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1

Rheology of nematic liquid crystals with highly polar molecules  

NASA Astrophysics Data System (ADS)

We report experimental studies on the rheology of a few nematic liquid crystals with highly polar molecules (CCH-7, PCH-7, CB-7). The selected molecules have the same alkyl chain (-C7H15) and cyano (-CN) end group. In the core part of the molecule, CCH-7 has two cyclohexane rings, PCH-7 has one cyclohexane and one aromatic ring, and CB-7 has two aromatic rings. Two viscosities were measured as a function of temperature, namely, ?2 (director parallel to the shear direction) and ?1 (director perpendicular to the shear direction). The orientation of the director was studied using small angle light scattering techniques. ?2 was measured in presheared sample, whereas the electrorheological technique was used to measure ?1. We show that both viscosities of the liquid crystals depend on the number of aromatic rings and Kirkwood correlation factor. The temperature dependent viscosities can be understood based on the intramolecular ?-electron conjugation and intermolecular association of highly polar molecules.

Ananthaiah, J.; Sahoo, Rasmita; Rasna, M. V.; Dhara, Surajit

2014-02-01

2

Polarization-insensitive resonances with high quality-factors in meta-molecule metamaterials.  

PubMed

Achieving narrow resonance is an area of interest within the field of metamaterials. However, only a few studies have investigated the polarization-insensitive resonances. A general principle for improving quality Q-factor of a sharp resonance is still unclear. In this work, we proposed a kind of planar meta-molecule metamaterials, which can exhibit polarization-insensitive resonance with high Q-factor. The proposed structures have a unit cell consisting of four arrayed ring resonant elements with two different sizes. Moreover, the investigation on surface current and two referential simulated structures confirm a principle for improving Q-factor. PMID:24977554

Wu, Lin; Yang, Zhenyu; Zhao, Ming; Zheng, Yu; Duan, Ji'an; Yuan, Xiuhua

2014-06-16

3

Microwave Lens for Polar Molecules  

E-print Network

We here report on the implementation of a microwave lens for neutral polar molecules suitable to focus molecules both in low-field-seeking and in high-field-seeking states. By using the TE_11m modes of a 12 cm long cylindrically symmetric microwave resonator, Stark-decelerated ammonia molecules are transversally confined. We investigate the focusing properties of this microwave lens as a function of the molecules' velocity, the detuning of the microwave frequency from the molecular resonance frequency, and the microwave power. Such a microwave lens can be seen as a first important step towards further microwave devices, such as decelerators and traps.

Odashima, Hitoshi; Enomoto, Katsunari; Schnell, Melanie; Meijer, Gerard

2010-01-01

4

An electrostatic mirror for neutral polar molecules  

Microsoft Academic Search

An electrostatic mirror for neutral polar molecules has been constructed using an array of electrodes of alternating polarity between which a high potential was applied. This configuration produces an exponentially evanescing electric field that interacts with polar molecules by the Stark effect. The spatial gradients of the Stark energies produce forces which were used to reflect a pulsed beam of

S. J. Wark; G. I. Opat

1992-01-01

5

An electrostatic mirror for neutral polar molecules  

Microsoft Academic Search

An electrostatic mirror for neutral polar molecules was constructed using an array of electrodes of alternating polarity between which a high potential was applied. This configuration produces an exponentially evanescing electric field that interacts with polar molecules by the Stark effect. The spatial gradients of the Stark energies produce forces which were used to reflect a pulsed beam of chloromethane

S. J. Wark; G. I. Opat

1992-01-01

6

Tilting and Wobble of Myosin V by High-Speed Single-Molecule Polarized Fluorescence Microscopy  

PubMed Central

Myosin V is biomolecular motor with two actin-binding domains (heads) that take multiple steps along actin by a hand-over-hand mechanism. We used high-speed polarized total internal reflection fluorescence (polTIRF) microscopy to study the structural dynamics of single myosin V molecules that had been labeled with bifunctional rhodamine linked to one of the calmodulins along the lever arm. With the use of time-correlated single-photon counting technology, the temporal resolution of the polTIRF microscope was improved ?50-fold relative to earlier studies, and a maximum-likelihood, multitrace change-point algorithm was used to objectively determine the times when structural changes occurred. Short-lived substeps that displayed an abrupt increase in rotational mobility were detected during stepping, likely corresponding to random thermal fluctuations of the stepping head while it searched for its next actin-binding site. Thus, myosin V harnesses its fluctuating environment to extend its reach. Additional, less frequent angle changes, probably not directly associated with steps, were detected in both leading and trailing heads. The high-speed polTIRF method and change-point analysis may be applicable to single-molecule studies of other biological systems. PMID:23528086

Beausang, JohnF.; Shroder, DeborahY.; Nelson, PhilipC.; Goldman, YaleE.

2013-01-01

7

Properties of water Polar molecule  

E-print Network

bonds. · These strong bonds determine almost every physical property of water and many of its chemical1 Water · Properties of water ­ Polar molecule · Hydrogen bonds with other water molecules · This is the foundation for all the properties of water Water · Water is the solvent, the medium and the participant

Cochran-Stafira, D. Liane

8

Nano trap for polar molecules  

NASA Astrophysics Data System (ADS)

A new ac/dc monopole trap for neutral polar particles, introduced and explored by Blmel (2011 Phys. Rev. A 83 045402 and 2011 Eur. Phys. J. D 64 85-101), is significantly advanced in several directions. (1) Previously shown to work only for polar classical particles and polar macro-molecules, the trap is shown to work for polar diatomic molecules. (2) A homogeneous electric field, optionally switched on for improved stability in the angular direction, leads to stable trapping in higher order stability regions of the Mathieu equation. (3) Based on the Floquet formalism, analytical and numerical calculations are presented that show that the trap is quantum mechanically stable. (4) Definition and derivation of a quantum pseudo-potential allow a qualitative understanding of the quantum trapping mechanism. (5) It is shown that the proposed ac/dc trap may be realized experimentally using currently available scanning tunnelling microscopy technology.

Blmel, R.

2012-07-01

9

Electrostatic trapping of ultracold polar molecules  

NASA Astrophysics Data System (ADS)

This thesis describes the progress made in the production, spectroscopic characterization, and confinement of ultracold, polar NaCs molecules. A two-species MOT for the simultaneous cooling and trapping of sodium and cesium atoms is utilized for the creation of ultracold NaCs molecules via photoassociation. The molecules are detected via resonance-enhanced multi-photon ionization and subsequent ion detection with a channel electron multiplier. Spectra are obtained by scanning the frequencies of the photoassociating laser and the photoionizing laser. The resulting discovery that deeply bound, strongly polar molecules are created via one-step photoassociation has lead to efforts to confine the molecules via electric field trapping. The design of an electric field trap for polar molecules that can be superposed onto a magneto-optical trap is presented. This 'Thin WIre electro-Static Trap' (TWIST) has been built and successfully implemented. First experiments beyond the demonstration of successful trapping of NaCs molecules have been conducted, showing the effects of dissociative photoionization and inelastic collisions of electrically trapped NaCs molecules with cesium atoms confined by a MOT. An outline of a possible pathway to a quantum degenerate dipolar gas, exploiting the properties of the TWIST, is given at the end of this thesis.

Kleinert, Jan

10

Controlling polar molecules in optical lattices  

SciTech Connect

We theoretically investigate the interaction of polar molecules with optical lattices and microwave fields. We demonstrate the existence of frequency windows in the optical domain where the complex internal structure of the molecule does not influence the trapping potential of the lattice. In such frequency windows the Franck-Condon factors are so small that near-resonant interaction of vibrational levels of the molecule with the lattice fields have a negligible contribution to the polarizability, and light-induced decoherences are kept to a minimum. In addition, we show that microwave fields can induce a tunable dipole-dipole interaction between ground-state rotationally symmetric (J=0) molecules. A combination of a carefully chosen lattice frequency and microwave-controlled interaction between molecules will enable trapping of polar molecules in a lattice and possibly realize molecular quantum logic gates. Our results are based on ab initio relativistic electronic structure calculations of the polar KRb and RbCs molecules combined with calculations of their rovibrational motion.

Kotochigova, S. [Department of Physics, Temple University, Philadelphia, Pennsylvania 19122 (United States); National Institute of Standards and Technology, 100 Bureau Drive, Stop 8423, Gaithersburg, Maryland 20899 (United States); Tiesinga, E. [Department of Physics, Temple University, Philadelphia, Pennsylvania 19122 (United States)

2006-04-15

11

Controlling Polar Molecules in Optical Lattices  

E-print Network

We investigate theoretically the interaction of polar molecules with optical lattices and microwave fields. We demonstrate the existence of frequency windows in the optical domain where the complex internal structure of the molecule does not influence the trapping potential of the lattice. In such frequency windows the Franck-Condon factors are so small that near-resonant interaction of vibrational levels of the molecule with the lattice fields have a negligible contribution to the polarizability and light-induced decoherences are kept to a minimum. In addition, we show that microwave fields can induce a tunable dipole-dipole interaction between ground-state rotationally symmetric (J=0) molecules. A combination of a carefully chosen lattice frequency and microwave-controlled interaction between molecules will enable trapping of polar molecules in a lattice and possibly realize molecular quantum logic gates. Our results are based on ab initio relativistic electronic structure calculations of the polar KRb and RbCs molecules combined with calculations of their rovibrational motion.

S. Kotochigova; E. Tiesinga

2006-02-01

12

Decelerating polar molecules using traveling microwave lattices  

NASA Astrophysics Data System (ADS)

We propose a scheme to decelerate polar molecules by using traveling microwave lattices in a waveguide. Two counterpropagating microwave fields with different frequencies create a traveling microwave lattice and decelerate polar molecules by exploiting their first-order ac Stark shift. During deceleration, molecules are always close to the field maximum, thus reducing the potential particle loss due to nonadiabatic transitions occurring in the low-field region. The method can be used for molecules in a rotational ground state, which is suitable for further sympathetic or evaporative cooling. Numerical trajectory simulations are carried out, and the results show that the phase-space acceptance area is comparable to that of some other deceleration methods.

Hu, Zhong-Kun; Ke, Yi; Zhao, Jin-Bo; Deng, Xiao-Bing; Luo, Jun

2014-05-01

13

Prospects for Making Polar Molecules with Microwave Fields Svetlana Kotochigova  

E-print Network

, although the number of vibrationally cold molecules was relatively small and probably insufficientProspects for Making Polar Molecules with Microwave Fields Svetlana Kotochigova Department 17 August 2007) We propose a mechanism to produce ultracold polar molecules with microwave fields

Kotochigova, Svetlana

14

Tunable Holstein model with cold polar molecules  

NASA Astrophysics Data System (ADS)

We show that ultracold polar molecules trapped on an optical lattice can be used for quantum simulation of the Holstein polaron model. Rotational excitation of molecules on the lattice produces excitons that are coupled to lattice phonons due to long-range dipole - dipole interactions. We show that the properties of the excitons and the phonons as well as the exciton-phonon couplings can be controlled by applying a dc electric field and by varying the intensity of the trapping laser field. We discuss the application of polar molecules on an optical lattice for quantum simulation of non-Markovian open quantum systems. We also explore the possibilty of realizing a transition from the strongly coupled Holstein polaron limit to the polaron regime described by the Su-Schrieffer-Heeger model. Reference: F. Herrera and R. V. Krems, Phys. Rev. A 84, 051401(R) (2011)

Herrera, Felipe; Krems, Roman V.

2012-06-01

15

Tunable Holstein model with cold polar molecules  

SciTech Connect

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.

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

2011-11-15

16

Atomic Rydberg reservoirs for polar molecules.  

PubMed

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

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

2012-05-11

17

Interlayer Superfluidity in Bilayer Systems of Fermionic Polar Molecules  

SciTech Connect

We consider fermionic polar molecules in a bilayer geometry where they are oriented perpendicularly to the layers, which permits both low inelastic losses and superfluid pairing. The dipole-dipole interaction between molecules of different layers leads to the emergence of interlayer superfluids. The superfluid regimes range from BCS-like fermionic superfluidity with a high T{sub c} to Bose-Einstein (quasi-)condensation of interlayer dimers, thus exhibiting a peculiar BCS-Bose-Einstein condensation crossover. We show that one can cover the entire crossover regime under current experimental conditions.

Pikovski, A.; Santos, L. [Institut fuer Theoretische Physik, Leibniz Universitaet Hannover, Appelstrasse 2, 30169, Hannover (Germany); Klawunn, M. [Institut fuer Theoretische Physik, Leibniz Universitaet Hannover, Appelstrasse 2, 30169, Hannover (Germany); INO-CNR BEC Center and Dipartimento di Fisica, Universita di Trento, 38123 Povo (Italy); Shlyapnikov, G. V. [Laboratoire de Physique Theorique et Modeles Statistique, Universite Paris Sud, CNRS, 91405 Orsay (France); Van der Waals-Zeeman Institute, University of Amsterdam, Valckenierstraat 65/67, 1018 XE Amsterdam (Netherlands)

2010-11-19

18

Spontaneous interlayer superfluidity in bilayer systems of cold polar molecules  

SciTech Connect

Recent experimental progress in producing ultracold polar molecules with a net electric dipole moment opens up possibilities for realizing quantum phases governed by the long-range and anisotropic dipole-dipole interactions. In this work we predict the existence of experimentally observable broken-symmetry states with spontaneous interlayer coherence in cold polar molecule bilayers. These exotic states, which are manifestations of collective bilayer quantum entanglement, appear due to strong repulsive interlayer interactions and exhibit properties of superfluids, ferromagnets, and excitonic condensates.

Lutchyn, Roman M.; Das Sarma, S. [Joint Quantum Institute, Department of Physics, University of Maryland, College Park, Maryland 20742 (United States); Condensed Matter Theory Center, Department of Physics, University of Maryland, College Park, Maryland 20742 (United States); Rossi, Enrico [Condensed Matter Theory Center, Department of Physics, University of Maryland, College Park, Maryland 20742 (United States)

2010-12-15

19

Rotational correlation time of polar molecules  

E-print Network

Page IN TROD". . ' CTIO. '. THEOM' EXPE'%MEii I'AI PROCEKN3BE DATA ~EC i:ON. ANPI. ""'8 SECTION CONC''U y'iON. 25 32 LIST OF FIGURES Figure Page A 8'jock Diagram of' &ne Nuclear- Magnetic meso. . ani e Suectrometex 24 f'ne Values of ~t... ~? in prove the manuscript. INTRODUCTION Nuclear magnetic resonance can be used to study physical and dynamical properties of moliecules and atoms, which contain nuclei with magnetic nipole moments. If a large number of these molecules, referred to as a...

Allen, Carl Wayne

2012-06-07

20

Confinement Induced Quantum Phase Transition and Polarization Cooling in a Dipolar Crystal of Polar Molecules  

E-print Network

It is well-known that the liquid properties in a strongly confined system can be very different from their ordinary behaviors in an extended system, due to the competition between the thermal energy and the interaction energy. Here we show that, in a low-dimensional self-assembled dipolar crystal, the parabolic optical confinement potential can also strongly affect the quantum many-body properties in the low temperature regime. For example, by changing the confinement aspect ratio, the bulk of the system can undergo a quantum phase transition between a liquid state and a solid state via a nonmonotonic pattern formation of the domain wall. Furthermore, the entropy of a trapped dipolar crystal can be much larger than the liquid state in the weak dipole limit, indicating an intrinsic polarization cooling mechanism via increasing the external field. These highly correlated confinement effects are very important to the experimental preparation of a self-assembled dipolar crystal using ultracold polar molecules.

Yi-Ya Tian; Daw-Wei Wang

2008-08-09

21

Precision Spectroscopy of Polarized Molecules in an Ion Trap  

E-print Network

Polar molecules are desirable systems for quantum simulations and cold chemistry. Molecular ions are easily trapped, but a bias electric field applied to polarize them tends to accelerate them out of the trap. We present a general solution to this issue by rotating the bias field slowly enough for the molecular polarization axis to follow but rapidly enough for the ions to stay trapped. We demonstrate Ramsey spectroscopy between Stark-Zeeman sublevels in 180Hf19F+ with a coherence time of 100 ms. Frequency shifts arising from well-controlled topological (Berry) phases are used to determine magnetic g-factors. The rotating-bias-field technique may enable using trapped polar molecules for precision measurement and quantum information science, including the search for an electron electric dipole moment.

Loh, Huanqian; Grau, Matt; Ni, Kang-Kuen; Meyer, Edmund R; Bohn, John L; Ye, Jun; Cornell, Eric A

2013-01-01

22

Spin Waves and Dielectric Softening of Polar Molecule Condensates  

NASA Astrophysics Data System (ADS)

We consider an oblate Bose-Einstein condensate of heteronuclear polar molecules in a weak applied electric field. This system supports a rich quasiparticle spectrum that plays a critical role in determining its bulk dielectric properties. In particular, in sufficiently weak fields the system undergoes a polarization wave rotonization, leading to the development of textured electronic structure and a dielectric instability that is characteristic of the onset of a negative static dielectric function.

Wilson, Ryan M.; Peden, Brandon M.; Clark, Charles W.; Rittenhouse, Seth T.

2014-04-01

23

Spin-orbital dynamics in a system of polar molecules.  

PubMed

Spin-orbit coupling in solids normally originates from the electron motion in the electric field of the crystal. It is key to understanding a variety of spin-transport and topological phenomena, such as Majorana fermions and recently discovered topological insulators. Implementing and controlling spin-orbit coupling is thus highly desirable and could open untapped opportunities for the exploration of unique quantum physics. Here we show that dipole-dipole interactions can produce an effective spin-orbit coupling in two-dimensional ultracold polar molecule gases. This spin-orbit coupling generates chiral excitations with a non-trivial Berry phase 2?. These excitations, which we call chirons, resemble low-energy quasiparticles in bilayer graphene and emerge regardless of the quantum statistics and for arbitrary ratios of kinetic to interaction energies. Chirons manifest themselves in the dynamics of the spin density profile, spin currents and spin coherences, even for molecules pinned in a deep optical lattice and should be observable in current experiments. PMID:25377238

Syzranov, Sergey V; Wall, Michael L; Gurarie, Victor; Rey, Ana Maria

2014-01-01

24

Infrared Spectra of Polar Diatomic Molecules in Quadrupolar Condensed Solvents  

Microsoft Academic Search

The present paper is devoted to the computation of the infrared spectral properties of couples containing a polar and a quadrupolar molecule located at fixed distances which are permanently realized in condensed media. A study of the orientational quantum states of such couples using an asymptotic method is presented. This method is particularly suited when the angle dependent variation of

C. Girardet; D. Robert; L. Galatry

1971-01-01

25

Rotational Frenkel excitons in optical lattices with polar molecules  

NASA Astrophysics Data System (ADS)

Ultracold polar molecules trapped in an optical lattice may form crystal-like structures with unique properties. Here, I will discuss a Mott insulator phase of ultracold molecules with one molecule per lattice site under conditions that can be realized in ongoing experiments with optical lattices. I will show that dipole-dipole interactions between molecules in different lattice sites give rise to collective excitations, such as Frenkel excitons, characteristic of solid-state molecular crystals. Due to the perturbative nature of the intermolecular interactions, the collective excitations in this system can be controlled by an external electric field. This can be used to realize Frenkel excitons in the presence of dynamically tunable disorder or an ensemble of Frenkel excitons with tunable exciton - exciton interactions. An external electric field can thus be used to induce strong localization or delocalization of Frenkel excitons as well as bi-exciton annihilation. The latter can be used to produce dark exciton states and entangled exciton pairs. The complicated quantum statistics of excitons leads to kinematic interactions. Our results show that the kinematic interactions can be eliminated by varying an external electric field, effectively leading to a system of quantum quasi-particles with tunable quantum statistics. [4pt] [1] ``Tunable disorder in a crystal of cold polar molecules,'' Felipe Herrera, Marina Litinskaya, Roman V. Krems, Phys. Rev. A 82, 033428 (2010).

Litinskaya, Marina

2011-06-01

26

Dissociation of Highly Excited Molecules  

NASA Astrophysics Data System (ADS)

A survey of the spectroscopy and dynamics of the dissociation of highly excited molecules is presented with emphasis on superexcited molecules by electron- and photon-impact.(See review articles: a) Y. Hatano, The Physics of Electronic and Atomic Collisions, eds., L. J. Dube et al., AIP Press, New York (1995) pp.67-88; b) N.Kouchi et al., J. Phys. B, 30, 2319 (1997); c) Y. Hatano, Dynamics of Excited Molecules, ed., K. Kuchitsu, Elsevier, Amsterdam (1994) Chapter 6.) Topics will include newly developed experimental methods covering two-dimensional spectroscopy of photodissociation(M. Ukai et al., Phys. Rev. Lett., 74, 239 (1995).) (S. Machida et al., J. Phys. Chem. A. 101, 656 (1997).) (A. Ehresmann et al., J. Phys. B, 29, 3629 (1996).), and coincident electron-energy-loss spectroscopy of the dissociation dynamics of highly excited molecules.(T. Odagiri et al., J. Phys. B, 28, L465 (1995).)(T. Odagiri et al., J. Phys. B, 29, 1829 (1996).) The measurement of absolute photoionization quantum yields will also be discussed.(K. Kameta et al., J. Chem. Phys., 99, 2487 (1993).) Comparative studies of electron- and photon-impact dissociative excitation of molecules will be summarized. The molecules studied are H_2, N_2, O_2, CO, CO_2, N_2O, hydrocarbons, and some Si-containing compounds.

Hatano, Yoshihiko

1997-10-01

27

Frenkel biexcitons in optical lattices with polar molecules  

NASA Astrophysics Data System (ADS)

Rotational excitation of ultracold polar molecules trapped on an optical lattice produces rotational Frenkel excitons (collective rotational excitations) [1]. We show that non-linear interactions between these excitons can be tuned by applying a dc electric field. We show that, at electric fields greater than a critical value, rotational Frenkel excitons form bound pairs -- biexcitons [2]. Frenkel biexcitons are strongly correlated states of two collective excitations in a molecular crystal, which are exceedingly hard to create and observe in solid-state crystals. We demonstrate that the binding energy of the rotational biexcitons can be controlled by tuning the angle between the applied field and the molecular array. Frenkel biexcitons can be used for many applications ranging from the controlled preparation of entanglement between quasi-particles to the study of bipolarons. [4pt] [1] ``Frenkel biexcitons in optical lattices with polar molecules,'' Ping Xiang, M. Litinskaya, R. V. Krems; cond-mat/1112.3942. [0pt] [2] ``Tunable disorder in a crystal of cold polar molecules,'' F. Herrera, M. Litinskaya, R. V. Krems, Phys. Rev. A 82, 033428 (2010).

Litinskaya, Marina; Xiang, Ping; Krems, Roman

2012-06-01

28

Far-from-Equilibrium Quantum Magnetism with Ultracold Polar Molecules  

NASA Astrophysics Data System (ADS)

Recent theory has indicated how to emulate tunable models of quantum magnetism with ultracold polar molecules. Here we show that present molecule optical lattice experiments can accomplish three crucial goals for quantum emulation, despite currently being well below unit filling and not quantum degenerate. The first is to verify and benchmark the models proposed to describe these systems. The second is to prepare correlated and possibly useful states in well-understood regimes. The third is to explore many-body physics inaccessible to existing theoretical techniques. Our proposal relies on a nonequilibrium protocol that can be viewed either as Ramsey spectroscopy or an interaction quench. The proposal uses only routine experimental tools available in any ultracold molecule experiment. To obtain a global understanding of the behavior, we treat short times pertubatively, develop analytic techniques to treat the Ising interaction limit, and apply a time-dependent density matrix renormalization group to disordered systems with long range interactions.

Hazzard, Kaden R. A.; Manmana, Salvatore R.; Foss-Feig, Michael; Rey, Ana Maria

2013-02-01

29

Stable Topological Superfluid Phase of Ultracold Polar Fermionic Molecules  

SciTech Connect

We show that single-component fermionic polar molecules confined to a 2D geometry and dressed by a microwave field may acquire an attractive 1/r{sup 3} dipole-dipole interaction leading to superfluid p-wave pairing at sufficiently low temperatures even in the BCS regime. The emerging state is the topological p{sub x}+ip{sub y} phase promising for topologically protected quantum information processing. The main decay channel is via collisional transitions to dressed states with lower energies and is rather slow, setting a lifetime of the order of seconds at 2D densities approx10{sup 8} cm{sup -2}.

Cooper, N. R. [TCM Group, University of Cambridge, Cavendish Laboratory, J. J. Thomson Avenue, Cambridge CB3 0HE (United Kingdom); Laboratoire de Physique Theorique et Modeles Statistiques, Universite Paris Sud, CNRS, 91405 Orsay (France); Shlyapnikov, G. V. [Laboratoire de Physique Theorique et Modeles Statistiques, Universite Paris Sud, CNRS, 91405 Orsay (France); van der Waals-Zeeman Institute, University of Amsterdam, Valckenierstraat 65/67, 1018 XE Amsterdam (Netherlands)

2009-10-09

30

Tunable disorder in a crystal of cold polar molecules  

SciTech Connect

We show that a two-species mixture of polar molecules trapped on an optical lattice gives rise to a system of rotational excitons in the presence of tunable impurities. The exciton-impurity interactions can be controlled by an external electric field, which can be exploited for quantum simulation of localization phenomena in disordered media. We demonstrate that an external electric field can be used to induce resonant enhancement of the exciton-impurity scattering cross sections and delocalization of excitonic states in a correlated one-dimensional disorder potential.

Herrera, Felipe; Krems, Roman V. [Department of Chemistry, University of British Columbia, Vancouver, British Columbia, V6T 1Z1 (Canada); Litinskaya, Marina [Department of Chemistry, University of British Columbia, Vancouver, British Columbia, V6T 1Z1 (Canada); Institute of Spectroscopy RAS, Troitsk, Moscow Region 142190 (Russian Federation)

2010-09-15

31

Topological phases in ultracold polar-molecule quantum magnets  

NASA Astrophysics Data System (ADS)

We show how to use polar molecules in an optical lattice to engineer quantum spin models with arbitrary spin S?1/2 and with interactions featuring a direction-dependent spin anisotropy. This is achieved by encoding the effective spin degrees of freedom in microwave-dressed rotational states of the molecules and by coupling the spins through dipolar interactions. We demonstrate how one of the experimentally most accessible anisotropies stabilizes symmetry protected topological phases in spin ladders. Using the numerically exact density matrix renormalization group method, we find that these interacting phasespreviously studied only in the nearest-neighbor casesurvive in the presence of long-range dipolar interactions. We also show how to use our approach to realize the bilinear-biquadratic spin-1 and the Kitaev honeycomb models. Experimental detection schemes and imperfections are discussed.

Manmana, Salvatore R.; Stoudenmire, E. M.; Hazzard, Kaden R. A.; Rey, Ana Maria; Gorshkov, Alexey V.

2013-02-01

32

Symmetry Protected Topological Phases in Polar Molecule Spin Ladder Systems  

NASA Astrophysics Data System (ADS)

We show how to use polar molecules in an optical lattice to engineer quantum spin models with arbitrary spin S >=1/2 and with interactions featuring a direction-dependent spin anisotropy. This is achieved by encoding the effective spin degrees of freedom in microwave-dressed rotational states of the molecules and by coupling the spins through dipolar interactions. We demonstrate how one of the experimentally most accessible anisotropies stabilizes symmetry protected topological phases in spin ladders. Using the numerically exact density matrix renormalization group method, we find that these phases -- previously studied only in the nearest-neighbor case -- survive in the presence of long-range dipolar interactions. We also show how to use our approach to realize the bilinear-biquadratic spin-1 and the Kitaev honeycomb models. Experimental detection schemes and imperfections are discussed.

Manmana, S. R.; Stoudenmire, E. M.; Hazzard, K. R. A.; Rey, A. M.; Gorshkov, A. V.

2013-03-01

33

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

PubMed

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

Sagawa, Naoya; Shikata, Toshiyuki

2014-07-14

34

Multi-channel modelling of the formation of vibrationally cold polar KRb molecules.  

E-print Network

Multi-channel modelling of the formation of vibrationally cold polar KRb molecules. Svetlana, PA 19122-6082, USA 2 Joint Quantum Institute, NIST and University of Maryland, Gaithersburg, Maryland of vibrationally and translationally cold polar 40K87Rb molecules [1, 2]. Cold molecules were created from very

Kotochigova, Svetlana

35

Density Waves in Layered Systems with Fermionic Polar Molecules  

E-print Network

A layered system of two-dimensional planes containing fermionic polar molecules can potentially realize a number of exotic quantum many-body states. Among the predictions, are density-wave instabilities driven by the anisotropic part of the dipole-dipole interaction in a single layer. However, in typical multilayer setups it is reasonable to expect that the onset and properties of a density-wave are modified by adjacent layers. Here we show that this is indeed the case. For multiple layers the critical strength for the density-wave instability decreases with the number of layers. The effect depends on density and is more pronounced in the low density regime. The lowest solution of the instability corresponds to the density waves in the different layers being in-phase, whereas higher solutions have one or several adjancet layers that are out of phase. The parameter regime needed to explore this instability is within reach of current experiments.

N. T. Zinner; G. M. Bruun

2011-02-08

36

Beam broadening of polar molecules and clusters in deflection experiments.  

PubMed

A beam of rotating dipolar particles (molecules or clusters) will broaden when passed through an electric or magnetic field gradient region. This broadening, which is a common experimental observable, can be expressed in terms of the variance of the distribution of the resulting polarization orientation (the direction cosine). Here, the broadening for symmetric-top and linear rotors is discussed. These two types of rotors have qualitatively different low-field orientation distribution functions, but behave similarly in a strong field. While analytical expressions for the polarization variance can be derived from first-order perturbation theory, for experimental guidance it is important to identify the applicability and limitations of these expressions, and the general dependence of the broadening on the experimental parameters. For this purpose, the analytical results are compared with the full diagonalization of the rotational Stark-effect matrices. Conveniently for experimental estimations, it is found that for symmetric tops, the dependence of the broadening parameter on the rotational constant, the axial ratio, and the field strength remains similar to the analytical expression even outside of the perturbative regime. Also, it is observed that the shape envelope, the centroid, and the width of the orientation distribution function for a symmetric top are quite insensitive to the value of its rotational constant (except at low rotational temperatures). PMID:22239775

Bulthuis, J; Kresin, V V

2012-01-01

37

Search for Asymmetric Interactions between Chiral Molecules and Spin-Polarized Electrons  

E-print Network

Search for Asymmetric Interactions between Chiral Molecules and Spin-Polarized Electrons EXPERIMENT In this experiment, spin-polarized electrons with alternating forward valve; (7) chiral target cell; (8) optical polarimeter target cell; (9) lens; (10

Gay, Timothy J.

38

Dynamic nuclear polarization at high magnetic fields  

PubMed Central

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 mechanismsthe 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

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

39

Development of techniques for cooling and trapping polar diatomic molecules  

NASA Astrophysics Data System (ADS)

The study of ultracold dipolar molecules is an important emerging frontier in atomic physics. This thesis discusses the development of techniques for cooling diatomic molecules, focussing specifically on the idea of using a microwave frequency quasi-optical dipole trap for evaporative cooling. A prototype for such a trap has been designed, constructed, and tested. In order to load the microwave trap, a helium buffer gas cooled molecular beam source has been developed and characterized - in a variety of flow regimes, ranging from the effusive (thermal mean velocity, moderate flux), to the deeply hydrodynamic (large forward velocity, high-flux, high collimation). We explain the development of this source in detail. In particular, we describe recent work towards demonstrating direct laser cooling of a hydrodynamic SrF molecular beam. We have identified a set of quasi-closed transitions which should enable more than 104 photon scattering events, sufficient to decelerate a hydrodynamic beam to the Doppler limit. We present experimental results demonstrating optical deflection of a SrF beam by radiative force using this scheme, in which each molecule scatters on the order of 150 photons, limited by its interaction time with the lasers.

Glenn, David R.

40

Toward scalable information processing with ultracold polar molecules in an electric field: a numerical investigation  

E-print Network

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 focuse 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-Josza 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 hundred of microseconds, opening promising perspectives for the manipulation of a large number of qubits in these systems.

Latitia Bomble; Philippe Pellegrini; Pierre Ghesquire; Michle Desouter-Lecomte

2010-08-16

41

Observation of rotational polarization produced in molecule-surface collisions  

Microsoft Academic Search

The rotational polarization produced by scattering a rotationally cold beam of NO from Ag(111) has been measured by laser-induced fluorescence. A strong rotational polarization perpendicular to the surface normal is observed. The degree of polarization depends strongly on final rotational state, incident energy, and incident angle.

A. C. Luntz; A. W. Kleyn; D. J. Auerbach

1982-01-01

42

Observation of rotational polarization produced in molecule-surface collisions  

Microsoft Academic Search

The rotational polarization produced by scattering a rotationally cold beam of NO from Ag(111) has been measured by laser-induced fluorescence. A strong rotational polarization perpendicular to the surface normal is observed. The degree of polarization depends strongly on final rotational state, incident energy, incident angle, and surface temperature.

A. C. Luntz; A. W. Kleyn; D. J. Auerbach

1982-01-01

43

High-energy electron scattering from molecules  

NASA Astrophysics Data System (ADS)

Waller-Hartree and first Born cross sections for the inelastic and elastic scattering of X-rays and fast electrons from molecules are investigated. The effects of one particle basis set size, correlation and vibration are examined. The results of a search for the basis set of reasonable size that best approximates an estimated Hartree-Fock limit for the four molecules, B 2H6, H2O, N2, and SiH4 recommend the general use of a double zeta plus polarization plus an additional diffuse function of each symmetry. The effect of correlation on cross sections for the series of molecules: N2, O2, CO2, H2O, SiH4, B2H6, NH3 is considered. We report calculations of elastic and inelastic scattering factors for these molecules accounting for the effects of electron correlation using high quality multi- reference Cl wavefunctions. Cross sections for the elastic scattering of X-rays and fast electrons by H2O are calculated using self-consistent-field electronic wave functions and are then averaged over the five lowest vibrational states. The differences between the vibrationally averaged cross sections and their equilibrium counterparts are small. Atomic and orbitalwise Compton defects are evaluated for the closed-shell inert atomic systems: He, Ne, Ar, and Kr, by employing the Hohenberg-Kohn-Sham density- functional approach. These corrections to the Compton profiles are seen to compare well with earlier effective hydrogenic estimates. Koga and Thakkar's reoptimized (9s5p)/[4s2p] and (12s7p)/[7s4p] Gaussian basis sets for the atoms Li to Ne, and their (4s)/[2s] and (6s)/[4s] sets for H and He, respectively, are tested by performing self-consistent- field (SCF) geometry optimizations on LiH, BeH2, B2H 6, CH4, NH3, H2O and HF. The equilibrium geometries of hydrogen peroxide and hydrazine are determined at both the SCF and fourth-order many body perturbation theory level. Segmented contractions of Koga and Thakkar's reoptimized (12s8p)/[6s4p] and (12s9p)/[6s5p] Gaussian basis sets for the atoms Na to Ar, are tested by performing self- consistent-field (SCF) geometry optimizations on NaH, MgH2, A12Cl6, SiH4, P 2H4, H2S2, SO3, HCl and CIF3.

Hoffmeyer, Ruth Ellen

1998-12-01

44

Electrostatic versus polarization effects in the adsorption of aromatic molecules of varied polarity on an insulating hydrophobic surface  

NASA Astrophysics Data System (ADS)

Ab initio calculations have been used to investigate the electronic and energetic behaviour accompanying the adsorption of aromatic molecules of different polarities onto an insulating hydrophobic surface, as a convenient model for the study of characteristic weak adsorption processes in biochemistry (ligand-receptor interactions) and geochemistry (aromatic pollutants on soil minerals). Four poly-chlorinated dibenzo-p-dioxin molecules of different polarities were chosen as adsorbates; the surface was the (001) surface of pyrophyllite, a chemically inert, weakly polar, covalently bonded surface. The fairly weak interactions were observed to be dominated by local electrostatics rather than global multipoles or hybridization. The polarization induced on the adsorbate has been analysed. A small transfer of electron density was also observed from the molecule to the surface.

Austen, Kat F.; White, Toby O. H.; Marmier, Arnaud; Parker, Steve C.; Artacho, Emilio; Dove, Martin T.

2008-01-01

45

Microgels for the encapsulation and stimulus-responsive release of molecules with distinct polarities.  

PubMed

A microfluidic strategy for the encapsulation and stimulus-responsive release of molecules with distinct polarities from the interior of microgels is reported. The approach relies on (i) the generation of a primary O/W emulsion by the ultrasonication method, (ii) MF emulsification of the primary emulsion, and (iii) photopolymerization of the monomer present in the aqueous phase of the droplets, thereby transforming them into microgels. Non-polar molecules are dissolved in oil droplets embedded in the microgels. Polar molecules are physically associated with the hydrogel network. Upon heating, the microgels contract and release polar and non-polar cargo molecules. The approach paves the way for stimuli-responsive vehicles for multiple drug delivery. PMID:21504069

Jagadeesan, Dinesh; Nasimova, Irina; Gourevich, Ilya; Starodubtsev, Sergey; Kumacheva, Eugenia

2011-07-01

46

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

SciTech Connect

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.

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

47

Implementation of quantum logic gates using polar molecules in pendular states.  

PubMed

We present a systematic approach to implementation of basic quantum logic gates operating on polar molecules in pendular states as qubits for a quantum computer. A static electric field prevents quenching of the dipole moments by rotation, thereby creating the pendular states; also, the field gradient enables distinguishing among qubit sites. Multi-target optimal control theory is used as a means of optimizing the initial-to-target transition probability via a laser field. We give detailed calculations for the SrO molecule, a favorite candidate for proposed quantum computers. Our simulation results indicate that NOT, Hadamard and CNOT gates can be realized with high fidelity, as high as 0.985, for such pendular qubit states. PMID:23320665

Zhu, Jing; Kais, Sabre; Wei, Qi; Herschbach, Dudley; Friedrich, Bretislav

2013-01-14

48

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

PubMed

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 H2 (+) (or D2 (+)) ions into the Lamb-shift polarimeter. PMID:25362391

Engels, Ralf; Gorski, Robert; Grigoryev, Kiril; Mikirtychyants, Maxim; Rathmann, Frank; Seyfarth, Hellmut; Strher, Hans; Weiss, Philipp; Kochenda, Leonid; Kravtsov, Peter; Trofimov, Viktor; Tschernov, Nikolay; Vasilyev, Alexander; Vznuzdaev, Marat; Schieck, Hans Paetz Gen

2014-10-01

49

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

NASA Astrophysics Data System (ADS)

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.

Odak, S.; ?erki?, A.; Busuladi?, M.; Hasovi?, E.; Gazibegovi?-Busuladi?, A.; Miloevi?, D. B.

2014-09-01

50

Orientational imaging of single molecules by using azimuthal and radial polarizations.  

PubMed

Three-dimensional molecular orientations of single fluorescence molecules in polymeric thin films were measured by focused azimuthally and radially polarized light, in which we found that the fluorescence intensity was dependent on the depth position of the molecule with respect to the film surface. We found that the fluorescence intensity for a molecule which is 80 nm deep in the film excited by radial polarization is appreciably larger when compared with the fluorescence intensity for a molecule which is also excited by radial polarization but which is closer to the polymer/air interface, a feature which leads to different fluorescence intensities, under excitation by radial polarization, for molecules with the same polar orientation but with different depths inside the film. We also found that the variation of fluorescence intensity from a molecule inside an 80 nm film in radial polarization is appreciably larger compared with one in azimuthal polarization. These findings were confirmed by comparing experiments using different thickness films with theoretically calculated electric field distributions. PMID:20146536

Ishitobi, Hidekazu; Nakamura, Issei; Hayazawa, Norihiko; Sekkat, Zouheir; Kawata, Satoshi

2010-03-01

51

Spin-Polarized Electron Induced Asymmetric Reactions in Chiral Molecules  

NASA Astrophysics Data System (ADS)

Understanding the origin of chirality in nature has been an active area of research since the time of Pasteur. In this chapter we examine one possible route by which this asymmetry could have arisen, namely chiral-specific chemistry induced by spin-polarized electrons. The various sources of spin-polarized electrons (parity violation, photoemission, and secondary processes) are discussed. Experiments aimed at exploring these interactions are reviewed starting with those based on the Vester-Ulbricht hypothesis through recent studies of spin polarized secondary electrons from a magnetic substrate. We will conclude with a discussion of possible new avenues of research that could impact this area.

Rosenberg, Richard A.

52

Investigations of electron helicity in optically active molecules using polarized beams of electrons and positrons  

NASA Technical Reports Server (NTRS)

A positronium-formation experiment with a high sensitivity to a possible relation between the helicity of beta particles emitted in nuclear beta decay and the optical asymmetry of biological molecules is presented. The experiment is based on a mechanism in which the electrons in optically active molecules possess a helicity of less than 0.001, too weak to detect in radiolysis experiments, the sign of which depends on the chirality of the isomer. A helicity-dependent asymmetry is sought in the formation of the triplet ground state of positronium when a low-energy beam of polarized positrons of reversible helicity interacts with an optically active substance coating a channel electron multiplier. Asymmetries between positronium decays observed at positive and negative helicities for the same substance can thus be determined with a sensitivity of 0.0001, which represents a factor of 100 improvement over previous positronium experiments.

Gidley, D. W.; Rich, A.; Van House, J. C.; Zitzewitz, P. W.

1981-01-01

53

Dynamic nuclear polarization of amorphous and crystalline small molecules  

E-print Network

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 ...

Ong, Ta-Chung

2014-01-01

54

New quasiparticles hystons and coherent photoinduced dynamics of molecules in polar disordered media  

Microsoft Academic Search

Using methods of statistical thermodynamics, it is shown that after pulse excitation the evolution of a polar luminescent\\u000a probepolar disordered medium system is described by an equation of damping vibrations. This allows the conclusion that in\\u000a the solvate shell of the probe molecule synchronous rotational vibrations (librations) of the molecules of the medium occur,\\u000a whose damping is caused by dielectric

V. S. Pavlovich

1998-01-01

55

Universalities in ultracold reactions of alkali-metal polar molecules  

SciTech Connect

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}.

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

56

Universalities in ultracold reactions of alkali-metal polar molecules  

NASA Astrophysics Data System (ADS)

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.

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

2011-12-01

57

Surface-induced heating of cold polar molecules  

E-print Network

We study the rotational and vibrational heating of diatomic molecules placed near a surface at finite temperature on the basis of macroscopic quantum electrodynamics. The internal molecular evolution is governed by transition rates that depend on both temperature and position. Analytical and numerical methods are used to investigate the heating of several relevant molecules near various surfaces. We determine the critical distances at which the surface itself becomes the dominant source of heating and we investigate the transition between the long-range and short-range behaviour of the heating rates. A simple formula is presented that can be used to estimate the surface-induced heating rates of other molecules of interest. We also consider how the heating depends on the thickness and composition of the surface.

Stefan Yoshi Buhmann; M. R. Tarbutt; Stefan Scheel; E. A. Hinds

2008-06-18

58

Polarization-specific adsorption of organic molecules on ferroelectric LiNbO3 surfaces  

NASA Astrophysics Data System (ADS)

Polarization effect on adsorption of d-cysteine molecules on ferroelectric LiNbO3 surfaces is studied by a combination of infrared spectramicroscopy and spatially resolved x-ray absorption near edge spectroscopy. It is shown that even in the absence of any electronic excitation (optical or thermal), the adsorption is still polarization-specific with preferential d-cysteine deposition occurring on positive domains. This observation rules out molecular adsorption solely due to pyroelectric or photoinduced charge and suggests possible dipole-dipole interaction between polar d-cysteine molecules and ferroelectric polarization dipoles. The surface chemistry related to polarization-dependent variations in Li/Nb concentration is also implicated as a contributing factor in the domain-specific adsorption of d-cysteine.

Zhang, Zhengzheng; Sharma, P.; Borca, C. N.; Dowben, P. A.; Gruverman, A.

2010-12-01

59

Slowing polar molecules using a wire Stark decelerator  

NASA Astrophysics Data System (ADS)

We have designed and implemented a new Stark decelerator based on wire electrodes, which is suitable for ultrahigh vacuum applications. The 100 deceleration stages are fashioned out of 0.6 mm diameter tantalum and the array's total length is 110 mm, approximately 10 times smaller than a conventional Stark decelerator with the same number of electrode pairs. Using the wire decelerator, we have removed more than 90% of the kinetic energy from metastable CO molecules in a beam.

Marian, A.; Haak, H.; Geng, P.; Meijer, G.

2010-08-01

60

High harmonic interferometry of multi-electron dynamics in molecules.  

PubMed

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-Angstrm 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

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

2009-08-20

61

Polarization justified Fukui functions: The theory and applications for molecules  

NASA Astrophysics Data System (ADS)

The Fukui functions based on the computable local polarizability vector have been presented for a group of simple molecules. The necessary approximation for the density functional theory softness kernel has been supported by a theoretical analysis unifying and generalizing early concepts produced by the several authors. The exact relation between local polarizability vector and the derivative of the nonlocal part of the electronic potential over the electric field has been demonstrated. The resulting Fukui functions are unique and represent a reasonable refinement when compared to the classical ones that are calculated as the finite difference of the density in molecular ions. The new Fukui functions are strongly validated by their direct link to electron dipole polarizabilities that are reported experimentally and by other computational methods.

Komorowski, Ludwik; Lipi?ski, Jzef; Szarek, Pawe?; Ordon, Piotr

2011-07-01

62

Electric field-dependent dynamic polarizability and "magic'' conditions for optical trapping of polar molecules  

E-print Network

Selection of ``magic'' trapping conditions with ultracold atoms or molecules, where pairs of internal states experience identical trapping potentials, brings substantial benefits to precision measurements and quantum computing schemes. Working at such conditions could ensure that detrimental effects of inevitable inhomogeneities across an ultracold sample are significantly reduced. However, this aspect of confinement remains unexplored for ultracold polar molecules. Here, we present means to control the AC Stark shift of rotational states of ultracold polar molecules, when subjected to both trapping laser light and an external electric field. We show that both the strength and relative orientation of the two fields influence the trapping potential. In particular, we predict ``magic electric field strengths" and a ``magic angle", where the Stark shift is independent of the DC external field and rotational states of the molecule.

Kotochigova, Svetlana

2010-01-01

63

Electric field-dependent dynamic polarizability and "magic" conditions for optical trapping of polar molecules  

E-print Network

Selection of "magic" trapping conditions with ultracold atoms or molecules, where pairs of internal states experience identical trapping potentials, brings substantial benefits to precision measurements and quantum computing schemes. Working at such conditions could ensure that detrimental effects of inevitable inhomogeneities across an ultracold sample are significantly reduced. However, this aspect of confinement remains unexplored for ultracold polar molecules. Here, we present means to control the AC Stark shift of rotational states of ultracold polar molecules, when subjected to both trapping laser light and an external electric field. We show that both the strength and relative orientation of the two fields influence the trapping potential. In particular, we predict "magic electric field strengths" and a "magic angle", where the Stark shift is independent of the DC external field and rotational states of the molecule.

Svetlana Kotochigova; David DeMille

2010-08-23

64

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

SciTech Connect

We present combined experimental and theoretical results on strong-field ionization of oriented carbonyl sulfide 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. The focus of the present article is to understand the strong-field ionization of one-dimensionally-oriented polar molecules, in particular asymmetries in the emission direction of the photoelectrons. In the following article [Phys. Rev. A 83, 023406 (2011)] the focus is to understand strong-field ionization from three-dimensionally-oriented asymmetric top molecules, in particular the suppression of electron emission in nodal planes of molecular orbitals.

Dimitrovski, Darko; Abu-samha, Mahmoud; Madsen, Lars Bojer; Filsinger, Frank; Meijer, Gerard; Kuepper, Jochen [Lundbeck Foundation Theoretical Center for Quantum System Research, Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C (Denmark); Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin (Germany); Holmegaard, Lotte; Kalhoej, Line [Department of Chemistry, Aarhus University, DK-8000 Aarhus C (Denmark); Nielsen, Jens H. [Department of Physics, 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)

2011-02-15

65

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

SciTech Connect

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.

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

66

Student construction of small molecule models using Spartan Model to explore polarity  

NASA Astrophysics Data System (ADS)

This study compared the attitudes and the gains of knowledge concerning Lewis structures and polarity of molecules. The students performed a lab exercise in which they drew Lewis structures, constructed models of the molecules, determined the geometry of the molecules, and determined the polarity of the molecules. The control group students constructed models using physical ball-and-stick models. The treatment group students used Spartan Model to construct models. Students from a university and a community college participated in this study. Four lab classes at each school made up the treatment group. Five lab classes at the university and three lab classes at the community college made up the control group. The treatment group classes were selected based on available computer resources. All students in the study were given the Lab Pre Test, Lab Post Test, and the Lecture Post Test to assess the student's ability to answer questions pertaining to Lewis structures and polarity of molecules. An Attitudinal Survey assessed the attitudes of the students who participated in the study. Student interviews were performed to assess the student's attitudes towards the lab exercise. The interviews investigated attitudes about the modeling exercise, Lewis structures, and polarity of molecules. There were no significant differences in the performance of the treatment group when compared to the control group on the performance assessment instruments at the university or the community college. The treatment group students at the university had a more positive attitude about the lab activity. They believed that the lab activity helped them better understand the concepts of Lewis structure and molecular polarity. At the community college, the control group students had a more positive attitude about the lab activity. The students involved in the study believed that the lab activity helped them to understand the concepts of molecular geometry and polarity. The interviews of the treatment group students indicated that they strongly believed that the lab activity helped them better understand the concept of Lewis structures and of molecular polarity. As reflected in the interviews of the treatment group and the control group, the lab activity did not help the students be able to look at a Lewis structure and build a mental image of the molecule. The students believed the electrostatic potential plots generated by Spartan Model were very insightful into the concept of polarity. It gave them a visual representation of a difficult topic.

Dale, Glenn Lamar

67

High Energy Polarization - Historical Remarks  

NASA Technical Reports Server (NTRS)

We discuss the history and briefly outline the potential scientific impact of X-ray polarimetry and in particular studies of the Crab nebula and its pulsar. Despite major progress in X-ray imaging, spectroscopy, and timing, there have been only modest attempts at X-ray polarimetry. The last dedicated experiment, conducted by us over three decades ago, had such limited observing time and sensitivity that even a ten percent degree of polarization would not have been detected from some of the brightest X-ray sources in the sky, and statistically-significant X-ray polarization was detected in only the subject of this meeting, the Crab Nebula. Radio and optical astronomers use polarimetry extensively to probe the radiation physics and the geometry of sources. Sensitive X-ray polarimetry promises to reveal unique and crucial information about physical processes and structure of of all classes of X-ray sources. X-ray polarimetry remains the last undeveloped tool for the X-ray study of astronomical objects and needs to be properly exploited. We hope that this conference may mark the beginning of a new era for for this important scientific window.

Weisskopf, Martin C.

2008-01-01

68

Rate coefficients of the reactions of ions with polar molecules at interstellar temperatures  

NASA Astrophysics Data System (ADS)

A theory has been developed recently which predicts that the rate coefficients, k, for the reactions of ions with polar molecules at low temperatures will be much greater than the canonical value of 10 to the -9th cu cm/s. The new theory indicates that k is greatest for low-lying rotational states and increases rapidly with decreasing temperature. Recent laboratory measurements which validate the theory, are examined, calculated values of k for the reactions of H3(+) ions with several polar molecules are presented, and their significance to interstellar chemistry is discussed. For the reactions of ions with molecules having large dipole moments, it is recommended that k values as large as 10 to the -7th cu cm/s should be used in ion-chemical models of low-temperature instellar clouds.

Adams, N. G.; Smith, D.; Clary, D. C.

1985-09-01

69

Extension of High Polymer Molecule and Energy Change by Mixing  

Microsoft Academic Search

The change in intermolecular potential energy produced by mixing some low molecular liquids, which are considered as the substitute for the chain elements of polystyrene molecule, with several non-polar solvents and the extension of polystyrene molecule in these solvents were measured, and the obtained results were compared with the theory. Determination of the energy change was made by means of

Hiroshi Mizutani

1961-01-01

70

Quantum state selection of polar molecules: Alignment, orientation and conformational control  

NASA Astrophysics Data System (ADS)

Building on ideas that go back to Stern in the 1920s we use an inhomogeneous static electric field to deflect a cold beam of polar molecules. The deflection spatially disperses the rotational quantum states of the molecules. We show that the molecules residing in the lowest-lying rotational states can be selected and used as targets for further experiments. In particular, the quantum-state-selected molecules enable unprecedented strong alignment, induced by a moderately intense laser pulse, as well as strong orientation induced by a mixed laser and static electric field. Here, alignment refers to confinement of one or more molecule-fixed axes along laboratory-fixed axes, and orientation refers to the molecular dipole moments pointing in a specific direction. Also, it is shown that the deflection enables separation of the different conformers of a single molecule. We discuss new opportunities offered by the enhanced degree of orientational control, made possibly by quantum state selection, including time resolved studies of torsion, and eventually enantiomeric conversion, of axially chiral molecules. Collaborators: J. Kpper, G. Meijer, L. B. Madsen. [4pt] [1] Laser-Induced Alignment and Orientation of Quantum-State-Selected Large Molecules, L. Holmegaard, J. H. Nielsen, I. Nevo, H. Stapelfeldt, F. Filsinger, J. Kpper, and G. Meijer, Phys. Rev. Lett. 102. 023001 (2009).

Stapelfeldt, Henrik

2009-05-01

71

Cytoskeletal polarization and redistribution of cell-surface molecules during T cell antigen recognition.  

PubMed

T cell antigen recognition is accompanied by cytoskeletal polarization towards the APC and large-scale redistribution of cell surface molecules into 'supramolecular activation clusters' (SMACs), forming an organized contact interface termed the 'immunological synapse' (IS). Molecules are arranged in the IS in a micrometer scale bull's eye pattern with a central accumulation of TCR/peptide-MHC (the cSMAC) surrounded by a peripheral ring of adhesion molecules (the pSMAC). We propose that segregation of cell surface molecules on a much smaller scale initiates TCR triggering, which drives the formation of the IS by active transport processes. IS formation may function as a checkpoint for full T cell activation, integrating information on the presence and quality of TCR ligands and the nature and activation state of the APC. PMID:10723794

Anton van der Merwe, P; Davis, S J; Shaw, A S; Dustin, M L

2000-02-01

72

Critical binding and electron scattering by symmetric-top polar molecules.  

PubMed

Quantum treatments of electron interactions with polar symmetric-top rotor molecules show features not present in the treatment of the linear-polar-rotor model. For symmetric tops possessing non-zero angular momentum about the symmetry axis, a new critical dipole can be defined that guarantees an infinite set of dipole-bound states independent of the values of the components of the inertial tensor. Additionally, for this same class, the scattering cross section diverges for all nonzero values of dipole moments and inertial moments, similar to solutions for the fixed linear dipole. Additional predictions are presented for electron affinities and rotational resonances of these systems. PMID:25362310

Garrett, W R

2014-10-28

73

Pulse train induced rotational excitation and orientation of a polar molecule.  

PubMed

We investigate theoretically the rotational excitation and field free molecular orientation of polar HBr molecule, interacting with train of ultrashort laser pulses. By adjusting the number of pulses, pulse period and the intensity of the pulse, one can suppress a population while simultaneously enhancing the desired population in particular rotational state. We have used train of laser pulses of different shaped pulse envelopes. The dynamics and orientation of molecules in the presence of pulse train of different shapes is studied and explained. PMID:24747844

Tyagi, Ashish; Arya, Urvashi; Vidhani, Bhavna; Prasad, Vinod

2014-08-14

74

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

E-print Network

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.

A. Kapanowski; T. Wietecha

2011-02-03

75

Performance of the SLC polarized electron source with high polarization  

SciTech Connect

For the 1992 operating cycle of the SLAC Linear Collider (SLC), the polarized electron source (PES) during its maiden run successfully met the pulse intensity and overall efficiency requirements of the SLC. However, the polarization of the bulk GaAs cathode was low ({approximately}27%) and the pulse-to-pulse stability was marginal. We have shown that adequate charge for the SLC can be extracted from a strained layer cathode having P{sub e}{approximately}80% even though the quantum efficiency (QE) is < 1%. The recent addition of a separate chamber to the PES-which allows cathodes to be loaded into the gun after the vacuum bake and after high voltage (HV) processing without breaking vacuum-increases the reliability for achieving an adequate photoelectron yield. A new SLAC-built pulsed Ti:sapphire laser permits operation of the PES at the required wavelength with sufficient power to fully saturate the yield, and thus improve the e{sup {minus}} beam stability. The performance of the PES during the 1993 SLC operating cycle with these and other improvements is discussed.

Clendenin, J.E.; Alley, R.K.; Aoyagi, H. [and others

1993-04-01

76

Dynamic orbitals in high-order harmonic generation from CO molecules  

NASA Astrophysics Data System (ADS)

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.

Zhang, Bin; Yuan, Jianmin; Zhao, Zengxiu

2014-09-01

77

Probing the alignment of ultracold spin-polarized $\\textrm{Rb}_2$ molecules  

E-print Network

We demonstrate a method to probe the alignment of the molecular axis of spin-polarized ultracold dimers. Diatomic $^{87}$Rb$_2$ molecules are held in the lowest Bloch band of a far-off resonance 3D optical lattice. Using lattice modulation spectroscopy we measure the molecular polarizabilities, which are directly linked to the alignment, along each of the $x$-, $y$-, and $z$-directions of the lab coordinate system. In contrast to nonrotating molecules, we observe that rotating molecules have an anisotropic orientation of the molecular axis. Furthermore, we derive the dynamical polarizabilities for a laser wavelength of 1064.5 nm parallel and orthogonal to the molecular axis of the dimer, $\\alpha_\\parallel=8.9(9)\\times10^3\\:\\textrm{a.u.}$ and $\\alpha_\\perp=0.9(4)\\times10^3\\:\\textrm{a.u.}$, respectively.

Deis, Markus; Deissler, Benjamin; Denschlag, Johannes Hecker

2014-01-01

78

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

E-print Network

In this study, we investigate the structure of the polar alkali-Strontium diatomic molecules as possible candidates for the realization of samples of new species of ultracold polar molecules. 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 $^2\\Sigma^+$ ground state are determined as functions of the internuclear distances 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-Rb molecules.

Romain Gurout; Mireille Aymar; Olivier Dulieu

2010-07-12

79

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

E-print Network

In this study, we investigate the structure of the polar alkali-Strontium diatomic molecules as possible candidates for the realization of samples of new species of ultracold polar molecules. 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 $^2\\Sigma^+$ ground state are determined as functions of the internuclear distances 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-Rb molecules.

Gurout, Romain; Dulieu, Olivier

2010-01-01

80

Orientation effects in elastic scattering of polarized X-rays by linear molecules.  

PubMed

Strong orientation effect is discovered theoretically upon the change of the scheme of suggested experiment on anomalous elastic x-ray scattering of linearly polarized x-ray radiation by linear diatomics near the ionization thresholds of inner molecular orbitals. Studied are the effects on the shape of theoretical scattering spectra of additional excitations/ionizations of outer-shell electrons. Within the one-centre approximation for the molecular orbitals wavefunctions the analytical structure of the linear molecule's formfactor is obtained. The dipole transition matrix elements and photoabsorption cross sections are calculated by the methods of the theory of non-orthogonal orbitals. PMID:11512739

Yavna, V; Hopersky, A; Nadolinsky, A; Yavna, S

2001-03-01

81

Selecting rotational two-level coherence in polar molecules by double terahertz pulses  

NASA Astrophysics Data System (ADS)

We demonstrate experimentally a method for controlling two-level coherence in jet-cooled rotating polar molecules by using a pair of intense terahertz pulses. The broad spectra of the terahertz pulses can induce resonant population transfer between four rotational states J =0 ,1 ,2 ,3 to establish two-level coherence. This coherence is controlled by the delay between the two terahertz pulses, resulting in selection of a single two-level coherence. This scheme can be extended to select a specific two-level coherence in a thermally distributed molecular ensemble by applying a train of terahertz pulses.

Kitano, Kenta; Ishii, Nobuhisa; Kanai, Teruto; Itatani, Jiro

2014-10-01

82

Role of quantum fluctuations in the hexatic phase of cold polar molecules.  

PubMed

Two-dimensional crystals melt via an intermediate hexatic phase, which is characterized by an anomalous scaling of spatial and orientational correlation functions and the absence of an attraction between dislocations. We propose a protocol to study the effect of quantum fluctuations on the nature of this phase with a model system of strongly correlated ultracold polar molecules. Dislocations can be located in experiment from local energy differences which induce internal stark shifts in the molecules. We present a criterion to identify the hexatic phase from the statistics of the end points of topological defect strings and find a hexatic phase, which is dominated by quantum fluctuations, between the crystal and superfluid phases. PMID:25014821

Lechner, Wolfgang; Bchler, Hans-Peter; Zoller, Peter

2014-06-27

83

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

PubMed Central

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

2013-01-01

84

Two-center minima in harmonic spectra from aligned polar molecules  

SciTech Connect

We extend a model of two-center interference to include the superposition of opposite orientations in aligned polar molecules. We show that the position of the minimum in the harmonic spectrum from both aligned and oriented CO depends strongly on the relative recombination strength at different atoms, not just the relative phase. We reinterpret the minimum in aligned CO as an interference between opposite orientations, and obtain good agreement with numerical calculations. Inclusion of the first-order Stark effect shifts the position of the interference minimum in aligned CO even though aligned molecules do not posses total permanent dipoles. We explain the shift in terms of the phase that the electron of oriented CO accumulates due to the Stark effect.

Etches, Adam [Lundbeck Foundation Theoretical Center for Quantum System Research, Department of Physics and Astronomy, Aarhus University, 8000 Aarhus C (Denmark); Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803-4001 (United States); Gaarde, Mette B. [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803-4001 (United States); Madsen, Lars Bojer [Lundbeck Foundation Theoretical Center for Quantum System Research, Department of Physics and Astronomy, Aarhus University, 8000 Aarhus C (Denmark)

2011-08-15

85

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

E-print Network

polarity in non-neuronal mammalian cell types. The discovery of molecularly distinct axon domains didNeuronal 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

Oregon, University of

86

Benefiting from Polarization: Effects at High-NA Imaging  

E-print Network

157nm F2 Laser Mirror MirrorMirror Illuminator Mask Projection Lens Wafer Polarizer F2 Laser Mirror MirrorMirror Illuminator Mask Projection Lens Wafer Polarizer linearly polarized output beam unpolarizedBenefiting from Polarization: Effects at High-NA Imaging Bruce W. Smith L. Zavyalova, A. Estroff, Y

Zanibbi, Richard

87

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

SciTech Connect

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.

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

88

Rotational movement of formins evaluated by using single-molecule fluorescence polarization.  

PubMed

Formin homology proteins (formins) are responsible for the formation of actin structures such as actin stress fibers, actin cables, and cytokinetic contractile rings. Formins are the major actin filament (F-actin) nucleators in the cell. Because formins remain bound to the barbed end after nucleating an actin filament, it was expected that formins might rotate along the double-helical structure of F-actin during processive actin elongation (helical rotation). Here, we describe a method to detect the rotational movement of F-actin elongating from immobilized formins using single-molecule fluorescence polarization (FLP). Tetramethylrhodamine (TMR) attached to Cys-374 of actin emits polarized fluorescence at ?45 with respect to the filament axis. When the TMR-labeled F-actin laying at 45 in the visual field rotates, the vertical- and horizontal-polarized fluorescence (FLV and FLH, respectively) of TMR alternately become bright. This technique allowed us to demonstrate the helical rotation of mDia1, a mammalian formin. Adenosine triphosphate (ATP) hydrolysis in actin subunits is not required for helical rotation; however, ATP appears to contribute to accelerating actin elongation by mDia1. When helical rotation is limited by trapping both mDia1 and the pointed-end side, the processive filament elongation is blocked. Thus, mDia1 faithfully rotates along the long-pitch helix of F-actin. In this chapter, we introduce the theoretical concept of single-molecule FLP, the optical setup, the preparation of adenosine diphosphate-bound actin, and the procedure to observe the rotational movement of F-actin elongating from immobilized formins. PMID:24630102

Mizuno, Hiroaki; Watanabe, Naoki

2014-01-01

89

Complement, c1q, and c1q-related molecules regulate macrophage polarization.  

PubMed

Complement is a critical system of enzymes, regulatory proteins, and receptors that regulates both innate and adaptive immune responses. Natural mutations in complement molecules highlight their requirement in regulation of a variety of human conditions including infectious disease and autoimmunity. As sentinels of the immune system, macrophages are specialized to respond to infectious microbes, as well as normal and altered self, and dictate appropriate immune responses. Complement components such as anaphylatoxins (C3a and C5a) and opsonins [C3b, C1q, mannan binding lectin (MBL)] influence macrophage responses. While anaphylatoxins C3a and C5a trigger inflammasome activation, opsonins such as C1q and related molecules (MBL and adiponectin) downregulate inflammasome activation and inflammation, and upregulate engulfment of apoptotic cells consistent with a pro-resolving or M2 macrophage phenotype. This review summarizes our current understanding of the influence of the complement system on macrophage polarization with an emphasis on C1q and related molecules. PMID:25191325

Bohlson, Suzanne S; O'Conner, Sean D; Hulsebus, Holly Jo; Ho, Minh-Minh; Fraser, Deborah A

2014-01-01

90

Three-dimensional structural dynamics of myosin V by single-molecule fluorescence polarization  

NASA Astrophysics Data System (ADS)

The structural change that generates force and motion in actomyosin motility has been proposed to be tilting of the myosin light chain domain, which serves as a lever arm. Several experimental approaches have provided support for the lever arm hypothesis; however, the extent and timing of tilting motions are not well defined in the motor protein complex of functioning actomyosin. Here we report three-dimensional measurements of the structural dynamics of the light chain domain of brain myosin V using a single-molecule fluorescence polarization technique that determines the orientation of individual protein domains with 20-40-ms time resolution. Single fluorescent calmodulin light chains tilted back and forth between two well-defined angles as the myosin molecule processively translocated along actin. The results provide evidence for lever arm rotation of the calmodulin-binding domain in myosin V, and support a `hand-over-hand' mechanism for the translocation of double-headed myosin V molecules along actin filaments. The technique is applicable to the study of real-time structural changes in other biological systems.

Forkey, Joseph N.; Quinlan, Margot E.; Alexander Shaw, M.; Corrie, John E. T.; Goldman, Yale E.

2003-03-01

91

Collectively Induced Quantum-Confined Stark Effect in Monolayers of Molecules Consisting of Polar Repeating Units  

PubMed Central

The electronic structure of terpyrimidinethiols is investigated by means of density-functional theory calculations for isolated molecules and monolayers. In the transition from molecule to self-assembled monolayer (SAM), we observe that the band gap is substantially reduced, frontier states increasingly localize on opposite sides of the SAM, and this polarization in several instances is in the direction opposite to the polarization of the overall charge density. This behavior can be analyzed by analogy to inorganic semiconductor quantum-wells, which, as the SAMs studied here, can be regarded as semiperiodic systems. There, similar observations are made under the influence of a, typically external, electric field and are known as the quantum-confined Stark effect. Without any external perturbation, in oligopyrimidine SAMs one encounters an energy gradient that is generated by the dipole moments of the pyrimidine repeat units. It is particularly strong, reaching values of about 1.6 eV/nm, which corresponds to a substantial electric field of 1.6 107 V/cm. Close-lying ?- and ?-states turn out to be a particular complication for a reliable description of the present systems, as their order is influenced not only by the docking groups and bonding to the metal, but also by the chosen computational approach. In the latter context we demonstrate that deliberately picking a hybrid functional allows avoiding pitfalls due to the infamous self-interaction error. Our results show that when aiming to build a monolayer with a specific electronic structure one can not only resort to the traditional technique of modifying the molecular structure of the constituents, but also try to exploit collective electronic effects. PMID:21955058

2011-01-01

92

Alignment and orientation of diatomic molecules induced by polarized electron impact This article has been downloaded from IOPscience. Please scroll down to see the full text article.  

E-print Network

Alignment and orientation of diatomic molecules induced by polarized electron impact This article induced by polarized electron impact J W Maseberg and T J Gay Behlen Laboratory of Physics, University induced by spin-polarized electron impact. Circular polarizations resulting from some Fulcher- transitions

Gay, Timothy J.

93

Towards efficient ab initio calculations of electron scattering by polyatomic molecules: III. Modelling correlation-polarization interactions  

NASA Astrophysics Data System (ADS)

We explore an implementation of correlation-polarization interactions for electron scattering by polyatomic molecules. The short-range correlation is approximated by local and nonlocal density functional theory (DFT) models commonly used in quantum chemistry and solid-state physics. The long-range polarization is represented by general full tensor components. Furthermore, we propose a robust and stable technique to calculate momentum-space matrix elements of such a composite potential. The quality of several selected DFT potentials is tested by elastic scattering calculations for a class of small hydrocarbon molecules represented by propane and cyclopropane.

?urk, R.; ulc, M.

2010-09-01

94

Electric-field-dependent dynamic polarizability and state-insensitive conditions for optical trapping of diatomic polar molecules  

SciTech Connect

Selection of state-insensitive or 'magic' trapping conditions with ultracold atoms or molecules, where pairs of internal states experience identical trapping potentials, brings substantial benefits to precision measurements and quantum computing schemes. Working at such conditions could ensure that the detrimental effects of inevitable inhomogeneities across an ultracold sample are significantly reduced. However, this aspect of confinement remains unexplored for ultracold polar molecules. Here, we present means to control the ac Stark shift of rotational states of ultracold diatomic polar molecules, when subjected to both trapping laser light and an external electric field. We show that both the strength and relative orientation of the two fields influence the trapping potential. In particular, we predict 'magic electric field strengths' and a 'magic angle', where the Stark shift is independent of the dc external field for certain rotational states of the molecule.

Kotochigova, Svetlana [Department of Physics, Temple University, Philadelphia, Pennsylvania 19122-6082 (United States); DeMille, David [Department of Physics, Yale University, New Haven, Connecticut 06520 (United States)

2010-12-15

95

Mask-induced polarization effects at high numerical aperture  

E-print Network

Mask-induced polarization effects at high numerical aperture Andrew Estroff Yongfa Fan Anatoly at higher numerical apertures NAs due to mask-induced polarization effects. We study how different photomask.21.240.32. Terms of Use: http://spiedl.org/terms #12;pass. The electric field of the TE polarized light induces

Zanibbi, Richard

96

Electrostatic actuation based modulation of polar molecules and associated force interaction studies  

NASA Astrophysics Data System (ADS)

Seamless integration of artificial components with biological systems to form an elegant biotic-abiotic interface or smart surface has promising application potential in biomedical engineering. The specific aim of this study is to implement the actuation and modulation of binding behavior between biomolecules under electrostatic stimuli, and investigate the corresponding force interaction between the complementary pairs. The nanofabrication technology was utilized to establish the patterned binding pair of thrombin and DNA aptamer on gold substrate, and different electrical fields were applied on the system to evaluate electrostatic influence. The atomic force microscopy (AFM) surface imaging was then used to explicate the surface height change after the removal of the electrical fields. The height change of the surface showed that positive electrical fields can successfully break the bonds between thrombin and aptamer, while moderate negative electrical fields kept the integral structure. The experimental studies implement the idea of electrostatic actuation and modulation of the complementary pair. The force interaction between the pair was then investigated through AFM based dynamic force spectroscopy (DFS). The open circuit DFS experiment was conducted first to clarify the magnitude of single molecule level force interaction between thrombin and aptamer, and the linear dependence of rupture force on logarithmic loading rate was observed. A single energy barrier model was used to understand the binding physics and kinetics. By fitting the model with experiment data, we could acquire important kinetic parameters toff and xbeta. Then in-situ electrochemical atomic force microscopy (ECAFM) based DFS experiment was conducted to investigate the electrostatic influence upon molecular force interaction between thrombin and aptamer. The force interaction difference showed that positive electrical fields lowered the dissociation force between thrombin and aptamer, while negative electrical fields held similar force level with zero potential. The ECAFM experimental studies further support the conclusion of electrostatic actuation and modulation of the complementary pair. Besides, the root cause for the change of binding behavior and force interaction between the biomolecules under electrostatic fields is the conformational transition of the molecules, which might be illustrated by the molecular dynamics (MD) simulation. Therefore, a MD based computational study was performed on self-assembled monolayer (SAM) with polar end group under the application of electrical fields to clarify the conformational transition and associated friction change of the monomolecular thin films. The simulation results showed that positive electrical fields can generate larger conformational transition of the SAMs, which led to a greater frictional coefficient drop of the surface, while negative electrical fields kept similar conformational state and frictional response as the zero potential. The simulation result provides another explanation of the electrostatic actuation based modulation of polar molecule functionalized surface.

Ma, Xiao

97

High energy polarized beams from hyperon decays  

SciTech Connect

The use of various ways to utilize lambda decays to obtain polarized beams of protons and antiprotons is emphasized. Examples described are the Fermilab polarized beam, now under construction, and the use of similar techniques at other energies. Beam transport, spin precession and reversal systems, and polarimeters are also discussed. 8 refs., 4 figs.

Underwood, D.G.

1986-01-01

98

THE JOURNAL OF CHEMICAL PHYSICS 135, 024201 (2011) Stark-induced adiabatic Raman passage for preparing polarized molecules  

E-print Network

THE JOURNAL OF CHEMICAL PHYSICS 135, 024201 (2011) Stark-induced adiabatic Raman passage for preparing polarized molecules Nandini Mukherjee and Richard N. Zarea) Department of Chemistry, Stanford online 8 July 2011) We propose a method based on Stark-induced adiabatic Raman passage (SARP

Zare, Richard N.

99

The computation of nuclear motion and mass polarization adiabatic energy corrections for several states of the hydrogen molecule  

Microsoft Academic Search

This paper reports the computation of the diagonal matrix elements of the nuclear motion and mass polarization operators (often referred to as adiabatic corrections) for several electronic states of the hydrogen molecule. It is observed that reasonably simple wavefunctions will yield accurate expectation values for the nuclear motion operators. The present calculation covers a greater range of R for the

A. Lewis Ford; E. M. Greenawalt; J. C. Browne

1977-01-01

100

Completely monolithic linearly polarized high-power fiber laser oscillator  

NASA Astrophysics Data System (ADS)

We have demonstrated a linearly polarized cw all-in-fiber oscillator providing 1 kW of output power and a polarization extinction ratio (PER) of up to 21.7 dB. The design of the laser oscillator is simple and consists of an Ytterbium-doped polarization maintaining large mode area (PLMA) fiber and suitable fiber Bragg gratings (FBG) in matching PLMA fibers. The oscillator has nearly diffraction-limited beam quality (M < 1.2). Pump power is delivered via a high power 6+1:1 pump coupler. The slope efficiency of the laser is 75 %. The electro/optical efficiency of the complete laser system is ~30 % and hence in the range of Rofin's cw non-polarized fiber lasers. Choosing an adequate bending diameter for the Yb-doped PLMA fiber, one polarization mode as well as higher order modes are sufficiently supressed1. Resulting in a compact and robust linearly polarized high power single mode laser without external polarizing components. Linearly polarized lasers are well established for one dimensional cutting or welding applications. Using beam shaping optics radially polarized laser light can be generated to be independent from the angle of incident to the processing surface. Furthermore, high power linearly polarized laser light is fundamental for nonlinear frequency conversion of nonlinear materials.

Belke, Steffen; Becker, Frank; Neumann, Benjamin; Ruppik, Stefan; Hefter, Ulrich

2014-03-01

101

High resolution electron crystallography of protein molecules  

SciTech Connect

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.

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

102

The influence of non polar and polar molecules in mouse motile cells membranes and pure lipid bilayers.  

PubMed

We report an experimental study of mouse sperm motility that shows chief aspects characteristic of neurons: the anesthetic (produced by tetracaine) and excitatory (produced by either caffeine or calcium) effects and their antagonic action. While tetracaine inhibits sperm motility and caffeine has an excitatory action, the combination of these two substances balance the effects, producing a motility quite similar to that of control cells. We also study the effects of these agents (anesthetic and excitatory) on the melting points of pure lipid liposomes constituted by 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and dipalmitoyl phosphatidic acid (DPPA). Tetracaine induces a large fluidization of the membrane, shifting the liposomes melting transition temperature to much lower values. The effect of caffeine is null, but its addition to tetracaine-doped liposomes greatly screen the fluidization effect. A high calcium concentration stiffens pure lipid membranes and strongly reduces the effect of tetracaine. Molecular Dynamics Simulations are performed to further understand our experimental findings at the molecular level. We find a strong correlation between the effect of antagonic molecules that could explain how the mechanical properties suitable for normal cell functioning are affected and recovered. PMID:23565149

Sierra-Valdez, Francisco J; Forero-Quintero, Linda S; Zapata-Morin, Patricio A; Costas, Miguel; Chavez-Reyes, Arturo; Ruiz-Surez, Jess C

2013-01-01

103

The Influence of Non Polar and Polar Molecules in Mouse Motile Cells Membranes and Pure Lipid Bilayers  

PubMed Central

We report an experimental study of mouse sperm motility that shows chief aspects characteristic of neurons: the anesthetic (produced by tetracaine) and excitatory (produced by either caffeine or calcium) effects and their antagonic action. While tetracaine inhibits sperm motility and caffeine has an excitatory action, the combination of these two substances balance the effects, producing a motility quite similar to that of control cells. We also study the effects of these agents (anesthetic and excitatory) on the melting points of pure lipid liposomes constituted by 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and dipalmitoyl phosphatidic acid (DPPA). Tetracaine induces a large fluidization of the membrane, shifting the liposomes melting transition temperature to much lower values. The effect of caffeine is null, but its addition to tetracaine-doped liposomes greatly screen the fluidization effect. A high calcium concentration stiffens pure lipid membranes and strongly reduces the effect of tetracaine. Molecular Dynamics Simulations are performed to further understand our experimental findings at the molecular level. We find a strong correlation between the effect of antagonic molecules that could explain how the mechanical properties suitable for normal cell functioning are affected and recovered. PMID:23565149

Sierra-Valdez, Francisco J.; Forero-Quintero, Linda S.; Zapata-Morin, Patricio A.; Costas, Miguel; Chavez-Reyes, Arturo; Ruiz-Surez, Jess C.

2013-01-01

104

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

SciTech Connect

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.

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

105

Highly Polarized Ion Sources for Electron Ion Colliders (EIC)  

SciTech Connect

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.

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

2010-03-01

106

Mask-induced polarization effects at high NA  

NASA Astrophysics Data System (ADS)

It is important to understand how a photomask will polarize incident radiation. This paper presents data collected on binary mask and various attenuated phase shifting mask materials, feature sizes, duty ratios, and illumination schemes via rigorous coupled wave analysis, extinction spectroscopy, and 193nm lithographic evaluation. Additionally, the result of polarization effects due to the photomask on imaging has been studied. It was found that in the majority of the cases, higher NA led to greater polarization effects. All mask materials predominantly pass the TM polarization state for the 0 order, whereas different materials and duty ratios affect the polarization of the first diffracted orders differently. The polarization effects contributed by mask materials being considered for use in high NA imaging systems need to be examined. The degree of polarization as a function of n and k is presented, providing an introduction to the desirable properties of future mask materials. Materials with higher refractive indices and lower extinction coefficients tend to pass more of the TM polarization state, which is undesirable. Materials with lower indices and relatively wide range of extinction coefficients pass more TE polarized radiation. The duty ratio, critical dimension, mask material, material thickness, and illumination scheme all influence mask induced polarization effects.

Estroff, Andrew; Fan, Yongfa; Bourov, Anatoly; Smith, Bruce; Foubert, Philippe; Leunissen, L. H. A.; Philipsen, Vicky; Aksenov, Yuri

2005-05-01

107

Evidence for Extremely High Dust Polarization Efficiency in NGC 3184  

E-print Network

Recent studies have found the Type II-plateau supernova (SN) 1999gi to be highly polarized (p_max = 5.8%, where p_max is the highest degree of polarization measured in the optical bandpass; Leonard & Filippenko 2001) and minimally reddened (E[B-V] = 0.21 +/- 0.09 mag; Leonard et al. 2002). From multiple lines of evidence, including the convincing fit of a ``Serkowski'' interstellar polarization (ISP) curve to the continuum polarization shape, we conclude that the bulk of the observed polarization is likely due to dust along the line of sight (l-o-s), and is not intrinsic to SN 1999gi. We present new spectropolarimetric observations of four distant Galactic stars close to the l-o-s to SN 1999gi (two are within 0.02 degrees), and find that all are null to within 0.2%, effectively eliminating Galactic dust as the cause of the high polarization. The high ISP coupled with the low reddening implies an extraordinarily high polarization efficiency for the dust along this l-o-s in NGC 3184: ISP / E(B-V) = 31^{+22}_{-9} % mag^{-1}. This is inconsistent with the empirical Galactic limit (ISP / E[B-V] < 9% mag^{-1}), and represents the highest polarization efficiency yet confirmed for a single sight line in either the Milky Way or an external galaxy.

Douglas C. Leonard; Alexei V. Filippenko; Ryan Chornock; Weidong Li

2002-08-05

108

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

PubMed Central

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

2010-01-01

109

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

PubMed

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

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

2009-12-01

110

Compact polarizers with single layer high-index contrast gratings  

NASA Astrophysics Data System (ADS)

A single-layer broadband polarizer has been designed for operating in the telecommunication wavelength band. The rigorous coupled-wave analysis (RCWA) is applied to study the optical spectrum for the optimized structure. High polarization efficiency, high extinction ratio with a broad wavelength range (1.45-1.75 ?m) are obtained. Both of the transmission efficiencies of TM-polarization and reflection efficiencies of TE-polarization are over 95%. The extinction ratio of transmission is over 30 dB in the 1.45-1.75 ?m wavelength range, and the value is 114 dB for the central wavelength. The designed polarizer may lead to potential application in optical communication and infrared imaging polarimetry.

Zheng, Gaige; Cong, Jiawei; Xu, Linhua; Su, Wei

2014-11-01

111

Verifying high NA polarization OPC treatment on wafer  

NASA Astrophysics Data System (ADS)

High NA scanners with adjustable polarization are becoming commercially available. Linear polarization has been shown to significantly improve imaging performance of preferentially oriented lines. Azimuthal and tangential polarization are now becoming commercially available. The latter has less asymmetry in its imaging and can resolve critical features oriented in multiple directions at the same time. Linear y-oriented or vertical polarization was used, since at the time of this work, azimuthal and tangential polarization were not available. Such x- and y-oriented linear polarization could be used in double exposure imaging, for example. Just as for unpolarized imaging, OPC models are required for polarized imaging that are accurate in (a) fitting and predicting experimental CD values, (b) fragmenting layout, and (c) correcting the fragmented layout to target. This paper describes the results of such a first OPC verification loop. Experimental proximity data in X- and Y-orientation were measured. Source polarization and wafer stack thin film effects were included in the empirically fit OPC simulation model. A parallel investigation was undertaken using an unpolarized source. It served as the reference case. Simple test patterns as well product-like 2D layout was treated with the vertically polarized and unpolarized OPC models. A test mask was written and wafer printing results obtained. They demonstrated the validity of the approach and pointed to further OPC model improvements.

Schlief, Ralph E.; Hennig, Mario; Pforr, Rainer; Thiele, Jrg; Hoepfl, Max

2006-03-01

112

Ground- and excited-state properties of the polar and paramagnetic RbSr molecule: A comparative study  

NASA Astrophysics Data System (ADS)

This paper deals with the electronic structure of RbSr, a molecule possessing both a magnetic dipole moment and an electric dipole moment in its own frame, allowing its manipulation with external fields. Two complementary ab initio approaches are used for the ground and lowest excited states: first, an approach relying on optimized effective core potentials with core polarization potentials based on a full configuration interaction involving three valence electrons and second, an approach using a small-size effective core potential with 19 correlated electrons in the framework of coupled-cluster theory. We have found excellent agreement between these two approaches for the ground-state properties including the permanent dipole moment. We have focused on studies of excited states correlated to the two lowest asymptotes Rb (5p2P)+Sr(5s21S) and Rb (5s2S)+Sr(5s5p3P) relevant for ongoing experiments on ultracold quantum degenerate gases. We also present approximate potential curves including spin-orbit interaction based on atomic spin-orbit constants. These potential curves are an excellent starting point for experimental studies of molecular structure of RbSr using high-resolution spectroscopy.

?uchowski, Piotr S.; Gurout, R.; Dulieu, O.

2014-07-01

113

Theory of high-precision Zeeman effect in diatomic molecules  

Microsoft Academic Search

A theoretical description of the Zeeman effect in a diatomic molecule is given on the basis of exact numerical diagonalization of the perturbation matrix. In this way it is also possible to include the fine and hyperfine structures to the desired degree of accuracy, and this is highly important for a complete theory of the molecular Zeeman effect. The present

L. Veseth

1976-01-01

114

Thermodynamic properties of oxygen molecules at high temperatures  

Microsoft Academic Search

Calculations of the second virial coefficients and their derivatives, obtained by fitting the Hulburt-Hirschfelder potential to accurate ab initio quantum mechanical calculations for the seven bound states of molecular oxygen that dissociate to ground state atoms, are used to determine thermodynamic properties of oxygen molecules at high temperatures. Unlike the usual statistical thermodynamic method for obtaining partition functions by summing

L. Biolsi; P. M. Holland

1996-01-01

115

High polarization single dipole mode photonic crystal microlaser  

Microsoft Academic Search

A photonic crystal microlaser with elongate lattice was fabricated. Lasing action of single mode, y-dipole mode, was observed. With this mode, a high polarization extinction ratio of 51:1 was obtained.

Wei Chen; Mingxin Xing; Wenjun Zhou; Anjin Liu; Lianghui Chen; Wanhua Zheng

2009-01-01

116

Synthesis of high titer infectious prions with cofactor molecules.  

PubMed

Recently, synthetic prions with a high level of specific infectivity have been produced from chemically defined components in vitro. A major insight arising from these studies is that various classes of host-encoded cofactor molecules such as phosphatidylethanolamine and RNA molecules are required to form and maintain the specific conformation of infectious prions. Synthetic mouse prions formed with phosphatidylethanolamine exhibit levels of specific infectivity ?1 million-fold greater than "protein-only" prions (Deleault, N. R., Walsh, D. J., Piro, J. R., Wang, F., Wang, X., Ma, J., Rees, J. R., and Supattapone, S. (2012) Proc. Natl. Acad. Sci. U.S.A. 109, E1938-E1946). Moreover, cofactor molecules also appear to regulate prion strain properties by limiting the potential conformations of the prion protein (see Deleault et al. above). The production of fully infectious synthetic prions provides new opportunities to study the mechanism of prion infectivity directly by structural and biochemical methods. PMID:24860097

Supattapone, Surachai

2014-07-18

117

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

E-print Network

separate injections into the tail vein of a laboratory ratinjection of a polarized xenon/Intralipid (30%) solution into a rat's tail vein. (tail vein in the muscle of the rat's thigh, depending on the desired location of the injection.

Goodson, B.M.

2010-01-01

118

Rotational Excitations of Polar Molecules on AN Optical Lattice:. from Novel Exciton Physics to Quantum Simulation of New Lattice Models  

NASA Astrophysics Data System (ADS)

Ultracold polar molecules trapped on an optical lattice is a many-body system that, under appropriate conditions, may support collective excitations reminiscent of excitons in solid state crystals. Here, we discuss the rotational excitations of molecules on an optical lattice leading to rotational Frenkel excitons. Apart from solid hydrogen, there is no other natural system that exhibits rotational excitons. The rotational excitons have unique properties that can be exploited for tuning exciton-exciton interactions and exciton-impurity scattering by applying an external electric field. We show that this can be used to explore the competing role of the dynamical and kinematic exciton-exciton interactions in excitonic energy transfer and to study quantum localization in a dynamically tunable disordered potential. The rotational excitons can also be used as a basis for quantum simulation of condensed matter models that cannot be realized with ultracold atoms. As an example, we discuss the possibility of engineering the Holstein model with polar molecules on an optical lattice.

Litinskaya, Marina; Krems, Roman V.

2013-12-01

119

In situ High-Field Dynamic Nuclear Polarization-Direct and Indirect Polarization of [superscript 13]C nuclei  

E-print Network

In situ High-Field Dynamic Nuclear Polarization: Direct and indirect polarization of [superscript 13]C nuclei by DNP is investigated (see graphic). The field-dependent enhancement profile for both processes are investigated ...

Maly, Thorsten

120

Polarized high pressure 3H?e target at MAMI  

NASA Astrophysics Data System (ADS)

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%.

Rohe, Daniela; Bartsch, P.; Baumann, D.; Becker, J.; Bermuth, J.; de Bever, L. J.; Bhm, 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.; Mller, U.; Mhlbauer, 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

121

Polarization of high-energy emissions from the Crab pulsar  

E-print Network

We investigate polarization of high-energy emissions from the Crab pulsar in the frame work of the outer gap accelerator, following previous works of Cheng and coworkers. The recent version of the outer gap, which extends from inside the null charge surface to the light cylinder, is used for examining the synchrotron radiations from the secondary and the tertiary pairs, which are produced outside the gap. We calculate the light curve, the spectrum and the polarization characteristics, simultaneously, by taking into account gyration motion of the particles. The polarization position angle curve and the polarization degree are calculated to compare with the Crab optical data. We demonstrate that the radiations from inside the null charge surface make outer-wing and off-pulse emissions in the light curve, and the tertiary pairs contribute to bridge emissions. The emissions from the secondary pairs explain the main features of the observed light curve and spectrum. On the other hand, both emissions from inside the null charge surface and from the tertiary pairs are required to explain the optical polarization behavior of the Crab pulsar. The energy dependence of the polarization features is expected by the present model. For the Crab pulsar, the polarization position angle curve indicates that the viewing angle of the observer measured from the rotational axis is greater than $90^{\\circ}$.

J. Takata; H. -K. Chang; K. S. Cheng

2006-10-12

122

Polar and high latitude substorms and solar wind conditions  

NASA Astrophysics Data System (ADS)

All substorm disturbances observed in polar latitudes can be divided into two types: polar, which are observable at geomagnetic latitudes higher than 70 in the absence of substorms below 70, and high latitude substorms, which travel from auroral (<70) to polar (>70) geomagnetic latitudes. The aim of this study is to compare conditions in the IMF and solar wind, under which these two types of substorms are observable on the basis of data from meridional chain of magnetometers IMAGE and OMNI database for 1995, 2000, and 2006-2011. In total, 105 polar and 55 high latitude substorms were studied. It is shown that polar substorms are observable at a low velocity of solar wind after propagation of a high-speed recurrent stream during the late recovery phase of a magnetic storm. High latitude substorms, in contrast, are observable with a high velocity of solar wind, increased values of the Bz component of the IMF, the Ey component of the electric field, and solar wind temperature and pressure, when a high-speed recurrent stream passes by the Earth.

Despirak, I. V.; Lyubchich, A. A.; Kleimenova, N. G.

2014-09-01

123

High-throughput single-molecule optofluidic analysis  

PubMed Central

We describe a high-throughput, automated single-molecule measurement system, equipped with microfluidics. the microfluidic mixing device has integrated valves and pumps to accurately accomplish titration of biomolecules with picoliter resolution. We demonstrate that the approach enabled rapid sampling of biomolecule conformational landscape and of enzymatic activity, in the form of transcription by Escherichia coli RNA polymerase, as a function of the chemical environment. PMID:21297618

Kim, Soohong; Streets, Aaron M; Lin, Ron R; Quake, Stephen R; Weiss, Shimon; Majumdar, Devdoot S

2011-01-01

124

Solvatochromic shifts of polar and non-polar molecules in ambient and supercritical water: A sequential quantum mechanics/molecular mechanics study including solute-solvent electron exchange-correlation  

NASA Astrophysics Data System (ADS)

Polar and non-polar solutes (acetone and benzene) dissolved in ambient water and supercritical water are investigated theoretically using a sequential quantum mechanics (QM)/molecular mechanics (MM) method which combines classical molecular dynamics simulations and QM/MM calculations. From the detailed analysis of the dependence of the QM region size and point charge background region size as well as the different functionals, it is found that the inclusion of the solvent molecules within the first solvation shell into the QM region to account for the exchange-correlation between a solute and neighboring solvent molecules is important for the highly accurate spectral shift calculations, especially vital for the non-polar solutes whose interactions with the solvents are dominated by the quantum dispersions. At the same time, sufficiently large surrounding partial charge region (rcutoff ?15 ) as well as the functional corrections to describe the long-range dispersion-corrections are also essential for the study of the electronic excited states in condensed phase. Our calculated solvatochromic shift values and their density dependencies at ambient and high temperature conditions are found to be in good agreements with experimental observations. This indicates that sound theoretical studies of solvatochromic shift can be achieved provided that a reasonable computational scheme with sufficiently large N^{QM}_{water} and rcutoff values is implemented. We also find both of aqueous acetone and aqueous benzene under high temperatures present three distinctive regions: low-density gas-like region, supercritical region, and high-density liquid-like region. The plateau behavior of solvatochromic shift in the supercritical region can be ascribed to the solvent clustering around the solute, which is a fundamental phenomenon of supercritical fluids (SCFs). The density dependence of our calculated coordination number of the first solvation shell nicely reproduces the trend of spectral shift and verifies the solvent clustering phenomenon of SCFs and its relationship with SCF's physicochemical properties.

Ma, Haibo; Ma, Yingjin

2012-12-01

125

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

E-print Network

the description of polymerization reaction of the living anionic polymerization of styrene. In summary, several approaches have been investigated for utilizing a large hyperpolarization initially produced on small molecules, for the benefit of characterizing...

Lee, Youngbok

2013-03-13

126

Bose-Einstein condensation and many-body localization of rotational excitations of polar molecules following a microwave pulse  

NASA Astrophysics Data System (ADS)

We study theoretically the collective dynamics of rotational excitations of polar molecules loaded into an optical lattice in two dimensions. We explore the collective many-body phases that form following a microwave pulse. We show that, owing to the long-range interactions between molecules and energy conservation in this isolated system, the rotational excitations can form a Bose-Einstein condensate with long-range order, even for the natural (undressed) dipole interactions. This manifests itself as a divergent T2 coherence time of the rotational transition even in the presence of inhomogeneous broadening. The dynamical evolution of a dense gas of rotational excitations shows regimes of nonergodicity, characteristic of many-body localization and localization protected quantum order.

Kwasigroch, M. P.; Cooper, N. R.

2014-08-01

127

Propagation of coherent polarized light in turbid highly scattering medium.  

PubMed

Within the framework of further development of unified Monte Carlo code for the needs of biomedical optics and biophotonics, we present an approach for modeling of coherent polarized light propagation in highly scattering turbid media, such as biological tissues. The temporal coherence of light, linear and circular polarization, interference, and the helicity flip of circularly polarized light due to reflection at the medium boundary and/or backscattering events are taken into account. To achieve higher accuracy in the results and to speed up the modeling, the implementation of the code utilizes parallel computing on NVIDIA graphics processing units using Compute Unified Device Architecture. The results of the simulation of coherent linearly and circularly polarized light are presented in comparison with the results of known theoretical studies and the results of alternative modelings. PMID:24556700

Doronin, Alexander; Macdonald, Callum; Meglinski, Igor

2014-02-01

128

Direct observation of a highly spin-polarized organic spinterface at room temperature.  

PubMed

Organic semiconductors constitute promising candidates toward large-scale electronic circuits that are entirely spintronics-driven. Toward this goal, tunneling magnetoresistance values above 300% at low temperature suggested the presence of highly spin-polarized device interfaces. However, such spinterfaces have not been observed directly, let alone at room temperature. Thanks to experiments and theory on the model spinterface between phthalocyanine molecules and a Co single crystal surface, we clearly evidence a highly efficient spinterface. Spin-polarised direct and inverse photoemission experiments reveal a high degree of spin polarisation at room temperature at this interface. We measured a magnetic moment on the molecule's nitrogen ? orbitals, which substantiates an ab-initio theoretical description of highly spin-polarised charge conduction across the interface due to differing spinterface formation mechanisms in each spin channel. We propose, through this example, a recipe to engineer simple organic-inorganic interfaces with remarkable spintronic properties that can endure well above room temperature. PMID:23412079

Djeghloul, F; Ibrahim, F; Cantoni, M; Bowen, M; Joly, L; Boukari, S; Ohresser, P; Bertran, F; Le Fvre, P; Thakur, P; Scheurer, F; Miyamachi, T; Mattana, R; Seneor, P; Jaafar, A; Rinaldi, C; Javaid, S; Arabski, J; Kappler, J-P; Wulfhekel, W; Brookes, N B; Bertacco, R; Taleb-Ibrahimi, A; Alouani, M; Beaurepaire, E; Weber, W

2013-01-01

129

High performance low-cost polarizer using depolarization of a polarized light by reactive mesogen.  

PubMed

Currently, the polyethlene terephthalate (PET) film challenges to substitute Tri-acetyl cellulouse (TAC) film which is a protection film in a polarizer layer, because of low cost of PET film. On the contrary, the PET film shows an optical problem such that color shift or interference optical pattern in oblique direction can occur because the film is made with the lamination process, which induces high phase retardation. In this paper, we propose a color shift free low cost polarizer by polymerization of random oriented reactive mesogen (RM) on the PET film. We calculate the viewing angle performance of the polarizer with the conventional PET film, with the TAC film and with the proposed PET film. As a result, we confirm that the proposed optical configuration can satisfy the optical performance equivalent to that of conventional TAC film uses in addition to the cost-down. PMID:21934952

Kim, Bong Choon; Lim, Young Jin; Ha, Kyung Su; Lee, Seung Hee; Kang, Wan-Seok; Lee, Gi-Dong

2011-08-15

130

High performance low-cost polarizer using depolarization of a polarized light by reactive mesogen  

NASA Astrophysics Data System (ADS)

Currently, the polyethlene terephthalate (PET) film challenges to substitute Tri-acetyl cellulouse (TAC) film which is a protection film in a polarizer layer, because of low cost of PET film. On the contrary, the PET film shows an optical problem such that color shift or interference optical pattern in oblique direction can occur because the film is made with the lamination process, which induces high phase retardation. In this paper, we propose a color shift free low cost polarizer by polymerization of random oriented reactive mesogen (RM) on the PET film. We calculate the viewing angle performance of the polarizer with the conventional PET film, with the TAC film and with the proposed PET film. As a result, we confirm that the proposed optical configuration can satisfy the optical performance equivalent to that of conventional TAC film uses in addition to the cost-down.

Kim, Bong Choon; Lim, Young Jin; Ha, Kyung Su; Lee, Seung Hee; Kang, Wan-Seok; Lee, Gi-Dong

2011-08-01

131

Multiquantum vibrational exchange in highly excited CO molecules  

SciTech Connect

The kinetics of exchange by vibrational quanta is studied theoretically and experimentally in highly excited CO molecules by analysing the recovery time of the inversion population on the selected vibrational-rotational transitions in a doubly Q-switched pulsed CO laser. A model of vibrational kinetics that takes into account the multiquantum vibrational exchange between CO molecules in the temperature range between 100 and 300 K is described in detail for the first time. This model is compared with the model of single-quantum vibrational exchange. Good agreement between experimental data and theoretical calculations performed using the model of multiquantum vibrational exchange is the first direct confirmation of the validity of this model. (active media)

Ionin, Andrei A; Klimachev, Yu M; Sinitsyn, D V; Terekhov, Yu V [P.N. Lebedev Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation); Konev, Yu B [Scientific Association for High Temperatures, Russian Academy of Sciences, Moscow (Russian Federation); Kurnosov, A K; Napartovich, A P [State Research Center of Russian Federation 'Troitsk Institute for Innovation and Fusion Research', Troitsk, Moscow Region (Russian Federation)

2000-07-31

132

Molecular Dynamics Simulations on Parallel Computers: a Study of Polar Versus Nonpolar Media Effects in Small Molecule Solvation.  

NASA Astrophysics Data System (ADS)

Solvent effects were studied and described via molecular dynamics (MD) and free energy perturbation (FEP) simulations using the molecular mechanics program AMBER. The following specific topics were explored:. Polar solvents cause a blue shift of the rm nto pi^* transition band of simple alkyl carbonyl compounds. The ground- versus excited-state solvation effects responsible for the observed solvatochromism are described in terms of the molecular level details of solute-solvent interactions in several modeled solvents spanning the range from polar to nonpolar, including water, methanol, and carbon tetrachloride. The structure and dynamics of octanol media were studied to explore the question: "why is octanol/water media such a good biophase analog?". The formation of linear and cyclic polymers of hydrogen-bonded solvent molecules, micelle-like clusters, and the effects of saturating waters are described. Two small drug-sized molecules, benzene and phenol, were solvated in water-saturated octanol. The solute-solvent structure and dynamics were analysed. The difference in their partitioning free energies was calculated. MD and FEP calculations were adapted for parallel computation, increasing their "speed" or the time span accessible by a simulation. The non-cyclic polyether ionophore salinomycin was studied in methanol solvent via parallel FEP. The path of binding and release for a potassium ion was investigated by calculating the potential of mean force along the "exit vector".

Debolt, Stephen Edward

133

Excited Atoms and Molecules in High Pressure Gas Discharges  

SciTech Connect

Various types of high-pressure non-thermal discharges are increasingly drawing attention in view of many interesting applications. These, partially ionized media in non-equilibrium state, tend to generate complex effects that are difficult to interpret without a detailed knowledge of elementary processes involved. Electronically excited molecules and atoms may play an important role as intermediate states in a wide range of atomic and molecular processes, many of which are important in high-pressure discharges. They can serve also as reservoirs of energy or as sources of high energy electrons either through the energy pooling or through superelastic collisions. By presenting the analysis of current situation on the processes involving excited atoms and molecules of interest for high-pressure gas discharges, we will attempt to draw attention on the insufficiency of available data. In the same time we will show how to circumvent this situation and still be able to develop accurate models and interpretations of the observed phenomena.

Vuskovic, L.; Popovic, S. [Old Dominion University, Department of Physics, 4600 Elkhorn Avenue, Norfolk, VA 23529 (United States)

2003-08-26

134

Students' Use of Three Different Visual Representations to Interpret Whether Molecules Are Polar or Nonpolar  

ERIC Educational Resources Information Center

Visualizing molecular properties is often crucial for constructing conceptual understanding in chemistry. However, research has revealed numerous challenges surrounding students' meaningful interpretation of the relationship between the geometry and electrostatic properties of molecules. This study explored students' (n = 18) use of three visual

Host, Gunnar E.; Schonborn, Konrad J.; Palmerius, Karljohan E. Lundin

2012-01-01

135

Formation of tilted smectic-C liquid crystal phase in polar Gay Berne molecules  

NASA Astrophysics Data System (ADS)

We perform molecular dynamics simulation for a system of Gay Berne molecules having two terminal dipole moments to generate tilted smectic-C liquid crystal phase. We investigate the effect of dipolar orientation with respect to the long molecular axis on phase behaviour. The study indicates that larger dipolar angle can give rise to greater tilt in molecular organization within a layer.

Saha, J.; Bose, T. R.; Ghosh, D.; Saha, M.

2005-03-01

136

A Very High Charge, High Polarization Gradient-Doped Strained GaAs Photocathode  

SciTech Connect

A high-gradient-doping technique is applied to strained polarized photocathodes. The electron spin-polarization increases significantly as the highly-doped layer thickness is reduced. A 5.0-7.5 nm p-type surface layer doped to 5 x 10{sup 19} cm{sup -3} is found sufficient to overcome the surface charge limit. It is shown that the charge requirements of the Next Linear Collider can be met with a polarization approaching 80%.

Maruyama, Takashi

2002-03-25

137

The microsporidian polar tube: A highly specialised invasion organelle  

PubMed Central

All of the members of the Microsporidia possess a unique, highly specialised structure, the polar tube. This article reviews the available data on the organisation, structure and function of this invasion organelle. It was over 100 years ago that Thelohan accurately described the microsporidian polar tube and the triggering of its discharge. In the spore, the polar tube is connected at the anterior end, and then coils around the sporoplasm. Upon appropriate environmental stimulation the polar tube rapidly discharges out of the spore pierces a cell membrane and serves as a conduit for sporoplasm passage into the new host cell. The mechanism of germination of spores, however, remains to be definitively determined. In addition, further studies on the characterisation of the early events in the rupture of the anterior attachment complex, eversion of the polar tube as well as the mechanism of host cell attachment and penetration are needed in order to clarify the function and assembly of this structure. The application of immunological and molecular techniques has resulted in the identification of three polar tube proteins referred to as PTP1, PTP2 and PTP3. The interactions of these identified proteins in the formation and function of the polar tube remain to be determined. Data suggest that PTP1 is an O-mannosylated glycoprotein, a post-translational modification that may be important for its function. With the availability of the Encephalitozoon cuniculi genome it is now possible to apply proteomic techniques to the characterisation of the components of the microsporidian spore and invasion organelle. PMID:16005007

Xu, Yanji; Weiss, Louis M.

2011-01-01

138

Polarization induced water molecule dissociation below the first-order electronic-phase transition temperature  

Microsoft Academic Search

Hydrogen produced from the photocatalytic splitting of water is one of the reliable alternatives to replace the polluting fossil and the radioactive nuclear fuels. Here, we provide unequivocal evidence for the existence of blue- and red-shifting O$-$H covalent bonds within a single water molecule adsorbed on MgO surface as a result of asymmetric displacement polarizabilities. The adsorbed H-O-H on MgO

Andrew Das Arulsamy; Zlatko Kregar; Kristina Elersic; Martina Modic; Uma Shankar Subramani

2011-01-01

139

Polarization induced water molecule dissociation below the first-order electronic-phase transition temperature  

E-print Network

Hydrogen produced from the photocatalytic splitting of water is one of the reliable alternatives to replace the polluting fossil and the radioactive nuclear fuels. Here, we provide unequivocal evidence for the existence of blue- and red-shifting O$-$H covalent bonds within a single water molecule adsorbed on MgO surface as a result of asymmetric displacement polarizabilities. The adsorbed H-O-H on MgO gives rise to one weaker H-O bond, while the other O-H covalent bond from the same adsorbed water molecule compensates this effect with a stronger bond. The weaker bond (nearest to the surface), the interlayer tunneling electrons and the silver substrate are shown to be the causes for the smallest dissociative activation energy on MgO monolayer. The origin that is responsible to initiate the splitting mechanism is proven to be due to the changes in the polarizability of an adsorbed water molecule, which are further supported by the temperature-dependent static dielectric constant measurements for water below the...

Arulsamy, Andrew Das; Elersic, Kristina; Modic, Martina; Subramani, Uma Shankar

2011-01-01

140

Stellar and 0ther high-temperature molecules.  

PubMed

Optical spectroscopy of stellar molecules trapped at 4 degrees K is particularly valuable when the data can be used to complement the corresponding gas data. The ground state is then directly established by measurement of the absorption spectrum at the low temperature, since all transitions beginning from excited states are eliminated. Isotopic substitution establishes the (0,0) bands of transitions to excited electronic states, and when these data are combined with infrared and fluorescence measurements at 4 degrees K, most of the vibrational properties of the ground and excited states can be obtained. Of the many examples cited and discussed here, C(3) is perhaps the most outstanding. Because the various molecules trapped in matrices are usually identified through prior mass spectrometric work, the optical observations often lead to the discovery of band systems of molecules whose spectra have not previously been observed-for example, those of Si(2)C(3), TaO(2), and WO(2). In these cases the location of the spectral regions in which molecular transitions appear may also serve to encourage the gas spectroscopist to further exploration with high-dispersion spectrographs. I share Ramsay's view (4, p. 204) that further investigation of f-number determinations from matrix spectra should be encouraged, particularly because of the lack of such data for molecules in stars. The principal source of error probably lies in the estimation of the number of molecules per square centimeter in the matrix, but no real test of this has been made. The only existing f values from matrix spectra are those for the C(3) (43, 44) and C(2) (51) molecules, and these are not ideal for test purposes. Because of the anomalous nature of the matrix results discussed above, the rather good agreement between f values for the solid and gas phases of C(2) (51) cannot be considered as support for the matrix determinations. What is needed is a matrix determination of several f(v'v") values (that is, determinations for specific bands) for molecules such as CN and NO or, preferably, for a gas vaporized at high temperature, for which these f values are relatively well established in the gas phase. In this connection the possibility of determining other molecular properties in matrices comes to mind. However, it has been clearly shown that the shape of the potential energy function in the electronic states of molecules can be affected when molecules are trapped in matrices. Brewer, Brabson, and Meyer, in work on S(2) (55), and Schnepp and Dressler, in work on O(2) (56), have examined the anharmonicity in matrices over many vibrational levels. Distortion of the gas potential energy curves occurs in the heavier matrices and sometimes at high vibrational levels in the light ones. Recently work has been begun on comparing the Franck-Condon factors connecting the ground state and two excited states of ScF trapped in a neon matrix (57) with factors calculated from the gas-spectrum data of R. F. Barrow et al. (58) (Deltar(e), the change in interatomic distance upon excitation, has a relatively large value of ~ 0.1 A in these systems). As is well known, such factors are particularly sensitive to the value of Deltar(e), but differences in anharmonicity do not, however, have as significant an effect upon the Franck-Condon factors. Hence a comparison of the matrix and gas factors will lead to further information about matrix effects and will indicate whether Franck-Condon factors can be obtained from matrix spectra. One of the important problems in the study of stellar molecules is the determination of the low-lying electronically excited states, similar to the (1)Delta <--> X(3)Delta difference (~ 580 cm(-1)) in TiO measured by Phillips. Most of the transition-metal oxides have such low-lying levels, and they must be taken into consideration in any calculation of thermodynamic effects at high temperature. It appears that the study of emission spectra in the infrared at 4 degrees K may be one approach to this problem, and an attempt is now being made to confir

Weltner, W

1967-01-13

141

Spectropolarimetry of the unusual high-polarization quasar OI 287  

SciTech Connect

New spectropolarimetry observations of the quasar OI 287, which appears to be the only high-polarization quasar which does not fall into either the category of broad-absorption line QSO or the category of blazars, is presented. The spectropolarimetry, which has a resolution of about 6-8 A, demonstrates that the broad permitted lines are polarized at about the same level as the continuum and that the narrow forbidden lines are essentially unpolarized. The polarigenic mechanism and the relationship of OI 187 to other broad-line objects is discussed. 15 references.

Goodrich, R.W.; Miller, J.S.

1988-08-01

142

Interstellar Polarization at High Galactic Latitudes: A New Insight  

NASA Astrophysics Data System (ADS)

We report the results of our study of interstellar polarization at high Galactic latitudes, carried out with the TurPol polarimeter on the 2.52 m Nordic Optical Telescope and DiPol polarimeter on the remotely controlled 60 cm KVA telescope (La Palma, Canary Islands). More than 2000 stars with accurate distances have been observed, and a complete map of the interstellar polarization for galactic latitudes +40< b <+90 has been built. We use these data to study the distribution of interstellar dust, extinction, and the direction of the local Galactic magnetic field up to distances of 500 pc.

Berdyugin, A.; Piirola, V.; Teerikorpi, P.

2011-11-01

143

Re-radiation enhancement in polarized surface-enhanced resonant Raman scattering of randomly oriented molecules on self-organized gold nanowires.  

PubMed

We explore the effect of re-radiation in surface-enhanced Raman scattering (SERS) through polarization-sensitive experiments on self-organized gold nanowires on which randomly oriented Methylene Blue molecules are adsorbed. We provide the exact laws ruling the polarized, unpolarized, and parallel- and cross-polarized SERS intensity as a function of the field polarizations. We show that SERS is polarized along the wire-to-wire nanocavity axis, independently from the excitation polarization. This proves the selective enhancement of the Raman dipole component parallel to the nanocavity at the single molecule level. Introducing a field enhancement tensor to account for the anisotropic polarization response of the nanowires, we work out a model that correctly predicts the experimental results for any excitation/detection polarization and goes beyond the E(4) approximation. We also show how polarization-sensitive SERS experiments permit one to evaluate independently the excitation and the re-radiation enhancement factors accessing the orientation-averaged non-diagonal components of the molecular Raman polarizability tensor. PMID:21688789

Fazio, Barbara; D'Andrea, Cristiano; Bonaccorso, Francesco; Irrera, Alessia; Calogero, Giuseppe; Vasi, Cirino; Gucciardi, Pietro Giuseppe; Allegrini, Maria; Toma, Andrea; Chiappe, Daniele; Martella, Christian; Buatier de Mongeot, Francesco

2011-07-26

144

Polarization control of a high power laser by adjoint feedback control  

NASA Astrophysics Data System (ADS)

A novel technique of polarizing a high power laser with unstable resonator optics is described which places the polarizing elements in a low power feedback path external to the parent resonator structure. The technique has been used to polarize a high power industrial CO2 laser. Rejection ratios for the unwanted polarization can exceed 20 dB. The polarization vector can be rotated at will by rotating the polarizer in the low power beam path.

Blaszuk, Paul R.; Benda, John A.; Forgham, James L.; Cohen, Harold L.

1993-04-01

145

Polarized photoluminescence of highly oriented poly(p-phenylene-vinylene)  

NASA Astrophysics Data System (ADS)

We report on the anisotropic photoluminescence (PL) properties of stretch-oriented free standing films of poly(p-phenylene-vinylene) (PPV) at different temperatures. The PL quantum efficiency is strongly dependent on the pump polarization; it is higher when the pump is polarized perpendicularly to the polymer chain orientation. Independently of the pump polarization, we find that the PL emission spectra are mainly polarized along the polymer chain axis. The PL spectra show high-energy features, close to the onset of the HOMO-LUMO transition, that are significantly affected by self-absorption of the emitted light in the optically thick samples as well as by refractive effects at the polymer-air interface. In order to clarify the origin of these features, we have made a detailed characterization of the anisotropic optical constants of the PPV film. The optical constants have been derived from polarized reflectance and transmittance measurements and were used for the renormalisation of the PL spectra using the Fresnel equations. Frank-Condon analysis for the absorption oscillator strength and for the corrected emission spectra suggests that two different emitting states contribute to the optical properties. The connection of these states with film morphology and intermolecular interactions is described.

Soci, Cesare; Comoretto, Davide; Marabelli, Franco; Moses, Daniel

2004-10-01

146

Interaction of intense beams of highly vibrationally excited molecules with molecules (clusters) condensed on a cold surface  

SciTech Connect

The interaction of intense beams of SF{sub 6} and CF{sub 3}I molecules, excited by powerful IR laser radiation to high vibrational states (0.3 eV {<=} E{sub vib} {<=} 2.0 eV), with molecules (clusters) condensed on a cold surface (T{sub s} {approx} 80-85 K) has been studied. The probability that the excited and unexcited molecules are reflected from the cold metal surface covered by condensed molecules (clusters), as well as the probability that such excited and unexcited molecules are transmitted through a cooled multichannel metal plate and a converging cone oriented at an angle relative to the molecular beam axis, has been determined. Expressions for these probabilities of reflection and transmission as functions of the angle of incidence and the parameters of the exciting laser radiation and the molecular beam are obtained. It is shown that highly vibrationally excited molecules are reflected from the surface and transmitted through the plates and cones with a much higher probability than unexcited molecules. The results suggest that this phenomenon can be used for the separation of molecules in a beam with respect to isotope (or atomic) composition.

Makarov, G. N. [Russian Academy of Sciences, Institute of Spectroscopy (Russian Federation)], E-mail: gmakarov@isan.troitsk.ru; Petin, A. N. [Troitsk Institute for Innovation and Thermonuclear Research (Russian Federation)

2006-11-15

147

Interaction of intense beams of highly vibrationally excited molecules with molecules (clusters) condensed on a cold surface  

NASA Astrophysics Data System (ADS)

The interaction of intense beams of SF6 and CF3I molecules, excited by powerful IR laser radiation to high vibrational states (0.3 eV ? E vib ? 2.0 eV), with molecules (clusters) condensed on a cold surface ( T s ? 80-85 K) has been studied. The probability that the excited and unexcited molecules are reflected from the cold metal surface covered by condensed molecules (clusters), as well as the probability that such excited and unexcited molecules are transmitted through a cooled multichannel metal plate and a converging cone oriented at an angle relative to the molecular beam axis, has been determined. Expressions for these probabilities of reflection and transmission as functions of the angle of incidence and the parameters of the exciting laser radiation and the molecular beam are obtained. It is shown that highly vibrationally excited molecules are reflected from the surface and transmitted through the plates and cones with a much higher probability than unexcited molecules. The results suggest that this phenomenon can be used for the separation of molecules in a beam with respect to isotope (or atomic) composition.

Makarov, G. N.; Petin, A. N.

2006-11-01

148

Ab initio properties of the ground-state polar and paramagnetic europium-alkali-metal-atom and europium-alkaline-earth-metal-atom molecules  

NASA Astrophysics Data System (ADS)

The properties of the electronic ground state of the polar and paramagnetic europium-S-state-atom molecules have been investigated. Ab initio techniques have been applied to compute the potential energy curves for the europium-alkali-metal-atom, EuX(X=Li,Na,K,Rb,Cs), europium-alkaline-earth-metal-atom, EuY(Y=Be,Mg,Ca,Sr,Ba), and europium-ytterbium, EuYb, molecules in the Born-Oppenheimer approximation for the high-spin electronic ground state. The spin restricted open-shell coupled cluster method restricted to single, double, and noniterative triple excitations, RCCSD(T), was employed and the scalar relativistic effects within the small-core energy-consistent pseudopotentials were included. The permanent electric dipole moments and static electric dipole polarizabilities were computed. The leading long-range coefficients describing the dispersion interaction between atoms at large internuclear distances C6 are also reported. The EuK, EuRb, and EuCs molecules are examples of species possessing both large electric and magnetic dipole moments making them potentially interesting candidates for ultracold many-body quantum simulations when confined in an optical lattice in combined electric and magnetic fields.

Tomza, Micha?

2014-08-01

149

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

SciTech Connect

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.

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

2000-06-21

150

Strong Circularly Polarized Luminescence from Highly Emissive Terbium Complexes in Aqueous Solution  

SciTech Connect

Two luminescent terbium(III) complexes have been prepared from chiral ligands containing 2-hydroxyisophthalamide (IAM) antenna chromophores and their non-polarized and circularly-polarized luminescence properties have been studied. These tetradentate ligands, which form 2:1 ligand/Tb{sup III} complexes, utilize diaminocyclohexane (cyLI) and diphenylethylenediamine (dpenLI) backbones, which we reasoned would impart conformational rigidity and result in Tb{sup III} complexes that display both large luminescence quantum yield ({phi}) values and strong circularly polarized luminescence (CPL) activities. Both Tb{sup III} complexes are highly emissive, with {phi} values of 0.32 (dpenLI-Tb) and 0.60 (cyLI-Tb). Luminescence lifetime measurements in H{sub 2}O and D{sub 2}O indicate that while cyLI-Tb exists as a single species in solution, dpenLI-Tb exists as two species: a monohydrate complex with one H{sub 2}O molecule directly bound to the Tb{sup III} ion and a complex with no water molecules in the inner coordination sphere. Both cyLI-Tb and dpenLI-Tb display increased CPL activity compared to previously reported Tb{sup III} complexes made with chiral IAM ligands. The CPL measurements also provide additional confirmation of the presence of a single emissive species in solution in the case of cyLI-Tb, and multiple emissive species in the case of dpenLI-Tb.

Samuel, Amanda; Lunkley, Jamie; Muller, Gilles; Raymond, Kenneth

2010-03-15

151

01/21/2007 08:15 PMScienceDaily: Scientists Discover Way To Order Polar Molecules In Crystals Page 1 of 3http://www.sciencedaily.com/releases/2007/01/070118130029.htm  

E-print Network

01/21/2007 08:15 PMScienceDaily: Scientists Discover Way To Order Polar Molecules In Crystals Page of Water Scientists Discover Way To Order Polar Molecules In Crystals Science Daily -- Researchers-Columbia researchers, who have found a way to organize molecules in a crystal so that the poles align in the same

Glaser, Rainer

152

02/03/2007 12:23 PMScience: Scientists Order Crystal Polar Molecules -The Post Chronicle Page 1 of 2http://www.postchronicle.com/cgi-bin/artman/exec/view.cgi?archive=5&num=59707  

E-print Network

molecules so the poles align in the same direction, but they also discovered aligned crystals hold potential02/03/2007 12:23 PMScience: Scientists Order Crystal Polar Molecules - The Post Chronicle Page 1 Send Us A Tip Scientists Order Crystal Polar Molecules By Staff Jan 18, 2007 U.S. scientists have found

Glaser, Rainer

153

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

E-print Network

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 ...

Hu, Kan-Nian

2006-01-01

154

High-output-power polarization-insensitive semiconductor optical amplifier  

Microsoft Academic Search

A high-output-power 1550 nm polarization-insensitive semiconductor optical amplifier (SOA) was developed for use as a compact in-line optical amplifier. A very thin tensile-strained bulk structure was used for the active layer and active width-tapered spot-size converters (SSCs) were integrated on both input and output sides. The SOA module exhibited a high saturation output power of +17 dBm together with a

Ken Morito; Mitsuru Ekawa; Takayuki Watanabe; Yuji Kotaki

2003-01-01

155

High intensity polarized atomic beam source for polarized internal storage ring targets  

NASA Astrophysics Data System (ADS)

In collaboration with the Max-Planck-Institut (MPI) fr Kernphysik in Heidelberg and the University of Marburg we presently design and construct a high intensity polarized atomic beam source. It is intended to deliver 1*1017 atoms/sec in one hyperfine state into a storage cell for FILTEX. FILTEX is an abbreviation for FILTer EXperiment aiming to polarize storage ring beams. The structure and the vacuum chambers of this source are completed and installed at the Heidelberg Test Storage Ring (TSR). Vacuum pumps, gauges etc. are mounted and partly connected to a logical operation system. When atomic beam nozzle and skimmer geometries and distances as well as the nozzle temperature are optimized, the final geometrical arrangement or our new hybrid sixpole magnets will be decided and the whole source should be completed by the end of 1989.

Schiemenz, P.

1989-05-01

156

High-flux normal incidence monochromator for circularly polarized synchrotron radiation  

NASA Astrophysics Data System (ADS)

A 6.5-m normal incidence monochromator installed at the storage ring BESSY, which is optimized for a high throughput of circularly polarized off-plane radiation at moderate resolution is described. The monochromator employs two exit slits and is specially designed and used for low-signal experiments such as spin- and angle-resolved photoelectron spectroscopy on solids, adsorbates, free atoms, and molecules. The Monk-Gillieson mounting (plane grating in a convergent light beam) allows for large apertures with relatively little astigmatism. With two gratings, a flux of more than 1011 photons s-1 bandwidth-1 (0.2-0.5 nm) with a circular polarization of more than 90% in the wavelength range from 35 to 675 nm is achieved.

Schfers, F.; Peatman, W.; Eyers, A.; Heckenkamp, Ch.; Schnhense, G.; Heinzmann, U.

1986-06-01

157

Diamagnetic Orientation of Polymerized Molecules under High Magnetic Field  

Microsoft Academic Search

Diamagnetic alignment of polymerized organic molecules is discussed both from the theoretical and experimental points of view. When a number of molecules aggregate with their diamagnetic principal axes along the same direction, the resultant diamagnetic anisotropy energy becomes comparable to the thermal energy and the aggregated molecule can align under a conventional magnetic field, even at room temperatures. Polymerization of

Akio Yamagishi; Tetsuya Takeuchi; Terumasa Higashi; Muneyuki Date

1989-01-01

158

Influence of charge distribution on the thermophysical and dynamical properties of polar linear molecules  

NASA Astrophysics Data System (ADS)

Gibbs ensemble Monte Carlo and molecular dynamics simulations were used to study thermophysical and dynamical properties of Kihara fluids consisting of linear molecules with dipolar symmetry. Two models differing in the electrostatic part of the intermolecular potential have been considered. The first one is an ideal dipole (ID) model where electrostatic interactions are modeled as point dipoles placed on the molecular center of mass, and the second one is a discrete charge (DC) model with single positive and negative charges placed at opposite ends of the molecules. The magnitude of the charges and the distance between them were chosen to reproduce the dipole moment of the ID model. In addition, an effective ionic strength for the DC model has been defined. Simulations were performed at several densities and temperatures in a wide range of molecular lengths and at three dipole moments. For all the systems, vapor-liquid equilibrium, thermodynamic, and structural properties, autocorrelation functions, correlation times, and transport properties such as diffusion, shear viscosity, and thermal conductivity have been obtained and analyzed. The results of the present study are in agreement with those found in previous works and they confirm that, although differences between the DC model and the ID model are small for the lower molecular lengths, they become more pronounced at higher molecular lengths. Finally, the influence of the effective ionic strength on the different properties of the system is discussed.

Calero, Sofa; Garzn, Benito; Lago, Santiago

2003-06-01

159

Quantitative polarized Raman spectroscopy in highly turbid bone tissue  

PubMed Central

Polarized Raman spectroscopy allows measurement of molecular orientation and composition and is widely used in the study of polymer systems. Here, we extend the technique to the extraction of quantitative orientation information from bone tissue, which is optically thick and highly turbid. We discuss multiple scattering effects in tissue and show that repeated measurements using a series of objectives of differing numerical apertures can be employed to assess the contributions of sample turbidity and depth of field on polarized Raman measurements. A high numerical aperture objective minimizes the systematic errors introduced by multiple scattering. We test and validate the use of polarized Raman spectroscopy using wild-type and genetically modified (oim?oim model of osteogenesis imperfecta) murine bones. Mineral orientation distribution functions show that mineral crystallites are not as well aligned (p<0.05) in oim?oim bones (283 deg) compared to wild-type bones (223 deg), in agreement with small-angle X-ray scattering results. In wild-type mice, backbone carbonyl orientation is 762 deg and in oim?oim mice, it is 724 deg (p>0.05). We provide evidence that simultaneous quantitative measurements of mineral and collagen orientations on intact bone specimens are possible using polarized Raman spectroscopy. PMID:20615030

Raghavan, Mekhala; Sahar, Nadder D.; Wilson, Robert H.; Mycek, Mary-Ann; Pleshko, Nancy; Kohn, David H.; Morris, Michael D.

2010-01-01

160

Quantitative polarized Raman spectroscopy in highly turbid bone tissue  

NASA Astrophysics Data System (ADS)

Polarized Raman spectroscopy allows measurement of molecular orientation and composition and is widely used in the study of polymer systems. Here, we extend the technique to the extraction of quantitative orientation information from bone tissue, which is optically thick and highly turbid. We discuss multiple scattering effects in tissue and show that repeated measurements using a series of objectives of differing numerical apertures can be employed to assess the contributions of sample turbidity and depth of field on polarized Raman measurements. A high numerical aperture objective minimizes the systematic errors introduced by multiple scattering. We test and validate the use of polarized Raman spectroscopy using wild-type and genetically modified (oim/oim model of osteogenesis imperfecta) murine bones. Mineral orientation distribution functions show that mineral crystallites are not as well aligned (p<0.05) in oim/oim bones (28+/-3 deg) compared to wild-type bones (22+/-3 deg), in agreement with small-angle X-ray scattering results. In wild-type mice, backbone carbonyl orientation is 76+/-2 deg and in oim/oim mice, it is 72+/-4 deg (p>0.05). We provide evidence that simultaneous quantitative measurements of mineral and collagen orientations on intact bone specimens are possible using polarized Raman spectroscopy.

Raghavan, Mekhala; Sahar, Nadder D.; Wilson, Robert H.; Mycek, Mary-Ann; Pleshko, Nancy; Kohn, David H.; Morris, Michael D.

2010-05-01

161

The High-Altitude Polar Wind: Simulation and Observation  

NASA Astrophysics Data System (ADS)

In comparing the transport and semikinetic descriptions of the expansion of the polar wind, it is found that the transport model produces shocks in the profiles of all moments, while a generalized semikinetic (GSK) model produces smooth profiles. The inadequacy of the transport model to deal with velocity dispersion, phase mixing and multiple -streams is clearly demonstrated. In the study of the effects of hot magnetospheric electrons on polar outflow, it is found that by imposing a large increase in electron temperature (T_{rm e}) over a short altitude range, a potential barrier is formed at which H^+ is partially reflected. For cases in which the T_{rm e} profile is established by thermal conduction from a high upper boundary T_{rm e }, the upward flux of H^+ decreases with increasing upper boundary T_ {rm e}, while O^+ shows a peak in the upward flux. The polar cap O^+ data collected by the DE1/RIMS are analyzed by fitting drifting Maxwellian distributions to the retarding potential curves, so that the O ^+ characteristics in terms of its density, velocity and temperature are determined. The results show that these observed data can be matched by the GSK model which includes the effect of centrifugal acceleration due to E times B convection. The model results also match other observed low- and mid-altitude polar wind density profiles. The matching with satellite data is obtained by using the GSK model which uses observed low-altitude O^+ polar wind data as lower boundary conditions. Model polar wind density profiles that match mid-altitude satellite data, as well as the newly analyzed O^+ velocity and temperature, can be obtained when an electron temperature and base ion temperature of 9000 K and an ionospheric convection electric field of 70 mV/m are assumed.

Ho, Chi Wing

162

High quality UV: NIR thin film interference polarizers  

NASA Astrophysics Data System (ADS)

Interference polarizers can be successfully used in lasers and laser devices as independent optical element substituted crystal polarizers. Today, the use of crystal polarizers in some cases can lead to definite difficulties in accordance with peculiarities of laser cavity construction. The novel laser technologies and design of laser elements defined the new demands to optical coatings. In modern lasers interference polarizer can be considered as one of the main element that operates laser radiation. According to special optical outline and the requirements to optical characteristics of laser polarizers can be bryuster or mirror-type. The stable of spectral characteristic at a definite angle is one of the most important parameter. It was shown how optical thickness of each layer influence on angle stability. On the other hand high stable was achieved by using electron-beam ion assisted deposition. The coatings were deposited on the surface of optical glass BK-7 or quartz. Generally, refractory oxides were used. The achievement of the condensation layers structure was provided by active O2 + ions. It was shown, that smooth cleaning by neutral ions as before the evaporation definite separate layer, as after stabilized the optical properties of polarizer. Moreover, the using of ion source allowed increase laser damage threshold. It can be underline that some advantages of ion source revealed during evaporation materials in visible and especially ultra violet region. Also, laser strength was rather more at 1535 nm for ion-assisted deposited films. The average parameters were: minimum transmission efficiency TP < 97%, extinction ratio TP/TS <500, laser damage more than 10 J/cm2, 10 nanosecond pulse at 1064 nm in laser spot 200 ?m.

Novopashin, Vladimir V.; Shestakov, Alexsandr V.

2014-09-01

163

Radio properties of the highly polarized, quiescent quasar OI 287  

NASA Technical Reports Server (NTRS)

The highly polarized, quiescent quasar OI 287 has been observed with high resolution at 2 cm and 6 cm in an effort to determine the origin of some of the object's peculiar properties. The results seem to rule out the classification of OI 287 as a blazar. Extrapolation of the radio core spectrum to midinfrared wavelengths fails to predict the infrared flux by at least an order of magnitude. This supports the conclusion that the infrared emission and the radio emission do not originate in the same synchrotron-emitting component. The high optical polarization could be related to possible broad absorption lines in the unobserved UV regime, or it could be caused by reflection into the line of sight by scattering agents distributed in a thin disk.

Ulvestad, James S.; Antonucci, Robert R. J.

1988-01-01

164

Radio properties of the highly polarized, quiescent quasar OI 287  

SciTech Connect

The highly polarized, quiescent quasar OI 287 has been observed with high resolution at 2 cm and 6 cm in an effort to determine the origin of some of the object's peculiar properties. The results seem to rule out the classification of OI 287 as a blazar. Extrapolation of the radio core spectrum to midinfrared wavelengths fails to predict the infrared flux by at least an order of magnitude. This supports the conclusion that the infrared emission and the radio emission do not originate in the same synchrotron-emitting component. The high optical polarization could be related to possible broad absorption lines in the unobserved UV regime, or it could be caused by reflection into the line of sight by scattering agents distributed in a thin disk. 30 references.

Ulvestad, J.S.; Antonucci, R.R.J.

1988-05-01

165

Magnetic accretion in high-accretion rate polars  

NASA Astrophysics Data System (ADS)

The spectral components of polars -- strongly magnetic CVs -- are barely disentangled without sufficient spectral coverage. XMM-Newton plus NuSTAR can solve the riddle but the frequent low states of the brightest members prevented systematic studies of high-accretion rate polars (HARPs). We thus began TOO-like XMM-Newton observations of the brightest systems in their high states and propose to continue in AO13 with one further trigger. We will investigate the physics of the hard X-ray emitting shock, the heated accretion pole cap, the atmosphere of the white dwarf, the absorption in the shock and in the flow, the lines in the accretion flow and the reflection from the white dwarf by phase-resolved X-ray spectroscopy and high-speed OM-photometry.

Schwope, Axel

2013-10-01

166

Applications of highly spin-polarized xenon in NMR  

SciTech Connect

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).

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

1993-09-01

167

Laser Optical Pumping of Potassium in a High Magnetic Field Using Linearly Polarized Light  

Microsoft Academic Search

This thesis reports the demonstration, of the optical pumping of a potassium vapor to a high electron spin polarization, in a high magnetic field, with linearly polarized light. The method of optical pumping with linearly polarized light, is used to produce a polarized potassium vapor for the study of the diffusion constant D _0 of potassium in argon, and the

Cody Marshall Martin

1995-01-01

168

Junctional adhesion molecule-C (JAM-C) regulates polarized neutrophil transendothelial cell migration in vivo  

PubMed Central

Neutrophil migration into inflamed tissues is a fundamental component of innate immunity. A decisive step in this process is the polarised migration of blood neutrophils through endothelial cells (ECs) lining the venular lumen (transendothelial cell migration; TEM) in a luminal to abluminal direction. Using real-time confocal imaging we report that neutrophils can exhibit disrupted polarised TEM (hesitant and reverse) in vivo. These events were noted in inflammation following ischemia-reperfusion injury, characterised by reduced expression of junctional adhesion molecule C (JAM-C) from EC junctions, and were enhanced by EC JAM-C blockade or genetic deletion. The results identify JAM-C as a key regulator of polarised neutrophil TEM in vivo and suggest that reverse TEM neutrophils can contribute to dissemination of systemic inflammation. PMID:21706006

Woodfin, Abigail; Voisin, Mathieu-Benoit; Beyrau, Martina; Colom, Bartomeu; Caille, Dorothee; Diapouli, Frantzeska-Maria; Nash, Gerard B; Chavakis, Triantafyllos; Albelda, Steven M.; Rainger, G Ed; Meda, Paolo; Imhof, Beat A.; Nourshargh, Sussan

2011-01-01

169

Stripe and line textures in the B2 phase of bent-shape molecules in samples with polar surface anchoring  

NASA Astrophysics Data System (ADS)

In the B2 phase formed by bent-shaped molecules a dense line texture is frequently observed. For the texture description a model is proposed consisting of a periodic system of anticlinic antiferroelectric bulk domains with opposite chiralities separated by ? walls in which polarization rotates. The bulk domains are situated between layers of synclinic ferroelectric phase near the upper and lower surfaces. In the surface layers induced by polar anchoring domains of opposite chirality are separated by defect lines. Under the electric field the ferroelectric layer near one sample surface is growing against the antiferroelectric structure in the sample bulk and the stripe texture is fading out, but still in the saturated field surface lines or walls persist separating ferroelectric domains of opposite chirality. The proposed model is adapted also for a case when the anticlinic antiferroelectric structure in the sample bulk is sandwiched between anticlinic ferroelectric layers near the surfaces. In that case the applied electric field eliminates all the lines because the resulting anticlinic ferroelectric structure is racemic, with no chiral domains.

Lej?ek, Lubor; Novotn, Vladimra; Glogarov, Milada

2011-12-01

170

Polar switching in the smectic- A(d)P(A) phase composed of asymmetric bent-core molecules.  

PubMed

We have studied mesogenic properties in the smectic- A(d)P(A) phase of an asymmetric bent-core liquid crystal by means of polarizing optical microscopy, second-harmonic generation (SHG), electro-optical (EO), and dielectric measurements. In homeotropically aligned cells, EO switching is clearly observed from a schlieren texture with both four- and two-brush defects to a uniform bright domain under the application of very low in-plane electric field below 1 V/microm. The phase is SHG active under an electric field, i.e., SHG gradually increases without a threshold and saturates with the increasing field. In homogeneous cells, by applying triangular wave field at saturated voltage, the splitting of the polarization switching current peak is observed, indicating that the mesophase is antiferroelectric. The dielectric studies indicate a Debye-type relaxation of the transverse dipoles associated with the rotation of the molecules about their long axis. The dc bias-dependent dielectric relaxation time and the dielectric strength suggest that a field-induced antiferroelectric-ferroelectric phase transition occurs continuously beyond 1.2 V/microm and is reversible. The field-dependent texture observation is consistent with the dielectric measurements. Two possible models are proposed to interpret the continuous phase transition. PMID:20365387

Guo, Lingfeng; Dhara, Surajit; Sadashiva, B K; Radhika, S; Pratibha, R; Shimbo, Yoshio; Araoka, Fumito; Ishikawa, Ken; Takezoe, Hideo

2010-01-01

171

High-order harmonic generation in laser-aligned molecules * R. Velotta,1,  

E-print Network

the similarity of HHG in atoms and small molecules 3,4 , and recently it was shown that if suf- ficiently shortHigh-order harmonic generation in laser-aligned molecules N. Hay,1, * R. Velotta,1, M. Lein,1 R. de demonstrate high-order harmonic generation in high-density vapors of laser-aligned molecules. En- sembles

Lein, Manfred

172

Energy levels of a polarizable linear polar molecule in a dc electric field obtained by analogy with the nonrelativistic hydrogen atom  

SciTech Connect

We note that an equation governing the dynamics of a polarizable linear polar molecule in a dc electric field coincides with one of two equations describing a hydrogen atom in the prolate spheroidal coordinate system. Using this analogy, as well as the known algebra of the angular momentum and Runge-Lenz-Pauli operators for the case of a hydrogen atom, the energy levels of a polarizable linear polar molecule in a dc electric field are calculated. For some cases, these energy values are exact.

Sekatskii, S. K. [Laboratoire de Physique de la Matiere Vivante, IPMC, Ecole Polytechnique Federale de Lausanne, BSP, CH 1015 Lausanne (Switzerland)

2007-05-15

173

Status of high polarization DC high voltage Gallium Arsenide photoelectron guns  

SciTech Connect

Users receive very high beam polarization from reliable GaAs photoelectron guns at facilities worldwide. Satisfaction with beam quality (and a number of lab closures) has reduced the level of polarized source R&D from the heyday of 1990s. However, new experiments and new accelerators proposals including high current unpolarized machines, require GaAs photoguns with capabilities that exceed today's state of the art. This submission describes the capabilities of today's high- polarization DC high voltage GaAs photoguns and discusses issues that must be addressed to meet new demands.

M. Poelker, P. Adderley, J. Brittian, J. Clark, J. Grames, J. Hansknecht, J. McCarter, M. Stutzman, R. Suleiman, K. Surles-Law

2008-01-01

174

Anisotropic-Fermi-liquid theory of ultracold fermionic polar molecules: Landau parameters and collective modes  

SciTech Connect

We study the Fermi liquid properties of the cold atomic dipolar Fermi gases with the explicit dipolar anisotropy using perturbative approaches. Due to the explicit dipolar anisotropy, Fermi surfaces exhibit distortions of the d{sub r}{sup 2}{sub -3z}{sup 2} type in three dimensions and of the d{sub x}{sup 2}{sub -y}{sup 2} type in two dimensions. The fermion self-energy, effective mass, and Fermi velocity develop the same anisotropy at the Hartree-Fock level proportional to the interaction strength. The Landau interaction parameters in the isotropic Fermi liquids become the tridiagonal Landau interaction matrices in the dipolar Fermi liquids which renormalize thermodynamic susceptibilities. With large dipolar interaction strength, the Fermi surface collapses along directions perpendicular to the dipole orientation. The dynamic collective zero sound modes exhibit an anisotropic dispersion with the largest sound velocity propagating along the polar directions. Similarly, the longitudinal p-wave channel spin mode becomes a propagating mode with an anisotropic dispersion in multicomponent dipolar systems.

Chan, Ching-Kit; Wu Congjun; Lee, Wei-Cheng [Department of Physics, University of California, San Diego, California 92093 (United States); Sarma, S. Das [Condensed Matter Theory Center, Department of Physics, University of Maryland, College Park, Maryland 20742 (United States)

2010-02-15

175

Magnetic accretion in high-accretion rate polars  

NASA Astrophysics Data System (ADS)

The spectral components of polars were barely disentangled by previous X-ray missions. The physics of magnetic accretion non-relativistic environment is therefore still puzzling. XMM-Newton can solve the riddle, but the frequent low states prevented systematic studies of high-accretion rate polars (HARPs). We thus began TOO-like XMM-Newton observations of the brightest systems in their heigh states. We are in the process creating a synoptic view on the HARPs and propose to continue in AO8 with one further trigger. We investigate the hard X-ray emitting shock, the heated accretion pole cap, the atmosphere of the white dwarf, absorption in the shock and in the flow, the lines in the flow and the reflection from the white dwarf by phase-resolved CCD- and RGS-spectroscopy and high-speed OM-photometry.

Schwope, Axel

2008-10-01

176

Magnetic accretion in high-accretion rate polars  

NASA Astrophysics Data System (ADS)

The spectral components of polars were barely disentangled by previous X-ray missions. The physics of magnetic accretion non-relativistic environment is therefore still puzzling. XMM-Newton can solve the riddle, but the frequent low states prevented systematic studies of high-accretion rate polars (HARPs). We thus began T00-like XMM-Newton observations of the brightest systems in their heigh states. We are in the process creating a synoptic view on the HARPs and propose to continue in AO11 with one further trigger. We investigate the hard X-ray emitting shock, the heated accretion pole cap, the atmosphere of the white dwarf, absorption in the shock and in the flow, the lines in the flow and the reflection from the white dwarf by phase-resolved CCD- and RGS-spectroscopy and high-speed OM-photometry.

Schwope, Axel

2011-10-01

177

Magnetic accretion in high-accretion rate polars  

NASA Astrophysics Data System (ADS)

The spectral components of polars -- strongly magnetic CVs -- were barely disentangled by previous X-ray missions. The physics of accretion in a strongly magnetic, non-relativistic environment is therefore still puzzling. XMM-Newton, in principle, can solve the riddle. But even in its 7th year, only one of the bright, classical polars was observed in a high accretion state by XMM-Newton. We propose a triggered observation of a further such system. We will investigate the physics of the hard X-ray emitting shock, the heated accretion pole cap, the atmosphere of the white dwarf, the absorption in the shock and in the flow, the lines in the accretion flow and the reflection from the white dwarf by phase-resolved CCD- and RGS-spectroscopy and by high-speed OM-photometry.

Schwope, Axel

2007-10-01

178

Amplification without inversion and high refractive index in heterogeneous molecules  

NASA Astrophysics Data System (ADS)

The system of interest is a closed three-level V-type system with two excited near degenerated levels in a weak probe field and a strong coupling field, in the presence of an incoherent pumping field. We investigate analytically the conditions to have amplification without population inversion or high index of refraction without absorption due to spontaneously generated coherence and incoherent pumping. The perturbation solution of the density matrix equation in the steady state case is derived. We find that the refractive index and absorption coefficient have a periodic dependence on the relative phase of the probe and coupling fields. The relative phase values for which the system exhibits a high refractive index without absorption are obtained. The conditions on incoherent pumping rate related to that for the angle between the two transition dipole moments and spontaneous emission rates of the two excited states to obtain the probe field gain without population inversion are derived. We propose a three-level V-type system with spontaneously generated coherence from LiH molecule which can achieve quasi-high index of refraction without absorption and amplification without population inversion.

Budriga, O.

2014-10-01

179

A High-Throughput Screening Method to Identify Small Molecule Inhibitors of Thyroid Hormone Receptor Coactivator Binding  

NSDL National Science Digital Library

To provide alternative methods for regulation of gene transcription initiated by the binding of thyroid hormone (T3) to the thyroid receptor (TR), we have developed a high-throughput method for discovering inhibitors of the interaction of TR with its transcriptional coactivators. The screening method is based on fluorescence polarization (FP), one of the most sensitive and robust high-throughput methods for the study of protein-protein interactions. A fluorescently labeled coactivator is excited by polarized light. The emitted polarized light is a function of the molecular properties of the labeled coactivator, especially Brownian molecular rotation, which is very sensitive to changes in the molecular mass of the labeled complex. Dissociation of hormone receptor from fluorescently labeled coactivator peptide in the presence of small molecules can be detected by this competition method, and the assay can be performed in a high-throughput screening format. Hit compounds identified by this method are evaluated by several secondary assay methods, including a dose-response analysis, a semiquantitative glutathione-S-transferase assay, and a hormone displacement assay. Subsequent in vitro transcription assays can detect inhibition of thyroid signaling at low micromolar concentrations of small molecules in the presence of T3.

Leggy A. Arnold (; REV); Eva Estebanez-Perpina (; REV); Marie Togashi (San Francisco;University of California REV); Anang Shelat (; REV); Cory A. Ocasio (San Francisco;University of California REV); Andrea C. McReynolds (San Francisco;University of California REV)

2006-06-27

180

Highly convergent focusing of light based on rotating dipole polarization  

NASA Astrophysics Data System (ADS)

Focusing properties of transverse circular polarization modes that bring light to a small focal spot are investigated. Two particular illumination polarization distributions are discussed. Rotating electric dipole polarization results in a central lobe diameter 8% smaller than for the circularly polarized aplanatic case at a NA of 0.95 in air and is also smaller than for radial polarization at NAs less than 0.90. Azimuthal polarization with a phase singularity of charge unity results in a small central lobe width that is smaller than that produced by focusing radially polarized light, having a width that is 17% smaller than for circularly polarized illumination at a NA of 0.95.

Sheppard, Colin J. R.; Rehman, Shakil

2011-08-01

181

HCN ice in Titan's high-altitude southern polar cloud  

NASA Astrophysics Data System (ADS)

Titan's middle atmosphere is currently experiencing a rapid change of season after northern spring arrived in 2009 (refs 1, 2). A large cloud was observed for the first time above Titan's southern pole in May 2012, at an altitude of 300 kilometres. A temperature maximum was previously observed there, and condensation was not expected for any of Titan's atmospheric gases. Here we report that this cloud is composed of micrometre-sized particles of frozen hydrogen cyanide (HCN ice). The presence of HCN particles at this altitude, together with temperature determinations from mid-infrared observations, indicate a dramatic cooling of Titan's atmosphere inside the winter polar vortex in early 2012. Such cooling is in contrast to previously measured high-altitude warming in the polar vortex, and temperatures are a hundred degrees colder than predicted by circulation models. These results show that post-equinox cooling at the winter pole of Titan is much more efficient than previously thought.

de Kok, Remco J.; Teanby, Nicholas A.; Maltagliati, Luca; Irwin, Patrick G. J.; Vinatier, Sandrine

2014-10-01

182

HCN ice in Titan's high-altitude southern polar cloud.  

PubMed

Titan's middle atmosphere is currently experiencing a rapid change of season after northern spring arrived in 2009 (refs 1, 2). A large cloud was observed for the first time above Titan's southern pole in May 2012, at an altitude of 300 kilometres. A temperature maximum was previously observed there, and condensation was not expected for any of Titan's atmospheric gases. Here we report that this cloud is composed of micrometre-sized particles of frozen hydrogen cyanide (HCN ice). The presence of HCN particles at this altitude, together with temperature determinations from mid-infrared observations, indicate a dramatic cooling of Titan's atmosphere inside the winter polar vortex in early 2012. Such cooling is in contrast to previously measured high-altitude warming in the polar vortex, and temperatures are a hundred degrees colder than predicted by circulation models. These results show that post-equinox cooling at the winter pole of Titan is much more efficient than previously thought. PMID:25279918

de Kok, Remco J; Teanby, Nicholas A; Maltagliati, Luca; Irwin, Patrick G J; Vinatier, Sandrine

2014-10-01

183

High Efficacy Green LEDs by Polarization Controlled MOVPE  

SciTech Connect

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

Wetzel, Christian

2013-03-31

184

Quantum Drude oscillator model of atoms and molecules: Many-body polarization and dispersion interactions for atomistic simulation  

NASA Astrophysics Data System (ADS)

Treating both many-body polarization and dispersion interactions is now recognized as a key element in achieving the level of atomistic modeling required to reveal novel physics in complex systems. The quantum Drude oscillator (QDO), a Gaussian-based, coarse grained electronic structure model, captures both many-body polarization and dispersion and has linear scale computational complexity with system size, hence it is a leading candidate next-generation simulation method. Here, we investigate the extent to which the QDO treatment reproduces the desired long-range atomic and molecular properties. We present closed form expressions for leading order polarizabilities and dispersion coefficients and derive invariant (parameter-free) scaling relationships among multipole polarizability and many-body dispersion coefficients that arise due to the Gaussian nature of the model. We show that these combining rules hold to within a few percent for noble gas atoms, alkali metals, and simple (first-row hydride) molecules such as water; this is consistent with the surprising success that models with underlying Gaussian statistics often exhibit in physics. We present a diagrammatic Jastrow-type perturbation theory tailored to the QDO model that serves to illustrate the rich types of responses that the QDO approach engenders. QDO models for neon, argon, krypton, and xenon, designed to reproduce gas phase properties, are constructed and their condensed phase properties explored via linear scale diffusion Monte Carlo (DMC) and path integral molecular dynamics (PIMD) simulations. Good agreement with experimental data for structure, cohesive energy, and bulk modulus is found, demonstrating a degree of transferability that cannot be achieved using current empirical models or fully ab initio descriptions.

Jones, Andrew P.; Crain, Jason; Sokhan, Vlad P.; Whitfield, Troy W.; Martyna, Glenn J.

2013-04-01

185

High-Resolution Optical Tweezers for Single-Molecule Manipulation  

PubMed Central

Forces hold everything together and determine its structure and dynamics. In particular, tiny forces of 1-100 piconewtons govern the structures and dynamics of biomacromolecules. These forces enable folding, assembly, conformational fluctuations, or directional movements of biomacromolecules over sub-nanometer to micron distances. Optical tweezers have become a revolutionary tool to probe the forces, structures, and dynamics associated with biomacromolecules at a single-molecule level with unprecedented resolution. In this review, we introduce the basic principles of optical tweezers and their latest applications in studies of protein folding and molecular motors. We describe the folding dynamics of two strong coiled coil proteins, the GCN4-derived protein pIL and the SNARE complex. Both complexes show multiple folding intermediates and pathways. ATP-dependent chromatin remodeling complexes translocate DNA to remodel chromatin structures. The detailed DNA translocation properties of such molecular motors have recently been characterized by optical tweezers, which are reviewed here. Finally, several future developments and applications of optical tweezers are discussed. These past and future applications demonstrate the unique advantages of high-resolution optical tweezers in quantitatively characterizing complex multi-scale dynamics of biomacromolecules. PMID:24058311

Zhang, Xinming; Ma, Lu; Zhang, Yongli

2013-01-01

186

HCN ice in Titan's high-altitude southern polar cloud  

E-print Network

Titan's middle atmosphere is currently experiencing a rapid change of season after northern spring arrived in 2009. A large cloud was observed for the first time above Titan's southern pole in May 2012, at an altitude of 300 km. This altitude previously showed a temperature maximum and condensation was not expected for any of Titan's atmospheric gases. Here we show that this cloud is composed of micron-sized hydrogen cyanide (HCN) ice particles. The presence of HCN particles at this altitude, together with new temperature determinations from mid-infrared observations, indicate a very dramatic cooling of Titan's atmosphere inside the winter polar vortex in early 2012. Such a cooling is completely contrary to previously measured high-altitude warming in the polar vortex, and temperatures are a hundred degrees colder than predicted by circulation models. Besides elucidating the nature of Titan's mysterious polar cloud, these results thus show that post-equinox cooling at the winter pole is much more efficient th...

de Kok, Remco J; Maltagliati, Luca; Irwin, Patrick G J; Vinatier, Sandrine

2014-01-01

187

High bandwidth single polarization fiber with elliptical central air hole  

Microsoft Academic Search

A novel design of single polarization fiber is presented. The structure of the fiber comprises an elliptical central air hole with depressed cladding surrounding the core. Parameters that affect the performance of the single polarization fiber in terms of the location of the single polarization operating window and single polarization bandwidth are analyzed. The analysis results in the identification of

Ming-Jun Li; Xin Chen; D. A. Nolan; G. E. Berkey; Ji Wang; W. A. Wood; L. A. Zenteno

2005-01-01

188

High efficiency polyethylene glycol diacrylate monoliths for reversed-phase capillary liquid chromatography of small molecules.  

PubMed

Highly cross-linked monolithic networks (i.e., polyethylene glycol diacrylate, PEGDA) synthesized from monomers containing varying ethylene oxide chain lengths were fabricated inside fused silica capillary columns for use in liquid chromatography (LC) of small molecules. Tergitol was used as a surfactant porogen in combination with other typical organic liquid porogens. Column performance was correlated with quantitative descriptors of the physical/chemical properties of the monomers and porogens using a statistical model. Solubility and viscosity values of the components were identified as important predictors of monolith morphology and efficiency. The chromatographic retention mechanism was determined to be principally reversed-phase (RP) with additional hydrogen bonding between the polar groups of the analytes and the ethylene oxide groups embedded in the monolith structure. The fabricated monolithic columns were evaluated under RPLC conditions using phenols, hydroxy benzoic acids, and alkyl parabens as test compounds. Isocratic elution of hydroxy benzoic acids at a linear velocity of 0.04cm/s using a PEGDA-700 monolith gave chromatographic peaks with little tailing (i.e., tailing factor<1.28). The chromatographic efficiency measured for a non-retained compound (uracil) using this column was 186,000plates/m when corrected for injector dead volume. High resolution gradient separations of selected pharmaceutical compounds and phenylurea herbicides were achieved in less than 18min. Optimized monoliths synthesized from all four crosslinking monomers exhibited high permeability and demonstrated little swelling or shrinking in different polarity solvents. Column preparation was highly reproducible, with relative standard deviation (RSD) values less than 2.1%, based on retention times of the phenol standards (3 different columns). PMID:25193173

Aggarwal, Pankaj; Lawson, John S; Tolley, H Dennis; Lee, Milton L

2014-10-17

189

Highly spin-polarized chromium dioxide thin films prepared by chemical vapor deposition from chromyl chloride  

E-print Network

Highly spin-polarized chromium dioxide thin films prepared by chemical vapor deposition from 2000 Highly spin-polarized chromium dioxide (CrO2) thin films were deposited on 100 TiO2 substrates materials that provide current with a high de- gree of spin polarization ideally 100% . Chromium dioxide (Cr

Nadgorny, Boris

190

High resolution polar Kerr magnetometer for nanomagnetism and nanospintronics.  

PubMed

A new high resolution polar magneto-optical (MO) Kerr magnetometer, devoted to the study of nanometer sized elements with perpendicular magnetic anisotropy, is described. The unique performances of this setup in terms of sensitivity (1.2x10(-15) emu), stability (lateral drift +/-35 nm over 3 h), and resolution (laser spot full width at half maximum down to 470 nm) are demonstrated, and illustrated by Kerr hysteresis loop measurements on a unique ultrathin magnetic nanodot, and over small segments of ultranarrow magnetic tracks. Large scanning MO Kerr microscopy images were also obtained with the same performances. PMID:18377014

Cormier, M; Ferr, J; Mougin, A; Cromires, J-P; Klein, V

2008-03-01

191

High resolution polar Kerr magnetometer for nanomagnetism and nanospintronics  

NASA Astrophysics Data System (ADS)

A new high resolution polar magneto-optical (MO) Kerr magnetometer, devoted to the study of nanometer sized elements with perpendicular magnetic anisotropy, is described. The unique performances of this setup in terms of sensitivity (1.210-15emu), stability (lateral drift 35nm over 3h), and resolution (laser spot full width at half maximum down to 470nm) are demonstrated, and illustrated by Kerr hysteresis loop measurements on a unique ultrathin magnetic nanodot, and over small segments of ultranarrow magnetic tracks. Large scanning MO Kerr microscopy images were also obtained with the same performances.

Cormier, M.; Ferr, J.; Mougin, A.; Cromires, J.-P.; Klein, V.

2008-03-01

192

Ground and excited state properties of the polar and paramagnetic RbSr molecule: a comparative study  

E-print Network

This paper deals with the electronic structure of RbSr, a molecule possessing both a permanent magnetic and electric dipole moment in its own frame allowing its manipulation with external fields. Two complementary ab-initio approaches are used for the ground and lowest excited states: first, an approach relying on optimized effective core potentials with core polarization potentials based on a full configuration interaction involving three valence electrons, and second, an approach using a small-size effective core potential with 19 correlated electrons in the framework of coupled-cluster theory. We have found excellent agreement between these two approaches for the ground state properties including the permanent dipole moment. We have focused on studies of excited states correlated to the two lowest asymptotes Rb(5p)+Sr(5s) and Rb(5s)+Sr(5s5p) relevant for ongoing experiments on quantum degenerate gases. We present also the Hund c) case potential curves obtained using atomic spin-orbit constants. These poten...

?uchowski, Piotr S; Dulieu, Olivier

2014-01-01

193

Interaction between Metal Cation and Unnatural Peptide Backbone Mediated by Polarized Water Molecules: Study of Infrared Spectroscopy and Computations.  

PubMed

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

Shi, Jipei; Wang, Jianping

2014-10-30

194

Polar Cap Model for Pulsar High-Energy Emission  

E-print Network

The study of physical processes associated with particle acceleration in the open field line region above the polar cap (PC) of an isolated neutron star (NS) plays a fundamental role in our understanding and interpretation of high-energy emission from pulsars. The systematic study of particle acceleration and formation of electron-positron pair fronts above the PCs of NSs was initiated two decades ago. The detailed analysis of these processes is now possible with the development of pair cascade codes that enables us to calculate the spectra and pulse profiles of high-energy emission from pulsars. The calculation of pair formation and gamma-ray production is being improved to include new results on the PC physics. We briefly outline the current status of the PC model for pulsar high-energy emission, focusing on some of our most recent results on the theoretical modeling of the PC acceleration and gamma-ray emission.

Alice K. Harding; Alexander G. Muslimov

1998-02-03

195

Electronic and vibrational properties of molecules at high pressures. Hydrogen molecule in a rigid spheroidal box  

SciTech Connect

A variational calcuation employing a five-term James-Coolidge wave function is presented for a hydrogen molecule enclosed within an infinte-walled spheroidal box. Properties examined include the pressure dependence of the equilibrium bond length, the vibrational force constant, the total energy, the ionization potential, the electronic kinetic energy, and the electronic correlation energy. Comparison is made with similar calculations for the H/sub 2//sup +/ molecular ion and the He and H atoms. A Badger's rule correlation of force constant and bond length is found to hold over a wide pressure range. Comparisons with the available experimental results show that generally the rigid-box model greatly exaggerates the effects of compression.

LeSar, R.; Herschbach, D.R.

1981-09-17

196

Dissociation energies of some high temperature molecules containing aluminum  

NASA Technical Reports Server (NTRS)

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.

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

1972-01-01

197

Laser optical pumping of potassium in a high magnetic field using linearly polarized light  

Microsoft Academic Search

It is shown experimentally that in a high magnetic field a potassium vapor can be optically pumped to a high electron spin polarization by light polarized parallel to the magnetic field and incident normal to the magnetic field. The polarization of the K vapor is measured both by observing the fluorescence and by the Faraday effect. This method of optical

Cody Martin; T. Walker; L. W. Anderson; D. R. Swenson

1993-01-01

198

Vacuum Polarization in High Energy Physics: (MZ) and at ILC scale 1. Introduction  

E-print Network

Vacuum Polarization in High Energy Physics: (MZ) and at ILC scale 1. Introduction 2. (MZ. The running electric charge at high energies 179-1 #12;Physics of vacuum polarization ... 1. Introduction Non" (E) (charge screening by vacuum polarization) Of particular interest: (MZ) and aµ (g - 2)µ/2 (mµ

Röder, Beate

199

Polarization Measurements in High-Energy Deuteron Photodisintegration  

SciTech Connect

We present measurements of the recoil proton polarization for the d(polarized y, polarized p)n reaction at thetac.m. = 90 degrees for photon energies up to 2.4 GeV. These are the first data in this reaction for polarization transfer with circularly polarized photons. The induced polarization py vanishes above 1 GeV, contrary to meson-baryon model expectations, in which resonances lead to large polarizations. However, the polarization transfer Cx does not vanish above 1 GeV, inconsistent with hadron helicity conservation. Thus, we show that the scaling behavior observed in the d(y,p)n cross sections is not a result of perturbative QCD. These data should provide important tests of new nonperturbative calculations in the intermediate energy regime.

Adam Sarty; Andrei Afanasev; Arunava Saha; Bogdan Wojtsekhowski; Brendan Fox; C. Chang; Cathleen Jones; Charles Glashausser; Charles Perdrisat; Cornelis De Jager; Cornelis de Jager; D. Crovelli; Daniel Simon; David Meekins; Demetrius Margaziotis; Dipangkar Dutta; Edgar Kooijman; Edward Brash; Edward Kinney; Elaine Schulte; Eugene Chudakov; Feng Xiong; Franco Garibaldi; Garth Huber; Gerfried Kumbartzki; Guido Urciuoli; Haiyan Gao; James Kelly; Javier Gomez; Jens-Ole Hansen; Jian-Ping Chen; John Calarco; John LeRose; Jordan Hovdebo; Joseph Mitchell; Juncai Gao; Kamal Benslama; Kathy McCormick; Kevin Fissum; Konrad Aniol; Krishni Wijesooriya; Louis Bimbot; Ludyvine Morand; Luminita Todor; Marat Rvachev; Mark Jones; Martin Epstein; Meihua Liang; Michael Kuss; Moskov Amarian; Nilanga Liyanage; Oleksandr Glamazdin; Olivier Gayou; Paul Ulmer; Pete Markowitz; Peter Bosted; R. Holt; Riad Suleiman; Richard Lindgren; Rikki Roche; Robert Michaels; Roman Pomatsalyuk; Ronald Gilman; Ronald Ransome; Salvatore Frullani; Scott Dumalski; Seonho Choi; Sergey Malov; Sonja Dieterich; Steffen Strauch; Stephen Becher; Steve Churchwell; Ting Chang; Viktor Gorbenko; Vina Punjabi; Xiaodong Jiang; Zein-Eddine Meziani; Zhengwei Chai; Wang Xu

2001-04-01

200

Polarization of high energy gamma quanta in strong electromagnetic fields  

Microsoft Academic Search

The behaviour of refractive indices for gamma quanta with different polarization in strong electromagnetic fields has been considered by the operator quasiclassical method. Birefringence in uniform electromagnetic fields and in interplanar electric fields in single crystals has been analyzed. Possibilities to use this effect in obtaining linearly and circularly polarized gamma quanta as well as longitudinally polarized conversion electrons with

A. M. Frolov; V. A. Maisheev; V. L. Mikhaljov

1987-01-01

201

Abstract --This letter presents highly-polarized edge light emitting diodes with high-confinement, strained, multiple  

E-print Network

,2]. In devices that require very high polarization extinction, such as a fiber-optic gyroscope (FOG), greater the polarization extinction and gain of devices with different lengths and optical confinement, we show, ELED, photonic ICs. S photonic devices evolve towards highly-integrated architectures, polarization

Coldren, Larry A.

202

NCTM of liquids at high temperatures using polarization techniques  

NASA Technical Reports Server (NTRS)

Temperature measurement and control is extremely important in any materials processing application. However, conventional techniques for non-contact temperature measurement (mainly optical pyrometry) are very uncertain because of unknown or varying surface emittance. Optical properties like other properties change during processing. A dynamic, in-situ measurement of optical properties including the emittance is required. Intersonics is developing new technologies using polarized laser light scattering to determine surface emittance of freely radiating bodies concurrent with conventional optical pyrometry. These are sufficient to determine the true surface temperature of the target. Intersonics is currently developing a system called DAPP, the Division of Amplitude Polarimetric Pyrometer, that uses polarization information to measure the true thermodynamic temperature of freely radiating objects. This instrument has potential use in materials processing applications in ground and space based equipment. Results of thermophysical and thermodynamic measurements using laser reflection as a temperature measuring tool are presented. The impact of these techniques on thermophysical property measurements at high temperature is discussed.

Krishnan, Shankar; Weber, J. K. Richard; Nordine, Paul C.; Schiffman, Robert A.

1990-01-01

203

Anti-Hyperon polarization in high energy pp collisions withpolarized beams  

SciTech Connect

We study the longitudinal polarization of the {bar {Sigma}}{sup -}, {bar {Sigma}}{sup +}, {bar {Xi}}{sup 0} and {bar {Xi}}{sup +} anti-hyperons in polarized high energy pp collisions at large transverse momenta, extending a recent study for the {bar {Lambda}} antihyperon. We make predictions by using different parameterizations of the polarized parton densities and models for the polarized fragmentation functions. Similar to the {bar {Lambda}} polarization, the {bar {Xi}}{sup 0} and {bar {Xi}}{sup +} polarizations are found to be sensitive to the polarized anti-strange sea, {Delta}{bar s}(x), in the nucleon. The {bar {Sigma}}{sup -} and {bar {Sigma}}{sup +} polarizations show sensitivity to the light sea quark polarizations, {Delta}{bar u}(x) and {Delta}{bar d}(x), and their asymmetry.

Chen, Ye; Liang, Zuo-tang; Sichtermann, Ernst; Xu, Qing-hua; Zhou, Shan-shan

2007-11-20

204

Generation of High Efficiency Longitudinally Polarized Beam using High NA Lens Axicon and Dedicated Phase Filter  

Microsoft Academic Search

We propose to use pure phase filter in combination with high NA lens axicon to achieve high efficient longitudinally polarized beam with a subwavelength spot size and large depth of focus using hyper geometric Gaussian beam. Using this system, the spot size is reduced to 0.392 lambda and the depth of focus is increased to 7 lambda. The efficiency of

K. B. Rajesh; Z. Jaroszewicz; R. Mohankumar; C. Amala Prathibajanet; T. V. S. Pillai

2011-01-01

205

Generation of High Efficiency Longitudinally Polarized Beam using High NA Lens Axicon and Dedicated Phase Filter  

Microsoft Academic Search

We propose to use pure phase filter in combination with high NA lens axicon to achieve high efficient longitudinally polarized beam with a subwavelength spot size and large depth of focus using hyper geometric Gaussian beam. Using this system, the spot size is reduced to 0.392 ? and the depth of focus is increased to 7 ?. The efficiency of

K. B. Rajesh; Z. Jaroszewicz; R. Mohankumar; C. Amala Prathibajanet; T. V. S. Pillai

2011-01-01

206

Magnetic accretion in high-accretion rate polars  

NASA Astrophysics Data System (ADS)

The spectral components of polars strongly magnetic CVs were barely disentangled by previous X-ray missions. The physics of accretion in a strongly magnetic, non-relativistic environment is therefore still puzzling. XMM-Newton can solve the riddle, but the frequent low states of the brightest members prevented systematic studies. We thus began TOO-like XMM-Newton observations of the brightest systems in their high states. We are in the process creating a synoptic view on the HARPs and propose to continue in AO12 with one further trigger. We will investigate the physics of the hard X-ray emitting shock, the heated accretion pole cap, the atmosphere of the white dwarf, the absorption in the shock and in the flow, the lines in the accretion flow and the reflection from the white dwarf.

Schwope, Axel

2012-10-01

207

QED and the high polarization of the thermal radiation from neutron stars  

Microsoft Academic Search

The thermal emission of strongly magnetized neutron-star atmospheres is thought to be highly polarized. However, because of the different orientations of the magnetic field over the surface of the neutron star (NS), it is commonly assumed that the net observed polarization will be significantly reduced as the polarization from different regions will cancel each other. We show that the birefringence

Jeremy S. Heyl; Nir J. Shaviv

2002-01-01

208

A protocol for the culture and differentiation of highly polarized human retinal pigment epithelial cells  

Microsoft Academic Search

We provide our detailed, standardized in vitro protocol for the culture and differentiation of human retinal pigment epithelial (RPE) cells into a highly polarized and functional monolayer. Disruption of the polarized RPE function plays an important role in the pathogenesis of common blinding disorders of the retina. The availability of this polarized RPE monolayer allows for reproducible evaluation of RPE

Shozo Sonoda; Christine Spee; Ernesto Barron; Stephen J Ryan; Ram Kannan; David R Hinton

2009-01-01

209

Mask induced polarization effects at high NA Andrew Estroff, Yongfa Fan, Anatoly Bourov, Bruce Smith  

E-print Network

Mask induced polarization effects at high NA Andrew Estroff, Yongfa Fan, Anatoly Bourov, Bruce, material thickness, and illumination scheme all influence mask induced polarization effects. Keywords field of the TE polarized light induces a current in the length of the wires. Forward transmitted

Zanibbi, Richard

210

Highly spin-polarized photoemission near threshold from physisorbed xenon and krypton atoms  

NASA Astrophysics Data System (ADS)

By use of circularly polarized synchrotron radiation at BESSY, spin-polarized photoemission from the valence orbitals of Xe and Kr atoms adsorbed on the Pt(111) single-crystal surface has been studied. Under certain conditions almost complete photoelectron polarization parallel or antiparallel to the photon spin was observed, allowing a direct assignment of quantum numbers of the states involved. Highly resolved intensity and polarization spectra in the threshold region exhibit pronounced variations versus photon energy.

Schnhense, G.; Eyers, A.; Friess, U.; Schfers, F.; Heinzmann, U.

1985-02-01

211

Spectroscopic and dynamical studies of highly energized small polyatomic molecules  

SciTech Connect

The authors have initiated a program to perform spectroscopic and dynamic studies of small molecules. Large amplitude motions in excited acetylene were discussed along with plans to record the dispersed fluorescence (DF) and the stimulated emission pumping (SEP) spectra. SEP spectra were reported for the formyl radical. A Fourier transform spectrometer was discussed with respect to its ability to probe the structure of radicals. This instrument is capable of performing studies using various techniques such as magnetic rotation spectroscopy and sub-Doppler sideband-OODR Zeman (SOODRZ) spectroscopy.

Field, R.W.; Silbey, R.J. [Massachusetts Institute of Technology, Cambridge (United States)

1993-12-01

212

Probing molecular frame photoionization via laser generated high-order harmonics from aligned molecules.  

PubMed

Present experiments cannot measure molecular frame photoelectron angular distributions (MFPAD) for ionization from the outermost valence orbitals of molecules. We show that the details of MFPAD can be retrieved with high-order harmonics generated by infrared lasers from aligned molecules. Using accurately calculated photoionization transition dipole moments for fixed-in-space molecules, we show that the dependence of the magnitude and phase of the high-order harmonics on the alignment angle of the molecules observed in recent experiments can be quantitatively reproduced. This result provides the needed theoretical basis for ultrafast dynamic chemical imaging using infrared laser pulses. PMID:19519025

Le, Anh-Thu; Lucchese, R R; Lee, M T; Lin, C D

2009-05-22

213

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

E-print Network

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

Byer, Robert L.

214

Elliptical polarization of Saturn Kilometric Radiation observed from high latitudes  

E-print Network

radiation is mainly observed by a space- craft at northern (southern) latitudes. There are also regions) experiment onboard Voyager 1 [Kaiser et al., 1980] it has been known that SKR is circularly polarized. The recorded SKR polar- ization during the two encounters with Saturn by both Voyagers suggested the existence

Gurnett, Donald A.

215

Highly stable polarization independent Mach-Zehnder interferometer  

E-print Network

We experimentally demonstrate optical Mach-Zehnder interferometer utilizing displaced Sagnac configuration to enhance its phase stability. The interferometer with footprint of 27x40 cm offers individually accessible paths and shows phase deviation less than 0.4 deg during a 250 s long measurement. The phase drift, evaluated by means of Allan deviation, stays below 3 deg or 7 nm for 1.5 hours 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 ...

Micuda, Michal; Straka, Ivo; Mikova, Martina; Dusek, Miloslav; Fiurasek, Jaromir; Jezek, Miroslav

2014-01-01

216

Enhancing the intestinal absorption of molecules containing the polar guanidino functionality: a double-targeted prodrug approach  

PubMed Central

A prodrug strategy was applied to guanidino-containing analogs to increase oral absorption via hPEPT1 and hVACVase. L-Valine, L-isoleucine and L-phenylalanine esters of [3-(hydroxymethyl)phenyl]guanidine (3-HPG) were synthesized and evaluated for transport and activation. In HeLa/hPEPT1 cells, Val-3-HPG and Ile-3-HPG exhibited high affinity to hPEPT1 (IC50: 0.65 and 0.63 mM, respectively), and all three L-amino acid esters showed higher uptake (2.6- to 9-fold) than the parent compound 3-HPG. Val-3-HPG and Ile-3-HPG demonstrated remarkable Caco-2 permeability enhancement, and Val-3-HPG exhibited comparable permeability to valacyclovir. In rat perfusion studies, Val-3-HPG and Ile-3-HPG permeabilities were significantly higher than 3-HPG, and exceeded/matched the high-permeability standard metoprolol, respectively. All the L-amino acid 3-HPG esters were effectively activated in HeLa and Caco-2 cell homogenates, and were found to be good substrates of hVACVase (kcat/Km in mM?1s?1: Val-3-HPG, 3370; Ile-3-HPG, 1580; Phe-3-HPG, 1660). In conclusion, a prodrug strategy is effective at increasing the intestinal permeability of polar guanidino analogs via targeting hPEPT1 for transport and hVACVase for activation. PMID:19957998

Sun, Jing; Dahan, Arik; Amidon, Gordon L.

2011-01-01

217

A High-Pressure Polarized $^3$He Gas Target for Nuclear Physics Experiments Using A Polarized Photon Beam  

E-print Network

Following the first experiment on three-body photodisintegration of polarized $^3$He utilizing circularly polarized photons from High Intensity Gamma Source (HI$\\gamma$S) at Duke Free Electron Laser Laboratory (DFELL), a new high-pressure polarized $^3$He target cell made of pyrex glass coated with a thin layer of sol-gel doped with aluminum nitrate nonahydrate has been built in order to reduce the photon beam induced background. The target is based on the technique of spin-exchange optical pumping of hybrid rubidium and potassium and the highest polarization achieved is $\\sim$62% determined from both NMR-AFP and EPR polarimetry. The $X$ parameter is estimated to be $\\sim0.06$ and the performance of the target is in good agreement with theoretical predictions. We also present beam test results from this new target cell and the comparison with the GE180 $^3$He target cell used previously at HI$\\gamma$S. This is the first time that sol-gel coating technique has been used in a polarized $^3$He target for nuclear physics experiments.

Q. Ye; G. Laskaris; H. Gao; W. Chen; W. Zheng; X. Zong; T. Averett; G. D. Cates; W. A. Tobias

2009-11-18

218

A High-Pressure Polarized $^3$He Gas Target for Nuclear Physics Experiments Using A Polarized Photon Beam  

E-print Network

Following the first experiment on three-body photodisintegration of polarized $^3$He utilizing circularly polarized photons from High Intensity Gamma Source (HI$\\gamma$S) at Duke Free Electron Laser Laboratory (DFELL), a new high-pressure polarized $^3$He target cell made of pyrex glass coated with a thin layer of sol-gel doped with aluminum nitrate nonahydrate has been built in order to reduce photon beam induced backgrounds. The target is based on the technique of spin-exchange optical pumping of hybrid rubidium and potassium and the highest polarization achieved is $\\sim$62\\% determined from both NMR-AFP and EPR polarimetry. The $X$ parameter is estimated to be $0.17\\pm0.06$ and the performance of the target is in good agreement with theoretical predictions. We also present beam test results from this new target cell and the comparison with the GE180 $^3$He target cell used previously at HI$\\gamma$S. This is the first time that sol-gel coating technique has been used in a polarized $^3$He target for nuclea...

Ye, Q; Chen, W; Gao, H; Zheng, W; Zong, X; Averett, T; Cates, G D; Tobias, W A

2009-01-01

219

High spatial resolution spin-polarized scanning electron microscopy (abstract)  

NASA Astrophysics Data System (ADS)

Spin-polarized scanning electron microscopy (spin SEM) to observe magnetic domains has the potential for spatial resolution as high as 10 nm. The best resolution from spin SEMs attained so far, however, is around 50 nm. In this talk, we report a newly developed spin SEM with 20 nm resolution. The major factor determining the resolution of a spin SEM is probe diameter. A smaller probe diameter, however, results in lower probe current. This is a serious issue in spin SEM because the efficiency of a spin detector is very low. Thus, to get high resolution with a reasonable signal/noise (S/N) image, higher efficiency in the spin detector and/or higher probe current are needed in addition to get a smaller probe diameter. The higher probe current has been attained by using a thermal assisted field emission cathode in an electron gun. The higher efficiency in the spin detector was achieved by increasing the acceptance angle of electron detectors inside the spin detector and optimizing both a secondary collector and transport optics. Obtaining a smaller probe diameter required a low aberration objective lens and a short working distance. Those were achieved by computer calculation so that there was no interference between the objective lens and the secondary collector. This achieved both a short working distance of 20 mm and high secondary collection efficiency. As a result, magnetic images of 20 nm resolution with a 25 keV and 1 nA probe beam have been attained. We have applied this spin SEM to observing recorded bits of longitudinal thin film media at high recording densities.

Matsuyama, H.; Koike, K.; Tomiyama, F.; Aoi, H.; Shiroishi, Y.; Ishikawa, A.

1994-05-01

220

Phagemid Encoded Small Molecules for High Throughput Screening of Chemical Libraries  

E-print Network

affinity ligands with the target protein may be impossible to elute due to the multivalent binding and thus with the binding of small molecules to the target proteins, and at the same time the DNA bar code is protected from to the multivalent binding of the small molecules carried by the same phage. This may give high background binding

Yin, Jun

221

Highly anisotropic metasurface: a polarized beam splitter and hologram.  

PubMed

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

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

2014-01-01

222

Highly anisotropic metasurface: a polarized beam splitter and hologram  

NASA Astrophysics Data System (ADS)

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.

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

2014-09-01

223

Highly anisotropic metasurface: a polarized beam splitter and hologram  

PubMed Central

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

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

2014-01-01

224

Highly precise and accurate terahertz polarization measurements based on electro-optic sampling with polarization modulation of probe pulses.  

PubMed

We have developed an electro-optic (EO) sampling method with polarization modulation of probe pulses; this method allows us to measure the direction of a terahertz (THz) electric-field vector with a precision of 0.1 mrad in a data acquisition time of 660 ms using a 14.0-kHz repetition rate pulsed light source. Through combination with a THz time-domain spectroscopy technique, a time-dependent two-dimensional THz electric field was obtained. We used a photoelastic modulator for probe-polarization modulation and a (111)-oriented zincblende crystal as the EO crystal. Using the tilted pulse front excitation method with stable regeneratively amplified pulses, we prepared stable and intense THz pulses and performed pulse-by-pulse analog-to-digital conversion of the signals. These techniques significantly reduced statistical errors and enabled sub-mrad THz polarization measurements. We examined the performance of this method by measuring a wire-grid polarizer as a sample. The present method will open a new frontier of high-precision THz polarization sensitive measurements. PMID:25089412

Nemoto, Natsuki; Higuchi, Takuya; Kanda, Natsuki; Konishi, Kuniaki; Kuwata-Gonokami, Makoto

2014-07-28

225

High deuteron polarization in trityl radical doped deuterated polystyrene  

NASA Astrophysics Data System (ADS)

Deuterated polystyrene for polarized solid targets has been prepared by chemical doping with the trityl radical Finland D36 (AH 110 355 deutero acid form). Thin foils doped with various radical densities have been produced using tetrahydrofuran as solvent. Dynamic nuclear polarization technique has been applied to polarize deuterons in the samples (98%-D) at the temperature range of about 1 K and magnetic fields of 2.5 T and 5.0 T. A maximum deuteron polarization of -61.5% with a build-up time of 100 min has been achieved at 5.0 T and about 500 mK at a radical density of 1.161019 spins/g.

Wang, Li; Berlin, A.; Doshita, N.; Herick, J.; Hess, C.; Iwata, T.; Kondo, K.; Meyer, W.; Reicherz, G.

2013-11-01

226

Highly polarization-sensitive thick gratings for a holographic Stokesmeter  

E-print Network

/polarizer architecture that split the beam into four parts and calculate the parameters in parallel require four times Stokesmeter, it is simple to design the hologram in such a way as to divide the incident power

Shahriar, Selim

227

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

NASA Astrophysics Data System (ADS)

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.

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

2014-09-01

228

High-Throughput Screening of Small Molecules Identifies Hepcidin Antagonists  

PubMed Central

Anemia of inflammation (AI) is common in patients with infection, autoimmune diseases, cancer, and chronic kidney disease. Unless the underlying condition can be reversed, treatment options are limited to erythropoiesis-stimulating agents with or without intravenous iron therapy, modalities that are not always effective and can cause serious adverse effects. Hepcidin, the iron regulatory hormone, has been identified as a pathogenic factor in the development of AI. To explore new therapeutic options for AI and other iron-related disorders caused by hepcidin excess, we developed a cell-based screen to identify hepcidin antagonists. Of the 70,000 small molecules in the library, we identified 14 compounds that antagonized the hepcidin effect on ferroportin. One of these was fursultiamine, a Food and Drug Administration (FDA)approved thiamine derivative. Fursultiamine directly interfered with hepcidin binding to its receptor, ferroportin, by blocking ferroportin C326 thiol residue essential for hepcidin binding. Consequently, fursultiamine prevented hepcidin-induced ferroportin ubiquitination, endocytosis, and degradation in vitro and allowed continuous cellular iron export despite the presence of hepcidin, with IC50 in the submicromolar range. Thiamine, the fursultiamine metabolite, and benfotiamine, another thiamine derivative, did not interfere with the effect of hepcidin on ferroportin. Other FDA-approved thiol-reactive compounds were at least 1000-fold less potent than fursultiamine in antagonizing hepcidin. In vivo, fursultiamine did not reproducibly antagonize the effect of hepcidin on serum iron, likely because of its rapid conversion to inactive metabolites. Fursultiamine is a unique antagonist of hepcidin in vitro that could serve as a template for the development of drug candidates that inhibit the hepcidin-ferroportin interaction. PMID:23292796

Fung, Eileen; Sugianto, Priscilla; Hsu, Jason; Damoiseaux, Robert; Ganz, Tomas

2013-01-01

229

Polarization control of high order harmonics in the EUV photon energy range.  

PubMed

We report the generation of circularly polarized high order harmonics in the extreme ultraviolet range (18-27 nm) from a linearly polarized infrared laser (40 fs, 0.25 TW) focused into a neon filled gas cell. To circularly polarize the initially linearly polarized harmonics we have implemented a four-reflector phase-shifter. Fully circularly polarized radiation has been obtained with an efficiency of a few percents, thus being 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 biology and materials science. The inherent femtosecond time resolution of high order harmonic generating table top laser sources renders these an ideal tool for the investigation of ultrafast magnetization dynamics now that the magnetic circular dichroism at the absorption M-edges of transition metals can be exploited. PMID:21369265

Vodungbo, Boris; Barszczak Sardinha, Anna; Gautier, Julien; Lambert, Guillaume; Valentin, Constance; Lozano, Magali; Iaquaniello, Grgory; Delmotte, Franck; Sebban, Stphane; Lning, Jan; Zeitoun, Philippe

2011-02-28

230

High-order harmonics with frequency-varying polarization within each harmonic  

E-print Network

We predict high-order harmonics in which the polarization within the spectral bandwidth of each harmonic varies continuously and significantly. For example, the interaction of counter-rotating circularly-polarized bichromatic drivers having close central frequencies with isotropic gas leads to the emission of polarization-fan harmonics which are nearly circularly-polarized in one tail of the harmonic peak, linear in the center of the peak and nearly circular with the opposite helicity in the opposite tail. Polarization fan harmonics are obtained as a result of multiple (at least two) head-on recollisions of electrons with their parent ions occurring from different angles. The process can be phase-matched using standard methods (e.g. pressure tuning phase matching) and maintains the single-atom polarization property through propagation. These polarization-fan harmonics may be used for exploring non-repetitive ultrafast chiral phenomena, e.g. dynamics of magnetic domains, in a single shot

Fleischer, Avner; Sidorenko, Pavel; Cohen, Oren

2014-01-01

231

Probing molecular frame photoelectron angular distributions via high-order harmonic generation from aligned molecules  

E-print Network

. In recent years, using high-energy XUV or x-ray photons, fixed-in-space PI has been investigated by using the inner orbital of a molecule and the molecular ion dissociates after photoabsorption. If the dissociation

Lin, Chii-Dong

232

A millimeter/submillimeter spectrometer for !high resolution studies of transient molecules  

E-print Network

A millimeter/submillimeter spectrometer for !high resolution studies of transient molecules L. M with a detachable Broida-type oven. The detector for the spectrometer is a helium-cooled InSb hot electron bolometer

Ziurys, Lucy M.

233

Automated high resolution optical mapping using arrayed, fluid-fixed DNA molecules  

PubMed Central

New mapping approaches construct ordered restriction maps from fluorescence microscope images of individual, endonuclease-digested DNA molecules. In optical mapping, molecules are elongated and fixed onto derivatized glass surfaces, preserving biochemical accessibility and fragment order after enzymatic digestion. Measurements of relative fluorescence intensity and apparent length determine the sizes of restriction fragments, enabling ordered map construction without electrophoretic analysis. The optical mapping system reported here is based on our physical characterization of an effect using fluid flows developed within tiny, evaporating droplets to elongate and fix DNA molecules onto derivatized surfaces. Such evaporation-driven molecular fixation produces well elongated molecules accessible to restriction endonucleases, and notably, DNA polymerase I. We then developed the robotic means to grid DNA spots in well defined arrays that are digested and analyzed in parallel. To effectively harness this effect for high-throughput genome mapping, we developed: (i) machine vision and automatic image acquisition techniques to work with fixed, digested molecules within gridded samples, and (ii) Bayesian inference approaches that are used to analyze machine vision data, automatically producing high-resolution restriction maps from images of individual DNA molecules. The aggregate significance of this work is the development of an integrated system for mapping small insert clones allowing biochemical data obtained from engineered ensembles of individual molecules to be automatically accumulated and analyzed for map construction. These approaches are sufficiently general for varied biochemical analyses of individual molecules using statistically meaningful population sizes. PMID:9653137

Jing, Junping; Reed, Jason; Huang, John; Hu, Xinghua; Clarke, Virginia; Edington, Joanne; Housman, Dan; Anantharaman, Thomas S.; Huff, Edward J.; Mishra, Bud; Porter, Brett; Shenker, Alexander; Wolfson, Estarose; Hiort, Catharina; Kantor, Ron; Aston, Christopher; Schwartz, David C.

1998-01-01

234

A high flux normal incidence monochromator for circularly polarized synchrotron radiation  

NASA Astrophysics Data System (ADS)

Design and performance of a 6.3 m normal incidence UHV-monochromator (see fig. 1) of the Gillieson type for synchrotron radiation are described. The monochromator will be used for simultaneously spin polarization and emission angle-resolved photoelectron spectroscopy; it combines a high photon flux and a high degree of circular polarization of the monochromatized radiation with a moderate resolution.

Eyers, A.; Heckenkamp, Ch.; Schfers, F.; Schnhense, G.; Heinzmann, U.

1983-04-01

235

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

NASA Technical Reports Server (NTRS)

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).

Lister, M.; Smith, P.

2000-01-01

236

Effective inclusion of polarization effects in calculations of the oscillator strengths and transition energies in atoms and molecules using the equation-of-motion method  

SciTech Connect

Equations of motion were solved by a modified method in a quasi-particle representation of the density functional taking into account the most important polarization effects, including the so-called 2p-2h two-particle-two-hole interactions. Based on these calculations, spectroscopic data on energies and oscillator strengths of the helium atom (the test computation), carbon monoxide, nitrogen molecule, and ethylene are presented that refine some previously reported experimental and theoretical results. It is shown that in some cases the inclusion of polarization corrections introduced by 2p-2h effects is of basic importance because it provides up to {approximately}30% contribution to the energies and oscillator strengths. 23 refs., 5 tabs.

Glushkov, A.V.; Kol`tsova, N.Yu. [Odessa Meterological Institute (Russian Federation)

1994-06-01

237

Highly stable polarization independent Mach-Zehnder interferometer.  

PubMed

We experimentally demonstrate optical Mach-Zehnder interferometer utilizing displaced Sagnac configuration to enhance its phase stability. The interferometer with footprint of 2740 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. PMID:25173242

Mi?uda, Michal; Dolkov, Ester; Straka, Ivo; Mikov, Martina; Duek, Miloslav; Fiurek, Jaromr; Jeek, Miroslav

2014-08-01

238

Highly stable polarization independent Mach-Zehnder interferometer  

E-print Network

We experimentally demonstrate optical Mach-Zehnder interferometer utilizing displaced Sagnac configuration to enhance its phase stability. The interferometer with footprint of 27x40 cm offers individually accessible paths and shows phase deviation less than 0.4 deg during a 250 s long measurement. The phase drift, evaluated by means of Allan deviation, stays below 3 deg or 7 nm for 1.5 hours 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.

Michal Micuda; Ester Dolakova; Ivo Straka; Martina Mikova; Miloslav Dusek; Jaromir Fiurasek; Miroslav Jezek

2014-07-19

239

Atomic charge transfer-counter polarization effects determine infrared CH intensities of hydrocarbons: a quantum theory of atoms in molecules model.  

PubMed

Atomic charge transfer-counter polarization effects determine most of the infrared fundamental CH intensities of simple hydrocarbons, methane, ethylene, ethane, propyne, cyclopropane and allene. The quantum theory of atoms in molecules/charge-charge flux-dipole flux model predicted the values of 30 CH intensities ranging from 0 to 123 km mol(-1) with a root mean square (rms) error of only 4.2 km mol(-1) without including a specific equilibrium atomic charge term. Sums of the contributions from terms involving charge flux and/or dipole flux averaged 20.3 km mol(-1), about ten times larger than the average charge contribution of 2.0 km mol(-1). The only notable exceptions are the CH stretching and bending intensities of acetylene and two of the propyne vibrations for hydrogens bound to sp hybridized carbon atoms. Calculations were carried out at four quantum levels, MP2/6-311++G(3d,3p), MP2/cc-pVTZ, QCISD/6-311++G(3d,3p) and QCISD/cc-pVTZ. The results calculated at the QCISD level are the most accurate among the four with root mean square errors of 4.7 and 5.0 km mol(-1) for the 6-311++G(3d,3p) and cc-pVTZ basis sets. These values are close to the estimated aggregate experimental error of the hydrocarbon intensities, 4.0 km mol(-1). The atomic charge transfer-counter polarization effect is much larger than the charge effect for the results of all four quantum levels. Charge transfer-counter polarization effects are expected to also be important in vibrations of more polar molecules for which equilibrium charge contributions can be large. PMID:25254435

Silva, Arnaldo F; Richter, Wagner E; Meneses, Helen G C; Bruns, Roy E

2014-10-01

240

The High-Energy Polarization-Limiting Radius of Neutron Star Magnetospheres II -- Magnetized Hydrogen Atmospheres  

E-print Network

In the presence of strong magnetic fields, the vacuum becomes a birefringent medium. We show that this QED effect couples the direction of the polarization of photons leaving the NS surface, to the direction of the magnetic field along the ray's path. We analyze the consequences that this effect has on aligning the polarization vectors to generate large net polarizations, while considering thermal radiation originating from a thermal hydrogen atmosphere. Counter to previous predictions, we show that the thermal radiation should be highly polarized even in the optical. When detected, this polarization will be the first demonstration of vacuum birefringence. It could be used as a tool to prove the high magnetic field nature of AXPs and it could also be used to constrain physical NS parameters, such as $R/M$, to which the net polarization is sensitive.

Jeremy S. Heyl; Don Lloyd; Nir J. Shaviv

2005-02-17

241

Study on polarization of high-energy photons from the Crab pulsar  

E-print Network

We investigate polarization of high-energy emissions from the Crab pulsar in the frame work of the outer gap accelerator. The recent version of the outer gap, which extends from inside the null charge surface to the light cylinder, is used for examining the light curve, the spectrum and the polarization characteristics, simultaneously. The polarization position angle curve and the polarization degree are calculated to compare with the Crab optical data. We show that the outer gap model explains the general features of the observed light curve, the spectrum and the polarization by taking into account the emissions from inside of the null charge surface and from tertiary pairs, which were produced by the high-energy photons from the secondary pairs. For the Crab pulsar, the polarization position angle curve indicates that the viewing angle of the observer measured from the rotational axis is greater than 90 degrees.

J. Takata; H. K. Chang; K. S. Cheng

2007-01-09

242

High Energy Emission from the Polar Cap: The Slot Gap Revisited  

E-print Network

The characteristics of the high-energy emission from polar cap accelerators will be discussed. Particles accelerated in the "slot gap" near the polar cap rim will reach altitudes of several stellar radii before initiating pair cascades, producing a wide hollow cone of emission in young pulsars and some millisecond pulsars. Model X-ray and gamma-ray spectra and pulse profiles, based on Monte-Carlo simulations of polar cap pair cascades, will be presented.

Alice K. Harding; Alexander G. Muslimov

2003-04-07

243

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

Microsoft Academic Search

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

Gultekin Gulsen; Orhan Nalcioglu

2005-01-01

244

Development of the ZJU polarized near-infrared high spectral resolution lidar  

NASA Astrophysics Data System (ADS)

Quantitative measurements of atmospheric aerosol optical properties are required for studies of the Earth's radiation budget and climate change. Taking advantage of the broad spectrum of the Cabannes-Brillouin scattering from atmospheric molecules, the high spectral resolution lidar (HSRL) technique employs a narrow spectral filter to reject the aerosol Mie scattering component in the lidar return signals. Therefore, an HSRL can directly measure the extinction and backscatter coefficient as well as the lidar ratio. Since the backscattering signal is proportional to 1/?4, it presents high requirements for the spectral filter to build a near-infrared HSRL. The atomic/molecular absorption filters are limited by the wavelength and it is also challenging for Fabry-Perot interferometers (FPI) due to their small field of view(FOV). The field-widened Michelson interferometer, which has a large FOV, is considered to be a good candidate for the spectral filter of near-infrared HSRL. A polarized near-infrared HSRL instrument, which employs a field-widened Michelson interferometer as the spectral filter, is under development at the Zhejiang University (ZJU), China. In this paper, the methodology and design process of the instrument will be described in detail. The capability of the HSRL in determining the properties of the atmosphere will be addressed. The retrieval of the aerosol optical properties, such as extinction-to-backscatter ratio and aerosol depolarization ratio, will be presented. Sensitivity of the aerosol retrieval to errors in characterizing the spectral filter will also be investigated.

Liu, Dong; Yang, Yongying; Cheng, Zhongtao; Huang, Hanlu; Zhang, Bo; Shen, Yibing

2013-09-01

245

Identification of Promiscuous Small Molecule Activators in High-Throughput Enzyme  

E-print Network

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

Hergenrother, Paul J.

246

High-resolution observations of the polar magnetic fields of the sun  

NASA Technical Reports Server (NTRS)

High-resolution magnetograms of the solar polar region were used for the study of the polar magnetic field. In contrast to low-resolution magnetograph observations which measure the polar magnetic field averaged over a large area, we focused our efforts on the properties of the small magnetic elements in the polar region. Evolution of the filling factor (the ratio of the area occupied by the magnetic elements to the total area) of these magnetic elements, as well as the average magnetic field strength, were studied during the maximum and declining phase of solar cycle 22, from early 1991 to mid-1993. We found that during the sunspot maximum period, the polar regions were occupied by about equal numbers of positive and negative magnetic elements, with equal average field strength. As the solar cycle progresses toward sunspot minimum, the magnetic field elements in the polar region become predominantly of one polarity. The average magnetic field of the dominant polarity elements also increases with the filling factor. In the meanwhile, both the filling factor and the average field strength of the non-dominant polarity elements decrease. The combined effects of the changing filling factors and average field strength produce the observed evolution of the integrated polar flux over the solar cycle. We compared the evolutionary histories of both filling factor and average field strength, for regions of high (70-80 deg) and low (60-70 deg) latitudes. For the south pole, we found no significant evidence of difference in the time of reversal. However, the low-latitude region of the north pole did reverse polarity much earlier than the high-latitude region. It later showed an oscillatory behavior. We suggest this may be caused by the poleward migration of flux from a large active region in 1989 with highly imbalanced flux.

Lin, H.; Varsik, J.; Zirin, H.

1994-01-01

247

Dynamics of the serine chemoreceptor in the Escherichia coli inner membrane: a high-speed single-molecule tracking study.  

PubMed

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 ?m(2) 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

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

2014-01-01

248

Polar Kerr effect in high-Tc superconductors - The rotating-plate technique  

Microsoft Academic Search

A technique for measuring the complex polar Kerr rotation in high-Tc superconductors is discussed using a Jones matrix approach. It is concluded that this technique provides excellent discrimination against linear polarization effects, but remains sensitive to reciprocal signal due to sample inhomogeneity. While the presence of Kerr ellipticity has been demonstrated in cuprate and bismuthate samples, it cannot be definitely

K. B. Lyons; J. F. Dillon Jr.; M. McGlashan-Powell

1991-01-01

249

Tight focusing of double ring shaped radially polarized beam with high NA lens axicon  

Microsoft Academic Search

A method is presented for generation of a sub wavelength (0.45?) longitudinally polarized beam, which propagates without divergence over lengths of about 8? in free space. This is achieved by tight focusing of double ring shaped radially polarized beam with a high NA lens axicon that utilizes spherical aberration to duplicate the performance of an axicon and to create an

K. B. Rajesh; N. Veerabagu Suresh; P. M. Anbarasan; K. Gokulakrishnan; G. Mahadevan

2011-01-01

250

High-order harmonic generation in graphene flakes exposed to circularly polarized femtosecond pulses  

NASA Astrophysics Data System (ADS)

We calculate high-order harmonic spectra from graphene based on the strong-field approximation using circularly polarized infrared laser pulses. We allow for the plane of polarization to be tilted with respect to the two-dimensional graphene sheet, demonstrating that the structure of the harmonic spectra strongly depends on the tilt angle.

Simonsen, S. I.; Srngrd, S. A.; Frre, M.; Hansen, J. P.

2014-03-01

251

Sensitivity of single crystals to the circular polarization of high-energy gamma-quanta  

E-print Network

It is shown that single crystals are sensitive to the initial circular polarization of gamma-quanta with energies in tens GeV and more. The possibility of measurement of gamma-beam polarization is discussed. The obtained results may be useful for creation of polarimeters for high energy beams of gamma-quanta.

V. A. Maisheev

1999-12-21

252

Equarin, a novel soluble molecule expressed with polarity at chick embryonic lens equator, is involved in eye formation  

Microsoft Academic Search

The lens plays an important role in eye development. To investigate the molecular mechanisms involved, we used signal sequence trap screens with a chicken lens cDNA library and identified a novel secreted molecule, equarin. Equarin encodes consensus repeat domains conserved in human SRPX and mouse Urb. In the embryonic eye, equarin transcript is detected exclusively in the lens, and persists

Hong Mu; Kunimasa Ohta; Sei Kuriyama; Naoko Shimada; Hidenobu Tanihara; Kunio Yasuda; Hideaki Tanaka

2003-01-01

253

Microfiber-based, highly nonlinear graphene saturable absorber for formation of versatile structural soliton molecules in a fiber laser.  

PubMed

We reported on the generation of versatile soliton molecules in a fiber laser mode-locked by a microfiber-based graphene saturable absorber (GSA). By virtue of the highly nonlinear effect of the microfiber-based GSA, the soliton molecules could be easily observed. In addition to regular soliton molecules, it is found that the "soliton atoms" in molecules could exhibit different characteristics and show ultra-narrow pulse separations, which was termed as 'structural soliton molecule'. The pulse profiles of 'structural soliton molecules' were further reconstructed theoretically. The obtained results would give further insight towards understanding the dynamics of soliton molecules in fiber lasers. PMID:25401852

Luo, Ai-Ping; Zhu, Peng-Fei; Liu, Hao; Zheng, Xu-Wu; Zhao, Nian; Liu, Meng; Cui, Hu; Luo, Zhi-Chao; Xu, Wen-Cheng

2014-11-01

254

September 15, 2000 / Vol. 25, No. 18 / OPTICS LETTERS 1355 High-speed fiberbased polarization-sensitive optical  

E-print Network

­based polarization-sensitive optical coherence tomography (PS OCT) system was developed. With a polarizationSeptember 15, 2000 / Vol. 25, No. 18 / OPTICS LETTERS 1355 High-speed fiber­based polarization-sensitive optical coherence tomography (PS OCT) has per- mitted additional information on the polarization

Chen, Zhongping

255

High stable single-polarization tunable fiber laser based on Opto-DMD processor and polarization-maintaining fiber devices  

NASA Astrophysics Data System (ADS)

A high stable wavelength-tunable fiber laser is experimentally demonstrated by using a digital-micromirror-device (DMD) processor and a polarization-maintaining erbium-doped fiber amplifier (EDFA).The electronic-addressed DMD processor is able to select and couple a waveband from of the polarization-maintaining EDFA back into the fiber ring to generate a narrow line-width laser output. The tunable fiber laser shows a line-width of 0.02nm, a tuning step of 0.08nm over the c-band and a side mode suppression ratio (SMSR) greater than 50 dB. The output power uniformity of 0.016dB is achieved by using the automatic power control (APC) system under room temperature. The center wavelength fluctuation during 1 hour is below 0.01 nm.

Huang, Kuizhi; Yan, Binbin; Chen, Xiao; Chen, Genxiang; Ai, Qi; Wang, Kuiru; Wang, Yiquan; Zhang, Ying; Song, Feijun; Sang, Xinzhu

2012-11-01

256

High stable single-polarization tunable fiber laser based on Opto-DMD processor and polarization-maintaining fiber devices  

NASA Astrophysics Data System (ADS)

A high stable wavelength-tunable fiber laser is experimentally demonstrated by using a digital-micromirror-device (DMD) processor and a polarization-maintaining erbium-doped fiber amplifier (EDFA).The electronic-addressed DMD processor is able to select and couple a waveband from of the polarization-maintaining EDFA back into the fiber ring to generate a narrow line-width laser output. The tunable fiber laser shows a line-width of 0.02 nm, a tuning step of 0.08 nm over the c-band and a side mode suppression ratio (SMSR) greater than 50 dB. The output power uniformity of 0.01 mW is achieved by using the automatic power control (APC) system under room temperature. The center wavelength fluctuation during 1 h is below 0.01 nm.

Huang, Kuizhi; Yan, Binbin; Chen, Xiao; Chen, Gengxiang; Ai, Qi; Wang, Kuiru; Wang, Yiquan; Zhang, Ying; Song, Feijun; Wu, Qiang; Sang, Xinzhu

2012-12-01

257

Unravelling the genomic targets of small molecules using high-throughput sequencing.  

PubMed

Small molecules - including various approved and novel cancer therapeutics - can operate at the genomic level by targeting the DNA and protein components of chromatin. Emerging evidence suggests that functional interactions between small molecules and the genome are non-stochastic and are influenced by a dynamic interplay between DNA sequences and chromatin states. The establishment of genome-wide maps of small-molecule targets using unbiased methodologies can help to characterize and exploit drug responses. In this Review, we discuss how high-throughput sequencing strategies, such as ChIP-seq (chromatin immunoprecipitation followed by sequencing) and Chem-seq (chemical affinity capture and massively parallel DNA sequencing), are enabling the comprehensive identification of small-molecule target sites throughout the genome, thereby providing insights into unanticipated drug effects. PMID:25311424

Rodriguez, Raphal; Miller, Kyle M

2014-12-01

258

In situ Formation of Highly Conducting Covalent Au-C Contacts for Single-Molecule Junctions  

SciTech Connect

Charge transport across metal-molecule interfaces has an important role in organic electronics. Typically, chemical link groups such as thiols or amines are used to bind organic molecules to metal electrodes in single-molecule circuits, with these groups controlling both the physical structure and the electronic coupling at the interface. Direct metal-carbon coupling has been shown through C60, benzene and {pi}-stacked benzene but ideally the carbon backbone of the molecule should be covalently bonded to the electrode without intervening link groups. Here, we demonstrate a method to create junctions with such contacts. Trimethyl tin (SnMe{sub 3})-terminated polymethylene chains are used to form single-molecule junctions with a break-junction technique. Gold atoms at the electrode displace the SnMe{sub 3} linkers, leading to the formation of direct Au-C bonded single-molecule junctions with a conductance that is {approx}100 times larger than analogous alkanes with most other terminations. The conductance of these Au-C bonded alkanes decreases exponentially with molecular length, with a decay constant of 0.97 per methylene, consistent with a non-resonant transport mechanism. Control experiments and ab initio calculations show that high conductances are achieved because a covalent Au-C sigma ({sigma}) bond is formed. This offers a new method for making reproducible and highly conducting metal-organic contacts.

Cheng, Z.L.; Hybertsen, M.; Skouta, R.; Vazquez, H.; Widawsky, J.R.; Schneebeli, S.; Chen, W.; Breslow, R.; Venkataraman, L.

2011-06-01

259

Retrieval and analysis of a polarized high-spectral-resolution lidar for profiling aerosol optical properties.  

PubMed

Taking advantage of the broad spectrum of the Cabannes-Brillouin scatter from atmospheric molecules, the high spectral resolution lidar (HSRL) technique employs a narrow spectral filter to separate the aerosol and molecular scattering components in the lidar return signals and therefore can obtain the aerosol optical properties as well as the lidar ratio (i.e., the extinction-to-backscatter ratio) which is normally selected or modeled in traditional backscatter lidars. A polarized HSRL instrument, which employs an interferometric spectral filter, is under development at the Zhejiang University (ZJU), China. In this paper, the theoretical basis to retrieve the aerosol lidar ratio, depolarization ratio and extinction and backscatter coefficients, is presented. Error analyses and sensitivity studies have been carried out on the spectral transmittance characteristics of the spectral filter. The result shows that a filter that has as small aerosol transmittance (i.e., large aerosol rejection rate) and large molecular transmittance as possible is desirable. To achieve accurate retrieval, the transmittance of the spectral filter for molecular and aerosol scattering signals should be well characterized. PMID:23736562

Liu, Dong; Yang, Yongying; Cheng, Zhongtao; Huang, Hanlu; Zhang, Bo; Ling, Tong; Shen, Yibing

2013-06-01

260

`Shotgun DNA synthesis' for the high-throughput construction of large DNA molecules  

E-print Network

,2). However, typically employed DNA synthe- sis procedures (2) impose significant challenges for scalable`Shotgun DNA synthesis' for the high-throughput construction of large DNA molecules Hwangbeom Kim1 a highly scalable `shotgun' DNA synthesis technology by utilizing microchip oligo- nucleotides, shotgun

Bang, Duhee

261

Localization and orientation of functional water molecules in bacteriorhodopsin as revealed by polarized Fourier transform infrared spectroscopy.  

PubMed Central

Linear dichroic difference Fourier transform infrared spectra upon formation of the M photointermediate were recorded with oriented purple membranes. The purpose was to determine the angle of the directions of the dipole moments of 1) the water molecule whose O-H stretching vibration appears at 3643 cm-1 for the unphotolyzed state and 3671 cm-1 for the M intermediate, and 2) the C=O bond of protonated Asp85 in the M intermediate. The angle of 36 degrees we find for the C=O of the protonated Asp85 in the M intermediate is not markedly different from 26 degrees for unprotonated Asp85 in the model based on cryoelectron diffraction, indicating the absence of gross orientation changes in Asp85 upon its protonation. The O-H band at 3671 cm-1 of a water molecule in the M intermediate, although its position has not determined, is fixed almost parallel to the membrane plane. For the unphotolyzed state the angle of the water O-H to the membrane normal was determined to be 60 degrees. On the basis of these data and the structural model, we place the water molecule in the unphotolyzed state at a position where it forms hydrogen bonds with the Schiff base, Asp85, Asp212, and Trp86. Images FIGURE 4 FIGURE 6 FIGURE 7 PMID:9251817

Hatanaka, M; Kandori, H; Maeda, A

1997-01-01

262

A new family of four-ring bent-core nematic liquid crystals with highly polar transverse and end groups  

PubMed Central

Summary Non-symmetrically substituted four-ring achiral bent-core compounds with polar substituents, i.e.., chloro in the bent or transverse direction in the central core and cyano in the lateral direction at one terminal end of the molecule, are designed and synthesized. These molecules possess an alkoxy chain attached at only one end of the bent-core molecule. The molecular structure characterization is consistent with data from elemental and spectroscopic analysis. The materials thermal behaviour and phase characterization have been investigated by differential scanning calorimetry and polarizing microscopy. All the compounds exhibit a wide-ranging monotropic nematic phase. PMID:23400045

Upadhyaya, Kalpana; Gude, Venkatesh; Mohiuddin, Golam

2013-01-01

263

PPARc Ligands Switched High Fat Diet-Induced Macrophage M2b Polarization toward M2a Thereby  

E-print Network

PPARc Ligands Switched High Fat Diet-Induced Macrophage M2b Polarization toward M2a Thereby the activation of alternative M2 macrophage polarization. Here, we evaluated the impact of high fat diet (HFD)-induced present a M2b polarization (TNF-ahigh , IL-10high , MR, Dectin-1). Interestingly, rosiglitazone induces

Boyer, Edmond

264

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

SciTech Connect

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.

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

265

Highly sensitive twist sensor based on tilted fiber Bragg grating of polarization-dependent properties  

NASA Astrophysics Data System (ADS)

The transmission intensity of the tilted fiber Bragg grating (TFBG) is strongly dependent on the polarization properties of the TFBG. The polarization characteristic of the cladding modes can be used for twist measuring. In this paper, a highly sensitive fiber twist sensor is proposed. The transmission intensity on the strong loss wavelength showed a quasi-sin ? changing with the twist angle ranging from 0 to 180 for S- or P-polarized input. A high sensitivity of 0.299 dB/ is achieved, which is almost 17.9 times higher than that of the current similar existing twist sensor. The twist angle can be measured precisely with the matrix.

Lu, Yanfang; Shen, Changyu; Chen, Debao; Chu, Jinlei; Wang, Qiang; Dong, Xinyong

2014-10-01

266

Neuronal Polarity and the Kinesin Superfamily Proteins  

NSDL National Science Digital Library

Neurons are highly polarized cells, typically with a long axon and relatively short dendrites. A wealth of recent data has identified a number of signaling molecules that are involved in neuronal polarization. Kinesin superfamily proteins (KIFs) contribute to the establishment and maintenance of neuronal polarity by selectively transporting various proteins and vesicles to either the axon or dendrites. Now evidence is emerging that KIFs also play an important role in axonal formation, the initial event of neuronal polarization. In particular, KIF13B transports phosphatidylinositol (3,4,5)-trisphosphate, which, based on current hypotheses, is one of the most upstream molecules in the intracellular signaling cascades involved in axonal formation.

Takao Nakata (University of Tokyo;Department of Cell Biology and Anatomy REV); Nobutaka Hirokawa (University of Tokyo;Department of Cell Biology and Anatomy REV)

2007-02-06

267

Magnetic coupling of Fe-porphyrin molecules adsorbed on clean and c(22) oxygen-reconstructed Co(100) investigated by spin-polarized photoemission spectroscopy  

NASA Astrophysics Data System (ADS)

The spin-polarized electronic structure of iron octaethylporphyrin (FeOEP) molecules adsorbed on a pristine and on a c(22) oxygen-reconstructed Co(100) surface has been analyzed by means of spin-polarized photoemission spectroscopy (SPPES) and first-principles density functional theory with the on-site Coulomb repulsion U term (DFT+U) calculations with and without Van der Waals corrections. The aim is to examine the magnetic exchange mechanism between the FeOEP molecules and the Co(100) substrate in the presence or absence of the oxygen mediator. The results demonstrate that the magnetic coupling from the ferromagnetic substrate to the adsorbed FeOEP molecules is ferromagnetic, whereas, the coupling is antiferromagnetic for the FeOEP on the c(22)O/Co(100) system. Spin-resolved partial densities of states extracted from ab initio DFT+U modeling are in fairly good comparison with the electronic spectral densities seen in angle-integrated SPPES energy dispersion curves for submonolayer coverages of FeOEP. Through combined analysis of these spectra and theoretical results, we determine that hybridization of 2p orbitals of N and O with Co 3d orbitals facilitates indirect magnetic exchange interactions between Fe and Co, whereas, a direct Fe-Co interaction involving the Fe dz2 orbital is also found for FeOEP on Co. It is observed through SPPES that the spin polarization of the photoemission-visible molecular overlayers decreases to zero as coverage is increased beyond the submonolayer regime, indicating that only interfacial magnetic coupling is at work. Microspot low-energy electron diffraction and low-energy electron microscopy were performed to characterize the physical order of the molecular coverage, revealing that FeOEP structural domains are orders of magnitude greater in size on c(22)O/Co(100) than on clean Co(100), which coincides with reduced scattering from the disorder and sharper features seen in SPPES.

Weber, A. P.; Caruso, A. N.; Vescovo, E.; Ali, Md. E.; Tarafder, K.; Janjua, S. Z.; Sadowski, J. T.; Oppeneer, P. M.

2013-05-01

268

The high optical polarization in the Be/X-ray binary EXO 2030+375  

NASA Astrophysics Data System (ADS)

Polarization in classical Be stars results from Thomson scattering of the unpolarized light from the Be star in the circumstellar disc. Theory and observations agree that the maximum degree of polarization from isolated Be stars is ?4 per cent. We report on the first optical polarimetric observations of the Be/X-ray binary EXO 2030+375. We find that the optical (R-band) light is strongly linearly polarized with a degree of polarization of 19 per cent, the highest ever measured either in a classical or Be/X-ray binary. We argue that the interstellar medium cannot account for this high-polarization degree and that a substantial amount must be intrinsic to the source. We propose that it may result from the alignment of non-spherical ferromagnetic grains in the Be star disc due to the strong neutron star magnetic field.

Reig, P.; Blinov, D.; Papadakis, I.; Kylafis, N.; Tassis, K.

2014-12-01

269

Gamma-Ray Polarization of the Synchrotron Self-compton Process from a Highly Relativistic Jet  

NASA Astrophysics Data System (ADS)

The high polarization observed in the prompt phase of some gamma-ray bursts invites extensive study of the emission mechanism. In this paper, we investigate the polarization properties of the synchrotron self-Compton (SSC) process from a highly relativistic jet. A magnetic-dominated, baryon-loaded jet ejected from the central engine travels with a large Lorentz factor. Shells with slightly different velocities collide with each other and produce shocks. The shocks accelerate electrons to a power-law distribution and, at the same time, magnify the magnetic field. Electrons move in the magnetic field and produce synchrotron photons. Synchrotron photons suffer from the Compton scattering (CS) process and then are detected by an observer located slightly off-axis. We analytically derive the formulae of photon polarization in the SSC process in two magnetic configurations: a magnetic field in the shock plane and perpendicular to the shock plane. We show that photons induced by the SSC process can be highly polarized, with the maximum polarization ? ~ 24% in the energy band [0.5, 5] MeV. The polarization depends on the viewing angles, peaking in the plane perpendicular to the magnetic field. In the energy band [0.05, 0.5] MeV, in which most ?-ray polarimeters are active, the polarization is about twice that in the Thomson limit, reaching ? ~ 20%. This implies that the Klein-Nishina effect, which is often neglected in the literature, should be carefully considered.

Chang, Zhe; Lin, Hai-Nan

2014-11-01

270

Signatures of symmetry and electronic structure in high-order harmonic generation in polyatomic molecules  

SciTech Connect

We report detailed measurements of high-order harmonic generation in chloromethane molecules (CCl{sub 4}, CHCl{sub 3}, and CH{sub 2}Cl{sub 2}) to show that fingerprints of symmetry and electronic structure can be decoded from high-order harmonic generation even in complex randomly oriented molecules. In our measurements, orbital symmetries of these molecules are manifested as both extended harmonic cutoffs and a local minimum in the ellipticity dependence of the cut-off harmonics, suggesting the occurrence of quantum interferences during ionization. The harmonic spectra exhibit distinct interference minima at {approx}42 and {approx}60 eV. We attribute the former to the Cooper minimum in the photoionization cross section and the latter to intramolecular interference during the recombination process.

Wong, M. C. H.; Brichta, J.-P.; Bhardwaj, V. R. [Department of Physics, University of Ottawa, 150 Louis Pasteur, Ottawa, Ontario, K1N 6N5 (Canada)

2010-06-15

271

A protocol for the culture and differentiation of highly polarized human retinal pigment epithelial cells.  

PubMed Central

We provide our detailed, standardized in vitro protocol for culture and differentiation of human retinal pigment epithelial (RPE) cells into a highly polarized, functional monolayer. Disruption of polarized RPE function plays an important role in the pathogenesis of common blinding disorders of the retina. The availability of this polarized RPE monolayer allows for reproducible evaluation of RPE function, modeling of RPE dysfunction in retinal disease, and in vitro evaluation of novel therapies. The protocol, which takes approximately 6 weeks, describes the culture of RPE from human fetal donor eyes, and the differentiation of these cells into a polarized monolayer with high transepithelial resistance, and morphologic characteristics that mimic the RPE monolayer in vivo. By modifying the procedure for initial isolation of pure RPE cells, and culture conditions used in existing protocols, we have established a standardized protocol that provides highly reproducible RPE monolayers from the same donor eye. PMID:19373231

Sonoda, Shozo; Spee, Christine; Barron, Ernesto; Ryan, Stephen J; Kannan, Ram; Hinton, David R

2009-01-01

272

High-Field Dynamic Nuclear Polarization for Solid and Solution Biological NMR  

PubMed Central

Dynamic nuclear polarization (DNP) results in a substantial nuclear polarization enhancement through a transfer of the magnetization from electrons to nuclei. Recent years have seen considerable progress in the development of DNP experiments directed towards enhancing sensitivity in biological nuclear magnetic resonance (NMR). This review covers the applications, hardware, polarizing agents, and theoretical descriptions that were developed at the Francis Bitter Magnet Laboratory at Massachusetts Institute of Technology for high-field DNP experiments. In frozen dielectrics, the enhanced nuclear polarization developed in the vicinity of the polarizing agent can be efficiently dispersed to the bulk of the sample via 1H spin diffusion. This strategy has been proven effective in polarizing biologically interesting systems, such as nanocrystalline peptides and membrane proteins, without leading to paramagnetic broadening of the NMR signals. Gyrotrons have been used as a source of high-power (510 W) microwaves up to 460 GHz as required for the DNP experiments. Other hardware has also been developed allowing in situ microwave irradiation integrated with cryogenic magic-angle-spinning solid-state NMR. Advances in the quantum mechanical treatment are successful in describing the mechanism by which new biradical polarizing agents yield larger enhancements at higher magnetic fields. Finally, pulsed methods and solution experiments should play a prominent role in the future of DNP. PMID:19194532

Barnes, A.B.; Paepe, G. De; van der Wel, P.C.A.; Hu, K.-N.; Joo, C.-G.; Bajaj, V.S.; Mak-Jurkauskas, M.L.; Sirigiri, J.R.; Herzfeld, J.; Temkin, R.J.; Griffin, R.G.

2008-01-01

273

High-throughput screening of small molecules in miniaturized mammalian cell-based assays involving post-translational  

E-print Network

High-throughput screening of small molecules in miniaturized mammalian cell-based assays involving systems using small molecules, rather than mutations, as the source of gene- product alterations of small molecules in nanoliter to microliter culture volumes. We refer to this assay format as a `cytoblot

Stockwell, Brent R.

274

Semiclassical wave packet study of V-V energy transfer in highly vibrationally excited CO molecules  

Microsoft Academic Search

Application of a semiclassical wave packet approach to the study of vibrational energy transfer in collision between highly vibrationally excited diatomic molecules is discussed. The method uses a quantum mechanical description based on the solution to the time-dependent Schrdinger equation to describe the vibrational motions and a classical mechanical treatment for the rotational and translational motions. The quantum and classical

N. Balakrishnan; G. D. Billing

1996-01-01

275

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

SciTech Connect

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.

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

1999-06-27

276

Capillary Electrophoretic Study of Small, Highly Sulfated, Non-Sugar Molecules Interacting With Antithrombin  

E-print Network

that the tetrahydroisoquinoline-based molecules do not compete with a high-affinity heparin pentasaccharide. In contrast, the affinity of these tetrahydroisoquinoline derivatives decreases dramatically in the presence of an extended-heparin electrophoresis EHBS, extended heparin-binding site HBS, heparin-binding site PBS, pentasaccharide-binding site

Desai, Umesh R

277

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

PubMed Central

Electronnuclei 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 FranckCondon 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

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

2013-01-01

278

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

SciTech Connect

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.

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

279

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

SciTech Connect

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.

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

280

Generation of needle of longitudinally polarized beam by tight focusing of double-ring-shaped radially polarized beam with high NA lens axicon  

Microsoft Academic Search

A method is presented for generation of a sub wavelength (0.25lambda) longitudinally polarized beam, which propagates without divergence over lengths of about 3lambda in free space. This is achieved by tight focusing of double ring shaped radially polarized beam with a high NA lens axicon that utilizes spherical aberration to duplicate the performance of an axicon and to create an

P. M. Anbarasan; K. B. Rajesh

2010-01-01

281

Generation of needle of longitudinally polarized beam by tight focusing of double-ring-shaped radially polarized beam with high NA lens axicon  

Microsoft Academic Search

A method is presented for generation of a sub wavelength (0.25?) longitudinally polarized beam, which propagates without divergence over lengths of about 3? in free space. This is achieved by tight focusing of double ring shaped radially polarized beam with a high NA lens axicon that utilizes spherical aberration to duplicate the performance of an axicon and to create an

P. M. Anbarasan; K. B. Rajesh

2010-01-01

282

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

PubMed

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

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

2011-01-01

283

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

NASA Astrophysics Data System (ADS)

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.

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

2011-12-01

284

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

SciTech Connect

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.

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

2007-06-25

285

Obtaining and measuring high nuclear polarizations in optically pumped He-3  

NASA Astrophysics Data System (ADS)

Nuclear orientation of 3He gas through optical pumping of the 23S1 metastable state is a method to produce large spin polarization using high power lamp pumped LNA lasers operating at 1.08 ?m on the 23S-23P transition [1]. Polarized 3He gas targets have applications in nuclear and high energy physics. They are also considered as possible spin polarizers for thermal and epithermal neutron beams, using the largely different scattering cross-sections of the two neutron spin states by the 3He nucleus [2]. All these experiments require that M, the nuclear 3He polarization, be both large and precisely known. In this paper we summarize the ideas underlying an accurate optical measurement of M that we recently performed [3]. We then discuss how its accuracy can be transferred to different experiments and how certain parameters influence both the reachable M values and the build-up time constants.

Leduc, M.; Nacher, P. J.; Bigelow, N.; Larat, C.

1993-12-01

286

Gamma-ray polarization of synchrotron-self-Compton process from a highly relativistic jet  

E-print Network

The high polarization observed in the prompt phase of some gamma-ray bursts (GRBs) arouses extensive studies on the emission mechanism. In this paper, we investigate the polarization properties of synchrotron-self-Compton (SSC) process from a highly relativistic jet. A magnetic-dominated, baryon-loaded jet ejected from central engine travels with a large Lorentz factor. Shells with slightly different velocities collides with each other and produce shocks. The shocks accelerate electrons to power-law distribution, and at the same time, magnify the magnetic field. Electrons move in the magnetic field and produce synchrotron photons. The synchrotron photons suffer from Compton scattering process and then escape from the jet and are detected by an observer locating slightly off-axis. We derive analytical formulae of polarization in the SSC process, based on the cross section of an initially polarized photon scattered by an unpolarized electron with any momentum. We show that photons induced by the SSC process can...

Chang, Zhe

2014-01-01

287

Maintained expression of the planar cell polarity molecule Vangl2 and reformation of hair cell orientation in the regenerating inner ear.  

PubMed

The avian inner ear possesses a remarkable ability to regenerate sensory hair cells after ototoxic injury. Regenerated hair cells possess phenotypes and innervation that are similar to those found in the undamaged ear, but little is known about the signaling pathways that guide hair cell differentiation during the regenerative process. The aim of the present study was to examine the factors that specify the orientation of hair cell stereocilia bundles during regeneration. Using organ cultures of the chick utricle, we show that hair cells are properly oriented after having regenerated entirely in vitro and that orientation is not affected by surgical removal of the striolar reversal zone. These results suggest that the orientation of regenerating stereocilia is not guided by the release of a diffusible morphogen from the striolar reversal zone but is specified locally within the regenerating sensory organ. In order to determine the nature of the reorientation cues, we examined the expression patterns of the core planar cell polarity molecule Vangl2 in the normal and regenerating utricle. We found that Vangl2 is asymmetrically expressed on cells within the sensory epithelium and that this expression pattern is maintained after ototoxic injury and throughout regeneration. Notably, treatment with a small molecule inhibitor of c-Jun-N-terminal kinase disrupted the orientation of regenerated hair cells. Both of these results are consistent with the hypothesis that noncanonical Wnt signaling guides hair cell orientation during regeneration. PMID:20177731

Warchol, Mark E; Montcouquiol, Mireille

2010-09-01

288

Device for high-resolution frequency-modulated absorption spectroscopy of jet-cooled molecules  

NASA Astrophysics Data System (ADS)

A device for high-resolution frequency-modulated absorption spectroscopy of jet-cooled molecules is described and demonstrated. Direct absorption spectra of jet-cooled molecules are recorded by multipassing an infrared laser beam through a free-jet expansion with all light rays perpendicular to the nozzle axis. In sliced-jet spectroscopy sub-Doppler resolution is obtained by inserting a small blade upstream from the laser crossing to obstruct molecules that would otherwise absorb at the center of the Doppler profile. Here the sliced-jet technique is extended by replacing the blade by a stainless-steel string vibrating at a frequency of about 10 kHz. Phase sensitive detection of the frequency-modulated absorption signal is accomplished with a lock-in amplifier. A resolution of 12 MHz is demonstrated using the modulated sliced-jet technique.

Bethardy, G. A.; Perry, David S.

1995-04-01

289

QED and the high polarization of the thermal radiation from neutron stars  

Microsoft Academic Search

The thermal emission of strongly magnetized neutron-star atmospheres is\\u000athought to be highly polarized. However, because of the different orientations\\u000aof the magnetic field over the surface of the neutron star (NS), it is commonly\\u000aassumed that the net observed polarization will be significantly reduced as the\\u000apolarization from different regions will cancel each other. We show that the\\u000abirefringence

Jeremy S. Heyl; Nir J. Shaviv

2002-01-01

290

High speed spectral domain polarization sensitive optical coherence tomography of the human retina  

Microsoft Academic Search

We developed a high-speed polarization sensitive optical coherence tomography (PS-OCT) system for retinal imaging based on spectral domain OCT. The system uses two spectrometers, one for each polarization channel, that operate in parallel at 20000 A-lines\\/s each. It provides reflectivity, retardation, and cumulative optic axis orientation simultaneously. We present our instrument and discuss the requirements for the alignment of the

Erich Gtzinger; Michael Pircher; Christoph K. Hitzenberger

2005-01-01

291

TOPICAL REVIEW: Highly spin-polarized materials and devices for spintronics  

Microsoft Academic Search

The performance of spintronics depends on the spin polarization of the current. In this study half-metallic Co-based full-Heusler alloys and a spin filtering device (SFD) using a ferromagnetic barrier have been investigated as highly spin-polarized current sources. The multilayers were prepared by magnetron sputtering in an ultrahigh vacuum and microfabricated using photolithography and Ar ion etching. We investigated two systems

Koichiro Inomata; Naomichi Ikeda; Nobuki Tezuka; Ryogo Goto; Satoshi Sugimoto; Marek Wojcik; Eva Jedryka

2008-01-01

292

Highly spin-polarized materials and devices for spintronicsInvited paper  

Microsoft Academic Search

The performance of spintronics depends on the spin polarization of the current. In this study half-metallic Co-based full-Heusler alloys and a spin filtering device (SFD) using a ferromagnetic barrier have been investigated as highly spin-polarized current sources. The multilayers were prepared by magnetron sputtering in an ultrahigh vacuum and microfabricated using photolithography and Ar ion etching. We investigated two systems

Koichiro Inomata; Naomichi Ikeda; Nobuki Tezuka; Ryogo Goto; Satoshi Sugimoto; Marek Wojcik; Eva Jedryka

2008-01-01

293

High precision fabrication of polarization insensitive resonant grating filters  

NASA Astrophysics Data System (ADS)

Resonant subwavelength gratings have been designed and fabricated as wavelength-specific reflectors for application as a rotary position encoder utilizing ebeam based photolithography. The first grating design used a two-dimensional layout to provide polarization insensitivity with separate layers for the grating and waveguide. The resulting devices had excellent pattern fidelity and the resonance peaks and widths closely matched the expected results. Unfortunately, the gratings were particularly angle sensitive and etch depth errors led to shifts in the center wavelength of the resonances. A second design iteration resulted in a double grating period to reduce the angle sensitivity as well as different materials and geometry; the grating and waveguide being the same layer. The inclusion of etch stop layers provided more accurate etch depths; however, the tolerance to changes in the grating duty cycle was much tighter. Results from these devices show the effects of small errors in the pattern fidelity. The fabrication process flows for both iterations of devices will be reviewed as well as the performance of the fabricated devices. A discussion of the relative merits of the various design choices provides insight into the importance of fabrication considerations during the design stage.

Boye, R. R.; Peters, D. W.; Wendt, J. R.; Samora, S.; Stevens, J.; Shul, R. J.; Hunker, J.; Kellogg, R. A.; Kemme, S. A.

2012-03-01

294

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

PubMed

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 (110 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

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

2013-08-28

295

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

PubMed Central

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

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

2013-01-01

296

Multi-instrument, high-resolution imaging of polar cap plasma transportation  

NASA Astrophysics Data System (ADS)

The plasma of Earth's ionosphere at high latitudes is subject to redistribution by strong electric fields of magnetospheric origin. The large-scale motion of the plasma most often conforms to a two-cell pattern, with antisunward flow from the dayside across the polar cap to the nightside and return flow at auroral latitudes in the dawn and dusk sectors. Polar cap patches are discrete plasma structures in the F-region ionosphere characterized by electron densities at least twice those of the background polar cap plasma. These features are known to be closely related to scintillations on communications signals and are a productive source for decameter-scale plasma irregularity formation. We focus on an hours-long interval during a geomagnetic storm on 22 January 2012 when a series of patches were simultaneously observed with high spatial and temporal resolution by two 630.0 nm all-sky airglow imagers located within the polar cap at Resolute Bay, Canada and Longyearbyen, Norway. Comparisons with global maps of GPS total electron content (TEC) allow for the identification of patch generation from storm enhanced density (SED) near the dayside cusp and subsequent antisunward patch transportation to the nightside polar cap boundary. Finally, we examine the characteristics of SuperDARN radar observations of HF backscatter within these high density polar cap patches.

Thomas, E. G.; Hosokawa, K.; Sakai, J.; Baker, J. B.; Ruohoniemi, J.; Taguchi, S.; Shiokawa, K.; Otsuka, Y.; Coster, A. J.; St-Maurice, J.; McWilliams, K. A.; Lester, M.

2013-12-01

297

The Polarization of Scattered Lyman Alpha Radiation Around High-Redshift Galaxies  

E-print Network

The high-redshift Universe contains luminous Lyman Alpha (hereafter Lya) emitting sources such as galaxies and quasars. The emitted Lya radiation is often scattered by surrounding neutral hydrogen atoms. We show that the scattered Lya radiation obtains a high level of polarization for a wide range of likely environments of high-redshift galaxies. For example, the back-scattered Lya flux observed from galaxies surrounded by a superwind-driven outflow may reach a fractional polarization as high as ~40%. Equal levels of polarization may be observed from neutral collapsing protogalaxies. Resonant scattering in the diffuse intergalactic medium typically results in a lower polarization amplitude (<7%), which depends on the flux of the ionizing background. Spectral polarimetry can differentiate between Lya scattering off infalling gas and outflowing gas; for an outflow the polarization should increase towards longer wavelengths while for infall the opposite is true. Our numerical results suggest that Lya polarimetry is feasible with existing instruments, and may provide a new diagnostic of the distribution and kinematics of neutral hydrogen around high-redshift galaxies. Moreover, polarimetry may help suppress infrared lines originating in the Earth's atmosphere, and thus improve the sensitivity of ground-based observations to high-redshift Lya emitting galaxies outside the currently available redshift windows.

Mark Dijkstra; Abraham Loeb

2007-11-15

298

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

SciTech Connect

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

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

2007-02-01

299

Permeation of protons, potassium ions, and small polar molecules through phospholipid bilayers as a function of membrane thickness  

NASA Technical Reports Server (NTRS)

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.

Paula, S.; Volkov, A. G.; Van Hoek, A. N.; Haines, T. H.; Deamer, D. W.

1996-01-01

300

Experimental setup for laser spectroscopy of molecules in a high magnetic field  

NASA Astrophysics Data System (ADS)

An experimental setup to measure the effects of a high magnetic field on the structure and decay dynamics of molecules is designed and constructed. A vacuum chamber is mounted in the bore of a superconducting magnet. A molecular beam passes in the chamber. Pulsed laser light excites the molecules in the field. The parent or fragment ions are extracted by an electric field parallel to the magnetic field. They are detected by a microchannel plate. Their mass and charge are determined by the time-of-flight method. The performance of the setup was examined using resonance-enhanced two-photon ionization through the X2 Pi- A2? + transition of nitric oxide (NO) molecules. The ions were detected with sufficient mass resolution to discriminate the species in a field of up to 10 T. This is the first experiment to succeed in the mass-selective detection of ions by the time-of-flight method in a high magnetic field. By measuring NO+ ion current as a function of the laser frequency, the X2Pi- A2 ? + rotational transition lines, separated clearly from the background noise, were observed in fields of up to 10 T. From the relative strengths of the transition lines, the ion detection efficiency was determined as a function of the magnetic field strength. This setup was shown to be applicable in a field higher than 10 T. The Landau levels of molecules were successfully observed to demonstrate the setup.

Takazawa, Yasuyuki Kimura; Ken

2011-01-01

301

Generation of a highly phase sensitive polarization squeezed N-photon state by collinear parametric downconversion and coherent photon subtraction  

E-print Network

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 downconversion. 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.

Holger F. Hofmann

2005-10-02

302

Vacuum-UV spectroscopy of interstellar ice analogs. I. Absorption cross-sections of polar-ice molecules  

NASA Astrophysics Data System (ADS)

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/

Cruz-Diaz, G. A.; Muoz Caro, G. M.; Chen, Y.-J.; Yih, T.-S.

2014-02-01

303

Detecting very-high-frequency relic gravitational waves by electromagnetic wave polarizations in a waveguide  

E-print Network

The polarization vector (PV) of an electromagnetic wave (EW) will experience a rotation in a region of spacetime perturbed by gravitational waves (GWs). Based on this idea, Cruise's group has built an annular waveguide to detect GWs. We give detailed calculations of the rotations of the polarization vector of an EW caused by incident GWs from various directions and in various polarization states, and then analyze the accumulative effects on the polarization vector when the EW passes n cycles along the annular waveguide. We reexamine the feasibility and limitation of this method to detect GWs of high frequency around 100 MHz, in particular, the relic gravitational waves (RGWs). By comparing the spectrum of RGWs in the accelerating universe with the detector sensitivity of the current waveguide, it is found that the amplitude of the RGWs is too low to be detected by the waveguide detectors currently running. Possible ways of improvements on detection are discussed also.

M. L. Tong; Y. Zhang

2007-11-30

304

BaFe2S e3 : A High TC Magnetic Multiferroic with Large Ferrielectric Polarization  

NASA Astrophysics Data System (ADS)

The iron selenides are important because of their superconducting properties. Here, an unexpected phenomenon is predicted to occur in an iron-selenide compound with a quasi-one-dimensional ladder geometry: BaFe2S e3 should be a magnetic ferrielectric system, driven by its magnetic block order via exchange striction. A robust performance (high TC and large polarization) is expected. Different from most multiferroics, BaFe2S e3 is ferrielectric, with a polarization that mostly cancels between ladders. However, its strong magnetostriction still produces a net polarization that is large (0.1 ? C /cm2 ) as compared with most magnetic multiferroics. Its fully ferroelectric state, with energy only slightly higher than the ferrielectric, has a giant improper polarization 2 - 3 ? C /cm2 .

Dong, Shuai; Liu, J.-M.; Dagotto, Elbio

2014-10-01

305

High Latitude Meridional Flow on the Sun May Explain North-South Polar Field Asymmetry  

NASA Technical Reports Server (NTRS)

We measured the flows of magnetic elements on the Sun at very high latitudes by analyzing magnetic images from the Helioseismic and Magnetic Imager (HMI) on the NASA Solar Dynamics Observatory (SDO) Mission. Magnetic maps constructed using a fixed, and north ]south symmetric, meridional flow profile give weaker than observed polar fields in the North and stronger than observed polar fields in the South during the decline of Cycle 23 and rise of Cycle 24. Our measurements of the meridional flow at high latitudes indicate systematic north ]south differences. There was a strong flow in the North while the flow in the South was weaker. With these results, we have a possible solution to the polar field asymmetry. The weaker flow in the South should keep the polar fields from becoming too strong while the stronger flow in the North should strengthen the field there. In order to gain a better understanding of the Solar Cycle and magnetic flux transport on the Sun, we need further observations and analyses of the Sun fs polar regions in general and the polar meridional flow in particular

Kosak, Katie; Upton, Lisa; Hathaway, David

2012-01-01

306

High Latitude Meridional Flow on the Sun May Explain North-South Polar Field Asymmetry  

NASA Technical Reports Server (NTRS)

We measured the flows of magnetic elements on the Sun at very high latitudes by analyzing magnetic images from the Helioseismic and Magnetic Imager (HMI) on the NASA Solar Dynamics Observatory (SDO) Mission. Magnetic maps constructed using a fixed, and north-south symmetric, meridional flow profile give weaker than observed polar fields in the North and stronger than observed polar fields in the South during the decline of Cycle 23 and rise of Cycle 24. Our measurements of the meridional flow at high latitudes indicate systematic north-south differences. There was a strong flow in the North while the flow in the South was weaker. With these results, we have a possible solution to the polar field asymmetry. The weaker flow in the South should keep the polar fields from becoming too strong while the stronger flow in the North should strengthen the field there. In order to gain a better understanding of the Solar Cycle and magnetic flux transport on the Sun, we need further observations and analyses of the Sun's polar regions in general and the polar meridonal flow in particular.

Kosak, Katie; Upton, Lisa; Hathaway, David

2012-01-01

307

High Latitude Meridional Flow on the Sun May Explain North-South Polar Field Asymmetry  

NASA Technical Reports Server (NTRS)

We measured the flows of magnetic elements on the Sun at very high latitudes by analyzing magnetic images from the Helioseismic and Magnetic Imager (HMI) on the NASA Solar Dynamics Observatory (SDO) Mission. Magnetic maps constructed using a fixed, and north-south symmetric, meridional flow profile give weaker than observed polar fields in the North and stronger than observed polar fields in the South during the decline of Cycle 23 and rise of Cycle 24. Our measurements of the meridional flow at high latitudes indicate systematic north-south differences. In the fall of 2010 (when the North Pole was most visible), there was a strong flow in the North while in the spring of 2011 (when the South Pole was most visible) the flow there was weaker. With these results, we have a possible solution to this polar field asymmetry. The weaker flow in the South should keep the polar fields from becoming too strong while the stronger flow in the North should strengthen the field there. In order to gain a better understanding of the Solar Cycle and magnetic flux transport on the Sun, we need further observations and analyses of the Sun s polar regions in general and the polar meridional flow in particular.

Kosak, Katie; Upton, Lisa; Hathaway, David

2012-01-01

308

Separation Technique for the Determination of Highly Polar Metabolites in Biological Samples  

PubMed Central

Metabolomics is a new approach that is based on the systematic study of the full complement of metabolites in a biological sample. Metabolomics has the potential to fundamentally change clinical chemistry and, by extension, the fields of nutrition, toxicology, and medicine. However, it can be difficult to separate highly polar compounds. Mass spectrometry (MS), in combination with capillary electrophoresis (CE), gas chromatography (GC), or high performance liquid chromatography (HPLC) is the key analytical technique on which emerging "omics" technologies, namely, proteomics, metabolomics, and lipidomics, are based. In this review, we introduce various methods for the separation of highly polar metabolites. PMID:24957644

Iwasaki, Yusuke; Sawada, Takahiro; Hatayama, Kentaro; Ohyagi, Akihito; Tsukuda, Yuri; Namekawa, Kyohei; Ito, Rie; Saito, Koichi; Nakazawa, Hiroyuki

2012-01-01

309

Molecule matters  

Microsoft Academic Search

Carbon dioxide is a fascinating molecule; its gaseous, liquid, solid and even supercritical fluid states have unique properties\\u000a and applications. The linear triatomic structure of carbon dioxide molecule with two carbon-oxygen double bonds is all too\\u000a familiar. However a whole new world has been opened up by high pressure-high temperature experiments that effected the polymerization\\u000a of this small molecule into

T. P. Radhakrishnan

2006-01-01

310

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

NASA Technical Reports Server (NTRS)

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.

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

2001-01-01

311

Speckle noise reduction in high speed polarization sensitive spectral domain optical coherence tomography.  

PubMed

We present a high speed polarization sensitive spectral domain optical coherence tomography system based on polarization maintaining fibers and two high speed CMOS line scan cameras capable of retinal imaging with up to 128 k A-lines/s. This high imaging speed strongly reduces motion artifacts and therefore averaging of several B-scans is possible, which strongly reduces speckle noise and improves image quality. We present several methods for averaging retardation and optic axis orientation, the best one providing a 5 fold noise reduction. Furthermore, a novel scheme of calculating images of degree of polarization uniformity is presented. We quantitatively compare the noise reduction depending on the number of averaged frames and discuss the limits of frame numbers that can usefully be averaged. PMID:21934820

Gtzinger, Erich; Pircher, Michael; Baumann, Bernhard; Schmoll, Tilman; Sattmann, Harald; Leitgeb, Rainer A; Hitzenberger, Christoph K

2011-07-18

312

High Resolution Infrared Spectroscopy of Molecules of Terrestrial and Planetary Interest  

NASA Technical Reports Server (NTRS)

In collaboration with the laboratory spectroscopy group of the Ames Atmospheric Physics Research Branch (SGP), high resolution infrared spectra of molecules that are of importance for the dynamics of the earth's and other planets' atmospheres were acquired using the SGP high resolution Fourier transform spectrometer and gas handling apparatus. That data, along with data acquired using similar instrumentation at the Kitt Peak National Observatory was analyzed to determine the spectral parameters for each of the rotationally resolved transitions for each molecule. Those parameters were incorporated into existing international databases (e.g. HITRANS and GEISA) so that field measurements could be converted into quantitative information regarding the physical and chemical structures of earth and planetary atmospheres.

Freedman, Richard S.

2001-01-01

313

Massively Parallel Haplotyping on Microscopic Beads for the High-Throughput Phase Analysis of Single Molecules  

PubMed Central

In spite of the many advances in haplotyping methods, it is still very difficult to characterize rare haplotypes in tissues and different environmental samples or to accurately assess the haplotype diversity in large mixtures. This would require a haplotyping method capable of analyzing the phase of single molecules with an unprecedented throughput. Here we describe such a haplotyping method capable of analyzing in parallel hundreds of thousands single molecules in one experiment. In this method, multiple PCR reactions amplify different polymorphic regions of a single DNA molecule on a magnetic bead compartmentalized in an emulsion drop. The allelic states of the amplified polymorphisms are identified with fluorescently labeled probes that are then decoded from images taken of the arrayed beads by a microscope. This method can evaluate the phase of up to 3 polymorphisms separated by up to 5 kilobases in hundreds of thousands single molecules. We tested the sensitivity of the method by measuring the number of mutant haplotypes synthesized by four different commercially available enzymes: Phusion, Platinum Taq, Titanium Taq, and Phire. The digital nature of the method makes it highly sensitive to detecting haplotype ratios of less than 1?10,000. We also accurately quantified chimera formation during the exponential phase of PCR by different DNA polymerases. PMID:22558329

Tiemann-Boege, Irene

2012-01-01

314

Identification of Small Molecules with Type I Interferon Inducing Properties by High-Throughput Screening  

PubMed Central

The continuous emergence of virus that are resistant to current anti-viral drugs, combined with the introduction of new viral pathogens for which no therapeutics are available, creates an urgent need for the development of novel broad spectrum antivirals. Type I interferon (IFN) can, by modulating the cellular expression profile, stimulate a non-specific antiviral state. The antiviral and adjuvant properties of IFN have been extensively demonstrated; however, its clinical application has been so far limited. We have developed a human cell-based assay that monitors IFN-? production for use in a high throughput screen. Using this assay we screened 94,398 small molecules and identified 18 compounds with IFN-inducing properties. Among these, 3 small molecules (C3, E51 and L56) showed activity not only in human but also in murine and canine derived cells. We further characterized C3 and showed that this molecule is capable of stimulating an anti-viral state in human-derived lung epithelial cells. Furthermore, the IFN-induction by C3 is not diminished by the presence of influenza A virus NS1 protein or hepatitis C virus NS3/4A protease, which make this molecule an interesting candidate for the development of a new type of broad-spectrum antiviral. In addition, the IFN-inducing properties of C3 also suggest its potential use as vaccine adjuvant. PMID:23145065

Martinez-Gil, Luis; Ayllon, Juan; Ortigoza, Mila Brum; Garcia-Sastre, Adolfo; Shaw, Megan L.; Palese, Peter

2012-01-01

315

High resolution electronic spectroscopy of p-toluidine. A precessing rotor model for G12 molecules  

Microsoft Academic Search

Based on a study of the high resolution S1?S0 fluorescence excitation spectrum of p-toluidine (p-methylaniline) and related G12 molecules, we propose that the threefold axis of the methyl group is tilted slightly with respect to the symmetry axis of the molecular frame, and exhibits a kind of precessional motion in the course of its hindered internal rotation. We derive a

Xue-Qing Tan; David W. Pratt

1994-01-01

316

PolarBase: A Database of High-Resolution Spectropolarimetric Stellar Observations  

NASA Astrophysics Data System (ADS)

PolarBase is an evolving database 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 2000 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 pseudoline 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 anticorrelated with the stellar effective temperature. This unique set of Zeeman detections offers the first opportunity to run homogeneous magnetometry studies throughout the H-R diagram. The Web interface of PolarBase is available at http://polarbase.irap.omp.eu.

Petit, P.; Louge, T.; Thado, S.; Paletou, F.; Manset, N.; Morin, J.; Marsden, S. C.; Jeffers, S. V.

2014-05-01

317

Imaging polarimetry of the fogbow: polarization characteristics of white rainbows measured in the high Arctic.  

PubMed

The knowledge on the optics of fogbows is scarce, and their polarization characteristics have never been measured to our knowledge. To fill this gap we measured the polarization features of 16 fogbows during the Beringia 2005 Arctic polar research expedition by imaging polarimetry in the red, green and blue spectral ranges. We present here the first polarization patterns of the fogbow. In the patterns of the degree of linear polarization p, fogbows and their supernumerary bows are best visible in the red spectral range due to the least dilution of fogbow light by light scattered in air. In the patterns of the angle of polarization ? fogbows are practically not discernible because their ?-pattern is the same as that of the sky: the direction of polarization is perpendicular to the plane of scattering and is parallel to the arc of the bow, independently of the wavelength. Fogbows and their supernumeraries were best seen in the patterns of the polarized radiance. In these patterns the angular distance ? between the peaks of the primary and the first supernumerary and the angular width ? of the primary bow were determined along different radii from the center of the bow. ? ranged between 6.08 and 13.41, while ? changed from 5.25 to 19.47. Certain fogbows were relatively homogeneous, meaning small variations of ? and ? along their bows. Other fogbows were heterogeneous, possessing quite variable ?- and ?-values along their bows. This variability could be a consequence of the characteristics of the high Arctic with open waters within the ice shield resulting in the spatiotemporal change of the droplet size within the fog. PMID:22016248

Horvth, Gbor; Hegeds, Ramn; Barta, Andrs; Farkas, Alexandra; kesson, Susanne

2011-10-01

318

Generation of bright circularly-polarized extreme ultraviolet high harmonics for magnetic circular dichroism spectroscopy  

E-print Network

Circularly-polarized extreme UV and X-ray radiation provides valuable access to the structural, electronic and magnetic properties of materials. To date, such experiments have been possible only using large-scale free-electron lasers or synchrotrons. Here we demonstrate the first bright extreme UV circularly-polarized high harmonics and use this new light source for magnetic circular dichroism measurements at the M-shell absorption edges of cobalt. This work paves the way towards element-specific imaging and spectroscopy of multiple elements simultaneously in magnetic and other chiral media with very high spatio-temporal resolution, all on a tabletop.

Kfir, Ofer; Turgut, Emrah; Knut, Ronny; Zusin, Dmitriy; Popmintchev, Dimitar; Popmintchev, Tenio; Nembach, Hans; Shaw, Justin M; Fleicher, Avner; Kapteyn, Henry; Murnane, Margaret; Cohen, Oren

2014-01-01

319

Response to ``Comment on `Solvatochromic shifts of polar and non-polar molecules in ambient and supercritical water: A sequential quantum mechanics/molecular mechanics study including solute-solvent electron exchange-correlation''' [J. Chem. Phys. 138, 217101 (2013)  

NASA Astrophysics Data System (ADS)

In this response to Schwabe's recent comment [J. Chem. Phys. 138, 217101 (2013), 10.1063/1.4807839], we discuss the validity of Schwabe's interpretation of why a large quantum mechanics (QM) region is needed to converge the quantum mechanics/molecular mechanics (QM/MM) results for aqueous benzene, which he ascribed to our insufficient electrostatic potential or neglect of polarization effect. It is shown that improving the electrostatic potential with ground-state polarizable effective fragment potential and fragment molecular orbital methods instead of simple point charge embedding still deviates much from the experimental determinations for aqueous benzene, and solvent polarization in response to the solute excitation for such a system is also very small. We then resuggest enlarging the QM region size or incorporating new exchange repulsion potentials in QM/MM calculations to account for exchange interaction between a solute and its nearby solvents for the highly accurate electronic spectral shift calculations of non-polar solutes dissolved in water.

Ma, Haibo; Ma, Yingjin

2013-06-01

320

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

321

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

PubMed

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. PMID:23483197

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

2013-04-21

322

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

E-print Network

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.

Matthew L. Lister; Paul S. Smith

2000-03-21

323

Physiological ecology of Mesozoic polar forests in a high CO2 environment.  

PubMed

Fossils show that coniferous forests extended into polar regions during the Mesozoic, a time when models and independent paleo-CO2 indicators suggest that the atmospheric CO2 concentration was at least double that of the present day. Consequently, such polar forests would have experienced high CO2 interacting with an extreme variation in light. Here we describe an experiment investigating this plant-environment interaction for extant tree species that were important components of polar forests, and give results from the first year of treatment. Specifically, we tested the hypotheses that growth in elevated CO2 (1) stimulates photosynthesis; (2) reduces photoinhibition during the polar summer; and (3) reduces respiration of above- and below-ground plant organs. Our results indicate that CO2 fertilization generally does not affect photosynthesis under continuous daylight characteristic of the polar summer but does increase it when the period of illumination is shorter. Growth in elevated CO2 did not alter the potential for photoinhibition. CO2 enrichment significantly reduced leaf and root respiration rates by 50 and 25 %, respectively, in a range of evergreen taxa. Incorporating these observed CO2 effects into numerical simulations using a process-based model of coniferous forest growth indicates that a high paleo-CO2 concentration would have increased the productivity of Cretaceous conifer forests in northern Alaska. This results from decreased respiratory costs that more than compensate for the absence of high CO2-high temperature interactions during the polar summer. The longer-term effects of CO2 enrichment on seasonal changes in the above- and below-ground carbon balance of trees are discussed. PMID:12096745

Beerling, D J; Osborne, C P

2002-03-01

324

Physiological Ecology of Mesozoic Polar Forests in a High CO2 Environment  

PubMed Central

Fossils show that coniferous forests extended into polar regions during the Mesozoic, a time when models and independent palaeo?CO2 indicators suggest that the atmospheric CO2 concentration was at least double that of the present day. Consequently, such polar forests would have experienced high CO2 interacting with an extreme variation in light. Here we describe an experiment investigating this plantenvironment interaction for extant tree species that were important components of polar forests, and give results from the first year of treatment. Specifically, we tested the hypotheses that growth in elevated CO2 (1) stimulates photosynthesis; (2) reduces photoinhibition during the polar summer; and (3) reduces respiration of above? and below?ground plant organs. Our results indicate that CO2 fertilization generally does not affect photosynthesis under continuous daylight characteristic of the polar summer but does increase it when the period of illumination is shorter. Growth in elevated CO2 did not alter the potential for photoinhibition. CO2 enrichment significantly reduced leaf and root respiration rates by 50 and 25 %, respectively, in a range of evergreen taxa. Incorporating these observed CO2 effects into numerical simulations using a process?based model of coniferous forest growth indicates that a high palaeo?CO2 concentration would have increased the productivity of Cretaceous conifer forests in northern Alaska. This results from decreased respiratory costs that more than compensate for the absence of high CO2high temperature interactions during the polar summer. The longer?term effects of CO2 enrichment on seasonal changes in the above? and below?ground carbon balance of trees are discussed. PMID:12096745

BEERLING, D. J.; OSBORNE, C. P.

2002-01-01

325

High-throughput screening for small molecule modulators of motor protein Kinesin.  

PubMed

Abstract The kinesin superfamily of motor proteins are involved in the active transport of a large number of cargos such as organelles, proteins, and RNAs from the neuronal cell body to distal neuronal processes. Previously, we have shown that kinesin-mediated axonal transport of proteins and RNAs are important for long-term memory storage. Identification of small molecules that can activate or inhibit kinesins is of specific interest due to the significance of kinesin-mediated functions in neuronal health and plasticity. Here, we describe a high-throughput screening assay designed to specifically identify compounds that inhibit or activate adenosine triphosphatase activity of the kinesin 5B of humans. The luminescence-based assay that we developed is highly reproducible and robust. Using this approach, we screened a pharmacologically characterized compound collection and have identified small molecules with either activator or inhibitor-like activity. To further characterize screening hits, we also developed an orthogonal assay based on absorbance and a counter screen assay based on luminescence. Development of such assays is important to help identify small molecules that can be used in potential drug development efforts targeted at modulating the function of kinesin. PMID:25383721

Kadakkuzha, Beena M; Spicer, Timothy P; Chase, Peter; Richman, Jeffery B; Hodder, Peter; Puthanveettil, Sathyanarayanan V

2014-10-01

326

Limits on asymmetric orthopositronium formation in high Z optically active molecules  

NASA Astrophysics Data System (ADS)

The proposed connection between the parity violating handedness of beta particles in radioactive decay and the sign (L) of biological chirality (the Vester-Ulbricht [V-U] hypothesis) is experimentally tested. The theoretically predicted asymmetry in triplet positronium formation (A Ps) is measured in several highZ optically active molecules using low energy positrons with a net helicity. We findA Ps<310-4 in selenocystine (Z=34) and thyroxine (Z=53), excluding part of the theoretically predicted range of 410-3> A Ps>210-6 in these molecules. The connection between these limits and limits on asymmetric radiolysis (A R) is made, with a new limit ofA R>10-9 being placed. This limit onA R, which is thirty times lower than a previous measurement in the amino acid leucine (Z=6), is still not small enough to rule out the V-U hypothesis.

van House, J.; Rich, A.; Zitzewitz, P. W.

1985-03-01

327

Diamond nanowires for highly sensitive matrix-free mass spectrometry analysis of small molecules.  

PubMed

This paper reports on the use of boron-doped diamond nanowires (BDD NWs) as an inorganic substrate for matrix-free laser desorption/ionization mass spectrometry (LDI-MS) analysis of small molecules. The diamond nanowires are prepared by reactive ion etching (RIE) with oxygen plasma of highly boron-doped (the boron level is 10(19) B cm(-3)) or undoped nanocrystalline diamond substrates. The resulting diamond nanowires are coated with a thin silicon oxide layer that confers a superhydrophilic character to the surface. To minimize droplet spreading, the nanowires were chemically functionalized with octadecyltrichlorosilane (OTS) and then UV/ozone treated to reach a final water contact angle of 120. The sub-bandgap absorption under UV laser irradiation and the heat confinement inside the nanowires allowed desorption/ionization, most likely via a thermal mechanism, and mass spectrometry analysis of small molecules. A detection limit of 200 zeptomole for verapamil was demonstrated. PMID:22080363

Coffinier, Yannick; Szunerits, Sabine; Drobecq, Herv; Melnyk, Oleg; Boukherroub, Rabah

2012-01-01

328

Diamond nanowires for highly sensitive matrix-free mass spectrometry analysis of small molecules  

NASA Astrophysics Data System (ADS)

This paper reports on the use of boron-doped diamond nanowires (BDD NWs) as an inorganic substrate for matrix-free laser desorption/ionization mass spectrometry (LDI-MS) analysis of small molecules. The diamond nanowires are prepared by reactive ion etching (RIE) with oxygen plasma of highly boron-doped (the boron level is 1019 B cm-3) or undoped nanocrystalline diamond substrates. The resulting diamond nanowires are coated with a thin silicon oxide layer that confers a superhydrophilic character to the surface. To minimize droplet spreading, the nanowires were chemically functionalized with octadecyltrichlorosilane (OTS) and then UV/ozone treated to reach a final water contact angle of 120. The sub-bandgap absorption under UV laser irradiation and the heat confinement inside the nanowires allowed desorption/ionization, most likely via a thermal mechanism, and mass spectrometry analysis of small molecules. A detection limit of 200 zeptomole for verapamil was demonstrated.

Coffinier, Yannick; Szunerits, Sabine; Drobecq, Herv; Melnyk, Oleg; Boukherroub, Rabah

2011-12-01

329

Dipole Polarizability of Alkali-Metal (Na, K, Rb) - Alkaline-Earth-Metal (Ca,Sr) Polar molecules - Prospects of Alignment  

E-print Network

Electronic open-shell ground-state properties of selected alkali-metal (AM) - alkaline-earth-metal (AEM) polar molecules are investigated. We determine potential energy curves of the 2{\\Sigma}+ ground state at the coupled-cluster singles and doubles with partial triples (CCSD(T)) level of electron correlation. Calculated spectroscopic constants for the isotopes (23Na, 39K, 85Rb) - (40Ca, 88Sr) are compared with available theoretical and experimental results. The variation of the permanent dipole moment (PDM), average dipole polarizability, and polarizability anisotropy with internuclear distance is determined using finite-field perturbation theory at the CCSD(T) level. Owing to moderate PDM (KCa: 1.67 D, RbCa: 1.75 D, KSr: 1.27 D, RbSr: 1.41 D) and large polarizability anisotropy (KCa: 566 a.u., RbCa: 604 a.u., KSr: 574 a.u., RbSr: 615 a.u.), KCa, RbCa, KSr, and RbSr are potential candidates for alignment and orientation in combined intense laser and external static electric fields.

Gopakumar, Geetha; Hada, Masahiko; Kajita, Masatoshi

2014-01-01

330

High Resolution Continuous Flow Analysis System for Polar Ice Cores  

NASA Astrophysics Data System (ADS)

In the last decades, Continuous Flow Analysis (CFA) technology for ice core analyses has been developed to reconstruct the past changes of the climate system 1), 2). Compared with traditional analyses of discrete samples, a CFA system offers much faster and higher depth resolution analyses. It also generates a decontaminated sample stream without time-consuming sample processing procedure by using the inner area of an ice-core sample.. The CFA system that we have been developing is currently able to continuously measure stable water isotopes 3) and electrolytic conductivity, as well as to collect discrete samples for the both inner and outer areas with variable depth resolutions. Chemistry analyses4) and methane-gas analysis 5) are planned to be added using the continuous water stream system 5). In order to optimize the resolution of the current system with minimal sample volumes necessary for different analyses, our CFA system typically melts an ice core at 1.6 cm/min. Instead of using a wire position encoder with typical 1mm positioning resolution 6), we decided to use a high-accuracy CCD Laser displacement sensor (LKG-G505, Keyence). At the 1.6 cm/min melt rate, the positioning resolution was increased to 0.27mm. Also, the mixing volume that occurs in our open split debubbler is regulated using its weight. The overflow pumping rate is smoothly PID controlled to maintain the weight as low as possible, while keeping a safety buffer of water to avoid air bubbles downstream. To evaluate the system's depth-resolution, we will present the preliminary data of electrolytic conductivity obtained by melting 12 bags of the North Greenland Eemian Ice Drilling (NEEM) ice core. The samples correspond to different climate intervals (Greenland Stadial 21, 22, Greenland Stadial 5, Greenland Interstadial 5, Greenland Interstadial 7, Greenland Stadial 8). We will present results for the Greenland Stadial -8, whose depths and ages are between 1723.7 and 1724.8 meters, and 35.520 to 35.636 kyr b2k 7), respectively. The results show the conductivity measured upstream and downstream of the debubbler. We will calculate the depth resolution of our system and compare it with earlier studies. 1) Bigler at al, "Optimization of High-Resolution Continuous Flow Analysis For Transient Climate Signals in Ice Cores". Environ. Sci. Technol. 2011, 45, 4483-4489 2) Kaufmann et al, "An Improved Continuous Flow Analysis System for High Resolution Field Measurements on Ice Cores". Environmental Environ. Sci. Technol. 2008, 42, 8044-8050 3) Gkinis, V., T. J. Popp, S. J. Johnsen and T, Blunier, 2010: A continuous stream flash evaporator for the calibration of an IR cavity ring down spectrometer for the isotopic analysis of water. Isotopes in Environmental and Health Studies, 46(4), 463-475. 4) McConnell et al, "Continuous ice-core chemical analyses using inductively coupled plasma mass spectrometry. Environ. Sci. Technol. 2002, 36, 7-11 5) Rhodes et al, "Continuous methane measurements from a late Holocene Greenland ice core : Atmospheric and in-situ signals" Earth and Planetary Science Letters. 2013, 368, 9-19 6) Breton et al, "Quantifying Signal Dispersion in a Hybrid Ice Core Melting System". Environ. Sci. Technol. 2012, 46, 11922-11928 7) Rasmussen et al, " A first chronology for the NEEM ice core". Climate of the Past. 2013, 9, 2967--3013

Dallmayr, Remi; Azuma, Kumiko; Yamada, Hironobu; Kjr, Helle Astrid; Vallelonga, Paul; Azuma, Nobuhiko; Takata, Morimasa

2014-05-01

331

COMPLEX ORGANIC MOLECULES AT HIGH SPATIAL RESOLUTION TOWARD ORION-KL. I. SPATIAL SCALES  

SciTech Connect

Here we present high spatial resolution (<1'') observations of molecular emission in Orion-KL conducted using the Combined Array for Research in Millimeter-wave Astronomy. This work was motivated by recent millimeter continuum imaging studies of this region conducted at a similarly high spatial resolution, which revealed that the bulk of the emission arises from numerous compact sources, rather than the larger-scale extended structures typically associated with the Orion Hot Core and Compact Ridge. Given that the spatial extent of molecular emission greatly affects the determination of molecular abundances, it is important to determine the true spatial scale for complex molecules in this region. Additionally, it has recently been suggested that the relative spatial distributions of complex molecules in a source might give insight into the chemical mechanisms that drive complex chemistry in star-forming regions. In order to begin to address these issues, this study seeks to determine the spatial distributions of ethyl cyanide [C{sub 2}H{sub 5}CN], dimethyl ether [(CH{sub 3}){sub 2}O], methyl formate [HCOOCH{sub 3}], formic acid [HCOOH], acetone [(CH{sub 3}){sub 2}CO], SiO, methanol [CH{sub 3}OH], and methyl cyanide [CH{sub 3}CN] in Orion-KL at {lambda} = 3 mm. We find that for all observed molecules, the molecular emission arises from multiple components of the cloud that include a range of spatial scales and physical conditions. Here, we present the results of these observations and discuss the implications for studies of complex molecules in star-forming regions.

Widicus Weaver, Susanna L. [Department of Chemistry, Emory University, Atlanta, GA 30322 (United States); Friedel, Douglas N., E-mail: susanna.widicus.weaver@emory.edu, E-mail: friedel@astro.illinois.edu [Department of Astronomy, University of Illinois, 1002 West Green Street, Urbana, IL 61801 (United States)

2012-08-01

332

High-Contrast NIR Polarization Imaging of MWC480  

NASA Technical Reports Server (NTRS)

One of the key predictions of modeling from the IR excess of Herbig Ae stars is that for protoplanetary disks, where significant grain growth and settling has occurred, the dust disk has flattened to the point that it can be partially or largely shadowed by the innermost material at or near the dust sublimation radius. When the self-shadowing has already started, the outer disk is expected to be detected in scattered light only in the exceptional cases that the scale height of the dust disk at the sublimation radius is smaller than usual. High-contrast imaging combined with the IR spectral energy distribution allow us to measure the degree of flattening of the disk, as well as to determine the properties of the outer disk. We present polarimetric differential imaging in H band obtained with Subaru/HiCIAO of one such system, MWC 480. The HiCIAO data were obtained at a historic minimum of the NIR excess. The disk is detected in scattered light from 0".2-1"0 (27.4-137 AU). Together with the marginal detection of the disk from 1998 February 24 by HST / NICMOS, our data constrain the opening half angle for the disk to lie between 1.3 <= Theta <=2.2 deg. When compared with similar measures in CO for the gas disk from the literature, the dust disk subtends only approx 30% of the gas disk scale height (H/R approx 0. 03). Such a dust disk is a factor of 5-7 flatter than transitional disks, which have structural signatures that giant planets have formed.

McElwain, M. W.; Kusakabe, N.; Hashimoto, J.; Kudo, T.; Kandori, R.; Miyama, S.; Morino, J.-I.; Suto, H.; Suzuki, R.; Tamura, M.; Grady, C. A.; Sitko, M. L.; Werren, C.; Day, A. N.; Beerman, C.; Iye, M.; Lynch, D. K.; Russell, R. W.; Brafford, S. M.

2012-01-01

333

Recoil Polarization Measurements of the Proton Electromagnetic Form Factor Ratio to High Momentum Transfer  

SciTech Connect

The electromagnetic form factors of the nucleon characterize the effect of its internal structure on its response to an electromagnetic probe as studied in elastic electronnucleon scattering. These form factors are functions of the squared four-momentum transfer Q2 between the electron and the proton. The two main classes of observables of this reaction are the scattering cross section and polarization asymmetries, both of which are sensitive to the form factors in different ways. When considering large f momentum transfers, double-polarization observables offer superior sensitivity to the electric form factor. This thesis reports the results of a new measurement of the ratio of the electric and magnetic form factors of the proton at high momentum transfer using the recoil polarization technique. A polarized electron beam was scattered from a liquid hydrogen target, transferring polarization to the recoiling protons. These protons were detected in a magnetic spectrometer which was used to reconstruct their kinematics, including their scattering angles and momenta, and the position of the interaction vertex. A proton polarimeter measured the polarization of the recoiling protons by measuring the azimuthal asymmetry in the angular distribution of protons scattered in CH2 analyzers. The scattered electron was detected in a large acceptance electromagnetic calorimeter in order to suppress inelastic backgrounds. The measured ratio of the transverse and longitudinal polarization components of the scattered proton is directly proportional to the ratio of form factors GpE=GpM. The measurements reported in this thesis took place at Q2 =5.2, 6.7, and 8.5 GeV2, and represent the most accurate measurements of GpE in this Q2 region to date.

Andrew Puckett

2010-02-01

334

Grain surface polarization: ferroelectric mantles?  

Microsoft Academic Search

Recent experiments have shown that films of molecules such as nitrous oxide, propane etc. spontaneously harbour very high electric fields exceeding 108 Vm-11 . This arises through dipole alignment with polarization at the film surface, giving rise to large voltages at the surface. Potentials are measured with a cold electron beam technique using the ASTRID synchrotron at Aarhus. The electric

A. M. Cassidy; R. Balog; D. Field; N. Jones; O. Plekan

2011-01-01

335

Polar Kerr effect in high- T sub c superconductors: The rotating-plate technique  

Microsoft Academic Search

A technique recently used for measurement of the complex polar Kerr rotation in high-{ital T}{sub {ital c}} superconductors is discussed in a tutorial manner, making use of a Jones matrix approach. The primary concern addressed is the rejection of effects caused by linear birefringence and dichroism effects in the sample and associated optical components. This rejection is accomplished by the

K. B. Lyons; J. F. Jr. Dillon; M. McGlashan-Powell

1991-01-01

336

Polar Kerr effect in high-Tc superconductors: The rotating-plate technique  

Microsoft Academic Search

A technique recently used for measurement of the complex polar Kerr rotation in high-Tc superconductors is discussed in a tutorial manner, making use of a Jones matrix approach. The primary concern addressed is the rejection of effects caused by linear birefringence and dichroism effects in the sample and associated optical components. This rejection is accomplished by the use of a

K. B. Lyons; J. F. Dillon; M. McGlashan-Powell

1991-01-01

337

Circularly polarized multi-beam lens antenna system for High Altitude Platforms (HAPS)  

Microsoft Academic Search

In this paper a 30 GHz multi-beam antenna prototype has been developed for High Altitude Platform Stations (HAPS) applications. When mounted on a HAPS at the stationary altitude of 21Km, this antenna provides cellular coverage on the ground. The antenna consists of a dielectric lens fed by circular waveguides terminated with small horns. Circular polarization is achieved by integrating a

Marco Letizia; Jean-Francois Zurcher; Benjamin Fuchs; Juan Ramon Mosig; Anja Skrivervik

2011-01-01

338

A new omnidirectional vertical polarization antenna with low profile and high gain  

Microsoft Academic Search

A new omnidirectional vertical polarization antenna array with low profile and high gain is presented. The antenna exhibits good radiation performance and the measured gain is more than 10dBi despite the miniaturized volume, which shows attractive future for HDTV on vehicles.

Junping Geng; Ronghong Jin; Zhiguo Wang; Zhihao Yuan; Jinliang Dong; Jiaqiang Li; Wei Wang; Wei He; Min Ding

2005-01-01

339

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, suggesting the presence of hydrocarbon lakes similar to those later detected at Titan's North Pole

340

All-optical XOR gate using polarization rotation in single highly nonlinear fiber  

Microsoft Academic Search

We demonstrate a 10-Gb\\/s all-optical XOR gate based on polarization rotation induced by Kerr effect in a single highly nonlinear fiber (HNLF). Using 2 km of HNLF with a nonlinear coefficient of 9.1 W-1km-1, we obtain a 25-dB extinction ratio at the XOR output.

Changyuan Yu; Louis Christen; Ting Luo; Yan Wang; Zhongqi Pan; Lian-Shan Yan; Alan E. Willner

2005-01-01

341

FUNDAMENTAL AREAS OF PHENOMENOLOGY (INCLUDING APPLICATIONS): High Polarization Single Mode Photonic Crystal Microlaser  

Microsoft Academic Search

Generally, dipole mode is a doubly degenerate mode. Theoretical calculations have indicated that the single dipole mode of two-dimensional photonic crystal single point defect cavity shows high polarization property. We present a structure with elongated lattice, which only supports a single y-dipole mode. With this structure we can eliminate the degeneracy, control the lasing action of the cavity and demonstrate

Wei Chen; Ming-Xin Xing; Wen-Jun Zhou; An-Jin Liu; Wan-Hua Zheng

2009-01-01

342

High-resolution high-frequency dynamic nuclear polarization for biomolecular solid state NMR  

E-print Network

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 ...

Barnes, Alexander B. (Alexander Benjamin)

2011-01-01

343

Possibilities of polarized protons in Sp anti p S and other high energy hadron colliders  

SciTech Connect

The requirements for collisions with polarized protons in hadron colliders above 200 GeV are listed and briefly discussed. Particular attention is given to the use of the ''Siberan snake'' to eliminate depolarizing resonances, which occur when the spin precession frequency equals a frequency contained in the spectrum of the field seen by the beam. The Siberian snake is a device which makes the spin precession frequency essentially constant by using spin rotators, which precess the spin by 180/sup 0/ about either the longitudinal or transverse horizontal axis. It is concluded that operation with polarized protons should be possible at all the high energy hadron colliders. (LEW)

Courant, E.D.

1984-01-01

344

High intensity induced photocurrent polarity switching in lead sulfide nanowire field effect transistors  

NASA Astrophysics Data System (ADS)

We report an optoelectronic investigation of lead sulfide nanowires (NWs) by scanning photocurrent microscopy. The photocurrent in p-type lead sulfide NW field effect transistors has demonstrated unusually nonlinear dependence on the intensity of local excitation. Surprisingly, the photocurrent polarity can be reversed under high illumination intensity on the order of 100 W cm-2. The origin of this photocurrent polarity switching is that the photo-injected carriers flip the direction of the electric field near the contact. These observations shed light on the nonlinear optoelectronic characteristics in semiconductor nanostructures and may provide an innovative method for optically tailoring local band structures.

Yang, Yiming; Peng, Xingyue; Yu, Dong

2014-05-01

345

Long lifetime and high-fidelity quantum memory of photonic polarization qubit by lifting zeeman degeneracy.  

PubMed

Long-lived and high-fidelity memory for a photonic polarization qubit (PPQ) is crucial for constructing quantum networks. We present a millisecond storage system based on electromagnetically induced transparency, in which a moderate magnetic field is applied on a cold-atom cloud to lift Zeeman degeneracy and, thus, the PPQ states are stored as two magnetic-field-insensitive spin waves. Especially, the influence of magnetic-field-sensitive spin waves on the storage performances is almost totally avoided. The measured average fidelities of the polarization states are 98.6% at 200???s and 78.4% at 4.5ms, respectively. PMID:24483636

Xu, Zhongxiao; Wu, Yuelong; Tian, Long; Chen, Lirong; Zhang, Zhiying; Yan, Zhihui; Li, Shujing; Wang, Hai; Xie, Changde; Peng, Kunchi

2013-12-13

346

Long Lifetime and High-Fidelity Quantum Memory of Photonic Polarization Qubit by Lifting Zeeman Degeneracy  

NASA Astrophysics Data System (ADS)

Long-lived and high-fidelity memory for a photonic polarization qubit (PPQ) is crucial for constructing quantum networks. We present a millisecond storage system based on electromagnetically induced transparency, in which a moderate magnetic field is applied on a cold-atom cloud to lift Zeeman degeneracy and, thus, the PPQ states are stored as two magnetic-field-insensitive spin waves. Especially, the influence of magnetic-field-sensitive spin waves on the storage performances is almost totally avoided. The measured average fidelities of the polarization states are 98.6% at 200?s and 78.4% at 4.5 ms, respectively.

Xu, Zhongxiao; Wu, Yuelong; Tian, Long; Chen, Lirong; Zhang, Zhiying; Yan, Zhihui; Li, Shujing; Wang, Hai; Xie, Changde; Peng, Kunchi

2013-12-01

347

Long lifetime and high-fidelity quantum memory of photonic polarization qubit by lifting Zeeman degeneracy  

E-print Network

Long-lived and high-fidelity memory for photonic polarization qubit (PPQ) is crucial for constructing quantum networks. Here we present an EIT-based millisecond storage system in which a moderate magnetic field is applied on a cold-atom cloud to lift Zeeman degeneracy. PPQ states are stored as two magnetic-field-insensitive spin waves. Especially, the influence of magnetic-field-sensitive spin waves on the storage performances is almost totally avoided. The measured average fidelities of polarization states are 98.6% at 200 us and 78.4% at 4.5 ms, respectively.

Zhongxiao Xu; Yuelong Wu; Long Tian; Lirong Chen; Zhiying Zhang; Zhihui Yan; Shujing Li; Hai Wang; Changde Xie; Kunchi Peng

2013-06-18

348

Polar Lows  

NASA Astrophysics Data System (ADS)

Providing a comprehensive review of our understanding of the small, high latitude weather systems known as polar lows, Erik Rasmussen and John Turner describe the climatological distribution of these depressions. They cover observational investigations into their structure, the operational forecasting of polar lows and the theoretical research into why they develop. They also discuss the experiments that reveal that some polar lows can be predicted. This book is of value to researchers and professional weather forecasters concerned with polar regions.

Rasmussen, Erik A.; Turner, John

2003-06-01

349

Characterization of highly scattering media by measurement of diffusely backscattered polarized light  

DOEpatents

An apparatus and method for recording spatially dependent intensity patterns of polarized light that is diffusely backscattered from highly scattering media are described. These intensity patterns can be used to differentiate different turbid media, such as polystyrene-sphere and biological-cell suspensions. Polarized light from a He-Ne laser (.lambda.=543 nm) is focused onto the surface of the scattering medium, and a surface area of approximately 4.times.4 cm centered on the light input point is imaged through polarization analysis optics onto a CCD camera. A variety of intensity patterns may be observed by varying the polarization state of the incident laser light and changing the analyzer configuration to detect different polarization components of the backscattered light. Experimental results for polystyrene-sphere and Intralipid suspensions demonstrate that the radial and azimuthal variations of the observed pattern depend on the concentration, size, and anisotropy factor, g, of the particles constituting the scattering medium. Measurements performed on biological cell suspensions show that intensity patterns can be used to differentiate between suspensions of cancerous and non-cancerous cells. Introduction of the Mueller-matrix for diffusely backscattered light, permits the selection of a subset of measurements which comprehensively describes the optical properties of backscattering media.

Hielscher, Andreas H. (Brooklyn, NY); Mourant, Judith R. (Los Alamos, NM); Bigio, Irving J. (Los Alamos, NM)

2000-01-01

350

PolarBase: a data base of high resolution spectropolarimetric stellar observations  

E-print Network

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 ...

Petit, P; Thado, S; Paletou, F; Manset, N; Morin, J; Marsden, S C; Jeffers, S V

2014-01-01

351

Synthesis of highly focused fields with circular polarization at any transverse plane.  

PubMed

We develop a method for generating focused vector beams with circular polarization at any transverse plane. Based on the Richards-Wolf vector model, we derive analytical expressions to describe the propagation of these set of beams near the focal area. Since the polarization and the amplitude of the input beam are not uniform, an interferometric system capable of generating spatially-variant polarized beams has to be used. In particular, this wavefront is manipulated by means of spatial light modulators displaying computer generated holograms and subsequently focused using a high numerical aperture objective lens. Experimental results using a NA = 0.85 system are provided: irradiance and Stokes images of the focused field at different planes near the focal plane are presented and compared with those obtained by numerical simulation. PMID:24664034

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

2014-03-24

352

Possible high-frequency geomagnetic polarity changes in Lower-Middle Jurassic carbonates in Iraq  

NASA Astrophysics Data System (ADS)

Palaeomagnetic results from Iraqi standard 2.5-cm Jurassic limestone specimens show weak intensities and directions of remanence that are initially randomly scattered, other than an absence of high inclinations. When these are sliced parallel to the bedding in 1-cm discs, their intensity increases and their directions show greater stratigraphic consistency. The age of the remanence appears to be primary (early diagenetic) on the basis of their sedimentological properties. The magnetization is unrelated to mineralogy and is interpreted as normal and reversely magnetized components within standard sized samples. This suggests that, at this time, frequent polarity changes took place resulting in similar polarities within stratigraphic zones < 2-3 cm thick, corresponding to at least five polarity transitions per million years.

Hijab, B. R.; Tarling, D. H.

1990-12-01

353

Gas dynamics in high-luminosity polarized He-3 targets using diffusion and convection  

E-print Network

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.

P. A. M. Dolph; J. Singh; T. Averett; A. Kelleher; K. E. Mooney; V. Nelyubin; W. A. Tobias; B. Wojtsekhowski; G. D. Cates

2011-07-10

354

Transport/magnetotransport of high-performance graphene transistors on organic molecule-functionalized substrates  

NASA Astrophysics Data System (ADS)

We present the transport and magnetotransport of high-quality graphene transistors on conventional SiO2/Si substrates by modification with organic molecule self-assembled monolayers (SAMs). Graphene devices on organic SAM-functionalized substrates exhibit high carrier mobility, low intrinsic doping, suppressed carrier scattering, and reduced thermal activation of resistivity at room temperature. Magnetotransport of graphene devices with pronounced quantum Hall effect and Shubnikov-de Haas oscillations also confirms the high quality of graphene on this ultrasmooth organic SAM-modified platform. The high-performance graphene transistors on the solution-processable SAM-functionalized SiO2/Si substrates are promising for the future development of large-area and low-cost fabrications of graphene-based nanoelectronics.

Chen, Shao-Yu; Ho, Po-Hsun; Shiue, Ren-Jye; Chen, Chun-Wei; Wang, Wei-Hua

2012-02-01

355

High-throughput scanning confocal microscope for single molecule Chandran R. Sabanayagam, John S. Eid, and Amit Mellera)  

E-print Network

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

Meller, Amit

356

NMR spectroscopy of hyperpolarized ^129Xe at high fields: Maintaining spin polarization after optical pumping.  

NASA Astrophysics Data System (ADS)

Spin-polarized ^129Xe has become an invaluable tool in nuclear magnetic resonance research, with applications ranging from medical imaging to high-resolution spectroscopy. High-field NMR studies using hyperpolarized xenon as a spectroscopic probe benefit from the high signal-to-noise ratios and large chemical shifts typical of optically-pumped noble gases. The experimental sensitivity is ultimately determined by the absolute polarization of the xenon in the sample, which can be substantially decreased during purification and transfer. NMR of xenon at high fields (9.4 Tesla) will be discussed, and potential mechanisms of spin relaxation during the distillation, storage(N. N. Kuzma, B. Patton, K. Raman, and W. Happer, Phys. Rev. Lett. 88), 147602 (2002)., and delivery of hyperpolarized xenon will be analyzed.

Patton, Brian; Kuzma, Nicholas N.; Lisitza, Natalia V.; Happer, William

2003-05-01

357

The last polar dinosaurs: high diversity of latest Cretaceous arctic dinosaurs in Russia  

NASA Astrophysics Data System (ADS)

A latest Cretaceous (68 to 65 million years ago) vertebrate microfossil assemblage discovered at Kakanaut in northeastern Russia reveals that dinosaurs were still highly diversified in Arctic regions just before the Cretaceous-Tertiary mass extinction event. Dinosaur eggshell fragments, belonging to hadrosaurids and non-avian theropods, indicate that at least several latest Cretaceous dinosaur taxa could reproduce in polar region and were probably year-round residents of high latitudes. Palaeobotanical data suggest that these polar dinosaurs lived in a temperate climate (mean annual temperature about 10C), but the climate was apparently too cold for amphibians and ectothermic reptiles. The high diversity of Late Maastrichtian dinosaurs in high latitudes, where ectotherms are absent, strongly questions hypotheses according to which dinosaur extinction was a result of temperature decline, caused or not by the Chicxulub impact.

Godefroit, Pascal; Golovneva, Lina; Shchepetov, Sergei; Garcia, Graldine; Alekseev, Pavel

2009-04-01

358

High throughput fabrication of disposable nanofluidic lab-on-chip devices for single molecule studies  

PubMed Central

An easy method is introduced allowing fast polydimethylsiloxane (PDMS) replication of nanofluidic lab-on-chip devices using accurately fabricated molds featuring cross-sections down to 60?nm. A high quality master is obtained through proton beam writing and UV lithography. This master can be used more than 200 times to replicate nanofluidic devices capable of handling single DNA molecules. This method allows to fabricate nanofluidic devices through simple PDMS casting. The extensions of YOYO-1 stained bacteriophage T4 and ??DNA inside these nanochannels have been investigated using fluorescence microscopy and follow the scaling prediction of a large, locally coiled polymer chain confined in nanochannels. PMID:23898358

van Kan, Jeroen A.; Zhang, Ce; Perumal Malar, Piravi; van der Maarel, Johan R. C.

2012-01-01

359

High Resolution UV Emission Spectroscopy of Molecules Excited by Electron Impact  

NASA Technical Reports Server (NTRS)

Photodissociation via discrete line absorption into predissociating Rydberg and valence states is the dominant destruction mechanism of CO and other molecules in the interstellar medium and molecular clouds. Accurate values for the rovibronic oscillator strengths of these transitions and predissociation yields of the excited states are required for input into the photochemical models that attempt to reproduce observed abundances. We report here on our latest experimental results of the electron collisional properties of CO and N2 obtained using the 3-meter high resolution single-scattering spectroscopic facility at JPL.

James, G. K.; Ajello, J. M.; Beegle, L.; Ciocca, M.; Dziczek, D.; Kanik, I.; Noren, C.; Jonin, C.; Hansen, D.

1999-01-01

360

Highly Parallel Transport Recordings on a Membrane-on-Nanopore Chip at Single Molecule Resolution  

PubMed Central

Membrane proteins are prime drug targets as they control the transit of information, ions, and solutes across membranes. Here, we present a membrane-on-nanopore platform to analyze nonelectrogenic channels and transporters that are typically not accessible by electrophysiological methods in a multiplexed manner. The silicon chip contains 250?000 femtoliter cavities, closed by a silicon dioxide top layer with defined nanopores. Lipid vesicles containing membrane proteins of interest are spread onto the nanopore-chip surface. Transport events of ligand-gated channels were recorded at single-molecule resolution by high-parallel fluorescence decoding. PMID:24524682

2014-01-01

361

Metal-containing block copolymer thin films yield wire grid polarizers with high aspect ratio.  

PubMed

Highly selective etch masks are formed by thin films of a polystyrene-b-poly(ferrocenylisopropylmethylsilane) diblock copolymer, PS-PFiPMS, containing hemicylindrical domains of PFiPMS. These domains, with a period of 35 nm, are readily aligned through mechanical shear. Aligned PS-PFiPMS templates are employed to fabricate high-aspect-ratio nanowire grids from amorphous silicon, which can polarize deep ultraviolet radiation, including 193 nm, at >90% efficiency. PMID:24123385

Kim, So Youn; Gwyther, Jessica; Manners, Ian; Chaikin, Paul M; Register, Richard A

2014-02-01

362

High-Latitude Gravity Wave Measurements in Noctilucent Clouds and Polar Mesospheric Clouds  

Microsoft Academic Search

\\u000a Distinct wave forms traditionally observed in Noctilucent Cloud (NLC) photographs and most recently captured in high-resolution\\u000a panoramic images of Polar Mesospheric Clouds (PMC) provide an exceptionally rich resource for quantifying gravity wave activity\\u000a and properties in the high-latitude summer mesopause region. Using extensive image data on PMC structures obtained by the\\u000a Cloud Imaging and Particle Size (CIPS) ultraviolet instrument onboard

Michael J. Taylor; P.-D. Pautet; Y. Zhao; C. E. Randall; J. Lumpe; S. M. Bailey; J. Carstens; K. Nielsen; James M. Russell; J. Stegman

363

Interstellar polarization at high galactic latitudes from distant stars. III. Distribution of the polarization vectors - evidence for distinct zones  

Microsoft Academic Search

We make a map of interstellar polarization direction around the North Galactic Pole and study the distribution of the revealed magnetic field lines. We study in detail Markkanen's (\\\\cite{markkanen79}) cloud and other local features apparent in the polarization map, and compare them with the IRAS 100 micron map. The elongated Markkanen's cloud (at a distance of 100-200 pc) and its

A. Berdyugin; P. Teerikorpi; L. Haikala

2000-01-01

364

The 20 GHz circularly polarized, high temperature superconducting microstrip antenna array  

NASA Technical Reports Server (NTRS)

The primary goal was to design and characterize a four-element, 20 GHz, circularly polarized microstrip patch antenna fabricated from YBa2Cu3O(x) superconductor. The purpose is to support a high temperature superconductivity flight communications experiment between the space shuttle orbiter and the ACTS satellite. This study is intended to provide information into the design, construction, and feasibility of a circularly polarized superconducting 20 GHz downlink or cross-link antenna. We have demonstrated that significant gain improvements can be realized by using superconducting materials for large corporate fed array antennas. In addition, we have shown that when constructed from superconducting materials, the efficiency, and therefore the gain, of microstrip patches increases if the substrate is not so thick that the dominant loss mechanism for the patch is radiation into the surface waves of the conductor-backed substrate. We have considered two design configurations for a superconducting 20 GHz four-element circularly polarized microstrip antenna array. The first is the Huang array that uses properly oriented and phased linearly polarized microstrip patch elements to realize a circularly polarized pattern. The second is a gap-coupled array of circularly polarized elements. In this study we determined that although the Huang array operates well on low dielectric constant substrates, its performance becomes extremely sensitive to mismatches, interelement coupling, and design imperfections for substrates with high dielectric constants. For the gap-coupled microstrip array, we were able to fabricate and test circularly polarized elements and four-element arrays on LaAlO3 using sputtered copper films. These antennas were found to perform well, with relatively good circular polarization. In addition, we realized a four-element YBa2Cu3O(x) array of the same design and measured its pattern and gain relative to a room temperature copper array. The patterns were essentially the same as that for the copper array. The measured gain of the YBCO antenna was greater than that for the room temperature copper design at temperatures below 82K, reaching a value of 3.4 dB at the lowest temperatures.

Morrow, Jarrett D.; Williams, Jeffery T.; Long, Stuart A.; Wolfe, John C.

1994-01-01

365

High resolution laser spectroscopy of selected molecules in the gas phase  

NASA Astrophysics Data System (ADS)

In this thesis, various types of metal-bearing molecules (diatomic, linear poly-atomic, and symmetric top) have been studied via high-resolution laser spectroscopy. The molecules were produced in either a Broida oven or in a supersonic jet created in a laser ablation apparatus. The motivations for the studies ranged from basic studies of metal-ligand bonding and validation of theoretical calculations on the structure of metal-bearing molecules, to applications in catalysis and in the characterization of astrophysically relevant species. Two diatomic molecules were investigated: SmO and IrS. SmO was produced in the Broida oven, and three new electronically excited states ([15.3] 1, [15.6] 2 and [16.2] 2) were characterized, adding to the seven excited states and twelve low lying states previously observed and analyzed by Guo et al. [1]. Seventeen bands of 193IrS and eleven of the 191 IrS isotopologue were observed in experiments conducted using the laser ablation source apparatus, but the analysis has not yet led to a conclusive identification of the ground electronic state nor to a definite description of the low-lying electronically excited state just above the ground state. A combination of experimental data and theoretical calculations suggest that these two low lying states may be identified as 2Delta 5/2 and 4Delta7/2. Isotopologues of the linear polyatomics MgCCH, CaCCH and SrCCH were also examined to precisely determine the bond lengths in these molecules. Analyses of the Mg12C12CD, Mg13C 13CH, Ca13C13CH and Sr13C 13CH spectra presented in this thesis were combined with those from previously observed spectra of the normal and deuterated isotopes. Surprisingly, the results showed an unexpected and significant increase in the C-C bond length as the alkaline earth metal changed from Mg to Ca to Sr. A more physically realistic result in which the C-C lengths were more consistent from metal to metal was obtained when the analysis was performed with the C-H bond length constrained to that of HCCH. While scanning spectra of MgCCH, bands of longer magnesium-bearing molecules MgC4H and MgC6H were observed as well. The signal strength was sufficient in MgC4H to obtain and analyze its rotationally resolved spectrum. Finally, on the basis of the work done by Hopkins et al [3], the symmetric top molecule strontium monomethoxide was scanned at high resolution. A two-laser optical-optical double resonance technique was employed to conclusively assign and analyze the A2E -- X2A1 spectrum in SrO12CH3 and the B 2A1 -- X 2A1 spectrum in SrO 12CH3 and SrO13CH3. A strong perturbation, the origin of which is still unknown, was observed in the B2A1 state in SrO 12CH3, which exhibits as well the Jahn-Teller effect in its A2E state, through the Jahn-Teller related rotational parameter h1. An empirical deperturbation was successfully performed by introducing a new parameter Bmod into the Hamiltonian, which adjusted the rotational constant B for one parity component of a specific set of K' levels.

Forthomme, Damien

366

Nitrogen-rich graphene from small molecules as high performance anode material  

NASA Astrophysics Data System (ADS)

Nitrogen-rich graphene sheets were successfully achieved via facile thermal condensation of glucose and dicyandiamide at different temperatures during which dicyandiamide acts both as nitrogen source and sacrifice template. Devoid of surfactants or poisonous organic solvents, this small-molecule synthetic approach is a simple and cost-effective way to obtain nitrogen-rich graphene sheets (NRGS) with high specific surface area and large pore volume. Shown to be a promising anode material, the NRGS displayed high reversible capacity, excellent rate capability, and superior cycle performance. The superior lithium-storage performance is ascribed to the unique features of NRGS, including a large quantity of defects due to the high nitrogen doping level, favorable lithium ion transportation channels by virtue of the large surface area, and ultrahigh pore volume, as well as the crumpled two-dimensional structure.

Gao, Weiwei; Huang, Hao; Shi, Hongyan; Feng, Xun; Song, Wenbo

2014-10-01

367

Chiral Metafoils for Terahertz Broadband High-Contrast Flexible Circular Polarizers  

NASA Astrophysics Data System (ADS)

Metamaterial concepts have opened the door to high-optical anisotropy beyond levels of naturally occurring materials but usually with limited spectral bandwidth. Here, we report on the design, realization, and experimental and numerical characterization of broadband chiral metafoils exhibiting at the same time exceptionally high-contrast circular polarization in the THz range. We demonstrate that the observed chirality is achieved by a simple modification of the structure of well-established metafoils, namely, through a shift of interconnecting lines by half a unit cell length between each row. The bandwidth of the observed circular-polarization-selective response is demonstrated to be up to about one octave at a center frequency of 2.4 THz and the ratio of the transmission of oppositely circularly polarized radiation is shown to reach about 700%, with the maximum transmittance being approximately 70%. Although implemented here at THz frequencies, broadband chiral metafoils may be extended to higher infrared and optical frequencies by hot embossing or nanoimprinting. They may be used as circular polarizers and beam stops in THz optical and infrared systems.

Wu, Jianfeng; Ng, Binghao; Liang, Haidong; Breese, Mark B. H.; Hong, Minghui; Maier, Stefan A.; Moser, Herbert O.; Hess, Ortwin

2014-07-01

368

Electromagnetic Ion Cyclotron Waves in the High Altitude Cusp: Polar Observations  

NASA Technical Reports Server (NTRS)

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.

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

369

Performance of GAASP/GAAS Superlattice Photocathodes in High Energy Experiments using Polarized Electrons  

SciTech Connect

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.

Brachmann, A.; Clendenin, J.E.; Maruyama, T.; Garwin, E.L.; Ioakemidi, K.; Prescott, C.Y.; Turner, J.L.; /SLAC; Prepost, R.; /Wisconsin U., Madison

2006-02-27

370

High-fidelity polarization storage in a gigahertz bandwidth quantum memory  

NASA Astrophysics Data System (ADS)

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.

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

371

Laser Focusing System for High Brightness Polarized Electron Source for SPLEEM  

SciTech Connect

For construction of a high brightness polarized electron source for SPLEEM (Spin Polarized Low Energy Electronic Microscope), a new transmission type photocathode has been developed at Nagoya Univ. In our scheme, a laser light is injected from backside of the photocathode and an electron beam is emitted forward from the surface. A high numerical aperture lens with a short focal length can focus the laser lights into a small spot of photocathode. A laser spot with a diameter of 2.2{mu}m could be achieved by our laser system, and it contributed to realize the high beam brightness of 105A{center_dot}cm-2{center_dot}sr-1 or more for a total current of 5{mu}A.

Mano, A.; Yamamoto, N.; Tamagaki, K.; Okumi, S.; Yamamoto, M.; Kuwahara, M.; Sakai, R.; Morino, T.; Utsu, A.; Nakanishi, T. [Department of Physics, Nagoya University (Japan); Ohshima, T. [Central Research labs. Hitachi Ltd (Japan)

2007-06-13

372

Polarization maintaining, high-power and high-efficiency (6+1)1 pump/signal combiner  

NASA Astrophysics Data System (ADS)

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.

Kopp, Victor I.; Park, Jongchul; Wlodawski, Mitchell; Singer, Jonathan; Neugroschl, Dan

2014-03-01

373

Cellulose ester film, polarizing plate and liquid crystal display  

US Patent & Trademark Office Database

An object of the present invention is to provide a polarizing plate protective film exhibiting a reduced variation value retardation, which is highly stable against polarizing plate degradation, polarizing plate dimension, and polarizing plate curl. Disclosed is a cellulose ester film possessing cellulose ester, polymer X having a weight average molecular weight of 2000-30000 prepared by copolymerizing ethylenic unsaturated monomer Xa containing no aromatic ring and hydrophilic group within a molecule and ethylenic unsaturated monomer Xb containing no aromatic ring but a hydrophilic group within a molecule, and polymer Y having a weight average molecular weight of 500-3000 prepared by polymerizing ethylenic unsaturated monomer Ya containing no aromatic ring.

2010-07-06

374

Horizontal polarization of ground motion in the Hayward fault zone at Fremont, California: dominant fault-high-angle polarization and fault-induced cracks  

NASA Astrophysics Data System (ADS)

We investigate shear wave polarization in the Hayward fault zone near Niles Canyon, Fremont, CA. Waveforms of 12 earthquakes recorded by a seven-accelerometer seismic array around the fault are analysed to clarify directional site effects in the fault damage zone. The analysis is performed in the frequency domain through H/V spectral ratios with horizontal components rotated from 0 to 180, and in the time domain using the eigenvectors and eigenvalues of the covariance matrix method employing three component records. The near-fault ground motion tends to be polarized in the horizontal plane. At two on-fault stations where the local strike is N160, ground motion polarization is oriented N88 19 and N83 32, respectively. At a third on-fault station, the motion is more complex with horizontal polarization varying in different frequency bands. However, a polarization of N86 7, similar to the results at the other two on-fault stations, is found in the frequency band 6-8 Hz. The predominantly high-angle polarization from the fault strike at the Hayward Fault is consistent with similar results at the Parkfield section of the San Andreas Fault and the Val d'Agri area (a Quaternary extensional basin) in Italy. In all these cases, comparisons of the observed polarization directions with models of fracture orientation based on the fault movement indicate that the dominant horizontal polarization is near-orthogonal to the orientation of the expected predominant cracking direction. The results help to develop improved connections between fault mechanics and near-fault ground motion.

Pischiutta, M.; Salvini, F.; Fletcher, J.; Rovelli, A.; Ben-Zion, Y.

2012-03-01

375

A high-content screening assay for small molecule modulators of oncogene-induced senescence  

PubMed Central

Cellular senescence is a state of stable cell growth arrest. Activation of oncogenes such as RAS in mammalian cells typically triggers cellular senescence. Oncogene-induced senescence (OIS) is an important tumor suppression mechanism, and suppression of OIS contributes to cell transformation. Oncogenes trigger senescence through a multitude of incompletely understood downstream signaling events that frequently involve protein kinases. To identify target proteins required for RAS-induced senescence, we developed a small molecule screen in primary human fibroblasts undergoing senescence induced by oncogenic RAS (H-RasG12V). Using a high-content imaging system to monitor two hallmarks of senescence, senescence-associated ?-galactosidase activity expression and inhibition of proliferation, we screened a library of known small molecule kinase inhibitors for those that suppressed OIS. Identified compounds were subsequently validated and confirmed using a third marker of senescence, senescence-associated heterochromatin foci. In summary, we have established a novel high-content screening platform that may be useful for elucidating signaling pathways mediating OIS by targeting critical pathway components. PMID:23733845

Bitler, BG; Fink, LS; Wei, Z; Peterson, JR; Zhang, R

2013-01-01

376

Single-Molecule Analysis of the Rotation of F1-ATPase under High Hydrostatic Pressure  

PubMed Central

F1-ATPase is the water-soluble part of ATP synthase and is an ATP-driven rotary molecular motor that rotates the rotary shaft against the surrounding stator ring, hydrolyzing ATP. Although the mechanochemical coupling mechanism of F1-ATPase has been well studied, the molecular details of individual reaction steps remain unclear. In this study, we conducted a single-molecule rotation assay of F1 from thermophilic bacteria under various pressures from 0.1 to 140 MPa. Even at 140 MPa, F1 actively rotated with regular 120 steps in a counterclockwise direction, showing high conformational stability and retention of native properties. Rotational torque was also not affected. However, high hydrostatic pressure induced a distinct intervening pause at the ATP-binding angles during continuous rotation. The pause was observed under both ATP-limiting and ATP-saturating conditions, suggesting that F1 has two pressure-sensitive reactions, one of which is evidently ATP binding. The rotation assay using a mutant F1(?E190D) suggested that the other pressure-sensitive reaction occurs at the same angle at which ATP binding occurs. The activation volumes were determined from the pressure dependence of the rate constants to be+1003 and+883 for ATP binding and the other pressure-sensitive reaction, respectively. These results are discussed in relation to recent single-molecule studies of F1 and pressure-induced protein unfolding. PMID:24094404

Okuno, Daichi; Nishiyama, Masayoshi; Noji, Hiroyuki

2013-01-01

377

High-speed fiber-based polarization-sensitive optical coherence tomography of in vivo human skin  

Microsoft Academic Search

A high-speed single-mode fiber-based polarization-sensitive optical coherence tomography (PS OCT) system was developed. With a polarization modulator, Stokes parameters of reflected flight for four input polarization states are measured as a function of depth. A phase modulator in the reference arm of a Michelson interferometer permits independent control of the axial scan rate and carrier frequency. In vivo PS OCT

Christopher E. Saxer; Johannes F. de Boer; B. Hyle Park; Yonghua Zhao; Zhongping Chen; J. Stuart Nelson

2000-01-01

378

Translational diffusion of probe molecules under high pressure: A study by fluorescence recovery after photobleaching technique  

NASA Astrophysics Data System (ADS)

We present fluorescence recovery measurements after photobleaching performed under high pressure in liquids that fill square-section fused silica micro-capillaries. These micro-capillaries withstand pressure up to 2500 bar for a wall thickness of about 140 ?m and fit easily on the microscope stage. This technique allows the translational diffusion coefficient of fluorescent molecules in liquids to be measured as a function of pressure. When the liquid sample is far from its glass transition the translational diffusive coefficient is in agreement with the Stokes-Einstein equation. As the glass transition is approached by further increasing the pressure, decoupling of the measured diffusion coefficient from the Stokes-Einstein relation is observed. These are the first measurements that combine the fluorescence recovery technique and high hydrostatic pressures. This experimental setup can also be used either with diamond or sapphire anvil cells in order to span a larger pressure range.

Bonetti, Marco; Roger, Michel

2013-02-01

379

A highly specific gold nanoprobe for live-cell single-molecule imaging  

E-print Network

Single molecule tracking in live cells is the ultimate tool to study subcellular protein dynamics, but it is often limited by the probe size and photostability. Due to these issues, long-term tracking of proteins in confined and crowded environments, such as intracellular spaces, remains challenging. We have developed a novel optical probe consisting of 5-nm gold nanoparticles functionalized with a small fragment of camelid antibodies that recognize widely used GFPs with a very high affinity, which we call GFP-nanobodies. These small gold nanoparticles can be detected and tracked using photothermal imaging for arbitrarily long periods of time. Surface and intracellular GFP-proteins were effectively labeled even in very crowded environments such as adhesion sites and cytoskeletal structures both in vitro and in live cell cultures. These nanobody-coated gold nanoparticles are probes with unparalleled capabilities; small size, perfect photostability, high specificity, and versatility afforded by combination with...

Leduc, Cecile; Gautier, Jrmie; Soto-Ribeiro, Martinho; Wehrle-Haller, B; Gautreau, Alexis; Giannone, Gregory; Cognet, Laurent; Lounis, Brahim

2013-01-01

380

Complex Organic Molecules at High Spatial Resolution Toward Orion-KL II: Kinematics  

E-print Network

It has recently been suggested that chemical processing can shape the spatial distributions of complex molecules in the Orion-KL region and lead to the nitrogen-oxygen "chemical differentiation" seen in previous observations of this source. Orion-KL is a very dynamic region, and it is therefore also possible that physical conditions can shape the molecular distributions in this source. Only high spatial resolution observations can provide the information needed to disentangle these effects. Here we present millimeter imaging studies of Orion-KL at various beam sizes using the Combined Array for Research in Millimeter-Wave Astronomy (CARMA). We compare molecular images with high spatial resolution images that trace the temperature, continuum column density, and kinematics of the source in order to investigate the effects of physical conditions on molecular distributions. These observations were conducted at \\lambda = 3 mm and included transitions of ethyl cyanide [C2H5CN], methyl formate [HCOOCH3], formic acid...

Friedel, D N

2012-01-01

381

Polarization shift keying for high-bit-rate multilevel soliton transmissions  

NASA Astrophysics Data System (ADS)

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.

Midrio, M.; Franco, P.; Crivellari, M.; Romagnoli, M.; Matera, F.

1996-07-01

382

High-speed polarization sensitive optical coherence tomography for retinal diagnostics  

NASA Astrophysics Data System (ADS)

We report design and construction of an FPGA-based high-speed swept-source polarization-sensitive optical coherence tomography (SS-PS-OCT) system for clinical retinal imaging. Clinical application of the SS-PS-OCT system is accurate measurement and display of thickness, phase retardation and birefringence maps of the retinal nerve fiber layer (RNFL) in human subjects for early detection of glaucoma. The FPGA-based SS-PS-OCT system provides three incident polarization states on the eye and uses a bulk-optic polarization sensitive balanced detection module to record two orthogonal interference fringe signals. Interference fringe signals and relative phase retardation between two orthogonal polarization states are used to obtain Stokes vectors of light returning from each RNFL depth. We implement a Levenberg-Marquardt algorithm on a Field Programmable Gate Array (FPGA) to compute accurate phase retardation and birefringence maps. For each retinal scan, a three-state Levenberg-Marquardt nonlinear algorithm is applied to 360 clusters each consisting of 100 A-scans to determine accurate maps of phase retardation and birefringence in less than 1 second after patient measurement allowing real-time clinical imaging-a speedup of more than 300 times over previous implementations. We report application of the FPGA-based SS-PS-OCT system for real-time clinical imaging of patients enrolled in a clinical study at the Eye Institute of Austin and Duke Eye Center.

Yin, Biwei; Wang, Bingqing; Vemishetty, Kalyanramu; Nagle, Jim; Liu, Shuang; Wang, Tianyi; Rylander, Henry G., III; Milner, Thomas E.

2012-01-01

383

NMR-based structural biology enhanced by dynamic nuclear polarization at high magnetic field.  

PubMed

Dynamic nuclear polarization (DNP) has become a powerful method to enhance spectroscopic sensitivity in the context of magnetic resonance imaging and nuclear magnetic resonance spectroscopy. We show that, compared to DNP at lower field (400MHz/263GHz), high field DNP (800MHz/527GHz) can significantly enhance spectral resolution and allows exploitation of the paramagnetic relaxation properties of DNP polarizing agents as direct structural probes under magic angle spinning conditions. Applied to a membrane-embedded K(+) channel, this approach allowed us to refine the membrane-embedded channel structure and revealed conformational substates that are present during two different stages of the channel gating cycle. High-field DNP thus offers atomic insight into the role of molecular plasticity during the course of biomolecular function in a complex cellular environment. PMID:25284462

Koers, Eline J; van der Cruijsen, Elwin A W; Rosay, Melanie; Weingarth, Markus; Prokofyev, Alexander; Sauve, Claire; Ouari, Olivier; van der Zwan, Johan; Pongs, Olaf; Tordo, Paul; Maas, Werner E; Baldus, Marc

2014-11-01

384

On the high Mach number shock structure singularity caused by overreach of Maxwellian molecules  

NASA Astrophysics Data System (ADS)

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.

Myong, R. S.

2014-05-01

385

Characterization of structural irregularities in highly birefringent photonic crystal fiber based on polarization coupling by torsional acoustic wave  

Microsoft Academic Search

We propose and demonstrate a novel method to characterize the variation of the birefringence induced by structural irregularities in highly birefringent photonic crystal fiber with high accuracy based on polarization coupling by torsional acoustic wave.

Kee Suk Hong; Kwang Jo Lee; Dong Il Yeom; Byoung Yoon Kim

2010-01-01

386

Identification of polar, ionic, and highly water soluble organic pollutants in untreated industrial wastewaters  

Microsoft Academic Search

This paper presents a generic protocol for the determination of polar, ionic, and highly water soluble organic pollutants on untreated industrial wastewaters involving the use of two different solid-phase extraction (SPE) methodologies followed by liquid chromatography-mass spectrometry (LC-MS). Untreated industrial wastewaters might contain natural and synthetic dissolved organic compounds with total organic carbon (TOC) values varying between 100 and 3000

Montserrat Castillo; M. Carmen Alonso; Josep Riu; D. Barcelo

1999-01-01

387

High power CW red VECSEL with linearly polarized TEM00 output beam.  

PubMed

High-power, continuous-wave operation at red wavelengths has been achieved with a vertical external cavity surface emitting laser based on the GaInP/AlGaInP/GaAs material system. Output power of 0.4W was obtained in a linearly polarized, circularly symmetric, diffraction-limited beam. A birefringent filter inserted in the cavity allowed tuning of the laser output spectrum over a 10nm range around 674nm. PMID:19488329

Hastie, Jennifer; Calvez, Stephane; Dawson, Martin; Leinonen, Tomi; Laakso, Antti; Lyytikinen, Jari; Pessa, Markus

2005-01-10

388

Highly efficient and polarization-independent Fresnel lens based on dye-doped liquid crystal  

Microsoft Academic Search

We demonstrated a highly efficient, polarization-independent and electrically tunable Fresnel lens based on dye-doped liquid crystal using double-side photoalignment technique. The maximum diffraction efficiency reaches 37%, which approaches the theoretical limit ~41%. Such a lens functions as a half-wave plate, and this feature could be well preserved under the applied voltage. In addition, the device is simple to fabricate, and

Liang-Chen Lin; Hung-Chang Jau; Tsung-Hsien Lin; Andy Y. Fuh

2007-01-01

389

RESOLVING POLARITY AND HYDROGEN BOND ENVIRONMENT AT PROTEIN LIPID- BINDING SITES USING HIGH FIELD EPR  

E-print Network

Nitroxide spin labeling in combination with EPR spectroscopy has found many applications in studying structure and dynamics of proteins and biological membranes. Recently, there has been a substantial interest in utilizing High Field EPR to characterize local effects of polarity and hydrogen bonding in proteins and model phospholipid systems. Specifically, with the help of HF EPR it has been shown that two components of the nitroxide magnetic tensors, gx, and Az, are the most

T. I. Smirnova (ncsu; A. Ozarowski; H. Van Tol; L. -c. Brunel (nhmfl

390

The role of silica gel in lipase-catalyzed esterification reactions of high-polar substrates  

Microsoft Academic Search

The crucial role of silica gel in lipase-catalyzed esterification reactions using adsorbed high-polar substates was established.\\u000a It was found that in these kinds of reactions, the presence of silica gel-adsorbed substrates did not alter the kinetic mechanisms\\u000a of the synthesis of acylglycerides but improved significantly the conversion yields. An explanation for the critical role\\u000a of silica gel in these kinds

Edmundo Castillo; Valrie Dossat; Alain Marty; J. Stphane Condoret; Didier Combes

1997-01-01

391

Mechanically induced generation of highly reactive excited-state oxygen molecules in cluster scattering.  

PubMed

Molecular electronic excitation in (O(2))(n) clusters induced by mechanical collisions via the "chemistry with a hammer" is investigated by a combination of molecular dynamics simulations and quantum chemistry calculations. Complete active space self-consistent field augmented with triple-zeta polarizable basis set quantum chemistry calculations of a compressed (O(2))(2) cluster model in various configurations reveal the emergence of possible pathways for the generation of electronically excited singlet O(2) molecules upon cluster compression and vibrational excitation, due to electronic curve-crossing and spin-orbit coupling. Extrapolation of the model (O(2))(2) results to larger clusters suggests a dramatic increase in the population of electronically excited O(2) products, and may account for the recently observed cluster-catalyzed oxidation of silicon surfaces, via singlet oxygen generation induced by cluster impact, followed by surface reaction of highly reactive singlet O(2) molecules. Extensive molecular dynamics simulations of (O(2))(n) clusters colliding onto a hot surface indeed reveal that cluster compression is sufficient under typical experimental conditions for nonadiabatic transitions to occur. This work highlights the importance of nonadiabatic effects in the "chemistry with a hammer." PMID:21322678

Nguyen, Tao-Nhn V; Timerghazin, Qadir K; Vach, Holger; Peslherbe, Gilles H

2011-02-14

392

Micropatterned substrates coated with neuronal adhesion molecules for high-content study of synapse formation.  

PubMed

Studying the roles of different proteins and the mechanisms involved in synaptogenesis is hindered by the complexity and heterogeneity of synapse types, and by the spatial and temporal unpredictability of spontaneous synapse formation. Here we demonstrate a robust and high-content method to induce selectively presynaptic or postsynaptic structures at controlled locations. Neurons are cultured on micropatterned substrates comprising arrays of micron-scale dots coated with various synaptogenic adhesion molecules. When plated on neurexin-1?-coated micropatterns, neurons expressing neuroligin-1 exhibit specific dendritic organization and selective recruitment of the postsynaptic scaffolding molecule PSD-95. Furthermore, functional AMPA receptors are trapped at neurexin-1? dots, as revealed by live-imaging experiments. In contrast, neurons plated on SynCAM1-coated substrates exhibit strongly patterned axons and selectively assemble functional presynapses. N-cadherin coating, however, is not able to elicit synapses, indicating the specificity of our system. This method opens the way to both fundamental and therapeutic studies of various synaptic systems. PMID:23934334

Czndr, Katalin; Garcia, Mikael; Argento, Amlie; Constals, Audrey; Breillat, Christelle; Tessier, Batrice; Thoumine, Olivier

2013-01-01

393

Highly Precise Quantification of Protein Molecules per Cell During Stress and Starvation Responses in Bacillus subtilis.  

PubMed

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

Maa?, Sandra; Wachlin, Gerhild; Bernhardt, Jrg; Eymann, Christine; Fromion, Vincent; Riedel, Katharina; Becher, Drte; Hecker, Michael

2014-09-01

394

Symmetry-Based Tunnelings in High-Resolution Rovibrational Spectra of Octahedral Molecules  

NASA Astrophysics Data System (ADS)

High-resolution spectra of spherical-top molecules are known to demonstrate rotational level clustering. This clustering is well described as a rotational phase-space effect Multiple equivalent phase-space regions allow tunneling and thus splitting of the rotational clusters. So far this has been done with an ad hoc tunneling Hamiltonian. Similar splittings have been shown for low dimensional systems, also with an ad hoc parameterization. While ad hoc tunneling parameterization is simple to understand, it becomes extremely difficult to apply for higher symmetries and for locally low-symmetry clustering when many tunneling paths are possible. Symmetry-based parameterization mitigates this complication. This presentation will discuss how symmetry-based tunneling is applied for octahedral molecules and demonstrate how local-C1, C2, C3 or C4 clusters may be evaluated perturbatively. Connections to non-rotational systems, such as large amplitude motion, will be discussed as well. W.G. Harter and C.W. Patterson, Phys Rev Lett 38, 224 (1977) W.G. Harter and C.W. Patterson, J Chem Phys 66, 4872 (1977) J.T. Hougen J Mol Spect 123, 197 (1987)

Mitchell, Justin; Harter, William

2010-06-01

395

Development of a field-widened Michelson spectroscopic filter for a polarized near-infrared high spectral resolution lidar  

NASA Astrophysics Data System (ADS)

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.

Liu, Dong; Yang, Yongying; Cheng, Zhongtao; Ling, Tong; Huang, Hanlu; Zhou, Yudi; Zhang, Qiaoshuang; Zhang, Bo; Shen, Yibing

2013-09-01

396

Highly polarized light from stable ordered magnetic fields in GRB?120308A.  

PubMed

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

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

397

High-speed fiber-based polarization-sensitive optical coherence tomography of in vivo human skin  

SciTech Connect

A high-speed single-mode fiber-based polarization-sensitive optical coherence tomography (PS OCT) system was developed. With a polarization modulator, Stokes parameters of reflected flight for four input polarization states are measured as a function of depth. A phase modulator in the reference arm of a Michelson interferometer permits independent control of the axial scan rate and carrier frequency. In vivo PS OCT images of human skin are presented, showing subsurface structures that are not discernible in conventional OCT images. A phase retardation image in tissue is calculated based on the reflected Stokes parameters of the four input polarization states. (c) 2000 Optical Society of America.

Saxer, Christopher E.; Boer, Johannes F. de; Park, B. Hyle; Zhao, Yonghua; Chen, Zhongping; Nelson, J. Stuart

2000-09-15

398

IEEE PHOTONICS TECHNOLOGY LETTERS, VOL. 20, NO. 14, JULY 15, 2008 1267 Highly Polarized Single-Chip ELED Sources Using  

E-print Network

modes in excess of about 20 dB in InGaAsP­InP [1], [2]. Devices such as fiber-optic gyroscopes demandIEEE PHOTONICS TECHNOLOGY LETTERS, VOL. 20, NO. 14, JULY 15, 2008 1267 Highly Polarized Single components with polarization extinctions >40 dB are desirable for state-of-the-art photonic in- tegrated

Coldren, Larry A.

399

High-Throughput Screening of Small Molecule Ligands Targeted to Live Bacteria Surface  

PubMed Central

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

Lee, Jeong Heon; Park, Sunny; Hyun, Hoon; Bordo, Mark W.; Oketokoun, Rafiou; Nasr, Khaled A.; Frangioni, John V.; Choi, Hak Soo

2013-01-01

400

High-Resolution ?=1 mm CARMA Observations of Large Molecules in Orion-KL  

NASA Astrophysics Data System (ADS)

We present high-resolution Combined Array for Research in Millimeter-Wave Astronomy (CARMA) ?=1 mm observations of several molecular species toward Orion-KL. These are the highest spatial and spectral resolution 1 mm observations of these molecules to date. Our observations show that ethyl cyanide [C2H5CN] and vinyl cyanide [C2H3CN] originate from multiple cores near the Orion hot core and IRc7. In addition we show that dimethyl ether [(CH3)2O] and methyl formate [HCOOCH3] originate from IRc5 and IRc6 and that acetone [(CH3)2CO] originates only from areas where both N-bearing and O-bearing species are present.

Friedel, D. N.; Snyder, L. E.

2008-01-01

401

High resolution studies of dissociative electron attachment to molecules: dependence on electron and vibrational energy  

NASA Astrophysics Data System (ADS)

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.

Ruf, M.-W.; Braun, M.; Marienfeld, S.; Fabrikant, I. I.; Hotop, H.

2007-11-01

402

A high-throughput assay for small molecule destabilizers of the KRAS oncoprotein.  

PubMed

Mutations in the Ras family of small GTPases, particularly KRAS, occur at high frequencies in cancer and represent a major unmet therapeutic need due to the lack of effective targeted therapies. Past efforts directed at inhibiting the activity of the Ras oncoprotein have proved difficult. We propose an alternative approach to target Ras by eliminating Ras protein from cells with pharmacological means. In this study, we developed a cell-based, high-content screening platform to identify small molecules that could promote the degradation of the KRAS oncoprotein. We generated an EGFP-KRASG12V fluorescence reporter system and implemented it for automated screening in 1536-well plates using high-throughput cellular imaging. We screened a library of clinically relevant compounds at wide dose range and identified Ponatinib and AMG-47a as two candidate compounds that selectively reduced the levels of EGFP-KRASG12V protein but did not affect EGFP protein in cells. This proof-of-principle study demonstrates that it is feasible to use a high-throughput screen to identify compounds that promote the degradation of the Ras oncoprotein as a new approach to target Ras. PMID:25093678

Carver, Joseph; Dexheimer, Thomas S; Hsu, Dennis; Weng, Meng-Tzu; Smith, Jordan L; Guha, Rajarshi; Jadhav, Ajit; Simeonov, Anton; Luo, Ji

2014-01-01

403

Identification of polar, ionic, and highly water soluble organic pollutants in untreated industrial wastewaters  

SciTech Connect

This paper presents a generic protocol for the determination of polar, ionic, and highly water soluble organic pollutants on untreated industrial wastewaters involving the use of two different solid-phase extraction (SPE) methodologies followed by liquid chromatography-mass spectrometry (LC-MS). Untreated industrial wastewaters might contain natural and synthetic dissolved organic compounds with total organic carbon (TOC) values varying between 100 and 3000 mg/L. All polar, ionic and highly water soluble compounds comprising more than 95% of the organic content and with major contribution to the total toxicity of the sample cannot be analyzed by conventional gas chromatography-mass spectrometry (GC-MS), and LC-MS is a good alternative. In this work two extraction procedures were used to obtain fractionated extracts of the nonionic polar compounds: a polymeric Isolute ENV + SPE cartridge for the preconcentration of anionic analytes and a sequential solid-phase extraction (SSPE) method percolating the samples first in octadecylsilica cartridge in series with the polymeric Lichrolut EN cartridge. Average recoveries ranging from 72% to 103% were obtained for a variety of 23 different analytes. Determination of nonionic pollutants was accomplished by reverse-phase liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry (LC-APCI-MS), while anionic compounds were analyzed by ion pair chromatography-electrospray-mass spectrometry (IP-ESI-MS) and LC-ESI-MS. This protocol was applied to a pilot survey of textile and tannery wastewaters leading to the identification and quantification of 33 organic pollutants.

Castillo, M.; Alonso, M.C.; Riu, J.; Barcelo, D. [IIQAB-CSIC, Barcelona (Spain). Dept. of Environmental Chemistry] [IIQAB-CSIC, Barcelona (Spain). Dept. of Environmental Chemistry

1999-04-15

404

The surprising composition of Titans high-altitude southern polar cloud  

NASA Astrophysics Data System (ADS)

Titan's middle atmosphere is currently experiencing a rapid change of season after northern spring arrived in 2009. A large cloud was observed by Cassinis imaging science subsystem for the first time above Titan's southern pole in May 2012, at an altitude of 300 km (West et al., DPS 305.03, 2013). This altitude previously showed a temperature maximum and condensation was not expected for any of Titan's atmospheric gases. We analysed VIMS observations of the polar cloud and could determine its composition from near-infrared spectral features. We will present constraints on the properties of Titans high-altitude southern polar cloud, as well as new temperature retrievals at the south pole that can help in understanding its surprising composition.

de Kok, Remco; Teanby, Nicholas; Maltagliati, Luca; Irwin, Patrick; Vinatier, Sandrine

2014-11-01

405

Polarization-preserving confocal microscope for optical experiments in a dilution refrigerator with high magnetic field  

E-print Network

We present the design and operation of a fiber-based cryogenic confocal microscope. It is designed as a compact cold-finger that fits inside the bore of a superconducting magnet, and which is a modular unit that can be easily swapped between use in a dilution refrigerator and other cryostats. We aimed at application in quantum optical experiments with electron spins in semiconductors and the design has been optimized for driving with, and detection of optical fields with well-defined polarizations. This was implemented with optical access via a polarization maintaining fiber together with Voigt geometry at the cold finger, which circumvents Faraday rotations in the optical components in high magnetic fields. Our unit is versatile for use in experiments that measure photoluminescence, reflection, or transmission, as we demonstrate with a quantum optical experiment with an ensemble of donor-bound electrons in a thin GaAs film.

Sladkov, Maksym; Chaubal, A U; Reuter, D; Wieck, A D; van der Wal, C H

2010-01-01

406

Polarization-preserving confocal microscope for optical experiments in a dilution refrigerator with high magnetic field  

E-print Network

We present the design and operation of a fiber-based cryogenic confocal microscope. It is designed as a compact cold-finger that fits inside the bore of a superconducting magnet, and which is a modular unit that can be easily swapped between use in a dilution refrigerator and other cryostats. We aimed at application in quantum optical experiments with electron spins in semiconductors and the design has been optimized for driving with, and detection of optical fields with well-defined polarizations. This was implemented with optical access via a polarization maintaining fiber together with Voigt geometry at the cold finger, which circumvents Faraday rotations in the optical components in high magnetic fields. Our unit is versatile for use in experiments that measure photoluminescence, reflection, or transmission, as we demonstrate with a quantum optical experiment with an ensemble of donor-bound electrons in a thin GaAs film.

Maksym Sladkov; M. P. Bakker; A. U. Chaubal; D. Reuter; A. D. Wieck; C. H. van der Wal

2010-10-09

407

Survey of TES high albedo events in Mars' northern polar craters  

USGS Publications Warehouse

Following the work exploring Korolev Crater (Armstrong et al., 2005) for evidence of crater interior ice deposits, we have conducted a survey of Thermal Emission Spectroscopy (TES) temperature and albedo measurements for Mars' northern polar craters larger than 10 km. Specifically, we identify a class of craters that exhibits brightening in their interiors during a solar longitude, Ls, of 60 to 120 degrees, roughly depending on latitude. These craters vary in size, latitude, and morphology, but appear to have a specific regional association on the surface that correlates with the distribution of subsurface hydrogen (interpreted as water ice) previously observed on Mars. We suggest that these craters, like Korolev, exhibit seasonal high albedo frost events that indicate subsurface water ice within the craters. A detailed study of these craters may provide insight in the geographical distribution of the ice and context for future polar missions. Copyright 2007 by the American Geophysical Union.

Armstrong, J. C.; Nielson, S. K.; Titus, T. N.

2007-01-01

408

High-energy bremsstrahlung from polarized electrons colliding with spin-(1)/(2) nuclei  

NASA Astrophysics Data System (ADS)

The Born theory for bremsstrahlung from high-energy electrons colliding with extended (finite-mass) nuclei is reexamined. Higher-order effects are included into the Born approximation by making use of the weak-potential Sommerfeld-Maue prescription in an additional contribution to the transition amplitude. Predictions are made for the differential cross section (with respect to the photon degrees of freedom) and for the polarization correlations between the incoming electron and the emitted photon. It is found that at collision energies exceeding 20 MeV the cross section as well as the polarization correlations are strongly influenced by nuclear recoil and nuclear structure effects, particularly at backward photon angles. Numerical results are presented for bremsstrahlung from 10-100 MeV electrons colliding with protons, 19F and 89Y nuclei.

Jakubassa-Amundsen, D. H.

2013-06-01

409

Special high speed imaging techniques using phase, aperture, and polarization effects  

NASA Astrophysics Data System (ADS)

The present paper gives an overview on some special techniques for high speed video recording used and investigated in our department for observing the behaviour of transparent media under high temperature, pressure and stress conditions. Such techniques are shadowgraph and schlieren imaging for objects in gaseous environment, and cross polarization techniques for transparent liquids and solid bodies. The examples shown are derived from investigations of exploding conductors and impact studies on glass, plastic and gelatine. Further some concepts for the extraction of slides along the optical axis by decreasing the depth of field using ring apertures are discussed in short.

Zhao, Wenjing; Skaloud, Daniel C.; Kutz, Sascha; Rothe, Hendrik; Hahlweg, Cornelius F.

2013-09-01

410

New high-intensity source of polarization-entangled photon pairs  

NASA Astrophysics Data System (ADS)

We report on a high-intensity source of polarization-entangled photon pairs with high momentum definition. Type-II noncollinear phase matching in parametric down conversion produces true entanglement: No part of the wave function must be discarded, in contrast to previous schemes. With two-photon fringe visibilities in excess of 97%, we demonstrated a violation of Bell's inequality by over 100 standard deviations in less than 5 min. The new source allowed ready preparation of all four of the EPR-Bell states.

Kwiat, Paul G.; Mattle, Klaus; Weinfurter, Harald; Zeilinger, Anton; Sergienko, Alexander V.; Shih, Yanhua

1995-12-01

411

Interstellar Extinction, Polarization, and Grain Alignment in High-Latitude Clouds  

NASA Technical Reports Server (NTRS)

From new near-infrared photometry and optical and near-infrared polarimetry, we determine the ratio of total-to-selective extinction and the wavelength of maximum polarization for a sample of stars behind molecular clouds at high Galactic latitude. In general, we find that at high latitude, these parameters have values comparable to those observed closer to the Galactic plane. One notable exception is the line of sight towards HD 210121, where unusually small values of these parameters suggest an abundance of small grains in the foreground cloud.

Larson, K. A.; Whittet, D. C. B.

1996-01-01

412

High-sensitivity determination of birefringence in turbid media with enhanced polarization-sensitive optical coherence tomography  

Microsoft Academic Search

Polarization-sensitive optical coherence tomography provides high-resolution cross-sectional characterization of birefringence in turbid media. Weakly birefringent biological tissues such as the retinal nerve fiber layer (RNFL) require advanced speckle noise reduction for high-sensitivity measurement of form birefringence. We present a novel method for high-sensitivity birefringence quantification by using enhanced polarization-sensitive optical coherence tomography (EPS-OCT) and introduce the polarimetric signal-to-noise ratio, a

Nate J. Kemp; Haitham N. Zaatari; H. Grady Rylander; Thomas E. Milner

2005-01-01

413

Catalytic and Molecular Beacons for Amplified Detection of Metal Ions and Organic Molecules with High Sensitivity  

PubMed Central

Catalytic beacon has emerged as a general platform for sensing metal ions and organic molecules. However, few reports have taken advantage of the true potential of catalytic beacons in signal amplification through multiple enzymatic turnovers, as existing designs require either equal concentrations of substrate and DNAzyme or an excess of DNAzyme in order to maintain efficient quenching, eliminating the excess of substrate necessary for multiple turnovers. Based on the large difference in the melting temperatures between the intramolecular molecular beacon stem and intermolecular products of identical sequences, we here report a general strategy of catalytic and molecular beacon (CAMB) that combines the advantages of the molecular beacon for highly efficient quenching with the catalytic beacon for amplified sensing through enzymatic turnovers. Such a CAMB design allows detection of metal ions such as Pb2+ with a high sensitivity (LOD=600 pM). Furthermore, aptamer sequence has been introduced into DNAzyme to use the modified CAMB for amplified sensing of adenosine with similar high sensitivity. These results together demonstrate that CAMB provides a general platform for amplified detection of a wide range of targets. PMID:20481627

Zhang, Xiao-Bing; Wang, Zidong; Xing, Hang; Xiang, Yu; Lu, Yi

2010-01-01

414

Polarization developments  

SciTech Connect

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.

Prescott, C.Y.

1993-07-01

415

Hubble Space Telescope ultraviolet spectroscopy of the highly polarized but quiescent quasar OI 287  

NASA Technical Reports Server (NTRS)

The quasar OI 287 has a unique combination of properties, including a high and constant optical polarization oriented parallel to the radio axis, a quiescent optical flux, and a lobe-dominant radio source. Previous studies have led to the picture of an edge-on thin dusty torus occulting a featureless continuum (FC) source and a broad line region (BLR) in this object. The FC source and the BLR are seen only in reflected (polarized) light. In the unified models, this makes OI 287 a 'quasar 2', analogous to the type 2 Seyfert galaxies and the narrow-line radio galaxies. Our UV spectrum adds two bits of information consistent with the above ideas. First, the spectrum neither turns up in the UV, as expected for optically thin dust scattering, nor turns down as expected for polarization by dust transmission. It is consistent with reflection by free electrons or optically thick dust. Second, there are in fact blueshifted absorption troughs associated with the C IV 1549 A line, supporting the analogy with BALs, as well as the idea that the BALs are objects which present a nearly edge-on view of a disk structure.

Antonucci, Robert; Kinney, Anne L.; Hurt, Todd

1993-01-01

416

Transfer-printing of single DNA molecule arrays on graphene for high resolution electron imaging and analysis  

PubMed Central

Graphene represents the ultimate substrate for high-resolution transmission electron microscopy, but the deposition of biological samples on this highly hydrophobic material has until now been a challenge. We present a reliable method for depositing ordered arrays of individual elongated DNA molecules on single-layer graphene substrates for high resolution electron beam imaging and electron energy loss spectroscopy analysis. This method is a necessary step towards the observation of single elongated DNA molecules with single base spatial resolution to directly read genetic and epigenetic information. PMID:21919532

Cerf, Aline; Alava, Thomas; Barton, Robert A.; Craighead, Harold G.

2011-01-01

417

Protein-DNA interactions in high speed AFM: single molecule diffusion analysis of human RAD54.  

PubMed

High-speed AFM (atomic force microscopy also called scanning force microscopy) provides nanometre spatial resolution and sub-second temporal resolution images of individual molecules. We exploit these features to study diffusion and motor activity of the RAD54 DNA repair factor. Human RAD54 functions at critical steps in recombinational-DNA repair. It is a member of the Swi2/Snf2 family of chromatin remodelers that translocate on DNA using ATP hydrolysis. A detailed single molecular description of DNA-protein interactions shows intermediate states and distribution of variable states, usually hidden by ensemble averaging. We measured the motion of individual proteins using single-particle tracking and observed that random walks were affected by imaging-buffer composition. Non-Brownian diffusion events were characterized in the presence and in the absence of nucleotide cofactors. Double-stranded DNA immobilized on the surface functioned as a trap reducing Brownian motion. Distinct short range slides and hops on DNA were visualized by high-speed AFM. These short-range interactions were usually inaccessible by other methods based on optical resolution. RAD54 monomers displayed a diffusive behavior unrelated to the motor activity. PMID:21986699

Sanchez, Humberto; Suzuki, Yuki; Yokokawa, Masatoshi; Takeyasu, Kunio; Wyman, Claire

2011-11-01

418

Slit-Jet Discharge Studies of Polyacetylenic Molecules: Synthesis and High Resolution Infrared Spectroscopy of Diacetylene  

NASA Astrophysics Data System (ADS)

Polyacetylenic molecules play an important role in both combustion chemistry as well as chemistry of the interstellar medium. This talk presents first high resolution infrared spectroscopic efforts on the simplest jet-cooled polyacetylene, namely diacetylene (C_4H_2). Specifically, the fundamental anti-symmetric C-H stretching mode (near 3333 cm^{-1}) and several hot combination bands of diacetylene have been investigated under sub-Doppler, jet cooled conditions in a pulsed supersonic slit discharge. Local Coriolis perturbations in the fundamental anti-symmetric C-H stretch manifold are observed and analyzed. Six hot bands are observed, including the H-C-C bending mode (v_8) not observed in previous room temperature studies. The observation of these hot bands under rotationally jet cooled conditions (T_{rot}=15.7(4) K) indicate the presence of highly non-equilibrium relaxation processes between vibration and rotation. G. Guelachvili, A. M. Craig, and D. A. Ramsay, J. Mol. Spectrosc. 105, 156 (1984)

Chang, Chih-Hsuan; Roberts, Melanie A.; Nesbitt, David J.

2013-06-01

419

High-quality source of fiber-coupled polarization-entangled photons at 1.56 [mu]m  

E-print Network

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 ...

Stelmakh, Veronika

2012-01-01

420

High-throughput platform for real-time monitoring of biological processes by multicolor single-molecule fluorescence  

PubMed Central

Zero-mode waveguides provide a powerful technology for studying single-molecule real-time dynamics of biological systems at physiological ligand concentrations. We customized a commercial zero-mode waveguide-based DNA sequencer for use as a versatile instrument for single-molecule fluorescence detection and showed that the system provides long fluorophore lifetimes with good signal to noise and low spectral cross-talk. We then used a ribosomal translation assay to show real-time fluidic delivery during data acquisition, showing it is possible to follow the conformation and composition of thousands of single biomolecules simultaneously through four spectral channels. This instrument allows high-throughput multiplexed dynamics of single-molecule biological processes over long timescales. The instrumentation presented here has broad applications to single-molecule studies of biological systems and is easily accessible to the biophysical community. PMID:24379388

Chen, Jin; Dalal, Ravindra V.; Petrov, Alexey N.; Tsai, Albert; O'Leary, Sean E.; Chapin, Karen; Cheng, Janice; Ewan, Mark; Hsiung, Pei-Lin; Lundquist, Paul; Turner, Stephen W.; Hsu, David R.; Puglisi, Joseph D.

2014-01-01