effect (QCSE) on carrier transport and recombination dynamics of Ga- and N-polar InGaN/GaN light-emitting diodes (LEDs) are reported. The N-polar LED exhibits shorter ns-scale response, rising, delay, and recombination times than the Ga-polar one does. Stronger carrier localization and the combined effects of suppressed QCSE and electric field and lower potential barrier acting upon the forward bias in an N-polar LED provide the advantages of more efficient carrier relaxation and faster carrier recombination. By optimizing growth conditions to enhance the radiative recombination, the advantages of more efficient carrier relaxation and faster carrier recombination in a competitive performance N-polar LED can be realized for applications of high-speed flash LEDs. The research results provide important information for carrier transport and recombination dynamics of an N-polar InGaN/GaN LED.

  13. Ultrafast carrier relaxation through Auger recombination in the topological insulator B i1.5S b0.5T e1.7S e1.3

    Science.gov (United States)

    Onishi, Yoshito; Ren, Zhi; Segawa, Kouji; Kaszub, Wawrzyniec; Lorenc, Maciej; Ando, Yoichi; Tanaka, Koichiro

    2015-02-01

    Ultrafast carrier dynamics have great significance for our understanding of the transport properties of the surface state in topological insulator (TI) materials. We report midinfrared pump-probe measurements on the intrinsic TI material B i1.5S b0.5T e1.7S e1.3 and show that the change in photoinduced reflectivity can be decomposed into a fast negative part and a slow positive part. Calculations of the dielectric function made at various carrier temperatures and densities reveal that the fast negative component corresponds to the disappearance of the phase-space filling effect due to hot carriers around the probe energy and the decay component corresponds to the recombination of carriers near the band edge. The ratio of the fast negative component to the slow positive component is larger in the excitations conducted at the higher carrier densities, which suggests that the carrier temperature increases through Auger recombination. A qualitative analysis using rate equations reinforces this assumption, so we conclude that Auger recombination is the main cause of the population relaxation at carrier densities higher than 1018c m-3 and that we determined the Auger coefficient for B i1.5S b0.5T e1.7S e1.3 as C =0.4 ×10-26c m6/s .

  14. Characterization of temperature-dependent carrier transport in disordered indium-tin-oxide/poly (3,4-ethylenedioxythiophene):poly(styrenesulfonate)/polyfluorene/Ca/Al polymer structures

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Joe-Air [Department of Bio-Industrial Mechatronics Engineering, National Taiwan University, 1, Sec. 4, Roosevelt Road, Taipei 106, Taiwan (China); Wang, Jen-Cheng; Fang, Chia-Hui [Graduate Institute of Electro-Optical Engineering and Department of Electronic Engineering, Chang Gung University, 259 Wen-Hwa 1st Road, Kwei-Shan, Tao-Yuan 333, Taiwan (China); Wu, Ya-Fen [Department of Electronic Engineering, Ming Chi University of Technology, No. 84, Gongzhuan Road, Taishan Dist., New Taipei City 243, Taiwan (China); Teng, Jen-Wei; Chen, Yu-Ting [Graduate Institute of Electro-Optical Engineering and Department of Electronic Engineering, Chang Gung University, 259 Wen-Hwa 1st Road, Kwei-Shan, Tao-Yuan 333, Taiwan (China); Fan, Ping-Lin [Department of Digital Technology Design and Graduate School of Toy and Game Design, National Taipei University of Education, No. 134, Sec. 2, Heping E. Road, Taipei 106, Taiwan (China); Nee, Tzer-En, E-mail: neete@mail.cgu.edu.tw [Graduate Institute of Electro-Optical Engineering and Department of Electronic Engineering, Chang Gung University, 259 Wen-Hwa 1st Road, Kwei-Shan, Tao-Yuan 333, Taiwan (China)

    2011-04-29

    The temperature-dependent electrical characteristics of polyfluorene-based polymer structures over a temperature range from 200 to 300 K are systematically investigated in this study. Initially, using the definitions of the Berthelot-type model, it is found that the sample exhibits a higher Berthelot-type temperature T{sub B} with high driving voltage, indicating that carrier transport in a disordered system manifests Berthelot-type behaviors. The ideal current density-voltage curve for the polymer structures given the carrier transmit mechanism is further elucidated by taking into account the ohmic conduction, trap charge limited current, and Mott and Gurney model of space charge limited current. The proposed procedure is simple and can be used to characterize the material with reasonable accuracy. We also study the density of the traps H{sub t}, and the characteristic energy of the distribution E{sub t} to better understand the carrier-transport process in organic materials and structures.

  15. Dependence of InGaN solar cell performance on polarization-induced electric field and carrier lifetime

    International Nuclear Information System (INIS)

    The effects of Mg-induced net acceptor doping concentration and carrier lifetime on the performance of a p—i—n InGaN solar cell are investigated. It is found that the electric field induced by spontaneous and piezoelectric polarization in the i-region could be totally shielded when the Mg-induced net acceptor doping concentration is sufficiently high. The polarization-induced potential barriers are reduced and the short circuit current density is remarkably increased from 0.21 mA/cm2 to 0.95 mA/cm2 by elevating the Mg doping concentration. The carrier lifetime determined by defect density of i-InGaN also plays an important role in determining the photovoltaic properties of solar cell. The short circuit current density severely degrades, and the performance of InGaN solar cell becomes more sensitive to the polarization when carrier lifetime is lower than the transit time. This study demonstrates that the crystal quality of InGaN absorption layer is one of the most important challenges in realizing high efficiency InGaN solar cells. (interdisciplinary physics and related areas of science and technology)

  16. Carrier Load Balancing and Packet Scheduling for Multi-Carrier Systems

    DEFF Research Database (Denmark)

    Wang, Yuanye; Pedersen, Klaus; Sørensen, Troels Bundgaard;

    2010-01-01

    methods for allocating the CCs to the users- Round Robin (RR) and Mobile Hashing (MH) balancing by means of a simple theoretical formulation, as well as system level simulations. At Layer-2 we propose a simple cross-CC packet scheduling algorithm that improves the coverage performance and the resource...... allocation fairness among users, as compared to independent scheduling per CC. The Long Term Evolution (LTE)-Advanced is selected for the case study of a multi-carrier system. In such a system, RR provides better performance than MH balancing, and the proposed simple scheduling algorithm is shown...

  17. How Europe's Low-Cost Carriers Sidestepped Traditional Carriers' Competitive Advantages

    DEFF Research Database (Denmark)

    Hvass, Kristian Anders

    The initial appearance of U.S. low-cost carriers forced incumbents to create new forms of competitive advantage. These were successful hindrances for nearly two decades. Concurrently, incumbents in Europe implemented similar tools, although within a regulated market. However, Europe's low......-cost airlines were more successful and had a greater initial impact in their early years than their U.S. compatriots. This paper will attempt to highlight some of the differences between the two markets and explain why European low-cost airlines had more advantages following their market deregulation...

  18. Hybrid Perovskites for Photovoltaics: Charge-Carrier Recombination, Diffusion, and Radiative Efficiencies.

    Science.gov (United States)

    Johnston, Michael B; Herz, Laura M

    2016-01-19

    values extracted from OPTP measurements and their dependence on perovskite composition and morphology. The significance of the reviewed charge-carrier recombination and mobility parameters is subsequently evaluated in terms of the charge-carrier diffusion lengths and radiative efficiencies that may be obtained for such hybrid perovskites. We particularly focus on calculating such quantities in the limit of ultra-low trap-related recombination, which has not yet been demonstrated but could be reached through further advances in material processing. We find that for thin films of hybrid lead iodide perovskites with typical charge-carrier mobilities of ∼30cm(2)/(V s), charge-carrier diffusion lengths at solar (AM1.5) irradiation are unlikely to exceed ∼10 μm even if all trap-related recombination is eliminated. We further examine the radiative efficiency for hybrid lead halide perovskite films and show that if high efficiencies are to be obtained for intermediate charge-carrier densities (n ≈ 10(14) cm(-3)) trap-related recombination lifetimes will have to be enhanced well into the microsecond range. PMID:26653572

  19. Utilization of Waste Materials for Microbial Carrier in Wastewater Treatment

    Directory of Open Access Journals (Sweden)

    H. T. Le

    2016-01-01

    Full Text Available This research focused on the ammonium-nitrogen (NH4-N removal from the domestic wastewater using the attached growth reactors. Two types of waste material of corncob (biodegradable material and concrete (nonbiodegradable material were used as the carrier for microorganisms’ attachment. During operation, both reactors achieved absolutely high performance of ammonium removal (up to 99% and total nitrogen removal (up to 95%. The significant advantage of corncob carrier was that the corncob was able to be a source of carbon for biological denitrification, leading to no external carbon requirement for operating the system. However, the corncob caused an increasing turbidity of the effluent. On the other hand, the concrete carrier required the minimal external carbon of 3.5 C/N ratio to reach the good performance. Moreover, a longer period for microorganisms’ adaptation was found in the concrete carrier rather than the corncob carrier. Further, the same physiological and biochemical characteristics of active bacteria were found at the two carriers, which were negative gram, cocci shape, and smooth and white-turbid colony. Due to the effluent quality, the concrete was more appropriate carrier than the corncob for wastewater treatment.

  20. Hybrid nanostructured drug carrier with tunable and controlled drug release

    International Nuclear Information System (INIS)

    We describe here a transformative approach to synthesize a hybrid nanostructured drug carrier that exhibits the characteristics of controlled drug release. The synthesis of the nanohybrid architecture involved two steps. The first step involved direct crystallization of biocompatible copolymer along the long axis of the carbon nanotubes (CNTs), followed by the second step of attachment of drug molecule to the polymer via hydrogen bonding. The extraordinary inorganic–organic hybrid architecture exhibited high drug loading ability and is physically stable even under extreme conditions of acidic media and ultrasonic irradiation. The temperature and pH sensitive characteristics of the hybrid drug carrier and high drug loading ability merit its consideration as a promising carrier and utilization of the fundamental aspects used for synthesis of other promising drug carriers. The higher drug release response during the application of ultrasonic frequency is ascribed to a cavitation-type process in which the acoustic bubbles nucleate and collapse releasing the drug. Furthermore, the study underscores the potential of uniquely combining CNTs and biopolymers for drug delivery. - Graphical abstract: Block-copolymer crystallized on carbon nanotubes (CNTs). Nanohybrid drug carrier synthesized by attaching doxorubicin (DOX) to polymer crystallized CNTs. Crystallized polymer on CNTs provide mechanical stability. Triggered release of DOX. Highlights: ► The novel synthesis of a hybrid nanostructured drug carrier is described. ► The drug carrier exhibits high drug loading ability and is physically stable. ► The high drug release is ascribed to a cavitation-type process.

  1. Analysis of Ionospheric Delay Estimates from GNSS Carrier Phase Measurements

    Science.gov (United States)

    Gao, Yang

    2016-07-01

    There is an increased demand for more precise ionospheric information such as ionospheric augmentation for fast ambiguity convergence and resolution in real-time kinematic (RTK) and precise point positioning (PPP). More precise ionospheric information is also highly desired to improve the understanding of the space weather dynamics and its impacts on various applications such as aviation and communication systems. Carrier phase measurements from GNSS offer the best precision for precise applications. Current ionospheric models, however, are mostly derived from code or carrier-smoothed code measurements. Ionopsheric models based on carrier phase measurements are expected to provide improved accuracy and should be investigated. In this contribution, various data analyses will be conducted on ionospheric estimates from carrier phase measurements. Since carrier phase measurements are ambiguous and they are also affected by fractional biases, proper observation model is necessary and will be developed. With proper observation model, the analysis results are used to investigate the differences and characteristics of the ionospheric estimates between the code and carrier phase derived estimates and subsequently to help develop methods for precise estimation of the biases in carrier phase measurements and the recovery of the ionospheric effects. Data acquired at different geographic locations and under different ionospheric conditions will be processed for numerical analysis.

  2. Kinetics of Ca2+ carrier in rat liver mitochondria.

    Science.gov (United States)

    Bragadin, M; Pozzan, T; Azzone, G F

    1979-12-25

    The rate of aerobic Ca2+ transport is limited by the rate of the H+ pump rather than by the Ca2+ carrier. The kinetics of the Ca2+ carrier has therefore been studied by using the K+ diffusion potential as the driving force. The apparent Vmax of the Ca2+ carrier is, at 20 degrees C, about 900 nmol (mg of protein)-1 min-1, more than twice the rate of the H+ pump. The apparent Vmax is depressed by Mg2+ and Li+. This supports the view that the electrolytes act as noncompetitive inhibitors of the Ca2+ carrier. The degree of sigmoidicity of the kinetics of Ca2+ transport increases with the lowering of the temperature and proportionally with the concentration of impermeant electrolytes such as Mg2+ and Li+ but not choline. The effects of temperature and of electrolyte do not support the view that the sigmoidicity is due to modifications of the surface potential. Rather, they suggest that Ca2+ transport occurs through a multisubunit carrier, where cooperative phenomena are the result of ligand-induced conformational changes due to the interaction of several allosteric effectors with the carrier subunits. In contrast with La3+ which acts as a competitive inhibitor, Ruthenium Red affects the kinetics by inducing phenomena both of positive and of negative cooperativity. The Ruthenium Red induced kinetics has been reproduced through curve-fitting procedures by applying the Koshland sequential interaction hypothesis to a four-subunit Ca2+ carrier model. PMID:42437

  3. Continuous GPS Carrier-Phase Time Transfer

    Science.gov (United States)

    Yao, Jian

    Time transfer (TT) is the process of transmitting a timing signal from one place to another place. It has applications to the formation and realization of Coordinated Universal Time (UTC), telecommunications, electrical power grids, and even stock exchanges. TT is the actual bottleneck of the UTC formation and realization since the technology of atomic clocks is almost always ahead of that of TT. GPS carrier-phase time transfer (GPSCPTT), as a mainstream TT technique accepted by most national timing laboratories, has suffered from the day-boundary-discontinuity (day-BD) problem for many years. This makes us difficult to observe a remote Cesium fountain clock behavior even after a few days. We find that day-BD comes from the GPS code noise. The day-BD can be lowered by ˜40% if more satellite-clock information is provided and if a few GPS receivers at the same station are averaged. To completely eliminate day-BD, the RINEX-Shift (RS) and revised RS (RRS) algorithms have been designed. The RS/RRS result matches the two-way satellite time/frequency transfer (TWSTFT) result much better than the conventional GPSCPTT result. With the RS/RRS algorithm, we are able to observe a remote Cesium fountain after half a day. We also study the BD due to GPS data anomalies (anomaly-BD). A simple curve-fitting strategy can eliminate the anomaly-BD. Thus, we achieve continuous GPSCPTT after eliminating both day-BD and anomaly-BD.

  4. Bone mineral density test

    Science.gov (United States)

    ... Paula FJA, Black DM, Rosen CJ. Osteoporosis and bone biology.In: Melmed S, Polonsky KS, Larsen PR, Kronenberg HM, eds. Williams Textbook of Endocrinology . 13th ed. Philadelphia, ... Bone-density testing interval and transition to osteoporosis in ...

  5. Bone mineral density test

    Science.gov (United States)

    BMD test; Bone density test; Bone densitometry; DEXA scan; DXA; Dual-energy x-ray absorptiometry; p-DEXA; Osteoporosis-BMD ... need to undress. This scan is the best test to predict your risk of fractures. Peripheral DEXA ( ...

  6. The local mass density

    Science.gov (United States)

    Veeder, G. J.

    1974-01-01

    An improved mass-luminosity relation for faint main-sequence stars derived from recently revised masses for some faint double stars is presented. The total local mass density is increased to nearly 0.2 solar masses per cu pc. This estimate is as large as the mass density required by Oort's (1965) dynamical analysis of stellar motions perpendicular to the galactic plane if the mass is concentrated in a narrow layer.

  7. Energy in density gradient

    OpenAIRE

    Vranjes, J.; Kono, M

    2015-01-01

    Inhomogeneous plasmas and fluids contain energy stored in inhomogeneity and they naturally tend to relax into lower energy states by developing instabilities or by diffusion. But the actual amount of energy in such inhomogeneities has remained unknown. In the present work the amount of energy stored in a density gradient is calculated for several specific density profiles in a cylindric configuration. This is of practical importance for drift wave instability in various plasmas, and in partic...

  8. 自旋极化度对GaAs量子阱中吸收饱和效应与载流子复合动力学的影响研究%Effects of spin p olarization on absorption saturation and recombination dynamics of carriers in (001) GaAs quantum wells

    Institute of Scientific and Technical Information of China (English)

    方少寅; 陆海铭; 赖天树

    2015-01-01

    In this paper, the ultrafast dynamics of spin relaxation and recombination of photoexcited carriers has been studied in (001) GaAs quantum wells using a time-resolved pump-probe absorption spectroscopy under a nearly resonant excitation of heavy-hole excitons. It is found that the spin polarization of carriers influences both absorption saturation of linear polarized light and recombination dynamics of carriers. Pump fluence dependence of the ultrafast dynamics of spin relaxation and recombination of carriers is further studied, which shows that the effect of spin polarization on linearly polarized absorption saturation is reduced with lowering pump fluence. Spin-polarization-dependent absorption saturation effect can be ignored only as the pump fluence is weak. However, spin-polarization dependence of recombination dynamics is presented in turn at low pump fluence. Our analysis shows that such dependence originates from the spinpolarization dependence of the density of excitons formed in the excited carriers because recombination time constants of excitons and free carriers are very different so that the ratio of exciton density to free carrier density can influence the recombination dynamics. The spin-polarization dependence of ultrafast recombination dynamics of photoexcited carriers implies that the recombination time constant in the calculation of spin relaxation time from spin relaxation dynamics should be the recombination time of spin-polarized carriers, rather than the recombination lifetime of non-spin-polarized carriers as done currently. Exciton density is estimated based on 2D mass action law, which agrees very well with our experimental results. The good agreement between theoretical calculation and experimental results reveals that the effect of Coulomb screening on the formation of excitons may be ignored for a lower excited carrier density.

  9. Distribution of charge carriers in dissipative structure of semiconductors

    CERN Document Server

    Kamilov, I K; Kovalev, A S

    2002-01-01

    It has been shown experimentally that redistribution of the charge carrier concentration takes place in the volume of Te and InSb monocrystals under formation and excitation by the strong field of a dissipative structure in nonequilibrium electron-hole plasma. This leads to a situation when the presence of only longitudinal autosolitons in the dissipative structure reduces the charge carrier concentration outside autosolitons while the presence of only transversal autosolitons makes the charge carriers concentration larger. These effects are explained in the following manner: longitudinal autosolitons, occurring in nonequilibrium electron-hole plasma created by the Joule heating are considered as cold and transversal autosolitons are considered as hot ones

  10. Laccase immobilized on magnetic carriers for biotechnology applications

    Energy Technology Data Exchange (ETDEWEB)

    Rotkova, Jana [Department of Biological and Biochemical Sciences, University of Pardubice, Strossova 239, 530 03 Pardubice (Czech Republic); Sulakova, Romana [Department of Technology of Organic Compounds, Doubravice 41, 533 53 Pardubice (Czech Republic); Korecka, Lucie; Zdrazilova, Pavla; Jandova, Miroslava [Department of Biological and Biochemical Sciences, University of Pardubice, Strossova 239, 530 03 Pardubice (Czech Republic); Lenfeld, Jiri; Horak, Daniel [Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovskeho nam. 2, 162 06 Praha (Czech Republic); Bilkova, Zuzana [Department of Biological and Biochemical Sciences, University of Pardubice, Strossova 239, 530 03 Pardubice (Czech Republic)], E-mail: Zuzana.Bilkova@upce.cz

    2009-05-15

    Laccase catalyzing the oxidation of p-diphenols has been applied in many industrial and biotechnology areas. Immobilized form of laccase has overcome the problem with contamination of the final product. Nevertheless sensitive enzymes immobilized to the matrix can be inactivated by the environmental conditions. The aim of this research was to prepare carrier with improved activity and responsible stability even under extreme reaction conditions. Laccase immobilized through carbohydrate moieties on magnetic hydrazide bead cellulose with a final activity of 0.63 I.U./1 ml of settled carrier confirmed that carriers with oriented immobilized enzyme might be useful in routine biocatalytic applications.

  11. Recent advances in topical formulation carriers of antifungal agents.

    Science.gov (United States)

    Bseiso, Eman Ahmed; Nasr, Maha; Sammour, Omaima; Abd El Gawad, Nabaweya A

    2015-01-01

    Fungal infections are amongst the most commonly encountered diseases affecting the skin. Treatment approaches include both topical and oral antifungal agents. The topical route is generally preferred due to the possible side effects of oral medication. Advances in the field of formulation may soon render outdated conventional products such as creams, ointments and gels. Several carrier systems loaded with antifungal drugs have demonstrated promising results in the treatment of skin fungal infections. Examples of these newer carriers include micelles, lipidic systems such as solid lipid nanoparticles and nanostructured lipid carriers, microemulsions and vesicular systems such as liposomes, niosomes, transfersomes, ethosomes, and penetration enhancer vesicles. PMID:26261140

  12. Safety and environmental aspects in LNG carrier design

    International Nuclear Information System (INIS)

    'Safety and Reliability' has been and will continue to be a key phr ase in marine transportation of LNG. Mitsui Engineering and Shipbuilding Co.,Ltd. has utilized its all expertise and state of art technologies to realize this objective, resulting in exceptionally successful operations of LNG carrier built by the Co. In line with growing global concern about environmental issues, we need to pay more attention to the environmental aspects of the design and construction of LNG carriers. Accordingly, in this paper, we present some topics related safety and environmental concerns which need to be taken into consideration in LNG carriers design and construction. (Author). 7 figs

  13. Proposal for tutorial: Resilience in carrier Ethernet transport

    DEFF Research Database (Denmark)

    Berger, Michael Stübert; Wessing, Henrik; Ruepp, Sarah Renée

    2009-01-01

    Operation, Administration and Management (OAM) functionalities and support for Quality of Service (QoS), required to obtain carrier grade quality. This tutorial provides an overview of the current level of standardization followed by an exhaustive survey of Carrier Ethernet reliability. A number...... of enhancements are still required to make Carrier Ethernet ready for large scale deployments of reliable point-to-multipoint services. The tutorial highlights the necessary enhancements and shows possible solutions and directions towards reliable multicast. Explicit focus is on OAM for multicast, where...

  14. Do Low Cost Carriers Provide Low Quality Service?

    Directory of Open Access Journals (Sweden)

    Tejashree Sayanak

    2008-03-01

    Full Text Available This paper addresses the question of whether low cost carriers provide low quality service. Considerable work has been done on various aspects of airline service quality, including: examining the causes of flight delays and cancellations, investigating service quality during irregular airport operations, and exploring the link between on-time performance and airline ticket prices. Little research has been conducted, however, on the performance of low cost carriers. This paper attempts to fill this void in the literature by examining the on-time performance of six million domestic flights in 2006. We find considerable evidence indicating that low cost carriers offer more reliable flight schedules.

  15. Recent advances in topical formulation carriers of antifungal agents

    Directory of Open Access Journals (Sweden)

    Eman Ahmed Bseiso

    2015-01-01

    Full Text Available Fungal infections are amongst the most commonly encountered diseases affecting the skin. Treatment approaches include both topical and oral antifungal agents. The topical route is generally preferred due to the possible side effects of oral medication. Advances in the field of formulation may soon render outdated conventional products such as creams, ointments and gels. Several carrier systems loaded with antifungal drugs have demonstrated promising results in the treatment of skin fungal infections. Examples of these newer carriers include micelles, lipidic systems such as solid lipid nanoparticles and nanostructured lipid carriers, microemulsions and vesicular systems such as liposomes, niosomes, transfersomes, ethosomes, and penetration enhancer vesicles.

  16. Wafer-scale characterization of carrier dynamics in graphene

    DEFF Research Database (Denmark)

    Buron, Jonas Christian Due; Petersen, Dirch Hjorth; Bøggild, Peter;

    2015-01-01

    The electronic properties of single-layer graphene, such as surface conductance, carrier concentration, scattering time and mobility, can be characterized in a noncontact manner by THz time-domain spectroscopy. Standard spectroscopic imaging reveals the AC conductance over large areas with a few...... hundred μm resolution, and spectroscopic imaging on back-gated graphene allows for extraction of both the carrier concentration and the mobility. We find that spatial variations of the conductance of single-layer CVD-grown graphene are predominantly due to variations in mobility rather than in carrier...

  17. Novel Anti-Nicotine Vaccine Using a Trimeric Coiled-Coil Hapten Carrier.

    Directory of Open Access Journals (Sweden)

    Keith D Miller

    Full Text Available Tobacco addiction represents one of the largest public health problems in the world and is the leading cause of cancer and heart disease, resulting in millions of deaths a year. Vaccines for smoking cessation have shown considerable promise in preclinical models, although functional antibody responses induced in humans are only modestly effective in preventing nicotine entry into the brain. The challenge in generating serum antibodies with a large nicotine binding capacity is made difficult by the fact that this drug is non-immunogenic and must be conjugated as a hapten to a protein carrier. To circumvent the limitations of traditional carriers like keyhole limpet hemocyanin (KLH, we have synthesized a short trimeric coiled-coil peptide (TCC that creates a series of B and T cell epitopes with uniform stoichiometry and high density. Here we compared the relative activities of a TCC-nic vaccine and two control KLH-nic vaccines using Alum as an adjuvant or GLA-SE, which contains a synthetic TLR4 agonist formulated in a stable oil-in-water emulsion. The results showed that the TCC's high hapten density correlated with a better immune response in mice as measured by anti-nicotine Ab titer, affinity, and specificity, and was responsible for a reduction in anti-carrier immunogenicity. The Ab responses achieved with this synthetic vaccine resulted in a nicotine binding capacity in serum that could prevent >90% of a nicotine dose equivalent to three smoked cigarettes (0.05 mg/kg from reaching the brain.

  18. Electronic shell structure and carrier dynamics of high aspect ratio InP single quantum dots

    Science.gov (United States)

    Beirne, Gareth J.; Reischle, Matthias; Roßbach, Robert; Schulz, Wolfgang-Michael; Jetter, Michael; Seebeck, Jan; Gartner, Paul; Gies, Christopher; Jahnke, Frank; Michler, Peter

    2007-05-01

    Systematic excitation-power-density dependent and time-resolved single-dot photoluminescence studies have been performed on type-I InP/Ga0.51In0.49P quantum dots. These dots are rather flat and therefore exhibit larger than normal single-dot ground-state transition energies ranging from 1.791 to 1.873eV . As a result of their low height, the dots have a very high aspect ratio (ratio of width to height) of approximately 27:1 . In general, even at high excitation power densities, the dots with ground-state transition energies above 1.82eV exhibit only s -shell emission, while the larger dots exhibiting ground-state emission below 1.82eV tend to exhibit emission from several (in some cases up to eight) shells. Calculations indicate that this change is due to the smaller dots having only one confined election level while the larger dots have two or more. Time-resolved investigations indicate the presence of fast carrier relaxation and recombination processes for both dot types, however, only the larger dots display clear interlevel relaxation effects as expected. The temporal behavior has been qualitatively simulated using a rate equation model. Also, in a more detailed analysis, the fast carrier relaxation is described on the basis of a quantum kinetic treatment of the carrier-phonon interaction. Finally, the dots display a clear single-photon emission signature in photon statistics measurements.

  19. BiasMDP: Carrier lifetime characterization technique with applied bias voltage

    Energy Technology Data Exchange (ETDEWEB)

    Jordan, Paul M., E-mail: paul.jordan@namlab.com; Simon, Daniel K.; Dirnstorfer, Ingo [Nanoelectronic Materials Laboratory gGmbH (NaMLab), Nöthnitzer Straße 64, 01187 Dresden (Germany); Mikolajick, Thomas [Nanoelectronic Materials Laboratory gGmbH (NaMLab), Nöthnitzer Straße 64, 01187 Dresden (Germany); Technische Universität Dresden, Institut für Halbleiter- und Mikrosystemtechnik, 01062 Dresden (Germany)

    2015-02-09

    A characterization method is presented, which determines fixed charge and interface defect densities in passivation layers. This method bases on a bias voltage applied to an electrode on top of the passivation layer. During a voltage sweep, the effective carrier lifetime is measured by means of microwave detected photoconductivity. When the external voltage compensates the electric field of the fixed charges, the lifetime drops to a minimum value. This minimum value correlates to the flat band voltage determined in reference impedance measurements. This correlation is measured on p-type silicon passivated by Al{sub 2}O{sub 3} and Al{sub 2}O{sub 3}/HfO{sub 2} stacks with different fixed charge densities and layer thicknesses. Negative fixed charges with densities of 3.8 × 10{sup 12 }cm{sup −2} and 0.7 × 10{sup 12 }cm{sup −2} are determined for Al{sub 2}O{sub 3} layers without and with an ultra-thin HfO{sub 2} interface, respectively. The voltage and illumination dependencies of the effective carrier lifetime are simulated with Shockley Read Hall surface recombination at continuous defects with parabolic capture cross section distributions for electrons and holes. The best match with the measured data is achieved with a very low interface defect density of 1 × 10{sup 10 }eV{sup −1} cm{sup −2} for the Al{sub 2}O{sub 3} sample with HfO{sub 2} interface.

  20. Charge trapping and carrier transport mechanism in silicon-rich silicon oxynitride

    Energy Technology Data Exchange (ETDEWEB)

    Yu Zhenrui [Department of Electronics, INAOE, Apdo. 51, Puebla, Pue. 72000 (Mexico)]. E-mail: yinaoep@yahoo.mx; Aceves, Mariano [Department of Electronics, INAOE, Apdo. 51, Puebla, Pue. 72000 (Mexico); Carrillo, Jesus [CIDS, BUAP, Puebla, Pue. (Mexico); Lopez-Estopier, Rosa [Department of Electronics, INAOE, Apdo. 51, Puebla, Pue. 72000 (Mexico)

    2006-12-05

    The charge-trapping and carrier transport properties of silicon-rich silicon oxynitride (SRO:N) were studied. The SRO:N films were deposited by low pressure chemical vapor deposition. Infrared (IR) and transmission electron microscopic (TEM) measurements were performed to characterize their structural properties. Capacitance versus voltage and current versus voltage measurements (I-V) were used to study the charge-trapping and carrier transport mechanism. IR and TEM measurements revealed the existence of Si nanodots in SRO:N films. I-V measurements revealed that there are two conduction regimes divided by a threshold voltage V {sub T}. When the applied voltage is smaller than V {sub T}, the current is dominated by the charge transfer between the SRO:N and substrate; and in this regime only dynamic charging/discharging of the SRO:N layer is observed. When the voltage is larger than V {sub T}, the current increases rapidly and is dominated by the Poole-Frenkel mechanism; and in this regime, large permanent trapped charge density is obtained. Nitrogen incorporation significantly reduced the silicon nanodots or defects near the SRO:N/Si interface. However, a significant increase of the density of silicon nanodot in the bulk of the SRO:N layer is obtained.

  1. A pseudodeficiency allele common in non-Jewish Tay-Sachs carriers: Implications for carrier screening

    Energy Technology Data Exchange (ETDEWEB)

    Triggs-Raine, B.L.; Akerman, B.R.; Gravel, R.A. (McGill Univ.-Montreal Children' s Hospital Research Institute, Montreal, Quebec (Canada)); Mules, E.H.; Thomas, G.H.; Dowling, C.E. (Johns Hopkins School of Medicine, Baltimore, MD (United States)); Kaback, M.M.; Lim-Steele, J.S.T. (Univ. of California, San Diego, CA (United States)); Natowicz, M.R. (Eunice Kennedy Shriver Center for Mental Retardation, Waltham, MA (United States)); Grebner, E.E. (Thomas Jefferson Univ., Philadelphia, PA (United States)); Navon, R.R. (Tel-Aviv Univ., Kfar-Sava (Israel)); Welch, J.P. (Dalhousie Univ., Halifax, Nova, Scotia (Canada)); Greenberg, C.R. (Univ. of Manitoba, Winnipeg (Canada))

    1992-10-01

    Deficiency of [beta]-hexosaminidase A (Hex A) activity typically results in Tay-Sachs disease. However, healthy subjects found to be deficient in Hex A activity (i.e., pseudodeficient) by means of in vitro biochemical tests have been described. The authors analyzed the HEXA gene of one pseudodeficient subject and identified both a C[sub 739]-to-T substitution that changes Arg[sub 247][yields]Trp on one allele and a previously identified Tay-Sachs disease mutation of the second allele. Six additional pseudodeficient subjects were found to have the C[sub 739]-to-T but for none of 36 Jewish enzyme-defined carries who did not have one of three known mutations common to this group. The C[sub 739]-to-T allele, together with a [open quotes]true[close quotes] Tay-Sachs disease allele, causes Hex A pseudodeficiency. Given both the large proportion of non-Jewish carriers with this allele and that standard biochemical screening cannot differentiate between heterozygotes for the C[sub 739]-to-T mutations and Tay-Sachs disease carriers, DNA testing for this mutation in at-risk couples is essential. This could prevent unnecessary or incorrect prenatal diagnoses. 40 refs., 3 figs., 4 tabs.

  2. Aging in Fragile X Premutation Carriers.

    Science.gov (United States)

    Lozano, Reymundo; Saito, Naomi; Reed, Dallas; Eldeeb, Marwa; Schneider, Andrea; Hessl, David; Tassone, Flora; Beckett, Laurel; Hagerman, Randi

    2016-10-01

    It is now recognized that FMR1 premutation carriers (PC) are at risk to develop a range of neurological, psychiatric, and immune-mediated disorders during adulthood. There are conflicting findings regarding the incidence of hypertension, hypothyroidism, diabetes, and cancer in these patients that warrant further study. A retrospective controlled study was performed in a convenience sample of 248 controls (130 men, 118 women) and 397 FMR1 PC with and without fragile X-associated tremor ataxia syndrome (FXTAS) (176 men, 221 women); all participants were at least 45 years old (men: mean 62.4, SD 9.5; women: mean 62.8, SD 9.9; p = 0.63). Memory and cognitive assessments (Wechsler Adult Intelligence Scale (WAIS-III), Wechsler Memory Scale (WMS-III)) and molecular testing (CGG repeats and FMR1-mRNA levels) were performed. Additional data included body mass index (BMI), cholesterol levels, blood pressure, hemoglobin A1c (HbA1c) levels, and medical history. A higher percentage of PC subjects self-reported having a diagnosis of hypertension (50.0 vs. 35.0 %, p = 0.006) and thyroid problems (20.4 vs. 10.0 %, p = 0.012) than control subjects. When comparing controls versus PC with FXTAS, the association was higher for diabetes (p = 0.043); however, the effect was not significant after adjusting for demographic predictors. Blood pressure, blood glucose levels, HbA1c, and BMI values were not significantly different between the two groups. The PC with FXTAS group performed consistently lower in neuropsychological testing compared with the PC without FXTAS group, but the differences were very small for all but the WAIS full-scale IQ. Based on these findings, it appears that the risk for hypertension, thyroid problems, and diabetes may be more frequent in PC with FXTAS, which will require verification in future studies. PMID:27334385

  3. Allothermal gasification of biomass into chemicals and secondary energy carriers

    Energy Technology Data Exchange (ETDEWEB)

    Zwart, R.W.R. [ECN Biomass, Coal and Environmental Research, Petten (Netherlands)

    2009-09-15

    The outline of this presentation on the title subject states: Motivation for polygeneration; Allothermal gasification: the MILENA at ECN; Primary gas cleaning: the OLGA for tar removal; Possible secondary energy carriers; Possible chemicals; Polygeneration concept and its feasibility.

  4. Discriminator aided phase lock acquisition for suppressed carrier signals

    Science.gov (United States)

    Carson, L. M.; Krasin, F. E. (Inventor)

    1982-01-01

    A discriminator aided technique for acquisition of phase lock to a suppressed carrier signal utilizes a Costas loop which is initially operated open loop and control voltage for its VCXO is derived from a phase detector that compares the VCXO to a reference frequency thus establishing coarse frequency resolution with the received signal. Then the Costas loop is closed with the low-pass filter of the channel having a bandwidth much greater (by a factor of about 10) than in the I channel so that a frequency discriminator effect results to aid carrier resolution. Finally, after carrier acquisition, the Q-channel filter of the Costas loop is switched to a bandwidth substantially equal to that of the I-channel for carrier tracking.

  5. 47 CFR 54.405 - Carrier obligation to offer Lifeline.

    Science.gov (United States)

    2010-10-01

    ... (CONTINUED) UNIVERSAL SERVICE Universal Service Support for Low-Income Consumers § 54.405 Carrier obligation... service, as defined in § 54.401, to qualifying low-income consumers, and (b) Publicize the availability...

  6. Low temperature carrier transport properties in isotopically controlled germanium

    Energy Technology Data Exchange (ETDEWEB)

    Itoh, K.

    1994-12-01

    Investigations of electronic and optical properties of semiconductors often require specimens with extremely homogeneous dopant distributions and precisely controlled net-carrier concentrations and compensation ratios. The previous difficulties in fabricating such samples are overcome as reported in this thesis by growing high-purity Ge single crystals of controlled {sup 75}Ge and {sup 70}Ge isotopic compositions, and doping these crystals by the neutron transmutation doping (NTD) technique. The resulting net-impurity concentrations and the compensation ratios are precisely determined by the thermal neutron fluence and the [{sup 74}Ge]/[{sup 70}Ge] ratios of the starting Ge materials, respectively. This method also guarantees unprecedented doping uniformity. Using such samples the authors have conducted four types of electron (hole) transport studies probing the nature of (1) free carrier scattering by neutral impurities, (2) free carrier scattering by ionized impurities, (3) low temperature hopping conduction, and (4) free carrier transport in samples close to the metal-insulator transition.

  7. Carrier screening in preconception consultation in primary care.

    Science.gov (United States)

    Metcalfe, Sylvia A

    2012-07-01

    Discussing carrier screening during preconception consultation in primary care has a number of advantages in terms of promoting autonomy and enabling the greatest range of reproductive choices. For those with a family history of an inherited condition, this ought to be a routine discussion; however, this can be expanded to include the wider population, especially for those conditions for which carrier frequencies are considered relatively common. There is published literature from around the world regarding experiences with carrier screening in primary care for cystic fibrosis, haemoglobinopathies, fragile X syndrome, Tay-Sachs disease and spinal muscular atrophy, although many of these have tended to focus on consultations during rather than before pregnancy. Overall, these studies reveal that population carrier screening is well received by the participants with apparent minimal psychosocial harms; however, challenges exist in terms of approaches to ensure couples receive adequate information to make personally relevant decisions and for ongoing health professional engagement. PMID:22183783

  8. Extending the unambiguous velocity range using multiple carrier frequencies

    DEFF Research Database (Denmark)

    Zhang, Z.; Jakobsson, A.; Nikolov, Svetoslav;

    2005-01-01

    Typically, velocity estimators based on the estimation of the Doppler shift will suffer from a limited unambiguous velocity range. Proposed are two novel multiple carrier based velocity estimators extending the velocity range above the Nyquist velocity limit. Numerical simulations indicate...

  9. Next-generation carrier screening: are we ready?

    OpenAIRE

    Thomas W Prior

    2014-01-01

    Editorial summary Next-generation sequencing (NGS) methodology allows for a major expansion in current carrier screening tests. NGS testing has been shown to be analytically accurate and cost-effective, but major challenges include educational and counseling issues.

  10. Synthetic heat carrier oil compositions based on polyalkylene glycols

    International Nuclear Information System (INIS)

    The results of syntheses of heat carrier oils based on polyalkylene glycols (PAGs) using suitable additives have been reported. Polyalkylene glycols have been prepared by heating diethylene glycol, propylene oxide, glycols, adipic acid and 2-ethyhexanol in the presence of KOH and stannyl octoate as catalyst in the molar ratio to give proper physical properties and viscosity-temperature index. The prepared PAGs have been taken as basic components for heat carrier oil compositions. In order to improve the thermal stability and viscosity indices, as well as other specifications, anti-oxidant and anti-foaming additives were added to the base material to reach optimum compositions. Thermal stability, mass loss on vaporization at 250 oC, 350 oC and changing the specifications after heating at 300 oC for 10 h have also been investigated. The obtained heat carrier oils showed comparable improved properties in comparison with commercially available heat carriers

  11. GUI Application for ATCA-based LLRF Carrier Board Management

    CERN Document Server

    Wychowaniak, Jan; Predki, Pawel; Napieralski, Andrzej

    2011-01-01

    The Advanced Telecommunications Computing Architecture (ATCA) standard describes an efficient and powerful platform, implementation of which was adopted to be used as a base for control systems in high energy physics. The ATCA platform is considered to be applied for the X-ray Free Electron Laser (X-FEL), being built at Deutsches Electronen- Synchrotron (DESY) in Hamburg, Germany. The Low Level Radio Frequency (LLRF) control system is composed of a few ATCA Carrier Boards. Carrier Board hosts Intelligent Platform Management Controller (IPMC), which is developed in compliance with the PICMG specifications. IPMC is responsible for management and monitoring of sub-modules installed on Carrier Boards and pluggable Advanced Mezzanine Card (AMC) modules. The ATCA Shelf Manager is the main control unit of a single ATCA crate, responsible for all power and fan modules and Carrier Boards installed in ATCA shelf. The device provides a system administrator with a set of control and diagnostic capabilities regarding the ...

  12. 47 CFR 73.1545 - Carrier frequency departure tolerances.

    Science.gov (United States)

    2010-10-01

    ... carrier offset, including those stations licensed with a maximum effective radiated power and/or antenna... offset. See Memorandum Opinion and Order on Reconsideration, In the Matter of Establishment of a Class...

  13. An Estimation Method for number of carrier frequency

    Directory of Open Access Journals (Sweden)

    Xiong Peng

    2015-01-01

    Full Text Available This paper proposes a method that utilizes AR model power spectrum estimation based on Burg algorithm to estimate the number of carrier frequency in single pulse. In the modern electronic and information warfare, the pulse signal form of radar is complex and changeable, among which single pulse with multi-carrier frequencies is the most typical one, such as the frequency shift keying (FSK signal, the frequency shift keying with linear frequency (FSK-LFM hybrid modulation signal and the frequency shift keying with bi-phase shift keying (FSK-BPSK hybrid modulation signal. In view of this kind of single pulse which has multi-carrier frequencies, this paper adopts a method which transforms the complex signal into AR model, then takes power spectrum based on Burg algorithm to show the effect. Experimental results show that the estimation method still can determine the number of carrier frequencies accurately even when the signal noise ratio (SNR is very low.

  14. Cell carriers for oncolytic viruses: current challenges and future directions.

    Science.gov (United States)

    Roy, Dominic G; Bell, John C

    2013-01-01

    The optimal route for clinical delivery of oncolytic viruses is thought to be systemic intravenous injection; however, the immune system is armed with several highly efficient mechanisms to remove pathogens from the circulatory system. To overcome the challenges faced in trying to delivery oncolytic viruses specifically to tumors via the bloodstream, carrier cells have been investigated to determine their suitability as delivery vehicles for systemic administration of oncolytic viruses. Cell carriers protect viruses from neutralization, one of the most limiting aspects of oncolytic virus interaction with the immune system. Cell carriers can also possess inherent tumor tropism, thus directing the delivery of the virus more specifically to a tumor. With preclinical studies already demonstrating the success and feasibility of this approach with multiple oncolytic viruses, clinical evaluation of cell-mediated delivery of viruses is on the horizon. Meanwhile, ongoing preclinical studies are aimed at identifying new cellular vehicles for oncolytic viruses and improving current promising cell carrier platforms. PMID:27512657

  15. High Density Matter

    Directory of Open Access Journals (Sweden)

    Stone J.R.

    2013-12-01

    Full Text Available The microscopic composition and properties of matter at super-saturation densities have been the subject of intense investigation for decades. The scarcity of experimental and observational data has led to the necessary reliance on theoretical models. There remains great uncertainty in these models which, of necessity, have to go beyond the over-simple assumption that high density matter consists only of nucleons and leptons. Heavy strange baryons, mesons and quark matter in different forms and phases have to be included to fulfil basic requirements of fundamental laws of physics. In this contribution latest developments in construction of the Equation of State (EoS of high-density matter at zero and finite temperature assuming different composition of matter will be discussed. Critical comparison of model EoS with available experimental data from heavy ion collisions and observations on neutron stars, including gravitational mass, radii and cooling patterns and data on X-ray burst sources and low mass X-ray binaries are made. Fundamental differences between the EoS of low-density, high temperature matter, such as is created in heavy ion collisions and of high-density, low temperature compact objects is discussed.

  16. Suspended biofilm carrier and activated sludge removal of acidic pharmaceuticals

    DEFF Research Database (Denmark)

    Falås, Per; Baillon-Dhumez, Aude; Andersen, Henrik Rasmus;

    2012-01-01

    Removal of seven active pharmaceutical substances (ibuprofen, ketoprofen, naproxen, diclofenac, clofibric acid, mefenamic acid, and gemfibrozil) was assessed by batch experiments, with suspended biofilm carriers and activated sludge from several full-scale wastewater treatment plants. A distinct ...... bacteria to degrade or transform the target pharmaceuticals was further demonstrated by the limited pharmaceutical removal in an experiment with continuous nitritation and biofilm carriers from a partial nitritation/anammox sludge liquor treatment process....

  17. Study on Papain Immobilization on a Macroporous Polymer Carrier

    OpenAIRE

    Ding, Liang; YAO, Zihua; Li, Tong

    2003-01-01

    Macroporous resin microbeads of methyl methacrylate-divinyl benzene copolymer were synthesized by radical suspension polymerization of acrolein with divinylbenzene in the presence of a pore-creating agent, petroleum ether. The microbeads had a large specific surface area and large pores covered the entire surface of the resin. This macroporous polymer carrier was aminated by hydrazine hydrate that produced a large number of amino groups on the carrier. Papain was immobilized on the ...

  18. Dispersion and polarization dependence of mobile carrier optical nonlinearities

    Science.gov (United States)

    Rustagi, K. C.

    1984-06-01

    Based on the author's earlier work, it is shown that the proper inclusion of carrier scattering should strongly modify the frequency and polarization dependence of optical nonlinearities due to mobile carriers in semiconductors. When the momentum relaxation is much faster than the energy relaxation, the intensity dependent refractive index is enhanced, the induced birefringence becomes a sharp function of the difference frequency ωa-ωb, and a collision induced stimulated Raman effect becomes important.

  19. Carrier screening in preconception consultation in primary care

    OpenAIRE

    Metcalfe, Sylvia A

    2011-01-01

    Discussing carrier screening during preconception consultation in primary care has a number of advantages in terms of promoting autonomy and enabling the greatest range of reproductive choices. For those with a family history of an inherited condition, this ought to be a routine discussion; however, this can be expanded to include the wider population, especially for those conditions for which carrier frequencies are considered relatively common. There is published literature from around the ...

  20. Review of Magnetic Carrier Technologies for Metal Ion Removal

    OpenAIRE

    Broomberg, J.; Gélinas, S.; Finch, James A.; Xu, Z.

    1999-01-01

    Magnetic carriers are magnetic materials designed to bind selectively on some non -magnetic materials to make them separable using magnetic separation. It allows magnetic separation, a fast, efficient, high capacity and well-developed industrial technology, to be applied to the separation of materials that are otherwise non-magnetic. One application is in metal ion recovery from dilute effluents. Magnetic carrier technologies offer some advantages over other more conventional metal ion separa...

  1. The plant mitochondrial carrier family: functional and evolutionary aspects

    OpenAIRE

    Ilka eHaferkamp; Stephan eSchmitz-Esser

    2012-01-01

    Mitochondria play a key role in respiration and energy production and are involved in multiple eukaryotic but also in several plant specific metabolic pathways. Solute carriers in the inner mitochondrial membrane connect the internal metabolism with that of the surrounding cell. Because of their common basic structure, these transport proteins affiliate to the mitochondrial carrier family (MCF). Generally, MCF proteins consist of six membrane-spanning helices, exhibit typical conserved domain...

  2. Decision feedback loop for tracking a polyphase modulated carrier

    Science.gov (United States)

    Simon, M. K. (Inventor)

    1974-01-01

    A multiple phase modulated carrier tracking loop for use in a frequency shift keying system is described in which carrier tracking efficiency is improved by making use of the decision signals made on the data phase transmitted in each T-second interval. The decision signal is used to produce a pair of decision-feedback quadrature signals for enhancing the loop's performance in developing a loop phase error signal.

  3. Effects of copper on the carrier dynamics in black silicon

    DEFF Research Database (Denmark)

    Porte, Henrik; Turchinovich, Dmitry; Persheyev, S.;

    2011-01-01

    Black silicon is produced by laser annealing of a-Si:H films. We show that by adding a thin Cu film on top of the a-Si:H film before laser annealing, the carrier lifetime can be significantly reduced.......Black silicon is produced by laser annealing of a-Si:H films. We show that by adding a thin Cu film on top of the a-Si:H film before laser annealing, the carrier lifetime can be significantly reduced....

  4. Hot-carrier reliability in OPTVLD-LDMOS

    Institute of Scientific and Technical Information of China (English)

    Cheng Junji; Chen Xingbi

    2012-01-01

    An improved structure that eliminates hot-carrier effects (HCE) in optimum variation lateral doping (OPTVLD) LDMOS is proposed.A formula is proposed showing that the surface electric field intensity of the conventional structure is strong enough to make a hot-carrier injected into oxide.However,the proposed structure effectively reduces the maximum surface electric field from 268 to 100 kV/cm and can be realized without changing any process,and thereby reduces HCE significantly.

  5. Subtle changes among presymptomatic carriers of the Huntington's disease gene

    OpenAIRE

    Kirkwood, S.; Siemers, E; Hodes, M.; Conneally, P; Christian, J.; Foroud, T

    2000-01-01

    OBJECTIVES—To compare the neurological and psychometric characteristics of presymptomatic gene carriers and non-gene carriers who are at risk for developing Huntington's disease so as to characterise early signs of disease and to identify markers of neurological function that could be used to assess the impact of experimental therapies on the progression of disease, even among those who are clinically presymptomatic.
METHODS—A sample of people at risk for Huntington's dis...

  6. Test probe for surface mounted leadless chip carrier

    Science.gov (United States)

    Meyer, Kerry L.; Topolewski, John

    1989-05-23

    A test probe for a surface mounted leadless chip carrier is disclosed. The probed includes specially designed connector pins which allow size reductions in the probe. A thermoplastic housing provides spring action to ensure good mechanical and electrical contact between the pins and the contact strips of a leadless chip carrier. Other features include flexible wires molded into the housing and two different types of pins alternately placed in the housing. These features allow fabrication of a smaller and simpler test probe.

  7. Flight control system design for autonomous UAV carrier landing

    OpenAIRE

    Fitzgerald, Pio

    2004-01-01

    The challenge of integrating the UAV fleet into the carrier landing operational structure with respect to navigation and control strategies is addressed. A simulation model was developed which includes an aircraft model, an atmosphere model and an aircraft carrier motion model. The six degree of freedom non-linear aircraft model is based on the aerodynamic characteristics of the Mk 4a Jindivik extended to include rudder, spoiler and thrust vectoring controls, and an undercarria...

  8. Mucosal genetic immunization through microsphere–based oral carriers

    OpenAIRE

    Rosli, Rozita; Nograles, Nadine; Hanafi, Aimi; Nor Shamsudin, Mariana; Abdullah, Syahril

    2013-01-01

    Polymeric carriers in the form of cellulose acetate phthalate (CAP) and alginate (ALG) microspheres were used for encapsulation of plasmid DNA for oral mucosal immunization. Access into the intestinal mucosa by pVAX1 eukaryotic expression plasmid vectors carrying gene-coding sequences, either for the cholera enterotoxin B subunit (ctxB) immunostimulatory antigen or the green fluorescent protein (GFP), delivered from both types of microsphere carriers were examined in orally immunized BALB/c m...

  9. A Carrier Estimation Method for MF-TDMA Signal Monitoring

    Directory of Open Access Journals (Sweden)

    Xi Liu

    2012-08-01

    Full Text Available Based on the need of MF-TDMA signal monitoring, this paper investigates the estimation method for frequency offset and carrier phase. The procedure for timing recovery is introduced, and then an effective algorithm is deduced for estimating carrier frequency and phase. The proposed open-loop algorithm demands no preambles and has a wide capture range. In addition, the overall block diagram of a monitoring receiver, which we designed with the proposed estimation algorithm, is presented.

  10. Carrier-phonon interaction in semiconductor quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Seebeck, Jan

    2009-03-10

    In recent years semiconductor quantum dots have been studied extensively due to their wide range of possible applications, predominantly for light sources. For successful applications, efficient carrier scattering processes as well as a detailed understanding of the optical properties are of central importance. The aims of this thesis are theoretical investigations of carrier scattering processes in InGaAs/GaAs quantum dots on a quantum-kinetic basis. A consistent treatment of quasi-particle renormalizations and carrier kinetics for non-equilibrium conditions is presented, using the framework of non-equilibrium Green's functions. The focus of our investigations is the interaction of carriers with LO phonons. Important for the understanding of the scattering mechanism are the corresponding quasi-particle properties. Starting from a detailed study of quantum-dot polarons, scattering and dephasing processes are discussed for different temperature regimes. The inclusion of polaron and memory effects turns out to be essential for the description of the carrier kinetics in quantum-dot systems. They give rise to efficient scattering channels and the obtained results are in agreement with recent experiments. Furthermore, a consistent treatment of the carrier-LO-phonon and the carrier-carrier interaction is presented for the optical response of semiconductor quantum dots, both giving rise to equally important contributions to the dephasing. Beside the conventional GaAs material system, currently GaN based light sources are of high topical interest due to their wide range of possible emission frequencies. In this material additionally intrinsic properties like piezoelectric fields and strong band-mixing effects have to be considered. For the description of the optical properties of InN/GaN quantum dots a procedure is presented, where the material properties obtained from an atomistic tight-binding approach are combined with a many-body theory for non

  11. Cellular uptake of steroid carrier proteins – mechanisms and implications

    OpenAIRE

    Willnow, T E; Nykjaer, A

    2009-01-01

    Abstract Steroid hormones are believed to enter cells solely by free diffusion through the plasma membrane. However, recent studies suggest the existence of cellular uptake pathways for carrier-bound steroids. Similar to the clearance of cholesterol via lipoproteins, these pathways involve the recognition of carrier proteins by endocytic receptors on the surface of target cells, followed by internalization and cellular delivery of the bound sterols. Here, we discuss the emerging co...

  12. Precise effective masses from density functional perturbation theory

    Science.gov (United States)

    Laflamme Janssen, J.; Gillet, Y.; Poncé, S.; Martin, A.; Torrent, M.; Gonze, X.

    2016-05-01

    The knowledge of effective masses is a key ingredient to analyze numerous properties of semiconductors, like carrier mobilities, (magneto)transport properties, or band extrema characteristics yielding carrier densities and density of states. Currently, these masses are usually calculated using finite-difference estimation of density functional theory (DFT) electronic band curvatures. However, finite differences require an additional convergence study and are prone to numerical noise. Moreover, the concept of effective mass breaks down at degenerate band extrema. We assess the former limitation by developing a method that allows to obtain the Hessian of DFT bands directly, using density functional perturbation theory. Then, we solve the latter issue by adapting the concept of "transport equivalent effective mass" to the k .p ̂ framework. The numerical noise inherent to finite-difference methods is thus eliminated, along with the associated convergence study. The resulting method is therefore more general, more robust, and simpler to use, which makes it especially appropriate for high-throughput computing. After validating the developed techniques, we apply them to the study of silicon, graphane, and arsenic. The formalism is implemented into the abinit software and supports the norm-conserving pseudopotential approach, the projector augmented-wave method, and the inclusion of spin-orbit coupling. The derived expressions also apply to the ultrasoft pseudopotential method.

  13. High density matter

    CERN Document Server

    Stone, J R

    2013-01-01

    The microscopic composition and properties of matter at super-saturation densities have been the subject of intense investigation for decades. The scarcity of experimental and observational data has lead to the necessary reliance on theoretical models. However, there remains great uncertainty in these models, which, of necessity, have to go beyond the over-simple assumption that high density matter consists only of nucleons and leptons. Heavy strange baryons, mesons and quark matter in different forms and phases have to be included to fulfil basic requirements of fundamental laws of physics. In this review the latest developments in construction of the Equation of State (EoS) of high-density matter at zero and finite temperature assuming different composition of the matter are surveyed. Critical comparison of model EoS with available observational data on neutron stars, including gravitational masses, radii and cooling patterns is presented. The effect of changing rotational frequency on the composition of ne...

  14. Tay-Sachs disease carrier screening: a 21-year experience.

    Science.gov (United States)

    D'Souza, G; McCann, C L; Hedrick, J; Fairley, C; Nagel, H L; Kushner, J D; Kessel, R

    2000-01-01

    This paper presents the findings of a community-based carrier screening program for Tay-Sachs disease, initiated on the University of Wisconsin-Madison campus in 1978. The Madison Community Tay-Sachs Screening Program (MCTSSP) is a collaborative, interdisciplinary program that organizes and conducts periodic screening for Tay-Sachs disease (TSD) for the purpose of identifying Tay-Sachs carriers. We present and analyze data on carrier detection with regard to various demographics, including family history of TSD, ancestry, gender, medication exposure, and illness. Individuals participating in the MCTSSP between 1978 and 1999 were primarily of the target population, and the carrier rate was within the expected range (1/25). Despite aggressive publicity efforts and a well-established program, attendance at the screens has declined. A recent survey of Jewish undergraduate students at the University of Wisconsin-Madison showed poor recall of family screen history and carrier status and reinforced the perception that utilization of the Madison screening program has been low. Ways to increase awareness of and interest in carrier screening for TSD are explored. PMID:11142756

  15. Preclinical studies on new proteins as carrier for glycoconjugate vaccines.

    Science.gov (United States)

    Tontini, M; Romano, M R; Proietti, D; Balducci, E; Micoli, F; Balocchi, C; Santini, L; Masignani, V; Berti, F; Costantino, P

    2016-07-29

    Glycoconjugate vaccines are made of carbohydrate antigens covalently bound to a carrier protein to enhance their immunogenicity. Among the different carrier proteins tested in preclinical and clinical studies, five have been used so far for licensed vaccines: Diphtheria and Tetanus toxoids, the non-toxic mutant of diphtheria toxin CRM197, the outer membrane protein complex of Neisseria meningitidis serogroup B and the Protein D derived from non-typeable Haemophilus influenzae. Availability of novel carriers might help to overcome immune interference in multi-valent vaccines containing several polysaccharide-conjugate antigens, and also to develop vaccines which target both protein as well saccharide epitopes of the same pathogen. Accordingly we have conducted a study to identify new potential carrier proteins. Twenty-eight proteins, derived from different bacteria, were conjugated to the model polysaccharide Laminarin and tested in mice for their ability in inducing antibodies against the carbohydrate antigen and eight of them were subsequently tested as carrier for serogroup meningococcal C oligosaccharides. Four out of these eight were able to elicit in mice satisfactory anti meningococcal serogroup C titers. Based on immunological evaluation, the Streptococcus pneumoniae protein spr96/2021 was successfully evaluated as carrier for serogroups A, C, W, Y and X meningococcal capsular saccharides. PMID:27317455

  16. Ultrafast carrier dynamics in Landau-quantized graphene

    Directory of Open Access Journals (Sweden)

    Wendler Florian

    2015-01-01

    Full Text Available In an external magnetic field, the energy of massless charge carriers in graphene is quantized into non-equidistant degenerate Landau levels including a zero-energy level. This extraordinary electronic dispersion gives rise to a fundamentally new dynamics of optically excited carriers. Here, we review the state of the art of the relaxation dynamics in Landau-quantized graphene focusing on microscopic insights into possible many-particle relaxation channels.We investigate optical excitation into a non equilibrium distribution followed by ultrafast carrier- carrier and carrier-phonon scattering processes. We reveal that surprisingly the Auger scattering dominates the relaxation dynamics in spite of the non-equidistant Landau quantization in graphene. Furthermore, we demonstrate how technologically relevant carrier multiplication can be achieved and discuss the possibility of optical gain in Landau-quantized graphene. The provided microscopic view on elementary many-particle processes can guide future experimental studies aiming at the design of novel graphene-based optoelectronic devices, such as highly efficient photodetectors, solar cells, and spectrally broad Landau level lasers.

  17. Holographic Magnetisation Density Waves

    CERN Document Server

    Donos, Aristomenis

    2016-01-01

    We numerically construct asymptotically $AdS$ black brane solutions of $D=4$ Einstein theory coupled to a scalar and two $U(1)$ gauge fields. The solutions are holographically dual to $d=3$ CFTs in a constant external magnetic field along one of the $U(1)$'s. Below a critical temperature the system's magnetisation density becomes inhomogeneous, leading to spontaneous formation of current density waves. We find that the transition can be of second order and that the solutions which minimise the free energy locally in the parameter space of solutions have averaged stressed tensor of a perfect fluid.

  18. Polarizable Density Embedding

    DEFF Research Database (Denmark)

    Olsen, Jógvan Magnus Haugaard; Steinmann, Casper; Ruud, Kenneth;

    2015-01-01

    We present a new QM/QM/MM-based model for calculating molecular properties and excited states of solute-solvent systems. We denote this new approach the polarizable density embedding (PDE) model and it represents an extension of our previously developed polarizable embedding (PE) strategy. The PDE...... model is a focused computational approach in which a core region of the system studied is represented by a quantum-chemical method, whereas the environment is divided into two other regions: an inner and an outer region. Molecules belonging to the inner region are described by their exact densities...

  19. Investigation of field-dependent charge carrier generation and recombination in polymer based solar cells by transient extraction currents

    Energy Technology Data Exchange (ETDEWEB)

    Kniepert, Juliane; Blakesley, James; Neher, Dieter [University of Potsdam (Germany)

    2011-07-01

    There is an ongoing discussion as to whether photoinduced charge transfer in P3HT:PCBM solar cells leads to fully separated electrons and holes, independent of an electric field, or Coulombically bound interfacial charge pairs. While recent studies by R.A. Marsh et al. with transient absorption spectroscopy gave clear evidence for the formation and field-induced dissociation of bound polaron pairs, measurements by I.A. Howard et al. were in favour of hot exciton dissociation. Here, we present the results of bias-dependent Time Delayed Collection Field (TDCF) measurements to access directly the density of free charge carriers in P3HT:PCBM blends coated from dichlorobenzene. Solvent annealing was applied to yield a phase-separated morphology and the corresponding solar cells exhibit high values for the external quantum efficiency and fill factor. Our setup allowed us to follow the generation and recombination of photogenerated charges with a so far unattained time resolution of 40 ns. Our experiments show that the number of collected carriers is independent of the applied bias during pulsed illumination implying that extractable carriers in P3HT:PCBM blends are not generated by the field-assisted separation of bound polaron pairs. In addition, our experiments support the view that bimolecular recombination of free carriers is strongly suppressed in phase-separated P3HT:PBCM blends.

  20. Accelerated pericyte degeneration and blood-brain barrier breakdown in apolipoprotein E4 carriers with Alzheimer's disease.

    Science.gov (United States)

    Halliday, Matthew R; Rege, Sanket V; Ma, Qingyi; Zhao, Zhen; Miller, Carol A; Winkler, Ethan A; Zlokovic, Berislav V

    2016-01-01

    The blood–brain barrier (BBB) limits the entry of neurotoxic blood-derived products and cells into the brain that is required for normal neuronal functioning and information processing. Pericytes maintain the integrity of the BBB and degenerate in Alzheimer’s disease (AD). The BBB is damaged in AD, particularly in individuals carrying apolipoprotein E4 (APOE4) gene, which is a major genetic risk factor for late-onset AD. The mechanisms underlying the BBB breakdown in AD remain, however, elusive. Here, we show accelerated pericyte degeneration in AD APOE4 carriers >AD APOE3 carriers >non-AD controls, which correlates with the magnitude of BBB breakdown to immunoglobulin G and fibrin. We also show accumulation of the proinflammatory cytokine cyclophilin A (CypA) and matrix metalloproteinase-9 (MMP-9) in pericytes and endothelial cells in AD (APOE4 >APOE3), previously shown to lead to BBB breakdown in transgenic APOE4 mice. The levels of the apoE lipoprotein receptor, low-density lipoprotein receptor-related protein-1 (LRP1), were similarly reduced in AD APOE4 and APOE3 carriers. Our data suggest that APOE4 leads to accelerated pericyte loss and enhanced activation of LRP1-dependent CypA–MMP-9 BBB-degrading pathway in pericytes and endothelial cells, which can mediate a greater BBB damage in AD APOE4 compared with AD APOE3 carriers.

  1. Optical properties and carrier dynamics in differently strained GaN epilayers grown on Si by MOVPE

    Energy Technology Data Exchange (ETDEWEB)

    Lutsenko, E.V.; Pavlovskii, V.N.; Danilchyk, A.V.; Osipov, K.A.; Rzheutskii, N.V.; Zubialevich, V.Z.; Gurskii, A.L.; Yablonskii, G.P. [Stepanov Institute of Physics, National Acad. Sci. of Belarus, F. Skaryna Ave. 68, 220072 Minsk (Belarus); Malinauskas, T.; Jarasiunas, K.; Kazlauskas, K.; Jursenas, S.; Miasojedovas, S.; Zukauskas, A. [Institute of Materials Science and Applied Research, Vilnius University, Sauletekio ave. 9-3, 10222 Vilnius (Lithuania); Dikme, Y.; Kalisch, H.; Jansen, R.H. [Institut fuer Theoretische Elektrotechnik, RWTH Aachen, Kopernikusstr. 16, 52074 Aachen (Germany); Schineller, B.; Heuken, M. [AIXTRON AG, Kackertstr. 15-17, 52072 Aachen (Germany)

    2006-05-15

    Optical properties and carrier dynamics were investigated in a set of samples grown on Si utilizing different layer combinations between the topmost GaN layer and the Si substrate, including AlN/GaN distributed Bragg reflector (DBR) superlattices as well as AlGaN/GaN strain-reducing layers. The use of the AlN/AlGaN superlattice acting both as buffer layer and as DBR opens the way to control the strain in the upper epitaxial layer in GaN-based heterostructures grown on Si. It also can lead to a decrease of the concentration of non-radiative defects in the upper GaN layers, which, in turn, approximately doubles the carrier lifetime and increases the concentration of non-equilibrium carriers. Carrier lifetimes at high excitation energy densities increased from 50-78 ps to 75-200 ps in the layers with DBR. These effects lead to improved PL efficiency and to an increase of the value of optical gain from 300 cm{sup -1} up to 4000 cm{sup -1}. The use of DBR reduces the absorption of light in the Si substrate and may improve the properties of the laser waveguide. All these effects result in a reduction of the laser threshold from 700 to 270 kW/cm{sup 2}. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  2. Infrared studies of impurity states and ultrafast carrier dynamics in semiconductor quantum structures

    Energy Technology Data Exchange (ETDEWEB)

    Stehr, D.

    2007-12-28

    density, many-body effects such as the depolarization and their influence on the spectral position as well as on the lineshape on the intersubband dephasing are studied. Also the difference of excitonic and free-carrier type excitation is discussed, and indication of an excitonic intersubband transition is found. (orig.)

  3. Literature review of the passenger airline business models: Full service carrier, low-cost carrier and charter airlines

    OpenAIRE

    Carmona Benitez, R.B.; Lodewijks, G.

    2008-01-01

    The deregulation and liberalization of the air transportation industry have developed three main passenger business models: full service carriers, low-cost carriers, and charter airlines. Deregulation removed regulated fares and routes increasing competition and yields. Airlines business models main objectives are to minimize operation costs and fares, and to maximize profits based on cost leadership, differentiation and focus strategy. This paper presents a literature review about airline bu...

  4. Care for MRSA carriers in the outpatient sector: a survey among MRSA carriers and physicians in two regions in Germany.

    OpenAIRE

    Raupach-Rosin, Heike; Rübsamen, Nicole; Szkopek, Sebastian; Schmalz, Oliver; Karch, André; Mikolajczyk, Rafael; Castell, Stefanie

    2016-01-01

    Background Little is known about the management of methicillin-resistant Staphylococcus aureus (MRSA) carriers in the German outpatient sector and about the impact of MRSA on their daily life. Reimbursement for MRSA related costs in the German outpatient sector is available since 2012, but its impact has not been studied yet. The aim of the study was to analyze the outpatient management of MRSA carriers from both, physicians’ and MRSA carriers’ perspective. Methods Paper-based questionnaires ...

  5. Density-dependent electron scattering in photoexcited GaAs in strongly diffusive regime

    DEFF Research Database (Denmark)

    Mics, Zoltán; D’Angio, Andrea; Jensen, Søren A.;

    2013-01-01

    In a series of systematic optical pump–terahertz probe experiments, we study the density-dependent electron scattering rate in photoexcited GaAs in the regime of strong carrier diffusion. The terahertz frequency-resolved transient sheet conductivity spectra are perfectly described by the Drude...

  6. Density of states determination in organic donor-acceptor blend layers enabled by molecular doping

    Science.gov (United States)

    Fischer, Janine; Ray, Debdutta; Kleemann, Hans; Pahner, Paul; Schwarze, Martin; Koerner, Christian; Vandewal, Koen; Leo, Karl

    2015-06-01

    Charge carrier transport is a key parameter determining the efficiency of organic solar cells, and is closely related to the density of free and trapped states. For trap characterization, impedance spectroscopy is a suitable, non-invasive method, applicable to complete organic semiconductor devices. In order to contribute to the capacitive signal, the traps must be filled with charge carriers. Typically, trap filling is achieved by illuminating the device or by injecting charge carriers through application of a forward bias voltage. However, in both cases, the exact number of charge carriers in the device is not known and depends strongly on the measurement conditions. Here, hole trap states of the model blend layer ZnPc:C60 are filled by weak p-doping, enabling trap characterization in a blend layer at a controlled hole density. We evaluate impedance spectra at different temperatures in order to determine the density of occupied states (DOOS) directly from the capacitance-frequency spectra by assuming a simple energy diagram. The reconstructed DOOS distribution is analyzed at different doping concentrations and device thicknesses and compared to thermally stimulated current measurements performed on the same devices. In both methods, a pronounced Gaussian peak at about 0.4 eV below the transport level is found as well as deep, exponential tail states, providing a deeper insight into the density of states distribution of this donor-acceptor blend layer. Additionally, the effect of doping-induced trap filling on the solar cell characteristics is studied in these devices.

  7. Energy in density gradient

    Energy Technology Data Exchange (ETDEWEB)

    Vranjes, J., E-mail: jvranjes@yahoo.com [Instituto de Astrofísica de Canarias, 38205 La Laguna, Tenerife (Spain); Departamento de Astrofísica, Universidad de La Laguna, 38205 La Laguna, Tenerife (Spain); Kono, M., E-mail: kono@fps.chuo-u.ac.jp [Faculty of Policy Studies, Chuo University, Tokyo (Japan)

    2015-01-15

    Inhomogeneous plasmas and fluids contain energy stored in inhomogeneity and they naturally tend to relax into lower energy states by developing instabilities or by diffusion. But the actual amount of energy in such inhomogeneities has remained unknown. In the present work, the amount of energy stored in a density gradient is calculated for several specific density profiles in a cylindrical configuration. This is of practical importance for drift wave instability in various plasmas, and, in particular, in its application in models dealing with the heating of solar corona because the instability is accompanied with stochastic heating, so the energy contained in inhomogeneity is effectively transformed into heat. It is shown that even for a rather moderate increase of the density at the axis in magnetic structures in the corona by a factor 1.5 or 3, the amount of excess energy per unit volume stored in such a density gradient becomes several orders of magnitude greater than the amount of total energy losses per unit volume (per second) in quiet regions in the corona. Consequently, within the life-time of a magnetic structure such energy losses can easily be compensated by the stochastic drift wave heating.

  8. Hadronic property at finite density

    OpenAIRE

    Takaishi, Tetsuya

    2004-01-01

    We report on three topics on finite density simulations: (i) the derivative method for hadronic quantities, (ii) phase fluctuations in the vicinity of the critical temperature and (iii) the density of states method at finite isospin density.

  9. Partition density functional theory

    Science.gov (United States)

    Nafziger, Jonathan

    Partition density functional theory (PDFT) is a method for dividing a molecular electronic structure calculation into fragment calculations. The molecular density and energy corresponding to Kohn Sham density-functional theory (KS-DFT) may be exactly recovered from these fragments. Each fragment acts as an isolated system except for the influence of a global one-body 'partition' potential which deforms the fragment densities. In this work, the developments of PDFT are put into the context of other fragment-based density functional methods. We developed three numerical implementations of PDFT: One within the NWChem computational chemistry package using basis sets, and the other two developed from scratch using real-space grids. It is shown that all three of these programs can exactly reproduce a KS-DFT calculation via fragment calculations. The first of our in-house codes handles non-interacting electrons in arbitrary one-dimensional potentials with any number of fragments. This code is used to explore how the exact partition potential changes for different partitionings of the same system and also to study features which determine which systems yield non-integer PDFT occupations and which systems are locked into integer PDFT occupations. The second in-house code, CADMium, performs real-space calculations of diatomic molecules. Features of the exact partition potential are studied for a variety of cases and an analytical formula determining singularities in the partition potential is derived. We introduce an approximation for the non-additive kinetic energy and show how this quantity can be computed exactly. Finally a PDFT functional is developed to address the issues of static correlation and delocalization errors in approximations within DFT. The functional is applied to the dissociation of H2 + and H2.

  10. Renewable Hydrogen Carrier — Carbohydrate: Constructing the Carbon-Neutral Carbohydrate Economy

    Directory of Open Access Journals (Sweden)

    Y.-H. Percival Zhang

    2011-01-01

    Full Text Available The hydrogen economy presents an appealing energy future but its implementation must solve numerous problems ranging from low-cost sustainable production, high-density storage, costly infrastructure, to eliminating safety concern. The use of renewable carbohydrate as a high-density hydrogen carrier and energy source for hydrogen production is possible due to emerging cell-free synthetic biology technology—cell-free synthetic pathway biotransformation (SyPaB. Assembly of numerous enzymes and co-enzymes in vitro can create complicated set of biological reactions or pathways that microorganisms or catalysts cannot complete, for example, C6H10O5 (aq + 7 H2O (l à 12 H2 (g + 6 CO2 (g (PLoS One 2007, 2:e456. Thanks to 100% selectivity of enzymes, modest reaction conditions, and high-purity of generated hydrogen, carbohydrate is a promising hydrogen carrier for end users. Gravimetric density of carbohydrate is 14.8 H2 mass% if water can be recycled from proton exchange membrane fuel cells or 8.33% H2 mass% without water recycling. Renewable carbohydrate can be isolated from plant biomass or would be produced from a combination of solar electricity/hydrogen and carbon dioxide fixation mediated by high-efficiency artificial photosynthesis mediated by SyPaB. The construction of this carbon-neutral carbohydrate economy would address numerous sustainability challenges, such as electricity and hydrogen storage, CO2 fixation and long-term storage, water conservation, transportation fuel production, plus feed and food production.

  11. Impact of the intermixed phase and the channel network on the carrier mobility of nanostructured solar cells.

    Science.gov (United States)

    Woellner, Cristiano F; Freire, José A

    2016-02-28

    We analyzed the impact of the complex channel network of donor and acceptor domains in nanostructured solar cells on the mobility of the charge carriers moving by thermally activated hopping. Particular attention was given to the so called intermixed phase, or interface roughness, that has recently been shown to promote an increase in the cell efficiency. The domains were obtained from a Monte Carlo simulation of a two-species lattice gas. We generated domain morphologies with controllable channel size and interface roughness. The field and density dependence of the carrier hopping mobility in different morphologies was obtained by solving a master equation. Our results show that the mobility decreases with roughness and increases with typical channel sizes. The deleterious effect of the roughness on the mobility is quite dramatic at low carrier densities and high fields. The complex channel network is shown to be directly responsible for two potentially harmful effects to the cell performance: a remarkable decrease of the mobility with increasing field and the accumulation of charge at the domains interface, which leads to recombination losses.

  12. Carrier-number fluctuations in the 2-dimensional electron gas at the LaAlO{sub 3}/SrTiO{sub 3} interface

    Energy Technology Data Exchange (ETDEWEB)

    Barone, C., E-mail: cbarone@unisa.it; Romeo, F.; Pagano, S. [Dipartimento di Fisica “E. R. Caianiello” and CNR-SPIN Salerno, Università di Salerno, I-84084 Fisciano, Salerno (Italy); Di Gennaro, E.; Miletto Granozio, F.; Scotti di Uccio, U. [CNR-SPIN Napoli and Dipartimento di Fisica, Università di Napoli “Federico II,” I-80126 Napoli (Italy); Pallecchi, I.; Marrè, D. [CNR-SPIN Genova and Dipartimento di Fisica, Università di Genova, I-16152 Genova (Italy)

    2013-12-02

    The voltage-spectral density S{sub V} (f) of the 2-dimensional electron gas formed at the interface of LaAlO{sub 3}/SrTiO{sub 3} has been thoroughly investigated. The low-frequency component has a clear 1/f behavior with a quadratic bias current dependence, attributed to resistance fluctuations. However, its temperature dependence is inconsistent with the classical Hooge model, based on carrier-mobility fluctuations. The experimental results are, instead, explained in terms of carrier-number fluctuations, due to an excitation-trapping mechanism of the 2-dimensional electron gas.

  13. Carrier-number fluctuations in the 2-dimensional electron gas at the LaAlO3/SrTiO3 interface

    Science.gov (United States)

    Barone, C.; Romeo, F.; Pagano, S.; Di Gennaro, E.; Miletto Granozio, F.; Pallecchi, I.; Marrè, D.; Scotti di Uccio, U.

    2013-12-01

    The voltage-spectral density SV (f) of the 2-dimensional electron gas formed at the interface of LaAlO3/SrTiO3 has been thoroughly investigated. The low-frequency component has a clear 1/f behavior with a quadratic bias current dependence, attributed to resistance fluctuations. However, its temperature dependence is inconsistent with the classical Hooge model, based on carrier-mobility fluctuations. The experimental results are, instead, explained in terms of carrier-number fluctuations, due to an excitation-trapping mechanism of the 2-dimensional electron gas.

  14. Incorporating medical interventions into carrier probability estimation for genetic counseling

    Directory of Open Access Journals (Sweden)

    Katki Hormuzd A

    2007-03-01

    Full Text Available Abstract Background Mendelian models for predicting who may carry an inherited deleterious mutation of known disease genes based on family history are used in a variety of clinical and research activities. People presenting for genetic counseling are increasingly reporting risk-reducing medical interventions in their family histories because, recently, a slew of prophylactic interventions have become available for certain diseases. For example, oophorectomy reduces risk of breast and ovarian cancers, and is now increasingly being offered to women with family histories of breast and ovarian cancer. Mendelian models should account for medical interventions because interventions modify mutation penetrances and thus affect the carrier probability estimate. Methods We extend Mendelian models to account for medical interventions by accounting for post-intervention disease history through an extra factor that can be estimated from published studies of the effects of interventions. We apply our methods to incorporate oophorectomy into the BRCAPRO model, which predicts a woman's risk of carrying mutations in BRCA1 and BRCA2 based on her family history of breast and ovarian cancer. This new BRCAPRO is available for clinical use. Results We show that accounting for interventions undergone by family members can seriously affect the mutation carrier probability estimate, especially if the family member has lived many years post-intervention. We show that interventions have more impact on the carrier probability as the benefits of intervention differ more between carriers and non-carriers. Conclusion These findings imply that carrier probability estimates that do not account for medical interventions may be seriously misleading and could affect a clinician's recommendation about offering genetic testing. The BayesMendel software, which allows one to implement any Mendelian carrier probability model, has been extended to allow medical interventions, so future

  15. Suppression of thermal carrier escape and efficient photo-carrier generation by two-step photon absorption in InAs quantum dot intermediate-band solar cells using a dot-in-well structure

    Energy Technology Data Exchange (ETDEWEB)

    Asahi, S.; Teranishi, H.; Kasamatsu, N.; Kada, T.; Kaizu, T.; Kita, T. [Department of Electrical and Electronic Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501 (Japan)

    2014-08-14

    We investigated the effects of an increase in the barrier height on the enhancement of the efficiency of two-step photo-excitation in InAs quantum dot (QD) solar cells with a dot-in-well structure. Thermal carrier escape of electrons pumped in QD states was drastically reduced by sandwiching InAs/GaAs QDs with a high potential barrier of Al{sub 0.3}Ga{sub 0.7}As. The thermal activation energy increased with the introduction of the barrier. The high potential barrier caused suppression of thermal carrier escape and helped realize a high electron density in the QD states. We observed efficient two-step photon absorption as a result of the high occupancy of the QD states at room temperature.

  16. Hadron form factors using density-density correlators

    OpenAIRE

    Alexandrou, C.; Koutsou, G.; Neff, H.

    2006-01-01

    Gauge invariant density-density correlators yield detailed information on hadron structure. Hadron deformation and form factors can be extracted for momentum transfers up to about 6 GeV$^2$. We use stochastic techniques and dilution to compute the all to all propagator required for the exact evaluation of density-density correlators. We present first results for the pion form factor.

  17. Gluon density in nuclei

    CERN Document Server

    Ayala, A P; Levin, E M

    1996-01-01

    In this talk we present our detail study ( theory and numbers) [1] on the shadowing corrections to the gluon structure functions for nuclei. Starting from rather contraversial information on the nucleon structure function which is originated by the recent HERA data, we develop the Glauber approach for the gluon density in a nucleus based on Mueller formula [2] and estimate the value of the shadowing corrections in this case. Than we calculate the first corrections to the Glauber approach and show that these corrections are big. Based on this practical observation we suggest the new evolution equation which takes into account the shadowing corrections and solve it. We hope to convince you that the new evolution equation gives a good theoretical tool to treat the shadowing corrections for the gluons density in a nucleus and, therefore, it is able to provide the theoretically reliable initial conditions for the time evolution of the nucleus - nucleus cascade.

  18. Quasiconvexity and density topology

    CERN Document Server

    Rabier, Patrick J

    2012-01-01

    We prove that if f : R^N --> R is quasiconvex and U is open in the density topology of R^N, then sup_U f = ess sup_U f, while inf_U f = ess inf_U f if and only if the equality holds when U = R^N. The first (second) property is typical of lsc (usc) functions and, even when U is an ordinary open subset, there seems to be no record that they both hold for all quasiconvex functions. This property ensures that the pointwise extrema of f on any nonempty density open subset can be arbitrarily closely approximated by values of f achieved on "large" subsets, which may be of relevance in a variety of issues. To support this claim, we use it to characterize the common points of continuity, or approximate continuity, of two quasiconvex functions that coincide away from a set of measure zero.

  19. Degenerate density perturbation theory

    Science.gov (United States)

    Palenik, Mark C.; Dunlap, Brett I.

    2016-09-01

    Fractional occupation numbers can be used in density functional theory to create a symmetric Kohn-Sham potential, resulting in orbitals with degenerate eigenvalues. We develop the corresponding perturbation theory and apply it to a system of Nd degenerate electrons in a harmonic oscillator potential. The order-by-order expansions of both the fractional occupation numbers and unitary transformations within the degenerate subspace are determined by the requirement that a differentiable map exists connecting the initial and perturbed states. Using the X α exchange-correlation (XC) functional, we find an analytic solution for the first-order density and first- through third-order energies as a function of α , with and without a self-interaction correction. The fact that the XC Hessian is not positive definite plays an important role in the behavior of the occupation numbers.

  20. Degenerate Density Perturbation Theory

    CERN Document Server

    Palenik, Mark C

    2016-01-01

    Fractional occupation numbers can be used in density functional theory to create a symmetric Kohn-Sham potential, resulting in orbitals with degenerate eigenvalues. We develop the corresponding perturbation theory and apply it to a system of $N_d$ degenerate electrons in a harmonic oscillator potential. The order-by-order expansions of both the fractional occupation numbers and unitary transformations within the degenerate subspace are determined by the requirement that a differentiable map exists connecting the initial and perturbed states. Using the X$\\alpha$ exchange-correlation (XC) functional, we find an analytic solution for the first-order density and first through third-order energies as a function of $\\alpha$, with and without a self-interaction correction. The fact that the XC Hessian is not positive definite plays an important role in the behavior of the occupation numbers.

  1. Quantal density functional theory

    CERN Document Server

    Sahni, Viraht

    2016-01-01

    This book deals with quantal density functional theory (QDFT) which is a time-dependent local effective potential theory of the electronic structure of matter. The treated time-independent QDFT constitutes a special case. In the 2nd edition, the theory is extended to include the presence of external magnetostatic fields. The theory is a description of matter based on the ‘quantal Newtonian’ first and second laws which is in terms of “classical” fields that pervade all space, and their quantal sources. The fields, which are explicitly defined, are separately representative of electron correlations due to the Pauli exclusion principle, Coulomb repulsion, correlation-kinetic, correlation-current-density, and correlation-magnetic effects. The book further describes Schrödinger theory from the new physical perspective of fields and quantal sources. It also describes traditional Hohenberg-Kohn-Sham DFT, and explains via QDFT the physics underlying the various energy functionals and functional derivatives o...

  2. Density-of-states

    CERN Document Server

    Langfeld, Kurt

    2016-01-01

    Although Monte Carlo calculations using Importance Sampling have matured into the most widely employed method for determining first principle results in QCD, they spectacularly fail for theories with a sign problem or for which certain rare configurations play an important role. Non-Markovian Random walks, based upon iterative refinements of the density-of-states, overcome such overlap problems. I will review the Linear Logarithmic Relaxation (LLR) method and, in particular, focus onto ergodicity and exponential error suppression. Applications include the high-state Potts model, SU(2) and SU(3) Yang-Mills theories as well as a quantum field theory with a strong sign problem: QCD at finite densities of heavy quarks.

  3. 78 FR 5168 - BE-29: Survey of Foreign Ocean Carriers' Expenses in the United States

    Science.gov (United States)

    2013-01-24

    ...), calling at U.S. ports. (e) Foreign Carriers means those carriers whose residence is outside the United... Bureau of Economic Analysis XRIN 0691-XC004 BE-29: Survey of Foreign Ocean Carriers' Expenses in the... public that it is conducting the mandatory survey titled Survey of Foreign Ocean Carriers' Revenues...

  4. 29 CFR 780.155 - Delivery “to carriers for transportation to market.”

    Science.gov (United States)

    2010-07-01

    ..., rail, water, etc.) for transportation by such carrier to market. The market referred to is the farmer's... 29 Labor 3 2010-07-01 2010-07-01 false Delivery âto carriers for transportation to market.â 780... “to carriers for transportation to market.” The term “delivery * * * to carriers for transportation...

  5. 30 CFR 75.1403-6 - Criteria-Self-propelled personnel carriers.

    Science.gov (United States)

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Criteria-Self-propelled personnel carriers. 75... § 75.1403-6 Criteria—Self-propelled personnel carriers. (a) Each self-propelled personnel carrier..., each track-mounted self-propelled personnel carrier should: (1) Be provided with a suitable...

  6. 78 FR 24463 - Sunshine Act Meetings; Unified Carrier Registration Plan Board of Directors

    Science.gov (United States)

    2013-04-25

    ... Federal Motor Carrier Safety Administration Sunshine Act Meetings; Unified Carrier Registration Plan Board... Unified Carrier Registration Plan Board of Directors Meeting. TIME AND DATE: The meeting will be held on... Carrier Registration Plan Board of Directors (the Board) will continue its work in developing...

  7. 76 FR 16471 - Sunshine Act Meetings; Unified Carrier Registration Plan Board of Directors

    Science.gov (United States)

    2011-03-23

    ... Federal Motor Carrier Safety Administration Sunshine Act Meetings; Unified Carrier Registration Plan Board.... STATUS: Open to the public. MATTERS TO BE CONSIDERED: The Unified Carrier Registration Plan Board of Directors (the Board) will continue its work in developing and implementing the Unified Carrier...

  8. 77 FR 52116 - Sunshine Act Meetings; Unified Carrier Registration Plan Board of Directors

    Science.gov (United States)

    2012-08-28

    ... Federal Motor Carrier Safety Administration Sunshine Act Meetings; Unified Carrier Registration Plan Board... Unified Carrier Registration Plan Board of Directors Meeting. TIME AND DATE: The meeting will be held on... Carrier Registration Plan Board of Directors (the Board) will continue its work in developing...

  9. 75 FR 65551 - Sunshine Act Meetings; Unified Carrier Registration Plan Board of Directors

    Science.gov (United States)

    2010-10-25

    ... Federal Motor Carrier Safety Administration Sunshine Act Meetings; Unified Carrier Registration Plan Board.... Status: Open to the public. Matters To Be Considered: The Unified Carrier Registration Plan Board of Directors (the Board) will continue its work in developing and implementing the Unified Carrier...

  10. 76 FR 69793 - Sunshine Act Meetings; Unified Carrier Registration Plan Board of Directors

    Science.gov (United States)

    2011-11-09

    ... Federal Motor Carrier Safety Administration Sunshine Act Meetings; Unified Carrier Registration Plan Board.... STATUS: Open to the public. MATTERS TO BE CONSIDERED: The Unified Carrier Registration Plan Board of Directors (the Board) will continue its work in developing and implementing the Unified Carrier...

  11. 77 FR 45715 - Sunshine Act Meetings; Unified Carrier Registration Plan Board of Directors

    Science.gov (United States)

    2012-08-01

    ... Federal Motor Carrier Safety Administration Sunshine Act Meetings; Unified Carrier Registration Plan Board.... STATUS: Open to the public. MATTERS TO BE CONSIDERED: The Unified Carrier Registration Plan Board of Directors (the Board) will continue its work in developing and implementing the Unified Carrier...

  12. 77 FR 62601 - Sunshine Act Meetings; Unified Carrier Registration Plan Board of Directors

    Science.gov (United States)

    2012-10-15

    ... Federal Motor Carrier Safety Administration Sunshine Act Meetings; Unified Carrier Registration Plan Board... Unified Carrier Registration Plan Board of Directors Meeting. Time and Date: The meeting will be held on... Carrier Registration Plan Board of Directors (the Board) will continue its work in developing...

  13. 77 FR 70529 - Sunshine Act Meetings; Unified Carrier Registration Plan Board of Directors

    Science.gov (United States)

    2012-11-26

    ... Federal Motor Carrier Safety Administration Sunshine Act Meetings; Unified Carrier Registration Plan Board... Unified Carrier Registration Plan Board of Directors Meeting. Time and Date: The meeting will be held on... Carrier Registration Plan Board of Directors (the Board) will continue its work in developing...

  14. 77 FR 3326 - Sunshine Act Meetings; Unified Carrier Registration Plan Board of Directors

    Science.gov (United States)

    2012-01-23

    ... Federal Motor Carrier Safety Administration Sunshine Act Meetings; Unified Carrier Registration Plan Board.... STATUS: Open to the public. MATTERS TO BE CONSIDERED: The Unified Carrier Registration Plan Board of Directors (the Board) will continue its work in developing and implementing the Unified Carrier...

  15. 76 FR 55161 - Sunshine Act Meetings; Unified Carrier Registration Plan Board of Directors

    Science.gov (United States)

    2011-09-06

    ... Federal Motor Carrier Safety Administration Sunshine Act Meetings; Unified Carrier Registration Plan Board.... STATUS: Open to the public. MATTERS TO BE CONSIDERED: The Unified Carrier Registration Plan Board of Directors (the Board) will continue its work in developing and implementing the Unified Carrier...

  16. Bidding Strategies for Carrier in Combinatorial Transportation Auction

    Directory of Open Access Journals (Sweden)

    Pittawat Ueasangkomsate

    2012-02-01

    Full Text Available In combinatorial auction for truckload transportation service procurement, we introduce thebidding strategy for carrier facing the hard valuation problem to all possible routes. The modeluses a bid-to-cost ratio of carriers surveyed in Thailand to represent the bidding behavior incombinatorial freight procurement. This model facilitates carrier to value the bid price forinterested packages that involve with pattern of transportation service under different competitiveenvironment. The results of analysis with hypotheses in regression model reveal significantly thata pattern of transportation service, a number of competitors, and a pre-empty backhaul to newlane distance ratio with number of competitors do impact negatively on a bid-to-cost ratio ofcarrier, whereas a pre-empty backhaul to new lane distance ratio does impact positively on a bidto-cost ratio of carrier in combinatorial transportation auction. To find optimal bid price forinterested packages in the incomplete information game, the empirical study in stochasticoptimization problem with Monte Carlo method can provide the best solution for carrier in order toacquire the maximum expected profit in the auction. The results present that the expected profitwith optimal solution of bidder is more than the average benefit in the competition marketobviously. While in turn the results also show that shipper could potentially reduce the cost oftransportation service procurement regarding our solution algorithm considerably.

  17. Non-equilibrium hot carrier dynamics in plasmonic nanostructures

    Science.gov (United States)

    Narang, Prineha; Sundararaman, Ravishankar; Jermyn, Adam; Cortes, Emiliano; Maier, Stefan A.; Goddard, William A., III

    Decay of surface plasmons to hot carriers is a new direction that has attracted considerable fundamental and application interest, yet a fundamental understanding of ultrafast plasmon decay processes and the underlying microscopic mechanisms remain incomplete. Ultrafast experiments provide insights into the relaxation of non-equilibrium carriers at the tens and hundreds of femtoseconds time scales, but do not yet directly probe shorter times with nanometer spatial resolution. Here we report the first ab initio calculations of non equilibrium transport of plasmonic hot carriers in metals and experimental observation of the injection of these carriers into molecules tethered to the metal surface. Specifically, metallic nanoantennas functionalized with a molecular monolayer allow for the direct probing of electron injection via surface enhanced Raman spectroscopy of the original and reduced molecular species. We combine first principles calculations of electron-electron and electron-phonon scattering rates with Boltzmann transport simulations to predict the ultrafast dynamics and transport of carriers in real materials. We also predict and compare the evolution of electron distributions in ultrafast experiments on noble metal nanoparticles.

  18. Carrier doping by current injection into LaOFFeAs

    Energy Technology Data Exchange (ETDEWEB)

    Lazareva, Irina; Koval, Yury; Steiner, Christian; Mueller, Paul [Department of Physics, Universitaet Erlangen (Germany); Wurmehl, Sabine; Buechner, Bernd [IFW Dresden (Germany); Stuerzer, Tobias; Johrendt, Dirk [Department Chemie, LMU Muenchen (Germany)

    2013-07-01

    Recently, we were able to change the carrier concentration of hole-doped high-T{sub c} superconductors by injection of large currents along the c-axis. We extend this type of experiments to electron-doped pnictides. From our earlier interpretation we should expect that trapping of electrons caused by current injection would decrease the available carrier concentration. Indeed, by various experiments with superconductors from the LaO{sub 1-x}F{sub x}FeAs family we are able to show that trapped electrons caused by current injection perpendicular to the FeAs planes decrease the carrier concentration. We present a spectacular confirmation of this interpretation by the T{sub c} increase by more than 15 K in heavily overdoped La{sub 0.74}F{sub 0.26}FeAs. We performed similar experiments with the recently discovered 1048 layered pnictides of the composition Ca{sub 10}(FeAs){sub 10}(Pt{sub 4}As{sub 8}). The general tendency of carrier doping by trapped electrons was confirmed. A rather interesting discovery was the evolution of hysteretic c-axis IV-characteristics. This is a strong indication of intrinsic Josephson effects. We discuss these results in terms of a change of anisotropy by carrier doping.

  19. Plasmon-induced hot carrier science and technology

    Science.gov (United States)

    Brongersma, Mark L.; Halas, Naomi J.; Nordlander, Peter

    2015-01-01

    The discovery of the photoelectric effect by Heinrich Hertz in 1887 set the foundation for over 125 years of hot carrier science and technology. In the early 1900s it played a critical role in the development of quantum mechanics, but even today the unique properties of these energetic, hot carriers offer new and exciting opportunities for fundamental research and applications. Measurement of the kinetic energy and momentum of photoejected hot electrons can provide valuable information on the electronic structure of materials. The heat generated by hot carriers can be harvested to drive a wide range of physical and chemical processes. Their kinetic energy can be used to harvest solar energy or create sensitive photodetectors and spectrometers. Photoejected charges can also be used to electrically dope two-dimensional materials. Plasmon excitations in metallic nanostructures can be engineered to enhance and provide valuable control over the emission of hot carriers. This Review discusses recent advances in the understanding and application of plasmon-induced hot carrier generation and highlights some of the exciting new directions for the field.

  20. Mechanisms of Carrier Transport Induced by a Microswimmer Bath

    Energy Technology Data Exchange (ETDEWEB)

    Kaiser, Andreas; Sokolov, Andrey; Aranson, Igor S.; Lowen, Hartmut

    2015-04-01

    Recently, it was found that a wedgelike microparticle (referred to as ”carrier”) which is only allowed to translate but not to rotate exhibits a directed translational motion along the wedge cusp if it is exposed to a bath of microswimmers. Here we model this effect in detail by resolving the microswimmers explicitly using interaction models with different degrees of mutual alignment. Using computer simulations we study the impact of these interactions on the transport efficiency of V-shaped carrier. We show that the transport mechanisms itself strongly depends on the degree of alignment embodied in the modelling of the individual swimmer dynamics. For weak alignment, optimal carrier transport occurs in the turbulent microswimmer state and is induced by swirl depletion inside the carrier. For strong aligning interactions, optimal transport occurs already in the dilute regime and is mediated by a polar cloud of swimmers in the carrier wake pushing the wedge-particle forward. We also demonstrate that the optimal shape of the carrier leading to maximal transport speed depends on the kind of interaction model used.

  1. Interfacing materials science and biology for drug carrier design.

    Science.gov (United States)

    Such, Georgina K; Yan, Yan; Johnston, Angus P R; Gunawan, Sylvia T; Caruso, Frank

    2015-04-01

    Over the last ten years, there has been considerable research interest in the development of polymeric carriers for biomedicine. Such delivery systems have the potential to significantly reduce side effects and increase the bioavailability of poorly soluble therapeutics. The design of carriers has relied on harnessing specific variations in biological conditions, such as pH or redox potential, and more recently, by incorporating specific peptide cleavage sites for enzymatic hydrolysis. Although much progress has been made in this field, the specificity of polymeric carriers is still limited when compared with their biological counterparts. To synthesize the next generation of carriers, it is important to consider the biological rationale for materials design. This requires a detailed understanding of the cellular microenvironments and how these can be harnessed for specific applications. In this review, several important physiological cues in the cellular microenvironments are outlined, with a focus on changes in pH, redox potential, and the types of enzymes present in specific regions. Furthermore, recent studies that use such biologically inspired triggers to design polymeric carriers are highlighted, focusing on applications in the field of therapeutic delivery.

  2. Fundamental Limitations to Plasmonic Hot-Carrier Solar Cells.

    Science.gov (United States)

    Zhang, Yu; Yam, ChiYung; Schatz, George C

    2016-05-19

    Detailed balance between photon-absorption and energy loss constrains the efficiency of conventional solar cells to the Shockley-Queisser limit. However, if solar illumination can be absorbed over a wide spectrum by plasmonic structures, and the generated hot-carriers can be collected before relaxation, the efficiency of solar cells may be greatly improved. In this work, we explore the opportunities and limitations for making plasmonic solar cells, here considering a design for hot-carrier solar cells in which a conventional semiconductor heterojunction is attached to a plasmonic medium such as arrays of gold nanoparticles. The underlying mechanisms and fundamental limitations of this cell are studied using a nonequilibrium Green's function method, and the numerical results indicate that this cell can significantly improve the absorption of solar radiation without reducing open-circuit voltage, as photons can be absorbed to produce mobile carriers in the semiconductor as long as they have energy larger than the Schottky barrier rather than above the bandgap. However, a significant fraction of the hot-carriers have energies below the Schottky barrier, which makes the cell suffer low internal quantum efficiency. Moreover, quantum efficiency is also limited by hot-carrier relaxation and metal-semiconductor coupling. The connection of these results to recent experiments is described, showing why plasmonic solar cells can have less than 1% efficiency. PMID:27136049

  3. Cell carriers for oncolytic viruses: current challenges and future directions

    Directory of Open Access Journals (Sweden)

    Roy DG

    2013-10-01

    Full Text Available Dominic G Roy,1,2 John C Bell1–31Centre for Innovative Cancer Therapeutics, Ottawa Hospital Research Institute, 2Department of Biochemistry, Immunology and Microbiology, 3Department of Medicine, University of Ottawa, Ottawa, ON, CanadaAbstract: The optimal route for clinical delivery of oncolytic viruses is thought to be systemic intravenous injection; however, the immune system is armed with several highly efficient mechanisms to remove pathogens from the circulatory system. To overcome the challenges faced in trying to delivery oncolytic viruses specifically to tumors via the bloodstream, carrier cells have been investigated to determine their suitability as delivery vehicles for systemic administration of oncolytic viruses. Cell carriers protect viruses from neutralization, one of the most limiting aspects of oncolytic virus interaction with the immune system. Cell carriers can also possess inherent tumor tropism, thus directing the delivery of the virus more specifically to a tumor. With preclinical studies already demonstrating the success and feasibility of this approach with multiple oncolytic viruses, clinical evaluation of cell-mediated delivery of viruses is on the horizon. Meanwhile, ongoing preclinical studies are aimed at identifying new cellular vehicles for oncolytic viruses and improving current promising cell carrier platforms.Keywords: oncolytic virus, cell carrier, systemic delivery, tumor targeting, cancer

  4. Ultra--fast carriers relaxation in bulk silicon following photo--excitation with a short and polarized laser pulse

    CERN Document Server

    Sangalli, Davide

    2014-01-01

    A novel approach based on the merging of the out--of--equilibrium Green's function method with the ab-initio, Density--Functional--Theory is used to describe the ultra--fast carriers relaxation in Silicon. The results are compared with recent two photon photo--emission measurements. We show that the interpretation of the carrier relaxation in terms of L -> X inter--valley scattering is not correct. The ultra--fast dynamics measured experimentally is, instead, due to the scattering between degenerate $L$ states that is activated by the non symmetric population of the conduction bands induced by the laser field. This ultra--fast relaxation is, then, entirely due to the specific experimental setup and it can be interpreted by introducing a novel definition of the quasi--particle lifetimes in an out--of--equilibrium context.

  5. Analysis of thermoelectric properties of amorphous InGaZnO thin film by controlling carrier concentration

    Directory of Open Access Journals (Sweden)

    Yuta Fujimoto

    2015-09-01

    Full Text Available We have investigated the thermoelectric properties of amorphous InGaZnO (a-IGZO thin films optimized by adjusting the carrier concentration. The a-IGZO films were produced under various oxygen flow ratios. The Seebeck coefficient and the electrical conductivity were measured from 100 to 400 K. We found that the power factor (PF at 300 K had a maximum value of 82 × 10−6 W/mK2, where the carrier density was 7.7 × 1019 cm−3. Moreover, the obtained data was analyzed by fitting the percolation model. Theoretical analysis revealed that the Fermi level was located approximately above the potential barrier when the PF became maximal. The thermoelectric properties were controlled by the relationship between the position of Fermi level and the height of potential energy barriers.

  6. Contingent kernel density estimation.

    Directory of Open Access Journals (Sweden)

    Scott Fortmann-Roe

    Full Text Available Kernel density estimation is a widely used method for estimating a distribution based on a sample of points drawn from that distribution. Generally, in practice some form of error contaminates the sample of observed points. Such error can be the result of imprecise measurements or observation bias. Often this error is negligible and may be disregarded in analysis. In cases where the error is non-negligible, estimation methods should be adjusted to reduce resulting bias. Several modifications of kernel density estimation have been developed to address specific forms of errors. One form of error that has not yet been addressed is the case where observations are nominally placed at the centers of areas from which the points are assumed to have been drawn, where these areas are of varying sizes. In this scenario, the bias arises because the size of the error can vary among points and some subset of points can be known to have smaller error than another subset or the form of the error may change among points. This paper proposes a "contingent kernel density estimation" technique to address this form of error. This new technique adjusts the standard kernel on a point-by-point basis in an adaptive response to changing structure and magnitude of error. In this paper, equations for our contingent kernel technique are derived, the technique is validated using numerical simulations, and an example using the geographic locations of social networking users is worked to demonstrate the utility of the method.

  7. Visual function and cortical organization in carriers of blue cone monochromacy.

    Directory of Open Access Journals (Sweden)

    Ethan A Rossi

    Full Text Available Carriers of blue cone monochromacy have fewer cone photoreceptors than normal. Here we examine how this disruption at the level of the retina affects visual function and cortical organization in these individuals. Visual resolution and contrast sensitivity was measured at the preferred retinal locus of fixation and visual resolution was tested at two eccentric locations (2.5° and 8° with spectacle correction only. Adaptive optics corrected resolution acuity and cone spacing were simultaneously measured at several locations within the central fovea with adaptive optics scanning laser ophthalmoscopy (AOSLO. Fixation stability was assessed by extracting eye motion data from AOSLO videos. Retinotopic mapping using fMRI was carried out to estimate the area of early cortical regions, including that of the foveal confluence. Without adaptive optics correction, BCM carriers appeared to have normal visual function, with normal contrast sensitivity and visual resolution, but with AO-correction, visual resolution was significantly worse than normal. This resolution deficit is not explained by cone loss alone and is suggestive of an associated loss of retinal ganglion cells. However, despite evidence suggesting a reduction in the number of retinal ganglion cells, retinotopic mapping showed no reduction in the cortical area of the foveal confluence. These results suggest that ganglion cell density may not govern the foveal overrepresentation in the cortex. We propose that it is not the number of afferents, but rather the content of the information relayed to the cortex from the retina across the visual field that governs cortical magnification, as under normal viewing conditions this information is similar in both BCM carriers and normal controls.

  8. Implications of alkaline solutions-induced etching on optical and minority carrier lifetime features of monocrystalline silicon

    Energy Technology Data Exchange (ETDEWEB)

    Bachtouli, N. [Photovoltaic Laboratory, Research and Technology Centre of Energy, Borj-Cedria Science and Technology Park, BP 95, 2050 Hammam-Lif (Tunisia); Aouida, S., E-mail: salma.aouida@crten.rnrt.tn [Photovoltaic Laboratory, Research and Technology Centre of Energy, Borj-Cedria Science and Technology Park, BP 95, 2050 Hammam-Lif (Tunisia); Laajimi, R. Hadj [Water Researches and Technologies Center, Science and Technology Park, BP 273, route touristique Soliman Borj-Cedria, 8020 Soliman (Tunisia); Department of Chemistry, College of Science, University of Hail, P.O. Box 1560, Hail (Saudi Arabia); Boujmil, M.F.; Bessais, B. [Photovoltaic Laboratory, Research and Technology Centre of Energy, Borj-Cedria Science and Technology Park, BP 95, 2050 Hammam-Lif (Tunisia)

    2012-09-01

    Highlights: Black-Right-Pointing-Pointer Three alkaline solutions: NaOH, KOH and TMAH are used to form pyramidal structure on silicon surface wafer. Black-Right-Pointing-Pointer The apex angle of the formed pyramids varies between 75 Degree-Sign and 82 Degree-Sign . Black-Right-Pointing-Pointer The heights and bases range from 230 nm to 30 {mu}m. Black-Right-Pointing-Pointer The photoconductivity enhancement is related to pyramidal sizes and reflectivity behavior Black-Right-Pointing-Pointer The QSSPC measurement reveals an apparent increase in the minority carrier lifetime. - Abstract: In this work, we search to optimize the surface textures of monocrystalline silicon (c-Si) intended to be used in silicon solar cells. For this purpose, we studied the morphology of formed etch hillocks during anisotropic etching of silicon using alkaline solutions based on sodium hydroxide (NaOH), potassium hydroxide (KOH) and tetramethylammonium hydroxide (TMAH). Such treatments lead to the formation of various pyramids-like textures that can be well optimized to improve the photocurrent of c-Si-based solar cells. The produced textures were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), UV-visible optical reflectivity and minority carrier lifetime measurements. These investigations allow evaluating the size and density of the formed pyramidal textures; the apex angles vary between 75 Degree-Sign and 82 Degree-Sign , while the heights and bases of the pyramids range from a few hundred nanometers to several micrometers. A minimum reflectivity value of about 6% was obtained at specific conditions using NaOH, whereas it was found that the apparent effective minority carrier lifetime ({tau}{sub eff}) is sensitive to the injection level ({Delta}n), which shows an apparent increase from 1.2 {mu}s to 2.4 {mu}s for a minority carrier density of about {Delta}n = 210{sup 14} cm{sup -3}.

  9. Density measures and additive property

    OpenAIRE

    Kunisada, Ryoichi

    2015-01-01

    We deal with finitely additive measures defined on all subsets of natural numbers which extend the asymptotic density (density measures). We consider a class of density measures which are constructed from free ultrafilters on natural numbers and study a certain additivity property of such density measures.

  10. The DOE Transportation Management Division's Motor Carrier Evaluation Program

    International Nuclear Information System (INIS)

    The movement of hazardous materials and wastes over the nation's highways by commercial motor carriers presents a challenge for the purchaser of transportation services. During the next decade the volume of hazardous materials and wastes is expected to increase dramatically. Along with this increase in the shipments of these hazardous materials and wastes comes the responsibility of selecting a motor carrier to transport these materials. The selection of the open-quotes rightclose quotes motor carrier to transport a generator's hazardous materials and/or waste is a decision that, in today's regulatory environment, can't be left to chance. The legal ramifications and potential liability are such today, that a company should be very selective in deciding who to allow to transport these hazardous commodities. Shippers of hazardous materials must come to the realization that they are responsible for the shipment, long after the truck leaves their plant gates

  11. Carrier multiplication in silicon nanocrystals: ab initio results

    Directory of Open Access Journals (Sweden)

    Ivan Marri

    2015-02-01

    Full Text Available One of the most important goals in the field of renewable energy is the development of original solar cell schemes employing new materials to overcome the performance limitations of traditional solar cell devices. Among such innovative materials, nanostructures have emerged as an important class of materials that can be used to realize efficient photovoltaic devices. When these systems are implemented into solar cells, new effects can be exploited to maximize the harvest of solar radiation and to minimize the loss factors. In this context, carrier multiplication seems one promising way to minimize the effects induced by thermalization loss processes thereby significantly increasing the solar cell power conversion. In this work we analyze and quantify different types of carrier multiplication decay dynamics by analyzing systems of isolated and coupled silicon nanocrystals. The effects on carrier multiplication dynamics by energy and charge transfer processes are also discussed.

  12. LNG Carrier Market: The Next Main Battleground For Shipbuilding Enterprises

    Institute of Scientific and Technical Information of China (English)

    Han Guang

    2012-01-01

    Last year, 51 LNG carriers were delivered in the world. From January to February this year, more than 10 LNG carriers have been deliveredglobally. Some shipowners are planning to expand LNG carrier fleet, which is a stark contrast to the look of the three main ship types which is embarrassing. As the recognized clean fuel, natural gas plays an important role in carbon politics and low carbon economy. At present, LNG powered vessel is growing vigorously. LNG fueled vessels have also emerged in Europe. Now, discussion about natural gas application on inland water transport is gradually warming up. Although there are still many technical problems to be solved about LNG powered vessel, the trend is irreversible.

  13. On the road toward a hot carrier solar cell

    Science.gov (United States)

    Taylor, P. C.; Fields, J. D.; Collins, R. T.

    2015-09-01

    We suggest a new paradigm for solar cells that uses a nanostructured crystalline collector (silicon) in an amorphous absorber matrix (hydrogenated amorphous silicon). Previously amorphous absorbers have received no serious consideration because of their low carrier mobilities. Specifically, we demonstrate that carriers generated in the amorphous region are transported out of this region before losing their energy to heat. This result establishes the possibility of using a wide range of nanostructured amorphous matrices to dramatically increase the efficiencies of solar cells. The use of an amorphous absorber provides a highly desirable and flexible approach to producing low-cost, hot carrier solar cells. Since amorphous materials can be grown over a much wider composition space than crystalline materials, this surprising result greatly broadens the absorbing materials that can be used to dramatically increase the efficiencies of solar cells.

  14. Niosomes as Nanoparticular Drug Carriers: Fundamentals and Recent Applications

    Directory of Open Access Journals (Sweden)

    Didem Ag Seleci

    2016-01-01

    Full Text Available Drug delivery systems are defined as formulations aiming for transportation of a drug to the desired area of action within the body. The basic component of drug delivery systems is an appropriate carrier that protects the drug from rapid degradation or clearance and thereby enhances drug concentration in target tissues. Based on their biodegradable, biocompatible, and nonimmunogenic structure, niosomes are promising drug carriers that are formed by self-association of nonionic surfactants and cholesterol in an aqueous phase. In recent years, numerous research articles have been published in scientific journals reporting the potential of niosomes to serve as a carrier for the delivery of different types of drugs. The present review describes preparation methods, characterization techniques, and recent studies on niosomal drug delivery systems and also gives up to date information regarding recent applications of niosomes in drug delivery.

  15. Is oral absorption of vigabatrin carrier-mediated?

    DEFF Research Database (Denmark)

    Nøhr, M. K.; Juul, R. V.; Thale, Z. I.;

    2015-01-01

    by significant increases in the apparent Michaelis constant. Based on the mechanistic model, a high capacity low affinity carrier is proposed to be involved in intestinal vigabatrin absorption. PAT1-ligands increased the Michaelis constant of vigabatrin after oral co-administration indicating that this carrier......The aim of the study was to investigate the intestinal transport mechanisms responsible for vigabatrin absorption in rats by developing a population pharmacokinetic (PK) model of vigabatrin oral absorption. The PK model was used to investigate whether vigabatrin absorption was carrier......-mediated and if the proton-coupled amino acid transporter 1 (PAT1) was involved in the absorption processes. Vigabatrin (0.3-300 mg/kg) was administered orally or intravenously to Sprague Dawley rats in the absence or presence of PAT1-ligands l-proline, l-tryptophan or sarcosine. The PK profiles of vigabatrin were described...

  16. Augmenting drug-carrier compatibility improves tumour nanotherapy efficacy

    Science.gov (United States)

    Zhao, Yiming; Fay, François; Hak, Sjoerd; Manuel Perez-Aguilar, Jose; Sanchez-Gaytan, Brenda L.; Goode, Brandon; Duivenvoorden, Raphaël; de Lange Davies, Catharina; Bjørkøy, Astrid; Weinstein, Harel; Fayad, Zahi A.; Pérez-Medina, Carlos; Mulder, Willem J. M.

    2016-04-01

    A major goal of cancer nanotherapy is to use nanoparticles as carriers for targeted delivery of anti-tumour agents. The drug-carrier association after intravenous administration is essential for efficient drug delivery to the tumour. However, a large number of currently available nanocarriers are self-assembled nanoparticles whose drug-loading stability is critically affected by the in vivo environment. Here we used in vivo FRET imaging to systematically investigate how drug-carrier compatibility affects drug release in a tumour mouse model. We found the drug's hydrophobicity and miscibility with the nanoparticles are two independent key parameters that determine its accumulation in the tumour. Next, we applied these findings to improve chemotherapeutic delivery by augmenting the parent drug's compatibility; as a result, we achieved better antitumour efficacy. Our results help elucidate nanomedicines' in vivo fate and provide guidelines for efficient drug delivery.

  17. Local-oscillator-free wireless-optical-wireless data link at 1.25 Gbit/s over a 40 GHz carrier employing carrier preservation and envelope detection

    DEFF Research Database (Denmark)

    Seoane, Jorge; Tafur Monroy, Idelfonso; Prince, Kamau;

    2008-01-01

    A local-oscillator-free wireless-optical-wireless system at 1.25 Gb/s over a 40 GHz carrier and 100 km of NZDSF is demonstrated employing optical half-wave rectification, carrier remodulation and envelope detection.......A local-oscillator-free wireless-optical-wireless system at 1.25 Gb/s over a 40 GHz carrier and 100 km of NZDSF is demonstrated employing optical half-wave rectification, carrier remodulation and envelope detection....

  18. Vaccination Strategies against Malaria: novel carrier(s) more than a tour de force.

    Science.gov (United States)

    Tyagi, Rajeev K; Garg, Neeraj K; Sahu, Tejram

    2012-08-20

    The introduction of vaccine technology has facilitated an unprecedented multi-antigen approach to develop an effective vaccine against complex systemic inflammatory pathogens such as Plasmodium spp. that cause severe malaria. The capacity of multi subunit DNA vaccine encoding different stage Plasmodium antigens to induce CD8(+) cytotoxic T lymphocytes and interferon-γ responses in mice, monkeys and humans has been observed. Moreover, genetic vaccination may be capable of eliciting both cell mediated and humoral immune responses. The cytotoxic T cell responses are categorically needed against intracellular hepatic stage and humoral response with antibodies targeted against antigens from all stages of malaria parasite life cycle. Therefore, the key to success for any DNA based vaccine is to design a vector able to serve as a safe and efficient delivery system. This has encouraged the development of non-viral DNA-mediated gene transfer techniques such as liposome, virosomes, microsphere and nanoparticles. Efficient and relatively safe DNA transfection using lipoplexes makes them an appealing alternative to be explored for gene delivery. Also, liposome-entrapped DNA has been shown to enhance the potency of DNA vaccines, possibly by facilitating uptake of the plasmid by antigen-presenting cells (APC). Another recent technology using cationic lipids has been deployed and has generated substantial interest in this approach to gene transfer. In this review we discussed various aspects that could be decisive in the formulation of efficient and stable carrier system(s) for the development of malaria vaccine.

  19. Distribution of a pseudodeficiency allele among Tay-Sachs carriers

    Energy Technology Data Exchange (ETDEWEB)

    Tomczak, J.; Grebner, E.E. (Thomas Jefferson Univ., Philadelphia, PA (United States)); Boogen, C. (Univ. of Essen Medical School (Germany))

    1993-08-01

    Recently Triggs-Raine et al. (1992) identified a new mutation in the gene coding for the [alpha]-subunit of [beta]-hexosaminidase A (hex A), the enzyme whose deficiency causes Tay-Sachs disease. This mutation, a C[sub 739]-to-T transition in exon 7, results in an altered enzyme that is active (albeit at reduced levels) in cells but that has essentially no activity in serum. This so-called pseudodeficient allele was first detected in compound heterozygotes who also carried a Tay-Sachs disease allele and therefore had no detectable hex A in their serum but who were in good health. Carriers of this apparently benign mutation are generally indistinguishable from carriers of a lethal mutation by means of routine enzyme-based screening tests, because the product of the pseudodeficient allele is not detectable in serum and has decreased activity in cells. This suggests that some individuals who have been classified as Tay-Sachs carriers are actually carriers of the pseudodeficient allele and are not at risk to have a child affected with Tay-Sachs disease. The pseudodeficient allele may also be responsible for some inconclusive diagnoses, where leukocyte values fall below the normal range but are still above the carrier range. The fact that there are now two mutant alleles (the psuedodeficient and the adult) that are indistinguishable from the lethal infantile mutations by means of enzyme assay yet that are phenotypically very different and that together may account for as much as 12% of enzyme-defined carriers on the basis of the data here suggests that DNA analysis should be part of a comprehensive screening program. It will be particularly useful to identify the mutations in couples at risk, before they undergo prenatal diagnosis. DNA analysis will also resolve some inconclusive diagnoses.

  20. Graded Carrier Concentration Absorber Profile for High Efficiency CIGS Solar Cells

    Directory of Open Access Journals (Sweden)

    Antonino Parisi

    2015-01-01

    Full Text Available We demonstrate an innovative CIGS-based solar cells model with a graded doping concentration absorber profile, capable of achieving high efficiency values. In detail, we start with an in-depth discussion concerning the parametrical study of conventional CIGS solar cells structures. We have used the wxAMPS software in order to numerically simulate cell electrical behaviour. By means of simulations, we have studied the variation of relevant physical and chemical parameters—characteristic of such devices—with changing energy gap and doping density of the absorber layer. Our results show that, in uniform CIGS cell, the efficiency, the open circuit voltage, and short circuit current heavily depend on CIGS band gap. Our numerical analysis highlights that the band gap value of 1.40 eV is optimal, but both the presence of Molybdenum back contact and the high carrier recombination near the junction noticeably reduce the crucial electrical parameters. For the above-mentioned reasons, we have demonstrated that the efficiency obtained by conventional CIGS cells is lower if compared to the values reached by our proposed graded carrier concentration profile structures (up to 21%.