Anti-parallel polarization switching in a triglycine sulfate organic ferroelectric insulator: The role of surface charges

Science.gov (United States)

Ma, He; Wu, Zhuangchun; Peng, Dongwen; Wang, Yaojin; Wang, Yiping; Yang, Ying; Yuan, Guoliang

2018-04-01

Four consecutive ferroelectric polarization switchings and an abnormal ring-like domain pattern can be introduced by a single tip bias of a piezoresponse force microscope in the (010) triglycine sulfate (TGS) crystal. The external electric field anti-parallel to the original polarization induces the first polarization switching; however, the surface charges of TGS can move toward the tip location and induce the second polarization switching once the tip bias is removed. The two switchings allow a ring-like pattern composed of the central domain with downward polarization and the outer domain with upward polarization. Once the two domains disappear gradually as a result of depolarization, the other two polarization switchings occur one by one at the TGS where the tip contacts. However, the backswitching phenomenon does not occur when the external electric field is parallel to the original polarization. These results can be explained according to the surface charges instead of the charges injected inside.

Improper ferroelectric polarization in a perovskite driven by intersite charge transfer and ordering

Science.gov (United States)

Chen, Wei-Tin; Wang, Chin-Wei; Wu, Hung-Cheng; Chou, Fang-Cheng; Yang, Hung-Duen; Simonov, Arkadiy; Senn, M. S.

2018-04-01

It is of great interest to design and make materials in which ferroelectric polarization is coupled to other order parameters such as lattice, magnetic, and electronic instabilities. Such materials will be invaluable in next-generation data storage devices. Recently, remarkable progress has been made in understanding improper ferroelectric coupling mechanisms that arise from lattice and magnetic instabilities. However, although theoretically predicted, a compact lattice coupling between electronic and ferroelectric (polar) instabilities has yet to be realized. Here we report detailed crystallographic studies of a perovskite HgAMn3A'Mn4BO12 that is found to exhibit a polar ground state on account of such couplings that arise from charge and orbital ordering on both the A'- and B-sites, which are themselves driven by a highly unusual MnA '-MnB intersite charge transfer. The inherent coupling of polar, charge, orbital, and hence magnetic degrees of freedom make this a system of great fundamental interest, and demonstrating ferroelectric switching in this and a host of recently reported hybrid improper ferroelectrics remains a substantial challenge.

A charge-polarized porous metal-organic framework for gas chromatographic separation of alcohols from water.

Science.gov (United States)

Sun, Jian-Ke; Ji, Min; Chen, Cheng; Wang, Wu-Gen; Wang, Peng; Chen, Rui-Ping; Zhang, Jie

2013-02-25

A bipyridinium ligand with a charge separated skeleton has been introduced into a metal-organic framework to yield a porous material with charge-polarized pore space, which exhibits selective adsorption for polar guest molecules and can be further used in gas chromatography for the separation of alcohol-water mixtures.

Computer simulations analysis for determining the polarity of charge generated by high energy electron irradiation of a thin film

DEFF Research Database (Denmark)

Malac, Marek; Hettler, Simon; Hayashida, Misa

2017-01-01

Detailed simulations are necessary to correctly interpret the charge polarity of electron beam irradiated thin film patch. Relying on systematic simulations we provide guidelines and movies to interpret experimentally the polarity of the charged area, to be understood as the sign of the electrost......Detailed simulations are necessary to correctly interpret the charge polarity of electron beam irradiated thin film patch. Relying on systematic simulations we provide guidelines and movies to interpret experimentally the polarity of the charged area, to be understood as the sign...... of the electrostatic potential developed under the beam with reference to a ground electrode. We discuss the two methods most frequently used to assess charge polarity: Fresnel imaging of the irradiated area and Thon rings analysis. We also briefly discuss parameter optimization for hole free phase plate (HFPP...

Charged-Higgs on R_D"_("_*"_), τ polarization, and FBA

International Nuclear Information System (INIS)

Chen, Chuan-Hung; Nomura, Takaaki

2017-01-01

We study the influence of a charged-Higgs on the excess of branching fraction ratio, R_M = BR(anti B → Mτ anti ν_τ)/BR(anti B → Ml anti ν_l) (M = D, D*), in a generic two-Higgs-doublet model. In order to investigate the lepton polarization, the detailed decay amplitudes with lepton helicity are given. When the charged-Higgs is used to resolve excesses, it is found that two independent Yukawa couplings are needed to explain the R_D and R_D_* anomalies. We show that when the upper limit of BR(B_c → τ anti ν_τ) < 30% is included, R_D can be significantly enhanced while R_D_* < 0.27. With the BR(B_c → τ anti ν_τ) constraint, we find that the τ-lepton polarizations can be still affected by the charged-Higgs effects, where the standard model (SM) predictions are obtained: P"τ_D ∼ 0.324 and P"τ_D_* ∼ -0.500, and they can be enhanced to be P"τ_D ∼ 0.5 and P"τ_D_* ∼ -0.41 by the charged-Higgs. The integrated lepton forward-backward asymmetry (FBA) is also studied, where the SM result is anti A"D""(""*"")","τ_F_B ∼ -0.359(0.064), and they can be enhanced (decreased) to be anti A"D""(""*"")","τ_F_B ∼ -0.33(0.02). (orig.)

Coupled spin and charge collective excitations in a spin polarized electron gas

International Nuclear Information System (INIS)

Marinescu, D.C.; Quinn, J.J.; Yi, K.S.

1997-01-01

The charge and longitudinal spin responses induced in a spin polarized quantum well by a weak electromagnetic field are investigated within the framework of the linear response theory. The authors evaluate the excitation frequencies for the intra- and inter-subband transitions of the collective charge and longitudinal spin density oscillations including many-body corrections beyond the random phase approximation through the spin dependent local field factors, G σ ± (q,ω). An equation-of-motion method was used to obtain these corrections in the limit of long wavelengths, and the results are given in terms of the equilibrium pair correlation function. The finite degree of spin polarization is shown to introduce coupling between the charge and spin density modes, in contrast with the result for an unpolarized system

Self-screening of the quantum confined Stark effect by the polarization induced bulk charges in the quantum barriers

International Nuclear Information System (INIS)

Zhang, Zi-Hui; Liu, Wei; Ju, Zhengang; Tiam Tan, Swee; Ji, Yun; Kyaw, Zabu; Zhang, Xueliang; Wang, Liancheng; Wei Sun, Xiao; Volkan Demir, Hilmi

2014-01-01

InGaN/GaN light-emitting diodes (LEDs) grown along the polar orientations significantly suffer from the quantum confined Stark effect (QCSE) caused by the strong polarization induced electric field in the quantum wells, which is a fundamental problem intrinsic to the III-nitrides. Here, we show that the QCSE is self-screened by the polarization induced bulk charges enabled by designing quantum barriers. The InN composition of the InGaN quantum barrier graded along the growth orientation opportunely generates the polarization induced bulk charges in the quantum barrier, which well compensate the polarization induced interface charges, thus avoiding the electric field in the quantum wells. Consequently, the optical output power and the external quantum efficiency are substantially improved for the LEDs. The ability to self-screen the QCSE using polarization induced bulk charges opens up new possibilities for device engineering of III-nitrides not only in LEDs but also in other optoelectronic devices.

Self-screening of the quantum confined Stark effect by the polarization induced bulk charges in the quantum barriers

Energy Technology Data Exchange (ETDEWEB)

Zhang, Zi-Hui; Liu, Wei; Ju, Zhengang; Tiam Tan, Swee; Ji, Yun; Kyaw, Zabu; Zhang, Xueliang; Wang, Liancheng; Wei Sun, Xiao, E-mail: exwsun@ntu.edu.sg, E-mail: volkan@stanfordalumni.org [LUMINOUS Centre of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronic Engineering, School of Physical and Mathematical Sciences, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Volkan Demir, Hilmi, E-mail: exwsun@ntu.edu.sg, E-mail: volkan@stanfordalumni.org [LUMINOUS Centre of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronic Engineering, School of Physical and Mathematical Sciences, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Department of Electrical and Electronics, Department of Physics, and UNAM-Institute of Material Science and Nanotechnology, Bilkent University, TR-06800 Ankara (Turkey)

2014-06-16

InGaN/GaN light-emitting diodes (LEDs) grown along the polar orientations significantly suffer from the quantum confined Stark effect (QCSE) caused by the strong polarization induced electric field in the quantum wells, which is a fundamental problem intrinsic to the III-nitrides. Here, we show that the QCSE is self-screened by the polarization induced bulk charges enabled by designing quantum barriers. The InN composition of the InGaN quantum barrier graded along the growth orientation opportunely generates the polarization induced bulk charges in the quantum barrier, which well compensate the polarization induced interface charges, thus avoiding the electric field in the quantum wells. Consequently, the optical output power and the external quantum efficiency are substantially improved for the LEDs. The ability to self-screen the QCSE using polarization induced bulk charges opens up new possibilities for device engineering of III-nitrides not only in LEDs but also in other optoelectronic devices.

Nuclear-charge polarization at scission in fission from moderately excited light-actinide nuclei

International Nuclear Information System (INIS)

Nishinaka, Ichiro

2009-01-01

Fragment mass yields and the average neutron multiplicity in the proton-induced fission of 232 Th and 238 U were measured by a double time-of-flight method. The most probable charges of secondary fragments were evaluated from the fragment mass yields measured by the double time-of-flight method and the fractional cumulative and independent yields reported in literature. The nuclear-charge polarization of primary fragments at scission was obtained by correcting the most probable charge of secondary fragments for neutron evaporation. The results show that the nuclear-charge polarization at scission is associated with the liquid-drop properties of nuclei and the proton shell effect with Z = 50 of heavy fragments and that it is practically insensitive to mass and excitation energy of the fissioning nucleus in the region of light-actinide nuclei. (author)

Polarized parton distributions from charged-current deep-inelastic scattering

International Nuclear Information System (INIS)

Ridolfi, G

2003-01-01

We investigate the capabilities of a neutrino factory in the determination of polarized parton distributions from charged-current deep-inelastic scattering experiments, with special attention to the accuracy of this kind of measurements. We show that a neutrino factory would allow to distinguish between different theoretical scenarios for the proton spin structure

Metallicity at interphase boundaries due to polar catastrophe induced by charge density discontinuity

KAUST Repository

Albar, Arwa

2018-02-09

The electronic properties of interphase boundaries are of basic importance for most materials, particularly when those properties deviate strongly from the bulk behavior. We introduce a mechanism that can result in metallicity at stoichiometric interphase boundaries between semiconductors based on the idea of polar catastrophe, which is usually considered only in the context of heterostructures. To this end, we perform ab initio calculations within density functional theory to investigate the electronic states at stoichiometric SnO/SnO2 (110) interphase boundaries. In this system, one would not expect polar catastrophe to have a role according to state-of-the-art theory because the interface lacks formal charge discontinuity. However, we observe the formation of a hole gas between the semiconductors SnO and SnO2. To explain these findings, we provide a generalized theory based on the idea that the charge density discontinuity between SnO and SnO2, a consequence of lattice mismatch, drives a polar catastrophe scenario. As a result, SnO/SnO2 (110) interphase boundaries can develop metallicity depending on the grain size. The concept of metallicity due to polar catastrophe induced by charge density discontinuity is of general validity and applies to many interphase boundaries with lattice mismatch.

Applying electric field to charged and polar particles between metallic plates: extension of the Ewald method.

Science.gov (United States)

Takae, Kyohei; Onuki, Akira

2013-09-28

We develop an efficient Ewald method of molecular dynamics simulation for calculating the electrostatic interactions among charged and polar particles between parallel metallic plates, where we may apply an electric field with an arbitrary size. We use the fact that the potential from the surface charges is equivalent to the sum of those from image charges and dipoles located outside the cell. We present simulation results on boundary effects of charged and polar fluids, formation of ionic crystals, and formation of dipole chains, where the applied field and the image interaction are crucial. For polar fluids, we find a large deviation of the classical Lorentz-field relation between the local field and the applied field due to pair correlations along the applied field. As general aspects, we clarify the difference between the potential-fixed and the charge-fixed boundary conditions and examine the relationship between the discrete particle description and the continuum electrostatics.

Magnetic Field Generation through Angular Momentum Exchange between Circularly Polarized Radiation and Charged Particles

CERN Document Server

Shvets, G

2002-01-01

The interaction between circularly polarized (CP) radiation and charged particles can lead to generation of magnetic field through an inverse Faraday effect. The spin of the circularly polarized electromagnetic wave can be converted into the angular momentum of the charged particles so long as there is dissipation. We demonstrate this by considering two mechanisms of angular momentum absorption relevant for laser-plasma interactions: electron-ion collisions and ionization. The precise dissipative mechanism, however, plays a role in determining the efficiency of the magnetic field generation.

Magnetic Field Generation through Angular Momentum Exchange between Circularly Polarized Radiation and Charged Particles

International Nuclear Information System (INIS)

G. Shvets; N.J. Fisch; J.-M. Rax

2002-01-01

The interaction between circularly polarized (CP) radiation and charged particles can lead to generation of magnetic field through an inverse Faraday effect. The spin of the circularly polarized electromagnetic wave can be converted into the angular momentum of the charged particles so long as there is dissipation. We demonstrate this by considering two mechanisms of angular momentum absorption relevant for laser-plasma interactions: electron-ion collisions and ionization. The precise dissipative mechanism, however, plays a role in determining the efficiency of the magnetic field generation

Polarization of Λ hyperons produced inclusively in v p andbar v p charged current interactions

Science.gov (United States)

Jones, G. T.; Kennedy, B. W.; O'Neale, S. W.; Böckmann, K.; Gebel, W.; Geich-Gimbel, C.; Nellen, B.; Cooper-Sarkar, A. M.; Grant, A.; Klein, H.; Morrison, D. R. O.; Schmid, P.; Wachsmuth, H.; Barnham, K. W. J.; Clayton, E. F.; Miller, D. B.; Mobayyen, M. M.; Villalobos-Baillie, O.; Aderholz, M.; Deck, L.; Schmitz, N.; Settles, R.; Wernhard, K. L.; Wittek, W.; Corrigan, G.; Myatt, G.; Radojicic, D.; Saitta, B.; Wells, J.

1985-03-01

Lambda hyperons from v p andbar v p charged current interactions have been analysed for polarization. A significant polarization is observed for Λ particles in the quasi-elastic region for both types of interactions. Part of this polarization is due to the decay of highly polarized Σ(1385) resonances. The results are compared with simple predictions of the quark parton model.

Polarized fine structure in the excitation spectrum of a negatively charged quantum dot

OpenAIRE

Ware, M. E.; Stinaff, E. A.; Gammon, D.; Doty, M. F.; Bracker, A. S.; Gershoni, D.; Korenev, V. L.; Badescu, S. C.; Lyanda-Geller, Y.; Reinecke, T. L.

2005-01-01

We report polarized photoluminescence excitation spectroscopy of the negative trion in single charge tunable InAs/GaAs quantum dots. The spectrum exhibits a p-shell resonance with polarized fine structure arising from the direct excitation of the electron spin triplet states. The energy splitting arises from the axially symmetric electron-hole exchange interaction. The magnitude and sign of the polarization are understood from the spin character of the triplet states and a small amount of qua...

Optical pumping and negative luminescence polarization in charged GaAs quantum dots

Science.gov (United States)

Shabaev, Andrew; Stinaff, Eric A.; Bracker, Allan S.; Gammon, Daniel; Efros, Alexander L.; Korenev, Vladimir L.; Merkulov, Igor

2009-01-01

Optical pumping of electron spins and negative photoluminescence polarization are observed when interface quantum dots in a GaAs quantum well are excited nonresonantly by circularly polarized light. Both observations can be explained by the formation of long-lived dark excitons through hole spin relaxation in the GaAs quantum well prior to exciton capture. In this model, optical pumping of resident electron spins is caused by capture of dark excitons and recombination in charged quantum dots. Negative polarization results from accumulation of dark excitons in the quantum well and is enhanced by optical pumping. The dark exciton model describes the experimental results very well, including intensity and bias dependence of the photoluminescence polarization and the Hanle effect.

DeVelopment of the high-intensity polarized H- source with proton charge exchange on sodium optically oriented atoms

International Nuclear Information System (INIS)

Zelenskij, A.N.; Kokhanovskij, S.A.

1982-01-01

The results of experimental study on the source of polarized H - ions at polarized electron capture by proton from optically oriented sodium atoms are presented. Circular-polarized dye laser radiation with lamp pumping is used for polarization of highly dense sodium vapors in the pulsed mode. A facility for polarization measurement in the ion source is described. Dependence of the counting rate of metastables for the right and left circular radiation polarization in respect to wave length is presented. The results of measuring the degree of polarization under change of sodium density are revealed. The measurements have disclosed that obtaining of high polarization degree at 20-30% charge exchange effectiveness is possible but large radiation power is required. Use of a dense charge exchange target provides high effectiveness of hte whole polarization process. Yield of polarized H - ions can approach 10 μA/1 mA of the initial proton current

Polarization of Λ hyperons produced inclusively in νp and anti νp charged current interactions

International Nuclear Information System (INIS)

Jones, G.T.; Kennedy, B.W.; O'Neale, S.W.; Barnham, K.W.J.; Clayton, E.F.; Miller, D.B.; Mobayyen, M.M.; Villalobos-Baillie, O.; Corrigan, G.; Myatt, G.; Radojicic, D.; Saitta, B.; Wells, J.; Aderholz, M.; Deck, L.; Schmitz, N.; Settles, R.; Wernhard, K.L.; Wittek, W.

1985-01-01

Lambda hyperons from νp and anti np charged current interactions have been analysed for polarization. A significant polarization is observed for Λ particles in the quasi-elastic region for both types of interactions. Part of this polarization is due to the decay of highly polarized Σ(1385) resonances. The results are compared with simple predictions of the quark parton model. (orig.)

Polarization of Λ hyperons produced inclusively in νp and anti νp charged current interactions

International Nuclear Information System (INIS)

Jones, G.T.; Kennedy, B.W.; O'Neale, S.W.; Barnham, K.W.J.; Clayton, E.F.; Miller, D.B.; Mobayyen, M.M.; Villalobos-Baillie, O.; Corrigan, G.; Myatt, G.; Radojicic, D.; Saitta, B.; Wells, J.

1985-01-01

Lambda hyperons from νp charged current interactions have been analysed for polarization. A significant polarization is observed for Λ particles in the quasi-elastic region for both types of interactions. Part of this polarization is due to the decay of highly polarized phi(1,385) resonances. The results are compared with simple predictions of the quark parton model. (orig.)

Polarization effects in radiative recombination of an electron with a highly charged ion

International Nuclear Information System (INIS)

Klasnikov, A.E.; Shabaev, V.M.; Artemyev, A.N.; Kovtun, A.V.; Stoehlker, T.

2005-01-01

The radiative recombination of an unpolarized electron with a polarized highly charged H-like ion in its ground state is studied. The absolute and relative values of the electron spin-flip contribution to the cross section of the process for various scattering angles and photon polarizations are calculated. It is shown that, in addition to the forward and backward directions, there are some other scattering angles of the emitted photon, where, at a fixed linear photon polarization, the spin-flip transition gives a dominant contribution to the differential cross section

Direct visualization of polarization reversal of organic ferroelectric memory transistor by using charge modulated reflectance imaging

Science.gov (United States)

Otsuka, Takako; Taguchi, Dai; Manaka, Takaaki; Iwamoto, Mitsumasa

2017-11-01

By using the charge modulated reflectance (CMR) imaging technique, charge distribution in the pentacene organic field-effect transistor (OFET) with a ferroelectric gate insulator [P(VDF-TrFE)] was investigated in terms of polarization reversal of the P(VDF-TrFE) layer. We studied the polarization reversal process and the carrier spreading process in the OFET channel. The I-V measurement showed a hysteresis behavior caused by the spontaneous polarization of P(VDF-TrFE), but the hysteresis I-V curve changes depending on the applied drain bias, possibly due to the gradual shift of the polarization reversal position in the OFET channel. CMR imaging visualized the gradual shift of the polarization reversal position and showed that the electrostatic field formed by the polarization of P(VDF-TrFE) contributes to hole and electron injection into the pentacene layer and the carrier distribution is significantly dependent on the direction of the polarization. The polarization reversal position in the channel region is governed by the electrostatic potential, and it happens where the potential reaches the coercive voltage of P(VDF-TrFE). The transmission line model developed on the basis of the Maxwell-Wagner effect element analysis well accounts for this polarization reversal process in the OFET channel.

Macroscopic polarization in crystalline dielectrics: the geometric phase approach

International Nuclear Information System (INIS)

Resta, R.

1994-01-01

The macroscopic electric polarization of a crystal is often defined as the dipole of a unit cell. In fact, such a dipole moment is ill defined, and the above definition is incorrect. Looking more closely, the quantity generally measured is differential polarization, defined with respect to a ''reference state'' of the same material. Such differential polarizations include either derivatives of the polarization (dielectric permittivity, Born effective charges, piezoelectricity, pyroelectricity) or finite differences (ferroelectricity). On the theoretical side, the differential concept is basic as well. Owing to continuity, a polarization difference is equivalent to a macroscopic current, which is directly accessible to the theory as a bulk property. Polarization is a quantum phenomenon and cannot be treated with a classical model, particularly whenever delocalized valence electrons are present in the dielectric. In a quantum picture, the current is basically a property of the phase of the wave functions, as opposed to the charge, which is a property of their modulus. An elegant and complete theory has recently been developed by King-Smith and Vanderbilt, in which the polarization difference between any two crystal states--in a null electric field--takes the form of a geometric quantum phase. This gives a comprehensive account of this theory, which is relevant for dealing with transverse-optic phonons, piezoelectricity, and ferroelectricity. Its relation to the established concepts of linear-response theory is also discussed. Within the geometric phase approach, the relevant polarization difference occurs as the circuit integral of a Berry connection (or ''vector potential''), while the corresponding curvature (or ''magnetic field'') provides the macroscopic linear response

Polarization of X rays of multiply charged ions in dense high-temperature plasma

NARCIS (Netherlands)

Baronova, EO; Dolgov, AN; Yakubovskii, LK

2004-01-01

The development of a method for studying the features of X-ray emission by multiply charged ions in a dense hot plasma is considered. These features are determined by the radiation polarization phenomenon.

Charge-Dipole Acceleration of Polar Gas Molecules towards Charged Nanoparticles: Involvement in Powerful Charge-Induced Catalysis of Heterophase Chemical Reactions and Ball Lightning Phenomenon

Directory of Open Access Journals (Sweden)

Oleg Meshcheryakov

2010-01-01

Full Text Available In humid air, the substantial charge-dipole attraction and electrostatic acceleration of surrounding water vapour molecules towards charged combustible nanoparticles cause intense electrostatic hydration and preferential oxidation of these nanoparticles by electrostatically accelerated polar water vapour molecules rather than nonaccelerated nonpolar oxygen gas molecules. Intense electrostatic hydration of charged combustible nanoparticles converts the nanoparticle's oxide-based shells into the hydroxide-based electrolyte shells, transforming these nanoparticles into reductant/air core-shell nanobatteries, periodically short-circuited by intraparticle field and thermionic emission. Partially synchronized electron emission breakdowns within trillions of nanoparticles-nanobatteries turn a cloud of charged nanoparticles-nanobatteries into a powerful radiofrequency aerosol generator. Electrostatic oxidative hydration and charge-catalyzed oxidation of charged combustible nanoparticles also contribute to a self-oscillating thermocycling process of evolution and periodic autoignition of inflammable gases near to the nanoparticle's surface. The described effects might be of interest for the improvement of certain nanotechnological heterophase processes and to better understand ball lightning phenomenon.

Polarization correction in the theory of energy losses by charged particles

Energy Technology Data Exchange (ETDEWEB)

Makarov, D. N., E-mail: makarovd0608@yandex.ru; Matveev, V. I. [Lomonosov Northern (Arctic) Federal University (Russian Federation)

2015-05-15

A method for finding the polarization (Barkas) correction in the theory of energy losses by charged particles in collisions with multielectron atoms is proposed. The Barkas correction is presented in a simple analytical form. We make comparisons with experimental data and show that applying the Barkas correction improves the agreement between theory and experiment.

Polarization Energies at Organic–Organic Interfaces: Impact on the Charge Separation Barrier at Donor–Acceptor Interfaces in Organic Solar Cells

KAUST Repository

Ryno, Sean

2016-05-31

We probe the energetic landscape at a model pentacene/fullerene-C60 interface to investigate the interactions between positive and negative charges, which are critical to the processes of charge separation and recombination in organic solar cells. Using a polarizable force field, we find that polarization energy, i.e. the stabilization a charge feels due to its environment, is larger at the interface than in the bulk for both a positive and a negative charge. The combination of the charge being more stabilized at the interface and the Coulomb attraction between the charges, results in a barrier to charge separation at the pentacene-C60 interface that can be in excess of 0.7 eV for static configurations of the donor and acceptor locations. However, the impact of molecular motions, i.e., the dynamics, at the interface at room temperature results in a distribution of polarization energies and in charge separation barriers that can be significantly reduced. The dynamic nature of the interface is thus critical, with the polarization energy distributions indicating that sites along the interface shift in time between favorable and unfavorable configurations for charge separation.

Polarized Fine Structure in the Photoluminescence Excitation Spectrum of a Negatively Charged Quantum Dot

Science.gov (United States)

Ware, M. E.; Stinaff, E. A.; Gammon, D.; Doty, M. F.; Bracker, A. S.; Gershoni, D.; Korenev, V. L.; Bădescu, Ş. C.; Lyanda-Geller, Y.; Reinecke, T. L.

2005-10-01

We report polarized photoluminescence excitation spectroscopy of the negative trion in single charge-tunable InAs/GaAs quantum dots. The spectrum exhibits a p-shell resonance with polarized fine structure arising from the direct excitation of the electron spin triplet states. The energy splitting arises from the axially symmetric electron-hole exchange interaction. The magnitude and sign of the polarization are understood from the spin character of the triplet states and a small amount of quantum dot asymmetry, which mixes the wave functions through asymmetric e-e and e-h exchange interactions.

Charge-Shift Corrected Electronegativities and the Effect of Bond Polarity and Substituents on Covalent-Ionic Resonance Energy.

Science.gov (United States)

James, Andrew M; Laconsay, Croix J; Galbraith, John Morrison

2017-07-13

Bond dissociation energies and resonance energies for H n A-BH m molecules (A, B = H, C, N, O, F, Cl, Li, and Na) have been determined in order to re-evaluate the concept of electronegativity in the context of modern valence bond theory. Following Pauling's original scheme and using the rigorous definition of the covalent-ionic resonance energy provided by the breathing orbital valence bond method, we have derived a charge-shift corrected electronegativity scale for H, C, N, O, F, Cl, Li, and Na. Atomic charge shift character is defined using a similar approach resulting in values of 0.42, 1.06, 1.43, 1.62, 1.64, 1.44, 0.46, and 0.34 for H, C, N, O, F, Cl, Li, and Na, respectively. The charge-shift corrected electronegativity values presented herein follow the same general trends as Pauling's original values with the exception of Li having a smaller value than Na (1.57 and 1.91 for Li and Na respectively). The resonance energy is then broken down into components derived from the atomic charge shift character and polarization effects. It is then shown that most of the resonance energy in the charge-shift bonds H-F, H 3 C-F, and Li-CH 3 and borderline charge-shift H-OH is associated with polarity rather than the intrinsic atomic charge-shift character of the bonding species. This suggests a rebranding of these bonds as "polar charge-shift" rather than simply "charge-shift". Lastly, using a similar breakdown method, it is shown that the small effect the substituents -CH 3 , -NH 2 , -OH, and -F have on the resonance energy (<10%) is mostly due to changes in the charge-shift character of the bonding atom.

Polarization properties of linearly polarized parabolic scaling Bessel beams

Energy Technology Data Exchange (ETDEWEB)

Guo, Mengwen; Zhao, Daomu, E-mail: zhaodaomu@yahoo.com

2016-10-07

The intensity profiles for the dominant polarization, cross polarization, and longitudinal components of modified parabolic scaling Bessel beams with linear polarization are investigated theoretically. The transverse intensity distributions of the three electric components are intimately connected to the topological charge. In particular, the intensity patterns of the cross polarization and longitudinal components near the apodization plane reflect the sign of the topological charge. - Highlights: • We investigated the polarization properties of modified parabolic scaling Bessel beams with linear polarization. • We studied the evolution of transverse intensity profiles for the three components of these beams. • The intensity patterns of the cross polarization and longitudinal components can reflect the sign of the topological charge.

Theory of space-charge polarization for determining ionic constants of electrolytic solutions

Science.gov (United States)

Sawada, Atsushi

2007-06-01

A theoretical expression of the complex dielectric constant attributed to space-charge polarization has been derived under an electric field calculated using Poisson's equation considering the effects of bound charges on ions. The frequency dependence of the complex dielectric constant of chlorobenzene solutions doped with tetrabutylammonium tetraphenylborate (TBATPB) has been analyzed using the theoretical expression, and the impact of the bound charges on the complex dielectric constant has been clarified quantitatively in comparison with a theory that does not consider the effect of the bound charges. The Stokes radius of TBA +(=TPB-) determined by the present theory shows a good agreement with that determined by conductometry in the past; hence, the present theory should be applicable to the direct determination of the mobility of ion species in an electrolytic solution without the need to measure ionic limiting equivalent conductance and transport number.

Metallicity at interphase boundaries due to polar catastrophe induced by charge density discontinuity

KAUST Repository

Albar, Arwa; Tahini, Hassan Ali; Schwingenschlö gl, Udo

2018-01-01

the electronic states at stoichiometric SnO/SnO2 (110) interphase boundaries. In this system, one would not expect polar catastrophe to have a role according to state-of-the-art theory because the interface lacks formal charge discontinuity. However, we observe

Influence of solvent polarization and non-uniform ion size on electrostatic properties between charged surfaces in an electrolyte solution

Science.gov (United States)

Sin, Jun-Sik

2017-12-01

In this paper, we study electrostatic properties between two similar or oppositely charged surfaces immersed in an electrolyte solution by using the mean-field approach accounting for solvent polarization and non-uniform size effects. Applying a free energy formalism accounting for unequal ion sizes and orientational ordering of water dipoles, we derive coupled and self-consistent equations to calculate electrostatic properties between charged surfaces. Electrostatic properties for similarly charged surfaces depend on the counterion size but not on the coion size. Moreover, electrostatic potential and osmotic pressure between similarly charged surfaces are found to be increased with increasing counterion size. On the other hand, the corresponding ones between oppositely charged surfaces are related to both sizes of positive and negative ions. For oppositely charged surfaces, the electrostatic potential, number density of solvent molecules, and relative permittivity of an electrolyte having unequal ion sizes are not symmetric about the centerline between the charged surfaces. For either case, the consideration of solvent polarization results in a decrease in the electrostatic potential and the osmotic pressure compared to the case without the effect.

Spin polarization driven by a charge-density wave in monolayer 1T−TaS2

KAUST Repository

Zhang, Qingyun

2014-08-06

Using first-principles calculations, we investigate the electronic and vibrational properties of monolayer T-phase TaS2. We demonstrate that a charge-density wave is energetically favorable at low temperature, similar to bulk 1T-TaS2. Electron-phonon coupling is found to be essential for the lattice reconstruction. The charge-density wave results in a strong localization of the electronic states near the Fermi level and consequently in spin polarization, transforming the material into a magnetic semiconductor with enhanced electronic correlations. The combination of inherent spin polarization with a semiconducting nature distinguishes the monolayer fundamentally from the bulk compound as well as from other two-dimensional transition metal dichalcogenides. Monolayer T-phase TaS2 therefore has the potential to enable two-dimensional spintronics. © 2014 American Physical Society.

Spin polarization driven by a charge-density wave in monolayer 1T−TaS2

KAUST Repository

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

2014-01-01

Using first-principles calculations, we investigate the electronic and vibrational properties of monolayer T-phase TaS2. We demonstrate that a charge-density wave is energetically favorable at low temperature, similar to bulk 1T-TaS2. Electron-phonon coupling is found to be essential for the lattice reconstruction. The charge-density wave results in a strong localization of the electronic states near the Fermi level and consequently in spin polarization, transforming the material into a magnetic semiconductor with enhanced electronic correlations. The combination of inherent spin polarization with a semiconducting nature distinguishes the monolayer fundamentally from the bulk compound as well as from other two-dimensional transition metal dichalcogenides. Monolayer T-phase TaS2 therefore has the potential to enable two-dimensional spintronics. © 2014 American Physical Society.

Charge-Transfer States in Organic Solar Cells: Understanding the Impact of Polarization, Delocalization, and Disorder

KAUST Repository

Zheng, Zilong

2017-05-08

We investigate the impact of electronic polarization, charge delocalization, and energetic disorder on the charge-transfer (CT) states formed at a planar C60/pentacene interface. The ability to examine large complexes containing up to seven pentacene molecules and three C60 molecules allows us to take explicitly into account the electronic polarization effects. These complexes are extracted from a bilayer architecture modeled by molecular dynamics simulations and evaluated by means of electronic-structure calculations based on long-range-separated functionals (ωB97XD and BNL) with optimized range-separation parameters. The energies of the lowest charge-transfer states derived for the large complexes are in very good agreement with the experimentally reported values. The average singlet-triplet energy splittings of the lowest CT states are calculated not to exceed 10 meV. The rates of geminate recombination as well as of dissociation of the triplet excitons are also evaluated. In line with experiment, our results indicate that the pentacene triplet excitons generated through singlet fission can dissociate into separated charges on a picosecond time scale, despite the fact that their energy in C60/pentacene heterojunctions is slightly lower than the energies of the lowest CT triplet states.

The use of charge extraction by linearly increasing voltage in polar organic light-emitting diodes

Science.gov (United States)

Züfle, Simon; Altazin, Stéphane; Hofmann, Alexander; Jäger, Lars; Neukom, Martin T.; Schmidt, Tobias D.; Brütting, Wolfgang; Ruhstaller, Beat

2017-05-01

We demonstrate the application of the CELIV (charge carrier extraction by linearly increasing voltage) technique to bilayer organic light-emitting devices (OLEDs) in order to selectively determine the hole mobility in N,N0-bis(1-naphthyl)-N,N0-diphenyl-1,10-biphenyl-4,40-diamine (α-NPD). In the CELIV technique, mobile charges in the active layer are extracted by applying a negative voltage ramp, leading to a peak superimposed to the measured displacement current whose temporal position is related to the charge carrier mobility. In fully operating devices, however, bipolar carrier transport and recombination complicate the analysis of CELIV transients as well as the assignment of the extracted mobility value to one charge carrier species. This has motivated a new approach of fabricating dedicated metal-insulator-semiconductor (MIS) devices, where the extraction current contains signatures of only one charge carrier type. In this work, we show that the MIS-CELIV concept can be employed in bilayer polar OLEDs as well, which are easy to fabricate using most common electron transport layers (ETLs), like Tris-(8-hydroxyquinoline)aluminum (Alq3). Due to the macroscopic polarization of the ETL, holes are already injected into the hole transport layer below the built-in voltage and accumulate at the internal interface with the ETL. This way, by a standard CELIV experiment only holes will be extracted, allowing us to determine their mobility. The approach can be established as a powerful way of selectively measuring charge mobilities in new materials in a standard device configuration.

Long-Term Charge/Discharge Cycling Stability of MnO2 Aqueous Supercapacitor under Positive Polarization

KAUST Repository

Ataherian, Fatemeh; Wu, Nae-Lih

2011-01-01

The long-term charge/discharge cycling stability of MnO 2 electrode under positive polarization in aqueous KCl electrolyte has been studied over different potential windows spanning from the open circuit potential to varied higher-end potential

Measurement of the {lambda}-bar polarization in {nu}{sub {mu}} charged current interactions in the NOMAD experiment

Energy Technology Data Exchange (ETDEWEB)

Astier, P.; Autiero, D.; Baldisseri, A.; Baldo-Ceolin, M.; Banner, M.; Bassompierre, G.; Besson, N.; Bird, I.; Blumenfeld, B.; Bobisut, F.; Bouchez, J.; Boyd, S.; Bueno, A.; Bunyatov, S.; Camilleri, L.; Cardini, A.; Cattaneo, P.W.; Cavasinni, V.; Cervera-Villanueva, A.; Chukanov, A.; Collazuol, G.; Conforto, G.; Conta, C.; Contalbrigo, M.; Cousins, R.; Daniels, D.; Degaudenzi, H.; Del Prete, T.; De Santo, A.; Dignan, T.; Di Lella, L.; Couto e Silva, E. do; Dumarchez, J.; Ellis, M.; Fazio, T.; Feldman, G.J.; Ferrari, R.; Ferrere, D.; Flaminio, V.; Fraternali, M.; Gaillard, J.-M.; Gangler, E.; Geiser, A.; Geppert, D.; Gibin, D.; Gninenko, S.; Godley, A.; Gomez-Cadenas, J.-J.; Gosset, J.; Goessling, C.; Gouanere, M.; Grant, A.; Graziani, G.; Guglielmi, A.; Hagner, C.; Hernando, J.; Hubbard, D.; Hurst, P.; Hyett, N.; Iacopini, E.; Joseph, C.; Juget, F.; Kirsanov, M.; Klimov, O.; Kokkonen, J.; Kovzelev, A.; Krasnoperov, A.; Kustov, D.; Kuznetsov, V.; Lacaprara, S.; Lachaud, C.; Lakic, B.; Lanza, A.; La Rotonda, L.; Laveder, M.; Letessier-Selvon, A.; Levy, J.-M.; Linssen, L.; Ljubicic, A.; Long, J.; Lupi, A.; Marchionni, A.; Martelli, F.; Mechain, X.; Mendiburu, J.-P.; Meyer, J.-P.; Mezzetto, M.; Mishra, S.R.; Moorhead, G.F.; Naumov, D.; Nedelec, P.; Nefedov, Yu.; Nguyen-Mau, C.; Orestano, D.; Pastore, F.; Peak, L.S.; Pennacchio, E.; Pessard, H.; Petti, R.; Placci, A.; Polesello, G.; Pollmann, D.; Polyarush, A.; Popov, B. E-mail: boris.popov@cern.ch; Poulsen, C.; Rico, J.; Riemann, P.; Roda, C.; Rubbia, A.; Salvatore, F.; Schahmaneche, K.; Schmidt, B.; Schmidt, T.; Sevior, M.; Sillou, D.; Soler, F.J.P.; Sozzi, G.; Steele, D.; Stiegler, U.; Stipcevic, M.; Stolarczyk, Th.; Tareb-Reyes, M.; Taylor, G.N.; Tereshchenko, V.; Toropin, A.; Touchard, A.-M.; Tovey, S.N.; Tran, M.-T.; Tsesmelis, E.; Ulrichs, J.; Vacavant, L.; Valdata-Nappi, M.; Valuev, V.; Vannucci, F.; Varvell, K.E.; Veltri, M.; Vercesi, V.; Vidal-Sitjes, G.; Vieira, J.-M.; Vinogradova, T.; Weber, F.V.[and others

2001-07-02

We present a measurement of the polarization of {lambda}-bar hyperons produced in {nu}{sub {mu}} charged current interactions. The full data sample from the NOMAD experiment has been analyzed using the same V{sup 0} identification procedure and analysis method reported in a previous paper [NOMAD Collaboration, Nucl. Phys. B 588 (2000) 3] for the case of {lambda} hyperons. The {lambda}-bar polarization has been measured for the first time in a neutrino experiment. The polarization vector is found to be compatible with zero.

Polar order in nanostructured organic materials

Science.gov (United States)

Sayar, M.; Olvera de la Cruz, M.; Stupp, S. I.

2003-02-01

Achiral multi-block liquid crystals are not expected to form polar domains. Recently, however, films of nanoaggregates formed by multi-block rodcoil molecules were identified as the first example of achiral single-component materials with macroscopic polar properties. By solving an Ising-like model with dipolar and asymmetric short-range interactions, we show here that polar domains are stable in films composed of aggregates as opposed to isolated molecules. Unlike classical molecular systems, these nanoaggregates have large intralayer spacings (a approx 8 nm), leading to a reduction in the repulsive dipolar interactions which oppose polar order within layers. In finite-thickness films of nanostructures, this effect enables the formation of polar domains. We compute exactly the energies of the possible structures consistent with the experiments as a function of film thickness at zero temperature (T). We also provide Monte Carlo simulations at non-zero T for a disordered hexagonal lattice that resembles the smectic-like packing in these nanofilms.

Dynamics of space and polarization charges of ferroelectric thin films measured by atomic force microscopy

International Nuclear Information System (INIS)

Oh, Y.J.; Lee, J.H.; Jo, W.

2006-01-01

Retention behavior and local hysteresis characteristics in Pb(Zr 0.52 Ti 0.48 )O 3 (PZT) thin films on Pt electrodes have been investigated by electrostatic force microscopy (EFM). A sol-gel method is used to synthesize PZT thin films and drying conditions are carefully explored over a wide range of temperature. Decay and retention mechanisms of single-poled and reverse-poled regions of the ferroelectric thin films are explained by space charge redistribution. Trapping behavior of space charges is dependent on the nature of interface between ferroelectric thin films and bottom electrodes. Local measurement of polarization-electric field curves by EFM shows inhomogeneous space charge entrapment

Polarization transfer in x-ray transitions due to photoionization in highly charged copper-like ions

Science.gov (United States)

Ma, Kun; Chen, Zhan-Bin; Xie, Lu-You; Dong, Chen-Zhong

2018-02-01

Using the density matrix theory and the multi-configuration Dirac-Fock method, the 3{d}3/2 subshell photoionization of highly charged ions is studied, together with their subsequent radiative decay. The effects of polarization transfer on the linear polarization and angular distribution of the 3{d}94{s}2{}2{D}3/2\\to 3{d}104p{}2{P}1/2 characteristic line photoemission for selected Cu-like Zn+, Ba27+, {{{W}}}45+, and {{{U}}}63+ ions are investigated. Our results show that the polarization transfer, arising from the originally polarized incident light, may lead to a considerable change in the alignment parameters and the polarization properties of the radiation, the character of which is highly sensitive to the initial photon polarization, yet virtually independent of the photon energy. These characteristics are very similar to those of the electron bremsstrahlung process reported by Märtin et al (2012 Phys. Rev. Lett. 108 264801). The present results are compared with available experimental results and show a good quantitative agreement.

Electronic structure, Born effective charges and spontaneous polarization in magnetoelectric gallium ferrite

International Nuclear Information System (INIS)

Roy, Amritendu; Garg, Ashish; Mukherjee, Somdutta; Gupta, Rajeev; Prasad, Rajendra; Auluck, Sushil

2011-01-01

We present a theoretical study of the structure-property correlation in gallium ferrite, based on first-principles calculations followed by a subsequent comparison with experiments. The local spin density approximation (LSDA + U) of the density functional theory has been used to calculate the ground state structure, electronic band structure, density of states and Born effective charges. The calculations reveal that the ground state structure is orthorhombic Pc 2 1 n having A-type antiferromagnetic spin configuration, with lattice parameters matching well with those obtained experimentally. Plots of the partial density of states of constituent ions exhibit noticeable hybridization of Fe 3d, Ga 4s, Ga 4p and O 2p states. However, the calculated charge density and electron localization function show a largely ionic character of the Ga/Fe-O bonds which is also supported by a lack of any significant anomaly in the calculated Born effective charges with respect to the corresponding nominal ionic charges. The calculations show a spontaneous polarization of ∼ 59 μC cm -2 along the b-axis which is largely due to asymmetrically placed Ga1, Fe1, O1, O2 and O6 ions.

Charged-Higgs on R{sub D}{sup {sub (}{sub *}{sub )}}, τ polarization, and FBA

Energy Technology Data Exchange (ETDEWEB)

Chen, Chuan-Hung [National Cheng-Kung University, Department of Physics, Tainan (China); Nomura, Takaaki [KIAS, School of Physics, Seoul (Korea, Republic of)

2017-09-15

We study the influence of a charged-Higgs on the excess of branching fraction ratio, R{sub M} = BR(anti B → Mτ anti ν{sub τ})/BR(anti B → Ml anti ν{sub l}) (M = D, D*), in a generic two-Higgs-doublet model. In order to investigate the lepton polarization, the detailed decay amplitudes with lepton helicity are given. When the charged-Higgs is used to resolve excesses, it is found that two independent Yukawa couplings are needed to explain the R{sub D} and R{sub D*} anomalies. We show that when the upper limit of BR(B{sub c} → τ anti ν{sub τ}) < 30% is included, R{sub D} can be significantly enhanced while R{sub D*} < 0.27. With the BR(B{sub c} → τ anti ν{sub τ}) constraint, we find that the τ-lepton polarizations can be still affected by the charged-Higgs effects, where the standard model (SM) predictions are obtained: P{sup τ}{sub D} ∼ 0.324 and P{sup τ}{sub D*} ∼ -0.500, and they can be enhanced to be P{sup τ}{sub D} ∼ 0.5 and P{sup τ}{sub D*} ∼ -0.41 by the charged-Higgs. The integrated lepton forward-backward asymmetry (FBA) is also studied, where the SM result is anti A{sup D{sup ({sup *{sup ),τ}{sub FB}}}} ∼ -0.359(0.064), and they can be enhanced (decreased) to be anti A{sup D{sup ({sup *{sup ),τ}{sub FB}}}} ∼ -0.33(0.02). (orig.)

Polarization of electron-beam irradiated LDPE films: contribution to charge generation and transport

Science.gov (United States)

Banda, M. E.; Griseri, V.; Teyssèdre, G.; Le Roy, S.

2018-04-01

Electron-beam irradiation is an alternative way to generate charges in insulating materials, at controlled position and quantity, in order to monitor their behaviour in regard to transport phenomena under the space charge induced electric field or external field applied. In this study, low density polyethylene (LDPE) films were irradiated by a 80 keV electron-beam with a flux of 1 nA cm‑2 during 10 min in an irradiation chamber under vacuum conditions, and were then characterized outside the chamber using three experimental methods. The electrical behaviour of the irradiated material was assessed by space charge measurements using the pulsed electro-acoustic (PEA) method under dc stress. The influence of the applied electric field polarity and amplitude has been tested in order to better understand the charge behaviour after electron-beam irradiation. Fourier transform infra-red spectroscopy (FTIR) and photoluminescence (PL) measurements were performed to evaluate the impact of the electron beam irradiation, i.e. deposited charges and energy, on the chemical structure of the irradiated samples. The present results show that the electrical behaviour in LDPE after irradiation is mostly driven by charges, i.e. by physical process functions of the electric field, and that changes in the chemical structure seems to be mild.

Dynamic simulation of charging processes in polar dielectrics irradiated by the electron bunches of middle level energy

International Nuclear Information System (INIS)

Maslovskaya, A.G.

2011-01-01

Nowadays the scanning electron microscopy techniques are widely used practically in condenser matter physics to study properties and structure of solids. The electron probe of scanning electron microscope is not merely a passive indicator of the geometrical or potential profile of the sample surface, but also the source producing ionizing, electric and thermal action on the sample. The application of raster electron methods to polar materials, responding to electric and heat exposures of the electron bunches allows us to get a response and create new modes of image formation. Let assume, that a sample surface of dielectric is irradiated by thin focused electron bunches of middle level energy (with order 1÷50 keV). When electrons bombard the dielectric sample the accumulation of absorbed electrons occurs. As a result generated charged areas can irregular drift the initial bunches. Charging effect occurs at any magnifications and any actual probe current. This work considers the results of dynamic simulation of charging process in polar dielectrics under the investigation with the scanning electron microscope. The purpose of present study is design and model implementation of three-dimensional dynamic model of charge relaxation in polar materials irradiated by electron bunches of middle level energy. The mathematical problem definition is given by the system of the continuity equation and Poisson equation. Final system of equations was modified in terms of intrinsic radiation-induced conductivity in sample as well as cylindrical symmetry of the problem. The simulation is based on numerical method solving of boundary problem for partial derivative equation system. In addition the initial electron distribution is determined by Monte-Carlo method using the programming implementation. To solve this problem we used the computational methods of solution of nonstationary mathematical physics problem such as finite difference method and finite element method realized with

Tridodecylamine, an efficient charge control agent in non-polar media for electrophoretic inks application

Science.gov (United States)

Noel, Amélie; Mirbel, Déborah; Cloutet, Eric; Fleury, Guillaume; Schatz, Christophe; Navarro, Christophe; Hadziioannou, Georges; CyrilBrochon

2018-01-01

In order to obtain efficient electrophoretic inks, Tridodecylamine (Dod3N), has been studied as charge control agent (CCA) in a non-polar paraffin solvent (Isopar G) for various inorganic pigments (TiO2 and Fe2O3). All hydrophobic mineral oxides, i.e. treated with octyltrimethoxysilane (C8) or dodecyltrimethoxysilane (C12), were found to be negatively charged in presence of Dod3N. The electrophoretic mobilities of inorganic pigments seemed to be strongly dependent of their isoelectric point (IEP) and also of the concentration of dod3N with an optimum range between 10 and 20 mM depending on the pigments. Finally, an electrophoretic ink constituted of hydrophobic mineral oxides in presence of Dod3N was tested in a device. Its efficiency as charge control agent to negatively charge hydrophobic particles was confirmed through good optical properties and fast response time (220 ms at 200 kV m-1).

Charge polarization effects and hole spectra characteristics in AlxGa1-xN/GaN superlattices

International Nuclear Information System (INIS)

Assaoui, Fatna; Pereyra, Pedro

2001-10-01

We study the effects of charge polarization on the extended physical properties of superlattices, such as transmission coefficients and valence band structure. We consider both linear and parabolic modulation of the band edge. Based on the theory of finite periodic systems (TFPS), analytic expressions and high precision calculations of the relevant physical quantities for n-cell systems are obtained. New and also well-known features of these systems are identified. Besides the well-known energy bandstructure, we also have the field bandstructure, with interesting characteristics. Wider field gaps at stronger internal electric fields and higher density of field bands for larger layer widths are some of these characteristics. Well defined level density asymmetries identify the minibands induced by charge polarization or the so-called Quantum Confining Stark Effect. We present the n-cell transmission amplitudes, transmission coefficients and miniband structures for different values of the relevant parameters. (author)

Charge and Polarity Preferences for N-Glycosylation: A Genome-Wide In Silico Study and Its Implications Regarding Constitutive Proliferation and Adhesion of Carcinoma Cells.

Science.gov (United States)

Manwar Hussain, Muhammad Ramzan; Iqbal, Zeeshan; Qazi, Wajahat M; Hoessli, Daniel C

2018-01-01

The structural and functional diversity of the human proteome is mediated by N - and O- linked glycosylations that define the individual properties of extracellular and membrane-associated proteins. In this study, we utilized different computational tools to perform in silico based genome-wide mapping of 1,117 human proteins and unravel the contribution of both penultimate and vicinal amino acids for the asparagine-based, site-specific N -glycosylation. Our results correlate the non-canonical involvement of charge and polarity environment of classified amino acids (designated as L, O, A, P, and N groups) in the N -glycosylation process, as validated by NetNGlyc predictions, and 130 literature-reported human proteins. From our results, particular charge and polarity combinations of non-polar aliphatic, acidic, basic, and aromatic polar side chain environment of both penultimate and vicinal amino acids were found to promote the N -glycosylation process. However, the alteration in side-chain charge and polarity environment of genetic variants, particularly in the vicinity of Asn-containing epitope, may induce constitutive glycosylation (e.g., aberrant glycosylation at preferred and non-preferred sites) of membrane proteins causing constitutive proliferation and triggering epithelial-to-mesenchymal transition. The current genome-wide mapping of 1,117 proteins (2,909 asparagine residues) was used to explore charge- and polarity-based mechanistic constraints in N -glycosylation, and discuss alterations of the neoplastic phenotype that can be ascribed to N -glycosylation at preferred and non-preferred sites.

Nonlinear waves in viscoelastic magnetized complex astroplasmas with polarized dust-charge variations

Directory of Open Access Journals (Sweden)

Papari Das

2018-01-01

Full Text Available A nonextensive nonthermal magnetized viscoelastic astrofluid, compositionally containing nonthermal electrons and ions together with massive polarized dust micro-spherical grains of variable electric charge, is allowed to endure weakly nonlinear perturbation around its equilibrium. The nonextensivity originating from the large-scale non-local effects is included via the Tsallis thermo-statistical distribution laws describing the lighter species. Assuming the equilibrium as a homogeneous hydrostatic one, the dust polarization effects are incorporated via the conventional homogeneous polarization force law. The perturbed fluid model evolves as a unique conjugate pair of coupled extended Korteweg-de Vries (e-KdV equations. A constructed numerical tapestry shows the collective excitations of a new pair of distinct classes of nonlinear mode structures in new parametric space. The first family indicates periodic electrostatic compressive eigenmodes in the form of soliton-chains. Likewise, the second one reveals gravitational rarefactive solitary patterns. Their microphysical multi-parametric dependencies of the eigen-patterns are illustratively analyzed and bolstered. The paper ends up with some promising implications and applications in the astro-cosmo-plasmic context of wave-induced accretive triggering processes responsible for gravitationally bounded (gravito-condensed astro-structure formation, such as stellesimals, planetsimals, etc.

Nonlinear waves in viscoelastic magnetized complex astroplasmas with polarized dust-charge variations

Science.gov (United States)

Das, Papari; Karmakar, Pralay Kumar

2018-01-01

A nonextensive nonthermal magnetized viscoelastic astrofluid, compositionally containing nonthermal electrons and ions together with massive polarized dust micro-spherical grains of variable electric charge, is allowed to endure weakly nonlinear perturbation around its equilibrium. The nonextensivity originating from the large-scale non-local effects is included via the Tsallis thermo-statistical distribution laws describing the lighter species. Assuming the equilibrium as a homogeneous hydrostatic one, the dust polarization effects are incorporated via the conventional homogeneous polarization force law. The perturbed fluid model evolves as a unique conjugate pair of coupled extended Korteweg-de Vries (e-KdV) equations. A constructed numerical tapestry shows the collective excitations of a new pair of distinct classes of nonlinear mode structures in new parametric space. The first family indicates periodic electrostatic compressive eigenmodes in the form of soliton-chains. Likewise, the second one reveals gravitational rarefactive solitary patterns. Their microphysical multi-parametric dependencies of the eigen-patterns are illustratively analyzed and bolstered. The paper ends up with some promising implications and applications in the astro-cosmo-plasmic context of wave-induced accretive triggering processes responsible for gravitationally bounded (gravito-condensed) astro-structure formation, such as stellesimals, planetsimals, etc.

Electronic device for measuring the polarization parameter in the π-p → π0n charge exchange reaction on a polarized proton target

International Nuclear Information System (INIS)

Brehin, S.

1967-12-01

An electronic apparatus has been constructed to measure the polarization parameter P 0 (t) in π - p → π 0 n charge exchange scattering at 5.9 GeV/c and 11,2 GeV/c on polarized proton target. This device insures triggering of a heavy plate spark chamber, allowing visualisation of γ rays from the π 0 decays when the associated neutron offers suitable characteristics in direction and energy. The neutron is detected by an array of 32 counters and his energy is measured by a time of flight method. Electronic circuits of this apparatus are described as test and calibration methods used. (author) [fr

Polar surface energies of iono-covalent materials: implications of a charge-transfer model tested on Li2FeSiO4 surfaces.

Science.gov (United States)

Hörmann, Nicolas G; Groß, Axel

2014-07-21

The ionic compounds that are used as electrode materials in Li-based rechargeable batteries can exhibit polar surfaces that in general have high surface energies. We derive an analytical estimate for the surface energy of such polar surfaces assuming charge redistribution as a polarity compensating mechanism. The polar contribution to the converged surface energy is found to be proportional to the bandgap multiplied by the surface charge necessary to compensate for the depolarization field, and some higher order correction terms that depend on the specific surface. Other features, such as convergence behavior, coincide with published results. General conclusions are drawn on how to perform polar surface energy calculations in a slab configuration and upper boundaries of "purely" polar surface energies are estimated. Furthermore, we compare these findings with results obtained in a density functional theory study of Li(2)FeSiO(4) surfaces. We show that typical polar features are observed and provide a decomposition of surface energies into polar and local bond-cutting contributions for 29 different surfaces. We show that the model is able to explain subtle differences of GGA and GGA+U surface energy calculations. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A next-to-leading determination of the singlet axial charge and the polarized gluon content of the nucleon

CERN Document Server

Ball, R D; Ridolfi, G

1996-01-01

We perform a full next-to-leading analysis of the the available experimental data on the polarized structure function g_1 of the nucleon, and give a precise determination of its singlet axial charge together with a thorough assessment of the theoretical uncertainties. We find that the data are now sufficient to separately determine first moments of the polarized quark and gluon distributions and show in particular that the gluon contribution is large and positive.

Controlling charge on levitating drops.

Science.gov (United States)

Hilger, Ryan T; Westphall, Michael S; Smith, Lloyd M

2007-08-01

Levitation technologies are used in containerless processing of materials, as microscale manipulators and reactors, and in the study of single drops and particles. Presented here is a method for controlling the amount and polarity of charge on a levitating drop. The method uses single-axis acoustic levitation to trap and levitate a single, initially neutral drop with a diameter between 400 microm and 2 mm. This drop is then charged in a controllable manner using discrete packets of charge in the form of charged drops produced by a piezoelectric drop-on-demand dispenser equipped with a charging electrode. The magnitude of the charge on the dispensed drops can be adjusted by varying the voltage applied to the charging electrode. The polarity of the charge on the added drops can be changed allowing removal of charge from the trapped drop (by neutralization) and polarity reversal. The maximum amount of added charge is limited by repulsion of like charges between the drops in the trap. This charging scheme can aid in micromanipulation and the study of charged drops and particles using levitation.

Charging process analysis of an opposed-piston two-stroke aircraft Diesel engine

Directory of Open Access Journals (Sweden)

Grabowski Łukasz

2017-01-01

Full Text Available This paper presents the research results on a 1D model of an opposed-piston two-stroke aircraft Diesel engine. The research aimed at creating a model of the engine in question to investigate how engine performance is affected by the compressor gear ratio. The power was constant at all the operating points. The research results are presented as graphs of power consumed by the compressor, compressor efficiency and brake specific fuel consumption. The optimal range of compressor gear ratio in terms of engine efficiency was defined from the research results.

Multiply charged negative ions of hydrogen in linearly polarized laser fields

International Nuclear Information System (INIS)

van Duijn, E.; Muller, H.G.

1997-01-01

Motivated by the prediction of the appearance of atomic multiply charged negative ions (AMCNI) of hydrogen, induced by a linearly polarized laser field, we present an analytical quantum mechanical treatment of the appearance and structure of AMCNI in a linearly polarized field, based on high-frequency Floquet theory (HFFT). For the simplest AMCNI of hydrogen, H 2- and H 3- , the values of α 0 at which the first bound state appears are α 0 =1.62x10 2 and α 0 =1.02x10 4 , where α 0 =I 1/2 /ω 2 is the amplitude of the oscillation of a free electron in the field with frequency ω and intensity I (unless stated otherwise, we use atomic units throughout this paper). Whereas in vacuum at least one of the electrons of an AMCNI autodetaches, an intense high-frequency field can change the character of the ion dramatically, such that bound states of AMCNI can appear. Due to the interaction with the field, the electrons of the AMCNI oscillate in phase along the polarization axis. This open-quotes quiverclose quotes motion enables the electrons to be spatially separated over distances of order α 0 , reducing the repulsive e-e interaction as α 0 increases. In other words, for α 0 large enough, the field enables a configuration in which the electrons, while widely separated, are bound to one proton. For the prediction of bound states of H N- with N>3, however, a relativistic description or low-frequency theory is required. copyright 1997 The American Physical Society

Charge orders in organic charge-transfer salts

International Nuclear Information System (INIS)

Kaneko, Ryui; Valentí, Roser; Tocchio, Luca F; Becca, Federico

2017-01-01

Motivated by recent experimental suggestions of charge-order-driven ferroelectricity in organic charge-transfer salts, such as κ -(BEDT-TTF) 2 Cu[N(CN) 2 ]Cl, we investigate magnetic and charge-ordered phases that emerge in an extended two-orbital Hubbard model on the anisotropic triangular lattice at 3/4 filling. This model takes into account the presence of two organic BEDT-TTF molecules, which form a dimer on each site of the lattice, and includes short-range intramolecular and intermolecular interactions and hoppings. By using variational wave functions and quantum Monte Carlo techniques, we find two polar states with charge disproportionation inside the dimer, hinting to ferroelectricity. These charge-ordered insulating phases are stabilized in the strongly correlated limit and their actual charge pattern is determined by the relative strength of intradimer to interdimer couplings. Our results suggest that ferroelectricity is not driven by magnetism, since these polar phases can be stabilized also without antiferromagnetic order and provide a possible microscopic explanation of the experimental observations. In addition, a conventional dimer-Mott state (with uniform density and antiferromagnetic order) and a nonpolar charge-ordered state (with charge-rich and charge-poor dimers forming a checkerboard pattern) can be stabilized in the strong-coupling regime. Finally, when electron–electron interactions are weak, metallic states appear, with either uniform charge distribution or a peculiar 12-site periodicity that generates honeycomb-like charge order. (paper)

Measurement of the polarized forward-backward asymmetry of B quarks using momentum-weighted track charge at SLD

International Nuclear Information System (INIS)

Junk, T.R.

1995-11-01

This thesis presents a direct measurement of the parity-violating parameter A b by analyzing the polarized forward-backward asymmetry of b quarks in e + e - → Z 0 → b bar b. Data were taken at the Stanford Linear Accelerator Center (SLAC), with the Stanford Large Detector (SLD), which records the products of e + e - interactions at a center of mass energy √s = 91.2 GeV/c 2 at the SLAC Linear Collider (SLC). The SLC/SLD experimental apparatus provides a unique and ideal environment for measuring electroweak asymmetries. Heavy flavor decays of the Z 0 were identified inclusively by taking advantage of the long lifetime of B hadrons, the small, stable SLC beam spot, and SLD's precise tracking detectors. Two analysis techniques for measuring A b are presented: a binned fit to the left-right forward-backwards asymmetry of tagged events signed with momentum-weighted track charge, and a self-calibrating maximum-likelihood technique using momentum-weighted charge from the two hemispheres in each tagged event. From our 1994-1995 sample of 3.6 pb -1 , having a luminosity-weighted average e - polarization of 77.3%, and our 1993 sample of 1.8 pb -1 , having a luminosity-weighted polarization of 63.1%, we obtain A b = 0.848 ± 0.046(stat.) ± 0.050(syst.)

Coin Tossing Explains the Activity of Opposing Microtubule Motors on Phagosomes.

Science.gov (United States)

Sanghavi, Paulomi; D'Souza, Ashwin; Rai, Ashim; Rai, Arpan; Padinhatheeri, Ranjith; Mallik, Roop

2018-05-07

How the opposing activity of kinesin and dynein motors generates polarized distribution of organelles inside cells is poorly understood and hotly debated [1, 2]. Possible explanations include stochastic mechanical competition [3, 4], coordinated regulation by motor-associated proteins [5-7], mechanical activation of motors [8], and lipid-induced organization [9]. Here, we address this question by using phagocytosed latex beads to generate early phagosomes (EPs) that move bidirectionally along microtubules (MTs) in an in vitro assay [9]. Dynein/kinesin activity on individual EPs is recorded as real-time force generation of the motors against an optical trap. Activity of one class of motors frequently coincides with, or is rapidly followed by opposite motors. This leads to frequent and rapid reversals of EPs in the trap. Remarkably, the choice between dynein and kinesin can be explained by the tossing of a coin. Opposing motors therefore appear to function stochastically and independently of each other, as also confirmed by observing no effect on kinesin function when dynein is inhibited on the EPs. A simple binomial probability calculation based on the geometry of EP-microtubule contact explains the observed activity of dynein and kinesin on phagosomes. This understanding of intracellular transport in terms of a hypothetical coin, if it holds true for other cargoes, provides a conceptual framework to explain the polarized localization of organelles inside cells. Copyright © 2018 The Author(s). Published by Elsevier Ltd.. All rights reserved.

A salt water battery with high stability and charging rates made from solution processed conjugated polymers with polar side chains

KAUST Repository

Moia, Davide; Giovannitti, Alexander; Szumska, Anna A.; Schnurr, Martin; Rezasoltani, Elham; Maria, Iuliana P.; Barnes, Piers R. F.; McCulloch, Iain; Nelson, Jenny

2017-01-01

conjugated polymer backbones, allowed the films to maintain constant capacity at high charge and discharge rates (>1000 C-rate). The electrodes also show good stability during electrochemical cycling (less than 30% decrease in capacity over >1000 cycles) and an output voltage up to 1.4 V. The performance of these semiconducting polymers with polar side-chains demonstrates the potential of this material class for fast-charging, water based electrochemical energy storage devices.

LO-TO splittings, effective charges and interactions in electro-optic meta-nitroaniline crystal as studied by polarized IR reflection and transmission spectra

Science.gov (United States)

Szostak, M. M.; Le Calvé, N.; Romain, F.; Pasquier, B.

1994-10-01

The polarized IR reflection spectra of the meta-nitroaniline ( m-NA) single crystal along the a, b and c crystallographic axes as well as the b and c polarized transmission spectra have been measured in the 100-400 cm -1 region. The LO-TO splitting values have been calculated from the reflection spectra by fitting them with the four parameter dielectric function. The dipole moment derivatives, relevant to dynamic effective charges, of the vibrations have also been calculated and used to check the applicability of the oriented gas model (OGM) to reflection spectra. The discrepancies from the OGM have been discussed in terms of vibronic couplings, weak hydrogen bondings (HB) and intramolecular charge transfer.

Charge-transport simulations in organic semiconductors

Energy Technology Data Exchange (ETDEWEB)

May, Falk

2012-07-06

In this thesis we have extended the methods for microscopic charge-transport simulations for organic semiconductors, where weak intermolecular interactions lead to spatially localized charge carriers, and the charge transport occurs as an activated hopping process between diabatic states. In addition to weak electronic couplings between these states, different electrostatic environments in the organic material lead to a broadening of the density of states for the charge energies which limits carrier mobilities. The contributions to the method development include (i) the derivation of a bimolecular charge-transfer rate, (ii) the efficient evaluation of intermolecular (outer-sphere) reorganization energies, (iii) the investigation of effects of conformational disorder on intramolecular reorganization energies or internal site energies and (iv) the inclusion of self-consistent polarization interactions for calculation of charge energies. These methods were applied to study charge transport in amorphous phases of small molecules used in the emission layer of organic light emitting diodes (OLED). When bulky substituents are attached to an aromatic core in order to adjust energy levels or prevent crystallization, a small amount of delocalization of the frontier orbital to the substituents can increase electronic couplings between neighboring molecules. This leads to improved charge-transfer rates and, hence, larger charge-mobility. We therefore suggest using the mesomeric effect (as opposed to the inductive effect) when attaching substituents to aromatic cores, which is necessary for example in deep blue OLEDs, where the energy levels of a host molecule have to be adjusted to those of the emitter. Furthermore, the energy landscape for charges in an amorphous phase cannot be predicted by mesoscopic models because they approximate the realistic morphology by a lattice and represent molecular charge distributions in a multipole expansion. The microscopic approach shows that

QCD analysis of light charged Higgs production through polarized top quark decay in two different frames

Energy Technology Data Exchange (ETDEWEB)

Nejad, S. Mohammad Moosavi [Faculty of Physics, Yazd University,P.O. Box 89195-741, Yazd (Iran, Islamic Republic of); School of Particles and Accelerators, Institute for Research in Fundamental Sciences (IPM),P.O. Box 19395-5531, Tehran (Iran, Islamic Republic of); Abbaspour, S. [Faculty of Physics, Yazd University,P.O. Box 89195-741, Yazd (Iran, Islamic Republic of)

2017-03-09

Light and heavy charged Higgs bosons are predicted by many models with an extended Higgs sector such as the two-Higgs-doublet model (2HDM). Searches for the charged Higgs bosons have been done by the ATLAS and the CMS experiments at the Large Hadron Collider (LHC) in proton-proton collision. However, a definitive search of charged Higgs bosons still has to be carried out by the LHC experiments. The experimental observation of charged Higgs bosons would indicate physics beyond the Standard Model. In the present work we study the O(α{sub s}) correction to the energy spectrum of the inclusive bottom-flavored mesons (X{sub b}) in polarized top quark decays into a light charged Higgs boson (m{sub H{sup +}}charged Higgs bosons. To present our phenomenological predictions, we restrict ourselves to the constraints on the m{sub H{sup +}}−tan β parameter space determined by the recent results of the CMS and the ATLAS collaborations.

Incorporation of charge transfer into the explicit polarization fragment method by grand canonical density functional theory.

Science.gov (United States)

Isegawa, Miho; Gao, Jiali; Truhlar, Donald G

2011-08-28

Molecular fragmentation algorithms provide a powerful approach to extending electronic structure methods to very large systems. Here we present a method for including charge transfer between molecular fragments in the explicit polarization (X-Pol) fragment method for calculating potential energy surfaces. In the conventional X-Pol method, the total charge of each fragment is preserved, and charge transfer between fragments is not allowed. The description of charge transfer is made possible by treating each fragment as an open system with respect to the number of electrons. To achieve this, we applied Mermin's finite temperature method to the X-Pol wave function. In the application of this method to X-Pol, the fragments are open systems that partially equilibrate their number of electrons through a quasithermodynamics electron reservoir. The number of electrons in a given fragment can take a fractional value, and the electrons of each fragment obey the Fermi-Dirac distribution. The equilibrium state for the electrons is determined by electronegativity equalization with conservation of the total number of electrons. The amount of charge transfer is controlled by re-interpreting the temperature parameter in the Fermi-Dirac distribution function as a coupling strength parameter. We determined this coupling parameter so as to reproduce the charge transfer energy obtained by block localized energy decomposition analysis. We apply the new method to ten systems, and we show that it can yield reasonable approximations to potential energy profiles, to charge transfer stabilization energies, and to the direction and amount of charge transferred. © 2011 American Institute of Physics

Polarized secondary radioactive beams

International Nuclear Information System (INIS)

Zaika, N.I.

1992-01-01

Three methods of polarized radioactive nuclei beam production: a) a method nuclear interaction of the non-polarized or polarized charged projectiles with target nuclei; b) a method of polarization of stopped reaction radioactive products in a special polarized ion source with than following acceleration; c) a polarization of radioactive nuclei circulating in a storage ring are considered. Possible life times of the radioactive ions for these methods are determined. General schemes of the polarization method realizations and depolarization problems are discussed

Inertial polarization of dielectrics

OpenAIRE

Zavodovsky, A. G.

2011-01-01

It was proved that accelerated motion of a linear dielectric causes its polarization. Accelerated translational motion of a dielectric's plate leads to the positive charge of the surface facing the direction of motion. Metal plates of a capacitor were used to register polarized charges on a dielectric's surface. Potential difference between the capacitor plates is proportional to acceleration, when acceleration is constant potential difference grows with the increase of a dielectric's area, o...

Measurement of the polarized forward-backward asymmetry of B quarks using momentum-weighted track charge at SLD

Energy Technology Data Exchange (ETDEWEB)

Junk, Thomas Robert [Stanford Univ., CA (United States)

1995-11-01

This thesis presents a direct measurement of the parity-violating parameter A_b by analyzing the polarized forward-backward asymmetry of b quarks in e⁺e^- → Z⁰ → b$\\bar{b}$. Data were taken at the Stanford Linear Accelerator Center (SLAC), with the Stanford Large Detector (SLD), which records the products of e⁺e^- interactions at a center of mass energy √s = 91.2 GeV/c² at the SLAC Linear Collider (SLC). The SLC/SLD experimental apparatus provides a unique and ideal environment for measuring electroweak asymmetries. Heavy flavor decays of the Z⁰ were identified inclusively by taking advantage of the long lifetime of B hadrons, the small, stable SLC beam spot, and SLD`s precise tracking detectors. Two analysis techniques for measuring A_b are presented: a binned fit to the left-right forward-backwards asymmetry of tagged events signed with momentum-weighted track charge, and a self-calibrating maximum-likelihood technique using momentum-weighted charge from the two hemispheres in each tagged event. From our 1994-1995 sample of 3.6 pb^-1, having a luminosity-weighted average e^- polarization of 77.3%, and our 1993 sample of 1.8 pb^-1, having a luminosity-weighted polarization of 63.1%, we obtain A_b = 0.848 ± 0.046(stat.) ± 0.050(syst.).

The net charge at interfaces between insulators

International Nuclear Information System (INIS)

Bristowe, N C; Littlewood, P B; Artacho, Emilio

2011-01-01

The issue of the net charge at insulating oxide interfaces is briefly reviewed with the ambition of dispelling myths of such charges being affected by covalency and related charge density effects. For electrostatic analysis purposes, the net charge at such interfaces is defined by the counting of discrete electrons and core ion charges, and by the definition of the reference polarization of the separate, unperturbed bulk materials. The arguments are illustrated for the case of a thin film of LaAlO 3 over SrTiO 3 in the absence of free carriers, for which the net charge is exactly 0.5e per interface formula unit, if the polarization response in both materials is referred to zero bulk values. Further consequences of the argument are extracted for structural and chemical alterations of such interfaces, in which internal rearrangements are distinguished from extrinsic alterations (changes of stoichiometry, redox processes), only the latter affecting the interfacial net charge. The arguments are reviewed alongside the proposal of Stengel and Vanderbilt (2009 Phys. Rev. B 80 241103) of using formal polarization values instead of net interfacial charges, based on the interface theorem of Vanderbilt and King-Smith (1993 Phys. Rev. B 48 4442-55). Implications for non-centrosymmetric materials are discussed, as well as for interfaces for which the charge mismatch is an integer number of polarization quanta. (viewpoint)

Suzaku and XMM-Newton observations of the North Polar Spur: Charge exchange or ISM absorption?

Science.gov (United States)

Gu, Liyi; Mao, Junjie; Costantini, Elisa; Kaastra, Jelle

2016-10-01

By revisiting the Suzaku and XMM-Newton data of the North Polar Spur, we discovered that the spectra are inconsistent with the traditional model consisting of pure thermal emission and neutral absorption. The most prominent discrepancies are the enhanced O vii and Ne ix forbidden-to-resonance ratios, and a high O viii Lyβ line relative to other Lyman series. A collisionally ionized absorption model can naturally explain both features, while a charge exchange component can only account for the former. By including the additional ionized absorption, the plasma in the North Polar Spur can be described by a single-phase collisional ionization equilibrium (CIE) component with a temperature of 0.25 keV, and nitrogen, oxygen, neon, magnesium, and iron abundances of 0.4-0.8 solar. The abundance pattern of the North Polar Spur is well in line with those of the Galactic halo stars. The high nitrogen-to-oxygen ratio reported in previous studies can be migrated to the large transmission of the O viii Lyα line. The ionized absorber is characterized by a balance temperature of 0.17-0.20 keV and a column density of 3-5 × 1019 cm-2. Based on the derived abundances and absorption, we speculate that the North Polar Spur is a structure in the Galactic halo, so that the emission is mostly absorbed by the Galactic interstellar medium in the line of sight.

What Protein Charging (and Supercharging) Reveal about the Mechanism of Electrospray Ionization

Science.gov (United States)

Ogorzalek Loo, Rachel R.; Lakshmanan, Rajeswari; Loo, Joseph A.

2014-10-01

Understanding the charging mechanism of electrospray ionization is central to overcoming shortcomings such as ion suppression or limited dynamic range, and explaining phenomena such as supercharging. Towards that end, we explore what accumulated observations reveal about the mechanism of electrospray. We introduce the idea of an intermediate region for electrospray ionization (and other ionization methods) to account for the facts that solution charge state distributions (CSDs) do not correlate with those observed by ESI-MS (the latter bear more charge) and that gas phase reactions can reduce, but not increase, the extent of charging. This region incorporates properties (e.g., basicities) intermediate between solution and gas phase. Assuming that droplet species polarize within the high electric field leads to equations describing ion emission resembling those from the equilibrium partitioning model. The equations predict many trends successfully, including CSD shifts to higher m/z for concentrated analytes and shifts to lower m/z for sprays employing smaller emitter opening diameters. From this view, a single mechanism can be formulated to explain how reagents that promote analyte charging ("supercharging") such as m-NBA, sulfolane, and 3-nitrobenzonitrile increase analyte charge from "denaturing" and "native" solvent systems. It is suggested that additives' Brønsted basicities are inversely correlated to their ability to shift CSDs to lower m/z in positive ESI, as are Brønsted acidities for negative ESI. Because supercharging agents reduce an analyte's solution ionization, excess spray charge is bestowed on evaporating ions carrying fewer opposing charges. Brønsted basicity (or acidity) determines how much ESI charge is lost to the agent (unavailable to evaporating analyte).

Modelling molecular adsorption on charged or polarized surfaces: a critical flaw in common approaches.

Science.gov (United States)

Bal, Kristof M; Neyts, Erik C

2018-03-28

A number of recent computational material design studies based on density functional theory (DFT) calculations have put forward a new class of materials with electrically switchable chemical characteristics that can be exploited in the development of tunable gas storage and electrocatalytic applications. We find systematic flaws in almost every computational study of gas adsorption on polarized or charged surfaces, stemming from an improper and unreproducible treatment of periodicity, leading to very large errors of up to 3 eV in some cases. Two simple corrective procedures that lead to consistent results are proposed, constituting a crucial course correction to the research in the field.

Observer-dependent sign inversions of polarization singularities.

Science.gov (United States)

Freund, Isaac

2014-10-15

We describe observer-dependent sign inversions of the topological charges of vector field polarization singularities: C points (points of circular polarization), L points (points of linear polarization), and two virtually unknown singularities we call γ(C) and α(L) points. In all cases, the sign of the charge seen by an observer can change as she changes the direction from which she views the singularity. Analytic formulas are given for all C and all L point sign inversions.

Polarized Photocathode R&D for Future Linear Collliders

Energy Technology Data Exchange (ETDEWEB)

Zhou, F; Brachmann, A.; Maruyama, T.; Sheppard, J.C.; /SLAC

2009-01-23

It is a challenge to generate full charge electrons from the electron sources without compromising polarization for the proposed ILC and CLIC. It is essential to advance polarized photocathodes to meet the requirements. SLAC has worldwide unique dedicated test facilities, Cathode Test System and dc-Gun Test Laboratory, to fully characterize polarized photocathodes. Recent systematic measurements on a strained-well InAlGaAs/AlGaAs cathode at the facilities show that 87% polarization and 0.3% QE are achieved. The QE can be increased to {approx}1.0% with atomic hydrogen cleaning. The surface charge limit at a very low current intensity and the clear dependence of the polarization on the surface charge limit are observed for the first time. On-going programs to develop photocathodes for the ILC and CLIC are briefly introduced.

A review of polarized ion sources

International Nuclear Information System (INIS)

Schmor, P.W.

1995-06-01

The two main types of polarized ion sources in use on accelerators today are the Atomic Beam Polarized Ion Source (ABIS) source and the Optically Pumped Polarized Ion Source (OPPIS). Both types can provide beams of nuclearly polarized light ions which are either positively or negatively charged. Heavy ion polarized ion sources for accelerators are being developed. (author). 35 refs., 1 tab

Precision measurement of the cross section of charged-current and neutral current processes at large Q2 at HERA with the polarized-electron beam

International Nuclear Information System (INIS)

Tran, Trong Hieu

2010-03-01

The inclusive cross sections for both charged and neutral current processes have been measured in interactions of longitudinally polarized electrons (positrons) with unpolarized protons using the full data samples collected by H1 at HERA-II. The data taken at a center-of-mass energy of 319 GeV correspond to an integrated luminosity of 149.1 pb -1 and 180.0 pb -1 for e - p and e + p collisions, representing an increase in statistics of a factor of 10 and 2, respectively, over the data from HERA-I. The measured double differential cross sections d 2 σ/dxdQ 2 cover more than two orders of magnitude in both Q 2 , the negative four-momentum transfer squared, up to 30000 GeV 2 , and Bjorken x, down to 0.003. The cross section data are compared to predictions of the Standard Model which is able to provide a good description of the data. The polarization asymmetry as a function of Q 2 is measured with improved precision, confirming the previous observation of P violation effect in neutral current ep scattering at distances down to 10 -18 m. The total cross sections of the charged current process, for Q 2 > 400 GeV 2 and inelasticity y ± beams and different polarization values. Together with the corresponding cross section obtained from the previously published unpolarized data, the polarization dependence of the charged current cross section is measured and found to be in agreement with the Standard Model prediction with the absence of right-handed charged current. The cross sections are combined with previously published data from H1 to obtain the most precise unpolarized measurements. These are used to extract the structure function xF 3 γZ which is sensitive to the valence quark distributions down to low x values. The new cross sections have also been used in a combined electroweak and QCD fit to significantly improve the light quark couplings to the Z-boson than those obtained based on the HERA-I data alone. (orig.)

Interfacial charge-induced polarization switching in Al{sub 2}O{sub 3}/Pb(Zr,Ti)O{sub 3} bi-layer

Energy Technology Data Exchange (ETDEWEB)

Kim, Yu Jin; Park, Min Hyuk; Jeon, Woojin; Kim, Han Joon; Moon, Taehwan; Lee, Young Hwan; Kim, Keum Do; Hyun, Seung Dam; Hwang, Cheol Seong, E-mail: cheolsh@snu.ac.kr [Department of Materials Science & Engineering and Inter-University Semiconductor Research Center, College of Engineering, Seoul National University, Seoul 151-744 (Korea, Republic of)

2015-12-14

Detailed polarization switching behavior of an Al{sub 2}O{sub 3}/Pb(Zr,Ti)O{sub 3} (AO/PZT) structure is examined by comparing the phenomenological thermodynamic model to the experimental polarization–voltage (P-V) results. Amorphous AO films with various thicknesses (2–10 nm) were deposited on the polycrystalline 150-nm-thick PZT film. The thermodynamic calculation showed that the transition from the ferroelectric-like state to the paraelectric-like state with increasing AO thickness occurs at ∼3 nm thickness. This paraelectric-like state should have exhibited a negative capacitance effect without permanent polarization switching if no other adverse effects are involved. However, experiments showed typical ferroelectric-like hysteresis loops where the coercive voltage increased with the increasing AO thickness, which could be explained by the carrier injection through the thin AO layer and trapping of the carriers at the AO/PZT interface. The fitting of the experimental P-V loops using the thermodynamic model considering the depolarization energy effect showed that trapped charge density was ∼±0.1 Cm{sup −2} and critical electric field at the Pt electrode/AO interface, at which the carrier transport occurs, was ∼±10 MV/cm irrespective of the AO thickness. Energy band model at each electrostatic state along the P-V loop was provided to elucidate correlation between macroscopic polarization and internal charge state of the stacked films.

Study of the space-time structure of the leptonic weak charged current by measurement of the muon polarization from the reaction anti νsub(μ)+Fe->X+μ+

International Nuclear Information System (INIS)

Metz, E.

1982-01-01

An experiment for the measurement of the longitudinal polarization of muons was performed which were produced in the deep inelastic anti ν-nucleon scattering in an irontarget (CDHS detector). The muon decay was applied as indicator of the muon polarization. As polarimeter served a marmor-scintillator calorimeter (CHARM detector). The experiment was performed in the broad-band beam of the CERN SPS. Measured was the longitudinal polarization P = 0.82 +- 0.07 (stat.) +- 0.12 (syst.). That means that the weak charged current possesses a dominant vector and/or axial-vector structure. Regarding the measuring errors of the muon polarization an upper limit for possible S-, P-, and T- contributions to the weak charged current can be stated: sigmasub(S,P,T)/sigmasub(TOT) 0.5) relatively to the muon polarization for small y (y 0.5) = 1.10 +- 0.24 (stat.). The systematic error vanishes in this relative measurement. Measured value and error lead to an upper limit for S- and/or P-contributions: sigmasub(S,P):sigmasub(TOT) 2 approx.= 4 (GeV/c) 2 ) a vector and/or axial-vector structure. (orig./HSI) [de

A Classroom Activity for Teaching Electric Polarization of Insulators and Conductors

Science.gov (United States)

Deligkaris, Christos

2018-01-01

The phenomenon of electric polarization is crucial to student understanding of forces exerted between charged objects and insulators or conductors, the process of charging by induction, and the behavior of electroscopes near charged objects. In addition, polarization allows for microscopic-level models of everyday-life macroscopic-level phenomena.…

H- ion current from a polarized vapor target

International Nuclear Information System (INIS)

Cornelius, W.D.

1984-01-01

A method of determining the polarization transferred to hydrogen atoms in charge-exchange reactions is outlined. The method also provides a means of determining target polarizations once the polarization transfer function is known

Electron distribution in polar heterojunctions within a realistic model

Energy Technology Data Exchange (ETDEWEB)

Tien, Nguyen Thanh, E-mail: thanhtienctu@gmail.com [College of Natural Science, Can Tho University, 3-2 Road, Can Tho City (Viet Nam); Thao, Dinh Nhu [Center for Theoretical and Computational Physics, College of Education, Hue University, 34 Le Loi Street, Hue City (Viet Nam); Thao, Pham Thi Bich [College of Natural Science, Can Tho University, 3-2 Road, Can Tho City (Viet Nam); Quang, Doan Nhat [Institute of Physics, Vietnamese Academy of Science and Technology, 10 Dao Tan Street, Hanoi (Viet Nam)

2015-12-15

We present a theoretical study of the electron distribution, i.e., two-dimensional electron gas (2DEG) in polar heterojunctions (HJs) within a realistic model. The 2DEG is confined along the growth direction by a triangular quantum well with a finite potential barrier and a bent band figured by all confinement sources. Therein, interface polarization charges take a double role: they induce a confining potential and, furthermore, they can make some change in other confinements, e.g., in the Hartree potential from ionized impurities and 2DEG. Confinement by positive interface polarization charges is necessary for the ground state of 2DEG existing at a high sheet density. The 2DEG bulk density is found to be increased in the barrier, so that the scattering occurring in this layer (from interface polarization charges and alloy disorder) becomes paramount in a polar modulation-doped HJ.

An omnipotent Li-ion battery charger with multimode control and polarity reversible techniques

Science.gov (United States)

Chen, Jiann-Jong; Ku, Yi-Tsen; Yang, Hong-Yi; Hwang, Yuh-Shyan; Yu, Cheng-Chieh

2016-07-01

The omnipotent Li-ion battery charger with multimode control and polarity reversible techniques is presented in this article. The proposed chip is fabricated with TSMC 0.35μm 2P4M complementary metal-oxide- semiconductor processes, and the chip area including pads is 1.5 × 1.5 mm2. The structure of the omnipotent charger combines three charging modes and polarity reversible techniques, which adapt to any Li-ion batteries. The three reversible Li-ion battery charging modes, including trickle-current charging, large-current charging and constant-voltage charging, can charge in matching polarities or opposite polarities. The proposed circuit has a maximum charging current of 300 mA and the input voltage of the proposed circuit is set to 4.5 V. The maximum efficiency of the proposed charger is about 91% and its average efficiency is 74.8%. The omnipotent charger can precisely provide the charging current to the battery.

The polar 2e/12c bond in phenalenyl-azaphenalenyl hetero-dimers: Stronger stacking interaction and fascinating interlayer charge transfer

Energy Technology Data Exchange (ETDEWEB)

Zhong, Rong-Lin; Li, Zhi-Ru, E-mail: hlxu@nenu.edu.cn, E-mail: lzr@jlu.edu.cn [Institute of Theoretical Chemistry, Jilin University, Changchun 130023 (China); Xu, Hong-Liang, E-mail: hlxu@nenu.edu.cn, E-mail: lzr@jlu.edu.cn [Institute of Functional Material Chemistry, Faculty of Chemistry, Northeast Normal University, Changchun, Jilin 130024 (China)

2016-08-07

An increasing number of chemists have focused on the two-electron/multicenter bond (2e/mc) that was first introduced to interpret the bonding mechanism of radical dimers. Herein, we report the polar two-electron/twelve center (2e/12c) bonding character in a series of phenalenyl-azaphenalenyl radical hetero-dimers. Interestingly, the bonding energy of weaker polar hetero-dimer (P-TAP) is dominated by the overlap of the two different singly occupied molecular orbital of radicals, while that of stronger polar hetero-dimer (P-HAP) is dominated by the electrostatic attraction. Results show that the difference between the electronegativity of the monomers plays a prominent role in the essential attribution of the polar 2e/12c bond. Correspondingly, a stronger stacking interaction in the hetero-dimer could be effectively achieved by increasing the difference of nitrogen atoms number between the monomers. It is worthy of note that an interesting interlayer charge transfer character is induced in the polar hetero-dimers, which is dependent on the difference between the electronegativity of the monomers. It is our expectation that the new knowledge about the bonding nature of radical hetero-dimers might provide important information for designing radical based functional materials with various applications.

Charge loss experiments in surface channel CCD's explained by the McWhorter interface states model

NARCIS (Netherlands)

Penning De Vries, R.G.M.; Wallinga, Hans

1985-01-01

On the basis of the McWhorter interface states model the CCD charge loss is derived as a function of bias charge, signal charge and channel width. As opposed to existing models, the charge loss is now attributed to interface states in the entire gate area, even for high bias charge levels.

Planar density of vacuum charge induced by a supercritical Coulomb potential

Directory of Open Access Journals (Sweden)

V.R. Khalilov

2017-06-01

Full Text Available Analytical expressions for the planar density of an induced vacuum charge are obtained in a strong Coulomb potential in coordinate space. Treatment is based on a self-adjoint extension approach for constructing of the Green's function of a charged fermion in an external electromagnetic field. Induced vacuum charge density is calculated and analyzed in subcritical and supercritical Coulomb potentials for massless and massive fermions. We argue that the virtual and so-called real vacuum polarizations contribute in an induced vacuum charge in a supercritical Coulomb potential. The behavior of the polarization vacuum charge density is investigated at long and short distances from the Coulomb center. The induced vacuum charge has a screening sign. Screening of a Coulomb impurity in graphene is briefly discussed. The real vacuum polarization charge density that acquires the quantum electrodynamics vacuum in a supercritical Coulomb potential due to the real vacuum polarization is calculated. It is shown that the vacuum charge densities essentially differ in massive and massless cases. We expect that our results can, as a matter of principle, be tested in graphene with a supercritical Coulomb impurity.

Planar density of vacuum charge induced by a supercritical Coulomb potential

Energy Technology Data Exchange (ETDEWEB)

Khalilov, V.R., E-mail: khalilov@phys.msu.ru; Mamsurov, I.V.

2017-06-10

Analytical expressions for the planar density of an induced vacuum charge are obtained in a strong Coulomb potential in coordinate space. Treatment is based on a self-adjoint extension approach for constructing of the Green's function of a charged fermion in an external electromagnetic field. Induced vacuum charge density is calculated and analyzed in subcritical and supercritical Coulomb potentials for massless and massive fermions. We argue that the virtual and so-called real vacuum polarizations contribute in an induced vacuum charge in a supercritical Coulomb potential. The behavior of the polarization vacuum charge density is investigated at long and short distances from the Coulomb center. The induced vacuum charge has a screening sign. Screening of a Coulomb impurity in graphene is briefly discussed. The real vacuum polarization charge density that acquires the quantum electrodynamics vacuum in a supercritical Coulomb potential due to the real vacuum polarization is calculated. It is shown that the vacuum charge densities essentially differ in massive and massless cases. We expect that our results can, as a matter of principle, be tested in graphene with a supercritical Coulomb impurity.

Some developments in polarized ion sources

International Nuclear Information System (INIS)

Witteveen, G.J.

1979-01-01

Investigations concerning an atomic beam source are presented and a new polarized ion source of a more universal type is introduced. Polarized and unpolarized beams of positively or negatively charged ions can be produced with this new version and the theoretical limits are a polarized negative hydrogen ion beam with an intensity of about 1 mH and a polarized proton beam with an intensity of 10 mH. (C.F.)

Managing focal fields of vector beams with multiple polarization singularities.

Science.gov (United States)

Han, Lei; Liu, Sheng; Li, Peng; Zhang, Yi; Cheng, Huachao; Gan, Xuetao; Zhao, Jianlin

2016-11-10

We explore the tight focusing behavior of vector beams with multiple polarization singularities, and analyze the influences of the number, position, and topological charge of the singularities on the focal fields. It is found that the ellipticity of the local polarization states at the focal plane could be determined by the spatial distribution of the polarization singularities of the vector beam. When the spatial location and topological charge of singularities have even-fold rotation symmetry, the transverse fields at the focal plane are locally linearly polarized. Otherwise, the polarization state becomes a locally hybrid one. By appropriately arranging the distribution of the polarization singularities in the vector beam, the polarization distributions of the focal fields could be altered while the intensity maintains unchanged.

π--induced single charge exchange on polarized 3He

International Nuclear Information System (INIS)

Zhao, Q.; Burleson, S.; Blanchard, T.

1995-01-01

Asymmetries, A y , for the (π - ,π 0 ) reaction on polarized 3 He were measured using the pion beam of the P3W channel at LAMPF. The π 0 were detected with the new Neutral Meson Spectrometer (NMS) in coincidence with recoiling tritons. The recoil detector consisted of scintillation-counter telescopes and a wire chamber that provided energy-loss and direction information, respectively. The polarized gaseous 3 He target developed at TRIUMF was modified and run with the use of two diode lasers. Polarizations were typically 50%. The A y taken at T π = 200 MeV between 60 and 105 degrees were found to be strongly angle-dependent. The results will be compared with the theoretical predictions

A Classroom Activity for Teaching Electric Polarization of Insulators and Conductors

Science.gov (United States)

Deligkaris, Christos

2018-04-01

The phenomenon of electric polarization is crucial to student understanding of forces exerted between charged objects and insulators or conductors, the process of charging by induction, and the behavior of electroscopes near charged objects. In addition, polarization allows for microscopic-level models of everyday-life macroscopic-level phenomena. Textbooks may adequately discuss polarization, but there is little material in active learning labs and tutorials on this topic. Since polarization of materials is a microscopic phenomenon, instructors often use diagrams and figures on the classroom board to explain the process in a lecture setting. In this paper I will describe a classroom activity where the students play the role of electrons as an alternative option.

The impacts of surface polarity on the solubility of nanoparticle

International Nuclear Information System (INIS)

Zhu, Jianzhuo; Su, Jiguo; Ou, Xinwen; Li, Jingyuan

2016-01-01

In order to study the dependence of water solubility and hydration behavior of nanoparticles on their surface polarity, we designed polar nanoparticles with varying surface polarity by assigning atomic partial charge to the surface of C60. The water solubility of the nanoparticle is enhanced by several orders of magnitude after the introduction of surface polarity. Nevertheless, when the atomic partial charge grows beyond a certain value (q M ), the solubility continuously decreases to the level of nonpolar nanoparticle. It should be noted that such q M is comparable with atomic partial charge of a variety of functional groups. The hydration behaviors of nanoparticles were then studied to investigate the non-monotonic dependence of solubility on the surface polarity. The interaction between the polar nanoparticle and the hydration water is stronger than the nonpolar counterpart, which should facilitate the dissolution of the nanoparticles. On the other hand, the surface polarity also reduces the interaction of hydration water with the other water molecules and enhances the interaction between the nanoparticles which may hinder their dispersion. Besides, the introduction of surface polarity disturbs and even rearranges the hydration structure of nonpolar nanoparticle. Interestingly, the polar nanoparticle with less ordered hydration structure tends to have higher water solubility.

Interfacial polarization phenomena in organic molecular films

International Nuclear Information System (INIS)

Iwamoto, Mitsumasa; Manaka, Takaaki

2006-01-01

Electrostatic phenomena occurring at the interface between metal/organic and organic/organic materials are discussed from the viewpoint of dielectrics physics. Focusing on two important origins of surface polarization phenomena, orientational ordering of polar molecules and displacement of excess charges at the interface, surface polarization phenomena of organic thin films are discussed. To define the orientational order of polar molecules, orientational order parameters are introduced, and surface polarization due to the alignment of dipoles is expressed. The generation of Maxwell displacement current (MDC) and optical second harmonic generation (SHG) that are specific for surface organic monomolecular films are discussed, and some experimental evidence are shown. As an extension of the concept of surface Fermi level introduced to discuss the electrostatic phenomena due to electron transfer at the interface between metal-organic insulators, the surface Fermi level is extended to the discussion on the electrostatic phenomena of organic semiconductor materials on metals. In this paper, some experimental evidence of surface polarization originating from polar molecules and displacement of excess charges are shown. After that, with consideration of these surface phenomena, single electron tunneling of organic films are briefly discussed in association with surface polarization phenomena

Polarized Electrons for Linear Colliders

International Nuclear Information System (INIS)

Clendenin, J.

2004-01-01

Future electron-positron linear colliders require a highly polarized electron beam with a pulse structure that depends primarily on whether the acceleration utilizes warm or superconducting rf structures. The International Linear Collider (ILC) will use cold structures for the main linac. It is shown that a dc-biased polarized photoelectron source such as successfully used for the SLC can meet the charge requirements for the ILC micropulse with a polarization approaching 90%

A salt water battery with high stability and charging rates made from solution processed conjugated polymers with polar side chains

KAUST Repository

Moia, Davide

2017-11-28

We report a neutral salt water based battery which uses p-type and n-type solution processed polymer films as the cathode and the anode of the cell. The specific capacity of the electrodes (approximately 30 mAh cm-3) is achieved via formation of bipolarons in both the p-type and n-type polymers. By engineering ethylene glycol and zwitterion based side chains attached to the polymer backbone we facilitate rapid ion transport through the non-porous polymer films. This, combined with efficient transport of electronic charge via the conjugated polymer backbones, allowed the films to maintain constant capacity at high charge and discharge rates (>1000 C-rate). The electrodes also show good stability during electrochemical cycling (less than 30% decrease in capacity over >1000 cycles) and an output voltage up to 1.4 V. The performance of these semiconducting polymers with polar side-chains demonstrates the potential of this material class for fast-charging, water based electrochemical energy storage devices.

Determining Polarities Of Distant Lightning Strokes

Science.gov (United States)

Blakeslee, Richard J.; Brook, Marx

1990-01-01

Method for determining polarities of lightning strokes more than 400 km away. Two features of signal from each stroke correlated. New method based on fact each stroke observed thus far for which polarity determined unambiguously, initial polarity of tail same as polarity of initial deflection before initial-deflection signal altered by propagation effects. Receiving station equipped with electric-field-change antenna coupled to charge amplifier having time constant of order of 1 to 10 seconds. Output of amplifier fed to signal-processing circuitry, which determines initial polarity of tail.

Effect of polar surfaces on organic molecular crystals

Science.gov (United States)

Sharia, Onise; Tsyshevskiy, Roman; Kuklja, Maija; University of Maryland College Park Team

Polar oxide materials reveal intriguing opportunities in the field of electronics, superconductivity and nanotechnology. While behavior of polar surfaces has been widely studied on oxide materials and oxide-oxide interfaces, manifestations and properties of polar surfaces in molecular crystals are still poorly understood. Here we discover that the polar catastrophe phenomenon, known on oxides, also takes place in molecular materials as illustrated with an example of cyclotetramethylene tetranitramine (HMX) crystals. We show that the surface charge separation is a feasible compensation mechanism to counterbalance the macroscopic dipole moment and remove the electrostatic instability. We discuss the role of surface charge on degradation of polar surfaces, electrical conductivity, optical band-gap closure and surface metallization. Research is supported by the US ONR (Grants N00014-16-1-2069 and N00014-16-1-2346) and NSF. We used NERSC, XSEDE and MARCC computational resources.

Analysis of polarization in hydrogen bonded complexes: An asymptotic projection approach

Science.gov (United States)

Drici, Nedjoua

2018-03-01

The asymptotic projection technique is used to investigate the polarization effect that arises from the interaction between the relaxed, and frozen monomeric charge densities of a set of neutral and charged hydrogen bonded complexes. The AP technique based on the resolution of the original Kohn-Sham equations can give an acceptable qualitative description of the polarization effect in neutral complexes. The significant overlap of the electron densities, in charged and π-conjugated complexes, impose further development of a new functional, describing the coupling between constrained and non-constrained electron densities within the AP technique to provide an accurate representation of the polarization effect.

Polarization versus Temperature in Pyridinium Ionic Liquids

DEFF Research Database (Denmark)

Chaban, V. V.; Prezhdo, O. V.

2014-01-01

Electronic polarization and charge transfer effects play a crucial role in thermodynamic, structural, and transport properties of room-temperature ionic liquids (RTILs). These nonadditive interactions constitute a useful tool for tuning physical chemical behavior of RTILs. Polarization and charge...... interactions changes negligibly between 300 and 900 K, while the average dipole moment increases due to thermal fluctuations of geometries. Our results contribute to the fundamental understanding of electronic effects in the condensed phase of ionic systems and foster progress in physical chemistry...

Surface charge sensing by altering the phase transition in VO2

Science.gov (United States)

Kumar, S.; Esfandyarpour, R.; Davis, R.; Nishi, Y.

2014-08-01

Detection of surface charges has various applications in medicine, electronics, biotechnology, etc. The source of surface charge induction may range from simple charge-polarized molecules like water to complicated proteins. It was recently discovered that surface charge accumulation can alter the temperature at which VO2 undergoes a Mott transition. Here, we deposited polar molecules onto the surface of two-terminal thin-film VO2 lateral devices and monitored the joule-heating-driven Mott transition, or conductance switching. We observed that the power required to induce the conductance switching reduced upon treatment with polar molecules and, using in-situ blackbody-emission direct measurement of local temperature, we show that this reduction in power was accompanied by reduction in the Mott transition temperature. Further evidence suggested that this effect has specificity to the nature of the species used to induce surface charges. Using x-ray absorption spectroscopy, we also show that there is no detectable change in oxidation state of vanadium or structural phase in the bulk of the 40 nm VO2 thin-film even as the phase transition temperature is reduced by up to 20 K by the polar molecules. The ability to alter the phase transition parameters by depositing polar molecules suggests a potential application in sensing surface charges of different origins and this set of results also highlights interesting aspects of the phase transition in VO2.

Circular polarization memory in single Quantum Dots

International Nuclear Information System (INIS)

Khatsevich, S.; Poem, E.; Benny, Y.; Marderfeld, I.; Gershoni, D.; Badolato, A.; Petroff, P. M.

2010-01-01

Under quasi-resonant circularly polarized optical excitation, charged quantum dots may emit polarized light. We measured various transitions with either positive, negative or no circular-polarization memory. We explain these observations and quantitatively calculate the polarization spectrum. Our model use the full configuration-interaction method, including the electron-hole exchange interaction, for calculating the quantum dot's confined many-carrier states, along with one assumption regarding the spin relaxation of photoexcited carriers: Electrons maintain their initial spin polarization, while holes do not.

Measuring top-quark polarization in top-pair + missing-energy events.

Science.gov (United States)

Berger, Edmond L; Cao, Qing-Hong; Yu, Jiang-Hao; Zhang, Hao

2012-10-12

The polarization of a top quark can be sensitive to new physics beyond the standard model. Since the charged lepton from top-quark decay is maximally correlated with the top-quark spin, it is common to measure the polarization from the distribution in the angle between the charged lepton and the top-quark directions. We propose a novel method based on the charged lepton energy fraction and illustrate the method with a detailed simulation of top-quark pairs produced in supersymmetric top squark pair production. We show that the lepton energy ratio distribution that we define is very sensitive to the top-quark polarization but insensitive to the precise measurement of the top-quark energy.

A high intensity Stern-Gerlach polarized hydrogen source for the Munich MP-Tandem laboratory using ECR ionization and charge exchange in cesium vapor

International Nuclear Information System (INIS)

Hertenberger, R.; Eisermann, Y.; Metz, A.; Schiemenz, P.; Graw, G.

2001-01-01

The 14 year old Lamb-Shift hydrogen source of the Munich Tandem laboratory is presently replaced by a newly developed Stern-Gerlach type atomic beam source (ABS) with electron-cyclotron-resonance (ECR) ionization and subsequent double charge exchange in a supersonic cesium vapor jet target. The atomic beam source provides an intensity of 6.4*10 16 atoms/sec of polarized hydrogen and of about 5*10 16 atoms/sec of polarized deuterium. Beam intensities larger than 100 μA were observed for positive H-vector + and D-vector + ion beams after ECR ionization and intensities larger than 10 μA for negative D-vector - ion beams in three magnetic substates

Optically pumped polarized H- ion source

International Nuclear Information System (INIS)

Anderson, L.W.

1986-01-01

The current status and future prospects for the optically pumped polarized H - ion source are discussed. At the present time H - ion currents of 60 μA and with a polarization of 65% have been produced. The ion current and polarization can be increased significantly if the optically pumped Na charge exchange target density and polarization can be increased. Studies of wall surfaces that permit many bounces before depolarizing the Na electron spin and studies of radiation trapping in optically pumped Na indicate that the Na target density and polarization can be increased substantially. 27 refs., 6 figs., 2 tabs

The Physics of Polarization

Science.gov (United States)

Landi Degl'Innocenti, Egidio

2015-10-01

The introductory lecture that has been delivered at this Symposium is a condensed version of an extended course held by the author at the XII Canary Island Winter School from November 13 to November 21, 2000. The full series of lectures can be found in Landi Degl'Innocenti (2002). The original reference is organized in 20 Sections that are here itemized: 1. Introduction, 2. Description of polarized radiation, 3. Polarization and optical devices: Jones calculus and Muller matrices, 4. The Fresnel equations, 5. Dichroism and anomalous dispersion, 6. Polarization in everyday life, 7. Polarization due to radiating charges, 8. The linear antenna, 9. Thomson scattering, 10. Rayleigh scattering, 11. A digression on Mie scattering, 12. Bremsstrahlung radiation, 13. Cyclotron radiation, 14. Synchrotron radiation, 15. Polarization in spectral lines, 16. Density matrix and atomic polarization, 17. Radiative transfer and statistical equilibrium equations, 18. The amplification condition in polarized radiative transfer, and 19. Coupling radiative transfer and statistical equilibrium equations.

Ferroelectric ferrimagnetic LiFe2F6 : Charge-ordering-mediated magnetoelectricity

Science.gov (United States)

Lin, Ling-Fang; Xu, Qiao-Ru; Zhang, Yang; Zhang, Jun-Jie; Liang, Yan-Ping; Dong, Shuai

2017-12-01

Trirutile-type LiFe2F6 is a charge-ordered material with an Fe2 +/Fe3 + configuration. Here, its physical properties, including magnetism, electronic structure, phase transition, and charge ordering, are studied theoretically. On one hand, the charge ordering leads to improper ferroelectricity with a large polarization. On the other hand, its magnetic ground state can be tuned from the antiferromagnetic to ferrimagnetic by moderate compressive strain. Thus, LiFe2F6 can be a rare multiferroic with both large magnetization and polarization. Most importantly, since the charge ordering is the common ingredient for both ferroelectricity and magnetization, the net magnetization may be fully switched by flipping the polarization, rendering intrinsically strong magnetoelectric effects and desirable functions.

Efficient ionizer for polarized H- formation

International Nuclear Information System (INIS)

Alessi, J.G.

1985-01-01

An ionizer is under development for a polarized H - source based on the resonant charge exchange reaction polarized H 0 + D - → polarized H - + D 0 . The polarized H 0 beam passes through the center of a magnetron surface-plasma source having an annular geometry, where it crosses a high current (approx.0.5 A), 200 eV D - beam. Calculations predict an H 0 → H - ionization efficiency of approx.7%, more than an order of magnitude higher than that obtained on present ground state atomic beam sources. In initial experiments using an unpolarized H 0 beam, H - currents in excess of 100 μA have been measured. While the ionization efficiency is now only about the same as other methods (Cs beam, for example), the results are encouraging since it appears that by injecting positive ions to improve the space-charge neutralization, and by improving the extraction optics, considerable gains in intensity will be made. We will then use this ionizer with a polarized H 0 beam, and measure the polarization of the resulting H - beam. If no depolarization is observed this ionizer will be combined with an atomic beam, cooled to 5 to 6 K, to give a polarized H - beam expected to be in the milliampere range for use in the AGS

Defect-Induced Hedgehog Polarization States in Multiferroics

Science.gov (United States)

Li, Linze; Cheng, Xiaoxing; Jokisaari, Jacob R.; Gao, Peng; Britson, Jason; Adamo, Carolina; Heikes, Colin; Schlom, Darrell G.; Chen, Long-Qing; Pan, Xiaoqing

2018-03-01

Continuous developments in nanotechnology require new approaches to materials synthesis that can produce novel functional structures. Here, we show that nanoscale defects, such as nonstoichiometric nanoregions (NSNRs), can act as nano-building blocks for creating complex electrical polarization structures in the prototypical multiferroic BiFeO3 . An array of charged NSNRs are produced in BiFeO3 thin films by tuning the substrate temperature during film growth. Atomic-scale scanning transmission electron microscopy imaging reveals exotic polarization rotation patterns around these NSNRs. These polarization patterns resemble hedgehog or vortex topologies and can cause local changes in lattice symmetries leading to mixed-phase structures resembling the morphotropic phase boundary with high piezoelectricity. Phase-field simulations indicate that the observed polarization configurations are mainly induced by charged states at the NSNRs. Engineering defects thus may provide a new route for developing ferroelectric- or multiferroic-based nanodevices.

Measurement of "pretzelosity" asymmetry of charged pion production in semi-inclusive deep inelastic scattering on a polarized 3He target

Science.gov (United States)

Zhang, Y.; Qian, X.; Allada, K.; Dutta, C.; Huang, J.; Katich, J.; Wang, Y.; Aniol, K.; Annand, J. R. M.; Averett, T.; Benmokhtar, F.; Bertozzi, W.; Bradshaw, P. C.; Bosted, P.; Camsonne, A.; Canan, M.; Cates, G. D.; Chen, C.; Chen, J.-P.; Chen, W.; Chirapatpimol, K.; Chudakov, E.; Cisbani, E.; Cornejo, J. C.; Cusanno, F.; Dalton, M. M.; Deconinck, W.; de Jager, C. W.; De Leo, R.; Deng, X.; Deur, A.; Ding, H.; Dolph, P. A. M.; Dutta, D.; El Fassi, L.; Frullani, S.; Gao, H.; Garibaldi, F.; Gaskell, D.; Gilad, S.; Gilman, R.; Glamazdin, O.; Golge, S.; Guo, L.; Hamilton, D.; Hansen, O.; Higinbotham, D. W.; Holmstrom, T.; Huang, M.; Ibrahim, H. F.; Iodice, M.; Jiang, X.; Jin, G.; Jones, M. K.; Kelleher, A.; Kim, W.; Kolarkar, A.; Korsch, W.; LeRose, J. J.; Li, X.; Li, Y.; Lindgren, R.; Liyanage, N.; Long, E.; Lu, H.-J.; Margaziotis, D. J.; Markowitz, P.; Marrone, S.; McNulty, D.; Meziani, Z.-E.; Michaels, R.; Moffit, B.; Muñoz Camacho, C.; Nanda, S.; Narayan, A.; Nelyubin, V.; Norum, B.; Oh, Y.; Osipenko, M.; Parno, D.; Peng, J. C.; Phillips, S. K.; Posik, M.; Puckett, A. J. R.; Qiang, Y.; Rakhman, A.; Ransome, R. D.; Riordan, S.; Saha, A.; Sawatzky, B.; Schulte, E.; Shahinyan, A.; Shabestari, M. H.; Širca, S.; Stepanyan, S.; Subedi, R.; Sulkosky, V.; Tang, L.-G.; Tobias, W. A.; Urciuoli, G. M.; Vilardi, I.; Wang, K.; Wojtsekhowski, B.; Yan, X.; Yao, H.; Ye, Y.; Ye, Z.; Yuan, L.; Zhan, X.; Zhang, Y.-W.; Zhao, B.; Zheng, X.; Zhu, L.; Zhu, X.; Zong, X.; Jefferson Lab Hall A Collaboration

2014-11-01

An experiment to measure single-spin asymmetries of semi-inclusive production of charged pions in deep-inelastic scattering on a transversely polarized 3He target was performed at Jefferson Laboratory in the kinematic region of 0.16 polarization approximation, we extracted the corresponding neutron asymmetries from the measured 3He asymmetries and cross-section ratios between the proton and 3He. Our results show that both π± on 3He and on neutron pretzelosity asymmetries are consistent with zero within experimental uncertainties.

Charged Higgs production from polarized top-quark decay in the 2HDM considering the general-mass variable-flavor-number scheme

Science.gov (United States)

Abbaspour, S.; Mohammad Moosavi Nejad, S.

2018-05-01

Charged Higgs bosons are predicted by some non-minimal Higgs scenarios, such as models containing Higgs triplets and two-Higgs-doublet models, so that the experimental observation of these bosons would indicate physics beyond the Standard Model. In the present work, we introduce a channel to indirect search for the charged Higgses through the hadronic decay of polarized top quarks where a top quark decays into a charged Higgs H+ and a bottom-flavored meson B via the hadronization process of the produced bottom quark, t (↑) →H+ + b (→ B + jet). To obtain the energy spectrum of produced B-mesons we present, for the first time, an analytical expression for the O (αs) corrections to the differential decay width of the process t →H+ b in presence of a massive b-quark in the General-Mass Variable-Flavor-Number (GM-VFN) scheme. We find that the most reliable predictions for the B-hadron energy spectrum are made in the GM-VFN scheme, specifically, when the Type-II 2HDM scenario is concerned.

Polarization and charge-transfer effect on the transport properties in two-dimensional electron gases/LaNiO3 heterostructure

Science.gov (United States)

Chen, M. J.; Ning, X. K.; Wang, Z. J.; Liu, P.; Wang, S. F.; Wang, J. L.; Fu, G. S.; Ma, S.; Liu, W.; Zhang, Z. D.

2018-01-01

The film thickness dependent transport properties of the LaNiO3 (LNO) layer epitaxially grown on LaAlO3/SrTiO3 (LAO) 2-dimensional electronic gas (2DEG) have been investigated. The ultrathin LNO films grown on the 2DEG have a sheet resistance below the values of h/e2 in all temperature ranges. The electron density is enhanced by more than one order of magnitude by capping LNO films. X-ray photoelectron spectroscopy shows that the interface undergoes unambiguous charge transfer and electronic reconstruction, leading to modulation doping of such atomically engineered complex oxide heterointerfaces. The polar-catastrophe of the 2DEG is directly linked to the electronic structure and transport properties of the LNO. The transport properties can be well modulated by the thickness of the LAO in the 2DEG, and the data can be well fitted with the polar-catastrophe scenario. These results suggest a general approach to tunable functional films in oxide heterostructures with the 2DEG.

Linear particle accelerator

International Nuclear Information System (INIS)

Richards, J.A.

1977-01-01

A linear particle accelerator which provides a pulsed beam of charged particles of uniform energy is described. The accelerator is in the form of an evacuated dielectric tube, inside of which a particle source is located at one end of the tube, with a target or window located at the other end of the dielectric tube. Along the length of the tube are externally located pairs of metal plates, each insulated from each other in an insulated housing. Each of the plates of a pair are connected to an electrical source of voltage of opposed polarity, with the polarity of the voltage of the plates oriented so that the plate of a pair, nearer to the particle source, is of the opposed polarity to the charge of the particle emitted by the source. Thus, a first plate about the tube located nearest the particle source, attracts a particle which as it passes through the tube past the first plate is then repelled by the reverse polarity of the second plate of the pair to continue moving towards the target

Dispersing surface-modified imogolite nanotubes in polar and non-polar solvents

Science.gov (United States)

Li, Ming; Brant, Jonathan A.

2018-02-01

Furthering the development of nanocomposite structures, namely membranes for water treatment applications, requires that methods be developed to ensure nanoparticle dispersion in polar and non-polar solvents, as both are widely used in associated synthesis techniques. Here, we report on a two-step method to graft polyvinylpyrrolidone (PVP), and a one-step method for octadecylphosphonic acid (OPA), onto the outer surfaces of imogolite nanotubes. The goal of these approaches was to improve and maintain nanotube dispersion in polymer compatible polar and non-polar solvents. The PVP coating modified the imogolite surface charge from positive to weakly negative at pH ≤ 9; the OPA made it weakly positive at acidic pH values to negative at pH ≥ 7. The PVP surface coating stabilized the nanotubes through steric hindrance in polar protic, dipolar aprotic, and chloroform. In difference to the PVP, the OPA surface coating allowed the nanotubes to be dispersed in n-hexane and chloroform, but not in the polar solvents. The lack of miscibility in the polar solvents, as well as the better dispersion in n-hexane, was attributed to the stronger hydrophobicity of the OPA polymer relative to the PVP. [Figure not available: see fulltext.

Influence of bulk dielectric polarization upon PD transients

DEFF Research Database (Denmark)

Pedersen, Aage; Crichton, George C; McAllister, Iain Wilson

1995-01-01

associated with the actual space charge in the void, and one related to changes in the bulk polarization brought about by changes in the field external to the void due to this space charge. The magnitude of the induced charge and its components are discussed in relation to a heterogeneous bulk dielectric...

Charge sniffer for electrostatics demonstrations

Science.gov (United States)

Dinca, Mihai P.

2011-02-01

An electronic electroscope with a special design for demonstrations and experiments on static electricity is described. It operates as an electric charge sniffer by detecting slightly charged objects when they are brought to the front of its sensing electrode. The sniffer has the advantage of combining high directional sensitivity with a logarithmic bar display. It allows for the identification of electric charge polarity during charge separation by friction, peeling, electrostatic induction, batteries, or secondary coils of power transformers. Other experiments in electrostatics, such as observing the electric field of an oscillating dipole and the distance dependence of the electric field generated by simple charge configurations, are also described.

Effect of silicon, tantalum, and tungsten doping and polarization on bioactivity of hydroxyapatite

Science.gov (United States)

Dhal, Jharana

Hydroxyapatite (HAp) ceramics has important applications as bone graft because of the structural and compositional similarities with bone tissue. However, inferior osteogenic capacity to bone and poor mechanical properties have been identified to be major disadvantages of synthetic HAp compared to the living bone tissue. The objective of the current study is to evaluate the effect of doping with higher valent cations (Tungsten, tantalum, and silicon) and polarization or combination of both on change in property of doped HAp and subsequent impact its bioactivity. In vitro study with human osteoblast cells was used to investigate the influences of doping and polarization on bone cell-materials interactions. The bioactivity of doped HAp was compared with pure HAp. Effect of doping and polarization on the change in HAp was investigated by monitoring change in mineral phases, stored charge, and activation energy of HAp. Activation energy of depolarization was used to explain the possible mechanism of polarization in doped samples. Bioactivity of HAp increased when doped with tantalum and tungsten. Polarization further increased the bioactivity of tungsten- and tantalum-doped samples. Increase in bioactivity on polarized and doped samples was attributed to increase in surface energy and increase in surface wettability. Whereas, an increase in bioactivity on doped unpolarized surface was attributed to change in microstructure. Polarized charge calculated from TSDC indicates that polarized charge decreases on tantalum- and tungsten-doped HAp. The decrease in polarized charge was attributed to the presence of significant amount of different phases that may hinder the ionic motion in doped samples. However, for silicon-doped HAp, TSDC study showed no difference in the mechanism of polarization between doped and undoped samples. Increase in silicon doping decreased the grain size though mechanism is not affected by grain size. Total stored charge decreased with increase in

Performance of the SLC polarized electron source with high polarization

International Nuclear Information System (INIS)

Clendenin, J.E.; Alley, R.K.; Aoyagi, H.

1993-04-01

For the 1992 operating cycle of the SLAC Linear Collider (SLC), the polarized electron source (PES) during its maiden run successfully met the pulse intensity and overall efficiency requirements of the SLC. However, the polarization of the bulk GaAs cathode was low (∼27%) and the pulse-to-pulse stability was marginal. We have shown that adequate charge for the SLC can be extracted from a strained layer cathode having P e ∼80% even though the quantum efficiency (QE) is - beam stability. The performance of the PES during the 1993 SLC operating cycle with these and other improvements is discussed

Atomic-scale compensation phenomena at polar interfaces.

Science.gov (United States)

Chisholm, Matthew F; Luo, Weidong; Oxley, Mark P; Pantelides, Sokrates T; Lee, Ho Nyung

2010-11-05

The interfacial screening charge that arises to compensate electric fields of dielectric or ferroelectric thin films is now recognized as the most important factor in determining the capacitance or polarization of ultrathin ferroelectrics. Here we investigate using aberration-corrected electron microscopy and density-functional theory to show how interfaces cope with the need to terminate ferroelectric polarization. In one case, we show evidence for ionic screening, which has been predicted by theory but never observed. For a ferroelectric film on an insulating substrate, we found that compensation can be mediated by an interfacial charge generated, for example, by oxygen vacancies.

Polarization spectroscopy of positive and negative trions in an InAs quantum dot

Science.gov (United States)

Ware, Morgan E.; Bracker, Allan S.; Stinaff, Eric; Gammon, Daniel; Gershoni, David; Korenev, Vladimir L.

2005-02-01

Using polarization-sensitive photoluminescence and photoluminescence excitation spectroscopy, we study single InAs/GaAs self-assembled quantum dots. The dots were embedded in an n-type, Schottky diode structure allowing for control of the charge state. We present here the exciton, singly charged exciton (positive and negative trions), and the twice negatively charged exciton. For non-resonant excitation below the wetting layer, we observed a large degree of polarization memory from the radiative recombination of both the positive and negative trions. In excitation spectra, through the p-shell, we have found several sharp resonances in the emission from the s-shell recombination of the dot in all charged states. Some of these excitation resonances exhibit strong coulomb shifts upon addition of charges into the quantum dot. One particular resonance of the negatively charged trion was found to exhibit a fine structure doublet under circular polarization. This observation is explained in terms of resonant absorption into the triplet states of the negative trion.

Efficient ionizer for polarized H/sup -/ formation

Energy Technology Data Exchange (ETDEWEB)

Alessi, J.G.

1985-01-01

An ionizer is under development for a polarized H/sup -/ source based on the resonant charge exchange reaction polarized H/sup 0/ + D/sup -/ ..-->.. polarized H/sup -/ + D/sup 0/. The polarized H/sup 0/ beam passes through the center of a magnetron surface-plasma source having an annular geometry, where it crosses a high current (approx.0.5 A), 200 eV D/sup -/ beam. Calculations predict an H/sup 0/ ..-->.. H/sup -/ ionization efficiency of approx.7%, more than an order of magnitude higher than that obtained on present ground state atomic beam sources. In initial experiments using an unpolarized H/sup 0/ beam, H/sup -/ currents in excess of 100 ..mu..A have been measured. While the ionization efficiency is now only about the same as other methods (Cs beam, for example), the results are encouraging since it appears that by injecting positive ions to improve the space-charge neutralization, and by improving the extraction optics, considerable gains in intensity will be made. We will then use this ionizer with a polarized H/sup 0/ beam, and measure the polarization of the resulting H/sup -/ beam. If no depolarization is observed this ionizer will be combined with an atomic beam, cooled to 5 to 6 K, to give a polarized H/sup -/ beam expected to be in the milliampere range for use in the AGS.

Escape of charged particles from a neutron star

International Nuclear Information System (INIS)

Pelizzari, M.A.

1976-01-01

The theory of particle trajectories in an axisymmetric magnetic field, formulated by C. Stormer, can be extended to cover conservative force fields as well. As such, it is an ideal tool to study the escape of charged particles from a rapidly rotating neutron star, enabling one to determine the maximum range of their trajectories in space. With the aid of this theory, it is shown that a neutron star, rotating in a vacuum with rotation and magnetic axes aligned, will not evolve a perfectly conducting magnetosphere if the neutron star is the only source of charge. The sign of charge accelerated from the equatorial regions will be magnetically trapped to a toroidal region very near the star, and the opposite sign of charge, emerging from the polar regions, will escape from the magnetosphere until a critical stellar charge is reached, after which polar charges will be electrostatically bound to the magnetosphere. This selective magnetic trapping of one sign of charge, which prevents the formation of a stellar wind, is a consequence of the magnetic field's orientation relative to the internal charge density of the neutron star

Atomically-resolved mapping of polarization and electric fields across ferroelectric-oxide interfaces by Z-contrast imaging

Science.gov (United States)

Borisevich, Albina; Chang, Hye Jung; Kalinin, Sergei; Morozovska, Anna; Chu, Ying-Hao; Yu, Pu; Ramesh, Ramamoorthy; Pennycook, Stephen

2011-03-01

Polarization, electric field, charge and potential across ferroelectric-oxide interfaces are obtained from direct atomic position mapping by aberration corrected scanning transmission electron microscopy combined with Ginsburg-Landau-Devonshire theory. We compare two antiparallel polarization orientations, which allows separation of the polarization and intrinsic interface charge contributions. Using the Born effective charges, the complete interface electrostatics is obtained in real space, providing an alternative method to holography. The results provide new microscopic insight into the thermodynamics of polarization distribution at the atomic level. Research is sponsored by the of Materials Sciences and Engineering Division, U.S. DOE.

Moral opinion polarization and the erosion of trust

DEFF Research Database (Denmark)

Rapp, Carolin

2016-01-01

generalized trust, we focus on opinion polarization as another potential impact factor on trust. In more detail, we investigate the extent to which polarization over morally charged issues such as homsexuality, abortion and euthanasia affects individuals' likelihood to trust others. We hypothesize that moral...

Thermodynamics of polarized relativistic matter

Energy Technology Data Exchange (ETDEWEB)

Kovtun, Pavel [Department of Physics and Astronomy, University of Victoria,PO Box 1700 STN CSC, Victoria BC, V8W 2Y2 (Canada)

2016-07-05

We give the free energy of equilibrium relativistic matter subject to external gravitational and electromagnetic fields, to one-derivative order in the gradients of the external fields. The free energy allows for a straightforward derivation of bound currents and bound momenta in equilibrium. At leading order, the energy-momentum tensor admits a simple expression in terms of the polarization tensor. Beyond the leading order, electric and magnetic polarization vectors are intrinsically ambiguous. The physical effects of polarization, such as the correlation between the magneto-vortically induced surface charge and the electro-vortically induced surface current, are not ambiguous.

Ejectile polarization and nuclear orbitals

International Nuclear Information System (INIS)

Ohnishi, A.; Maruyama, T.; Horiuchi, H.

1992-01-01

Ejectile polarization phenomena are studied by the use of 'Quantum Molecular Dynamics plus external mean field' model. It is shown that the far-side contribution increases as the incident energy increases or the target charge decreases. The incident energy and the target dependence of ejectile polarization data is reproduced qualitatively. The near- and far-side contributions themselves are calculated to be almost monotone functions of ejectile momentum as is predicted in a simple projectile fragmentation scheme without the assumption that the linear and angular momentum transfers are negligible, and their statistical average results in various shapes in ejectile polarization

Effect of a radial space-charge field on the movement of particles in a magneto-static field and under the influence of a circularly polarized wave

International Nuclear Information System (INIS)

Buffa, A.

1967-06-01

The effect of a circularly polarized wave on a cylindrical plasma in a axial magnetostatic field and a radial space-charge field proportional to r is studied. Single particle motion is considered. The electrostatic field produces a shift in the cyclotron resonance frequency and,in case of high charge density, a radial movement of the off-resonance particles. In these conditions a radio-frequency-particle resonance is also possible called 'drift-resonance'. The drift resonance can be produced, with whistler mode, and may be employed in ion acceleration. Afterwards parametrical resonances produced by space-charge field oscillations and collisional limits of theory are studied. Cases in which ion acceleration is possible are considered on the basis of a quantitative analysis of results. (author) [fr

Long-Term Charge/Discharge Cycling Stability of MnO2 Aqueous Supercapacitor under Positive Polarization

KAUST Repository

Ataherian, Fatemeh

2011-01-01

The long-term charge/discharge cycling stability of MnO 2 electrode under positive polarization in aqueous KCl electrolyte has been studied over different potential windows spanning from the open circuit potential to varied higher-end potential limited by O 2 evolution. Cycling up to 1.2 V (vs Ag/AgCl (aq)) causes partial (35) capacitance fading to a plateau value within the initial cycles, accompanied by morphological reconstruction, reduction of surface Mn ions and oxygen evolution. The surface Mn-ion reduction has been attributed to a two-step oxidation-reduction mechanism involving OH oxidation in electrolyte, based on electrochemical analysis. When cycling potential extends to 1.4 V, extensive oxygen evolution takes place. The combination of surface passivation of current collector and extensive gas bubbling, which deteriorates electrical contact among the constituent particles within the electrode, results in further monotonic capacitance reduction. © 2011 The Electrochemical Society.

The Natural Charge On The Surface Of The Earth | Mamah | Global ...

African Journals Online (AJOL)

The natural electric charge or its artificial analogue as the fundamental unit of exploration has been fundamentally derived and compared for both the equatorial region and the polar region. The ratio of the unit charge on the surface of the earth at the equatorial region (ω ± ω0) = 0.59 rad where ω0 = 1.65; to that at the polar ...

Setup and proof of principle of SAPIS (Stored Atoms Polarized Ion Source), a novel source of polarized H-/D- ions

International Nuclear Information System (INIS)

Emmerich, R.

2007-01-01

The objective of this work was the setup and the proof-of-principle of a new type of negative polarized hydrogen or deuterium ion source, which is based on the charge-exchange reaction vectorH 0 +Cs 0 →vectorH - +Cs + , as for instance the Colliding-Beams-Source (CBS) at the Cooler Synchrotron COSY in Juelich. In contrast to the CBS, the use of a storage cell for the charge-exchange region promises an increase in H - current by at least an order of magnitude without considerable polarization losses. For these purposes, a new laboratory was equipped and both a polarized hydrogen/deuterium atomic beam source and an intense neutral cesium-beam source have been build-on. A Lambshift polarimeter, which allows the measurement of the nuclear polarization of the atomic as well as ionic beams, was completed with the construction of a new spin-filter. After commissioning and optimizing each of these sources, a storage cell was developed and installed in the charge-exchange region with a magnetic field. Additionally, components for the extraction, detection and analysis of the negative ion beam were installed. Following the decisive proof of principle, investigation of the properties of the storage cell, especially as to H recombination and depolarisation, was begun. Furthermore, a number of software programs was developed for the control and monitoring of different components of the sources as well as a universal measuring software for the complete installation, including the measurement and calculation of the beam polarization. At the same time, the remote control system of the Cologne source of polarized ions LASCO at the FN tandem accelerator was completely modernized. (orig.)

Religious coalition opposes gene patents.

Science.gov (United States)

James, J S

1995-05-19

The biotechnology industry is concerned about a coalition of mainstream religious leaders, working with Jeremy Rifkin of the Foundation of Economic Trends, who oppose the patenting of human and animal life forms, body parts, and genes. The coalition called a press conference on May 18 to ask the government to prohibit the current patenting practices for genetic engineering. The biotechnology industry argues that patents indicate that a company's research tool has significant value, and encourages capitalists to invest their dollars in the development of new treatments for diseases. They also argue that the 29 biotech drugs that are on the market have been developed as a result of patents on genes. Although most business leaders are united in opposing restrictions, many scientists are divided, citing both religious and scientific reasons.

Charge-field formulation of quantum electrodynamics (QEMED)

International Nuclear Information System (INIS)

Leiter, D.

1980-01-01

By expressing classical electron theory in terms of 'charge-field' functional structures, it is shown that a finite formulation of the classical electrodynamics of point charges emerges in a simple and elegant fashion. This is used to construct a 'charge-field' quantum electrodynamic theory. It is found that interacting photon states are generated as a secondary manifestation of electron-positron quantization, and do not require the usual 'free' canonical quantization scheme. The possibility is discussed that this approach may lead to a better formulation of quantum electrodynamics in the Heisenberg picture and suggests a crucial experimental test to distinguish this new 'charge-field' quantum electrodynamics 'QEMED' from the standard QED formulation. Specifically QEMED predicts that the 'Einstein principle of separability' should be found to be valid for correlated photon polarization measurements, in which the polarizers are changed more rapidly than a characteristic photon travel time. Such an experiment (Aspect 1976) can distinguish between QEMED and QED in a complete and clear-cut fashion. (U.K.)

Optimization of AGS Polarized Proton Operation with the Warm Helical Snake

CERN Document Server

Takano, Junpei; Bai, Mei; Brown, Kevin A; Gardner, Chris J; Glenn, Joseph; Hattori, Toshiyuki; Huang, Haixin; Luccio, Alfredo U; MacKay, William W; Okamura, Masahiro; Roser, Thomas; Tepikian, Steven; Tsoupas, Nicholaos

2005-01-01

A normal conducting helical dipole partial Siberian snake (Warm Snake) has been installed in the Alternating Gradient Synchrotron (AGS) at Brookhaven National Laboratory (BNL) for overcoming all of imperfection depolarizing resonances and reducing the transverse coupling resonances caused by the solenoidal Siberian snake which had been operated in AGS before the last polarized run. The polarized proton beam has been accelerated successfully with the warm snake and the polarization at extraction of the AGS was increased to 50% as opposed to 40% with the solenoidal snake. The magnetic field and beam trajectory in the warm snake was calculated by using the OPERA-3D/TOSCA software. We present optimization of the warm snake with beam during RUN5.

On the feasibility of a negative polarity electric sail

Directory of Open Access Journals (Sweden)

P. Janhunen

2009-04-01

Full Text Available An electric solar wind sail is a recently introduced propellantless space propulsion method whose technical development has also started. In its original version, the electric sail consists of a set of long, thin, centrifugally stretched and conducting tethers which are charged positively and kept in a high positive potential of 20 kV by an onboard electron gun. The positively charged tethers deflect solar wind protons, thus tapping momentum from the solar wind stream and producing thrust. Here we consider a variant of the idea with negatively charged tethers. The negative polarity electric sail seems to be more complex to implement than the positive polarity variant since it needs an ion gun instead of an electron gun as well as a more complex tether structure to keep the electron field emission current in check with the tether surface. However, since this first study of the negative polarity electric sail does not reveal any fundamental issues, more detailed studies would be warranted.

A dual-optically-pumped polarized negative deuterium ion source

International Nuclear Information System (INIS)

Kinsho, M.; Mori, Y.; Ikegami, K.; Takagi, A.

1994-01-01

An optically pumped polarized H - source (OPPIS), which is based on the charge exchange between H + ions and electron-spin-polarized alkali atoms has been developed at KEK. Just by applying this scheme to a deuteron beam, it is difficult to obtain a highly vector polarized deuteron beam. To obtain highly vector polarized D - ions, we have developed a 'dual optical pumping type' of polarized D - source. With this scheme, a 100% vector nuclear-spin polarization for D - ions is possible in principle. In a preliminary experiment, a 60% of vector nuclear-spin polarized D - ions was obtained. (author)

Polarized target as analyzer of polarization of particle beam with spin Ssub(B)=1/2

International Nuclear Information System (INIS)

Golovin, V.M.; Golubeva, M.B.; Gornushkin, Yu.A.

1982-01-01

A possibility of using a polarized target as a target analyzer of beam particle polarization (Ssub(T)=1/2 Psub(T) vector) so that all the components of beam polarization Ssub(B)=1/2 anti Psub(B) should be determined in one experiment, is revealed. A proton polarization target is considered as a polarization target-analyzer. Asub(SK) and Asub(kk) asymmetry tensors are considered for elastic pp and pn scatterings by amplitudes of NN scattering which attain the values of 0.3-0.9 at 95-400 MeV. Asub(kk)(pp) and Asub(sk)(pp) are experimentally measured in the 445-576 MeV range. It is found that their highest absolute values are equal to 0.4-0.5 and 0.2-0.3 respectively. Elastic proton scattering on polarized electrons may be another variant of using polarized target for measuring proton beam polarization. Asub(sk) and Asub(kk) components of asymmetry tensor of elastic pe scattering are graphically presented. A possibility of using a polarized charge with spin I=1/2 as a target-analyzer of particle beam polarization is marked

Photoinduced Bulk Polarization and Its Effects on Photovoltaic Actions in Perovskite Solar Cells.

Science.gov (United States)

Wu, Ting; Collins, Liam; Zhang, Jia; Lin, Pei-Ying; Ahmadi, Mahshid; Jesse, Stephen; Hu, Bin

2017-11-28

This article reports an experimental demonstration of photoinduced bulk polarization in hysteresis-free methylammonium (MA) lead-halide perovskite solar cells [ITO/PEDOT:PSS/perovskite/PCBM/PEI/Ag]. An anomalous capacitance-voltage (CV) signal is observed as a broad "shoulder" in the depletion region from -0.5 to +0.5 V under photoexcitation based on CV measurements where a dc bias is gradually scanned to continuously drift mobile ions in order to detect local polarization under a low alternating bias (50 mV, 5 kHz). Essentially, gradually scanning the dc bias and applying a low alternating bias can separately generate continuously drifting ions and a bulk CV signal from local polarization under photoexcitation. Particularly, when the device efficiency is improved from 12.41% to 18.19% upon chlorine incorporation, this anomalous CV signal can be enhanced by a factor of 3. This anomalous CV signal can be assigned as the signature of photoinduced bulk polarization by distinguishing from surface polarization associated with interfacial charge accumulation. Meanwhile, replacing easy-rotational MA + with difficult-rotational formamidinium (FA + ) cations largely minimizes such anomalous CV signal, suggesting that photoinduced bulk polarization relies on the orientational freedom of dipolar organic cations. Furthermore, a Kelvin probe force microscopy study shows that chlorine incorporation can suppress the density of charged defects and thus enhances photoinduced bulk polarization due to the reduced screening effect from charged defects. A bias-dependent photoluminescence study indicates that increasing bulk polarization can suppress carrier recombination by decreasing charge capture probability through the Coulombic screening effect. Clearly, our studies provide an insightful understanding of photoinduced bulk polarization and its effects on photovoltaic actions in perovskite solar cells.

Polarized particle levitation in hexapole field

International Nuclear Information System (INIS)

Jones, T.B.; Kallio, G.A.; Robinson, K.S.

1976-06-01

Proposed here is a novel electrostatic levitation scheme which uses the force exerted by a non-uniform electric field on a polarized particle. The scheme differs from conventional quadrupole levitation devices principally in that the levitated particle is uncharged. In order to provide the proper force required to achieve dynamic stabilization, a very intense non-uniform time-varying electric field produced by a three-dimensional hexapole electrode structure is utilized. The primary advantage of this levitation scheme might accrue in target fabrication operations where particle charge is undesirable or where reproducible charging of the particles themselves is difficult, due to high resistivity. The disadvantages of this scheme, as compared to charged particle levitation, are (i) a more complex electrode structure and (ii) significantly higher voltages. The scheme has possible application to molecular mass spectrometry, in situations where un-ionized but strongly polar or polarizable molecules are to be trapped or confined for analysis

Spin-polarized light-emitting diodes based on organic bipolar spin valves

Science.gov (United States)

Vardeny, Zeev Valentine; Nguyen, Tho Duc; Ehrenfreund, Eitan Avraham

2017-10-25

Spin-polarized organic light-emitting diodes are provided. Such spin-polarized organic light-emitting diodes incorporate ferromagnetic electrodes and show considerable spin-valve magneto-electroluminescence and magneto-conductivity responses, with voltage and temperature dependencies that originate from the bipolar spin-polarized space charge limited current.

Charging and switching of ferroelectrets: how much can ferroelectrets behave like ferroelectrics?

International Nuclear Information System (INIS)

Schwoediauer, R.; Graz, I.; Bauer, S.

2004-01-01

Dielectrics with good charge storage capability, so called charge electrets, are non or weakly-polar materials. Despite their non-polar nature porous charge electrets with internally charged surfaces can exhibit very pronounced piezoelectricity. Such systems have been termed 'ferroelectrets' and they have been receiving growing attention over the last few years. Their puzzling and unexpected features resemble very much those normally known from traditional ferroelectrics: ferroelectrets are piezo- and pyroelectric, their polarization can be reversed by means of an external field and electrical as well as mechanical hysteresis loops were observed. As conventional ferroelectrics are different and more complicated than ferromagnets, so are ferroelectrets different and more complex than most ferroelectrics. Here we report about the very different charging and switching mechanism in ferroelectrets, both in simple model-systems and in less simple foam structures. These mechanisms are crucial and form the basis for the striking phenomenological similarities to ferroelectrics. We also want to address some of the specific peculiarities and pitfalls related to present ferroelectrets and their characterization. Interfacial charge injection at high electric fields and anelastic non-linearities, for instance, can be the cause for false ferroelectric-like hysteresis effects which do not reflect any polarization reversal. Our contribution is an attempt towards a more comprehensive picture of how much ferroelectrets behave like ferroelectrics. (author)

Polarization tunable photogenerated carrier transfer of CH3NH3PbI3/polyvinylidene fluoride heterostructure

Science.gov (United States)

Yang, Kang; Deng, Zun-Yi; Feng, Hong-Jian

2017-10-01

The integration of ferroelectrics and organic-inorganic halide perovskites could be a promising way to facilitate the separation of electron-hole pairs and charge extraction for the application of solar cells. To explore the effect of the external ferroelectric layer on the CH3NH3PbI3 (MAPbI3) side, we perform first-principles calculations to study the charge transfer properties of the MAPbI3/polyvinylidene fluoride (PVDF) heterostructure. Our calculations demonstrate that the ferroelectric polarization pointing to the PVDF side can clearly facilitate the separation of photo-induced carriers and enhance charge extraction from MAPbI3, while opposite polarization direction hinders the charge extraction and collection. Notably, the carrier behavior at the interface is strongly tuned by the electric field associated with the ferroelectric polarization. In addition, excited state simulation confirms the tunable charge transfer of the MAPbI3/PVDF heterojunction. Therefore, the polarization-driven charge transfer mechanism provides a route for fabricating the ferroelectrics-based high-efficiency photovoltaics and switchable diode devices.

Wind wave source functions in opposing seas

KAUST Repository

Langodan, Sabique

2015-08-26

The Red Sea is a challenge for wave modeling because of its unique two opposed wave systems, forced by opposite winds and converging at its center. We investigate the different physical aspects of wave evolution and propagation in the convergence zone. The two opposing wave systems have similar amplitude and frequency, each driven by the action of its own wind. Wave patterns at the centre of the Red Sea, as derived from extensive tests and intercomparison between model and measured data, suggest that the currently available wave model source functions may not properly represent the evolution of the local fields that appear to be characterized by a less effective wind input and an enhanced white-capping. We propose and test a possible simple solution to improve the wave-model simulation under opposing winds and waves condition. This article is protected by copyright. All rights reserved.

Nonuniform charging effects on ion drag force in drifting dusty plasmas

International Nuclear Information System (INIS)

Chang, Dong-Man; Chang, Won-Seok; Jung, Young-Dae

2006-01-01

The nonuniform polarization charging effects on the ion drag force are investigated in drifting dusty plasmas. The ion drag force due to the ion-dust grain interaction is obtained as a function of the dust charge, ion charge, plasma temperature, Mach number, Debye length, and collision energy. The result shows that the nonuniform charging effects enhance the momentum transfer cross section as well as the ion drag force. It is found that the momentum transfer cross section and the ion drag force including nonuniform polarization charging effects increase with increasing the Mach number and also the ion drag force increases with increasing the temperature. In addition, it is found that the ion drag force is slightly decreasing with an increase of the Debye length

Spin-polarized charge transport in HgTe/CdTe quantum well topological insulator under a ferromagnetic metal strip

Science.gov (United States)

Wu, Zhenhua; Luo, Kun; Yu, Jiahan; Wu, Xiaobo; Lin, Liangzhong

2018-02-01

Electron tunneling through a single magnetic barrier in a HgTe topological insulator has been theoretically investigated. We find that the perpendicular magnetic field would not lead to spin-flip of the edge states due to the conservation of the angular moment. By tuning the magnetic field and the Fermi energy, the edge channels can be transited from switch-on states to switch-off states and the current from unpolarized states can be filtered to fully spin polarized states. These features offer us an efficient way to control charge/spin transport in a HgTe/CdTe quantum well, and pave a way to construct the nanoelectronic devices utilizing the topological edge states.

Imaging with Polarized Neutrons

Directory of Open Access Journals (Sweden)

Nikolay Kardjilov

2018-01-01

Full Text Available Owing to their zero charge, neutrons are able to pass through thick layers of matter (typically several centimeters while being sensitive to magnetic fields due to their intrinsic magnetic moment. Therefore, in addition to the conventional attenuation contrast image, the magnetic field inside and around a sample can be visualized by detecting changes of polarization in a transmitted beam. The method is based on the spatially resolved measurement of the cumulative precession angles of a collimated, polarized, monochromatic neutron beam that traverses a magnetic field or sample.

Tuning polarity and improving charge transport in organic semiconductors

Science.gov (United States)

Oh, Joon Hak; Han, A.-Reum; Yu, Hojeong; Lee, Eun Kwang; Jang, Moon Jeong

2013-09-01

Although state-of-the-art ambipolar polymer semiconductors have been extensively reported in recent years, highperformance ambipolar polymers with tunable dominant polarity are still required to realize on-demand, target-specific, high-performance organic circuitry. Herein, dithienyl-diketopyrrolopyrrole (TDPP)-based polymer semiconductors with engineered side-chains have been synthesized, characterized and employed in ambipolar organic field-effect transistors, in order to achieve controllable and improved electrical properties. Thermally removable tert-butoxycarbonyl (t-BOC) groups and hybrid siloxane-solubilizing groups are introduced as the solubilizing groups, and they are found to enable the tunable dominant polarity and the enhanced ambipolar performance, respectively. Such outstanding performance based on our molecular design strategies makes these ambipolar polymer semiconductors highly promising for low-cost, large-area, and flexible electronics.

The rate of charge tunneling is insensitive to polar terminal groups in self-assembled monolayers in Ag(TS)S(CH2)(n)M(CH2)(m)T//Ga2O3/EGaIn junctions.

Science.gov (United States)

Yoon, Hyo Jae; Bowers, Carleen M; Baghbanzadeh, Mostafa; Whitesides, George M

2014-01-08

This paper describes a physical-organic study of the effect of uncharged, polar, functional groups on the rate of charge transport by tunneling across self-assembled monolayer (SAM)-based large-area junctions of the form Ag(TS)S(CH2)(n)M(CH2)(m)T//Ga2O3/EGaIn. Here Ag(TS) is a template-stripped silver substrate, -M- and -T are "middle" and "terminal" functional groups, and EGaIn is eutectic gallium-indium alloy. Twelve uncharged polar groups (-T = CN, CO2CH3, CF3, OCH3, N(CH3)2, CON(CH3)2, SCH3, SO2CH3, Br, P(O)(OEt)2, NHCOCH3, OSi(OCH3)3), having permanent dipole moments in the range 0.5 < μ < 4.5, were incorporated into the SAM. A comparison of the electrical characteristics of these junctions with those of junctions formed from n-alkanethiolates led to the conclusion that the rates of charge tunneling are insensitive to the replacement of terminal alkyl groups with the terminal polar groups in this set. The current densities measured in this work suggest that the tunneling decay parameter and injection current for SAMs terminated in nonpolar n-alkyl groups, and polar groups selected from common polar organic groups, are statistically indistinguishable.

Polarization of {sup 23}Ne, {sup 24m,25}Al and {sup 28}P produced through single nucleon pickup and charge-exchange reactions at 100 AMeV

Energy Technology Data Exchange (ETDEWEB)

Ohtsubo, T., E-mail: tohtsubo@np.gs.niigata-u.ac.jp; Hirano, H.; Takahashi, S. [Niigata Univ. (Japan); Matsuta, K.; Mihara, M.; Fukuda, M. [Osaka Univ. (Japan); Nagatomo, T. [RIKEN (Japan); Izumikawa, T. [Niigata Univ., RI Center (Japan); Momota, S. [Kochi Univ. of Tech. (Japan); Nishimura, D.; Komurasaki, J.; Ishikawa, D. [Osaka Univ. (Japan); Zhou, D. M.; Zheng, Y. N.; Zhu, S. Y. [China Institute of Atomic Energy (China); Kitagawa, A.; Kanazawa, M.; Torikoshi, M.; Sato, S. [Inage-ku, NIRS (Japan); Minamisono, T. [Fukui Univ. of Tech. (Japan)

2007-11-15

We measured the polarization of the {beta}-emitting {sup 23}Ne (I{sup {pi}} 5/2{sup +}, T{sub 1/2} = 37.24 s) and {sup 25}Al(I{sup {pi}} = 5/2{sup +}, T{sub 1/2} = 7.18 s) produced through the one nucleon pickup reactions and {sup 24m}Al(I{sup {pi}} = 1{sup +}, T{sub 1/2} 131 ms, E{sub ex} = 426 keV) and {sup 28}P(I{sup {pi}} = 3{sup +}, T{sub 1/2} = 270 ms) produced through charge-exchange reactions in the intermediate energy heavy ion collisions. We compared them with those from the projectile fragmentation process. The larger polarization seems to persistently be positive throughout the momentum distribution, and sharper momentum distributions suggest that nuclear friction mechanism is responsible for the polarization phenomena.

Aerosol charging state at an urban site: new analytical approach and implications for ion-induced nucleation

Directory of Open Access Journals (Sweden)

S. Gagné

2012-05-01

Full Text Available The charging state of aerosol populations was determined using an Ion-DMPS in Helsinki, Finland between December 2008 and February 2010. We extrapolated the charging state and calculated the ion-induced nucleation fraction to be around 1.3 % ± 0.4 % at 2 nm and 1.3 % ± 0.5 % at 1.5 nm, on average. We present a new method to retrieve the average charging state for a new particle formation event, at a given size and polarity. We improve the uncertainty assessment and fitting technique used previously with an Ion-DMPS. We also use a new theoretical framework that allows for different concentrations of small ions for different polarities (polarity asymmetry. We extrapolate the ion-induced fraction using polarity symmetry and asymmetry. Finally, a method to calculate the growth rates from the behaviour of the charging state as a function of the particle diameter using polarity symmetry and asymmetry is presented and used on a selection of new particle formation events.

Spontaneous spin polarization and charge localization in metal nanowires: the role of a geometric constriction

Energy Technology Data Exchange (ETDEWEB)

Cortes-Huerto, R; Ballone, P [Atomistic Simulation Centre, Queen' s University Belfast, Belfast BT7 1NN (United Kingdom)

2010-07-28

An idealized jellium model of conducting nanowires with a geometric constriction is investigated by density functional theory (DFT) in the local spin density (LSD) approximation. The results reveal a fascinating variety of spin and charge patterns arising in wires of sufficiently low (r{sub s} {>=} 15) average electron density, pinned at the indentation by an apparent attractive interaction with the constriction. The spin-resolved frequency-dependent conductivity shows a marked asymmetry in the two spin channels, reflecting the spontaneous spin polarization around the wire neck. The relevance of the computational results is discussed in relation to the so-called 0.7 anomaly found by experiments in the low-frequency conductivity of nanowires at near-breaking conditions (see 2008 J. Phys.: Condens Matter 20, special issue on the 0.7 anomaly). Although our mean-field approach cannot account for the intrinsic many-body effects underlying the 0.7 anomaly, it still provides a diagnostic tool to predict impending transitions in the electronic structure.

Geomagnetic Polarity Epochs: Sierra Nevada II.

Science.gov (United States)

Cox, A; Doell, R R; Dalrymple, G B

1963-10-18

Ten new determinations on volcanic extrusions in the Sierra Nevada with potassium-argon ages of 3.1 million years or less indicate that the remanent magnetizations fall into two groups, a normal group in which the remanent magnetization is directed downward and to the north, and a reversed group magnetized up and to the south. Thermomagnetic experiments and mineralogic studies fail to provide an explanation of the opposing polarities in terms of mineralogic control, but rather suggest that the remanent magnetization reflects reversals of the main dipole field of the earth. All available radiometric ages are consistent with this field-reversal hypothesis and indicate that the present normal polarity epoch (N1) as well as the previous reversed epoch (R1) are 0.9 to 1.0 million years long, whereas the previous normal epoch (N2) was at least 25 percent longer.

Transition density of charge-exchange processes

International Nuclear Information System (INIS)

Lovas, R.G.

1983-01-01

The transition density between parent and analogue states is studied with special reference to its role in charge-exchange nuclear reactions. The structure of the target nucleus is described in a perturbative approach, in which the Coulomb and asymmetry potentials mix the eigenstates of a charge-independent single-particle Hamiltonian. In this model formulae are derived for the transition density, the Coulomb displacement energy and the neutron-proton density difference, and their relationship is used to estimate the transition density. This estimate shows that: the largest contribution comes from the density of the excess neutrons; the weight of the Coulomb-mixing effect is small up to excess neutron number 10, and grows rapidly beyond; the weight of the core polarization term induced by the excess neutrons is modest and is the same for all nuclei. It is indicated that the Coulomb effect may explain the departure from the Lane model of nucleon charge-exchange scattering found for heavy nuclei, whereas the core polarization may account for the observed anomalous dependence of the deg 0 pion charge-exchange cross section on the number of excess neutrons. (author)

Competitive photocyclization/rearrangement of 4-aryl-1,1-dicyanobutenes controlled by intramolecular charge-transfer interaction. Effect of medium polarity, temperature, pressure, excitation wavelength, and confinement.

Science.gov (United States)

Ito, Tadashi; Nishiuchi, Emi; Fukuhara, Gaku; Inoue, Yoshihisa; Mori, Tadashi

2011-09-01

A series of 4-aryl-1,1-dicyanobutenes (1a-1f) with different substituents were synthesized to control the intramolecular donor-acceptor or charge-transfer (C-T) interactions in the ground state. Photoexcitation of these C-T substrates led to competitive cyclization and rearrangement, the ratio being critically controlled by various environmental factors, such as solvent polarity, temperature and static pressure, and also by excitation wavelength and supramolecular confinement (polyethylene voids). In non-polar solvents, the rearrangement was dominant (>10 : 1) for all examined substrates, while the cyclization was favoured in polar solvents, in particular at low temperatures. Selective excitation at the C-T band further enhanced the cyclization up to >50 : 1 ratios. More importantly, the cyclization/rearrangement ratio was revealed to be a linear function of the C-T transition energy. However, the substrates with a sterically demanding or highly electron-donating substituent failed to give the cyclization product.

Electro-optical Detection of Charged Particles

International Nuclear Information System (INIS)

Lazarus, D.M.

2001-01-01

The electric field of charged particles can induce transient changes in the polarization of light that produce sub-picosecond modulation of a laser beam. This is a consequence of the electro-optical effect in which the presence of the electric field in an electro-optical medium produces a change in the index of refraction of the medium resulting in a phase retardation between polarization components parallel and perpendicular to the electric field. We have observed the electro-optical effect due to 10 picosecond electron beam bunches with rise times that were limited by the bandwidth of our data acquisition system. This technology is being applied to particle beam diagnostics and has the potential to produce charged particle detectors combining excellent spatial resolution with unprecedented temporal precision.

Opposing incentives for collaboration

DEFF Research Database (Denmark)

Dorch, Bertil F.; Wien, Charlotte; Larsen, Asger Væring

, and gives a bonus for publications done through inter-institutionary collaboration. Credits given to universities are fractionalized between the participating universities. So far credits are not assigned to the individual authors but only to their institutions. However, it turns out that research...... collaboration is associated with a higher number of citations than single authorship which may present the author with two opposing incentives for research collaboration....

Polarization-tuned diode behaviour in multiferroic BiFeO3 thin films

KAUST Repository

Yao, Yingbang

2012-12-28

Asymmetric rectifying I-V behaviour of multiferroic BiFeO3 (BFO) thin films grown on transparent ITO-coated glass was quantitatively studied as a function of ferroelectric polarization. Different polarized states were established by unipolar or bipolar poling with various applied electric fields. The effects of polarization relaxation and fatigue on the currents were also investigated. We found that the conduction currents and the associated rectifications were controlled by the amplitude and direction of the polarization. We clearly observed the linear dependence of the current on the polarization. It is suggested that the space-charge-limited conduction and the charge injection at the Schottky interface between the film and the electrodes dominate the current. The electrically controlled rectifying behaviour observed in this study may be useful in nonvolatile resistance memory devices or tunable diodes. © 2013 IOP Publishing Ltd.

Development of spin polarized electron beam

International Nuclear Information System (INIS)

Nakanishi, Tsutomu

2001-01-01

Physical structure of the polarized electron beam production is explained in this paper. Nagoya University group has been improving the quality of beam. The present state of quality and the development objects are described. The new results of the polarized electron reported in 'RES-2000 Workshop' in October 2000, are introduced. The established ground of GaAs type polarized electron beam source, observation of the negative electron affinity (NEA) surface, some problems of NEA surface of high energy polarized electron beam such as the life, time response, the surface charge limited phenomena of NEA surface are explained. The interested reports in the RES-2000 Workshop consisted of observation by SPLEEM (Spin Low Energy Electron Microscope), Spin-STM and Spin-resolved Photoelectron Spectroscopy. To increase the performance of the polarized electron source, we will develop low emittance and large current. (S.Y.)

Polarized H- source development at BNL

International Nuclear Information System (INIS)

Alessi, J.G.; Hershcovitch, A.; Kponou, A.; Niinikoski, T.; Sluyters, T.

1986-01-01

The AGS polarized H - source (PONI-1) now produces currents of 25-40 μA, and has operated reliably during polarized physics runs. A new polarized source, having as its goal mA's of H-vector, is now under development. An atomic hydrogen beam has been cooled to about 20 K with a forward flux of approx.10 19 atoms/s/sr. A superconducting solenoid having a calculated acceptance angle of 0.1 sr for the cold H 0 beam, is now being built. An ionizer for the resulting polarized H 0 beam based on resonant charge exchange of H 0 with D - , is being tested. 500 μA of H - have been produced by ionizing an unpolarized H 0 beam using this ionizer

The high peak current polarized electron source of the Stanford Linear Collider

International Nuclear Information System (INIS)

Schultz, D.; Alley, R.; Aoyagi, H.; Clendenin, J.; Frisch, J.; Garden, C.; Hoyt, E.; Kirby, R.; Klaisner, L.; Kulikov, A.; Mulhollan, G.; Prescott, C.; Saez, P.; Tang, H.; Turner, J.; Woods, M.; Yeremian, D.; Zolotorev, M.

1994-01-01

The Stanford Linear Collider injector requires two 2 ns pulses of 4.5-5.5 x 10 10 electrons, separated by 61 ns at 120 Hz, from its source. Since 1992, these currents have been provided by a polarized electron source based on GaAs photocathodes. A beam polarization of 76±4% has been measured at the end of the 50 GeV linac. At low photocathode quantum efficiencies, and for excitation near threshold, the maximum current delivered by the source is constrained, not by the space charge limit of the gun, but by a ''charge limit'' of the photocathode. The charge limited current is proportional to the photocathode quantum efficiency, but the proportionality varies for different photocathode types. Experience with high polarization strained GaAs photocathodes on a test beamline and on the SLC is presented. (orig.)

Alleviating polarity-conflict at the heterointerfaces of KTaO3/GdScO3 polar complex-oxides

International Nuclear Information System (INIS)

Thompson, J.; Nichols, J.; Connell, J. G.; Seo, S. S. A.; Hwang, J.; Stemmer, S.

2014-01-01

We have synthesized and investigated the heterointerfaces of KTaO 3 (KTO) and GdScO 3 (GSO), which are both polar complex-oxides along the pseudo-cubic [001] direction. Since their layers have the same, conflicting net charges at interfaces, i.e., KO(−1)/ScO 2 (−1) or TaO 2 (+1)/GdO(+1), forming the heterointerface of KTO/GSO should be forbidden due to strong Coulomb repulsion, the so-called polarity conflict. However, we have discovered that atomic reconstruction occurs at the heterointerfaces between KTO thin-films and GSO substrates, which effectively alleviates the polarity conflict without destroying the hetero-epitaxy. Our result demonstrates one of the important ways to create artificial heterostructures from polar complex-oxides.

Charge Splitting In Situ Recorder (CSIR) for Real-Time Examination of Plasma Charging Effect in FinFET BEOL Processes

Science.gov (United States)

Tsai, Yi-Pei; Hsieh, Ting-Huan; Lin, Chrong Jung; King, Ya-Chin

2017-09-01

A novel device for monitoring plasma-induced damage in the back-end-of-line (BEOL) process with charge splitting capability is first-time proposed and demonstrated. This novel charge splitting in situ recorder (CSIR) can independently trace the amount and polarity of plasma charging effects during the manufacturing process of advanced fin field-effect transistor (FinFET) circuits. Not only does it reveal the real-time and in situ plasma charging levels on the antennas, but it also separates positive and negative charging effect and provides two independent readings. As CMOS technologies push for finer metal lines in the future, the new charge separation scheme provides a powerful tool for BEOL process optimization and further device reliability improvements.

The RHIC polarized H{sup −} ion source

Energy Technology Data Exchange (ETDEWEB)

Zelenski, A., E-mail: zelenski@bnl.gov; Atoian, G.; Raparia, D.; Ritter, J.; Steski, D. [Brookhaven National Laboratory, Upton, New York 11973 (United States)

2016-02-15

A novel polarization technique had been successfully implemented for the Relativistic Heavy Ion Collider (RHIC) polarized H{sup −} ion source upgrade to higher intensity and polarization. In this technique, a proton beam inside the high magnetic field solenoid is produced by ionization of the atomic hydrogen beam (from external source) in the He-gaseous ionizer cell. Further proton polarization is produced in the process of polarized electron capture from the optically pumped Rb vapor. The use of high-brightness primary beam and large cross sections of charge-exchange cross sections resulted in production of high intensity H{sup −} ion beam of 85% polarization. The source very reliably delivered polarized beam in the RHIC Run-2013 and Run-2015. High beam current, brightness, and polarization resulted in 75% polarization at 23 GeV out of Alternating Gradient Synchrotron (AGS) and 60%-65% beam polarization at 100-250 GeV colliding beams in RHIC.

Sources of polarized negative ions: progress and prospects

International Nuclear Information System (INIS)

Haeberli, W.

1980-01-01

A summary of recent progress in the art of producing beams of polarized ions is given. In all sources of polarized ions, one first produces (or selects) neutral atoms which are polarized in electron spin. Those types of sources which use a beam of thermal polarized hydrogen atoms are discussed. Progress made in the preparation of the atomic beam and the methods used to convert the neutral atoms to polarized ions is summarized. The second type of source discussed is based on fast (keV) polarized hydrogen atoms. Conversion to negative ions is very simple because one only needs to pass the fast atoms through a suitable charge exchange medium (gas or vapor). However, the production of the polarized atoms is more difficult in this case. The proposal to employ polarized alkali vapor to form a beam of polarized fast H atoms, where the polarized alkali atoms are produced either by an atomic beam apparatus or by optical pumping is discussed

Effect of surface topography and morphology on space charge packets in polyethylene

International Nuclear Information System (INIS)

Zhou Yuanxiang; Wang Yunshan; Sun Qinghua; Wang Ninghua

2009-01-01

Polyethylene (PE) is a major kind of internal insulating material. With great progresses of space charge measurement technologies in the last three decades, lots of researches are focused on space charge in PE. The heat pressing and annealing condition of polyethylene affect its morphology obviously. During the heat pressing, the surface of PE forms different surface topographies because of different substrate materials. Surface topography has great relation to the epitaxial crystallization layer and influences the space charge characteristic of PE dramatically. This paper studied the formation process of different surface topographies and their micrographic characters in low density polyethylene (LDPE). pulsed electro-acoustic (PEA) method was used to measure the space charge distribution of samples with different surface topographies and morphologies in LDPE. The effect of surface topography and morphology to space charge packet were studied. The surface topography has great influence on space charge packet polarity and morphology has influence on both movement speed rate and polarity of space charge packet.

Interplanetary Radiation and Internal Charging Environment Models for Solar Sails

Science.gov (United States)

Minow, Joseph I.; Altstatt, Richard L.; NeegaardParker, Linda

2005-01-01

A Solar Sail Radiation Environment (SSRE) model has been developed for defining charged particle environments over an energy range from 0.01 keV to 1 MeV for hydrogen ions, helium ions, and electrons. The SSRE model provides the free field charged particle environment required for characterizing energy deposition per unit mass, charge deposition, and dose rate dependent conductivity processes required to evaluate radiation dose and internal (bulk) charging processes in the solar sail membrane in interplanetary space. Solar wind and energetic particle measurements from instruments aboard the Ulysses spacecraft in a solar, near-polar orbit provide the particle data over a range of heliospheric latitudes used to derive the environment that can be used for radiation and charging environments for both high inclination 0.5 AU Solar Polar Imager mission and the 1.0 AU L1 solar missions. This paper describes the techniques used to model comprehensive electron, proton, and helium spectra over the range of particle energies of significance to energy and charge deposition in thin (less than 25 micrometers) solar sail materials.

Measurement of the topological charge and index of vortex vector optical fields with a space-variant half-wave plate.

Science.gov (United States)

Liu, Gui-Geng; Wang, Ke; Lee, Yun-Han; Wang, Dan; Li, Ping-Ping; Gou, Fangwang; Li, Yongnan; Tu, Chenghou; Wu, Shin-Tson; Wang, Hui-Tian

2018-02-15

Vortex vector optical fields (VVOFs) refer to a kind of vector optical field with an azimuth-variant polarization and a helical phase, simultaneously. Such a VVOF is defined by the topological index of the polarization singularity and the topological charge of the phase vortex. We present a simple method to measure the topological charge and index of VVOFs by using a space-variant half-wave plate (SV-HWP). The geometric phase grating of the SV-HWP diffracts a VVOF into ±1 orders with orthogonally left- and right-handed circular polarizations. By inserting a polarizer behind the SV-HWP, the two circular polarization states project into the linear polarization and then interfere with each other to form the interference pattern, which enables the direct measurement of the topological charge and index of VVOFs.

Penatalaksanaan Repair Palatoplasty dengan Teknik Furlow Double Opposing Z Plasty

Directory of Open Access Journals (Sweden)

Pingky Krisna Arindra

2015-06-01

metode Furlow double opposing z plasty dengan kombinasi insisi lateral, dan didapatkan hasil menutupnya celah di palatum mole sampai dengan uvula. Telah dilakukan operasi repair palatoplasi dengan metode Furlow double opposing z plasty. Teknik ini dilakukan untuk menghindari insisi yang terlalu luas dikarenakan terdapatnya jaringan fibrous yang tebal pada mukosa palatum pasca operasi sebelumnya. Tujuan studi kasus adalah untuk mengetahui kemampuan teknik Furlow Double Opposing Z Plasty sebagai prosedur repair palatoplasty.   Repair Palatoplasty Management with Furlow Double Opposing Z Plasty Technique. Cases of cleft lip and palate are one of the deformity disorders that often occur. There are variety of clinical appearance ranging from incomplete to complete cases. Clinical appearance with different width requires proper surgical technique. Patients with cleft lip and palate had undergone surgical intervention, so that they needed surgical correction to repair the result or failure of the previous surgery. A Four year old boy complain there was cleft on the soft palate. The patient was diagnosed with labiognatopalatoscisis. The patient had undergone two stages of cleft lip surgery and twice of cleft palate surgery with pushback method and repair with z plasty, however the result was unsatisfactory. Further, the patient underwent repair palatoplasty surgery with Furlow double opposing z plasty method combined with lateral relaxing insicion. The result in the post surgery was the closure of cleft soft palate up to uvula. Repair palataplasty surgery has been done with Furlow double opposing z plasty method. This technique could avoid extended incision due to thick fibrous tissue on the palatum mucosa as the result of serial previous surgery. The aim of this case case study is to determine the technical capabilities of Furlow Double Opposing Z Plasty as palatoplasty repair procedure.

Manipulating the dipole layer of polar organic molecules on metal surfaces via different charge-transfer channels

Science.gov (United States)

Lin, Meng-Kai; Nakayama, Yasuo; Zhuang, Ying-Jie; Wang, Chin-Yung; Pi, Tun-Wen; Ishii, Hisao; Tang, S.-J.

The key properties of organic films such as energy level alignment (ELA), work functions, and injection barriers are closely linked to this dipole layer. Using angle resolved photoemission spectroscopy (ARPES), we systemically investigate the coverage-dependent work functions and spectra line shapes of occupied molecular orbital states of a polar molecule, chloroaluminium phthalocyanine (ClAlPc), grown on Ag(111) to show that the orientations of the first ClAlPc layer can be manipulated via the molecule deposition rate and post annealing, causing ELA at organic-metal interface to differ for about 0.3 eV between Cl-up and Cl-down configuration. Moreover, by comparing the experimental results with the calculations based on both gas-phase model and realistic model of ClAlPc on Ag(111) , we evidence that the different orientations of ClAlPc dipole layers lead to different charge-transfer channels between ClAlPc and Ag, a key factor that controls the ELA at organic-metal interface.

Stability of polarization in organic ferroelectric metal-insulator-semiconductor (MIS) structures

Energy Technology Data Exchange (ETDEWEB)

Kalbitz, Rene; Fruebing, Peter; Gerhard, Reimund [Department of Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Strasse 24-25, 14476, Potsdam (Germany); Taylor, Martin [School of Electronic Engineering, Bangor University, Dean Street, Bangor Gwynedd, LL57 1UT (United Kingdom)

2011-07-01

Ferroelectric field effect transistors (FeFETs) offer the prospect of an organic-based memory device. Since the charge transport in such devices is confined to the interface between the insulator and the semiconductor, the focus of the present study was on the investigation of this region. Capacitance-voltage (C-V) measurements of all-organic MIS devices with poly(vinylidenefluoride- trifluoroethylene) (P(VDF-TrFE)) as gate insulator and poly(3-hexylthiophene)(P3HT) as semiconductor were carried out. When the structure was driven into depletion, a positive flat-band voltage shift was observed arising from the change in polarization state of the ferroelectric insulator. When driven into accumulation, the polarization was reversed. It is shown that both polarization states are stable. However, negative charge trapped at the interface during the depletion cycle masks the negative shift in flat-band voltage expected during the sweep to accumulation voltages. Measurements on P(VDF-TrFE)/P3HT based FeFETs yield further evidence for fixed charges at the interface. Output characteristics suggest the injection of negative charges into the interface region when a depletion voltage is applied between source and gate contact.

Hard Quasi-real Photo-production of Charged Hadrons at COMPASS energies

CERN Document Server

Morréale, Astrid

2011-01-01

The Common Muon Proton Apparatus for Structure and Spectroscopy (COMPASS) at CERN with its use of beams of naturally polarized muons scattered of a polarized deuteron target, provides an environment of hard scattering between quasi-real photons and partons. Hard hadron quasi-real photo-production with polarized initial states is sensitive to the polarized gluon distribution $\\Delta$G through $\\gamma$-gluon($g$) direct channels as well as $q$-$g$ resolved processes. Comparisons of unpolarized differential cross section measurements to next-to-leading order (NLO) pQCD calculations are essential to develop our understanding of proton-proton and lepton-nucleon scattering at varying center of mass energies. These measurements are important to asses the applicability of NLO pQCD in interpreting polarized processes. In this talk we will discuss unidentified charged separated hadron production at low $Q^{2}$ (Q$^{2}1.0\\,GeV/c$). $$ spectra of charged hadrons at $Q^{2}>1 GeV^{2}/c^{2}$ will also be discussed.

Effect of polarization force on the Jeans instability of self-gravitating dusty plasma

International Nuclear Information System (INIS)

Prajapati, R.P.

2011-01-01

The effect of polarization force acting on massive charged dust grains is investigated analytically on the Jeans instability of self-gravitating dusty plasma. The gravitational force acting on the massive negatively charged interstellar dust grains are considered in presence of both electrical and polarization forces. The basic equations of the problem are formulated and a general dispersion relation is obtained using plane wave approximation in low frequency wave mode. The effect of polarization force in the dispersion relation of the problem, condition of the Jeans instability and expression of the critical Jeans wave number is examined. The unstable growing modes due to self-gravitational force are studied in the situation when polarization force on the dust grain exceeds over the electrical force in magnitude. It is observed that the polarization force increases the growth rate of the system. -- Highlights: → Jeans instability of gravitating dusty plasma with polarization force is investigated. → The fundamental Jeans instability criterion is modified due to polarization effect. → The critical Jeans length decreases due to increase in polarization force. → Polarization force destabilizes the unstable Jeans mode. → The collapsing of interstellar dusty cloud is discussed.

Interracial America. Opposing Viewpoints Series.

Science.gov (United States)

Szumski, Bonnie, Ed.

Books in the Opposing Viewpoints Series present debates about current issues that can be used to teach critical reading and thinking skills. The varied opinions in each book examine different aspects of a single issue. The topics covered in this volume explore the racial and ethnic tensions that concern many Americans today. The racial divide…

Effect of Fullerene Passivation on the Charging and Discharging Behavior of Perovskite Solar Cells: Reduction of Bound Charges and Ion Accumulation.

Science.gov (United States)

Shih, Yen-Chen; Wang, Leeyih; Hsieh, Hsiao-Chi; Lin, King-Fu

2018-04-11

Ion accumulation of organometal halide perovskites (OHPs) induced by electrode polarization of perovskite solar cells (PSCs) under illumination has been intensely studied and associated with a widely observed current-voltage hysteresis behavior. This work is dedicated to the investigation of the behavior of charged species at the compact TiO 2 /OHP interface with respect to electrode polarization in PSC devices. By providing a comprehensive discussion of open-circuit voltage ( V OC ) buildup and V OC decay under illumination and in the dark for the PSCs modified with [6,6]-phenyl-C 61 butyric acid methyl ester (PCBM) at the TiO 2 /OHP interface and their corresponding electrochemical impedance spectroscopies (EISs), a justified mechanism is proposed attempting to elucidate the dynamics of interfacial species with respect to the time and frequency domains. Our results demonstrate that the retarded V OC buildup and decay observed in PSC devices are related to the formation of bound charges in TiO 2 , which is essential to neutralize the oppositely charged ions accumulating at the OHP side. Besides, inserting a thicker PCBM at the TiO 2 /OHP interface as a passivation layer can alleviate the electrode polarization more efficiently as verified by the low dielectric constant measured from EIS. Moreover, photoluminescence measurements indicate that PCBM at the TiO 2 /OHP interface is capable of passivating a trap state and improving charge transfer. However, with respect to the time scale investigated in this work, the reduction of the hysteresis behavior on a millisecond scale is more likely due to less bound charge formation at the interface rather than shallow trap-state passivation by PCBM. After all, this work comprehensively demonstrates the interfacial properties of PSCs associated with PCBM passivation and helps to further understand its impact on charging/discharging as well as device performance.

The BNL polarized H- ion source development program

International Nuclear Information System (INIS)

Kponou, A.; Alessi, J.; Hershcovitch, A.; DeVito, B.

1992-01-01

Polarized protons have been available for acceleration in the AGS for the high energy physics program since 1984. The polarized H - source, PONI-1, has routinely supplied a 0.4 Hz, 400 μsec pulse having a nominal intensity of 40 μA. Polarization is ∼80% out of the ion source. After PONI- 1 became operational, a program was initiated to develop a more intense source based on a cold ground state atomic beam source, followed by ionization of the polarized H degrees beam by D - charge exchange. Various phases of this work have been fully reported elsewhere, and only a summary is given here

Polarization-induced Zener tunnel diodes in GaN/InGaN/GaN heterojunctions

Energy Technology Data Exchange (ETDEWEB)

Yan, Xiaodong; Li, Wenjun; Islam, S. M.; Pourang, Kasra; Fay, Patrick [Department of Electrical Engineering, University of Notre Dame, Notre Dame, Indiana 46556 (United States); Xing, Huili; Jena, Debdeep, E-mail: djena@cornell.edu [Department of Electrical Engineering, University of Notre Dame, Notre Dame, Indiana 46556 (United States); Departments of ECE and MSE, Cornell University, Ithaca, New York 14853 (United States)

2015-10-19

By the insertion of thin In{sub x}Ga{sub 1−x}N layers into Nitrogen-polar GaN p-n junctions, polarization-induced Zener tunnel junctions are studied. The reverse-bias interband Zener tunneling current is found to be weakly temperature dependent, as opposed to the strongly temperature-dependent forward bias current. This indicates tunneling as the primary reverse-bias current transport mechanism. The Indium composition in the InGaN layer is systematically varied to demonstrate the increase in the interband tunneling current. Comparing the experimentally measured tunneling currents to a model helps identify the specific challenges in potentially taking such junctions towards nitride-based polarization-induced tunneling field-effect transistors.

Polarization-induced Zener tunnel diodes in GaN/InGaN/GaN heterojunctions

International Nuclear Information System (INIS)

Yan, Xiaodong; Li, Wenjun; Islam, S. M.; Pourang, Kasra; Fay, Patrick; Xing, Huili; Jena, Debdeep

2015-01-01

By the insertion of thin In x Ga 1−x N layers into Nitrogen-polar GaN p-n junctions, polarization-induced Zener tunnel junctions are studied. The reverse-bias interband Zener tunneling current is found to be weakly temperature dependent, as opposed to the strongly temperature-dependent forward bias current. This indicates tunneling as the primary reverse-bias current transport mechanism. The Indium composition in the InGaN layer is systematically varied to demonstrate the increase in the interband tunneling current. Comparing the experimentally measured tunneling currents to a model helps identify the specific challenges in potentially taking such junctions towards nitride-based polarization-induced tunneling field-effect transistors

Nonclassical polarization effects in fluorescence emission spectra from microdroplets

Science.gov (United States)

Arnold, S.; Goddard, N. L.; Hill, S. C.

1999-12-01

We report a pronounced nonclassical polarization effect on the shape of fluorescence emission spectra from isolated microdroplets containing a dilute solution of soluble fluors or a dilute layer of surfactant fluors. We see different spectral shapes for 90° scattering when comparing between IVV, IVH, IHH, IHV. However, we measure the largest difference in spectral shape in the surfactant case, with the incident polarization directed toward the detector (IHV vs IHH). Imaging reveals that the emission in this case principally arises from two distinct regions near the surface of the droplet, which are diametrically opposed and along the axis of the incident laser beam. The effect appears to be the direct result of coupling between molecular emission moments and electromagnetic modes of the droplet. It is not the molecule which radiates but the molecule microvessel. Directional emission is sensitive to the polarization of the electromagnetic mode which is stimulated by the coupling.

High current polarized electron source

Science.gov (United States)

Suleiman, R.; Adderley, P.; Grames, J.; Hansknecht, J.; Poelker, M.; Stutzman, M.

2018-05-01

Jefferson Lab operates two DC high voltage GaAs photoguns with compact inverted insulators. One photogun provides the polarized electron beam at the Continuous Electron Beam Accelerator Facility (CEBAF) up to 200 µA. The other gun is used for high average current photocathode lifetime studies at a dedicated test facility up to 4 mA of polarized beam and 10 mA of un-polarized beam. GaAs-based photoguns used at accelerators with extensive user programs must exhibit long photocathode operating lifetime. Achieving this goal represents a significant challenge for proposed facilities that must operate in excess of tens of mA of polarized average current. This contribution describes techniques to maintain good vacuum while delivering high beam currents, and techniques that minimize damage due to ion bombardment, the dominant mechanism that reduces photocathode yield. Advantages of higher DC voltage include reduced space-charge emittance growth and the potential for better photocathode lifetime. Highlights of R&D to improve the performance of polarized electron sources and prolong the lifetime of strained-superlattice GaAs are presented.

Vector optical fields with polarization distributions similar to electric and magnetic field lines.

Science.gov (United States)

Pan, Yue; Li, Si-Min; Mao, Lei; Kong, Ling-Jun; Li, Yongnan; Tu, Chenghou; Wang, Pei; Wang, Hui-Tian

2013-07-01

We present, design and generate a new kind of vector optical fields with linear polarization distributions modeling to electric and magnetic field lines. The geometric configurations of "electric charges" and "magnetic charges" can engineer the spatial structure and symmetry of polarizations of vector optical field, providing additional degrees of freedom assisting in controlling the field symmetry at the focus and allowing engineering of the field distribution at the focus to the specific applications.

Overeruption of teeth opposing removable partial dentures: a preliminary study.

Science.gov (United States)

Matsuda, Ken-Ichi; Miyashita, Yuji; Ikebe, Kazunori; Enoki, Kaori; Kurushima, Yuko; Mihara, Yusuke; Maeda, Yoshinobu

2014-01-01

One of the purposes of prosthodontic treatment is to prevent overeruption of opposing teeth, but there is currently minimal literature describing the efficacy of removable partial dentures (RPDs) in performing this function. This study investigated overeruption following RPD treatment. The study participants were 33 patients treated with RPDs, and overeruption was evaluated by comparing the surface computeraided design data of dental casts made at two different time points-before and after RPD treatment. Overeruption was observed in 38.1% of teeth opposed by the RPD, which was much less than the proportion of teeth that overerupted when not opposed by the RPD.

Setup and proof of principle of SAPIS (Stored Atoms Polarized Ion Source), a novel source of polarized H{sup -}/D{sup -} ions; Aufbau und Funktionsnachweis von SAPIS (Stored Atoms Polarized Ion Source), einer neuartigen Quelle polarisierter H{sup -}/D{sup -}-Ionen

Energy Technology Data Exchange (ETDEWEB)

Emmerich, R.

2007-02-14

The objective of this work was the setup and the proof-of-principle of a new type of negative polarized hydrogen or deuterium ion source, which is based on the charge-exchange reaction (vector)H{sup 0}+Cs{sup 0}{yields}(vector)H{sup -}+Cs{sup +}, as for instance the Colliding-Beams-Source (CBS) at the Cooler Synchrotron COSY in Juelich. In contrast to the CBS, the use of a storage cell for the charge-exchange region promises an increase in H{sup -} current by at least an order of magnitude without considerable polarization losses. For these purposes, a new laboratory was equipped and both a polarized hydrogen/deuterium atomic beam source and an intense neutral cesium-beam source have been build-on. A Lambshift polarimeter, which allows the measurement of the nuclear polarization of the atomic as well as ionic beams, was completed with the construction of a new spin-filter. After commissioning and optimizing each of these sources, a storage cell was developed and installed in the charge-exchange region with a magnetic field. Additionally, components for the extraction, detection and analysis of the negative ion beam were installed. Following the decisive proof of principle, investigation of the properties of the storage cell, especially as to H recombination and depolarisation, was begun. Furthermore, a number of software programs was developed for the control and monitoring of different components of the sources as well as a universal measuring software for the complete installation, including the measurement and calculation of the beam polarization. At the same time, the remote control system of the Cologne source of polarized ions LASCO at the FN tandem accelerator was completely modernized. (orig.)

Sources for charged particles

International Nuclear Information System (INIS)

Arianer, J.

1997-01-01

This document is a basic course on charged particle sources for post-graduate students and thematic schools on large facilities and accelerator physics. A simple but precise description of the creation and the emission of charged particles is presented. This course relies on every year upgraded reference documents. Following relevant topics are considered: electronic emission processes, technological and practical considerations on electron guns, positron sources, production of neutral atoms, ionization, plasma and discharge, different types of positive and negative ion sources, polarized particle sources, materials for the construction of ion sources, low energy beam production and transport. (N.T.)

Causal electric charge diffusion and balance functions in relativistic heavy-ion collisions

Science.gov (United States)

Kapusta, Joseph I.; Plumberg, Christopher

2018-01-01

We study the propagation and diffusion of electric charge fluctuations in high-energy heavy-ion collisions using the Cattaneo form for the dissipative part of the electric current. As opposed to the ordinary diffusion equation this form limits the speed at which charge can propagate. Including the noise term in the current, which arises uniquely from the fluctuation-dissipation theorem, we calculate the balance functions for charged hadrons in a simple 1+1-dimensional Bjorken hydrodynamical model. Limiting the speed of propagation of charge fluctuations increases the height and reduces the width of these balance functions when plotted versus rapidity. We also estimate the numerical value of the associated diffusion time constant from anti-de Sitter-space/conformal-field theory.

Quasinormal modes of semiclassical electrically charged black holes

Energy Technology Data Exchange (ETDEWEB)

Fernandez Piedra, Owen Pavel [Departamento de Fisica y Quimica, Facultad de Mecanica, Universidad de Cienfuegos, Carretera a Rodas, km 4, Cuatro Caminos, Cienfuegos (Cuba); De Oliveira, Jeferson, E-mail: opavel@ucf.edu.cu, E-mail: jeferson@fma.if.usp.br [Instituto de Fisica, Universidade de Sao Paulo, CP 66318, 05315-970, Sao Paulo (Brazil)

2011-04-21

We report the results concerning the influence of vacuum polarization due to quantum massive vector, scalar and spinor fields on the scalar sector of quasinormal modes in spherically symmetric charged black holes. The vacuum polarization from quantized fields produces a shift in the values of the quasinormal frequencies, and correspondingly the semiclassical system becomes a better oscillator with respect to the classical Reissner-Nordstroem black hole.

Pore Polarity and Charge Determine Differential Block of Kir1.1 and Kir7.1 Potassium Channels by Small-Molecule Inhibitor VU590.

Science.gov (United States)

Kharade, Sujay V; Sheehan, Jonathan H; Figueroa, Eric E; Meiler, Jens; Denton, Jerod S

2017-09-01

VU590 was the first publicly disclosed, submicromolar-affinity (IC 50 = 0.2 μ M), small-molecule inhibitor of the inward rectifier potassium (Kir) channel and diuretic target, Kir1.1. VU590 also inhibits Kir7.1 (IC 50 ∼ 8 μ M), and has been used to reveal new roles for Kir7.1 in regulation of myometrial contractility and melanocortin signaling. Here, we employed molecular modeling, mutagenesis, and patch clamp electrophysiology to elucidate the molecular mechanisms underlying VU590 inhibition of Kir1.1 and Kir7.1. Block of both channels is voltage- and K + -dependent, suggesting the VU590 binding site is located within the pore. Mutagenesis analysis in Kir1.1 revealed that asparagine 171 (N171) is the only pore-lining residue required for high-affinity block, and that substituting negatively charged residues (N171D, N171E) at this position dramatically weakens block. In contrast, substituting a negatively charged residue at the equivalent position in Kir7.1 enhances block by VU590, suggesting the VU590 binding mode is different. Interestingly, mutations of threonine 153 (T153) in Kir7.1 that reduce constrained polarity at this site (T153C, T153V, T153S) make wild-type and binding-site mutants (E149Q, A150S) more sensitive to block by VU590. The Kir7.1-T153C mutation enhances block by the structurally unrelated inhibitor VU714 but not by a higher-affinity analog ML418, suggesting that the polar side chain of T153 creates a barrier to low-affinity ligands that interact with E149 and A150. Reverse mutations in Kir1.1 suggest that this mechanism is conserved in other Kir channels. This study reveals a previously unappreciated role of membrane pore polarity in determination of Kir channel inhibitor pharmacology. Copyright © 2017 by The American Society for Pharmacology and Experimental Therapeutics.

3D electric field calculation with surface charge method

International Nuclear Information System (INIS)

Yamada, S.

1992-01-01

This paper describes an outline and some examples of three dimensional electric field calculations with a computer code developed at NIRS. In the code, a surface charge method is adopted because of it's simplicity in the mesh establishing procedure. The charge density in a triangular mesh is assumed to distribute with a linear function of the position. The electric field distribution is calculated for a pair of drift tubes with the focusing fingers on the opposing surfaces. The field distribution in an acceleration gap is analyzed with a Fourier-Bessel series expansion method. The calculated results excellently reproduces the measured data with a magnetic model. (author)

Lightning mapping and dual-polarization radar observations of electrified storms at Langmuir Laboratory

Science.gov (United States)

Krehbiel, P. R.; Hyland, P. T.; Edens, H. E.; Rison, W.

2013-12-01

Observations being made at Langmuir Laboratory with the NM Tech Lightning Mapping Array (LMA) and the University of Oklahoma ARRC PX-1000 dual polarization X-band radar strongly confirm and expand upon the normal polarity tripolar electrical structure of central New Mexico storms. This is in sharp contrast with the anomalously electrified storm structures observed in northern Colorado during and subsequent to the 2012 DC3 field campaign, as seen with North Colorado LMA and CSU CHILL dual-polarization radar observations. In this presentation we focus on the New Mexico observations, and several modes in which the tripolar structure appears initially to develop and evolve with time. Central New Mexico storms are often prolific producers of negative cloud-to-ground (CG) flashes, but rarely produce positive CGs. By contrast, many or most north Colorado storms are CG-deficient, with the relatively few CG discharges being of predominantly positive polarity. In addition, NM storms commonly produce bolt-from-the-blue (BFB) negative CGs, whereas anomalously electrified Colorado storms produce none. The occurrence of BFBs is indicative of a relatively weak lower positive charge region, while the occurrence of normal downward -CGs is indicative of a somewhat stronger lower positive charge. The lack of -CGs in Colorado storms results from lower positive charge being a dominant storm charge that is elevated in altitude. These and other basic features of the electrically activity of storms, coupled with dual polarization and Doppler radar observations of hydrometeor types and motions, are leading to a better understanding of the storm electrification processes.

Effects of polarization of polar semiconductor on electrical properties of poly(vinylidene fluoride-trifluoroethylene)/ZnO heterostructures

International Nuclear Information System (INIS)

Yamada, Hiroaki; Yoshimura, Takeshi; Fujimura, Norifumi

2015-01-01

The electrical properties of heterostructures composed of poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) and ZnO with different crystallographic polarities, i.e., O- and Zn-polar ZnO, were investigated. Distinct differences in the capacitance-voltage and polarization-voltage characteristics between the P(VDF-TrFE)/O- and Zn-polar ZnO were obtained in the depletion regions of ZnO. The band configurations were determined by X-ray photoelectron spectroscopy (XPS) using a synchrotron radiation beam to analyze the differences in the electrical properties of the P(VDF-TrFE)/O- and Zn-polar ZnO. The XPS spectra indicated that the valence band maximum of P(VDF-TrFE) is 2.9 and 2.7 eV higher than Zn- and O-polar ZnO, respectively. Thus, both structures have staggered band configurations with large valence band offsets, and the spontaneous polarization of ZnO is less effective on the band lineup. The electrical properties of the P(VDF-TrFE)/ZnO heterostructures are modulated through carrier generation because of the polarization-mediated interface charges and the staggered band alignments of the P(VDF-TrFE)/ZnO with a large valence band offset

Theoretical Study of the Charge-Transfer State Separation within Marcus Theory

DEFF Research Database (Denmark)

Volpi, Riccardo; Nassau, Racine; Nørby, Morten Steen

2016-01-01

We study, within Marcus theory, the possibility of the charge-transfer (CT) state splitting at organic interfaces and a subsequent transport of the free charge carriers to the electrodes. As a case study we analyze model anthracene-C60 interfaces. Kinetic Monte Carlo (KMC) simulations on the cold...... CT state were performed at a range of applied electric fields, and with the fields applied at a range of angles to the interface to simulate the action of the electric field in a bulk heterojunction (BHJ) interface. The results show that the inclusion of polarization in our model increases CT state...... dissociation and charge collection. The effect of the electric field on CT state splitting and free charge carrier conduction is analyzed in detail with and without polarization. Also, depending on the relative orientation of the anthracene and C60 molecules at the interface, CT state splitting shows different...

Dynamics of a charged particle in a linearly polarized traveling wave. Hamiltonian approach to laser-matter interaction at very high intensities

International Nuclear Information System (INIS)

Bourdier, A.; Patin, D.

2005-01-01

The basic physical processes in laser-matter interaction, up to 10 17 W/cm 2 (for a neodymium laser) are now well understood, on the other hand, new phenomena evidenced in particle-in-cell code simulations have to be investigated above 10 18 W/cm 2 . Thus, the relativistic motion of a charged particle in a linearly polarized homogeneous electromagnetic wave is studied, here, using the Hamiltonian formalism. First, the motion of a single particle in a linearly polarized traveling wave propagating in a non-magnetized space is explored. The problem is shown to be integrable. The results obtained are compared to those derived considering a cold electron plasma model. When the phase velocity is close to c, it is shown that the two approaches are in good agreement during a finite time. After this short time, when the plasma response is taken into account no chaos take place at least when considering low densities and/or high wave intensities. The case of a charged particle in a traveling wave propagating along a constant homogeneous magnetic field is then considered. The problem is shown to be integrable when the wave propagates in vacuum. The existence of a synchronous solution is shown very simply. In the case when the wave propagates in a low density plasma, using a simplifying Lorentz transformation, it is shown that the system can be reduced to a time-dependent system with two degrees of freedom. The system is shown to be non-integrable, chaos appears when a secondary resonance and a primary resonance overlap. Finally, stochastic instabilities are studied by considering the motion of one particle in a very high intensity wave perturbed by one or two low intensity traveling waves. Resonances are identified and conditions for resonance overlap are studied. (authors)

Single spin asymmetries in charged kaon production from semi-inclusive deep inelastic scattering on a transversely polarized 3He target

Science.gov (United States)

Zhao, Y. X.; Wang, Y.; Allada, K.; Aniol, K.; Annand, J. R. M.; Averett, T.; Benmokhtar, F.; Bertozzi, W.; Bradshaw, P. C.; Bosted, P.; Camsonne, A.; Canan, M.; Cates, G. D.; Chen, C.; Chen, J.-P.; Chen, W.; Chirapatpimol, K.; Chudakov, E.; Cisbani, E.; Cornejo, J. C.; Cusanno, F.; Dalton, M. M.; Deconinck, W.; de Jager, C. W.; De Leo, R.; Deng, X.; Deur, A.; Ding, H.; Dolph, P. A. M.; Dutta, C.; Dutta, D.; El Fassi, L.; Frullani, S.; Gao, H.; Garibaldi, F.; Gaskell, D.; Gilad, S.; Gilman, R.; Glamazdin, O.; Golge, S.; Guo, L.; Hamilton, D.; Hansen, O.; Higinbotham, D. W.; Holmstrom, T.; Huang, J.; Huang, M.; Ibrahim, H. F.; Iodice, M.; Jiang, X.; Jin, G.; Jones, M. K.; Katich, J.; Kelleher, A.; Kim, W.; Kolarkar, A.; Korsch, W.; LeRose, J. J.; Li, X.; Li, Y.; Lindgren, R.; Liyanage, N.; Long, E.; Lu, H.-J.; Margaziotis, D. J.; Markowitz, P.; Marrone, S.; McNulty, D.; Meziani, Z.-E.; Michaels, R.; Moffit, B.; Muñoz Camacho, C.; Nanda, S.; Narayan, A.; Nelyubin, V.; Norum, B.; Oh, Y.; Osipenko, M.; Parno, D.; Peng, J.-C.; Phillips, S. K.; Posik, M.; Puckett, A. J. R.; Qian, X.; Qiang, Y.; Rakhman, A.; Ransome, R.; Riordan, S.; Saha, A.; Sawatzky, B.; Schulte, E.; Shahinyan, A.; Shabestari, M. H.; Širca, S.; Stepanyan, S.; Subedi, R.; Sulkosky, V.; Tang, L.-G.; Tobias, A.; Urciuoli, G. M.; Vilardi, I.; Wang, K.; Wojtsekhowski, B.; Yan, X.; Yao, H.; Ye, Y.; Ye, Z.; Yuan, L.; Zhan, X.; Zhang, Y.; Zhang, Y.-W.; Zhao, B.; Zheng, X.; Zhu, L.; Zhu, X.; Zong, X.; Jefferson Lab Hall A Collaboration

2014-11-01

We report the first measurement of target single spin asymmetries of charged kaons produced in semi-inclusive deep inelastic scattering of electrons off a transversely polarized 3He target. Both the Collins and Sivers moments, which are related to the nucleon transversity and Sivers distributions, respectively, are extracted over the kinematic range of 0.1

Polarization effects on spectra of spherical core/shell nanostructures: Perturbation theory against finite difference approach

International Nuclear Information System (INIS)

Ibral, Asmaa; Zouitine, Asmaa; Assaid, El Mahdi

2015-01-01

Poisson equation is solved analytically in the case of a point charge placed anywhere in a spherical core/shell nanostructure, immersed in aqueous or organic solution or embedded in semiconducting or insulating matrix. Conduction and valence band-edge alignments between core and shell are described by finite height barriers. Influence of polarization charges induced at the surfaces where two adjacent materials meet is taken into account. Original expressions of electrostatic potential created everywhere in the space by a source point charge are derived. Expressions of self-polarization potential describing the interaction of a point charge with its own image–charge are deduced. Contributions of double dielectric constant mismatch to electron and hole ground state energies as well as nanostructure effective gap are calculated via first order perturbation theory and also by finite difference approach. Dependencies of electron, hole and gap energies against core to shell radii ratio are determined in the case of ZnS/CdSe core/shell nanostructure immersed in water or in toluene. It appears that finite difference approach is more efficient than first order perturbation method and that the effect of polarization charge may in no case be neglected as its contribution can reach a significant proportion of the value of nanostructure gap

Polarization effects on spectra of spherical core/shell nanostructures: Perturbation theory against finite difference approach

Energy Technology Data Exchange (ETDEWEB)

Ibral, Asmaa [Equipe d' Optique et Electronique du Solide, Département de Physique, Faculté des Sciences, Université Chouaïb Doukkali, B. P. 20 El Jadida principale, El Jadida, Royaume du Maroc (Morocco); Laboratoire d' Instrumentation, Mesure et Contrôle, Département de Physique, Faculté des Sciences, Université Chouaïb Doukkali, B. P. 20 El Jadida principale, El Jadida, Royaume du Maroc (Morocco); Zouitine, Asmaa [Département de Physique, Ecole Nationale Supérieure d' Enseignement Technique, Université Mohammed V Souissi, B. P. 6207 Rabat-Instituts, Rabat, Royaume du Maroc (Morocco); Assaid, El Mahdi, E-mail: eassaid@yahoo.fr [Equipe d' Optique et Electronique du Solide, Département de Physique, Faculté des Sciences, Université Chouaïb Doukkali, B. P. 20 El Jadida principale, El Jadida, Royaume du Maroc (Morocco); Laboratoire d' Instrumentation, Mesure et Contrôle, Département de Physique, Faculté des Sciences, Université Chouaïb Doukkali, B. P. 20 El Jadida principale, El Jadida, Royaume du Maroc (Morocco); and others

2015-02-01

Poisson equation is solved analytically in the case of a point charge placed anywhere in a spherical core/shell nanostructure, immersed in aqueous or organic solution or embedded in semiconducting or insulating matrix. Conduction and valence band-edge alignments between core and shell are described by finite height barriers. Influence of polarization charges induced at the surfaces where two adjacent materials meet is taken into account. Original expressions of electrostatic potential created everywhere in the space by a source point charge are derived. Expressions of self-polarization potential describing the interaction of a point charge with its own image–charge are deduced. Contributions of double dielectric constant mismatch to electron and hole ground state energies as well as nanostructure effective gap are calculated via first order perturbation theory and also by finite difference approach. Dependencies of electron, hole and gap energies against core to shell radii ratio are determined in the case of ZnS/CdSe core/shell nanostructure immersed in water or in toluene. It appears that finite difference approach is more efficient than first order perturbation method and that the effect of polarization charge may in no case be neglected as its contribution can reach a significant proportion of the value of nanostructure gap.

Charge Mediated Compaction and Rearrangement of Gas-Phase Proteins: A Case Study Considering Two Proteins at Opposing Ends of the Structure-Disorder Continuum

Science.gov (United States)

Jhingree, Jacquelyn R.; Bellina, Bruno; Pacholarz, Kamila J.; Barran, Perdita E.

2017-07-01

Charge reduction in the gas phase provides a direct means of manipulating protein charge state, and when coupled to ion mobility mass spectrometry (IM-MS), it is possible to monitor the effect of charge on protein conformation in the absence of solution. Use of the electron transfer reagent 1,3-dicyanobenzene, coupled with IM-MS, allows us to monitor the effect of charge reduction on the conformation of two proteins deliberately chosen from opposite sides of the order to disorder continuum: bovine pancreatic trypsin inhibitor (BPTI) and beta casein. The ordered BPTI presents compact conformers for each of three charge states accompanied by narrow collision cross-section distributions (TWCCSDN2→He). Upon reduction of BPTI, irrespective of precursor charge state, the TWCCSN2→He decreases to a similar distribution as found for the nESI generated ion of identical charge. The behavior of beta casein upon charge reduction is more complex. It presents over a wide charge state range (9-28), and intermediate charge states (13-18) have broad TWCCSDN2→He with multiple conformations, where both compaction and rearrangement are seen. Further, we see that the TWCCSDN2→He of the latter charge states are even affected by the presence of radical anions. Overall, we conclude that the flexible nature of some proteins result in broad conformational distributions comprised of many families, even for single charge states, and the barrier between different states can be easily overcome by an alteration of the net charge.

Polar User’s Manual.

Science.gov (United States)

1985-10-01

spere 4 .11 . Flig us -pee 4.2-I 4.21 FINITE ELEMENTS 4.21.1 GENERAL Consider a charged object isolated in space. The potential 6 everywhere is given...Belo, fom eftto rghtarequai- spere ocago righ cylnde, teraheron w de, ad rctanula paraleleiped 6.1-6 TABLE 6/1. POLAR BUILDING BLOCKS AND THEIR KEYWORDS

Dynamics of a charged particle in a circularly polarized travelling electromagnetic wave. Self-consistent model for the wave-particle dynamical interaction

International Nuclear Information System (INIS)

Bourdier, A.

1999-01-01

This work concerns mainly the dynamics of a charged particle in an electromagnetic wave. It is a first step in elaborating a more general model permitting to predict the wave-particle interaction. We show how deriving a first integral gives an idea on how to create an electron current in a cold electron plasma. We present results which can be used to test the 2D and 3D Vlasov-Maxwell codes being built up in CEA-DAM. These codes will allow the calcination of the magnetic field created by an electromagnetic wave like the one due to the inverse Faraday effect when a circularly polarized wave drives the electrons of a plasma into circular orbits. (author)

Dual descriptors within the framework of spin-polarized density functional theory.

Science.gov (United States)

Chamorro, E; Pérez, P; Duque, M; De Proft, F; Geerlings, P

2008-08-14

Spin-polarized density functional theory (SP-DFT) allows both the analysis of charge-transfer (e.g., electrophilic and nucleophilic reactivity) and of spin-polarization processes (e.g., photophysical changes arising from electron transitions). In analogy with the dual descriptor introduced by Morell et al. [J. Phys. Chem. A 109, 205 (2005)], we introduce new dual descriptors intended to simultaneously give information of the molecular regions where the spin-polarization process linking states of different multiplicity will drive electron density and spin density changes. The electronic charge and spin rearrangement in the spin forbidden radiative transitions S(0)-->T(n,pi(*)) and S(0)-->T(pi,pi(*)) in formaldehyde and ethylene, respectively, have been used as benchmark examples illustrating the usefulness of the new spin-polarization dual descriptors. These quantities indicate those regions where spin-orbit coupling effects are at work in such processes. Additionally, the qualitative relationship between the topology of the spin-polarization dual descriptors and the vertical singlet triplet energy gap in simple substituted carbene series has been also discussed. It is shown that the electron density and spin density rearrangements arise in agreement with spectroscopic experimental evidence and other theoretical results on the selected target systems.

Image charge forces inside conducting boundaries

International Nuclear Information System (INIS)

Tinkle, Mark D.; Barlow, S. E.

2001-01-01

The common description of the electrostatic force, F(x)=-q∇φ(x), provides an incomplete description of the force on the charge q at a point x when the charge itself induces additional fields, e.g., image charges, polarizations, etc. The equation may be corrected through the introduction of a ''pseudopotential'' formalism. Exploration of some of the elementary properties of the pseudopotential demonstrates its essential simplicity. This simplicity allows it to be incorporated directly into dynamics calculations. We explicitly evaluate the pseudopotential in a number of simple but important cases including the sphere, parallel plates, the rectangular prism, and the cylindrical box. The pseudopotential formalism may be expanded to include extended charge distributions; in this latter form we are able to directly apply the results to experimental measurements

Assessment of Sub-Micron Particles by Exploiting Charge Differences with Dielectrophoresis

Directory of Open Access Journals (Sweden)

Maria F. Romero-Creel

2017-08-01

Full Text Available The analysis, separation, and enrichment of submicron particles are critical steps in many applications, ranging from bio-sensing to disease diagnostics. Microfluidic electrokinetic techniques, such as dielectrophoresis (DEP have proved to be excellent platforms for assessment of submicron particles. DEP is the motion of polarizable particles under the presence of a non-uniform electric field. In this work, the polarization and dielectrophoretic behavior of polystyrene particles with diameters ranging for 100 nm to 1 μm were studied employing microchannels for insulator based DEP (iDEP and low frequency (<1000 Hz AC and DC electric potentials. In particular, the effects of particle surface charge, in terms of magnitude and type of functionalization, were examined. It was found that the magnitude of particle surface charge has a significant impact on the polarization and dielectrophoretic response of the particles, allowing for successful particle assessment. Traditionally, charge differences are exploited employing electrophoretic techniques and particle separation is achieved by differential migration. The present study demonstrates that differences in the particle’s surface charge can also be exploited by means of iDEP; and that distinct types of nanoparticles can be identified by their polarization and dielectrophoretic behavior. These findings open the possibility for iDEP to be employed as a technique for the analysis of submicron biological particles, where subtle differences in surface charge could allow for rapid particle identification and separation.

Polarization singularities of optical fields caused by structural dislocations in crystals

International Nuclear Information System (INIS)

Savaryn, V; Vasylkiv, Yu; Krupych, O; Skab, I; Vlokh, R

2013-01-01

We analyze polarization singularities of optical beams that propagate through crystals possessing structural dislocations. We show that screw dislocations of crystalline structure can lead to the appearance of purely screw-type dislocations of light wavefronts. This can happen only in crystals that belong to trigonal and cubic systems. These polarization singularities will give rise to optical vortices with the topological charge equal to ±1, whenever a crystal sample is placed between crossed circular polarizers. We have also found that edge dislocations present in the cubic and trigonal crystals, with the Burgers vector perpendicular to the three-fold symmetry axes, can impose mixed screw-edge dislocations in the wavefronts of optical beams and generate singly charged optical vortices. The results of our analysis can be applied for detecting and identifying dislocations of different types available in crystals. (paper)

Long-range interaction between heterogeneously charged membranes.

Science.gov (United States)

Jho, Y S; Brewster, R; Safran, S A; Pincus, P A

2011-04-19

Despite their neutrality, surfaces or membranes with equal amounts of positive and negative charge can exhibit long-range electrostatic interactions if the surface charge is heterogeneous; this can happen when the surface charges form finite-size domain structures. These domains can be formed in lipid membranes where the balance of the different ranges of strong but short-ranged hydrophobic interactions and longer-ranged electrostatic repulsion result in a finite, stable domain size. If the domain size is large enough, oppositely charged domains in two opposing surfaces or membranes can be strongly correlated by the electrostatic interactions; these correlations give rise to an attractive interaction of the two membranes or surfaces over separations on the order of the domain size. We use numerical simulations to demonstrate the existence of strong attractions at separations of tens of nanometers. Large line tensions result in larger domains but also increase the charge density within the domain. This promotes correlations and, as a result, increases the intermembrane attraction. On the other hand, increasing the salt concentration increases both the domain size and degree of domain anticorrelation, but the interactions are ultimately reduced due to increased screening. The result is a decrease in the net attraction as salt concentration is increased. © 2011 American Chemical Society

The 50 kV inverted source of polarized electrons at ELSA

International Nuclear Information System (INIS)

Hillert, Wolfgang; Gowin, Michael; Neff, Berhold

2001-01-01

The future medium energy physics program at the electron stretcher accelerator ELSA of Bonn University mainly relies on experiments requiring a beam of polarized electrons and a polarized target. To provide a polarized beam with high polarization and sufficient intensity a pulsed 50 kV inverted gun of polarized electrons has been set into operation. The gun is operated in space charge limitation, producing a peak current of 100 mA in rectangular 1μs long electron pulses. Photocathode lifetime during operation is higher than 3000 hours. Using a Be-InGaAs/Be-AlGaAs superlattice photocathode a polarization of 80% and a corresponding quantum efficiency of 0.4% could be obtained

Spin polarized and density modulated phases in symmetric electron-electron and electron-hole bilayers.

Science.gov (United States)

Kumar, Krishan; Moudgil, R K

2012-10-17

We have studied symmetric electron-electron and electron-hole bilayers to explore the stable homogeneous spin phase and the feasibility of inhomogeneous charge-/spin-density ground states. The former is resolved by comparing the ground-state energies in states of different spin polarizations, while the latter is resolved by searching for a divergence in the wavevector-dependent static charge/spin susceptibility. For this endeavour, we have used the dielectric approach within the self-consistent mean-field theory of Singwi et al. We find that the inter-layer interactions tend to change an abrupt spin-polarization transition of an isolated layer into a nearly gradual one, even though the partially spin-polarized phases are not clearly stable within the accuracy of our calculation. The transition density is seen to decrease with a reduction in layer spacing, implying a suppression of spin polarization by inter-layer interactions. Indeed, the suppression shows up distinctly in the spin susceptibility computed from the spin-polarization dependence of the ground-state energy. However, below a critical layer spacing, the unpolarized liquid becomes unstable against a charge-density-wave (CDW) ground state at a density preceding full spin polarization, with the transition density for the CDW state increasing on further reduction in the layer spacing. Due to attractive e-h correlations, the CDW state is found to be more pronounced in the e-h bilayer. On the other hand, the static spin susceptibility diverges only in the long-wavelength limit, which simply represents a transition to the homogeneous spin-polarized phase.

Precision measurement of the cross section of charged-current and neutral current processes at large Q{sup 2} at HERA with the polarized-electron beam; Mesures de precision de la section efficace des processus courant charge et courant neutre a grand Q{sup 2} a HERA avec le faisceau d'electrons polarises

Energy Technology Data Exchange (ETDEWEB)

Tran, Trong Hieu

2011-04-15

The inclusive cross sections for both charged and neutral current processes have been measured in interactions of longitudinally polarized electrons (positrons) with unpolarized protons using the full data samples collected by H1 at HERA-II. The data taken at a center-of-mass energy of 319 GeV correspond to an integrated luminosity of 149.1 pb{sup -1} and 180.0 pb{sup -1} for e{sup -}p and e{sup +}p collisions, representing an increase in statistics of a factor of 10 and 2, respectively, over the data from HERA-I. The measured double differential cross sections d{sup 2}{sigma}/dxdQ{sup 2} cover more than two orders of magnitude in both Q{sup 2}, the negative four-momentum transfer squared, up to 30000 GeV{sup 2}, and Bjorken x, down to 0.003. The cross section data are compared to predictions of the Standard Model which is able to provide a good description of the data. The polarization asymmetry as a function of Q{sup 2} is measured with improved precision, confirming the previous observation of P violation effect in neutral current ep scattering at distances down to 10{sup -18} m. The total cross sections of the charged current process, for Q{sup 2} > 400 GeV{sup 2} and inelasticity y < 0.9 are measured for 4 independent data samples with e{sup {+-}} beams and different polarization values. Together with the corresponding cross section obtained from the previously published unpolarized data, the polarization dependence of the charged current cross section is measured and found to be in agreement with the Standard Model prediction with the absence of right-handed charged current. The cross sections are combined with previously published data from H1 to obtain the most precise unpolarized measurements. These are used to extract the structure function xF{sub 3}{sup {gamma}}{sup Z} which is sensitive to the valence quark distributions down to low x values. The new cross sections have also been used in a combined electroweak and QCD fit to significantly improve the

Space-charge-mediated anomalous ferroelectric switching in P(VDF-TrEE) polymer films

KAUST Repository

Hu, Weijin; Wang, Zhihong; Du, Yuanmin; Zhang, Xixiang; Wu, Tao

2014-01-01

We report on the switching dynamics of P(VDF-TrEE) copolymer devices and the realization of additional substable ferroelectric states via modulation of the coupling between polarizations and space charges. The space-charge-limited current

Factors affecting the electrostatic charge of ceramic powders

International Nuclear Information System (INIS)

Lorite, I.; Romero, J.; Fernandez, J. F.

2011-01-01

The phenomenon of electrostatic charge in ceramic powders takes place when the particle surfaces enter in contact between them or with the containers. The accumulation of electrostatic charge is of relevance in ceramic powders in view of their insulating character and the risk of explosions during the material handling. In this work the main factors that affect the appearance of intrinsic charge and tribo-charge in ceramic powder have been studied. In ceramic powders of alumina it has been verified that the smallest particle sizes present an increase of the electrostatic charge of negative polarity. A correlation has been observed between the nature of the OH -surface groups and the electrostatic charge. The intrinsic charge and the tribocharge in ceramic powders can be diminished by compensating the surface groups that support the charge. The dry dispersion of nanoparticles on microparticles allows surface charge compensation with a noticeable modification of the powder agglomeration. (Author) 19 refs.

Through space and through bridge channels of charge transfer at p-n nano-junctions: A DFT study

Energy Technology Data Exchange (ETDEWEB)

Dandu, Naveen [Department of Chemistry and Biochemistry, NDSU, Fargo, ND 58108 (United States); Tretiak, Sergei [Theoretical Division, Center for Nonlinear Studies (CNLS) and Center for Integrated Nanotechnologies (CINT), Los Alamos National Laboratory, Los Alamos, 57069, NM 87454 (United States); Kilina, Svetlana [Department of Chemistry and Biochemistry, NDSU, Fargo, ND 58108 (United States); Kilin, Dmitri, E-mail: Dmitri.Kilin@ndsu.edu [Department of Chemistry and Biochemistry, NDSU, Fargo, ND 58108 (United States)

2016-12-20

Highlights: • Properties of interacting QDs depend on the fashion of interaction: through-bond or through-space. • The disconnected and undoped dimer models shows FÓ§rster band formation. • Dimer models with some doping exhibit degenerate charge-transfer excitons. • p- and n-doped qds shows polarization at the interface. • A photoexcitation polarizes p-n interface, in relation to phototovoltaic effect. - Abstract: Details of charge density distribution at p-n nano interface are analyzed with density functional theory techniques using model system of dimers of doped silicon quantum dots interacting through bond and through space. Spatial distributions of transition densities between the ground and excited states suggest the character of essential electronic excitations, which have a FÓ§rster, bound, unbound, or charge transfer character. A redistribution of electronic density from n-impurities to p-impurities results in a ground state polarization and creates an offset of energies of the bands localized on p-doped quantum dot and the bands localized on n-doped quantum dot. Although impurities contribute very few orbitals to the total density, a ground state charge redistribution and polarization are both responsible for the presence of a large number of charge transfer excitations involving solely silicon orbitals.

Filter material charging apparatus for filter assembly for radioactive contaminants

International Nuclear Information System (INIS)

Goldsmith, J.M.; O'Nan, A. Jr.

1977-01-01

A filter charging apparatus for a filter assembly is described. The filter assembly includes a housing with at least one filter bed therein and the filter charging apparatus for adding filter material to the filter assembly includes a tank with an opening therein, the tank opening being disposed in flow communication with opposed first and second conduit means, the first conduit means being in flow communication with the filter assembly housing and the second conduit means being in flow communication with a blower means. Upon activation of the blower means, the blower means pneumatically conveys the filter material from the tank to the filter housing

La-doped BaTiO3 heterostructures: Compensating the polarization discontinuity

Directory of Open Access Journals (Sweden)

D. P. Kumah

2013-12-01

Full Text Available We demonstrate a route to manipulate the polarization and internal electric field of a complex oxide heterostructure using a layering sequence based on the LaAlO3-SrTiO3 interface. By combining sensitive atomic-level mapping of the structure using direct x-ray phase-retrieval methods with theoretical modeling of the electrostatic charge and polarization, we have devised a novel single-domain polar heterostructure. We find that ionic rearrangement results in strain and free energy minimization, and eliminates the polarization discontinuity leading to a two-fold increase of the spontaneous polarization towards the surface of an ultra-thin single-domain BaTiO3 film.

Ab-initio study of the relation between electric polarization and electric field gradients in ferroelectrics

CERN Document Server

Gonçalves, J N; Correia, J G; Butz, T; Picozzi, S; Fenta, A S; Amaral, V S

2012-01-01

The hyperfine interaction between the quadrupole moment of atomic nuclei and the electric field gradient (EFG) provides information on the electronic charge distribution close to a given atomic site. In ferroelectric materials, the loss of inversion symmetry of the electronic charge distribution is necessary for the appearance of the electric polarization. We present first-principles density functional theory calculations of ferroelectrics such as BaTiO$_{3}$, KNbO$_{3}$, PbTiO$_{3}$ and other oxides with perovskite structures, by focusing on both EFG tensors and polarization. We analyze the EFG tensor properties such as orientation and correlation between components and their relation with electric polarization. This work supports previous studies of ferroelectric materials where a relation between EFG tensors and polarization was observed, which may be exploited to study the ferroelectric order when standard techniques to measure polarization are not easily applied.

[Computer mediated discussion and attitude polarization].

Science.gov (United States)

Shiraishi, Takashi; Endo, Kimihisa; Yoshida, Fujio

2002-10-01

This study examined the hypothesis that computer mediated discussions lead to more extreme decisions than face-to-face (FTF) meeting. Kiesler, Siegel, & McGuire (1984) claimed that computer mediated communication (CMC) tended to be relatively uninhibited, as seen in 'flaming', and that group decisions under CMC using Choice Dilemma Questionnaire tended to be more extreme and riskier than FTF meetings. However, for the same reason, CMC discussions on controversial social issues for which participants initially hold strongly opposing views, might be less likely to reach a consensus, and no polarization should occur. Fifteen 4-member groups discussed a controversial social issue under one of three conditions: FTF, CMC, and partition. After discussion, participants rated their position as a group on a 9-point bipolar scale ranging from strong disagreement to strong agreement. A stronger polarization effect was observed for FTF groups than those where members were separated with partitions. However, no extreme shift from their original, individual positions was found for CMC participants. There results were discussed in terms of 'expertise and status equalization' and 'absence of social context cues' under CMC.

Enhanced Photocatalytic Activity of TiO2 Nanoparticles Supported on Electrically Polarized Hydroxyapatite.

Science.gov (United States)

Zhang, Xuefei; Yates, Matthew Z

2018-05-23

Fast recombination of photogenerated charge carriers in titanium dioxide (TiO 2 ) remains a challenging issue, limiting the photocatalytic activity. This study demonstrates increased photocatalytic performance of TiO 2 nanoparticles supported on electrically polarized hydroxyapatite (HA) films. Dense and thermally stable yttrium and fluorine co-doped HA films with giant internal polarization were synthesized as photocatalyst supports. TiO 2 nanoparticles deposited on the support were then used to catalyze the photochemical reduction of aqueous silver ions to produce silver nanoparticles. It was found that significantly more silver nanoparticles were produced on polarized HA supports than on depolarized HA supports. In addition, the photodegradation of methyl orange with TiO 2 nanoparticles on polarized HA supports was found to be much faster than with TiO 2 nanoparticles on depolarized HA supports. It is proposed that separation of photogenerated electrons and holes in TiO nanoparticles is promoted by the internal polarization of the HA support, and consequently, the recombination of charge carriers is mitigated. The results imply that materials with large internal polarization can be used in strategies for enhancing quantum efficiency of photocatalysts.

Polarization and charge transfer in the hydration of chloride ions

International Nuclear Information System (INIS)

Zhao Zhen; Rogers, David M.; Beck, Thomas L.

2010-01-01

A theoretical study of the structural and electronic properties of the chloride ion and water molecules in the first hydration shell is presented. The calculations are performed on an ensemble of configurations obtained from molecular dynamics simulations of a single chloride ion in bulk water. The simulations utilize the polarizable AMOEBA force field for trajectory generation and MP2-level calculations are performed to examine the electronic structure properties of the ions and surrounding waters in the external field of more distant waters. The ChelpG method is employed to explore the effective charges and dipoles on the chloride ions and first-shell waters. The quantum theory of atoms in molecules (QTAIM) is further utilized to examine charge transfer from the anion to surrounding water molecules. The clusters extracted from the AMOEBA simulations exhibit high probabilities of anisotropic solvation for chloride ions in bulk water. From the QTAIM analysis, 0.2 elementary charges are transferred from the ion to the first-shell water molecules. The default AMOEBA model overestimates the average dipole moment magnitude of the ion compared to the quantum mechanical value. The average magnitude of the dipole moment of the water molecules in the first shell treated at the MP2-level, with the more distant waters handled with an AMOEBA effective charge model, is 2.67 D. This value is close to the AMOEBA result for first-shell waters (2.72 D) and is slightly reduced from the bulk AMOEBA value (2.78 D). The magnitude of the dipole moment of the water molecules in the first solvation shell is most strongly affected by the local water-water interactions and hydrogen bonds with the second solvation shell, rather than by interactions with the ion.

Nuclear polarization study: new frontiers for tests of QED in heavy highly charged ions.

Science.gov (United States)

Volotka, Andrey V; Plunien, Günter

2014-07-11

A systematic investigation of the nuclear polarization effects in one- and few-electron heavy ions is presented. The nuclear polarization corrections in the zeroth and first orders in 1/Z are evaluated to the binding energies, the hyperfine splitting, and the bound-electron g factor. It is shown that the nuclear polarization contributions can be substantially canceled simultaneously with the rigid nuclear corrections. This allows for new prospects for probing the QED effects in a strong electromagnetic field and the determination of fundamental constants.

Influence of pentavalent dopant addition to polarization and bioactivity of hydroxyapatite

International Nuclear Information System (INIS)

Dhal, Jharana; Bose, Susmita; Bandyopadhyay, Amit

2013-01-01

Influence of pentavalent tantalum doping in bulk hydroxyapatite (HAp) ceramics has been investigated for polarizability and bioactivity. Phase analysis from X-ray diffraction measurement indicates that increasing dopant concentration decreased the amount of HAp phase and increased β-TCP and/or α-TCP phases during sintering at 1250 °C in a muffle furnace. Results from thermally stimulated depolarization current (TSDC) measurements showed that doping hindered charge storage ability in HAp ceramics, and doped samples stored fewer charge compared to pure HAp. However, doping enhanced wettability of HAp samples, which was improved further due to polarization. In vitro human osteoblast cell–material interaction study revealed an increase in bioactivity due to dopant addition and polarization compared to pure HAp. This increase in bioactivity was attributed to the increase in wettability due to surface charge and dopant addition. - Highlights: • Tantalum doping makes HAp unstable during sintering at 1250 °C and forms TCP. • Tantalum doping reduces charge storage ability of HAp ceramics. • Even with lower charge storage ability tantalum doping improves wettability. • Tantalum doping enhances bioactivity of calcium phosphate based sintered compacts

Neutral and charged scalar mesons, pseudoscalar mesons, and diquarks in magnetic fields

Science.gov (United States)

Liu, Hao; Wang, Xinyang; Yu, Lang; Huang, Mei

2018-04-01

We investigate both (pseudo)scalar mesons and diquarks in the presence of external magnetic field in the framework of the two-flavored Nambu-Jona-Lasinio (NJL) model, where mesons and diquarks are constructed by infinite sum of quark-loop chains by using random phase approximation. The polarization function of the quark-loop is calculated to the leading order of 1 /Nc expansion by taking the quark propagator in the Landau level representation. We systematically investigate the masses behaviors of scalar σ meson, neutral and charged pions as well as the scalar diquarks, with respect to the magnetic field strength at finite temperature and chemical potential. It is shown that the numerical results of both neutral and charged pions are consistent with the lattice QCD simulations. The mass of the charge neutral pion keeps almost a constant under the magnetic field, which is preserved by the remnant symmetry of QCD ×QED in the vacuum. The mass of the charge neutral scalar σ is around two times quark mass and increases with the magnetic field due to the magnetic catalysis effect, which is an typical example showing that the polarized internal quark structure cannot be neglected when we consider the meson properties under magnetic field. For the charged particles, the one quark-antiquark loop contribution to the charged π± increases essentially with the increase of magnetic fields due to the magnetic catalysis of the polarized quarks. However, the one quark-quark loop contribution to the scalar diquark mass is negative comparing with the point-particle result and the loop effect is small.

Solar polar rotation and its effect on heliospheric neutral fluxes

Science.gov (United States)

Sokol, J. M.; Grzedzielski, S.; Bzowski, M.

2016-12-01

The magnetic field in the solar polar corona exhibit a regular "ray-like" structure associated with large polar coronal holes during solar minimum. The solar rotation twists the magnetic field lines of the expanding fast solar wind over the poles. The twist induces a toroidal component of the polar magnetic field which results in magnetic forces directed towards the rotation axis. That is tantamount to a (weak) zeta pinch, known also in other astrophysical contexts (e.g. AGN plasmas). The pinch compresses the polar solar corona plasma and a cone-like enhancement in the solar wind density forms along the rotation axis. Though the effect is likely very dynamic, a time independent description is used here to get an order-of-magnitude estimate. The weak pinch is treated as a 1st order perturbation to the zero-order radial flow. The obtained density enhancement may affect the near and far heliosphere, modifying the charge-exchange and electron impact ionization rates of neutral atoms in interplanetary space. The charge exchange is the most effective ionization process for hydrogen and oxygen atoms, and electron impact ionization is a significant loss reaction for the helium atoms at close distances to the Sun. The change in the polar density due to the solar polar corona rotation could be of importance in the inner heliosphere for low energy atoms. We will present the influence of this effect on interstellar neutral gas distribution and H ENA fluxes observed by IBEX.

Vorticity and Λ polarization in baryon rich matter

Science.gov (United States)

Baznat, Mircea; Gudima, Konstantin; Prokhorov, George; Sorin, Alexander; Teryaev, Oleg; Zakharov, Valentin

2018-02-01

The polarization of Λ hyperons due to axial chiral vortical effect is discussed. The effect is proportional to (strange) chemical potential and is pronounced at lower energies in baryon-rich matter. The polarization of ¯ has the same sihn and larger magnitude. The emergence of vortical structures is observed in kinetic QGSM models. The hydrodynamical helicity separation receives the contribution of longitudinal velocity and vorticity implying the quadrupole structure of the latter. The transition from the quark vortical effects to baryons in confined phase may be achieved by exploring the axial charge. At the hadronic level the polarization corresponds to the cores of quantized vortices in pionic superfluid. The chiral vortical effects may be also studied in the frmework of Wigner function establishing the relation to the thermodynamical approach to polarization.

Influence of nanopore surface charge and magnesium ion on polyadenosine translocation

International Nuclear Information System (INIS)

Lepoitevin, Mathilde; Bechelany, Mikhael; Janot, Jean-Marc; Balme, Sebastien; Coulon, Pierre Eugène; Cambedouzou, Julien

2015-01-01

We investigate the influence of a nanopore surface state and the addition of Mg 2+ on poly-adenosine translocation. To do so, two kinds of nanopores with a low aspect ratio (diameter ∼3–5 nm, length 30 nm) were tailored: the first one with a negative charge surface and the second one uncharged. It was shown that the velocity and the energy barrier strongly depend on the nanopore surface. Typically if the nanopore and polyA exhibit a similar charge, the macromolecule velocity increases and its global energy barrier of entrance in the nanopore decreases, as opposed to the non-charged nanopore. Moreover, the addition of a divalent chelating cation induces an increase of energy barrier of entrance, as expected. However, for a negative nanopore, this effect is counterbalanced by the inversion of the surface charge induced by the adsorption of divalent cations. (paper)

Giessen polarization facility. II. 1. 2 MeV tandem accelerator

Energy Technology Data Exchange (ETDEWEB)

Arnold, W; Ulbricht, J; Berg, H; Keiner, P; Krause, H H; Schmidt, R; Clausnitzer, G [Giessen Univ. (Germany, F.R.). Strahlenzentrum

1977-06-15

A small pressure insulated tandem accelerator with 600 kV terminal voltage was constructed for the application of a polarized ion source of the Lambshift type: thin carbon foils or gas stripping is used for the charge exchange in the high voltage terminal. The calculated ion optical properties were realized in the construction; transmission and energy resolution are sufficient to obtain high intensity polarized beams on target (maximum 0.6..mu..A protons with P=0.75 ) for precision polarization experiments in the 0.2-1.2 MeV energy region.

DFT study of the polarization behaviors of various distorted barium titanate crystals: The role of atomic displacements

Science.gov (United States)

Mirseraji, Mojtaba; Shahraki, Mehran Gholipour

2018-06-01

A Local Density Approximation (LDA) was employed to investigate the influence of applied strains on valence charge distributions, atomic displacements, Tisbnd O (3) bond distances and the total polarizations in barium titanate (BaTiO3). Four types of various strains were imposed on perfect tetragonal BaTiO3 along the a, c, ab and abc axial directions. Electromechanical properties of BaTiO3 were evaluated in LDA framework and a good agreement with previous results was achieved. The results show that, in the cases of a, ab strains, the values of polarization are almost constant in negative strains and increased by gradual increasing of the positive strains after a sudden enhancement at about +0.1% strain. In the case of c-strain, axial oxygen and Ti atoms underwent the highest displacements and the polarization linearly increased by applied strain. The case of abc-strain, represent the both types of features. In negative abc-strain show a similar polarization behavior like c-strain case and in positive region, polarization behavior is the same as a- and ab-strain cases. In the abc-strains of -0.3% and +0.1%, an abrupt jump in total polarization curve and a small change, are observed due to abnormal atomic displacements. In the most cases a direct relation between polarization and Tisbnd O (3) bond distance was also beheld. Finally, the effects of valence charge distributions on the atomic displacements and total polarizations are studied. It is found that there is a direct relation between polarization and Valence Charge Asymmetry of 3d -orbitals.

Design of a device for sky light polarization measurements.

Science.gov (United States)

Wang, Yujie; Hu, Xiaoping; Lian, Junxiang; Zhang, Lilian; Xian, Zhiwen; Ma, Tao

2014-08-14

Sky polarization patterns can be used both as indicators of atmospheric turbidity and as a sun compass for navigation. The objective of this study is to improve the precision of sky light polarization measurements by optimal design of the device used. The central part of the system is composed of a Charge Coupled Device (CCD) camera; a fish-eye lens and a linear polarizer. Algorithms for estimating parameters of the polarized light based on three images are derived and the optimal alignments of the polarizer are analyzed. The least-squares estimation is introduced for sky light polarization pattern measurement. The polarization patterns of sky light are obtained using the designed system and they follow almost the same patterns of the single-scattering Rayleigh model. Deviations of polarization angles between observation and the theory are analyzed. The largest deviations occur near the sun and anti-sun directions. Ninety percent of the deviations are less than 5° and 40% percent of them are less than 1°. The deviations decrease evidently as the degree of polarization increases. It also shows that the polarization pattern of the cloudy sky is almost identical as in the blue sky.

Polarized positrons in Jefferson lab electron ion collider (JLEIC)

Science.gov (United States)

Lin, Fanglei; Grames, Joe; Guo, Jiquan; Morozov, Vasiliy; Zhang, Yuhong

2018-05-01

The Jefferson Lab Electron Ion Collider (JLEIC) is designed to provide collisions of electron and ion beams with high luminosity and high polarization to reach new frontier in exploration of nuclear structure. The luminosity, exceeding 1033 cm-2s-1 in a broad range of the center-of-mass (CM) energy and maximum luminosity above 1034 cm-2s-1, is achieved by high-rate collisions of short small-emittance low-charge bunches with proper cooling of the ion beam and synchrotron radiation damping of the electron beam. The polarization of light ion species (p, d, 3He) and electron can be easily preserved, manipulated and maintained by taking advantage of the unique figure-8 shape rings. With a growing physics interest, polarized positron-ion collisions are considered to be carried out in the JLEIC to offer an additional probe to study the substructure of nucleons and nuclei. However, the creation of polarized positrons with sufficient intensity is particularly challenging. We propose a dedicated scheme to generate polarized positrons. Rather than trying to accumulate "hot" positrons after conversion, we will accumulate "cold" electrons before conversion. Charge accumulation additionally provides a novel means to convert high repetition rate (>100 MHz) electron beam from the gun to a low repetition rate (<100 MHz) positron beam for broad applications. In this paper, we will address the scheme, provide preliminary estimated parameters and explain the key areas to reach the desired goal.

Electronic device for measuring the polarization parameter in the {pi}{sup -}p {yields} {pi}{sup 0}n charge exchange reaction on a polarized proton target; Un appareillage electronique destine a la mesure du parametre de polarisation dans la reaction d'echange de charge {pi}{sup -}p {yields} {pi}{sup 0}n sur cible de protons polarises

Energy Technology Data Exchange (ETDEWEB)

Brehin, S [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1967-12-15

An electronic apparatus has been constructed to measure the polarization parameter P{sub 0}(t) in {pi}{sup -}p {yields} {pi}{sup 0}n charge exchange scattering at 5.9 GeV/c and 11,2 GeV/c on polarized proton target. This device insures triggering of a heavy plate spark chamber, allowing visualisation of {gamma} rays from the {pi}{sup 0} decays when the associated neutron offers suitable characteristics in direction and energy. The neutron is detected by an array of 32 counters and his energy is measured by a time of flight method. Electronic circuits of this apparatus are described as test and calibration methods used. (author) [French] Un appareillage electronique a ete realise pour mesurer le parametre de polarisation P{sub 0}(t) dans la reaction d'echange de charge {pi}{sup -}p {yields} {pi}{sup 0}n a 5,9 GeV/c et 11,2 GeV/c sur une cible de protons polarises. Ce dispositif assure le declenchement d'une chambre a etincelles a plaques lourdes, permettant de visualiser les {gamma} de desitegration du {pi}{sup 0}, lorsque le neutron associe presente les caracteristiques convenables en direction et en energie. Le neutron est detecte par un ensemble de 32 compteurs et son energie est mesuree par une methode de temps de vol. Les circuits composant cet appareillage sont decrits ainsi que les methodes d'etalonnage et de verification utilisees. (auteur)

Electronic device for measuring the polarization parameter in the {pi}{sup -}p {yields} {pi}{sup 0}n charge exchange reaction on a polarized proton target; Un appareillage electronique destine a la mesure du parametre de polarisation dans la reaction d'echange de charge {pi}{sup -}p {yields} {pi}{sup 0}n sur cible de protons polarises

Energy Technology Data Exchange (ETDEWEB)

Brehin, S. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1967-12-15

An electronic apparatus has been constructed to measure the polarization parameter P{sub 0}(t) in {pi}{sup -}p {yields} {pi}{sup 0}n charge exchange scattering at 5.9 GeV/c and 11,2 GeV/c on polarized proton target. This device insures triggering of a heavy plate spark chamber, allowing visualisation of {gamma} rays from the {pi}{sup 0} decays when the associated neutron offers suitable characteristics in direction and energy. The neutron is detected by an array of 32 counters and his energy is measured by a time of flight method. Electronic circuits of this apparatus are described as test and calibration methods used. (author) [French] Un appareillage electronique a ete realise pour mesurer le parametre de polarisation P{sub 0}(t) dans la reaction d'echange de charge {pi}{sup -}p {yields} {pi}{sup 0}n a 5,9 GeV/c et 11,2 GeV/c sur une cible de protons polarises. Ce dispositif assure le declenchement d'une chambre a etincelles a plaques lourdes, permettant de visualiser les {gamma} de desitegration du {pi}{sup 0}, lorsque le neutron associe presente les caracteristiques convenables en direction et en energie. Le neutron est detecte par un ensemble de 32 compteurs et son energie est mesuree par une methode de temps de vol. Les circuits composant cet appareillage sont decrits ainsi que les methodes d'etalonnage et de verification utilisees. (auteur)

Effect of frequency variation on electromagnetic pulse interaction with charges and plasma

NARCIS (Netherlands)

Khachatryan, A.G.; van Goor, F.A.; Verschuur, Jeroen W.J.; Boller, Klaus J.

2005-01-01

The effect of frequency variation (chirp) in an electromagnetic (EM) pulse on the pulse interaction with a charged particle and plasma is studied. Various types of chirp and pulse envelopes are considered. In vacuum, a charged particle receives a kick in the polarization direction after interaction

Perceiving political polarization in the United States: party identity strength and attitude extremity exacerbate the perceived partisan divide.

Science.gov (United States)

Westfall, Jacob; Van Boven, Leaf; Chambers, John R; Judd, Charles M

2015-03-01

An important component of political polarization in the United States is the degree to which ordinary people perceive political polarization. We used over 30 years of national survey data from the American National Election Study to examine how the public perceives political polarization between the Democratic and Republican parties and between Democratic and Republican presidential candidates. People in the United States consistently overestimate polarization between the attitudes of Democrats and Republicans. People who perceive the greatest political polarization are most likely to report having been politically active, including voting, trying to sway others' political beliefs, and making campaign contributions. We present a 3-factor framework to understand ordinary people's perceptions of political polarization. We suggest that people perceive greater political polarization when they (a) estimate the attitudes of those categorized as being in the "opposing group"; (b) identify strongly as either Democrat or Republican; and (c) hold relatively extreme partisan attitudes-particularly when those partisan attitudes align with their own partisan political identity. These patterns of polarization perception occur among both Democrats and Republicans. © The Author(s) 2015.

Motion of charged particle in Reissner-Nordstroem spacetime. A Jacobi-metric approach

Energy Technology Data Exchange (ETDEWEB)

Das, Praloy; Sk, Ripon; Ghosh, Subir [Indian Statistical Institute, Physics and Applied Mathematics Unit, Kolkata (India)

2017-11-15

The present work discusses motion of neutral and charged particles in Reissner-Nordstroem spacetime. The constant energy paths are derived in a variational principle framework using the Jacobi metric which is parameterized by conserved particle energy. Of particular interest is the case of particle charge and Reissner-Nordstroem black hole charge being of same sign, since this leads to a clash of opposing forces - gravitational (attractive) and Coulomb (repulsive). Our paper aims to complement the recent work of Pugliese et al. (Eur Phys J C 77:206. arXiv:1304.2940, 2017; Phys Rev D 88:024042. arXiv:1303.6250, 2013). The energy dependent Gaussian curvature (induced by the Jacobi metric) plays an important role in classifying the trajectories. (orig.)

Formation of oxide-trapped charges in 6H-SiC MOS structures

Energy Technology Data Exchange (ETDEWEB)

Yoshikawa, Masahito; Ohshima, Takeshi; Itoh, Hisayoshi; Nashiyama, Isamu [Japan Atomic Energy Research Inst., Takasaki, Gunma (Japan). Takasaki Radiation Chemistry Research Establishment; Okumura, Hajime; Yoshida, Sadafumi

1997-03-01

The silicon and the carbon faces of hexagonal silicon carbide (6H-SiC) substrates were oxidized pyrogenically at 1100degC, and the metal-oxide-semiconductor structures were formed on these faces. The MOS capacitors developed using the silicon and the carbon faces were irradiated with {sup 60}Co gamma-rays under argon atmosphere at room temperature. The bias voltages with the different polarity were applied to the gate electrode during irradiation to examine the formation mechanisms of the trapped charges in the oxides of these MOS capacitors. The amount of the trapped charges in the oxide were obtained from capacitance pulse voltage characteristics. The generation of the trapped charges are affects with not only the absorbed dose but also the bias polarity applied to the gate electrodes during irradiation. The formation mechanisms of the trapped charges in the oxides were estimated in conjunction with the surface orientation of 6H-SiC substrates. (author)

Influence of bulk dielectric polarization upon partial discharge transients: Effect of void geometry and orientation

DEFF Research Database (Denmark)

McAllister, Iain Wilson; Crichton, G.C.

2005-01-01

The induced charge arising from a partial discharge consists of 2 components. One is associated with the actual space charge in the void. The other is related to changes in the polarization of the bulk dielectric. These changes are a direct consequence of the field produced by the space charge...

Spin polarized electron tunneling and magnetoresistance in molecular junctions.

Science.gov (United States)

Szulczewski, Greg

2012-01-01

This chapter reviews tunneling of spin-polarized electrons through molecules positioned between ferromagnetic electrodes, which gives rise to tunneling magnetoresistance. Such measurements yield important insight into the factors governing spin-polarized electron injection into organic semiconductors, thereby offering the possibility to manipulate the quantum-mechanical spin degrees of freedom for charge carriers in optical/electrical devices. In the first section of the chapter a brief description of the Jullière model of spin-dependent electron tunneling is reviewed. Next, a brief description of device fabrication and characterization is presented. The bulk of the review highlights experimental studies on spin-polarized electron tunneling and magnetoresistance in molecular junctions. In addition, some experiments describing spin-polarized scanning tunneling microscopy/spectroscopy on single molecules are mentioned. Finally, some general conclusions and prospectus on the impact of spin-polarized tunneling in molecular junctions are offered.

The Polarized Electron Source at ELSA

International Nuclear Information System (INIS)

Drachenfels, Wolther von; Frommberger, Frank; Gowin, Michael; Hillert, Wolfgang; Hoffmann, Markus; Neff, Bernhold

2003-01-01

At the electron stretcher accelerator ELSA in Bonn a pulsed 50 kV inverted gun of polarized electrons has been in operation since February 2000. A strained-layer superlattice crystal is used to deliver a beam with a polarization of about 80 %. A flashlamp-pumped Ti-Sapphire laser with a pulse repetition rate of 50 Hz serves as source of light. The gun is operated in space charge limitation. The current can be chosen by varying the distance between cathode and anode. With 1 μs pulses of 100 mA the source was particularly used together with a polarized target for a GDH sum rule experiment. The high photocathode lifetime allows continuous operation at 100 mA typically for periods of about two weeks without maintenance. So far no change of the crystal was necessary

Bone cell-material interactions on metal-ion doped polarized hydroxyapatite

International Nuclear Information System (INIS)

Bodhak, Subhadip; Bose, Susmita; Bandyopadhyay, Amit

2011-01-01

The objective of this work is to study the influence of Mg 2+ and Sr 2+ dopants on in vitro bone cell-material interactions of electrically polarized hydroxyapatite [HAp, Ca 10 (PO 4 ) 6 (OH) 2 ] ceramics with an aim to achieve additional advantage of matching bone chemistry along with the original benefits of electrical polarization treatment relevant to biomedical applications. To achieve our research objective, commercial phase pure HAp has been doped with MgO, and SrO in single, and binary compositions. All samples have been sintered at 1200 deg. C for 2 h and subsequently polarized using an external d.c. field (2.0 kV/cm) at 400 deg. C for 1 h. Combined addition of 1 wt.% MgO/1 wt.% SrO in HAp has been most beneficial in enhancing the polarizability in which stored charge was 4.19 μC/cm 2 compared to pure HAp of 2.23 μC/cm 2 . Bone cell-material interaction has been studied by culturing with human fetal osteoblast cells (hFOB) for a maximum of 7 days. Scanning electron microscope (SEM) images of cell morphology reveal that favorable surface properties and dopant chemistry lead to good cellular adherence and spreading on negatively charged surfaces of both Sr 2+ and Mg 2+ doped HAp samples over undoped HAp. MTT assay results at 7 days show the highest viable cell densities on the negatively charged surfaces of binary doped HAp samples, while positive charged doped HAp surfaces exhibit limited cellular growth in comparison to neutral surfaces.

Discretization of 3d gravity in different polarizations

Science.gov (United States)

Dupuis, Maïté; Freidel, Laurent; Girelli, Florian

2017-10-01

We study the discretization of three-dimensional gravity with Λ =0 following the loop quantum gravity framework. In the process, we realize that different choices of polarization are possible. This allows us to introduce a new discretization based on the triad as opposed to the connection as in the standard loop quantum gravity framework. We also identify the classical nontrivial symmetries of discrete gravity, namely the Drinfeld double, given in terms of momentum maps. Another choice of polarization is given by the Chern-Simons formulation of gravity. Our framework also provides a new discretization scheme of Chern-Simons, which keeps track of the link between the continuum variables and the discrete ones. We show how the Poisson bracket we recover between the Chern-Simons holonomies allows us to recover the Goldman bracket. There is also a transparent link between the discrete Chern-Simons formulation and the discretization of gravity based on the connection (loop gravity) or triad variables (dual loop gravity).

Optically induced rotation of Rayleigh particles by vortex beams with different states of polarization

International Nuclear Information System (INIS)

Li, Manman; Yan, Shaohui; Yao, Baoli; Liang, Yansheng; Lei, Ming; Yang, Yanlong

2016-01-01

Optical vortex beams carry optical orbital angular momentum (OAM) and can induce an orbital motion of trapped particles in optical trapping. We show that the state of polarization (SOP) of vortex beams will affect the details of this optically induced orbital motion to some extent. Numerical results demonstrate that focusing the vortex beams with circular, radial or azimuthal polarizations can induce a uniform orbital motion on a trapped Rayleigh particle, while in the focal field of the vortex beam with linear polarization the particle experiences a non-uniform orbital motion. Among the formers, the vortex beam with circular polarization induces a maximum optical torque on the particle. Furthermore, by varying the topological charge of the vortex beams, the vortex beam with circular polarization gives rise to an optimum torque superior to those given by the other three vortex beams. These facts suggest that the circularly polarized vortex beam is more suitable for rotating particles. - Highlights: • States of polarization of vortex beams affect the optically induced orbital motion of particles. • The dependences of the force and orbital torque on the topological charge, the size and the absorptivity of particles were calculated. • Focused vortex beams with circular, radial or azimuthal polarizations induce a uniform orbital motion on particles. • Particles experience a non-uniform orbital motion in the focused linearly polarized vortex beam. • The circularly polarized vortex beam is a superior candidate for rotating particles.

Solar Illumination Control of the Polar Wind

Science.gov (United States)

Maes, L.; Maggiolo, R.; De Keyser, J.; André, M.; Eriksson, A. I.; Haaland, S.; Li, K.; Poedts, S.

2017-11-01

Polar wind outflow is an important process through which the ionosphere supplies plasma to the magnetosphere. The main source of energy driving the polar wind is solar illumination of the ionosphere. As a result, many studies have found a relation between polar wind flux densities and solar EUV intensity, but less is known about their relation to the solar zenith angle at the ionospheric origin, certainly at higher altitudes. The low energy of the outflowing particles and spacecraft charging means it is very difficult to measure the polar wind at high altitudes. We take advantage of an alternative method that allows estimations of the polar wind flux densities far in the lobes. We analyze measurements made by the Cluster spacecraft at altitudes from 4 up to 20 RE. We observe a strong dependence on the solar zenith angle in the ion flux density and see that both the ion velocity and density exhibit a solar zenith angle dependence as well. We also find a seasonal variation of the flux density.

Polarized electron sources for linear colliders

International Nuclear Information System (INIS)

Clendenin, J.E.; Ecklund, S.D.; Miller, R.H.; Schultz, D.C.; Sheppard, J.C.

1992-07-01

Linear colliders require high peak current beams with low duty factors. Several methods to produce polarized e - beams for accelerators have been developed. The SLC, the first linear collider, utilizes a photocathode gun with a GaAs cathode. Although photocathode sources are probably the only practical alternative for the next generation of linear colliders, several problems remain to be solved, including high voltage breakdown which poisons the cathode, charge limitations that are associated with the condition of the semiconductor cathode, and a relatively low polarization of ≤5O%. Methods to solve or at least greatly reduce the impact of each of these problems are at hand

Spin-polarization reversal at the interface between benzene and Fe(100)

KAUST Repository

Goumri-Said, Souraya

2013-01-03

The spin-polarization at the interface between Fe(100) and a benzene is investigated theoretically using density functional theory for two positions of the organic molecule: planar and perpendicular with respect to the substrate. The electronic and magnetic properties as well as the spin-polarization close to the Fermi level strongly depend on the benzene position on the iron surface. An inversion of the spin-polarization is induced by p-d hybridization and charge transfer from the iron to the carbon sites in both configurations.

Spin-polarization reversal at the interface between benzene and Fe(100)

KAUST Repository

Goumri-Said, Souraya; Benali Kanoun, Mohammed; Manchon, Aurelien; Schwingenschlö gl, Udo

2013-01-01

The spin-polarization at the interface between Fe(100) and a benzene is investigated theoretically using density functional theory for two positions of the organic molecule: planar and perpendicular with respect to the substrate. The electronic and magnetic properties as well as the spin-polarization close to the Fermi level strongly depend on the benzene position on the iron surface. An inversion of the spin-polarization is induced by p-d hybridization and charge transfer from the iron to the carbon sites in both configurations.

Stored polarized beams: MILES, LIMES, SMILE, sine-Bessels and SODOM2 too

International Nuclear Information System (INIS)

Mane, S.R.

2008-01-01

The fundamental theory underlying several computational algorithms for the spin dynamics of stored polarized beams is analyzed. Particular attention is paid to the consequences of the use of finite-dimensional matrices and/or Fourier series. The single resonance model with a pair of diametrically opposed nonorthogonal pointlike Siberian Snakes is analyzed in detail to clarify several points pertaining to the above algorithms, and more generally to the spin dynamics of stored polarized beams in rings with Snakes. New analytical results are also presented, e.g. for the spin tune shift in the nonorthogonal Snakes model, and the sine-Bessel functions for the orthogonal Snakes model. Many results are derived using multiple algorithms, which serves as a check on their mutual consistency

Measurement of the left-right asymmetry in pion-proton radiative exchange and charge exchange scattering from 301 to 625 MeV/c on a transversely polarized target

International Nuclear Information System (INIS)

Kim, George Jung-Kwang.

1988-05-01

The left-right asymmetry A/sub N/ in π/sup /minus//p → γn has been measured at p/sub π = 301, 316, 427, 471, 547, 586, and 625 MeV/c using a transversely polarized target. The final-state neutron and gamma were detected in coincidence by two states of matching neutron and gamma detectors at gamma angles centered around 90/degree and 110/degree/ c.m. A gamma detector consisted of an array of 15 counters, each was 15/times/15/times/25 cm 3 block of lead-glass. A neutron detector consisted of 15 counters also, each one was a cylindrical plastic scintillator 7.6 cm in diameter and 45.7 cm long. The A/sub N/ results are compared with the predictions from the most recent single-pion photoproduction partial-wave analysis by Arai and Fujii. The agreement is poor, casting doubt on the correctness of the value for the radiative-decay amplitude of the neutral Roper resonance now in use. A comparison is made with the 90/degree/recoil proton polarization data of the inverse reaction derived from γd scattering, there are substantial discrepencies. Charge exchange (π/sup /minus/p/ → γ/degree/n) events were the major yield in this experiment. Very precise values of the charge exchange analyzing power were obtained with an error of typically 3%. The charge exchange results are compared with the predictions from recent γn partial wave analyses. At the lower incident energies little difference is seen between the VPI, Karlsruhe-Helsinki, and CMU-LBL analyses, and there is excellent agreement with our experiment. From the onset of the Roper resonance the VPI solution is strongly favored

Operation of the optically pumped polarized H- source at LAMPF

International Nuclear Information System (INIS)

York, R.L.; Tupa, D.; Swenson, D.R.; van Dyck, O.B.

1991-01-01

We report on the first five months of operation of the Optically Pumped Polarized Ion Source (OPPIS) for the nuclear physics research program at LAMPF. The LAMPF OPPIS is unique in using Ti: Sapphire lasers to polarize the potassium charge-exchange medium, and until recently was unique in using a superconducting magnet in the ECR source and polarizer regions. The ECR extraction electrode biasing arrangement is also unique. Typical performance was 25 microamps of peak current (measured at 750 keV) with 55% beam polarization or 15 microamps at 62%. Ion source availability was greater than 90%. We also report our planned improvements in preparation for research operation in May of 1991. 3 refs., 4 figs

Polarization Switching and Light-Enhanced Piezoelectricity in Lead Halide Perovskites.

Science.gov (United States)

Coll, Mariona; Gomez, Andrés; Mas-Marza, Elena; Almora, Osbel; Garcia-Belmonte, Germà; Campoy-Quiles, Mariano; Bisquert, Juan

2015-04-16

We investigate the ferroelectric properties of photovoltaic methylammonium lead halide CH3NH3PbI3 perovskite using piezoelectric force microscopy (PFM) and macroscopic polarization methods. The electric polarization is clearly observed by amplitude and phase hysteresis loops. However, the polarization loop decreases as the frequency is lowered, persisting for a short time only, in the one second regime, indicating that CH3NH3PbI3 does not exhibit permanent polarization at room temperature. This result is confirmed by macroscopic polarization measurement based on a standard capacitive method. We have observed a strong increase of piezoelectric response under illumination, consistent with the previously reported giant photoinduced dielectric constant at low frequencies. We speculate that an intrinsic charge transfer photoinduced dipole in the perovskite cage may lie at the origin of this effect.

Polarization in heavy quark decays

Energy Technology Data Exchange (ETDEWEB)

Alimujiang, K.

2006-07-01

In this thesis I concentrate on the angular correlations in top quark decays and their next.to.leading order (NLO) QCD corrections. I also discuss the leading.order (LO) angular correlations in unpolarized and polarized hyperon decays. In the first part of the thesis I calculate the angular correlation between the top quark spin and the momentum of decay products in the rest frame decay of a polarized top quark into a charged Higgs boson and a bottom quark in Two-Higgs-Doublet-Models: t({up_arrow}) {yields} b + H{sup +}. I provide closed form formulae for the O({alpha}{sub s}) radiative corrections to the unpolarized and the polar correlation functions for m{sub b}{ne}0 and m{sub b}=0. In the second part I concentrate on the semileptonic rest frame decay of a polarized top quark into a bottom quark and a lepton pair: t({up_arrow}){yields}X{sub b}+l{sup +}+{nu}{sub l}. I present closed form expressions for the O({alpha}{sub s}) radiative corrections to the unpolarized part and the polar and azimuthal correlations for m{sub b}{ne}0 and m{sub b}=0. In the last part I turn to the angular distribution in semileptonic hyperon decays. Using the helicity method I derive complete formulas for the leading order joint angular decay distributions occurring in semileptonic hyperon decays including lepton mass and polarization effects. (orig.)

Transport synthetic acceleration with opposing reflecting boundary conditions

Energy Technology Data Exchange (ETDEWEB)

Zika, M R; Adams, M L

2000-02-01

The transport synthetic acceleration (TSA) scheme is extended to problems with opposing reflecting boundary conditions. This synthetic method employs a simplified transport operator as its low-order approximation. A procedure is developed that allows the use of the conjugate gradient (CG) method to solve the resulting low-order system of equations. Several well-known transport iteration algorithms are cast in a linear algebraic form to show their equivalence to standard iterative techniques. Source iteration in the presence of opposing reflecting boundary conditions is shown to be equivalent to a (poorly) preconditioned stationary Richardson iteration, with the preconditioner defined by the method of iterating on the incident fluxes on the reflecting boundaries. The TSA method (and any synthetic method) amounts to a further preconditioning of the Richardson iteration. The presence of opposing reflecting boundary conditions requires special consideration when developing a procedure to realize the CG method for the proposed system of equations. The CG iteration may be applied only to symmetric positive definite matrices; this condition requires the algebraic elimination of the boundary angular corrections from the low-order equations. As a consequence of this elimination, evaluating the action of the resulting matrix on an arbitrary vector involves two transport sweeps and a transmission iteration. Results of applying the acceleration scheme to a simple test problem are presented.

Weak production of strangeness at threshold with polarization observables

International Nuclear Information System (INIS)

Baker, O.K.

2002-01-01

The differential cross section for the charged current electroweak reaction e → +p → ν → e +Λ → at threshold with polarization observables is presented. The form of the cross section at threshold for the reaction is simplified compared to higher energy. An expression is given for the invariant matrix element appropriate for the reaction when the incident electron is polarized, and the final state hyperon polarization is determined. The energy dependence of the resulting cross section is shown near threshold. Under the right kinematic conditions, there can be a sizeable enhancement in the cross section, making an experimental measurement of the weak axial-vector form factor feasible

First time measurements of polarization observables for the charged cascade hyperon in photoproduction

Energy Technology Data Exchange (ETDEWEB)

Bono, Jason [Florida Intl Univ., Miami, FL (United States)

2014-08-31

The parity violating weak decay of hyperons offers a valuable means of measuring their polarization, providing insight into the production of strange quarks and the matter they compose. Jefferson Lab's CLAS collaboration has utilized this property of hyperons, publishing the most precise polarization measurements for the Lambda and Sigma in both photoproduction and electroproduction to date. In contrast, cascades, which contain two strange quarks, can only be produced through indirect processes and as a result, exhibit low cross sections thus remaining experimentally elusive.

At present, there are two aspects in cascade physics where progress has been minimal: characterizing their production mechanism, which lacks theoretical and experimental developments, and observation of the numerous excited cascade resonances that are required to exist by flavor SU(3)F symmetry. However, CLAS data were collected in 2008 with a luminosity of 68 pb^-1 using a circularly polarized photon beam with energies up to 5.45 GeV, incident on a liquid hydrogen target. This dataset is, at present, the world's largest for meson photoproduction in its energy range and provides a unique opportunity to study cascade physics with polarization measurements.

The current analysis explores hyperon production through the yp -> K^+ K^+ Xi^- reaction by providing the first ever determination of spin observables P, Cx and Cz for the cascade. Three of our primary goals are to test the only cascade photoproduction model in existence, examine the underlying processes that give rise to hyperon polarization, and to stimulate future theoretical developments while providing constraints for their parameters. Our research is part of a broader program to understand the production of strange quarks and hadrons with strangeness. The remainder of this document discusses the motivation behind such research, the method of data collection, details of their analysis, and the significance of

Modeling alignment enhancement for solid polarized targets

Energy Technology Data Exchange (ETDEWEB)

Keller, D. [University of Virginia, Charlottesville, VA (United States)

2017-07-15

A model of dynamic orientation using optimized radiofrequency (RF) irradiation produced perpendicular to the holding field is developed for the spin-1 system required for tensor-polarized fixed-target experiments. The derivation applies to RF produced close to the Larmor frequency of the nucleus and requires the electron spin-resonance linewidth to be much smaller than the nuclear magnetic resonance frequency. The rate equations are solved numerically to study a semi-saturated steady-state resulting from the two sources of irradiation: microwave from the DNP process and the additional RF used to manipulate the tensor polarization. The steady-state condition and continuous-wave NMR lineshape are found that optimize the spin-1 alignment in the polycrystalline materials used as solid polarized targets in charged-beam nuclear and particle physics experiments. (orig.)

Impact of Molecular Orientation and Packing Density on Electronic Polarization in the Bulk and at Surfaces of Organic Semiconductors

KAUST Repository

Ryno, Sean

2016-05-16

The polarizable environment surrounding charge carriers in organic semiconductors impacts the efficiency of the charge transport process. Here, we consider two representative organic semiconductors, tetracene and rubrene, and evaluate their polarization energies in the bulk and at the organic-vacuum interface using a polarizable force field that accounts for induced-dipole and quadrupole interactions. Though both oligoacenes pack in a herringbone motif, the tetraphenyl substituents on the tetracene backbone of rubrene alter greatly the nature of the packing. The resulting change in relative orientations of neighboring molecules is found to reduce the bulk polarization energy of holes in rubrene by some 0.3 eV when compared to tetracene. The consideration of model organic-vacuum interfaces highlights the significant variation in the electrostatic environment for a charge carrier at a surface although the net change in polarization energy is small; interestingly, the environment of a charge even just one layer removed from the surface can be viewed already as representative of the bulk. Overall, it is found that in these herringbone-type layered crystals the polarization energy has a much stronger dependence on the intralayer packing density than interlayer packing density.

Polarizing PVC — A Discrepant Event

Science.gov (United States)

Headly, David; Karabatek, Mohamed

2016-01-01

Each year when teaching polarization phenomena and the Triboelectric Series in a unit on electrostatics, I would balance some rods (2-3 ft in length) made from wood, aluminum, PVC, and Plexiglas on an inverted watch glass and demonstrate to the class how a party balloon rubbed with fake rabbit fur (charging the balloon negative) would always attract the uncharged rods, causing them to rotate towards the balloon (see Fig. 1). The fact that a charged object always attracts a neutral object due to the induced dipole in the latter is a great way to test if something is in fact charged. Surprisingly, the PVC pipe would usually, but not always, repel the charged balloon and rotate away! Repulsion means that neither of the objects are electrically neutral. In a separate test, after rubbing together a Plexiglas rod with a polyethylene grocery bag (making the rod positively charged and the bag negatively charged), the PVC usually attracts the rod. With the help of a student as part of his senior project, I finally decided to investigate further the source of the negative charge that exists on PVC. Specifically, is it nothing more than static charge that builds up on the pipe from unavoidable contact with its surroundings, or is it somehow intrinsic to the manufacturing process?

Operational experience with the TRIUMF optically pumped polarized H- ion source

International Nuclear Information System (INIS)

Schmor, P.W.; Buchmann, L.; Jayamanna, K.; Levy, C.D.P.; McDonald, M.; Ruegg, R.

1991-05-01

The initial goal of a polarized proton beam extracted from the TRIUMF cyclotron, having a current of 5 μA with 60% polarization, has been achieved with the development of the optically pumped polarized H - ion source. This beam is now being used to produce an intense secondary beam of polarized neutrons for the TRIUMF experimental program. Much of the recent development effort has addressed the reliability requirements for routine operation. This paper describes the results with emphasis on the laser stabilization subsystem, the modifications to the electron cyclotron resonance proton ion source (ECRIS), the sodium charge exchange cells and the development of a low energy polarimeter. Also discussed are the developments which should lead to a higher polarization. (Author) 7 refs

Opposed slant tube diabatic sorber

Science.gov (United States)

Erickson, Donald C.

2004-01-20

A sorber comprised of at least three concentric coils of tubing contained in a shell with a flow path for liquid sorbent in one direction, a flow path for heat transfer fluid which is in counter-current heat exchange relationship with sorbent flow, a sorbate vapor port in communication with at least one of sorbent inlet or exit ports, wherein each coil is coiled in opposite direction to those coils adjoining it, whereby the opposed slant tube configuration is achieved, with structure for flow modification in the core space inside the innermost coil.

Effects of the fermionic vacuum polarization in QED

Energy Technology Data Exchange (ETDEWEB)

Medeiros, M.F.X.P.; Barone, F.A. [IFQ-Universidade Federal de Itajuba, Itajuba, MG (Brazil); Barone, F.E.

2018-01-15

Some effects of vacuum polarization in QED due to the presence of field sources are investigated. We focus on effects with no counter-part in Maxwell electrodynamics. The Uehling interaction energy between two stationary point-like charges is calculated exactly in terms of Meijer-G functions. Effects induced on a hydrogen atom by the vacuum polarization in the vicinity of a Dirac string are considered. We also calculate the interaction between two parallel Dirac strings and corrections to the energy levels of a quantum particle constrained to move on a ring circumventing a solenoid. (orig.)

Polarization in heavy-ion collisions: magnetic field and vorticity

Science.gov (United States)

Baznat, M.; Gudima, K.; Prokhorov, G.; Sorin, A.; Teryaev, O.; Zakharov, V.

2017-12-01

The polarization of hyperons due to axial chiral vortical effect is discussed. The effect is proportional to (strange) chemical potential and is pronounced at lower energies, contrary to that of magnetic field. The polarization of antihyperons has the same sign and larger magnitude. The emergence of vortical structures is observed in kinetic QGSM models. The hydrodynamical helicity separation receives the contribution of longitudinal velocity and vorticity implying the quadrupole structure of the latter. The transition from the quark vortical effects to baryons in confined phase may be achieved by exploring the axial charge. At the hadronic level the polarization corresponds to the cores of quantized vortices in pionic superfluid. The chiral vortical effects may be also studied in the frmework of Wigner function establishing the relation to the thermodynamical approach to polarization.

Electrostatic charging and control of droplets in microfluidic devices.

Science.gov (United States)

Zhou, Hongbo; Yao, Shuhuai

2013-03-07

Precharged droplets can facilitate manipulation and control of low-volume liquids in droplet-based microfluidics. In this paper, we demonstrate non-contact electrostatic charging of droplets by polarizing a neutral droplet and splitting it into two oppositely charged daughter droplets in a T-junction microchannel. We performed numerical simulation to analyze the non-contact charging process and proposed a new design with a notch at the T-junction in aid of droplet splitting for more efficient charging. We experimentally characterized the induced charge in droplets in microfabricated devices. The experimental results agreed well with the simulation. Finally, we demonstrated highly effective droplet manipulation in a path selection unit appending to the droplet charging. We expect our work could enable precision manipulation of droplets for more complex liquid handling in microfluidics and promote electric-force based manipulation in 'lab-on-a-chip' systems.

Magnetic field induced strong valley polarization in the three-dimensional topological semimetal LaBi

Science.gov (United States)

Kumar, Nitesh; Shekhar, Chandra; Klotz, J.; Wosnitza, J.; Felser, Claudia

2017-10-01

LaBi is a three-dimensional rocksalt-type material with a surprisingly quasi-two-dimensional electronic structure. It exhibits excellent electronic properties such as the existence of nontrivial Dirac cones, extremely large magnetoresistance, and high charge-carrier mobility. The cigar-shaped electron valleys make the charge transport highly anisotropic when the magnetic field is varied from one crystallographic axis to another. We show that the electrons can be polarized effectively in these electron valleys under a rotating magnetic field. We achieved a polarization of 60% at 2 K despite the coexistence of three-dimensional hole pockets. The valley polarization in LaBi is compared to the sister compound LaSb where it is found to be smaller. The performance of LaBi is comparable to the highly efficient bismuth.

Consecutive opposed interactions of light waves

International Nuclear Information System (INIS)

Volkov, V V; Chirkin, Anatolii S

1999-01-01

The conditions were determined for the occurrence of the opposed interaction of waves having multiple frequencies in two consecutive three-frequency processes in periodically inhomogeneous nonlinear optical crystals. The necessary nonlinear susceptibility modulation period was calculated for an MgO:LiNbO 3 crystal. The characteristic features of the energy exchange between counterpropagating waves with parametric amplification in a low-frequency pump field were investigated. (nonlinear optical phenomena)

Screening of spontaneous polarization in lead titanate crystals

International Nuclear Information System (INIS)

Gavrilyachenko, V.G.; Semenchev, A.F.; Fesenko, E.G.

1996-01-01

Results of experimental investigations into electric conductivity of lead titanate crystals with different domain structure including single-domain are reported. The data obtained give grounds to believe that spontaneous titanate polarization is realized by the surface level and charge volumetric of free carriers and ionized impurity

Using polarized positrons to probe physics beyond the standard model

Science.gov (United States)

Furletova, Yulia; Mantry, Sonny

2018-05-01

A high intensity polarized positron beam, as part of the JLAB 12 GeV program and the proposed electron-ion collider (EIC), can provide a unique opportunity for testing the Standard Model (SM) and probing for new physics. The combination of high luminosity with polarized electrons and positrons incident on protons and deuterons can isolate important effects and distinguish between possible new physics scenarios in a manner that will complement current experimental efforts. A comparison of cross sections between polarized electron and positron beams will allow for an extraction of the poorly known weak neutral current coupling combination 2C3u - C3d and would complement the proposed plan for a precision extraction of the combination 2C2u - Cd at the EIC. Precision measurements of these neutral weak couplings would constrain new physics scenarios including Leptoquarks, R-parity violating supersymmetry, and electron and quark compositeness. The dependence of the charged current cross section on the longitudinal polarization of the positron beam will provide an independent probe to test the chiral structure of the electroweak interactions. A polarized positron can probe charged lepton flavor violation (CLFV) through a search for e+ → τ+ transitions in a manner that is independent and complementary to the proposed e- → τ- search at the EIC. A positron beam incident on an electron in a stationary nuclear target will also allow for a dark-photon (A') search via the annihilation process e+ + e- → A' + γ.

Properties of the plasma of the scrape-off layer including the effects of polarization drift

International Nuclear Information System (INIS)

Petrov, V.G.

1987-01-01

The plasma of the scrape-off layer of a tokamak is analyzed. The toroidal electric drift and the polarization drift of the charged particles are taken into account. The buildup of electric charge in the shadow of the poloidal limiter which results from toroidal drift is offset by a current to the limiter. The radial electric current associated with the polarization drift of ions is important near the inner boundary of the scrape-off layer. The distributions of the electric potential and the plasma density in the scrape-off layer are derived

Renormalized vacuum polarization for finite range potentials

International Nuclear Information System (INIS)

Lewin, J.D.

1975-10-01

This report presents computed vacuum polarization effects for leptons in a spherical potential well of radius large compared with the lepton Compton wavelength. These results, together with those previously obtained for small radius wells, show that the total charge generated is independent of well radius and lepton mass; thus the quadratic divergence obtained for the total unrenormalized charge can be removed by the subtraction of the contribution computed for a lepton of mass M(→ infinity) as in the case of the Coulomb potential. Various other problems arising from the earlier study are clarified by the present results. (author)

Inverted Polarity Thunderstorms Linked with Elevated Cloud Base Height

Science.gov (United States)

Cummins, K. L.; Williams, E.

2016-12-01

The great majority of thunderstorms worldwide exhibit gross positive dipole structure, produce intracloud lightning that reduces this positive dipole (positive intracloud flashes), and produce negative cloud-to-ground lightning from the lower negative end of this dipole. During the STEPS experiment in 2000 much new evidence for thunderstorms (or cells within multi-cellular storms) with inverted polarity came to light, both from balloon soundings of electric field and from LMA analysis. Many of the storms with inverted polarity cells developed in eastern Colorado. Fleenor et al. (2009) followed up after STEPS to document a dominance of positive polarity CG lightning in many of these cases. In the present study, surface thermodynamic observations (temperature and dew point temperature) have been used to estimate the cloud base heights and temperatures at the time of the Fleenor et al. lightning observations. It was found that when more than 90% of the observed CG lightning polarity within a storm is negative, the cloud base heights were low (2000 m AGL or lower, and warmer, with T>10 C), and when more than 90% of the observed CG lightning within a storm was positive, the cloud base heights were high (3000 m AGL or higher, and colder, with Tmixed polarity were generally associated with intermediate cloud base heights. These findings on inverted polarity thunderstorms are remarkably consistent with results in other parts of the world where strong instability prevails in the presence of high cloud base height: the plateau regions of China (Liu et al., 1989; Qie et al., 2005), and in pre-monsoon India (Pawar et al., 2016), particularly when mixed polarity cases are excluded. Calculations of adiabatic cloud water content for lifting from near 0 oC cast some doubt on earlier speculation (Williams et al., 2005) that the graupel particles in these inverted polarity storms attain a wet growth condition, and so exhibit positive charging following laboratory experiments. This

Radiotherapy high energy surface dose measurements: effects of chamber polarity

International Nuclear Information System (INIS)

Cheung, T.; Yu, P.K.N.; Butson, M.J.; Cancer Services, Wollongong, NSW

2004-01-01

Full text: The effects of chamber polarity have been investigated for the measurement of 6MV and 18MV x-ray surface dose using a parallel plate ionization chamber. Results have shown that a significant difference in measured ionization is recorded between to polarities at 6MV and 18MV at the phantom surface. A polarity ratio ranging from 1 062 to 1 005 is seen for 6MV x-rays at the phantom surface for field sizes 5cm x 5cm to 40cm x 40cm when comparing positive to negative polarity. These ratios range from 1.024 to 1.004 for 18MV x-rays with the same field sizes. When these charge reading are compared to the D max readings of the same polarity it is found that these polarity effects are minimal for the calculation of percentage dose results with variations being less than 1% of maximum. Copyright (2004) Australasian College of Physical Scientists and Engineers in Medicine

Measurement of the Λb polarization in Z decays

Science.gov (United States)

Buskulic, D.; Casper, D.; de Bonis, I.; Decamp, D.; Ghez, P.; Goy, C.; Lees, J.-P.; Lucotte, A.; Minard, M.-N.; Odier, P.; Pietrzyk, B.; Chmeissani, M.; Crespo, J. M.; Efthymiopoulos, I.; Fernandez, E.; Fernandez-Bosman, M.; Garrido, Ll; Juste, A.; Martinez, M.; Orteu, S.; Pacheco, A.; Padilla, C.; Palla, F.; Pascual, A.; Perlas, J. A.; Riu, I.; Sanchez, F.; Teubert, F.; Colaleo, A.; Creanza, D.; de Palma, M.; Farilla, A.; Gelao, G.; Girone, M.; Iaselli, G.; Maggi, G.; Maggi, M.; Marinelli, N.; Natali, S.; Nuzzo, S.; Ranieri, A.; Raso, G.; Romano, F.; Ruggieri, F.; Selvaggi, G.; Silvestris, L.; Tempesta, P.; Zito, G.; Huang, X.; Lin, J.; Ouyang, Q.; Wang, T.; Xie, Y.; Xu, R.; Xue, S.; Zhang, J.; Zhang, L.; Zhao, W.; Alemany, R.; Bazarko, A. O.; Bonvicini, G.; Cattaneo, M.; Comas, P.; Coyle, P.; Drevermann, H.; Forty, R. W.; Frank, M.; Hagelberg, R.; Harvey, J.; Jacobsen, R.; Janot, P.; Jost, B.; Kneringer, E.; Knobloch, J.; Lehraus, I.; Martin, E. B.; Mato, P.; Minten, A.; Miquel, R.; Mir, Ll. M.; Moneta, L.; Oest, T.; Palazzi, P.; Pater, J. R.; Pusztaszeri, J.-F.; Ranjard, F.; Rensing, P.; Rolandi, L.; Schlatter, D.; Schmelling, M.; Schneider, O.; Tejessy, W.; Tomalin, I. R.; Venturi, A.; Wachsmuth, H.; Wildish, T.; Witzeling, W.; Wotschack, J.; Ajaltouni, Z.; Bardadin-Otwinowska, M.; Barres, A.; Boyer, C.; Falvard, A.; Gay, P.; Guicheney, C.; Henrard, P.; Jousset, J.; Michel, B.; Monteil, S.; Montret, J.-C.; Pallin, D.; Perret, P.; Podlyski, F.; Proriol, J.; Rossignol, J.-M.; Saadi, F.; Fearnley, T.; Hansen, J. B.; Hansen, J. D.; Hansen, J. R.; Hansen, P. H.; Nilsson, B. S.; Kyriakis, A.; Markou, C.; Simopoulou, E.; Siotis, I.; Vayaki, A.; Zachariadou, K.; Blondel, A.; Bonneaud, G.; Brient, J. C.; Bourdon, P.; Rougé, A.; Rumpf, M.; Tanaka, R.; Valassi, A.; Verderi, M.; Videau, H.; Candlin, D. J.; Parsons, M. I.; Focardi, E.; Parrini, G.; Corden, M.; Delfino, M.; Georgiopoulos, C.; Jaffe, D. E.; Antonelli, A.; Bencivenni, G.; Bologna, G.; Bossi, F.; Campana, P.; Capon, G.; Chiarella, V.; Felici, G.; Laurelli, P.; Mannocchi, G.; Murtas, F.; Murtas, G. P.; Passalacqua, L.; Pepe-Altarelli, M.; Curtis, L.; Dorris, S. J.; Halley, A. W.; Knowles, I. G.; Lynch, J. G.; O'Shea, V.; Raine, C.; Reeves, P.; Scarr, J. M.; Smith, K.; Thompson, A. S.; Thomson, F.; Thorn, S.; Turnbull, R. M.; Becker, U.; Braun, O.; Geweniger, C.; Graefe, G.; Hanke, P.; Hepp, V.; Kluge, E. E.; Putzer, A.; Rensch, B.; Schmidt, M.; Sommer, J.; Stenzel, H.; Tittel, K.; Werner, S.; Wunsch, M.; Abbaneo, D.; Beuselinck, R.; Binnie, D. M.; Cameron, W.; Colling, D. J.; Dornan, P. J.; Konstantinidis, N.; Moutoussi, A.; Nash, J.; San Martin, G.; Sedgbeer, J. K.; Stacey, A. M.; Dissertori, G.; Girtler, P.; Kuhn, D.; Rudolph, G.; Bowdery, C. K.; Brodbeck, T. J.; Colrain, P.; Crawford, G.; Finch, A. J.; Foster, F.; Hughes, G.; Sloan, T.; Whelan, E. P.; Williams, M. I.; Galla, A.; Greene, A. M.; Kleinknecht, K.; Quast, G.; Raab, J.; Renk, B.; Sander, H.-G.; Wanke, R.; van Gemmeren, P.; Zeitnitz, C.; Aubert, J. J.; Bencheikh, A. M.; Benchouk, C.; Bonissent, A.; Bujosa, G.; Calvet, D.; Carr, J.; Diaconu, C.; Etienne, F.; Thulasidas, M.; Nicod, D.; Payre, P.; Rousseau, D.; Talby, M.; Abt, I.; Assmann, R.; Bauer, C.; Blum, W.; Brown, D.; Dietl, H.; Dydak, F.; Ganis, G.; Gotzhein, C.; Jakobs, K.; Kroha, H.; Lütjens, G.; Lutz, G.; Männer, W.; Moser, H.-G.; Richter, R.; Rosado-Schlosser, A.; Schael, S.; Settles, R.; Seywerd, H.; Denis, R. St; Wiedenmann, W.; Wolf, G.; Boucrot, J.; Callot, O.; Cordier, A.; Courault, F.; Davier, M.; Duflot, L.; Grivaz, J.-F.; Heusse, Ph; Jacquet, M.; Kim, D. W.; Le Diberder, F.; Lefrançois, J.; Lutz, A.-M.; Nikolic, I.; Park, H. J.; Park, I. C.; Schune, M.-H.; Simion, S.; Veillet, J.-J.; Videau, I.; Azzurri, P.; Bagliesi, G.; Batignani, G.; Bettarini, S.; Bozzi, C.; Calderini, G.; Carpinelli, M.; Ciocci, M. A.; Ciulli, V.; Dell'Orso, R.; Fantechi, R.; Ferrante, I.; Foà, L.; Forti, F.; Giassi, A.; Giorgi, M. A.; Gregorio, A.; Ligabue, F.; Lusiani, A.; Marrocchesi, P. S.; Messineo, A.; Rizzo, G.; Sanguinetti, G.; Sciabà, A.; Spagnolo, P.; Steinberger, J.; Tenchini, R.; Tonelli, G.; Vannini, C.; Verdini, P. G.; Walsh, J.; Betteridge, A. P.; Blair, G. A.; Bryant, L. M.; Cerutti, F.; Chambers, J. T.; Gao, Y.; Green, M. G.; Johnson, D. L.; Medcalf, T.; Perrodo, P.; Strong, J. A.; von Wimmersperg-Toeller, J. H.; Botterill, D. R.; Clifft, R. W.; Edgecock, T. R.; Haywood, S.; Edwards, M.; Maley, P.; Norton, P. R.; Thompson, J. C.; Bloch-Devaux, B.; Colas, P.; Emery, S.; Kozanecki, W.; Lançon, E.; Lemaire, M. C.; Locci, E.; Marx, B.; Perez, P.; Rander, J.; Renardy, J.-F.; Roussarie, A.; Schuller, J.-P.; Schwindling, J.; Trabelsi, A.; Vallage, B.; Johnson, R. P.; Kim, H. Y.; Litke, A. M.; McNeil, M. A.; Taylor, G.; Beddall, A.; Booth, C. N.; Boswell, R.; Brew, C. A. J.; Cartwright, S.; Combley, F.; Koksal, A.; Letho, M.; Newton, W. M.; Rankin, C.; Reeve, J.; Thompson, L. F.; Böhrer, A.; Brandt, S.; Cowan, G.; Feigl, E.; Grupen, C.; Lutters, G.; Minguet-Rodriguez, J.; Rivera, F.; Saraiva, P.; Smolik, L.; Stephan, F.; Apollonio, M.; Bosisio, L.; Della Marina, R.; Giannini, G.; Gobbo, B.; Musolino, G.; Ragusa, F.; Rothberg, J.; Wasserbaech, S.; Armstrong, S. R.; Bellantoni, L.; Elmer, P.; Feng, Z.; Ferguson, D. P. S.; Gao, Y. S.; González, S.; Grahl, J.; Greening, T. C.; Harton, J. L.; Hayes, O. J.; Hu, H.; McNamara, P. A.; Nachtman, J. M.; Orejudos, W.; Pan, Y. B.; Saadi, Y.; Schmitt, M.; Scott, I. J.; Sharma, V.; Turk, J. D.; Walsh, A. M.; Wu, Sau Lan; Wu, X.; Yamartino, J. M.; Zheng, M.; Zobernig, G.; Aleph Collaboration

1996-02-01

The Λb polarization in hadronic Z decays is measured in semileptonic decays from the average energies of the charged lepton and the neutrino. In a data sample of approximately 3 million hadronic Z decays collected by the ALEPH detector at LEP between 1991 and 1994, 462 ± 31 Λb candidates are selected using ( Λπ+)-lepton correlations. From this event sample, the Λb polarization is measured to be PΛ b = -0.23 -0.20+0.24(stat.) -0.07+0.08(syst.).

The electrostatics of charged insulating sheets peeled from grounded conductors

International Nuclear Information System (INIS)

Datta, M J; Horenstein, M N

2008-01-01

The physics of a charged, insulating sheet peeled from a ground-plane conductor is examined. Contact charging is ensured by charging a sheet to 10-12 kV with corona to establish intimate electrostatic contact with the underlying conductor. The surface potential is next forced to zero by sweeping the sheet with a stainless-steel brush, and the surface recharged to a new potential between 0 and 11 kV. The sheet is then peeled from the ground plane and its residual charge density is measured. Results show that the residual charge equals the breakdown-limiting value, but its polarity depends on the surface potential acquired just prior to peeling. The results have relevance to studies of industrial webs and insulating sheets.

Electro-optical detection of charged particles

International Nuclear Information System (INIS)

Semertzidis, Y.K.; Castillo, V.; Kowalski, L.; Kraus, D.E.; Larsen, R.; Lazarus, D.M.; Magurno, B.; Nikas, D.; Ozben, C.; Srinivasan-Rao, T.; Tsang, T.

2000-01-01

We have made the first observation of a charged particle beam by means of its electro-optical effect on the polarization of laser light in a LiNbO 3 crystal. The modulation of the laser light during the passage of a pulsed electron beam was observed using a fast photodiode and a digital oscilloscope. The fastest rise time measured, 120 ps, was obtained in the single shot mode and was limited by the bandwidth of the oscilloscope and the associated electronics. This technology holds good for detectors of greatly improved spatial and temporal resolution for single relativistic charged particles as well as particle beams

Electro-optical detection of charged particles

CERN Document Server

Semertzidis, Y K; Kowalski, L A; Kraus, D E; Larsen, R; Lazarus, D M; Magurno, B; Nikas, D; Ozben, C; Srinivasan-Rao, T; Tsang, Thomas

2000-01-01

We have made the first observation of a charged particle beam by means of its electro-optical effect on the polarization of laser light in a LiNbO sub 3 crystal. The modulation of the laser light during the passage of a pulsed electron beam was observed using a fast photodiode and a digital oscilloscope. The fastest rise time measured, 120 ps, was obtained in the single shot mode and was limited by the bandwidth of the oscilloscope and the associated electronics. This technology holds good for detectors of greatly improved spatial and temporal resolution for single relativistic charged particles as well as particle beams.

Electro-optical detection of charged particles

Energy Technology Data Exchange (ETDEWEB)

Semertzidis, Y.K.; Castillo, V.; Kowalski, L.; Kraus, D.E.; Larsen, R.; Lazarus, D.M. E-mail: lazarus@sun2.bnl.gov; Magurno, B.; Nikas, D.; Ozben, C.; Srinivasan-Rao, T.; Tsang, T

2000-10-01

We have made the first observation of a charged particle beam by means of its electro-optical effect on the polarization of laser light in a LiNbO{sub 3} crystal. The modulation of the laser light during the passage of a pulsed electron beam was observed using a fast photodiode and a digital oscilloscope. The fastest rise time measured, 120 ps, was obtained in the single shot mode and was limited by the bandwidth of the oscilloscope and the associated electronics. This technology holds good for detectors of greatly improved spatial and temporal resolution for single relativistic charged particles as well as particle beams.

Spin-polarized current generated by magneto-electrical gating

International Nuclear Information System (INIS)

Ma Minjie; Jalil, Mansoor Bin Abdul; Tan, Seng Ghee

2012-01-01

We theoretically study spin-polarized current through a single electron tunneling transistor (SETT), in which a quantum dot (QD) is coupled to non-magnetic source and drain electrodes via tunnel junctions, and gated by a ferromagnetic (FM) electrode. The I–V characteristics of the device are investigated for both spin and charge currents, based on the non-equilibrium Green's function formalism. The FM electrode generates a magnetic field, which causes a Zeeman spin-splitting of the energy levels in the QD. By tuning the size of the Zeeman splitting and the source–drain bias, a fully spin-polarized current is generated. Additionally, by modulating the electrical gate bias, one can effect a complete switch of the polarization of the tunneling current from spin-up to spin-down current, or vice versa. - Highlights: ► The spin polarized transport through a single electron tunneling transistor is systematically studied. ► The study is based on Keldysh non-equilibrium Green's function and equation of motion method. ► A fully spin polarized current is observed. ► We propose to reverse current polarization by the means of gate voltage modulation. ► This device can be used as a bi-polarization current generator.

Atomic polar tensors and acid-base properties of metal-oxide building blocks

International Nuclear Information System (INIS)

Ferris, K.F.

1993-02-01

The sensitivity of the atomic polar tensor to compositional substituents is reported for the alkali silicate series. Rotational invariants, effective atomic charge (GAPT) and charge normalized anisotropy and dipole (α n and γ n ) are used to characterize the charge distribution and chemical environment of the atomic sites. Comparison of α n and γ n with a series of known Bronsted and Lewis acids and bases suggests that these rotational invariants may act as indicators for metal-oxide site acidities. Basis set and electron correlation particularly affect the determined effective charge, but show minimal effect on α and γ quantities

Motion of charged particle in Reissner-Nordström spacetime: a Jacobi-metric approach

Science.gov (United States)

Das, Praloy; Sk, Ripon; Ghosh, Subir

2017-11-01

The present work discusses motion of neutral and charged particles in Reissner-Nordström spacetime. The constant energy paths are derived in a variational principle framework using the Jacobi metric which is parameterized by conserved particle energy. Of particular interest is the case of particle charge and Reissner-Nordström black hole charge being of same sign, since this leads to a clash of opposing forces—gravitational (attractive) and Coulomb (repulsive). Our paper aims to complement the recent work of Pugliese et al. (Eur Phys J C 77:206. arXiv:1304.2940, 2017; Phys Rev D 88:024042. arXiv:1303.6250, 2013). The energy dependent Gaussian curvature (induced by the Jacobi metric) plays an important role in classifying the trajectories.

Bidirectional transport of organelles: unity and struggle of opposing motors.

Science.gov (United States)

Bryantseva, Sofiya A; Zhapparova, Olga N

2012-01-01

Bidirectional transport along microtubules is ensured by opposing motor proteins: cytoplasmic dynein that drives cargo to the minus-ends and various kinesins that generally move to the plus-ends of microtubules. Regulation of motor proteins that are simultaneously bound to the same organelle is required to maintain directional transport and prevent pausing of cargo pulled away by motors of opposite polarity. Debates of the recent decade have been focused on two possible mechanisms of such regulation: (i) coordination, which implies that only one type of motors is active at a given time, and (ii) tug-of-war, which assumes that both motors are active at the same time and that direction of transport depends on the outcome of motor's confrontation. The initial idea of coordination has been challenged by observations of simultaneous activity of plus- and minus-end-directed motors applied to the same cargo. Analysis of the available data indicates that coordination and tug-of-war theories rather complement than contradict each other: cargo interacts with two teams of active motors, the resulting direction and the winner team are determined by coordination complexes, but the activity of the loser team is never completely inhibited and remains at some background level. Such persisting activity might enhance the overall efficiency of transport by increasing processivity or helping to overcome the obstacles on microtubule track. © The Author(s) Journal compilation © 2012 Portland Press Limited

Three-dimensional calculations of charge neutralization by neutral gas release

International Nuclear Information System (INIS)

Mandell, M.J.; Jongeward, G.A.; Katz, I.

1993-01-01

There have been numerous observations of high rocket or spacecraft potentials, both positive and negative, and both naturally and artificially induced, being neutralized during thruster firings. Two current studies, CHARGE-2B (positive polarity) and SPEAR3 (negative polarity), attempt a more systematic exploration of this phenomenon. The authors present here calculations performed in support of the SPEAR-3 program. (1) Conventional phenomenology of breakdown is applied to the three-dimensional system formed by the electrostatic potential and plume density fields. Using real cross sections, they calculate the paths along which the nozzle plume can support breakdown. This leads to a recommendation that the higher flow rate on SPEAR-3 be 2 g/s of argon, equal to the CHARGE-2B flow rate. (2) In a laboratory chamber, conditions (pressure of ∼ 2 x 10 - 5 torr) favor breakdown of the positive (electron-collecting) sheath for SPEAR-3 geometry. Three-dimensional calculations illustrate the evolution of the space charge and potential structure during the breakdown process. These calculations demonstrate the ability to apply accepted phenomenology to real systems with three dimensional electrostatic potential fields, space charge fields, and neutral density fields, including magnetic field effects and real cross-section data

Measurement of $\\Lambda_{b}$ polarization in Z decays

CERN Document Server

Buskulic, Damir; De Bonis, I; Décamp, D; Ghez, P; Goy, C; Lees, J P; Lucotte, A; Minard, M N; Odier, P; Pietrzyk, B; Chmeissani, M; Crespo, J M; Efthymiopoulos, I; Fernández, E; Fernández-Bosman, M; Garrido, L; Juste, A; Martínez, M; Orteu, S; Pacheco, A; Padilla, C; Palla, Fabrizio; Pascual, A; Perlas, J A; Riu, I; Sánchez, F; Teubert, F; Colaleo, A; Creanza, D; De Palma, M; Farilla, A; Gelao, G; Girone, M; Iaselli, Giuseppe; Maggi, G; Maggi, M; Marinelli, N; Natali, S; Nuzzo, S; Ranieri, A; Raso, G; Romano, F; Ruggieri, F; Selvaggi, G; Silvestris, L; Tempesta, P; Zito, G; Huang, X; Lin, J; Ouyang, Q; Wang, T; Xie, Y; Xu, R; Xue, S; Zhang, J; Zhang, L; Zhao, W; Alemany, R; Bazarko, A O; Bonvicini, G; Cattaneo, M; Comas, P; Coyle, P; Drevermann, H; Forty, Roger W; Frank, M; Hagelberg, R; Harvey, J; Jacobsen, R; Janot, P; Jost, B; Kneringer, E; Knobloch, J; Lehraus, Ivan; Martin, E B; Mato, P; Minten, Adolf G; Miquel, R; Mir, L M; Moneta, L; Oest, T; Palazzi, P; Pater, J R; Pusztaszeri, J F; Ranjard, F; Rensing, P E; Rolandi, Luigi; Schlatter, W D; Schmelling, M; Schneider, O; Tejessy, W; Tomalin, I R; Venturi, A; Wachsmuth, H W; Wildish, T; Witzeling, W; Wotschack, J; Ajaltouni, Ziad J; Bardadin-Otwinowska, Maria; Barrès, A; Boyer, C; Falvard, A; Gay, P; Guicheney, C; Henrard, P; Jousset, J; Michel, B; Monteil, S; Montret, J C; Pallin, D; Perret, P; Podlyski, F; Proriol, J; Rossignol, J M; Saadi, F; Fearnley, Tom; Hansen, J B; Hansen, J D; Hansen, J R; Hansen, P H; Nilsson, B S; Kyriakis, A; Markou, C; Simopoulou, Errietta; Siotis, I; Vayaki, Anna; Zachariadou, K; Blondel, A; Bonneaud, G R; Brient, J C; Bourdon, P; Rougé, A; Rumpf, M; Tanaka, R; Valassi, Andrea; Verderi, M; Videau, H L; Candlin, D J; Parsons, M I; Focardi, E; Parrini, G; Corden, M; Delfino, M C; Georgiopoulos, C H; Jaffe, D E; Antonelli, A; Bencivenni, G; Bologna, G; Bossi, F; Campana, P; Capon, G; Chiarella, V; Felici, G; Laurelli, P; Mannocchi, G; Murtas, F; Murtas, G P; Passalacqua, L; Pepé-Altarelli, M; Curtis, L; Dorris, S J; Halley, A W; Knowles, I G; Lynch, J G; O'Shea, V; Raine, C; Reeves, P; Scarr, J M; Smith, K; Thompson, A S; Thomson, F; Thorn, S; Turnbull, R M; Becker, U; Braun, O; Geweniger, C; Graefe, G; Hanke, P; Hepp, V; Kluge, E E; Putzer, A; Rensch, B; Schmidt, M; Sommer, J; Stenzel, H; Tittel, K; Werner, S; Wunsch, M; Abbaneo, D; Beuselinck, R; Binnie, David M; Cameron, W; Colling, D J; Dornan, Peter J; Konstantinidis, N P; Moutoussi, A; Nash, J; San Martin, G; Sedgbeer, J K; Stacey, A M; Dissertori, G; Girtler, P; Kuhn, D; Rudolph, G; Bowdery, C K; Brodbeck, T J; Colrain, P; Crawford, G; Finch, A J; Foster, F; Hughes, G; Sloan, Terence; Whelan, E P; Williams, M I; Galla, A; Greene, A M; Kleinknecht, K; Quast, G; Raab, J; Renk, B; Sander, H G; Wanke, R; Van Gemmeren, P; Zeitnitz, C; Aubert, Jean-Jacques; Bencheikh, A M; Benchouk, C; Bonissent, A; Bujosa, G; Calvet, D; Carr, J; Diaconu, C A; Etienne, F; Thulasidas, M; Nicod, D; Payre, P; Rousseau, D; Talby, M; Abt, I; Assmann, R W; Bauer, C; Blum, Walter; Brown, D; Dietl, H; Dydak, Friedrich; Ganis, G; Gotzhein, C; Jakobs, K; Kroha, H; Lütjens, G; Lutz, Gerhard; Männer, W; Moser, H G; Richter, R H; Rosado-Schlosser, A; Schael, S; Settles, Ronald; Seywerd, H C J; Saint-Denis, R; Wiedenmann, W; Wolf, G; Boucrot, J; Callot, O; Cordier, A; Courault, F; Davier, M; Duflot, L; Grivaz, J F; Heusse, P; Jacquet, M; Kim, D W; Le Diberder, F R; Lefrançois, J; Lutz, A M; Nikolic, I A; Park, H J; Park, I C; Schune, M H; Simion, S; Veillet, J J; Videau, I; Azzurri, P; Bagliesi, G; Batignani, G; Bettarini, S; Bozzi, C; Calderini, G; Carpinelli, M; Ciocci, M A; Ciulli, V; Dell'Orso, R; Fantechi, R; Ferrante, I; Foà, L; Forti, F; Giassi, A; Giorgi, M A; Gregorio, A; Ligabue, F; Lusiani, A; Marrocchesi, P S; Messineo, A; Rizzo, G; Sanguinetti, G; Sciabà, A; Spagnolo, P; Steinberger, Jack; Tenchini, Roberto; Tonelli, G; Vannini, C; Verdini, P G; Walsh, J; Betteridge, A P; Blair, G A; Bryant, L M; Cerutti, F; Chambers, J T; Gao, Y; Green, M G; Johnson, D L; Medcalf, T; Perrodo, P; Strong, J A; Von Wimmersperg-Töller, J H; Botterill, David R; Clifft, R W; Edgecock, T R; Haywood, S; Edwards, M; Maley, P; Norton, P R; Thompson, J C; Bloch-Devaux, B; Colas, P; Emery, S; Kozanecki, Witold; Lançon, E; Lemaire, M C; Locci, E; Marx, B; Pérez, P; Rander, J; Renardy, J F; Roussarie, A; Schuller, J P; Schwindling, J; Trabelsi, A; Vallage, B; Johnson, R P; Kim, H Y; Litke, A M; McNeil, M A; Taylor, G; Beddall, A; Booth, C N; Boswell, R; Brew, C A J; Cartwright, S L; Combley, F; Köksal, A; Letho, M; Newton, W M; Rankin, C; Reeve, J; Thompson, L F; Böhrer, A; Brandt, S; Cowan, G D; Feigl, E; Grupen, Claus; Lutters, G; Minguet-Rodríguez, J A; Rivera, F; Saraiva, P; Smolik, L; Stephan, F; Apollonio, M; Bosisio, L; Della Marina, R; Giannini, G; Gobbo, B; Musolino, G; Ragusa, F; Rothberg, J E; Wasserbaech, S R; Armstrong, S R; Bellantoni, L; Elmer, P; Feng, Z; Ferguson, D P S; Gao, Y S; González, S; Grahl, J; Greening, T C; Harton, J L; Hayes, O J; Hu, H; McNamara, P A; Nachtman, J M; Orejudos, W; Pan, Y B; Saadi, Y; Schmitt, M; Scott, I J; Sharma, V; Turk, J; Walsh, A M; Wu Sau Lan; Wu, X; Yamartino, J M; Zheng, M; Zobernig, G

1996-01-01

The \\Lambda_{\\mathrm{b}} polarization in hadronic \\mathrm{Z} decays is measured in semileptonic decays from the average energies of the charged lepton and the neutrino. In a data sample of approximately 3 million hadronic \\mathrm{Z} decays collected by the ALEPH detector at LEP between 1991 and 1994, 462\\pm 31 \\Lambda_{\\mathrm{b}} candidates are selected using (\\Lambda \\pi^+)--lepton correlations. From this event sample, the \\Lambda_{\\m athrm{b}} polarization is measured to be \\cal P_{\\Lambda_{\\mathrm{b}}}=-0.23^{+0.24}_{-0.20}(\\m athrm{stat}.)^{+0.08}_{-0.07} (\\mathrm{syst.})\\,.

Full Polarization Analysis of Resonant Superlattice and Forbidden x-ray Reflections in Magnetite

International Nuclear Information System (INIS)

Wilkins, S.B.; Bland, S.R.; Detlefs, B.; Beale, T.A.W.; Mazzoli, C.; Joly, Y.; Hatton, P.D.; Lorenzo, J.E.; Brabers, V.A.M.

2009-01-01

Despite being one of the oldest known magnetic materials, and the classic mixed valence compound, thought to be charge ordered, the structure of magnetite below the Verwey transition is complex and the presence and role of charge order is still being debated. Here, we present resonant x-ray diffraction data at the iron K-edge on forbidden (0, 0, 2n+1) C and superlattice (0, 0, 2n+1/2)C reflections. Full linear polarization analysis of the incident and scattered light was conducted in order to explore the origins of the reflections. Through simulation of the resonant spectra we have confirmed that a degree of charge ordering takes place, while the anisotropic tensor of susceptibility scattering is responsible for the superlattice reflections below the Verwey transition. We also report the surprising result of the conversion of a significant proportion of the scattered light from linear to nonlinear polarization.

New stable multiply charged negative atomic ions in linearly polarized superintense laser fields

International Nuclear Information System (INIS)

Wei Qi; Kais, Sabre; Moiseyev, Nimrod

2006-01-01

Singly charged negative atomic ions exist in the gas phase and are of fundamental importance in atomic and molecular physics. However, theoretical calculations and experimental results clearly exclude the existence of any stable doubly-negatively-charged atomic ion in the gas phase, only one electron can be added to a free atom in the gas phase. In this report, using the high-frequency Floquet theory, we predict that in a linear superintense laser field one can stabilize multiply charged negative atomic ions in the gas phase. We present self-consistent field calculations for the linear superintense laser fields needed to bind extra one and two electrons to form He - , He 2- , and Li 2- , with detachment energies dependent on the laser intensity and maximal values of 1.2, 0.12, and 0.13 eV, respectively. The fields and frequencies needed for binding extra electrons are within experimental reach. This method of stabilization is general and can be used to predict stability of larger multiply charged negative atomic ions

Nuclear polarization in hydrogenlike 82208Pb81+

International Nuclear Information System (INIS)

Haga, Akihiro; Tanaka, Yasutoshi; Horikawa, Yataro

2002-01-01

We calculate nuclear-polarization energy shifts for the hydrogenlike 82 208 Pb 81+ . The retarded transverse part as well as the longitudinal part is taken into account as the electromagnetic interaction between an electron and the nucleus. With a finite charge distribution for the nuclear ground state and the random-phase approximation to describe the nuclear excitations, we obtain nuclear-polarization energy of the 1s 1/2 state as -38.2 (-37.0) meV in the Feynman (Coulomb) gauge. For the 2s 1/2 , 2p 1/2 , and 2p 3/2 states, they are -6.7 (-6.4), -0.2 (-0.2), and +0.0 (+0.0) meV, respectively. The transverse contribution is small in comparison with the longitudinal nuclear-polarization correction. It is about 12% both for the 1s 1/2 and 2s 1/2 states. The seagull term in the two-photon exchange diagrams is also shown to be quite important to obtain the gauge-invariant nuclear-polarization energies

The color of polarization in cuprate superconductors

International Nuclear Information System (INIS)

Hoff, H.A.; Osofsky, M.S.; Lechter, W.L.; Pande, C.S.

1991-01-01

A technique for the identification of individual anisotropic grains in a heterogeneous and opaque material involves the observation of grain color in reflected light through crossed polarizers (color of polarization). Such colors are generally characteristic of particular phases. When grains of many members of the class of hole carrier cuprate superconductors are so viewed at room temperature with a 'daylight' source, a characteristic color of polarization is observed. This color was studied in many of these cuprate superconductors and a strong correlation was found between color and the existence of superconductivity. Two members were also examined of the electron cuprate superconductors and it was found that they possess the same color of polarization as the hole carrier cuprate superconductors so far examined. The commonality of the characteristic color regardless of charge carrier indicates that the presence of this color is independent of carrier type. The correlation of this color with the existence of superconductivity in the cuprate superconductors suggests that the origin of the color relates to the origin of superconductivity. Photometric techniques are also discussed

The edentulous mandible opposing maxillary natural teeth: treatment considerations utilizing implant overdentures.

Science.gov (United States)

Winkler, S; Monasky, G E

1993-01-01

The restoration of the edentulous mandible opposing all or part of the maxillary natural dentition with implant overdentures is described. There are many situations in which the maxillary teeth opposing an edentulous mandible can and should be retained. Mandibular implant overdentures can be utilized as long as health considerations, morphologic features of the resorbed mandible, and maxillomandibular jaw relationships are satisfactory.

Large Spin-Valley Polarization in Monolayer MoTe2 on Top of EuO(111)

KAUST Repository

Zhang, Qingyun

2015-12-08

The electronic properties of monolayer MoTe2 on top of EuO(111) are studied by first-principles calculations. Strong spin polarization is induced in MoTe2, which results in a large valley polarization. In a longitudinal electric field this will result in a valley and spin-polarized charge Hall effect. The direction of the Hall current as well as the valley and spin polarizations can be tuned by an external magnetic field. Copyright © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Polar semiconductor heterojunction structure energy band diagram considerations

International Nuclear Information System (INIS)

Lin, Shuxun; Wen, Cheng P.; Wang, Maojun; Hao, Yilong

2016-01-01

The unique nature of built-in electric field induced positive/negative charge pairs of polar semiconductor heterojunction structure has led to a more realistic device model for hexagonal III-nitride HEMT. In this modeling approach, the distribution of charge carriers is dictated by the electrostatic potential profile instead of Femi statistics. The proposed device model is found suitable to explain peculiar properties of GaN HEMT structures, including: (1) Discrepancy in measured conventional linear transmission line model (LTLM) sheet resistance and contactless sheet resistance of GaN HEMT with thin barrier layer. (2) Below bandgap radiation from forward biased Nickel Schottky barrier diode on GaN HEMT structure. (3) GaN HEMT barrier layer doping has negligible effect on transistor channel sheet charge density.

Polar semiconductor heterojunction structure energy band diagram considerations

Energy Technology Data Exchange (ETDEWEB)

Lin, Shuxun; Wen, Cheng P., E-mail: cpwen@ieee.org; Wang, Maojun; Hao, Yilong [Institute of Microelectronics, Peking University, Beijing (China)

2016-03-28

The unique nature of built-in electric field induced positive/negative charge pairs of polar semiconductor heterojunction structure has led to a more realistic device model for hexagonal III-nitride HEMT. In this modeling approach, the distribution of charge carriers is dictated by the electrostatic potential profile instead of Femi statistics. The proposed device model is found suitable to explain peculiar properties of GaN HEMT structures, including: (1) Discrepancy in measured conventional linear transmission line model (LTLM) sheet resistance and contactless sheet resistance of GaN HEMT with thin barrier layer. (2) Below bandgap radiation from forward biased Nickel Schottky barrier diode on GaN HEMT structure. (3) GaN HEMT barrier layer doping has negligible effect on transistor channel sheet charge density.

Numerical study of the influence of solid polarization on electrophoresis at finite Debye thickness.

Science.gov (United States)

Bhattacharyya, Somnath; De, Simanta

2015-09-01

The influence of solid polarization on the electrophoresis of a uniformly charged dielectric particle for finite values of the particle-to-fluid dielectric permittivity ratio is analyzed quantitatively without imposing the thin Debye length or weak-field assumption. Present analysis is based on the computation of the coupled Poisson-Nernst-Planck and Stokes equations in the fluid domain along with the Laplace equation within the solid. The electrophoretic velocity is determined through the balance of forces acting on the particle. The solid polarization of the charged particle produces a reduction on its electrophoretic velocity compared to a nonpolarizable particle of the same surface charge density. In accordance with the existing thin-layer analysis, our computed results for thin Debye layer shows that the solid polarization is important only when the applied electric field is strong. When the Debye length is in the order of the particle size, the electrophoretic velocity decreases with the rise of the particle permittivity and attains a saturation limit at large values of the permittivity. Our computed solution for electrophoretic velocity is in agreement with the existing asymptotic analyses based on a thin Debye layer for limiting cases.

Charged Hadron Properties in Background Electric Fields

International Nuclear Information System (INIS)

Detmold, William; Tiburzi, Brian C.; Walker-Loud, Andre

2010-01-01

We report on a lattice calculation demonstrating a novel new method to extract the electric polarizability of charged pseudo-scalar mesons by analyzing two point correlation functions computed in classical background electric fields. A staple component of any electrodynamics or quantum mechanics course is the electric polarizability. Neutral material immersed in a weak external field polarizes, internally setting up an electric dipole moment, aligned so as to minimize the energy. At the atomic level, the electron clouds are distorted creating these microscopic dipole moments. The same process occurs at the hadronic level but the polarization effects are now constrained by the strong force. Polarizabilities of these bound QCD states can be viewed as a distortion of the charged pion cloud of a given hadron. One can use lattice QCD to non-perturbatively compute the quark and gluon interactions in the presence of background electric (or magnetic) fields. For sufficiently weak background fields, the low energy properties of the hadrons can be rigorously computed using effective field theory. With this treatment, a picture of hadrons emerges from chiral dynamics: that of a hadronic core surrounded by a pseudoscalar meson cloud. As some pseudoscalar mesons are charged, polarizabilities of hadrons encode the stiffness of the charged meson cloud (as well as that of the core). The form of pseudoscalar meson polarizabilities is consequently strongly constrained by chiral dynamics. However, beyond the leading order, the results depend upon essentially unknown low-energy constants, which must currently be estimated in a model-dependent fashion. In the case of the charged pion, the experimental measurement of the polarizability has proven difficult, both in the original measurement as well as the most recent published result. Currently, there is a 2-3 sigma discrepancy between the two-loop cPT prediction and the measured charged pion polarizability. New results with higher

Infrared intensities and charge mobility in hydrogen bonded complexes

Energy Technology Data Exchange (ETDEWEB)

Galimberti, Daria; Milani, Alberto; Castiglioni, Chiara [Dipartimento di Chimica, Materiali e Ingegneria Chimica “Giulio Natta,” Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano (Italy)

2013-08-21

The analytical model for the study of charge mobility in the molecules presented by Galimberti et al.[J. Chem. Phys. 138, 164115 (2013)] is applied to hydrogen bonded planar dimers. Atomic charges and charge fluxes are obtained from density functional theory computed atomic polar tensors and related first derivatives, thus providing an interpretation of the IR intensity enhancement of the X–H stretching band observed upon aggregation. Our results show that both principal and non-principal charge fluxes have an important role for the rationalization of the spectral behavior; moreover, they demonstrate that the modulation of the charge distribution during vibrational motions of the –XH⋯Y– fragment is not localized exclusively on the atoms directly involved in hydrogen bonding. With these premises we made some correlations between IR intensities, interaction energies, and charge fluxes. The model was tested on small dimers and subsequently to the bigger one cytosine-guanine. Thus, the model can be applied to complex systems.

Charging effects and surface potential variations of Cu-based nanowires

Energy Technology Data Exchange (ETDEWEB)

Nunes, D., E-mail: daniela.gomes@fct.unl.pt [i3N/CENIMAT, Department of Materials Science, Faculty of Science and Technology, Universidade NOVA de Lisboa, Campus de Caparica, 2829-516 Caparica (Portugal); Calmeiro, T.R.; Nandy, S.; Pinto, J.V.; Pimentel, A.; Barquinha, P. [i3N/CENIMAT, Department of Materials Science, Faculty of Science and Technology, Universidade NOVA de Lisboa, Campus de Caparica, 2829-516 Caparica (Portugal); Carvalho, P.A. [SINTEF Materials and Chemistry, PB 124 Blindern, NO-0314, Oslo (Norway); CeFEMA, Instituto Superior Técnico, Universidade de Lisboa, 1049-001, Lisboa (Portugal); Walmsley, J.C. [SINTEF Materials and Chemistry, Materials and Nanotechnology, Høgskoleringen 5, 7034 Trondheim (Norway); Fortunato, E., E-mail: emf@fct.unl.pt [i3N/CENIMAT, Department of Materials Science, Faculty of Science and Technology, Universidade NOVA de Lisboa, Campus de Caparica, 2829-516 Caparica (Portugal); Martins, R., E-mail: rm@uninova.pt [i3N/CENIMAT, Department of Materials Science, Faculty of Science and Technology, Universidade NOVA de Lisboa, Campus de Caparica, 2829-516 Caparica (Portugal)

2016-02-29

The present work reports charging effects and surface potential variations in pure copper, cuprous oxide and cupric oxide nanowires observed by electrostatic force microscopy (EFM) and Kelvin probe force microscopy (KPFM). The copper nanowires were produced by wet synthesis, oxidation into cuprous oxide nanowires was achieved through microwave irradiation and cupric oxide nanowires were obtained via furnace annealing in atmospheric conditions. Structural characterization of the nanowires was carried out by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and energy dispersive X-ray spectroscopy. During the EFM experiments the electrostatic field of the positive probe charged negatively the Cu-based nanowires, which in turn polarized the SiO{sub 2} dielectric substrate. Both the probe/nanowire capacitance as well as the substrate polarization increased with the applied bias. Cu{sub 2}O and CuO nanowires behaved distinctively during the EFM measurements in accordance with their band gap energies. The work functions (WF) of the Cu-based nanowires, obtained by KPFM measurements, yielded WF{sub CuO} > WF{sub Cu} > WF{sub Cu{sub 2O}}. - Highlights: • Charge distribution study in Cu, Cu{sub 2}O and CuO nanowires through electrostatic force microscopy • Structural/surface defect role on the charge distribution along the Cu nanowires • Determination of the nanowire work functions by Kelvin probe force microscopy • Three types of nanowires give a broad idea of charge behavior on Cu based-nanowires.

Charged particle layers in the Debye limit.

Science.gov (United States)

Golden, Kenneth I; Kalman, Gabor J; Kyrkos, Stamatios

2002-09-01

We develop an equivalent of the Debye-Hückel weakly coupled equilibrium theory for layered classical charged particle systems composed of one single charged species. We consider the two most important configurations, the charged particle bilayer and the infinite superlattice. The approach is based on the link provided by the classical fluctuation-dissipation theorem between the random-phase approximation response functions and the Debye equilibrium pair correlation function. Layer-layer pair correlation functions, screened and polarization potentials, static structure functions, and static response functions are calculated. The importance of the perfect screening and compressibility sum rules in determining the overall behavior of the system, especially in the r--> infinity limit, is emphasized. The similarities and differences between the quasi-two-dimensional bilayer and the quasi-three-dimensional superlattice are highlighted. An unexpected behavior that emerges from the analysis is that the screened potential, the correlations, and the screening charges carried by the individual layers exhibit a marked nonmonotonic dependence on the layer separation.

Charged particle layers in the Debye limit

International Nuclear Information System (INIS)

Golden, Kenneth I.; Kalman, Gabor J.; Kyrkos, Stamatios

2002-01-01

We develop an equivalent of the Debye-Hueckel weakly coupled equilibrium theory for layered classical charged particle systems composed of one single charged species. We consider the two most important configurations, the charged particle bilayer and the infinite superlattice. The approach is based on the link provided by the classical fluctuation-dissipation theorem between the random-phase approximation response functions and the Debye equilibrium pair correlation function. Layer-layer pair correlation functions, screened and polarization potentials, static structure functions, and static response functions are calculated. The importance of the perfect screening and compressibility sum rules in determining the overall behavior of the system, especially in the r→∞ limit, is emphasized. The similarities and differences between the quasi-two-dimensional bilayer and the quasi-three-dimensional superlattice are highlighted. An unexpected behavior that emerges from the analysis is that the screened potential, the correlations, and the screening charges carried by the individual layers exhibit a marked nonmonotonic dependence on the layer separation

Transient charging and discharging of spin-polarized electrons in a quantum dot

DEFF Research Database (Denmark)

De Souza, Fabricio; Leao, S.A.; Gester, R. M.

2007-01-01

We study spin-polarized transient transport in a quantum dot coupled to two ferromagnetic leads subjected to a rectangular bias voltage pulse. Time-dependent spin-resolved currents, occupations, spin accumulation, and tunneling magnetoresistance TMR are calculated using both nonequilibrium Green ...

Molecular electron recollision dynamics in intense circularly polarized laser pulses

Science.gov (United States)

Bandrauk, André D.; Yuan, Kai-Jun

2018-04-01

Extreme UV and x-ray table top light sources based on high-order harmonic generation (HHG) are focused now on circular polarization for the generation of circularly polarized attosecond pulses as new tools for controlling electron dynamics, such as charge transfer and migration and the generation of attosecond quantum electron currents for ultrafast magneto-optics. A fundamental electron dynamical process in HHG is laser induced electron recollision with the parent ion, well established theoretically and experimentally for linear polarization. We discuss molecular electron recollision dynamics in circular polarization by theoretical analysis and numerical simulation. The control of the polarization of HHG with circularly polarized ionizing pulses is examined and it is shown that bichromatic circularly polarized pulses enhance recollision dynamics, rendering HHG more efficient, especially in molecules because of their nonspherical symmetry. The polarization of the harmonics is found to be dependent on the compatibility of the rotational symmetry of the net electric field created by combinations of bichromatic circularly polarized pulses with the dynamical symmetry of molecules. We show how the field and molecule symmetry influences the electron recollision trajectories by a time-frequency analysis of harmonics. The results, in principle, offer new unique controllable tools in the study of attosecond molecular electron dynamics.

Impact of molecular packing on electronic polarization in organic crystals: the case of pentacene vs TIPS-pentacene.

Science.gov (United States)

Ryno, Sean M; Risko, Chad; Brédas, Jean-Luc

2014-04-30

Polarization energy corresponds to the stabilization of the cation or anion state of an atom or molecule when going from the gas phase to the solid state. The decrease in ionization energy and increase in electron affinity in the solid state are related to the (electronic and nuclear) polarization of the surrounding atoms and molecules in the presence of a charged entity. Here, through a combination of molecular mechanics and quantum mechanics calculations, we evaluate the polarization energies in two prototypical organic semiconductors, pentacene and 6,13-bis(2-(tri-isopropylsilyl)ethynyl)pentacene (TIPS-pentacene). Comparison of the results for the two systems reveals the critical role played by the molecular packing configurations in the determination of the polarization energies and provides physical insight into the experimental data reported by Lichtenberger and co-workers (J. Amer. Chem. Soc. 2010, 132, 580; J. Phys. Chem. C 2010, 114, 13838). Our results underline that the impact of packing configurations, well established in the case of the charge-transport properties, also extends to the polarization properties of π-conjugated materials.

A numerical study on charging mechanism in leaky dielectric liquids inside the electrostatic atomizers

Science.gov (United States)

Kashir, Babak; Perri, Anthony; Yarin, Alexander L.; Mashayek, Farzad

2017-11-01

The charging of leaky dielectric liquids inside an electrostatic atomizer is studied numerically by developed codes based on OpenFOAM platform. Faradaic reactions are taken into account as the electrification mechanism. The impact of ionic finite size (steric terms) in high voltages is also investigated. The fundamental electrohydrodynamic understanding of the charging mechanism is aimed in the present work where the creation of polarized near-electrode layer and the movement of charges due to hydrodynamic flow are studied in conjunction with the solution of the Navier-Stokes equations. The case of a micro channel electrohydrodynamic flow subjected to two electrodes of the opposite polarity is considered as an example, with the goal to predict the resulting net charge at the exit. Even though the electrodes constitute a small portion of the channel wall, otherwise insulated, it is indicated that the channel length plays a dominant role in the discharging net charge. The ionic fluxes at the electrode surfaces are accounted through the Frumkin-Butler-Volmer relation found from the concurrent in-house experimental investigations. This projects was supported by National science Foundation (NSF) GOALI Grant CBET-1505276.

Coherent polarization radiation of relativistic electrons in crystals

International Nuclear Information System (INIS)

Morokhovskii, V.L.

2014-01-01

A brief narration about the history of those heated arguments and discussions around the nature of so-called parametric X-radiation, which were concluded by the recognition of the discovery the phenomenon of coherent polarization bremsstrahlung of relativistic charged particles in crystals. Some important information and comments, which stay over of notice of specialists till now are reported.

Mutually opposing forces during locomotion can eliminate the tradeoff between maneuverability and stability

Science.gov (United States)

Cowan, Noah; Sefati, Shahin; Neveln, Izaak; Roth, Eatai; Mitchell, Terence; Snyder, James; Maciver, Malcolm; Fortune, Eric

A surprising feature of animal locomotion is that organisms typically produce substantial forces in directions other than what is necessary to move the animal through its environment, such as perpendicular to, or counter to, the direction of travel. The effect of these forces has been difficult to observe because they are often mutually opposing and therefore cancel out. Using a combination of robotic physical modeling, computational modeling, and biological experiments, we discovered that these forces serve an important role: to simplify and enhance the control of locomotion. Specifically, we examined a well-suited model system, the glass knifefish Eigenmannia virescens, which produces mutually opposing forces during a hovering behavior. By systematically varying the locomotor parameters of our biomimetic robot, and measuring the resulting forces and kinematics, we demonstrated that the production and differential control of mutually opposing forces is a strategy that generates passive stabilization while simultaneously enhancing maneuverability. Mutually opposing forces during locomotion are widespread across animal taxa, and these results indicate that such forces can eliminate the tradeoff between stability and maneuverability, thereby simplifying robotic and neural control.

Interface reconstruction with emerging charge ordering in hexagonal manganite

Science.gov (United States)

Xu, Changsong; Han, Myung-Geun; Bao, Shanyong; Nan, Cewen; Bellaiche, Laurent

2018-01-01

Multiferroic materials, which simultaneously have multiple orderings, hold promise for use in the next generation of memory devices. We report a novel self-assembled MnO double layer forming at the interface between a multiferroic YMnO3 film and a c-Al2O3 substrate. The crystal structures and the valence states of this MnO double layer were studied by atomically resolved scanning transmission electron microscopy and spectroscopy, as well as density functional theory (DFT) calculations. A new type of charge ordering has been identified within this MnO layer, which also contributes to a polarization along the [001] direction. DFT calculations further establish the occurrence of multiple couplings between charge and lattice in this novel double layer, in addition to the polarization in nearby YMnO3 single layer. The interface reconstruction reported here creates a new playground for emergent physics, such as giant ferroelectricity and strong magnetoelectric coupling, in manganite systems. PMID:29795782

Diffusive charge transport in graphene

Science.gov (United States)

Chen, Jianhao

The physical mechanisms limiting the mobility of graphene on SiO 2 are studied and printed graphene devices on a flexible substrate are realized. Intentional addition of charged scattering impurities is used to study the effects of charged impurities. Atomic-scale defects are created by noble-gas ions irradiation to study the effect of unitary scatterers. The results show that charged impurities and atomic-scale defects both lead to conductivity linear in density in graphene, with a scattering magnitude that agrees quantitatively with theoretical estimates. While charged impurities cause intravalley scattering and induce a small change in the minimum conductivity, defects in graphene scatter electrons between the valleys and suppress the minimum conductivity below the metallic limit. Temperature-dependent measurements show that longitudinal acoustic phonons in graphene produce a small resistivity which is linear in temperature and independent of carrier density; at higher temperatures, polar optical phonons of the SiO2 substrate give rise to an activated, carrier density-dependent resistivity. Graphene is also made into high mobility transparent and flexible field effect device via the transfer-printing method. Together the results paint a complete picture of charge carrier transport in graphene on SiO2 in the diffusive regime, and show the promise of graphene as a novel electronic material that have potential applications not only on conventional inorganic substrates, but also on flexible substrates.

Polarity Control of Heteroepitaxial GaN Nanowires on Diamond.

Science.gov (United States)

Hetzl, Martin; Kraut, Max; Hoffmann, Theresa; Stutzmann, Martin

2017-06-14

Group III-nitride materials such as GaN nanowires are characterized by a spontaneous polarization within the crystal. The sign of the resulting sheet charge at the top and bottom facet of a GaN nanowire is determined by the orientation of the wurtzite bilayer of the different atomic species, called N and Ga polarity. We investigate the polarity distribution of heteroepitaxial GaN nanowires on different substrates and demonstrate polarity control of GaN nanowires on diamond. Kelvin Probe Force Microscopy is used to determine the polarity of individual selective area-grown and self-assembled nanowires over a large scale. At standard growth conditions, mixed polarity occurs for selective GaN nanowires on various substrates, namely on silicon, on sapphire and on diamond. To obtain control over the growth orientation on diamond, the substrate surface is modified by nitrogen and oxygen plasma exposure prior to growth, and the growth parameters are adjusted simultaneously. We find that the surface chemistry and the substrate temperature are the decisive factors for obtaining control of up to 93% for both polarity types, whereas the growth mode, namely selective area or self-assembled growth, does not influence the polarity distribution significantly. The experimental results are discussed by a model based on the interfacial bonds between the GaN nanowires, the termination layer, and the substrate.

Comparative evaluation of heart rate-based monitors: Apple Watch vs Fitbit Charge HR.

Science.gov (United States)

Bai, Yang; Hibbing, Paul; Mantis, Constantine; Welk, Gregory J

2018-08-01

The purpose of this investigation was to examine the validity of energy expenditure (EE), steps, and heart rate measured with the Apple Watch 1 and Fitbit Charge HR. Thirty-nine healthy adults wore the two monitors while completing a semi-structured activity protocol consisting of 20 minutes of sedentary activity, 25 minutes of aerobic exercise, and 25 minutes of light intensity physical activity. Criterion measures were obtained from an Oxycon Mobile for EE, a pedometer for steps, and a Polar heart rate strap worn on the chest for heart rate. For estimating whole-trial EE, the mean absolute percent error (MAPE) from Fitbit Charge HR (32.9%) was more than twice that of Apple Watch 1 (15.2%). This trend was consistent for the individual conditions. Both monitors accurately assessed steps during aerobic activity (MAPE Apple : 6.2%; MAPE Fitbit : 9.4%) but overestimated steps in light physical activity. For heart rate, Fitbit Charge HR produced its smallest MAPE in sedentary behaviors (7.2%), followed by aerobic exercise (8.4%), and light activity (10.1%). The Apple Watch 1 had stronger validity than the Fitbit Charge HR for assessing overall EE and steps during aerobic exercise. The Fitbit Charge HR provided heart rate estimates that were statistically equivalent to Polar monitor.

Studies of the pulse charge of lead-acid batteries for PV applications. Part I. Factors influencing the mechanism of the pulse charge of the positive plate

Energy Technology Data Exchange (ETDEWEB)

Kirchev, A.; Perrin, M.; Lemaire, E.; Karoui, F.; Mattera, F. [Commissariat de l' Energie Atomique, Institut National de l' Energie Solaire, INES-RDI, Parc Technologique de Savoie Technolac, 50 Avenue du Lac Leman, 73377 Le Bourget du Lac Cedex (France)

2008-02-15

The mechanism of the positive plate charge in pulse regime was studied in model lead-acid cells with one positive and two negative plates (8 Ah each) and Ag/Ag{sub 2}SO{sub 4} reference electrodes. The results showed that the evolution of the electrode potential is much slower on the positive plate than on the negative plate. Regardless of this fact, the calculated capacitive current of charge and self-discharge of the electrochemical double layer (EDL) during the 'ON' and 'OFF' half-periods of the pulse current square waves is comparable with the charge current amplitude. The result is due to the high values of the EDL on the surface of the lead dioxide active material. The influence of different factors like state of charge, state of health, pulse frequency, current amplitude and open circuit stay before the polarization was discussed. The previously determined optimal frequency of 1 Hz was associated with a maximum in the average double layer current on frequency dependence. The average double layer current is also maximal at SOC between 75 and 100%. The exchange of the constant current polarization with pulse polarization does not change substantially the mechanism and the overvoltage of the oxygen evolution reaction on the positive plate. The mechanism of the self-discharge of the EDL was also estimated analyzing long-time PPP transients (up to 2 h). It was found that when the PPP is lower than 1.2 V the preferred mechanism of EDL self-discharge is by coupling with the lead sulphate oxidation reaction. At higher values of PPP the EDL self-discharge happens via oxygen evolution. The high faradic efficiency of the pulse charge is due to the chemical oxidation of the Pb(II) ions by the O atoms and OH radicals formed at the oxygen evolution both during the 'ON' and 'OFF' periods. (author)

Interaction of free charged particles with a chirped electromagnetic pulse

International Nuclear Information System (INIS)

Khachatryan, A.G.; Goor, F.A. van; Boller, K.-J.

2004-01-01

We study the effect of chirp on electromagnetic (EM) pulse interaction with a charged particle. Both the one-dimensional (1D) and 3D cases are considered. It is found that, in contrast to the case of a nonchirped pulse, the charged particle energy can be changed after the interaction with a 1D EM chirped pulse. Different types of chirp and pulse envelopes are considered. In the case of small chirp, an analytical expression is found for arbitrary temporal profiles of the chirp and the pulse envelope. In the 3D case, the interaction with a chirped pulse results in a polarization-dependent scattering of charged particles

Two Opposing Effects (Yin and Yang) Determine Cancer Progression.

Science.gov (United States)

Huang, Shujun; Kurubanjerdjit, Nilubon; Xu, Wayne

2017-01-01

In this review, we introduce a new vision of cancer describing opposing effects that control progression. Cancer is a paradigm of opposing of "Yin" and "Yang," with Yin being the effect to promote cancer and Yang that to maintain the normal state. This Yin Yang hypothesis has been used to select Yin and Yang genes to develop multigene signatures for determining prognosis in lung and breast cancer. Most of the Yin genes are involved in cell survival, growth, and proliferation, whereas most Yang genes are involved in cell apoptosis. Furthermore, Yin and Yang pathways have been identified in breast cancer and compounds that can inhibit the Yin pathways or activate the Yang pathways have been examined, suggesting a new promising targeting therapy for cancer. We are building a Yin Yang model to represent the dynamic change of Yin and Yang genes and pathways.

Experimental and Theoretical Investigations of Glass Surface Charging Phenomena

Science.gov (United States)

Agnello, Gabriel

Charging behavior of multi-component display-type (i.e. low alkali) glass surfaces has been studied using a combination of experimental and theoretical methods. Data obtained by way of a Rolling Sphere Test (RST), streaming/zeta potential and surface energy measurements from commercially available display glass surfaces (Corning EAGLE XGRTM and Lotus(TM) XT) suggest that charge accumulation is highly dependent on surface treatment (chemical and/or physical modification) and measurement environment, presumably through reactionary mechanisms at the surface with atmospheric moisture. It has been hypothesized that water dissociation, along with the corresponding hydroxylation of the glass surface, are important processes related to charging in glass-metal contact systems. Classical Molecular Dynamics (MD) simulations, in conjunction with various laboratory based measurements (RST, a newly developed ElectroStatic Gauge (ESG) and Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS)) on simpler Calcium AluminoSilicate (CAS) glass surfaces were used to further explore these phenomena. Analysis of simulated high-silica content (≥50%) (CAS) glass structures suggest that controlled variation of bulk chemistry can directly affect surface defect concentrations, such as non-bridging oxygen (NBO), which can be suitable high-energy sites for hydrolysis-type reactions to occur. Calculated NBO surface concentrations correlate well with charge based measurements on laboratory fabricated CAS surfaces. The data suggest that a directional/polar shift in contact-charge transfer occurs at low silica content (≤50%) where the highest concentrations of NBOs are observed. Surface charging sensitivity with respect to NBO concentration decreases as the relative humidity of the measurement environment increases; which should be expected as the highly reactive sites are progressively covered by liquid water layers. DRIFTS analysis of CAS powders expand on this analysis showing

Simultaneous Determination of Electrochemical Impedance of Lithium-ion Rechargeable Batteries with Measurement of Charge-discharge Curves by Wavelet Transformation

International Nuclear Information System (INIS)

Itagaki, Masayuki; Ueno, Masaki; Hoshi, Yoshinao; Shitanda, Isao

2017-01-01

Highlights: • Wavelet transformation (WT) was used to obtain electrochemical impedance (EI) from time domain data. • Complex Morlet mother wavelet was employed to transform current and voltage time series from time domain to frequency domain. • An analytical method to determine EI of LIRB at arbitrary state of charge was proposed. • EI of LIRB was determined at arbitrary state of charge without stopping galvanostatic polarization for charge and discharge. - Abstract: A new analytical method was developed to determine the electrochemical impedance of lithium-ion rechargeable batteries (LIRB) at an arbitrary state of charge (SOC). Wavelet transformation (WT) is one of the waveform analysis methods, which allows the determination of frequency domain data as a function of time. The frequency domain data are obtained by convolution integral of a mother wavelet and original time domain data via the WT. A complex Morlet mother wavelet is used to obtain the complex number data in the frequency domain. The time series data of input current and output voltage signals are recorded by superimposing the double pulse current as an input signal to constant charge current for the charge of LIRB without stopping galvanostatic polarization. The double pulse current is composed of symmetrical positive and negative square waves. In this case, the SOC of LIRB is not affected by the input signal because the total amount of charge calculated from double pulse current is 0C. The impedance spectrum of LIRB at SOC 25% is determined in the frequency range from 0.1 to 100 Hz during charge/discharge cycles without stopping galvanostatic polarization for the charge/discharge.

Polarized Neutron Reflectometry of Nickel Corrosion Inhibitors.

Science.gov (United States)

Wood, Mary H; Welbourn, Rebecca J L; Zarbakhsh, Ali; Gutfreund, Philipp; Clarke, Stuart M

2015-06-30

Polarized neutron reflectometry has been used to investigate the detailed adsorption behavior and corrosion inhibition mechanism of two surfactants on a nickel surface under acidic conditions. Both the corrosion of the nickel surface and the structure of the adsorbed surfactant layer could be monitored in situ by the use of different solvent contrasts. Layer thicknesses and roughnesses were evaluated over a range of pH values, showing distinctly the superior corrosion inhibition of one negatively charged surfactant (sodium dodecyl sulfate) compared to a positively charged example (dodecyl trimethylammonium bromide) due to its stronger binding interaction with the surface. It was found that adequate corrosion inhibition occurs at significantly less than full surface coverage.

Triboelectricity: macroscopic charge patterns formed by self-arraying ions on polymer surfaces.

Science.gov (United States)

Burgo, Thiago A L; Ducati, Telma R D; Francisco, Kelly R; Clinckspoor, Karl J; Galembeck, Fernando; Galembeck, Sergio E

2012-05-15

Tribocharged polymers display macroscopically patterned positive and negative domains, verifying the fractal geometry of electrostatic mosaics previously detected by electric probe microscopy. Excess charge on contacting polyethylene (PE) and polytetrafluoroethylene (PTFE) follows the triboelectric series but with one caveat: net charge is the arithmetic sum of patterned positive and negative charges, as opposed to the usual assumption of uniform but opposite signal charging on each surface. Extraction with n-hexane preferentially removes positive charges from PTFE, while 1,1-difluoroethane and ethanol largely remove both positive and negative charges. Using suitable analytical techniques (electron energy-loss spectral imaging, infrared microspectrophotometry and carbonization/colorimetry) and theoretical calculations, the positive species were identified as hydrocarbocations and the negative species were identified as fluorocarbanions. A comprehensive model is presented for PTFE tribocharging with PE: mechanochemical chain homolytic rupture is followed by electron transfer from hydrocarbon free radicals to the more electronegative fluorocarbon radicals. Polymer ions self-assemble according to Flory-Huggins theory, thus forming the experimentally observed macroscopic patterns. These results show that tribocharging can only be understood by considering the complex chemical events triggered by mechanical action, coupled to well-established physicochemical concepts. Patterned polymers can be cut and mounted to make macroscopic electrets and multipoles.

Quadrature detection for the separation of the signals of positive and negative ions in fourier transform ion cyclotron resonance mass spectrometry

International Nuclear Information System (INIS)

Schweikhard, Lutz; Drader, Jared J.; Shi, Stone D.-H.; Hendrickson, Christopher L.; Marshall, Alan G.

2002-01-01

Positive and negative ions may be confined simultaneously in a nested open cylindrical Malmberg-Penning trap. However, ion charge sign cannot be distinguished by conventional dipolar (linearly-polarized) detection with a single pair of opposed electrodes. Here, the signals from each of two orthogonal pairs of opposed detection electrodes are acquired simultaneously and stored as real and imaginary parts of mathematically complex data. Complex Fourier transformation yields separate spectra for positive and negative ions. For a fullerene sample, experimental quadrature detection yields C 60 + and C 60 - signals separated by ∼1440 u rather than by the mass of two electrons, ∼0.001 u in conventional dipolar detection

Parallel Finite Element Particle-In-Cell Code for Simulations of Space-charge Dominated Beam-Cavity Interactions

International Nuclear Information System (INIS)

Candel, A.; Kabel, A.; Ko, K.; Lee, L.; Li, Z.; Limborg, C.; Ng, C.; Prudencio, E.; Schussman, G.; Uplenchwar, R.

2007-01-01

Over the past years, SLAC's Advanced Computations Department (ACD) has developed the parallel finite element (FE) particle-in-cell code Pic3P (Pic2P) for simulations of beam-cavity interactions dominated by space-charge effects. As opposed to standard space-charge dominated beam transport codes, which are based on the electrostatic approximation, Pic3P (Pic2P) includes space-charge, retardation and boundary effects as it self-consistently solves the complete set of Maxwell-Lorentz equations using higher-order FE methods on conformal meshes. Use of efficient, large-scale parallel processing allows for the modeling of photoinjectors with unprecedented accuracy, aiding the design and operation of the next-generation of accelerator facilities. Applications to the Linac Coherent Light Source (LCLS) RF gun are presented

Comparison study for multiple ionization of carbonyl sulfide by linearly and circularly polarized intense femtosecond laser fields using Coulomb explosion imaging

Science.gov (United States)

Ma, Pan; Wang, Chuncheng; Luo, Sizuo; Yu, Xitao; Li, Xiaokai; Wang, Zhenzhen; Hu, Wenhui; Yu, Jiaqi; Yang, Yizhang; Tian, Xu; Cui, Zhonghua; Ding, Dajun

2018-05-01

We studied the relative yields and dissociation dynamics for two- and three-body Coulomb explosion (CE) channels from highly charged carbonyl sulfide molecules in intense laser fields using the CE imaging technique. The electron recollision contributions are evaluated by comparing the relative yields for the multiple ionization process in linearly polarized and circularly polarized (LP and CP) laser fields. The nonsequential multiple ionization is only confirmed for the charge states of 2 to 4 because the energy for further ionization from the inner orbital is much larger than the maximum recollision energy, 3.2U p . The novel deviations of kinetic energy releases distributions between LP and CP pulses are observed for the charge states higher than 4. It can be attributed to the stronger molecular bending in highly charged states before three-body CE with CP light, in which the bending wave packet is initialed by the triple or quartic ionization and spread along their potential curves. Compared to LP light, CP light ionizes a larger fraction of bending molecules in the polarization plane.

Charge asymmetry in alignment of atoms excited by protons and antiprotons

International Nuclear Information System (INIS)

Balashov, V.V.; Sokolik, A.A.; Stysin, A.V.

2007-01-01

The multichannel diffraction approximation is used to consider excitation of lithium atom by proton and antiproton impact. Calculations are performed for the energy range 100 keV - 1 MeV of incoming proton and anti-proton which should be reliable enough due to the general requirements of the multichannel diffraction approximation. The sign-of-charge effect in the alignment of produced 1s 2 3d excited state and in the linear polarization of the subsequent spontaneous 1s 2 3d → 1s 2 2p radiation is expected to be considerable. The clear sign-of-charge effect in the polarization occurs for projectile energies below 1 MeV and become stronger when going to lower energies and the difference between the proton case and the anti-proton one looks considerable enough for experimental observation

Angular Distribution and Linear Polarization of X-ray Radiation Resulting from Electron Impact Excitation of Highly Charged Ions in Debye Plasmas

Science.gov (United States)

Chen, Zhanbin

2018-05-01

Plasma-screening effects on the 1s _{1/2} → 2l (l = s , p ) and 1s _{1/2} → 3d _{3/2} electron-impact excitation of highly charged ions are investigated, together with their subsequent radiative decay. The analysis is performed based on the multi-configuration Dirac-Fock method and the fully relativistic distorted-wave method incorporating the Debye-Hückel potential. To explore the nature of the effects, calculations are carried out based on detailed analyses of the integrated total and magnetic sublevel cross sections, the alignment parameters, the linear polarizations, and the angular distribution of the X-ray photoemission, as well as on corresponding data calculated in various Debye lengths/environments, taking the 2p _{3/2}→ 1s _{1/2} and 3d _{3/2}→ 1s _{1/2} characteristic lines of H-like Fe^{25+} ion as an example. The present results are compared with experimental data and other theoretical predictions where available.

Effect of solvent polarity and temperature on the spectral and thermodynamic properties of exciplexes of 1-cyanonaphthalene with hexamethylbenzene in organic solvents

International Nuclear Information System (INIS)

Asim, Sadia; Mansha, Asim; Grampp, Günter; Landgraf, Stephan; Zahid, Muhammad; Bhatti, Ijaz Ahmad

2014-01-01

Study of the effect of solvent polarity and temperature is done on the exciplex emission spectra of 1-cyanonaphthalene with hexamethylbenzene. Exciplex system is studied in the range of partially polar solvents and in solvent mixture of propyl acetate and butyronitrile. The unique feature of this solvent mixture is that only the solvent polarity changes (6.0≤ε s ≤24.7) with the change in the mole fraction of solvents whereas the solvent viscosity and refractive index remains unaffected. Thermodynamic properties are calculated according to the models developed by Weller and Kuzmin. Fluorescence lifetimes for both the fluorophore as well as the exciplex are evaluated in all used solvents. Exciplex energetics as a function of solvent polarity and temperature are also discussed. Kuzmin model of self-consistent polarization is used for the explanation of the exciplex emission spectra. The effects of solvent polarity and temperature on energy of zero–zero transitions (hv 0 / ), Huang–Rhys factor (S), Gauss broadening of vibronic level (σ) and the dominant high-frequency vibration (hν ν ) are investigated. The strong dependence of exciplex stability and energetics upon the solvent polarity and temperature are observed. Full charge transfer exciplexes were observed in solvents of all polarities and stronger exciplex with large emission intensities were found in solvents of low polarities but with the increase in solvent polarity the exciplex becomes weak and they dissociate fastly into radical ion pairs. The kinetic model of Kuzmin was observed to reduce into the Weller kinetic model for this exciplex system with ∆G ET = −0.22 eV and the spectral shift, h∆ν>0.2 eV. - Highlights: • Exciplex formed as a result of mixing of charge transfer and locally excited states. • Effect of solvents polarity and temperature on the exciplex stability and thermodynamics. • Solvent polarity will decide the formation of contact radical ion pair or solvent separated

Topological events on the lines of circular polarization in nonparaxial vector optical fields.

Science.gov (United States)

Freund, Isaac

2017-02-01

In nonparaxial vector optical fields, the following topological events are shown to occur in apparent violation of charge conservation: as one translates the observation plane along a line of circular polarization (a C line), the points on the line (C points) are seen to change not only the signs of their topological charges, but also their handedness, and, at turning points on the line, paired C points with the same topological charge and opposite handedness are seen to nucleate. These counter-intuitive events cannot occur in paraxial fields.

Studies of nuclear structure via polarization transfer experiments

International Nuclear Information System (INIS)

Moss, J.M.

1985-01-01

Inelastic scattering and charge exchange reactions at medium energies are discussed. Theoretical treatments of these phenomena based on the Dirac equation are presented. A LAMPF experiment in which polarization observables were employed in the search for collective effects in the nuclear pion field is discussed. This experiment is compared with the EMC (European Muon Collaboration) effect. 37 refs., 11 figs

Influence of Surface Charge/Potential of a Gold Electrode on the Adsorptive/Desorptive Behaviour of Fibrinogen

International Nuclear Information System (INIS)

Dargahi, Mahdi; Konkov, Evgeny; Omanovic, Sasha

2015-01-01

Highlights: • Adsorptive/desorptive behavior of fibrinogen (FG) on an electrochemically-polarized gold substrate is reported. • The adsorption affinity of FG (afFG) is constant on a negatively-charged substrate surface. • The afFG increases linearly with an increase in positive substrate surface charge. • The FG adsorption kinetics is strongly dependant on substrate surface charge. • The adsorbed FG layer can be desorbed by electrochemical evolution of hydrogen and oxygen. - Abstract: The effect of gold substrate surface charge (potential) on adsorptive/desorptive behaviour of fibrinogen (FG) was studied by employing differential capacitance (DC) and polarization modulated infrared reflection absorption spectroscopy (PM-IRRAS), in terms of FG adsorption thermodynamics, kinetics, and desorption kinetics. The gold substrate surface charge was modulated in-situ within the electrochemical double-layer region by means of electrochemical potentiostatic polarization in a FG-containing electrolyte, thus avoiding the interference of other physico-chemical properties of the gold surface on FG’s interfacial behaviour. The FG adsorption equilibrium was modeled using the Langmuir isotherm. Highly negative values of apparent Gibbs free energy of adsorption (ranging from from −52.1 ± 0.4 to −55.8 ± 0.8 kJ mol −1 , depending on the FG adsorption potential) indicated a highly spontaneous and strong adsorption of FG onto the gold surface. The apparent Gibbs free energy of adsorption was found to be independent of surface charge when the surface was negatively charged. However, when the gold surface was positively charged, the apparent Gibbs free energy of adsorption exhibited a pronounced linear relationship with the surface charge, shifting to more negative values with an increase in positive electrode potential. The adsorption kinetics of FG was also found to be dependent on gold surface charge in a similar manner to the apparent Gibbs free energy of adsorption

Broadband polarized emission from P(NDI2OD-T2) polymer.

Science.gov (United States)

Ulrich, Steve; Sutch, Tabitha; Szulczewski, Greg; Schweizer, Matthias; Barbosa, Newton; Araujo, Paulo

2018-05-18

We investigate the P(NDI2OD-T2) photophysical properties via absorbance and fluorescence spectroscopy, in association with the experimental approach baptized Stokes Spectroscopy, which provides valuable material information through the acquisition and analysis of the fluorescence polarization degree. By changing solvents and using different samples such as solutions, thick, and thin films, it is possible to control the polarization degree spectrum associated to the fluorescence emitted by the polymer's isolated chains and aggregates. We show that the polarization degree could become a powerful tool to obtain information related to the samples morphology, which is connected to their microscopic structure. Moreover, the polarization degree spectra suggest that depolarization effects linked to energy and charge transfer mechanisms are likely taking place. Our findings indicate that P(NDI2OD-T2) polymers are excellent candidates for the advancement of organic technologies that rely on the emission and detection of polarized lights. © 2018 IOP Publishing Ltd.

Space-charge-mediated anomalous ferroelectric switching in P(VDF-TrEE) polymer films

KAUST Repository

Hu, Weijin

2014-11-12

We report on the switching dynamics of P(VDF-TrEE) copolymer devices and the realization of additional substable ferroelectric states via modulation of the coupling between polarizations and space charges. The space-charge-limited current is revealed to be the dominant leakage mechanism in such organic ferroelectric devices, and electrostatic interactions due to space charges lead to the emergence of anomalous ferroelectric loops. The reliable control of ferroelectric switching in P(VDF-TrEE) copolymers opens doors toward engineering advanced organic memories with tailored switching characteristics.

Statistical mechanics of dense plasmas and implications for the plasma polarization shift

International Nuclear Information System (INIS)

Rogers, F.J.

1984-01-01

A brief description of the statistical mechanics of reacting, dense, plasmas is given. The results do not support a Debye-like polarization shift at low density. It is shown that the electronic charge density factors into a strongly quantum mechanical part, that is not much affected by many body correlations and a weakly quantum mechanical part, that is considerably effected by many body correlations. The few body charge density is obtained from direct solution of the Schroedinger equation and the many body charge density is obtained from the hypernetted chain equation through the introduction of a pseudopotential

Intramolecular, Exciplex-Mediated, Proton-Coupled, Charge-Transfer Processes in N,N-Dimethyl-3-(1-pyrenyl)propan-1-ammonium Cations: Influence of Anion, Solvent Polarity, and Temperature.

Science.gov (United States)

Safko, Trevor M; Faleiros, Marcelo M; Atvars, Teresa D Z; Weiss, Richard G

2016-06-16

An intramolecular exciplex-mediated, proton-coupled, charge-transfer (PCCT) process has been investigated for a series of N,N-dimethyl-3-(1-pyrenyl)propan-1-ammonium cations with different anions (PyS) in solvents of low to intermediate polarity over a wide temperature range. Solvent mediates both the equilibrium between conformations of the cation that place the pyrenyl and ammonium groups in proximity (conformation C) or far from each other (conformation O) and the ability of the ammonium group to transfer a proton adiabatically in the PyS excited singlet state. Thus, exciplex emission, concurrent with the PCCT process, was observed only in hydrogen-bond accepting solvents of relatively low polarity (tetrahydrofuran, ethyl acetate, and 1,4-dioxane) and not in dichloromethane. From the exciplex emission and other spectroscopic and thermodynamic data, the acidity of the ammonium group in conformation C of the excited singlet state of PyS (pKa*) has been estimated to be ca. -3.4 in tetrahydrofuran. The ratios between the intensities of emission from the exciplex and the locally excited state (IEx/ILE) appear to be much more dependent on the nature of the anion than are the rates of exciplex formation and decay, although the excited state data do not provide a quantitative measure of the anion effect on the C-O equilibrium. The activation energies associated with exciplex formation in THF are calculated to be 0.08 to 0.15 eV lower than for the neutral amine, N,N-dimethyl-3-(1-pyrenyl)propan-1-amine. Decay of the exciplexes formed from the deprotonation of PyS is hypothesized to occur through charge-recombination processes. To our knowledge, this is the first example in which photoacidity and intramolecular exciplex formation (i.e., a PCCT reaction) are coupled.

Polar catastrophe at the MgO(100)/SnO2(110) interface

KAUST Repository

Albar, Arwa

2016-11-14

First principles calculations, based on density functional theory, are used to investigate the structural and electronic properties of the epitaxial MgO(100)/SnO2(110) interface of wide band gap insulators. Depending on the interface termination, nonmagnetic metallic and half-metallic interface states are observed. The formation of these states is explained by a polar catastrophe model for nonpolar-polar interfaces. Strong lattice distortions and buckling develop in SnO2, which influence the interface properties as the charge discontinuity is partially screened. Already a single unit cell of SnO2 is sufficient to drive the polar catastrophe scenario. © 2016 The Royal Society of Chemistry.

A Wnt5 Activity Asymmetry and Intercellular Signaling via PCP Proteins Polarize Node Cells for Left-Right Symmetry Breaking.

Science.gov (United States)

Minegishi, Katsura; Hashimoto, Masakazu; Ajima, Rieko; Takaoka, Katsuyoshi; Shinohara, Kyosuke; Ikawa, Yayoi; Nishimura, Hiromi; McMahon, Andrew P; Willert, Karl; Okada, Yasushi; Sasaki, Hiroshi; Shi, Dongbo; Fujimori, Toshihiko; Ohtsuka, Toshihisa; Igarashi, Yasunobu; Yamaguchi, Terry P; Shimono, Akihiko; Shiratori, Hidetaka; Hamada, Hiroshi

2017-03-13

Polarization of node cells along the anterior-posterior axis of mouse embryos is responsible for left-right symmetry breaking. How node cells become polarized has remained unknown, however. Wnt5a and Wnt5b are expressed posteriorly relative to the node, whereas genes for Sfrp inhibitors of Wnt signaling are expressed anteriorly. Here we show that polarization of node cells is impaired in Wnt5a -/- Wnt5b -/- and Sfrp mutant embryos, and also in the presence of a uniform distribution of Wnt5a or Sfrp1, suggesting that Wnt5 and Sfrp proteins act as instructive signals in this process. The absence of planar cell polarity (PCP) core proteins Prickle1 and Prickle2 in individual cells or local forced expression of Wnt5a perturbed polarization of neighboring wild-type cells. Our results suggest that opposing gradients of Wnt5a and Wnt5b and of their Sfrp inhibitors, together with intercellular signaling via PCP proteins, polarize node cells along the anterior-posterior axis for breaking of left-right symmetry. Copyright © 2017 Elsevier Inc. All rights reserved.

Theoretical Study of the Charge-Transfer State Separation within Marcus Theory: The C60-Anthracene Case Study.

Science.gov (United States)

Volpi, Riccardo; Nassau, Racine; Nørby, Morten Steen; Linares, Mathieu

2016-09-21

We study, within Marcus theory, the possibility of the charge-transfer (CT) state splitting at organic interfaces and a subsequent transport of the free charge carriers to the electrodes. As a case study we analyze model anthracene-C60 interfaces. Kinetic Monte Carlo (KMC) simulations on the cold CT state were performed at a range of applied electric fields, and with the fields applied at a range of angles to the interface to simulate the action of the electric field in a bulk heterojunction (BHJ) interface. The results show that the inclusion of polarization in our model increases CT state dissociation and charge collection. The effect of the electric field on CT state splitting and free charge carrier conduction is analyzed in detail with and without polarization. Also, depending on the relative orientation of the anthracene and C60 molecules at the interface, CT state splitting shows different behavior with respect to both applied field strength and applied field angle. The importance of the hot CT in helping the charge carrier dissociation is also analyzed in our scheme.

Top-quark polarization and asymmetries at the LHC in the effective description of squark interactions

International Nuclear Information System (INIS)

Abrahantes, A.; Arganda, E.; Penaranda, S.

2015-01-01

Adetailed study of top-quark polarizations and tt - charge asymmetries, induced by top-squark-pair production at the LHC and the subsequent decays t → tχ 1 0 , is performed within the effective description of squark interactions, which includes the effective Yukawa couplings and another logarithmic term encoding the supersymmetry breaking. This effective approach is more suitable for its introduction into Monte-Carlo simulations and we make use of its implementation in MadGraph in order to investigate the possibilities of the charge asymmetry A C , measured at the LHC and consistent with SM expectations, to discriminate between different SUSY scenarios and analyze the implications of these scenarios in the top polarizations and related observables. (orig.)

Charge exchange injection for Nuclotron and Nuclotron booster

International Nuclear Information System (INIS)

Dinev, D.; Mikhajlov, V.

2000-01-01

The acceleration of polarized beams is between the major items in the JINR LHE's heavy ion superconducting synchrotron Nuclotron research programme. One effective way to increase the intensities of polarized deuteron beams is the application of the charge exchange injection into the Nuclotron. The paper represents the results of a new analytical description of the heavy ion stripping injection based on the Boltzmann kinetic equation. Expressions for the ion density evolution in the transverse phase plane for the emittance growth due to the elastic scattering and to energy losses in the stripping foil and for the number of successfully stored particles have been derived. These results have been applied to the stripping injection of polarized deuterons into the Nuclotron as well as to the stripping injection of heavy ions into the now under consideration Nuclotron rapid cycling booster. It has been shown that an estimated 40-fold intensity gain could be achieved for the stripping injection of polarized D - into the Nuclotron and that an effective stripping injection of light and medium ions into the booster could be realized

Temporal evolution of atmosphere pressure plasma jets driven by microsecond pulses with positive and negative polarities

Science.gov (United States)

Shao, Tao; Yang, Wenjin; Zhang, Cheng; Fang, Zhi; Zhou, Yixiao; Schamiloglu, Edl

2014-09-01

Current-voltage characteristics, discharge images, and optical spectra of atmospheric pressure plasma jets (APPJs) are studied using a microsecond pulse length generator producing repetitive output pulses with different polarities. The experimental results show that the APPJs excited by the pulses with positive polarity have longer plume, faster propagation speed, higher power, and more excited species, such as \\text{N}2 , O, He, \\text{N}2+ , than that with the negatively excited APPJs. The images taken using an intensified charge-coupled device show that the APPJs excited by pulses with positive polarity are characterized by a bullet-like structure, while the APPJs excited by pulses with negative polarity are continuous. The propagation speed of the APPJs driven by a microsecond pulse length generator is about tens of km/s, which is similar to the APPJs driven by a kHz frequency sinusoidal voltage source. The analysis shows that the space charge accumulation effect plays an important role during the discharge. The transient enhanced electric field induced by the accumulated ions between the needle-like electrode and the nozzle in the APPJs excited by pulses with negative polarity enhances electron field emission from the cathode, which is illustrated by the bright line on the time-integrated images. This makes the shape of the APPJ excited using pulses with negative polarity different from the bullet-like shape of the APPJs excited by pulses with positive polarity.

np Elastic-scattering experiments with polarized neutron beams

International Nuclear Information System (INIS)

Chalmers, J.S.; Ditzler, W.R.; Hill, D.

1985-01-01

Measurements of the spin transfer parameters, K/sub NN/ and K/sub LL/, at 500, 650, and 800 MeV are presented for the reaction p-vector d → n-vector pp at 0 0 . The data are useful input to the NN data base and indicate that the quasi-free charge exchange (CEX) reaction is a useful mechanism for producing neutrons with at least 40% polarization at energies as low as 500 MeV. Measurements of np elastic scattering observables C/sub LL/ and C/sub SL/ covering 35 0 to 172 0 are performed using a polarized neutron beam at 500, 650, and 800 MeV. Preliminary results are presented. 3 refs., 6 figs

Polarity analysis of GaN nanorods by photo-assisted Kelvin probe force microscopy

Energy Technology Data Exchange (ETDEWEB)

Wei, Jiandong; Neumann, Richard; Wang, Xue; Li, Shunfeng; Fuendling, Soenke; Merzsch, Stephan; Al-Suleiman, Mohamed A.M.; Soekmen, Uensal; Wehmann, Hergo-H.; Waag, Andreas [Institut fuer Halbleitertechnik, TU Braunschweig (Germany)

2011-07-15

Polarity dependence (N-polar (000-1) and Ga-polar (0001)) of surface photovoltage of epitaxially grown, vertically aligned GaN nanorods has been investigated by photo-assisted Kelvin probe force microscopy (KPFM). Commercial GaN substrates with known polarities are taken as reference samples. The polarity of GaN substrates can be well distinguished by the change in surface photovoltage upon UV illumination in air ambient. These different behaviors of Ga- and N-polar surfaces are attributed to the polarity-related surface-bound charges and photochemical reactivity. GaN nanorods were grown on patterned SiO{sub 2}/sapphire templates by metal-organic vapor phase epitaxy (MOVPE). In order to analyze the bottom surface of the grown GaN nanorods, a technique known from high power electronics and joining techniques is applied to remove the substrate. The top and bottom surfaces of the GaN nanorods are identified to be N-polar and Ga-polar according to the KPFM results, respectively. Our experiments demonstrate that KPFM is a simple and suitable method capable to identify the polarity of GaN nanorods. (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Measurement and control of electrostatic charges on solids in a gaseous suspension

Science.gov (United States)

Nieh, S.; Nguyen, T.

1985-10-01

Measurements of mean particle charges and charge distributions on Medium Volatile Bituminous (MVB) coals and Lignite A (LIGA) coals in a 51 mm ID grounded copper pipe loop have been made with the upgraded Faraday cage system. Both negative and positive charges were found for coals in all experiments. The dual polarities of charges are believed to be due to the nonuniform materials and chemical composition contained in coals. As expected, increasing velocity or decreasing air humidity has a significant effect to increase the mean particle charge and the standard deviation of distribution. Charge elimination by the addition of coal fines has been explored. Effective suppression of particle charges was achieved by adding 0.1% by mass of minus 1 micron coal dust into the pipe flow. A neutralization mechanism was proposed to interpret the measured results. The results of charge control obtained to date has been significant and encouraging. More work is needed to validate the proposed mechanism.

Charge effects controlling the current hysteresis and negative differential resistance in periodical nanosize Si/CaF sub 2 structures

CERN Document Server

Berashevich, Y A; Kholod, A N; Borisenko, V E

2002-01-01

A kinetic model of charge carrier transport in nanosize periodical Si/CaF sub 2 structures via localized states in dielectric is proposed. Computer simulation of the current-voltage characteristics of such structures has shown that the built-in field arises in a dielectric due to polarization of the trapped charge by localized centers. This results in current hysteresis and negative differential resistance region at the current-voltage characteristics when the bias polarity is changed. At temperature below 250 K, the portion of negative differential resistance vanishes

Localized surface phonon polariton resonances in polar gallium nitride

Energy Technology Data Exchange (ETDEWEB)

Feng, Kaijun, E-mail: kfeng@nd.edu; Islam, S. M.; Verma, Jai; Hoffman, Anthony J. [Department of Electrical Engineering, University of Notre Dame, Notre Dame, Indiana 46556 (United States); Streyer, William; Wasserman, Daniel [Department of Electrical and Computer Engineering, University of Illinois Urbana-Champaign, Urbana, Illinois 61801 (United States); Jena, Debdeep [Department of Electrical Engineering, University of Notre Dame, Notre Dame, Indiana 46556 (United States); School of Electrical and Computer Engineering, Cornell University, Ithaca, New York 14850 (United States)

2015-08-24

We demonstrate the excitation of localized surface phonon polaritons in an array of sub-diffraction pucks fabricated in an epitaxial layer of gallium nitride (GaN) on a silicon carbide (SiC) substrate. The array is characterized via polarization- and angle-dependent reflection spectroscopy in the mid-infrared, and coupling to several localized modes is observed in the GaN Reststrahlen band (13.4–18.0 μm). The same structure is simulated using finite element methods and the charge density of the modes are studied; transverse dipole modes are identified for the transverse electric and magnetic polarizations and a quadrupole mode is identified for the transverse magnetic polarization. The measured mid-infrared spectrum agrees well with numerically simulated spectra. This work could enable optoelectronic structures and devices that support surface modes at mid- and far-infrared wavelengths.

Thunderstorm Charge Structures Producing Negative Gigantic Jets

Science.gov (United States)

Boggs, L.; Liu, N.; Riousset, J. A.; Shi, F.; Rassoul, H.

2016-12-01

Here we present observational and modeling results that provide insight into thunderstorm charge structures that produce gigantic jet discharges. The observational results include data from four different thunderstorms producing 9 negative gigantic jets from 2010 to 2014. We used radar, very high frequency (VHF) and low frequency (LF) lightning data to analyze the storm characteristics, charge structures, and lightning activity when the gigantic jets emerged from the parent thunderstorms. A detailed investigation of the evolution of one of the charge structures by analyzing the VHF data is also presented. The newly found charge structure obtained from the observations was analyzed with fractal modeling and compared with previous fractal modeling studies [Krehbiel et al., Nat. Geosci., 1, 233-237, 2008; Riousset et al., JGR, 115, A00E10, 2010] of gigantic jet discharges. Our work finds that for normal polarity thunderstorms, gigantic jet charge structures feature a narrow upper positive charge region over a wide middle negative charge region. There also likely exists a `ring' of negative screening charge located around the perimeter of the upper positive charge. This is different from previously thought charge structures of the storms producing gigantic jets, which had a very wide upper positive charge region over a wide middle negative charge region, with a very small negative screening layer covering the cloud top. The newly found charge structure results in leader discharge trees in the fractal simulations that closely match the parent flashes of gigantic jets inside and outside the thundercloud. The previously used charge structures, while vital to the understanding of gigantic jet initiation and the role of charge imbalances inside the cloud, do not produce leader discharge trees that agree with observed gigantic jet discharges.Finally, the newly discovered gigantic jet charge structures are formed near the end of a convective pulse [Meyer et al., JGR, 118

Electrostatic charge characteristics of jet nebulized aerosols.

Science.gov (United States)

Kwok, Philip Chi Lip; Trietsch, Sebastiaan J; Kumon, Michiko; Chan, Hak-Kim

2010-06-01

Liquid droplets can be spontaneously charged in the absence of applied electric fields by spraying. It has been shown by computational simulation that charges may influence particle deposition in the airways. The electrostatic properties of jet nebulized aerosols and their potential effects on lung deposition have hardly been studied. A modified electrical low pressure impactor (ELPI) was employed to characterize the aerosol charges generated from jet nebulized commercial products. The charge and size measurements were conducted at 50% RH and 22 degrees C with a modified ELPI. Ventolin, Bricanyl, and Atrovent were nebulized using PARI LC Plus jet nebulizers coupled to a DeVilbiss Pulmo-Aide compressor. The aerosols were sampled in 30-sec durations. The drug deposits on the impactor stages were assayed chemically using high-performance liquid chromatography (HPLC). The charges of nebulized deionized water, isotonic saline, and the three commercial products diluted with saline were also measured to analyze the contributions of the major nebule ingredients on charging. No mass assays were performed on these runs. All three commercial nebules generated net negative charges. The magnitude of the charges reduced over the period of nebulization. Ventolin and Bricanyl yielded similar charge profiles. Highly variable charges were produced from deionized water. On the other hand, nebulized saline reproducibly generated net positive charges. Diluted commercial nebules showed charge polarity inversion. The charge profiles of diluted salbutamol and terbutaline solutions resembled those of saline, while the charges from diluted ipratropium solutions fluctuated near neutrality. The charge profiles were shown to be influenced by the concentration and physicochemical properties of the drugs, as well as the history of nebulization. The drugs may have unique isoelectric concentrations in saline at which the nebulized droplets would carry near-zero charges. According to results from

The Variable Transition State in Polar Additions to Pi Bonds

Science.gov (United States)

Weiss, Hilton M.

2010-01-01

A vast majority of polar additions of Bronsted acids to alkynes involve a termolecular transition state. With strong acids, considerable positive charge is developed on carbon and Markovnikov addition predominates. In less acidic solutions, however, the reaction is much slower and the transition state more closely resembles the olefinic product.…

Atomic physics of highly charged ions in an electron beam ion trap

International Nuclear Information System (INIS)

Marrs, R.E.

1990-07-01

Two electron beam ion traps are in use at LLNL for the purpose of studying the properties of very highly charged ions and their interactions with electrons. This paper reviews the operation of the traps and discusses recent experiments in three areas: precision transition energy measurements in the limit of very high ion charge, dielectronic recombination measurements for the He-like isoelectronic sequence, and measurements of x-ray polarization. 22 refs., 11 figs., 1 tab

Spin current induced by a charged tip in a quantum point contact

Energy Technology Data Exchange (ETDEWEB)

Shchamkhalova, B.S., E-mail: s.bagun@gmail.com

2017-03-15

We show that the charged tip of the probe microscope, which is widely used in studying the electron transport in low-dimensional systems, induces a spin current. The effect is caused by the spin–orbit interaction arising due to an electric field produced by the charged tip. The tip acts as a spin-flip scatterer giving rise to the spin polarization of the net current and the occurrence of a spin density in the system.

STANFORD: Highly polarized SLC electron beams

International Nuclear Information System (INIS)

Anon.

1993-01-01

Full text: Using specialized photocathodes made with 'strained' gallium arsenide, physicists at the Stanford Linear Accelerator Center (SLAC) have generated electron beams with polarizations in excess of 60 percent a year ahead of schedule. Together with recent luminosity increases, this breakthrough will have a major impact on the physics output of the Stanford Linear Collider (SLC). Beam polarization was almost tripled using photocathodes in which a gallium arsenide layer was grown epitaxially over a substrate of gallium arsenide phosphide. The mismatch between these two layers deforms the crystal structure and removes a degeneracy in the valence band structure, permitting selective optical pumping of one unique spin state. Whereas conventional gallium arsenide photocathodes are limited to 50 percent polarization because of this degeneracy (and realistic cathodes fall substantially below this theoretical limit), such strained crystal lattices have the potential to yield polarizations close to 100 percent. Polarization enhancement with strained lattices was first demonstrated in 1991 by a SLAC/Wisconsin/ Berkeley group (May 1991, page 6) with a 71 percent polarization in a laboratory experiment. More recently this group has achieved polarization in excess of 90 percent, reported last November at the Nagoya Spin Symposium. (In a complementary development, a Japanese KEK/ Nagoya/KEK obtains polarized beams using a 'superlattice' - May 1991, page 4.) The 1993 SLC run, the strained gallium arsenide photocathode technique's debut in an operating particle accelerator, has proved to be a resounding, unqualified success - as have physics experiments on the Z particles produced by the highly polarized beam. A conservative approach was called for, due to concerns about possible charge saturation effects. A relatively thick (0.3 micron) gallium arsenide layer was used for the photocathode in the SLC polarized electron source. With a titanium

Electrochemical transformation of trichloroethylene in aqueous solution by electrode polarity reversal.

Science.gov (United States)

Rajic, Ljiljana; Fallahpour, Noushin; Yuan, Songhu; Alshawabkeh, Akram N

2014-12-15

Electrode polarity reversal is evaluated for electrochemical transformation of trichloroethylene (TCE) in aqueous solution using flow-through reactors with mixed metal oxide electrodes and Pd catalyst. The study tests the hypothesis that optimizing electrode polarity reversal will generate H2O2 in Pd presence in the system. The effect of polarity reversal frequency, duration of the polarity reversal intervals, current intensity and TCE concentration on TCE removal rate and removal mechanism were evaluated. TCE removal efficiencies under 6 cycles h(-1) were similar in the presence of Pd catalyst (50.3%) and without Pd catalyst (49.8%), indicating that Pd has limited impact on TCE degradation under these conditions. The overall removal efficacies after 60 min treatment under polarity reversal frequencies of 6, 10, 15, 30 and 90 cycles h(-1) were 50.3%, 56.3%, 69.3%, 34.7% and 23.4%, respectively. Increasing the frequency of polarity reversal increases TCE removal as long as sufficient charge is produced during each cycle for the reaction at the electrode. Electrode polarity reversal shifts oxidation/reduction and reduction/oxidation sequences in the system. The optimized polarity reversal frequency (15 cycles h(-1) at 60 mA) enables two reaction zones formation where reduction/oxidation occurs at each electrode surface. Published by Elsevier Ltd.

Ionic character of polar crystals: An extended Mulliken scheme for electronegativities

International Nuclear Information System (INIS)

Watson, R.E.; Bennett, L.H.; Davenport, J.W.

1983-01-01

The total energy of an atom can be expressed in terms of the charge q on the atom as E(q) = E(0)+αq+βq 2 +γq 3 . It is shown that the expected charge transfer q, which brings the intra-atomic energy of the atoms to a minimum, between otherwise isolated noninteracting atoms, is proportional to the difference in the α's of the constituent elements, i.e., q = c Δα. Thus α provides a well-defined electronegativity scale, and if the third-order term γq 3 may be neglected, then α = Phi/sub m/, which is the original Mulliken scale. The quadratic term βq 2 acts to oppose charge transfer, and therefore the coefficient c, relating q to Δα, depends on what elements are involved and on their relative concentration in a well-defined manner. This implies an asymmetry in charge transfer with concentration. Spectroscopic data indicate that γ, though small, is not negligible and, in such a case Phi/sub m/ is not a proper electronegativity. The extended Mulliken scheme, involving α and β, is relevant to the energetics of charge transfer and hence to the ionic character of insulating and semiconducting compounds. It allows simple baseline estimates to be made of such character. Other factors contribute to charge transfer and some of the complications associated with transition-metal compound formation are explored

Research and development on optically pumped polarized ion sources. Technical progress report, July 1, 1985-June 30, 1986

International Nuclear Information System (INIS)

Anderson, L.W.

1986-07-01

The development of an optically pumped polarized 23 Na target is discussed. The three categories of research are: (1) electron spin relaxation of the 23 Na due to wall collisions; (2) effects of radiation trapping on the polarization that can be produced in an alkali target by optical pumping; and (3) the effects of spin exchange collisions in the polarization of a fast H 0 beam formed by charge transfer as an H + beam passes through a polarized alkali target. 90 refs., 7 figs

Dielectric and polarization behaviour of cellulose electro-active paper (EAPap)

International Nuclear Information System (INIS)

Yun, Gyu-Young; Kim, Joo-Hyung; Kim, Jaehwan

2009-01-01

Dielectric and polarization behaviour of electro-active paper (EAPap) were studied to understand the detailed material behaviour of EAPap as a novel smart material. It was revealed that the dielectric constant of EAPap was temperature and frequency dependent. The largest change in the dielectric constant was observed near 0 0 C while the highest dielectric constant was obtained at around 100 0 C, which might be related to the dipolar behaviour of the hydroxyl structure of cellulose and adsorbed or existing internal water molecules in cellulose EAPap. By thermal stimulated current measurement for polarization behaviour of cellulose EAPap, it was shown that the maximum current was observed in the temperature range 105-110 0 C. Compared with the polarization behaviour in the low temperature range, abnormal polarization was observed under an applied field mainly due to the trapped space charge in EAPap, which indicates that cellulose EAPap has a similar material behaviour to that of electret polymers. (fast track communication)

A new model for the spectral induced polarization signature of bacterial growth in porous media

Science.gov (United States)

Zhang, C.; Revil, A.; Atekwana, E. A.; Jardani, A.; Smith, S.

2012-12-01

Recent biogeophysics studies demonstrated the sensitivity of complex conductivity to bacterial growth and microbial mediated mineral transformations in porous media. Frequency-domain induced polarization is a minimally invasive manner to measure the complex conductivity of a material over a broad range of frequencies. The real component of complex conductivity is associated with electromigration of the charge carriers, and the imaginary component represents reversible energy storage of charge carriers at polarization length scales. Quantitative relationship between frequency-domain induced polarization responses and bacterial growth and decay in porous media is analyzed in this study using a new developed model. We focus on the direct contribution of bacteria themselves to the complex conductivity in porous media in the absence of biomineralization. At low frequencies, the induced polarization of bacteria (α-polarization) is related to the properties of the electrical double layer surrounding the membrane surface of bacteria. Surface conductivity and α-polarization are due to the Stern layer of the counterions occurring in a brush of polymers coating the surface of the bacteria, and can be related to the cation exchange capacity of the bacteria. From the modeling results, at low frequencies (model with reactive transport modeling in which the evolution of bacterial populations are usually described by Monod kinetics, we show that the changes in imaginary conductivity with time can be used to determine bacterial growth kinetics parameters such as the growth and endogenous decay coefficient.

Cleft Palate Repair Using a Double Opposing Z-Plasty.

Science.gov (United States)

Moores, Craig; Shah, Ajul; Steinbacher, Derek M

2016-07-01

Cleft palate is a common congenital defect with several described surgical repairs. The most successful treatment modality remains a controversy. The goals of repair focus on achievement of normal speech and optimizing velopharyngeal function while minimizing both fistula formation and facial growth restriction. In this video, the authors demonstrate use of the double opposing Z-plasty technique in the repair of a Veau II type cleft palate. The video demonstrates the marking, incisions, dissection, and repair of the cleft. It also examines the use of von Langenbeck-type relaxing incisions and demonstrates a specific approach to the repair of this particular cleft. The authors believe that the Furlow double opposing Z-plasty with the von Langenbeck relaxing incision can provide the best postoperative outcome by combining the benefits of each individual operation. The Z-plasty technique works to correct the aberrant muscle of the soft palate while increasing the length of the palate. The authors believe that this results in better velopharyngeal function.

Effects of low charge carrier wave function overlap on internal quantum efficiency in GaInN quantum wells

Energy Technology Data Exchange (ETDEWEB)

Netzel, Carsten; Hoffmann, Veit; Wernicke, Tim; Knauer, Arne; Weyers, Markus [Ferdinand-Braun-Institut fuer Hoechstfrequenztechnik, Gustav-Kirchhoff-Strasse 4, 12489 Berlin (Germany); Kneissl, Michael [Ferdinand-Braun-Institut fuer Hoechstfrequenztechnik, Gustav-Kirchhoff-Strasse 4, 12489 Berlin (Germany); Institut fuer Festkoerperphysik, Technische Universitaet Berlin, Hardenbergstrasse 36, 10623 Berlin (Germany)

2010-07-15

To determine relevant processes affecting the internal quantum efficiency in GaInN quantum well structures, we have studied the temperature and excitation power dependent photoluminescence intensity for quantum wells with different well widths on (0001) c-plane GaN and for quantum wells on nonpolar (11-20) a-plane GaN. In thick polar quantum wells, the quantum confined Stark effect (QCSE) causes a stronger intensity decrease with increasing temperature as long as the radiative recombination dominates. At higher temperatures, when the nonradiative recombination becomes more important, thick polar quantum wells feature a lower relative intensity decrease than thinner polar or nonpolar quantum wells. Excitation power dependent photoluminescence points to a transition from a recombination of excitons to a bimolecular recombination of uncorrelated charge carriers for thick polar quantum wells in the same temperature range. This transition might contribute to the limitation of nonradiative recombination by a reduced diffusivity of charge carriers. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

MEASUREMENT OF POLARIZATION OBSERVABLES IN VECTOR MESON PHOTOPRODUCTION USING A TRANSVERSELY-POLARIZED FROZEN-SPIN TARGET AND POLARIZED PHOTONS AT CLAS, JEFFERSON LAB

Energy Technology Data Exchange (ETDEWEB)

Roy, Priyashree [Florida State Univ., Tallahassee, FL (United States); Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)

2016-11-30

The study of baryon resonances provides a deeper understanding of the strong interaction because the dynamics and relevant degrees of freedom hidden within them are re ected by the properties of the excited states of baryons. Higher-lying excited states at and above 1.7 GeV/c2 are generally predicted to have strong couplings to final states involving a heavier meson, e. g. one of the vector mesons, ρ, ω φ, as compared to a lighter pseudoscalar meson, e. g. π and η. Decays to the ππΝ final states via πΔ also become more important through the population of intermediate resonances. We observe that nature invests in mass rather than momentum. The excited states of the nucleon are usually found as broadly overlapping resonances which may decay into a multitude of final states involving mesons and baryons. Polarization observables make it possible to isolate single resonance contributions from other interference terms. The CLAS g9 (FROST) experiment, as part of the N* spectroscopy program at Je?erson Laboratory, accumulated photoproduction data using circularly- & linearly-polarized photons incident on a transversely-polarized butanol target (g9b experiment) in the photon energy range 0:3-2:4 GeV & 0:7-2:1 GeV, respectively. In this work, the analysis of reactions and polarization observables which involve two charged pions, either in the fully exclusive reaction γρ -> ρπ+π- or in the semi-exclusive reaction with a missing neutral pion, γρ -> ρπ+π-(π0) will be presented. For the reaction ρπ+π-, eight polarization observables (Is, Ic, Px, Py, Psx; y, Pcx; y) have been extracted. The high statistics data rendered it possible to extract these observables in three dimensions. All of them are first-time measurements. The fairly good agreement of Is, Ic obtained from this analysis with the experimental results from a previous CLAS experiment provides support for the first-time measurements. For the reaction γρ -> ρω -> ρπ+π(π0, five polarization

Sources for charged particles; Les sources de particules chargees

Energy Technology Data Exchange (ETDEWEB)

Arianer, J.

1997-09-01

This document is a basic course on charged particle sources for post-graduate students and thematic schools on large facilities and accelerator physics. A simple but precise description of the creation and the emission of charged particles is presented. This course relies on every year upgraded reference documents. Following relevant topics are considered: electronic emission processes, technological and practical considerations on electron guns, positron sources, production of neutral atoms, ionization, plasma and discharge, different types of positive and negative ion sources, polarized particle sources, materials for the construction of ion sources, low energy beam production and transport. (N.T.).

Extraordinary Mechanism of the Diels-Alder Reaction: Investigation of Stereochemistry, Charge Transfer, Charge Polarization, and Biradicaloid Formation.

Science.gov (United States)

Sexton, Thomas; Kraka, Elfi; Cremer, Dieter

2016-02-25

The Diels-Alder reaction between 1,3-butadiene and ethene is investigated from far-out in the entrance channel to the very last step in the exit channel thus passing two bifurcation points and extending the range of the reaction valley studied with URVA (Unified Reaction Valley Approach) by 300% compared to previous studies. For the first time, the pre- and postchemical steps of the reaction are analyzed at the same level of theory as the actual chemical processes utilizing the path curvature and its decomposition into internal coordinate or curvilinear coordinate components. A first smaller charge transfer to the dienophile facilitates the rotation of gauche butadiene into its cis form. The actual chemical processes are initiated by a second larger charge transfer to the dienophile that facilitates pyramidalization of the reacting carbon centers, bond equalization, and biradicaloid formation of the reactants. The transition state is aromatically stabilized and moved by five path units into the entrance channel in line with the Hammond-Leffler postulate. The pseudorotation of the boat form into the halfchair of cyclohexene is analyzed. Predictions are made for the Diels-Alder reaction based on a 11-phase mechanism obtained by the URVA analysis.

Quantum Monte Carlo formulation of volume polarization in dielectric continuum theory

NARCIS (Netherlands)

Amovilli, Claudio; Filippi, Claudia; Floris, Franca Maria

2008-01-01

We present a novel formulation based on quantum Monte Carlo techniques for the treatment of volume polarization due to quantum mechanical penetration of the solute charge density in the solvent domain. The method allows to accurately solve Poisson’s equation of the solvation model coupled with the

Strength training and testosterone treatment have opposing effects on migration inhibitor factor levels in ageing men

DEFF Research Database (Denmark)

Glintborg, D.; Christensen, L. L.; Kvorning, T.

2013-01-01

Strength Training and Testosterone Treatment Have Opposing Effects on Migration Inhibitor Factor Levels in Ageing Men......Strength Training and Testosterone Treatment Have Opposing Effects on Migration Inhibitor Factor Levels in Ageing Men...

On conserved charges and thermodynamics of the AdS{sub 4} dyonic black hole

Energy Technology Data Exchange (ETDEWEB)

Cárdenas, Marcela [Centro de Estudios Científicos (CECs),Av. Arturo Prat 514, Valdivia (Chile); Departamento de Física, Universidad de Concepción,Casilla 160-C, Concepción (Chile); Fuentealba, Oscar; Matulich, Javier [Centro de Estudios Científicos (CECs),Av. Arturo Prat 514, Valdivia (Chile)

2016-05-02

We consider four-dimensional gravity in the presence of a dilatonic scalar field and an Abelian gauge field. This theory corresponds to the bosonic sector of a Kaluza-Klein reduction of eleven-dimensional supergravity which induces a specific self-interacting potential for the scalar field. We compute the conserved charges and carry out the thermodynamics of an anti-de Sitter (AdS) dyonic black hole solution that was proposed recently. The charges coming from symmetries of the action are computed using the Regge-Teitelboim Hamiltonian approach. They correspond to the mass, which acquires contributions from the scalar field, and the electric charge. We introduce integrability conditions because the scalar field leads to non-integrable terms in the variation of the mass. These conditions are generically solved by introducing boundary conditions that relate the leading and subleading terms of the scalar field fall-off. The Hamiltonian Euclidean action, computed in the grand canonical ensemble, is obtained by demanding the action to have an extremum. Its value is given by a radial boundary term plus an additional polar angle boundary term due to the presence of a magnetic monopole. Remarkably, the magnetic charge can be identified from the variation of the additional polar angle boundary term, confirming that the first law of black hole thermodynamics is a consequence of having a well-defined and finite Hamiltonian action principle, even if the charge does not come from a symmetry of the action. The temperature and electrostatic potential are determined by demanding regularity of the black hole solution, whereas the value of the magnetic potential is determined by the variation of the additional polar angle boundary term. Consequently, the first law of black hole thermodynamics is identically satisfied by construction.

POLARIZED EXTENDED Ly{alpha} EMISSION FROM A z = 2.3 RADIO GALAXY

Energy Technology Data Exchange (ETDEWEB)

Humphrey, A. [Centro de Astrofisica da Universidade do Porto, Rua das Estrelas, 4150-762 Porto (Portugal); Vernet, J.; Fosbury, R. A. E. [European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching (Germany); Villar-Martin, M. [Centro de Astrobiologia (INTA-CSIC), Carretera de Ajalvir, km 4, E-28850 Torrejon de Ardoz, Madrid (Spain); Di Serego Alighieri, S. [INAF-Osservatorio Astrofisico di Arcetri, L.go E. Fermi 5, I-50125 Firenze (Italy); Cimatti, A., E-mail: andrew.humphrey@astro.up.pt [Dipartimento di Astronomia, Universita di Bologna, Via Ranzani 1, I-40127 Bologna (Italy)

2013-05-01

We present spatially resolved spectropolarimetric measurements of the 100 kpc scale gaseous environment of the z = 2.34 radio galaxy TXS 0211-122. The polarization level of the narrow Ly{alpha} emission is low centrally (P < 5%), but rises to P = 16.4% {+-} 4.6% in the eastern part of the nebula, indicating that the nebula is at least partly powered by the scattering of Ly{alpha} photons by H I. Not only is this the first detection of polarized Ly{alpha} around a radio-loud active galaxy, it is also the second detection to date for any kind of Ly{alpha} nebula. We also detect a pair of diametrically opposed UV continuum sources along the slit, at the outer edges of the Ly{alpha} nebula, which we suggest may be the limb of a dusty shell, related to the large-scale H I absorbers often associated with high-z radio galaxies.

Spin-polarized electron gas in Co2MSi/SrTiO3(M= Ti, V, Cr, Mn, and Fe) heterostructures

KAUST Repository

Nazir, S.

2016-06-08

Spin-polarized density functional theory is used to study the TiO2 terminated interfaces between the magnetic Heusler alloys Co2Si (M = Ti, V, Cr, Mn, and Fe) and the non-polar band insulator SrTiO3. The structural relaxation at the interface turns out to depend systematically on the lattice mis- match. Charge transfer from the Heusler alloys (mainly the M 3d orbitals) to the Ti dxy orbitals of the TiO2 interface layer is found to gradually grow from M = Ti to Fe, resulting in an electron gas with increasing density of spin-polarized charge carriers. (© 2016 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim). © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Polarization effect of CdZnTe imaging detector based on high energy γ source

International Nuclear Information System (INIS)

Li Miao; Xiao Shali; Wang Xi; Shen Min; Zhang Liuqiang; Cao Yulin; Chen Yuxiao

2011-01-01

The inner electric potential distribution of CdZnTe detector was derived by applying poisson equation with the first type boundary condition, and the polarization effect of CdZnTe pixellated detector for imaging 137 Cs γ source was investigated. The results of numerical calculation and experiment indicate that electric potential distribution is mainly influenced by applied bias for low charge density in CdZnTe crystal and, in turn, there is linear relationship between electric potential distribution and applied bias that induces uniform electric field under low irradiated flux. However, the electric potential appears polarization phenomenon, and the electric field in CdZnTe crystal is distorted when CdZnTe detector is under high irradiated flux. Consequently, charge carriers in CdZnTe crystal drift towards the edge pixels of irradiated region, and hence, the shut-off central pixels are surrounded by a ring of low counting pixels. The polarization effect indeed deteriorates the performance of CdZnTe detector severely and the event counts of edge pixels for irradiated region reduce about 70%. (authors)

Tip-induced domain structures and polarization switching in ferroelectric amino acid glycine

Energy Technology Data Exchange (ETDEWEB)

Seyedhosseini, E., E-mail: Seyedhosseini@ua.pt; Ivanov, M. [CICECO-Aveiro Institute of Materials and Department of Physics, University of Aveiro, 3810-193 Aveiro (Portugal); Bdikin, I. [TEMA and Department of Mechanical Engineering, University of Aveiro, 3810-193 Aveiro (Portugal); Vasileva, D. [Institute of Natural Sciences, Ural Federal University, 620000 Ekaterinburg (Russian Federation); Kudryavtsev, A. [Moscow State Institute of Radioengineering, Electronics and Automation, 119454 Moscow (Russian Federation); Rodriguez, B. J. [Conway Institute of Biomolecular and Biomedical Research and School of Physics, University College Dublin, Dublin (Ireland); Kholkin, A. L. [CICECO-Aveiro Institute of Materials and Department of Physics, University of Aveiro, 3810-193 Aveiro (Portugal); Institute of Natural Sciences, Ural Federal University, 620000 Ekaterinburg (Russian Federation)

2015-08-21

Bioorganic ferroelectrics and piezoelectrics are becoming increasingly important in view of their intrinsic compatibility with biological environment and biofunctionality combined with strong piezoelectric effect and a switchable polarization at room temperature. Here, we study tip-induced domain structures and polarization switching in the smallest amino acid β-glycine, representing a broad class of non-centrosymmetric amino acids. We show that β-glycine is indeed a room-temperature ferroelectric and polarization can be switched by applying a bias to non-polar cuts via a conducting tip of atomic force microscope (AFM). Dynamics of these in-plane domains is studied as a function of an applied voltage and pulse duration. The domain shape is dictated by polarization screening at the domain boundaries and mediated by growth defects. Thermodynamic theory is applied to explain the domain propagation induced by the AFM tip. Our findings suggest that the properties of β-glycine are controlled by the charged domain walls which in turn can be manipulated by an external bias.

Initial research of np scattering with polarized deuterium target at ANKE/COSY

Energy Technology Data Exchange (ETDEWEB)

Gou, Boxing [Institut fuer Kernphysik, Forschungszentrum Juelich, 52425 Juelich (Germany); Institute of Modern Physics, Chinese Academy of Sciences, 73000 Lanzhou (China); Collaboration: ANKE-Collaboration

2014-07-01

With the goal of understanding the nuclear forces, the ANKE collaboration has been working on a systematic NN spin program for many years. Due to the lack of free neutron sources experimental data of np scattering are very rare, especially at higher energies. It has been shown that using phase shift analysis (PSA) it is possible to reconstruct np scattering amplitudes from the spin observables of pd → {pp}{sub {sup 1}S{sub 0}}n charge-exchange reaction. So far experiments were conducted using polarized deuteron beams and hydrogen target, which led to valuable results. To extend the research up to the highest nucleon energy available at COSY (2.8 GeV), proton beam and polarized deuterium target will be used. This talk presents the results of the commissioning experiment of a deuterium target at ANKE with emphasis on the initial research of charge-exchange reaction.

Hardness and softness reactivity kernels within the spin-polarized density-functional theory

International Nuclear Information System (INIS)

Chamorro, Eduardo; De Proft, Frank; Geerlings, Paul

2005-01-01

Generalized hardness and softness reactivity kernels are defined within a spin-polarized density-functional theory (SP-DFT) conceptual framework. These quantities constitute the basis for the global, local (i.e., r-position dependent), and nonlocal (i.e., r and r ' -position dependents) indices devoted to the treatment of both charge-transfer and spin-polarization processes in such a reactivity framework. The exact relationships between these descriptors within a SP-DFT framework are derived and the implications for chemical reactivity in such context are outlined

Proceedings of the 3rd US-Japan Workshop on Plasma Polarization Spectroscopy

International Nuclear Information System (INIS)

Beiersdorfer, P; Flyimoto, T

2002-01-01

The third US-Japan Workshop on Plasma Polarization Spectroscopy was held at the Lawrence Livermore National Laboratory in Livermore, California, on June 18-21, 2001. The talks presented at this workshop are summarized in these proceedings. The papers cover both experimental investigation and applications of plasma polarization spectroscopy as well as the theoretical foundation and formalisms to understand and describe the polarization phenomena. The papers give an overview of the history of plasma polarization spectroscopy, derive the formal aspects of polarization spectroscopy, including the effects of electric and magnetic fields, discuss spectra perturbed by intense microwave fields, charge exchange, and dielectronic recombination, and present calculations of various collisional excitation and ionization cross sections and the modeling of plasma polarization spectroscopy phenomena. Experimental results are given from the WT-3 tokamak, the MST reverse field pinch, the Large Helical Device, the GAMMA 10 mirror machine, the Nevada Terrawatt Facility, the Livermore EBIT-II electron beam ion trap, and beam-foil spectroscopy. In addition, results were presented from studies of several laser-produced plasma experiments and new instrumental techniques were demonstrated

A Raman study of the charge-density-wave state in A(0.3)MoO(3) (A = K, Rb)

NARCIS (Netherlands)

Sagar, D. M.; Fausti, D.; Yue, S.; Kuntscher, C. A.; van Smaalen, S.; van Loosdrecht, P. H. M.

2008-01-01

We report a comparative Raman spectroscopic study of the quasi-one-dimensional charge-density-wave (CDW) systems A(0.3)MoO(3) (A = K, Rb). Temperature- and polarization-dependent experiments reveal charge-coupled vibrational Raman features. The strongly temperature-dependent collective amplitudon

Polarization Properties and Magnetic Field Structures in the High-mass Star-forming Region W51 Observed with ALMA

Science.gov (United States)

Koch, Patrick M.; Tang, Ya-Wen; Ho, Paul T. P.; Yen, Hsi-Wei; Su, Yu-Nung; Takakuwa, Shigehisa

2018-03-01

We present the first ALMA dust polarization observations toward the high-mass star-forming regions W51 e2, e8, and W51 North in Band 6 (230 GHz) with a resolution of about 0\\buildrel{\\prime\\prime}\\over{.} 26 (∼5 mpc). Polarized emission in all three sources is clearly detected and resolved. Measured relative polarization levels are between 0.1% and 10%. While the absolute polarization shows complicated structures, the relative polarization displays the typical anticorrelation with Stokes I, although with a large scatter. Inferred magnetic (B) field morphologies are organized and connected. Detailed substructures are resolved, revealing new features such as comet-shaped B-field morphologies in satellite cores, symmetrically converging B-field zones, and possibly streamlined morphologies. The local B-field dispersion shows some anticorrelation with the relative polarization. Moreover, the lowest polarization percentages together with largest dispersions coincide with B-field convergence zones. We put forward \\sin ω , where ω is the measurable angle between a local B-field orientation and local gravity, as a measure of how effectively the B field can oppose gravity. Maps of \\sin ω for all three sources show organized structures that suggest a locally varying role of the B field, with some regions where gravity can largely act unaffectedly, possibly in a network of narrow magnetic channels, and other regions where the B field can work maximally against gravity.

Ultracold Fermi and Bose gases and Spinless Bose Charged Sound Particles

Directory of Open Access Journals (Sweden)

Minasyan V.

2011-10-01

Full Text Available We propose a novel approach for investigation of the motion of Bose or Fermi liquid (or gas which consists of decoupled electrons and ions in the uppermost hyperfine state. Hence, we use such a concept as the fluctuation motion of “charged fluid particles” or “charged fluid points” representing a charged longitudinal elastic wave. In turn, this elastic wave is quantized by spinless longitudinal Bose charged sound particles with the rest mass m and charge e 0 . The existence of spinless Bose charged sound particles allows us to present a new model for description of Bose or Fermi liquid via a non-ideal Bose gas of charged sound particles . In this respect, we introduce a new postulation for the superfluid component of Bose or Fermi liquid determined by means of charged sound particles in the condensate, which may explain the results of experiments connected with ultra-cold Fermi gases of spin-polarized hydrogen, 6 Li and 40 K, and such a Bose gas as 87 Rb in the uppermost hyperfine state, where the Bose- Einstein condensation of charged sound particles is realized by tuning the magnetic field.

Fast Atomic Charge Calculation for Implementation into a Polarizable Force Field and Application to an Ion Channel Protein

Directory of Open Access Journals (Sweden)

Raiker Witter

2015-01-01

Full Text Available Polarization of atoms plays a substantial role in molecular interactions. Class I and II force fields mostly calculate with fixed atomic charges which can cause inadequate descriptions for highly charged molecules, for example, ion channels or metalloproteins. Changes in charge distributions can be included into molecular mechanics calculations by various methods. Here, we present a very fast computational quantum mechanical method, the Bond Polarization Theory (BPT. Atomic charges are obtained via a charge calculation method that depend on the 3D structure of the system in a similar way as atomic charges of ab initio calculations. Different methods of population analysis and charge calculation methods and their dependence on the basis set were investigated. A refined parameterization yielded excellent correlation of R=0.9967. The method was implemented in the force field COSMOS-NMR and applied to the histidine-tryptophan-complex of the transmembrane domain of the M2 protein channel of influenza A virus. Our calculations show that moderate changes of side chain torsion angle χ1 and small variations of χ2 of Trp-41 are necessary to switch from the inactivated into the activated state; and a rough two-side jump model of His-37 is supported for proton gating in accordance with a flipping mechanism.

Effect of solvent polarity and temperature on the spectral and thermodynamic properties of exciplexes of 1-cyanonaphthalene with hexamethylbenzene in organic solvents

Energy Technology Data Exchange (ETDEWEB)

Asim, Sadia [Institute of Physical and Theoretical Chemistry, Graz University of Technology, Stremaryrgasse 9, A-8010 Graz (Austria); Department of Chemistry and Biochemistry, University of Agriculture, Faisalabad (Pakistan); Mansha, Asim [Institute of Physical and Theoretical Chemistry, Graz University of Technology, Stremaryrgasse 9, A-8010 Graz (Austria); Department of Chemistry, Government College University, Faisalabad (Pakistan); Grampp, Günter, E-mail: grampp@tugraz.at [Institute of Physical and Theoretical Chemistry, Graz University of Technology, Stremaryrgasse 9, A-8010 Graz (Austria); Landgraf, Stephan [Institute of Physical and Theoretical Chemistry, Graz University of Technology, Stremaryrgasse 9, A-8010 Graz (Austria); Zahid, Muhammad [Institute of Physical and Theoretical Chemistry, Graz University of Technology, Stremaryrgasse 9, A-8010 Graz (Austria); Department of Chemistry and Biochemistry, University of Agriculture, Faisalabad (Pakistan); Bhatti, Ijaz Ahmad [Department of Chemistry and Biochemistry, University of Agriculture, Faisalabad (Pakistan)

2014-09-15

Study of the effect of solvent polarity and temperature is done on the exciplex emission spectra of 1-cyanonaphthalene with hexamethylbenzene. Exciplex system is studied in the range of partially polar solvents and in solvent mixture of propyl acetate and butyronitrile. The unique feature of this solvent mixture is that only the solvent polarity changes (6.0≤ε{sub s}≤24.7) with the change in the mole fraction of solvents whereas the solvent viscosity and refractive index remains unaffected. Thermodynamic properties are calculated according to the models developed by Weller and Kuzmin. Fluorescence lifetimes for both the fluorophore as well as the exciplex are evaluated in all used solvents. Exciplex energetics as a function of solvent polarity and temperature are also discussed. Kuzmin model of self-consistent polarization is used for the explanation of the exciplex emission spectra. The effects of solvent polarity and temperature on energy of zero–zero transitions (hv{sub 0}{sup /}), Huang–Rhys factor (S), Gauss broadening of vibronic level (σ) and the dominant high-frequency vibration (hν{sub ν}) are investigated. The strong dependence of exciplex stability and energetics upon the solvent polarity and temperature are observed. Full charge transfer exciplexes were observed in solvents of all polarities and stronger exciplex with large emission intensities were found in solvents of low polarities but with the increase in solvent polarity the exciplex becomes weak and they dissociate fastly into radical ion pairs. The kinetic model of Kuzmin was observed to reduce into the Weller kinetic model for this exciplex system with ∆G{sub ET} = −0.22 eV and the spectral shift, h∆ν>0.2 eV. - Highlights: • Exciplex formed as a result of mixing of charge transfer and locally excited states. • Effect of solvents polarity and temperature on the exciplex stability and thermodynamics. • Solvent polarity will decide the formation of contact radical ion pair

Proceedings of the workshop on photocathodes for polarized electron sources for accelerators

International Nuclear Information System (INIS)

Chatwell, M.; Clendenin, J.; Maruyama, T.; Schultz, D.

1994-04-01

Application of the GaAs polarized electron source to studies of surface magnetism; thermal stability of Cs on NES III-V-Photocathodes and its effect on quantum efficiency; AFEL accelerator; production and detection of SPIN polarized electrons; emittance measurements on a 100-keV beam from a GaAs photocathode electron gun; modern theory of photoemission and its applications to practical photocathodes; experimental studies of the charge limit phenomenon in GaAs photocathodes; new material for photoemission electron source; semiconductor alloy InGaAsP grown on GaAs substrate; NEA photocathode surface preparation; technology and physics; metalorganic chemical vapor deposition of GaAs-GaAsP spin-polarized photocathodes; development of photocathodes injectors for JLC-ATF; effect of radiation trapping on polarization of photoelectrons from semiconductors; and energy analysis of electrons emitted by a semiconductor photocathode

Analysis of the international distribution of per capita CO2 emissions using the polarization concept

International Nuclear Information System (INIS)

Duro, Juan Antonio; Padilla, Emilio

2008-01-01

The concept of polarization is linked to the extent that a given distribution leads to the formation of homogeneous groups with opposing interests. This concept, which is basically different from the traditional one of inequality, is related to the level of inherent potential conflict in a distribution. The polarization approach has been widely applied in the analysis of income distribution. The extension of this approach to the analysis of international distribution of CO 2 emissions is quite useful as it gives a potent informative instrument for characterizing the state and evolution of the international distribution of emissions and its possible political consequences in terms of tensions and the probability of achieving agreements. In this paper we analyze the international distribution of per capita CO 2 emissions between 1971 and 2001 through the adaptation of the polarization concept and measures. We find that the most interesting grouped description deriving from the analysis is a two groups' one, which broadly coincide with Annex B and non-Annex B countries of the Kyoto Protocol, which shows the power of polarization analysis for explaining the generation of groups in the real world. The analysis also shows a significant reduction in international polarization in per capita CO 2 emissions between 1971 and 1995, but not much change since 1995, which might indicate that polarized distribution of emission is still one of the important factors leading to difficulties in achieving agreements for reducing global emissions. (author)

Label-free investigation of the effects of lithium niobate polarization on cell adhesion

Science.gov (United States)

Mandracchia, B.; Gennari, O.; Paturzo, M.; Grilli, S.; Ferraro, P.

2017-06-01

The determination of contact area is pivotal to understand how biomaterials properties influence cell adhesion. In particular, the influence of surface charges is well-known but still controversial, especially when new functional materials and methods are introduced. Here, we use for the first time Holographic Total Internal Reflection Microscopy (HoloTIRM) to study the influence of the spontaneous polarization of ferroelectric lithium niobate (LN) on the adhesion properties of fibroblast cells. The selective illumination of a very thin region directly above the substrate, achieved by Total Internal Reflection, provides high-contrast images of the contact regions. Holographic recording, on the other hand, allows for label-free quantitative phase imaging of the contact areas between cells and LN. Phase signal is more sensitive in the first 100nm and, thus more reliable in order to locate focal contacts. This work shows that cells adhering on negatively polarized LN present a significant increase of the contact area in comparison with cells adhering on the positively polarized LN substrate, as well as an intensification of contact vicinity. This confirms the potential of LN as a platform for investigating the role of charges on cellular processes. The similarity of cell adhesion behavior on negatively polarized LN and glass control also confirms the possibility to use LN as an active substrate without impairing cell behavior.

Development of a high average current polarized electron source with long cathode operational lifetime

Energy Technology Data Exchange (ETDEWEB)

C. K. Sinclair; P. A. Adderley; B. M. Dunham; J. C. Hansknecht; P. Hartmann; M. Poelker; J. S. Price; P. M. Rutt; W. J. Schneider; M. Steigerwald

2007-02-01

Substantially more than half of the electromagnetic nuclear physics experiments conducted at the Continuous Electron Beam Accelerator Facility of the Thomas Jefferson National Accelerator Facility (Jefferson Laboratory) require highly polarized electron beams, often at high average current. Spin-polarized electrons are produced by photoemission from various GaAs-based semiconductor photocathodes, using circularly polarized laser light with photon energy slightly larger than the semiconductor band gap. The photocathodes are prepared by activation of the clean semiconductor surface to negative electron affinity using cesium and oxidation. Historically, in many laboratories worldwide, these photocathodes have had short operational lifetimes at high average current, and have often deteriorated fairly quickly in ultrahigh vacuum even without electron beam delivery. At Jefferson Lab, we have developed a polarized electron source in which the photocathodes degrade exceptionally slowly without electron emission, and in which ion back bombardment is the predominant mechanism limiting the operational lifetime of the cathodes during electron emission. We have reproducibly obtained cathode 1/e dark lifetimes over two years, and 1/e charge density and charge lifetimes during electron beam delivery of over 2?105???C/cm2 and 200 C, respectively. This source is able to support uninterrupted high average current polarized beam delivery to three experimental halls simultaneously for many months at a time. Many of the techniques we report here are directly applicable to the development of GaAs photoemission electron guns to deliver high average current, high brightness unpolarized beams.

Higher-Dimensional Solitons Stabilized by Opposite Charge

CERN Document Server

Binder, B

2002-01-01

In this paper it is shown how higher-dimensional solitons can be stabilized by a topological phase gradient, a field-induced shift in effective dimensionality. As a prototype, two instable 2-dimensional radial symmetric Sine-Gordon extensions (pulsons) are coupled by a sink/source term such, that one becomes a stable 1d and the other a 3d wave equation. The corresponding physical process is identified as a polarization that fits perfectly to preliminary considerations regarding the nature of electric charge and background of 1/137. The coupling is iterative with convergence limit and bifurcation at high charge. It is driven by the topological phase gradient or non-local Gauge potential that can be mapped to a local oscillator potential under PSL(2,R).

Numerical and experimental study of two turbulent opposed plane jets

Energy Technology Data Exchange (ETDEWEB)

Besbes, Sonia; Mhiri, Hatem [Laboratoire de Mecanique des Fluides et Thermique, Ecole Nationale d' Ingenieurs de Monastir, Route de Ouardanine, Monastir (Tunisia); Le Palec, Georges; Bournot, Philippe [Institut de Mecanique de Marseille, UNIMECA, Technopole de Chateau-Gombert, 60 rue Joliot-Curie, 13453 Marseille (France)

2003-09-01

The turbulent interaction between two opposed plane jets separated by a distance H is experimentally studied by using a PIV (Particle Image Velocimetry) method and numerically investigated by means of a finite volume code. Two turbulence models have been tested: the standard k-{epsilon} model and a second-order model. The validation of the numerical study was performed by comparing the results with experimental data obtained for the case of two interacting opposed jets at ambient temperature (isothermal case). The effect of the angle of inclination of the jets is studied. Conclusions of the validation are then used to study the interaction between two jets, one being maintained at ambient temperature whereas the other is heated. Results show that the stagnation point moves towards the heated jet. It is shown that the heating induces a stabilizing effect on the flow. (orig.)

Tuning the polarization-induced free hole density in nanowires graded from GaN to AlN

Science.gov (United States)

Golam Sarwar, A. T. M.; Carnevale, Santino D.; Kent, Thomas F.; Yang, Fan; McComb, David W.; Myers, Roberto C.

2015-01-01

We report a systematic study of p-type polarization-induced doping in graded AlGaN nanowire light emitting diodes grown on silicon wafers by plasma-assisted molecular beam epitaxy. The composition gradient in the p-type base is varied in a set of samples from 0.7%Al/nm to 4.95%Al/nm corresponding to negative bound polarization charge densities of 2.2 × 1018 cm-3 to 1.6 × 1019 cm-3. Capacitance measurements and energy band modeling reveal that for gradients greater than or equal to 1.30%Al/nm, the deep donor concentration is negligible and free hole concentrations roughly equal to the bound polarization charge density are achieved up to 1.6 × 1019 cm-3 at a gradient of 4.95%Al/nm. Accurate grading lengths in the p- and n-side of the pn-junction are extracted from scanning transmission electron microscopy images and are used to support energy band calculation and capacitance modeling. These results demonstrate the robust nature of p-type polarization doping in nanowires and put an upper bound on the magnitude of deep donor compensation.

Opposing Amygdala and Ventral Striatum Connectivity during Emotion Identification

Science.gov (United States)

Satterthwaite, Theodore D.; Wolf, Daniel H.; Pinkham, Amy E.; Ruparel, Kosha; Elliott, Mark A.; Valdez, Jeffrey N.; Overton, Eve; Seubert, Janina; Gur, Raquel E.; Gur, Ruben C.; Loughead, James

2011-01-01

Lesion and electrophysiological studies in animals provide evidence of opposing functions for subcortical nuclei such as the amygdala and ventral striatum, but the implications of these findings for emotion identification in humans remain poorly described. Here we report a high-resolution fMRI study in a sample of 39 healthy subjects who performed…

Optical Pumping of the Electronic and Nuclear Spin of Single Charge-Tunable Quantum Dots

Science.gov (United States)

Bracker, A. S.; Stinaff, E. A.; Gammon, D.; Ware, M. E.; Tischler, J. G.; Shabaev, A.; Efros, Al. L.; Park, D.; Gershoni, D.; Korenev, V. L.; Merkulov, I. A.

2005-02-01

We present a comprehensive examination of optical pumping of spins in individual GaAs quantum dots as we change the net charge from positive to neutral to negative with a charge-tunable heterostructure. Negative photoluminescence polarization memory is enhanced by optical pumping of ground state electron spins, which we prove with the first measurements of the Hanle effect on an individual quantum dot. We use the Overhauser effect in a high longitudinal magnetic field to demonstrate efficient optical pumping of nuclear spins for all three charge states of the quantum dot.

MRI of bone marrow: opposed-phase gradient-echo sequences with long repetition time

International Nuclear Information System (INIS)

Seiderer, M.; Staebler, A.; Wagner, H.

1999-01-01

Signal intensity for opposed-phase gradient-echo (GE) sequences of tissues composed of fat- and water-equivalent cells such as red bone marrow is extremely sensitive to variation of the ratio of both cell populations (fat-to-water ratio Q F/W ). Because most bone marrow pathology results in variation of Q F/W , GE sequences are characterized by high-contrast imaging of pathology. The aim of this study was to evaluate the influence of TR, TE, FA, Q F/W and histology on signal intensity. Signal intensity of opposed-phase GE sequences as a function of TR, TE, FA, and Q F/W was measured for a fat-water phantom and cadaver specimens of normal bone marrow (red and yellow) and pathological bone marrow (tumors). All specimens were correlated to histology. Opposed-phase GE imaging of red bone marrow pathology results in low-signal-intensity imaging of intact red bone marrow and high-signal-intensity positive contrast imaging of pathology associated with a change in Q F/W . In first-order approximation the signal intensity of pathology is linearly correlated to the change in Q F/W . Opposed-phase GE imaging is a sensitive imaging technique for red bone marrow pathology. Relative contrast of red bone marrow pathology is similar to fat-suppressed imaging techniques. Acquisition time is identical to T1-weighted SE sequences. (orig.)

2D scattering of unpolarized beams of electrons by charged nanomagnets

Energy Technology Data Exchange (ETDEWEB)

Senbeta, Teshome, E-mail: teshearada@yahoo.com [Department of Physics, Addis Ababa University, P.O. Box 1176, Addis Ababa (Ethiopia); Mal' nev, V.N., E-mail: vnmalnev@aau.edu.et [Department of Physics, Addis Ababa University, P.O. Box 1176, Addis Ababa (Ethiopia)

2012-07-15

2D spin-dependent scattering of slow unpolarized beams of electrons by charged nanomagnets is analyzed in the Born approximation. The obtained scattering lengths are larger than those from the neutral nanomagnets approximately by one order. It is shown that for particular parameters of the system it is possible to polarize completely the scattered electrons in a narrow range of scattering angles. The most suitable system for realization of these effects is 2D Si electron gas with immersed nanomagnets. - Highlights: Black-Right-Pointing-Pointer We study 2D spin dependent electron scattering by charged nanomagnets. Black-Right-Pointing-Pointer The applicability of the Born approximation to the problem is discussed. Black-Right-Pointing-Pointer Unpolarized incident beams used to obtain completely polarized scattered electrons. Black-Right-Pointing-Pointer The study shows peculiarities of 2D spin dependent scattering enhanced by Coulomb potential. Black-Right-Pointing-Pointer The result obtained can be used as one method of controlling spin currents.

Experimental studies of the charge limit phenomenon in NEA GaAs photocathodes

International Nuclear Information System (INIS)

Tang, H.; Alley, R.K.; Aoyagi, H.; Clendenin, J.E.; Frisch, J.C.; Mulhollan, G.A.; Saez, P.J.; Schultz, D.C.; Turner, J.L.

1994-06-01

Negative electron affinity GaAs photocathodes have been in continuous use at SLAC for generating polarized electron beams since early 1992. If the quantum efficiency of a GaAs cathode is below a critical value, the maximum photoemitted charge with photons of energies close to the band gap in a 2-ns pulse is found to be limited by the intrinsic properties of the cathode instead of by the space charge limit. We have studied this novel charge limit phenomenon in a variety of GaAs photocathodes of different structures and doping densities. We find that the charge limit is strongly dependent on the cathode's quantum efficiency and the extraction electric field, and to a lesser degree on the excitation laser wavelength. In addition, we show that the temporal behavior of the charge limit depends critically on the doping density

Polarization measurement for internal polarized gaseous targets

International Nuclear Information System (INIS)

Ye Zhenyu; Ye Yunxiu; Lv Haijiang; Mao Yajun

2004-01-01

The authors present an introduction to internal polarized gaseous targets, polarization method, polarization measurement method and procedure. To get the total nuclear polarization of hydrogen atoms (including the polarization of the recombined hydrogen molecules) in the target cell, authors have measured the parameters relating to atomic polarization and polarized hydrogen atoms and molecules. The total polarization of the target during our measurement is P T =0.853 ± 0.036. (authors)

Design and Calibration of a Novel Bio-Inspired Pixelated Polarized Light Compass

Directory of Open Access Journals (Sweden)

Guoliang Han

2017-11-01

Full Text Available Animals, such as Savannah sparrows and North American monarch butterflies, are able to obtain compass information from skylight polarization patterns to help them navigate effectively and robustly. Inspired by excellent navigation ability of animals, this paper proposes a novel image-based polarized light compass, which has the advantages of having a small size and being light weight. Firstly, the polarized light compass, which is composed of a Charge Coupled Device (CCD camera, a pixelated polarizer array and a wide-angle lens, is introduced. Secondly, the measurement method of a skylight polarization pattern and the orientation method based on a single scattering Rayleigh model are presented. Thirdly, the error model of the sensor, mainly including the response error of CCD pixels and the installation error of the pixelated polarizer, is established. A calibration method based on iterative least squares estimation is proposed. In the outdoor environment, the skylight polarization pattern can be measured in real time by our sensor. The orientation accuracy of the sensor increases with the decrease of the solar elevation angle, and the standard deviation of orientation error is 0 . 15 ∘ at sunset. Results of outdoor experiments show that the proposed polarization navigation sensor can be used for outdoor autonomous navigation.

TNF-α decreases VEGF secretion in highly polarized RPE cells but increases it in non-polarized RPE cells related to crosstalk between JNK and NF-κB pathways.

Directory of Open Access Journals (Sweden)

Hiroto Terasaki

Full Text Available Asymmetrical secretion of vascular endothelial growth factor (VEGF by retinal pigment epithelial (RPE cells in situ is critical for maintaining the homeostasis of the retina and choroid. VEGF is also involved in the development and progression of age-related macular degeneration (AMD. We studied the effect of tumor necrosis factor-α (TNF-α on the secretion of VEGF in polarized and non-polarized RPE cells (P-RPE cells and N-RPE cells, respectively in culture and in situ in rats. A subretinal injection of TNF-α caused a decrease in VEGF expression and choroidal atrophy. Porcine RPE cells were seeded on Transwell™ filters, and their maturation and polarization were confirmed by the asymmetrical VEGF secretion and trans electrical resistance. Exposure to TNF-α decreased the VEGF secretion in P-RPE cells but increased it in N-RPE cells in culture. TNF-α inactivated JNK in P-RPE cells but activated it in N-RPE cells, and TNF-α activated NF-κB in P-RPE cells but not in N-RPE cells. Inhibition of NF-κB activated JNK in both types of RPE cells indicating crosstalk between JNK and NF-κB. TNF-α induced the inhibitory effects of NF-κB on JNK in P-RPE cells because NF-κB is continuously inactivated. In N-RPE cells, however, it was not evident because NF-κB was already activated. The basic activation pattern of JNK and NF-κB and their crosstalk led to opposing responses of RPE cells to TNF-α. These results suggest that VEGF secretion under inflammatory conditions depends on cellular polarization, and the TNF-α-induced VEGF down-regulation may result in choroidal atrophy in polarized physiological RPE cells. TNF-α-induced VEGF up-regulation may cause neovascularization by non-polarized or non-physiological RPE cells.

Technical Note: An investigation of polarity effects for wide-angle free-air chambers

Energy Technology Data Exchange (ETDEWEB)

Shen, H., E-mail: Hong.Shen@nrc-cnrc.gc.ca; Ross, C. K. [Ionizing Radiation Standards, National Research Council, Ottawa, Ontario K1A 0R6 (Canada); Culberson, W. S. [Department of Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin 53705 (United States)

2016-07-15

Purpose: Wide-angle free-air chambers (WAFACs) are used as primary standard measurement devices for establishing the air-kerma strength of low-energy, low-dose rate brachytherapy seeds. The National Research Council of Canada (NRC) is commissioning a primary standard wide-angle free-air chamber (NRC WAFAC) to serve the calibration needs of Canadian clients. The University of Wisconsin has developed a similar variable-aperture free-air chamber (UW VAFAC) to be used as a research tool. As part of the NRC commissioning, measurements were carried out for both polarities of the applied bias voltage and the resulting effects were observed to be very large. Similar effects were identified with the UW VAFAC. The authors describe the measurements carried out to determine the underlying causes of the polarity effect and the approach used to eliminate it. Methods: The NRC WAFAC is based on the WAFAC design developed at the National Institute of Standards and Technology in the USA. Charge measurements for {sup 125}I and {sup 241}Am sources were carried out for both negative and positive polarities on the NRC WAFAC and UW VAFAC. Two aperture sizes were also investigated with the UW VAFAC. In addition, measurements on the NRC WAFAC were carried out with a small bias between the collecting electrode and the shield foil at the downstream end of the chamber. To mitigate all of the polarity effects, the downstream surface of the collecting electrode was covered with a thin layer of graphite on both the NRC and UW chambers. Results: Both chamber designs showed a difference of more than 30 % between the charge collected with positive and negative bias voltages for the smallest electrode separation. It was shown for the NRC WAFAC that charge could be collected in the small gap downstream of the collecting volume by applying a voltage between the shield foil and the collecting electrode, even though an insulating foil (Mylar or polyimide film) separated the conducting surface from the

Technical Note: An investigation of polarity effects for wide-angle free-air chambers

International Nuclear Information System (INIS)

Shen, H.; Ross, C. K.; Culberson, W. S.

2016-01-01

Purpose: Wide-angle free-air chambers (WAFACs) are used as primary standard measurement devices for establishing the air-kerma strength of low-energy, low-dose rate brachytherapy seeds. The National Research Council of Canada (NRC) is commissioning a primary standard wide-angle free-air chamber (NRC WAFAC) to serve the calibration needs of Canadian clients. The University of Wisconsin has developed a similar variable-aperture free-air chamber (UW VAFAC) to be used as a research tool. As part of the NRC commissioning, measurements were carried out for both polarities of the applied bias voltage and the resulting effects were observed to be very large. Similar effects were identified with the UW VAFAC. The authors describe the measurements carried out to determine the underlying causes of the polarity effect and the approach used to eliminate it. Methods: The NRC WAFAC is based on the WAFAC design developed at the National Institute of Standards and Technology in the USA. Charge measurements for 125 I and 241 Am sources were carried out for both negative and positive polarities on the NRC WAFAC and UW VAFAC. Two aperture sizes were also investigated with the UW VAFAC. In addition, measurements on the NRC WAFAC were carried out with a small bias between the collecting electrode and the shield foil at the downstream end of the chamber. To mitigate all of the polarity effects, the downstream surface of the collecting electrode was covered with a thin layer of graphite on both the NRC and UW chambers. Results: Both chamber designs showed a difference of more than 30 % between the charge collected with positive and negative bias voltages for the smallest electrode separation. It was shown for the NRC WAFAC that charge could be collected in the small gap downstream of the collecting volume by applying a voltage between the shield foil and the collecting electrode, even though an insulating foil (Mylar or polyimide film) separated the conducting surface from the small gap

Qweak: First Direct Measurement of the Proton’s Weak Charge

Directory of Open Access Journals (Sweden)

Androic D.

2017-01-01

Full Text Available The Qweak experiment, which took data at Jefferson Lab in the period 2010 - 2012, will precisely determine the weak charge of the proton by measuring the parity-violating asymmetry in elastic e-p scattering at 1.1 GeV using a longitudinally polarized electron beam and a liquid hydrogen target at a low momentum transfer of Q2 = 0.025 (GeV/c2. The weak charge of the proton is predicted by the Standard Model and any significant deviation would indicate physics beyond the Standard Model. The technical challenges and experimental apparatus for measuring the weak charge of the proton will be discussed, as well as the method of extracting the weak charge of the proton. The results from a small subset of the data, that has been published, will also be presented. Furthermore an update will be given of the current status of the data analysis.

Polarization phenomena in Al/p-CdTe/Pt X-ray detectors

Energy Technology Data Exchange (ETDEWEB)

Principato, F., E-mail: fabio.principato@unipa.it; Turturici, A.A.; Gallo, M.; Abbene, L.

2013-12-01

Over the last decades, CdTe detectors are widely used for the development of room temperature X-ray and gamma ray spectrometers. Typically, high resolution CdTe detectors are fabricated with blocking contacts (indium and aluminum) ensuring low leakage currents and high electric field for optimum charge collection. As well known, time instability under bias voltage (termed as polarization) is the major drawback of CdTe diode detectors. Polarization phenomena cause a progressive degradation of the spectroscopic performance with time, due to hole trapping and detrapping from deep acceptors levels. In this work, we studied the polarization phenomenon on new Al/p-CdTe/Pt detectors, manufactured by Acrorad (Japan), through electrical and spectroscopic approaches. In particular, we investigated on the time degradation of the spectroscopic response of the detectors at different temperatures, voltages and energies. Current transient measurements were also performed to better understand the properties of the deep acceptor levels and their correlation with the polarization effect.

Perturbed stationary-state description of the polarization effect in innershell ionization

International Nuclear Information System (INIS)

Basbas, G.; Land, D.J.

1983-01-01

A one-parameter trial initial-state wavefunction correlated to a projectile (polarized) is described and used to calculate innershell ionization cross sections for collisions with heavy charged particles. The variational principle is used to determine the parameter. The minimized energy gives the binding effect as a function of projectile position. Existing codes can be readily adapted to incorporate the trial wavefunction. Comparison with the previous theory of the polarization effect is made. Results for K-shell ionization of titanium by protons in the 0.3 to 2.4 MeV energy range agree with measured values

Photodissociation and charge transfer dynamics of negative ions studied with femtosecond photoelectron spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Zanni, Martin Thomas [Univ. of California, Berkeley, CA (United States)

1999-12-01

This dissertation presents studies aimed at understanding the potential energy surfaces and dynamics of isolated negative ions, and the effects of solvent on each. Although negative ions play important roles in atmospheric and solution phase chemistry, to a large extent the ground and excited state potential energy surfaces of gas phase negative ions are poorly characterized, and solvent effects even less well understood. In an effort to fill this gap, the author's coworkers and the author have developed a new technique, anion femtosecond photoelectron spectroscopy, and applied it to gas phase photodissociation and charge transfer processes. Studies are presented that (1) characterize the ground and excited states of isolated and clustered anions, (2) monitor the photodissociation dynamics of isolated and clustered anions, and (3) explore the charge-transfer-to-solvent states of atomic iodide clustered with polar and non-polar solvents.

Photodissociation and charge transfer dynamics of negative ions studied with femtosecond photoelectron spectroscopy

International Nuclear Information System (INIS)

Zanni, Martin T.

1999-01-01

This dissertation presents studies aimed at understanding the potential energy surfaces and dynamics of isolated negative ions, and the effects of solvent on each. Although negative ions play important roles in atmospheric and solution phase chemistry, to a large extent the ground and excited state potential energy surfaces of gas phase negative ions are poorly characterized, and solvent effects even less well understood. In an effort to fill this gap, the author's coworkers and the author have developed a new technique, anion femtosecond photoelectron spectroscopy, and applied it to gas phase photodissociation and charge transfer processes. Studies are presented that (1) characterize the ground and excited states of isolated and clustered anions, (2) monitor the photodissociation dynamics of isolated and clustered anions, and (3) explore the charge-transfer-to-solvent states of atomic iodide clustered with polar and non-polar solvents

Investigation on Surface Polarization of Al2O3-capped GaN/AlGaN/GaN Heterostructure by Angle-Resolved X-ray Photoelectron Spectroscopy.

Science.gov (United States)

Duan, Tian Li; Pan, Ji Sheng; Wang, Ning; Cheng, Kai; Yu, Hong Yu

2017-08-17

The surface polarization of Ga-face gallium nitride (GaN) (2 nm)/AlGaN (22 nm)/GaN channel (150 nm)/buffer/Si with Al 2 O 3 capping layer is investigated by angle-resolved X-ray photoelectron spectroscopy (ARXPS). It is found that the energy band varies from upward bending to downward bending in the interface region, which is believed to be corresponding to the polarization variation. An interfacial layer is formed between top GaN and Al 2 O 3 due to the occurrence of Ga-N bond break and Ga-O bond forming during Al 2 O 3 deposition via the atomic layer deposition (ALD). This interfacial layer is believed to eliminate the GaN polarization, thus reducing the polarization-induced negative charges. Furthermore, this interfacial layer plays a key role for the introduction of the positive charges which lead the energy band downward. Finally, a N 2 annealing at 400 °C is observed to enhance the interfacial layer growth thus increasing the density of positive charges.

Opposing flow in square porous annulus: Influence of Dufour effect

International Nuclear Information System (INIS)

Athani, Abdulgaphur; Al-Rashed, Abdullah A. A. A.; Khaleed, H. M. T.

2016-01-01

Heat and mass transfer in porous medium is very important area of research which is also termed as double diffusive convection or thermo-solutal convection. The buoyancy ratio which is the ratio of thermal to concentration buoyancy can have negative values thus leading to opposing flow. This article is aimed to study the influence of Dufour effect on the opposing flow in a square porous annulus. The partial differential equations that govern the heat and mass transfer behavior inside porous medium are solved using finite element method. A three node triangular element is used to divide the porous domain into smaller elements. Results are presented with respect to geometric and physical parameters such as duct diameter ratio, Rayleigh number, radiation parameter etc. It is found that the heat transfer increase with increase in Rayleigh number and radiation parameter. It is observed that Dufour coefficient has more influence on velocity profile.

Opposing flow in square porous annulus: Influence of Dufour effect

Energy Technology Data Exchange (ETDEWEB)

Athani, Abdulgaphur, E-mail: abbu.bec@gmail.com [Dept. of Mechanical Engineering, Anjuman Institute of Technology & Management, Bhatkal (India); Al-Rashed, Abdullah A. A. A., E-mail: aa.alrashed@paaet.edu.kw [Dept. of Automotive and Marine Engineering Technology, College of Technological Studies, The Public Authority for Applied Education and Training (Kuwait); Khaleed, H. M. T., E-mail: khalid-tan@yahoo.com [Dept of Mechanical Engineering, Faculty of Engineering, Islamic University, Madinah Munawwarra (Saudi Arabia)

2016-06-21

Heat and mass transfer in porous medium is very important area of research which is also termed as double diffusive convection or thermo-solutal convection. The buoyancy ratio which is the ratio of thermal to concentration buoyancy can have negative values thus leading to opposing flow. This article is aimed to study the influence of Dufour effect on the opposing flow in a square porous annulus. The partial differential equations that govern the heat and mass transfer behavior inside porous medium are solved using finite element method. A three node triangular element is used to divide the porous domain into smaller elements. Results are presented with respect to geometric and physical parameters such as duct diameter ratio, Rayleigh number, radiation parameter etc. It is found that the heat transfer increase with increase in Rayleigh number and radiation parameter. It is observed that Dufour coefficient has more influence on velocity profile.

The origin of polarized blackbody radiation from resistively heated multiwalled carbon nanotubes

International Nuclear Information System (INIS)

Aliev, Ali E.; Kuznetsov, Alexander A.

2008-01-01

We observed very pronounced polarization of light emitted by highly aligned free-standing multiwall carbon nanotube (MWNT) sheet in axial direction which is turned to the perpendicular polarization when a number of layers are increased. The radiation spectrum of resistively heated MWNT sheet closely follows to the Plank's blackbody radiation distribution. The obtained polarization features can be described by a classical dielectric cylindrical shell model, taking into consideration the contribution of delocalized π-electrons (π surface plasmons). In absorption (emission) the optical transverse polarizability, which is much smaller than longitudinal one, is substantially suppressed by depolarization effect due to screening by induced charges. This phenomenon suggests very simple and precise method to estimate the alignment of nanotubes in bundles or large assemblies

Quantifying microbe-mineral interactions leading to remotely detectable induced polarization signals

Energy Technology Data Exchange (ETDEWEB)

Ntarlagiannis, Dimitrios; Moysey, Stephen; Dean, Delphine

2013-11-14

The objective of this project was to investigate controls on induced polarization responses in porous media. The approach taken in the project was to compare electrical measurements made on mineral surfaces with atomic force microscopy (AFM) techniques to observations made at the column-scale using traditional spectral induced polarization measurements. In the project we evaluated a number of techniques for investigating the surface properties of materials, including the development of a new AFM measurement protocol that utilizes an external electric field to induce grain-scale polarizations that can be probed using a charged AFM tip. The experiments we performed focused on idealized systems (i.e., glass beads and silica gel) where we could obtain the high degree of control needed to understand how changes in the pore environment, which are determined by biogeochemical controls in the subsurface, affect mechanisms contributing to complex electrical conductivity, i.e., conduction and polarization, responses. The studies we performed can be classified into those affecting the chemical versus physical properties of the grain surface and pore space. Chemical alterations of the surface focused on evaluating how changes in pore fluid pH and ionic composition control surface conduction. These were performed as column flow through experiments where the pore fluid was exchanged in a column of silica gel. Given that silica gel has a high surface area due to internal grain porosity, high-quality data could be obtained where the chemical influences on the surface are clearly apparent and qualitatively consistent with theories of grain (i.e., Stern layer) polarization controlled by electrostatic surface sorption processes (i.e., triple layer theory). Quantitative fitting of the results by existing process-based polarization models (e.g., Leroy et al., 2008) has been less successful, however, due to what we have attributed to differences between existing models developed for

Blue Light Emitting Polyphenylene Dendrimers with Bipolar Charge Transport Moieties

Directory of Open Access Journals (Sweden)

Guang Zhang

2016-10-01

Full Text Available Two light-emitting polyphenylene dendrimers with both hole and electron transporting moieties were synthesized and characterized. Both molecules exhibited pure blue emission solely from the pyrene core and efficient surface-to-core energy transfers when characterized in a nonpolar environment. In particular, the carbazole- and oxadiazole-functionalized dendrimer (D1 manifested a pure blue emission from the pyrene core without showing intramolecular charge transfer (ICT in environments with increasing polarity. On the other hand, the triphenylamine- and oxadiazole-functionalized one (D2 displayed notable ICT with dual emission from both the core and an ICT state in highly polar solvents. D1, in a three-layer organic light emitting diode (OLED by solution processing gave a pure blue emission with Commission Internationale de l’Éclairage 1931 CIE xy = (0.16, 0.12, a peak current efficiency of 0.21 cd/A and a peak luminance of 2700 cd/m2. This represents the first reported pure blue dendrimer emitter with bipolar charge transport and surface-to-core energy transfer in OLEDs.

Blue Light Emitting Polyphenylene Dendrimers with Bipolar Charge Transport Moieties.

Science.gov (United States)

Zhang, Guang; Auer-Berger, Manuel; Gehrig, Dominik W; Blom, Paul W M; Baumgarten, Martin; Schollmeyer, Dieter; List-Kratochvil, E J W; Müllen, Klaus

2016-10-20

Two light-emitting polyphenylene dendrimers with both hole and electron transporting moieties were synthesized and characterized. Both molecules exhibited pure blue emission solely from the pyrene core and efficient surface-to-core energy transfers when characterized in a nonpolar environment. In particular, the carbazole- and oxadiazole-functionalized dendrimer ( D1 ) manifested a pure blue emission from the pyrene core without showing intramolecular charge transfer (ICT) in environments with increasing polarity. On the other hand, the triphenylamine- and oxadiazole-functionalized one ( D2 ) displayed notable ICT with dual emission from both the core and an ICT state in highly polar solvents. D1 , in a three-layer organic light emitting diode (OLED) by solution processing gave a pure blue emission with Commission Internationale de l'Éclairage 1931 CIE xy = (0.16, 0.12), a peak current efficiency of 0.21 cd/A and a peak luminance of 2700 cd/m². This represents the first reported pure blue dendrimer emitter with bipolar charge transport and surface-to-core energy transfer in OLEDs.

Study of polarization phenomena in Schottky CdTe diodes using infrared light illumination

Energy Technology Data Exchange (ETDEWEB)

Sato, Goro, E-mail: gsato@astro.isas.jaxa.jp [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan); Fukuyama, Taro [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan); University of Tokyo, 7-3-1, Hongo, Bunkyo, Tokyo 113-0033 (Japan); Watanabe, Shin; Ikeda, Hirokazu; Ohta, Masayuki; Ishikawa, Shin' nosuke [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan); Takahashi, Tadayuki [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan); University of Tokyo, 7-3-1, Hongo, Bunkyo, Tokyo 113-0033 (Japan); Shiraki, Hiroyuki; Ohno, Ryoichi [ACRORAD Co., Ltd., 13-23 Suzaki, Uruma, Okinawa 904-2234 (Japan)

2011-10-01

Schottky CdTe diode detectors suffer from a polarization phenomenon, which is characterized by degradation of the spectral properties over time following exposure to high bias voltage. This is considered attributable to charge accumulation at deep acceptor levels. A Schottky CdTe diode was illuminated with an infrared light for a certain period during a bias operation, and two opposite behaviors emerged. The detector showed a recovery when illuminated after the bias-induced polarization had completely progressed. Conversely, when the detector was illuminated before the emergence of bias-induced polarization, the degradation of the spectral properties was accelerated. Interpretation of these effects and discussion on the energy level of deep acceptors are presented.

Intermediate energy charge-exchange reactions induced by polarized 3He

International Nuclear Information System (INIS)

Kim, B.T.

1998-01-01

Spin polarization transfer is proven to be very useful in obtaining detailed information of the continuum nuclear responses. The data, taken for the (vector p,vector n) reactions, have enabled us to separate the response into the spin longitudinal and transverse components. These partial nuclear responses have been successfully used to make critical tests of nuclear structure models. In the present paper, we first summarize the results of the data and the theoretical analyses made so far. We then discuss information obtainable from the ( 3 vector He,vector t) reaction, emphasizing on the differences and similarities in comparison with the (vector p,vector n) reaction. The results of numerical calculations made for ( 3 vector He,vector t) reactions based on the microscopic distorted wave impulse approximation will also be reported. (orig.)

Polarized ionic source of the tandem accelerator in Kyoto University

Energy Technology Data Exchange (ETDEWEB)

Nakamura, Masanobu; Kuwamoto, Shuichi; Takahashi, Seiji [Kyoto Univ. (Japan). Dept. of Physics] [and others

1997-02-01

A polarized ion source developed under the National Laboratory of High Energy Physics was transferred to the tandem accelerator in Kyoto University at beginning of 1993 to constitute a displacement of incidence into the accelerator. This was an atomic beam type polarized ion source, which is designed to adopt permanent magnets for 6 poles magnet to polarize the electron, to take out atomic nucleus on a shape of positive ion by ECR ionizer after transferring its polarization through transition using radio frequency (RFT), to make it negative ion by charge conversion using alkaline metal vapor, and to put it into the tandem accelerator. Test of the positive ion was finished at the National Laboratory of High Energy Physics, and test in Kyoto University was required after its negative ionization. As the estimated cost was unsufficient and entrance into the ion source facility in the tandem accelerator building was limited in Kyoto University, step of development was slow. Here is reported on present state of the ion source which is now operating stably. (G.K.)

Measurement of charm in charged current at HERA

International Nuclear Information System (INIS)

Zimmermann, Tobias

2008-12-01

A measurement of charm production in charged current (CC) polarized electron-proton deep inelastic scattering processes with data from the H1 detector at the HERA collider is presented. This process in principle allows access to the strange quark density in the proton. In total 5460 CC candidate events in e + p and 6253 in e - p data are selected in the kinematic range Q 2 >223 GeV 2 and 0.03 CC =(28.9± 1.4)+P e .(28.6±4.7) pb for e + p and σ CC =(49.2±2.3)-P e .(42.5 ±6.8) pb for e - p, where P e is the lepton beam polarization. While the measured cross section for e + p data is in agreement with the theoretical prediction, the cross section for e - p data shows a weaker dependence on P e than predicted. The charm fractions in the selected CC candidate event samples are extracted using the muon charge asymmetry. Muons originating from charmed hadron decays in CC events at HERA always have the same charge as the beam lepton. The extracted charm fractions in the selected CC candidate event samples are F c =9.5±8.9±3.0 % for e + p and F c =4.4±6.9±2.6 % for e - p. Due to the large statistical errors of the measured charm fractions, the strange quark density in the proton has not been extracted. (orig.)

Boost Up Carrier Mobility for Ferroelectric Organic Transistor Memory via Buffering Interfacial Polarization Fluctuation

Science.gov (United States)

Sun, Huabin; Wang, Qijing; Li, Yun; Lin, Yen-Fu; Wang, Yu; Yin, Yao; Xu, Yong; Liu, Chuan; Tsukagoshi, Kazuhito; Pan, Lijia; Wang, Xizhang; Hu, Zheng; Shi, Yi

2014-11-01

Ferroelectric organic field-effect transistors (Fe-OFETs) have been attractive for a variety of non-volatile memory device applications. One of the critical issues of Fe-OFETs is the improvement of carrier mobility in semiconducting channels. In this article, we propose a novel interfacial buffering method that inserts an ultrathin poly(methyl methacrylate) (PMMA) between ferroelectric polymer and organic semiconductor layers. A high field-effect mobility (μFET) up to 4.6 cm2 V-1 s-1 is obtained. Subsequently, the programming process in our Fe-OFETs is mainly dominated by the switching between two ferroelectric polarizations rather than by the mobility-determined charge accumulation at the channel. Thus, the ``reading'' and ``programming'' speeds are significantly improved. Investigations show that the polarization fluctuation at semiconductor/insulator interfaces, which affect the charge transport in conducting channels, can be suppressed effectively using our method.

Why do older people oppose physician-assisted dying? A qualitative study.

Science.gov (United States)

Malpas, Phillipa J; Wilson, Maria K R; Rae, Nicola; Johnson, Malcolm

2014-04-01

Physician-assisted dying at the end of life has become a significant issue of public discussion. While legally available in a number of countries and jurisdictions, it remains controversial and illegal in New Zealand. The study aimed to explore the reasons some healthy older New Zealanders oppose physician-assisted dying in order to inform current debate. Recorded interviews were transcribed and analysed by the authors after some edits had been made by respondents. In all, 11 older participants (over 65 years) who responded to advertisements placed in Grey Power magazines and a University of Auckland email list were interviewed for around 1 h and asked a number of open-ended questions. Four central themes opposing physician-assisted dying were identified from the interviews: one's personal experience with health care and dying and death, religious reasoning and beliefs, slippery slope worries and concern about potential abuses if physician-assisted dying were legalised. An important finding of the study suggests that how some older individuals think about physician-assisted dying is strongly influenced by their past experiences of dying and death. While some participants had witnessed good, well-managed dying and death experiences which confirmed for them the view that physician-assisted dying was unnecessary, those who had witnessed poor dying and death experiences opposed physician-assisted dying on the grounds that such practices could come to be abused by others.

Electron scattering with polarized targets at TESLA

International Nuclear Information System (INIS)

Anselmino, M.; Aschenauer, E.C.; Belostotski, S.

2000-11-01

Measurements of polarized electron-nucleon scattering can be realized at the TESLA linear collider facility with projected luminosities that are about two orders of magnitude higher than those expected of other experiments at comparable energies. Longitudinally polarized electrons, accelerated as a small fraction of the total current in the e + arm of TESLA, can be directed onto a solid state target that may be either longitudinally or transversely polarized. A large variety of polarized parton distribution and fragmentation functions can be determined with unprecedented accuracy, many of them for the first time. A main goal of the experiment is the precise measurement of the x- and Q 2 -dependence of the experimentally totally unknown quark transversity distributions that will complete the information on the nucleon's quark spin structure as relevant for high energy processes. Comparing their Q 2 -evolution to that of the corresponding helicity distributions constitutes an important precision test of the predictive power of QCD in the spin sector. Measuring transversity distributions and tensor charges allows access to the hitherto unmeasured chirally odd operators in QCD which are of great importance to understand the role of chiral symmetry. The possibilities of using unpolarized targets and of experiments with a real photon beam turn TESLA-N into a versatile next-generation facility at the intersection of particle and nuclear physics. (orig.)

Arginine side chain interactions and the role of arginine as a gating charge carrier in voltage sensitive ion channels

Science.gov (United States)

Armstrong, Craig T.; Mason, Philip E.; Anderson, J. L. Ross; Dempsey, Christopher E.

2016-02-01

Gating charges in voltage-sensing domains (VSD) of voltage-sensitive ion channels and enzymes are carried on arginine side chains rather than lysine. This arginine preference may result from the unique hydration properties of the side chain guanidinium group which facilitates its movement through a hydrophobic plug that seals the center of the VSD, as suggested by molecular dynamics simulations. To test for side chain interactions implicit in this model we inspected interactions of the side chains of arginine and lysine with each of the 19 non-glycine amino acids in proteins in the protein data bank. The arginine guanidinium interacts with non-polar aromatic and aliphatic side chains above and below the guanidinium plane while hydrogen bonding with polar side chains is restricted to in-plane positions. In contrast, non-polar side chains interact largely with the aliphatic part of the lysine side chain. The hydration properties of arginine and lysine are strongly reflected in their respective interactions with non-polar and polar side chains as observed in protein structures and in molecular dynamics simulations, and likely underlie the preference for arginine as a mobile charge carrier in VSD.

Proceedings of the workshop on photocathodes for polarized electron sources for accelerators. Revision

Energy Technology Data Exchange (ETDEWEB)

Chatwell, M.; Clendenin, J.; Maruyama, T.; Schultz, D. [eds.

1994-04-01

Application of the GaAs polarized electron source to studies of surface magnetism; thermal stability of Cs on NES III-V-Photocathodes and its effect on quantum efficiency; AFEL accelerator; production and detection of SPIN polarized electrons; emittance measurements on a 100-keV beam from a GaAs photocathode electron gun; modern theory of photoemission and its applications to practical photocathodes; experimental studies of the charge limit phenomenon in GaAs photocathodes; new material for photoemission electron source; semiconductor alloy InGaAsP grown on GaAs substrate; NEA photocathode surface preparation; technology and physics; metalorganic chemical vapor deposition of GaAs-GaAsP spin-polarized photocathodes; development of photocathodes injectors for JLC-ATF; effect of radiation trapping on polarization of photoelectrons from semiconductors; and energy analysis of electrons emitted by a semiconductor photocathode.

Detection of charged particles with a methylammonium lead tribromide perovskite single crystal

Energy Technology Data Exchange (ETDEWEB)

Xu, Qiang [Nuclear Engineering Program, Department of Mechanical and Aerospace Engineering, The Ohio State University, Columbus, Ohio 43210 (United States); Wei, Haotong; Wei, Wei [Department of Mechanical and Materials Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska 68588 (United States); Chuirazzi, William; DeSantis, Dylan [Nuclear Engineering Program, Department of Mechanical and Aerospace Engineering, The Ohio State University, Columbus, Ohio 43210 (United States); Huang, Jinsong, E-mail: jhuang2@unl.edu [Department of Mechanical and Materials Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska 68588 (United States); Cao, Lei, E-mail: cao.152@osu.edu [Nuclear Engineering Program, Department of Mechanical and Aerospace Engineering, The Ohio State University, Columbus, Ohio 43210 (United States)

2017-03-11

Methylammonium lead tribromide (MAPbBr{sub 3}) perovskite crystals have attracted significant attention due to their attractive performance in various optoelectronic applications such as solar cells, light-emitting devices, photodetectors, and recently in X-ray detectors. In this study, we demonstrate a possible use of perovskite-based devices for detection of charged particles (which can be applied in basic scientific research, health physics, and environmental analysis) and investigate the mechanism of fundamental charge transport inside perovskite crystals. It was found that inexpensive MAPbBr{sub 3} single crystals could be used for measuring the energy spectrum of charged particles through direct collection of the produced charge. After fitting the plot of the centroid peak position versus voltage with the Hecht equation for single-polarity charge transport, the obtained hole mobility-lifetime product was in the range of (0.4–1.6)×10{sup −3} cm{sup 2}/V.

Detection of charged particles with a methylammonium lead tribromide perovskite single crystal

International Nuclear Information System (INIS)

Xu, Qiang; Wei, Haotong; Wei, Wei; Chuirazzi, William; DeSantis, Dylan; Huang, Jinsong; Cao, Lei

2017-01-01

Methylammonium lead tribromide (MAPbBr_3) perovskite crystals have attracted significant attention due to their attractive performance in various optoelectronic applications such as solar cells, light-emitting devices, photodetectors, and recently in X-ray detectors. In this study, we demonstrate a possible use of perovskite-based devices for detection of charged particles (which can be applied in basic scientific research, health physics, and environmental analysis) and investigate the mechanism of fundamental charge transport inside perovskite crystals. It was found that inexpensive MAPbBr_3 single crystals could be used for measuring the energy spectrum of charged particles through direct collection of the produced charge. After fitting the plot of the centroid peak position versus voltage with the Hecht equation for single-polarity charge transport, the obtained hole mobility-lifetime product was in the range of (0.4–1.6)×10"−"3 cm"2/V.

Scalar Aharonov-Bohm effect with longitudinally polarized neutrons

International Nuclear Information System (INIS)

Allman, B. E.; Lee, W.-T.; Motrunich, O. I.; Werner, S. A.

1999-01-01

In the scalar Aharonov-Bohm effect, a charged particle (electron) interacts with the scalar electrostatic potential U in the field-free (i.e., force-free) region inside an electrostatic cylinder (Faraday cage). Using a perfect single-crystal neutron interferometer we have performed a ''dual'' scalar Aharonov-Bohm experiment by subjecting polarized thermal neutrons to a pulsed magnetic field. The pulsed magnetic field was spatially uniform, precluding any force on the neutrons. Aligning the direction of the pulsed magnetic field to the neutron magnetic moment also rules out any classical torque acting to change the neutron polarization. The observed phase shift is purely quantum mechanical in origin. A detailed description of the experiment, performed at the University of Missouri Research Reactor, and its interpretation is given in this paper. (c) 1999 The American Physical Society

Influence of the polarity of the applied voltage on the reignition of a discharge below a dielectric layer in air at atmospheric pressure

International Nuclear Information System (INIS)

Pechereau, François; Bourdon, Anne

2014-01-01

The dynamics of an atmospheric pressure air discharge in a point-to-plane geometry with a dielectric layer obstacle on the discharge path is investigated numerically for different applied voltages. Whatever the polarity of the voltage applied, first, a streamer discharge of the same polarity ignites at the point and propagates towards the dielectric layer. After the impact on the dielectric surface, the streamer discharge spreads along the upper dielectric surface and charges it positively or negatively depending on its polarity. On the bottom surface of the dielectric layer, charges with an opposite polarity are deposited. Surface charges on both faces of the dielectric layer are shown to have a significant influence on the discharge reignition for a negative applied voltage, but not for a positive one. Furthermore, it is shown that the dynamics of the discharge reignition below the dielectric layer depends on the polarity of the applied voltage at the point electrode. For a positive applied voltage, the reignited discharge is a positive ionization wave propagating towards the grounded plane. For a negative applied voltage, a double headed discharge is observed with positive and negative fronts propagating in opposite directions. Finally, the minimal value of the ionization integral to have a discharge reignition below the dielectric obstacle is found to be less for a negative applied voltage than for a positive one. (paper)

The Reactive Oxygen Species in Macrophage Polarization: Reflecting Its Dual Role in Progression and Treatment of Human Diseases

Science.gov (United States)

Tan, Hor-Yue; Li, Sha; Hong, Ming; Wang, Xuanbin

2016-01-01

High heterogeneity of macrophage is associated with its functions in polarization to different functional phenotypes depending on environmental cues. Macrophages remain in balanced state in healthy subject and thus macrophage polarization may be crucial in determining the tissue fate. The two distinct populations, classically M1 and alternatively M2 activated, representing the opposing ends of the full activation spectrum, have been extensively studied for their associations with several disease progressions. Accumulating evidences have postulated that the redox signalling has implication in macrophage polarization and the key roles of M1 and M2 macrophages in tissue environment have provided the clue for the reasons of ROS abundance in certain phenotype. M1 macrophages majorly clearing the pathogens and ROS may be crucial for the regulation of M1 phenotype, whereas M2 macrophages resolve inflammation which favours oxidative metabolism. Therefore how ROS play its role in maintaining the homeostatic functions of macrophage and in particular macrophage polarization will be reviewed here. We also review the biology of macrophage polarization and the disturbance of M1/M2 balance in human diseases. The potential therapeutic opportunities targeting ROS will also be discussed, hoping to provide insights for development of target-specific delivery system or immunomodulatory antioxidant for the treatment of ROS-related diseases. PMID:27143992

Injection and detection of a spin-polarized current in a light-emitting diode

Science.gov (United States)

Fiederling, R.; Keim, M.; Reuscher, G.; Ossau, W.; Schmidt, G.; Waag, A.; Molenkamp, L. W.

1999-12-01

The field of magnetoelectronics has been growing in practical importance in recent years. For example, devices that harness electronic spin-such as giant-magnetoresistive sensors and magnetoresistive memory cells-are now appearing on the market. In contrast, magnetoelectronic devices based on spin-polarized transport in semiconductors are at a much earlier stage of development, largely because of the lack of an efficient means of injecting spin-polarized charge. Much work has focused on the use of ferromagnetic metallic contacts, but it has proved exceedingly difficult to demonstrate polarized spin injection. More recently, two groups have reported successful spin injection from an NiFe contact, but the observed effects of the spin-polarized transport were quite small (resistance changes of less than 1%). Here we describe a different approach, in which the magnetic semiconductor BexMnyZn1-x-ySe is used as a spin aligner. We achieve injection efficiencies of 90% spin-polarized current into a non-magnetic semiconductor device. The device used in this case is a GaAs/AlGaAs light-emitting diode, and spin polarization is confirmed by the circular polarization state of the emitted light.

New Perspectives on the Charging Mechanisms of Supercapacitors

Science.gov (United States)

2016-01-01

Supercapacitors (or electric double-layer capacitors) are high-power energy storage devices that store charge at the interface between porous carbon electrodes and an electrolyte solution. These devices are already employed in heavy electric vehicles and electronic devices, and can complement batteries in a more sustainable future. Their widespread application could be facilitated by the development of devices that can store more energy, without compromising their fast charging and discharging times. In situ characterization methods and computational modeling techniques have recently been developed to study the molecular mechanisms of charge storage, with the hope that better devices can be rationally designed. In this Perspective, we bring together recent findings from a range of experimental and computational studies to give a detailed picture of the charging mechanisms of supercapacitors. Nuclear magnetic resonance experiments and molecular dynamics simulations have revealed that the electrode pores contain a considerable number of ions in the absence of an applied charging potential. Experiments and computer simulations have shown that different charging mechanisms can then operate when a potential is applied, going beyond the traditional view of charging by counter-ion adsorption. It is shown that charging almost always involves ion exchange (swapping of co-ions for counter-ions), and rarely occurs by counter-ion adsorption alone. We introduce a charging mechanism parameter that quantifies the mechanism and allows comparisons between different systems. The mechanism is found to depend strongly on the polarization of the electrode, and the choice of the electrolyte and electrode materials. In light of these advances we identify new directions for supercapacitor research. Further experimental and computational work is needed to explain the factors that control supercapacitor charging mechanisms, and to establish the links between mechanisms and performance

Electrical control of truly two-dimensional neutral and charged excitons in monolayer MoSe2

Science.gov (United States)

Ross, Jason; Wu, Sanfeng; Yu, Hongyi; Ghimire, Nirmal; Jones, Aaron; Aivazian, Grant; Yan, Jiaqiang; Mandrus, David; Xiao, Di; Xiao, Di; Xu, Xiaodong

2013-03-01

Monolayer transition metal dichalcogenides (TMDs) have emerged as ideal 2D semiconductors with valley and spin polarized excitations expected to enable true valley-tronics. Here we investigate MoSe2, a TMD which has yet to be characterized in the monolayer limit. Specifically, we examine excitons and trions (their singly charged counterparts) in the ultimate 2D limit. Utilizing high quality exfoliated MoSe2 monolayers, we report the observation and electrostatic tunability of positively charged (X +) , neutral (Xo), and negatively charged (X-) excitons via photoluminescence in FETs. The trion charging energy is large (30 meV), enhanced by strong confinement and heavy effective masses, while the linewidth is narrow (5 meV) at temperatures below 55 K. This is greater spectral contrast than in any known quasi-2D system. Further, the charging energies for X + and X- to are nearly identical implying the same effective mass for electrons and holes, which supports their recent description as massive Dirac fermions. This work demonstrates that monolayer MoSe2 is an ultimate 2D semiconductor opening the door for the investigation of truly 2D exciton physics while laying the ground work necessary to begin valley-spin polarization studies. Support: US DoE, BES, Division of MSE. HY and WY supported by Research Grant Council of Hong Kong

Development of a high average current polarized electron source with long cathode operational lifetime

Directory of Open Access Journals (Sweden)

C. K. Sinclair

2007-02-01

Full Text Available Substantially more than half of the electromagnetic nuclear physics experiments conducted at the Continuous Electron Beam Accelerator Facility of the Thomas Jefferson National Accelerator Facility (Jefferson Laboratory require highly polarized electron beams, often at high average current. Spin-polarized electrons are produced by photoemission from various GaAs-based semiconductor photocathodes, using circularly polarized laser light with photon energy slightly larger than the semiconductor band gap. The photocathodes are prepared by activation of the clean semiconductor surface to negative electron affinity using cesium and oxidation. Historically, in many laboratories worldwide, these photocathodes have had short operational lifetimes at high average current, and have often deteriorated fairly quickly in ultrahigh vacuum even without electron beam delivery. At Jefferson Lab, we have developed a polarized electron source in which the photocathodes degrade exceptionally slowly without electron emission, and in which ion back bombardment is the predominant mechanism limiting the operational lifetime of the cathodes during electron emission. We have reproducibly obtained cathode 1/e dark lifetimes over two years, and 1/e charge density and charge lifetimes during electron beam delivery of over 2×10^{5}   C/cm^{2} and 200 C, respectively. This source is able to support uninterrupted high average current polarized beam delivery to three experimental halls simultaneously for many months at a time. Many of the techniques we report here are directly applicable to the development of GaAs photoemission electron guns to deliver high average current, high brightness unpolarized beams.

Surface chemistry and electronic structure of nonpolar and polar GaN films

Energy Technology Data Exchange (ETDEWEB)

Mishra, Monu; Krishna, T.C. Shibin; Aggarwal, Neha; Gupta, Govind, E-mail: govind@nplindia.org

2015-08-01

Highlights: • Surface chemistry and electronic structure of polar and nonpolar GaN is reported. • Influence of polarization on electron affinity of p & np GaN films is investigated. • Correlation between surface morphology and polarity has been deduced. - Abstract: Photoemission and microscopic analysis of nonpolar (a-GaN/r-Sapphire) and polar (c-GaN/c-Sapphire) epitaxial gallium nitride (GaN) films grown via RF-Molecular Beam Epitaxy is reported. The effect of polarization on surface properties like surface states, electronic structure, chemical bonding and morphology has been investigated and correlated. It was observed that polarization lead to shifts in core level (CL) as well as valence band (VB) spectra. Angle dependent X-ray Photoelectron Spectroscopic analysis revealed higher surface oxide in polar GaN film compared to nonpolar GaN film. On varying the take off angle (TOA) from 0° to 60°, the Ga−O/Ga−N ratio varied from 0.11–0.23 for nonpolar and 0.17–0.36 for polar GaN film. The nonpolar film exhibited N-face polarity while Ga-face polarity was perceived in polar GaN film due to the inherent polarization effect. Polarization charge compensated surface states were observed on the polar GaN film and resulted in downward band bending. Ultraviolet photoelectron spectroscopic measurements revealed electron affinity and ionization energy of 3.4 ± 0.1 eV and 6.8 ± 0.1 eV for nonpolar GaN film and 3.8 ± 0.1 eV and 7.2 ± 0.1 eV for polar GaN film respectively. Field Emission Scanning Electron Microscopy measurements divulged smooth morphology with pits on polar GaN film. The nonpolar film on the other hand showed pyramidal structures having facets all over the surface.

Diffusive charge transport in graphene on SiO 2

Science.gov (United States)

Chen, J.-H.; Jang, C.; Ishigami, M.; Xiao, S.; Cullen, W. G.; Williams, E. D.; Fuhrer, M. S.

2009-07-01

We review our recent work on the physical mechanisms limiting the mobility of graphene on SiO 2. We have used intentional addition of charged scattering impurities and systematic variation of the dielectric environment to differentiate the effects of charged impurities and short-range scatterers. The results show that charged impurities indeed lead to a conductivity linear in density ( σ(n)∝n) in graphene, with a scattering magnitude that agrees quantitatively with theoretical estimates; increased dielectric screening reduces the scattering from charged impurities, but increases the scattering from short-range scatterers. We evaluate the effects of the corrugations (ripples) of graphene on SiO 2 on transport by measuring the height-height correlation function. The results show that the corrugations cannot mimic long-range (charged impurity) scattering effects, and have too small an amplitude-to-wavelength ratio to significantly affect the observed mobility via short-range scattering. Temperature-dependent measurements show that longitudinal acoustic phonons in graphene produce a resistivity that is linear in temperature and independent of carrier density; at higher temperatures, polar optical phonons of the SiO 2 substrate give rise to an activated, carrier density-dependent resistivity. Together the results paint a complete picture of charge carrier transport in graphene on SiO 2 in the diffusive regime.

Determination of polarization fields in group III-nitride heterostructures by capacitance-voltage-measurements

Energy Technology Data Exchange (ETDEWEB)

Rychetsky, Monir, E-mail: monir.rychetsky@physik.tu-berlin.de; Avinc, Baran; Wernicke, Tim; Bellmann, Konrad; Sulmoni, Luca [Institute of Solid State Physics, Technische Universität Berlin, Berlin (Germany); Koslow, Ingrid; Rass, Jens; Kneissl, Michael [Institute of Solid State Physics, Technische Universität Berlin, Berlin (Germany); Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Berlin (Germany); Hoffmann, Veit; Weyers, Markus [Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Berlin (Germany); Wild, Johannes; Zweck, Josef [Fakultät für Physik, University of Regensburg, Regensburg (Germany); Witzigmann, Bernd [Computational Electronics and Photonics Group and CINSaT, University of Kassel, Kassel (Germany)

2016-03-07

The polarization fields in wurtzite group III-nitrides strongly influence the optical properties of InAlGaN-based light emitters, e.g., the electron and hole wave function overlap in quantum wells. In this paper, we propose a new approach to determine these fields by capacitance-voltage measurements (CVM). Sheet charges generated by a change of the microscopic polarization at heterointerfaces influence the charge distribution in PIN junctions and therefore the depletion width and the capacitance. We show that it is possible to determine the strength and direction of the internal fields by comparing the depletion widths of two PIN junctions, one influenced by internal polarization fields and one without as a reference. For comparison, we conducted coupled Poisson/carrier transport simulations on the CVM of the polarization-influenced sample. We also demonstrate the feasibility and limits of the method by determining the fields in GaN/InGaN and GaN/AlGaN double heterostructures on (0001) c-plane grown by metal organic vapor phase epitaxy and compare both evaluation methods. The method yields (−0.50 ± 0.07) MV/cm for In{sub 0.08}Ga{sub 0.92}N/GaN, (0.90 ± 0.13) MV/cm for Al{sub 0.18}Ga{sub 0.82}N/GaN, and (2.0 ± 0.3) MV/cm for Al{sub 0.31}Ga{sub 0.69}N/GaN heterostructures.

Modeling all-electrical detection of the inverse Edelstein effect by spin-polarized tunneling in a topological-insulator/ferromagnetic-metal heterostructure

Science.gov (United States)

Dey, Rik; Register, Leonard F.; Banerjee, Sanjay K.

2018-04-01

The spin-momentum locking of the surface states in a three-dimensional topological insulator (TI) allows a charge current on the surface of the TI induced by an applied spin current onto the surface, which is known as the inverse Edelstein effect (IEE), that could be achieved either by injecting pure spin current by spin-pumping from a ferromagnetic metal (FM) layer or by injecting spin-polarized charge current by direct tunneling of electrons from the FM to the TI. Here, we present a theory of the observed IEE effect in a TI-FM heterostructure for the spin-polarized tunneling experiments. If an electrical current is passed from the FM to the surface of the TI, because of density-of-states polarization of the FM, an effective imbalance of spin-polarized electrons occurs on the surface of the TI. Due to the spin-momentum helical locking of the surface states in the TI, a difference of transverse charge accumulation appears on the TI surface in a direction orthogonal to the direction of the magnetization of the FM, which is measured as a voltage difference. Here, we derive the two-dimensional transport equations of electrons on the surface of a diffusive TI, coupled to a FM, starting from the quantum kinetic equation, and analytically solve the equations for a rectangular geometry to calculate the voltage difference.

Energy of charged states in the acetanilide crystal: Trapping of charge-transfer states at vacancies as a possible mechanism for optical damage

Science.gov (United States)

Tsiaousis, D.; Munn, R. W.

2004-04-01

Calculations for the acetanilide crystal yield the effective polarizability (16.6 Å3), local electric field tensor, effective dipole moment (5.41 D), and dipole-dipole energy (-12.8 kJ/mol). Fourier-transform techniques are used to calculate the polarization energy P for a single charge in the perfect crystal (-1.16 eV); the charge-dipole energy WD is zero if the crystal carries no bulk dipole moment. Polarization energies for charge-transfer (CT) pairs combine with the Coulomb energy EC to give the screened Coulomb energy Escr; screening is nearly isotropic, with Escr≈EC/2.7. For CT pairs WD reduces to a term δWD arising from the interaction of the charge on each ion with the change in dipole moment on the other ion relative to the neutral molecule. The dipole moments calculated by density-functional theory methods with the B3LYP functional at the 6-311++G** level are 3.62 D for the neutral molecule, changing to 7.13 D and 4.38 D for the anion and cation, relative to the center of mass. Because of the large change in the anion, δWD reaches -0.9 eV and modifies the sequence of CT energies markedly from that of Escr, giving the lowest two CT pairs at -1.98 eV and -1.41 eV. The changes in P and WD near a vacancy are calculated; WD changes for the individual charges because the vacancy removes a dipole moment and modifies the crystal dielectric response, but δWD and EC do not change. A vacancy yields a positive change ΔP that scatters a charge or CT pair, but the change ΔWD can be negative and large enough to outweigh ΔP, yielding traps with depths that can exceed 150 meV for single charges and for CT pairs. Divacancies yield traps with depths nearly equal to the sum of those produced by the separate vacancies and so they can exceed 300 meV. These results are consistent with a mechanism of optical damage in which vacancies trap optically generated CT pairs that recombine and release energy; this can disrupt the lattice around the vacancy, thereby favoring

On the Control of the Fixed Charge Densities in Al2O3-Based Silicon Surface Passivation Schemes.

Science.gov (United States)

Simon, Daniel K; Jordan, Paul M; Mikolajick, Thomas; Dirnstorfer, Ingo

2015-12-30

A controlled field-effect passivation by a well-defined density of fixed charges is crucial for modern solar cell surface passivation schemes. Al2O3 nanolayers grown by atomic layer deposition contain negative fixed charges. Electrical measurements on slant-etched layers reveal that these charges are located within a 1 nm distance to the interface with the Si substrate. When inserting additional interface layers, the fixed charge density can be continuously adjusted from 3.5 × 10(12) cm(-2) (negative polarity) to 0.0 and up to 4.0 × 10(12) cm(-2) (positive polarity). A HfO2 interface layer of one or more monolayers reduces the negative fixed charges in Al2O3 to zero. The role of HfO2 is described as an inert spacer controlling the distance between Al2O3 and the Si substrate. It is suggested that this spacer alters the nonstoichiometric initial Al2O3 growth regime, which is responsible for the charge formation. On the basis of this charge-free HfO2/Al2O3 stack, negative or positive fixed charges can be formed by introducing additional thin Al2O3 or SiO2 layers between the Si substrate and this HfO2/Al2O3 capping layer. All stacks provide very good passivation of the silicon surface. The measured effective carrier lifetimes are between 1 and 30 ms. This charge control in Al2O3 nanolayers allows the construction of zero-fixed-charge passivation layers as well as layers with tailored fixed charge densities for future solar cell concepts and other field-effect based devices.

An Estimation of Hybrid Quantum Mechanical Molecular Mechanical Polarization Energies for Small Molecules Using Polarizable Force-Field Approaches.

Science.gov (United States)

Huang, Jing; Mei, Ye; König, Gerhard; Simmonett, Andrew C; Pickard, Frank C; Wu, Qin; Wang, Lee-Ping; MacKerell, Alexander D; Brooks, Bernard R; Shao, Yihan

2017-02-14

In this work, we report two polarizable molecular mechanics (polMM) force field models for estimating the polarization energy in hybrid quantum mechanical molecular mechanical (QM/MM) calculations. These two models, named the potential of atomic charges (PAC) and potential of atomic dipoles (PAD), are formulated from the ab initio quantum mechanical (QM) response kernels for the prediction of the QM density response to an external molecular mechanical (MM) environment (as described by external point charges). The PAC model is similar to fluctuating charge (FQ) models because the energy depends on external electrostatic potential values at QM atomic sites; the PAD energy depends on external electrostatic field values at QM atomic sites, resembling induced dipole (ID) models. To demonstrate their uses, we apply the PAC and PAD models to 12 small molecules, which are solvated by TIP3P water. The PAC model reproduces the QM/MM polarization energy with a R 2 value of 0.71 for aniline (in 10,000 TIP3P water configurations) and 0.87 or higher for other 11 solute molecules, while the PAD model has a much better performance with R 2 values of 0.98 or higher. The PAC model reproduces reference QM/MM hydration free energies for 12 solute molecules with a RMSD of 0.59 kcal/mol. The PAD model is even more accurate, with a much smaller RMSD of 0.12 kcal/mol, with respect to the reference. This suggests that polarization effects, including both local charge distortion and intramolecular charge transfer, can be well captured by induced dipole type models with proper parametrization.

Partition coefficients of methylated DNA bases obtained from free energy calculations with molecular electron density derived atomic charges.

Science.gov (United States)

Lara, A; Riquelme, M; Vöhringer-Martinez, E

2018-05-11

Partition coefficients serve in various areas as pharmacology and environmental sciences to predict the hydrophobicity of different substances. Recently, they have also been used to address the accuracy of force fields for various organic compounds and specifically the methylated DNA bases. In this study, atomic charges were derived by different partitioning methods (Hirshfeld and Minimal Basis Iterative Stockholder) directly from the electron density obtained by electronic structure calculations in a vacuum, with an implicit solvation model or with explicit solvation taking the dynamics of the solute and the solvent into account. To test the ability of these charges to describe electrostatic interactions in force fields for condensed phases, the original atomic charges of the AMBER99 force field were replaced with the new atomic charges and combined with different solvent models to obtain the hydration and chloroform solvation free energies by molecular dynamics simulations. Chloroform-water partition coefficients derived from the obtained free energies were compared to experimental and previously reported values obtained with the GAFF or the AMBER-99 force field. The results show that good agreement with experimental data is obtained when the polarization of the electron density by the solvent has been taken into account, and when the energy needed to polarize the electron density of the solute has been considered in the transfer free energy. These results were further confirmed by hydration free energies of polar and aromatic amino acid side chain analogs. Comparison of the two partitioning methods, Hirshfeld-I and Minimal Basis Iterative Stockholder (MBIS), revealed some deficiencies in the Hirshfeld-I method related to the unstable isolated anionic nitrogen pro-atom used in the method. Hydration free energies and partitioning coefficients obtained with atomic charges from the MBIS partitioning method accounting for polarization by the implicit solvation model

A new method of thermal protection by opposing jet for a hypersonic aeroheating strut

Science.gov (United States)

Qin, Jiang; Ning, Dongpo; Feng, Yu; Zhang, Junlong; Feng, Shuo; Bao, Wen

2017-06-01

This paper presents the numerical investigation of thermal protection of scramjet strut by opposing jet in supersonic stream of Mach number 6 with a hydrogen fueled scramjet strut model using CFD software. Simulation results indicate that when a small amount of fuel is injected from the nose of the strut, the bow shock is pushed away from the strut, and the heat flux is reduced in the strut, especially at the leading edge. Opposing jet forms a recirculation region near the nozzle so that the strut is covered with low temperature fuel and separated from free stream. An appropriate total pressure ratio can be used to reduce not only aerodynamic heating but also the drag of strut. It is therefore concluded that thermal protection of scramjet strut by opposing jet is one of the promising ways to protect scramjet strut in high enthalpy stream.