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Sample records for angular dependent nexafs

  1. Structural vs electronic origin of renormalized band widths in TTF-TCNQ: An angular dependent NEXAFS study

    NASA Astrophysics Data System (ADS)

    Sing, M.; Meyer, J.; Hoinkis, M.; Glawion, S.; Blaha, P.; Gavrila, G.; Jacobsen, C. S.; Claessen, R.

    2007-12-01

    We have performed angle-dependent near-edge x-ray absorption fine structure measurements in the Auger electron yield mode on the correlated quasi-one-dimensional organic conductor tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) in order to determine the orientation of the molecules in the topmost surface layer. We find that the tilt angles of the molecules with respect to the one-dimensional axis are essentially the same as in the bulk. Thus, we can rule out surface relaxation as the origin of the renormalized band widths which were inferred from the analysis of photoemission data within the one-dimensional Hubbard model. Thereby, recent theoretical results are corroborated which invoke long-range Coulomb repulsion as alternative explanation to understand the spectral dispersions of TTF-TCNQ quantitatively within an extended Hubbard model.

  2. Radially dependent angular acceleration of twisted light.

    PubMed

    Webster, Jason; Rosales-Guzmán, Carmelo; Forbes, Andrew

    2017-02-15

    While photons travel in a straight line at constant velocity in free space, the intensity profile of structured light may be tailored for acceleration in any degree of freedom. Here we propose a simple approach to control the angular acceleration of light. Using Laguerre-Gaussian modes as our twisted beams carrying orbital angular momentum, we show that superpositions of opposite handedness result in a radially dependent angular acceleration as they pass through a focus (waist plane). Due to conservation of orbital angular momentum, we find that propagation dynamics are complex despite the free-space medium: the outer part of the beam (rings) rotates in an opposite direction to the inner part (petals), and while the outer part accelerates, the inner part decelerates. We outline the concepts theoretically and confirm them experimentally. Such exotic structured light beams are topical due to their many applications, for instance in optical trapping and tweezing, metrology, and fundamental studies in optics.

  3. Time-dependent photoelectron angular distributions

    NASA Astrophysics Data System (ADS)

    Wang, Xiangyang

    1999-09-01

    I show that the angular distribution of electrons photoionized from gas phase targets by short light pulses is time-dependent, when the orbital momentum composition of the photocurrent changes with excitation energy so evolves with the time of detection. A theory of time- dependent photoionization is outlined and general formulas of time-dependent photoelectron flux and angular distribution are given. Two general propagator methods suitable to describe the time-dependent photoionization and scattering processes are developed. The photoionization process is viewed as a local excitation followed by a half scattering. The local excitation process is solved theoretically in a small region around the target core. This approach has been generalized to describe the evolution of a wavepacket in an unbound system. An asymptotic propagator theorem is discovered and used to derive analytic expressions for asymptotic propagators. The origin of the time dependence is explored by parameterizing the time delay and orbital momentum coupling in a two channel model. K-shell photoionization of N2 and CO are calculated with this time- dependent photoionization theory, implemented using a multiple scattering model. Numerical results demonstrate that the time dependence of photoelectron angular distributions is a realistic effect.

  4. A Fast Method of Fully Characterizing Sputtering Angular Dependence (Preprint)

    DTIC Science & Technology

    2008-06-17

    A new method has been demonstrated in which a single experiment is used to fully define the sputtering angular dependence of a given material. The...profilometry; the full sputtering angular dependence curve is then extracted using a numerical approach.

  5. Angular dependence of a simple accident dosimeter

    SciTech Connect

    Devine, R. T.; Romero, L. L.; Olsher, R. H.

    2004-01-01

    A simple dosimeter made of a sulfur tablet, bare and cadmium covered indium foils and a cadmium covered copper foil has been modeled using MCNP5. Studies of the model without phantom or other confounding factors have shown that the cross sections and fluence-to-dose factors generated by the Monte Carlo method agree with those generated by analytic expressions for the high energy component. The threshold cross sections for the detectors on a phantom were calculated. The resulting doses assigned agree well with exposures made to three critical assemblies. In this study the angular dependence on a phantom is studied and compared with measurements taken on the GODIVA reactor. The dosimeter positions on the phantom are facing the source, on the back and the side. In previous papers the modeling of a simple dosimeter made of a sulfur tablet, bare and cadmium covered indium foils and a cadmium covered copper foil has been modeled using MCNP5. The conclusion made was that most of the neutron dose from criticality assemblies results from the high energy neutron fluences determined by the sulfur and indium detectors. The results using doses measured from the GODIVA, SHEBA, and bare and lead shielded SILENE reactors confirmed this. The angular dependence of an accident dosemeter is of interest in evaluating the exposure of personnel. To investigate this effect accident dosemeters were placed on a phantom and exposed to the GODIVA reactor at phantom orientations of 0{sup o}, 45{sup o}, 90{sup o}, 135{sup o}, and 180{sup o} to the assembly center line.

  6. Probing biomolecules at surfaces by NEXAFS spectroscopy

    NASA Astrophysics Data System (ADS)

    Liu, Xiaosong

    2009-12-01

    Surface science has made great strides towards tailoring surface properties via self-assembly of nanoscale molecular adsorbates. It is now possible to functionalize surfaces with complex organic molecules and biomolecules. This leads a wide range of technological applications such as molecular electronic devices, biosensors, and bio-inspired photovoltaic devices. However, these macromolecules have complicated chemical sequences and internal structures and can assemble into multihierarchical, complex assemblies on surfaces. On the other hand, surface properties also play an important role because they determine the interaction of adsorbed molecules with the environment. Better understanding of the structural and electrical characteristics of surfaces and adsorbed molecules is therefore crucial and calls for a diversity of analysis methods. This thesis shows how Near Edge X-ray Absorption Fine Structure spectroscopy (NEXAFS), a synchrotron-based spectroscopic technique, can be used to characterize the assembly of molecules at surfaces in atom- and orbital-specific fashion. To illustrate the range of applications I begin with simple self-assembled monolayers (SAMs) with functional groups, proceed to polymer films, and finish with a small protein containing 124 amino acids (Ribonuclease A). NEXAFS provides element-specific and bond-specific information on the attachment of macromolecules to surfaces. In particular, the orientation of adsorbed molecules is revealed from the polarization dependence of the NEXAFS intensity, which can be explained with quantitative models. All these applications demonstrate that NEXAFS is particularly powerful in extracting orientational information in parallel with information on electronic structure of biomolecules at surfaces.

  7. Influence of dielectric substrate modification and deposition temperature on structure and morphology of CuPc thin films: X-ray reflectivity and angle dependent NEXAFS study

    NASA Astrophysics Data System (ADS)

    Sinha, Sumona; Wang, C.-H.; Mukherjee, M.

    2017-09-01

    The performances of organic thin film transistor devices are significantly linked with the structural properties at organic semiconductor/dielectric interface. The changes in internal structure, molecular ordering and morphology of 20 nm thick CuPc thin films have been investigated by modifying surface of the dielectric substrate with various organic buffer layers at different deposition temperatures. CuPc films are prepared on bare and modified SiO2 substrates at three deposition temperatures. Dielectric surface modification and deposition temperature modify the CuPc /dielectric interfaces accordingly and growth of subsequent CuPc layer. The internal structure, ordering and morphology of CuPc film strongly depends on the behavior of the dielectric layers at various temperatures as well as the diffusion of CuPc molecules. The XRR results reveal that the thickness and ordering of periodic part of CuPc film is varied with dielectric substrate modification as well as deposition temperature. The periodicity of CuPc molecules in the film is always obtained in its α-form. In addition, the angle dependent NEXAFS data determine the angle of CuPc molecular orientation in the range 64° to 71° in the range of 40° to 120 °C deposition temperature, independent of surface modification. The results pave the way for the design and realization of CuPc based thin film transistor devices.

  8. Calculating Sputter Rate Angular Dependence Using Optical Profilometry (Preprint)

    DTIC Science & Technology

    2007-07-26

    This work attempts to determine angular dependence curves for sputter rates of a material based on a single experimental measurement. An aluminum...angular dependence curve to match the given erosion profile. The calculated profile matched well with the experimental profile; however, neither matched...the optimization routine, the angular dependence curve was input to the COLISEUM plasma modeling code, which generated the same erosion profile as the experimental data.

  9. Electronic structure differences between H(2)-, Fe-, Co-, and Cu-phthalocyanine highly oriented thin films observed using NEXAFS spectroscopy.

    PubMed

    Willey, T M; Bagge-Hansen, M; Lee, J R I; Call, R; Landt, L; van Buuren, T; Colesniuc, C; Monton, C; Valmianski, I; Schuller, Ivan K

    2013-07-21

    Phthalocyanines, a class of macrocyclic, square planar molecules, are extensively studied as semiconductor materials for chemical sensors, dye-sensitized solar cells, and other applications. In this study, we use angular dependent near-edge x-ray absorption fine structure (NEXAFS) spectroscopy as a quantitative probe of the orientation and electronic structure of H2-, Fe-, Co-, and Cu-phthalocyanine molecular thin films. NEXAFS measurements at both the carbon and nitrogen K-edges reveal that phthalocyanine films deposited on sapphire have upright molecular orientations, while films up to 50 nm thick deposited on gold substrates contain prostrate molecules. Although great similarity is observed in the carbon and nitrogen K-edge NEXAFS spectra recorded for the films composed of prostrate molecules, the H2-phthalocyanine exhibits the cleanest angular dependence due to its purely out-of-plane π* resonances at the absorption onset. In contrast, organometallic-phthalocyanine nitrogen K-edges have a small in-plane resonance superimposed on this π* region that is due to a transition into molecular orbitals interacting with the 3dx(2)-y(2) empty state. NEXAFS spectra recorded at the metal L-edges for the prostrate films reveal dramatic variations in the angular dependence of specific resonances for the Cu-phthalocyanines compared with the Fe-, and Co-phthalocyanines. The Cu L3,2 edge exhibits a strong in-plane resonance, attributed to its b1g empty state with dx(2)-y(2) character at the Cu center. Conversely, the Fe- and Co- phthalocyanine L3,2 edges have strong out-of-plane resonances; these are attributed to transitions into not only b1g (dz(2)) but also eg states with dxz and dyz character at the metal center.

  10. Asymmetric angular dependence of domain wall motion in magnetic nanowires.

    PubMed

    Nam, Chunghee

    2013-03-01

    An angular dependence of domain wall (DW) motion is studied in a magnetic wire consisting of a giant-magnetoresistance spin-valve. A DW pinning site is formed by a single notch, where a conventional linear one and a specially designed tilted one are compared. The asymmetric angular dependence was found in the DW depinning behavior with the tilted notch. The geometry control of the pinning site can be useful for DW diode devices using a rotating magnetic field.

  11. Tracing the Angular Dependence of the CGM

    NASA Astrophysics Data System (ADS)

    Nattinger, Michael; Christensen, Charlotte

    2017-01-01

    The circumgalactic media (CGM) is enriched with metals through a process called the baryon cycle, which may play a significant role in the regulation of star formation. While the relationship between the CGM’s baryonic makeup and impact parameter is well documented, the relationship between the baryonic distribution of the CGM and the azimuthal angle out of the plane of the galaxy remains an open question. We investigated the angular distribution of baryons in the CGM by creating mock-absorption line spectra for a high-resolution simulation of a Milky Way-like galaxy at redshift zero. By comparison with data from the Cosmic Origins Spectrograph-Halos survey, we determined that our equivalent widths of HI, MgII, CIII, SiII, and SiIII are consistent with observations. Using our data, we found that low ionization state material is more prevalent at low azimuthal angles and that high ionization state material is more prevalent at high angles within the virial radius. We attributed this increased ionization to higher temperatures at high angles. We also found that the highest metallicity levels appear at high and low azimuthal angles, with lower metallicities at middle angles. This evidence supports the recycled accretion model of CGM baryon flow.

  12. Angular dependence of anisotropic magnetoresistance in magnetic systems

    NASA Astrophysics Data System (ADS)

    Zhang, Steven S.-L.; Zhang, Shufeng

    2014-05-01

    Anisotropic magnetoresistance (AMR), whose physical origin is attributed to the combination of spin dependent scattering and spin orbital coupling (SOC), usually displays simple angular dependence for polycrystalline ferromagnetic metals. By including generic spin dependent scattering and spin Hall (SH) terms in the Ohm's law, we explicitly show that various magneto-transport phenomena such as anomalous Hall (AH), SH, planar Hall (PH) and AMR could be quantitatively related for bulk polycrystalline ferromagnetic metals. We also discuss how AMR angular dependence is affected by the presence of interfacial SOC in magnetic layered structure.

  13. Angular dependence of anisotropic magnetoresistance in magnetic systems

    SciTech Connect

    Zhang, Steven S.-L. Zhang, Shufeng

    2014-05-07

    Anisotropic magnetoresistance (AMR), whose physical origin is attributed to the combination of spin dependent scattering and spin orbital coupling (SOC), usually displays simple angular dependence for polycrystalline ferromagnetic metals. By including generic spin dependent scattering and spin Hall (SH) terms in the Ohm's law, we explicitly show that various magneto-transport phenomena such as anomalous Hall (AH), SH, planar Hall (PH) and AMR could be quantitatively related for bulk polycrystalline ferromagnetic metals. We also discuss how AMR angular dependence is affected by the presence of interfacial SOC in magnetic layered structure.

  14. Angular and Energy Dependence of Proton Upset in Optocouplers

    NASA Technical Reports Server (NTRS)

    Johnston, A. H.; Miyahira, T.; Swift, G. M.; Guertin, S.; Edmonds, L. D.

    2000-01-01

    Proton upset effects in optocouplers were reported by LaBel, et al. that showed an unexpected increase in cross section for incident angles above 80 degrees. Although it appeared that the angular dependence was related to direct ionization from protons, the angular dependence was weaker than expected from basic geometrical arguments using a shallow charge collection depth. Later work showed that the angular dependence of proton upset observed in the earlier studies at a single energy could be explained by considering the distribution of proton recoil energies along with the assumption of a deeper charge collection depth, which was consistent with upset tests from heavy ions. However, an experimental test of the underlying assumptions in the latter work has yet to be done. Protons in space not only arrive over a wide range of incident angles, but also involve a distribution of proton energies. It is necessary to understand both the angular dependence and the dependence of proton upset on energy in order to determine how optocouplers will respond in space. If the angular dependence only occurs for extreme angles of incidence, it will have little impact on the overall cross section because of the narrow acceptance angle. The present work examines mechanisms for proton upset in optocouplers in more detail, investigating the energy dependence and the effects of different load conditions. A model for proton upset is developed, along with a laboratory screening method to determine whether direct ionization is significant for specific device types.

  15. Modeling of the angular dependence of plasma etching

    SciTech Connect

    Guo Wei; Sawin, Herbert H.

    2009-11-15

    An understanding of the angular dependence of etching yield is essential to investigate the origins of sidewall roughness during plasma etching. In this article the angular dependence of polysilicon etching in Cl{sub 2} plasma was modeled as a combination of individual angular-dependent etching yields for ion-initiated processes including physical sputtering, ion-induced etching, vacancy generation, and removal. The modeled etching yield exhibited a maximum at {approx}60 degree sign off-normal ion angle at low flux ratio, indicative of physical sputtering. It transformed to the angular dependence of ion-induced etching with the increase in the neutral-to-ion flux ratio. Good agreement between the modeling and the experiments was achieved for various flux ratios and ion energies. The variation of etching yield in response to the ion angle was incorporated in the three-dimensional profile simulation and qualitative agreement was obtained. The surface composition was calculated and compared to x-ray photoelectron spectroscopy (XPS) analysis. The modeling indicated a Cl areal density of 3x10{sup 15} atoms/cm{sup 2} on the surface that is close to the value determined by the XPS analysis. The response of Cl fraction to ion energy and flux ratio was modeled and correlated with the etching yields. The complete mixing-layer kinetics model with the angular dependence effect will be used for quantitative surface roughening analysis using a profile simulator in future work.

  16. Possible Angular Momentum Dependence of Dissipation in Nuclear Fission

    NASA Astrophysics Data System (ADS)

    Ye, Wei; Toke, Jan; Udo Schroeder, W.

    2008-04-01

    A comparative analysis of the pre-scission neutron multiplicities observed in a new experiment [1] and one reported earlier [2] suggests that, besides known deformation [3] and temperature [4] dependencies, nuclear dissipation in fission may have an angular momentum dependence. The analysis based on a Langevin equation coupled with a statistical decay model [3] considers angular momentum effects on fission dynamics. Pre-saddle reduced dissipation coefficients of β = 2 x10^21s-1 and 3 x10^21s-1 have been extracted for the matched reactions ^16O + ^181Ta and ^19F + ^178Hf [1],respectively. The difference in the extracted β values is attributed to the difference in the angular momenta contributing to the fission process in the two reactions. Work attempting to derive a quantitative expression for an angular momentum dependence of the dissipation strength is in progress. [1] H.Singh et al., Phys. Rev. C76 (2007) 044610 [2] L.G.Moretto et al., Phys. Rev. Lett. 75 (1995) 4186; Phys. Rev. C54 (1996) 3062 [3] P.Frobrich and I.I.Gontchar, Phys. Rep. 292(1998) 131 [4] P.Paul and M.Thoennessen, Ann. Rev. Part. Sci. 44(1994) 65

  17. Time and 'angular' dependent backgrounds from stationary axisymmetric solutions

    SciTech Connect

    Obregon, Octavio; Quevedo, Hernando; Ryan, Michael P.

    2004-09-15

    Backgrounds depending on time and on angular variable, namely, polarized and unpolarized S{sup 1}xS{sup 2} Gowdy models, are generated as the sector inside the horizons of the manifold corresponding to axisymmetric solutions. As is known, an analytical continuation of ordinary D-branes, iD-branes allow one to find S-brane solutions. Simple models have been constructed by means of analytic continuation of the Schwarzschild and the Kerr metrics. The possibility of studying the i-Gowdy models obtained here is outlined with an eye toward seeing if they could represent some kind of generalized S-branes depending not only on time but also on an angular variable.

  18. Temperature dependence of angular momentum transport across interfaces

    NASA Astrophysics Data System (ADS)

    Chen, Kai; Lin, Weiwei; Chien, C. L.; Zhang, Shufeng

    2016-08-01

    Angular momentum transport in magnetic multilayered structures plays a central role in spintronic physics and devices. The angular momentum currents or spin currents are carried by either quasiparticles such as electrons and magnons, or by macroscopic order parameters such as local magnetization of ferromagnets. Based on the generic interface exchange interaction, we develop a microscopic theory that describes interfacial spin conductance for various interfaces among nonmagnetic metals, ferromagnetic insulators, and antiferromagnetic insulators. Spin conductance and its temperature dependence are obtained for different spin batteries including spin pumping, temperature gradient, and spin Hall effect. As an application of our theory, we calculate the spin current in a trilayer made of a ferromagnetic insulator, an antiferromagnetic insulator, and a nonmagnetic heavy metal. The calculated results on the temperature dependence of spin conductance quantitatively agree with the existing experiments.

  19. Angular dependence of Wigner time delay: Relativistic Effects

    NASA Astrophysics Data System (ADS)

    Mandal, A.; Deshmukh, P. C.; Manson, S. T.; Kkeifets, A. S.

    2016-05-01

    Laser assisted photoionization time delay mainly consists of two parts: Wigner time delay, and time delay in continuum-continuum transition. Wigner time delay results from the energy derivative of the phase of the photoionization amplitude (matrix element). In general, the photoionization time delay is not the same in all directions relative to the incident photon polarization, although when a single transition dominates the amplitude, the resultant time delay is essentially isotropic. The relativistic-random-phase approximation is employed to determine the Wigner time delay in photoionization from the outer np subshells of the noble gas atoms, Ne through Xe. The time delay is found to significantly depend on angle, as well as energy. The angular dependence of the time delay is found to be quite sensitive to atomic dynamics and relativistic effects, and exhibit strong energy and angular variation in the neighborhood of Cooper minima. Work supported by DOE, Office of Chemical Sciences and DST (India).

  20. Angular dependence of phonon transmission through a Fibonacci superlattice

    NASA Astrophysics Data System (ADS)

    Hurley, D. C.; Tamura, S.; Wolfe, J. P.; Ploog, K.; Nagle, J.

    1988-05-01

    Phonon imaging is employed to examine the propagation of acoustic phonons through a Fibonacci superlattice. Ballistic transmission of phonons with ν>850 GHz through 750 superlattice interfaces is detected. In addition, sharp variations in the phonon intensity with propagation angle are observed. These measurements are consistent with Monte Carlo simulations presented in this paper. Distinct stop bands are expected theoretically, and the angular dependence of these structures is remarkably similar to those predicted for a periodic superlattice.

  1. Angular Momentum Dependent Orbital Free Density Functional Theory

    NASA Astrophysics Data System (ADS)

    Ke, Youqi; Libisch, Florian; Xia, Junchao; Wang, Lin-Wang; Carter, Emily A.

    2013-03-01

    We report a novel and general formalism for linear scaling, angular momentum dependent (AMD) orbital free (OF) density functional theory (DFT) to advance the accuracy and applicability of OFDFT. To introduce angular momentum dependence in OFDFT, we devise a hybrid scheme by partitioning the system into muffin-tin spheres and an interstitial region: the electron density inside the spheres is expressed by a set of Kohn-Sham (KS) DFT derived atom-centered basis functions combined with an on-site density matrix NR. A general OFDFT total energy functional is introduced with a crucial nonlocal energy term ENL which is neglected in conventional implementations of OFDFT. ENL corrects the errors due to the use of approximate kinetic energy density functionals and local pseudopotentials for ion-electron interactions. We approximate ENL to include AMD contributions inside the spheres: as a first step, a linear dependence on the NR is considered with a set of AMD energies ERl.ERlare determined by fitting a small set of bulk properties to KSDFT. We find AMD-OFDFT offers substantial improvements over conventional OFDFT, as we show for various properties of the transition metal Ti and its alloys (TixAl1-x) .

  2. Engineering of angular dependence of high-contrast grating mirror for transverse mode control of VCSELs

    NASA Astrophysics Data System (ADS)

    Koyama, Fumio

    2014-02-01

    We present our recent activity on highly angular-dependent high contrast grating (HCG) for the transverse mode control of VCSELs. The modeling and the experiment show the design flexibility of HCG to manage the angular dependence of HCG. The optimized angular dependent HCG functions as a spatial frequency filter. We are able to use the engineered angular dependence of HCG for the transverse-mode control of VCSELs by filtering out high-order transverse-modes. We fabricated and characterized amorphous Si HCG mirrors, which clearly show the large angular dependence. We demonstrated single-mode 980nm VCSELs with a HCG mirror functioning as a spatial frequency filter.

  3. Angular dependence models for radiance to flux conversion

    NASA Technical Reports Server (NTRS)

    Green, Richard N.; Suttles, John T.; Wielicki, Bruce A.

    1990-01-01

    Angular dependence models (ADM) used for converting the measured radiance to flux at the top of the atmosphere are reviewed, and emphasis is placed on the measure of their effectiveness and the implications of requiring the ADMs to satisfy reciprocity. The overall significance of the ADMs is figured out by analyzing the same satellite data with a single Lambertian model, single mean model, and the 12 Earth Radiation Budget Experiment (ERBE) ADMs. It is shown that the Lambertian ADM is inadequate, while the mean ADM results in nearly unbiased fluxes but creates substantial differences for individual pixel fluxes. The standard ERBE ADM works well except for a 10-pct to 15-pct albedo growth across the scan; a modified ADM based on the standard ERBE ADM but forced to satisfy the principle of reciprocity increases the limb brightening and reduces the albedo growth but does not improve the scanner and nonscanner intercomparison.

  4. Angular dependence of the coercivity in arrays of ferromagnetic nanowires

    NASA Astrophysics Data System (ADS)

    Holanda, J.; Silva, D. B. O.; Padrón-Hernández, E.

    2015-03-01

    We present a new magnetic model for polycrystalline nanowires arrays in porous anodic aluminum oxide. The principal consideration here is the crystalline structure and the morphology of the wires and them the dipolar interactions between the crystals into the wire. Other aspect here is the direct calculation of the dipolar energy for the interaction of one wire with the others in the array. The free energy density was formulated for polycrystalline nanowires arrays in order to determinate the anisotropy effective field. It was using the microstructure study by scanning and transmission electron microscopy for the estimation of the real structure of the wires. After the structural analysis we used the angular dependences for the coercivity field and for the remnant magnetization to determine the properties of the wires. All analysis were made by the theory treatment proposed by Stoner and Wohlfarth.

  5. Angular Dependence of Quantum Oscillations in SmB6

    NASA Astrophysics Data System (ADS)

    Hartstein, M.; Tan, B. S.; Hsu, Y.-T.; Zeng, B.; Ciomaga Hatnean, M.; Harrison, N.; Zhu, Z.; Kiourlappou, M.; Srivastava, A.; Johannes, M. D.; Murphy, T. P.; Park, J.-H.; Balicas, L.; Shitsevalova, N.; Lonzarich, G. G.; Balakrishnan, G.; Sebastian, S. E.

    Recent proposals of low-dimensional electronic states in the Kondo insulator, SmB6 have lead to renewed interest in the material. In this study we present quantum oscillation measurements of high quality single-crystals of SmB6. Magnetic torque was measured in magnetic fields up to 40 T, allowing the observation of quantum oscillation frequencies ranging from 50 T to 15,000 T in multiple samples prepared by different groups. The size and the angular dependence of the oscillations indicate the striking concurrence of an electronically insulating bulk and a large, bulk Fermi surface. Comparison of the measured oscillations with similar measurements of metallic rare-earth hexaborides supports such a Fermi surface. Our model, previously employed for the metallic hexaborides, describes large ellipsoidally distorted spheres centred at X-points of the Brillouin zone, and smaller ellipsoids positioned at neck points, and gives a good account of the observed frequencies.

  6. Angular dependence models for radiance to flux conversion

    NASA Technical Reports Server (NTRS)

    Green, Richard N.; Suttles, John T.; Wielicki, Bruce A.

    1990-01-01

    Angular dependence models (ADM) used for converting the measured radiance to flux at the top of the atmosphere are reviewed, and emphasis is placed on the measure of their effectiveness and the implications of requiring the ADMs to satisfy reciprocity. The overall significance of the ADMs is figured out by analyzing the same satellite data with a single Lambertian model, single mean model, and the 12 Earth Radiation Budget Experiment (ERBE) ADMs. It is shown that the Lambertian ADM is inadequate, while the mean ADM results in nearly unbiased fluxes but creates substantial differences for individual pixel fluxes. The standard ERBE ADM works well except for a 10-pct to 15-pct albedo growth across the scan; a modified ADM based on the standard ERBE ADM but forced to satisfy the principle of reciprocity increases the limb brightening and reduces the albedo growth but does not improve the scanner and nonscanner intercomparison.

  7. Angular dependence of photoemission time delay in helium

    NASA Astrophysics Data System (ADS)

    Heuser, Sebastian; Jiménez Galán, Álvaro; Cirelli, Claudio; Marante, Carlos; Sabbar, Mazyar; Boge, Robert; Lucchini, Matteo; Gallmann, Lukas; Ivanov, Igor; Kheifets, Anatoli S.; Dahlström, J. Marcus; Lindroth, Eva; Argenti, Luca; Martín, Fernando; Keller, Ursula

    2016-12-01

    Time delays of electrons emitted from an isotropic initial state with the absorption of a single photon and leaving behind an isotropic ion are angle independent. Using an interferometric method involving XUV attosecond pulse trains and an IR-probe field in combination with a detection scheme, which allows for full three-dimensional momentum resolution, we show that measured time delays between electrons liberated from the 1 s2 spherically symmetric ground state of helium depend on the emission direction of the electrons relative to the common linear polarization axis of the ionizing XUV light and the IR-probing field. Such time delay anisotropy, for which we measure values as large as 60 as, is caused by the interplay between final quantum states with different symmetry and arises naturally whenever the photoionization process involves the exchange of more than one photon. With the support of accurate theoretical models, the angular dependence of the time delay is attributed to small phase differences that are induced in the laser-driven continuum transitions to the final states. Since most measurement techniques tracing attosecond electron dynamics involve the exchange of at least two photons, this is a general and significant effect that must be taken into account in all measurements of time delays involving photoionization processes.

  8. Energy dependence and angular dependence of an optically stimulated luminescence dosimeter in the mammography energy range.

    PubMed

    Kawaguchi, Ai; Matsunaga, Yuta; Suzuki, Shoichi; Chida, Koichi

    2017-03-01

    This study aimed to investigate the energy dependence and the angular dependence of commercially available optically stimulated luminescence (OSL) point dosimeters in the mammography energy range. The energy dependence was evaluated to calculate calibration factors (CFs). The half-value layer range was 0.31-0.60 mmAl (Mo/Mo 22-28 kV, Mo/Rh 28-32 kV, and W/Rh 30-34 kV at 2-kV intervals). Mo/Rh 28 kV was the reference condition. Angular dependence was tested by rotating the X-ray tube from -90° to 90° in 30° increments, and signal counts from angled nanoDots were normalized to the 0° signal counts. Angular dependence was compared with three tube voltage and target/filter combinations (Mo/Mo 26 kV, Mo/Rh 28 kV and W/Rh 32 kV). The CFs of energy dependence were 0.94-1.06. In Mo/Mo 26-28 kV and Mo/Rh 28-32 kV, the range of CF was 0.99-1.01, which was very similar. For angular dependence, the most deteriorated normalized values (Mo/Mo, 0.37; Mo/Rh, 0.43; and W/Rh, 0.58) were observed when the X-ray tube was rotated at a 90° angle, compared to 0°. The most angular dependences of ± 30°, 60°, and 90° decreased by approximately 4%, 14%, and 63% respectively. The mean deteriorated measurement 30° intervals from 0° to ± 30° was 2%, from ± 30° to ± 60° was 8%, and from ± 60° to ± 90° was 40%. The range of energy dependence in typical mammography energy range was not as much as that in general radiography and computed tomography. For accurate measurement using nanoDot, the tilt needs to be under 30°.

  9. Technical Note: Ion chamber angular dependence in a magnetic field.

    PubMed

    Reynolds, Michael; Rathee, Satyapal; Fallone, B Gino

    2017-08-01

    There have been several studies investigating dose deposition effects within radiation detectors in the presence of a magnetic field. However, to date there has only been a passing investigation which explicitly investigates detector dose-response as a function of detector orientation. Herein we will investigate the dose-response as a function angular orientation of a PR06C ionization chamber. We will also benchmark the Monte Carlo code PENELOPE with the newly developed magnetic field Fano test. The PENELOPE Monte Carlo package was used to simulate a PR06C ionization chamber in 0.35 T through 1.5 T magnetic fields oriented either parallel or orthogonal to an incident 6 MV radiation beam. The ionization chamber was rotated through a number of polar and azimuthal angles. The dose deposited within the chamber at each angular position and magnetic field strength was scored then normalized to that deposited in the same orientation with no magnetic field. The simulation was also benchmarked via a Fano test in magnetic field. The Fano test yielded a 0.4% difference between simulation and expected result, which is similar to previous findings and sufficient for the purposes of this study. The angular dose-response map in all cases where the magnetic field is oriented orthogonal to the radiation beam is quite varied and can range from 0.89 to 1.08. Angular deviations as small as 3° can lead to dose-response changes in excess of 1%. When the magnetic field is parallel to the photon beam, the angular dose-response map is homogeneous and less than 1% below 1.0 T. Within a magnetic field-oriented orthogonal to the radiation beam, the ionization chamber dose-response fluctuates greatly as a function of polar and azimuthal angle, where a parallel field yields a more homogeneous dose-response. © 2017 American Association of Physicists in Medicine.

  10. Laser-polarization-dependent photoelectron angular distributions from polar molecules.

    PubMed

    Zhu, Xiaosong; Zhang, Qingbin; Hong, Weiyi; Lu, Peixiang; Xu, Zhizhan

    2011-11-21

    Photoelectron angular distributions (PADs) of oriented polar molecules in response to different polarized lasers are systematically investigated. It is found that the PADs of polar CO molecules show three distinct styles excited by linearly, elliptically and circularly polarized lasers respectively. In the case of elliptical polarization, a deep suppression is observed along the major axis and the distribution concentrates approximately along the minor axis. Additionally, it is also found that the concentrated distributions rotate clockwise as the ellipticity increases. Our investigation presents a method to manipulate the motion and angular distribution of photoelectrons by varying the polarization of the exciting pulses, and also implies the possibility to control the processes in laser-molecule interactions in future work.

  11. Depth and latitude dependence of the solar internal angular velocity

    SciTech Connect

    Rhodes, E.J. Jr.; Cacciani, A.; Korzennik, S.; Tomczyk, S.; Ulrich, R.K.; Woodard, M.F. JPL, Pasadena, CA Roma I Universita California Univ., Los Angeles )

    1990-03-01

    One of the design goals for the dedicated helioseismology observing state located at Mount Wilson Observatory was the measurement of the internal solar rotation using solar p-mode oscillations. In this paper, the first p-mode splittings obtained from Mount Wilson are reported and compared with those from several previously published studies. It is demonstrated that the present splittings agree quite well with composite frequency splittings obtained from the comparisons. The splittings suggest that the angular velocity in the solar equatorial plane is a function of depth below the photosphere. The latitudinal differential rotation pattern visible at the surface appears to persist at least throughout the solar convection zone. 43 refs.

  12. Depth and latitude dependence of the solar internal angular velocity

    NASA Technical Reports Server (NTRS)

    Rhodes, Edward J., Jr.; Cacciani, Alessandro; Korzennik, Sylvain; Tomczyk, Steven; Ulrich, Roger K.; Woodard, Martin F.

    1990-01-01

    One of the design goals for the dedicated helioseismology observing state located at Mount Wilson Observatory was the measurement of the internal solar rotation using solar p-mode oscillations. In this paper, the first p-mode splittings obtained from Mount Wilson are reported and compared with those from several previously published studies. It is demonstrated that the present splittings agree quite well with composite frequency splittings obtained from the comparisons. The splittings suggest that the angular velocity in the solar equatorial plane is a function of depth below the photosphere. The latitudinal differential rotation pattern visible at the surface appears to persist at least throughout the solar convection zone.

  13. Angular dependent study on ferromagnetic resonance and spin excitations by spin rectification

    SciTech Connect

    Zhang, Yichao; Fan, Xiaolong Zhao, Xiaobing; Rao, Jinwei; Zhou, Hengan; Guo, Dangwei; Xue, Desheng; Gui, Y. S.; Hu, C.-M.

    2015-01-14

    We report angular dependent spin rectification spectra which are applied to studying spin excitations in single permalloy stripe. Based on planar Hall effect, those spin excitations generate special resonant dc Hall voltages, which have been characterized as functions of the amplitude and direction of applied magnetic field. Through high angular resolution 2D mappings, the evolutions of different spin excitation can be directly presented, and the dynamic magnetic parameters such as the gyromagnetic ratio, effective exchange field, as well as the quantized numbers of standing spin waves can be accurately determined through fitting the angular evolution of each resonance.

  14. Angular dependence of light trapping in nanophotonic thin-film solar cells.

    PubMed

    Smeets, Michael; Smirnov, Vladimir; Bittkau, Karsten; Meier, Matthias; Carius, Reinhard; Rau, Uwe; Paetzold, Ulrich W

    2015-11-30

    The angular dependence of light-trapping in nanophotonic thin-film solar cells is inherent due to the wavelength-scale dimensions of the periodic nanopatterns. In this paper, we experimentally investigate the dependence of light coupling to waveguide modes for light trapping in a-Si:H solar cells deposited on nanopatterned back contacts. First, we accurately determine the spectral positions of individual waveguide modes in thin-film solar cells in external quantum efficiency and absorptance. Second, we demonstrate the strong angular dependence of this spectral position for our solar cells. Third, a moderate level of disorder is introduced to the initially periodic nanopattern of the back contacts. As a result, the angular dependence is reduced. Last, we experimentally compare this dependence on the angle of incidence for randomly textured, 2D periodically nanopatterned and 2D disordered back contacts in external quantum efficiency and short-circuit current density.

  15. Higher order treatment on temporal derivative of angular flux for time-dependent MOC

    SciTech Connect

    Tsujita, K.; Endo, T.; Yamamoto, A.; Kamiyama, Y.; Kirimura, K.

    2013-07-01

    A new kinetic analysis method, whose angular dependence of temporal derivative for angular flux is accurately treated within practical memory requirement, is proposed. The method of characteristics (MOC) is being widely used for reactor analysis thanks to the advances of numerical algorithms and computer hardware. However, the computational resources, i.e., the memory capacity, can be still a crucial problem for rigorous kinetic calculations using MOC. In the straightforward approach for kinetic calculation using MOC, the segment-averaged angular fluxes should be stored on the memory in order to explicitly calculate the temporal derivative of the angular flux, which would require huge memory. Thus, in the conventional kinetic calculation code using MOC, the temporal derivative of the angular flux has been approximated as angularly isotropic in order to reduce the memory requirement (isotropic assumption). However, the approximation error caused by the conventional isotropic assumption has not been thoroughly and quantitatively investigated so far and an accurate kinetic calculation method, which can quantitatively estimate the above approximation error within practical memory storage, has not been developed. The present study tries to address this issue with a newly developed approach. Effect of the approximate treatment for the temporal derivative of angular flux is evaluated through benchmark calculations. (authors)

  16. Generalization of Equivalent Crystal Theory to Include Angular Dependence

    NASA Technical Reports Server (NTRS)

    Ferrante, John; Zypman, Fredy R.

    2004-01-01

    In the original Equivalent Crystal Theory, each atomic site in the real crystal is assigned an equivalent lattice constant, in general different from the ground state one. This parameter corresponds to a local compression or expansion of the lattice. The basic method considers these volumetric transformations and, in addition, introduces the possibility that the reference lattice is anisotropically distorted. These distortions however, were introduced ad-hoc. In this work, we generalize the original Equivalent Crystal Theory by systematically introducing site-dependent directional distortions of the lattice, whose corresponding distortions account for the dependence of the energy on anisotropic local density variations. This is done in the spirit of the original framework, but including a gradient term in the density. This approach is introduced to correct a deficiency in the original Equivalent Crystal Theory and other semiempirical methods in quantitatively obtaining the correct ratios of the surface energies of low index planes of cubic metals (100), (110), and (111). We develop here the basic framework, and apply it to the calculation of Fe (110) and Fe (111) surface energy formation. The results, compared with first principles calculations, show an improvement over previous semiempirical approaches.

  17. The angular dependence of a two dimensional monolithic detector array for dosimetry in small radiation fields

    NASA Astrophysics Data System (ADS)

    Stansook, N.; Petasecca, M.; Utitsarn, K.; Newall, M.; Metcalfe, P.; Carolan, M.; Lerch, M.; Rosenfeld, A. B.

    2017-01-01

    The purpose of this study is to investigate the directional dependence of a two dimensional monolithic detector array (M512) under 6 MV photon irradiation and to evaluate the effect of field size on angular dependence. Square fields of sizes: 3x3 cm2 and 10x10 cm2 were measured at the iso-centre of a cylindrical phantom. Beam angles with incidences from 00- 1800 in increments of 150 were used to investigate the central pixel angular response of M512, normalized to the pixel response for normal (0°) beam incidence. The angular response of the detector was compared to the response of EBT3 radiochromic film in the identical geometric orientation. The maximum angular dependence was observed at the angle 90°±15° to be -18.62% and -17.70% for the field sizes 3x3 cm2 and 10x10 cm2, respectively. The angular dependence of M512 showed no significant difference between field sizes of 3x3 cm2 and 10x10 cm2 (p>0.05). The maximum dose difference measured by the central pixel of M512 and EBT3 for all angles are -20% for 3x3 cm2 field size and -18.58% for the 10x10 cm2 field. The diode array’s size and packaging effects the angular response of the detector. The angular correction factor is necessary to apply to increase accuracy in dosimetry for arc treatment delivery.

  18. Angular dependence of giant Zeeman effect for semimagnetic cavity polaritons

    NASA Astrophysics Data System (ADS)

    Mirek, R.; Król, M.; Lekenta, K.; Rousset, J.-G.; Nawrocki, M.; Kulczykowski, M.; Matuszewski, M.; Szczytko, J.; Pacuski, W.; Pietka, B.

    2017-02-01

    The observation of spin-related phenomena of microcavity polaritons has been limited due to the weak Zeeman effect of nonmagnetic semiconductors. We demonstrate that the incorporation of magnetic ions into quantum wells placed in a nonmagnetic microcavity results in enhanced effects of magnetic field on exciton-polaritons. We show that in such a structure the Zeeman splitting of exciton-polaritons strongly depends on the photon-exciton detuning and polariton wave vector. Our experimental data are explained by a model where the impact of magnetic field on the lower polariton state is directly inherited from the excitonic component, and the coupling strength to the cavity photon is modified by an external magnetic field.

  19. Energy and angular dependence of active-type personal dosemeter for high-energy neutron.

    PubMed

    Rito, Hirotaka; Yamauchi, Tomoya; Oda, Keiji

    2011-07-01

    In order to develop an active-type personal dosemeter having suitable sensitivity to high-energy neutrons, the characteristic response of silicon surface barrier detector has been investigated experimentally and theoretically. An agreement of the shape of pulse-height distribution, its change with radiator thickness and the relative sensitivity was confirmed between the calculated and experimental results for 14.8-MeV neutrons. The angular dependence was estimated for other neutron energies, and found that the angular dependence decreased with the incident energy. The reason was also discussed with regard to the radiator thickness relative to maximum range of recoil protons.

  20. An angular frequency dependence on the Aharonov–Casher geometric phase

    SciTech Connect

    Barboza, P.M.T.; Bakke, K.

    2015-10-15

    A quantum effect characterized by a dependence of the angular frequency associated with the confinement of a neutral particle to a quantum ring on the quantum numbers of the system and the Aharonov–Casher geometric phase is discussed. Then, it is shown that persistent spin currents can arise in a two-dimensional quantum ring in the presence of a Coulomb-type potential. A particular contribution to the persistent spin currents arises from the dependence of the angular frequency on the geometric quantum phase.

  1. Angular dependence of circular magnetic x-ray dichroism in rare-earth compounds

    SciTech Connect

    Lang, J.C.; Wang, X.; Harmon, B.N.; Goldman, A.I. ); Dennis, K.W.; McCallum, R.W. ); Finkelstein, K.D. )

    1994-11-01

    The angular dependence of the circular magnetic x-ray dichroism (CMXD) at the [ital L][sub 2] and [ital L][sub 3] edges of grain-oriented [ital R]Fe[sub 2] compounds has been studied to ascertain the multipolar nature of the features above and below the absorption edge. Within experimental error, all features in the CMXD spectra are consistent with dipole transitions between 2[ital p] core levels and the unoccupied spin-polarized states. We discuss some possible reasons for the apparent absence of the predicted quadrupolar angular dependence of the features below [ital E][sub [ital f

  2. Angular momentum dependence of the nuclear level density in the A ≈170 -200 region

    NASA Astrophysics Data System (ADS)

    Gohil, M.; Roy, Pratap; Banerjee, K.; Bhattacharya, C.; Kundu, S.; Rana, T. K.; Ghosh, T. K.; Mukherjee, G.; Pandey, R.; Pai, H.; Srivastava, V.; Meena, J. K.; Banerjee, S. R.; Mukhopadhyay, S.; Pandit, D.; Pal, S.; Bhattacharya, S.

    2015-01-01

    Neutron evaporation spectra along with γ multiplicity has been measured from 201Tl*,185Re*, and 169Tm* compound nuclei at the excitation energies of ˜27 and 37 MeV. Statistical model analysis of the experimental data has been carried out to extract the value of the inverse level density parameter k at different angular-momentum (J ) regions corresponding to different γ multiplicities. It is observed that, for the present systems the value of k remains almost constant for different J . The present results for the angular-momentum dependence of the nuclear level density (NLD) parameter a ˜(=A /k ) , for nuclei with A ˜180 are quite different from those obtained in earlier measurements in the case of light- and medium-mass systems. The present study provides useful information to understand the angular-momentum dependence of the NLD at different nuclear mass regions.

  3. Angular and positional dependence of Purcell effect for layered metal-dielectric structures

    NASA Astrophysics Data System (ADS)

    Gubaydullin, A. R.; Mazlin, V. A.; Ivanov, K. A.; Kaliteevski, M. A.; Balocco, C.

    2016-04-01

    We study the angular dependence of the spontaneous emission enhancement of a dipole source inserted into a layered metal-dielectric metamaterial. We analyse the dependence of Purcell effect from the position of the dipole in the layered hyperbolic media. We analyse the impact of the complex structure of eigenmodes of the system operating in hyperbolic regime. We have shown that the spontaneous emission rate of the dipole emitter depends on its position, which mainly affect the interaction with Langmuir modes.

  4. Angular dependent FORC and FMR of exchange-biased NiFe multilayer films

    NASA Astrophysics Data System (ADS)

    Gallardo, R. A.; Khanal, S.; Vargas, J. M.; Spinu, L.; Ross, C. A.; Garcia, C.

    2017-02-01

    Dynamic ferromagnetic resonance (FMR, X-band 9.8 GHz) and static first-order reversal curve (FORC) techniques are combined to study the intrinsic exchange-bias distribution via measurements of in-plane angular variation in (FeNi/IrMn)n multilayers. The angular dependence of the exchange bias field was qualitatively and quantitatively investigated using both methods, which are sensitive to different couplings between the ferromagnetic layers. We have used the analysis of the angular dependence of first-order reversal curve (AFORC) data, extracted from FORC curves measured from {{0}\\circ} up to {{360}\\circ} in {{10}\\circ} steps. In addition, its counterpart angular dependence of FMR (AFMR) measurements were carried out and correlated with the AFORC results. The AFORC proved to be useful for simultaneously studying the magnetization reversal processes and magnetic interactions between the layers of the (FeNi/IrMn)n. These interactions are related to the structure and interfaces in the (FeNi/IrMn), and the results obtained by AFMR and AFORC are contrasted with a modified theoretical model for domain-wall formation.

  5. Angular dependence of coercivity with temperature in Co-based nanowires

    NASA Astrophysics Data System (ADS)

    Bran, C.; Espejo, A. P.; Palmero, E. M.; Escrig, J.; Vázquez, M.

    2015-12-01

    The magnetic behavior of arrays of Co and CoFe nanowire arrays has been measured in the temperature range between 100 and 300 K. We have paid particular attention to the angular dependence of magnetic properties on the applied magnetic field orientation. The experimental angular dependence of coercivity has been modeled according to micromagnetic analytical calculations, and we found that the propagation of a transversal domain wall mode gives the best fitting with experimental observations. That reversal mode holds in the whole measuring temperature range, for nanowires with different diameters and crystalline structure. Moreover, the quantitative strength of the magnetocrystalline anisotropy and its magnetization easy axis are determined to depend on the crystalline structure and nanowires diameter. The evolution of the magnetocrystalline anisotropy with temperature for nanowires with different composition gives rise to an opposite evolution of coercivity with increasing temperature: it decreases for CoFe while it increases for Co nanowire arrays.

  6. Instability in the dense supernova neutrino gas with flavor-dependent angular distributions.

    PubMed

    Mirizzi, Alessandro; Serpico, Pasquale Dario

    2012-06-08

    The usual description of self-induced flavor conversions for neutrinos (ν's) in supernovae is based on the simplified assumption that all the ν's of the different species are emitted "half-isotropically" by a common neutrinosphere, in analogy to a blackbody emission. However, realistic supernova simulations show that ν angular distributions at decoupling are far from being half-isotropic and, above all, are flavor dependent. We show that flavor-dependent angular distributions may lead to crossing points in the angular spectra of different ν species (where F(ν(e))=F(ν(x)) and F(ν(e))=F(ν(x))) around which a new multiangle instability can develop. To characterize this effect, we carry out a linearized flavor stability analysis for different supernova neutrino angular distributions. We find that this instability can shift the onset of the flavor conversions toward low radii and produce a smearing of the splitting features found with trivial ν emission models. As a result the spectral differences among ν's of different flavors could be strongly reduced.

  7. Angular-dependent Raman study of a- and s-plane InN

    NASA Astrophysics Data System (ADS)

    Filintoglou, K.; Katsikini, M.; Arvanitidis, J.; Christofilos, D.; Lotsari, A.; Dimitrakopulos, G. P.; Vouroutzis, N.; Ajagunna, A. O.; Georgakilas, A.; Zoumakis, N.; Kourouklis, G. A.; Ves, S.

    2015-02-01

    Angular-dependent polarized Raman spectroscopy was utilized to study nonpolar a-plane ( 1 1 ¯ 20 ) and semipolar s-plane ( 10 1 ¯ 1 ) InN epilayers. The intensity dependence of the Raman peaks assigned to the vibrational modes A1(TO), E1(TO), and E2 h on the angle ψ that corresponds to rotation around the growth axis, is very well reproduced by using expressions taking into account the corresponding Raman tensors and the experimental geometry, providing thus a reliable technique towards assessing the sample quality. The s- and a-plane InN epilayers grown on nitridated r-plane sapphire (Al2O3) exhibit good crystalline quality as deduced from the excellent fitting of the experimental angle-dependent peak intensities to the theoretical expressions as well as from the small width of the Raman peaks. On the contrary, in the case of the s-plane epilayer grown on non-nitridated r-plane sapphire, fitting of the angular dependence is much worse and can be modeled only by considering the presence of two structural modifications, rotated so as their c-axes are almost perpendicular to each other. Although the presence of the second variant is verified by transmission electron and atomic force microscopies, angular dependent Raman spectroscopy offers a non-destructive and quick way for its quantification. Rapid thermal annealing of this sample did not affect the angular dependence of the peak intensities. The shift of the E1(TO) and E2 h Raman peaks was used for the estimation of the strain state of the samples.

  8. Angular-dependent Raman study of a- and s-plane InN

    SciTech Connect

    Filintoglou, K.; Katsikini, M. Arvanitidis, J.; Lotsari, A.; Dimitrakopulos, G. P.; Vouroutzis, N.; Ves, S.; Christofilos, D.; Kourouklis, G. A.; Ajagunna, A. O.; Georgakilas, A.; Zoumakis, N.

    2015-02-21

    Angular-dependent polarized Raman spectroscopy was utilized to study nonpolar a-plane (11{sup ¯}20) and semipolar s-plane (101{sup ¯}1) InN epilayers. The intensity dependence of the Raman peaks assigned to the vibrational modes A{sub 1}(TO), E{sub 1}(TO), and E{sub 2}{sup h} on the angle ψ that corresponds to rotation around the growth axis, is very well reproduced by using expressions taking into account the corresponding Raman tensors and the experimental geometry, providing thus a reliable technique towards assessing the sample quality. The s- and a-plane InN epilayers grown on nitridated r-plane sapphire (Al{sub 2}O{sub 3}) exhibit good crystalline quality as deduced from the excellent fitting of the experimental angle-dependent peak intensities to the theoretical expressions as well as from the small width of the Raman peaks. On the contrary, in the case of the s-plane epilayer grown on non-nitridated r-plane sapphire, fitting of the angular dependence is much worse and can be modeled only by considering the presence of two structural modifications, rotated so as their c-axes are almost perpendicular to each other. Although the presence of the second variant is verified by transmission electron and atomic force microscopies, angular dependent Raman spectroscopy offers a non-destructive and quick way for its quantification. Rapid thermal annealing of this sample did not affect the angular dependence of the peak intensities. The shift of the E{sub 1}(TO) and E{sub 2}{sup h} Raman peaks was used for the estimation of the strain state of the samples.

  9. NEXAFS Chemical State and Bond Lengths of p-Aminobenzoic Acid in Solution and Solid State

    NASA Astrophysics Data System (ADS)

    Stevens, J. S.; Gainar, A.; Suljoti, E.; Xiao, J.; Golnak, R.; Aziz, E. F.; Schroeder, S. L. M.

    2016-05-01

    Solid-state and solution pH-dependent NEXAFS studies allow direct observation of the electronic state of para-aminobenzoic acid (PABA) as a function of its chemical environment, revealing the chemical state and bonding of the chemical species. Variations in the ionization potential (IP) and 1s→π* resonances unequivocally identify the chemical species (neutral, cationic, or anionic) present and the varying local environment. Shifts in σ* shape resonances relative to the IP in the NEXAFS spectra vary with C-N bond length, and the important effect of minor alterations in bond length is confirmed with nitrogen FEFF calculations, leading to the possibility of bond length determination in solution.

  10. SU-E-T-472: Improvement of IMRT QA Passing Rate by Correcting Angular Dependence of MatriXX

    SciTech Connect

    Chen, Q; Watkins, W; Kim, T; Neal, B

    2015-06-15

    Purpose: Multi-channel planar detector arrays utilized for IMRT-QA, such as the MatriXX, exhibit an incident-beam angular dependent response which can Result in false-positive gamma-based QA results, especially for helical tomotherapy plans which encompass the full range of beam angles. Although MatriXX can use with gantry angle sensor to provide automatically angular correction, this sensor does not work with tomotherapy. The purpose of the study is to reduce IMRT-QA false-positives by correcting for the MatriXX angular dependence. Methods: MatriXX angular dependence was characterized by comparing multiple fixed-angle irradiation measurements with corresponding TPS computed doses. For 81 Tomo-helical IMRT-QA measurements, two different correction schemes were tested: (1) A Monte-Carlo dose engine was used to compute MatriXX signal based on the angular-response curve. The computed signal was then compared with measurement. (2) Uncorrected computed signal was compared with measurements uniformly scaled to account for the average angular dependence. Three scaling factor (+2%, +2.5%, +3%) were tested. Results: The MatriXX response is 8% less than predicted for a PA beam even when the couch is fully accounted for. Without angular correction, only 67% of the cases pass the >90% points γ<1 (3%, 3mm). After full angular correction, 96% of the cases pass the criteria. Of three scaling factors, +2% gave the highest passing rate (89%), which is still less than the full angular correction method. With a stricter γ(2%,3mm) criteria, the full angular correction method was still able to achieve the 90% passing rate while the scaling method only gives 53% passing rate. Conclusion: Correction for the MatriXX angular dependence reduced the false-positives rate of our IMRT-QA process. It is necessary to correct for the angular dependence to achieve the IMRT passing criteria specified in TG129.

  11. Time-dependent treatment of electron-hydrogen scattering for higher angular momenta (L>0)

    NASA Astrophysics Data System (ADS)

    Odero, D. O.; Peacher, J. L.; Schultz, D. R.; Madison, D. H.

    2001-02-01

    The time-dependent approach to electron-atom scattering is emerging as an alternative to more conventional methods of treating atomic collisions. Solving the time-dependent Schrödinger equation directly has several very attractive features including a completely nonperturbative solution, dense representation of the nonphysical positive energy states, circumvention of the need to explicitly impose boundary conditions for ionization, and the convenience of being able to ``watch'' the electronic probability density evolve though the collision. Two principal approaches have so far been applied to treat electron-atom scattering, namely, the time-dependent close couping (TDCC) method and what we refer to as the time-dependent Hylleraas (TDH) method. The TDCC method solves coupled equations with two variables within a truncated infinite sum over individual angular momenta for each total angular momentum L of the system. In contrast, the TDH method avoids an infinite summation over the angular momenta of the individual electrons at the expense of solving a coupled equation with three variables for each L. The TDH method has previously been used for L=0 only. An important question, therefore, concerns whether the TDH method would represent a numerical advantage over the TDCC method for higher L values. This issue is investigated in this paper.

  12. Angular dependence of ferromagnetic resonance and magnetization configuration of thin film Permalloy nanoellipse arrays

    NASA Astrophysics Data System (ADS)

    Pardavi-Horvath, M.; Ng, B. G.; Castaño, F. J.; Körner, H. S.; Garcia, C.; Ross, C. A.

    2011-09-01

    In-plane and out-of-plane angular dependence of ferromagnetic resonance (FMR) and magnetization measurements were performed on arrays of 20, 40, and 60 nm thick, 520 nm long, and 250 nm wide elliptical Permalloy elements. Besides the main FMR "volume" mode resonance, a well-defined second FMR mode was observed, which exhibits a very strong angular dependence. This mode originates from localized regions where the magnetization has a strong component perpendicular to the bias field and to the volume magnetization. These regions of nonuniform magnetization may be associated with magnetization canting at the edges of the ellipses, due to the nonuniformity of the demagnetizing tensor elements, and with magnetization vortices, which are predicted by micromagnetic simulation.

  13. Angular dependence of exchange bias and magnetization reversal controlled by electric-field-induced competing anisotropies

    NASA Astrophysics Data System (ADS)

    Zhao, Yonggang; Chen, Aitian; Li, Peisen; Zhang, Xu; Peng, Renci; Huang, Haoliang; Zou, Lvkuan; Zheng, Xiaoli; Zhang, Sen; Miao, Peixian; Lu, Yalin; Cai, Jian; Nan, Ce-Wen

    Combination of exchange-biased systems and FE materials gives a new avenue to study angular dependence of exchange bias and achieve reversible electric-field-controlled magnetization reversal. We study the angular dependence of electric-field-controlled exchange bias and magnetization reversal in CoFeB/IrMn/Pb(Mg1/3Nb2/3)0.7 Ti0.3O3. It is demonstrated that the ratio of the exchange-coupled unidirectional anisotropy and the uniaxial anisotropy of the FM layer, as well as their relative orientation can be dramatically and continuously tuned via electric fields. Simulations confirm that the electric-field-controlled exchange bias originates from the competition between the uniaxial anisotropy induced by the piezostrain and the exchange-coupled unidirectional anisotropy. Moreover, electric-field-controlled magnetization reversal was realized at zero magnetic field.

  14. Angular dependent ferromagnetic resonance analysis in a single micron sized cobalt stripe

    NASA Astrophysics Data System (ADS)

    Schoeppner, C.; Wagner, K.; Stienen, S.; Meckenstock, R.; Farle, M.; Narkowicz, R.; Suter, D.; Lindner, J.

    2014-07-01

    We demonstrate how planar microresonators (PMRs) can be utilized to investigate the angular dependent magnetic resonance response of single magnetic nanostructures. In contrast to alternative detection schemes like electrical or optical detection, the PMR approach provides a classical means of investigating the high frequency dynamics of single magnetic entities, enabling the use of well-established analysis methods of ferromagnetic resonance (FMR) spectroscopy. To demonstrate the performance of the PMR-based FMR setup for angular dependent measurements, we investigate the microwave excited magnons in a single Co stripe of 5 × 1 × 0.02 μm3 and compare the results to micromagnetic simulations. The evolution of excited magnons under rotation of one individual stripe with respect to a static magnetic field is investigated. Besides quasi uniform excitations, we observe magneto-static as well as localized excitations. We find a strong influence of inhomogeneous dynamic and static demagnetizing fields for all modes.

  15. Angular momentum dependence of variational transition states for selected association reactions

    NASA Astrophysics Data System (ADS)

    Aubanel, Eric E.; Wardlaw, David M.

    1990-03-01

    The total angular momentum dependence of variational transition states for several reactions without a potential energy barrier on the minimum energy path is illustrated. High-pressure thermal rate constants for Li ++(CH 3) 2O→Li +(CH 3) 2O and Li ++H 2O→Li +(H 2O) from 200 to 1000 K are obtained from flexible transition-state theory (FTST), with potential functions of Coriongiu, Clementi, Pretsch and Simon and of Clementi and Popkie, respectively. For Li +(H 2O) the canonically determined rate constants are 20-50% higher than the microcanonically determined ones, and for Li +(CH 3) 2O ≈ 55% higher. These differences are attributed to the strong dependence of the transition states on total angular momentum.

  16. Understanding stripe domains in Permalloy films via the angular dependence of permeability spectra

    NASA Astrophysics Data System (ADS)

    Wei, Jinwu; Feng, Hongmei; Zhu, Zengtai; Song, Chengkun; Wang, Xiangqian; Liu, Qingfang; Wang, Jianbo

    2017-06-01

    An investigation of the angular dependence of the dynamic permeability spectra has been performed. Three Permalloy films with different thickness were used as the study samples that possess the stripe domains. In order to better understand the magnetization distribution in stripe domains, a theoretical approach was proposed to analyze the variation of the resonance intensity of permeability spectra. By fitting the angular dependence of the μ″max using a theoretical function, a coefficient Λ that can be used to evaluate the average value of the periodic function of the anting angle θ in a periodic stripe is obtained. As the film thickness increases, the decrease of the ratio between domain wall width and stripe domain width is happen. This enables that the coefficient Λ decreases with the increase of film thickness. By deducing this coefficient Λ, one can estimate the maximum canting angle θ0 ∼ 8° for the Permalloy films in our experiments.

  17. Angular dependence correction of MatriXX and its application to composite dose verification.

    PubMed

    Shimohigashi, Yoshinobu; Araki, Fujio; Tominaga, Hirofumi; Sakata, Junichi; Kawasaki, Keiichi; Kanetake, Nagisa; Iwashita, Yuki; Yoshimura, Saori; Kawakami, Tamami; Ishihara, Terunobu; Okuda, Tomoko; Kogo, Kasei

    2012-09-06

    We measured the angular dependence of central and off-axis detectors in a 2D ionization chamber array, MatriXX, and applied correction factors (CFs) to improve the accuracy of composite dose verification of IMRT and VMAT. The MatriXX doses were measured with a 10° step for gantry angles (θ) of 0°-180°, and a 1° step for lateral angles of 90°-110° in a phantom, with a 30 × 10 cm2 field for 6 MV and 10 MV photons. The MatriXX doses were also calculated under the same conditions by the Monte Carlo (MC) algorithm. The CFs for the angular dependence of MatriXX were obtained as a function of θ from the ratios of MatriXX-measured doses to MC-calculated doses, and normalized at θ = 0°. The corrected MatriXX were validated with different fields, various simple plans, and clinical treatment plans. The dose distributions were compared with those of MC calculations and film. The absolute doses were also compared with ionization chamber and MC-calculated doses. The angular dependence of MatriXX showed over-responses of up to 6% and 4% at θ = 90° and under-responses of up to 15% and 11% at 92°, and 8% and 5% at 180° for 6 MV and 10 MV photons, respectively. At 92°, the CFs for the off-axis detectors were larger by up to 7% and 6% than those for the central detectors for 6 MV and 10 MV photons, respectively, and were within 2.5% at other gantry angles. For simple plans, MatriXX doses with angular correction were within 2% of those measured with the ionization chamber at the central axis and off-axis. For clinical treatment plans, MatriXX with angular correction agreed well with dose distributions calculated by the treatment planning system (TPS) for gamma evaluation at 3% and 3 mm. The angular dependence corrections of MatriXX were useful in improving the measurement accuracy of composite dose verification of IMRT and VMAT.

  18. Polarization-Dependent Measurements of Molecular Super Rotors with Oriented Angular Momenta

    NASA Astrophysics Data System (ADS)

    Murray, Matthew J.; Toro, Carlos; Liu, Qingnan; Mullin, Amy S.

    2014-05-01

    Controlling molecular motion would enable manipulation of energy flow between molecules. Here we have used an optical centrifuge to investigate energy transfer between molecular super rotors with oriented angular momenta. The polarizable electron cloud of the molecules interacts with the electric field of linearly polarized light that angularly accelerates over the time of the optical pulse. This process drives molecules into high angular momentum states that are oriented with the optical field and have energies far from equilibrium. High resolution transient IR spectroscopy reveals the dynamics of collisional energy transfer for these super excited rotors. The results of this study leads to a more fundamental understanding of energy balance in non-equilibrium environments and the physical and chemical properties of gases in a new regime of energy states. Results will be presented for several super rotor species including carbon monoxide, carbon dioxide, and acetylene. Polarization-dependent measurements reveal the extent to which the super rotors maintain spatial orientation of high angular momentum states.

  19. Angular Dependence of Exchange Bias and Magnetization Reversal Controlled by Electric-Field-Induced Competing Anisotropies.

    PubMed

    Chen, Aitian; Zhao, Yonggang; Li, Peisen; Zhang, Xu; Peng, Renci; Huang, Haoliang; Zou, Lvkuan; Zheng, Xiaoli; Zhang, Sen; Miao, Peixian; Lu, Yalin; Cai, Jianwang; Nan, Ce-Wen

    2016-01-13

    The combination of exchange-biased systems and ferroelectric materials offers a simple and effective way to investigate the angular dependence of exchange bias using one sample with electric-field-induced competing anisotropies. A reversible electric-field-controlled magnetization reversal at zero magnetic field is also realized through optimizing the anisotropy configuration, holding promising applications for ultralow power magnetoelectric devices. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Angular dependences of spin-wave resonance spectra of inhomogeneous films with orthorhombic anisotropy

    NASA Astrophysics Data System (ADS)

    Zyuzin, A. M.; Bakulin, M. A.; Radaikin, V. V.; Yantsen, N. V.

    2017-02-01

    Zero spin-wave mode in inhomogeneous magnetic films with orthorhombic anisotropy has been found to exhibit a change of its localization region in two of three typical angular dependences of resonance fields of high-intensity modes. It has been shown that the anisotropy fields on both sides of the film can be determined from the resonance fields of the zero and uppermost high-intensity spin-wave modes of spin-wave resonance spectra.

  1. Angular Dependence of 3 omega o/2 Spectra from Laser-Produced Plasmas

    NASA Astrophysics Data System (ADS)

    Young, P. E.; Moody, J. D.; Rozmus, W.

    1999-08-01

    Scattered light at three-halves of the incident laser frequency from solid targets is observed at five different angles. When the incident laser intensity is low enough, rescattering of two plasmon decay (TPD) instability electron plasma waves by ion acoustic waves is not significant. In this regime, Thomson scattering measurements of the electron temperature and the plasma flow velocity allow quantitative comparison of the angular dependence of the spectrum to theory.

  2. Visual ergonomic aspects of glare on computer displays: glossy screens and angular dependence

    NASA Astrophysics Data System (ADS)

    Brunnström, Kjell; Andrén, Börje; Konstantinides, Zacharias; Nordström, Lukas

    2007-02-01

    Recently flat panel computer displays and notebook computer are designed with a so called glare panel i.e. highly glossy screens, have emerged on the market. The shiny look of the display appeals to the costumers, also there are arguments that the contrast, colour saturation etc improves by using a glare panel. LCD displays suffer often from angular dependent picture quality. This has been even more pronounced by the introduction of Prism Light Guide plates into displays for notebook computers. The TCO label is the leading labelling system for computer displays. Currently about 50% of all computer displays on the market are certified according to the TCO requirements. The requirements are periodically updated to keep up with the technical development and the latest research in e.g. visual ergonomics. The gloss level of the screen and the angular dependence has recently been investigated by conducting user studies. A study of the effect of highly glossy screens compared to matt screens has been performed. The results show a slight advantage for the glossy screen when no disturbing reflexes are present, however the difference was not statistically significant. When disturbing reflexes are present the advantage is changed into a larger disadvantage and this difference is statistically significant. Another study of angular dependence has also been performed. The results indicates a linear relationship between the picture quality and the centre luminance of the screen.

  3. NEXAFS Study of the Annealing Effect on the Local Structure of FIB-CVD DLC

    SciTech Connect

    Saikubo, Akihiko; Kato, Yuri; Igaki, Jun-ya; Kanda, Kazuhiro; Matsui, Shinji; Kometani, Reo

    2007-01-19

    Annealing effect on the local structure of diamond like carbon (DLC) formed by focused ion beam-chemical vapor deposition (FIB-CVD) was investigated by the measurement of near edge x-ray absorption fine structure (NEXAFS) and energy dispersive x-ray (EDX) spectra. Carbon K edge absorption NEXAFS spectrum of FIB-CVD DLC was measured in the energy range of 275-320 eV. In order to obtain the information on the location of the gallium in the depth direction, incidence angle dependence of NEXAFS spectrum was measured in the incident angle range from 0 deg. to 60 deg. . The peak intensity corresponding to the resonance transition of 1s{yields}{sigma}* originating from carbon-gallium increased from the FIB-CVD DLC annealed at 200 deg. C to the FIB-CVD DLC annealed at 400 deg. C and decreased from that at 400 deg. C to that at 600 deg. C. Especially, the intensity of this peak remarkably enhanced in the NEXAFS spectrum of the FIB-CVD DLC annealed at 400 deg. C at the incident angle of 60 deg. . On the contrary, the peak intensity corresponding to the resonance transition of 1s{yields}{pi}* originating from carbon double bonding of emission spectrum decreased from the FIB-CVD DLC annealed at 200 deg. C to that at 400 deg. C and increased from that at 400 deg. C to that at 600 deg. C. Gallium concentration in the FIB-CVD DLC decreased from {approx_equal}2.2% of the as-deposited FIB-CVD DLC to {approx_equal}1.5% of the FIB-CVD DLC annealed at 600 deg. C from the elementary analysis using EDX. Both experimental results indicated that gallium atom departed from FIB-CVD DLC by annealing at the temperature of 600 deg. C.

  4. Technical Note: Angular dependence of a 2D monolithic silicon diode array for small field dosimetry.

    PubMed

    Stansook, Nauljun; Utitsarn, Kananan; Petasecca, Marco; Newall, Matthew K; Duncan, Mitchell; Nitschke, Kym; Carolan, Martin; Metcalfe, Peter; Lerch, Michael L F; Perevertaylo, Vladimir L; Tomé, Wolfgang A; Rosenfeld, Anatoly B

    2017-08-01

    This study aims to investigate the 2D monolithic silicon diode array size of 52 × 52 mm(2) (MP512) angular response. An angular correction method has been developed that improves the accuracy of dose measurement in a small field. The MP512 was placed at the center of a cylindrical phantom, irradiated using 6 MV and 10 MV photons and incrementing the incidence of the beam angle in 15° steps from 0° to 180°, and then in 1° steps between 85° and 95°. The MP512 response was characterized for square field sizes varying between 1 × 1 cm(2) and 10 × 10 cm(2) . The angular correction factor was obtained as the ratio of MP512 response to EBT3 film measured doses as a function of the incidence angle (Ɵ) and was normalized at 0° incidence angle. Beam profiles of the corrected MP512 responses were compared with the EBT3 responses to verify the effectiveness of the method adopted. The intrinsic angular dependence of the MP512 shows maximum relative deviation from the response normalized to 0° of 18.5 ± 0.5% and 15.5 ± 0.5% for 6 MV and 10 MV, respectively, demonstrating that the angular response is sensitive to the energy. In contrast, the variation of angular response is less affected by field size. Comparison of cross-plane profiles measured by the corrected MP512 and EBT3 shows an agreement within ±2% for all field sizes when the beams irradiated the array at 0°, 45°, 135°, and 180° angles of incidence from the normal to the detector plane. At 90° incidence, corresponding to a depth dose measurement, up to a 6% discrepancy was observed for a 1 × 1 cm(2) field of 6 MV. An angular correction factor can be adopted for small field sizes. Measurements discrepancies could be encountered when irradiating with very small fields parallel to the detector plane. Using this approach, the MP512 is shown to be a suitable detector for 2D dose mapping of small field size photon beams. © 2017 American Association of Physicists in Medicine.

  5. High resolution NEXAFS of perylene and PTCDI: a surface science approach to molecular orbital analysis.

    PubMed

    Fratesi, Guido; Lanzilotto, Valeria; Stranges, Stefano; Alagia, Michele; Brivio, Gian Paolo; Floreano, Luca

    2014-07-28

    We made use of synchrotron radiation to perform near edge X-ray absorption fine structure spectroscopy, NEXAFS, at the carbon K-edge of perylene and perylene-tetracarboxylic-diimide, PTCDI. Reference spectra measured for isolated molecules in the gas phase are compared with polarization dependent NEXAFS spectra measured on highly oriented thin films in order to study the symmetry of the molecular orbitals. The molecular overlayers are grown onto the rutile TiO2(110) surface for which the large anisotropic corrugation effectively drives the molecular orientation, while its dielectric nature prevents the rehybridization of the molecular orbitals. We employed density functional theory, DFT, calculations to disentangle the contribution of specific carbon atoms to the molecular density of states. Numerical simulations correctly predict the observed NEXAFS azimuthal dichroism of the σ* resonances above the ionization threshold, from which we determine the full geometric orientation of the overlayer molecules. A discrepancy observed for the spectral contribution of the imide carbon atom to the calculated unoccupied molecular orbitals has been explained in terms of initial state effects, as determined by Hartree-Fock corrections and in full agreement with the corresponding shift of the C 1s core level measured by X-ray photoelectron spectroscopy, XPS.

  6. Angular dependence of the ferromagnetic resonance spectrum in continuous/heterogeneous multilayers

    NASA Astrophysics Data System (ADS)

    Gómez, J.; Weston, J. L.; Butera, A.

    We present here a study of the angular dependence of the ferromagnetic resonance (FMR) spectra in trilayers formed by two continuous ferromagnetic layers, Fe and Ni 80Fe 20 (permalloy), separated by a granular film of Fe( x)-SiO 2(1- x). The study of the Fe/Fe-SiO 2/Ni 80Fe 20 trilayer was made for an Fe volume concentration x=0.75 and two thicknesses ( t=1 and 18 nm) of the granular layer. One microwave absorption line is in general found close to the field expected for Fe, while the other is coincident with the resonance field of permalloy. However, the Fe-like absorption is considerably wider than what is usually observed in pure Fe films, which suggests the presence of a strong exchange interaction between this layer and the granular spacer. The angular dependence of the resonance field and the line width could be very well fitted with a model that assumes an effective in-plane anisotropy for each layer, indicating that the shape anisotropy dominates the angular response of both modes. When the excitation frequency is increased, the line width of the permalloy-like mode increases by a similar factor. The width of the Fe-like mode is very similar at different frequencies because of the effect of the granular layer.

  7. Angular momentum dependence of quasifission dynamics in the reaction 48Ca+244Pu

    NASA Astrophysics Data System (ADS)

    Yu, Chong; Guo, Lu

    2017-09-01

    The quasifission dynamics in the reaction 48Ca+244Pu is investigated in the framework of time-dependent Hartree-Fock (TDHF) theory. The calculations are performed in three-dimensional Cartesian coordinate without any symmetry restrictions. The full Skyrme energy functional is incorporated in our TDHF implementation. The quasifission dynamics is quite sensitive to the angular momentum of colliding system. The contact time of quasifission decreases as a function of angular momentum and then forms a plateau with small oscillations. The quasifission process is accompanied by an important multi-nucleon transfer. The quantum shell effect plays a crucial role in the mass and charge of quasifission fragments. The mass-angle distribution of the fragments is calculated, which can be compared directly with future experiments.

  8. Multiple-scattering distributions and angular dependence of the energy loss of slow protons in copper and silver

    NASA Astrophysics Data System (ADS)

    Cantero, E. D.; Lantschner, G. H.; Eckardt, J. C.; Lovey, F. C.; Arista, N. R.

    2010-04-01

    Measurements of angular distributions and of the angular dependence of the energy loss of 4-, 6-, and 9-keV protons transmitted through thin Cu and Ag polycrystalline foils are presented. By means of standard multiple-scattering model calculations it is found that a V(r)∝r-2.8 potential leads to significantly better fits of the angular distributions than the standard Thomas Fermi, Lenz-Jensen, or Ziegler-Biersack-Littmark potentials. A theoretical model for the angular dependence of the energy loss based on considering geometric effects on a frictional inelastic energy loss plus an angular-dependent elastic contribution and the effects of foil roughness reproduces the experimental data. This agrees with previous results in Au and Al, therefore extending the applicability of the model to other metallic elements.

  9. Highly angular dependent high-contrast grating mirror and its application for transverse-mode control of VCSELs

    NASA Astrophysics Data System (ADS)

    Inoue, Shunya; Kashino, Junichi; Matsutani, Akihiro; Ohtsuki, Hideo; Miyashita, Takahiro; Koyama, Fumio

    2014-09-01

    We report on the design and fabrication of a highly angular dependent high contrast grating (HCG) mirror. The modeling and experiment on amorphous-Si/SiO2 HCG clearly show the large angular dependence of reflectivity, which enables single transverse-mode operations of large-area VCSELs. We fabricate 980 nm VCSELs with the angular dependent HCG functioning as a spatial frequency filter. We obtained the single transverse mode operation of the fabricated device in contrast to conventional VCSELs with semiconductor multilayer mirrors.

  10. Influence of the maximum applied magnetic field on the angular dependence of Magnetic Barkhausen Noise in API5L steels

    NASA Astrophysics Data System (ADS)

    Martínez-Ortiz, P.; Pérez-Benítez, J. A.; Espina-Hernández, J. H.; Caleyo, F.; Mehboob, N.; Grössinger, R.; Hallen, J. M.

    2016-03-01

    This work studies the influence of the maximum applied magnetic field on the angular dependence of the energy of the Magnetic Barkhausen Noise signal in three different API5L pipeline steels. The results show that the shape of the angular dependence of the Magnetic Barkhausen Noise energy changes with the increase of the amplitude of the applied magnetic field. This phenomenon is a consequence of the presence of unlike magnetization processes at different magnitudes of the applied magnetic field. The outcomes reveal the importance of controlling the value of the maximum applied field as parameter for the improvement of the MBN angular dependence measurements.

  11. Geometrical Characterization of Adenine And Guanine on Cu(110) By NEXAFS, XPS, And DFT Calculation

    SciTech Connect

    Furukawa, M.; Yamada, T.; Katano, S.; Kawai, M.; Ogasawara, H.; Nilsson, A.; /SLAC, SSRL /Stockholm U.

    2009-04-30

    Adsorption of purine DNA bases (guanine and adenine) on Cu(1 1 0) was studied by X-ray photoelectron spectroscopy (XPS), near-edge X-ray absorption fine-structure spectroscopy (NEXAFS), and density-functional theory (DFT) calculation. At coverages near 0.2 monolayers, Angular-resolved NEXAFS analysis revealed that adenine adsorbates lie almost flat and that guanine adsorbates are tilted up on the surface with the purine ring parallel to the atom rows of Cu(1 1 0). Referring to the previous studies on pyrimidine DNA bases [M. Furukawa, H. Fujisawa, S. Katano, H. Ogasawara, Y. Kim, T. Komeda, A. Nilsson, M. Kawai, Surf. Sci. 532-535 (2003) 261], the isomerization of DNA bases on Cu(1 1 0) was found to play an important role in the adsorption geometry. Guanine, thymine and cytosine adsorption have an amine-type nitrogen next to a carbonyl group, which is dehydrogenated into imine nitrogen on Cu(1 1 0). These bases are bonded by the inherent portion of - NH-CO - altered by conversion into enolic form and dehydrogenation. Adenine contains no CO group and is bonded to Cu(1 1 0) by participation of the inherent amine parts, resulting in nearly flatly-lying position.

  12. Effect of Angular Velocity on Sensors Based on Morphology Dependent Resonances

    PubMed Central

    Ali, Amir R.; Ioppolo, Tindaro

    2014-01-01

    We carried out an analysis to investigate the morphology dependent optical resonances shift (MDR) of a rotating spherical resonator. The spinning resonator experiences an elastic deformation due to the centrifugal force acting on it, leading to a shift in its MDR. Experiments are also carried out to demonstrate the MDR shifts of a spinning polydimethylsiloxane (PDMS) microsphere. The experimental results agree well with the analytical prediction. These studies demonstrated that spinning sensor based on MDR may experience sufficient shift in the optical resonances, therefore interfering with its desirable operational sensor design. Also the results show that angular velocity sensors could be designed using this principle. PMID:24759108

  13. Angular absorbed dose dependence of internal radiation-generating devices in radiotherapy.

    PubMed

    Bevelacqua, J J

    2012-01-01

    The angular dependence of the absorbed dose from internal radiation-generating devices located within a tumor mass is investigated. Given the systematics of proton and heavy-ion differential scattering cross sections, candidate internal radiation-generating devices will have a relatively constant absorbed dose output beyond a critical angle. Inside this angle, the absorbed dose output is suppressed because elastic and inelastic differential cross sections are peaked in the beam direction. This peaking increases in severity as the particle energy increases and suggests internal radiation-generating devices must have a limited rotation capability to compensate for the depression in the absorbed dose for angles near the beam direction.

  14. Daily and seasonal performance of angularly dependent fixed mount dual aperture holographic planar concentrator photovoltaic modules

    NASA Astrophysics Data System (ADS)

    Russo, Juan M.; Castillo, Jose E.; Aspnes, Eric D.; Kostuk, Raymond K.; Rosenberg, Glenn

    2010-08-01

    Dual aperture holographic planar concentrator (DA-HPC) technology consists of bifacial cells separated by strips of holographic film that diffract the light from the spacing into the cells for direct incident, diffuse, roof-reflected and albedo irradiance. The holographic film is angularly dependent of the seasonal sun angle. DA-HPC modules are compared to single aperture conventional modules for clear and cloudy days as well as for a seasonal period of eight months. Direct-current IV and alternating-current power curves are used to compare modules with comparable silicon active area and cell efficiency.

  15. Measuring the angular dependence of betatron x-ray spectra in a laser-wakefield accelerator

    SciTech Connect

    Albert, F.; Pollock, B. B.; Shaw, J. L.; Marsh, K. A.; Ralph, J. E.; Chen, Y. -H.; Alessi, D.; Pak, A.; Clayton, C. E.; Glenzer, S. H.; Joshi, C.

    2014-07-22

    This paper presents a new technique to measure the angular dependence of betatron x-ray spectra in a laser-wakefield accelerator. Measurements are performed with a stacked image plates spectrometer, capable of detecting broadband x-ray radiation up to 1 MeV. It can provide measurements of the betatron x-ray spectrum at any angle of observation (within a 40 mrad cone) and of the beam profile. A detailed description of our data analysis is given, along with comparison for several shots. As a result, these measurements provide useful information on the dynamics of the electrons are they are accelerated and wiggled by the wakefield.

  16. Angular-dependent interatomic potential for the aluminum-hydrogen system

    NASA Astrophysics Data System (ADS)

    Apostol, F.; Mishin, Y.

    2010-10-01

    We report on the development of an angular-dependent interatomic potential for hydrogen and the aluminum-hydrogen system. The potential reproduces properties of diatomic hydrogen gas, accurate solution energies of hydrogen atoms in crystalline Al, the energetic preference of the tetrahedral interstitial site occupation over octahedral, the hydrogen diffusion barrier in Al, and a number of other properties. Some of the results predicted by the potential have been tested by molecular dynamics simulations. It is suggested that the new potential can be used in atomistic simulations of the effect of dissolved hydrogen on deformation and fracture of Al, a problem which is relevant to hydrogen-induced degradation of Al alloys.

  17. Effect of angular velocity on sensors based on morphology dependent resonances.

    PubMed

    Ali, Amir R; Ioppolo, Tindaro

    2014-04-22

    We carried out an analysis to investigate the morphology dependent optical resonances shift (MDR) of a rotating spherical resonator. The spinning resonator experiences an elastic deformation due to the centrifugal force acting on it, leading to a shift in its MDR. Experiments are also carried out to demonstrate the MDR shifts of a spinning polydimethylsiloxane (PDMS) microsphere. The experimental results agree well with the analytical prediction. These studies demonstrated that spinning sensor based on MDR may experience sufficient shift in the optical resonances, therefore interfering with its desirable operational sensor design. Also the results show that angular velocity sensors could be designed using this principle.

  18. Angular dependence of magnetization reversal in epitaxial chromium telluride thin films with perpendicular magnetic anisotropy

    NASA Astrophysics Data System (ADS)

    Pramanik, Tanmoy; Roy, Anupam; Dey, Rik; Rai, Amritesh; Guchhait, Samaresh; Movva, Hema C. P.; Hsieh, Cheng-Chih; Banerjee, Sanjay K.

    2017-09-01

    We investigate magnetic anisotropy and magnetization reversal mechanism in chromium telluride thin films grown by molecular beam epitaxy. We report existence of strong perpendicular magnetic anisotropy in these thin films, along with a relatively strong second order anisotropy contribution. The angular variation of the switching field observed from the magnetoresistance measurement is explained quantitatively using a one-dimensional defect model. The model reveals the relative roles of nucleation and pinning in the magnetization reversal, depending on the applied field orientation. Micromagnetic simulations are performed to visualize the domain structure and switching process.

  19. Angular dependence of the attosecond time delay in the H 2 + ion

    NASA Astrophysics Data System (ADS)

    Kheifets, Anatoli; Serov, Vladislav

    2016-05-01

    Angular dependence of attosecond time delay relative to polarization of light can now be measured using combination of RABBITT and COLTRIMS techniques. This dependence brings particularly useful information in molecules where it is sensitive to the orientation of the molecular axis. Here we extend the theoretical studies of and consider a molecular ion H2+in combination of an attosecond pulse train and a dressing IR field which is a characteristic set up of a RABBIT measurement. We solve the time-dependent Schrödinger equation using a fast spherical Bessel transformation (SBT) for the radial variable, a discrete variable representation for the angular variables and a split-step technique for the time evolution. The use of SBT ensures correct phase of the wave function for a long time evolution which is especially important in time delay calculations. To speed up computations, we implement an expanding coordinate (EC) system which allows us to reach space sizes and time periods unavailable by other techniques. Australian Research Council DP120101805.

  20. Optimizing soft X-ray NEXAFS spectroscopy in the laboratory

    NASA Astrophysics Data System (ADS)

    Mantouvalou, I.; Jonas, A.; Witte, K.; Jung, R.; Stiel, H.; Kanngießer, B.

    2017-05-01

    Near edge X-ray absorption fine structure (NEXAFS) spectroscopy in the soft X-ray range is feasible in the laboratory using laser-produced plasma sources. We present a study using seven different target materials for optimized data analysis. The emission spectra of the materials with atomic numbers ranging from Z = 6 to Z = 79 show distinct differences, rendering the adapted selection of a suitable target material for specialized experiments feasible. For NEXAFS spectroscopy a 112.5 nm thick polyimide film is investigated as a reference exemplifying the superiority of quasi-continuum like emission spectra.

  1. Theoretical Investigation of the Angular-Momentum Dependence of the Mean Fission Lifetime of Excited Nuclei

    SciTech Connect

    Gontchar, I.I.; Ponomarenko, N.A.; Turkin, V.V.; Litnevsky, L.A.

    2004-11-01

    Mean fission lifetimes of nuclei excited to energies of 80 to 400 MeV were recently measured at the GANIL accelerator by the crystal-blocking technique. Those experiments served as a motivation for us to perform systematic calculations of the time distributions of fission events and the mean fission lifetimes versus the angular momentum, the initial excitation energy, and the fissility of a primary excited nucleus. The mean fission lifetimes are given as a function of the angular momentum L. The calculations were performed within the refined version of the combined dynamical-statistical model. It turned out that, if the height of the fission barrier at L = 0 is sizably greater than the neutron binding energy, the L dependence of the mean fission lifetimes has a resonance character. Such behavior of the mean fission lifetimes is obtained both from statistical calculations and from a dynamical simulation of the fission process with allowance for friction. It is shown that the maximum in the L dependence of is due to the fission of nuclei that lost a considerable part of the initial excitation energy through the emission of neutrons. The majority of the calculations were performed for {sup 190}Pt at an initial excitation energy of 150 eV. It is shown that the resonance behavior disappears with increasing fissility, but that it survives over a broad range of initial excitation energies. Systematic experimental studies are required for confirming or disproving our theoretical predictions.

  2. Inference of stress and texture from angular dependence of ultrasonic plate mode velocities

    NASA Technical Reports Server (NTRS)

    Thompson, R. B.; Smith, J. F.; Lee, S. S.

    1986-01-01

    The theory for the angular dependence of the ultrasonic wave velocity in a symmetry plane of an orthorhombic, stressed material is presented. The two waves having polarizations in this plane are shown to have velocities which can be estimated from measurements of the SH sub 0 and S sub 0 guided modes of a thin plate: the relationship being exact for the SH sub 0 mode and requiring a 10% correction for the S sub 0 mode at long wavelength. It is then shown how stress and texture can be independently inferred from various features of the angular dependence of these two velocities. From the SH sub 0 data, the ability to determine the directions and differences in magnitudes of principal stresses is described and supported by experimental data on several materials. From a combination of the SH sub 0 and S sub 0 data, a procedure is proposed for determining the coefficients W sub 400, W sub 420 and W sub 440 of an expansion of the crystallite orientation distribution function in terms of generalized Legendre functions. Possible applications in process control are indicated.

  3. Effect of misaligned unidirectional and uniaxial anisotropies on angular dependence of exchange bias

    NASA Astrophysics Data System (ADS)

    Hu, Yong; Wang, Xiaoling; Jia, Ning; Liu, Yan; Du, An

    2015-01-01

    We report a numerical study of the angular dependences of low-temperature exchange bias field (ADEB) and coercivity in the ferromagnetic/antiferromagnetic bilayers with misaligned unidirectional and uniaxial anisotropies. Through choosing a proper antiferromagnet the conventional symmetry in the ADEB may be broken, while the novel behaviors are also dependent on the angle between induced unidirectional and intrinsic uniaxial anisotropies. Finally, we draw conclusions that the two anisotropies with a small misalignment together determine the asymmetric ADEB properties around the easy axis. In contrast, after the magnetically hysteretic measurement rotating through the hard axis, a large misalignment between the anisotropies may change the magnetization reversal mode at the decreasing branch of loop, besides weakening the positive loop shift. Thus the strength of exchange bias field is suppressed while the coercivity is enhanced.

  4. Relation between the alignment dependence of coercive force decrease ratio and the angular dependence of coercive force of ferrite magnets

    NASA Astrophysics Data System (ADS)

    Matsuura, Yutaka; Kitai, Nobuyuki; Hosokawa, Seiichi; Hoshijima, Jun

    2016-08-01

    The relation of the coercive force decrease ratio (CFDR) and the angular dependence of the coercive force (ADCF) of ferrite magnets and their temperature properties were investigated. When we compared that against the angle of the magnetization reverse area obtained from these calculation results, which was obtained from the Gaussian distribution of the grain alignment and the postulation that every grain follows the Kondorskii law or the 1/cos θ law, and against the angle of the reverse magnetization area calculated from the experiment CFDR data of these magnets, it was found that this latter expanded at room temperature, to 36° from the calculated angle, for magnet with α=0.96. It was also found that, as temperature increased from room temperature to 413 K, the angle of the reverse magnetization area of ferrite magnets obtained from the experiment data expanded from 36° to 41°. When we apply these results to the temperature properties of ADCF, it seems that the calculated ADCF could qualitatively and reasonably explain these temperature properties, even though the difference between the calculated angular dependence and the experimental data still exists in the high angle range. These results strongly suggest that the coercive force of these magnets is determined by the magnetic domain wall motion. The magnetic domain walls are strongly pinned at tilted grains, and when the domain walls are de-pinned from their pinning sites, the coercive force is determined.

  5. Correction of measured Gamma-Knife output factors for angular dependence of diode detectors and PinPoint ionization chamber.

    PubMed

    Hršak, Hrvoje; Majer, Marija; Grego, Timor; Bibić, Juraj; Heinrich, Zdravko

    2014-12-01

    Dosimetry for Gamma-Knife requires detectors with high spatial resolution and minimal angular dependence of response. Angular dependence and end effect time for p-type silicon detectors (PTW Diode P and Diode E) and PTW PinPoint ionization chamber were measured with Gamma-Knife beams. Weighted angular dependence correction factors were calculated for each detector. The Gamma-Knife output factors were corrected for angular dependence and end effect time. For Gamma-Knife beams angle range of 84°-54°. Diode P shows considerable angular dependence of 9% and 8% for the 18 mm and 14, 8, 4 mm collimator, respectively. For Diode E this dependence is about 4% for all collimators. PinPoint ionization chamber shows angular dependence of less than 3% for 18, 14 and 8 mm helmet and 10% for 4 mm collimator due to volumetric averaging effect in a small photon beam. Corrected output factors for 14 mm helmet are in very good agreement (within ±0.3%) with published data and values recommended by vendor (Elekta AB, Stockholm, Sweden). For the 8 mm collimator diodes are still in good agreement with recommended values (within ±0.6%), while PinPoint gives 3% less value. For the 4 mm helmet Diodes P and E show over-response of 2.8% and 1.8%, respectively. For PinPoint chamber output factor of 4 mm collimator is 25% lower than Elekta value which is generally not consequence of angular dependence, but of volumetric averaging effect and lack of lateral electronic equilibrium. Diodes P and E represent good choice for Gamma-Knife dosimetry. Copyright © 2014 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

  6. Measuring the angular and seasonal dependence of the cosmic ray flux at the Earth's surface

    NASA Astrophysics Data System (ADS)

    Depoian, Amanda; Bellis, Matthew

    2016-03-01

    The angular dependence of cosmic rays hitting the Earth's surface is affected by solar winds, the Earth's magnetic field, attenuation factors, and other effects. The overall flux can be affected by the height and density of the atmosphere, which can vary seasonally. This seasonal modulation can affect the analyses of dark matter direct detection experiments, which also look for a modulation in dark matter recoils. We have constructed a standard cosmic ray telescope, consisting of two scintillating paddles, the associate photomultiplier tubes, and some older electronics. We will be pushing the sensitivity and stability of this detector to measure angular and temporal rates over the winter and spring and look for any seasonal variations that can be correlated with environmental conditions. While the location at the Earth's surface in Albany, NY is quite different than the underground laboratories where many dark matter experiments take place, we run this experiment as a proof-of-principle to see what seasonal effects can be measured with the basic equipment available in some undergraduate labs.

  7. Modeling and experimental validation of angular radiance and distance-dependent radiance in a turbid medium

    NASA Astrophysics Data System (ADS)

    Liu, Lingling; Li, Chenxi; Zhao, Huijuan; Yi, Xi; Gao, Feng; Meng, Wei; Lu, Yiming

    2014-03-01

    Radiance is sensitive to the variations of tissue optical parameters, such as absorption coefficient μa, scattering coefficient μs, and anisotropy factor g. Therefore, similar to fluence, radiance can be used for tissue characterization. Compared with fluence, radiance has the advantage of offering the direction information of light intensity. Taking such advantage, the optical parameters can be determined by rotating the detector through 360 deg with only a single optode pair. Instead of the translation mode used in the fluence-based technologies, the Rotation mode has less invasiveness in the clinical diagnosis. This paper explores a new method to obtain the optical properties by measuring the distribution of light intensity in liquid phantom with only a single optode pair and the detector rotation through 360 deg. The angular radiance and distance-dependent radiance are verified by comparing experimental measurement data with Monte Carlo (MC) simulation for the short source-detector separations and diffusion approximation for the large source-detector separations. Detecting angular radiance with only a single optode pair under a certain source-detection separation will present a way for prostate diagnose and light dose calculation during the photon dynamic therapy (PDT).

  8. An Analysis of the NEXAFS Spectra of a molecular crystal: alpha-Glycine

    SciTech Connect

    Schwartz, Craig P.; Saykally, Richard J.; Prendergast, David

    2010-06-18

    The nitrogen K-edge Near Edge X-ray Absorption Fine Structure (NEXAFS) spectrum of alpha-crystalline glycine has been calculated for temperatures ranging from 0 K to 450 K. Significant temperature dependent spectral changes are predicted. The calculated room temperature spectrum is in good agreement with experiment. At high temperatures, molecular motions strongly influence the spectrum, as any unique spectrum from an individual instantaneous configuration does not resemble the experimental result or the average calculated spectrum; complex coupled motions in this prototypical molecular crystal underlie the observed spectral changes.

  9. Vicinal fluorine-proton coupling constants. Ab initio calculations of angular dependence and substituent effects

    NASA Astrophysics Data System (ADS)

    San Fabián, J.; Guilleme, J.

    1996-06-01

    A data set of vicinal fluorine-proton coupling constants has been calculated by means of the SCF ab initio and semiempirical INDO/FPT methods. The angular dependence, the effect of individual substituents, and the effect of interaction between two substituents upon the 3JFH couplings have been studied for the molecules CH 2FCH 3, CHF 2CH 3, CH 2FCH 2F, CF 3CH 3, and CHF 2CH 2F. The four contributions to 3JFH ( JFC, JSD, JOD and JOP) have been computed using the standard basis sets 6-31G, 6-31G ∗, 6-31G ∗∗ and 6-311G ∗∗ and a double zeta basis set [4s2p1d/2s1p] with additional tight s functions on the H and F. The agreement with the experimental data is better for the last basis set but the trends of the angular dependence and substituent effects are also reproduced by the remaining basis sets. The major contribution arises from the FC term and the remaining contributions are much smaller being the OP the most important. The individual effect of an electronegative substituent depends on the carbon to which is bonded, being more important when the substituent is bonded to the carbon with the coupled hydrogen. The effect of interaction between two substituents seems to be not negligible, reaching values up to 6 Hz. The most important calculated interaction effects are the geminal δC012FF, δC034FF and δC134FF as well as the vicinal δC213FF and δC214FF.

  10. Angular multiplexing holograms of four images recorded on photopolymer films with recording-film-thickness-dependent holographic characteristics

    NASA Astrophysics Data System (ADS)

    Osabe, Keiichi; Kawai, Kotaro

    2017-03-01

    In this study, angular multiplexing hologram recording photopolymer films were studied experimentally. The films contained acrylamide as a monomer, eosin Y as a sensitizer, and triethanolamine as a promoter in a polyvinyl alcohol matrix. In order to determine the appropriate thickness of the photopolymer films for angular multiplexing, photopolymer films with thicknesses of 29-503 μm were exposed to two intersecting beams of a YVO laser at a wavelength of 532 nm to form a holographic grating with a spatial frequency of 653 line/mm. The diffraction efficiencies as a function of the incident angle of reconstruction were measured. A narrow angular bandwidth and high diffraction efficiency are required for angular multiplexing; hence, we define the Q value, which is the diffraction efficiency divided by half the bandwidth. The Q value of the films depended on the thickness of the films, and was calculated based on the measured diffraction efficiencies. The Q value of a 297-μm-thick film was the highest of the all films. Therefore, the angular multiplexing experiments were conducted using 300-μm-thick films. In the angular multiplexing experiments, the object beam transmitted by a square aperture was focused by a Fourier transform lens and interfered with a reference beam. The maximum order of angular multiplexing was four. The signal intensity that corresponds to the squared-aperture transmission and the noise intensity that corresponds to transmission without the square aperture were measured. The signal intensities decreased as the order of angular multiplexing increased, and the noise intensities were not dependent on the order of angular multiplexing.

  11. Dependence of the roll angular vestibuloocular reflex (aVOR) on gravity.

    PubMed

    Yakushin, Sergei B; Xiang, Yongqing; Cohen, Bernard; Raphan, Theodore

    2009-11-01

    Little is known about the dependence of the roll angular vestibuloocular reflex (aVOR) on gravity or its gravity-dependent adaptive properties. To study gravity-dependent characteristics of the roll aVOR, monkeys were oscillated about a naso-occipital axis in darkness while upright or tilted. Roll aVOR gains were largest in the upright position and decreased by 7-15% as animals were tilted from the upright. Thus the unadapted roll aVOR gain has substantial gravitational dependence. Roll gains were also decreased or increased by 0.25 Hz, in- or out-of-phase rotation of the head and the visual surround while animals were prone, supine, upright, or in side-down positions. Gain changes, determined as a function of head tilt, were fit with a sinusoid; the amplitudes represented the amount of the gravity-dependent gain change, and the bias, the gravity-independent gain change. Gravity-dependent gain changes were absent or substantially smaller in roll (approximately 5%) than in yaw (25%) or pitch (17%), whereas gravity-independent gain changes were similar for roll, pitch, and yaw (approximately 20%). Thus the high-frequency roll aVOR gain has an inherent dependence on head orientation re gravity in the unadapted state, which is different from the yaw/pitch aVORs. This inherent gravitational dependence may explain why the adaptive circuits are not active when the head is tilted re gravity during roll aVOR adaptation. These behavioral differences support the idea that there is a fundamental difference in the central organization of canal-otolith convergence of the roll and yaw/pitch aVORs.

  12. Angular dependence of the ultrasonic SH wave velocity in rolled metal sheets

    NASA Astrophysics Data System (ADS)

    Sayers, C. M.; Proudfoot, G. G.

    THE ULTRASONIC SH wave technique is a promising method for separating out the effects of texture and stress on the ultrasonic velocity, and allows the texture and stress to be determined separately. ALEN and LANGMAN (1985) have reported measurements of the angular dependence of the SH wave velocity in several unstressed rolled metal sheets of aluminium, stainless steel, copper and brass. In this paper neutron diffraction measurements of the texture of several of these sheets are presented, and parameters entering into an expansion of the crystallite orientation distribution function are determined. These are in good agreement with the values obtained by fitting the ultrasonic results to theory. The validity of the first order expression for the effect of texture is assessed, and the contribution due to beam skewing is calculated.

  13. Angular distribution and altitude dependence of atmospheric neutrons from 10 to 100 MeV

    NASA Technical Reports Server (NTRS)

    Preszler, A. M.; Simmett, G. M.; White, R. S.

    1974-01-01

    The altitude dependence of atmospheric neutrons from ground level to 5 g/sq cm of residual atmosphere at neutron energies of 10 to 100 MeV is reported. Ground level measurements were taken at Cape Girardeau, Missouri, on Sept. 18, 1972. The other measurements were made during ascent and float on launch from Palestine, Texas, on Sept. 26, 1971. The intensity of both the downward- and the upward-moving neutrons is maximum at about 100 g/sq cm of residual atmosphere. Neutron angular distributions are reported from 20 to 80 deg and from 100 to 160 deg for 10- to 100-MeV neutrons. Omnidirectional fluxes at altitudes of 5, 50, 100, and 200 g/sq cm of residual atmosphere are in good agreement with recent theoretical calculations of Armstrong et al. (1973) in the three energy intervals of 10 to 30, 30 to 50, and 50 to 100 MeV.

  14. Angular phase shift in polarization-angle dependence of microwave-induced magnetoresistance oscillations

    NASA Astrophysics Data System (ADS)

    Liu, Han-Chun; Samaraweera, Rasanga L.; Mani, R. G.; Reichl, C.; Wegscheider, W.

    2016-12-01

    We examine the microwave frequency (f ) variation of the angular phase shift, θ0, observed in the polarization-angle dependence of microwave-induced magnetoresistance oscillations in a high-mobility GaAs/AlGaAs two-dimensional electron system. By fitting the diagonal resistance Rx x versus θ plots to an empirical cosine square law, we extract θ0 and trace its quasicontinuous variation with f . The results suggest that the overall average of θ0 extracted from Hall bar device sections with length-to-width ratios of L /W =1 and 2 is the same. We compare the observations with expectations arising from the "ponderomotive force" theory for microwave radiation-induced transport phenomena.

  15. Angular distribution and altitude dependence of atmospheric neutrons from 10 to 100 MeV

    NASA Technical Reports Server (NTRS)

    Preszler, A. M.; Simmett, G. M.; White, R. S.

    1974-01-01

    The altitude dependence of atmospheric neutrons from ground level to 5 g/sq cm of residual atmosphere at neutron energies of 10 to 100 MeV is reported. Ground level measurements were taken at Cape Girardeau, Missouri, on Sept. 18, 1972. The other measurements were made during ascent and float on launch from Palestine, Texas, on Sept. 26, 1971. The intensity of both the downward- and the upward-moving neutrons is maximum at about 100 g/sq cm of residual atmosphere. Neutron angular distributions are reported from 20 to 80 deg and from 100 to 160 deg for 10- to 100-MeV neutrons. Omnidirectional fluxes at altitudes of 5, 50, 100, and 200 g/sq cm of residual atmosphere are in good agreement with recent theoretical calculations of Armstrong et al. (1973) in the three energy intervals of 10 to 30, 30 to 50, and 50 to 100 MeV.

  16. Versatile, high sensitivity, and automatized angular dependent vectorial Kerr magnetometer for the analysis of nanostructured materials.

    PubMed

    Teixeira, J M; Lusche, R; Ventura, J; Fermento, R; Carpinteiro, F; Araujo, J P; Sousa, J B; Cardoso, S; Freitas, P P

    2011-04-01

    Magneto-optical Kerr effect (MOKE) magnetometry is an indispensable, reliable, and one of the most widely used techniques for the characterization of nanostructured magnetic materials. Information, such as the magnitude of coercive fields or anisotropy strengths, can be readily obtained from MOKE measurements. We present a description of our state-of-the-art vectorial MOKE magnetometer, being an extremely versatile, accurate, and sensitivity unit with a low cost and comparatively simple setup. The unit includes focusing lenses and an automatized stepper motor stage for angular dependent measurements. The performance of the magnetometer is demonstrated by hysteresis loops of Co thin films displaying uniaxial anisotropy induced on growth, MnIr/CoFe structures exhibiting the so called exchange bias effect, spin valves, and microfabricated flux guides produced by optical lithography.

  17. Effective field analysis using the full angular spin-orbit torque magnetometry dependence

    NASA Astrophysics Data System (ADS)

    Schulz, Tomek; Lee, Kyujoon; Krüger, Benjamin; Lo Conte, Roberto; Karnad, Gurucharan V.; Garcia, Karin; Vila, Laurent; Ocker, Berthold; Ravelosona, Dafiné; Kläui, Mathias

    2017-06-01

    Spin-orbit torques promise ultraefficient magnetization switching used for advanced devices based on emergent quasiparticles such as domain walls and skyrmions. Recently, the spin structure dynamics, materials, and systems with tailored spin-orbit torques are being developed. A method, which allows one to detect the acting torques in a given system as a function of the magnetization direction is the torque magnetometry method based on a higher harmonics analysis of the anomalous Hall effect. Here we show that the effective fields acting on magnetic domain walls that govern the efficiency of their dynamics require a sophisticated analysis taking into account the full angular dependence of the torques. Using a one-dimensional model, we compared the spin-orbit torque efficiencies by depinning measurements and spin torque magnetometry. We show that the effective fields can be accurately determined and we find good agreement. Thus, our method allows us now to rapidly screen materials and predict the resulting quasiparticle dynamics.

  18. On the angular dependence of L X-ray intensity ratios for Au following photoionization

    NASA Astrophysics Data System (ADS)

    Wang, Xing; Xu, Zhongfeng; Zhang, Ying

    2017-04-01

    The typical L X-ray spectra for Au induced by 15.9 keV photons have been measured at emission angles ranging from 110° to 150° at intervals of 10°. The intensities of Lα, Lβ1, Lβ2 and Lγ1 X-rays are obtained and the angular dependence of L X-ray intensity ratios is determined experimentally. It is found that the Lβ1, Lβ2 and Lγ1 X-rays present isotropic emission, while the measured Lα X-rays show anisotropic distribution spatially. The unexpected isotropic emission of Lβ2 X-rays is explained with Coster-Kronig vacancy transfer process. Moreover, the anisotropy parameter for Lα X-ray emission is deduced.

  19. On the angular dependence and scattering model of polar mesospheric summer echoes at VHF

    NASA Astrophysics Data System (ADS)

    Sommer, Svenja; Stober, Gunter; Chau, Jorge L.

    2016-01-01

    We present measurements of the angular dependence of polar mesospheric summer echoes (PMSE) with the Middle Atmosphere Alomar Radar System in Northern Norway (69.30° N, 16.04° E). Our results are based on multireceiver and multibeam observations using beam pointing directions with off-zenith angles up to 25° as well as on spatial correlation analysis (SCA) from vertical beam observations. We consider a beam filling effect at the upper and lower boundaries of PMSE in tilted beams, which determines the effective mean angle of arrival. Comparing the average power of the vertical beam to the oblique beams suggests that PMSE are mainly not as aspect sensitive as in contrast to previous studies. However, from SCA, times of enhanced correlation are found, indicating aspect sensitivity or a localized scattering mechanism. Our results suggest that PMSE consist of nonhomogeneous isotropic scattering and previously reported aspect sensitivity values might have been influenced by the inhomogeneous nature of PMSE.

  20. Angular Dependence of Domain Wall Resistivity in Artificial Magnetic Domain Structures

    NASA Astrophysics Data System (ADS)

    Aziz, A.; Bending, S. J.; Roberts, H. G.; Crampin, S.; Heard, P. J.; Marrows, C. H.

    2006-11-01

    We exploit the ability to precisely control the magnetic domain structure of perpendicularly magnetized Pt/Co/Pt trilayers to fabricate artificial domain wall arrays and study their transport properties. The scaling behavior of this model system confirms the intrinsic domain wall origin of the magnetoresistance, and systematic studies using domains patterned at various angles to the current flow are excellently described by an angular-dependent resistivity tensor containing perpendicular and parallel domain wall resistivities. We find that the latter are fully consistent with Levy-Zhang theory, which allows us to estimate the ratio of minority to majority spin carrier resistivities, ρ↓/ρ↑˜5.5, in good agreement with thin film band structure calculations.

  1. Angular radiation temperature simulation for time-dependent capsule drive prediction in inertial confinement fusion

    SciTech Connect

    Jing, Longfei; Yang, Dong; Li, Hang; Zhang, Lu; Lin, Zhiwei; Li, Liling; Kuang, Longyu; Jiang, Shaoen Ding, Yongkun; Huang, Yunbao

    2015-02-15

    The x-ray drive on a capsule in an inertial confinement fusion setup is crucial for ignition. Unfortunately, a direct measurement has not been possible so far. We propose an angular radiation temperature simulation to predict the time-dependent drive on the capsule. A simple model, based on the view-factor method for the simulation of the radiation temperature, is presented and compared with the experimental data obtained using the OMEGA laser facility and the simulation results acquired with VISRAD code. We found a good agreement between the time-dependent measurements and the simulation results obtained using this model. The validated model was then used to analyze the experimental results from the Shenguang-III prototype laser facility. More specifically, the variations of the peak radiation temperatures at different view angles with the albedo of the hohlraum, the motion of the laser spots, the closure of the laser entrance holes, and the deviation of the laser power were investigated. Furthermore, the time-dependent radiation temperature at different orientations and the drive history on the capsule were calculated. The results indicate that the radiation temperature from “U20W112” (named according to the diagnostic hole ID on the target chamber) can be used to approximately predict the drive temperature on the capsule. In addition, the influence of the capsule on the peak radiation temperature is also presented.

  2. A strong angular dependence of magnetic properties of magnetosome chains: Implications for rock magnetism and paleomagnetism

    NASA Astrophysics Data System (ADS)

    Li, Jinhua; Ge, Kunpeng; Pan, Yongxin; Williams, Wyn; Liu, Qingsong; Qin, Huafeng

    2013-10-01

    Single-domain magnetite particles produced by magnetotactic bacteria (magnetosomes) and aligned in chains are of great interest in the biosciences and geosciences. Here, we investigated angular variation of magnetic properties of aligned Magnetospirillum magneticum AMB-1 cells, each of which contains one single fragmental chain of magnetosomes. With measurements at increasing angles from the chain direction, we observed that (i) the hysteresis loop gradually changes from nearly rectangular to a ramp-like shape (e.g., Bc and remanence decrease), (ii) the acquisition and demagnetization curves of IRM shift toward higher fields (e.g., Bcr increases), and (iii) the FORC diagram shifts toward higher coercivity fields (e.g., Bc,FORC increases). For low-temperature results, compared to unoriented samples, the samples containing aligned chains have a much lower remanence loss of field-cooled (δFC) and zero-field-cooled (δZFC) remanence upon warming through the Verwey transition, higher δ-ratio (δ = δFC/δZFC) for the measurement parallel to the chain direction, and lower δ-ratio, larger δFC and δZFC values for the perpendicular measurement. Micromagnetic simulations confirm the experimental observations and reveal that the magnetization reversal of magnetosome chain appears to be noncoherent at low angles and coherent at high angles. The simulations also demonstrate that the angular dependence of magnetic properties is related to the dispersion degree of individual chains, indicating that effects of anisotropy need to be accounted for when using rock magnetism to identify magnetosomes or magnetofossils once they have been preserved in aligned chains. Additionally, this study experimentally demonstrates an empirical correspondence of the parameter Bc,FORC to Bcr rather than Bc, at least for magnetite chains with strong shape anisotropy. This suggests FORC analysis is a good discriminant of magnetofossils in sediments and rocks.

  3. Angular Dependence of Ionization by Circularly Polarized Light Calculated with Time-Dependent Configuration Interaction with an Absorbing Potential.

    PubMed

    Hoerner, Paul; Schlegel, H Bernhard

    2017-02-16

    The angular dependence of ionization by linear and circularly polarized light has been examined for N2, NH3, H2O, CO2, CH2O, pyrazine, methyloxirane, and vinyloxirane. Time-dependent configuration interaction with single excitations and a complex absorbing potential was used to simulate ionization by a seven cycle 800 nm cosine squared pulse with intensities ranging from 0.56 × 10(14) to 5.05 × 10(14) W cm(-2). The shapes of the ionization yield for linearly polarized light can be understood primarily in terms of the nodal structure of the highest occupied orbitals. Depending on the orbital energies, ionization from lower-lying orbitals may also make significant contributions to the shapes. The shapes of the ionization yield for circularly polarized light can be readily explained in terms of the shapes for linearly polarized light. Averaging the results for linear polarization over orientations perpendicular to the direction of propagation yields shapes that are in very good agreement with direct calculations of the ionization yield by circularly polarized light.

  4. Micromagnetic simulation and the angular dependence of coercivity and remanence for array of polycrystalline nickel nanowires

    NASA Astrophysics Data System (ADS)

    Fuentes, G. P.; Holanda, J.; Guerra, Y.; Silva, D. B. O.; Farias, B. V. M.; Padrón-Hernández, E.

    2017-02-01

    We present here our experimental results for the preparation and characterization of nanowires of nickel and the analysis of the angular dependence of coercivity and remanence using experimental data and micromagnetic simulation. The fabrication was made by using aluminum oxide membranes as templates and deposited nickel by an electrochemical route. The magnetic measurements showed that coercivity and remanence are dependent of the angle of application of the external magnetic field. Our results are different than that expected for the coherent, vortex and transversal modes of the reversion for the magnetic moments. According to the transmission electron microscopy analysis we can see that our nanowires have not a perfect cylindrical format. That is why we have used the ellipsoids chain model for better understanding the real structure of wires and its relation with the magnetic behavior. In order to generate theoretical results for this configuration we have made micromagnetic simulation using Nmag code. Our numerical results for the realistic distances are in correspondence with the magnetic measurements and we can see that there are contradictions if we assume the transverse reversal mode. Then, we can conclude that structure of nanowires should be taken into account to understand the discrepancies reported in the literature for the reversion mechanism in arrays of nickel nanowires.

  5. Angular dependence of optical fibre thermoluminescent dosimeters irradiated using kilo- and megavoltage X-rays

    NASA Astrophysics Data System (ADS)

    Moradi, F.; Ung, N. M.; Mahdiraji, G. A.; Khandaker, M. U.; Entezam, A.; See, M. H.; Taib, N. A.; Amin, Y. M.; Bradley, D. A.

    2017-06-01

    Prior investigation of the suitability of optical fibres as thermoluminescent dosimeters for diagnostic and therapeutic radiation beams has not included detailed study of the effect of beam angulation. Present study of such response has made use of optical fibre of cylindrical shape, exposed to 30 kVp photons from an X-ray tube and a 6 MV photon beam from a linear accelerator. The effect of the irradiation medium was also studied, comparing response free-in-air against on-surface and in-depth irradiations through use of solid-water™ phantom. Standard optical fibre (ø =125 μm) shows non-uniform response to beams delivered at different incident angles. Monte Carlo simulation provided support for the experimental results, also obtaining absorbed dose in the fibres. The results of free-in-air condition simulated with mono-energy beam show angle-independent response for photons within the energy range 100-500 keV, while dependency has been observed for beam energies of <100 keV and >500 keV. Experimentally, the angular dependency up to 35% is observed in 30 kVp free-in-air, while in 6 MeV beam, this is reduced to 20%, 10%, and 3% in free-in-air, on phantom surface, and in-depth conditions, respectively. The observations have been justified by considering the range of secondary electrons in the dosimeter and the effect of scattered radiation.

  6. Features of angular dependence of secondary electron emission from metal single crystals

    NASA Astrophysics Data System (ADS)

    Minnebaev, K. F.; Khaidarov, A. A.; Ivanenko, I. P.; Minnebaev, D. K.; Yurasova, V. E.

    2017-09-01

    The dependence of secondary electron emission coefficient σ on the angle α of primary electron incidence onto single crystals of metals with different crystalline lattice has been studied for undisturbed surface and for disturbed one by sputtering. We used the single crystals of Cu (fcc), Mo (bcc), Zn (hcp) and Ni4Mo (tetragonal lattice). It was shown that the coefficient σ is smaller for the disturbed surface, than for initial one due to absorption of secondary and scattered electrons by the lateral surfaces of hills and cones which are formed as a result of sputtering. For the initial surfaces (of Cu, Mo and Ni4Mo) the maxima of σ(α) in the low-index directions of the crystal lattice arise as a result of primary and secondary electron scattering on the atoms in open channels. At the same time, for the preliminary highly oxidized single crystal surface (of Zn) the minimum of σ in the direction of open channel was observed. The last can be explained by a reduction of work function of surface, and increase in penetration depth of electrons in open channel and by a rise of electron-phonon interaction. Angular dependences of secondary electron emission for a sputtered surface have a more complicated structure with the additional maxima and minima caused by interaction of secondary and scattered electrons with a cone-shaped relief.

  7. Angular Dependent Magnetic Susceptibility with Photoexcitation Studies on Prussian Blue Analog Thin Films

    NASA Astrophysics Data System (ADS)

    Pajerowski, D. M.; Park, J.-H.; Meisel, M. W.; Frye, F. A.; Talham, D. R.

    2008-03-01

    Prussian blue analog systems are the topic of ongoing research because of their novel physical effects. One such effect is persistent photoinduced magnetism, found in CoFe analogs. For such an optical system, in an attempt to maximize the material's interaction with incident photons, a thin film geometry is often utilized; this geometry can produce new effects [1]. Samples of different starting materials have been characterized with respect to photoinduced states, angular dependent susceptibility, film thickness, and chemical formula. Notably, magnetic anisotropies present in the systems show a dependence on the studied factors. One class of interesting starting materials are RbjNik[Cr(CN)6]l.nH2O and RbjCok[Fe(CN)6]l.nH2O heterostructures, generated by sequential adsorption on a Melinex substrate, that display behavior different than a noninteracting admixture of the two materials by themselves. [1] J.-H. Park, E. Cizmar, M. W. Meisel, Y. D. Huh, F. Frye, S. Lane, and D. R. Talham, Appl. Phys. Lett. 85, 3797 (2004).

  8. Modeling gravity-dependent plasticity of the angular vestibuloocular reflex with a physiologically based neural network.

    PubMed

    Xiang, Yongqing; Yakushin, Sergei B; Cohen, Bernard; Raphan, Theodore

    2006-12-01

    A neural network model was developed to explain the gravity-dependent properties of gain adaptation of the angular vestibuloocular reflex (aVOR). Gain changes are maximal at the head orientation where the gain is adapted and decrease as the head is tilted away from that position and can be described by the sum of gravity-independent and gravity-dependent components. The adaptation process was modeled by modifying the weights and bias values of a three-dimensional physiologically based neural network of canal-otolith-convergent neurons that drive the aVOR. Model parameters were trained using experimental vertical aVOR gain values. The learning rule aimed to reduce the error between eye velocities obtained from experimental gain values and model output in the position of adaptation. Although the model was trained only at specific head positions, the model predicted the experimental data at all head positions in three dimensions. Altering the relative learning rates of the weights and bias improved the model-data fits. Model predictions in three dimensions compared favorably with those of a double-sinusoid function, which is a fit that minimized the mean square error at every head position and served as the standard by which we compared the model predictions. The model supports the hypothesis that gravity-dependent adaptation of the aVOR is realized in three dimensions by a direct otolith input to canal-otolith neurons, whose canal sensitivities are adapted by the visual-vestibular mismatch. The adaptation is tuned by how the weights from otolith input to the canal-otolith-convergent neurons are adapted for a given head orientation.

  9. Angular dependence of dose sensitivity of nanoDot optically stimulated luminescent dosimeters in different radiation geometries

    SciTech Connect

    Jursinic, Paul A.

    2015-10-15

    Purpose: A type of in vivo dosimeter, an optically stimulated luminescent dosimeter, OSLD, may have dose sensitivity that depends on the angle of incidence of radiation. This work measures how angular dependence of a nanoDot changes with the geometry of the phantom in which irradiation occurs and with the intrinsic structure of the nanoDot. Methods: The OSLDs used in this work were nanoDot dosimeters (Landauer, Inc., Glenwood, IL), which were read with a MicroStar reader (Landauer, Inc., Glenwood, IL). Dose to the OSLDs was delivered by 6 MV x-rays. NanoDots with various intrinsic sensitivities were irradiated in numerous phantoms that had geometric shapes of cylinders, rectangles, and a cube. Results: No angular dependence was seen in cylindrical phantoms, cubic phantoms, or rectangular phantoms with a thickness to width ratio of 0.3 or 1.5. An angular dependence of 1% was observed in rectangular phantoms with a thickness to width of 0.433–0.633. A group of nanoDots had sensitive layers with mass density of 2.42–2.58 g/cm{sup 3} and relative sensitivity of 0.92–1.09 and no difference in their angular dependence. Within experimental uncertainty, nanoDot measurements agree with a parallel-plate ion chamber at a depth of maximum dose. Conclusions: When irradiated in cylindrical, rectangular, and cubic phantoms, nanoDots show a maximum angular dependence of 1% or less at an incidence angle of 90°. For a sample of 78 new nanoDots, the range of their relative intrinsic sensitivity is 0.92–1.09. For a sample of ten nanoDots, on average, the mass in the sensitive layer is 73.1% Al{sub 2}O{sub 3}:C and 26.9% polyester. The mass density of the sensitive layer of a nanoDot disc is between 2.42 and 2.58 g/cm{sup 3}. The angular dependence is not related to Al{sub 2}O{sub 3}:C loading of the nanoDot disc. The nanoDot at the depth of maximum dose has no more angular dependence than a parallel-plate ion chamber.

  10. Angular dependence of dose sensitivity of nanoDot optically stimulated luminescent dosimeters in different radiation geometries.

    PubMed

    Jursinic, Paul A

    2015-10-01

    A type of in vivo dosimeter, an optically stimulated luminescent dosimeter, OSLD, may have dose sensitivity that depends on the angle of incidence of radiation. This work measures how angular dependence of a nanoDot changes with the geometry of the phantom in which irradiation occurs and with the intrinsic structure of the nanoDot. The OSLDs used in this work were nanoDot dosimeters (Landauer, Inc., Glenwood, IL), which were read with a MicroStar reader (Landauer, Inc., Glenwood, IL). Dose to the OSLDs was delivered by 6 MV x-rays. NanoDots with various intrinsic sensitivities were irradiated in numerous phantoms that had geometric shapes of cylinders, rectangles, and a cube. No angular dependence was seen in cylindrical phantoms, cubic phantoms, or rectangular phantoms with a thickness to width ratio of 0.3 or 1.5. An angular dependence of 1% was observed in rectangular phantoms with a thickness to width of 0.433-0.633. A group of nanoDots had sensitive layers with mass density of 2.42-2.58 g/cm(3) and relative sensitivity of 0.92-1.09 and no difference in their angular dependence. Within experimental uncertainty, nanoDot measurements agree with a parallel-plate ion chamber at a depth of maximum dose. When irradiated in cylindrical, rectangular, and cubic phantoms, nanoDots show a maximum angular dependence of 1% or less at an incidence angle of 90°. For a sample of 78 new nanoDots, the range of their relative intrinsic sensitivity is 0.92-1.09. For a sample of ten nanoDots, on average, the mass in the sensitive layer is 73.1% Al2O3:C and 26.9% polyester. The mass density of the sensitive layer of a nanoDot disc is between 2.42 and 2.58 g/cm(3). The angular dependence is not related to Al2O3:C loading of the nanoDot disc. The nanoDot at the depth of maximum dose has no more angular dependence than a parallel-plate ion chamber.

  11. Structure of tetracene films on hydrogen-passivated Si(001) studied via STM, AFM, and NEXAFS

    SciTech Connect

    Tersigni, A.; Shi, J.; Jiang, D. T.; Qin, X. R.

    2006-11-15

    Scanning tunneling microscopy (STM), atomic force microscopy (AFM), and near-edge x-ray absorption fine structure (NEXAFS) have been used to study the structure of tetracene films on hydrogen-passivated Si(001). STM imaging of the films with nominal thickness of three monolayers (3 ML) exhibits the characteristic 'herringbone' molecular packing known from the bulk crystalline tetracene, showing standing molecules on the ab plane. The dimensions and orientation of the herringbone lattice indicate a commensurate structural relationship between the lattice and the crystalline substrate. The corresponding AFM images illustrate that at and above the third layer of the films, the islands are anisotropic, in contrast with the submonolayer fractals, with two preferred growth directions appearing orthogonal to each other. The polarization dependent NEXAFS measurements indicate that the average molecular tilting angle with respect to the surface first increases with the film thickness up to 3 ML, then stabilizes at a value close to the bulk tetracene case afterwards. The combined results indicate a distinct growth morphological change that occurs around a few monolayers of thickness.

  12. Polarized angular dependent light scattering from plasmonic nanoparticles: Modeling, measurements, and biomedical applications

    NASA Astrophysics Data System (ADS)

    Fu, Kun

    Several significant applications have been realized for light scattering in biomedical imaging. In order to improve imaging results with light scattering-based techniques, a variety of nanoparticles have been investigated as contrast agents, including gold nanoshells. As a method for studying the optical properties of plasmonic gold nanoparticles used as contrast agents for molecular imaging, we developed an automated goniometer instrumentation system. This system, which allows us to specifically study polarized angular-dependent light scattering of plasmonic nanoparticles, allowed us to perform a series of theoretical and experimental step-wise studies. The basic optical properties of the following gold nanoparticles were progressively investigated: (1) bare nanoshells at multipolar plasmonic resonances, (2) nanoshells with PEG modifications, (3) surface-textured nanoshells and (4) immunotargeted nanoshells (nanoshell-antibody bioconjugates) for cancer imaging. Based on the results from these studies, a new technique was developed to quantitatively measure the number of immunotargeted nanoparticles that bind to HER2-positive SKBR3 human breast cancer cells. Preliminary studies of determining the minimal incubation time of immunotargeted nanoshells with SKBR3 cells were also carried out to evaluate the potential clinical application of using gold nanoshells intraoperatively. We, therefore, anticipate that our findings will provide the theoretical groundwork required for further studies aimed at optimizing the application of plasmonic nanoparticles in scattering-based optical imaging techniques.

  13. Angular Dependent Magnetic Properties of CeCoIn5 at Low Temperatures

    NASA Astrophysics Data System (ADS)

    Park, J.-H.; Stillwell, R. L.; Murphy, T. P.; Palm, E. C.; Tozer, S. W.; Cooley, J. C.

    2008-03-01

    The heavy-fermion compound CeCoIn5 exhibits a superconducting transition at 2.3 K. As an unconventional superconductor, many unusual physical properties of the compound have been actively studied. In particular, evidence of a Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) superconducting state in this compound was reported first by Radovan and co-workers.^ At the lowest temperature (˜ 20 mK), the FFLO state of CeCoIn5 was observed in fields between 10 and 11.7 T when the ab-plane of the compound was placed parallel to the external magnetic field. In addition, at these low temperatures, the angular dependent peak effect was observed and interpreted as a crossover between Abrikosov and Josephson vortex lattices.^ Further experimental studies of the low temperature (> 12 mK) magnetic properties of CeCoIn5, performed in various sample orientations with respect to magnetic field will be presented. ^H.A. Radovan, et al., Nature 425 (2003) 51. ^H.A. Radovan, et al., Philosophical Magazine 86 (2006) 3569.

  14. Light Scattering by Fractal Dust Aggregates. I. Angular Dependence of Scattering

    NASA Astrophysics Data System (ADS)

    Tazaki, Ryo; Tanaka, Hidekazu; Okuzumi, Satoshi; Kataoka, Akimasa; Nomura, Hideko

    2016-06-01

    In protoplanetary disks, micron-sized dust grains coagulate to form highly porous dust aggregates. Because the optical properties of these aggregates are not completely understood, it is important to investigate how porous dust aggregates scatter light. In this study, the light scattering properties of porous dust aggregates were calculated using a rigorous method, the T-matrix method, and the results were then compared with those obtained using the Rayleigh-Gans-Debye (RGD) theory and Mie theory with the effective medium approximation (EMT). The RGD theory is applicable to moderately large aggregates made of nearly transparent monomers. This study considered two types of porous dust aggregates—ballistic cluster-cluster agglomerates (BCCAs) and ballistic particle-cluster agglomerates. First, the angular dependence of the scattered intensity was shown to reflect the hierarchical structure of dust aggregates; the large-scale structure of the aggregates is responsible for the intensity at small scattering angles, and their small-scale structure determines the intensity at large scattering angles. Second, it was determined that the EMT underestimates the backward scattering intensity by multiple orders of magnitude, especially in BCCAs, because the EMT averages the structure within the size of the aggregates. It was concluded that the RGD theory is a very useful method for calculating the optical properties of BCCAs.

  15. Angular Dependence of the Facular-Sunspot Coverage Relation as Derived by MDI Magnetograms

    NASA Astrophysics Data System (ADS)

    Criscuoli, S.

    2016-08-01

    Previous studies have shown that the variation over the solar magnetic activity cycle of the area of facular/network features identified from broad-band and narrow-band imagery is positively correlated with the sunspot area and number, the relation being described as either linear or quadratic. On the other hand, the temporal variation of the spatial distributions of faculae, network and sunspots follows patterns that are less obviously correlated, so that we expect the relation that describes variation of the area coverage of different types of magnetic features to vary with the position over the disk. In this work we employ Michelson Doppler Interferometer (MDI) full-disk magnetograms acquired during solar cycle 23 and at the beginning of cycle 24 to investigate the relation between the coverage of magnetic elements characterized by different amounts of magnetic flux and located at different angular distances from disk center with the sunspot number. In agreement with some previous studies we find that daily data are best described by a quadratic function while data averaged over six months are best described by a linear function. In both cases the coefficients of the fits show large dependence on the position over the disk and the magnetic flux. We also find that toward disk center six-month averaged data show asymmetries between the ascending and the descending phases. The implications for solar irradiance modeling are discussed.

  16. Angular dependence of Doppler profiles of atomic emission produced in electron-molecule collisions: Estimation of anisotropy parameters

    NASA Astrophysics Data System (ADS)

    Nakashima, Keiji; Ogawa, Teiichiro

    1985-11-01

    The angular dependence of Doppler profiles of atomic fluorescence produced in electron impact dissociation of molecules was simulated in consideration of the effect of the anisotropy of dissociation and the ``polarization'' in magnetic sublevel. The asymmetry parameter b and the polarization of the electric vector of emission Jp are key parameters of Doppler profiles for the excited atom of known translational energy distribution. The difference of two Doppler profiles taken at 90° and 45°, which is denoted as angular difference Doppler profile, is shown to be useful to estimate these two key parameters.

  17. Measurement of Angular-Momentum-Dependent Fission Probabilities of 240Pu

    NASA Astrophysics Data System (ADS)

    Koglin, Johnathon; Burke, Jason; Jovanovic, Igor

    2016-09-01

    An experimental technique using the surrogate reaction method has been developed to measure fission probabilities of actinides as a function of angular momentum state of the fissioning nucleus near the fission barrier. In this work, the 240Pu (α ,α' f) reaction was used as a surrogate for 239Pu (n , f) . An array of 12 silicon telescopes positioned at 10 degree intervals from 40 to 140 degrees detect the outgoing reaction particle for identification and measurement of the excitation energy. The angular momentum state is determined by measuring the angular distribution of fission fragments. The expected distributions are predicted from the Wigner d function. An array of 50 photovoltaic (solar) cells detects fission fragments with 10-degree granularity. The solar cells are sensitive to fission fragments but have no response to light ions. Relative contributions from different angular momentum states are extracted from the measured distributions and compared across all α particle scattering angles to determine fission probability at a specific angular momentum state. The first experiment using this technique was recently completed using 37 MeV α particles incident on 240Pu. First results will be discussed. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. This material is based upon work supported by the U.S. Department of Homeland Security under Grant Award Nu.

  18. Energy Dependence of Angular Distributions of Sputtered Particles by Ion-Beam Bombardment at Normal Incidence

    NASA Astrophysics Data System (ADS)

    Matsuda, Yoshinobu; Yamamura, Yasunori; Ueda, Yasutoshi; Uchino, Kiichiro; Muraoka, Katsunori; Maeda, Mitsuo; Akazaki, Masanori

    1986-01-01

    The angular distributions of sputtered Fe-atoms were measured using the laser fluorescence technique during Ar-ion bombardment for energies of 0.6, 1, 2 and 3 keV at normal incidence. The measured cosine distribution at 0.6 keV progressively deviated to an over-cosine distribution at higher energies, and at 3 keV the angular distribution was an over-cosine distribution of about 20%. The experimental results agree qualitatively with calculations by a recent computer simulation code, ACAT. The results are explained by the competition between surface scattering and the effects of primary knock-on atoms, which tend to make the angular distributions over-cosine and under-cosine, respectively.

  19. Aging induced changes on NEXAFS fingerprints in individual combustion particles

    NASA Astrophysics Data System (ADS)

    Zelenay, V.; Mooser, R.; Tritscher, T.; Křepelová, A.; Heringa, M. F.; Chirico, R.; Prévôt, A. S. H.; Weingartner, E.; Baltensperger, U.; Dommen, J.; Watts, B.; Raabe, J.; Huthwelker, T.; Ammann, M.

    2011-11-01

    Soot particles can significantly influence the Earth's climate by absorbing and scattering solar radiation as well as by acting as cloud condensation nuclei. However, despite their environmental (as well as economic and political) importance, the way these properties are affected by atmospheric processing of the combustion exhaust gases is still a subject of discussion. In this work, individual soot particles emitted from two different vehicles, a EURO 2 transporter, a EURO 3 passenger car, and a wood stove were investigated on a single-particle basis. The emitted exhaust, including the particulate and the gas phase, was processed in a smog chamber with artificial solar radiation. Single particle specimens of both unprocessed and aged soot were characterized using near edge X-ray absorption fine structure spectroscopy (NEXAFS) and scanning electron microscopy. Comparison of NEXAFS spectra from the unprocessed particles and those resulting from exhaust photooxidation in the chamber revealed changes in the carbon functional group content. For the wood stove emissions, these changes were minor, related to the relatively mild oxidation conditions. For the EURO 2 transporter emissions, the most apparent change was that of carboxylic carbon from oxidized organic compounds condensing on the primary soot particles. For the EURO 3 car emissions oxidation of primary soot particles upon photochemical aging has likely contributed as well. Overall, the changes in the NEXAFS fingerprints were in qualitative agreement with data from an aerosol mass spectrometer. Furthermore, by taking full advantage of our in situ microreactor concept, we show that the soot particles from all three combustion sources changed their ability to take up water under humid conditions upon photochemical aging of the exhaust. Due to the selectivity and sensitivity of the NEXAFS technique for the water mass, also small amounts of water taken up into the internal voids of agglomerated particles could be

  20. DFTB3 Parametrization for Copper: The Importance of Orbital Angular Momentum Dependence of Hubbard Parameters.

    PubMed

    Gaus, Michael; Jin, Haiyun; Demapan, Darren; Christensen, Anders S; Goyal, Puja; Elstner, Marcus; Cui, Qiang

    2015-09-08

    We report the parametrization of a density functional tight binding method (DFTB3) for copper in a spin-polarized formulation. The parametrization is consistent with the framework of 3OB for main group elements (ONCHPS) and can be readily used for biological applications that involve copper proteins/peptides. The key to our parametrization is to introduce orbital angular momentum dependence of the Hubbard parameter and its charge derivative, thus allowing the 3d and 4s orbitals to adopt different sizes and responses to the change of charge state. The parametrization has been tested by applying to a fairly broad set of molecules of biological relevance, and the properties of interest include optimized geometries, ligand binding energies, and ligand proton affinities. Compared to the reference QM level (B3LYP/aug-cc-pVTZ, which is shown here to be similar to the B97-1 and CCSD(T) results, in terms of many properties of interest for a set of small copper containing molecules), our parametrization generally gives reliable structural properties for both Cu(I) and Cu(II) compounds, although several exceptions are also noted. For energetics, the results are more accurate for neutral ligands than for charged ligands, likely reflecting the minimal basis limitation of DFTB3; the results generally outperform NDDO based methods such as PM6 and even PBE with the 6-31+G(d,p) basis. For all ligand types, single-point B3LYP calculations at DFTB3 geometries give results very close (∼1-2 kcal/mol) to the reference B3LYP values, highlighting the consistency between DFTB3 and B3LYP structures. Possible further developments of the DFTB3 model for a better treatment of transition-metal ions are also discussed. In the current form, our first generation of DFTB3 copper model is expected to be particularly valuable as a method that drives sampling in systems that feature a dynamical copper binding site.

  1. DFTB3 Parametrization for Copper: The Importance of Orbital Angular Momentum Dependence of Hubbard Parameters

    PubMed Central

    2015-01-01

    We report the parametrization of a density functional tight binding method (DFTB3) for copper in a spin-polarized formulation. The parametrization is consistent with the framework of 3OB for main group elements (ONCHPS) and can be readily used for biological applications that involve copper proteins/peptides. The key to our parametrization is to introduce orbital angular momentum dependence of the Hubbard parameter and its charge derivative, thus allowing the 3d and 4s orbitals to adopt different sizes and responses to the change of charge state. The parametrization has been tested by applying to a fairly broad set of molecules of biological relevance, and the properties of interest include optimized geometries, ligand binding energies, and ligand proton affinities. Compared to the reference QM level (B3LYP/aug-cc-pVTZ, which is shown here to be similar to the B97-1 and CCSD(T) results, in terms of many properties of interest for a set of small copper containing molecules), our parametrization generally gives reliable structural properties for both Cu(I) and Cu(II) compounds, although several exceptions are also noted. For energetics, the results are more accurate for neutral ligands than for charged ligands, likely reflecting the minimal basis limitation of DFTB3; the results generally outperform NDDO based methods such as PM6 and even PBE with the 6-31+G(d,p) basis. For all ligand types, single-point B3LYP calculations at DFTB3 geometries give results very close (∼1–2 kcal/mol) to the reference B3LYP values, highlighting the consistency between DFTB3 and B3LYP structures. Possible further developments of the DFTB3 model for a better treatment of transition-metal ions are also discussed. In the current form, our first generation of DFTB3 copper model is expected to be particularly valuable as a method that drives sampling in systems that feature a dynamical copper binding site. PMID:26575916

  2. Vibronic coupling in the superoxide anion: the vibrational dependence of the photoelectron angular distribution.

    PubMed

    Van Duzor, Matthew; Mbaiwa, Foster; Wei, Jie; Singh, Tulsi; Mabbs, Richard; Sanov, Andrei; Cavanagh, Steven J; Gibson, Stephen T; Lewis, Brenton R; Gascooke, Jason R

    2010-11-07

    We present a comprehensive photoelectron imaging study of the O(2)(X  (3)Σ(g)(-),v(')=0-6)←O(2)(-)(X  (2)Π(g),v(")=0) and O(2)(a (1)Δ(g),v(')=0-4)←O(2)(-)(X  (2)Π(g),v(")=0) photodetachment bands at wavelengths between 900 and 455 nm, examining the effect of vibronic coupling on the photoelectron angular distribution (PAD). This work extends the v(')=1-4 data for detachment into the ground electronic state, presented in a recent communication [R. Mabbs, F. Mbaiwa, J. Wei, M. Van Duzor, S. T. Gibson, S. J. Cavanagh, and B. R. Lewis, Phys. Rev. A 82, 011401(R) (2010)]. Measured vibronic intensities are compared to Franck-Condon predictions and used as supporting evidence of vibronic coupling. The results are analyzed within the context of the one-electron, zero core contribution (ZCC) model [R. M. Stehman and S. B. Woo, Phys. Rev. A 23, 2866 (1981)]. For both bands, the photoelectron anisotropy parameter variation with electron kinetic energy, β(E), displays the characteristics of photodetachment from a d-like orbital, consistent with the π(g)(∗) 2p highest occupied molecular orbital of O(2)(-). However, differences exist between the β(E) trends for detachment into different vibrational levels of the X  (3)Σ(g)(-) and a (1)Δ(g) electronic states of O(2). The ZCC model invokes vibrational channel specific "detachment orbitals" and attributes this behavior to coupling of the electronic and nuclear motion in the parent anion. The spatial extent of the model detachment orbital is dependent on the final state of O(2): the higher the neutral vibrational excitation, the larger the electron binding energy. Although vibronic coupling is ignored in most theoretical treatments of PADs in the direct photodetachment of molecular anions, the present findings clearly show that it can be important. These results represent a benchmark data set for a relatively simple system, upon which to base rigorous tests of more sophisticated models.

  3. Vibronic coupling in the superoxide anion: The vibrational dependence of the photoelectron angular distribution

    NASA Astrophysics Data System (ADS)

    Van Duzor, Matthew; Mbaiwa, Foster; Wei, Jie; Singh, Tulsi; Mabbs, Richard; Sanov, Andrei; Cavanagh, Steven J.; Gibson, Stephen T.; Lewis, Brenton R.; Gascooke, Jason R.

    2010-11-01

    We present a comprehensive photoelectron imaging study of the O2(X Σg-3,v '=0-6)←O2-(X Π2g,v ″=0) and O2(aΔ1g,v '=0-4)←O2-(X Π2g,v ″=0) photodetachment bands at wavelengths between 900 and 455 nm, examining the effect of vibronic coupling on the photoelectron angular distribution (PAD). This work extends the v'=1-4 data for detachment into the ground electronic state, presented in a recent communication [R. Mabbs, F. Mbaiwa, J. Wei, M. Van Duzor, S. T. Gibson, S. J. Cavanagh, and B. R. Lewis, Phys. Rev. A 82, 011401-R (2010)]. Measured vibronic intensities are compared to Franck-Condon predictions and used as supporting evidence of vibronic coupling. The results are analyzed within the context of the one-electron, zero core contribution (ZCC) model [R. M. Stehman and S. B. Woo, Phys. Rev. A 23, 2866 (1981)]. For both bands, the photoelectron anisotropy parameter variation with electron kinetic energy, β(E ), displays the characteristics of photodetachment from a d-like orbital, consistent with the πg∗ 2p highest occupied molecular orbital of O2-. However, differences exist between the β(E ) trends for detachment into different vibrational levels of the X Σg-3 and a Δ1g electronic states of O2. The ZCC model invokes vibrational channel specific "detachment orbitals" and attributes this behavior to coupling of the electronic and nuclear motion in the parent anion. The spatial extent of the model detachment orbital is dependent on the final state of O2: the higher the neutral vibrational excitation, the larger the electron binding energy. Although vibronic coupling is ignored in most theoretical treatments of PADs in the direct photodetachment of molecular anions, the present findings clearly show that it can be important. These results represent a benchmark data set for a relatively simple system, upon which to base rigorous tests of more sophisticated models.

  4. Di-Hadron Angular Correlation Dependence on Leading Hadron Identity in Relativistic Heavy Ion Collisions

    NASA Astrophysics Data System (ADS)

    Kauder, Kolja

    A unique state of matter is created in ultra-relativistic heavy ion collisions at the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC), the Quark Gluon Plasma (QGP). It displays the properties of a near-perfect liquid of quarks and gluons (partons) interacting collectively via the strong force. Properties of this medium can be explored using high-energy probes created in the form of back-to-back pairs (jets) in hard scatterings. A distinct feature of the QGP is jet quenching, which describes the large energy loss of such probes observed in measurements of hadron distributions in head-on heavy ion collisions. A more differential measurement of jet quenching is achieved using di-hadron correlations, where relative angular distributions are studied with respect to a leading (high energy) "trigger" hadron. Two striking features found in di-hadron correlations are the emergence of a long-range plateau on the near-side (at small relative azimuth), the so-called "ridge", and a broadening and deformation of the away-side, back to back with the trigger. Using 200 GeV central gold-gold and minimum bias deuteron-gold collision data collected by the STAR detector at RHIC, a systematic study of the dependence of di-hadron correlation structures on the identity of the trigger particle is carried out in this work by statistically separating pion from non-pion (i.e. proton and kaon) triggers, offering new insights into the hadronization mechanisms in the QGP. The jet-like yield at small relative angles is found enhanced for leading pions in Au+Au data with respect to the d+Au reference, while leading non-pions (protons and kaons) do not elicit such an enhancement. These findings are discussed within the context of quark recombination. At large angles, the correlated yield is significantly higher for leading non-pions than pions. Parameters extracted from two-dimensional model fits are used to test consistency with the constituent quark scaling assumptions

  5. Electrolyte distribution around two like-charged rods: their effective attractive interaction and angular dependent charge reversal.

    PubMed

    Jiménez-Angeles, Felipe; Odriozola, Gerardo; Lozada-Cassou, Marcelo

    2006-04-07

    A simple model for two like-charged parallel rods immersed in an electrolyte solution is considered. We derived the three point extension (TPE) of the hypernetted chain/mean spherical approximation (TPE-HNC/MSA) and Poisson-Boltzmann (TPE-PB) integral equations. We numerically solve these equations and compare them to our results of Monte Carlo (MC) simulations. The effective interaction force, F(T), the charge distribution profiles, rho(el)(x,y), and the angular dependent integrated charge function, P(theta), are calculated for this system. The analysis of F(T) is carried out in terms of the electrostatic and entropic (depletion) contributions, F(E) and F(C). We studied several cases of monovalent and divalent electrolytes, for which the ionic size and concentration are varied. We find good qualitative agreement between TPE-HNC/MSA and MC in all the cases studied. The rod-rod force is found to be attractive when immersed in large size, monovalent or divalent electrolytes. In general, the TPE-PB has poor agreement with the MC. For large monovalent and divalent electrolytes, we find angular dependent charge reversal charge inversion and polarizability. We discuss the intimate relationship between this angular dependent charge reversal and rod-rod attraction.

  6. Irreversible evolution of angular-dependent coercivity in Fe80Ni20 nanowire arrays: Detection of a single vortex state

    NASA Astrophysics Data System (ADS)

    Alikhani, M.; Ramazani, A.; Almasi Kashi, M.; Samanifar, S.; Montazer, A. H.

    2016-09-01

    The irreversible evolution of magnetic coercivity in arrays of 75 nm diameter Fe80Ni20 nanowires (NWs) has been explored by means of first-order reversal curve (FORC) analysis as a function of the angle between the magnetic field and the NW axis (0°≤θ≤90°). The Fe80Ni20 NWs with lengths up to 60 μm were fabricated using a pulsed electrodeposition method into hard-anodic aluminum oxide templates with an interpore distance of 275 nm. Investigating the interwire and intrawire magnetostatic interactions, the angular FORC (AFORC) diagrams indicated enhanced intrawire interactions with increasing length and θ (<90°), induced by a magnetization reversal through vortex domain wall (VDW) propagation. Intriguingly, in addition to the VDW mode, a single vortex state with broad irreversible switching of nucleation and annihilation fields was detected at θ=83° for 60 μm long NWs. At θ=90°, the NWs reversed magnetization through transverse domain wall, involving a reversible component by a fraction of 95%. Furthermore, the transition angle between the reversal modes was found to decrease with increasing aspect ratio from 200 to 800. The irreversible angular-dependent coercivity (HcIrrev(θ)) of Fe80Ni20 NWs was extracted from the AFORC measurements and compared with the major angular dependence of coercivity (HcMajor(θ)) obtained from the conventional hysteresis loop measurements. While HcMajor(θ) showed a non-monotonic behavior, HcIrrev(θ) constantly increased with increasing θ (<90°). On the other hand, using analytical models, a 93% agreement was obtained between the theoretical angular-dependent nucleation field and experimental HcIrrev(θ) for irreversible switching of VDW when 0°≤θ≤86°.

  7. Dependencies of lepton angular distribution coefficients on the transverse momentum and rapidity of Z bosons produced in p p collisions at the LHC

    NASA Astrophysics Data System (ADS)

    Chang, Wen-Chen; McClellan, Randall Evan; Peng, Jen-Chieh; Teryaev, Oleg

    2017-09-01

    High precision data of lepton angular distributions for γ*/Z production in p p collisions at the LHC, covering broad ranges of dilepton transverse momenta (qT) and rapidity (y ), were recently reported. Strong qT dependencies were observed for several angular distribution coefficients, Ai, including A0-A4. Significant y dependencies were also found for the coefficients A1, A3 and A4, while A0 and A2 exhibit very weak rapidity dependence. Using an intuitive geometric picture, we show that the qT and y dependencies of the angular distributions coefficients can be well described.

  8. STXM/C 1s-NEXAFS study of Eu(III) and Uranyl humic acid aggregates at different pH

    NASA Astrophysics Data System (ADS)

    Plaschke, M.; Rothe, J.; Denecke, M. A.; Geckeis, H.

    2010-04-01

    Humic acids (HA) are chemically heterogeneous and structurally ill-defined biopolymers which are able to bind traces of actinides or lanthanides. Due to their dimensions in the colloidal size range they may affect transport of these elements in aquatic systems. Eu(III)- and UO22+-HA aggregates have been investigated by Scanning Transmission X-ray Microscopy (STXM) and C 1s-NEXAFS under systematic variation of pH. In the Eu(III)- and UO22+-HA systems aggregate morphologies at near neutral pH were similar to those observed in previous studies: optically dense zones (high absorption at the carbon K-edge) are embedded in a matrix of less dense material. C 1s-NEXAFS signatures observed in the different zones, i.e., the intensity of the characteristic complexation feature previously experimentally described and recently theoretically characterized, strongly depends on sample pH. In the alkaline regime (pH 9) with added carbonate, co-precipitation of Eu(III)-carbonate (or ternary carbonate/(oxo)hydroxide complexes) with the Eu(III)-HA majority fraction is observed but Eu(III) binding to HA over carbonate in the dense zones seems to be favoured. The UO22+-HA system exhibits in alkaline solution more compact morphologies combined with a strong metal ion complexation effect in the NEXAFS. Eu(III) and UO22+ polyacrylic acid (PAA) aggregates used as HA model systems show similar spectral trends; these aggregates exhibit highly branched morphologies without segregation into zones with different NEXAFS signatures. The chemical environment such as pH or the type of metal cation strongly influences both HA aggregate morphologies and NEXAFS spectral signatures. These can, in turn, be used as indicators of the strength of lanthanide or actinide ion bound HA interaction.

  9. Fast neutrino flavor conversions near the supernova core with realistic flavor-dependent angular distributions

    NASA Astrophysics Data System (ADS)

    Dasgupta, Basudeb; Mirizzi, Alessandro; Sen, Manibrata

    2017-02-01

    It has been recently pointed out that neutrino fluxes from a supernova can show substantial flavor conversions almost immediately above the core. Using linear stability analyses and numerical solutions of the fully nonlinear equations of motion, we perform a detailed study of these fast conversions, focussing on the region just above the supernova core. We carefully specify the instabilities for evolution in space or time, and find that neutrinos travelling towards the core make fast conversions more generic, i.e., possible for a wider range of flux ratios and angular asymmetries that produce a crossing between the zenith-angle spectra of νe and bar nue. Using fluxes and angular distributions predicted by supernova simulations, we find that fast conversions can occur within tens of nanoseconds, only a few meters away from the putative neutrinospheres. If these fast flavor conversions indeed take place, they would have important implications for the supernova explosion mechanism and nucleosynthesis.

  10. RADIUS-DEPENDENT ANGULAR MOMENTUM EVOLUTION IN LOW-MASS STARS. I

    SciTech Connect

    Reiners, Ansgar; Mohanty, Subhanjoy

    2012-02-10

    Angular momentum evolution in low-mass stars is determined by initial conditions during star formation, stellar structure evolution, and the behavior of stellar magnetic fields. Here we show that the empirical picture of angular momentum evolution arises naturally if rotation is related to magnetic field strength instead of to magnetic flux and formulate a corrected braking law based on this. Angular momentum evolution then becomes a strong function of stellar radius, explaining the main trends observed in open clusters and field stars at a few Gyr: the steep transition in rotation at the boundary to full convection arises primarily from the large change in radius across this boundary and does not require changes in dynamo mode or field topology. Additionally, the data suggest transient core-envelope decoupling among solar-type stars and field saturation at longer periods in very low mass stars. For solar-type stars, our model is also in good agreement with the empirical Skumanich law. Finally, in further support of the theory, we show that the predicted age at which low-mass stars spin down from the saturated to unsaturated field regimes in our model corresponds remarkably well to the observed lifetime of magnetic activity in these stars.

  11. Investigation into angular and frequency dependence of scattering matrices of elastodynamic scatterers

    NASA Astrophysics Data System (ADS)

    Zhang, Jie; Felice, Maria; Velichko, Alexander; Wilcox, Paul

    2016-02-01

    The scattering behaviour of a finite-sized elastodynamic scatterer in a homogeneous isotropic medium can be encapsulated in a scattering matrix (S-matrix) for each wave mode combination. Each S-matrix is a continuous complex function of 3 variables: incident wave angle, scattered wave angle and frequency. In the paper, the S-matrices for various scatterers (circular holes, straight smooth cracks, rough cracks and 4 circular holes in an area of interest) are investigated. It is shown that, for a given scatterer, the continuous data in the angular dimensions of an S-matrix can be represented to a prescribed level of accuracy by a finite number of complex Fourier coefficients. The finding is that the number of angular orders required to characterise a scatterer is a function of scatterer size and is related to the Nyquist theorem. The variation of scattering behaviour with frequency is examined next and is found to show periodic oscillation with a period which is a function of scatterer size and its geometry. The shortest period of these oscillations indicates the maximum frequency increment required to accurately describe the scattering behaviour in a specific frequency range. Finally, the maximum angular order and frequency increments for the chosen scatterers in a specific frequency range are suggested.

  12. Angular dependence of critical current density and magnetoresistance of sputtered high-T{sub c}-films

    SciTech Connect

    Geerkens, A.; Frenck, H.J.; Ewert, S.

    1994-12-31

    The angular dependence of the critical current density and the magnetoresistance of high-T{sub c}-films in high and low magnetic fields and for different temperatures were measured to investigate the flux pinning and the superconducting properties. A comparison of the results for the different superconductors shows their increasing dependence on the angle {Theta} between the magnetic field and the c-axis of the film due to the anisotropy of the chosen superconductor. Furthermore the influence of the current direction to the {Theta}-rotation plane is discussed.

  13. Angular dependence of critical current density and magnetoresistance of sputtered high-T(sub c)-films

    NASA Technical Reports Server (NTRS)

    Geerkens, A.; Meven, M.; Frenck, H.-J.; Ewert, S.

    1995-01-01

    The angular dependence of the critical current density and the magnetoresistance of high-T(sub c)-films in high and low magnetic fields and for different temperatures were measured to investigate the flux pinning and the superconducting properties. A comparison of the results for the different superconductors shows their increasing dependence on the angle Theta between the magnetic field and the c-axis of the film due to the anisotropy of the chosen superconductor. Furthermore the influence of the current direction to the Theta-rotation plane is discussed.

  14. Angular and temperature dependence of photon pair rates in spontaneous parametric down-conversion from a periodically poled crystal

    NASA Astrophysics Data System (ADS)

    Jimenez, G. Daniel; Garces, Veneranda G.; O'Donnell, Kevin A.

    2017-08-01

    We present a theoretical and experimental study of the angular and temperature dependence of the photon pairs produced by spontaneous parametric down-conversion in a periodically poled KTP crystal. In the experiment, two detectors are placed at different angles in the emitted light, and the detected photon pair rate is measured as a function of one angle or of crystal temperature. In the theoretical work, exact results for the pair rates are obtained through importance-sampled numerical integration of the fourth-order coherence function over regions representing the experimental integration parameters. Conditions studied range from well-resolved results in which detector angular and filter bandwidth integration effects are negligible, to other cases in which such effects are large and pair rates exceed 105s-1 . Throughout these cases, good agreement is often seen between experimental and theoretical results, while some differences that are noted provide insight into the actual crystal quasi-phase-matching function.

  15. General approach for the determination of the magneto-angular dependence of the critical current of YBCO coated conductors

    NASA Astrophysics Data System (ADS)

    Zhang, X.; Zhong, Z.; Ruiz, H. S.; Geng, J.; Coombs, T. A.

    2017-02-01

    The physical understanding and numerical modelling of superconducting devices which exploit the high performance of second generation high temperature superconducting tapes (2G-HTS), is commonly hindered by the lack of accurate functions which allow the consideration of the in-field dependence of the critical current. This is true regardless of the manufacturer of the superconducting tape. In this paper, we present a general approach for determining a unified function I c(B, θ), ultimately capable of describing the magneto-angular dependence of the in-field critical current of commercial 2G-HTS tapes in the Lorentz configuration. Five widely different superconducting tapes, provided by three different manufacturers, have been tested in a liquid nitrogen bath and external magnetic fields of up to 400 mT. The critical current was recorded at 90 different orientations of the magnetic field ranging from θ = 0°, i.e., with B aligned with the crystallographic ab-planes of the YBCO layer, towards ±90°, i.e., with B perpendicular to the wider surfaces of the 2G-HTS tape. The whole set of experimental data has been analysed using a novel multi-objective model capable of predicting a sole function I c(B, θ). This allows an accurate validation of the experimental data regardless of the fabrication differences and widths of the superconducting tapes. It is shown that, in spite of the wide set of differences between the fabrication and composition of the considered tapes, at liquid nitrogen temperature the magneto-angular dependence of the in-field critical current of YBCO-based 2G-HTS tapes, can be described by a universal function I c(f(B), θ), with a power law field dependence dominated by the Kim’s factor B/B 0, and an angular dependence moderated by the electron mass anisotropy ratio of the YBCO layer.

  16. Primary and Secondary Contributions to the Organic Aerosol Over the Amazon Determined by STXM-NEXAFS

    NASA Astrophysics Data System (ADS)

    Andreae, M. O.; Pöhlker, C.; Wiedemann, K. T.; Sinha, B.; Artaxo, P.; Kilcoyne, D.; Smith, M. L.; Martin, S. T.; Poeschl, U.

    2011-12-01

    We investigated the morphology and chemical composition of aerosol samples from a pristine tropical environment, the Amazon Basin, using Scanning Transmission X-ray Microscopy - Near Edge X-ray Absorption Fine Structure (STXMNEXAFS) analysis. The NEXAFS spectra were used to estimate the elemental ratios of C, N and O, as well as the chemical bonding state of these elements. The aim of this study was to investigate the microphysical and chemical properties of a tropical background aerosol and its internal mixing state. The samples were collected in the Amazonian rainforest during the rainy season and can be regarded as a nearly pristine background aerosol. Lab-generated SOA-samples (produced by the (photo)oxidation of isoprene, alpha-pinene and beta-caryophyllene), microtome slices of fungal spores, and aerosolized authentic organic compounds were measured as reference samples. The STXM-NEXAFS results of the lab-generated SOA have been analyzed and compared to SOA from the Amazonian region. In the lab samples, SOA occurred as droplets of different sizes, sometimes exhibiting internal structures ('raisin-like' structure). The spectral characteristics of the lab samples depend on the precursors applied for their generation. The Amazonian aerosol was found to be dominated by drop-like organic particles in the fine mode (often in internal mixture with solid particles), and Primary Biological Aerosol Particles (PBAP) in the coarse mode. Liquid organic aerosol coatings were also frequently observed on the PBAPs. Unexpectedly, many ambient SOA samples show a high content of N (around 20% or even more) as well as the frequent occurrence of potassium. Furthermore, the spectra exhibit characteristic signal patterns for different functional groups. In most cases, the spectrum near the C-edge is dominated by either the hydroxyl or the carboxylate signal, but prominent peaks for ketone carbonyls, alkanes and alkenes have also been observed. Based on these results, a new

  17. Monte Carlo study of the energy and angular dependence of the response of plastic scintillation detectors in photon beams

    SciTech Connect

    Wang, Lilie L. W.; Klein, David; Beddar, A. Sam

    2010-10-15

    Purpose: By using Monte Carlo simulations, the authors investigated the energy and angular dependence of the response of plastic scintillation detectors (PSDs) in photon beams. Methods: Three PSDs were modeled in this study: A plastic scintillator (BC-400) and a scintillating fiber (BCF-12), both attached by a plastic-core optical fiber stem, and a plastic scintillator (BC-400) attached by an air-core optical fiber stem with a silica tube coated with silver. The authors then calculated, with low statistical uncertainty, the energy and angular dependences of the PSDs' responses in a water phantom. For energy dependence, the response of the detectors is calculated as the detector dose per unit water dose. The perturbation caused by the optical fiber stem connected to the PSD to guide the optical light to a photodetector was studied in simulations using different optical fiber materials. Results: For the energy dependence of the PSDs in photon beams, the PSDs with plastic-core fiber have excellent energy independence within about 0.5% at photon energies ranging from 300 keV (monoenergetic) to 18 MV (linac beam). The PSD with an air-core optical fiber with a silica tube also has good energy independence within 1% in the same photon energy range. For the angular dependence, the relative response of all the three modeled PSDs is within 2% for all the angles in a 6 MV photon beam. This is also true in a 300 keV monoenergetic photon beam for PSDs with plastic-core fiber. For the PSD with an air-core fiber with a silica tube in the 300 keV beam, the relative response varies within 1% for most of the angles, except in the case when the fiber stem is pointing right to the radiation source in which case the PSD may over-response by more than 10%. Conclusions: At {+-}1% level, no beam energy correction is necessary for the response of all three PSDs modeled in this study in the photon energy ranges from 200 keV (monoenergetic) to 18 MV (linac beam). The PSD would be even closer

  18. Exploring the z-dependence of the two-point angular correlation function in galaxy clustering

    NASA Astrophysics Data System (ADS)

    Endres, Alyssa; Bellis, Matthew; Bard, Debbie

    2014-03-01

    The two-point angular correlation function (2ACF) is used to quantify the scales of clustering of galaxies. The 2ACF changes as we look further back in time (higher redshift z) and the clustering evolves. We calculate the exact Landy-Szalay estimator for the 2ACF using GPUs (Graphics Processing Units) and employ novel visualizations to observe the evolution of this function with increasing redshift. We use data from the MICE Grand Challenge dataset, a 70-billion particle n-body simulation that is publicly available, and compare to data from the Sloan Digital Sky Survey. The current status of this project will be presented.

  19. Lepton-Flavor-Dependent Angular Analysis of B →K*ℓ+ℓ-

    NASA Astrophysics Data System (ADS)

    Wehle, S.; Niebuhr, C.; Yashchenko, S.; Adachi, I.; Aihara, H.; Al Said, S.; Asner, D. M.; Aulchenko, V.; Aushev, T.; Ayad, R.; Aziz, T.; Babu, V.; Bakich, A. M.; Bansal, V.; Barberio, E.; Bartel, W.; Behera, P.; Bhuyan, B.; Biswal, J.; Bobrov, A.; Bondar, A.; Bonvicini, G.; Bozek, A.; Bračko, M.; Browder, T. E.; Červenkov, D.; Chang, P.; Chekelian, V.; Chen, A.; Cheon, B. G.; Chilikin, K.; Chistov, R.; Cho, K.; Choi, Y.; Cinabro, D.; Dash, N.; Dingfelder, J.; Doležal, Z.; Drásal, Z.; Dutta, D.; Eidelman, S.; Epifanov, D.; Farhat, H.; Fast, J. E.; Ferber, T.; Fulsom, B. G.; Gaur, V.; Gabyshev, N.; Garmash, A.; Gillard, R.; Goldenzweig, P.; Golob, B.; Grzymkowska, O.; Guido, E.; Haba, J.; Hara, T.; Hayasaka, K.; Hayashii, H.; Hedges, M. T.; Hou, W.-S.; Hsu, C.-L.; Iijima, T.; Inami, K.; Inguglia, G.; Ishikawa, A.; Itoh, R.; Iwasaki, Y.; Jacobs, W. W.; Jaegle, I.; Jeon, H. B.; Jin, Y.; Joffe, D.; Joo, K. K.; Julius, T.; Kaliyar, A. B.; Kang, K. H.; Karyan, G.; Katrenko, P.; Kawasaki, T.; Kichimi, H.; Kiesling, C.; Kim, D. Y.; Kim, H. J.; Kim, J. B.; Kim, K. T.; Kim, M. J.; Kim, S. H.; Kinoshita, K.; Koch, L.; Kodyš, P.; Korpar, S.; Kotchetkov, D.; Križan, P.; Krokovny, P.; Kuhr, T.; Kulasiri, R.; Kumita, T.; Kuzmin, A.; Kwon, Y.-J.; Lange, J. S.; Li, C. H.; Li, L.; Li, Y.; Li Gioi, L.; Libby, J.; Liventsev, D.; Lubej, M.; Luo, T.; Masuda, M.; Matsuda, T.; Miyabayashi, K.; Miyake, H.; Mizuk, R.; Mohanty, G. B.; Mori, T.; Mussa, R.; Nakano, E.; Nakao, M.; Nanut, T.; Nath, K. J.; Natkaniec, Z.; Nayak, M.; Nisar, N. K.; Nishida, S.; Ogawa, S.; Ono, H.; Onuki, Y.; Pakhlova, G.; Pal, B.; Park, C.-S.; Park, C. W.; Park, H.; Paul, S.; Pesántez, L.; Piilonen, L. E.; Pulvermacher, C.; Rauch, J.; Ritter, M.; Rostomyan, A.; Sakai, Y.; Sandilya, S.; Santelj, L.; Sanuki, T.; Sato, Y.; Savinov, V.; Schlüter, T.; Schneider, O.; Schnell, G.; Schwanda, C.; Schwartz, A. J.; Seino, Y.; Senyo, K.; Seon, O.; Seong, I. S.; Sevior, M. E.; Shen, C. P.; Shibata, T.-A.; Shiu, J.-G.; Shwartz, B.; Simon, F.; Sinha, R.; Solovieva, E.; Starič, M.; Strube, J. F.; Sumisawa, K.; Sumiyoshi, T.; Takizawa, M.; Tamponi, U.; Tenchini, F.; Trabelsi, K.; Tsuboyama, T.; Uchida, M.; Uglov, T.; Unno, Y.; Uno, S.; Urquijo, P.; Ushiroda, Y.; Usov, Y.; Vahsen, S. E.; Van Hulse, C.; Varner, G.; Varvell, K. E.; Vorobyev, V.; Vossen, A.; Waheed, E.; Wang, C. H.; Wang, M.-Z.; Wang, P.; Watanabe, M.; Watanabe, Y.; Widmann, E.; Williams, K. M.; Won, E.; Yamamoto, H.; Yamashita, Y.; Ye, H.; Yook, Y.; Yuan, C. Z.; Yusa, Y.; Zhang, Z. P.; Zhilich, V.; Zhukova, V.; Zhulanov, V.; Ziegler, M.; Zupanc, A.; Belle Collaboration

    2017-03-01

    We present a measurement of angular observables and a test of lepton flavor universality in the B →K*ℓ+ℓ- decay, where ℓ is either e or μ . The analysis is performed on a data sample corresponding to an integrated luminosity of 711 fb-1 containing 772 ×106 B B ¯ pairs, collected at the ϒ (4 S ) resonance with the Belle detector at the asymmetric-energy e+e- collider KEKB. The result is consistent with standard model (SM) expectations, where the largest discrepancy from a SM prediction is observed in the muon modes with a local significance of 2.6 σ .

  20. Lepton-Flavor-Dependent Angular Analysis of B→K^{*}ℓ^{+}ℓ^{-}.

    PubMed

    Wehle, S; Niebuhr, C; Yashchenko, S; Adachi, I; Aihara, H; Al Said, S; Asner, D M; Aulchenko, V; Aushev, T; Ayad, R; Aziz, T; Babu, V; Bakich, A M; Bansal, V; Barberio, E; Bartel, W; Behera, P; Bhuyan, B; Biswal, J; Bobrov, A; Bondar, A; Bonvicini, G; Bozek, A; Bračko, M; Browder, T E; Červenkov, D; Chang, P; Chekelian, V; Chen, A; Cheon, B G; Chilikin, K; Chistov, R; Cho, K; Choi, Y; Cinabro, D; Dash, N; Dingfelder, J; Doležal, Z; Drásal, Z; Dutta, D; Eidelman, S; Epifanov, D; Farhat, H; Fast, J E; Ferber, T; Fulsom, B G; Gaur, V; Gabyshev, N; Garmash, A; Gillard, R; Goldenzweig, P; Golob, B; Grzymkowska, O; Guido, E; Haba, J; Hara, T; Hayasaka, K; Hayashii, H; Hedges, M T; Hou, W-S; Hsu, C-L; Iijima, T; Inami, K; Inguglia, G; Ishikawa, A; Itoh, R; Iwasaki, Y; Jacobs, W W; Jaegle, I; Jeon, H B; Jin, Y; Joffe, D; Joo, K K; Julius, T; Kaliyar, A B; Kang, K H; Karyan, G; Katrenko, P; Kawasaki, T; Kichimi, H; Kiesling, C; Kim, D Y; Kim, H J; Kim, J B; Kim, K T; Kim, M J; Kim, S H; Kinoshita, K; Koch, L; Kodyš, P; Korpar, S; Kotchetkov, D; Križan, P; Krokovny, P; Kuhr, T; Kulasiri, R; Kumita, T; Kuzmin, A; Kwon, Y-J; Lange, J S; Li, C H; Li, L; Li, Y; Li Gioi, L; Libby, J; Liventsev, D; Lubej, M; Luo, T; Masuda, M; Matsuda, T; Miyabayashi, K; Miyake, H; Mizuk, R; Mohanty, G B; Mori, T; Mussa, R; Nakano, E; Nakao, M; Nanut, T; Nath, K J; Natkaniec, Z; Nayak, M; Nisar, N K; Nishida, S; Ogawa, S; Ono, H; Onuki, Y; Pakhlova, G; Pal, B; Park, C-S; Park, C W; Park, H; Paul, S; Pesántez, L; Piilonen, L E; Pulvermacher, C; Rauch, J; Ritter, M; Rostomyan, A; Sakai, Y; Sandilya, S; Santelj, L; Sanuki, T; Sato, Y; Savinov, V; Schlüter, T; Schneider, O; Schnell, G; Schwanda, C; Schwartz, A J; Seino, Y; Senyo, K; Seon, O; Seong, I S; Sevior, M E; Shen, C P; Shibata, T-A; Shiu, J-G; Shwartz, B; Simon, F; Sinha, R; Solovieva, E; Starič, M; Strube, J F; Sumisawa, K; Sumiyoshi, T; Takizawa, M; Tamponi, U; Tenchini, F; Trabelsi, K; Tsuboyama, T; Uchida, M; Uglov, T; Unno, Y; Uno, S; Urquijo, P; Ushiroda, Y; Usov, Y; Vahsen, S E; Van Hulse, C; Varner, G; Varvell, K E; Vorobyev, V; Vossen, A; Waheed, E; Wang, C H; Wang, M-Z; Wang, P; Watanabe, M; Watanabe, Y; Widmann, E; Williams, K M; Won, E; Yamamoto, H; Yamashita, Y; Ye, H; Yook, Y; Yuan, C Z; Yusa, Y; Zhang, Z P; Zhilich, V; Zhukova, V; Zhulanov, V; Ziegler, M; Zupanc, A

    2017-03-17

    We present a measurement of angular observables and a test of lepton flavor universality in the B→K^{*}ℓ^{+}ℓ^{-} decay, where ℓ is either e or μ. The analysis is performed on a data sample corresponding to an integrated luminosity of 711  fb^{-1} containing 772×10^{6} BB[over ¯] pairs, collected at the ϒ(4S) resonance with the Belle detector at the asymmetric-energy e^{+}e^{-} collider KEKB. The result is consistent with standard model (SM) expectations, where the largest discrepancy from a SM prediction is observed in the muon modes with a local significance of 2.6σ.

  1. Angular dependence of dissociative electron attachment topolyatomic molecules: application to the 2B1 metastable state of the H2Oand H2S anions

    SciTech Connect

    Haxton, Daniel J.; McCurdy, C. William; Rescigno, Thomas N.

    2006-01-12

    The angular dependence of dissociative electron attachment (DEA) to polyatomic targets is formulated in the local complex potential model, under the assumption that the axial recoil approximation describes the dissociation dynamics. An additional approximation, which is found to be valid in the case of H2O but not in the case of H2S, makes it possible to describe the angular dependence of DEA solely from an analysis of the fixed-nuclei entrance amplitude, without carrying out nuclear dynamics calculations. For H2S, the final-vibrational-state-specific angular dependence of DEA is obtained by incorporating the variation of the angular dependence of the entrance amplitude with nuclear geometry into the nuclear dynamics. Scattering calculations using the complex Kohn method and, for H2S, full quantum calculations of the nuclear dynamics using the Multi-Configuration Time-Dependent Hartree method, are performed.

  2. Toward an actual account for the angular dependence of the Brueckner-Bethe-Goldstone propagator in nuclear matter

    SciTech Connect

    Arellano, H. F.

    2011-04-15

    Angular correlations arising from particle-particle (pp) propagation in symmetric nuclear matter are investigated. Their account follows a detailed treatment of the angular dependence of the energy denominator of the propagator in the Brueckner-Bethe-Goldstone (BBG) equation, in conjunction with the Pauli exclusion principle for intermediate states. As a result, taking a monopole approximation for the propagator, a correlation form factor emerges from the Cauchy principal-value integral of the pp propagator, while the imaginary part becomes structurally different from those in Lippmann-Schwinger-type equations. These features are investigated within the continuous choice of the single-particle potential considering the Argonne v{sub 18} and Paris two-nucleon potentials. We find that the behavior of the mass operator is affected, deepening slightly the saturation point of symmetric nuclear matter relative to those based on angle-averaged energy denominators. Implications of these angular correlations were also investigated in the context of proton-nucleus scattering, showing clear effects on scattering observables below 100 MeV.

  3. Shear flow of angular grains: acoustic effects and nonmonotonic rate dependence of volume.

    PubMed

    Lieou, Charles K C; Elbanna, Ahmed E; Langer, J S; Carlson, J M

    2014-09-01

    Naturally occurring granular materials often consist of angular particles whose shape and frictional characteristics may have important implications on macroscopic flow rheology. In this paper, we provide a theoretical account for the peculiar phenomenon of autoacoustic compaction-nonmonotonic variation of shear band volume with shear rate in angular particles-recently observed in experiments. Our approach is based on the notion that the volume of a granular material is determined by an effective-disorder temperature known as the compactivity. Noise sources in a driven granular material couple its various degrees of freedom and the environment, causing the flow of entropy between them. The grain-scale dynamics is described by the shear-transformation-zone theory of granular flow, which accounts for irreversible plastic deformation in terms of localized flow defects whose density is governed by the state of configurational disorder. To model the effects of grain shape and frictional characteristics, we propose an Ising-like internal variable to account for nearest-neighbor grain interlocking and geometric frustration and interpret the effect of friction as an acoustic noise strength. We show quantitative agreement between experimental measurements and theoretical predictions and propose additional experiments that provide stringent tests on the new theoretical elements.

  4. Angular dependent torque measurements on CaFe0.88Co0.12AsF

    NASA Astrophysics Data System (ADS)

    Xiao, H.; Gao, B.; Ma, Y. H.; Li, X. J.; Mu, G.; Hu, T.

    2016-08-01

    Out-of-plane angular dependent torque measurements were performed on CaFe0.88Co0.12AsF (Ca1 1 1 1) single crystals. In the normal state, the torque data shows \\sin 2θ angular dependence and H 2 magnetic field dependence, as a result of paramagnetism. In the mixed state, the torque signal is a combination of the vortex torque and paramagnetic torque, and the former allows the determination of the anisotropy parameter γ. At T   =  11.5 K, γ (11.5 K ≃ 0.5 T c)  =  19.1, which is similar to the result of SmFeAsO0.8F0.2, γ ≃ 23 at T≃ 0.4{{T}\\text{c}} . So the 11 1 1 is more anisotropic compared to 11 and 122 families of iron-based superconductors. This may suggest that the electronic coupling between layers in 1 1 1 1 is less effective than in 11 and 122 families.

  5. Dependence of detection limits on angular alignment, substrate type and surface concentration in active mode standoff IR

    NASA Astrophysics Data System (ADS)

    Ortega-Zuñiga, Carlos A.; Galán-Freyle, Nataly Y.; Castro-Suarez, John R.; Aparicio-Bolaño, Joaquín.; Pacheco-Londoño, Leonardo C.; Hernández-Rivera, Samuel P.

    2013-05-01

    A standoff multivariate calibration for detection of highly energetic materials (HEM) using Fourier transform infrared spectroscopy is presented in this report. The procedure consists in standoff sensing at 1 m distance and the variation of three parameters of detection. The first variable considered was the angular dependence: 0° to 45‡ from source-target with respect to alignment of target-detector. The second variable consisted on the use of several surfaces on which the material was deposited. The substrates used were polished aluminum and anodized aluminum. The third variable studied was the dependence on some specific analyte loading surface concentration: from 10 μg/cm2 to200 μg/cm2. The HEM used in this work was PETN, synthesized in our lab. Calibration curves were based on the use of chemometrics routines such as partial least squares (PLS) regression analysis. This algorithm was used to evaluate the impact of the angular dependence about the limits of detection of different HME loadings on aluminum substrates.

  6. The angular dependence of pulse shape discrimination and detection sensitivity in cylindrical and cubic EJ-309 organic liquid scintillators

    NASA Astrophysics Data System (ADS)

    Jones, A. R.; Joyce, M. J.

    2017-01-01

    Liquid scintillators are used widely for neutron detection and for the assay of nuclear materials. However, due to the constituents of the detector and the nitrogen void within the detector cell, usually incorporated to accommodate any expansion that might occur to avoid leakage, fluctuations in detector response have been observed associated with the orientation of the detector when in use. In this work the angular dependence of the pulse-shape discrimination performance in an EJ309 liquid scintillator has been investigated with 252Cf in terms of the separation of γ -ray and neutron events, described quantitatively by the figure-of-merit. A subtle dependence in terms of pulse-shape discrimination is observed. In contrast, a more significant dependence of detection sensitivity with the angle of orientation is evident.

  7. Performance of scene dependent angular models in deriving top-of-atmosphere radiative fluxes from satellite radiance measurements

    NASA Technical Reports Server (NTRS)

    Suttles, John T.; Wielicki, Bruce A.; Vemury, Sastri

    1990-01-01

    The ERB experiment algorithm is applied to the Nimbus-7 scanner data for June 1979 to analyze the performance of scene-dependent angular models. The ERBE-derived albedo and LW flux are compared to results from the sorting-into-angular-bins (SAB) method described by Arking and Vemury (1984) and the ERB Matrix algorithm described by Jacobowitz et al. (1984). Results are given for the variation of ERBE-derived flux with viewing zenith angle. Comparing results derived from the ERBE algorithm and from the SAB method, zonal mean differences for the month were less than 0.01 for albedo and 2 W/ sq m for longwave flux. When compared to the ERB matrix algorithm, the ERBE algorithm gives less dependence on viewing zenith angle for SW fluxes, but more for LW fluxes. Cloud results from the ERBE method using broadband Nimbus-7 ERB radiances are compared with the new cloud ERB data results of Stowe et al. (1988). Agreement typically within 0.10 was found.

  8. Asymmetric angular dependence of spin-transfer torques in CoFe/Mg-B-O/CoFe magnetic tunnel junctions

    NASA Astrophysics Data System (ADS)

    Tang, Ling; Xu, Zhi-Jun; Zuo, Xian-Jun; Yang, Ze-Jin; Gao, Qing-He; Linghu, Rong-Feng; Guo, Yun-Dong

    2016-04-01

    Using a first-principles noncollinear wave-function-matching method, we studied the spin-transfer torques (STTs) in CoFe/Mg-B-O/CoFe(001) magnetic tunnel junctions (MTJs), where three different types of B-doped MgO in the spacer are considered, including B atoms replacing Mg atoms (Mg3BO4), B atoms replacing O atoms (Mg4BO3), and B atoms occupying interstitial positions (Mg4BO4) in MgO. A strong asymmetric angular dependence of STT can be obtained both in ballistic CoFe/Mg3BO4 and CoFe/Mg4BO4 based MTJs, whereas a nearly symmetric STT curve is observed in the junctions based on CoFe/Mg4BO3. Furthermore, the asymmetry of the angular dependence of STT can be suppressed significantly by the disorder of B distribution. Such skewness of STTs in the CoFe/Mg-B-O/CoFe MTJs could be attributed to the interfacial resonance states induced by the B diffusion into MgO spacer.

  9. Asymmetric angular dependence of spin-transfer torques in CoFe/Mg-B-O/CoFe magnetic tunnel junctions

    SciTech Connect

    Tang, Ling Xu, Zhi-Jun Zuo, Xian-Jun; Yang, Ze-Jin; Gao, Qing-He; Linghu, Rong-Feng; Guo, Yun-Dong

    2016-04-28

    Using a first-principles noncollinear wave-function-matching method, we studied the spin-transfer torques (STTs) in CoFe/Mg-B-O/CoFe(001) magnetic tunnel junctions (MTJs), where three different types of B-doped MgO in the spacer are considered, including B atoms replacing Mg atoms (Mg{sub 3}BO{sub 4}), B atoms replacing O atoms (Mg{sub 4}BO{sub 3}), and B atoms occupying interstitial positions (Mg{sub 4}BO{sub 4}) in MgO. A strong asymmetric angular dependence of STT can be obtained both in ballistic CoFe/Mg{sub 3}BO{sub 4} and CoFe/Mg{sub 4}BO{sub 4} based MTJs, whereas a nearly symmetric STT curve is observed in the junctions based on CoFe/Mg{sub 4}BO{sub 3}. Furthermore, the asymmetry of the angular dependence of STT can be suppressed significantly by the disorder of B distribution. Such skewness of STTs in the CoFe/Mg-B-O/CoFe MTJs could be attributed to the interfacial resonance states induced by the B diffusion into MgO spacer.

  10. Temperature properties of the alignment dependence of coercive force decrease ratio and the angular dependence of coercive force in Nd-Fe-B sintered magnets

    NASA Astrophysics Data System (ADS)

    Matsuura, Yutaka; Kitai, Nobuyuki; Ishii, Rintaro; Natsumeda, Mitsutoshi; Hoshijima, Jun; Kuniyoshi, Futoshi

    2016-01-01

    The temperature dependence of the coercive force decrease ratio for aligned magnets was investigated from room temperature (296 K) to 473 K. The temperature properties of the angular dependence of the coercive force were also measured from room temperature to 413 K, for comparison against the coercive force decrease ratio. From the temperature dependence of the coercive force decrease ratio of magnets with different alignment, it was found that the coercive force decrease ratio decreased as temperature increased until becoming close to the calculation results that were obtained from the Gaussian distribution for Nd2Fe14B grain alignment and from the postulation that every grain follows the Kondorskii law or the 1/cos θ law. When we compared the angle of the magnetization reverse area obtained from these calculation results and the angle of the reverse magnetization area calculated from the experimental data of the coercive force decrease ratio, it was found that this latter expanded to 30° for Nd13.48B5.76Co0.55Febal. having 0.95 alignment, at room temperature, from 14° that was the calculated angle obtained from the Gaussian distribution and the Kondorskii law. The angular dependence of coercive force of this magnet at room temperature agrees well with the calculation, when σ=31°, which is 30° for the reversed magnetization area, is applied as the standard deviation of Nd2Fe14B grain alignment distribution. For Nd12.75Dy0.84B5.81Co0.55Febal. with 0.96 for alignment, the reverse magnetization area also expanded to 36° and agreed well with the calculation result applied σ=44°, which has 36° for the reverse magnetization area. It was also found that, as temperature increased, the angle of the reverse magnetization area obtained from the experimental data shrunk towards the calculated angle. When we apply these results to the temperature properties of the angular dependence of the coercive force, it seems that the calculated angular dependence of the

  11. Interplay effect of angular dependence and calibration field size of MapCHECK 2 on RapidArc quality assurance.

    PubMed

    Jin, Hosang; Keeling, Vance P; Johnson, Daniel A; Ahmad, Salahuddin

    2014-05-08

    The purpose of this study is to investigate an effect of angular dependence and calibration field size of MapCHECK 2 on RapidArc QA for 6, 8, 10, and 15 MV. The angular dependence was investigated by comparing MapCHECK 2 measurements in MapPHAN-MC2 to the corresponding Eclipse calculations every 10° using 10× 10 cm2 and 3 × 3 cm2 fields. Fourteen patients were selected to make RapidArc plans using the four energies, and verification plans were delivered to two phantom setups: MapCHECK 2/MapPHAN phantom (MapPHAN QA) and MapCHECK 2 on an isocentric mounting fixture (IMF QA). Migration of MapCHECK 2 on IMF was simulated by splitting arcs every 10° and displacing an isocenter of each partial arc in the Eclipse system (IMFACTUAL QA). To investigate the effect of calibration field size, MapCHECK 2 was calibrated by two field sizes (10 × 10 cm2 and 3 × 3 cm2) and applied to all QA measurements. The γ test was implemented using criteria of 1%/1 mm, 2%/2 mm, and 3%/3 mm. A mean dose of all compared points for each plan was compared with respect to a mean effective field size of the RapidArc plan. The angular dependence was considerably high at gantry angles of 90° ± 10° and 270° ± 10° (for 10 × 10/3 × 3 cm2 at 90°, 30.6% ± 6.6%/33.4%± 5.8% (6 MV), 17.3% ± 5.3%/15.0% ± 6.8% (8 MV), 8.9%± 2.9%/7.8% ± 3.2% (10 MV), and 2.2% ± 2.3%/-1.3% ± 2.6% (15 MV)). For 6 MV, the angular dependence significantly deteriorated the γ passing rate for plans of large field size in MapPHAN QA (< 90% using 3%/3 mm); however, these plans passed the γ test in IMFACTUAL QA (> 95%). The different calibration field sizes did not make any significant dose difference for both MapPHAN QA and IMFACTUAL QA. For 8, 10, and 15 MV, the angular dependence does not make any clinically meaningful impact on MapPHAN QA. Both MapPHAN QA and IMFACTUAL QA presented clinically acceptable γ passing rates using 3%/3 mm. MapPHAN QA showed better passing rates than IMFACTUAL QA for the

  12. Heavy-ion versus 3He/4He fusion-fission reactions: Angular momentum dependence of dissipation in nuclear fission

    NASA Astrophysics Data System (ADS)

    Ye, W.

    2011-09-01

    The stochastic Langevin model is employed to study dissipation properties in fission in the 16O + 181Ta →197Tl system by analyzing prescission neutron yields measured in this reaction. It has been found that the 197Tl nuclei undergo fission that is not in accordance with the standard Bohr-Wheeler statistical theory. A detailed comparison with previously published work in which fission excitation functions measured in 3,4He + 197Au →200,201Tl are shown to be in excellent agreement with the fission width formula predicted by the traditional models of nuclear fission suggests that nuclear dissipation strength may have an angular momentum dependence in addition to the known deformation and temperature dependence. Implications for the basic understanding of the observed abnormal rise in prescission particles at high energy and the need for further experimental confirmations are discussed.

  13. Angular dependence of the response of the nanoDot OSLD system for measurements at depth in clinical megavoltage beams

    SciTech Connect

    Lehmann, Joerg; Dunn, Leon; Lye, Jessica E.; Kenny, John W.; Alves, Andrew D. C.; Cole, Andrew; Asena, Andre; Kron, Tomas; Williams, Ivan M.

    2014-06-15

    Purpose: The purpose of this investigation was to assess the angular dependence of a commercial optically stimulated luminescence dosimeter (OSLD) dosimetry system in MV x-ray beams at depths beyondd{sub max} and to find ways to mitigate this dependence for measurements in phantoms. Methods: Two special holders were designed which allow a dosimeter to be rotated around the center of its sensitive volume. The dosimeter's sensitive volume is a disk, 5 mm in diameter and 0.2 mm thick. The first holder rotates the disk in the traditional way. It positions the disk perpendicular to the beam (gantry pointing to the floor) in the initial position (0°). When the holder is rotated the angle of the disk towards the beam increases until the disk is parallel with the beam (“edge on,” 90°). This is referred to as Setup 1. The second holder offers a new, alternative measurement position. It positions the disk parallel to the beam for all angles while rotating around its center (Setup 2). Measurements with five to ten dosimeters per point were carried out for 6 MV at 3 and 10 cm depth. Monte Carlo simulations using GEANT4 were performed to simulate the response of the active detector material for several angles. Detector and housing were simulated in detail based on microCT data and communications with the manufacturer. Various material compositions and an all-water geometry were considered. Results: For the traditional Setup 1 the response of the OSLD dropped on average by 1.4% ± 0.7% (measurement) and 2.1% ± 0.3% (Monte Carlo simulation) for the 90° orientation compared to 0°. Monte Carlo simulations also showed a strong dependence of the effect on the composition of the sensitive layer. Assuming the layer to completely consist of the active material (Al{sub 2}O{sub 3}) results in a 7% drop in response for 90° compared to 0°. Assuming the layer to be completely water, results in a flat response within the simulation uncertainty of about 1%. For the new Setup 2

  14. Angular dependence of the response of the nanoDot OSLD system for measurements at depth in clinical megavoltage beams.

    PubMed

    Lehmann, Joerg; Dunn, Leon; Lye, Jessica E; Kenny, John W; Alves, Andrew D C; Cole, Andrew; Asena, Andre; Kron, Tomas; Williams, Ivan M

    2014-06-01

    The purpose of this investigation was to assess the angular dependence of a commercial optically stimulated luminescence dosimeter (OSLD) dosimetry system in MV x-ray beams at depths beyond d(max) and to find ways to mitigate this dependence for measurements in phantoms. Two special holders were designed which allow a dosimeter to be rotated around the center of its sensitive volume. The dosimeter's sensitive volume is a disk, 5 mm in diameter and 0.2 mm thick. The first holder rotates the disk in the traditional way. It positions the disk perpendicular to the beam (gantry pointing to the floor) in the initial position (0°). When the holder is rotated the angle of the disk towards the beam increases until the disk is parallel with the beam ("edge on," 90°). This is referred to as Setup 1. The second holder offers a new, alternative measurement position. It positions the disk parallel to the beam for all angles while rotating around its center (Setup 2). Measurements with five to ten dosimeters per point were carried out for 6 MV at 3 and 10 cm depth. Monte Carlo simulations using GEANT4 were performed to simulate the response of the active detector material for several angles. Detector and housing were simulated in detail based on microCT data and communications with the manufacturer. Various material compositions and an all-water geometry were considered. For the traditional Setup 1 the response of the OSLD dropped on average by 1.4% ± 0.7% (measurement) and 2.1% ± 0.3% (Monte Carlo simulation) for the 90° orientation compared to 0°. Monte Carlo simulations also showed a strong dependence of the effect on the composition of the sensitive layer. Assuming the layer to completely consist of the active material (Al2O3) results in a 7% drop in response for 90° compared to 0°. Assuming the layer to be completely water, results in a flat response within the simulation uncertainty of about 1%. For the new Setup 2, measurements and Monte Carlo simulations found the

  15. Mixed optical Cherenkov-Bremsstrahlung radiation in vicinity of the Cherenkov cone from relativistic heavy ions: Unusual dependence of the angular distribution width on the radiator thickness

    NASA Astrophysics Data System (ADS)

    Rozhkova, E. I.; Pivovarov, Yu. L.

    2016-07-01

    The Cherenkov radiation (ChR) angular distribution is usually described by the Tamm-Frank (TF) theory, which assumes that relativistic charged particle moves uniformly and rectilinearly in the optically transparent radiator. According to the TF theory, the full width at half maximum (FWHM) of the ChR angular distribution inversely depends on the radiator thickness. In the case of relativistic heavy ions (RHI) a slowing-down in the radiator may sufficiently change the angular distribution of optical radiation in vicinity of the Cherenkov cone, since there appears a mixed ChR-Bremsstrahlung radiation. As a result, there occurs a drastic transformation of the FWHM of optical radiation angular distribution in dependence on the radiator thickness: from inversely proportional (TF theory) to the linearly proportional one. In our paper we present the first analysis of this transformation taking account of the gradual velocity decrease of RHI penetrating through a radiator.

  16. On the time-dependent calculation of angular averaged vibronic absorption spectra with an application to molecular aggregates

    NASA Astrophysics Data System (ADS)

    Brüning, Christoph; Engel, Volker

    2017-01-01

    We introduce an efficient method to determine angular averaged absorption spectra for cases where electronic transitions take place to a manifold of N coupled excited states. The approach rests on the calculation of time-dependent auto-correlation functions which, upon Fourier-transform yield the spectrum. Assuming the Condon-approximation, it is shown that three wave-packet propagations are sufficient to calculate the spectrum. This is in contrast to a direct approach where it is necessary to perform N propagations to arrive at N2 cross-correlation functions. The reduction in computation time is of importance for larger molecular aggregates where the number N is determined by the aggregate size. We provide an example by determining spectra for macrocyclic dyes in different dipole-geometries.

  17. Azimuthal angular dependent hysteresis loops of Fe50Mn50/Ni81Fe19 bilayers grown under a magnetic field

    NASA Astrophysics Data System (ADS)

    Choi, Hyeok-Cheol; You, Chun-Yeol; Kim, Ki-Yeon

    2016-11-01

    The azimuthal angular dependence of the vectorial hysteresis loops in the Fe50Mn50(AF)/Ni81Fe19(F) bilayer grown under a magnetic field was investigated using a combination of vectorial magneto-optic Kerr effect and model calculation. From a comparison of the experimental and calculation results, it is found that the AF easy axis is not parallel with but rotated by about 20° away from the applied magnetic field during the sample growth. Moreover, the transverse loop at the AF easy axis does not vanish but displays an open full circle (i.e., magnetization changes sign between decreasing and increasing field branches for the full hysteresis measurement). Our model calculation reveals that they are reminiscent of the non-collinear uniaxial and unidirectional anisotropies. Specifically, the angular dependence of the transverse hysteresis is well reproduced with our model calculation taking non-collinear magnetic anisotropies into account. Coercivity determined from the longitudinal loops, on the other hand, is found to be nonzero and comparatively large at all azimuthal angles. This is in stark contrast with previous results regarding FeMn/NiFe bilayers field-cooled after sample growth. Neither domain wall nor incoherent magnetic rotation in the F layer is likely to be responsible for this coercivity discrepancy between theory and experiments. Apart from the uniaxial F and unidirectional AF-F anisotropies, we suggest that the F rotatable anisotropy equivalent of 40% to 60% of the interfacial coupling energy should be taken into account to properly address the coercivity enhancement in the FeMn/NiFe bilayer grown under a magnetic field.

  18. Improved model for the angular dependence of excimer laser ablation rates in polymer materials

    SciTech Connect

    Pedder, J. E. A.; Holmes, A. S.; Dyer, P. E.

    2009-10-26

    Measurements of the angle-dependent ablation rates of polymers that have applications in microdevice fabrication are reported. A simple model based on Beer's law, including plume absorption, is shown to give good agreement with the experimental findings for polycarbonate and SU8, ablated using the 193 and 248 nm excimer lasers, respectively. The modeling forms a useful tool for designing masks needed to fabricate complex surface relief by ablation.

  19. NMR investigation of novel superconductivity and angular dependent magnetic effects in Bechgaard salts

    NASA Astrophysics Data System (ADS)

    Shinagawa, Jun

    The Bechgaard salts, (TMTSF)2X where X = PF6, ClO 4, etc., are correlated, quasi-1D organic conductors. They exhibit remarkably diverse ground states, including metallic, superconducting and spin-density wave (SDW) phases; which is stabilized depends on the lattice constants, which are controlled by mechanical or chemical pressure (by exchanging one anion for another). Applied magnetic fields induce intriguing phenomena as well, including the stabilization of field-induced spin-density wave (FISDW) states and associated quantum Hall effect, and the non-Fermi liquid phenomena known as the magic angle effect (MAE) in the normal state. The MAE has been studied intensively, but its mechanisms are elusive. Similarly, the nature of the superconducting state has been controversial since its discovery a quarter-century ago. This thesis investigates these two significant problems in Bechgaard salt using NMR as a probe. 77Se spin-lattice relaxation rate ( T-11 ) in (TMTSF)2PF6 exhibited no observable change associated with MAE when the magnetic field was rotated through magic angles from non-magic angles. The temperature dependence of T-11 confirmed that there was no spin gap in the spin excitation spectrum, nor any sign to indicate enhancement of the threshold field of the FISDW state at the magic angles. 77Se T-11 for both H||a and H|| b' in the superconducting state at low fields (H ≤ 13kOe) showed weak temperature dependence below the transition temperature, consistent with an anisotropic superconducting gap. Knight shift measurements on 77Se for both H||a and H||b' at low fields showed frequency shifts consistent with the reduction of static spin susceptibilities in the superconducting state, indicating the pairing is singlet. The field dependence of T-11 at T = 100mK exhibits crossover within the superconducting state at H ≈ 13kOe, to a regime where T-11 approaches the normal-state value, suggesting a possible phase transition within the superconducting state from

  20. THE MASS-DEPENDENCE OF ANGULAR MOMENTUM EVOLUTION IN SUN-LIKE STARS

    SciTech Connect

    Matt, Sean P.; Baraffe, Isabelle; Chabrier, Gilles; Brun, A. Sacha

    2015-02-01

    To better understand the observed distributions of the rotation rate and magnetic activity of Sun-like and low-mass stars, we derive a physically motivated scaling for the dependence of the stellar wind torque on the Rossby number. The torque also contains an empirically derived scaling with stellar mass (and radius), which provides new insight into the mass-dependence of stellar magnetic and wind properties. We demonstrate that this new formulation explains why the lowest mass stars are observed to maintain rapid rotation for much longer than solar-mass stars, and simultaneously why older populations exhibit a sequence of slowly rotating stars, in which the low-mass stars rotate more slowly than solar-mass stars. The model also reproduces some previously unexplained features in the period-mass diagram for the Kepler field, notably: the particular shape of the ''upper envelope'' of the distribution, suggesting that ∼95% of Kepler field stars with measured rotation periods are younger than ∼4 Gyr; and the shape of the ''lower envelope'', corresponding to the location where stars transition between magnetically saturated and unsaturated regimes.

  1. Angular dependence of the reflectance from an isotropic polydomain medium: effect of large domain size on total reflection.

    PubMed

    Mayerhöfer, Thomas G; Popp, Jürgen

    2005-03-01

    We investigate the angular dependence of the reflectance from an isotropic medium consisting of optically large and anisotropic, randomly oriented domains, assuming a highly refractive, isotropic, and homogeneous incidence medium, which is presumed to have a higher refractive index than any of the domains' principal indices of refraction. By employing average reflectance and transmittance theory, we are able to show that the onset of total reflection is considerably shifted to higher angles of incidence compared with an isotropic medium with domains that are small compared with the wavelength. The onset of total reflection for a random medium with large domains is found to be dependent only on the largest principal index of refraction of the domains, assuming that all domains have the same optical properties. Therefore the shift of the onset depends on the magnitude of the optical anisotropy of the domains. Even in the case of a small optical anisotropy, large cross-polarization terms are predicted in the vicinity of the onset of total reflection. These terms show a pronounced maximum near that onset and extend beyond it.

  2. Simulations of the angular dependence of the dipole-dipole interaction among Rydberg atoms

    NASA Astrophysics Data System (ADS)

    Bigelow, Jacob L.; Hollingsworth, Jacob; Paul, Jacob T.; Peleg, Matan; Sanford, Veronica L.; Carroll, Thomas J.; Noel, Michael W.

    2016-05-01

    The dipole-dipole interaction between two Rydberg atoms depends on the relative orientation of the atoms and on the change in the magnetic quantum number. We simulate the effect of this anisotropy on the energy transport in an amorphous many atom system of ultracold Rydberg atoms subject to a homogeneous applied electric field. We consider two experimentally feasible geometries and find that the effects should be measurable in current generation imaging experiments. We also examine evidence for Anderson localization. This work was supported by the National Science Foundation under Grants No. 1205895 and No. 1205897 and used the Extreme Science and Engineering Discovery Environment (XSEDE), which is supported by National Science Foundation Grant Number OCI-1053575.

  3. False spin zeros in the angular dependence of magnetic quantum oscillations in quasi-two-dimensional metals

    NASA Astrophysics Data System (ADS)

    Grigoriev, P. D.; Mogilyuk, T. I.

    2017-05-01

    The interplay between angular and quantum magnetoresistance oscillations in quasi-two-dimensional metals leads to the angular oscillations of the amplitude of quantum oscillations. This effect becomes pronounced in high magnetic field, where the simple factorization of the angular and quantum oscillations is not valid. The amplitude of quantum magnetoresistance oscillations is reduced at the Yamaji angles, i.e., at the maxima of the angular magnetoresistance oscillations. These angular beats of the amplitude of quantum oscillations resemble and may be confused with the spin-zero effect, coming from the Zeeman splitting. The proposed effect of "false spin zeros" becomes stronger in the presence of incoherent channels of interlayer electron transport and can be used to separate the different contributions to the Dingle temperature and to check for violations of the standard factorization of angular and quantum magnetoresistance oscillations.

  4. Nuclear quantum effects in the structure and lineshapes of the N2 NEXAFS spectrum

    SciTech Connect

    Fatehi, Shervin; Schwartz, Craig P.; Saykally, Richard J.; Prendergast, David

    2009-12-04

    We study the relative ability of several models of the X-ray absorption spectrum to capture the Franck-Condon structure apparent from an experiment on gaseous nitrogen. In doing so, we adopt the Born-Oppenheimer approximation and a constrained density functional theory method for computing the energies of the X-ray-excited molecule. Starting from an otherwise classical model for the spectrum, we systematically introduce more realistic physics, first by substituting the quantum mechanical nuclear radial density in the bond separation R for the classical radial density, then by adding the effect of zero-point energy and other level shifts, and finally by including explicit rovibrational quantization of both the ground and excited states. The quantization is determined exactly, using a discrete variable representation. We show that the NEXAFS spectrum can be predicted semiquantiatively within this framework. We also address the possibility of non-trivial temperature dependence in the spectrum. Finally, we show that it is possible to improve the predicted spectrum by using constrained DFT in combination with more accurate potentials.

  5. Angular dependence of jet quenching indicates its strong enhancement near the QCD phase transition.

    PubMed

    Liao, Jinfeng; Shuryak, Edward

    2009-05-22

    We study dependence of jet quenching on matter density, using "tomography" of the fireball provided by RHIC data on azimuthal anisotropy v_{2} of high p_{t} hadron yield at different centralities. Slicing the fireball into shells with constant (entropy) density, we derive a "layer-wise geometrical limit" v_{2};{max} which is indeed above the data v_{2} < v_{2};{max}. Interestingly, the limit is reached only if quenching is dominated by shells with the entropy density exactly in the near-T_{c} region. We show two models that simultaneously describe the high p_{t} v_{2} and R_{A-A} data and conclude that such a description can be achieved only if the jet quenching is few times stronger in the near-T_{c} region relative to QGP at T > T_{c}. One possible reason for such enhancement may be recent indications that the near-T_{c} region is a magnetic plasma of relatively light color-magnetic monopoles.

  6. Angular dependence of optical modes in metal-insulator-metal coupled quantum well infrared photodetector

    SciTech Connect

    Jing, YouLiang; Li, ZhiFeng Chen, PingPing; Zhou, XiaoHao; Wang, Han; Li, Ning; Lu, Wei; Li, Qian

    2016-04-15

    We report the dependence of the near-field optical modes in metal-insulator-metal quantum well infrared photodetector (MIM-QWIP) on the incident angles. Three optical modes are observed and attributed to the 2nd- and the 3rd-order surface plasmon polariton (SPP) modes and the localized surface polariton (LSP) mode. In addition to the observation of a responsivity enhancement of 14 times by the LSP mode, the varying pattern of the three modes against the incident angle are revealed, in which the LSP mode is fixed while the 2nd SPP mode splits into two branches and the 3rd SPP mode red-shifts. The detailed mechanisms are analyzed and numerically simulated. The results fit the experiments very well, demonstrating the wavevector coupling effect between the incident light and the metal gratings on the SPP modes. Our work will pave the way to fully understanding the influence of incident angles on a detector’s response for applying the MIM-QWIP to focal plane arrays.

  7. Angular and polarization dependence of all optical diode in one-dimensional photonic crystal

    NASA Astrophysics Data System (ADS)

    Jamshidi-Ghaleh, Kazem; Safari, Zeinab; Moslemi, Fatemeh

    2015-05-01

    The effect of the incident angle on all-optical diode (AOD) efficiency in a one-dimensional photonic crystal structure (1DPC) for TE and TM polarizations was studied. An asymmetric hybrid Fabry Perot resonator type 1DPC structure composed of linear and nonlinear materials was considered in this communication. The nonlinear transmission curves around the defect mode resonant frequency inside the photonic band gap for both TE and TM polarizations at different incident angles, from left to right (L-R) and right to left (R-L) incidences, are illustrated. Results showed that with increasing the incident angle, AOD performance efficiency increases only for TM polarization. The AOD efficiency increased to 80% for an incident angle of 60 degrees because of the dynamical shifting of the defect mode peak frequency caused by the intensity-dependency of the nonlinear layer refractive index along the z-axes. For TE polarization, the z-component of the electric field remained constant for all incident angles. The results of this study can be important in optical data communications and information analysis in all-optical integrated circuits.

  8. Angular Dependence of Jet Quenching Indicates Its Strong Enhancement Near the QCD Phase Transition

    SciTech Connect

    Liao, Jinfeng; Shuryak, Edward

    2008-10-22

    We study dependence of jet quenching on matter density, using 'tomography' of the fireball provided by RHIC data on azimuthal anisotropy v{sub 2} of high p{sub t} hadron yield at different centralities. Slicing the fireball into shells with constant (entropy) density, we derive a 'layer-wise geometrical limit' v{sub 2}{sup max} which is indeed above the data v{sub 2} < v{sub x}{sup max}. Interestingly, the limit is reached only if quenching is dominated by shells with the entropy density exactly in the near-T{sub c} region. We show two models that simultaneously describe the high p{sub t} v{sub 2} and R{sub AA} data and conclude that such a description can be achieved only if the jet quenching is few times stronger in the near-T{sub c} region relative to QGP at T > T{sub c}. One possible reason for that may be recent indications that the near-T{sub c} region is a magnetic plasma of relatively light color-magnetic monopoles.

  9. Angular dependence of optical modes in metal-insulator-metal coupled quantum well infrared photodetector

    NASA Astrophysics Data System (ADS)

    Jing, YouLiang; Li, ZhiFeng; Li, Qian; Chen, PingPing; Zhou, XiaoHao; Wang, Han; Li, Ning; Lu, Wei

    2016-04-01

    We report the dependence of the near-field optical modes in metal-insulator-metal quantum well infrared photodetector (MIM-QWIP) on the incident angles. Three optical modes are observed and attributed to the 2nd- and the 3rd-order surface plasmon polariton (SPP) modes and the localized surface polariton (LSP) mode. In addition to the observation of a responsivity enhancement of 14 times by the LSP mode, the varying pattern of the three modes against the incident angle are revealed, in which the LSP mode is fixed while the 2nd SPP mode splits into two branches and the 3rd SPP mode red-shifts. The detailed mechanisms are analyzed and numerically simulated. The results fit the experiments very well, demonstrating the wavevector coupling effect between the incident light and the metal gratings on the SPP modes. Our work will pave the way to fully understanding the influence of incident angles on a detector's response for applying the MIM-QWIP to focal plane arrays.

  10. Azimuthal angular dependence study of the atmospheric muon charge ratio at sea level using Geant4

    NASA Astrophysics Data System (ADS)

    Arslan, Halil; Bektasoglu, Mehmet

    2012-05-01

    The azimuth dependence of the cosmic muon charge ratio at sea level was estimated using the Geant4 simulation package. Simulations were separately run at 12 azimuth angles ranging from 0° to 330° with 30° increment. Two hundred thousand proton and alpha particles were randomly distributed over the zenith angle range 30° < θ < 40° at each azimuth angle. The kinetic energy spectra of proton and helium nuclei were taken from the balloon-flight measurements. The atmospheric muon charge ratio was calculated at each azimuthal angle for low energy muons with a mean momentum around 0.5 GeV/c. The Geant4 simulation results have been compared with those of the CORSIKA simulation program and with the WILLI measurements. The simulation results reproduce well the measured east-west effect with a non-zero asymmetry AEW = 0.24. This asymmetry in the charge ratio decreases from 0.37 to 0.19 as the momentum increases from 0.22 to 0.70 GeV/c.

  11. Angular Dependence of Jet Quenching Indicates Its Strong Enhancement near the QCD Phase Transition

    SciTech Connect

    Liao Jinfeng; Shuryak, Edward

    2009-05-22

    We study dependence of jet quenching on matter density, using 'tomography' of the fireball provided by RHIC data on azimuthal anisotropy v{sub 2} of high p{sub t} hadron yield at different centralities. Slicing the fireball into shells with constant (entropy) density, we derive a 'layer-wise geometrical limit' v{sub 2}{sup max} which is indeed above the data v{sub 2}T{sub c}. One possible reason for such enhancement may be recent indications that the near-T{sub c} region is a magnetic plasma of relatively light color-magnetic monopoles.

  12. Angular dependent anisotropic terahertz response of vertically aligned multi-walled carbon nanotube arrays with spatial dispersion

    NASA Astrophysics Data System (ADS)

    Zhou, Yixuan; Yiwen, E.; Xu, Xinlong; Li, Weilong; Wang, Huan; Zhu, Lipeng; Bai, Jintao; Ren, Zhaoyu; Wang, Li

    2016-12-01

    Spatial dispersion effect of aligned carbon nanotubes (CNTs) in the terahertz (THz) region has significance for both theoretical and applied consideration due to the unique intrinsically anisotropic physical properties of CNTs. Herein, we report the angular dependent reflection of p-polarized THz wave from vertically aligned multi-walled CNT arrays in both experiment and theory. The spectra indicate that the reflection depends on the film thickness of vertically aligned CNTs, the incident angle, and the frequency. The calculation model is based on the spatial dispersion effect of aligned CNTs and performed with effective impedance method and the Maxwell-Garnett approximation. The results fit well with the experiment when the thickness of CNT film is thin, which reveals a coherent superposition mechanism of the CNT surface reflection and CNTs/Si interface reflection. For thick CNT films, the CNTs/Si interface response determines the reflection at small incident angles, while the CNTs surface effect dominates at large incident angles. This work investigates the spatial dispersion effect of vertically aligned CNT arrays in the THz region, and paves a way for potential anisotropic THz applications based on CNTs with oblique incidence requirements.

  13. Angular dependent anisotropic terahertz response of vertically aligned multi-walled carbon nanotube arrays with spatial dispersion

    PubMed Central

    Zhou, Yixuan; E., Yiwen; Xu, Xinlong; Li, Weilong; Wang, Huan; Zhu, Lipeng; Bai, Jintao; Ren, Zhaoyu; Wang, Li

    2016-01-01

    Spatial dispersion effect of aligned carbon nanotubes (CNTs) in the terahertz (THz) region has significance for both theoretical and applied consideration due to the unique intrinsically anisotropic physical properties of CNTs. Herein, we report the angular dependent reflection of p-polarized THz wave from vertically aligned multi-walled CNT arrays in both experiment and theory. The spectra indicate that the reflection depends on the film thickness of vertically aligned CNTs, the incident angle, and the frequency. The calculation model is based on the spatial dispersion effect of aligned CNTs and performed with effective impedance method and the Maxwell-Garnett approximation. The results fit well with the experiment when the thickness of CNT film is thin, which reveals a coherent superposition mechanism of the CNT surface reflection and CNTs/Si interface reflection. For thick CNT films, the CNTs/Si interface response determines the reflection at small incident angles, while the CNTs surface effect dominates at large incident angles. This work investigates the spatial dispersion effect of vertically aligned CNT arrays in the THz region, and paves a way for potential anisotropic THz applications based on CNTs with oblique incidence requirements. PMID:27966549

  14. Tuning of gravity-dependent and gravity-independent vertical angular VOR gain changes by frequency of adaptation.

    PubMed

    Yakushin, Sergei B

    2012-06-01

    The gain of the vertical angular vestibulo-ocular reflex (aVOR) was adaptively increased and decreased in a side-down head orientation for 4 h in two cynomolgus monkeys. Adaptation was performed at 0.25, 1, 2, or 4 Hz. The gravity-dependent and -independent gain changes were determined over a range of head orientations from left-side-down to right-side-down at frequencies from 0.25 to 10 Hz, before and after adaptation. Gain changes vs. frequency data were fit with a Gaussian to determine the frequency at which the peak gain change occurred, as well as the tuning width. The frequency at which the peak gravity-dependent gain change occurred was approximately equal to the frequency of adaptation, and the width increased monotonically with increases in the frequency of adaptation. The gravity-independent component was tuned to the adaptive frequency of 0.25 Hz but was uniformly distributed over all frequencies when the adaptation frequency was 1-4 Hz. The amplitude of the gravity-independent gain changes was larger after the aVOR gain decrease than after the gain increase across all tested frequencies. For the aVOR gain decrease, the phase lagged about 4° for frequencies below the adaptation frequency and led for frequencies above the adaptation frequency. For gain increases, the phase relationship as a function of frequency was inverted. This study demonstrates that the previously described dependence of aVOR gain adaptation on frequency is a property of the gravity-dependent component of the aVOR only. The gravity-independent component of the aVOR had a substantial tuning curve only at an adaptation frequency of 0.25 Hz.

  15. Tuning of gravity-dependent and gravity-independent vertical angular VOR gain changes by frequency of adaptation

    PubMed Central

    2012-01-01

    The gain of the vertical angular vestibulo-ocular reflex (aVOR) was adaptively increased and decreased in a side-down head orientation for 4 h in two cynomolgus monkeys. Adaptation was performed at 0.25, 1, 2, or 4 Hz. The gravity-dependent and -independent gain changes were determined over a range of head orientations from left-side-down to right-side-down at frequencies from 0.25 to 10 Hz, before and after adaptation. Gain changes vs. frequency data were fit with a Gaussian to determine the frequency at which the peak gain change occurred, as well as the tuning width. The frequency at which the peak gravity-dependent gain change occurred was approximately equal to the frequency of adaptation, and the width increased monotonically with increases in the frequency of adaptation. The gravity-independent component was tuned to the adaptive frequency of 0.25 Hz but was uniformly distributed over all frequencies when the adaptation frequency was 1–4 Hz. The amplitude of the gravity-independent gain changes was larger after the aVOR gain decrease than after the gain increase across all tested frequencies. For the aVOR gain decrease, the phase lagged about 4° for frequencies below the adaptation frequency and led for frequencies above the adaptation frequency. For gain increases, the phase relationship as a function of frequency was inverted. This study demonstrates that the previously described dependence of aVOR gain adaptation on frequency is a property of the gravity-dependent component of the aVOR only. The gravity-independent component of the aVOR had a substantial tuning curve only at an adaptation frequency of 0.25 Hz. PMID:22402654

  16. Surface Coverage and Structure of Mixed DNA/Alkylthiol Monolayers on Gold: Characterization by XPS, NEXAFS, and Fluorescence Intensity Measurements

    PubMed Central

    Lee, Chi-Ying; Gong, Ping; Harbers, Gregory M.; Grainger, David W.; Castner, David G.; Gamble, Lara J.

    2006-01-01

    Self-assembly of thiol-terminated single-stranded DNA (HS-ssDNA) on gold has served as an important model system for DNA immobilization at surfaces. Here, we report a detailed study of the surface composition and structure of mixed self-assembled DNA monolayers containing a short alkylthiol surface diluent [11-mercapto-1-undecanol (MCU)] on gold supports. These mixed DNA monolayers were studied with X-ray photoelectron spectroscopy (XPS), near-edge X-ray absorption fine structure spectroscopy (NEXAFS), and fluorescence intensity measurements. XPS results on sequentially adsorbed DNA/MCU monolayers on gold indicated that adsorbed MCU molecules first incorporate into the HS-ssDNA monolayer and, upon longer MCU exposures, displace adsorbed HS-ssDNA molecules from the surface. Thus, HS-ssDNA surface coverage steadily decreased with MCU exposure time. Polarization-dependent NEXAFS and fluorescence results both show changes in signals consistent with changes in DNA orientation after only 30 min of MCU exposure. NEXAFS polarization dependence (followed by monitoring the N 1s → π* transition) of the mixed DNA monolayers indicated that the DNA nucleotide base ring structures are oriented more parallel to the gold surface compared to DNA bases in pure HS-ssDNA monolayers. This indicates that HS-ssDNA oligomers reorient toward a more-upright position upon MCU incorporation. Fluorescence intensity results using end-labeled DNA probes on gold show little observable fluorescence on pure HS-ssDNA monolayers, likely due to substrate quenching effects between the fluorophore and the gold. MCU diluent incorporation into HS-ssDNA monolayers initially increases DNA fluorescence signal by densifying the chemisorbed monolayer, prompting an upright orientation of the DNA, and moving the terminal fluorophore away from the substrate. Immobilized DNA probe density and DNA target hybridization in these mixed DNA monolayers, as well as effects of MCU diluent on DNA hybridization in complex

  17. Surface Coverage and Structure of Mixed DNA/Alkylthiol Monolayers on Gold: Characterization by XPS, NEXAFS, and Fluorescence Intensity Measurements

    SciTech Connect

    Lee,C.; Gong, P.; Harbers, G.; Grainger, D.; Castner, D.; Gamble, L.

    2006-01-01

    Self-assembly of thiol-terminated single-stranded DNA (HS-ssDNA) on gold has served as an important model system for DNA immobilization at surfaces. Here, we report a detailed study of the surface composition and structure of mixed self-assembled DNA monolayers containing a short alkylthiol surface diluent [11-mercapto-1-undecanol (MCU)] on gold supports. These mixed DNA monolayers were studied with X-ray photoelectron spectroscopy (XPS), near-edge X-ray absorption fine structure spectroscopy (NEXAFS), and fluorescence intensity measurements. XPS results on sequentially adsorbed DNA/MCU monolayers on gold indicated that adsorbed MCU molecules first incorporate into the HS-ssDNA monolayer and, upon longer MCU exposures, displace adsorbed HS-ssDNA molecules from the surface. Thus, HS-ssDNA surface coverage steadily decreased with MCU exposure time. Polarization-dependent NEXAFS and fluorescence results both show changes in signals consistent with changes in DNA orientation after only 30 min of MCU exposure. NEXAFS polarization dependence (followed by monitoring the N 1s{yields}{pi}* transition) of the mixed DNA monolayers indicated that the DNA nucleotide base ring structures are oriented more parallel to the gold surface compared to DNA bases in pure HS-ssDNA monolayers. This indicates that HS-ssDNA oligomers reorient toward a more-upright position upon MCU incorporation. Fluorescence intensity results using end-labeled DNA probes on gold show little observable fluorescence on pure HS-ssDNA monolayers, likely due to substrate quenching effects between the fluorophore and the gold. MCU diluent incorporation into HS-ssDNA monolayers initially increases DNA fluorescence signal by densifying the chemisorbed monolayer, prompting an upright orientation of the DNA, and moving the terminal fluorophore away from the substrate. Immobilized DNA probe density and DNA target hybridization in these mixed DNA monolayers, as well as effects of MCU diluent on DNA hybridization in

  18. Non-contact small animal fluorescence imaging system for simultaneous multi-directional angular-dependent data acquisition

    PubMed Central

    Lee, Jong Hwan; Kim, Hyun Keol; Chandhanayingyong, Chandhanarat; Lee, Francis Young-In; Hielscher, Andreas H.

    2014-01-01

    We present a novel non-contact small animal fluorescent molecular tomography (FMT) imaging system. At the heart of the system is a new mirror-based imaging head that was designed to provide 360-degree measurement data from an entire animal surface in one step. This imaging head consists of two conical mirrors, which considerably reduce multiple back reflections between the animal and mirror surfaces. These back reflections are common in existing mirror-based imaging heads and tend to degrade the quality of raw measurement data. In addition, the introduction of a novel ray-transfer operator allows for the inclusion of the angular dependent data in the image reconstruction process, which results in higher image resolution. We describe in detail the system design and implementation of the hardware components as well as the transport-theory-based image reconstruction algorithm. Using numerical simulations, measurements on a well-defined phantom and a live animal, we evaluate the system performance and show the advantages of our approach. PMID:25071965

  19. Non-contact small animal fluorescence imaging system for simultaneous multi-directional angular-dependent data acquisition.

    PubMed

    Lee, Jong Hwan; Kim, Hyun Keol; Chandhanayingyong, Chandhanarat; Lee, Francis Young-In; Hielscher, Andreas H

    2014-07-01

    We present a novel non-contact small animal fluorescent molecular tomography (FMT) imaging system. At the heart of the system is a new mirror-based imaging head that was designed to provide 360-degree measurement data from an entire animal surface in one step. This imaging head consists of two conical mirrors, which considerably reduce multiple back reflections between the animal and mirror surfaces. These back reflections are common in existing mirror-based imaging heads and tend to degrade the quality of raw measurement data. In addition, the introduction of a novel ray-transfer operator allows for the inclusion of the angular dependent data in the image reconstruction process, which results in higher image resolution. We describe in detail the system design and implementation of the hardware components as well as the transport-theory-based image reconstruction algorithm. Using numerical simulations, measurements on a well-defined phantom and a live animal, we evaluate the system performance and show the advantages of our approach.

  20. A NEXAFS study of the bonding of corrosion inhibitors on ZnO(1 0 1 bar 0)

    NASA Astrophysics Data System (ADS)

    Walsh, J. F.; Dhariwal, H. S.; Gutiérrez-Sosa, A.; Lindsay, R.; Thornton, G.; Oldman, R. J.

    1995-05-01

    The orientation of benzotriazole and related molecules on ZnO (1 0 1 bar 0) has been studied using C and N K-edge near-edge X-ray absorption fine structure (NEXAFS). At sub-monolayer coverage, benzotriazole is found to adsorb in an upright geometry with the molecular plane within 35° of perpendicular to the substrate, as indicated by the polarization dependence of the π* resonances. Seven slightly different models of the bond geometry are consistent with the data. Indazole (C7H6N2), another corrosion inhibitor is found to bond in a similar manner. Related molecules, benzimidazole (C7H6N2) and 1-methyl benzotriazole (C7H7N3) are found not to be oriented at sub-monolayer coverage. In conjunction with multilayer data, this suggests a specific first-bonding-layer origin for the corrosion inhibition properties of benzotriazole.

  1. Nondestructive Characterization of Atomic Profiles in Layer-Structured Photovoltaic Materials Using the Method of Angular Dependence of X-Ray Fluorescence (ADXRF)

    SciTech Connect

    Kim, S.; Soo, Y. L.; Kioseoglou, G.; Huang, S.; Kao, Y. H.; Ramanathan, K.; Deb, S.

    2000-01-01

    Angular dependence of x-ray fluorescence technique has been applied to the study of atomic density profile in composite systems. This method is shown to be useful for probing the microstructures and intermixing of constituent elements in layer-structured photovoltaic materials.

  2. Observation of a Change in Twist of an RNA Kissing Complex Using the Angular Dependence of Fluorescence Resonance Energy Transfer

    NASA Astrophysics Data System (ADS)

    Rahmanseresht, Sheema; Milas, Peker; Parrot, Louis; Gamari, Ben D.; Goldner, Lori S.

    2015-01-01

    We report on the observation of a change in the bend angle of an RNA kissing complex upon Rop binding using single-molecular-pair FRET. The angular relationship between the dyes, rather than the distance between them, is shown to be responsible for the observed change in energy transfer. It has long been thought that Rop increases the bend angle of the R1inv-R2inv complex upon binding, but this has never been directly observed. In contrast, we find an increase in FRET upon the addition of Rop that is shown via modeling to be consistent with a decrease in the bend angle of the complex of $-15^{\\circ}\\pm7^{\\circ}$. The model predicts FRET from dye trajectories generated using molecular dynamics simulations of Cy3 and Cy5 attached to $5'$ terminal cytosine or guanosine on RNA. While FRET is commonly used to observe global changes in molecular structure attributed to changes in the distance between dyes, it is rarely, if ever, used to elucidate angular changes. Subtle global changes in molecular structure upon binding are generally difficult to discern using NMR or crystallography, but FRET is well suited to observe these changes because of its sensitivity at interdye distance around the F\\"orster radius, $R_F\\approx5$ nm. While FRET is often referred to and used as a "molecular ruler" for distances around $R_F$, for dye pairs that have minimal rotational freedom, FRET can also be used to observe changes in structure for which there is no significant change in distance between the dyes. This is the case for the R1inv-R2inv kissing complex studied here. This complex is derived from the RNA I - RNA II complex in E. coli. RNA II is a primer for replication of the ColE1 plasmid, its function is modulated by interaction with RNA II. Rop is known to stabilize the complex, and it is also known to bind kissing complexes in a structure, but not sequence, dependent fashion.

  3. Time-Dependent and Time-Integrated Angular Analysis of B -> phi Ks pi0 and B -> phi K+ pi-

    SciTech Connect

    Aubert, B; Bona, M; Karyotakis, Y; Lees, J P; Poireau, V

    2008-08-04

    We perform a time-dependent and time-integrated angular analysis of the B{sup 0} {yields} {psi}K*(892){sup 0}, {psi}K*{sub 2}(1430{sup 0}), and {psi}(K{pi}){sub S-wave}{sup 0} decays with the final sample of about 465 million B{bar B} pairs recorded with the BABAR detector. Overall, twelve parameters are measured for the vector-vector decay, nine parameters for the vector-tensor decay, and three parameters for the vector-scalar decay, including the branching fractions, CP-violation parameters, and parameters sensitive to final state interaction. We use the dependence on the K{pi} invariant mass of the interference between the scalar and vector or tensor components to resolve discrete ambiguities of the strong and weak phases. We use the time-evolution of the B {yields} {psi}K{sub S}{sup 0}{pi}{sup 0} channel to extract the CP-violation phase difference {Delta}{phi}{sub 00} = 0.28 {+-} 0.42 {+-} 0.04 between the B and {bar B} decay amplitudes. When the B {yields} {psi}K{sup {+-}}{pi}{sup {-+}} channel is included, the fractions of longitudinal polarization f{sub L} of the vector-vector and vector-tensor decay modes are measured to be 0.494 {+-} 0.034 {+-} 0.013 and 0.901{sub -0.058}{sup +0.046} {+-} 0.037, respectively. This polarization pattern requires the presence of a helicity-plus amplitude in the vector-vector decay from a presently unknown source.

  4. Energy and angular dependences of common types of personal dosemeters in the mirror of the First national intercomparison of individual dosimetric monitoring laboratories in Ukraine.

    PubMed

    Chumak, V; Deniachenko, N; Volosky, V

    2015-12-01

    In depth analysis of the results of the First National Intercomparison of individual dosimetry laboratories in Ukraine has revealed energy and angular responses of the most common types of personal dosemeters and dosi metric systems. Participating laboratories use 9 different types of dosimetric systems - automatic, semi automat ic and manual. If was found that energy dependences of the most common dosemeter types in Ukraine generally correspond to the literature data on respective TLD materials (LiF:Mg,Cu,P, LiF:Mg,TiandAl2O3:С), however, due to peculiarities of holders (filters) and dose algorithms, for some dosimetry systems the energy dependences can be improved (compensated). Angular dependences proved to be more pronounced: only two systems revealed weak dependence of response on the incident angle, for other systems at large angles (α=60°) dosemeters overestimate true dose values. V. Chumak, N. Deniachenko, V. Volosky.

  5. Processing of atmospheric particles caught in the act via STXM/NEXAFS

    NASA Astrophysics Data System (ADS)

    Steimer, S.; Lampimäki, M.; Grzinic, G.; Coz, E.; Watts, B.; Raabe, J.; Ammann, M.

    2012-12-01

    Atmospheric aerosols are an important focus of environmental research due to their effect on climate and human health. Among their main constituents are mineral dust and organic particles. Both types of particles directly and indirectly affect our climate through scattering and absorption of radiation and through acting as cloud condensation nuclei respectively. Organic particles are also of significant concern with respect to their health effects. Mineral dust particles in addition serve as a primary external iron source to the open ocean and the bioavailability of iron from these particles is highly dependent on the oxidation state of the metal. The environmental impact of atmospheric particles depends on their physical and chemical properties, which might change upon chemical ageing. In this study we therefore investigated the changes in chemical composition and morphology of mineral dust and organic particle proxies (Arizona test dust and shikimic acid, respectively) upon in situ exposure to ozone or nitrogen oxides in presence of humidity. This was achieved by monitoring changes at the C and O K-edges as well as the metal L-edges via scanning transmission X-ray microscopy (STXM) and near edge X-ray absorption fine structure (NEXAFS) spectroscopy. Measurements were conducted at the PolLux beamline at Swiss Light Source. All experiments were conducted in an environmental micro reactor, designed specifically for the end station, to enable the investigation in situ. We observed oxidation of shikimic acid particles in situ during exposure to ozone at different humidities, whereby humidity was found to be a critical factor controlling the rate of the reaction. We also obtained well resolved iron distribution maps from the individual submicrometer size mineral dust particles before and after exposure to nitrogen oxides.

  6. Angular Dependence of Strong Field Ionization of CH3X (X = F, Cl, Br, or I) Using Time-Dependent Configuration Interaction with an Absorbing Potential.

    PubMed

    Hoerner, Paul; Schlegel, H Bernhard

    2017-08-10

    Methyl halides have been used to test basis set effects on simulations of strong field ionization using time dependent configuration interaction with an absorbing potential. Standard atom centered basis sets need to be augmented by several sets of diffuse functions on each atom so that the wave function in the strong field can interact with the absorbing potential used to model ionization. An absorbing basis of 3 s functions, 2 p functions, 3 d functions, and 1 f function is sufficient for CH3F. Large absorbing basis sets with 4 s functions, 3 or 4 p functions, 4 or 5 d functions, and 2 f functions are recommended for the heavier halogens. The simulations used static fields in the 0.035-0.07 au range to explore the angular dependence of ionization of methyl halides. CH3F ionizes mainly from the methyl group; CH3Cl and CH3Br show ionization from both the methyl group and the halogen, and CH3I ionizes almost exclusively from the pπ orbitals of the iodine.

  7. Overview of nanoscale NEXAFS performed with soft X-ray microscopes.

    PubMed

    Guttmann, Peter; Bittencourt, Carla

    2015-01-01

    Today, in material science nanoscale structures are becoming more and more important. Not only for the further miniaturization of semiconductor devices like carbon nanotube based transistors, but also for newly developed efficient energy storage devices, gas sensors or catalytic systems nanoscale and functionalized materials have to be analysed. Therefore, analytical tools like near-edge X-ray absorption fine structure (NEXAFS) spectroscopy has to be applied on single nanostructures. Scanning transmission X-ray microscopes (STXM) as well as full-field transmission X-ray microscopes (TXM) allow the required spatial resolution to study individual nanostructures. In the soft X-ray energy range only STXM was used so far for NEXAFS studies. Due to its unique setup, the TXM operated by the Helmholtz-Zentrum Berlin (HZB) at the electron storage ring BESSY II is the first one in the soft X-ray range which can be used for NEXAFS spectroscopy studies which will be shown in this review. Here we will give an overview of the different microscopes used for NEXAFS studies and describe their advantages and disadvantages for different samples.

  8. Overview of nanoscale NEXAFS performed with soft X-ray microscopes

    PubMed Central

    Bittencourt, Carla

    2015-01-01

    Summary Today, in material science nanoscale structures are becoming more and more important. Not only for the further miniaturization of semiconductor devices like carbon nanotube based transistors, but also for newly developed efficient energy storage devices, gas sensors or catalytic systems nanoscale and functionalized materials have to be analysed. Therefore, analytical tools like near-edge X-ray absorption fine structure (NEXAFS) spectroscopy has to be applied on single nanostructures. Scanning transmission X-ray microscopes (STXM) as well as full-field transmission X-ray microscopes (TXM) allow the required spatial resolution to study individual nanostructures. In the soft X-ray energy range only STXM was used so far for NEXAFS studies. Due to its unique setup, the TXM operated by the Helmholtz-Zentrum Berlin (HZB) at the electron storage ring BESSY II is the first one in the soft X-ray range which can be used for NEXAFS spectroscopy studies which will be shown in this review. Here we will give an overview of the different microscopes used for NEXAFS studies and describe their advantages and disadvantages for different samples. PMID:25821700

  9. The Local and Surface Structure of Ordered Mesoporous Carbons from Nitrogen Sorption, NEXAFS and Synchrotron Radiation Studies

    SciTech Connect

    Smith,M.; Lobo, R.

    2006-01-01

    Ordered mesoporous carbon materials were prepared by pyrolysis of sucrose and furfuryl alcohol templated in the ordered mesoporous silicate SBA-15. The structure of SBA-15 template was modified by changing the calcination temperature, we investigate the structural transformation of the silica template with calcination temperature using X-ray diffraction and nitrogen adsorption isotherms. SBA-15 calcined to 300 C has a total pore volume of 1.13 cm{sup 3}/g, a BET surface area of 1100 m2/g, and a pore spacing of 114 Angstroms; when calcined to 90 C the corresponding values are 0.40 cm{sup 3}/g, 330 m{sup 2}/g and 92.5 Angstroms. Despite marked differences in SBA-15 template structure, the pore size distribution of the ordered mesoporous carbons is more dependent on the choice of precursor than on SBA-15 pore geometry. The BET surface areas of ordered mesoporous carbons made from aqueous sucrose solutions (850-1050 m2/g) are independent of template geometry; while surface area of materials made from furfuryl alcohol (530-1190 m2/g) are a reflection of template geometry. Near-edge X-ray fine-structure (NEXAFS) spectroscopy reveal that the template-carbon interaction during the pyrolysis of sucrose-based carbons exerts a strong influence on the surface structure of final product, and that such effects are largely absent in the furfuryl alcohol-based materials. The pair-distribution function (PDF) calculated from high-energy synchrotron scattering measurements corroborates the NEXAFS results, yet also show that the template effect on the bulk carbon is minimal. Template compression acting in conjunction with hydrothermally induced effects exerted on the carbon during pyrolysis drives the resulting carbon to a more graphitic state.

  10. Measurement of angularly dependent spectra of betatron gamma-rays from a laser plasma accelerator with quadrant-sectored range filters

    NASA Astrophysics Data System (ADS)

    Jeon, Jong Ho; Nakajima, Kazuhisa; Kim, Hyung Taek; Rhee, Yong Joo; Pathak, Vishwa Bandhu; Cho, Myung Hoon; Shin, Jung Hun; Yoo, Byung Ju; Jo, Sung Ha; Shin, Kang Woo; Hojbota, Calin; Bae, Lee Jin; Jung, Jaehyung; Cho, Min Sang; Sung, Jae Hee; Lee, Seong Ku; Cho, Byoung Ick; Choi, Il Woo; Nam, Chang Hee

    2016-07-01

    Measurement of angularly dependent spectra of betatron gamma-rays radiated by GeV electron beams from laser wakefield accelerators (LWFAs) are presented. The angle-resolved spectrum of betatron radiation was deconvolved from the position dependent data measured for a single laser shot with a broadband gamma-ray spectrometer comprising four-quadrant sectored range filters and an unfolding algorithm, based on the Monte Carlo code GEANT4. The unfolded gamma-ray spectra in the photon energy range of 0.1-10 MeV revealed an approximately isotropic angular dependence of the peak photon energy and photon energy-integrated fluence. As expected by the analysis of betatron radiation from LWFAs, the results indicate that unpolarized gamma-rays are emitted by electrons undergoing betatron motion in isotropically distributed orbit planes.

  11. Measurement of angularly dependent spectra of betatron gamma-rays from a laser plasma accelerator with quadrant-sectored range filters

    SciTech Connect

    Jeon, Jong Ho Nakajima, Kazuhisa Rhee, Yong Joo; Pathak, Vishwa Bandhu; Cho, Myung Hoon; Shin, Jung Hun; Yoo, Byung Ju; Jo, Sung Ha; Shin, Kang Woo; Kim, Hyung Taek; Sung, Jae Hee; Lee, Seong Ku; Choi, Il Woo; Hojbota, Calin; Bae, Lee Jin; Jung, Jaehyung; Cho, Min Sang; Cho, Byoung Ick; Nam, Chang Hee

    2016-07-15

    Measurement of angularly dependent spectra of betatron gamma-rays radiated by GeV electron beams from laser wakefield accelerators (LWFAs) are presented. The angle-resolved spectrum of betatron radiation was deconvolved from the position dependent data measured for a single laser shot with a broadband gamma-ray spectrometer comprising four-quadrant sectored range filters and an unfolding algorithm, based on the Monte Carlo code GEANT4. The unfolded gamma-ray spectra in the photon energy range of 0.1–10 MeV revealed an approximately isotropic angular dependence of the peak photon energy and photon energy-integrated fluence. As expected by the analysis of betatron radiation from LWFAs, the results indicate that unpolarized gamma-rays are emitted by electrons undergoing betatron motion in isotropically distributed orbit planes.

  12. Characterization of MOSFET dosimeter angular dependence in three rotational axes measured free-in-air and in soft-tissue equivalent material.

    PubMed

    Koivisto, Juha; Kiljunen, Timo; Wolff, Jan; Kortesniemi, Mika

    2013-09-01

    When performing dose measurements on an X-ray device with multiple angles of irradiation, it is necessary to take the angular dependence of metal-oxide-semiconductor field-effect transistor (MOSFET) dosimeters into account. The objective of this study was to investigate the angular sensitivity dependence of MOSFET dosimeters in three rotational axes measured free-in-air and in soft-tissue equivalent material using dental photon energy. Free-in-air dose measurements were performed with three MOSFET dosimeters attached to a carbon fibre holder. Soft tissue measurements were performed with three MOSFET dosimeters placed in a polymethylmethacrylate (PMMA) phantom. All measurements were made in the isocenter of a dental cone-beam computed tomography (CBCT) scanner using 5º angular increments in the three rotational axes: axial, normal-to-axial and tangent-to-axial. The measurements were referenced to a RADCAL 1015 dosimeter. The angular sensitivity free-in-air (1 SD) was 3.7 ± 0.5 mV/mGy for axial, 3.8 ± 0.6 mV/mGy for normal-to-axial and 3.6 ± 0.6 mV/mGy for tangent-to-axial rotation. The angular sensitivity in the PMMA phantom was 3.1 ± 0.1 mV/mGy for axial, 3.3 ± 0.2 mV/mGy for normal-to-axial and 3.4 ± 0.2 mV/mGy for tangent-to-axial rotation. The angular sensitivity variations are considerably smaller in PMMA due to the smoothing effect of the scattered radiation. The largest decreases from the isotropic response were observed free-in-air at 90° (distal tip) and 270° (wire base) in the normal-to-axial and tangent-to-axial rotations, respectively. MOSFET dosimeters provide us with a versatile dosimetric method for dental radiology. However, due to the observed variation in angular sensitivity, MOSFET dosimeters should always be calibrated in the actual clinical settings for the beam geometry and angular range of the CBCT exposure.

  13. Role of muscle pulleys in producing eye position-dependence in the angular vestibuloocular reflex: a model-based study

    NASA Technical Reports Server (NTRS)

    Thurtell, M. J.; Kunin, M.; Raphan, T.; Wall, C. C. (Principal Investigator)

    2000-01-01

    the roll gain of the angular vestibuloocular reflex was modified during the initial period of the response, while pulley coefficient was maintained at 0.5. Hence a roll gain modification allows stabilization of the retinal image without requiring a change in the pulley effect. Our results therefore indicate that the eye position-dependent velocity axis tilts could arise due to the effects of the pulleys and that a roll gain modification in the central vestibular structures may be responsible for countering the pulley effect.

  14. Role of muscle pulleys in producing eye position-dependence in the angular vestibuloocular reflex: a model-based study

    NASA Technical Reports Server (NTRS)

    Thurtell, M. J.; Kunin, M.; Raphan, T.; Wall, C. C. (Principal Investigator)

    2000-01-01

    the roll gain of the angular vestibuloocular reflex was modified during the initial period of the response, while pulley coefficient was maintained at 0.5. Hence a roll gain modification allows stabilization of the retinal image without requiring a change in the pulley effect. Our results therefore indicate that the eye position-dependent velocity axis tilts could arise due to the effects of the pulleys and that a roll gain modification in the central vestibular structures may be responsible for countering the pulley effect.

  15. Gravity-specific adaptation of the angular vestibuloocular reflex: dependence on head orientation with regard to gravity.

    PubMed

    Yakushin, Sergei B; Raphan, Theodore; Cohen, Bernard

    2003-01-01

    The gain of the vertical angular vestibuloocular reflex (aVOR) was adaptively altered by visual-vestibular mismatch during rotation about an interaural axis, using steps of velocity in three head orientations: upright, left-side down, and right-side down. Gains were decreased by rotating the animal and visual surround in the same direction and increased by visual and surround rotation in opposite directions. Gains were adapted in one head position (single-state adaptation) or decreased with one side down and increased with the other side down (dual-state adaptation). Animals were tested in darkness using sinusoidal rotation at 0.5 Hz about an interaural axis that was tilted from horizontal to vertical. They were also sinusoidally oscillated from 0.5 to 4 Hz about a spatial vertical axis in static tilt positions from yaw to pitch. After both single- and dual-state adaptation, gain changes were maximal when the monkeys were in the position in which the gain had been adapted, and the gain changes progressively declined as the head was tilted away from that position. We call this gravity-specific aVOR gain adaptation. The spatial distribution of the specific aVOR gain changes could be represented by a cosine function that was superimposed on a bias level, which we called gravity-independent gain adaptation. Maximal gravity-specific gain changes were produced by 2-4 h of adaptation for both single- and dual-state adaptations, and changes in gain were similar at all test frequencies. When adapted while upright, the magnitude and distribution of the gravity-specific adaptation was comparable to that when animals were adapted in side-down positions. Single-state adaptation also produced gain changes that were independent of head position re gravity particularly in association with gain reduction. There was no bias after dual-state adaptation. With this difference, fits to data obtained by altering the gain in separate sessions predicted the modulations in gain obtained

  16. Angular and temperature dependence of current induced spin-orbit effective fields in Ta/CoFeB/MgO nanowires

    PubMed Central

    Qiu, Xuepeng; Deorani, Praveen; Narayanapillai, Kulothungasagaran; Lee, Ki-Seung; Lee, Kyung-Jin; Lee, Hyun-Woo; Yang, Hyunsoo

    2014-01-01

    Current induced spin-orbit effective magnetic fields in metal/ferromagnet/oxide trilayers provide a new way to manipulate the magnetization, which is an alternative to the conventional current induced spin transfer torque arising from noncollinear magnetization. Ta/CoFeB/MgO structures are expected to be useful for non-volatile memories and logic devices due to its perpendicular anisotropy and large current induced spin-orbit effective fields. However many aspects such as the angular and temperature dependent phenomena of the effective fields are little understood. Here, we evaluate the angular and temperature dependence of the current-induced spin-orbit effective fields considering contributions from both the anomalous and planar Hall effects. The longitudinal and transverse components of effective fields are found to have strong angular dependence on the magnetization direction at 300 K. The transverse field decreases significantly with decreasing temperature, whereas the longitudinal field shows weaker temperature dependence. Our results reveal important features and provide an opportunity for a more comprehensive understanding of current induced spin-orbit effective fields. PMID:24670317

  17. Angular dependence of Raman scattering selection rules for long-wavelength optical phonons in short-period GaAs/AlAs superlattices

    SciTech Connect

    Volodin, V. A.; Sachkov, V. A.; Sinyukov, M. P.

    2016-07-15

    The angular dependence of Raman scattering selection rules for optical phonons in short-period (001) GaAs/AlAs superlattices is calculated and experimentally studied. Experiments are performed using a micro-Raman setup, in the scattering geometry with the wavevectors of the incident and scattered light lying in the plane of superlattices (so-called in-plane geometry). Phonon frequencies are calculated using the Born model taking the Coulomb interaction into account in the rigid-ion approximation. Raman scattering spectra are calculated in the framework of the deformation potential and electro-optical mechanisms. Calculations show an angular dependence of the selection rules for optical phonons with different directions of the wavevectors. Drastic differences in the selection rules are found for experimental and calculated spectra. Presumably, these differences are due to the Fröhlich mechanism in Raman scattering for short-period superlattices.

  18. Measurement of the Energy-Dependent Angular Response of the ARES Detector System and Application to Aerial Imaging

    NASA Astrophysics Data System (ADS)

    Joshi, Tenzing H. Y.; Quiter, Brian J.; Maltz, Jonathan S.; Bandstra, Mark S.; Haefner, Andrew; Eikmeier, Nicole; Wagner, Eric; Luke, Tanushree; Malchow, Russell; McCall, Karen

    2017-07-01

    The Airborne Radiological Enhanced-sensor System (ARES) includes a prototype helicopter-borne CsI(Na) detector array that has been developed as part of the DHS Domestic Nuclear Detection Office Advanced Technology Demonstration. The detector system geometry comprises two pairs of 23-detector arrays designed to function as active masks, providing additional angular resolution of measured gamma rays in the roll dimension. Experimental measurements, using five radioisotopes (137Cs, 60Co, 241Am, 131I, and 99mTc), were performed to map the detector response in both roll and pitch dimensions. This paper describes the acquisition and analysis of these characterization measurements, calculation of the angular response of the ARES system, and how this response function is used to improve aerial detection and localization of radiological and nuclear threat sources.

  19. Spectral and angular dependence of mid-infrared diffuse scattering from explosives residues for standoff detection using external cavity quantum cascade lasers

    SciTech Connect

    Suter, Jonathan D.; Bernacki, Bruce E.; Phillips, Mark C.

    2012-09-01

    We present a study of the spectral and angular dependence of scattered mid-infrared light from surfaces coated with explosives residues (TNT, RDX, and tetryl) detected at a 2 meter standoff distance. An external cavity quantum cascade laser provided tunable illumination between 7 and 8 µm. Important differences were identified in the spectral features between specular reflection and diffuse scattering which will impact most practical testing scenarios and complicate material identification. We discuss some of the factors influencing the dependence of observed spectra on the experimental geometry.

  20. Spectral and angular dependence of mid-infrared diffuse scattering from explosives residues for standoff detection using external cavity quantum cascade lasers

    NASA Astrophysics Data System (ADS)

    Suter, Jonathan D.; Bernacki, Bruce; Phillips, Mark C.

    2012-09-01

    We present a study of the spectral and angular dependence of scattered mid-infrared light from surfaces coated with explosives residues (TNT, RDX, and tetryl) detected at a 2 m standoff distance. An external cavity quantum cascade laser provided tunable illumination between 7 and 8 μm. Important differences were identified in the spectral features between specular reflection and diffuse scattering which will impact most practical testing scenarios and complicate material identification. We discuss some of the factors influencing the dependence of observed spectra on the experimental geometry.

  1. Perpendicular magnetic anisotropy at the interface between ultrathin Fe film and MgO studied by angular-dependent x-ray magnetic circular dichroism

    SciTech Connect

    Okabayashi, J.; Koo, J. W.; Mitani, S.; Sukegawa, H.; Takagi, Y.; Yokoyama, T.

    2014-09-22

    Interface perpendicular magnetic anisotropy (PMA) in ultrathin Fe/MgO (001) has been investigated using angular-dependent x-ray magnetic circular dichroism (XMCD). We found that anisotropic orbital magnetic moments deduced from the analysis of XMCD contribute to the large PMA energies, whose values depend on the annealing temperature. The large PMA energies determined from magnetization measurements are related to those estimated from the XMCD and the anisotropic orbital magnetic moments through the spin-orbit interaction. The enhancement of anisotropic orbital magnetic moments can be explained mainly by the hybridization between the Fe 3d{sub z}{sup 2} and O 2p{sub z} states.

  2. Angular Dependence of the Photoelectron Energy Distribution of InP(100) and GaAs(100) Negative Electron Affinity Photocathodes

    SciTech Connect

    Lee, Dong-Ick; Sun, Yun; Lu, Zhi; Sun, Shiyu; Pianetta, Piero; /SLAC, SSRL

    2007-10-15

    Energy distribution of the photoelectrons from InP(100) photocathodes are investigated with a photon energy range from 0.62eV to 2.76eV. When the photon energy is less than 1.8eV, only electrons emitted from the Gamma valley are observed in the energy distribution curves (EDC). At higher photon energies, electrons from the L valley are observed. The angular dependence of the electron energy distributions of InP and GaAs photocathodes are studied and compared. The electrons emitted from the L valley have a larger angular spread than the ones from the Gamma valley due to the larger effective mass of the L valley minimum.

  3. A velocity map ion-imaging study on ketene photodissociation at 208 and 213 nm: Rotational dependence of product angular anisotropy.

    PubMed

    Liu, Jie; Wang, Fengyan; Wang, Hua; Jiang, Bo; Yang, Xueming

    2005-03-08

    Photodissociation dynamics of ketene following excitation at 208.59 and 213.24 nm have been investigated using the velocity map ion-imaging method. Both the angular distribution and translational energy distribution of the CO products at different rotational and vibrational states have been obtained. No significant difference in the translational energy distributions for different CO rotational state products has been observed at both excitation wavelengths. The anisotropy parameter beta is, however, noticeably different for different CO rotational state products at both excitation wavelengths. For lower rotational states of the CO product, beta is smaller than zero, while beta is larger than zero for CO at higher rotational states. The observed rotational dependence of angular anisotropy is interpreted as the dynamical influence of a peculiar conical intersection between the (1)B(1) excited state and (1)A(2) state along the C(S)-I coordinate.

  4. Bonding and charge transfer in nitrogen-donor uranyl complexes: insights from NEXAFS spectra.

    PubMed

    Pemmaraju, C D; Copping, Roy; Wang, Shuao; Janousch, Markus; Teat, Simon J; Tyliszcak, Tolek; Canning, Andrew; Shuh, David K; Prendergast, David

    2014-11-03

    We investigate the electronic structure of three newly synthesized nitrogen-donor uranyl complexes [(UO2)(H2bbp)Cl2], [(UO)2(Hbbp)(Py)Cl], and [(UO2)(bbp)(Py)2] using a combination of near-edge X-ray absorption fine structure (NEXAFS) spectroscopy experiments and simulations. The complexes studied feature derivatives of the tunable tridentate N-donor ligand 2,6-bis(2-benzimidazyl)pyridine (bbp) and exhibit discrete chemical differences in uranyl coordination. The sensitivity of the N K-edge X-ray absorption spectrum to local bonding and charge transfer is exploited to systematically investigate the evolution of structural as well as electronic properties across the three complexes. A thorough interpretation of the measured experimental spectra is achieved via ab initio NEXAFS simulations based on the eXcited electron and Core-Hole (XCH) approach and enables the assignment of spectral features to electronic transitions on specific absorbing sites. We find that ligand-uranyl bonding leads to a signature blue shift in the N K-edge absorption onset, resulting from charge displacement toward the uranyl, while changes in the equatorial coordination shell of the uranyl lead to more subtle modulations in the spectral features. Theoretical simulations show that the flexible local chemistry at the nonbinding imidazole-N sites of the bbp ligand is also reflected in the NEXAFS spectra and highlights potential synthesis strategies to improve selectivity. In particular, we find that interactions of the bbp ligand with solvent molecules can lead to changes in ligand-uranyl binding geometry while also modulating the K-edge absorption. Our results suggest that NEXAFS spectroscopy combined with first-principles interpretation can offer insights into the coordination chemistry of analogous functionalized conjugated ligands.

  5. Polarization-dependent angular-optical reflectance in solar-selective SnOx:F/Al2O3/Al reflector surfaces.

    PubMed

    Mwamburi, Mghendi; Wäckelgård, Ewa; Roos, Arne; Kivaisi, Rogath

    2002-05-01

    Polarization-dependent angular-optical properties of spectrally selective reflector surfaces of fluorine-doped tin oxide (SnOx:F) deposited pyrolytically on anodized aluminum are reported. The angular-reflectance measurements, for which both s- and p-polarized light are used in the solar wavelength range 0.3-2.5 microm, reveal strong spectral selectivity, and the angular behavior is highly dependent on the polarizing component of the incident beam, the total film thickness, and the individual thickness of the Al2O3 and the SnO2:F layers. The anodic A12O3 layers were produced electrochemically and varied between 100 and 205 nm in thickness. The SnOx:F films were grown pyrolytically at a temperature of 400 degrees C with film thicknesses varying in the range 180-320 nm. The reflectors were aimed at silicon solar cells, and good spectrally selective reflector characteristics were achieved with these thinly preanodized, SnOx:F/Al samples; that is, high cell reflectance was obtained for wavelengths below 1.1 microm and low thermal reflectance for wavelengths above 1.1 microm, with the best samples having values of 0.80 and 0.42, respectively, at near-normal angles of incidence. This corresponds to an anodic layer thickness of 155 nm. Both the angular calculations and the experimental measurements show that the cell reflectance is relatively insensitive to the incidence angle, and a low thermal reflectance is maintained up to an angle of approximately 60 degrees.

  6. Carbon (1s) NEXAFS Spectroscopy of Biogeochemically Relevant Reference Organic Compounds

    SciTech Connect

    Solomon, D.; Lehmann, J; Kinyangi, J; Liang, B; Heymann, K; Dathe, L; Hanley, K; Wirick, S; Jacobsen, C

    2009-01-01

    Natural organic matter (NOM) is a highly active component of soils and sediments, and plays an important role in global C cycling. However, NOM has defied molecular-level structural characterization, owing to variations along the decomposition continuum and its existence as highly functionalized polyelectrolytes. We conducted a comprehensive systematic overview of spectral signatures and peak positions of major organic molecules that occur as part of NOM using near-edge x-ray absorption fine structure (NEXAFS) spectroscopy. This investigation provides a more comprehensive NEXAFS spectral library of biogeochemically relevant organic C compounds. The spectra of these reference organic compounds reveal distinct spectral features and peak positions at the C K-edge that are characteristic of the molecular orbitals bonding C atoms. Detailed structural information can be derived from these distinctive spectral features that could be used to build robust peak assignment criteria to exploit the chemical sensitivity of NEXAFS spectroscopy for in situ molecular-level spatial investigation and fingerprinting of complex organic C compounds in environmental samples.

  7. TXM-NEXAFS of TiO{sub 2}-Based Nanostructures

    SciTech Connect

    Guttmann, P.; Rehbein, S.; Heim, S.; Schneider, G.; Bittencourt, C.; Ke, X.; Van Tendeloo, G.; Umek, P.; Arcon, D.; Ewels, C. P.

    2011-09-09

    In this work, electronic properties of individual TiO{sub x}-pristine nanoribbons (NR) prepared by hydrothermal treatment of anatase TiO{sub 2} micro-particles were studied using the HZB transmission x-ray microscope (TXM) at the BESSY II undulator beamline U41-FSGM. NEXAFS is ideally suited to study TiO{sub 2}-based materials because both the O K-edge and Ti L-edge features are very sensitive to the local bonding environment, providing diagnostic information about the crystal structures and oxidation states of various forms of titanium oxides and sub-oxides. TXM-NEXAFS combines full-field x-ray microscopy with spectroscopy, allowing the study of the electronic structure of individual nanostructures with spatial resolution better than 25 nm and a spectral resolution of up to E/{Delta}E = 10000. The typical image field in TXM-NEXAFS measurements is about 10 {mu}mx10 {mu}m, which is large compared to the individual nanoparticle. Therefore, one image stack already contains statistically significant data. In addition, the directional electric field vector (E-bar) of the x-rays can be used as a 'search tool' for the direction of chemical bonds of the atom selected by its absorption edge.

  8. Local electronic structure and nanolevel hierarchical organization of bone tissue: theory and NEXAFS study

    NASA Astrophysics Data System (ADS)

    Pavlychev, A. A.; Avrunin, A. S.; Vinogradov, A. S.; Filatova, E. O.; Doctorov, A. A.; Krivosenko, Yu S.; Samoilenko, D. O.; Svirskiy, G. I.; Konashuk, A. S.; Rostov, D. A.

    2016-12-01

    Theoretical and experimental investigations of native bone are carried out to understand relationships between its hierarchical organization and local electronic and atomic structure of the mineralized phase. The 3D superlattice model of a coplanar assembly of the hydroxyapatite (HAP) nanocrystallites separated by the hydrated nanolayers is introduced to account the interplay of short-, long- and super-range order parameters in bone tissue. The model is applied to (i) predict and rationalize the HAP-to-bone spectral changes in the electronic structure and (ii) describe the mechanisms ensuring the link of the hierarchical organization with the electronic structure of the mineralized phase in bone. To check the predictions the near-edge x-ray absorption fine structure (NEXAFS) at the Ca 2p, P 2p and O 1s thresholds is measured for native bone and compared with NEXAFS for reference compounds. The NEXAFS analysis has demonstrated the essential hierarchy induced HAP-to-bone red shifts of the Ca and P 2p-to-valence transitions. The lowest O 1s excitation line at 532.2 eV in bone is assigned with superposition of core transitions in the hydroxide OH-(H2O) m anions, Ca2+(H2O) n cations, the carboxyl groups inside the collagen and [PO4]2- and [PO4]- anions with unsaturated P-O bonds.

  9. Impact of the angular dependence of the SNPP VIIRS solar diffuser BRDF degradation factor on the radiometric calibration of the reflective solar bands

    NASA Astrophysics Data System (ADS)

    Lei, Ning; Xiong, Xiaoxiong

    2015-09-01

    The Visible Infrared Imaging Radiometer Suite (VIIRS) aboard the Suomi National Polar-orbiting Partnership satellite performs radiometric calibration of its reflective solar bands (RSBs) primarily by observing an onboard solar diffuser (SD). The SD optical scattering property is measured by a bidirectional reflectance distribution function (BRDF). Once on orbit, the BRDF degrades over time and the degradation factor is determined by an onboard solar diffuser stability monitor (SDSM) which observes the Sun and the sunlit SD at almost the same time. We showed in a previous SPIE paper that the BRDF degradation factor is angle dependent. Consequently, due to that the SDSM and the VIIRS telescope SD views have very different angles, applying the BRDF degradation factor determined from the SDSM without any adjustments to the VIIRS RSB calibration can result in large systematic errors. In addition, the BRDF angular dependence impacts the determination of the SD screen transmittance viewed by both the SDSM detectors and the VIIRS telescope. We first use yaw maneuver data to determine the product of the SD attenuation screen transmittance and the BRDF at the initial time (when the BRDF just started to degrade) viewed by the VIIRS telescope, removing the impact of the SD BRDF degradation factor angular dependence over satellite orbits. By attributing the large bumps observed in the initially computed VIIRS detector gains for the M1-M4 bands to the angular dependence of the BRDF degradation factor and matching the computed VIIRS detector gains from the SD and the lunar observations, we find the relation between the BRDF degradation factors in the VIIRS telescope and SDSM SD view directions.

  10. Angular distributions of photoelectrons and interatomic-Coulombic-decay electrons from helium dimers: Strong dependence on the internuclear distance

    SciTech Connect

    Havermeier, T.; Kreidi, K.; Wallauer, R.; Voss, S.; Schoeffler, M.; Schoessler, S.; Foucar, L.; Neumann, N.; Titze, J.; Sann, H.; Kuehnel, M.; Voigtsberger, J.; Schmidt-Boecking, H.; Doerner, R.; Jahnke, T.; Sisourat, N.; Schoellkopf, W.; Grisenti, R. E.

    2010-12-15

    In the present paper, we show that the absorption of a single photon can singly ionize both atoms of a helium dimer (He{sub 2}): ionization with simultaneous excitation of one atom followed by de-excitation via interatomic Coulombic decay leads to the ejection of an electron from each of the the two atoms of the dimer. Using the Cold Target Recoil Ion Momentum Spectroscopy technique (COLTRIMS), we obtained angular distributions of these electrons in the laboratory frame and the molecular frame. We observe a pronounced variation of these distributions for different regions of kinetic-energy releases of the ions.

  11. Angular dependence of dissociative electron attachment to polyatomic molecules: Application to the {sup 2}B{sub 1} metastable state of the H{sub 2}O and H{sub 2}S anions

    SciTech Connect

    Haxton, Daniel J.; McCurdy, C. William; Rescigno, Thomas N.

    2006-06-15

    The angular dependence of dissociative electron attachment (DEA) to polyatomic targets is formulated in the local complex potential model, under the assumption that the axial recoil approximation describes the dissociation dynamics. An additional approximation, which is found to be valid in the case of H{sub 2}O but not in the case of H{sub 2}S, makes it possible to describe the angular dependence of DEA solely from an analysis of the fixed-nuclei entrance amplitude, without carrying out nuclear dynamics calculations. For H{sub 2}S, the final-vibrational-state-specific angular dependence of DEA is obtained by incorporating the variation of the angular dependence of the entrance amplitude with nuclear geometry into the nuclear dynamics. Scattering calculations using the complex Kohn method and, for H{sub 2}S, full quantum calculations of the nuclear dynamics using the multiconfiguration time-dependent Hartree method, are performed.

  12. Vibrationally resolved NEXAFS at C and N K-edges of pyridine, 2-fluoropyridine and 2,6-difluoropyridine: A combined experimental and theoretical assessment

    SciTech Connect

    Baiardi, Alberto; Mendolicchio, Marco; Barone, Vincenzo; Fronzoni, Giovanna; Cardenas Jimenez, Gustavo Adolfo; Stener, Mauro; Grazioli, Cesare; Simone, Monica de; Coreno, Marcello

    2015-11-28

    In the present work, the near edge X-ray absorption spectroscopy (NEXAFS) spectra at both C and N K-edges of pyridine, 2-fluoropyridine, and 2,6-difluoropyridine have been studied both experimentally and theoretically. From an electronic point of view, both transition potential density functional theory and time-dependent density functional theory approaches lead to reliable results provided that suitable basis sets and density functionals are employed. In this connection, the global hybrid B3LYP functional in conjunction with the EPR-III basis set appears particularly suitable after constant scaling of the band positions. For the N K-edge, vertical energies obtained at these levels and broadened by symmetric Gaussian distributions provide spectra in reasonable agreement with the experiment. Vibronic contributions further modulate the band-shapes leading to a better agreement with the experimental results, but are not strictly necessary for semi-quantitative investigations. On the other hand, vibronic contributions are responsible for strong intensity redistribution in the NEXAFS C K-edge spectra, and their inclusion is thus mandatory for a proper description of experiments. In this connection, the simple vertical gradient model is particularly appealing in view of its sufficient reliability and low computational cost. For more quantitative results, the more refined vertical Hessian approach can be employed, and its effectiveness has been improved thanks to a new least-squares fitting approach.

  13. Adsorption of acetic acid on ice studied by ambient-pressure XPS and partial-electron-yield NEXAFS spectroscopy at 230-240 K.

    PubMed

    Křepelová, Adéla; Bartels-Rausch, Thorsten; Brown, Matthew A; Bluhm, Hendrik; Ammann, Markus

    2013-01-17

    Ice plays a key role in the environment, and the ice-air interface influences heterogeneous chemical reactions between snowpack or cirrus clouds and the surrounding air. Soluble gases have been suspected to affect the topmost, disordered layer on ice (often referred to as a quasiliquid layer, QLL). Changes are especially expected in the hydrogen-bonding structure of water in the presence of solutes at the ice surface. Here, we used ambient-pressure X-ray photoelectron spectroscopy (XPS) to detect acetic acid at the ice surface at 230-240 K under atmospheric conditions for the first time. Electron-kinetic-energy-dependent C 1s spectra indicate that acetic acid remains confined to the topmost ice surface layers. Spectral analysis provides information about the protonation state of acetate at the ice surface. Surface-sensitive Auger-electron-yield C-edge near-edge X-ray absorption fine structure (NEXAFS) spectra were recorded to probe the molecular state of the adsorbed species. The O-edge NEXAFS spectra show only minor differences between clean ice and ice with adsorbed acetic acid and thus indicate that acetic acid does not lead to an extended disordered layer on the ice surface between 230 and 240 K.

  14. Multielectron effects on the orientation dependence and photoelectron angular distribution of multiphoton ionization of CO{sub 2} in strong laser fields

    SciTech Connect

    Son, Sang-Kil; Chu, S.-I

    2009-07-15

    We perform an ab initio study of multiphoton ionization (MPI) of carbon dioxide in intense linearly polarized laser pulses with arbitrary molecular orientation by means of a time-dependent density-functional theory (TDDFT) with proper long-range potential. We develop a time-dependent Voronoi-cell finite difference method with highly adaptive molecular grids for accurate solution of the TDDFT equations. Our results demonstrate that the orientation dependence of MPI is determined by multiple orbital contributions and that the electron correlation effects are significant. The maximum peak of MPI is predicted to be at 40 deg. in good agreement with recent experimental data. Photoelectron angular distribution reveals the delicate relation between the orientation dependence and the molecular orbital symmetry.

  15. Superconducting correlations above Tc in the pseudogap state of Bi2Sr2CaCu2O8 +δ cuprates revealed by angular-dependent magnetotunneling

    NASA Astrophysics Data System (ADS)

    Jacobs, Th.; Katterwe, S. O.; Krasnov, V. M.

    2016-12-01

    We present an angular-dependent magnetotunneling technique, which facilitates unambiguous separation of superconducting (supporting circulating screening currents) and nonsuperconducting (not supporting screening currents) contributions to the pseudogap phenomenon in layered Bi2Sr2CaCu2O8 +δ cuprates. Our data indicate persistence of superconducting correlations at temperatures up to 1.5 Tc in a form of both phase and amplitude fluctuations of the superconducting order parameter. However, despite a profound fluctuations region, only a small fraction of the pseudogap spectrum is caused by superconducting correlations, while the dominating part comes from a competing nonsuperconducting order, which does not support circulating orbital currents.

  16. Angular dependence of the pp elastic-scattering analyzing power between 0.8 and 2.8 GeV. II. Results for higher energies

    SciTech Connect

    Allgower, C.E.; Beddo, M.E.; Grosnick, D.P.; Kasprzyk, T.E.; Lopiano, D.; Spinka, H.M.; Ball, J.; Chamouard, P.; Combet, M.; Fontaine, J.; Kunne, R.; Sans, J.; Janout, Z.; Kalinnikov, V.A.; Khachaturov, B.A.; Matafonov, V.N.; Pisarev, I.L.; Popov, A.A.; Usov, Y.A.; Prokofiev, A.N.; Vikhrov, V.V.; Zhdanov, A.A.

    1999-11-01

    Measurements at 18 beam kinetic energies between 1975 and 2795 MeV and at 795 MeV are reported for the pp elastic-scattering single spin parameter A{sub ooon}=A{sub oono}=A{sub N}=P. The c.m. angular range is typically 60{endash}100{degree}. These results are compared to previous data from Saturne II and other accelerators. A search for energy-dependent structure at fixed c.m. angles is performed, but no rapid changes are observed. {copyright} {ital 1999} {ital The American Physical Society}

  17. Angular dependence of plasma parameters and film properties during high power impulse magnetron sputtering for deposition of Ti and TiO2 layers

    NASA Astrophysics Data System (ADS)

    Hippler, R.; Hubicka, Z.; Cada, M.; Ksirova, P.; Wulff, H.; Helm, C. A.; Stranak, V.

    2017-05-01

    Angular distribution measurements have been carried out during High Power Impulse Magnetron Sputtering (HiPIMS) of a titanium target and deposition of titanium and titanium oxide films. The HiPIMS system was operated at a repetition frequency f = 100 Hz with a duty cycle of 1%. Langmuir probe diagnostics has been carried out at a distance of 7.5 cm from the target at four different angles with respect to the surface normal of the target. Film properties were investigated by means of SEM, XR, and GIXD, and a dependence of film thickness and crystalline structure on the deposition angle is observed.

  18. Quasiclassical trajectory study of collisional energy transfer in toluene systems. II. Helium bath gas: Energy and temperature dependences, and angular momentum transfer

    NASA Astrophysics Data System (ADS)

    Lim, Kieran F.

    1994-11-01

    The collisional deactivation of highly vibrationally excited toluene-d0 and toluene-d8 by helium bath gas has been investigated using quasiclassical trajectory simulations. Collisional energy transfer was found to increase with initial toluene internal energy, in agreement with the experiments of Toselli and Barker [J. Chem. Phys. 97, 1809 (1992), and references therein]. The temperature dependence of <ΔE2>1/2 is predicted to be T(0.44±0.10), in agreement with the experiments of Heymann, Hippler, and Troe [J. Chem. Phys. 80, 1853 (1984)]. Toluene is found to have no net angular-momentum (rotational-energy) transfer to helium bath gas, although <ΔJ2>1/2 has a temperature dependence of T(0.31±0.07). Re-evaluation of earlier calculations [``Paper I:'' Lim, J. Chem. Phys. 100, 7385 (1994)] found that rotational energy transfer could be induced by increasing the mass of the collider, or by increasing the strength of the intermolecular interaction: in these cases, angular-momentum transfer depended on the initial excitation energy. In all cases, the final rotational distributions remained Boltzmann.

  19. Determination of the texture of arrays of aligned carbon nanotubes from the angular dependence of the X-ray emission and X-ray absorption spectra

    SciTech Connect

    Okotrub, A. V. Belavin, V. V.; Bulusheva, L. G.; Gusel'nikov, A. V.; Kudashov, A. G.; Vyalikh, D. V.; Molodtsov, S. L.

    2008-09-15

    The properties of materials containing carbon nanotubes depend on the degree of alignment and the internal structure of nanotubes. It is shown that the degree of misorientation of carbon nanotubes in samples can be evaluated from the measurements of the angular dependences of the carbon X-ray emission and carbon X-ray absorption spectra. The CK{sub {alpha}} emission and CK X-ray absorption spectra of the array of multiwalled carbon nanotubes synthesized by catalytic thermolysis of a mixture of fullerene and ferrocene are measured. A comparison of the calculated model dependences of the relative intensities of the {pi} and {sigma} bands in the spectra with the experimental results makes it possible to evaluate the degree of misorientation of nanotubes in the sample and their internal texture.

  20. Angular Momentum

    ERIC Educational Resources Information Center

    Shakur, Asif; Sinatra, Taylor

    2013-01-01

    The gyroscope in a smartphone was employed in a physics laboratory setting to verify the conservation of angular momentum and the nonconservation of rotational kinetic energy. As is well-known, smartphones are ubiquitous on college campuses. These devices have a panoply of built-in sensors. This creates a unique opportunity for a new paradigm in…

  1. Angular Momentum

    ERIC Educational Resources Information Center

    Shakur, Asif; Sinatra, Taylor

    2013-01-01

    The gyroscope in a smartphone was employed in a physics laboratory setting to verify the conservation of angular momentum and the nonconservation of rotational kinetic energy. As is well-known, smartphones are ubiquitous on college campuses. These devices have a panoply of built-in sensors. This creates a unique opportunity for a new paradigm in…

  2. A strategy to reduce the angular dependence of a dye-sensitized solar cell by coupling to a TiO2 nanotube photonic crystal.

    PubMed

    Guo, Min; Xie, Keyu; Liu, Xiaolin; Wang, Yu; Zhou, Limin; Huang, Haitao

    2014-11-07

    Almost all types of solar cells suffer from a decreased power output when the incident light is tilted away from normal since the incident intensity generally follows a cosine law of the incident angle. Making use of the blue shift nature of the Bragg position of a TiO2 nanotube photonic crystal (NT PC) under oblique incidence, we demonstrate experimentally that the use of the NT PC can partially compensate the cosine power loss of a dye-sensitized solar cell (DSSC). The strategy used here is to purposely choose the Bragg position of the NT PC to be at the longer wavelength side of the dye absorption peak. When the incident light is tilted, the blue shift of the Bragg position results in more overlap with the dye absorption peak, generating a higher efficiency that partially compensates the reduced photon flux due to light inclination. Moreover, the unique structure of the vertically aligned TiO2 nanotubes contributes an additional scattering effect when the incident light is tilted. As a result, the power output of a DSSC coupled with the NT PC layer shows a much flatter angular dependence than a DSSC without the NT PC. At all the incident angles, the DSSC coupled with the NT PC layer also shows a higher power conversion efficiency than the one without. The concept of using NT PC to mitigate the angular dependence of DSSCs can be easily extended to many other optoelectronic devices that are irradiance sensitive.

  3. Angular dependant micro-ESR characterization of a locally doped Gd3+:Al2O3 hybrid system for quantum applications

    NASA Astrophysics Data System (ADS)

    Wisby, I. S.; de Graaf, S. E.; Gwilliam, R.; Adamyan, A.; Kubatkin, S. E.; Meeson, P. J.; Tzalenchuk, A. Ya.; Lindstrom, T.

    Rare-earth doped crystals interfaced with superconducting quantum circuitry are an attractive platform for quantum memory and transducer applications. Here we present a detailed characterization of a locally implanted Gd3+ in Al2O3 system coupled to a superconducting micro-resonator, by performing angular dependent micro-electron-spin-resonance (micro-ESR) measurements at mK temperatures. The device is fabricated using a hard Si3N4 mask to facilitate a local ion-implantation technique for precision control of the dopant location. The technique is found not to degrade the internal quality factor of the resonators which remains above 105 (1). We find the measured angular dependence of the micro-ESR spectra to be in excellent agreement with the modelled Hamiltonian, supporting the conclusion that the dopant ions are successfully integrated into their relevant lattice sites whilst maintaining crystalline symmetries. Furthermore, we observe clear contributions from individual microwave field components of our micro-resonator, emphasising the need for controllable local implantation. 1 Wisby et al. Appl. Phys. Lett. 105, 102601 (2014)

  4. Angular dependence of direct current decay in a closed YBCO double-pancake coil under external AC magnetic field and reduction by magnetic shielding

    NASA Astrophysics Data System (ADS)

    Geng, J.; Zhang, H.; Li, C.; Zhang, X.; Shen, B.; Coombs, T. A.

    2017-03-01

    High T c superconducting (HTS) coils are ideal candidates in the use of high field magnets. HTS coils carrying a direct current, however, suffer a non-negligible loss when they are exposed to an external AC magnetic field. Although this phenomenon is well known, no study concerning AC magnetic field angular dependence of direct current decay has ever been shown. In this work, we experimentally investigate the direct current decay characteristics in a closed double pancake coil made of a YBCO coated conductor under external AC field. AC field of different angles with respect to the coil plane is applied. Results show that the current decay rate presents a strong angular dependence. The fastest decay occurs when the field is parallel to the coil plane, in which case the surface of the tape in the outermost layer experiences most flux variation. To reduce the decay rate, we propose wrapping superconducting tapes around the outermost layer of the coil to shield external AC field. This method significantly reduces direct current decay rate under parallel field, without affecting the perpendicular self-field of the coil.

  5. Pumping-power-dependent photoluminescence angular distribution from an opal photonic crystal composed of monodisperse Eu3+/SiO2 core/shell nanospheres.

    PubMed

    Tuyen, Le Dac; Lin, Jian Hung; Wu, Cheng Yi; Tai, Po-Tse; Tang, Jau; Minh, Le Quoc; Kan, Hung-Chih; Hsu, Chia Chen

    2012-07-02

    High quality opal photonic crystals (PhCs) were successfully fabricated by self-assembling of monodisperse Eu(3+)/SiO(2) core/shell nanospheres. Angular resolved photoluminescence (PL) spectra of a PhC sample were measured with different pumping powers, and its PL emission strongly depended on spectroscopic position of the photonic stop band and the optical pumping power. Suppression of the PL occurred in the directions where the emission lines aligned with the center of the photonic stop band. Suppression and enhancement of the PL were observed at low- and high-pumping powers, respectively, in the directions where the emission lines were located at the edges of the photonic stop band. When pumping power exceeded 6 µJ/pulse, a super-linear dependence was found between the pumping power and PL intensity. The dramatic enhancement of PL was attributed to the amplification of spontaneous emission resulted from the creation of large population inversion and the slow group velocity of the emitted light inside the PhC. The opal PhC provided highly angular-selective quasi-monochromatic PL output, which can be useful for a variety of optical applications.

  6. Heavy-ion versus {sup 3}He/{sup 4}He fusion-fission reactions: Angular momentum dependence of dissipation in nuclear fission

    SciTech Connect

    Ye, W.

    2011-09-15

    The stochastic Langevin model is employed to study dissipation properties in fission in the {sup 16}O + {sup 181}Ta {yields}{sup 197}Tl system by analyzing prescission neutron yields measured in this reaction. It has been found that the {sup 197}Tl nuclei undergo fission that is not in accordance with the standard Bohr-Wheeler statistical theory. A detailed comparison with previously published work in which fission excitation functions measured in {sup 3,4}He + {sup 197}Au {yields}{sup 200,201}Tl are shown to be in excellent agreement with the fission width formula predicted by the traditional models of nuclear fission suggests that nuclear dissipation strength may have an angular momentum dependence in addition to the known deformation and temperature dependence. Implications for the basic understanding of the observed abnormal rise in prescission particles at high energy and the need for further experimental confirmations are discussed.

  7. Angular dependent study of spatial order-disorder transitions in the vortex matter of superconducting Yb3Rh4Sn13

    NASA Astrophysics Data System (ADS)

    Kumar, Santosh; Singh, Ravi P.; Thamizhavel, A.; Tomy, C. V.; Grover, A. K.

    2016-05-01

    We present here the results of angular-dependent magnetization measurements (both ac and dc) carried out in a weakly-pinned single crystal of a low Tc superconductor, Yb3Rh4Sn13. Both dc magnetization data (M-H) as well as the ac magnetic susceptibility plots (χ´(H)) have revealed the fingerprints of an order-disorder transition in the vortex matter for various orientations of the crystal with respect to the external magnetic field. Our findings show that the quality of the ordered Bragg glass (BG) phase in this isotropic compound depends significantly on the direction of the magnetic field with respect to the crystallographic axes; a better spatially ordered vortex configuration is obtained when the magnetic field is applied along the [110] direction than that when the magnetic field is applied along the [100] axis. The present findings in Yb3Rh4Sn13 bear resemblance with similar results reported earlier for borocarbide superconductors.

  8. Rotational dependence of the proton-transfer reaction HBr+ + CO2-->HOCO+ + Br. I. Energy versus angular momentum effects.

    PubMed

    Paetow, Lisa; Unger, Franziska; Beichel, Witali; Frenking, Gernot; Weitzel, Karl-Michael

    2010-05-07

    Cross sections for the endothermic proton-transfer reactions of rotationally state-selected HBr(+) and DBr(+) ions with CO(2) were measured in a guided ion beam apparatus in order to determine the influence of rotational excitation and collision energy in the center of mass (c.m.) system on the cross section. Ab initio calculations were performed to obtain energetic information about reactants, intermediates, and products. In the experiment HBr(+) and DBr(+) ions were prepared with the same mean rotational quantum number but different mean rotational energies as the rotational constants differ by about a factor of two. The mean rotational energy was varied from 1.4 to 66.3 meV for HBr(+) and from 0.7 to 43.0 meV for DBr(+). Collision energies (E(c.m.)) ranged from 0.32 to 1.00 eV. Under all conditions considered, an increase in the rotational excitation leads to a decrease in the cross section for both reactions. However, the effect is more pronounced for the higher collision energies. For E(c.m.)=1.00 and 0.85 eV; a comparison between the results for HBr(+) and DBr(+) indicates that the cross section is dominated by effects of rotational energy rather than angular momentum. For lower collision energies the cross sections for the deuteron transfer and the proton transfer are in best agreement if not compared for the same c.m. collision energy but for the same value of the difference between the collision energy and the reaction enthalpy.

  9. Determination of the angular and energy dependence of hard constituent scattering from. pi. /sup 0/ pair events at the CERN intersecting storage rings

    SciTech Connect

    Angelis, A.L.S.; Besch, H.J.; Blumenfeld, B.J.

    1982-08-23

    We present data on proton-proton collisions, obtained at the CERN Intersecting Storage Rings, in which two roughly back-to-back ..pi../sup 0/'s of high transverse momentum (p/sub T/) were produced. The angular distribution of the dipion axis relative to the collision axis is found to be independent of both the effective mass m of the dipion system and the centre-of-mass energy ..sqrt..s of the proton-proton collision. The cross-sections dsigma/dm at the two values of ..sqrt..s satisfy a scaling law of the form dsigma/dm = G(x)/m/sup n/, where x = m(..pi../sup 0/,..pi../sup 0/)/..sqrt..s and n = 6.5 +- 0.5. We show from our data that the leading ..pi../sup 0/ carries most of the momentum of the scattered parton. Given this fact, the axis of the dipion system follows closely the direction of the scattered constituents, and we exploit this to determine the angular dependence of the hard-scattering subprocess. We also compare our data with the lowest order QCD predictions using structure functions as determined in deep-inelastic scattering and fragmentation functions from electron-positron annihilation.

  10. Time-dependent quantum mechanical calculations on H+O2 for total angular momentum J>0. III. Total cross sections

    NASA Astrophysics Data System (ADS)

    Goldfield, Evelyn M.; Meijer, Anthony J. H. M.

    2000-12-01

    The H+O2→OH+O reaction has been studied with a time-dependent wave packet method for total angular momentum J=15, 20, 25, 35. This work is a continuation of previous studies for J⩽10. The calculations were performed combining a real wave packet method with the Coriolis coupled method on parallel computers. We find that for most energies there is a monotonic decrease of reaction probability with increasing J. Nevertheless, due to the 2J+1 degeneracy, higher angular momentum states contribute significantly to the total reaction cross section. A smoothing/interpolation/extrapolation scheme is employed to compute total reaction cross sections. These cross sections are compared with quasiclassical results on the same potential energy surface, and the most recent experimental cross sections. Comparisons with quasiclassical results show the significance of zero-point energy constraints. The quantum mechanical theoretical cross sections are smaller than the experimental ones everywhere, suggesting that a more accurate potential energy surface is required. There is also some possibility that nonadiabatic effects play a role in this reaction.

  11. Electron-beam transmission through a micrometer-sized tapered-glass capillary: Dependence on incident energy and angular tilt angle

    NASA Astrophysics Data System (ADS)

    Wickramarachchi, S. J.; Ikeda, T.; Dassanayake, B. S.; Keerthisinghe, D.; Tanis, J. A.

    2016-08-01

    An experimental study of 500- and 1000-eV incident electrons transmitted through a micrometer-sized funnel-shaped (tapered) glass capillary with inlet diameter 0.80 mm, outlet diameter 0.10 mm, and a length of 35 mm is reported. The properties of the electron beam transmitted were measured as a function of the emerging angle and the incident energy dependence. The angular profiles were found to be comprised of up to three peaks for both 500 and 1000 eV showing evidence for transmission going straight through the capillary without interacting with the walls (direct), as well as transmission resulting from Coulomb deflection of the electrons from a negative charge patch or by scattering from nuclei close to the surface of the capillary (indirect). The energy spectra show that elastically transmitted electrons dominate at 500 eV for increasing sample tilt angles up to ˜5.0°, while inelastic processes dominate for 1000 eV already at tilt angles of ˜1.0°. The angular width of the emitted electrons was found to constitute a narrow beam for direct (˜0.4°) and indirect (<0.6° for 500 eV and <1.0° for 1000 eV) transmission for both energies with the widths decreasing for the largest tilt angles measured and approaching the inherent resolution (˜0.3°) of the electron analyzer.

  12. SU-E-T-644: Evaluation of Angular Dependence Correction for 2D Array Detector Using for Quality Assurance of Volumetric Modulated Arc Therapy

    SciTech Connect

    Karthikeyan, N; Ganesh, K M; Vikraman, S; Shariff, MH

    2014-06-15

    Purpose: To evaluate the angular dependence correction for Matrix Evolution 2D array detector in quality assurance of volumetric modulated arc therapy(VMAT). Methods: Total ten patients comprising of different sites were planned for VMAT and taken for the study. Each plan was exposed on Matrix Evolution 2D array detector with Omnipro IMRT software based on the following three different methods using 6MV photon beams from Elekta Synergy linear accelerator. First method, VMAT plan was delivered on Matrix Evolution detector as it gantry mounted with dedicated holder with build-up of 2.3cm. Second, the VMAT plan was delivered with the static gantry angle on to the table mounted setup. Third, the VMAT plan was delivered with actual gantry angle on Matrix Evolution detector fixed in Multicube phantom with gantry angle sensor and angular dependence correction were applied to quantify the plan quality. For all these methods, the corresponding QA plans were generated in TPS and the dose verification was done for both point and 2D fluence analysis with pass criteria of 3% dose difference and 3mm distance to agreement. Results: The measured point dose variation for the first method was observed as 1.58±0.6% of mean and SD with TPS calculated. For second and third method, the mean and standard deviation(SD) was observed as 1.67±0.7% and 1.85±0.8% respectively. The 2D fluence analysis of measured and TPS calculated has the mean and SD of 97.9±1.1%, 97.88±1.2% and 97.55±1.3% for first, second and third methods respectively. The calculated two-tailed Pvalue for point dose and 2D fluence analysis shows the insignificance with values of 0.9316 and 0.9015 respectively, among the different methods of QA. Conclusion: The qualitative evaluation of angular dependence correction for Matrix Evolution 2D array detector shows its competency in accuracy of quality assurance measurement of composite dose distribution of volumetric modulated arc therapy.

  13. SU-E-J-206: A Comparison of Different Hardware Design Approaches for Feature-Supported Optical Head-Tracking with Respect to Angular Dependencies

    SciTech Connect

    Stueber, P; Wissel, T; Wagner, B; Bruder, R; Schweikard, A; Ernst, F

    2014-06-01

    Purpose: Recent research has shown that optical features significantly improve marker-less optical head-tracking for cranial radiotherapy. Simulations, however, showed that these optical features, which are used to derive tissue thickness, depend on the incident angle of the IR scanning laser beam and the perspective of the camera analyzing the reflective patterns. We present an experimental analysis determining which is the most robust optical setup concerning angular influences. Methods: In three consecutive experiments, the incident angle of the laser (1), the perspective of the camera (2) or both simultaneously (3, ‘inBeam’-perspective) were changed with respect to the target. We analyzed how this affects feature intensity. These intensities were determined from seven concentric regions of interest (ROIs) around the laser spot. Two targets were used: a tissue-like silicone phantom and a human's forehead. Results: For each experiment, the feature intensity generally decreases with increasing angle. We found that the optical properties of the silicone phantom do not fit the properties of human skin. Furthermore, the angular influence of the laser on the features is significantly higher than the perspective of the camera. With the ‘inBeam’- perspective, the smoothest decays of feature intensity were found. We suppose that this is because of a fixed relationship between both devices. This smoothness, suggesting a predictable functional relationship, may simplify angle compensation for machine learning algorithms. This is particularly prominent for the medial ROIs. The inner ROIs highly depend on the angle and power of the laser. The outer ROIs show less angular dependency but the signal strength is critically low and prone to artifacts. Therefore and because of the smooth decays, medial ROIs are a suitable tradeoff between susceptibility, signal-noise-ratio and distance to the center of the laser spot. Conclusion: For tissue thickness correlated feature

  14. Surface chemistry of alanine on Cu{111}: Adsorption geometry and temperature dependence

    NASA Astrophysics Data System (ADS)

    Baldanza, Silvia; Cornish, Alix; Nicklin, Richard E. J.; Zheleva, Zhasmina V.; Held, Georg

    2014-11-01

    Adsorption of L-alanine on the Cu{111} single crystal surface was investigated as a model system for interactions between small chiral modifier molecules and close-packed metal surfaces. Synchrotron-based X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy are used to determine the chemical state, bond coordination and out-of-plane orientation of the molecule on the surface. Alanine adsorbs in its anionic form at room temperature, whilst at low temperature the overlayer consists of anionic and zwitterionic molecules. NEXAFS spectra exhibit a strong angular dependence of the π* resonance associated with the carboxylate group, which allows determining the tilt angle of this group with respect to the surface plane (48° ± 2°) at room temperature. Low-energy electron diffraction (LEED) shows a p(2√{ 13} × 2√{ 13}) R 13 ° superstructure with only one domain, which breaks the mirror symmetry of the substrate and, thus, induces global chirality to the surface. Temperature-programmed XPS (TP-XPS) and temperature-programmed desorption (TPD) experiments indicate that the zwitterionic form converts into the anionic species (alaninate) at 293 K. The latter desorbs/decomposes between 435 K and 445 K.

  15. Vibrationally resolved high-resolution NEXAFS and XPS spectra of phenanthrene and coronene

    SciTech Connect

    Fronzoni, Giovanna; Baseggio, Oscar; Stener, Mauro; Hua, Weijie; Tian, Guangjun; Luo, Yi; Apicella, Barbara; Alfé, Michela; Simone, Monica de; Kivimäki, Antti; Coreno, Marcello

    2014-07-28

    We performed a combined experimental and theoretical study of the C1s Near-Edge X-ray Absorption Fine-Structure (NEXAFS) spectroscopy and X-ray Photoelectron Spectroscopy in the gas phase of two polycyclic aromatic hydrocarbons (phenanthrene and coronene), typically formed in combustion reactions. In the NEXAFS of both molecules, a double-peak structure appears in the C1s → LUMO region, which differ by less than 1 eV in transition energies. The vibronic coupling is found to play an important role in such systems. It leads to weakening of the lower-energy peak and strengthening of the higher-energy one because the 0 − n (n > 0) vibrational progressions of the lower-energy peak appear in nearly the same region of the higher-energy peak. Vibrationally resolved theoretical spectra computed within the Frank-Condon (FC) approximation and linear coupling model agree well with the high-resolution experimental results. We find that FC-active normal modes all correspond to in-plane vibrations.

  16. C-1s NEXAFS spectroscopy reveals chemical fractionation of humic acid by cation-induced coagulation

    SciTech Connect

    Christl,I.; Kretzschmar, R.

    2007-01-01

    The influence of cation-induced coagulation on the chemical composition of dissolved and coagulated fractions of humic acid was investigated in batch coagulation experiments for additions of aluminum at pH 4 and 5, iron at pH 4, and calcium and lead at pH 6. The partitioning of organic carbon and metals was determined by analyzing total organic carbon and total metal contents of the dissolved phase. Both the dissolved and the coagulated humic acid fractions were characterized using synchrotron scanning transmission X-ray microscopy (STXM) and C-1s near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. Intensities of {pi}* transitions of carboxyl carbon and {sigma}* transitions of alkyl, O-alkyl, and carboxyl carbon decreased with increasing metal concentration for the dissolved humic acid fractions. This decrease was accompanied by an increase of the respective intensities in the coagulated fraction as shown for lead. Intensities of aromatic and phenolic carbon were affected to a larger extent only by aluminum and iron additions. The changes observed in the C-1s NEXAFS spectra coincided with an increasing removal of organic carbon from the dissolved phase with increasing total metal concentrations. We conclude that humic acid was chemically fractionated by cation-induced coagulation, which preferentially removed functional groups involved in metal-cation binding from solution.

  17. The nature of nitrate at the ice surface studied by XPS and NEXAFS.

    PubMed

    Krepelová, Adéla; Newberg, John; Huthwelker, Thomas; Bluhm, Hendrik; Ammann, Markus

    2010-08-21

    Trace contaminants such as strong acids have been suggested to affect the thickness of the quasi-liquid layer at the ice/air interface, which is at the heart of heterogeneous chemical reactions between snowpacks or cirrus clouds and the surrounding air. We used X-ray photoelectron spectroscopy (XPS) and electron yield near edge X-ray absorption fine structure (NEXAFS) spectroscopy at the Advanced Light Source (ALS) to probe the ice surface in the presence of HNO(3) formed from the heterogeneous hydrolysis of NO(2) at 230 K. We studied the nature of the adsorbed species at the ice/vapor interfaces as well as the effect of HNO(3) on the hydrogen bonding environment at the ice surface. The NEXAFS spectrum of ice with adsorbed HNO(3) can be represented as linear combination of the clean ice and nitrate solution spectrum, thus indicating that in the presence of HNO(3) the ice surface consists of a mixture of clean ice and nitrate ions that are coordinated as in a concentrated solution at the same temperature but higher HNO(3) pressures.

  18. Topological dependence of Kepler's third law for collisionless periodic three-body orbits with vanishing angular momentum and equal masses

    NASA Astrophysics Data System (ADS)

    Dmitrašinović, V.; Šuvakov, Milovan

    2015-09-01

    We present results of numerical calculations showing a three-body orbit's period's T dependence on its topology. This dependence is a simple linear one, when expressed in terms of appropriate variables, suggesting an exact mathematical law. This is the first known relation between topological and kinematical properties of three-body systems. We have used these results to predict the periods of several sets of as yet undiscovered orbits, but the relation also indicates that the number of periodic three-body orbits with periods shorter than any finite number is countable.

  19. Probing the Orientation of Surface Immobilized Protein G B1 using ToF SIMS, Sum Frequency Generation, and NEXAFS Spectroscopy

    PubMed Central

    Baugh, Loren; Weidner, Tobias; Baio, J.E.; Nguyen, Phuong Cac; Gamble, Lara J.; Stayton, Patrick S.; Castner, David G.

    2010-01-01

    The ability to orient active proteins on surfaces is a critical aspect of many medical technologies. An important related challenge is characterizing protein orientation in these surface films. This study uses a combination of time-of-flight secondary ion mass spectrometry (ToF-SIMS), sum frequency generation (SFG) vibrational spectroscopy, and near edge x-ray absorption fine structure (NEXAFS) spectroscopy to characterize the orientation of surface-immobilized Protein G B1, a rigid 6 kDa domain that binds the Fc fragment of IgG. Two Protein G B1 variants with a single cysteine introduced at either end were immobilized via the cysteine thiol onto maleimide-oligo(ethylene glycol)-functionalized gold and bare gold substrates. X-ray photoelectron spectroscopy was used to measure the amount of immobilized protein and ToF-SIMS was used to measure the amino acid composition of the exposed surface of the protein films and to confirm covalent attachment of protein thiol to the substrate maleimide groups. SFG and NEXAFS were used to characterize the ordering and orientation of peptide or side chain bonds. On both substrates and for both cysteine positions, ToF-SIMS data showed enrichment of mass peaks from amino acids located at the end of the protein opposite the cysteine surface position compared with nonspecifically immobilized protein, indicating end-on protein orientations. Orientation on the maleimide substrate was enhanced by increasing pH (7.0 to 9.5) and salt concentration (0 to 1.5 M NaCl). SFG spectral peaks characteristic of ordered α-helix and β-sheet elements were observed for both variants but not for cysteine-free wild type protein on the maleimide surface. The phase of the α-helix and β-sheet peaks indicated a predominantly upright orientation for both variants, consistent with an end-on protein binding configuration. Polarization dependence of the NEXAFS signal from the N 1s toπ* transition of β-sheet peptide bonds also indicated protein ordering

  20. Heat capacity, resistivity, and angular dependent magnetization studies of single crystal Nd1+ϵFe4B4 for ϵ≈17

    DOE PAGES

    Conner, Benjamin S.; Susner, Michael A.; Lampen-Kelley, Paula; ...

    2017-04-04

    Advances in crystal growth have allowed for synthesis of large single crystals of Nd1+ϵFe4B4, a well-known phase with a modulated structure. As a result we are able to report heat capacity and resistivity measurements on a single crystal Nd1+ϵFe4B4 sample with a distribution of ϵ that skews towards the solubility limit of Nd near ϵ ≈ 17. Heat capacity measurements show evidence of crystal field splitting at temperatures higher than the long-range ferromagnetic Curie temperature. Heat capacity, resistivity, and magnetization measurements all confirm a Curie temperature of 7 K which is lower than previously reported values in the Nd1+ϵFe4B4 system.more » Here, we also perform measurements of the angular dependence of the magnetization and discover behavior associated with the magnetic anisotropy that is inconsistent with the simple description previously proposed.« less

  1. Large anisotropic Fe orbital moments in perpendicularly magnetized Co2FeAl Heusler alloy thin films revealed by angular-dependent x-ray magnetic circular dichroism

    NASA Astrophysics Data System (ADS)

    Okabayashi, Jun; Sukegawa, Hiroaki; Wen, Zhenchao; Inomata, Koichiro; Mitani, Seiji

    2013-09-01

    Perpendicular magnetic anisotropy (PMA) in Heusler alloy Co2FeAl thin films sharing an interface with a MgO layer is investigated by angular-dependent x-ray magnetic circular dichroism. Orbital and spin magnetic moments are deduced separately for Fe and Co 3d electrons. In addition, the PMA energies are estimated using the orbital magnetic moments parallel and perpendicular to the film surfaces. We found that PMA in Co2FeAl is determined mainly by the contribution of Fe atoms with large orbital magnetic moments, which are enhanced at the interface between Co2FeAl and MgO. Furthermore, element specific magnetization curves of Fe and Co are found to be similar, suggesting the existence of ferromagnetic coupling between Fe and Co PMA directions.

  2. First-order chiral to non-chiral transition in the angular dependence of the upper critical induction of the Scharnberg-Klemm p-wave pair state.

    PubMed

    Zhang, J; Lörscher, C; Gu, Q; Klemm, R A

    2014-06-25

    We calculate the temperature T and angular (θ, ϕ) dependencies of the upper critical induction Bc2(θ, ϕ, T) for parallel-spin superconductors with an axially symmetric p-wave pairing interaction pinned to the lattice and a dominant ellipsoidal Fermi surface (FS). For all FS anisotropies, the chiral Scharnberg-Klemm (SK) state Bc2(θ, ϕ, T) exceeds that of the chiral Anderson-Brinkman-Morel (ABM) state and exhibits a kink at θ = θ*(T, ϕ), indicative of a first-order transition from its chiral, nodal-direction behavior to its non-chiral, antinodal-direction behavior. Applicabilities to Sr2RuO4, UCoGe and the candidate topological superconductor CuxBi2Se3 are discussed.

  3. A generic π* shape resonance observed in energy-dependent photoelectron angular distributions from two-colour, resonant multiphoton ionization of difluorobenzene isomers.

    PubMed

    Staniforth, Michael; Daly, Steven; Reid, Katharine L; Powis, Ivan

    2013-08-14

    We present new evidence for the existence of a near threshold π* shape resonance as a common feature in the photoionization of each isomer of difluorobenzene. Experimentally, this is revealed by significant changes in the anisotropy of the photoelectron angular distributions (PADs) following the ionization of the optically aligned S1 state of these molecules at varying photon energies. Continuum multiple scattering Xα calculations reproduce this behaviour well, and allow the visualisation of the continuum shape resonances. The resonances are unusually narrow in energy (<1 eV), but nevertheless appear to extend right down to the ionization thresholds--exactly the low energy range typically accessed in laser-based resonance enhanced multiphoton ionization (REMPI) schemes. The anticipation of such pronounced energy dependence in the PADs and cross-sections sought for other molecules, and an ability to accurately predict such features, should be important for the reliable application and interpretation of experiments involving REMPI probing of those molecules.

  4. Heat capacity, resistivity, and angular dependent magnetization studies of single crystal Nd1+ɛFe4B4 for ɛ ≈ 1/7

    NASA Astrophysics Data System (ADS)

    Conner, B. S.; Susner, M. A.; Lampen-Kelley, P.; May, A. F.; McGuire, M. A.; Yan, J.-Q.; Sales, B. C.

    2017-08-01

    Advances in crystal growth have allowed for synthesis of large single crystals of Nd1+ɛFe4B4 , a well-known phase with a modulated structure. As a result we are able to report heat capacity and resistivity measurements on a single crystal Nd1+ɛFe4B4 sample with a distribution of ɛ that skews towards the solubility limit of Nd near ɛ ≈ 1/7. Heat capacity measurements show evidence of crystal field splitting at temperatures higher than the long-range ferromagnetic Curie temperature. Heat capacity, resistivity, and magnetization measurements all confirm a Curie temperature of 7 K which is lower than previously reported values in the Nd1+ɛFe4B4 system. We also perform measurements of the angular dependence of the magnetization and discover behavior associated with the magnetic anisotropy that is inconsistent with the simple description previously proposed.

  5. Electrically Addressable Optical Devices Using A System Of Composite Layered Flakes Suspended In A Fluid Host To Obtain Angularly Depende

    DOEpatents

    Kosc, Tanya Z.; Marshall, Kenneth L.; Jacobs, Stephen D.

    2004-12-07

    Composite or layered flakes having a plurality of layers of different materials, which may be dielectric materials, conductive materials, or liquid crystalline materials suspended in a fluid host and subjected to an electric field, provide optical effects dependent upon the angle or orientation of the flakes in the applied electric field. The optical effects depend upon the composition and thickness of the layers, producing reflectance, interference, additive and/or subtractive color effects. The composition of layered flakes may also be selected to enhance and/or alter the dielectric properties of flakes, whereby flake motion in an electric field is also enhanced and/or altered. The devices are useful as active electro-optical displays, polarizers, filters, light modulators, and wherever controllable polarizing, reflecting and transmissive optical properties are desired.

  6. Angular dependence of the magnetoresistance below T c of epitaxial Bi 2Sr 2CuO y thin films

    NASA Astrophysics Data System (ADS)

    Rifi, H.; Li, Z. Z.; Megtert, S.; Raffy, H.; Laborde, O.; Monceau, P.

    1994-12-01

    Magnetoresistance of high quality epitaxial Bi 2Sr 2CuO y thin films has been measured for temperatures below T c (1.5Kdepend uniquely on the transverse component of the magnetic field as it is the case in the strongly anisotropic Bi 2Sr 2CaCu 2O y phase. The behavior with the magnetic field perpendicular to the CuO 2 planes is briefly discussed.

  7. In-plane angular dependence of the spin-wave nonreciprocity of an ultrathin film with Dzyaloshinskii-Moriya interaction

    SciTech Connect

    Zhang, Vanessa Li; Di, Kai; Lim, Hock Siah; Ng, Ser Choon; Kuok, Meng Hau; Yu, Jiawei; Yoon, Jungbum; Qiu, Xuepeng; Yang, Hyunsoo

    2015-07-13

    The nonreciprocal propagation of spin waves in an ultrathin Pt/Co/Ni film has been measured by Brillouin light scattering. The frequency nonreciprocity, due to the interfacial Dzyaloshinskii-Moriya interaction (DMI), has a sinusoidal dependence on the in-plane angle between the magnon wavevector and the applied magnetic field. The results, which are in good agreement with analytical predictions reported earlier, yield a value of the DMI constant which is the same as that obtained previously from a study of the magnon dispersion relations. We have demonstrated that our magnon-dynamics based method can experimentally ascertain the DMI constant of multilayer thin films.

  8. Carbon speciation of diesel exhaust and urban particulate matter NIST standard reference materials with C(1s) NEXAFS spectroscopy.

    PubMed

    Braun, Artur; Mun, Bongjin Simon; Huggins, Frank E; Huffman, Gerald P

    2007-01-01

    The U.S. National Institute of Standards and Technology (NIST) provides a number of particulate matter (PM) standard reference materials (SRM) for use in environmental and toxicological methodology and research. We present here the first analysis with respect to the molecular structure of the carbon in three such NIST SRM samples, i.e., diesel engine exhaust soot from heavy duty equipment engines (SRM 1650), diesel soot from a forklift engine (SRM 2975), and urban PM collected in St. Louis, MO (SRM 1648), with near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. The NEXAFS spectra of the two diesel soot samples appear quite similar, while they differ significantly from the urban PM spectrum, in agreement with X-ray diffraction data published recently. Such comparison is made in terms of aromatic and aliphatic carbon species, as well as by a general comparison with graphitic materials. Both diesel soot SRM samples contain basic graphitic structures, but the presence of exciton resonance and extended X-ray absorption fine structure oscillations in SRM 1650 and the lack therof in SRM 2975 suggest that SRM 1650 is the more graphitic material. The presence of polycyclic aromatic hydrocarbons, which have a characteristic NEXAFS resonance at the same position as graphite, can obscure the graphitic character of soot, unless an extraction of the organic matter is made. Our NEXAFS data do not suggest that the urban PM sample SRM 1648 contains a substantial amount of graphite-like material.

  9. SU-E-T-44: Angular Dependence of Surface Dose Enhancement Measured On Several Inhomogeneities Using Radiochromic EBT3 Films

    SciTech Connect

    Jansen, A; Schoenfeld, A; Poppinga, D; Chofor, N; Poppe, B

    2014-06-01

    Purpose: The quantification of the relative surface dose enhancement in dependence on the angle of incidence and the atomic number Z of the surface material. Methods: Experiments were performed with slabs made of aluminum, titanium, copper, silver, dental gold and lead. The metal slabs with equal sizes of 1.0×8.0×8.8mm{sup 3} were embedded in an Octavius 4D phantom (PTW Freiburg, Germany). Radiochromic EBT3 films were used to measure the surface dose for angles of incidence ranging from 0° to 90°. The setup with the metals slabs at the isocenter was irradiated with acceleration voltages of 6MV and 10MV. Water reference measurements were taken under equal conditions. Results: The surface dose enhancement is highest for angles of incidence below 30° and drops significantly for higher. The surface dose enhancement produced by lead and dental gold at 6MV showed a peak of 65%. At 90°, the surface dose enhancement dropped to 15% for both materials. The surface dose enhancements for silver, copper, titanium and aluminum were 45%, 32%, 22% and 12% at 0°, respectively. At an angle of incidence of 80°, the values dropped to 22%, 18%, 12% und 6%. The values for 10MV were very similar. Lead and dental gold showed peaks of 65% und 60%. Their values dropped to 18% at an angle of 90°. The surface dose enhancements for silver, copper, titanium and aluminum were 45%, 30%, 20% and 8% at 0°. At 80° the values dropped to 30%, 20%, 12% and 5%. A dependence of the magnitude of the surface dose enhancement on the atomic number of the surface material can be seen, which is in consistence with literature. Conclusion: The results show that the surface dose enhancements near implant materials with high Z-values should be taken into consideration in radio therapy, even when the angle of incidence is flat.

  10. Physical and Chemical Behaviors of HCl on Ice Surface: Insights from an XPS and NEXAFS Study

    NASA Astrophysics Data System (ADS)

    Kong, X.; Waldner, A.; Orlando, F.; Birrer, M.; Artiglia, L.; Ammann, M.; Bartels-Rausch, T.

    2016-12-01

    Ice and snow play active roles for the water cycle, the energy budget of the Earth, and environmental chemistry in the atmosphere and cryosphere. Trace gases can be taken up by ice, and physical and chemical fates of the impurities could modify surface properties significantly and consequently influence atmospheric chemistry and the climate system. However, the understanding of chemical behaviour of impurities on ice surface are very poor, which is largely limited by the difficulties to apply high sensitivity experimental approaches to ambient air conditions, e.g. studies of volatile surfaces, because of the strict requirements of vacuum experimental conditions. In this study, we employed synchrotron-based X-ray photoelectron spectroscopy (XPS) and partial electron yield Near Edge X-ray Absorption Fine Structure (NEXAFS) in a state-of-the-art near-ambient pressure photoelectron (NAPP) spectroscopy end station. The NAPP enables to utilize the surface sensitive experimental methods, XPS and NEXAFS, on volatile surfaces, i.e. ice at temperatures approaching 0°C. XPS and NEXAFS together provide unique information of hydrogen bonding network, dopants surface concentration, dopant depth profile, and acidic dissociation on the surfaces1. Taking the advantages of the highly sensitive techniques, the adsorption, dissociation and depth profile of Hydrogen Chloride (HCl) on ice were studied. In brief, two states of Chloride on ice surface are identified from the adsorbed HCl, and they are featured with different depth profiles along the ice layers. Combining our results and previously reported constants from literatures (e.g. HCl diffusion coefficients in ice)2, a layered kinetic model has been constructed to fit the depth profiles of two states of Chloride. On the other side, pure ice and doped ice are compared for their surface structure change caused by temperature and the presence of HCl, which shows how the strong acid affect the ice surface in turn. 1. Orlando, F., et

  11. Vibration-dependent photoelectron angular distributions and branching ratios observed across the Cooper-minimum region of bromobenzene

    NASA Astrophysics Data System (ADS)

    Powis, Ivan; Patanen, Minna; Antonsson, Egill; Nicolas, Christophe; Miron, Catalin; Holland, David M. P.

    2017-07-01

    Vibrational state-resolved photoelectron anisotropy parameters, β , for the X ˜2B1 , B ˜2B2 , and C ˜2B1 state ionizations of bromobenzene have been recorded at photon energies ranging from 20.5 to 94 eV, thus spanning the region of the expected bromine Cooper minimum (CM). The X ˜ state displays no CM and its β value is also independent of vibrational level, in accord with the Franck-Condon approximation. The B ˜ and C ˜ state β values display the CM to differing degrees, but both show a vibrational dependence that extends to energies well below the obvious CM dip. Calculations are presented that replicate these observations. We thus demonstrate a wide-ranging Franck-Condon approximation breakdown detected in the β anisotropy parameter in the absence of any resonance. Measured and calculated vibrational branching ratios for these states are also presented. Although the B ˜ state branching ratios remain constant, in accord with Franck-Condon expectations, the X ˜ and (especially) the C ˜ state ratios display weak, quasilinear variations across the studied range of photon energy, but with no apparent correlation with the CM position.

  12. Spectral studies on sulfur poisoning of Pd/Mg6Ni by NEXAFS and XPS

    NASA Astrophysics Data System (ADS)

    Yagi, S.; Nambu, M.; Tsukada, C.; Ogawa, S.; Kutluk, G.; Namatame, H.; Taniguchi, M.

    2013-02-01

    We have studied on the hydrogen storage materials based on Mg-Ni alloy and fabricated the sample constructed with the Pd thin layer (TL) on Mg6Ni alloy substrate. The adsorption behavior of the dimethyl disulfide (DMS) molecules on the sample has been measured to reveal the sulfur poisoning of the Pd TL/Mg6Ni by means of XPS and Sulfur K-edge NEXAFS techniques. The chemisorbed DMS, methanethiolate (MT) and atomic S have been observed on the surface. Especially, it is clear that some atomic S has been oxidized by air and detected the adsorbate of the SO32- and SO42- species. During exposure to the atmosphere, most of the adsorbed DMS and MT adsorbates desorb from the Pd TL surface. We thus conclude the Pd TL might be able to prevent the hydrogen storage materials from the sulfur poisoning.

  13. The structure of a-C: What NEXAFS and EXAFS see

    SciTech Connect

    Hussain, Zahid; Diaz, J.; Monteiro, O.R.; Hussain, Z.

    2006-08-01

    Mechanically hard ha-C and soft sa-C amorphous carbon films of 2.9 and 2.2 g cm-3 approximate densities were prepared by filtered cathodic arc deposition and analyzed by near-edge x-ray absorption spectroscopy NEXAFS and extended x-ray absorption spectroscopy EXAFS to determine their structure. The analysis observed an insignificant level of pi bond conjugation in both kind of films. EXAFS distinguished two types of atomic environments in them: one semiordered with well defined bond lengths, and the other with so strong bond disorder that its contribution to EXAFS was undetectable. The proportion of atoms in the semiordered atomic environments was of less than 40percent in both films. Their bond lengths were similar to those of diamond in the ha-C films and to graphite in the sa-C. NEXAFS spectra analysis was based on the linear relation between sigma* energy and bond length. It served to quantify the proportion of sp3 bonded atoms in a-C, to deduce the average bond length of the atoms undetected by EXAFS, and to determine the level of bond conjugation in the films. The sp3 concentration estimated with the proposed method was of 44percent in the ha-C films and 10percent in the sa-C films. These values were consistent with the EXAFS results, but disagreed with those obtained based on the traditional pi*/sigma* intensity ratio method which overestimated sp3 concentrations. Annealing of the ha-C films up to its almost complete graphitization caused a gradual reduction in bond length of the semiordered environments with no differentiation between two phases, diamondlike and graphitelike, at any temperature. This resultsupport models that explain sp3 bond promotion in a-C as caused by the high compressive stress attained by a strongly disordered sp2 dense structure during film deposition.

  14. NEXAFS Depth Profiling of Surface Segregation in Block Copolymer Thin Films

    SciTech Connect

    Krishnan, S.; Paik, M; Ober, C; Martinelli, E; Galli, G; Sohn, K; Kramer, E; Fischer, D

    2010-01-01

    NEXAFS spectroscopy was used to probe the surface composition and under-water surface reconstruction of thin films of comb-like diblock copolymers with cylindrical and spherical microphases. The polymers consisted of a polystyrene block, and a second block prepared from a styrenic monomer grafted with fluoroalkyl-tagged poly(ethylene glycol) side chains. Compositional depth profiling of the microphase separated block copolymer films, in the top 1-3 nm of the film, was performed to understand the role of block copolymer microstructure and self-assembly on surface composition. Using experimentally determined concentration profiles, the surface concentration of phenyl ring carbon atoms was quantified and compared with those of homopolymer and random copolymer controls. The carbon atoms from the relatively high surface energy phenyl groups were depleted or excluded from the surface, in favor of the low surface-energy fluoroalkyl groups. While it is expected that block copolymer surfaces will be completely covered by a wetting lamellar layer of the lower surface energy block, a significant amount of the higher surface energy polystyrene block was found to be present in the surface region of the cylinder-forming block copolymer. Evidently, the spontaneous formation of the cylindrical polystyrene microdomains in the near-surface region compensated for the lowering of the free energy that could have been achieved by completely covering the surfaces with a lamellar layer of the lower surface energy fluorinated block. All surfaces underwent molecular reconstruction after immersion in water. The experimental concentration depth profiles indicated an increased surface depletion of phenyl ring carbon atoms in the water-immersed thin films, due to the tendency of hydrophilic PEG side groups to be present at the polymer-water interface. Such a detailed characterization of the outermost layers of the block copolymer surfaces was possible because of the exceptional depth resolution

  15. Study of CP Symmetry Violation in the Charmonium-K*(892) Channel By a Complete Time Dependent Angular Analysis (BaBar Experiment)

    SciTech Connect

    T'Jampens, Stephane; /Orsay

    2006-09-18

    This thesis presents the full-angular time-dependent analysis of the vector-vector channel B{sub d}{sup 0} {yields} J/{psi}(K{sub S}{sup 0}{pi}{sup 0})*{sup 0}. After a review of the CP violation in the B meson system, the phenomenology of the charmonium-K*(892) channels is exposed. The method for the measurement of the transversity amplitudes of the B {yields} J/{psi}K*(892), based on a pseudo-likelihood method, is then exposed. The results from a 81.9 fb{sup -1} of collected data by the BABAR detector at the {Upsilon}(4S) resonance peak are |A{sub 0}|{sup 2} = 0.565 {+-} 0.011 {+-} 0.004, |A{sub {parallel}}|{sup 2} = 0.206 {+-} 0.016 {+-} 0.007, |A{sub {perpendicular}}|{sup 2} = 0.228 {+-} 0.016 {+-} 0.007, {delta}{sub {parallel}} = -2.766 {+-} 0.105 {+-} 0.040 and {delta}{sub {perpendicular}} = 2.935 {+-} 0.067 {+-} 0.040. Note that ({delta}{sub {parallel}}, {delta}{sub {perpendicular}}) {yields} (-{delta}{sub {parallel}}, {pi} - {delta}{sub {perpendicular}}) is also a solution. The strong phases {delta}{sub {parallel}} and {delta}{sub {perpendicular}} are at {approx}> 3{sigma} from {+-}{pi}, signing the presence of final state interactions and the breakdown of the factorization hypothesis. The forward-backward analysis of the K{pi} mass spectrum revealed the presence of a coherent S-wave interfering with the K*(892). It is the first evidence of this wave in the K{pi} system coming from a B meson. The particularity of the B{sub d}{sup 0} {yields} J/{psi}(K{sub S}{sup 0}{pi}{sup 0})*{sup 0} channel is to have a time-dependent but also an angular distribution which allows to measure sin 2{beta} but also cos2{beta}. The results from an unbinned maximum likelihood fit are sin 2{beta} = -0.10 {+-} 0.57 {+-} 0.14 and cos 2{beta} = 3.32{sub -0.96}{sup +0.76} {+-} 0.27 with the transversity amplitudes fixed to the values given above. The other solution for the strong phases flips the sign of cos 2{beta}. Theoretical considerations based on the s-quark helicity

  16. Angular-dependent vortex pinning mechanism and magneto-optical characterizations of FeSe0.5Te0.5 thin films grown on CaF2 substrates

    NASA Astrophysics Data System (ADS)

    Yuan, Pusheng; Xu, Zhongtang; Ma, Yanwei; Sun, Yue; Tamegai, Tsuyoshi

    2016-03-01

    Magneto-optical (MO) characterizations and the angular-dependent critical current density (J c(Θ)) of epitaxial FeSe0.5Te0.5 (FST) thin films grown on CaF2 single-crystalline substrates were performed. The MO images show typical rooftop patterns in the remanent state from which a large, homogeneous, and almost isotropic self-field J c over 2 × 106 A cm-2 at 8 K was obtained. The vortex pinning mechanism is investigated measuring the magnetic field and angular-dependent critical current density J c. The FST films exhibit small anisotropy of J c in the whole applied magnetic field range below 15 K. The Dew-Hughes model and angular scaling analyses prove that pointlike normal cores, which are distributed randomly in the FST film, dominate the pinning in the FST films on CaF2 substrates.

  17. An angular-dependent embedded atom method (A-EAM) interatomic potential to model thermodynamic and mechanical behavior of Al/Si composite materials

    NASA Astrophysics Data System (ADS)

    Dongare, Avinash M.; LaMattina, Bruce; Irving, Douglas L.; Rajendran, Arunachalam M.; Zikry, Mohammed A.; Brenner, Donald W.

    2012-04-01

    A new interatomic potential is developed for the Al/Si system in the formulation of the recently developed angular-dependent embedded atom method (A-EAM). The A-EAM is formulated by combining the embedded atom method potential for Al with the Stillinger-Weber potential for Si. The parameters of the Al/Si cross-interactions are fitted to reproduce the structural energetics of Al/Si bulk alloys determined based on the results of density functional theory calculations and the experimentally observed mixing behavior of the AlSi liquid alloy at high temperatures. The ability to investigate the thermodynamic properties of the Al/Si system is demonstrated by computing the binary phase diagram of the Al-Si system as predicted by the A-EAM potential and comparing with that obtained using experiments. The ability to study the mechanical behavior of the Al/Si composite systems is demonstrated by investigating the micromechanisms related to dynamic failure of the Al/Si nanocomposites using MD simulations.

  18. Depth Profile of Mn in GaAs/Mn/GaAs Heterostuctures and Thermal Annealing Effects Studied by Angular Dependence of X-ray Fluorescence

    NASA Astrophysics Data System (ADS)

    Kim, S.; Soo, Y. L.; Kioseoglou, G.; Chen, X.; Luo, H.; Kao, Y. H.; Sasaki, Y.; Liu, X.; Furdyna, J. K.

    2003-03-01

    Angular dependence of x-ray fluorescence (ADXRF) technique has been utilized to study Mn depth profile in GaAs (60 ÅMn (5 Åstructures MBE-grown on GaAs and annealed at temperatures 350, 450, and 550^oC. The nominal structure for as-grown sample was confirmed from detailed fluorescence analysis. We have found that a large amount of Mn migrate into the top GaAs layer in the sample annealed at 550^oC while the other samples showed only a slight change in the Mn profile as compared to the as-grown sample. These results provide unique information on the depth distribution of Mn atoms in Mn/GaAs magnetic digital alloys as a function of temperature in addition to those obtained previously^1 by means of grazing incidence x-ray scattering (GIXS) and x-ray diffraction. We have thus demonstrated that ADXRF technique is a useful nondestructive tool for probing the depth profile of samples with an ultra thin overlay or containing a small amount of impurity atoms. 1. G. Kioseoglou, S. Kim, Y. L. Soo, X. Chen, H. Luo, Y. H. Kao, Y. Sasaki, X. Liu, and J. K. Furdyna, Appl. Phys. Lett. 80, 1150 (2002).

  19. Ambiguity-Free Measurement of cos2beta: Time-Intergrated and Time-Dependent Angular Analyses of B to J/psi K pi

    SciTech Connect

    Aubert, B.

    2004-11-02

    We present results on B {yields} J/{psi} K{pi} decays using e{sup +}e{sup -} annihilation data collected with the BABAR detector at the {Upsilon}(4S) resonance. The detector is located at the PEP-II asymmetric-energy storage ring facility at the Stanford Linear Accelerator Center. Using approximately 88 million B{bar B} pairs, we measure the decay amplitudes for the flavor eigenmodes and observe strong-phase differences indicative of final-state interactions with a significance of 7.6 standard deviations. We use the interference between the K{pi} S-wave and P-wave amplitudes in the region of the K*(892) to resolve the ambiguity in the determination of these strong phases. We then perform an ambiguity-free measurement of cos 2{beta} using the angular and time-dependent asymmetry in B {yields} J/{psi} K*{sup 0} (K{sub S}{sup 0}{pi}{sup 0}) decays. With sin2{beta} fixed at its measured value and cos2{beta} treated as an independent parameter, we find cos 2{beta} = 2.72{sub -0.79}{sup +0.50}(stat) {+-} 0.27(syst), determining the sign of cos 2{beta} to be positive at 86% CL.

  20. pH-dependent structural change of reduced spinach plastocyanin studied by perturbed angular correlation of gamma-rays and dynamic light scattering.

    PubMed

    Sas, Klára Nárcisz; Haldrup, Anna; Hemmingsen, Lars; Danielsen, Eva; Øgendal, Lars Holm

    2006-06-01

    In this study the pH-dependent structural changes of reduced spinach plastocyanin were investigated using perturbed angular correlation (PAC) of gamma-rays and dynamic light scattering (DLS). PAC data of Ag-substituted plastocyanin indicated that the coordinating ligands are two histidine residues (His37, His87) and a cysteine residue (Cys84) in a planar configuration, whereas the methionine (Met92) found perpendicular to this plane is not a coordinating ligand at neutral pH. Two slightly different conformations with differences in the Cys-metal ion-His angles could be observed with PAC spectroscopy. At pH 5.3 a third coordination geometry appears which can be explained as the absence of the His87 residue and the coordination of Met92 as a ligand. With DLS the aggregation of reduced plastocyanin could be observed below pH 5.3, indicating that not only the metal binding site but also the aggregation properties of the protein change upon pH reduction. Both the structural changes at the metal binding site and the aggregation are shown to be reversible. These results support the hypothesis that the pH of the thylakoid lumen has to remain moderate during steady-state photosynthesis and indicate that low pH induced aggregation of plastocyanin might serve as a regulatory switch for photosynthesis.

  1. On the Angular Dependence of the Vicinal Fluorine-Fluorine Coupling Constant in 1,2-Difluoroethane:  Deviation from a Karplus-like Shape.

    PubMed

    Provasi, Patricio F; Sauer, Stephan P A

    2006-07-01

    The angular dependence of the vicinal fluorine-fluorine coupling constant, (3)JFF, for 1,2-difluoroethane has been investigated with several polarization propagator methods. (3)JFF and its four Ramsey contributions were calculated using the random phase approximation (RPA), its multiconfigurational generalization, and both second-order polarization propagator approximations (SOPPA and SOPPA(CCSD)), using locally dense basis sets. The geometries were optimized for each dihedral angle at the level of density functional theory using the B3LYP functional and fourth-order Møller-Plesset perturbation theory. The resulting coupling constant curves were fitted to a cosine series with 8 coefficients. Our results are compared with those obtained previously and values estimated from experiment. It is found that the inclusion of electron correlation in the calculation of (3)JFF reduces the absolute values. This is mainly due to changes in the FC contribution, which for dihedral angles around the trans conformation even changes its sign. This sign change is responsible for the breakdown of the Karplus-like curve.

  2. The angular dependence of a 2-dimensional diode array and the feasibility of its application in verifying the composite dose distribution of intensity-modulated radiation therapy.

    PubMed

    Li, Qi-Lin; Deng, Xiao-Wu; Chen, Li-Xin; Huang, Xiao-Yan; Huang, Shao-Min

    2010-06-01

    The planning dose distribution of intensity-modulated radiation therapy (IMRT) has to be verified before clinical implementation. The commonly used verification method is to measure the beam fluency at 0 degree gantry angle with a 2-dimensional (2D) detector array, but not the composite dose distribution of the real delivery in the planned gantry angles. This study was to investigate the angular dependence of a 2D diode array (2D array) and the feasibility of using it to verify the composite dose distribution of IMRT. Angular response of the central detector in the 2D array was measured for 6 MV X-ray, 10 cmx10 cm field and 100 cm source axis distance (SAD) in different depths. With the beam incidence angle of 0-60 degrees, at intervals of 10 degrees, and inherent buildup of the 2D array (2 g/cm2), the array was irradiated and the readings of the central diode were compared with the measurement of thimble ionization chamber. Using a combined 30 cmx30 cmx30 cm phantom which consisted of solid water slabs on top and underlying the 2D array, with the diode detectors placed at 8 g/cm2 depth, measurements were taken for beam angles of 0 degrees-180 degrees at intervals of 10 degrees and compared with the calculation of treatment planning system (TPS) that pre-verified with ion chamber measuring. Differences between the array detector and thimble chamber measurements were greater than 1% and 3.5% when the beam angle was larger than 30 degrees and 60 degrees, respectively. The measurements in the combined phantom were different from the calculation as high as 20% for 90 degrees beam angle, 2% at 90 degrees+/-5 degrees and less than 1% for all the other beam angles. The 2D diode array is capable of being used in composite dose verification of IMRT when the beam angles of 90 degrees+/-5 degrees and 270 degrees+/-5 degrees are avoided.

  3. The energy dependence of p_t angular correlations inferred frommean -pt fluctuation scale dependence in heavy ion collisions at the SPSand RHIC

    SciTech Connect

    Adams, J.; Aggarwal, M.M.; Ahammed, Z.; Amonett, J.; Anderson,B.D.; Anderson, M.; Arkhipkin, D.; Averichev, G.S.; Bai, Y.; Balewski,J.; Barannikova, O.; Barnby, L.S.; Baudot, J.; Bekele, S.; Belaga, V.V.; Bellingeri-Laurikainen, A.; Bellwied, R.; Benedosso, F.; Bhardwaj, S.; Bhasin, A.; Bhati, A.K.; Bichsel, H.; Bielcik, J.; Bielcikova, J.; Bland,L.C.; Blyth, S.-L.; Bonner, B.E.; Botje, M.; Bouchet, J.; Brandin, A.V.; Bravar, A.; Bystersky, M.; Cadman, R.V.; Cai, X.Z.; Caines, H.; Calderonde la Barca Sanchez, M.; Castillo, J.; Catu, O.; Cebra, D.; Chajecki, Z.; Chaloupka, P.; Chattopadhyay, S.; Chen, H.F.; Chen, J.H.; Cheng, J.; Cherney, M.; Chikanian, A.; Christie, W.; Coffin, J.P.; Cormier, T.M.; Cosentino, M.R.; Cramer, J.G.; Crawford, H.J.; Das, D.; Das, S.; Daugherity, M.; de Moura, M.M.; Dedovich, T.G.; DePhillips, M.; Derevschikov, A.A.; Didenko, L.; Dietel, T.; Djawotho, P.; Dogra, S.M.; Dong, W.J.; Dong, X.; Draper, J.E.; Du, F.; Dunin, V.B.; Dunlop, J.C.; Dutta Mazumdar, M.R.; Eckardt, V.; Edwards, W.R.; Efimov, L.G.; Emelianov, V.; Engelage, J.; Eppley, G.; Erazmus, B.; Estienne, M.; Fachini, P.; Fatemi, R.; Fedorisin, J.; Filimonov, K.; Filip, P.; Finch,E.; Fine, V.; Fisyak, Y.; Fu, J.; Gagliardi, C.A.; Gaillard, L.; Ganti,M.S.; Ghazikhanian, V.; Ghosh, P.; Gonzalez, J.S.; Gorbunov, Y.G.; Gos,H.; Grebenyuk, O.; Grosnick, D.; Guertin, S.M.; Guimaraes, K.S.F.F.; Guo,Y.; Gupta, N.; Gutierrez, T.D.; Haag, B.; Hallman, T.J.; Hamed, A.; Harris, J.W.; He, W.; Heinz, M.; Henry, T.W.; Hepplemann, S.; Hippolyte,B.; Hirsch, A.; Hjort, E.; Hoffman, A.M.; Hoffmann, G.W.; Horner, M.J.; Huang, H.Z.; Huang, S.L.; Hughes, E.W.; Humanic, T.J.; Igo, G.; Jacobs,P.; Jacobs, W.W.; Jakl, P.; Jia, F.; Jiang, H.; Jones, P.G.; Judd, E.G.; Kabana, S.; Kang, K.; Kapitan, J.; Kaplan, M.; Keane, D.; Kechechyan, A.; Khodyrev, V.Yu.; Kim, B.C.; Kiryluk, J.; Kisiel, A.; Kislov, E.M.; Klein,S.R.; Kocoloski, A.; Koetke, D.D.; Kollegger, T.; et al.

    2006-05-17

    We present the first study of the energy dependence of ptangular correlations inferred from event-wise mean transverse momentumfluctuations in heavy ion collisions. We compare ourlarge-acceptance measurements at CM energies sqrt sNN = 19.6, 62.4, 130and 200 GeV to SPS measurements at 12.3 and 17.3 GeV. pt angularcorrelation structure suggests that the principal source of ptcorrelations and fluctuations is minijets (minimum-bias partonfragments). We observe a dramatic increase in correlations andfluctuations from SPS to RHIC energies, increasing linearly with ln sqrtsNN from the onset of observable jet-related pt fluctuations near 10GeV.

  4. Angular dependence of the flux pinning for YBa{sub 2}Cu{sub 3}O{sub y}/PrBa{sub 2}Cu{sub 3}O{sub y} superlattice

    SciTech Connect

    Horng, H.E.; Wu, J.M.; Yang, H.C.

    1997-06-01

    The angular dependence of the magnetic relaxation for YBa{sub 2}Cu{sub 3}O{sub y}/PrBa{sub 2}Cu{sub 3}O{sub y} (YBCO/PBCO) superlattice was measured under magnetic field to investigate the flux pinning. The applied magnetic field was 0.1 Tesla. The direction of the applied magnetic field makes an angle of 10{degrees}, 20{degrees}, 30{degrees}, 45{degrees}... with the c-axis of YBCO/PBCO superlattice. Based on the Anderson-Kim model the authors derive the pinning energy of this film. The pinning energy is angular independent. The results are discussed.

  5. XPS and NEXAFS studies of VUV/O₃-treated aromatic polyurea and its application to microchip electrophoresis.

    PubMed

    Shinohara, H; Nakahara, A; Kitagawa, F; Takahashi, Y; Otsuka, K; Shoji, S; Ohara, O; Mizuno, J

    2011-12-01

    In this study, the authors performed X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) studies of vacuum ultraviolet (VUV)/O₃-treated aromatic polyurea films to investigate their treatment effects. XPS and NEXAFS spectra indicate that the benzene ring was cleaved after treatment and that carboxyl, hydroxyl, ketone and aldehyde groups were formed at the cleaved sites. The VUV/O₃-treated polyurea film was applied to a polymethylmethacrylate (PMMA) microchip for microchip electrophoresis (MCE) of bovine serum albumin (BSA). Fast electro-osmotic mobility of 4.6×10(-4) cm²/V/s as well as reduction of the BSA adhesion was achieved. This functional surface is useful for high-speed MCE analysis.

  6. Vulcanization reaction of squalene and S8 powder studied by Sulfur K-edge NEXAFS under liquid phase

    NASA Astrophysics Data System (ADS)

    Yagi, S.; Menjo, Y.; Tsukada, C.; Ogawa, S.; Kutluk, G.; Namatame, H.; Taniguchi, M.

    2015-03-01

    Vulcanized rubber materials are useful in our surroundings. However, detail structure and reaction are not revealed even in present. Since squalene molecule possesses some same properties compared with natural rubber, we have prepared the samples of vulcanized squalene at 140 °C for several hours. To understand the vulcanization reaction,sulfur K-edge NEXAFS measurements have been carried out for the vulcanized squalene under liquid phase with He-path system and fluorescence detection mode. Moreover, we have tried curve fitting analysis of NEXAFS spectra. The results indicate that the squalene has been vulcanized by the S8 molecule at 140 °C and the S8 molecule length is shortened from 8 to 5-6 after the vulcanization reaction.

  7. NEXAFS study on the local structures of DLC thin films formed by Ar cluster ion beam assisted deposition

    NASA Astrophysics Data System (ADS)

    Kanda, Kazuhiro; Kitagawa, Teruyuki; Shimizugawa, Yutaka; Tsubakino, Harushige; Yamada, Isao; Matsui, Shinji

    2003-08-01

    Near-edge X-ray absorption fine structure (NEXAFS) spectra were measured for the optimization of synthesis conditions on the production of diamond-like carbon (DLC) thin films by the Ar gas cluster ion beam (GCIB) assisted deposition of fullerene. The sp2 contents of DLC films were estimated from the analysis of the peak corresponding to the transition of the excitation electron from a carbon 1s orbital to a π* orbital in the NEXAFS spectrum of the carbon K-edge over the excitation energy range 275-320 eV. Substrate temperature and Ar cluster ion acceleration voltage in the synthesis conditions of DLC films were optimized to make the sp2 content minimum.

  8. XPS, TOF-SIMS, NEXAFS, and SPR Characterization of Nitrilotriacetic Acid-Terminated Self-Assembled Monloyers for Controllable Immobiliztion of Proteins

    SciTech Connect

    Cheng,F.; Gamble, L.; Castner, D.

    2008-01-01

    For immobilization of proteins onto surfaces in a specific and controlled manner, it is important to start with a well-defined surface that contains specific binding sites surrounded by a nonfouling background. For immobilizing histidine-tagged (his-tagged) proteins, surfaces containing nitrilotriacetic acid (NTA) headgroups and oligo(ethylene glycol) (OEG) moieties are a widely used model system. The surface composition, structure, and reactivity of mixed NTA/OEG self-assembled monolayers (SAMs) on Au substrates were characterized in detail using X-ray photoelectron spectroscopy (XPS), near-edge X-ray absorption fine structure spectroscopy (NEXAFS), time-of-flight secondary ion mass spectrometry (TOF-SIMS), and surface plasmon resonance (SPR) biosensoring. XPS results for sequential adsorption of NTA thiols followed by OEG thiols showed that OEG molecules were incorporated into an incompletely formed NTA monolayer until a complete mixed SAM was formed. The surface concentration of NTA headgroups was estimated to be 0.9-1.3 molecule/nm2 in the mixed NTA/OEG monolayers, compared to 1.9 molecule/nm2 in pure NTA monolayers. Angle-dependent XPS indicated NTA headgroups were slightly reoriented toward an upright position after OEG incorporation, and polarization-dependent NEXAFS results indicated increased ordering of the alkane chains of the molecules. Nitrogen-containing and OEG-related secondary ion fragments from the TOF-SIMS experiments confirmed the presence of NTA headgroups and OEG moieties in the monolayers. A multivariate peak intensity ratio was developed for estimating the relative NTA concentration in the outermost (10 Angstroms ) of the monolayers. SPR measurements of a his-tagged, humanized anti-lysozyme variable fragment (HuLys Fv) immobilized onto Ni(II)-treated mixed NTA/OEG and pure NTA monolayers demonstrated the reversible, site-specific immobilization of his-tagged HuLys Fv (108-205 ng/cm2) with dissociation rates (koff) between 1.0 x 10-4 and 2

  9. Characterization of microscale wear in a ploysilicon-based MEMS device using AFM and PEEM-NEXAFS spectromicroscopy.

    SciTech Connect

    Grierson, D. S.; Konicek, A. R.; Wabiszewski, G. E.; Sumant, A. V.; de Boer, M. P.; Corwin, A. D.; Carpick, R. W.

    2009-12-01

    Mechanisms of microscale wear in silicon-based microelectromechanical systems (MEMS) are elucidated by studying a polysilicon nanotractor, a device specifically designed to conduct friction and wear tests under controlled conditions. Photoelectron emission microscopy (PEEM) was combined with near-edge X-ray absorption fine structure (NEXAFS) spectroscopy and atomic force microscopy (AFM) to quantitatively probe chemical changes and structural modification, respectively, in the wear track of the nanotractor. The ability of PEEM-NEXAFS to spatially map chemical variations in the near-surface region of samples at high lateral spatial resolution is unparalleled and therefore ideally suited for this study. The results show that it is possible to detect microscopic chemical changes using PEEM-NEXAFS, specifically, oxidation at the sliding interface of a MEMS device. We observe that wear induces oxidation of the polysilicon at the immediate contact interface, and the spectra are consistent with those from amorphous SiO{sub 2}. The oxidation is correlated with gouging and debris build-up in the wear track, as measured by AFM and scanning electron microscopy (SEM).

  10. The effect of symmetry on the U L3 NEXAFS of octahedral coordinated uranium(vi)

    NASA Astrophysics Data System (ADS)

    Bagus, Paul S.; Nelin, Connie J.; Ilton, Eugene S.

    2017-03-01

    We describe a detailed theoretical analysis of how distortions from ideal cubic or Oh symmetry to tetrahedral, D4h, symmetry affect the shape, in particular the width, of the U L3-edge NEXAFS for U(vi) in octahedral coordination. The full-width-half-maximum (FWHM) of the L3-edge white line decreases with increasing distortion from Oh symmetry. In particular, the FWHM of the white line narrows whether the tetragonal distortion is to compression or to extension. The origin of this decrease in the FWHM is analyzed in terms of the electronic structure of the excited levels arising from the unoccupied U(6d). The relative importance of ligand field and of spin-orbit effects is examined, where the dominant role of ligand field effects is established. Especially at higher distortions, the ligand splittings decrease rapidly and lead to an accelerated, quadratic decrease in the FWHM with increasing distortion. This is related to the increase of covalent character in the appropriate component of the Oh derived eg orbitals. Our ab initio theory uses relativistic wavefunctions for cluster models of the structures; empirical or semi-empirical parameters were not used to adjust prediction to experiment. A major advantage is that it provides a transparent approach for determining how the character and extent of the covalent mixing of the relevant U and O orbitals affect the U L3-edge white line.

  11. Measures and models for angular correlation and angular-linear correlation. [correlation of random variables

    NASA Technical Reports Server (NTRS)

    Johnson, R. A.; Wehrly, T.

    1976-01-01

    Population models for dependence between two angular measurements and for dependence between an angular and a linear observation are proposed. The method of canonical correlations first leads to new population and sample measures of dependence in this latter situation. An example relating wind direction to the level of a pollutant is given. Next, applied to pairs of angular measurements, the method yields previously proposed sample measures in some special cases and a new sample measure in general.

  12. THE DEPENDENCE OF STELLAR MASS AND ANGULAR MOMENTUM LOSSES ON LATITUDE AND THE INTERACTION OF ACTIVE REGION AND DIPOLAR MAGNETIC FIELDS

    SciTech Connect

    Garraffo, Cecilia; Drake, Jeremy J.; Cohen, Ofer

    2015-11-01

    Rotation evolution of late-type stars is dominated by magnetic braking and the underlying factors that control this angular momentum loss are important for the study of stellar spin-down. In this work, we study angular momentum loss as a function of two different aspects of magnetic activity using a calibrated Alfvén wave-driven magnetohydrodynamic wind model: the strengths of magnetic spots and their distribution in latitude. By driving the model using solar and modified solar surface magnetograms, we show that the topology of the field arising from the net interaction of both small-scale and large-scale field is important for spin-down rates and that angular momentum loss is not a simple function of large scale magnetic field strength. We find that changing the latitude of magnetic spots can modify mass and angular momentum loss rates by a factor of two. The general effect that causes these differences is the closing down of large-scale open field at mid- and high-latitudes by the addition of the small-scale field. These effects might give rise to modulation of mass and angular momentum loss through stellar cycles, and present a problem for ab initio attempts to predict stellar spin-down based on wind models. For all the magnetogram cases considered here, from dipoles to various spotted distributions, we find that angular momentum loss is dominated by the mass loss at mid-latitudes. The spin-down torque applied by magnetized winds therefore acts at specific latitudes and is not evenly distributed over the stellar surface, though this aspect is unlikely to be important for understanding spin-down and surface flows on stars.

  13. Relative weight of the inverse spin-Hall and spin-rectification effects for metallic polycrystalline Py/Pt, epitaxial Fe/Pt, and insulating YIG/Pt bilayers: Angular dependent spin pumping measurements

    NASA Astrophysics Data System (ADS)

    Keller, S.; Greser, J.; Schweizer, M. R.; Conca, A.; Lauer, V.; Dubs, C.; Hillebrands, B.; Papaioannou, E. Th.

    2017-07-01

    We quantify and compare the relative weight of inverse spin-Hall and spin-rectification effects occurring in metallic polycrystalline (Py/Pt), epitaxial (Fe/Pt), and insulating (YIG/Pt) bilayers. To distinguish the spin rectification signal from the inverse spin-Hall voltage the external magnetic field is rotated in plane to take advantage of the different angular dependencies of the prevailing effects. We prove that in permalloy anisotropic magnetoresistance is the dominant source for spin rectification while in epitaxial iron the anomalous Hall effect has a comparable strength. The rectification in yttrium-iron-garnet/platinum bilayers reveals an angular dependence imitating the one seen for anisotropic magnetoresistance and anomalous Hall effect caused by spin-Hall magnetoresistance.

  14. Quantification of black carbon in soil: introducing a sliding scale with NEXAFS spectroscopy

    NASA Astrophysics Data System (ADS)

    Heymann, K.; Lehmann, J.; Baldock, J.; Skjemstad, J.; Krull, E.; Schmidt, M.; Blyth, R.; Regier, T.

    2009-04-01

    Quantification of black carbon in soils continues to be one of the greatest challenges in advancing our understanding of black carbon properties and dynamics. This challenge mainly arises from the fact that black carbon constitutes a continuum of substances with a range of different properties. Previous methods have used specific chemical property limits to define whether a certain form of carbon is considered black carbon or not. These chemical cutoff points are difficult to define. In addition, different study objectives as well as diverse environments may necessitate a range of definitions for black carbon. These constraints may make a method favorable that uses a sliding scale of organo-chemical properties that can be developed for different types of black carbon or research questions. We used synchrotron-based Scanning Transmission X-ray Microscopy (STXM) in combination with Near-Edge X-ray Absorption Fine Structure (NEXAFS) to develop criteria for chemical properties that warrant defining a specific form of organic matter as black carbon. A mathematical mixing model was used to resolve total soil carbon spectra using representative bio-molecular components of soil organic carbon (carbohydrate, protein, fatty acid, amino acids, black carbon). In addition, a linear combination method was used to fit spectra of ecological fractions (plant, microbe, black carbon) to the total soil spectra. The variation in chemical forms within black carbon properties was accounted for by using a sliding scale of spectral properties determined by STXM of individual black carbon particles. This method represents an significant advance in studying black carbon dynamics in soils.

  15. Angular Limb Deformities: Growth Retardation.

    PubMed

    McCarrel, Taralyn M

    2017-08-01

    Angular limb deformities are common in foals; however, the importance of the deformity and if treatment is required depend on the degree of deformity relative to normal conformation for stage of growth, the breed and discipline expectations, age, and response to conservative therapies. This article addresses the importance of the foal conformation examination to determine which foals need surgical intervention to correct an angular deformity and when. Techniques for surgical growth retardation include the transphyseal staple, screw and wire transphyseal bridge, and transphyseal screw. Appropriate timing for intervention for each location and complications associated with each procedure are discussed. Copyright © 2017 Elsevier Inc. All rights reserved.

  16. The effect of the time dependent angular distribution of the intergrain magnetic field on the transport critical current in Ag-(Bi,Pb)2Sr2Ca2Cu3Ox tapes

    NASA Astrophysics Data System (ADS)

    Glowacki, B. A.; Noji, H.; Oota, A.

    1996-08-01

    Changes in the energy dissipation of the tape form Ag-(Bi,Pb)2Sr2Ca2Cu3Ox conductor have been interpreted in terms of magnetic flux movement from, or into, the intergrain regions of the highly textured plate like grain structure. The time dependent increase or decrease of the transport critical current (Ic), originates from time dependent angular superposition of the current induced self field (HSF), and external magnetic field [field cooling (HFC), and zero-field cooling (HZFC)] at the intergrain regions. The existence of time dependent changes of Ic can be explained in terms of the time dependent flux redistribution in grains and grain boundaries caused by thermal relaxation processes.

  17. On Angular Momentum

    DOE R&D Accomplishments Database

    Schwinger, J.

    1952-01-26

    The commutation relations of an arbitrary angular momentum vector can be reduced to those of the harmonic oscillator. This provides a powerful method for constructing and developing the properties of angular momentum eigenvectors. In this paper many known theorems are derived in this way, and some new results obtained. Among the topics treated are the properties of the rotation matrices; the addition of two, three, and four angular momenta; and the theory of tensor operators.

  18. The Fulde-Ferrell-Larkin-Ovchinnikov state in layered d-wave superconductors: in-plane anisotropy and resonance effects in the angular dependence of the upper critical field.

    PubMed

    Croitoru, M D; Buzdin, A I

    2013-03-27

    We study the anisotropy of the in-plane upper critical magnetic field coupled to the orbital motion and the spins of electrons in a layered d(x2-y2) organic superconductor in the spatially modulated Fulde-Ferrell-Larkin-Ovchinnikov phase. We show that the interplay between the nodal structure of the order parameter and its spatial modulation results in the very peculiar angular dependence of the onset of superconductivity in the high-field regime. The principal axis of the field-direction dependence of the onset of superconductivity is tilted by π/4 in the temperature range 0.056 < or approximately equal T < 0.56. In some cases the resonance between the modulation wavevector and the vector potential of a parallel magnetic field may lead to anomalous cusps in the temperature and in-plane angular dependences of the onset of superconductivity. The obtained results support the interpretation of the recent experiments as evidence of the FFLO state.

  19. Angular Momentum and Topological Dependence of Kepler's Third Law in the Broucke-Hadjidemetriou-Hénon Family of Periodic Three-Body Orbits.

    PubMed

    Janković, Marija R; Dmitrašinović, V

    2016-02-12

    We use 57 recently found topological satellites of Broucke-Hadjidemetriou-Hénon's periodic orbits with values of the topological exponent k ranging from k=3 to k=58 to plot the angular momentum L as a function of the period T, with both L and T rescaled to energy E=-0.5. Upon plotting L(T/k) we find that all our solutions fall on a curve that is virtually indiscernible by the naked eye from the L(T) curve for nonsatellite solutions. The standard deviation of the satellite data from the sixth-order polynomial fit to the progenitor data is σ=0.13. This regularity supports Hénon's 1976 conjecture that the linearly stable Broucke-Hadjidemetriou-Hénon orbits are also perpetually, or Kol'mogorov-Arnol'd-Moser, stable.

  20. Angular Momentum and Topological Dependence of Kepler's Third Law in the Broucke-Hadjidemetriou-Hénon Family of Periodic Three-Body Orbits

    NASA Astrophysics Data System (ADS)

    Janković, Marija R.; Dmitrašinović, V.

    2016-02-01

    We use 57 recently found topological satellites of Broucke-Hadjidemetriou-Hénon's periodic orbits with values of the topological exponent k ranging from k =3 to k =58 to plot the angular momentum L as a function of the period T , with both L and T rescaled to energy E =-0.5 . Upon plotting L (T /k ) we find that all our solutions fall on a curve that is virtually indiscernible by the naked eye from the L (T ) curve for nonsatellite solutions. The standard deviation of the satellite data from the sixth-order polynomial fit to the progenitor data is σ =0.13 . This regularity supports Hénon's 1976 conjecture that the linearly stable Broucke-Hadjidemetriou-Hénon orbits are also perpetually, or Kol'mogorov-Arnol'd-Moser, stable.

  1. Optical devices having flakes suspended in a host fluid to provide a flake/fluid system providing flakes with angularly dependent optical properties in response to an alternating current electric field due to the dielectric properties of the system

    SciTech Connect

    Kosc, Tanya Z.; Marshall, Kenneth L.; Jacobs, Stephen D.

    2006-05-09

    Optical devices utilizing flakes (also called platelets) suspended in a host fluid have optical characteristics, such as reflective properties, which are angular dependent in response to an AC field. The reflectivity may be Bragg-like, and the characteristics are obtained through the use of flakes of liquid crystal material, such as polymer liquid crystal (PLC) materials including polymer cholesteric liquid crystal (PCLC) and polymer nematic liquid crystal (PNLC) material or birefringent polymers (BP). The host fluid may be propylene carbonate, poly(ethylene glycol) or other fluids or fluid mixtures having fluid conductivity to support conductivity in the flake/host system. AC field dependent rotation of 90.degree. can be obtained at rates and field intensities dependent upon the frequency and magnitude of the AC field. The devices are useful in providing displays, polarizers, filters, spatial light modulators and wherever switchable polarizing, reflecting, and transmission properties are desired.

  2. Angular Acceleration without Torque?

    ERIC Educational Resources Information Center

    Kaufman, Richard D.

    2012-01-01

    Hardly. Just as Robert Johns qualitatively describes angular acceleration by an internal force in his article "Acceleration Without Force?" here we will extend the discussion to consider angular acceleration by an internal torque. As we will see, this internal torque is due to an internal force acting at a distance from an instantaneous center.

  3. Angular Acceleration without Torque?

    ERIC Educational Resources Information Center

    Kaufman, Richard D.

    2012-01-01

    Hardly. Just as Robert Johns qualitatively describes angular acceleration by an internal force in his article "Acceleration Without Force?" here we will extend the discussion to consider angular acceleration by an internal torque. As we will see, this internal torque is due to an internal force acting at a distance from an instantaneous center.

  4. The angular dependence of optical interference filters in the Near IR can be greatly reduced through the use of novel coating materials and design strategies

    NASA Astrophysics Data System (ADS)

    Sprague, Robert W.

    2017-06-01

    The bandwidth of an optical interference filter when used in an optical system is limited by the angular range of its illumination. The limitation has two main aspects: The central wavelength of the filter shifts to shorter wavelength and the shape of the transmission band degrades. The first effect results in filters with increased transmission width and decrease average transmission while the second results in reduction in the average transmission of the filter. For compact systems with high numerical aperture these effects can be pronounced. By minimizing the propagation angles in the filters these effects can be substantially reduced in the near infra red (NIR) to levels similar to IR filters. We have recently developed materials and design techniques that permit us to obtain low angle shift coating that maintain very high transmission in the spectral range from 800 to 1100 nm. In this paper we will demonstrate the performance, design and fabrication, of fully blocked (200 to 1200 nm) narrow band pass filters and their measured performance over a range of angles (0-30°). Filters with bandwidths from 15 to 100 nm will be shown to illustrate the versatility of these techniques.

  5. Measurement of angular dependence of M X-ray production cross-sections in Re, Bi and U at 5.96 keV

    NASA Astrophysics Data System (ADS)

    Apaydın, G.; Tıraşoǧlu, E.; Söǧüt, Ã.-.

    2008-03-01

    The M X-ray production differential cross sections in Re, Bi and U elements have been measured at the 5.96 keV incident photon energy in an angular range 135° 155°. The measurements were performed using a 55Fe source and a Si(Li) detector. The present results contradict the predictions of Cooper and Zare [ Atomic Collision Processes, Gordon and Breach, New York (1969)] and experimental results of Kumar et al. [J. Phys. B: At. Mol. Opt. 34, 613 (2001)]. that, after photoionization of inner shells, the vacancy state has equal population of magnetic substates and the subsequent X-ray emission is isotropic, but confirm the predictions of the calculations of Flügge et al. [Phys. Rev. Lett. 29, 7 (1972)] and experimental results of Sharma and Allawadhi [J. Phys. B: At. Mol. Opt. 32, 2343 (1999)] and Ertugrul [Nucl. Instrum. Meth. B 119, 345 (1996)]. Total M X-ray production cross sections from the decay at the 5.96 keV photon energies are found to be in good agreement with the calculated theoretical results using the theoretical values of M shell photoionization cross section.

  6. DVL Angular Velocity Recorder

    NASA Technical Reports Server (NTRS)

    Liebe, Wolfgang

    1944-01-01

    In many studies, especially of nonstationary flight motion, it is necessary to determine the angular velocities at which the airplane rotates about its various axes. The three-component recorder is designed to serve this purpose. If the angular velocity for one flight attitude is known, other important quantities can be derived from its time rate of change, such as the angular acceleration by differentiations, or - by integration - the angles of position of the airplane - that is, the angles formed by the airplane axes with the axis direction presented at the instant of the beginning of the motion that is to be investigated.

  7. Recurrence of angular cheilitis.

    PubMed

    Ohman, S C; Jontell, M; Dahlen, G

    1988-08-01

    The incidence of recurrence of angular cheilitis following a successful antimicrobial treatment was studied in 48 patients. Clinical assessments including a microbial examination were carried out 8 months and 5 yr after termination of treatment. Eighty percent of the patients reported recurrence of their angular cheilitis on one or more occasions during the observation period. Patients with cutaneous disorders associated with dry skin or intraoral leukoplakia had an increased incidence of recrudescence. Neither the presence of denture stomatitis nor the type of microorganisms isolated from the original lesions of angular cheilitis, i.e. Candida albicans and/or Staphylococcus aureus, were associated with the number of recurrences. The present observations indicate that treatment of the majority of patients with angular cheilitis should be considered in a longer perspective than previously supposed, due to the short lasting therapeutic effects of the antimicrobial therapy.

  8. [Malignant angular cheilitis].

    PubMed

    Seoane, J; Vázquez, J; Cazenave, A; de la Cruz Mera, A; Argila, F; Aguado, A

    1996-01-01

    A case of chronic angular cheilitis is reported. Candida albicans was isolated repeatedly and the process developed into epitheliomatous carcinoma. The etiopathogenic role of Candida albicans and possible mechanism of action are discussed.

  9. Angular velocity discrimination

    NASA Technical Reports Server (NTRS)

    Kaiser, Mary K.

    1990-01-01

    Three experiments designed to investigate the ability of naive observers to discriminate rotational velocities of two simultaneously viewed objects are described. Rotations are constrained to occur about the x and y axes, resulting in linear two-dimensional image trajectories. The results indicate that observers can discriminate angular velocities with a competence near that for linear velocities. However, perceived angular rate is influenced by structural aspects of the stimuli.

  10. Angular velocity discrimination

    NASA Technical Reports Server (NTRS)

    Kaiser, Mary K.

    1990-01-01

    Three experiments designed to investigate the ability of naive observers to discriminate rotational velocities of two simultaneously viewed objects are described. Rotations are constrained to occur about the x and y axes, resulting in linear two-dimensional image trajectories. The results indicate that observers can discriminate angular velocities with a competence near that for linear velocities. However, perceived angular rate is influenced by structural aspects of the stimuli.

  11. Determination of g-tensors of low-symmetry Nd{sup 3+} centers in LiNbO{sub 3} by rectification of angular dependence of electron paramagnetic resonance spectra

    SciTech Connect

    Grachev, V. Malovichko, G.; Munro, M.; Kokanyan, E.

    2015-07-28

    Two procedures for facilitation of line tracing and deciphering of complicated spectra of electron paramagnetic resonance (EPR) were developed: a correction of microwave frequencies for every orientation of external magnetic field on the base of known values of g-tensor components for a reference paramagnetic center and followed rectification of measured angular dependences using plots of effective deviation of g{sup 2}-factors of observed lines from effective g{sup 2}-factors of the reference center versus angles or squared cosines of angles describing magnetic field orientations. Their application to EPR spectra of nearly stoichiometric lithium niobate crystals doped with neodymium allowed identifying two axial and six different low-symmetry Nd{sup 3+} centers, to determine all components of their g-tensors, and to propose common divacancy models for a whole family of Nd{sup 3+} centers.

  12. Angular momentum radio

    NASA Astrophysics Data System (ADS)

    Thidé, B.; Tamburini, F.; Then, H.; Someda, C. G.; Mari, Elletra; Parisi, G.; Spinello, F.; Romanato, Fra

    2014-02-01

    Wireless communication amounts to encoding information onto physical observables carried by electromagnetic (EM) fields, radiating them into surrounding space, and detecting them remotely by an appropriate sensor connected to an informationdecoding receiver. Each observable is second order in the fields and fulfills a conservation law. In present-day radio only the EM linear momentum observable is fully exploited. A fundamental physical limitation of this observable, which represents the translational degrees of freedom of the charges (typically an oscillating current along a linear antenna) and the fields, is that it is single-mode. This means that a linear-momentum radio communication link comprising one transmitting and one receiving antenna, known as a single-input-single-output (SISO) link, can provide only one transmission channel per frequency (and polarization). In contrast, angular momentum, which represents the rotational degrees of freedom, is multi-mode, allowing an angular-momentum SISO link to accommodate an arbitrary number of independent transmission channels on one and the same frequency (and polarization). We describe the physical properties of EM angular momentum and how they can be exploited, discuss real-world experiments, and outline how the capacity of angular momentum links may be further enhanced by employing multi-port techniques, i.e., the angular momentum counterpart of linear-momentum multiple-input-multiple-output (MIMO).

  13. The Angular Momentum Dichotomy

    NASA Astrophysics Data System (ADS)

    Teklu, Adelheid; Remus, Rhea-Silvia; Dolag, Klaus; Burkert, Andreas

    2015-02-01

    In the context of the formation of spiral galaxies the evolution and distribution of the angular momentum of dark matter halos have been discussed for more than 20 years, especially the idea that the specific angular momentum of the halo can be estimated from the specific angular momentum of its disk (e.g. Fall & Efstathiou (1980), Fall (1983) and Mo et al. (1998)). We use a new set of hydrodynamic cosmological simulations called Magneticum Pathfinder which allow us to split the galaxies into spheroidal and disk galaxies via the circularity parameter ɛ, as commonly used (e.g. Scannapieco et al. (2008)). Here, we focus on the dimensionless spin parameter λ = J |E|1/2 / (G M5/2) (Peebles 1969, 1971), which is a measure of the rotation of the total halo and can be fitted by a lognormal distribution, e.g. Mo et al. (1998). The spin parameter allows one to compare the relative angular momentum of halos across different masses and different times. Fig. 1 reveals a dichotomy in the distribution of λ at all redshifts when the galaxies are split into spheroids (dashed) and disk galaxies (dash-dotted). The disk galaxies preferentially live in halos with slightly larger spin parameter compared to spheroidal galaxies. Thus, we see that the λ of the whole halo reflects the morphology of its central galaxy. For more details and a larger study of the angular momentum properties of disk and spheroidal galaxies, see Teklu et al. (in prep.).

  14. Fluidic angular velocity sensor

    NASA Technical Reports Server (NTRS)

    Berdahl, C. M. (Inventor)

    1986-01-01

    A fluidic sensor providing a differential pressure signal proportional to the angular velocity of a rotary input is described. In one embodiment the sensor includes a fluid pump having an impeller coupled to a rotary input. A housing forming a constricting fluid flow chamber is connected to the fluid input of the pump. The housing is provided with a fluid flow restrictive input to the flow chamber and a port communicating with the interior of the flow chamber. The differential pressure signal measured across the flow restrictive input is relatively noise free and proportional to the square of the angular velocity of the impeller. In an alternative embodiment, the flow chamber has a generally cylindrical configuration and plates having flow restrictive apertures are disposed within the chamber downstream from the housing port. In this embodiment, the differential pressure signal is found to be approximately linear with the angular velocity of the impeller.

  15. Study of angular dependence of exchange bias and misalignment in uniaxial and unidirectional anisotropy in NiFe(111)/FeMn(111)/CoFeB(amorphous) stack

    NASA Astrophysics Data System (ADS)

    Singh, Braj Bhusan; Chaudhary, Sujeet

    2015-07-01

    We report the investigation of the in-plane azimuthal angular dependence of the magnetization reversal in the ion beam sputtered exchanged biased NiFe(111)/FeMn(111)/CoFeB(amorphous) stack. Compared to the as-deposited case, the magnetic annealing resulted in 3 fold enhancement in exchange bias but decrease in coercivity. The observed cosine dependence of exchange biased CoFeB layer on the in-plane azimuthal angle of applied field is corroborated with Meiklejohn and Bean model. The training effect associated with the exchange bias showed unconventional increase in coercivity after first cycle of hysteresis loop, while the exchange bias decreases sharply, and for subsequent cycles the exchange bias follows the empirical relation based on the energy dissipation in the AF layer. The ferromagnetic resonance (FMR) measurements also exhibited the in-plane azimuthal angle dependence of the magnetic resonance field indicating that the uniaxial and unidirectional anisotropies are not collinear, although they lie in the same plane. However, no misalignment between the unidirectional anisotropy and the exchange bias direction is observed. The misalignment angle between the uniaxial and unidirectional anisotropy, as measured by FMR, is found to be 10° and 14° for CoFeB and NiFe, respectively. This misalignment is attributed to the interface roughness as revealed by x-ray reflectance measurements.

  16. Angular shear plate

    DOEpatents

    Ruda, Mitchell C [Tucson, AZ; Greynolds, Alan W [Tucson, AZ; Stuhlinger, Tilman W [Tucson, AZ

    2009-07-14

    One or more disc-shaped angular shear plates each include a region thereon having a thickness that varies with a nonlinear function. For the case of two such shear plates, they are positioned in a facing relationship and rotated relative to each other. Light passing through the variable thickness regions in the angular plates is refracted. By properly timing the relative rotation of the plates and by the use of an appropriate polynomial function for the thickness of the shear plate, light passing therethrough can be focused at variable positions.

  17. Optical orbital angular momentum.

    PubMed

    Barnett, Stephen M; Babiker, Mohamed; Padgett, Miles J

    2017-02-28

    We present a brief introduction to the orbital angular momentum of light, the subject of our theme issue and, in particular, to the developments in the 13 years following the founding paper by Allen et al. (Allen et al. 1992 Phys. Rev. A 45, 8185 (doi:10.1103/PhysRevA.45.8185)). The papers by our invited authors serve to bring the field up to date and suggest where developments may take us next.This article is part of the themed issue 'Optical orbital angular momentum'.

  18. Optical orbital angular momentum

    PubMed Central

    Barnett, Stephen M.; Babiker, Mohamed; Padgett, Miles J.

    2017-01-01

    We present a brief introduction to the orbital angular momentum of light, the subject of our theme issue and, in particular, to the developments in the 13 years following the founding paper by Allen et al. (Allen et al. 1992 Phys. Rev. A 45, 8185 (doi:10.1103/PhysRevA.45.8185)). The papers by our invited authors serve to bring the field up to date and suggest where developments may take us next. This article is part of the themed issue ‘Optical orbital angular momentum’. PMID:28069775

  19. Unveiling Angular Momentum

    NASA Astrophysics Data System (ADS)

    Robinson, Stephen

    2015-03-01

    Angular momentum is a notoriously difficult concept to grasp. Visualization often requires three-dimensional pictures of vectors pointing in seemingly arbitrary directions. A simple student-run laboratory experiment coupled with intuitive explanations by an instructor can clear up some of the inherent ambiguity of rotational motion. Specifically, the precessional period of a suspended spinning bicycle wheel can be related to the spinning frequency through a simple algebraic expression. An explanation of this precession apart from the concept of angular momentum will be given.

  20. Optical orbital angular momentum

    NASA Astrophysics Data System (ADS)

    Barnett, Stephen M.; Babiker, Mohamed; Padgett, Miles J.

    2017-02-01

    We present a brief introduction to the orbital angular momentum of light, the subject of our theme issue and, in particular, to the developments in the 13 years following the founding paper by Allen et al. (Allen et al. 1992 Phys. Rev. A 45, 8185 (doi:10.1103/PhysRevA.45.8185)). The papers by our invited authors serve to bring the field up to date and suggest where developments may take us next. This article is part of the themed issue 'Optical orbital angular momentum'.

  1. Angular Scaling In Jets

    SciTech Connect

    Jankowiak, Martin; Larkoski, Andrew J.; /SLAC

    2012-02-17

    We introduce a jet shape observable defined for an ensemble of jets in terms of two-particle angular correlations and a resolution parameter R. This quantity is infrared and collinear safe and can be interpreted as a scaling exponent for the angular distribution of mass inside the jet. For small R it is close to the value 2 as a consequence of the approximately scale invariant QCD dynamics. For large R it is sensitive to non-perturbative effects. We describe the use of this correlation function for tests of QCD, for studying underlying event and pile-up effects, and for tuning Monte Carlo event generators.

  2. Nano-Scale Spatial Assessment of Calcium Distribution in Coccolithophores Using Synchrotron-Based Nano-CT and STXM-NEXAFS

    PubMed Central

    Sun, Shiyong; Yao, Yanchen; Zou, Xiang; Fan, Shenglan; Zhou, Qing; Dai, Qunwei; Dong, Faqin; Liu, Mingxue; Nie, Xiaoqin; Tan, Daoyong; Li, Shuai

    2014-01-01

    Calcified coccolithophores generate calcium carbonate scales around their cell surface. In light of predicted climate change and the global carbon cycle, the biomineralization ability of coccoliths has received growing interest. However, the underlying biomineralization mechanism is not yet well understood; the lack of non-invasive characterizing tools to obtain molecular level information involving biogenic processes and biomineral components remain significant challenges. In the present study, synchrotron-based Nano-computed Tomography (Nano-CT) and Scanning Transmission X-ray Microscopy-Near-edge X-ray Absorption Fine Structure Spectromicroscopy (STXM-NEXAFS) techniques were employed to identify Ca spatial distribution and investigate the compositional chemistry and distinctive features of the association between biomacromolecules and mineral components of calcite present in coccoliths. The Nano-CT results show that the coccolith scale vesicle is similar as a continuous single channel. The mature coccoliths were intracellularly distributed and immediately ejected and located at the exterior surface to form a coccoshpere. The NEXAFS spectromicroscopy results of the Ca L edge clearly demonstrate the existence of two levels of gradients spatially, indicating two distinctive forms of Ca in coccoliths: a crystalline-poor layer surrounded by a relatively crystalline-rich layer. The results show that Sr is absorbed by the coccoliths and that Sr/Ca substitution is rather homogeneous within the coccoliths. Our findings indicate that synchrotron-based STXM-NEXAFS and Nano-CT are excellent tools for the study of biominerals and provide information to clarify biomineralization mechanism. PMID:25530614

  3. Dirac Green function for angular projection potentials.

    PubMed

    Zeller, Rudolf

    2015-11-25

    The aim of this paper is twofold: first, it is shown that the angular dependence of the Dirac Green function can be described analytically for potentials with non-local dependence on the angular variables if they are chosen as projection potentials in angular momentum space. Because the local dependence on the radial variable can be treated to any precision with present computing capabilities, this means that the Green function can be calculated practically exactly. Second, it is shown that a result of this kind not only holds for a single angular projection potential but also more generally, for instance if space is divided into non-overlapping cells and a separate angular projection potential is used in each cell. This opens the way for relativistic density-functional calculations within a different perspective than the conventional one. Instead of trying to obtain the density for a given potential approximately as well as possible, the density is determined exactly for non-local potentials which can approximate arbitrary local potentials as well as desired.

  4. Angular dependence of light trapping in In{sub 0.3}Ga{sub 0.7}As/GaAs quantum-well solar cells

    SciTech Connect

    Li, X. H.; Li, P. C.; Yu, E. T.; Hu, D. Z.; Schaadt, D. M.

    2014-01-28

    The dependence of light trapping effects in In{sub 0.3}Ga{sub 0.7}As/GaAs quantum-well solar cells on wavelength and incident angle is experimentally characterized and analyzed. Separation of active device layers from their epitaxial growth substrate enables integration of thin-film semiconductor device layers with nanostructured metal/dielectric rear contacts to increase optical absorption via coupling to both Fabry-Perot resonances and guided lateral propagation modes in the semiconductor. The roles of Fabry-Perot resonances and coupling to guided modes are analyzed via photocurrent response measurements and numerical modeling for light incident at angles of 0° (normal incidence) to 30° off normal. Light trapping enables external quantum efficiency at long wavelengths as high as 2.9% per quantum well to be achieved experimentally, substantially exceeding the ∼1% per quantum well level typically observed. Increased long wavelength quantum efficiency is shown in experimental measurements to persist with increasing angle of incidence and is explained as a consequence of the large number of guided modes available in the device structure.

  5. Angular dependence of light trapping in In0.3Ga0.7As/GaAs quantum-well solar cells

    NASA Astrophysics Data System (ADS)

    Li, X. H.; Li, P. C.; Hu, D. Z.; Schaadt, D. M.; Yu, E. T.

    2014-01-01

    The dependence of light trapping effects in In0.3Ga0.7As/GaAs quantum-well solar cells on wavelength and incident angle is experimentally characterized and analyzed. Separation of active device layers from their epitaxial growth substrate enables integration of thin-film semiconductor device layers with nanostructured metal/dielectric rear contacts to increase optical absorption via coupling to both Fabry-Perot resonances and guided lateral propagation modes in the semiconductor. The roles of Fabry-Perot resonances and coupling to guided modes are analyzed via photocurrent response measurements and numerical modeling for light incident at angles of 0° (normal incidence) to 30° off normal. Light trapping enables external quantum efficiency at long wavelengths as high as 2.9% per quantum well to be achieved experimentally, substantially exceeding the ˜1% per quantum well level typically observed. Increased long wavelength quantum efficiency is shown in experimental measurements to persist with increasing angle of incidence and is explained as a consequence of the large number of guided modes available in the device structure.

  6. Impacts of the Angular Dependence of the Solar Diffuser BRDF Degradation Factor on the SNPP VIIRS Reflective Solar Band On-Orbit Radiometric Calibration

    NASA Technical Reports Server (NTRS)

    Lei, Ning; Xiong, Xiaoxiong

    2016-01-01

    Using an onboard sunlit solar diffuser (SD) as the primary radiance source, the visible infrared imaging radiometer suite (VIIRS) on the Suomi National Polar-orbiting Partnership satellite regularly performs radiometric calibration of its reflective solar bands (RSBs). The SD bidirectional reflectance distribution function (BRDF) value decreases over time. A numerical degradation factor is used to quantify the degradation and is determined by an onboard SD stability monitor (SDSM), which observes the sun and the sunlit SD at almost the same time. We had shown previously that the BRDF degradation factor was angle-dependent. Consequently, due to that the SDSM and the RSB view the SD at very different angles relative to both the solar and the SD surface normal vectors, directly applying the BRDF degradation factor determined by the SDSM to the VIIRS RSB calibration can result in large systematic errors. We develop a phenomenological model to calculate the BRDF degradation factor for the RSB SD view from the degradation factor for the SDSM SD view. Using the yearly undulations observed in the VIIRS detector gains for the M1-M4 bands calculated with the SD BRDF degradation factor for the SDSM SD view and the difference between the VIIRS detector gains calculated from the SD and the lunar observations, we obtain the model parameter values and thus establish the relation between the BRDF degradation factors for the RSB and the SDSM SD view directions.

  7. "Angular" plasma cell cheilitis.

    PubMed

    da Cunha Filho, Roberto Rheingantz; Tochetto, Lucas Baldissera; Tochetto, Bruno Baldissera; de Almeida, Hiram Larangeira; Lorencette, Nádia Aparecida; Netto, José Fillus

    2014-03-17

    Plasma cell cheilitis is an extremely rare disease, characterized by erythematous-violaceous, ulcerated and asymptomatic plaques, which evolve slowly. The histological characteristics include dermal infiltrate composed of mature plasmocytes. We report a case of Plasma cell angular cheilitis in a 58-year-old male, localized in the lateral oral commissure.

  8. Induced Angular Momentum

    ERIC Educational Resources Information Center

    Parker, G. W.

    1978-01-01

    Discusses, classically and quantum mechanically, the angular momentum induced in the bound motion of an electron by an external magnetic field. Calculates the current density and its magnetic moment, and then uses two methods to solve the first-order perturbation theory equation for the required eigenfunction. (Author/GA)

  9. Induced Angular Momentum

    ERIC Educational Resources Information Center

    Parker, G. W.

    1978-01-01

    Discusses, classically and quantum mechanically, the angular momentum induced in the bound motion of an electron by an external magnetic field. Calculates the current density and its magnetic moment, and then uses two methods to solve the first-order perturbation theory equation for the required eigenfunction. (Author/GA)

  10. Investigation of reactions between trace gases and functional CuO nanospheres and octahedrons using NEXAFS-TXM imaging

    PubMed Central

    Henzler, Katja; Heilemann, Axel; Kneer, Janosch; Guttmann, Peter; Jia, He; Bartsch, Eckhard; Lu, Yan; Palzer, Stefan

    2015-01-01

    In order to take full advantage of novel functional materials in the next generation of sensorial devices scalable processes for their fabrication and utilization are of great importance. Also understanding the processes lending the properties to those materials is essential. Among the most sought-after sensor applications are low-cost, highly sensitive and selective metal oxide based gas sensors. Yet, the surface reactions responsible for provoking a change in the electrical behavior of gas sensitive layers are insufficiently comprehended. Here, we have used near-edge x-ray absorption fine structure spectroscopy in combination with x-ray microscopy (NEXAFS-TXM) for ex-situ measurements, in order to reveal the hydrogen sulfide induced processes at the surface of copper oxide nanoparticles, which are ultimately responsible for triggering a percolation phase transition. For the first time these measurements allow the imaging of trace gas induced reactions and the effect they have on the chemical composition of the metal oxide surface and bulk. This makes the new technique suitable for elucidating adsorption processes in-situ and under real operating conditions. PMID:26631608

  11. Investigation of reactions between trace gases and functional CuO nanospheres and octahedrons using NEXAFS-TXM imaging.

    PubMed

    Henzler, Katja; Heilemann, Axel; Kneer, Janosch; Guttmann, Peter; Jia, He; Bartsch, Eckhard; Lu, Yan; Palzer, Stefan

    2015-12-03

    In order to take full advantage of novel functional materials in the next generation of sensorial devices scalable processes for their fabrication and utilization are of great importance. Also understanding the processes lending the properties to those materials is essential. Among the most sought-after sensor applications are low-cost, highly sensitive and selective metal oxide based gas sensors. Yet, the surface reactions responsible for provoking a change in the electrical behavior of gas sensitive layers are insufficiently comprehended. Here, we have used near-edge x-ray absorption fine structure spectroscopy in combination with x-ray microscopy (NEXAFS-TXM) for ex-situ measurements, in order to reveal the hydrogen sulfide induced processes at the surface of copper oxide nanoparticles, which are ultimately responsible for triggering a percolation phase transition. For the first time these measurements allow the imaging of trace gas induced reactions and the effect they have on the chemical composition of the metal oxide surface and bulk. This makes the new technique suitable for elucidating adsorption processes in-situ and under real operating conditions.

  12. A study of the initial film growth of PEG-like plasma polymer films via XPS and NEXAFS

    NASA Astrophysics Data System (ADS)

    Li, Yali; Muir, Benjamin W.; Easton, Christopher D.; Thomsen, Lars; Nisbet, David R.; Forsythe, John S.

    2014-01-01

    The chemistry of substrate-film interface (underside) of di(ethylene glycol) dimethyl ether plasma polymer (DGpp) films has been studied directly and compared to the top layer of the film (topside). By depositing the plasma polymer films onto indium tin oxide (ITO) glass, the films were easily delaminated from the substrate. The top- and underside of the films were examined by X-ray photoelectron spectroscopy (XPS) and near edge X-ray absorption fine structure (NEXAFS) spectroscopy. It was found that a rapid increase in pressure during plasma polymerization results in steep chemical gradients in the films, while small pressure changes do not lead to chemical gradient formation. These observations validate the findings of previous neutron reflectometry modeling studies of this class of plasma polymer thin film. In addition, subtle variations in plasma polymer film chemistry were observed between different substrates they were deposited onto. This approach will allow additional studies on the mechanisms of early plasma polymer thin film formation with various monomers.

  13. Quantum Heuristics of Angular Momentum

    ERIC Educational Resources Information Center

    Levy-Leblond, Jean-Marc

    1976-01-01

    Discusses the quantization of angular momentum components, Heisenberg-type inequalities for their spectral dispersions, and the quantization of the angular momentum modulus, without using operators or commutation relations. (MLH)

  14. Angular cheilitis after tonsillectomy.

    PubMed

    England, R J; Lau, M; Ell, S R

    1999-08-01

    The operation of tonsillectomy requires the oral cavity to be held open mechanically in an unconscious patient, and intra-oral instrumentation to occur. Angular cheilitis may arise as a result of this after operation. This can cause morbidity and delay the re-establishment of a normal diet. The aim of this study was to identify what factors increase the likelihood of developing this problem postoperatively. Sixty patients were randomly selected in a prospective manner. Preoperative, intraoperative and postoperative variables were recorded. The frequency of development of postoperative angular cheilitis was recorded. The prevalence of the condition was related to the prerecorded variables. Parametric analysis showed that the chance of developing angular cheilitis was directly related to the use of diathermy haemostasis (P = 0.05). Logistic regression analysis showed that the odds ratio of developing this complication if diathermy was used is 3.5 (95% confidence intervals 0.99, 12.4) and operation difficulty may also be a relevant variable. No other recorded variables were found to be significant.

  15. Strong polaritonic interaction between flux-flow and phonon resonances in Bi2Sr2CaCu2O8+x intrinsic Josephson junctions: Angular dependence and the alignment procedure

    NASA Astrophysics Data System (ADS)

    Motzkau, H.; Katterwe, S. O.; Rydh, A.; Krasnov, V. M.

    2013-08-01

    Bi2Sr2CaCu2O8+x single crystals represent natural stacks of atomic scale intrinsic Josephson junctions, formed between metallic CuO2-Ca-CuO2 and ionic insulating SrO-2BiO-SrO layers. Electrostriction effect in the insulating layers leads to excitation of c-axis phonons by the ac-Josephson effect. Here we study experimentally the interplay between and velocity matching (Eck) electromagnetic resonances in the flux-flow state of small mesa structures with c-axis optical phonons. A very strong interaction is reported, which leads to formation of phonon-polaritons with infrared and Raman-active transverse optical phonons. A special focus in this work is made on analysis of the angular dependence of the resonances. We describe an accurate sample alignment procedure that prevents intrusion of Abrikosov vortices in fields up to 17 T, which is essential for achieving high-quality resonances at record high frequencies up to 13 THz.

  16. STXM-NEXAFS measurements of rock varnish, investigating element distributions and carbon occurrences in the Mn-rich rock coating

    NASA Astrophysics Data System (ADS)

    Macholdt, D.; Pöhlker, C.; Jochum, K. P.; Förster, J. D.; Weber, B.; Kilcoyne, A. L. D.; Weigand, M.; Müller, M.; Kappl, M.; Scholz, D.; Haug, G. H.; Andreae, M. O.

    2016-12-01

    Rock varnish, a black, Mn-rich sedimentary coating on rock surfaces, has been a matter of debate for many decades. Manganese oxyhydroxides and mineral dust are the major components of this material, whose genesis remains highly controversial. A biogenic compound was proposed by several researchers as an inducer and initiator of the gradual growth of up to 250 µm thick varnish layers. To finally unravel this mystery, we employed several cutting-edge techniques. One of the techniques that proved to be effective in investigating rock varnish is scanning transmission X-ray microscopy-near-edge X-ray absorption fine structure spectroscopy (STXM-NEXAFS) on focused ion beam (FIB) ultra-thin sections (100-200 nm) of layered rock varnishes. With these measurements, which were conducted at two synchrotron facilities providing soft X-rays [Advanced Light Source (ALS) in Berkeley and BESSY II in Berlin], nm-sized structures can be observed by element distribution mapping. To this end, we utilized two microscopes, one at beamline 5.3.2.2 at the ALS, and the MAXYMUS microscope at beamline UE46-PGM-2 at BESSY II. Carbon abundances and bonds were examined in detail, and the oxidation states of Mn and Fe were determined. We observed layered sequences of Mn- and Fe-rich layers in several varnishes, which are thought to represent wet and dry climate episodes. Element abundance changes of K and Ca between different layers, and mineral grain sizes and shapes are of interest to evaluate changing dust compositions over time. Carbon distribution maps can help to verify biogenic activity during the genesis, and Mn- and Fe-oxidation states reveal changes within single rock varnishes. Therefore, results of this research combined with results of other state-of-the-art microanalytical techniques provide important and detailed information that might help to resolve the question about the genesis of rock varnish, and its applicability as paleoclimate archive for desert environments.

  17. Creating high-harmonic beams with controlled orbital angular momentum.

    PubMed

    Gariepy, Genevieve; Leach, Jonathan; Kim, Kyung Taec; Hammond, T J; Frumker, E; Boyd, Robert W; Corkum, P B

    2014-10-10

    A beam with an angular-dependant phase Φ = ℓϕ about the beam axis carries an orbital angular momentum of ℓℏ per photon. Such beams are exploited to provide superresolution in microscopy. Creating extreme ultraviolet or soft-x-ray beams with controllable orbital angular momentum is a critical step towards extending superresolution to much higher spatial resolution. We show that orbital angular momentum is conserved during high-harmonic generation. Experimentally, we use a fundamental beam with |ℓ| = 1 and interferometrically determine that the harmonics each have orbital angular momentum equal to their harmonic number. Theoretically, we show how any small value of orbital angular momentum can be coupled to any harmonic in a controlled manner. Our results open a route to microscopy on the molecular, or even submolecular, scale.

  18. Creating High-Harmonic Beams with Controlled Orbital Angular Momentum

    NASA Astrophysics Data System (ADS)

    Gariepy, Genevieve; Leach, Jonathan; Kim, Kyung Taec; Hammond, T. J.; Frumker, E.; Boyd, Robert W.; Corkum, P. B.

    2014-10-01

    A beam with an angular-dependant phase Φ =ℓϕ about the beam axis carries an orbital angular momentum of ℓℏ per photon. Such beams are exploited to provide superresolution in microscopy. Creating extreme ultraviolet or soft-x-ray beams with controllable orbital angular momentum is a critical step towards extending superresolution to much higher spatial resolution. We show that orbital angular momentum is conserved during high-harmonic generation. Experimentally, we use a fundamental beam with |ℓ|=1 and interferometrically determine that the harmonics each have orbital angular momentum equal to their harmonic number. Theoretically, we show how any small value of orbital angular momentum can be coupled to any harmonic in a controlled manner. Our results open a route to microscopy on the molecular, or even submolecular, scale.

  19. Angular Momentum in Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    Del Popolo, A.

    We study the ``angular momentum catastrophe" in the framework of interaction among baryons and dark matter through dynamical friction. By means of Del Popolo (2009) model we simulate 14 galaxies similar to those investigated by van den Bosch, Burkert and Swaters (2001), and calculate the distribution of their spin parameters and the angular momenta. Our model gives the angular momentum distribution which is in agreement with the van den Bosch et al. observations. Our result shows that the ``angular momentum catastrophe" can be naturally solved in a model that takes into account the baryonic physics and the exchange of energy and angular momentum between the baryonic clumps and dark matter through dynamical friction.

  20. A Multi-technique Characterization of Adsorbed Protein Films: Orientation and Structure by ToF-SIMS, NEXAFS, SFG, and XPS

    NASA Astrophysics Data System (ADS)

    Baio, Joseph E.

    There are many techniques that allow surface scientists to study interfaces. However, few are routinely applied to probe biological surfaces. The work presented here demonstrates how detailed information about the conformation, orientation, chemical state, and molecular structure of biological molecules immobilized onto a surface can be assessed by electron spectroscopy, mass spectrometry, and nonlinear vibrational spectroscopy techniques. This investigation began with the development of simple model systems (small proteins, and peptides) and evolved into a study of more complex --- real world systems. Initially, two model systems based on the chemical and electrostatic immobilization of a small rigid protein (Protein G B1 domain, 6kDa) were built to develop the capabilities of time-of-flight secondary ion mass spectrometry (ToFSIMS), near edge X-ray absorption fine structure spectroscopy (NEXAFS) and sum frequency generation (SFG) spectroscopy as tools to probe the structure of surface immobilized proteins. X-ray photoelectron spectroscopy (XPS) was used to measure the amount of immobilized protein and ToF-SIMS sampled the amino acid composition of the exposed surface of the protein film. Within the ToF-SIMS spectra, an enrichment of secondary ions from amino acids located at opposite ends of the proteins were used to describe protein orientation. SFG spectral peaks characteristic of ordered alpha-helix and beta-sheet elements were observed for both systems and the phase of the peaks indicated a predominantly upright orientation for both the covalent and electrostatic configurations. Polarization dependence of the NEXAFS signal from the N 1s to pi* transition of the peptide bonds that make up the beta-sheets also indicated protein ordering at the surface. Building upon the Protein G B1 studies, the orientation and structure of a surface immobilized antibody (HuLys Fv: variant of humanized anti-lysozyme variable fragment, 26kDa) was characterized across two

  1. An orbital angular momentum spectrometer for electrons

    NASA Astrophysics Data System (ADS)

    Harvey, Tyler; Grillo, Vincenzo; McMorran, Benjamin

    2016-05-01

    With the advent of techniques for preparation of free-electron and neutron orbital angular momentum (OAM) states, a basic follow-up question emerges: how do we measure the orbital angular momentum state distribution in matter waves? Control of both the energy and helicity of light has produced a range of spectroscopic applications, including molecular fingerprinting and magnetization mapping. Realization of an analogous dual energy-OAM spectroscopy with matter waves demands control of both initial and final energy and orbital angular momentum states: unlike for photons, final state post-selection is necessary for particles that cannot be annihilated. We propose a magnetic field-based mechanism for quantum non-demolition measurement of electron OAM. We show that OAM-dependent lensing is produced by an operator of form U =exp iLzρ2/ℏb2 where ρ =√{x2 +y2 } is the radial position operator, Lz is the orbital angular momentum operator along z, and b is the OAM dispersion length. We can physically realize this operator as a term in the time evolution of an electron in magnetic round lens. We discuss prospects and practical challenges for implementation of a lensing orbital angular momentum measurement. This work was supported by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES), under the Early Career Research Program Award # DE-SC0010466.

  2. Optical angular momentum and atoms.

    PubMed

    Franke-Arnold, Sonja

    2017-02-28

    Any coherent interaction of light and atoms needs to conserve energy, linear momentum and angular momentum. What happens to an atom's angular momentum if it encounters light that carries orbital angular momentum (OAM)? This is a particularly intriguing question as the angular momentum of atoms is quantized, incorporating the intrinsic spin angular momentum of the individual electrons as well as the OAM associated with their spatial distribution. In addition, a mechanical angular momentum can arise from the rotation of the entire atom, which for very cold atoms is also quantized. Atoms therefore allow us to probe and access the quantum properties of light's OAM, aiding our fundamental understanding of light-matter interactions, and moreover, allowing us to construct OAM-based applications, including quantum memories, frequency converters for shaped light and OAM-based sensors.This article is part of the themed issue 'Optical orbital angular momentum'.

  3. Optical angular momentum and atoms

    NASA Astrophysics Data System (ADS)

    Franke-Arnold, Sonja

    2017-02-01

    Any coherent interaction of light and atoms needs to conserve energy, linear momentum and angular momentum. What happens to an atom's angular momentum if it encounters light that carries orbital angular momentum (OAM)? This is a particularly intriguing question as the angular momentum of atoms is quantized, incorporating the intrinsic spin angular momentum of the individual electrons as well as the OAM associated with their spatial distribution. In addition, a mechanical angular momentum can arise from the rotation of the entire atom, which for very cold atoms is also quantized. Atoms therefore allow us to probe and access the quantum properties of light's OAM, aiding our fundamental understanding of light-matter interactions, and moreover, allowing us to construct OAM-based applications, including quantum memories, frequency converters for shaped light and OAM-based sensors. This article is part of the themed issue 'Optical orbital angular momentum'.

  4. Electronic structure of DNA polynucleotides under the chemical-doping condition investigated by PES and NEXAFS

    NASA Astrophysics Data System (ADS)

    Furukawa, Masashi; Kato, H. S.; Taniguchi, M.; Hatsui, T.; Kosugi, N.; Komeda, T.; Kawai, Maki; Kawai, T.

    2003-03-01

    During the last several years, the carrier transport through DNA between nm- spaced electrodes has been discussed without the understanding of their intrinsic electronic structures. As a result, its 'scattered' results in the controversial magnitude of conductivity, from a good conductor to an insulator, which is also assumed to be dependent on the chemical species surrounding DNA (H^+, counterion, etc.)@[ref.]. In this talk, we show electronic structures of the occupied- and unoccupied-states near the Fermi level. Systems exhibited here are well-defined sequence of DNA polynucleotides, Poly(dG)-poly(dC) and Poly(dA)-poly(dT), with- and without- chemical-doping (carrier-doping), in order to evaluate such an effect into DNA and also to propose the carrier conduction mechanism through DNA. [ref.] M. Taniguchi et al., submitted to JACS.

  5. Angular distributions in multifragmentation

    SciTech Connect

    Stoenner, R.W.; Klobuchar, R.L.; Haustein, P.E.; Virtes, G.J.; Cumming, J.B.; Loveland, W.

    2006-04-15

    Angular distributions are reported for {sup 37}Ar and {sup 127}Xe from 381-GeV {sup 28}Si+Au interactions and for products between {sup 24}Na and {sup 149}Gd from 28-GeV {sup 1}H+Au. Sideward peaking and forward deficits for multifragmentation products are significantly enhanced for heavy ions compared with protons. Projectile kinetic energy does not appear to be a satisfactory scaling variable. The data are discussed in terms of a kinetic-focusing model in which sideward peaking is due to transverse motion of the excited product from the initial projectile-target interaction.

  6. Angular Asteroid Composite

    NASA Image and Video Library

    2017-02-10

    This composite of 25 images of asteroid 2017 BQ6 was generated with radar data collected using NASA's Goldstone Solar System Radar in California's Mojave Desert. The images were gathered on Feb. 7, 2017, between 8:39 and 9:50 p.m. PST (11:39 p.m. EST and 12:50 a.m., Feb. 7), revealing an irregular, angular-appearing asteroid about 660 feet (200 meters) in size that rotates about once every three hours. The images have resolutions as fine as 12 feet (3.75 meters) per pixel. http://photojournal.jpl.nasa.gov/catalog/PIA21452

  7. Toward Quantifying the Mass-Based Hygroscopicity of Individual Submicron Atmospheric Aerosol Particles with STXM/NEXAFS and SEM/EDX

    NASA Astrophysics Data System (ADS)

    Yancey Piens, D.; Kelly, S. T.; OBrien, R. E.; Wang, B.; Petters, M. D.; Laskin, A.; Gilles, M. K.

    2014-12-01

    The hygroscopic behavior of atmospheric aerosols influences their optical and cloud-nucleation properties, and therefore affects climate. Although changes in particle size as a function of relative humidity have often been used to quantify the hygroscopic behavior of submicron aerosol particles, it has been noted that calculations of hygroscopicity based on size contain error due to particle porosity, non-ideal volume additivity and changes in surface tension. We will present a method to quantify the hygroscopic behavior of submicron aerosol particles based on changes in mass, rather than size, as a function of relative humidity. This method results from a novel experimental approach combining scanning transmission x-ray microscopy with near-edge x-ray absorption fine spectroscopy (STXM/NEXAFS), as well as scanning electron microscopy with energy dispersive x-ray spectroscopy (SEM/EDX) on the same individual particles. First, using STXM/NEXAFS, our methods are applied to aerosol particles of known composition ‒ for instance ammonium sulfate, sodium bromide and levoglucosan ‒ and validated by theory. Then, using STXM/NEXAFS and SEM/EDX, these methods are extended to mixed atmospheric aerosol particles collected in the field at the DOE Atmospheric Radiation Measurement (ARM) Climate Research Facility at the Southern Great Planes sampling site in Oklahoma, USA. We have observed and quantified a range of hygroscopic behaviors which are correlated to the composition and morphology of individual aerosol particles. These methods will have implications for parameterizing aerosol mixing state and cloud-nucleation activity in atmospheric models.

  8. A theoretical study of the XP and NEXAFS spectra of alanine: gas phase molecule, crystal, and adsorbate at the ZnO(10 ̅10) surface.

    PubMed

    Gao, You Kun; Traeger, Franziska; Kotsis, Konstantinos; Staemmler, Volker

    2011-06-14

    The adsorption of alanine on the mixed-terminated ZnO(10 ̅10) surface is studied by means of quantum-chemical ab initio calculations. Using a finite cluster model and the adsorption geometry as obtained both by periodic CPMD and embedded cluster calculations, the C1s, N1s and O1s X-ray photoelectron spectra (XPS) and near-edge X-ray absorption fine structure (NEXAFS) spectra are calculated for single alanine molecules on ZnO(10 ̅10). These spectra are compared with the spectra calculated for alanine in the gas phase and in its crystalline form and with experimental XPS and NEXAFS data for the isolated alanine molecule and for alanine adsorbed on ZnO(10 ̅10) at multilayer and monolayer coverage. The excellent agreement between the experimental and calculated XP and NEXAFS spectra confirms the calculated adsorption geometry: A single alanine molecule is bound to ZnO(10 ̅10) in a dissociated bidentate form with the two O atoms of the acid group bound to two Zn atoms of the surface and the proton transferred to one O atom of the surface. Other possible structures, such as adsorption of alanine in one of its neutral or zwitterionic forms in which the proton of the -COOH group remains at this group or is transferred to the amino group, can be excluded since they would give rise to quite different XP spectra. In the multilayer coverage regime, on the other hand, alanine is in its crystalline form as is also shown by the analysis of the XP spectra.

  9. Composition and Morphology of Individual Combustion, Biomass Burning, and Secondary Organic Particle Types Obtained Using ATOFMS and STXM-NEXAFS Measurements (Invited)

    NASA Astrophysics Data System (ADS)

    Russell, L. M.; Bahadur, R.; Liu, S.; Takahama, S.; Prather, K. A.

    2010-12-01

    Complementary single particle measurements of organic aerosols using aerosol time-of-flight mass spectrometry (ATOFMS) and Scanning Transmission X-ray Microscopy—Near Edge X-ray Absorption Fine Structure (STXM-NEXAFS) are compared to examine the relationships between particle morphologies and chemical composition of particles having similar sources. ATOFMS measurements from field campaigns in polluted or urban (Riverside/SOAR 2005; Mexico City/MILAGRO 2006; Port of Long Beach 2007) and clean or marine (Arabian Sea/INDOEX 1999; Sea of Japan/ACE-Asia 2001; Trinidad Head/CIFEX 2004) locations illustrate regional differences in the amount and types of organic particles. The majority (≥ 85%) of the number of submicron particles are carbonaceous (including elemental and organic carbon), but represent less than 10% of the number of supermicron particles. Organic carbon (OC) particles are classified into three meta-classes corresponding to (1) combustion-generated OC/EC internalmixtures, (2) biomass burning generated K/OC mixtures, and (3) OC/High MassOC (HMOC) mixtures containing secondary markers of atmospheric processing. Normalized dot products are used to quantify similarity among fragment spectra and indicate that OC particle types are consistent across (and within) platforms. Single particle carbon STXM-NEXAFS measurements during ACE-Asia 2001 and MILAGRO 2006 yield similar source categories based on relative abundances of aromatic, alkane, and carboxylic acid functional groups. All three organic particle types correspond to a variety of very heterogeneous particle morphologies, although the highly oxygenated OC particles with likely secondary organic contributions frequently are nearly spherical, liquid-like particles. Similar particle types are observed at many other locations, including recent measurements at Bakersfield, Tijuana, and the R/V Atlantis as part of CalNex and CalMex. Size-resolved number fractions of the major ATOFMS organic particle types show

  10. C 1s Near Edge X-ray Absorption Fine Structure (NEXAFS) of substituted benzoic acids: a theoretical and experimental study

    SciTech Connect

    Baldea,I.; Schimmelpfennig, B.; Plaschke, M.; Rothe, J.; Schirmer, J.; Trofimov, A.; Fanghaenel, T.

    2007-01-01

    Ab initio calculations are performed to explain the discrete transitions in experimental C 1s-NEXAFS (near edge X-ray absorption fine structure) spectra of various benzoic acid derivates. Transition energies and oscillator strengths of the contributing C 1s-{pi}* excitations are computed using the ADC(2) (second-order algebraic-diagrammatic construction) method. This method is demonstrated to be well suited for the finite electronic systems represented by these simple organic acids. There is good agreement between experiment and theory reproducing all the relevant spectral features. Some transitions can only be assigned based on a theoretical foundation. Remaining discrepancies between experimental and computed spectra are discussed.

  11. Orbital angular momentum entanglement

    NASA Astrophysics Data System (ADS)

    Romero, Mary Jacquiline Romero

    Entanglement in higher dimensions is an attractive concept that is a challenge to realise experimentally. To this end, the entanglement of the orbital angular momentum (OAM) of photons holds promise. The OAM state-space is discrete and theoretically unbounded. In the work that follows, we investigate various aspects of OAM entanglement. We show how the correlations in OAM and its conjugate variable, angular position, are determined by phase- matching and the shape of the pump beam in spontaneous parametric down- conversion. We implement tests of quantum mechanics which have been previously done for other variables. We show the Einstein-Podolsky-Rosen paradox for OAM and angle, supporting the incompatibility of quantum mechanics with locality and realism. We demonstrate violations of Bell-type inequalities, thereby discounting local hidden variables for describing the correlations we observe. We show the Hardy paradox using OAM, again highlighting the nonlocal nature of quantum mechanics. We demonstrate violations of Leggett-type inequalities, thereby discounting nonlocal hidden variables for describing correlations. Lastly, we have looked into the entanglement of topological vortex structures formed from a special superposition of OAM modes and show violations of Bell-type inequalities confined to a finite, isolated volume.

  12. Angular displacement measuring device

    NASA Technical Reports Server (NTRS)

    Seegmiller, H. Lee B. (Inventor)

    1992-01-01

    A system for measuring the angular displacement of a point of interest on a structure, such as aircraft model within a wind tunnel, includes a source of polarized light located at the point of interest. A remote detector arrangement detects the orientation of the plane of the polarized light received from the source and compares this orientation with the initial orientation to determine the amount or rate of angular displacement of the point of interest. The detector arrangement comprises a rotating polarizing filter and a dual filter and light detector unit. The latter unit comprises an inner aligned filter and photodetector assembly which is disposed relative to the periphery of the polarizer so as to receive polarized light passing the polarizing filter and an outer aligned filter and photodetector assembly which receives the polarized light directly, i.e., without passing through the polarizing filter. The purpose of the unit is to compensate for the effects of dust, fog and the like. A polarization preserving optical fiber conducts polarized light from a remote laser source to the point of interest.

  13. Angular displacement measuring device

    NASA Astrophysics Data System (ADS)

    Seegmiller, H. Lee B.

    1992-08-01

    A system for measuring the angular displacement of a point of interest on a structure, such as aircraft model within a wind tunnel, includes a source of polarized light located at the point of interest. A remote detector arrangement detects the orientation of the plane of the polarized light received from the source and compares this orientation with the initial orientation to determine the amount or rate of angular displacement of the point of interest. The detector arrangement comprises a rotating polarizing filter and a dual filter and light detector unit. The latter unit comprises an inner aligned filter and photodetector assembly which is disposed relative to the periphery of the polarizer so as to receive polarized light passing the polarizing filter and an outer aligned filter and photodetector assembly which receives the polarized light directly, i.e., without passing through the polarizing filter. The purpose of the unit is to compensate for the effects of dust, fog and the like. A polarization preserving optical fiber conducts polarized light from a remote laser source to the point of interest.

  14. Orbital angular momentum microlaser

    NASA Astrophysics Data System (ADS)

    Miao, Pei; Zhang, Zhifeng; Sun, Jingbo; Walasik, Wiktor; Longhi, Stefano; Litchinitser, Natalia M.; Feng, Liang

    2016-07-01

    Structured light provides an additional degree of freedom for modern optics and practical applications. The effective generation of orbital angular momentum (OAM) lasing, especially at a micro- and nanoscale, could address the growing demand for information capacity. By exploiting the emerging non-Hermitian photonics design at an exceptional point, we demonstrate a microring laser producing a single-mode OAM vortex lasing with the ability to precisely define the topological charge of the OAM mode. The polarization associated with OAM lasing can be further manipulated on demand, creating a radially polarized vortex emission. Our OAM microlaser could find applications in the next generation of integrated optoelectronic devices for optical communications in both quantum and classical regimes.

  15. Orbital angular momentum microlaser.

    PubMed

    Miao, Pei; Zhang, Zhifeng; Sun, Jingbo; Walasik, Wiktor; Longhi, Stefano; Litchinitser, Natalia M; Feng, Liang

    2016-07-29

    Structured light provides an additional degree of freedom for modern optics and practical applications. The effective generation of orbital angular momentum (OAM) lasing, especially at a micro- and nanoscale, could address the growing demand for information capacity. By exploiting the emerging non-Hermitian photonics design at an exceptional point, we demonstrate a microring laser producing a single-mode OAM vortex lasing with the ability to precisely define the topological charge of the OAM mode. The polarization associated with OAM lasing can be further manipulated on demand, creating a radially polarized vortex emission. Our OAM microlaser could find applications in the next generation of integrated optoelectronic devices for optical communications in both quantum and classical regimes. Copyright © 2016, American Association for the Advancement of Science.

  16. A direct Fe-O coordination at the FePc/MoO(x) interface investigated by XPS and NEXAFS spectroscopies.

    PubMed

    Liu, Lingyun; Zhang, Wenhua; Guo, Panpan; Wang, Kai; Wang, Jiaou; Qian, Haijie; Kurash, Ibrahim; Wang, Chia-Hsin; Yang, Yaw-Wen; Xu, Faqiang

    2015-02-07

    Molecule-substrate interaction plays a vital role in determining the electronic structures and charge transfer properties in organic-transition metal oxides (TMOs) hybridized devices. In this work, the interactions at the FePc/MoO3 interface has been investigated in detail by using synchrotron radiation photoemission spectroscopy (SRPES) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. Compared with the annealing of the bare MoO3 film, the FePc adsorption is found to promote the thermal reduction of the underlying MoO3 film. XPS and NEXAFS experimental results unanimously demonstrate a strong electronic coupling between FePc molecules and the MoOx (x < 3) substrate. A direct Fe-O coordination at the interface as well as an electron transfer from the molecules toward the substrate is proposed. This strong coupling is compatible with a facile electron transfer from FePc molecules toward electrode through a MoOx interlayer. The understanding of the molecule-substrate interaction at the atomic level is of significance in engineering functionalized surfaces with potential applications in nanoscience, molecular electronics and photonics.

  17. Impact of Ferrocene on the Structure of Diesel Exhaust Soot as Probed with Wide-Angle X-ray Scattering and C(1s) NEXAFS Spectroscopy

    SciTech Connect

    Braun,A.; Huggins, F.; Kelly, K.; Mun, B.; Ehrlich, S.; Huffman, G.

    2006-01-01

    We report on the structure of a set of diesel exhaust samples that were obtained from reference diesel fuel and diesel fuel mixed with ferrocene. Characterization was carried out with X-ray absorption spectroscopy (C(1s) NEXAFS) and wide-angle X-ray scattering (WAXS). The reference diesel soot shows a pronounced graphite-like microstructure and molecular structure, with a strong (0 0 2) graphite Bragg reflex and a strong aromatic C{double_bond}C resonance at 285 eV. The mineral matter in the reference soot could be identified as Fe{sub 2}O{sub 3} hematite. The soot specimen from the diesel mixed with ferrocene has an entirely different structure and lacks significantly in graphite-like characteristics. NEXAFS spectra of such soot barely show aromatics but pronounced contributions from aliphatic structures. WAXS patterns show almost no intensity at the Bragg (0 0 2) reflection of graphite, but a strong aliphatic {gamma}-side band. The iron from the ferrocene transforms to Fe{sub 2}O{sub 3} maghemite.

  18. Electronic structure of individual hybrid colloid particles studied by near-edge X-ray absorption fine structure (NEXAFS) spectroscopy in the X-ray microscope.

    PubMed

    Henzler, Katja; Guttmann, Peter; Lu, Yan; Polzer, Frank; Schneider, Gerd; Ballauff, Matthias

    2013-02-13

    The electronic structure of individual hybrid particles was studied by nanoscale near-edge X-ray absorption spectromicroscopy. The colloidal particles consist of a solid polystyrene core and a cross-linked poly-N-(isopropylacrylamide) shell with embedded crystalline titanium dioxide (TiO(2)) nanoparticles (d = 6 ± 3 nm). The TiO(2) particles are generated in the carrier network by a sol-gel process at room temperature. The hybrid particles were imaged with photon energy steps of 0.1 eV in their hydrated environment with a cryo transmission X-ray microscope (TXM) at the Ti L(2,3)-edge. By analyzing the image stacks, the obtained near-edge X-ray absorption fine structure (NEXAFS) spectra of our individual hybrid particles show clearly that our synthesis generates TiO(2) in the anastase phase. Additionally, our spectromicroscopy method permits the determination of the density distribution of TiO(2) in single carrier particles. Therefore, NEXAFS spectroscopy combined with TXM presents a unique method to get in-depth insight into the electronic structure of hybrid materials.

  19. Microscopic origin of the charge transfer in single crystals based on thiophene derivatives: A combined NEXAFS and density functional theory approach

    NASA Astrophysics Data System (ADS)

    Chernenkaya, A.; Morherr, A.; Backes, S.; Popp, W.; Witt, S.; Kozina, X.; Nepijko, S. A.; Bolte, M.; Medjanik, K.; Öhrwall, G.; Krellner, C.; Baumgarten, M.; Elmers, H. J.; Schönhense, G.; Jeschke, H. O.; Valentí, R.

    2016-07-01

    We have investigated the charge transfer mechanism in single crystals of DTBDT-TCNQ and DTBDT-F4TCNQ (where DTBDT is dithieno[2,3-d;2',3'-d'] benzo[1,2-b;4,5-b']dithiophene) using a combination of near-edge X-ray absorption spectroscopy (NEXAFS) and density functional theory calculations (DFT) including final state effects beyond the sudden state approximation. In particular, we find that a description that considers the partial screening of the electron-hole Coulomb correlation on a static level as well as the rearrangement of electronic density shows excellent agreement with experiment and allows to uncover the details of the charge transfer mechanism in DTBDT-TCNQ and DTBDT-F4 TCNQ, as well as a reinterpretation of previous NEXAFS data on pure TCNQ. Finally, we further show that almost the same quality of agreement between theoretical results and experiment is obtained by the much faster Z+1/2 approximation, where the core hole effects are simulated by replacing N or F with atomic number Z with the neighboring atom with atomic number Z+1/2.

  20. Near-edge X-ray Absorption Fine Structure (NEXAFS) Spectroscopy study on Chlorinated Graphene through Plasma-based Surface Functionalization

    NASA Astrophysics Data System (ADS)

    Zhang, Xu; Schiros, Theanne; Nordlund, Dennis; Shin, Yong Cheol; Kong, Jing; Dresselhaus, Mildred; Palacios, Tomas; MIT/Columbia University/SLAC Collaboration

    2015-03-01

    Plasma-based chlorination is a promising technique to realize controllable doping in graphene, while maintaining its high mobility. Meanwhile, synchrotron-based X-ray spectroscopy provides us a sensitive probe to investigate the surface states of functionalizing dopants in graphene. Here, we systematically studied the electronic states of chlorinated graphene on different substrates, including surface binding energy, dopant concentration and work function shift by use of Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy, XPS and photoemission threshold measurements. The concentration of absorbed chlorine is high enough to generate a distinct NEXAFS resonance at 286.2 eV (1s -> π* transition for C-Cl bonds). It is remarkable that the sp2 carbon core-hole exciton (291.85eV) retained its sharpness even after treatment, indicating the long-range periodicity in graphene is largely preserved. This distinguishes our approach as a noninvasive and effective doping method. The interaction between Cl and graphene also exhibits strong substrate effects: for Cu, graphene's Fermi level is shifted downwards by 0.35eV, while for graphene on SiO2, the much (4-5 times) higher chlorine concentration causes EF to shift by 0.9eV.

  1. The influence of oxygen adsorption on the NEXAFS and core-level XPS spectra of the C{sub 60} derivative PCBM

    SciTech Connect

    Brumboiu, Iulia Emilia Eriksson, Olle; Brena, Barbara; Ericsson, Leif; Hansson, Rickard; Moons, Ellen

    2015-02-07

    Fullerenes have been a main focus of scientific research since their discovery due to the interesting possible applications in various fields like organic photovoltaics (OPVs). In particular, the derivative [6,6]-phenyl-C{sub 60}-butyric acid methyl ester (PCBM) is currently one of the most popular choices due to its higher solubility in organic solvents compared to unsubstituted C{sub 60}. One of the central issues in the field of OPVs is device stability, since modules undergo deterioration (losses in efficiency, open circuit voltage, and short circuit current) during operation. In the case of fullerenes, several possibilities have been proposed, including dimerization, oxidation, and impurity related deterioration. We have studied by means of density functional theory the possibility of oxygen adsorption on the C{sub 60} molecular moiety of PCBM. The aim is to provide guidelines for near edge X-ray absorption fine structure (NEXAFS) and X-ray photoelectron spectroscopy (XPS) measurements which can probe the presence of atomic or molecular oxygen on the fullerene cage. By analysing several configurations of PCBM with one or more adsorbed oxygen atoms, we show that a joint core level XPS and O1s NEXAFS investigation could be effectively used not only to confirm oxygen adsorption but also to pinpoint the bonding configuration and the nature of the adsorbate.

  2. γ - γ Angular Correlation Measurements With GRIFFIN

    NASA Astrophysics Data System (ADS)

    Maclean, Andrew; Griffin Collaboration

    2015-10-01

    When an excited nuclear state emits successive γ-rays causing a γ - γ cascade an anisotropy is found in the spatial distribution of γ2 with respect to γ1. Defining the direction of γ1 as the z-axis, the intermediate level, in general will have an uneven distribution of m-states. This causes an anisotropy in the angular correlation of the second γ-ray with respect to the first. These angular correlations are expressed by the W (θ) that depends on numerical coefficients described by the sequence of spin-parity values for the nuclear states involved, the multipolarities and mixing ratios. Angular correlations can be used for the assignment of spins and parities for the nuclear states, and thus provide a powerful means to elucidate the structure of nuclei far from stability through β - γ - γ coincidence measurements. In order to explore the sensitivity of the new 16 clover-detector GRIFFIN γ-ray spectrometer at TRIUMF-ISAC to such γ - γ angular correlations, and to optimize its performance for these measurements we have studied a well known γ - γ cascade from 60Co decay through both experimental measurements and Geant4 simulation. Results will be shown in this talk. Work supported by the Canada Foundation for Innovation, the Natural Sciences and Engineering Research Council of Canada and the National Research Council of Canada.

  3. Intrinsic Angular Momentum of Light.

    ERIC Educational Resources Information Center

    Santarelli, Vincent

    1979-01-01

    Derives a familiar torque-angular momentum theorem for the electromagnetic field, and includes the intrinsic torques exerted by the fields on the polarized medium. This inclusion leads to the expressions for the intrinsic angular momentum carried by the radiation traveling through a charge-free medium. (Author/MA)

  4. Lunar occultation angular diameter measurements.

    NASA Astrophysics Data System (ADS)

    Beavers, W. I.; Eitter, J. J.; Dunham, D. W.; Stein, W. L.

    1980-11-01

    The analysis of one dozen lunar occultation diameter candidate observations are reported. Within this set of occultation measurements at Fick Observatory, six of the stars provide sensible angular diameters, and the remainder appear as virtual point sources. Angular diameter measurements are reported for ɛ Gem, BD+24°0571, υ Cap, R Gem, and BD+23°1518.

  5. Intrinsic Angular Momentum of Light.

    ERIC Educational Resources Information Center

    Santarelli, Vincent

    1979-01-01

    Derives a familiar torque-angular momentum theorem for the electromagnetic field, and includes the intrinsic torques exerted by the fields on the polarized medium. This inclusion leads to the expressions for the intrinsic angular momentum carried by the radiation traveling through a charge-free medium. (Author/MA)

  6. Switching mechanism senses angular acceleration

    NASA Technical Reports Server (NTRS)

    1966-01-01

    Switching mechanism actuates an electrical circuit when a predetermined angular acceleration and displacement are reached. A rotor in the mechanism overcomes the restraint of a magnetic detent when the case in which the detent is mounted reaches the predetermined angular acceleration.

  7. Aliasing Detection and Reduction Scheme on Angularly Undersampled Light Fields.

    PubMed

    Xiao, Zhaolin; Wang, Qing; Zhou, Guoqing; Yu, Jingyi

    2017-05-01

    When using plenoptic camera for digital refocusing, angular undersampling can cause severe (angular) aliasing artifacts. Previous approaches have focused on avoiding aliasing by pre-processing the acquired light field via prefiltering, demosaicing, reparameterization, and so on. In this paper, we present a different solution that first detects and then removes angular aliasing at the light field refocusing stage. Different from previous frequency domain aliasing analysis, we carry out a spatial domain analysis to reveal whether the angular aliasing would occur and uncover where in the image it would occur. The spatial analysis also facilitates easy separation of the aliasing versus non-aliasing regions and angular aliasing removal. Experiments on both synthetic scene and real light field data sets (camera array and Lytro camera) demonstrate that our approach has a number of advantages over the classical prefiltering and depth-dependent light field rendering techniques.

  8. High-dimensional quantum nature of ghost angular Young's diffraction

    SciTech Connect

    Chen Lixiang; Leach, Jonathan; Jack, Barry; Padgett, Miles J.; Franke-Arnold, Sonja; She Weilong

    2010-09-15

    We propose a technique to characterize the dimensionality of entangled sources affected by any environment, including phase and amplitude masks or atmospheric turbulence. We illustrate this technique on the example of angular ghost diffraction using the orbital angular momentum (OAM) spectrum generated by a nonlocal double slit. We realize a nonlocal angular double slit by placing single angular slits in the paths of the signal and idler modes of the entangled light field generated by parametric down-conversion. Based on the observed OAM spectrum and the measured Shannon dimensionality spectrum of the possible quantum channels that contribute to Young's ghost diffraction, we calculate the associated dimensionality D{sub total}. The measured D{sub total} ranges between 1 and 2.74 depending on the opening angle of the angular slits. The ability to quantify the nature of high-dimensional entanglement is vital when considering quantum information protocols.

  9. Resolution analysis of an angular domain imaging system with two dimensional angular filters

    NASA Astrophysics Data System (ADS)

    Ng, Eldon; Carson, Jeffrey J. L.

    2013-02-01

    Angular Domain Imaging (ADI) employs an angular filter to distinguish between quasi-ballistic and scattered photons based on trajectory. A 2D angular filter array was constructed using 3D printing technology to generate an array of micro-channels 500 μm x 500 μm with a length of 12 cm. The main barrier to 2D imaging with the 2D angular filter array was the shadows cast on the image by the 500 μm walls of the angular filter. The objective of this work was to perform a resolution analysis of the 2D angular filter array. The approach was to position the AFA with a two dimensional positioning stage to obtain images of areas normally obstructed by the walls of the AFA. A digital light processor was also incorporated to generate various light patterns to improve the contrast of the images. A resolution analysis was completed by imaging a knife edge submerged in various uniform scattering media (Intralipid® dilutions with water). The edge response functions obtained were then used to compute the line spread function and the theoretical resolution of the imaging system. The theoretical system resolution was measured to be between 110 μm - 180 μm when the scattering level was at or below 0.7% Intralipid®. The theoretical resolution was in agreement with a previous resolution analysis of a silicon-based angular filter with a similar aspect ratio. The measured resolution was also found to be smaller than the size of an individual channel, suggesting that the resolution of an AFA based ADI system is not dependent on the size of the micro-channel.

  10. Implementation of the dynamic laser goniometer for noncontact measurement of angular movement

    NASA Astrophysics Data System (ADS)

    Bohkman, Eugene; Burnashev, Mikhail; Filatov, Yuri; Pavlov, Petr

    2016-07-01

    The dynamic laser goniometer (LG) implementation for noncontact measurements of an object's angular position is presented. One of the possible implementations involves determining the time dependence of the scanning mirror's angular position. Another application is aimed at determining the oscillatory movement parameters on the test table. The results obtained in the course of the research show that the dynamic LG makes it possible to calibrate various kinds of test beds making angular oscillations or angular movement of arbitrary law.

  11. Beam Quality Deterioration Due to Angular Dispersion

    NASA Astrophysics Data System (ADS)

    Mokhov, Sergiy

    2014-03-01

    Laser pulses are often manipulated by different optical elements in free space for purposes of filtering, stretching/compression, shaping, and splitting. This is due to the impossibility of using fiber optical components to withstand high energy pulses. The beam quality factor for free-space propagating optical beams, M2, is typically used to characterize the performance of optical elements. Optical element which preserves M2 in the CW regime may in fact worsen M2 for pulses with the same time-averaged power if this optical element exhibits dispersion in the spectral range of the pulse's bandwidth. Basic dispersive effects can be expressed in terms of aberration-free monochromatic beam optics, and they are longitudinal shift of the waist position, transversal shift of the waist center and angular shift of the propagation direction with wavelength tuning. The first two effects are negligible for optical elements much shorter than the Rayleigh length. We have found an analytical expression for the deterioration of M2 from unity due to angular dispersion for a test pulse which has transverse Gaussian beam profile. This expression depends on both the transverse size of the pulse and the mean square variation of the spectral-angular characteristic of the optical element averaged with the spectral weight distribution of the pulse. In particular, with decreasing of beam size, the M2 deteriorates less because the spectral-angular variation of the propagation direction is mitigated by increasing beam divergence due to diffraction. In our judgment, an optical element should be characterized by its angular dispersion properties rather than measurements of M2.

  12. Control of Angular Intervals for Angle-Multiplexed Holographic Memory

    NASA Astrophysics Data System (ADS)

    Kinoshita, Nobuhiro; Muroi, Tetsuhiko; Ishii, Norihiko; Kamijo, Koji; Shimidzu, Naoki

    2009-03-01

    In angle-multiplexed holographic memory, the full width at half maximum of the Bragg selectivity curves is dependent on the angle formed between the medium and incident laser beams. This indicates the possibility of high density and high multiplexing number by varying the angular intervals between adjacent holograms. We propose an angular interval scheduling for closely stacking holograms into medium even when the angle range is limited. We obtained bit error rates of the order of 10-4 under the following conditions: medium thickness of 1 mm, laser beam wavelength of 532 nm, and angular multiplexing number of 300.

  13. Effect of angular momentum conservation on hydrodynamic simulations of colloids.

    PubMed

    Yang, Mingcheng; Theers, Mario; Hu, Jinglei; Gompper, Gerhard; Winkler, Roland G; Ripoll, Marisol

    2015-07-01

    In contrast to most real fluids, angular momentum is not a locally conserved quantity in some mesoscopic simulation methods. Here we quantify the importance of this conservation in the flow fields associated with different colloidal systems. The flow field is analytically calculated with and without angular momentum conservation for the multiparticle collision dynamics (MPC) method, and simulations are performed to verify the predictions. The flow field generated around a colloidal particle moving under an external force with slip boundary conditions depends on the conservation of angular momentum, and the amplitude of the friction force is substantially affected. Interestingly, no dependence on the angular momentum conservation is found for the flow fields generated around colloids under the influence of phoretic forces. Moreover, circular Couette flow between a no-slip and a slip cylinder is investigated, which allows us to validate one of the two existing expressions for the MPC stress tensor.

  14. Two-color ghost imaging with enhanced angular resolving power

    SciTech Connect

    Karmakar, Sanjit; Shih, Yanhua

    2010-03-15

    This article reports an experimental demonstration on nondegenerate, two-color, biphoton ghost imaging which reproduced a ghost image with enhanced angular resolving power by means of a greater field of view compared with that of classical imaging. With the same imaging magnification, the enhanced angular resolving power and field of view compared with those of classical imaging are 1.25:1 and 1.16:1, respectively. The enhancement of angular resolving power depends on the ratio between the idler and the signal photon frequencies, and the enhancement of the field of view depends mainly on the same ratio and also on the distances of the object plane and the imaging lens from the two-photon source. This article also reports the possibility of reproducing a ghost image with the enhancement of the angular resolving power by means of a greater imaging amplification compared with that of classical imaging.

  15. Performance criteria for dosimeter angular response

    SciTech Connect

    Roberson, P.L.; Fox, R. A.; Cummings, F. M.; McDonald, J. C.; Jones, K.L.

    1988-06-01

    This report provides criteria for evaluating the response of personnel dosimeters to radiation at nonperpendicular incidence. The US Department of Energy Laboratory Accreditation Program (DOELAP) ensures that dosimetry systems at DOE facilities meet acceptable standards for precision and accuracy. In the past, these standards were limited to tests for system variability, energy dependence, and level of detection. The proposed criteria will broaden the scope of DOELAP to include the angular response of personnel dosimeters. Because occupational exposures in the workplace are rarely due to radiation from only one direction, dosimeters must accurately assign individual dose equivalent from irradiation at any forward angle of incidence. Including an angular response criterion in DOELAP would improve the quality of personnel monitoring provided that the criterion is developed from appropriate dose quantities. This report provides guidance for assigning individual dose equivalents for radiation fields at nonperpendicular incidence to the dosimeter. 21 refs., 10 figs., 10 tabs.

  16. Critical angular velocity for vortex lines formation

    NASA Astrophysics Data System (ADS)

    Guadagnini, Enore

    2017-07-01

    For helium II inside a rotating cylinder, it is proposed that the formation of vortex lines of the frictionless superfluid component of the liquid is caused by the presence of the rotating quasi-particles gas. By minimising the free energy of the system, the critical value Ω0 of the angular velocity for the formation of the first vortex line is determined. This value nontrivially depends on the temperature, and numerical estimations of its temperature behaviour are produced. It is shown that the latent heat for a vortex formation and the associated discontinuous change in the angular momentum of the quasi-particles gas determine the slope of Ω0 (T) via some kind of Clapeyron equation.

  17. NEXAFS study of electronic and atomic structure of active layer in Al/indium tin oxide/TiO2 stack during resistive switching.

    PubMed

    Filatova, Elena; Konashuk, Aleksei; Petrov, Yuri; Ubyivovk, Evgeny; Sokolov, Andrey; Selivanov, Andrei; Drozd, Victor

    2016-01-01

    We have studied the stability of the resistive switching process in the Al/(In2O3)0.9(SnO2)0.1/TiO2 assembly grown by atomic layer deposition. Besides electrical characterization the effect of electric field on the atomic electronic structure of the TiO2 layer was studied using near edge X-ray absorption fine structure (NEXAFS) spectroscopy. The region of the current instability in the I-V characteristics was revealed. Presumably this current instability is supported by the amorphous structure of the TiO2 film but is initiated by the surface morphology of the Al substrate. A formation of the O2 molecules was established which occurs specifically in the region of the current instability that is a result of electrical Joule heating manifestation.

  18. NEXAFS study of electronic and atomic structure of active layer in Al/indium tin oxide/TiO2 stack during resistive switching

    PubMed Central

    Filatova, Elena; Konashuk, Aleksei; Petrov, Yuri; Ubyivovk, Evgeny; Sokolov, Andrey; Selivanov, Andrei; Drozd, Victor

    2016-01-01

    Abstract We have studied the stability of the resistive switching process in the Al/(In2O3)0.9(SnO2)0.1/TiO2 assembly grown by atomic layer deposition. Besides electrical characterization the effect of electric field on the atomic electronic structure of the TiO2 layer was studied using near edge X-ray absorption fine structure (NEXAFS) spectroscopy. The region of the current instability in the I-V characteristics was revealed. Presumably this current instability is supported by the amorphous structure of the TiO2 film but is initiated by the surface morphology of the Al substrate. A formation of the O2 molecules was established which occurs specifically in the region of the current instability that is a result of electrical Joule heating manifestation. PMID:27877880

  19. Near-edge X-ray absorption fine structure (NEXAFS) spectroscopy for mapping nano-scale distribution of organic carbon forms in soil: Application to black carbon particles

    NASA Astrophysics Data System (ADS)

    Lehmann, Johannes; Liang, Biqing; Solomon, Dawit; Lerotic, Mirna; LuizãO, Flavio; Kinyangi, James; SchäFer, Thorsten; Wirick, Sue; Jacobsen, Chris

    2005-03-01

    Small-scale heterogeneity of organic carbon (C) forms in soils is poorly quantified since appropriate analytical techniques were not available up to now. Specifically, tools for the identification of functional groups on the surface of micrometer-sized black C particles were not available up to now. Scanning Transmission X-ray Microscopy (STXM) using synchrotron radiation was used in conjunction with Near-Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy to investigate nano-scale distribution (50-nm resolution) of C forms in black C particles and compared to synchrotron-based FTIR spectroscopy. A new embedding technique was developed that did not build on a C-based embedding medium and did not pose the risk of heat damage to the sample. Elemental sulfur (S) was melted to 220°C until it polymerized and quenched with liquid N2 to obtain a very viscous plastic S in which the black C could be embedded until it hardened to a noncrystalline state and was ultrasectioned. Principal component and cluster analysis followed by singular value decomposition was able to resolve distinct areas in a black carbon particle. The core of the studied biomass-derived black C particles was highly aromatic even after thousands of years of exposure in soil and resembled the spectral characteristics of fresh charcoal. Surrounding this core and on the surface of the black C particle, however, much larger proportions of carboxylic and phenolic C forms were identified that were spatially and structurally distinct from the core of the particle. Cluster analysis provided evidence for both oxidation of the black C particle itself as well as adsorption of non-black C. NEXAFS spectroscopy has great potential to allow new insight into black C properties with important implications for biogeochemical cycles such as mineralization of black C in soils and sediments, and adsorption of C, nutrients, and pollutants as well as transport in the geosphere, hydrosphere, and atmosphere.

  20. Transverse angular momentum of photons

    SciTech Connect

    Aiello, Andrea

    2010-05-15

    We develop the quantum theory of transverse angular momentum of light beams. The theory applies to paraxial and quasiparaxial photon beams in vacuum and reproduces the known results for classical beams when applied to coherent states of the field. Both the Poynting vector, alias the linear momentum, and the angular-momentum quantum operators of a light beam are calculated including contributions from first-order transverse derivatives. This permits a correct description of the energy flow in the beam and the natural emergence of both the spin and the angular momentum of the photons. We show that for collimated beams of light, orbital angular-momentum operators do not satisfy the standard commutation rules. Finally, we discuss the application of our theory to some concrete cases.

  1. MBL Experiment in Angular Momentum

    NASA Astrophysics Data System (ADS)

    Gluck, Paul

    2002-04-01

    Among the series of beautiful take-home experiments designed by A.P. French and J.G. King for MIT students, the one on angular momentum studies the loss and conservation of angular momentum using a small dc motor as generator. Here we describe a version of the experiment that increases its accuracy, enables students to perform detailed rotational dynamics calculations, and sharpens the ability to isolate the region where the collision occurs.

  2. Angular momentum evolution of galaxies in EAGLE

    NASA Astrophysics Data System (ADS)

    Lagos, Claudia del P.; Theuns, Tom; Stevens, Adam R. H.; Cortese, Luca; Padilla, Nelson D.; Davis, Timothy A.; Contreras, Sergio; Croton, Darren

    2017-02-01

    We use the EAGLE cosmological hydrodynamic simulation suite to study the specific angular momentum of galaxies, j, with the aims of (i) investigating the physical causes behind the wide range of j at fixed mass and (ii) examining whether simple, theoretical models can explain the seemingly complex and non-linear nature of the evolution of j. We find that j of the stars, jstars, and baryons, jbar, are strongly correlated with stellar and baryon mass, respectively, with the scatter being highly correlated with morphological proxies such as gas fraction, stellar concentration, (u-r) intrinsic colour, stellar age and the ratio of circular velocity to velocity dispersion. We compare with available observations at z = 0 and find excellent agreement. We find that jbar follows the theoretical expectation of an isothermal collapsing halo under conservation of specific angular momentum to within ≈50 per cent, while the subsample of rotation-supported galaxies are equally well described by a simple model in which the disc angular momentum is just enough to maintain marginally stable discs. We extracted evolutionary tracks of the stellar spin parameter of EAGLE galaxies and found that the fate of their jstars at z = 0 depends sensitively on their star formation and merger histories. From these tracks, we identified two distinct physical channels behind low jstars galaxies at z = 0: (i) galaxy mergers, and (ii) early star formation quenching. The latter can produce galaxies with low jstars and early-type morphologies even in the absence of mergers.

  3. Angular dependence of the pp elastic-scattering analyzing power between 0.8 and 2.8 GeV. I. Results for 1.80{endash}2.24 GeV

    SciTech Connect

    Allgower, C.E.; Beddo, M.E.; Grosnick, D.P.; Kasprzyk, T.E.; Lopiano, D.; Spinka, H.M.; Ball, J.; Beauvais, P.; Bedfer, Y.; Chamouard, P.; Combet, M.; Fontaine, J.; Kunne, R.; Lagniel, J.M.; Lemaire, J.L.; Milleret, G.; Sans, J.; Boutefnouchet, A.; Ghazikhanian, V.; Whitten, C.A.; Demierre, P.; Hess, R.; Janout, Z.F.; Rapin, D.; Vuaridel, B.; Prokofiev, A.N.; Vikhrov, V.V.; Zhdanov, A.A.

    1999-11-01

    Experimental results are presented for the pp elastic-scattering single spin observable A{sub oono}=A{sub ooon}=A{sub N}=P, or the analyzing power, at 19 beam kinetic energies between 1795 and 2235 MeV. The typical c.m. angular range is 60{endash}100{degree}. The measurements were performed at Saturne II with a vertically polarized beam and target (transverse to the beam direction and scattering plane), a magnetic spectrometer and a recoil detector, both instrumented with multiwire proportional chambers, and beam polarimeters. {copyright} {ital 1999} {ital The American Physical Society}

  4. Factors influencing perceived angular velocity

    NASA Technical Reports Server (NTRS)

    Kaiser, Mary K.; Calderone, Jack B.

    1991-01-01

    Angular velocity perception is examined for rotations both in depth and in the image plane and the influence of several object properties on this motion parameter is explored. Two major object properties are considered, namely, texture density which determines the rate of edge transitions for rotations in depth, i.e., the number of texture elements that pass an object's boundary per unit of time, and object size which determines the tangential linear velocities and 2D image velocities of texture elements for a given angular velocity. Results of experiments show that edge-transition rate biased angular velocity estimates only when edges were highly salient. Element velocities had an impact on perceived angular velocity; this bias was associated with 2D image velocity rather than 3D tangential velocity. Despite these biases judgements were most strongly determined by the true angular velocity. Sensitivity to this higher order motion parameter appeared to be good for rotations both in depth (y-axis) and parallel to the line of sight (z-axis).

  5. Stellar diameters and temperatures. IV. Predicting stellar angular diameters

    SciTech Connect

    Boyajian, Tabetha S.; Van Belle, Gerard; Von Braun, Kaspar

    2014-03-01

    The number of stellar angular diameter measurements has greatly increased over the past few years due to innovations and developments in the field of long baseline optical interferometry. We use a collection of high-precision angular diameter measurements for nearby, main-sequence stars to develop empirical relations that allow the prediction of stellar angular sizes as a function of observed photometric color. These relations are presented for a combination of 48 broadband color indices. We empirically show for the first time a dependence on metallicity of these relations using Johnson (B – V) and Sloan (g – r) colors. Our relations are capable of predicting diameters with a random error of less than 5% and represent the most robust and empirical determinations of stellar angular sizes to date.

  6. All joint moments significantly contribute to trunk angular acceleration

    PubMed Central

    Nott, Cameron R.; Zajac, Felix E.; Neptune, Richard R.; Kautz, Steven A.

    2010-01-01

    Computationally advanced biomechanical analyses of gait demonstrate the often counter intuitive roles of joint moments on various aspects of gait such as propulsion, swing initiation, and balance. Each joint moment can produce linear and angular acceleration of all body segments (including those on which the moment does not directly act) due to the dynamic coupling inherent in the interconnected musculoskeletal system. This study presents the quantitative relationships between individual joint moments and trunk control with respect to balance during gait to show that the ankle, knee, and hip joint moments all affect the angular acceleration of the trunk. We show that trunk angular acceleration is affected by all the joints in the leg with varying degrees of dependence during the gait cycle. Furthermore, it is shown that inter-planar coupling exists and a two dimensional analysis of trunk balance neglects important out-of-plane joint moments that affect trunk angular acceleration. PMID:20646711

  7. Quantum optimal control of photoelectron spectra and angular distributions

    NASA Astrophysics Data System (ADS)

    Goetz, R. Esteban; Karamatskou, Antonia; Santra, Robin; Koch, Christiane P.

    2016-01-01

    Photoelectron spectra and photoelectron angular distributions obtained in photoionization reveal important information on, e.g., charge transfer or hole coherence in the parent ion. Here we show that optimal control of the underlying quantum dynamics can be used to enhance desired features in the photoelectron spectra and angular distributions. To this end, we combine Krotov's method for optimal control theory with the time-dependent configuration interaction singles formalism and a splitting approach to calculate photoelectron spectra and angular distributions. The optimization target can account for specific desired properties in the photoelectron angular distribution alone, in the photoelectron spectrum, or in both. We demonstrate the method for hydrogen and then apply it to argon under strong XUV radiation, maximizing the difference of emission into the upper and lower hemispheres, in order to realize directed electron emission in the XUV regime.

  8. A model of visual detection of angular speed for bees.

    PubMed

    Riabinina, Olena; Philippides, Andrew O

    2009-03-07

    A fly or bee's responses to widefield image motion depend on two basic parameters: temporal frequency and angular speed. Rotational optic flow is monitored using temporal frequency analysers, whereas translational optic flow seems to be monitored in terms of angular speed. Here we present a possible model of an angular speed detector which processes input signals through two parallel channels. The output of the detector is taken as the ratio of the two channels' outputs. This operation amplifies angular speed sensitivity and depresses temporal frequency tuning. We analyse the behaviour of two versions of this model with different filtering properties in response to a variety of input signals. We then embody the detector in a simulated agent's visual system and explore its behaviour in experiments on speed control and odometry. The latter leads us to suggest a new algorithm for optic flow driven odometry.

  9. Variations in atmospheric angular momentum

    NASA Technical Reports Server (NTRS)

    Rosen, R. D.; Salstein, D. A.

    1981-01-01

    Twice-daily values of the atmosphere's angular momentum about the polar axis during the five years from 1976 through 1980 are presented in graphs and a table. The compilation is based on a global data set, incorporating 90 percent of the mass of the atmosphere. The relationship between changes in the angular momentum of the atmosphere and changes in the length of day is described, as are the main sources of error in the data. The variability in angular momentum is revealed in a preliminary fashion by means of a spectral decomposition. The data presented should stimulate comparisons with other measures of the length of day and so provide a basis for greater understanding of Earth-atmosphere interactions.

  10. Interferometric measurement of angular motion

    NASA Astrophysics Data System (ADS)

    Peña Arellano, Fabián Erasmo; Panjwani, Hasnain; Carbone, Ludovico; Speake, Clive C.

    2013-04-01

    This paper describes the design and realization of a homodyne polarization interferometer for measuring angular motion. The optical layout incorporates carefully designed cat's eye retroreflectors that maximize the measurable range of angular motion and facilitate initial alignment. The retroreflectors are optimized and numerically characterized in terms of defocus and spherical aberrations using Zemax software for optical design. The linearity of the measurement is then calculated in terms of the aberrations. The actual physical interferometer is realized as a compact device with optical components from stock and without relying on adjustable holders. Evaluation of its performance using a commercial autocollimator confirmed a reproducibility within 0.1%, a non-linearity of less than 1 ppm with respect to the autocollimator, an upper limit to its sensitivity of about 5 × 10-11 rad/sqrt{textrm {Hz}} from audioband down to 100 mHz and an angular measurement range of more than ±1°.

  11. Non-Colinearity of Angular Velocity and Angular Momentum

    ERIC Educational Resources Information Center

    Burr, A. F.

    1974-01-01

    Discusses the principles, construction, and operation of an apparatus which serves to demonstrate the non-colinearity of the angular velocity and momentum vectors as well as the inertial tensors. Applications of the apparatus to teaching of advanced undergraduate mechanics courses are recommended. (CC)

  12. Non-Colinearity of Angular Velocity and Angular Momentum

    ERIC Educational Resources Information Center

    Burr, A. F.

    1974-01-01

    Discusses the principles, construction, and operation of an apparatus which serves to demonstrate the non-colinearity of the angular velocity and momentum vectors as well as the inertial tensors. Applications of the apparatus to teaching of advanced undergraduate mechanics courses are recommended. (CC)

  13. Solar cell angular position transducer

    NASA Technical Reports Server (NTRS)

    Sandford, M. C.; Gray, D. L. (Inventor)

    1980-01-01

    An angular position transducer utilizing photocells and a light source is disclosed. The device uses a fully rotatable baffle which is connected via an actuator shaft to the body whose rotational displacement is to be measured. The baffle blocks the light path between the light source and the photocells so that a constant semicircular beam of light reaches the photocells. The current produced by the photocells is fed through a resistor, a differential amplifier measures the voltage drop across the resistor which indicates the angular position of the actuator shaft and hence of the object.

  14. Automated Angular Momentum Recoupling Algebra

    NASA Astrophysics Data System (ADS)

    Williams, H. T.; Silbar, Richard R.

    1992-04-01

    We present a set of heuristic rules for algebraic solution of angular momentum recoupling problems. The general problem reduces to that of finding an optimal path from one binary tree (representing the angular momentum coupling scheme for the reduced matrix element) to another (representing the sub-integrals and spin sums to be done). The method lends itself to implementation on a microcomputer, and we have developed such an implementation using a dialect of LISP. We describe both how our code, called RACAH, works and how it appears to the user. We illustrate the use of RACAH for several transition and scattering amplitude matrix elements occurring in atomic, nuclear, and particle physics.

  15. Preliminary optical design of a varied line-space spectrograph for the multi-channel detection of near-edge X-ray absorption fine structure (NEXAFS) spectra in the 280-550 eV energy range

    SciTech Connect

    Wheeler, B.S.; McKinney, W.R.; Hussain, Z.; Padmore, H.

    1996-07-01

    The optical design of a varied line-space spectrograph for the multi-channel recording of NEXAFS spectra in a single {open_quotes}snapshot{close_quotes} is proposed. The spectrograph is to be used with a bending magnet source on beamline 7.3.2 at the Advanced Light Source (ALS). Approximately 20 volts of spectra are simultaneously imaged across a small square of material sample at each respective K absorption edge of carbon, nitrogen, and oxygen. Photoelectrons emitted from the material sample will be collected by an electron imaging microscope, the view field of which determines the sampling size. The sample also forms the exit slit of the optical system. This dispersive method of NEXAFS data acquisition is three to four orders of magnitude faster than the conventional method of taking data point-to-point using scanning of the grating. The proposed design is presented along with the design method and supporting SHADOW raytrace analysis.

  16. Twisted molecular excitons as mediators for changing the angular momentum of light

    NASA Astrophysics Data System (ADS)

    Zang, Xiaoning; Lusk, Mark T.

    2017-07-01

    Molecules with CN or CN h symmetry can absorb quanta of optical angular momentum to generate twisted excitons with well-defined quasiangular momenta of their own. Angular momentum is conserved in such interactions at the level of a paraxial approximation for the light beam. A sequence of absorption events can thus be used to create a range of excitonic angular momenta. Subsequent decay can produce radiation with a single angular momentum equal to that accumulated. Such molecules can thus be viewed as mediators for changing the angular momentum of light. This sidesteps the need to exploit nonlinear light-matter interactions based on higher-order susceptibilities. A tight-binding paradigm is used to verify angular momentum conservation and demonstrate how it can be exploited to change the angular momentum of light. The approach is then extended to a time-dependent density functional theory setting where the key results are shown to hold in a many-body, multilevel setting.

  17. System size dependence of cluster properties from two-particle angular correlations in Cu+Cu and Au+Au collisions at sq root(s{sub NN})=200 GeV

    SciTech Connect

    Alver, B.; Ballintijn, M.; Busza, W.; Gulbrandsen, K.; Henderson, C.; Kane, J. L.; Kulinich, P.; Li, W.; Loizides, C.; Reed, C.; Roland, C.; Roland, G.; Stephans, G. S. F.; Nieuwenhuizen, G. J. van; Vaurynovich, S. S.; Verdier, R.; Veres, G. I.; Wenger, E.; Wyslouch, B.; Back, B. B.

    2010-02-15

    We present results on two-particle angular correlations in Cu+Cu and Au+Au collisions at a center-of-mass energy per nucleon pair of 200 GeV over a broad range of pseudorapidity (eta) and azimuthal angle (phi) values as a function of collision centrality. The PHOBOS detector at the Relativistic Heavy Ion Collider has a uniquely large angular coverage for inclusive charged particles, which allows for the study of correlations on both long- and short-range scales. A complex two-dimensional correlation structure in {Delta}{eta} and {Delta}{phi} emerges, which is interpreted in the context of a cluster model. The effective cluster size and decay width are extracted from the two-particle pseudorapidity correlation functions. The effective cluster size found in semicentral Cu+Cu and Au+Au collisions is comparable to that found in proton-proton collisions but a nontrivial decrease in size with increasing centrality is observed. Moreover, a comparison of results from Cu+Cu versus Au+Au collisions shows an interesting scaling of the effective cluster size with the measured fraction of total cross section (which is related to the ratio of the impact parameter to the nuclear radius, b/2R), suggesting a geometric origin. Further analysis for pairs from restricted azimuthal regions shows that the effective cluster size at {Delta}{phi}{approx}180 deg. drops more rapidly toward central collisions than the size at {Delta}{phi}{approx}0 deg. The effect of limited {eta} acceptance on the cluster parameters is also addressed, and a correction is applied to present cluster parameters for full {eta} coverage, leading to much larger effective cluster sizes and widths than previously noted in the literature. These results should provide insight into the hot and dense medium created in heavy ion collisions.

  18. Probing the Orientation and Conformation of alpha-Helix and beta-Strand Model Peptides on Self-Assembled Monolayers Using Sum Frequency Generation and NEXAFS Spectroscopy

    SciTech Connect

    Weidner, T.; Apte, J; Gamble, L; Castner, D

    2010-01-01

    The structure and orientation of amphiphilic {alpha}-helix and {beta}-strand model peptide films on self-assembled monolayers (SAMs) have been studied with sum frequency generation (SFG) vibrational spectroscopy and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. The {alpha}-helix peptide is a 14-mer, and the {beta}-strand is a 15-mer of hydrophilic lysine and hydrophobic leucine residues with hydrophobic periodicities of 3.5 and 2, respectively. These periodicities result in the leucine side chains located on one side of the peptides and the lysine side chains on the other side. The SAMs were prepared from the assembly of either carboxylic acid- or methyl-terminated alkyl thiols onto gold surfaces. For SFG studies, the deuterated analog of the methyl SAM was used. SFG vibrational spectra in the C-H region of air-dried peptides films on both SAMs exhibit strong peaks near 2965, 2940, and 2875 cm{sup -1} related to ordered leucine side chains. The orientation of the leucine side chains was determined from the phase of these features relative to the nonresonant gold background. The relative phase for both the {alpha}-helix and {beta}-strand peptides showed that the leucine side chains were oriented away from the carboxylic acid SAM surface and oriented toward the methyl SAM surface. Amide I peaks observed near 1656 cm{sup -1} for the {alpha}-helix peptide confirm that the secondary structure is preserved on both SAMs. Strong linear dichroism related to the amide {pi}* orbital at 400.8 eV was observed in the nitrogen K-edge NEXAFS spectra for the adsorbed {beta}-strand peptides, suggesting that the peptide backbones are oriented parallel to the SAM surface with the side chains pointing toward or away from the interface. For the {alpha}-helix the dichroism of the amide {pi}* is significantly weaker, probably because of the broad distribution of amide bond orientations in the {alpha}-helix secondary structure.

  19. High angular resolution at LBT

    NASA Astrophysics Data System (ADS)

    Conrad, A.; Arcidiacono, C.; Bertero, M.; Boccacci, P.; Davies, A. G.; Defrere, D.; de Kleer, K.; De Pater, I.; Hinz, P.; Hofmann, K. H.; La Camera, A.; Leisenring, J.; Kürster, M.; Rathbun, J. A.; Schertl, D.; Skemer, A.; Skrutskie, M.; Spencer, J. R.; Veillet, C.; Weigelt, G.; Woodward, C. E.

    2015-12-01

    High angular resolution from ground-based observatories stands as a key technology for advancing planetary science. In the window between the angular resolution achievable with 8-10 meter class telescopes, and the 23-to-40 meter giants of the future, LBT provides a glimpse of what the next generation of instruments providing higher angular resolution will provide. We present first ever resolved images of an Io eruption site taken from the ground, images of Io's Loki Patera taken with Fizeau imaging at the 22.8 meter LBT [Conrad, et al., AJ, 2015]. We will also present preliminary analysis of two data sets acquired during the 2015 opposition: L-band fringes at Kurdalagon and an occultation of Loki and Pele by Europa (see figure). The light curves from this occultation will yield an order of magnitude improvement in spatial resolution along the path of ingress and egress. We will conclude by providing an overview of the overall benefit of recent and future advances in angular resolution for planetary science.

  20. Noncontact measurement of angular deflection

    NASA Technical Reports Server (NTRS)

    Bryant, E. L.

    1978-01-01

    Technique for measuring instantaneous angular deflection of object requires no physical contact. Technique utilizes two flat refractors, converging lens, and different photocell. Distinction of method is its combination of optical and electromechanical components into feedback system in which measurement error is made to approach zero. Application is foreseen in measurement of torsional strain.

  1. Gas Accretion and Angular Momentum

    NASA Astrophysics Data System (ADS)

    Stewart, Kyle R.

    In this chapter, we review the role of gas accretion to the acquisition of angular momentum, both in galaxies and in their gaseous halos. We begin by discussing angular momentum in dark matter halos, with a brief review of tidal torque theory and the importance of mergers, followed by a discussion of the canonical picture of galaxy formation within this framework, where halo gas is presumed to shock-eat to the virial temperature of the halo, following the same spin distribution as the dark matter halo before cooling to the center of the halo to form a galaxy there. In the context of recent observational evidence demonstrating the presence of high angular momentum gas in galaxy halos, we review recent cosmological hydrodynamic simulations that have begun to emphasize the role of "cold flow" accretion—anisotropic gas accretion along cosmic filaments that does not shock-heat before sinking to the central galaxy. We discuss the implications of these simulations, reviewing a number of recent developments in the literature, and suggest a revision to the canonical model as it relates to the expected angular momentum content of gaseous halos around galaxies.

  2. Olympic Wrestling and Angular Momentum.

    ERIC Educational Resources Information Center

    Carle, Mark

    1988-01-01

    Reported is the use of a wrestling photograph in a noncalculus introductory physics course. The photograph presents a maneuver that could serve as an example for a discussion on equilibrium, forces, torque, and angular motion. Provided are some qualitative thoughts as well as quantitative calculations. (YP)

  3. Aldebaran's angular diameter: How well do we know it?

    NASA Astrophysics Data System (ADS)

    Richichi, A.; Roccatagliata, V.

    2005-04-01

    The bright, well-known K5 giant Aldebaran, α Tau, is probably the star with the largest number of direct angular diameter determinations, achieved over a long time by several authors using various techniques. In spite of this wealth of data, or perhaps as a direct result of it, there is not a very good agreement on a single angular diameter value. This is particularly unsettling if one considers that Aldebaran is also used as a primary calibrator for some angular resolution methods, notably for optical and infrared long baseline interferometry. Directly connected to Aldebaran's angular diameter and its uncertainties is its effective temperature, which also has been used for several empirical calibrations. Among the proposed explanations for the elusiveness of an accurate determination of the angular diameter of Aldebaran are the possibility of temporal variations as well as a possible dependence of the angular diameter on the wavelength. We present here a few, very accurate new determinations obtained by means of lunar occultations and long baseline interferometry. We derive an average value of 19.96±0.03 milliarcsec for the uniform disk diameter. The corresponding limb-darkened value is 20.58±0.03 milliarcsec, or 44.2±0.9 R⊙. We discuss this result, in connection with previous determinations and with possible problems that may affect such measurements. Based on observations collected at TIRGO (Gornergrat, Switzerland). TIRGO is operated by CNR - CAISMI Arcetri, Italy.

  4. Dissociating the effects of angular disparity and image similarity in mental rotation and object recognition.

    PubMed

    Cheung, Olivia S; Hayward, William G; Gauthier, Isabel

    2009-10-01

    Performance is often impaired linearly with increasing angular disparity between two objects in tasks that measure mental rotation or object recognition. But increased angular disparity is often accompanied by changes in the similarity between views of an object, confounding the impact of the two factors in these tasks. We examined separately the effects of angular disparity and image similarity on handedness (to test mental rotation) and identity (to test object recognition) judgments with 3-D novel objects. When similarity was approximately equated, an effect of angular disparity was only found for handedness but not identity judgments. With a fixed angular disparity, performance was better for similar than dissimilar image pairs in both tasks, with a larger effect for identity than handedness judgments. Our results suggest that mental rotation involves mental transformation procedures that depend on angular disparity, but that object recognition is predominately dependent on the similarity of image features.

  5. Plate tectonics conserves angular momentum

    NASA Astrophysics Data System (ADS)

    Bowin, C.

    2009-03-01

    A new combined understanding of plate tectonics, Earth internal structure, and the role of impulse in deformation of the Earth's crust is presented. Plate accelerations and decelerations have been revealed by iterative filtering of the quaternion history for the Euler poles that define absolute plate motion history for the past 68 million years, and provide an unprecedented precision for plate angular rotation variations with time at 2-million year intervals. Stage poles represent the angular rotation of a plate's motion between adjacent Euler poles, and from which the maximum velocity vector for a plate can be determined. The consistent maximum velocity variations, in turn, yield consistent estimates of plate accelerations and decelerations. The fact that the Pacific plate was shown to accelerate and decelerate, implied that conservation of plate tectonic angular momentum must be globally conserved, and that is confirmed by the results shown here (total angular momentum ~1.4 E+27 kgm2s-1). Accordingly, if a plate decelerates, other plates must increase their angular momentums to compensate. In addition, the azimuth of the maximum velocity vectors yields clues as to why the "bend" in the Emperor-Hawaiian seamount trend occurred near 46 Myr. This report summarizes processing results for 12 of the 14 major tectonic plates of the Earth (except for the Juan de Fuca and Philippine plates). Plate accelerations support the contention that plate tectonics is a product of torques that most likely are sustained by the sinking of positive density anomalies due to phase changes in subducted gabbroic lithosphere at depth in the upper lower mantle (above 1200 km depth). The tectonic plates are pulled along by the sinking of these positive mass anomalies, rather than moving at near constant velocity on the crests of convection cells driven by rising heat. These results imply that spreading centers are primarily passive reactive features, and fracture zones (and wedge-shaped sites

  6. Angular Distributions of Sputtered Atoms from Semiconductor Targets at Grazing Ion Beam Incidence Angles

    SciTech Connect

    Sekowski, M.; Burenkov, A.; Martinez-Limia, A.; Hernandez-Mangas, J.; Ryssel, H.

    2008-11-03

    Angular distributions of ion sputtered germanium and silicon atoms are investigated within this work. Experiments are performed for the case of grazing ion incidence angles, where the resulting angular distributions are asymmetrical with respect to the polar angle of the sputtered atoms. The performed experiments are compared to Monte-Carlo simulations from different programs. We show here an improved model for the angular distribution, which has an additional dependence of the ion incidence angle.

  7. On Dunkl angular momenta algebra

    NASA Astrophysics Data System (ADS)

    Feigin, Misha; Hakobyan, Tigran

    2015-11-01

    We consider the quantum angular momentum generators, deformed by means of the Dunkl operators. Together with the reflection operators they generate a subalgebra in the rational Cherednik algebra associated with a finite real reflection group. We find all the defining relations of the algebra, which appear to be quadratic, and we show that the algebra is of Poincaré-Birkhoff-Witt (PBW) type. We show that this algebra contains the angular part of the Calogero-Moser Hamiltonian and that together with constants it generates the centre of the algebra. We also consider the gl( N ) version of the subalge-bra of the rational Cherednik algebra and show that it is a non-homogeneous quadratic algebra of PBW type as well. In this case the central generator can be identified with the usual Calogero-Moser Hamiltonian associated with the Coxeter group in the harmonic confinement.

  8. Phonons with orbital angular momentum

    SciTech Connect

    Ayub, M. K.; Ali, S.; Mendonca, J. T.

    2011-10-15

    Ion accoustic waves or phonon modes are studied with orbital angular momentum (OAM) in an unmagnetized collissionless uniform plasma, whose constituents are the Boltzmann electrons and inertial ions. For this purpose, we have employed the fluid equations to obtain a paraxial equation in terms of ion density perturbations and discussed its Gaussian beam and Laguerre-Gauss (LG) beam solutions. Furthermore, an approximate solution for the electrostatic potential problem is presented, allowing to express the components of the electric field in terms of LG potential perturbations. The energy flux due to phonons is also calculated and the corresponding OAM is derived. Numerically, it is shown that the parameters such as azimuthal angle, radial and angular mode numbers, and beam waist, strongly modify the profiles of the phonon LG potential. The present results should be helpful in understanding the phonon mode excitations produced by Brillouin backscattering of laser beams in a uniform plasma.

  9. Nuclei at High Angular Momentum

    SciTech Connect

    Diamond, R. M.; Stephens, F. S.

    1980-12-01

    It appears that most nuclei show a compromise between purely collective and purely non-collective behavior at very high spins.non~collective behavior in nuclei has been seen only as high as 36 or 37{bar h}, at which point a more collective structure seems to develop. The concepts underlying the study of high angular momentum states are discussed. The factors that limit angular momentum in nuclei are considered. The currently emerging state of physics of very high spin states is reviewed. The detailed calculations currently made for high spin states are described, focusing not on the calculations themselves, but on the physical input to them and results that come out. Production of high-spin states using heavy-ion reactions is reviewed. Studies of {gamma}-rays de-exciting the evaporation residues from heavy-ion reactions are covered. Two types of {gamma} rays occur: those that cool the nucleus to or toward the yrast line, called "statistical," and those that are more or less parallel to the yrast line and remove the angular momentum, called "yrast~like." Collective rotation, in simplest form the motion of a deformed nucleus around an axis perpendicular to its symmetry axis, is also covered.

  10. Achromatic orbital angular momentum generator

    NASA Astrophysics Data System (ADS)

    Bouchard, Frédéric; Mand, Harjaspreet; Mirhosseini, Mohammad; Karimi, Ebrahim; Boyd, Robert W.

    2014-12-01

    We describe a novel approach for generating light beams that carry orbital angular momentum (OAM) by means of total internal reflection in an isotropic medium. A continuous space-varying cylindrically symmetric reflector, in the form of two glued hollow axicons, is used to introduce a nonuniform rotation of polarization into a linearly polarized input beam. This device acts as a full spin-to-orbital angular momentum convertor. It functions by switching the helicity of the incoming beam's polarization, and by conservation of total angular momentum thereby generates a well-defined value of OAM. Our device is broadband, since the phase shift due to total internal reflection is nearly independent of wavelength. We verify the broad-band behaviour by measuring the conversion efficiency of the device for three different wavelengths corresponding to the RGB colours, red, green and blue. An average conversion efficiency of 95% for these three different wavelengths is observed. This device may find applications in imaging from micro- to astronomical systems where a white vortex beam is needed.

  11. Understanding GRETINA using angular correlation method

    NASA Astrophysics Data System (ADS)

    Austin, Madeline

    2015-10-01

    The ability to trace the path of gamma rays through germanium is not only necessary for taking full advantage of GRETINA but also a promising possibility for homeland security defense against nuclear threats. This research tested the current tracking algorithm using the angular correlation method by comparing results from raw and tracked data to the theoretical model for Co-60. It was found that the current tracking method is unsuccessful in reproducing angular correlation. Variations to the tracking algorithm were made in the FM value, tracking angle, number of angles of separation observed, and window of coincidence in attempt to improve correlation results. From these variations it was observed that having a larger FM improved results, reducing the number of observational angles worsened correlation, and that overall larger tracking angles improved with larger windows of coincidence and vice-verse. Future research would be to refine the angle of measurement for raw data and to explore the possibility of an energy dependence by testing other elements. This work is supported by the United States Department of Energy, Office of Science, under Contract Number DE-AC02-06CH11357

  12. Orbital angular momentum of general astigmatic modes

    SciTech Connect

    Visser, Jorrit; Nienhuis, Gerard

    2004-07-01

    We present an operator method to obtain complete sets of astigmatic Gaussian solutions of the paraxial wave equation. In case of general astigmatism, the astigmatic intensity and phase distribution of the fundamental mode differ in orientation. As a consequence, the fundamental mode has a nonzero orbital angular momentum, which is not due to phase singularities. Analogous to the operator method for the quantum harmonic oscillator, the corresponding astigmatic higher-order modes are obtained by repeated application of raising operators on the fundamental mode. The nature of the higher-order modes is characterized by a point on a sphere, in analogy with the representation of polarization on the Poincare sphere. The north and south poles represent astigmatic Laguerre-Gaussian modes, similar to circular polarization on the Poincare sphere, while astigmatic Hermite-Gaussian modes are associated with points on the equator, analogous to linear polarization. We discuss the propagation properties of the modes and their orbital angular momentum, which depends on the degree of astigmatism and on the location of the point on the sphere.

  13. Angular Momentum and Galaxy Formation Revisited

    NASA Astrophysics Data System (ADS)

    Romanowsky, Aaron J.; Fall, S. Michael

    2012-12-01

    Motivated by a new wave of kinematical tracers in the outer regions of early-type galaxies (ellipticals and lenticulars), we re-examine the role of angular momentum in galaxies of all types. We present new methods for quantifying the specific angular momentum j, focusing mainly on the more challenging case of early-type galaxies, in order to derive firm empirical relations between stellar j sstarf and mass M sstarf (thus extending earlier work by Fall). We carry out detailed analyses of eight galaxies with kinematical data extending as far out as 10 effective radii, and find that data at two effective radii are generally sufficient to estimate total j sstarf reliably. Our results contravene suggestions that ellipticals could harbor large reservoirs of hidden j sstarf in their outer regions owing to angular momentum transport in major mergers. We then carry out a comprehensive analysis of extended kinematic data from the literature for a sample of ~100 nearby bright galaxies of all types, placing them on a diagram of j sstarf versus M sstarf. The ellipticals and spirals form two parallel j sstarf-M sstarf tracks, with log-slopes of ~0.6, which for the spirals are closely related to the Tully-Fisher relation, but for the ellipticals derives from a remarkable conspiracy between masses, sizes, and rotation velocities. The ellipticals contain less angular momentum on average than spirals of equal mass, with the quantitative disparity depending on the adopted K-band stellar mass-to-light ratios of the galaxies: it is a factor of ~3-4 if mass-to-light ratio variations are neglected for simplicity, and ~7 if they are included. We decompose the spirals into disks and bulges and find that these subcomponents follow j sstarf-M sstarf trends similar to the overall ones for spirals and ellipticals. The lenticulars have an intermediate trend, and we propose that the morphological types of galaxies reflect disk and bulge subcomponents that follow separate, fundamental j sstarf

  14. Angular momentum decomposition for an electron

    SciTech Connect

    Burkardt, Matthias; Hikmat, BC

    2009-04-01

    We calculate the orbital angular momentum of the 'quark' in the scalar diquark model as well as that of the electron in QED (to order {alpha}). We compare the orbital angular momentum obtained from the Jaffe-Manohar decomposition to that obtained from the Ji relation and estimate the importance of the vector potential in the definition of orbital angular momentum.

  15. Angular Momentum Decomposition for an Electron

    SciTech Connect

    Burkardt, Matthias; BC, Hikmat

    2009-01-01

    We calculate the orbital angular momentum of the `quark' in the scalar diquark model as well as that of the electron in QED (to order $\\alpha$). We compare the orbital angular momentum obtained from the Jaffe-Manohar decomposition to that obtained from the Ji relation and estimate the importance of the vector potential in the definition of orbital angular momentum.

  16. Effect of slow rotational diffusion on angular correlations.

    NASA Technical Reports Server (NTRS)

    Marshall, A. G.; Meares, C. F.

    1972-01-01

    The theory for perturbed angular correlations of gamma radiation has been extended to include the possibility of adiabatic variation in the interaction Hamiltonian, K, for the intermediate state. The calculation begins from a polycrystalline model. It is shown that adiabatic variation in K introduces a time dependence into the angles which express the orientation of the molecular frame. The relevance of the adiabatic limit to the use of perturbed angular correlations of gamma radiation for study of the motion of radioactive species in viscous media is discussed.

  17. A Universal Angular Momentum Profile for Dark Matter Halos

    NASA Astrophysics Data System (ADS)

    Liao, Shihong; Chen, Jianxiong; Chu, M.-C.

    2017-07-01

    The angular momentum distribution in dark matter halos and galaxies is a key ingredient in understanding their formation. Specifically, the internal distribution of angular momenta is closely related to the formation of disk galaxies. In this article, we use halos identified from a high-resolution simulation, the Bolshoi simulation, to study the spatial distribution of specific angular momenta, j(r,θ ). We show that by stacking halos with similar masses to increase the signal-to-noise ratio, the profile can be fitted as a simple function, j{(r,θ )={j}s{\\sin }2{(θ /{θ }s)(r/{r}s)}2/(1+r/{r}s)}4, with three free parameters, {j}s,{r}s, and {θ }s. Specifically, j s correlates with the halo mass M vir as {j}s\\propto {M}{vir}2/3, r s has a weak dependence on the halo mass as {r}s\\propto {M}{vir}0.040, and {θ }s is independent of M vir. This profile agrees with that from a rigid shell model, though its origin is unclear. Our universal specific angular momentum profile j(r,θ ) is useful in modeling the angular momenta of halos. Furthermore, by using an empirical stellar mass-halo mass relation, we can infer the average angular momentum distribution of a dark matter halo. The specific angular momentum-stellar mass relation within a halo computed from our profile is shown to share a similar shape as that from the observed disk galaxies.

  18. Large spatial and angular spin splitting in a thin anisotropic ε-near-zero metamaterial.

    PubMed

    Zhu, Wenguo; Yu, Jianhui; Guan, Heyuan; Lu, Huihui; Tang, Jieyuan; Luo, Yuanhan; Chen, Zhe

    2017-03-06

    We show theoretically that after transmitted through a thin anisotropic ε-near-zero metamaterial, a linearly polarized Gaussian beam can undergo both transverse spatial and angular spin splitting. The upper limits of spatial and angular spin splitting are found to be the beam waist and divergence angle of incident Gaussian beam, respectively. The spin splitting of transmitted beam after propagating a distance z depends on both the spatial and angular spin splitting. By combining the spatial and angular spin splitting properly, we can maximize the spin splitting of propagated beam, which is nearly equal to the spot size of Gaussian beam w(z).

  19. Two-dimensional angular filter array for angular domain imaging with 3D printed angular filters

    NASA Astrophysics Data System (ADS)

    Ng, Eldon; Carson, Jeffrey J. L.

    2013-02-01

    Angular Domain Imaging (ADI) is a technique that is capable of generating two dimensional shadowgrams of attenuating targets embedded in a scattering medium. In ADI, an angular filter array (AFA) is positioned between the sample and the detector to distinguish between quasi-ballistic photons and scattered photons. An AFA is a series of micro-channels with a high aspect ratio. Previous AFAs from our group were constructed by micro-machining the micro-channels into a silicon wafer, limiting the imaging area to a one dimensional line. Two dimensional images were acquired via scanning. The objective of this work was to extend the AFA design to two dimensions to allow for two dimensional imaging with minimal scanning. The second objective of this work was to perform an initial characterization of the imaging capabilities of the 2D AFA. Our approach was to use rapid 3D prototyping techniques to generate an array of micro-channels. The imaging capabilities were then evaluated by imaging a 0.9 mm graphite rod submerged in a scattering media. Contrast was observed to improve when a second angular filter array was placed in front of the sample to mask the incoming light.

  20. Angular Spacing Control for Segmented Data Pages in Angle-Multiplexed Holographic Memory

    NASA Astrophysics Data System (ADS)

    Kinoshita, Nobuhiro; Muroi, Tetsuhiko; Ishii, Norihiko; Kamijo, Koji; Kikuchi, Hiroshi; Shimidzu, Naoki; Ando, Toshio; Masaki, Kazuyoshi; Shimizu, Takehiro

    2011-09-01

    To improve the recording density of angle-multiplexed holographic memory, it is effective to increase the numerical aperture of the lens and to shorten the wavelength of the laser source as well as to increase the multiplexing number. The angular selectivity of a hologram, which determines the multiplexing number, is dependent on the incident angle of not only the reference beam but also the signal beam to the holographic recording medium. The actual signal beam, which is a convergent or divergent beam, is regarded as the sum of plane waves that have different propagation directions, angular selectivities, and optimal angular spacings. In this paper, focusing on the differences in the optimal angular spacing, we proposed a method to control the angular spacing for each segmented data page. We investigated the angular selectivity of a hologram and crosstalk for segmented data pages using numerical simulation. The experimental results showed a practical bit-error rate on the order of 10-3.

  1. Angular two-point correlation of NVSS galaxies revisited

    NASA Astrophysics Data System (ADS)

    Chen, Song; Schwarz, Dominik J.

    2016-06-01

    We measure the angular two-point correlation and angular power spectrum from the NRAO VLA Sky Survey (NVSS) of radio galaxies. They are found to be consistent with the best-fit cosmological model from the Planck analysis, and with the redshift distribution obtained from the Combined EIS-NVSS Survey Of Radio Sources (CENSORS). Our analysis is based on an optimal estimation of the two-point correlation function and makes use of a new mask that takes into account direction dependent effects of the observations, sidelobe effects of bright sources and galactic foreground. We also set a flux threshold and take the cosmic radio dipole into account. The latter turns out to be an essential step in the analysis. This improved cosmological analysis of the NVSS emphasizes the importance of a flux calibration that is robust and stable on large angular scales for future radio continuum surveys.

  2. Optical angular momentum in classical electrodynamics

    NASA Astrophysics Data System (ADS)

    Mansuripur, Masud

    2017-06-01

    Invoking Maxwell’s classical equations in conjunction with expressions for the electromagnetic (EM) energy, momentum, force, and torque, we use a few simple examples to demonstrate the nature of the EM angular momentum. The energy and the angular momentum of an EM field will be shown to have an intimate relationship; a source radiating EM angular momentum will, of necessity, pick up an equal but opposite amount of mechanical angular momentum; and the spin and orbital angular momenta of the EM field, when absorbed by a small particle, will be seen to elicit different responses from the particle.

  3. Astrophysical applications of high angular resolution array-telescopes

    NASA Technical Reports Server (NTRS)

    Linsley, J.

    1985-01-01

    The air shower array-telescopes which are currently being used to search for and study point sources of UHE gamma-rays have angular resolution similar to 1 deg, limited by either the small total area of particle detectors or poor timing resolution. As the signal to noise ratio depends sensitively on the angular resolution, it seems certain that this figure will quickly be surpassed when second generation instruments come into operation. Since the trajectories of galactic cosmic rays with E 100,000 GeV are practically straight lines on scales of 1 A.U. or less, these new instruments will be able to observe a shadow cast by the Moon (angular diameter 0.5 deg). Although the angular diameter of the Sun is practically the same, its shadow will be more complex because of its magnetic field. Thus, high angular resolution observations of the Sun afford a means of investigating the solar magnetic field, and also the charge composition of cosmic rays, including the ratio of antiprotons to protons.

  4. The human ocular torsion position response during yaw angular acceleration.

    PubMed

    Smith, S T; Curthoys, I S; Moore, S T

    1995-07-01

    Recent results by Wearne [(1993) Ph.D. thesis] using the scleral search-coil method of measuring eye position indicate that changes in ocular torsion position (OTP) occur during yaw angular acceleration about an earth vertical axis. The present set of experiments, using an image processing method of eye movement measurement free from the possible confound of search coil slippage, demonstrates the generality and repeatability of this phenomenon and examines its possible causes. The change in torsion position is not a linear vestibulo-ocular reflex (LVOR) response to interaural linear acceleration stimulation of the otoliths, but rather the effect is dependent on the characteristics of the angular acceleration stimulus, commencing at the onset and decaying at the offset of the angular acceleration. In the experiments reported here, the magnitude of the angular acceleration stimulus was varied and the torsion position response showed corresponding variations. We consider that the change in torsion position observed during angular acceleration is most likely to be due to activity of the semicircular canals.

  5. Plate tectonics conserves angular momentum

    NASA Astrophysics Data System (ADS)

    Bowin, C.

    2010-03-01

    A new combined understanding of plate tectonics, Earth internal structure, and the role of impulse in deformation of the Earth's crust is presented. Plate accelerations and decelerations have been revealed by iterative filtering of the quaternion history for the Euler poles that define absolute plate motion history for the past 68 million years, and provide an unprecedented precision for plate angular rotation variations with time at 2-million year intervals. Stage poles represent the angular rotation of a plate's motion between adjacent Euler poles, and from which the maximum velocity vector for a plate can be determined. The consistent maximum velocity variations, in turn, yield consistent estimates of plate accelerations and decelerations. The fact that the Pacific plate was shown to accelerate and decelerate, implied that conservation of plate tectonic angular momentum must be globally conserved, and that is confirmed by the results shown here (total angular momentum ~1.4+27 kg m2 s-1). Accordingly, if a plate decelerates, other plates must increase their angular momentums to compensate. In addition, the azimuth of the maximum velocity vectors yields clues as to why the "bend" in the Emperor-Hawaiian seamount trend occurred near 46 Myr. This report summarizes processing results for 12 of the 14 major tectonic plates of the Earth (except for the Juan de Fuca and Philippine plates). Plate accelerations support the contention that plate tectonics is a product of torques that most likely are sustained by the sinking of positive density anomalies revealed by geoid anomalies of the degree 4-10 packet of the Earth's spherical harmonic coefficients. These linear positive geoid anomalies underlie plate subduction zones and are presumed due to phase changes in subducted gabbroic lithosphere at depth in the upper lower mantle (above 1200 km depth). The tectonic plates are pulled along by the sinking of these positive mass anomalies, rather than moving at near constant

  6. High Orbital Angular Momentum Harmonic Generation

    NASA Astrophysics Data System (ADS)

    Vieira, J.; Trines, R. M. G. M.; Alves, E. P.; Fonseca, R. A.; Mendonça, J. T.; Bingham, R.; Norreys, P.; Silva, L. O.

    2016-12-01

    We identify and explore a high orbital angular momentum (OAM) harmonics generation and amplification mechanism that manipulates the OAM independently of any other laser property, by preserving the initial laser wavelength, through stimulated Raman backscattering in a plasma. The high OAM harmonics spectra can extend at least up to the limiting value imposed by the paraxial approximation. We show with theory and particle-in-cell simulations that the orders of the OAM harmonics can be tuned according to a selection rule that depends on the initial OAM of the interacting waves. We illustrate the high OAM harmonics generation in a plasma using several examples including the generation of prime OAM harmonics. The process can also be realized in any nonlinear optical Kerr media supporting three-wave interactions.

  7. Angular response of hot wire probes

    NASA Astrophysics Data System (ADS)

    di Mare, L.; Jelly, T. O.; Day, I. J.

    2017-03-01

    A new equation for the convective heat loss from the sensor of a hot-wire probe is derived which accounts for both the potential and the viscous parts of the flow past the prongs. The convective heat loss from the sensor is related to the far-field velocity by an expression containing a term representing the potential flow around the prongs, and a term representing their viscous effect. This latter term is absent in the response equations available in the literature but is essential in representing some features of the observed response of miniature hot-wire probes. The response equation contains only four parameters but it can reproduce, with great accuracy, the behaviour of commonly used single-wire probes. The response equation simplifies the calibration the angular response of rotated slanted hot-wire probes: only standard King’s law parameters and a Reynolds-dependent drag coefficient need to be determined.

  8. Angular reduction in multiparticle matrix elements

    NASA Astrophysics Data System (ADS)

    Lehman, D. R.; Parke, W. C.

    1989-12-01

    A general method for reduction of coupled spherical harmonic products is presented. When the total angular coupling is zero, the reduction leads to an explicitly real expression in the scalar products of the unit vector arguments of the spherical harmonics. For nonscalar couplings, the reduction gives Cartesian tensor forms for the spherical harmonic products; tensors built from the physical vectors in the original expression. The reduction for arbitrary couplings is given in closed form, making it amenable to symbolic manipulation on a computer. The final expressions do not depend on a special choice of coordinate axes, nor do they contain azimuthal quantum number summations, or do they have complex tensor terms for couplings to a scalar; consequently, they are easily interpretable from the properties of the physical vectors they contain.

  9. Angular momentum effects in subbarrier fusion

    SciTech Connect

    Halbert, M.L.; Beene, J.R.; Hensley, D.C.; Honkanen, K.; Semkow, T.M.; Abenante, V.; Sarantites, D.G.; Li, Z.

    1988-01-01

    Angular-momentum distributions sigma/sub L/ for the compound nucleus /sup 164/Yb were deduced from measurements of ..gamma..-ray multiplicity for all significant evaporation residues from fusion of /sup 64/Ni and /sup 100/Mo at and below the Coulomb barrier. The excitation functions can be reproduced with coupled-channels calculations only if additional coupling beyond the known inelastic strengths is included. Even with this augmented coupling, however, at the lowest bombarding energies the experimental sigma/sub L/ extend to higher L values than the predictions. Single-barrier penetration models for a potential with an energy-dependent depth and shape fitted to the excitation function likewise underestimate the role of high-L partial waves. Somewhat better success is achieved with models in which fission is allowed to occur at distances comparable with or even larger than the Coulomb barrier radius. 24 refs., 3 figs., 2 tabs.

  10. High Orbital Angular Momentum Harmonic Generation.

    PubMed

    Vieira, J; Trines, R M G M; Alves, E P; Fonseca, R A; Mendonça, J T; Bingham, R; Norreys, P; Silva, L O

    2016-12-23

    We identify and explore a high orbital angular momentum (OAM) harmonics generation and amplification mechanism that manipulates the OAM independently of any other laser property, by preserving the initial laser wavelength, through stimulated Raman backscattering in a plasma. The high OAM harmonics spectra can extend at least up to the limiting value imposed by the paraxial approximation. We show with theory and particle-in-cell simulations that the orders of the OAM harmonics can be tuned according to a selection rule that depends on the initial OAM of the interacting waves. We illustrate the high OAM harmonics generation in a plasma using several examples including the generation of prime OAM harmonics. The process can also be realized in any nonlinear optical Kerr media supporting three-wave interactions.

  11. CONNECTING ANGULAR MOMENTUM AND GALACTIC DYNAMICS: THE COMPLEX INTERPLAY BETWEEN SPIN, MASS, AND MORPHOLOGY

    SciTech Connect

    Teklu, Adelheid F.; Remus, Rhea-Silvia; Dolag, Klaus; Beck, Alexander M.; Burkert, Andreas; Schulze, Felix; Steinborn, Lisa K.; Schmidt, Andreas S.

    2015-10-10

    The evolution and distribution of the angular momentum of dark matter (DM) halos have been discussed in several studies over the past decades. In particular, the idea arose that angular momentum conservation should allow us to infer the total angular momentum of the entire DM halo from measuring the angular momentum of the baryonic component, which is populating the center of the halo, especially for disk galaxies. To test this idea and to understand the connection between the angular momentum of the DM halo and its galaxy, we use a state-of-the-art, hydrodynamical cosmological simulation taken from the set of Magneticum Pathfinder simulations. Thanks to the inclusion of the relevant physical processes, the improved underlying numerical methods, and high spatial resolution, we successfully produce populations of spheroidal and disk galaxies self-consistently. Thus, we are able to study the dependence of galactic properties on their morphology. We find that (1) the specific angular momentum of stars in disk and spheroidal galaxies as a function of their stellar mass compares well with observational results; (2) the specific angular momentum of the stars in disk galaxies is slightly smaller compared to the specific angular momentum of the cold gas, in good agreement with observations; (3) simulations including the baryonic component show a dichotomy in the specific stellar angular momentum distribution when splitting the galaxies according to their morphological type (this dichotomy can also be seen in the spin parameter, where disk galaxies populate halos with slightly larger spin compared to spheroidal galaxies); (4) disk galaxies preferentially populate halos in which the angular momentum vector of the DM component in the central part shows a better alignment to the angular momentum vector of the entire halo; and (5) the specific angular momentum of the cold gas in disk galaxies is approximately 40% smaller than the specific angular momentum of the total DM halo

  12. Two-axis angular effector

    DOEpatents

    Vaughn, Mark R.; Robinett, III, Rush D.; Phelan, John R.; Van Zuiden, Don M.

    1997-01-21

    A new class of coplanar two-axis angular effectors. These effectors combine a two-axis rotational joint analogous to a Cardan joint with linear actuators in a manner to produce a wider range of rotational motion about both axes defined by the joint. This new class of effectors also allows design of robotic manipulators having very high strength and efficiency. These effectors are particularly suited for remote operation in unknown surroundings, because of their extraordinary versatility. An immediate application is to the problems which arise in nuclear waste remediation.

  13. The tetrahexahedric angular Calogero model

    NASA Astrophysics Data System (ADS)

    Correa, Francisco; Lechtenfeld, Olaf

    2015-10-01

    The spherical reduction of the rational Calogero model (of type A n-1 and after removing the center of mass) is considered as a maximally superintegrable quantum system, which describes a particle on the ( n-2)-sphere subject to a very particular potential. We present a detailed analysis of the simplest non-separable case, n=4, whose potential is singular at the edges of a spherical tetrahexahedron. A complete set of independent conserved charges and of Hamiltonian intertwiners is constructed, and their algebra is elucidated. They arise from the ring of polynomials in Dunkl-deformed angular momenta, by classifying the subspaces invariant and antiinvariant under all Weyl reflections, respectively.

  14. Variable Distance Angular Symbology Reader

    NASA Technical Reports Server (NTRS)

    Schramm, Harry F., Jr. (Inventor); Corder, Eric L. (Inventor)

    2006-01-01

    A variable distance angular symbology, reader utilizes at least one light source to direct light through a beam splitter and onto a target. A target may be angled relative to the impinging light beam up to and maybe even greater than 45deg. A reflected beam from the target passes through the beam splitter and is preferably directed 90deg relative to the light source through a telecentric lens to a scanner which records an image of the target such as a direct part marking code.

  15. Metal-ion Complexation Effects in C 1s-NEXAFS Spectra of Carboxylic Acids—Evidence by Quantum Chemical Calculations

    SciTech Connect

    Armbruster, M.; Schimmelpfennig, B; Plaschke, M; Rothe, J; Denecke, M; Klenze, R

    2009-01-01

    Previous systematic C 1s-NEXAFS studies carried out for humic acid (HA) loaded with polyvalent metal cations (Mn+) reveal spectral features which were postulated to result from metal ion complexation: a strong decrease of the C 1s (COO-) ? p*Cdouble bond; length as m-dashO transition intensity and the appearance of a new absorption feature at slightly lower energy adjacent to the carboxyl resonance. Although spectroscopic results for the Mn+-PAA (polyacrylic acid) system (selected as model for structurally ill-defined HA) reveal the same spectral features, evidence by an independent approach for interpretation of these features is desirable. It is well established that quantum chemical calculations are capable of reproducing transition features in C 1s core excitation spectra of small organic molecules, e.g., acetate, which is chosen here as a fragment containing the complexing group to model the macromolecular HA and PAA systems. In this study, the RI-ADC(2) approach, as implemented in the TURBOMOLE program package, is applied to calculate vertical core excitation spectra of various metal acetates and the acetate anion. An energy shift (?f) between the C 1s (COO-) ? p*Cdouble bond; length as m-dashO transition of the acetate anion and various metal cation acetates is established. Calculated shifts are very similar to the experimentally observed values for the energy difference between the C 1s (COO-) ? p*Cdouble bond; length as m-dashO peak and the absorption feature appearing after metal ion complexation in Mn+-PAA/PAA. According to our computations, structural changes of the acetate complexes (e.g., the O-CeO bond angle) compared to the free acetate anion are predominantly responsible for the spectral changes observed upon metal ion complexation.

  16. Zebra tape identification for the instantaneous angular speed computation and angular resampling of motorbike valve train measurements

    NASA Astrophysics Data System (ADS)

    Rivola, Alessandro; Troncossi, Marco

    2014-02-01

    An experimental test campaign was performed on the valve train of a racing motorbike engine in order to get insight into the dynamic of the system. In particular the valve motion was acquired in cold test conditions by means of a laser vibrometer able to acquire displacement and velocity signals. The valve time-dependent measurements needed to be referred to the camshaft angular position in order to analyse the data in the angular domain, as usually done for rotating machines. To this purpose the camshaft was fitted with a zebra tape whose dark and light stripes were tracked by means of an optical probe. Unfortunately, both manufacturing and mounting imperfections of the employed zebra tape, resulting in stripes with slightly different widths, precluded the possibility to directly obtain the correct relationship between camshaft angular position and time. In order to overcome this problem, the identification of the zebra tape was performed by means of the original and practical procedure that is the focus of the present paper. The method consists of three main steps: namely, an ad-hoc test corresponding to special operating conditions, the computation of the instantaneous angular speed, and the final association of the stripes with the corresponding shaft angular position. The results reported in the paper demonstrate the suitability of the simple procedure for the zebra tape identification performed with the final purpose to implement a computed order tracking technique for the data analysis.

  17. Controlling neutron orbital angular momentum.

    PubMed

    Clark, Charles W; Barankov, Roman; Huber, Michael G; Arif, Muhammad; Cory, David G; Pushin, Dmitry A

    2015-09-24

    The quantized orbital angular momentum (OAM) of photons offers an additional degree of freedom and topological protection from noise. Photonic OAM states have therefore been exploited in various applications ranging from studies of quantum entanglement and quantum information science to imaging. The OAM states of electron beams have been shown to be similarly useful, for example in rotating nanoparticles and determining the chirality of crystals. However, although neutrons--as massive, penetrating and neutral particles--are important in materials characterization, quantum information and studies of the foundations of quantum mechanics, OAM control of neutrons has yet to be achieved. Here, we demonstrate OAM control of neutrons using macroscopic spiral phase plates that apply a 'twist' to an input neutron beam. The twisted neutron beams are analysed with neutron interferometry. Our techniques, applied to spatially incoherent beams, demonstrate both the addition of quantum angular momenta along the direction of propagation, effected by multiple spiral phase plates, and the conservation of topological charge with respect to uniform phase fluctuations. Neutron-based studies of quantum information science, the foundations of quantum mechanics, and scattering and imaging of magnetic, superconducting and chiral materials have until now been limited to three degrees of freedom: spin, path and energy. The optimization of OAM control, leading to well defined values of OAM, would provide an additional quantized degree of freedom for such studies.

  18. Measurement of the Angular Distributions of Drell-Yan Dimuons

    NASA Astrophysics Data System (ADS)

    Bowen, Brandon; Fermilab E-906/SeaQuest Collaboration

    2011-10-01

    The angular differential cross section for the Drell-Yan (DY) process can be parametrized by dσ/dΩ ~ 1 + λcos2 θ + μsin 2 θcosφ +ν/2sin2 θcos 2 φ , where λ, μ, and ν are the angular distribution parameters vs pT. θ and φ denote the polar and azimuthal angles, respectively for the positive lepton produced. The Lam-Tung relation, 1 - λ = 2 ν , was validated by Fermilab E-866 for proton induced Drell-Yan scattering; However pion induced DY shows a much stronger cos2 θ angular dependence and a violation of the Lam-Tung relation. In pion induced DY the antiquark is a valance quark, whereas in proton induced DY (in a forward acceptance spectrometer) it is a sea quark, so E-866 probed the antiquark sea of the nucleon. The SeaQuest experiment, also using proton induced DY, will improve on the measurement of the angular dependencies at a lower energy (120 GeV), taking advantage lower backgrounds and an increase in Drell-Yan cross section at lower energies. The Boer-Mulders correlates the quark correlates between the quark transverse spin and momentum. Improved data from SeaQuest will help determine the Boer-Mulders function. Funding for this work was provided in part by the U.S. DOE Office of Science.

  19. Relaxation of rotational angular momentum of polar diatomic molecules in simple liquids

    SciTech Connect

    Padilla, A.; Perez, J.

    2007-03-15

    The relaxation processes of rotational angular momentum of polar diatomic molecules diluted in simple liquids are analyzed by applying a non-Markovian relaxation theory to the study of the binary time autocorrelation function of the angular momentum. This non-Markovian theory was previously applied to the study of the infrared and Raman spectroscopy, and also to the analysis of the rotational energy relaxation processes. We have obtained non-Markovian evolution equations for the two-time j-level angular momentum correlation components involved in the angular momentum correlation function. In these equations, the time-dependent angular momentum transfer rates and the pure orientational angular transfer rates are given in terms of the binary time autocorrelation function of the diatomic-solvent anisotropic interaction. The non-Markovian evolution equations converge to Markovian ones in the long time limit, reaching the angular momentum transfer rates in the usual time-independent form. Alternative time scales for the angular relaxation processes, relative to the individual rotational processes as well as to the global decay correlations, are introduced and analyzed. The theory is applied to the study of the angular momentum relaxation processes of HCl diluted in liquid SF{sub 6}, a system for which rotational energy relaxation and infrared and Raman spectroscopy was previously analyzed in the scope of the same theory.

  20. Angular Positioning Sensor for Space Mechanisms

    NASA Astrophysics Data System (ADS)

    Steiner, Nicolas; Chapuis, Dominique

    2013-09-01

    Angular position sensors are used on various rotating mechanisms such as solar array drive mechanisms, antenna pointing mechanisms, scientific instruments, motors or actuators.Now a days, potentiometers and encoders are mainly used for angular measurement purposes. Both of them have their own pros and cons.As alternative, Ruag Space Switzerland Nyon (RSSN) is developing and qualifying two innovative technologies of angular position sensors which offer easy implementation, medium to very high lifetime and high flexibility with regards to the output signal shape/type.The Brushed angular position sensor uses space qualified processes which are already flying on RSSN's sliprings for many years. A large variety of output signal shape can be implemented to fulfill customer requirements (digital, analog, customized, etc.).The contactless angular position sensor consists in a new radiation hard Application Specific Integrated Circuit (ASIC) based on the Hall effect and providing the angular position without complex processing algorithm.

  1. Oral candidiasis and angular cheilitis.

    PubMed

    Sharon, Victoria; Fazel, Nasim

    2010-01-01

    Candidiasis, an often encountered oral disease, has been increasing in frequency. Most commonly caused by the overgrowth of Candida albicans, oral candidiasis can be divided into several categories including acute and chronic forms, and angular cheilitis. Risk factors for the development of oral candidiasis include immunosuppression, wearing of dentures, pharmacotherapeutics, smoking, infancy and old age, endocrine dysfunction, and decreased salivation. Oral candidiasis may be asymptomatic. More frequently, however, it is physically uncomfortable, and the patient may complain of burning mouth, dysgeusia, dysphagia, anorexia, and weight loss, leading to nutritional deficiency and impaired quality of life. A plethora of antifungal treatments are available. The overall prognosis of oral candidiasis is good, and rarely is the condition life threatening with invasive or recalcitrant disease.

  2. GPDs and Orbital Angular Momentum

    NASA Astrophysics Data System (ADS)

    Burkardt, Matthias

    2017-05-01

    Generalized Parton Distributions provide information on the distribution of quarks in impact parameter space. For transversely polarized nucleons, these impact parameter distributions are transversely distorted and this deviation from axial symmetry leads on average to a net transverse force from the spectators on the active quark in a DIS experiment. This force when acting along the whole trajectory of the active quark leads to transverse single-spin asymmetries. For a longitudinally polarized nucleon target, the transverse force implies a torque acting on the quark Orbital Angular Momentum (OAM). The resulting change in OAM as the quark leaves the target equals the difference between the Jaffe-Manohar and Ji OAMs. In the context of the scalar diquark model we demonstrate that the effect from that torque contributes at the same order as single-spin asymmetries.

  3. Chirality and the angular momentum of light.

    PubMed

    Cameron, Robert P; Götte, Jörg B; Barnett, Stephen M; Yao, Alison M

    2017-02-28

    Chirality is exhibited by objects that cannot be rotated into their mirror images. It is far from obvious that this has anything to do with the angular momentum of light, which owes its existence to rotational symmetries. There is nevertheless a subtle connection between chirality and the angular momentum of light. We demonstrate this connection and, in particular, its significance in the context of chiral light-matter interactions.This article is part of the themed issue 'Optical orbital angular momentum'.

  4. Chirality and the angular momentum of light

    NASA Astrophysics Data System (ADS)

    Cameron, Robert P.; Götte, Jörg B.; Barnett, Stephen M.; Yao, Alison M.

    2017-02-01

    Chirality is exhibited by objects that cannot be rotated into their mirror images. It is far from obvious that this has anything to do with the angular momentum of light, which owes its existence to rotational symmetries. There is nevertheless a subtle connection between chirality and the angular momentum of light. We demonstrate this connection and, in particular, its significance in the context of chiral light-matter interactions. This article is part of the themed issue 'Optical orbital angular momentum'.

  5. Orbital angular momentum in phase space

    SciTech Connect

    Rigas, I.; Sanchez-Soto, L.L.; Klimov, A.B.; Rehacek, J.; Hradil, Z.

    2011-02-15

    Research Highlights: > We propose a comprehensive Weyl-Wigner formalism for the canonical pair angle-angular momentum. > We present a simple and useful toolkit for the practitioner. > We derive simple evolution equations in terms of a star product in the semiclassical limit. - Abstract: A comprehensive theory of the Weyl-Wigner formalism for the canonical pair angle-angular momentum is presented. Special attention is paid to the problems linked to rotational periodicity and angular-momentum discreteness.

  6. The Angular Momentum of the Solar System

    NASA Astrophysics Data System (ADS)

    Cang, Rongquin; Guo, Jianpo; Hu, Juanxiu; He, Chaoquiong

    2016-05-01

    The angular momentum of the Solar System is a very important physical quantity to the formation and evolution of the Solar System. Previously, the spin angular momentum of the Sun and the orbital angular momentum of the Eight Giant Planets were only taken into consideration, when researchers calculated the angular momentum of the Solar System. Nowadays, it seems narrow and conservative. Using Eggleton's code, we calculate the rotational inertia of the Sun. Furthermore, we obtain that the spin angular momentum of the Sun is 1.8838 x 10^41 kg m^2 s^-1. Besides the spin angular momentum of the Sun and the orbital angular momentum of the Eight Giant Planets, we also account for the orbital angular momentum of the Asteroid Belt, the Kuiper Belt, the Oort Cloud, the Ninth Giant Planet and the Solar Companion. We obtain that the angular momentum of the whole Solar System is 3.3212 x 10^45 kg m^2 s^-1.

  7. Angular momentum algebra for symbolic expansions in atomic structure theory

    NASA Astrophysics Data System (ADS)

    Matulioniene, Rasa

    angular momentum theory, we derive the explicit dependence of the expansion coefficients on the quantum numbers of the correlation orbitals. Both relativistic (jj-coupled) and nonrelativistic (LS-coupled) multiconfiguration bases are considered. In addition, we report on a preliminary computer program that illustrates the application of this new method in parallel computations.

  8. Semiclassical model for attosecond angular streaking.

    PubMed

    Smolarski, M; Eckle, P; Keller, U; Dörner, R

    2010-08-16

    Attosecond angular streaking is a new technique to achieve unsurpassed time accuracy of only a few attoseconds. Recently this has been successfully used to set an upper limit on the electron tunneling delay time in strong laser field ionization. The measurement technique can be modeled with either the time-dependent Schrödinger equation (TDSE) or a more simple semiclassical approach that describes the process in two steps in analogy to the three-step model in high harmonic generation (HHG): step one is the tunnel ionization and step two is the classical motion in the strong laser field. Here we describe in detail a semiclassical model which is based on the ADK theory for the tunneling step, with subsequent classical propagation of the electron in the laser field. We take into account different ellipticities of the laser field and a possible wavelength-dependent ellipticity that is typically observed for pulses in the two-optical-cycle regime. This semiclassical model shows excellent agreement with the experimental result.

  9. Possibility of high gradient magnetic separation in angular steps

    SciTech Connect

    Iacob, G.; Rezlescu, N.

    1997-11-01

    Using a rotating HGMS ordered matrix in a quasi-transversal configuration, experiments have been performed to study the dependence of the captured mass m{sub S} on the angle {alpha} between the direction of the applied field H{sub 0} and the ferromagnetic wires. The ordered dependence of m{sub S} on {alpha} registered experimentally reveals the possibility to successively separate a granular mixture by an adequate choice of the inclination angles (angular steps) without modifying the applied field H{sub 0} or the average flow velocity v{sub a}. Relationships were derived connecting the magnetic susceptibilities of the mixture components with the inclination angle {alpha} in order to accomplish such a separation in angular steps.

  10. Stellar angular diameters from occultation observations.

    NASA Astrophysics Data System (ADS)

    Qian, B.-C.

    This paper reviews the history of measuring stellar angular diameters from lunar occultation observations and the techniques of data analysis. Several effects which can affect the results of measurement are discussed. The author finds that there may be systematic errors in angular diameters measured by various observatories for Aldebaran.

  11. The Orbital Angular Momentum Sum Rule

    NASA Astrophysics Data System (ADS)

    Aslan, Fatma; Burkardt, Matthias

    2015-10-01

    As an alternative to the Ji sum rule for the quark angular momentum, a sum rule for the quark orbital angular momentum, based on a twist-3 generalized parton distribution, has been suggested. We study the validity of this sum rule in the context of scalar Yukawa interactions as well as in QED for an electron.

  12. Orbital angular momentum: a personal memoir.

    PubMed

    Allen, L

    2017-02-28

    A definitive statement of the model used to describe orbital angular momentum is essentially now available. Its early history, and the interaction of those who played key roles in its development over 20 years ago in its development, is outlined in this Memoir.This article is part of the themed issue 'Optical orbital angular momentum'.

  13. Angular Momentum Eigenstates for Equivalent Electrons.

    ERIC Educational Resources Information Center

    Tuttle, E. R.; Calvert, J. B.

    1981-01-01

    Simple and efficient methods for adding angular momenta and for finding angular momentum eigenstates for systems of equivalent electrons are developed. Several different common representations are used in specific examples. The material is suitable for a graduate course in quantum mechanics. (SK)

  14. Orbital angular momentum: a personal memoir

    NASA Astrophysics Data System (ADS)

    Allen, L.

    2017-02-01

    A definitive statement of the model used to describe orbital angular momentum is essentially now available. Its early history, and the interaction of those who played key roles in its development over 20 years ago in its development, is outlined in this Memoir. This article is part of the themed issue 'Optical orbital angular momentum'.

  15. Angular momentum decomposition of Richardson's pairs

    SciTech Connect

    Dussel, G. G.; Sofia, H. M.

    2008-07-15

    The angular momentum decomposition of pairs obtained using Richardson's exact solution of the pairing Hamiltonian for the deformed {sup 174}Yb nucleus are displayed. The probabilities for low angular momenta of the collective pairs are strikingly different from the ones obtained in the BCS ground state.

  16. Lunar occultation stellar angular diameter measurements. II

    NASA Astrophysics Data System (ADS)

    Beavers, W. I.; Eitter, J. J.; Cadmus, R. R., Jr.

    1981-09-01

    The results of analyses from 14 of the 200 lunar occultation events observed at the Fick Observatory between November 1972 and January 1975 are reported. These include two measurements with large angular diameters, seven with small or barely resolvable diameters, two point sources, and three cases in which the records are too noisy to allow angular diameter measurements.

  17. Angular Momentum Eigenstates for Equivalent Electrons.

    ERIC Educational Resources Information Center

    Tuttle, E. R.; Calvert, J. B.

    1981-01-01

    Simple and efficient methods for adding angular momenta and for finding angular momentum eigenstates for systems of equivalent electrons are developed. Several different common representations are used in specific examples. The material is suitable for a graduate course in quantum mechanics. (SK)

  18. Orbital angular momentum in the nucleon

    SciTech Connect

    Garvey, Gerald T.

    2010-05-15

    Analysis of the measured value of the integrated d-bar-u-bar asymmetry (I{sub fas} = 0.147 +- 0.027) in the nucleon show it to arise from nucleon fluctuations into baryon plus pion. Requiring angular momentum conservation in these fluctuations shows the associated orbital angular momentum is equal to the value of the flavor asymmetry.

  19. Angular sensitivity for a Fabry-Perot structure incorporating different dielectric materials

    NASA Astrophysics Data System (ADS)

    Wu, Shangliang; Ye, Yan; Zhou, Yun; Huang, Wenbin; Liu, Yanhua; Qiao, Wen; Wang, Yanyan; Luo, Minghui; Chen, Linsen

    2016-11-01

    Color filters based on different Fabry-Perot structures are investigated extensively, and incident angle dependency is an important characteristic in practical applications. Here, we investigated a color filter incorporating a Fabry-Perot structure, discussing its reflective angular sensitivity related to refractive index of its dielectric material. By finite difference time domain(FDTD) theory, the refractive index of the dielectric material is found to influence the angular sensitivity greatly while the optical thickness keeps constant. The simulated results shows that the higher the dielectric layer's refractive index is, the more angular insensitive of the reflection will be obtained and a good angular insensitive will achieved when the refractive index is larger than 2.1. Finally, samples with different dielectric layer are fabricated in experiment and the measured results verify influence of the refractive index of dielectric layer on the spectra angular sensitivity, which is helpful for the application of color filter in color display, image sensors and decoration.

  20. Generation of angular-momentum-dominated electron beams from a photoinjector

    NASA Astrophysics Data System (ADS)

    Sun, Y.-E.; Piot, P.; Kim, K.-J.; Barov, N.; Lidia, S.; Santucci, J.; Tikhoplav, R.; Wennerberg, J.

    2004-12-01

    Various projects under study require an angular-momentum-dominated electron beam generated by a photoinjector. Some of the proposals directly use the angular-momentum-dominated beams (e.g., electron cooling of heavy ions), while others require the beam to be transformed into a flat beam (e.g., possible electron injectors for light sources and linear colliders). In this paper we report our experimental study of an angular-momentum-dominated beam produced in a photoinjector, addressing the dependencies of angular momentum on initial conditions. We also briefly discuss the removal of angular momentum. The results of the experiment, carried out at the Fermilab/NICADD Photoinjector Laboratory, are found to be in good agreement with theoretical and numerical models.

  1. The angular momentum of the Oort cloud

    SciTech Connect

    Weissman, P.R. )

    1991-01-01

    An evaluation is made of the work of Marochnik et al. (1988), which estimated that the angular momentum of the Oort cloud is 2-3 orders of magnitude greater than the planetary system's total angular momentum. It is noted that most of the angular momentum in the currently observed Oort cloud is the result of the effects of external perturbers over the solar system's history, and it is demonstrated that the total current angular momentum is probably in the 6.0 x 10 to the 50th to 1.1 x 10 to the 51st g sq cm/sec range; original angular momentum was probably a factor of 5 below such values. 21 refs.

  2. The angular momentum of the Oort cloud

    NASA Technical Reports Server (NTRS)

    Weissman, Paul R.

    1991-01-01

    An evaluation is made of the work of Marochnik et al. (1988), which estimated that the angular momentum of the Oort cloud is 2-3 orders of magnitude greater than the planetary system's total angular momentum. It is noted that most of the angular momentum in the currently observed Oort cloud is the result of the effects of external perturbers over the solar system's history, and it is demonstrated that the total current angular momentum is probably in the 6.0 x 10 to the 50th to 1.1 x 10 to the 51st g sq cm/sec range; original angular momentum was probably a factor of 5 below such values.

  3. Physical angular momentum separation for QED

    NASA Astrophysics Data System (ADS)

    Sun, Weimin

    2017-04-01

    We study the non-uniqueness problem of the gauge-invariant angular momentum separation for the case of QED, which stems from the recent controversy concerning the proper definitions of the orbital angular momentum and spin operator of the individual parts of a gauge field system. For the free quantum electrodynamics without matter, we show that the basic requirement of Euclidean symmetry selects a unique physical angular momentum separation scheme from the multitude of the possible angular momentum separation schemes constructed using the various gauge-invariant extensions (GIEs). Based on these results, we propose a set of natural angular momentum separation schemes for the case of interacting QED by invoking the formalism of asymptotic fields. Some perspectives on such a problem for the case of QCD are briefly discussed.

  4. Angular Resolution Enhanced Spitzer images

    NASA Astrophysics Data System (ADS)

    Velusamy, T.; Beichman, C. A.; Backus, C. R.; Marsh, K. A.; Thompson, T. J.

    2004-05-01

    We have developed a 'HiRes' software for deconvolution of Spitzer images that increases the angular resolution by a factor of two to three over that obtainable in a standard mosaiced image. This software is an extension of the Maximum Correlation Method (MCM) described by Aumann et al. (1990 AJ, 99, 1674), incorporating features that are applicable to the Spitzer data and FFT convolutions to speed up. While the Spitzer Space Telescope provides unprecedented sensitivity in the infrared, its spatial resolution is limited by the relatively small aperture (0.85 m) of the primary mirror. In this paper we present resolution enhanced Spitzer images demonstrating the benefits of HiRes imaging: (1) The ability to detect sources below the diffraction-limited confusion level; at 160 micron, the corresponding increase in confusion-limited sensitivity is about a factor of two. (2) The ability to separate blended sources, and thereby provide guidance to point-source extraction procedures. (3) An improved ability to show the spatial morphology of resolved sources. This work was performed by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.

  5. Angular Momentum of Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    Butler, Kirsty M.; Obreschkow, Danail; Oh, Se-Heon

    2017-01-01

    We present measurements of baryonic mass {M}{{b}} and specific angular momentum (sAM) {j}{{b}} in 14 rotating dwarf Irregular (dIrr) galaxies from the LITTLE THINGS sample. These measurements, based on 21 cm kinematic data from the Very Large Array and stellar mass maps from the Spitzer Space Telescope, extend previous AM measurements by more than two orders of magnitude in {M}{{b}}. The dwarf galaxies show systematically higher {j}{{b}} values than expected from the {j}{{b}}\\propto {M}{{b}}2/3 scaling of spiral galaxies, representative of a scale-free galaxy formation scenario. This offset can be explained by decreasing baryon mass fractions {f}{{M}}={M}{{b}}/{M}{dyn} (where {M}{dyn} is the dynamical mass) with decreasing {M}{{b}} (for {M}{{b}}< {10}11 {M}ȯ ). We find that the sAM of neutral atomic hydrogen (H i) alone is about 2.5 times higher than that of the stars. The M–j relation of H i is significantly steeper than that of the stars, as a direct consequence of the systematic variation of the H i fraction with {M}{{b}}.

  6. Power calculation of linear and angular incremental encoders

    NASA Astrophysics Data System (ADS)

    Prokofev, Aleksandr V.; Timofeev, Aleksandr N.; Mednikov, Sergey V.; Sycheva, Elena A.

    2016-04-01

    Automation technology is constantly expanding its role in improving the efficiency of manufacturing and testing processes in all branches of industry. More than ever before, the mechanical movements of linear slides, rotary tables, robot arms, actuators, etc. are numerically controlled. Linear and angular incremental photoelectric encoders measure mechanical motion and transmit the measured values back to the control unit. The capabilities of these systems are undergoing continual development in terms of their resolution, accuracy and reliability, their measuring ranges, and maximum speeds. This article discusses the method of power calculation of linear and angular incremental photoelectric encoders, to find the optimum parameters for its components, such as light emitters, photo-detectors, linear and angular scales, optical components etc. It analyzes methods and devices that permit high resolutions in the order of 0.001 mm or 0.001°, as well as large measuring lengths of over 100 mm. In linear and angular incremental photoelectric encoders optical beam is usually formulated by a condenser lens passes through the measuring unit changes its value depending on the movement of a scanning head or measuring raster. Past light beam is converting into an electrical signal by the photo-detecter's block for processing in the electrical block. Therefore, for calculating the energy source is a value of the desired value of the optical signal at the input of the photo-detecter's block, which reliably recorded and processed in the electronic unit of linear and angular incremental optoelectronic encoders. Automation technology is constantly expanding its role in improving the efficiency of manufacturing and testing processes in all branches of industry. More than ever before, the mechanical movements of linear slides, rotary tables, robot arms, actuators, etc. are numerically controlled. Linear and angular incremental photoelectric encoders measure mechanical motion and

  7. Angular-momentum effects in subbarrier fusion

    SciTech Connect

    Halbert, M.L.; Beene, J.R.

    1993-11-01

    It has been known since about 1980 that fusion of heavy ions is greatly enhanced below the Coulomb barrier compared with normal barrier-penetration expectations. The excitation function for fusion of {sup 64}Ni + {sup 100}Mo measured in collaboration with a group at Washington University shows the effect clearly. The barrier energy is about 142 MeV; the lowest point is at about 90% of the barrier energy. The dotted curve is the prediction of a one-dimensional-barrier-penetration calculation of a type that reproduces the fusion of light projectiles very well. Several theoretical approaches have been successful in explaining the enhancement seen in much of the excitation-function data, but it cannot be said that a full understanding of the physics is in hand even after more than a decade of hard work. In fact, the reasonable success of several rather different models shows that the underlying phenomena are not well understood. Other types of data might be helpful in distinguishing among the many different theoretical approaches. An important kind of information not measured in most of the experiments is the dependence on {ell}, the angular momentum of the fusing system. We obtained such information on the cross sections, {sigma}{ell}, as a function of {ell} for the fusion of {sup 64}Ni and {sup 100}Mo using the Spin Spectrometer. This paper will first review the experimental method and data and then present results from a more sophisticated analysis of the same data.

  8. Wave Angular Momentum in Nonneutral Plasmas

    NASA Astrophysics Data System (ADS)

    Gould, Roy W.

    1999-11-01

    We show that angular momentum and energy are added or removed when exciting a mode, such as a diocotron, Trivelpiece-Gould, or Dubin mode, and we calculate the rates (with sign) at which angular momentum and energy are added by the application of a ``rotating wall" field. Excitation of a mode which rotates faster than the plasma increases the total angular momentum and total energy and compresses the plasma, whereas excitation of a mode which rotates slower than the plasma decreases the total angular momentum and total energy and expands the plasma, in accord with recent ``rotating wall" experiments^1. Furthermore, the transfer rates are sharply peaked when the angular velocity of the ``rotating wall" is equal to the angular velocity of a mode, because mode excitation is a resonant process. Thus mode excitation is a very efficient way to transfer angular momentum and energy to or from the plasma. We also calculate the torque on a spheroidal Coulomb crystal which is phase-locked^2 to a ``rotating wall" field, and discuss phase oscillations and the maximum rate of acceleration which can be achieved. 1 F. Anderegg et al, Phys. Rev. Lett. 81 4875 (1998). 2 X.-P. Huang et al, Phys. Rev. Lett. 80 73 (1998).

  9. Spectro-angular mapping of localized gold inclusions in Intralipid phantoms

    NASA Astrophysics Data System (ADS)

    Grabtchak, Serge; Palmer, Tyler J.; Whelan, William M.

    2012-06-01

    We have applied an interstitial radiance-based technique based on a spectro-angular mapping approach to the identification and angular localization of 250-nm and 5-nm Au nanoparticle-based inclusions and non-scattering (water only) inclusions in the Intralipid-1% liquid phantom. A combination of the point radiance spectroscopy and white light spectroscopy was used to measure angular resolved light distribution in 450-900 nm spectral range in Intralipid-1% with and without localized inclusions. Characteristic spectro-angular snapshots of the liquid phantom alone and with the localized inclusions were obtained. For liquid phantoms without inclusions, the snapshots demonstrate wavelength dependent light distribution inside the turbid medium. For liquid phantoms with gold inclusions, the approach allows to isolate the spectroscopic signatures of the inclusions from the background, identify locations of the inclusions in the angular domain and show how a presence of water in the inclusion affects spectral identification and angular localization of the target. For liquid phantoms with water-based inclusions, an ability of the inclusion to enhance photon density above reference values and angular dependent signatures were demonstrated. The technique is seen as a potential tool in prostate treatment and diagnostics with gold nanoparticles.

  10. Ground-state angular momentum, spectral asymmetry, and topology in chiral superfluids and superconductors

    NASA Astrophysics Data System (ADS)

    Ojanen, Teemu

    2016-05-01

    Recently, it was discovered that the ground-state orbital angular momentum in two-dimensional chiral superfluids with pairing symmetry (px+i py) ν depends on the winding number ν in a striking manner. The ground-state value for the ν =1 case is Lz=ℏ N /2 as expected by counting the Cooper pairs, while a dramatic cancellation takes place for ν >1 . The origin of the cancellation is associated with the topological edge states that appear in a finite geometry and give rise to a spectral asymmetry. Here, we study the reduction of orbital angular momentum for different potential profiles and pairing strengths, showing that the result Lz=ℏ N /2 is robust for ν =1 under all studied circumstances. We study how angular momentum depends on the gap size Δ /EF and obtain the result Lz=ℏ/ν 2 N (1 -μ/EF) for ν =2 ,3 . Thus, the gap dependence of Lz for ν <4 enters at most through the chemical potential while ν ≥4 is qualitatively different. In addition, we generalize the spectral asymmetry arguments to total angular momentum in the ground state of triplet superfluids where due to a spin-orbit coupling Lz is not a good quantum number. We find that the ground-state total angular momentum also behaves very differently depending on total angular momentum of the Cooper pairs.

  11. Angular Dependence of Vortex Annihilation Fields in Asymmetric Co Dots

    DTIC Science & Technology

    2009-07-15

    eScholarship provides open access, scholarly publishing services to the University of California and delivers a dynamic research platform to scholars...a dynamic research platform to scholars worldwide. the half loop and the vortex chirality can be well controlled. At intermediate angles the chirality...and the changing energy landscape during field cycling. The vortex annihilation along the half loop faces a higher energy barrier than along the

  12. Angular dependence of magnetic properties of 2% silicon electrical steel

    NASA Astrophysics Data System (ADS)

    Emura, M.; de Campos, M. F.; Landgraf, F. J. G.; Teixeira, J. C.

    2001-05-01

    In this work, we studied the anisotropy of the magnetic properties of a 2% silicon steel. Permeability, core losses, remanence and coercivity were analyzed in Epstein strips cut at 0°, 15°, 30°, 45°, 60°, 75° and 90° from the rolling direction. Coercive force monotonically increased from 0° to 90°, accompanied with a remanence decrease. On the other hand, a minimum in B50 and B25 was observed between 45 o and 60 o. This behavior can be explained by the steel sheet crystallographic texture, that shows a strong (1 1 0) [0 0 1] component, which develops the best properties in rolling direction (0 0 1) and is worse at 54°, where <1 1 1> lies. Losses behavior is more complex.

  13. Wave angular momentum in nonneutral plasmas

    NASA Astrophysics Data System (ADS)

    Gould, Roy W.

    1999-12-01

    Angular momentum and energy are added (or removed) when exciting a mode, such as a diocotron, Trivelpiece-Gould, or Dubin mode, and we discuss rates at which mode angular momentum and energy are added by applied fields. Excitation of a plasma mode is an effective way to transfer angular momentum and energy to the plasma because it is a resonant process. We relate this to recent experiments on compression and expansion of plasmas using a "rotating wall" field. We also calculate the torque on a Coulomb crystal which is phase-locked to a "rotating wall" field and describe phase oscillations and the maximum rate of acceleration which can be achieved.

  14. Angular momentum in the Local Group

    SciTech Connect

    Dunn, A.; Laflamme, R.

    1994-04-01

    We briefly review models for the Local Group and the acquisition of its angular momentum. We describe early attempts to understand the origin of the spin of the galaxies discussing the hypothesis that the Local Group has little angular momentum. Finally we show that using Peebles` least action principle there should be a rather large amount of orbital angular momentum compared to the magnitude of the spin of its galaxies. Therefore the Local Group cannot be thought as tidally isolated. Using Peebles` trajectories we give a possible set of trajectories for Local Group galaxies which would predict their spin.

  15. Chirality and the angular momentum of light

    PubMed Central

    Götte, Jörg B.; Barnett, Stephen M.; Yao, Alison M.

    2017-01-01

    Chirality is exhibited by objects that cannot be rotated into their mirror images. It is far from obvious that this has anything to do with the angular momentum of light, which owes its existence to rotational symmetries. There is nevertheless a subtle connection between chirality and the angular momentum of light. We demonstrate this connection and, in particular, its significance in the context of chiral light–matter interactions. This article is part of the themed issue ‘Optical orbital angular momentum’. PMID:28069764

  16. Orbital-angular-momentum transfer to optically levitated microparticles in vacuum

    NASA Astrophysics Data System (ADS)

    Mazilu, Michael; Arita, Yoshihiko; Vettenburg, Tom; Auñón, Juan M.; Wright, Ewan M.; Dholakia, Kishan

    2016-11-01

    We demonstrate the transfer of orbital angular momentum to an optically levitated microparticle in vacuum. The microparticle is placed within a Laguerre-Gaussian beam and orbits the annular beam profile with increasing angular velocity as the air drag coefficient is reduced. We explore the particle dynamics as a function of the topological charge of the levitating beam. Our results reveal that there is a fundamental limit to the orbital angular momentum that may be transferred to a trapped particle, dependent upon the beam parameters and inertial forces present.

  17. Optical Momentum, Spin, and Angular Momentum in Dispersive Media

    NASA Astrophysics Data System (ADS)

    Bliokh, Konstantin Y.; Bekshaev, Aleksandr Y.; Nori, Franco

    2017-08-01

    We examine the momentum, spin, and orbital angular momentum of structured monochromatic optical fields in dispersive inhomogeneous isotropic media. There are two bifurcations in this general problem: the Abraham-Minkowski dilemma and the kinetic (Poynting-like) versus canonical (spin-orbital) pictures. We show that the kinetic Abraham momentum describes the energy flux and group velocity of the wave in the medium. At the same time, we introduce novel canonical Minkowski-type momentum, spin, and orbital angular momentum densities of the field. These quantities exhibit fairly natural forms, analogous to the Brillouin energy density, as well as multiple advantages as compared with previously considered formalisms. As an example, we apply this general theory to inhomogeneous surface plasmon-polariton (SPP) waves at a metal-vacuum interface and show that SPPs carry a "supermomentum," proportional to the wave vector kp>ω /c , and a transverse spin, which can change its sign depending on the frequency ω .

  18. Properties of Angular Distributions in Drell-Yan Dilepton Production

    NASA Astrophysics Data System (ADS)

    McClellan, R. Evan; Peng, Jen-Chieh; Chang, Wen-Chen; Teryaev, Oleg

    2016-09-01

    We present a simple geometric model of the Drell-Yan process based on the unobserved `natural axis' (quark-anti-quark axis) in the dilepton rest frame. We utilize this model to interpret the recent high-precision Z-boson ``Drell-Yan'' angular distributions data from CMS. We find good agreement with the pT-dependence of the angular parameters, and extract the relative contributions from the quark-anti-quark and quark-gluon subprocesses, as well as the average degree of `non-coplanarity' between the quark axis and the hadron plane. We interpret the non-coplanarity as a result of higher-order QCD contributions, and as the cause of the observed Lam-Tung violation. Supported in part by the U.S. National Science Foundation (NSF PHY 15-06416) and the National Science Council of the Republic of China.

  19. Properties of Angular Distributions in Drell-Yan Dilepton Production

    NASA Astrophysics Data System (ADS)

    McClellan, R. Evan; Peng, Jen-Chieh; Chang, Wen-Chen; Teryaev, Oleg

    2017-01-01

    We present a simple geometric model of the Drell-Yan process based on the unobserved `natural axis' (quark-anti-quark axis) in the dilepton rest frame. We utilize this model to interpret the recent high-precision Z-boson ``Drell-Yan'' angular distributions data from CMS. We find good agreement with the pT-dependence of the angular parameters, and extract the relative contributions from the quark-anti-quark and quark-gluon subprocesses, as well as the average degree of `non-coplanarity' between the quark axis and the hadron plane. We interpret the non-coplanarity as a result of higher-order QCD contributions, and as the cause of the observed Lam-Tung violation.

  20. Optical Momentum, Spin, and Angular Momentum in Dispersive Media.

    PubMed

    Bliokh, Konstantin Y; Bekshaev, Aleksandr Y; Nori, Franco

    2017-08-18

    We examine the momentum, spin, and orbital angular momentum of structured monochromatic optical fields in dispersive inhomogeneous isotropic media. There are two bifurcations in this general problem: the Abraham-Minkowski dilemma and the kinetic (Poynting-like) versus canonical (spin-orbital) pictures. We show that the kinetic Abraham momentum describes the energy flux and group velocity of the wave in the medium. At the same time, we introduce novel canonical Minkowski-type momentum, spin, and orbital angular momentum densities of the field. These quantities exhibit fairly natural forms, analogous to the Brillouin energy density, as well as multiple advantages as compared with previously considered formalisms. As an example, we apply this general theory to inhomogeneous surface plasmon-polariton (SPP) waves at a metal-vacuum interface and show that SPPs carry a "supermomentum," proportional to the wave vector k_{p}>ω/c, and a transverse spin, which can change its sign depending on the frequency ω.

  1. Resolving enantiomers using the optical angular momentum of twisted light

    PubMed Central

    Brullot, Ward; Vanbel, Maarten K.; Swusten, Tom; Verbiest, Thierry

    2016-01-01

    Circular dichroism and optical rotation are crucial for the characterization of chiral molecules and are of importance to the study of pharmaceutical drugs, proteins, DNA, and many others. These techniques are based on the different interactions of enantiomers with circularly polarized components of plane wave light that carries spin angular momentum (SAM). For light carrying orbital angular momentum (OAM), for example, twisted or helical light, the consensus is that it cannot engage with the chirality of a molecular system as previous studies failed to demonstrate an interaction between optical OAM and chiral molecules. Using unique nanoparticle aggregates, we prove that optical OAM can engage with materials’ chirality and discriminate between enantiomers. Further, theoretical results show that compared to circular dichroism, mainly based on magnetic dipole contributions, the OAM analog helical dichroism (HD) is critically dependent on fundamentally different chiral electric quadrupole contributions. Our work opens new venues to study chirality and can find application in sensing and chiral spectroscopy. PMID:26998517

  2. Temperature dependent evolution of the local electronic structure of atmospheric plasma treated carbon nanotubes: Near edge x-ray absorption fine structure study

    SciTech Connect

    Roy, S. S.; Papakonstantinou, P.; Okpalugo, T. I. T.; Murphy, H.

    2006-09-01

    Near edge x-ray absorption fine structure (NEXAFS) spectroscopy has been employed to obtain the temperature dependent evolution of the electronic structure of acid treated carbon nanotubes, which were further modified by dielectric barrier discharge plasma processing in an ammonia atmosphere. The NEXAFS studies were performed from room temperature up to 900 deg. C. The presence of oxygen and nitrogen containing functional groups was observed in C K edge, N K edge, and O K edge NEXAFS spectra of the multiwalled carbon nanotubes. The N K edge spectra revealed three types of {pi}* features, the source of which was decisively identified by their temperature dependent evolution. It was established that these features are attributed to pyridinelike, NO, and graphitelike structures, respectively. The O K edge indicated that both carbonyl (C=O), {pi}*(CO), and ether C-O-C, {sigma}*(CO), functionalities were present. Upon heating in a vacuum to 900 deg. C the {pi}*(CO) resonances disappeared while the {sigma}*(CO) resonances were still present confirming their higher thermal stability. Heating did not produce a significant change in the {pi}* feature of the C K edge spectrum indicating that the tabular structure of the nanotubes is essentially preserved following the thermal decomposition of the functional groups on the nanotube surface.

  3. Angular Distribution of Ly(alpha) Resonant Photons Emergent from Optically Thick Medium

    DTIC Science & Technology

    2012-02-26

    solutions with the Eddington approximation, which assume I to be linearly dependent on the angular variable µ, yield similar frequency profiles of the photon...flux as that without the Eddington approximation. However, the solutions of the µ distribution evolution are significantly different from that given...by Eddington approximation. First, the angular distribution of I are found to be substantially de- pendent on the frequency of photons. For photons

  4. Observation of Interaction of Spin and Intrinsic Orbital Angular Momentum of Light.

    PubMed

    Vitullo, Dashiell L P; Leary, Cody C; Gregg, Patrick; Smith, Roger A; Reddy, Dileep V; Ramachandran, Siddharth; Raymer, Michael G

    2017-02-24

    The interaction of spin and intrinsic orbital angular momentum of light is observed, as evidenced by length-dependent rotations of both spatial patterns and optical polarization in a cylindrically symmetric isotropic optical fiber. Such rotations occur in a straight few-mode fiber when superpositions of two modes with parallel and antiparallel orientation of spin and intrinsic orbital angular momentum (IOAM=2ℏ) are excited, resulting from a degeneracy splitting of the propagation constants of the modes.

  5. Observation of Interaction of Spin and Intrinsic Orbital Angular Momentum of Light

    NASA Astrophysics Data System (ADS)

    Vitullo, Dashiell L. P.; Leary, Cody C.; Gregg, Patrick; Smith, Roger A.; Reddy, Dileep V.; Ramachandran, Siddharth; Raymer, Michael G.

    2017-02-01

    The interaction of spin and intrinsic orbital angular momentum of light is observed, as evidenced by length-dependent rotations of both spatial patterns and optical polarization in a cylindrically symmetric isotropic optical fiber. Such rotations occur in a straight few-mode fiber when superpositions of two modes with parallel and antiparallel orientation of spin and intrinsic orbital angular momentum (IOAM =2 ℏ ) are excited, resulting from a degeneracy splitting of the propagation constants of the modes.

  6. Polarization resolved angular optical scattering of aerosol particles

    NASA Astrophysics Data System (ADS)

    Redding, B.; Pan, Y.; Wang, C.; Videen, G.; Cao, Hui

    2014-05-01

    Real-time detection and identification of bio-aerosol particles are crucial for the protection against chemical and biological agents. The strong elastic light scattering properties of airborne particles provides a natural means for rapid, non-invasive aerosol characterization. Recent theoretical predictions suggested that variations in the polarization dependent angular scattering cross section could provide an efficient means of classifying different airborne particles. In particular, the polarization dependent scattering cross section of aggregate particles is expected to depend on the shape of the primary particles. In order to experimentally validate this prediction, we built a high throughput, sampling system, capable of measuring the polarization resolved angular scattering cross section of individual aerosol particles flowing through an interrogating volume with a single shot of laser pulse. We calibrated the system by comparing the polarization dependent scattering cross section of individual polystyrene spheres with that predicted by Mie theory. We then used the system to study different particles types: Polystyrene aggregates composed 500 nm spheres and Bacillus subtilis (BG, Anthrax simulant) spores composed of elongated 500 nm × 1000 nm cylinder-line particles. We found that the polarization resolved scattering cross section depends on the shape of the constituent elements of the aggregates. This work indicates that the polarization resolved scattering cross section could be used for rapid discrimination between different bio-aerosol particles.

  7. Supernovae at the Highest Angular Resolution

    NASA Technical Reports Server (NTRS)

    Dyk, S. Van; Weiler, K.; Sramek, R.; Panagia, N.; Lacey, C.; Montes, M.; Mercaide, J.; Lewin, W.; Fox, D.; Filippenko, A.; Peng, C.

    2000-01-01

    The study of supernovae (SNe) and their environments in host galaxies at the highest possible angular resolution in a number of wavelength regimes is providing vital clues to the nature of their progenitor stars.

  8. Unipolar motor and angular momentum conservation law

    NASA Astrophysics Data System (ADS)

    Mayer, V. V.; Varaksina, E. I.

    2017-07-01

    A simple unipolar electric motor is described. The motor is a closed electromechanical system. The proposed apparatus allows us to demonstrate angular momentum conservation law at a qualitative level.

  9. Angular velocity-based structural damage detection

    NASA Astrophysics Data System (ADS)

    Liao, Yizheng; Kiremidjian, Anne S.; Rajagopal, Ram; Loh, Chin-Hsiung

    2016-04-01

    Damage detection is an important application of structural health monitoring. With the recent development of sensing technology, additional information about structures, angular velocity, has become available. In this paper, the angular velocity signals obtained from gyroscopes are modeled as an autoregressive (AR) model. The damage sensitive features (DSFs) are defined as a function of the AR coefficients. It is found that the mean values of the DSF for the damaged and undamaged signals are different. Also, we show that the angular velocity- based AR model has a linear relationship with the acceleration-based AR model. To test the proposed damage detection method, the algorithm has been tested with the experimental data from a recent shake table test where the damage is introduced systemically. The results indicate that the change of DSF means is statistically significant, and the angular velocity-based DSFs are sensitive to damage.

  10. Orbital angular momentum 25 years on [Invited].

    PubMed

    Padgett, Miles J

    2017-05-15

    Twenty-five years ago Allen, Beijersbergen, Spreeuw, and Woerdman published their seminal paper establishing that light beams with helical phase-fronts carried an orbital angular momentum. Previously orbital angular momentum had been associated only with high-order atomic/molecular transitions and hence considered to be a rare occurrence. The realization that every photon in a laser beam could carry an orbital angular momentum that was in excess of the angular momentum associated with photon spin has led both to new understandings of optical effects and various applications. These applications range from optical manipulation, imaging and quantum optics, to optical communications. This brief review will examine some of the research in the field to date and consider what future directions might hold.

  11. Generalized Uncertainty Principle and angular momentum

    NASA Astrophysics Data System (ADS)

    Bosso, Pasquale; Das, Saurya

    2017-08-01

    Various models of quantum gravity suggest a modification of the Heisenberg's Uncertainty Principle, to the so-called Generalized Uncertainty Principle, between position and momentum. In this work we show how this modification influences the theory of angular momentum in Quantum Mechanics. In particular, we compute Planck scale corrections to angular momentum eigenvalues, the hydrogen atom spectrum, the Stern-Gerlach experiment and the Clebsch-Gordan coefficients. We also examine effects of the Generalized Uncertainty Principle on multi-particle systems.

  12. Angular performance measure for tighter uncertainty relations

    SciTech Connect

    Hradil, Z.; Rehacek, J.; Klimov, A. B.; Rigas, I.; Sanchez-Soto, L. L.

    2010-01-15

    The uncertainty principle places a fundamental limit on the accuracy with which we can measure conjugate quantities. However, the fluctuations of these variables can be assessed in terms of different estimators. We propose an angular performance that allows for tighter uncertainty relations for angle and angular momentum. The differences with previous bounds can be significant for particular states and indeed may be amenable to experimental measurement with the present technology.

  13. Relativistic Electron Wave Packets Carrying Angular Momentum

    NASA Astrophysics Data System (ADS)

    Bialynicki-Birula, Iwo; Bialynicka-Birula, Zofia

    2017-03-01

    There are important differences between the nonrelativistic and relativistic description of electron beams. In the relativistic case the orbital angular momentum quantum number cannot be used to specify the wave functions and the structure of vortex lines in these two descriptions is completely different. We introduce analytic solutions of the Dirac equation in the form of exponential wave packets and we argue that they properly describe relativistic electron beams carrying angular momentum.

  14. Relativistic Electron Wave Packets Carrying Angular Momentum.

    PubMed

    Bialynicki-Birula, Iwo; Bialynicka-Birula, Zofia

    2017-03-17

    There are important differences between the nonrelativistic and relativistic description of electron beams. In the relativistic case the orbital angular momentum quantum number cannot be used to specify the wave functions and the structure of vortex lines in these two descriptions is completely different. We introduce analytic solutions of the Dirac equation in the form of exponential wave packets and we argue that they properly describe relativistic electron beams carrying angular momentum.

  15. Angular independent silicon detector for dosimetry in external beam radiotherapy.

    PubMed

    Petasecca, M; Alhujaili, S; Aldosari, A H; Fuduli, I; Newall, M; Porumb, C S; Carolan, M; Nitschke, K; Lerch, M L F; Kalliopuska, J; Perevertaylo, V; Rosenfeld, A B

    2015-08-01

    In this work, the "edgeless" silicon detector technology is investigated, in combination with an innovative packaging solution, to manufacture silicon detectors with negligible angular response. The new diode is also characterized as a dosimeter for radiotherapy with the aim to verify its suitability as a single detector for in vivo dosimetry as well as large area 2D array that does not require angular correction to their response. For the characterisation of the "edgeless-drop-in" detector technology, a set of samples have been manufactured with different sensitive areas (1 × 1 and 0.5 × 0.5 mm(2)) and different thicknesses (0.1 and 0.5 mm) in four different combinations of top and peripheral p-n junction fabricated on p-type and n-type silicon substrates. The diode probes were tested in terms of percentage depth dose (PDD), dose rate, and linearity and compared to ion chambers. Measurements of the output factor have been compared to film. The angular response of the diodes probes has been tested in a cylindrical PMMA phantom, rotated with bidirectional accuracy of 0.25° under 10 × 10 cm(2) 6 MV Linac photon beam. The radiation hardness has been investigated as well as the effect of radiation damage on the angular and dose rate response of the diode probes when irradiated with photons from a Co-60 gamma source up to dose of 40 kGy. The PDDs measured by the edgeless detectors show an agreement with the data obtained using ion chambers within ±2%. The output factor measured with the smallest area edgeless diodes (0.5 × 0.5 mm(2)-0.1 and 0.5 mm thick) matches EBT3 film to within 2% for square field size from 10 to 0.5 cm side equivalent distance. The dose rate dependence in a dose per pulse range of 0.9 × 10(-5)-2.7 × 10(-4) Gy/pulse was less than -7% and +300% for diodes fabricated on p-type and n-type substrates, respectively. The edgeless diodes fabricated on the p-type substrate demonstrated degradation of the response as a function of the irradiation

  16. Angular independent silicon detector for dosimetry in external beam radiotherapy

    SciTech Connect

    Petasecca, M. Aldosari, A. H.; Newall, M.; Porumb, C. S.; Lerch, M. L. F.; Rosenfeld, A. B.; Alhujaili, S.; Fuduli, I.; Carolan, M.; Nitschke, K.; Kalliopuska, J.; Perevertaylo, V.

    2015-08-15

    Purpose: In this work, the “edgeless” silicon detector technology is investigated, in combination with an innovative packaging solution, to manufacture silicon detectors with negligible angular response. The new diode is also characterized as a dosimeter for radiotherapy with the aim to verify its suitability as a single detector for in vivo dosimetry as well as large area 2D array that does not require angular correction to their response. Methods: For the characterisation of the “edgeless-drop-in” detector technology, a set of samples have been manufactured with different sensitive areas (1 × 1 and 0.5 × 0.5 mm{sup 2}) and different thicknesses (0.1 and 0.5 mm) in four different combinations of top and peripheral p–n junction fabricated on p-type and n-type silicon substrates. The diode probes were tested in terms of percentage depth dose (PDD), dose rate, and linearity and compared to ion chambers. Measurements of the output factor have been compared to film. The angular response of the diodes probes has been tested in a cylindrical PMMA phantom, rotated with bidirectional accuracy of 0.25° under 10 × 10 cm{sup 2} 6 MV Linac photon beam. The radiation hardness has been investigated as well as the effect of radiation damage on the angular and dose rate response of the diode probes when irradiated with photons from a Co-60 gamma source up to dose of 40 kGy. Results: The PDDs measured by the edgeless detectors show an agreement with the data obtained using ion chambers within ±2%. The output factor measured with the smallest area edgeless diodes (0.5 × 0.5 mm{sup 2}—0.1 and 0.5 mm thick) matches EBT3 film to within 2% for square field size from 10 to 0.5 cm side equivalent distance. The dose rate dependence in a dose per pulse range of 0.9 × 10{sup −5}–2.7 × 10{sup −4} Gy/pulse was less than −7% and +300% for diodes fabricated on p-type and n-type substrates, respectively. The edgeless diodes fabricated on the p-type substrate

  17. Trunk rotation monitor using angular velocity sensors.

    PubMed

    Seo, A; Uda, S

    1997-04-01

    To monitor the low back risk imposed by asymmetric postures at workplaces, a method using angular velocity sensors was studied. According to a simple model analysis, trunk rotation could be calculated from the angular velocities measured at both the waist and shoulder and from the inclination of each angular velocity sensor. We thus developed a new detector consisting of an angular velocity sensor (ENC-05D, Murata, Japan) for detecting angular velocity and an acceleration sensor (ADXL05, Analog Devices, USA) for measuring inclination. The precision of the angular velocity sensor was high as the correlation coefficient between the output of the sensor and the true value was 0.9996. When the detectors were affixed to a subject and compared with data measured by a Vicon System 370 (Oxford Metrics, UK), the correlation coefficients between the two methods were 0.949 and 0.815 during model tasks of box transfer and box lifting, respectively. In a model of lifting boxes at different rates, the mean and standard deviation increased according to the task speed. This method was shown to be of practical use for monitoring trunk rotation.

  18. Partial angular coherence and the angular Schmidt spectrum of entangled two-photon fields

    SciTech Connect

    Jha, Anand Kumar; Boyd, Robert W.; Agarwal, Girish S.

    2011-12-15

    We study partially coherent fields that have a coherent-mode representation in the orbital-angular-momentum-mode basis. For such fields, we introduce the concepts of the angular coherence function and the coherence angle. Such fields are naturally produced by the process of parametric down-conversion--a second-order nonlinear optical process in which a pump photon breaks up into two entangled photons, known as the signal and idler photons. We show that the angular coherence functions of the signal and idler fields are directly related to the angular Schmidt (spiral) spectrum of the down-converted two-photon field and thus that the angular Schmidt spectrum can be measured directly by measuring the angular coherence function of either the signal or the idler field, without requiring coincidence detection.

  19. Mass and Angular Momentum Loss of B[e] Stars via Decretion Disks

    NASA Astrophysics Data System (ADS)

    Krtička, J. K.; Owocki, S. P.; Kurfürst, P.

    2017-02-01

    We study the disks of B[e] stars assuming that the disks stem from the angular momentum loss from the central object. The angular momentum loss may be induced either by evolution of the stellar interior of critically rotating star or by merger event in a binary. In contrast to the usual stellar wind mass loss set by driving from the stellar luminosity, such decretion-disk mass loss is determined by the angular momentum loss needed to keep the central object in equilibrium. The angular momentum loss is given either by the interior evolution and decline in the star's moment of inertia, or by excess angular momentum present in a merging binary. Because the specific angular momentum in a Keplerian disk increases with the square root of the radius, the decretion mass loss associated with a required level of angular momentum loss depends crucially on the outer radius for viscous coupling of the disk. The magnetorotational instability can be the source of anomalous viscosity in decretion disks. The instability operates close to the star and disappears in the region where the disk orbital velocity is roughly equal to the sound speed. We study the differences between Be and B[e] star disks and discuss the reasons why stars of the stellar type B have disks, while other stars do not.

  20. Spin and orbital angular momentum of a class of nonparaxial light beams having a globally defined polarization

    SciTech Connect

    Li Chunfang

    2009-12-15

    It is shown that the momentum density of free electromagnetic field splits into two parts. One has no contribution to the net momentum due to the transversality condition. The other yields all the momentum. The angular momentum that originates from the former part is spin, and the angular momentum that originates from the latter part is orbital angular momentum. Expressions for the spin and orbital angular momentum are given in terms of the electric vector in reciprocal space. The spin and orbital angular momentum defined this way are used to investigate the angular momentum of nonparaxial beams that are described in a recently published paper [Phys. Rev. A 78, 063831 (2008)]. It is found that the orbital angular momentum depends, apart from an l-dependent term, on two global quantities, the polarization represented by a generalized Jones vector and another characteristic represented by a unit vector I, though the spin depends only on the polarization. The polarization dependence of orbital angular momentum through the effect of I is obtained and discussed. Some applications of the result obtained here are also made. The fact that the spin originates from the part of momentum density that has no contribution to the net momentum is used to show that there does not exist the paradox on the spin of circularly polarized plane wave. The polarization dependence of both spin and orbital angular momentum is shown to be the origin of conversion from the spin of a paraxial Laguerre-Gaussian beam into the orbital angular momentum of the focused beam through a high numerical aperture.

  1. Angularly Adaptive P1--Double P0 Diffusion Solutions of Non-Equilibrium Grey Radiative Transfer Problems in Planar Geometry

    SciTech Connect

    Brantley, P S

    2005-06-06

    The double spherical harmonics angular approximation in the lowest order, i.e. double P{sub 0} (DP{sub 0}), is developed for the solution of time-dependent non-equilibrium grey radiative transfer problems in planar geometry. The standard P{sub 1} angular approximation represents the angular dependence of the radiation specific intensity using a linear function in the angular domain -1 {le} {mu} {le} 1. In contrast, the DP{sub 0} angular approximation represents the angular dependence as isotropic in each half angular range -1 {le} {mu} < 0 and 0 < {mu} {le} 1. Neglecting the time derivative of the radiation flux, both the P{sub 1} and DP{sub 0} equations can be written as a single diffusion equation for the radiation energy density. Although the DP{sub 0} diffusion approximation is expected to be less accurate than the P{sub 1} diffusion approximation at and near thermodynamic equilibrium, the DP{sub 0} angular approximation can more accurately capture the complicated angular dependence near the non-equilibrium wave front. We develop an adaptive angular technique that locally uses either the DP{sub 0} or the P{sub 1} diffusion approximation depending on the degree to which the radiation and material fields are in thermodynamic equilibrium. Numerical results are presented for a test problem due to Su and Olson for which a semi-analytic transport solution exists. The numerical results demonstrate that the adaptive P{sub 1}-DP{sub 0} diffusion approximation can yield improvements in accuracy over the standard P{sub 1} diffusion approximation for non-equilibrium grey radiative transfer.

  2. Anomalous contours and illusion of angularity: phenomenal and theoretical comparisons.

    PubMed

    Pinna, B

    1991-01-01

    Many experimental comparisons between real and anomalous contours have proven the functional equivalence of the two conditions; however, there are some contradictory findings. One of these is obtained by analyzing the anomalous contours in the light of a new illusion, called the 'illusion of angularity'. A circle becomes a polygon when it covers the centre of a radial arrangement of black stripes, and a polygon changes its perceptual shape depending on its orientation with respect to the same radial arrangement. Phenomenally, it appears like a very pointed polygon, in which every side is concave or, alternatively, a shape that looks like a circle with angles added in the spaces between the radial stripes, or a polygonal shape in which every side is convex. The reciprocal anomalous counterparts of these conditions, obtained by removing the geometrical/polygonal contours, reveal different results. In the first case, one sees a perfect circle; in the second case, a polygon with blunted vertices, or a circular shape with angular protrusions; in the third case, a deformed circle. These results are inconsistent with some theoretical models proposed to explain the emergence of anomalous contours, namely, all the top-down models expressed in terms of cognitive constructions and perceptual hypotheses, or in terms of global figural organizations. Rather, these comparisons suggest a different interpretation for the two phenomena (the illusion of angularity and anomalous contours). This interpretation is based on dynamic interactions or on network computations that synthesize both real and anomalous contours.

  3. Unexpected angular or rotational deformity after corrective osteotomy

    PubMed Central

    2014-01-01

    Background Codman’s paradox reveals a misunderstanding of geometry in orthopedic practice. Physicians often encounter situations that cannot be understood intuitively during orthopedic interventions such as corrective osteotomy. Occasionally, unexpected angular or rotational deformity occurs during surgery. This study aimed to draw the attention of orthopedic surgeons toward the concepts of orientation and rotation and demonstrate the potential for unexpected deformity after orthopedic interventions. This study focused on three situations: shoulder arthrodesis, femoral varization derotational osteotomy, and femoral derotation osteotomy. Methods First, a shoulder model was generated to calculate unexpected rotational deformity to demonstrate Codman’s paradox. Second, femoral varization derotational osteotomy was simulated using a cylinder model. Third, a reconstructed femoral model was used to calculate unexpected angular or rotational deformity during femoral derotation osteotomy. Results Unexpected external rotation was found after forward elevation and abduction of the shoulder joint. In the varization and derotation model, closed-wedge osteotomy and additional derotation resulted in an unexpected extension and valgus deformity, namely, under-correction of coxa valga. After femoral derotational osteotomy, varization and extension of the distal fragment occurred, although the extension was negligible. Conclusions Surgeons should be aware of unexpected angular deformity after surgical procedure involving bony areas. The degree of deformity differs depending on the context of the surgical procedure. However, this study reveals that notable deformities can be expected during orthopedic procedures such as femoral varization derotational osteotomy. PMID:24886469

  4. Shocks in the low angular momentum accretion flow

    NASA Astrophysics Data System (ADS)

    Suková, Petra; Janiuk, Agnieszka

    2015-04-01

    We address the variability of low luminous galactic nuclei including the Sgr A* or other transient accreting systems, e.g. the black hole X-ray binaries, such as GX 339-4 or IGR J17091. These sources exhibit bright X-ray flares and quasi-periodical oscillations and are theoretically interpreted as the quasi-spherical accretion flows, formed instead of or around Keplerianaccretion disks. In low angular momentum flows the existence of shocks for some range of leading parameters (energy, angular momentum and adiabatic constant of the gas) was studied semi-analytically. The possible hysteresis effect, caused by the fact that the evolution of the flow and the formation of the shock depends on its own history, was discovered. The presence of the shock in the accreted material is important for the observable properties of the out-coming radiation. In the shocked region the gas is dense and hot, thus much more luminous than in the other case. We study the appearance of standing shocks in low angular momentum gas accreting onto a black hole with numerical hydrodynamicalsimulations, using the ZEUS code with Paczynski-Wiitapseudo-Newtonian potential.

  5. Magnetic field and angular momentum evolution models

    NASA Astrophysics Data System (ADS)

    Gallet, F.

    2013-11-01

    The magnetic field in young stellar object is clearly the most important component when one dealing with the angular momentum evolution of solar-like stars. It controls this latter one from the pre-main sequence, during the ``disk locking'' phase where the stars magnetically interact with their surrounding disk, to the main-sequence through powerful stellar winds that remove angular momentum from the stellar surface. We present new models for the rotational evolution of solar-like stars between 1 Myr and 10 Gyr with the aim to reproduce the distributions of rotational periods observed for star forming regions and young open clusters within this age range. Our simulations are produced by a recent model dedicated to the study of the angular momentum evolution of solar-type stars. This model include a new wind braking law based on recent numerical simulations of magnetized stellar winds and a specific dynamo and mass-loss prescription are used to link the angular momentum loss-rate to angular velocity evolution. The model additionally allows for a core/envelope decoupling with an angular momentum transfer between these two regions. Since this former model didn't include any physical star/disk interaction description, two star/disk interaction processes are eventually added to it in order to reproduce the apparent small angular velocities to which the stellar surface is subject during the disk accretion phase. We have developed rotational evolution models for slow, median and fast rotators including two star/disk interaction scenarios that are the magnetospheric ejection and the accretion powered stellar winds processes. The models appear to fail at reproducing the rotational behaviour of solar-type stars except when a more intense magnetic field is used during the disk accretion phase.

  6. Influence of an ellipsoid on the angular order in a two-dimensional cluster.

    PubMed

    Nelissen, K; Partoens, B; Peeters, F M

    2011-09-01

    The influence of an ellipsoid on the angular order of two-dimensional classical clusters is investigated through Brownian dynamics simulations. We found the following: (1) The presence of an ellipsoid does not influence the start of the angular melting, but reduces the rate at which the inner rings can rotate with respect to each other. (2) Even a small eccentricity of the ellipsoid leads to a stabilization of the angular order of the system. (3) Depending on the position of the ellipsoid in the cluster, a reentrant behavior in the angular order is observed before full radial melting of the cluster sets in. (4) The ellipsoid can lead to a two-step angular melting process: First, the rotation of the inner rings with respect to each other is hindered by the ellipsoid, but on further increasing the kinetic energy of the system, the ellipsoid just starts to behave as a spherical particle with different mobility. The effect of an ellipsoid on the molten system does not depend crucially on the interparticle interaction, but a softer parabolic confinement reduces the angular stabilization.

  7. Vector correlation analysis for inelastic and reactive collisions between partners possessing spin and orbital angular momentum.

    PubMed

    Balint-Kurti, Gabriel G; Vasyutinskii, Oleg S

    2009-12-31

    A general reactive collision of the type A + B --> C + D is considered where both the collision partners (A and B) or the products (C and D) may possess internal, i.e., spin, orbital or rotational, angular momenta. Compact expressions are derived using a rigorous quantum mechanical analysis for the angular momentum anisotropy of either of the products (C or D) arising from an initially polarized distribution of the reactant angular momentum. The angular momentum distribution of the product is expressed in terms of canonical spherical tensors multiplied by anisotropy-transforming coefficients c(K(i)q(k))(K)(K(r),L). These coefficients act as transformation coefficients between the angular momentum anisotropy of the reactants and that of the product. They are independent of scattering angle but depend on the details of the scattering dynamics. The relationship between the coefficients c(K(i)q(k))(K)(K(r),L) and the body-fixed scattering S matrix is given and the methodology for the quantum mechanical calculation of the anisotropy-transforming coefficients is clearly laid out. The anisotropy-transforming coefficients are amenable to direct experimental measurement in a similar manner to vector correlation and alignment parameters in photodissociation processes. A key aspect of the theory is the use of projections of both reactant and product angular momenta onto the product recoil vector direction. An important new conservation rule is revealed through the analysis, namely that if the state multipole for reactant angular momentum distribution has a projection q(k) onto the product recoil vector the state multipoles for the product angular momentum distribution all have this same projection. Expressions are also presented for the distribution of the product angular momentum when its components are evaluated relative to the space-fixed Z-axis. Notes with detailed derivations of all the formulas are available as Supporting Information.

  8. Ultrafast angular momentum transfer in multisublattice ferrimagnets.

    PubMed

    Bergeard, N; López-Flores, V; Halté, V; Hehn, M; Stamm, C; Pontius, N; Beaurepaire, E; Boeglin, C

    2014-03-11

    Femtosecond laser pulses can be used to induce ultrafast changes of the magnetization in magnetic materials. However, one of the unsolved questions is that of conservation of the total angular momentum during the ultrafast demagnetization. Here we report the ultrafast transfer of angular momentum during the first hundred femtoseconds in ferrimagnetic Co0.8Gd0.2 and Co0.74Tb0.26 films. Using time-resolved X-ray magnetic circular dichroism allowed for time-resolved determination of spin and orbital momenta for each element. We report an ultrafast quenching of the magnetocrystalline anisotropy and show that at early times the demagnetization in ferrimagnetic alloys is driven by the local transfer of angular momenta between the two exchange-coupled sublattices while the total angular momentum stays constant. In Co0.74Tb0.26 we have observed a transfer of the total angular momentum to an external bath, which is delayed by ~150 fs.

  9. Laboratory-Frame Photoelectron Angular Distributions in Anion Photodetachment: Insight into Electronic Structure and Intermolecular Interactions

    NASA Astrophysics Data System (ADS)

    Sanov, Andrei

    2014-04-01

    This article provides an overview of some recent advances in the modeling of photoelectron angular distributions in negative-ion photodetachment. Building on the past developments in threshold photodetachment spectroscopy that first tackled the scaling of the partial cross sections with energy, depending on the angular momentum quantum number ℓ, it examines the corresponding formulation of the central potential model and extends it to the more general case of hybrid molecular orbitals. Several conceptual approaches to understanding photoelectron angular distributions are discussed. In one approach, the angular distributions are examined based on the contributions of the symmetry-allowed s and p partial waves of the photodetached electron. In another related approach, the parent molecular orbitals are described based on their dominant s and p characters, whereas the continuum electron is described in terms of interference of the corresponding ℓ = ±1 photodetachment channels.

  10. Molecular above-threshold-ionization angular distributions with attosecond bichromatic intense XUV laser pulses

    NASA Astrophysics Data System (ADS)

    Yuan, Kai-Jun; Bandrauk, André D.

    2012-01-01

    Angular distributions of molecular above-threshold ionization (MATI) in bichromatic attosecond extreme ultraviolet (XUV) linear polarization laser pulses have been theoretically investigated. Multiphoton ionization in a prealigned molecular ion H2+ produces clear MATI spectra which show a forward-backward asymmetry in angular and momentum distributions which is critically sensitive to the carrier envelope phase (CEP) φ, the time delay Δτ between the two laser pulses, and the photoelectron kinetic energies Ee. The features of the asymmetry in MATI angular distributions are described well by multiphoton perturbative ionization models. Phase differences of continuum electron wave functions can be extracted from the CEP φ and time delay Δτ dependent ionization asymmetry ratio created by interfering multiphoton ionization pathways. At large internuclear distances MATI angular distributions exhibit more complex features due to laser-induced electron diffraction where continuum electron wavelengths are less than the internuclear distance.

  11. Spin angular momentum induced by optical quasi-phonons activated in birefringent uniaxial crystals

    NASA Astrophysics Data System (ADS)

    Mohamadou, B.; Maïmounatou, B.; Erasmus, R. M.

    2017-09-01

    The present report formally establishes the expression of the angular momentum of the quasi-phonons induced by linearly polarized light. The transferred mechanical torque due to phonons is then determined from the spin angular momentum and is shown to be measurable from Raman scattering experiments. To investigate this, the electric field due the excited dipoles and the associated macroscopic dielectric polarization vectors were first calculated using a lattice dynamical model in order to derive in a second step the analytical expression of the angular momentum density arising from the inelastic light scattering by quasi-phonons. The numerical results of the calculated angle dependent mode electric fields and the induced spin angular moments as well as the transferred torques were analyzed with regard to some typical behaviors of the interacting modes and it is shown that the fluctuations of the effective charges is their main origin.

  12. Angular velocity of a spheroid log rolling in a simple shear at small Reynolds number

    NASA Astrophysics Data System (ADS)

    Meibohm, Jan; Candelier, Fabien; Rosen, Tomas; Einarsson, Jonas; Lundell, Fredrik; Mehlig, Bernhard

    2016-11-01

    We analyse the angular velocity of a small neutrally buoyant spheroid log rolling in a simple shear. When the effect of fluid inertia is negligible the angular velocity ω -> equals half the fluid vorticity. We compute by singular perturbation theory how weak fluid inertia reduces the angular velocity in an unbounded shear, and how this reduction depends upon the shape of the spheroid (on its aspect ratio). In addition we determine the angular velocity by direct numerical simulations. The results are in excellent agreement with the theory at small but not too small values of the shear Reynolds number, for all aspect ratios considered. For the special case of a sphere we find ω / s = - 1 / 2 + 0 . 0540Re 3 / 2 where s is the shear rate and Re is the shear Reynolds number. This result differs from that derived by Lin et al. who obtained a numerical coefficient roughly three times larger.

  13. Variation in Angular Velocity and Angular Acceleration of a Particle in Rectilinear Motion

    ERIC Educational Resources Information Center

    Mashood, K. K.; Singh, V. A.

    2012-01-01

    We discuss the angular velocity ([image omitted]) and angular acceleration ([image omitted]) associated with a particle in rectilinear motion with constant acceleration. The discussion was motivated by an observation that students and even teachers have difficulty in ascribing rotational motion concepts to a particle when the trajectory is a…

  14. Variation in Angular Velocity and Angular Acceleration of a Particle in Rectilinear Motion

    ERIC Educational Resources Information Center

    Mashood, K. K.; Singh, V. A.

    2012-01-01

    We discuss the angular velocity ([image omitted]) and angular acceleration ([image omitted]) associated with a particle in rectilinear motion with constant acceleration. The discussion was motivated by an observation that students and even teachers have difficulty in ascribing rotational motion concepts to a particle when the trajectory is a…

  15. Young's Interference Experiment with Electron Beams Carrying Orbital Angular Momentum

    NASA Astrophysics Data System (ADS)

    Hasegawa, Yuya; Saitoh, Koh; Tanaka, Nobuo; Tanimura, Shogo; Uchida, Masaya

    2013-03-01

    A Young's-type double-slit experiment using electron beams carrying orbital angular momentum (OAM) is demonstrated in a transmission electron microscope. Each of the slits is replaced by a grating mask with a fork dislocation, which generates electron beams with OAM as diffracted beams. Interference fringes produced by two diffracted electron beams with OAM appear at the observation screen. The interference fringe patterns exhibit dislocation features depending on the topological charges of the two electron beams. The experimental results clearly show the wave nature of the electron beams with OAM and gives potential applications in electron physics and quantum mechanics.

  16. Classical and quantum chaotic angular-momentum pumps.

    PubMed

    Dittrich, T; Dubeibe, F L

    2015-03-06

    We study directed transport of charge and intrinsic angular momentum by periodically driven scattering in the regime of fast and strong driving. A spin-orbit coupling through a kicked magnetic field confined to a compact region in space leads to irregular scattering and triggers spin flips in a spatially asymmetric manner which allows us to generate polarized currents. The dynamical mechanisms responsible for the spin separation carry over to the quantum level and give rise to spin pumping. Our theory based on the Floquet formalism is confirmed by numerical solutions of the time-dependent inhomogeneous Schrödinger equation with a continuous source term.

  17. Teleportation of a controllable orbital angular momentum generator

    SciTech Connect

    Chen Lixiang; She Weilong

    2009-12-15

    We report on a teleportation scheme, in which a controllable orbital angular momentum (OAM) generator is teleported. Via our scheme, Alice is able to--according to another independent photon's spin state (polarization) sent by Carol--electrically control the remote OAM generation on Bob's photon. To this end, we introduce a local electrically tunable and spin-dependent OAM generator to transfer a preliminary OAM-OAM entanglement to a spin-OAM hybrid entanglement, which then makes a joint Bell-state measurement on Alice and Carol's photons play its role. We show that the quantum state tomography can be introduced to evaluate the performance of the teleportation.

  18. Two-body scattering without angular-momentum decomposition

    SciTech Connect

    Rodriguez-Gallardo, M.; Deltuva, A.; Cravo, E.; Fonseca, A. C.; Crespo, R.

    2008-09-15

    Two-body scattering is studied by solving the Lippmann-Schwinger equation in momentum space without angular-momentum decomposition for a local spin-dependent short-range interaction plus Coulomb. The screening and renormalization approach is employed to treat the Coulomb interaction. Benchmark calculations are performed by comparing our procedure with partial-wave calculations in configuration space for p-{sup 10}Be,p-{sup 16}O, and {sup 12}C-{sup 10}Be elastic scattering, using a simple optical potential model.

  19. Supermode fiber for orbital angular momentum (OAM) transmission.

    PubMed

    Li, Shuhui; Wang, Jian

    2015-07-13

    We present a multi-orbital-angular-momentum (OAM) multi-core supermode fiber (MOMCSF) to transmit OAM modes. The MOMCSF consists of equally-spaced and circularly-arranged multiple cores, in which the core pitch is small enough to support strong coupling OAM supermodes. The characteristics of OAM modes in MOMCSFs with different core pitches and core numbers are analyzed. The performances of mode coupling and nonlinearity are optimized by designing multiple degrees of freedom of the supermode fiber. The obtained results show that the designed MOMCSF can transmit multiple OAM modes with favorable performance of low mode coupling, low nonlinearity, and low modal dependent loss.

  20. Measurements of electron density profiles using an angular filter refractometer

    SciTech Connect

    Haberberger, D. Ivancic, S.; Hu, S. X.; Boni, R.; Barczys, M.; Craxton, R. S.; Froula, D. H.

    2014-05-15

    A novel diagnostic technique, angular filter refractometry (AFR), has been developed to characterize high-density, long-scale-length plasmas relevant to high-energy-density physics experiments. AFR measures plasma densities up to 10{sup 21} cm{sup −3} with a 263-nm probe laser and is used to study the plasma expansion from CH foil and spherical targets that are irradiated with ∼9 kJ of ultraviolet (351-nm) laser energy in a 2-ns pulse. The data elucidate the temporal evolution of the plasma profile for the CH planar targets and the dependence of the plasma profile on target radius for CH spheres.