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1

Polar-Molecule-Dominated Electrorheological Fluids Featuring High Yield Stresses  

E-print Network

Polar-Molecule-Dominated Electrorheological Fluids Featuring High Yield Stresses By Rong Shen of the external electric field, and the yield stress displays a quadratic dependence on the field strength been made to improve the performance of ER fluids, however, the yield stresses available were still

Zexian, Cao

2

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

SciTech Connect

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

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

2011-04-15

3

Properties of water Polar molecule  

E-print Network

1 Water · Properties of water ­ Polar molecule · Hydrogen bonds with other water molecules, as a solid (ice) or as a gas (water vapor). · Water molecules are attracted to each other, creating hydrogen properties. Cohesion · Water molecules stick to each other. · The attraction between the water molecules

Cochran-Stafira, D. Liane

4

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

PubMed Central

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

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

2013-01-01

5

Nano trap for polar molecules  

NASA Astrophysics Data System (ADS)

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

Blmel, R.

2012-07-01

6

Hybrid Quantum Information Processing with Polar Molecules  

NASA Astrophysics Data System (ADS)

We describe the integration of polar molecules with mesoscopic solid state devices in a way that produces robust, coherent, quantum-level control with applications for quantum information processing. The exceptional features of polar molecules, i.e. long-lived rotational states in combination with electric dipole moments of several Debye, provide the necessary ingredients to achieve strong coupling to the quantized field of a high-Q microwave cavity. We discuss two scenarios, where quantum information is stored either in rotational states of a single molecule or in collective spin excitation of an ensemble of molecules. In the latter case we benefit from an enhanced coupling strength, which allows a coherent transfer of quantum information between molecules and solid state qubits.

Andr, A.; DeMille, D.; Doyle, J. M.; Lukin, M. D.; Maxwell, S. E.; Rabl, P.; Schoelkopf, R. J.; Zoller, P.

2006-11-01

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 MonteCarlo 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

Fluorescence polarization immunoassays and related methods for simple, high-throughput screening of small molecules  

Microsoft Academic Search

Fluorescence polarization immunoassay (FPIA) is a homogeneous (without separation) competitive immunoassay method based on\\u000a the increase in fluorescence polarization (FP) of fluorescent-labeled small antigens when bound by specific antibody. The\\u000a minimum detectable quantity of FPIAs with fluorescein label (about 0.1ng analyte) is comparable with chromatography and ELISA\\u000a methods, although this may be limited by sample matrix interference. Because of its

David S. Smith; Sergei A. Eremin

2008-01-01

9

High-throughput fluorescence polarization assay to identify small molecule inhibitors of BRCT domains of breast cancer gene 1.  

PubMed

The C-terminus region of the 1863 residue early onset of breast cancer gene 1 (BRCA1) nuclear protein contains a tandem globular carboxy terminus domain termed BRCT. The BRCT repeats in BRCA1 are phosphoserine- and/or phosphothreonine-specific binding modules. The interaction of the BRCT(BRCA1) domains with phosphorylated BRCA1-associated carboxyl terminal helicase (BACH1) is cell cycle regulated and is essential for DNA damage-induced checkpoint control during the transition from the G(2) phase to the M phase of the cell cycle. Development of a competitive, homogeneous, high-throughput fluorescence polarization (FP) assay to identify small molecule inhibitors of BRCT(BRCA1)-BACH1 interaction is reported here. The FP assay was used for measuring binding affinities and inhibition constants of BACH1 peptides and small molecule inhibitors of BRCT(BRCA1) domains, respectively. A fluorescently labeled wild-type BACH1 decapeptide (BDP1) containing the critical phosphoserine, a phenylalanine at (P+3), and a GST-BRCT fusion protein were used to establish the FP assay. BDP1 has a dissociation constant (K(d)) of 1.58+/-0.01microM and a dynamic range (DeltamP) of 164.9+/-1.9. The assay tolerates 20% dimethyl sulfoxide, which enables screening poorly soluble compounds. Under optimized conditions, a Z' factor of 0.87 was achieved in a 384-well format for high-throughput screening. PMID:16500609

Lokesh, G L; Rachamallu, Aparna; Kumar, G D Kishore; Natarajan, Amarnath

2006-05-01

10

Trapping polar molecules in an ac trap  

SciTech Connect

Polar molecules in high-field seeking states cannot be trapped in static traps as Maxwell's equations do not allow a maximum of the electric field in free space. It is possible to generate an electric field that has a saddle point by superposing an inhomogeneous electric field to an homogeneous electric field. In such a field, molecules are focused along one direction, while being defocused along the other. By reversing the direction of the inhomogeneous electric field the focusing and defocusing directions are reversed. When the fields are being switched back and forth at the appropriate rate, this leads to a net focusing force in all directions. We describe possible electrode geometries for creating the desired fields and discuss their merits. Trapping of {sup 15}ND{sub 3} ammonia molecules in a cylindrically symmetric ac trap is demonstrated. We present measurements of the spatial distribution of the trapped cloud as a function of the settings of the trap and compare these to both a simple model assuming a linear force and to full three-dimensional simulations of the experiment. With the optimal settings, molecules within a phase-space volume of 270 mm{sup 3} (m/s){sup 3} remain trapped. This corresponds to a trap depth of about 5 mK and a trap volume of about 20 mm{sup 3}.

Bethlem, Hendrick L. [Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin (Germany); Laser Centre Vrije Universiteit, De Boelelaan 1081, NL-1081HV Amsterdam (Netherlands); Veldhoven, Jacqueline van [Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin (Germany); FOM-Institute for Plasmaphysics Rijnhuizen, P.O. Box 1207, NL-3430 BE Nieuwegein (Netherlands); Schnell, Melanie; Meijer, Gerard [Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin (Germany)

2006-12-15

11

Polar stacking of molecules in liquid chloroform.  

PubMed

Using neutron diffraction and the isotopic substitution technique we have investigated the local structure of liquid chloroform. A strong tendency for polar stacking of molecules with collinear alignment of dipole moments is found. We speculate that these polar stacks contribute to the performance of chloroform as a solvent. PMID:25562307

Shephard, J J; Soper, A K; Callear, S K; Imberti, S; Evans, J S O; Salzmann, C G

2015-03-01

12

Ultracold Polar KRb Molecules in Optical Lattices  

NASA Astrophysics Data System (ADS)

The creation of a gas of ultracold polar molecules with a high phase space density brings new possibilities beyond experiments with ultracold atomic gases. In particular, long-range, anisotropic, and tunable dipole-dipole interactions open the way for novel quantum gases, with applications including strongly correlated many-body systems, and ultracold chemistry. This thesis will present the final steps to complete control over both internal and external degrees of freedom of the molecule which allows us to control, and even completely suppress, the chemical reactions between molecules. First, the control over internal states has been achieved through coherent state transfer to the ro-vibronic ground state and coherent manipulations of the hyperfine and rotational states with microwave radiation. Second, external degrees of freedom are controlled by loading the gas into an optical lattice. With the molecules loaded into a one-dimensional lattice, the orientation of the molecular collisions is controlled by manipulating both internal (hyperfine states) and external (motional states in the direction of tight confinement) degrees of freedom. Most striking is that by preparing the molecules all in the lowest band of the lattice in the same internal state, the molecular collisions can only occur in a side-by-side" orientation, where the chemical reaction rate is suppressed by the repulsive dipole-dipole interactions. The chemical reaction can be suppressed completely by further constraining the motion in the trap in a strong 3D lattice. Here we see lifetimes longer than 20 s, limited by off-resonant light scattering. Finally, the ac polarizability of the molecules is explored and controlled. The different rotational states of the molecule have different polarizabilities and will experience a different trapping force in both the optical dipole trap or lattice. We show that there is a magic angle" between the quantization axis and the polarization of the trapping laser at which the polarizabilities of two different rotational states can be matched, eliminating dephasing and allowing for coherent manipulations between rotational states.

Neyenhuis, Brian

13

Fluorescence Polarization Assays in Small Molecule Screening  

PubMed Central

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

Lea, Wendy A.; Simeonov, Anton

2011-01-01

14

Entanglement of polar molecules in pendular states.  

PubMed

In proposals for quantum computers using arrays of trapped ultracold polar molecules as qubits, a strong external field with appreciable gradient is imposed in order to prevent quenching of the dipole moments by rotation and to distinguish among the qubit sites. That field induces the molecular dipoles to undergo pendular oscillations, which markedly affect the qubit states and the dipole-dipole interaction. We evaluate entanglement of the pendular qubit states for two linear dipoles, characterized by pairwise concurrence, as a function of the molecular dipole moment and rotational constant, strengths of the external field and the dipole-dipole coupling, and ambient temperature. We also evaluate a key frequency shift, ??, produced by the dipole-dipole interaction. Under conditions envisioned for the proposed quantum computers, both the concurrence and ?? become very small for the ground eigenstate. In principle, such weak entanglement can be sufficient for operation of logic gates, provided the resolution is high enough to detect the ?? shift unambiguously. In practice, however, for many candidate polar molecules it appears a challenging task to attain adequate resolution. Simple approximate formulas fitted to our numerical results are provided from which the concurrence and ?? shift can be obtained in terms of unitless reduced variables. PMID:21456645

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

2011-03-28

15

Photodetachment microscopy of polar molecules  

NASA Astrophysics Data System (ADS)

Observations of spatial distribution of electrons photodetached in an external static electric field, so-called photodetachment microscopy^1,2, can provide very accurate information about properties of negative ions. In order to extract information about scattering of very low-energy electrons by neutral targets, it is necessary to investigate the rescattering effect in the spatial distribution^3. Typically, elastic cross sections for electron-atom scattering are not large enough to induce a substantial rescattering effect at moderate static fields. However, for molecules the situation might be quite different. In the present paper we show that for molecules with substantial permanent dipole moments, particularly for LiF, the rescattering effect is large enough to change significantly the spatial distribution of electrons photodetached from corresponding negative ions. ^1Yu. N. Demkov, V. D. Kondratovich, and V. N. Ostrovsky, JETP Lett. 34, 404 (1981). ^2C. Blondel, C. Delsart, and F. Dulieu, Phys. Rev. Lett. 77, 3755 (1996). ^3I. I. Fabrikant, Phys. Rev. A 66, 010703(R) (2002).

Fabrikant, Ilya

2003-05-01

16

Dynamics of reactive ultracold alkali polar molecules  

NASA Astrophysics Data System (ADS)

Recently, ultracold polar molecules of KRb have been created. These molecules are chemically reactive and their lifetime in a trap is limited [1]. However, their lifetime increases when they are loaded into a 1D optical lattice in the presence of an electric field [2]. These results naturally raise the question of manipulating ultracold collisions of other species of alkali dimer molecules, with an eye toward both novel stereochemistry, as well as suppressing unwanted reactions, to enable condensed matter applications. In this talk, we report on a comparative study between the bi-alkali polar molecules of LiNa, LiK, LiRb, LiCs which have been predicted to be reactive [3]. We compute the isotropic C6 coefficients of these systems and we predict the elastic and reactive rate coefficients when an electric field is applied in a 1D optical lattice. We will discuss the efficacy of evaporative cooling for each species.[4pt] [1] Ni et al., Science 322, 231 (2008); Ospelkaus et al., Science 327, 853 (2010); Ni et al., Nature 464, 1324 (2010). [2] Qu'em'ener et al., Phys. Rev. A 81, 060701(R) (2010) ; Qu'em'ener et al., Phys. Rev. A 83, 012705 (2011); de Miranda et al., arXiv:1010.3731, to appear in Nature Physics. [3] Zuchowski et al., Phys. Rev. A 81, 060703(R) (2010).

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

2011-06-01

17

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

2009-10-07

18

Vacuum-polarization correction in muonic molecules  

NASA Astrophysics Data System (ADS)

The vacuum-polarization correction (given by the expectation value of the Uehling potential) to the energies of the S states of muonic molecules is calculated using very accurate wave functions. The present results indicate that the values accepted so far in the literature for this correction had been underestimated by a factor of 2-8 (depending on the state of interest) due to insufficient quality of the wave functions used. Expectation values of the interparticle distances, the distances squared, and the inverses of the distances are presented.

Petelenz, Piotr; Smith, Vedene H., Jr.

1989-02-01

19

Towards Hybrid Quantum Information Processing with Polar Molecules  

NASA Astrophysics Data System (ADS)

With the ongoing miniaturization of on-chip traps for atoms and ions it is timely to think about coherent interfaces between AMO and solid state systems with potential applications for new hybrid implementations for quantum computers. In this talk I will discuss a potential scenario, where ensembles of polar molecules serve as long-lived quantum memories for superconducting qubits and quantum information is transmitted via a high-Q microwave cavity. Polar molecules combine the exceptional features of a large electric dipole moment and long-lived rotational states with level splittings in the GHz regime. When trapped close to the surface of a chip this combination allows strong interactions with coherent solid state devices, e.g., superconducting microwave cavities or Josephson qubits. I will first introduce the system consisting of a single polar molecule coupled to a stripline cavity which realizes a cavity QED system in the microwave regime and discuss applications for quantum information processing, state detection and new cavity-assisted cooling schemes for polar molecules. I will then switch to molecular ensemble qubits where quantum information is encoded in collective spin or rotational excitations of an ensemble of N molecules. Ensemble qubits benefit from a collectively enhanced coupling ?N which allows quantum state transfer between the molecules and, e.g., a charge qubit on a timescale that is compatible with typical coherence times in a solid state environment. With the goal to protect ensemble qubits from collisions, I will finally discuss a scenario, where molecules are prepared in a crystalline phase under 1D trapping conditions and dipole moments aligned by an external field.

Rabl, Peter

2008-05-01

20

Interlayer Superfluidity in Bilayer Systems of Fermionic Polar Molecules  

SciTech Connect

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

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

2010-11-19

21

Interlayer superfluidity in bilayer systems of fermionic polar molecules.  

PubMed

We consider fermionic polar molecules in a bilayer geometry where they are oriented perpendicularly to the layers, which permits both low inelastic losses and superfluid pairing. The dipole-dipole interaction between molecules of different layers leads to the emergence of interlayer superfluids. The superfluid regimes range from BCS-like fermionic superfluidity with a high Tc to Bose-Einstein (quasi-)condensation of interlayer dimers, thus exhibiting a peculiar BCS-Bose-Einstein condensation crossover. We show that one can cover the entire crossover regime under current experimental conditions. PMID:21231317

Pikovski, A; Klawunn, M; Shlyapnikov, G V; Santos, L

2010-11-19

22

High-Throughput Screening for Small Molecule Inhibitors of LARG-Stimulated RhoA Nucleotide Binding via a Novel Fluorescence Polarization Assay  

PubMed Central

Guanine nucleotide-exchange factors (GEFs) stimulate guanine nucleotide exchange and the subsequent activation of Rho-family proteins in response to extracellular stimuli acting upon cytokine, tyrosine kinase, adhesion, integrin, and G-protein coupled receptors (GPCRs). Upon Rho activation, several downstream events occur, such as morphological and cytokskeletal changes, motility, growth, survival, and gene transcription. The RhoGEF Leukemia-Associated RhoGEF (LARG) is a member of the Regulators of G-protein Signaling Homology Domain (RH) family of GEFs originally identified as a result of chromosomal translocation in acute myeloid leukemia. Using a novel fluorescence polarization guanine nucleotide binding assay utilizing BODIPY-Texas Red-GTP?S (BODIPY-TR-GTP?S), we performed a ten-thousand compound high-throughput screen for inhibitors of LARG-stimulated RhoA nucleotide binding. Five compounds identified from the high-throughput screen were confirmed in a non-fluorescent radioactive guanine nucleotide binding assay measuring LARG-stimulated [35S] GTP?S binding to RhoA, thus ruling out non-specific fluorescent effects. All five compounds selectively inhibited LARG-stimulated RhoA [35S] GTP?S binding, but had little to no effect upon RhoA or G?o [35S] GTP?S binding. Therefore, these five compounds should serve as promising starting points for the development of small molecule inhibitors of LARG-mediated nucleotide exchange as both pharmacological tools and therapeutics. In addition, the fluorescence polarization guanine nucleotide binding assay described here should serve as a useful approach for both high-throughput screening and general biological applications. PMID:19196702

Evelyn, Chris R.; Ferng, Timothy; Rojas, Rafael J.; Larsen, Martha J.; Sondek, John; Neubig, Richard R.

2009-01-01

23

Ultracold polar molecules composed of strongly magnetic atoms  

E-print Network

In a combined experimental and theoretical effort, we demonstrate a novel type of dipolar system made of ultracold bosonic polar molecules with large magnetic dipole moments. Our polar molecules are formed in weakly bound Feshbach molecular states from a sample of strongly magnetic bosonic erbium atoms. We show that the ultracold magnetic molecules can carry very large dipole moments and we demonstrate how to create and characterize them, and how to change their orientation. Finally, we confirm that the relaxation rates of molecules in a quasi-two dimensional geometry can be reduced by using the anisotropy of the dipole-dipole interaction and that this reduction follows a universal dipolar behavior.

Frisch, A; Aikawa, K; Baier, S; Grimm, R; Petrov, A; Kotochigova, S; Qumner, G; Lepers, M; Dulieu, O; Ferlaino, F

2015-01-01

24

Quantum phase gate and controlled entanglement with polar molecules  

SciTech Connect

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

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

2007-03-15

25

Polarization Shaping for Unidirectional Rotational Motion of Molecules  

NASA Astrophysics Data System (ADS)

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

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

2015-03-01

26

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

E-print Network

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

Yi-Ya Tian; Daw-Wei Wang

2008-09-16

27

Electron Capture and Scaling Anomaly in Polar Molecules  

E-print Network

We present a new analysis of the electron capture mechanism in polar molecules, based on von Neumann's theory of self-adjoint extensions. Our analysis suggests that it is theoretically possible for polar molecules to form bound states with electrons, even with dipole moments smaller than the critical value D_0 given by 1.63\\times10^{-18} esu cm. This prediction is consistent with the observed anomalous electron scattering in H_2S and HCl, whose dipole moments are smaller than the critical value D_0. We also show that for a polar molecule with dipole moment less than D_0, typically there is only a single bound state, which is in qualitative agreement with observations. We argue that the quantum mechanical scaling anomaly is responsible for the formation of these bound states.

Pulak Ranjan Giri; Kumar S. Gupta; S. Meljanac; A. Samsarov

2007-03-13

28

Spinorbital dynamics in a system of polar molecules  

NASA Astrophysics Data System (ADS)

Spinorbit 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 spinorbit coupling is thus highly desirable and could open untapped opportunities for the exploration of unique quantum physics. Here we show that dipoledipole interactions can produce an effective spinorbit coupling in two-dimensional ultracold polar molecule gases. This spinorbit 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.

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

2014-11-01

29

Solvation and proton transfer in polar molecule nanoclusters  

Microsoft Academic Search

Proton transfer in a phenol-amine complex dissolved in polar molecule nanoclusters is investigated. The proton transfer rates and mechanisms, as well as the solvation of the complex in the cluster, are studied using both adiabatic and nonadiabatic dynamics. The phenol-amine complex exists in ionic and covalent forms and as the size of the cluster increases the ionic form gains stability

Hyojoon Kim; Raymond Kapral

2006-01-01

30

Anisotropic Polarizability of Ultracold Polar K40Rb87 Molecules  

NASA Astrophysics Data System (ADS)

We report the measurement of the anisotropic ac polarizability of ultracold polar K40Rb87 molecules in the ground and first rotationally excited states. Theoretical analysis of the polarizability agrees well with experimental findings. Although the polarizability can vary by more than 30%, a magic angle between the laser polarization and the quantization axis is found where the polarizability of the |N=0,mN=0? and the |N=1,mN=0? states match. At this angle, rotational decoherence due to the mismatch in trapping potentials is eliminated, and we observe a sharp increase in the coherence time. This paves the way for precise spectroscopic measurements and coherent manipulations of rotational states as a tool in the creation and probing of novel quantum many-body states of polar molecules.

Neyenhuis, B.; Yan, B.; Moses, S. A.; Covey, J. P.; Chotia, A.; Petrov, A.; Kotochigova, S.; Ye, J.; Jin, D. S.

2012-12-01

31

On the nature of interactions of radicals with polar molecules.  

PubMed

Solvated radicals play an important role in many areas of chemistry, but to date, the nature of their interactions with polar solvent molecules lacks chemical interpretation. We present a computational quantum chemical analysis of the binding motives of binary complexes involving electron-poor and electron-rich radicals bound to water and hydrogen fluoride, considered here as model polar solvent molecules. By comparing the binding strengths of several open-shell and closed-shell complexes, in combination with natural localized molecular orbital analysis, we show that open-shell complexes can exhibit additional donor-acceptor interactions relative to analogous closed-shell systems. This may explain the unexpectedly large binding energies observed in some open-shell complexes. These exploratory results show that specific interactions in open-shell systems deserve more attention, and they imply that the quantum mechanical description of explicit solvent molecules needs to be considered carefully when designing simulation protocols for solvated radicals. PMID:24224466

Tentscher, Peter R; Arey, J Samuel

2013-11-27

32

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

33

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

34

Novel Fermi Liquid of 2D Polar Molecules  

E-print Network

We study Fermi liquid properties of a weakly interacting 2D gas of single-component fermionic polar molecules with dipole moments $d$ oriented perpendicularly to the plane of their translational motion. This geometry allows the minimization of inelastic losses due to chemical reactions for reactive molecules and, at the same time, provides a possibility of a clear description of many-body (beyond mean field) effects. The long-range character of the dipole-dipole repulsive interaction between the molecules, which scales as $1/r^3$ at large distances $r$, makes the problem drastically different from the well-known problem of the two-species Fermi gas with repulsive contact interspecies interaction. We solve the low-energy scattering problem and develop a many-body perturbation theory beyond the mean field. The theory relies on the presence of a small parameter $k_Fr_*$, where $k_F$ is the Fermi momentum, and $r_*=md^2/\\hbar^2$ is the dipole-dipole length, with $m$ being the molecule mass. We obtain thermodynamic quantities as a series of expansion up to the second order in $k_Fr_*$ and argue that many-body corrections to the ground-state energy can be identified in experiments with ultracold molecules, like it has been recently done for ultracold fermionic atoms. Moreover, we show that only many-body effects provide the existence of zero sound and calculate the sound velocity.

Zhen-Kai Lu; G. V. Shlyapnikov

2011-11-30

35

Beam broadening of polar molecules and clusters in deflection experiments  

E-print Network

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 ...

Bulthuis, Jaap

2011-01-01

36

Solvation and proton transfer in polar molecule nanoclusters  

NASA Astrophysics Data System (ADS)

Proton transfer in a phenol-amine complex dissolved in polar molecule nanoclusters is investigated. The proton transfer rates and mechanisms, as well as the solvation of the complex in the cluster, are studied using both adiabatic and nonadiabatic dynamics. The phenol-amine complex exists in ionic and covalent forms and as the size of the cluster increases the ionic form gains stability at the expense of the covalent form. Both the adiabatic and nonadiabatic transfer reaction rates increase with cluster size. Given a fixed cluster size, the stability of the covalent state increases with increasing temperature. The proton transfer rates do not change monotonously with an increase in temperature. A strong correlation between the solvent polarization reaction coordinate and the location of the phenol-amine complex in the cluster is found. The ionic form of the complex strongly prefers the interior of the cluster while the covalent form prefers to lie on the cluster surface.

Kim, Hyojoon; Kapral, Raymond

2006-12-01

37

Polar molecules near superconducting resonators: a coherent, all-electrical, molecule-mesoscopic interface  

E-print Network

The challenge of building a scalable quantum processor requires consolidation of the conflicting requirements of achieving coherent control and preservation of quantum coherence in a large scale quantum system. Moreover, the system should be compatible with miniaturization and integration of quantum circuits. Mesoscopic solid state systems such as superconducting islands and quantum dots feature robust control techniques using local electrical signals and self-evident scaling based on advances in fabrication; however, in general the quantum states of solid state devices tend to decohere rapidly. In contrast, quantum optical systems based on trapped ions and neutral atoms exhibit dramatically better coherence properties, while miniaturization of atomic and molecular systems, and their integration with mesoscopic electrical circuits, remains an important challenge. Below we describe methods for the integration of a single particle system -- an isolated polar molecule -- with mesoscopic solid state devices in a way that produces robust, coherent, quantum-level control. The methods described include the trapping, cooling, detection, coherent manipulation and quantum coupling of isolated polar molecules at sub-micron dimensions near cryogenic stripline microwave resonators. We show that electrostatically trapped polar molecules can exhibit strong confinement and fast, purely electrical gate control. Furthermore, the effect of electrical noise sources, a key issue in quantum information processing, can be suppressed to very low levels via appropriate preparation and manipulation of the polar molecules. Our setup provides a scalable cavity QED-type quantum computer architecture, where entanglement of distant qubits stored in long-lived rotational molecular states is achieved via exchange of microwave photons.

A. Andre; D. DeMille; J. M. Doyle; M. D. Lukin; S. E. Maxwell; P. Rabl; R. Schoelkopf; P. Zoller

2006-05-23

38

Stable Topological Superfluid Phase of Ultracold Polar Fermionic Molecules  

SciTech Connect

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

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

2009-10-09

39

Stable topological superfluid phase of ultracold polar fermionic molecules.  

PubMed

We show that single-component fermionic polar molecules confined to a 2D geometry and dressed by a microwave field may acquire an attractive 1/r(3) dipole-dipole interaction leading to superfluid p-wave pairing at sufficiently low temperatures even in the BCS regime. The emerging state is the topological p(x) + ip(y) phase promising for topologically protected quantum information processing. The main decay channel is via collisional transitions to dressed states with lower energies and is rather slow, setting a lifetime of the order of seconds at 2D densities approximately 10(8) cm(-2). PMID:19905648

Cooper, N R; Shlyapnikov, G V

2009-10-01

40

A traveling wave decelerator for neutral polar molecules  

NASA Astrophysics Data System (ADS)

Recently, a decelerator for neutral polar molecules has been presented that operates on the basis of macroscopic, three-dimensional, traveling electrostatic traps [A. Osterwalder, S. A. Meek, G. Hammer, H. Haak, and G. Meijer, Phys. Rev. A 81, 051401 (2010)], 10.1103/PhysRevA.81.051401. In the present paper, a complete description of this decelerator is given, with emphasis on the electronics and the mechanical design. Experimental results showing the transverse velocity distributions of guided molecules are shown and compared to trajectory simulations. An assessment of non-adiabatic losses is made by comparing the deceleration signals from 13CO with those from 12CO and with simulated signals.

Meek, Samuel A.; Parsons, Maxwell F.; Heyne, Georg; Platschkowski, Viktor; Haak, Henrik; Meijer, Gerard; Osterwalder, Andreas

2011-09-01

41

Theory of cavity-assisted microwave cooling of polar molecules  

NASA Astrophysics Data System (ADS)

We analyze cavity-assisted cooling schemes for polar molecules in the microwave domain, where molecules are excited on a rotational transition and energy is dissipated via strong interactions with a lossy stripline cavity, as recently proposed by Andr et al 2006 Nat. Phys. 2 636. We identify the dominant cooling and heating mechanisms in this setup and study cooling rates and final temperatures in various parameter regimes. In particular, we analyze the effects of a finite environment temperature on the cooling efficiency, and find minimal temperature and optimized cooling rate in the strong drive regime. Further, we discuss the trade-off between efficiency of cavity cooling and robustness with respect to ubiquitous imperfections in a realistic experimental setup, such as anharmonicity of the trapping potential.

Wallquist, Margareta; Rabl, Peter; Lukin, Mikhail D.; Zoller, Peter

2008-06-01

42

Dynamic nuclear polarization at high magnetic fields  

PubMed Central

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

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

2009-01-01

43

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

44

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

45

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

NASA Astrophysics Data System (ADS)

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.

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

2015-02-01

46

Single molecule polarization microscopy for investigating real time structural dynamics of biological macromolecules  

Microsoft Academic Search

To quantitatively monitor structural dynamics of individual biomolecules in real time, a single-molecule polarization microscopy technique has been developed. This novel approach combines the single molecule sensitivity of total internal reflection fluorescence microscopy with orientation measurements by time-resolved fluorescence polarization. With this technique, functionally relevant conformational changes of individual biomolecules can be continuously detected at 10 ms time resolution or

Joseph N. Forkey; Margot E. Quinlan; J. E. T. Corrie; Y. E. Goldman

1999-01-01

47

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

48

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

PubMed

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

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

2013-01-14

49

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

SciTech Connect

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

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

2011-07-15

50

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

51

Stacking of conical molecules with a fullerene apex into polar columns in crystals and liquid crystals  

NASA Astrophysics Data System (ADS)

Polar liquid crystalline materials can be used in optical and electronic applications, and recent interest has turned to formation strategies that exploit the shape of polar molecules and their interactions to direct molecular alignment. For example, banana-shaped molecules align their molecular bent within smectic layers, whereas conical molecules should form polar columnar assemblies. However, the flatness of the conical molecules used until now and their ability to flip have limited the success of this approach to making polar liquid crystalline materials. Here we show that the attachment of five aromatic groups to one pentagon of a C60 fullerene molecule yields deeply conical molecules that stack into polar columnar assemblies. The stacking is driven by attractive interactions between the spherical fullerene moiety and the hollow cone formed by the five aromatic side groups of a neighbouring molecule in the same column. This packing pattern is maintained when we extend the aromatic groups by attaching flexible aliphatic chains, which yields compounds with thermotropic and lyotropic liquid crystalline properties. In contrast, the previously reported fullerene-containing liquid crystals all exhibit thermotropic properties only, and none of them contains the fullerene moiety as a functional part of its mesogen units. Our design strategy should be applicable to other molecules and yield a range of new polar liquid crystalline materials.

Sawamura, Masaya; Kawai, Kenji; Matsuo, Yutaka; Kanie, Kiyoshi; Kato, Takashi; Nakamura, Eiichi

2002-10-01

52

Novel cathode interlayers based on neutral alcohol-soluble small molecules with a triphenylamine core featuring polar phosphonate side chains for high-performance polymer light-emitting and photovoltaic devices.  

PubMed

A new family of neutral alcohol-soluble small molecular materials comprised of electron-rich triphenylamine (TPA) and fluorene featuring phosphonate side chains (FEP) is reported, namely 3TPA-FEP, 2TPA-2FEP and TPA-3FEP, which have different TPA and FEP contents. Due to their good solubility in polar solvents like alcohol, multilayer devices can be fabricated by a wet process from orthogonal solvents. Polymer light-emitting devices with these materials as a cathode interlayer and Al as the cathode show greatly enhanced efficiencies in contrast to control devices without such a cathode interlayer, and their efficiencies are comparable with or even higher than devices with the low work-function metal Ba/Al as the cathode. In addition, high-performance polymer solar cells based on the poly[N-9''-hepta-decanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)] (PCDTBT):[6,6]-phenyl C71 -butyric acid methyl ester (PC71 BM) system are also achieved with power conversion efficiencies of 7.21%, 6.90% and 6.89%, by utilizing 3TPA-FEP, 2TPA-2FEP and TPA-3FEP as the cathode interlayer, respectively. These efficiencies are also much higher than those for control devices without the cathode interlayer. Although TPA is well-known as a hole-transport unit, the current findings indicate that alcohol-soluble TPA-based small molecules are also a promising cathode interlayer for both electron injection and extraction. PMID:23386362

Chen, Dongcheng; Zhou, Hu; Liu, Ming; Zhao, Wei-Ming; Su, Shi-Jian; Cao, Yong

2013-04-12

53

Single photon detector with high polarization sensitivity.  

PubMed

Polarization is one of the key parameters of light. Most optical detectors are intensity detectors that are insensitive to the polarization of light. A superconducting nanowire single photon detector (SNSPD) is naturally sensitive to polarization due to its nanowire structure. Previous studies focused on producing a polarization-insensitive SNSPD. In this study, by adjusting the width and pitch of the nanowire, we systematically investigate the preparation of an SNSPD with high polarization sensitivity. Subsequently, an SNSPD with a system detection efficiency of 12% and a polarization extinction ratio of 22 was successfully prepared. PMID:25875225

Guo, Qi; Li, Hao; You, LiXing; Zhang, WeiJun; Zhang, Lu; Wang, Zhen; Xie, XiaoMing; Qi, Ming

2015-01-01

54

Single photon detector with high polarization sensitivity  

PubMed Central

Polarization is one of the key parameters of light. Most optical detectors are intensity detectors that are insensitive to the polarization of light. A superconducting nanowire single photon detector (SNSPD) is naturally sensitive to polarization due to its nanowire structure. Previous studies focused on producing a polarization-insensitive SNSPD. In this study, by adjusting the width and pitch of the nanowire, we systematically investigate the preparation of an SNSPD with high polarization sensitivity. Subsequently, an SNSPD with a system detection efficiency of 12% and a polarization extinction ratio of 22 was successfully prepared. PMID:25875225

Guo, Qi; Li, Hao; You, LiXing; Zhang, WeiJun; Zhang, Lu; Wang, Zhen; Xie, XiaoMing; Qi, Ming

2015-01-01

55

Small-molecule axon-polarization studies enabled by a shear-free microfluidic gradient generator.  

PubMed

A deep understanding of the mechanisms behind neurite polarization and axon path-finding is important for interpreting how the human body guides neurite growth during development and response to injury. Further, it is of great clinical importance to identify diffusible chemical cues that promote neurite regeneration for nervous tissue repair. Despite the fast development of various types of concentration gradient generators, it has been challenging to fabricate neuron-friendly (i.e. shear-free and biocompatible for neuron growth and maturation) devices to create stable gradients, particularly for fast diffusing small molecules, which typically require high flow and shear rates. Here we present a finite element analysis for a polydimethylsiloxane/polyethylene glycol diacrylate (PDMS/PEG-DA) based gradient generator, describe the microfabrication process, and validate its use for neuronal axon polarization studies. This device provides a totally shear-free, biocompatible microenvironment with a linear and stable concentration gradient of small molecules such as forskolin. The gradient profile in this device can be customized by changing the composition or width of the PEG-DA barriers during direct UV photo-patterning within a permanently bonded PDMS device. Primary rat cortical neurons (embryonic E18) exposed to soluble forskolin gradients for 72 h exhibited statistically significant polarization and guidance of their axons. This device provides a useful platform for both chemotaxis and directional guidance studies, particularly for shear sensitive and non-adhesive cell cultures, while allowing fast new device design prototyping at a low cost. PMID:24781157

Xu, Hui; Ferreira, Meghaan M; Heilshorn, Sarah C

2014-06-21

56

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; Strher, Hans; Weiss, Philipp [Institut fr Kernphysik, Forschungszentrum Jlich, Wilhelm-Johnen-Str. 1, 52428 Jlich (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 fr Kernphysik, Universitt zu Kln, Zlpicher Str. 77, 50937 Kln (Germany)

2014-10-15

57

Control of tunnel ionization in molecules by intense femtosecond laser pulses with time-dependent polarization  

NASA Astrophysics Data System (ADS)

We propose a new way of Controlling tunnel ionization in molecules by time-dependent polarization pulses. The model consists of the successful combination of the molecular ADK theory reflecting the symmetry of molecular orbitals and Landau-Zener resonances.

Kanai, Tsuneto; Minemoto, Shinichirou; Sakai, Hirofumi

58

ACCELERATING POLARIZED PROTONS TO HIGH ENERGY.  

SciTech Connect

The Relativistic Heavy Ion Collider (RHIC) is designed to provide collisions of high energy polarized protons for the quest of understanding the proton spin structure. Polarized proton collisions at a beam energy of 100 GeV have been achieved in RHIC since 2001. Recently, polarized proton beam was accelerated to 250 GeV in RHIC for the first time. Unlike accelerating unpolarized protons, the challenge for achieving high energy polarized protons is to fight the various mechanisms in an accelerator that can lead to partial or total polarization loss due to the interaction of the spin vector with the magnetic fields. We report on the progress of the RHIC polarized proton program. We also present the strategies of how to preserve the polarization through the entire acceleration chain, i.e. a 200 MeV linear accelerator, the Booster, the AGS and RHIC.

BAI, M.; AHRENS, L.; ALEKSEEV, I.G.; ALESSI, J.; BEEBE-WANG, J.; BLASKIEWICZ, M.; BRAVAR, A.; BRENNAN, J.M.; BRUNO, D.; BUNCE, G.; ET AL.

2006-10-02

59

Fast atom bombardment mass spectrometry: a powerful technique for the study of polar molecules  

Microsoft Academic Search

A study of a range of polar organic molecules by fast atom bombardment (FAB) mass spectrometry is reported. Compounds studied include organic salts, polar antibiotics, nucleoside phosphates, and underivatized peptides. In these classes of compounds, molecular weights in the range 300 to 2000 daltons have been routinely determined, operating in both positive and negative ion modes. Molecular weights of peptides

Dudley H. Williams; Carol Bradley; Gustav Bojesen; Sitthivet Santikarn; Lester C. E. Taylor

1981-01-01

60

Dynamic nuclear polarization of amorphous and crystalline small molecules  

E-print Network

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

Ong, Ta-Chung

2014-01-01

61

Prospects for measuring the electric dipole moment of the electron using electrically trapped polar molecules  

Microsoft Academic Search

Heavy polar molecules can be used to measure the electric dipole moment of the electron, which is a sensitive probe of physics beyond the Standard Model. The value is determined by measuring the precession of the molecule's spin in a plane perpendicular to an applied electric field. The longer this precession evolves coherently, the higher the precision of the measurement.

M. R. Tarbutt; J. J. Hudson; B. E. Sauer; E. A. Hinds

2009-01-01

62

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

Microsoft Academic Search

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

M. F. Gelin; D. S. Kosov

2006-01-01

63

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; Schn, Gerd

2014-12-01

64

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

2009-12-14

65

Nano-doped weakly polar versus highly polar liquid crystal  

NASA Astrophysics Data System (ADS)

Nanoparticles doped liquid crystal show changed dielectric properties in comparison to pure liquid crystals. These changes are strongly dependent on the inherent properties of guest and host particles. In the present work we have done comparative dielectric study of highly polar nematic liquid crystals 5CB and weakly polar liquid crystal D6AOB and its 1 % wt/wt concentration with zinc oxide nanoparticles (1 % Cu) doped. The relaxation modes in pure and nano doped samples are explained properly. We have also analyzed the dielectric anisotropy and relaxation frequency for all the samples.

Pandey, Kamal Kumar; Misra, Abhishek Kumar; Manohar, Rajiv

2015-03-01

66

Ultralong-range polyatomic Rydberg molecules formed by a polar perturber  

E-print Network

The internal electric field of a Rydberg atom electron can bind a polar molecule to form a giant ultralong-range stable polyatomic molecule. Such molecules not only share their properties with Rydberg atoms, they possess huge permanent electric dipole moments and in addition allow for coherent control of the polar molecule orientation. In this work, we include additional Rydberg manifolds which couple to the nearly degenerate set of Rydberg states employed in [S. T. Rittenhouse and H. R. Sadeghpour, Phys. Rev. Lett. 104, 243002 (2010)]. The coupling of a set of $(n+3)s$ Rydberg states with the $n(l>2)$ nearly degenerate Rydberg manifolds in alkali metal atoms leads to pronounced avoided crossings in the Born-Oppenheimer potentials. Ultimately, these avoided crossings enable the formation of the giant polyatomic Rydberg molecules with standard two-photon laser photoassociation techniques.

Rittenhouse, Seth T; Schmelcher, P; Sadeghpour, H R

2011-01-01

67

Ultralong-range polyatomic Rydberg molecules formed by a polar perturber  

NASA Astrophysics Data System (ADS)

The internal electric field of a Rydberg atom electron can bind a polar molecule to form a giant ultralong-range stable polyatomic molecule. Such molecules not only share their properties with Rydberg atoms (such as long lifetimes and large sizes) but they also possess huge permanent electric dipole moments and in addition allow for coherent control of the polar molecule orientation. In this work, we include additional Rydberg manifolds which couple to the nearly degenerate set of Rydberg states employed in the previous work (S T Rittenhouse and H R Sadeghpour 2010 Phys. Rev. Lett. 104 243002). The coupling of a set of (n + 3)s Rydberg states with the n(l > 2) nearly degenerate Rydberg manifolds in alkali metal atoms leads to pronounced avoided crossings in the Born-Oppenheimer potentials. Ultimately, these avoided crossings enable the formation of the giant polyatomic Rydberg molecules with standard two-photon laser photoassociation techniques.

Rittenhouse, Seth T.; Mayle, M.; Schmelcher, P.; Sadeghpour, H. R.

2011-09-01

68

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

69

Clustering of cold polar molecules in arrays of one-dimensional tubes  

NASA Astrophysics Data System (ADS)

Cold polar molecules allow to study exciting new phenomena which arise from the long-range and anisotropic nature of their mutual interactions. Here, we demonstrate that a Wigner crystal of polar molecules confined in planar arrays of one-dimensional tubes can be made unstable with respect to the formation of clusters of particles. By controlling the orientation of the external electric field which aligns the dipolar moments, increasingly complex structures with a varying number of particles per cluster and thus varying periodicity are formed. The spatial agglomeration of multiple polar molecules results from the interaction and can be described classically. However, we show that the effect survives when quantum fluctuations are present. For systems of a finite number of tubes, the result is a sequence of ''clustered`` Luttinger liquid states. Finally, we determine the ratio between the interaction and the kinetic energy which is necessary for the spatial agglomeration of polar molecules. We find that the requirements for clustering are reachable in current experiments with cold polar molecules.

Knap, Michael; Berg, Erez; Demler, Eugene

2012-02-01

70

The role of dipole interactions of molecules with charged particles in the polar stratosphere  

NASA Astrophysics Data System (ADS)

On the basis of the analysis of the reported balloon, airborne and ground based lidar experiments in the polar regions a new pathway explaining the photochemical processes in the polar stratosphere is considered. A close relationship of these processes with the electric phenomena in the stratosphere such as an accumulation of charged particles on the upper and lower boundaries of the polar stratospheric clouds as a result of the global electric circuit operation is shown. The dipole interaction of molecules with charged particles, mainly with ionic clusters, results in a sticking and decay of some molecules. The additional energy for molecules that becomes available on the surface of charged particles allows such reactions, which are not otherwise possible in space.

Belikov, Yury; Nikolayshvili, Sergey

71

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

72

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

PubMed

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

Horikawa, Toshihide; Zeng, Yonghong; Do, D D; Sotowa, Ken-Ichiro; Alcntara Avila, Jess Rafael

2015-02-01

73

Supersolid Phase with Cold Polar Molecules on a Triangular Lattice  

SciTech Connect

We study a system of heteronuclear molecules on a triangular lattice and analyze the potential of this system for the experimental realization of a supersolid phase. The ground state phase diagram contains superfluid, solid, and supersolid phases. At finite temperatures and strong interactions there is an additional emulsion region, in contrast with similar models with short-range interactions. We derive the maximal critical temperature T{sub c} and the corresponding entropy S/N=0.04(1) for supersolidity and find feasible experimental conditions for its realization.

Pollet, L. [Physics Department, Harvard University, Cambridge, Massachusetts 02138 (United States); Department of Physics, University of Massachusetts, Amherst, Massachusetts 01003 (United States); Theoretische Physik, ETH Zurich, 8093 Zurich (Switzerland); Picon, J. D. [Theoretische Physik, ETH Zurich, 8093 Zurich (Switzerland); Institute of Theoretical Physics, Ecole polytechnique federale de Lausanne, CH-1015 Lausanne (Switzerland); Buechler, H. P. [Institute of Theoretical Physics III, Universitaet Stuttgart, 70550 Stuttgart (Germany); Troyer, M. [Theoretische Physik, ETH Zurich, 8093 Zurich (Switzerland)

2010-03-26

74

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 présence 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

75

Suppression of inelastic collisions between polar molecules with a repulsive shield.  

PubMed

We propose and analyze a technique that allows one to suppress inelastic collisions and simultaneously enhance elastic interactions between cold polar molecules. The main idea is to cancel the leading dipole-dipole interaction with a suitable combination of static electric and microwave fields in such a way that the remaining van der Waals-type potential forms a three-dimensional repulsive shield. We analyze the elastic and inelastic scattering cross sections relevant for evaporative cooling of polar molecules and discuss the prospect for the creation of stable crystalline structures. PMID:18764530

Gorshkov, A V; Rabl, P; Pupillo, G; Micheli, A; Zoller, P; Lukin, M D; Bchler, H P

2008-08-15

76

Suppression of Inelastic Collisions Between Polar Molecules With a Repulsive Shield  

NASA Astrophysics Data System (ADS)

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

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

2008-08-01

77

Steering population transfer of a five-level polar NaK molecule by Stark shifts  

NASA Astrophysics Data System (ADS)

Steering the population transfer of a five-level polar diatomic NaK molecule with two ultrashort transform-limited laser pulses is theoretically investigated using the time-dependent wave packet method. The dynamic Stark shifts resulted from the interaction of polar molecule with laser pulses can be utilized to modulate the transition frequency and transfer efficiently population. The influence of neighboring electronic states on the population transfer is taken into account. By choosing suitable laser pulse parameters, a complete population transfer can be realized. The concept of light-induced potential (LIP) is used to describe the population transfer dynamic process.

Shu, Chuan-Cun; Yuan, Kai-Jun; Han, Yong-Chang; Hu, Wen-Hui; Cong, Shu-Lin

2008-02-01

78

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

SciTech Connect

We present combined experimental and theoretical results on strong-field ionization of oriented carbonyl sulfide molecules by circularly polarized laser pulses. The obtained molecular frame photoelectron angular distributions show pronounced asymmetries perpendicular to the direction of the molecular electric dipole moment. These findings are explained by a tunneling model invoking the laser-induced Stark shifts associated with the dipoles and polarizabilities of the molecule and its unrelaxed cation. The focus of the present article is to understand the strong-field ionization of one-dimensionally-oriented polar molecules, in particular asymmetries in the emission direction of the photoelectrons. In the following article [Phys. Rev. A 83, 023406 (2011)] the focus is to understand strong-field ionization from three-dimensionally-oriented asymmetric top molecules, in particular the suppression of electron emission in nodal planes of molecular orbitals.

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

2011-02-15

79

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

E-print Network

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

Svetlana Kotochigova; David DeMille

2011-01-03

80

Prospects for measuring the electric dipole moment of the electron using electrically trapped polar molecules  

Microsoft Academic Search

Heavy polar molecules can be used to measure the electric dipole moment of\\u000athe electron, which is a sensitive probe of physics beyond the Standard Model.\\u000aThe value is determined by measuring the precession of the molecule's spin in a\\u000aplane perpendicular to an applied electric field. The longer this precession\\u000aevolves coherently, the higher the precision of the measurement.

M. R. Tarbutt; J. J. Hudson; B. E. Sauer; E. A. Hinds

2009-01-01

81

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

Microsoft Academic Search

T cell antigen recognition is accompanied by cytoskeletal polarization towards the APC and large-scale redistribution of cell surface molecules into `supramolecular activation clusters' (SMACs), forming an organized contact interface termed the `immunological synapse' (IS). Molecules are arranged in the IS in a micrometer scale bull's eye pattern with a central accumulation of TCR\\/peptideMHC (the cSMAC) surrounded by a peripheral ring

P. Anton van der Merwe; Simon J. Davis; Andrey S. Shaw; Michael L. Dustin

2000-01-01

82

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

83

Destruction of p-wave weakly bound molecules in a gas of spin-polarized fermions  

NASA Astrophysics Data System (ADS)

We have studied collisional aspects which might affect the lifetime of p-wave molecules created in ultracold spin-polarized fermi gases near a Feshbach resonance [1]. Atom-molecule inelastic collisions might be the main process in which the collision products can be released from typical traps. Our study allows us describe the dependence of the collision rates on the p-wave scattering length, which is crucial for understanding the stability of such molecules in the strongly interacting regime. [1] H. Suno, B. D. Esry, and C. H. Greene, Phys. Rev. Lett. 90, 053202 (2003). This work was supported in part by the National Science Foundation.

D'Incao, Jose P.; Greene, Chris H.

2007-03-01

84

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

85

Evidence of the improvement of photovoltaic efficiency by polar molecule orientation in a new semiconducting polymer  

Microsoft Academic Search

Storage of an internal field in a polymeric semiconductor device should be of great interest for applications like photovoltaic solar cells to facilitate exciton dissociation and improve charge transport in the structure. Orientation of polar molecules, contained inside a polymer binder, induces a rectifying effect, behaving as a distributed homojunction within a single polymeric film. To investigate this concept, a

Carole Sentein; Licinio Rocha; Aleksandra Apostoluk; Paul Raimond; Iris Duyssens; Ineke Van Severen; Thomas Cleij; Laurence Lutsen; Dirk Vanderzande; Vaidotas Kaukauskas; Mindaugas Pranaitis; Valius ?yras

2007-01-01

86

Electrostatic surface guiding of cold polar molecules with a single charged wire  

Microsoft Academic Search

This paper proposes a scheme to guide cold polar molecules by using a single charged wire half embanked in an insulating substrate and a homogeneous bias electric field, which is generated by a plate capacitor composed of two infinite parallel metal plates. The spatial distributions of the electrostatic field produced by the combination of the charged wire and the plate

Lian-Zhong Deng; Yong Xia; Jian-Ping Yin

2007-01-01

87

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

E-print Network

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 non-orthogonal 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 second can be extracted from C(t).

Gelin, M F

2006-01-01

88

Effects of molecular asymmetry of optically active molecules on the polarization properties of multiply scattered light  

NASA Astrophysics Data System (ADS)

The use of polarized light for investigation of optically turbid systems has generated much recent interest since it has been shown that multiple scattering does not fully scramble the incident polarization states. It is possible under some conditions to measure polarization signals in diffusely scattered light, and use this information to characterize the structure or composition of the turbid medium. Furthermore, the idea of quantitative detection of optically active (chiral) molecules contained in such a system is attractive, particularly in clinical medicine where it may contribute to the development of a non-invasive method of glucose sensing in diabetic patients. This study uses polarization modulation and synchronous detection in the perpendicular and in the exact backscattering orientations to detect scattered light from liquid turbid samples containing varying amounts of L and D (left and right) isomeric forms of a chiral sugar. Polarization preservation increased with chiral concentrations in both orientations. In the perpendicular orientation, the optical rotation of the linearly polarized fraction also increased with the concentration of chiral solute, but in different directions for the two isomeric forms. There was no observed optical rotation in the exact backscattering geometry for either isomer. The presence of the chiral species is thus manifest in both detection directions, but the sense of the chiral asymmetry is not resolvable in retroreflection. The experiments show that useful information may be extracted from turbid chiral samples using polarized light.

Vitkin, I. Alex; Laszlo, Richard D.; Whyman, Claire L.

2002-02-01

89

Critical binding and electron scattering by symmetric-top polar molecules  

SciTech Connect

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., E-mail: wrg@utk.edu [Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996 (United States)

2014-10-28

90

Symmetries and physical properties of polar columnar phases in materials composed of achiral molecules  

NASA Astrophysics Data System (ADS)

Motivated by puzzling experimental observations made in compounds composed of banana-shaped molecules, we investigate the symmetries and the physical properties of liquid crystalline columnar phases with a macroscopic polarization in achiral materials. This study is driven by two key observations made for the still poorly understood B7 phase: a) freely suspended films decompose spontaneously into strands and b) several of the textures observed for the B7 phase are reminiscent of textures observed for liquid crystalline columnar phases. One of the main results of our analysis is that a chiral phase of C1-symmetry results as soon as the macroscopic polarization includes an angle different from zero or 90 with the columnar axes. We argue that a chiral columnar phase composed of achiral molecules, not previously considered for classic columnar phases, is sufficient to account for many of the unusual physical properties of B7.

Brand, H. R.; Cladis, P. E.; Pleiner, H.

2002-02-01

91

Theory of Polarized and Depolarized Light Scattering from Liquids of Anisotropic Molecules  

NASA Astrophysics Data System (ADS)

The theory of light scattering from liquids of anisotropic molecules near the liquid-glass transition has been reexamined by Dreyfus et al*. Their phenomenological approach including translation-rotation coupling and memory functions for all transport coefficients predicts modifications for both polarized and depolarized spectra. The theory will be reiviewed together with strategies for determining the memory functions and analyzing experimental data. *C. Dreyfus, T. Franosch, A. Latz, and R.M. Pick (in preparation)

Zhang, H.; Brodin, A.; Barshilia, H. C.; Cummins, H. Z.

2002-03-01

92

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

93

Prospects for measuring the electric dipole moment of the electron using electrically trapped polar molecules.  

PubMed

Heavy polar molecules can be used to measure the electric dipole moment of the electron, which is a sensitive probe of physics beyond the Standard Model. The value is determined by measuring the precession of the molecule's spin in a plane perpendicular to an applied electric field. The longer this precession evolves coherently, the higher the precision of the measurement. For molecules in a trap, this coherence time could be very long indeed. We evaluate the sensitivity of an experiment where neutral molecules are trapped electrically, and compare this to an equivalent measurement in a molecular beam. We consider the use of a Stark decelerator to load the trap from a supersonic source, and calculate the deceleration efficiency for YbF molecules in both strong-field seeking and weak-field seeking states. With a 1 s holding time in the trap, the statistical sensitivity could be ten times higher than it is in the beam experiment, and this could improve by a further factor of five if the trap can be loaded from a source of larger emittance. We study some effects due to field inhomogeneity in the trap and find that rotation of the electric field direction, leading to an inhomogeneous geometric phase shift, is the primary obstacle to a sensitive trap-based measurement. PMID:20151537

Tarbutt, M R; Hudson, J J; Sauer, B E; Hinds, E A

2009-01-01

94

Infrared-dressed entanglement of cold open-shell polar molecules for universal matchgate quantum computing  

NASA Astrophysics Data System (ADS)

Implementing a scalable quantum information processor using polar molecules in optical lattices requires precise control over the long-range dipole-dipole interaction between molecules in selected lattice sites. We present here a scheme using trapped open-shell ^{2}\\Sigma polar molecules that allows dipolar exchange processes between nearest and next-nearest neighbors to be controlled in order to construct a generalized transverse Ising spin Hamiltonian with tunable XX, YY and XY couplings in the rotating frame of the driving lasers. The scheme requires a moderately strong bias magnetic field together with near-infrared light to provide local tuning of the qubit energy gap, and mid-infrared pulses to perform rotational state transfer via stimulated Raman adiabatic passage. No interaction between qubits occurs in the absence of the infrared driving. We analyze the fidelity of the resulting two-qubit matchgate, and demonstrate its robustness as a function of the driving parameters. We discuss a realistic application of the system for universal matchgate quantum computing in optical lattices.

Herrera, Felipe; Cao, Yudong; Kais, Sabre; Whaley, K. Birgitta

2014-07-01

95

Multielectron signatures in the polarization of high-order harmonic radiation  

SciTech Connect

The polarization of high-order harmonic radiation emitted from N{sub 2} molecules interacting with a linearly polarized laser pulse is investigated theoretically. We find that the exchange effect between the recombining electron and the bound core electrons imprints a clear signature onto the high-order harmonic polarization and its dependence on the alignment angle between the molecular axis and driving laser electric field. Our analysis reveals an observable for the experimental investigation of many-electron dynamics in intense laser fields.

Zhao Zengxiu; Yuan Jianmin [Department of Physics, National University of Defense Technology, Changsha 410073 (China); Brabec, Thomas [Physics Department and Center for Research in Photonics, University of Ottawa, 150 Louis Pasteur, Ottawa, Ontario, K1N 6N5 (Canada)

2007-09-15

96

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

NASA Astrophysics Data System (ADS)

Toward the design of large-scale electronic circuits that are entirely spintronics-driven, organic semiconductors have been identified as a promising medium to transport information using the electron spin. This requires a ferromagnetic metal-organic interface that is highly spin-polarized at and beyond room temperature, but this key building block is still lacking. We show how the interface between Co and phthalocyanine molecules constitutes a promising candidate. In fact, spin-polarized direct and inverse photoemission experiments reveal a high degree of spin polarization at room temperature at this interface.

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

2014-08-01

97

INFRARED SPECTROSCOPY OF CONJUGATED ORGANIC MOLECULES UNDER HIGH PRESSURE  

E-print Network

INFRARED SPECTROSCOPY OF CONJUGATED ORGANIC MOLECULES UNDER HIGH PRESSURE By KIRILL KHAMIDOVICH. iii #12;INFRARED SPECTROSCOPY OF CONJUGATED ORGANIC MOLECULES UNDER HIGH PRESSURE Abstract By Kirill the p-terphenyl structure in the twisted conformation. They also demonstrated that high-pressure IR

Collins, Gary S.

98

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

99

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

100

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

101

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

NASA Astrophysics Data System (ADS)

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

Iwamoto, Mitsumasa; Zhong-can, Ou-Yang

2012-11-01

102

Storage and adiabatic cooling of polar molecules in a microstructured trap.  

PubMed

We present a versatile electric trap for the exploration of a wide range of quantum phenomena in the interaction between polar molecules. The trap combines tunable fields, homogeneous over most of the trap volume, with steep gradient fields at the trap boundary. An initial sample of up to 10(8), CH(3)F molecules is trapped for as long as 60 s, with a 1/e storage time of 12 s. Adiabatic cooling down to 120 mK is achieved by slowly expanding the trap volume. The trap combines all ingredients for opto-electrical cooling, which, together with the extraordinarily long storage times, brings field-controlled quantum-mechanical collision and reaction experiments within reach. PMID:22243155

Englert, B G U; Mielenz, M; Sommer, C; Bayerl, J; Motsch, M; Pinkse, P W H; Rempe, G; Zeppenfeld, M

2011-12-23

103

Nonsequential double ionization of stretched molecules by circularly polarizedlaser pulses  

NASA Astrophysics Data System (ADS)

Using the classical ensemble method, we have investigated double ionization (DI) of stretched molecules by circularly polarized laser pulses. Back analysis of the DI trajectories shows that most DI occurs through a process of collision, indicating the nonsequential feature of DI. In contrast to the common recollision picture for nonsequential double ionization, here the first electron ionizes over the inner potential barrier of the molecule, moves directly towards the other nucleus and leads to excitation or ionization of the second electron by collision. The correlated momentum distributions for the electron pairs from this collision-induced nonsequential process show an obvious correlation pattern in the direction parallel to the molecular axis, whereas they show an anticorrelation pattern in the direction perpendicular to the molecular axis.

Tong, Aihong; Zhou, Yueming; Huang, Cheng; Lu, Peixiang

2014-01-01

104

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

NASA Astrophysics Data System (ADS)

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

Zhou, Y. L.; Ortner, M.; Rabl, P.

2011-11-01

105

Two-center minima in harmonic spectra from aligned polar molecules  

SciTech Connect

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

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

2011-08-15

106

Identification of immobile single molecules using polarization-modulated asynchronous TDI-mode scanning  

PubMed Central

We report the development of a data acquisition method for identifying single molecules on large surfaces with simultaneous characterization of their absorption dipole. The method is based on a previously described device for microarray readout at single molecule sensitivity1. Here, we introduced asynchronous time delay and integration- (TDI-) mode imaging to record also the time course of fluorescence signals: the images thus contain both spatial and temporal information. We demonstrate the principle by modulating the signals via rotating excitation polarization, which allows for discriminating static absorption dipoles against multiple or freely rotating single absorption dipoles. Experiments on BSA carrying different numbers of fluorophores demonstrate the feasibility of the method. Protein species with average labeling degree of 0.55 and 2.89 fluorophores per protein can be readily distinguished. PMID:20380382

Jacak, Jaroslaw; Hesch, Clemens; Hesse, Jan; Schtz, Gerhard J.

2015-01-01

107

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

SciTech Connect

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

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

2010-10-15

108

High Performance Circularly Polarized Microstrip Antenna  

NASA Technical Reports Server (NTRS)

A microstrip antenna for radiating circularly polarized electromagnetic waves comprising a cluster array of at least four microstrip radiator elements, each of which is provided with dual orthogonal coplanar feeds in phase quadrature relation achieved by connection to an asymmetric T-junction power divider impedance notched at resonance. The dual fed circularly polarized reference element is positioned with its axis at a 45 deg angle with respect to the unit cell axis. The other three dual fed elements in the unit cell are positioned and fed with a coplanar feed structure with sequential rotation and phasing to enhance the axial ratio and impedance matching performance over a wide bandwidth. The centers of the radiator elements are disposed at the corners of a square with each side of a length d in the range of 0.7 to 0.9 times the free space wavelength of the antenna radiation and the radiator elements reside in a square unit cell area of sides equal to 2d and thereby permit the array to be used as a phased array antenna for electronic scanning and is realizable in a high temperature superconducting thin film material for high efficiency.

Bondyopadhyay, Probir K. (Inventor)

1997-01-01

109

Theoretical Compton profile anisotropies in molecules and solids. VII. Zero point Compton profile anisotropies and bond polarities in alkali halide diatomic molecules  

Microsoft Academic Search

A correlation between bond polarities and zero point Compton profile anisotropies is shown for alkali halide molecules. The correlation derives from the fact that both quantities are determined by molecular binding and antibinding forces and are thus functionally related to nuclear charge ratios.

Robert L. Matcha; Bernard M. Pettitt

1980-01-01

110

High-Confinement Strained MQW for Highly Polarized High-Power Broadband Light Source  

Microsoft Academic Search

This letter presents highly polarized edge light-emitting diodes with high-confinement, strained, multiple quantum-well active regions. We demonstrate +40 dB of polarization extinction along with 16 dBm of output power from an 800-mum-long centered quantum-well device. By characterizing the polarization extinction and gain of devices with different lengths and optical confinement, we show that the polarization extinction is dominated by the

Steven C. Nicholes; James W. Raring; Mathew Dummer; Anna Tauke-Pedretti; Larry A. Coldren

2007-01-01

111

The Future of High Energy Polarized Proton Beams  

SciTech Connect

The acceleration and storage of high energy polarized proton beams has made tremendous progress over the last forty years challenging along the way the technologies, precision and the understanding of the beam dynamics of accelerators. This progress is most evident in that one can now contemplate high energy colliders with polarized beams and high luminosity at the same time. After a brief summary of the development and history of polarized proton beam acceleration the paper will focus on the highest energy polarized beams and the possibility of accelerating polarized beams to even higher energies in the future.

Roser, Thomas [Brookhaven National Laboratory, Upton, New York 11793-5000 (United States)

2009-08-04

112

Mask-induced polarization effects at high numerical aperture  

E-print Network

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

Zanibbi, Richard

113

A High Density Polarized Hydrogen Gas Target for Storage Rings  

E-print Network

A High Density Polarized Hydrogen Gas Target for Storage Rings K. Zapfe \\Lambday , B. Braun z , H of gaseous polarized hydrogen was formed by injecting polarized H atoms (produced by Stern­Gerlach spin separation) into a storage cell consisting of a cylindrical tube open at both ends. The target was placed

114

Polarization Splay as the Origin of Modulation in the B1 and B7 Smectic Phases of Bent-Core Molecules  

SciTech Connect

We report a generalized scenario for the formation of modulated smectic phases of bent-core molecules based on locally ferroelectric layering and spontaneous splay of the polarization. Twelve phases are proposed, distinguished by neighboring splay stripes with either syn- or antiorder of the polarization and undulation slope, in addition to layer continuity versus layer discontinuity at the intervening defects. We outline the experimental techniques necessary to differentiate among the phases and interpret previous results in the present context, using high resolution x-ray scattering diffraction and block and undulation models of the layer organization to distinguish among the three 2D lattice types which emerge.

Coleman,D.; Jones, C.; Nakata, M.; Clark, N.; Walba, D.; Weissflog, W.; Fodor-Csorba, K.; Watanabe, J.; Novotna, V.; Hamplova, V.

2008-01-01

115

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

E-print Network

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

Gay, Timothy J.

116

A coherent all-electrical interface between polar molecules and mesoscopic superconducting resonators  

NASA Astrophysics Data System (ADS)

Building a scalable quantum processor requires coherent control and preservation of quantum coherence in a large-scale quantum system. Mesoscopic solid-state systems such as Josephson junctions and quantum dots feature robust control techniques using local electrical signals and self-evident scaling; however, in general the quantum states decohere rapidly. In contrast, quantum optical systems based on trapped ions and neutral atoms exhibit much better coherence properties, but their miniaturization and integration with electrical circuits remains a challenge. Here we describe methods for the integration of a single-particle system-an isolated polar molecule-with mesoscopic solid-state devices in a way that produces robust, coherent, quantum-level control. Our setup provides a scalable cavity-QED-type quantum computer architecture, where entanglement of distant qubits stored in long-lived rotational molecular states is achieved via exchange of microwave photons.

Andr, A.; Demille, D.; Doyle, J. M.; Lukin, M. D.; Maxwell, S. E.; Rabl, P.; Schoelkopf, R. J.; Zoller, P.

2006-09-01

117

Single-Molecule Fluorescence Polarization Study of Conformational Change in Archaeal Group II Chaperonin  

PubMed Central

Group II chaperonins found in archaea and in eukaryotic cytosol mediate protein folding without a GroES-like cofactor. The function of the cofactor is substituted by the helical protrusion at the tip of the apical domain, which forms a built-in lid on the central cavity. Although many studies on the change in lid conformation coupled to the binding and hydrolysis of nucleotides have been conducted, the molecular mechanism of lid closure remains poorly understood. Here, we performed a single-molecule polarization modulation to probe the rotation of the helical protrusion of a chaperonin from a hyperthermophilic archaeum, Thermococcus sp. strain KS-1. We detected approximately 35 rotation of the helical protrusion immediately after photorelease of ATP. The result suggests that the conformational change from the open lid to the closed lid state is responsible for the approximately 35 rotation of the helical protrusion. PMID:21779405

Iizuka, Ryo; Ueno, Taro; Morone, Nobuhiro; Funatsu, Takashi

2011-01-01

118

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

SciTech Connect

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

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

2010-12-15

119

Excitation Studies in the Rare Gases and Simple Molecules Using a High Resolution Electron Spectrometer.  

NASA Astrophysics Data System (ADS)

A high resolution electron spectrometer has been used to perform electron scattering studies with both atomic and molecular targets. Work has been done on negative ion resonance production in the rare gases and on polarization correlation measurements in diatomic molecules. High resolution metastable excitation function measurements have been made in the doubly excited state region for Ne, Ar and Kr targets. Comparison of the spectra obtained suggests that the gross features are due to negative ion resonances. Previous techniques which have proved successful in the identification and classification of resonances in the rare gases at energies below the first ionization threshold are shown to be applicable in this energy region also and assignments for a number of resonances are suggested. Where appropriate, comparisons have been made with data obtained by other techniques. The modified Rydberg formula has been used to predict energies for both doubly and triply excited configurations. Polarization correlation measurements have been made with the target molecules N(,2) and H(,2). In H(,2) the radiation resulting from excitation of the C('1)(PI)(,u) v' = 0 band was studied. In N(,2), excitation of the. (DIAGRAM, TABLE OR GRAPHIC OMITTED...PLEASE SEE DAI). band was studied. Pseudo-threshold polarization measurements were made for these targets and comparisons with theoretical predictions were made. Systematic polarization correlation data for electron scattering angles up to 20 degrees have also been obtained and preliminary attempts have been made to analyze these.

Dassen, Henricus W.

120

High energy polarized beams from hyperon decays  

SciTech Connect

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

Underwood, D.G.

1986-01-01

121

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

E-print Network

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

Zare, Richard N.

122

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

ERIC Educational Resources Information Center

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

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

2000-01-01

123

Induction of circularly polarized electroluminescence from an achiral light-emitting polymer via a chiral small-molecule dopant.  

PubMed

By simply doping the conventional light-emitting polymer F8BT with a helically chiral aromatic molecule, it is shown that substantial levels of CP-electroluminescence can be generated directly. Both photoluminescent and electroluminescent emission from the polymer are observed to become circularly polarized, with the sign of the CP emission directly determined by the handedness of the dopant. PMID:23554220

Yang, Ying; da Costa, Rosenildo Correa; Smilgies, Detlef-M; Campbell, Alasdair J; Fuchter, Matthew J

2013-05-14

124

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

125

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, Bjrn; Deissler, Benjamin; Hecker Denschlag, Johannes

2014-12-01

126

Probing the axis alignment of an ultracold spin-polarized Rb(2) molecule.  

PubMed

We present a novel method for probing the alignment of the molecular axis of an ultracold, nonpolar dimer. These results are obtained using diatomic ^{87}Rb_{2} molecules in the vibrational ground state of the lowest triplet potential a^{3}?_{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 1064.5nm parallel and orthogonal to the molecular axis of the dimer, ?_{?}=(8.90.9)10^{3}??a.u. and ?_{?}=(0.90.4)10^{3}??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. PMID:25526128

Deiss, Markus; Drews, Bjrn; Deissler, Benjamin; Hecker Denschlag, Johannes

2014-12-01

127

Electron scattering by highly polar molecules. II - LiF  

NASA Technical Reports Server (NTRS)

The crossed electron-beam - molecular-beam scattering technique has been used to measure relative values of differential 'elastic' scattering cross sections at electron impact energies of 5.4 and 20 eV for the angular range from 20 to 130 deg. The absolute values of these cross sections have been obtained by normalization to the classical perturbation theory of Dickinson (1977) at a scattering angle of 40 deg. These differential cross sections have then been used to calculate the integral and momentum-transfer cross sections. An energy-loss spectrum at 100 eV electron impact energy and 15 deg scattering angle has also been obtained. Two weak features at the energy losses of 6.74 and 8.82 eV appear. Their energy positions are compared with the recent calculations of Kahn et al. (1974).

Vuskovic, L.; Srivastavas, S. K.; Trajmar, S.

1978-01-01

128

Electron scattering by highly polar molecules. III - CsCl  

NASA Technical Reports Server (NTRS)

Utilizing a crossed electron-beam-molecular-beam scattering geometry, relative values of differential electron scattering cross sections for cesium chloride at 5 and 20 eV electron impact energies and at scattering angles between 10 and 120 deg have been measured. These relative cross sections have been normalized to the cross section at 15 deg scattering angle calculated by the hybrid S-matrix technique. In the angular range between 0 and 10 deg and between 120 and 180 deg extrapolations have been made to obtain integral and momentum transfer cross sections. An energy-loss spectrum is also presented which gives various spectral features lying between the 4 and 10 eV regions in CsCl.

Vuskovic, L.; Srivastava, S. K.

1981-01-01

129

High Precision Assembly Line Synthesis for Molecules with Tailored Shapes  

PubMed Central

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

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

2014-01-01

130

High resolution electron crystallography of protein molecules  

SciTech Connect

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

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

1993-06-01

131

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

132

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

SciTech Connect

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

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

2011-02-15

133

S 1.1.1 Highly Polarized Non-polar GaN-based LED Unpolarized LED  

E-print Network

S 1.1.1 Highly Polarized Non-polar GaN-based LED Shi You Polar GaN Unpolarized LED Non-polar GaN Polarized LED #12;n-side contact p-side contact S1.2.1 GaN Based Coaxial LEDs Ashwin Rishinaramangalam High Battery Life Lensless Microscope #12;Green GaN Micro and Nano LEDs Christoph Stark Efficiency Current

Lü, James Jian-Qiang

134

High Density Single-Molecule-Bead Arrays for Parallel Single Molecule Force Spectroscopy  

PubMed Central

The assembly of a highly-parallel force spectroscopy tool requires careful placement of single-molecule targets on the substrate and the deliberate manipulation of a multitude of force probes. Since the probe must approach the target biomolecule for covalent attachment, while avoiding irreversible adhesion to the substrate, the use of the polymer microsphere as force probes to create the tethered bead array poses a problem. Therefore, the interactions between the force probe and the surface must be repulsive at very short distances (< 5 nm) and attractive at long distances. To achieve this balance, the chemistry of the substrate, force probe, and solution must be tailored to control the probe-surface interactions. In addition to an appropriately designed chemistry, it is necessary to control the surface density of the target molecule in order to ensure that only one molecule is interrogated by a single force probe. We used gold-thiol chemistry to control both the substrates surface chemistry and the spacing of the studied molecules, through a competitive binding of the thiol-terminated DNA and an inert thiol forming a blocking layer. For our single molecule array, we modeled the forces between the probe and the substrate using DLVO theory and measured their magnitude and direction with colloidal probe microscopy. The practicality of each system was tested using a probe binding assay to evaluate the proportion of the beads remaining adhered to the surface after application of force. We have translated the results specific for our system to general guiding principles for preparation of tethered bead arrays and demonstrated the ability of this system to produce a high yield of active force spectroscopy probes in a microwell substrate. This study outlines the characteristics of the chemistry needed to create such a force spectroscopy array. PMID:22548234

Barrett, Michael J.; Oliver, Piercen M.; Cheng, Peng; Cetin, Deniz; Vezenov, Dmitri

2012-01-01

135

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

136

Highly polarized HLA class II antigen processing and presentation by human intestinal epithelial cells.  

PubMed Central

The high concentration of foreign antigen in the lumen of the gastrointestinal tract is separated from the underlying lymphocytes by a single cell layer of polarized epithelium. Intestinal epithelial cells can express HLA class II antigens and may function as antigen-presenting cells to CD4(+) T cells within the intestinal mucosa. Using tetanus toxoid specific and HLA-DR-restricted T lymphocytes, we show that polarized intestinal epithelial cells directed to express HLA-DR molecules are able to initiate class II processing only after internalization of antigen from their apical surface. Coexpression of the class II transactivator CIITA in these cells, which stimulates highly efficient class II processing without the characteristic decline in barrier function seen in polarized monolayers treated with the proinflammatory cytokine gamma-IFN, facilitates antigen processing from the basolateral surface. In both cases, peptide presentation to T cells via class II molecules was restricted to the basolateral surface. These data indicate a highly polarized functional architecture for antigen processing and presentation by intestinal epithelial cells, and suggest that the functional outcome of antigen processing by the intestinal epithelium is both dependent on the cellular surface at which the foreign antigen is internalized and by the underlying degree of mucosal inflammation. PMID:9710448

Hershberg, R M; Cho, D H; Youakim, A; Bradley, M B; Lee, J S; Framson, P E; Nepom, G T

1998-01-01

137

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

138

Polarization states of charged excitons in coupled InAs\\/GaAs quantum dot molecules  

Microsoft Academic Search

The polarization state of charged excitons in coupled InAs\\/GaAs dots can reveal useful information about the spin state of its charge carriers. In this study, we examine the complete polarization state through Stokes parameter measurements to relate the polarization parameters of the luminescence to the spin configurations of the various charged excitons they originate from. We demonstrate that this method

Ramana Thota; Swati Ramanathan; Kushal Wijesundara; Eric Stinaff; Allan Bracker; Dan Gammon

2011-01-01

139

Exchange and polarization effect in high-order harmonic imaging of molecular structures  

SciTech Connect

We analyze the importance of exchange, polarization, and electron-electron correlation in high-order harmonic generation in molecules interacting with intense laser fields. We find that electron exchange can become particularly important for harmonic emission associated with intermediate excitations in the molecular ion. In particular, for orbitals associated with two-hole one-particle excitations, exchange effects can eliminate structure-related minima and maxima in the harmonic spectra. Laser-induced polarization of the neutral molecule may also have major effects on orbital structure-related minima and maxima in the harmonic spectra. Finally, we show how exchange terms in recombination can be viewed as a shakedownlike process induced by sudden electronic excitation in the ion.

Sukiasyan, Suren; Ivanov, Misha Yu. [Department of Physics, Imperial College London, South Kensington Campus, SW7 2AZ London (United Kingdom); Patchkovskii, Serguei [National Research Council, 100 Sussex Drive, Ottawa, Ontario K1A 0R6 (Canada); Smirnova, Olga [Max-Born Institute for Nonlinear Optics and Short Pulse Spectroscopy, Max-Born-Strasse 2A, D-12489 Berlin (Germany); Brabec, Thomas [Physics Department and Center for Research in Photonics, University of Ottawa, 150 Louis Pasteur, Ottawa, Ontario K1N 6N5 (Canada)

2010-10-15

140

Ultracold collisional properties of weakly-bound p-wave molecules in a gas of spin-polarized fermions  

NASA Astrophysics Data System (ADS)

: We study three-atom collisional physics relevant to spin-polarized fermionic molecules, under conditions where the interatomic interactions are strongly modified by the presence of a Feshbach resonance [1]. We have explored how both the size and binding energy of p-wave molecules modify their collisional properties. We also have studied the effects of a non-negligible energy dependence, and of the finite atom-atom p-wave scattering length, on the s-wave elastic atom-dimer scattering length. We then speculate about the relevance of these results to ultracold spin-polarized fermi gas experiments. [1] H. Suno, B. D. Esry, and C. H. Greene, Phys. Rev. Lett. 90, 053202 (2003). This work was supported in part by the National Science Foundation.

D'Incao, Jose P.; Greene, Chris H.

2007-06-01

141

Super-Gaussian mirror for high-field-seeking molecules  

SciTech Connect

A matter wave mirror using a single, pulsed, super-Gaussian (SG) optical beam for specular reflection of neutral ground-state molecules is studied. The mirror has a high reflectivity close to 100% and nearly perfect specular reflection over a large incident angle. This mirror avoids the usual problems due to surface roughness and the van der Waals interactions that occur in conventional atomic mirrors. Further, it is capable of reflectance and transmittance with applications to velocity filtering and deceleration of cold molecules.

Dong Guangjiong; Edvadsson, Sverker [Electronic Division, ITM, Mid Sweden University, 851 70, Sundsvall (Sweden); Lu Weiping; Barker, P.F. [Physics Department, School of Engineering and Physical Science, Heriot-Watt University, Edinburgh, Scotland (United Kingdom)

2005-09-15

142

Quantum walk and localization dynamics of rotational excitations in disordered ensembles of polar molecules  

E-print Network

We consider the dynamics of rotational excitations placed on a single molecule in spatially disordered 1D, 2D and 3D ensembles of ultracold molecules trapped in optical lattices. The disorder arises from incomplete populations of optical lattices with molecules. We show that for realistic experimental parameters this specific type of disorder leads to disorder-induced localization in 1D and 2D systems on a time scale $t \\sim 1$ sec. For 3D lattices with $55$ sites in each dimension and vacancy concentrations $\\leq 90 \\%$, the rotational excitations generated in the middle of the lattice diffuse to the edges of the lattice. We observe that the diffusion of rotational excitations in highly disordered 2D and 3D lattices has three distinct time scales. At short times, the rotational excitations diffuse as quantum particles expanding ballistically. At later times, the diffusion character changes to be the same as for the classical particles in Brownian motion. At still later times, the rotational excitations transition to a sub-diffusive regime. While the ballistic expansion is brief ($\\sim 10$ ms), the classical-like diffusion can last as long as 200-300 ms. We also examine the role of the long-range tunnelling amplitudes allowing for transfer of rotational excitations between distant lattice sites. Our results show that the long-range tunnelling has little impact on the dynamics in the diffusive regime but affects significantly the localization dynamics in lattices with large concentrations of vacancies, enhancing the width of the localized distributions in 2D lattices by more than a factor of 2.

Tianrui Xu; Roman V. Krems

2015-01-21

143

High Resolution Studies of Electron Attachment to Molecules  

NASA Astrophysics Data System (ADS)

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

Braun, M.; Ruf, M.-W.; Fabrikant, I. I.; Hotop, H.

2009-05-01

144

Molecules  

NSDL National Science Digital Library

The Switzerland-based society, Molecular Diversity Preservation International (MDPI) provides this free, online journal, Molecules. This journal of synthetic and natural product chemistry encourages chemists to publish their experimental detail, particularly synthetic procedures and characterization information. "Any scattered unassembled experimental data for individual compounds which is conventionally not publishable is particularly welcomed," says the site. The idea is to get information out as quickly as possible to the scientific community. To access Molecules, follow the instructions on how to request a username and password.

1995-01-01

145

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

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

146

Orientation and Rotational Motions of Single Molecules by Polarized Total Internal Reflection Fluorescence Microscopy (polTIRFM)  

PubMed Central

In this article, we describe methods to detect the spatial orientation and rotational dynamics of single molecules using polarized total internal reflection fluorescence microscopy (polTIRFM). polTIRFM determines the three-dimensional angular orientation and the extent of wobble of a fluorescent probe bound to the macromolecule of interest. We discuss single-molecule versus ensemble measurements, as well as single-molecule techniques for orientation and rotation, and fluorescent probes for orientation studies. Using calmodulin (CaM) as an example of a target protein, we describe a method for labeling CaM with bifunctional rhodamine (BR). We also describe the physical principles and experimental setup of polTIRFM. We conclude with a brief introduction to assays using polTIRFM to assess the interaction of actin and myosin. PMID:22550303

Beausang, John F.; Sun, Yujie; Quinlan, Margot E.; Forkey, Joseph N.; Goldman, Yale E.

2013-01-01

147

High-Altitude Observations of the Polar Wind  

NASA Technical Reports Server (NTRS)

Plasma outflows, escaping from Earth through the high-altitude polar caps into the tail of the magnetosphere, have been observed with a xenon plasma source instrument to reduce the floating potential of the POLAR spacecraft. The largest component of H(+) flow, along the local magnetic field (30 to 60 kilometers per second), is faster than predicted by theory. The flows contain more O(+) than predicted by theories of thermal polar wind, but also have elevated ion temperatures. These plasma outflows contribute to the plasmas energized in the elongated nightside tail of the magnetosphere, creating auroras, substorms, and storms. They also constitute an appreciable loss of terrestrial water dissociation products into space.

Moore, T. E.; Chappell, C. R.; Chandler, M. O.; Craven, P. D.; Giles, B. L.; Pollock, C. J.; Burch, J. L.; Young, D. T.; Waite, J. H., Jr.; Nordholt, J. E.; Thomsen, M. F.; McComas, D. J.; Berthelier, J. J.; Williamson, W. S.; Robson, R.; Mozer, F. S.

1997-01-01

148

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

E-print Network

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

Maly, Thorsten

149

Inelastic collisions of cold polar molecules in nonparallel electric and magnetic fields  

NASA Astrophysics Data System (ADS)

The authors present a detailed study of low-temperature collisions between CaD molecules and He atoms in superimposed electric and magnetic fields with arbitrary orientations. Electric fields do not interact with the electron spin of the molecules directly but modify their rotational structure and, consequently, the spin-rotation interactions. The authors examine molecular Stark and Zeeman energy levels as functions of the angle between the fields and show that rotating fields may induce and shift avoided crossings between the Zeeman levels of the rotationally ground and rotationally excited states of the molecule. The dynamics of molecular collisions are extremely sensitive to external fields near these avoided crossings and it is shown that molecular collisions may be controlled by varying both the strength and the relative orientation of the fields. The effects observed in this study are due to interactions of the isolated molecules with external fields so the conclusions should be relevant for collisions of molecules with other atoms or collisions of molecules with each other. This study demonstrates that electric fields may be used to enhance or suppress spin-rotation interactions in molecules. The spin-rotation interactions induce nonadiabatic couplings between states of different total spins in systems of two open-shell species and it is suggested that electric fields might be used for controlling nonadiabatic spin transitions and spin-forbidden chemical reactions of cold molecules in a magnetic trap.

Abrahamsson, E.; Tscherbul, T. V.; Krems, R. V.

2007-07-01

150

Inelastic collisions of cold polar molecules in nonparallel electric and magnetic fields.  

PubMed

The authors present a detailed study of low-temperature collisions between CaD molecules and He atoms in superimposed electric and magnetic fields with arbitrary orientations. Electric fields do not interact with the electron spin of the molecules directly but modify their rotational structure and, consequently, the spin-rotation interactions. The authors examine molecular Stark and Zeeman energy levels as functions of the angle between the fields and show that rotating fields may induce and shift avoided crossings between the Zeeman levels of the rotationally ground and rotationally excited states of the molecule. The dynamics of molecular collisions are extremely sensitive to external fields near these avoided crossings and it is shown that molecular collisions may be controlled by varying both the strength and the relative orientation of the fields. The effects observed in this study are due to interactions of the isolated molecules with external fields so the conclusions should be relevant for collisions of molecules with other atoms or collisions of molecules with each other. This study demonstrates that electric fields may be used to enhance or suppress spin-rotation interactions in molecules. The spin-rotation interactions induce nonadiabatic couplings between states of different total spins in systems of two open-shell species and it is suggested that electric fields might be used for controlling nonadiabatic spin transitions and spin-forbidden chemical reactions of cold molecules in a magnetic trap. PMID:17672685

Abrahamsson, E; Tscherbul, T V; Krems, R V

2007-07-28

151

Polarizing Agents and Mechanisms for High-Field Dynamic Nuclear Polarization of Frozen Dielectric Solids  

PubMed Central

This article provides an overview of polarizing mechanisms involved in high-frequency dynamic nuclear polarization (DNP) of frozen biological samples at temperatures maintained using liquid nitrogen, compatible with contemporary magic-angle spinning (MAS) nuclear magnetic resonance (NMR). Typical DNP experiments require unpaired electrons that are usually exogenous in samples via paramagnetic doping with polarizing agents. Thus, the resulting nuclear polarization mechanism depends on the electron and nuclear spin interactions induced by the paramagnetic species. The Overhauser Effect (OE) DNP, which relies on time-dependent spin-spin interactions, is excluded from our discussion due the lack of conducting electrons in frozen aqueous solutions containing biological entities. DNP of particular interest to us relies primarily on time-independent, spin interactions for significant electron-nucleus polarization transfer through mechanisms such as the Solid Effect (SE), the Cross Effect (CE) or Thermal Mixing (TM), involving one, two or multiple electron spins, respectively. Derived from monomeric radicals initially used in DNP experiments, bi- or multiple-radical polarizing agents facilitate CE/TM to generate significant NMR signal enhancements in dielectric solids at low temperatures (< 100 K). For example, large DNP enhancements (~300 times at 5 T) from a biologically compatible biradical, 1-(TEMPO-4-oxy)-3-(TEMPO-4-amino)propan-2-ol (TOTAPOL), have enabled high-resolution MAS NMR in sample systems existing in submicron domains or embedded in larger biomolecular complexes. The scope of this review is focused on recently developed DNP polarizing agents for high-field applications and leads up to future developments per the CE DNP mechanism. Because DNP experiments are feasible with a solid-state microwave source when performed at <20 K, nuclear polarization using lower microwave power (< 100 mW) is possible by forcing a high proportion of biradicals to fulfill the frequency matching condition of CE (two EPR frequencies separated by the NMR frequency) using the strategies involving hetero-radical moieties and/or molecular alignment. In addition, the combination of an excited triplet and a stable radical might provide alternative DNP mechanisms without the microwave requirement. PMID:21855299

Hu, Kan-Nian

2011-01-01

152

Numerical Simulations of femtosecond-laser-induced dynamic alignment of molecules in the high-frequency off-resonance regime  

Microsoft Academic Search

The motion equation for ? between the molecular axis and laser polarization direction in a high-frequency off-resonance femtosecond\\u000a laser field is deduced while simultaneously examining the effects of a permanent dipole moment and field-induced polarizability\\u000a and hyperpolarizability to molecular rotation. Femtosecond-laser-induced dynamic alignment of CO, N2, and Br2 molecules are investigated by numerically solving the obtained rotation equation for the

J. Chen; X. Cui; S. Zhuo; B. Huang; X. Jiang

2006-01-01

153

Implementation of quantum logic gates using polar molecules in pendular states Jing Zhu, Sabre Kais, Qi Wei, Dudley Herschbach, and Bretislav Friedrich  

E-print Network

operating on polar molecules in pendular states as qubits for a quantum computer. A static electric field calculations for the SrO molecule, a favorite candidate for proposed quantum computers. Our simulation results. INTRODUCTION Quantum computers take direct advantage of superpo- sition and entanglement to perform

Kais, Sabre

154

Quantum control of molecular vibrational and rotational excitations in a homonuclear diatomic molecule: A full three-dimensional treatment with polarization forces  

Microsoft Academic Search

The optimal control of the vibrational excitation of the hydrogen molecule [Balint-Kurti et al., J. Chem. Phys. 122, 084110 (2005)] utilizing polarization forces is extended to three dimensions. The polarizability of the molecule, to first and higher orders, is accounted for using explicit ab initio calculations of the molecular electronic energy in the presence of an electric field. Optimal control

Qinghua Ren; Gabriel G. Balint-Kurti; Frederick R. Manby; Maxim Artamonov; Tak-San Ho; Herschel Rabitz

2006-01-01

155

Generation of macroscopic entangled coherent states for distant ensembles of polar molecules via effective coupling to a superconducting charge qubit  

NASA Astrophysics Data System (ADS)

We propose a potentially practical scheme for creating macroscopic entangled coherent states (ECSs) between two distant ensembles of polar molecules (PMs) placed, respectively, in separate transmission-line resonators (TLRs) interconnected by a superconducting charge qubit. The ECS between two PM ensembles can be generated in the dispersive regime through control of the superconducting qubit under classical strong-driving conditions, during which the TLRs are only virtually excited. The tunable coupling of the TLR hybrid system provides us the potential of extending the ECS generation to multimode cases. The experimental feasibility of the scheme is discussed briefly based on currently available techniques.

Chen, Qiong; Yang, Wanli; Feng, Mang

2012-10-01

156

Prospects for the formation of ultracold polar ground state KCs molecules via an optical process  

E-print Network

Heteronuclear alkali-metal dimers represent the class of molecules of choice for creating samples of ultracold molecules exhibiting an intrinsic large permanent electric dipole moment. Among them, the KCs molecule, with a permanent dipole moment of 1.92 Debye still remains to be observed in ultracold conditions. Based on spectroscopic studies available in the literature completed by accurate ab initio calculations, we propose several optical coherent schemes to create ultracold bosonic and fermionic KCs molecules in their absolute rovibrational ground level, starting from a weakly bound level of their electronic ground state manifold. The processes rely on the existence of convenient electronically excited states allowing an efficient stimulated Raman adiabatic transfer of the level population.

Borsalino, D; Aymar, M; Luc-Koenig, E; Dulieu, O; Bouloufa-Maafa, N

2015-01-01

157

Prospects for the formation of ultracold polar ground state KCs molecules via an optical process  

E-print Network

Heteronuclear alkali-metal dimers represent the class of molecules of choice for creating samples of ultracold molecules exhibiting an intrinsic large permanent electric dipole moment. Among them, the KCs molecule, with a permanent dipole moment of 1.92 Debye still remains to be observed in ultracold conditions. Based on spectroscopic studies available in the literature completed by accurate ab initio calculations, we propose several optical coherent schemes to create ultracold bosonic and fermionic KCs molecules in their absolute rovibrational ground level, starting from a weakly bound level of their electronic ground state manifold. The processes rely on the existence of convenient electronically excited states allowing an efficient stimulated Raman adiabatic transfer of the level population.

D Borsalino; R Vexiau; M Aymar; E Luc-Koenig; O Dulieu; N Bouloufa-Maafa

2015-01-26

158

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

E-print Network

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

Lee, Youngbok

2013-03-13

159

Tensor polarization of the varphi meson photoproduced at high t  

Microsoft Academic Search

As part of a measurement [E. Anciant et al., Phys. Rev. Lett. 85, 4682 (2000)] of the cross section of varphi meson photoproduction to high momentum transfer, we measured the polar angular decay distribution of the outgoing K+ in the channel varphi--> K+ K- in the varphi center-of-mass frame (the helicity frame). We find that s -channel helicity conservation (SCHC)

K. McCormick; G. Audit; J. M. Laget; G. Adams; P. Ambrozewicz; E. Anciant; M. Anghinolfi; B. Asavapibhop; T. Auger; H. Avakian; H. Bagdasaryan; J. P. Ball; S. Barrow; M. Battaglieri; K. Beard; M. Bektasoglu; M. Bellis; N. Benmouna; B. L. Berman; N. Bianchi; A. S. Biselli; S. Boiarinov; B. E. Bonner; S. Bouchigny; R. Bradford; W. K. Brooks; V. D. Burkert; C. Butuceanu; J. R. Calarco; D. S. Carman; B. Carnahan; C. Cetina; S. Chen; P. L. Cole; A. Coleman; J. Connelly; D. Cords; P. Corvisiero; D. Crabb; H. Crannell; J. P. Cummings; E. de Sanctis; R. Devita; P. V. Degtyarenko; H. Denizli; L. Dennis; K. V. Dharmawardane; C. Djalali; G. E. Dodge; D. Doughty; P. Dragovitsch; M. Dugger; S. Dytman; O. P. Dzyubak; M. Eckhause; H. Egiyan; K. S. Egiyan; L. Elouadrhiri; P. Eugenio; L. Farhi; R. J. Feuerbach; J. Ficenec; T. A. Forest; V. Frolov; H. Funsten; S. J. Gaff; M. Gai; M. Garon; G. Gavalian; S. Gilad; G. P. Gilfoyle; K. L. Giovanetti; P. Girard; C. I. Gordon; K. Griffioen; M. Guidal; M. Guillo; L. Guo; V. Gyurjyan; C. Hadjidakis; R. S. Hakobyan; D. Hancock; J. Hardie; D. Heddle; F. W. Hersman; K. Hicks; R. S. Hicks; M. Holtrop; C. E. Hyde-Wright; M. M. Ito; D. Jenkins; K. Joo; H. G. Juengst; J. H. Kelley; M. Khandaker; W. Kim; A. Klein; F. J. Klein; A. Klimenko; M. Klusman; M. Kossov; L. H. Kramer; Y. Kuang; S. E. Kuhn; J. Kuhn; J. Lachniet; J. Langheinrich; D. Lawrence; Ji Li; K. Lukashin; W. Major; J. J. Manak; C. Marchand; S. McAleer; J. W. McNabb; B. A. Mecking; S. Mehrabyan; J. J. Melone; M. D. Mestayer; C. A. Meyer; R. Minehart; M. Mirazita; R. Miskimen; L. Morand; S. A. Morrow; V. Muccifora; J. Mueller; G. S. Mutchler; J. Napolitano; R. Nasseripour; S. O. Nelson; S. Niccolai; G. Niculescu; I. Niculescu; B. B. Niczyporuk; R. A. Niyazov; M. Nozar; M. Osipenko; E. Pasyuk; G. Peterson; S. A. Philips; N. Pivnyuk; D. Pocanic; O. Pogorelko; E. Polli; B. M. Preedom; J. W. Price; Y. Prok; D. Protopopescu; L. M. Qin; B. A. Raue; G. Riccardi; G. Ricco; M. Ripani; B. G. Ritchie; F. Ronchetti; P. Rossi; D. Rowntree; P. D. Rubin; F. Sabati; K. Sabourov; C. Salgado; J. P. Santoro; M. Sanzone-Arenhovel; V. Sapunenko; M. Sargsyan; R. A. Schumacher; V. S. Serov; A. Shafi; Y. G. Sharabian; J. Shaw; A. V. Skabelin; E. S. Smith; T. Smith; L. C. Smith; D. I. Sober; M. Spraker; S. Stepanyan; P. Stoler; S. Strauch; M. Taiuti; S. Taylor; D. J. Tedeschi; U. Thoma; R. Thompson; L. Todor; C. Tur; M. Ungaro; M. F. Vineyard; A. V. Vlassov; K. Wang; L. B. Weinstein; H. Weller; D. P. Weygand; C. S. Whisnant; M. Witkowski; E. Wolin; M. H. Wood; A. Yegneswaran; J. Yun; J. Zhao; Z. Zhou

2004-01-01

160

Polarization-independent active metamaterial for high-frequency  

E-print Network

Polarization-independent active metamaterial for high-frequency terahertz modulation Oliver Paul1-independent metamaterial design for the construction of electrically tunable terahertz (THz) devices. The implemented Optical Society of America OCIS codes: (160.3918) Metamaterials; (230.4110) Modulators; (300.6495) THz

161

High-Throughput Continuous Beam Steering Using Rotating Polarization Gratings  

Microsoft Academic Search

A new beam steering concept comprising independently rotating, inline polarization gratings (PGs) is experimentally demonstrated. The approach, which we term Risley gratings, achieves high steering throughput within a large field-of-regard (FOR) in a fashion similar to Risley prisms, composed of wedged prisms. However, because PGs are patterned in thin liquid crystal layers, they enable a system with far less thickness,

Chulwoo Oh; Jihwan Kim; John Muth; Steve Serati; Michael J. Escuti

2010-01-01

162

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

163

Constraining molecules at the closest approach: chemistry at high pressure.  

PubMed

The purpose of this tutorial review is to illustrate the effects that the application of high pressures can have on chemical reactions involving highly compressible molecular materials. The essentials of the high-pressure technology (generation and in situ control of high pressures) are described with particular attention to the versatile diamond anvil cell (DAC) apparatus. The general effects of pressure on chemical equilibrium, reaction rate and reaction mechanism are discussed. The motivation for application of high-pressure methods (in the 1-300 MPa range) to chemical synthesis and in biochemistry are illustrated focusing the attention on environmental effects and with an excursus on developing biotechnological applications. The peculiarities and the unexpected outcomes of chemical reactions occurring at very high pressures (>or=300 MPa) are discussed considering the extraordinary results obtained in polymerization and amorphization of simple molecules and of unsaturated hydrocarbons. The possible connection of the high temperature-high pressure thresholds for chemical reactions with microscopic counterparts (intermolecular distances, molecular orientations) is also discussed. PMID:17534474

Schettino, Vincenzo; Bini, Roberto

2007-06-01

164

The microsporidian polar tube: A highly specialised invasion organelle  

PubMed Central

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

Xu, Yanji; Weiss, Louis M.

2011-01-01

165

Multielectron effects in high harmonic generation in N_2 and benzene: simulation using a non-adiabatic quantum molecular dynamics approach for laser-molecule interactions  

E-print Network

A mixed quantum-classical approach is introduced which allows the dynamically response of molecules driven far from equilibrium to be modeled. This method is applied here to the interaction of molecules with intense, short-duration laser pulses. The electronic response of the molecule is described using time-dependent density functional theory (TDDFT) and the resulting Kohn-Sham equations are solved numerically using finite difference techniques in conjunction with local and global adaptations of an underlying grid in curvilinear coordinates. Using this approach, simulations can be carried out for a wide range of molecules and both all-electron and pseudopotential calculations can be performed. The approach is applied to the study of high harmonic generation in N_2 and benzene using linearly-polarized laser pulses and to the best of our knowledge, the results for benzene represent the first TDDFT calculations of high harmonic generation in benzene using linearly polarized laser pulses. For N_2 an enhancement ...

Dundas, Daniel

2012-01-01

166

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

NASA Astrophysics Data System (ADS)

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

Debolt, Stephen Edward

167

Defect Pinning in Monolayer Films by Highly Controlled Graphite Defects: Molecule Corrals  

E-print Network

Defect Pinning in Monolayer Films by Highly Controlled Graphite Defects: Molecule Corrals David L monolayer deep etch pits in the basal plane of graphite ("molecule corrals"). Molecule corrals are shown of molecules. A model for grain boundary motion is developed and used to analyze two types of boundaries: those

Patrick, David L.

168

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

169

High resolution studies of dissociative electron attachment to molecules  

NASA Astrophysics Data System (ADS)

Experimental advances involving laser photoelectron sources have recently allowed detailed studies of low-energy electron attachment to several small molecules and molecular clusters at (sub)meV resolution [1]. For the first time, conclusive investigations of the limiting (E arrow 0) threshold behaviour for the attachment cross section became possible with the laser photoelectron (LPA) method [1]. Absolute attachment cross sections over the energy range E = (0.5 - 200) meV are established by normalizing the LPA yields for negative ion formation to reliable attachment rate coefficients, determined at well-defined electron and gas temperature in swarm experiments. Towards higher energies, the attachment cross sections may exhibit sharp cusp-type structure at vibrational onsets, due to the interaction of the attachment process with other scattering channels, e.g. for SF6 and CCl4 [1]. For electron-molecule systems with sufficiently strong long-range interactions and suitable crossings of the diabatic anion potential with the neutral potential curve (e.g. CH_3Br or CH_3I), narrow and prominent vibrational Feshbach resonances occur in the cross section for dissociative attachment [1]. At the conference we highlight these topics by discussing specific molecules (including Cl_2, CF_3I, and CH_3I) for which the high resolution attachment data can be compared with theoretical calculations.For suitable cases (e.g. Cl_2, CH_3I), semiempirical input to the theory is fixed with reference to attachment cross sections and then offers a platform for theoretical predictions of elastic scattering and vibrational excitation cross sections [1]. This work has been supported by the Deutsche Forschungsgemeinschaft and by the Forschungszentrum OTLAP. [1] H. Hotop, M.-W. Ruf, M. Allan, I. I. Fabrikant, Adv. At. Mol. Opt. Phys. 49 (2003) 85-216

Hotop, H.; Barsotti, S.; Braun, M.; Marienfeld, S.; Ruf, M.-W.; Fabrikant, I. I.

2004-09-01

170

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

E-print Network

The properties of the electronic ground state of the polar and paramagnetic europium-$S$-state-atom molecules have been investigated. Ab initio techniques have been applied to compute the potential energy curves for the europium-alkali-metal-atom, Eu$X$ ($X$=Li, Na, K, Rb, Cs), europium-alkaline-earth-metal-atom, Eu$Y$ ($Y$=Be, Mg, Ca, Sr, Ba), and europium-ytterbium, EuYb, molecules in the Born-Oppenheimer approximation for the high-spin electronic ground state. The spin restricted open-shell coupled cluster method restricted to single, double, and noniterative triple excitations, RCCSD(T), was employed and the scalar relativistic effects within the small-core energy-consistent pseudopotentials were included. The permanent electric dipole moments and static electric dipole polarizabilities were computed. The leading long-range coefficients describing the dispersion interaction between atoms at large internuclear distances $C_6$ are also reported. The EuK, EuRb, and EuCs molecules are examples of species poss...

Tomza, Micha?

2014-01-01

171

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

NASA Astrophysics Data System (ADS)

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

Tomza, Micha?

2014-08-01

172

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

ERIC Educational Resources Information Center

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

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

2012-01-01

173

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

SciTech Connect

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

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

2000-06-21

174

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

NASA Astrophysics Data System (ADS)

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

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

1988-08-01

175

When is O+ Observed in the High Altitude Polar Cap?  

NASA Technical Reports Server (NTRS)

Solar wind and IMF properties are correlated with the properties of O+ and H+ in the polar cap at altitudes greater than 5.5 Re geocentric using the Thermal Ion Dynamics Experiment (TIDE) on the Polar satellite. O+ is of primary interest in this study because the fraction of O+ present in the magnetosphere is commonly used as a measure of the ionospheric contribution to the magnetosphere. O+ is observed to be most abundant at lower latitudes when the solar wind speed is low and across most of the polar cap at high solar winds speeds and Kp. As the solar wind dynamic pressures increases more O+ is present in the polar cap. The O+ density is also shown to be more highly correlated with the solar wind dynamic pressure when IMF Bz is positive. H+ was not as well correlated with solar wind and IMF parameters although some correlation with IMF By is observed. H+ is more plentiful when IMF By is negative than when it is positive. In this data set H+ is very dominate so that if this plasma makes it to the plasma sheet its contribution to the plasma sheet would have a very low O+ to H+ ratio.

Elliott, H. A.; Comfort, R. H.; Craven, P. D.; Chandler, M. O.; Moore, T. E.

2000-01-01

176

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-Castejn; Alberto Baroja-Mazo; Pablo Pelegrn

177

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

178

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

179

Applications of highly spin-polarized xenon in NMR  

SciTech Connect

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

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

1993-09-01

180

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

181

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

E-print Network

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

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

2015-02-19

182

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

PubMed

MUC1 glycoprotein is overexpressed and its intracellular localization altered during breast carcinoma tumorigenesis. The present study aimed to clarify the relationship of cytoplasmic localization of MUC1 with the breast cancer subtype and the correlation of 10 molecules associated with cell polarity in breast cancer subtypes. We immunostained 131 formalin-fixed and paraffin-embedded breast cancer specimens with an anti-MUC1 antibody (MUC1/CORE). For 48 of the 131 tumor specimens, laser-assisted microdissection and real-time quantitative RT-PCR were performed to analyze mRNA levels of MUC1 and 10 molecules, ?-catenin, E-cadherin, claudin3, claudin4, claudin7, RhoA, cdc42, Rac1, Par3 and Par6. Localization of MUC1 protein varied among breast cancer subtypes, that is, both the apical domain and cytoplasm in luminal A-like tumors (P<0.01) and both the cytoplasm and cell membrane in luminal B-like (growth factor receptor 2 [HER2]+) tumors (P<0.05), and no expression was found in triple negative tumors (P<0.001). Estrogen receptor (ER)+ breast cancers showed higher MUC1 mRNA levels than ER- breast cancers (P<0.01). The incidence of mutual correlations of expression levels between two of the 10 molecules (55 combinations) was 54.5% in normal breast tissue and 38.2% in luminal A-like specimens, 16.4% in luminal B-like (HER2+), 3.6% in HER2 and 18.2% in triple negative specimens. In conclusion, each breast cancer subtype has characteristic cytoplasmic localization patterns of MUC1 and different degrees of disrupted correlation of the expression levels between the 10 examined molecules in comparison with normal breast tissue. PMID:25556893

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

2015-03-01

183

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)

2006-06-27

184

Single molecule high-resolution colocalization of Cy3 and Cy5 attached to macromolecules measures  

E-print Network

Single molecule high-resolution colocalization of Cy3 and Cy5 attached to macromolecules measures, 2004 Here we present a technique called single-molecule high-resolution colocalization (SHREC molecules as probes, we are able to circumvent the Rayleigh criterion and measure distances much smaller

Spudich, James A.

185

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

PubMed

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

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

2014-05-01

186

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 off-the-shelf components and enables the concept of printing on demand. The utility of this SEOP setup is demonstrated here to obtain near-unity 129Xe polarization values in a 0.5 L optical pumping cell, including ~74 7% at 1000 Torr xenon partial pressure, a record value at such high Xe density. Values for the 129Xe polarization exponential build-up rate [(3.63 0.15) 10?2 min?1] and in-cell 129Xe spin?lattice relaxation time (T1 = 2.19 0.06 h) for 1000 Torr Xe were in excellent agreement with the ratio of the gas-phase polarizations for 129Xe and Rb (PRb ~ 96%). Hyperpolarization-enhanced 129Xe gas imaging was demonstrated with a spherical phantom following automated gas transfer from the polarizer. Taken together, these results support the development of a wide range of chemical, biochemical, material science, and biomedical applications. PMID:24400919

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

187

A rapid and sensitive method for the simultaneous analysis of aliphatic and polar molecules containing free carboxyl groups in plant extracts by LC-MS/MS  

PubMed Central

Background Aliphatic molecules containing free carboxyl groups are important intermediates in many metabolic and signalling reactions, however, they accumulate to low levels in tissues and are not efficiently ionized by electrospray ionization (ESI) compared to more polar substances. Quantification of aliphatic molecules becomes therefore difficult when small amounts of tissue are available for analysis. Traditional methods for analysis of these molecules require purification or enrichment steps, which are onerous when multiple samples need to be analyzed. In contrast to aliphatic molecules, more polar substances containing free carboxyl groups such as some phytohormones are efficiently ionized by ESI and suitable for analysis by LC-MS/MS. Thus, the development of a method with which aliphatic and polar molecules -which their unmodified forms differ dramatically in their efficiencies of ionization by ESI- can be simultaneously detected with similar sensitivities would substantially simplify the analysis of complex biological matrices. Results A simple, rapid, specific and sensitive method for the simultaneous detection and quantification of free aliphatic molecules (e.g., free fatty acids (FFA)) and small polar molecules (e.g., jasmonic acid (JA), salicylic acid (SA)) containing free carboxyl groups by direct derivatization of leaf extracts with Picolinyl reagent followed by LC-MS/MS analysis is presented. The presence of the N atom in the esterified pyridine moiety allowed the efficient ionization of 25 compounds tested irrespective of their chemical structure. The method was validated by comparing the results obtained after analysis of Nicotiana attenuata leaf material with previously described analytical methods. Conclusion The method presented was used to detect 16 compounds in leaf extracts of N. attenuata plants. Importantly, the method can be adapted based on the specific analytes of interest with the only consideration that the molecules must contain at least one free carboxyl group. PMID:19939243

2009-01-01

188

High-performance organic small-molecule panchromatic photodetectors.  

PubMed

High-performance panchromatic organic photodetectors (OPDs) containing small molecules lead phthalocyanine (PbPc) and C70 fullerene as donor and acceptor, respectively, were demonstrated. The OPDs had either a PbPc/C70 planar heterojunction (PHJ) or a PbPc/PbPc:C70/C70 hybrid planar-mixed molecular heterojunction (PM-HJ) structure. Both the PHJ and the PM-HJ devices showed a broad-band response that covered wavelengths from 300 to 1100 nm. An external quantum efficiency (EQE) higher than 10% and detectivity on the order of 10(12) Jones were obtained in the wavelength region from 400 to 900 nm for the PHJ device. The EQE in the near-infrared region was enhanced by using the PM-HJ device structure, and a maximum EQE of 30.2% at 890 nm was observed for the optimized device with a 5% PbPc-doped C70 layer. Such an EQE is the highest at this wavelength of reported OPDs. The detectivity of the PM-HJ devices was also higher than that of the PHJ one, which is attributed to the increased efficiency of exciton dissociation in bulk heterojunction structure, increased absorption efficiency caused by formation of triclinic PbPc in the PbPc:C70 mixed film when it was deposited on a pristine PbPc layer, and high hole mobility of the PbPc-doped C70 layer. PMID:25591117

Su, Zisheng; Hou, Fuhua; Wang, Xing; Gao, Yuan; Jin, Fangming; Zhang, Guang; Li, Yantao; Zhang, Ligong; Chu, Bei; Li, Wenlian

2015-02-01

189

Polarization interferometric nulling coronagraph for high-contrast imaging.  

PubMed

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

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

2010-06-01

190

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

191

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

PubMed

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

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

2014-10-01

192

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

SciTech Connect

The tert-butyl iodide molecule is readily focused with the electrostatic hexapole, via its first-order Stark effect as a pseudo-symmetric top. The pulsed, seeded supersonic focused beam, characterized by = V/sub th// V/sub 0/ (where theta is the angle between the molecular dipole axis ..mu.. and the electric field E; +- V/sub 0/ the hexapole ''rod voltage,'' and V/sub th/ the so-called threshold voltage), passes into a small homogeneous electric field in which it is oriented. The degree of laboratory orientation achieved is measured using the method of linearly polarized laser-induced photofragmentation (S. R. Gandhi, T. J. Curtiss, and R. B. Bernstein, Phys. Rev. Lett. 59, 2951 (1987)), operating (at three laser wavelengths) on the I(/sup 2/P/sub 3//sub ///sub 2/) and I(/sup 2/P/sub 1//sub ///sub 2/) as well as the t-C/sub 4/H/sub 9/ radical photofragments. The results show that the oriented beam molecules of t-butyl iodide (at a rotational temperature near 15 K) have a higher degree of orientation than the prototype CH/sub 3/I molecules (JKM state-selected and focused similarly), explainable by the greater importance of the so-called hyperfine disorientation effect for the prolate symmetric top (CH/sub 3/I) than for the t-C/sub 4/H/sub 9/I. For the latter, orientations with photofragment up--down asymmetry ratios as large as a factor of 10 can be achieved, suggesting that t-C/sub 4/H/sub 9/I is an excellent candidate reagent for reactive asymmetry studies.

Xu, Q.; Jung, K.; Bernstein, R.B.

1988-08-15

193

The V-shaped polar molecules encapsulated into Cs (10528)-C72: stability and nonlinear optical response.  

PubMed

Recently, a new sulfide cluster fullerene, Sc2S@Cs (10528)-C72 containing two pairs of fused pentagons has been isolated and characterized (Chen et al., J. Am. Chem. Soc., 2012, 134, 7851). Inspired by this investigation, we propose a question: what properties will be influenced by the interaction between the encapsulated V-shaped polar molecule and C72? To answer this question, four encapsulated metallic fullerenes (EMFs) M2N@C72 (M = Sc or Y, N = S or O) along with pristine Cs-C72 (10528) were investigated by quantum chemistry methods. The results show that the Egap (3.01-3.14 eV) of M2N@C72 are significantly greater than that of pristine Cs-C72 (10528) (2.34 eV). This indicates that the stabilities of these EMFs increase by encapsulating the V-shaped polar molecule into the fullerene. Furthermore, the natural bond orbital (NBO) charge analysis indicates electron transfer from M2N to C72 cage, which plays a crucial role in enhancing first hyperpolarizability (?tot). The ?tot follows the order of 1174 au (Y2O@C72) ? 1179 au (Sc2O@C72) > 886 au (Y2S@C72) ? 864 au (Sc2S@C72) > 355 au (C72). This indicates that the ?tot of M2N@C72 is more remarkable than that of pristine Cs-C72 (10528) due to the induction effect of the encapsulated molecule. Compared with sulfide cluster fullerenes (Y2S@C72 and Sc2S@C72), oxide cluster fullerenes (Sc2O@C72 and Y2O@C72) show much larger ?tot due to the small ionic radius and the large electronegativity of oxygen. In contrast, the metal element (scandium and yttrium) has a slight influence on the ?tot. Thus, oxide cluster fullerenes are candidates to become promising nonlinear optical materials with higher performance. PMID:24839638

Wang, Li-Jie; Zhong, Rong-Lin; Sun, Shi-Ling; Xu, Hong-Liang; Pan, Xiu-Mei; Su, Zhong-Min

2014-07-01

194

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

195

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

196

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

197

Dynamic nuclear polarization of high- and low-crystallinity polyethylenes  

NASA Astrophysics Data System (ADS)

We carried out a dynamic nuclear polarization (DNP) study of high- and low-crystallinity polyethylene films defined as HPE and LPE, respectively, which were doped with TEMPO (2,2,6,6-tetra-methyl-piperidine-1-oxyl) by the same amount (11019 spins/cm3). The proton polarization of 323% was obtained for LPE and 234% for HPE at 3.35 T and 1.4 K. With increase in the concentration of TEMPO, the electron spin resonance (ESR) linewidth of TEMPO in HPE increased more steeply than that in LPE, indicating that TEMPO did not incorporated into the crystalline part, and was localized only at the amorphous part, hence the local concentration of TEMPO in the amorphous regions of HPE varied more steeply than that of LPE with the net amount of TEMPO fed into the film. We suggest that the smaller nuclear polarization for HPE is related to the localization of TEMPO in the smaller amorphous regions.

Kumada, Takayuki; Yohei, Noda; Hashimoto, Takeji; Koizumi, Satoshi

2009-07-01

198

Molecular motion, dielectric response, and phase transition of charge-transfer crystals: acquired dynamic and dielectric properties of polar molecules in crystals.  

PubMed

Molecules in crystals often suffer from severe limitations on their dynamic processes, especially on those involving large structural changes. Crystalline compounds, therefore, usually fail to realize their potential as dielectric materials even when they have large dipole moments. To enable polar molecules to undergo dynamic processes and to provide their crystals with dielectric properties, weakly bound charge-transfer (CT) complex crystals have been exploited as a molecular architecture where the constituent polar molecules have some freedom of dynamic processes, which contribute to the dielectric properties of the crystals. Several CT crystals of polar tetrabromophthalic anhydride (TBPA) molecules were prepared using TBPA as an electron acceptor and aromatic hydrocarbons, such as coronene and perylene, as electron donors. The crystal structures and dielectric properties of the CT crystals as well as the single-component crystal of TBPA were investigated at various temperatures. Molecular reorientation of TBPA molecules did not occur in the single-component crystal, and the crystal did not show a dielectric response due to orientational polarization. We have found that the CT crystal formation provides a simple and versatile method to develop molecular dielectrics, revealing that the molecular dynamics of the TBPA molecules and the dielectric property of their crystals were greatly changed in CT crystals. The TBPA molecules underwent rapid in-plane reorientations in their CT crystals, which exhibited marked dielectric responses arising from the molecular motion. An order-disorder phase transition was observed for one of the CT crystals, which resulted in an abrupt change in the dielectric constant at the transition temperature. PMID:25781627

Harada, Jun; Ohtani, Masaki; Takahashi, Yukihiro; Inabe, Tamotsu

2015-04-01

199

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.

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

2007-05-04

200

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

201

(Interaction of slow electrons with high-pressure gases (quasi-liquids): synthesis of our knowledge on slow electron-molecule interactions. Progress report for year ending May 31, 1981  

SciTech Connect

Research on electron interactions with molecules at high pressure is reported. This includes electron collisions with chlorofluoroethanes; temperature dependence of electron attachment to halocarbons; electron energy distribution functions in argon; the role of electron attachment in the breakdown strength of gaseous dielectrics; a new high temperature swarm experiment; electron scattering from molecules of environmental interest; negative ions of polyatomic molecules; electron motion in high pressure polar gases (NH/sub 3/); fast gases for radiation detectors; and electron affinities of atoms and molecules. (GHT)

Christophorou, L.G.; McCorkle, D.L.

1981-01-01

202

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 (g - 2)/2 (m

Rder, Beate

203

Final warming of the Southern Hemisphere polar vortex in high-and low-  

E-print Network

Final warming of the Southern Hemisphere polar vortex in high- and low- top CMIP5 models 1234567 89­2546, doi:10.1002/jgrd.50254, 2013 Final warming of the Southern Hemisphere polar vortex in high- and low; accepted 06 February 2013; published 25 March 2013. [1] The final warming date of the polar vortex is a key

Wirosoetisno, Djoko

204

Final warming of the Southern Hemisphere polar vortex in high-and low-  

E-print Network

Final warming of the Southern Hemisphere polar vortex in high- and low- top CMIP5 models 1234567 warming of the Southern Hemisphere polar1 vortex in high- and low-top CMIP5 models2 L. J. Wilcox and A. JBB, UK5 Abstract6 The final warming date of the polar vortex is a key component of7 Southern

Wirosoetisno, Djoko

205

Highly specialized microbial diversity in hyper-arid polar desert  

PubMed Central

The McMurdo Dry Valleys in Antarctica are a cold hyperarid polar desert that present extreme challenges to life. Here, we report a culture-independent survey of multidomain microbial biodiversity in McKelvey Valley, a pristine example of the coldest desert on Earth. We demonstrate that life has adapted to form highly-specialized communities in distinct lithic niches occurring concomitantly within this terrain. Endoliths and chasmoliths in sandstone displayed greatest diversity, whereas soil was relatively depauperate and lacked a significant photoautotrophic component, apart from isolated islands of hypolithic cyanobacterial colonization on quartz rocks in soil contact. Communities supported previously unreported polar bacteria and fungi, but archaea were absent from all niches. Lithic community structure did not vary significantly on a landscape scale and stochastic moisture input due to snowmelt resulted in increases in colonization frequency without significantly affecting diversity. The findings show that biodiversity near the cold-arid limit for life is more complex than previously appreciated, but communities lack variability probably due to the high selective pressures of this extreme environment. PMID:19850879

Pointing, Stephen B.; Chan, Yuki; Lacap, Donnabella C.; Lau, Maggie C. Y.; Jurgens, Joel A.; Farrell, Roberta L.

2009-01-01

206

Highly specialized microbial diversity in hyper-arid polar desert.  

PubMed

The McMurdo Dry Valleys in Antarctica are a cold hyperarid polar desert that present extreme challenges to life. Here, we report a culture-independent survey of multidomain microbial biodiversity in McKelvey Valley, a pristine example of the coldest desert on Earth. We demonstrate that life has adapted to form highly-specialized communities in distinct lithic niches occurring concomitantly within this terrain. Endoliths and chasmoliths in sandstone displayed greatest diversity, whereas soil was relatively depauperate and lacked a significant photoautotrophic component, apart from isolated islands of hypolithic cyanobacterial colonization on quartz rocks in soil contact. Communities supported previously unreported polar bacteria and fungi, but archaea were absent from all niches. Lithic community structure did not vary significantly on a landscape scale and stochastic moisture input due to snowmelt resulted in increases in colonization frequency without significantly affecting diversity. The findings show that biodiversity near the cold-arid limit for life is more complex than previously appreciated, but communities lack variability probably due to the high selective pressures of this extreme environment. PMID:19850879

Pointing, Stephen B; Chan, Yuki; Lacap, Donnabella C; Lau, Maggie C Y; Jurgens, Joel A; Farrell, Roberta L

2009-11-24

207

Global dust storms and highly polarizing clouds on Mars.  

NASA Astrophysics Data System (ADS)

The paper reviews our results about photometric ground-based observations of Mars during its great opposition of 1971 and near-perihelion oppositions of 1973 and 1975, as well as polarimetric observations of Mars with the Hubble Space Telescope (HST) at the time ofthe great opposition of 2003. The photometric observations cover long-term (1-3 months) disk-integrated and disk-resolved photometry of Mars during three global dust storms in 1971, 1973 and 1975, including the stages of development, maximum, and attenuation of the dust storms. Using data which showed anomalous changes of Martian brightness, the parameters of dust particles and dust storm as a whole were determined. These include the mean radius and single-scattering albedo of particles, the optical thickness of atmosphere in the maximum of a dust storm and the total mass of dust lifted up in atmosphere, and the temperature pulldown of Martian surface caused by dust storm. Polarimetric observations of Mars with HST revealed for the first time optically thin clouds made of highly polarizing scatterers in UV (330 nm). Analysis of HST data and their comparison with theoretical models allowed us to conclude that the Martian highly polarizing clouds can be formed in the very beginning of the nucleation of H2O ice crystals on submicron dust. Measurements of cloud dynamics has suggested the clouds to be located at 30-40 km above the Martian surface and migrate with velocity of 40-100 m/s.

Lupishko, D.; Kaydash, V.; Shkuratov, Yu

208

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

209

Spectroscopic and dynamical studies of highly energized small polyatomic molecules  

SciTech Connect

The formyl radical and the acetylene molecule were chosen for these studies. The visible and fluorescence spectra of the formyl radical were recorded, and the spectral results are used as a basis to explain the electronic structure. Optical-optical double resonance studies of acetylene were recorded, and the spectral results are interpreted. The results of Zeeman and Stark anticrossing and quantum beat studies of acetylene are reported, and they provide an unusually detailed view of both Intersystem Crossing and Internal Conversion in small polyatomic molecules. 22 references are cited as resulting from Department of Energy sponsorship of this project.

Field, R.W.; Silbey, R.J.

1990-01-01

210

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

2014-12-01

211

Dynamic nuclear polarization of high-density atomic hydrogen in solid mixtures of molecular hydrogen isotopes.  

PubMed

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 ?310(19)??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 2.610(21)??cm(-3). This opens up a way to build a metallic state of atomic hydrogen at zero pressure. PMID:25615349

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

2014-12-31

212

The synchrotron continuum of the highly polarized quasar PKS 1546+027  

NASA Technical Reports Server (NTRS)

The wavelength dependence of optical linear polarization of the highly polarized quasar (HPQ) PKS 1546+027 is investigated for the first time. Both spectropolarimetry and broad-band filter polarimetry are presented for a period when the object was undergoing a strong ourburst in flux and polarization. The rapid polarization variations observed argues that an optically thin synchrotron-emitting region, similar in polarization properties to BL Lacertae objects and optically violent variable (OVV) quasars, is the major source of polarized flux from this object. The continuum polarization increases dramatically with wavelength and is about twice as high at 8000 A than at 4000 A. Spectropolarimetry reveals that the emission-line flux from PKS 1546+027 dilutes the continuum polarization and is probably unpolarized. There is no evidence for any variation in polarization position angle with wavelength. The polarized flux spectrum is well-represented by a steep power law with a spectral index of -2.2, supporting the view that the polarized flux has a nonthermal origin. The observed polarization properties of PKS 1546+027 are consistent with a model that has been proposed to explain the optical to ultraviolet continua of several OVVs. In this model the optical to near-UV spectral flux distribution is a combination of light from a polarized synchrotron component plus an unpolarized component with spectral properties typical of low-polarization quasars.

Smith, Paul S.; Schmidt, Gary D.; Jannuzi, Buell T.; Elston, Richard

1994-01-01

213

Vibrationally highly excited molecules and intramolecular mode coupling through high-overtone spectroscopy  

SciTech Connect

High overtone spectra of organic molecules can be interpreted using the local mode model for absorptions by the inequivalent C-H bonds. The spectra can be assigned using either observed C-H bond lengths or isolated fundamental frequencies. The spectra of trihalomethanes indicate that the dominant intramolecular mode coupling for the C-H stretching overtones is Fermi resonance with combination states with one less C-H stretching quantum plus two quanta of the C-H bending vibrations.

Wong, J.S.; Moore, C.B.

1981-08-01

214

Encoding high-order cylindrically polarized light beams.  

PubMed

In this work we present a setup for the experimental production of cylindrically polarized beams, as well as other variations of polarized light beams. The optical system uses a single transmissive phase-only spatial light modulator, which is used to apply different spatial phase modulation to two output collinear R and L circularly polarized components. Different cylindrically polarized light beams can be obtained by applying different phase shifts to these two circularly polarized components. The system is very efficient since modulation is directly applied to the light beam (as opposed to other common methods operating in the first order of encoded diffraction gratings). Different variations to the cylindrically polarized light beams are also reported, obtained by adding linear or quadratic relative phase shifts between the two circular polarization components of the light beam. Experimental results are provided in all cases. PMID:25321124

Moreno, Ignacio; Davis, Jeffrey A; Cottrell, Don M; Donoso, Ramiro

2014-08-20

215

High-Fidelity, Weak-Light Polarization Gate Using Room-Temperature Atomic Vapor  

NASA Astrophysics Data System (ADS)

Using a polarization-selective-Kerr-phase-shift technique we demonstrate a fast, all-optical, high-fidelity polarization gate in a room-temperature atomic medium. By writing a ?-phase shift to one selected circularly-polarized component of a linearly-polarized input signal field and by equalizing the gain of both circularly-polarized components we can maintain the original strength of the signal field and yet achieve a perfect 90 rotation of its linear polarization, demonstrating a fast, high-fidelity, dynamically-controlled polarization gate operation. The orthogonal linear polarization switching field intensity can be as low as 2 mW/cm2 using a warm rubidium vapor, which is equivalent to a 100-nanosecond pulse containing about 200 photons and confined in a typical commercial photonic hollow-core fiber with a 5-?m mode diameter.

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

2015-03-01

216

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

E-print Network

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

Zanibbi, Richard

217

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

218

Chiral molecular films as electron polarizers and polarization modulators  

NASA Astrophysics Data System (ADS)

Recent experiments on electron scattering through molecular films have shown that chiral molecules can be efficient sources of polarized electrons even in the absence of heavy nuclei as source of a strong spin-orbit interaction. We show that self-assembled monolayers (SAMs) of chiral molecules are strong electron polarizers due to the high-density effect of the monolayers and explicitly compute the scattering amplitude off a helical molecular model of carbon atoms. Longitudinal polarization is shown to be the signature of chiral scattering. For elastic scattering, we find that at least double-scattering events must take place for longitudinal polarization to arise. We predict energy windows for strong polarization, determined by the energy dependences of spin-orbit strength and multiple scattering probability. An incoherent mechanism for polarization amplification is proposed, that increases the polarization linearly with the number of helix turns, consistent with recent experiments on DNA SAMs.

Medina, Ernesto; Lpez, Floralba; Ratner, Mark A.; Mujica, Vladimiro

2012-07-01

219

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

E-print Network

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

Byer, Robert L.

220

High-throughput single-molecule studies of protein-DNA interactions.  

PubMed

Fluorescence and force-based single-molecule studies of protein-nucleic acid interactions continue to shed critical insights into many aspects of DNA and RNA processing. As single-molecule assays are inherently low-throughput, obtaining statistically relevant datasets remains a major challenge. Additionally, most fluorescence-based single-molecule particle-tracking assays are limited to observing fluorescent proteins that are in the low-nanomolar range, as spurious background signals predominate at higher fluorophore concentrations. These technical limitations have traditionally limited the types of questions that could be addressed via single-molecule methods. In this review, we describe new approaches for high-throughput and high-concentration single-molecule biochemical studies. We conclude with a discussion of outstanding challenges for the single-molecule biologist and how these challenges can be tackled to further approach the biochemical complexity of the cell. PMID:24859086

Robison, Aaron D; Finkelstein, Ilya J

2014-10-01

221

Silicene as a highly sensitive molecule sensor for NH3, NO and NO2.  

PubMed

On the basis of first-principles calculations, we demonstrate the potential application of silicene as a highly sensitive molecule sensor for NH3, NO, and NO2 molecules. NH3, NO and NO2 molecules chemically adsorb on silicene via strong chemical bonds. With distinct charge transfer from silicene to molecules, silicene and chemisorbed molecules form charge-transfer complexes. The adsorption energy and charge transfer in NO2-adsorbed silicene are larger than those of NH3- and NO-adsorbed silicones. Depending on the adsorbate types and concentrations, the silicene-based charge-transfer complexes exhibit versatile electronic properties with tunable band gap opening at the Dirac point of silicene. The calculated charge carrier concentrations of NO2-chemisorbed silicene are 3 orders of magnitude larger than intrinsic charge carrier concentration of graphene at room temperature. The results present a great potential of silicene for application as a highly sensitive molecule sensor. PMID:24595614

Hu, Wei; Xia, Nan; Wu, Xiaojun; Li, Zhenyu; Yang, Jinlong

2014-04-21

222

From a Molecule to a Micelle: Small Angle Neutron Scattering Study of a Perfluoro Ionomer in Polar Solvents  

NASA Astrophysics Data System (ADS)

The solution structure of perfluorosulfonimide ionomer has been investigated using small angle neutron scattering (SANS). The significance of this ionomer lies in its high potential as proton Exchange membrane for fuel cells. In polar solvents, the hydrophobicity of the fluorinated backbone drives aggregation. SANS measurements have been carried out as a function of the concentration of the ionomer, temperature as well as ionic strength. With increasing concentration, a clear transition from a molecular form factor to micellar one has been observed. Above the critical micelle concentration (CMC), SANS data revealed cylindrical aggregates. Bellow the CMC, it corresponds to a Gaussian chain. This expended configuration is intriguing since the density of the polar groups is rather low and in poor solvent one would expect a collapsed chain. The micelles were found to be extremely stable and did not brake up with increasing temperature. The radius of the micelle did not change much as a function of temperature or ionic strength. Increasing the salt concentration resulted in a significant increase in the length of the micelle. Further studies are currently underway way to discern the factors, which affect the shape and stability of these micelles.

Jiao, Xuesong; Thomas, Brian; Desmartaue, Darryl D.; Perahia, Dvora; Lal, Jyotsna

2001-03-01

223

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

224

An all-small-molecule organic solar cell with high efficiency nonfullerene acceptor.  

PubMed

An efficient bulk heterojunction all-small-molecule organic solar cell composed of a high-performance small-molecule donor and a self-assembling nonfullerene acceptor is demonstrated. Favorable nanoscale phase separation and enhanced charge carrier generation with transport in this donor-acceptor system assures a maximum power conversion efficiency of 5.4%. PMID:25655948

Kwon, Oh Kyu; Park, Jung-Hwa; Kim, Dong Won; Park, Sang Kyu; Park, Soo Young

2015-03-01

225

THE ACCURACY OF PRESENT MODELS OF THE HIGH ALTITUDE POLAR MAGNETOSPHERE  

E-print Network

THE ACCURACY OF PRESENT MODELS OF THE HIGH ALTITUDE POLAR MAGNETOSPHERE C. T. Russell1 , J. G of Alberta, Canada ABSTRACT The Polar satellite has explored the high-latitude, high-altitude magnetosphere of the magnetic field in the surrounding region. Near the cusp the magnetosphere is quite sensitive to solar wind

Russell, Christopher T.

226

Large, accessible, highly polarized frozen-spin solid HD targets  

NASA Astrophysics Data System (ADS)

New advances in frozen-spin polarized solid HD make practical the use of large targets of independently polarizable H and D for experiments in fusion, photonuclear and particle physics. Long polarization-retention times of about a year at 1.5 K and 7.5 Tesla allow multiple target production and long term storage in economical cryostats, for off-the-shelf availability of polarized HD material and targets. Polarization-retention times at sub-Tesla fields, which exceed a week, provide a fair match between polarization-production time and target-utilization time in moderate fields, for weakly ionizing beam fluxes in which radiation damage to the target is small. Because of the convenient 1.5-4 K frozen-spin temperature range, cold-transfer (4 K) portable apparatuses, which have already been constructed and used, can move the targets readily from polarization-production systems to storage or in-beam cryostats with negligible polarization loss. This permits total separation of polarization-production and target-utilization apparatuses, and the possibility of assembling very large targets.

Honig, A.; Fan, Q.; Wei, X.; Rigney, M.; Sandorfi, A. M.; Whisnant, C. S.

1995-09-01

227

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

E-print Network

for the future deuteron Electron Dipole Moment (EDM) experiment, and the 3 He++ ion beam is a part of the experimental program for the future eRHIC (Relativistic Electron-Heavy Ion) collider. INTRODUCTION Polarized.8 ~ 3.0 keV energy, which is converted to electron-spin polarized H atoms by electron pick

228

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 kp 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

229

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

230

Fast polarization switching panel with high brightness and contrast ratio for three-dimensional display  

NASA Astrophysics Data System (ADS)

We propose a polarization switching device using optically compensated pi cell for polarization-glass-type three-dimensional display. This device shows good optical properties such as high transmittance and low cross-talk ratio because of its fast dynamic response characteristics. To improve the brightness and contrast ratio on the right- and left-hand sides, we attach optical retardation films on each side of the polarization glasses instead of attaching the films on the polarization switching panel. From the calculation and experiment, we obtain high contrast ratios, over 200:1, on both sides and a high brightness using only one film on each side.

Shin, Hun Ki; Lee, Joong Ha; Kim, Jung-Wook; Yoon, Tae-Hoon; Kim, Jae Chang

2011-02-01

231

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

Microsoft Academic Search

We show that strongly polarized very-high-n (600) potassium Rydberg atoms can be produced by manipulating lower-n (350) polarized atoms using a tailored sequence of ultrashort half-cycle pulses (HCPs). The protocol for this involves first a weak HCP that generates transient phase-space localization whereupon a second large HCP of opposite polarity excites the electron to a broad distribution of highly elongated

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

2005-01-01

232

Polarization Transfer in Proton Compton Scattering at High Momentum Transfer  

SciTech Connect

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

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

2005-06-24

233

LD-pumped all-solid-stated green laser with high polarization rate and high conversion efficiency  

Microsoft Academic Search

A high-power-output and high polarization rate Nd:YVO4\\/KTP green laser has been presented. By analyzing the factors which affect the conversion efficiency and polarization rate, we used a short folded-cavity resonator, the maximum output power of 320 mW is obtained at 532 nm with the LD pumping power of 1 W, the optical-to-optical conversion efficiency is 32% and the polarization rate

Er-juan Hao; Hui-ming Tan; Chang-ling Yan; Long-sheng Qian

2005-01-01

234

Highly anisotropic metasurface: a polarized beam splitter and hologram  

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

235

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

236

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

PubMed

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

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

2011-02-28

237

Absolute S- and P-plane polarization efficiencies for high frequency holographic gratings in the VUV  

NASA Technical Reports Server (NTRS)

High frequency plane gratings (3500 and 3600 gr/mm) have been holographically ruled and blazed for the VUV spectral region. All gratings were coated with 70 nm Al + 25 nm MgF2. Absolute unpolarized and S- and P-plane polarization efficiencies have been measured for the first and second orders in the 120- to 450-nm spectral region at 18.5 and 30 deg angles of deviation. For deep grooves, anomalous features are more pronounced for the P-plane polarization efficiency than for the S-plane polarization efficiency. Holographic gratings can be tailored to produce high polarization or low polarization in the VUV. For comparison, efficiencies and polarization of the best conventional high frequency gratings were also determined. Measurements show that scattered light is significantly lower for holographic gratings in the VUV when compared with the conventional gratings.

Caruso, A. J.; Woodgate, B. E.; Mount, G. H.

1981-01-01

238

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

239

Development of a Fluorescence Polarization Based High-Throughput Assay to Identify Casitas B-Lineage Lymphoma RING Domain Regulators  

PubMed Central

The E3 ubiquitin protein ligase Casitas B-lineage Lymphoma (Cbl) proteins and their binding partners play an important role in regulating signal transduction pathways. It is important to utilize regulators to study the protein-protein interactions (PPIs) between these proteins. However, finding specific small-molecule regulators of PPIs remains a significant challenge due to the fact that the interfaces involved in PPIs are not well suited for effective small molecule binding. We report the development of a competitive, homogeneous, high-throughput fluorescence polarization (FP) assay to identify small molecule regulators of Cbl (RING) domain. The FP assay was used to measure binding affinities and inhibition constants of UbCH7 peptides and small molecule regulators of Cbl (RING) domains, respectively. In order to rule out promiscuous, aggregation-based inhibition, two assay conditions were developed and compared side by side. Under optimized conditions, we screened a 10,000 natural compound library in detergent-free and detergent-present (0.01% Triton X-100) systems. The results indicate that the detergent-present system is more suitable for high-throughput screens. Three potential compounds, methylprotodioscin, leonuride and catalpol, have been identified that bind to Cbl (RING) domain and interfere with the Cbl (RING)-UbCH7 protein-protein interaction. PMID:24205080

Pessetto, Ziyan Yuan; Zhao, Yan; Zang, Zhihe; Zhong, Ling; Wu, Min; Su, Qing; Gao, Xiurong; Zan, Wang; Sun, Yiyi

2013-01-01

240

High-Frequency Dynamic Nuclear Polarization in MAS Spectra of Membrane and Soluble Proteins  

E-print Network

High-Frequency Dynamic Nuclear Polarization in MAS Spectra of Membrane and Soluble Proteins Melanie The success of these experiments is due largely to the ability to record multidimensional MAS NMR spectra this sensitivity problem, we have recently developed high-field dynamic nuclear polarization (DNP) experiments

Griffin, Robert G.

241

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

242

Detailed Studies of a HighDensity Polarized Hydrogen Gas Target for Storage Rings  

E-print Network

Detailed Studies of a High­Density Polarized Hydrogen Gas Target for Storage Rings Kirsten Zapfe 1 (1996) 293 Abstract A high­density target of polarized atomic hydrogen gas for applications in storage rings was produced by injecting atoms from an atomic beam source into a T­shaped storage cell

243

High deuteron polarization in trityl radical doped deuterated polystyrene  

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

244

Charge Exchange Processes for Highly Charged Ion -Atom, Molecule  

E-print Network

for Fusion Science H.A.Sakaue #12;Charge Exchange Processes Highly charged ions (HCI's) exist as an impurity ion in high temperature plasma. Charge exchange cross sections of HCI's are very large (~10-14cm2) Charge Exchange Processes of HCI's are very important for understanding the edge plasma behavior

Princeton Plasma Physics Laboratory

245

Highly circularly polarized electroluminescence from a chiral europium complex.  

PubMed

The first circularly polarized OLED (CP-OLED) based on a chiral lanthanide complex is developed. With a simple architecture, this proof-of-concept device attains the highest polarization reported so far and additionally presents the first example of a Ln-based OLED that can be turned into a CP-OLED, fully retaining the special features of Ln-based OLEDs. PMID:25604886

Zinna, Francesco; Giovanella, Umberto; Bari, Lorenzo Di

2015-03-01

246

Highly Polarized Photoluminescence and Photodetection from Single Indium Phosphide Nanowires  

Microsoft Academic Search

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

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

2001-01-01

247

High-throughput screening of small molecules identifies hepcidin antagonists.  

PubMed

Anemia of inflammation (AI) is common in patients with infection, autoimmune diseases, cancer, and chronic kidney disease. Unless the underlying condition can be reversed, treatment options are limited to erythropoiesis-stimulating agents with or without intravenous iron therapy, modalities that are not always effective and can cause serious adverse effects. Hepcidin, the iron regulatory hormone, has been identified as a pathogenic factor in the development of AI. To explore new therapeutic options for AI and other iron-related disorders caused by hepcidin excess, we developed a cell-based screen to identify hepcidin antagonists. Of the 70,000 small molecules in the library, we identified 14 compounds that antagonized the hepcidin effect on ferroportin. One of these was fursultiamine, a Food and Drug Administration (FDA)-approved thiamine derivative. Fursultiamine directly interfered with hepcidin binding to its receptor, ferroportin, by blocking ferroportin C326 thiol residue essential for hepcidin binding. Consequently, fursultiamine prevented hepcidin-induced ferroportin ubiquitination, endocytosis, and degradation in vitro and allowed continuous cellular iron export despite the presence of hepcidin, with IC(50) in the submicromolar range. Thiamine, the fursultiamine metabolite, and benfotiamine, another thiamine derivative, did not interfere with the effect of hepcidin on ferroportin. Other FDA-approved thiol-reactive compounds were at least 1000-fold less potent than fursultiamine in antagonizing hepcidin. In vivo, fursultiamine did not reproducibly antagonize the effect of hepcidin on serum iron, likely because of its rapid conversion to inactive metabolites. Fursultiamine is a unique antagonist of hepcidin in vitro that could serve as a template for the development of drug candidates that inhibit the hepcidin-ferroportin interaction. PMID:23292796

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

2013-03-01

248

High-Throughput Screening of Small Molecules Identifies Hepcidin Antagonists  

PubMed Central

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

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

2013-01-01

249

N-polar GaN epitaxy and high electron mobility transistors  

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

250

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

251

Highly stable polarization independent Mach-Zehnder interferometer.  

PubMed

We experimentally demonstrate optical Mach-Zehnder interferometer utilizing displaced Sagnac configuration to enhance its phase stability. The interferometer with footprint of 2740 cm offers individually accessible paths and shows phase deviation less than 0.4 during a 250 s long measurement. The phase drift, evaluated by means of Allan deviation, stays below 3 or 7 nm for 1.5 h without any active stabilization. The polarization insensitive design is verified by measuring interference visibility as a function of input polarization. For both interferometer's output ports and all tested polarization states the visibility stays above 93%. The discrepancy in visibility for horizontal and vertical polarization about 3.5% is caused mainly by undesired polarization dependence of splitting ratio of the beam splitter used. The presented interferometer device is suitable for quantum-information and other sensitive applications where active stabilization is complicated and common-mode interferometer is not an option as both the interferometer arms have to be accessible individually. PMID:25173242

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

2014-08-01

252

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.

253

Expression of highly polysialylated neural cell adhesion molecule in calcitonin-producing cells.  

PubMed

Calcitonin-producing cells are endocrine derivatives of the neural crest and have several neuron-like properties. Expression of the neural cell adhesion molecule in calcitonin-producing cells was examined using two types of antibodies to neural cell adhesion molecule: monoclonal antibody 12E3 recognizes the polysialic acid portion of highly polysialylated neural cell adhesion molecule, and monoclonal antibody AF11 and polyclonal antiserum react with the polypeptide portion common to three major isoforms of neural cell adhesion molecule. An immunohistochemical study revealed that highly polysialylated neural cell adhesion molecule was expressed both in fetal rat thyroidal calcitonin-producing cells and in a calcitonin-producing cell line, rMTC 6-23, established from explantable neoplasm of rat calcitonin-producing cells. The neural cell adhesion molecule in the rMTC 6-23 cells was further characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblot analysis. Two anti-neural cell adhesion molecule monoclonal antibodies, 12E3 and AF11, revealed a broad positive band around 200,000-250,000 mol. wt in solubilized proteins. When the polysialic acids were eliminated by neuraminidase treatment, the immunoreactivity to monoclonal antibody 12E3 was completely abolished, and core polypeptide corresponding to neural cell adhesion molecule with a molecular weight of 120,000 was detected by monoclonal antibody AF11. These results suggest that cells of the calcitonin-producing cell line express on their surfaces highly polysialylated 120,000 mol. wt form of neural cell adhesion molecule polypeptide. PMID:8255434

Nishiyama, I; Seki, T; Oota, T; Ohta, M; Ogiso, M

1993-10-01

254

Observation of New Dynamics in the State-Resolved Collisional Relaxation of Highly Excited Molecules  

NASA Astrophysics Data System (ADS)

The dynamics of collisional deactivation of highly energized molecules, pyrazine-h_{4} and pyrazine-d_{4}, by HCl molecules at 300 K show evidence of a new mechanism for collisional energy transfer. Highly vibrationally excited (E_{vib} = 37,900 wn) pyrazine-h_{4} and pyrazine-d_{4} molecules are produced in separate experiments by pulsed excitation with the fourth harmonic output of a Nd:YAG laser at ? = 266 nm. Collisions between the energized isotopes and HCl molecules are monitored by measuring the nascent transient IR absorption of scattered HCl in individual rotational states. The results indicate that HCl molecules are scattered with a gain in rotational and translational energy, but the largest recoil energies are observed for the lowest rotational energy states of HCl. This behavior is opposite to that seen for other bath molecules including DCl and CO_{2}. The results point to differences in intermolecular interactions between the energy donor and acceptor molecules as contributing factors to the observed differences in the mechanism of energy transfer.

Echebiri, Geraldine O.; Smarte, Matthew; Walters, Wendell W.; Cleveland, Jill M.; McCarl, Christine; Kunin, Alice; Mullin, Amy S.

2013-06-01

255

Ultra high-throughput single molecule spectroscopy with a 1024 pixel SPAD  

PubMed Central

Single-molecule spectroscopy is a powerful approach to measuring molecular properties such as size, brightness, conformation, and binding constants. Due to the low concentrations in the single-molecule regime, measurements with good statistical accuracy require long acquisition times. Previously we showed a factor of 8 improvement in acquisition speed using a custom-CMOS 8x1 SPAD array. Here we present preliminary results with a 64X improvement in throughput obtained using a liquid crystal on silicon spatial light modulator (LCOS-SLM) and a novel standard CMOS 1024 pixel SPAD array, opening the way to truly high-throughput single-molecule spectroscopy. PMID:24386535

Colyer, Ryan A.; Scalia, Giuseppe; Villa, Federica A.; Guerrieri, Fabrizio; Tisa, Simone; Zappa, Franco; Cova, Sergio; Weiss, Shimon; Michalet, Xavier

2013-01-01

256

Notch Signaling Molecules Activate TGF- ? in Rat Mesangial Cells under High Glucose Conditions.  

PubMed

The involvement of the Notch signaling pathway in the cellular differentiation of the mammalian kidney is established. Recently, the dysregulation of Notch signaling molecules has been identified in acute and chronic renal injuries, fibrosis models, and diabetic kidney biopsies. The canonical Notch ligand , Jagged1, is upregulated in a transforming growth factor-beta- (TGF- ? -) dependent manner during chronic kidney disease. TGF- ? , a central mediator of renal fibrosis, also is a major contributor to the development of diabetic nephropathy. To explore the roles and possible mechanisms of Notch signaling molecules in the pathogenesis of diabetic nephropathy, we exposed cultured rat mesangial cells to a ? -secretase inhibitor (DAPT) or high glucose and measured the expression of Notch signaling molecules and the fibrosis index. Notch pathway-related molecules, TGF- ? , and fibronectin increased with exposure to high glucose and decreased with DAPT treatment. Our results suggest that the Notch signaling pathway may precipitate diabetic nephropathy via TGF- ? activation. PMID:23691527

Liu, Li; Gao, Chenlin; Chen, Guo; Li, Xia; Li, Jia; Wan, Qin; Xu, Yong

2013-01-01

257

Tracing the structure of asymmetric molecules from high-order harmonic generation  

SciTech Connect

We investigate high-order harmonic generation (HHG) from asymmetric molecules exposed to intense laser fields. We show that the emissions of odd and even harmonics depend differently on the orientation angle, the internuclear distance, as well as the effective charge. This difference mainly comes from different roles of intramolecular interference in the HHG of odd and even harmonics. These roles map the structure of the asymmetric molecule to the odd vs even HHG spectra.

Chen Yanjun [Beijing Computational Science Research Center, Beijing (China); Zhang, Bing [Department of Physics, Harbin Institute of Technology, Harbin (China)

2011-11-15

258

A new theoretical foundation for the polarized-oriented multilayer theory of cell water and for inanimate systems demonstrating long-range dynamic structuring of water molecules.  

PubMed

Over the centuries, a vast amount of evidence has been gathering that layers of water sometimes measuring tens of thousands of water molecules thick exhibit altered properties in consequence of exposure to some solid surfaces. Yet, a clear cut theory based on the laws of physics that would predict this kind of long range dynamic ordering of water molecules has been long missing. It is thus with great joy that I announce that a new theory has been developed, which offers theoretical confirmation of the phenomena of long-range dynamic structuring of water by appropriate solid surfaces and which gives clear cut quantitative answers to some key questions about the phenomenon. Thus, for example, under an ideal condition, an idealized checkerboard of alternatingly positively-, and negatively-charged sites of the correct size and distribution could polarize and orient deep layers of water molecules ad infinitum. Based on the quantitative data thus obtained and a relevant simple statistical mechanical law, the new theory predicts that a thin layer of water held between two juxtaposed ideal or near-ideal NP surfaces will not freeze at any (attainable) temperature. On the other hand, water polarized and oriented by an ideal or near-ideal NP-NP system may also not evaporate at temperature hundreds of degrees higher than the normal boiling temperature of water. Both predictions have been confirmed (retroactively) by experimental observations made in the past, accidentally or by design. In a following paper, I will demonstrate that the conclusion reached from the study of the two-dimensional NP surface can be smoothly passed on to the living cells. In the living cell, only one-dimensional linear chains of fully extended protein chains exist. Nonetheless, by proper orientation and distribution, they can achieve similar though less intense water polarization-orientation--as experimentally demonstrated worldwide during the 40 years past. PMID:15552723

Ling, Gilbert N

2003-01-01

259

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

260

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 1000Hz. 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 15nm and showed restricted diffusion at an inner barrier found at 170 10nm. At the shortest length-scales (<170nm), 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, BarryL.; Ritchie, Ken

2014-01-01

261

A Gaussian Beam Method for High Frequency Solution of Symmetric Hyperbolic Systems with Polarized Waves  

E-print Network

A Gaussian Beam Method for High Frequency Solution of Symmetric Hyperbolic Systems with Polarized wave equations and the acoustic equations [26]. In this paper we extend the Gaussian beam method to polarized waves, in which the dispersion matrix of the hyperbolic system has eigenvalues with constant

Jin, Shi

262

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

E-print Network

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

Dietz, Nikolaus

263

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

264

Laser mass spectrometry with circularly polarized light: circular dichroism of cold molecules in a supersonic gas beam.  

PubMed

An experiment on chiral molecules that combines circular dichroism (CD) spectroscopy, mass-selective detection by laser mass spectrometry (MS), and cooling of molecules by using a supersonic beam is presented. The combination of the former two techniques (CD-laser-MS) is a new method to investigate chiral molecules and is now used by several research groups. Cooling in a supersonic beam supplies a substantial increase in spectroscopic resolution, a feature that has not yet been used in CD spectroscopy. In the experiments reported herein, a large variation in the electronic CD of carbonyl 3-methylcyclopentanone was observed depending on the excited vibrational modes in the n ? ?* transition. This finding should be of interest for the detection of chiral molecules and for the theoretical understanding of the CD of vibronic bands. It is expected that this effect will show up in other chiral carbonyls because the n ? ?* transition is typical for the carbonyl group. PMID:25044352

Titze, Katharina; Zollitsch, Tilo; Heiz, Ulrich; Boesl, Ulrich

2014-09-15

265

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

266

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

PubMed Central

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

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

2015-01-01

267

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

268

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

269

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

270

Single molecule investigations of DNA looping using the tethered particle method and translocation by acto-myosin using polarized total internal reflection fluorescence microscopy  

NASA Astrophysics Data System (ADS)

Single molecule biophysics aims to understand biological processes by studying them at the single molecule level in real time. The proteins and nucleic acids under investigation typically exist in an aqueous environment within ten degrees of room temperature. These seemingly benign conditions are actually quite chaotic at the nanoscale, where single bio-molecules perform their function. As a result, sensitive experiments and statistical analyses are required to separate the weak single molecule signal from its background. Protein-DNA interactions were investigated by monitoring DNA looping events in tethered particle experiments. A new analysis technique, called the Diffusive hidden Markov method, was developed to extract kinetic rate constants from experimental data without any filtering of the raw data; a common step that improves the signal to noise ratio, but at the expense of lower time resolution. In the second system, translocation of the molecular motor myosin along its actin filament track was studied using polarized total internal reflection (polTIRF) microscopy, a technique that determines the orientation and wobble of a single fluorophore attached to the bio-molecule of interest. The range of resolvable angles was increased 4-fold to include a hemisphere of possible orientations. As a result, the handedness of actin filament twirling as it translocated along a myosin-coated surface was determined to be left-handed. The maximum time resolution of a polTIRF setup was increased 50-fold, in part by recording the arrival times and polarization state of single photons using a modified time-correlated single photon counting device. A new analysis, the Multiple Intensity Change Point algorithm, was developed to detect changes in molecular orientation and wobble using the raw time-stamped data with no user-defined bins or thresholds. The analysis objectively identified changes in the orientation of a bifunctional-rhodamine labeled calmodulin that was attached to a myosin V molecule translocating along an actin filament. Long intervals corresponding to stable positions between tilting motions of the lever arm during each step were routinely observed. Substeps in the cycle that preceded these long dwells were measured, but only occasionally most likely because of the low number of photons detected during these rapid events.

Beausang, John F.

271

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

E-print Network

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

Boyer, Edmond

272

High Energy Proton Ejection from Hydrocarbon Molecules Driven by Highly Efficient Field Ionization  

Microsoft Academic Search

We investigated the ejection of energetic protons from a series of polyatomic hydrocarbon molecules exposed to 790 nm 27 fs laser pulses. Using multiparticle coincidence imaging we were able to decompose the observed proton energy spectra into the contributions of individual fragmentation channels. It is shown that the molecules can completely fragment already at relatively low peak intensities of a

Stefan Roither; Xinhua Xie; Daniil Kartashov; Li Zhang; Markus Schffler; Huailiang Xu; Atsushi Iwasaki; Tomoya Okino; Kaoru Yamanouchi; Andrius Baltuska; Markus Kitzler

2011-01-01

273

Spin-Polarized to Valley-Polarized Transition in Graphene Bilayers at ?=0 in High Magnetic Fields  

NASA Astrophysics Data System (ADS)

We investigate the transverse electric field (E) dependence of the ?=0 quantum Hall state (QHS) in dual-gated graphene bilayers in high magnetic fields. The longitudinal resistivity ?xx measured at ?=0 shows an insulating behavior which is strongest in the vicinity of E=0, as well as at large E fields. At a fixed perpendicular magnetic field (B), the ?=0 QHS undergoes a transition as a function of the applied E, marked by a minimum, temperature-independent ?xx. This observation is explained by a transition from a spin-polarized ?=0 QHS at small E fields to a valley- (layer-)polarized ?=0 QHS at large E fields. The E field value at which the transition occurs follows a linear dependence on B.

Kim, Seyoung; Lee, Kayoung; Tutuc, E.

2011-07-01

274

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

Microsoft Academic Search

Solvent effects were studied and described via molecular dynamics (MD) and free energy perturbation (FEP) simulations using the molecular mechanics program AMBER. The following specific topics were explored:. Polar solvents cause a blue shift of the rm nto pi^* transition band of simple alkyl carbonyl compounds. The ground- versus excited-state solvation effects responsible for the observed solvatochromism are described in

Stephen Edward Debolt

1993-01-01

275

Effect of Sugar Molecules on the Viscosity of High Concentration Monoclonal Antibody Solutions  

Microsoft Academic Search

PurposeTo assess the effect of sugar molecules on solution viscosity at high protein concentrations.\\u000a \\u000a \\u000a \\u000a MethodsA high throughput dynamic light scattering method was used to measure the viscosity of monoclonal antibody solutions. The\\u000a effects of protein concentration, type of sugar molecule (trehalose, sucrose, sorbitol, glucose, fructose, xylose and galactose),\\u000a temperature and ionic strength were evaluated. Differential scanning fluorimetry was used to

Feng He; Christopher E. Woods; Jennifer R. Litowski; Lauren A. Roschen; Himanshu S. Gadgil; Vladimir I. Razinkov; Bruce A. Kerwin

2011-01-01

276

Molecules in QSOs and QSO Absorption Line Systems at High Redshift  

E-print Network

Molecules dominate the cooling function of neutral metal-poor gas at high density. Observation of molecules at high redshift is thus an important tool toward understanding the physical conditions prevailing in collapsing gas. Up to now, detections are sparse because of small filling factor and/or sensitivity limitations. However, we are at an exciting time where new capabilities offer the propect of a systematic search either in absorption using the UV Lyman-Werner H2 bands or in emission using the CO emission lines redshifted in the sub-millimeter.

Patrick Petitjean

1998-04-24

277

Solution-processed small molecules using different electron linkers for high-performance solar cells.  

PubMed

Conjugated acceptor-donor-acceptor small molecules using different electron linkers are designed, synthesized, and used in organic solar cells. All of these small molecules show high photoconversion efficiencies (PCEs), ranging from 3.18-6.15% under simulated AM 1.5G condition. A maximum PCE of 6.15% combined with a high Voc of 0.85 V, a Jsc of 10.79 mA cm(-2) and a notable FF of 67.1% are achieved with T3/PC71 BM blend based devices using polydimethylsiloxane as additive. PMID:23824701

Liu, Yongsheng; Yang, Yang Michael; Chen, Chun-Chao; Chen, Qi; Dou, Letian; Hong, Ziruo; Li, Gang; Yang, Yang

2013-09-01

278

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

SciTech Connect

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

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

2005-12-01

279

Solvent involved self-crystallization of C70 molecules into high definition cube microstructure  

NASA Astrophysics Data System (ADS)

C70 molecules dissolved in mesitylene (good solvent) are self-crystallized into cube shape microstructure by the addition of isopropyl alcohol (poor solvent). Through control experiments attempted with different types of alcohols as well as in the replacement of mesitylene with other similar solvents, such as toluene, m-xylene, and m-dichlorobenzene, it is confirmed that mesitylene plays a critical role to guide C70 molecules to form cube microcrystal with high definition edges and surfaces. Thermal gravimetric and crystallographic analyses show that the crystal structure is simple cubic whose unit cell is composed of one C70 and two mesitylene molecules. The photoluminescence intensity from C70 cube crystals are enormously increased compared to C70 powder. Such abnormal photoluminescence increase is mainly attributed to the high crystallinity of C70 cubes as confirmed by time-resolved photoluminescence lifetime measurements.

Park, Chibeom; Cheul Choi, Hee

2011-03-01

280

Thermal deposition of intact tetrairon(III) single-molecule magnets in high-vacuum conditions.  

PubMed

A tetrairon(III) single-molecule magnet is deposited using a thermal evaporation technique in high vacuum. The chemical integrity is demonstrated by time-of-flight secondary ion mass spectrometry on a film deposited on Al foil, while superconducting quantum interference device magnetometry and alternating current susceptometry of a film deposited on a kapton substrate show magnetic properties identical to the pristine powder. High-frequency electron paramagnetic resonance spectra confirm the characteristic behavior for a system with S = 5 and a large Ising-type magnetic anisotropy. All these results indicate that the molecules are not damaged during the deposition procedure keeping intact the single-molecule magnet behavior. PMID:19283797

Margheriti, Ludovica; Mannini, Matteo; Sorace, Lorenzo; Gorini, Lapo; Gatteschi, Dante; Caneschi, Andrea; Chiappe, Daniele; Moroni, Riccardo; de Mongeot, Francesco Buatier; Cornia, Andrea; Piras, Federica M; Magnani, Agnese; Sessoli, Roberta

2009-06-01

281

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

SciTech Connect

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

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

2010-06-15

282

High-efficiency generation of circularly polarized light via symmetry-induced anomalous reflection  

NASA Astrophysics Data System (ADS)

Great efforts have been devoted to control the polarization state, the transmission direction, and the phase of light within a very confined space in recent decades. Here, we present a two-dimensional metastructure made of an array of unisized split rings with different opening orientations on the surface of a Si O2 -silver bilayer. This structure possesses an unexpectedly high polarization conversion ratio and generates significantly strong anomalous reflection beams (over 70% of incident light intensity) over a broad frequency range (1100-1750 nm). Functionally, it is able to turn either a linearly polarized incident light or natural light into two perfect circularly polarized beams with the same amplitude yet different handedness to different directions. These features demonstrate a clear example of momentum conservation and can be applied to detect/manipulate the propagation of circularly polarized light.

Jiang, Shang-Chi; Xiong, Xiang; Hu, Yuan-Sheng; Jiang, Sheng-Wei; Hu, Yu-Hui; Xu, Di-Hu; Peng, Ru-Wen; Wang, Mu

2015-03-01

283

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

284

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 alkyneazide cycloaddition reaction. Excess terminal alkynes were covalently attached to the probe, and a bi-functional molecule containing an azide at one end and a carboxylic acid at the other was dissolved in the reaction solution. By simply contacting the probe and the Cu substrate, controlled carboxylation on the probe apex could be achieved, since the click reaction requires the co-exist of alkyne, azide and Cu(I). The finite contact area would result in a highly defined surface functionality of the probe down to single molecule level with high reproducibility. PMID:25551040

Khanal, Ashok

2014-01-01

285

The Polar Vegetation Photosynthesis and Respiration Model (PolarVPRM): a parsimonious, satellite data-driven model of high-latitude CO2 exchange  

NASA Astrophysics Data System (ADS)

We introduce the Polar Vegetation Photosynthesis and Respiration Model (PolarVPRM), a remote-sensing based approach for generating accurate, high resolution (?1 km2, three-hourly) estimates of net ecosystem CO2 exchange (NEE). PolarVPRM simulates NEE using polar-specific vegetation classes, and by representing high-latitude influences on NEE. We present a description, validation, and error analysis (first-order Taylor expansion) of PolarVPRM, followed by an examination of per-pixel trends (2001-2012) in model output for the North American terrestrial region north of 55 N. PolarVPRM was validated against eddy covariance observations from nine North American sites, of which three were used in model calibration. PolarVPRM performed well over all sites. Model intercomparisons indicated that PolarVPRM showed slightly better agreement with eddy covariance observations relative to existing models. Trend analysis (2001-2012) indicated that warming air temperatures and drought stress in forests increased growing season rates of respiration, and decreased rates of net carbon uptake by vegetation when air temperatures exceeded optimal temperatures for photosynthesis. Concurrent increases in growing season length at Arctic tundra sites allowed increases in photosynthetic uptake over time by tundra vegetation. PolarVPRM estimated that the North American high-latitude region changed from a carbon source (2001-2004) to sink (2005-2010) to source (2011-2012) in response to changing environmental conditions.

Luus, K. A.; Lin, J. C.

2015-02-01

286

High-order harmonic generation in vibrating two-electron molecules  

E-print Network

-active-electron (SAE) model. The isotope effect can be understood as follows. In general, the first step of the three¨odinger equation numerically, we simulate high-order harmonic generation from one-dimensional hydrogen molecules.C. Chirila) Preprint submitted to Elsevier September 29, 2009 #12;with electric field amplitude E0

Lein, Manfred

287

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

E-print Network

We present a scheme for the production of circularly polarized multiple high-order harmonic generation (HHG). The proposed experimental setup involves the use of two-color laser fields, consisting of a circularly polarized ...

Tong, Xiao-Min; Chu, Shih-I

1998-10-01

288

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.; Pape, 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

289

Charge-sharing in fragmentation of nitrogen molecules in collision with highly charged ions  

NASA Astrophysics Data System (ADS)

An apparatus for low-energy collision of highly charged ions with molecules, comprising a position sensitive time-of-flight measurement devise for recoil ions and a charge state analyser for the scattered projectile, was newly constructed at a beam line of an electron cyclotron resonance ion source. Collision experiments of 120 keV Ar8+ with the target of nitrogen molecules were conducted as a test run of this apparatus. Focusing on the dissociation channels with asymmetric sharing of the charges by fragmentation, correlation between Auger electron emission of the projectile and Coulomb explosion of the target is discussed.

Matsumoto, J.; Tezuka, H.; Shiromaru, H.

2015-01-01

290

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

SciTech Connect

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

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

2008-02-06

291

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

SciTech Connect

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

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

2007-11-28

292

High repetition rate Q-switched radially polarized laser with a graphene-based output coupler  

NASA Astrophysics Data System (ADS)

We demonstrate a Q-switched radially polarized all-solid-state laser by transferring a graphene film directly onto an output coupler. The laser generates Q-switched radially polarized beam (QRPB) with a pulse width of 192 ns and 2.7 W average output power. The corresponding single pulse energy is up to 16.2 ?J with a high repetition rate of 167 kHz. The M2 factor and the polarization purity are 2.1 and 96%, respectively. Our QRPB source is a simple and low-cost source for a variety of applications, such as industrial material processing, optical trapping, and microscopy.

Li, Lifei; Zheng, Xinliang; Jin, Chenjie; Qi, Mei; Chen, Xiaoming; Ren, Zhaoyu; Bai, Jintao; Sun, Zhipei

2014-12-01

293

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

294

High-intensity, high-brightness polarized and unpolarized beam production in charge-exchange collisions  

SciTech Connect

Basic limitations on the high-intensity H{sup -} ion beam production were experimentally studied in charge-exchange collisions of the neutral atomic hydrogen beam in the Na-vapour jet ionizer cell. These studies are the part of the polarized source upgrade (to 10 mA peak current and 85% polarization) project for RHIC. In the source the atomic hydrogen beam of a 5-10 keV energy and total (equivalent) current up to 5 A is produced by neutralization of proton beam in pulsed hydrogen gas target. Formation of the proton beam (from the surface of the plasma emitter with a low transverse ion temperature {approx}0.2 eV) is produced by four-electrode spherical multi-aperture ion-optical system with geometrical focusing. The hydrogen atomic beam intensity up to 1.0 A/cm{sup 2} (equivalent) was obtained in the Na-jet ionizer aperture of a 2.0 cm diameter. At the first stage of the experiment H-beam with 36 mA current, 5 keV energy and {approx}1.0 cm {center_dot} mrad normalized emittance was obtained using the flat grids and magnetic focusing.

Zelenski, A.; Ritter, J.; Zubets, V.; Steski, D.; Atoian, G.; Davydenko, V.; Ivanov, A.; Kolmogorov, A.

2011-03-28

295

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

296

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

297

Shallow surface gratings for high-power VCSELs with one preferred polarization for all modes  

Microsoft Academic Search

Monolithically integrated full-aperture surface gratings are shown to control the polarization of all modes of even highly multimode 850-nm oxide-confined standard industrial vertical-cavity surface-emitting lasers (VCSELs). An orthogonal polarization suppression ratio (OPSR) of more than 11 dB up to thermal rollover is achieved for an output power of 23 mW. For devices with 8-mW output power, an OPSR of more

Johannes Michael Ostermann; Pierluigi Debernardi; Christof Jalics; Rainer Michalzik

2005-01-01

298

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

SciTech Connect

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

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

2010-04-19

299

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

Microsoft Academic Search

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

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

1994-01-01

300

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

301

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

302

High resolution measures of polarization and color of selected lunar areas  

NASA Technical Reports Server (NTRS)

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

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

1972-01-01

303

MCSCF wave functions for excited states of polar molecules - Application to BeO. [Multi-Configuration Self-Consistent Field  

NASA Technical Reports Server (NTRS)

A previously reported multi-configuration self-consistent field (MCSCF) algorithm based on the generalized Brillouin theorem is extended in order to treat the excited states of polar molecules. In particular, the algorithm takes into account the proper treatment of nonorthogonality in the space of single excitations and invokes, when necessary, a constrained optimization procedure to prevent the variational collapse of excited states. In addition, a configuration selection scheme (suitable for use in conjunction with extended configuration interaction methods) is proposed for the MCSCF procedure. The algorithm is used to study the low-lying singlet states of BeO, a system which has not previously been studied using an MCSCF procedure. MCSCF wave functions are obtained for three 1 Sigma + and two 1 Pi states. The 1 Sigma + results are juxtaposed with comparable results for MgO in order to assess the generality of the description presented here.

Bauschlicher, C. W., Jr.; Yarkony, D. R.

1980-01-01

304

First high-spatial- and high-temporal-resolution optical imagery of polar regions from Formosat-2  

NASA Astrophysics Data System (ADS)

Coordinating and collecting satellite data of changing polar environments is one of the prime activities during the International Polar Year (IPY) 2007-2008. Earlier efforts in manoeuvring Radarsat-1 in a special mode provided the radar images with a spatial resolution of 30m of the entirety of Antarctica during September to October 1997. Limited to their swath and pointing capability, however, the operation of optical satellites with high-spatial- resolution sensors is generally restricted to certain latitudes. For example, Landsat and SPOT missions have been able to provide high-spatial-resolution optical imagery only to latitude ~81 degree North and South since 1980s. The coverage is now extended to ~86 degree by ASTER since 2000s, but there is still no space-borne optical image of the polar regions with latitudes higher than 86 degree. Another limitation is the temporal- resolution of the optical satellite operated in the general near-polar orbit, which is usually low from a few days to a few tens of days. To detect the subtle and dynamic changes occurred in the polar region of higher latitude, we need to resort to a new system with both high-spatial- and high-temporal-resolution. The successful operation of Formosat-2 launched on 21 May 2004 proved the concept that the temporal resolution of a remote sensing system can be much improved by deploying a high-spatial-resolution sensor in a daily revisit orbit, and each accessible scene can be systematically observed from the same angle under the similar illumination conditions. These characteristics make Formosat-2 an ideal satellite for site surveillance, particular in the polar regions. To support IPY 2007-2008, the National Space Organization (NSPO) of Taiwan launched a Polar Imaging Campaign (PIC) from March 2006. In this paper, we describe the imaging procedure and present (1) the first high-spatial-resolution (2m) and multi-spectral (red, green, blue and near-infrared) image of Amundsen-Scoot South Polar Station taken by Formosat-2, (2) the digital elevation model of Alert, the northernmost permanently inhabited place in the world, generated from the across-track stereo images taken by Formosat-2, and (3) the daily change of the ice shelf and the track of floating ice with size of tens of meters for five consecutive days. The results demonstrate that the high-spatial- and high-temporal-resolution optical imagery of polar regions taken from Formosat-2 could be a very useful source of data for researches in polar regions. To support IPY 2007-2008, NSPO provides access to all of its Formosat-2 imagery collected during PIC.

Liu, C.; Chang, Y.; Huang, S.; Wu, F.; Wu, A.

2007-12-01

305

Optical attosecond mapping by polarization selective detection  

SciTech Connect

We propose a general concept to use the spatial information encoded in the time-dependent polarization of high-order harmonic radiation generated by orthogonally polarized two-color laser fields. Based on polarization selective detection, we present two examples of applications: (i) a method for isolating a single attosecond pulse from an attosecond pulse train which is more efficient than the cutoff selection method and (ii) a technique for orbital tomography of molecules with attosecond resolution.

Kitzler, Markus; Xie Xinhua; Scrinzi, Armin; Baltuska, Andrius [Photonics Institute, Vienna University of Technology, Vienna (Austria)

2007-07-15

306

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)based cAMP assay in 1536-well microplate format for high throughput screening of small molecule libraries. A small molecule library of 343,768 compounds was screened to identify modulators of gsp activity. A total of 1,356 compounds with inhibitory activity were initially identified and reconfirmed when tested in concentration dose responses. Six hundred eighty-six molecules were selected for further analysis after removing cytotoxic compounds and those that were active in forskolin-induced WT cells. These molecules were grouped by potency, efficacy, and structural similarities to yield 22 clusters with more than 5 of structurally similar members and 144 singleton molecules. Seven chemotypes of the major clusters were identified for further testing and analyses. PMID:24667240

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

307

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

SciTech Connect

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

Bassan, Nicola [SISSA, Via Beirut 24, 34014 Trieste (Italy); Mirizzi, Alessandro [II. Institut fr theoretische Physik, Universitt Hamburg, Luruper Chaussee 149, 22761 Hamburg (Germany); Roncadelli, Marco, E-mail: nicola.bassan@sissa.it, E-mail: alessandro.mirizzi@desy.de, E-mail: marco.roncadelli@pv.infn.it [INFN, Sezione di Pavia, Via A. Bassi 6, 27100 Pavia (Italy)

2010-05-01

308

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

309

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

NASA Astrophysics Data System (ADS)

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

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

2015-03-01

310

Transport of Mars atmospheric water into high northern latitudes during a polar warming  

NASA Technical Reports Server (NTRS)

Several numerical experiments were conducted with a simplified tracer transport model in order to attempt to examine the poleward transport of Mars atmospheric water during a polar warming like that which occurred during the winter solstice dust storm of 1977. The flow for the transport experiments was taken from numerical simulations with a nonlinear beta-plane dynamical model. Previous studies with this model have demonstrated that a polar warming having essential characteristics like those observed during the 1977 dust storm can be produced by a planetary wave mechanism analogous to that responsible for terrestrial sudden stratospheric warmings. Several numerical experiments intended to simulate water transport in the absence of any condensation were carried out. These experiments indicate that the flow during a polar warming can transport very substantial amounts of water to high northern latitudes, given that the water does not condense and fall out before reaching the polar region.

Barnes, J. R.; Hollingsworth, J. L.

1988-01-01

311

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

E-print Network

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

M. L. Tong; Y. Zhang

2007-11-30

312

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

313

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

314

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

315

High resolution non-hydrostatic GCM simulations of Venus polar vortices  

NASA Astrophysics Data System (ADS)

Non-hydrostatic general circulation model of the Venus atmosphere is capable of reproducing both superrotatoin and subsolar-antisolar circulation, providing proper parameterization of the peculiar heat balance. Using high resolution (0.7 (o) in longitude and latitude, 250 m in height) simulations from the bottom to 120 km, we explore the response of the circulation system to perturbation of heating and cooling rates in the polar regions. It is shown that diurnal tide results in off-axis displacement of the polar vortex external part at the upper cloud level, consistent with the patterns retrieved from cloud tracking observations. On the other hand, minor (3 (o) -7 (o) ) displacement of the polar vortex central part constrains the diurnal variations of the heating/cooling rates within main cloud deck. Based on the recently developed radiative transfer code, we simulate heat balance in the polar Venus atmosphere, that results in realistic circulation pattern. It is shown that Hadley cell circulation provides extra heating above the clouds, resulting in the effective damping of superrotation and development of subsolar-antisolar circulation at higher altitudes. In turin high slant opacity of the polar atmosphere within the clouds provides the effective cooling near the pole, that causes non-hydrostatic downwelling flow, manifested as a core of the observed polar vortex. The work has been supported by the Ministry of Education and Science of Russian Federation grant #11.G34.31.0074

Rodin, Alexander V.; Orlov, Konstantin; Mingalev, Igor

316

Circularly polarized high-efficiency cholesteric liquid crystal lasers with a tunable  

E-print Network

of highly ordered polymer-dyes for lasing in chiral nematic liquid crystals," Jpn. J. Appl. Phys. 43(2), 631Circularly polarized high-efficiency cholesteric liquid crystal lasers with a tunable nematic phase-doped cholesteric liquid crystal (CLC) is demonstrated by optimizing the dye concentration and using an electrically

Wu, Shin-Tson

317

Functional recombinant MHC class II molecules and high-throughput peptide-binding assays  

PubMed Central

Background Molecules of the class II major histocompability complex (MHC-II) specifically bind and present exogenously derived peptide epitopes to CD4+ T helper cells. The extreme polymorphism of the MHC-II hampers the complete analysis of peptide binding. It is also a significant hurdle in the generation of MHC-II molecules as reagents to study and manipulate specific T helper cell responses. Methods to generate functional MHC-II molecules recombinantly, and measure their interaction with peptides, would be highly desirable; however, no consensus methodology has yet emerged. Results We generated ? and ? MHC-II chain constructs, where the membrane-spanning regions were replaced by dimerization motifs, and the C-terminal of the ? chains was fused to a biotinylation signal peptide (BSP) allowing for in vivo biotinylation. These chains were produced separately as inclusion bodies in E. coli , extracted into urea, and purified under denaturing and non-reducing conditions using conventional column chromatography. Subsequently, diluting the two chains into a folding reaction with appropriate peptide resulted in efficient peptide-MHC-II complex formation. Several different formats of peptide-binding assay were developed including a homogeneous, non-radioactive, high-throughput (HTS) binding assay. Binding isotherms were generated allowing the affinities of interaction to be determined. The affinities of the best binders were found to be in the low nanomolar range. Recombinant MHC-II molecules and accompanying HTS peptide-binding assay were successfully developed for nine different MHC-II molecules including the DPA1*0103/DPB1*0401 (DP401) and DQA1*0501/DQB1*0201, where both ? and ? chains are polymorphic, illustrating the advantages of producing the two chains separately. Conclusion We have successfully developed versatile MHC-II resources, which may assist in the generation of MHC class II -wide reagents, data, and tools. PMID:19416502

Justesen, Sune; Harndahl, Mikkel; Lamberth, Kasper; Nielsen, Lise-Lotte B; Buus, Sren

2009-01-01

318

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

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

319

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

PubMed Central

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

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

2013-01-01

320

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

321

High inertness of W@Si12 cluster toward O2 molecule  

NASA Astrophysics Data System (ADS)

The geometry, electronic structure, and reactivity with O2 molecules of an isolated W@Si12 cluster have been investigated by first principles simulations. The results confirm that O2 can weakly adsorb on the HP-W@Si12 cage with a binding energy of 0.004 to 0.027 eV. O2 may dissociate on the cluster by overcoming energy barrier of at least 0.593 eV. However, this is a spin-forbidden reaction, rendering the high inertness of the HP-W@Si12 cluster toward O2. These results confirm the high inertness of the W@Si12 cluster toward O2 molecules in ambient conditions, in close agreement with experimental observations of magic cluster of W@Si12.

Li, S. F.; Xue, Xinlian; Zhai, Hao; Nie, Xinchuang; Wang, Fei; Sun, Q.; Jia, Yu; Guo, Z. X.; Shevlin, S. A.

2012-03-01

322

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

NASA Astrophysics Data System (ADS)

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

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

2011-07-01

323

Observation of a translational energy threshold for a highly exoergic ion?molecule reaction  

E-print Network

of 1 Januarv 1974 for a fuller description of Letters to the Editor. COMMUNICATIONS Observation of a translational energy threshold for a highly exoergic ion-molecule reaction * J. R. Wyattt, L. W. Strattan, S. C. Snyder, and P. M. Hierl Department...V (c. m.). The beam instrument (single beam-collision chamber configuration with product velocity and angular analysis) used in this study has been described. 2 The product velocity vector distributions peak considerably forward of the center...

Wyatt, J. R.; Strattan, L. W.; Snyder, S. C.; Hierl, Peter M.

1974-01-01

324

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; Jelnek, Pavel

2014-11-01

325

Small Molecule Inhibitors of Phospholipase C from a Novel High-throughput Screen*  

PubMed Central

Phospholipase C (PLC) isozymes are important signaling molecules, but few small molecule modulators are available to pharmacologically regulate their function. With the goal of developing a general approach for identification of novel PLC inhibitors, we developed a high-throughput assay based on the fluorogenic substrate reporter WH-15. The assay is highly sensitive and reproducible: screening a chemical library of 6280 compounds identified three novel PLC inhibitors that exhibited potent activities in two separate assay formats with purified PLC isozymes in vitro. Two of the three inhibitors also inhibited G protein-coupled receptor-stimulated PLC activity in intact cell systems. These results demonstrate the power of the high-throughput assay for screening large collections of small molecules to identify novel PLC modulators. Potent and selective modulators of PLCs will ultimately be useful for dissecting the roles of PLCs in cellular processes, as well as provide lead compounds for the development of drugs to treat diseases arising from aberrant phospholipase activity. PMID:23297405

Huang, Weigang; Barrett, Matthew; Hajicek, Nicole; Hicks, Stephanie; Harden, T. Kendall; Sondek, John; Zhang, Qisheng

2013-01-01

326

Non-intrusive measurement of In-Band OSNR of high bitrate polarization-multiplexed signals  

NASA Astrophysics Data System (ADS)

The In-Band OSNR of polarization-multiplexed signals in deployed networks may be determined non-intrusively with a novel modulation-format-agnostic approach suitable for implementation in field-portable optical spectrum analyzers. This approach advantageously makes use of available optical taps in the network for simultaneous measurement of all the channels of a high-bandwidth DWDM system. We have confirmed the validity of this approach using measurements acquired on polarization-multiplexed signals in representative high-bandwidth network testbeds.

Garipy, Daniel; He, Gang; Schinn, Gregory W.

2011-10-01

327

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

328

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

E-print Network

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

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

2014-01-01

329

Generation of bright phase-matched circularly-polarized extreme ultraviolet high harmonics  

NASA Astrophysics Data System (ADS)

Circularly-polarized extreme ultraviolet and X-ray radiation is useful for analysing the structural, electronic and magnetic properties of materials. To date, such radiation has only been available at large-scale X-ray facilities such as synchrotrons. Here, we demonstrate the first bright, phase-matched, extreme ultraviolet circularly-polarized high harmonics source. The harmonics are emitted when bi-chromatic counter-rotating circularly-polarized laser pulses field-ionize a gas in a hollow-core waveguide. We use this new light source for magnetic circular dichroism measurements at the M-shell absorption edges of Co. We show that phase-matching of circularly-polarized harmonics is unique and robust, producing a photon flux comparable to linearly polarized high harmonic sources. This work represents a critical advance towards the development of table-top systems for element-specific imaging and spectroscopy of multiple elements simultaneously in magnetic and other chiral media with very high spatial and temporal resolution.

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

2015-02-01

330

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

331

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

PubMed

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

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

2011-10-01

332

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

333

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

DOEpatents

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

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

2010-03-02

334

A Fixed-Charge Model for Alcohol Polarization in the Condensed Phase, and Its Role in Small Molecule Hydration  

PubMed Central

We present a simple optimization strategy for incorporating experimental dielectric response information on neat liquids in classical molecular models of alcohol. Using this strategy, we determine simple and transferable hydroxyl modulation rules that, when applied to an existing molecular parameter set, result in a newly dielectric corrected (DC) parameter set. We applied these rules to the general Amber force field (GAFF) to form an initial set of GAFF-DC parameters, and we found this to lead to significant improvement in the calculated dielectric constant and hydration free energy values for a wide variety of small molecule alcohol models. Tests of the GAFF-DC parameters in the SAMPL4 blind prediction event for hydration show these changes improve agreement with experiment. Surprisingly, these simple modifications also outperform detailed quantum mechanical electric field calculations using a self-consistent reaction field environment coupling term. This work provides a potential benchmark for future developments in methods for representing condensed-phase environments in electronic structure calculations. PMID:24702668

2015-01-01

335

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

336

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

NASA Technical Reports Server (NTRS)

Two mechanisms have been proposed to account for solute permeation of lipid bilayers. Partitioning into the hydrophobic phase of the bilayer, followed by diffusion, is accepted by many for the permeation of water and other small neutral solutes, but transient pores have also been proposed to account for both water and ionic solute permeation. These two mechanisms make distinctively different predictions about the permeability coefficient as a function of bilayer thickness. Whereas the solubility-diffusion mechanism predicts only a modest variation related to bilayer thickness, the pore model predicts an exponential relationship. To test these models, we measured the permeability of phospholipid bilayers to protons, potassium ions, water, urea, and glycerol. Bilayers were prepared as liposomes, and thickness was varied systematically by using unsaturated lipids with chain lengths ranging from 14 to 24 carbon atoms. The permeability coefficient of water and neutral polar solutes displayed a modest dependence on bilayer thickness, with an approximately linear fivefold decrease as the carbon number varied from 14 to 24 atoms. In contrast, the permeability to protons and potassium ions decreased sharply by two orders of magnitude between 14 and 18 carbon atoms, and leveled off, when the chain length was further extended to 24 carbon atoms. The results for water and the neutral permeating solutes are best explained by the solubility-diffusion mechanism. The results for protons and potassium ions in shorter-chain lipids are consistent with the transient pore model, but better fit the theoretical line predicted by the solubility-diffusion model at longer chain lengths.

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

1996-01-01

337

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

338

High Intensity Electrodeless Lamps Excited by Circularly Polarized Microwave Discharges  

Microsoft Academic Search

We report on the demonstration of high intensity electrodeless lamps using rotating microwave discharges of molecular vapors at 100-400 kPa with no external magnetic fields, including sulfur and indium-monobromide. We place in a cylindrical waveguide a quartz ball of 3-cm-diam filled with 10 Torr of argon gas and a few mg of a molecular fill. The waveguide system generates circularly

Jin Joong Kim; Dong Ho Won; Jung Tae Ko; Jeong Won Kim

2003-01-01

339

Catalyst-site-controlled coordination polymerization of polar vinyl monomers to highly syndiotactic polymers.  

PubMed

This contribution reports a combined synthetic, kinetic, mechanistic, and theoretical/computational study of the recently discovered catalyst-site-controlled coordination polymerization of polar vinyl monomers [such as methyl methacrylate (MMA) and N,N-dimethylacrylamide (DMAA)] into highly syndiotactic polymers. Among the 12 C(s)-ligated ansa-cyclopentadienyl (Cp)-R(2)E(C,Si)-fluorenyl (Flu) group 4 metallocene catalyst systems examined-which varied in metal center, anion structure, bridging atom and substituents, and ligand substitution pattern-cationic ansa-metallocene ester enolate catalyst 6(+)[B(C(6)F(5))(4)](-), derived from the activation of the precatalyst [Ph(2)C(Cp)(2,7-(t)Bu(2)-Flu)]Zr[OC(O(i)Pr)=CMe(2)](2) with [Ph(3)C][B(C(6)F(5))(4)], stood out as the best catalyst in all aspects of the MMA polymerization at room temperature, including the highest activity (1554 h(-1) TOF), efficiency (98% I*), syndiotacticity (94% rr), and control (predicted number-average molecular weight and 1.14 molecular weight distribution). Kinetic and mechanistic results are consistent with a catalyst-site-controlled, monometallic coordination-addition mechanism, involving fast intramolecular addition within the catalyst-monomer complex leading to the resting eight-membered ester enolate chelate, followed by the rate-limiting ring-opening of the chelate to regenerate the active species. This work has also uncovered several unique features of this polymerization system that are in marked contrast to the propylene polymerization by analogous C(s)-ligated cationic alkyl catalysts: a constant syndiotacticity of PMMA produced over a wide polymerization temperature range (i.e., from 0 degrees C, 94% rr to 25 degrees C, 94% rr to 50 degrees C, 93% rr); insensitivity of its high activity, degree of control, and stereoselectivity to solvent polarity and structure of weakly coordinating anions; and deviation from a pure site-control mechanism at high [MMA]/[catalyst] ratios. Computational results provide theoretical support for the proposed monomer-assisted, catalyst-site epimerization, after an enantiofacial mistake, to a thermodynamically more stable resting state, which accounts for the observed higher than expected [mr] contents based on a pure site-controlled mechanism. DFT calculations rationalize why the Ph(2)C< bridged catalyst 6 exhibits higher stereoselectivity than other catalysts with the Me(2)C< or Me(2)Si< bridge: the bridge rigidity pushes the eta(3)-bound Flu ligand closer to the growing chain and the monomer, thereby increasing DeltaE(stereo) between the competing transition states for the addition of a monomer molecule to the opposite (correct and wrong) enantiofaces of the enolate growing chain. The relative polymerization activity of this catalyst series is shown to correlate with the relative energetics of the back-biting of the penultimate unit and ion-pair formation. PMID:20121281

Zhang, Yuetao; Ning, Yalan; Caporaso, Lucia; Cavallo, Luigi; Chen, Eugene Y-X

2010-03-01

340

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

341

Highly enantioselective adsorption of small prochiral molecules on a chiral intermetallic compound.  

PubMed

Intrinsically chiral surfaces of intermetallic compounds are shown to be novel materials for enantioselective processes. Their advantage is the significantly higher thermal and chemical stability, and therefore their extended application range for catalyzed chiral reactions compared to surfaces templated with chiral molecular modifiers or auxiliaries. On the Pd1 -terminated PdGa(111) surface, room-temperature adsorption of a small prochiral molecule (9-ethynylphenanthrene) leads to exceptionally high enantiomeric excess ratios of up to 98?%. Our findings highlight the great potential of intrinsically chiral intermetallic compounds for the development of novel, enantioselective catalysts that can be operated at high temperatures and potentially also in harsh chemical environments. PMID:25655521

Prinz, Jan; Grning, Oliver; Brune, Harald; Widmer, Roland

2015-03-23

342

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

343

Physiological Ecology of Mesozoic Polar Forests in a High CO2 Environment  

PubMed Central

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

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

2002-01-01

344

Small-molecule inducer of ? cell proliferation identified by high-throughput screening.  

PubMed

The identification of factors that promote ? cell proliferation could ultimately move type 1 diabetes treatment away from insulin injection therapy and toward a cure. We have performed high-throughput, cell-based screens using rodent ? cell lines to identify molecules that induce proliferation of ? cells. Herein we report the discovery and characterization of WS6, a novel small molecule that promotes ? cell proliferation in rodent and human primary islets. In the RIP-DTA mouse model of ? cell ablation, WS6 normalized blood glucose and induced concomitant increases in ? cell proliferation and ? cell number. Affinity pulldown and kinase profiling studies implicate Erb3 binding protein-1 and the I?B kinase pathway in the mechanism of action of WS6. PMID:23330637

Shen, Weijun; Tremblay, Matthew S; Deshmukh, Vishal A; Wang, Weidong; Filippi, Christophe M; Harb, George; Zhang, You-qing; Kamireddy, Anwesh; Baaten, Janine E; Jin, Qihui; Wu, Tom; Swoboda, Jonathan G; Cho, Charles Y; Li, Jing; Laffitte, Bryan A; McNamara, Peter; Glynne, Richard; Wu, Xu; Herman, Ann E; Schultz, Peter G

2013-02-01

345

Synthesis of reference substances for highly polar metabolites of nitroaromatic compounds  

Microsoft Academic Search

Transformation processes of nitroaromatic compounds (NAC) lead to polar and highly hydrophilic metabolites. For the unequivocal identification of proposed metabolites reference substances are needed. Since most of them are not commercially available, their synthesis was done in our group. In many cases no satisfying synthesis schemes were found in the literature. In this communication, we therefore describe the preparation, structural

Torsten C. Schmidt; Klaus Steinbach; Ulf Buetehorn; Kerstin Heck; Ute Volkwein; Gottfried Stork

1999-01-01

346

Fluoresceinated FKBP12 ligands for a high-throughput fluorescence polarization assay  

Microsoft Academic Search

Several fluoresceinated FKBP12 ligands have been prepared for a high-throughput fluorescence polarization assay. Kis for FKBP12 rotamase inhibition by these ligands range from 1.3 ?M to 32 nM, and their design is based on X-ray crystal structures of FKBP12 complexed with known immunophilin ligands.

Gene M Dubowchik; Jonathan L Ditta; John J Herbst; Sagarika Bollini; Alexander Vinitsky

2000-01-01

347

SAMPLING AND ANALYSIS FOR HIGH-MOLECULAR-WEIGHT POLAR ORGANIC COMPOUNDS  

EPA Science Inventory

The report gives results of preliminary investigations into the determination of high-molecular-weight polar organic compounds from wood-combustion residues. It is intended as a reference to be used by laboratories that are developing methods for the identification and quantifica...

348

Cassini imaging of Titan's high-latitude lakes, clouds, and south-polar surface changes  

E-print Network

Cassini imaging of Titan's high-latitude lakes, clouds, and south-polar surface changes E. P 2009. [1] Cassini's Imaging Science Subsystem (ISS) has been observing Titan since April 2004, suggesting the presence of hydrocarbon lakes similar to those later detected at Titan's North Pole

349

LETTER doi:10.1038/nature12814 Highly polarized light from stable ordered magnetic  

E-print Network

the central engine3,4 , with a position angle that is predicted to remain stable in magnetized baryonic jet and a reverse shock propagates backwards into the oncoming collimated flow, or `jet'1,2 . Light from the reverse shock should be highly polarized if the jet's magnetic field is glob- ally ordered and advected from

Cai, Long

350

A fluorescence-based high throughput assay for the determination of small moleculehuman serum albumin protein binding  

PubMed Central

Herein, we describe the development of a fluorescence-based high throughput assay to determine the small molecule binding towards human serum albumin (HSA). This innovative competition assay is based on the use of a novel fluorescent small molecule Red Mega 500 with unique spectroscopic and binding properties. The commercially available probe displays a large fluorescence intensity difference between the protein-bound and protein-unbound state. The competition of small molecules for HSA binding in the presence of probe resulted in low fluorescence intensities. The assay was evaluated with the LOPAC small molecule library of 1280 compounds identifying known high protein binders. The small molecule competition of HSARed Mega 500 binding was saturable at higher compound concentrations and exhibited IC50 values between 324 ?M. The compound affinity towards HSA was confirmed by isothermal titration calorimetry indicating that the new protein binding assay is a valid high throughput assay to determine plasma protein binding. PMID:24390461

McCallum, Megan M.; Pawlak, Alan J.; Shadrick, William R.; Simeonov, Anton; Jadhav, Ajit; Yasgar, Adam; Maloney, David J.; Arnold, Leggy A.

2014-01-01

351

Disintegration of argon clusters in collisions with highly vibrationally excited SF6 molecules in crossed molecular and cluster beams  

NASA Astrophysics Data System (ADS)

It has been found that collisions of highly vibrationally excited SF6 molecules (with the vibrational energy E vib ? 0.5-2.0 eV) with Ar N clusters (where N ? 30-40 is the number of atoms in a cluster) in crossed molecular and cluster beams result in capture of molecules followed by complete disintegration of the clusters. Possible applications of the effect for selective doping of clusters with molecules, laser separation of isotopes, and selective transport of molecules to the surface are discussed.

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

2013-03-01

352

High Resolution Continuous Flow Analysis System for Polar Ice Cores  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

353

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

354

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

PubMed Central

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 LCPolScope 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 either instrument, and touch on the physical connection between refractive index, birefringence, transmittance, diattenuation, and dichroism. PMID:24273640

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

2013-01-01

355

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

356

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

357

High-Throughput 1,536-Well Fluorescence Polarization Assays for ?1-Acid Glycoprotein and Human Serum Albumin Binding  

PubMed Central

Two major plasma proteins in humans are primarily responsible for drug binding, the ?1-acid-glycoprotein (AGP) and human serum albumin (HSA). The availability of at least a semiquantitative high-throughput assay for assessment of protein binding is expected to aid in bridging the current gap between high-throughput screening and early lead discovery, where cell-based and biochemical assays are deployed routinely to test up to several million compounds rapidly, as opposed to the late-stage candidate drug profiling methods which test at most dozens of compounds at a time. Here, we describe the miniaturization of a pair of assays based on the binding- and displacement-induced changes in fluorescence polarization (FP) of fluorescent small molecule probes known to specifically target the drug-binding sites of these two proteins. A robust and reproducible assay performance was achieved in ?4 L assay volume in 1,536-well format. The assays were tested against a validation set of 10 known protein binders, and the results compared favorably with data obtained using protein-coated beads with high-performance liquid chromatography analysis. The miniaturized assays were taken to a high-throughput level in a screen of the LOPAC1280 collection of 1,280 pharmacologically active compounds. The adaptation of the AGP and HSA FP assays to a 1,536-well format should allow their use in early-stage profiling of large-size compound sets. PMID:23029124

Yasgar, Adam; Furdas, Silviya D.; Maloney, David J.; Jadhav, Ajit; Jung, Manfred; Simeonov, Anton

2012-01-01

358

Development of spin-polarized positron source using high energy proton beam  

NASA Astrophysics Data System (ADS)

To obtain a highly spin polarized positron beam, 68Ge isotope have been produced using a nuclear reaction of 69Ga(p,2n)68Ge. As target materials, we examined a metal form 69Ga stable isotope and a GaN substrate. By 20 MeV proton irradiation, the production of 68Ge source was confirmed in both targets. The production rates of 68Ge were 0.16 and 0.53 MBq/?A/h for the metal Ga and GaN target, respectively. The spin polarizations of positrons emitted from 68Ge was estimated to be approximately 50 to 70%.

Maekawa, M.; Fukaya, Y.; Yabuuchi, Y.; Kawasuso, A.

2011-01-01

359

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

PubMed

We report an optoelectronic investigation of lead sulfide nanowires (NWs) by scanning photocurrent microscopy. The photocurrent in p-type lead sulfide NW field effect transistors has demonstrated unusually nonlinear dependence on the intensity of local excitation. Surprisingly, the photocurrent polarity can be reversed under high illumination intensity on the order of 100 W cm(-2). The origin of this photocurrent polarity switching is that the photo-injected carriers flip the direction of the electric field near the contact. These observations shed light on the nonlinear optoelectronic characteristics in semiconductor nanostructures and may provide an innovative method for optically tailoring local band structures. PMID:24763392

Yang, Yiming; Peng, Xingyue; Yu, Dong

2014-05-16

360

Extraction of ions from polar solutions by high-strength electric field pulses  

NASA Astrophysics Data System (ADS)

Extraction of ions from solutions of salts in ethylene glycol and water-glycerol mixture by high-strength electric field pulses is investigated. The conditions for stable extraction of ions from a polar liquid in the pulsed regime are ensured by using a track membrane with channels of a nanosize diameter as the interface between the liquid solution and vacuum. The possibility of barrier-free field evaporation of ions from polar liquids in electromembrane ion source for mass-spectrometric analysis of solutions is considered.

Balakin, A. A.; Khidirov, S. G.

2014-11-01

361

An evaluation of fluorescence polarization and lifetime discriminated polarization for high throughput screening of serine/threonine kinases.  

PubMed

We used two kinases, c-jun N terminal kinase (JNK-1) and protein kinase C (PKC), as model enzymes to evaluate the potential of fluorescence polarization (FP) for high-throughput screening and the susceptibility of these assays to compound interference. For JNK-1 the enzyme kinetics in the FP assay were consistent with those found in a [gamma-33P]ATP filter wash assay. Determined pIC(50)s for nonfluorescent JNK-1 inhibitors were also consistent with those found in the filter wash assay. In contrast, fluorescent compounds were found to interfere with the JNK-1 FP assay, appearing as false positives, defined by their lack of activity in the filter wash assay. We also developed a second assay using a different kinase, protein kinase C, which was used to test a 5000 compound diversity set. As for JNK-1, interference from fluorescent compounds caused a high false positive rate. The Molecular Devices Corporation 'FLARe' instrument is capable of discriminating between fluorophores on the basis of their fluorescence (excited state) lifetime, and may assist in reducing compound interference in fluorescent assays. In both model FP kinase assays described here some, although not complete, reduction in interference from fluorescent compounds was achieved by the use of FLARe. PMID:12419333

Fowler, Ann; Swift, Denise; Longman, Emma; Acornley, Anne; Hemsley, Paul; Murray, Dave; Unitt, John; Dale, Ian; Sullivan, Elaine; Coldwell, Martin

2002-09-15

362

Highly sensitive immunoassay of protein molecules based on single nanoparticle fluorescence detection in a nanowell  

NASA Astrophysics Data System (ADS)

A nanoarray based-single molecule detection system was developed for detecting proteins with extremely high sensitivity. The nanoarray was able to effectively trap nanoparticles conjugated with biological sample into nanowells by integrating with an electrophoretic particle entrapment system (EPES). The nanoarray/EPES is superior to other biosensor using immunoassays in terms of saving the amounts of biological solution and enhancing kinetics of antibody binding due to reduced steric hindrance from the neighboring biological molecules. The nanoarray patterned onto a layer of PMMA and LOL on conductive and transparent indium tin oxide (ITO)-glass slide by using e-beam lithography. The suspension of 500 nm-fluorescent (green emission)-carboxylated polystyrene (PS) particles coated with protein-A followed by BDE 47 polyclonal antibody was added to the chip that was connected to the positive voltage. The droplet was covered by another ITO-coated-glass slide and connected to a ground terminal. After trapping the particles into the nanowells, the solution of different concentrations of anti-rabbit- IgG labeled with Alexa 532 was added for an immunoassay. A single molecule detection system could quantify the anti-rabbit IgG down to atto-mole level by counting photons emitted from the fluorescent dye bound to a single nanoparticle in a nanowell.

Han, Jin-Hee; Kim, Hee-Joo; Lakshmana, Sudheendra; Gee, Shirley J.; Hammock, Bruce D.; Kennedy, Ian M.

2011-03-01

363

Single-molecule dissection of the high-affinity cohesin-dockerin complex.  

PubMed

Cellulose-degrading enzyme systems are of significant interest from both a scientific and technological perspective due to the diversity of cellulase families, their unique assembly and substrate binding mechanisms, and their potential applications in several key industrial sectors, notably cellulose hydrolysis for second-generation biofuel production. Particularly fascinating are cellulosomes, the multimodular extracellular complexes produced by numerous anaerobic bacteria. Using single-molecule force spectroscopy, we analyzed the mechanical stability of the intermolecular interfaces between the cohesin and the dockerin modules responsible for self-assembly of the cellulosomal components into the multienzyme complex. The observed cohesin-dockerin rupture forces (>120 pN) are among the highest reported for a receptor-ligand system to date. Using an atomic force microscope protocol that quantified single-molecule binding activity, we observed force-induced dissociation of calcium ions from the duplicated loop-helix F-hand motif located within the dockerin module, which in the presence of EDTA resulted in loss of affinity to the cohesin partner. A cohesin amino acid mutation (D39A) that eliminated hydrogen bonding with the dockerin's critically conserved serine residues reduced the observed rupture forces. Consequently, no calcium loss occurred and dockerin activity was maintained throughout multiple forced dissociation events. These results offer insights at the single-molecule level into the stability and folding of an exquisite class of high-affinity protein-protein interactions that dictate fabrication and architecture of cellulose-degrading molecular machines. PMID:23188794

Stahl, Stefan W; Nash, Michael A; Fried, Daniel B; Slutzki, Michal; Barak, Yoav; Bayer, Edward A; Gaub, Hermann E

2012-12-11

364

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, Bjrn; Smith, Albert A.; Griffin, Robert G.

2014-01-01

365

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

366

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

367

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

E-print Network

The dynamics of the movement of gas is discussed for two-chambered polarized He-3 target cells of the sort that have been used successfully for many electron scattering experiments. A detailed analysis is presented showing that diffusion is a limiting factor in target performance, particularly as these targets are run at increasingly high luminosities. Measurements are presented on a new prototype polarized He-3 target cell in which the movement of gas is due largely to convection instead of diffusion. NMR tagging techniques have been used to visualize the gas flow, showing velocities along a cylindrically-shaped target of between 5-80 cm/min. The new target design addresses one of the principle obstacles to running polarized He-3 targets at substantially higher luminosities while simultaneously providing new flexibility in target geometry.

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

2011-09-15

368

Comparison of sugar molecule decomposition through glucose and fructose: a high-level quantum chemical study.  

SciTech Connect

Efficient chemical conversion of biomass is essential to produce sustainable energy and industrial chemicals. Industrial level conversion of glucose to useful chemicals, such as furfural, hydroxymethylfurfural, and levulinic acid, is a major step in the biomass conversion but is difficult because of the formation of undesired products and side reactions. To understand the molecular level reaction mechanisms involved in the decomposition of glucose and fructose, we have carried out high-level quantum chemical calculations [Gaussian-4 (G4) theory]. Selective 1,2-dehydration, keto-enol tautomerization, isomerization, retro-aldol condensation, and hydride shifts of glucose and fructose molecules were investigated. Detailed kinetic and thermodynamic analyses indicate that, for acyclic glucose and fructose molecules, the dehydration and isomerization require larger activation barriers compared to the retro-aldol reaction at 298 K in neutral medium. The retro-aldol reaction results in the formation of C2 and C4 species from glucose and C3 species from fructose. The formation of the most stable C3 species, dihydroxyacetone from fructose, is thermodynamically downhill. The 1,3-hydride shift leads to the cleavage of the C-C bond in the acyclic species; however, the enthalpy of activation is significantly higher (50-55 kcal/mol) than that of the retro-aldol reaction (38 kcal/mol) mainly because of the sterically hindered distorted four-membered transition state compared to the hexa-membered transition state in the retro-aldol reaction. Both tautomerization and dehydration are catalyzed by a water molecule in aqueous medium; however, water has little effect on the retro-aldol reaction. Isomerization of glucose to fructose and glyceraldehyde to dihydroxyacetone proceeds through hydride shifts that require an activation enthalpy of about 40 kcal/mol at 298 K in water medium. This investigation maps out accurate energetics of the decomposition of glucose and fructose molecules that is needed to help find more efficient catalysts for the conversion of hexose to useful chemicals.

Assary, R. S.; Curtiss, L. A. (Center for Nanoscale Materials); ( MSD); (Northwestern Univ.)

2012-02-01

369

Long term observation of low altitude atmosphere by high precision polarization lidar  

NASA Astrophysics Data System (ADS)

Prediction of weather disaster such as heavy rain and light strike is an earnest desire. Successive monitoring of the low altitude atmosphere is important to predict it. The weather disaster often befalls with a steep change in a local area. It is hard for usual meteorological equipments to capture and alert it speedily. We have been developed the near range lidar to capture and analyze the low altitude atmosphere. In this study, high precision polarization lidar was developed to observe the low altitude atmosphere. This lidar has the high extinction ratio of polarization of >30dB to detect the small polarization change of the atmosphere. The change of the polarization in the atmosphere leads to the detection of the depolarization effect and the Faraday effect, which are caused by ice-crystals and lightning discharge, respectively. As the lidar optics is "inline" type, which means common use of optics for transmitter and receiver, it can observe the near range echo with the narrow field of view. The long-term observation was accomplished at low elevation angle. It aims to monitor the low altitude atmosphere under the cloud base and capture its spatial distribution and convection process. In the viewpoint of polarization, the ice-crystals' flow and concentration change of the aerosols are monitored. The observation has been continued in the cloudy and rainy days. The thunder cloud is also a target. In this report, the system specification is explained to clear the potential and the aims. The several observation data including the long-term observation will be shown with the consideration of polarization analysis.

Shiina, Tatsuo; Noguchi, Kazuo; Fukuchi, Tetsuo

2011-11-01

370

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

NASA Astrophysics Data System (ADS)

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

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

2009-04-01

371

High Resolution UV Emission Spectroscopy of Molecules Excited by Electron Impact  

NASA Technical Reports Server (NTRS)

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

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

1999-01-01

372

Supported Lipid Bilayers and DNA Curtains for High-Throughput Single-Molecule Studies  

PubMed Central

Single-molecule studies of proteinDNA interactions continue to yield new information on numerous DNA processing pathways. For example, optical microscopy-based techniques permit the real-time observation of proteins that interact with DNA substrates, which in turn allows direct insight into reaction mechanisms. However, these experiments remain technically challenging and are limited by the paucity of stable chromophores and the difficulty of acquiring statistically significant observations. In this protocol, we describe a novel, high-throughput, nanofabricated experimental platform enabling real-time imaging of hundreds of individual proteinDNA complexes over hour timescales. PMID:21660710

Finkelstein, Ilya J.; Greene, Eric C.

2012-01-01

373

A novel carrier molecule for high-level expression of peptide antibiotics in Escherichia coli.  

PubMed

Peptide antibiotics are often hard to express in engineered bacteria at high level. According to the properties of peptide antibiotics, a heterologous protein PaP3.30, encoded by ORF30 of Pseudomonas aeruginosa bacteriophage PaP3, was selected as a carrier molecule. The gene of the carrier molecule was constructed into the plasmid pQE-32 to give rise to the vector pQE-PaP30 for expression of peptide antibiotics in Escherichia coli. A his-tagged fusion protein was genetically constructed with a peptide antibiotic at its carboxy terminus. The novel carrier molecule was used for high-level expression of six peptide antibiotics with different sizes and isoelectric points in E. coli, which are hPAB-beta, MSI-78, Melletin, hBD-1, Cecropin A, and an ovine anion peptide. And further, one of six peptide antibiotics, hPAB-beta (an analog of a human peptide antibiotic), was taken as an example for studies of recovery of interesting products from the fusion partner, purification and antimicrobial activity evaluation. The results indicated that the expressed fusion protein existed as an inclusion body in the cytoplasm and the expression amounts of six peptide antibiotic fusions are all higher than 34% of the total cell protein. The expression products could be easily purified by Ni-NTA chromatography. Cyanogen bromide was used to cut at the methionine linker between the carrier and hPAB-beta peptide. hPAB-beta was recovered from the fusion partner and purified to homogeneity with High S cation-exchange and Bio-gel P6 gel chromatography. The bactericidal activities of the purified recombinant hPAB-beta against P. aeruginosa are 31-64 microg/ml, and against Staphylococcus aureus are > or = 128 microg/ml, being comparable to that of the chemical synthesis peptide. These results show that the carrier molecule can result in high-level expression of peptide antibiotics, and expression products can be easily recovered from their fusion partner and retain their bioactivity. PMID:15177279

Rao, Xian C; Li, Shu; Hu, Jin C; Jin, Xiao L; Hu, Xiao M; Huang, Jian J; Chen, Zi J; Zhu, Jun M; Hu, Fu Q

2004-07-01

374

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

PubMed

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

2012-09-01

375

Non-basic high-performance molecules for solution-processed organic solar cells.  

PubMed

A new small molecule, p-DTS(FBTTh(2))(2), is designed for incorporation into solution-fabricated high-efficiency organic solar cells. Of primary importance is the incorporation of electron poor heterocycles that are not prone to protonation and thereby enable the incorporation of commonly used interlayers between the organic semiconductor and the charge collecting electrodes. These features have led to the creation of p-DTS(FBTTh(2))(2)/PC(71)BM solar cells with power conversion efficiencies of up to 7%. PMID:22674636

van der Poll, Thomas S; Love, John A; Nguyen, Thuc-Quyen; Bazan, Guillermo C

2012-07-17

376

Highly efficient organic light-emitting diodes based on donor-acceptor small molecules  

Microsoft Academic Search

The authors have fabricated highly efficient organic light-emitting diodes from donor-acceptor small molecules, 2-(4-methyl-quinolin-2-yl)-10-phenyl-phenothiazine (MQPTZ) and 2-(4-phenyl-quinolin-2-yl)-10-phenyl-phenothiazine (PQPTZ). Their devices turned on at 4.0 V and emitted strong green light near 510 nm. The maximum luminance of 60 000 and 55 000 cd\\/m2 at 10.4 V and the maximum power efficiencies of 5.75 and 2.5 lm\\/W at 5 V were

Jae-Jin Oh; Ki-Won Kim; Min-Sook Kim; Tae-Woo Kwon; Dong-Kyu Park; Seong-Jin Cho; Hyung-Suk Woo

2006-01-01

377

High temperature electrical conductivity due to small polaron hopping motion in DNA molecules  

NASA Astrophysics Data System (ADS)

We present a small polaron hopping model to interpret the high-temperature electrical conductivity measured along the DNA molecules. The model takes into account the one-dimensional character of the system and the presence of disorder in the DNA double helix. The experimental data for the lambda phage DNA (?-DNA) and the poly(dA)-poly(dT) DNA follow nicely the theoretically predicted behavior leading to realistic values of the maximum hopping distances supporting the idea of multiphonon-assisted hopping of small polarons between next nearest neighbors of the DNA molecular "wire".

Triberis, G. P.; Karavolas, V. C.; Simserides, C. D.

2005-01-01

378

Fourfold Increase in Quantum Efficiency in Highly Spin-Polarized Transmission-Type Photocathode  

NASA Astrophysics Data System (ADS)

We developed a new transmission-type GaAs/GaAsP strained superlattice photocathode with an AlGaAs transparent inter-layer and Si3N4 anti-reflection coating. The electrons emitted from this photocathode demonstrate a high spin-polarization of 90% with quantum efficiency as high as 0.4% that is a fourfold increase at room temperature compared with our previous photocathode.

Jin, Xiuguang; Ichihashi, Fumiaki; Mano, Atsushi; Yamamoto, Naoto; Takeda, Yoshikazu

2012-10-01

379

High-level spacecraft charging in the low-altitude polar auroral environment  

Microsoft Academic Search

Regions of intense keV electron precipitation, such as inverted-V structures, at times colocate with ionospheric plasma depletion regions in the high-latitude polar ionosphere. When Defense Meteorological Satellite Program (DMSP) F6 and F7 satellites, at 840 km, enter these regions in darkness, ion signatures of high spacecraft-to-ambient plasma potential differences (several hundred volts negative) are observed with the new SSJ\\/4 ion

M. S. Gussenhoven; D. A. Hardy; F. Rich; W. J. Burke; H.-C. Yeh

1985-01-01

380

High-level spacecraft charging in the low-altitude polar auroral environment  

Microsoft Academic Search

Regions of intense keV-electron precipitation, such as inverted-V structures, at times colocate with ionospheric-plasma depletion regions in the high-latitude polar ionosphere. When Defense Meterological Satellite Program (DMSP) F6 and F7 satellites, at 840 km, enter these regions in darkness, ion signatures of high spacecraft-to-ambient plasma potential differences(several hundred volts negative) are observed with the new SSJ\\/4 ion detectors. A systematic

M. S. Gussenhoven; D. A. Hardy; F. Rich; W. J. Burke; H.-C. Yeh

1985-01-01

381

Single-molecule imaging at high fluorophore concentrations by local activation of dye.  

PubMed

Single-molecule fluorescence microscopy is a powerful tool for observing biomolecular interactions with high spatial and temporal resolution. Detecting fluorescent signals from individual labeled proteins above high levels of background fluorescence remains challenging, however. For this reason, the concentrations of labeled proteins in invitro assays are often kept low compared to their invivo concentrations. Here, we present a new fluorescence imaging technique by which single fluorescent molecules can be observed in real time at high, physiologically relevant concentrations. The technique requires a protein and its macromolecular substrate to be labeled each with a different fluorophore. Making use of short-distance energy-transfer mechanisms, only the fluorescence from those proteins that bind to their substrate is activated. This approach is demonstrated by labeling a DNA substrate with an intercalating stain, exciting the stain, and using energy transfer from the stain to activate the fluorescence of only those labeled DNA-binding proteins bound to the DNA. Such an experimental design allowed us to observe the sequence-independent interaction of Cy5-labeled interferon-inducible protein 16 with DNA and the sliding via one-dimensional diffusion of Cy5-labeled adenovirus protease on DNA in the presence of a background of hundreds of nanomolar Cy5 fluorophore. PMID:25692599

Geertsema, Hylkje J; Schulte, Aartje C; Spenkelink, Lisanne M; McGrath, William J; Morrone, Seamus R; Sohn, Jungsan; Mangel, Walter F; Robinson, Andrew; van Oijen, Antoine M

2015-02-17

382

Synthesis and SAR of ??mTc/Re-labeled small molecule prostate specific membrane antigen inhibitors with novel polar chelates.  

PubMed

Prostate specific membrane antigen (PSMA) is recognized as an attractive molecular target for the development of radiopharmaceuticals to image and potentially treat metastatic prostate cancer. A series of novel (99m)Tc/Re-tricarbonyl radiolabeled PSMA inhibitors were therefore synthesized by the attachment of glutamate-urea-lysine (Glu-urea-Lys) and glutamate-urea-glutamate (Glu-urea-Glu) pharmacophore to single amino acid chelate (SAAC) where the SAAC ligand was either bis(pyridin-2-ylmethyl)amino (DPA), bis((1-methyl-1H-imidazol-2-yl)methyl)amino (NMI), bis((1-(carboxymethyl)-1H-imidazol-2-yl)methyl)amino (CIM) or bis((1-(2-(bis(carboxymethyl)amino)-2-oxoethyl)-1H-imidazol-2-yl)methyl)amino (TIM). The in vitro binding affinity of the rhenium complexes was evaluated using PSMA-expressing human prostate cancer LNCaP cells. IC(50) values ranged from 3.8 2 to >2000 nM. A linker between the SAAC chelate and pharmacophore was required for high affinity binding. However, extending the length of the linker did not substantially improve binding. PSMA binding was also influenced by the nature of the SAAC chelate. One of the most potent compounds, 23b (IC(50)=4.8 2.7 nM), was radiolabeled with technetium tricarbonyl ({(99m)Tc(CO)(3)}(+)) to afford the {(99m)Tc(CO)(3)}(+) complex in excellent yield and high purity. This effort has led to the identification of a diverse series of promising high affinity {(99m)Tc(CO)(3)}(+) radiolabeled PSMA inhibitors. PMID:23333070

Lu, Genliang; Maresca, Kevin P; Hillier, Shawn M; Zimmerman, Craig N; Eckelman, William C; Joyal, John L; Babich, John W

2013-03-01

383

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

384

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

385

Organizing polarized delivery of exosomes at synapses.  

PubMed

Exosomes are extracellular vesicles that transport different molecules between cells. They are formed and stored inside multivesicular bodies (MVB) until they are released to the extracellular environment. MVB fuse along the plasma membrane, driving non-polarized secretion of exosomes. However, polarized signaling potentially directs MVBs to a specific point in the plasma membrane to mediate a focal delivery of exosomes. MVB polarization occurs across a broad set of cellular situations, e.g. in immune and neuronal synapses, cell migration and in epithelial sheets. In this review, we summarize the current state of the art of polarized MVB docking and the specification of secretory sites at the plasma membrane. The current view is that MVB positioning and subsequent exosome delivery requires a polarizing, cytoskeletal dependent-trafficking mechanism. In this context, we propose scenarios in which biochemical and mechanical signals could drive the polarized delivery of exosomes in highly polarized cells, such as lymphocytes, neurons and epithelia. PMID:25614958

Mittelbrunn, Maria; Vicente-Manzanares, Miguel; Snchez-Madrid, Francisco

2015-04-01

386

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

387

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

NASA Technical Reports Server (NTRS)

High-resolution magnetic field data from the Polar Magnetic Field Experiment (MFE) show that narrow band waves at frequencies approximately 0.2 to 3 Hz are a permanent feature in the vicinity of the polar cusp. The waves have been found in the magnetosphere adjacent to the cusp (both poleward and equatorward of the cusp) and in the cusp itself. The occurrence of waves is coincident with depression of magnetic field strength associated with enhanced plasma density, indicating the entry of magnetosheath plasma into the cusp region. The wave frequencies are generally scaled by the local proton cyclotron frequency, and vary between 0.2 and 1.7 times local proton cyclotron frequency. This suggests that the waves are generated in the cusp region by the precipitating magnetosheath plasma. The properties of the waves are highly variable. The waves exhibit both lefthanded and right-handed polarization in the spacecraft frame. The propagation angles vary from nearly parallel to nearly perpendicular to the magnetic field. We find no correlation among wave frequency, propagation angle and polarization. Combined magnetic field and electric field data for the waves indicate that the energy flux of the waves is guided by the background magnetic field and points downward toward the ionosphere.

Le, Guan; Blanco-Cano, X.; Russell, C. T.; Zhou, X.-W.; Mozer, F.; Trattner, K. J.; Fuselier, S. A.; Anderson, B. J.; Vondrak, Richard R. (Technical Monitor)

2001-01-01

388

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

NASA Technical Reports Server (NTRS)

High-resolution magnetic field data from the Polar Magnetic Field Experiment (MFE) show that narrow-band waves at frequencies approx. 0.2-3 Hz are a permanent feature in the vicinity of the polar cusp. The waves have been found in the magnetosphere adjacent to the cusp (both poleward and equatorward of the cusp) and in the cusp itself. The occurrence of waves is coincident with depression of magnetic field strength associated with enhanced plasma density, indicating the entry of magnetosheath plasma into the cusp region. The wave frequencies are generally scaled by the local proton cyclotron frequency and vary between 0.2 and 1.7 times local proton cyclotron frequency. This suggests that the waves are generated in the cusp region by the precipitating magnetosheath plasma. The properties of the waves are highly variable. The waves exhibit both left-handed and right-handed polarization in the spacecraft frame. The propagation angles vary from nearly parallel to nearly perpendicular to the magnetic field. We find no correlation among wave frequency, propagation angle, and polarization. Combined magnetic field and electric field data for the waves indicate that the energy flux of the waves is guided by the background magnetic field and points downward toward the ionosphere.

Le, G.; Blanco-Cano, X.; Russell, C. T.; Zhou, X.-W.; Mozer, F.; Trattner, K. J.; Fuselier, S. A.; Anderson, B. J.

2005-01-01

389

Rapid screening of polar compounds in Brazilian propolis by high-temperature high-resolution gas chromatography-mass spectrometry.  

PubMed

Methanol extracts of propolis from six different places, five in Rio de Janeiro state and one in So Paulo state, both in the Southeast of Brazil, were investigated using high-temperature high-resolution gas chromatography (HT-HRGC) and HT-HRGC-mass spectometry. The main purpose of the study was to establish the applicability of HT-HRGC as an analytical method for systematic studies of polar propolis fractions. Several compounds, including carbohydrates, phenolic acid derivatives, and high molecular weight compounds (e.g., wax esters of long chain fatty alcohols) could be readily characterized in the crude extracts by HT-HRGC-MS. HT-HRGC and HT-HRGC-MS were shown to be quick and informative tools for rapid analysis of crude polar extracts without cleanup. PMID:11087464

Pereira, A S; Norsell, M; Cardoso, J N; Aquino Neto, F R; Ramos, M F

2000-11-01

390

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

391

High-resolution human genome structure by single-molecule analysis.  

PubMed

Variation in genome structure is an important source of human genetic polymorphism: It affects a large proportion of the genome and has a variety of phenotypic consequences relevant to health and disease. In spite of this, human genome structure variation is incompletely characterized due to a lack of approaches for discovering a broad range of structural variants in a global, comprehensive fashion. We addressed this gap with Optical Mapping, a high-throughput, high-resolution single-molecule system for studying genome structure. We used Optical Mapping to create genome-wide restriction maps of a complete hydatidiform mole and three lymphoblast-derived cell lines, and we validated the approach by demonstrating a strong concordance with existing methods. We also describe thousands of new variants with sizes ranging from kb to Mb. PMID:20534489

Teague, Brian; Waterman, Michael S; Goldstein, Steven; Potamousis, Konstantinos; Zhou, Shiguo; Reslewic, Susan; Sarkar, Deepayan; Valouev, Anton; Churas, Christopher; Kidd, Jeffrey M; Kohn, Scott; Runnheim, Rodney; Lamers, Casey; Forrest, Dan; Newton, Michael A; Eichler, Evan E; Kent-First, Marijo; Surti, Urvashi; Livny, Miron; Schwartz, David C

2010-06-15

392

High crystalline dithienosilole-cored small molecule semiconductor for ambipolar transistor and nonvolatile memory.  

PubMed

We characterized the electrical properties of a field-effect transistor (FET) and a nonvolatile memory device based on a solution-processable low bandgap small molecule, Si1TDPP-EE-C6. The small molecule consisted of electron-rich thiophene-dithienosilole-thiophene (Si1T) units and electron-deficient diketopyrrolopyrrole (DPP) units. The as-spun Si1TDPP-EE-C6 FET device exhibited ambipolar transport properties with a hole mobility of 7.310(-5) cm2/(Vs) and an electron mobility of 1.610(-5) cm2/(Vs). Thermal annealing at 110 C led to a significant increase in carrier mobility, with hole and electron mobilities of 3.710(-3) and 5.110(-4) cm2/(Vs), respectively. This improvement is strongly correlated with the increased film crystallinity and reduced ?-? intermolecular stacking distance upon thermal annealing, revealed by grazing incidence X-ray diffraction (GIXD) and atomic force microscopy (AFM) measurements. In addition, nonvolatile memory devices based on Si1TDPP-EE-C6 were successfully fabricated by incorporating Au nanoparticles (AuNPs) as charge trapping sites at the interface between the silicon oxide (SiO2) and cross-linked poly(4-vinylphenol) (cPVP) dielectrics. The device exhibited reliable nonvolatile memory characteristics, including a wide memory window of 98 V, a high on/off-current ratio of 110(3), and good electrical reliability. Overall, we demonstrate that donor-acceptor-type small molecules are a potentially important class of materials for ambipolar FETs and nonvolatile memory applications. PMID:24708562

Kang, Woonggi; Jung, Minwoo; Cha, Wonsuk; Jang, Sukjae; Yoon, Youngwoon; Kim, Hyunjung; Son, Hae Jung; Lee, Doh-Kwon; Kim, BongSoo; Cho, Jeong Ho

2014-05-14

393

Polar zipper sequence in the high-affinity hemoglobin of Ascaris suum: amino acid sequence and structural interpretation.  

PubMed Central

The extracellular hemoglobin of Ascaris has an extremely high oxygen affinity (P50 = 0.004 mmHg). It consists of eight identical subunits of molecular weight 40,600. Their sequence, determined by protein chemistry, shows two tandemly linked globin-like sequences and an 18-residue C-terminal extension. Two N-linked glycosylation sites contain equal ratios of mannose/glucosamine/fucose of 3:2:1. Electron micrographs suggest that the eight subunits form a polyhedron of point symmetry D4, or 42. The C-terminal extension contains a repeat of the sequence Glu-Glu-His-Lys, which would form a pattern of alternate glutamate and histidine side chains on one side and of glutamate and lysine side chains on the other side of a beta strand. We propose that this represents a polar zipper sequence and that the C-terminal extensions are joined in an eight-stranded beta barrel at the center of the molecule, with histidine and glutamate side chains inside and lysine and glutamate side chains outside the barrel compensating each other's charges. The amino acid sequence of Ascaris hemoglobin fails to explain its high oxygen affinity. Images PMID:1584800

De Baere, I; Liu, L; Moens, L; Van Beeumen, J; Gielens, C; Richelle, J; Trotman, C; Finch, J; Gerstein, M; Perutz, M

1992-01-01

394

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

NASA Astrophysics Data System (ADS)

The high Mach number shock structure singularity arising in moment equations of the Boltzmann equation was investigated. The source of the singularity is shown to be the unbalanced treatment between two high order kinematic and dissipation terms caused by the overreach of Maxwellian molecule assumption. In compressive gaseous flow, the high order stress-strain coupling term of quadratic nature will grow far faster than the strain term, resulting in an imbalance with the linear dissipation term and eventually a blow-up singularity in high thermal nonequilibrium. On the other hand, the singularity arising from unbalanced treatment does not occur in the case of velocity shear and expansion flows, since the high order effects are cancelled under the constraint of the free-molecular asymptotic behavior. As an alternative method to achieve the balanced treatment, Eu's generalized hydrodynamics, consistent with the second law of thermodynamics, was revisited. After introducing the canonical distribution function in exponential form and applying the cumulant expansion to the explicit calculation of the dissipation term, a natural platform suitable for the balanced treatment was derived. The resulting constitutive equation with the nonlinear factor was then shown to be well-posed for all regimes, effectively removing the high Mach number shock structure singularity.

Myong, R. S.

2014-05-01

395

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

396

Recent STAR results in high-energy polarized proton-proton collisions at RHIC  

E-print Network

The STAR experiment at the Relativistic Heavy-Ion Collider at Brookhaven National Laboratory is carrying out a spin physics program in high-energy polarized $\\vec{p}+\\vec{p}$ collisions at $\\sqrt{s}=200-500\\,$GeV to gain a deeper insight into the spin structure and dynamics of the proton. One of the main objectives of the spin physics program at RHIC is the extraction of the polarized gluon distribution function based on measurements of gluon initiated processes, such as hadron and jet production. The STAR detector is well suited for the reconstruction of various final states involving jets, $\\pi^{0}$, $\\pi^{\\pm}$, e$^{\\pm}$ and $\\gamma$, which allows to measure several different processes. Recent results will be shown on the measurement of jet production and hadron production at $\\sqrt{s}=200\\,$GeV. The RHIC spin physics program has recently completed the first data taking period in 2009 of polarized $\\vec{p}+\\vec{p}$ collisions at $\\sqrt{s}=500\\,$GeV. This opens a new era in the study of the spin-flavor structure of the proton based on the production of $W^{-(+)}$ bosons. Recent STAR results on the first measurement of $W$ boson production in polarized $\\vec{p}+\\vec{p}$ collisions will be shown.

Bernd Surrow; for the STAR Collaboration

2010-04-27

397

High-speed polarization sensitive optical coherence tomography for retinal diagnostics  

NASA Astrophysics Data System (ADS)

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

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

2012-01-01

398

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

399

A new high-pressure polar phase of crystalline bromoform: a first-principles study.  

PubMed

The high-pressure phases of bromoform at zero temperature have been investigated by first-principles pseudopotential plane-wave calculations based on the density functional theory. A new high-pressure polar phase, ?, with space group CC has been found after a series of simulated annealing and geometry optimizations. Our calculated enthalpies showed that the transition from ? phase to ? phase occurs at 1 GPa, then the ? phase transforms to the ? phase at 90 GPa. In addition, the BrBr and C-HBr interactions are the key factors for the polar aggregation in the ? phase. Further calculations show that the insulate-metal transition in ? phase due to band overlap happens at ~130 GPa. PMID:20949926

Bao, Gang; Duan, Defang; Zhou, Dawei; Jin, Xilian; Liu, Bingbing; Cui, Tian

2010-11-11

400

Characterization of structural irregularities in highly birefringent photonic crystal fiber using torsional acoustic polarization coupling  

NASA Astrophysics Data System (ADS)

We demonstrate a novel method to characterize structural irregularities in a highly birefringent photonic crystal fiber (HB PCF) with high accuracy based on polarization coupling by torsional acoustic wave. Birefringence variation induced by the irregularities of air-hole structure in the fiber cross-section is analyzed via the transmission spectra of the acousto-optic coupling between two orthogonal polarization modes propagating along the fiber. The estimated maximum birefringence variation of two sections in the same batch of the HB PCF is 3 10 - 6 and 10 - 5 , respectively, from nominal birefringence value of 4.86 10 - 4 . The comparison between the experimental results and the numerical simulation resulted in the estimation of few tens of nm variation in the air-hole structure in the PCF.

Hong, Kee Suk; Lee, Kwang Jo; Yeom, Dong-IL; Kim, Byoung Yoon

2010-10-01

401

Vectorial analytical description of the polarized light of a high-power laser diode.  

PubMed

A mathematical model to describe the far-field of a high-power laser diode (LD) beam is presented. The laser beam propagation is studied by the vector Rayleigh-Sommerfeld far-field diffraction integral formula The far-field distribution of the LD beam is studied in detail; the light polarized parallel and perpendicular to the junction plane are all considered. This model is employed to predict the light intensity of high-power LDs. The computed intensity distributions are in a good agreement with the corresponding measurements. This model can be easily used to analyze the propagation properties of the high-power LD beam. PMID:23478776

Xu, Qiang; Wang, Jiajie; Han, Yiping; Wu, Zhensen

2013-03-10

402

Response of highly polarized Rydberg states to trains of half-cycle pulses  

Microsoft Academic Search

The response of very-high- n strongly polarized potassium Rydberg atoms to a sequence of impulsive perturbations provided by a train of short unidirectional electric pulses is investigated. Each pulse, termed a half-cycle pulse (HCP), has a duration Tp≪Tn , where Tn is the classical electron orbital period. Pronounced differences in the survival probability are observed when the sequence of HCPs

C. O. Reinhold; W. Zhao; J. C. Lancaster; F. B. Dunning; E. Persson; D. G. Arb; S. Yoshida; J. Burgdoerfer

2004-01-01

403

Dual polarized circular microstrip space-fed antenna array design with high isolation and broad bandwidth  

Microsoft Academic Search

This paper presents a novel approach to design dual polarized antenna with high isolation and broad bandwidth using space-fed antenna arrays. The three layer stacked configuration is used for the antenna array design. Space-fed antenna array design removes the complexity and losses of the feed networks and achieves better efficiency. FR4 substrate of ?r = 4.4, tan? = 0.02 and

Prashant Kumar Mishra; Girish Kumar

2012-01-01

404

The role of silica gel in lipase-catalyzed esterification reactions of high-polar substrates  

Microsoft Academic Search

The crucial role of silica gel in lipase-catalyzed esterification reactions using adsorbed high-polar substates was established.\\u000a It was found that in these kinds of reactions, the presence of silica gel-adsorbed substrates did not alter the kinetic mechanisms\\u000a of the synthesis of acylglycerides but improved significantly the conversion yields. An explanation for the critical role\\u000a of silica gel in these kinds

Edmundo Castillo; Valrie Dossat; Alain Marty; J. Stphane Condoret; Didier Combes

1997-01-01

405

Acetone in Orion: high-resolution images of a special oxygen-bearing molecule  

NASA Astrophysics Data System (ADS)

The Orion Molecular Cloud (414 pc) is one of the most-studied astrophysical testbeds in the sky, where the interstellar medium interacts strongly with the ultraviolet radiation from the Trapezium cluster. Inside the cloud, the luminous Orion BN/KL region is well-known for its rich and complex chemistry, especially in the vicinity of the Orion hot molecular core, or Hot Core. It has been known that large oxygen- and nitrogen-bearing molecules have different distributions in this region, where N-bearing species are located near the Hot Core but O-bearing species are located close to the Orion Compact Ridge. However, (CH_3)_2CO (acetone) is one molecule which does not show this tendency. Therefore, it is of interest to carry out detailed study on the distribution of the acetone emission in the Orion BN/KL region. Our high-resolution images (1.8'' 0.8'') from the IRAM Plateau de Bure Interferometer show that the acetone emission is originated mostly from the southwest of the Hot Core and the regions close to the infrared sources IRc7 and IRc6, where the CS J=1-0 emission has been detected before. It also indicates that the acetone emission in the Orion BN/KL region is associated with dense cores in a size of a few hundred AU. We will discuss the velocity structure of the acetone emission and its physical properties in this region.

Peng, T. C.; Brouillet, N.; Favre, C.; Despois, D.; Baudry, A.; Remijan, A.; Wilson, T.; Wootten, A.

2011-05-01

406

Separations method for polar molecules  

DOEpatents

A method for separating at least one compound from a liquid mixture containing different compounds where anew crystalline manganese phosphate composition with the formula Mn.sub.3 (PO.sub.4).sub.4.2(H.sub.3 NCH.sub.2 CH.sub.2).sub.3 N.6(H.sub.2 O) is dispersed in the liquid mixture, selectively intercalating one or more compounds into the crystalline structure of the Mn.sub.3 (PO.sub.4).sub.4.2(H.sub.3 NCH.sub.2 CH.sub.2).sub.3 N.6(H.sub.2 O).

Thoma, Steven G.; Bonhomme, Francois R.

2004-07-27

407

Highly polarized light from stable ordered magnetic fields in GRB?120308A.  

PubMed

After the initial burst of ?-rays that defines a ?-ray burst (GRB), expanding ejecta collide with the circumburst medium and begin to decelerate at the onset of the afterglow, during which a forward shock travels outwards and a reverse shock propagates backwards into the oncoming collimated flow, or 'jet'. Light from the reverse shock should be highly polarized if the jet's magnetic field is globally ordered and advected from the central engine, with a position angle that is predicted to remain stable in magnetized baryonic jet models or vary randomly with time if the field is produced locally by plasma or magnetohydrodynamic instabilities. Degrees of linear polarization of P???10 per cent in the optical band have previously been detected in the early afterglow, but the lack of temporal measurements prevented definitive tests of competing jet models. Hours to days after the ?-ray burst, polarization levels are low (P?polarization position angle remains stable, changing by no more than 15 degrees over this time, with a possible trend suggesting gradual rotation and ruling out plasma or magnetohydrodynamic instabilities. Instead, the polarization properties show that GRBs contain magnetized baryonic jets with large-scale uniform fields that can survive long after the initial explosion. PMID:24305162

Mundell, C G; Kopa?, D; Arnold, D M; Steele, I A; Gomboc, A; Kobayashi, S; Harrison, R M; Smith, R J; Guidorzi, C; Virgili, F J; Melandri, A; Japelj, J

2013-12-01

408

Fluorescence Polarization Immunoassay of a High-Molecular-Weight Antigen Based on a Long-Lifetime Ru-Ligand Complex  

Microsoft Academic Search

We describe a new class of fluorescence polarization immunoassays based on the luminescence from an asymmetrical Ru-ligand complex. We found that such a complex displays larger polarization values than those of comparable symmetrical complexes and appear to be highly photostable in aqueous solution. We synthesized a conjugatable Ru-ligand complex, which was used to label human serum albumin (HSA) as the

E. Terpetschnig; H. Szmacinski; J. R. Lakowicz

1995-01-01

409

Penicillium roqueforti: a multifunctional cell factory of high value-added molecules.  

PubMed

This is a comprehensive review, with 114 references, of the chemical diversity found in the fungus Penicillium roqueforti. Secondary metabolites of an alkaloidal nature are described, for example, ergot alkaloids such as festuclavine, isofumigaclavines A and B, and diketopiperazine alkaloids such as roquefortines A-D, which are derived from imidazole. Other metabolites are marcfortines A-C, PR-toxin, eremofortines A-E, mycophenolic and penicillic acids, and some ?-lactones. Also, recent developments related to the structural characteristics of botryodiplodin and andrastin are studied-the latter has anticancer properties. Finally, we discuss the enzymes of P.roqueforti, which can participate in the biotechnological production of high value-added molecules, as well as the use of secondary metabolite profiles for taxonomic purposes. PMID:25421646

Mioso, R; Toledo Marante, F J; Herrera Bravo de Laguna, I

2015-04-01

410

High-Temperature Slow Relaxation of the Magnetization in Ni10 Magnetic Molecules  

NASA Astrophysics Data System (ADS)

We investigate a family of molecular crystals containing noninteracting Ni10 magnetic molecules. We find slow relaxation of the magnetization below a temperature as high as 17 K and we show that this behavior is not associated with an anisotropy energy barrier. Ni10 has a characteristic magnetic energy spectrum structured in dense bands, the lowest of which makes the crystal opaque to phonons of energy below about 1 meV. We ascribe the nonequilibrium behavior to the resulting resonant trapping of these low-energy phonons. Trapping breaks up spin relaxation paths leading to a novel kind of slow magnetic dynamics which occurs in the lack of anisotropy, magnetic interactions and quenched disorder.

Carretta, S.; Santini, P.; Amoretti, G.; Affronte, M.; Candini, A.; Ghirri, A.; Tidmarsh, I. S.; Laye, R. H.; Shaw, R.; McInnes, E. J. L.

2006-11-01

411

High-temperature slow relaxation of the magnetization in Ni10 magnetic molecules.  

PubMed

We investigate a family of molecular crystals containing noninteracting Ni10 magnetic molecules. We find slow relaxation of the magnetization below a temperature as high as 17 K and we show that this behavior is not associated with an anisotropy energy barrier. Ni10 has a characteristic magnetic energy spectrum structured in dense bands, the lowest of which makes the crystal opaque to phonons of energy below about 1 meV. We ascribe the nonequilibrium behavior to the resulting resonant trapping of these low-energy phonons. Trapping breaks up spin relaxation paths leading to a novel kind of slow magnetic dynamics which occurs in the lack of anisotropy, magnetic interactions and quenched disorder. PMID:17155708

Carretta, S; Santini, P; Amoretti, G; Affronte, M; Candini, A; Ghirri, A; Tidmarsh, I S; Laye, R H; Shaw, R; McInnes, E J L

2006-11-17

412

Intensity-dependent multiorbital effect in high-order harmonics generated from aligned O2 molecules  

NASA Astrophysics Data System (ADS)

High-order harmonics generated from multiple orbitals of aligned O2 molecules are studied theoretically and we focus on the effect of two-center interference during photoexcitation. We find that the contribution of the harmonics generated from different molecular orbitals to the total harmonics varies distinctively with the laser intensity. The total harmonic spectra are dominated by the harmonics generated from a 1?g valence shell at lower intensities, but are dominated by those generated from a 1?u valence shell at higher intensities. This change is a sequence of the structure-induced two-center interference during photoexcitation of harmonic generation. This study indicates that by properly choosing the intensity of driving laser pulses, one can extract the orbital information of both the 1?g and the 1?u valence shells by the generated harmonics. This provides a potential way to tomographically reconstruct the low-lying 1?u valence shell.

Zhang, Jingtao; Wu, Yan; Zeng, Zhinan; Xu, Zhizhan

2013-09-01

413

High-Throughput Screening of Small Molecule Ligands Targeted to Live Bacteria Surface  

PubMed Central

The discovery of small molecule ligands targeted to the surface of live pathogenic bacteria would enable an entirely new class of antibiotics. We report the development and validation of a microarray-based high-throughput screening platform for bacteria that exploits 300 ?m diameter chemical spots in a 1 3 nano-layered glass slide format. Using 24 model compounds and 4 different bacterial strains we optimized the screening technology, including fluorophore-based optical deconvolution for automated scoring of affinity and cyan-magenta-yellow-black (CMYK) color-coding for scoring of both affinity and specificity. The latter provides a lossless, one-dimensional view of multidimensional data. By linking in silico analysis with cell binding affinity and specificity, we could also begin to identify the physicochemical factors that affect ligand performance. The technology we describe could form the foundation for developing new classes of antibiotics. PMID:23461528

Lee, Jeong Heon; Park, Sunny; Hyun, Hoon; Bordo, Mark W.; Oketokoun, Rafiou; Nasr, Khaled A.; Frangioni, John V.; Choi, Hak Soo

2013-01-01

414

Use of a Long-Lifetime Re(I) Complex in Fluorescence Polarization Immunoassays of High-Molecular-Weight Analytes  

Microsoft Academic Search

We describe a new class of fluorescence polarization immunoassays based on the luminescence from a Re(I) metal-ligand complex. Re(I) complexes are extremely photostable and possess useful photophysical properties including long lifetimes, high quantum yields, and high emission polarization in the absence of rotational diffu- sion. In the present study, a conjugatable, highly lumi- nescent Re(I) metal-ligand complex, (Re(bcp)(CO) 3(4- COOHPy))(ClO4),

Xiang-Qun Guo; Felix N. Castellano; Joseph R. Lakowicz

1998-01-01

415

High resolution studies of dissociative electron attachment to molecules: dependence on electron and vibrational energy  

NASA Astrophysics Data System (ADS)

For several molecules which are important for plasma processing and gaseous dielectrics (CF3I, CF3Br, CH3Br, and SF6), we have studied the dependence of dissociative electron attachment (DEA) on both the electron energy and on the initial vibrational energy. With reference to electron swarm data, we determine highly-resolved absolute DEA cross sections over a broad energy range, using the Laser Photoelectron Attachment (LPA) method (E = 0-0.2 eV, ?E ? 1-3 meV) and the EXtended Laser Photoelectron Attachment (EXLPA) method (0-2 eV, ?E ? 15-30 meV). The experimental data are compared with the results of R-matrix calculations, involving ab initioinformation on the potential energy curves and semiempirical autodetachment widths. For CF3I and CF3Br, previous DEA cross sections are found to be substantially too high. For CH3Br, the measurements confirm a predicted vibrational Feshbach resonance, associated with the v3 = 4 vibrational threshold, and the value of the activation energy (due to an intermediate barrier) for this exothermic DEA process. For SF6, we report absolute cross sections for SF6- as well as SF5- formation for vibrational temperatures ranging from 200 to 500 K. Moreover, the first absoluteDEA cross sections (SF5- formation) for CO2-laser excited SF6 molecules have been obtained at different initial vibrational temperatures. The results indicate that the effect of the mode-selective energy input into the v3-mode (predominantly v3 = 1) on the enhancement of SF5- formation is very similar to that of a corresponding rise of the average vibrational energy by thermal heating; at E = 2 meV electron energy, the results indicate an activation energy of about 0.38 eV.

Ruf, M.-W.; Braun, M.; Marienfeld, S.; Fabrikant, I. I.; Hotop, H.

2007-11-01

416

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

PubMed

We developed a high-speed polarization sensitive optical coherence tomography (PS-OCT) system for retinal imaging based on spectral domain OCT. The system uses two spectrometers, one for each polarization channel, that operate in parallel at 20000 A-lines/s each. It provides reflectivity, retardation, and cumulative optic axis orientation simultaneously. We present our instrument and discuss the requirements for the alignment of the two spectrometers specific for our setup. We show 2D spectral domain PS-OCT images and - to the best of our knowledge - the first 3D spectral domain PS-OCT data sets in form of fly-through movies and volume rendered data sets recorded in human retina in vivo. PMID:19503236

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

2005-12-12

417

High Performance Polarized Electron Photocathodes Based on InGaAlAs/AlGaAs Superlattices  

NASA Astrophysics Data System (ADS)

Highly efficient emitters of polarized electrons based on the InAlGaAs/AlGaAs superlattice give an optimistic prognosis to explorations of such structures as the sources for accelerators. A new set of these SL structures with minimized conduction band offset was designed and recently tested. A new technology of surface protection in MBE growth leads to a significantly reduced heat-cleaning temperature. At these lowered cleaning temperatures, the thermal degradation of the working structure parameters is avoided. As a result a polarization P of up to 91% at corresponding quantum efficiency (QE) of 0.3% was achieved at room temperature. A 50% increase in the photocathode lifetime has been achieved with Sb coverage.

Mamaev, Y. A.; Subashiev, A. V.; Yashin, Y. P.; Gerchikov, L. G.; Luh, D.; Maruyama, T.; Clendenin, J. E.; Ustinov, V. M.; Zhukov, A. E.

2005-08-01

418

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

419

In-band OSNR monitor with high-speed integrated Stokes polarimeter for polarization division multiplexed signal.  

PubMed

An in-band optical signal-to-noise ratio (OSNR) monitor is proposed, based on an instantaneous polarization state distribution analysis. The proposed monitor is simple, and is applicable to polarization division multiplexed signals. We fabricate a high-speed Stokes polarimeter that integrates a planar lightwave circuit (PLC) based polarization filter, high-speed InP/InGaAs photodiodes and InP hetero-junction bipolar transistor (HBT) trans-impedance amplifiers (TIA). We carry out proof-of-concept experiments with the fabricated polarimeter, and successfully measure the OSNR dependent polarization distribution with 100-Gb/s dual polarization quadrature phase shift keying (DP-QPSK) signals. PMID:23262848

Saida, Takashi; Ogawa, Ikuo; Mizuno, Takayuki; Sano, Kimikazu; Fukuyama, Hiroyuki; Muramoto, Yoshifumi; Hashizume, Yasuaki; Nosaka, Hideyuki; Yamamoto, Shuto; Murata, Koichi

2012-12-10

420

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

421

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

422

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

423

Influence of Polar Ozone Loss On Northern Mid-latitude Regions Estimated By A High Resolution Chemistry Transport Model  

NASA Astrophysics Data System (ADS)

The MIMOSA-CHIM three dimensional high resolution chemical transport model has been developped to estimate the contribution of polar ozone destruction to the lower stratosphere ozone budget at mid-latitudes. A PV-based analysis is performed to estimate the area covered by polar air, vortex, and filaments in the 45N-55N latitude band at 475K during winter 1999/2000, and their contribution to ozone loss. The polar air contribution was found to represent usually between 20% and 40% of the total ozone loss in this latitude band, but can reach 50% during large vortex intrusions. At 475K, the total chemical ozone loss in non polar air between 45N-55N increases from 1% in mid-December to 15% at the end of March. Several chemical ozone tracers are considered to investigate the origin of the ozone loss in non polar air. These tracers allow us to quantify the amount of chemical ozone destruction that occured in the vortex, in the polar filamentary structures, and in the non polar air. Until February, the main contributor to the non polar ozone loss is in-situ destruction at mid-latitudes, but the contribution from the ozone destruction in the polar vortex increases steadily during the winter and represents about 50% of the total mid-latitude ozone loss in April, after the vortex breakup.

Marchand, M.; Godin, S.; Hauchecorne, A.; Lefvre, F.; Bekki, S.; Chipperfield, M. P.

424

A Manual Small Molecule Screen Approaching High-throughput Using Zebrafish Embryos  

PubMed Central

Zebrafish have become a widely used model organism to investigate the mechanisms that underlie developmental biology and to study human disease pathology due to their considerable degree of genetic conservation with humans. Chemical genetics entails testing the effect that small molecules have on a biological process and is becoming a popular translational research method to identify therapeutic compounds. Zebrafish are specifically appealing to use for chemical genetics because of their ability to produce large clutches of transparent embryos, which are externally fertilized. Furthermore, zebrafish embryos can be easily drug treated by the simple addition of a compound to the embryo media. Using whole-mount in situ hybridization (WISH), mRNA expression can be clearly visualized within zebrafish embryos. Together, using chemical genetics and WISH, the zebrafish becomes a potent whole organism context in which to determine the cellular and physiological effects of small molecules. Innovative advances have been made in technologies that utilize machine-based screening procedures, however for many labs such options are not accessible or remain cost-prohibitive. The protocol described here explains how to execute a manual high-throughput chemical genetic screen that requires basic resources and can be accomplished by a single individual or small team in an efficient period of time. Thus, this protocol provides a feasible strategy that can be implemented by research groups to perform chemical genetics in zebrafish, which can be useful for gaining fundamental insights into developmental processes, disease mechanisms, and to identify novel compounds and signaling pathways that have medically relevant applications. PMID:25407322

Poureetezadi, Shahram Jevin; Donahue, Eric K.; Wingert, Rebecca A.

2014-01-01

425

Single-molecule detection and radiation control in solutions at high concentrations via a heterogeneous optical slot antenna.  

PubMed

We designed a heterogeneous optical slot antenna (OSA) that is capable of detecting single molecules in solutions at high concentrations, where most biological processes occur. A heterogeneous OSA consists of a rectangular nanoslot fabricated on heterogeneous metallic films formed by sequential deposition of gold and aluminum on a glass substrate. The rectangular nanoslot gives rise to large field and fluorescence enhancement for single molecules. The near-field intensity inside a heterogeneous OSA is 170 times larger than that inside an aluminum zero-mode waveguide (ZMW), and the fluorescence emission rate of a molecule inside the heterogeneous OSA is about 70 times higher than that of the molecule in free space. Our proposed heterogeneous optical antenna enables excellent balance between performance and cost. The design takes into account the practical experimental conditions so that the parameters chosen in the simulation are well within the reach of current nano-fabrication technologies. Our results can be used as a direct guidance for designing high-performance, low-cost plasmonic nanodevices for the study of bio-molecule and enzyme dynamics at the single-molecule level. PMID:24976558

Zhao, Chenglong; Liu, Yongmin; Yang, Jing; Zhang, Jiasen

2014-08-01

426

Analysis of experiments on high-level cloud sensing with a satellite radiometer and a ground-based polarization lidar  

NASA Astrophysics Data System (ADS)

We present results of joint analysis of the data of high-level cloud sensing with a polarization lidar and satellite radiometer MODIS. The possibility of detection from space of cirrus clouds with preferred orientation of ice crystals is discussed.

Samokhvalov, I. V.; Belov, V. V.; Kaul, B. V.; Bryukhanova, V. V.; Nasonov, S. V.; Bryukhanov, I. D.; Tarasenkov, M. V.

2014-11-01

427

Characterizing polarized illumination in high numerical aperture optical lithography with phase shifting masks  

NASA Astrophysics Data System (ADS)

The primary objective of this dissertation is to develop the phase shifting mask (PSM) as a precision instrument to characterize effects in optical lithography related to the use of polarized partially coherent illumination. The intent is to provide an in-situ characterization technique to add to the lithographer's tool-kit to help enable the stable and repeatable mass production of integrated circuits with feature sizes approaching 1/6th the wavelength of light being used. A series of complex-valued mathematical functions have been derived from basic principles and recent advances in photomask fabrication technology have enabled their implementation with four-phase mask making. When located in the object plane of an imaging system, these test functions serve to engineer a wavefiront that interacts with one particular optical effect, creating a measurable signal in the image plane. In most cases, these test patterns leverage proximity effects to create a central image intensity and are theoretically the most sensitive to the desired effect. Five novel classes of test patterns have been developed for in-situ characterization. The first two classes, The Linear Phase Grating (LPG) and Linear Phase Ring (LPR), both serve to characterize illumination angular distribution and uniformity by creating signals dependent on illumination angular frequency. The third class consists of the Radial Phase Grating (RPG) and Proximity Effect Polarization Analyzers (PEPA), which each create a polarization-dependent signal by taking advantage of the image reversal of one polarization component at high numerical aperture (NA). PSM Polarimetry employs a series of these patterns to form a complete polarization characterization of any arbitrary illumination scheme. The fourth and fifth classes employ sub-resolution interferometric reference probes to coherently interact with proximity effect spillover from a surrounding pattern. They measure the effective phase and transmission of the shifted regions of an alternating PSM and projection lens birefringence, respectively. A secondary objective of this dissertation has been to leverage some of these functions to extend the application of pattern matching software to rapidly identify areas in a circuit design layout that may be vulnerable to polarization and high-NA effects. Additionally, polarization aberrations have been investigated, as they may become important with hyper-NA imaging systems. Three multi-phase test reticles have been developed for this thesis and have pushed the limits of photomask fabrication. Coupled with a variety of experimental and simulation studies at 193nm wavelength, they have validated the scientific principles of the PSM monitors and have offered unique insight into implementation issues such as electromagnetic (EM) effects and mask making tolerances. Although all five classes are novel theoretical concepts, it is believed that PSM Polarimetry is commercially viable. Despite a 70% loss of sensitivity due to mask making limitations and a 20% loss due to EM effects, it can likely still monitor polarization to within 2%. Experimental results are comparable to the only other known technique, which requires special equipment. Taken collectively, the five novel classes of PSM monitors offer the lithographer an independent tool-kit to ensure proper tool operation. They also provide circuit designers an understanding of the impact of imaging on layouts. Although they have been developed for optical lithography, their principles are relevant to any image-forming optical system and are likely to find applications in other fields of optics or acoustics.

McIntyre, Gregory Russell

428

Spectral Stokes singularities of partially coherent radially polarized beams focused by a high numerical aperture objective  

NASA Astrophysics Data System (ADS)

The dynamic behavior of spectral Stokes singularities of partially coherent radially polarized beams focused by a high numerical aperture (NA) objective is studied by using the vectorial Debye diffraction theory and complex spectral Stokes fields. It is shown that there exist s12, s23, and s31 singularities, as well as P (completely polarized) and U (unpolarized) singularities. The motion, pair creation and annihilation, and changes in the degree of polarization of s12, s23, and s31 singularities, and the handedness reversal of s12 singularities (C-points) may appear by varying a controlling parameter, such as the truncation parameter, NA, or spatial correlation length. The creation and annihilation occur for a pair of s12 singularities with opposite topological charge but the same handedness, and for a pair of oppositely charged s23 or s31 singularities. The critical value of the truncation parameter, at which the pair annihilation takes place, increases as the semi-angle of the aperture lens (or, equivalently, NA) or spatial correlation length increases. The collision of an s12 singularity with an L-line (s3 = 0 contour) leads to a V-point, which is located at the intersection of contours of s12 = 0 and s23 = 0 (or s31 = 0) and is unstable.

Luo, Yamei; L, Baida

2010-11-01

429

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 fo