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1

Probing polar molecules with high harmonic spectroscopy.  

PubMed

We bring the methodology of orienting polar molecules together with the phase sensitivity of high harmonic spectroscopy to experimentally compare the phase difference of attosecond bursts of radiation emitted upon electron recollision from different ends of a polar molecule. This phase difference has an impact on harmonics from aligned polar molecules, suppressing emission from the molecules parallel to the driving laser field while favoring the perpendicular ones. For oriented molecules, we measure the amplitude ratio of even to odd harmonics produced when intense light irradiates CO molecules and determine the degree of orientation and the phase difference of attosecond bursts using molecular frame ionization and recombination amplitudes. The sensitivity of the high harmonic spectrum to subtle phase differences in the emitted radiation makes it a detailed probe of polar molecules and will drive major advances in the theory of high harmonic generation. PMID:23368205

Frumker, E; Kajumba, N; Bertrand, J B; W鰎ner, H J; Hebeisen, C T; Hockett, P; Spanner, M; Patchkovskii, S; Paulus, G G; Villeneuve, D M; Naumov, A; Corkum, P B

2012-12-01

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

Qubit-induced high-order nonlinear interaction of the polar molecules in a stripline cavity  

SciTech Connect

By the exchange of virtual microwave photon induced by a stripline cavity, we present a collective spin-qubit model for the indirect interaction between a superconducting charge-phase qubit and an ensemble of the polar molecules. More importantly, the high-order nonlinear interaction among the polar molecules is generated successfully by using the SU(2) commutation relations of the qubit. Numerical simulation shows that this high-order nonlinear interaction can lead to a strong macroscopic quantum coherent effect, even if the parameters including the molecular number are small. For a large molecular number, the Kerr nonlinear interaction is also obtained. Moreover, it is found that this Kerr nonlinear parameter depends linearly on the molecular number, and as a result, has a giant value, which is 2 to 3 orders of magnitude larger than that in the other proposal schemes of the solid-state systems. Our results present a way to investigate the quantum nonlinear dynamics of the polar molecules.

Chen Gang [State Key Laboratory of Quantum Optics and Quantum Optics Devices, Shanxi University, Taiyuan 030006 (China); Department of Physics, Shaoxing University, Shaoxing 312000 (China); Zhang Hao; Yang Yonggang; Xiao Liantuan; Jia Suotang [State Key Laboratory of Quantum Optics and Quantum Optics Devices, Shanxi University, Taiyuan 030006 (China); Wang Rui [Department of Physics, Zhejiang Ocean University, ZhouShan 316000 (China)

2010-07-15

4

Properties of water Polar molecule  

E-print Network

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

Cochran-Stafira, D. Liane

5

Laser-based circular dichroism detection of molecules in flowing liquid systems using high frequency polarization modulation  

NASA Astrophysics Data System (ADS)

A highly sensitive laser-based circular dichroism detector for flowing liquid systems, specifically liquid chromatography, is presented. Both transmission and fluorescence detected circular dichroism were developed. High frequency polarization modulation was used to reduce laser amplitude noise. Detection selectivity was demonstrated since optically inactive, yet absorbing, molecules do not produce an appreciable detector response. Riboflavin was detected at sub-ng levels, with optical activity information.

Synovec, Robert E.; Yeung, Edward S.

1987-09-01

6

Probing the origin of elliptical high-order harmonic generation from aligned molecules in linearly polarized laser fields  

SciTech Connect

A recent experiment [Phys. Rev. Lett. 102, 073902 (2009)] has demonstrated that elliptically polarized high-order harmonic generation can be produced from linearly polarized driving fields for aligned molecular systems. In order to reveal the underlying physical mechanisms of elliptical harmonics, we present fully ab initio and high-precision calculations and analyses of the amplitude, phase, and polarization state of the harmonic radiation from molecular hydrogen ions with arbitrary orientation. We find that high ellipticity arises from molecular orbital symmetry and two-center interference effects. Our ab initio exploration and findings lead to a general rule that the ellipticity becomes high for molecular orbitals represented by a symmetric combination of atomic orbitals, whereas it becomes low for molecular orbitals represented by an antisymmetric combination. This finding also applies to the general case of aligned linear molecules.

Son, Sang-Kil [Department of Chemistry, University of Kansas, Lawrence, Kansas 66045 (United States); Telnov, Dmitry A. [Department of Physics, St. Petersburg State University, St. Petersburg 198504 (Russian Federation); Chu, Shih-I. [Department of Chemistry, University of Kansas, Lawrence, Kansas 66045 (United States); Center for Quantum Science and Engineering, Department of Physics, National Taiwan University, Taipei 10617, Taiwan (China)

2010-10-15

7

Adiabatic cooling for cold polar molecules on a chip using a controllable high-efficiency electrostatic surface trap  

NASA Astrophysics Data System (ADS)

We propose a controllable high-efficiency electrostatic surface trap for cold polar molecules on a chip by using two insulator-embedded charged rings and a grounded conductor plate. We calculate Stark energy structure pattern of ND3 molecules in an external electric field using the method of matrix diagonalization. We analyze how the voltages that are applied to the ring electrodes affect the depth of the efficient well and the controllability of the distance between the trap center and the surface of the chip. To obtain a better understanding, we simulate the dynamical loading and trapping processes of ND3 molecules in a |J,KM> = |1, ? 1> state by using classical Monte桟arlo method. Our study shows that the loading efficiency of our trap can reach ~ 88%. Finally, we study the adiabatic cooling of cold molecules in our surface trap by linearly lowering the potential-well depth (i.e., lowering the trapping voltage), and find that the temperature of the trapped ND3 molecules can be adiabatically cooled from 34.5 mK to ~ 5.8 mK when the trapping voltage is reduced from ?35 kV to ?3 kV.

Li, Sheng-Qiang; Xu, Liang; Xia, Yong; Wang, Hai-Ling; Yin, Jian-Ping

2014-12-01

8

Formation and analysis of ultracold polar molecules  

NASA Astrophysics Data System (ADS)

Alkali hydride molecules are polar, exhibiting large ground-state dipole moments. As ultracold sources of alkali atoms, as well as hydrogen, have been created in the laboratory, we explore theoretically the feasibility of forming such molecules from a mixture of the ultracold atomic gases, employing various photoassociation schemes. In this work we use lithium and sodium hydride as benchmark systems to calculate molecule formation rates through stimulated one-photon radiative association directly from the continuum as well as two-photon stimulated radiative association (Raman transfer) and excitation to bound levels of an excited state followed by spontaneous emission to the ground state. Using accurate molecular potential energy curves and dipole transition moments and with laser intensities and MOT densities that are easily attainable experimentally, we have found that substantial molecule formation rates can be realized even after the effect of back-stimulation has been accounted for. We examine the spontaneous emission cascade which takes place from the upper vibrational levels of the singlet ground state on a time scale of milliseconds. Because photon emission in the cascade process does not contribute to trap loss, a sizable population of molecules in the lowest vibrational level can be achieved. The triplet ground electronic state is of particular interest for experimental efforts since, although it has never been observed experimentally, molecular structure calculations of the a3Sigma+ state for LiH and NaH predict a small van der Waals attraction, with a potential energy well so shallow that it can support only one bound rotational-vibrational level. Any molecule formed in the triplet ground state would then be immediately in the lowest and most stable level of that state and would be quite long-lived, unlike molecules in high vibrational levels which have significantly shorter lifetimes. As an analysis of our method of calculating molecule formation rates, we investigate more thoroughly the two-photon stimulated photoassociation process by employing the exact treatment of Dalgarno & Lewis to solve the Raman scattering problem.

Juarros, Elizabeth Ann

9

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

10

Optical Production of Ultracold Polar Molecules  

SciTech Connect

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

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

2005-05-27

11

Opto-Electrical Cooling of Polar Molecules  

E-print Network

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

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

2009-04-27

12

Direct absorption imaging of ultracold polar molecules  

E-print Network

We demonstrate a scheme for direct absorption imaging of an ultracold ground-state polar molecular gas near quantum degeneracy. A challenge in imaging molecules is the lack of closed optical cycling transitions. Our technique relies on photon shot-noise limited absorption imaging on a strong bound-bound molecular transition. We present a systematic characterization of this imaging technique. Using this technique combined with time-of-flight (TOF) expansion, we demonstrate the capability to determine momentum and spatial distributions for the molecular gas. We anticipate that this imaging technique will be a powerful tool for studying molecular quantum gases.

D. Wang; B. Neyenhuis; M. H. G. de Miranda; K. -K. Ni; S. Ospelkaus; D. S. Jin; J. Ye

2010-03-12

13

Rotational correlation time of polar molecules  

E-print Network

~B "~' "'?&' '!~?~? '?) gsT [50] AB 18 AH 0- 1'1!A + In ! in n!, ? [51] 1 fs ft!e!'. &o&;!e; i ?f ". i, erfi. oi mose&. ! |e B about its center of mass B '' '' *' m is thc n& ', . of ¬e(. "a&e A! m xs in?uu:~i! of in:i!? ~fe B I is tn!e &x??r&er&f of inertia... January 19B3 Major Field Physics ROTAT1ONAL CORRELATiON 'llME OF POLAR MOLECULE S A Thesis by Carl Wayne Allen Approved as to style and content by: [Chairman of Committee] ead f Department or Student Advisor, ' January 1963 TABI E OF CONTENTS...

Allen, Carl Wayne

1963-01-01

14

Transport of polar molecules by an alternating-gradient guide  

NASA Astrophysics Data System (ADS)

An alternating-gradient electric guide provides a way to transport a wide variety of polar molecules, including those in high-field-seeking states. We investigate the motion of polar molecules in such a guide by measuring the transmission of CaF molecules in their high-field-seeking ground state, with the guide operating at a variety of switching frequencies and voltages. We model the guide using analytical and numerical techniques and compare the predictions of these models to the experimental results and to one another. The analytical results are approximate but provide simple and useful estimates for the maximum phase-space acceptance of the guide and for the switching frequency required. The numerical methods provide more accurate results over the full range of switching frequencies. Our investigation shows that, even when the fields are static, some high-field-seeking molecules are able to pass through the guide on metastable trajectories. We show that the maximum possible transmission requires accurate alignment within the guide and between the guide and detector.

Wall, T. E.; Armitage, S.; Hudson, J. J.; Sauer, B. E.; Dyne, J. M.; Hinds, E. A.; Tarbutt, M. R.

2009-10-01

15

Continuous centrifuge decelerator for polar molecules.  

PubMed

Producing large samples of slow molecules from thermal-velocity ensembles is a formidable challenge. Here we employ a centrifugal force to produce a continuous molecular beam with a high flux at near-zero velocities. We demonstrate deceleration of three electrically guided molecular species, CH3F, CF3H, and CF3CCH, with input velocities of up to 200??m?s(-1) to obtain beams with velocities below 15??m?s(-1) and intensities of several 10(9)??mm(-2)?s(-1). The centrifuge decelerator is easy to operate and can, in principle, slow down any guidable particle. It has the potential to become a standard technique for continuous deceleration of molecules. PMID:24483892

Chervenkov, S; Wu, X; Bayerl, J; Rohlfes, A; Gantner, T; Zeppenfeld, M; Rempe, G

2014-01-10

16

Molecular polarizability in quantum defect theory: polar molecules  

SciTech Connect

The reduced-added Green's function technique in the quantum defect theory combines the advantages of analytical and ab initio methods in calculating frequency-dependent (dynamic) polarizabilities of atoms and molecules, providing an exact account for the high-excited and continuum electronic states. In the present paper this technique is modified to take into account the long-range dipole potential of a polar molecule core. The method developed is applied to calculation of the dynamic polarizability tensors of alkali-metal hydrides LiH and NaH as well as to some fluorides (CaF and BF) in the frequency range up to the first resonances. The results are in good agreement with ab initio calculations available for some frequencies.

Akindinova, E. V.; Chernov, V. E.; Kretinin, I. Yu.; Zon, B. A. [Voronezh State University, Voronezh RU-394693 (Russian Federation)

2010-04-15

17

Single-molecule orientational wave packet in ultrafast optical polarization  

NASA Astrophysics Data System (ADS)

The explicit derivation of the ultrafast optical polarization of a single molecule is presented. It is shown that an orientational wave packet carried by the excited molecular electron can provide a sharp definition for the space configuration of the laser-molecule interaction.

Mainos, C.

2006-09-01

18

Enantiospecific spin polarization of electrons photoemitted through layers of homochiral organic molecules.  

PubMed

Electrons photoemitted through layers of purely organic chiral molecules become strongly spin-polarized even at room temperature and for double-monolayer thicknesses. The substitution of one enantiomer for its mirror image does not revert the sign of the spin polarization, rather its direction in space. These findings might lead to the obtention of highly efficient spin filters for spintronic applications. PMID:25183637

Ni駉, Miguel 羘gel; Kowalik, Iwona Agnieszka; Luque, Francisco Jes鷖; Arvanitis, Dimitri; Miranda, Rodolfo; de Miguel, Juan Jos

2014-11-01

19

Energy dependence of scattering ground-state polar molecules  

SciTech Connect

We explore the total collisional cross section of ground-state polar molecules in an electric field at various energies, focusing on RbCs and RbK. An external electric field polarizes the molecules and induces strong dipolar interactions, leading to nonzero partial waves contributing to the scattering even as the collision energy goes to zero. This results in the need to compute scattering problems with many different values of total M to converge the total cross section. An accurate and efficient approximate total cross section is introduced and used to study the low-field temperature dependence. To understand the scattering of the polar molecules we compare a semiclassical cross section with the quantum unitarity limit. This comparison leads to the ability to characterize the scattering based on the value of the electric field and the collision energy. General and simple forms of the characteristic electric field and energy are given, enabling characterization of the scattering.

Ticknor, Christopher [ARC Centre of Excellence for Quantum-Atom Optics and Centre for Atom Optics and Ultrafast Spectroscopy, Swinburne University of Technology, Hawthorn, Victoria 3122 (Australia)

2007-11-15

20

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

21

Manufacturing a thin wire electrostatic trap for ultracold polar molecules  

SciTech Connect

We present a detailed description on how to build a thin wire electrostatic trap (TWIST) for ultracold polar molecules. It is the first design of an electrostatic trap that can be superimposed directly onto a magneto-optical trap (MOT). We can thus continuously produce ultracold polar molecules via photoassociation from a two species MOT and instantaneously trap them in the TWIST without the need for complex transfer schemes. Despite the spatial overlap of the TWIST and the MOT, the two traps can be operated and optimized completely independently due to the complementary nature of the utilized trapping mechanisms.

Kleinert, J.; Haimberger, C.; Zabawa, P. J.; Bigelow, N. P. [Department of Physics and Astronomy and Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14627 (United States)

2007-11-15

22

Electrostatic model for treating long-range lateral interactions between polar molecules adsorbed on metal surfaces  

NASA Astrophysics Data System (ADS)

A classical polarizable point-dipole model for the adsorption of polar molecules on metal surfaces is presented. The main usefulness of the model is that lattice sums are represented by simple functions in closed form. This allows a simple extrapolation of adsorption energies of polar molecules梐s calculated by first-principles calculations employing periodic boundary conditions梩o the zero-coverage limit. Such an extrapolation is rather important for the proper evaluation of adsorption energy of highly polar molecules, because their long-range lateral interactions can extend beyond the nearest-neighbor distances of 50 bohrs. Moreover, the dependence of the adsorption energy on the orientation and configuration of molecular dipoles can be straightforwardly analyzed. It is demonstrated that an accumulation of polar molecules on the surface is favored provided that the molecular dipoles point parallel to the surface in the adsorbed state, whereas adsorbed molecules displaying dipoles oriented perpendicular to the surface would prefer to stay well separated due to repulsive lateral interactions. Further, the model is used to analyze the density-functional theory (DFT) calculated data of two polar molecules, triazole and benzotriazole, adsorbed onto Cu(111) surface. The DFT-calculated adsorption energies are about -0.5 eV, and it is shown that the main contribution to the molecule-surface bonding comes from the dipole-dipole electrostatic interactions.

Kokalj, Anton

2011-07-01

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

Feasibility of a synchrotron storage ring for neutral polar molecules  

Microsoft Academic Search

Using calculations and mathematical modeling, we demonstrate the feasibility of constructing a synchrotron storage ring for neutral polar molecules. The lattice is a racetrack type 3.6 m in circumference consisting of two 180 arcs, six bunchers, and two long straight sections. Each straight section contains two triplet focusing lenses and space for beam injection and experiments. The design also includes

Hiroshi Nishimura; Glen Lambertson; Juris G. Kalnins; Harvey Gould

2003-01-01

25

Electrostatic surface trap for cold polar molecules on a chip  

NASA Astrophysics Data System (ADS)

We propose a simple scheme for trapping cold polar molecules in low-field seeking states on the surface of a chip by using a grounded metal plate and two finite-length charged wires that half embanked in an insulating substrate, calculate the electric field distributions generated by our charged-wire layout in free space and the corresponding Stark potentials for ND3 molecules, and analyze the dependence of the trapping center position on the geometric parameters. Moreover, the loading and trapping processes of cold ND3 molecules are studied by using the Monte Carlo method. Our study shows that the loading efficiency of the trap scheme can reach 11.5%, and the corresponding temperature of the trapped cold molecules is about 26.4 mK.

Wang, Qin; Li, Sheng-Qiang; Hou, Shun-Yong; Xia, Yong; Wang, Hai-Ling; Yin, Jian-Ping

2014-01-01

26

High Energy Polarized Electron Beams  

SciTech Connect

In nearly all high energy electron storage rings the effect of beam polarization by synchrotron radiation has been measured. The buildup time for polarization in storage rings is of the order of 10{sup 6} to 10{sup 7} revolutions; the spins must remain aligned over this time in order to avoid depolarization. Even extremely small spin deviations per revolution can add up and cause depolarization. The injection and acceleration of polarized electrons in linacs is much easier. Although some improvements are still necessary, reliable polarized electron sources with sufficiently high intensity and polarization are available. With the linac-type machines SLC at Stanford and CEBAF in Virginia, experiments with polarized electrons will be possible.

Robert Rossmanith

1987-05-01

27

Model Independence in Two Dimensions and Polarized Cold Dipolar Molecules  

SciTech Connect

We calculate the energy and wave functions of two particles confined to two spatial dimensions interacting via arbitrary anisotropic potentials with negative or zero net volume. The general rigorous analytic expressions are given in the weak coupling limit where universality or model independence are approached. The monopole part of anisotropic potentials is crucial in the universal limit. We illustrate the universality with a system of two arbitrarily polarized cold dipolar molecules in a bilayer. We discuss the transition to universality as a function of polarization and binding energy and compare analytic and numerical results obtained by the stochastic variational method. The universal limit is essentially reached for experimentally accessible strengths.

Volosniev, A. G.; Fedorov, D. V.; Jensen, A. S.; Zinner, N. T. [Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C (Denmark)

2011-06-24

28

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

29

Polar molecule reactive collisions in quasi-1D systems  

NASA Astrophysics Data System (ADS)

We study polar molecule scattering in quasi-one-dimensional geometries. Elastic and reactive collision rates are computed as a function of collision energy and electric dipole moment for different confinement strengths. The numerical results are interpreted in terms of first order scattering and of adiabatic models. Universal dipolar scattering is also discussed. Our results are relevant to experiments where control of the collision dynamics through one-dimensional confinement and an applied electric field is envisioned.

Simoni, A.; Srinivasan, S.; Launay, J.-M.; Jachymski, K.; Idziaszek, Z.; Julienne, P. S.

2015-01-01

30

High intensity polarized electron sources  

SciTech Connect

The status of the polarized electron source development program at SLAC will be reviewed. Emission currents of 60 A, corresponding to a space charge limited current density of 180 A/cm/sup 2/, have been obtained from GaAs photocathodes. Electron beam polarization 20% greater than that obtainable from GaAs cathodes has been observed from multilayer GaAs-GaAlAs structures. Work in progress to produce high beam polarization from II-IV-V/sub 2/ chalcopyrite photocathodes will also be described.

Sinclair, C.K.

1980-10-01

31

Three-body interactions with cold polar molecules  

E-print Network

We show that polar molecules driven by microwave fields give naturally rise to strong three-body interactions, while the two-particle interaction can be independently controlled and even switched off. The derivation of these effective interaction potentials is based on a microscopic understanding of the underlying molecular physics, and follows from a well controlled and systematic expansion into many-body interaction terms. For molecules trapped in an optical lattice, we show that these interaction potentials give rise to Hubbard models with strong nearest-neighbor two-body and three-body interaction. As an illustration, we study the one-dimensional Bose-Hubbard model with dominant three-body interaction and derive its phase diagram.

H. P. B點hler; A. Micheli; P. Zoller

2007-03-26

32

Application of ex situ dynamic nuclear polarization in studying small molecules.  

PubMed

Dynamic nuclear polarization (DNP) has become an attractive technique to boost the sensitivity of NMR experiments. In the case of ex situ polarizations two-dimensional (2D) spectra are limited by the short lifetime of the polarization after dissolution and sample transfer to a high field NMR magnet. This limitation can be overcome by various approaches. Here we show how the use of (13)C-labelled acetyl tags can help to obtain 2D-HMQC spectra for many small molecules, owing to a nuclear Overhauser enhancement between (13)C spins originating from the long-lived carbonyl carbon, which extends the lifetimes of other (13)C spins with shorter longitudinal relaxation times. We also show an alternative approach of using an optimized polarization matrix. PMID:20454737

Ludwig, Christian; Marin-Montesinos, Ildefonso; Saunders, Martin G; Emwas, Abdul-Hamid; Pikramenou, Zoe; Hammond, Stephen P; G黱ther, Ulrich L

2010-06-14

33

High Frequency Dynamic Nuclear Polarization  

PubMed Central

Conspectus During the three decades 19802010, magic angle spinning (MAS) NMR developed into the method of choice to examine many chemical, physical and biological problems. In particular, a variety of dipolar recoupling methods to measure distances and torsion angles can now constrain molecular structures to high resolution. However, applications are often limited by the low sensitivity of the experiments, due in large part to the necessity of observing spectra of low-? nuclei such as the I = species 13C or 15N. The difficulty is still greater when quadrupolar nuclei, like 17O or 27Al, are involved. This problem has stimulated efforts to increase the sensitivity of MAS experiments. A particularly powerful approach is dynamic nuclear polarization (DNP) which takes advantage of the higher equilibrium polarization of electrons (which conventionally manifests in the great sensitivity advantage of EPR over NMR). In DNP, the sample is doped with a stable paramagnetic polarizing agent and irradiated with microwaves to transfer the high polarization in the electron spin reservoir to the nuclei of interest. The idea was first explored by Overhauser and Slichter in 1953. However, these experiments were carried out on static samples, at magnetic fields that are low by current standards. To be implemented in contemporary MAS NMR experiments, DNP requires microwave sources operating in the subterahertz regime roughly 150660 GHz and cryogenic MAS probes. In addition, improvements were required in the polarizing agents, because the high concentrations of conventional radicals that are required to produce significant enhancements compromise spectral resolution. In the last two decades scientific and technical advances have addressed these problems and brought DNP to the point where it is achieving wide applicability. These advances include the development of high frequency gyrotron microwave sources operating in the subterahertz frequency range. In addition, low temperature MAS probes were developed that permit in-situ microwave irradiation of the samples. And, finally, biradical polarizing agents were developed that increased the efficiency of DNP experiments by factors of ~4 at considerably lower paramagnet concentrations. Collectively these developments have made it possible to apply DNP on a routine basis to a number of different scientific endeavors, most prominently in the biological and material sciences. This Account reviews these developments, including the primary mechanisms used to transfer polarization in high frequency DNP, and the current choice of microwave sources and biradical polarizing agents. In addition, we illustrate the utility of the technique with a description of applications to membrane and amyloid proteins that emphasizes the unique structural information that is available in these two cases. PMID:23597038

Ni, Qing Zhe; Daviso, Eugenio; Can, Thach V.; Markhasin, Evgeny; Jawla, Sudheer K.; Swager, Timothy M.; Temkin, Richard J.; Herzfeld, Judith; Griffin, Robert G.

2013-01-01

34

Deterministically Polarized Fluorescence from Single Dye Molecules Aligned in Liquid Crystal Host  

SciTech Connect

We demonstrated for the first time to our konwledge deterministically polarized fluorescence from single dye molecules. Planar aligned nematic liquid crystal hosts provide deterministic alignment of single dye molecules in a preferred direction.

Lukishova, S.G.; Schmid, A.W.; Knox, R.; Freivald, P.; Boyd, R. W.; Stroud, Jr., C. R.; Marshall, K.L.

2005-09-30

35

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

36

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

PubMed Central

Fluorescence polarization measurements in the condensed phase provide rich information on rotational dynamics and interactions between macromolecules. An important parameter in these studies is the limiting polarization or po which is the emission polarization in the absence of molecular rotation. Here we explore how molecular number averaging affects the observed value of po. Using a simple mathematical model we show that for a collection of fluorescent dipoles (150 molecules) the fluorescence polarization (p) increases with the number of molecules (N) due to the progressive onset of photo-selection with a relation of the form p = po(1 ? N??). This concept is demonstrated experimentally using single molecule polarization measurements of perylene diimide dye molecules in a rigid polymer matrix where it is shown that the average emission polarization increases significantly when the number of molecules per averaging window is increased from 1 to 10 molecules. These results suggest that the definition of limiting polarization needs to be refined in the quasi-single molecule regime. Moreover, these results pave a new way for measuring clustering of molecules from single cluster polarization histograms. PMID:25640875

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

2015-01-01

37

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

PubMed

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

Bell, Toby D M; Clayton, Andrew H A

2015-01-01

38

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

SciTech Connect

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

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

2010-12-15

39

Giant polarization in high polymers  

NASA Astrophysics Data System (ADS)

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

Pohl, Herbert A.

1986-07-01

40

Detection of bio-molecules of different polarities by Boron Nitride Nanotoube  

NASA Astrophysics Data System (ADS)

The effect of molecular polarity on the interaction between a boron nitride nanotube (BNNT) and amino acids is investigated with density functional theory. Three representative amino acids, namely, tryptophane (Trp), a nonpolar aromatic amino acid, and asparatic acid (Asp) and argenine (Arg), both polar amino acids are considered for their interactions with BNNT. The polar molecules, Asp and Arg, exhibit relatively stronger binding with the tubular surface of BNNT. The binding between the polar amino acid molecules and BNNT is accompanied by a charge transfer, suggesting that stabilization of the bioconjugated complex is mainly governed by electrostatic interactions. The results show modulation of the BNNT band gap by Trp. Interestingly, no change in band gap of BNNT is seen for the polar molecules Asp and Arg. The predicted higher sensitivity of BNNTs compared to carbon nanotubes (CNTs) toward amino acid polarity suggests BNNTs to be a better substrate for protein immobilization than CNTs.

Mukhopadhyay, Saikat; Scheicher, Ralph; Pandey, Ravindra; Karna, Shashi

2012-02-01

41

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

SciTech Connect

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

Engels, Ralf, E-mail: r.w.engels@fz-juelich.de; Gorski, Robert; Grigoryev, Kiril; Mikirtychyants, Maxim; Rathmann, Frank; Seyfarth, Hellmut; Str鰄er, Hans; Weiss, Philipp [Institut f黵 Kernphysik, Forschungszentrum J黮ich, Wilhelm-Johnen-Str. 1, 52428 J黮ich (Germany); Kochenda, Leonid; Kravtsov, Peter; Trofimov, Viktor; Tschernov, Nikolay; Vasilyev, Alexander; Vznuzdaev, Marat [Laboratory of Cryogenic and Superconductive Technique, Petersburg Nuclear Physics Institute, Orlova Roscha 1, 188300 Gatchina (Russian Federation); Schieck, Hans Paetz gen. [Institut f黵 Kernphysik, Universit鋞 zu K鰈n, Z黮picher Str. 77, 50937 K鰈n (Germany)

2014-10-15

42

High efficiency reflective liquid crystal polarization gratings  

Microsoft Academic Search

We experimentally demonstrate a reflective-mode liquid crystal polarization grating with high reflectance, small grating period, and subms switching times. This switchable optical element can diffract ~100% into a single order, have highly polarization-sensitive first orders, and have a polarization-insensitive zero order. Here we introduce an absorbing layer that overcomes the reflection of the (ultraviolet) holographic beams, which otherwise prevents high

R. K. Komanduri; M. J. Escuti

2009-01-01

43

High efficiency reflective liquid crystal polarization gratings  

Microsoft Academic Search

We experimentally demonstrate a reflective-mode liquid crystal polarization grating with high reflectance, small grating period, and subms switching times. This switchable optical element can diffract ?100% into a single order, have highly polarization-sensitive first orders, and have a polarization-insensitive zero order. Here we introduce an absorbing layer that overcomes the reflection of the (ultraviolet) holographic beams, which otherwise prevents high

R. K. Komanduri; M. J. Escuti

2009-01-01

44

Electrostatic model for treating long-range lateral interactions between polar molecules adsorbed on metal surfaces  

Microsoft Academic Search

A classical polarizable point-dipole model for the adsorption of polar molecules on metal surfaces is presented. The main usefulness of the model is that lattice sums are represented by simple functions in closed form. This allows a simple extrapolation of adsorption energies of polar molecules---as calculated by first-principles calculations employing periodic boundary conditions---to the zero-coverage limit. Such an extrapolation is

Anton Kokalj

2011-01-01

45

Observation of dipolar spin-exchange interactions with lattice-confined polar molecules.  

PubMed

With the production of polar molecules in the quantum regime, long-range dipolar interactions are expected to facilitate understanding of strongly interacting many-body quantum systems and to realize lattice spin models for exploring quantum magnetism. In ordinary atomic systems, where contact interactions require wavefunction overlap, effective spin interactions on a lattice can be mediated by tunnelling, through a process referred to as superexchange; however, the coupling is relatively weak and is limited to nearest-neighbour interactions. In contrast, dipolar interactions exist even in the absence of tunnelling and extend beyond nearest neighbours. This allows coherent spin dynamics to persist even for gases with relatively high entropy and low lattice filling. Measured effects of dipolar interactions in ultracold molecular gases have been limited to the modification of inelastic collisions and chemical reactions. Here we use dipolar interactions of polar molecules pinned in a three-dimensional optical lattice to realize a lattice spin model. Spin is encoded in rotational states of molecules that are prepared and probed by microwaves. Resonant exchange of rotational angular momentum between two molecules realizes a spin-exchange interaction. The dipolar interactions are apparent in the evolution of the spin coherence, which shows oscillations in addition to an overall decay of the coherence. The frequency of these oscillations, the strong dependence of the spin coherence time on the lattice filling factor and the effect of a multipulse sequence designed to reverse dynamics due to two-body exchange interactions all provide evidence of dipolar interactions. Furthermore, we demonstrate the suppression of loss in weak lattices due to a continuous quantum Zeno mechanism. Measurements of these tunnelling-induced losses allow us to determine the lattice filling factor independently. Our work constitutes an initial exploration of the behaviour of many-body spin models with direct, long-range spin interactions and lays the groundwork for future studies of many-body dynamics in spin lattices. PMID:24048478

Yan, Bo; Moses, Steven A; Gadway, Bryce; Covey, Jacob P; Hazzard, Kaden R A; Rey, Ana Maria; Jin, Deborah S; Ye, Jun

2013-09-26

46

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

47

Trapping of Ultracold Polar Molecules with a Thin-Wire Electrostatic Trap  

SciTech Connect

We describe the realization of a dc electric-field trap for ultracold polar molecules, the thin-wire electrostatic trap (TWIST). The thin wires that form the electrodes of the TWIST allow us to superimpose the trap onto a magneto-optical trap (MOT). In our experiment, ultracold polar NaCs molecules in their electronic ground state are created in the MOT via photoassociation, achieving a continuous accumulation in the TWIST of molecules in low-field seeking states. Initial measurements show that the TWIST trap lifetime is limited only by the background pressure in the chamber.

Kleinert, J.; Haimberger, C.; Zabawa, P. J.; Bigelow, N. P. [Department of Physics and Astronomy, and The Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14627 (United States)

2007-10-05

48

Circular-polarization-sensitive metamaterial based on triple-quantum-dot molecules.  

PubMed

We propose a new type of chiral metamaterial based on an ensemble of artificial molecules formed by three identical quantum dots in a triangular arrangement. A static magnetic field oriented perpendicular to the plane breaks mirror symmetry, rendering the molecules sensitive to the circular polarization of light. By varying the orientation and magnitude of the magnetic field one can control the polarization and frequency of the emission spectrum. We identify a threshold frequency ?, above which we find strong birefringence. In addition, Kerr rotation and circular-polarized lasing action can be implemented. We investigate the single-molecule lasing properties for different energy-level arrangements and demonstrate the possibility of circular-polarization conversion. Finally, we analyze the effect of weak stray electric fields or deviations from the equilateral triangular geometry. PMID:25526146

Kotetes, Panagiotis; Jin, Pei-Qing; Marthaler, Michael; Sch鰊, Gerd

2014-12-01

49

Circular-Polarization-Sensitive Metamaterial Based on Triple-Quantum-Dot Molecules  

NASA Astrophysics Data System (ADS)

We propose a new type of chiral metamaterial based on an ensemble of artificial molecules formed by three identical quantum dots in a triangular arrangement. A static magnetic field oriented perpendicular to the plane breaks mirror symmetry, rendering the molecules sensitive to the circular polarization of light. By varying the orientation and magnitude of the magnetic field one can control the polarization and frequency of the emission spectrum. We identify a threshold frequency ? , above which we find strong birefringence. In addition, Kerr rotation and circular-polarized lasing action can be implemented. We investigate the single-molecule lasing properties for different energy-level arrangements and demonstrate the possibility of circular-polarization conversion. Finally, we analyze the effect of weak stray electric fields or deviations from the equilateral triangular geometry.

Kotetes, Panagiotis; Jin, Pei-Qing; Marthaler, Michael; Sch鰊, Gerd

2014-12-01

50

Saturated Orientational Polarization of Polar Molecules in Giant Electrorheological Fluids P. Tan, W. J. Tian, X. F. Wu, J. Y. Huang, L. W. Zhou,* and J. P. Huang*  

E-print Network

of these ER fluids violate the induced polarization model of dielectric ER fluids. These PMER particles wereSaturated Orientational Polarization of Polar Molecules in Giant Electrorheological Fluids P. Tan 27, 2008; ReVised Manuscript ReceiVed: May 9, 2009 Many researches on polar

Huang, Ji-Ping

51

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

52

Prospects for ultracold polar and magnetic chromium-closed-shell-atom molecules  

E-print Network

The properties of the electronic ground state of the polar and paramagnetic chromium--closed-shell-atom molecules have been investigated. State-of-the-art \\textit{ab initio} techniques have been applied to compute the potential energy curves for the chromium--alkaline-earth-metal-atom, CrX (X = Be, Mg, Ca, Sr, Ba), and chromium--ytterbium, CrYb, molecules in the Born-Oppenheimer approximation for the $X^7\\Sigma^+$ 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 Douglas-Kroll-Hess Hamiltonian or 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 interatomic distances, $C_6$, are also reported. Molecules under investigation are an example of species p...

Tomza, Micha?

2013-01-01

53

Spin-polarized transport through single-molecule magnet Mn6 complexes  

NASA Astrophysics Data System (ADS)

The coherent transport properties of a device, constructed by sandwiching a Mn6 single-molecule magnet between two gold surfaces, are studied theoretically by using the non-equilibrium Green's function approach combined with density functional theory. Two spin states of such Mn6 complexes are explored, namely the ferromagnetically coupled configuration of the six MnIII cations, leading to the S = 12 ground state, and the low S = 4 spin state. For voltages up to 1 volt the S = 12 ground state shows a current one order of magnitude larger than that of the S = 4 state. Furthermore this is almost completely spin-polarized, since the Mn6 frontier molecular orbitals for S = 12 belong to the same spin manifold. As such the high-anisotropy Mn6 molecule appears as a promising candidate for implementing, at the single molecular level, both spin-switches and low-temperature spin-valves.The coherent transport properties of a device, constructed by sandwiching a Mn6 single-molecule magnet between two gold surfaces, are studied theoretically by using the non-equilibrium Green's function approach combined with density functional theory. Two spin states of such Mn6 complexes are explored, namely the ferromagnetically coupled configuration of the six MnIII cations, leading to the S = 12 ground state, and the low S = 4 spin state. For voltages up to 1 volt the S = 12 ground state shows a current one order of magnitude larger than that of the S = 4 state. Furthermore this is almost completely spin-polarized, since the Mn6 frontier molecular orbitals for S = 12 belong to the same spin manifold. As such the high-anisotropy Mn6 molecule appears as a promising candidate for implementing, at the single molecular level, both spin-switches and low-temperature spin-valves. Electronic supplementary information (ESI) available: Calculated total and projected density of states of an isolated [Mn6O2(Et-sao)6{O2CPh(Me)2}2(EtOH)6] original SMM complex (Fig. S1). Calculated total and projected density of states of an isolated [Mn6O2(Me-sao)6{O2CPh(SH)}2(MeOH)6] model complex (Fig. S2). Transmission spectra calculated at different voltages corresponding to the S = 12 and S = 4 ground states for the Mn6-Au(111) layer system (Fig. S3). Cell parameters and Cartesian coordinates of the Mn6-Au(111) layer system. See DOI: 10.1039/c3nr00054k

Cremades, Eduard; Pemmaraju, C. D.; Sanvito, Stefano; Ruiz, Eliseo

2013-05-01

54

PROPERTIES OF RUBIDIUM-ARGON VAN DER WAALS MOLECULES FROM THE RELAXATION OF POLARIZED Rb ATOMS  

E-print Network

1075 PROPERTIES OF RUBIDIUM-ARGON VAN DER WAALS MOLECULES FROM THE RELAXATION OF POLARIZED Rb ATOMS pr茅sence d'argon entre 0,1 et 5 torrs. La relaxation est due principalement au couplage spin-rotation dans between 0.1and 10 G on opti- cally polarized Rb atoms in Argon at pressures ranging from 0.1to 5 torrs

Boyer, Edmond

55

Molecular dynamics simulations of water molecule-bridges in polar domains of humic acids.  

PubMed

The stabilizing effect of water molecule bridges on polar regions in humic substances (HSs) has been investigated by means of molecular dynamics (MD) simulations. The purpose of these investigations was to show the effect of water molecular bridges (WAMB) for cross-linking distant locations of hydrophilic groups. For this purpose, a tetramer of undecanoid fatty acids connected to a network of water molecules has been constructed, which serve as a model for spatially fixed aliphatic chains in HSs terminated by a polar (carboxyl) group. The effect of environmental polarity has been investigated by using solvents of low and medium polarity in force-field MD. A nonpolar environment simulated by n-hexane was chosen to mimic the stability of WAMB in a hydrophilic hotspot surrounded by a nonpolar environment, while the more polar acetonitrile environment was chosen to simulate a more even distribution of polarity around the carboxylic groups and the water molecules. The dynamics simulations show that the rigidity of the oligomer chains is significantly enhanced as soon as the water cluster is large enough to comprise all four carboxyl groups. Increasing the temperature leads to evaporization processes which destabilize the rigidity of the tetramer-water cluster. Embedding it into the nonpolar environment introduces a pronounced cage effect which significantly impedes removal of water molecules from the cluster region. On the other hand, a polar environment facilitates their diffusion from the polar region. One important consequence of these simulations is that although the local water network is the stabilizing factor for the organic matter matrix, the degree of stabilization is additionally affected by the presence of nonpolar surroundings. PMID:21863811

Aquino, Adelia J A; Tunega, Daniel; Pasali?, Hasan; Schaumann, Gabriele E; Haberhauer, Georg; Gerzabek, Martin H; Lischka, Hans

2011-10-01

56

High Energy Polarization of Blazars: Detection Prospects  

NASA Astrophysics Data System (ADS)

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

Chakraborty, N.; Pavlidou, V.; Fields, B. D.

2015-01-01

57

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

58

Managing light polarization via plasmonmolecule interactions within an asymmetric metal nanoparticle trimer  

PubMed Central

The interaction of light with metal nanoparticles leads to novel phenomena mediated by surface plasmon excitations. In this article 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. PMID:18927232

Shegai, Timur; Li, Zhipeng; Dadosh, Tali; Zhang, Zhenyu; Xu, Hongxing; Haran, Gilad

2008-01-01

59

High Energy Polarization of Blazars : Detection Prospects  

E-print Network

Emission from blazar jets in the ultraviolet, optical, and infrared is polarized. If these low-energy photons were inverse-Compton scattered, the upscattered high-energy photons retain a fraction of the polarization. Current and future X-ray and gamma-ray polarimeters such as INTEGRAL-SPI, PoGOLITE, X-Calibur, Gamma-Ray Burst Polarimeter, GEMS-like missions, ASTRO-H, and POLARIX have the potential to discover polarized X-rays and gamma-rays from blazar jets for the first time. Detection of such polarization will open a qualitatively new window into high-energy blazar emission; actual measurements of polarization degree and angle will quantitatively test theories of jet emission mechanisms. We examine the detection prospects of blazars by these polarimetry missions using examples of 3C 279, PKS 1510-089, and 3C 454.3, bright sources with relatively high degrees of low-energy polarization. We conclude that while balloon polarimeters will be challenged to detect blazars within reasonable observational times (wit...

Chakraborty, Nachiketa; Fields, Brian

2015-01-01

60

Raman-induced rotational coherence in gaseous molecules observed by the ultrafast polarization spectroscopy  

Microsoft Academic Search

Raman-induced rotational coherence in the ground vibronic state of gaseous molecules, air, nitrogen, and oxygen, was studied by using the femtosecond polarization spectroscopy. Coherence-burst signals due to the rotational coherences were observed in picosecond region. Their Fourier spectra give the frequencies of the induced coherences between the rotational levels.

T. Kohmoto; Y. Fukuda; M. Kunitomo

2000-01-01

61

Photoelectron angular distributions from polar molecules probed by intense femtosecond lasers  

SciTech Connect

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

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

2010-10-15

62

What can be learned about molecular reorientation from single molecule polarization microscopy?  

NASA Astrophysics Data System (ADS)

We have developed a general approach for the calculation of the single molecule polarization correlation function C(t ), which delivers a correlation of the emission dichroisms at time 0 and t. The approach is model independent and valid for general asymmetric top molecules. The key dynamic quantities of our analysis are the even-rank orientational correlation functions, the weighted sum of which yields C(t ). We have demonstrated that the use of nonorthogonal schemes for the detection of the single molecule polarization responses makes it possible to manipulate the weighting coefficients in the expansion of C(t ). Thus valuable information about the orientational correlation functions of the rank higher than the second can be extracted from C(t ).

Gelin, M. F.; Kosov, D. S.

2006-08-01

63

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

E-print Network

The ground state of the polar alkali-Strontium molecules: potential energy curve and permanent In this study, we investigate the structure of the polar alkali-Strontium diatomic molecules as possible already been reported, while quantum degeneracy in Ytterbium [22, 23], Calcium [24], and Strontium [25, 26

Paris-Sud XI, Universit茅 de

64

Oxidized polyethylene films for orienting polar molecules for linear dichroism spectroscopy.  

PubMed

Stretched polyethylene (PE) films have been used to orient small molecules for decades by depositing solutions on their surface and allowing the solvent to evaporate leaving the analyte absorbed on the polymer film. However, the non-polar hydrophobic nature of PE is an obstacle to aligning polar molecules and biological samples. In this work PE film was treated with oxygen plasma in order to increase surface hydrophilicity. Different treatment conditions were evaluated using contact angle measurement and X-ray photoelectron spectroscopy. Treated PE (PE(OX)) films are shown to be able to align molecules of different polarities including progesterone, 1-pyrenecarboxaldehyde, 4',6-diamidino-2-phenylindole (DAPI) and anthracene. The degree of alignment of each molecule was studied by running series of linear dichroism (LD) experiments and the polarizations of electronic transition moments were determined. For the first time optimal conditions (such as stretching factor and concentration of the sample) for stretched film LD were determined. PE(OX) aligning ability was compared to that of normal PE films. Progesterone showed a slightly better alignment on PE(OX) than PE. 1-Pyrenecarboxaldehyde oriented differently on the two different films which enabled transition moment assignment for this low symmetry molecule. DAPI (which does not align on PE) aligned well on PE(OX) and enabled us to obtain better LD data than had previously been collected with polyvinyl alcohol. Anthracene alignment and formation of dimers and higher order structures were studied in much more detail than previously possible, showing a variety of assemblies on PE and PE(OX) films. PMID:24482800

Razmkhah, Kasra; Chmel, Nikola Paul; Gibson, Matthew I; Rodger, Alison

2014-03-21

65

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

66

Critical binding and electron scattering by symmetric-top polar molecules  

NASA Astrophysics Data System (ADS)

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.

Garrett, W. R.

2014-10-01

67

Quantitative rescattering theory of high-order harmonic generation for polyatomic molecules  

NASA Astrophysics Data System (ADS)

We report applications of the quantitative rescattering theory (QRS) for calculation of high-order-harmonic generation (HHG) from polyatomic molecules in ultrashort linearly polarized intense laser pulses, using the example of the CCl4 molecule. In particular, we present a detailed analysis and a treatment for the phase of the electron returning wave packet, which recollides with the parent molecular ion to emit high-energy photons. Our results show that Cooper-type minimum structures in the molecular photoionization cross section lead to quite distinguishable minima in the HHG spectra, even for unaligned polyatomic molecules.

Le, Anh-Thu; Lucchese, R. R.; Lin, C. D.

2013-06-01

68

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

69

Solids and Supersolids of Three-Body Interacting Polar Molecules on an Optical Lattice  

Microsoft Academic Search

We study the physics of cold polar molecules loaded into an optical lattice in the regime of strong three-body interactions, as put forward recently by B點hler et al. [Nature Phys.NPAHAX1745-2481 3, 726 (2007)10.1038\\/nphys678]. To this end, quantum Monte Carlo simulations, exact diagonalization, and a semiclassical approach are used to explore hard-core bosons on the 2D square lattice which interact solely

Kai P. Schmidt; Julien Dorier; Andreas M. L鋟chli

2008-01-01

70

Polar molecules with three-body interactions on the honeycomb lattice  

Microsoft Academic Search

We study the phase diagram of ultra-cold bosonic polar molecules loaded on a two-dimensional optical lattice of hexagonal symmetry controlled by external electric and microwave fields. Following a recent proposal in (B點hler et al 2007 Nat. Phys. 3 726), such a system is described by an extended Bose-Hubbard model of hard-core bosons that includes both extended two- and three-body repulsions.

Lars Bonnes; Hanspeter B點hler; Stefan Wessel

2010-01-01

71

Solids and Supersolids of Three-Body Interacting Polar Molecules on an Optical Lattice  

Microsoft Academic Search

We study the physics of cold polar molecules loaded into an optical lattice in the regime of strong three-body interactions, as put forward recently by Buechler et al.[Nature Phys. 3, 726 (2007)]. To this end, quantum Monte Carlo simulations, exact diagonalization, and a semiclassical approach are used to explore hard-core bosons on the 2D square lattice which interact solely by

Kai P. Schmidt; Julien Dorier; Andreas M. Laeuchli

2008-01-01

72

Feasibility of a storage ring for polar molecules in strong-field-seeking states  

Microsoft Academic Search

We show, through modeling and simulation, that it is feasible to construct a storage ring that will store dense bunches of strong-field-seeking polar molecules at 30 m\\/s (kinetic energy of 2 K) and hold them, for several minutes, against losses due to defocusing, oscillations, and diffusion. The ring, 3 m in diameter, has straight sections that afford access to the

Hiroshi Nishimura; Glen Lambertson; Juris G. Kalnins; Harvey Gould

2004-01-01

73

Quantum simulation of many-body spin interactions with ultracold polar molecules  

E-print Network

We present an architecture for the quantum simulation of many-body spin interactions based on ultracold polar molecules trapped in optical lattices. Our approach employs digital quantum simulation, i.e., the dynamics of the simulated system is reproduced by the quantum simulator in a stroboscopic pattern, and allows to simulate both coherent and dissipative dynamics. We discuss the realization of Kitaev's toric code Hamiltonian, a paradigmatic model involving four-body interactions, and we analyze the requirements for an experimental implementation.

Hendrik Weimer

2013-01-07

74

Author's personal copy High field dynamic nuclear polarization at 6.7 T: Carbon-13 polarization  

E-print Network

Author's personal copy High field dynamic nuclear polarization at 6.7 T: Carbon-13 polarization s t r a c t In most applications of dissolution-DNP, the polarization of nuclei with low gyromagnetic lines such as Trityl at low temperatures T = 1.2 K in polarizing fields B0 6 5 T. In a field B0 = 6

75

Stretching DNA molecules on a flexible substrate, a polarization-dependent fluorescence microscopy study  

NASA Astrophysics Data System (ADS)

DNA molecules absorbed and stretched onto surfaces can be used to analyze DNA structure by imaging fluorescence of labeled hybridization probes or enzymes. A recently proposed method for sequencing by electron microscopy requires either adsorbed single-stranded DNAs or untwisted double-stranded DNA. In this experiment, studies were performed on the adsorption of isolated DNA molecules to a flexible PDMS substrate, which permits continuous stretching, until breakage of the DNA molecules. Lambda and T4 DNAs (48.5 and 165.6 kilobase pairs, respectively) were absorbed onto PDMS out of solution by withdrawing a submerged substrate at a rate of 2mm/s, producing linear molecules deposited on the surface. Incident light polarization was varied and fluorescence emission intensity measured as a function of polarization angle and degree of stretching of the DNA. The stretching and breakage properties of lambda and T-4 DNA on the PDMS substrate were determined. The amount of stretching before breakage occurred was found to be up to 40% relative to the as-deposited length. Supported by NSF-DMR MRSEC program.

Zhu, Ke; Mele, John; Budassi, Julia; Sokolov, Jonathon

2013-03-01

76

Role of ellipticity in high-order harmonic generation by homonuclear diatomic molecules  

SciTech Connect

We present a theory of high-order harmonic generation by diatomic molecules exposed to an elliptically polarized laser field. This theory is based on the molecular strong-field approximation with the laser-field-dressed initial bound state and the undressed final state. The interference minima, observed for linear polarization, are blurred with the increase of the laser-field ellipticity. The nth harmonic emission rate has contributions of the components of the T-matrix element in the direction of the laser-field polarization and in the direction perpendicular to it. We analyze the destructive interference condition for this perpendicular component. Taking into account that the aligned molecules are an anisotropic medium for high-harmonic generation, we introduce elliptic dichroism as a measure of this anisotropy and discuss possibilities of its use for determining the molecular structure.

Odzak, S. [Faculty of Science, University of Sarajevo, Zmaja od Bosne 35, 71000 Sarajevo (Bosnia and Herzegowina); Milosevic, D. B. [Faculty of Science, University of Sarajevo, Zmaja od Bosne 35, 71000 Sarajevo (Bosnia and Herzegowina); Max-Born-Institut, Max-Born-Strasse 2a, D-12489 Berlin (Germany)

2010-08-15

77

Anti-Lambda polarization in high energy pp collisions with polarized beam  

E-print Network

We study the polarization of the anti-Lambda particle in polarized high energy pp collisions at large transverse momenta. The anti-Lambda polarization is found to be sensitive to the polarization of the anti-strange sea of the nucleon. We make predictions using different parameterizations of the polarized quark distribution functions. The results show that the measurement of longitudinal anti-Lambda polarization can distinguish different parameterizations, and that similar measurements in the transversely polarized case can give some insights into the transversity distribution of the anti-strange sea of nucleon.

Qing-hua Xu; Zuo-tang Liang; Ernst Sichtermann

2005-11-06

78

Dielectric relaxation phenomena of rigid polar liquid molecules under giga hertz electric field  

NASA Astrophysics Data System (ADS)

The dielectric relaxation phenomena of rigid polar liquid molecules chloral and ethyltrichloroacetate (j) in benzene, n-hexane and n-heptane (i) under 4.2, 9.8 and 24.6 GHz electric fields at 30oC are studied to show the possible existence of double relaxation times t2 and t1 for rotations of the whole and the flexible parts of molecules. The probability of showing double relaxation is more in aliphatic solvents indicating their nonrigidity. The symmetric and asymmetric distribution parameters g and d are obtained from c 'ij /c 0ij and c''ij/c0ij at wj --> 0 where c'ij and c'ij are real and imaginary parts of the complex orientational susceptibility c*ij and c0ij is the low frequency susceptibility which is real. cij's are involved with the measured dielectric relative permittivities e'ij, e''ij, e 0ij and eij of solutions. The theoretical weighted contributions c1 and c2 towards dielectric dispersions by Fr鰄lich's method are compared with the experimental ones obtained from the graphical variation of c'ij /c0ij and c''ij/c0ij with weight fractions wj's at wj --> 0. The measured dipole moments m2 and m 1 of the whole and the flexible part of a polar molecule in terms of the linear coefficients b's of c'ij's with wj's and the estimated t2 and t1 reveal their associations with aliphatic solvents. The theoretical dipole moments mtheo's from the available bond angles and bond moments of the substituent polar groups of the molecules with the estimated m's suggest the mesomeric, inductive and electromeric effects in them under GHz electric field.

Dutta, K.; Sit, S. K.; Acharyya, S.

2001-10-01

79

Spinning CO2 Molecules into High Rotational States with an Optical Centrifuge  

NASA Astrophysics Data System (ADS)

We have performed the first spectroscopic measurements of molecules in an optical centrifuge. The optical centrifuge is a means to generate molecules in very high rotational states using a pulsed laser. The optical centrifuge consists of two ultrafast laser pulses with reverse chirp and circular polarization that are combined to generate an intense electric field that undergoes angular acceleration. Molecules with polarizability anisotropy are driven by the field into high rotational states. We have used an optical centrifuge to promote CO2 molecules into high rotational states (J200) and monitored the effect of the centrifuge on different quantum states using high-resolution transient IR diode laser absorption at ?=4.3 ?m. The depletion of low angular momentum (J=14) states and the appearance (and subsequent depletion) of middle-J (J=76) states that are populated by a collisional cascade have been observed and characterized. Direct detection of CO2 molecules in states near J=200 will allow further characterization of the centrifuge. Transient signals were observed only in the presence of both optical centrifuge pulses and for pulses with circular polarization. The ability to control molecular rotation using the optical centrifuge opens a new realm of investigation into the behavior of energized molecules.

Mullin, Amy S.; Yuan, Liwei; Teitelbaum, Sam; Robinson, Allison

2009-05-01

80

Spinning CO2 Molecules into High Rotational States with an Optical Centrifuge  

NASA Astrophysics Data System (ADS)

We report the first spectroscopic measurements of molecules in an optical centrifuge which generates molecules in very high rotational states. The optical centrifuge combines two ultrafast laser pulses having reverse chirp and circular polarization to generate an intense electric field that undergoes angular acceleration. Molecules with non-uniform polarizability are driven by the field into high rotational states. We have used the optical centrifuge to promote CO2 molecules into high rotational states (J200) and monitored the effect of the centrifuge on different quantum states using high-resolution transient mid-IR laser absorption. We have observed and characterized the depletion of low angular momentum (J=14) states and the appearance (and subsequent depletion) of middle-J (J=76) states populated by a collisional cascade. Direct detection of CO2 molecules in states near J=200 will allow further characterization of the centrifuge. Transient signals are observed only in the presence of both optical centrifuge pulses and for pulses with circular polarization. The ability to control molecular rotation using the optical centrifuge opens a new realm of investigation into the behavior of energized molecules.

Mullin, Amy; Yuan, Liwei; Robinson, Allison; Teitelbaum, Samuel

2010-03-01

81

Dual-polarized microstrip array with high isolation and low cross-polarization  

NASA Technical Reports Server (NTRS)

A 2 x 2 dual-polarized microstrip array antenna with high isolation between the two input ports and low cross-polarization level has been developed. The technical background for this achievement and antenna performance results are presented.

Huang, John

1991-01-01

82

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 Gu閞out; Mireille Aymar; Olivier Dulieu

2010-07-12

83

Adiabatic Charge Dynamics in Molecules Dissolved in A Polar Solvent. Application to Charge Migration in DNA  

NASA Astrophysics Data System (ADS)

We develop an adiabatic hopping model for charge migration through molecules dissolved in a polar liquid (water), based on an analytical approach [1]. The charge hopping between donor and acceptor states is due to a rare fluctuation of the solvent polarization forming a deeper well at the target places. The results are applied to the photoexcited hole migration in DNA [2] using the model parameters, obtained from the first principles studies. Theory can explain the length dependence of the transfer rate, becoming distant independent at long distances where correlations in fluctuations are weak, and one sees low absolute value of charge hopping rate, defined entirely by the slow kinetics of the solvent. Strong energy and weak temperature dependence of the transfer rate, observed experimentally can be due to the entropy control of water fluctuations at room temperature. Clarifying experiments are suggested. 1.A. L. Burin, et al, Phys. Rev. Lett. 86, 5616, 2001. 2.F. D. Lewis, et al, Nature 406, 51, 2000

Burin, A. L.; Berlin, Yu. A.; Kurnikov, I.; Ratner, M. A.

2002-03-01

84

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

SciTech Connect

Conventional nuclear magnetic resonance (NMR) spectroscopy and magnetic resonance imaging (MRI) are fundamentally challenged by the insensitivity that stems from the ordinarily low spin polarization achievable in even the strongest NMR magnets. However, by transferring angular momentum from laser light to electronic and nuclear spins, optical pumping methods can increase the nuclear spin polarization of noble gases by several orders of magnitude, thereby greatly enhancing their NMR sensitivity. This dissertation is primarily concerned with the principles and practice of optically pumped nuclear magnetic resonance (OPNMR). The enormous sensitivity enhancement afforded by optical pumping noble gases can be exploited to permit a variety of novel NMR experiments across many disciplines. Many such experiments are reviewed, including the void-space imaging of organisms and materials, NMR and MRI of living tissues, probing structure and dynamics of molecules in solution and on surfaces, and zero-field NMR and MRI.

Goodson, Boyd M.

1999-12-01

85

Solids and Supersolids of Three-Body Interacting Polar Molecules on an Optical Lattice  

SciTech Connect

We study the physics of cold polar molecules loaded into an optical lattice in the regime of strong three-body interactions, as put forward recently by Buechler et al.[Nature Phys. 3, 726 (2007)]. To this end, quantum Monte Carlo simulations, exact diagonalization, and a semiclassical approach are used to explore hard-core bosons on the 2D square lattice which interact solely by long-ranged three-body terms. The resulting phase diagram shows a sequence of solid and supersolid phases. Our findings are directly relevant for future experimental implementations and open a new route towards the discovery of a lattice supersolid phase in experiment.

Schmidt, Kai P. [Lehrstuhl fuer theoretische Physik I, Otto-Hahn-Str. 4, TU Dortmund, D-44221 Dortmund (Germany); Dorier, Julien [Institute of Theoretical Physics, Ecole Polytechnique Federale de Lausanne, CH 1015 Lausanne (Switzerland); Laeuchli, Andreas M. [Institut Romand de Recherche Numerique en Physique des Materiaux (IRRMA), CH-1015 Lausanne (Switzerland); Max Planck Institut fuer Physik komplexer Systeme, Noethnitzer Str. 38, D-01187 Dresden (Germany)

2008-10-10

86

Solids and supersolids of three-body interacting polar molecules on an optical lattice.  

PubMed

We study the physics of cold polar molecules loaded into an optical lattice in the regime of strong three-body interactions, as put forward recently by B點hler et al. [Nature Phys. 3, 726 (2007)]. To this end, quantum Monte Carlo simulations, exact diagonalization, and a semiclassical approach are used to explore hard-core bosons on the 2D square lattice which interact solely by long-ranged three-body terms. The resulting phase diagram shows a sequence of solid and supersolid phases. Our findings are directly relevant for future experimental implementations and open a new route towards the discovery of a lattice supersolid phase in experiment. PMID:18999578

Schmidt, Kai P; Dorier, Julien; L鋟chli, Andreas M

2008-10-10

87

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

88

Non-adiabatic preparation of spin crystals with ultracold polar molecules  

E-print Network

We study the growth dynamics of ordered structures of strongly interacting polar molecules in optical lattices. Using dipole blockade of microwave excitations, we map the system onto an interacting spin-1/2 model possessing ground states with crystalline order, and describe a way to prepare these states by non-adiabatically driving the transitions between molecular rotational levels. The proposed technique bypasses the need to cross a phase transition and allows for the creation of ordered domains of considerably larger size compared to approaches relying on adiabatic preparation.

Mikhail Lemeshko; Roman V. Krems; Hendrik Weimer

2012-02-29

89

Directional properties of polar paramagnetic molecules subject to congruent electric, magnetic and optical fields  

E-print Network

We show that congruent electric, magnetic and non-resonant optical fields acting concurrently on a polar paramagnetic (and polarisable) molecule offer possibilities to both amplify and control the directionality of the ensuing molecular states that surpass those available in double-field combinations or in single fields alone. At the core of these triple-field effects is the lifting of the degeneracy of the projection quantum number $M$ by the magnetic field superimposed on the optical field and a subsequent coupling of the members of the "doubled" (for states with $M \

Sharma, Ketan

2015-01-01

90

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

91

Mixed-field orientation of a thermal ensemble of linear polar molecules  

NASA Astrophysics Data System (ADS)

We present a theoretical study of the impact of an electrostatic field combined with nonresonant linearly polarized laser pulses on the rotational dynamics of a thermal ensemble of linear molecules. We solve the time-dependent Schr鰀inger equation within the rigid rotor approximation for several rotational states. Using the carbonyl sulfide (OCS) molecule as a prototype, the mixed-field orientation of a thermal sample is analyzed in detail for experimentally accessible static field strengths and laser pulses. We demonstrate that for a characteristic field configuration used in current mixed-field orientation experiments, a significant orientation is obtained for rotational temperatures below 0.7 K as well as using stronger dc fields.

Omiste, Juan J.; Gonz醠ez-F閞ez, Rosario

2013-12-01

92

Nonadiabatic effects in long-pulse mixed-field orientation of a linear polar molecule  

NASA Astrophysics Data System (ADS)

We present a theoretical study of the impact of an electrostatic field combined with nonresonant linearly polarized laser pulses on the rotational dynamics of linear molecules. Within the rigid rotor approximation, we solve the time-dependent Schr鰀inger equation for several field configurations. Using the carbonyl sulfide molecule as the prototype, the field-dressed dynamics is analyzed in detail for experimentally accessible static-field strengths and laser pulses. Results for directional cosines are presented and compared to the predictions of the adiabatic theory. We demonstrate that for the prototypical field configuration used in current mixed-field orientation experiments, the molecular field dynamics is, in general, nonadiabatic, and a time-dependent description of these systems is mandatory. We investigate several field regimes identifying the sources of nonadiabatic effects and provide the field parameters under which the adiabatic dynamics would be achieved.

Omiste, Juan J.; Gonz醠ez-F閞ez, Rosario

2012-10-01

93

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

94

Spectroscopy, reaction, and photodissociation in highly vibrationally excited molecules  

SciTech Connect

Highly vibrationally excited molecules often control the course of chemical reactions in the atmosphere, combustion, plasmas, and many other environments. The research described in this Progress Report uses laser excitation and interrogation techniques to study and control the dynamics of highly vibrationally excited molecules. In particular, they show that it is possible to unravel the details and influence the course of photodissociation and bimolecular reaction. The experiments use laser excitation of overtone vibrations to prepare highly vibrationally excited molecules, frequently with single quantum state resolution, and laser spectroscopy to monitor the subsequent behavior of the excited molecule. We have studied the vibrationally mediated photodissociation and the bond- and state-selected bimolecular reaction of highly vibrationally excited molecules. In the first process, one photon creates a highly excited molecule, a second photon from another laser dissociates it, and light from a third laser detects the population of individual product quantum states. This approach allows us to explore otherwise inaccessible regions of the ground and excited state potential energy surface and, by exciting to the proper regions of the surface, to control the breaking of a selected chemical bond. In the second process, the highly vibrationally excited molecule reacts with an atom formed either in a microwave discharge or by photolysis and another laser interrogates the products. We have used this approach to demonstrate mode- and bond-selected bimolecular reactions in which the initial excitation controls the subsequent chemistry. 30 refs., 8 figs.

Not Available

1991-01-01

95

Generating long-lasting 1H and 13C hyperpolarization in small molecules with parahydrogen-induced polarization  

NASA Astrophysics Data System (ADS)

Recently, Levitt and co-workers demonstrated that conserving the population of long-lasting nuclear singlet states in weak magnetic fields can lead to a preservation of nuclear spin information over times substantially longer than governed by the (high-field) spin-lattice relaxation time T1. Potential benefits of the prolonged spin information for magnetic resonance imaging and spectroscopy were pointed out, particularly when combined with the parahydrogen induced polarization (PHIP) methodology. In this contribution, we demonstrate that an increase of the effective relaxation time by a factor up to three is achieved experimentally, when molecules hyperpolarized by PHIP are kept in a weak magnetic field instead of the strong field of a typical NMR magnet. This increased lifetime of spin information makes the known PHIP phenomena more compatible with the time scales of biological processes and, thus, more attractive for future investigations.

Jonischkeit, Thorsten; Bommerich, Ute; Stadler, J鰎g; Woelk, Klaus; Niessen, Heiko G.; Bargon, Joachim

2006-05-01

96

Highly polarized photonic crystal fiber laser  

Microsoft Academic Search

We report on the design of a polarization maintaining, double-clad, Yb doped photonic crystal fiber and demonstrate its lasing properties. The polarizing properties of the fiber rely on birefringence and differential loss introduced by an anisotropic hole structure. Due to a slight leak from the core to the inner cladding only ~80% of the output light is in the core

Fiona C. McNeillie; Erling Riis; Jes Broeng; Jacob Riis Folkenberg; Anders Petersson; Harald Simonsen; Christian Jacobsen

2004-01-01

97

Orbital geometry determined by orthogonal high-order harmonic polarization components  

SciTech Connect

We study the polarization state of high-order harmonics produced by linearly polarized light interacting with two-center molecules. By generating high-harmonic 'polarization maps' from Radon transformations of excited electronic wave functions, we show that the polarization of the harmonic radiation can be linked to the geometry of the molecular orbital. While in the Radon transformation the plane-wave approximation for the rescattered electron is implicitly assumed, numerical solutions of the two-dimensional time-dependent Schro{center_dot}{center_dot}dinger equation, in which this approximation is not made, confirm the validity of this topological connection. We also find that measuring two orthogonal amplitude components of the harmonics provides a method for quantum tomography that substantially improves the quality of reconstructed molecular states.

Hijano, Eliot [ICFO-Institut de Ciencies Fotoniques, Mediterranean Technology Park, E-08860 Castelldefels (Barcelona) (Spain); Serrat, Carles [ICFO-Institut de Ciencies Fotoniques, Mediterranean Technology Park, E-08860 Castelldefels (Barcelona) (Spain); DTDI, Universitat de Vic, Carrer de la Laura 13, E-08500 Vic (Barcelona) (Spain); Gibson, George N. [Department of Physics, University of Connecticut, Storrs, Connecticut 06269 (United States); Biegert, Jens [ICFO-Institut de Ciencies Fotoniques, Mediterranean Technology Park, E-08860 Castelldefels (Barcelona) (Spain); ICREA-Institucio Catalana de Recerca i Estudis Avancats, E-08010 Barcelona (Spain)

2010-04-15

98

Intracluster Ion Molecule Reactions Following the Generation of Mg+ Within Polar Clusters  

PubMed Central

In this work we investigated the intracluster ion molecule reactions following the generation of Mg+ within the polar clusters (water, methanol, ether and acetonitrile), using time of flight mass spectrometry. In the case of Mg+/water and Mg+/methanol, dehydrogenation reactions are observed after the addition of five molecules. However, no dehydrogenation reactions are observed in the case of Mg+/ether or Mg+/acetonitrile clusters. This confirms the role of the H atom in (O朒) in the dehydrogenation reaction, and rules out any contribution from the H atom in the CH3 group. In addition, the magic numbers in the time of flight (TOF) mass spectra of the Mg+Xn clusters (X = H2O, CH3OH, CH3OCH3 and CH3CN) have been investigated. Finally, the role of ground electronic magnesium ion Mg+(2S1/2), and excited electronic magnesium ion Mg+(2P1/2) in the dehydrogenation reaction were investigated using Ion Mobility Mass spectrometry. The results offer direct evidence confirming the absence of the electronically excited, Mg+(2P1/2). PMID:22272121

Alsharaeh, Edreese H.

2011-01-01

99

Polarization characteristics of stimulated emission of organic molecules when excited by intense XeCl laser radiation  

NASA Astrophysics Data System (ADS)

We study the influence of the molecular structure, medium, and exciting-radiation parameters on the polarization, energy, and spectral characteristics of the emission of laser-active media based on the dicarboxylic derivative of p-terphenyl, rhodamine 101, and phenalemine 512. We found that the polarization of the stimulated emission of molecules when strongly excited under the conditions studied significantly depends on their structure, the pumping mode, the intensity and polarization of the exciting radiation, the shape and dimensions of the excited volume, and the phase state of the medium.

Kuznetsova, R. T.; Shaposhnikov, A. A.; Filinov, D. N.; Kopylova, T. N.; Tel'Minov, E. N.

2003-09-01

100

Polarity inversion in high Mg-doped In-polar InN epitaxial layers  

SciTech Connect

To investigate the Mg-dopability in In-polar InN epilayers grown by molecular beam epitaxy, polarity inversion dependence on Mg-doping level is studied. A multiple-InN layer-structure sample with different Mg-doping levels is grown and analyzed by transmission electron microscopy. Formation of high density V-shaped inversion domains is observed for the Mg-doped InN with Mg concentration ([Mg]) of 2.9x10{sup 19} cm{sup -3}. These domains lead to polarity inversion from In to N polarity. Further study for Mg-doped InN epilayers shows that polarity inversion takes place when [Mg] increases above 1.6x10{sup 19} cm{sup -3}. It is also shown that the Mg-sticking coefficient is almost independent of the polarity.

Wang Xinqiang; Che, Song-Bek; Ishitani, Yoshihiro; Yoshikawa, Akihiko; Sasaki, Hirokazu; Shinagawa, Tatsuyuki; Yoshida, Seikoh [Graduate Course of Electrical and Electronics Engineering, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522 (Japan) and InN-Project as a CREST program of JST, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522 (Japan); Yokohama R and D Laboratories, Furukawa Electric Co., Ltd., 2-4-3 Okano, Nishi-ku, Yokohama 220-0073 (Japan)

2007-08-20

101

Tethering of intercellular adhesion molecule on target cells is required for LFA-1-dependent NK cell adhesion and granule polarization.  

PubMed

Alpha(L)beta(2) integrin (LFA-1) has an important role in the formation of T cell and NK cell cytotoxic immunological synapses and in target cell killing. Binding of LFA-1 to ICAM on target cells promotes not only adhesion but also polarization of cytolytic granules in NK cells. In this study, we tested whether LFA-1-dependent NK cell responses are regulated by the distribution and mobility of ICAM at the surface of target cells. We show that depolymerization of F-actin in NK-sensitive target cells abrogated LFA-1-dependent conjugate formation and granule polarization in primary NK cells. Degranulation, which is not controlled by LFA-1, was not impaired. Fluorescence recovery after photobleaching experiments and particle tracking by total internal reflection fluorescence microscopy revealed that ICAM-1 and ICAM-2 were distributed in largely immobile clusters. ICAM clusters were maintained and became highly mobile after actin depolymerization. Moreover, reducing ICAM-2 mobility on an NK-resistant target cell through expression of ezrin, an adaptor molecule that tethers proteins to the actin cytoskeleton, enhanced LFA-1-dependent adhesion and granule polarization. Finally, although NK cells kept moving over freely diffusible ICAM-1 on a lipid bilayer, they bound and spread over solid-phase ICAM-1. We conclude that tethering, rather than clustering of ICAM, promotes proper signaling by LFA-1 in NK cells. Our findings suggest that the lateral diffusion of integrin ligands on cells may be an important determinant of susceptibility to lysis by cytotoxic lymphocytes. PMID:20675589

Gross, Catharina C; Brzostowski, Joseph A; Liu, Dongfang; Long, Eric O

2010-09-01

102

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

103

Probing the Axis Alignment of an Ultracold Spin-polarized Rb2 Molecule  

NASA Astrophysics Data System (ADS)

We present a novel method for probing the alignment of the molecular axis of an ultracold, nonpolar dimer. These results are obtained using diatomic 87Rb2 molecules in the vibrational ground state of the lowest triplet potential a3?u+ trapped in a 3D optical lattice. 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. By preparing the molecules in various, precisely defined rotational quantum states we can control the degree of alignment of the molecular axis with high precision over a large range. Furthermore, we derive the dynamical polarizabilities for a laser wavelength of 1064.5 nm parallel and orthogonal to the molecular axis of the dimer, ??=(8.9 0.9 )1 03 a .u . and ??=(0.9 0.4 )1 03 a .u . , respectively. Our findings highlight that the depth of an optical lattice strongly depends on the rotational state of the molecule, which has to be considered in collision experiments. The present work paves the way for reaction studies between aligned molecules in the ultracold temperature regime.

Dei, Markus; Drews, Bj鰎n; Deissler, Benjamin; Hecker Denschlag, Johannes

2014-12-01

104

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

PubMed

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

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

2014-04-01

105

Spin-polarized lasing in a highly photoexcited semiconductor microcavity  

E-print Network

Lasing in semiconductors is generally independent of the spins of electrons and holes, which constitute the gain medium. However, in a few spin-controlled lasers, spin-polarized carriers with long spin relaxation times ($\\sim$1 ns) result in continuous or sub-nanosecond pulsed circularly polarized stimulated emission. In these spin-controlled semiconductor lasers, a spin-imbalanced population inversion has been considered necessary. Here, we demonstrate room-temperature spin-polarized ultrafast ($\\sim$10 ps) lasing in a highly optically excited GaAs microcavity embedded with InGaAs multiple quantum wells within which the spin relaxation time is less than 10 ps. The laser radiation remains highly circularly polarized even when excited by \\emph{nonresonant} \\emph{elliptically} polarized light. In contrast to conventional semiconductor lasers, it exhibits a nonlinear input-output relation, energy shifts, and spectral broadening as a function of the photoexcited density. Such spin-polarized lasing is attributed t...

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

2015-01-01

106

Polarization-dependent detection of cylinder nanoparticles with mode splitting in a high-Q whispering-gallery microresonator  

NASA Astrophysics Data System (ADS)

Using the single-scatterer-induced coupling mechanism of a pair of counterpropagating high-Q whispering-gallery modes (WGMs), we investigate the highly sensitive detection of single nonspherical nanoparticles. The nonspherical particle may produce distinct frequency splitting and additional damping for TE and TM WGMs. This polarization-dependent effect allows for studying the orientation of single biomolecule, molecule-molecule interaction on the microcavity surface, and possibly distinguishing different inner configurations of similar biomolecules.

Yi, Xu; Xiao, Yun-Feng; Li, Yan; Liu, Yong-Chun; Li, Bei-Bei; Liu, Zhao-Pei; Gong, Qihuang

2010-11-01

107

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

108

Visualization of the polarity of isolated titin molecules: a single globular head on a long thin rod as the M band anchoring domain?  

PubMed Central

TII, the extractable form of titin, was purified from myofibrils and separated by high resolution gel permeation chromatography into two fractions (TIIA and TIIB). Novel specimen orientation methods used before metal shadowing and EM result in striking pictures of the two forms. Molecules layered on mica become uniformly oriented when subjected to centrifugation. TIIB comprises a very homogeneous fraction. All molecules reveal a single globular head at one end on a long and very thin rod of uniform diameter. The lengths of the rods have a very narrow distribution (900 +/- 50 nm). TIIA molecules seem lateral oligomers of TIIB, attached to each other via the head regions. While dimers are the predominant species, trimers and some higher oligomers can also be discerned. Mild proteolysis destroys the heads and converts TIIA and TIIB into TIIB-like rods. Similar molecules also result from titin purified from myofibrils by certain established purification schemes. Headless titin molecules show in gel electrophoresis only the TII band, while head bearing molecules give rise to two additional polypeptides at 165 and 190 kD. Immunoelectron microscopy of myofibrils identifies both titin-associated proteins as M band constituents. We speculate that in the polar images of TII the globular head region corresponds to the M band end of the titin molecules. This hypothesis is supported by immunoelectron micrographs of TIIB molecules using titin antibodies of known epitope location in the half sarcomere. This proposal complements our previous immunoelectron microscopic data on myofibrils. They showed that epitopes present only on the nonextractable TI species locate to the Z line and its immediately adjacent region (Furst, D. O., M. Osborn, R. Nave, and K. Weber. 1988. J. Cell Biol. 106:1563-1572). Thus, the two distinct ends of the titin molecule attach to Z and M band material respectively. PMID:2478565

1989-01-01

109

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

110

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-Su醨ez, Jes鷖 C.

2013-01-01

111

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

112

Dynamic-polarization forces on fast ions and molecules moving over supported graphene  

SciTech Connect

We use a two-dimensional, two-fluid hydrodynamic model to describe the high-frequency plasmon excitations of the carbon valence electrons responding to fast ions and electric dipoles, which move parallel to a single sheet of graphene supported by an insulating substrate. We calculate the stopping and the image forces on ions and dipoles, as well as the dynamic torque on dipoles about their center of mass, resulting from the dynamic polarization of graphene. While the results for ions are similar to those obtained earlier for ion channeling through carbon nanotubes in dielectric media, the stopping and the image forces on dipoles show strong directional dependencies. The torque on point dipoles implies a strong alignment effect in the direction of motion at lower speeds, as well as a tendency of the dipole to 'roll' over the graphene at high speeds.

Radovic, I.; Hadzievski, Lj.; Bibic, N.; Miskovic, Z. L. [VINCA Institute of Nuclear Sciences, P.O. Box 522, 11001 Belgrade (Serbia); Department of Applied Mathematics, University of Waterloo, Waterloo, Ontario, N2L 3G1 (Canada)

2007-10-15

113

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

114

Polarized neutron reflectometry in high magnetic fields  

SciTech Connect

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

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

2005-11-15

115

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

E-print Network

by hyperpolarization of the nuclear spins. NMR signals of hyperpolarized samples are enhanced by several orders of magnitude. Dissolution Dynamic Nuclear Polarization (D-DNP) is a versatile technique capable of polarizing many different nuclei in the solid state...

Lee, Youngbok

2013-03-13

116

High-order-harmonic generation in homonuclear and heteronuclear diatomic molecules: Exploration of multiple orbital contributions  

SciTech Connect

We present a time-dependent density functional theory (TDDFT) approach with proper asymptotic long-range potential for nonperturbative treatment of high-order harmonic generation (HHG) of diatomic molecules with their molecular axis parallel to the laser field polarization. A time-dependent two-center generalized pseudospectral method in prolate spheroidal coordinate system is used for accurate and efficient treatment of the TDDFT equations in space and time. The theory is applied to a detailed all-electron nonperturbative investigation of HHG processes of homonuclear (N{sub 2} and F{sub 2}) and heteronuclear (CO, BF, and HF) molecules in intense ultrashort laser pulses with the emphasis on the role of multiple molecular orbitals (MOs). The results reveal intriguing and substantially different nonlinear optical response behaviors for homonuclear and heteronuclear molecules. In particular, we found that the HHG spectrum for homonuclear molecules features a destructive interference of MO contributions while heteronuclear molecules show mostly constructive interference of orbital contributions.

Heslar, John [Center for Quantum Science and Engineering, Department of Physics, National Taiwan University, Taipei 10617, Taiwan (China); Telnov, Dmitry [Department of Physics, St. Petersburg State University, 198504 St. Petersburg (Russian Federation); Chu, Shih-I [Center for Quantum Science and Engineering, Department of Physics, National Taiwan University, Taipei 10617, Taiwan (China); Department of Chemistry, University of Kansas, Lawrence, Kansas 66045 (United States)

2011-04-15

117

High throughput extraction of plant, marine and fungal specimens for preservation of biologically active molecules.  

PubMed

The Developmental Therapeutics Program (DTP) of the U.S. National Cancer Institute (NCI), at its NCI-Frederick facility, has built perhaps the largest and most diverse natural products screening library in the world for drug discovery. Composed of plant, marine organism and microbial extracts, it currently contains in excess of 230,000 unique materials. From the inception of this program to identify new anticancer chemotherapeutics from natural products sources in 1987, two extracts have been sequentially prepared from each specimen: one produced by organic solvent extraction, which yields a complex material that contains non- to moderately polar small molecules, and a water-soluble extract, a milieu largely unexplored for useful drugs in earlier years, which contains polar small to medium-sized molecules. Plant specimens and microbial ferments are extracted by modified traditional methods, while the method developed to produce extracts from marine organisms is unique and very different from that used by marine natural products chemists previously, but again yields both an organic solvent soluble and a water soluble material for inclusion into the screening library. Details of high throughput extract production for preservation of biologically active molecules are presented. PMID:20657375

McCloud, Thomas G

2010-07-01

118

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.; Gu閞out, R.; Dulieu, O.

2014-07-01

119

Dispersion interactions with linear scaling DFT: a study of planar molecules on charged polar surfaces  

NASA Astrophysics Data System (ADS)

The placement of organic molecules such as CuPc (copper phthalocyanine) on wurtzite ZnO (zinc oxide) charged surfaces has been proposed as a way of creating photovoltaic solar cellsfootnotetextG.D. Sharma et al., Solar Energy Materials & Solar Cells 90, 933 (2006) ; optimising their performance may be aided by computational simulation. Electronic structure calculations provide high accuracy at modest computational cost but two challenges are encountered for such layered systems. First, the system size is at or beyond the limit of traditional cubic-scaling Density Functional Theory (DFT). Second, traditional exchange-correlation functionals do not account for van der Waals (vdW) interactions, crucial for determining the structure of weakly bonded systems. We present an implementation of recently developed approachesfootnotetextP.L. Silvestrelli, P.R.L. 100, 102 (2008) to include vdW in DFT within ONETEPfootnotetextC.-K. Skylaris, P.D. Haynes, A.A. Mostofi and M.C. Payne, J.C.P. 122, 084119 (2005) , a linear-scaling package for performing DFT calculations using a basis of localised functions. We have applied this methodology to simple planar organic molecules, such as benzene and pentacene, on ZnO surfaces.

Andrinopoulos, Lampros; Hine, Nicholas; Haynes, Peter; Mostofi, Arash

2010-03-01

120

Luminescent systems based on the isolation of conjugated PI systems and edge charge compensation with polar molecules on a charged nanostructured surface  

SciTech Connect

A photoluminescent or electroluminescent system and method of making a non-luminescent nanostructured material into such a luminescent system is presented. The method of preparing the luminescent system, generally, comprises the steps of modifying the surface of a nanostructured material to create isolated regions to act as luminescent centers and to create a charge imbalance on the surface; applying more than one polar molecule to the charged surface of the nanostructured material; and orienting the polar molecules to compensate for the charge imbalance on the surface of the nanostructured material. The compensation of the surface charge imbalance by the polar molecules allows the isolated regions to exhibit luminescence.

Ivanov, Ilia N.; Puretzky, Alexander A.; Zhao, Bin; Geohegan, David B.; Styers-Barnett, David J.; Hu, Hui

2014-07-15

121

High Harmonic Spectroscopy of the Cooper Minimum in Molecules  

NASA Astrophysics Data System (ADS)

The Cooper minimum (CM) has been studied using high harmonic generation solely in atoms. Here, we present detailed experimental and theoretical studies on the CM in molecules probed by high harmonic generation using a range of near-infrared light pulses from ?=1.3 to 1.8?m. We demonstrate the CM to occur in CS2 and CCl4 at 42 and 40eV, respectively, by comparing the high harmonic spectra with the known partial photoionization cross sections of different molecular orbitals, confirmed by theoretical calculations of harmonic spectra. We use CM to probe electron localization in Cl-containing molecules (CCl4, CH2Cl2, and trans-C2H2Cl2) and show that the position of the minimum is influenced by the molecular environment.

Wong, M. C. H.; Le, A.-T.; Alharbi, A. F.; Boguslavskiy, A. E.; Lucchese, R. R.; Brichta, J.-P.; Lin, C. D.; Bhardwaj, V. R.

2013-01-01

122

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

PubMed Central

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 F鑦re, 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

123

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

124

High-risk molecules or insufficient scientific data?  

PubMed

When I was invited to author an ethics policy piece on the "approach to high-risk molecules" as a contribution to the theme of "Innovation in Drug Development" of this Clinical Pharmacology & Therapeutics issue, I thought there was a need to evaluate whether questioning the transition from preclinical to clinical development after the TGN 1412 serious adverse event may freeze the development of innovating tools in drug development. PMID:18091760

Mignot, A

2008-02-01

125

Polarization of High-Energy Emission from the Crab Pulsar  

NASA Astrophysics Data System (ADS)

We investigate the polarization of the high-energy emission from the Crab pulsar within the framework of the outer gap accelerator, following previous studies by Cheng and coworkers. A recent version of the outer gap, in which the gap extends from inside the null charge surface to the light cylinder, is used to examine the synchrotron radiation from the secondary and tertiary pairs that are produced outside the gap. We are able to simultaneously reproduce the light curve, the spectrum, and the polarization characteristics by taking into account the gyration of the particles. The polarization position angle curve and the degree of polarization are calculated and compared with the Crab optical data. We demonstrate that the radiation from inside the null charge surface produces the outer wing and off-pulse portions of the light curve and that the tertiary pairs contribute to the bridge emission. The emission from the secondary pairs explains the main features of the observed light curve and spectrum. On the other hand, the emissions both from inside the null charge surface and from the tertiary pairs are required in order to explain the optical polarization behavior of the Crab pulsar. The energy dependence of the polarization features is predicted by the model. The polarization position angle curve indicates that our viewing angle as measured from the pulsar's rotational axis is greater than 90.

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

2007-02-01

126

Polarization of high-energy emissions from the Crab pulsar  

NASA Astrophysics Data System (ADS)

We discuss polarization characteristics of high-energy photons from pulsar magnetospheres For the Crab pulsar the polarization in the optical band has been measured and the next generation Compton telescope may be able to do that in soft gamma -ray bands Polarization measurements will play an important role to discriminate the various models that successfully explain observed spectra or light curves As indicated by the outer gap model of Cheng et al 2000 the Crab optical and soft gamma -ray spectrum can be easily explained by the synchrotron radiation We therefore study the polarization predicted by the synchrotron emission in the framework of the outer gap model and the two-pole caustic model Dyks et al 2004 We assume that the emitted photons are linearly polarized at degree of p 1 p 7 3 in the direction of particle acceleration which is perpendicular to the magnetic field line for which the rotating dipole field is used Emission direction and Stokes parameters Q and U are appropriately treated with the effects of particle s gyration and aberration A radial-distance dependent emissivity Cheng et al 2000 is employed for the outer gap model and a constant one is assumed for the caustic model We find that the degree of polarization predicted by the synchrotron emission in general is more consistent with observation than that of curvature radiation We find however that the minimum in the polarization degree is 10 at bridge phase for both models and the maximum is

Takata, J.; Chang, H.-K.

127

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

128

Construction of polar and hydrophobic pores and channels by assembly of peptide molecules  

NASA Astrophysics Data System (ADS)

Selected peptides and hybrid peptides (combinations of peptide sequences with organic moieties in a single molecule) self-assemble to form pores, channels and tubules. The assemblies occur in a variety of motifs. Various physiological functions, such as ion transport through cell membranes, and physical functions, such as solubilizing difficult-to-dissolve molecules, are facilitated by the tubes that are formed by molecular assemblies. Examples from nature are the ionophores zervamicin and antiamoebin that transport K + ions through cell membranes. In the area of the constriction of the hour-glass shaped channel in the ionophores, the channel becomes quite convoluted and contains the double-gating mechanism that controls the ion passage. The formation of fairly straight tubules has been accomplished by designing cyclic peptides that have a relatively flat backbone, with extended side-chains, and with amide groups and carbonyl groups that are perpendicular to the plane of the backbone. Further, the amide groups and carbonyl groups have to be spaced so that they are in register from one peptide to another, stacked over or under it, in order to form intermolecular NH⋯O?C hydrogen bonds. Tubules of this type can be made if the amino acid residues alternate between ?- and ?-residues or between D- and L-residues. In order to obviate the register problem with all ?-amino acid residues of the same hand, peptide segments have been interspersed with a number of different organic moieties, such as 1,3-adamantane dicarbonyl, norbornene dicarbonyl, 2,6-pyridyl dicarbonyl, cystine and -(CH 2) n chains. Macrocycles that stacked vertically and formed tubules through hydrogen bonding, are hollow, open-ended, and continue to infinity. The inside diameter of the hollow tubules has varied to more than 10 . The hydrophobic tubules are able to accommodate highly lipophilic substances. Successes and failures to make tubules and crystal structures of a number of the tubules will be shown.

Karle, Isabella; Ranganathan, Darshan

2003-02-01

129

39.4: Polarization-Independent Switching With High Contrast from a Liquid Crystal Polarization Grating  

Microsoft Academic Search

We report experimental results of a liquid crystal polarization grating (LCPG) modulating unpolarized light with high contrast for the first time. Striking results are observed: nearly ideal diffraction into the first orders at > 99%, contrast ratios of up to 600:1 for monochromatic light, switching times of ~ 2 ms for nematic LCs, and threshold voltage of 1.65 Vrms. 1.

Michael J. Escuti; W. Michael Jones

2006-01-01

130

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

131

Possibilities with pulsed polarized high density slow positrons  

NASA Astrophysics Data System (ADS)

A particularly bright and intense polarized slow positron beam could be formed from isotopically enriched 79Kr produced at a reactor. After moderation with solid Ne, accumulation, compression, and bunching, this type of positron beam would enable a number of experiments including: (1) Long term storage of a neutral polarized electron-positron plasma in a cold box; (2) Pulsed e+ ACAR with a pulsed magnet to measure Fermi surfaces of paramagnetic metals; (3) Single shot measurements of positron annihilation in laser-imploding plasmas; (4) Study of a spin-polarized positronium gas at a density around that of ordinary air to produce a Ps Bose-Einstein condensate at room temperature; (5) High energy polarized positron channelling experiments to study polarized electron spatial wave functions in ferromagnets; and (6) Study of supersonic free expansion spin polarized BEC Ps jets formed from, for example, 1011 m=1 triplet Ps atoms created within an open ended 1 ?m diameter cylindrical cavity 100 ?m in length.

Mills, A. P., Jr.

2014-04-01

132

Single-molecule high-resolution imaging with photobleaching  

PubMed Central

Conventional light microscopy is limited in its resolving power by the Rayleigh limit to length scales on the order of 200 nm. On the other hand, spectroscopic techniques such as fluorescence resonance energy transfer cannot be used to measure distances >10 nm, leaving a 揼ap in the ability of optical techniques to measure distances on the 10- to 100-nm scale. We have previously demonstrated the ability to localize single dye molecules to a precision of 1.5 nm with subsecond time resolution. Here we locate the position of two dyes and determine their separation with 5-nm precision, using the quantal photobleaching behavior of single fluorescent dye molecules. By fitting images both before and after photobleaching of one of the dyes, we may localize both dyes simultaneously and compute their separation. Hence, we have circumvented the Rayleigh limit and achieved nanometer-scale resolution. Specifically, we demonstrate the technique by measuring the distance between single fluorophores separated by 1020 nm via attachment to the ends of double-stranded DNA molecules immobilized on a surface. In addition to bridging the gap in optical resolution, this technique may be useful for biophysical or genomic applications, including the generation of super-high-density maps of single-nucleotide polymorphisms. PMID:15096603

Gordon, Matthew P.; Ha, Taekjip; Selvin, Paul R.

2004-01-01

133

Correcting systematic errors in high-sensitivity deuteron polarization measurements  

NASA Astrophysics Data System (ADS)

This paper reports deuteron vector and tensor beam polarization measurements taken to investigate the systematic variations due to geometric beam misalignments and high data rates. The experiments used the In-Beam Polarimeter at the KVI-Groningen and the EDDA detector at the Cooler Synchrotron COSY at J黮ich. By measuring with very high statistical precision, the contributions that are second-order in the systematic errors become apparent. By calibrating the sensitivity of the polarimeter to such errors, it becomes possible to obtain information from the raw count rate values on the size of the errors and to use this information to correct the polarization measurements. During the experiment, it was possible to demonstrate that corrections were satisfactory at the level of 10 -5 for deliberately large errors. This may facilitate the real time observation of vector polarization changes smaller than 10 -6 in a search for an electric dipole moment using a storage ring.

Brantjes, N. P. M.; Dzordzhadze, V.; Gebel, R.; Gonnella, F.; Gray, F. E.; van der Hoek, D. J.; Imig, A.; Kruithof, W. L.; Lazarus, D. M.; Lehrach, A.; Lorentz, B.; Messi, R.; Moricciani, D.; Morse, W. M.; Noid, G. A.; Onderwater, C. J. G.; 謟ben, C. S.; Prasuhn, D.; Levi Sandri, P.; Semertzidis, Y. K.; da Silva e Silva, M.; Stephenson, E. J.; Stockhorst, H.; Venanzoni, G.; Versolato, O. O.

2012-02-01

134

Doping of graphene by adsorption of polar molecules at oxidized zigzag edges  

E-print Network

We have theoretically investigated the electronic and magnetic properties of graphene whose zigzag edges are oxidized. The alteration of these properties by adsorption of $\\mathrm{H_{2}O}$ and $\\mathrm{NH_3}$ molecules have been considered. It was found that the adsorbed molecules form a cluster along the oxidized zigzag edges of graphene due to interaction with the electro-negative oxygen. Graphene tends to donate a charge to the adsorbates through the oxygen atoms and the efficiency of donation depends on the intermolecular distance and on the location of the adsorbed molecules relative to the plane of graphene. It was found that by appropriate selection of the adsorbates, a controllable and gradual growth of $p$-doping in graphene with a variety of adsorbed molecules can be achieved

Berashevich, Julia

2009-01-01

135

Dipole moment of ultra-cold polar molecules:A quantum Monte Carlo study  

Microsoft Academic Search

There has been recently a great interest in the ultra-cold heteronuclear molecules that have a large electric dipole moment interaction both theoretically and experimentally. In this work, we calculate the dipole moment of a two-atom alkaline molecule, LiSr. We use two approaches: the configuration interaction and the quantum Monte Carlo method. We take the wavefunction calculated by configuration interaction and

Shi Guo; Lubos Mitas

2010-01-01

136

Influences of DMI on spin-polarized current through a single-molecule magnet  

NASA Astrophysics Data System (ADS)

We theoretically investigate the influences of the Dzyaloshinskii-Moriya interaction (DMI) on the spin-polarized transport through a single-molecular magnets, which is weakly coupled to ferromagnetic lead-L(pL) and nonmagnetic lead-R. The spin current is obtained by means of the rate-equation approach in the sequential-tunneling region. Due to the coherent superposition of the molecular state |1 induced by the DMI, we can observe the continuous pure spin current and negative differential conductance (NDC) under the full polarization pL=1 condition and polarization reversal of spin-current in the case of 0

Luo, Bo; Liu, Juan; Yao, Kai-Lun

2013-11-01

137

High-quality Reflection Separation using Polarized Images  

E-print Network

Abstract桰n this paper, we deal with a problem of separating the effect of reflection from images captured behind glass. The input consists of multiple polarized images captured from the same view point but with different polarizer angles. The output is the high quality separation of the reflection layer and the background layer from the images. We formulate this problem as a constrained optimization problem and propose a framework that allows us to fully exploit the mutually exclusive image information in our input data. We test our approach on various images and demonstrate that our approach can generate good reflection separation results. Index Terms梤eflection separation, image enhancement (a) (b)

Naejin Kong; Yu-wing Tai; Sung Yong Shin

138

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

PubMed

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(III) complexes, utilize diaminocyclohexane (cyLI) and diphenylethylenediamine (dpenLI) backbones, which we reasoned would impart conformational rigidity and result in Tb(III) complexes that display both large luminescence quantum yield (?) values and strong circularly polarized luminescence (CPL) activities. Both Tb(III) complexes are highly emissive, with ? values of 0.32 (dpenLI-Tb) and 0.60 (cyLI-Tb). Luminescence lifetime measurements in H(2)O and D(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(2)O molecule directly bound to the Tb(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(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. PMID:20730030

Samuel, Amanda P S; Lunkley, Jamie L; Muller, Gilles; Raymond, Kenneth N

2010-07-01

139

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

PubMed Central

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/TbIII complexes, utilize diaminocyclohexane (cyLI) and diphenylethylenediamine (dpenLI) backbones, which we reasoned would impart conformational rigidity and result in TbIII complexes that display both large luminescence quantum yield (?) values and strong circularly polarized luminescence (CPL) activities. Both TbIII complexes are highly emissive, with ? values of 0.32 (dpenLI-Tb) and 0.60 (cyLI-Tb). Luminescence lifetime measurements in H2O and D2O indicate that while cyLI-Tb exists as a single species in solution, dpenLI-Tb exists as two species: a monohydrate complex with one H2O molecule directly bound to the TbIII 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 TbIII 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. PMID:20730030

Samuel, Amanda P. S.; Lunkley, Jamie L.; Muller, Gilles

2010-01-01

140

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

141

Radiative polarization in high-energy storage rings  

SciTech Connect

Electron and positron beams circulating in high-energy storage rings become spontaneously polarized by the emission of synchrotron radiation. The asymptotic degree of polarization that can be attained is strongly affected by so-called depolarizing resonances. Detailed experimental measurements of the polarization were made SPEAR about ten years ago, but due to lack of a suitable theory only a limited theoretical fit to the data has so far been achieved. I present a general formalism for calculating depolarizing resonances, which as been coded into a computer program called SMILE, and use it to fit the SPEAR data. By the use of suitable approximations, I am able to fit both higher order and nonlinear resonances, and thereby to interpret many hitherto unexplained features in the data, and to resolve a puzzle concerning the asymmetry of certain resonance widths seen in the data. 18 refs., 2 figs.

Mane, S.R.

1989-03-01

142

Endless Polarization Stabilizer for High Bit-rate Polarization-Division Multiplexed Optical Systems  

Microsoft Academic Search

An endless polarization stabilization method is applied to a 40-Gbit\\/s RZ-DQPSK polarization-division multiplexed optical system. The effectivness of the polarization stabilizer in allowing the polarization demultiplexing of the two orthogonally polarized channels is experimentally verified.

Paolo Martelli; Pierpaolo Boffi; Maddalena Ferrario; Lucia Marazzi; Paola Parolari; Silvia M. Pietralunga; Aldo Righetti; Rocco Siano; Matteo Torregiani; Mario Martinelli

2008-01-01

143

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

PubMed

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

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

2015-01-20

144

Influence of molecular size, polarity and charge on the retention of organic molecules by nanofiltration  

Microsoft Academic Search

Because of the growing interest in nanofiltration for industrial use, a better insight in the retention mechanisms in nanofiltration is needed, which will make it possible to understand membrane performances for specific applications. In this paper, the retention of a series of organic molecules by four nanofiltration membranes was studied. The membranes that were used are NF70 (Dow\\/FilmTec), NTR 7450

B. Van der Bruggen; J. Schaep; D. Wilms; C. Vandecasteele

1999-01-01

145

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

146

High resolution X-ray scattering study of the multiply reentrant polar mesogen DB9ONO2  

E-print Network

temp茅rature SA1 et Sc. Abstract. 2014 Liquid crystal phases of the polar molecule DB9ONO2 display fluctuations- tions of liquid crystals composed of polar molecules. Many different thermodynamic phases are found known. Polar liquid crystals also com- monly display a 芦 reentrant 禄 nematic phase appear- ing

Boyer, Edmond

147

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

148

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

149

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

150

Novel macrophage polarization model: from gene expression to identification of new anti-inflammatory molecules  

Microsoft Academic Search

Plasticity is a well-known property of macrophages that is controlled by different changes in environmental signals. Macrophage\\u000a polarization is regarded as a spectrum of activation phenotypes adjusted from one activation extreme, the classic (M1), to\\u000a the other, the alternative (M2) activation. Here we show, in vitro and in vivo, that both M1 and M2 macrophage phenotypes\\u000a are tightly coupled to

Gloria Lopez-Castej髇; Alberto Baroja-Mazo; Pablo Pelegr韓

151

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

152

Decay of Polarons and Molecules in a Strongly Polarized Fermi Gas  

SciTech Connect

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

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

2010-07-09

153

Fusion with highly spin polarized HD and D2  

NASA Astrophysics Data System (ADS)

The experimental efforts over the past 5 years have been aimed at carrying out inertial confinement fusion (ICF) shots with spin-polarized D fuel. The authors successfully prepared polarized D in HD, and solved the problems of loading target shells with their carefully prepared isotopic mixtures, polarizing them so that the D polarization remains metastably frozen-in for about half a day, and carrying out the various cold transfer requirements at Syracuse, where the target is prepared, and at Rochester, where the cold target is inserted into the OMEGA fusion chamber. A principal concern during this past year was overcoming difficulties encountered in maintaining the integrity of the fragile cold target during the multitude of cold-transfers required for the experiment. These difficulties arose from insufficient rigidity of the cold transfer systems, which were constrained to be of small diameter by the narrow central access bore of the dilution refrigerator, and were exacerbated by the multitude of required target shell manipulations between different environments, each with different coupling geometry, including target shell permeation, polarization, storage, transport, retrieval and insertion into OMEGA. The authors did solve all of these problems, and were able to position a cold, high density but unpolarized target with required precision in OMEGA. Upon shooting the accurately positioned unpolarized high density cold target, no neutron yield was observed. Inspection inside the OMEGA tank after the shot indicated the absence of neutron yield was due to mal-timing or insufficient retraction rate of OMEGA's fast shroud mechanism, resulting in interception of at least 20 of the 24 laser beams by the faulty shroud. In spite of this, all elements of the complex experiment the authors originally undertook have been successfully demonstrated, and the cold retrieval concepts and methods they developed are being utilized on the ICF upgrades at Rochester and at Livermore.

Honig, A.; Letzring, S.; Skupsky, S.

1993-12-01

154

Rotational Cooling of Polar Molecules by Stark-tuned Cavity Resonance  

E-print Network

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

C. H. Raymond Ooi

2003-06-04

155

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

156

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

PubMed

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 the 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 the 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 first-order electronic-phase transition temperature. PMID:21776515

Das Arulsamy, Andrew; Kregar, Zlatko; Eler歩?, Kristina; Modic, Martina; Subramani, Uma Shankar

2011-09-01

157

Time-dependent polarization states of high-power, ultrashort laser pulses during atmospheric propagation  

NASA Astrophysics Data System (ADS)

We investigate, through simulation, the polarization state evolution of high-power, ultrashort laser pulses during atmospheric propagation. A dielectric response model for the molecular rotation handling arbitrary, transverse polarization couples both the amplitude and phase of the polarization states. We find that, while circularly and linearly polarized pulses maintain their polarization, elliptically polarized pulses become depolarized due to energy equilibration between left and right circularly polarized states. The depolarization can be detrimental to remote radiation generation schemes and obscures time-integrated polarization measurements.

Palastro, J. P.

2014-01-01

158

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

159

High performance photovoltaic applications using solution-processed small molecules.  

PubMed

Energy remains a critical issue for the survival and prosperity of humancivilization. Many experts believe that the eventual solution for sustainable energy is the use of direct solar energy as the main energy source. Among the options for renewable energy, photovoltaic technologies that harness solar energy offer a way to harness an unlimited resource and minimum environment impact in contrast with other alternatives such as water, nuclear, and wind energy. Currently, almost all commercial photovoltaic technologies use Si-based technology, which has a number of disadvantages including high cost, lack of flexibility, and the serious environmental impact of the Si industry. Other technologies, such as organic photovoltaic (OPV) cells, can overcome some of these issues. Today, polymer-based OPV (P-OPV) devices have achieved power conversion efficiencies (PCEs) that exceed 9%. Compared with P-OPV, small molecules based OPV (SM-OPV) offers further advantages, including a defined structure for more reproducible performance, higher mobility and open circuit voltage, and easier synthetic control that leads to more diversified structures. Therefore, while largely undeveloped, SM-OPV is an important emerging technology with performance comparable to P-OPV. In this Account, we summarize our recent results on solution-processed SM-OPV. We believe that solution processing is essential for taking full advantage of OPV technologies. Our work started with the synthesis of oligothiophene derivatives with an acceptor-donor-acceptor (A-D-A) structure. Both the backbone conjugation length and electron withdrawing terminal groups play an important role in the light absorption, energy levels and performance of the devices. Among those molecules, devices using a 7-thiophene-unit backbone and a 3-ethylrhodanine (RD) terminal unit produced a 6.1% PCE. With the optimized conjugation length and terminal unit, we borrowed from the results with P-OPV devices to optimize the backbone. Thus we selected BDT (benzo[1,2-b:4,5-b']dithiophene) and DTS (dithienosilole) to replace the central thiophene unit, leading to a PCE of 8.12%. In addition to our molecules, Bazan and co-workers have developed another excellent system using DTS as the core unit that has also achieved a PCE greater than 8%. PMID:23902284

Chen, Yongsheng; Wan, Xiangjian; Long, Guankui

2013-11-19

160

A 3D-Printed High Power Nuclear Spin Polarizer  

PubMed Central

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

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

2015-01-01

161

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

162

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

SciTech Connect

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

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

2011-10-15

163

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

164

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 0.04 cm/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 186,000 plates/m when corrected for injector dead volume. High resolution gradient separations of selected pharmaceutical compounds and phenylurea herbicides were achieved in less than 18 min. 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

165

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

166

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

SciTech Connect

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

X. Jiang; J. Arrington; F. Benmokhtar; A. Camsonne; J. P. Chen; S. Choi; E. Chudakov; F. Cusanno; A. Deur; D. Dutta; F. Garibaldi; D. Gaskell; O. Gayou; R. Gilman; C. Glashauser; D. Hamilton; O. Hansen; D. W. Higinbotham; R. J. Holt; C. W. de Jager; M. K. Jones; L. J. Kaufman; E. R. Kinney; K. Kramer; L. Lagamba; R. de Leo; J. Lerose; D. Lhuillier; R. Lindgren; N. Liyanage; K. McCormick; Z.-E. Meziani; R. Michaels; B. Mof?t; P. Monaghan; S. Nanda; K. D. Paschke; C. F. Perdrisat; V. Punjabi; I. A. Qattan; R. D. Ransome; P. E. Reimer; B. Reitz; A. Saha; E. C. Schulte; R. Sheyor; K. Slifer; P. Solvignon; V. Sulkosky; G. M. Urciuoli; E. Voutier; K. Wang; K. Wijesooriya; B. Wojtsekhowski; and L. Zhu

2007-05-01

167

Recoil-proton polarization in high-energy deuteron photodisintegration with circularly polarized photons.  

PubMed

We measured the angular dependence of the three recoil-proton polarization components in two-body photodisintegration of the deuteron at a photon energy of 2 GeV. These new data provide a benchmark for calculations based on quantum chromodynamics. Two of the five existing models have made predictions of polarization observables. Both explain the longitudinal polarization transfer satisfactorily. Transverse polarizations are not well described, but suggest isovector dominance. PMID:17501566

Jiang, X; Arrington, J; Benmokhtar, F; Camsonne, A; Chen, J P; Choi, S; Chudakov, E; Cusanno, F; Deur, A; Dutta, D; Garibaldi, F; Gaskell, D; Gayou, O; Gilman, R; Glashauser, C; Hamilton, D; Hansen, O; Higinbotham, D W; Holt, R J; de Jager, C W; Jones, M K; Kaufman, L J; Kinney, E R; Kramer, K; Lagamba, L; de Leo, R; Lerose, J; Lhuillier, D; Lindgren, R; Liyanage, N; McCormick, K; Meziani, Z-E; Michaels, R; Moffit, B; Monaghan, P; Nanda, S; Paschke, K D; Perdrisat, C F; Punjabi, V; Qattan, I A; Ransome, R D; Reimer, P E; Reitz, B; Saha, A; Schulte, E C; Sheyor, R; Slifer, K; Solvignon, P; Sulkosky, V; Urciuoli, G M; Voutier, E; Wang, K; Wijesooriya, K; Wojtsekhowski, B; Zhu, L

2007-05-01

168

Polar vortex dynamics during spring and fall diagnosed using trace gas observations from the Atmospheric Trace Molecule Spectroscopy instrument  

NASA Astrophysics Data System (ADS)

Trace gases measured by the Atmospheric Trace Molecule Spectroscopy (ATMOS) instrument during three Atmospheric Laboratory for Applications and Science (ATLAS) space-shuttle missions, in March/April 1992 (AT-1), April 1993 (AT-2), and November 1994 (AT-3) have been mapped into equivalent latitude/potential temperature (EqL/?) coordinates. The asymmetry of the spring vortices results in coverage of subtropical to polar EqLs. EqL/? fields of long-lived tracers in spring in both hemispheres show the net effects of descent at high EqL throughout the winter, reflecting strong descent in the upper stratosphere, decreasing descent at lower altitudes, and evidence of greater descent at the edge of the lower stratospheric vortex than in the vortex center; these results are consistent with trajectory calculations examining the history of the air measured by ATMOS in the month prior to each mission. EqL/? tracer fields, the derived fields CH4-CH4* (CH4* is the expected CH4 calculated from a prescribed relationship with N2O for fall) and NOy-NOy* (analogous to CH4*), and parcel histories all indicate regions of strong mixing in the 1994 Southern Hemisphere (SH) spring vortex above 500 K, with the strongest mixing confined to the vortex edge region between 500 and 700 K, and mixing throughout the Northern Hemisphere (NH) spring vortex in 1993 below about 850 K. Parcel histories indicate mixing of extravortex air with air near the vortex edge below 500 K in the SH but not with air in the vortex core; they show extravortex air mixing well into the vortex above 450 K in the NH and into the vortex edge region below. The effects of severe denitrification are apparent in EqL/? HNO3 in the SH lower stratospheric spring vortex. The morphology of HNO3 in the Arctic spring lower stratospheric vortex is consistent with the effects of descent. EqL/? fields of ATMOS NOy-NOy* show decreases consistent with the effects of mixing throughout the NH lower stratospheric vortex. The EqL/?-mapped ATMOS data thus indicate no significant denitrification during the 1992-1993 NH winter. Examination of H2O+2CH4 shows that dehydration in SH spring 1994 extended up to 600 K; it also suggests the possibility of a small amount of dehydration in the NH 1993 spring vortex below 465 K. Ozone depletion is evident in the spring vortices in both hemispheres. Differences in autumn EqL/? tracer fields between the missions reflect the fact that each succeeding mission took place 2 weeks later in the season, when the vortex had developed further. There was greater average descent and greater isolation of air in the developing vortex during each succeeding mission, consistent with progressively larger downward excursions of long-lived tracer contours observed in the upper stratosphere at high EqL.

Manney, G. L.; Michelsen, H. A.; Santee, M. L.; Gunson, M. R.; Irion, F. W.; Roche, A. E.; Livesey, N. J.

1999-08-01

169

Spin rotation of polarized beams in high energy storage ring  

E-print Network

The equations for spin evolution of a particle in a storage ring are obtained considering contributions from the tensor electric and magnetic polarizabilities of the particle along with the contributions from spin rotation and birefringence effect in polarized matter of an internal target. % Study of the spin rotation and birefringence effects for a particle in a high energy storage ring provides for measurement both the spin-dependent real part of the coherent elastic zero-angle scattering amplitude and tensor electric (magnetic) polarizabilities.

V. G. Baryshevsky

2006-03-23

170

High-Resolution Waveguide THz Spectroscopy of Biological Molecules?  

PubMed Central

Abstract Low-frequency vibrational modes of biological molecules consist of intramolecular modes, which are dependent on the molecule as a whole, as well as intermolecular modes, which arise from hydrogen-bonding interactions and van der Waals forces. Vibrational modes thus contain important information about conformation dynamics of biological molecules, and can also be used for identification purposes. However, conventional Fourier transform infrared spectroscopy and terahertz time-domain spectroscopy (THz-TDS) often result in broad, overlapping features that are difficult to distinguish. The technique of waveguide THz-TDS has been recently developed, resulting in sharper features. For this technique, an ordered polycrystalline film of the molecule is formed on a metal sample plate. This plate is incorporated into a metal parallel-plate waveguide and probed via waveguide THz-TDS. The planar order of the film reduces the inhomogeneous broadening, and cooling of the samples to 77K reduces the homogenous broadening. This combination results in the line-narrowing of THz vibrational modes, in some cases to an unprecedented degree. Here, this technique has been demonstrated with seven small biological molecules, thymine, deoxycytidine, adenosine, D-glucose, tryptophan, glycine, and L-alanine. The successful demonstration of this technique shows the possibilities and promise for future studies of internal vibrational modes of large biological molecules. PMID:17933879

Laman, N.; Harsha, S. Sree; Grischkowsky, D.; Melinger, Joseph S.

2008-01-01

171

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

PubMed

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

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

2008-01-01

172

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 a碌 (g - 2)碌/2 (m碌

R枚der, Beate

173

High polar content of long buried blocks of sequence in protein domains suggests selection against amyloidogenic non-polar sequences.  

PubMed

Native protein structures achieve stability in part by burying hydrophobic side-chains. About 75% of all amino acid residues buried in protein interiors are non-polar. Buried residues are not uniformly distributed in protein sequences, but sometimes cluster as contiguous polypeptide stretches that run through the interior of protein domain structures. Such regions have an intrinsically high local sequence density of non-polar residues, creating a potential problem: local non-polar sequences also promote protein misfolding and aggregation into non-native structures such as the amyloid fibrils in Alzheimer's disease. Here we show that long buried blocks of sequence in protein domains of known structure have, on average, a lower content of non-polar amino acids (about 70%) than do isolated buried residues (about 80%). This trend is observed both in small and in large protein domains and is independent of secondary structure. Long, completely non-polar buried stretches containing many large side-chains are particularly avoided. Aspartate residues that are incorporated in long buried stretches were found to make fewer polar interactions than those in short stretches, hinting that they may be destabilizing to the native state. We suggest that evolutionary pressure is acting on non-native properties, causing buried polar residues to be placed at positions where they would break up aggregation-prone non-polar sequences, perhaps even at some cost to native state stability. PMID:16935301

Patki, Aniruddha U; Hausrath, Andrew C; Cordes, Matthew H J

2006-09-29

174

A high-performance aluminum wire-grid polarizer for the optical telecommunication applications  

Microsoft Academic Search

In this study, we propose a high-performance polarizer with Aluminum wire-grid structure that an antireflection layer (AR) is deposited between the metal wires and the transparent substrate. The polarization properties of the polarizer are analyzed in detail using rigorous coupled wave analysis (RCWA). The theoretical research shows that aluminum wire-grid polarizer has high transmission coefficient and extinction ratio in near

Changkui Hu; Deming Liu

2008-01-01

175

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

176

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

SciTech Connect

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 such system is found to be 87%. This high efficient longitudinally polarized beam generated by hyper geometric Gaussian beam is useful for most of the near-field optics applications.

Rajesh, K. B.; Mohankumar, R.; Prathibajanet, C. Amala; Pillai, T. V. S. [Department of Physics, Anna University of Technology Tirunelveli (India); Jaroszewicz, Z. [Institute of Applied Optics, Department of Physical Optics, Warsaw (Poland)

2011-10-20

177

High voltage processing of the SLC polarized electron gun  

SciTech Connect

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

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

1993-04-01

178

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

PubMed

We propose and experimentally demonstrate a novel architecture for a W-band integrated optical wireless system, which adopts a 22 multiple-input multiple-output (MIMO) wireless link based on antenna polarization diversity, and can realize 80 km single-mode fiber-28 transmission and 2 m wireless delivery for up to 39 Gbaud polarization-division-multiplexing quadrature-phase-shift-keying (PDM-QPSK) signal at 100 GHz. Classic constant-modulus-algorithm (CMA) equalization is adopted at the receiver to implement polarization demultiplexing. The 22 MIMO wireless link adopts one pair of horizontal-polarization (H-polarization) horn antennas (HAs) and one pair of vertical-polarization (V-polarization) HAs. Because the two pairs of HAs are fully isolated, the wireless cross talk can be effectively avoided. Thus, compared to the 22 MIMO wireless link at the same antenna polarization, the adoption of antenna polarization diversity cannot only make the HA adjustment easier but can also reduce the required CMA tap number. After removing 20% forward-error-correction overhead, the 39 Gbaud baud rate corresponds to a net bit rate of 130??Gb/s, which, to our best knowledge, is the highest bit rate per PDM channel demonstrated for wireless signal delivery up to now. PMID:24690698

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

2014-03-01

179

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

180

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

181

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

SciTech Connect

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

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

2008-03-31

182

Multiple-polarization microstrip reflectarray antenna with high efficiency and low cross-polarization  

Microsoft Academic Search

This paper presents the study and prototype demonstration of the concepts of antenna focusing, cross-polarization reduction, and multiple-polarization capability of a planar microstrip reflectarray antenna. A square patch with two equal microstrip delay lines connected to its two orthogonal feeding points is used as the antenna element of the planar reflectarray. The length of the delay lines, which varies from

Dau-Chyrh Chang; Ming-Chih Huang

1995-01-01

183

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

E-print Network

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

Cai, Long

184

Metal-organic frameworks from chiral square-pyramidal copper(II) complexes: Enantiospecific inclusion and perfectly polar alignment of guest and host molecules  

NASA Astrophysics Data System (ADS)

The physical properties of [CuL 12(H 2O)] ( 1) and [CuL 22(H 2O)] ( 2) and preparation and crystal structures of the inclusion compounds 1( P)-C 2H 4Br 2, 2( M)-C 2H 4Br 2, 1稢H 3CN and 2稢H 3CN are described. HL 1 and HL 2 (H represents the dissociable phenolic proton) are the N,O-donor chiral reduced Schiff bases N-(2-hydroxy-5-nitrobenzyl)-( R)- ?-methyl-benzylamine and N-(2-hydroxy-5-nitrobenzyl)-( S)- ?-methylbenzylamine, respectively. All the compounds crystallize in the non-centrosymmetric space group C2. In the crystal lattice, the host [CuL n2(H 2O)] ( 1 and 2) molecules connected by O-H⋯O and C-H⋯O interactions form perfectly polar two-dimensional networks. In these chiral and polar host frameworks, enantiospecific inclusion with polar ordering of the right-handed ( P) and the left-handed ( M) gauche form of 1,2-dibromoethane as well as polar alignment of acetonitrile molecules are observed. The host and guest molecules are linked by C-H⋯O interactions. The O-atoms of the nitro substituent on the ligands of 1 and 2 act as the acceptors in all these intermolecular O-H⋯O and C-H⋯O interactions. The structures reported in this work provide rare examples of enantiospecific trapping of the chiral rotamers of 1,2-dibromoethane as well as perfectly polar alignment of both guest and host molecules.

Muppidi, Vamsee Krishna; Zacharias, Panthapally S.; Pal, Samudranil

2007-01-01

185

Dual-Band and Dual-Polarization Patch Antenna with High Isolation Characteristic  

E-print Network

1 Dual-Band and Dual-Polarization Patch Antenna with High Isolation Characteristic Dong-Hyuk Choi and Seong-Ook Park, Member, IEEE Abstract--A patch antenna with dual-band and dual-polarization operation--Coplanar waveguide (CPW) resonant cell, dual-band, dual-polarization, isolation, patch antenna I. INTRODUCTION

Park, Seong-Ook

186

Experimental study of polarization properties of highly birefringent photonic crystal fibers  

Microsoft Academic Search

We analyze experimentally the polarization properties of highly nonlinear small-core photonic crystal fibers (PCFs) with no intentional birefringence. The properties of recently emerged polarization maintaining PANDA PCFs are also investigated. The wavelength and temperature dependence of phase and group delay of these fibers are examined in the telecommunications wavelength range. Compared to a standard PANDA fiber, the polarization characteristics and

Tuomo Ritari; H. Ludvigsen; M. Wegmuller; M. Legr; N. Gisin; J. R. Folkenberg; M. D. Nielsen

2004-01-01

187

Electrical conductivity of single organic molecules in ultra high vacuum  

NASA Astrophysics Data System (ADS)

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

Pires, Ellis John

188

Submillimeterwave Spectroscopy of Highly Astrophysical Interest Molecule: Hydroxyacetonitrile  

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

189

High-efficiency broadband and multiband cross-polarization conversion using chiral metamaterial  

NASA Astrophysics Data System (ADS)

Metamaterials with tailored electromagnetic properties present incomparable advantages in manipulation and control of electromagnetic polarization states. Here, we report a unique chiral metamaterial (CMM) composed of three layers of metasurfaces. Taking advantage of the Fabry朠閞ot-like interference effect, the suggested CMM is capable of achieving high-efficiency broadband or multiband cross-polarization conversion for different linearly polarized incident waves, while also showing strong asymmetric transmission effect for the opposite propagation directions. With the specially designed geometry, the present CMM can even simultaneously accomplish nearly 90-polarization rotation for both the x- and y-polarized incident waves, thereby enabling more opportunities for designing high-performance polarimetric devices.

Song, Kun; Liu, Yahong; Luo, Chunrong; Zhao, Xiaopeng

2014-12-01

190

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

191

Invited Review. Imaging of Single DNA Molecule: Applications to High-Resolution Genomic Studies  

Microsoft Academic Search

Single molecule analysis of DNA has revealed new insights into its structural and physical properties. The application of new methods for manipulating and visualizing DNA has resulted in important advances in high-resolution physical mapping of the genome and quantitative cytogenetic studies of genomic abnormalities (Lichter 1997). Studies of single molecules of DNA have employed a variety of approaches including electron

John Herrick; Aaron Bensimon

1999-01-01

192

Quantum-classical correspondence in circularly polarized high harmonic generation F. Mauger and A. D. Bandrauk  

E-print Network

, short laser pulse with atoms/molecules is of great interest to the strong field and attosecond science generation, HHG, with a circularly polarized laser field offers an ideal framework for quantum have been investigated from var- ious angles ranging from experimental to numerical and analytical

193

Spectroscopy, reaction, and photodissociation in highly vibrationally excited molecules. Technical progress report  

SciTech Connect

Highly vibrationally excited molecules often control the course of chemical reactions in the atmosphere, combustion, plasmas, and many other environments. The research described in this Progress Report uses laser excitation and interrogation techniques to study and control the dynamics of highly vibrationally excited molecules. In particular, they show that it is possible to unravel the details and influence the course of photodissociation and bimolecular reaction. The experiments use laser excitation of overtone vibrations to prepare highly vibrationally excited molecules, frequently with single quantum state resolution, and laser spectroscopy to monitor the subsequent behavior of the excited molecule. We have studied the vibrationally mediated photodissociation and the bond- and state-selected bimolecular reaction of highly vibrationally excited molecules. In the first process, one photon creates a highly excited molecule, a second photon from another laser dissociates it, and light from a third laser detects the population of individual product quantum states. This approach allows us to explore otherwise inaccessible regions of the ground and excited state potential energy surface and, by exciting to the proper regions of the surface, to control the breaking of a selected chemical bond. In the second process, the highly vibrationally excited molecule reacts with an atom formed either in a microwave discharge or by photolysis and another laser interrogates the products. We have used this approach to demonstrate mode- and bond-selected bimolecular reactions in which the initial excitation controls the subsequent chemistry. 30 refs., 8 figs.

Not Available

1991-12-31

194

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

Microsoft Academic Search

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

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

2012-01-01

195

High degree of polarization of the near-band-edge photoluminescence in ZnO nanowires  

PubMed Central

We investigated the polarization dependence of the near-band-edge photoluminescence in ZnO strain-free nanowires grown by vapor phase technique. The emission is polarized perpendicular to the nanowire axis with a large polarization ratio (as high as 0.84 at 4.2 K and 0.63 at 300 K). The observed polarization ratio is explained in terms of selection rules for excitonic transitions derived from the k穚 theory for ZnO. The temperature dependence of the polarization ratio evidences a gradual activation of the XC excitonic transition. PACS: 78.55.Cr, 77.22.Ej, 81.07.Gf. PMID:21854578

2011-01-01

196

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

2009-12-31

197

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

198

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

199

Polarization of high-energy electrons traversing a laser beam  

E-print Network

When polarized electrons traverse a region where the laser light is focused their polarization varies even if their energy and direction of motion are not changed. This effect is due to interference of the incoming electron wave and an electron wave scattered at zero angle. Equations are obtained which determine the variation of the electron density matrix, and their solutions are given. The change in the electron polarization depends not only on the Compton cross section but on the real part of the forward Compton amplitude as well. It should be taken into account, for example, in simulations of the $e \\to \\gamma$ conversion for future $\\gamma \\gamma$ colliders.

G. L. Kotkin; H. Perlt; V. G. Serbo

1997-06-18

200

Effectiveness of organic molecules for spin filtering in an organic spin valve: Reaction-induced spin polarization for Co atop Alq 3  

NASA Astrophysics Data System (ADS)

The spin polarization of organic-ferromagnetic interfaces in an organic spin valve critically affects the efficiency of spin injection or detection. We examined the chemical and electronic properties of ferromagnetic Co deposited on organic Al q3 and the interfacial spin-polarized capability of the electronic states. Our x-ray photoemission spectra and calculations with density-functional theory indicate a sequential and unequal distribution of charge from Co clusters to N and then to O atoms in Al q3 . The preferential orbital hybridization at specific functional sites produces efficient spin polarization of organic molecules. Element-specific measurements of x-ray magnetic circular dichroism demonstrate the preferential spin polarization in the lowest unoccupied molecular orbital state of N atoms at the complex interface for Co atop Al q3 , which agrees satisfactorily with calculation. Our results indicate that an induced interfacial spin polarization on engineering the dominant reaction of Co with mainly N and O atoms in Al q3 might pave a way for effective spin filtering in organic spintronics.

Lam, Tu-Ngoc; Lai, Yu-Ling; Chen, Chih-Han; Chen, Po-Hung; Chan, Yuet-Loy; Wei, Der-Hsin; Lin, Hong-Ji; Chen, C. T.; Wang, Jeng-Han; Sheu, Jeng-Tzong; Hsu, Yao-Jane

2015-01-01

201

Measurement of the instrumental polarization of a high resolution ultraviolet spectrometer  

NASA Astrophysics Data System (ADS)

The polarization properties of a high-resolution echelle grating spectrometer have been characterized. Large variations of instrument response with incident polarization state at ultraviolet wavelengths were found. Measurements of the sensitivity of ISUS (Imaging Stratospheric Ultraviolet Spectrometer) to linearly polarized light at 312.6 nm showed a peak-to-peak variation of 72 percent as the plane of polarization is rotated. The results of these measurements are presented and nine elements of the 16-element system Mueller matrix which descibes the behavior of ISUS in partially linearized polarized light are measured. The implications of the observed instrumental polarization for remote sensing observations and its impact on a technique for discriminating against the polarized Rayleigh-scattered background to improve the measurement sensitivity are discussed.

Morgan, M. Frank; Chipman, Russell A.; Torr, Douglas G.

1990-02-01

202

Generation and application of a high-average-power polarized soft-x-ray laser beam  

E-print Network

demonstrate the generation of a highly polarized soft-x-ray beam with a compact high-repetition-rate table generated by compact tabletop sources has the potential to affect numerous other applications. 漏 2001 have also been con- ducted with polarized soft-x-ray radiation from laser- produced plasmas.2

Rocca, Jorge J.

203

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

204

High-frequency modulation of continuous-wave laser beams by maximally coherent molecules  

SciTech Connect

We suggest a technique where a molecular Raman transition is prepared near a maximally coherent state with continuous-wave (CW) laser beams. The key idea is to put the molecules inside a high-finesse cavity and to drive the molecular transition with two lasers whose frequency difference is slightly detuned from the Raman resonance. In this regime, the molecules become very efficient CW modulators with a modulation frequency that can be as high as 100 THz.

Yavuz, D. D. [Department of Physics, University of Wisconsin, 1150 University Avenue, Madison, Wisconsin 53706 (United States)

2007-07-15

205

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

206

Surface Properties of Mars' Northern High and Polar Latitudes, Including the Phoenix Landing Site  

Microsoft Academic Search

The unprecedented spatial resolution of the Mars Odyssey Thermal Emission Imaging System (THEMIS) is used to infer and compare the optical and thermal infrared properties of martian high-latitude and polar surfaces. Materials of interest include the north polar layered deposits (NPLD), the dark, dune-forming material associated with the north polar cap complex, and the ground ice-rich, latitude-dependent layer (the landing

A. R. Vasavada; M. I. Richardson; P. R. Christensen

2003-01-01

207

Highly stable polarization independent Mach-Zehnder interferometer  

NASA Astrophysics Data System (ADS)

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.

Mi?uda, Michal; Dol醟ov, Ester; Straka, Ivo; Mikov, Martina; Du歟k, Miloslav; Fiur釟ek, Jarom韗; Je瀍k, Miroslav

2014-08-01

208

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

2014-08-12

209

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.

210

Metal-organic frameworks from chiral square-pyramidal copper(II) complexes: Enantiospecific inclusion and perfectly polar alignment of guest and host molecules  

SciTech Connect

The physical properties of [CuL{sup 1} {sub 2}(H{sub 2}O)] (1) and [CuL{sup 2} {sub 2}(H{sub 2}O)] (2) and preparation and crystal structures of the inclusion compounds 1.(P)-C{sub 2}H{sub 4}Br{sub 2}, 2.(M)-C{sub 2}H{sub 4}Br{sub 2}, 1.CH{sub 3}CN and 2.CH{sub 3}CN are described. HL{sup 1} and HL{sup 2} (H represents the dissociable phenolic proton) are the N,O-donor chiral reduced Schiff bases N-(2-hydroxy-5-nitrobenzyl)-(R)-{alpha}-methyl-benzylamine and N-(2-hydroxy-5-nitrobenzyl)-(S)-{alpha}-methylbenzylamine, respectively. All the compounds crystallize in the non-centrosymmetric space group C2. In the crystal lattice, the host [CuL {sup n} {sub 2}(H{sub 2}O)] (1 and 2) molecules connected by O-H...O and C-H...O interactions form perfectly polar two-dimensional networks. In these chiral and polar host frameworks, enantiospecific inclusion with polar ordering of the right-handed (P) and the left-handed (M) gauche form of 1,2-dibromoethane as well as polar alignment of acetonitrile molecules are observed. The host and guest molecules are linked by C-H...O interactions. The O-atoms of the nitro substituent on the ligands of 1 and 2 act as the acceptors in all these intermolecular O-H...O and C-H...O interactions. The structures reported in this work provide rare examples of enantiospecific trapping of the chiral rotamers of 1,2-dibromoethane as well as perfectly polar alignment of both guest and host molecules. - Graphical abstract: The square-pyramidal Cu(II) complexes [CuL {sup n} {sub 2}(H{sub 2}O)] with the bidentate HL {sup n} (HL{sup 1}=N-(2-hydroxy-5-nitrobenzyl)-(R)-{alpha}-methyl-benzylamine and HL{sup 2}=N-(2-hydroxy-5-nitrobenzyl)-(S)-{alpha}-methylbenzylamine) form 1:1 host-guest compounds with Br(CH{sub 2}){sub 2}Br and CH{sub 3}CN. The X-ray structures of these species reveal the enantiospecific confinement of the chiral rotamers of Br(CH{sub 2}){sub 2}Br and perfectly polar ordering of both host and guest molecules in the crystal lattice. The figure shows the polar alignments of (a) [CuL{sup 1} {sub 2}(H{sub 2}O)].(P)-C{sub 2}H{sub 4}Br{sub 2} and (b) [CuL{sup 2} {sub 2}(H{sub 2}O)].CH{sub 3}CN.

Muppidi, Vamsee Krishna [School of Chemistry, University of Hyderabad, Hyderabad 500 046 (India); Zacharias, Panthapally S. [School of Chemistry, University of Hyderabad, Hyderabad 500 046 (India); Pal, Samudranil [School of Chemistry, University of Hyderabad, Hyderabad 500 046 (India)], E-mail: spsc@uohyd.ernet.in

2007-01-15

211

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

Microsoft Academic Search

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

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

2005-01-01

212

Towards understanding hydrophobic recovery of plasma treated polymers: Storing in high polarity liquids suppresses hydrophobic recovery  

NASA Astrophysics Data System (ADS)

The phenomenon of hydrophobic recovery was studied for cold air plasma treated polyethylene films. Plasma-treated polymer films were immersed into liquids with very different polarities such as ethanol, acetone, carbon tetrachloride, benzene and carbon disulphide. Hydrophobic recovery was studied by measurement of contact angles. Immersion into high polarity liquids slows markedly the hydrophobic recovery. We relate this slowing to dipole-dipole interaction of polar groups of the polymer with those of the liquids. This kind of interaction becomes decisive when polar groups of polymer chains are at least partially spatially fixed.

Bormashenko, Edward; Chaniel, Gilad; Grynyov, Roman

2013-05-01

213

Variation in polarization of high-energy $?$-quanta traversing a bunch of polarized laser photons  

E-print Network

The elastic light-light scattering below the threshold of the $e^+e^-$ pair production leads to a variation in polarization of hard $\\gamma$-quanta traversing without loss a region where the laser light is focused. Equations are obtained which determine the variation of Stokes parameters of $\\gamma$-quanta in this case, and their solutions are given. It is pointed out that this effect can be observed in the experiment E-144 at SLAC. It should be taken into account (and, perhaps, it can be used) in experiments at future $\\gamma \\gamma$ colliders.

G. L. Kotkin; V. G. Serbo

1996-11-18

214

Theory of Kerr Effect in Benzene C6H6(Anisotropic Molecule), Nitrobenzene C6H5NO2 and Water H2O (Polar Molecules)  

Microsoft Academic Search

The Kerr constants in C6H6 and C6H5NO2 are discussed by means of the statistical mechanics of Maxwell-Boltzmann's distribution of the molecules under the biasing field. The anisotropic electronic polarizabilities are obtained as alpha1{=}12.06 (3) (parallel to C6H6 plane) and alpha2{=}7.143 (3) (perpendicular to C6H6 plane) for the Kerr constant 6.0 10-18 in C6H6, and also alpha3{=}13.644 (3) (parallel to the

Wataru Kinase; Hitoshi Kato; Yukiko Otsuka; Masayuki Miyanaga

1986-01-01

215

High-fidelity quantum memory utilizing inhomogeneous nuclear polarization in a quantum dot  

NASA Astrophysics Data System (ADS)

We numerically investigate the encoding and retrieval processes for quantum memory realized in a semiconductor quantum dot by focusing on the effect of inhomogeneously polarized nuclear spins whose polarization depends on the local hyperfine coupling strength. We find that the performance of quantum memory is significantly improved by inhomogeneous nuclear polarization, as compared with homogeneous nuclear polarization. Moreover, the narrower the nuclear polarization distribution is, the better is the performance of the quantum memory. We ascribe the improvement in performance to the full harnessing of the highly polarized and strongly coupled nuclear spins by carefully studying the entropy change of individual nuclear spins during the encoding process. Our results shed light on the implementation of quantum memory in a quantum dot.

Ding, Wenkui; Shi, Anqi; You, J. Q.; Zhang, Wenxian

2014-12-01

216

Maintenance of Neuronal Polarity  

PubMed Central

Neurons are highly polarized cells with distinct domains responsible for receiving, transmitting, and propagating electrical signals. Central to these functions is the axon initial segment (AIS), a short region of the axon adjacent to the cell body that is enriched in voltage-gated ion channels, cell adhesion molecules, and cytoskeletal scaffolding proteins. Traditionally, the function of the AIS has been limited to its role in action potential initiation and modulation. However, recent experiments indicate that it also plays essential roles in neuronal polarity. Here, we review how initial segments are assembled, and discuss proposed mechanisms for how the AIS contributes to maintenance of neuronal polarity. PMID:21557501

Ho, Tammy Szu-Yu; Rasband, Matthew N.

2010-01-01

217

Polar Desert Adaptations of a High Arctic Plant Species  

Microsoft Academic Search

Plants of Saxifraga oppositifolia (Saxifragaceae) possess metabolic adaptations that allow them to grow successfully in polar desert microenvironments. Net photosynthesis (net carbon uptake) continues to be positive during drought until the leaf water stress declines to the range of -21 to -29 bars, which is considerably below the nonstress range of 0 to -10 bars. The plants can survive leaf

J. A. Teeri

1973-01-01

218

Elliptical polarization of Saturn Kilometric Radiation observed from high latitudes  

E-print Network

,2 B. Cecconi,3 L. Lamy,3 S.-Y. Ye,2 U. Taubenschuss,1 W. Macher,1 P. Zarka,3 W. S. Kurth,2 and D. A. Taubenschuss, W. Macher, P. Zarka, W. S. Kurth, and D. A. Gurnett (2009), Elliptical polarization of Saturn by Kaiser et al. [1984] or Zarka [1998]). Since the detection of SKR by the PRA (Planetary Radio Astronomy

Gurnett, Donald A.

219

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

220

Modeling and Simulation of Microwave Heating Microwave heating is very popular in warming up foods quickly and efficiently. In microwave heating, the time-varying electric field polarizes the molecules in dielectric  

E-print Network

quickly and efficiently. In microwave heating, the time-varying electric field polarizes the molecules in dielectric materials and creates electric dipole moments that cause these molecules to rotate. The friction with energy equation. The Maxwell's equations are solved to obtain the electric and magnetic field

Collins, Gary S.

221

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

PubMed Central

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燞z. A fraction (7%) of all Tsr molecules shows free diffusion over the entire cell surface with an average diffusion coefficient of 0.40 0.01 ?m2 s?1. The remaining molecules were found to be ultimately confined in compartments of size 290 15爊m and showed restricted diffusion at an inner barrier found at 170 10爊m. At the shortest length-scales (<170爊m), 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燣.; Ritchie, Ken

2014-01-01

222

1.5um Polarization-Entangled Bell States Generation Based on Birefringence in High Nonlinear Microstructure Fiber  

E-print Network

Polarization-entangled photon pair generation based on two scalar scattering processes of the vector four photon scattering has been demonstrated experimentally in high nonlinear microstructure fiber with birefringence. By controlling the pump polarization state, polarization-entangled Bell states can be realized. It is provides a simple way to realize efficient and compact fiber based polarization-entangled photon pair sources.

Qiang Zhou; Wei Zhang; Jierong Cheng; Yidong Huang; Jiangde Peng

2009-08-10

223

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

224

Bombardment of gas molecules on single graphene layer at high temperature  

NASA Astrophysics Data System (ADS)

Graphite is widely used as a material for rocket-nozzle inserts due to its excellent thermo-physical properties as well as low density. During the operation of rockets, the surface of the graphite nozzle is subjected to very high heat fluxes and the undesirable erosion of the surface occurs due to the bombardment of gas molecules with high kinetic energy, which causes a significant reduction of nozzle performance. However, the understanding and quantification of such bombardment is not satisfactory due to its complexity: The bond breaking-forming happens simultaneously for the carbon atoms of graphene, some gas molecules penetrate through the surface, some of them are reflected from the surface, etc. In the present study, we perform extensive molecular dynamics (MD) simulations to examine the bombardment phenomena in high temperature environment (several thousand Kelvin). Advanced from the previous studies that have focused on the bombardment by light molecules (e.g., H2), we will concentrate on the impact by realistic molecules (e.g., CO2 and H2O ). LAMMPS is employed for the MD simulations with NVE ensemble and AIREBO potential for graphene. The molecular understanding of the interaction between graphene and highly energetic gas molecules will enable us to design an efficient thermo-mechanical protection system.

Murugesan, Ramki; Park, Jae Hyun; Ha, Dong Sung

2014-12-01

225

Polar desert adaptations of a high arctic plant species.  

PubMed

Plants of Saxifraga oppositifolia (Saxifragaceae) possess metabolic adaptations that allow them to grow successfully in polar desert microenvironments. Net photosynthesis (net carbon uptake) continues to be positive during drought until the leaf water stress declines to the range of -21 to -29 bars, which is considerably below the nonstress range of 0 to -10 bars. The plants can survive leaf water stresses of at least -44 bars in the field and leaf water stresses of -55 bars in a growth chamber. PMID:17739145

Teeri, J A

1973-02-01

226

Polar pixels for high resolution small animal PET  

Microsoft Academic Search

In this work, we introduce polar-pixel basis functions for iterative reconstruction of small animal PET data. Our aim was to accelerate the reconstruction when using a system matrix stored on-disk, as well as the Monte-Carlo simulations related to the calculation of the matrix. The study was restricted to 2D. A common approach to reduce the number of the system matrix

C. Mora; M. Rafecas

2006-01-01

227

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

228

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

PubMed

High-order harmonic generation is a powerful and sensitive tool for probing atomic and molecular structures, combining in the same measurement an unprecedented attosecond temporal resolution with a high spatial resolution of the order of an angstrom. Imaging of the outermost molecular orbital by high-order harmonic generation has been limited for a long time to very simple molecules, like nitrogen. Recently we demonstrated a technique that overcame several of the issues that have prevented the extension of molecular orbital tomography to more complex species, showing that molecular imaging can be applied to a triatomic molecule like carbon dioxide. Here we report on the application of such a technique to nitrous oxide (N2O) and acetylene (C2H2). This result represents a first step towards the imaging of fragile compounds, a category which includes most of the fundamental biological molecules. PMID:25415258

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

2014-01-01

229

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

230

Origin of the highly efficient third-order optical response in small organic molecules  

NASA Astrophysics Data System (ADS)

The search for materials with high optical nonlinearity has driven decades of research, with little success in developing materials that are suitable for third-order nonlinear optical applications that utilize the intensity-dependent refractive index or intensity-dependent absorption, for example. Organic materials, with their highly delocalized electron systems that lead to large nonlinearities and fast (10-15 s) optical response times and the relative ease at which their molecular properties can be tailored (allowing certain molecular properties to be isolated and optimized through molecular structure variations), are ideal candidates for the next generation of nonlinear optical materials. These materials have led to the largest molecular nonlinearities measured, but still remained several orders of magnitude below their theoretical limits. Our aim in this work is to approach the absolute limit, but also to keep the molecular size small. This research direction should lead to a dense packing of molecules with high nonlinearity in the solid state, which will then lead to the large bulk nonlinearities necessary for all-optical applications. With donor-substituted cyanoethynylethene molecules, we have measured off-resonant nonlinearities within a factor of 50 of their theoretical limits and predict that solid-state devices made from these materials can be up to an order of magnitude larger than other materials made from organic molecules. By measuring a large number of molecules with different structural variations, we have isolated the electron donor and acceptor structures as necessities for large third-order nonlinearities in small molecules. Our best molecule has a molecular third-order polarizability per mass of g rot = 6.5 x 10-23 m5V-2Kg-1, the highest value measured to date. We have also measured our molecules on resonance, which leads to measurements of the two-photon absorption cross-section sigma TPA. These measurements give a value of 9 x 10 -48 cm4s/photon for our best molecule, which is an order of magnitude larger than a chromophore optimized for two-photon absorption. Because of the record high results measured in these molecules, along with their ability to be vapor deposited into integrated devices, we suggest that this family of molecules may be the predecessors to the next generation of applied third-order nonlinear optical materials.

May, Joshua C.

2007-05-01

231

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)

2007-02-06

232

A high field SQUID magnetometer for studying spin-polarized liquid {sup 3}He  

SciTech Connect

The authors present the SQUID magnetometer working in a field of 11T that they recently developed to study transiently polarized liquid {sup 3}He. Emphasis is on the problems posed by the high magnetic field. 5 refs., 2 figs.

Bravin, M.; Wiegers, S.A.J.; Wolf, P.E.; Puech, L. [CRTBT-CNRS, Grenoble (France)

1992-11-01

233

Reflective liquid crystal polarization gratings with high efficiency and small pitch  

Microsoft Academic Search

We report our experimental success in realizing high efficiency liquid crystal polarization gratings (LCPGs) on reflective substrates, with periods as small as 2.2mum, enabling the largest switchable LCPG diffraction angles reported yet for red light. Moreover, these gratings retain nearly ideal electro-optical properties, including > 95% hologram efficiency, high polarization contrast, sub-millisecond total switching times, and relatively low voltage operation

Ravi K. Komanduri; Chulwoo Oh; Michael J. Escuti

2008-01-01

234

Reflective liquid crystal polarization gratings with high efficiency and small pitch  

Microsoft Academic Search

We report our experimental success in realizing high efficiency liquid crystal polarization gratings (LCPGs) on reflective substrates, with periods as small as 2.2祄, enabling the largest switchable LCPG diffraction angles reported yet for red light. Moreover, these gratings retain nearly ideal electro-optical properties, including > 95% hologram efficiency, high polarization contrast, sub-millisecond total switching times, and relatively low voltage operation

Ravi K. Komanduri; Chulwoo Oh; Michael J. Escuti

2008-01-01

235

High-Throughput RT-PCR for small-molecule screening assays  

PubMed Central

Quantitative measurement of the levels of mRNA expression using real-time reverse transcription polymerase chain reaction (RT-PCR) has long been used for analyzing expression differences in tissue or cell lines of interest. This method has been used somewhat less frequently to measure the changes in gene expression due to perturbagens such as small molecules or siRNA. The availability of new instrumentation for liquid handling and real-time PCR analysis as well as the commercial availability of start-to-finish kits for RT-PCR has enabled the use of this method for high-throughput small-molecule screening on a scale comparable to traditional high-throughput screening (HTS) assays. This protocol focuses on the special considerations necessary for using quantitative RT-PCR as a primary small-molecule screening assay, including the different methods available for mRNA isolation and analysis. PMID:23487248

Bittker, Joshua A.

2012-01-01

236

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

237

Highly oriented mesoporous silica channels synthesized in microgrooves and visualized with single-molecule diffusion.  

PubMed

A novel synthesis method for large-pore, well-aligned 2D hexagonal mesoporous silica thin films is reported. The alignment was achieved by confinement in poly(dimethylsiloxane) (PDMS) microgrooves without the necessity of additional forces (such as electric fields). We describe the influence of various experimental conditions including the way the grooves are filled, surface modification at the solid/liquid interfaces, and the height-to-width ratio of the microgrooves on mesopore alignment. With this technique, highly oriented mesoporous silica channels can be obtained at a length scale of several millimeters. For a nondestructive, detailed, and wide-ranging structural and dynamic characterization of the as-synthesized mesochannel silica network, dye molecules were incorporated into the channels at concentrations suitable for single-molecule microscopy. A "maximum projection" of individual frames recorded with a fluorescence microscope immediately gives a global overview ("map") of the pore structure, thus providing direct feedback for tuning synthesis conditions. In addition, deeper insights into the real nanoscale structure of the mesoporous silica framework were obtained through high-accuracy single-molecule tracking experiments. The high spatial accuracy of the experiments allowed for the direct observation of jumps of single dye molecules between individual channels in the mesoporous silica host. Nevertheless, due to the low concentration of defects, the diffusion could be described as a 1D random walk where the molecules diffuse along the highly oriented, parallel channels and sometimes switch from channel to channel through small defects in the pore walls. Furthermore, it could be shown with single-molecule microscopy that template removal and calcination of the aligned films results in an increased defect concentration; however, the overall order of the structures remained intact. PMID:22270886

R黨le, Bastian; Davies, Melari; Lebold, Timo; Br鋟chle, Christoph; Bein, Thomas

2012-03-27

238

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

PubMed Central

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

Khanal, Ashok

2014-01-01

239

All-reflective, highly accurate polarization rotator for high-power short-pulse laser systems.  

PubMed

We present the setup of a polarization rotating device and its adaption for high-power short-pulse laser systems. Compared to conventional halfwave plates, the all-reflective principle using three zero-phase shift mirrors provides a higher accuracy and a higher damage threshold. Since plan-parallel plates, e.g. these halfwave plates, generate postpulses, which could lead to the generation of prepulses during the subsequent laser chain, the presented device avoids parasitic pulses and is therefore the preferable alternative for high-contrast applications. Moreover the device is easily scalable for large beam diameters and its spectral reflectivity can be adjusted by an appropriate mirror coating to be well suited for ultra-short laser pulses. PMID:23037123

Keppler, S; Hornung, M; B鰀efeld, R; Kahle, M; Hein, J; Kaluza, M C

2012-08-27

240

High Harmonic Spectroscopy of the Cooper Minimum in Molecules M. C. H. Wong,1  

E-print Network

in CS2 and CCl4 at $42 and $40 eV, respectively, by comparing the high harmonic spectra with the known calculations of harmonic spectra. We use CM to probe electron localization in Cl-containing molecules (CCl4, CH

Lin, Chii-Dong

241

INNER SHELL EXCITATION OF ATOMS AND MOLECULES BY ELECTRON IMPACT WITH HIGH ENERGY RESOLUTION  

E-print Network

INNER SHELL EXCITATION OF ATOMS AND MOLECULES BY ELECTRON IMPACT WITH HIGH ENERGY RESOLUTION F. H. Introduction. -- Electrons have always been used in inner shell studies, both as the bombarding particles will be made. The detection of inner shell excited reso- nances at incident electron energies of a few 100 e

Paris-Sud XI, Universit茅 de

242

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.; Pa雙e, 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

243

High field dynamic nuclear polarization NMR with surfactant sheltered biradicals.  

PubMed

We illustrate the ability to place a water-insoluble biradical, bTbk, into a glycerol/water matrix with the assistance of a surfactant, sodium octyl sulfate (SOS). This surfactant approach enables a previously water insoluble biradical, bTbk, with favorable electron-electron dipolar coupling to be used for dynamic nuclear polarization (DNP) nuclear magnetic resonance (NMR) experiments in frozen, glassy, aqueous media. Nuclear Overhauser enhancement (NOE) and paramagnetic relaxation enhancement (PRE) experiments are conducted to determine the distribution of urea and several biradicals within the SOS macromolecular assembly. We also demonstrate that SOS assemblies are an effective approach by which mixed biradicals are created through an assembly process. PMID:24506193

Kiesewetter, Matthew K; Michaelis, Vladimir K; Walish, Joseph J; Griffin, Robert G; Swager, Timothy M

2014-02-20

244

High-precision spectroscopy of ultracold molecules in an optical lattice  

E-print Network

The study of ultracold molecules tightly trapped in an optical lattice can expand the frontier of precision measurement and spectroscopy, and provide a deeper insight into molecular and fundamental physics. Here we create, image, and probe microkelvin $^{88}$Sr$_2$ molecules in a lattice, and demonstrate precise measurements of molecular parameters as well as coherent control of molecular quantum states using optical fields. We discuss the sensitivity of the system to dimensional effects, a new bound-to-continuum spectroscopy technique for highly accurate binding energy measurements, and prospects for new physics with this rich experimental system.

McGuyer, B H; Iwata, G Z; Tarallo, M G; Grier, A T; Apfelbeck, F; Zelevinsky, T

2015-01-01

245

Coulomb excitation of highly charged projectile ions in relativistic collisions with diatomic molecules  

SciTech Connect

We investigate the Coulomb excitation of highly charged ions colliding with diatomic molecules. In this process, the coherent interaction between the projectile electron and two molecular centers may cause clear interference patterns in the (collision) energy dependencies of the total cross sections and alignment parameters. We discuss such a Young-type interference for the particular case of the K{yields}L excitation of hydrogen- and helium-like projectile ions. Calculations, performed for the scattering of these ions on nitrogen molecules, indicate that the interference effects are extremely sensitive to the collisional geometry and are pronounced only if the molecular axis is aligned almost parallel to the incident beam trajectory.

Artemyev, A. N.; McConnell, S. R.; Surzhykov, A.; Najjari, B.; Voitkiv, A. B. [Physikalisches Institut, Universitaet Heidelberg, Philosophenweg 12, D-69120 Heidelberg, Germany and GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, D-64291 Darmstadt (Germany); Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, D-69117 Heidelberg (Germany)

2011-10-15

246

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

PubMed

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

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

2015-01-01

247

Giant Viscosity Enhancement in a Spin-Polarized Fermi Liquid National High Magnetic Field Laboratory  

E-print Network

Giant Viscosity Enhancement in a Spin-Polarized Fermi Liquid National High Magnetic Field liquid mixtures. The viscosity was measured for extremely high magnetic field/temperature conditions (B dependence of viscosity of 3 He-4 He mixtures in high magnetic fields. Schematic illustration of method

Weston, Ken

248

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

249

Transport spin polarization of high Curie temperature MnBi films  

NASA Astrophysics Data System (ADS)

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

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

2011-01-01

250

Transport Spin Polarization of High-Curie Temperature MnBi Films  

NASA Astrophysics Data System (ADS)

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

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

2011-03-01

251

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

SciTech Connect

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

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

2011-03-15

252

Highly sensitive detection of target molecules using a new fluorescence-based bead assay  

NASA Astrophysics Data System (ADS)

Development of immunoassays with improved sensitivity, specificity and reliability are of major interest in modern bioanalytical research. We describe the development of a new immunomagnetic fluorescence detection (IM-FD) assay based on specific antigen/antibody interactions and on accumulation of the fluorescence signal on superparamagnetic PE beads in combination with the use of extrinsic fluorescent labels. IM-FD can be easily modified by varying the order of coatings and assay conditions. Depending on the target molecule, antibodies (ABs), entire proteins, or small protein epitopes can be used as capture molecules. The presence of target molecules is detected by fluorescence microscopy using fluorescently labeled secondary or detection antibodies. Here, we demonstrate the potential of the new assay detecting the two tumor markers IGF-I and p53 antibodies in the clinically relevant concentration range. Our data show that the fluorescence-based bead assay exhibits a large dynamic range and a high sensitivity down to the subpicomolar level.

Scheffler, Silvia; Strau, Denis; Sauer, Markus

2007-07-01

253

High-throughput single-molecule fluorescence spectroscopy using parallel detection  

PubMed Central

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

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

2011-01-01

254

High isolation dual-polarized patch antenna using integrated defected ground structure  

Microsoft Academic Search

This letter presents a high isolation dual-frequency orthogonally polarized rectangular patch antenna utilizing microstrip feed line integrated with a defected ground structure (DGS). The demonstrated approach results in a significant improvement in port isolation in comparison to a conventional dual-polarized antenna fed by simple microstrip lines. Measurements show an improvement of 20 dB in port isolation relative to the conventional

Younkyu Chung; Seong-Sik Jeon; Dal Ahn; Jae-Ick Choi; Tatsuo Itoh

2004-01-01

255

Nonlinear polarization coupling and its application to high resolution distributed fiber sensing  

Microsoft Academic Search

A technique for time-resolved, high-resolution distributed pressure sensing utilizing nonlinearly induced birefringence and polarization coupling in optical fibers is proposed. A theory of cross-interaction between two counterpropagating waves which agrees well with numerical simulations is presented. By measuring the relative power of the two principal polarizations of a probe wave at the fiber output, distribution of the linear birefringence along

W. Zhao; E. Bourkoff

1993-01-01

256

Internal spin structure of the proton from high energy polarized e-p scattering  

SciTech Connect

A review is given of experimental knowledge of the spin dependent structure functions of the proton, which is based on inclusive high energy scattering of longitudinal polarized electrons by longitudinally polarized protons in both the deep inelastic and resonance regions, and includes preliminary results from our most recent SLAC experiment. Implications for scaling, sum rules, models of proton structure, and the hyperfine structure interval in hydrogen are given. Possible future directions of research are indicated.

Hughes, V.W.; Baum, G.; Bergstroem, M.R.

1981-02-01

257

High-definition vertically aligned liquid crystal microdisplays using a circularly polarized light  

NASA Astrophysics Data System (ADS)

A high-definition vertically aligned liquid crystal (LC) microdisplay exhibits a excellent contrast ratio, but its fringing field effect splits the bright state unevenly and leads to a very slow response time. By utilizing a circularly polarized light instead of conventional linearly polarized light, we have overcome the long-standing problems of poor sharpness, low brightness, and slow response time. Confirming computer simulations agree with the experimental results well. This approach can be applied to both reflective and transmissive LC microdisplays.

Fan-Chiang, Kuan-Hsu; Chen, Shu-Hsia; Wu, Shin-Tson

2005-07-01

258

Spin Polarization versus Color-Flavor-Locking in High Density Quark Matter  

E-print Network

It is shown that spin polarization with respect to each flavor in three-flavor quark matter occurs instead of the color-flavor locking at high baryon density by using the Nambu-Jona-Lasinio model with four-point tensor-type interaction. Also, it is indicated that the order of phase transition between the color-flavor locked phase and the spin polarized phase is the first order by means of the second order perturbation theory.

Y. Tsue; J. da Providencia; C. Providencia; M. Yamamura; H. Bohr

2014-11-27

259

Relativistic Effects and Polarization in Three High-Energy Pulsar Models  

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

260

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

NASA Astrophysics Data System (ADS)

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

Gulsen, Gultekin; Nalcioglu, Orhan

2005-04-01

261

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

PubMed Central

Although single-molecule fluorescence spectroscopy was first demonstrated at near-absolute zero temperatures (1.8 K)1, the field has since advanced to include room-temperature observations2, largely owing to the use of objective lenses with high numerical aperture, brighter fluorophores and more sensitive detectors. This has opened the door for many chemical and biological systems to be studied at native temperatures at the single-molecule level both in vitro34 and in vivo56. However, it is difficult to study systems and phenomena at temperatures above 37 癈, because the index-matching fluids used with high-numerical-aperture objective lenses can conduct heat from the sample to the lens, and sustained exposure to high temperatures can cause the lens to fail. Here, we report that TiO2 colloids with diameters of 2 ?m and a high refractive index can act as lenses that are capable of single-molecule imaging at 70 癈 when placed in immediate proximity to an emitting molecule. The optical system is completed by a low-numerical-aperture optic that can have a long working distance and an air interface, which allows the sample to be independently heated. Colloidal lenses were used for parallel imaging of surface-immobilized single fluorophores and for real-time single-molecule measurements of mesophilic and thermophilic enzymes at 70 癈. Fluorophores in close proximity to TiO2 also showed a 40% increase in photostability due to a reduction of the excited-state lifetime. PMID:20023643

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

2014-01-01

262

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

263

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

264

Time Resolved Spectroscopy of High Field Polars (FUSE 00)  

NASA Technical Reports Server (NTRS)

The following work has been accomplished: 1) The emission lines of O VI1 and He II were used to produce Doppler tomograms of the plasma emission. 2) An improved interstellar absorption model is being developed for the CIAO spectral fitting program, Sherpa. Use of the earlier version of this model showed it to be inadequate for its purpose. Once this model is working, we intend to complete our analysis of V884 Her and those of other FUSE programs. In addition to the above work, this grant has helped support the following related work: 1) The publication of the paper "Periodicities in the X-ray intensity variations of TV Columbae: an Intermediate Polar" by Rana, V. R., Singh, K. P., Schlegel, E. M., & Barrett, P. 2004, AJ, 126,489, and 2) FUSE data of a possible nova-like variable Ret 1 has been analyzed and shown to contain a hot (37000 deg) white dwarf (WD 0334-6400). The FUV spectrum shows strong absorption lines of C III.

Barrett, Paul

2004-01-01

265

Complex Organic Molecules at High Spatial Resolution toward ORION-KL. I. Spatial Scales  

NASA Astrophysics Data System (ADS)

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 [C2H5CN], dimethyl ether [(CH3)2O], methyl formate [HCOOCH3], formic acid [HCOOH], acetone [(CH3)2CO], SiO, methanol [CH3OH], and methyl cyanide [CH3CN] in Orion-KL at ? = 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.; Friedel, Douglas N.

2012-08-01

266

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

2006-05-23

267

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

268

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

PubMed Central

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

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

2014-01-01

269

Photonic generation of triangular pulses based on nonlinear polarization rotation in a highly nonlinear fiber.  

PubMed

We propose a novel method to generate triangular pulses based on the nonlinear polarization rotation (NPR) effect in a highly nonlinear fiber. A continuous wave probe beam is polarization-rotated by an intensity-modulated control beam via the NPR effect. A polarization-division-multiplexing emulator is exploited to split the probe beam into two orthogonally polarized states with imbalanced time delay. After detection by a photodetector, a 90 microwave phase shifter is used to compensate the phases of the fundamental and the third-order harmonic components in order to generate triangular pulses. Triangular pulses at 5 and 6 GHz with full duty cycles are experimentally generated. The root mean square errors between the generated and the simulated waveforms are 3.6e-4 and 1e-4 for triangular pulses at 5 and 6 GHz, respectively. PMID:25121867

Li, Wei; Wang, Wei Yu; Sun, Wen Hui; Wang, Wen Ting; Liu, Jian Guo; Zhu, Ning Hua

2014-08-15

270

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

271

Differences in the polar clustering of the high- and low-abundance chemoreceptors of Escherichia coli  

PubMed Central

The chemosensory complexes in Escherichia coli are localized predominantly in large aggregates at one or both of the cell poles, however, neither the role of the polar localization nor the role of the clustering is understood. In E. coli, the two classes of chemoreceptors or transducers, high- and low-abundance, differ in their ability to support chemotaxis when expressed as the sole chemoreceptor type in the cell. In this study, we examined both the contribution of individual chemoreceptors to polar clustering and the ability of each chemoreceptor type to cluster in the absence of all others. We found that polar clustering of methyl-accepting chemotaxis proteins (MCPs) is not dependent on any one chemoreceptor type. Remarkably, when expressed individually at similar levels, the chemoreceptors display differential clustering abilities. The high-abundance transducers cluster at the cell pole almost as well as do the MCPs in cells expressing all four species, whereas the low-abundance transducers, although polar, are not particularly clustered. CheA and CheW distributions in strains expressing only one chemoreceptor type coincide with MCP localization, indicating that the low-abundance chemoreceptors are competent for ternary complex formation but are defective in aggregation. These studies reveal that, in contrast to our previous model, polarity of the chemoreceptors is independent of clustering, suggesting that the polar localization of the chemoreceptors is not simply caused by diffusion limitations on large protein aggregates. PMID:10859356

Lybarger, S. R.; Maddock, J. R.

2000-01-01

272

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

273

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

274

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

275

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

NASA Astrophysics Data System (ADS)

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, M.; Upton, L.; Hathaway, D.

2012-12-01

276

Polarization properties of ion-excitation mechanisms in high-voltage gaps E. Stambulchik and Y. Maron  

E-print Network

Polarization properties of ion-excitation mechanisms in high-voltage gaps E. Stambulchik and Y-energy ions accelerated near the ion-emitting surface. By accounting for the polarization properties polarization spectroscopy PPS 7 has recently become of an increasing interest. The idea behind PPS

277

High tunnel magnetoresistance in spin-polarized scanning tunneling microscopy of Co nanoparticles on Pt(111)  

E-print Network

High tunnel magnetoresistance in spin-polarized scanning tunneling microscopy of Co nanoparticles and 850% magnetoresistance of the tip-sample tunnel junction with tip and sample at 300 K and 160 K to lead to very high magnetoresistance values. 漏 2005 American Institute of Physics. DOI: 10

Brune, Harald

278

Polarization of High Energy Emission from the Crab Pulsar: Model Prediction Versus Observation  

NASA Astrophysics Data System (ADS)

We discuss polarization characteristics of high-energy photons from pulsar magnetospheres. Polarization measurements play an important role to discriminate the various models that successfully explain observed spectra or light curves. As indicated by the outer gap model of Cheng et al. (2000), the Crab optical and soft -ray spectrum can be easily explained by the synchrotron radiation. We therefore study the polarization predicted by the synchrotron emission in the framework of the outer gap model and the two-pole caustic model (Dyks et al. 2004).We assume that the emitted photons are linearly polarized in the direction of particle acceleration, which is perpendicular to the magnetic field line, for which the rotating dipole field is used. Emission direction and Stokes parameters Q and U are appropriately treated with the effects of particle抯 gyration and aberration. A radial-distance dependent emissivity (Cheng et al. 2000) is employed for the outer gap model and a constant one is assumed for the caustic model. We find that the minimum in the polarization degree is < 10% at the bridge phase for both models, and the maximum is 60% at outer wings of peaks for the outer gap model and 20% at trailing of peaks for the caustic model. These patterns are not similar to the Crab optical data, in which the minimum is at both peaks and the maximum is at the bridge phase. The computed position angle swing does not match with the data either.The curvature radiation model predicts too high a degree of polarization (Dyks et al. 2004) and no successful spectra have been achieved up to date. On the other hand, none of the models discussed above is able to reproduce the Crab optical polarization. To understand the Crab polarization, we may need a more realistic structure of the pulsar magnetosphere.

Chang, Hsiang-Kuang; Takata, J.

2006-06-01

279

Theoretical study on the ground state of the polar alkali-metal-barium molecules: Potential energy curve and permanent dipole moment  

NASA Astrophysics Data System (ADS)

In this paper, we systematically investigate the electronic structure for the 2?+ ground state of the polar alkali-metal-alkaline-earth-metal molecules BaAlk (Alk = Li, Na, K, Rb, and Cs). Potential energy curves and permanent dipole moments (PDMs) are determined using power quantum chemistry complete active space self-consistent field and multi-reference configuration interaction methods. Basic spectroscopic constants are derived from ro-vibrational bound state calculation. From the calculations, it is shown that BaK, BaRb, and BaCs molecules have moderate values of PDM at the equilibrium bond distance (BaK:1.62 D, BaRb:3.32 D, and BaCs:4.02 D). Besides, the equilibrium bond length (4.93 and 5.19 ) and dissociation energy (0.1825 eV and 0.1817 eV) for the BaRb and BaCs are also obtained.

Gou, Dezhi; Kuang, Xiaoyu; Gao, Yufeng; Huo, Dongming

2015-01-01

280

Theoretical study on the ground state of the polar alkali-metal-barium molecules: Potential energy curve and permanent dipole moment.  

PubMed

In this paper, we systematically investigate the electronic structure for the (2)?(+) ground state of the polar alkali-metal-alkaline-earth-metal molecules BaAlk (Alk = Li, Na, K, Rb, and Cs). Potential energy curves and permanent dipole moments (PDMs) are determined using power quantum chemistry complete active space self-consistent field and multi-reference configuration interaction methods. Basic spectroscopic constants are derived from ro-vibrational bound state calculation. From the calculations, it is shown that BaK, BaRb, and BaCs molecules have moderate values of PDM at the equilibrium bond distance (BaK:1.62 D, BaRb:3.32 D, and BaCs:4.02 D). Besides, the equilibrium bond length (4.93 and 5.19 ) and dissociation energy (0.1825 eV and 0.1817 eV) for the BaRb and BaCs are also obtained. PMID:25612710

Gou, Dezhi; Kuang, Xiaoyu; Gao, Yufeng; Huo, Dongming

2015-01-21

281

Simulations of multiply scattered polarized returns of a spaceborne lidar from a model atmosphere consisting of a mixture of molecules, aerosols, and water clouds  

NASA Astrophysics Data System (ADS)

In lidar remote sensing the classical lidar equation is normally used for the retrieval of environmental parameters from the return signal. One of the most important reasons for this is the simplicity of this equation which describes the contribution of single scattering to the return signal only. But it is well known that multiple scattering occurs in lidar sensing of dense clouds and remote cirrus clouds. Therefore a more precise description of lidar returns is needed. We use a general stochastic model for the description of the transport of light through the atmosphere. This model is a 'corpuscular stochastic multiple scattering process including polarization, and random change of type of scatterers (for fixed wavelength)' which is (under mild conditions) equivalent to a corresponding general radiative transfer equation. From this exact multiple scattering lidar equation a hierarchy of lidar equations including the classical lidar equation may be derived by introducing simplifying assumptions step by step. Of course, more information about the scattering behavior of the scattering particles or molecules of the atmosphere is needed for such an exact multiple scattering equation, but the more input is necessary the more output is possible. Indeed, it is possible to obtain simultaneously quite different environmental parameters (e.g. extinction and size distribution) from one multiply scattered return signal. We show examples of simulations of multiply scattered returns of a spaceborne lidar from an atmosphere consisting of a mixture of molecules, cirrus, water clouds, and haze with a height dependent extinction coefficient for each component.

Oppel, Ulrich G.

2001-04-01

282

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

PubMed Central

Electron杗uclei coupling accompanying excitation and relaxation processes is a fascinating phenomenon in molecular dynamics. A striking and unexpected example of such coupling is presented here in the context of photoelectron circular dichroism measurements on randomly oriented, chiral methyloxirane molecules, unaffected by any continuum resonance. Here, we report that the forward-backward asymmetry in the electron angular distribution, with respect to the photon axis, which is associated with photoelectron circular dichroism can surprisingly reverse direction according to the ion vibrational mode excited. This vibrational dependence represents a clear breakdown of the usual Franck朇ondon 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

283

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

284

High-Volume Meandering Channels in Titan's South Polar Region  

NASA Astrophysics Data System (ADS)

Morphological measurements of two wide meandering channels near Sikun Labyrinthus, Titan, reveal characteristics similar to high-volume rivers on Earth. The channels are compared to a stretch of the Mississippi River near Mayersville, Mississippi.

Malaska, M.; Radebaugh, J.; Le Gall, A.; Mitchell, K.; Lopes, R.; Wall, S.

2011-03-01

285

Polarized high-brilliance and high-resolution soft x-ray source at ELETTRA: The performance of beamline BACH  

NASA Astrophysics Data System (ADS)

BACH, a soft x-ray beamline for polarization-dependent experiments at the Italian synchrotron radiation facility ELETTRA, was recently completed and characterized. Its performance, in terms of energy resolution, flux and polarization, is presented. Based on two APPLE II undulators, BACH covers the energy range between 35 and 1600 eV with the control of the light polarization. The monochromator is equipped with four gratings and allows one to work either in a high resolution or in a high flux mode. After the monochromator, the beamline is split into two branches with different refocusing properties. One is optimized to exploit the performance of the soft x-ray spectrometer (ComIXS) available at the beamline. Resolving powers between 12000 at 90 eV photon energy and 6600 near 867 eV were achieved using the high-resolution gratings and the smallest available slit width (10 ?m). For the high-brilliance grating, which works between 290 and 1600 eV, resolving powers between 7000 at 400 eV and 2200 at 867 eV were obtained. The flux in the experimental chamber, measured with the high-resolution gratings for linearly polarized light at the best achievable resolution, ranges between 41011 photons/s at 125 eV and 21010 photons/s between 900 and 1250 eV. In circularly polarized mode the flux is two times larger for energies up to 380 eV. A gain of nearly one order of magnitude is obtained for the high-brilliance grating, in accordance with theoretical predictions. Flux beyond 1.31011 photons/s was measured up to 1300 eV, and thus over nearly the complete energy range covered by this high-brilliance grating, with a maximum of 1.61011 photons/s between 800 and 1100 eV. First results from polarization measurements confirm a polarization above 99.7% for both linearly and circularly polarized modes at low energies. Circular dichroism experiments indicate a circular polarization beyond 90% at the Fe L2/L3 edge near 720 eV.

Zangrando, M.; Zacchigna, M.; Finazzi, M.; Cocco, D.; Rochow, R.; Parmigiani, F.

2004-01-01

286

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

287

Origin of High-Resolution IETS-STM Images of Organic Molecules with Functionalized Tips  

NASA Astrophysics Data System (ADS)

Recently, the family of high-resolution scanning probe imaging techniques using decorated tips has been complemented by a method based on inelastic electron tunneling spectroscopy (IETS). The new technique resolves the inner structure of organic molecules by mapping the vibrational energy of a single carbon monoxide (CO) molecule positioned at the apex of a scanning tunneling microscope (STM) tip. Here, we explain high-resolution IETS imaging by extending a model developed earlier for STM and atomic force microscopy (AFM) imaging with decorated tips. In particular, we show that the tip decorated with CO acts as a nanoscale sensor that changes the energy of its frustrated translation mode in response to changes of the local curvature of the surface potential. In addition, we show that high resolution AFM, STM, and IETS-STM images can deliver information about the charge distribution within molecules deposited on a surface. To demonstrate this, we extend our mechanical model by taking into account electrostatic forces acting on the decorated tip in the surface Hartree potential.

Hapala, Prokop; Temirov, Ruslan; Tautz, F. Stefan; Jel韓ek, Pavel

2014-11-01

288

Observation of high-order polarization-locked vector solitons in a fiber laser  

E-print Network

We report on the experimental observation of a novel type of polarization locked vector soliton in a passively mode-locked fiber laser. The vector soliton is characterized by that not only the two orthogonally polarized soliton components are phase locked, but also one of the components has a double-humped intensity profile. Multiple such phase-locked high order vector solitons with identical soliton parameters and harmonic mode-locking of the vector solitons were also obtained in the laser. Numerical simulations confirmed the existence of stable high-order vector solitons in fiber lasers.

D. Y. Tang; H. Zhang; L. M. Zhao; X. Wu

2009-03-13

289

Polarization measurements and high spin structure in 131Ba  

NASA Astrophysics Data System (ADS)

The high spin states of 131Ba have been populated in the fusion evaporation reaction 122Sn(overflow="scroll">13C,4n)131Ba at Ebeam = 65MeV. The ? transitions belonging to various band structures were detected using an array of fifteen Clover Germanium detectors. Some of new transitions have been placed in high spin states. Spin and parity for a band has been calculated for first time in 131Ba. The said band is interpreted in term of multi-quasiparticle configurations, based on Total Rothian Surfaces (TRS) calculations.

Kaur, Navneet; Kumar, A.; Mukherjee, G.; Singh, Amandeep; Singh, Varinderjit; Sandal, Rohit; Kaur, Rajbir; Behera, B. R.; Singh, K. P.; Singh, G.; Sharma, H. P.; Kumar, Suresh; Raja, M. K.; Madhusudhan Rao, P. V.; Muralithar, S.; Singh, R. P.; Kumar, Rakesh; Madhavan, N.; Praharaj, C. R.; Naik, Z.

2013-04-01

290

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

Horv醫h, G醔or; Heged黶, Ram髇; Barta, Andr醩; Farkas, Alexandra; 舓esson, Susanne

2011-10-01

291

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

292

Fast, high-fidelity, all-optical and dynamically-controlled polarization gate using room-temperature atomic vapor  

NASA Astrophysics Data System (ADS)

We demonstrate a fast, all-optical polarization gate in a room-temperature atomic medium. Using a Polarization-Selective-Kerr-Phase-Shift (PSKPS) technique, we selectively write a ? phase shift to one circularly-polarized component of a linearly-polarized input signal field. The output signal field maintains its original strength but acquires a 90 linear polarization rotation, demonstrating fast, high-fidelity, dynamically-controlled polarization gate operation. The intensity of the polarization-switching field used in this PKSPK-based polarization gate operation is only 2 mW/cm2, which would be equivalent to 0.5 nW of light power (? = 800 nm) confined in a typical commercial photonic hollow-core fiber. This development opens a realm of possibilities for potential future extremely low light level telecommunication and information processing systems.

Li, Runbing; Zhu, Chengjie; Deng, L.; Hagley, E. W.

2014-10-01

293

Transport of dust to high northern latitudes in a Martian polar warming  

NASA Technical Reports Server (NTRS)

The transport of dust in the Martian atmosphere into high northern latitudes as a result of a Martian polar-warming (and global-dust-storm) event was investigated using a simplified transport model in conjunction with a beta-plane dynamical model to simulate the transport of dust. Numerical experiments were performed to examine the influence of different warming dynamics and to assess the sensitivity of the transport to the initial dust distribution. Results indicate that substantial amounts of dust could be transported and deposited at high northern latitudes (extending to the pole) in a polar-warming event. The potential for the transport of water was also examined through simulations, with results indicating that large amounts of water could be transported to the north polar region in a warming, on the condition that substantial condensation and precipitation do not take place in the subpolar regions. However, the warmth of the Martian atmosphere during global dust storms makes the latter possible.

Barnes, Jeffrey R.

1990-01-01

294

Transport of dust to high northern latitudes in a Martian polar warming  

NASA Astrophysics Data System (ADS)

The transport of dust in the Martian atmosphere into high northern latitudes as a result of a Martian polar-warming (and global-dust-storm) event was investigated using a simplified transport model in conjunction with a beta-plane dynamical model to simulate the transport of dust. Numerical experiments were performed to examine the influence of different warming dynamics and to assess the sensitivity of the transport to the initial dust distribution. Results indicate that substantial amounts of dust could be transported and deposited at high northern latitudes (extending to the pole) in a polar-warming event. The potential for the transport of water was also examined through simulations, with results indicating that large amounts of water could be transported to the north polar region in a warming, on the condition that substantial condensation and precipitation do not take place in the subpolar regions. However, the warmth of the Martian atmosphere during global dust storms makes the latter possible.

Barnes, J. R.

1990-02-01

295

High-symmetry polarization domains in low-symmetry ferroelectrics.  

PubMed

We present experimental evidence for polygonal domain faceting in the ferroelectric polymer poly(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE) films with the lower orthorhombic crystallographic symmetry. It is proposed that this effect can arise from purely electrostatic depolarizing forces. We show that, in contrast to magnetic bubble shape domains, where such type of deformation instability has a predominantly elliptical character, the emergence of more symmetrical circular harmonics is favored in ferroelectrics with high dielectric constants. PMID:25420186

Lukyanchuk, I; Sharma, P; Nakajima, T; Okamura, S; Scott, J F; Gruverman, A

2014-12-10

296

High-Symmetry Polarization Domains in Low-Symmetry Ferroelectrics  

NASA Astrophysics Data System (ADS)

We present experimental evidence for hexagonal domain faceting in the ferroelectric polymer PVDF-TrFE films having the lower orthorhombic crystallographic symmetry. This effect can arise from purely electrostatic depolarizing forces. We show that in contrast to magnetic bubble shape domains where such type of deformation instability has a predominantly elliptical character, the emergence of more symmetrical circular harmonics is favored in ferroelectrics with high dielectric constant.

Lukyanchuk, I.; Sharma, P.; Nakajima, T.; Okamura, S.; Scott, J. F.; Gruverman, A.

2014-12-01

297

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

298

Highly efficient broadband polarization retarders and tunable polarization filters made of composite stacks of ordinary wave plates.  

PubMed

By using the formal analogy between the evolution of the state vector in quantum mechanics and the Jones vector in polarization optics, we construct and demonstrate experimentally efficient broadband half-wave polarization retarders and tunable narrowband polarization filters. Both the broadband retarders and the filters are constructed by the same set of stacked standard multiorder optical wave plates (WPs) rotated at different angles with respect to their fast polarization axes: for a certain set of angles this device behaves as a broadband polarization retarder, while for another set of angles it turns into a narrowband polarization filter. We demonstrate that the transmission profile of our filter can be centered around any desired wavelength in a certain vicinity of the design wavelength of the WPs solely by selecting appropriate rotation angles. PMID:24979626

Dimova, E St; Ivanov, S S; Popkirov, G St; Vitanov, N V

2014-05-01

299

Ultra high resolution molecular beam cars spectroscopy with application to planetary atmospheric molecules  

NASA Technical Reports Server (NTRS)

The measurement of high resolution pulsed and continuous wave (CW) coherent anti-Stokes Raman spectroscopy (CARS) measurements in pulsed and steady state supersonic expansions were demonstrated. Pulsed molecular beam sources were characterized, and saturation of a Raman transition and, for the first time, the Raman spectrum of a complex molecular cluster were observed. The observation of CW CARS spectra in a molecular expansion and the effects of transit time broadening is described. Supersonic expansion is established as a viable technique for high resolution Raman spectroscopy of cold molecules with resolutions of 100 MH2.

Byer, R. L.

1982-01-01

300

Highly efficient C-band circularly polarized rectifying antenna array for wireless microwave power transmission  

Microsoft Academic Search

This paper reports a new circularly polarized (CP) high-gain, high-efficiency rectifying antenna (rectenna) array designed in a coplanar stripline (CPS) circuit. The array can maintain a constant dc output voltage regardless of its broadside orientation. The array is etched on Rogers Duroid 5870 substrate with ?r=2.33 and 10 mil thickness. High-gain dual rhombic loop antennas and a reflecting plane are

Berndie Strassner; Kai Chang

2003-01-01

301

Effective Rotation-Pseudorotation Hamiltonian for X3-Type Molecules in the High-Barrier Limit  

NASA Astrophysics Data System (ADS)

The rotation-pseudorotation problem in X3-type molecules has been treated group-theoretically for the high-barrier tunneling case. Explicit expressions for rotation-pseudorotation Hamiltonian matrix elements, which take into account the interaction of overall rotation with the rotation of principal axes accompanying pseudorotation motion and with the angular momentum generated by pseudorotation motion, have been derived using an m-fold extended group of the G12 permutation-inversion group. Illustrative pseudorotation tunneling splitting patterns have been derived by numerically diagonalizing the resulting Hamiltonian matrix for J = 5, using rotational constants appropriate for Na 3 in the B state, together with various sets of tunneling parameters. These tunneling splittings can be qualitatively understood using the concept of twofold energy level clusters in asymmetric rotor molecules.

Ohashi, N.; Tsuura, M.; Hougen, J. T.

1995-09-01

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.; Mu駉z Caro, G. M.; Chen, Y.-J.; Yih, T.-S.

2014-02-01

303

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

SciTech Connect

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 X{sup 2} {Pi}-A{sup 2}{Sigma}{sup +} 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{sup +} ion current as a function of the laser frequency, the X{sup 2}{Pi}-A{sup 2} {Sigma}{sup +} 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 and Ken [Quantum Dot Research Center, National Institute for Materials Science, 3-13 Sakura, Tsukuba 305-0003 (Japan)

2011-01-15

304

Polarized photoconductivity and photoinduced absorption measurements in highly stretched trans-polyacetylene films  

NASA Technical Reports Server (NTRS)

Photoinduced near infrared absorption, parallel and perpendicular photoconductivity of an highly oriented form of trans-polyacetylene have been studied as a function of the angle between the laser polarization and the fiber axis. The results are discussed on the basis of the phonon-assisted hopping model for the transport of the charge carriers.

Dorsinville, R.; Krimchansky, S.; Alfano, R. R.; Birman, J. L.; Tubino, R.

1985-01-01

305

Retrofit of a high power Nd:glass laser system with liquid crystal polarizers  

Microsoft Academic Search

The glass development laser (GDL), has been operating at the Laboratory for Laser Energetics since 1978. This Nd:phosphate glass system produces high peak power optical radiation at lambda = 1054 nm or lambda = 351 nm for use in studying the interaction physics of intense laser beams with matter. The amplifier staging incoroprates the propagation of linearly and circularly polarized

S. D. Jacobs; K. A. Ceruga; T. J. Kessler; W. Seka; R. Bahr

1985-01-01

306

EDITORIAL: New materials with high spin polarization: half-metallic Heusler compounds  

Microsoft Academic Search

The development of magnetic Heusler compounds, specifically designed as materials for spintronic applications, has made tremendous progress in the very recent past [1-21]. Heusler compounds can be made as half-metals, showing a high spin polarization of the conduction electrons of up to 100% [1]. These materials are exceptionally well suited for applications in magnetic tunnel junctions acting, for example, as

Claudia Felser; Burkard Hillebrands

2007-01-01

307

Polarization control of high order harmonics in the EUV photon energy  

E-print Network

Polarization control of high order harmonics in the EUV photon energy range Boris Vodungbo,1,* Anna 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. 漏 2011 Optical

308

Observations of the plasma density enhancement in the high-altitude polar region during geomagnetic storms  

Microsoft Academic Search

Recent satellite observations have clarified that plasma outflows play an important role in abrupt changes in the ion composition in the plasmasheet and ring current during geomagnetic storms. In the present study, we perform case studies of enhancement of the plasma density and ion upflow in the high-altitude polar region during geomagnetic storms using the data observed by the Akebono

Naritoshi Kitamura; Atsuki Shinbori; Yukitoshi Nishimura; Takayuki Ono; Masahide Iizima; Atsushi Kumamoto; Manabu Yamada; Shigeto Watanabe; Takumi Abe; Andrew W. Yau

2008-01-01

309

High-speed electro-optic modulators utilizing polarization-reversed structures  

Microsoft Academic Search

The polarization reversal technology of ferroelectric optical crystals enables us to construct new high-speed electro-optic modulators with advanced functions; quasi-velocity-matched phase\\/intensity modulators, single-side band (SSB) \\/frequency-shift-keying (FSK) modulators operated with a single microwave signal, and duo-binary modulators. These devices are attractive for applications in many microwave photonic systems.

Hiroshi Murata; Yasuyuki Okamura

2008-01-01

310

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; Kj鎟, Helle Astrid; Vallelonga, Paul; Azuma, Nobuhiko; Takata, Morimasa

2014-05-01

311

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

312

Polarized light imaging of birefringence and diattenuation at high resolution and high sensitivity  

NASA Astrophysics Data System (ADS)

Polarized light microscopy provides unique opportunities for analyzing the molecular order in man-made and natural materials, including biological structures inside living cells, tissues, and whole organisms. 20 years ago, the LC-PolScope was introduced as a modern version of the traditional polarizing microscope enhanced by liquid crystal devices for the control of polarization, and by electronic imaging and digital image processing for fast and comprehensive image acquisition and analysis. The LC-PolScope is commonly used for birefringence imaging, analyzing the spatial and temporal variations of the differential phase delay in ordered and transparent materials. Here we describe an alternative use of the LC-PolScope for imaging the polarization dependent transmittance of dichroic materials. We explain the minor changes needed to convert the instrument between the two imaging modes, discuss the relationship between the quantities measured with each instrument, and touch on the physical connection between refractive index, birefringence, transmittance, diattenuation, and dichroism.

Mehta, Shalin B.; Shribak, Michael; Oldenbourg, Rudolf

2013-09-01

313

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

314

Polarization Measurements of Radiative Electron Capture Transitions in Highly Charged Ions  

NASA Astrophysics Data System (ADS)

A dedicated Si(Li) Compton polarimeter combining energy and time resolution with a large detection area of 6464 mm2 and a two dimensional position resolution of 2 mm has been used for the first time to study the polarization of x-rays emitted via radiative electron capture (REC) into the K and L-shell of heavy highly charged ions. First data for the collision system 96.6 MeV/u U92+?H2 are presented. The angular distribution of the Compton scattered photons inside the detector indicates that both K- and L-REC processes lead to the emission of strongly linearly polarized light.

Br鋟ning, H.; Hess, S.; Geyer, S.; Spillmann, U.; Kozhuharov, Ch.; Krings, Th.; Kumar, A.; M鋜tin, R.; Protic, D.; Reuschl, R.; Trassinelli, M.; Trotsenko, S.; Weber, G.; Winters, D.; St鰄lker, Th.

2009-03-01

315

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

316

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

317

Two-pulse orientation dynamics and high-harmonic spectroscopy of strongly-oriented molecules  

NASA Astrophysics Data System (ADS)

We present the detailed analysis of a new two-pulse orientation scheme that achieves macroscopic field-free orientation at the high particle densities required for attosecond and high-harmonic spectroscopies (Kraus et al 2013 arXiv:1311.3923). Carbon monoxide molecules are oriented by combining one-colour and delayed two-colour non-resonant femtosecond laser pulses. High-harmonic generation is used to probe the oriented wave-packet dynamics and reveals that a very high degree of orientation (Nup/Ntotal = 0.73-0.82) is achieved. We further extend this approach to orienting carbonyl sulphide molecules. We show that the present two-pulse scheme selectively enhances orientation created by the hyperpolarizability interaction whereas the ionization-depletion mechanism plays no role. We further control and optimize orientation through the delay between the one- and two-colour pump pulses. Finally, we demonstrate a complementary encoding of electronic-structure features, such as shape resonances, in the even- and odd-harmonic spectrum. The achieved progress makes two-pulse field-free orientation an attractive tool for a broad class of time-resolved measurements.

Kraus, P. M.; Baykusheva, D.; W鰎ner, H. J.

2014-06-01

318

Mapping of intracellular halogenous molecules by low and high resolution SIMS microscopy.  

PubMed

The subcellular distribution of halogenous molecules has been studied by SIMS microscopy in cultured cells of a human breast carcinoma (MCF-7 cell line). Two instruments of microanalysis were used. A low lateral resolution ion microscope (SMI 300 CAMECA) and a prototype scanning ion microscope equipped with a cesium gun that gives high lateral resolution images. This apparatus has been developed by G Slodzian, in Onera Laboratories (Office National d'Etudes et de Recherches A閞ospatiales). Molecules studied by low lateral resolution ion microscope were halogenous steroids: fluorometholone, triamcinolone, bromocriptine and bromoandrosterone. Analytical images show that the first two compounds are mainly localized in the nuclear structure of MCF-7 cells whereas the last two molecules are localized in cytoplasm of these cells. Images were obtained with a resolution of 1 micron. With the scanning ion microscope, it is now possible to obtain images at the ultrastructural level. Four analytical images can be simultaneously obtained by a single scan of the imaged area, corresponding to a depth of erosion of the section of ten nm. The intranuclear distributions of three pyrimidine analogs, 5-bromo-2'-deoxyuridine, 5-iodo-2'-deoxyuridine and 5-fluorouracil have been studied in phase S and M of MCF-7 cells and these images have been compared to the distribution of sulfur, nitrogen and phosphorus. All these images have been obtained with a lateral resolution better than 100 nm. PMID:1511252

Berry, J P; Galle, P; Chassoux, D; Escaig, F; Linarez-Cruz, L G; Lespinats, G

1992-01-01

319

Compact gain-switching linearly polarized high-power Yb pulse fiber laser  

NASA Astrophysics Data System (ADS)

A compact gain-switching pumped linearly polarized high-power Yb pulse fiber laser is experimentally demonstrated. The laser was mainly composed of a piece of polarization-maintaining (PM) Yb-doped fiber and a pair of PM FBGs. Three fiber pig-tailed laser diodes (LDs) were applied as the pump source through a (6+1)??1 fiber coupler and configured in a pulse-working scheme. Stable pulse operation was achieved with repetition rate up to 200?kHz, pulse duration of 120?ns and a spectral FWHM of 0.08?nm. A maximum average laser output power of 21?W was obtained at 200?kHz with respect to the pump power of 30.3?W. The polarization extinction ratio was as good as 15?dB.

Wei, K. H.; Cai, S. S.; Jiang, P. P.; Hua, D. C.; Yan, Y. X.; Wu, B.; Shen, Y. H.

2014-08-01

320

Enhanced tunneling magnetroresistance and high spin polarization in polystyrene coated Fe3O4 granular system  

NASA Astrophysics Data System (ADS)

Polystyrene coated Fe3O4 nanoparticles through surface engineering exhibit intergranular tunneling magnetoresistance (MR) ratio of 22.8% at room temperature and a maximum MR of 40.9% at 110 K. The drastic enhancement of the MR ratio clearly suggests that there is high degree of spin polarization even at room temperature for half metallic Fe3O4. The derived spin polarization P is about 54% and 83% at room temperature and 110 K, respectively. It is possible that a simple tunnel junction made of Fe3O4 exhibits large MR in a relatively small field. Fe3O4 may also be used as an effective spin injector. Knowing that our results provided only a lower limit on the spin polarization of Fe3O4, it has the potential to play an important role in spintronic devices.

Tang, Jinke

2008-05-01

321

A Circularly Symmetric Antenna Design With High Polarization Purity and Low Spillover  

E-print Network

We describe the development of two circularly symmetric antennas with high polarization purity and low spillover. Both were designed to be used in an all-sky polarization and intensity survey at 5 GHz (the C-Band All-Sky Survey, C-BASS). The survey requirements call for very low levels of cross-polar leakage and far-out sidelobes. Two different existing antennas, with 6.1-m and 7.6-m diameter primaries, were adapted by replacing the feed and secondary optics, resulting in identical beam performances of 0.73deg FWHM, cross-polarization better than -50 dB, and far-out sidelobes below -70 dB. The polarization purity was realized by using a symmetric low-loss dielectric foam support structure for the secondary mirror, avoiding the need for secondary support struts. Ground spill-over was largely reduced by using absorbing baffles around the primary and secondary mirrors, and by the use of a low-sidelobe profiled corrugated feedhorn. The 6.1-m antenna and receiver have been completed and test results show that the ...

Holler, C M; Jones, M E; King, O G; Muchovej, S J C; Stevenson, M A; Wylde, R J; Copley, C J; Davis, R J; Pearson, T J; Readhead, A C S

2011-01-01

322

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

323

Subunits of highly Fluorescent Protein R-Phycoerythrin as Probes for Cell Imaging and Single-Molecule Detection  

SciTech Connect

The purposes of our research were: (1) To characterize subunits of highly fluorescent protein R-Phycoerythrin (R-PE) and check their suitability for single-molecule detection (SMD) and cell imaging, (2) To extend the use of R-PE subunits through design of similar proteins that will be used as probes for microscopy and spectral imaging in a single cell, and (3) To demonstrate a high-throughput spectral imaging method that will rival spectral flow cytometry in the analysis of individual cells. We first demonstrated that R-PE subunits have spectroscopic and structural characteristics that make them suitable for SMD. Subunits were isolated from R-PE by high-performance liquid chromatography (HPLC) and detected as single molecules by total internal reflection fluorescence microscopy (TIRFM). In addition, R-PE subunits and their enzymatic digests were characterized by several separation and detection methods including HPLC, capillary electrophoresis, sodium dodecyl sulfate-polyacrilamide gel electrophoresis (SDS-PAGE) and HPLC-electrospray ionization mass spectrometry (ESI-MS). Favorable absorption and fluorescence of the R-PE subunits and digest peptides originate from phycoerythrobilin (PEB) and phycourobilin (PUB) chromophores that are covalently attached to cysteine residues. High absorption coefficients and strong fluorescence (even under denaturing conditions), broad excitation and emission fluorescence spectra in the visible region of electromagnetic spectrum, and relatively low molecular weights make these molecules suitable for use as fluorescence labels of biomolecules and cells. We further designed fluorescent proteins both in vitro and in vivo (in Escherichia coli) based on the highly specific attachment of PEB chromophore to genetically expressed apo-subunits of R-PE. In one example, apo-alpha and apo-beta R-PE subunits were cloned from red algae Polisiphonia boldii (P. boldii), and expressed in E. coli. Although expressed apo-subunits formed inclusion bodies, fluorescent holo-subunits were formed after incubation of E. coli cells with PEB. Spectroscopic characterization of holo-subunits confirmed that the attachment of PEB chromophore to apo-subunits yielded holo-subunits containing both PEB and urobilin (UB). Fluorescence and differential interference contrast (DIC) microscopy showed polar location of holo-subunit inclusion bodies in E. coli cells. In another example, R-PE apo-subunits were genetically fused to cytoplasmic and periplasmic versions of E. coli maltose binding protein (MBP). Fluorescent proteins formed after attachment of PEB to MBP-subunit fusions in vitro and in vivo contained PEB as the sole chromophore, were soluble, and displayed high orange fluorescence. Fluorescence microscopy showed that fusions are located either throughout cells or at cell poles. In addition, cells containing fluorescent holo-subunits or MBP-subunit fusions were up to ten times brighter than control cells as measured by flow cytometry. Results show that the fluorescent proteins formed after non-enzymatic attachment of PEB to R-PE subunit fusions could be used as reporters of gene expression and protein localization in cells as well as fluorescence labels in flow cytometry. Finally, we demonstrated a high-throughput method able to record emission fluorescence spectra of individual cells containing fluorescent proteins. Upon excitation with a 488 mn argon-ion laser many bacterial cells were imaged by a 20X microscope objective while they moved through a capillary tube. Fluorescence was dispersed by a transmission diffraction grating, and an intensified charge-coupled device (ICCD) camera simultaneously recorded the zero and the first orders of the fluorescence from each cell. Single-cell fluorescence spectra were reconstructed from the distance between zero-order and first-order maxima as well as the length and the pixel intensity distribution of the first-order images. By using this approach, the emission spectrum of E. coli cells expressing green fluorescent protein (GFP) was reconstructed. Also, fluorescence spectra of E

Dragan Isailovic

2005-12-17

324

Efficient small molecule bulk heterojunction solar cells with high fill factors via pyrene-directed molecular self-assembly.  

PubMed

Efficient organic photovoltaic (OPV) materials are constructed by attaching completely planar, symmetric end-groups to donor-acceptor electroactive small molecules. Appending C2-pyrene as the small molecule end-group to a diketopyrrolopyrrole core leads to materials with a tight, aligned crystal packing and favorable morphology dictated by ?-? interactions, resulting in high power conversion efficiencies and high fill factors. The use of end-groups to direct molecular self-assembly is an effective strategy for designing high-performance small molecule OPV devices. PMID:22021084

Lee, Olivia P; Yiu, Alan T; Beaujuge, Pierre M; Woo, Claire H; Holcombe, Thomas W; Millstone, Jill E; Douglas, Jessica D; Chen, Mark S; Fr閏het, Jean M J

2011-12-01

325

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 10癈), 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, G閞aldine; Alekseev, Pavel

2009-04-01

326

Dynamic Nuclear Polarization of 17O: Direct Polarization  

PubMed Central

Dynamic nuclear polarization of 17O was studied using four different polarizing agents the biradical TOTAPOL, and the monoradicals trityl and SA-BDPA, as well as a mixture of the latter two. Field profiles, DNP mechanisms and enhancements were measured to better understand and optimize directly polarizing this low-gamma quadrupolar nucleus using both mono- and bi-radical polarizing agents. Enhancements were recorded < 88 K and were > 100 using the trityl (OX063) radical and < 10 with the other polarizing agents. The > 10,000 fold savings in acquisition time enabled a series of biologically relevant small molecules to be studied with small sample sizes and the measurement of various quadrupolar parameters. The results are discussed with comparison to room temperature studies and GIPAW quantum chemical calculations. These experimental results illustrate the strength of high field DNP and the importance of radical selection for studying low-gamma nuclei. PMID:24195759

Michaelis, Vladimir K.; Corzilius, Bj鰎n; Smith, Albert A.; Griffin, Robert G.

2014-01-01

327

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

328

Generation of circularly polarized multiple high-order harmonic emission from two-color crossed laser beams  

E-print Network

Generation of circularly polarized multiple high-order harmonic emission from two-color crossed for the production of circularly polarized multiple high-order harmonic generation HHG . The proposed experimental as the mechanism for the generation of continuous background radiation. S1050-2947 98 50410-6 PACS number s : 42

Chu, Shih-I

329

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

PubMed

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. PMID:25258306

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

2014-10-17

330

High performance small molecule photodetector with broad spectral response range from 200 to 900 nm  

NASA Astrophysics Data System (ADS)

We demonstrate a photodetector (PD) with broad spectral response by taking the advantages of more flexible device design in using small molecule materials. The optimized device shows an external quantum efficiency of over 20% from 200 to 900 nm. The high performance is achieved by jointing two donor (D)/acceptor (A) hetero-junctions [m-MTDATA(D)/TiOPc(A) and TiOPc(D)/F16CuPc: PTCDI-C8(A)] such that photoresponses over the deep-ultraviolet (UV) and visible-near infrared regions can be independently optimized. By choosing D- and A-materials with matched energy level alignment, high carrier mobility, and balanced carrier transporting properties, the present PD shows a fast response of 56 ns. The high speed and deep-UV sensitivity might lead to potential military applications such as missile tracking in addition to optical communications, chemical/biological sensing etc.

Wu, Shuang-hong; Li, Wen-lian; Chu, Bei; Su, Zi-sheng; Zhang, Feng; Lee, C. S.

2011-07-01

331

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

332

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

333

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+100犈3 and+88犈3 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

334

A High Throughput Assay to Identify Small Molecule Modulators of Alternative pre-mRNA Splicing  

PubMed Central

Alternative splicing (AS) is an efficient mechanism that involves the generation of transcriptome and protein diversity from a single gene. Defects in pre-mRNA splicing are an important cause of numerous diseases, including cancer. AS of pre-mRNA as a target for cancer therapy has not been well studied. We have reported previously that a splicing factor, polypyrimidine tract-binding protein (PTB) is overexpressed in ovarian tumors, compared to matched normal controls, and knockdown (KD) of PTB expression by shRNA impairs ovarian tumor cell growth, colony formation and invasiveness. Given the complexity of PTB抯 molecular functions, a chemical method for controlling PTB activity might provide a therapeutic and experimental tool. However, no commercially available PTB inhibitors have yet been described. To expand our ability to find novel inhibitors, we developed a robust, fluorometric, cell-based high throughput screening HTS assay in 96-well plates that reports on the splicing activity of PTB. In an attempt to use the cells for large-scale chemical screens to identify PTB modulators, we established cell lines stably expressing the reporter gene. Our results suggest that this high throughput assay could be used to identify small molecule modulators of PTB activity. Based on these findings and the role that upregulated PTB has on cell proliferation and malignant properties of tumors targeting PTB for inhibition with small molecules offers a promising strategy for cancer therapy. PMID:22972848

Arslan, Ahmet Dirim; He, Xiaolong; Wang, Minxiu; Rumschlag-Booms, Emily; Rong, Lijun; Beck, William T.

2012-01-01

335

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

336

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

SciTech Connect

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., E-mail: myong@gnu.ac.kr [Department of Aerospace and System Engineering and Research Center for Aircraft Parts Technology, Gyeongsang National University, Jinju, Gyeongnam 660-701 (Korea, Republic of)

2014-05-15

337

Polarization effects for pair creation by photon in oriented crystals at high energy  

E-print Network

Pair creation by a photon in an oriented crystal is considered in a frame of the quasiclassical operator method, which includes processes with polarized particles. Under some quite generic assumptions the general expression is derived for the probability of pair creation of longitudinally polarized electron (positron) by circularly polarized photon in oriented crystal. In particular cases $\\vartheta_0 \\ll V_0/m$ and $\\vartheta_0 \\gg V_0/m$ ($\\vartheta_0$ is the angle of incidence, angle between the momentum of initial photon and axis (plane) of crystal, $V_0$ is the scale of a potential of axis or a plane relative to which the angle $\\vartheta_0$ is defined) one has constant field approximation and the coherent pair production theory correspondingly. Side by side with coherent process the probability of incoherent pair creation is calculated, which differs essentially from amorphous one. At high energy the pair creation in oriented crystals is strongly enhanced comparing with amorphous medium. In appendixes the integral polarization of positron is found in external field and for coherent and incoherent mechanisms.

V. N. Baier; V. M. Katkov

2005-04-21

338

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

339

Harnessing randomness to control the polarization of light transmitted through highly scattering media.  

PubMed

We show that the multiple scattering events taking place inside a highly scattering medium, in conjunction with wavefront shaping, can be used to control the state of polarization of the light transmitted through a highly scattering medium. This control is achieved by using the intensity, phase, and polarization changing behavior of a scattering medium captured by a vector transmission matrix (VTM). We use a single beam incident upon a scattering medium to measure the absolute value of the VTM elements, in contrast to the multiple beams required in our previously reported approach. Further, the phase-only spatial light modulator based on a low-cost (< US$600) deformable micro-mirror array used in our work will make similar experiments accessible to other researchers. PMID:24663764

Tripathi, Santosh; Toussaint, Kimani C

2014-02-24

340

Slow-light birefringence and high precision polarization interferometry in liquid crystal light-valves  

NASA Astrophysics Data System (ADS)

Liquid crystals are characterized by a strong anisotropy of their physical properties, which is at the origin of their high birefringence. By performing two-wave mixing experiments in a liquid crystal light-valve, we show that the anisotropic nature of the beam coupling occurring in the liquid crystal layer leads to a slow-light birefringence phenomenon, that is, orthogonal polarization states of the input pulse travel at very different group velocities. Such a slow-light birefringence effect comports a large difference in the group index for the ordinary and the extraordinary wave. The resulting high contrast of the group index can be exploited for realizing a common-path polarization interferometer working at enhanced sensitivity, where very small phase variations can be efficiently detected.

Residori, Stefania; Bortolozzo, Umberto; Huignard, Jean-Pierre

2010-08-01

341

Highly polarized emission of the liquid crystalline conjugated polymer by controlling the surface anchoring energy  

NASA Astrophysics Data System (ADS)

We demonstrated a highly polarized organic light-emitting diode (OLED) through the enhancement of the orientational ordering of the emitting polymer with a nematic liquid crystalline (LC) phase. The highly ordered state of the conjugate polymer was obtained by thermal annealing at the nematic temperature and strong azimuthal anchoring energy of the underlying polyimide. The order parameter of the conjugate polymer was analyzed using a second-harmonic generation model and the dichroic ratio was measured to be 22 : 1. Also, we applied our optimized OLED with high optical polarizability to an effective light source for a twisted nematic LC display.

In Jo, Soo; Kim, Youngsik; Baek, Ji-Ho; Yu, Chang-Jae; Kim, Jae-Hoon

2014-01-01

342

High Performance Radiating Elements For Dual Circularly Polarized S- Band Feed  

Microsoft Academic Search

A high performance feed for 11 meters reflector antenna system in cassegrain configuration is designed, developed and tested. Dual shaping technique has been adopted to enhance the efficiency of the antenna or G\\/T. Radiating elements for the feed are designed and the inter-element spacing is optimized for the required illumination. Dual polarization (RHC\\/LHC) capability for the station is implemented by

Praveen Kumar; V Senthil Kumar; VV Srinivasan

343

An UltraHigh Definition Spatial Light Modulation Device Driven by Spin-Polarized Electrons  

Microsoft Academic Search

We propose a new type of magneto-optical (MO) spatial light-modulation device, driven by spin-polarized current flow, i.e. spin transfer switching (STS-SLM). Its basic operation and characteristics were experimentally confirmed. The proposed SLM device has a spatial resolution as small as several hundred nanometers, and an ultra-high drive speed of several tens of nanoseconds, and its basic operation is possible without

Kenichi Aoshima; Nobuhiko Funabashi; Kenji Machida; Yasuyoshi Miyamoto; Kiyoshi Kuga; Naoki Shimidzu; Fumio Sato

2009-01-01

344

High power CW red VECSEL with linearly polarized TEM00 output beam  

Microsoft Academic Search

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.

Jennifer E. Hastie; Stephane Calvez; Martin D. Dawson; Tomi Leinonen; Antti Laakso; Jari Lyytik鋓nen; Markus Pessa

2005-01-01

345

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; Lyytik鋓nen, Jari; Pessa, Markus

2005-01-10

346

Spin-polarized photoemission from AlGaAs/GaAs heterojunction: A convenient highly polarized electron source  

SciTech Connect

We analyze the operation of a spin-polarized electron source, consisting of a 100 A GaAs cap on top of Al/sub 0.3/Ga/sub 0.7/As, excited at 300 or 120 K by a He-Ne laser. The cap allows easy activation to negative electron affinity while the alloy permits gap matching to the light source, and thus large electron spin polarization (30% at 300 K, 36% at 120 K). We compare yield curves, energy distribution curves, and polarized energy distribution curves obtained on samples with 100 and 1000 A caps and on bulk GaAs. The X conduction minimum position in the alloy is also determined.

Ciccacci, F.; Drouhin, H.; Hermann, C.; Houdre, R.; Lampel, G.

1989-02-13

347

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

348

High Resolution $?$=1mm CARMA Observations of Large Molecules in Orion-KL  

E-print Network

We present high resolution, Combined Array for Research in Millimeter-Wave Astronomy (CARMA), $\\lambda$=1mm observations of several molecular species toward Orion-KL. These are the highest spatial and spectral resolution 1mm observations of these molecules to date. Our observations show that ethyl cyanide [C$_2$H$_5$CN] and vinyl cyanide [C$_2$H$_3$CN] originate from multiple cores near the Orion hot core and IRc7. Additionally we show that dimethyl ether [(CH$_3$)$_2$O] and methyl formate [HCOOCH$_3$] originate from IRc5 and IRc6 and that acetone [(CH$_3$)$_2$CO] originates only from areas where both N-bearing and O-bearing species are present.

D. N. Friedel; L. E. Snyder

2007-09-20

349

Polarized XAFS study of high-temperature phases of NaNbO3.  

PubMed

Temperature dependence of the Nb displacement relative to the center of oxygen octahedron in NaNbO3 has been studied by polarized Nb K XAFS. Spectra were measured at two orientations of a single crystalline sample. Room temperature EXAFS data are in a good agreement with earlier X-ray diffraction data: Nb antiferroelectric displacements were found to be orthogonal to the b axis. Analysis of the temperature dependent EXAFS data didn't reveal any abrupt changes of Nb-O distances in the phase transition points. In all high-temperature paraelectric phases Nb appeared to be displaced to the off-center positions. Displacements, orthogonal to b axis, remained almost constant, while displacement along b axis gradually increased with temperature, so that in the cubic phase the displacements along all axes became equal. This shows, that disorder plays an important role in the high temperature phases. The above results are supported also by the analysis of the pre-edge structure, - the integral intensity of the pre-edge peak was temperature-independent when the polarization vector of the X-rays was orthogonal to b axis and gradually increased with temperature when the polarization was parallel to b. PMID:11512948

Shuvaeva, V A; Azuma, Y; Yagi, K; Sakaue, K; Terauchi, H

2001-03-01

350

Evidence of high densities and ion outflows in the polar cap during the recovery phase  

NASA Technical Reports Server (NTRS)

The composition and characteristics of the polar cap plasma for an Oct. 14, 1981 outflow of polar wind ions are examined using data from the DE 1 satellite. The on-board instruments included a plasma wave instrument, a retarding ion mass spectrometer (RIMS) and a high altitude plasma instrument (HAPI). The outflow took place at an altitude of about 19,000 km at a magnetic local time of about midnight. The total plasma density measured was about 50/cu cm, which was an order of magnitude higher than normally recorded at that location and altitude. The background hydrogen plasma was disturbed by highly collimated flows of hydrogen and oxygen ions. The H(+) ions had a mean energy of 0.15 eV and a density of 6-10/cu cm. The O(+) ions had an average density of 20/cu cm and a temperature of 0.26 eV. The total flux of outflowing H(+) and O(+) was about 10 million/sq cm per sec. The HAPI data indicated that the O(+) ions appeared in the dayside ionosphere and the H(+) ions detected by the RIMS originated in the nightside polar cap.

Gallagher, D. L.; Waite, J. H., Jr.; Chappell, C. R.; Menietti, J. D.; Burch, J. L.

1986-01-01

351

Structural determination of cerebrosides isolated from Asterias amurensis starfish eggs using high-energy collision-induced dissociation of sodium-adducted molecules.  

PubMed

Six cerebrosides were isolated from the eggs of the starfish Asterias amurensis using solvent extraction, silica gel column chromatography, and reversed-phase high-performance liquid chromatography. This study demonstrated that the structures of cerebrosides could be completely characterized, based on their sodium-adducted molecules, using fast atom bombardment (FAB) tandem mass spectrometry. The high-energy collision-induced dissociation of the sodium-adducted molecule, [M?+?Na](+), of each cerebroside molecular species generated abundant ions, providing information on the compositions of the 2-hydroxy fatty acids and long-chain sphingoid bases, as well as the sugar moiety polar head group. Each homologous ion series along the fatty acid and aliphatic chain of the sphingoid base was useful for locating the double-bond positions of both chains and the methyl branching position of the long-chain base. The N-fatty acyl portions were primarily long-chain saturated or monoenoic acids (C16 to C24) with an ?-hydroxy group. The sphingoid long-chain base portions were aliphatic chains (C18 or C22) with two or three degrees of unsaturation and with or without methyl branching. PMID:21290443

Park, Taeseong; Park, Young Seung; Rho, Jung-Rae; Kim, Young Hwan

2011-03-15

352

Polarization-preserving confocal microscope for optical experiments in a dilution refrigerator with high magnetic field.  

PubMed

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. PMID:21528993

Sladkov, Maksym; Bakker, M P; Chaubal, A U; Reuter, D; Wieck, A D; van der Wal, C H

2011-04-01

353

High efficiency, linearly polarized, directly diode-pumped Er:YAG laser at 1617??nm.  

PubMed

An efficient, directly diode-pumped Er:YAG laser at 1617爊m was demonstrated. A folding mirror with high reflectivity for the s-polarized light at the laser wavelength was used to achieve a linearly polarized laser. A maximum continuous-wave output power of 7.73燱 was yielded under incident pump power of 50.57燱, and the optical conversion efficiency with respect to incident pump power was ?15.28%, which was the highest optical conversion efficiency with directly diode-pumped Er:YAG lasers up to now; in Q-switched operation, the maximum pulse energy of 7.82爉J was generated with pulse duration of about 80爊s at a pulse repetition frequency of 500燞z. PMID:25607959

Yu, Zhenzhen; Wang, Mingjian; Hou, Xia; Chen, Weibiao

2014-12-01

354

High power single frequency linear-polarized all-fiber MOPA system for coherent detection  

NASA Astrophysics Data System (ADS)

In the paper, we reported a single-frequency(SF), single-mode(SM), linear-polarized ytterbium-doped all-fiber master oscillator power amplifier (MOPA) system consisting of two stage amplifier which could be used in coherent detection. With a pump power of 17.5W at 976nm, the system emitted up to 12.7 W of single-frequency radiation at a wavelength of 1064 nm with the polarization-extinction ratio (PER) more than 35dB and signal-to-noise ratio (SNR) more than 40dB. The final-stage amplifier operated with a high conversion efficiency of 73% and the gain of the whole amplifier achieved 31 dB, it has nearly diffraction-limited beam quality.

Ding, Ya-qian; Qi, Yun-feng; Liu, Chi; He, Jing; Zhou, Jun

2011-06-01

355

The high precision gamma-ray spectrometer for lunar polar orbiter SELENE  

NASA Astrophysics Data System (ADS)

The high precision gamma-ray spectrometer (GRS) is scheduled to be launched on the lunar polar orbiter of the SELENE mission in 2007. The GRS consists of a large Ge crystal as a main detector and massive bismuth germanate crystals as an anticoincidence detector. A Stirling cryocooler was adopted in cooling the Ge detector. The flight model of SELENE GRS has been completed and an energy resolution of 3.0 keV (FWHM) at 1.332 MeV has been achieved. The spectrometer aims to observe nuclear line gamma rays emitted from the lunar surface in a wide energy range from 100 keV to 12 MeV for one year and more to obtain chemical composition on the entire lunar surface. The gamma-ray data enable us to study lunar geoscience problems including crust and mantle composition, and volatile reservoirs at polar regions.

Hasebe, N.; Yamashita, N.; Okudaira, O.; Kobayashi, S.; Yamamoto, H.; Ishizaki, T.; Hirano, K.; Sakurai, K.; Miyachi, T.; Miyajima, M.; Fujii, M.; Kobayashi, M.-N.; Takashima, T.; Shibamura, E.; Gasnault, O.; Maurice, S.; D'Uston, C.; Reedy, R.; Grande, M.

2008-07-01

356

Circularly polarized light with high degree of circularity and low azimuthal error sensitivity.  

PubMed

The generation of circularly polarized light with a high circularity degree and low azimuthal error sensitivity was analyzed using a system composed by two waveplates. It is shown how the high circularity degree is achieved using a combination of a half- (?/2) and a quarter- (?/4) waveplate ?/2+?/4 configuration. However, the lowest azimuthal sensitivity under small variations in the azimuths of the waveplates is obtained by employing a ?/4+?/2 configuration. Analytical calculus particularized for quartz and MgF? waveplates is presented. PMID:24922413

Vilas, Jose Luis; Bernabeu, Eusebio; Sanchez-Brea, Luis Miguel; Espinosa-Luna, Rafael

2014-06-01

357

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

358

High throughput screen identifies small molecule inhibitors specific for Mycobacterium tuberculosis phosphoserine phosphatase.  

PubMed

The emergence of drug-resistant strains of Mycobacterium tuberculosis makes identification and validation of newer drug targets a global priority. Phosphoserine phosphatase (PSP), a key essential metabolic enzyme involved in conversion of O-phospho-l-serine to l-serine, was characterized in this study. The M. tuberculosis genome harbors all enzymes involved in l-serine biosynthesis including two PSP homologs: Rv0505c (SerB1) and Rv3042c (SerB2). In the present study, we have biochemically characterized SerB2 enzyme and developed malachite green-based high throughput assay system to identify SerB2 inhibitors. We have identified 10 compounds that were structurally different from known PSP inhibitors, and few of these scaffolds were highly specific in their ability to inhibit SerB2 enzyme, were noncytotoxic against mammalian cell lines, and inhibited M. tuberculosis growth in vitro. Surface plasmon resonance experiments demonstrated the relative binding for these inhibitors. The two best hits identified in our screen, clorobiocin and rosaniline, were bactericidal in activity and killed intracellular bacteria in a dose-dependent manner. We have also identified amino acid residues critical for these SerB2-small molecule interactions. This is the first study where we validate that M. tuberculosis SerB2 is a druggable and suitable target to pursue for further high throughput assay system screening. PMID:25037224

Arora, Garima; Tiwari, Prabhakar; Mandal, Rahul Shubhra; Gupta, Arpit; Sharma, Deepak; Saha, Sudipto; Singh, Ramandeep

2014-09-01

359

High-resolution atomic force microscopy of duplex and triplex DNA molecules  

NASA Astrophysics Data System (ADS)

Double-stranded poly(dG)-poly(dC) and triple-stranded poly(dG)-poly(dG)-poly(dC) DNA were deposited on the modified surface of highly oriented pyrolitic graphite (HOPG) and visualized using atomic force microscopy with high-resolution (radius of ~1 nm) tips. The high resolution attained by this technique enabled us to detect single-stranded regions in double-stranded poly(dG)-poly(dC) and double-stranded and single-stranded regions in poly(dG)-poly(dG)-poly(dC) triplexes, as well as to resolve the helical pitch of the triplex molecules. We could also follow the reaction of G-strand extension in poly(dG)-poly(dC) by the Klenow exo- fragment of DNA polymerase I. This approach to molecular visualization could serve as a useful tool for the investigation of irregular structures in canonical DNA and other biopolymers, as well as studies of the molecular mechanisms of DNA replication and transcription.

Klinov, Dmitry; Dwir, Benjamin; Kapon, Eli; Borovok, Natalia; Molotsky, Tatiana; Kotlyar, Alexander

2007-06-01

360

Interaction of highly vibrationally excited molecules with clean metal surfaces. Final technical report  

SciTech Connect

The authors present results from a grant funded under the Department of Energy Office of Basic Energy Sciences. A collaboration between Prof. Alec Wodtke of the Department of Chemistry at UCSB and Daniel J. Auerbach of IBM Almaden Research Labs has allowed new experiments on the dynamics of surface chemical reactivity to be successfully executed. High quality data has been generated which provides an excellent test of theoretical models of surface reactivity, a topic of importance to catalysis. The authors have obtained the first experimental measurements on the influence of reactant velocity on the steric effect in a chemical reaction: the dissociative adsorption of hydrogen on copper. They have also designed and built a molecular beam scattering apparatus for the study of highly vibrationally excited molecules and their interactions with clean and oxidized metal surfaces. With this apparatus they have observed the vibrational energy exchange of highly vibrationally excited NO with an oxidized copper surface. Multi-quantum vibrational relaxation was found ({Delta}v = 1-5). Such remarkably strong and efficient vibrational energy transfer represents a qualitatively new phenomenon and is representative of the exciting new behavior that they had hoped might be observable in this project. Evidence of chemical reactivity of vibrationally excited NO on a clean copper surface was also found.

Wodtke, A.M. [Univ. of California, Santa Barbara, CA (United States). Dept. of Chemistry; Auerbach, D.J. [IBM Almaden Research Center, San Jose, CA (United States)

1998-11-01

361

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

362

Histamine inhibits high mobility group box 1-induced adhesion molecule expression on human monocytes.  

PubMed

Cell-cell interaction through binding of adhesion molecules on monocytes to their ligands on T-cells plays roles in cytokine production and lymphocyte proliferation. High mobility group box 1 (HMGB1), an abundant and conserved nuclear protein, acts in the extracellular environment as a primary pro-inflammatory signal. HMGB1 induces expression of intercellular adhesion molecule (ICAM), B7.1, B7.2 and CD40 on monocytes, resulting in production of interferon (IFN)-? and tumor necrosis factor (TNF)-? production and lymphocyte proliferation in human peripheral blood mononuclear cells (PBMCs). Histamine inhibits pro-inflammatory cytokine production via histamine H2-receptors; however, it is not known whether histamine inhibits HMGB1 activity. This study was designed to study the inhibitory effect of histamine on HMGB1 activity. We examined the effect of histamine on HMGB1-induced expression of ICAM-1, B7.1, B7.2 and CD40 on monocytes, production of IFN-? and TNF-? and lymphocyte proliferation in PBMCs. Histamine inhibited HMGB1 activity in a concentration-dependent manner. The effects of histamine were partially ablated by the H2-receptor antagonist, famotidine, and mimicked by the H2/H4-receptor agonists, dimaprit and 4-methylhistamine. Histamine induced cyclic adenosine monophosphate (cAMP) production in the presence and absence of HMGB1. The effects of histamine were reversed by the protein kinase A (PKA) inhibitor, H89, and mimicked by the membrane-permeable cAMP analog, dibutyryl cAMP (dbcAMP), and the adenylate cyclase activator, forskolin. These results together indicated that histamine inhibited HMGB1 activity. PMID:24012904

Takahashi, Hideo; Sadamori, Hiroshi; Teshigawara, Kiyoshi; Niwa, Atsuko; Liu, Keyue; Wake, Hidenori; Mori, Shuji; Yoshino, Tadashi; Nishibori, Masahiro

2013-10-15

363

High Throughput Screening of Small Molecule Libraries for Modifiers of Radiation Responses  

PubMed Central

Purpose An unbiased approach of drug discovery through high-throughput screening (HTS) of libraries of chemically defined and bioactive small molecule compounds was used to identify modulators of radiation injury with an emphasis on radioprotectors and mitigators rather than radiosensitizers. Assay system endpoints included radiation-induced genotoxicity and DNA damage in yeast and apoptosis in murine lymphocytes. Large-scale data mining of chemically diverse libraries identified agents that were effective with all endpoints. HTS of bioactive compound libraries against murine lymphocytes profiled tetracycline and fluoroquinolone antibiotics and cyclopiazonic acid as having activity, and structure-activity analysis showed a common pharmacophore. Purine nucleosides, the interferon inducer tilorone, and linoleic acid were also identified as potential mitigators of radiation damage that often were also radioprotective. Many of these compounds enhance DNA repair, have anti-inflammatory activity, and stimulate hematopoiesis. Selected compounds within these initial verified hits from both types of libraries identified potent mitigators of lethal whole body irradiation (WBI) in mice. Conclusion In spite of the fact that in vitro HTS has limitations and is unable to fully recapitulate all aspects of the complex in vivo acute radiation response, it identified several classes of molecules that had activity as radioprotectors and radiomitigators of the hematopoietic system in vivo. In the future, addition of 3 dimensional (3D) or stem cell cultures or pathway analysis, may improve the power of HTS, but our findings indicate that common, evolutionary conserved, canonical pathways can be identified that could be exploited to mitigate radiation-induced defects. PMID:21401317

Kim, Kwanghee; Damoiseaux, Robert; Norris, Andrew J.; Rivina, Leena; Bradley, Kenneth; Jung, Michael E.; Gatti, Richard A.; Schiestl, Robert H.; McBride, William H.

2011-01-01

364

Historical Review on Solid Polarized Targets  

NASA Astrophysics Data System (ADS)

Protons in the crystal of La2Mg3(NO3)1224H2O were found to be polarized dynamically by means of the solid effect at the beginning of 1960's. Organic materials were polarized up to 80 % in 3He cryostats in 1969. It can be interpreted as the equal spin temperature model. The spin frozen targets with dilution refrigerators were constructed in 1974. Such targets have been used for experiments which require wide access angles. The NH3, LiH and LiD were polarized in 1980's. Static polarization of HD has been tried and proton polarization higher than 60 % was obtained with small amount of ortho H2 in 2000. We mention also the dynamic polarization of aromatic molecules in high temperature.

Masaike, Akira

2007-04-01

365

How cytochrome c oxidase can pump four protons per oxygen molecule at high electrochemical gradient.  

PubMed

Experiments have shown that the A-family cytochrome c oxidases pump four protons per oxygen molecule, also at a high electrochemical gradient. This has been considered a puzzle, since two of the reduction potentials involved, Cu(II) and Fe(III), were estimated from experiments to be too low to afford proton pumping at a high gradient. The present quantum mechanical study (using hybrid density functional theory) suggests a solution to this puzzle. First, the calculations show that the charge compensated Cu(II) potential for CuB is actually much higher than estimated from experiment, of the same order as the reduction potentials for the tyrosyl radical and the ferryl group, which are also involved in the catalytic cycle. The reason for the discrepancy between theory and experiment is the very large uncertainty in the experimental observations used to estimate the equilibrium potentials, mainly caused by the lack of methods for direct determination of reduced CuB. Second, the calculations show that a high energy metastable state, labeled EH, is involved during catalytic turnover. The EH state mixes the low reduction potential of Fe(III) in heme a3 with another, higher potential, here suggested to be that of the tyrosyl radical, resulting in enough exergonicity to allow proton pumping at a high gradient. In contrast, the corresponding metastable oxidized state, OH, is not significantly higher in energy than the resting state, O. Finally, to secure the involvement of the high energy EH state it is suggested that only one proton is taken up via the K-channel during catalytic turnover. PMID:25529353

Blomberg, Margareta R A; Siegbahn, Per E M

2015-03-01

366

Polarization Issues with High Power Injection and Low Power Emission in Fusion Experiments  

SciTech Connect

All tokamak experiments using ECCD require setting of the beam elliptical polarization for proper coupling to the plasma. This is done either in the matching optics unit (MOU) at the output of the gyrotron, or in a couple of miter bends of the transmission line. Similarly, oblique ECE receivers require selection of the correct elliptical polarization to provide localized measurements. For the TCV tokamak at the CRPP, gyrotron and oblique-ECE polarizers are characterized during either high- or low- power testing of equipment: for the gyrotrons the behaviour is determined at a single frequency, but for the oblique-ECE the broadband response is needed. These characteristics are included in the calibration database and used during subsequent analysis of the power coupling to, or from, the sources (gyrotron, plasma, or low power transmitting antenna). A more detailed characterization has been carried out (at low power) with the MOU for the EU, 170 GHz, 2 MW, gyrotron prototype for ITER. This paper discusses the methodology and results of these measurements, as well as a review of nearly a decade's worth of experimental data from the 6 gyrotron, 3 MW, 82.6 GHz TCV system. In particular, the consistency between the calibrations and the subsequent data from tokamak experiments is analysed.

Goodman, T. P.; Felici, F.; Udintsev, V. S. [Ecole Polytechnique Federate de Lausanne (EPFL), Centre de Recherches en Physique des plasmas, Association EURATOM-Confederation Suisse, CH-1015 Lausanne (Switzerland)

2009-11-26

367

First high-resolution stratigraphic column of the Martian north polar layered deposits  

USGS Publications Warehouse

This study achieves the first high-spatial-resolution, layer-scale, measured stratigraphic column of the Martian north polar layered deposits using a 1m-posting DEM. The marker beds found throughout the upper North Polar Layered Deposits range in thickness from 1.6 m-16.0 m +/-1.4 m, and 6 of 13 marker beds are separated by ???25-35 m. Thin-layer sets have average layer separations of 1.6 m. These layer separations may account for the spectral-power-peaks found in previous brightness-profile analyses. Marker-bed layer thicknesses show a weak trend of decreasing thickness with depth that we interpret to potentially be the result of a decreased accumulation rate in the past, for those layers. However, the stratigraphic column reveals that a simple rhythmic or bundled layer sequence is not immediately apparent throughout the column, implying that the relationship between polar layer formation and cyclic climate forcing is quite complex. Copyright ?? 2010 by the American Geophysical Union.

Fishbaugh, K.E.; Hvidberg, C.S.; Byrne, S.; Russell, P.S.; Herkenhoff, K.E.; Winstrup, M.; Kirk, R.

2010-01-01

368

High-resolution topography and albedo of the south polar layered deposits on Mars  

SciTech Connect

Using a new photoclinometric technique with high-resolution Mariner 9 images, maximum slopes of 10{degree}-20{degree} are found to occur on an exposure of layered deposits within the south polar residual cap of Mars. Stereophotogrammetry is used to constrain the photoclinometric solutions, which resolve layer thicknesses of 100-300 m. Albedo variations are correlated with slope, indicating that frost is present on level areas. There is evidence for temporal changes in frost distribution in the 7 days (4{degree} of L{sub 8}) between the two images used in this study. The magnitude of the slopes derived here and consideration of the stability of water ice at the surface of the layered deposits strongly suggest the presence of a competent weathering rind. The weathered surface may be composed of dark filamentary sublimation residue particles that protect the underlying ice from solar heating. This hypothesis is consistent with previous studies of the regional color and albedo of the layered deposits, which indicate that the deposits are slightly darker and less red than the bright dust that mantles much of the south polar region. Furthermore, the proposed weathering mechanism provides a plausible source of dark, saltating material for the Martian polar dune fields.

Herkenhoff, K.E.; Murray, B.C. (California Institute of Technology, Pasadena (USA))

1990-08-30

369

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

370

High-speed polarization sensitive optical frequency domain imaging with frequency multiplexing  

PubMed Central

Polarization sensitive optical coherence tomography (PS-OCT) provides a cross-sectional image of birefringence in biological samples that is complementary in many applications to the standard reflectance-based image. Recent ex vivo studies have demonstrated that birefringence mapping enables the characterization of collagen and smooth muscle concentration and distribution in vascular tissues. Instruments capable of applying these measurements percutaneously in vivo may provide new insights into coronary atherosclerosis and acute myocardial infarction. We have developed a polarization sensitive optical frequency domain imaging (PS-OFDI) system that enables high-speed intravascular birefringence imaging through a fiber-optic catheter. The novel design of this system utilizes frequency multiplexing to simultaneously measure reflectance of two incident polarization states, overcoming concerns regarding temporal variations of the catheter fiber birefringence and spatial variations in the birefringence of the sample. We demonstrate circular cross-sectional birefringence imaging of a human coronary artery ex vivo through a flexible fiber-optic catheter with an A-line rate of 62 kHz and a ranging depth of 6.2 mm. PMID:18542183

Yun, S.H.; Vakoc, B.J.; Shishkov, M.; Desjardins, A.E.; Park, B.H.; de Boer, J.F.; Tearney, G.J.; Bouma, B.E.

2009-01-01

371

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扡eary, Se醤 E.; Chapin, Karen; Cheng, Janice; Ewan, Mark; Hsiung, Pei-Lin; Lundquist, Paul; Turner, Stephen W.; Hsu, David R.; Puglisi, Joseph D.

2014-01-01

372

Multiple Scattering Approach to Polarization Dependence of F K-Edge XANES Spectra for Highly Oriented Polytetrafluoroethylene (PTFE) Thin Film  

SciTech Connect

The polarization dependence of F K-edge X-ray absorption near edge structure (XANES) spectra of highly-oriented thin-film of polytetrafluoroethylene (PTFE) has been analyzed by using multiple scattering theory. The spectra show clear polarization dependence due to the highly-oriented structure. The multiple scattering calculations reflects a local structure around an absorbing atom. The calculated results obtained by considering intermolecular-interactions are in good agreement with the observed polarization-dependence. We have also analyzed structural models of the radiation damaged PTFE films.

Nagamatsu, S.; Ono, M.; Kera, S.; Okudaira, K. K.; Fujikawa, T.; Ueno, N. [Graduate School of Sci. and Tech., Chiba Univ., Yayoicho 1-33, Inage-ku Chiba 263-8522 (Japan)

2007-02-02

373

A highly processive topoisomerase I: studies at the single-molecule level.  

PubMed

Amongst enzymes which relieve torsional strain and maintain chromosome supercoiling, type IA topoisomerases share a strand-passage mechanism that involves transient nicking and re-joining of a single deoxyribonucleic acid (DNA) strand. In contrast to many bacterial species that possess two type IA topoisomerases (TopA and TopB), Actinobacteria possess only TopA, and unlike its homologues this topoisomerase has a unique C-terminal domain that lacks the Zn-finger motifs characteristic of type IA enzymes. To better understand how this unique C-terminal domain affects the enzyme's activity, we have examined DNA relaxation by actinobacterial TopA from Streptomyces coelicolor (ScTopA) using real-time single-molecule experiments. These studies reveal extremely high processivity of ScTopA not described previously for any other topoisomerase of type I. Moreover, we also demonstrate that enzyme processivity varies in a torque-dependent manner. Based on the analysis of the C-terminally truncated ScTopA mutants, we propose that high processivity of the enzyme is associated with the presence of a stretch of positively charged amino acids in its C-terminal region. PMID:24880688

Szafran, Marcin Jan; Strick, Terence; Strza?ka, Agnieszka; Zakrzewska-Czerwi?ska, Jolanta; Jakimowicz, Dagmara

2014-07-01

374

Temperature-controlled microintaglio printing for high-resolution micropatterning of RNA molecules.  

PubMed

We have developed an advanced microintaglio printing method for fabricating fine and high-density micropatterns and applied it to the microarraying of RNA molecules. The microintaglio printing of RNA reported here is based on the hybridization of RNA with immobilized complementary DNA probes. The hybridization was controlled by switching the RNA conformation via the temperature, and an RNA microarray with a diameter of 1.5祄 and a density of 40,000spots/mm(2) with high contrast was successfully fabricated. Specifically, no size effects were observed in the uniformity of patterned signals over a range of microarray feature sizes spanning one order of magnitude. Additionally, we have developed a microintaglio printing method for transcribed RNA microarrays on demand using DNA-immobilized magnetic beads. The beads were arrayed on wells fabricated on a printing mold and the wells were filled with in vitro transcription reagent and sealed with a DNA-immobilized glass substrate. Subsequently, RNA was in situ synthesized using the bead-immobilized DNA as a template and printed onto the substrate via hybridization. Since the microintaglio printing of RNA using DNA-immobilized beads enables the fabrication of a microarray of spots composed of multiple RNA sequences, it will be possible to screen or analyze RNA functions using an RNA microarray fabricated by temperature-controlled microintaglio printing (TC-礗P). PMID:25106674

Kobayashi, Ryo; Biyani, Manish; Ueno, Shingo; Kumal, Subhashini Raj; Kuramochi, Hiromi; Ichiki, Takanori

2015-05-15

375

A highly processive topoisomerase I: studies at the single-molecule level  

PubMed Central

Amongst enzymes which relieve torsional strain and maintain chromosome supercoiling, type IA topoisomerases share a strand-passage mechanism that involves transient nicking and re-joining of a single deoxyribonucleic acid (DNA) strand. In contrast to many bacterial species that possess two type IA topoisomerases (TopA and TopB), Actinobacteria possess only TopA, and unlike its homologues this topoisomerase has a unique C-terminal domain that lacks the Zn-finger motifs characteristic of type IA enzymes. To better understand how this unique C-terminal domain affects the enzyme's activity, we have examined DNA relaxation by actinobacterial TopA from Streptomyces coelicolor (ScTopA) using real-time single-molecule experiments. These studies reveal extremely high processivity of ScTopA not described previously for any other topoisomerase of type I. Moreover, we also demonstrate that enzyme processivity varies in a torque-dependent manner. Based on the analysis of the C-terminally truncated ScTopA mutants, we propose that high processivity of the enzyme is associated with the presence of a stretch of positively charged amino acids in its C-terminal region. PMID:24880688

Szafran, Marcin Jan; Strick, Terence; Strza?ka, Agnieszka; Zakrzewska-Czerwi?ska, Jolanta; Jakimowicz, Dagmara

2014-01-01

376

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

377

Polarity inversion in aluminum nitride thin films under high sputtering power  

SciTech Connect

The authors have investigated the influence of sputtering power on the piezoelectric response of aluminum nitride (AlN) thin films prepared on titanium nitride bottom electrodes. The piezoelectric response strongly depends on the sputtering power. The polar inversion was found by piezoresponse force microscopy. The polarity gradually changes from the N polarity to Al polarity with increasing sputtering power. The piezoelectric response of the films changes from -2.7 to +4.3 pC/N with increasing sputtering power from 100 to 500 W. Furthermore, the polarity inversion from the N polarity to Al polarity is observed by increasing sputtering power during growth.

Akiyama, Morito; Kamohara, Toshihiro; Ueno, Naohiro; Sakamoto, Michiru; Kano, Kazuhiko; Teshigahara, Akihiko; Kawahara, Nobuaki [On-site Sensing and Diagnosis Research Laboratory, National Institute of Advanced Industrial Science and Technology, 807-1 Shuku, Tosu, Saga 841-0052 (Japan); Research Laboratories, DENSO Corporation, 500-1 Minamiyama, Komenoki, Nisshin, Aichi 470-0111 (Japan)

2007-04-09

378

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

379

Latitudinal TEC gradients over polar ionosphere using high latitude GPS measurements  

NASA Astrophysics Data System (ADS)

The GPS observations of Greenland network were used to analyze the latitudinal variations of TEC at the high-latitudes ionosphere. This network provides unique opportunity to monitor TEC variability in polar ionosphere on a regular base. GPS stations are arranged along the latitude over the range 60-83癗 (65-87 Corrected Geomagnetic Latitude) near of 30-40 longitudes. More than 20 GPS stations are located closely with one another along latitude. The distance between stations is about 1-2.Such spatial resolution provides the possibility to analyze the detailed structure of latitudinal TEC profiles. The standard procedure of processing GPS observations was used for TEC estimation. On this base it was obtained the diurnal TEC variations over all Greenland stations. The TEC data is used to form latitudinal profiles (TEC section) covered subauroral, auroral and polar ionosphere. In the report the observations of TEC for quiet and disturbed ionosphere during several geomagnetic storms occurred in September 2011 are presented. During quiet conditions in the night-time TEC profiles demonstrated invariable values about of 4-6 TECU in latitudinal region of 60-75癗; then it presented THE increase towards the higher latitude and reached the value of 10 TECU near 80癗. The daytime profiles revealed TEC decrease toward high latitude in keeping with 0.8 TECU/degree. During storm the structure of latitudinal TEC profiles was essentially changed with agreement to the development of geomagnetic storm. The positive effect was observed at subauroral and auroral latitudes, negative effect was prevailed at the polar region. During the night time the ionospheric trough can be observed. In the report features of the behavior of latitudinal profiles at high-latitude ionosphere for September 2011 events were discussed.

Shagimuratov, Irk; Cherniak, Iurii; Zakharenkova, Irina; Tepenitsyna, Nadezhda; Yakimova, Galina; Ephishov, I. I.

380

Highly polarized emission from electrical spin injection into an InGaAs quantum well with free carriers  

SciTech Connect

We report on a highly polarized emission from InGaAs/GaAs-quantum well light-emitting diodes in which we inject spin-polarized electrons from an Fe/Schottky contact. The emission spectra consist of the e{sub 1}h{sub 1} free exciton (FX) and a feature 12?meV below FX attributed to band-to-band (BB) recombination. The FX exhibits a maximum circular polarization of 22%, with a magnetic-field dependence characteristic of spin injection from Fe. The BB emission on the other hand exhibits a polarization that is strongly bias and temperature dependent, with intriguing magnetic-field dependence: The polarization exhibits a maximum of 78% at 2.5?T and 2?K, then decreases linearly with field and reaches ?78% at 7?T, attributed to magnetic-field dependent spin relaxation in the presence of excess electrons.

Li, C. H.; Jonker, B. T. [Naval Research Laboratory, Washington, D.C., 20375 (United States)] [Naval Research Laboratory, Washington, D.C., 20375 (United States); Kioseoglou, G. [Department of Materials Science and Technology, University of Crete, Heraklion Crete 71003 (Greece)] [Department of Materials Science and Technology, University of Crete, Heraklion Crete 71003 (Greece); Petrou, A. [SUNY Buffalo, Buffalo, New York 14260 (United States)] [SUNY Buffalo, Buffalo, New York 14260 (United States); Korkusinski, M.; Hawrylak, P. [Quantum Theory Group, Emerging Technologies Division, National Research Council, Ottawa K1A0R6 (Canada)] [Quantum Theory Group, Emerging Technologies Division, National Research Council, Ottawa K1A0R6 (Canada)

2013-11-18

381

Method for the production of highly charged ions with polarized nuclei and zero total electron angular momentum  

NASA Astrophysics Data System (ADS)

The capture of polarized electrons by H-like ions provides a method for polarizing the nuclei of He-like heavy ions with zero total electron angular momentum in storage rings for high-energy ions. A detailed analysis for Eu15163 ions with nuclear spin I =5 /2 predicts a nuclear polarization degree of about 47 % already after one passage through a target containing 100 % polarized electrons. Almost 50 % of the polarized He-like ions are predicted to be in states with zero total electron angular momentum. Such ions were recently considered as the most promising candidates in experiments at storage rings for the search for violations of the fundamental symmetries and for a nuclear and an electron electric dipole moment.

Bondarevskaya, A.; Mistonova, E. A.; Lyashchenko, K. N.; Andreev, O. Yu.; Surzhykov, A.; Labzowsky, L. N.; Plunien, G.; Liesen, D.; Bosch, F.; St鰄lker, Th.

2014-12-01

382

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

E-print Network

A novel high-throughput scanning microscope for label-free detection of protein and small January 2008 We describe a novel scanning optical microscope based on a polarization-modulated nulling ellipsometry. The new microscope employs a combination of scanning mirror and sample translation and thus

Zhu, Xiangdong

383

Research Paper Meteors Do Not Break Exogenous Organic Molecules into High Yields of Diatomics  

Microsoft Academic Search

Meteoroids that dominate the Earth' s extraterrestrial mass influx (50- 300 mm size range) may have contributed a unique blend of exogenous organic molecules at the time of the origin of life. Such meteoroids are so large that most of their mass is ablated in the Earth' s atmosphere. In the process, organic molecules are decomposed and chemically altered to

PETER JENNISKENS; EMILY L. SCHALLER; CHRISTOPHE O. LAUX; MICHAEL A. WILSON; GREG SCHMIDT; RICK L. RAIRDEN

384

High Spin Polarization and Magnetism in NiCrS Heusler Compound  

NASA Astrophysics Data System (ADS)

We have investigated magnetic properties of semi Heusler compound NiCrS to search the new candidate showing half-metallic ferromagnetism (HMF) using full potential linearized augmented plane wave (FPLAPW) method within generalized gradient approximation (GGA) formalism for exchange and correlation effects. We predict that this compound is a nearly half-metallic (HM) ferromagnet with high degree of spin polarization at Fermi level (EF). The total spin magnetic moment is in good agreement with Slater-Pauling (SP) rule and is dominated by Cr atom.

Singh, Mukhtiyar; Singh, Hardev; Kashyap, Manish K.

2011-07-01

385

First modulation of high-frequency polar mesospheric summer echoes by radio heating of the ionosphere  

NASA Astrophysics Data System (ADS)

The first high-frequency (HF, 8 MHz) observations of the modulation of polar mesospheric summer echoes (PMSE) by artificial radio heating of the ionosphere are presented and compared to observations at 224 MHz and model predictions. The experiments were performed at the European Incoherent Scatter facility in northern Norway. It is shown that model results are in qualitative and partial quantitative agreement with the observations, supporting the prediction that with certain ranges of ice particle radii and concentration, PMSE at HF radar wavelengths can be enhanced by heating due to the dominance of dust charging over plasma diffusion.

Senior, A.; Mahmoudian, A.; Pinedo, H.; La Hoz, C.; Rietveld, M. T.; Scales, W. A.; Kosch, M. J.

2014-08-01

386

High extinction ratio polarization beam splitter with multimode interference coupler on SOI  

NASA Astrophysics Data System (ADS)

A high extinction ratio polarization beam splitter based on multimode interference coupler has been obtained on silicon-on-insulator. The multimode interference coupler is designed by using quasi-state imaging theory, and fabricated with E-beam lithography and induced coupled plasma etching technology. The device has footprint of 8.16 ?m1034 ?m. The measured extinction ratios remain 45 dB for TE mode and 23 dB for TM mode at wavelength of 1.55 ?m. The extinction ratio of more than 20 dB for TE mode and 15 dB for TM mode is observed covering the whole C-band.

Huang, Yawen; Tu, Zhao; Yi, Huaxiang; Li, Yanping; Wang, Xingjun; Hu, Weiwei

2013-10-01

387

Ozone loss in the Arctic polar vortex inferred from high-altitude aircraft measurements  

NASA Technical Reports Server (NTRS)

The Arctic polar vortex in winter is known to be chemically primed for ozone depletion, yet it does not exhibit the large seasonal ozone decrease that characterizes its southern counterpart. This difference may be due in part to a net flux of ozone-rich air through the Arctic vortex, which can mask ozone loss. But by using a chemically conserved tracer as a reference, significant ozone loss can be identified. This loss is found to be correlated with high levels of chlorine monoxide, suggesting that much of the decrease in ozone is caused by anthropogenic emissions of chlorofluorocarbons.

Proffitt, M. H.; Margitan, J. J.; Kelly, K. K.; Loewenstein, M.; Podolske, J. R.

1990-01-01

388

? Sulphate PNA (PNA S): highly selective DNA binding molecule showing promising antigene activity.  

PubMed

Peptide Nucleic Acids (PNAs), nucleic acid analogues showing high stability to enzyme degradation and strong affinity and specificity of binding toward DNA and RNA are widely investigated as tools to interfere in gene expression. Several studies have been focused on PNA analogues with modifications on the backbone and bases in the attempt to overcome solubility, uptake and aggregation issues. ? PNAs, PNA derivatives having a substituent in the ? position of the backbone show interesting properties in terms of secondary structure and affinity of binding toward complementary nucleic acids. In this paper we illustrate our results obtained on new analogues, bearing a sulphate in the ? position of the backbone, developed to be more DNA-like in terms of polarity and charge. The synthesis of monomers and oligomers is described. NMR studies on the conformational properties of monomers and studies on the secondary structure of single strands and triplexes are reported. Furthermore the hybrid stability and the effect of mismatches on the stability have also been investigated. Finally, the ability of the new analogue to work as antigene, interfering with the transcription of the ErbB2 gene on a human cell line overexpressing ErbB2 (SKBR3), assessed by FACS and qPCR, is described. PMID:22586450

Avitabile, Concetta; Moggio, Loredana; Malgieri, Gaetano; Capasso, Domenica; Di Gaetano, Sonia; Saviano, Michele; Pedone, Carlo; Romanelli, Alessandra

2012-01-01

389

Accessible Passively Stored Highly Spin-Polarized Deuterium in Solid Hydrogen Deuterium, with Application to Inertially Confined Fusion  

NASA Astrophysics Data System (ADS)

Highly spin-polarized D in solid HD was produced in a dilution refrigerator-magnet system under conditions whereby the polarization remains high upon removal of the sample to a 1K, modest field (~0.1 T) environment. This retained polarization remains for many hours to days, sufficient to allow the polarized material to be transported to distant locations and utilized there. The first intended application of this system is for inertially confined fusion (ICF) experiments with spin-polarized D fuel. The actual (vector) polarization attained thus far is P^{rm D} = 38%. The maximum D polarization obtainable with our present refrigerator and magnet (8 mK and 13 T) is 61%. The difference is due to our reluctance to wait the full time constants in these demonstration experiments and due to the inability to attain full efficiency in radio-frequency dynamic polarization transfer between D and H, the maximum polarizability of the latter in our system equaling about 85%. In addition to implementation of the polarization method, it was also necessary to develop methods for cold (4 K) sample transfer with engagement and disengagement provisions for the dilution-refrigerator apparatus, a storage -transport cryostat, various sample-preparation and diagnostic apparatuses, and an interface to an experimental destination facility, in the present case, the OMEGA fusion chamber at the University of Rochester's Laboratory for Laser Energetics. The nature of the fusion experiments required designing and constructing a complex mating system with interchange of cold shrouds to ascertain the sample was always shielded from room temperature black body radiation, and still provide means for positioning the target to within a few microns of the intersection of the high power laser beams. Means of filling plastic target shells to high pressure (at room temperature) with our special isotopic composition of HD with H_2 and D_2 impurities, and condensing them at cryogenic temperatures, were also perfected.

Alexander, Neil Brooks

1992-01-01

390

Compton Scattering off Polarized Electrons with a High Finesse Fabry-Perot Cavity at JLAB  

SciTech Connect

We built and commissioned a new type of Compton polarimeter to measure the electron beam polarization at the Thomas Jefferson National Accelerator Facility (Virginia, USA). The heart of this polarimeter is a high-finesse monolithic Fabry-Perot cavity. Its purpose is to amplify a primary 300 mW laser beam in order to improve the signal to noise ratio of the polarimeter. It is the first time that a high-finesse Fabry-Perot cavity is enclosed in the vacuum of a particle accelerator to monitor the beam polarization by Compton polarimetry. The measured finesse and amplification gain of the cavity are F=26000 and G=7300. The electron beam crosses this high-power photon source at an angle of 23 mrad in the middle of the cavity where the photon beam power density is estimated to be 0.85MW/cm2. We have used this facility during the HAPPEX experiment (April-July 1999) and we give a preliminary measurement of Compton scattering asymmetry.

Nicholas Falletto; M. Authier; G. Bardin; Maud Baylac; M. Boyer; F. Bugeon; Etienne Burtin; Christian Cavata; N. Colombel; G. Congretel; R. Coquillard; G. Coulloux; B. Couzy; P. Deck; A. Delbart; D. Desforges; A. Donati; B. Duboue; Stephanie Escoffier; F. Farci; Bernard Frois; P. Girardot; J. Guillotau; C. Henriot; J. Jardillier; C. Jeanney; M. Juillard; J.P. Jorda; P. Legou; David Lhuillier; Y. Lussignol; P. Mangeot; X. Martin; F. Marie; Jacques Martino; M. Maurier; B. Mazeau; J.F. Millot; F. Molinie; J.P. Mols; J.P. Mouly; M. Mur; Damian Neyret; T. Pedrol; Stephane Platchkov; G. Pontet; Thierry Pussieux; Y. Queinec; P. Rebourgeard; J.C. Sellier; G. Tarte; C. Veyssiere; A. Zakharian; Pierre Bertin; Joseph Mitchell; J.M. Mackowski; L. Pinard

2000-08-01

391

High-time-resolution Measurements of the Polarization of the Crab Pulsar at 1.38 GHz  

NASA Astrophysics Data System (ADS)

Using the Westerbork Synthesis Radio Telescope, we obtained high-time-resolution measurements of the full polarization of the Crab pulsar. At a resolution of 1/8192 of the 34 ms pulse period (i.e., 4.1 ?s), the 1.38 GHz linear-polarization measurements are in general agreement with previous lower-time-resolution 1.4 GHz measurements of linear polarization in the main pulse (MP), in the interpulse (IP), and in the low-frequency component (LFC). We find the MP and IP to be linearly polarized at about 24% and 21% with no discernible difference in polarization position angle. However, contrary to theoretical expectations and measurements in the visible, we find no evidence for significant variation (sweep) in the polarization position angle over the MP, the IP, or the LFC. We discuss the implications, which appear to be in contradiction to theoretical expectations. We also detect weak circular polarization in the MP and IP, and strong (?20%) circular polarization in the LFC, which also exhibits very strong (?98%) linear polarization at a position angle of 40 from that of the MP or IP. The properties are consistent with the LFC, which is a low-altitude component, and the MP and IP, which are high-altitude caustic components. Current models for the MP and IP emission do not readily account for the absence of pronounced polarization changes across the pulse. We measure IP and LFC pulse phases relative to the MP consistent with recent measurements, which have shown that the phases of these pulse components are evolving with time.

S?owikowska, Agnieszka; Stappers, Benjamin W.; Harding, Alice K.; O'Dell, Stephen L.; Elsner, Ronald F.; van der Horst, Alexander J.; Weisskopf, Martin C.

2015-01-01

392

On stochastic spatial patterns and neuronal polarity  

NASA Astrophysics Data System (ADS)

Polarization refers to asymmetric changes in cellular organization that occur in response to external or internal signals. Although neurons can spontaneously establish and maintain asymmetric distributions of signaling molecules on the plasma membrane, it is not clear how intrinsic noise affects neuronal polarization. In this work we present a stochastic model based on endocytosis, exocytosis and lateral diffusion, to study the effects of low number of molecules (high noise intensity), on neuronal polarization. Numerical results were obtained by solving the master equation using Gillespie's algorithm. Our model suggests that the formation of a single pole of molecular asymmetry is very robust to noise; furthermore, in the presence of noise, neuronal polarization could occur even with reduced feedback strength.

Mench髇, Silvia A.; Wio, Horacio S.

2014-08-01

393

Insight into STM image contrast of n-tetradecane and n-hexadecane molecules on highly oriented pyrolytic graphite  

NASA Astrophysics Data System (ADS)

Two-dimensional ordered patterns of n-tetradecane (n-C14H30) and n-hexadecane (n-C16H34) molecules at liquid/graphite interface have been directly imaged using scanning tunneling microscope (STM) under ambient conditions. STM images reveal that the two different kinds of molecules self-organize into ordered lamellar structures in which alkane chains of the molecules extend along one of three equivalent lattice axes of highly oriented pyrolytic graphite (HOPG) basal plane. For n-C14H30 molecules, the molecular axes are observed to tilt by 60 with respect to inter-lamellar trough lines and the carbon backbones of the alkane chains are perpendicular to the HOPG basal plane in an all-trans conformation. However, for n-C16H34 molecules, the molecular axes are perpendicular to lamellar borders (90) and the planes of the all-trans carbon skeletons are parallel to the graphite basal plane. The results clearly indicate that outmost hydrogen atoms of the alkane chains dominate atom-scaled features of the STM images. That is, in the case of long-chain alkane molecules, topographic effects dominantly determine STM image contrast of the methylene regions of the alkane chains that are adsorbed on HOPG.

Zhao, Miao; Jiang, Peng; Deng, Ke; Yu, Ai-Fang; Hao, Yan-Zhong; Xie, Si-Shen; Sun, Jie-Lin

2011-02-01

394

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

NASA Astrophysics Data System (ADS)

In a previous communication [Hu et al., J. Am. Chem. Soc. 126, 10844 (2004)], an approach was demonstrated that improves the efficiency of the cross-effect polarization mechanism employed in high field dynamic nuclear polarization (DNP) experiments. Specifically, it was shown that tethering two TEMPO (2,2,6,6-tetramethylpiperidin-1-oxyl) radicals increases the electron-electron dipole coupling from 1MHz in solutions of monomeric TEMPO to 25MHz in a tethered biradical. The larger coupling resulted in an increase in the DNP enhancements by a factor of 3-4, from 45-50 to 165. Here, a second approach to improving the efficiency of the polarization process is described that involves approximately satisfying the matching condition ??2e-?1e?=?n, where ?2e and ?1e are two frequencies in the electron paramagnetic resonance (EPR) spectrum and ?n is the Larmor frequency of the nuclear spins being polarized. Specifically, in a mixture of TEMPO and trityl [tris (8-carboxy-2,2,6,6-tetramethyl(-d3)-benzo[1,2d:4,5-d']bis(1,3)dithiol-4-yl) methyl] radicals, the intensity maxima in the EPR spectra of these two species are approximately separated by the H1 NMR frequency. In this case the frequency difference between the gyy value of TEMPO and the narrow pseudo-isotropic g-value of trityl is 224MHz and the H1 Larmor frequency is 211MHz. The optimal magnetic field for DNP using the mixtures was found to coincide with the trityl EPR resonance. At 90K and 5T, a mixture of 20mM TEMPO and 20mM trityl enhanced the H1 polarization by a factor of 160, an improvement over the enhancement of 50 with 40mM TEMPO. The reasons for the improvement are discussed and evidence is presented suggesting that DNP enhancement can be improved further by tethering TEMPO and trityl or two similar radicals.

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

2007-01-01

395

Silicon-based broadband antenna for high responsivity and polarization-insensitive photodetection at telecommunication wavelengths.  

PubMed

Although the concept of using local surface plasmon resonance based nanoantenna for photodetection well below the semiconductor band edge has been demonstrated previously, the nature of local surface plasmon resonance based devices cannot meet many requirements of photodetection applications. Here we propose the concept of deep-trench/thin-metal (DTTM) active antenna that take advantage of surface plasmon resonance phenomena, three-dimensional cavity effects, and large-area metal/semiconductor junctions to effectively generate and collect hot electrons arising from plasmon decay and, thereby, increase photocurrent. The DTTM-based devices exhibited superior photoelectron conversion ability and high degrees of detection linearity under infrared light of both low and high intensity. Therefore, these DTTM-based devices have the attractive properties of high responsivity, extremely low power consumption, and polarization-insensitive detection over a broad bandwidth, suggesting great potential for use in photodetection and on-chip Si photonics in many applications of telecommunication fields. PMID:24518852

Lin, Keng-Te; Chen, Hsuen-Li; Lai, Yu-Sheng; Yu, Chen-Chieh

2014-01-01

396

Relativistic effects on the cross section and circular polarization of x-ray radiation following longitudinally-polarized electron impact excitation of highly charged ions  

NASA Astrophysics Data System (ADS)

Detailed calculations using a fully relativistic distorted-wave method are carried out for the cross sections of longitudinally polarized electron impact excitation from the ground state to the magnetic sublevels of the 1s2p3/2 (J=2) state of highly charged He-like ions. The relativistic effects on the cross sections and circular polarization of the x-ray photoemission are investigated in detail. For the excitation process, results show that the relativistic effects may become important leading to considerable enhancements in the cross sections. The inclusion of the relativistic effects can modify the cross sections by several orders of magnitude, especially to the Mf = -1 and -2 magnetic sublevels. For the de-excitation process, the relativistic effects make the degree of circular polarization decreases, these features are more pronounced when the incident electron energy and/or atomic number increase. The relativistic effects are found to be much larger compared to the case of the linear polarization of radiation.

Chen, Z. B.; Zeng, J. L.; Dong, C. Z.

2015-02-01

397

HIGH-FIDELITY RADIO ASTRONOMICAL POLARIMETRY USING A MILLISECOND PULSAR AS A POLARIZED REFERENCE SOURCE  

SciTech Connect

A new method of polarimetric calibration is presented in which the instrumental response is derived from regular observations of PSR J0437-4715 based on the assumption that the mean polarized emission from this millisecond pulsar remains constant over time. The technique is applicable to any experiment in which high-fidelity polarimetry is required over long timescales; it is demonstrated by calibrating 7.2 years of high-precision timing observations of PSR J1022+1001 made at the Parkes Observatory. Application of the new technique followed by arrival time estimation using matrix template matching yields post-fit residuals with an uncertainty-weighted standard deviation of 880 ns, two times smaller than that of arrival time residuals obtained via conventional methods of calibration and arrival time estimation. The precision achieved by this experiment yields the first significant measurements of the secular variation of the projected semimajor axis, the precession of periastron, and the Shapiro delay; it also places PSR J1022+1001 among the 10 best pulsars regularly observed as part of the Parkes Pulsar Timing Array (PPTA) project. It is shown that the timing accuracy of a large fraction of the pulsars in the PPTA is currently limited by the systematic timing error due to instrumental polarization artifacts. More importantly, long-term variations of systematic error are correlated between different pulsars, which adversely affects the primary objectives of any pulsar timing array experiment. These limitations may be overcome by adopting the techniques presented in this work, which relax the demand for instrumental polarization purity and thereby have the potential to reduce the development cost of next-generation telescopes such as the Square Kilometre Array.

Van Straten, W., E-mail: vanstraten.willem@gmail.com [Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Hawthorn, VIC 3122 (Australia)

2013-01-15

398

[Simultaneous determination of four highly polar anti-diabetic drugs in Chinese traditional patent medicines using high performance liquid chromatography].  

PubMed

A high performance liquid chromatographic (HPLC) method was established for the simultaneous determination of four highly polar anti-diabetic drugs, metformin hydrochloride, phenformin hydrochloride, acarbose, and voglibose, in Chinese traditional patent medicines. The separation was performed on a Thermo NH2 analytical column (4.6 mm x 250 mm, 5 microm), the mobile phase consisted of 30% A and 70% B, where A included 0.06% potassium dihydrogen phosphate and 0.028% disodium hydrogen phosphate, B was acetonitrile. The flow rate was 1 mL/min, the detection wavelength was set at 195 nm, and the column temperature was 30 degrees C. The limits bf detection were 0.1-3 mg/L. The linear regression equation for each component was obtained, and the correlation coefficients (r2) were better than 0.9981. The intra-day and inter-day relative standard deviations (RDSs) were 0.10%-5.07% and 0.19%-6.41%, respectively. The average recoveries of four anti-diabetic drugs spiked in blank Chinese traditional patent medicine matrixes were more than 80% except that for the low concentration of voglibose was 64.05%. The RSDs of the recoveries were 1.14%-4.82%. The method can be used in the analysis of the four highly polar anti-diabetic drugs in Chinese traditional patent medicines, and it is rapid, convenient, economic and specific. PMID:19626851

Guo, Dong; Nashunchaoketu; Wang, Jianghua; Liu, Xiaohui; Wu, Shuhong; Zhao, Xiumei; Yang, Binghu

2009-03-01

399

Analysis of single-molecule mechanical measurements with high spatio-temporal resolution  

NASA Astrophysics Data System (ADS)

Optical tweezers allow recording mechanical data from single biological molecules such as molecular motors, DNA processing enzymes, nucleic acids. Such data consist of time series that are dominated by thermal noise and such noisy recordings require proper analysis to correctly extract kinetic and mechanical information. Several different analysis approaches have been established in the past years. Here, we propose an analysis method for optical trapping recordings of non-processive motor proteins. The method does not assume any particular interaction kinetics, allows detection of sub-millisecond interactions and quantification of the number of false and lost events. Precise alignment of interaction events and ensemble averaging allow the investigation of the stepping dynamics of non-processive motors with a temporal resolution of few tens of microseconds and a spatial resolution of few angstroms. Our analysis is applied to the study of the motor protein myosin from fast skeletal muscle. Thanks to the high spatio-temporal resolution, we can distinguish three mechanical pathways in the acto-myosin interaction, with several orders of magnitude different kinetics, which contribute in a load-dependent manner to the myosin working stroke.

Capitanio, Marco; Gardini, Lucia; Pavone, Francesco S.

2013-09-01

400

Identification of Small-Molecule Frequent Hitters from AlphaScreen High-Throughput Screens  

PubMed Central

Although small-molecule drug discovery efforts have focused largely on enzyme, receptor, and ion-channel targets, there has been an increase in such activities to search for protein-protein interaction (PPI) disruptors by applying high-throughout screening (HTS)朿ompatible protein-binding assays. However, a disadvantage of these assays is that many primary hits are frequent hitters regardless of the PPI being investigated. We have used the AlphaScreen technology to screen four different robust PPI assays each against 25,000 compounds. These activities led to the identification of 137 compounds that demonstrated repeated activity in all PPI assays. These compounds were subsequently evaluated in two AlphaScreen counter assays, leading to classification of compounds that either interfered with the AlphaScreen chemistry (60 compounds) or prevented the binding of the protein His-tag moiety to nickel chelate (Ni2+-NTA) beads of the AlphaScreen detection system (77 compounds). To further triage the 137 frequent hitters, we subsequently confirmed by a time-resolved fluorescence resonance energy transfer assay that most of these compounds were only frequent hitters in AlphaScreen assays. A chemoinformatics analysis of the apparent hits provided details of the compounds that can be flagged as frequent hitters of the AlphaScreen technology, and these data have broad applicability for users of these detection technologies. PMID:24371213

Schorpp, Kenji; Rothenaigner, Ina; Salmina, Elena; Reinshagen, Jeanette; Low, Terence; Brenke, Jara K.; Gopalakrishnan, Jay; Tetko, Igor V.; Gul, Sheraz

2014-01-01

401

High pressure chemistry of red phosphorus by photo-activated simple molecules  

NASA Astrophysics Data System (ADS)

High pressure (HP) is very effective in reducing intermolecular distances and inducing unexpected chemical reactions. In addition the photo-activation of the reactants in HP conditions can lead to very efficient and selective processes. The chemistry of phosphorus is currently based on the white molecular form. The red polymeric allotrope, despite more stable and much less toxic, has not attracted much attention so far. However, switching from the white to the red form would benefit any industrial procedure, especially from an environmental point of view. On the other side, water and ethanol are renewable, environmental friendly and largely available molecules, usable as reactants and photo-activators in HP conditions. Here we report a study on the HP photo-induced reactivity of red phosphorus with water and ethanol, showing the possibility of very efficient and selective processes, leading to molecular hydrogen and valuable phosphorus compounds. The reactions have been studied by means of FTIR and Raman spectroscopy and pressure has been generated using membrane Diamond (DAC) and Sapphire (SAC) anvil cells. HP reactivity has been activated by the two-photon absorption of near-UV wavelengths and occurred in total absence of solvents, catalysts and radical initiators, at room T and mild pressure conditions (0.2-1.5 GPa).

Ceppatelli, M.; Fanetti, S.; Bini, R.; Caporali, M.; Peruzzini, M.

2014-05-01

402

Photoisomerization dynamics of a rhodopsin-based molecule (potential molecular switch) with high quantum yields  

NASA Astrophysics Data System (ADS)

It is worthwhile to explore the detailed reaction dynamics of various candidates for molecular switches, in order to understand, e.g., the differences in quantum yields and switching times. Here we report density-functional-based simulations for the rhodopsin-based molecule 4-[4-methylbenzylidene]-5-p-tolyl-3,4-dihydro-2H-pyrrole (MDP), synthesized by Sampedro et al We find that the photoisomerization quantum yields are remarkably high: 82% for cis-to-trans, and 68% for trans-to-cis. The lifetimes of the S1 excited state in cis-MDP in our calculations are in the range of 9001800 fs, with a mean value of 1270 fs, while the range of times required for full cis-to-trans isomerization are 11002000 fs, with a mean value of 1530 fs. In trans-MDP, the calculated S1 excited state lifetimes are 8602140 fs, with a mean value of 1330 fs, and with the full trans-to-cis isomerization completed about 200 fs later. In both cases, the dominant reaction mechanism is rotation around the central C=C bond (connected to the pyrroline ring), and de-excitation occurs at an avoided crossing between the ground state and the lowest singlet state, near the midpoint of the rotational pathway. Perhaps remarkably, but apparently because of electrostatic repulsion, the direction of rotation is the same for both reactions.

Jiang, Chen-Wei; Zhang, Xiu-Xing; Fang, Ai-Ping; Li, Hong-Rong; Xie, Rui-Hua; Li, Fu-Li; Allen, Roland E.

2015-02-01

403

Identification of Small-Molecule Frequent Hitters from AlphaScreen High-Throughput Screens.  

PubMed

Although small-molecule drug discovery efforts have focused largely on enzyme, receptor, and ion-channel targets, there has been an increase in such activities to search for protein-protein interaction (PPI) disruptors by applying high-throughout screening (HTS)-compatible protein-binding assays. However, a disadvantage of these assays is that many primary hits are frequent hitters regardless of the PPI being investigated. We have used the AlphaScreen technology to screen four different robust PPI assays each against 25,000 compounds. These activities led to the identification of 137 compounds that demonstrated repeated activity in all PPI assays. These compounds were subsequently evaluated in two AlphaScreen counter assays, leading to classification of compounds that either interfered with the AlphaScreen chemistry (60 compounds) or prevented the binding of the protein His-tag moiety to nickel chelate (Ni(2+)-NTA) beads of the AlphaScreen detection system (77 compounds). To further triage the 137 frequent hitters, we subsequently confirmed by a time-resolved fluorescence resonance energy transfer assay that most of these compounds were only frequent hitters in AlphaScreen assays. A chemoinformatics analysis of the apparent hits provided details of the compounds that can be flagged as frequent hitters of the AlphaScreen technology, and these data have broad applicability for users of these detection technologies. PMID:24371213

Schorpp, Kenji; Rothenaigner, Ina; Salmina, Elena; Reinshagen, Jeanette; Low, Terence; Brenke, Jara K; Gopalakrishnan, Jay; Tetko, Igor V; Gul, Sheraz; Hadian, Kamyar

2013-12-26

404

Collision dynamics of methyl radicals and highly vibrationally excited molecules using crossed molecular beams  

SciTech Connect

The vibrational to translational (V{yields}T) energy transfer in collisions between large highly vibrationally excited polyatomics and rare gases was investigated by time-of-flight techniques. Two different methods, UV excitation followed by intemal conversion and infrared multiphoton excitation (IRMPE), were used to form vibrationally excited molecular beams of hexafluorobenzene and sulfur hexafluoride, respectively. The product translational energy was found to be independent of the vibrational excitation. These results indicate that the probability distribution function for V{yields}T energy transfer is peaked at zero. The collisional relaxation of large polyatomic molecules with rare gases most likely occurs through a rotationally mediated process. Photodissociation of nitrobenzene in a molecular beam was studied at 266 nm. Two primary dissociation channels were identified including simple bond rupture to produce nitrogen dioxide and phenyl radical and isomerization to form nitric oxide and phenoxy radical. The time-of-flight spectra indicate that simple bond rupture and isomerization occurs via two different mechanisms. Secondary dissociation of the phenoxy radicals to carbon monoxide and cyclopentadienyl radicals was observed as well as secondary photodissociation of phenyl radical to give H atom and benzyne. A supersonic methyl radical beam source is developed. The beam source configuration and conditions were optimized for CH{sub 3} production from the thermal decomposition of azomethane. Elastic scattering of methyl radical and neon was used to differentiate between the methyl radicals and the residual azomethane in the molecular beam.

Chu, P.M.Y.

1991-10-01

405

High-throughput single-molecule force spectroscopy for membrane proteins  

NASA Astrophysics Data System (ADS)

Atomic force microscopy-based single-molecule force spectroscopy (SMFS) is a powerful tool for studying the mechanical properties, intermolecular and intramolecular interactions, unfolding pathways, and energy landscapes of membrane proteins. One limiting factor for the large-scale applicability of SMFS on membrane proteins is its low efficiency in data acquisition. We have developed a semi-automated high-throughput SMFS (HT-SMFS) procedure for efficient data acquisition. In addition, we present a coarse filter to efficiently extract protein unfolding events from large data sets. The HT-SMFS procedure and the coarse filter were validated using the proton pump bacteriorhodopsin (BR) from Halobacterium salinarum and the L-arginine/agmatine antiporter AdiC from the bacterium Escherichia coli. To screen for molecular interactions between AdiC and its substrates, we recorded data sets in the absence and in the presence of L-arginine, D-arginine, and agmatine. Altogether ~400 000 force-distance curves were recorded. Application of coarse filtering to this wealth of data yielded six data sets with ~200 (AdiC) and ~400 (BR) force-distance spectra in each. Importantly, the raw data for most of these data sets were acquired in one to two days, opening new perspectives for HT-SMFS applications.

Bosshart, Patrick D.; Casagrande, Fabio; Frederix, Patrick L. T. M.; Ratera, Merce; Bippes, Christian A.; M黮ler, Daniel J.; Palacin, Manuel; Engel, Andreas; Fotiadis, Dimitrios

2008-09-01

406

Combined versatile high-resolution optical tweezers and single-molecule fluorescence microscopy  

NASA Astrophysics Data System (ADS)

Optical trapping and single-molecule fluorescence are two major single-molecule approaches. Their combination has begun to show greater capability to study more complex systems than either method alone, but met many fundamental and technical challenges. We built an instrument that combines base-pair resolution dual-trap optical tweezers with single-molecule fluorescence microscopy. The instrument has complementary design and functionalities compared with similar microscopes previously described. The optical tweezers can be operated in constant force mode for easy data interpretation or in variable force mode for maximum spatiotemporal resolution. The single-molecule fluorescence detection can be implemented in either wide-field or confocal imaging configuration. To demonstrate the capabilities of the new instrument, we imaged a single stretched ? DNA molecule and investigated the dynamics of a DNA hairpin molecule in the presence of fluorophore-labeled complementary oligonucleotide. We simultaneously observed changes in the fluorescence signal and pauses in fast extension hopping of the hairpin due to association and dissociation of individual oligonucleotides. The combined versatile microscopy allows for greater flexibility to study molecular machines or assemblies at a single-molecule level.

Sirinakis, George; Ren, Yuxuan; Gao, Ying; Xi, Zhiqun; Zhang, Yongli

2012-09-01

407

Combined versatile high-resolution optical tweezers and single-molecule fluorescence microscopy  

PubMed Central

Optical trapping and single-molecule fluorescence are two major single-molecule approaches. Their combination has begun to show greater capability to study more complex systems than either method alone, but met many fundamental and technical challenges. We built an instrument that combines base-pair resolution dual-trap optical tweezers with single-molecule fluorescence microscopy. The instrument has complementary design and functionalities compared with similar microscopes previously described. The optical tweezers can be operated in constant force mode for easy data interpretation or in variable force mode for maximum spatiotemporal resolution. The single-molecule fluorescence detection can be implemented in either wide-field or confocal imaging configuration. To demonstrate the capabilities of the new instrument, we imaged a single stretched ? DNA molecule and investigated the dynamics of a DNA hairpin molecule in the presence of fluorophore-labeled complementary oligonucleotide. We simultaneously observed changes in the fluorescence signal and pauses in fast extension hopping of the hairpin due to association and dissociation of individual oligonucleotides. The combined versatile microscopy allows for greater flexibility to study molecular machines or assemblies at a single-molecule level. PMID:23020384

Sirinakis, George; Ren, Yuxuan; Gao, Ying; Xi, Zhiqun; Zhang, Yongli

2012-01-01

408

SEPARATION OF TWO CONTRIBUTIONS TO THE HIGH ENERGY EMISSION OF CYGNUS X-1: POLARIZATION MEASUREMENTS WITH INTEGRAL SPI  

SciTech Connect

Operational since 2002 on board the INTEGRAL observatory, the SPI spectrometer can be used to perform polarization measurements in the hard X-ray/soft{gamma}-ray domain ({approx}130 keV-8 MeV). However, this phenomenon is complex to measure at high energy and requires high fluxes. Cyg X-1 appears to be the best candidate amongst the X-ray binaries since it is one of the brightest persistent sources in this energy domain. Furthermore, a polarized component has recently been reported above 400 keV from IBIS data. We have therefore dedicated our efforts to developing the required tools to study the polarization in the INTEGRAL SPI data and have first applied them to 2.6 Ms of Cyg X-1 observations, covering 6.5 years of the INTEGRAL mission. We have found that the high energy emission of Cyg X-1 is indeed polarized, with a mean polarization fraction of 76% {+-} 15% at a position angle estimated to be 42 Degree-Sign {+-} 3 Degree-Sign , for energies above 230 keV. The polarization fraction clearly increases with energy. In the 130-230 keV band, the polarization fraction is lower than 20%, but exceeds 75% between 370 and 850 keV, with the (total) emission vanishing above this energy. This result strongly suggests that the emission originates from the jet structure known to emit in the radio domain. The same synchrotron process could be responsible for the emission from radio to MeV, implying the presence of high energy electrons. This illustrates why the polarization of the high energy emission in compact objects is an increasingly important observational objective.

Jourdain, E.; Roques, J. P.; Chauvin, M.; Clark, D. J. [Universite de Toulouse, UPS-OMP IRAP, Toulouse (France); CNRS, IRAP, 9 Av. colonel Roche, BP 44346, F-31028 Toulouse cedex 4 (France)

2012-12-10

409

Identification of Adiponectin Receptor Agonist Utilizing a Fluorescence Polarization Based High Throughput Assay  

PubMed Central

Adiponectin, the adipose-derived hormone, plays an important role in the suppression of metabolic disorders that can result in type 2 diabetes, obesity, and atherosclerosis. It has been shown that up-regulation of adiponectin or adiponectin receptor has a number of therapeutic benefits. Given that it is hard to convert the full size adiponectin protein into a viable drug, adiponectin receptor agonists could be designed or identified using high-throughput screening. Here, we report on the development of a two-step screening process to identify adiponectin agonists. First step, we developed a high throughput screening assay based on fluorescence polarization to identify adiponectin ligands. The fluorescence polarization assay reported here could be adapted to screening against larger small molecular compound libraries. A natural product library containing 10,000 compounds was screened and 9 hits were selected for validation. These compounds have been taken for the second-step in vitro tests to confirm their agonistic activity. The most active adiponectin receptor 1 agonists are matairesinol, arctiin, (-)-arctigenin and gramine. The most active adiponectin receptor 2 agonists are parthenolide, taxifoliol, deoxyschizandrin, and syringin. These compounds may be useful drug candidates for hypoadiponectin related diseases. PMID:23691032

Sun, Yiyi; Zang, Zhihe; Zhong, Ling; Wu, Min; Su, Qing; Gao, Xiurong; Zan, Wang; Lin, Dong; Zhao, Yan; Zhang, Zhonglin

2013-01-01

410

High Bacterial Diversity of Biological Soil Crusts in Water Tracks over Permafrost in the High Arctic Polar Desert  

PubMed Central

In this study we report the bacterial diversity of biological soil crusts (biocrusts) inhabiting polar desert soils at the northern land limit of the Arctic polar region (83 05 N). Employing pyrosequencing of bacterial 16S rRNA genes this study demonstrated that these biocrusts harbor diverse bacterial communities, often as diverse as temperate latitude communities. The effect of wetting pulses on the composition of communities was also determined by collecting samples from soils outside and inside of permafrost water tracks, hill slope flow paths that drain permafrost-affected soils. The intermittent flow regime in the water tracks was correlated with altered relative abundance of phylum level taxonomic bins in the bacterial communities, but the alterations varied between individual sampling sites. Bacteria related to the Cyanobacteria and Acidobacteria demonstrated shifts in relative abundance based on their location either inside or outside of the water tracks. Among cyanobacterial sequences, the proportion of sequences belonging to the family Oscillatoriales consistently increased in relative abundance in the samples from inside the water tracks compared to those outside. Acidobacteria showed responses to wetting pulses in the water tracks, increasing in abundance at one site and decreasing at the other two sites. Subdivision 4 acidobacterial sequences tended to follow the trends in the total Acidobacteria relative abundance, suggesting these organisms were largely responsible for the changes observed in the Acidobacteria. Taken together, these data suggest that the bacterial communities of these high latitude polar biocrusts are diverse but do not show a consensus response to intermittent flow in water tracks over high Arctic permafrost. PMID:23967218

Steven, Blaire; Lionard, Marie; Kuske, Cheryl R.; Vincent, Warwick F.

2013-01-01

411

Micro injector sample delivery system for charged molecules  

DOEpatents

A micro injector sample delivery system for charged molecules. The injector is used for collecting and delivering controlled amounts of charged molecule samples for subsequent analysis. The injector delivery system can be scaled to large numbers (>96) for sample delivery to massively parallel high throughput analysis systems. The essence of the injector system is an electric field controllable loading tip including a section of porous material. By applying the appropriate polarity bias potential to the injector tip, charged molecules will migrate into porous material, and by reversing the polarity bias potential the molecules are ejected or forced away from the tip. The invention has application for uptake of charged biological molecules (e.g. proteins, nucleic acids, polymers, etc.) for delivery to analytical systems, and can be used in automated sample delivery systems.

Davidson, James C. (Livermore, CA); Balch, Joseph W. (Livermore, CA)

1999-11-09

412

Complex Organic Molecules at High Spatial Resolution toward ORION-KL. II. Kinematics  

NASA Astrophysics Data System (ADS)

It has recently been suggested that chemical processing can shape the spatial distributions of complex molecules in the Orion-KL region and leads 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. We compare molecular images with high spatial resolution images that trace the temperature, density, and kinematics of the source in order to investigate the effects of physical conditions on molecular distributions. These observations were conducted at ? = 3 mm and included transitions of ethyl cyanide [C2H5CN], methyl formate [HCOOCH3], formic acid [HCOOH], acetone [(CH3)2CO], SiO, and methanol [CH3OH]. We find differences in the molecular distributions as a function of each of the aforementioned physical factors. These results indicate that acetone may be produced by chemical processing and is robust to large changes in physical conditions, while formic acid is readily destroyed by gas-phase processing in warm and dense regions. We also find that while the spatial distributions of ethyl cyanide and methyl formate are not distinct as is suggested by the concept of "chemical differentiation," local physical conditions shape the small-scale emission structure for these species.

Friedel, D. N.; Widicus Weaver, S. L.

2012-08-01

413

Double electron removal and fragmentation model of the H2 molecule by highly charged ions  

NASA Astrophysics Data System (ADS)

A five-body classical trajectory Monte Carlo model has been developed to study double electron removal from H2 by collisions with highly charged ions at impact energies ranging from 1 eV/u to 1 GeV/u. The longitudinal and transverse final-state correlation between ejected electrons is calculated for double ionization of H2 by impact of Se28+ at 3.6 MeV/u and U92+ at 1 GeV/u; the electron-electron interaction is dynamically included during the collision when one of the electron's total energy becomes positive. Relativistic corrections are incorporated to reflect the Lorentz contraction of the projectile's electric field. The cross section dependence on the alignment of the H2 molecular axis was investigated. Here, transfer ionization of H2 by O8+ at 500 keV/u is found to have a maximum for the molecular axis aligned perpendicular to the projectile velocity, while no orientation dependence is found for double ionization at 500 keV/u. In contrast, a minimum in the cross section at 90 is found for 1-GeV/u U92++H2 collisions. A systematic study of the energy partitioning between the two product H+ ions has been made for Xe54++H2 from 1 eV/u to 1 MeV/u. Large deviations from Franck-Condon behavior are found for impact energies E<~10 keV/u. At low energies the proton energies are very energetic with the main contribution arising from collisional transfer from the projectile, while the proton energy spectrum at high impact energy is due to the Coulomb explosion of the isolated molecule.

Wood, C. J.; Olson, R. E.

1999-02-01

414

Highly anisotropic rhenium(IV) complexes: new examples of mononuclear single-molecule magnets.  

PubMed

The rhenium(IV) complex (NBu4)2[ReBr4(ox)] (1) (ox = oxalate and NBu4(+) = tetra-n-butylammonium cation) has been prepared and its crystal structure determined by X-ray diffraction. The structure is made up of discrete [ReBr4(ox)](2-) anions and bulky NBu4(+) cations. Each [ReBr4(ox)](2-) anion is surrounded by six NBu4(+) cations, which preclude any significant intermolecular contact between the anionic entities, the shortest rhenium贩穜henium distance being 9.373(1) . Variable temperature dc and ac magnetic susceptibility measurements and field-dependent magnetization experiments on polycrystalline samples of 1 reveal the occurrence of highly anisotropic magnetically isolated Re(IV) centers (S(Re) = 3/2), which exhibit slow relaxation of the magnetization at very low temperatures in a dc field. Ac measurements conducted on a polycrystalline sample of the complex (NBu4)2[ReCl4(ox)] (2) [compound isostructural to 1 whose structure and dc magnetic susceptibility study were previously reported in Tomkiewicz, A.; Bartczak, T. J.; Kruszy?ski, R.; Mrozi?ski, J. J. Mol. Struct. 2001, 595, 225] show a similar behavior, both complexes thus constituting new examples of mononuclear single-molecule magnets. High-frequency and -field electron paramagnetic resonance on polycrystalline samples of 1 and 2 and on single crystals of 2 allowed for the determination for the first time of the negative sign and confirmed a significant magnitude and rhombicity (E/D) of the zero-field splitting tensor of the [ReCl4(ox)](2-) and [ReBr4(ox)](2-) centers, originating from a combination of spin-orbit coupling and low molecular symmetry. D and E values of 1 and 2 were estimated through magnetization measurements and theoretically calculated through complete active space and density functional theory methodologies. PMID:23957361

Mart韓ez-Lillo, Jos; Mastropietro, Teresa F; Lhotel, Elsa; Paulsen, Carley; Cano, Joan; De Munno, Giovanni; Faus, Juan; Lloret, Francesc; Julve, Miguel; Nellutla, Saritha; Krzystek, J

2013-09-18

415

New frontier in transmission IR spectroscopy of molecules adsorbed on high surface area solids: Experiments below liquid nitrogen temperature  

Microsoft Academic Search

IR spectroscopy of adsorbed probe molecules is one of the most powerful characterization techniques for the investigation of surface active sites on high surface area materials like oxides and zeolites. In the last 20 years the use of specific IR cells allowing the in situ sample activation, gas dosage and sample cooling down to liquid nitrogen temperature has remarkably improved

G. Spoto; S. Bordiga; A. Zecchina; D. Cocina; E. N. Gribov; L. Regli; E. Groppo; C. Lamberti

2006-01-01

416

High-Resolution Waveguide THz Spectroscopy of Biological Molecules N. Laman,* S. Sree Harsha,* D. Grischkowsky,* and Joseph S. Melingery  

E-print Network

High-Resolution Waveguide THz Spectroscopy of Biological Molecules N. Laman,* S. Sree Harsha,* D be used for identification purposes. However, conventional Fourier transform infrared spectroscopy and terahertz time- domain spectroscopy (THz-TDS) often result in broad, overlapping features that are difficult

417

Synergistic effect of polymer and small molecules for high-performance ternary organic solar cells.  

PubMed

A ternary blend system with two donors and one acceptor provides an effective route to improve the performance of organic solar cells. A synergistic effect of polymer and small molecules is observed in ternary solar cells, and the power conversion effi ciency (PCE) of the ternary system (8.40%) is higher than those of binary systems based on small molecules (7.48%) or polymers (6.85%). PMID:25655181

Zhang, Yajie; Deng, Dan; Lu, Kun; Zhang, Jianqi; Xia, Benzheng; Zhao, Yifan; Fang, Jin; Wei, Zhixiang

2015-02-01

418

High spectral and time resolution observations of the eclipsing polar RX J0719.2+6557  

E-print Network

We present phase-resolved spectral and multicolor CCD-photometric observations of the eclipsing polar RX J0719.2+6557 obtained with relatively high time (~600 sec/15 sec) and spectral (2.1 A) resolution when the system was in a high accretion state. The trailed spectrograms clearly reveal the presence of three different line components with different width and radial velocity variation. We were able to resolve all three components by line deblending, and by means of Doppler tomography were able to unambiguously identify the emission components with the secondary star, the ballistic part of the accretion stream and the magnetically funnelled part of the stream. The light curves and eclipse profiles provide additional information about the system geometry.

G. H. Tovmassian; P. Szkody; J. Greiner; S. Vrielmann; P. Kroll; S. Howell; R. Saxton; D. Ciardi; P. A. Mason; N. C. Hastings

1998-09-24

419

High carrier suppression double sideband modulation using polarization state rotation filter and optical external modulator  

NASA Astrophysics Data System (ADS)

We propose a high carrier suppression double sideband modulation technique using a Mach-Zehnder modulator (MZM) and an integrated polarization state rotation filter (PSRF), which is designed to improve the carrier suppression ratio. With the functions of MZM and PSRF, about 30 dB carrier suppression ratio relative to first-order sidebands is demonstrated. Moreover, we demonstrate the optical generation of microwave/millimeter-wave signals by beating the carrier suppressed double sideband (DSB-SC) lightwave signals. The experimental results show that the improvement of carrier suppression ratio with PSRF can effectively cancel the modulating RF frequency component. A tunable and high purity microwave signal, which is limited by the bandwidth of MZM and photodetector (PD), is obtained, and it does not suffer from obvious phase noise degradation with 25 km transmission.

Yu, Xianbin; Zhang, Hanyi; Zheng, Xiaoping

2006-11-01

420

The Most Probable Cause for the High Gamma-Ray Polarization in GRB 021206  

E-print Network

The exciting detection of a very high degree of linear polarization, $P=(80\\pm 20)%$, in the prompt gamma-ray emission of GRB 021206, supports synchrotron emission as being the dominant radiation mechanism. There were also claims that this implies a magnetic field ordered on large scales within the ejecta, that must therefore be produced at the source, which in turn was used as an argument in favor magnetic fields playing an active role in the production of GRB jets. However, an alternative explanation was suggested which also works with a magnetic field that is generated in the internal shocks and does not originate at the source: a very narrow jet, of opening angle $\\theta_j\\sim 1/\\gamma$, where $\\gamma\\gtrsim 100$ is the Lorentz factor during the GRB, viewed at $\\theta_j<\\theta_{obs}\\lesssim\\theta_j+1/\\gamma$. We calculate $P$ for these two scenarios, and find that it is significantly easier to produce $P\\gtrsim 50%$ with an ordered field. More specifically, we obtain $P\\sim(43-61)%$ for an ordered transverse magnetic field, $B_{ord}$, whereas a random field within the plane of the shock, $B_\\perp$, produces $P\\lesssim(38-54)%$ for a single pulse in the GRB light curve, but the integrated emission over many pulses (as measured in GRB 021206) is a factor of $\\sim 2$ lower. A magnetic field normal to the shock front, $B_\\parallel$, produces $P\\sim(35-62)%$ for the emission integrated over many pulses. However, polarization measurements from GRB afterglows suggest a more isotropic shock-produced field configuration that would reduce $P$ by a factor $\\sim 2-3$. Therefore, an ordered magnetic field, $B_{ord}$, that originates at the source, can produce the observed polarization most naturally, while $B_\\parallel$ is less likely, and $B_\\perp$ is the least likely of the above.

Jonathan Granot

2003-09-05

421

Angular dependence of recoil proton polarization in high-energy \\gamma d \\to p n  

E-print Network

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

Jiang, X; Benmokhtar, F; Camsonne, A; Chen, J P; Choi, S; Chudakov, E; Cusanno, F; De Jager, C W; De Leo, R; Deur, A; Dutta, D; Garibaldi, F; Gaskell, D; Gayou, O; Gilman, R; Glashauser, C; Hamilton, D; Hansen, O; Higinbotham, D W; Holt, R J; Jones, M K; Kaufman, L J; Kinney, E R; Kr鋗er, K; Lagamba, L; Lerose, J; Lhuillier, D; Lindgren, R; Liyanage, N; McCormick, K; Meziani, Z E; Michaels, R; Moffit, B; Monaghan, P; Nanda, S; Paschke, K D; Perdrisat, C F; Punjabi, V; Qattan, I A; Ransome, R D; Reimer, P E; Reitz, B; Saha, A; Schulte, E C; Sheyor, R; Slifer, K J; Solvignon, P; Sulkosky, V; Urciuoli, G M; Voutier, E; Wang, K; Wijesooriya, K; Wojtsekhowski, B; Zhu, L

2007-01-01

422

Angular dependence of recoil proton polarization in high-energy ?d \\to p n  

E-print Network

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

X. Jiang; J. Arrington; F. Benmokhtar; A. Camsonne; J. P. Chen; S. Choi; E. Chudakov; F. Cusanno; A. Deur; D. Dutta; F. Garibaldi; D. Gaskell; O. Gayou; R. Gilman; C. Glashauser; D. Hamilton; O. Hansen; D. W. Higinbotham; R. J. Holt; C. W. de Jager; M. K. Jones; L. J. Kaufman; E. R. Kinney; K. Kramer; L. Lagamba; R. de Leo; J. Lerose; D. Lhuillier; R. Lindgren; N. Liyanage; K. McCormick; Z. -E. Meziani; R. Michaels; B. Moffit; P. Monaghan; S. Nanda; K. D. Paschke; C. F. Perdrisat; V. Punjabi; I. A. Qattan; R. D. Ransome; P. E. Reimer; B. Reitz; A. Saha; E. C. Schulte; R. Sheyor; K. Slifer; P. Solvignon; V. Sulkosky; G. M. Urciuoli; E. Voutier; K. Wang; K. Wijesooriya; B. Wojtsekhowski; L. Zhu

2007-02-02

423

Angular dependence of recoil proton polarization in high-energy \\gamma d \\to p n  

SciTech Connect

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

X. Jiang; J. Arrington; F. Benmokhtar; A. Camsonne; J.P. Chen; S. Choi; E. Chudakov; F. Cusanno; A. Deur; D. Dutta; F. Garibaldi; D. Gaskell; O. Gayou; R. Gilman; C. Glashauser; D. Hamilton; O. Hansen; D.W. Higinbotham; R.J. Holt; C.W. de Jager; M.K. Jones; L.J. Kaufman; E.R. Kinney; K. Kramer; L. Lagamba; R. de Leo; J. Lerose; D. Lhuillier; R. Lindgren; N. Liyanage; K. McCormick; Z.-E. Meziani; R. Michaels; B. Moffit; P. Monaghan; S. Nanda; K.D. Paschke; C.F. Perdrisat; V. Punjabi; I.A. Qattan; R.D. Ransome; P.E. Reimer; B. Reitz; A. Saha; E.C. Schulte; R. Sheyor; K. Slifer; P. Solvignon; V. Sulkosky; G.M. Urciuoli; E. Voutier; K. Wang; K. Wijesooriya; B. Wojtsekhowski; L. Zhu

2007-02-26

424

A multi-transition study of molecules toward NGC 1068 based on high-resolution imaging observations with ALMA  

NASA Astrophysics Data System (ADS)

We present 0.8-mm band molecular images and spectra obtained with the Atacama Large Millimeter/submillimeter Array (ALMA) toward one of the nearest galaxies with an active galactic nucleus (AGN), NGC 1068. Distributions of CO isotopic species (13CO and C18O) J = 3-2, CN N = 3-2, and CS J = 7-6 are observed toward the circumnuclear disk (CND) and a part of the starburst ring with an angular resolution of 1{^''.}3 1{^''.}2. The physical properties of these molecules and shock-related molecules, such as HNCO, CH3CN, SO, and CH3OH, detected in the 3-mm band were estimated using rotation diagrams under the assumption of local thermodynamic equilibrium. The rotational temperatures of the CO isotopic species and the shock-related molecules in the CND are, respectively, 14-22 K and upper limits of 20-40 K. Although the column densities of the CO isotopic species in the CND are only from one-fifth to one-third of that in the starburst ring, those of the shock-related molecules are enhanced by a factor of 3-10 in the CND. We also discuss the chemistry of each species, and compare the fractional abundances in the CND and starburst ring with those of Galactic sources such as cold cores, hot cores, and shocked molecular clouds in order to study the overall characteristics. We find that the abundances of shock-related molecules are more similar to abundances in hot cores and/or shocked clouds than to cold cores. The CND hosts relatively complex molecules, which are often associated with shocked molecular clouds or hot cores. Because a high X-ray flux can dissociate these molecules, they must also reside in regions shielded from X-rays.

Nakajima, Taku; Takano, Shuro; Kohno, Kotaro; Harada, Nanase; Herbst, Eric; Tamura, Yoichi; Izumi, Takuma; Taniguchi, Akio; Tosaki, Tomoka

2015-01-01

425

Servo Control of High Degree of Linear Polarization Output from Polarization-Maintaining Fiber and its Application in Fiber-Component Based Frequency Modulation Spectroscopy  

NASA Astrophysics Data System (ADS)

A novel servo control method has been developed to output a highly linear state of polarization (SOP) from a polarization-maintaining (PM) fiber. The correc