Sample records for highly polar molecules

  1. Molecule Polarity

    NSDL National Science Digital Library

    The PhET project at the University of Colorado creates "fun, interactive, research-based simulations of physical phenomena." This particular one deals with molecular polarity. When is a molecule polar? Change the electronegativity of atoms in a molecule to see how it affects polarity. This simulation will allow visitors to see how molecules behave in an electric field, and change the bond angle to see how shape affects polarity for real molecules in 3D. The simulation is also paired with teaching tips and user-contirubed Teaching Ideas, lessons using the simulation in context, that can be found near the bottom of the page. The simulation is also available in multiple languages.

  2. A High Phase-Space-Density Gas of Polar Molecules

    Microsoft Academic Search

    K.-K. Ni; S. Ospelkaus; M. H. G. de Miranda; A. Pe'er; B. Neyenhuis; J. J. Zirbel; S. Kotochigova; P. S. Julienne; D. S. Jin; J. Ye

    2008-01-01

    A quantum gas of ultracold polar molecules, with long-range and anisotropic interactions, not only would enable explorations of a large class of many-body physics phenomena but also could be used for quantum information processing. We report on the creation of an ultracold dense gas of potassium-rubidium (40K87Rb) polar molecules. Using a single step of STIRAP (stimulated Raman adiabatic passage) with

  3. Polarization and ellipticity of high-order harmonics from aligned molecules generated by linearly polarized intense laser pulses

    SciTech Connect

    Le, Anh-Thu; Lin, C. D. [Department of Physics, Cardwell Hall, Kansas State University, Manhattan, Kansas 66506 (United States); Lucchese, R. R. [Department of Chemistry, Texas A and M University, College Station, Texas 77843-3255 (United States)

    2010-08-15

    We present theoretical calculations for polarization and ellipticity of high-order harmonics from aligned N{sub 2}, CO{sub 2}, and O{sub 2} molecules generated by linearly polarized lasers. Within the rescattering model, the two polarization amplitudes of the harmonics are determined by the photo-recombination amplitudes for photons emitted with polarization parallel or perpendicular to the direction of the same returning electron wave packet. Our results show clear species-dependent polarization states, in excellent agreement with experiments. We further note that the measured polarization ellipse of the harmonic furnishes the needed parameters for a 'complete' experiment in molecules.

  4. Nonadiabatic molecular high-order harmonic generation from polar molecules: Spectral redshift

    SciTech Connect

    Bian Xuebin; Bandrauk, Andre D. [Departement de Chimie, Universite de Sherbrooke, Sherbrooke, Quebec, J1K 2R1 (Canada)

    2011-04-15

    Molecular high-order harmonic generation (MHOHG) from the polar diatomic molecule HeH{sup 2+} in short intense laser fields is studied numerically. Due to the nonadiabatic response of the molecular dipole to the rapid change of laser intensity, a spectral redshift is predicted in high-intensity and ultrashort laser pulses, contrary to the blueshift observed in the harmonics generated from atoms in long laser pulses. The MHOHG temporal structures are investigated by a wavelet time-frequency analysis, which shows that the enhanced excitation of localized long lifetime excited states shifts the harmonic generation spectrum in the falling part of short laser pulses, due to the presence of a permanent dipole moment, and thus is unique to polar molecules.

  5. Dipole-bound anions of highly polar molecules: Ethylene carbonate and vinylene carbonate

    NASA Astrophysics Data System (ADS)

    Hammer, Nathan I.; Hinde, Robert J.; Compton, Robert N.; Diri, Kadir; Jordan, Kenneth D.; Radisic, Dunja; Stokes, Sarah T.; Bowen, Kit H.

    2004-01-01

    Results of experimental and theoretical studies of dipole-bound negative ions of the highly polar molecules ethylene carbonate (EC, C3H4O3,?=5.35 D) and vinylene carbonate (VC, C3H2O3,?=4.55 D) are presented. These negative ions are prepared in Rydberg electron transfer (RET) reactions in which rubidium (Rb) atoms, excited to ns or nd Rydberg states, collide with EC or VC molecules to produce EC- or VC- ions. In both cases ions are produced only when the Rb atoms are excited to states described by a relatively narrow range of effective principal quantum numbers, n*; the greatest yields of EC- and VC- are obtained for nmax*=9.0±0.5 and 11.6±0.5, respectively. Charge transfer from low-lying Rydberg states of Rb is characteristic of a large excess electron binding energy (Eb) of the neutral parent; employing the previously derived empirical relationship Eb=23/nmax*2.8 eV, the electron binding energies are estimated to be 49±8 meV for EC and 24±3 meV for VC. Electron photodetachment studies of EC- show that the excess electron is bound by 49±5 meV, in excellent agreement with the RET results, lending credibility to the empirical relationship between Eb and nmax*. Vertical electron affinities for EC and VC are computed employing aug-cc-pVDZ atom-centered basis sets supplemented with a (5s5p) set of diffuse Gaussian primitives to support the dipole-bound electron; at the CCSD(T) level of theory the computed electron affinities are 40.9 and 20.1 meV for EC and VC, respectively.

  6. Repulsive shield between polar molecules

    E-print Network

    A. V. Gorshkov; P. Rabl; G. Pupillo; A. Micheli; P. Zoller; M. D. Lukin; H. P. Büchler

    2008-05-05

    We propose and analyze a technique that allows to suppress inelastic collisions and simultaneously enhance elastic interactions between cold polar molecules. The main idea is to cancel the leading dipole-dipole interaction with a suitable combination of static electric and microwave fields in such a way that the remaining van-der-Waals-type potential forms a three-dimensional repulsive shield. We analyze the elastic and inelastic scattering cross sections relevant for evaporative cooling of polar molecules and discuss the prospect for the creation of crystalline structures.

  7. ATOMIC AND MOLECULAR PHYSICS: High order correlation-polarization potential for vibrational excitation scattering of diatomic molecules by low-energy electrons

    NASA Astrophysics Data System (ADS)

    Feng, Hao; Sun, Wei-Guo; Zeng, Yang-Yang

    2009-11-01

    This paper introduces a correlation-polarization potential with high order terms for vibrational excitation in electron-molecule scattering. The new polarization potential generalizes the two-term approximation so that it can better reflect the dependence of correlation and polarization effects on the position coordinate of the scattering electron. It applies the new potential on the vibrational excitation scattering from N2 in an energy range which includes the 2?g shape resonance. The good agreement of theoretical resonant peaks with experiments shows that polarization potentials with high order terms are important and should be included in vibrational excitation scattering.

  8. The Stark effect in Rydberg states of a highly polar diatomic molecule: CaF.

    PubMed

    Petrovi?, Vladimir S; Kay, Jeffrey J; Coy, Stephen L; Field, Robert W

    2009-08-14

    The Stark effect in molecular Rydberg states is qualitatively different from the Stark effect in atomic Rydberg states because of the anisotropy of the ion core and the existence of rotational and vibrational degrees of freedom. These uniquely molecular features cause the electric-field-induced decoupling of the Rydberg electron from the body frame to proceed in several stages in a molecule. Because the transition dipole moment among the same-n* Rydberg states is much larger than the permanent dipole moment of the ion core, the decoupling of the Rydberg electron from the ion core proceeds gradually. In the first stage, analyzed in detail in this paper, l and N are mixed by the external electric field, while N+ is conserved. In the further stages, as the external electric field increases, N+, n*, and v+ are expected to undergo mixing. We have characterized these stages in n*=13, v+=1 states of CaF. The large permanent dipole moment of CaF+ makes CaF qualitatively different from the other molecules in which the Stark effect in Rydberg states has been described (H2, Na2, Li2, NO, and H3) and makes it an ideal testbed for documenting the competition between the external and CaF+ dipole electric fields. We use the weak-field Stark effect to gain access to the lowest-N rotational levels of f, g, and h states and to assign their actual or nominal N+ quantum number. Lowest-N rotational levels provide information needed to disentangle the short-range and long-range interactions between the Rydberg electron and the ion core. We diagonalize an effective Hamiltonian matrix to determine the l-characters of the 3 < or = l < or = 5 core-nonpenetrating 2Sigma+ states and to characterize their mixing with the core-penetrating states. We conclude that the mixing of the l=4, N-N+=-4(g(-4)) state with lower-l 2Sigma+ states is stronger than documented in our previous multichannel quantum defect theory and long-range fits to zero-field spectra. PMID:19691382

  9. Fluorescence Polarization Assays in Small Molecule Screening

    PubMed Central

    Lea, Wendy A.; Simeonov, Anton

    2011-01-01

    Importance of the field Fluorescence polarization (FP) is a homogeneous method that allows rapid and quantitative analysis of diverse molecular interactions and enzyme activities. This technique has been widely utilized in clinical and biomedical settings, including the diagnosis of certain diseases and monitoring therapeutic drug levels in body fluids. Recent developments in the field has been symbolized by the facile adoption of FP in high-throughput screening (HTS) and small molecule drug discovery of an increasing range of target classes. Areas covered in this review The article provides a brief overview on the theoretical foundation of FP, followed by updates on recent advancements in its application for various drug target classes, including G-protein coupled receptors (GPCRs), enzymes and protein-protein interactions (PPIs). The strengths and weaknesses of this method, practical considerations in assay design, novel applications, and future directions are also discussed. What the reader will gain The reader will be informed of the most recent advancements and future directions of FP application to small molecule screening. Take home message In addition to its continued utilization in high-throughput screening, FP has expanded into new disease and target areas and has been marked by increased use of labeled small molecule ligands for receptor binding studies. PMID:22328899

  10. Population redistribution in optically trapped polar molecules

    E-print Network

    Deiglmayr, J; Dulieu, O; Wester, R; Weidemüller, M

    2011-01-01

    We investigate the rovibrational population redistribution of polar molecules in the electronic ground state induced by spontaneous emission and blackbody radiation. As a model system we use optically trapped LiCs molecules formed by photoassociation in an ultracold two-species gas. The population dynamics of vibrational and rotational states is modeled using an ab-initio electric dipole moment function and experimental potential energy curves. Comparison with the evolution of the v"=3 electronic ground state yields good qualitative agreement. The analysis provides important input to assess applications of ultracold LiCs molecules in quantum simulation and ultracold chemistry.

  11. Broadband large-ellipticity harmonic generation with polar molecules.

    PubMed

    Qin, Meiyan; Zhu, Xiaosong; Zhang, Qingbin; Hong, Weiyi; Lu, Peixiang

    2011-12-01

    We investigate the polarization properties of high harmonic generation from polar molecules with a linearly polarized field. It is found that elliptically polarized harmonics are observed in a wide spectral range from the plateau to the cutoff. Further analyses show that the nonsymmetric structure of the highest occupied molecular orbital is the origin of ellipticity of the harmonics. The results provide a method for generation of large-ellipticity XUV pulses, which will benefit the application of HHG as a tool of detection in materials and biology science. PMID:22273900

  12. Tunable Holstein model with cold polar molecules

    SciTech Connect

    Herrera, Felipe; Krems, Roman V. [Department of Chemistry, University of British Columbia, Vancouver, British Columbia, V6T 1Z1 (Canada)

    2011-11-15

    We show that an ensemble of polar molecules trapped in an optical lattice can be considered as a controllable open quantum system. The coupling between collective rotational excitations and the motion of the molecules in the lattice potential can be controlled by varying the strength and orientation of an external dc electric field as well as the intensity of the trapping laser. The system can be described by a generalized Holstein Hamiltonian with tunable parameters and can be used as a quantum simulator of excitation energy transfer and polaron phenomena. We show that the character of excitation energy transfer can be modified by tuning experimental parameters.

  13. Optical Production of Ultracold Polar Molecules

    SciTech Connect

    Sage, Jeremy M.; Sainis, Sunil; DeMille, David [Department of Physics, Yale University, New Haven, Connecticut 06520 (United States); Bergeman, Thomas [Department of Physics and Astronomy, SUNY, Stony Brook, New York 11794-3800 (United States)

    2005-05-27

    We demonstrate the production of ultracold polar RbCs molecules in their vibronic ground state, via photoassociation of laser-cooled atoms followed by a laser-stimulated state transfer process. The resulting sample of X{sup 1}{sigma}{sup +}(v=0) molecules has a translational temperature of {approx}100 {mu}K and a narrow distribution of rotational states. With the method described here it should be possible to produce samples even colder in all degrees of freedom, as well as other bialkali species.

  14. Dynamics of reactive ultracold alkali polar molecules

    NASA Astrophysics Data System (ADS)

    Quéméner, Goulven; Bohn, John; Petrov, Alexander; Kotochigova, Svetlana

    2011-05-01

    Recently, ultracold polar molecules of KRb have been created. These molecules are chemically reactive and their lifetime in a trap is limited. However, their lifetime increases when they are loaded into a 1D optical lattice in the presence of an electric field. These results naturally raise the question of manipulating ultracold collisions of other species of alkali dimer molecules, with an eye toward both novel stereochemistry, as well as suppressing unwanted reactions, to enable condensed matter applications. In this talk, we report on a comparative study between the bi-alkali polar molecules of LiNa, LiK, LiRb, LiCs which have been predicted to be reactive. We compute the isotropic C6 coefficients of these systems and we predict the elastic and reactive rate coefficients when an electric field is applied in a 1D optical lattice. We will discuss the efficacy of evaporative cooling for each species. This work was supported by a MURI-AFOSR grant.

  15. Opto-Electrical Cooling of Polar Molecules

    E-print Network

    M. Zeppenfeld; M. Motsch; P. W. H. Pinkse; G. Rempe

    2009-10-07

    We present an opto-electrical cooling scheme for polar molecules based on a Sisyphus-type cooling cycle in suitably tailored electric trapping fields. Dissipation is provided by spontaneous vibrational decay in a closed level scheme found in symmetric-top rotors comprising six low-field-seeking rovibrational states. A generic trap design is presented. Suitable molecules are identified with vibrational decay rates on the order of 100Hz. A simulation of the cooling process shows that the molecular temperature can be reduced from 1K to 1mK in approximately 10s. The molecules remain electrically trapped during this time, indicating that the ultracold regime can be reached in an experimentally feasible scheme.

  16. Dynamics of thermal Casimir-Polder forces on polar molecules

    SciTech Connect

    Ellingsen, Simen Aadnoey; Buhmann, Stefan Yoshi; Scheel, Stefan [Department of Energy and Process Engineering, Norwegian University of Science and Technology, N-7491 Trondheim (Norway); Quantum Optics and Laser Science, Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2AZ (United Kingdom)

    2009-05-15

    We study the influence of thermal Casimir-Polder forces on the near-surface trapping of cold polar molecules, with emphasis on LiH and YbF near a Au surface at room temperature. We show that even for a molecule initially prepared in its electronic and rovibrational ground state, the Casimir-Polder force oscillates with the molecule-wall separation. The nonresonant force and the evanescent part of the resonant force almost exactly cancel at high temperature which results in a saturation of the (attractive) force in this limit. This implies that the Casimir-Polder force on a fully thermalized molecule can differ dramatically from that obtained using a naive perturbative expansion of the Lifshitz formula based on the molecular ground-state polarizability. A dynamical calculation reveals how the spatial oscillations die out on a typical time scale of several seconds as thermalization of the molecule with its environment sets in.

  17. Atomic Rydberg reservoirs for polar molecules.

    PubMed

    Zhao, B; Glaetzle, A W; Pupillo, G; Zoller, P

    2012-05-11

    We discuss laser-dressed dipolar and van der Waals interactions between atoms and polar molecules, so that a cold atomic gas with laser admixed Rydberg levels acts as a designed reservoir for both elastic and inelastic collisional processes. The elastic scattering channel is characterized by large elastic scattering cross sections and repulsive shields to protect from close encounter collisions. In addition, we discuss a dissipative (inelastic) collision where a spontaneously emitted photon carries away (kinetic) energy of the collision partners, thus providing a significant energy loss in a single collision. This leads to the scenario of rapid thermalization and cooling of a molecule in the mK down to the ?K regime by cold atoms. PMID:23003036

  18. Dynamics of thermal Casimir-Polder forces on polar molecules

    E-print Network

    S. A. Ellingsen; S. Y. Buhmann; S. Scheel

    2010-01-04

    We study the influence of thermal Casimir-Polder forces on the near-surface trapping of cold polar molecules, with emphasis on LiH and YbF near an Au surface at room temperature. We show that for a molecule initially prepared in its electronic and rovibrational ground state, the Casimir-Polder force oscillates with the molecule-wall separation. The non-resonant force contribution and the evanescent part of the resonant force contribution almost exactly cancel at high temperature which results in a saturation of the (attractive) force in this limit. A dynamical calculation reveals how the spatial oscillations die out as thermalisation of the molecule with its environment sets in.

  19. Cooling and trapping polar molecules in an electrostatic trap

    NASA Astrophysics Data System (ADS)

    Wang, Zhen-Xia; Zhen-Xing, Gu; Deng, Lian-Zhong; Yin, Jian-Ping

    2015-05-01

    An electrostatic trap for polar molecules is proposed. Loading and trapping of polar molecules can be realized by applying different voltages to the two electrodes of the trap. For ND3 molecular beams centered at ?10 m/s, a high loading efficiency of ?67% can be obtained, as confirmed by our Monte Carlo simulations. The volume of our trap is as large as ?3.6 cm3, suitable for study of the adiabatic cooling of trapped molecules. Our simulations indicate that trapped ND3 molecules can be cooled from ?23.3 mK to 1.47 mK by reducing the trapping voltages on the electrodes from 50.0 kV to 1.00 kV. Project supported by the National Natural Science Foundation of China (Grant Nos. 10674047, 10804031, 10904037, 10974055, 11034002, and 11274114), the National Key Basic Research and Development Program of China (Grant Nos. 2006CB921604 and 2011CB921602), the Basic Key Program of Shanghai Municipality, China (Grant No. 07JC14017), and the Shanghai Leading Academic Discipline Project, China (Grant No. B408).

  20. Schemes for robust quantum computation with polar molecules

    SciTech Connect

    Yelin, S. F.; Cote, Robin [Department of Physics, University of Connecticut, Storrs, Connecticut 06269 (United States); ITAMP, Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts 02138 (United States); Kirby, K. [ITAMP, Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts 02138 (United States)

    2006-11-15

    We show how ultracold polar molecules, suggested as a new platform for quantum computation, can be manipulated to switch ''on'' and ''off'' their strong dipole-dipole interactions. This can be accomplished through selective excitation of states with considerably different dipole moments. We discuss different schemes for quantum gates using real molecules: CO, LiH, and CaF, as examples of polar molecules which are being experimentally studied at ultracold temperatures. These schemes can be realized in several recently proposed architectures.

  1. Quantum phase gate and controlled entanglement with polar molecules

    SciTech Connect

    Charron, Eric; Keller, Arne; Atabek, Osman [Laboratoire de Photophysique Moleculaire du CNRS, Universite Paris-Sud, Batiment 210, 91405 Orsay Cedex (France); Milman, Perola [Laboratoire de Photophysique Moleculaire du CNRS, Universite Paris-Sud, Batiment 210, 91405 Orsay Cedex (France); CERMICS, Ecole Nationale des Ponts et Chaussees, 6 et 8 av. Blaise Pascal, Cite Descartes, Champs-sur-Marne, 77455 Marne-la-Vallee (France)

    2007-03-15

    We propose an alternative scenario for the generation of entanglement between rotational quantum states of two polar molecules. This entanglement arises from dipole-dipole interaction, and is controlled by a sequence of laser pulses simultaneously exciting both molecules. We study the efficiency of the process, and discuss possible experimental implementations with cold molecules trapped in optical lattices or in solid matrices. Finally, various entanglement detection procedures are presented, and their suitability for these two physical situations is analyzed.

  2. Dynamics of thermal Casimir-Polder forces on polar molecules

    Microsoft Academic Search

    Simen Ådnøy Ellingsen; Stefan Yoshi Buhmann; Stefan Scheel

    2009-01-01

    We study the influence of thermal Casimir-Polder forces on the near-surface trapping of cold polar molecules, with emphasis on LiH and YbF near a Au surface at room temperature. We show that even for a molecule initially prepared in its electronic and rovibrational ground state, the Casimir-Polder force oscillates with the molecule-wall separation. The nonresonant force and the evanescent part

  3. Polarization shaping for unidirectional rotational motion of molecules.

    PubMed

    Karras, G; Ndong, M; Hertz, E; Sugny, D; Billard, F; Lavorel, B; Faucher, O

    2015-03-13

    Control of the orientation of the angular momentum of linear molecules is demonstrated by means of laser polarization shaping. For this purpose, we combine two orthogonally polarized and partially time-overlapped femtosecond laser pulses so as to produce a spinning linear polarization which in turn induces unidirectional rotation of N2 molecules. The evolution of the rotational response is probed by a third laser beam that can be either linearly or circularly polarized. The physical observable is the frequency shift imparted to the probe beam as a manifestation of the angular Doppler effect. Our experimental results are confirmed by theoretical computations, which allow one to gain a deep physical insight into the laser-molecule interaction. PMID:25815926

  4. A model for positron binding to polar molecules

    E-print Network

    Gribakin, G F

    2015-01-01

    A model for positron binding to polar molecules is considered by combining the dipole potential outside the molecule with a strongly repulsive core of a given radius. Using existing experimental data on binding energies leads to unphysically small core radii for all of the molecules studied. This suggests that electron-positron correlations neglected in the simple model play a large role in determining the binding energy. We account for these by including polarization potential via perturbation theory. The improved model enables reliable predictions of binding energies to be made for a range of polar organic molecules and hydrogen cyanide, whose binding energy is known from accurate quantum chemistry calculations. The model explains the linear dependence of the binding energies on the polarizability inferred from the experimental data [Danielson et al 2009 J. Phys. B: At. Mol. Opt. Phys. 42 235203].

  5. Thermal and quantum fluctuations in chains of ultracold polar molecules

    E-print Network

    G. E. Astrakharchik; Gabriele De Chiara; Giovanna Morigi; Jordi Boronat

    2009-03-09

    Ultracold polar molecules, in highly anisotropic traps and interacting via a repulsive dipolar potential, may form one-dimensional chains at high densities. According to classical theory, at low temperatures there exists a critical value of the density at which a second order phase transition from a linear to a zigzag chain occurs. We study the effect of thermal and quantum fluctuations on these self-organized structures using classical and quantum Monte Carlo methods, by means of which we evaluate the pair correlation function and the static structure factor. Depending on the parameters, these functions exhibit properties typical of a crystalline or of a liquid system. We compare the thermal and the quantum results, identifying analogies and differences. Finally, we discuss experimental parameter regimes where the effects of quantum fluctuations on the linear - zigzag transition can be observed.

  6. Giant molecules composed of polar molecules and atoms in mixed dimensions

    NASA Astrophysics Data System (ADS)

    Qi, Ran; Tan, Shina

    2014-05-01

    Two or three polar molecules, confined to one or two dimensions, can form stable bound states with a single atom living in three dimensions, if the molecule and the atom can interact resonantly such that their mixed dimensional scattering length is large. We call these bound states ``giant molecules'' since it's a molecule composed of smaller molecules and atoms. We study their properties using techniques including exact numerical solution, exact qunatum diffusion Monte Carlo (QMC), Born-Oppenheimer approximation (BOA), and semiclassical approximation. These bound states have a hierarchical structure reminiscent of the celestial systems.

  7. Investigating polaron phase transitions with polar molecules

    E-print Network

    Herrera, Felipe; Krems, Roman V; Berciu, Mona

    2013-01-01

    We determine the phase diagram of a polaron model with mixed breathing-mode and Su-Schrieffer-Heeger couplings and show that it has two sharp transitions, in contrast to pure models which exhibit one (for Su-Schrieffer-Heeger coupling) or no (for breathing-mode coupling) transition. Our results indicate that the physics of realistic mixed polaron models is much richer than that of simplified models. We then show that ultracold molecules trapped in optical lattices can be used to study precisely this mixed Hamiltonian, and that the relative contributions of the two couplings can be tuned with external electric fields. The parameters of current experimental set-ups place them in the region where one of the transitions occurs. We propose a scheme to measure the polaron dispersion using stimulated Raman spectroscopy.

  8. A coherent all-electrical interface between polar molecules and mesoscopic

    E-print Network

    Loss, Daniel

    leads to large mechanical forces, allowing trapping of the molecules. Finally, polar molecules alsoARTICLES A coherent all-electrical interface between polar molecules and mesoscopic superconducting describe methods for the integration of a single-particle system--an isolated polar molecule

  9. Are all polar molecules hydrophilic? Hydration numbers of ketones and esters in aqueous solution.

    PubMed

    Shikata, Toshiyuki; Okuzono, Misumi

    2013-06-27

    Hydration numbers of typical polar compounds like ketones and esters in aqueous solution were precisely determined using high-frequency dielectric relaxation techniques up to a frequency of 50 GHz at 25 °C. Because the hydration number is one of the most quantitative parameters to demonstrate how much are molecules hydrophilic, it is a critical parameter to determine the hydrophilicity of compounds. Hydration numbers of some ketones bearing carbonyl groups were determined to be ca. 0 irrespective of the species of molecules. Moreover, hydration numbers of some esters were also evaluated to be ca. 0 as well as the ketones. These findings suggested that there is no hydrogen bond formation between the ester group and water molecules, nor is there the hydrogen bond formation between the carbonyl group and water molecules. Consequently, esters and ketones bearing typical polar groups are not classified into hydrophilic compounds, but into "hydroneutral" compounds positioned between hydrophilic and hydrophobic ones. Molecular motions of the examined polar molecules in aqueous solution were well described with single Debye-type rotational relaxation modes without strong interaction between solute and water molecules, and also between solute molecules because of the obtained Kirkwood factor close to unity. This independent rotational mode for the polar compounds results from the hydroneutral characteristics caused by the relationship n(H) = 0. PMID:23738825

  10. Graphene Transport Under the Influence of Polar Molecules

    NASA Astrophysics Data System (ADS)

    Worley, Barrett; Kim, Seohee; Park, Saungeun; Rossky, Peter; Akinwande, Deji; Dodabalapur, Ananth

    2015-03-01

    Charged defects and impurities play a very important role in charge transport in graphene field-effect transistors (FETs). They influence the mobility, residual doping, and the Dirac voltage. Long-range scattering by charged impurities in fabricated graphene FETs lowers the mobility of charge carriers, while short range scattering affects the value of residual carrier concentration. Our group has shown that the electrical properties of graphene FETs are significantly improved upon exposure to fluoropolymers or polar organic vapors. We have demonstrated favorable Dirac voltage shifts, increases in mobility, and reduction in residual carrier concentration as a result of polar molecules altering the dielectric environment surrounding the graphene/substrate interface of a graphene FET. Screening of charged impurity scattering is hypothesized to be the principal effect by which the polar molecules of the altered dielectric layer bring about improvements. We employ computational chemistry to model polar organic molecule-graphene systems. Such modeling will help explain experimental results. We acknowledge support from NASCENT NSF EEC-1160494 and NSF CHE-1362381.

  11. Precision measurements with polar molecules: the role of the black body radiation

    Microsoft Academic Search

    Nicolas Vanhaecke; Olivier Dulieu

    2008-01-01

    In the perspective of the outstanding developments of high-precision measurements of fundamental constants using polar molecules related to ultimate checks of fundamental theories, we investigate the possibly counterproductive role of black-body radiation on a series of diatomic molecules which would be trapped and observed for long durations. We show that the absorption of black-body radiation at room temperature may indeed

  12. Precision measurements with polar molecules: the role of the black body radiation

    Microsoft Academic Search

    Nicolas Vanhaecke; Olivier Dulieu

    2007-01-01

    In the perspective of the outstanding developments of high-precision\\u000ameasurements of fundamental constants using polar molecules related to ultimate\\u000achecks of fundamental theories, we investigate the possibly counterproductive\\u000arole of black-body radiation on a series of diatomic molecules which would be\\u000atrapped and observed for long durations. We show that the absorption of\\u000ablack-body radiation at room temperature may indeed

  13. Dielectric behavior of some small ketones as ideal polar molecules.

    PubMed

    Shikata, Toshiyuki; Yoshida, Nao

    2012-05-17

    The dielectric behaviors of some small symmetric ketone molecules, including acetone, 3-pentanone, cyclopentanone, 4-heptanone, and cyclohexanone, were investigated as a function of temperature (T) over a wide frequency range from 50 MHz (3.14 × 10(8) s(-1), in angular frequency) to 3 THz (1.88 × 10(13) s(-1)). The temperature dependencies of the rotational diffusion times (?(r)) determined using (17)O NMR spin-lattice relaxation time (T(1)) measurements and viscosities of the ketones were also examined. The obtained temperature dependencies of the parameters for the ketones were compared with those of ideal polar molecules, which obey the Stokes-Einstein-Debye (SED) relationship without the formation of intermolecular dimeric associations and without orientational correlations between dipoles (molecular axes), that is, free rotation. Kirkwood correlation factors (g(K)) of only acetone and 3-pentanone were close to unity over a wide temperature range, whereas those of other ketones were obviously less than unity. These results revealed that no correlations exist between the rotational motions of dipoles in acetone and 3-pentanone, as expected in ideal polar molecules. However, other ketones exhibited orientational correlations in their dipoles because of dipole-dipole interactions via antiparallel configurations. Furthermore, because acetone and 3-pentanone satisfied the SED relationship and because their microscopic dielectric relaxation times (?(?)), which were calculated from the determined dielectric relaxation times (?(D)) via the relationship ?(?) = ?(D)g(K)(-1), were identical to 3?(r) and were proportional to V?(k(B)T)(-1) over the wide temperature range examined, where V, k(B), and ? represent the effective molecular volume, Boltzmann's constant, and the viscosity of the liquid molecules, respectively, these two ketone molecules behave as ideal polar molecules. In addition, other ketones not significantly larger than acetone and 3-pentanone in molecular size likely form dimeric intermolecular associations with antiparallel cyclic configurations, which demonstrates the g(K) values less than unity. PMID:22530697

  14. A traveling wave decelerator for neutral polar molecules

    E-print Network

    Meek, Samuel A; Heyne, Georg; Platschkowski, Viktor; Haak, Henrik; Meijer, Gerard; Osterwalder, Andreas

    2011-01-01

    Recently, a decelerator for neutral polar molecules has been presented that operates on the basis of macroscopic, three-dimensional, traveling electrostatic traps (Osterwalder et al., Phys. Rev. A 81, 051401 (2010)). In the present paper, a complete description of this decelerator is given, with emphasis on the electronics and the mechanical design. Experimental results showing the transverse velocity distributions of guided molecules are shown and compared to trajectory simulations. An assessment of non-adiabatic losses is made by comparing the deceleration signals from 13-CO with those from 12-CO and with simulated signals.

  15. Cold polar molecules for novel collision experiments at low Brian Sawyer

    E-print Network

    Jin, Deborah

    Cold polar molecules for novel collision experiments at low energies by Brian Sawyer B of Physics 2010 #12;#12;iii Sawyer, Brian (Ph.D., Physics) Cold polar molecules for novel collision experiments at low energies Thesis directed by Prof. Jun Ye Research in the field of cold polar molecules

  16. Spectromicroscopy Study of the Organic Molecules Utilizing Polarized Radiation

    SciTech Connect

    Hsu, Y.J.; Wei, D.H.; Yin, G.C.; Chung, S.C. [National Synchrotron Radiation Research Center, Hsinchu, 30077, Taiwan (China); Hu, W.S.; Tao, Y.T. [Institute of Chemistry, Academia Sinica, Taipei, 115, Taiwan (China)

    2004-05-12

    Spectromicroscopy combined with polarized synchrotron radiation is a powerful tool for imaging and characterizing the molecular properties on surface. In this work we utilized the photoemission electron microscopy (PEEM) with linear polarized radiation provided by an elliptically polarized undulator to investigate the molecular orientations of pentacene on self-assembled monolayer (SAMs) modified gold surface and to observe the cluster domain of mixed monolayers after reorganization on silver. Varying the electric vector parallel or perpendicular to the surface, the relative intensity of {pi}* and {sigma}* transition in carbon K-edge can be used to determine the orientation of the planar-shaped pentacene molecule or long carbon chain of carboxylic acids which are important for organic semiconductor.

  17. Are all polar molecules hydrophilic? Hydration numbers of nitro compounds and nitriles in aqueous solution.

    PubMed

    Sagawa, Naoya; Shikata, Toshiyuki

    2014-07-14

    The hydration numbers of typical aprotic polar substances bearing dipole moments larger than 3 D, such as nitro compounds and nitriles, were precisely determined in aqueous solution using high frequency dielectric relaxation techniques up to a frequency of 50 GHz at 25 °C. The hydration number is one of the most quantitative parameters for determining the hydrophilicity or hydrophobicity of a compound. The hydration numbers of various nitriles, such as acetonitrile, propionitrile and n-butyronitrile bearing cyano groups, were determined to be ca. 0, irrespective of the species of molecule. Moreover, the hydration numbers of various nitro compounds, such as nitromethane, nitroethane and 1-nitropropane, were also evaluated to be ca. 0. These findings clearly reveal that neither cyano nor nitro functional groups form strong hydrogen bonds to water molecules. Consequently, neither nitro compounds nor nitriles are hydrophilic, despite their high polarities due to their large dipole moments. Rather, these compounds are "hydroneutral," with hydrophilicities intermediate between those of hydrophilic and hydrophobic molecules. The molecular motions of the examined highly polar molecules in aqueous solution were well described with single Debye-type rotational relaxation modes without strong interactions between the solute and water molecules, but with relatively strong interactions between the polar solute molecules due to the Kirkwood factor being less than unity. This small Kirkwood factor indicated that both nitro and cyano groups have a tendency to align in an anti-parallel intermolecular configuration due to their strong dipole-dipole interactions as a result of their dipole moments greater than 3 D. PMID:24871926

  18. Ellipticity of odd-even harmonics from oriented asymmetric molecules in strong linearly polarized laser fields

    NASA Astrophysics Data System (ADS)

    Yu, Shujuan; Zhang, Bing; Li, Yanpeng; Yang, Shiping; Chen, Yanjun

    2014-11-01

    We investigate the polarization of odd versus even high-order-harmonic generation (HHG) from oriented asymmetric molecules exposed to a strong and linearly polarized laser field. Our numerical simulations show that the properties of polarization of harmonics at diverse orientation angles differ significantly from each other. In particular, odd and even harmonics show different angle dependences of ellipticity. Our analyses reveal that the interplay of intramolecular interference and the contributions of different HHG routes plays an important role in the ellipticity of odd-even harmonics. In addition, the excited states also have nontrivial influence on this ellipticity. While the minimum arising from two-center interference is not easy to identify in the odd-even HHG spectra of asymmetric molecules, we show that the ellipticity of harmonics can be used as a sensitive tool to probe the position of the minimum, which is important in asymmetric molecular orbital imaging.

  19. Growth-induced polarity formation in solid solutions of organic molecules: Markov mean-field model and Monte Carlo simulations

    NASA Astrophysics Data System (ADS)

    Wüst, Thomas; Hulliger, Jürg

    2005-02-01

    A layer-by-layer growth model is presented for the theoretical investigation of growth-induced polarity formation in solid solutions H1-XGX of polar (H) and nonpolar (G) molecules (X: molar fraction of G molecules in the solid, 0molecules and to an exchange of H and G molecules, while previously attached layers are kept frozen. The model is analyzed by means of a Markov mean-field description and Monte Carlo simulations. In solid solutions, polarity results from a combined effect of orientational selectivity by H and G molecules with respect to the alignment of the dipoles of H molecules and miscibility between the two components. Even though both native structures (H,G) may be centrosymmetric, polarity can arise just from the admixture of G molecules in the H crystal upon growth. An overview of possible phenomena is given by random selection of molecular interaction energies within an assumed but realistic energy range. The analytical approach describes sufficiently basic phenomena and is in good agreement with simulations. High probabilities for significant vectorial alignment of H molecules are found for low (X?0.2) and high (X?0.8) fractions of G molecules, respectively, as well as for ordered HG compounds (X=0.5).

  20. High polarization photocathode R D at SLAC

    SciTech Connect

    Maruyama, Takashi; Garwin, E.L. (Stanford Linear Accelerator Center, Menlo Park, CA (United States)); Prepost, R.; Zaplac, G.H. (Wisconsin Univ., Madison, WI (United States). Dept. of Physics)

    1993-01-01

    This paper describes recent progress on the development of high polarization photocathodes for polarized electron sources. A strained InGaAs cathode has achieved a maximum electron-spin polarization of 71% and has demonstrated the strain enhancement of polarization for the first time. Strained GaAs cathodes have yielded polarizations as high as 90% with much higher quantum efficiency.

  1. Photofragment angular momentum polarization in the photolysis of symmetric top molecules: Production, detection, and rotational depolarization

    E-print Network

    Photofragment angular momentum polarization in the photolysis of symmetric top molecules: Photodissociation Symmetric top molecule Photofragment Angular momentum Polarization a b s t r a c t We present the fully quantum mechanical distribution of the photofragment angular momentum polar- ization

  2. Dynamic nuclear polarization at high magnetic fields

    PubMed Central

    Maly, Thorsten; Debelouchina, Galia T.; Bajaj, Vikram S.; Hu, Kan-Nian; Joo, Chan-Gyu; Mak–Jurkauskas, Melody L.; Sirigiri, Jagadishwar R.; van der Wel, Patrick C. A.; Herzfeld, Judith; Temkin, Richard J.; Griffin, Robert G.

    2009-01-01

    Dynamic nuclear polarization (DNP) is a method that permits NMR signal intensities of solids and liquids to be enhanced significantly, and is therefore potentially an important tool in structural and mechanistic studies of biologically relevant molecules. During a DNP experiment, the large polarization of an exogeneous or endogeneous unpaired electron is transferred to the nuclei of interest (I) by microwave (?w) irradiation of the sample. The maximum theoretical enhancement achievable is given by the gyromagnetic ratios (?e/?l), being ?660 for protons. In the early 1950s, the DNP phenomenon was demonstrated experimentally, and intensively investigated in the following four decades, primarily at low magnetic fields. This review focuses on recent developments in the field of DNP with a special emphasis on work done at high magnetic fields (?5 T), the regime where contemporary NMR experiments are performed. After a brief historical survey, we present a review of the classical continuous wave (cw) DNP mechanisms—the Overhauser effect, the solid effect, the cross effect, and thermal mixing. A special section is devoted to the theory of coherent polarization transfer mechanisms, since they are potentially more efficient at high fields than classical polarization schemes. The implementation of DNP at high magnetic fields has required the development and improvement of new and existing instrumentation. Therefore, we also review some recent developments in ?w and probe technology, followed by an overview of DNP applications in biological solids and liquids. Finally, we outline some possible areas for future developments. PMID:18266416

  3. Charge exchange of a polar molecule at its cation

    SciTech Connect

    Buslov, E. Yu., E-mail: buslov@phys.vsu.ru; Zon, B. A., E-mail: zon@niif.vsu.ru [Voronezh State University (Russian Federation)

    2011-01-15

    The Landau-Herring method is used to derive an analytic expression for the one-electron exchange interaction of a polar molecule with its positively charged ion, induced by a {sigma}-electron. Analogously to the classical Van der Pole method, the exchange interaction potential is averaged over the rotational states of colliding particles. The resonant charge-transfer cross section is calculated, and the effect of the dipole moments of the core on the cross section is analyzed. It is shown that allowance for the dependence of the exchange potential on the orientation of the dipole moments relative to the molecular axis may change the dependence of the cross section on the velocity of colliding particles, which is typical of the resonant charge exchange, from the resonance to the quasi-resonance dependence.

  4. High Intensity Polarized Electron Gun

    SciTech Connect

    Redwine, Robert

    2012-07-31

    The goal of the project was to investigate the possibility of building a very high intensity polarized electron gun for the Electron-Ion Collider. This development is crucial for the eRHIC project. The gun implements a large area cathode, ring-shaped laser beam and active cathode cooling. A polarized electron gun chamber with a large area cathode and active cathode cooling has been built and tested. A preparation chamber for cathode activation has been built and initial tests have been performed. Major parts for a load-lock chamber, where cathodes are loaded into the vacuum system, have been manufactured.

  5. Toward scalable information processing with ultracold polar molecules in an electric field: A numerical investigation

    SciTech Connect

    Bomble, Laeetitia; Pellegrini, Philippe; Ghesquiere, Pierre [Laboratoire de Chimie Physique, Universite Paris-Sud, UMR 8000, Orsay F-91405 (France); Desouter-Lecomte, Michele [Laboratoire de Chimie Physique, Universite Paris-Sud, UMR 8000, Orsay F-91405 (France); Departement de Chimie, Universite de Liege, Bat B6c Sart Tilman, B-4000 Liege Belgium (Belgium)

    2010-12-15

    We numerically investigate the possibilities of driving quantum algorithms with laser pulses in a register of ultracold NaCs polar molecules in a static electric field. We focus on the possibilities of performing scalable logical operations by considering circuits that involve intermolecular gates (implemented on adjacent interacting molecules) to enable the transfer of information from one molecule to another during conditional laser-driven population inversions. We study the implementation of an arithmetic operation (the addition of 0 or 1 on a binary digit and a carry in) which requires population inversions only and the Deutsch-Jozsa algorithm which requires a control of the phases. Under typical experimental conditions, our simulations show that high-fidelity logical operations involving several qubits can be performed in a time scale of a few hundreds of microseconds, opening promising perspectives for the manipulation of a large number of qubits in these systems.

  6. The transition from single molecule to ensemble revealed by fluorescence polarization.

    PubMed Central

    Bell, Toby D. M.; Clayton, Andrew H. A.

    2015-01-01

    Fluorescence polarization measurements in the condensed phase provide rich information on rotational dynamics and interactions between macromolecules. An important parameter in these studies is the limiting polarization or po which is the emission polarization in the absence of molecular rotation. Here we explore how molecular number averaging affects the observed value of po. Using a simple mathematical model we show that for a collection of fluorescent dipoles (1–50 molecules) the fluorescence polarization (p) increases with the number of molecules (N) due to the progressive onset of photo-selection with a relation of the form p = po(1 ? N??). This concept is demonstrated experimentally using single molecule polarization measurements of perylene diimide dye molecules in a rigid polymer matrix where it is shown that the average emission polarization increases significantly when the number of molecules per averaging window is increased from 1 to 10 molecules. These results suggest that the definition of limiting polarization needs to be refined in the quasi-single molecule regime. Moreover, these results pave a new way for measuring clustering of molecules from single cluster polarization histograms. PMID:25640875

  7. Topological p{sub x}+ip{sub y} superfluid phase of fermionic polar molecules

    SciTech Connect

    Levinsen, J.; Cooper, N. R. [T.C.M. Group, University of Cambridge, Cavendish Laboratory, J.J. Thomson Ave., Cambridge CB3 0HE (United Kingdom); Laboratoire de Physique Theorique et Modeles Statistiques, CNRS and Universite Paris Sud, UMR8626, 91405 Orsay (France); Shlyapnikov, G. V. [Laboratoire de Physique Theorique et Modeles Statistiques, CNRS and Universite Paris Sud, UMR8626, 91405 Orsay (France); Van der Waals-Zeeman Institute, University of Amsterdam, Science Park 904, 1098 XH Amsterdam (Netherlands); Kavli Institute for Theoretical Physics, University of California, Santa Barbara, California 93106-4030 (United States)

    2011-07-15

    We discuss the topological p{sub x}+ip{sub y} superfluid phase in a two-dimensional (2D) gas of single-component fermionic polar molecules dressed by a circularly polarized microwave field. This phase emerges because the molecules may interact with each other via a potential V{sub 0}(r) that has an attractive dipole-dipole 1/r{sup 3} tail, which provides p-wave superfluid pairing at fairly high temperatures. We calculate the amplitude of elastic p-wave scattering in the potential V{sub 0}(r) taking into account both the anomalous scattering due to the dipole-dipole tail and the short-range contribution. This amplitude is then used for the analytical and numerical solution of the renormalized BCS gap equation which includes the second-order Gor'kov-Melik-Barkhudarov corrections and the correction related to the effective mass of the quasiparticles. We find that the critical temperature T{sub c} can be varied within a few orders of magnitude by modifying the short-range part of the potential V{sub 0}(r). The decay of the system via collisional relaxation of molecules to dressed states with lower energies is rather slow due to the necessity of a large momentum transfer. The presence of a constant transverse electric field reduces the inelastic rate, and the lifetime of the system can be of the order of seconds even at 2D densities {approx}10{sup 9} cm{sup -2}. This leads to T{sub c} of up to a few tens of nanokelvins and makes it realistic to obtain the topological p{sub x}+ip{sub y} phase in experiments with ultracold polar molecules.

  8. Giant polarization in high polymers

    NASA Astrophysics Data System (ADS)

    Pohl, Herbert A.

    1986-07-01

    In the course of studying the properties of highly conjugated polymers we found that long range orbital delocalization conferred unexpected properties. The presence of giant electronic orbitals made these materials electroactive yet very stable. A new mode of electronic polarizability resulted, a giant nomadic polarization, making these organic polymers among the most polarizable materials ever encountered. In addition, yet other attributes could be found, such as remanent magnetization, or metallic conductivity, or unusual pressure sensitivity. The giant orbital concept opens up new vistas of materials properties. We note that one can tailor giant orbital polymers to produce pure and highly stable super-dielectrics with high dielectric constants, from 6 to 100,000. Such materials will be useful in the electric power control, as in large motor starting capacitors and in power factor correction. They will doubtless also be useful in low visibility coatings, in obscuration, in EMP shielding, in microcircuitry, in transducers, and in parametric circuits. It remains to be proven if this new molecular mode, nomadic polarization, proves superior in energy storage and loss to that of the conventional “dipole orientation” mode. Preliminary results indicate an advantage for the new giant orbital materials.

  9. Measurement of the nuclear polarization of hydrogen and deuterium molecules using a Lamb-shift polarimeter

    SciTech Connect

    Engels, Ralf, E-mail: r.w.engels@fz-juelich.de; Gorski, Robert; Grigoryev, Kiril; Mikirtychyants, Maxim; Rathmann, Frank; Seyfarth, Hellmut; Ströher, Hans; Weiss, Philipp [Institut für Kernphysik, Forschungszentrum Jülich, Wilhelm-Johnen-Str. 1, 52428 Jülich (Germany); Kochenda, Leonid; Kravtsov, Peter; Trofimov, Viktor; Tschernov, Nikolay; Vasilyev, Alexander; Vznuzdaev, Marat [Laboratory of Cryogenic and Superconductive Technique, Petersburg Nuclear Physics Institute, Orlova Roscha 1, 188300 Gatchina (Russian Federation); Schieck, Hans Paetz gen. [Institut für Kernphysik, Universität zu Köln, Zülpicher Str. 77, 50937 Köln (Germany)

    2014-10-15

    Lamb-shift polarimeters are used to measure the nuclear polarization of protons and deuterons at energies of a few keV. In combination with an ionizer, the polarization of hydrogen and deuterium atoms was determined after taking into account the loss of polarization during the ionization process. The present work shows that the nuclear polarization of hydrogen or deuterium molecules can be measured as well, by ionizing the molecules and injecting the H{sub 2}{sup +} (or D{sub 2}{sup +}) ions into the Lamb-shift polarimeter.

  10. Heteronuclear diatomic molecules in a strong laser field with an arbitrary polarization

    NASA Astrophysics Data System (ADS)

    Odžak, S.; ?erki?, A.; Busuladži?, M.; Hasovi?, E.; Gazibegovi?-Busuladži?, A.; Miloševi?, D. B.

    2014-09-01

    Processes of above-threshold ionization (ATI) and high-order harmonic generation (HHG) for heteronuclear diatomic molecules are investigated. By analyzing the HHG and ATI spectra for different molecular orientation with respect to the main laser polarization axis and for different values of the photon energies and electron energies and emission angle, we are able to draw some conclusions about the molecular structure. The partial elliptic dichroism effect in HHG spectra is also analyzed. Regarding the ATI spectra, two-center interference minima are visible, even for a circularly polarized laser field. The positions of the minima depend on the internuclear distance, on the relative contributions of the atomic orbitals to the highest occupied molecular orbital and on the laser field parameters.

  11. Creation of a low-entropy quantum gas of polar molecules in an optical lattice

    E-print Network

    Moses, Steven A; Miecnikowski, Matthew T; Yan, Bo; Gadway, Bryce; Ye, Jun; Jin, Deborah S

    2015-01-01

    Ultracold polar molecules, with their long-range electric dipolar interactions, offer a unique platform for studying correlated quantum many-body phenomena such as quantum magnetism. However, realizing a highly degenerate quantum gas of molecules with a low entropy per particle has been an outstanding experimental challenge. In this paper, we report the synthesis of a low entropy molecular quantum gas by creating molecules at individual sites of a three-dimensional optical lattice that is initially loaded from a low entropy mixture of K and Rb quantum gases. We make use of the quantum statistics and interactions of the initial atom gases to load into the optical lattice, simultaneously and with good spatial overlap, a Mott insulator of bosonic Rb atoms and a single-band insulator of fermionic K atoms. Then, using magneto-association and optical state transfer, we efficiently produce ground-state molecules in the lattice at those sites that contained one Rb and one K atom. The achieved filling fraction of 25% ...

  12. Single Molecule Raman Spectroscopy Under High Pressure

    NASA Astrophysics Data System (ADS)

    Fu, Yuanxi; Dlott, Dana

    2014-06-01

    Pressure effects on surface-enhanced Raman scattering spectra of Rhdoamine 6G adsorbed on silver nanoparticle surfaces was studied using a confocal Raman microscope. Colloidal silver nanoparticles were treated with Rhodamine 6G (R6G) and its isotopically substituted partner, R6G-d4. Mixed isotopomers let us identify single-molecule spectra, since multiple-molecule spectra would show vibrational transitions from both species. The nanoparticles were embedded into a poly vinyl alcohol film, and loaded into a diamond anvil cell for the high-pressure Raman scattering measurement. Argon was the pressure medium. Ambient pressure Raman scattering spectra showed few single-molecule spectra. At moderately high pressure ( 1GPa), a surprising effect was observed. The number of sites with observable spectra decreased dramatically, and most of the spectra that could be observed were due to single molecules. The effects of high pressure suppressed the multiple-molecule Raman sites, leaving only the single-molecule sites to be observed.

  13. High harmonic interferometry of multi-electron dynamics in molecules.

    PubMed

    Smirnova, Olga; Mairesse, Yann; Patchkovskii, Serguei; Dudovich, Nirit; Villeneuve, David; Corkum, Paul; Ivanov, Misha Yu

    2009-08-20

    High harmonic emission occurs when an electron, liberated from a molecule by an incident intense laser field, gains energy from the field and recombines with the parent molecular ion. The emission provides a snapshot of the structure and dynamics of the recombining system, encoded in the amplitudes, phases and polarization of the harmonic light. Here we show with CO(2) molecules that high harmonic interferometry can retrieve this structural and dynamic information: by measuring the phases and amplitudes of the harmonic emission, we reveal 'fingerprints' of multiple molecular orbitals participating in the process and decode the underlying attosecond multi-electron dynamics, including the dynamics of electron rearrangement upon ionization. These findings establish high harmonic interferometry as an effective approach to resolving multi-electron dynamics with sub-Angström spatial resolution arising from the de Broglie wavelength of the recombining electron, and attosecond temporal resolution arising from the timescale of the recombination event. PMID:19626004

  14. Cross sections of collision induced rotational transitions of polar molecules perturbed by isotropic projectiles

    Microsoft Academic Search

    Masatoshi Kajita; Hitoshi Odashima; Tadao Shimizu

    1991-01-01

    A semiempirical formula for the cross section of collision induced rotational relaxation is presented, which allows one to estimate fairly accurate values of cross sections for any pairs of polar molecules and isotropic perturbers. The cross section does not critically depend on the quantum states, but is described simply by the parameters of colliding atoms and molecules, such as van

  15. Universalities in ultracold reactions of alkali-metal polar molecules

    NASA Astrophysics Data System (ADS)

    Quéméner, Goulven; Bohn, John L.; Petrov, Alexander; Kotochigova, Svetlana

    2011-12-01

    We consider ultracold collisions of ground-state heteronuclear alkali-metal dimers that are susceptible to four-center chemical reactions 2AB?A2+B2 even at submicrokelvin temperatures. These reactions depend strongly on species, temperature, electric field, and confinement in an optical lattice. We calculate ab initio van der Waals coefficients for these interactions and use a quantum formalism to study the scattering properties of such molecules under an external electric field and optical lattice. We also apply a quantum threshold model to explore the dependence of reaction rates on the various parameters. We find that, among the heteronuclear alkali-metal fermionic species, LiNa is the least reactive, whereas LiCs is the most reactive. For the bosonic species, LiK is the most reactive in zero field, but all species considered, LiNa, LiK, LiRb, LiCs, and KRb, share a universal reaction rate once a sufficiently high electric field is applied. For indistinguishable bosons, the inelastic/reactive rate increases as d2 in the quantum regime, where d is the dipole moment induced by the electric field. This is a weaker power-law dependence than for indistinguishable fermions, for which the rate behaves as d6.

  16. Universalities in ultracold reactions of alkali-metal polar molecules

    SciTech Connect

    Quemener, Goulven; Bohn, John L.; Petrov, Alexander; Kotochigova, Svetlana [JILA, University of Colorado, Boulder, Colorado 80309 (United States); Temple University, Philadelphia, Pennsylvania 19122 (United States)

    2011-12-15

    We consider ultracold collisions of ground-state heteronuclear alkali-metal dimers that are susceptible to four-center chemical reactions 2AB{yields}A{sub 2}+B{sub 2} even at submicrokelvin temperatures. These reactions depend strongly on species, temperature, electric field, and confinement in an optical lattice. We calculate ab initio van der Waals coefficients for these interactions and use a quantum formalism to study the scattering properties of such molecules under an external electric field and optical lattice. We also apply a quantum threshold model to explore the dependence of reaction rates on the various parameters. We find that, among the heteronuclear alkali-metal fermionic species, LiNa is the least reactive, whereas LiCs is the most reactive. For the bosonic species, LiK is the most reactive in zero field, but all species considered, LiNa, LiK, LiRb, LiCs, and KRb, share a universal reaction rate once a sufficiently high electric field is applied. For indistinguishable bosons, the inelastic/reactive rate increases as d{sup 2} in the quantum regime, where d is the dipole moment induced by the electric field. This is a weaker power-law dependence than for indistinguishable fermions, for which the rate behaves as d{sup 6}.

  17. Dynamic nuclear polarization of amorphous and crystalline small molecules

    E-print Network

    Ong, Ta-Chung

    2014-01-01

    Solid-state NMR has emerged to become an important technique in the studies of pharmaceutical formulations consisting of active pharmaceutical ingredients (API) and excipients. Dynamic nuclear polarization (DNP), which ...

  18. Two-electron exchange interaction between polar molecules and atomic ions — Asymptotic approach

    NASA Astrophysics Data System (ADS)

    Karbovanets, Oleksandr M.; Karbovanets, Myroslav I.; Khoma, Mykhaylo V.; Lazur, Volodymyr Yu.

    2015-05-01

    We have described the asymptotic approach for calculation of the two-electron exchange interaction between atomic ion and polar molecule responsible for direct double electron transfer processes. The closed analytic expression for matrix element of exchange interaction has been obtained in the framework of the semiclassical version of the asymptotic theory and point-dipole approximation for description of the polar molecule. Contribution to the Topical Issue "Elementary Processes with Atoms and Molecules in Isolated and Aggregated States", edited by Friedrich Aumayr, Bratislav Marinkovic, Štefan Matej?ik, John Tanis and Kurt H. Becker.

  19. The ground state of the polar alkali-Strontium molecules: potential energy curve and permanent dipole moment

    E-print Network

    Paris-Sud XI, Université de

    The ground state of the polar alkali-Strontium molecules: potential energy curve and permanent In this study, we investigate the structure of the polar alkali-Strontium diatomic molecules as possible those of the alkali-Rb molecules. O. Dulieu: olivier.dulieu@u-psud.fr 1 hal-00499637,version1-11Jul2010

  20. Universal ultracold collision rates for polar molecules of two alkali-metal atoms

    NASA Astrophysics Data System (ADS)

    Julienne, Paul; Hanna, Thomas; Idziaszek, Zbigniew

    2011-05-01

    Highly reactive ultracold polar molecules have universal near-threshold reaction rate constants that depend only on the long-range interaction potential, as shown for the KRb molecule. We extend these calculations to estimate universal reaction rate constants for the bosonic and fermionic isotopes of the reactive species LiNa, LiK, LiRb, LiCs, and also the universal vibrational quenching rate constants for vibrationally excited states of the non-reactive species NaK, NaRb, NaCs, KCs, and RbCs. We also examine the variation with electric field of the universal collision rates for these species in quasi-2D geometry in a one-dimensional optical lattice. For many of these species an electric field of a few kV/cm perpendicular to the lattice plane should be effective in shielding the molecules from destructive collisions even at relatively modest lattice confinement strength. Supported by an AFOSR MURI and a Polish government grant.

  1. Reactive collisions of ultracold polar molecules in quasi-one-dimensional traps

    NASA Astrophysics Data System (ADS)

    Idziaszek, Zbigniew; Jachymski, Krzysztof; Julienne, Paul; Simoni, Andrea

    2011-05-01

    We investigate reactive and elastic rates of quasi-one-dimensional collisions of highly reactive polar molecules. Such molecules exhibit universal near-threshold rates dependent only on the long-range part of the interaction potential,, and their collision rates are determined by the van der Waals coefficient, the dipole moment, and the trap frequency. We consider a setup with an electric field perpendicular to the axis of a quasi-one-dimensional trap. In such a geometry the reactive rates will be suppressed for sufficiently strong dipole-dipole interactions. Based on the adiabatic approximation, we calculate correlation diagrams and collision rates of some reactive bialkali molecules: KRb, LiNa, LiK, LiRb and LiCs. The adiabatic results are further verified by comparing to exact analytical expressions in the limit of a zero electric field, and to the unitarized Born approximation for elastic rates at nonzero electric fields. Supported by an AFOSR MURI and a Polish government grant.

  2. Simple quantum model of ultracold polar molecule collisions

    SciTech Connect

    Idziaszek, Zbigniew; Quemener, Goulven; Bohn, John L.; Julienne, Paul S. [Faculty of Physics, University of Warsaw, PL-00-681 Warsaw (Poland); JILA, NIST, and University of Colorado, Boulder, Colorado, 80309-0440 (United States); Joint Quantum Institute, NIST, and the University of Maryland, Gaithersburg, Maryland 20899-8423 (United States)

    2010-08-15

    We present a unified formalism for describing chemical reaction rates of trapped, ultracold molecules. This formalism reduces the scattering to its essential features, namely, a propagation of the reactant molecules through a gauntlet of long-range forces before they ultimately encounter one another, followed by a probability for the reaction to occur once they do. In this way, the electric-field dependence should be readily parametrized in terms of a pair of fitting parameters (along with a C{sub 6} coefficient) for each asymptotic value of partial-wave quantum numbers |L,M{sub L}>. From this, the electric-field dependence of the collision rates follows automatically. We present examples for reactive species, such as KRb, and nonreactive species, such as RbCs.

  3. Switching surface polarization of atomic force microscopy probe utilizing photoisomerization of photochromic molecules

    SciTech Connect

    Aburaya, Yoshihiro; Nomura, Hikaru; Kageshima, Masami; Naitoh, Yoshitaka; Li, Yan Jun; Sugawara, Yasuhiro [Department of Applied Physics, Graduate School of Engineering, Osaka University 2-1 Yamada-oka, Suita, Osaka 565-0871 (Japan)

    2011-03-15

    An attempt to develop an atomic force microscopy (AFM) probe with optically switchable polarization is described. Modification with a single molecular layer of photochromic molecules was attempted onto a Si substrate that is a prototype for a probe surface. Polarization switching caused by alternate irradiation of UV and visible lights were detected using the electrostatic force?>spectroscopy (EFS) technique. Si substrates modified with spiropyran and azobenzene exhibited reversible polarization switching that caused changes in CPD of about 100 and 50 mV, respectively. Modification with spiropyran was also attempted onto a Si probe and resulted in a CPD change of about 100 mV. It was confirmed that modification of an AFM probe or substrate with a single molecular layer of photochromic molecules can generate surface polarization switching of a mechanically detectable level.

  4. Partial-photoelectron-wave analysis in diatomic molecule photoionization by fluorescence polarization experiments

    SciTech Connect

    Demekhin, Ph. V. [Institute of Physics and CINSaT, University of Kassel, D-34132 Kassel (Germany); Rostov State University of Transport Communications, 344038 Rostov-on-Don (Russian Federation); Petrov, I. D. [Rostov State University of Transport Communications, 344038 Rostov-on-Don (Russian Federation); Ehresmann, A. [Institute of Physics and CINSaT, University of Kassel, D-34132 Kassel (Germany)

    2010-10-15

    Parameters {beta}1 and {beta}2 describing the angular distribution of circularly polarized fluorescence photons emitted by randomly oriented diatomic molecules excited by circularly polarized radiation are derived. We prove theoretically that measuring these parameters allows a partial-wave analysis of the emitted photoelectrons in the case of closed-shell diatomic molecules. The determination of the relative partial cross sections for emission of the {epsilon}{sigma}, {epsilon}{pi}, and {epsilon}{delta} photoelectrons is of fundamental importance for a sensitive test of corresponding calculations.

  5. On the isosteric heat of adsorption of non-polar and polar fluids on highly graphitized carbon black.

    PubMed

    Horikawa, Toshihide; Zeng, Yonghong; Do, D D; Sotowa, Ken-Ichiro; Alcántara Avila, Jesús Rafael

    2015-02-01

    Isosteric heat of adsorption is indispensable in probing the energetic behavior of interaction between adsorbate and solid, and it can shed insight into how molecules interact with a solid by studying the dependence of isosteric heat on loading. In this study, we illustrated how this can be used to explain the difference between adsorption of non-polar (and weakly polar) fluids and strong polar fluids on a highly graphitized carbon black, Carbopack F. This carbon black has a very small quantity of functional group, and interestingly we showed that no matter how small it is the analysis of the isosteric heat versus loading can identify its presence and how it affects the way polar molecules adsorb. We used argon and nitrogen as representatives of non-polar fluid and weakly polar fluid, and methanol and water for strong polar fluid. The pattern of the isosteric heat versus loading can be regarded as a fingerprint to determine the mechanism of adsorption for strong polar fluids, which is very distinct from that for non-polar fluids. This also allows us to estimate the interplay between the various interactions: fluid-fluid, fluid-basal plane and fluid-functional group. PMID:25463168

  6. Ionization of oriented carbonyl-sulfide molecules by intense circularly polarized laser pulses

    E-print Network

    Dimitrovski, Darko; Madsen, Lars Bojer; Filsinger, Frank; Meijer, Gerard; Küpper, Jochen; Holmegaard, Lotte; Kalhøj, Line; Nielsen, Jens H; Stapelfeldt, Henrik

    2010-01-01

    We present combined experimental and theoretical results on strong-field ionization of oriented carbonyl-sulphide molecules by circularly-polarized laser pulses. The obtained molecular frame photoelectron angular distributions show pronounced asymmetries perpendicular to the direction of the molecular electric dipole moment. These findings are explained by a tunneling model invoking the laser-induced Stark shifts associated with the dipoles and polarizabilities of the molecule and its unrelaxed cation.

  7. Managing light polarization via plasmon-molecule interactions within an asymmetric metal nanoparticle trimer

    SciTech Connect

    Shegai, Timur [Weizmann Institute of Science, Rehovot, Israel; Li, Zhipeng [Chinese Academy of Sciences; Zhang, Zhenyu [ORNL; Xu, Hongxing [ORNL; Haran, Gilad [Chinese Academy of Sciences

    2008-01-01

    The interaction of light with metal nanoparticles leads to novel phenomena mediated by surface plasmon excitations. In this paper we use single molecules to characterize the interaction of surface plasmons with light, and show that such interaction can strongly modulate the polarization of the emitted light. The simplest nanostructures that enable such polarization modulation are asymmetric silver nanocrystal trimers, where individual Raman scattering molecules are located in the gap between two of the nanoparticles. The third particle breaks the dipolar symmetry of the two-particle junction, generating a wavelength-dependent polarization pattern. Indeed, the scattered light becomes elliptically polarized and its intensity pattern is rotated in the presence of the third particle. We use a combination of spectroscopic observations on single molecules, scanning electron microscope imaging, and generalized Mie theory calculations to provide a full picture of the effect of particles on the polarization of the emitted light. Furthermore, our theoretical analysis allows us to show that the observed phenomenon is very sensitive to the size of the trimer particles and their relative position, suggesting future means for precise control of light polarization on the nanoscale.

  8. Augmented stability of hydrogen clathrate hydrates by weakly polar molecules.

    PubMed

    Nakayama, Takato; Koga, Kenichiro; Tanaka, Hideki

    2009-12-01

    Thermodynamic stability of hydrogen clathrate hydrates has been examined in a wide range of pressure based solely on the intermolecular interactions involved. We show that the stability is indeed augmented by a second guest species (here acetone) called a promoter, a consequence of which is notable reduction in the dissociation pressure of the hydrates encaging hydrogen alone. This evaluation is made by extension of the van der Waals-Platteeuw theory combined with semi-grand-canonical Monte Carlo (GCMC) simulations where the number of hydrogen molecules is allowed to vary while those of host water and promoter acetone molecules are fixed. The GCMC simulations then provide various types of cage occupancies of hydrogen from single to quadruple, from which the chemical potential of water in the clathrate hydrate is obtained as a function of the cage occupancy by acetone and the pressure. These occupancies are used to calculate the chemical potential of water in the clathrate hydrate. The stability is estimated by comparison of the chemical potential of water in the clathrate hydrate with that in hexagonal ice. We show the extent to which the dissociation pressure is reduced with increasing the occupancy of the larger cages by acetone. PMID:19968350

  9. Single molecules probe the polarization dynamics of poly (methyl methacrylate) in external electric field

    NASA Astrophysics Data System (ADS)

    Chen, Ruiyun; Zhang, Guofeng; Gao, Yan; Xiao, Liantuan; Jia, Suotang

    2012-05-01

    We demonstrate the electric field (EF) induced polarization dynamics of poly (methyl methacrylate) (PMMA) by observing the fluorescence modulation of embedded non-polar single squaraine-derived rotaxane molecules. It is established that interaction between the molecular energy level and the potential valley formed by surrounding PMMA matrix can be detuned by the EF, which induces the changing of electron transfer rates between them effectively. The EF-induced response time of the fluorescence quenching or enhancement and the fluorescence recovery time reflect the diverse polarization and relaxation dynamics of PMMA.

  10. [Polarization selectivity of interaction of DNA molecules by the action of X-ray radiation].

    PubMed

    Semchenko, I V; Kakhomov, S A; Balmakov, A P

    2010-01-01

    The optimum form of a long helical molecule, which DNA is, has been calculated in terms of the classical electromagnetic theory. Three different methods of classical electrodynamics are used: the theory of dipole radiation of electromagnetic waves, the energetic power approach, and a helical model of molecules of chiral medium. In all three cases, an identical result for the optimum geometrical form of a long spiral molecule has been obtained. The lead angle between the tangent to the helix and the plane normal to the axis of the helix should be equal to 24.5 degrees. This condition imposes restrictions on the radius and the pitch of the helical molecule. The experimentally measured geometrical characteristics of the DNA molecule satisfy the theoretically calculated condition precisely enough. Having the optimum geometrical form, the DNA molecule is not influenced by a circularly right-handed polarized electromagnetic wave in the soft X-ray range lambda = 7-8 nm. This wave, for which the right-handed DNA molecule is "transparent", should propagate orthogonally to the helix axis and form a right-handed screw in space. The wave radiated by the right-handed DNA molecule orthogonally to helix axis in the range of lambda = 7-8 nm has, accordingly, the left-handed circular polarization. The polarization selectivity of the DNA molecule by the action of X-ray radiation is exhibited strongly enough in the wavelength range of lambda = 1-35 nm. The results obtained are valid for any distribution of electric currents in DNA, i.e., for any sequence of nitrus bases in DNA. PMID:20429275

  11. HIGH ENERGY POLARIZATION OF BLAZARS: DETECTION PROSPECTS

    SciTech Connect

    Chakraborty, N. [Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, D-69117 Heidelberg (Germany); Pavlidou, V. [Department of Physics, University of Crete, 71003 Heraklion (Greece); Fields, B. D. [Department of Astronomy and Department of Physics, University of Illinois, Urbana, IL 61801 (United States)

    2015-01-01

    Emission from blazar jets in the ultraviolet, optical, and infrared is polarized. If these low-energy photons were inverse-Compton scattered, the upscattered high-energy photons retain a fraction of the polarization. Current and future X-ray and gamma-ray polarimeters such as INTEGRAL-SPI, PoGOLITE, X-Calibur, Gamma-Ray Burst Polarimeter, GEMS-like missions, ASTRO-H, and POLARIX have the potential to discover polarized X-rays and gamma-rays from blazar jets for the first time. Detection of such polarization will open a qualitatively new window into high-energy blazar emission; actual measurements of polarization degree and angle will quantitatively test theories of jet emission mechanisms. We examine the detection prospects of blazars by these polarimetry missions using examples of 3C 279, PKS 1510-089, and 3C 454.3, bright sources with relatively high degrees of low-energy polarization. We conclude that while balloon polarimeters will be challenged to detect blazars within reasonable observational times (with X-Calibur offering the most promising prospects), space-based missions should detect the brightest blazars for polarization fractions down to a few percent. Typical flaring activity of blazars could boost the overall number of polarimetric detections by nearly a factor of five to six purely accounting for flux increase of the brightest of the comprehensive, all-sky, Fermi-LAT blazar distribution. The instantaneous increase in the number of detections is approximately a factor of two, assuming a duty cycle of 20% for every source. The detectability of particular blazars may be reduced if variations in the flux and polarization fraction are anticorrelated. Simultaneous use of variability and polarization trends could guide the selection of blazars for high-energy polarimetric observations.

  12. Investigating Polaron Transitions with Polar Molecules Felipe Herrera,1,2,3

    E-print Network

    Krems, Roman

    Investigating Polaron Transitions with Polar Molecules Felipe Herrera,1,2,3 Kirk W. Madison,4 Roman the phase diagram of a polaron model with mixed breathing-mode and Su-Schrieffer- Heeger couplings and show to measure the polaron dispersion using stimulated Raman spectroscopy. DOI: 10.1103/PhysRevLett.110

  13. CMB and Molecules at High Redshift

    E-print Network

    F. Combes

    1999-01-17

    It becomes possible now to detect cold molecules at high redshift in the millimeter domain. Since the first discovery in 1992 by Brown and van den Bout of CO lines at z=2.28 in a gravitationally lensed starburst galaxy, nearly ten objects are now known to possess large quantities of molecular gas beyond z=1 and up to z = 5, through millimeter and sub-millimeter emission lines. The continuum dust emission is the most easily detected: in the mm domain, the emission is stronger for the more redshifted objects. For the CO lines, the situation is less favorable, and the reported detections are helped by gravitational amplification. The increase of the CMB temperature T_{bg} with redshift helps the rotational line excitation (especially at high z), but not its detection. Absorption in front of quasars is a more sensitive probe of cold gas at high redshift, able to detect individual clouds of a few solar masses (instead of 10^{10} Mo for emission). From the diffuse components, one can measure the cosmic black body temperature as a function of redshift. The high column densities component allow to observe important molecules not observable from the ground, like O2, H2O and LiH for example.

  14. Photoelectron angular distributions from polar molecules probed by intense femtosecond lasers

    SciTech Connect

    Abu-samha, M.; Madsen, L. B. [Lundbeck Foundation Theoretical Center for Quantum System Research, Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C (Denmark)

    2010-10-15

    We present numerical calculations of molecular-frame photoelectron angular distributions in strong-field ionization of oriented polar HF and LiF molecules by linearly polarized laser pulses with durations of about 20 fs (seven cycles at 800 nm). The calculations are performed within the single-active-electron and frozen-nuclei approximations. Our analysis shows that for the HF and LiF molecules, anisotropies in the molecular potential and the probed orbital lead to enhanced ionization during laser half cycles with the field pointing antiparallel to the permanent dipole of the dipole term in a multipolar expansion of the anisotropic molecular potential. This is manifested as a strong asymmetry in the computed photoelectron angular distributions: The photoelectrons are preferentially detected opposite to the permanent dipole of the molecular potential. This phenomenon is very sensitive to the probed system (the probed orbital and the molecular potential) and the orientation angle between the molecular axis and the laser polarization.

  15. Dynamic orbitals in high-order harmonic generation from CO molecules

    NASA Astrophysics Data System (ADS)

    Zhang, Bin; Yuan, Jianmin; Zhao, Zengxiu

    2014-09-01

    We identify that both the dynamic core polarization and dynamic orbital deformation are important in the orientation-dependent high-order harmonic generation of CO molecules subjected to intense few cycle laser fields. These polarization dynamics allow for the observation of strong orientation effects and dynamic minimum in the harmonic spectra. The generated attosecond pulses can be greatly affected by these multielectron effects. This work sheds light on future development of dynamic orbital imaging on attosecond time scale.

  16. High-order harmonic generation from molecules

    NASA Astrophysics Data System (ADS)

    Wagner, Nicholas L.

    High harmonic generation in atoms is well understood in terms of the three step model (ionization, propagation and recombination), and much attention has been payed to the dynamics of the continuum electron in the propagation step. However, a molecular medium can be used to further understand the ionization and recombination steps. High harmonic generation can also be used to probe the dynamics of rotational and vibrational wave packets in molecular media. This thesis reports on two experiments using high harmonic generation from molecular media. In the first experiment, an impulsive Raman pump is used to excite a rotational wave packet in the molecular system, and a second time-delayed pulse generates high harmonics from the rotationally excited medium. Both the intensity and the phase of the high harmonic emission are measured. The general features of the orientational dipole are extracted from the phase and intensity modulations. A second experiment uses a vibrationally excited molecule as the high harmonic generation medium. The coherently excited molecular vibrations modulate the intensity of the high harmonic generation. Using high harmonic generation as a probe makes it possible to see all excited modes include two modes which were not present using a comparable visible probe. The rotational dephasing of the vibrational wave packet is also observed.

  17. Nuclear magnetic resonance of laser-polarized noble gases in molecules, materials, and organisms.

    PubMed

    Goodson, Boyd M

    2002-04-01

    The sensitivity of conventional nuclear magnetic resonance (NMR) techniques is fundamentally limited by the ordinarily low spin polarization achievable in even the strongest NMR magnets. However, by transferring angular momentum from laser light to electronic and nuclear spins, optical pumping methods can increase the nuclear spin polarization of noble gases by several orders of magnitude, thereby greatly enhancing their NMR sensitivity. This review describes the principles and magnetic resonance applications of laser-polarized noble gases. The enormous sensitivity enhancement afforded by optical pumping can be exploited to permit a variety of novel NMR experiments across numerous disciplines. Many such experiments are reviewed, including the void-space imaging of organisms and materials, NMR and MRI of living tissues, probing structure and dynamics of molecules in solution and on surfaces, NMR sensitivity enhancement via polarization transfer, and low-field NMR and MRI. PMID:12036331

  18. Systematic analysis of long-range interactions between vibrating polar bialkali molecules

    NASA Astrophysics Data System (ADS)

    Dulieu, Olivier; Vexiau, Romain; Lepers, Maxence; Aymar, Mireille; Bouloufa, Nadia

    2012-06-01

    The determination of the long-range anisotropic interactions between polar bialkali molecules is of crucial importance for the achievement of a quantum gas of ultracold polar molecules. In particular, the dispersion coefficient C6 of the van der Waals interaction depends on the dynamic polarizability of the molecule evaluated at imaginary frequencies, expressed as a sum over all possible radiative transitions of electronic dipole moments. Using a mixture of up-to-date spectroscopic data and accurate ab initio data for potential energy curves, and permanent and transition dipole moments, we have obtained the values of the dispersion coefficients between identical polar molecules (LiNa, LiK, LiRb, LiCs, NaK, NaRb, NaCs, KRb, KCs, RbCs) in an arbitrary vibrational level of their electronic ground state. A careful analysis of the importance of the various kinds of transitions contributing to the sum has been performed. The C6 values significantly decrease with increasing vibrational levels towards the sum of the C6 coefficients between the four involved atomic pairs. For the lowest vibrational levels the C6 parameter varies from about 10^4 atomic units for KRb up to 10^7 atomic units for NaCs, which will lead to different collisional regimes at ultracold temperature.

  19. Relationship between the dipole moments and the electron affinities for some polar organic molecules

    NASA Astrophysics Data System (ADS)

    Gutsev, Gennady L.; Adamowicz, Ludwik

    1995-03-01

    The electronic and geometrical structures of fourteen polar molecules are investigated with the Hartree-Fock (HF) method and the second-order Møller-Plesset (MP2) perturbation theory. The molecules are: formaldehyde, H 2CO, propanol, CH 3CH 2CHO, pivalaldehyde, (CH 3) 3CCHO, butanal, CH 3CH 2CH 2CHO, acetaldehyde, CH 3CHO, 2-butanone, CH 3CH 2COCH 3, trifluoromethylbenzene, C 7H 5F 3, cyclohexanone, C 6H 10O, acetone, CH 3COCH 3, cyclopentanone, C 5H 8O, cyclobutanone, C 4H 6O, methylacrylonitrile, CH 2CCH 3CN, acrylonitrile, CH 2CHCN, acetonitrile, CH 3CN. The electron affinities corresponding to the formation of the dipole-bound states of the anions are calculated. For all the molecules considered, except formaldehyde, the molecules are found to be able to support dipole-bound states.

  20. HIGH LUMINOSITY POLARIZED PROTON COLLISIONS AT RHIC.

    SciTech Connect

    ROSER,T.

    2001-03-26

    The Brookhaven Relativistic Heavy Ion Collider (RHIC) provides the unique opportunity to collide polarized proton beams at a center-of-mass energy of up to 500 GeV and luminosities of up to 2 x 10{sup 32} cm{sup {minus}2} s{sup {minus}1}. Such high luminosity and high energy polarized proton collisions will open up the possibility of studying spin effects in hard processes. However, the acceleration of polarized beams in circular accelerators is complicated by the numerous depolarizing spin resonances. Using a partial Siberian snake and a rf dipole that ensure stable adiabatic spin motion during acceleration has made it possible to accelerate polarized protons to 25 GeV at the Brookhaven AGS. After successful operation of RHIC with gold beams polarized protons from the AGS have been successfully injected into RHIC and accelerated using a full Siberian snakes built from four superconducting helical dipoles. A new high energy proton polarimeter was also successfully commissioned. Operation with two snakes per RHIC ring is planned for next year.

  1. Wavelength-dependent ionization suppression of diatomic molecules in intense circularly polarized laser fields

    NASA Astrophysics Data System (ADS)

    Kang, HuiPeng; Lin, ZhiYang; Xu, SongPo; Wang, ChuanLiang; Quan, Wei; Lai, XuanYang; Liu, XiaoJun; Jia, XinYan; Hao, XiaoLei; Chen, Jing; Chu, Wei; Yao, JinPing; Zeng, Bin; Cheng, Ya; Xu, ZhiZhan

    2014-12-01

    We perform an experimental study on comparison between the ionization of homonuclear diatomic molecules (O2 and N2) and their companion atoms (Xe and Ar) radiated by circularly polarized intense laser fields. We find that the ionization of O2 shows suppression with respect to its companion atom Xe, which exhibits a clear wavelength and intensity dependence similar to that in linearly polarized laser field, while the ionization of N2 behaves like its companion atom Ar. With the help of S -matrix theoretical analysis, our observations can be attributed to both the molecular orbital and the two-center interference effect in molecular ionization process.

  2. Theory of the dielectric susceptibility of liquid crystals with polar nonuniaxial molecules

    E-print Network

    A. Kapanowski; T. Wietecha

    2011-02-03

    Statistical theory of the dielectric susceptibility of polar liquid crystals is proposed. The molecules are not uniaxial but similar to cones. It is assumed that the permanent dipole moment of a molecule is parallel to the axis of the rotational symmetry. The ordering of the phase is described by means of the mean field theory based on the Maier-Saupe approach. The theory was used to calculate the temperature dependence of the order parameters and the susceptibilities. Predictions of the model for different sets of parameters are investigated.

  3. Interaction-induced ferroelectricity in the rotational states of polar molecules

    SciTech Connect

    Lin, C.-H.; Hsu, Y.-T.; Lee Hao [Physics Department, National Tsing-Hua University, Hsinchu 300, Taiwan (China); Wang, D.-W. [Physics Department, National Tsing-Hua University, Hsinchu 300, Taiwan (China); Physics Division, National Center for Theoretical Sciences, Hsinchu 300, Taiwan (China)

    2010-03-15

    We show that a ferroelectric quantum phase transition can be driven by the dipolar interaction of polar molecules in the presence a microwave field. The obtained ferroelectricity crucially depends on the harmonic confinement potential, and the macroscopic dipole moment persists even when the external field is turned off adiabatically. The transition is shown to be second order for fermions and for bosons of a smaller permanent dipole moment, but is first order for bosons of a larger moment. Our results suggest the possibility of manipulating the microscopic rotational state of polar molecules by tuning the trap's aspect ratio (and other mesoscopic parameters), even though the later's energy scale is smaller than the former's by six orders of magnitude.

  4. Polarization sensitive, three-dimensional, single-molecule imaging of cells with a double-helix system.

    PubMed

    Pavani, Sri Rama Prasanna; DeLuca, Jennifer G; Piestun, Rafael

    2009-10-26

    Double-helix point spread function photoactivation-localization microscopy allows three-dimensional (3D) superresolution imaging of objects smaller than the optical diffraction-limit. We demonstrate polarization sensitive detection with 3D super-localization of single-molecules and unveil 3D polarization specific characteristics of single-molecules within the intracellular structure of PtK1 cells expressing photoactivatable green fluorescent protein. The system modulates orthogonal polarization components of single-molecule emissions with a single spatial light modulator and detects them separately with a single detector. Information obtained from the two polarization channels demonstrates polarization based contrast in 3D superresolution imaging. Further, we show that the 3D information from the two channels can be optimally combined to yield up to 30% improvement in localization precision relative to a single polarization channel system. PMID:19997184

  5. Dust and Molecules at High Redshift

    E-print Network

    F. Combes

    1998-12-23

    In the last years, progress has been very rapid in the domain of molecules at high redshift, and we know in better detail now the molecular and dust content in several systems beyond z=1 and up to z = 5. The first discovery in 1992 by Brown and van den Bout of CO lines at z=2.28 in a gravitationally lensed starburst galaxy, strongly stimulated searches of other systems, but these were harder than foreseen, and less than 10 other systems have been discovered in CO emission. Redshifts range between 2 and 5, the largest being BR1202-0725 at z=4.69. Most of these systems, if not all, are gravitationally amplified objects. Some have been discovered first through their dust emission, relatively easy to detect because of the negative K-correction effect. The detection of all these systems could give an answer about the debated question of the star-formation rate as a function of redshift. The maximum of star-formation rate, found around z=2 from optical studies, could shift to higher z if the most remote objects are hidden by dust. Absorption in front of quasars can also probe cold gas at high redshift, taking advantage of very high spatial (milli arcsec) and spectral (30m/s) resolutions. From the diffuse components, one can measure the cosmic black body temperature as a function of redshift. All these preliminary studies will be carried out at large scales with future millimeter instruments, and some perspectives are given.

  6. Role of proton ordering in adsorption preference of polar molecule on ice surface

    PubMed Central

    Sun, Zhaoru; Pan, Ding; Xu, Limei; Wang, Enge

    2012-01-01

    Adsorption of polar monomers on ice surface, relevant to the physical/chemical reaction in ice clouds as well as growth of ice, remains an open issue partially due to the unusual surface characteristics with protons at the top layer of ice. Using first-principle calculations, we explore the adsorption properties of ice surface in terms of a surface proton order parameter, which characterizes the inhomogeneity of the dangling atoms on ice surface. We show that, due to an effective electric field created by dangling OH bonds and lone pairs of water molecules not only directly neighboring but also further away from the adsorbed polar molecule on the ice surface, the adsorption energy of polar monomer on ice surface exhibits large variance and a strong correlation with the proton order parameter of ice surface. Our results about the positive correlation between the inhomogeneity of ice surface and adsorption energies suggest that the physical/chemical reactions as well as the growth of ice may prefer to occur firstly on surfaces with larger proton order parameter. PMID:22837403

  7. Vibrational, electronic, and vibronic excitations of polar C60F18 molecules: Experimental and theoretical study

    NASA Astrophysics Data System (ADS)

    Popov, A. A.; Senyavin, V. M.; Korepanov, V. I.; Goldt, I. V.; Lebedev, A. M.; Stankevich, V. G.; Menshikov, K. A.; Svechnikov, N. Yu.; Boltalina, O. V.; Kareev, I. E.; Kimura, S.; Sidorova, O.; Kanno, K.; Akimoto, I.

    2009-01-01

    Polarized optical conductivity spectra in the IR and visible range and variable-temperature photoluminescence spectra of the C60F18 single crystals in the 4-300 K temperature range are reported. Density-functional theory (DFT) calculations of vibrational spectra and time-dependent DFT calculations of the excitation energies of the C60F18 molecule are performed to interpret experimentally observed phenomena. Orientation of the C3v -symmetric C60F18 molecules in the single crystal is revealed by comparison of the experimental polarized IR spectra and vibrational DFT calculations. A2 symmetry is assigned to the lowest energy singlet excited state of C60F18 , and hence pure electronic S0?S1 excitation is found to be dipole forbidden. Fine vibronic structure found at low temperature is interpreted in terms of Herzberg-Teller and Franck-Condon mechanisms. Considerable similarity with vibronic spectra of C60 is found and explained by presumable localization of the lowest energy electronic excitation of C60F18 on the fullerenelike part of the molecule.

  8. Enhancement of metallic silver monomer evaporation by the adhesion of polar molecules to silver nanocluster ions

    SciTech Connect

    Fagerquist, C.K.; Sensharma, D.K.; El-Sayed, M.A. [Univ. of California, Los Angeles, CA (United States); Rubio, A.; Cohen, M.L. [Univ. of California, Berkeley, CA (United States)]|[Lawrence Berkeley Lab., CA (United States)

    1995-05-11

    We have compared the metallic evaporation channels from metastable [Ag{sub X=5,7,11}(AgI){sub Y=1-4}]{sup +} clusters in the first field free region of a double focusing mass spectrometer with that of the corresponding pure metallic clusters, [Ag{sub X=5,7,11}]{sup +}. It is found that the presence of the polar AgI molecules increases the rate of silver monomer evaporation relative to that of silver dimer evaporation. Using thermodynamic expressions for the heat of evaporation of the different evaporation processes and assuming the absence of reverse activation energies, an expression for the difference between the activation energy of silver monomer and dimer evaporation is derived. It is shown that dipole/induced-dipole forces resulting from the presence of AgI polar molecules lead to an enhancement of silver monomer evaporation if the polarizability of the pure metallic cluster ions increases with the number of Jellium electrons. Our theoretical calculations of the static polarizabilities of [Ag{sub x}]{sup +}, using time dependent density functional theory within the local density approximation, shows a smooth increase in the polarizabilities with the number of the Jellium electrons in these clusters. Finally, we observe that the enhancement of Ag monomer evaporation per AgI needed is smaller for clusters with an even number of AgI molecules than with an odd number of them. 46 refs., 5 figs., 2 tabs.

  9. Polarization converters in highly birefringent microfibers.

    PubMed

    Xuan, HaiFeng; Ma, Jun; Jin, Wa; Jin, Wei

    2014-02-10

    A novel type of polarization converters (PCs) based on highly birefringent (Hi-Bi) microfibers is presented. Analytical formulation based on the Jones Matrix method and a numerical code based on the Full Vectorial Finite Difference Beam Propagation Method are developed to analyze the polarization evolutions in such PCs. Two different design configurations, namely the "one-side" and "two-side" perturbation configurations, are studied by use of the two methods, and the results obtained agree well with each others. The PCs can be flexibly designed to have different operating wavelengths, spectral bandwidths, and devices lengths. A particular PC based on an elliptical microfiber demonstrates a bandwidth of ? 600 nm around 1550 nm with a device length of ? 150 ?m. PMID:24663656

  10. Putting the pieces together: contribution of fluorescence polarization assays to small-molecule lead optimization

    NASA Astrophysics Data System (ADS)

    Keating, Susan M.; Marsters, Jim; Beresini, Maureen; Ladner, Carmen; Zioncheck, Kim; Clark, Kevin; Arellano, Fred; Bodary, Sarah

    2000-04-01

    Fluorescence polarization assays with both purified receptor and intact cells have been developed to assess potency and selectivity of antagonists of the interaction of the lymphocyte receptor, LFA-1, and its endothelial ligand, ICAM-1. Fluorescein isothiocyanate conjugated small molecule probes were optimized for use in binding assay with LFA-1 and a closely related receptor, MAC-1. In the assays, the antagonists compete with the fluorescent probe for binding to the receptor. This enables the determination of IC50 and consequently Ki values of the antagonists for each of the receptors. Routine use of polarization assay with tranfected cells, in addition to purified receptors, has become feasible with the availability of sensitive plate readers that are able to detect 1 nM fluorescent probe in 15 (mu) l sample volumes with good signal to noise. These measurements aid in the iterative synthesis of more potent and selective compounds.

  11. High Intensity Polarized Electron Gun Studies at MIT-Bates

    SciTech Connect

    Tsentalovich, E. [MIT-Bates Linear Accelerator Center, Middleton, MA (United States)

    2009-08-04

    A proposed new high-luminosity electron-ion collider requires a polarized electron source of extremely high intensity. An ion back bombardment of the cathode is the main factor limiting the intensity of modern polarized electron guns. This study examines the possibility of building a very high intensity polarized electron gun.

  12. Efficient conversion of ultracold Feshbach-resonance-related polar molecules into ultracold ground state (X 1?^+ v = 0, J = 0) molecules

    NASA Astrophysics Data System (ADS)

    Stwalley, W. C.

    2004-11-01

    It is proposed that bound states of ultracold heteronuclear alkali dimer molecules derived from Feshbach resonances can be efficiently converted into true ground state ultracold molecules (X 1? + v = 0, J = 0) by a stimulated Raman process via b 3{Pi} ˜ A 1? + mixed levels. This is illustrated and discussed for five of the ten polar heteronuclear alkali dimers: LiNa, NaK, NaRb, RbCs, and especially KRb.

  13. Polarized Protein-Specific Charges from Atoms-in-Molecule Electron Density Partitioning

    PubMed Central

    2013-01-01

    Atomic partial charges for use in traditional force fields for biomolecular simulation are often fit to the electrostatic potentials of small molecules and, hence, neglect large-scale electronic polarization. On the other hand, recent advances in atoms-in-molecule charge derivation schemes show promise for use in flexible force fields but are limited in size by the underlying quantum mechanical calculation of the electron density. Here, we implement the density derived electrostatic and chemical charges method in the linear-scaling density functional theory code ONETEP. Our implementation allows the straightforward derivation of partial atomic charges for systems comprising thousands of atoms, including entire proteins. We demonstrate that the derived charges are chemically intuitive, reproduce ab initio electrostatic potentials of proteins and are transferable between closely related systems. Simulated NMR data derived from molecular dynamics of three proteins using force fields based on the ONETEP charges are in good agreement with experiment. PMID:23894231

  14. Spherical tensor analysis of polar liquid crystals with biaxial and chiral molecules

    NASA Astrophysics Data System (ADS)

    Iwamoto, Mitsumasa; Zhong-can, Ou-Yang

    2012-11-01

    With the help of spherical tensor expression, an irreducible calculus of a Lth-rank macroscopic susceptibility ? for a polar liquid crystal (PLC) of biaxial and chiral molecules written as the average of molecular hyperpolarizability tensor ? associated with their spherical orientational order parameters (0?l?L) is presented. Comprehensive formulas of L=1,2 have been obtained and the latter explains the optical activity and spontaneous splay texture observed in bent-core PLC. The expression of L=3 specifies for the molecules with D2 symmetry which can be applied to analyze the nonlinear optical second harmonic generation (SHG) observed in proteins, peptides, and double-stranded DNA at interfaces.

  15. Evaporative cooling of reactive polar molecules confined in a two-dimensional geometry

    E-print Network

    Bihui Zhu; Goulven Quéméner; Ana M. Rey; Murray J. Holland

    2013-11-03

    Recent experimental developments in the loading of ultracold KRb molecules into quasi-two-dimensional traps, combined with the ability to tune the ratio between elastic and loss (inelastic/reactive) collisions through application of an external electric field, are opening the door to achieving efficient evaporative cooling of reactive polar molecules. In this paper, we use Monte Carlo simulations and semianalytic models to study theoretically the experimental parameter regimes in which evaporative cooling is feasible under current trapping conditions. We investigate the effect of the anisotropic character of dipole-dipole collisions and reduced dimensionality on evaporative cooling. We also present an analysis of the experimentally relevant anti-evaporation effects that are induced by chemical reactions that take place when more than one axial vibrational state is populated.

  16. Evaporative cooling of reactive polar molecules confined in a two-dimensional geometry

    E-print Network

    Zhu, Bihui; Rey, Ana M; Holland, Murray J

    2013-01-01

    Recent experimental developments in the loading of ultracold KRb molecules into quasi-two-dimensional traps, combined with the ability to tune the ratio between elastic and loss (inelastic/reactive) collisions through application of an external electric field, are opening the door to achieving efficient evaporative cooling of reactive polar molecules. In this paper, we use Monte Carlo simulations and semianalytic models to study theoretically the experimental parameter regimes in which evaporative cooling is feasible under current trapping conditions. We investigate the effect of the anisotropic character of dipole-dipole collisions and reduced dimensionality on evaporative cooling. We also present an analysis of the experimentally relevant anti-evaporation effects that are induced by chemical reactions that take place when more than one axial vibrational state is populated.

  17. Long-range and frustrated spin-spin interactions in crystals of cold polar molecules

    SciTech Connect

    Zhou, Y. L. [College of Science, National University of Defense Technology, Changsha, 410073 (China); Ortner, M. [Institute for Theoretical Physics, University of Innsbruck, AT-6020 Innsbruck (Austria); Institute for Quantum Optics and Quantum Information of the Austrian Academy of Sciences, AT-6020 Innsbruck (Austria); Rabl, P. [Institute for Quantum Optics and Quantum Information of the Austrian Academy of Sciences, AT-6020 Innsbruck (Austria)

    2011-11-15

    We describe a simple scheme for the implementation and control of effective spin-spin interactions in self-assembled crystals of cold polar molecules. In our scheme, spin states are encoded in two long-lived rotational states of the molecules and coupled via state-dependent dipole-dipole forces to the lattice vibrations. We show that, by choosing an appropriate time-dependent modulation of the induced dipole moments, the resulting phonon-mediated interactions compete with the direct dipole-dipole coupling and lead to long-range and tunable spin-spin interaction patterns. We illustrate how this technique can be used for the generation of multiparticle entangled spin states and the implementation of spin models with long-range and frustrated interactions, which exhibit nontrivial phases of magnetic ordering.

  18. Supersolid Phase of Cold Fermionic Polar Molecules in 2D Optical Lattices

    Microsoft Academic Search

    Liang He; Walter Hofstetter

    2011-01-01

    We study a system of ultra-cold fermionic polar molecules in a\\u000atwo-dimensional square lattice interacting via both the long-ranged\\u000adipole-dipole interaction and a short-ranged on-site attractive interaction.\\u000aSinglet superfluid, charge density wave, and supersolid phases are found to\\u000aexist in the system. We map out the zero temperature phase diagram and find\\u000athat the supersolid phase is considerably stabilized by

  19. Ground state of the polar alkali-metal-atom-strontium molecules: Potential energy curve and permanent dipole moment

    SciTech Connect

    Guerout, R. [Laboratoire Kastler-Brossel, CNRS, ENS, Univ Pierre et Marie Curie case 74, Campus Jussieu, F-75252 Paris Cedex 05 (France); Aymar, M.; Dulieu, O. [Laboratoire Aime Cotton, CNRS, UPR3321, Bat. 505, Univ Paris-Sud, F-91405 Orsay Cedex (France)

    2010-10-15

    In this study, we investigate the structure of the polar alkali-metal-atom-strontium diatomic molecules as possible candidates for the realization of samples of ultracold polar molecular species not yet investigated experimentally. Using a quantum chemistry approach based on effective core potentials and core polarization potentials, we model these systems as effective three-valence-electron systems, allowing for calculation of electronic properties with full configuration interaction. The potential curve and the permanent dipole moment of the {sup 2}{Sigma}{sup +} ground state are determined as functions of the internuclear distance for LiSr, NaSr, KSr, RbSr, and CsSr molecules. These molecules are found to exhibit a significant permanent dipole moment, though smaller than those of the alkali-metal-atom-Rb molecules.

  20. Manipulating one- and two-dimensional stimulated-x-ray resonant-Raman signals in molecules by pulse polarizations

    NASA Astrophysics Data System (ADS)

    Healion, Daniel; Biggs, Jason D.; Mukamel, Shaul

    2012-09-01

    The simulation of spontaneous (RIXS) and stimulated x-ray Raman scattering (SXRS) signals in isotropic samples requires rotational averaging of a fourth-rank tensor product of two polarizabilities. Attosecond stimulated x-ray Raman spectroscopy excites multiple valence transitions covered by the pulse bandwidths. These excitations depend on the orientation of the molecule with respect to the pulse polarizations in the laboratory frame, making the response a high-rank tensor operator. Many contributions to the response coming from different tensor components complicate the analysis and interpretation of these measurements. By using the magic angle between the excitation and detection fields these signals may be expressed as correlation functions of the scalar isotropic polarizabilities, which greatly simplifies their interpretation. We show that a similar simplification of three-pulse two-dimensional stimulated x-ray Raman scattering (2D-SXRS), which depends on a rotationally averaged sixth-rank tensor, is possible by a super magic angle (SMA) combination of two measurements with specific pulse polarization configurations. Calculated SMA 2D-SXRS signals for trans-N-methylacetamide (NMA) at the nitrogen K edge reveal different features compared with the all-parallel polarization configuration.

  1. Highly efficient broadband conversion of light polarization by composite retarders

    E-print Network

    S. S. Ivanov; A. A. Rangelov; N. V. Vitanov; T. Peters; T. Halfmann

    2011-10-06

    Driving on an analogy with the technique of composite pulses in quantum physics, we propose highly efficient broadband polarization converters composed of sequences of ordinary retarders rotated at specific angles with respect to their fast-polarization axes.

  2. Highly efficient broadband conversion of light polarization by composite retarders

    NASA Astrophysics Data System (ADS)

    Ivanov, Svetoslav S.; Rangelov, Andon A.; Vitanov, Nikolay V.; Peters, Thorsten; Halfmann, Thomas

    2012-03-01

    Driving on an analogy with the technique of composite pulses in quantum physics, we propose highly efficient broadband polarization converters composed of sequences of ordinary retarders rotated at specific angles with respect to their fast-polarization axes.

  3. Nuclear magnetic resonance of laser-polarized noble gases in molecules, materials and organisms

    E-print Network

    Goodson, B.M.

    2010-01-01

    of alkali metal atoms are polarized with laser light (Fig.Alkali metal spin-exchange optical pumping Batch optical pumping apparatus OPNMR of laser-laser beam can be directed into the magnet's bore. For a description of high-field alkali

  4. Supersolid phase of cold fermionic polar molecules in two-dimensional optical lattices

    SciTech Connect

    He Liang; Hofstetter, Walter [Institut fuer Theoretische Physik, Goethe-Universitaet, D-60438 Frankfurt am Main (Germany)

    2011-05-15

    We study a system of ultracold fermionic polar molecules in a two-dimensional square lattice interacting via both the long-range dipole-dipole interaction and a short-range on-site attractive interaction. Singlet-superfluid, change density wave, and supersolid phases are found to exist in the system. We map out the zero-temperature phase diagram and find that the supersolid phase is considerably stabilized by the dipole-dipole interaction and thus can exist over a large region of filling factors. We study the melting of the supersolid phase with increasing temperature, map out a finite-temperature phase diagram of the system at fixed filling, and determine the parameter region where the supersolid phase can possibly be observed in experiments.

  5. Neuronal Polarity in 2011 Neurons appear to be the most highly polarized cell

    E-print Network

    Oregon, University of

    could provide clues for improving regeneration of severed neurons following injury. The special issueNeuronal Polarity in 2011 Neurons appear to be the most highly polarized cell type in our bodies, often exhibiting a very long axon and highly branched dendrites. How neurons esta- blish and maintain

  6. Quantum path selection in high-order harmonic generation from aligned molecules.

    PubMed

    Zhu, Xun; Zhang, Chaojin; Gu, Mingliang; Yao, Jinping

    2014-04-01

    We theoretically investigate high-order harmonic generation (HHG) from aligned N(2) molecules with a driving field composed of two-color circularly polarized laser pulses. It is shown that the combination of N(2) molecules and the waveform-controlled laser field allows us to select either long or short quantum path, depending on molecular alignment angles, while in atom Ar, two paths show comparable contribution to HHG. The selection of single quantum path in aligned N(2) molecules leads to an ultrabroad and smooth XUV supercontinuum, giving rise to isolated attosecond pulses generation. Moreover, we can control the intensity ratio of two attosecond pulses by adjusting the molecular alignment angles, providing an opportunity for attosecond pump-probe technique. PMID:24718170

  7. High Precision Assembly Line Synthesis for Molecules with Tailored Shapes

    PubMed Central

    Burns, Matthew; Essafi, Stephanie; Bame, Jessica R.; Bull, Stephanie P.; Webster, Matthew P.; Balieu, Sebastien; Dale, James W.; Butts, Craig P.; Harvey, Jeremy N.; Aggarwal, Varinder K.

    2014-01-01

    Molecular assembly lines, where molecules undergo iterative processes involving chain elongation and functional group manipulation are hallmarks of many processes found in Nature. We have sought to emulate Nature in the development of our own molecular assembly line through iterative homologations of boronic esters. Here we report a reagent (?-lithioethyl triispopropylbenzoate) which inserts into carbon-boron bonds with exceptionally high fidelity and stereocontrol. Through repeated iteration we have converted a simple boronic ester into a complex molecule (a carbon chain with ten contiguous methyl groups) with remarkably high precision over its length, its stereochemistry and therefore its shape. Different stereoisomers were targeted and it was found that they adopted different shapes (helical/linear) according to their stereochemistry. This work should now enable scientists to rationally design and create molecules with predictable shape, which could have an impact in all areas of molecular sciences where bespoke molecules are required. PMID:25209797

  8. Single-molecule diodes with high rectification ratios through environmental control.

    PubMed

    Capozzi, Brian; Xia, Jianlong; Adak, Olgun; Dell, Emma J; Liu, Zhen-Fei; Taylor, Jeffrey C; Neaton, Jeffrey B; Campos, Luis M; Venkataraman, Latha

    2015-06-01

    Molecular electronics aims to miniaturize electronic devices by using subnanometre-scale active components. A single-molecule diode, a circuit element that directs current flow, was first proposed more than 40?years ago and consisted of an asymmetric molecule comprising a donor-bridge-acceptor architecture to mimic a semiconductor p-n junction. Several single-molecule diodes have since been realized in junctions featuring asymmetric molecular backbones, molecule-electrode linkers or electrode materials. Despite these advances, molecular diodes have had limited potential for applications due to their low conductance, low rectification ratios, extreme sensitivity to the junction structure and high operating voltages. Here, we demonstrate a powerful approach to induce current rectification in symmetric single-molecule junctions using two electrodes of the same metal, but breaking symmetry by exposing considerably different electrode areas to an ionic solution. This allows us to control the junction's electrostatic environment in an asymmetric fashion by simply changing the bias polarity. With this method, we reliably and reproducibly achieve rectification ratios in excess of 200 at voltages as low as 370?mV using a symmetric oligomer of thiophene-1,1-dioxide. By taking advantage of the changes in the junction environment induced by the presence of an ionic solution, this method provides a general route for tuning nonlinear nanoscale device phenomena, which could potentially be applied in systems beyond single-molecule junctions. PMID:26005998

  9. Single-molecule diodes with high rectification ratios through environmental control

    NASA Astrophysics Data System (ADS)

    Capozzi, Brian; Xia, Jianlong; Adak, Olgun; Dell, Emma J.; Liu, Zhen-Fei; Taylor, Jeffrey C.; Neaton, Jeffrey B.; Campos, Luis M.; Venkataraman, Latha

    2015-06-01

    Molecular electronics aims to miniaturize electronic devices by using subnanometre-scale active components. A single-molecule diode, a circuit element that directs current flow, was first proposed more than 40?years ago and consisted of an asymmetric molecule comprising a donor–bridge–acceptor architecture to mimic a semiconductor p–n junction. Several single-molecule diodes have since been realized in junctions featuring asymmetric molecular backbones, molecule–electrode linkers or electrode materials. Despite these advances, molecular diodes have had limited potential for applications due to their low conductance, low rectification ratios, extreme sensitivity to the junction structure and high operating voltages. Here, we demonstrate a powerful approach to induce current rectification in symmetric single-molecule junctions using two electrodes of the same metal, but breaking symmetry by exposing considerably different electrode areas to an ionic solution. This allows us to control the junction's electrostatic environment in an asymmetric fashion by simply changing the bias polarity. With this method, we reliably and reproducibly achieve rectification ratios in excess of 200 at voltages as low as 370?mV using a symmetric oligomer of thiophene-1,1-dioxide. By taking advantage of the changes in the junction environment induced by the presence of an ionic solution, this method provides a general route for tuning nonlinear nanoscale device phenomena, which could potentially be applied in systems beyond single-molecule junctions.

  10. Functional Fixedness and Functional Reduction as Common Sense Reasonings in Chemical Equilibrium and in Geometry and Polarity of Molecules.

    ERIC Educational Resources Information Center

    Furio, C.; Calatayud, M. L.; Barcenas, S. L.; Padilla, O. M.

    2000-01-01

    Focuses on learning difficulties in procedural knowledge, and assesses the procedural difficulties of grade 12 and first- and third-year university students based on common sense reasoning in two areas of chemistry--chemical equilibrium and geometry, and polarity of molecules. (Contains 55 references.) (Author/YDS)

  11. PHYSICAL REVIEW B 86, 064501 (2012) Clustered Wigner-crystal phases of cold polar molecules in arrays of one-dimensional tubes

    E-print Network

    Demler, Eugene

    2012-01-01

    PHYSICAL REVIEW B 86, 064501 (2012) Clustered Wigner-crystal phases of cold polar molecules layers,1,2 and the chain formation of magnetic particles in three-dimensional ferrofluids.3 Long-range interactions with systems of cold polar molecules10­15 can allow us to explore emergent emulsion phases

  12. High resolution electron crystallography of protein molecules

    SciTech Connect

    Glaeser, R.M. [California Univ., Berkeley, CA (United States). Dept. of Molecular and Cell Biology]|[Lawrence Berkeley Lab., CA (United States); Downing, K.H. [Lawrence Berkeley Lab., CA (United States)

    1993-06-01

    Electron diffraction data and high resolution images can now be used to obtain accurate, three-dimensional density maps of biological macromolecules. These density maps can be interpreted by building an atomic-resolution model of the structure into the experimental density. The Cowley-Moodie formalism of dynamical diffraction theory has been used to validate the use of kinematic diffraction theory, strictly the weak phase object approximation, in producing such 3-D density maps. Further improvements in the preparation of very flat specimens and in the retention of diffraction to a resolution of 0.2 nm or better could result in electron crystallography becoming as important a technique as x-ray crystallography currently is for the field of structural molecular biology.

  13. Linear polarization measurements at high temperatures in hypersaline geothermal brines

    Microsoft Academic Search

    S. D. Cramer; P. B. Needham Jr.

    1978-01-01

    The Bureau of Mines conducted a series of in situ linear polarization measurements in high-temperature, high-pressure typesaline geothermal brines at the Bureau of Mines Geothermal Test Facility in the Imperial Valley of California. The measurements represented an evaluation of the linear polarization technique for obtaining instantaneous corrosion rates of materials of construction in flowing hypersaline hydrothermal fluids that rapidly form

  14. INFRARED SPECTROSCOPY OF CONJUGATED ORGANIC MOLECULES UNDER HIGH PRESSURE

    E-print Network

    Collins, Gary S.

    INFRARED SPECTROSCOPY OF CONJUGATED ORGANIC MOLECULES UNDER HIGH PRESSURE By KIRILL KHAMIDOVICH with germanium detectors. Brooke Bafus work on taking p-quaterphenyl spectra was very supportive and Slade Jokela's help with the vapor deposition system is extremely highly appreciated. I personally want to thank my

  15. Polarization of focal spot for high numerical aperture radially polarized beam

    NASA Astrophysics Data System (ADS)

    Xiao, Yun; Zhang, Yunhai; Chang, Jian; Wei, Tongda

    2015-04-01

    According to Wolf and Richards vectorial diffraction theory, an electric field intensity model of focal spot for high numerical aperture radially polarized beam is established to analyze the intensity distributions of the focal spot and the polarization components of the electric field along the x, y and z axis, separately. In the reflection-mode confocal of imaging system, the intensity distributions of focal spot is obtained utilizing the gold nanoparticles, and the intensity distributions of the polarization components of the electric field along the x, y and z axis are obtained utilizing the gold nanorods. In the incident light, the polarization component along the z axis is nonexistent in front of the objective. But there is the polarization component along the z axis, which is relative to the numerical aperture, in the focal spot behind the objective. When the numerical aperture increases from 0.8 to 1.4, the ratio of the polarization component maximum along the z axis to that along the x axis or y axis increases from 0.57 to 3.16. The results show that the focal spot of radially polarized beam through high numerical aperture objective have the polarization component along the x, y and z axis, separately, and polarization component along z axis is much more than the other.

  16. UV absorption spectra of vibrationally highly excited toluene molecules

    NASA Astrophysics Data System (ADS)

    Hippler, H.; Troe, J.; Wendelken, H. J.

    1983-05-01

    Vibrationally highly excited toluene molecules with an energy of 52 000 cm-1 have been prepared by UV laser excitation and subsequent isomerization of the isomer cycloheptatriene. The UV absorption spectrum of the toluene, whose vibrational energy would correspond to the average energy of thermal molecules at 2800 K, has been measured over the range 210-270 nm. It is compared with the UV spectrum of thermal molecules heated in shock waves up to 1800 K. All spectra, corresponding either to microcanonical or canonical energy distributions, can be represented by a modified Sulzer-Wieland equation. It is concluded that the absorption coefficients can be expressed to a first approximation by the average energy of the excited molecules independent of their energy distribution.

  17. Polarization of GRB by scattering off relativistically moving material: Compton sailing and high polarization

    E-print Network

    Amir Levinson; David Eichler

    2004-02-19

    The polarization of gamma ray emission scattered off the baryon rich material that collimates a GRB fireball and the coasting speed of the irradiated matter are calculated numerically for different geometries of the radiation source and the collimating wall. It is shown that when the scattering material is Compton sailing, the direction of maximum polarization is quite generally well within the beaming cone of scattered radiation. As a result, the probability for observing bright highly polarized GRB's increases considerably, provided the Lorentz factor of the coasting matter is not well below 30, and the scattered radiation is highly polarized even when the beam thickness is large compared to $1/\\Gamma$. It is suggested that correlation between polarization and intensity could provide clues as to whether energy flows from matter to photons or the reverse.

  18. Control of the high harmonic generation spectra by changing the molecule-laser field relative orientation

    SciTech Connect

    Daniele, Rosalba; Castiglia, Giuseppe; Corso, Pietro Paolo; Orlando, Gianfranco; Fiordilino, Emilio [Dipartimento di Scienze Fisiche e Astronomiche, Universita degli Studi di Palermo, Via Archirafi 36, 90123 Palermo (Italy); Morales, Francesca [Dipartimento di Fisica e Tecnologie Relative, Universita degli Studi di Palermo, Viale delle Scienze, 90128 Palermo (Italy)

    2010-04-15

    The time dependent Schroedinger equation of a homonuclear diatomic molecule in the presence of a linearly polarized laser field is numerically solved by means of a split-operator parallel code. The calculations are carried out by assuming a single active electron model with fixed nuclei; a simplified two-dimensional model of the system is used. The highly nonlinear response of the electron wave function to the laser electric field stimulates the molecule to emit electromagnetic radiation consisting of a wide plateau of odd harmonics of the laser field. It is shown that the emitted spectrum can be finely controlled by changing the angle between the laser electric field and the molecular axis; this can be used to achieve a tunable source of high frequency radiation.

  19. Relaxation of rotational angular momentum of polar diatomic molecules in simple liquids

    SciTech Connect

    Padilla, A.; Perez, J. [Departamento de Fisica Fundamental y Experimental, Electronica y Sistemas, Universidad de La Laguna, 38204 Tenerife (Spain)

    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. Ionization of one- and three-dimensionally-oriented asymmetric-top molecules by intense circularly polarized femtosecond laser pulses

    SciTech Connect

    Hansen, Jonas L. [Interdisciplinary Nanoscience Center (iNANO), Aarhus University, DK-8000 Aarhus C (Denmark); Holmegaard, Lotte; Kalhoej, Line; Kragh, Sofie Louise [Department of Chemistry, Aarhus University, DK-8000 Aarhus C (Denmark); Stapelfeldt, Henrik [Department of Chemistry, Aarhus University, DK-8000 Aarhus C (Denmark); Interdisciplinary Nanoscience Center (iNANO), Aarhus University, DK-8000 Aarhus C (Denmark); Filsinger, Frank; Meijer, Gerard; Kuepper, Jochen; Dimitrovski, Darko; Abu-samha, Mahmoud; Martiny, Christian Per Juul; Madsen, Lars Bojer [Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin (Germany); Lundbeck Foundation Theoretical Center for Quantum System Research, Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C (Denmark)

    2011-02-15

    We present a combined experimental and theoretical study on strong-field ionization of a three-dimensionally-oriented asymmetric top molecule, benzonitrile (C{sub 7}H{sub 5}N), by circularly polarized, nonresonant femtosecond laser pulses. Prior to the interaction with the strong field, the molecules are quantum-state selected using a deflector and three-dimensionally (3D) aligned and oriented adiabatically using an elliptically polarized laser pulse in combination with a static electric field. A characteristic splitting in the molecular frame photoelectron momentum distribution reveals the position of the nodal planes of the molecular orbitals from which ionization occurs. The experimental results are supported by a theoretical tunneling model that includes and quantifies the splitting in the momentum distribution. The focus of the present article is to understand strong-field ionization from 3D-oriented asymmetric top molecules, in particular the suppression of electron emission in nodal planes of molecular orbitals. In the preceding article [Dimitrovski et al., Phys. Rev. A 83, 023405 (2011)] the focus is to understand the strong-field ionization of one-dimensionally-oriented polar molecules, in particular asymmetries in the emission direction of the photoelectrons.

  1. Highly Polarized Ion Sources for Electron Ion Colliders (EIC)

    SciTech Connect

    V.G. Dudnikov, R.P. Johnson, Y.S. Derbenev, Y. Zhang

    2010-03-01

    The operation of the RHIC facility at BNL and the Electron Ion Colliders (EIC) under development at Jefferson Laboratory and BNL need high brightness ion beams with the highest polarization. Charge exchange injection into a storage ring or synchrotron and Siberian snakes have the potential to handle the needed polarized beam currents, but first the ion sources must create beams with the highest possible polarization to maximize collider productivity, which is proportional to a high power of the polarization. We are developing one universal H-/D- ion source design which will synthesize the most advanced developments in the field of polarized ion sources to provide high current, high brightness, ion beams with greater than 90% polarization, good lifetime, high reliability, and good power efficiency. The new source will be an advanced version of an atomic beam polarized ion source (ABPIS) with resonant charge exchange ionization by negative ions. An integrated ABPIS design will be prepared based on new materials and an optimized magnetic focusing system. Polarized atomic and ion beam formation, extraction, and transport for the new source will be computer simulated.

  2. Obtaining circularly polarized highly focused fields: a proposal

    NASA Astrophysics Data System (ADS)

    Maluenda, David; Martínez-Herrero, Rosario; Juvells, Ignasi; Carnicer, Artur

    2013-11-01

    The target of this communication is to present a method for tailoring the complex amplitude and the polarization at the entrance pupil of a high numerical aperture objective lens in order to obtain focused fields with transverse circular polarization at any plane. Analytical expressions within the framework of the Richards-Wolf vectorial model are derived and some numerical results are presented.

  3. High-intensity lasers: interactions with atoms, molecules and clusters

    E-print Network

    Ditmire, Todd

    of the ionization and dissociation of clusters of noble gas atoms is reviewed with special emphasisHigh-intensity lasers: interactions with atoms, molecules and clusters B y M. H. R. Hutchinson2 , T 2BZ, UK 2 Central Laser Facility, Rutherford Appleton Laboratory, Chilton, Didcot OX11 0QX, UK

  4. Enhanced narrow-bandwidth emission during high-order harmonic generation from aligned molecules.

    PubMed

    Zhang, Chaojin; Yao, Jinping; Umran, Fadhil A; Ni, Jielei; Zeng, Bin; Li, Guihua; Lin, Di

    2013-02-11

    We theoretically investigate the selective enhancement of high-harmonic generation (HHG) in a small spectral range when an orthogonal-polarized two-color laser field interacts with aligned O(2) molecules. It is shown clearly that the enhanced narrow-bandwidth emission near the cutoff of the HHG spectrum can be effectively controlled by the molecular alignment angle, laser intensity and the relative phase of two-color laser fields. Furthermore, the strong dependence of narrow-bandwidth HHG on molecular alignment angle indicates that it encodes information about O(2) molecular orbitals, so it may be an alternative method for reconstruction of O(2) molecular orbitals. PMID:23481785

  5. High throughput single molecule detection for monitoring biochemical reactions.

    PubMed

    Okagbare, Paul I; Soper, Steven A

    2009-01-01

    The design, performance and application of a novel optical system for high throughput single molecule detection (SMD) configured in a continuous flow format using microfluidics is reported. The system consisted of a microfabricated polymer-based multi-channel fluidic network situated within the optical path of a laser source (lambda(ex) = 660 nm) with photon transduction accomplished using an electron-multiplying charge coupled device (EMCCD) operated in a frame transfer mode that allowed tracking single molecules as they passed through a large field-of-view (FoV) illumination zone. The microfluidic device consisted of 30 microchannels possessing dimensions of 30 microm (width) x 20 microm (depth) with a 25 microm pitch. Individual molecules were electrokinetically driven through the fluidic network and excited within the wide-field illumination area with the resulting fluorescence collected via an objective and imaged onto the EMCCD camera. The detection system demonstrated sufficient sensitivity to detect single DNA molecules labeled with a fluorescent tag (AlexaFluor 660) identified through their characteristic emission wavelength and the burst of photons produced during their transit through the excitation volume. In its present configuration and fluidic architecture, the sample processing throughput was approximately 4.02 x 10(5) molecules s(-1), but could be increased dramatically through the use of narrower channels and a smaller pitch. The system was further evaluated using a single molecule-based fluorescence quenching assay for measuring the population differences between duplexed and single-stranded DNA molecules as a function of temperature for determining the duplex melting temperature, T(m). PMID:19082181

  6. 13C nuclear Overhauser polarization nuclear magnetic resonance in rotating solids: Replacement of cross polarization in uniformly 13C labeled molecules with methyl groups

    NASA Astrophysics Data System (ADS)

    Takegoshi, K.; Terao, Takehiko

    2002-07-01

    A new 13C polarization technique in solids is presented on the basis of a recently proposed 13C-13C recoupling sequence [13C-1H dipolar-assisted rotational resonance (DARR), K. Takegoshi, S. Nakamura, and T. Terao, Chem. Phys. Lett. 344, 631 (2001)] operative under fast magic angle spinning (MAS), in which a rf field is applied to 1H with a rotary resonance condition but none to 13C. The 1H irradiation in DARR saturates 1H signals, leading to the 13C signal enhancement due to the nuclear Overhauser effect for fast rotating methyl groups, if any. If we use a uniformly 13C labeled sample, 13C-13C polarization transfer enhanced by DARR successively distributes the enhanced methyl carbon polarization to the other 13C spins, leading to uniform enhancement for all 13C spins even under very fast MAS. In uniformly 13C labeled rotating samples, the enhancement factor in cross polarization (CP) is about 2.4, while in the present nuclear Overhauser polarization (NOP), it is 3.0 in the fast rotation limit of the methyl groups. While the CP enhancement becomes smaller for molecules with short T1rho of 1H or 13C, NOP would work well for such mobile molecules, and also NOP enables us to acquire a signal with a short repetition time even if 1H T1 is long. Further, NOP has the advantage of quantitativeness, and is very easy to carry out, being insensitive to the adjustment of rf field intensity and requiring only very low rf power. These features are demonstrated for uniformly 13C, 15N-labeled L-threonine and uniformly 13C, 15N-labeled glycylisoleucine. NOP-MAS is also applied for a naturally abundant 13C sample.

  7. Polarization maintaining fiber based ultra-high resolution spectral domain polarization sensitive optical coherence tomography.

    PubMed

    Götzinger, Erich; Baumann, Bernhard; Pircher, Michael; Hitzenberger, Christoph K

    2009-12-01

    We present a new ultra high resolution spectral domain polarization sensitive optical coherence tomography (PS-OCT) system based on polarization maintaining (PM) fibers. The method transfers the principles of our previous bulk optic PS-OCT systems to a fiberized setup. The phase shift between the orthogonal polarization states travelling in the two orthogonal modes of the PM fiber is compensated by software in post processing. Thereby, the main advantage of our bulk optics setups, i.e. the use of only a single input polarization state to simultaneously acquire reflectivity, retardation, optic axis orientation, and Stokes vector, is maintained. The use of a broadband light source of 110 nm bandwidth provides improved depth resolution and smaller speckle size. The latter is important for improved resolution of depolarization imaging. We demonstrate our instrument for high-resolution PS-OCT imaging of the healthy human retina. PMID:20052196

  8. Organic molecules in the polar ice: from chemical analysis to environmental proxies

    NASA Astrophysics Data System (ADS)

    Barbante, Carlo; Zennaro, Piero; Giorio, Chiara; Kehrwald, Natalie; Benton, Alisa K.; Wolff, Eric W.; Kalberer, Markus; Kirchgeorg, Torben; Zangrando, Roberta; Barbaro, Elena; Gambaro, Andrea

    2015-04-01

    The molecular and isotopic compositions of organic matter buried in ice contains information that helps reconstruct past environmental conditions, evaluate histories of climate change, and assess impacts of humans on ecosystems. In recent years novel analytical techniques were developed to quantify molecular compounds in ice cores. As an example, biomass burning markers, including monosaccharide anhydrides, lightweight carboxylic acids, lignin and resin pyrolysis products, black carbon, and charcoal records help in reconstructing past fire activity across seasonal to millennial time scales. Terrestrial biomarkers, such as plant waxes (e.g. long-chain n-alkanes) are also a promising paleo vegetation proxy in ice core studies. Polycyclic aromatic hydrocarbons are ubiquitous pollutants recently detected in ice cores. These hydrocarbons primarily originate from incomplete combustion of organic matter and fossil fuels (e.g. diesel engines, domestic heating, industrial combustion) and therefore can be tracers of past combustion activities. In order to be suitable for paloeclimate purposes, organic molecular markers detected in ice cores should include the following important features. Markers have to be stable under oxidizing atmospheric conditions, and ideally should not react with hydroxyl radicals, during their transport to polar regions. Organic markers must be released in large amounts in order to be detected at remote distances from the sources. Proxies must be specific, in order to differentiate them from other markers with multiple sources. The extraction of glaciochemical information from ice cores is challenging due to the low concentrations of some impurities, thereby demanding rigorous control of external contamination sources and sensitive analytical techniques. Here, we review the analysis and use of organic molecules in ice as proxies of important environmental and climatic processes.

  9. Topical Developments in High-Field Dynamic Nuclear Polarization

    E-print Network

    Michaelis, Vladimir K.

    We report our recent efforts directed at improving high-field dynamic nuclear polarization (DNP) experiments. We investigated a series of thiourea nitroxide radicals and the associated DNP enhancements ranging from ?=25 ...

  10. Lipid Membrane Polarity Profiles by High-Field EPR

    PubMed Central

    Kurad, Dieter; Jeschke, Gunnar; Marsh, Derek

    2003-01-01

    Profiles of polarity across biological membranes are essential determinants of the cellular permeability barrier and of the stability of transmembrane proteins. High-field electron paramagnetic resonance of systematically spin-labeled lipid chains is used here to determine the polarity profiles of cholesterol-containing phospholipid membranes. The polarity dependence of the gxx-tensor element is opposite to the dependence on chain dynamics, and additionally has enhanced sensitivity to hydrogen bonding. Both features make high-field measurements superior to conventional determinations of local polarity from spin-label hyperfine couplings. The profile of gxx in dimyristoyl phosphatidylcholine membranes with 5 or 40 mol% cholesterol is established with eleven positional isomers of phosphatidylcholine, spin labeled at positions n = 4–14 in the sn-2 chain. A sigmoidal barrier, centered about chain position no ? 8, mirrors the corresponding sigmoidal trough obtained from the spin-label hyperfine coupling, Azz. For the different positions, n, it is found that ?gxx/?Azz = ?2.4 T?1, a high value that is characteristic of hydrogen-bonded spin labels. This demonstrates that the transmembrane polarity profile registered by spin labels corresponds to water penetration into the membrane. Inhomogeneous broadening of the gxx-spectral feature demonstrates heterogeneities of the water distribution in the regions of higher intramembrane polarity defined by n < 8. In the transition region between high- and low-polarity regions (n ? 8), the gxx-feature consists of two components characteristic of coexisting hydrated and nonhydrated states. PMID:12885649

  11. Polarized neutron reflectometry in high magnetic fields

    SciTech Connect

    Fritzsche, H. [National Research Council Canada, Canadian Neutron Beam Centre, Chalk River Laboratories, Chalk River, Ontario K0J 1J0 (Canada)

    2005-11-15

    A simple method is described to maintain the polarization of a neutron beam on its way through the large magnetic stray fields produced by a vertical field of a cryomagnet with a split-coil geometry. The two key issues are the proper shielding of the neutron spin flippers and an additional radial field component in order to guide the neutron spin through the region of the null point (i.e., point of reversal for the vertical field component). Calculations of the neutron's spin rotation as well as polarized neutron reflectometry experiments on an ErFe{sub 2}/DyFe{sub 2} multilayer show the perfect performance of the used setup. The recently commissioned cryomagnet M5 with a maximum vertical field of up to 7.2 T in asymmetric mode for polarized neutrons and 9 T in symmetric mode for unpolarized neutrons was used on the C5 spectrometer in reflectometry mode, at the NRU reactor in Chalk River, Canada.

  12. An electron spin polarization study of the interaction of photoexcited triplet molecules with mono- and polynitroxyl stable free radicals

    SciTech Connect

    Turro, N.J.; Khudyakov, I.V.; Bossmann, S.H. (Columbia Univ., New York, NY (United States)); Dwyer, D.W. (State Univ. of New York, Brockport (United States))

    1993-02-11

    Time-resolved electron spin resonance (TR ESR) has been used to investigate the chemically induced dynamic electron polarization (CIDEP) generated by the interaction of stable free radicals with the triplet states of benzophenone, benzil, and 2-acetylnaphthalene. The stable radicals were mono-, di-, tri-, and tetranitroxyl free radicals possessing the 2,2,6,6-tetramethylpiperidine-N-oxyl moiety. All of the stable radical systems investigated were found to be emissively polarized by interaction with the triplet states, and the phase of polarization was independent of the sign of zero-field splitting (D) of the interacting triple molecule. Possible and likely mechanisms of polarization transfer (creation) resulting from the interaction of photoexcited triplet molecules with nitroxyls in the strong electron exchange are discussed. The emissive CIDEP of nitroxyls observed in the interactions with triplet benzil, which has D > 0, provides strong support for the operation of the radical-triplet pair mechanism. Within the time scale of TR ESR experiments ([approximately]10[sup [minus]7]--10[sup [minus]6] s) no significant variation in the shape of the CIDEP spectra of the nitroxyls was observed, either in viscous media or in micelles. It is concluded that intramolecular spin exchange (or conformational change) of polynitroyls occurs much faster than the time resolution of the experiment. 24 refs., 6 figs., 1 tab.

  13. Enhancement of metallic silver monomer evaporation by the adhesion of polar molecules to silver nanocluster ions. Technical report

    SciTech Connect

    Fagerquist, C.; Sensharma, D.K.; Rubio, A.; Cohen, M.L.; El-Sayed, M.A.

    1994-09-21

    The authors have compared the metallic evaporation channels from metastable Ag(X=5,7,11)(AgI)(Y=1-4)(+) clusters in the 1st FFR of a double focussing mass spectrometer with that of the corresponding pure metallic clusters, Ag(X=5,7,11)(+). It is found that the presence of the polar AgI molecules increases the rate of silver monomer evaporation relative to that of silver dimer evaporation. Using thermodynamic expressions for the heat of evaporation of the different evaporation processes and assuming the absence of reverse activation energies, an expression for the difference between the activation energy of silver monomer and dimer evaporation is derived. It is shown that dipole/induced-dipole forces resulting from the presence of AgI polar molecules lead to an enhancement of silver monomer evaporation if the polarizability of the pure metallic cluster ions increases with the number of Jellium electrons. The authors theoretical calculations of the static polarizabilities of (Ag(x))(+) using time dependent density functional theory within the local density approximation, shows a smooth increase in the polarizabilities with the number of the Jellium electrons in these clusters. Finally, the authors observe that the enhancement of Ag monomer evaporation per AgI added is smaller for clusters with even number of AgI molecules than with odd numbers. This was proposed to result from the contribution of configurations with dipole 'pairing' of the AgI molecules in clusters with even number of AgI molecules. Dipole pairing would decrease the average dipole/induced-dipole interaction between the AgI molecules and the metallic part of these 'mixed' clusters.

  14. Polarized high pressure 3H?e target at MAMI

    NASA Astrophysics Data System (ADS)

    Rohe, Daniela; Bartsch, P.; Baumann, D.; Becker, J.; Bermuth, J.; de Bever, L. J.; Böhm, R.; Buttazoni, S.; Caprano, T.; Clawiter, N.; Deninger, A.; Derber, S.; Ding, M.; Distler, M.; Ebbes, A.; Ebert, M.; Ewald, I.; Friedrich, J.; Friedrich, J. M.; Geiges, R.; Grossmann, T.; Klein, A.; Hauger, M.; Heil, W.; Hofmann, D.; Honegger, A.; Jennewein, P.; Jourdan, J.; Kahrau, M.; Korn, M.; Krygier, K. W.; Kubon, G.; Lauer, L.; Liesenfeld, A.; Merkel, H.; Merle, K.; Merle, P.; Müller, U.; Mühlbauer, M.; Neuhausen, R.; Otten, E. W.; Petitjean, Th.; Pospischil, Th.; Rohe, D.; Rosner, G.; Schmieden, H.; Sick, I.; Surkau, R.; Wagner, A.; Walcher, Th.; Warren, G.; Weis, M.; Wolf, S.; Woehrle, H.; Zhao, J.; Zeier, M.

    1998-01-01

    In the frame of the A1-Collaboration at the Mainz Microtron a test measurement of doubly polarized 3H?e(e?,e'n) scattering from a high pressure target was performed in July aiming for the determination of the neutron electric form factor Gen at high momentum transfer (Q2=0.7(GeV/c)2). Due to the small value of Gen compared to Gmn a preferred procedure is to determine the asymmetry in the exclusive quasi elastic scattering of polarized electrons (P?70%, I?2?A) from polarized 3H?e. The scattered electrons are detected in a high resolution magnetic spectrometer while the scattering angles of the outgoing neutrons are measured in a plastic scintillator. In this reaction the polarized 3H?e nucleus serves as an effective polarized neutron target. Because of the large magnetic field gradients caused by the spectrometer and limited space at the target place, the 3H?e gas is polarized elsewhere and transported to the target place in specially prepared glass cells. The glass cells are designed for high pressure (up to 10 bar) and with thin windows to prevent background. To reduce the relaxation due to the magnetic field gradients a ?-metal shielded guiding field of 4 Gauss is used. The guiding field is generated by three independent coils which permit the rotation of the target spin in any direction desired, especially perpendicular and parallel with respect to q?. So we are able to take the ratio of the asymmetries A?/A?, which in first order depends only on kinematical factors and the ratio Gen/Gmn. The method of metastable optical pumping is used to polarize the 3H?e at about 1 mbar with a LNA laser (?6W). Subsequently the gas is compressed by means of a two-stage-piston compressor up to 6 bar with a polarization of roughly 45%.

  15. Nuclear magnetic resonance of laser-polarized noble gases in molecules, materials, and organisms

    Microsoft Academic Search

    Boyd Mclean Goodson; Boyd M

    1999-01-01

    Conventional nuclear magnetic resonance (NMR) spectroscopy and magnetic resonance imaging (MRI) are fundamentally challenged by the insensitivity that stems from the ordinarily low spin polarization achievable in even the strongest NMR magnets. However, by transferring angular momentum from laser light to electronic and nuclear spins, optical pumping methods can increase the nuclear spin polarization of noble gases by several orders

  16. Nuclear Magnetic Resonance of Laser-Polarized Noble Gases in Molecules, Materials, and Organisms

    Microsoft Academic Search

    Boyd M. Goodson

    2002-01-01

    The sensitivity of conventional nuclear magnetic resonance (NMR) techniques is fundamentally limited by the ordinarily low spin polarization achievable in even the strongest NMR magnets. However, by transferring angular momentum from laser light to electronic and nuclear spins, optical pumping methods can increase the nuclear spin polarization of noble gases by several orders of magnitude, thereby greatly enhancing their NMR

  17. Polarization disks in near-infrared high-resolution imaging

    NASA Astrophysics Data System (ADS)

    Murakawa, K.

    2010-07-01

    A polarization disk is a characteristic feature of optical and near-infrared (NIR) polarimetric images of young stellar objects (YSOs) and is regarded as convincing evidence that a dust disk is present. We analyze high-resolution linear polarization maps of a sample of low-mass YSO disk models by means of radiative transfer calculations to investigate the effects of the disk geometry and grain sizes on polarization properties. Our modeling assumes spherical grains with a power-law size distribution of n(a)? a-3.5; 0.005 ?m ? a ? a_max and with a fixed a_max of 0.25 ?m for the outer envelope and a different a_max for the disk. The parameters to examine are the disk height (i.e. the ratio of the disk height to the outer disk radius H of 0.1 to 1.0) and the dust sizes in the disk (i.e. a_max of 0.25 to 1000.0 ?m). In a near pole-on view, the polarization vectors are centro-symmetrically aligned even towards the disk, but the degree of polarization can be different from the envelope. We predict that the pole-on disk can be distinguished from the envelope. In contrast, the model images show a bipolar nebulosity and a polarization disk with a vector alignment in edge-on view. The polarization is low (<10%) for large grains or low H values and high (up to ~80%) for small grains and high H values. In contrast, comparably constant polarizations (20-40%) are obtained in the optical. The wavelength dependence in low NIR polarization cases is often detected in many T Tauri stars, suggesting that grain growth or an advanced disk accretion is expected in these objects. The opposite trend in high NIR polarization cases, which is found in some low-mass protostars, is reproduced with spherical grain models. To understand our results, we developed a generalized scattering model, which is an extension of the vector alignment mechanism. In the low-mass star disk case, multiple-scattered light behaves as if it chooses paths of comparably low optical density region (e.g. the disk surface), avoiding a high density, equatorial region, which we call the roundabout effect. The single-scattered light does not reach the observer, and the double-scattered light contributes the most flux. However, the effect of the first scattering still appears in the final polarization status. The higher the disk height in our models, the closer to 90° the scattering angle on the disk surface, resulting in a higher polarization. The variety of the wavelength dependence on the polarization is also an example of the roundabout effect. In the optical, only stray light passed through the envelope reaches the observer. Thus, the optical polarization is characterized by scattering by small grains in the envelope. On the other hand, since the NIR photons can pass through a somewhat inner part of the disk, the NIR polarization can still offer information on the dust and geometry of the disk. We expect that a polarization disk analysis in high-resolution data, such as the one we present, offers opportunities to investigate the grain growth and dust settling in YSOs, and our new scattering model is also fundamental for nonspherical grain models.

  18. Polar Lows in Reanalyses and High Resolution Global Climate Models

    NASA Astrophysics Data System (ADS)

    Shaffrey, Len; Zappa, Giuseppe; Hodges, Kevin; Vidale, Pier Luigi

    2015-04-01

    Polar lows are maritime meso-cyclones associated with intense surface wind speeds and oceanic heat fluxes at high latitudes. The ability of the ERA-Interim (ERAI) reanalysis to represent polar lows in the North Atlantic is assessed by comparing ERAI and the ECMWF operational analysis for the period 2008-2011. The operational analysis has vorticity structures that better resemble the observed cloud patterns and stronger surface wind speed intensities compared to those in ERAI. By applying objective identification criteria, about 55% of the satellite observed polar lows are identified and tracked in ERAI, while this fraction increases to about 70% in the operational analysis. Particularly in ERAI, the remaining observed polar lows are mainly not identified because they have too weak wind speed and vorticity intensity compared to the tested criteria. The implications of the tendency of ERAI to underestimate the polar low dynamical intensity for future studies of polar lows is discussed. The ability of the Met Office HadGEM3 global climate model at different horizontal resolutions (150km, 60km and 25km) to capture Polar Lows will also be discussed.

  19. High Resolution Studies of Electron Attachment to Molecules

    SciTech Connect

    Braun, M.; Ruf, M.-W.; Hotop, H. [Fachbereich Physik, Technische Universitaet Kaiserslautern, 67653 Kaiserslautern (Germany); Fabrikant, I. I. [Fachbereich Physik, Technische Universitaet Kaiserslautern, 67653 Kaiserslautern (Germany); Department of Physics and Astronomy, University of Nebraska, Lincoln, NE (United States)

    2009-05-02

    In this paper, we survey recent progress in studies of anion formation via (dissociative) electron attachment (DEA) to simple molecules, as measured with the laser photoelectron attachment (LPA) method at high resolution. The limiting (E{yields}0) threshold behavior of the cross sections is elucidated for s-wave and p-wave attachment. Cusps at onsets for vibrational excitation (VE), due to interaction of the DEA channnel with the VE channel, are clearly detected, and vibrational Feshbach resonances just below vibrational onsets are observed for molecules with sufficiently strong long-range attraction between the electron and the molecule. From the LPA anion yields, absolute DEA cross sections (energy range typically E = 0.001-2 eV) are determined with reference to rate coefficients for thermal electron attachment at the appropriate gas temperature (normally T{sub G} = 300 K). The experimental data are compared with theoretical cross sections, calculated within the framework of an R-matrix or an Effective Range theory approach.

  20. Polarization gating and circularly-polarized high harmonic generation using plasmonic enhancement in metal nanostructures.

    PubMed

    Husakou, A; Kelkensberg, F; Herrmann, J; Vrakking, M J J

    2011-12-01

    We investigate possibilities to utilize field enhancement by specifically designed metal nanostructures for the generation of single attosecond pulses using the polarization gating technique. We predict the generation of isolated 59-attosecond-long pulses using 15-fs pump pulses with only a 0.6 TW/cm2 intensity. Our simulations also indicate the possibility to generate previously inaccessible high-harmonics with circular polarization by using an ensemble of vertically and horizontally orientated bow-tie structures. In the numerical simulation we used an extended Lewenstein model, which includes the spatial inhomogeneity in the hot spots and collisions of electrons with the metal surface. PMID:22273926

  1. Quantum coherent ?-electron rotations in a non-planar chiral molecule induced by using a linearly polarized UV laser pulse

    NASA Astrophysics Data System (ADS)

    Mineo, Hirobumi; Fujimura, Yuichi

    2015-06-01

    We propose an ultrafast quantum switching method of ?-electron rotations, which are switched among four rotational patterns in a nonplanar chiral aromatic molecule (P)-2,2’- biphenol and perform the sequential switching among four rotational patterns which are performed by the overlapped pump-dump laser pulses. Coherent ?-electron dynamics are generated by applying the linearly polarized UV pulse laser to create a pair of coherent quasidegenerated excited states. We also plot the time-dependent ?-electron ring current, and discussed ring current transfer between two aromatic rings.

  2. High contrast single molecule tracking in the pericellular coat

    NASA Astrophysics Data System (ADS)

    Scrimgeour, Jan; McLane, Louis T.; Curtis, Jennifer E.

    2014-03-01

    The pericellular coat is a robust, hydrated, polymer brush-like structure that can extend several micrometers into the extracellular space around living cells. By controlling access to the cell surface, acting as a filter and storage reservoir for proteins, and actively controlling tissue-immune system interactions, the cell coat performs many important functions at scales ranging from the single cell to whole tissues. The cell coat consists of a malleable backbone - the large polysaccharide hyaluronic acid (HA) - with its structure, material properties, and ultimately its bio-functionality tuned by a diverse set of HA binding proteins. These proteins add charge, cross-links and growth factor-like ligands to the coat To probe the dynamic behavior of this soft biomaterial we have used high contrast single molecule imaging, based on highly inclined laser illumination, to observe individual fluorescently labeled HA binding proteins within the cell coat. Our work focuses on the cell coat of living chondrocyte (cartilage) cells, and in particular the effect of the large, highly charged, protein aggrecan on the properties of the coat. Through single molecule imaging we observe that aggrecan is tightly tethered to HA, and plays an important role in cell coat extension and stiffening.

  3. Application of Dissolution Dynamic Nuclear Polarization to the Characterization of Reactions Involving Large Molecules 

    E-print Network

    Lee, Youngbok

    2013-03-13

    Nuclear magnetic resonance (NMR) spectroscopy is one of the most important analytical tools for organic and biological chemistry. It provides not only detailed information on the structure of small molecules and macromolecules, ...

  4. Dipole moments of ultra-cold polar molecules: a quantum Monte Carlo study

    Microsoft Academic Search

    Michal Bajdich; Shi Guo; Lubos Mitas; Peter J. Reynolds

    2009-01-01

    Recently, there has been a great deal of interest in the production of ultra-cold heteronuclear molecules having large electric dipole moments [1]. This is of interest both for fundamental reasons as well as for applications such as qubits for quantum computing [2]. In this work, we calculate the dipole moment of a potentially implementable two-atom alkaline-alkaline-earth molecule, LiSr. We use

  5. Polarization dependence of microwave ionization of hydrogen at high scaled frequencies

    Microsoft Academic Search

    John William Wilson

    2003-01-01

    We have measured the polarization dependance of microwave ionization of hydrogen at high scaled frequencies. The survival probability of hydrogen Rydberg atoms with principle quantum numbers n0 = 40--81 was measured as a function of microwave field amplitude for three polarizations of the microwave field: circular polarization (CP), linear polarization (LP), and elliptical polarization (CP). The range of n0 covered

  6. Starch granules as a probe for the polarization at the sample plane of a high resolution multiphoton microscope

    NASA Astrophysics Data System (ADS)

    Psilodimitrakopoulos, Sotiris; Amat-Roldán, Ivan; Santos, Susana; Mathew, Manoj; Thayil K. N., Anisha; Zalvidea, Dobryna; Artigas, David; Loza-Alvarez, Pablo

    2008-02-01

    Because of its polarization sensitivity, SHG microscopy can provide information about the orientation and degree of structural organization inside biological samples. To fully exploit the above potential, the state of the polarization at the sample plane needs to be known. In this work we present starch granules as a reliable probe for the polarization state of the excitation beam at the sample plane of a high resolution multiphoton microscope. Polarization dependent SHG series of images demonstrated the radial distribution of SHG active molecules inside starch granules. This allowed the granule to exhibit symmetrical SHG emission regions. The pattern rotates along with the rotation of a ?/2 waveplate and thus, can demonstrate the polarization at the sample plane. Maximum signal in the forward detected geometry appears when imaging starch granules exactly at the hemisphere plane. Symmetric SHG regions rotating with the incoming linear polarization were also recorded in the backward detected geometry. A portion of the backwards detected SHG signal, which corresponds to two rotating equator arcs, does not overlap with the forward SHG signal. Importantly, polarization measurements, performed either in the forward or the backwards directions, have demonstrated the suitability and flexibility of this technique for both detection schemes. As result, observation of the starch signal allowed us to know the polarization of our SHG microscope. Furthermore, by coding this information in an angular representation, we corrected the input values in a theoretical model that predicts the average orientation of SHG active molecules. This has allowed us to map the mean orientation of SHG active molecules in body walls muscle of Caenorhabditis elegans, with pixel resolution.

  7. Circular polarization of synchrotron radiation in high magnetic fields

    NASA Astrophysics Data System (ADS)

    de Búrca, D.; Shearer, A.

    2015-06-01

    The general model for incoherent synchrotron radiation has long been known, with the first theory being published by Westfold in 1959 and continued by Westfold and Legg in 1968. When this model was first developed, it was applied to radiation from Jupiter, with a magnetic field of ?1G. Pulsars have a magnetic field of ?1012 G. The Westfold and Legg model predict a circular polarization which is proportional to the square root of the magnetic field, and consequently predicts greater than 100 per cent circular polarization at high magnetic fields. Here a new model is derived based upon a more detailed analysis of the pitch angle distribution. This model is concerned with the frequency range f_{B_0}/? ? flesssim f_{B_0}, noting that f_{B_0} = 2.7× 10^7B, which for a relatively high magnetic field (˜106-108 G) leaves emission in the optical range. This is much lower than the expected frequency peak for a mono-energetic particle of 0.293eB/4? m_e c? ^2. We predict the circular polarization peaks around 107G in the optical regime with the radiation almost 15 per cent circularly polarized. The linear polarization changes from about 60 to 80 per cent in the same regime. We examine implications of this for pulsar studies.

  8. Broadening and shifting of the methanol 119 {mu}m gain line of linear and circular polarization by collision with chiral molecules

    SciTech Connect

    J.S. Bakos; G. Djotyan; Zsuzsa Soerlei; J. Szigeti; D. K. Mansfield; J. Sarkozi

    2000-06-21

    Evidence of circular dichroism has been observed in the spectral properties of a gas of left-right symmetric molecules. This dichroism comes about as the result of collisions of the symmetric molecules with left-right asymmetric molecules introduced as a buffer gas. In this sense, the dichroism can be said to have been transferred from the chiral buffer molecules to the symmetric, non-chiral molecules of the background vapor. This transferred dichroism appears as broadening in the gain line of the symmetric molecule which is asymmetric with respect to the right or left handedness of a circularly polarized probe. The broadening of the 119 {mu}m line of the methanol molecule was observed using infrared-far infrared double resonance spectroscopy.

  9. Polarization characteristics of nonlinear transmission in rigidly held saturable-dye molecules with random orientations

    NASA Astrophysics Data System (ADS)

    Miyanaga, S.; Sato, T.

    2015-04-01

    Polarization-dependent nonlinear transmissions are investigated by a pump-probe method in saturable-dye-doped films in which optically anisotropic saturable dyes are rigidly held with random orientations. The nonlinear transmissions measured by using uranine-doped poly(vinyl alcohol) films are compared with the theoretical predictions that are obtained by considering the effects of pump propagation and molecular orientation on the basis of a rate equation analysis for a four-energy-level model including an excited-state absorption. The measurements were conducted for the two cases of polarization states for which the polarization direction of the probe wave is either parallel or perpendicular to that of the pump wave; the experimental results considerably deviated from the theoretical ones for the probe wave perpendicularly polarized to the pump wave. It is shown that this is explained by modifying the energy level model to include the existence of a nearly-orthogonal component of the transition dipole moment associated with the ground-state absorption in uranine dyes.

  10. The effect of spin polarization on zero field splitting parameters in paramagnetic pi-electron molecules.

    PubMed

    van Gastel, Maurice

    2009-09-28

    Spin polarization effects play an important role in the theory of isotropic hyperfine interactions for aromatic protons. The spin polarization gives rise to significant isotropic proton hyperfine interactions--spin-dependent one-electron properties--smaller than 0 MHz and the effect has been theoretically described [H. M. McConnell and D. B. J. Chesnut, Chem. Phys. 28, 107 (1958)]. The influence of spin polarization on the zero field splitting parameters, which are spin-dependent two-electron properties, has not been clearly identified yet. A phenomenological equation is proposed here for the contribution of spin polarization to the zero field splitting parameter D in analogy to McConnell's equation for hyperfine interactions. The presence of the effect is demonstrated in a series of calculations on polyacenes in the triplet state and turns out to be responsible for up to 50% of the D parameter in the case of naphthalene! It is found that spin-unrestricted single-determinant methods, including the widely used density functional theory methods, do not accurately reproduce the two-electron reduced electron density required for the evaluation of two-electron spin-dependent properties. For the accurate calculation of zero field splitting parameters by quantum chemical methods, it thus seems necessary to resort to correlated ab initio methods which do not give rise to spin contamination and which do provide an accurate description of the two-electron reduced electron density. PMID:19791856

  11. Single-molecule tracking of small GTPase Rac1 uncovers spatial regulation of membrane translocation and mechanism for polarized signaling

    PubMed Central

    Das, Sulagna; Yin, Taofei; Yang, Qingfen; Zhang, Jingqiao; Wu, Yi I.; Yu, Ji

    2015-01-01

    Polarized Rac1 signaling is a hallmark of many cellular functions, including cell adhesion, motility, and cell division. The two steps of Rac1 activation are its translocation to the plasma membrane and the exchange of nucleotide from GDP to GTP. It is, however, unclear whether these two processes are regulated independent of each other and what their respective roles are in polarization of Rac1 signaling. We designed a single-particle tracking (SPT) method to quantitatively analyze the kinetics of Rac1 membrane translocation in living cells. We found that the rate of Rac1 translocation was significantly elevated in protrusions during cell spreading on collagen. Furthermore, combining FRET sensor imaging with SPT measurements in the same cell, the recruitment of Rac1 was found to be polarized to an extent similar to that of the nucleotide exchange process. Statistical analysis of single-molecule trajectories and optogenetic manipulation of membrane lipids revealed that Rac1 membrane translocation precedes nucleotide exchange, and is governed primarily by interactions with phospholipids, particularly PI(3,4,5)P3, instead of protein factors. Overall, the study highlights the significance of membrane translocation in spatial Rac1 signaling, which is in addition to the traditional view focusing primarily on GEF distribution and exchange reaction. PMID:25561548

  12. Quantum-classical correspondence in circularly polarized high harmonic generation

    NASA Astrophysics Data System (ADS)

    Mauger, F.; Bandrauk, A. D.; Kamor, A.; Uzer, T.; Chandre, C.

    2014-02-01

    Using numerical simulations, we show that atomic high order harmonic generation (HHG) with a circularly polarized laser field offers an ideal framework for quantum-classical correspondence in strong field physics. With an appropriate initialization of the system, corresponding to a superposition of ground and excited state(s), simulated HHG spectra display a narrow strip of strong harmonic radiation preceded by a gap of missing harmonics in the lower part of the spectrum. In specific regions of the spectra, HHG tends to lock to circularly polarized harmonic emission. All these properties are shown to be closely related to a set of key classical periodic orbits that organize the recollision dynamics in an intense, circularly polarized field.

  13. Oriented molecule beams: Focusing and orientation of t-butyl iodide with analysis by polarized laser photofragmentation

    NASA Astrophysics Data System (ADS)

    Xu, Qi-Xun; Jung, Kyung-Hoon; Bernstein, Richard B.

    1988-08-01

    The tert-butyl iodide molecule is readily focused with the electrostatic hexapole, via its first-order Stark effect as a pseudo-symmetric top. The pulsed, seeded supersonic focused beam, characterized by =Vth/ V0 (where ? is the angle between the molecular dipole axis ? and the electric field E; ±V0 the hexapole ``rod voltage,'' and Vth the so-called threshold voltage), passes into a small homogeneous electric field in which it is oriented. The degree of laboratory orientation achieved is measured using the method of linearly polarized laser-induced photofragmentation [S. R. Gandhi, T. J. Curtiss, and R. B. Bernstein, Phys. Rev. Lett. 59, 2951 (1987)], operating (at three laser wavelengths) on the I(2P3/2) and I(2P1/2) as well as the t-C4H9 radical photofragments. The results show that the oriented beam molecules of t-butyl iodide (at a rotational temperature near 15 K) have a higher degree of orientation than the prototype CH3I molecules (JKM state-selected and focused similarly), explainable by the greater importance of the so-called hyperfine disorientation effect for the prolate symmetric top (CH3I) than for the t-C4H9I. For the latter, orientations with photofragment up-down asymmetry ratios as large as a factor of 10 can be achieved, suggesting that t-C4H9I is an excellent candidate reagent for reactive asymmetry studies.

  14. Quantum walk and Anderson localization of rotational excitations in disordered ensembles of polar molecules

    NASA Astrophysics Data System (ADS)

    Xu, T.; Krems, R. V.

    2015-06-01

    We consider the dynamics of rotational excitations placed on a single molecule in spatially disordered one-dimensional (1D), two-dimensional (2D) and three-dimensional (3D) ensembles of ultracold molecules trapped in optical lattices. The disorder arises from incomplete populations of optical lattices with molecules. This leads to a model corresponding to a quantum particle with long-range tunnelling amplitudes moving on a lattice with the same on-site energy but with forbidden access to random sites (vacancies). We examine the time and length scales of Anderson localization for this type of disorder with realistic experimental parameters in the Hamiltonian. We show that for an experimentally realized system of KRb molecules on an optical lattice this type of disorder leads to disorder-induced localization in 1D and 2D systems on a time scale t? 1 s. For 3D lattices with 55 sites in each dimension and vacancy concentration 90%, the rotational excitations diffuse to the edges of the lattice and show no signature of Anderson localization. We examine the role of the long-range tunnelling amplitudes allowing for transfer of rotational excitations between distant lattice sites. Our results show that the long-range tunnelling has little impact on the dynamics in the diffusive regime but affects significantly the localization dynamics in lattices with large concentrations of vacancies, enhancing the width of the localized distributions in 2D lattices by more than a factor of 2.

  15. Quantitative isoform-profiling of highly diversified recognition molecules

    PubMed Central

    Schreiner, Dietmar; Simicevic, Jovan; Ahrné, Erik; Schmidt, Alexander; Scheiffele, Peter

    2015-01-01

    Complex biological systems rely on cell surface cues that govern cellular self-recognition and selective interactions with appropriate partners. Molecular diversification of cell surface recognition molecules through DNA recombination and complex alternative splicing has emerged as an important principle for encoding such interactions. However, the lack of tools to specifically detect and quantify receptor protein isoforms is a major impediment to functional studies. We here developed a workflow for targeted mass spectrometry by selected reaction monitoring that permits quantitative assessment of highly diversified protein families. We apply this workflow to dissecting the molecular diversity of the neuronal neurexin receptors and uncover an alternative splicing-dependent recognition code for synaptic ligands. DOI: http://dx.doi.org/10.7554/eLife.07794.001 PMID:25985086

  16. HIGH EFFICIENCY THREE-DIMENSIONAL MANIPULATION OF SUB-MICRON PARTICLES AND DNA MOLECULES

    E-print Network

    Kassegne, Samuel Kinde

    HIGH EFFICIENCY THREE-DIMENSIONAL MANIPULATION OF SUB-MICRON PARTICLES AND DNA MOLECULES Molecules _____________________________________________ Samuel Kinde Kassegne, Chair Department that the eyes glazing over when I described in intricate detail the pitfalls of non-coupled forces were merely

  17. Optically isotropic liquid-crystal phase of bent-core molecules with polar nanostructure.

    PubMed

    Liao, G; Stojadinovic, S; Pelzl, G; Weissflog, W; Sprunt, S; Jákli, A

    2005-08-01

    We found that the optically isotropic (I(M)) mesophase observed recently below the nematic phase of the bent-core liquid crystal 4-chlororesorcinol bis[4-(4-n-dodecyloxybenzoyloxy)benzoate] shows ferroelectric-type switching. Polarizing microscopic, electric current, dielectric, and dynamic light scattering studies lead us to propose that the I(M) phase is composed of interconnected orthoconic racemic smectic (Sm-Ca P(F)) nanodomains with random layer orientations. Near the nematic phase, where the polarization can be saturated by electric fields, the system responds in a fashion analogous to the granular structure of a magnetic spin glass--in particular, we observed that the relaxation back to the nonpoled structure follows a similar, inverse logarithmic rule. PMID:16196588

  18. Phase-controlled polarization coherent anti-Stokes Raman scattering microscopy for high-sensitivity and high-contrast molecular imaging

    Microsoft Academic Search

    Fake Lu; Wei Zheng; Zhiwei Huang

    2008-01-01

    We report on a phase-controlled polarization coherent anti-Stokes Raman scattering (CARS) microscopy for high-sensitivity and high-contrast molecule vibrational imaging. By changing the phase difference between the two CARS signals (i.e., a weak resonant CARS and a strong nonresonant CARS signal) simultaneously gen- erated from the same focal volume of the sample, the complete constructive (in-phase) and destructive (out-of- phase) interference

  19. Rotaviruses require basolateral molecules for efficient infection of polarized MDCKII cells.

    PubMed

    Realpe, Mauricio; Espinosa, Rafaela; López, Susana; Arias, Carlos F

    2010-02-01

    In this work we evaluated the ability of rotavirus strains with different receptor requirements to infect the apical and basolateral surfaces of polarized MDCKII cells. We used neuraminidase (NA)-sensitive (RRV and TFR-1) and neuraminidase-resistant (Wa and UK) viruses that differ in their use of integrins. Regardless of their receptor requirements, all virus strains tested were found to efficiently infect cells from both membrane surface domains, with preference for the basolateral domain, since: (i) disruption of tight junctions of polarized cell monolayers by calcium chelation led to a reversible increase of rotavirus infectivity, (ii) the viruses infected preferentially the cells located at the borders of microcolonies of polarized cells, and (iii) in cells grown on a permeable support all four virus strains were able to start the infection by either plasma membrane domain. Preferential infection (5-11-fold more efficiently) of the basolateral surface correlated with the neuraminidase resistance of the virus strains, but not with their requirement for integrins, which in MDCKII cells seem to be used by all four viruses. The infection of both cell surface domains by RRV was found to depend on the presence of terminal sialic acids, since its infectivity was reduced by neuraminidase treatment of the cells and it was also blocked by incubation of the virus with glycophorin A. The efficient infection through the basolateral membrane surface of polarized cells might be relevant for the pathogenesis of rotavirus, especially given the recent reports of antigenemia and extraintestinal spread of the virus in children and animal models. PMID:19932141

  20. High energy sources and materials: High-temperature molecules and molecular energy storage

    Microsoft Academic Search

    W. Weltner Jr.

    1980-01-01

    The objective of this research was the characterization of molecular species which are important because of (a) their occurrence in high-temperature environments, as for example in the vapor over refractory solids, and in combustion, flames, and propellant burning; (b) their relevance to clarification and\\/or extension of the basic theory of molecular properties. The molecules studied were usually highly reactive or

  1. Altered intracellular region of MUC1 and disrupted correlation of polarity-related molecules in breast cancer subtypes.

    PubMed

    Iizuka, Misato; Nakanishi, Yoko; Fuchinoue, Fumi; Maeda, Tetsuyo; Murakami, Eriko; Obana, Yukari; Enomoto, Katsuhisa; Tani, Mayumi; Sakurai, Kenichi; Amano, Sadao; Masuda, Shinobu

    2015-03-01

    MUC1 glycoprotein is overexpressed and its intracellular localization altered during breast carcinoma tumorigenesis. The present study aimed to clarify the relationship of cytoplasmic localization of MUC1 with the breast cancer subtype and the correlation of 10 molecules associated with cell polarity in breast cancer subtypes. We immunostained 131 formalin-fixed and paraffin-embedded breast cancer specimens with an anti-MUC1 antibody (MUC1/CORE). For 48 of the 131 tumor specimens, laser-assisted microdissection and real-time quantitative RT-PCR were performed to analyze mRNA levels of MUC1 and 10 molecules, ?-catenin, E-cadherin, claudin 3, claudin 4, claudin 7, RhoA, cdc42, Rac1, Par3 and Par6. Localization of MUC1 protein varied among breast cancer subtypes, that is, both the apical domain and cytoplasm in luminal A-like tumors (P < 0.01) and both the cytoplasm and cell membrane in luminal B-like (growth factor receptor 2 [HER2]+) tumors (P < 0.05), and no expression was found in triple negative tumors (P < 0.001). Estrogen receptor (ER)+ breast cancers showed higher MUC1 mRNA levels than ER- breast cancers (P < 0.01). The incidence of mutual correlations of expression levels between two of the 10 molecules (55 combinations) was 54.5% in normal breast tissue and 38.2% in luminal A-like specimens, 16.4% in luminal B-like (HER2+), 3.6% in HER2 and 18.2% in triple negative specimens. In conclusion, each breast cancer subtype has characteristic cytoplasmic localization patterns of MUC1 and different degrees of disrupted correlation of the expression levels between the 10 examined molecules in comparison with normal breast tissue. PMID:25556893

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

    SciTech Connect

    Bruun, G. M.; Massignan, P. [Mathematical Physics, Lund Institute of Technology, P.O. Box 118, SE-22100 Lund (Sweden); Grup de Fisica Teorica, Universitat Autonoma de Barcelona, 08193 Bellaterra (Spain) and ICFO-Institut de Ciencies Fotoniques, Mediterranean Technology Park, 08860 Castelldefels, Barcelona (Spain)

    2010-07-09

    The ground state of an impurity immersed in a Fermi sea changes from a polaron to a molecule as the interaction strength is increased. We show here that the coupling between these two states is strongly suppressed due to a combination of phase-space effects and Fermi statistics, and that it vanishes much faster than the energy difference between the two states, thereby confirming the first order nature of the polaron-molecule transition. In the regime where each state is metastable, we find quasiparticle lifetimes which are much longer than what is expected for a usual Fermi liquid. Our analysis indicates that the decay rates are sufficiently slow to be experimentally observable.

  3. Applications of highly spin-polarized xenon in NMR

    SciTech Connect

    Long, H.W. [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry; [Lawrence Berkeley Lab., CA (United States)

    1993-09-01

    The main goal of the work presented in this thesis is produce highly spin-polarized xenon to create much greater signal intensities (up to 54,000 times greater) so as to allow studies to be made on systems with low surface area and long spin-lattice relaxation times. The spin-exchange optical pumping technique used to create high nuclear spin polarization is described in detail in chapter two. This technique is initially applied to some multiple-pulse optically detected NMR experiments in low magnetic field (50G) that allow the study of quadrupoler interactions with a surface of only a few square centimeters. In chapter three the apparatus used to allow high field {sup 129}Xe NMR studies to be performed with extremely high sensitivity is described and applied to experiments on diamagnetic susceptibility effects in thin ({approximately}2000 layers) films of frozen xenon. Preliminary surface investigations of laser polarized {sup 129}Xe adsorbed an a variety of materials (salts, molecular crystals, amorphous carbon, graphite) are then discussed. A full detailed study of the surface of a particular polymer, poly(acrylic acid), is presented in chapter four which shows the kind of detailed information that can be obtained from this technique. Along with preliminary results for several similar polymers, a summary is given of xenon studies of a novel ultra-high surface area polymer, poly(triarylcarbinol). Finally in chapter five the exciting possibility of transferring the high spin order of the laser polarized xenon has been used to transfer nuclear spin order to {sup 13}CO{sub 2} in a xenon matrix and to protons on poly(triarylcarbinol).

  4. Rotational Cooling of Polar Molecules by Stark-tuned Cavity Resonance

    E-print Network

    C. H. Raymond Ooi

    2003-06-04

    A general scheme for rotational cooling of diatomic heteronuclear molecules is proposed. It uses a superconducting microwave cavity to enhance the spontaneous decay via Purcell effect. Rotational cooling can be induced by sequentially tuning each rotational transition to cavity resonance, starting from the highest transition level to the lowest using an electric field. Electrostatic multipoles can be used to provide large confinement volume with essentially homogeneous background electric field.

  5. Quantum walk and Anderson localization of rotational excitations in disordered ensembles of polar molecules

    E-print Network

    Tianrui Xu; Roman V. Krems

    2015-05-05

    We consider the dynamics of rotational excitations placed on a single molecule in spatially disordered 1D, 2D and 3D ensembles of ultracold molecules trapped in optical lattices. The disorder arises from incomplete populations of optical lattices with molecules. This leads to a model corresponding to a quantum particle with long-range tunnelling amplitudes moving on a lattice with the same on-site energy but with forbidden access to random sites (vacancies). We examine the time and length scales of Anderson localization for this type of disorder with realistic experimental parameters in the Hamiltonian. We show that for an experimentally realized system of KRb molecules on an optical lattice this type of disorder leads to disorder-induced localization in 1D and 2D systems on a time scale $t \\sim 1$ sec. For 3D lattices with $55$ sites in each dimension and vacancy concentration $ 90~\\%$, the rotational excitations diffuse to the edges of the lattice and show no signature of Anderson localization. We examine the role of the long-range tunnelling amplitudes allowing for transfer of rotational excitations between distant lattice sites. Our results show that the long-range tunnelling has little impact on the dynamics in the diffusive regime but affects significantly the localization dynamics in lattices with large concentrations of vacancies, enhancing the width of the localized distributions in 2D lattices by more than a factor of 2. Our results raise a general question whether quantum particles with long-range tunnelling can undergo quantum localization in 3D lattices with substitutional disorder.

  6. Long-range interactions between polar bialkali ground-state molecules in arbitrary vibrational levels.

    PubMed

    Vexiau, R; Lepers, M; Aymar, M; Bouloufa-Maafa, N; Dulieu, O

    2015-06-01

    We have calculated the isotropic C6 coefficients characterizing the long-range van der Waals interaction between two identical heteronuclear alkali-metal diatomic molecules in the same arbitrary vibrational level of their ground electronic state X(1)?(+). We consider the ten species made up of (7)Li, (23)Na, (39)K, (87)Rb, and (133)Cs. Following our previous work [Lepers et al., Phys. Rev. A 88, 032709 (2013)], we use the sum-over-state formula inherent to the second-order perturbation theory, composed of the contributions from the transitions within the ground state levels, from the transition between ground-state and excited state levels, and from a crossed term. These calculations involve a combination of experimental and quantum-chemical data for potential energy curves and transition dipole moments. We also investigate the case where the two molecules are in different vibrational levels and we show that the Moelwyn-Hughes approximation is valid provided that it is applied for each of the three contributions to the sum-over-state formula. Our results are particularly relevant in the context of inelastic and reactive collisions between ultracold bialkali molecules in deeply bound or in Feshbach levels. PMID:26049492

  7. Long-range interactions between polar bialkali ground-state molecules in arbitrary vibrational levels

    NASA Astrophysics Data System (ADS)

    Vexiau, R.; Lepers, M.; Aymar, M.; Bouloufa-Maafa, N.; Dulieu, O.

    2015-06-01

    We have calculated the isotropic C6 coefficients characterizing the long-range van der Waals interaction between two identical heteronuclear alkali-metal diatomic molecules in the same arbitrary vibrational level of their ground electronic state X1?+. We consider the ten species made up of 7Li, 23Na, 39K, 87Rb, and 133Cs. Following our previous work [Lepers et al., Phys. Rev. A 88, 032709 (2013)], we use the sum-over-state formula inherent to the second-order perturbation theory, composed of the contributions from the transitions within the ground state levels, from the transition between ground-state and excited state levels, and from a crossed term. These calculations involve a combination of experimental and quantum-chemical data for potential energy curves and transition dipole moments. We also investigate the case where the two molecules are in different vibrational levels and we show that the Moelwyn-Hughes approximation is valid provided that it is applied for each of the three contributions to the sum-over-state formula. Our results are particularly relevant in the context of inelastic and reactive collisions between ultracold bialkali molecules in deeply bound or in Feshbach levels.

  8. Long-range interactions between polar bialkali ground-state molecules in arbitrary vibrational levels

    E-print Network

    R. Vexiau; M. Lepers; M. Aymar; N. Bouloufa-Maafa; O. Dulieu

    2015-02-19

    We have calculated the isotropic $C\\_6$ coefficients characterizing the long-range van der Waals interaction between two identical heteronuclear alkali-metal diatomic molecules in the same arbitrary vibrational level of their ground electronic state $X^1\\Sigma^+$. We consider the ten species made up of $^7$Li, $^{23}$Na, $^{39}$K, $^{87}$Rb and $^{133}$Cs. Following our previous work [M.~Lepers \\textit{et.~al.}, Phys.~Rev.~A \\textbf{88}, 032709 (2013)] we use the sum-over-state formula inherent to the second-order perturbation theory, composed of the contributions from the transitions within the ground state levels, from the transition between ground-state and excited state levels, and from a crossed term. These calculations involve a combination of experimental and quantum-chemical data for potential energy curves and transition dipole moments. We also investigate the case where the two molecules are in different vibrational levels and we show that the Moelwyn-Hughes approximation is valid provided that it is applied for each of the three contributions to the sum-over-state formula. Our results are particularly relevant in the context of inelastic and reactive collisions between ultracold bialkali molecules, in deeply bound or in Feshbach levels.

  9. Polarizing agents for high-frequency Dynamic Nuclear Polarization : development and applications

    E-print Network

    Hu, Kan-Nian

    2006-01-01

    Dynamic Nuclear Polarization (DNP) is utilized to enhance NMR signal intensities in systems including metals, ceramics, polymers and biological solids. The enhancement results from polarization transfers from unpaired ...

  10. Ultracold spin-polarized mixtures of {sup 2}{Sigma} molecules with S-state atoms: Collisional stability and implications for sympathetic cooling

    SciTech Connect

    Tscherbul, T. V. [Harvard-MIT Center for Ultracold Atoms, Cambridge, Massachusetts 02138 (United States); ITAMP, Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts 02138 (United States); Klos, J. [Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742 (United States); Buchachenko, A. A. [Department of Chemistry, Moscow State University, Moscow RU-119991 (Russian Federation)

    2011-10-15

    The prospects of sympathetic cooling of polar molecules with magnetically cotrapped alkali-metal atoms are generally considered poor due to strongly anisotropic atom-molecule interactions leading to large spin relaxation rates. Using rigorous quantum scattering calculations based on ab initio interaction potentials, we show that inelastic spin relaxation in low-temperature collisions of CaH({sup 2}{Sigma}) molecules with Li and Mg atoms occurs at a slow rate despite the strongly anisotropic interactions. This unexpected result, which we rationalize using multichannel quantum-defect theory, opens up the possibility of sympathetic cooling of polar {sup 2}{Sigma} molecules with alkali-metal atoms in a magnetic trap and with alkaline-earth-metal atoms in an optical dipole trap.

  11. Fluorescence polarization for the evaluation of small-molecule inhibitors of PCAF?BRD/Tat-AcK50 association.

    PubMed

    Hu, Ping; Wang, Xinghui; Zhang, Baiqun; Zhang, Shuai; Wang, Qiang; Wang, Zhiyong

    2014-05-01

    A fluorescence polarization competitive assay was developed to efficiently screen and evaluate inhibitors of PCAF bromodomain/Tat-AcK50 protein-peptide interaction. A series of pyridine 1-oxide derivatives were synthesized and evaluated. Some of the novel compounds, 2-(3-aminopropylamino) pyridine 1-oxide derivatives, could be effective inhibitors of PCAF bromodomain/Tat-AcK50 association. Specifically, 2-(3-aminopropylamino)-5-(hydroxymethyl)pyridine 1-oxide hydrochloride (15) and the 5-((3-aminopropylamino)methyl) derivative (20) were found to be effective ligands for the PCAF?BRD pocket. First preliminary cellular studies indicate that these small-molecule inhibitors have lower cytotoxicities and are potential leads for the anti-HIV/AIDS therapeutic strategy by targeting host-cell protein PCAF?BRD to block HIV replication. PMID:24474698

  12. Application of Dissolution Dynamic Nuclear Polarization to the Characterization of Reactions Involving Large Molecules

    E-print Network

    Lee, Youngbok

    2013-03-13

    IV-3 a) Scheme for the living anionic polymerization of styrene. Two living ends are represented in a dimer molecule. b) Expanded views of 1H decoupled 13C spectrum of the reaction of hyperpolarized styrene. c) As in (b), except without 1H... rubidium, or cesium) from a lower energy state to a higher energy state. Nobel gas (129Xe, or 3He) and Quenching gas (normally N2) transfer electrons of alkali metal between two sublevels of the excited state (collisional mixing), and deexcites...

  13. Polarization mode beating techniques for high-sensitivity intracavity sensing

    NASA Astrophysics Data System (ADS)

    Rosales-Garcia, Andrea

    Several industries, including semiconductor, space, defense, medical, chemical and homeland security, demand precise and accurate measurements in the nanometer and sub-nanometer scale. Optical interferometers have been widely investigated due to its dynamic-range, non-contact and high-precision features. Although commercially available interferometers can have sub-nanometer resolution, the practical accuracy exceeds the nanometer range. The fast development of nanotechnology requires more sensitive, reliable, compact and lower cost alternatives than those in existence. This work demonstrates a compact, versatile, accurate and cost-effective fiber laser sensor based on intracavity polarization mode beating (PMB) techniques for monitoring intracavity phase changes with very high sensitivity. Fiber resonators support two orthogonal polarization modes that can behave as two independent lasing channels within the cavity. The fiber laser incorporates an intracavity polarizing beamsplitter that allows for adjusting independently the polarization modes. The heterodyne detection of the laser output produces a beating (PMB) signal, whose frequency is a function of the phase difference between the polarization modes. The optical phase difference is transferred from the optical frequency to a much lower frequency and thus electronic methods can be used to obtain very precise measurements. Upon changing the pathlength of one mode, changes iu the PMB frequency can be effectively measured. Furthermore, since the polarization nodes share the same cavity, the PMB technique provides a simple means to achieve suppression of common mode noise and laser source instabilities. Frequency changes of the PMB signal are evaluated as a function of displacement, intracavity pressure and air density. Refractive index changes of 10 -9 and sub-nanometer displacement measurements are readily attained. Increased refractive index sensitivity and sub-picometer displacement can be reached owing to the high finesse and resolution of the system. Experimental changes in the refractive index of air as a function of pressure are in good agreement with theoretical predictions. An alternative fiber laser configuration, which incorporates non-reciprocal elements, allows measuring the optical activity of enantiomeric mixtures using PMB techniques. The sensitivity attained through PMB techniques demonstrates a potential method for ultra-sensitive biochemical sensing and explosive detection.

  14. A 3D-printed high power nuclear spin polarizer.

    PubMed

    Nikolaou, Panayiotis; Coffey, Aaron M; Walkup, Laura L; Gust, Brogan M; LaPierre, Cristen D; Koehnemann, Edward; Barlow, Michael J; Rosen, Matthew S; Goodson, Boyd M; Chekmenev, Eduard Y

    2014-01-29

    Three-dimensional printing with high-temperature plastic is used to enable spin exchange optical pumping (SEOP) and hyperpolarization of xenon-129 gas. The use of 3D printed structures increases the simplicity of integration of the following key components with a variable temperature SEOP probe: (i) in situ NMR circuit operating at 84 kHz (Larmor frequencies of (129)Xe and (1)H nuclear spins), (ii) <0.3 nm narrowed 200 W laser source, (iii) in situ high-resolution near-IR spectroscopy, (iv) thermoelectric temperature control, (v) retroreflection optics, and (vi) optomechanical alignment system. The rapid prototyping endowed by 3D printing dramatically reduces production time and expenses while allowing reproducibility and integration of "off-the-shelf" components and enables the concept of printing on demand. The utility of this SEOP setup is demonstrated here to obtain near-unity (129)Xe polarization values in a 0.5 L optical pumping cell, including ?74 ± 7% at 1000 Torr xenon partial pressure, a record value at such high Xe density. Values for the (129)Xe polarization exponential build-up rate [(3.63 ± 0.15) × 10(-2) min(-1)] and in-cell (129)Xe spin-lattice relaxation time (T1 = 2.19 ± 0.06 h) for 1000 Torr Xe were in excellent agreement with the ratio of the gas-phase polarizations for (129)Xe and Rb (PRb ? 96%). Hyperpolarization-enhanced (129)Xe gas imaging was demonstrated with a spherical phantom following automated gas transfer from the polarizer. Taken together, these results support the development of a wide range of chemical, biochemical, material science, and biomedical applications. PMID:24400919

  15. A 3D-Printed High Power Nuclear Spin Polarizer

    PubMed Central

    Nikolaou, Panayiotis; Coffey, Aaron M.; Walkup, Laura L.; Gust, Brogan M.; LaPierre, Cristen D.; Koehnemann, Edward; Barlow, Michael J.; Rosen, Matthew S.; Goodson, Boyd M.; Chekmenev, Eduard Y.

    2015-01-01

    Three-dimensional printing with high-temperature plastic is used to enable spin exchange optical pumping (SEOP) and hyperpolarization of xenon-129 gas. The use of 3D printed structures increases the simplicity of integration of the following key components with a variable temperature SEOP probe: (i) in situ NMR circuit operating at 84 kHz (Larmor frequencies of 129Xe and 1H nuclear spins), (ii) <0.3 nm narrowed 200 W laser source, (iii) in situ high-resolution near-IR spectroscopy, (iv) thermoelectric temperature control, (v) retroreflection optics, and (vi) optomechanical alignment system. The rapid prototyping endowed by 3D printing dramatically reduces production time and expenses while allowing reproducibility and integration of “off-the-shelf” components and enables the concept of printing on demand. The utility of this SEOP setup is demonstrated here to obtain near-unity 129Xe polarization values in a 0.5 L optical pumping cell, including ~74 ± 7% at 1000 Torr xenon partial pressure, a record value at such high Xe density. Values for the 129Xe polarization exponential build-up rate [(3.63 ± 0.15) × 10?2 min?1] and in-cell 129Xe spin?lattice relaxation time (T1 = 2.19 ± 0.06 h) for 1000 Torr Xe were in excellent agreement with the ratio of the gas-phase polarizations for 129Xe and Rb (PRb ~ 96%). Hyperpolarization-enhanced 129Xe gas imaging was demonstrated with a spherical phantom following automated gas transfer from the polarizer. Taken together, these results support the development of a wide range of chemical, biochemical, material science, and biomedical applications. PMID:24400919

  16. Prediction of polar surface area of drug molecules: a QSPR approach.

    PubMed

    Noorizadeh, H; Farmany, A; Noorizadeh, M; Kohzadi, M

    2013-04-01

    A quantitative structure-property relationship (QSPR) study based on an artificial neural network (ANN) was carried out for the prediction of the microemulsion liquid chromatography polar surface area (PSA) of a set of 32 drug compounds. The genetic algorithm-kernel partial least squares (GA-KPLS) method was used as a variable selection tool. A KPLS method was used to select the best descriptors and the selected descriptors were used as input neurons in neural network model. For choosing the best predictive model from among comparable models, square correlation coefficient Q(2) for the whole set calculated based on leave-group-out predicted values of the training set and model-derived predicted values for the test set compounds is suggested to be a good criterion. Finally, to improve the results, structure-property relationships were followed by nonlinear approach using artificial neural networks and consequently better results were obtained. Also this demonstrates the advantages of ANN. PMID:21539000

  17. Bioluminescence in the high Arctic during the polar night.

    PubMed

    Berge, J; Båtnes, A S; Johnsen, G; Blackwell, S M; Moline, M A

    2012-01-01

    This study examines the composition and activity of the planktonic community during the polar night in the high Arctic Kongsfjord, Svalbard. Our results are the first published evidence of bioluminescence among zooplankton during the Arctic polar night. The observations were collected by a bathyphotometer detecting bioluminescence, integrated into an autonomous underwater vehicle, to determine the concentration and intensity of bioluminescent flashes as a function of time of day and depth. To further understand community dynamics and composition, plankton nets were used to collect organisms passing through the bathyphotometer along with traditional vertical net tows. Additionally, using a moored bathyphotometer closed to the sampling site, the bioluminescence potential itself was shown not to have a diurnal or circadian rhythm. Rather, our results provide evidence for a diel vertical migration of bioluminescent zooplankton that does not correspond to any externally detectable changes in illumination. PMID:24489409

  18. Polarization interferometric nulling coronagraph for high-contrast imaging.

    PubMed

    Murakami, Naoshi; Yokochi, Kaito; Nishikawa, Jun; Tamura, Motohide; Kurokawa, Takashi; Takeda, Mitsuo; Baba, Naoshi

    2010-06-01

    We propose a novel, high-contrast imager called a polarization interferometric nulling coronagraph (PINC) for direct detection of extrasolar planets. The PINC uses achromatic half-wave plates (HWPs) installed in a fully symmetric beam combiner based on polarizing beam splitters. Jones calculus suggests that a stellar halo suppression level of 10(-10) can be achieved at 5 lambda/D for a broad wavelength range from 1.6 to 2.2 microm by using Fresnel-rhomb HWPs made of BK7. Laboratory experiments on the PINC used two laser light sources (wavelengths of lambda=532 and 671 nm), and we obtained a halo suppression level of approximately 10(-6) at 5 lambda/D for both wavelengths. PMID:20517351

  19. A novel high-throughput scanning microscope for label-free detection of protein and small-molecule chemical microarrays

    PubMed Central

    Fei, Y.Y.; Landry, J.P.; Sun, Y.S.; Luo, J.T.; Wang, X.B.; Lam, K.S; Zhu, X.D.

    2009-01-01

    We describe a novel scanning optical microscope based on a polarization-modulated nulling ellipsometry. The new microscope employs a combination of scanning mirror and sample translation and thus enables high-throughput label-free detection of biomolecular microarrays with more than 10,000 protein or small molecule targets. For illustration, we show the image of a 2760-spot protein microarray on a functionalized glass slide obtained with such a microscope. The new scanning microscope is also capable of determining, in parallel, the real-time binding kinetics of multiple molecular species under aqueous conditions. PMID:18248040

  20. The integrated spintronic functionalities of an individual high-spin state spin-crossover molecule between graphene nanoribbon electrodes.

    PubMed

    Zhu, L; Zou, F; Gao, J H; Fu, Y S; Gao, G Y; Fu, H H; Wu, M H; Lü, J T; Yao, K L

    2015-08-01

    The spin-polarized transport properties of a high-spin-state spin-crossover molecular junction with zigzag-edge graphene nanoribbon electrodes have been studied using density functional theory combined with the nonequilibrium Green's-function formalism. The molecular junction presents integrated spintronic functionalities such as negative differential resistance behavior, spin filter and the spin rectifying effect, associated with the giant magnetoresistance effect by tuning the external magnetic field. Furthermore, the transport properties are almost unaffected by the electrode temperature. The microscopic mechanism of these functionalities is discussed. These results represent a step toward multifunctional molecular spintronic devices on the level of the individual spin-crossover molecule. PMID:26180074

  1. High thermopower of mechanically stretched single-molecule junctions

    PubMed Central

    Tsutsui, Makusu; Morikawa, Takanori; He, Yuhui; Arima, Akihide

    2015-01-01

    Metal-molecule-metal junction is a promising candidate for thermoelectric applications that utilizes quantum confinement effects in the chemically defined zero-dimensional atomic structure to achieve enhanced dimensionless figure of merit ZT. A key issue in this new class of thermoelectric nanomaterials is to clarify the sensitivity of thermoelectricity on the molecular junction configurations. Here we report simultaneous measurements of the thermoelectric voltage and conductance on Au-1,4-benzenedithiol (BDT)-Au junctions mechanically-stretched in-situ at sub-nanoscale. We obtained the average single-molecule conductance and thermopower of 0.01 G0 and 15??V/K, respectively, suggesting charge transport through the highest occupied molecular orbital. Meanwhile, we found the single-molecule thermoelectric transport properties extremely-sensitive to the BDT bridge configurations, whereby manifesting the importance to design the electrode-molecule contact motifs for optimizing the thermoelectric performance of molecular junctions. PMID:26112999

  2. High thermopower of mechanically stretched single-molecule junctions.

    PubMed

    Tsutsui, Makusu; Morikawa, Takanori; He, Yuhui; Arima, Akihide; Taniguchi, Masateru

    2015-01-01

    Metal-molecule-metal junction is a promising candidate for thermoelectric applications that utilizes quantum confinement effects in the chemically defined zero-dimensional atomic structure to achieve enhanced dimensionless figure of merit ZT. A key issue in this new class of thermoelectric nanomaterials is to clarify the sensitivity of thermoelectricity on the molecular junction configurations. Here we report simultaneous measurements of the thermoelectric voltage and conductance on Au-1,4-benzenedithiol (BDT)-Au junctions mechanically-stretched in-situ at sub-nanoscale. We obtained the average single-molecule conductance and thermopower of 0.01 G0 and 15??V/K, respectively, suggesting charge transport through the highest occupied molecular orbital. Meanwhile, we found the single-molecule thermoelectric transport properties extremely-sensitive to the BDT bridge configurations, whereby manifesting the importance to design the electrode-molecule contact motifs for optimizing the thermoelectric performance of molecular junctions. PMID:26112999

  3. State Resolved Surface Dynamics of Highly Vibrationally Excited Molecules

    Microsoft Academic Search

    Daniel Auerbach

    2001-01-01

    We have measured state-to-state cross sections for the inelastic scattering of NO molecules from surfaces. Vibrational overtone pumping is used to prepare NO(v=2) and stimulated emission pumping (SEP) to prepare NO with in vibrational states up to v=22. Using REMPI detection we probe the final quantum state distributions of the scattered molecules as well as their velocity and angular distributions.

  4. High Efficacy Green LEDs by Polarization Controlled MOVPE

    SciTech Connect

    Wetzel, Christian

    2013-03-31

    Amazing performance in GaInN/GaN based LEDs has become possible by advanced epitaxial growth on a wide variety of substrates over the last decade. An immediate push towards product development and worldwide competition for market share have effectively reduced production cost and generated substantial primary energy savings on a worldwide scale. At all times of the development, this economic pressure forced very fundamental decisions that would shape huge industrial investment. One of those major aspects is the choice of epitaxial growth substrate. The natural questions are to what extend a decision for a certain substrate will limit the ultimate performance and to what extent, the choice of a currently more expensive substrate such as native GaN could overcome any of the remaining performance limitations. Therefore, this project has set out to explore what performance characteristic could be achieved under the utilization of bulk GaN substrate. Our work was guided by the hypotheses that line defects such as threading dislocations in the active region should be avoided and the huge piezoelectric polarization needs to be attenuated – if not turned off – for higher performing LEDs, particularly in the longer wavelength green and deep green portions of the visible spectrum. At their relatively lower performance level, deep green LEDs are a stronger indicator of relative performance improvements and seem particular sensitive to the challenges at hand. The project therefore made use of recently developed non-polar and semipolar bulk GaN substrates that were made available at Kyma Technologies by crystallographic cuts from thick polar growth of GaN. This approach naturally leads to rather small pieces of substrates, cm along the long side while mm along the short one. Small size and limited volume of sample material therefore set the limits of the ensuing development work. During the course of the project we achieved green and deep green LEDs in all those crystal growth orientations: polar c-plane, non- polar a-plane, non-polar m-plane, and semipolar planes. The active region in those structures shows dramatically reduced densities of threading dislocations unless the wavelength was extended as far as 510 nm and beyond. With the appearance of such defects, the light output power dropped precipitously supporting the necessity to avoid any and all of such defects to reach the active region. Further aspects of the non-polar growth orientation proved extremely promising for the development of such structures. Chief among them is our success to achieve extremely uniform quantum wells in these various crystal orientations that prove devoid of any alloy fluctuation beyond the theoretical limit of a binominal distribution. This became very Rensselaer Wetzel DE?EE0000627 3 directly apparent in highly advanced atom probe tomography performed in collaboration at Northwestern University. Furthermore, under reduced or absence of piezoelectric polarization, green emitters in those growth geometries exhibit an unsurpassed wavelength stability over very wide excitation and drive current ranges. Such a performance had not been possible in any polar c-plane growth and now places green LEDs in terms of wavelength stability up par with typical 450 nm blue emitters. The project also incorporated enabling opportunities in the development of micro and nano- patterned substrate technologies. Originally developped as a means to enhance generated light extraction we have demonstrated that the method of nano-patterning, in contrast to micro- patterning also results in a substantial reduction of threading dislocation generation. In green LEDs, we thereby see equal contributions of enhanced light extraction and reduced defect generation to a threefold enhancement of the green light output power. These results have opened entirely new approaches for future rapid and low cost epitaxial material development by avoidance of thick defect accommodation layers. All methods developed within this project have meanwhile widely been publicized by the members o

  5. Recoil-Proton Polarization in High-Energy Deuteron Photodisintegration with Circularly Polarized Photons

    SciTech Connect

    Jiang, X.; Benmokhtar, F.; Glashauser, C.; McCormick, K.; Ransome, R. D. [Rutgers, State University of New Jersey, Piscataway, New Jersey 08854 (United States); Arrington, J.; Holt, R. J.; Reimer, P. E.; Schulte, E. C.; Wijesooriya, K. [Argonne National Laboratory, Argonne, Illinois 60439 (United States); Camsonne, A. [Universite Blaise Pascal/IN2P3, F-63177 Aubiere (France); Chen, J. P.; Chudakov, E.; Gaskell, D.; Hansen, O.; Higinbotham, D. W.; Jager, C. W. de; Jones, M. K.; Lerose, J.; Michaels, R. [Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606 (United States)] (and others)

    2007-05-04

    We measured the angular dependence of the three recoil-proton polarization components in two-body photodisintegration of the deuteron at a photon energy of 2 GeV. These new data provide a benchmark for calculations based on quantum chromodynamics. Two of the five existing models have made predictions of polarization observables. Both explain the longitudinal polarization transfer satisfactorily. Transverse polarizations are not well described, but suggest isovector dominance.

  6. Dissociation energies of some high temperature molecules containing aluminum

    NASA Technical Reports Server (NTRS)

    Stearns, C. A.; Kohl, F. J.

    1972-01-01

    The Knudsen cell mass spectrometric method has been used to investigate the gaseous molecules Al2, AlSi,AlSiO, AlC2, Al2C2, and AlAuC2. Special attention was given to the experimental considerations and techniques needed to identify and to measure ion intensities for very low abundance molecular species. Second- and third-law procedures were used to obtain reaction enthalpies for pressure calibration independent and isomolecular exchange reactions. Dissociation energies for the molecules were derived from the measured ion intensities, free-energy functions obtained from estimated molecular constants, and auxiliary thermodynamic data. The bonding and stability of these aluminum containing molecules are compared with other similar species.

  7. Spectroscopic and dynamical studies of highly energized small polyatomic molecules

    NASA Astrophysics Data System (ADS)

    Field, Robert W.; Silbey, Robert J.

    The formyl radical and the acetylene molecule were chosen for these studies. The visible and fluorescence spectra of the formyl radical were recorded, and the spectral results are used as a basis to explain the electronic structure. Optical-optical double resonance studies of acetylene were recorded, and the spectral results are interpreted. The results of Zeeman and Stark anticrossing and quantum beat studies of acetylene are reported, and they provide an unusually detailed view of both Intersystem Crossing and Internal Conversion in small polyatomic molecules. Twenty-two references are cited as resulting from Department of Energy sponsorship of this project.

  8. Vibrational relaxation of highly excited CO molecules on CO{sub 2} molecules in the active medium of a CO laser

    SciTech Connect

    Grigorian, G M [V.A. Fock Institute of Physics, St. Petersburg State University, Petrodvorets, St. Petersburg (Russian Federation); Kochetov, I V [State Research Center of Russian Federation 'Troitsk Institute for Innovation and Fusion Research', Troitsk, Moscow Region (Russian Federation)

    2008-03-31

    The stationary vibrational distribution functions (VDFs) of CO molecules are measured in the axial region of a glow discharge in a glass tube at different concentrations of CO{sub 2} molecules. The relaxation constants of CO(v) molecules in excited vibrational states colliding with CO{sub 2} molecules are estimated for high vibrational levels with v = 17-29 by comparing experimental and calculated VDFs of CO molecules. Mechanisms explaining large relaxation rates are discussed. The dependence of the emission spectrum of a CO laser on the concentration of CO{sub 2} molecules is studied experimentally. (active media)

  9. Effect of nuclear vibration on high-order-harmonic generation of aligned H2 + molecules

    NASA Astrophysics Data System (ADS)

    Telnov, Dmitry A.; Heslar, John; Chu, Shih-I.

    2014-12-01

    High-order-harmonic generation (HHG) spectra have been calculated for H2 + molecules aligned parallel to the polarization of the laser field. We make use of the Jacobi coordinates and neglect the rotation of the nuclei. The remaining time-dependent Schrödinger equation is three dimensional in spatial coordinates, one of them being the internuclear separation and the other two describing the electronic motion. The problem is solved using the accurate and efficient time-dependent generalized pseudospectral method in prolate spheroidal coordinates for the electronic coordinates and Fourier grid method for the internuclear separation. Laser pulses with a carrier wavelength of 800 nm, a duration of ten optical cycles, and a peak intensity of 2 ×1014 W/cm2 have been used in the calculations. Our HHG spectra, which incorporate the effect of nuclear vibration, generally exhibit a significant deviation from those calculated for the fixed internuclear separations. The low-energy regions of the spectra, however, resemble those for the nuclei fixed at larger separations, while the high-energy regions are closer to those for the nuclei fixed at smaller internuclear distances. The dynamics of the nuclear vibrational wave packet is also obtained and analyzed.

  10. Effect of nuclear vibration on high-order harmonic generation of aligned H2+ molecules

    NASA Astrophysics Data System (ADS)

    Telnov, Dmitry A.; Heslar, John; Chu, Shih-I.

    2014-05-01

    High-order harmonic generation (HHG) spectra have been calculated for H2+molecules aligned in the direction parallel to the polarization of the laser field. We make use of the Jacobi coordinates and neglect the rotation of the nuclei. The remaining time-dependent Schrödinger equation is 3D in spatial coordinates, one of them being the internuclear separation and the other two describing the electronic motion. The problem is solved using the accurate and efficient time-dependent generalized pseudospectral method in prolate spheroidal coordinates for the electronic coordinates and Fourier grid method for the internuclear separation. Laser pulses with the carrier wavelength of 800 nm, duration of 10 optical cycles, and several peak intensities have been used in the calculations. Our HHG spectra obtained fully beyond the Born-Oppenheimer approximation generally exhibit a significant deviation from those calculated for the fixed internuclear separations. The low-energy regions of the spectra, however, resemble those for the nuclei fixed at larger separations while the high-energy regions are closer to those for the nuclei fixed at smaller internuclear distances. The dynamics of the nuclear vibrational wave packet is also obtained and analyzed. This work is partially supported by DOE.

  11. High-density single-molecule analysis of cell surface dynamics in C. elegans embryos

    E-print Network

    Cai, Long

    High-density single-molecule analysis of cell surface dynamics in C. elegans embryos Francois B in GFP::Actin embryos. Supplementary Figure 3 Tunable and high-density sampling of single molecule vs axial position, measured across the field of illumination in a GFP::Utrophin embryo during

  12. Incorporation of ionic liquid into porous polymer monoliths to enhance the separation of small molecules in reversed-phase high-performance liquid chromatography.

    PubMed

    Wang, Jiafei; Bai, Ligai; Wei, Zhen; Qin, Junxiao; Ma, Yamin; Liu, Haiyan

    2015-06-01

    An ionic liquid was incorporated into the porous polymer monoliths to afford stationary phases with enhanced chromatographic performance for small molecules in reversed-phase high-performance liquid chromatography. The effect of the ionic liquid in the polymerization mixture on the performance of the monoliths was studied in detail. While monoliths without ionic liquid exhibited poor resolution and low efficiency, the addition of ionic liquid to the polymerization mixture provides highly increased resolution and high efficiency. The chromatographic performances of the monoliths were demonstrated by the separations of various small molecules including aromatic hydrocarbons, isomers, and homologues using a binary polar mobile phase. The present column efficiency reached 27 000 plates/m, which showed that the ionic liquid monoliths are alternative stationary phases in the separation of small molecules by high-performance liquid chromatography. PMID:25864707

  13. Dynamic Nuclear Polarization of High-Density Atomic Hydrogen in Solid Mixtures of Molecular Hydrogen Isotopes

    NASA Astrophysics Data System (ADS)

    Sheludiakov, S.; Ahokas, J.; Järvinen, J.; Zvezdov, D.; Vainio, O.; Lehtonen, L.; Vasiliev, S.; Mao, S.; Khmelenko, V. V.; Lee, D. M.

    2014-12-01

    We report on magnetic resonance studies of high-density atomic hydrogen and deuterium in solid hydrogen matrices at temperatures below 1 K. Average concentrations of H atoms ?3 ×1019 cm-3 are obtained in chemical tunneling reactions of isotope exchange with D atoms. The products of these reactions are closely located pairs of H atoms near D2 molecules with strong exchange interactions. We discovered a dynamic nuclear polarization effect on H atoms created by pumping the center of the H electron spin resonance spectrum, similar to the Overhauser effect in metals. Our results indicate that H atoms may be arranged inside molecular matrices at separations equivalent to local concentrations of 2.6 ×1021 cm-3 . This opens up a way to build a metallic state of atomic hydrogen at zero pressure.

  14. Interaction between metal cation and unnatural peptide backbone mediated by polarized water molecules: study of infrared spectroscopy and computations.

    PubMed

    Shi, Jipei; Wang, Jianping

    2014-10-30

    In this work, the interaction between metal cation and a model ?-peptide N-ethylpropionamide (NEPA) in aqueous solution is investigated using infrared absorption spectroscopy. Monovalent (Na(+)), divalent (Ca(2+), Mg(2+)), and trivalent (Al(3+)) metal cations added to NEPA/water solution at moderate concentrations split the amide-I frequency into a red- and blue-shifted component. Molecular dynamics simulations of NEPA in moderate cationic strength are conducted to gain insight into the structural details of the peptide-salt-water system, particularly in the vicinity of the amide group. Our results do not suggest a direct contact between cation and amide oxygen in the solution phase; otherwise, only a significant red shift in the amide-I frequency would occur due to the vibrational Stark effect, as evidenced by quantum chemistry computations. Instead, our results suggest it is the dynamical interaction between the formed cation/water/anion complexes and the amide group that causes the observed split in the amide-I peak, which indicates the presence of both salting-in (red-shifted) and salting-out (blue-shifted) NEPA species. The presence of dynamic and polarized water molecules between the amide oxygen and the cation complex is believed to be the key to the split amide-I peaks in the cation-rich environment. Our results can be useful to better understand the cationic Hofmeister series. PMID:25275795

  15. Polarization patterns of the twilight sky

    Microsoft Academic Search

    Thomas W. Cronin; Eric J. Warrant; Birgit Greiner

    2005-01-01

    Although natural light sources produce depolarized light, patterns of partially linearly polarized light appear in the sky due to scattering from air molecules, dust, and aerosols. Many animals, including bees and ants, orient themselves to patterns of polarization that are present in daytime skies, when the intensity is high and skylight polarization is strong and predictable. The halicitid bee Megalopta

  16. High voltage processing of the SLC polarized electron gun

    SciTech Connect

    Saez, P.; Clendenin, J.; Garden, C.; Hoyt, E.; Klaisner, L.; Prescott, C.; Schultz, D.; Tang, H.

    1993-04-01

    The SLC polarized electron gun operates at 120 kV with very low dark current to maintain the ultra high vacuum (UHV). This strict requirement protects the extremely sensitive photocathode from contaminants caused by high voltage (HV) activity. Thorough HV processing is thus required x-ray sensitive photographic film, a nanoammeter in series with gun power supply, a radiation meter, a sensitive residual gas analyzer and surface x-ray spectrometry were used to study areas in the gun where HV activity occurred. By reducing the electric field gradients, carefully preparing the HV surfaces and adhering to very strict clean assembly procedures, we found it possible to process the gun so as to reduce both the dark current at operating voltage and the probability of HV discharge. These HV preparation and processing techniques are described.

  17. Electrical conductivity of single organic molecules in ultra high vacuum

    NASA Astrophysics Data System (ADS)

    Pires, Ellis John

    Measurement of the I(V ) characteristics of single molecules is the first step towards the realisation of molecular electronic devices. In this thesis, the electronic transport properties of alkanedithiol (ADT) and alkylthiol-terminated oligothiophene molecules are investigated under ultrahigh vacuum (UHV) using a scanning tunnelling microscope (STM). Two techniques are employed that rely upon stochastic molecular bridge formation between gold STM tip and substrate; a novel I(V; s) method is proven to be a powerful alternative to the well-known I(s) method. For ADTs, three temperature-independent (180 - 390 K) conduction groups are identified, which arise from different contact-substrate coordination geometries. The anomalous reduction of conductance at small chain lengths reported by other groups for non-UHV conditions is far less pronounced here; all groups closely follow the anticipated exponential decay.

  18. High-throughput multispot single-molecule spectroscopy

    NASA Astrophysics Data System (ADS)

    Colyer, Ryan A.; Scalia, Giuseppe; Kim, Taiho; Rech, Ivan; Resnati, Daniele; Marangoni, Stefano; Ghioni, Massimo; Cova, Sergio; Weiss, Shimon; Michalet, Xavier

    2010-02-01

    Solution-based single-molecule spectroscopy and fluorescence correlation spectroscopy (FCS) are powerful techniques to access a variety of molecular properties such as size, brightness, conformation, and binding constants. However, this is limited to low concentrations, which results in long acquisition times in order to achieve good statistical accuracy. Data can be acquired more quickly by using parallelization. We present a new approach using a multispot excitation and detection geometry made possible by the combination of three powerful new technologies: (i) a liquid crystal spatial light modulator to produce multiple diffraction-limited excitation spots; (ii) a multipixel detector array matching the excitation pattern and (iii) a low-cost reconfigurable multichannel counting board. We demonstrate the capabilities of this technique by reporting FCS measurements of various calibrated samples as well as single-molecule burst measurements.

  19. Diamond-like carbon doped with highly ?-conjugated molecules by plasma-assisted CVD

    NASA Astrophysics Data System (ADS)

    Xie, Wei; Muraya, Naoki; Yanase, Takashi; Nagahama, Taro; Shimada, Toshihiro

    2014-01-01

    We demonstrate the synthesis of diamond-like carbon (DLC) doped with highly ?-conjugated molecules by codepositing organic semiconductor molecules during the plasma-assisted chemical vapor deposition of DLC. From the results of optical absorption spectroscopy, it was revealed that organic semiconductor molecules reacted with plasma but were not completely decomposed. The results of Raman spectroscopy strongly suggested that a certain chemical moiety remained in the film.

  20. Highly polarized light emission by isotropic quantum dots integrated with magnetically aligned segmented nanowires

    NASA Astrophysics Data System (ADS)

    Uran, Can; Erdem, Talha; Guzelturk, Burak; Perkgöz, Nihan Kosku; Jun, Shinae; Jang, Eunjoo; Demir, Hilmi Volkan

    2014-10-01

    In this work, we demonstrate a proof-of-concept system for generating highly polarized light from colloidal quantum dots (QDs) coupled with magnetically aligned segmented Au/Ni/Au nanowires (NWs). Optical characterizations reveal that the optimized QD-NW coupled structures emit highly polarized light with an s-to p-polarization (s/p) contrast as high as 15:1 corresponding to a degree of polarization of 0.88. These experimental results are supported by the finite-difference time-domain simulations, which demonstrate the interplay between the inter-NW distance and the degree of polarization.

  1. Antenna polarization diversity for high-speed polarization multiplexing wireless signal delivery at W-band.

    PubMed

    Li, Xinying; Yu, Jianjun; Chi, Nan; Xiao, Jiangnan

    2014-03-01

    We propose and experimentally demonstrate a novel architecture for a W-band integrated optical wireless system, which adopts a 2×2 multiple-input multiple-output (MIMO) wireless link based on antenna polarization diversity, and can realize 80 km single-mode fiber-28 transmission and 2 m wireless delivery for up to 39 Gbaud polarization-division-multiplexing quadrature-phase-shift-keying (PDM-QPSK) signal at 100 GHz. Classic constant-modulus-algorithm (CMA) equalization is adopted at the receiver to implement polarization demultiplexing. The 2×2 MIMO wireless link adopts one pair of horizontal-polarization (H-polarization) horn antennas (HAs) and one pair of vertical-polarization (V-polarization) HAs. Because the two pairs of HAs are fully isolated, the wireless cross talk can be effectively avoided. Thus, compared to the 2×2 MIMO wireless link at the same antenna polarization, the adoption of antenna polarization diversity cannot only make the HA adjustment easier but can also reduce the required CMA tap number. After removing 20% forward-error-correction overhead, the 39 Gbaud baud rate corresponds to a net bit rate of 130??Gb/s, which, to our best knowledge, is the highest bit rate per PDM channel demonstrated for wireless signal delivery up to now. PMID:24690698

  2. Submillimeterwave Spectroscopy of Highly Astrophysical Interest Molecule: Hydroxyacetonitrile

    NASA Astrophysics Data System (ADS)

    Margules, L.; Motiyenko, R. A.; Guillemin, J.-C.

    2013-06-01

    Hydroxyacetonitrile is a simple derivative of methanol. This molecule has a strong astrophysical interest. In astrophysical environment, the formation of hydroxyacetonitrile (HOCH_2CN), has been shown to compete with aminomethanol (NH_2CH_2OH), a glycine precursor, through the Strecker synthesis, in addition its photochemistry leads to the formation of formylcyanide (CHOCN), ketenimine (CH_2CNH), formaldehyde (CH_2O), hydrogen cyanide (HCN), carbon monoxyde (CO). Its detection in the ISM will provide crucial hints in the formation process of complex organic molecules. The lack of data about this molecule, only studied up to 50 GHz, is mainly due to two reasons. First, this is not commercially available, the synthesis should be perform. Second, the most stable conformer is the gauche one. This exhibits large amplitude motion due to the two equivalent configurations possible. Due to tunneling effect, each level is split into 0^+ and 0^- substates. This makes the analysis of the spectra delicate. We will report here the very first results obtained. This work was supported by the CNES and the Action sur Projets de l'INSU, PCMI. Danger, G. et al.ApJ {756}, (2012) 11 Danger, G. et al.A&A {549}, (2012) A93 Cazzoli, G. et al.J. Chem. Soc., Faraday Trans. 2 {69}, (1973) 569

  3. Reversed polarized emission in highly strained a -plane GaN\\/AlN multiple quantum wells

    Microsoft Academic Search

    R. Mata; A. Cros; J. A. Budagosky; A. Molina-Sánchez; N. Garro; A. García-Cristóbal; J. Renard; S. Founta; B. Gayral; E. Bellet-Amalric; C. Bougerol; B. Daudin

    2010-01-01

    The polarization of the emission from a set of highly strained a -plane GaN\\/AlN multiple quantum wells of varying well widths has been studied. A single photoluminescence peak is observed that shifts to higher energies as the quantum well thickness decreases due to quantum confinement. The emitted light is linearly polarized. For the thinnest samples the preferential polarization direction is

  4. High-extinction-ratio resonant cavity polarizer for quantum-optics measurements

    E-print Network

    Byer, Robert L.

    High-extinction-ratio resonant cavity polarizer for quantum-optics measurements Shailendhar Saraf,1 of round-trip reflections enables its use as a resonant polarizer with a high-extinction ratio. A -phase of a high-finesse Fabry­Perot ring cavity with an odd number of reflections as a high-extinction- ratio

  5. Charge Density and Correlation Study of Atoms and Molecules by High-Energy Electron Scattering

    Microsoft Academic Search

    Yuheng Zhang

    1989-01-01

    Energy resolved differential scattering cross sections of high energy electrons and small molecules were measured during the course of this study. The coherent X-ray scattering form factors, which can be derived from the electron scattering experiments, are directly related to the charge density distributions of the target molecules. The difference between the data and the calculations based on the independent

  6. Molecular high-order-harmonic generation due to the recollision mechanism by a circularly polarized laser pulse

    NASA Astrophysics Data System (ADS)

    Zhu, Xiaosong; Liu, Xi; Li, Yang; Qin, Meiyan; Zhang, Qingbin; Lan, Pengfei; Lu, Peixiang

    2015-04-01

    High-order-harmonic generation (HHG) from small linear molecules driven by a circularly polarized laser pulse (CPLP) is investigated. It is found that the obtained high-order harmonics are more pronounced than those from reference atoms with equal ionization potential driven by the same CPLP. By analyzing the dependence of the cutoff position on laser parameters and calculating the recollision trajectories, it is shown that this molecular HHG originates from the recollision mechanism, instead of the bound-bound transition mechanism found to be responsible for molecular HHG by CPLP in earlier works. A semiclassical model is used to analyze the HHG process and discuss the origin of the higher efficiency of molecular HHG. It is found that the higher HHG efficiency for molecules is mainly contributed in the recombination step and at least partly due to the higher recollision probability of continuum electrons.

  7. Ionization of low-Rydberg-state He atoms by polar molecules. II. Large rotational-energy transfers and absolute values of the cross sections

    Microsoft Academic Search

    A. Pesnelle; C. Ronge; M. Perdrix; G. Watel

    1988-01-01

    The absolute values of cross sections for the collisional ionization of low-Rydberg-state He atoms in the n 1P state (n=14) by the polar molecules NH3, SO2, and acetone (C3H6O) are measured in a crossed-beam experiment at thermal kinetic energies, for a well-defined relative velocity. Simultaneous Penning ionization of NH3 by metastable He(23S) atoms is carried out in situ for calibration.

  8. High-polarized (??m HIGH) mitochondria are spatially polarized in human oocytes and early embryos in stable subplasmalemmal domains: developmental significance and the concept of vanguard mitochondria

    Microsoft Academic Search

    Jonathan Van Blerkom; Patrick Davis

    2006-01-01

    The spatial specificity and stability of subplasmalemmal domains of high-polarized mitochondria (??mHIGH) in human oocytes and cleavage stage embryos were investigated in instances where changes in pericortical\\/subplasmalemmal organization resulted in the corresponding cytoplasm becoming translucent and largely devoid of mitochondria, either by experimental manipulation or as a result of spontaneous, stage-specific morphodynamic processes. The developmental significance of high-polarized mitochondria was

  9. Observations of unusually high-plasma density in the high-altitude polar cap

    NASA Astrophysics Data System (ADS)

    Abe, T.; Ichikawa, Y.; Yau, A.

    The plasma density in the polar cap ionosphere is generally low (< 103 cm-3 above 3000 km), mainly because of plasma escape from the ionosphere along open magneticfield lines, compared with the auroral or the cusp region, where particle precipitation plays a significant role and solar EUV photoionization is more effective in creating ionization. The measured electron density in the polar cap is typically on the order of 102 cm-3 above 3000 km altitude near solar maximum. However, the Akebono satellite occasionally encounters regions of unusually high plasma density ( 103 cm-3 ) above 4000 km altitude. We present the characteristic features of the plasma density, electron temperature, and parallel ion drift velocity in such regions. A survey of Akebono observations of all orbit passes from 1989 (before solar maximum) to 1998 (after solar minimum) found a total of only 11 events in which the plasma density exceeds 103 cm-3 above 4000 km altitude in the polar cap over a horizontal scale of 1000 km or greater. Common characteristics of high-density plasma events observed in the high-altitude polar cap on Akebono are summarized as follows: 1) The plasma density exceeds 103 cm-3 above 4000 km, and is more than an order of magnitude higher than in surrounding regions. 2) The electron temperature is significantly lower than that of the surrounding plasma. 3) The thermal (particularly H+ ) ion velocity is much lower than the median value at the same altitude. 4) The events are predominantly observed on the duskside of the polar cap (10-23 MLT). 5) The high-density plasma regions are almost exclusively observed in the northern hemisphere during negative IMF By and in the southern hemisphere during positive By conditions. The occurrence of low electron temperature and ion drift velocity appears to suggest the anti-sunward convection of high-density plasma into the polar cap, and the decrease in electron temperature due to the disruption of field-aligned heat flux in the high-altitude polar cap. In this presentation, we will discuss the implications of these observational features and the possible scenario for high-plasma-density events at high altitude (4000 km).

  10. Polarization Transfer in Proton Compton Scattering at High Momentum Transfer

    Microsoft Academic Search

    D. J. Hamilton; V. H. Mamyan; K. A. Aniol; J. R. Annand; P. Y. Bertin; L. Bimbot; P. Bosted; J. R. Calarco; A. Camsonne; G. C. Chang; T.-H. Chang; Seonho Choi; E. Chudakov; A. Danagoulian; P. Degtyarenko; C. W. de Jager; A. Deur; D. Dutta; K. Egiyan; H. Gao; F. Garibaldi; O. Gayou; R. Gilman; A. Glamazdin; C. Glashausser; J. Gomez; J.-O. Hansen; D. Higinbotham; W. Hinton; T. Horn; C. Howell; T. Hunyady; C. E. Hyde-Wright; X. Jiang; M. K. Jones; M. Khandaker; A. Ketikyan; V. Kubarovsky; K. Kramer; G. Kumbartzki; G. Laveissière; J. Lerose; R. A. Lindgren; D. J. Margaziotis; P. Markowitz; K. McCormick; Z.-E. Meziani; R. Michaels; P. Moussiegt; S. Nanda; A. M. Nathan; D. M. Nikolenko; V. Nelyubin; B. E. Norum; K. Paschke; L. Pentchev; C. F. Perdrisat; E. Piasetzky; R. Pomatsalyuk; V. A. Punjabi; I. Rachek; A. Radyushkin; B. Reitz; R. Roche; M. Roedelbronn; G. Ron; F. Sabatie; A. Saha; N. Savvinov; A. Shahinyan; Y. Shestakov; S. Sirca; K. Slifer; P. Solvignon; P. Stoler; S. Tajima; V. Sulkosky; L. Todor; B. Vlahovic; L. B. Weinstein; K. Wang; B. Wojtsekhowski; H. Voskanyan; H. Xiang; X. Zheng; L. Zhu

    2005-01-01

    Compton scattering from the proton was investigated at s=6.9 GeV2 and t=-4.0 GeV2 via polarization transfer from circularly polarized incident photons. The longitudinal and transverse components of the recoil proton polarization were measured. The results are in disagreement with a prediction of perturbative QCD based on a two-gluon exchange mechanism, but agree well with a prediction based on a reaction

  11. Ultra-broadband, high-gain, polarization-independent optical parametric amplification in type-II quasi-phase-

    E-print Network

    Kolner, Brian H.

    -independent operation. Ref [1] demonstrated polarization insensitive wavelength conversion using DFG over 40 nm 1-dUltra-broadband, high-gain, polarization-independent optical parametric amplification in type (300 nm) and uniform (20 dB) with polarization

  12. Above- and below-threshold high-order-harmonic generation of H2+ in intense elliptically polarized laser fields

    NASA Astrophysics Data System (ADS)

    Nasiri Avanaki, K.; Telnov, Dmitry A.; Chu, Shih-I.

    2014-09-01

    We present an ab initio three-dimensional precision calculation and analysis of high-order-harmonic generation (HHG) of the hydrogen molecular ion subject to intense elliptically polarized laser pulses by means of the time-dependent generalized pseudospectral method in two-center prolate spheroidal coordinates. The calculations are performed for the ground and first excited electronic states of H2+ at the equilibrium internuclear separation R =2 a.u. as well as for the stretched molecule at R =7 a.u. The spectral and temporal structures of the HHG signal are explored by means of the wavelet time-frequency analysis. Several aspects of ellipticity-dependent dynamical behaviors are uncovered. We found that the production of above-threshold harmonics for nonzero ellipticity is generally reduced, as compared with linearly polarized fields. However, below-threshold harmonics still appear quite strong except when the polarization plane is perpendicular to the molecular axis. Weak even harmonics are detected in the HHG spectra of stretched molecules. This effect can be explained by the broken inversion symmetry due to dynamic localization of the electron density near one of the nuclei. Multiphoton resonance and two-center interference effects are analyzed for the exploration of the quantum origin of the predicted HHG spectral and dynamical behavior.

  13. Development of high-speed polarizing imaging system for operation in high pulsed magnetic field.

    PubMed

    Katakura, I; Tokunaga, M; Matsuo, A; Kawaguchi, K; Kindo, K; Hitomi, M; Akahoshi, D; Kuwahara, H

    2010-04-01

    A high-speed polarizing microscope system combined with a 37 T pulse magnet has been developed. This system was applied to successfully visualize the field-induced collapse of charge-orbital ordering in a layered manganite La(1/2)Sr(3/2)MnO(4). Quantitative analyses of the obtained polarizing microscope images provided clear evidence of this transition in contrast to rather moderate changes in magnetization and magnetoresistance. The ability of this system to carry out quantitative analysis was further tested through the observation of Faraday rotation in a Tb(3)Ga(5)O(12) crystal. The Verdet constant determined from the polarizing images is in reasonable agreement with that in literature. Local intensity analyses of the images indicate that we can investigate magneto-optical signals within an accuracy of 0.85% in an area of 9.6 x 9.6 microm(2). PMID:20441339

  14. Development of high-speed polarizing imaging system for operation in high pulsed magnetic field

    NASA Astrophysics Data System (ADS)

    Katakura, I.; Tokunaga, M.; Matsuo, A.; Kawaguchi, K.; Kindo, K.; Hitomi, M.; Akahoshi, D.; Kuwahara, H.

    2010-04-01

    A high-speed polarizing microscope system combined with a 37 T pulse magnet has been developed. This system was applied to successfully visualize the field-induced collapse of charge-orbital ordering in a layered manganite La1/2Sr3/2MnO4. Quantitative analyses of the obtained polarizing microscope images provided clear evidence of this transition in contrast to rather moderate changes in magnetization and magnetoresistance. The ability of this system to carry out quantitative analysis was further tested through the observation of Faraday rotation in a Tb3Ga5O12 crystal. The Verdet constant determined from the polarizing images is in reasonable agreement with that in literature. Local intensity analyses of the images indicate that we can investigate magneto-optical signals within an accuracy of 0.85% in an area of 9.6×9.6 ?m2.

  15. Thermodynamic study of gaseous sodium-phosphorous-oxygen ternary molecules by high temperature mass spectrometry 

    E-print Network

    Miller, Federico

    1974-01-01

    THERMODYNAMIC STUDY OF GASEOUS SODIUM-PHOSPHOROUS-OXYGEN TERNARY MOLECULES BY HIGH TEMPERATURE MASS SPECTROMETRY A Thesis by FEDERICO MILLER Submitted to the Graduate College of Texas A&M University in Partial fulfillment of the requirement... for the degree of MASTER OF SCIENCE May 1974 Major Subject: Chemistry THERMODYNAMIC STUDY OF GASEOUS SODIUM-PHOSPHOROUS-OXYGEN TERNARY MOLECULES BY HIGH TEMPERATURE MASS SPECTROMETRY A Thesis FEDERICO MILLER Approved as to style and content by: Y...

  16. Determining factors for anodic polarization curves of typical structural materials of boiling water reactors in high temperature – high purity water

    Microsoft Academic Search

    Masahiko Tachibana; Kazushige Ishida; Yoichi Wada; Ryosuke Shimizu; Nobuyuki Ota; Nobuyoshi Hara

    2012-01-01

    In order to examine the anodic polarization characteristics of typical structural materials of boiling water reactors (BWRs), the anodic polarization curves of type 316L stainless steel (316L SS) and Alloy 182 were measured in deaerated high purity water at 553 K using the previously reported measurement method which was confirmed suitable for high temperature – high purity water. In order to

  17. Improved photoacoustic detector for monitoring polar molecules such as ammonia with a 1.53 ?m DFB diode laser

    NASA Astrophysics Data System (ADS)

    Miklós, A.; Hess, P.; Mohácsi, Á.; Sneider, J.; Kamm, S.; Schäfer, S.

    1999-03-01

    A new differential photoacoustic (PA) detector equipped with band-rejecting acoustic filters has been developed for diode laser photoacoustics. The differential design provides good flow and electric noise suppression. The detector was used for monitoring ammonia in continuous flow operation. The first test measurements of synthetic air-ammonia mixtures were carried out using a 5 mW distributed feedback (DFB) diode laser at 1.53 ?m, providing a sensitivity limit of about 300 ppbV. Because of the adsorption of ammonia molecules on the walls of the detector and the gas tubing, high flow rates were needed for the measurements in the 1-100 ppmV concentration range. The smallest concentration detected was 1 ppmV.

  18. High-power, efficient and azimuthally polarized ytterbium-doped fiber laser.

    PubMed

    Zou, Lin; Yao, Yao; Li, Jianlang

    2015-01-15

    An ytterbium-doped fiber laser was demonstrated to emit azimuthally polarized light with high laser power and efficiency, in which a birefringent yttrium vanadate (YVO(4)) crystal was used as the intracavity polarization discriminator. The laser power reached 3.94 W with a slope efficiency of ?71%. Our study proved that an efficient, high-power vector fiber laser would be realistic under the utilization of a simple and low-cost birefringent crystal as polarization discriminator. PMID:25679851

  19. Engineering Very-High-n Polarized Rydberg States Using Tailored Half-Cycle-Pulse Sequences

    Microsoft Academic Search

    W. Zhao; J. J. Mestayer; J. C. Lancaster; F. B. Dunning; Carlos O Reinhold; S. Yoshida; J. Burgdörfer

    2005-01-01

    We show that strongly polarized very-high-n (ñ600) potassium Rydberg atoms can be produced by manipulating lower-n (ñ350) polarized atoms using a tailored sequence of ultrashort half-cycle pulses (HCPs). The protocol for this involves first a weak HCP that generates transient phase-space localization whereupon a second large HCP of opposite polarity excites the electron to a broad distribution of highly elongated

  20. Polarization and bonding of the intrinsic characteristic contours of hydrogen and fluorine atoms of forming a hydrogen fluoride molecule based on an ab initio study

    NASA Astrophysics Data System (ADS)

    Yang, Zhong-Zhi; Zhao, Dong-Xia; Wu, Yang

    2004-08-01

    The spatial changing feature of the shapes and sizes of the system consisted of one hydrogen atom and one fluorine atom of forming a hydrogen fluoride molecule is investigated. We give formalism of the potential acting on an electron in a molecule and derive its concrete expression in Hartree-Fock self-consistent molecular orbital theory including configuration interaction. The program of calculating the potential acting on an electron in a molecule is programmed and compiled in the framework of the MELD program package. We formulate briefly the approach of the molecular intrinsic characteristic contour (MICC) which is defined in terms of the classical turning points of electronic motion. The MICC for a molecular system is intrinsic and can be calculated by means of an ab initio CI method. Then, the polarization and bonding features of the intrinsic characteristic contours of hydrogen and fluorine atoms forming a hydrogen fluoride molecule are presented and discussed from ab initio calculations. Furthermore, electron density distribution as an added dimension has been demonstrated on the changing MICC and thus the vivid polarization and bonding features for a chemical process have been shown. It seems that at the early stage (internuclear distance Ind=5.0-20.0 a.u.) the fluorine atom gives more enthusiastic with the sensitive and expanded polarization to welcome coupling with the hydrogen atom while the latter has little response even "shy" with shrinking a bit its size at the beginning of putting the two atoms into a system and it is only around the critical point, the contact point (Ind=4.73 a.u.), that both of them stretch their hands and arms to meet and then fuse together.

  1. Identification of Promiscuous Small Molecule Activators in High-Throughput Enzyme

    E-print Network

    Hergenrother, Paul J.

    Letters Identification of Promiscuous Small Molecule Activators in High-Throughput Enzyme, Illinois 61801 ReceiVed December 17, 2007 Abstract: It is recognized that high-throughput enzyme inhibition screens often return nonspecific inhibitors as "hits". Recently, high- throughput screens for enzyme

  2. A highly parallel microfluidic droplet method enabling single-molecule counting for digital enzyme detection

    PubMed Central

    Guan, Zhichao; Zou, Yuan; Zhang, Mingxia; Lv, Jiangquan; Shen, Huali; Yang, Pengyuan; Zhang, Huimin; Zhu, Zhi; James Yang, Chaoyong

    2014-01-01

    Although digital detection of nucleic acids has been achieved by amplification of single templates in uniform microfluidic droplets and widely used for genetic analysis, droplet-based digital detection of proteins has rarely been reported, largely due to the lack of an efficient target amplification method for protein in droplets. Here, we report a key step towards digital detection of proteins using a highly parallel microfluidic droplet approach for single enzyme molecule detection in picoliter droplets via enzyme catalyzed signal amplification. An integrated microfluidic chip was designed for high throughput uniform droplet generation, monolayer droplet collection, incubation, detection, and release. Single ?-galatosidase (?-Gal) molecules and the fluorogenic substrate fluorescein di-?-D-galactopyranoside were injected from two separated inlets to form uniform 20??m droplets in fluorinated oil at a frequency of 6.6?kHz. About 200?000 droplets were captured as a monolayer in a capture well on-chip for subsequent imaging detection. A series of ?-Gal solutions at different concentrations were analyzed at the single-molecule level. With no enzyme present, no droplets were found to fluoresce, while brightly fluorescent droplets were observed under single-enzyme molecule conditions. Droplet fluorescence intensity distribution analysis showed that the distribution of enzyme molecules under single-molecule conditions matched well with theoretical prediction, further proving the feasibility of detecting single enzyme molecules in emulsion droplets. Moreover, the population of fluorescent droplets increased as the ?-Gal concentration increased. Based on a digital counting method, the measured concentrations of the enzyme were found to match well with input enzyme concentration, establishing the accuracy of the digital detection method for the quantification of ?-Gal enzyme molecules. The capability of highly parallel detection of single enzyme molecules in uniform picoliter droplets paves the way to microdroplet based digital detection of proteins. PMID:24753730

  3. Intrinsic Differences in the Inner Jets of High and Low Optically Polarized Radio Quasars

    NASA Technical Reports Server (NTRS)

    Lister, M.; Smith, P.

    2000-01-01

    We have conducted a high-resolution polarization study with the VLBA at 22 and 43 GHz to look for differences in the parsec-scale magnetic field structures of 18 high- and low-optically polarized, compact radio-loud quasars (HPQs and LPRQs, respectively).

  4. Linear polarization measurements at high temperatures in hypersaline geothermal brines. Report of investigations

    Microsoft Academic Search

    S. D. Cramer; P. B. Jr. Needham

    1978-01-01

    The Bureau of Mines conducted a series of in situ linear polarization measurements in high-temperature, high-pressure hypersaline geothermal brines at the Bureau of Mines Geothermal Test Facility in the Imperial Valley of California. The measurements represented an evaluation of the linear polarization technique for obtaining instantaneous corrosion rates of materials of construction in flowing hypersaline hydrothermal fluids that rapidly form

  5. Highly anisotropic metasurface: a polarized beam splitter and hologram

    PubMed Central

    Zheng, Jun; Ye, Zhi-Cheng; Sun, Nan-Ling; Zhang, Rui; Sheng, Zheng-Ming; Shieh, Han-Ping D.; Zhang, Jie

    2014-01-01

    Two-dimensional metasurface structures have recently been proposed to reduce the challenges of fabrication of traditional plasmonic metamaterials. However, complex designs and sophisticated fabrication procedures are still required. Here, we present a unique one-dimensional (1-D) metasurface based on bilayered metallic nanowire gratings, which behaves as an ideal polarized beam splitter, producing strong negative reflection for transverse-magnetic (TM) light and efficient reflection for transverse-electric (TE) light. The large anisotropy resulting from this TE-metal-like/TM-dielectric-like feature can be explained by the dispersion curve based on the Bloch theory of periodic metal-insulator-metal waveguides. The results indicate that this photon manipulation mechanism is fundamentally different from those previously proposed for 2-D or 3-D metastructures. Based on this new material platform, a novel form of metasurface holography is proposed and demonstrated, in which an image can only be reconstructed by using a TM light beam. By reducing the metamaterial structures to 1-D, our metasurface beam splitter exhibits the qualities of cost-efficient fabrication, robust performance, and high tunability, in addition to its applicability over a wide range of working wavelengths and incident angles. This development paves a foundation for metasurface structure designs towards practical metamaterial applications. PMID:25262791

  6. Highly anisotropic metasurface: a polarized beam splitter and hologram

    NASA Astrophysics Data System (ADS)

    Zheng, Jun; Ye, Zhi-Cheng; Sun, Nan-Ling; Zhang, Rui; Sheng, Zheng-Ming; Shieh, Han-Ping D.; Zhang, Jie

    2014-09-01

    Two-dimensional metasurface structures have recently been proposed to reduce the challenges of fabrication of traditional plasmonic metamaterials. However, complex designs and sophisticated fabrication procedures are still required. Here, we present a unique one-dimensional (1-D) metasurface based on bilayered metallic nanowire gratings, which behaves as an ideal polarized beam splitter, producing strong negative reflection for transverse-magnetic (TM) light and efficient reflection for transverse-electric (TE) light. The large anisotropy resulting from this TE-metal-like/TM-dielectric-like feature can be explained by the dispersion curve based on the Bloch theory of periodic metal-insulator-metal waveguides. The results indicate that this photon manipulation mechanism is fundamentally different from those previously proposed for 2-D or 3-D metastructures. Based on this new material platform, a novel form of metasurface holography is proposed and demonstrated, in which an image can only be reconstructed by using a TM light beam. By reducing the metamaterial structures to 1-D, our metasurface beam splitter exhibits the qualities of cost-efficient fabrication, robust performance, and high tunability, in addition to its applicability over a wide range of working wavelengths and incident angles. This development paves a foundation for metasurface structure designs towards practical metamaterial applications.

  7. Highly anisotropic metasurface: a polarized beam splitter and hologram.

    PubMed

    Zheng, Jun; Ye, Zhi-Cheng; Sun, Nan-Ling; Zhang, Rui; Sheng, Zheng-Ming; Shieh, Han-Ping D; Zhang, Jie

    2014-01-01

    Two-dimensional metasurface structures have recently been proposed to reduce the challenges of fabrication of traditional plasmonic metamaterials. However, complex designs and sophisticated fabrication procedures are still required. Here, we present a unique one-dimensional (1-D) metasurface based on bilayered metallic nanowire gratings, which behaves as an ideal polarized beam splitter, producing strong negative reflection for transverse-magnetic (TM) light and efficient reflection for transverse-electric (TE) light. The large anisotropy resulting from this TE-metal-like/TM-dielectric-like feature can be explained by the dispersion curve based on the Bloch theory of periodic metal-insulator-metal waveguides. The results indicate that this photon manipulation mechanism is fundamentally different from those previously proposed for 2-D or 3-D metastructures. Based on this new material platform, a novel form of metasurface holography is proposed and demonstrated, in which an image can only be reconstructed by using a TM light beam. By reducing the metamaterial structures to 1-D, our metasurface beam splitter exhibits the qualities of cost-efficient fabrication, robust performance, and high tunability, in addition to its applicability over a wide range of working wavelengths and incident angles. This development paves a foundation for metasurface structure designs towards practical metamaterial applications. PMID:25262791

  8. Polarization Transfer in Proton Compton Scattering at High Momentum Transfer

    SciTech Connect

    Hamilton, D.J.; Annand, J.R.M. [University of Glasgow, Glasgow G12 8QQ (United Kingdom); Mamyan, V.H. [Yerevan Physics Institute, Yerevan 375036 (Armenia); Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606 (United States); Aniol, K.A.; Margaziotis, D.J. [California State University Los Angeles, Los Angeles, California 90032 (United States); Bertin, P.Y.; Camsonne, A.; Laveissiere, G. [Universite Blaise Pascal/IN2P3, F-63177 Aubiere (France); Bimbot, L. [IPN, Orsay B.P. no. 1 F-91406, Orsay (France); Bosted, P.; Paschke, K. [University of Massachusetts, Amherst, Massachusetts 01003 (United States); Calarco, J.R. [University of New Hampshire, Durham, New Hampshire 03824 (United States); Chang, G.C.; Horn, T.; Savvinov, N. [University of Maryland, College Park, Maryland 20742 (United States); Chang, T.-H.; Danagoulian, A.; Nathan, A.M.; Roedelbronn, M. [University of Illinois, Urbana-Champaign, Illinois 61801 (United States); Chen, J.-P. [Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606 (United States)] [and others

    2005-06-24

    Compton scattering from the proton was investigated at s=6.9 GeV{sup 2} and t=-4.0 GeV{sup 2} via polarization transfer from circularly polarized incident photons. The longitudinal and transverse components of the recoil proton polarization were measured. The results are in disagreement with a prediction of perturbative QCD based on a two-gluon exchange mechanism, but agree well with a prediction based on a reaction mechanism in which the photon interacts with a single quark carrying the spin of the proton.

  9. Two-center interference during the high harmonic generation in aligned O2 molecules.

    PubMed

    Wei, Pengfei; Yu, Yongli; Guo, Xiaodong; Ge, Xiaochun; Liu, Peng; Zeng, Zhinan; Li, Ruxin

    2011-01-01

    We experimentally investigate the angular distribution and the laser intensity dependence of the two-center interference in high-order harmonic generation (HHG) from O2 molecules by comparing with CO2 molecules. Through the measurement of both the temporal evolution and the angular distribution of HHG, the characteristic enhancement and suppression are observed, which can be well explained by the modified interference model. Furthermore, we demonstrate that the spectral region of the constructive enhancement in aligned O2 molecules can be shifted by tuning the driving laser intensity. PMID:21263551

  10. HIGH-INTENSITY POLARIZED H-(PROTON), DEUTERON AND 3

    E-print Network

    the "Siberian snake" technique was very successfully implemented to avoid resonance depolarization during beam it in the transverse plane. Final polarization alignment to the vertical direction is adjusted by a spin

  11. Highly Polarized Photoluminescence and Photodetection from Single Indium Phosphide Nanowires

    Microsoft Academic Search

    Jianfang Wang; Mark S. Gudiksen; Xiangfeng Duan; Yi Cui; Charles M. Lieber

    2001-01-01

    We have characterized the fundamental photoluminescence (PL) properties of individual, isolated indium phosphide (InP) nanowires to define their potential for optoelectronics. Polarization-sensitive measurements reveal a striking anisotropy in the PL intensity recorded parallel and perpendicular to the long axis of a nanowire. The order-of-magnitude polarization anisotropy was quantitatively explained in terms of the large dielectric contrast between these free-standing nanowires

  12. Demonstrating multibit magnetic memory in the Fe8 high-spin molecule by muon spin rotation

    Microsoft Academic Search

    Oren Shafir; Amit Keren; Satoru Maegawa; Miki Ueda; Alex Amato; Chris Baines

    2005-01-01

    We develop a method to detect the quantum nature of high-spin molecules using muon spin rotation and a three-step field cycle ending always with the same field. We use this method to demonstrate that the Fe8 molecule can remember six (possibly eight) different histories (bits). A wide range of fields can be used to write a particular bit, and the

  13. A High-Conversion-Factor, Double-Resonance Structure for High-Field Dynamic Nuclear Polarization

    Microsoft Academic Search

    G. Annino; J. A. Villanueva-Garibay; P. J. M. van Bentum; A. A. K. Klaassen; A. P. M. Kentgens

    2010-01-01

    This contribution presents a novel design of a double-resonance structure for high-field dynamic nuclear polarization operating\\u000a at 95 GHz and 144 MHz, in which a miniaturized radiofrequency coil is integrated within a single-mode nonradiative dielectric\\u000a resonator. After a detailed discussion of the design principles, the conversion factors of this system are determined by means\\u000a of microwave and radiofrequency measurements. The obtained results,

  14. Dynamics of the Serine Chemoreceptor in the Escherichia coli Inner Membrane: A High-Speed Single-Molecule Tracking Study

    PubMed Central

    Oh, Dongmyung; Yu, Yang; Lee, Hochan; Wanner, Barry L.; Ritchie, Ken

    2014-01-01

    We investigated the mobility of the polar localized serine chemoreceptor, Tsr, labeled by the fluorescent protein Venus in the inner membrane of live Escherichia coli cells at observation rates up to 1000 Hz. A fraction (7%) of all Tsr molecules shows free diffusion over the entire cell surface with an average diffusion coefficient of 0.40 ± 0.01 ?m2 s?1. The remaining molecules were found to be ultimately confined in compartments of size 290 ± 15 nm and showed restricted diffusion at an inner barrier found at 170 ± 10 nm. At the shortest length-scales (<170 nm), all Tsr molecules diffuse equally. Disruption of the cytoskeleton and rounding of the cells resulted in an increase in the mobile fraction of Tsr molecules and a fragmenting of the previously polar cluster of Tsr consistent with a curvature-based mechanism of Tsr cluster maintenance. PMID:24411246

  15. High-resolution photoelectron spectroscopy in atoms and molecules

    Microsoft Academic Search

    N. Berrah; O. Nayandin; S. E. Conton-Rogan; E. Kukk; A. A. Wills; T. W. Gorczyca; G. Snell; Chien-Nan Liu; J. D. Bozek; M. Wiedenhoeft

    2001-01-01

    New features are revealed by critically combining high photon resolution from the Advances Light Source and differential photoelectron spectroscopic techniques. Two LS-forbidden doubly-excited resonances have been observed in the 3p-13\\/2,1\\/2 partial cross-sections of Ar which exhibit mirroring profiles, resulting in complete cancellation in the total photoionization cross-section as was predicted by Liu and Starace [Phys. Rev. A 59, R1731 (1999)].

  16. N-polar GaN epitaxy and high electron mobility transistors

    NASA Astrophysics Data System (ADS)

    Hoi Wong, Man; Keller, Stacia; Nidhi; Dasgupta, Sansaptak; Denninghoff, Daniel J.; Kolluri, Seshadri; Brown, David F.; Lu, Jing; Fichtenbaum, Nicholas A.; Ahmadi, Elaheh; Singisetti, Uttam; Chini, Alessandro; Rajan, Siddharth; DenBaars, Steven P.; Speck, James S.; Mishra, Umesh K.

    2013-07-01

    This paper reviews the progress of N-polar (000\\mathop 1\\limits^\\_) GaN high frequency electronics that aims at addressing the device scaling challenges faced by GaN high electron mobility transistors (HEMTs) for radio-frequency and mixed-signal applications. Device quality (Al, In, Ga)N materials for N-polar heterostructures are developed using molecular beam epitaxy and metalorganic chemical vapor deposition. The principles of polarization engineering for designing N-polar HEMT structures will be outlined. The performance, scaling behavior and challenges of microwave power devices as well as highly-scaled depletion- and enhancement-mode devices employing advanced technologies including self-aligned processes, n+ (In,Ga)N ohmic contact regrowth and high aspect ratio T-gates will be discussed. Recent research results on integrating N-polar GaN with Si for prospective novel applications will also be summarized.

  17. Extracellular and Intracellular Signaling for Neuronal Polarity.

    PubMed

    Namba, Takashi; Funahashi, Yasuhiro; Nakamuta, Shinichi; Xu, Chundi; Takano, Tetsuya; Kaibuchi, Kozo

    2015-07-01

    Neurons are one of the highly polarized cells in the body. One of the fundamental issues in neuroscience is how neurons establish their polarity; therefore, this issue fascinates many scientists. Cultured neurons are useful tools for analyzing the mechanisms of neuronal polarization, and indeed, most of the molecules important in their polarization were identified using culture systems. However, we now know that the process of neuronal polarization in vivo differs in some respects from that in cultured neurons. One of the major differences is their surrounding microenvironment; neurons in vivo can be influenced by extrinsic factors from the microenvironment. Therefore, a major question remains: How are neurons polarized in vivo? Here, we begin by reviewing the process of neuronal polarization in culture conditions and in vivo. We also survey the molecular mechanisms underlying neuronal polarization. Finally, we introduce the theoretical basis of neuronal polarization and the possible involvement of neuronal polarity in disease and traumatic brain injury. PMID:26133936

  18. Highly stable polarization independent Mach-Zehnder interferometer

    SciTech Connect

    Mi?uda, Michal, E-mail: micuda@optics.upol.cz; Doláková, Ester; Straka, Ivo; Miková, Martina; Dušek, Miloslav; Fiurášek, Jaromír; Ježek, Miroslav, E-mail: jezek@optics.upol.cz [Department of Optics, Faculty of Science, Palacký University, 17. listopadu 1192/12, 77146 Olomouc (Czech Republic)

    2014-08-15

    We experimentally demonstrate optical Mach-Zehnder interferometer utilizing displaced Sagnac configuration to enhance its phase stability. The interferometer with footprint of 27×40 cm offers individually accessible paths and shows phase deviation less than 0.4° during a 250 s long measurement. The phase drift, evaluated by means of Allan deviation, stays below 3° or 7 nm for 1.5 h without any active stabilization. The polarization insensitive design is verified by measuring interference visibility as a function of input polarization. For both interferometer's output ports and all tested polarization states the visibility stays above 93%. The discrepancy in visibility for horizontal and vertical polarization about 3.5% is caused mainly by undesired polarization dependence of splitting ratio of the beam splitter used. The presented interferometer device is suitable for quantum-information and other sensitive applications where active stabilization is complicated and common-mode interferometer is not an option as both the interferometer arms have to be accessible individually.

  19. High-throughput screening identifies small molecules that enhance the pharmacological effects of oligonucleotides

    PubMed Central

    Yang, B.; Ming, X.; Cao, C.; Laing, B.; Yuan, A.; Porter, M. A.; Hull-Ryde, E. A.; Maddry, J.; Suto, M.; Janzen, W. P.; Juliano, R. L.

    2015-01-01

    The therapeutic use of antisense and siRNA oligonucleotides has been constrained by the limited ability of these membrane-impermeable molecules to reach their intracellular sites of action. We sought to address this problem using small organic molecules to enhance the effects of oligonucleotides by modulating their intracellular trafficking and release from endosomes. A high-throughput screen of multiple small molecule libraries yielded several hits that markedly potentiated the actions of splice switching oligonucleotides in cell culture. These compounds also enhanced the effects of antisense and siRNA oligonucleotides. The hit compounds preferentially caused release of fluorescent oligonucleotides from late endosomes rather than other intracellular compartments. Studies in a transgenic mouse model indicated that these compounds could enhance the in vivo effects of a splice-switching oligonucleotide without causing significant toxicity. These observations suggest that selected small molecule enhancers may eventually be of value in oligonucleotide-based therapeutics. PMID:25662226

  20. High Resolution Core Valence Valence Auger Electron Specroscopy on Free Molecules

    NASA Astrophysics Data System (ADS)

    Svensson, S.; Karlsson, L.

    1992-01-01

    Recent experimental results from Core Valence Valence (CVV) Auger electron spectroscopy on free molecules are discussed. The practical use of calculated potential curves for the dicationic final states is illustrated using the NO molecule as an example. The assignment of the CVV spectra to get experimental potential curves for the dicationic states of diatomic molecules is reviewed. The spin-orbit splitting of the initial core hole state in the Auger process is discussed and is related to the molecular field splitting of the Core levels. The importance of making monochromatized photon-impact experiments in order to study the high energy satellites is underlined. The Auger shake-up satellite spectrum of the N2 molecule is discussed as an example and it is found that the participator transitions dominate this spectrum.

  1. “Lossless” compression of high resolution mass spectra of small molecules

    PubMed Central

    Blanckenburg, Bo; van der Burgt, Yuri E. M.; Deelder, André M.

    2010-01-01

    Fourier transform ion cyclotron resonance (FTICR) provides the highest resolving power of any commercially available mass spectrometer. This advantage is most significant for species of low mass-to-charge ratio (m/z), such as metabolites. Unfortunately, FTICR spectra contain a very large number of data points, most of which are noise. This is most pronounced at the low m/z end of spectra, where data point density is the highest but peak density low. We therefore developed a filter that offers lossless compression of FTICR mass spectra from singly charged metabolites. The filter relies on the high resolving power and mass measurement precision of FTICR and removes only those m/z channels that cannot contain signal from singly charged organic species. The resulting pseudospectra still contain the same signal as the original spectra but less uninformative background. The filter does not affect the outcome of standard downstream chemometric analysis methods, such as principal component analysis, but use of the filter significantly reduces memory requirements and CPU time for such analyses. We demonstrate the utility of the filter for urinary metabolite profiling using direct infusion electrospray ionization and a 15 tesla FTICR mass spectrometer. Electronic supplementary material The online version of this article (doi:10.1007/s11306-010-0202-2) contains supplementary material, which is available to authorized users. PMID:20676216

  2. "Lossless" compression of high resolution mass spectra of small molecules.

    PubMed

    Blanckenburg, Bo; van der Burgt, Yuri E M; Deelder, André M; Palmblad, Magnus

    2010-09-01

    Fourier transform ion cyclotron resonance (FTICR) provides the highest resolving power of any commercially available mass spectrometer. This advantage is most significant for species of low mass-to-charge ratio (m/z), such as metabolites. Unfortunately, FTICR spectra contain a very large number of data points, most of which are noise. This is most pronounced at the low m/z end of spectra, where data point density is the highest but peak density low. We therefore developed a filter that offers lossless compression of FTICR mass spectra from singly charged metabolites. The filter relies on the high resolving power and mass measurement precision of FTICR and removes only those m/z channels that cannot contain signal from singly charged organic species. The resulting pseudospectra still contain the same signal as the original spectra but less uninformative background. The filter does not affect the outcome of standard downstream chemometric analysis methods, such as principal component analysis, but use of the filter significantly reduces memory requirements and CPU time for such analyses. We demonstrate the utility of the filter for urinary metabolite profiling using direct infusion electrospray ionization and a 15 tesla FTICR mass spectrometer. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s11306-010-0202-2) contains supplementary material, which is available to authorized users. PMID:20676216

  3. High-order harmonic spectroscopy for molecular imaging of polyatomic molecules.

    PubMed

    Negro, M; Devetta, M; Faccialá, D; De Silvestri, S; Vozzi, C; Stagira, S

    2014-01-01

    High-order harmonic generation is a powerful and sensitive tool for probing atomic and molecular structures, combining in the same measurement an unprecedented attosecond temporal resolution with a high spatial resolution of the order of an angstrom. Imaging of the outermost molecular orbital by high-order harmonic generation has been limited for a long time to very simple molecules, like nitrogen. Recently we demonstrated a technique that overcame several of the issues that have prevented the extension of molecular orbital tomography to more complex species, showing that molecular imaging can be applied to a triatomic molecule like carbon dioxide. Here we report on the application of such a technique to nitrous oxide (N(2)O) and acetylene (C(2)H(2)). This result represents a first step towards the imaging of fragile compounds, a category which includes most of the fundamental biological molecules. PMID:25415258

  4. Polarization dependence of microwave ionization of hydrogen at high scaled frequencies

    NASA Astrophysics Data System (ADS)

    Wilson, John William

    We have measured the polarization dependance of microwave ionization of hydrogen at high scaled frequencies. The survival probability of hydrogen Rydberg atoms with principle quantum numbers n0 = 40--81 was measured as a function of microwave field amplitude for three polarizations of the microwave field: circular polarization (CP), linear polarization (LP), and elliptical polarization (CP). The range of n0 covered in the experiment corresponds to a range of scaled frequency O0, defined as the ratio of the driving frequency o to the Kepler frequency of the unperturbed atom o k, of 0.350--2.909. Comparison of experimental data with 3d classical numerical calculations shows that above a scaled frequency of O 0 ? 1, classical mechanics fails to reproduce experimental ionization thresholds. For scaled frequencies O0 > 0.6, when a particular scaling of the field amplitude that was suggested by classical theory is used, ionization thresholds are found to be nearly independant of polarization.

  5. Polarization splitting filter characteristics of Au-filled high-birefringence photonic crystal fiber

    NASA Astrophysics Data System (ADS)

    Du, Y.; Li, S.-G.; Liu, S.; Zhu, X.-P.; Zhang, X.-X.

    2012-10-01

    Polarization splitting wavelength-selective characteristics of Au-filled high-birefringence photonic crystal fiber (HB-PCF) based on the finite element method is investigated. Numerical results show that the polarization splitting effect can be observed in metal-filled HB-PCF. The resonances points and strength in two polarizations can be adjusted by changing the fiber birefringence, the pitch between the adjacent air holes and the size of the metal wires. Finally, two kinds of Au-filled HB-PCFs with completely polarization splitting and filtering characteristics in communication wavelength are designed. Results show that this polarization splitting effect in metal-filled HB-PCF is very useful for further studies in polarization-dependent wavelength-selective applications and other fiber-based plasmonic devices.

  6. Transport Spin polarization of highTransport Spin polarization of high Curie temperatureCurie temperature MnBiMnBi filmsfilms

    E-print Network

    Baskaran, Mark

    Curie temperature MnBiMnBi filmsfilms Pushkal Thapa1 Boris Nadgorny1 Parashu Kharel2,3Parashu Kharel Pavel Lukashev;Why MnBi? Spin injection from ferromagnet to semiconductors needs well-conducting ferromagnet with high Curie temperature, and high spin polarization (~half metallic) MnBi is a good candidate as spin

  7. Introduction Ascidian oocytes are highly polarized along the animal-vegetal

    E-print Network

    Sardet, Christian

    Introduction Ascidian oocytes are highly polarized along the animal-vegetal (a-v) axis before fertilization (Sardet et al., 1989; Sardet et al., 1992). This polarity principally concerns two peripheral of reorganizations of cortical domains and the cytoskeleton after fertilization in these two species. The cortical c

  8. High-Frequency Dynamic Nuclear Polarization in the Nuclear Rotating Frame

    E-print Network

    Griffin, Robert G.

    spin are simulta- neously flipped, results in a population redistribution among the electron-nuclearHigh-Frequency Dynamic Nuclear Polarization in the Nuclear Rotating Frame C. T. Farrar,* D. A. Hall, 2000 A proton dynamic nuclear polarization (DNP) NMR signal enhancement ( ) close to thermal

  9. Surface structure, composition, and polarity of indium nitride grown by high-pressure chemical vapor deposition

    E-print Network

    Dietz, Nikolaus

    Surface structure, composition, and polarity of indium nitride grown by high-pressure chemical of the surface was observed, N-polarity indium nitride is indicated. © 2006 American Institute of Physics. DOI: 10.1063/1.2187513 Research on the growth and characterization of indium nitride InN has increased

  10. High-performance optical fiber polarizers based on long-period gratings in birefringent optical fibers

    Microsoft Academic Search

    B. Ortega; L. Dong; W. F. Liu; J. P. de Sandro; L. Reekie; S. I. Tsypina; V. N. Bagratashvili; R. I. Laming

    1997-01-01

    We have demonstrated the feasibility of achieving high-performance fiber polarizers (insertion loss 30 dB), based on polarization mode dispersion in a long-period grating. Chirped operation with 100-nm bandwidth has also been achieved, showing the possibility of a broad-band device.

  11. GENERAL: Phase and Polarization State of High-Frequency Relic Gravitational Waves

    Microsoft Academic Search

    Fang-Yu Li; Nan Yang

    2009-01-01

    The displaying condition of strength, phase and polarization states of high-frequency relic gravitational waves (HFRGWs) in electromagnetic (EM) detecting systems is studied. It is shown that the displaying condition depends not only on the sensitivity of EM detecting systems and the amplitudes of HFRGWs, but also on the phase, the polarization states of HFRGWs and their matching to the EM

  12. High physisorption affinity of water molecules to the hydroxylated aluminum oxide (001) surface.

    PubMed

    Kittaka, Shigeharu; Yamaguchi, Keisuke; Takahara, Shuichi

    2012-02-15

    The adsorption mechanism of water on the hydroxylated (001) plane of ?-Al(2)O(3) was studied by measuring adsorption isotherms and GCMC simulations. The experimental adsorption isotherms for three ?-Al(2)O(3) samples from different sources are typical type II, in which adsorption starts sharply at low pressures, suggesting a high affinity of water to the Al(2)O(3) surface. Water molecules are adsorbed in two registered forms (bilayer structure). In the first form, water is registered at the center of three surface hydroxyl groups by directing a proton of the water. In the second form, a water molecule is adsorbed by bridging two of the first-layer water molecules through hydrogen bonding, by which a hexagonal ring network is constructed over the hydroxylated surface. The network domains are spread over the surface, and their size decreases as the temperature increases. The simulated adsorption isotherms present a characteristic two-dimensional (2D) phase diagram including a 2D critical point at 365K, which is higher than that on the hydroxylated Cr(2)O(3) surface (319 K). This fact substantiates the high affinity of water molecules to the ?-Al(2)O(3) surfaces, which enhances the adsorbability originating from higher heat of adsorption. The higher affinity of water molecules to the ?-Al(2)O(3) (001) plane is ascribed to the high compatibility of the crystal plane to form a hexagonal ring network of (001) plane of ice Ih. PMID:22178567

  13. New highly polar semiconductor ferroelectrics for solar energy conversion devices

    Microsoft Academic Search

    Andrew M. Rappe; Ilya Grinberg; Joseph W. Bennett

    2009-01-01

    Solar energy is a promising long-term solution for future energy requirements; however, current solar energy conversion devices are plagued by low efficiency. The use of ferroelectric ABO3 perovskite oxides is one approach for boosting conversion efficiency. Ferroelectric oxides possess spontaneous polarization and have been shown to produce a bulk photovoltaic effect, in which charged carriers, specifically electrons and holes, separate

  14. Quantifying and Optimizing Single-Molecule Switching Nanoscopy at High Speeds

    PubMed Central

    Lin, Yu; Long, Jane J.; Huang, Fang; Duim, Whitney C.; Kirschbaum, Stefanie; Zhang, Yongdeng; Schroeder, Lena K.; Rebane, Aleksander A.; Velasco, Mary Grace M.; Virrueta, Alejandro; Moonan, Daniel W.; Jiao, Junyi; Hernandez, Sandy Y.; Zhang, Yongli; Bewersdorf, Joerg

    2015-01-01

    Single-molecule switching nanoscopy overcomes the diffraction limit of light by stochastically switching single fluorescent molecules on and off, and then localizing their positions individually. Recent advances in this technique have greatly accelerated the data acquisition speed and improved the temporal resolution of super-resolution imaging. However, it has not been quantified whether this speed increase comes at the cost of compromised image quality. The spatial and temporal resolution depends on many factors, among which laser intensity and camera speed are the two most critical parameters. Here we quantitatively compare the image quality achieved when imaging Alexa Fluor 647-immunolabeled microtubules over an extended range of laser intensities and camera speeds using three criteria – localization precision, density of localized molecules, and resolution of reconstructed images based on Fourier Ring Correlation. We found that, with optimized parameters, single-molecule switching nanoscopy at high speeds can achieve the same image quality as imaging at conventional speeds in a 5–25 times shorter time period. Furthermore, we measured the photoswitching kinetics of Alexa Fluor 647 from single-molecule experiments, and, based on this kinetic data, we developed algorithms to simulate single-molecule switching nanoscopy images. We used this software tool to demonstrate how laser intensity and camera speed affect the density of active fluorophores and influence the achievable resolution. Our study provides guidelines for choosing appropriate laser intensities for imaging Alexa Fluor 647 at different speeds and a quantification protocol for future evaluations of other probes and imaging parameters. PMID:26011109

  15. Polarization spectroscopy of x-ray transitions from beam-excited highly charged ions

    SciTech Connect

    Beiersdorfer, P.; Lopez-Urrutia, J.C.; Decaux, V.; Widmann, K. [Department of Physics and Space Technology, Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)] [Department of Physics and Space Technology, Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Neill, P. [Department of Physics, University of Nevada, Reno, Nevada 89557 (United States)] [Department of Physics, University of Nevada, Reno, Nevada 89557 (United States)

    1997-01-01

    Polarization spectroscopy of x-ray lines represents a diagnostic tool to ascertain the presence of electron beams in high-temperature plasmas. Making use of the Livermore electron beam ion trap, which optimizes the linear x-ray line polarization by exciting highly charged ions with a monoenergetic electron beam, we have begun to develop polarization diagnostics and test theoretical models. Our measurement relies on the sensitivity of crystal spectrometers to the linear polarization of x-ray lines which depends on the value of the Bragg angle. We employed two spectrometers with differing analyzing crystals and simultaneously recorded the K-shell emission from heliumlike Fe{sup 24+} and lithiumlike Fe{sup 23+} ions at two different Bragg angles. A clear difference in the relative intensities of the dominant transitions is observed, which is attributed to the amount of linear polarization of the individual lines. {copyright} {ital 1997 American Institute of Physics.}

  16. Modification of a single-molecule AFM probe with highly defined surface functionality

    PubMed Central

    Khanal, Ashok

    2014-01-01

    Summary Single-molecule force spectroscopy with an atomic force microscope has been widely used to study inter- and intramolecular interactions. To obtain data consistent with single molecular events, a well-defined method is critical to limit the number of molecules at the apex of an AFM probe to one or to a few. In this paper, we demonstrate an easy method for single-molecule probe modification by using the Cu-catalyzed alkyne–azide cycloaddition reaction. Excess terminal alkynes were covalently attached to the probe, and a bi-functional molecule containing an azide at one end and a carboxylic acid at the other was dissolved in the reaction solution. By simply contacting the probe and the Cu substrate, controlled carboxylation on the probe apex could be achieved, since the ‘click’ reaction requires the co-exist of alkyne, azide and Cu(I). The finite contact area would result in a highly defined surface functionality of the probe down to single molecule level with high reproducibility. PMID:25551040

  17. Hindered Diffusion of Polar Molecules Through and Effective Pore Radii Estimates of Intact and Ethanol Treated Human Epidermal Membrane

    Microsoft Academic Search

    Kendall D. Peck; Abdel-Halim Ghanem; William I. Higuchi

    1994-01-01

    The in vitro passive transport of urea, mannitol, sucrose and raffinose across intact and ethanol treated human epidermal membrane was investigated. The intent of this study was to characterize the barrier properties and permeation pathways of these membranes for polar permeants under passive conditions. Based upon the relative permeabilities of these four solutes and hindered diffusion theory, the experimental data

  18. Effects of atomic hydrogen and deuterium exposure on high polarization GaAs photocathodes

    SciTech Connect

    M. Baylac; P. Adderley; J. Brittian; J. Clark; T. Day; J. Grames; J. Hansknecht; M. Poelker; M. Stutzman; A. T. Wu; A. S. Terekhov

    2005-12-01

    Strained-layer GaAs and strained-superlattice GaAs photocathodes are used at Jefferson Laboratory to create high average current beams of highly spin-polarized electrons. High electron yield, or quantum efficiency (QE), is obtained only when the photocathode surface is atomically clean. For years, exposure to atomic hydrogen or deuterium has been the photocathode cleaning technique employed at Jefferson Laboratory. This work demonstrates that atomic hydrogen cleaning is not necessary when precautions are taken to ensure that clean photocathode material from the vendor is not inadvertently dirtied while samples are prepared for installation inside photoemission guns. Moreover, this work demonstrates that QE and beam polarization can be significantly reduced when clean high-polarization photocathode material is exposed to atomic hydrogen from an rf dissociator-style atomic hydrogen source. Surface analysis provides some insight into the mechanisms that degrade QE and polarization due to atomic hydrogen cleaning.

  19. High dynamic, spectral, and polarized natural light environment acquisition

    NASA Astrophysics Data System (ADS)

    Porral, Philippe; Callet, Patrick; Fuchs, Philippe; Muller, Thomas; Sandré-Chardonnal, Etienne

    2015-03-01

    In the field of image synthesis, the simulation of material's appearance requires a rigorous resolution of the light transport equation. This implies taking into account all the elements that may have an influence on the spectral radiance, and that are perceived by the human eye. Obviously, the reflectance properties of the materials have a major impact in the calculations, but other significant properties of light such as spectral distribution and polarization must also be taken into account, in order to expect correct results. Unfortunately real maps of the polarized or spectral environment corresponding to a real sky do not exist. Therefore, it seemed necessary to focus our work on capturing such data, in order to have a system that qualifies all the properties of light and capable of powering simulations in a renderer software. As a consequence, in this work, we develop and characterize a device designed to capture the entire light environment, by taking into account both the dynamic range of the spectral distribution and the polarization states, in a measurement time of less than two minutes. We propose a data format inspired by polarimetric imaging and fitted for a spectral rendering engine, which exploits the "Stokes-Mueller formalism."

  20. Mass Spectrometric Studies of Atom–Molecule Reactions Using High-Intensity Crossed Molecular Beams

    Microsoft Academic Search

    S. N. Foner; R. L. Hudson

    1970-01-01

    Elementary gas phase reactions have been studied with high-intensity crossed molecular beams. A detailed analysis is presented on the sensitivity factors involved in mass spectrometric detection of free radicals formed in ordinary chemical reactions as contrasted to surface ionization detection of the products of alkali atom reactions. Free radicals have been observed in a number of atom–molecule reactions, including: (1)

  1. Interference effects in double ionization of spatially aligned hydrogen molecules by fast highly charged ions

    E-print Network

    Interference effects in double ionization of spatially aligned hydrogen molecules by fast highly asymmetry is attributed to interference effects, analogous to Young's two-slit experiment, arising from scattering model based on two center interference. DOI: 10.1103/PhysRevA.70.042702 PACS number(s): 34.50.Gb I

  2. State-resolved collisional energy transfer in highly vibrationally excited polyatomic molecules

    Microsoft Academic Search

    F. F. Crim

    1992-01-01

    The transfer of energy in isolated or colliding molecules is a fundamental process with practical consequences for complex phenomena occurring in atmospheric chemistry, combustion, molecular lasers, plasmas, and a host of other environments containing energetic species. We have developed a technique that combines vibrational overtone excitation, to prepare highly vibrationally excited initial states, and time-resolved spectroscopic detection, to probe the

  3. Enhanced Electron Attachment to Highly-Excited Molecules and Its Applications in Pulsed Plasmas

    SciTech Connect

    Ding, W.X.; Ma, C.Y.; McCorkle, D.L.; Pinnaduwage, L.A.

    1999-06-27

    Studies conducted over the past several years have shown that electron attachment to highly-excited states of molecules have extremely large cross sections. We will discuss the implications of this for pulsed discharges used for H- generation, material processing, and plasma remediation.

  4. Nonlinear-polarization-rotation based multiwavelength erbium-doped fiber lasers with highly nonlinear fiber

    Microsoft Academic Search

    Z. X. Zhang; Z. Q. Ye; M. H. Sang; Y. Y. Nie

    2011-01-01

    A multiwavelength erbium-doped fiber laser based on nonlinear polarization rotation with incorporation of a highly nonlinear fiber has been demonstrated. Stable multi-wavelength operation at room temperature is realized owing to the intensity-dependent transmission in fiber laser with nonlinear-polarization-rotation effect. And benefiting from the four-wave mixing in the highly nonlinear fiber, the uniformity and stabilization of the output multi-wavelength lasing have

  5. Single molecule tracking fluorescence microscopy in mitochondria reveals highly dynamic but confined movement of Tom40

    PubMed Central

    Kuzmenko, Anton; Tankov, Stoyan; English, Brian P.; Tarassov, Ivan; Tenson, Tanel; Kamenski, Piotr; Elf, Johan; Hauryliuk, Vasili

    2011-01-01

    Tom40 is an integral protein of the mitochondrial outer membrane, which as the central component of the Translocase of the Outer Membrane (TOM) complex forms a channel for protein import. We characterize the diffusion properties of individual Tom40 molecules fused to the photoconvertable fluorescent protein Dendra2 with millisecond temporal resolution. By imaging individual Tom40 molecules in intact isolated yeast mitochondria using photoactivated localization microscopy with sub-diffraction limited spatial precision, we demonstrate that Tom40 movement in the outer mitochondrial membrane is highly dynamic but confined in nature, suggesting anchoring of the TOM complex as a whole. PMID:22355710

  6. High harmonic spectra contributed by HOMO-1 orbital of aligned CO2 molecules.

    PubMed

    Li, Jiawei; Liu, Peng; Yang, Hua; Song, Liwei; Zhao, Shitong; Lu, Hui; Li, Ruxin; Xu, Zhizhan

    2013-03-25

    We observe the high harmonic generation (HHG) from anti-aligned CO(2) molecules when the on-axis peak of HHG from HOMO-2 orbital disappears. The harmonic emission at anti-alignment can be attributed to the contribution of HOMO-1 orbital. Simulations reproduce these observations and reveal the angular distributions of tunneling ionization from HOMO and HOMO-1 respectively at different intensity. The determination of HOMO-1 orbital contributions in harmonic spectra is important for the tomography imaging of aligned molecules and analysis of the time evolved harmonic emission. PMID:23546143

  7. Small-molecule high-throughput screening utilizing Xenopus egg extract.

    PubMed

    Broadus, Matthew R; Yew, P Renee; Hann, Stephen R; Lee, Ethan

    2015-01-01

    Screens for small-molecule modulators of biological pathways typically utilize cultured cell lines, purified proteins, or, recently, model organisms (e.g., zebrafish, Drosophila, C. elegans). Herein, we describe a method for using Xenopus laevis egg extract, a biologically active and highly tractable cell-free system that recapitulates a legion of complex chemical reactions found in intact cells. Specifically, we focus on the use of a luciferase-based fusion system to identify small-molecule modulators that affect protein turnover. PMID:25618336

  8. Small-Molecule High-Throughput Screening Utilizing Xenopus Egg Extract

    PubMed Central

    Broadus, Matthew R.; Yew, P. Renee; Hann, Stephen R.; Lee, Ethan

    2015-01-01

    Screens for small-molecule modulators of biological pathways typically utilize cultured cell lines, purified proteins, or, recently, model organisms (e.g., zebrafish, Drosophila, C. elegans). Herein, we describe a method for using Xenopus laevis egg extract, a biologically active and highly tractable cell-free system that recapitulates a legion of complex chemical reactions found in intact cells. Specifically, we focus on the use of a luciferase-based fusion system to identify small-molecule modulators that affect protein turnover. PMID:25618336

  9. High-throughput single-molecule fluorescence spectroscopy using parallel detection

    PubMed Central

    Michalet, X.; Colyer, R. A.; Scalia, G.; Kim, T.; Levi, Moran; Aharoni, Daniel; Cheng, Adrian; Guerrieri, F.; Arisaka, Katsushi; Millaud, Jacques; Rech, I.; Resnati, D.; Marangoni, S.; Gulinatti, A.; Ghioni, M.; Tisa, S.; Zappa, F.; Cova, S.; Weiss, S.

    2011-01-01

    Solution-based single-molecule fluorescence spectroscopy is a powerful new experimental approach with applications in all fields of natural sciences. The basic concept of this technique is to excite and collect light from a very small volume (typically femtoliter) and work in a concentration regime resulting in rare burst-like events corresponding to the transit of a single-molecule. Those events are accumulated over time to achieve proper statistical accuracy. Therefore the advantage of extreme sensitivity is somewhat counterbalanced by a very long acquisition time. One way to speed up data acquisition is parallelization. Here we will discuss a general approach to address this issue, using a multispot excitation and detection geometry that can accommodate different types of novel highly-parallel detector arrays. We will illustrate the potential of this approach with fluorescence correlation spectroscopy (FCS) and single-molecule fluorescence measurements obtained with different novel multipixel single-photon counting detectors. PMID:21625288

  10. High-order-harmonic generation using gas-phase H{sub 2}O molecules

    SciTech Connect

    Zhao Songfeng [J. R. Macdonald Laboratory, Department of Physics, Kansas State University, Manhattan, Kansas 66506 (United States); Key Laboratory of Atomic and Molecular Physics and Functional Materials of Gansu Province, College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070 (China); Jin, Cheng; Le, Anh-Thu; Lin, C. D. [J. R. Macdonald Laboratory, Department of Physics, Kansas State University, Manhattan, Kansas 66506 (United States); Lucchese, R. R. [Department of Chemistry, Texas A and M University, College Station, Texas 77843-3255 (United States)

    2011-03-15

    We investigate high-order-harmonic generation of isotropically distributed gas-phase H{sub 2}O molecules exposed to an intense laser field. The induced dipole of each individual molecule by the laser field is first calculated using the recently developed quantitative rescattering theory. In a thin medium, harmonic spectra generated coherently from all the molecules are then calculated by solving Maxwell's equation of propagation. By using accurate transition dipoles of H{sub 2}O, we show that the harmonics in the lower plateau region are quite different from models that employ the simpler strong-field approximation. We also examine the magnitude and phase of the harmonics and their dependence on laser focusing conditions.

  11. High-order-harmonic generation using gas-phase H2O molecules

    NASA Astrophysics Data System (ADS)

    Zhao, Song-Feng; Jin, Cheng; Lucchese, R. R.; Le, Anh-Thu; Lin, C. D.

    2011-03-01

    We investigate high-order-harmonic generation of isotropically distributed gas-phase H2O molecules exposed to an intense laser field. The induced dipole of each individual molecule by the laser field is first calculated using the recently developed quantitative rescattering theory. In a thin medium, harmonic spectra generated coherently from all the molecules are then calculated by solving Maxwell’s equation of propagation. By using accurate transition dipoles of H2O, we show that the harmonics in the lower plateau region are quite different from models that employ the simpler strong-field approximation. We also examine the magnitude and phase of the harmonics and their dependence on laser focusing conditions.

  12. Polarization Insensitive Wavelength Conversion Based on Orthogonal Pump Four-Wave Mixing for Polarization Multiplexing Signal in High-Nonlinear Fiber

    Microsoft Academic Search

    Jia Lu; Lin Chen; Z. Dong; Z. Cao; Shuangchun Wen

    2009-01-01

    We have theoretically and experimentally investigated polarization insensitive all-optical wavelength conversion for polarization multiplexing signal based on orthogonal pump four-wave mixing in nonlinear optical fiber. After wavelength conversion based on 1 km high-nonlinear optical fiber with polarization insensitivity, the power penalties of 2.5 Gbit\\/s optical OOK intensity and 10 Gbit\\/s differential phase-shift keying orthogonal signals are less than 0.5 and

  13. Ultrafast spin-polarized lasing in a highly photoexcited semiconductor microcavity at room temperature

    NASA Astrophysics Data System (ADS)

    Hsu, Feng-kuo; Xie, Wei; Lee, Yi-Shan; Lin, Sheng-Di; Lai, Chih-Wei

    2015-05-01

    We demonstrate room-temperature spin-polarized ultrafast (˜10 ps ) lasing in a highly optically excited GaAs microcavity. This microcavity is embedded with InGaAs multiple quantum wells in which the spin relaxation time is less than 10 ps. The laser radiation remains highly circularly polarized even when excited by nonresonant elliptically polarized light. The lasing energy is not locked to the bare cavity resonance, and shifts ˜10 meV as a function of the photoexcited density. Such spin-polarized lasing is attributed to a spin-dependent stimulated process of correlated electron-hole pairs. These pairs are formed near the Fermi edge in a high-density electron-hole plasma coupled to the cavity light field.

  14. A new high resolution radioimager for the quantitative analysis of radiolabelled molecules in tissue section

    Microsoft Academic Search

    P. Laniece; Y. Charon; A. Cardona; L. Pinot; S. Maitrejean; R. Mastrippolito; B. Sandkamp; L. Valentin

    1998-01-01

    We present a high-speed, high-resolution imager of ? particles. It is devoted to be used in autoradiography experiments such as receptor binding or in situ hybridization experiments, either instead of, or in complement with autoradiographic film and emulsions. It allows the user to locate and perform quantitative analyses of (3H, 14C, 35S, 33P, 32P, 125I) labelled molecules with a 15

  15. Advantages of Single-Molecule Real-Time Sequencing in High-GC Content Genomes

    PubMed Central

    Shin, Seung Chul; Ahn, Do Hwan; Kim, Su Jin; Lee, Hyoungseok; Oh, Tae-Jin; Lee, Jong Eun; Park, Hyun

    2013-01-01

    Next-generation sequencing has become the most widely used sequencing technology in genomics research, but it has inherent drawbacks when dealing with high-GC content genomes. Recently, single-molecule real-time sequencing technology (SMRT) was introduced as a third-generation sequencing strategy to compensate for this drawback. Here, we report that the unbiased and longer read length of SMRT sequencing markedly improved genome assembly with high GC content via gap filling and repeat resolution. PMID:23894349

  16. Identification of novel small molecule inhibitors of adenovirus gene transfer using a high throughput screening approach.

    PubMed

    Duffy, Margaret R; Parker, Alan L; Kalkman, Eric R; White, Katie; Kovalskyy, Dmytro; Kelly, Sharon M; Baker, Andrew H

    2013-08-28

    Due to many favourable attributes adenoviruses (Ads) are the most extensively used vectors for clinical gene therapy applications. However, following intravascular administration, the safety and efficacy of Ad vectors are hampered by the strong hepatic tropism and induction of a potent immune response. Such effects are determined by a range of complex interactions including those with neutralising antibodies, blood cells and factors, as well as binding to native cellular receptors (coxsackie adenovirus receptor (CAR), integrins). Once in the bloodstream, coagulation factor X (FX) has a pivotal role in determining Ad liver transduction and viral immune recognition. Due to difficulties in generating a vector devoid of multiple receptor binding motifs, we hypothesised that a small molecule inhibitor would be of value. Here, a pharmacological approach was implemented to block adenovirus transduction pathways. We developed a high throughput screening (HTS) platform to identify small molecule inhibitors of FX-mediated Ad5 gene transfer. Using an in vitro fluorescence and cell-based HTS, we evaluated 10,240 small molecules. Following sequential rounds of screening, three compounds, T5424837, T5550585 and T5660138 were identified that ablated FX-mediated Ad5 transduction with low micromolar potency. The candidate molecules possessed common structural features and formed part of the one pharmacophore model. Focused, mini-libraries were generated with structurally related molecules and in vitro screening revealed novel hits with similar or improved efficacy. The compounds did not interfere with Ad5:FX engagement but acted at a subsequent step by blocking efficient intracellular transport of the virus. In vivo, T5660138 and its closely related analogue T5660136 significantly reduced Ad5 liver transgene expression at 48 h post-intravenous administration of a high viral dose (1×10¹¹ vp/mouse). Therefore, this study identifies novel and potent small molecule inhibitors of the Ad5 transduction which may have applications in the Ad gene therapy setting. PMID:23702233

  17. Colloidal lenses allow high-temperature single-molecule imaging and improve fluorophore photostability.

    PubMed

    Schwartz, Jerrod J; Stavrakis, Stavros; Quake, Stephen R

    2010-02-01

    Although single-molecule fluorescence spectroscopy was first demonstrated at near-absolute zero temperatures (1.8 K), the field has since advanced to include room-temperature observations, largely owing to the use of objective lenses with high numerical aperture, brighter fluorophores and more sensitive detectors. This has opened the door for many chemical and biological systems to be studied at native temperatures at the single-molecule level both in vitro and in vivo. However, it is difficult to study systems and phenomena at temperatures above 37 degrees C, because the index-matching fluids used with high-numerical-aperture objective lenses can conduct heat from the sample to the lens, and sustained exposure to high temperatures can cause the lens to fail. Here, we report that TiO(2) colloids with diameters of 2 microm and a high refractive index can act as lenses that are capable of single-molecule imaging at 70 degrees C when placed in immediate proximity to an emitting molecule. The optical system is completed by a low-numerical-aperture optic that can have a long working distance and an air interface, which allows the sample to be independently heated. Colloidal lenses were used for parallel imaging of surface-immobilized single fluorophores and for real-time single-molecule measurements of mesophilic and thermophilic enzymes at 70 degrees C. Fluorophores in close proximity to TiO(2) also showed a 40% increase in photostability due to a reduction of the excited-state lifetime. PMID:20023643

  18. Hyperfine energy levels of alkali-metal dimers: Ground-state polar molecules in electric and magnetic fields

    Microsoft Academic Search

    J. Aldegunde; Ben A. Rivington; Piotr S. Zuchowski; Jeremy M. Hutson

    2008-01-01

    We investigate the energy levels of heteronuclear alkali-metal dimers in levels correlating with the lowest rotational level of the ground electronic state, which are important in efforts to produce ground-state ultracold molecules. We use density-functional theory to calculate nuclear quadrupole and magnetic coupling constants for KRb and RbCs and explore the hyperfine structure in the presence of electric and magnetic

  19. High-harmonic homodyne detection of the ultrafast dissociation of Br2 molecules.

    PubMed

    Wörner, H J; Bertrand, J B; Corkum, P B; Villeneuve, D M

    2010-09-01

    We report the time-resolved observation of the photodissociation of Br2 using high-harmonic generation (HHG) as a probe. The simultaneous measurement of the high-harmonic and ion yields shows that high harmonics generated by the electronically excited state interfere with harmonics generated by the ground state. The resulting homodyne effect provides a high sensitivity to the excited state dynamics. We present a simple theoretical model that accounts for the main observations. Our experiment paves the way towards the dynamic imaging of molecules using HHG. PMID:20867516

  20. High resolution spectroscopy of methyltrioxorhenium: towards the observation of parity violation in chiral molecules.

    PubMed

    Stoeffler, Clara; Darquié, Benoît; Shelkovnikov, Alexander; Daussy, Christophe; Amy-Klein, Anne; Chardonnet, Christian; Guy, Laure; Crassous, Jeanne; Huet, Thérèse R; Soulard, Pascale; Asselin, Pierre

    2011-01-21

    Originating from the weak interaction, parity violation in chiral molecules has been considered as a possible origin of biohomochirality. We have proposed the observation of molecular parity violation using the two-photon Ramsey fringes technique on a supersonic beam. As a first step in this direction, a detailed spectroscopic study of methyltrioxorhenium (MTO) has been undertaken. It is an ideal test molecule as the achiral parent molecule of chiral candidates for a parity violation experiment. For the (187)Re MTO isotopologue, a combined analysis of Fourier transform microwave and infrared spectra as well as ultra-high resolution CO(2) laser absorption spectra enabled the assignment of 28 rotational lines and 71 rovibrational lines, some of them with a resolved hyperfine structure. A set of spectroscopic parameters in the ground and first excited state, including hyperfine structure constants, was obtained for the ?(as) antisymmetric Re=O stretching mode of this molecule. This result validates the experimental approach to be followed once a chiral derivative of MTO is synthesized, and shows the benefit of the combination of several spectroscopic techniques in different spectral regions, with different set-ups and resolutions. The first high resolution spectra of jet-cooled MTO, obtained on a set-up being developed for the observation of molecular parity violation, are shown, which constitutes a major step towards the targeted objective. PMID:21120236

  1. Highly Effective Polarized Electron Sources Based on Strained Semiconductor Superlattice with Distributed Bragg Reflector

    SciTech Connect

    Gerchikov, L.G.; Aulenbacher, K.; Clendenin, J.E.; Kuz'michev, V.V.; Mamaev, Yu.A.; Maruyama, T.; Mikhrin, V.S.; Roberts, J.S.; Utstinov, V.M.; Vasiliev, D.A.; Vasiliev, A.P.; Yashin, Yu.P.; Zhukov, A.E.; /St. Petersburg Polytechnic Inst. /Mainz U., Inst. Kernphys. /SLAC /Ioffe Phys. Tech. Inst. /Sheffield U.

    2007-11-28

    Resonance enhancement of the quantum efficiency of new polarized electron photocathodes based on a short-period strained superlattice structures is reported. The superlattice is a part of an integrated Fabry-Perot optical cavity. We demonstrate that the Fabry-Perot resonator enhances the quantum efficiency by the order of magnitude in the wavelength region of the main polarization maximum. The high structural quality implied by these results points to the very promising application of these photocathodes for spin-polarized electron sources.

  2. Highly Effective Polarized Electron Sources Based on Strained Semiconductor Superlattice with Distributed Bragg Reflector

    SciTech Connect

    Gerchikov, L. G.; Kuz'michev, V. V.; Mamaev, Yu. A.; Vasiliev, D. A.; Yashin, Yu. P. [St. Petersburg State Polytechnic University (Russian Federation); Aulenbacher, K. [Institute of Nuclear Physics, Mainz University, Mainz (Germany); Clendenin, J. E.; Maruyama, T. [Stanford Linear Accelerator Center, Stanford, CA (United States); Mikhrin, V. S.; Ustinov, V. M.; Vasiliev, A. P.; Zhukov, A. E. [A.F. Ioffe Physicotechnical Institute RAS (Russian Federation); Roberts, J. S. [Department of Electronic and Electrical Engineering, University of Sheffield (United Kingdom)

    2008-02-06

    Resonance enhancement of the quantum efficiency of new polarized electron photocathodes based on a short-period strained superlattice structures is reported. The superlattice is a part of an integrated Fabry-Perot optical cavity. We demonstrate that the Fabry-Perot resonator enhances the quantum efficiency by the order of magnitude in the wavelength region of the main polarization maximum. The high structural quality implied by these results points to the very promising application of these photocathodes for spin-polarized electron sources.

  3. A High Throughput Screening Assay System for the Identification of Small Molecule Inhibitors of gsp

    PubMed Central

    Bhattacharyya, Nisan; Hu, Xin; Chen, Catherine Z.; Mathews Griner, Lesley A.; Zheng, Wei; Inglese, James; Austin, Christopher P.; Marugan, Juan J.; Southall, Noel; Neumann, Susanne; Northup, John K.; Ferrer, Marc; Collins, Michael T.

    2014-01-01

    Mis-sense mutations in the ?-subunit of the G-protein, Gs?, cause fibrous dysplasia of bone/McCune-Albright syndrome. The biochemical outcome of these mutations is constitutively active Gs? and increased levels of cAMP. The aim of this study was to develop an assay system that would allow the identification of small molecule inhibitors specific for the mutant Gs? protein, the so-called gsp oncogene. Commercially available Chinese hamster ovary cells were stably transfected with either wild-type (WT) or mutant Gs? proteins (R201C and R201H). Stable cell lines with equivalent transfected Gs? protein expression that had relatively lower (WT) or higher (R201C and R201H) cAMP levels were generated. These cell lines were used to develop a fluorescence resonance energy transfer (FRET)–based cAMP assay in 1536-well microplate format for high throughput screening of small molecule libraries. A small molecule library of 343,768 compounds was screened to identify modulators of gsp activity. A total of 1,356 compounds with inhibitory activity were initially identified and reconfirmed when tested in concentration dose responses. Six hundred eighty-six molecules were selected for further analysis after removing cytotoxic compounds and those that were active in forskolin-induced WT cells. These molecules were grouped by potency, efficacy, and structural similarities to yield 22 clusters with more than 5 of structurally similar members and 144 singleton molecules. Seven chemotypes of the major clusters were identified for further testing and analyses. PMID:24667240

  4. High-contrast coherent population trapping based on crossed polarizers method.

    PubMed

    Yano, Yuichiro; Goka, Shigeyoshi

    2014-12-01

    A method based on crossed polarizers to observe high-contrast coherent population trapping (CPT) resonance has been developed. Because crossed polarizers have a simple optical system, our method is suitable for chip-scale atomic clocks (CSACs). In CPT, the Faraday rotation in a linearly polarized light field (lin||lin) was calculated using two pairs of ?-system models; the spectrum of the Faraday rotation is also estimated. After measuring the contrast and linewidth with the crossed-polarizer method, a comparison of the theoretical model and experimental data showed they were in good agreement. Moreover, the experimental results showed that a high contrast (88.4%) and narrow linewidth (1.15 kHz) resonance could be observed using a Cs gas cell and D1-line verticalcavity surface-emitting laser (VCSEL). PMID:25474771

  5. Transport Spin Polarization of High-Curie Temperature MnBi Films

    NASA Astrophysics Data System (ADS)

    Thapa, Pushkal; Kharel, Parashu; Lukashev, Pavel; Sabirianov, Renat; Tsymbal, Evgeny; Sellmyer, David; Nadgorny, Boris

    2011-03-01

    We report on the study of the structural, magnetic and transport properties of highly textured MnBi films with the Curie temperature of 628 K. In addition to detailed measurements of resistivity and magnetization, we measure transport spin polarization of MnBi by Andreev reflection spectroscopy and perform first-principles electronic structure calculations. A transport spin polarization of up to 63% is observed, consistent with the calculations and with a recent observation of a large magnetoresistance in MnBi contacts. The band structure calculations indicate that, in spite of almost identical densities of states at the Fermi energy, the large disparity in the Fermi velocities leads to high transport spin polarization of MnBi. The correlation between the values of magnetization and spin polarization observed in MnBi will be discussed.

  6. Transport spin polarization of high Curie temperature MnBi films

    NASA Astrophysics Data System (ADS)

    Kharel, P.; Thapa, P.; Lukashev, P.; Sabirianov, R. F.; Tsymbal, E. Y.; Sellmyer, D. J.; Nadgorny, B.

    2011-01-01

    We report on the study of the structural, magnetic, and transport properties of highly textured MnBi films with the Curie temperature of 628 K. In addition to detailed measurements of resistivity and magnetization, we measure transport spin polarization of MnBi by Andreev reflection spectroscopy and perform fully relativistic band-structure calculations of MnBi. A spin polarization from 51% ± 1% to 63% ± 1% is observed, consistent with the calculations and with an observation of a large magnetoresistance in MnBi contacts. The band-structure calculations indicate that in spite of almost identical densities of states at the Fermi energy, the large disparity in the Fermi velocities leads to high transport spin polarization of MnBi. The correlation between the values of magnetization and spin polarization is discussed.

  7. ABSOLUTE MEASUREMENT OF THE POLARIZATION OF HIGH ENERGY PROTON BEAMS AT RHIC

    SciTech Connect

    MAKDISI,Y.; BRAVAR, A. BUNCE, G. GILL, R.; HUANG, H.; ET AL.

    2007-06-25

    The spin physics program at the Relativistic Heavy Ion Collider (RHIC) requires knowledge of the beam polarization to better than 5%. Such a goal is made the more difficult by the lack of knowledge of the analyzing power of high energy nuclear physics processes. To overcome this, a polarized hydrogen jet target was constructed and installed at one intersection region in RHIC where it intersects both beams and utilizes the precise knowledge of the jet atomic hydrogen beam polarization to measure the analyzing power in proton-proton elastic scattering in the Nuclear Coulomb Interference (CNI) region at the prescribed RHIC proton beam energy. The reverse reaction is used to assess the absolute beam polarization. Simultaneous measurements taken with fast high statistics polarimeters that measure the p-Carbon elastic scattering process also in the CNI region use the jet results to calibrate the latter.

  8. Ion—polar-molecule reactions: A CRESU study of He +, C +, N + + H 2O, NH 3 at 27, 68 and 163 K

    NASA Astrophysics Data System (ADS)

    Marquette, J. B.; Rowe, B. R.; Dupeyrat, G.; Poissant, G.; Rebrion, C.

    1985-12-01

    The first measurements of ion—polar-molecule reaction rate constants at very low temperatures are presented. They have been obtained using the CRESU (cine_.tique de reactions en ecoulement supersonique uniforme) technique for H +.C + and N + ions reacting with H 2O and NH 3 at 27 and 68 K in helium buffer. Additional data have been obtained for N + reactions at 163 K in nitrogen buffer. In the 27-300 K (27-163 K for N + + NH 3) temperature range, all the results yield a power law, k = k0T- n (0 < n < 1), for the rate coefficient of each reaction, which should be applied in interstellar cloud model in place of the room-temperature values. The results are compared with various theoretical calculations. Rather good agreement is found although no general behavior can be simply drawn from these experiments.

  9. Advanced high-performance liquid chromatography method for highly polar nitroaromatic compounds in ground water samples from ammunition waste sites.

    PubMed

    Preiss, A; Bauer, A; Berstermann, H-M; Gerling, S; Haas, R; Joos, A; Lehmann, A; Schmalz, L; Steinbach, K

    2009-06-19

    An advanced HPLC-photodiode array detection method for the determination of 12 selected highly polar nitroaromatic compounds in ground water samples of ammunition waste sites has been developed and validated. After solid-phase extraction the limits of detection were in the range 0.1-0.5 microg/l. To prove the applicability of the method to other polar nitroaromatic compounds the retention time of another 32 polar compounds under the specified chromatographic conditions were determined and their UV spectra recorded. To review the method, interlaboratory comparisons were performed with a spiked and a real ground water sample. PMID:19446826

  10. High-frequency dynamic nuclear polarization using mixtures of TEMPO and trityl radicals

    Microsoft Academic Search

    Kan-Nian Hu; Vikram S. Bajaj; Melanie Rosay; Robert G. Griffin

    2007-01-01

    In a previous communication [\\u000aHu et al., J. Am. Chem. Soc. 126, 10844 (2004)\\u000a], an approach was demonstrated that improves the efficiency of the cross-effect polarization mechanism employed in high field dynamic nuclear polarization {(DNP)} experiments. Specifically, it was shown that tethering two {TEMPO} (2,2,6,6-tetramethylpiperidin-1-oxyl) radicals increases the electron-electron dipole coupling from ? 1?{MHz} in solutions of monomeric

  11. High-frequency dynamic nuclear polarization using mixtures of TEMPO and trityl radicals

    Microsoft Academic Search

    Kan-Nian Hu; Vikram S. Bajaj; Melanie Rosay; Robert G. Griffin

    2007-01-01

    In a previous communication [Hu et al., J. Am. Chem. Soc. 126, 10844 (2004)], an approach was demonstrated that improves the efficiency of the cross-effect polarization mechanism employed in high field dynamic nuclear polarization (DNP) experiments. Specifically, it was shown that tethering two TEMPO (2,2,6,6-tetramethylpiperidin-1-oxyl) radicals increases the electron-electron dipole coupling from ~1 MHz in solutions of monomeric TEMPO to

  12. High-frequency dynamic nuclear polarization using mixtures of TEMPO and trityl radicals

    Microsoft Academic Search

    Kan-Nian Hu; Vikram S. Bajaj; Melanie Rosay; Robert G. Griffin

    2007-01-01

    In a previous communication [Hu &etal;, J. Am. Chem. Soc. 126, 10844 (2004)], an approach was demonstrated that improves the efficiency of the cross-effect polarization mechanism employed in high field dynamic nuclear polarization (DNP) experiments. Specifically, it was shown that tethering two TEMPO (2,2,6,6-tetramethylpiperidin-1-oxyl) radicals increases the electron-electron dipole coupling from ?1 MHz in solutions of monomeric TEMPO to ?25

  13. Signatures of Pulsar Polar-Cap Emission at the High-Energy Spectral Cut-off

    E-print Network

    J. Dyks; B. Rudak

    2003-04-18

    We address four unique signatures in pulsar gamma-ray radiation as predicted by polar-cap models. These signatures are expected to be present nearby the spectral high-energy cutoff at around several GeV. Their magnitude and, therefore, their observability depends strongly on the orientational factors, the rotation, as well as on the details of the polar cap structure. These strong predictions are likely to be verified by the NASA's future gamma-ray mission GLAST.

  14. High-speed all-optical terahertz polarization switching by a transient plasma phase modulator

    SciTech Connect

    Wen Haidan [SLAC National Accelerator Laboratory, PULSE Institute, Menlo Park, California 94025 (United States); Daranciang, Dan [Department of Chemistry, Stanford University, Stanford, California 94305 (United States); Lindenberg, Aaron M. [SLAC National Accelerator Laboratory, PULSE Institute, Menlo Park, California 94025 (United States); Department of Materials Science and Engineering, Stanford University, Stanford, California 94305 (United States)

    2010-04-19

    We demonstrate high-speed all-optical polarization switching of broadband terahertz frequency electromagnetic fields with subpicosecond switch-on time. This is achieved through the use of a two-plasma configuration in an orthogonal geometry in which one plasma modulates the relative phase of a two-color optical pump field, enabling rapid terahertz polarization modulation at rates limited by the repetition-rate of the control pulse.

  15. High-speed polarization-sensitive optical coherence tomography for the investigation of tissue birefringence

    NASA Astrophysics Data System (ADS)

    Gulsen, Gultekin; Nalcioglu, Orhan

    2005-04-01

    Polarization-sensitive optical coherence tomography (PSOCT) is an optical imaging modality that is sensitive to the birefringence properties of tissues. Birefringence is related to various biological components and therefore, polarization can provide novel contrast mechanisms for imaging. In this work, we will describe the design of a high-speed polarization sensitive optical coherence tomography system. A broadband source centered at 1310nm with 35nm bandwidth was utilized as the light source. The output power of the source and the resolution of the system were around 20mW and ~20 micrometers, respectively. To achieve high-speed scan, a rapid scan optical delay line (RSOD) was utilized in the reference arm. It provided depth scanning up to 1000 A-scan/s and controlled the carrier frequency of the interference of fridge pattern. Two galvo-mounted mirrors were used for lateral scanning of the beam. The polarization state of the incident light was altered between horizontal and vertical states by using a fast polarization rotator. The combined light from the reference and the sample arms was split into two orthogonal polarization components by a polarizing beam splitter and coupled into two single-mode optical fibers that are connected to the photodiodes. The roundtrip Jones matrix of the sample arm was measured and used to calibrate the measurements of polarization properties of the sample. The elements of the Jones matrix of the sample were calculated by the using the output Jones vectors for the incident polarization states. The performance of the system was evaluated with standard samples such as a quarter-wave plate. The animal studies are currently undertaken to assess the performance of the system in-vivo.

  16. Relativistic Effects and Polarization in Three High-Energy Pulsar Models

    NASA Technical Reports Server (NTRS)

    Dyks, J.; Harding, Alice K.; Rudak, B.

    2004-01-01

    We present the influence of the special relativistic effects of aberration and light travel time delay on pulsar high-energy lightcurves and polarization characteristics predicted by three models: the two-pole caustic model, the outer gap model, and the polar cap model. Position angle curves and degree of polarization are calculated for the models and compared with the optical data on the Crab pulsar. The relative positions of peaks in gamma-ray and radio lightcurves are discussed in detail for the models. We find that the two-pole caustic model can reproduce qualitatively the optical polarization characteristics of the Crab pulsar - fast swings of the position angle and minima in polarization degree associated with both peaks. The anticorrelation between the observed flux and the polarization degree (observed in the optical band also for B0656+14) naturally results from the caustic nature of the peaks which are produced in the model due to the superposition of radiation from many different altitudes, ie. polarized at different angles. The two-pole caustic model also provides an acceptable interpretation of the main features in the Crab's radio profile. Neither the outer gap model nor the polar cap model are able to reproduce the optical polarization data on the Crab. Although the outer gap model is very successful in reproducing the relative positions of gamma-ray and radio peaks in pulse profiles, it can reproduce the high-energy lightcurves only when photon emission from regions very close to the light cylinder is included.

  17. High-frequency modulation of continuous-wave laser beams by maximally coherent molecules D. D. Yavuz

    E-print Network

    Yavuz, Deniz

    High-frequency modulation of continuous-wave laser beams by maximally coherent molecules D. D become very efficient CW modulators with a modulation frequency that can be as high as 100 THz. DOI: 10 with phase matching play- ing a negligible role. In essence, molecules act as frequency modulators

  18. High resolution measures of polarization and color of selected lunar areas

    NASA Technical Reports Server (NTRS)

    Riley, L. A.; Hall, J. S.

    1972-01-01

    High resolution observations of intensity, color (UBV) and polarization were obtained with scanning techniques for a number of lunar areas of special interest, including boundaries of some of the brightest and darkest lunar regions, certain Apollo landing sites and prominent craters. Two dimensional raster scans of colors were obtained for Alphonsus, Aristarchus, and Herodotus. The degree of polarization for any given phase angle appears to be roughly indicative of age. The darker younger mare surface are more highly polarized than the lighter and older mare surfaces, which appear to be more contaminated by lighter material from the highlands or by ray material thrown out from fresh craters. All mare surfaces are more highly polarized than the still older and lighter terra regions surrounding the maria. The very oldest craters are either dark-floored and show polarization characteristics similar to those of the mare surfaces, or if located in the highlands, they are less and less distinguishable from the highland background with greater age, and show the general highland polarization characteristics.

  19. RHIC: The World's First High-Energy, Polarized-Proton Collider (423rd Brookhaven Lecture)

    SciTech Connect

    Bai, Mei (Collider-Accelerator Department) [Collider-Accelerator Department

    2007-03-28

    The Relativistic Heavy Ion Collider (RHIC) at BNL has been colliding polarized proton at a beam energy of 100 billion electron volts (GeV) since 2001. In addition to reporting upon the progress of RHIC polarized-proton program, this talk will focus upon the mechanisms that cause the beam to depolarize and the strategies developed to overcome this. As the world first polarized-proton collider, RHIC is designed to collide polarized protons up to an energy of 250 GeV, thereby providing an unique opportunity to measure the contribution made by the gluon to a proton's spin and to study the spin structure of proton. Unlike other high-energy proton colliders, however, the challenge for RHIC is to overcome the mechanisms that cause partial or total loss of beam polarization, which is due to the interaction of the spin vector with the magnetic fields. In RHIC, two Siberian snakes have been used to avoid these spin depolarizing resonances, which are driven by vertical closed-orbit distortion and vertical betatron oscillations. As a result, polarized-proton beams have been accelerated to 100 GeV without polarization loss, although depolarization has been observed during acceleration from 100 GeV to 205 GeV.

  20. Salmonella enterica invasion of polarized epithelial cells is a highly cooperative effort.

    PubMed

    Lorkowski, Martin; Felipe-López, Alfonso; Danzer, Claudia A; Hansmeier, Nicole; Hensel, Michael

    2014-06-01

    The invasion of polarized epithelial cells by Salmonella enterica requires the cooperative activity of the Salmonella pathogenicity island 1 (SPI1)-encoded type III secretion system (T3SS) and the SPI4-encoded adhesin SiiE. The invasion of polarized cells is more efficient than that of nonpolarized cells, and we observed the formation of clusters of bacteria on infected cells. Here we demonstrate that the invasion of polarized cells is a highly cooperative activity. Using a novel live-cell imaging approach, we visualized the cooperative entry of multiple bacteria into ruffles induced on the apical surfaces of polarized cells. The induction of membrane ruffles by activity of Salmonella enables otherwise noninvasive mutant strains to enter polarized host cells. Bacterial motility and chemotaxis were of lower importance for cooperativity in polarized-cell invasion. We propose that cooperative invasion is a key factor for the very efficient entry into polarized cells and a factor contributing to epithelial damage and intestinal inflammation. PMID:24711567

  1. High-throughput Screening for Bioactive Molecules Using Primary Cell Culture of Transgenic Zebrafish Embryos

    PubMed Central

    Huang, Haigen; Lindgren, Anne; Wu, Xinrong; Liu, Ning-Ai; Lin, Shuo

    2012-01-01

    Summary Transgenic zebrafish embryos expressing tissue specific GFP can provide unlimited supply of primary embryonic cells. Agents promoting the differentiation of these cells may be beneficial for therapeutics. We report a high-throughput approach for screening small molecules that regulate cell differentiation using lineage-specific GFP transgenic zebrafish embryonic cells. After validating several known regulators of the differentiation of endothelial and other cell types, we performed a screen for pro-angiogenic molecules using undifferentiated primary cells from flk1-GFP transgenic zebrafish embryos. Cells were grown in 384-well plates with 12,128 individual small molecules and GFP expression was analyzed by an automated imaging system, allowing screening thousands of compounds weekly. As a result, 23 molecules were confirmed to enhance angiogenesis and 11 of them were validated to promote mammalian HUVEC proliferation and induce Flk1+ cells from mESCs. This strategy is generally applicable, as demonstrated by analyzing additional cell lineages using zebrafish expressing GFP in pancreatic, cardiac and dopaminergic cells. PMID:22999940

  2. Highly Ordered Surface Self-Assembly of Fe4 Single Molecule Magnets.

    PubMed

    Erler, Philipp; Schmitt, Peter; Barth, Nicole; Irmler, Andreas; Bouvron, Samuel; Huhn, Thomas; Groth, Ulrich; Pauly, Fabian; Gragnaniello, Luca; Fonin, Mikhail

    2015-07-01

    Single molecule magnets (SMMs) have attracted considerable attention due to low-temperature magnetic hysteresis and fascinating quantum effects. The investigation of these properties requires the possibility to deposit well-defined monolayers or spatially isolated molecules within a well-controlled adsorption geometry. Here we present a successful fabrication of self-organized arrays of Fe4 SMMs on hexagonal boron nitride (h-BN) on Rh(111) as template. Using a rational design of the ligand shell optimized for surface assembly and electrospray as a gentle deposition method, we demonstrate how to obtain ordered arrays of molecules forming perfect hexagonal superlattices of tunable size, from small islands to an almost perfect monolayer. High-resolution low temperature scanning tunneling microscopy (STM) reveals that the Fe4 molecule adsorbs on the substrate in a flat geometry, meaning that its magnetic easy axis is perpendicular to the surface. By scanning tunneling spectroscopy (STS) and density functional theory (DFT) calculations, we infer that the majority- and minority-spin components of the spin-split lowest unoccupied molecular orbital (LUMO) can be addressed separately on a submolecular level. PMID:26086677

  3. Nonequilibrium electronic structure of interacting single-molecule nanojunctions: vertex corrections and polarization effects for the electron-vibron coupling.

    PubMed

    Dash, L K; Ness, H; Godby, R W

    2010-03-14

    We consider the interaction between electrons and molecular vibrations in the context of electronic transport in nanoscale devices. We present a method based on nonequilibrium Green's functions to calculate both equilibrium and nonequilibrium electronic properties of a single-molecule junction in the presence of electron-vibron interactions. We apply our method to a model system consisting of a single electronic level coupled to a single vibration mode in the molecule, which is in contact with two electron reservoirs. Higher-order diagrams beyond the usual self-consistent Born approximation (SCBA) are included in the calculations. In this paper we consider the effects of the double-exchange diagram and the diagram in which the vibron propagator is renormalized by one electron-hole bubble. We study in detail the effects of the first- and second-order diagrams on the spectral functions for a large set of parameters and for different transport regimes (resonant and off-resonant cases), both at equilibrium and in the presence of a finite applied bias. We also study the linear response (linear conductance) of the nanojunction for all the different regimes. We find that it is indeed necessary to go beyond the SCBA in order to obtain correct results for a wide range of parameters. PMID:20232953

  4. Nonequilibrium electronic structure of interacting single-molecule nanojunctions: Vertex corrections and polarization effects for the electron-vibron coupling

    NASA Astrophysics Data System (ADS)

    Dash, L. K.; Ness, H.; Godby, R. W.

    2010-03-01

    We consider the interaction between electrons and molecular vibrations in the context of electronic transport in nanoscale devices. We present a method based on nonequilibrium Green's functions to calculate both equilibrium and nonequilibrium electronic properties of a single-molecule junction in the presence of electron-vibron interactions. We apply our method to a model system consisting of a single electronic level coupled to a single vibration mode in the molecule, which is in contact with two electron reservoirs. Higher-order diagrams beyond the usual self-consistent Born approximation (SCBA) are included in the calculations. In this paper we consider the effects of the double-exchange diagram and the diagram in which the vibron propagator is renormalized by one electron-hole bubble. We study in detail the effects of the first- and second-order diagrams on the spectral functions for a large set of parameters and for different transport regimes (resonant and off-resonant cases), both at equilibrium and in the presence of a finite applied bias. We also study the linear response (linear conductance) of the nanojunction for all the different regimes. We find that it is indeed necessary to go beyond the SCBA in order to obtain correct results for a wide range of parameters.

  5. High pressure synchrotron X-ray diffraction studies of biological molecules using the diamond anvil technique

    Microsoft Academic Search

    C. Czeslik; R. Malessa; R. Winter; G. Rapp

    1996-01-01

    A system for high pressure synchrotron X-ray diffraction studies of biological samples in a diamond anvil cell (DAC) is described. It is capable of operating in the whole temperature and pressure range of interest for studies of biological molecules, i.e., in the temperature range from ?40 to 100°C at pressures between 1 bar and 50 kbar. The pressure is calibrated

  6. Ab initio potential energy surface for the highly nonlinear dynamics of the KCN molecule

    SciTech Connect

    Párraga, H.; Arranz, F. J., E-mail: fj.arranz@upm.es; Benito, R. M., E-mail: rosamaria.benito@upm.es [Grupo de Sistemas Complejos, ETSI Agrónomos, Universidad Politécnica de Madrid, 28040 Madrid (Spain); Borondo, F., E-mail: f.borondo@uam.es [Departamento de Química and Instituto de Ciencias Matemáticas (ICMAT), Universidad Autónoma de Madrid, Cantoblanco, 28049-Madrid (Spain)

    2013-11-21

    An accurate ab initio quantum chemistry study at level of quadratic configuration interaction method of the electronic ground state of the KCN molecule is presented. A fitting of the results to an analytical series expansion was performed to obtain a global potential energy surface suitable for the study of the associated vibrational dynamics. Additionally, classical Poincaré surfaces of section for different energies and quantum eigenstates were calculated, showing the highly nonlinear behavior of this system.

  7. Spectral modulation of high-order harmonic generation from prealigned CO2 molecules.

    PubMed

    Peng, Peng; Li, Na; Li, Jiawei; Yang, Hua; Liu, Peng; Li, Ruxin; Xu, Zhizhan

    2013-11-15

    We demonstrate experimentally that prealigned molecules produce observable spectral redshift or blueshift on the high-order harmonic generation. We distinguish two effects of molecular alignment on the phase modulation of the harmonics; one is from the gradient of alignment degree and the other is the plasma density varied by the molecular alignment. The finding provides an insight on the spectral distribution of molecular harmonics and a method of fine-tuning the harmonic spectrum. PMID:24322154

  8. Preparation and evaluation of poly(alkyl methacrylate-co-methacrylic acid-co-ethylene dimethacrylate) monolithic columns for separating polar small molecules by capillary liquid chromatography.

    PubMed

    Lin, Shu-Ling; Wu, Yu-Ru; Lin, Tzuen-Yeuan; Fuh, Ming-Ren

    2015-04-29

    In this study, methacrylic acid (MAA) was incorporated with alkyl methacrylates to increase the hydrophilicity of the synthesized ethylene dimethacrylate-based (EDMA-based) monoliths for separating polar small molecules by capillary LC analysis. Different alkyl methacrylate-MAA ratios were investigated to prepare a series of 30% alkyl methacrylate-MAA-EDMA monoliths in fused-silica capillaries (250-?m i.d.). The porosity, permeability, and column efficiency of the synthesized MAA-incorporated monolithic columns were characterized. A mixture of phenol derivatives is employed to evaluate the applicability of using the prepared monolithic columns for separating small molecules. Fast separation of six phenol derivatives was achieved in 5 min with gradient elution using the selected poly(lauryl methacrylate-co-MAA-co-EDMA) monolithic column. In addition, the effect of acetonitrile content in mobile phase on retention factor and plate height as well as the plate height-flow velocity curves were also investigated to further examine the performance of the selected poly(lauryl methacrylate-co-MAA-co-EDMA) monolithic column. Moreover, the applicability of prepared polymer-based monolithic column for potential food safety applications was also demonstrated by analyzing five aflatoxins and three phenicol antibiotics using the selected poly(lauryl methacrylate-co-MAA-co-EDMA) monolithic column. PMID:25847162

  9. High-density single-particle tracking: quantifying molecule organization and dynamics at the nanoscale.

    PubMed

    Sibarita, Jean-Baptiste

    2014-06-01

    The organization and dynamics of proteins are fundamental parameters for cellular function. Their study, at the single-molecule level, provides precise information on molecular interactions. Over the last 30 years, the single-particle tracking imaging technique has proven its capability to efficiently quantify such parameters in many biological systems, with nanometric accuracy and millisecond temporal resolutions. Nevertheless, the low concentration of labeling required for single-molecule imaging usually prevents the extraction of large statistics. The advent of high-density single-molecule-based super-resolution techniques has revolutionized the field, allowing monitoring of thousands of biomolecules in the minute timescale and providing unprecedented insight into the molecular organization and dynamics of cellular compounds. In this issue, I will review the main principles of single-particle tracking, a highly interdisciplinary technique at the interface between microscopy, image analysis and labeling strategies. I will point out the advantages brought by high-density single-particle tracking which will be illustrated with a few recent biological results. PMID:24671496

  10. High efficiency pure blue thermally activated delayed fluorescence molecules having 10H-phenoxaborin and acridan units.

    PubMed

    Numata, Masaki; Yasuda, Takuma; Adachi, Chihaya

    2015-05-26

    Highly efficient blue thermally activated delayed fluorescence molecules having 10H-phenoxaborin and acridan units were reported. Pure blue emission peaking at around 450 nm with a high external electroluminescence quantum efficiency of around 20% was demonstrated. PMID:25959457

  11. Self-assembled, robust titanate nanoribbon membranes for highly efficient nanosolid capture and molecule discrimination

    NASA Astrophysics Data System (ADS)

    Cao, Xuebo; Zhou, Yun; Wu, Jun; Tang, Yuxin; Zhu, Lianwen; Gu, Li

    2013-03-01

    Supersaturation-directing self-assembly strategy for growing titanate nanoribbon membrane with capabilities of nanosolid capture and small molecule discrimination is reported. Owing to the distinct morphology of the nanoribbons and the accurate self-assembly process, the resulting membrane possesses outstanding mechanical properties (rupture strength exceeding 10 kg) and surprisingly high porosity (~97%), although there are no strong bonds among the nanoribbons. On the basis of the robustness of the membrane, we fabricated a column-shaped filter apparatus where the membrane acted as self-standing permeation barrier to evaluate its permeability and practical uses as molecule filter and nanosolid filter. The test of the membrane with pure water reveals that the membrane possesses a fast permeability while consumes very low energy due to the significantly high porosity. The test of the membrane with 13 nm Au solution and yellow-emitting CdTe QDs reveals that both the nanosolids are completely removed from the solution, indicating the membrane is an efficient nanosolid filter. The high efficiency is because the membrane is free of deficiencies and the flat and broad surfaces of the nanoribbons are ideal permeation barriers. The test of the membrane with charged molecules reveals that cationic species and anionic species are discriminated and at the same time the cationic species are enriched on the membrane, which indicate that the membrane is an ideal molecule filter too. The present work should provide a significant step forward to bringing macroscopic architectures assembled by 1D nanostructure much closer to real-world applications involving isolation and enrichment of biomolecules, catalyst reclamation, environmental remediation, and water purification. More broadly, through the on-demand capture of tiny nanosolids with optical, electrical, magnetic, and/or catalytic functionality, it is able to design and construct novel macroscopic nanocomposites readily; this will extend the applications of the titanate nanoribbon membrane beyond separation to the areas of photoelectrochemical devices, chemical sensors, catalysis, plasmonics, and so on.Supersaturation-directing self-assembly strategy for growing titanate nanoribbon membrane with capabilities of nanosolid capture and small molecule discrimination is reported. Owing to the distinct morphology of the nanoribbons and the accurate self-assembly process, the resulting membrane possesses outstanding mechanical properties (rupture strength exceeding 10 kg) and surprisingly high porosity (~97%), although there are no strong bonds among the nanoribbons. On the basis of the robustness of the membrane, we fabricated a column-shaped filter apparatus where the membrane acted as self-standing permeation barrier to evaluate its permeability and practical uses as molecule filter and nanosolid filter. The test of the membrane with pure water reveals that the membrane possesses a fast permeability while consumes very low energy due to the significantly high porosity. The test of the membrane with 13 nm Au solution and yellow-emitting CdTe QDs reveals that both the nanosolids are completely removed from the solution, indicating the membrane is an efficient nanosolid filter. The high efficiency is because the membrane is free of deficiencies and the flat and broad surfaces of the nanoribbons are ideal permeation barriers. The test of the membrane with charged molecules reveals that cationic species and anionic species are discriminated and at the same time the cationic species are enriched on the membrane, which indicate that the membrane is an ideal molecule filter too. The present work should provide a significant step forward to bringing macroscopic architectures assembled by 1D nanostructure much closer to real-world applications involving isolation and enrichment of biomolecules, catalyst reclamation, environmental remediation, and water purification. More broadly, through the on-demand capture of tiny nanosolids with optical, electrical, magnetic, and/or catalytic functionality, it

  12. High circular polarization ratios in radar scattering from geologic targets

    NASA Astrophysics Data System (ADS)

    Campbell, Bruce A.

    2012-06-01

    We examine and model the occurrence of circular polarization ratio (CPR or ?c) values greater than unity in terrestrial and planetary radar observations as a guide to the range of associated surface morphology. Lunar crater deposits exhibit maximum ?c values at 12.6 and 70-cm wavelength of 2 to 3. CPR values for Maxwell Montes on Venus range up to about 1.5 at 12.6-cm wavelength. Echoes from SP Flow in Arizona exhibit ?c up to 2 at 24-cm wavelength. Scattering from rock edges and cracks (dipole-like) produces ?c of unity for single scattering and up to about 2 for multiple reflections. Scattering from natural corner reflectors (dihedrals) formed by pairs of rock facets can yield an average ?c of 3-4, but likely requires non-random or scale-limited surface roughness properties in order to dominate the observed echo. The dihedral mechanism is required to satisfy the highest lunar ?c observations, while echoes from SP Flow and Maxwell Montes could be explained by just the dipole mechanism. The dihedral scenario requires rocky facets on scales many times the radar wavelength, which the blocks at SP Flow (and the unknown surface texture of Maxwell) may not provide. The random dipole model is less demanding in terms of structures and scales, and likely increases the CPR of lunar or asteroid regoliths through scattering from and between rocks.

  13. Axion-like particle effects on the polarization of cosmic high-energy gamma sources

    SciTech Connect

    Bassan, Nicola [SISSA, Via Beirut 2–4, 34014 Trieste (Italy); Mirizzi, Alessandro [II. Institut für theoretische Physik, Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg (Germany); Roncadelli, Marco, E-mail: nicola.bassan@sissa.it, E-mail: alessandro.mirizzi@desy.de, E-mail: marco.roncadelli@pv.infn.it [INFN, Sezione di Pavia, Via A. Bassi 6, 27100 Pavia (Italy)

    2010-05-01

    Various satellite-borne missions are being planned to measure the polarization of a large number of gamma-ray bursts (GRBs). We show that the polarization pattern resulting from the current models of GRB emission can be drastically modified by the existence of very light axion-like particles (ALPs), which are predicted by many extensions of the Standard Model of particle physics. Basically, the propagation of photons emitted by a GRB through cosmic magnetic fields with a domain-like structure induces photon-ALP mixing, which is expected to produce a strong modification of the initial photon polarization. Because of the random orientation of the magnetic field in each domain, this effect strongly depends on the orientation of the line of sight. As a consequence, photon-ALP conversion considerably broadens the initial polarization distribution. Searching for such a peculiar feature through future high-statistics polarimetric measurements therefore offers a new opportunity to discover very light ALPs.

  14. Terahertz laminated-structure polarizer with high extinction ratio and transmission power

    NASA Astrophysics Data System (ADS)

    Kishi, Yudai; Nagai, Masaya; Young, John C.; Takano, Keisuke; Hangyo, Masanori; Suzuki, Takehito

    2015-03-01

    A terahertz polarizer consisting of a laminated metal-slit array on a polymer film is presented. Here, the iterative design is efficiently performed with a mode-matching method; the proposed polarizer’s characteristics are shown to be superior to those of conventional polarizers. To verify the proposed design, a copper metal-slit array was fabricated on a cyclo-olefin polymer film by sputtering and punching. Measurements confirm a high extinction ratio, below ?50 dB from 0.28 to 1.09 THz and below ?40 dB from 0.2 to 1.98 THz, with a TM-mode transmission power that averages 76% from 0.2 to 1.95 THz.

  15. Polarization-insensitive optical gain characteristics of highly stacked InAs/GaAs quantum dots

    SciTech Connect

    Kita, Takashi; Suwa, Masaya; Kaizu, Toshiyuki; Harada, Yukihiro [Department of Electrical and Electronic Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501 (Japan)

    2014-06-21

    The polarized optical gain characteristics of highly stacked InAs/GaAs quantum dots (QDs) with a thin spacer layer fabricated on an n{sup +}-GaAs (001) substrate were studied in the sub-threshold gain region. Using a 4.0-nm-thick spacer layer, we realized an electronically coupled QD superlattice structure along the stacking direction, which enabled the enhancement of the optical gain of the [001] transverse-magnetic (TM) polarization component. We systematically studied the polarized electroluminescence properties of laser devices containing 30 and 40 stacked InAs/GaAs QDs. The net modal gain was analyzed using the Hakki-Paoli method. Owing to the in-plane shape anisotropy of QDs, the polarization sensitivity of the gain depends on the waveguide direction. The gain showing polarization isotropy between the TM and transverse-electric polarization components is high for the [110] waveguide structure, which occurs for higher amounts of stacked QDs. Conversely, the isotropy of the [?110] waveguide is easily achieved even if the stacking is relatively low, although the gain is small.

  16. Vibrationally induced inversion of photoelectron forward-backward asymmetry in chiral molecule photoionization by circularly polarized light

    PubMed Central

    Garcia, Gustavo A.; Nahon, Laurent; Daly, Steven; Powis, Ivan

    2013-01-01

    Electron–nuclei coupling accompanying excitation and relaxation processes is a fascinating phenomenon in molecular dynamics. A striking and unexpected example of such coupling is presented here in the context of photoelectron circular dichroism measurements on randomly oriented, chiral methyloxirane molecules, unaffected by any continuum resonance. Here, we report that the forward-backward asymmetry in the electron angular distribution, with respect to the photon axis, which is associated with photoelectron circular dichroism can surprisingly reverse direction according to the ion vibrational mode excited. This vibrational dependence represents a clear breakdown of the usual Franck–Condon assumption, ascribed to the enhanced sensitivity of photoelectron circular dichroism (compared with other observables like cross-sections or the conventional anisotropy parameter-?) to the scattering phase off the chiral molecular potential, inducing a dependence on the nuclear geometry sampled in the photoionization process. Important consequences for the interpretation of such dichroism measurements within analytical contexts are discussed. PMID:23828557

  17. High resolution mass spectrometry method and system for analysis of whole proteins and other large molecules

    DOEpatents

    Reilly, Peter T. A. (Knoxville, TN) [Knoxville, TN; Harris, William A. (Naperville, IL) [Naperville, IL

    2010-03-02

    A matrix assisted laser desorption/ionization (MALDI) method and related system for analyzing high molecular weight analytes includes the steps of providing at least one matrix-containing particle inside an ion trap, wherein at least one high molecular weight analyte molecule is provided within the matrix-containing particle, and MALDI on the high molecular weight particle while within the ion trap. A laser power used for ionization is sufficient to completely vaporize the particle and form at least one high molecular weight analyte ion, but is low enough to avoid fragmenting the high molecular weight analyte ion. The high molecular weight analyte ion is extracted out from the ion trap, and is then analyzed using a detector. The detector is preferably a pyrolyzing and ionizing detector.

  18. Investigation of High-Latitude Phenomena Using Polar Data and Global Simulations

    NASA Technical Reports Server (NTRS)

    Russell, Christopher T.; Hoffman, Robert (Technical Monitor)

    2001-01-01

    The goal of this one-year project was to use data from the Polar satellite in conjunction with global simulations of Earth's magnetosphere to investigate phenomena in the high-latitude magnetosphere. Specifically, we addressed reconnection at the cusp during periods of northward interplanetary magnetic field (IMF), and the effects of substorms on the high-latitude magnetosphere.

  19. Intensity distribution near focal point of high aperture optical system formed by partly polarized light

    Microsoft Academic Search

    Volodymyr Borovytsky; Viktoriia Chorna

    2009-01-01

    The paper presents the mathematical technique for calculation of three dimensional intensity distribution near a focal point of a high aperture optical system in case of quasi monochromatic partly polarized light. This technique is extension of the vector diffraction theory for high aperture optical systems. It is based on Huygens-Fresnel principle: spherical wave at an exit pupil is considered as

  20. Polarization insensitive wavelength conversion based on four-wave mixing for polarization multiplexing signal in high-nonlinear fiber

    Microsoft Academic Search

    J. Lu; Z. Dong; L. Chen; J. Yu

    2009-01-01

    We have theoretically and experimentally investigated polarization insensitive of all optical wavelength conversion for polarization multiplexing signal based on four-wave mixing (FWM) in nonlinear optical fiber. Optical polarization multiplexing technique can be used to double the transmission bit rate by adding data on each of two orthogonal optical states. At the receiver side, the two orthogonal signals can be obtained

  1. Burn depth determination using high-speed polarization-sensitive Mueller optical coherence tomography with continuous polarization modulation

    NASA Astrophysics Data System (ADS)

    Todorovi?, Miloš; Ai, Jun; Pereda Cubian, David; Stoica, George; Wang, Lihong

    2006-02-01

    National Health Interview Survey (NHIS) estimates more than 1.1 million burn injuries per year in the United States, with nearly 15,000 fatalities from wounds and related complications. An imaging modality capable of evaluating burn depths non-invasively is the polarization-sensitive optical coherence tomography. We report on the use of a high-speed, fiber-based Mueller-matrix OCT system with continuous source-polarization modulation for burn depth evaluation. The new system is capable of imaging at near video-quality frame rates (8 frames per second) with resolution of 10 ?m in biological tissue (index of refraction: 1.4) and sensitivity of 78 dB. The sample arm optics is integrated in a hand-held probe simplifying the in vivo experiments. The applicability of the system for burn depth determination is demonstrated using biological samples of porcine tendon and porcine skin. The results show an improved imaging depth (1 mm in tendon) and a clear localization of the thermally damaged region. The burnt area determined from OCT images compares well with the histology, thus proving the system's potential for burn depth determination.

  2. Vibrational-state and isotope dependence of high-order harmonic generation in water molecules

    SciTech Connect

    Falge, Mirjam; Engel, Volker [Universitaet Wuerzburg, Institut fuer Physikalische Chemie, Am Hubland, D-97074 Wuerzburg (Germany); Lein, Manfred [Centre for Quantum Engineering and Space-Time Research (QUEST) and Institut fuer Theoretische Physik, Leibniz Universitaet Hannover, Appelstrasse 2, D-30167 Hannover (Germany)

    2010-02-15

    We report calculations on high-order harmonic generation in water molecules. Spectra are determined for various initial vibrational states of H{sub 2}O and its isotope D{sub 2}O. It is demonstrated that the ratio of the spectra for D{sub 2}O and H{sub 2}O is close to unity when the initial state is the vibronic ground state, indicating that nuclear dynamics is of minor importance. For vibrationally excited initial states, the high-harmonic intensities show a clear dependence on both the initial-state quantum number and the isotopic species.

  3. Ultra high resolution molecular beam cars spectroscopy with application to planetary atmospheric molecules

    NASA Technical Reports Server (NTRS)

    Byer, R. L.

    1982-01-01

    The measurement of high resolution pulsed and continuous wave (CW) coherent anti-Stokes Raman spectroscopy (CARS) measurements in pulsed and steady state supersonic expansions were demonstrated. Pulsed molecular beam sources were characterized, and saturation of a Raman transition and, for the first time, the Raman spectrum of a complex molecular cluster were observed. The observation of CW CARS spectra in a molecular expansion and the effects of transit time broadening is described. Supersonic expansion is established as a viable technique for high resolution Raman spectroscopy of cold molecules with resolutions of 100 MH2.

  4. Multiphoton ionization and high-order harmonic generation of H2+ in intense ultrashort elliptically polarized laser fields

    NASA Astrophysics Data System (ADS)

    Nasiri Avanaki, Kobra; Chu, Shih-I.; Telnov, Dmitry A.

    2014-05-01

    We present an ab initio 3D calculation of multiphoton ionization (MPI) and high-order harmonic generation (HHG) of the hydrogen molecular ion subject to intense elliptically polarized laser pulses. The numerical procedure involves the extension of the generalized pseudospectral (GPS) method for non-uniform spatial discretization of the Hamiltonian and wave functions in prolate spheroidal coordinates; the time propagation scheme is based on the split-operator technique in the energy representation. The calculations are performed for the ground and first excited electronic states of H2+at the equilibrium internuclear separation R = 2 a.u. as well as for the stretched molecule at R = 7 a.u. The dependence of the HHG spectra on the ellipticity parameter is analyzed. The spectral and temporal structures of the HHG signal are studied by means of the wavelet time-frequency analysis. The results provide new insights regarding the detailed HHG mechanisms in elliptically polarized laser fields. This work is partially supported by DOE.

  5. Ordered Arrays of Native Chromatin Molecules for High-Resolution Imaging and Analysis

    PubMed Central

    Cerf, Aline; Tian, Harvey C.; Craighead, Harold G.

    2012-01-01

    Individual chromatin molecules contain valuable genetic and epigenetic information. To date, there have not been reliable techniques available for the controlled stretching and manipulation of individual chromatin fragments for high-resolution imaging and analysis of these molecules. We report the controlled stretching of single chromatin fragments extracted from two different cancerous cell types (M091 and HeLa) characterized through fluorescence microscopy and atomic force microscopy (AFM). Our method combines soft-lithography with molecular stretching to form ordered arrays of more than 250,000 individual chromatin fragments immobilized into a beads-on-a-string structure on a solid transparent support. Using fluorescence microscopy and AFM, we verified the presence of histone proteins after the stretching and transfer process. PMID:22816516

  6. Correlating Molecular Structures with Transport Dynamics in High-Efficiency Small-Molecule Organic Photovoltaics.

    PubMed

    Peng, Jiajun; Chen, Yani; Wu, Xiaohan; Zhang, Qian; Kan, Bin; Chen, Xiaoqing; Chen, Yongsheng; Huang, Jia; Liang, Ziqi

    2015-06-24

    Efficient charge transport is a key step toward high efficiency in small-molecule organic photovoltaics. Here we applied time-of-flight and organic field-effect transistor to complementarily study the influences of molecular structure, trap states, and molecular orientation on charge transport of small-molecule DRCN7T (D1) and its analogue DERHD7T (D2). It is revealed that, despite the subtle difference of the chemical structures, D1 exhibits higher charge mobility, the absence of shallow traps, and better photosensitivity than D2. Moreover, charge transport is favored in the out-of-plane structure within D1-based organic solar cells, while D2 prefers in-plane charge transport. PMID:26066398

  7. Introducing a high gravity field to enhance infiltration of small molecules into polyelectrolyte multilayers.

    PubMed

    Liu, Xiaolin; Zhao, Kun; Jiang, Chao; Wang, Yue; Shao, Lei; Zhang, Yajun; Shi, Feng

    2015-07-01

    Loading functional small molecules into nano-thin films is fundamental to various research fields such as membrane separation, molecular imprinting, interfacial reaction, drug delivery etc. Currently, a general demand for enhancing the loading rate without affecting the film structures exists in most infiltration phenomena. To handle this issue, we have introduced a process intensification method of a high gravity technique, which is a versatile energy form of mechanical field well-established in industry, into the investigations on diffusion/infiltration at the molecular level. By taking a polyelectrolyte multilayer as a model thin film and a photo-reactive molecule, 4,4'-diazostilbene-2,2'-disulfonic acid disodium salt (DAS), as a model small functional molecule, we have demonstrated remarkably accelerated adsorption/infiltration of DAS into a poly(allylamine hydrochloride) (PAH)/poly(acrylic acid) (PAA) multilayer by as high as 20-fold; meanwhile, both the film property of the multilayer and photoresponsive-crosslinking function of DAS were not disturbed. Furthermore, the infiltration of DAS and the surface morphology of the multilayer could be tuned based on their high dependence on the intensity of the high gravity field regarding different rotating speeds. The mechanism of the accelerated adsorption/infiltration under the high gravity field was interpreted by the increased turbulence of the diffusing layer with the thinned laminar boundary layer and the stepwise delivery of the local concentration gradient from the solution to the interior of the multilayer. The introduction of mechanical field provides a simple and versatile strategy to address the paradox of the contradictory loading amount and loading rate, and thus to promote applications of various membrane processes. PMID:26086776

  8. Linear polarization of x-ray transitions due to dielectronic recombination in highly charged ions

    NASA Astrophysics Data System (ADS)

    Jörg, Holger; Hu, Zhimin; Bekker, Hendrik; Blessenohl, Michael A.; Hollain, Daniel; Fritzsche, Stephan; Surzhykov, Andrey; Crespo López-Urrutia, José R.; Tashenov, Stanislav

    2015-04-01

    The linear polarization of x rays produced by dielectronic recombination into highly charged xenon ions was measured at an electron beam ion trap using the Compton polarimetry technique. This opens numerous possibilities for diagnostics of anisotropies of hot plasmas. Moreover, it was observed that the polarization of x rays, following the dielectronic capture populating the [1s 2 s22 p1/2] 1 state, is highly sensitive to the Breit interaction. The experimental results for this transition rule out by 5 ? calculations not taking the Breit interaction into account.

  9. Detection of high and variable Optical Polarization in Blazar S5 0716+71 from MIRO

    NASA Astrophysics Data System (ADS)

    Baliyan, Ks; Ganesh, S.; Chandra, S.; Joshi, Uc

    2009-12-01

    Blazar S5 0716+714 (PKS 0716+71) is highly variable at short and long term timescales in all energy regimes. We monitored it for linear Optical Polarization using 1.2m Telescope at Mt Abu IR Observatory, India, mounted with two-channel PRL Polarimeter. It was found to have high and variable polarization during Dec 12-13, 2009. The source has been reported to be undergoing flaring activity at sub-mm (ATEL #2342) and a multifrequency campaign is already on.

  10. A fluorescence-based high throughput assay for the determination of small molecule–human serum albumin protein binding

    PubMed Central

    McCallum, Megan M.; Pawlak, Alan J.; Shadrick, William R.; Simeonov, Anton; Jadhav, Ajit; Yasgar, Adam; Maloney, David J.; Arnold, Leggy A.

    2014-01-01

    Herein, we describe the development of a fluorescence-based high throughput assay to determine the small molecule binding towards human serum albumin (HSA). This innovative competition assay is based on the use of a novel fluorescent small molecule Red Mega 500 with unique spectroscopic and binding properties. The commercially available probe displays a large fluorescence intensity difference between the protein-bound and protein-unbound state. The competition of small molecules for HSA binding in the presence of probe resulted in low fluorescence intensities. The assay was evaluated with the LOPAC small molecule library of 1280 compounds identifying known high protein binders. The small molecule competition of HSA–Red Mega 500 binding was saturable at higher compound concentrations and exhibited IC50 values between 3–24 ?M. The compound affinity towards HSA was confirmed by isothermal titration calorimetry indicating that the new protein binding assay is a valid high throughput assay to determine plasma protein binding. PMID:24390461

  11. Novel liquid crystal displays based on highly polarized photoluminescent polymer films

    SciTech Connect

    Sarwa, C.; Montali, A.; Bastiaansen, C.; Weder, C.; Smith, P.

    1998-07-01

    Since the early 90's, much research has focused on the photoluminescence (PL) and electroluminescence (EL) properties of conjugated polymers, because of their potential application as emitting layer in EL devices. The introduction of uniaxial molecular orientation into films of luminescent polymers was naturally found to yield structures that emit polarized light. Rather surprisingly, the photoluminescence properties of oriented, conjugated polymers have attracted substantially less attention, especially from an application point of view. In this paper the authors report the fabrication of highly-polarized photoluminescent polymer films based on poly(2,5-dialkoxy-p-phenyleneethynylene)s (PPE), and their use in a new family of liquid crystal displays (LCDs). As one relevant example, a back-lit twisted-nematic configuration of an LCD was built, in which one of the absorbing polarizers was replaced by a polarized PL film, characterized by a dichroic ratio in excess of 70. Such devices can exhibit a substantial improvement in brightness, contrast and viewing angle, since the polarized photoluminescent films can combine two separate features, i.e., the functions of a polarizer and an efficient color filter.

  12. Decrease in highly polysialylated neuronal cell adhesion molecules and in spatial learning during ageing are not correlated

    Microsoft Academic Search

    D. N. Abrous; M. F. Montaron; K. G. Petry; G. Rougon; M. Darnaudery; M. Le Moal; W. Mayo

    1997-01-01

    Age-dependent spatial memory impairments have been related to a decline in hippocampal plasticity. Highly polysialylated neuronal cell adhesion molecules (PSA-NCAM) show a strong expression during adulthood within regions associated with neuroplastic events. Furthermore, NCAM molecules have been proposed to mediate neuronal plasticity during learning and memory. The aim of the present study was to examine the effect of ageing on

  13. High-throughput scanning confocal microscope for single molecule Chandran R. Sabanayagam, John S. Eid, and Amit Mellera)

    E-print Network

    Meller, Amit

    High-throughput scanning confocal microscope for single molecule analysis Chandran R. Sabanayagam and programmable confocal microscope that can acquire upwards of 103 single-molecule fluorescence resonance energy transfer FRET time traces is presented. The microscope augments the capabilities of current instruments

  14. High Field Dynamic Nuclear Polarization with High-Spin Transition Metal Ions

    E-print Network

    Barnes, Alexander

    We report the dynamic nuclear polarization of 1H spins in magic-angle-spinning spectra recorded at 5 T and 84 K via the solid effect using Mn2+ and Gd[superscript 3+] complexes as polarizing agents. We show that the magnitude ...

  15. Extracting the phase of high-order harmonic emission from a molecule using transient alignment in mixed samples

    NASA Astrophysics Data System (ADS)

    Wagner, Nicholas; Zhou, Xibin; Lock, Robynne; Li, Wen; Wüest, Andrea; Murnane, Margaret; Kapteyn, Henry

    2007-12-01

    We report measurements of both the phase and intensity of high-order harmonic emission from aligned CO2 molecules, using a mixture of a molecular and an atomic gas. The molecules are transiently aligned using an ultrashort pulse, and a subsequent stronger pulse is used to generate high-order harmonics from a mixed Kr/CO2 sample. The high-order harmonic emission from the molecules interferes with the reference emission from the atoms. By monitoring the change in harmonic emission as a function of gas mixture and molecular alignment, we can retrieve the orientational dipole that has general features consistent with a two-center emission model.

  16. Permeation of protons, potassium ions, and small polar molecules through phospholipid bilayers as a function of membrane thickness.

    PubMed Central

    Paula, S; Volkov, A G; Van Hoek, A N; Haines, T H; Deamer, D W

    1996-01-01

    Two mechanisms have been proposed to account for solute permeation of lipid bilayers. Partitioning into the hydrophobic phase of the bilayer, followed by diffusion, is accepted by many for the permeation of water and other small neutral solutes, but transient pores have also been proposed to account for both water and ionic solute permeation. These two mechanisms make distinctively different predictions about the permeability coefficient as a function of bilayer thickness. Whereas the solubility-diffusion mechanism predicts only a modest variation related to bilayer thickness, the pore model predicts an exponential relationship. To test these models, we measured the permeability of phospholipid bilayers to protons, potassium ions, water, urea, and glycerol. Bilayers were prepared as liposomes, and thickness was varied systematically by using unsaturated lipids with chain lengths ranging from 14 to 24 carbon atoms. The permeability coefficient of water and neutral polar solutes displayed a modest dependence on bilayer thickness, with an approximately linear fivefold decrease as the carbon number varied from 14 to 24 atoms. In contrast, the permeability to protons and potassium ions decreased sharply by two orders of magnitude between 14 and 18 carbon atoms, and leveled off, when the chain length was further extended to 24 carbon atoms. The results for water and the neutral permeating solutes are best explained by the solubility-diffusion mechanism. The results for protons and potassium ions in shorter-chain lipids are consistent with the transient pore model, but better fit the theoretical line predicted by the solubility-diffusion model at longer chain lengths. PMID:8770210

  17. N-Polarity InN/GaN/InAlN High-Electron-Mobility Transistors

    NASA Astrophysics Data System (ADS)

    Kuzmík, Ján

    2012-04-01

    Using a coupled Schrödinger-Poisson equation solver, we propose an N-polarity InN-channel quantum well high-electron-mobility transistors. The structure comprises from the bottom, a relaxed InAlN buffer with Al mole fraction between 0.1 and 0.3, GaN spacer with thickness less than 1 nm, 5 nm strained InN, and 5 nm ZrO2 or HfO2 to insulate a gate. Depending on the Al mole fraction, calculations indicate highly confined electrons in the channel with a two-dimensional density ranging from 1.6×1013 to 3.5×1013 cm-2. The polarity of the structure provides a possibility to grow InN as the last III-N layer with a relatively low polarization charge at the surface.

  18. Two-pulse orientation dynamics and high-harmonic spectroscopy of strongly-oriented molecules

    NASA Astrophysics Data System (ADS)

    Kraus, P. M.; Baykusheva, D.; Wörner, H. J.

    2014-06-01

    We present the detailed analysis of a new two-pulse orientation scheme that achieves macroscopic field-free orientation at the high particle densities required for attosecond and high-harmonic spectroscopies (Kraus et al 2013 arXiv:1311.3923). Carbon monoxide molecules are oriented by combining one-colour and delayed two-colour non-resonant femtosecond laser pulses. High-harmonic generation is used to probe the oriented wave-packet dynamics and reveals that a very high degree of orientation (Nup/Ntotal = 0.73-0.82) is achieved. We further extend this approach to orienting carbonyl sulphide molecules. We show that the present two-pulse scheme selectively enhances orientation created by the hyperpolarizability interaction whereas the ionization-depletion mechanism plays no role. We further control and optimize orientation through the delay between the one- and two-colour pump pulses. Finally, we demonstrate a complementary encoding of electronic-structure features, such as shape resonances, in the even- and odd-harmonic spectrum. The achieved progress makes two-pulse field-free orientation an attractive tool for a broad class of time-resolved measurements.

  19. Intrinsic Differences in the Inner Jets of High- and Low-Optically Polarized Radio Quasars

    E-print Network

    Matthew L. Lister; Paul S. Smith

    2000-03-21

    A significant fraction of compact radio-loud quasars display most of the characteristics of relativistically beamed, high-optical polarization blazars, yet are weakly polarized in the optical regime. We have used the VLBA at 22 and 43 GHz to look for differences in the parsec-scale magnetic field structures of 18 high- and low-optically polarized, compact radio-loud quasars (HPQs and LPRQs, respectively). We find a strong correlation between the polarization level of the unresolved parsec-scale radio core at 43 GHz and overall optical polarization of the source, which suggests a common (possibly co-spatial) origin for the emission at these two wavelengths. The magnetic fields of the polarized 43 GHz radio cores are aligned roughly transverse to the jet axis. Similar orientations are seen in the optical, suggesting that the polarized flux at both wavelengths is due to one or more strong transverse shocks located very close to the base of the jet. In LPRQs, these shocks appear to be weak near the core, and gradually increase in strength down the jet. The LPRQs in our sample tend to have less luminous radio cores than the HPQs, and jet components with magnetic fields predominantly parallel to the flow. The components in HPQ jets, on the other hand, tend to have transverse alignments. These differences cannot be accounted for by a simple model in which HPQs and LPRQs are the same type of object, seen at different angles to the line of sight. A more likely scenario is that LPRQs represent a quiescent phase of blazar activity, in which the inner jet flow does not undergo strong shocks.

  20. Subunits of highly Fluorescent Protein R-Phycoerythrin as Probes for Cell Imaging and Single-Molecule Detection

    SciTech Connect

    Dragan Isailovic

    2005-12-17

    The purposes of our research were: (1) To characterize subunits of highly fluorescent protein R-Phycoerythrin (R-PE) and check their suitability for single-molecule detection (SMD) and cell imaging, (2) To extend the use of R-PE subunits through design of similar proteins that will be used as probes for microscopy and spectral imaging in a single cell, and (3) To demonstrate a high-throughput spectral imaging method that will rival spectral flow cytometry in the analysis of individual cells. We first demonstrated that R-PE subunits have spectroscopic and structural characteristics that make them suitable for SMD. Subunits were isolated from R-PE by high-performance liquid chromatography (HPLC) and detected as single molecules by total internal reflection fluorescence microscopy (TIRFM). In addition, R-PE subunits and their enzymatic digests were characterized by several separation and detection methods including HPLC, capillary electrophoresis, sodium dodecyl sulfate-polyacrilamide gel electrophoresis (SDS-PAGE) and HPLC-electrospray ionization mass spectrometry (ESI-MS). Favorable absorption and fluorescence of the R-PE subunits and digest peptides originate from phycoerythrobilin (PEB) and phycourobilin (PUB) chromophores that are covalently attached to cysteine residues. High absorption coefficients and strong fluorescence (even under denaturing conditions), broad excitation and emission fluorescence spectra in the visible region of electromagnetic spectrum, and relatively low molecular weights make these molecules suitable for use as fluorescence labels of biomolecules and cells. We further designed fluorescent proteins both in vitro and in vivo (in Escherichia coli) based on the highly specific attachment of PEB chromophore to genetically expressed apo-subunits of R-PE. In one example, apo-alpha and apo-beta R-PE subunits were cloned from red algae Polisiphonia boldii (P. boldii), and expressed in E. coli. Although expressed apo-subunits formed inclusion bodies, fluorescent holo-subunits were formed after incubation of E. coli cells with PEB. Spectroscopic characterization of holo-subunits confirmed that the attachment of PEB chromophore to apo-subunits yielded holo-subunits containing both PEB and urobilin (UB). Fluorescence and differential interference contrast (DIC) microscopy showed polar location of holo-subunit inclusion bodies in E. coli cells. In another example, R-PE apo-subunits were genetically fused to cytoplasmic and periplasmic versions of E. coli maltose binding protein (MBP). Fluorescent proteins formed after attachment of PEB to MBP-subunit fusions in vitro and in vivo contained PEB as the sole chromophore, were soluble, and displayed high orange fluorescence. Fluorescence microscopy showed that fusions are located either throughout cells or at cell poles. In addition, cells containing fluorescent holo-subunits or MBP-subunit fusions were up to ten times brighter than control cells as measured by flow cytometry. Results show that the fluorescent proteins formed after non-enzymatic attachment of PEB to R-PE subunit fusions could be used as reporters of gene expression and protein localization in cells as well as fluorescence labels in flow cytometry. Finally, we demonstrated a high-throughput method able to record emission fluorescence spectra of individual cells containing fluorescent proteins. Upon excitation with a 488 mn argon-ion laser many bacterial cells were imaged by a 20X microscope objective while they moved through a capillary tube. Fluorescence was dispersed by a transmission diffraction grating, and an intensified charge-coupled device (ICCD) camera simultaneously recorded the zero and the first orders of the fluorescence from each cell. Single-cell fluorescence spectra were reconstructed from the distance between zero-order and first-order maxima as well as the length and the pixel intensity distribution of the first-order images. By using this approach, the emission spectrum of E. coli cells expressing green fluorescent protein (GFP) was reconstructed. Also, fluorescence spectra of E

  1. Highly sensitive immunoassay of protein molecules based on single nanoparticle fluorescence detection in a nanowell

    NASA Astrophysics Data System (ADS)

    Han, Jin-Hee; Kim, Hee-Joo; Lakshmana, Sudheendra; Gee, Shirley J.; Hammock, Bruce D.; Kennedy, Ian M.

    2011-03-01

    A nanoarray based-single molecule detection system was developed for detecting proteins with extremely high sensitivity. The nanoarray was able to effectively trap nanoparticles conjugated with biological sample into nanowells by integrating with an electrophoretic particle entrapment system (EPES). The nanoarray/EPES is superior to other biosensor using immunoassays in terms of saving the amounts of biological solution and enhancing kinetics of antibody binding due to reduced steric hindrance from the neighboring biological molecules. The nanoarray patterned onto a layer of PMMA and LOL on conductive and transparent indium tin oxide (ITO)-glass slide by using e-beam lithography. The suspension of 500 nm-fluorescent (green emission)-carboxylated polystyrene (PS) particles coated with protein-A followed by BDE 47 polyclonal antibody was added to the chip that was connected to the positive voltage. The droplet was covered by another ITO-coated-glass slide and connected to a ground terminal. After trapping the particles into the nanowells, the solution of different concentrations of anti-rabbit- IgG labeled with Alexa 532 was added for an immunoassay. A single molecule detection system could quantify the anti-rabbit IgG down to atto-mole level by counting photons emitted from the fluorescent dye bound to a single nanoparticle in a nanowell.

  2. High-harmonic spectroscopy of isoelectronic molecules: Wavelength scaling of electronic-structure and multielectron effects

    NASA Astrophysics Data System (ADS)

    Rupenyan, A.; Kraus, P. M.; Schneider, J.; Wörner, H. J.

    2013-03-01

    We study the interplay of electronic-structure and multielectron effects in high-harmonic spectra of the two isoelectronic molecules CO2 and N2O as a function of the near-infrared driving wavelength and intensity. We show that the minima observed in the spectra of aligned molecules (=0.54-0.64) are intensity dependent at the shortest investigated wavelength (1.17 ?m) but become gradually intensity independent at longer wavelengths (1.36 and 1.46 ?m). These results combined with detailed theoretical modeling show that the contributions of several ionization channels are important in the spectra recorded with short-wavelength driving pulses because the minima are located in the cutoff region where the contributions from different channels are comparable. In spectra recorded with longer driving wavelengths, the minima are located in the plateau region of the spectrum and are caused by the electronic structure of the molecules. Our results also rationalize and reconcile previous results and provide general guidelines for future studies.

  3. Optical detection of target molecule induced aggregation of nanoparticles by means of high-Q resonators.

    PubMed

    Witzens, Jeremy; Hochberg, Michael

    2011-04-11

    We theoretically investigate a novel scheme to detect target molecule induced, or suppressed, aggregation of nanoparticles. High-Q optical resonators are used to both optically trap gold nanoparticle clusters and to detect their presence via a shift in the resonance wavelength. The well depth of the optical trap is chosen to be relatively low compared to the thermal energy of the nanoparticles, so that trapping of single nanoparticles is marginal and results in a comparatively small wavelength shift. Aggregation of functionalized gold nanoparticles is mediated or suppressed via binding to a target molecule. The well depth for the resulting nanoparticle clusters scales much more favorably relative to Brownian motion, resulting in large nanoparticle concentration enhancements in the evanescent field region of the resonator. We predict a target molecule sensitivity in the tens of fM range. In order to predict the resonator response, a complete theory of time resolved nanoparticle cluster trapping dynamics is derived. In particular, the formalism of Kramers' escape time is adapted to 2D (silicon wire) and 3D (ring resonator) optical traps. PMID:21503017

  4. Adsorption-induced chirality in highly symmetric hydrocarbon molecules: lattice matching to substrates of lower symmetry

    NASA Astrophysics Data System (ADS)

    Richardson, Neville V.

    2007-10-01

    For molecules of high symmetry and lateral interactions dominated by van der Waals' interactions, such as some planar aromatic hydrocarbons, there is a preference for hexagonal close packing on adsorption. Optimization of packing by minimization of the interadsorbate spacing may favour correlated rotations of the molecules, which reduces the symmetry and leads to chiral properties in the two-dimensional overlayer. Independently, mapping of the preferred hexagonal packing on to lower symmetry substrates, which provide pseudo-hexagonal lattices, can lead to alternative mirror image lattices. The interaction of these independent chiral phenomena gives rise to diastereoisomerism in the adsorbed array. Coronene and its substituted, larger derivative hexa-tert-butyl hexabenzocoronene adsorbed on copper surfaces provide examples of these phenomena. A new structure is proposed for coronene on Cu{100} while new STM and LEED data are presented for this molecule adsorbed on Cu{110}. Finally, the adsorption of hexa-tert-butyl hexabenzocoronene on Cu{110} is re-examined and the implications of the competition between two, closely related, pseudo-hexagonal lattices are considered.

  5. Mapping of intracellular halogenous molecules by low and high resolution SIMS microscopy.

    PubMed

    Berry, J P; Galle, P; Chassoux, D; Escaig, F; Linarez-Cruz, L G; Lespinats, G

    1992-01-01

    The subcellular distribution of halogenous molecules has been studied by SIMS microscopy in cultured cells of a human breast carcinoma (MCF-7 cell line). Two instruments of microanalysis were used. A low lateral resolution ion microscope (SMI 300 CAMECA) and a prototype scanning ion microscope equipped with a cesium gun that gives high lateral resolution images. This apparatus has been developed by G Slodzian, in Onera Laboratories (Office National d'Etudes et de Recherches Aérospatiales). Molecules studied by low lateral resolution ion microscope were halogenous steroids: fluorometholone, triamcinolone, bromocriptine and bromoandrosterone. Analytical images show that the first two compounds are mainly localized in the nuclear structure of MCF-7 cells whereas the last two molecules are localized in cytoplasm of these cells. Images were obtained with a resolution of 1 micron. With the scanning ion microscope, it is now possible to obtain images at the ultrastructural level. Four analytical images can be simultaneously obtained by a single scan of the imaged area, corresponding to a depth of erosion of the section of ten nm. The intranuclear distributions of three pyrimidine analogs, 5-bromo-2'-deoxyuridine, 5-iodo-2'-deoxyuridine and 5-fluorouracil have been studied in phase S and M of MCF-7 cells and these images have been compared to the distribution of sulfur, nitrogen and phosphorus. All these images have been obtained with a lateral resolution better than 100 nm. PMID:1511252

  6. Vacuum-UV spectroscopy of interstellar ice analogs. I. Absorption cross-sections of polar-ice molecules

    NASA Astrophysics Data System (ADS)

    Cruz-Diaz, G. A.; Muñoz Caro, G. M.; Chen, Y.-J.; Yih, T.-S.

    2014-02-01

    Context. The vacuum-UV (VUV) absorption cross sections of most molecular solids present in interstellar ice mantles with the exception of H2O, NH3, and CO2 have not been reported yet. Models of ice photoprocessing depend on the VUV absorption cross section of the ice to estimate the penetration depth and radiation dose, and in the past, gas phase cross section values were used as an approximation. Aims: We aim to estimate the VUV absorption cross section of molecular ice components. Methods: Pure ices composed of CO, H2O, CH3OH, NH3, or H2S were deposited at 8 K. The column density of the ice samples was measured in situ by infrared spectroscopy in transmittance. VUV spectra of the ice samples were collected in the 120-160 nm (10.33-7.74 eV) range using a commercial microwave-discharged hydrogen flow lamp. Results: We provide VUV absorption cross sections of the reported molecular ices. Our results agree with those previously reported for H2O and NH3 ices. Vacuum-UV absorption cross section of CH3OH, CO, and H2S in solid phase are reported for the first time. H2S presents the highest absorption in the 120-160 nm range. Conclusions: Our method allows fast and readily available VUV spectroscopy of ices without the need to use a synchrotron beamline. We found that the ice absorption cross sections can be very different from the gas-phase values, and therefore, our data will significantly improve models that simulate the VUV photoprocessing and photodesorption of ice mantles. Photodesorption rates of pure ices, expressed in molecules per absorbed photon, can be derived from our data. Data can be found at http://ghosst.osug.fr/

  7. Comparison of sugar molecule decomposition through glucose and fructose: a high-level quantum chemical study.

    SciTech Connect

    Assary, R. S.; Curtiss, L. A. (Center for Nanoscale Materials); ( MSD); (Northwestern Univ.)

    2012-02-01

    Efficient chemical conversion of biomass is essential to produce sustainable energy and industrial chemicals. Industrial level conversion of glucose to useful chemicals, such as furfural, hydroxymethylfurfural, and levulinic acid, is a major step in the biomass conversion but is difficult because of the formation of undesired products and side reactions. To understand the molecular level reaction mechanisms involved in the decomposition of glucose and fructose, we have carried out high-level quantum chemical calculations [Gaussian-4 (G4) theory]. Selective 1,2-dehydration, keto-enol tautomerization, isomerization, retro-aldol condensation, and hydride shifts of glucose and fructose molecules were investigated. Detailed kinetic and thermodynamic analyses indicate that, for acyclic glucose and fructose molecules, the dehydration and isomerization require larger activation barriers compared to the retro-aldol reaction at 298 K in neutral medium. The retro-aldol reaction results in the formation of C2 and C4 species from glucose and C3 species from fructose. The formation of the most stable C3 species, dihydroxyacetone from fructose, is thermodynamically downhill. The 1,3-hydride shift leads to the cleavage of the C-C bond in the acyclic species; however, the enthalpy of activation is significantly higher (50-55 kcal/mol) than that of the retro-aldol reaction (38 kcal/mol) mainly because of the sterically hindered distorted four-membered transition state compared to the hexa-membered transition state in the retro-aldol reaction. Both tautomerization and dehydration are catalyzed by a water molecule in aqueous medium; however, water has little effect on the retro-aldol reaction. Isomerization of glucose to fructose and glyceraldehyde to dihydroxyacetone proceeds through hydride shifts that require an activation enthalpy of about 40 kcal/mol at 298 K in water medium. This investigation maps out accurate energetics of the decomposition of glucose and fructose molecules that is needed to help find more efficient catalysts for the conversion of hexose to useful chemicals.

  8. Coronal origin of the polarization of the high-energy emission of Cygnus X-1

    NASA Astrophysics Data System (ADS)

    Romero, G. E.; Vieyro, F. L.; Chaty, S.

    2014-02-01

    Context. Cygnus X-1 is the candidate with the highest probability of containing a black hole among the X-ray binary systems in the Galaxy. It is also by far the most often studied of these objects. Recently, the International Gamma-Ray Astrophysics Laboratory Imager on board the Integral satellite (INTEGRAL/IBIS) detected strong polarization in the high-energy radiation of this source, between 400 keV and 2 MeV. This radiation has been attributed to a jet launched by the black hole. Aims: We consider whether the corona around the black hole might be the site of production of the polarized emission instead of the jet. Methods: We studied self-consistently the injection of nonthermal particles in the hot, magnetized plasma around the black hole. Results: We show that both the high-energy spectrum and polarization of Cygnus X-1 in the low-hard state can originate in the corona, without needing to invoke a jet. We estimate the degree of polarization in the intermediate state, where there is no jet, to provide a tool to test our model. Conclusions: Contrary to the commonly accepted view, the jet might not be the source of the MeV polarized tail in the spectrum of Cygnus X-1.

  9. Highly efficient broadband polarization retarders and tunable polarization filters made of composite stacks of ordinary wave plates

    NASA Astrophysics Data System (ADS)

    Dimova, E. St.; Ivanov, S. S.; Popkirov, G. St.; Vitanov, N. V.

    2014-05-01

    By using the formal analogy between the evolution of the state vector in quantum mechanics and the Jones vector in polarization optics, we construct and demonstrate experimentally efficient broadband half-wave polarization retarders and tunable narrowband polarization filters. Both the broadband retarders and the filters are constructed by the same set of stacked standard multi-order optical wave plates rotated at different angles with respect to their fast polarization axes: for a certain set of angles this device behaves as a broadband polarization retarder while for another set of angles it turns into a narrowband polarization filter. We demonstrate that the transmission profile of our filter can be centered around any desired wavelength in a certain vicinity of the design wavelength of the wave plates solely by selecting appropriate rotation angles.

  10. High-throughput 1,536-well fluorescence polarization assays for ?(1)-acid glycoprotein and human serum albumin binding.

    PubMed

    Yasgar, Adam; Furdas, Silviya D; Maloney, David J; Jadhav, Ajit; Jung, Manfred; Simeonov, Anton

    2012-01-01

    Two major plasma proteins in humans are primarily responsible for drug binding, the ?(1)-acid-glycoprotein (AGP) and human serum albumin (HSA). The availability of at least a semiquantitative high-throughput assay for assessment of protein binding is expected to aid in bridging the current gap between high-throughput screening and early lead discovery, where cell-based and biochemical assays are deployed routinely to test up to several million compounds rapidly, as opposed to the late-stage candidate drug profiling methods which test at most dozens of compounds at a time. Here, we describe the miniaturization of a pair of assays based on the binding- and displacement-induced changes in fluorescence polarization (FP) of fluorescent small molecule probes known to specifically target the drug-binding sites of these two proteins. A robust and reproducible assay performance was achieved in ?4 µL assay volume in 1,536-well format. The assays were tested against a validation set of 10 known protein binders, and the results compared favorably with data obtained using protein-coated beads with high-performance liquid chromatography analysis. The miniaturized assays were taken to a high-throughput level in a screen of the LOPAC(1280) collection of 1,280 pharmacologically active compounds. The adaptation of the AGP and HSA FP assays to a 1,536-well format should allow their use in early-stage profiling of large-size compound sets. PMID:23029124

  11. High-Throughput 1,536-Well Fluorescence Polarization Assays for ?1-Acid Glycoprotein and Human Serum Albumin Binding

    PubMed Central

    Yasgar, Adam; Furdas, Silviya D.; Maloney, David J.; Jadhav, Ajit; Jung, Manfred; Simeonov, Anton

    2012-01-01

    Two major plasma proteins in humans are primarily responsible for drug binding, the ?1-acid-glycoprotein (AGP) and human serum albumin (HSA). The availability of at least a semiquantitative high-throughput assay for assessment of protein binding is expected to aid in bridging the current gap between high-throughput screening and early lead discovery, where cell-based and biochemical assays are deployed routinely to test up to several million compounds rapidly, as opposed to the late-stage candidate drug profiling methods which test at most dozens of compounds at a time. Here, we describe the miniaturization of a pair of assays based on the binding- and displacement-induced changes in fluorescence polarization (FP) of fluorescent small molecule probes known to specifically target the drug-binding sites of these two proteins. A robust and reproducible assay performance was achieved in ?4 µL assay volume in 1,536-well format. The assays were tested against a validation set of 10 known protein binders, and the results compared favorably with data obtained using protein-coated beads with high-performance liquid chromatography analysis. The miniaturized assays were taken to a high-throughput level in a screen of the LOPAC1280 collection of 1,280 pharmacologically active compounds. The adaptation of the AGP and HSA FP assays to a 1,536-well format should allow their use in early-stage profiling of large-size compound sets. PMID:23029124

  12. Non perturbative approach for a polar and polarizable linear molecule in an inhomogeneous electric field: Application to molecular beam deviation experiments

    NASA Astrophysics Data System (ADS)

    Benichou, E.; Allouche, A. R.; Antoine, R.; Aubert-Frecon, M.; Bourgoin, M.; Broyer, M.; Dugourd, Ph.; Hadinger, G.; Rayane, D.

    A non perturbative approach is used to solve the problem of a rigid linear molecule with both a permanent dipole moment and a static dipole polarizability, in a static electric field. Eigenenergies are obtained and compared to perturbative low field and high field approximations. Analytical expressions for the orientation parameters and for the gradient of the energy are given. This non perturbative approach is applied to the simulation of beam deviation experiments in strong electric field. Results of simulations are given for inhomogeneous alkali dimers. For LiNa, the simulations are compared to experimental data. For LiK, deviation profiles have been simulated in order to prepare future experiments on this molecule.

  13. An x-ray probe of laser-aligned molecules

    Microsoft Academic Search

    E. R. Peterson; Christian Buth; D. A. Arms; R. W. Dunford; E. P. Kanter; B. Krässig; E. C. Landahl; S. T. Pratt; Robin Santra; S. H. Southworth; Linda Young

    2008-01-01

    We demonstrate a hard x-ray probe of laser-aligned small molecules. To align small molecules with optical lasers, high intensities at nonresonant wavelengths are necessary. We use 95 ps pulses focused to 40 mum from an 800 nm Ti:sapphire laser at a peak intensity of 1012 W\\/cm2 to create an ensemble of aligned bromotrifluoromethane (CF3Br) molecules. Linearly polarized, 120 ps x-ray

  14. Polarized Electrons for Polarized Positrons

    NASA Astrophysics Data System (ADS)

    Fanchini, Erica

    2012-03-01

    Recently, the nuclear and high-energy physics communities have shown a growing interest in the availability of high current, highly spin-polarized positron beams. The Polarized Electrons for Polarized Positrons (PEPPo) experiment at the Thomas Jefferson National Accelerator Facility (Jefferson Lab) aims to measure the transfer of polarization from a low energy 10 MeV highly spin polarized electron beam to positrons. A sufficiently energetic polarized photon or lepton may generate, via bremsstrahlung and pair creation processes within a target foil, electron-positron pairs that will carry a fraction of the initial polarization. This approach has been successfully tested using polarized photons created with a multi-GeV unpolarized electron beam, resulting in positrons with polarization of 80%. Although pair creation yield is reduced at lower energy, recent advances in high current milliampere spin-polarized electron sources at Jefferson Lab offer the perspective of creating polarized positrons using a low energy electron beam. A successful demonstration of this technique would provide an alternative scheme to produce low energy polarized positrons, as well as useful information to optimize the design of a polarized positron source using sub-GeV electron beam. An overview and status of the PEPPo experiment will be presented, along with some of the motivations in the context of the Jefferson Lab nuclear physics program.

  15. Highly fluorescent semiconducting polymer dots for single-molecule imaging and biosensing

    NASA Astrophysics Data System (ADS)

    Sun, Wei; Yu, Jiangbo; Ye, Fangmao; Rong, Yu; Chiu, Daniel T.

    2013-09-01

    This paper describes the preparation of semiconducting polymer dots (Pdots) and their application for single-molecule imaging and biosensing. The Pdots possessed high fluorescence brightness, with a 16 nm Pdot being ~9 times brighter than 13 nm Quantum Dots (Qdots). The surface of Pdots was successfully conjugated with streptavidin, which made Pdots suitable for specific subcellular labeling and targeting. The interior composition of Pdots was also successfully modified, through which the Pdots obtained additional functionalities. We demonstrated the utility of gold nanoparticle embedded Pdots in dual-modality imaging. We also demonstrated that Rhodamine B embedded Pdots were able to function as ratiometric temperature sensor in live-cell imaging mode.

  16. Pump-probe study of atoms and small molecules with laser driven high order harmonics

    NASA Astrophysics Data System (ADS)

    Cao, Wei

    A commercially available modern laser can emit over 1015 photons within a time window of a few tens of femtoseconds (10-15second), which can be focused into a spot size of about 10 mum, resulting in a peak intensity above 1014W/cm2. This paves the way for table-top strong field physics studies such as above threshold ionization (ATI), non-sequential double ionization (NSDI), high order harmonic generation (HHG), etc.. Among these strong laser-matter interactions, high order harmonic generation, which combines many photons of the fundamental laser field into a single photon, offers a unique way to generate light sources in the vacuum ultraviolet (VUV) or extreme ultraviolet (EUV) region. High order harmonic photons are emitted within a short time window from a few tens of femtoseconds down to a few hundreds of attoseconds (10 -18second). This highly coherent nature of HHG allows it to be synchronized with an infrared (IR) laser pulse, and the pump-probe technique can be adopted to study ultrafast dynamic processes in a quantum system. The major work of this thesis is to develop a table-top VUV(EUV) light source based on HHG, and use it to study dynamic processes in atoms and small molecules with the VUV(EUV)-pump IR-probe method. A Cold Target Recoil Ion Momentum Spectroscopy (COLTRIMS) apparatus is used for momentum imaging of the interaction products. Two types of high harmonic pump pulses are generated and applied for pump-probe studies. The first one consists of several harmonics forming a short attosecond pulse train (APT) in the EUV regime (around 40 eV). We demonstrate that, (1) the auto-ionization process triggered by the EUV in cation carbon-monoxide and oxygen molecules can be modified by scanning the EUV-IR delay, (2) the phase information of quantum trajectories in bifurcated high harmonics can be extracted by performing an EUV-IR cross-correlation experiment, thus disclosing the macroscopic quantum control in HHG. The second type of high harmonic source implemented in this work is a single harmonic in the VUV regime (around 15 eV) filtered out from a monochromator. Experiments on D2 molecules have been conducted using the 9th or the 11th harmonic as the pump pulse. Novel dissociative ionization pathways via highly excited states of D 2 have been revealed, thus suggesting potential applications for time-resolved studies and control of photochemistry processes.

  17. Polarization measurements through space-to-ground atmospheric propagation paths by using a highly polarized laser source in space.

    PubMed

    Toyoshima, Morio; Takenaka, Hideki; Shoji, Yozo; Takayama, Yoshihisa; Koyama, Yoshisada; Kunimori, Hiroo

    2009-12-01

    The polarization characteristics of an artificial laser source in space were measured through space-to-ground atmospheric transmission paths. An existing Japanese laser communication satellite and optical ground station were used to measure Stokes parameters and the degree of polarization of the laser beam transmitted from the satellite. As a result, the polarization was preserved within an rms error of 1.6 degrees, and the degree of polarization was 99.4+/-4.4% through the space-to-ground atmosphere. These results contribute to the link estimation for quantum key distribution via space and provide the potential for enhancements in quantum cryptography worldwide in the future. PMID:20052156

  18. Single-molecule imaging at high fluorophore concentrations by local activation of dye

    DOE PAGESBeta

    Geertsema, Hylkje J.; Mangel, Walter F.; Schulte, Aartje C.; Spenkelink, Lisanne M.; McGrath, William J.; Morrone, Seamus R.; Sohn, Jungsan; Robinson, Andrew; van Oijen, Antoine M.

    2015-02-01

    Single-molecule fluorescence microscopy is a powerful approach to observe biomolecular interactions with high spatial and temporal resolution. Detecting fluorescent signals from individual, labeled proteins above high levels of background fluorescence remains challenging, however. For this reason, the concentrations of labeled proteins in in vitro assays are often kept low compared to their in vivo concentrations. Here, we present a new fluorescence imaging technique by which single fluorescent molecules can be observed in real time at high, physiologically relevant concentrations. The technique requires a protein and its macromolecular substrate to be labeled each with a different fluorophore. Then, making use ofmore »short-distance energy-transfer mechanisms, the fluorescence from only those proteins bound to their substrate are selectively activated. This approach is demonstrated by labeling a DNA substrate with an intercalating stain, exciting the stain, and using energy transfer from the stain to activate the fluorescence of only those labeled DNA-binding proteins bound to the DNA. Such an experimental design allowed us to observe the sequence-independent interaction of Cy5-labeled interferon-inducible protein 16 (IFI16) with DNA and the sliding via one-dimensional diffusion of Cy5-labeled adenovirus protease (pVIc-AVP) on DNA in the presence of a background of hundreds of nM Cy5 fluorophore.« less

  19. Single-molecule imaging at high fluorophore concentrations by local activation of dye

    DOE PAGESBeta

    Geertsema, Hylkje J. [Zernike Inst. of Advanced Materials, Groningen (The Netherlands); Mangel, Walter F. [Brookhaven National Lab. (BNL), Upton, NY (United States); Schulte, Aartje C. [Zernike Inst. of Advanced Materials, Groningen (The Netherlands); Spenkelink, Lisanne M. [Zernike Inst. of Advanced Materials, Groningen (The Netherlands); McGrath, William J. [Brookhaven National Lab. (BNL), Upton, NY (United States); Morrone, Seamus R. [John Hopkins School of Medicine, Baltimore, MD (United States); Sohn, Jungsan [John Hopkins School of Medicine, Baltimore, MD (United States); Robinson, Andrew [Zernike Inst. of Advanced Materials, Groningen (The Netherlands); van Oijen, Antoine M. [Zernike Inst. of Advanced Materials, Groningen (The Netherlands)

    2015-02-01

    Single-molecule fluorescence microscopy is a powerful approach to observe biomolecular interactions with high spatial and temporal resolution. Detecting fluorescent signals from individual, labeled proteins above high levels of background fluorescence remains challenging, however. For this reason, the concentrations of labeled proteins in in vitro assays are often kept low compared to their in vivo concentrations. Here, we present a new fluorescence imaging technique by which single fluorescent molecules can be observed in real time at high, physiologically relevant concentrations. The technique requires a protein and its macromolecular substrate to be labeled each with a different fluorophore. Then, making use of short-distance energy-transfer mechanisms, the fluorescence from only those proteins bound to their substrate are selectively activated. This approach is demonstrated by labeling a DNA substrate with an intercalating stain, exciting the stain, and using energy transfer from the stain to activate the fluorescence of only those labeled DNA-binding proteins bound to the DNA. Such an experimental design allowed us to observe the sequence-independent interaction of Cy5-labeled interferon-inducible protein 16 (IFI16) with DNA and the sliding via one-dimensional diffusion of Cy5-labeled adenovirus protease (pVIc-AVP) on DNA in the presence of a background of hundreds of nM Cy5 fluorophore.

  20. POLARIZATION OF A PARAMAGNET BY A FAST HIGH INTENSITY MAGNETIC FIELD PULSE : SPIN AND PHONON RELAXATION,

    E-print Network

    Boyer, Edmond

    989 POLARIZATION OF A PARAMAGNET BY A FAST HIGH INTENSITY MAGNETIC FIELD PULSE : SPIN AND PHONON of the response of the magnetization to a fast 2 wave sinusoidal field pulse can give very direct information) the phonon relaxation ; iv) the magnetic ordering of the paramagnet. FIG. 1. - Form of magnetic field pulse

  1. Ku Band Planar Antenna with High Efficiency and Excellent Cross Polarization Isolation

    Microsoft Academic Search

    Hirohiko Yamamoto; Koichi Tsunekawa; Hiroshi Nakano; Tomozo Ohta

    1992-01-01

    The design and performance of the planar antenna having high efficiency and excellent cross polarization isolation for the consumer use are described. The antenna is mainly composed of microstrip radiating elements and the triplate feeder line. It is constructed with foam dielectric spacers and the flexible printed circuit board between two metal sheets. The radiating element is built by the

  2. Single-Layer Resonant High Reflector in TE Polarization: Theory and Experiment

    Microsoft Academic Search

    Kyu J. Lee; Robert Magnusson

    2011-01-01

    We present the fabrication and characterization of a guided-mode resonance- based high reflector operating in transverse-electric (TE) polarization. This reflector consists of a single periodic layer of amorphous silicon on a glass substrate. It is fabricated by silicon sputtering, holographic interference patterning, and dry etching. The measured reflectance exceeds 90% over a ? 130-nm wavelength range with maximum reflectance of

  3. Cassini imaging of Titan's high-latitude lakes, clouds, and south-polar surface changes

    E-print Network

    Cassini imaging of Titan's high-latitude lakes, clouds, and south-polar surface changes E. P 2009. [1] Cassini's Imaging Science Subsystem (ISS) has been observing Titan since April 2004 observed by Cassini's RADAR. These observations demonstrate dynamic processes at work on Titan

  4. Production of highly polarized 3 He using spectrally narrowed diode laser

    E-print Network

    Walker, Thad G.

    Production of highly polarized 3 He using spectrally narrowed diode laser array bars B. Chann, E obtained with either a spectrally narrowed laser or one type of broadband laser. Based on tests of several is typically three times lower for the spectrally narrowed laser. This last result indicates that spectrally

  5. The extremely rapid oligonucleotide hybridization and high throughput detection of microbial gene sequences using fluorescence polarization

    Microsoft Academic Search

    Makoto Tsuruoka; Setsuko Murano; Makoto Okada; Isao Ohiso; Takaaki Fujii

    2001-01-01

    The hybridization of oligonucleotide sequences complementary to the genes of Shiga toxins (verotoxins) types 1 and 2 of enterohaemorrhagic Escherichia coli (EHEC) and human hepatitis C virus (HCV) was monitored using fluorescence polarization under the reaction condition of high salt concentration (0.8 M NaCl), which was optimized to obtain a higher rate of hybridization. The time courses of hybridization of

  6. High-speed all-optical terahertz polarization switching by a transient plasma phase modulator

    E-print Network

    been widely used to realize key functionalities in photonic devices, including fiber optic constraints on the bandwidths of optical elements. Recent efforts have focused on engineering metamaterialsHigh-speed all-optical terahertz polarization switching by a transient plasma phase modulator

  7. EDITORIAL: New materials with high spin polarization: half-metallic Heusler compounds

    Microsoft Academic Search

    Claudia Felser; Burkard Hillebrands

    2007-01-01

    The development of magnetic Heusler compounds, specifically designed as materials for spintronic applications, has made tremendous progress in the very recent past [1-21]. Heusler compounds can be made as half-metals, showing a high spin polarization of the conduction electrons of up to 100% [1]. These materials are exceptionally well suited for applications in magnetic tunnel junctions acting, for example, as

  8. High-Frequency Dynamic Nuclear Polarization in MAS Spectra of Membrane and Soluble Proteins

    E-print Network

    Griffin, Robert G.

    High-Frequency Dynamic Nuclear Polarization in MAS Spectra of Membrane and Soluble Proteins Melanie of the principal promises of magic angle spinning (MAS) solid-state NMR (SSNMR) experiments is the possibility The success of these experiments is due largely to the ability to record multidimensional MAS NMR spectra

  9. Optical properties of side-polished polarization maintaining fiber coupled with a high index planar waveguide

    Microsoft Academic Search

    Kwang Taek Kim; Dae Sung Yoon; Gyeong-il Kwoen

    2004-01-01

    We have investigated the behavior of an asymmetric directional coupler made of a side-polished polarization maintaining (PM) fiber covered with a high index planar waveguide (PWG). The effects of the modal birefringence of the side-polished PM fiber, the structural parameters of PWG and the deformation of the PM fiber on the transmission characteristics of the coupler has been measured and

  10. The Origin of the Ultra-Violet Spectral Components in the Polar-Like Intermediate Polar, RE075 Cycle 4 High

    Microsoft Academic Search

    Simon Rosen

    1994-01-01

    RE0751+14, is arguably the most important magnetic cataclysmic variable (CV) to be discovered for many years. Although it is undoubtedly an intermediate polar, it also exhibits highly unusual properties (e.g. a strong EUV component, modulated optical\\/IR polarization, X-ray, optical and IR dips in its rotational light curve and a very red rotational pulsation) which strongly suggest that its white dwarf

  11. High performance small molecule photodetector with broad spectral response range from 200 to 900 nm

    NASA Astrophysics Data System (ADS)

    Wu, Shuang-hong; Li, Wen-lian; Chu, Bei; Su, Zi-sheng; Zhang, Feng; Lee, C. S.

    2011-07-01

    We demonstrate a photodetector (PD) with broad spectral response by taking the advantages of more flexible device design in using small molecule materials. The optimized device shows an external quantum efficiency of over 20% from 200 to 900 nm. The high performance is achieved by jointing two donor (D)/acceptor (A) hetero-junctions [m-MTDATA(D)/TiOPc(A) and TiOPc(D)/F16CuPc: PTCDI-C8(A)] such that photoresponses over the deep-ultraviolet (UV) and visible-near infrared regions can be independently optimized. By choosing D- and A-materials with matched energy level alignment, high carrier mobility, and balanced carrier transporting properties, the present PD shows a fast response of 56 ns. The high speed and deep-UV sensitivity might lead to potential military applications such as missile tracking in addition to optical communications, chemical/biological sensing etc.

  12. High-order harmonic generation from polyatomic molecules including nuclear motion and a nuclear modes analysis

    SciTech Connect

    Madsen, C. B.; Abu-samha, M.; Madsen, L. B. [Lundbeck Foundation Theoretical Center for Quantum System Research, Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C (Denmark)

    2010-04-15

    We present a generic approach for treating the effect of nuclear motion in high-order harmonic generation from polyatomic molecules. Our procedure relies on a separation of nuclear and electron dynamics where we account for the electronic part using the Lewenstein model and nuclear motion enters as a nuclear correlation function. We express the nuclear correlation function in terms of Franck-Condon factors, which allows us to decompose nuclear motion into modes and identify the modes that are dominant in the high-order harmonic generation process. We show results for the isotopes CH{sub 4} and CD{sub 4} and thereby provide direct theoretical support for a recent experiment [S. Baker et al., Science 312, 424 (2006)] that uses high-order harmonic generation to probe the ultrafast structural nuclear rearrangement of ionized methane.

  13. A high-rate detection system to study parity violation with polarized epithermal neutrons at LANSCE

    SciTech Connect

    Knudson, J.N.; Bowman, J.D. [Los Alamos National Lab., NM (United States); Crawford, B.E. [Duke Univ., Durham, NC (United States)]|[Triangle Universities Nuclear Laboratory, Durham, NC (United States)

    1995-07-01

    We describe an apparatus for studies of parity violation in neutron-nucleus scattering. This experiment requires longitudinally polarized neutrons from the Los Alamos Neutron Scattering Center over the energy-range from 1 to 1000 eV, the ability to reverse the neutron spin without otherwise affecting the apparatus, the ability to detect neutrons at rates up to 500 MHz, and an appropriate data acquisition system. We will discuss the neutron polarizer, fast neutron spin reverser, detector for transmitted neutrons, and high rate data acquisition system.

  14. High Transparency of Photosphere Plasma for Electromagnetic Waves Polarized Across Strong Magnetic Field on White Dwarfs

    NASA Astrophysics Data System (ADS)

    Koryagin, S. A.

    2015-06-01

    We showed that, in the photosphere of a white dwarf with strong magnetic field, the collisional absorption significantly decreases at the frequencies below the electron cyclotron frequency for the electromagnetic waves linearly polarized across the magnetic field lines (for the so-called extraordinary waves in a magnetized plasma). As a result, the extraordinary waves can escape from the deeper and hotter photosphere layers than the ordinary waves and, in this way, can determine the high linear polarization at the infrared and optical continuum.

  15. Development of high-performance alkali-hybrid polarized 3He targets for electron scattering

    NASA Astrophysics Data System (ADS)

    Singh, Jaideep T.; Dolph, P. A. M.; Tobias, W. A.; Averett, T. D.; Kelleher, A.; Mooney, K. E.; Nelyubin, V. V.; Wang, Yunxiao; Zheng, Yuan; Cates, G. D.

    2015-05-01

    Background: Polarized 3He targets have been used as effective polarized neutron targets for electron scattering experiments for over twenty years. Over the last ten years, the effective luminosity of polarized 3He targets based on spin-exchange optical pumping has increased by over an order of magnitude. This has come about because of improvements in commercially-available lasers and an improved understanding of the physics behind the polarization process. Purpose: We present the development of high-performance polarized 3He targets for use in electron scattering experiments. Improvements in the performance of polarized 3He targets, target properties, and operating parameters are documented. Methods: We utilize the technique of alkali-hybrid spin-exchange optical pumping to polarize the 3He targets. Spectrally narrowed diode lasers used for the optical pumping greatly improved the performance. A simulation of the alkali-hybrid spin-exchange optical pumping process was developed to provide guidance in the design of the targets. Data was collected during the characterization of 24 separate glass target cells, each of which was constructed while preparing for one of four experiments at Jefferson Laboratory in Newport News, Virginia. Results: From the data obtained we made determinations of the so-called X -factors that quantify a temperature-dependent and as-yet poorly understood spin-relaxation mechanism that limits the maximum achievable 3He polarization to well under 100%. The presence of the X -factor spin-relaxation mechanism was clearly evident in our data. Good agreement between the simulation and the actual target performance was obtained by including details such as off-resonant optical pumping. Included in our results is a measurement of the K -3He spin-exchange rate coefficient kseK=(7.46 ±0.62 ) ×10-20cm3/s over the temperature range 503 K to 563 K. Conclusions: In order to achieve high performance under the operating conditions described in this paper, the K to Rb alkali vapor density ratio should be about 5 ±2 and the line width of the optical pumping lasers should be no more than 0.3 nm. Our measurements of the X -factors under these conditions seem to indicate the 3He polarization is limited to ?90 %. The simulation results, now benchmarked against experimental data, are useful for the design of future targets. Further work is required to better understand the temperature dependence of the X -factor spin-relaxation mechanism and the limitations of our optical pumping simulation.

  16. A high-throughput UPLC method for the characterization of chemical modifications in monoclonal antibody molecules.

    PubMed

    Stackhouse, Nicole; Miller, Amanda K; Gadgil, Himanshu S

    2011-12-01

    Development of high-throughput release and characterization assays is critical for the effective support of the rapidly growing biologics pipeline for biotherapeutics. Clipping of polypeptide chains is commonly monitored during process optimization, formulation development, and stability studies. A reduced capillary electrophoresis-sodium dodecyl sulfate (rCE -SDS) method is often used as a purity release assay for monitoring clips in monoclonal antibodies (mAbs); however, it has a cycle time of approximately 40 min, which is not suited for high-throughput screening. Additionally, the characterization of clips and variants from electropherograms is not straightforward and takes significant time. Reduced reversed-phase (RP) chromatography has been a popular assay for the characterization and identification of clips and variants because it can be directly coupled with online mass spectrometric analysis. However, the high-column temperature and low pH required for RP assays can induce on-column cleavage and therefore skew the results. To minimize on-column degradation, we have developed a high-throughput method with a significantly shorter cycle time of 5 min. The short cycle time was achieved using an ultra-high-pressure liquid chromatography (UPLC) system with a 1.7 ?m phenyl column. This UPLC method allowed quantitation of hinge clipping in an IgG1 molecule and acid induced aspartic acid/proline (D/P) clip in an IgG2 molecule. The results from the UPLC method were comparable to those obtained with rCE-SDS. Additionally, the phenyl column offered partial resolution of oxidation and other chemical modifications, making this technique an attractive assay for high-throughput process characterization and formulation screens. PMID:21789770

  17. High-resolution high-frequency dynamic nuclear polarization for biomolecular solid state NMR

    E-print Network

    Barnes, Alexander B. (Alexander Benjamin)

    2011-01-01

    Dynamic Nuclear Polarization (DNP) has exploded in popularity over the last few years, finally realizing its potential to overcome the detrimental lack of sensitivity that has plagued performing NMR experiments. Applied ...

  18. Gas dynamics in high-luminosity polarized He-3 targets using diffusion and convection

    E-print Network

    P. A. M. Dolph; J. Singh; T. Averett; A. Kelleher; K. E. Mooney; V. Nelyubin; W. A. Tobias; B. Wojtsekhowski; G. D. Cates

    2011-09-15

    The dynamics of the movement of gas is discussed for two-chambered polarized He-3 target cells of the sort that have been used successfully for many electron scattering experiments. A detailed analysis is presented showing that diffusion is a limiting factor in target performance, particularly as these targets are run at increasingly high luminosities. Measurements are presented on a new prototype polarized He-3 target cell in which the movement of gas is due largely to convection instead of diffusion. NMR tagging techniques have been used to visualize the gas flow, showing velocities along a cylindrically-shaped target of between 5-80 cm/min. The new target design addresses one of the principle obstacles to running polarized He-3 targets at substantially higher luminosities while simultaneously providing new flexibility in target geometry.

  19. Ultracold dipolar collisions of KRb molecules

    Microsoft Academic Search

    Goulven Quemener; John Bohn; Kang-Kuen Ni; Silke Ospelkaus; Dajun Wang; Brian Neyenhuis; Marcio de Miranda; Jun Ye; Deborah Jin

    2010-01-01

    Ultracold fermionic polar molecules of ^40K^87Rb in their absolute rovibronic anf hyperfine state [1] have been recently created in a magnetic trap. This enables experiments to probe ultracold molecular chemistry of polar molecules [2] in well defined quantum states. In addition, KRb molecules are polar and can be manipulated by an electric field. We present theoretical predictions for ultracold dipolar

  20. Circularly polarized high harmonic generation for element-selective probing of magnetic materials on a tabletop

    NASA Astrophysics Data System (ADS)

    Grychtol, Patrick; Turgut, Emrah; Zusin, Dmitriy; Popmintchev, Dimitar; Popmintchev, Tenio; Kapteyn, Henry; Murnane, Margaret; Knut, Ronny; Nembach, Hans; Shaw, Justin; Kfir, Ofer; Fleischer, Avner; Cohen, Oren

    2014-03-01

    Ultrafast short wavelength sources based on high harmonic upconversion of femtosecond lasers are unique in their ability to simultaneously probe the magnetically-sensitive M absorption edges of the 3d ferromagnets Fe, Co and Ni. This novel capability to capture the fastest spin dynamics in materials has uncovered a wealth of new fundamental understanding about spin scattering and transport on few-femtosecond timescales. However, to date these investigations have used linearly polarized higher harmonics, since it has not been possible to generate circularly polarized harmonics with sufficient flux for scientific applications. In this contribution, we present a simple setup that enables the efficient generation of circularly polarized harmonics, and demonstrates that they are bright enough for studies of magnetic materials. The fundamental and second harmonic of a Ti:sapphire laser are focused into a gas filled waveguide under good phase matching conditions, with opposite chirality circular polarizations. Thus, circularly-polarized harmonics are produced that are then used to perform magnetic circular dichroism studies in the extreme ultraviolet photon energy range.

  1. PolarBase: a data base of high resolution spectropolarimetric stellar observations

    E-print Network

    Petit, P; Théado, S; Paletou, F; Manset, N; Morin, J; Marsden, S C; Jeffers, S V

    2014-01-01

    PolarBase is an evolving data base that contains all stellar data collected with the ESPaDOnS and NARVAL high-resolution spectropolarimeters, in their reduced form, as soon as they become public. As of early 2014, observations of 2,000 stellar objects throughout the Hertzsprung-Russell diagram are available. Intensity spectra are available for all targets, and the majority of the observations also include simultaneous spectra in circular or linear polarization, with the majority of the polarimetric measurements being performed only in circularly polarized light (Stokes V). Observations are associated with a cross-correlation pseudo-line profile in all available Stokes parameters, greatly increasing the detectability of weak polarized signatures. Stokes V signatures are detected for more than 300 stars of all masses and evolutionary stages, and linear polarization is detected in 35 targets. The detection rate in Stokes V is found to be anti-correlated with the stellar effective temperature. This unique set of ...

  2. High Optical Polarization from Electrical Spin Injection into an InGaAs QW

    NASA Astrophysics Data System (ADS)

    Li, C. H.; Kioseoglou, G.; Holub, M.; van't Erve, O. M. J.; Jonker, B. T.; Ali, T.; Khan, I.; Yasar, M.; Petrou, A.

    2009-03-01

    We have fabricated spin light emitting diodes (LEDs) with Fe as the spin injector and 100å In0.1Ga0.9As/GaAs QWs as the detector. The emission efficiency from the InGaAs QW is extremely high, with a narrow linewidth of 4meV at 5K. The free exciton exhibits 25% optical polarization due to the injection of spin polarized carriers from the reverse-biased Fe Schttky contact. At low biases, a feature 10meV below the free exciton appears which exhibits a much larger polarization with a peculiar magnetic field dependence. Similar to that of the free exciton, the circular polarization of this lower energy feature first increases with magnetic field, and reaches a maximum of 67% at 2.5T, indicating injection from Fe. However, this behavior is superposed on a large diamagnetic background of 21%/T which dominates above 2.5T. The intensity and polarization of this feature is strongly bias dependent, and the feature disappears above 15K, suggesting that it originates from a weakly bound complex. The origin of this feature and its dependence on the magnetic field will be discussed at the meeting. Supported by ONR, NRL core funds, and NSF.

  3. Conjugated Polymer-Small Molecule Alloy Leads to High Efficient Ternary Organic Solar Cells.

    PubMed

    Zhang, Jianqi; Zhang, Yajie; Fang, Jin; Lu, Kun; Wang, Zaiyu; Ma, Wei; Wei, Zhixiang

    2015-07-01

    Ternary organic solar cells are promising candidates for bulk heterojunction solar cells; however, improving the power conversion efficiency (PCE) is quite challenging because the ternary system is complicated on phase separation behavior. In this study, a ternary organic solar cell (OSC) with two donors, including one polymer (PTB7-Th), one small molecule (p-DTS(FBTTH2)2), and one acceptor (PC71BM), is fabricated. We propose the two donors in the ternary blend forms an alloy. A notable averaged PCE of 10.5% for ternary OSC is obtained due to the improvement of the fill factor (FF) and the short-circuit current density (Jsc), and the open-circuit voltage (Voc) does not pin to the smaller Voc of the corresponding binary blends. A highly ordered face-on orientation of polymer molecules is obtained due to the formation of an alloy structure, which facilitates the enhancement of charge separation and transport and the reduction of charge recombination. This work indicates that a high crystallinity and the face-on orientation of polymers could be obtained by forming alloy with two miscible donors, thus paving a way to largely enhance the PCE of OSCs by using the ternary blend strategy. PMID:26052738

  4. A model for energy transfer in collisions of atoms with highly excited molecules.

    PubMed

    Houston, Paul L; Conte, Riccardo; Bowman, Joel M

    2015-05-21

    A model for energy transfer in the collision between an atom and a highly excited target molecule has been developed on the basis of classical mechanics and turning point analysis. The predictions of the model have been tested against the results of trajectory calculations for collisions of five different target molecules with argon or helium under a variety of temperatures, collision energies, and initial rotational levels. The model predicts selected moments of the joint probability distribution, P(Jf,?E) with an R(2) ? 0.90. The calculation is efficient, in most cases taking less than one CPU-hour. The model provides several insights into the energy transfer process. The joint probability distribution is strongly dependent on rotational energy transfer and conservation laws and less dependent on vibrational energy transfer. There are two mechanisms for rotational excitation, one due to motion normal to the intermolecular potential and one due to motion tangential to it and perpendicular to the line of centers. Energy transfer is found to depend strongly on the intermolecular potential and only weakly on the intramolecular potential. Highly efficient collisions are a natural consequence of the energy transfer and arise due to collisions at "sweet spots" in the space of impact parameter and molecular orientation. PMID:25907301

  5. Auroral spectrometer AF6 for the POLAR HIGH ATMOSPHERE rocket campaign

    NASA Astrophysics Data System (ADS)

    Fischer, F.; Knothe, M.; Schmidtke, G.

    1981-02-01

    An extreme ultraviolet (EUV) spectrometer for the polar high atmosphere experiment and the results of two flights are presented. The optical concept is based on Rowland grating geometry using the blaze effect and providing a high efficiency spectrometer. Height, profiles of important spectral emissions such as O2 and O1 are obtained and strong differences in the spatial distribution of emissions with different optical depths are shown in the spectral region.

  6. Polarization maintaining, high-power and high-efficiency (6+1)×1 pump/signal combiner

    NASA Astrophysics Data System (ADS)

    Kopp, Victor I.; Park, Jongchul; Wlodawski, Mitchell; Singer, Jonathan; Neugroschl, Dan

    2014-03-01

    We have developed an all-glass, fusion spliceable polarization maintaining (6+1)× 1 pump/signal combiner for fiber lasers and amplifiers. We utilize an enhanced tapered fiber bundle technology for multimode pump channels and a vanishing core fiber for the single mode polarization maintaining large mode area (PLMA) signal channel. The signal channel of the combiner is optimized to match a double-clad PLMA fiber with 20 micron core and 400 micron glass cladding with 0.065 numerical aperture (NA). The multimode pump channels have 200 micron core and 240 micron cladding with NA of 0.22 designed to deliver high power 980 nm pump light. The same double-clad PLMA fiber is used as both the signal input channel and the combined output for the device. Polarization axes of the input and output PLMA fibers are aligned during the fusion splices to achieve polarization crosstalk below -20 dB. Utilizing this approach, we have achieved coupling loss of ~0.4 dB for the signal channel as measured from the input PLMA to the output PLMA at a wavelength of 1060 nm and coupling loss below 0.01 dB for all pump channels as determined from the measured temperature rise of the combiner package temperature as the optical pump power at 974 nm is increased up to 45 W. Low signal and pump losses result in high efficiency lasing or amplification at over a kW of pump power for high power applications where a single mode, high polarization extinction ratio output is required.

  7. On the high Mach number shock structure singularity caused by overreach of Maxwellian molecules

    SciTech Connect

    Myong, R. S., E-mail: myong@gnu.ac.kr [Department of Aerospace and System Engineering and Research Center for Aircraft Parts Technology, Gyeongsang National University, Jinju, Gyeongnam 660-701 (Korea, Republic of)

    2014-05-15

    The high Mach number shock structure singularity arising in moment equations of the Boltzmann equation was investigated. The source of the singularity is shown to be the unbalanced treatment between two high order kinematic and dissipation terms caused by the overreach of Maxwellian molecule assumption. In compressive gaseous flow, the high order stress-strain coupling term of quadratic nature will grow far faster than the strain term, resulting in an imbalance with the linear dissipation term and eventually a blow-up singularity in high thermal nonequilibrium. On the other hand, the singularity arising from unbalanced treatment does not occur in the case of velocity shear and expansion flows, since the high order effects are cancelled under the constraint of the free-molecular asymptotic behavior. As an alternative method to achieve the balanced treatment, Eu's generalized hydrodynamics, consistent with the second law of thermodynamics, was revisited. After introducing the canonical distribution function in exponential form and applying the cumulant expansion to the explicit calculation of the dissipation term, a natural platform suitable for the balanced treatment was derived. The resulting constitutive equation with the nonlinear factor was then shown to be well-posed for all regimes, effectively removing the high Mach number shock structure singularity.

  8. Rotational Relaxation in Rigid Media by Polarized Photoselection

    Microsoft Academic Search

    J. R. Lombardi; J. W. Raymonda; A. C. Albrecht

    1964-01-01

    A study is made of the rotational relaxation of solute molecules in media ranging in viscosity from 106 to 1012 P. Viscosities are determined for various mixtures of 3-methylpentane and isopentane at 77°K The solute relaxation is observed by two distinctly different methods both based on polarized photoselection. At the high viscosities a dichroism is produced by polarized photochemistry and

  9. Polarization dependent guiding in liquid crystal filled photonic crystal fibers

    Microsoft Academic Search

    Guobin Ren; Ping Shum; Xia Yu; Juanjuan Hu; Guanghui Wang; Yandong Gong

    2008-01-01

    A theoretical study of nematic liquid crystal filled photonic crystal fibers (LCPCFs) is presented. Detailed investigations including the polarization dependent bandgap formation and the modal properties are given for LCPCFs, in which alignment of the molecules could be controlled by external static electric field. The polarization dependent bandgap splitting caused by the high index difference between the ordinary and the

  10. Performance of Gaasp/gaas Superlattice Photocathodes in High Energy Experiments Using Polarized Electrons

    NASA Astrophysics Data System (ADS)

    Brachmann, A.; Clendenin, J. E.; Maruyama, T.; Garwin, E. L.; Ioakeimidi, K.; Prescott, C. Y.; Turner, J. L.; Prepost, R.

    2007-04-01

    The GaAsP/GaAs strained superlattice photocathode structure has proven to be a significant advance for polarized electron sources operating with high peak currents per microbunch and relatively low duty factor. This is the characteristic type of operation for SLAC and is also planned for the ILC. This superlattice structure was studied at SLAC [1], and an optimum variation was chosen for the final stage of E-158, a high-energy parity violating experiment at SLAC. Following E-158, the polarized source was maintained on standby with the cathode being re-cesiated about once a week while a thermionic gun, which is installed in parallel with the polarized gun, supplied the linac electron beams. However, in the summer of 2005, while the thermionic gun was disabled, the polarized electron source was again used to provide electron beams for the linac. The performance of the photocathode 24 months after its only activation is described and factors making this possible are discussed.

  11. Electromagnetic Ion Cyclotron Waves in the High-Altitude Cusp: Polar Observations

    NASA Technical Reports Server (NTRS)

    Le, G.; Blanco-Cano, X.; Russell, C. T.; Zhou, X.-W.; Mozer, F.; Trattner, K. J.; Fuselier, S. A.; Anderson, B. J.

    2005-01-01

    High-resolution magnetic field data from the Polar Magnetic Field Experiment (MFE) show that narrow-band waves at frequencies approx. 0.2-3 Hz are a permanent feature in the vicinity of the polar cusp. The waves have been found in the magnetosphere adjacent to the cusp (both poleward and equatorward of the cusp) and in the cusp itself. The occurrence of waves is coincident with depression of magnetic field strength associated with enhanced plasma density, indicating the entry of magnetosheath plasma into the cusp region. The wave frequencies are generally scaled by the local proton cyclotron frequency and vary between 0.2 and 1.7 times local proton cyclotron frequency. This suggests that the waves are generated in the cusp region by the precipitating magnetosheath plasma. The properties of the waves are highly variable. The waves exhibit both left-handed and right-handed polarization in the spacecraft frame. The propagation angles vary from nearly parallel to nearly perpendicular to the magnetic field. We find no correlation among wave frequency, propagation angle, and polarization. Combined magnetic field and electric field data for the waves indicate that the energy flux of the waves is guided by the background magnetic field and points downward toward the ionosphere.

  12. Electromagnetic Ion Cyclotron Waves in the High Altitude Cusp: Polar Observations

    NASA Technical Reports Server (NTRS)

    Le, Guan; Blanco-Cano, X.; Russell, C. T.; Zhou, X.-W.; Mozer, F.; Trattner, K. J.; Fuselier, S. A.; Anderson, B. J.; Vondrak, Richard R. (Technical Monitor)

    2001-01-01

    High-resolution magnetic field data from the Polar Magnetic Field Experiment (MFE) show that narrow band waves at frequencies approximately 0.2 to 3 Hz are a permanent feature in the vicinity of the polar cusp. The waves have been found in the magnetosphere adjacent to the cusp (both poleward and equatorward of the cusp) and in the cusp itself. The occurrence of waves is coincident with depression of magnetic field strength associated with enhanced plasma density, indicating the entry of magnetosheath plasma into the cusp region. The wave frequencies are generally scaled by the local proton cyclotron frequency, and vary between 0.2 and 1.7 times local proton cyclotron frequency. This suggests that the waves are generated in the cusp region by the precipitating magnetosheath plasma. The properties of the waves are highly variable. The waves exhibit both lefthanded and right-handed polarization in the spacecraft frame. The propagation angles vary from nearly parallel to nearly perpendicular to the magnetic field. We find no correlation among wave frequency, propagation angle and polarization. Combined magnetic field and electric field data for the waves indicate that the energy flux of the waves is guided by the background magnetic field and points downward toward the ionosphere.

  13. Highly sensitive naphthalimide-based fluorescence polarization probe for detecting cancer cells.

    PubMed

    Jia, Ti; Fu, Congying; Huang, Chusen; Yang, Haotian; Jia, Nengqin

    2015-05-13

    Fluorescence polarization (FP)-based signal is a self-referencing fluorescence signal, and it is less dependent on dye concentration and environmental interferences, which makes FP measurement an attractive alternative sensing technology to fluorescence intensity-based detection. However, most of the fluorescence polarization probes were constructed by introducing fluorescein, rhodamine, and cyanine dyes, which have relatively shorter excited-state lifetimes compared with BODIPY and naphthalimide dyes. Herein, a first naphthalimide based fluorescence polarization probe (BIO) was designed and synthesized for selective and direct detection of cancer cells. The relatively longer excited-state lifetimes and high photostability of naphthalimide makes BIO more sensitive and accuracy in quantitative determination of HeLa cells in homogeneous solution without cell lysis and further separation steps. The detection limit of BIO for HeLa cells was about 85 cells mL(-1), the linear range was from 2.5 × 10(2) cells mL(-1) to 1 × 10(6) cells mL(-1) and the response time is no more than 25 min. Moreover, due to the relatively high photostability of naphthalimide, BIO was particularly suitable for live cell imaging under continuous irradiation with confocal microscopy, and the specific interaction of BIO with CD44-overexpressing cell lines was clearly visualized. Importantly, this BIO based sensing platform offers a direct and real-time tool for cancer cell diagnosis when complemented with the use of naphthalimide-based fluorescence polarization probe. PMID:25898141

  14. High-Fidelity Polarization Storage in a Gigahertz Bandwidth Quantum Memory

    E-print Network

    England, D G; Champion, T F M; Reim, K F; Lee, K C; Sprague, M R; Jin, X -M; Langford, N K; Kolthammer, W S; Nunn, J; Walmsley, I A

    2011-01-01

    We demonstrate a dual-rail optical Raman memory inside a polarization interferometer; this enables us to store polarization-encoded information at GHz bandwidths in a room-temperature atomic ensemble. By performing full process tomography on the system we measure up to 97\\pm1% process fidelity for the storage and retrieval process. At longer storage times, the process fidelity remains high, despite a loss of efficiency. The fidelity is 86\\pm4% for 1.5 \\mu s storage time, which is 5,000 times the pulse duration. Hence high fidelity is combined with a large time-bandwidth product. This high performance, with an experimentally simple setup, demonstrates the suitability of the Raman memory for integration into large-scale quantum networks.

  15. High-Fidelity Polarization Storage in a Gigahertz Bandwidth Quantum Memory

    E-print Network

    D. G. England; P. S. Michelberger; T. F. M. Champion; K. F. Reim; K. C. Lee; M. R. Sprague; X. -M. Jin; N. K. Langford; W. S. Kolthammer; J. Nunn; I. A. Walmsley

    2012-02-09

    We demonstrate a dual-rail optical Raman memory inside a polarization interferometer; this enables us to store polarization-encoded information at GHz bandwidths in a room-temperature atomic ensemble. By performing full process tomography on the system we measure up to 97\\pm1% process fidelity for the storage and retrieval process. At longer storage times, the process fidelity remains high, despite a loss of efficiency. The fidelity is 86\\pm4% for 1.5 \\mu s storage time, which is 5,000 times the pulse duration. Hence high fidelity is combined with a large time-bandwidth product. This high performance, with an experimentally simple setup, demonstrates the suitability of the Raman memory for integration into large-scale quantum networks.

  16. High-fidelity polarization storage in a gigahertz bandwidth quantum memory

    NASA Astrophysics Data System (ADS)

    England, D. G.; Michelberger, P. S.; Champion, T. F. M.; Reim, K. F.; Lee, K. C.; Sprague, M. R.; Jin, X.-M.; Langford, N. K.; Kolthammer, W. S.; Nunn, J.; Walmsley, I. A.

    2012-06-01

    We demonstrate a dual-rail optical Raman memory inside a polarization interferometer; this enables us to store polarization-encoded information at GHz bandwidths in a room-temperature atomic ensemble. By performing full process tomography on the system, we measure up to 97 ± 1% process fidelity for the storage and retrieval process. At longer storage times, the process fidelity remains high, despite a loss of efficiency. The fidelity is 86 ± 4% for 1.5 ?s storage time, which is 5000 times the pulse duration. Hence, high fidelity is combined with a large time-bandwidth product. This high performance, with an experimentally simple setup, demonstrates the suitability of the Raman memory for integration into large-scale quantum networks.

  17. High-Frequency Dynamic Nuclear Polarization in the Nuclear Rotating Frame

    NASA Astrophysics Data System (ADS)

    Farrar, C. T.; Hall, D. A.; Gerfen, G. J.; Rosay, M.; Ardenkjær-Larsen, J.-H.; Griffin, R. G.

    2000-05-01

    A proton dynamic nuclear polarization (DNP) NMR signal enhancement (?) close to thermal equilibrium, ? = 0.89, has been obtained at high field (B0 = 5 T, ?epr = 139.5 GHz) using 15 mM trityl radical in a 40:60 water/glycerol frozen solution at 11 K. The electron-nuclear polarization transfer is performed in the nuclear rotating frame with microwave irradiation during a nuclear spin-lock pulse. The growth of the signal enhancement is governed by the rotating frame nuclear spin-lattice relaxation time (T1?), which is four orders of magnitude shorter than the nuclear spin-lattice relaxation time (T1n). Due to the rapid polarization transfer in the nuclear rotating frame the experiment can be recycled at a rate of 1/T1? and is not limited by the much slower lab frame nuclear spin-lattice relaxation rate (1/T1n). The increased repetition rate allowed in the nuclear rotating frame provides an effective enhancement per unit time1/2 of ?t = 197. The nuclear rotating frame-DNP experiment does not require high microwave power; significant signal enhancements were obtained with a low-power (20 mW) Gunn diode microwave source and no microwave resonant structure. The symmetric trityl radical used as the polarization source is water-soluble and has a narrow EPR linewidth of 10 G at 139.5 GHz making it an ideal polarization source for high-field DNP/NMR studies of biological systems.

  18. Palmitoleate Reverses High Fat-induced Proinflammatory Macrophage Polarization via AMP-activated Protein Kinase (AMPK).

    PubMed

    Chan, Kenny L; Pillon, Nicolas J; Sivaloganathan, Darshan M; Costford, Sheila R; Liu, Zhi; Théret, Marine; Chazaud, Benedicte; Klip, Amira

    2015-07-01

    A rise in tissue-embedded macrophages displaying "M1-like" proinflammatory polarization is a hallmark of metabolic inflammation during a high fat diet or obesity. Here we show that bone marrow-derived macrophages (BMDM) from high fat-fed mice retain a memory of their dietary environment in vivo (displaying the elevated proinflammatory genes Cxcl1, Il6, Tnf, Nos2) despite 7-day differentiation and proliferation ex vivo. Notably, 6-h incubation with palmitoleate (PO) reversed the proinflammatory gene expression and cytokine secretion seen in BMDM from high fat-fed mice. BMDM from low fat-fed mice exposed to palmitate (PA) for 18 h ex vivo also showed elevated expression of proinflammatory genes (Cxcl1, Il6, Tnf, Nos2, and Il12b) associated with M1 polarization. Conversely, PO treatment increased anti-inflammatory genes (Mrc1, Tgfb1, Il10, Mgl2) and oxidative metabolism, characteristic of M2 macrophages. Therefore, saturated and unsaturated fatty acids bring about opposite macrophage polarization states. Coincubation of BMDM with both fatty acids counteracted the PA-induced Nos2 expression in a PO dose-dependent fashion. PO also prevented PA-induced I?B? degradation, RelA nuclear translocation, NO production, and cytokine secretion. Mechanistically, PO exerted its anti-inflammatory function through AMP-activated protein kinase as AMP kinase knockout or inhibition by Compound C offset the PO-dependent prevention of PA-induced inflammation. These results demonstrate a nutritional memory of BMDM ex vivo, highlight the plasticity of BMDM polarization in response to saturated and unsaturated fatty acids, and identify the potential to reverse diet- and saturated fat-induced M1-like polarization by administering palmitoleate. These findings could have applicability to reverse obesity-linked inflammation in metabolically relevant tissues. PMID:25987561

  19. Polarity and Excursion Transitions: Can they be Adequately Recorded in High-Sedimentation-Rate Marine Sediments?

    NASA Astrophysics Data System (ADS)

    Channell, J. E. T.

    2014-12-01

    Polarity transitions and magnetic excursions have durations of a few thousand years, or less. Transition/excursion records in volcanic sequences are, at best, partial snap-shots of the transition/excursion field. Records from high-sedimentation-rate marine sediments may be more continuous but they are always smoothed by progressive acquisition of detrital remanent magnetization (DRM), and by sampling/measurement limitations. North Atlantic records of the Matuyama-Brunhes (M-B) polarity transition are compared with records of the Iceland Basin excursion (190 ka). Virtual geomagnetic polar (VGP) paths are used to map characteristic magnetization directions during the transition/excursion. Relative paleointensity (RPI) proxies indicate partial recovery of field intensity during the transition/excursion, with RPI minima coinciding with abrupt VGP shifts at the onset and end of the transition/excursion. Discrepancies in VGP paths among holes at the same site, among sites, and a comparison of u-channel and discrete sample measurements, reveal limitations in resolution of the transition/excursion fields. During the M-B polarity transition, VGP clusters appear in the NW Pacific, NE Asia and in the South Atlantic. Similarities in VGP clustering for the M-B boundary and the Iceland Basin excursion imply that the polarity transition and excursion fields had common characteristics. Similarities with the modern non-axial dipole (NAD) field imply that polarity transitions and excursions involve the demise of the Earth's axial dipole relative to the NAD field, and that the NAD field has long-lasting features locked in place by the lowermost mantle.

  20. Circularly polarized high order harmonics in the EUV photon energy range: toward table-top nanometric magnetic imaging

    NASA Astrophysics Data System (ADS)

    Vodungbo, Boris; Barszczak Sardinha, A.; Gautier, Julien; Lambert, Guillaume; Sebban, Stéphane; Lüning, Jan; Zeitoun, Philippe

    2011-09-01

    Circularly polarized high order harmonics in the extreme ultraviolet range (18 - 27 nm) have been obtained by a two steps process. Harmonics were generated from a linearly polarized infrared laser (40 fs, 0.25 TW) focused into a neon filled gas cell. The harmonics have then been circularly polarized by a four-reflector phase-shifter. The polarization of the harmonics have been measured using a rotating multilayer broadband mirror set at an incidence angle of 45°. Fully circularly polarized radiation has been obtained with an efficiency of a few percents. This is significantly more efficient than currently demonstrated direct generation of elliptically polarized harmonics. This demonstration opens up new experimental capabilities based on high order harmonics, for example, in materials science for time-resolved nanometric magnetic imaging.

  1. Highly precise quantification of protein molecules per cell during stress and starvation responses in Bacillus subtilis.

    PubMed

    Maa?, Sandra; Wachlin, Gerhild; Bernhardt, Jörg; Eymann, Christine; Fromion, Vincent; Riedel, Katharina; Becher, Dörte; Hecker, Michael

    2014-09-01

    Systems biology based on high quality absolute quantification data, which are mandatory for the simulation of biological processes, successively becomes important for life sciences. We provide protein concentrations on the level of molecules per cell for more than 700 cytosolic proteins of the Gram-positive model bacterium Bacillus subtilis during adaptation to changing growth conditions. As glucose starvation and heat stress are typical challenges in B. subtilis' natural environment and induce both, specific and general stress and starvation proteins, these conditions were selected as models for starvation and stress responses. Analyzing samples from numerous time points along the bacterial growth curve yielded reliable and physiologically relevant data suitable for modeling of cellular regulation under altered growth conditions. The analysis of the adaptational processes based on protein molecules per cell revealed stress-specific modulation of general adaptive responses in terms of protein amount and proteome composition. Furthermore, analysis of protein repartition during glucose starvation showed that biomass seems to be redistributed from proteins involved in amino acid biosynthesis to enzymes of the central carbon metabolism. In contrast, during heat stress most resources of the cell, namely those from amino acid synthetic pathways, are used to increase the amount of chaperones and proteases. Analysis of dynamical aspects of protein synthesis during heat stress adaptation revealed, that these proteins make up almost 30% of the protein mass accumulated during early phases of this stress. PMID:24878497

  2. High-resolution spectroscopy and dynamics of multiphoton processes in atoms and molecules

    NASA Astrophysics Data System (ADS)

    Dehmer, P. M.; Dehmer, J. L.

    1985-06-01

    This report summarizes research on resonantly enhanced multiphoton absorption dissociation, and ionization processes in atoms and molecules. Multiphoton processes are studied using from one to three independently tunable visible and/or UV laser beams in order to establish both the underlying physics and the high degree of selectivity of multiphoton processes. Measurements are made to probe both the formation of excited molecular states and the subsequent behavior of excited states either in the presence or in the abscence of further intense laser radiation. Detection methods include laser-induced fluorescence, ion mass analysis, and electron energy analysis. During the current reporting period, we have studied resonant multiphoton ionization processes for the molecules N2, CO, O2, NO, NeXe, ArXe, KrXe, and Xe2 and for the atoms C, I, and S using both mass spectrometry and photoelectron spectroscopy to analyze the products of the ionizations. In addition, we are developing three new instruments that will provide significantly enhanced resolution, collection efficiency, and versatility in both the ion mass and the electron kinetic energy detection channels.

  3. Development of a field-widened Michelson spectroscopic filter for a polarized near-infrared high spectral resolution lidar

    NASA Astrophysics Data System (ADS)

    Liu, Dong; Yang, Yongying; Cheng, Zhongtao; Ling, Tong; Huang, Hanlu; Zhou, Yudi; Zhang, Qiaoshuang; Zhang, Bo; Shen, Yibing

    2013-09-01

    Standard backscatter lidars encounter problems when solving the two unknowns (aerosol backscatter coefficient and extinction coefficient) from the only one recorded lidar equation. With the help of the high-spectral-resolution filter, high spectral resolution lidars (HSRLs) can provide unambiguous retrieval without critical assumptions. Spectral discrimination between scattering from molecules and aerosols or cloud particles is the basis of the HSRL technique, and several lidar approaches have been developed to obtain this discrimination. Iodine cell filter, which is a kind of atomic/molecular absorption filter, is robust, stable, and can achieve very good separation of aerosol Mie scattering from atmosphere molecular Cabannes scattering. However, absorption filters are lossy and gaseous absorption lines do not exist at many convenient laser wavelengths. Fabry-Perot interferometers are simple and can be tuned to any wavelength, but are limited by acceptance angle. Field-widened Michelson interferometer (FWMI) is considered to have the ability to overcome the deficiencies of the aforementioned filters as it can perform well at relatively large off-axis angles, is nearly lossless, and can be built to any wavelength. In this paper, the development process of an FWMI that is introduced to be the spectroscopic filter for a polarized near-infrared HSRL instrument will be present. The retrieval process of the aerosol optical properties, the design requirements with special focus on the selection of the free spectral range (FSR) of the FWMI, as well as the design result will be described in detail.

  4. Temporal and spacial changes of highly polysialylated neural cell adhesion molecule immunoreactivity in amygdala kindling development.

    PubMed

    Sato, K; Iwai, M; Nagano, I; Shoji, M; Abe, K

    2003-01-01

    To investigate the migration of neural stem cells as well as neural plastic changes in epileptic brain, spaciotemporal expression of immunoreactive highly polysialylated neural cell adhesion molecule (PSA-NCAM) was examined in amygdala kindling development of rat. The neural migration and synaptic remodeling detected with PSA-NCAM staining occurred in dentate gyrus of hippocampus, subventricular zone and pyriform cortex with amygdaloid kindling in generalized seizure but not in partial seizure. Although PSA-NCAM positive dendrite in dentate gyrus was minimally found in the control brain, it extended slightly in animals with partial seizure, and greatly toward the molecular layer with generalized seizure. Thus, the migration of neural stem cells as well as neural plastic changes were specially and temporally different between brain regions depending on different kindling stages. These changes may mainly contribute to the reorganization of neural network in epileptic brain. PMID:12564130

  5. High-Throughput Screening of Small Molecule Ligands Targeted to Live Bacteria Surface

    PubMed Central

    Lee, Jeong Heon; Park, Sunny; Hyun, Hoon; Bordo, Mark W.; Oketokoun, Rafiou; Nasr, Khaled A.; Frangioni, John V.; Choi, Hak Soo

    2013-01-01

    The discovery of small molecule ligands targeted to the surface of live pathogenic bacteria would enable an entirely new class of antibiotics. We report the development and validation of a microarray-based high-throughput screening platform for bacteria that exploits 300 ?m diameter chemical spots in a 1” × 3” nano-layered glass slide format. Using 24 model compounds and 4 different bacterial strains we optimized the screening technology, including fluorophore-based optical deconvolution for automated scoring of affinity and cyan-magenta-yellow-black (CMYK) color-coding for scoring of both affinity and specificity. The latter provides a lossless, one-dimensional view of multidimensional data. By linking in silico analysis with cell binding affinity and specificity, we could also begin to identify the physicochemical factors that affect ligand performance. The technology we describe could form the foundation for developing new classes of antibiotics. PMID:23461528

  6. Field-Induced Anisotropy in Microwave Absorption of HIGH-TcPOWDERS Intercalated by Organic Molecules

    NASA Astrophysics Data System (ADS)

    Grigoryan, L. S.; Chakravarty, N.; Capri, A. Z.

    The room-temperature microwave absorption spectra of the benzene- and nickel phthalocyanine-intercalated powder samples of Bi- and Tl-oxide high-Tc superconductors have been studied. The powder samples become magnetically anisotropic after magnetization by external dc field. Analysis of the angular variations of the microwave absorption spectra of the magnetized powder samples in three-orthogonal planes has shown that the angular curves are asymmetric with respect to the external dc field, indicating that the magnetic moment induced in the sample is not exactly collinear with the external dc field. The origin of the observed anisotropic microwave absorption is tentatively ascribed to the persistent orbital moments, associated with the circulation of ?-electrons within the conjugated rings of the guest organic molecules.

  7. Highly spin-polarized Dirac fermions at the graphene/Co interface

    NASA Astrophysics Data System (ADS)

    Marchenko, D.; Varykhalov, A.; Sánchez-Barriga, J.; Rader, O.; Carbone, C.; Bihlmayer, G.

    2015-06-01

    The interface of graphene with ferromagnets is highly relevant for spintronics, because graphene on Co(0001) shows a largely intact Dirac cone and strong hybridization with Co 3 d states breaking the sublattice symmetry that had been considered mutually exclusive. Here we show by spin- and angle-resolved photoemission that the Dirac cone and Dirac point are also highly spin polarized (˜-25 % ), which reinforces the puzzling issue of a strong graphene-substrate interaction. The problem is solved by our ab initio calculations which show that (i) the upper and lower halves of the Dirac cone belong to different sublattices and (ii) one half is spin polarized by spin-dependent hybridization because it is situated at the edge of a minority-spin band gap of the Co substrate.

  8. Polarization shift keying for high-bit-rate multilevel soliton transmissions

    NASA Astrophysics Data System (ADS)

    Midrio, M.; Franco, P.; Crivellari, M.; Romagnoli, M.; Matera, F.

    1996-07-01

    A novel scheme for high-capacity optical transmission is studied. The proposed system is based on a multilevel modulation technique that uses solitons. The basic idea relies on the property of solitons that the evolution of the state of polarization during propagation can be represented with a good degree of approximation with a rigid rotation of the Poincare sphere. Therefore, besides the rigid rotation that can be compensated for at the receiver, the state of polarization of the signal can be used to carry information. Here the limits of the rigid rotation that are due to polarization mode dispersion and amplified spontaneous emission noise are envisaged. Results show how this scheme permits the transmission-distance limit to be overcome for single-channel intensity-modulated direct-detection soliton systems. As an example we show how a 2.5-Gsymbol / s system with 24 polarization levels leads to a total capacity of 10 Gbits / s over distances up to 3000 km in links encompassing standard dispersion fibers.

  9. High resolution studies of dissociative electron attachment to molecules: dependence on electron and vibrational energy

    NASA Astrophysics Data System (ADS)

    Ruf, M.-W.; Braun, M.; Marienfeld, S.; Fabrikant, I. I.; Hotop, H.

    2007-11-01

    For several molecules which are important for plasma processing and gaseous dielectrics (CF3I, CF3Br, CH3Br, and SF6), we have studied the dependence of dissociative electron attachment (DEA) on both the electron energy and on the initial vibrational energy. With reference to electron swarm data, we determine highly-resolved absolute DEA cross sections over a broad energy range, using the Laser Photoelectron Attachment (LPA) method (E = 0-0.2 eV, ?E ? 1-3 meV) and the EXtended Laser Photoelectron Attachment (EXLPA) method (0-2 eV, ?E ? 15-30 meV). The experimental data are compared with the results of R-matrix calculations, involving ab initioinformation on the potential energy curves and semiempirical autodetachment widths. For CF3I and CF3Br, previous DEA cross sections are found to be substantially too high. For CH3Br, the measurements confirm a predicted vibrational Feshbach resonance, associated with the v3 = 4 vibrational threshold, and the value of the activation energy (due to an intermediate barrier) for this exothermic DEA process. For SF6, we report absolute cross sections for SF6- as well as SF5- formation for vibrational temperatures ranging from 200 to 500 K. Moreover, the first absoluteDEA cross sections (SF5- formation) for CO2-laser excited SF6 molecules have been obtained at different initial vibrational temperatures. The results indicate that the effect of the mode-selective energy input into the v3-mode (predominantly v3 = 1) on the enhancement of SF5- formation is very similar to that of a corresponding rise of the average vibrational energy by thermal heating; at E = 2 meV electron energy, the results indicate an activation energy of about 0.38 eV.

  10. Impact ionization in N-polar AlGaN/GaN high electron mobility transistors

    NASA Astrophysics Data System (ADS)

    Killat, N.; Uren, M. J.; Keller, S.; Kolluri, S.; Mishra, U. K.; Kuball, M.

    2014-08-01

    The existence of impact ionization as one of the open questions for GaN device reliability was studied in N-polar AlGaN/GaN high electron mobility transistors. Electroluminescence (EL) imaging and spectroscopy from underneath the device gate contact revealed the presence of hot electrons in excess of the GaN bandgap energy even at moderate on-state bias conditions, enabling impact ionization with hole currents up to several hundreds of pA/mm. The detection of high energy luminescence from hot electrons demonstrates that EL analysis is a highly sensitive tool to study degradation mechanisms in GaN devices.

  11. Impact ionization in N-polar AlGaN/GaN high electron mobility transistors

    SciTech Connect

    Killat, N., E-mail: Nicole.Killat@bristol.ac.uk, E-mail: Martin.Kuball@bristol.ac.uk; Uren, M. J.; Kuball, M., E-mail: Nicole.Killat@bristol.ac.uk, E-mail: Martin.Kuball@bristol.ac.uk [Center for Device Thermography and Reliability (CDTR), H. H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL (United Kingdom); Keller, S.; Kolluri, S.; Mishra, U. K. [Department of Electrical and Computer Engineering, University of Santa Barbara California, Santa Barbara, California 93106 (United States)

    2014-08-11

    The existence of impact ionization as one of the open questions for GaN device reliability was studied in N-polar AlGaN/GaN high electron mobility transistors. Electroluminescence (EL) imaging and spectroscopy from underneath the device gate contact revealed the presence of hot electrons in excess of the GaN bandgap energy even at moderate on-state bias conditions, enabling impact ionization with hole currents up to several hundreds of pA/mm. The detection of high energy luminescence from hot electrons demonstrates that EL analysis is a highly sensitive tool to study degradation mechanisms in GaN devices.

  12. Electro-absorption and fast electro-optics in highly polar molecular crystals

    Microsoft Academic Search

    Ch. Bosshard; R. Spreiter; P. Günter

    2001-01-01

    Polar organic crystals show great promise for use in photonic devices such as electro-optic amplitude or phase modulators for telecommunication. We discuss the structural requirements for large electro-optic effects and demonstrate through high frequency electro-optic experiments that acoustic phonon contributions to the linear electro-optic effect can be neglected in the crystals presented here. The small effect of acoustic modes was

  13. Electro-optic response of some chiral liquid crystals with high spontaneous polarization

    NASA Astrophysics Data System (ADS)

    Dascalu, Constanta; Motoc, Cornelia; Petrescu, Emil; Rosu, Constantin; Koswig, H. D.; Labes, U.

    1998-07-01

    The electrooptical properties of some SSFLC devices with high spontaneous polarization liquid crystals are presented. The switching time was determined as function of electric field strength and a.c. frequency. Using the switching time the rotational viscosity (gamma) $curly phi was determined. The results are explained by considering the spectacular molecular relaxation, known as Goldstone mode. The surface stabilized ferroelectric liquid crystal (SSFLC) devices offer memory (bistable) capability, fast response speed and sharp threshold and have a variety of applications in electronics.

  14. Superflat high-reflectivity semitransparent polarizer for soft x-ray

    Microsoft Academic Search

    Tsuneyuki Haga; Marcia C. Tinone; Masaru Shimada; Takashi Ohkubo; Akira Ozawa

    1996-01-01

    We have developed semi-transparent multilayer polarizers for polarimetry or ellipsometry in the soft x-ray region. We have studied the fabrication processes to achieve a flat and smooth freestanding reflection surface for high-performance semi-transparent multilayer beam-splitters, mainly the stress control of Mo\\/Si multilayer films and the surface roughness of the support membrane. In this work, we verified that these processes can

  15. Probability density function and detection threshold in high contrast imaging with partially polarized light

    E-print Network

    Yaitskova, Natalia

    2009-01-01

    We obtain an expression for the probability density function (PDF) of partially developed speckles formed by light with an arbitrary degree of polarization. From the probability density we calculate the detection threshold corresponding to the 5sigma confidence level of a normal distribution. We show that unpolarized light has an advantage in high contrast imaging for low ratios of the deterministic part of the point spread function (DL PSF) to the halo, typical in coronagraphy.

  16. Wavelength and polarization dependence of spectral hole-burning efficiency in highly oriented J-aggregates

    Microsoft Academic Search

    Kazuhiko Misawa; Shinjiro Machida; Kazuyuki Horie; Takayoshi Kobayashi

    1995-01-01

    From the concentration dependence of the dichroic spectrum of highly oriented J-aggregates as well as the strong dependences of the spectral hole-burning efficiency on the burning wavelength and polarization, a system of cyanine dye aggregates was concluded to have a hierarchic structure of mesoscopic and macroscopic aggregates. The observed low efficiency, by a factor of 10?3, on the higher-energy side

  17. Separations method for polar molecules

    DOEpatents

    Thoma, Steven G.; Bonhomme, Francois R.

    2004-07-27

    A method for separating at least one compound from a liquid mixture containing different compounds where anew crystalline manganese phosphate composition with the formula Mn.sub.3 (PO.sub.4).sub.4.2(H.sub.3 NCH.sub.2 CH.sub.2).sub.3 N.6(H.sub.2 O) is dispersed in the liquid mixture, selectively intercalating one or more compounds into the crystalline structure of the Mn.sub.3 (PO.sub.4).sub.4.2(H.sub.3 NCH.sub.2 CH.sub.2).sub.3 N.6(H.sub.2 O).

  18. Modulation of polar patches in the high-latitude nightside ionosphere by substorm activity

    NASA Astrophysics Data System (ADS)

    Wood, A. G.; Pryse, S. E.; Moen, J.

    2009-04-01

    Results are presented from a multi-instrument study showing the influence of geomagnetic substorm activity on the spatial distribution of the high-latitude ionospheric plasma. Incoherent scatter radar and radio tomography measurements were used to directly observe the remnants of polar patches in the nightside ionosphere and to investigate their characteristics. The patches occurred under conditions of IMF Bz negative and IMF By negative. They were attributed to dayside photoionisation transported by the high-latitude convection pattern across the polar cap and into the nighttime European sector. The patches on the nightside were separated by some 5° latitude during substorm expansion, but this was reduced to some 2° when the activity had subsided. The different patch separations resulted from the expansion and contraction of the high-latitude plasma convection pattern on the nightside in response to the substorm activity. The patches of larger separation occurred in the antisunward cross-polar flow as it entered the nightside sector. Those of smaller separation were also in antisunward flow, but close to the equatorward edge of the convection pattern, in the slower, diverging flow at the Harang discontinuity. A patch repetition time of some 10 to 30 min was estimated depending on the phase of the substorm.

  19. Low Beat-Noise, Highly Polarized Tunable Fiber Ring Laser H. L. Liu, H. Y. Tam, W. H. Chung,

    E-print Network

    Wai, Ping-kong Alexander

    1 Low Beat-Noise, Highly Polarized Tunable Fiber Ring Laser H. L. Liu, H. Y. Tam, W. H. Chung: A low beat-noise polarized tunable fiber ring laser is reported. The laser utilized a FP-LD to achieve amplifiers and oscillators; (140.3560 ) Lasers, ring 1. Introduction Fiber ring lasers have attracted

  20. High-field Overhauser dynamic nuclear polarization in silicon below the metal-insulator transition.

    PubMed

    Dementyev, Anatoly E; Cory, David G; Ramanathan, Chandrasekhar

    2011-04-21

    Single crystal silicon is an excellent system to explore dynamic nuclear polarization (DNP), as it exhibits a continuum of properties from metallic to insulating as a function of doping concentration and temperature. At low doping concentrations DNP has been observed to occur via the solid effect, while at very high-doping concentrations an Overhauser mechanism is responsible. Here we report the hyperpolarization of (29)Si in n-doped silicon crystals, with doping concentrations in the range of (1-3)?× 10(17) cm(-3). In this regime exchange interactions between donors become extremely important. The sign of the enhancement in our experiments and its frequency dependence suggest that the (29)Si spins are directly polarized by donor electrons via an Overhauser mechanism within exchange-coupled donor clusters. The exchange interaction between donors only needs to be larger than the silicon hyperfine interaction (typically much smaller than the donor hyperfine coupling) to enable this Overhauser mechanism. Nuclear polarization enhancement is observed for a range of donor clusters in which the exchange energy is comparable to the donor hyperfine interaction. The DNP dynamics are characterized by a single exponential time constant that depends on the microwave power, indicating that the Overhauser mechanism is a rate-limiting step. Since only about 2% of the silicon nuclei are located within 1 Bohr radius of the donor electron, nuclear spin diffusion is important in transferring the polarization to all the spins. However, the spin-diffusion time is much shorter than the Overhauser time due to the relatively weak silicon hyperfine coupling strength. In a 2.35 T magnetic field at 1.1 K, we observed a DNP enhancement of 244 ± 84 resulting in a silicon polarization of 10.4 ± 3.4% following 2 h of microwave irradiation. PMID:21513399

  1. Highly polarized light from stable ordered magnetic fields in GRB?120308A.

    PubMed

    Mundell, C G; Kopa?, D; Arnold, D M; Steele, I A; Gomboc, A; Kobayashi, S; Harrison, R M; Smith, R J; Guidorzi, C; Virgili, F J; Melandri, A; Japelj, J

    2013-12-01

    After the initial burst of ?-rays that defines a ?-ray burst (GRB), expanding ejecta collide with the circumburst medium and begin to decelerate at the onset of the afterglow, during which a forward shock travels outwards and a reverse shock propagates backwards into the oncoming collimated flow, or 'jet'. Light from the reverse shock should be highly polarized if the jet's magnetic field is globally ordered and advected from the central engine, with a position angle that is predicted to remain stable in magnetized baryonic jet models or vary randomly with time if the field is produced locally by plasma or magnetohydrodynamic instabilities. Degrees of linear polarization of P???10 per cent in the optical band have previously been detected in the early afterglow, but the lack of temporal measurements prevented definitive tests of competing jet models. Hours to days after the ?-ray burst, polarization levels are low (P?polarization position angle remains stable, changing by no more than 15 degrees over this time, with a possible trend suggesting gradual rotation and ruling out plasma or magnetohydrodynamic instabilities. Instead, the polarization properties show that GRBs contain magnetized baryonic jets with large-scale uniform fields that can survive long after the initial explosion. PMID:24305162

  2. High throughput screen identifies small molecule inhibitors specific for Mycobacterium tuberculosis phosphoserine phosphatase.

    PubMed

    Arora, Garima; Tiwari, Prabhakar; Mandal, Rahul Shubhra; Gupta, Arpit; Sharma, Deepak; Saha, Sudipto; Singh, Ramandeep

    2014-09-01

    The emergence of drug-resistant strains of Mycobacterium tuberculosis makes identification and validation of newer drug targets a global priority. Phosphoserine phosphatase (PSP), a key essential metabolic enzyme involved in conversion of O-phospho-l-serine to l-serine, was characterized in this study. The M. tuberculosis genome harbors all enzymes involved in l-serine biosynthesis including two PSP homologs: Rv0505c (SerB1) and Rv3042c (SerB2). In the present study, we have biochemically characterized SerB2 enzyme and developed malachite green-based high throughput assay system to identify SerB2 inhibitors. We have identified 10 compounds that were structurally different from known PSP inhibitors, and few of these scaffolds were highly specific in their ability to inhibit SerB2 enzyme, were noncytotoxic against mammalian cell lines, and inhibited M. tuberculosis growth in vitro. Surface plasmon resonance experiments demonstrated the relative binding for these inhibitors. The two best hits identified in our screen, clorobiocin and rosaniline, were bactericidal in activity and killed intracellular bacteria in a dose-dependent manner. We have also identified amino acid residues critical for these SerB2-small molecule interactions. This is the first study where we validate that M. tuberculosis SerB2 is a druggable and suitable target to pursue for further high throughput assay system screening. PMID:25037224

  3. Length-dependent thermopower of highly conducting Au-C bonded single molecule junctions.

    PubMed

    Widawsky, J R; Chen, W; Vázquez, H; Kim, T; Breslow, R; Hybertsen, M S; Venkataraman, L

    2013-06-12

    We report the simultaneous measurement of conductance and thermopower of highly conducting single-molecule junctions using a scanning tunneling microscope-based break-junction setup. We start with molecular backbones (alkanes and oligophenyls) terminated with trimethyltin end groups that cleave off in situ to create junctions where terminal carbons are covalently bonded to the Au electrodes. We apply a thermal gradient across these junctions and measure their conductance and thermopower. Because of the electronic properties of the highly conducting Au-C links, the thermoelectric properties and power factor are very high. Our results show that the molecular thermopower increases nonlinearly with the molecular length while conductance decreases exponentially with increasing molecular length. Density functional theory calculations show that a gateway state representing the Au-C covalent bond plays a key role in the conductance. With this as input, we analyze a series of simplified models and show that a tight-binding model that explicitly includes the gateway states and the molecular backbone states accurately captures the experimentally measured conductance and thermopower trends. PMID:23682792

  4. Two-dimensional quantum dots in high magnetic fields: Rotating-electron-molecule versus composite-fermion approach

    E-print Network

    Yannouleas, Constantine

    Two-dimensional quantum dots in high magnetic fields: Rotating-electron-molecule versus composite-fermion electrons in strong mag- netic fields in the range of high angular momenta, 70 L 140 covering, and transport properties specifically, magic angular momenta, radial electron densities, occupation number

  5. Dynamic Two-Center Interference in High-Order Harmonic Generation from Molecules with Attosecond Nuclear Motion

    E-print Network

    Lein, Manfred

    in high-harmonic generation from H2, in which the attosecond nuclear motion of H 2 initiated at ionizationDynamic Two-Center Interference in High-Order Harmonic Generation from Molecules with Attosecond Nuclear Motion S. Baker,1 J. S. Robinson,1 M. Lein,2 C. C. Chirila,2 R. Torres,1 H. C. Bandulet,3 D

  6. Single-molecule detection and radiation control in solutions at high concentrations via a heterogeneous optical slot antenna.

    PubMed

    Zhao, Chenglong; Liu, Yongmin; Yang, Jing; Zhang, Jiasen

    2014-08-01

    We designed a heterogeneous optical slot antenna (OSA) that is capable of detecting single molecules in solutions at high concentrations, where most biological processes occur. A heterogeneous OSA consists of a rectangular nanoslot fabricated on heterogeneous metallic films formed by sequential deposition of gold and aluminum on a glass substrate. The rectangular nanoslot gives rise to large field and fluorescence enhancement for single molecules. The near-field intensity inside a heterogeneous OSA is 170 times larger than that inside an aluminum zero-mode waveguide (ZMW), and the fluorescence emission rate of a molecule inside the heterogeneous OSA is about 70 times higher than that of the molecule in free space. Our proposed heterogeneous optical antenna enables excellent balance between performance and cost. The design takes into account the practical experimental conditions so that the parameters chosen in the simulation are well within the reach of current nano-fabrication technologies. Our results can be used as a direct guidance for designing high-performance, low-cost plasmonic nanodevices for the study of bio-molecule and enzyme dynamics at the single-molecule level. PMID:24976558

  7. Identification of small molecule inhibitors of neurite loss induced by A? peptide using high content screening.

    PubMed

    Ofengeim, Dimitry; Shi, Peng; Miao, Benchun; Fan, Jing; Xia, Xiaofeng; Fan, Yubo; Lipinski, Marta M; Hashimoto, Tadafumi; Polydoro, Manuela; Yuan, Junying; Wong, Stephen T C; Degterev, Alexei

    2012-03-16

    Multiple lines of evidence indicate a strong relationship between ?? peptide-induced neurite degeneration and the progressive loss of cognitive functions in Alzheimer disease (AD) patients and in AD animal models. This prompted us to develop a high content screening assay (HCS) and Neurite Image Quantitator (NeuriteIQ) software to quantify the loss of neuronal projections induced by A? peptide neurons and enable us to identify new classes of neurite-protective small molecules, which may represent new leads for AD drug discovery. We identified thirty-six inhibitors of A?-induced neurite loss in the 1,040-compound National Institute of Neurological Disorders and Stroke (NINDS) custom collection of known bioactives and FDA approved drugs. Activity clustering showed that non-steroidal anti-inflammatory drugs (NSAIDs) were significantly enriched among the hits. Notably, NSAIDs have previously attracted significant attention as potential drugs for AD; however their mechanism of action remains controversial. Our data revealed that cyclooxygenase-2 (COX-2) expression was increased following A? treatment. Furthermore, multiple distinct classes of COX inhibitors efficiently blocked neurite loss in primary neurons, suggesting that increased COX activity contributes to A? peptide-induced neurite loss. Finally, we discovered that the detrimental effect of COX activity on neurite integrity may be mediated through the inhibition of peroxisome proliferator-activated receptor ? (PPAR?) activity. Overall, our work establishes the feasibility of identifying small molecule inhibitors of A?-induced neurite loss using the NeuriteIQ pipeline and provides novel insights into the mechanisms of neuroprotection by NSAIDs. PMID:22277654

  8. High Throughput Screening of Small Molecule Libraries for Modifiers of Radiation Responses

    PubMed Central

    Kim, Kwanghee; Damoiseaux, Robert; Norris, Andrew J.; Rivina, Leena; Bradley, Kenneth; Jung, Michael E.; Gatti, Richard A.; Schiestl, Robert H.; McBride, William H.

    2011-01-01

    Purpose An unbiased approach of drug discovery through high-throughput screening (HTS) of libraries of chemically defined and bioactive small molecule compounds was used to identify modulators of radiation injury with an emphasis on radioprotectors and mitigators rather than radiosensitizers. Assay system endpoints included radiation-induced genotoxicity and DNA damage in yeast and apoptosis in murine lymphocytes. Large-scale data mining of chemically diverse libraries identified agents that were effective with all endpoints. HTS of bioactive compound libraries against murine lymphocytes profiled tetracycline and fluoroquinolone antibiotics and cyclopiazonic acid as having activity, and structure-activity analysis showed a common pharmacophore. Purine nucleosides, the interferon inducer tilorone, and linoleic acid were also identified as potential mitigators of radiation damage that often were also radioprotective. Many of these compounds enhance DNA repair, have anti-inflammatory activity, and stimulate hematopoiesis. Selected compounds within these initial verified hits from both types of libraries identified potent mitigators of lethal whole body irradiation (WBI) in mice. Conclusion In spite of the fact that in vitro HTS has limitations and is unable to fully recapitulate all aspects of the complex in vivo acute radiation response, it identified several classes of molecules that had activity as radioprotectors and radiomitigators of the hematopoietic system in vivo. In the future, addition of 3 dimensional (3D) or stem cell cultures or pathway analysis, may improve the power of HTS, but our findings indicate that common, evolutionary conserved, canonical pathways can be identified that could be exploited to mitigate radiation-induced defects. PMID:21401317

  9. Histamine inhibits high mobility group box 1-induced adhesion molecule expression on human monocytes.

    PubMed

    Takahashi, Hideo; Sadamori, Hiroshi; Teshigawara, Kiyoshi; Niwa, Atsuko; Liu, Keyue; Wake, Hidenori; Mori, Shuji; Yoshino, Tadashi; Nishibori, Masahiro

    2013-10-15

    Cell-cell interaction through binding of adhesion molecules on monocytes to their ligands on T-cells plays roles in cytokine production and lymphocyte proliferation. High mobility group box 1 (HMGB1), an abundant and conserved nuclear protein, acts in the extracellular environment as a primary pro-inflammatory signal. HMGB1 induces expression of intercellular adhesion molecule (ICAM), B7.1, B7.2 and CD40 on monocytes, resulting in production of interferon (IFN)-? and tumor necrosis factor (TNF)-? production and lymphocyte proliferation in human peripheral blood mononuclear cells (PBMCs). Histamine inhibits pro-inflammatory cytokine production via histamine H2-receptors; however, it is not known whether histamine inhibits HMGB1 activity. This study was designed to study the inhibitory effect of histamine on HMGB1 activity. We examined the effect of histamine on HMGB1-induced expression of ICAM-1, B7.1, B7.2 and CD40 on monocytes, production of IFN-? and TNF-? and lymphocyte proliferation in PBMCs. Histamine inhibited HMGB1 activity in a concentration-dependent manner. The effects of histamine were partially ablated by the H2-receptor antagonist, famotidine, and mimicked by the H2/H4-receptor agonists, dimaprit and 4-methylhistamine. Histamine induced cyclic adenosine monophosphate (cAMP) production in the presence and absence of HMGB1. The effects of histamine were reversed by the protein kinase A (PKA) inhibitor, H89, and mimicked by the membrane-permeable cAMP analog, dibutyryl cAMP (dbcAMP), and the adenylate cyclase activator, forskolin. These results together indicated that histamine inhibited HMGB1 activity. PMID:24012904

  10. A Manual Small Molecule Screen Approaching High-throughput Using Zebrafish Embryos

    PubMed Central

    Poureetezadi, Shahram Jevin; Donahue, Eric K.; Wingert, Rebecca A.

    2014-01-01

    Zebrafish have become a widely used model organism to investigate the mechanisms that underlie developmental biology and to study human disease pathology due to their considerable degree of genetic conservation with humans. Chemical genetics entails testing the effect that small molecules have on a biological process and is becoming a popular translational research method to identify therapeutic compounds. Zebrafish are specifically appealing to use for chemical genetics because of their ability to produce large clutches of transparent embryos, which are externally fertilized. Furthermore, zebrafish embryos can be easily drug treated by the simple addition of a compound to the embryo media. Using whole-mount in situ hybridization (WISH), mRNA expression can be clearly visualized within zebrafish embryos. Together, using chemical genetics and WISH, the zebrafish becomes a potent whole organism context in which to determine the cellular and physiological effects of small molecules. Innovative advances have been made in technologies that utilize machine-based screening procedures, however for many labs such options are not accessible or remain cost-prohibitive. The protocol described here explains how to execute a manual high-throughput chemical genetic screen that requires basic resources and can be accomplished by a single individual or small team in an efficient period of time. Thus, this protocol provides a feasible strategy that can be implemented by research groups to perform chemical genetics in zebrafish, which can be useful for gaining fundamental insights into developmental processes, disease mechanisms, and to identify novel compounds and signaling pathways that have medically relevant applications. PMID:25407322

  11. Polarization-Insensitive Wavelength Conversion by FWM in a Highly Nonlinear PCF of Polarization-Scrambled 10Gb\\/s RZ-OOK and RZ-DPSK Signals

    Microsoft Academic Search

    W. Astar; A. S. Lenihan; G. M. Carter

    2007-01-01

    Wavelength conversion of polarization-scrambled 10-Gb\\/s on-off keyed and differential phase-shift-keyed signals for which the pulse format was 33% return-to-zero, has been achieved by partially degenerate four-wave mixing in a record 20-m-short highly nonlinear photonic crystal fiber. It was found that a minimum pump-probe detuning of ~9 nm was required to achieve polarization-insensitive wavelength conversion of <1 dB, resulting in a

  12. How cytochrome c oxidase can pump four protons per oxygen molecule at high electrochemical gradient.

    PubMed

    Blomberg, Margareta R A; Siegbahn, Per E M

    2015-03-01

    Experiments have shown that the A-family cytochrome c oxidases pump four protons per oxygen molecule, also at a high electrochemical gradient. This has been considered a puzzle, since two of the reduction potentials involved, Cu(II) and Fe(III), were estimated from experiments to be too low to afford proton pumping at a high gradient. The present quantum mechanical study (using hybrid density functional theory) suggests a solution to this puzzle. First, the calculations show that the charge compensated Cu(II) potential for CuB is actually much higher than estimated from experiment, of the same order as the reduction potentials for the tyrosyl radical and the ferryl group, which are also involved in the catalytic cycle. The reason for the discrepancy between theory and experiment is the very large uncertainty in the experimental observations used to estimate the equilibrium potentials, mainly caused by the lack of methods for direct determination of reduced CuB. Second, the calculations show that a high energy metastable state, labeled EH, is involved during catalytic turnover. The EH state mixes the low reduction potential of Fe(III) in heme a3 with another, higher potential, here suggested to be that of the tyrosyl radical, resulting in enough exergonicity to allow proton pumping at a high gradient. In contrast, the corresponding metastable oxidized state, OH, is not significantly higher in energy than the resting state, O. Finally, to secure the involvement of the high energy EH state it is suggested that only one proton is taken up via the K-channel during catalytic turnover. PMID:25529353

  13. Optical properties of side-polished polarization maintaining fiber coupled with a high index planar waveguide

    NASA Astrophysics Data System (ADS)

    Kim, Kwang Taek; Yoon, Dae Sung; Kwoen, Gyeong-il

    2004-01-01

    We have investigated the behavior of an asymmetric directional coupler made of a side-polished polarization maintaining (PM) fiber covered with a high index planar waveguide (PWG). The effects of the modal birefringence of the side-polished PM fiber, the structural parameters of PWG and the deformation of the PM fiber on the transmission characteristics of the coupler has been measured and explained. Experimental results show that the coincidence of resonance wavelengths for transverse electric and transverse magnetic polarizations can be achieved through proper control of device parameters. Furthermore, the fabricated devices revealed a superior immunity to deformation of PM fibers. The device fabrication procedure, particularly, alignment of the birefringence axis with PWG is described in detail.

  14. Femtosecond laser pumped by high-brightness coherent polarization locked diodes.

    PubMed

    Purnawirman; Phua, P B

    2011-08-01

    We demonstrate, for the first time to our knowledge, the use of a coherent polarization locked diode as the high-brightness pump source for a femtosecond laser. Four diode emitters are coherently locked to produce more than 5 W linearly polarized, narrow linewidth, and single-lobed pump beam. This gives >10× brightness improvement over the conventional diode array. The diode beam is then used to pump a Yb:KYW laser to obtain 2 W output with 57% slope efficiency in cw laser operation. By using a saturable absorber mirror, we achieved cw mode-locking operation with a 177 fs pulse width at an average power of 0.55 W. PMID:21808316

  15. High Performance Polarized Electron Photocathodes Based on InGaAlAs/AlGaAs Superlattices

    SciTech Connect

    Mamaev, Yu.

    2004-12-10

    Highly efficient emitters of polarized electrons based on the InAlGaAs/AlGaAs superlattice give an optimistic prognosis to explorations of such structures as the sources for accelerators. A new set of these SL structures with minimized conduction band offset was designed and recently tested. A new technology of surface protection in MBE growth leads to a significantly reduced heat-cleaning temperature. At these lowered cleaning temperatures, the thermal degradation of the working structure parameters is avoided. As a result a polarization P of up to 91% at corresponding quantum efficiency (QE) of 0.3% was achieved at room temperature. A 50% increase in the photocathode lifetime has been achieved with Sb coverage.

  16. Micro injector sample delivery system for charged molecules

    DOEpatents

    Davidson, James C. (Livermore, CA); Balch, Joseph W. (Livermore, CA)

    1999-11-09

    A micro injector sample delivery system for charged molecules. The injector is used for collecting and delivering controlled amounts of charged molecule samples for subsequent analysis. The injector delivery system can be scaled to large numbers (>96) for sample delivery to massively parallel high throughput analysis systems. The essence of the injector system is an electric field controllable loading tip including a section of porous material. By applying the appropriate polarity bias potential to the injector tip, charged molecules will migrate into porous material, and by reversing the polarity bias potential the molecules are ejected or forced away from the tip. The invention has application for uptake of charged biological molecules (e.g. proteins, nucleic acids, polymers, etc.) for delivery to analytical systems, and can be used in automated sample delivery systems.

  17. A novel high-throughput scanning microscope for label-free detection of protein and small-molecule chemical microarrays

    E-print Network

    Zhu, Xiangdong

    A novel high-throughput scanning microscope for label-free detection of protein and small January 2008 We describe a novel scanning optical microscope based on a polarization-modulated nulling ellipsometry. The new microscope employs a combination of scanning mirror and sample translation and thus

  18. Dietary flavonoid apigenin inhibits high glucose and tumor necrosis factor alpha-induced adhesion molecule expression in human endothelial cells.

    PubMed

    Yamagata, Kazuo; Miyashita, Akinori; Matsufuji, Hiroshi; Chino, Makoto

    2010-02-01

    Diabetes mellitus is associated with increased endothelial dysfunction and development of atherosclerotic vascular diseases. In contrast, an increased intake of dietary flavonoids is associated with a decreased risk of cardiovascular diseases. Here we demonstrate that high glucose (HG) and tumor necrosis factor alpha (TNFalpha) result in the expression of adhesion molecules and junctional molecules on endothelial cells (EC) within a short time. Simultaneously, we examined the regulatory effects of several dietary flavonoids. We demonstrated the short-term expression of adhesion molecules in a human EC line cultured with normal glucose (5.5 mM), HG (30 mM) and TNFalpha (10 ng/ml) by reverse transcription-polymerase chain reaction (RT-PCR), immunocytochemistry and adhesion assay. The expression of intercellular adhesion molecule-1 (ICAM1) and vascular cell adhesion molecule-1 (VCAM1) increased, but that of occludin decreased. Apigenin strongly inhibited the expression of VCAM1, IkappaB kinase (IKK) alpha and IKKepsilon/IKKi, and suppressed the adhesion of U937 cells. From the structure and inhibitory activity of several dietary flavonoids, it was recognized that a double bond between apigenin and the third hydroxyl group was required for inhibition of gene expression. HG and TNFalpha induced the expression of cell adhesion molecules and reduced that of occludin in EC. These flavonoids modified the expression of cloudin 5 and occludin. These results demonstrated that apigenin inhibits HG- and TNFalpha-induced adhesion molecule expression and that flavonoids regulate the expression of junctional molecules in human EC. It is suggested that apigenin inhibited the expression of several genes through inhibition of IKKs. PMID:19195861

  19. High-quality source of fiber-coupled polarization-entangled photons at 1.56 [mu]m

    E-print Network

    Stelmakh, Veronika

    2012-01-01

    This thesis describes the development of a high-quality source of single-mode fibercoupled polarization-entangled photon pairs based on a collinear spontaneous parametric down-conversion process in a bidirectionally pumped ...

  20. Highly polarization-dependent periodic coupling in mechanically induced long period grating over air-silica fibers

    NASA Astrophysics Data System (ADS)

    Lee, D.; Jung, Y.; Jeong, Y. S.; Oh, K.; Kobelke, J.; Schuster, K.; Kirchhof, J.

    2006-02-01

    A very flexible and versatile tunable mechanical grating platform is introduced, with which highly polarization-dependent mode coupling is observed for three types of air-silica microstructured fibers: hollow core fiber, hexagonal-boundary holey fiber (HHF), and circular-boundary holey fiber. The resonances of gratings showed highly polarization-dependent broadband coupling compared with conventional single-mode fibers due to their unique beat-length dispersions between the core and the cladding modes, which could find applications in wideband polarization-dependent loss compensation. We further present significance of the spatial symmetry of HHF in distinct mode coupling for different rotation angles around the fiber axis.

  1. Theory of effect of near-infrared laser polarization direction on high-order terahertz sideband generation in semiconductors.

    PubMed

    Liu, Houquan; She, Weilong

    2015-04-20

    In a semiconductor illuminated by a strong terahertz (THz) field, the electron-hole pairs excited by linear polarized near-infrared (NIR) laser can recombine to emit high-order THz sideband. Previous experimental results have shown, under the same condition of excitation intensity, the polarization direction of the NIR laser could affect the sideband intensity. In this letter, we theoretically investigate the effect of the NIR laser polarization direction on high-order terahertz sideband generation in bulk GaAs. PMID:25969106

  2. STEREO observations of quasi-periodically driven high velocity outflows in polar plumes

    NASA Astrophysics Data System (ADS)

    McIntosh, S. W.; Innes, D. E.; de Pontieu, B.; Leamon, R. J.

    2010-02-01

    Context. Plumes are one of the most ubiquitous features seen at the limb in polar coronal holes and are considered to be a source of high density plasma streams to the fast solar wind. Aims: We analyze STEREO observations of plumes and aim to reinterpret and place observations with previous generations of EUV imagers within a new context that was recently developed from Hinode observations. Methods: We exploit the higher signal-to-noise, spatial and temporal resolution of the EUVI telescopes over that of SOHO/EIT to study the temporal variation of polar plumes in high detail. We employ recently developed insight from imaging (and spectral) diagnostics of active region, plage, and quiet Sun plasmas to identify the presence of apparent motions as high-speed upflows in magnetic regions as opposed to previous interpretations of propagating waves. Results: In almost all polar plumes observed at the limb in these STEREO sequences, in all coronal passbands, we observe high speed jets of plasma traveling along the structures with a mean velocity of 135 km s-1 at a range of temperatures from 0.5-1.5 MK. The jets have an apparent brightness enhancement of ~5% above that of the plumes they travel on and repeat quasi-periodically, with repeat-times ranging from five to twenty-five minutes. We also notice a very weak, fine scale, rapidly evolving, but ubiquitous companion of the plumes that covers the entire coronal hole limb. Conclusions: The observed jets are remarkably similar in intensity enhancement, periodicity and velocity to those observed in other magnetic regions of the solar atmosphere. They are multi-thermal in nature. We infer that the jets observed on the plumes are a source of heated mass to the fast solar wind. Further, based on the previous results that motivated this study, we suggest that these jets originated in the upper chromosphere. Five movies are only available in electronic form at http://www.aanda.org

  3. High-frequency microstrip cross resonators for circular polarization electron paramagnetic resonance spectroscopy

    NASA Astrophysics Data System (ADS)

    Henderson, J. J.; Ramsey, C. M.; Quddusi, H. M.; del Barco, E.

    2008-07-01

    In this article we discuss the design and implementation of a novel microstrip resonator which allows absolute control of the microwaves polarization degree for frequencies up to 30 GHz. The sensor is composed of two half-wavelength microstrip line resonators, designed to match the 50 ? impedance of the lines on a high dielectric constant GaAs substrate. The line resonators cross each other perpendicularly through their centers, forming a cross. Microstrip feed lines are coupled through small gaps to three arms of the cross to connect the resonator to the excitation ports. The control of the relative magnitude and phase between the two microwave stimuli at the input ports of each line allows for tuning the degree and type of polarization of the microwave excitation at the center of the cross resonator. The third (output) port is used to measure the transmitted signal, which is crucial to work at low temperatures, where reflections along lengthy coaxial lines mask the signal reflected by the resonator. Electron paramagnetic resonance spectra recorded at low temperature in an S =5/2 molecular magnet system show that 82% fidelity circular polarization of the microwaves is achieved over the central area of the resonator.

  4. Polarization of 3 He, D 2 and (eventually) 129 Xe Using Low Temperatures and High Magnetic Fields

    Microsoft Academic Search

    G. Frossati

    1998-01-01

    The recent discovery that inhaling polarized3He or129Xe allows high resolution MRI images of the lungs to be made is having a large impact among the medical and physics communities. In fact, this technique could become the first high resolution, harmless diagnostic tool for several lung diseases. Neutron–lean nuclear fusion would also benefit from the use of polarized fuel (D,3He) through

  5. Combined versatile high-resolution optical tweezers and single-molecule fluorescence microscopy

    PubMed Central

    Sirinakis, George; Ren, Yuxuan; Gao, Ying; Xi, Zhiqun; Zhang, Yongli

    2012-01-01

    Optical trapping and single-molecule fluorescence are two major single-molecule approaches. Their combination has begun to show greater capability to study more complex systems than either method alone, but met many fundamental and technical challenges. We built an instrument that combines base-pair resolution dual-trap optical tweezers with single-molecule fluorescence microscopy. The instrument has complementary design and functionalities compared with similar microscopes previously described. The optical tweezers can be operated in constant force mode for easy data interpretation or in variable force mode for maximum spatiotemporal resolution. The single-molecule fluorescence detection can be implemented in either wide-field or confocal imaging configuration. To demonstrate the capabilities of the new instrument, we imaged a single stretched ? DNA molecule and investigated the dynamics of a DNA hairpin molecule in the presence of fluorophore-labeled complementary oligonucleotide. We simultaneously observed changes in the fluorescence signal and pauses in fast extension hopping of the hairpin due to association and dissociation of individual oligonucleotides. The combined versatile microscopy allows for greater flexibility to study molecular machines or assemblies at a single-molecule level. PMID:23020384

  6. Collision dynamics of methyl radicals and highly vibrationally excited molecules using crossed molecular beams

    SciTech Connect

    Chu, P.M.Y.

    1991-10-01

    The vibrational to translational (V{yields}T) energy transfer in collisions between large highly vibrationally excited polyatomics and rare gases was investigated by time-of-flight techniques. Two different methods, UV excitation followed by intemal conversion and infrared multiphoton excitation (IRMPE), were used to form vibrationally excited molecular beams of hexafluorobenzene and sulfur hexafluoride, respectively. The product translational energy was found to be independent of the vibrational excitation. These results indicate that the probability distribution function for V{yields}T energy transfer is peaked at zero. The collisional relaxation of large polyatomic molecules with rare gases most likely occurs through a rotationally mediated process. Photodissociation of nitrobenzene in a molecular beam was studied at 266 nm. Two primary dissociation channels were identified including simple bond rupture to produce nitrogen dioxide and phenyl radical and isomerization to form nitric oxide and phenoxy radical. The time-of-flight spectra indicate that simple bond rupture and isomerization occurs via two different mechanisms. Secondary dissociation of the phenoxy radicals to carbon monoxide and cyclopentadienyl radicals was observed as well as secondary photodissociation of phenyl radical to give H atom and benzyne. A supersonic methyl radical beam source is developed. The beam source configuration and conditions were optimized for CH{sub 3} production from the thermal decomposition of azomethane. Elastic scattering of methyl radical and neon was used to differentiate between the methyl radicals and the residual azomethane in the molecular beam.

  7. Photoisomerization dynamics of a rhodopsin-based molecule (potential molecular switch) with high quantum yields

    NASA Astrophysics Data System (ADS)

    Allen, Roland; Jiang, Chen-Wei; Zhang, Xiu-Xing; Fang, Ai-Ping; Li, Hong-Rong; Xie, Rui-Hua; Li, Fu-Li

    2015-03-01

    It is worthwhile to explore the detailed reaction dynamics of various candidates for molecular switches, in order to understand, e.g., the differences in quantum yields and switching times. Here we report density-functional-based simulations for the rhodopsin-based molecule 4-[4-Methylbenzylidene]-5-p-tolyl-3,4-dihydro-2H-pyrrole (MDP), synthesized by Sampedro et al. We find that the photoisomerization quantum yields are remarkably high: 82% for cis-to-trans, and 68% for trans-to-cis. The lifetimes of the S1 excited state in cis-MDP in our calculations are in the range of 900-1800 fs, with a mean value of 1270 fs, while the range of times required for full cis-to-trans isomerization are 1100-2000 fs, with a mean value of 1530 fs. In trans-MDP, the calculated S1 excited state lifetimes are 860-2140 fs, with a mean value of 1330 fs, and with the full trans-to-cis isomerization completed about 200 fs later. In both cases, the dominant reaction mechanism is rotation around the central C =C bond (connected to the pyrroline ring), and de-excitation occurs at an avoided crossing between the ground state and the lowest singlet state, near the midpoint of the rotational pathway. Research Fund for the Doctoral Program of Higher Education of China; Fundamental Research Funds for the Central Universities; Robert A. Welch Foundation; National Natural Science Foundation of China.

  8. Identification of Small-Molecule Frequent Hitters from AlphaScreen High-Throughput Screens

    PubMed Central

    Schorpp, Kenji; Rothenaigner, Ina; Salmina, Elena; Reinshagen, Jeanette; Low, Terence; Brenke, Jara K.; Gopalakrishnan, Jay; Tetko, Igor V.; Gul, Sheraz

    2014-01-01

    Although small-molecule drug discovery efforts have focused largely on enzyme, receptor, and ion-channel targets, there has been an increase in such activities to search for protein-protein interaction (PPI) disruptors by applying high-throughout screening (HTS)–compatible protein-binding assays. However, a disadvantage of these assays is that many primary hits are frequent hitters regardless of the PPI being investigated. We have used the AlphaScreen technology to screen four different robust PPI assays each against 25,000 compounds. These activities led to the identification of 137 compounds that demonstrated repeated activity in all PPI assays. These compounds were subsequently evaluated in two AlphaScreen counter assays, leading to classification of compounds that either interfered with the AlphaScreen chemistry (60 compounds) or prevented the binding of the protein His-tag moiety to nickel chelate (Ni2+-NTA) beads of the AlphaScreen detection system (77 compounds). To further triage the 137 frequent hitters, we subsequently confirmed by a time-resolved fluorescence resonance energy transfer assay that most of these compounds were only frequent hitters in AlphaScreen assays. A chemoinformatics analysis of the apparent hits provided details of the compounds that can be flagged as frequent hitters of the AlphaScreen technology, and these data have broad applicability for users of these detection technologies. PMID:24371213

  9. High-throughput single-molecule force spectroscopy for membrane proteins

    NASA Astrophysics Data System (ADS)

    Bosshart, Patrick D.; Casagrande, Fabio; Frederix, Patrick L. T. M.; Ratera, Merce; Bippes, Christian A.; Müller, Daniel J.; Palacin, Manuel; Engel, Andreas; Fotiadis, Dimitrios

    2008-09-01

    Atomic force microscopy-based single-molecule force spectroscopy (SMFS) is a powerful tool for studying the mechanical properties, intermolecular and intramolecular interactions, unfolding pathways, and energy landscapes of membrane proteins. One limiting factor for the large-scale applicability of SMFS on membrane proteins is its low efficiency in data acquisition. We have developed a semi-automated high-throughput SMFS (HT-SMFS) procedure for efficient data acquisition. In addition, we present a coarse filter to efficiently extract protein unfolding events from large data sets. The HT-SMFS procedure and the coarse filter were validated using the proton pump bacteriorhodopsin (BR) from Halobacterium salinarum and the L-arginine/agmatine antiporter AdiC from the bacterium Escherichia coli. To screen for molecular interactions between AdiC and its substrates, we recorded data sets in the absence and in the presence of L-arginine, D-arginine, and agmatine. Altogether ~400 000 force-distance curves were recorded. Application of coarse filtering to this wealth of data yielded six data sets with ~200 (AdiC) and ~400 (BR) force-distance spectra in each. Importantly, the raw data for most of these data sets were acquired in one to two days, opening new perspectives for HT-SMFS applications.

  10. Polarization developments

    SciTech Connect

    Prescott, C.Y.

    1993-07-01

    Recent developments in laser-driven photoemission sources of polarized electrons have made prospects for highly polarized electron beams in a future linear collider very promising. This talk discusses the experiences with the SLC polarized electron source, the recent progress with research into gallium arsenide and strained gallium arsenide as a photocathode material, and the suitability of these cathode materials for a future linear collider based on the parameters of the several linear collider designs that exist.

  11. A High Content Screening Approach to Identify Molecules Neuroprotective for Photoreceptor Cells

    PubMed Central

    Shaw, Gillian C.; Bonnet-Wersinger, Delphine; Hansen, Baranda S.; Berlinicke, Cynthia A.; Inglese, James; Zack, Donald J.

    2014-01-01

    Purpose Retinal degenerations are a heterogeneous group of diseases in which there is slow but progressive loss of photoreceptors (PR). There are currently no approved therapies for treating retinal degenerations. In an effort to identify novel small molecules that are (1) neuroprotective and (2) promote PR differentiation, we have developed microscale (1,536 well) cell culture assays using primary retinal neurons. Methods Primary murine retinal cells are isolated, seeded, treated with a 1,280 compound chemical library in a 7 point titration and then cultured under conditions developed to assay protection against an introduced stress or enhance PR differentiation. In the protection assays a chemical insult is introduced and viability assessed after 72 h using CellTiterGlo, a single-step chemiluminescent reagent. In the differentiation assay, cells are isolated from the rhodopsin-GFP knock-in mouse and PR differentiation is assessed by fixing cells after 21 days in culture and imaging with the Acumen plate-based laser cytometer (TTP Labtech) to determine number and intensity of GFP-expressing cells. Positive wells are re-imaged at higher resolution with an INCell2000 automated microscope (GE). Concentration-response curves are generated to pharmacologically profile each compound and hits identified by xx. Results We have developed PR differentiation and neuroprotection assays with a signal to background (S/B) ratios of 11 and 3, and a coefficient of variation (CV) of 20 and 9 %, suitable for chemical screening. Staurosporine has been shown in our differentiation assay to simultaneously increase the number of rhodopsin positive objects while decreasing the mean rhodopsin intensity and punctate rhodopsin fluorescent objects. Conclusions Using primary murine retinal cells, we developed high throughput assays to identify small molecules that influence PR development and survival. By screening multiple compound concentrations, dose-response curves can be generated, and the false negative rate minimized. It is hoped that this work will identify both potential preclinical candidates as well as molecular probes that will be useful for analysis of the molecular mechanisms that promote PR differentiation and survival. PMID:24664770

  12. Highly spin-polarized electron emission from InGaAlAs strained layer with enlarged effective negative electron affinity

    NASA Astrophysics Data System (ADS)

    Mamaev, Yuri A.; Drouhin, Henri-Jean; Lampel, G.; Subashiev, Arsen V.; Yashin, Yuri P.; Roshchansky, Alexander

    2003-10-01

    Integrated polarization and quantum yield spectra of the electrons, photoemitted from strained AlInGaAs layer, capped by heavily doped thin GaAs quantum well layer, as well as high resolution energy distriubtion curves and a polarization versus energy distribution curves are studied as a function fo light excitation energy and power. The polarization P of up to 83% in conjunction with quantum yield Y=0.5 at T=130K have been measured. At high excitation intensity decrease of Y and P is observed which is attributed to the surface photovoltage effects, i.e. decrease of the negative electron affinity, narrowing of the band-bending region and an increase of the hole concentration in the quatnum well layer. The narrow-band quantum well is shown to provide high effective negative electron afffinity values with no harm to electron polarization.

  13. Introducing Bond-Line Organic Structures in High School Biology: An Activity that Incorporates Pleasant-Smelling Molecules

    ERIC Educational Resources Information Center

    Rios, Andro C.; French, Gerald

    2011-01-01

    Chemical education occurs in settings other than just the chemistry classroom. High school biology courses are frequently where students are introduced to organic molecules and their importance to cellular chemistry. However, structural representations are often intimidating because students have not been introduced to the language. As part of a…

  14. High-Resolution Waveguide THz Spectroscopy of Biological Molecules N. Laman,* S. Sree Harsha,* D. Grischkowsky,* and Joseph S. Melingery

    E-print Network

    High-Resolution Waveguide THz Spectroscopy of Biological Molecules N. Laman,* S. Sree Harsha,* D and terahertz time- domain spectroscopy (THz-TDS) often result in broad, overlapping features that are difficult to distinguish. The technique of waveguide THz-TDS has been recently developed, resulting in sharper features

  15. High spin-polarization in ultrathin Co2MnSi/CoPd multilayers

    NASA Astrophysics Data System (ADS)

    Galanakis, I.

    2015-03-01

    Half-metallic Co2MnSi finds a broad spectrum of applications in spintronic devices either in the form of thin films or as spacer in multilayers. Using state-of-the-art ab-initio electronic structure calculations we exploit the electronic and magnetic properties of ultrathin Co2MnSi/CoPd multilayers. We show that these heterostructures combine high values of spin-polarization at the Co2MnSi spacer with the perpendicular magnetic anisotropy of binary compounds such as CoPd. Thus they could find application in spintronic/magnetoelectronic devices.

  16. High-quality fiber-optic polarization entanglement distribution at 1.3 microm telecom wavelength.

    PubMed

    Zhong, Tian; Hu, Xiaolong; Wong, Franco N C; Berggren, Karl K; Roberts, Tony D; Battle, Philip

    2010-05-01

    We demonstrate high-quality distribution of 1.3 microm polarization-entangled photons generated from a fiber-coupled periodically poled KTiOPO(4) waveguide over 200 m fiber-optic cables. Time-multiplexed measurements with a 19% efficient superconducting nanowire single-photon detector at the remote location show a detected flux of 5.8 pairs/s at a pump power of 25 microW and an average two-photon quantum-interference visibility of 97.7% without subtraction of accidentals. PMID:20436580

  17. Compton Scattering off Polarized Electrons with a High Finesse Fabry-Perot Cavity at JLAB

    SciTech Connect

    Nicholas Falletto; M. Authier; G. Bardin; Maud Baylac; M. Boyer; F. Bugeon; Etienne Burtin; Christian Cavata; N. Colombel; G. Congretel; R. Coquillard; G. Coulloux; B. Couzy; P. Deck; A. Delbart; D. Desforges; A. Donati; B. Duboue; Stephanie Escoffier; F. Farci; Bernard Frois; P. Girardot; J. Guillotau; C. Henriot; J. Jardillier; C. Jeanney; M. Juillard; J.P. Jorda; P. Legou; David Lhuillier; Y. Lussignol; P. Mangeot; X. Martin; F. Marie; Jacques Martino; M. Maurier; B. Mazeau; J.F. Millot; F. Molinie; J.P. Mols; J.P. Mouly; M. Mur; Damian Neyret; T. Pedrol; Stephane Platchkov; G. Pontet; Thierry Pussieux; Y. Queinec; P. Rebourgeard; J.C. Sellier; G. Tarte; C. Veyssiere; A. Zakharian; Pierre Bertin; Joseph Mitchell; J.M. Mackowski; L. Pinard

    2000-08-01

    We built and commissioned a new type of Compton polarimeter to measure the electron beam polarization at the Thomas Jefferson National Accelerator Facility (Virginia, USA). The heart of this polarimeter is a high-finesse monolithic Fabry-Perot cavity. Its purpose is to amplify a primary 300 mW laser beam in order to improve the signal to noise ratio of the polarimeter. It is the first time that a high-finesse Fabry-Perot cavity is enclosed in the vacuum of a particle accelerator to monitor the beam polarization by Compton polarimetry. The measured finesse and amplification gain of the cavity are F=26000 and G=7300. The electron beam crosses this high-power photon source at an angle of 23 mrad in the middle of the cavity where the photon beam power density is estimated to be 0.85MW/cm2. We have used this facility during the HAPPEX experiment (April-July 1999) and we give a preliminary measurement of Compton scattering asymmetry.

  18. Study of a Polar Sigma-Delta Transmitter associated to a High Efficiency Switched Mode Power Amplifier for Mobile WiMax

    E-print Network

    Paris-Sud XI, Université de

    Study of a Polar Sigma-Delta Transmitter associated to a High Efficiency Switched Mode Power -- This paper presents the analysis and simulation of a high efficiency transmitter combining a polar sigma the amplifier was associated to the polar transmitter to analyze the overall performances. Results confirm

  19. Ultra high-throughput single molecule spectroscopy with a 1024 pixel SPAD

    E-print Network

    Michalet, Xavier

    , structural biochemistry, and single-protein tracking in live cells, yielding insights into outstanding@chem.ucla.edu, Phone: 1-310-794-6693, Fax: 1-310-267-4672 Invited Paper Single Molecule Spectroscopy and Imaging IV

  20. High-order-harmonic generation in homonuclear and heteronuclear diatomic molecules: Exploration of multiple orbital contributions

    E-print Network

    Heslar, John; Telnov, Dmitry A.; Chu, Shih-I

    2011-04-22

    -electron nonperturbative investigation of HHG processes of homonuclear (N2 and F2) and heteronuclear (CO, BF, and HF) molecules in intense ultrashort laser pulses with the emphasis on the role of multiple molecular orbitals (MOs). The results reveal intriguing...

  1. Influence of ionization suppression on high-harmonic generation in molecules: Dependence of cutoff energy on driver wavelength

    NASA Astrophysics Data System (ADS)

    Li, Guihua; Yao, Jinping; Zhang, Haisu; Jing, Chenrui; Zeng, Bin; Chu, Wei; Ni, Jielei; Xie, Hongqiang; Liu, Xiaojun; Chen, Jing; Cheng, Ya; Xu, Zhizhan

    2013-10-01

    We experimentally investigate high-order-harmonic generation (HHG) of diatomic molecules (O2, N2) and their companion atoms (Xe, Ar, respectively, which are of nearly the same ionization potentials as the corresponding molecules) with midinfrared femtosecond laser pulses. It is found that the cutoff of O2 extends to higher energy as compared to that of Xe, and the extension of cutoff energy of O2 depends on the driver wavelength. Our theoretical analysis shows that the ionization suppression induced by two-center interference should be responsible for the harmonic cutoff extension of O2.

  2. A molecular dynamics simulation of the destruction of explosive molecules at high-velocity collisions

    Microsoft Academic Search

    A. A. Selezenev; A. Yu. Aleinikov; I. V. Briginas

    2008-01-01

    The infrared spectra and the energies of dissociation of R-NO2 bonds (R?C, N, and O) were calculated for explosive molecules (trinitrotoluene, hexogen, octogen, pentaerythrityl tetranitrate,\\u000a triaminotrinitrobenzene, and nitromethane). The time of kinetic energy redistribution over intramolecular vibrational modes\\u000a for these molecules (the V-V relaxation time) was calculated by the molecular dynamics simulation method. Molecular dynamics simulations were also used\\u000a to

  3. Thermodynamics of Long Supercoiled Molecules: Insights from Highly Efficient Monte Carlo Simulations.

    PubMed

    Lepage, Thibaut; Képès, François; Junier, Ivan

    2015-07-01

    Supercoiled DNA polymer models for which the torsional energy depends on the total twist of molecules (Tw) are a priori well suited for thermodynamic analysis of long molecules. So far, nevertheless, the exact determination of Tw in these models has been based on a computation of the writhe of the molecules (Wr) by exploiting the conservation of the linking number, Lk=Tw+Wr, which reflects topological constraints coming from the helical nature of DNA. Because Wr is equal to the number of times the main axis of a DNA molecule winds around itself, current Monte Carlo algorithms have a quadratic time complexity, O(L(2)), with respect to the contour length (L) of the molecules. Here, we present an efficient method to compute Tw exactly, leading in principle to algorithms with a linear complexity, which in practice is O(L(1.2)). Specifically, we use a discrete wormlike chain that includes the explicit double-helix structure of DNA and where the linking number is conserved by continuously preventing the generation of twist between any two consecutive cylinders of the discretized chain. As an application, we show that long (up to 21 kbp) linear molecules stretched by mechanical forces akin to magnetic tweezers contain, in the buckling regime, multiple and branched plectonemes that often coexist with curls and helices, and whose length and number are in good agreement with experiments. By attaching the ends of the molecules to a reservoir of twists with which these can exchange helix turns, we also show how to compute the torques in these models. As an example, we report values that are in good agreement with experiments and that concern the longest molecules that have been studied so far (16 kbp). PMID:26153710

  4. Polar-fluoropolymer blends with tailored nanostructures for high energy density low loss capacitor applications

    NASA Astrophysics Data System (ADS)

    Wu, Shan; Lin, Minren; Lu, S. G.; Zhu, Lei; Zhang, Q. M.

    2011-09-01

    A polar-fluoropolymer blend consisting of a high energy density poly(vinylidene fluoride-chlorotrifluoroethylene) (P(VDF-CTFE)) and a low dielectric loss poly(ethylene-chlorotrifluoroethylene) (ECTFE) was developed. Both the blend and crosslinked blend films exhibit a dielectric constant of 7 and low loss (˜1%), as expected from the classical composite theory. Moreover, introducing crosslinking in the blends can lead to a marked reduction of losses in blend films at high fields while maintaining a high energy density. At 250 MV/m, a loss of 3% can be achieved in the crosslinked blend compared with 7% loss in pure blend, which is already much below that of neat P(VDF-CTFE) (˜35%).

  5. Screening small-molecule compound microarrays for protein ligands without fluorescence labeling with a high-throughput scanning microscope

    NASA Astrophysics Data System (ADS)

    Fei, Yiyan; Landry, James P.; Sun, Yungshin; Zhu, Xiangdong; Wang, Xiaobing; Luo, Juntao; Wu, Chun-Yi; Lam, Kit S.

    2010-01-01

    We describe a high-throughput scanning optical microscope for detecting small-molecule compound microarrays on functionalized glass slides. It is based on measurements of oblique-incidence reflectivity difference and employs a combination of a y-scan galvometer mirror and an x-scan translation stage with an effective field of view of 2 cm×4 cm. Such a field of view can accommodate a printed small-molecule compound microarray with as many as 10,000 to 20,000 targets. The scanning microscope is capable of measuring kinetics as well as endpoints of protein-ligand reactions simultaneously. We present the experimental results on solution-phase protein reactions with small-molecule compound microarrays synthesized from one-bead, one-compound combinatorial chemistry and immobilized on a streptavidin-functionalized glass slide.

  6. Neuronal polarization.

    PubMed

    Takano, Tetsuya; Xu, Chundi; Funahashi, Yasuhiro; Namba, Takashi; Kaibuchi, Kozo

    2015-06-15

    Neurons are highly polarized cells with structurally and functionally distinct processes called axons and dendrites. This polarization underlies the directional flow of information in the central nervous system, so the establishment and maintenance of neuronal polarization is crucial for correct development and function. Great progress in our understanding of how neurons establish their polarity has been made through the use of cultured hippocampal neurons, while recent technological advances have enabled in vivo analysis of axon specification and elongation. This short review and accompanying poster highlight recent advances in this fascinating field, with an emphasis on the signaling mechanisms underlying axon and dendrite specification in vitro and in vivo. PMID:26081570

  7. Full three-dimensional ab initio studies of interference effects in high-energy ion-molecule collisions

    NASA Astrophysics Data System (ADS)

    Sælen, L.; Birkeland, T.; Sisourat, N.; Hansen, J. P.; Dubois, A.

    2009-11-01

    Following ab initio 1D and 2D calculations by Sisourat et. al. [1] we here report full three dimensional calculations of the single ionization of an H2-molecule by a highly charged Kr+34 ion at high velocity impact (60 MeV/u). Prior theoretical investigations have all failed to account for any second order interference effects. Final results will be presented at the conference.

  8. High-power Yb:YAG single-crystal fiber amplifiers for femtosecond lasers in cylindrical polarization.

    PubMed

    Lesparre, Fabien; Gomes, Jean Thomas; Délen, Xavier; Martial, Igor; Didierjean, Julien; Pallmann, Wolfgang; Resan, Bojan; Eckerle, Michael; Graf, Thomas; Ahmed, Marwan Abdou; Druon, Frederic; Balembois, François; Georges, Patrick

    2015-06-01

    We demonstrate a three-stage diode-pumped Yb:YAG single-crystal-fiber amplifier to generate femtosecond pulses at high average powers with linear or cylindrical (i.e., radial or azimuthal) polarization. At a repetition rate of 20 MHz, 750-fs pulses were obtained at an average power of 85 W in cylindrical polarization and at 100 W in linear polarization. The report includes investigations on the use of Yb:YAG single-crystal fibers with different length/doping ratio and the zero-phonon pumping at a wavelength of 969 nm in order to optimize the performance. PMID:26030546

  9. High Bacterial Diversity of Biological Soil Crusts in Water Tracks over Permafrost in the High Arctic Polar Desert

    PubMed Central

    Steven, Blaire; Lionard, Marie; Kuske, Cheryl R.; Vincent, Warwick F.

    2013-01-01

    In this study we report the bacterial diversity of biological soil crusts (biocrusts) inhabiting polar desert soils at the northern land limit of the Arctic polar region (83° 05 N). Employing pyrosequencing of bacterial 16S rRNA genes this study demonstrated that these biocrusts harbor diverse bacterial communities, often as diverse as temperate latitude communities. The effect of wetting pulses on the composition of communities was also determined by collecting samples from soils outside and inside of permafrost water tracks, hill slope flow paths that drain permafrost-affected soils. The intermittent flow regime in the water tracks was correlated with altered relative abundance of phylum level taxonomic bins in the bacterial communities, but the alterations varied between individual sampling sites. Bacteria related to the Cyanobacteria and Acidobacteria demonstrated shifts in relative abundance based on their location either inside or outside of the water tracks. Among cyanobacterial sequences, the proportion of sequences belonging to the family Oscillatoriales consistently increased in relative abundance in the samples from inside the water tracks compared to those outside. Acidobacteria showed responses to wetting pulses in the water tracks, increasing in abundance at one site and decreasing at the other two sites. Subdivision 4 acidobacterial sequences tended to follow the trends in the total Acidobacteria relative abundance, suggesting these organisms were largely responsible for the changes observed in the Acidobacteria. Taken together, these data suggest that the bacterial communities of these high latitude polar biocrusts are diverse but do not show a consensus response to intermittent flow in water tracks over high Arctic permafrost. PMID:23967218

  10. Phase-resolved high-resolution spectrophotometry of the eclipsing polar HU Aquarii

    E-print Network

    Axel D. Schwope; Karl-Heinz Mantel; Keith Horne

    1997-01-15

    We present phase-resolved spectroscopy of the bright, eclipsing polar HU Aqr obtained with high time (~30sec) and spectral (1.6 A) resolution when the system was in a high accretion state. The trailed spectrograms reveal clearly the presence of three different line components with different width and radial velocity variation. By means of Doppler tomography their origin could be located unequivocally (a) on the secondary star, (b) the ballistic part of the accretion stream (horizontal stream), and (c) the magnetically funnelled part of the stream (vertical stream). For the first time we were able to derive a (near-)complete map of the stream in a polar. We propose to use Doppler tomography of AM Herculis stars as a new tool for the mass determination of these binaries. This method, however, still needs to be calibrated by an independent method. The asymmetric light curve of the narrow emission line originating on the mass-donating companion star reveals evidence for significant shielding of 60% of the leading hemisphere by the gas between the two stars.

  11. Evidence of plasma polarization shift of Ti He-? resonance line in high density laser produced plasmas

    NASA Astrophysics Data System (ADS)

    Khattak, F. Y.; Percie du Sert, O. A. M. B.; Rosmej, F. B.; Riley, D.

    2012-12-01

    A spectroscopic study of the He-? (1s2 1s0 - ls2p 1p1) line emission (4749.73 eV) from high density plasma was conducted. The plasma was produced by irradiating Ti targets with intense (I ? l×l019 W/cm2), 400nm wavelength high contrast, short (45fs) p-polarized laser pulses at an angle of 45°. A line shift up to 3.4+1.0 eV (1.9±0.55 mÅ) was observed in the He-? line. The line width of the resonance line at FWHM was measured to be 12.1±0.6 eV (6.7±0.35 mÅ). For comparison, we looked into the emission of the same spectral line from plasma produced by irradiating the same target with laser pulses of reduced intensities (?1017 W/cm2): we observed a spectral shift of only 1.8+1.0 eV (0.9+0.55mÅ) and the line-width measures up to 5.8+0.25 eV (2.7+0.35 mÅ). These data provide evidence of plasma polarization shift of the Ti He-? line.

  12. Magic angle spinning NMR of proteins: high-frequency dynamic nuclear polarization and (1)h detection.

    PubMed

    Su, Yongchao; Andreas, Loren; Griffin, Robert G

    2015-06-01

    Magic angle spinning (MAS) NMR studies of amyloid and membrane proteins and large macromolecular complexes are an important new approach to structural biology. However, the applicability of these experiments, which are based on (13)C- and (15)N-detected spectra, would be enhanced if the sensitivity were improved. Here we discuss two advances that address this problem: high-frequency dynamic nuclear polarization (DNP) and (1)H-detected MAS techniques. DNP is a sensitivity enhancement technique that transfers the high polarization of exogenous unpaired electrons to nuclear spins via microwave irradiation of electron-nuclear transitions. DNP boosts NMR signal intensities by factors of 10(2) to 10(3), thereby overcoming NMR's inherent low sensitivity. Alternatively, it permits structural investigations at the nanomolar scale. In addition, (1)H detection is feasible primarily because of the development of MAS rotors that spin at frequencies of 40 to 60 kHz or higher and the preparation of extensively (2)H-labeled proteins. PMID:25839340

  13. Quaternary Semiconductors with Positive Crystal Field Splitting: Potential High-Efficiency Spin-Polarized Electron Sources

    SciTech Connect

    Chen, S. Y.; Yin, W. J.; Yang, J. H.; Gong, X. G.; Walsh, A.; Wei, S. H.

    2009-01-01

    Traditional high efficiency spin-polarized electron sources (SPES) consist mainly of binary or pseudobinary zinc-blende GaAs based materials, whereas their ternary analogs II-IV-V{sub 2} (II = Zn, Cd, IV = Si, Ge, Sn, and V = As) as well as II-VI ternary analogs I-III-VI{sub 2} (I = Cu, Ag, III = Al, Ga, In, and VI = Se) have not drawn wide attention because their crystal field splitting {Delta}{sub CF} near the valence band maximum is either negative or close to zero in their ground state chalcopyrite structure. Using first-principles calculations, we show that some derivative quaternary I-III-II{sub 2}-VI{sub 4} and II-IV-III{sub 2}-V{sub 4} compounds can have coherent ground state stannite or kesterite structures with large and positive {Delta}{sub CF} due to their increased chemical and structural flexibility. We propose that ZnSiAl{sub 2}As{sub 4} and CdGeAl{sub 2}As{sub 4} in the stannite structure, and ZnSnGa{sub 2}As{sub 4} and CuAlCd{sub 2}Se{sub 4} in the kesterite structure could be good candidate SPES materials with high polarization and quantum efficiency.

  14. High-resolution soft x-ray photoionization studies of selected molecules

    SciTech Connect

    Hudson, E.A.

    1993-08-01

    Near-edge soft x-ray photoionization spectra were measured for CO, SF{sub 6}, H{sub 2}S, and D{sub 2}S in the gas phase, using the Free University of Berlin plane-grating SX-700-II monochromator at the synchrotron radiation source BESSY. Photoionization spectra of carbon monoxide were measured near the carbon and oxygen K edges. Vibrational spacings and bond lengths are derived for several resonances. Results are consistent with equivalent-core model and indicate the different influences of the carbon and oxygen Is core holes. Corresponding spectra of H{sub 2}CO and D{sub 2}CO were also measured. Assignment of complex vibrational structure in valence-shell and Rydberg resonances is facilitated by comparison of spectra for the two isotopic species. Geometric and vibrational parameters are derived for several carbon 1s core-excited states. Isotopic shifts are observed in the energies and linewidths of some core-excited states. Sulfur hexafluoride photoionization spectra, measured near the sulfur L{sub 2,3} edges, show several series of weak, narrow Rydberg resonances. High resolution and good counting statistics allow a complete assignment of these states. Lineshapes of the broad inner-well resonances are analyzed to establish the magnitudes of vibrational and lifetime broadening in these states. Spectra of the H{sub 2}S and D{sub 2}S molecules were also measured near the sulfur L{sub 2,3} edges. Besides lower-energy transitions to inner-well states, a complex manifold of overlapping Rydberg resonances is observed. The rich fine structure of these states arises mainly from removal of orbital degeneracies in molecular field. Additional structure due to vibrational excitations in the final state is identified by comparison of the spectra for the two isotopic species.

  15. Polarization-independent, high-power, and angle-flared superluminescent diode for WDM-PON applications

    Microsoft Academic Search

    D. Heo; J. S. Lee; I. K. Yun; H. C. Shin; S. W. Kim; D. K. Jung; D. J. Shin; H. S. Kim; H. S. Shin; S. B. Park; S. T. Hwang; Y. J. Oh; Y. K. Oh; D. H. Jang; C. S. Shim

    2005-01-01

    We developed polarization-independent high-power superluminescent diodes (SLDs) for wavelength division multiplexed-passive optical network (WDM-PON) applications. The SLD presents CW output power of 150 mW, spectral bandwidth of 40 nm, polarization-dependent power variation of less than 1 dB, and spectral ripple of 3 dB at current of 1.47 A and temperature of 25 degC

  16. High peak power operation and harmonic generation of a single-polarization, Yb-doped photonic crystal fiber amplifier

    Microsoft Academic Search

    Christopher D. Brooks; Fabio di Teodoro

    2007-01-01

    We report on the use of a single-polarization, 41 mum core-diameter, intrinsically single-mode photonic crystal fiber (PCF) to obtain high peak power (up to ˜800 kW), 1 ns-duration pulses in a 100:1 linearly polarized, intrinsically single-mode (M2 ˜ 1.2) output. By transmitting the PCF output through nonlinear crystals, we also obtained efficient second, third, and fourth harmonic generation resulting in

  17. Strain-compensated AlInGaAs–GaAsP superlattices for highly polarized electron emission

    Microsoft Academic Search

    A. V. Subashiev; L. G. Gerchikov; Yu. A. Mamaev; Yu. P. Yashin; J. S. Roberts; D.-A. Luh; T. Maruyama; J. E. Clendenin

    2005-01-01

    Spin-polarized electron emission from superlattice photocathodes developed with strain compensation is investigated. An opposite strain in the quantum well and barrier layers is accomplished using an InAlGaAs?GaAsP superlattice structure. The measured values of maximum polarization and quantum yield for the structure with a 0.18 ?m thick working layer are excellent results for a strained superlattice photocathode structure, demonstrating the high

  18. Surface hydrophobic amino acid residues in cellulase molecules as a structural factor responsible for their high denim-washing performance.

    PubMed

    Gusakov; Sinitsyn; Berlin; Markov; Ankudimova

    2000-11-15

    The denim-washing performance of six purified fungal cellulases (four endo-1,4-beta-D-glucanases and two cellobiohydrolases) was compared using a model microassay. The performance of cellobiohydrolases per mg of protein was much lower than that of endoglucanases. For endoglucanases, it varied up to 5 times between the best and the worst enzyme. Experiments with amino acids immobilized on cross-linked agarose showed that their side chains may bind indigo owing to hydrophobic interactions and formation of hydrogen bonds. The best binding effects provided Tyr and Phe. Analysis of three-dimensional structures of cellulase molecules showed that a certain correlation exists between the washing performance of enzyme and (i) quantity (percentage) of aromatic residues exposed to solvent on the surface of protein globule or (ii) overall percentage of the surface hydrophobic residues. Data presented provide an evidence that the molecules of certain cellulases, which have hydrophobic domains (clusters of closely located non-polar residues) on their surface, may bind indigo and thus act as emulsifiers helping the dye to float out of cellulose fibers to the bulk solution. PMID:11064048

  19. Antisymmetric polar modes of thermal convection in rotating spherical fluid shells at high taylor numbers.

    PubMed

    Garcia, Ferran; Sánchez, Juan; Net, Marta

    2008-11-01

    The onset of thermal convection in a rotating spherical shell of intermediate radius ratio eta=0.4 is studied numerically for Taylor numbers Ta > or = 10(11) and the Prandtl number of the liquid sodium (sigma=0.01). For the first time, it is shown that at very high Taylor numbers the first unstable mode can be antisymmetric with respect to the equator and confined inside a cylinder tangent to the inner sphere at the equator (polar mode). The exponent of the power law determined from the asymptotic dependence of the critical Rayleigh number for very high Ta is 0.57, lower than 2/3, given theoretically for the spiraling columnar modes, and than 0.63, found numerically for the outer equatorially attached modes. PMID:19113270

  20. Switchable polarization-sensitive surface plasmon resonance of highly stable gold nanorods liquid crystals composites

    NASA Astrophysics Data System (ADS)

    Liu, Qingkun; Qian, Jun; Cai, Fuhong; Smalyukh, Ivan I.; He, Sailing

    2011-12-01

    In this work, we demonstrate the bulk self-alignment of gold nanorods (GNRs) dispersed in lyotropic nematic liquid crystals (LCs) with high optical absorption coefficient at the surface plasmon resonant wavelength. The polymer-coated GNRs which show spontaneous long-range orientational ordering along the director of LC host exhibit long-term stability as well as high concentration. External magnetic field and shearing allow for alignment and realignment of the orientation of gold nanorods by changing the director of the liquid crystal matrix. This results in a switchable polarization-sensitive surface plasmon resonance exhibiting stark differences from that of the same nanorods in isotropic fluids. The devise-scale bulk nanoparticle alignment may enable optical metamaterial mass production and control of surface plasmon resonance of nanoparticles.

  1. The development of high-performance alkali-hybrid polarized He3 targets for electron scattering

    DOE PAGESBeta

    Singh, Jaideep T.; Dolph, Peter A.M.; Tobias, William Al; Averett, Todd D.; Kelleher, Aiden; Mooney, K. E.; Nelyubin, Vladimir V.; Wang, Yunxiao; Zheng, Yuan; Cates, Gordon D.

    2015-05-01

    We present the development of high-performance polarized ³He targets for use in electron scattering experiments that utilize the technique of alkali-hybrid spin-exchange optical pumping. We include data obtained during the characterization of 24 separate target cells, each of which was constructed while preparing for one of four experiments at Jefferson Laboratory in Newport News, Virginia. The results presented here document dramatic improvement in the performance of polarized ³He targets, as well as the target properties and operating parameters that made those improvements possible. Included in our measurements were determinations of the so-called X-factors that quantify a temperature-dependent and as-yet poorlymore »understood spin-relaxation mechanism that limits the maximum achievable ³He polarization to well under 100%. The presence of this spin-relaxation mechanism was clearly evident in our data. We also present results from a simulation of the alkali-hydrid spin-exchange optical pumping process that was developed to provide guidance in the design of these targets. Good agreement with actual performance was obtained by including details such as off-resonant optical pumping. Now benchmarked against experimental data, the simulation is useful for the design of future targets. Included in our results is a measurement of the K- ³He spin-exchange rate coefficient $k^\\mathrm{K}_\\mathrm{se} = \\left ( 7.46 \\pm 0.62 \\right )\\!\\times\\!10^{-20}\\ \\mathrm{cm^3/s}$ over the temperature range 503 K to 563 K.« less

  2. Anomalous high-frequency wave activity flux preceding anomalous changes in the Northern polar jet

    NASA Astrophysics Data System (ADS)

    Nakamura, Mototaka; Kadota, Minoru; Yamane, Shozo

    2010-05-01

    Anomalous forcing by quasi-geostrophic (QG) waves has been reported as an important forcing factor in the Northern Annular Mode (NAM) in recent literatures. In order to shed a light on the dynamics of the NAM from a different angle, we have examined anomalous behavior of the winter jets in the upper troposphere and stratosphere by focusing our diagnosis on not the anomalous geopotential height (Z) itself, but on the anomalous change in the Z (dZ) between two successive months and preceding transient QG wave activity flux during the cold season. We calculated EOFs of dZ between two successive months at 150hPa for a 46-year period, from 1958 to 2003, using the monthly mean NCEP reanalysis data. We then formed anomaly composites of changes in Z and the zonal velocity (U), as well as the preceding and following wave activity flux, Z, U, and temperature at various heights, for both positive and negative phases of the first EOF. For the wave forcing fields, we adopted the diagnostic system for the three-dimensional QG transient wave activity flux in the zonally-varying three-dimensional mean flow developed by Plumb (1986) with a slight modification in its application to the data. Our choice of the Plumb86 is based on the fact that the winter mean flow in the Northern Hemisphere is characterized by noticeable zonal asymmetry, and has a symbiotic relationship with waves in the extra-tropics. The Plumb86 flux was calculated for high-frequency (period of 2 to 7 days) and low-frequency (period of 10 to 20 days) waves with the ultra-low-frequency (period of 30 days or longer) flow as the reference state for each time frame of the 6 hourly NCEP reanalysis data from 1958 to 2003. By replacing the mean flow with the ultra-low-frequency flow in the application of the Plumb86 formula, the flux fields were calculated as time series at 6 hour intervals. The time series of the wave activity flux was then averaged for each month. The patterns of composited anomalous dZ and dU clearly show anomalous acceleration or deceleration of U in the polar region, accompanied by anomalies of the opposite sign in the subtropics throughout the troposphere and stratosphere. The anomalies are conspicuously large in the polar stratosphere. The composited anomalous Z and U in the preceding and following months indicate that these large anomalies in dZ and dU occur when the polar troposphere and stratosphere are relaxing back toward the climatology from strongly anomalous states that closely resemble the positive and negative phases of the NAM. In this process of relaxation, the atmosphere actually overshoots the climatology and develops anomalies of the sign opposite to those existed initially. The anomalous wave activity flux exhibit strong signals of anomalous upward (downward) propagation of high-frequency waves in the North Atlantic storm track from the bottom of the atmosphere, penetrating up to the stratosphere, when the polar jet is anomalously strong (weak) in the preceding month. The anomalous horizontal wave activity flux shows anomalous eastward (westward) flux emanating from the North Atlantic storm track when the polar jet is anomalously strong (weak) in the preceding month. These patterns suggest that anomalous high-frequency waves originating from the North Atlantic storm track in the lower troposphere contribute to the destruction of both phases of the NAM. However, the anomalous flux divergence is very noisy everywhere due to the noisiness of the advective horizontal flux, making it difficult to ascertain the role of the high-frequency transients in the destruction of the NAM.

  3. Adsorption and binding of capping molecules for highly luminescent CdSe nanocrystals - DFT simulation studies

    NASA Astrophysics Data System (ADS)

    Chou, Hung-Lung; Tseng, Chih-Hsiang; Pillai, K. Chandrasekara; Hwang, Bing-Joe; Chen, Liang-Yih

    2010-12-01

    During CdSe nanocrystal growth, loss of surface capping molecules occurs leading to a decrease of photoluminescence (PL) quantum yield. In general, aliphatic capping molecules are applied to passivate the surface of CdSe nanocrystals to modulate the optical properties of the CdSe. In this work, two kinds of alkylamine (n-butylamine (n-BA) and n-hexylamine (n-HA)) and oleic acid (OA) were used to modify the surfaces of the CdSe nanocrystals. From the PL spectra and quantum yield analyses, we observed that the PL emission peak positions of the modified CdSe nanocrystals have blue shifted for all three capping molecules. However, the PL quantum yield of the CdSe nanocrystals increased after introduction of the alkylamine molecules, but decreased with oleic acid. The detailed mechanism was not clear until now. In this study, a density function theory (DFT) simulation was employed to demonstrate binding energy and charge analyses of CdSe with n-BA, n-HA and OA. By comparing the binding energy of the bare CdSe nanocrystals to that of the CdSe with the capping molecules, it was shown that n-BA and n-HA as capping molecules help to increase the charge on Se and decrease it on cadmium of the CdSe.During CdSe nanocrystal growth, loss of surface capping molecules occurs leading to a decrease of photoluminescence (PL) quantum yield. In general, aliphatic capping molecules are applied to passivate the surface of CdSe nanocrystals to modulate the optical properties of the CdSe. In this work, two kinds of alkylamine (n-butylamine (n-BA) and n-hexylamine (n-HA)) and oleic acid (OA) were used to modify the surfaces of the CdSe nanocrystals. From the PL spectra and quantum yield analyses, we observed that the PL emission peak positions of the modified CdSe nanocrystals have blue shifted for all three capping molecules. However, the PL quantum yield of the CdSe nanocrystals increased after introduction of the alkylamine molecules, but decreased with oleic acid. The detailed mechanism was not clear until now. In this study, a density function theory (DFT) simulation was employed to demonstrate binding energy and charge analyses of CdSe with n-BA, n-HA and OA. By comparing the binding energy of the bare CdSe nanocrystals to that of the CdSe with the capping molecules, it was shown that n-BA and n-HA as capping molecules help to increase the charge on Se and decrease it on cadmium of the CdSe. Electronic supplementary information (ESI) available: Figure S1. See DOI: 10.1039/c0nr00569j

  4. High-resolution polarization sensitive OCT for ocular imaging in rodents

    NASA Astrophysics Data System (ADS)

    Fialová, Stanislava; Rauscher, Sabine; Gröger, Marion; Pircher, Michael; Hitzenberger, Christoph K.; Baumann, Bernhard

    2015-03-01

    A new high-resolution polarization sensitive optical coherence tomography system was developed for imaging rodent retina. Various light-tissue interactions such as birefringence and depolarization can change the polarization state of light. In the eye, there are several tissues that have these properties, for example retinal pigment epithelium (depolarization) and sclera (birefringence). These layers play key roles in diseases like age-related macular degeneration or glaucoma. Animal models are an important component for understanding disease pathogenesis. The gold standard for the evaluation of preclinical experiments is histology, which is an invasive and terminal procedure. Since OCT is non-invasive, it has the potential to be an alternative to histology with the benefit of long-term study of the disease progression in the same animal. In this study, a superluminescent diode with spectrum width 100 nm and mean wavelength 840 nm is used as a light source in order to enable high axial resolution. Spectrometers are custom built to enable high imaging speed that allows acquiring 3D data sets with 1024x200x1536 voxels in 3.44 s. From the acquired data, images displaying phase retardation induced by birefringence and orientation of birefringent axis were calculated. In first measurements, we were able to identify the RPE-choroid complex (depolarization effect) and the sclera (strong birefringence) in the retina of Long-Evans and Sprague-Dawley rats. Our preliminary results demonstrate the feasibility of the system for high speed/resolution imaging of the rodent retina. This is useful for longitudinal studies of disease models of retinal disease in rats and mice

  5. A high-speed GaAs-based electro-optic modulator for polarization, intensity, and phase modulation

    NASA Astrophysics Data System (ADS)

    Kato, Hiroshi; Bull, Jeffrey D.; Tsou, Benjamin P. C.; Jaeger, Nicolas A. F.

    2013-10-01

    We review the development of a unique, electro-optic, polarization modulator fabricated on epitaxial layers of aluminum gallium arsenide, grown on a gallium arsenide (GaAs) substrate. The device has a single waveguide structure combined with travelling-wave, slow-wave electrodes. This design allows for high-speed modulation of the polarization state of light with low differential group delay and low optical loss at frequencies in excess of 50 GHz. The devices are TE?TM mode convertors that modulate the state of light from one linear polarization state to an orthogonal linear state passing through elliptical and circular polarization states. These devices can also be configured to modulate the phase or intensity of an optical signal by appropriate alignment of the polarization axis of the input light or by placing a polarizer at the output. Key characteristics and important performance advantages of such devices are discussed. Applications that use these devices for enhancing digital and analog communication links, analog-to-digital signal conversion, and sending keys for encryption are reviewed to illustrate the diverse nature of the systems being developed and provide an overview of the versatility of the ways in which the GaAs polarization modulator may be used.

  6. Recoil-proton polarization in high-energy deuteron photodisintegration with circularly plarized photons.

    SciTech Connect

    Jiang, X.; Arrington, J.; Benmokhtar, F.; Camsonne, A.; Chen, J. P.; Holt, R. J.; Qattan, I. A.; Reimer, P. E.; Schulte, E. C.; Wijesooriya, K.; Physics; Rutgers Univ.; Univ. Blaise Pascal; Thomas Jefferson National Accelerator Facility

    2007-05-01

    We measured the angular dependence of the three recoil-proton polarization components in two-body photodisintegration of the deuteron at a photon energy of 2 GeV. These new data provide a benchmark for calculations based on quantum chromodynamics. Two of the five existing models have made predictions of polarization observables. Both explain the longitudinal polarization transfer satisfactorily. Transverse polarizations are not well described, but suggest isovector dominance.

  7. Angular dependence of recoil proton polarization in high-energy ?d \\to p n

    E-print Network

    X. Jiang; J. Arrington; F. Benmokhtar; A. Camsonne; J. P. Chen; S. Choi; E. Chudakov; F. Cusanno; A. Deur; D. Dutta; F. Garibaldi; D. Gaskell; O. Gayou; R. Gilman; C. Glashauser; D. Hamilton; O. Hansen; D. W. Higinbotham; R. J. Holt; C. W. de Jager; M. K. Jones; L. J. Kaufman; E. R. Kinney; K. Kramer; L. Lagamba; R. de Leo; J. Lerose; D. Lhuillier; R. Lindgren; N. Liyanage; K. McCormick; Z. -E. Meziani; R. Michaels; B. Moffit; P. Monaghan; S. Nanda; K. D. Paschke; C. F. Perdrisat; V. Punjabi; I. A. Qattan; R. D. Ransome; P. E. Reimer; B. Reitz; A. Saha; E. C. Schulte; R. Sheyor; K. Slifer; P. Solvignon; V. Sulkosky; G. M. Urciuoli; E. Voutier; K. Wang; K. Wijesooriya; B. Wojtsekhowski; L. Zhu

    2007-02-02

    We measured the angular dependence of the three recoil proton polarization components in two-body photodisintegration of the deuteron at a photon energy of 2 GeV. These new data provide a benchmark for calculations based on quantum chromodynamics. Two of the five existing models have made predictions of polarization observables. Both explain the longitudinal polarization transfer satisfactorily.. Transverse polarizations are not well described, but suggest isovector dominance.

  8. Generation of a highly-phase-sensitive polarization-squeezed N-photon state by collinear parametric down-conversion and coherent photon subtraction

    SciTech Connect

    Hofmann, Holger F. [Graduate School of Advanced Sciences of Matter, Hiroshima University, Kagamiyama 1-3-1, Higashi Hiroshima 739-8530 (Japan)

    2006-07-15

    It is shown that a highly-phase-sensitive polarization-squeezed (2n-1)-photon state can be generated by subtracting a diagonally polarized photon from the 2n photon component generated in collinear type II down-conversion. This polarization wedge state has the interesting property that its photon number distribution in the horizontal and vertical polarizations remains sharply defined for phase shifts of up to 1/n between the circularly polarized components. Phase shifts at the Heisenberg limit are therefore observed as nearly deterministic transfers of a single photon between the horizontal and vertical polarization components.

  9. Efficient generation of high beam-quality attosecond pulse with polarization-gating Bessel-Gauss beam from highly-ionized media.

    PubMed

    Li, Yang; Zhang, Qingbin; Hong, Weiyi; Wang, Shaoyi; Wang, Zhe; Lu, Peixiang

    2012-07-01

    Single attosecond pulse generation with polarization gating Bessel-Gauss beam in relatively strongly-ionized media is investigated. The results show that Bessel-Gauss beam has the ability to suppress the spatial plasma dispersion effects caused by high density of free electrons, thus the laser field can maintain its spatial profile through highly-ionized medium. This indicates the use of Bessel-Gauss beam has advantages over Gaussian beam in high harmonic generation under high ionization conditions. In our scheme, significant improvement of spatiotemporal properties of harmonics is achieved and an isolated attosecond pulse with high beam quality is filtered out using polarization gating. PMID:22772239

  10. Giant spin-driven ferroelectric polarization in TbMnO3 under high pressure

    NASA Astrophysics Data System (ADS)

    Aoyama, T.; Yamauchi, K.; Iyama, A.; Picozzi, S.; Shimizu, K.; Kimura, T.

    2014-09-01

    The recent research on multiferroics has provided solid evidence that the breaking of inversion symmetry by spin order can induce ferroelectric polarization P. This type of multiferroics, called spin-driven ferroelectrics, often show a gigantic change in P on application of a magnetic field B. However, their polarization (<~0.1??C?cm?2) is much smaller than that in conventional ferroelectrics (typically several to several tens of ?C?cm?2). Here we show that the application of external pressure to a representative spin-driven ferroelectric, TbMnO3, causes a flop of P and leads to the highest P (?1.0??C?cm?2) among spin-driven ferroelectrics ever reported. We explain this behaviour in terms of a pressure-induced magnetoelectric phase transition, based on the results of density functional simulations. In the high-pressure phase, the application of B further enhances P over 1.8??C?cm?2. This value is nearly an order of magnitude larger than those ever reported in spin-driven ferroelectrics.

  11. Polarization maintaining highly nonlinear photonic crystal fiber for supercontinuum generation at 1.55 ?m

    NASA Astrophysics Data System (ADS)

    Hossain, M. A.; Namihira, Y.; Islam, M. A.; Hirako, Y.

    2012-07-01

    A polarization maintaining highly nonlinear Germanium (Ge) doped photonic crystal fiber (HNL-GePCF) is proposed for supercontinuum (SC) generation at 1.55 ?m as polarization maintaining properties in a fiber enhance nonlinear interactions to generate SC using less optical power. By designing 3% higher refractive index Ge-doped core with core ellipticity ?=0.9 inside silica, nonlinear coefficient ? and birefringence B are increased as large as 83 W-1 km-1 and 2.82×10-4 respectively at 1.55 ?m. Using finite element method (FEM) with a circular perfectly matched boundary layer (PML), it is shown through simulations that the proposed HNL-GePCF offers an efficient SC generation at 1.55 ?m. By propagating sech2 picosecond optical pulses having 2.5 ps and 1.0 ps pulsewidth at a full width at half maximum (FWHM) through the proposed HNL-GePCF, output optical pulses are analyzed by the split-step Fourier method to obtain the spectral contents. The highest 10 dB bandwidth spectra at 1.55 ?m are observed as 100 nm and 150 nm for 2.5 ps input optical pulse and for 1.0 ps input optical pulse respectively.

  12. Parallel and series FED microstrip array with high efficiency and low cross polarization

    NASA Technical Reports Server (NTRS)

    Huang, John (inventor)

    1995-01-01

    A microstrip array antenna for vertically polarized fan beam (approximately 2 deg x 50 deg) for C-band SAR applications with a physical area of 1.7 m by 0.17 m comprises two rows of patch elements and employs a parallel feed to left- and right-half sections of the rows. Each section is divided into two segments that are fed in parallel with the elements in each segment fed in series through matched transmission lines for high efficiency. The inboard section has half the number of patch elements of the outboard section, and the outboard sections, which have tapered distribution with identical transmission line sections, terminated with half wavelength long open-circuit stubs so that the remaining energy is reflected and radiated in phase. The elements of the two inboard segments of the two left- and right-half sections are provided with tapered transmission lines from element to element for uniform power distribution over the central third of the entire array antenna. The two rows of array elements are excited at opposite patch feed locations with opposite (180 deg difference) phases for reduced cross-polarization.

  13. Leading-order determination of the gluon polarization from high- p T hadron electroproduction

    NASA Astrophysics Data System (ADS)

    Airapetian, A.; Akopov, N.; Akopov, Z.; Aschenauer, E. C.; Augustyniak, W.; Avakian, R.; Avetissian, A.; Avetisyan, E.; Belostotski, S.; Bianchi, N.; Blok, H. P.; Böttcher, H.; Bonomo, C.; Borissov, A.; Bryzgalov, V.; Capiluppi, M.; Capitani, G. P.; Cisbani, E.; Contalbrigo, M.; Dalpiaz, P. F.; Deconinck, W.; de Leo, R.; Demey, M.; de Nardo, L.; de Sanctis, E.; Diefenthaler, M.; di Nezza, P.; Dreschler, J.; Düren, M.; Ehrenfried, M.; Elbakian, G.; Ellinghaus, F.; Elschenbroich, U.; Fabbri, R.; Fantoni, A.; Felawka, L.; Frullani, S.; Gabbert, D.; Gapienko, G.; Gapienko, V.; Garibaldi, F.; Gavrilov, G.; Gharibyan, V.; Giordano, F.; Gliske, S.; Guler, H.; Hadjidakis, C.; Hartig, M.; Hasch, D.; Hasegawa, T.; Hill, G.; Hillenbrand, A.; Hoek, M.; Holler, Y.; Hommez, B.; Hristova, I.; Ivanilov, A.; Jackson, H. E.; Kaiser, R.; Keri, T.; Kinney, E.; Kisselev, A.; Kopytin, M.; Korotkov, V.; Kravchenko, P.; Lagamba, L.; Lamb, R.; Lapikás, L.; Lehmann, I.; Lenisa, P.; Liebing, P.; Linden-Levy, L. A.; Lorenzon, W.; Lu, X.-R.; Maiheu, B.; Makins, N. C. R.; Marianski, B.; Marukyan, H.; Mexner, V.; Miller, C. A.; Miyachi, Y.; Muccifora, V.; Murray, M.; Mussgiller, A.; Nappi, E.; Naryshkin, Y.; Nass, A.; Negodaev, M.; Nowak, W.-D.; Pappalardo, L. L.; Perez-Benito, R.; Pickert, N.; Raithel, M.; Reggiani, D.; Reimer, P. E.; Reischl, A.; Reolon, A. R.; Riedl, C.; Rith, K.; Rock, S. E.; Rosner, G.; Rostomyan, A.; Rubin, J.; Salomatin, Y.; Schäfer, A.; Schnell, G.; Schüler, K. P.; Seitz, B.; Shearer, C.; Shibata, T.-A.; Shutov, V.; Stancari, M.; Statera, M.; Steijger, J. J. M.; Stewart, J.; Stinzing, F.; Taroian, S.; Tchuiko, B.; Trzcinski, A.; Tytgat, M.; Vandenbroucke, A.; van der Nat, P. B.; van der Steenhoven, G.; van Haarlem, Y.; van Hulse, C.; Varanda, M.; Veretennikov, D.; Vilardi, I.; Vogel, C.; Wang, S.; Yaschenko, S.; Ye, H.; Ye, Z.; Yu, W.; Zeiler, D.; Zihlmann, B.; Zupranski, P.

    2010-08-01

    Longitudinal double-spin asymmetries of charged hadrons with high transverse momentum p T have been measured in electroproduction using the H ermes detector at H era. Processes involving gluons in the nucleon have been enhanced relative to others by selecting hadrons with p T typically above 1 GeV. In this kinematic domain the gluon polarization has been extracted in leading order making use of the model embedded in the Monte Carlo Generator P ythia 6.2. The gluon polarization obtained from single inclusive hadrons in the p T range 1 GeV < p T < 2.5 GeV using a deuterium target is {? g}/gleft( {left< x rightrangle, left< {{?^2}} rightrangle } right) = 0.049± 0.034left( {stat} right)± 0.010left( {systext{-}exp} right)_{ - 0.099}^{ + 0.126}left( {systext{-}models} right) at a scale left< {{?^2}} rightrangle = 1.35{text{Ge}}{{text{V}}^2} and left< x rightrangle = 0.22 . For different final states and kinematic domains, consistent values of {? g}/g have been found within statistical uncertainties using hydrogen and deuterium targets.

  14. Highly polarized Th17 cells induce EAE via a T-bet independent mechanism.

    PubMed

    Grifka-Walk, Heather M; Lalor, Stephen J; Segal, Benjamin M

    2013-11-01

    In the MOG35-55 induced EAE model, autoreactive Th17 cells that accumulate in the central nervous system acquire Th1 characteristics via a T-bet dependent mechanism. It remains to be determined whether Th17 plasticity and encephalitogenicity are causally related to each other. Here, we show that IL-23 polarized T-bet(-/-) Th17 cells are unimpaired in either activation or proliferation, and induce higher quantities of the chemokines RANTES and CXCL2 than WT Th17 cells. Unlike their WT counterparts, T-bet(-/-) Th17 cells retain an IL-17(hi) IFN-?(neg-lo) cytokine profile following adoptive transfer into syngeneic hosts. This population of highly polarized Th17 effectors is capable of mediating EAE, albeit with a milder clinical course. It has previously been reported that the signature Th1 and Th17 effector cytokines, IFN-? and IL-17, are dispensable for the development of autoimmune demyelinating disease. The current study demonstrates that the "master regulator" transcription factor, T-bet, is also not universally required for encephalitogenicity. Our results contribute to a growing body of data showing heterogeneity of myelin-reactive T cells and the independent mechanisms they employ to inflict damage to central nervous system tissues, complicating the search for therapeutic targets relevant across the spectrum of individuals with multiple sclerosis. PMID:23878008

  15. DEM Extraction from High-Resolution Stereoscopic Worldview 1 & 2 Imagery of Polar Outlet Glaciers

    NASA Astrophysics Data System (ADS)

    Porter, C. C.; Morin, P. J.; Howat, I. M.; Niebuhr, S.; Smith, B. E.

    2011-12-01

    There are few reliable digital elevation models (DEMs) in polar regions and most are of low resolution (on the order of 100's of meters to km) or of poor quality. Polar environments are changing rapidly and accurate DEMs are critical for correcting imagery, measuring glacier thickness changes and modeling ice flow and surface melt water drainage. Using in-track stereoscopic images from Worldview-1 and Worldview-2, we derived high-resolution DEMs for outlet glaciers and other areas of interest in Antarctica and the Arctic. We used ERDAS Imagine's LPS eATE (enhanced automated terrain extraction) algorithm to derive a dense point cloud of matches. The resulting point cloud is comparable in density to that obtained by LiDAR flown at 10,000 feet. Preliminary comparisons of our results to ground control points collected by field teams and airborne and satellite laser altimeters show 0.5 - 10 meter vertical error over glaciers and 2 - 10 meter error over ice-free terrain. The error is primarily due to approximations in the sensor model and is consistent across the DEM. Our results indicate that refinements in the sensor model and point matching algorithm will improve accuracy. Given the increasing interest in glacier change detection around the globe, DEMs extracted from frequent satellite stereo pairs can be used to monitor and quantify changes in both movement and volume.

  16. Polarization control in high power microwaves from a rectangular cross section gyrotron

    SciTech Connect

    Hochman, J.M.; Gilgenbach, R.M.; Jaynes, R.J.; Rintamaki, J.I.; Lau, Y.Y.; Spencer, T.A. [Univ. of Michigan, Ann Arbor, MI (United States)

    1997-12-31

    The authors summarize the results of experiments on a gyrotron utilizing rectangular-cross-section (RCS) interaction cavities. Current issues under investigation include polarization control as a function of magnetic field, power versus pulselength of microwave emission, and mode competition. The electron beam driver producing an annular beam is the Michigan Electron Long Beam Accelerator (MELBA). The annular e-beam is spun up into an axis-encircling beam by passing it through a magnetic cusp prior to entering the RCS interaction cavity. Initial experimental results show a high degree of polarization [P(TE{sub 10})/P(TE{sub 01}) = 30 or 1/30] as a function of cavity fields. Megawatt microwave output shifts from the fundamental mode, which dominates the next order mode by an order of magnitude, to the next order mode as the field is raised from 1.4 to 1.7 kGauss. Frequency measurements using microstrip bandpass filters and a superheterodyne mixer support this result as well as MAGIC simulations. MAGIC code simulations using various magnetic fields will be presented as well as results utilizing the E-gun code.

  17. Complete Control of Polarization and Phase of Light with High Efficiency and Sub-wavelength Spatial Resolution

    E-print Network

    Arbabi, Amir; Bagheri, Mahmood; Faraon, Andrei

    2014-01-01

    Meta-surfaces are planar structures that locally change polarization, phase, and amplitude of light, thus enabling flat, lithographically patterned free-space optical components with functionalities controlled by design. Several types of meta-surfaces have been reported, but low efficiency and the inability to provide simultaneous phase and polarization control have limited their applications. Here we demonstrate a platform based on high-contrast dielectric elliptical nano-posts providing complete and efficient control of polarization and phase with sub-wavelength spatial resolution. The unprecedented freedom in manipulating light not only enables realization of conventional free-space transmissive optical elements such as phase-plates, wave-plates and beam-splitters, but also elements with novel functionalities such as general polarization switchable phase holograms and arbitrary vector beam generators which will change the design paradigms for free-space optical systems.

  18. Study on differences between high contrast grating reflectors for TM and TE polarizations and their impact on VCSEL designs

    NASA Astrophysics Data System (ADS)

    Chung, Il-Sug

    2015-06-01

    A theoretical study of differences in broadband high-index-contrast grating (HCG) reflectors for TM and TE polarizations is presented, covering various grating parameters and properties of HCGs. It is shown that the HCG reflectors for TM polarization (TM HCG reflectors) have much thicker grating thicknesses and smaller grating periods than the TE HCG reflectors. This difference is found to originate from the different boundary conditions met for the electric field of each polarization. Due to this difference, the TM HCG reflectors have much shorter evanescent extension of HCG modes into low-refractive-index media surrounding the HCG. This enables to achieve a very short effective cavity length for VCSELs, which is essential for ultrahigh speed VCSELs and MEMS-tunable VCSELs. The obtained understandings on polarization dependences will be able to serve as important design guidelines for various HCG-based devices.

  19. Polarization-Insensitive Wavelength Conversion of DPSK Signal Using Four-Wave Mixing in 32-cm Bismuth-Oxide Highly Nonlinear Fiber

    Microsoft Academic Search

    Mable P. Fok; Chester Shu

    2007-01-01

    We demonstrate polarization-insensitive wavelength conversion of 10-Gb\\/s DPSK signal using a polarization-diversity scheme for four-wave mixing in 32-cm bismuth-oxide highly nonlinear fiber. The polarization dependence is <1 dB and the power penally is 3 dB.

  20. Astronomical sources of circularly polarized light and the origin of homochirality.

    PubMed

    Bailey, J

    2001-01-01

    Possible astronomical sources of ultraviolet circularly polarized light (UVCPL) which might be responsible for enantiomeric selection in interstellar organic molecules are considered, Synchrotron radiation from magnetic neutron stars has been suggested as a possible source of UVCPL. However, synchrotron radiation in these situations is not predicted to be strongly circularly polarized. Very few such sources show optical synchrotron radiation and in the few that do circular polarization has not been observed. Magnetic white dwarfs and white dwarf binaries (Polars) can be highly circularly polarized but any effect on molecular clouds and star formation regions must rely on rare chance encounters. Recent observations show that substantial levels of circular polarization are present in reflection nebulae in star formation regions. This mechanism produces polarized light exactly when and where it is needed in regions where star formation is occurring and organic molecules are known to be present. PMID:11296520